Insulin and islet cell transplant--effect on intestinal uptake of lipids.

A previously validated in vitro technique was used to determine the effect of once-daily injections of NPH insulin (NPH) and islet cell transplant (ICT) on the enhanced uptake (Jd) of lipids into the intestine of diabetic rats. Three months after ICT, the urine volume, urine glucose, and fasting blood sugars were near normal. The Jd of lauryl alcohol was used to measure the effective resistance of the unstirred water layer (UWL); NPH was associated with an increase in UWL in the jejunum when the bulk phase was stirred or unstirred and a rise in UWL in the ileum when the bulk phase was unstirred but had no effect on UWL in the colon. The Jd of a homologous series of saturated medium-chain-length fatty acids in untreated diabetic rats was reduced with NPH and ICT. The Jd of cholesterol was lower in diabetic rats treated with NPH or ICT than in untreated diabetic rats over a wide range of concentrations of cholesterol, bile acid, and bile acid/cholesterol. The colon was less permeable than the jejunum to fatty acids or fatty alcohols. In contrast to the small intestine, diabetes had no effect on colonic uptake of these probes. Thus, injection of exogenous insulin or endogenous insulin supplied by ICT in diabetic rats reduced the Jd of lipids, normalized the effective resistance of the UWL, and reduced the enhanced passive permeability of the jejunum observed in diabetic animals.