Type of dietary lipids exerts a major influence on the secretory activity of the exocrine pancreas: medium-term studies

Comparison of the effects of dietary sunflower oil and virgin olive oil on rat exocrine pancreatic secretion in vivo

The aim of this study was to investigate the functional consequences in vivo of adapting the rat exocrine pancreas to different dietary fats. Weanling rats were fed diets containing 10 wt% virgin olive oil or sunflower oil for 8 wk. We then examined resting and cholecystokinin-octapeptide (CCK-8)-stimulated pancreatic secretion in the anesthetized animals. To confirm a direct influence of the type of fat upon the gland, the FA composition of pancreatic membranes as well as tissue protein and amylase content were determined in separate rats. The membrane FA profile was profoundly altered by the diets, reflecting the type of dietary fat given, although this was not paralleled by variations in the pancreatic content of protein or amylase. Nevertheless, dietary intake of oils evoked different effects on in vivo secretory activity. Resting flow rate and amylase output were significantly (P < 0.05) enhanced by sunflower oil feeding. Time course changes in response to CCK-8 infusion also showed a different pattern in each group. Secretion of fluid, protein, and amylase increased markedly in all animals, reaching a maximum within 20-40 min of infusion that was followed by a dramatic decline in both groups. In the sunflower oil group, this resulted in values reaching the resting level as soon as 60 min after CCK-8 infusion was begun. However, after the initial decline, olive oil group values showed a prolonged plateau elevation above the baseline (P < 0.05) that was maintained for at least the infusion time. In addition, a positive correlation between flow rate and both protein concentration and amylase activity existed in the olive oil group, but not in the sunflower oil group. The precise mechanism by which these effects are produced remains to be elucidated.

Fatty acid and enzymatic compositional changes in the pancreas of rats fed dietary n-3 and n-6 polyunsaturated fatty acids

The influence of n-3 and n-6 PUFA on the fatty acid composition and the enzyme content of zymogen granules of the normal exocrine pancreas was tested on rats. The animals were fed on different diets comprising 5% fish oil (FO), safflower oil (SFO), and evening primrose oil (EPO) used singly or in combination as dietary fats. The results were compared with those from animals fed 5% hydrogenated beef tallow (HBT). The fatty acid composition and digestive enzyme content were analyzed after a 6-wk feeding period. Differences in the pancreatic fatty acid profiles were related to the fatty acid composition of the ingested fats. Equivalent levels of n-3 fatty acids and 20:3n-6 were obtained with either EPO or FO fed singly or in combination. Similar results were observed with SFO/FO. Higher C20:3n-6/C20:4n-6 ratios were obtained with the oil mixtures. An increase in amylase levels, but a decrease in serine protease (Band 21 kdalton) levels, was associated with EPO. An elevation in procarboxypeptidase levels paralleled an increase in 18:0 levels, whereas the proportion of lipase (Band 49 kdalton) varied inversely with the proportion of C20:3n-6. The SFO/FO mixture elevated the proportions of protease II and proelastase. These results suggest that specific fatty acids influence the proportion of specific digestive enzymes in the zymogen granules.