Effect of sampling site on fatty acid composition of human breast adipose tissue

The effect of sampling site and proximity of malignant tumor on the relative fatty acid composition of human breast adipose tissue was studied in 10 cases of breast cancer. The four anatomic quadrants of breast did not statistically significantly differ from each other in relation to any of the 30 fatty acids studied. Proximity of the malignant tumor did not affect the relative fatty acid composition of fat when compared with more distant sampling sites. Representative samples of breast adipose tissue for fatty acid composition analysis can be obtained from tissue adjacent to the tumor.     

Tocotrienol levels in adipose tissue of benign and malignant breast lumps in patients in Malaysia

Data on dietary exposure to vitamin E by plasma or adipose tissue concentrations of alpha-tocopherol (alpha-T) in observational studies have failed to provide consistent support for the idea that alpha-T provides women with any protection from breast cancer. In contrast, studies indicate that alpha, gamma, and delta-tocotrienols but not alpha-T have potent anti-proliferative effects in human breast cancer cells. Our aim was to investigate whether there was a difference in tocopherol and tocotrienol concentrations in malignant and benign adipose tissue, in a Malaysian population consuming predominantly a palm oil diet. The study was undertaken using fatty acid levels in breast adipose tissue as a biomarker of qualitative dietary intake of fatty acids. The major fatty acids in breast adipose tissue of patients (benign and malignant) were oleic acid (45-46%), palmitic (28-29%) and linoleic (11-12%). No differences were evident in the fatty acid composition of the two groups. There was a significant difference (p=0.006) in the total tocotrienol levels between malignant (13.7 +/- 6.0 microg/g) and benign (20+/-6.0 microg/g) adipose tissue samples. However, no significant differences were seen in the total tocopherol levels (p=0.42) in the two groups. The study reveals that dietary intake influences adipose tissue fatty acid levels and that adipose tissue is a dynamic reservoir of fat soluble nutrients. The higher adipose tissue concentrations of tocotrienols in benign patients provide support for the idea that tocotrienols may provide protection against breast cancer.     

Polyunsaturated fatty acids and conjugated linoleic acid isomers in breast milk are associated with plasma non-esterified and erythrocyte membrane fatty acid composition in lactating women

Maternal adipose tissue is a major contributor to breast milk long-chain fatty acids, probably through the pool of plasma NEFA. The fatty acid composition of the erythrocyte membrane (EM) is a biochemical index of the intake of fatty acids not synthesized endogenously and of PUFA and long-chain PUFA fatty acid status. The present study investigated the associations between breast milk fatty acid composition and the composition of plasma NEFA and of EM fatty acids with special reference to PUFA, long-chain PUFA and conjugated linoleic acid (CLA). The detailed fatty acid composition of mature breast milk was also reported. Thirty-three healthy, lactating Brazilian women donated milk samples; of these, twenty-four also donated blood samples in an observational cross-sectional study. Breast milk fatty acid composition presented several associations with NEFA and EM composition, which explained most (> or =50 %) of the variability of selected milk PUFA, long-chain PUFA and CLA. Milk CLA was associated with fatty acids that are markers of dairy fat intake in the diet, NEFA and EM. In general, breast milk n-3 fatty acids and CLA, but not n-6 fatty acids, were associated with EM composition, whereas both the n-6 and n-3 fatty acids and CLA in milk were associated with NEFA composition, possibly owing to its role as a direct source of fatty acids for breast milk. These findings emphasize the contribution of the NEFA pool derived from the adipose tissue to the long-chain fatty acid composition of breast milk.     

Subcutaneous adipose-tissue fatty acids and vitamin E in humans: relation to diet and sampling site

The influence of diet and sampling site on subcutaneous adipose-tissue fatty acid composition and vitamin E content was examined in 20 healthy subjects. A dietary history and adipose-tissue biopsies from the buttock were obtained from 14 individuals. In another six individuals, samples were taken from both waist and buttock. The relative dietary intake of both polyunsaturated and saturated fatty acids correlated with the relative content in adipose tissue (r = 0.6, p = 0.02). Adipose-tissue vitamin E was strongly associated with dietary intake (r = 0.76, p = 0.004). The content of n - 3 (omega-3) fatty acids in adipose tissue was shown to influence adipose-tissue vitamin E negatively. Waist and buttock fat differed (p less than 0.05) with regard to fatty acid composition whereas no systematic variation was seen in the vitamin E content. The use of adipose-tissue biopsies in epidemiologic studies as measures of the habitual relative intake of fatty acids and vitamin E is suggested.     

Effect of dietary tung oil on the growth and lipid metabolism of laying hens

The influence of dietary tung oil, containing a high level of alpha-eleostearic acid (cis-9, trans-11, trans-13-octadecatrienoic acid, EA) on growth, egg production, and lipid and fatty acid compositions in tissues and egg yolks of laying hens was studied in White Leghorn hens. Forty-week-old hens were divided into three groups of eight birds each and fed diets containing 0, 0.5, or 1.0% tung oil for 6 wk. The average body weight, feed consumption, rate of egg production, and weights of eggs and yolks were not affected. The weight of adipose tissue was remarkably small in hens fed tung oil, whereas the yolk lipid content did not change. Triglyceride level in heart and adipose tissue decreased in hens fed tung oil, and the level of linolenic acid (C18:3) in all tissues was decreased. Alpha-EA was not almost deposited in the tissues and egg yolk of hens fed tung oil, but conjugated linoleic acid (CLA) was detected in all tissues and egg yolks. The level of CLA in the tissues was significantly higher with increased dietary tung oil. The order of CLA level in tissue lipids was adipose tissue>liver>heart>breast muscle. Especially, the level of CLA in the lipids of adipose tissue and egg yolks of hens fed 1.0% tung oil was 2.0% of the total fatty acid. These results supposed that dietary tung oil affected the lipid metabolism of laying hens and could modify the lipid and fatty acid composition in tissues and eggs.     

Uptake of individual fatty acids into adipose tissue in relation to their presence in the diet

BACKGROUND: The fatty acid composition of adipose tissue triacylglycerol reflects, but is not identical to, the fatty acid composition of the habitual diet. OBJECTIVE: We investigated whether the fatty acid composition of adipose tissue is explained by differences between fatty acids in early storage in adipose tissue after a meal. DESIGN: Nine healthy men ate a meal containing several fatty acids. Blood samples were taken for 6 h after the meal from an arterialized hand vein and a vein draining the anterior abdominal subcutaneous adipose tissue. RESULTS: Net storage of fatty acids in adipose tissue occurred between 1 and 4 h after the meal. In relation to the amount fed, storage of fatty acids differed (P < 0. 01) between classes (n-3 polyunsaturated < saturated < n-6 polyunsaturated < monounsaturated); oleic acid was stored in the greatest amounts. These differences agreed closely with published data, except for n-3 polyunsaturated fatty acids. The only individual metabolic step at which significant differences between fatty acids was shown was incorporation of fatty acids into chylomicron triacylglycerol. Differences between fatty acids in rate of extraction from chylomicron triacylglycerol and net uptake into adipose tissue in the postprandial period were significant (P < 0. 01), but not when expressed in relation to proportions in chylomicron triacylglycerol. CONCLUSIONS: The characteristic fatty acid pattern of adipose tissue may predominantly reflect the early metabolic handling of different fatty acids. Adipose tissue uptake of n-3 polyunsaturated fatty acids is slow in relation to that of other fatty acids.     

Site-specific differences in the fatty acid composition of abdominal adipose tissue in an obese population from a Mediterranean area: relation with dietary fatty acids, plasma lipid profile, serum insulin, and central obesity.

BACKGROUND: Abdominal obesity is associated with coronary risk, although causality is not well established. OBJECTIVE: In an obese Mediterranean population, we measured the fatty acid composition of adipose tissue, its relation with dietary fatty acids and central fat deposition, and its influence on plasma lipids and insulin. DESIGN: Adipose tissue samples were obtained from 84 obese patients (29 men, 55 women) aged 30-70 y (body mass index, in kg/m(2): 27-35). We measured concentrations of insulin and lipids in plasma and fatty acids in subcutaneous, omental, and perivisceral fat. Dietary fatty acid intake was assessed with a 7-d diet record. RESULTS: The population studied was normolipidemic and normoinsulinemic. There were important differences in fatty acid composition between tissue sites: saturated fatty acids were higher and monounsaturated fatty acids were lower in perivisceral than in subcutaneous fat (P < 0.05). Significant correlations were found for oleic, linoleic, alpha-linolenic, and total n-6 polyunsaturated fatty acids between the subject's habitual diet and adipose tissue composition. Oleic and n-3 fatty acids from adipose regions were negatively correlated with apolipoprotein B and triacylglycerols; adipose tissue 22:1n-9, 20:2n-6, stearic acid, and eicosapentaenoic acid were positively correlated with HDL and apolipoprotein A; and adipose tissue myristic acid was negatively correlated with apolipoprotein A (P < 0.05). Central obesity was positively associated with n-6 polyunsaturated fatty acids and inversely associated with monounsaturated fatty acids and n-3 polyunsaturated fatty acids in adipose tissue (P < 0.05). CONCLUSION: The differences found in the composition and metabolism of perivisceral, omental, and subcutaneous fats may indicate that their atherogenic capacities also differ.     

Absence of the biochemical symptoms of essential fatty acid deficiency in surgical patients undergoing protein sparing therapy.

The biochemical symptoms of essential fatty acid deficiency appear within 7 to 10 days of fat-free total parenteral nutrition using glucose-amino acid mixtures. The linoleic acid (C18:2W6) content of all plasma lipid fractions decreases greatly and plasma eicosatrienoic acid (C20:3W9) increases. We have measured the fatty acid composition of the plasma lipid fractions in six surgical patients receiving parenteral nutritional solutions containing only amino acids, and completely free of glucose, before and after 10 to 14 days of such therapy. Biochemical symptoms of essential fatty acid deficiency did not occur. The fatty acid composition of all plasma lipid fractions remained unchanged after this time period. Mobilization of linoleic acid from the adipose tissue occurred with this treatment in contrast to the inhibition of lipolysis of adipose tissue triglyceride produced by continuous infusions of hypertonic glucose-amino acid mixtures.     

Adipose tissue fatty acid composition and its relations to diet and plasma lipid concentrations in hemodialysis patients

Adipose tissue fatty acid composition, serum lipid profile, and dietary intake of 37 patients on maintenance hemodialysis were studied. In August 1982, 1984, and 1986, analyses were carried out in 15 normotriglyceridemic (NTG) and 22 hypertriglyceridemic (HTG; type IV hyperlipidemia) patients. No correlations were found between dietary intake of polyunsaturated fatty acids (PUFAs), ratio of polyunsaturated to saturated fatty acids (P-S ratio), and carbohydrate content on the one hand and serum lipid concentrations on the other in the two groups. Adipose tissue linolenic acid correlated negatively with serum cholesterol in both groups. Strong correlations were found between dietary intake of PUFAs and adipose tissue linoleic acid content, between PUFAs and the double-bond index, between P-S ratio and adipose tissue linoleic acid content, and between P-S ratio and the double-bond index. No significant differences in dietary intake or adipose tissue fatty acid composition were observed between NTG and HTG patients. Thus, no evidence was found for exogenous dietary influences on serum lipid concentrations. The adipose tissue linoleic acid content did reflect the dietary intake of PUFAs.     

Conjugated linoleic acid content in breast adipose tissue of breast cancer patients and the risk of metastasis

The association between the level of conjugated linoleic acid (CLA) in breast adipose tissue at the time of diagnosis and the subsequent development of metastasis was examined in a cohort of 209 patients presenting with an initially localized breast cancer. CLA level in breast adipose tissue was used as a qualitative biomarker of its past dietary intake. Biopsies of adipose tissue were obtained at the time of initial surgery. A CLA-enriched fraction was prepared by high performance liquid chromatography and CLA measured as a percentage of total fatty acids, using capillary gas chromatography. Mean CLA level was low (0.44% of total fatty acids) and the range between patients was narrow (0.19-0.85). With a median follow-up time of 7.5 yr, 45 patients developed metastases. A Cox proportional hazard regression model was used to identify prognostic factors. We did not find any significant association between CLA level in adipose fat and either the prognostic factor (tumor size, nodal status, histoprognostic grade, mitotic index, and estrogen or progesterone receptors) or the risk of metastasis or death. We concluded that CLA are unlikely to be involved in survivorship. However, the hypothesis that a higher intake of CLA might have a protective effect on the risk of metastasis cannot be ruled out from these data, since the level of CLA in breast cancer patients' adipose tissue is likely to be too low and the range of CLA distribution too narrow for any protection to be detectable.     

Influence of sampling on fatty acid composition of human milk

To study effects of sampling on the fat and fatty acid composition of human milk, three subjects each obtained four complete expressions of milk in sequential fractions from each breast. Two subjects collected partial expressions of about 5 ml of milk from each breast frequently over a 2-mont period. Milk samples were analyzed gravimetrically for fat and by gas chromatography for the fatty acids 10:0, 12:0, 14:0, 14:1, 16:0, 16:1, 18:0, 18:1, and 18:2. While hindmilk contained a higher percentage of fat than foremilk, fatty acid composition of the milk fat did not vary throughout a nursing. Fatty acid composition from pairs of left and right breast samples collected at the same nursing did not differ. Therefore, fatty acid analyses of human milk will be representative of the entire nursing if the sample is taken from either breast at any time during the nursing.     

Fatty acid composition of human adipose tissue from two anatomical sites in a biracial community.

This report describes the age-race specific distribution of fatty acids in samples of adipose tissue taken from both the perirenal and buttock areas of 406 men autopsied in a community pathology study. This analysis of fatty acid composition of adipose tissue is part of a comprehensive investigation of atherosclerosis and coronary heart disease in a community setting. The findings from analysis of fatty acids are expressed as mass percentage of all fatty acids in adipose tissue triglyceride. For each age-site subgroup, white men tended to have higher mean percentages of myristic acid and palmitoleic acid than did black men. The converse was found for stearic acid. In the younger age groups only, the whites showed a higher mean percentage of linoleic acid than the blacks in adipose tissue from both sites. Age was associated with a decrease in mean percentage of stearic acid and an increase in mean percentage of oleic acid and palmitoleic acid in both races. The older age group had a lower mean percentage of linoleic acid than the younger age groups. The mean percentages of myristic, palmitic, and stearic acids were higher in perirenal tissue, while the mean percentages of palmitoleic and oleic acids were higher in buttock adipose tissue in both races.     

Adipose Fat Quality vs Quantity: Relationships with Children''s Serum Lipid Levels

BACKGROUND: There is a controversy as to the relative importance of obesity vs quality of dietary fat in the prediction of serum lipoproteins in children. A reason for this is an apparent lack of studies implementing biomarkers of long-term dietary fat intake among children. The objective of the present study was to assess the relative contribution of degree of obesity, fat centrality, and quality of adipose tissue fat in the prediction of serum lipids in 12-year-old children. METHODS: Pupils came from 40 schools randomly selected among 541 primary schools in three different provinces of the island of Crete. One thousand forty-six pupils were examined at age 6. At age 9, a representative sample from the original cohort (n = 579) was randomly selected for reevaluation. At the age of 12, a representative sample of 831 pupils was reexamined. At ages 6, 9, and 12, serum lipid measures were obtained from 941, 458, and 791 children, respectively. At age 12, data were obtained on pupils' anthropometry, serum lipids, dietary intake, physical fitness, and physical activity. Adipose tissue fatty acid data were obtained from a subsample of 194 children at age 12. RESULTS: Regression analyses indicated that children's serum triglycerides related positively to body mass index and waist-hip ratio (WHR). Serum HDL-C related negatively to WHR and positively to endurance run test, an index of physical fitness. Dietary fatty acids, assessed by a single administration of 3-day weighed-food records, did not relate to serum lipids. However, serum HDL-C related negatively to sum of adipose polyunsaturated fatty acids, a measure of long-term polyunsaturated fat intake. CONCLUSIONS: It appears that obesity and fat centrality are stronger predictors of children's serum lipids than the quality of long-term dietary fat intake or adipose tissue fatty acid composition. It is possible that this finding may relate to the particular subcutaneous depot studied. It is suggested that future studies study abdominal rather than buttock adipose tissue fatty acid composition in relation to children's serum lipid levels.     

Docosahexaenoic acid (DHA) at the sn-2 position of triacylglycerols increases DHA incorporation in brown,but not in white adipose tissue,of hamsters

We hypothesised that the incorporation of docosahexaenoic acid (DHA) across adipose tissues will be higher when it is ingested as triacylglycerols (TAG) structured at the sn-2 position. Ten-week old male hamsters were allocated to 4 dietary treatments (n?=?10): linseed oil (LSO-control group), fish oil (FO), fish oil ethyl esters (FO-EE) and structured DHA at the sn-2 position of TAG (DHA-SL) during 12?weeks. In opposition to the large variations found for fatty acid composition in retroperitoneal white adipose tissue (WAT), brown adipose tissue (BAT) was less responsive to diets. DHA was not found in subcutaneous and retroperitoneal WAT depots but it was successfully incorporated in BAT reaching the highest percentage in DHA-SL. The PCA on plasma hormones (insulin, leptin, adiponectin) and fatty acids discriminated BAT from WATs pointing towards an individual signature on fatty acid deposition, but did not allow for full discrimination of dietary treatments within each adipose tissue.     

Relationship of diet to the fatty acid composition of human adipose tissue structural and stored lipids

The habitual intake of 20 healthy free-living subjects was determined by two 7-day food records. Documented fatty acid intakes were utilized to examine the influence of fatty acid intake on fatty acid composition of stored and structural lipids in subcutaneous adipose tissue. Subjects with higher intakes of saturated fatty acids exhibited increased levels of total saturated fatty acids and decreased polyunsaturated fatty acids in adipose tissue triglycerides (p less than 0.01). The dietary P/S ratio was significantly related to the saturated and polyunsaturated content of stored lipids. In the phospholipid fraction, relationships were found between dietary C18:2(6) and the P/S ratio of phosphatidylcholine (p less than 0.05). The essential fatty acid content of the two phospholipids studied was related to the dietary fats consumed. Relationships were identified between major fatty acids in the triglyceride and phospholipid fraction. Although diet was found to relate to fatty acid composition, the structural lipids in human adipose tissue appear more resistant to compositional change than stored triglycerides.     

Long-chain n-3-to-n-6 polyunsaturated fatty acid ratios in breast adipose tissue from women with and without breast cancer

Animal studies suggest that dietary polyunsaturated fatty acids (PUFAs) of the n-6 class, found in corn and safflower oils, may be precursors of intermediates involved in the development of mammary tumors, whereas long-chain (LC) n-3 PUFAs, found in fish oil, can inhibit these effects. This case-control study was designed to examine the relationship between the PUFA composition of breast adipose tissue and the risk of breast cancer. Using fatty acid levels in breast adipose tissue as a biomarker of past qualitative dietary intake of fatty acids, we examined the hypothesis that breast cancer risk is negatively associated with specific LC n-3 PUFAs (eicosapentaenoic acid and docosahexaenoic acid) and positively associated with n-6 PUFAs (linoleic acid and arachidonic acid). Breast adipose tissue was collected from 73 breast cancer patients and 74 controls with macromastia. The fatty acid levels were determined by gas-liquid chromatography. A logistic regression model was used to obtain odds ratio estimates while adjusting for age. The age-adjusted n-6 PUFA (linoleic acid and arachidonic acid) content was significantly higher in cases than in controls (P = 0.02). There was a trend in the age-adjusted data suggesting that, at a given level of n-6 PUFA, LC n-3 PUFAs (eicosapentaenoic acid and docosahexaenoic acid) may have a protective effect (P = 0.06). A similar inverse relationship was observed with LC n-3-to-n-6 ratio when the data were adjusted for age (P = 0.09). We conclude that total n-6 PUFAs may be contributing to the high risk of breast cancer in the United States and that LC n-3 PUFAs, derived from fish oils, may have a protective effect.     

不同膳食脂肪酸对大鼠乳腺癌组织脂肪酸组成和脂代谢基因表达的影响

目的探讨不同膳食脂肪酸组成影响大鼠乳腺癌发生、发展的可能分子机制。方法用8种不同膳食脂肪酸组成(SFA、MUFA、n-6PUFA、n-3PUFA、1∶1n-6/n-3、5∶1n-6/n-3、10∶1n-6/n-3、1∶2∶1S/M/P其中n-6/n-31∶1)喂养SD雌性大鼠,并在大鼠乳腺癌模型的基础上,用气相色谱内标法观察大鼠乳腺组织脂肪酸组成改变,RT-PCR分析组织脂代谢调控基因(FAS、COX-2和5-LOX)的表达。结果在不同膳食脂肪酸构成中,只有1∶1n-6/n-3能有效抑制大鼠乳腺癌的发生。不同膳食脂肪酸构成可导致大鼠乳腺组织脂肪酸组成发生相应变化,且各组间的脂肪酸含量有显著差异。高乳腺癌诱发的SFA、MUFA、n-6PUFA、5∶1n-6/n-3、10∶1n-6/n-3和1∶2∶1S/M/P喂养组乳腺组织含有较多的C18∶1、C18∶2和C20∶4,而EPA和DHA含量极少。无或低乳腺癌诱发的n-3PUFA和1∶1n-6/n-3喂养组乳腺组织EPA和DHA明显增多,C20∶4含量显著减少。RT-PCR结果显示1∶1n-6/n-3低诱癌组较相应对喂组上调FAS、COX-2和5-LOXmRNA表达力度明显弱于其它高乳腺癌诱发组。结论不同膳食脂肪酸组成能明显改变大鼠乳腺组织脂肪酸组成,进而影响脂代谢基因FAS、COX-2和5-LOX表达,可能是大鼠乳腺癌发生的分子机制之一。     

Failure to demonstrate an effect of dietary fatty acid composition on body weight, body composition and parameters of lipid metabolism in mature rats

The objectives of the present study were to examine the effects of dietary fatty acid composition on body composition and on several parameters of lipid metabolism in adipose tissue and to assess the ease of weight loss with restricted dietary intake. Rats were fed diets containing 14% fish oil, safflower oil or beef fat plus 2% corn oil. These diets were fed ad libitum for 4 wk (first phase). A number of the animals from each group were killed, and the others were fed 50% of their first-phase food intake for an additional 4 wk (second phase). The diets used in the second phase contained 3% of the above fats plus 2% corn oil. Food consumption, food efficiency and body weights were monitored. After the rats were killed, fatty acid composition of epididymal fat pads was examined. In addition, in vivo lipolysis and in vitro lipogenesis in epididymal fat pads were examined. The results indicate that dietary fatty acid composition had no effect on body weight, food consumption, in vivo lipolysis and in vitro lipogenesis in epididymal fat pads. In addition, although dietary fatty acid manipulation resulted in alteration in adipose tissue fatty acid composition, it had no effect on the rate of weight loss, body composition, in vivo lipolysis and in vitro lipogenesis in epididymal fat pads. It is concluded that dietary fatty acid composition does not play a role in body composition and in lipid metabolism in adipose tissue of mature rats.     

Site differences in the fatty acid composition of subcutaneous adipose tissue of obese women.

1. Adipose tissue samples were obtained by needle biopsy from three subcutaneous sites (thigh, abdomen and upper arm) in twenty-two obese women. The fatty acid composition was determined using gas-liquid chromatography and the results presented relate to eleven component fatty acids. 2. The fatty acid composition of adipose tissue obtained from the arm and abdomen was remarkably similar, with the exception of the levels of lauric acid. 3. The analyses showed that the majority of the saturated fatty acids were present in smaller proportions whilst the majority of unsaturated fatty acids were present in larger proportions in the thigh than in the two other sites. Highly significant inter-site differences were demonstrated for six of the major fatty acids and also for both the total amounts of saturated and unsaturated fatty acids and their ratios. 4. No marked differences in the fatty acid composition of adipose tissue from obese subjects were revealed during this study when compared with previously reported results obtained from 'normal-weight' subjects.     

Modifications induced by dietary lipid source in adipose tissue phospholipid fatty acids and their consequences in lipid mobilization

The aim of the present work was to assess the influence of dietary lipid source on fatty acid phospholipid profiles and on lipid mobilization. Forty male Wistar rats were divided into four groups and fed on high-fat diets which provided olive oil, sunflower oil, palm oil or beef tallow. All rats received the same amount of energy to avoid hyperphagia and differences in energy intake among groups. Phospholipid fatty acids were determined by GC. Lipolysis was stimulated in subcutaneous and perirenal isolated adipocytes by several lipolytic agents, and assessed by the determination of released glycerol. After 4 weeks of feeding, differences in body and adipose tissue weights were not observed. Dietary regimens caused great changes in adipose tissue phospholipid composition: rats fed on palm oil and beef tallow had higher concentrations of saturated fatty acids and animals fed on olive oil or sunflower oil had greater amounts of oleic and linoleic acids, respectively. These modifications did not lead to important changes in adipocyte lipolysis. Significant differences were only observed between palm-oil- and beef-tallow-fed groups when lipolysis was stimulated by isoproterenol in subcutaneous adipocytes. The fact that our feeding protocol did not induce differences in fat accumulation among groups avoids misinterpretations due to adiposity changes. The differences observed between both saturated-fat-fed groups, therefore, should only be attributable to dietary lipids. Despite this effect, the data from this work indicate that some diet-induced changes in adipose tissue fatty acid composition may have little effect on overall function.