ALTERATIONS IN APOLIPOPROTEIN B-48 IN THE POSTPRANDIAL STATE IN NIDDM

The intestine is a major site of cholesterol synthesis and produces ap olipoprotein B-48, which is critical for intestinal cholesterol absorp tion and secretion. The purpose of this study was to examine postprand ial changes in apolipoprotein B-48 in diabetes. Six non-insulin-depend ent diabetic patients and six non-diabetic control subjects were given a high-fat meal (1300 kcal) and blood samples were taken pre- and pos tprandially, from which the triglyceride-rich lipoprotein fraction was isolated by ultracentrifugation (density < 1.006 g/ml). Apolipoprotei n B-48 was separated on 4-15 % gradient gels and quantified as a perce ntage of the fasting concentration by densitometric scanning. Total pr otein, triglyceride and cholesterol in the triglyceride-rich lipoprote in fraction, blood glucose, and serum insulin were also measured. Diab etic patients exhibited a postprandial triglyceride-rich apolipoprotei n B-48 profile significantly different from that of control subjects ( p < 0.05). The triglyceride and total protein concentration in the tri glyceride-rich lipoprotein fraction mirrored the post-prandial profile and apolipoprotein B-48 in both groups. Significantly different patte rns for triglyceride (p < 0.02) and total protein (p < 0.05) following the fat-rich meal were observed in the two groups. Fasting and postpr andial triglyceride-rich lipoprotein cholesterol and total apolipoprot ein B were significantly higher in diabetic patients than in control s ubjects (p < 0.05). Since apolipoprotein B-48 is the structural protei n of intestinally-derived lipoprotein particles, these studies suggest an abnormality in intestinal lipoprotein metabolism in diabetes.