Effects of marine n-3 fatty acid supplementation on lipoprotein subclasses measured by nuclear magnetic resonance in subjects with type II diabetes.

OBJECTIVE: To measure effects of fish oil supplements on lipoprotein subclasses by nuclear magnetic resonance (NMR) in subjects with type II diabetes and relate them to insulin sensitivity. DESIGN: Two-armed, parallel, placebo-controlled, randomized. SUBJECTS: Normotriglyceridemic subjects with type II diabetes without insulin treatment were given either fish oil (n=12, median intake 5.9 g/day total n-3 fatty acids (FA) (1.8 g 20:5n-3, 3.0 g 22:6n-3)) or corn oil (n=14, 8.5 g/day 18:2n-6 FA). METHODS: Size and concentration of lipoproteins subclasses were measured by NMR, insulin sensitivity by hyperinsulinemic, isoglycemic clamps. RESULTS: After 9 weeks, there were differences between those treated with fish and corn oil with respect to very low-density lipoprotein (VLDL) size (median -15 vs +0.6%, P=0.001), particle concentrations of large VLDL (-99 vs -4.1%, P=0.041) and small high-density lipoprotein (HDL) (-12 vs +10%, P=0.051). Compared with corn oil fish oil tended to increase HDL size and small low-density lipoprotein (LDL) concentration (P=0.063 and 0.068, respectively, for differences between groups). There was no effect on oxidized LDL. Insulin sensitivity (glucose utilization) decreased in the fish oil group compared with the corn oil group (P=0.049). The decrease in insulin sensitivity did not correlate with the effects on lipoprotein subclasses. CONCLUSIONS: A high intake of n-3 FA exerts effects on several lipoprotein subclasses without obvious influence from changes in insulin sensitivity.

Effects of a 3-day low-fat diet on metabolic control, insulin sensitivity, lipids and adipocyte hormones in Norwegian subjects with hypertriacylglycerolaemia and type 2 diabetes.

The metabolic and hormonal impact of rapid dietary changes in type 2 diabetes has not been clarified. The objective of this study was to test whether a short-term, low-fat diet affected metabolic control, insulin sensitivity, lipids and adipocyte hormones in patients with type 2 diabetes with hypertriacylglycerolaemia. Nineteen outpatient subjects (10 M, 9 F) with type 2 diabetes and triacylglycerols >2.2 mmol/L at screening were included in the study. Dietary intake was assessed by weighing during two periods of 3-day baseline diet followed by a 3-day low-fat dietary intervention. The two periods of baseline diet did not differ with respect to relevant variables during intervention. Subjects were advised to increase fibre-rich and low-fat foods and to decrease intake of visible fat in an isoenergetic manner. The percentage of energy from fat was reduced from 39 to 22 (p < 0.0001), median values. Daytime blood glucose did not change and fasting insulin and fasting glucose to insulin ratios were unaffected. Total cholesterol decreased from 6.3 to 6.2 mmol/L (p < 0.005), high-density lipoprotein cholesterol from 1.13 to 1.10 mmol/L (p < 0.048) and the ratio of n-6 to n-3 fatty acids in phospholipids from 2.5 to 1.9 (p < 0.003). Concentrations of leptin decreased from 12.1 to 9.9 ng/mL (p < 0.005) and adiponectin increased from 8.6 to 10.5 microg/mL (p < 0.024). The effect on leptin was confined to women. A low-fat diet intervention for 3 days in insulin-resistant type 2 diabetes affects lipid, adiponectin and leptin levels but fails to improve insulin sensitivity and metabolic control.

Alpha-linolenic acid deficiency in man: effect of essential fatty acids on fatty acid composition.

Alpha-linolenic acid deficiency (ALAD) is described in five adults receiving long-term gastric tube feeding with a commercially available powdered formula mixed with water and/or skimmed milk. Three patients receiving the same powder mixed with whole milk showed no signs of essential fatty acid deficiency (EFAD). The patients showed scaly dermatitis and skin atrophy. In four patients, supplementing with cod liver oil and soya oil for 4 weeks normalized n-3 acids in plasma and red cells, while n-6 acids remained unchanged or decreased slightly. At the same time, skin changes were normalized. In the fifth patient, supplementing with ethyl linolenate started to normalize skin changes within 5 days, and after 2 weeks had increased the red cell concentration of 22:6n-3 threefold. Simultaneously, 20:4n-6 increased twofold, to above control level. Minimal daily requirement of alpha-linolenic acid and of long-chain n-3 acids is estimated to be 0.2% to 0.4% and 0.1% to 0.2% of calories, respectively.

Alpha-linolenic acid deficiency in patients on long-term gastric-tube feeding: estimation of linolenic acid and long-chain unsaturated n-3 fatty acid requirement in man.

Alpha-linolenic acid deficiency is described in four adults fed by gastric tube. In plasma and erythrocytes, total lipid 20:3n-9 was slightly increased but total n-6 fatty acids, arachidonic acid, and dihomo-gamma-linolenic acid were normal. Total n-3 fatty acids, 18:3n-3, 20:5n-3, 22:5n-3, and 22:6n-3 were decreased in both plasma and erythrocytes. Patients had a slight but definite scaly dermatitis, which disappeared with essential fatty acids supplementation. Simultaneously, levels of 18:3n-3, 20:5n-3, 22:5n-3, 22:6n-3, 20:3n-9, and total n-3 fatty acids became normal while 18:2n-6, 20:3n-6, 20:4n-6, and total n-6 acids were unchanged or slightly lowered. Estimated minimal daily requirement of linolenic acid and of long-chain unsaturated n-3 acids in adults is approximately 0.2-0.3% and 0.1-0.2%, respectively, of total energy intake. Results suggest that conversion of linolenic acid to 22:6n-3 is increased in linolenic acid deficiency.