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

Abstract

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.

Effects of Olive Oil on Fatty Acid Composition of Pancreatic Cell Membranes

“…That our dietary protocol was appropriate for our purposes was also confirmed by the membrane fatty acid analyses showing, like in previous work (Díaz et al, 2003), the sensitivity of the pancreas to dietary fat changes. After 8 weeks on the diets we found again that the membrane fatty acids were profoundly affected by the diets; the rats fed the olive oil diet had higher levels of 18:1 n-9 and total MUFA compared with the animals fed the sunflower oil diet.…”

“…This work (Díaz et al, 2003) was carried out in male weaning Wistar rats. The rats were fed over an 8-week period with two semi-purified, isoenergetic and isonitrogenous diets that were essentially AIN-93G diets except that total fat content was increased from 7 to 10 wt% at the expense of carbohydrate.…”

“…The major differences between the dietary treatments concerned the magnitude of the secretion of fluid and amylase in resting conditions as well as the time course of changes in all major secretory parameters evoked by a continuous intravenous infusion of CCK-8 (Díaz et al, 2003).…”

Effects of the type of dietary fat on acetylcholine-evoked amylase secretion and calcium mobilization in isolated rat pancreatic acinar cells

“…After 8 weeks on the diet, pancreatic cell membranes of C animals had a higher level of total SFA and PUFA, whereas a greater level of total MUFA was found in OO animals. The existence of dietary-induced changes in the fatty acid profile of rat pancreatic membranes was previously found to be associated with modifications in CCK-8-evoked secretory activity in anaesthetized rats [18] and in acinar cell function and signaling evoked by the same secretagogue [16]. Thus, the results of the membrane fatty acid composition obtained in the present study after feeding rats the OO and C diet support the use of this model to assess if there is a differential response to ACh.…”

“…In the rat study, this was accompanied by a change in the secretory activity and mobilization of intracellular Ca 2+ stimulated by cholecystokinin-octapeptide (CCK-8) in viable pancreatic acini [16]. Interestingly, by using the method of direct cannulation of the pancreatic duct in anaesthetized rats, we have been able to find a modification of CCK-induced secretory output as a function of the type of fat previously fed [18], which indicates that the modulating effect of this nutrient on exocrine pancreatic function is not limited to the cellular level.…”