The Effect of Macronutrients on Insulin Receptors in Rat Small and Large Intestine


Authors: T.M. Craig, L.L. Greer, C.L. Mohesky, R.R. MacDonald (Spon: D.T. Gordon)

University of Missouri, Columbia, Mo  65211
Published: FASEB, 1989

Insulin receptors (IR) are present in the mucosa of the gastrointestinal tract (GIT) but their metabolic role is unknown.  We were interested to determine if the macronutrient composition of the diet influenced IR in the GIT of rats.  In a pilot experiment, 18 male Wistar rats were divided into 3 groups and fed semi-purified diets of balanced macronutrient composition (BM), high fat (60% kcal as lard, HF), or high carbohydrate (60% kcal as glucose, HC).  Diets contained equal nutrient value on an energy basis.  Two animals per group were euthanized on d 12, 13 and 14, the ileum (IM) and colon (C) were removed and wheatgerm agglutinin sepharose purified receptors prepared.  Specific insulin binding (SIB) was measured at 15oC for 24 h.  A significant increase in SIB was observed in IM from rats fed the HC compared to the HF or BM diet, but not in the C.  Serum triglyceride (STG) and glucose levels were higher in rats fed the HC compared to the HF or BM diet.  SIB in the IM tended to be positively correlated to SI and negatively correlated to STG.  No such trend was seen in C.  These results suggest that major changes in macronutrient composition of the diet can alter IR in the GIT but the response may be different in specific regions.  Future studies are aimed at further characterization of IR in the GIT, their metabolic role and the influence of dietary factors of them.