9 1986 by The Humana Press Inc. All rights of any nature whatsoever reserved. 0163-4984/86/1001-0011$02.00
Dietary Selenium Status and Plasma Thyroid Hormones in Chicks L. S. JENSEN,* G. L. COLNAGO, K. TAKAHASHI, AND Y. AKIBA
Department of Poultry Science, University of Georgia, Athens, Georgia 30602 Received S e p t e m b e r 13, 1985; Accepted N o v e m b e r 25, 1985
ABSTRACT Experiments were conducted to study the effect of marginal levels of selenium and vitamin E on plasma thyroid hormones of meattype chicks. Plasma thyroxine (T4) w a s significantly increased when a semipurified diet was supplemented with either selenium or vitamin E. Triiodothyronine (T3) was also significantly increased by vitamin E and in one experiment with selenium supplementation. No significant increase in these hormones was observed in birds fed a corn-soybean-meal diet supplemented with these nutrients. Plasma corticosterone level was reduced and weight of the bursa of Fabricius increased by selenium or vitamin E supplementation. These nutrients may be necessary for providing the optimum thyroid conditions for activity of thyroid peroxidase. Index Entries: Selenium; vitamin E; plasma thyroid hormones; thyroxine; triiodothyronine; plasma corticosterone, and selenium-vitamin E deficiency; selenium-vitamin E deficiency, and bursa of Fabricius weight.
INTRODUCTION Thyroid function of domestic animals is known to be altered by many environmental factors. Total caloric deprivation is associated with *Author to whom all correspondence and reprint requests should be addressed. Biological Trace Element Research
]]
Vol. 1O, 1986
12
Jensen et aL
a decrease in triiodothyronine (T3) production and s e r u m T3 concentration in man and rats (1-3). The mechanism of this fall in serum T3 seems to be impaired peripheral 5'-deiodination of thyroxine (T4), since liver homogenates from rats fasted for 2-3 d have shown impaired T 4 t o T 3 conversion in vitro (4-5). In chickens, short periods of fasting reduced serum T3 concentration and increased s e r u m T 4 (6). Thyroidal activity in rats (3) and laying hens (7) is influenced by dietary composition. Specific nutrient effects on thyroidal activity have also been studied. Vitamin-A-deficient rats had increased plasma T3, T4, and free thyroxine index (8). Plasma T 4 concentration and free T 4 increased in goats fed diets deficient in cobalt and vitamin B12 for 23 wk (9). Chicks fed diets deficient in aromatic amino acids, lysine, or valine had reduced thyroidal activity, but the deficiency had to be very severe (10,11). In rats, magnesium or potassium deficiency reduced thyroidal activity (12). Copper, iron, or zinc deficiency also resulted in decreased blood T 3 and/or T 4 in rats (13-16). Calves given selenium (Se) subcutaneously or vitamin E intramuscularly had increased T4 levels in the peripheral blood 48 h after dosage (17). In view of these results, the present studies were undertaken to determine if marginal dietary levels of Se and/or vitamin E would affect plasma thyroid hormones in the chick. METHODS Day-old male broiler chicks of the Hubbard or Arbor Acre strains, obtained from a commercial hatchery, were housed in electrically heated battery brooders under constant illumination, with feed and water supplied ad libitum. The composition of the basal diets, which contained no supplementary Se, vitamin E, or antioxidants, is shown in Table 1. Calculated vitamin E levels for the corn-soybean and semipurified diets were 14.5 and 2.5 IU/kg, respectively. Actual Se levels for the two diets were 0.07-0.08 and 0.04-0.06 mg/kg, respectively. Sodium selenite served as the source of supplemental Se and all-rac-ec-tocopheryl acetate as the source of vitamin E. Diets were analyzed for their Se content by the method of Wetter and Ullrey (18). Four groups of 10 chicks/group were used for each treatment in Expts. 1, 3, and 4 and eight groups of 10 chicks in Expt. 5. Twelve birds/ treatment were used in Expt. 2. Body weight and feed intake data were based on pen averages in all experiments, except Expt. 2, in which body weight was a mean of individual chicks, and feed intake was not measured. At 21 d of age, blood samples were taken by heart puncture, using a heparinized syringe from 10 chicks/treatment in Expts. 1 and 2 and eight chicks/treatment in Expts. 3, 4, and 5. Plasma samples were stored at -40~ until assayed for hormones. In Expts. 2, 3, and 4, chickens were killed by cervical dislocation after blood collection and the bursa of Fabricius was removed and weighed. Biological Trace Element Research
Vol. 1O, 1986
13
Selenium and Thyroid Hormones TABLE 1 Composition of Basal Diets (%) Diet Ingredients Glucose (cerelose) Isolated soy protein Torula yeast Yellow corn Soybean meal (49% protein) Poultry fat Dicalcium phosphate Limestone Cellulose Potassium carbonate Salt Magnesium sulfate 9 0.7 H 2 0 D,L-Methionine Choline chloride (50%) Vitamin mixture" Trace-mineral mixture h Calculated analysis ~ Crude protein (%) ME (kcal/kg) Calcium (%) Phosphorus, available (%) Vitamin E (IU/kg) Selenium (actual analysis) (mg/kg)
Corn-Soybean (CS) SemiPurified (SP) ---53.50 37.50 5.00 1.63 1.37 --0.50 --
0.20 -0.25 0.05 23.0 3200 0.95 0.45 14.5 0.07-0.08
54.10 20.12 10.00 5.00 -4.00 2.27 0.84 1.43 0.69 0.43 0.39 0.32 0.11 0.25 0.05 23.0 3200 0.95 0.52 2.3 0.04-0.06
~Supplying per kg of feed: vitamin A, 11,000 IU; vitamin D3, 1100 ICU.; menadione sodium bisulfite, 1.1 ing; riboflavin, 4.4 mg; Ca pantothenate, 12.0 mg; nicotinic acid, 44.0 mg; choline chloride, 220 mg; pyridoxine HCI, 2.2 rag; folic acid, 0.55 rag; D-biotin, 0.11 mg; thiamine mononitrate, 2.2 mg; vitamin Bl2, 6.6 ~g.
~Supplying mg/kg of feed: manganese, 60; zinc, 50; iron, 30; copper, 5; iodine, 1.05. ~Scott, M. L., Nesheim, M. C., and Young, R. J. Nutrition of The Chicken. Ithaca, NY (1982).
Plasma T 3 a n d T4 w e r e d e t e r m i n e d by r a d i o i m m u n o a s s a y , using commercial r a d i o i m m u n o a s s a y kits (Gammacoat [125I]thyroxine a n d [125I]triiodothyronine r a d i o i m m u n o a s s a y kits, Clinical Assays, Cambridge, MA). The use of these kits for chicken T 3 a n d T4 has b e e n valid a t e d (7). Plasma corticosterone was d e t e r m i n e d by r a d i o i m m u n o a s s a y
(19). The data g e n e r a t e d by these studies w e r e analyzed u s i n g the General Linear Models p r o c e d u r e of the Statistical Analysis System (20) in conjunction with the D u n c a n separation of m e a n options to locate significant (P < 0.05) differences a m o n g m e a n s . Biological Trace Element Research
VoL 10, 1986
14
J e n s e n et al.
RESULTS The results of t h e s e e x p e r i m e n t s (Tables 2-5) s h o w that f e e d i n g diets marginal in Se a n d vitamin E to chicks r e d u c e d p l a s m a T4 c o n c e n t r a t i o n . S u p p l e m e n t a t i o n of t h e s e m i p u r i f i e d diet w i t h 0.1 m g or m o r e Se/kg in all five e x p e r i m e n t s a n d with vitamin E in Expt. 4 significantly i n c r e a s e d p l a s m a T4 level. A significant increase in p l a s m a T3 w a s also o b s e r v e d w h e n v i t a m i n E in Expt. 4 a n d Se in Expt. 5 w e r e a d d e d to the s e m i p u r i f i e d diet (Tables 4,5). S e l e n i u m s u p p l e m e n t a t i o n of a c o r n s o y b e a n diet did not significantly affect p l a s m a T4 levels (Tables 3,4) a n d significantly r e d u c e d T3 level in o n e e x p e r i m e n t (Table 4). In Expt. 2, Se s u p p l e m e n t a t i o n of the s e m i p u r i f i e d diet significantly r e d u c e d p l a s m a corticosterone (Table 2). S e l e n i u m or vitamin E supplem e n t a t i o n of the s e m i p u r i f i e d diet also a p p e a r e d to r e d u c e p l a s m a corticosterone level in Expt. 4 (Table 4), b u t the differences w e r e n o t statistically significant (P > 0.05). A significant interaction b e t w e e n supplem e n t s a n d t y p e of diet on p l a s m a corticosterone level was o b s e r v e d , however. S u p p l e m e n t a t i o n of the semipurified diet w i t h 0.1 p p m of Se significantly i n c r e a s e d w e i g h t of the bursa of Fabricius in t w o experim e n t s (Tables 2,3). In Exp. 4 (Table 4), Se or vitamin E s u p p l e m e n t a t i o n TABLE 2 Effect of Selenium Supplementation of a Semipurified Diet on Plasma Thyroid Hormones and Other Parameters in Chicks ~ Experiment No. 2 Added Se (mg/kg) Parameter Analyzed dietary Se, mg/kg 2 Body wt gain, g + SEM Feed intake, g + SEM Bursal wt, rag/100 g
0
0.25
0
0.1
0.04 507 _+20 a 749 + 28 a
0.22 513 _+_11a 781 +_ 18a --
0.06 308 -----14a
0.16 445 _+ 20 b
131 + 15'~
252 _+ 11b
--
1.89 + .2 a
2.03 + 0.25 a
17.1 ___1.4 ~
31.9 --+ 2.7 b
21.5 + 1.4 ~
35.6 --+ 1.8 b
--
--
6.59-+ 1.5 a
2.64 + 0.43 b
BW ~
Plasma T3 n g / m L + SEM ~ Plasma T4 ng/mL + SEM 3 Plasma corticosterone, ng/mL _+ SEM ~
--
~Values w i t h i n a r o w a n d e x p e r i m e n t w i t h o u t a c o m m o n letter are significantly differe n t (P < 0.05). 2The basal diet c o n t a i n e d a calculated level of 2.5 IU v i t a m i n E/kg. 3Mean of 10 birds/treatment. Biological Trace Element Research
VoL 10, 1986
Selenium and Thyroid Hormones
15
TABLE 3 Effect of Se Supplementation of Semipurified and Corn-Soy Diets on Plasma Thyroid Hormones and Other Parameters in Chicks (Expt. 3) 1
Se added to diets, ppm Parameter
0
0.10
0.25
0.06 422 + 102 586 + 15a 176 _ 20 ~ 1.56_+0.22 22.3___ 2.0 a
0.17 476 _+ 15 b 644 _+ 14b 254 ---+2 9 b 1.45+0.11 ~ 29.8 + 0.9 b
0.33 460 _+ 7b 641 _+ 8b 221 • 2 0 a'b 2.00+0.35 "~ 27.1 .+ 2.0 b
0.08 495 ___14a 672 _+ 21 ~ 309 + 30~' 24.5___ 1.8 a
0.18 525 _+ 5a 731 + 7b 269 + 21 a 22.7+ 0.8 ~
0.29 516 + 10a 711 _+ 19 a'b 329 _ 31 a 22.4_+0.9 ~
Semipurified diet Analyzed dietary Se, mg/kg-' Body wt gain, g .+ SEM Feed intake, g _+ SEM Bursal wt, rag/100 g BW .+ SEM ~ Plasma T3, ng/mL _+ SEM3 Plasma T4, ng/mL _+ SEM 3 Corn-Soybean diet Analyzed dietary Se, mg/kg z Body wt gain, g + SEM Feed intake, g _+ SEM Bursal wt, rag/100 g BW + SEM ~ Plasma T4, ng/mL .+ SEM 3
~Values within a row without a common letter are significantly different (P < 0.05). ~The semipurified diet contained a calculated level of 2.5 and the c o r n - s o y b e a n diet 14.5 Iu vitamin E/kg. ~Mean of eight birds/treatment.
i n c r e a s e d m e a n b u r s a w e i g h t b y 27 a n d 24%, respectively, b u t the differe n c e s failed to be significant (P < 0.05). N o effect of either Se or v i t a m i n E s u p p l e m e n t a t i o n of the c o r n - s o y b e a n diet o n b u r s a w e i g h t w a s observed.
DISCUSSION The r e d u c t i o n in p l a s m a T4 c o n c e n t r a t i o n in chicks fed diets marginal in Se a n d v i t a m i n E f o l l o w s the s a m e p a t t e r n o b s e r v e d in t h e deficiency of c o p p e r , iron, zinc, a n d m a g n e s i u m in rats a n d s o m e a m i n o acids in chicks ( 1 0 - 1 6 ) . It is contrary, h o w e v e r , to the increase in T4 levels o b s e r v e d in vitamin A deficiency in rats a n d in cobalt-Bla-deficient g o a t s (8,9). T h y r o i d h o r m o n e levels of chicks fed the c o r n - s o y b e a n diet w e r e n o t significantly i n c r e a s e d b y Se or vitamin E s u p p l e m e n t a t i o n , e v e n t h o u g h Se levels of the basal diet w e r e n o t greatly different from t h o s e of the s e m i p u r i f i e d diet. The natural vitamin E p r e s e n t in corn a n d s o y b e a n meal p r o b a b l y a c c o u n t s for this observation. E x u d a t i v e diathesis w a s o b s e r v e d in a f e w of the chicks fed the s e m i p u r i f i e d diet, b u t n o t in chicks fed the c o r n - s o y b e a n diet. T h e variation in g r o w t h rate a m o n g e x p e r i m e n t s in chicks f e d similar diets is p r o b a b l y a result of the variation in chick source. Chicks w e r e o b t a i n e d f r o m a Biological Trace Element Research
Vol. I0, 1986
16
J e n s e n et al.
TABLE 4 Effect of Se a n d V i t a m i n E S u p p l e m e n t a t i o n o n P l a s m a T h y r o i d H o r m o n e s a n d O t h e r P a r a m e t e r s in C h i c k s (Expt. 4) I S u p p l e m e n t to diet Parameter
None
V i t a m i n E, 50 I U / k g
Se, 0.1 p p m
S e m i p u r i f i e d diet A n a l y z e d d i e t a r y Se, m g / k g 2 B o d y w t gain, g + S E M F e e d intake, g -+ SEM Bursal w t , mg/100 g BW +-- SEM ~ P l a s m a T3, n g / m L +_ SEM ~ P l a s m a T4, n g / m L +_ SEM 3 Corticosterone, ng/mU C o r n - S o y b e a n diet A n a l y z e d d i e t a r y Se, m g / k g 2 B o d y w t gain, g + SEM F e e d intake, g -+ S E M Bursal wt, mg/100 g BW + SEM ~ P l a s m a T3, n g / m L _ SEM ~ P l a s m a T4, n g / m L + S E M ' Corticosterone, ng/mL 3
0.04 358 +-- 14" 534 + 36" 157 +-- 13" 1.22----- 0.34 a 13.4 +-- 1.8" 20.3 + 4.6"
--406 +---24" 387 + 12 ~ 605 + 24 a 578 + 32 ~ 199 +---27" 194 +-- 18 a 1.97--+ 0.28 a'b 2.45 + 0.25 b 23.6 +-- 1.1 b 26.6 +-- 1.3 b 11.1 --+2.5 ~ 11.8 + 2.6"
0.07 488 + 25 a 750 + 48 a 279 + 31 a 2.40--+ 0.32" 22.0 + 1.8 a'b 8.8 -----0.9 a
502 746 224 0.95 27.2 14.6
--+ 19 a + 54 a + 21" --+0.12 b --+2.1 b --+2.6 a
473 692 283 1.69 18.3 6.4
-+ 19" + 24 a + 19 a +-- 0.23 a'b • 2.0 a + 0.8 ~
IValues within a row without a common letter are significantly different (P < 0.05). 2The semipurified diet contained a calculated level of 2.5 and the corn-soybean diet 14.5 IU vitamin E/kg. 3Mean of eight birds/treatment. commercial hatchery so that the age of the breeder hens and vitamin E and Se reserves in the chicks could result in variation in response to the experimental chick diets. Fasting or food deprivation has been shown to affect thyroid funct i o n (1,2,5,6). It is p o s s i b l e t h a t a s e v e r e d e f i c i e n c y o f a n u t r i e n t is folTABLE 5 Effect of S e l e n i u m A d d e d to a S e m i p u r i f i e d Diet o n P l a s m a T h y r o i d H o r m o n e s in C h i c k s (Expt. 5) ''2 A d d e d Se, m g / k g Parameter B o d y wt, g +-- SEM P l a s m a T3, n g / m L _+ SEM a P l a s m a T4, n g / m L +- S E M ~
0
0.1
0.25
494 + 17 b 497 + 24 b 346 +--44 a 2.32 + 0.16 b 2.34 + 0.21 b 1.54 + 0.13 a 22.2 + 0.9 b 23.4-+ 1.3 b 15.3 + 2.1 a
'Values within a row without a common letter are significantly different (P < 0.05). rl~he semipurified diet contained a calculated level of 2.5 IU vitamin E/kg. 'Mean of eight birds/treatment. Biological Trace Element Research
VoL 10, 1986
Selenium and Thyroid Hormones
17
lowed by a reduction in food intake, consequently masking the specific nutrient effect on thyroid function. The effect of Se on plasma T4 appeared to be independent of its effect on growth rate and feed intake. The Se effect on plasma T4 was observed in all five experiments, but no significant effect of Se on body weight and feed intake was observed in two experiments (Tables 2,4). Furthermore, fasting increased rather than reduced serum T4 in chicks (6). A severe nutrient deficiency may also indirectly affect the thyroid function by putting the animal under a stress situation that will result in elevated plasma corticosterone. There is an inverse relationship between plasma corticosterone and thyroid hormones in chickens (21). We found that Se-vitamin E deficiency elevated plasma corticosterone and reduced plasma T4. Thus, it is possible that the Se, or vitamin E effect on thyroid function is an indirect one via corticosterone. An essential condition for thyroid hormone production is the oxidation of iodide into elementary iodine, catalyzed by peroxidases. In vitro studies have shown that several peroxidases may oxidize iodide to iodine (22). Thus, it seems possible that Se, through the Se-dependent enzyme glutathione peroxidase, may also be involved in iodide oxidation. Reduced glutathione is a potent inhibitor of iodination of bovine serum albumin by thyroid peroxidase (22). Thus, in a deficiency of Se resulting in lower glutathione peroxidase activity, an increase in the level of reduced glutathione in the thyroid gland could inhibit thyroglobulin iodination and, consequently, the synthesis of thyroid hormones. Confirming a previous report (23), we also observed a reduced weight of bursa of Fabricius in chickens fed an Se--vitamin E-deficient diet. Corticosterone administration inhibits bursa of Fabricius growth in chickens (24). Therefore, the increase in plasma corticosterone in the Se-vitamin E-deficient chicks may explain the reduced bursa weight. It may also be an explanation for the immune depression observed in chicks fed Se-vitamin E-deficient diets (25).
ACKNOWLEDGMENT Supported by State and Hatch Funds allocated to the Georgia Agricultural Experiment Stations of the University of Georgia.
REFERENCES 1. T. J. Merimee and E. S. Fineberg, Metabolism 25, 79 (1976). 2. G. E. Shambaugh and J. F. Wilber, Endocrinology 94, 1145 (1974). 3. A. R. Glass, R. Mellitt, K. D. Burman, L. Wartofsky, and R. S. Swerdloff, Endocrinology 102, 1925 (1978). 4. M. M. Kaplan and R. D. Utiger, J. Clin. Invest. 61, 459 (1978). 5. P. W. Nathanielsz, ]. Physiol. 206, 701 (1970). 6. J. D. May, Gen. Comp. Endocr. 34, 323 (1978). BiologicalTraceElementResearch
Vol. 1O,1986
18
J e n s e n et al.
7. Y. Akiba, L. S. Jensen, C. R. Barb, and R. R. Kraeling, J. Nutr. 112, 299 (1982). 8. J. E. Morley, D. A. Damassa, J. Gordon, A. E. Pekary, and J. M. Hershrnan, Life Sci. 22, 190 (1978). 9. F. O. K. Mgongo, S. Gombe, and J. S. Ogaa, Vet. Rec. 109, 51 (1981). 10. K. R. Pastro, B. E. March, and J. Biely, Can. J. Physiol. Pharmacol. 47, 645 (1969). 11. R. G. Elkin, W. R. Featherson, and J. C. Rogler, J. Nutr. 110, 130 (1980). 12. H. P. Humpray and F. W. Heaton, J. Endocr. 53, 113 (1972). 13. M. Lewis and R. M. Iammarino, J. Lab. Clin. Med. 78, 546 (1971). 14. J. E. Morley, J. Gordon, and J. M. Hershman, Am. J. Clin. Nutr. 33, 1767 (1980). 15. S. C. H. Chen, M. R. S. Shirazi, and R. A. Orr, Nutr. Res. 3, 91 (1983). 16. D. K. Allen, C. A. Hassed, and K. Y. Lei, J. Nutr. 112, 2043 (1982). 17. R. Nowosad, Med. Weter 37, 116 (1981). 18. P. A. Wetter and D. E. Ullrey, J. Assoc. Off. Anal. Chem. 61, 927 (1978). 19. D. G. Satterlee, R. B. Abdullah, R. P. Gildersleeve, Poultry Sci, 59, 900 (1980). 20. Statistical Analysis System. User's Guide: 1979 edition. SAS Institute, Raleigh, NC. 21. M. W. Tomaszewska, T. Stelmasiak, and R. B. Cumming, Aus. J. Biol. Sci. 35, 393 (1982). 22. A. Taurog, Recent Prog. Horm. Res. 26, 189 (1970). 23. J. A. Marsh, R. R. Dietert, and G. F. Combs, Jr., Fed. Prod. 41, 341 (1982). 24. M. X. Zarrow, D. L. Greeman, and L. E. Peters, Poultry Sci. 40, 87 (1961). 25. J. A. Marsh, R. R. Dietert, and G. F. Combs, Jr., Proc. Soc. Exp. Biol. Med. 166, 228 (1981).
Biological Trace Element Research
VoL 1O, 1986
Dietary Selenium Status and Plasma Thyroid Hormones in Chicks L. S. JENSEN,* G. L. COLNAGO, K. TAKAHASHI, AND Y. AKIBA
Department of Poultry Science, University of Georgia, Athens, Georgia 30602 Received S e p t e m b e r 13, 1985; Accepted N o v e m b e r 25, 1985
ABSTRACT Experiments were conducted to study the effect of marginal levels of selenium and vitamin E on plasma thyroid hormones of meattype chicks. Plasma thyroxine (T4) w a s significantly increased when a semipurified diet was supplemented with either selenium or vitamin E. Triiodothyronine (T3) was also significantly increased by vitamin E and in one experiment with selenium supplementation. No significant increase in these hormones was observed in birds fed a corn-soybean-meal diet supplemented with these nutrients. Plasma corticosterone level was reduced and weight of the bursa of Fabricius increased by selenium or vitamin E supplementation. These nutrients may be necessary for providing the optimum thyroid conditions for activity of thyroid peroxidase. Index Entries: Selenium; vitamin E; plasma thyroid hormones; thyroxine; triiodothyronine; plasma corticosterone, and selenium-vitamin E deficiency; selenium-vitamin E deficiency, and bursa of Fabricius weight.
INTRODUCTION Thyroid function of domestic animals is known to be altered by many environmental factors. Total caloric deprivation is associated with *Author to whom all correspondence and reprint requests should be addressed. Biological Trace Element Research
]]
Vol. 1O, 1986
12
Jensen et aL
a decrease in triiodothyronine (T3) production and s e r u m T3 concentration in man and rats (1-3). The mechanism of this fall in serum T3 seems to be impaired peripheral 5'-deiodination of thyroxine (T4), since liver homogenates from rats fasted for 2-3 d have shown impaired T 4 t o T 3 conversion in vitro (4-5). In chickens, short periods of fasting reduced serum T3 concentration and increased s e r u m T 4 (6). Thyroidal activity in rats (3) and laying hens (7) is influenced by dietary composition. Specific nutrient effects on thyroidal activity have also been studied. Vitamin-A-deficient rats had increased plasma T3, T4, and free thyroxine index (8). Plasma T 4 concentration and free T 4 increased in goats fed diets deficient in cobalt and vitamin B12 for 23 wk (9). Chicks fed diets deficient in aromatic amino acids, lysine, or valine had reduced thyroidal activity, but the deficiency had to be very severe (10,11). In rats, magnesium or potassium deficiency reduced thyroidal activity (12). Copper, iron, or zinc deficiency also resulted in decreased blood T 3 and/or T 4 in rats (13-16). Calves given selenium (Se) subcutaneously or vitamin E intramuscularly had increased T4 levels in the peripheral blood 48 h after dosage (17). In view of these results, the present studies were undertaken to determine if marginal dietary levels of Se and/or vitamin E would affect plasma thyroid hormones in the chick. METHODS Day-old male broiler chicks of the Hubbard or Arbor Acre strains, obtained from a commercial hatchery, were housed in electrically heated battery brooders under constant illumination, with feed and water supplied ad libitum. The composition of the basal diets, which contained no supplementary Se, vitamin E, or antioxidants, is shown in Table 1. Calculated vitamin E levels for the corn-soybean and semipurified diets were 14.5 and 2.5 IU/kg, respectively. Actual Se levels for the two diets were 0.07-0.08 and 0.04-0.06 mg/kg, respectively. Sodium selenite served as the source of supplemental Se and all-rac-ec-tocopheryl acetate as the source of vitamin E. Diets were analyzed for their Se content by the method of Wetter and Ullrey (18). Four groups of 10 chicks/group were used for each treatment in Expts. 1, 3, and 4 and eight groups of 10 chicks in Expt. 5. Twelve birds/ treatment were used in Expt. 2. Body weight and feed intake data were based on pen averages in all experiments, except Expt. 2, in which body weight was a mean of individual chicks, and feed intake was not measured. At 21 d of age, blood samples were taken by heart puncture, using a heparinized syringe from 10 chicks/treatment in Expts. 1 and 2 and eight chicks/treatment in Expts. 3, 4, and 5. Plasma samples were stored at -40~ until assayed for hormones. In Expts. 2, 3, and 4, chickens were killed by cervical dislocation after blood collection and the bursa of Fabricius was removed and weighed. Biological Trace Element Research
Vol. 1O, 1986
13
Selenium and Thyroid Hormones TABLE 1 Composition of Basal Diets (%) Diet Ingredients Glucose (cerelose) Isolated soy protein Torula yeast Yellow corn Soybean meal (49% protein) Poultry fat Dicalcium phosphate Limestone Cellulose Potassium carbonate Salt Magnesium sulfate 9 0.7 H 2 0 D,L-Methionine Choline chloride (50%) Vitamin mixture" Trace-mineral mixture h Calculated analysis ~ Crude protein (%) ME (kcal/kg) Calcium (%) Phosphorus, available (%) Vitamin E (IU/kg) Selenium (actual analysis) (mg/kg)
Corn-Soybean (CS) SemiPurified (SP) ---53.50 37.50 5.00 1.63 1.37 --0.50 --
0.20 -0.25 0.05 23.0 3200 0.95 0.45 14.5 0.07-0.08
54.10 20.12 10.00 5.00 -4.00 2.27 0.84 1.43 0.69 0.43 0.39 0.32 0.11 0.25 0.05 23.0 3200 0.95 0.52 2.3 0.04-0.06
~Supplying per kg of feed: vitamin A, 11,000 IU; vitamin D3, 1100 ICU.; menadione sodium bisulfite, 1.1 ing; riboflavin, 4.4 mg; Ca pantothenate, 12.0 mg; nicotinic acid, 44.0 mg; choline chloride, 220 mg; pyridoxine HCI, 2.2 rag; folic acid, 0.55 rag; D-biotin, 0.11 mg; thiamine mononitrate, 2.2 mg; vitamin Bl2, 6.6 ~g.
~Supplying mg/kg of feed: manganese, 60; zinc, 50; iron, 30; copper, 5; iodine, 1.05. ~Scott, M. L., Nesheim, M. C., and Young, R. J. Nutrition of The Chicken. Ithaca, NY (1982).
Plasma T 3 a n d T4 w e r e d e t e r m i n e d by r a d i o i m m u n o a s s a y , using commercial r a d i o i m m u n o a s s a y kits (Gammacoat [125I]thyroxine a n d [125I]triiodothyronine r a d i o i m m u n o a s s a y kits, Clinical Assays, Cambridge, MA). The use of these kits for chicken T 3 a n d T4 has b e e n valid a t e d (7). Plasma corticosterone was d e t e r m i n e d by r a d i o i m m u n o a s s a y
(19). The data g e n e r a t e d by these studies w e r e analyzed u s i n g the General Linear Models p r o c e d u r e of the Statistical Analysis System (20) in conjunction with the D u n c a n separation of m e a n options to locate significant (P < 0.05) differences a m o n g m e a n s . Biological Trace Element Research
VoL 10, 1986
14
J e n s e n et al.
RESULTS The results of t h e s e e x p e r i m e n t s (Tables 2-5) s h o w that f e e d i n g diets marginal in Se a n d vitamin E to chicks r e d u c e d p l a s m a T4 c o n c e n t r a t i o n . S u p p l e m e n t a t i o n of t h e s e m i p u r i f i e d diet w i t h 0.1 m g or m o r e Se/kg in all five e x p e r i m e n t s a n d with vitamin E in Expt. 4 significantly i n c r e a s e d p l a s m a T4 level. A significant increase in p l a s m a T3 w a s also o b s e r v e d w h e n v i t a m i n E in Expt. 4 a n d Se in Expt. 5 w e r e a d d e d to the s e m i p u r i f i e d diet (Tables 4,5). S e l e n i u m s u p p l e m e n t a t i o n of a c o r n s o y b e a n diet did not significantly affect p l a s m a T4 levels (Tables 3,4) a n d significantly r e d u c e d T3 level in o n e e x p e r i m e n t (Table 4). In Expt. 2, Se s u p p l e m e n t a t i o n of the s e m i p u r i f i e d diet significantly r e d u c e d p l a s m a corticosterone (Table 2). S e l e n i u m or vitamin E supplem e n t a t i o n of the s e m i p u r i f i e d diet also a p p e a r e d to r e d u c e p l a s m a corticosterone level in Expt. 4 (Table 4), b u t the differences w e r e n o t statistically significant (P > 0.05). A significant interaction b e t w e e n supplem e n t s a n d t y p e of diet on p l a s m a corticosterone level was o b s e r v e d , however. S u p p l e m e n t a t i o n of the semipurified diet w i t h 0.1 p p m of Se significantly i n c r e a s e d w e i g h t of the bursa of Fabricius in t w o experim e n t s (Tables 2,3). In Exp. 4 (Table 4), Se or vitamin E s u p p l e m e n t a t i o n TABLE 2 Effect of Selenium Supplementation of a Semipurified Diet on Plasma Thyroid Hormones and Other Parameters in Chicks ~ Experiment No. 2 Added Se (mg/kg) Parameter Analyzed dietary Se, mg/kg 2 Body wt gain, g + SEM Feed intake, g + SEM Bursal wt, rag/100 g
0
0.25
0
0.1
0.04 507 _+20 a 749 + 28 a
0.22 513 _+_11a 781 +_ 18a --
0.06 308 -----14a
0.16 445 _+ 20 b
131 + 15'~
252 _+ 11b
--
1.89 + .2 a
2.03 + 0.25 a
17.1 ___1.4 ~
31.9 --+ 2.7 b
21.5 + 1.4 ~
35.6 --+ 1.8 b
--
--
6.59-+ 1.5 a
2.64 + 0.43 b
BW ~
Plasma T3 n g / m L + SEM ~ Plasma T4 ng/mL + SEM 3 Plasma corticosterone, ng/mL _+ SEM ~
--
~Values w i t h i n a r o w a n d e x p e r i m e n t w i t h o u t a c o m m o n letter are significantly differe n t (P < 0.05). 2The basal diet c o n t a i n e d a calculated level of 2.5 IU v i t a m i n E/kg. 3Mean of 10 birds/treatment. Biological Trace Element Research
VoL 10, 1986
Selenium and Thyroid Hormones
15
TABLE 3 Effect of Se Supplementation of Semipurified and Corn-Soy Diets on Plasma Thyroid Hormones and Other Parameters in Chicks (Expt. 3) 1
Se added to diets, ppm Parameter
0
0.10
0.25
0.06 422 + 102 586 + 15a 176 _ 20 ~ 1.56_+0.22 22.3___ 2.0 a
0.17 476 _+ 15 b 644 _+ 14b 254 ---+2 9 b 1.45+0.11 ~ 29.8 + 0.9 b
0.33 460 _+ 7b 641 _+ 8b 221 • 2 0 a'b 2.00+0.35 "~ 27.1 .+ 2.0 b
0.08 495 ___14a 672 _+ 21 ~ 309 + 30~' 24.5___ 1.8 a
0.18 525 _+ 5a 731 + 7b 269 + 21 a 22.7+ 0.8 ~
0.29 516 + 10a 711 _+ 19 a'b 329 _ 31 a 22.4_+0.9 ~
Semipurified diet Analyzed dietary Se, mg/kg-' Body wt gain, g .+ SEM Feed intake, g _+ SEM Bursal wt, rag/100 g BW .+ SEM ~ Plasma T3, ng/mL _+ SEM3 Plasma T4, ng/mL _+ SEM 3 Corn-Soybean diet Analyzed dietary Se, mg/kg z Body wt gain, g + SEM Feed intake, g _+ SEM Bursal wt, rag/100 g BW + SEM ~ Plasma T4, ng/mL .+ SEM 3
~Values within a row without a common letter are significantly different (P < 0.05). ~The semipurified diet contained a calculated level of 2.5 and the c o r n - s o y b e a n diet 14.5 Iu vitamin E/kg. ~Mean of eight birds/treatment.
i n c r e a s e d m e a n b u r s a w e i g h t b y 27 a n d 24%, respectively, b u t the differe n c e s failed to be significant (P < 0.05). N o effect of either Se or v i t a m i n E s u p p l e m e n t a t i o n of the c o r n - s o y b e a n diet o n b u r s a w e i g h t w a s observed.
DISCUSSION The r e d u c t i o n in p l a s m a T4 c o n c e n t r a t i o n in chicks fed diets marginal in Se a n d v i t a m i n E f o l l o w s the s a m e p a t t e r n o b s e r v e d in t h e deficiency of c o p p e r , iron, zinc, a n d m a g n e s i u m in rats a n d s o m e a m i n o acids in chicks ( 1 0 - 1 6 ) . It is contrary, h o w e v e r , to the increase in T4 levels o b s e r v e d in vitamin A deficiency in rats a n d in cobalt-Bla-deficient g o a t s (8,9). T h y r o i d h o r m o n e levels of chicks fed the c o r n - s o y b e a n diet w e r e n o t significantly i n c r e a s e d b y Se or vitamin E s u p p l e m e n t a t i o n , e v e n t h o u g h Se levels of the basal diet w e r e n o t greatly different from t h o s e of the s e m i p u r i f i e d diet. The natural vitamin E p r e s e n t in corn a n d s o y b e a n meal p r o b a b l y a c c o u n t s for this observation. E x u d a t i v e diathesis w a s o b s e r v e d in a f e w of the chicks fed the s e m i p u r i f i e d diet, b u t n o t in chicks fed the c o r n - s o y b e a n diet. T h e variation in g r o w t h rate a m o n g e x p e r i m e n t s in chicks f e d similar diets is p r o b a b l y a result of the variation in chick source. Chicks w e r e o b t a i n e d f r o m a Biological Trace Element Research
Vol. I0, 1986
16
J e n s e n et al.
TABLE 4 Effect of Se a n d V i t a m i n E S u p p l e m e n t a t i o n o n P l a s m a T h y r o i d H o r m o n e s a n d O t h e r P a r a m e t e r s in C h i c k s (Expt. 4) I S u p p l e m e n t to diet Parameter
None
V i t a m i n E, 50 I U / k g
Se, 0.1 p p m
S e m i p u r i f i e d diet A n a l y z e d d i e t a r y Se, m g / k g 2 B o d y w t gain, g + S E M F e e d intake, g -+ SEM Bursal w t , mg/100 g BW +-- SEM ~ P l a s m a T3, n g / m L +_ SEM ~ P l a s m a T4, n g / m L +_ SEM 3 Corticosterone, ng/mU C o r n - S o y b e a n diet A n a l y z e d d i e t a r y Se, m g / k g 2 B o d y w t gain, g + SEM F e e d intake, g -+ S E M Bursal wt, mg/100 g BW + SEM ~ P l a s m a T3, n g / m L _ SEM ~ P l a s m a T4, n g / m L + S E M ' Corticosterone, ng/mL 3
0.04 358 +-- 14" 534 + 36" 157 +-- 13" 1.22----- 0.34 a 13.4 +-- 1.8" 20.3 + 4.6"
--406 +---24" 387 + 12 ~ 605 + 24 a 578 + 32 ~ 199 +---27" 194 +-- 18 a 1.97--+ 0.28 a'b 2.45 + 0.25 b 23.6 +-- 1.1 b 26.6 +-- 1.3 b 11.1 --+2.5 ~ 11.8 + 2.6"
0.07 488 + 25 a 750 + 48 a 279 + 31 a 2.40--+ 0.32" 22.0 + 1.8 a'b 8.8 -----0.9 a
502 746 224 0.95 27.2 14.6
--+ 19 a + 54 a + 21" --+0.12 b --+2.1 b --+2.6 a
473 692 283 1.69 18.3 6.4
-+ 19" + 24 a + 19 a +-- 0.23 a'b • 2.0 a + 0.8 ~
IValues within a row without a common letter are significantly different (P < 0.05). 2The semipurified diet contained a calculated level of 2.5 and the corn-soybean diet 14.5 IU vitamin E/kg. 3Mean of eight birds/treatment. commercial hatchery so that the age of the breeder hens and vitamin E and Se reserves in the chicks could result in variation in response to the experimental chick diets. Fasting or food deprivation has been shown to affect thyroid funct i o n (1,2,5,6). It is p o s s i b l e t h a t a s e v e r e d e f i c i e n c y o f a n u t r i e n t is folTABLE 5 Effect of S e l e n i u m A d d e d to a S e m i p u r i f i e d Diet o n P l a s m a T h y r o i d H o r m o n e s in C h i c k s (Expt. 5) ''2 A d d e d Se, m g / k g Parameter B o d y wt, g +-- SEM P l a s m a T3, n g / m L _+ SEM a P l a s m a T4, n g / m L +- S E M ~
0
0.1
0.25
494 + 17 b 497 + 24 b 346 +--44 a 2.32 + 0.16 b 2.34 + 0.21 b 1.54 + 0.13 a 22.2 + 0.9 b 23.4-+ 1.3 b 15.3 + 2.1 a
'Values within a row without a common letter are significantly different (P < 0.05). rl~he semipurified diet contained a calculated level of 2.5 IU vitamin E/kg. 'Mean of eight birds/treatment. Biological Trace Element Research
VoL 10, 1986
Selenium and Thyroid Hormones
17
lowed by a reduction in food intake, consequently masking the specific nutrient effect on thyroid function. The effect of Se on plasma T4 appeared to be independent of its effect on growth rate and feed intake. The Se effect on plasma T4 was observed in all five experiments, but no significant effect of Se on body weight and feed intake was observed in two experiments (Tables 2,4). Furthermore, fasting increased rather than reduced serum T4 in chicks (6). A severe nutrient deficiency may also indirectly affect the thyroid function by putting the animal under a stress situation that will result in elevated plasma corticosterone. There is an inverse relationship between plasma corticosterone and thyroid hormones in chickens (21). We found that Se-vitamin E deficiency elevated plasma corticosterone and reduced plasma T4. Thus, it is possible that the Se, or vitamin E effect on thyroid function is an indirect one via corticosterone. An essential condition for thyroid hormone production is the oxidation of iodide into elementary iodine, catalyzed by peroxidases. In vitro studies have shown that several peroxidases may oxidize iodide to iodine (22). Thus, it seems possible that Se, through the Se-dependent enzyme glutathione peroxidase, may also be involved in iodide oxidation. Reduced glutathione is a potent inhibitor of iodination of bovine serum albumin by thyroid peroxidase (22). Thus, in a deficiency of Se resulting in lower glutathione peroxidase activity, an increase in the level of reduced glutathione in the thyroid gland could inhibit thyroglobulin iodination and, consequently, the synthesis of thyroid hormones. Confirming a previous report (23), we also observed a reduced weight of bursa of Fabricius in chickens fed an Se--vitamin E-deficient diet. Corticosterone administration inhibits bursa of Fabricius growth in chickens (24). Therefore, the increase in plasma corticosterone in the Se-vitamin E-deficient chicks may explain the reduced bursa weight. It may also be an explanation for the immune depression observed in chicks fed Se-vitamin E-deficient diets (25).
ACKNOWLEDGMENT Supported by State and Hatch Funds allocated to the Georgia Agricultural Experiment Stations of the University of Georgia.
REFERENCES 1. T. J. Merimee and E. S. Fineberg, Metabolism 25, 79 (1976). 2. G. E. Shambaugh and J. F. Wilber, Endocrinology 94, 1145 (1974). 3. A. R. Glass, R. Mellitt, K. D. Burman, L. Wartofsky, and R. S. Swerdloff, Endocrinology 102, 1925 (1978). 4. M. M. Kaplan and R. D. Utiger, J. Clin. Invest. 61, 459 (1978). 5. P. W. Nathanielsz, ]. Physiol. 206, 701 (1970). 6. J. D. May, Gen. Comp. Endocr. 34, 323 (1978). BiologicalTraceElementResearch
Vol. 1O,1986
18
J e n s e n et al.
7. Y. Akiba, L. S. Jensen, C. R. Barb, and R. R. Kraeling, J. Nutr. 112, 299 (1982). 8. J. E. Morley, D. A. Damassa, J. Gordon, A. E. Pekary, and J. M. Hershrnan, Life Sci. 22, 190 (1978). 9. F. O. K. Mgongo, S. Gombe, and J. S. Ogaa, Vet. Rec. 109, 51 (1981). 10. K. R. Pastro, B. E. March, and J. Biely, Can. J. Physiol. Pharmacol. 47, 645 (1969). 11. R. G. Elkin, W. R. Featherson, and J. C. Rogler, J. Nutr. 110, 130 (1980). 12. H. P. Humpray and F. W. Heaton, J. Endocr. 53, 113 (1972). 13. M. Lewis and R. M. Iammarino, J. Lab. Clin. Med. 78, 546 (1971). 14. J. E. Morley, J. Gordon, and J. M. Hershman, Am. J. Clin. Nutr. 33, 1767 (1980). 15. S. C. H. Chen, M. R. S. Shirazi, and R. A. Orr, Nutr. Res. 3, 91 (1983). 16. D. K. Allen, C. A. Hassed, and K. Y. Lei, J. Nutr. 112, 2043 (1982). 17. R. Nowosad, Med. Weter 37, 116 (1981). 18. P. A. Wetter and D. E. Ullrey, J. Assoc. Off. Anal. Chem. 61, 927 (1978). 19. D. G. Satterlee, R. B. Abdullah, R. P. Gildersleeve, Poultry Sci, 59, 900 (1980). 20. Statistical Analysis System. User's Guide: 1979 edition. SAS Institute, Raleigh, NC. 21. M. W. Tomaszewska, T. Stelmasiak, and R. B. Cumming, Aus. J. Biol. Sci. 35, 393 (1982). 22. A. Taurog, Recent Prog. Horm. Res. 26, 189 (1970). 23. J. A. Marsh, R. R. Dietert, and G. F. Combs, Jr., Fed. Prod. 41, 341 (1982). 24. M. X. Zarrow, D. L. Greeman, and L. E. Peters, Poultry Sci. 40, 87 (1961). 25. J. A. Marsh, R. R. Dietert, and G. F. Combs, Jr., Proc. Soc. Exp. Biol. Med. 166, 228 (1981).
Biological Trace Element Research
VoL 1O, 1986
