C-peptide but not insulin concentrations are related to the serum lipoprotein levels during insulin treatment of non-insulin-dependent diabetes mellitus (NIDDM) patients.
In 21 non-insulin-dependent diabetic patients with secondary drug failure, once-daily long-acting insulin lead to a moderately improved metabolic control. At the conclusion of the study (eight months) the fasting blood glucose and HbA1c concentrations were significantly decreased, but the postprandial blood glucose concentrations in the afternoon were unaltered. The peripheral insulin sensitivity, as measured by the intravenous insulin tolerance test, and the lipoprotein lipase activity in adipose and skeletal muscle tissue had increased. After initiation of insulin therapy there was a transient decrease of the fasting and glucagon-stimulated C-peptide concentrations. The very low density lipoprotein lipids and apolipoprotein B, A-I and A-II were also reduced transiently. The only significant difference in lipoprotein composition at eight months compared with on admission, was an increased cholesterol and decreased triglyceride concentration in the high density lipoproteins. There were significant relationships between the C-peptide, but not the peripheral insulin, concentrations and the serum lipid concentrations. This may indicate that high peripheral insulin concentrations after administration of exogenous insulin may affect the hepatic lipoprotein production less than the portal insulin concentrations mainly derived from endogenous production.