369
Atherosclerosis, 24 (1976) 369-380 @ Elsevier Scientific Publishing Company,
Amsterdam
- Printed
in The Netherlands
TREATMENT OF TYPE II HYPERLIPOPROTEINEMIA d-THYROXINE
A.D. RAKOW,
H.U. KLGR,
E. KgTER,
H.H. DITSCHUNEIT
WITH
and H. DITSCHUNEIT
Department of Medicine, Division of Metabolism and Nutrition, University of Urn, Ulm (West-Germany) (Received (Revised, (Accepted
8th October, 1975) received 4th May, 1976) 13th May, 1976)
Summary The effectiveness of a new, almost Z-thyroxine free preparation of d-thyroxine (Dynothel@) was tested in 15 patients with Type IIa and 4 patients with Type IIb hyperlipoproteinemia. Eleven patients with Type IIa and 3 with Type IIb were responsive to treatment and showed an average 26% decrease in plasma TC. This decrement in plasma TC was mirrored in a significant reduction of LDL cholesterol in Type IIa and IIb. While VLDL cholesterol slightly decreased in Type IIb, it remained the same in Type IIa and so did the HDL cholesterol in both types. As neither VLDL nor LDL or HDL triglyceride levels changed very much in either type, the total plasma triglycerides remained the same. The plasma phospholipids were higher in Type IIa and lower in Type IIb on therapy. Thus, Dynothel@ seems to be a potent d-thyroxine preparation for lowering plasma cholesterol, this decrease being brought about by reduction of LDL cholesterol levels. The effect of the drug on plasma TG and PL is less certain . Key words:
Hyperlipoproteinemia
Type II - Lipids - Lipoproteins
- d-Thyroxine
Gesellschaft fiir Innere * Part of this work has been presented at the 80th Meeting of the “Deutsche Medizin”, Wiesbaden. 1974. List of abbreviations: TC = total cholesterol, TG = triglycerides, PL = phospholipids, VLDL = very low density lipoproteins (d 1.006). LDL = low density lipoproteins (d 1.006-1.063). HDL = high density lipoproteins (d 1.063-1.21).
370
Introduction Recently, recognition and treatment of risk factors have become more and more inportant for the primary and secondary prevention of atherosclerotic vascular disease. Among these risk factors hyperlipoproteinemias do play an important, if not the most inportant role, as could be demonstrated in various prospective and retrospective studies [1,5,13,16,18,20]. Thus, it seems to be self-evident that the development and therapeutical use of lipid-lowering drugs has been largely promoted in the last decade. One of the most potent drugs for lowering elevated cholesterol levels is d-thyroxine [ 2,4,32]. However, serious cardiovascular side effects most likely stemming from a relatively high contamination with I-thyroxine (OS-1.2%) did not permit a widespread clinical application of the early d-thyroxine preparations [6,9]. One of the most thorough and promising clinical trials with this drug, the Coronary Drug Project, even’ had to be modified because myocardial infarction and death were more frequent in the treated than in the control group [6]. In the meantime, preparations of d-thyroxine are available with a very low ‘and almost negligible l-thyroxine content one of which is d-3,5,3’,5’-tetraiodothyroxine (Dynothel @, Henning, Berlin). Its Z-thyroxine content has been determined to be less than 0.2% [7]. The present study was devised to evaluate the effect of this new d-thyroxine preparation on the lipids in plasma and in the lipoprotein fractions VLDL, LDL, and HDL in patients with hyperlipoproteinemia Type IIa and IIb according to the Fredrickson and Lees typing system [ll]. The focus on the lipid changes in the lipoprotein fractions seemed to be justified because of the eminent importance of LDL cholesterol for at least the early phase of human atherogenesis and the well documented lowering effect of older, more l-thyroxine containing preparations on this lipoprotein fraction [ 30,311. Patients
and Methods
Patients Fifteen patients with hyperlipoproteinemia Type IIa and 4 with Type IIb were treated for 6 months with Dynothel@. Table 1 shows age, sex, body weight and other clinical as well as some laboratory data of these patients which helped to establish the diagnosis of primary hyperlipoproteinemia and to rule out secondary forms. Familial occurence could be proven in 6 patients with Type IIa, but in none with Type IIb. Experimental design Before entering the study the patients had to pass a diet period of at least 6 months. The diet which was maintained throughout the drug and placebo period was composed of 40% carbohydrate, E-20% protein, and 40-45% fat consisting largely of polyunsaturated fatty acids (P/S ratio more than 1.5). After the diet period d-thyroxine administration was started in a dosage of 2 mg daily for the first week and continued with one additional mg for each week to follow ‘up to a final dose of 6 mg daily. This schedule was chosen to prevent potential cardiogenic side effects in the patients with angina. After 6
371 TABLE 1 CLINICAL
AND LABORATORY
DATA
OF PATIENTS
WITH TYPE Ha (NOS. l-15) AND
IIb (NOS.
16-19)
Patient
Sex
Age
Weight
Height
number
Normal values
-
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
F F M F F
55 46 58 43 62 47 48 47 59 52 36 53 18 65 48 47 57 44 55
M
M F F F M F M F F M F M M
Patient
ESR
Uric acid
SGOT
SGPT
-
-
50-100 (mg/lOO ml)
-422 WMoW
Z-19 W/l)
5-24 (U/v
90 88 60 60 44 96 70 80 54 56 65 73 57 64 66 72 60 75 68
165 162 163 164 153 172 173 154 158 160 170 164 170 172 164 179 154 158 170
60 88 94 80 66 88 83 87 92 76 81 81 95 92 88 89 88 137 66
229 257 327 291 266 453 306 339 422 160 137 196 366 327 280 228 344 393 289
7 10 5 10 10 18 16 13 12 11 4 15 10 9 10 9 14 13 8
9 8 4 7 5 24 13 8 5 8 4 12 10 14 11 14 4 21 10
Coro-
number
Blood sugar
I=rY angio-
ECG alterations
Serum creatinine
Serum urea
Proteinuria
Glucosuria
-
-142
-10.8
4J
9
(1rMoI/0
(mMoI/I)
100 96 106 08 88 80 95 110 71 79 88 97 90 97 100 100 71 125 100
5.8 6.8 8.1 5.9 5.3 6.2 6.6 4.8 8.6 9.8 3.9 4.5 3.1 7.4 6.4 7.5 9.2 8.2 5.6
Plasma albumin
Braphy
Normal values
(n.W.)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
517 9120 15/25 20132 20130 9118 8123 20146 16/26 20136 13120 S/18 55117 10125 88112 12127 13132 315 25138
+
=
Positive,
5120
++
=
-
&J 0 @ Q, 4) @
++ + -
;
-’ + ++ ++ ++ + ++ ++ + ”
0
-
; @ 0 ; ;
+ +
strongly positive, 0 = negative. not done, -
35165
cm z
:
@ @ @ @ @ @ @ 0 :
d @ @ 0 cb @ 0 @ @ 0 0 cb z
0 @ @ @ 0
@ @ @
46.9 46.6 45.1 43.0 44.9 50.0 51.2 51.8 51.3 39.4 53.2 67.0 38.6 44.2 45.0 48.9 42.1 40.5 42.7
= no alteration. F = female, M = male.
312
months the drug was replaced by placebo for another 6 weeks, after which the final blood specimen was drawn. Body weight remained throughout the whole investigation.
stable within
f 2 kg
Methods Plasma TG and TC were determined after a 12 h fast several times during the initial diet period and the treatment period and once at the end of the placebo phase. Analysis of plasma phospholipids and measurements of the lipoprotein TC and TG in VLDL, LDL, and HDL was performed at the beginning and at the end of the drug period in 13 patients with Type IIa and in all with Type IIb. TG and TC were measured simultaneously in a Technicon-Analyzer according to Kessler and Lederer [17] and Levine and Zak [22], respectively. Lipoprotein electrophoresis was carried out essentially as described by Rapp and Kahlke [28]. Phospholipids were determined with a Boehringer test kit (No. ‘15920 TPAC, Boehringer, Mannheim). VLDL and LDL were isolated simultaneously from the HDL and plasma proteins by zonal ultracentrifugation as described earlier [7], and the TG, TC and PL content determined in the VLDL, LDL, and HDL plus plasma protein fraction, respectively. As the recovery of lipids in the isolated lipoprotein fractions never reached 100% (between 70 and 85%), the final figures for lipoprotein TG, TC, and PL were corrected for recovery. Results Figure 1 shows the course of plasma TG and TC levels in Type IIa and IIb during the drug and placebo period. The TG and TC figures at “0 months”, i.e. for the diet period, represent the mean of all samples withdrawn in that period. Although it started out from different levels of elevation (366 f 20 mg/ 100 ml in Type IIa and 311 + 14 mg/lOO ml in Type IIb), the cholesterol of both groups gradually decreased to a range of 280-290 mg/lOO ml. While Type IIa TG did not show any significant change in either drug or placebo period, distinct differences seemed to appear in Type IIb plasma TG under therapy. After having increased after the first month of treatment the TG in Type IIb were falling back to the original level on continuation of therapy. However, analysis of the TG values recorded just before the start of d-thyroxine medication reveals that all 4 patients had much higher values (320 f 80 mg/lOO ml) than was their average during the whole diet period (257 + 52 mg/lOO ml). Thus, the elevation of the mean TG after the first month of treatment may be either due to an effect of therapy or represent a spontaneous variation in TG level in Type IIb patients. Reports on seasonal variations in plasma TC [32], even under continuous therapy with d-thyroxine [14] prompted us to try to establish a firm therapeutic success in each individual case by computing several values in a given period rather than by choosing the last value in diet and drug period for comparison (Table 2). The figures in the “diet” column for TG and TC represent mean values for that period. The TC values listed under “drug” are the mean of all samples taken from the third to the sixth month of treatment. As can be seen from Table 2,9 out of 15 patients with Type IIa and 2 out of 4 with Type
373
T
@-@
TG
.-+
TC
In type
Ila
@-@TG in tvrx
lib
T
d-THYROXINE I 0
I 1
I 2
I 3
I I 4
I 5
I 6
I 7
1 8
months Fig. 1. Course of TG and TC in 15 patients with Type IIa and 4 patients with Type IIb under treatment with Dynothel@ (6 mg dally). Half filled circle in brackets at “0 months” represents the last TG value in Type IIb patients just prior to d-thyroxine treatment.
IIb were fully responsive to d-thyroxine showing a highly significant reduction of plasma TC of 20 to 35% of the mean pretreatment levels. A tendency towards a more pronounced decrement was observed in patients with higher initial values (more than 400 mg/lOO ml). In 1 patient with Type IIa (No. 11) and in 1 with Type IIb (No. 17) a successful1 treatment could not be definitely proven because the TC levels in the placebo phase did not return to the original range. Altogether 6 patients from both groups reached the normal TC range (less than 250 mg/lOO ml) on d-thyroxine. The mean plasma phospholipid value showed an increment from 271 + 21 to 318 + 18 mg/lOO ml in Type IIa and a decrement from 334 + 63 to 272 + 26 mg/lOO ml in Type IIb. Table 3 presents a comparison of the lipid concentrations in VLDL, LDL, and HDL before and after d-thyroxine treatment. In Type IIa and TC concen-
374
TABLE 2 TG,
TC AND
PL VALUES
BEFORE,
ON,
AND
OFF
TREATMENT
WITH d-THYROXINE
(DYN-
OTHEL~)INPATIENTSWITHTYPEIIa(NOS.1-l5)ANDTYPEITt,(NOS.16-l9) Data givenrepresentaveragef SEM. Patient Triglycerides (mg/lOOml) number Diet Drug Placebo
1 2 3
105k 10 137+ 4 98+ 24
4 5
109 89k
Totalcholesterol(mg/lOOml) Diet
Drug
PhosphoIipids(mg/ 100ml)
Placebo Diet
Drug
112+ 11 143 146k17
143 183
333+ 61 277 + 20 468r 2
267+ 41 290 303? 7
390 510
284 215 -
371 311 -
5
88? 2 92+12
123 83
454 311i18
328214 246+19
498 276
220 -
349 -
6 7 8 9 10
115+12 107+ 25 112+ 10 92+ 10 86k 4
135* 1 157+18 118+ 23 93? 6 162? 20
155 109 100 97 100
258+ 6 287? 22 328+15 334*13 518+ 17
265+10 209 *12 237+ 8 363* 6 482? 5
310 270 336 391 445
218 378 246 210 -
268 261 267 313 -
11 12 14 15
134 92 82 56? 84+
128+ 80+ lOO*ll 59? 82k
90 83 60 83
359* 39 537 409 332k 23 286 i16
311*19 367* 20 274+19 259k 8 281+13
298 522 498 314 -
275 341 398 197 -
299 415 411 242 -
ti
100 + 11
113 k10
108+
366? 20
298t14
389 f 26
271 + 21
318+18
16 17 18 19
203+ 22 232+ 60 378i- 42 218+ 9
191? 42 252+ 34 255 367+ 31
198 444 263 390
272+ 36 274+ 31 309+ 2 337+17
205+ 1 221+19 305 244t12
360 184 294 402
157 338 389 451
225 132 294 338
i
257 + 52
266 + 36
323 -t 56
311+14
243 + 22
310 * 47
334 + 63
272 k 26
i3
5 8
5 4 3 9
9
change, being higher in 6, lower in 4 tration in the VLDL did not consistently and unchanged in 3 cases after therapy. The LDL cholesterol markedly decreased in 10 patients with Type IIa. The HDL cholesterol did not change in average. However, there were more increments (7 cases) than decrement8 (5 cases) after treatment. In 3 of 4 patients with Type IIb the VLDL TC decreased. The LDL TC decreased in 3 and remained unchanged in 1 patient. There was no change in HDL TC upon therapy. Regarding the mean VLDL TG in Type IIa a slight tendency towards a decrease was encountered. The mean LDL TG value was also slightly though not significantly lower at the end of the drug period. In the HDL the TG level did not change in average. In Type IIb a decrease in VLDL TG was observed in 3 patients. The LDL- and HDL TG levels were not consistently influenced by d-thyroxine administration and remained the same in average. Due to loss of samples the PL content of the lipoprotein fractions could only be determined in 5 patients with Type IIa and in 2 patients with Type IIb hyperlipoproteinemia. In Type IIa there seemed to be a trend for an elevation of the PL in HDL and LDL, while in Type IIb the LDLand HDL PL were higher in 1 and lower in a second case. Symptoms that might have been expected as a side effect of the l-thyroxine contaminant like tachycardia, nervousness, feeling of unrest, diarrhea, etc. did
TABLE 3 TG, TC AND PL CONCENTRATION l-14) AND TYPE IIb (NOS. 16-19) Patient number
IN VLDL, LDL, AND HDL OF PATIENTS WITH TYPE IIa (NOS. IN DIET AND DRUG PERIOD, RESPECTIVELY
Triglycerides (mg/lOO ml) VLDL
LDL
HDL
Diet
Drug
Diet
Drug
Diet
Drug
1 2 3 4 5 6 I 8 9 11 12 13 14
40 83 82 20 15 29 55 21 30 52 29 41 14
12 57 58 31 21 12 1100 26 12 28 24 24 10
52 27 74 53 59 36 35 30 52 114 47 48 27
60 47 44 49 23 79 36 32 42 24 41 43 22
45 9 17 14 21 9 18 28 18 44 37 34 9
23 15 13 61 22 2’1 54 20 19 38 23 26 31
2
39 f 6
42 r 4
23.k 3
29 -t 4
49 75 63 57
47 22 32 57
33 23 65 62
61 k 5
40 + 8
46 k 10
32?
7
16 17 18 19
88 186 196 268
68 150 169 310
F
186k40
174 + 50
Patient number
Total cholesterol (mg/lOO ml) VLDL
50 + 6 40 82 112 52
72 f 16
LDL
HDL
Diet
Drw
Diet
Drw
Diet
1 2 3 4 5 6 7 8 9 11 12 13 14
18 30 42 12 3 18 33 30 32 77 13 18 16
11 34 51 11 15 3 51 12 30 41 22 11 5
200 187 295 291 192 271 191 184 271 201 232 265 298
208 215 229 235 107 210 111 156 214 192 217 205 146
58 53 27 81 53 19 67 35 82 70 95 29 27
x
26 C 5
23 + 5
237 f 12
188 k 12
53 f 7
60 + 7
16 17 18 19
49 48 64 74
29 26 43 90
186 197 167 175
132 165 172 100
62 25 26 56
43 19 79 65
32
59 -I 6
47 t 15
181 f 7
142 + 17
42 ?r 10
52 + 13
Drug 63 22 40 73 95 30 46 64 68 64 105 30 78
376
TABLE
3 (continued) Phospholipids (mg/lOO ml)
Patient number
VLDL
LDL
HDL
Diet
Drug
Diet
Drug
Diet
Dwx
1 2 3
-
-
-
-
-
-
4 5 6
-
3
12 -
117 -
221 -
101 -
116 -
7 8
26 -
28 -
197 -
-
66
154 -
-
67
9 11
-
8
10 -
128 -
180 -
-
74
123 -
12 13 14
44 8 -
11 27 -
227 271 -
208 332 -
70 119 -
197 51 -
x
18k 8
18+ 4
188 * 29
201 + 43
104 Yk15
111 + 26
16 17 18 19
37 51 -
32 32 -
49 196 -
105 46 -
x
25+ 7
22+ 4
169 + 28
165 k 38
-
72 91
97 + 12
-
88 54
99 f 19
not appear during the drug period. Moreover, neither vyas a change in frequency and intensity of attacks of angina - if already preexisting - reported nor could the onset of angina on treatment be observed. 3 patients complained about insomnia which had been present before the onset of therapy, too. Discussion The effectiveness of d-thyroxine almost free of l-thyroxine contamination is a definite proof that the successful therapy of hypercholesterolemias using older preparations [2,9,30] with a tenfold higher Z-thyroxine content was not due to this contaminant, although the high incidence of Z-thyroxine-caused side effects reported in those studies could have supported this concept. Concerning the degree of reduction of elevated cholesterol levels, previous investigators found decrements ranging from 11 to 48% of the pre-treatment levels on 5 to maximally 16 mg daily of the impure d-thyroxine preparations [2,4,9,14,30,31]. Recently, 3 different groups [3,19,21] reported an average decrease of plasma cholesterol in Type IIa and IIb of between 12 and 25% when the new, highly purified d-thyroxine (Dynothel@) was administered, In patients of our own group who responded to Dynothel @ therapy we found an average 26% decrease (range 20-35%) which is somewhat higher than the figures reported by the afore mentioned authors [3,19,21]. However, it has to be emphasized that 4 out of our 15 patients with Type IIa and 2 out of 4 patients with Type
377 IIb did not sufficiently respond to d-thyroxine treatment. Koschinsky et al. [21] and Klemens et al. [ 191 found about the same percentage of therapy failures as we, while Bommer et al. [3] observed no cases truly unresponsive patients. There is no apparent to Dynothel@ among 18 hypercholesterolemic reason why most of the patients are sensitive to d-thyroxine while a few are not. The non-responders do not represent a selection of excessive hypercholesterolemias; to the contrary, a great many of those having only slightly elevated plasma cholesterol values belong to this group. Adherence to a lipidlowering diet has been claimed to be of decisive importance for the effectiveness of d-thyroxine treatment [ 261. At least in our own unresponsive patients, diet was as well maintained as in the responsive ones. There are only a few reports on the effect of d-thyroxine on plasma TG. While Feldman and Carter [lo] saw in 10 patients a more or less constant reduction of sometimes even normal values in a range of 18-64%, the most recent studies [3,19,21] and our own investigation revealed no effect on TG levels in Type IIa and an uncertain decrement in Type IIb. A possible explanation for the difference between older and recent studies including our own may be that Feldman and Carter [lo] tested the TG response to an older preparation the high I-thyroxine content of which might have contributed to a higher potency for lowering TG as well. However, a different effect of d- and E-thyroxine on plasma TG has not been reported on in the literature. To our knowledge the effect of d-thyroxine on plasma PL in Type II has only been looked after by Jones and Cohen [ 151 who found lowered levels in 9 and unchanged levels in 6 patients. Unfortunately, the authors did not determine plasma TG in their patients so that no estimate is possible as to how many cases belonged to Types IIa and IIb, respectively. The decrease in PL in our Type IIb cases is in agreement with the results of that early investigation. Opposition results, however, were observed in Type IIa where plasma PL almost uniformly increased under d-thyroxine. No convincing explanation seems to be at hand for this discrepancy. Only a marked increase in the PL-rich HDL in compensation for a reduction of the TC-rich LDL could furnish a reasonable interpretation, but this was not the case, at least not to the necessary extent. The mechanism by which the reduction of plasma TC is attained in hypercholesterolemia becomes obvious when the changes occurring in the lipoprotein fractions are analyzed. Thus far, all investigators agree on the fact that both d- and l-thyroxine reduce the plasma TC in hypercholesterolemia by lowering the LDL cholesterol [ 10,15,19,30,31]. At least in Type IIa, our results do support this concept, too. Theoretically, the decrease of LDL cholesterol can be the consequence of 2 different processes, one being a change in composition of numerically identical particles and the other being a decrease of LDL unchanged in average molecular composition, The only way of distinguishing clmong these possibilities is to quantify the lipoprotein fractions with a technique other than measuring only one of its constituents. Strisower and Strisower [30] were able to demonstrate by analytic ultracentrifugation that the LDL (S, O-20) in Type IIa and Type IIb decreased on d-thyroxine administration. However, the analysis of S, classes in the analytic ultracentrifuge does not automatically rule out that changes in lipid composition of the LDL particle might have occurred on therapy as well. As an exchange of some TG for cho-
378
lesterol esters in the core of the LDL particle would not greatly change its flotation characteristics, such an alteration would not be discernable by means of the analytic ultracentrifugation. Without disposing of analytic centrifugation data we tried to draw tentative conclusions as to whether a decrease of unchanged lipoprotein particles or a change in composition has occurred by measuring 2 (TC and TG) of the 4 main constituents of the lipoprotein molecule (TC, TG, PL, and protein). If the ratio of TC and TG in the lipoprotein fraction remains roughly the same before and after therapy it appears likely to assume a decrease while a change in this ratio would indicate an alteration in composition rather than in concentration of the respective lipoprotein fraction. Concerning the LDL in Type IIa we found about the same TG/TC ratio in 7 patients and an increase in 4 cases. Thus, in the majority of cases with Type IIa hyperlipoproteinemia there seemed to be a decrease of normally composed LDL, but in a few patients the LDL became relatively “TC-depleted” after therapy. In the VLDL and HDL of Type IIa a concomitant decrease or increase of both TG and TC was seldom observed. Thus, a consistent lowering or elevating effect on these lipoprotein fractions is not likely. In all cases of Type IIb, however, we found a parallel decrease in VLDL TG and TC, making a de-
550.
mg/lOOml TC (mean of pretreatment
period ) A
500
/ ?? A
0
A 0
/:
450
r = 0.705 PC o.ool
f
400
0 0 - Bommer et al, 1975 A = Jepson 1963 X-Jones + Cohen 1961 ? -?own responsive patients
350
300
250
I”“I~“‘I’i”l’ 50 0
100
150
T&
mg/lOOml TC decrease (mean of drug period ) -
Fig. 2. Relationship of pretreatment TC to decrease IIb responsive to d-thyroxine therapy.
in TC upon
treatment
in patients
with Type IIa and
379
crement in number of a similarly composed VLDL population more probable than a mere shift of particle distributions within the VLDL range. This concept is corroborated by the finding of Strisower and Strisower [30] that the VLDL (Sf 20-105) in Type IIb are as much reduced under d-thyroxine therapy as the LDL (S, O-20). Finally, an interesting phenomenon should be mentioned in connection with the problem of how d-thyroxine operates in lowering TC values. On a mg/lOO ml basis TC values were observed to decrease much more in our grossly hypercholesterolemic patients responsive to therapy than in the ones with moderative elevations. When the decrement in TC was plotted against the pre-treatment values of responsive Type IIa and IIb cases of our own and of previous investigators [3,14,15] a highly significant positive correlation was found (Fig. 2). The meaning of this correlation remains obscure. One of several possible explanations is that d-thyroxine operates in a way that processes responsible for the removal from plasma and/or degradation of lipoprotein cholesterol may be maximally stimulated by the drug so that “substrate availability”, i.e., the LDL and, in IIb patients, the VLDL concentration determines the efficiency of the removal system. In other words, the higher the starting levels are the better can the removal system work. Supposing that the interdependence shown in Fig. 2 is valid in all ranges the cholesterol-lowering potency of d-thyroxine should be very low at approximately 150 mg/lOO ml plasma TC concentration, where the intercept lies between the regression line and the y-axis. It is at least of theoretical interest that this is a truly “physiological” range as judged by the results of prospective studies on risk factors for atherosclerosis [ 161 and of epidemiologic surveys of populations not prone to premature vascular disease [ 12,23,27]. Thus, the significant role of Z-thyroxine in the maintenance of a physiologically low plasma cholesterol level may explain the high hypocholesterolemic potency of the d-isomer, too. References 1 Albrink, M.J., Triglycerides, lipoproteins and coronary artery disease, Arch. Intern. Med.. 109 (1962) 145. 2 Bechtol, M.D. and Warner, W.L., Dextrothyroxine for lowering serum cholesterol, Angiology, 20 (1969) 565. 3 Bommer, J., Speders, H. and Ehrke, V.. Behandlung van Hypercholesteriniimie nach Herzinfarkt mit d-Thyroxin, Miinch. Med. Wschr., 117 (1975) 139. 4 Boyd. G.S. and Oliver, M.F.. The effect of certain thyroxine analogues on the serum lipids in human subjects, J. Endocrinol., 21 (1960) 33. 5 Carlson, L.A. and BGttiger, L.E., Isachaemic heart disease in relation to fasting values of plasma triglycerides and cholesterol, Lancet, 1 (1972) 865. 6 The Coronary Drug Project Research Group. The coronary drug project -~ Findings leading to further modifications of its protocol with respect to dextrothyroxine, J. Amer. Med. Ass.. 220 (1972) 996. 7 Ditschuneit, H.H. and K16r. H.U., Die Lipoproteinmunster van prim&en and sekundiiren Hyperlipoproteinimicn bei Ultrazanalzentrifugation. In: H. Ditschuneit (Ed.), Die Lipoproteine des Blutes Steinkopff Verlag, Darmstadt, 1973. 8 Dole, V.P. and Meinertz. Microdetermination of long chain fatty acids in plasma and tissues, J. Biol. Chem., 235 (1960) 2595. 9 Engelberg, H., Effect of sodium d-thyroxine on serum cholesterol and low density lipoproteins in man, Geriatrics, 17 (1962) 711. 10 Feldman, E.B. and Carter, A., Reduction of serum triglycerides in patients treated with sodium dthyroxine. Metabolism, 12 (1963) 1132. 11 Fredrickson, D.S., Levy, R.J. and Lees, R.S., Fat transport in lipoproteins -An integrated approach to mechanisms and disorders. New Engl. J. Med.. 276 (1967) 32,94,148, 215. 273.
380
12 Goldrick. R.B., Sinnet, P.F. and Whyte, H.M.. An assessment of coronary heart disease and coronary risk factors in a New Guinea highland population. In: R.J. Jones (Ed.), Atherosclerosis (Proceedings of the Second International Symposium), Springer-Verlag, Berlin, 1970. P. 366. 13 Heir&, R.A.. Levy, R.J. et al.. Lipid and carbohydrate anomalites in patients with angiographically documented coronary artery disease, Amer. J. Cardiol.. 24 (1969) 178. 14 Jepson, E.M., Long term trial of d-thyroxine in hypercholesterolemia. Brit. Med. J., 1 (1963) 1446. 15 Jones, R.J. and Cohen, L., Sodium dextro thyroxine in coronary disease and hypercholesterolemia. Circulation, 24 (1961) 164. 16 Kannel, W.B., CasteBi, W.P., Gordon, T. and McNamara, P.M., The Framingham study, Ann. Intern. Med., 74 (1971) 1. 17 Kessler, G. and Lederer, H., Automation in Analytical Chemistry 1965, Mediad Inc., New York, N.Y., 1966, p. 341. 18 Klemens. U.H.. L5wi.s of Menar, P.V.. Brenner, A., Wunck. E.V. and Schr5der. R., Hyperlipoproteitimien und Coronarerkrankungen - HPufigkeit. Typen-Verteilung, Abhiingigkeiten van Alter und Geschlecht. KIin. Wschr., 50 (1972) 139. 19 Klemens, U.H. and L&is of Menar, P.V., Behandlung primiirer Hyperlipoproteinffmien vom TYP Ha und Hb mit hochgereinigtem d-Thyroxln (D-T4). Dtsch. Med. Wschr.. 99 (1974) 487. 20 21 22
Kl5r. H.U. and Ditschuneit, H., Die Epidemiologic der Hyperlipidiimien. Miinch. Med. Wschr., 115 (1973) 626. primtier Hyperlipoproteiniimien des Koschinskey, T., Vogelberg, K.H. and Gries. F.A.. Therapie Typs Ha und IIb mit d-Thyroxin. Dtsch. Med. Wschr., 99 (1974) 494. Levine, L. and Zak. P., Automated determination of serum total cholesterol, Clin. Chim. Acta, 10
(1964) 381. 23 Mann, G.V.. Shaffer. R.D., Andersson.
R.S. and Sandsteat, H.H.. Cardiovascular disease in the Masai, J. Atheroscler. Res., 4 (1964) 289. 24 Mathur, K.S., Malhotra, K.K.. Sharma. R.D. and Srivastava. S.K., Dietary fats, serum cholesterol and serum lipid phosphorus in different socio-economic groups in Uttar Pradesh. J. Indian. Med. Ass.. 33 (1959) 303. 25 Neudecker, H. and Scheiffele, E., Die stereospezifische Bestimmung geringer Mengen I-Thyroxin in
d-Thyroxin, Arzneimittel-Forsch., 21 (1971) 432. 26 NJH Conference - Levy, R.J.. moderator, Treatment of primary hyperIipoproteinemia. 27 28 29 30 31 32
Ann. Intern.
Med., (1972) 267. Rabinowitz, J.L., Rodman, T. and Myerson. R.M., Effect of dextrothyroxine on metabolism of C14labelled cholesterol and tripalmitin. J. Amer. Med. Ass., 183 (No. 9) (1963) 758. Rapp, W. and Kahlke. W.. Lipoprotein-Elektrophorese in Agarose-Gel, Clin. Chim. Acta, 19 (1968) 493. responsible for the altered blood Rosenman, R.H., Byers, S.O. and Friedman, M., The mechanism cholesterol content in deranged thyroid states, J. Clin. Endocrinol., 12 (1952) 1287. Seamy, R.L., Hungerford, D.A. and Low, E.M.Y., Effects of dextrothyroxine on serum lipoprotein and cholesterol levels, Current Therap. Res.. 10 (4) (1968) 177. Strlsower. E.H. and Strisower. B., The separate hyperlipoproteinemic effects of dextrothyroxine and ethyl chlorophenoxisobutyrate, J. Clin. Endocrin. Metab.. 24 (2) (1964) 139. Thomas, C.B., HoIIges, H.W. and Eisenberg, F.F., Observations on seasonal variations in total serum cholesterol level among healthy young prisoners, Ann. Intern. Med., 54 (1961) 413.
Atherosclerosis, 24 (1976) 369-380 @ Elsevier Scientific Publishing Company,
Amsterdam
- Printed
in The Netherlands
TREATMENT OF TYPE II HYPERLIPOPROTEINEMIA d-THYROXINE
A.D. RAKOW,
H.U. KLGR,
E. KgTER,
H.H. DITSCHUNEIT
WITH
and H. DITSCHUNEIT
Department of Medicine, Division of Metabolism and Nutrition, University of Urn, Ulm (West-Germany) (Received (Revised, (Accepted
8th October, 1975) received 4th May, 1976) 13th May, 1976)
Summary The effectiveness of a new, almost Z-thyroxine free preparation of d-thyroxine (Dynothel@) was tested in 15 patients with Type IIa and 4 patients with Type IIb hyperlipoproteinemia. Eleven patients with Type IIa and 3 with Type IIb were responsive to treatment and showed an average 26% decrease in plasma TC. This decrement in plasma TC was mirrored in a significant reduction of LDL cholesterol in Type IIa and IIb. While VLDL cholesterol slightly decreased in Type IIb, it remained the same in Type IIa and so did the HDL cholesterol in both types. As neither VLDL nor LDL or HDL triglyceride levels changed very much in either type, the total plasma triglycerides remained the same. The plasma phospholipids were higher in Type IIa and lower in Type IIb on therapy. Thus, Dynothel@ seems to be a potent d-thyroxine preparation for lowering plasma cholesterol, this decrease being brought about by reduction of LDL cholesterol levels. The effect of the drug on plasma TG and PL is less certain . Key words:
Hyperlipoproteinemia
Type II - Lipids - Lipoproteins
- d-Thyroxine
Gesellschaft fiir Innere * Part of this work has been presented at the 80th Meeting of the “Deutsche Medizin”, Wiesbaden. 1974. List of abbreviations: TC = total cholesterol, TG = triglycerides, PL = phospholipids, VLDL = very low density lipoproteins (d 1.006). LDL = low density lipoproteins (d 1.006-1.063). HDL = high density lipoproteins (d 1.063-1.21).
370
Introduction Recently, recognition and treatment of risk factors have become more and more inportant for the primary and secondary prevention of atherosclerotic vascular disease. Among these risk factors hyperlipoproteinemias do play an important, if not the most inportant role, as could be demonstrated in various prospective and retrospective studies [1,5,13,16,18,20]. Thus, it seems to be self-evident that the development and therapeutical use of lipid-lowering drugs has been largely promoted in the last decade. One of the most potent drugs for lowering elevated cholesterol levels is d-thyroxine [ 2,4,32]. However, serious cardiovascular side effects most likely stemming from a relatively high contamination with I-thyroxine (OS-1.2%) did not permit a widespread clinical application of the early d-thyroxine preparations [6,9]. One of the most thorough and promising clinical trials with this drug, the Coronary Drug Project, even’ had to be modified because myocardial infarction and death were more frequent in the treated than in the control group [6]. In the meantime, preparations of d-thyroxine are available with a very low ‘and almost negligible l-thyroxine content one of which is d-3,5,3’,5’-tetraiodothyroxine (Dynothel @, Henning, Berlin). Its Z-thyroxine content has been determined to be less than 0.2% [7]. The present study was devised to evaluate the effect of this new d-thyroxine preparation on the lipids in plasma and in the lipoprotein fractions VLDL, LDL, and HDL in patients with hyperlipoproteinemia Type IIa and IIb according to the Fredrickson and Lees typing system [ll]. The focus on the lipid changes in the lipoprotein fractions seemed to be justified because of the eminent importance of LDL cholesterol for at least the early phase of human atherogenesis and the well documented lowering effect of older, more l-thyroxine containing preparations on this lipoprotein fraction [ 30,311. Patients
and Methods
Patients Fifteen patients with hyperlipoproteinemia Type IIa and 4 with Type IIb were treated for 6 months with Dynothel@. Table 1 shows age, sex, body weight and other clinical as well as some laboratory data of these patients which helped to establish the diagnosis of primary hyperlipoproteinemia and to rule out secondary forms. Familial occurence could be proven in 6 patients with Type IIa, but in none with Type IIb. Experimental design Before entering the study the patients had to pass a diet period of at least 6 months. The diet which was maintained throughout the drug and placebo period was composed of 40% carbohydrate, E-20% protein, and 40-45% fat consisting largely of polyunsaturated fatty acids (P/S ratio more than 1.5). After the diet period d-thyroxine administration was started in a dosage of 2 mg daily for the first week and continued with one additional mg for each week to follow ‘up to a final dose of 6 mg daily. This schedule was chosen to prevent potential cardiogenic side effects in the patients with angina. After 6
371 TABLE 1 CLINICAL
AND LABORATORY
DATA
OF PATIENTS
WITH TYPE Ha (NOS. l-15) AND
IIb (NOS.
16-19)
Patient
Sex
Age
Weight
Height
number
Normal values
-
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
F F M F F
55 46 58 43 62 47 48 47 59 52 36 53 18 65 48 47 57 44 55
M
M F F F M F M F F M F M M
Patient
ESR
Uric acid
SGOT
SGPT
-
-
50-100 (mg/lOO ml)
-422 WMoW
Z-19 W/l)
5-24 (U/v
90 88 60 60 44 96 70 80 54 56 65 73 57 64 66 72 60 75 68
165 162 163 164 153 172 173 154 158 160 170 164 170 172 164 179 154 158 170
60 88 94 80 66 88 83 87 92 76 81 81 95 92 88 89 88 137 66
229 257 327 291 266 453 306 339 422 160 137 196 366 327 280 228 344 393 289
7 10 5 10 10 18 16 13 12 11 4 15 10 9 10 9 14 13 8
9 8 4 7 5 24 13 8 5 8 4 12 10 14 11 14 4 21 10
Coro-
number
Blood sugar
I=rY angio-
ECG alterations
Serum creatinine
Serum urea
Proteinuria
Glucosuria
-
-142
-10.8
4J
9
(1rMoI/0
(mMoI/I)
100 96 106 08 88 80 95 110 71 79 88 97 90 97 100 100 71 125 100
5.8 6.8 8.1 5.9 5.3 6.2 6.6 4.8 8.6 9.8 3.9 4.5 3.1 7.4 6.4 7.5 9.2 8.2 5.6
Plasma albumin
Braphy
Normal values
(n.W.)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
517 9120 15/25 20132 20130 9118 8123 20146 16/26 20136 13120 S/18 55117 10125 88112 12127 13132 315 25138
+
=
Positive,
5120
++
=
-
&J 0 @ Q, 4) @
++ + -
;
-’ + ++ ++ ++ + ++ ++ + ”
0
-
; @ 0 ; ;
+ +
strongly positive, 0 = negative. not done, -
35165
cm z
:
@ @ @ @ @ @ @ 0 :
d @ @ 0 cb @ 0 @ @ 0 0 cb z
0 @ @ @ 0
@ @ @
46.9 46.6 45.1 43.0 44.9 50.0 51.2 51.8 51.3 39.4 53.2 67.0 38.6 44.2 45.0 48.9 42.1 40.5 42.7
= no alteration. F = female, M = male.
312
months the drug was replaced by placebo for another 6 weeks, after which the final blood specimen was drawn. Body weight remained throughout the whole investigation.
stable within
f 2 kg
Methods Plasma TG and TC were determined after a 12 h fast several times during the initial diet period and the treatment period and once at the end of the placebo phase. Analysis of plasma phospholipids and measurements of the lipoprotein TC and TG in VLDL, LDL, and HDL was performed at the beginning and at the end of the drug period in 13 patients with Type IIa and in all with Type IIb. TG and TC were measured simultaneously in a Technicon-Analyzer according to Kessler and Lederer [17] and Levine and Zak [22], respectively. Lipoprotein electrophoresis was carried out essentially as described by Rapp and Kahlke [28]. Phospholipids were determined with a Boehringer test kit (No. ‘15920 TPAC, Boehringer, Mannheim). VLDL and LDL were isolated simultaneously from the HDL and plasma proteins by zonal ultracentrifugation as described earlier [7], and the TG, TC and PL content determined in the VLDL, LDL, and HDL plus plasma protein fraction, respectively. As the recovery of lipids in the isolated lipoprotein fractions never reached 100% (between 70 and 85%), the final figures for lipoprotein TG, TC, and PL were corrected for recovery. Results Figure 1 shows the course of plasma TG and TC levels in Type IIa and IIb during the drug and placebo period. The TG and TC figures at “0 months”, i.e. for the diet period, represent the mean of all samples withdrawn in that period. Although it started out from different levels of elevation (366 f 20 mg/ 100 ml in Type IIa and 311 + 14 mg/lOO ml in Type IIb), the cholesterol of both groups gradually decreased to a range of 280-290 mg/lOO ml. While Type IIa TG did not show any significant change in either drug or placebo period, distinct differences seemed to appear in Type IIb plasma TG under therapy. After having increased after the first month of treatment the TG in Type IIb were falling back to the original level on continuation of therapy. However, analysis of the TG values recorded just before the start of d-thyroxine medication reveals that all 4 patients had much higher values (320 f 80 mg/lOO ml) than was their average during the whole diet period (257 + 52 mg/lOO ml). Thus, the elevation of the mean TG after the first month of treatment may be either due to an effect of therapy or represent a spontaneous variation in TG level in Type IIb patients. Reports on seasonal variations in plasma TC [32], even under continuous therapy with d-thyroxine [14] prompted us to try to establish a firm therapeutic success in each individual case by computing several values in a given period rather than by choosing the last value in diet and drug period for comparison (Table 2). The figures in the “diet” column for TG and TC represent mean values for that period. The TC values listed under “drug” are the mean of all samples taken from the third to the sixth month of treatment. As can be seen from Table 2,9 out of 15 patients with Type IIa and 2 out of 4 with Type
373
T
@-@
TG
.-+
TC
In type
Ila
@-@TG in tvrx
lib
T
d-THYROXINE I 0
I 1
I 2
I 3
I I 4
I 5
I 6
I 7
1 8
months Fig. 1. Course of TG and TC in 15 patients with Type IIa and 4 patients with Type IIb under treatment with Dynothel@ (6 mg dally). Half filled circle in brackets at “0 months” represents the last TG value in Type IIb patients just prior to d-thyroxine treatment.
IIb were fully responsive to d-thyroxine showing a highly significant reduction of plasma TC of 20 to 35% of the mean pretreatment levels. A tendency towards a more pronounced decrement was observed in patients with higher initial values (more than 400 mg/lOO ml). In 1 patient with Type IIa (No. 11) and in 1 with Type IIb (No. 17) a successful1 treatment could not be definitely proven because the TC levels in the placebo phase did not return to the original range. Altogether 6 patients from both groups reached the normal TC range (less than 250 mg/lOO ml) on d-thyroxine. The mean plasma phospholipid value showed an increment from 271 + 21 to 318 + 18 mg/lOO ml in Type IIa and a decrement from 334 + 63 to 272 + 26 mg/lOO ml in Type IIb. Table 3 presents a comparison of the lipid concentrations in VLDL, LDL, and HDL before and after d-thyroxine treatment. In Type IIa and TC concen-
374
TABLE 2 TG,
TC AND
PL VALUES
BEFORE,
ON,
AND
OFF
TREATMENT
WITH d-THYROXINE
(DYN-
OTHEL~)INPATIENTSWITHTYPEIIa(NOS.1-l5)ANDTYPEITt,(NOS.16-l9) Data givenrepresentaveragef SEM. Patient Triglycerides (mg/lOOml) number Diet Drug Placebo
1 2 3
105k 10 137+ 4 98+ 24
4 5
109 89k
Totalcholesterol(mg/lOOml) Diet
Drug
PhosphoIipids(mg/ 100ml)
Placebo Diet
Drug
112+ 11 143 146k17
143 183
333+ 61 277 + 20 468r 2
267+ 41 290 303? 7
390 510
284 215 -
371 311 -
5
88? 2 92+12
123 83
454 311i18
328214 246+19
498 276
220 -
349 -
6 7 8 9 10
115+12 107+ 25 112+ 10 92+ 10 86k 4
135* 1 157+18 118+ 23 93? 6 162? 20
155 109 100 97 100
258+ 6 287? 22 328+15 334*13 518+ 17
265+10 209 *12 237+ 8 363* 6 482? 5
310 270 336 391 445
218 378 246 210 -
268 261 267 313 -
11 12 14 15
134 92 82 56? 84+
128+ 80+ lOO*ll 59? 82k
90 83 60 83
359* 39 537 409 332k 23 286 i16
311*19 367* 20 274+19 259k 8 281+13
298 522 498 314 -
275 341 398 197 -
299 415 411 242 -
ti
100 + 11
113 k10
108+
366? 20
298t14
389 f 26
271 + 21
318+18
16 17 18 19
203+ 22 232+ 60 378i- 42 218+ 9
191? 42 252+ 34 255 367+ 31
198 444 263 390
272+ 36 274+ 31 309+ 2 337+17
205+ 1 221+19 305 244t12
360 184 294 402
157 338 389 451
225 132 294 338
i
257 + 52
266 + 36
323 -t 56
311+14
243 + 22
310 * 47
334 + 63
272 k 26
i3
5 8
5 4 3 9
9
change, being higher in 6, lower in 4 tration in the VLDL did not consistently and unchanged in 3 cases after therapy. The LDL cholesterol markedly decreased in 10 patients with Type IIa. The HDL cholesterol did not change in average. However, there were more increments (7 cases) than decrement8 (5 cases) after treatment. In 3 of 4 patients with Type IIb the VLDL TC decreased. The LDL TC decreased in 3 and remained unchanged in 1 patient. There was no change in HDL TC upon therapy. Regarding the mean VLDL TG in Type IIa a slight tendency towards a decrease was encountered. The mean LDL TG value was also slightly though not significantly lower at the end of the drug period. In the HDL the TG level did not change in average. In Type IIb a decrease in VLDL TG was observed in 3 patients. The LDL- and HDL TG levels were not consistently influenced by d-thyroxine administration and remained the same in average. Due to loss of samples the PL content of the lipoprotein fractions could only be determined in 5 patients with Type IIa and in 2 patients with Type IIb hyperlipoproteinemia. In Type IIa there seemed to be a trend for an elevation of the PL in HDL and LDL, while in Type IIb the LDLand HDL PL were higher in 1 and lower in a second case. Symptoms that might have been expected as a side effect of the l-thyroxine contaminant like tachycardia, nervousness, feeling of unrest, diarrhea, etc. did
TABLE 3 TG, TC AND PL CONCENTRATION l-14) AND TYPE IIb (NOS. 16-19) Patient number
IN VLDL, LDL, AND HDL OF PATIENTS WITH TYPE IIa (NOS. IN DIET AND DRUG PERIOD, RESPECTIVELY
Triglycerides (mg/lOO ml) VLDL
LDL
HDL
Diet
Drug
Diet
Drug
Diet
Drug
1 2 3 4 5 6 I 8 9 11 12 13 14
40 83 82 20 15 29 55 21 30 52 29 41 14
12 57 58 31 21 12 1100 26 12 28 24 24 10
52 27 74 53 59 36 35 30 52 114 47 48 27
60 47 44 49 23 79 36 32 42 24 41 43 22
45 9 17 14 21 9 18 28 18 44 37 34 9
23 15 13 61 22 2’1 54 20 19 38 23 26 31
2
39 f 6
42 r 4
23.k 3
29 -t 4
49 75 63 57
47 22 32 57
33 23 65 62
61 k 5
40 + 8
46 k 10
32?
7
16 17 18 19
88 186 196 268
68 150 169 310
F
186k40
174 + 50
Patient number
Total cholesterol (mg/lOO ml) VLDL
50 + 6 40 82 112 52
72 f 16
LDL
HDL
Diet
Drw
Diet
Drw
Diet
1 2 3 4 5 6 7 8 9 11 12 13 14
18 30 42 12 3 18 33 30 32 77 13 18 16
11 34 51 11 15 3 51 12 30 41 22 11 5
200 187 295 291 192 271 191 184 271 201 232 265 298
208 215 229 235 107 210 111 156 214 192 217 205 146
58 53 27 81 53 19 67 35 82 70 95 29 27
x
26 C 5
23 + 5
237 f 12
188 k 12
53 f 7
60 + 7
16 17 18 19
49 48 64 74
29 26 43 90
186 197 167 175
132 165 172 100
62 25 26 56
43 19 79 65
32
59 -I 6
47 t 15
181 f 7
142 + 17
42 ?r 10
52 + 13
Drug 63 22 40 73 95 30 46 64 68 64 105 30 78
376
TABLE
3 (continued) Phospholipids (mg/lOO ml)
Patient number
VLDL
LDL
HDL
Diet
Drug
Diet
Drug
Diet
Dwx
1 2 3
-
-
-
-
-
-
4 5 6
-
3
12 -
117 -
221 -
101 -
116 -
7 8
26 -
28 -
197 -
-
66
154 -
-
67
9 11
-
8
10 -
128 -
180 -
-
74
123 -
12 13 14
44 8 -
11 27 -
227 271 -
208 332 -
70 119 -
197 51 -
x
18k 8
18+ 4
188 * 29
201 + 43
104 Yk15
111 + 26
16 17 18 19
37 51 -
32 32 -
49 196 -
105 46 -
x
25+ 7
22+ 4
169 + 28
165 k 38
-
72 91
97 + 12
-
88 54
99 f 19
not appear during the drug period. Moreover, neither vyas a change in frequency and intensity of attacks of angina - if already preexisting - reported nor could the onset of angina on treatment be observed. 3 patients complained about insomnia which had been present before the onset of therapy, too. Discussion The effectiveness of d-thyroxine almost free of l-thyroxine contamination is a definite proof that the successful therapy of hypercholesterolemias using older preparations [2,9,30] with a tenfold higher Z-thyroxine content was not due to this contaminant, although the high incidence of Z-thyroxine-caused side effects reported in those studies could have supported this concept. Concerning the degree of reduction of elevated cholesterol levels, previous investigators found decrements ranging from 11 to 48% of the pre-treatment levels on 5 to maximally 16 mg daily of the impure d-thyroxine preparations [2,4,9,14,30,31]. Recently, 3 different groups [3,19,21] reported an average decrease of plasma cholesterol in Type IIa and IIb of between 12 and 25% when the new, highly purified d-thyroxine (Dynothel@) was administered, In patients of our own group who responded to Dynothel @ therapy we found an average 26% decrease (range 20-35%) which is somewhat higher than the figures reported by the afore mentioned authors [3,19,21]. However, it has to be emphasized that 4 out of our 15 patients with Type IIa and 2 out of 4 patients with Type
377 IIb did not sufficiently respond to d-thyroxine treatment. Koschinsky et al. [21] and Klemens et al. [ 191 found about the same percentage of therapy failures as we, while Bommer et al. [3] observed no cases truly unresponsive patients. There is no apparent to Dynothel@ among 18 hypercholesterolemic reason why most of the patients are sensitive to d-thyroxine while a few are not. The non-responders do not represent a selection of excessive hypercholesterolemias; to the contrary, a great many of those having only slightly elevated plasma cholesterol values belong to this group. Adherence to a lipidlowering diet has been claimed to be of decisive importance for the effectiveness of d-thyroxine treatment [ 261. At least in our own unresponsive patients, diet was as well maintained as in the responsive ones. There are only a few reports on the effect of d-thyroxine on plasma TG. While Feldman and Carter [lo] saw in 10 patients a more or less constant reduction of sometimes even normal values in a range of 18-64%, the most recent studies [3,19,21] and our own investigation revealed no effect on TG levels in Type IIa and an uncertain decrement in Type IIb. A possible explanation for the difference between older and recent studies including our own may be that Feldman and Carter [lo] tested the TG response to an older preparation the high I-thyroxine content of which might have contributed to a higher potency for lowering TG as well. However, a different effect of d- and E-thyroxine on plasma TG has not been reported on in the literature. To our knowledge the effect of d-thyroxine on plasma PL in Type II has only been looked after by Jones and Cohen [ 151 who found lowered levels in 9 and unchanged levels in 6 patients. Unfortunately, the authors did not determine plasma TG in their patients so that no estimate is possible as to how many cases belonged to Types IIa and IIb, respectively. The decrease in PL in our Type IIb cases is in agreement with the results of that early investigation. Opposition results, however, were observed in Type IIa where plasma PL almost uniformly increased under d-thyroxine. No convincing explanation seems to be at hand for this discrepancy. Only a marked increase in the PL-rich HDL in compensation for a reduction of the TC-rich LDL could furnish a reasonable interpretation, but this was not the case, at least not to the necessary extent. The mechanism by which the reduction of plasma TC is attained in hypercholesterolemia becomes obvious when the changes occurring in the lipoprotein fractions are analyzed. Thus far, all investigators agree on the fact that both d- and l-thyroxine reduce the plasma TC in hypercholesterolemia by lowering the LDL cholesterol [ 10,15,19,30,31]. At least in Type IIa, our results do support this concept, too. Theoretically, the decrease of LDL cholesterol can be the consequence of 2 different processes, one being a change in composition of numerically identical particles and the other being a decrease of LDL unchanged in average molecular composition, The only way of distinguishing clmong these possibilities is to quantify the lipoprotein fractions with a technique other than measuring only one of its constituents. Strisower and Strisower [30] were able to demonstrate by analytic ultracentrifugation that the LDL (S, O-20) in Type IIa and Type IIb decreased on d-thyroxine administration. However, the analysis of S, classes in the analytic ultracentrifuge does not automatically rule out that changes in lipid composition of the LDL particle might have occurred on therapy as well. As an exchange of some TG for cho-
378
lesterol esters in the core of the LDL particle would not greatly change its flotation characteristics, such an alteration would not be discernable by means of the analytic ultracentrifugation. Without disposing of analytic centrifugation data we tried to draw tentative conclusions as to whether a decrease of unchanged lipoprotein particles or a change in composition has occurred by measuring 2 (TC and TG) of the 4 main constituents of the lipoprotein molecule (TC, TG, PL, and protein). If the ratio of TC and TG in the lipoprotein fraction remains roughly the same before and after therapy it appears likely to assume a decrease while a change in this ratio would indicate an alteration in composition rather than in concentration of the respective lipoprotein fraction. Concerning the LDL in Type IIa we found about the same TG/TC ratio in 7 patients and an increase in 4 cases. Thus, in the majority of cases with Type IIa hyperlipoproteinemia there seemed to be a decrease of normally composed LDL, but in a few patients the LDL became relatively “TC-depleted” after therapy. In the VLDL and HDL of Type IIa a concomitant decrease or increase of both TG and TC was seldom observed. Thus, a consistent lowering or elevating effect on these lipoprotein fractions is not likely. In all cases of Type IIb, however, we found a parallel decrease in VLDL TG and TC, making a de-
550.
mg/lOOml TC (mean of pretreatment
period ) A
500
/ ?? A
0
A 0
/:
450
r = 0.705 PC o.ool
f
400
0 0 - Bommer et al, 1975 A = Jepson 1963 X-Jones + Cohen 1961 ? -?own responsive patients
350
300
250
I”“I~“‘I’i”l’ 50 0
100
150
T&
mg/lOOml TC decrease (mean of drug period ) -
Fig. 2. Relationship of pretreatment TC to decrease IIb responsive to d-thyroxine therapy.
in TC upon
treatment
in patients
with Type IIa and
379
crement in number of a similarly composed VLDL population more probable than a mere shift of particle distributions within the VLDL range. This concept is corroborated by the finding of Strisower and Strisower [30] that the VLDL (Sf 20-105) in Type IIb are as much reduced under d-thyroxine therapy as the LDL (S, O-20). Finally, an interesting phenomenon should be mentioned in connection with the problem of how d-thyroxine operates in lowering TC values. On a mg/lOO ml basis TC values were observed to decrease much more in our grossly hypercholesterolemic patients responsive to therapy than in the ones with moderative elevations. When the decrement in TC was plotted against the pre-treatment values of responsive Type IIa and IIb cases of our own and of previous investigators [3,14,15] a highly significant positive correlation was found (Fig. 2). The meaning of this correlation remains obscure. One of several possible explanations is that d-thyroxine operates in a way that processes responsible for the removal from plasma and/or degradation of lipoprotein cholesterol may be maximally stimulated by the drug so that “substrate availability”, i.e., the LDL and, in IIb patients, the VLDL concentration determines the efficiency of the removal system. In other words, the higher the starting levels are the better can the removal system work. Supposing that the interdependence shown in Fig. 2 is valid in all ranges the cholesterol-lowering potency of d-thyroxine should be very low at approximately 150 mg/lOO ml plasma TC concentration, where the intercept lies between the regression line and the y-axis. It is at least of theoretical interest that this is a truly “physiological” range as judged by the results of prospective studies on risk factors for atherosclerosis [ 161 and of epidemiologic surveys of populations not prone to premature vascular disease [ 12,23,27]. Thus, the significant role of Z-thyroxine in the maintenance of a physiologically low plasma cholesterol level may explain the high hypocholesterolemic potency of the d-isomer, too. References 1 Albrink, M.J., Triglycerides, lipoproteins and coronary artery disease, Arch. Intern. Med.. 109 (1962) 145. 2 Bechtol, M.D. and Warner, W.L., Dextrothyroxine for lowering serum cholesterol, Angiology, 20 (1969) 565. 3 Bommer, J., Speders, H. and Ehrke, V.. Behandlung van Hypercholesteriniimie nach Herzinfarkt mit d-Thyroxin, Miinch. Med. Wschr., 117 (1975) 139. 4 Boyd. G.S. and Oliver, M.F.. The effect of certain thyroxine analogues on the serum lipids in human subjects, J. Endocrinol., 21 (1960) 33. 5 Carlson, L.A. and BGttiger, L.E., Isachaemic heart disease in relation to fasting values of plasma triglycerides and cholesterol, Lancet, 1 (1972) 865. 6 The Coronary Drug Project Research Group. The coronary drug project -~ Findings leading to further modifications of its protocol with respect to dextrothyroxine, J. Amer. Med. Ass.. 220 (1972) 996. 7 Ditschuneit, H.H. and K16r. H.U., Die Lipoproteinmunster van prim&en and sekundiiren Hyperlipoproteinimicn bei Ultrazanalzentrifugation. In: H. Ditschuneit (Ed.), Die Lipoproteine des Blutes Steinkopff Verlag, Darmstadt, 1973. 8 Dole, V.P. and Meinertz. Microdetermination of long chain fatty acids in plasma and tissues, J. Biol. Chem., 235 (1960) 2595. 9 Engelberg, H., Effect of sodium d-thyroxine on serum cholesterol and low density lipoproteins in man, Geriatrics, 17 (1962) 711. 10 Feldman, E.B. and Carter, A., Reduction of serum triglycerides in patients treated with sodium dthyroxine. Metabolism, 12 (1963) 1132. 11 Fredrickson, D.S., Levy, R.J. and Lees, R.S., Fat transport in lipoproteins -An integrated approach to mechanisms and disorders. New Engl. J. Med.. 276 (1967) 32,94,148, 215. 273.
380
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