LACK OF DELAY IN HEPATIC INSULIN TRANSIT AS INDICATED BY CONCORDANCE OF INSULIN SECRETORY AND PERIPHERAL INSULIN PULSES

The liver is an important site of insulin metabolism and action. It ha s often been assumed that the liver may diminish the amplitude of the insulin secretory waveform without altering hepatic insulin transit ti me. However, the significant extraction and metabolism of hepatic insu lin has the potential to delay hepatic insulin transit. To examine hep atic insulin transit, we studied the concordance of calculated insulin secretory peaks with peripheral insulin peaks in 12 healthy men of va rying body weight and fat distribution. Adiposity was determined by pe rcent body fat, and fat distribution by the waist to hip ratio. Arteri alized peripheral venous samples for insulin and C-peptide assays were obtained every 2 minutes for 90 minutes. Pancreatic insulin secretion rates were estimated with individual C-peptide kinetics using a two c ompartment model. Concordance between insulin secretory peaks and peri pheral insulin peaks was assessed by the hypergeometric probability mo del. A significant concordance between secretory and peripheral insuli n pulses was demonstrated in seven of 12 subjects (P < .00001). The me an pulse intervals for insulin secretion were similar to the mean puls e intervals for peripheral insulin. The degree of concordance between the insulin secretory peaks and peripheral insulin pulses was unrelate d to adiposity or body fat distribution. Significant synchronicity exi sts between insulin secretory peaks and peripheral insulin peaks in he althy men. We conclude that despite significant hepatic insulin extrac tion and metabolism, hepatic insulin transit may not he delayed in hea lthy men. Copyright (C) 1994 by W.B. Saunders Company