Pancreatic exocrine response to long-term high-fat diets in rats

Although the synthesis and secretion of pancreatic enzymes are dependent on the composition of diet, little is known about the long-term adaptation of the exocrine pancreas to the chronic intake of high-fat, low-carbohydrate diets.

The effects of long-term (48-weeks) high-fat, low-carbohydrate feeding on the intracellular activity as well as on the secretory activities of the pancreas regarding the secretion of amylase and lipase in isolated pancreatic lobules of rats were investigated.

Twenty-six male Sprague-Dawley rats were randomly divided into two groups.

The high-fat diet group was fed a diet containing 12.3% Kcal of carbohydrates, 76.0% Kcal of fats, and 11.7% Kcal of proteins for 48 weeks. In the control group, the rats were fed a standard diet (50.3% Kcal of carbohydrates, 33.2% Kcal of fats, and 16.5% Kcal of proteins) for the same period of time.

The intracellular activity of alpha-amylase and lipase were defined as enzyme activity per 1 mg protein in the pancreatic homogenate. The secretory activity of the pancreatic enzymes was defined as enzyme activity per 1 mg protein or as the mean percentage of released enzyme activity in the medium to that initially retained in the lobules over the entire 90 minute incubation period.

The intracellular activity as well as the secretory activities of pancreatic amylase in the basal and in the cholecystokinin (10 pmol/L)-stimulated states of high-fat, low-carbohydrate diet fed rats were significantly lower than that in the control rats. Nevertheless, those of lipase were not significantly different between the two groups. However, when the secretory enzyme activity was illustrated as the percentage released, basal as well as CCK-stimulated amylase and lipase activity were not significantly different between the two groups.

The reduction of the intracellular amylase activity and the secretory amylase activity may be a long-term adaptive response of the pancreas to the reduced carbohydrate composition of the diets. Moreover, the reduction of the secretory amylase activity may be due to reduced intracellular amylase activity rather than to the altered sensitivity of the acinar cells to cholecystokinin. However, we failed to observe a long-term adaptive response of pancreatic lipase to increased fat composition of diets.