Cholesterol metabolism in type 1 diabetes

Little information is available on cholesterol absorption and synthesis in human type 1 diabetes. We studied these variables using serum cholesterol precursor sterol ratios to cholesterol as surrogate markers of cholesterol synthesis and those of cholestanol and plant sterols to reflect cholesterol absorption in seven type I diabetic subjects and in five age- and body weight-matched control subjects. Total and lipoprotein cholesterol levels were similar, but triglycerides in intermediate-density lipoprotein (IDL) and LDL were higher in type 1 diabetic than in control subjects. Most of the marker sterols were transported by LDL and HDL in both groups. The percentage of esterified cholesterol was lower in triglyceride-rich lipoproteins in diabetic patients than in control subjects. The ratios of the absorption marker sterols in serum were higher, and those of the synthesis markers were lower in type 1 diabetic than in control subjects. The increased cholestanol ratios were seen in all lipoproteins, and those of free and total plant sterols were mainly in LDL, whereas the decreased free and total synthesis markers were mainly in all lipoproteins. In conclusion, high absorption and low synthesis marker sterols seem to characterize human type 1 diabetes. These findings could be related to low expression of ABC G/5 G/8 genes, resulting in high absorption of cholesterol and sterols in general and low synthesis of cholesterol compared with type 2 diabetes.