Elevated triglyceride-rich lipoproteins in diabetes. A study of apolipoprotein B-48

The role of the intestine in cholesterol metabolism in human diabetes is unclear, although abnormalities have been demonstrated in cholesterol synthesis and absorption in diabetic animals. This study examines the relationship between fasting and post-prandial apolipoprotein B-48 in type 2 (non-insulin-dependent) diabetic and non-diabetic subjects. Eight type 2 diabetic patients and ten healthy non-diabetic control subjects were given a high-fat meal (1300 kcal), and the triglyceride-rich lipoprotein fraction was isolated by ultracentrifugation (d < 1.006 g/ml) from fasting and post-prandial plasma. Apolipoprotein B-48 and apo B-100 were separated on 4%-15% gradient gels and quantified by densitometric scanning with reference to a purified low-density lipoprotein (LDL) apo B-100 preparation. Diabetic patients had significantly higher concentrations of apo B-48 and apo B-100 in both the fasting (P < 0.05) and post-prandial (P < 0.001) triglyceride-rich lipoprotein samples compared with non-diabetic subjects. The diabetic patients also exhibited a significantly different post-prandial profile for apo B-48 and apo B-100, with a prolonged increase and a later post-prandial peak, than the non-diabetic subjects (P < 0.01). These results suggest that the raised fasting triglyceride-rich lipoproteins, often found in diabetes, are associated with apo B-48 and may be derived from increased intestinal chylomicron production. The post-prandial pattern suggests an abnormality in intestinal production as well as hepatic clearance of apo B-48 in type 2 diabetes.