The mechanisms for insulin resistance with type 2 diabetes have been studied extensively, but there is no generally accepted consensus about its etiology. In spontaneously hypertensive rats, we have shown that cleavage of the extracellular domain of the insulin receptors destroys its ability to signal after insulin binding, generating insulin resistance and reduced glucose uptake. Recent evidence suggests that insulin resistance in obese diabetic patients and in the spontaneously hypertensive rat is associated with increased proteolytic (e.g., MMP‐9 and elastase) activity in the blood. We hypothesized that rats given high fat diet (HFD) develop increased intestinal permeability allowing pancreatic trypsin to escape the intestinal lumen and cleave insulin receptors. We examined the insulin receptor and trypsin levels in the intestine, the liver, and the plasma in rats consuming normal diet (ND) and HFD. Immunohistochemistry (IHC) showed a decrease in submucosal and intestinal wall extracellular insulin receptor subunit IRa and an increase in submucosal and intestinal wall trypsin in HFD versus ND rats. In the liver, similar trends were observed, with increase in trypsin levels and decrease in IRa levels in HFD rats. Western blots of the blood plasma showed a marginal increase in plasma trypsin (p‐value=0.06) and IRa levels (p‐value=0.065) in HFD rats. The increase of trypsin in the intestine and liver of HFD rats suggests that a high fat diet alters intestinal permeability to allow digestive trypsin to escape out of the lumen into the blood stream, and cleave IRa in the intestinal wall and the liver.Support or Funding InformationSupported by HL 10881.