Substituting dietary saturated for monounsaturated fat impairs insulin sensitivity in healthy men and women: The KANWU study

Aims/hypothesis. The amount and quality of fat in the diet could be of importance for development of insulin resistance and related metabolic disorders. Our aim was to determine whether a change in dietary fat quality alone could alter insulin action in humans. Methods. The KANWU study included 162 healthy subjects chosen at random to receive a controlled, isoenergetic diet for 3 months containing either a high proportion of saturated (SAFA diet) or monounsaturated (MUFA diet) fatty acids. Within each group there was a second assignment at random to supplements with fish oil (3.6 g n-3 fatty acids/d) or placebo. Results. Insulin sensitivity was significantly impaired on the saturated fatty acid diet (-10 %, p = 0.03) but did not change on the monounsaturated fatty acid diet ( + 2 %, NS) (p = 0.05 for difference between diets). Insulin secretion was not affected. The addition of n-3 fatty acids influenced neither insulin sensitivity nor insulin secretion. The favourable effects of substituting a monounsaturated fatty acid diet for a saturated fatty acid diet on insulin sensitivity were only seen at a total fat intake below median (37E %). Here, insulin sensitivity was 12.5 % lower and 8.8 % higher on the saturated fatty acid diet and monounsaturated fatty acid diet respectively (p = 0.03). Low density lipoprotein cholesterol (LDL) increased on the saturated fatty acid diet ( + 4.1 %, p < 0.01) but decreased on the monounsaturated fatty acid diet (MUFA) (–5.2, p < 0.001), whereas lipoprotein (a) [Lp(a)] increased on a monounsaturated fatty acid diet by 12 % (p < 0.001). Conclusions/interpretation. A change of the proportions of dietary fatty acids, decreasing saturated fatty acid and increasing monounsaturated fatty acid, improves insulin sensitivity but has no effect on insulin secretion. A beneficial impact of the fat quality on insulin sensitivity is not seen in individuals with a high fat intake ( > 37E %). [Diabetologia (2001) 44: 312–319] Received: 21 August 2000 and in revised form: 8 November 2000     

Association between diet, lifestyle, metabolic cardiovascular risk factors, and plasma C-reactive protein levels

Increased C-reactive protein (CRP) levels have been associated with several of the components of the metabolic syndrome, but the direct influence of diet and lifestyle factors on CRP levels remains largely unknown. The purpose of the present study was to investigate the association between CRP and diet and lifestyle factors. Plasma CRP levels were determined by a highly sensitive enzyme-linked immunosorbent assay (ELISA) in 760 participants in the beta-Blocker Cholesterol-Lowering Asymptomatic Plaque Study (BCAPS). In accordance with previous findings, increased levels of CRP were associated with high body mass index (BMI) (P = .012), triglycerides (P = .001), systolic blood pressure (P = .019), cholesterol/high-density lipoprotein (HDL) ratio (P = .009), and low HDL cholesterol (P = .001). CRP was also increased in smokers (P = .023) and in subjects with a low vitamin C intake (P = .018). When men and women were analyzed together, there were no significant associations between CRP and dietary intake of total calories, total fat, saturated fat, monounsaturated fat, polyunsaturated fat, n-3 polyunsaturated fatty acids, n-6 polyunsaturated fatty acids, fiber, vitamin E, carotene, or selen, or in physical activity. However, in the female subgroup weak inverse relations were observed between CRP and the intake of total fat (r = -0.13, P = .011), saturated fat (r = -0.13, P = .011), monounsaturated fat (r = -0.13, P = .010), polyunsaturated fat (r = -0.14, P = .007), and n-3 PUFA (r = -0.14, P = .004). Stratified factor analyses in smoking subgroups, obese, and in under-reporters of energy, largely confirmed the results although in male never-smokers a combination of high fiber vitamin C/beta carotene intake was associated with low CRP levels. These observations suggest that CRP levels are only marginally associated with individual dietary and lifestyle factors. Surprisingly, a higher intake of fat tended to be associated with lower CRP values among women.     

Saturated fat intake and insulin resistance in men with coronary artery disease. The Stanford Coronary Risk Intervention Project Investigators and Staff

BACKGROUND. To determine whether there is an association between diet and plasma insulin concentration that is independent of obesity, we studied the relation of dietary composition and caloric intake to obesity and plasma insulin concentrations in 215 nondiabetic men aged 32-74 years with angiographically proven coronary artery disease. METHODS AND RESULTS. After adjusting for age, the intake of saturated fatty acids and cholesterol were positively correlated (p less than 0.05) with body mass index (r = 0.18, r = 0.16), waist-to-hip circumference ratio (r = 0.21, r = 0.22), and fasting insulin (r = 0.26, r = 0.23). Carbohydrate intake was negatively correlated with body mass index (r = -0.21), waist-to-hip ratio (r = -0.21), and fasting insulin (r = -0.16). Intake of monounsaturated fatty acids did not correlate significantly with body mass index or waist-to-hip circumference ratio but did correlate positively with fasting insulin (r = 0.24). Intake of dietary calories was negatively correlated with body mass index (r = -0.15). In multivariate analysis, intake of saturated fatty acids was significantly related to elevated fasting insulin concentration independently of body mass index. CONCLUSIONS. These cross-sectional findings in nondiabetic men with coronary artery disease suggest that increased consumption of saturated fatty acids is associated independently with higher fasting insulin concentrations.     

Habitual dietary intake versus glucose tolerance, insulin sensitivity and insulin secretion in postmenopausal women.

OBJECTIVE: The major aim was to study the relation between habitual dietary intake and glucose tolerance, insulin sensitivity and insulin secretion in postmenopausal women. Dietary intake was also compared between women with normal (NGT) or impaired glucose tolerance (IGT). DESIGN: Habitual dietary intake was studied using a modified diet history method, from which the energy, carbohydrate, fat and protein intake was calculated. Glucose tolerance was determined as the 2 h glucose value after a 75 g oral glucose tolerance test. Insulin sensitivity was studied with a euglycemic, hyperinsulinaemic clamp, whilst insulin secretion was measured as the acute (2-5 min) response to iv arginine (5 g) at fasting, 14 and >25 mmol L(-1) glucose. SETTING: Clinical research unit at the University Hospital in Malmo, Sweden. Subjects. A total of 74 women (mean+/-SD age 58.7+/-0.4 years). RESULTS: In the entire group, the 2 h glucose level correlated with polyunsaturated fat intake (PUFA, r = 0.41, P < 0.001), and negatively with carbohydrate intake (r = -0.23, P = 0.05). The relation between 2 h glucose and PUFA was independent of body fat content and insulin sensitivity in a multivariate model. Insulin sensitivity correlated with energy intake (r = 0.31, P = 0.007) and PUFA (r = -0.27. P = 0.022). However, these correlations were not significant after adjustment for body fat content in a multivariate model. There were no correlations between insulin secretory variables and habitual dietary intake. Of the 74 women, 60 had NGT and 14 had IGT. The NGT and IGT groups did not differ in intakes of total energy, carbohydrate or protein. The IGT women had higher intake of PUFA (P = 0.003), whilst the total, saturated and monounsaturated fat intake did not differ between the groups. CONCLUSION: Dietary parameters are not independently associated with insulin sensitivity or insulin secretion in postmenopausal women. Furthermore, dietary habits are largely similar in women with NGT and IGT, although subtle differences cannot be excluded due to the small study size. Therefore, habitual intake of total carbohydrate or total fat seems not to be the major determinant of glucose tolerance in nondiabetic Caucasian postmenopausal women.     

Plasma fatty acid composition and incidence of coronary heart disease in middle aged adults: the Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND AND AIM: To prospectively investigate the relation of plasma cholesterol ester (CE) and phospholipid (PL) fatty acid (FA) composition with incidence of coronary heart disease (CHD). METHODS AND RESULTS: 3,591 white participants in the Minneapolis field center of the Atherosclerosis Risk in Communities Study, aged 45-64 years, were studied. Plasma FA composition of CEs and PLs was quantified using gas-liquid chromatography and expressed as percentage of total FAs. Incident CHD was identified during 10.7 years of follow-up. In both CE and PL fractions, the proportions of stearic (18:0) acid, dihomo-gamma-linolenic (20:3n6) acid and total saturated fatty acids (SFAs) were significantly higher while arachidonic (20:4n6) acid and total polyunsaturated fatty acids (PUFAs) were significantly lower among participants who developed incident CHD (n = 282). After adjusting for age, gender, smoking, alcohol drinking, sports activity, and non-FA dietary factors, the incidence of CHD was significantly and positively associated with the proportion of dihomo-gamma-linolenic acid but inversely associated with arachiadonic acid. The multiply-adjusted rate ratios (RRs) of CHD incidence for the highest versus the lowest quintile were 1.31 in CE and 1.44 in PL for dihomo-gamma-linolenic acid (p for trend: 0.05 and 0.017, respectively), 0.59 in CE and 0.65 in PL for arachidonic acid (p: 0.016 and 0.024, respectively). Also significantly and positively associated with incident CHD were PL stearic acid and CE linolenic (18:3n3) acid. Only a borderline significant positive association was observed for total SFAs in CE (multivariate RRs across quintiles: 1.00, 1.15, 1.40, 1.62, 1.32; p = 0.07). Total PUFAs or monounsaturated FA were not independently associated with CHD. CONCLUSIONS: Our study found a weak positive association of SFAs with incident CHD. Our findings also confirm that FA metabolism in the body, such as the activity of delta-5 desaturase, which converts dihomo-gamma-linolenic acid to arachidonic acid, may affect the development of CHD.     

Association of glutathione peroxidase activity with insulin resistance and dietary fat intake during normal pregnancy

Glutathione peroxidase (GPx) is one of the most important antioxidant enzymes in humans. We studied the relationship between erythrocyte GPx activity and fasting serum insulin, plasma glucose, and C-peptide, estimates of insulin resistance from the homeostasis model of assessment as well as dietary fat intake in 408 normotensive nondiabetic pregnant women from Camden, NJ. GPx activity and the metabolic parameters were determined at entry to care (16 wk of pregnancy) and during the third trimester. GPx activity and the levels of insulin resistance increased significantly between entry and the third trimester. Statistically significant associations, all positive, were observed between GPx activity and fasting insulin (beta = 0.009, P < 0.001), glucose (beta = 0.975, P < 0.05), C-peptide (beta = 1.537, P < 0.01), and insulin resistance from the homeostasis model of assessment (beta = 0.209, P < 0.01). Dietary intakes of fat and polyunsaturated fatty acids were positively correlated with GPx activity as well. African Americans had significantly higher GPx activity, dietary fat, and polyunsaturated fatty acid intake than Hispanics and Caucasians. In conclusion, we demonstrated that normal pregnancy is associated with increased GPx activity and insulin resistance. There are ethnic differences in antioxidant response and dietary fat intake. Our findings suggest a potential link among antioxidant defenses, insulin resistance, and dietary fat intake.     

Effects of dietary saturated,monounsaturated and n-3 fatty acids on fasting lipoproteins,LDL size and post-prandial lipid metabolism in healthy subjects

BACKGROUND: The influence of the quality of dietary fat on some aspects of lipid metabolism-i.e. lipoprotein concentrations, post-prandial lipids and LDL size-is not completely understood, especially in healthy individuals. OBJECTIVES: Aim of this study was to evaluate the effects of different types of dietary fat (monounsaturated vs. saturated fatty acids, and n-3 or placebo supplementation) on fasting lipoproteins, LDL size and post-prandial lipids in healthy people. DESIGN: One hundred and sixty-two individuals were randomly assigned to follow two isoenergetic diets, one rich in saturated fatty acids (SFA diet) and the other in monounsaturated fatty acids (MUFA diet). Each group was further randomised to receive supplementation with fish oil (3.6 g/day) or placebo. RESULTS: The type of diet significantly affected LDL cholesterol and triacylglycerol content, which was higher with the SFA diet and lower with the MUFA diet. The changes between the two diets were statistically significant for cholesterol (P<0.01) and triacylglycerol (P<0.03). VLDL cholesterol and triacylglycerol were significantly reduced and LDL cholesterol significantly increased by fish oil supplementation. Plasma triacylglycerol was significantly lower in those taking n-3 fatty acids, also 1 and 3 h after a test-meal. Neither type of diet nor n-3 supplementation affected LDL size. CONCLUSIONS: A moderate substitution of saturated fatty acids with monounsaturated fatty acids has beneficial effects on lipid metabolism also in healthy individuals. A moderate supplementation of long-chain n-3 fatty acids in healthy individuals reduces both fasting and post-prandial triacylglycerol concentrations but increases LDL cholesterol, irrespective of the type of diet.     

Plasma cholesteryl ester fatty acid composition, insulin sensitivity, the menopause and hormone replacement therapy

This study was designed to determine the effect of menopause and hormone replacement therapy (HRT) on plasma cholesteryl ester fatty acid (CEFA) composition and insulin sensitivity and the relationships between these variables in perimenopausal women (aged 40-55 years) including 49 who were premenopausal and 32 who were postmenopausal. Plasma cholesteryl ester proportions of dihomo-gamma-linolenic acid (20:3 n-6) were correlated significantly with insulin sensitivity index (r=-0.319, P=0.005), fasting serum insulin levels (r=0.230, P=0.038), body mass index (r=0.242, P=0.03) and per cent body fat (r=0.329, P=0.003) in perimenopausal women (n=81). Similar associations were observed in premenopausal women. Regression analysis suggested the relationships between 20:3 n-6 proportions and indices of insulin action may be partly mediated by levels of adiposity. In postmenopausal women, 6 months of HRT significantly (P=0.008) increased the ratio of arachidonic acid (20:4 n-6) to linoleic acid (18:2 n-6), which is an indicator of activity in the pathway of 20:4 n-6 synthesis, compared with placebo. These findings suggest that the type of fat in the diet indicated by plasma CEFA composition is linked to adiposity and insulin action. They also suggest that in postmenopausal women, HRT may increase the synthesis of 20:4 n-6, which is the precursor for eicosanoids with important cardiovascular functions.     

n-3多不饱和脂肪酸对高脂诱导胰岛素抵抗大鼠肝脏和骨骼肌胰岛素受体及葡萄糖转运蛋白4的作用

目的探讨n-3脂肪酸对饱和脂肪酸诱导的大鼠胰岛素抵抗(IR)肝脏和骨骼肌胰岛素受体(InsR)及葡萄糖转运蛋白4(GluT-4)的作用。方法45只雄性Wistar大鼠分为对照组、高脂组和n-3脂肪酸组。各组饲养11周后测定有关指标。结果(1)与对照组比较，高脂组大鼠体内脂肪相对含量、空腹血糖(FBG)、血清胰岛素(Ins)、甘油三酯(TG)、胆固醇(TC)、胰岛素抵抗指数(IRI)、肝脏TC和TG含量、肌肉中TG含量均显著升高；而肌肉组织中TC含量无显著改变，高脂组肝脏和肌肉InsR含量、肌肉Glut-4蛋白的相对含量均明显下降。(2)n-3脂肪酸组体内脂肪相对含量、FBG、Ins、TG、TC、IRI、肝脏TC和TG含量、肌肉组织中TG含量较高脂组均明显降低，肝脏InsR含量和肌肉GluT-4较高脂组明显升高。结论适量n-3脂肪酸代替饱和脂肪酸的一部分热量后，可增加IR大鼠肝脏InsR含量和肌肉GluT-4蛋白表达。     

Differential effects of n-3 polyunsaturated fatty acids on metabolic control and vascular reactivity in the type 2 diabetic ob/ob mouse

Diets rich in monounsaturated fatty acids (MUFA) are recommended for individuals with type 2 diabetes mellitus (T2DM). The American Heart Association recommends increasing intakes of n-3 polyunsaturated fatty acids (PUFA) to reduce the risk of vascular disease in high-risk individuals; however, the long-term effects of these bioactive fatty acids on glucose metabolism in insulin resistance are controversial. The present studies were conducted to evaluate the effects of diets rich in both MUFA and alpha linolenic acid (C18:3n-3, ALA), eicosapentaenoic acid (C20:5n-3, EPA), or docosahexaenoic acid (C22:6n-3, DHA), on glycemic control and other parameters related to vascular health in a mouse model of T2DM and insulin resistance. Male ob/ob mice (n = 15 per treatment) were fed 1 of 4 lipid-modified formula diets (LFDs) for 4 weeks: (1) MUFA control, (2) ALA blend, (3) EPA blend, and (4) DHA blend. A portion of a MUFA-rich lipid blend in the control LFD was replaced with 11% to 14% energy as n-3 PUFA. After 4 weeks, plasma glucose response to a standard meal (1.5 g carbohydrate/kg body weight) and insulin challenge (2 U/kg body weight, IP) was assessed, and samples were collected for analysis of glucose, insulin, and lipids. Vascular reactivity of isolated aortic rings was assessed in an identical follow-up study. The results showed that insulin-resistant mice fed an LFD with EPA and/or DHA blends had significantly (P < .05) lower triglycerides and free fatty acids, but insulin sensitivity and fasting plasma glucose were not improved. However, mice fed with the ALA blend had significantly improved insulin sensitivity when compared to those fed with other LFD (P < .05). Animals fed an LFD with n-3 PUFA from marine or plant sources showed significantly improved vascular responses as compared with the MUFA-rich LFD (E(max), P < .05) and ob/ob reference mice consuming chow (E(max) and pEC(50), P < .05). In summary, long-term consumption of LFD with n-3 PUFAs improved blood lipids and vascular function in an animal model of insulin resistance and T2DM; however, only MUFA-rich LFD with ALA also improved both insulin sensitivity and glycemic responses. Further studies of MUFA-rich LFD with ALA with individuals who have T2DM are warranted.     

Associations between the fatty acid content of triglyceride, visceral adipose tissue accumulation, and components of the insulin resistance syndrome

Many factors are involved in the development of the insulin resistance syndrome, such as visceral obesity and the type of dietary fat. The main purpose of this study was to investigate the relationships between fatty acid content of triglyceride (TG), visceral adipose tissue (AT) accumulation, and metabolic components of the insulin resistance syndrome in a group of 97 Caucasian men with a mean age of 45.1 +/- 7.2 years (29 to 63 years). To reach these objectives, Spearman correlations, group comparisons, and stepwise multiple regression analyses were performed. The proportion of palmitic acid (16:0) in the TG fraction was positively associated with plasma fasting insulin (r =.25, P =.03), diastolic (r =.45, P <.001), and systolic (r =.29, P =.003) blood pressure. On the other hand, the proportion of alpha-linolenic acid (18:3n-3) was associated negatively with apolipoprotein (apo) B (r = -.29, P =.005) and positively with low-density lipoprotein (LDL) diameter (r =.29, P =.007), while the proportion of gamma-linolenic acid (18:3n-6) was associated negatively with plasma TG (r = -.33, P =.003), diastolic (r = -.29, P =.01), and systolic (r = -.35, P =.002) blood pressure and plasma fasting insulin (r = -.37, P =.0005) and positively with high-density lipoprotein (HDL)(2)-cholesterol (r =.27, P =.01) and LDL diameter (r =.25, P =.02). Stepwise multiple regression analyses were conducted to determine the contribution of visceral AT, body fat mass, and the fatty acid content of TG to the variance of metabolic variables studied. It was found that visceral AT contributed significantly to the variance in plasma TG (R(2) = 20.7%, P <.0001), apo B (R(2) = 9.0%, P =.007), HDL(2)-cholesterol (R(2) = 17.9%, P <.0001), LDL diameter (R(2) = 4.9%, P =.02), and area under the glucose curve (AUC-glucose) (R(2) = 8.2%, P =.006). On the other hand, body fat mass contributed significantly to the variance in fasting insulin (R(2) = 19.7%, P <.0001) and diastolic (R(2) = 6.8%, P =.007) and systolic (R(2) = 10.5%, P =.01) blood pressure. At least one fatty acid made a significant contribution to the variance of each metabolic variable studied. In fact, the proportion of 18:3n-6 contributed significantly to the variance in both TG (R(2) = 8.9%, P = 0.007) and HDL(2)-cholesterol (R(2) = 6.0%, P =.01). Moreover, 18:3n-3 contributed to the variance of apo B (R(2) = 7.0%, P =.02), while 18:3n-6 made the largest contribution to the variance of LDL diameter (R(2) = 7.6%, P =.02). Finally, 16:0 significantly contributed to the variance of AUC-glucose (R(2) = 11.4%, P =.0003), diastolic (R(2) = 25.2%, P <.0001), and systolic (R(2) = 6.8%, P =.002) blood pressure. In summary, results of this study suggest that the fatty acid content of TG is associated with many metabolic variables of the insulin resistance syndrome independently of body fat mass or visceral AT accumulation.     

Circulating fatty acids, non-high density lipoprotein cholesterol, and insulin-infused fat oxidation acutely influence whole body insulin sensitivity in nondiabetic men

Circulating lipids and tissue lipid depots predict insulin sensitivity. Associations between fat oxidation and insulin sensitivity are variable. We examined whether circulating lipids and fat oxidation independently influence insulin sensitivity. We also examined interrelationships among circulating lipids, fat oxidation, and tissue lipid depots. Fifty-nine nondiabetic males (age, 45.4 +/- 2 yr; body mass index, 29.1 +/- 0.5 kg/m(2)) had fasting circulating nonesterified fatty acids (NEFAs) and lipids measured, euglycemic-hyperinsulinemic clamp for whole body insulin sensitivity [glucose infusion rate (GIR)], substrate oxidation, body composition (determined by dual energy x-ray absorptiometry), and skeletal muscle triglyceride (SMT) measurements. GIR inversely correlated with fasting NEFAs (r = -0.47; P = 0.0002), insulin-infused NEFAs (n = 38; r = -0.62; P < 0.0001), low-density lipoprotein cholesterol (r = -0.50; P < 0.0001), non-high-density lipoprotein cholesterol (r = -0.52; P < 0.0001), basal fat oxidation (r = -0.32; P = 0.03), insulin-infused fat oxidation (r = -0.40; P = 0.02), SMT (r = -0.28; P < 0.05), and central fat (percentage; r = -0.59; P < 0.0001). NEFA levels correlated with central fat, but not with total body fat or SMT. Multiple regression analysis showed non-high-density lipoprotein cholesterol, fasting NEFAs, insulin-infused fat oxidation, and central fat to independently predict GIR, accounting for approximately 60% of the variance. Circulating fatty acids, although closely correlated with central fat, independently predict insulin sensitivity. Insulin-infused fat oxidation independently predicts insulin sensitivity across a wide range of adiposity. Therefore, lipolytic regulation as well as amount of central fat are important in modulating insulin sensitivity.     

Dietary fat and heart failure: moving from lipotoxicity to lipoprotection

There is growing evidence suggesting that dietary fat intake affects the development and progression of heart failure. Studies in rodents show that in the absence of obesity, replacing refined carbohydrate with fat can attenuate or prevent ventricular expansion and contractile dysfunction in response to hypertension, infarction, or genetic cardiomyopathy. Relatively low intake of n-3 polyunsaturated fatty acids from marine sources alters cardiac membrane phospholipid fatty acid composition, decreases the onset of new heart failure, and slows the progression of established heart failure. This effect is associated with decreased inflammation and improved resistance to mitochondrial permeability transition. High intake of saturated, monounsaturated, or n-6 polyunsaturated fatty acids has also shown beneficial effects in rodent studies. The underlying mechanisms are complex, and a more thorough understanding is needed of the effects on cardiac phospholipids, lipid metabolites, and metabolic flux in the normal and failing heart. In summary, manipulation of dietary fat intake shows promise in the prevention and treatment of heart failure. Clinical studies generally support high intake of n-3 polyunsaturated fatty acids from marine sources to prevent and treat heart failure. Additional clinical and animals studies are needed to determine the optimal diet in terms of saturated, monounsaturated, and n-6 polyunsaturated fatty acids intake for this vulnerable patient population.     

Polyunsaturated fatty acids may impair blood glucose control in type 2 diabetic patients.

Fifteen patients with Type 2 diabetes were given two diets rich in either saturated fat or polyunsaturated fat in alternate order over two consecutive 3-week periods on a metabolic ward. Both diets contained the same amount of fat, protein, carbohydrates, dietary fibre, and cholesterol. The proportions of saturated, monounsaturated and polyunsaturated fatty acids in the saturated fat diet were 16, 10, and 5%-energy and in the polyunsaturated fat diet (PUFA) 9, 10, and 12%-energy. The PUFA diet contained a high proportion of n-3 fatty acids. Metabolic control improved significantly in both dietary periods, due to both qualitative dietary changes and a negative energy balance. The serum lipoprotein concentrations decreased on both diets but the serum lipids were significantly lower after the PUFA diet (serum triglycerides -20%, p = 0.001; serum cholesterol -5%, p = 0.03; VLDL-triglycerides -29%, p less than 0.001; and VLDL-cholesterol -31%, p = 0.001) than after the saturated fat diet. Average blood glucose concentrations during the third week were significantly higher fasting (+15%, p less than 0.01), and during the day at 1100 h (+18%, p less than 0.001) and 1500 h (+17%, p = 0.002) on PUFA than on the saturated fat diet. Significantly higher blood glucose levels were also recorded with a standard breakfast, while the sum of the insulin values was lower (-19%, p = 0.01). HbA1c did not differ significantly between the two dietary periods.(ABSTRACT TRUNCATED AT 250 WORDS)     

Serum fatty acid composition predicts development of impaired fasting glycaemia and diabetes in middle-aged men.

AIMS: Dietary fatty acid intake is reflected in serum fatty acid composition. Studies prospectively investigating serum fatty acids and development of impaired fasting glycaemia (IFG) or diabetes mellitus (DM) are largely lacking. We assessed the association of serum fatty acid composition with development of IFG or DM. METHODS: Middle-aged normoglycaemic men (n = 895) participating in a prospective cohort study were followed up after 4 years. RESULTS: At baseline proportions of serum esterified and non-esterified saturated fatty acids were increased and polyunsaturated fatty acids decreased in men who after 4 years had developed IFG (n = 56) or DM (n = 34). No differences in dietary fatty acid composition as recorded in 4-day dietary records were noted. In logistic regression analyses adjusting for age; obesity; and fasting lipid, glucose and insulin concentrations, men with proportions of non-esterified and esterified linoleate in the upper third had nearly half the risk for IFG or DM compared with the lower third. In covariate analyses, baseline non-esterified linoleate proportions were associated with changes in fasting insulin and glucose concentrations over the 4-year follow-up. Baseline esterified fatty acid composition was also associated with changes in insulin. CONCLUSIONS: High serum linoleate proportions decreased the risk of developing IFG or DM in middle-aged men over a 4-year follow-up, possibly mediated in part by insulin resistance. These findings support recommendations to substitute vegetable fat for animal and dairy fat in the prevention of disturbances of glucose and lipid metabolism.     

Relationship between fat cell size and number and fatty acid composition in adipose tissue from different fat depots in overweight/obese humans

OBJECTIVE: To evaluate the body fat distribution and fat cell size and number in an overweight/obese population from both genders, and to determine the possible relationship between fat cell data from three different adipose tissue localizations (subcutaneous (SA), perivisceral and omental) and adipose tissue composition and dietary fatty acid. DESIGN: The sample consisted of 84 overweight/obese patients (29 men and 55 women) who have undergone abdominal surgery. The adipocyte size and total fat cell number was studied. Fat cell data were related with anthropometric, adipose tissue and subject's habitual diet fatty acid composition. MEASUREMENTS: Fat cell size was measured according to a Sj?str?m method from the three adipose depots. Total fat cell number was also calculated. The fatty acid composition of adipose tissue was examined by gas chromatography. The subjects diet was studied by a 7 days dietary record. RESULTS: Our data showed a negative relationship between the adipocyte size and the n-6 and n-3 fatty acids content of the SA adipose tissue (r=-0.286, P=0,040; r=-0.300, P=0.030) respectively, and the n-6 in the omental depots (r=-0.407, P=0.049) in the total population. Positive associations with the total of saturated (r=0.357, P=0.045) and negative (r=-0.544, P=0.001) with the n-9 fatty acids were observed when the relationship between the adipocyte number and the fatty acid composition of the different anatomical fat regions was studied. Dietary fatty acids composition positively correlated with fat cell size for the myristic acid (14:0) in men in the visceral depot (r=0.822, P=0.023), and for the saturated fatty acids (SFAs) in women in the omental depot (r=0.486, P=0.035). CONCLUSION: In the present study, for the first time in humans we found that n-3 and n-6 fatty acids are related to a reduced adipocyte size according to the depot localization. In contrast, adipose tissue and dietary SFAs significantly correlated with an increase in fat cell size and number. No significant associations were found between n-9 acids content and adipocyte size. However, n-9 adipose tissue fatty acids content was inversely associated with fat cell number showing that this type of fatty acid could limit hyperplasia in obese populations. The differences observed in the three different regions, perivisceral, omental and SA fat, indicate that this population adipose tissue have depot-specific differences.     

Adipose tissue levels of fatty acids and tocopherol in young and old women

Tocopherol concentration and fatty acid composition were determined in samples of subcutaneous adipose tissue from 33 young and 28 old women. Young women exhibited more saturated fatty acids and less monounsaturated fatty acids than old women (p less than 0.01). Adipose tissue tocopherol correlated with plasma tocopherol, with r = 0.49 and p less than 0.01, when the data for young and old were combined. A negative association was found between adipose tissue tocopherol and the n-3/n-6 fatty acid ratio in the old women (r = 0.42; p less than 0.05), suggesting that the tocopherol content of adipose tissue is determined not only by the intake of the nutrient but also by the tissue fatty acid composition.     

Nutrient intake, blood pressure, serum and urinary prostaglandins and serum thromboxane B2 in a controlled trial with a lacto-ovo-vegetarian diet

Fifty-nine healthy omnivores volunteered for a randomized crossover trial with a lacto-ovo-vegetarian (L-O-V) diet. Twenty-one 1-day diet records were kept throughout the project as a means of assessing food and nutrient intakes, and samples of serum and urine were assayed to evaluate change in prostanoid metabolism. While on the L-O-V diet subjects ate more vegetable protein, wholegrain cereals, polyunsaturated oils, fruits and vegetables, and avoided eating meat, fish or poultry. The L-O-V diet contained significantly more polyunsaturated fatty acids, fibre, vitamin C, vitamin E, magnesium, calcium and potassium, and less total protein, saturated fat, monounsaturated fat and vitamin B12 than the control omnivore diet. Changes in nutrient intakes were subjected to principal components analysis to identify dimensions of change in nutrient intakes. Three Factors accounted for 83% of the total variation in dietary intake. Blood pressure changes were significantly and negatively (F = 17.4, P less than 0.001 for systolic; F = 6.09, P = 0.02 for diastolic pressure) related to individual scores for only one Factor--that representing an increase in intake of polyunsaturated fat, fibre, vitamin C, vitamin E, calcium and magnesium, and a fall in intake of protein and vitamin B12. Blood pressure changes were unrelated to change in body weight or sodium intake. Serum and urinary prostanoids were not affected by eating the L-O-V diet.     

Fat and fish intake and asthma in Japanese women: baseline data from the Osaka Maternal and Child Health Study.

OBJECTIVE: It remains controversial whether the intake of n-3 polyunsaturated fatty acids and fish is preventive against asthma. This cross-sectional study investigated the relationship between fat and fish intake and the prevalence of asthma using baseline data from a prospective study. DESIGN: The subjects were 1002 pregnant Japanese females. A diet history questionnaire was used to assess dietary habits. Current asthma and asthma after age 18 were defined as present if subjects had been treated with medications at some time in the previous 12 months and after reaching the age of 18, respectively. RESULTS: Fish consumption was independently associated with a decreased prevalence of asthma after age 18 and current asthma. A significant inverse relationship was observed between the ratio of n-3 to n-6 polyunsaturated fatty acid intake and the prevalence of current asthma, but not asthma after age 18. Intake of total fat, saturated, monounsaturated, n-3 polyunsaturated and n-6 polyunsaturated fatty acids, cholesterol, meat, eggs or dairy products was not evidently related to either outcome for asthma. CONCLUSION: Our results suggest that fish consumption and the high ratio of n-3 to n-6 polyunsaturated fatty acid intake may be associated with a reduced prevalence of asthma in young female Japanese adults.     

The effect of dietary fat content and composition on adipocyte lipids in normal and diabetic states

Cellular insulin resistance is a common feature of the diabetic and obese state. To determine the effect of dietary fat and the insulin resistant state of diabetes on adipose tissue composition, control and streptozotocin-induced diabetic rats were fed four diets differing in fat content (10 percent w/w or 20% w/w) and polyunsaturated to saturated fatty acid (P/S) ratios (0.2 or 2.0) for 6 weeks. At 3 weeks diabetes was induced in half the animals in each diet group. Increasing the fat content and P/S ratio of the diet increased the content of polyunsaturated fatty acids and decreased the contents of monounsaturated and omega-3 fatty acids. The higher level of C-18:2(6) and the lower levels of C20:4(6) and monounsaturated fatty acids observed in diabetic animals is consistent with altered desaturase enzyme activity. Diet and diabetes induced compositional changes in essential and non-essential fatty acids in the adipose tissue may alter the total body pools of available fatty acids for the synthesis of other lipids such as phospholipids.