Dietary fat, plasma triglycerides and de novo lipogenesis in type 2 diabetes

Diabetes predisposes individuals to a high risk of cardiovascular disease. Perturbations in carbohydrate and fat processing in the body lead to detrimental effects on triglyceride metabolism, but the underlying mechanisms are not fully understood. Reduction in fat intake is often recommended to lower cardiovascular disease risk. However, decreasing fat and increasing carbohydrate intake consistently raises plasma triglyceride levels, an independent risk factor for the disease.;The second study examined whether diabetes and/or lower fat intake would result in higher fasting and postprandial triglycerides and if this was associated with de novo lipogenesis or plasma free fatty acids. A short-term lower fat diet was compared to a higher fat/high oleate diet in type 2 diabetic and matched non-diabetic control subjects in a blinded randomized crossover design. The amount of total and individual fatty acids in VLDL-triglyceride, free fatty acids, as well as hepatic and extra-hepatic de novo fatty acid was estimated. Deuterium incorporation techniques were used for the first time in humans to measure de novo lipogenesis of specific fatty acids. Diabetes and insulin resistance tended to affect aspects of fasting and postprandial concentration, whereas diet seemed to influence fatty acid composition and synthesis. Higher fat intake generally decreased de novo lipogenesis and did not increase postprandial triglycerides. Synthesis of both total and individual fatty acids varied greatly between subjects and diets. Lipogenesis potentially affects the amount of circulating saturated fatty acids in the body. Whether a difference in lipogenic capacity and/or "quality" contributes to hypertriglyceridemia, atherogenesis and other metabolic alterations that occur in diabetes requires further investigation.;The first study tested whether isocaloric replacement of carbohydrate with monounsaturated fat would reduce triglyceride levels and hepatic de novo lipogenesis in free-living type 2 diabetic and matched non-diabetic subjects. Fat intake was increased by adding olive oil to the usual diet, while decreasing carbohydrate-rich foods. This reduced plasma triglycerides in a subgroup of subjects with higher triglycerides but did not reduce fatty acid synthesis. However, a relationship was observed between fatty acid synthesis and plasma triglycerides in non-diabetic subjects that was not observed in type 2 diabetes subjects.