161
Arherosclerosis, 94 (1992) 161-169 0 1992 Elsevier Scientific Publishers Ireland, Ltd. All rights reserved. 0021-9150/92BO5.00 Printed and Published in Ireland
ATHERO 04828
Adipose tissue fatty acids in Scottish men and women: results from the Scottish Heart Health Study Roger Tavendale”, Amanda J. Leea, W. Cairns S. Smithb and Hugh Tunstall-Pedoe” Tardiovascular
Epidemiology
‘Community,
Unit, Ninewells Hospital and Medical School, Dundee DDI 9SY, Scotland (UK)
Occupational
and Family Medicine,
National
and
University of Singapore (Singapore)
(Received 23 October, 1991) (Revised, received 12 March, 1992) (Accepted 16 March, 1992)
Summary
The fatty acid composition of adipose tissue from 4114 men and women across 22 districts of Scotland is described. A biopsy of subcutaneous adipose tissue was obtained from the upper arm using a skin biopsy punch. Overall the proportion of saturated fatty acids was lower in women and those of monounsaturated and polyunsaturated higher than in men. There were significant effects of age on adipose tissue fatty acid composition, particularly in women, where the proportion of saturated fatty acids decreased and that of monounsaturated fatty acids increased with advancing age. The fatty acid composition of adipose tissue varied among the districts studied. The district standard&d mortality ratio for coronary heart disease was positively correlated with the district mean oleic acid value and inversely correlated with the district mean linoleic acid value. This paper supports the importance of adipose tissue fatty acids as indicators of risk factor status for coronary heart disease.
Key words: Fatty acids; Adipose tissue; Coronary heart disease
Introduction
The role of dietary fatty acids in coronary heart disease (CHD) has been investigated since Sinclair [l] suggested that a deficiency of essential fatty Correspondence
to: R. Tavendale,
Cardiovascular
Epidemi-
ology Unit, Ninewells Hospital and Medical School, Dundee DDI 9SY, Scotland, UK. Tel.: 0382632282; Fax: 0382641095.
acids may contribute to atherosclerosis. The fatty acid composition of adipose tissue reflects the long-term dietary intake of fatty acids [2,3] and in both population [4] and case-control [5] studies, it has been shown that low concentrations of linoleic acid in adipose tissue are associated with increased rates of CHD. The Scottish Heart Health Study (SHHS) [6] is a large cross-sectional study of coronary risk fac-
162
tors in men and women. As part of this study, the fatty acid composition of a subcutaneous specimen of adipose tissue was estimated. This paper reports the effect of age and sex on adipose tissue fatty acid composition and investigates the geographical variation of adipose tissue fatty acid composition within Scotland and its correlation with CHD mortality. Methods The aims and methods of the SHHS have been described in detail elsewhere [6]. Briefly, a target sample of450 men and women was recruited from general practitioners’ lists from each of 22 local government districts across Scotland during 1984-1986. Reports on the other major risk factors for CHD have been published [7,8]. Fatty acid estimation As part of a clinical examination, a specimen of adipose tissue was taken from the outer upper arm using a 3-mm skin biopsy punch [9]. This site was chosen because it is clean, convenient, less painful than other sites and is an area where subjects expect needles to be inserted. The punch removes a core of tissue (8 mm long by 3 mm diameter) consisting of skin, connective tissue and adipose tissue. After collection, the specimen was placed in a OS-ml conical tube and frozen at -20°C for up to 5 days. The specimens were subsequently stored at -4O’C before analysis. For estimation of fatty acids, the skin and connective tissue were removed from the biopsy. The remainder of the biopsy, approximately 2-3 mg, was placed in normal saline. If the sample floated, it was deemed to consist of adipose tissue and the analysis proceeded. If the tissue did not float, the specimen was deemed unacceptable and no further processing was carried out. The method used for the extraction and transesterification of fatty acids has been described previously [lo], with the exception that solvents were removed under nitrogen instead of under vacuum. The fatty acid methyl esters were separated on a 1.5 m x 4 mm glass column packed with 10% SP-2330 on 100/120 mesh Chromosorb WAW (Supelco) installed in a Hewlett-Packard 5890A gas chromatograph. Eluting peaks were detected using flame ionisation
and quantified using a VG minichrom data handling system. The fatty acid methyl esters were identified by comparison of retention times with. those of standard mixtures. The methyl esters of eicosanoic acid (20:0) and y-linolenic acid (18:3 n-6) and those of eicosenoic acid (20: 1 n-9) and Qlinolenic acid (18:3 n-3) co-eluted and relative constituents of each peak were not estimated. From the repeated analysis of a post-mortem sample of adipose tissue, the coefficients of variation for the estimation of individual fatty acids were found to range from 2% for the major peaks to 22% for the trace constituents (i.e., those peaks comprising less than 1% of total fatty acids). Individual fatty acids were quantified as a percentage of the total amount of fatty acids present in the sample. Statistical methods As some of the variables were skewed, twosample comparisons were made using the Wilcoxon rank sum W test. The Kruskal-Wallis one-way analysis of variance was used to compare more than two groups. Spearman’s rank correlations examined associations between fatty acids and standardised mortality ratios (SMRs). Statistical analyses were carried out using the SPSS software package (SPSS UK Ltd). Results Biopsies were obtained from 8061 (78%) of the 10 359 subjects who participated in the study. Of these, 108 (1%) were unsatisfactory at the time of collection. In the laboratory, 3594 (35%) were judged to contain only skin and connective tissue and no adipose tissue, while the chromatographic analysis of 245 (2%) specimens was unacceptable. (For most biopsies, all of the available adipose tissue was extracted for fatty acid analysis. This meant that repeat extractions could not be carried out.) Hence, acceptable fatty acid analyses were obtained from 4114 (40%) specimens. There was no significant difference in the mean age, body mass index value and social class distribution between the whole study population (10 359) and the subgroup (4114) which provided acceptable adipose tissue analysis. However, while the whole study population conta> ed 49.5% men, the sub-group contained 53.0% m: ‘.
163 TABLE I ADIPOSE TISSUE FATTY ACID COMPOSITION Fatty acid
IN MEN AND WOMEN Significance”
Mean u/ (S.D.)/sex Men n = 2185
Women n = 1929
Saturated Myristic Palmitic Stearic
14:o 16:O 18:O
26.98 2.34 20.99 3.66
(3.27) (0.75) (2. IO) (1.05)
25.25 (3.72) 2.27 (0.75) 19.49 (2.34) 3.49 (1.19)
Monounsaturated Palmitoleic Oleic EicosenoicC
62.58 8.88 50.55 3.15
(3.99)
16:l 18:l 20: 1
63.78 9.40 5 I .28 3.10
Polyunsaturated Linoleic y-Linolenicd Dihomo-y-linolenic Arachidonic Docosapentaenoic Docosahexaenoic
18:2 18:3 20:3 20:4 22~5 22~6
P/S ratio “Using Wilcoxon b(Womenimen x CComposite peak dComposite peak
**
??
* ?? ** ***
Difference b (%I)
-6.4 -3.0 -7.1 -4.6
(4.07) (2.01) (2.86) (0.55)
*** *** *** *
+1.9 +5.9 +I.4 -1.6
10.27 (2.81) 8.88 (2.75) 0.21 (0.14) 0. IO (0.05) 0.64 (0.16) 0.26 (0.08) 0.18 (0.08)
10.79 (2.56) 9.37 (2.50) 0.18 (0.09) 0. I5(0.06) 0.61 (0.15) 0.27 (0.09) 0.21 (0.09)
*** *** *** *** *** *** ***
+5.1 +5.5 -14.3 +50.0 -4.7 +3.8 +16.7
0.39 (0.13)
0.44 (0.14)
***
+12.8
(1.94) (2.72) (0.60)
rank sum W test: *P < 0.05, **P < 0.01, ***P< 0.001 100) - 100. containing wlinolenic acid. containing eicosanoic acid.
There were significant differences in adipose tissue fatty acid composition between men and women (Table 1). While saturated fatty acids were lower in women, monounsaturated and polyunsaturated fatty acids were higher. The magnitude of these differences varied. For the major constituents (e.g. oleic acid) the magnitude of the difference (1.4%) between men and women was small when compared to the amount of the fatty acid in the adipose tissue (51% of total fatty acids). However, for the trace constituents (e.g. dihomoy-linolenic acid, 0.1% of total fatty acids) the relative magnitude of the difference between the proportions in men and women was greater (the amount in women was 50% higher than that in men). The mean proportion of the essential fatty acid linoleic acid, was higher in women. The ratio of polyunsaturated to saturated fatty acids (P/S ratio) was also significantly higher in women.
The effect of age on adipose tissue fatty acid composition in men is shown in Table 2a. While age had no effect on most fatty acids, the proportions of linoleic acid and that of y-linolenic plus eicosanoic acid decreased in the older age groups. There were small increases in the proportions of the two long chain polyunsaturated fatty acids; docosapentaenoic and docosahexaenoic acids. The overall effect was a decrease in the total of polyunsaturated fatty acids with increasing age which was reflected by a decrease in the P/S ratio. In women, there were significant changes in the proportions of most of the fatty acids with age (Table 2b). The proportions of the saturated fatty acids decreased with increasing age. For the monounsaturated fatty acids, age had a varied effect on the individual fatty acids although when grouped together, there was a significant increase in the older age groups. Varied effects of age were also seen with the
164 TABLE 2a EFFECT OF AGE ON ADIPOSE TISSUE FATTY ACID COMPOSITION IN MEN Fatty acid
Mean % (S.D.)/age
Significance”
n = 529
45-49 n = 508
50-54 n = 593
n =
Saturated Myristic Palmitic Stearic
26.73 2.28 20.81 3.65
26.96 2.34 21.01 3.61
(3.25) (0.74) (2.08) (1.04)
27.04 (3.29) 2.36 (0.78) 21.00 (2.13) 3.67 (1.05)
27.19 (3.37) 2.37 (0.76) 21.13 (2.18) 3.70 (1.05)
Monounsaturated Palmitoleic Oleic Eicosenoic
62.62 (3.85) 8.79 (1.90) 50.71 (2.58) 3.13 (0.60)
62.62 (3.96) 8.93 (1.89) 50.50 (2.77) 3.19 (0.55)
62.59 (4.01) 8.92 (1.99) 50.52 (2.72) 3.15 (0.62)
62.48 (4.14) 8.89 (1.97) 50.47 (2.79) 3.11 (0.63)
Polyunsaturated Linoleic 7-Linolenic
10.46 (2.49) 9.07 (2.40) 0.24 (0.21)
10.25 (2.89) 8.85 (2.83) 0.21 (0.10)
10.22 (2.90) 8.84 (2.83) 0.21 (0.10)
10.16 (2.94) 8.78 (2.88) 0.20 (0.10)
40-44
Dihomo-y-linolenic Arachidonic Docosapentaenoic Docosahexaenoic
0.10 0.64 0.25 0.18
P/S Ratio ‘Using Kruskal-Wallis test: *P
(3.14) (0.69) (1.98) (1.06)
(0.05) (0.16) (0.08) (0.09)
0.40 (0.11) c
0.10 0.65 0.25 0.19
(0.04) (0.16) (0.07) (0.08)
0.39 (0.13)
0.10 0.64 0.26 0.19
(0.05) (0.17) (0.08) (0.08)
0.39 (0.13)
55-59 555
0.10 0.63 0.26 0.19
(0.05) (0.16) (0.08) (0.07)
0.38 (0.13)
* ** ***
** *** *
0.05, **P < 0.01, ***P < 0.001.
TABLE 2b EFFECT OF AGE ON ADIPOSE TISSUE FATTY ACID COMPOSITION IN WOMEN Fatty acid
Mean u/ (S.D.)/age
Signiticance’
40-44 n = 518
45-49 n = 469
50-54 n = 479
55-59 n = 463
25.24 (3.49)
25.64 (3.49)
25.29 (3.85)
24.83 (3.77)
*
2.27 (0.73) 19.38 (2.17) 3.59 (1.14)
2.28 (0.76) 19.76 (2.34) 3.59 (1.24)
2.30 (0.77) 19.53 (2.43) 3.46 (1.17)
2.25 (0.75) 19.28 (2.42) 3.30 (1.18)
***
Monounsaturated Palmitoleic Oleic Eicosenoic
63.51 9.07 51.30 3.15
(3.84) (1.91) (2.77) (0.54)
63.58 (4.06) 9.27 (1.99) 51.17 (2.87) 3.14 (0.58)
63.71 (4.24) 9.46 (1.99) 51.17 (2.94) 3.08 (0.56)
64.36 (4.13) 9.82 (2.07) 51.50 (2.85) 3.03 (0.53)
Polyunsaturated
11.07(2.50)
10.61 (2.34)
10.82 (2.70)
10.62 (2.66)
Saturated Myristic Pahnitic Stearic
Linoleic y-Linolenic Dihomo-y-linolenic Arachidonic Dccosapentaenoic Docosahexaenoic P/S Ratio
9.74 0.20 0.14 0.59 0.23 0.18
(2.45) (0.09) (0.05) (0.14) (0.08) (0.07)
0.45 (0.14)
9.23 0.18 0. I5 0.61 0.26 0.19
(2.28) (0.09) (0.06) (0.16) (0.08) (0.08)
0.43 (0.13)
‘Using Kruskal-Wallis test: *P < 0.05, **P < 0.01, ***k < 0.001.
9.37 0.17 0.16 0.62 0.29 0.23
(2.62) (0.08) (0.06) (0.14) (0.08) (0.09)
0.44 (0.15)
9.10 0.15 0.17 0.63 0.32 0.25
(2.60) (0.08) (0.06) (0.15) (0.08) (0.10)
0.44 (0.15)
??
* ***
??
** *+* ** *** ?? ** *** *** *** ??
*
165 TABLE 3 REGIONAL VARIATION IN ADIPOSE TISSUE LINOLEIC ACID CONTENT AND SMR FOR CHD District
Mean linoleic acid/sex Women
Men
Eastwood Stirling Edinburgh Aberdeen Banff and Buchan Roxburgh Perth and Kinross East Lothian Dunfermline Kyle and Carrick South Glasgow Dumbarton Kirkcaldy Nithsdale Cunninghame Inverness Hamilton North Glasgow Renfrew Monklands
n
Mean%
(S.D.)
SMRa
?I
Mean%
(S.D.)
SMRa
153 118 87 104 36 54 133 91 145 67 95 100 121 96 116 154‘ 112 190 117 85
10.47 8.85 9.38 8.99 8.85 9.35 9.02 8.16 8.51 9.86 8.52 9.35 8.31 9.19 8.95 9.21 8.44 8.13 8.81 7.70
(3.27) (2.47) (2.53) (2.15) (1.80) (2.71) (2.92) (2.41) (2.80) (3.72) (2.66) (2.40) (2.27) (2.58) (3.03) (2.58) (2.47) (2.58) (2.88) (2.42)
61 79 81 83 83 84 89 91 99 102 103 103 105 109 110 112 116 117 118 136
87 119 98 Ill 41 68 109 79 118 52 78 80 119 107 101 145 96 137 95 68
10.59 9.48 10.06 9.20 9.64 9.31 8.92 9.20 8.72 9.77 8.73 9.68 9.16 9.52 9.68 9.76 9.31 9.01 9.73 8.38
(2.74) (2.64) (2.71) (1.75) (2.44) (2.32) (2.00) (2.01) (2.71) (2.68) (2.16) (2.67) (2.47) (2.41) (2.86) (2.88) (2.43) (2.26) (2.54) (1.95)
50 94 83 72 85 79 81 87 115 98 110 88 112 106 112 91 126 121 109 147
‘Standardised mortality ratio for CHD in age group 35-64 years for 1979-1983.
polyunsaturated fatty acids. The proportion of linoleic acid decreased with increasing age while the longer chain polyunsaturated fatty acids increased with age. The fatty acid composition of adipose tissue varied between districts. In two of the districts (Dundee and Falkirk), a combined total of only 33 acceptable fatty acid analyses were carried out. In the remaining 20 districts, the mean total amount of saturated fatty acids ranged from 25.7% (Dumbarton) to 28.8% (Dunfermline) in men and from 23.3% (Renfrew) to 26.6% (Dunfermline) in women. For mean total monounsaturated fatty acids, Roxburgh had the lowest values for both men (60.4%) and women (61 .l%), while Monklands had the highest values for both men (64.5%) and women (66.1%). The lowest mean total amount of polyunsaturated fatty acids was in Monklands for men (9.2%) and Dunfermline for women (9.8%), while highest mean values were in
Eastwood for both men (12.0%) and women (12.2%). Dunfermline had the lowest P/S ratio for both men (0.34) and women (0.38), while Eastwood had the highest values (0.46 men, 0.47 women). The regional variation in adipose tissue linoleic acid is shown in Table 3. This table also lists the standard&d mortality ratios (SMRs) for CHD for each district. In all except three districts (Perth, Roxburgh and Kyle & Carrick), the mean proportion of linoleic acid was higher in women than in men. For both sexes, Monklands had the lowest mean values and Eastwood had the highest mean values. The Spearman rank correlation coefficients of age-adjusted mean adipose tissue fatty acid composition with the SMR for CHD for each district are listed in Table 4. In men, there were significant positive correlations between oleic acid, palmitoleic acid and total monounsaturated fatty acids
166 TABLE 4 RANK CORRELATION COEFFICIENTS BETWEEN AGE ADJUSTED DISTRICT MEAN ADIPOSE TISSUE FATTY ACID COMPOSITION AND DISTRICT SMR FOR CHD Fatty acid
Rank correlation coeff:cient/sex Men
Women
Saturated Myristic Palmitic Stearic
-0.12 -0.28 -0.02 -0.18
-0.39* -0.42* -0.31 -0.38
Monounsaturated Palmitoleic Oleic Eicosenoic
0.56* 0.50’ 0.59* -0.05
0.16* 0.51’ 0.73. -0.19
Polyunsaturated Linoleic y-Linolenic Dihomoy-linolenic Arachidonic Docosapentaenoic Docosahexaenoic
-0.58* -0.60* -0.02 0.04 0.02 -0.06 -0.20
-0.56* -0.62’ -0.31 0.06 0.20 -0.01 -0.18
P/S Ratio
-0.432
-0.20
?? P < 0.05.
CHD whilst adipose tissue linoleic acid, total polyunsaturated fatty acids and the P/S ratio were negatively correlated with CHD. Similar results were seen in women with the addition that myristic acid and saturated fatty acids correlated negatively with CHD. The relationships between district SMR for CHD and district mean value for both oleic and linoleic acid in each sex are shown in Figs. 1 and 2.
with
Discussion With over 4000 acceptable fatty acid analyses, the results reported here comprise the largest study of adipose tissue fatty acids in Scotland. The study would have been even larger if the number of successful biopsies could have been increased. A contributing factor to the low success rate was that initially 2 mm diameter punches were used and most of the biopsies taken with this diameter
punch contained no adipose tissue. Since the 3 mm punch produced enough adipose tissue in approximately 80% of the biopsies obtained, this method remains useful for large epidemiological studies due to the low cost, speed and simplicity of the method. For smaller studies where it is imperative to obtain a sample of adipose tissue, a more invasive technique should be used. In this study, since the sub-population from which acceptable biopsies were obtained was similar in age, BMI and social class to the whole study population, the data obtained are probably a true representation of the Scottish population. The fatty acid composition of adipose tissue has been shown to vary with the sample site chosen [3,11]. In previous studies of human adipose tissue fatty acid composition, specimens of subcutaneous adipose tissue have been obtained from the abdomen or buttock. The relationship of the fatty acid composition of subcutaneous adipose tissue from the upper arm with that from other sites is unknown. The fatty acid composition of adipose tissue in Scottish men has been reported previously [4,5,10]. For the saturated fatty acids, the results from this study are lower than previous reports and those for the monounsaturated fatty acids are higher. In our results, the chromatographic peak containing the co-eluting methyl esters of CXlinolenic and eicosenoic acids has been included in the total of monounsaturated fatty acids. Schafer et al. [12] have reported that human adipose tissue contains approximately three times the amount of eicosenoic acid as ar-linolenic acid. Although this may contribute to the higher total of monounsaturated fatty acids reported here, when the other individual fatty acids (palmitoleic, oleic) are compared, the results are also higher than previous reports. For the polyunsaturated fatty acids, our results are similar to the previous studies of Scottish men. In addition, at 0.39 the P/S ratio is very similar to the value of 0.37 reported by Wood et al. [5]. Analysis of the dietary questionnaire data from the SHHS revealed P/S ratios of 0.28-0.32 in dietary intake [ 131. There are no reports of adipose tissue fatty acid composition in Scottish women. For saturated fatty acids, the values reported here are similar to those found in both Danish [12] and Dutch [ 141
167
0
lLO-
a
CHD
.
SMR 120-
.
.
loo-
.
*.
.
.
.
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.
.
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.
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80-
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. r.0.57
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60-t L8
LQ
50 %
f 52
51
Oleic acid
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. .
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? ? ? ? ?? ? ? .
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.
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8
.
. ??? ? ? ? rz0.67
. LO',
LB
LQ
50
51 %
52
53
, 5L
Oleic acid
Fig. 1. (a) Relationship between district mean standard&d mortality ratio (SMR) for coronary heart disease (CHD) and district mean proportion of oleic acid in adipose tissue in men. (b) Relationship between district mean SMR for CHD and district mean proportion of oleic acid in women.
women, while our results for monounsaturated fatty acids are higher and those for polyunsaturated fatty acids lower. In this study, the fatty acid composition of adipose tissue was found to be significantly different in men and women. The pattern of lower saturated and higher monounsaturated and polyunsaturated fatty acids in women was also reported by van Staveren et al. [14]. In this study no difference in linoleic acid intake was found be-
tween men and women [ 151. In men, low levels of adipose tissue linoleic and dihomo-y-linolenic acids have been associated with increased occurrence of CHD [lo]. It is possible that the higher proportions found in women may contribute to their lower rates of disease. Age was shown to have significant effects on adipose tissue fatty acid composition, particularly in women. A decrease in saturated fatty acids and an increase in monounsaturated fatty acids with
168
0a
.
.
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.
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??
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? ?
? ?
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.
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.
e
.
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f 11
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acid
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. . .
.
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..
. . 80-
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.*
.
. . .
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r = -0.u
. 10
i
% Linoleic
11
acid
Fig. 2. (a) Relationship between district mean SMR for CHD and district mean prdportion of linoleic acid in men. (b) Relationship between district mean SMR for CHD and district mean proportion of linoleic acid in women.
increasing age, was also reported by Schafer et al. [12]. The effects of age are difficult to interpret since changes in adipose tissue fatty acid composition may be a result of changing diet and/or a change in the metabolism and storage of the fatty acids. The finding that adipose tissue fatty acid composition shows a greater change with age in women than in men is interesting in that other CHD risk factors (e.g., serum cholesterol) also show a larger age effect in women. In the results reported here, adipose tissue
linoleic acid was shown to vary throughout Scotland and there was a significant negative correlation between the district mean linoleic acid content and the district SMR for CHD in both sexes. This finding supports the hypothesis that low amounts of adipose tissue linoleic acid are associated with increased rates of CHD. In addition, for both sexes there was a significant correlation between the district mean oleic acid content and the district SMR for CHD and the magnitude of the correlation coefficients was greater than
169
that with linoleic acid. The underlying mechanism for this finding is unclear. The oleic acid content of adipose tissue has been found to be inversely related to the amount of linoleic acid in the diet (21. Thus, a low intake of dietary linoleic acid may contribute to both higher proportions of adipose tissue oleic acid and an increased occurrence of CHD. In summary, this study has reported the fatty acid composition of adipose tissue in a large sample of Scottish men and women and has described the effects of age, sex and geographical variation. The correlation of district rates of CHD with mean district values for oleic and linoleic acid has been demonstrated. The relationship of adipose tissue fatty acid composition with the other risk factors for CHD is currently being investigated and will be reported later. Acknowledgements We thank John Bruce, Susan Sharpe, Marion Milne and Michele Leslie for their technical help. This study was funded by the Scottish Home and Health Department with additional support from the Independent Scientific Committee on Smoking and Health, the Chest, Heart and Stroke Association and the British Heart Foundation. The opinions expressed here are those of the authors. References Sinclair, H.M., Deficiency of essential fatty acids and atherosclerosis, et cetera, Lancet. i (1956) 381. Field, C.J.. Angel. A. and Clandinin. M.T., Relationship of diet to the fatty acid composition of human adipose structural and stored lipids, Am. J. Clin. Nutr.. 42 (1985) 1206. Schafer, L. and Overvad. K.. Subcutaneous adipose-tissue fatty acids and vitamin E in humans: relation to diet and sampling site, Am. J. Clin. Nutr.. 52 (1990) 486. Riemersma, R.A., Wood, D.A., Butler, S., Elton, R.A., Oliver, M., Sale, M. et al., Linoleic acid content in
adipose tissue and coronary heart disease, Br. Med. J., 292 (1986) 1423. 5 Wood, D.A., Riemersma, R.A., Butler, S., Thomson, M., Macintyre, C., Elton, R.A. et al., Linoleic acid and eicosapentaenoic acids in adipose tissue and platelets and risk of coronary heart disease, Lancet, i (1987) 177. 6 Smith, W.C.S., Crombie, I.K., Tavendale, R., Irving, J.M., Kenicer, M.B. and Tunstall-Pedoe., H., The Scottish Heart Health Study: objectives and development of methods, Health Bull., 45 (1987) 211. 7 Smith, W.C.S., Tunstall-Pedoe, H., Crombie, I.K. and Tavendale, R., Concomitants of excess coronary deaths: Major risk factor and lifestyle findings from 10,359 men and women in the Scottish Heart Health Study, Scot. Med. J., 34 (1989) 550. 8 Tunstall-Pedoe, H., Smith, W.C.S., Crombie, I.K. and Tavendale, R., Coronary risk factor and lifestyle variation across Scotland: Results from the Scottish Heart Health Study, Scot. Med. J., 34 (1989) 556. 9 Smith, W.C.S. Tavendale, R. and Tunstall-Pedoe, H., Simplified subcutaneous fat biopsy for nutritional surveys, Hum. Nutr.: Clin. Nutr., 4Oc (1986) 323. IO Wood, D.A., Butler, S., Riemersma, R.A., Thomson, M., Oliver, M.F., F&on, M., et al. Adipose tissue and platelet fatty acids and coronary heart disease in Scottish men, Lancet, ii (1984) 117. II Malcolm, G.T.. Bhattacharyya, A.K., Velez-Duran, M., Guzman, M.A., Oalmann, M.C. and Strong, J.P., Fatty acid composition of adipose tissue in humans: differences between subcutaneous sites, Am. J. Clin. Nutr.. 50 (1989) 288. I2 Schafer, L., Overvad, K., Thorling, E.B. and Velander, G., Adipose tissue levels of fatty acids and tocopherol in young men and old women, Ann. Nutr. Metab., 33 (1989) 315. 13 Bolton-Smith, C., Smith, W.C.S., Woodward, M. and Tunstall-Pedoe, H., Nutrient intakes of different social class groups: Results from the Scottish Heart Health Study (SHHS), Br. J. Nutr., 65 (1991) 321. 14 Van Staveren. W., Deurenberg, P., Katan, M.B., Burema, J.. De Groat. L.C.P.G.M. and Hoffmans. M.D.A.F.. Validity of the fatty acid composition of subcutaneous fat tissue microbiopsies as an estimate of the long-term average fatty acid composition of the diet of separate individuals, Am. J. Epidemiol.. 123 (1986) 455. I5 Bolton-Smith, C., Woodward, M. and Tunstall-Pedoe, H., Smoking, and correlations between dietary fat and adipose tissue linoleate (Cl8:2) using a food frequency questionnaire (FFQ), Proc. Nutr. Sot., I5 (1992) in press.
Arherosclerosis, 94 (1992) 161-169 0 1992 Elsevier Scientific Publishers Ireland, Ltd. All rights reserved. 0021-9150/92BO5.00 Printed and Published in Ireland
ATHERO 04828
Adipose tissue fatty acids in Scottish men and women: results from the Scottish Heart Health Study Roger Tavendale”, Amanda J. Leea, W. Cairns S. Smithb and Hugh Tunstall-Pedoe” Tardiovascular
Epidemiology
‘Community,
Unit, Ninewells Hospital and Medical School, Dundee DDI 9SY, Scotland (UK)
Occupational
and Family Medicine,
National
and
University of Singapore (Singapore)
(Received 23 October, 1991) (Revised, received 12 March, 1992) (Accepted 16 March, 1992)
Summary
The fatty acid composition of adipose tissue from 4114 men and women across 22 districts of Scotland is described. A biopsy of subcutaneous adipose tissue was obtained from the upper arm using a skin biopsy punch. Overall the proportion of saturated fatty acids was lower in women and those of monounsaturated and polyunsaturated higher than in men. There were significant effects of age on adipose tissue fatty acid composition, particularly in women, where the proportion of saturated fatty acids decreased and that of monounsaturated fatty acids increased with advancing age. The fatty acid composition of adipose tissue varied among the districts studied. The district standard&d mortality ratio for coronary heart disease was positively correlated with the district mean oleic acid value and inversely correlated with the district mean linoleic acid value. This paper supports the importance of adipose tissue fatty acids as indicators of risk factor status for coronary heart disease.
Key words: Fatty acids; Adipose tissue; Coronary heart disease
Introduction
The role of dietary fatty acids in coronary heart disease (CHD) has been investigated since Sinclair [l] suggested that a deficiency of essential fatty Correspondence
to: R. Tavendale,
Cardiovascular
Epidemi-
ology Unit, Ninewells Hospital and Medical School, Dundee DDI 9SY, Scotland, UK. Tel.: 0382632282; Fax: 0382641095.
acids may contribute to atherosclerosis. The fatty acid composition of adipose tissue reflects the long-term dietary intake of fatty acids [2,3] and in both population [4] and case-control [5] studies, it has been shown that low concentrations of linoleic acid in adipose tissue are associated with increased rates of CHD. The Scottish Heart Health Study (SHHS) [6] is a large cross-sectional study of coronary risk fac-
162
tors in men and women. As part of this study, the fatty acid composition of a subcutaneous specimen of adipose tissue was estimated. This paper reports the effect of age and sex on adipose tissue fatty acid composition and investigates the geographical variation of adipose tissue fatty acid composition within Scotland and its correlation with CHD mortality. Methods The aims and methods of the SHHS have been described in detail elsewhere [6]. Briefly, a target sample of450 men and women was recruited from general practitioners’ lists from each of 22 local government districts across Scotland during 1984-1986. Reports on the other major risk factors for CHD have been published [7,8]. Fatty acid estimation As part of a clinical examination, a specimen of adipose tissue was taken from the outer upper arm using a 3-mm skin biopsy punch [9]. This site was chosen because it is clean, convenient, less painful than other sites and is an area where subjects expect needles to be inserted. The punch removes a core of tissue (8 mm long by 3 mm diameter) consisting of skin, connective tissue and adipose tissue. After collection, the specimen was placed in a OS-ml conical tube and frozen at -20°C for up to 5 days. The specimens were subsequently stored at -4O’C before analysis. For estimation of fatty acids, the skin and connective tissue were removed from the biopsy. The remainder of the biopsy, approximately 2-3 mg, was placed in normal saline. If the sample floated, it was deemed to consist of adipose tissue and the analysis proceeded. If the tissue did not float, the specimen was deemed unacceptable and no further processing was carried out. The method used for the extraction and transesterification of fatty acids has been described previously [lo], with the exception that solvents were removed under nitrogen instead of under vacuum. The fatty acid methyl esters were separated on a 1.5 m x 4 mm glass column packed with 10% SP-2330 on 100/120 mesh Chromosorb WAW (Supelco) installed in a Hewlett-Packard 5890A gas chromatograph. Eluting peaks were detected using flame ionisation
and quantified using a VG minichrom data handling system. The fatty acid methyl esters were identified by comparison of retention times with. those of standard mixtures. The methyl esters of eicosanoic acid (20:0) and y-linolenic acid (18:3 n-6) and those of eicosenoic acid (20: 1 n-9) and Qlinolenic acid (18:3 n-3) co-eluted and relative constituents of each peak were not estimated. From the repeated analysis of a post-mortem sample of adipose tissue, the coefficients of variation for the estimation of individual fatty acids were found to range from 2% for the major peaks to 22% for the trace constituents (i.e., those peaks comprising less than 1% of total fatty acids). Individual fatty acids were quantified as a percentage of the total amount of fatty acids present in the sample. Statistical methods As some of the variables were skewed, twosample comparisons were made using the Wilcoxon rank sum W test. The Kruskal-Wallis one-way analysis of variance was used to compare more than two groups. Spearman’s rank correlations examined associations between fatty acids and standardised mortality ratios (SMRs). Statistical analyses were carried out using the SPSS software package (SPSS UK Ltd). Results Biopsies were obtained from 8061 (78%) of the 10 359 subjects who participated in the study. Of these, 108 (1%) were unsatisfactory at the time of collection. In the laboratory, 3594 (35%) were judged to contain only skin and connective tissue and no adipose tissue, while the chromatographic analysis of 245 (2%) specimens was unacceptable. (For most biopsies, all of the available adipose tissue was extracted for fatty acid analysis. This meant that repeat extractions could not be carried out.) Hence, acceptable fatty acid analyses were obtained from 4114 (40%) specimens. There was no significant difference in the mean age, body mass index value and social class distribution between the whole study population (10 359) and the subgroup (4114) which provided acceptable adipose tissue analysis. However, while the whole study population conta> ed 49.5% men, the sub-group contained 53.0% m: ‘.
163 TABLE I ADIPOSE TISSUE FATTY ACID COMPOSITION Fatty acid
IN MEN AND WOMEN Significance”
Mean u/ (S.D.)/sex Men n = 2185
Women n = 1929
Saturated Myristic Palmitic Stearic
14:o 16:O 18:O
26.98 2.34 20.99 3.66
(3.27) (0.75) (2. IO) (1.05)
25.25 (3.72) 2.27 (0.75) 19.49 (2.34) 3.49 (1.19)
Monounsaturated Palmitoleic Oleic EicosenoicC
62.58 8.88 50.55 3.15
(3.99)
16:l 18:l 20: 1
63.78 9.40 5 I .28 3.10
Polyunsaturated Linoleic y-Linolenicd Dihomo-y-linolenic Arachidonic Docosapentaenoic Docosahexaenoic
18:2 18:3 20:3 20:4 22~5 22~6
P/S ratio “Using Wilcoxon b(Womenimen x CComposite peak dComposite peak
**
??
* ?? ** ***
Difference b (%I)
-6.4 -3.0 -7.1 -4.6
(4.07) (2.01) (2.86) (0.55)
*** *** *** *
+1.9 +5.9 +I.4 -1.6
10.27 (2.81) 8.88 (2.75) 0.21 (0.14) 0. IO (0.05) 0.64 (0.16) 0.26 (0.08) 0.18 (0.08)
10.79 (2.56) 9.37 (2.50) 0.18 (0.09) 0. I5(0.06) 0.61 (0.15) 0.27 (0.09) 0.21 (0.09)
*** *** *** *** *** *** ***
+5.1 +5.5 -14.3 +50.0 -4.7 +3.8 +16.7
0.39 (0.13)
0.44 (0.14)
***
+12.8
(1.94) (2.72) (0.60)
rank sum W test: *P < 0.05, **P < 0.01, ***P< 0.001 100) - 100. containing wlinolenic acid. containing eicosanoic acid.
There were significant differences in adipose tissue fatty acid composition between men and women (Table 1). While saturated fatty acids were lower in women, monounsaturated and polyunsaturated fatty acids were higher. The magnitude of these differences varied. For the major constituents (e.g. oleic acid) the magnitude of the difference (1.4%) between men and women was small when compared to the amount of the fatty acid in the adipose tissue (51% of total fatty acids). However, for the trace constituents (e.g. dihomoy-linolenic acid, 0.1% of total fatty acids) the relative magnitude of the difference between the proportions in men and women was greater (the amount in women was 50% higher than that in men). The mean proportion of the essential fatty acid linoleic acid, was higher in women. The ratio of polyunsaturated to saturated fatty acids (P/S ratio) was also significantly higher in women.
The effect of age on adipose tissue fatty acid composition in men is shown in Table 2a. While age had no effect on most fatty acids, the proportions of linoleic acid and that of y-linolenic plus eicosanoic acid decreased in the older age groups. There were small increases in the proportions of the two long chain polyunsaturated fatty acids; docosapentaenoic and docosahexaenoic acids. The overall effect was a decrease in the total of polyunsaturated fatty acids with increasing age which was reflected by a decrease in the P/S ratio. In women, there were significant changes in the proportions of most of the fatty acids with age (Table 2b). The proportions of the saturated fatty acids decreased with increasing age. For the monounsaturated fatty acids, age had a varied effect on the individual fatty acids although when grouped together, there was a significant increase in the older age groups. Varied effects of age were also seen with the
164 TABLE 2a EFFECT OF AGE ON ADIPOSE TISSUE FATTY ACID COMPOSITION IN MEN Fatty acid
Mean % (S.D.)/age
Significance”
n = 529
45-49 n = 508
50-54 n = 593
n =
Saturated Myristic Palmitic Stearic
26.73 2.28 20.81 3.65
26.96 2.34 21.01 3.61
(3.25) (0.74) (2.08) (1.04)
27.04 (3.29) 2.36 (0.78) 21.00 (2.13) 3.67 (1.05)
27.19 (3.37) 2.37 (0.76) 21.13 (2.18) 3.70 (1.05)
Monounsaturated Palmitoleic Oleic Eicosenoic
62.62 (3.85) 8.79 (1.90) 50.71 (2.58) 3.13 (0.60)
62.62 (3.96) 8.93 (1.89) 50.50 (2.77) 3.19 (0.55)
62.59 (4.01) 8.92 (1.99) 50.52 (2.72) 3.15 (0.62)
62.48 (4.14) 8.89 (1.97) 50.47 (2.79) 3.11 (0.63)
Polyunsaturated Linoleic 7-Linolenic
10.46 (2.49) 9.07 (2.40) 0.24 (0.21)
10.25 (2.89) 8.85 (2.83) 0.21 (0.10)
10.22 (2.90) 8.84 (2.83) 0.21 (0.10)
10.16 (2.94) 8.78 (2.88) 0.20 (0.10)
40-44
Dihomo-y-linolenic Arachidonic Docosapentaenoic Docosahexaenoic
0.10 0.64 0.25 0.18
P/S Ratio ‘Using Kruskal-Wallis test: *P
(3.14) (0.69) (1.98) (1.06)
(0.05) (0.16) (0.08) (0.09)
0.40 (0.11) c
0.10 0.65 0.25 0.19
(0.04) (0.16) (0.07) (0.08)
0.39 (0.13)
0.10 0.64 0.26 0.19
(0.05) (0.17) (0.08) (0.08)
0.39 (0.13)
55-59 555
0.10 0.63 0.26 0.19
(0.05) (0.16) (0.08) (0.07)
0.38 (0.13)
* ** ***
** *** *
0.05, **P < 0.01, ***P < 0.001.
TABLE 2b EFFECT OF AGE ON ADIPOSE TISSUE FATTY ACID COMPOSITION IN WOMEN Fatty acid
Mean u/ (S.D.)/age
Signiticance’
40-44 n = 518
45-49 n = 469
50-54 n = 479
55-59 n = 463
25.24 (3.49)
25.64 (3.49)
25.29 (3.85)
24.83 (3.77)
*
2.27 (0.73) 19.38 (2.17) 3.59 (1.14)
2.28 (0.76) 19.76 (2.34) 3.59 (1.24)
2.30 (0.77) 19.53 (2.43) 3.46 (1.17)
2.25 (0.75) 19.28 (2.42) 3.30 (1.18)
***
Monounsaturated Palmitoleic Oleic Eicosenoic
63.51 9.07 51.30 3.15
(3.84) (1.91) (2.77) (0.54)
63.58 (4.06) 9.27 (1.99) 51.17 (2.87) 3.14 (0.58)
63.71 (4.24) 9.46 (1.99) 51.17 (2.94) 3.08 (0.56)
64.36 (4.13) 9.82 (2.07) 51.50 (2.85) 3.03 (0.53)
Polyunsaturated
11.07(2.50)
10.61 (2.34)
10.82 (2.70)
10.62 (2.66)
Saturated Myristic Pahnitic Stearic
Linoleic y-Linolenic Dihomo-y-linolenic Arachidonic Dccosapentaenoic Docosahexaenoic P/S Ratio
9.74 0.20 0.14 0.59 0.23 0.18
(2.45) (0.09) (0.05) (0.14) (0.08) (0.07)
0.45 (0.14)
9.23 0.18 0. I5 0.61 0.26 0.19
(2.28) (0.09) (0.06) (0.16) (0.08) (0.08)
0.43 (0.13)
‘Using Kruskal-Wallis test: *P < 0.05, **P < 0.01, ***k < 0.001.
9.37 0.17 0.16 0.62 0.29 0.23
(2.62) (0.08) (0.06) (0.14) (0.08) (0.09)
0.44 (0.15)
9.10 0.15 0.17 0.63 0.32 0.25
(2.60) (0.08) (0.06) (0.15) (0.08) (0.10)
0.44 (0.15)
??
* ***
??
** *+* ** *** ?? ** *** *** *** ??
*
165 TABLE 3 REGIONAL VARIATION IN ADIPOSE TISSUE LINOLEIC ACID CONTENT AND SMR FOR CHD District
Mean linoleic acid/sex Women
Men
Eastwood Stirling Edinburgh Aberdeen Banff and Buchan Roxburgh Perth and Kinross East Lothian Dunfermline Kyle and Carrick South Glasgow Dumbarton Kirkcaldy Nithsdale Cunninghame Inverness Hamilton North Glasgow Renfrew Monklands
n
Mean%
(S.D.)
SMRa
?I
Mean%
(S.D.)
SMRa
153 118 87 104 36 54 133 91 145 67 95 100 121 96 116 154‘ 112 190 117 85
10.47 8.85 9.38 8.99 8.85 9.35 9.02 8.16 8.51 9.86 8.52 9.35 8.31 9.19 8.95 9.21 8.44 8.13 8.81 7.70
(3.27) (2.47) (2.53) (2.15) (1.80) (2.71) (2.92) (2.41) (2.80) (3.72) (2.66) (2.40) (2.27) (2.58) (3.03) (2.58) (2.47) (2.58) (2.88) (2.42)
61 79 81 83 83 84 89 91 99 102 103 103 105 109 110 112 116 117 118 136
87 119 98 Ill 41 68 109 79 118 52 78 80 119 107 101 145 96 137 95 68
10.59 9.48 10.06 9.20 9.64 9.31 8.92 9.20 8.72 9.77 8.73 9.68 9.16 9.52 9.68 9.76 9.31 9.01 9.73 8.38
(2.74) (2.64) (2.71) (1.75) (2.44) (2.32) (2.00) (2.01) (2.71) (2.68) (2.16) (2.67) (2.47) (2.41) (2.86) (2.88) (2.43) (2.26) (2.54) (1.95)
50 94 83 72 85 79 81 87 115 98 110 88 112 106 112 91 126 121 109 147
‘Standardised mortality ratio for CHD in age group 35-64 years for 1979-1983.
polyunsaturated fatty acids. The proportion of linoleic acid decreased with increasing age while the longer chain polyunsaturated fatty acids increased with age. The fatty acid composition of adipose tissue varied between districts. In two of the districts (Dundee and Falkirk), a combined total of only 33 acceptable fatty acid analyses were carried out. In the remaining 20 districts, the mean total amount of saturated fatty acids ranged from 25.7% (Dumbarton) to 28.8% (Dunfermline) in men and from 23.3% (Renfrew) to 26.6% (Dunfermline) in women. For mean total monounsaturated fatty acids, Roxburgh had the lowest values for both men (60.4%) and women (61 .l%), while Monklands had the highest values for both men (64.5%) and women (66.1%). The lowest mean total amount of polyunsaturated fatty acids was in Monklands for men (9.2%) and Dunfermline for women (9.8%), while highest mean values were in
Eastwood for both men (12.0%) and women (12.2%). Dunfermline had the lowest P/S ratio for both men (0.34) and women (0.38), while Eastwood had the highest values (0.46 men, 0.47 women). The regional variation in adipose tissue linoleic acid is shown in Table 3. This table also lists the standard&d mortality ratios (SMRs) for CHD for each district. In all except three districts (Perth, Roxburgh and Kyle & Carrick), the mean proportion of linoleic acid was higher in women than in men. For both sexes, Monklands had the lowest mean values and Eastwood had the highest mean values. The Spearman rank correlation coefficients of age-adjusted mean adipose tissue fatty acid composition with the SMR for CHD for each district are listed in Table 4. In men, there were significant positive correlations between oleic acid, palmitoleic acid and total monounsaturated fatty acids
166 TABLE 4 RANK CORRELATION COEFFICIENTS BETWEEN AGE ADJUSTED DISTRICT MEAN ADIPOSE TISSUE FATTY ACID COMPOSITION AND DISTRICT SMR FOR CHD Fatty acid
Rank correlation coeff:cient/sex Men
Women
Saturated Myristic Palmitic Stearic
-0.12 -0.28 -0.02 -0.18
-0.39* -0.42* -0.31 -0.38
Monounsaturated Palmitoleic Oleic Eicosenoic
0.56* 0.50’ 0.59* -0.05
0.16* 0.51’ 0.73. -0.19
Polyunsaturated Linoleic y-Linolenic Dihomoy-linolenic Arachidonic Docosapentaenoic Docosahexaenoic
-0.58* -0.60* -0.02 0.04 0.02 -0.06 -0.20
-0.56* -0.62’ -0.31 0.06 0.20 -0.01 -0.18
P/S Ratio
-0.432
-0.20
?? P < 0.05.
CHD whilst adipose tissue linoleic acid, total polyunsaturated fatty acids and the P/S ratio were negatively correlated with CHD. Similar results were seen in women with the addition that myristic acid and saturated fatty acids correlated negatively with CHD. The relationships between district SMR for CHD and district mean value for both oleic and linoleic acid in each sex are shown in Figs. 1 and 2.
with
Discussion With over 4000 acceptable fatty acid analyses, the results reported here comprise the largest study of adipose tissue fatty acids in Scotland. The study would have been even larger if the number of successful biopsies could have been increased. A contributing factor to the low success rate was that initially 2 mm diameter punches were used and most of the biopsies taken with this diameter
punch contained no adipose tissue. Since the 3 mm punch produced enough adipose tissue in approximately 80% of the biopsies obtained, this method remains useful for large epidemiological studies due to the low cost, speed and simplicity of the method. For smaller studies where it is imperative to obtain a sample of adipose tissue, a more invasive technique should be used. In this study, since the sub-population from which acceptable biopsies were obtained was similar in age, BMI and social class to the whole study population, the data obtained are probably a true representation of the Scottish population. The fatty acid composition of adipose tissue has been shown to vary with the sample site chosen [3,11]. In previous studies of human adipose tissue fatty acid composition, specimens of subcutaneous adipose tissue have been obtained from the abdomen or buttock. The relationship of the fatty acid composition of subcutaneous adipose tissue from the upper arm with that from other sites is unknown. The fatty acid composition of adipose tissue in Scottish men has been reported previously [4,5,10]. For the saturated fatty acids, the results from this study are lower than previous reports and those for the monounsaturated fatty acids are higher. In our results, the chromatographic peak containing the co-eluting methyl esters of CXlinolenic and eicosenoic acids has been included in the total of monounsaturated fatty acids. Schafer et al. [12] have reported that human adipose tissue contains approximately three times the amount of eicosenoic acid as ar-linolenic acid. Although this may contribute to the higher total of monounsaturated fatty acids reported here, when the other individual fatty acids (palmitoleic, oleic) are compared, the results are also higher than previous reports. For the polyunsaturated fatty acids, our results are similar to the previous studies of Scottish men. In addition, at 0.39 the P/S ratio is very similar to the value of 0.37 reported by Wood et al. [5]. Analysis of the dietary questionnaire data from the SHHS revealed P/S ratios of 0.28-0.32 in dietary intake [ 131. There are no reports of adipose tissue fatty acid composition in Scottish women. For saturated fatty acids, the values reported here are similar to those found in both Danish [12] and Dutch [ 141
167
0
lLO-
a
CHD
.
SMR 120-
.
.
loo-
.
*.
.
.
.
..
.
.
.
.
"
80-
.
. r.0.57
.
60-t L8
LQ
50 %
f 52
51
Oleic acid
0b
. .
.
? ? ? ? ?? ? ? .
. -
.
. .
8
.
. ??? ? ? ? rz0.67
. LO',
LB
LQ
50
51 %
52
53
, 5L
Oleic acid
Fig. 1. (a) Relationship between district mean standard&d mortality ratio (SMR) for coronary heart disease (CHD) and district mean proportion of oleic acid in adipose tissue in men. (b) Relationship between district mean SMR for CHD and district mean proportion of oleic acid in women.
women, while our results for monounsaturated fatty acids are higher and those for polyunsaturated fatty acids lower. In this study, the fatty acid composition of adipose tissue was found to be significantly different in men and women. The pattern of lower saturated and higher monounsaturated and polyunsaturated fatty acids in women was also reported by van Staveren et al. [14]. In this study no difference in linoleic acid intake was found be-
tween men and women [ 151. In men, low levels of adipose tissue linoleic and dihomo-y-linolenic acids have been associated with increased occurrence of CHD [lo]. It is possible that the higher proportions found in women may contribute to their lower rates of disease. Age was shown to have significant effects on adipose tissue fatty acid composition, particularly in women. A decrease in saturated fatty acids and an increase in monounsaturated fatty acids with
168
0a
.
.
.
.
?? ??
??
? ?
? ?
? ?
? ?
.
. ??
.
e
.
. rn -0.52
.
60’r 7
9
0 % Linoleic
f 11
10
acid
160-
0b
.
CHD SMR 120-
.
. . .
.
.
..
. . 80-
.
.*
.
. . .
.
r = -0.u
. 10
i
% Linoleic
11
acid
Fig. 2. (a) Relationship between district mean SMR for CHD and district mean prdportion of linoleic acid in men. (b) Relationship between district mean SMR for CHD and district mean proportion of linoleic acid in women.
increasing age, was also reported by Schafer et al. [12]. The effects of age are difficult to interpret since changes in adipose tissue fatty acid composition may be a result of changing diet and/or a change in the metabolism and storage of the fatty acids. The finding that adipose tissue fatty acid composition shows a greater change with age in women than in men is interesting in that other CHD risk factors (e.g., serum cholesterol) also show a larger age effect in women. In the results reported here, adipose tissue
linoleic acid was shown to vary throughout Scotland and there was a significant negative correlation between the district mean linoleic acid content and the district SMR for CHD in both sexes. This finding supports the hypothesis that low amounts of adipose tissue linoleic acid are associated with increased rates of CHD. In addition, for both sexes there was a significant correlation between the district mean oleic acid content and the district SMR for CHD and the magnitude of the correlation coefficients was greater than
169
that with linoleic acid. The underlying mechanism for this finding is unclear. The oleic acid content of adipose tissue has been found to be inversely related to the amount of linoleic acid in the diet (21. Thus, a low intake of dietary linoleic acid may contribute to both higher proportions of adipose tissue oleic acid and an increased occurrence of CHD. In summary, this study has reported the fatty acid composition of adipose tissue in a large sample of Scottish men and women and has described the effects of age, sex and geographical variation. The correlation of district rates of CHD with mean district values for oleic and linoleic acid has been demonstrated. The relationship of adipose tissue fatty acid composition with the other risk factors for CHD is currently being investigated and will be reported later. Acknowledgements We thank John Bruce, Susan Sharpe, Marion Milne and Michele Leslie for their technical help. This study was funded by the Scottish Home and Health Department with additional support from the Independent Scientific Committee on Smoking and Health, the Chest, Heart and Stroke Association and the British Heart Foundation. The opinions expressed here are those of the authors. References Sinclair, H.M., Deficiency of essential fatty acids and atherosclerosis, et cetera, Lancet. i (1956) 381. Field, C.J.. Angel. A. and Clandinin. M.T., Relationship of diet to the fatty acid composition of human adipose structural and stored lipids, Am. J. Clin. Nutr.. 42 (1985) 1206. Schafer, L. and Overvad. K.. Subcutaneous adipose-tissue fatty acids and vitamin E in humans: relation to diet and sampling site, Am. J. Clin. Nutr.. 52 (1990) 486. Riemersma, R.A., Wood, D.A., Butler, S., Elton, R.A., Oliver, M., Sale, M. et al., Linoleic acid content in
adipose tissue and coronary heart disease, Br. Med. J., 292 (1986) 1423. 5 Wood, D.A., Riemersma, R.A., Butler, S., Thomson, M., Macintyre, C., Elton, R.A. et al., Linoleic acid and eicosapentaenoic acids in adipose tissue and platelets and risk of coronary heart disease, Lancet, i (1987) 177. 6 Smith, W.C.S., Crombie, I.K., Tavendale, R., Irving, J.M., Kenicer, M.B. and Tunstall-Pedoe., H., The Scottish Heart Health Study: objectives and development of methods, Health Bull., 45 (1987) 211. 7 Smith, W.C.S., Tunstall-Pedoe, H., Crombie, I.K. and Tavendale, R., Concomitants of excess coronary deaths: Major risk factor and lifestyle findings from 10,359 men and women in the Scottish Heart Health Study, Scot. Med. J., 34 (1989) 550. 8 Tunstall-Pedoe, H., Smith, W.C.S., Crombie, I.K. and Tavendale, R., Coronary risk factor and lifestyle variation across Scotland: Results from the Scottish Heart Health Study, Scot. Med. J., 34 (1989) 556. 9 Smith, W.C.S. Tavendale, R. and Tunstall-Pedoe, H., Simplified subcutaneous fat biopsy for nutritional surveys, Hum. Nutr.: Clin. Nutr., 4Oc (1986) 323. IO Wood, D.A., Butler, S., Riemersma, R.A., Thomson, M., Oliver, M.F., F&on, M., et al. Adipose tissue and platelet fatty acids and coronary heart disease in Scottish men, Lancet, ii (1984) 117. II Malcolm, G.T.. Bhattacharyya, A.K., Velez-Duran, M., Guzman, M.A., Oalmann, M.C. and Strong, J.P., Fatty acid composition of adipose tissue in humans: differences between subcutaneous sites, Am. J. Clin. Nutr.. 50 (1989) 288. I2 Schafer, L., Overvad, K., Thorling, E.B. and Velander, G., Adipose tissue levels of fatty acids and tocopherol in young men and old women, Ann. Nutr. Metab., 33 (1989) 315. 13 Bolton-Smith, C., Smith, W.C.S., Woodward, M. and Tunstall-Pedoe, H., Nutrient intakes of different social class groups: Results from the Scottish Heart Health Study (SHHS), Br. J. Nutr., 65 (1991) 321. 14 Van Staveren. W., Deurenberg, P., Katan, M.B., Burema, J.. De Groat. L.C.P.G.M. and Hoffmans. M.D.A.F.. Validity of the fatty acid composition of subcutaneous fat tissue microbiopsies as an estimate of the long-term average fatty acid composition of the diet of separate individuals, Am. J. Epidemiol.. 123 (1986) 455. I5 Bolton-Smith, C., Woodward, M. and Tunstall-Pedoe, H., Smoking, and correlations between dietary fat and adipose tissue linoleate (Cl8:2) using a food frequency questionnaire (FFQ), Proc. Nutr. Sot., I5 (1992) in press.
