Short-term adaptation of pancreatic hydrolases to nutritional and physiological stimuli in adult rats

Insulin protects acinar cells during pancreatitis by preserving glycolytic ATP supply to calcium pumps

Acute pancreatitis (AP) is serious inflammatory disease of the pancreas. Accumulating evidence links diabetes with severity of AP, suggesting that endogenous insulin may be protective. We investigated this putative protective effect of insulin during cellular and in vivo models of AP in diabetic mice (Ins2^Akita) and Pancreatic Acinar cell-specific Conditional Insulin Receptor Knock Out mice (PACIRKO). Caerulein and palmitoleic acid (POA)/ethanol-induced pancreatitis was more severe in both Ins2^Akita and PACIRKO vs control mice, suggesting that endogenous insulin directly protects acinar cells in vivo. In isolated pancreatic acinar cells, insulin induced Akt-mediated phosphorylation of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 2 (PFKFB2) which upregulated glycolysis thereby preventing POA-induced ATP depletion, inhibition of the ATP-dependent plasma membrane Ca²⁺ ATPase (PMCA) and cytotoxic Ca²⁺ overload. These data provide the first mechanistic link between diabetes and severity of AP and suggest that phosphorylation of PFKFB2 may represent a potential therapeutic strategy for treatment of AP.

Fat encapsulation enhances dietary nutrients utilization and growth performance of nursery pigs

Encapsulation of fat may facilitate digestion and absorption of fat in nursery pigs. Two experiments were conducted to evaluate 1) effects of encapsulation of palm oil (PO) and coconut oil (CO) on growth performance, feed intake, feed efficiency, and blood parameters, and 2) effects of encapsulation of PO and CO on apparent total tract digestibility (ATTD) of nutrients, and the activity of digestive enzymes in nursery pigs. In Exp. 1, 540 pigs (28 d of age, 8.23 ± 0.22 kg BW) were allotted to five treatments based on a randomized complete block design (as-fed basis). Pigs were fed basal diets with five different fat sources: 6.0% soybean oil (SBO), 6.0% PO, 6.0% PO from encapsulated fat (EPO), 6.0% CO, and 6.0% CO from encapsulated fat (ECO), respectively, with six pens per treatment and 18 pigs per pen for a 4-wk feeding trial. Dried casein and whey powder used for encapsulation were included at identical levels in all diets. Pigs fed EPO had increased (P < 0.05) ADG during days 0 to 14 and overall compared to pigs fed SBO and PO, whereas ADG of pigs fed ECO was not different from pigs fed EPO and CO. There were no differences in ADFI among treatments. Pigs fed EPO had increased G:F (P < 0.05) during days 0 to 14 compared to SBO, PO, and CO. Serum urea nitrogen concentrations in pigs fed EPO, CO, and ECO were lower (P < 0.05) than that of pigs fed SBO and PO. In Exp. 2, 30 pigs (28 d of age, 8.13 ± 0.10 kg BW) were housed individually (n = 6 per treatment) and allotted to five treatments as described in Exp.1. Pigs were fed ad libitum for 4 wk to measure ATTD of diets weekly and digestive enzyme activity at week 4. Pigs fed EPO, CO, and ECO had increased (P < 0.05) ATTD of DM and GE compared to pigs fed SBO and PO. Pigs fed SBO had reduced (P < 0.05) ATTD of CP compared to other treatments. Pigs fed PO had reduced (P < 0.05) ATTD of ether extracts (EE) compared to other treatments. Pigs fed PO had greater (P < 0.05) trypsin activity in the pancreas than pigs fed SBO and CO. Pigs fed PO tended to have lower (P = 0.073) pancreatic lipase activity compared to other treatments, whereas dietary treatments had no effect on pancreatic amylase activity. In conclusion, this study indicates that encapsulation of PO improved growth performance and ATTD of diets in nursery pigs, whereas the limited effects of encapsulated CO were likely due to the high digestibility of the medium-chain triglycerides abundant in CO.

Effect of chemical structure of fats upon their apparent digestible energy value when given to growing/finishing pigs

Four metabolism trials were conducted. Trials 1 and 2 (Tl, T2) investigated degree of saturation of fats (ratio of unsaturated to saturated fatty acids, U/S) on digestible energy (DE) content. Fats evaluated were rape oil (RO) and tallow (T) for Tl (U/S 15·67 and 0·97 respectively) and RO and palm oil (PO) for T2 (U/S 15·33 and 0·85 respectively). Three fats of intermediary U/S for each trial were produced by blending the two fats in proportions to give U/S of 3·18,2·08 and 1·49 in both trials. Trials 3 and 4 (T3, T4) investigated the effect of free fatty acid (FFA) content of fats on DE value. Fats were soya-bean oil (SO) and soya-bean acid oil (SAO) for T3 (FFA 6·2 and 626·0 g/kg respectively) and T and tallow acid oil (TAO) for T4 (FFA 44·3 and 818·2 g/kg fat respectively). Three fats of intermediary FFA for each trial were formed by blending the two fats in the ratios of 72:25, 50: 50 and 25: 75 in both trials. The FFA content of the blends were 161·2, 316·1 and 471·1 g/kg fat for T3 and 237·8, 431·3 and 624·7 g/kg fat for T4. All trials evaluated five fats by substitution, at 40, 80 and 120 g/kg into a basal diet, in a cross-over design, with 16 gilts of 25 kg initial live weight evaluating 16 diets over four time periods. Diets were offered for 10 days followed by a 5-day collection period using the marker to marker technique. Fat content of food and faeces, with methodology based on acid hydrolysis, allowed calculation of apparent digestible fat (AFD) of experimental diets. Analysis of variance gave effects of fats (P < 0·001 for Tl, T3 and T4 and P = 0·014 for T2), rates of inclusion (P < 0·001 for all trials), and fats × rates (P > 0·05, P > 0·05, P < 0·001, P < 0·01 for T1, T2, T3 and T4 respectively). Extrapolation of the function obtained by regressing AFD of diets (y) on rate of inclusion of fat (x) to × = 1000 generated values for the fats. The product of the coefficient of apparent fat digestibility of fats and their respective gross energies gave DE values for fats which were MJ/kg: T1 RO = 35·8 and T = 31·2; T2 RO = 36·7 and PO = 33·1; T3 SO = 374 and SAO = 32·8 and T4 T = 33·8 and TAO = 28·9. Data for fat blends intermediary between the two fats showed that DE improved exponentially as a function of U/S and that DE declined linearly with increasing FFA content.

Regulation of pancreatic lipase by dietary medium chain triglycerides in the weanling rat

Pancreatic lipase (PL) and its related protein 1 (PLRP1) are regulated by the amount of dietary fat through an apparent transcriptional mechanism. Regulation of PL and PLRP1 by type of fat (chain length and degree of saturation) is less well understood. The aim of this study was to determine whether medium-chain triglycerides regulate PL and PLRP1. For 7 d, weanling (21-d-old) Sprague Dawley male rats were fed diets low (11% of energy), moderate (40% of energy), or high (67% of energy) in trioctanoate/tridecanoate (MCT) or safflower (low fat only) oils. Food consumption decreased as dietary MCT increased, and the consumption of MCT diets was lower than that of the low-safflower (control) diet. Final body weight was similar among rats fed the low- or moderate-MCT or control diets, but was significantly reduced (17%) in those fed the high-MCT diets. PL activity was significantly elevated 53-60% (p < 0.002) in rats fed low and moderate MCT diets, respectively, compared with that of rats fed high-MCT or control diets. PL and PLRP1 mRNA levels were not significantly different among diets, suggesting that chain length regulates PL and PLRP1 translationally or posttranslationally. The beta-hydroxybutyrate plasma concentration was significantly (p < 0.02) higher (85%) in rats consuming low-MCT diet compared with those of rats fed the control diet. MCT at low levels, but not high levels, increase PL activity without changing its mRNA levels.

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.

Exocrine pancreatic secretion is stimulated in piglets fed fish oil compared with those fed coconut oil or lard

An experiment was conducted to study the effect of feeding diets containing fat sources with different fatty acid composition (fish oil, coconut oil or lard, 10 g/100 g diet) on exocrine pancreatic secretion in piglets after weaning. A total of 16 barrows were weaned at 4 wk of age; 3 d later, they were surgically fitted with a catheter in the pancreatic duct for continuous collection of pancreatic juice. Collections of pancreatic juice were made every other day starting 4 d postsurgically. Piglets fed the fish oil diet secreted a significantly greater volume of pancreatic juice than piglets fed the coconut oil or lard diets. The output [U/(h. kg(0.75))] of lipase was higher in piglets fed fish oil than in piglets fed lard or coconut oil. The output of colipase was greater in piglets fed fish oil and coconut oil than in those fed lard. The dietary treatments did not affect the output of carboxylester hydrolase. The output of trypsin was significantly lower in piglets fed lard than in piglets fed fish oil or coconut oil diets and the output of carboxypeptidase B was greater in those fed the fish oil diet. Protein, chymotrypsin, carboxypeptidase A, elastase and amylase outputs did not differ among the dietary treatment groups. The apparent digestibilities of nutrients and energy were measured in feces and did not differ among groups. Thus, the greater output of lipase in fish oil-fed piglets did not result in a greater digestibility of fat in this diet.

Fats infused intraduodenally affect the postprandial secretion of the exocrine pancreas and the plasma concentration of cholecystokinin but not of peptide YY in growing pigs

In pigs, the spontaneous secretion of the exocrine pancreas and the release of cholecystokinin (CCK) and peptide YY (PYY) after intraduodenal infusion of fully saturated synthetic fats differing in chain length was studied. Growing pigs (n = 6) were prepared with pancreatic duct catheters, duodenal T-cannulas and catheters placed in the jugular vein. The pigs were fed 2 g/100 g body twice daily. Beginning with the morning feeding, a medium-chain triglyceride (MCT: glycerol tricaprylate), a long-chain triglyceride (LCT: glycerol tristearate) or saline was infused at a rate of 0.1 g/100 g body. Pancreatic juice was collected, beginning 1 h preprandially until 3 h postprandially. Blood samples were obtained 15 min preprandially and 15, 45, 90 and 150 min postprandially. The infusion of MCT evoked a change in the trend of the curve for the volume of secretion of pancreatic juice, lipase and colipase concentrations and outputs. The trend of the curve did not change over time for CCK and PYY. Differences between the trends of the curves for the saline and MCT treatment were observed for volume of secretion, protein output, lipase content and output, trypsin and colipase output. Differences in the trends of the curves between MCT and LCT were obtained for the outputs of protein, lipase and colipase. Plasma CCK levels were lower as a result of the MCT treatment compared with the saline and LCT treatments. The results suggest an immediate, distinguished response of the porcine exocrine pancreas to fats differing in chain length.

Adaptation of the exocrine pancreas to dietary fats

This article reviews studies on the adaptation of the exocrine pancreas to dietary fat. We include all the latest information about the mechanisms that underlie the adaptation of the secretory mechanism of the exocrine pancreas to the amount and the type of dietary fat. We review the kinetics of pancreatic adaptation and the mediators of the adaptive response of the pancreas including cellular and molecular mechanisms (modulation of intracellular messengers and gene expression of the different enzymes and secretagogues involved in the adaptation process). At the same time we include our results in this field in dogs and humans.

Response of rat exocrine pancreas to high-fat and high-carbohydrate diets

Intake of diets with high fat content is a risk factor for acute pancreatitis and pancreatic cancer. The underlying mechanisms leading to the development of these diseases due to high fat intake are currently unknown. The current study was designed in rats to determine the physiologic and pathological consequences of a highfat diet that contained excess amounts of cottonseed oil or a high-carbohydrate diet that contained high amounts of sucrose on the exocrine pancreas. Rats were maintained on the diets for 4 weeks, and a cannula was inserted into the right jugular vein and one into the pancreatic duct for collection of pancreatic juice. Volume of the pancreatic juice and concentrations of amylase, lipase, and trypsinogen in the pancreatic juice were measured before and after infusions of CCK-8. Results showed that basal and CCK-stimulated pancreatic outputs of volume, amylase and lipase but not trypsinogen, were significantly elevated in intact rats given a high-fat diet when compared with rats given a high-carbohydrate diet. Forty-eight hours later, rats were sacrificed, and parts of the pancreas were removed for isolation of pancreatic acinar cells and for histopathologic studies. Pancreatic acini isolated from rats on a high-fat diet showed significantly lower basal and CCK-stimulated amylase release when compared with those on a high-carbohydrate diet. Histology of the pancreas of rats on a high-carbohydrate diet appeared normal; however, the pancreas of rats on high-fat diet showed significant alterations in exocrine pancreas. These results showed abnormalities in the exocrine pancreas of rats on a high-fat diet, that were not found in rats on a high-carbohydrate diet; further, they support the contention that a high-fat diet has a deleterious effect on the pancreas.

Maternal and early dietary fatty acid intake: changes in lipid metabolism and liver enzymes in adult rats

Over the last decade, much evidence has emerged to suggest that alterations in maternal nutrition during pregnancy may irreversibly affect aspects of physiological and biochemical functions in the fetus. This study was designed to determine the mechanisms involved in these alterations. Our hypothesis was that the type of maternal dietary fat received in early life could determine the level of lipoprotein lipase (LPL; EC 3.1.1.34) activity and gene expression which would be maintained into later life. A diet high in (n-3) polyunsaturated fatty acids was predicted to be associated with higher levels of lipoprotein lipase (LPL) activity and expression and lower levels of plasma triglyceride after a high fat meal challenge. Using a 2x2 factorial design, Wistar Albino rats were pair-fed either a fish oil diet (50 g/kg) or a mixed oil diet (50 g/kg) for the last 2 wk of gestation, during lactation and pups were fed these diets until 5 wk of age. After 5 wk, the rats were fed nonpurified diet. The rats were killed at 5 wk (young) or 10 wk (adult) of age after a mixed oil (50 g/kg) test meal. There were significant age effects on plasma triglyceride (P<0.02), cholesterol (P<0.001), glucose-dependent insulinotrophic polypeptide (GIP) (P<0.001) and liver glutathione reductase activity (P<0.05) which were all higher in the young rats compared to the adults. There were significant effects of diet on triglyceride (P<0.001), cholesterol (P<0.001) and LPL mRNA levels (P<0.001). GIP and triglyceride levels were significantly correlated (r = 0.66; P<0.001). Omental adipose tissue LPL activity as significantly higher in the fish-oil fed groups compared to the other groups (P<0.001), whereas Epididymal adipose tissue LPL mRNA was significantly higher in the mixed oil-fed adults compared to the other groups (P<0.001). The latter result suggested an imprinting effect of fatty acid composition in early life on LPL gene expression. Liver superoxide dismutase activity was affected by age and diet and was higher in the young than in the adults and higher in the fish oil-fed young than in those fed the mixed oil-fed (P<0.005). Catalase activity was also affected by age (P<0.001) and diet (P<0.001), and there was a significant interaction between age and diet (P<0.001). Catalase activity was higher in rats fed fish oils at both stages of development, suggesting that feeding fish oils to rats in early life raises oxidative stress throughout life. The majority of the significant differences shown were between the age groups and not between the two dietary groups, suggesting that postprandial handling of a standard fat meal is affected more by age than by early dietary fatty acid composition. However, the mechanisms of biological imprinting of fatty acids on LPL expression and on enzymes related to oxidative stress requires more investigation.

Pancreatic enzyme secretion in response to test meals differing in the quality of dietary fat (olive and sunflowerseed oils) in human subjects

The aim of the present study was to investigate in human subjects whether or not the ingestion of two liquid meals that differed only in their fatty acid composition (due to the addition of olive oil (group O) or sunflowerseed oil (group S) as the source of dietary fat) would lead to differences in the pancreatic enzyme activities secreted into the duodenum. The experiments were performed in eighteen cholecystectomized subjects who, during the 30 d period immediately before surgery, modified their habitual diets in such a way that their fat composition would reflect, as far as possible, that of the experimental meals. Lipase (EC 3.1.1.3), colipase, amylase (EC 3.2.1.1), chymotrypsin (EC 3.4.21.1) and trypsin (EC 3.4.21.4) activities were measured in duodenal contents aspirated before and after the ingestion of the test meals. The plasma levels of secretin and cholecystokinin (CCK) were also examined. Duodenal enzyme activities were similar in resting conditions. No significant differences were revealed in postprandial enzyme activities, except for lipase activity, which was higher in group O, probably in relation to the greater plasma CCK concentrations observed in this group. In the absence of enzyme output data, we should not exclude the possibility that the type of dietary fat will affect human pancreatic enzyme secretion to a greater extent than is evident from the present study, for instance through a flow-mediated effect, as we previously observed in dogs.

Exocrine pancreatic secretion in suckling goats. Adaptative effects of maternal milk and a milk substitute

Suckling goats were fed ad libitum during the first month of their life by goat milk or by a milk replacer. These diets differed in the amount of fat and the type of protein. The composition of the exocrine pancreatic secretion in the basal period and in response to food were compared in both conditions. Pancreatic juice was collected one hour before meal intake up to the 8th postprandial hour. Pancreatic flow rate, bicarbonate and chloride levels, total protein and enzyme activities were measured. In resting conditions and in response to food, the lipase activity was found to be significantly lower in the group fed with milk replacer, which was poorer in fat. These results indicate an adaptation of the enzyme output to the available quantity of its substrate, similar to that described in the rat. Postprandial differences in the pancreatic flow rate, electrolytes and total protein were found between both groups. Their origin can be attributed to the protein used (soyabean) in the milk substitute. Such soya protein alters the normal clot formation in the abomasum and allows an accelerated abomasal digesta outflow and duodenal pH alkalinisation.

Effects of the amount and type of dietary fat on exocrine pancreatic secretion in dogs after different periods of adaptation

Mongrel dogs were fed, from weaning to 6 months of age, on one of two 9% lipid diets that differed only in the type of fat content (sunflower oil or virgin olive oil) to study their effects on exocrine pancreatic secretion, in the basal period and in response to food. In addition, the results were compared with those obtained in a previous work performed by us on dogs adapted for 8 months to diets containing a higher (15%) amount of the same dietary fats to further evaluate the influence of the amount of dietary fat and the length of the adaptation period. The results from the present study show that both the volume and bicarbonate secreted in the absence of stimuli are unaffected by the quality of dietary fat. In contrast, in response to food, the pancreatic juice flow and the bicarbonate output were significantly higher in the group of animals given the sunflower oil diet. The differences seem to be related with the oleic acid content in the diets and the effectiveness of this fatty acid in triggering the release of inhibitory peptides such as pancreatic polypeptide and peptide YY. The comparison between the results from our present and previous studies supports the afore-mentioned hypothesis and confirms the existence of a clear influence of the amount and type of dietary fat, especially the oleic acid content, upon the pancreatic response to food, without ruling out a role for the duration of the adaptation period.

Absence of rapid adaptation of the exocrine pancreas of conscious dogs to diets enriched in fat or carbohydrates

Adult mongrel dogs were fed during 8 days on one of two diets, one rich in fat (FR) and the other rich in carbohydrates (CR), in order to compare the exocrine pancreatic secretion in the basal period and in response to food. Under resting conditions, mean pancreatic juice flow and mean values of protein content, amylase and lipase activity and production were similar in both experimental groups, suggesting that the period of adaptation used did not produce any influence on the measured parameters. No significant difference between the two dietary groups was found in postprandial volume of pancreatic juice. The peak of pancreatic juice flow in FR-group was smaller but remained elevated until the end of the 5th h, possibly due to the fact of delayed gastric emptying when animals are fed with a high fat diet. No significant differences were found between the groups in neither postprandial amylase activity and secretion nor lipase activity. On the other hand, lipase output was significantly higher in FR-group but only during the 5 postprandial h. This fact may be related to some intestinal factor stimulated by the hydrolysis products of fat. Finally, our findings show that no rapid adaptation of exocrine pancreatic secretion exist to the diet, at least in our experimental conditions. Of course, this does not exclude that the phenomenon of adaptation may appear in the dog under long-term adaptation to the diet.

Effect of dietary canola oil and its degree of oxidation on exocrine pancreatic secretions in growing pigs

Four barrows, average initial weight 35 kg, were fitted with permanent pancreatic re-entrant cannulas and used to determine the effect of level and quality of dietary fat on exocrine pancreatic secretions. The pigs were fed four corn starch-based diets that contained 15% crude protein from isolated soy protein. Diet 1 contained no canola oil (C-0); diet 2, 15% canola oil (C-15); diet 3, 15% canola oil that was heated under vacuum at 180 degrees C for 12 h (C-15/12); diet 4, 15% canola oil that was heated under vacuum at 180 degrees C for 24 h (C-15/24). Heat treatment resulted in a 4- to 5-fold increase in the content of malonaldehyde which is derived from the oxidation of fatty acids and which is closely related to odour and rancidity in lipids. The experiment was carried out according to a 4 x 4 Latin square design. The pigs were fed twice daily, at 08:00 and 20:00 h, 900 g each meal. Following an adaptation period of 7 d, pancreatic juice was collected continuously for 24 h at 2-h intervals from 08:00 on d 8 until 08:00 on d 9 and from 08:00 on d 10 until 08:00 on d 11 during each experimental period. The volume of secretion of pancreatic juice peaked 6-10 h postprandially and was similar (P > .05) during day (08:00-20:00 h) and night (20:00-08:00 h). Replacement of 15% starch by 15% canola oil resulted in a decrease (P < .05) in the secretion of alpha-amylase and an increase (P < .05) in the secretion of lipase. The inclusion of oxidized fat caused a further increase (P < .05) in total lipase activities. It can be concluded that the exocrine pancreas is able to adapt to variations in the level and quality of dietary lipids.

The effect of non-starch polysaccharide supplementation on circulating bile acids, hormone and metabolite levels following a fat meal in human subjects

The effects of guar gum, sugar-beet fibre (SBF) and wheat bran supplementation of a high-fat test meal were compared with an NSP-free control meal and a meal containing an equivalent amount of the ion-exchange resin cholestyramine in healthy non-obese human volunteers. Their effects on gastric emptying, postprandial circulating bile acids, triacylglycerols and gastrointestinal hormone levels were studied. The in vitro binding of NSP and cholestyramine to [1-14C]glycocholic acid was measured and compared with their in vivo effect. Guar gum and cholestyramine supplementation significantly lowered circulating postprandial bile acid, triacylglycerol and gastric inhibitory polypeptide concentrations, but sugar-beet fibre and wheat bran were without effect. Liquid gastric emptying, as assessed by circulating paracetamol levels, was slightly accelerated in the guar gum-supplemented meal. Glycocholic acid bound strongly to the insoluble fraction of cholestyramine and the soluble fraction of guar gum. The insoluble fractions of SBF and wheat bran bound only small quantities of glycocholate; no bile acid binding was detected in the soluble fractions of these NSP. The study demonstrates that measurement of postprandial bile acids enables an indirect measurement to be made of bile acid binding to NSP in vivo. The results support the hypothesis that the hypocholesterolaemic action of guar gum is largely mediated via interruption of the enterohepatic bile acid circulation, but indicate that the hypocholesterolaemic action of SBF is mediated by another mechanism.

Are diets associated with different rates of human interdigestive and postprandial pancreatic enzyme secretion?

To determine if diets are associated with different rates of interdigestive and postprandial enzyme secretion and how quickly enzyme secretion is modulated by nutrients, 27 healthy humans were randomly selected to follow one of five diets. The calorie proportions of carbohydrate, fat, and protein in each diet was assigned by a mixture design. After the subjects followed a diet for 2 weeks, they were intubated with an oroduodenal tube, and enzyme outputs were measured during the interdigestive period and after eating a meal identical to meals eaten during the previous 2 weeks. For the next 24 hours subjects either followed the same diet or a diet that contained the same amount of fat, but the percent of carbohydrate and protein was changed by 30%. Then interdigestive and postprandial pancreatic enzyme outputs were remeasured. After 2 weeks, diets containing the most carbohydrate (50%-80%) were associated with the lowest interdigestive and postprandial amylase and lipase (P less than 0.05) and trypsin outputs (P less than or equal to 0.05). In contrast, diets containing the most fat (40%) were associated with the highest interdigestive and postprandial outputs of amylase (P less than 0.05) and trypsin (P less than 0.05). Maintaining or altering diets for 24 hours did not change interdigestive pancreatic enzyme outputs, but postprandial amylase output was significantly increased (P less than 0.05) by increasing protein and decreasing carbohydrate content of the diets by 30% for 24 hours. We conclude that diets containing a high proportion of calories as carbohydrate for 2 weeks are associated with lower interdigestive and postprandial pancreatic secretion than diets that have a high fat content. In response to diets, changes in postprandial pancreatic enzyme secretion occur within 24 hours whereas changes in interdigestive secretion (no nutrients in the lumen) occur after 24 hours.

Long-term adaptation of pancreatic response by dogs to dietary fats of different degrees of saturation: olive and sunflower oil

Mongrel dogs were fed, from weaning to 9 months of age, on one of two diets that differed only in the type of fat content (virgin olive oil or sunflower oil) to compare the composition of exocrine pancreatic secretion in the basal period and in response to food. In resting pancreatic flow, electrolytes and the specific activities of amylase, lipase and chymotrypsin were similar in both experimental groups. However, lipase and amylase outputs, and amylase and protein concentrations were significantly higher in the group fed on the diet rich in sunflower oil. Food intake was not followed by any change in flow-rate or electrolyte or protein content in the group given the diet rich in olive oil. Amylase activity and output were also lower in this group, as was lipase output, whereas activity and specific activity of chymotrypsin were lower in dogs fed on the diet containing sunflower oil. The differences traceable to the composition of the two types of dietary fat supplied may be related to the balance between factors that stimulate and inhibit pancreatic secretion.

Expression of rat pancreatic lipase gene is modulated by a lipid-rich diet at a transcriptional level

The amount of cytoplasmic mRNAs specific for pancreatic lipase and amylase as well as transcription of the corresponding genes were investigated in rats fed a diet containing 25% sunflower oil. Concentration of lipase mRNA was actually increased by the lipid-rich carbohydrate-low diet and reached a maximum level after 2 days, but further remained constant for at least 10 days. In contrast, about a two-fold decrease in the concentration of pancreatic amylase mRNA was only observed after rats were fed the high-lipid diet for 10 days. Transcription rate measurement on isolated nuclei from pancreatic tissue indicated that the concentration of nascent lipase and amylase transcripts was consistent with a transcriptional regulation of expression of these two genes.

Time-course of changes in pancreatic size and enzyme composition in rats during starvation

The effect of starvation for 3, 5, or 7 d on body weight, fat stores, pancreatic weight, and enzyme composition was studied in 300 g rats and was compared with a 3-d fast in 200 g rats. In the 300 g animals, fasting led to a gradual hypotrophy of the pancreas with a marked, continuous decrease in amylase content. Pancreatic lipase, trypsinogen, chymotrypsinogen, proelastase, and secretory trypsin inhibitor contents increased temporarily, but by d 7, they declined to about the initial values. This decline in enzyme levels coincided with the exhaustion of fat stores. The decrease in amylase content could be related to decreases in circulating insulin levels, whereas the temporary increase in lipase content may be owing to changes in plasma free fatty acid concentrations. In 200 g rats, starvation for 3 d led to exhaustion of fat stores that was accompanied by greater losses of pancreatic weight, protein, and amylase contents. In addition, the levels of trypsinogen and chymotrypsinogen decreased and lipase was unchanged. These findings indicate that during starvation, changes in pancreatic secretory enzymes are time-dependent and vary with the age, body weight, and/or adipose tissue mass of the rats.

Changes in mRNA levels of rat pancreatic lipase in the early days of consumption of a high-lipid diet

The time-course response of rat pancreatic enzymes to a diet containing 25% sunflower oil was investigated. A 1.2-fold enhancement in lipase specific activity was observed as early as the first day of diet consumption and was further increased up to 1.9-fold on the 5th day. On the other hand, colipase activity was slightly decreased during the first two days of high-lipid diet intake and then increased. An immediate and direct effect was also exerted by the 25% lipid diet on lipase biosynthesis. Both fractional synthetic rate and specific activity of lipase were comparably induced. Due to a 1.6-fold increase in the overall protein synthesis following 5 days of lipid diet consumption, the absolute synthesis of lipase and amylase was increased by 3.5-fold and 0.98-fold, respectively, as compared to control animals. By contrast, the synthesis of procarboxypeptidases and serine proteases did not increase before day 5, probably as the result of a distinct adaptive mechanism. The pancreatic mRNA levels in control and adapted animals, which were determined by dot-blot hybridization with amylase and lipase cDNAs, were consistent with a biphasic induction of lipase synthesis since a first increase in the level of the enzyme-specific mRNA during the first two days of diet intake (4-fold on day 1) was followed by a second increase after the fourth day (6.5-fold on day 5). On the other hand, amylase mRNA level was unchanged during the dietary manipulation. Thus, hyperlipidic diets exerted an both lipase activity and synthesis but a delayed effect on procarboxypeptidase and serine protease synthesis. In a similar manner, the immediate induction of lipase mRNA level by dietary fat, followed by another increase a few days later, suggested that at least two different mechanisms are involved in lipase mRNA induction.

Dietary regulation of amino acid transport activity in the exocrine pancreatic epithelium

Dietary-induced alterations in exocrine pancreatic amino acid transport were investigated in rats adapted for 14 days to isocaloric diets of varying casein and carbohydrate content. The kinetics of unidirectional (15 s) L-phenylalanine and L-lysine transport were measured relative to D-mannitol (extracellular tracer) in the perfused pancreas isolated from dietary adapted animals. In rats adapted to a 20% casein diet a weighted non-linear regression analysis of phenylalanine transport (1-24 mM) indicated an apparent Kt = 9.4 +/- 1.1 mM and Vmax = 14.8 +/- 0.9 mumol/min per g pancreas (n = 6). Saturation of lysine transport occurred at lower concentrations (0.05-10 mM) with an apparent Kt = 2.40 +/- 0.09 mM and Vmax = 2.44 +/- 0.18 mumol/min per g (n = 6). The characteristics of phenylalanine transport were modified after adaptation to either high (Kt = 3.6 +/- 1 mM, Vmax = 8.2 +/- 0.9 mumol/min per g, n = 3) or low (Kt = 4.2 +/- 0.9 mM, Vmax = 6.8 +/- 0.5 mumol/min per g, n = 3) carbohydrate diets. Increasing the dietary protein content (0-45% casein) led to a linear increase in the Kt for phenylalanine transport whereas Vmax values remained unchanged. Unlike phenylalanine, adaptation to a 0% casein diet significantly elevated the Vmax for lysine transport (4.82 +/- 0.21 mumol/min per g, n = 4) without altering the Kt (2.54 +/- 0.23 mM). The present findings suggest that changes in dietary composition induce select adaptive responses in the transport activities of System L (phenylalanine) and System y+ (lysine) in the basolateral membrane of the exocrine pancreatic epithelium.

Pancreatic adaptation to dietary lipids is mediated by changes in lipase mRNA

Lipase activity, rates of biosynthesis of lipase (triacylglycerol acylhydrolase, EC 3.1.1.3) and amylase (1,4-alpha-D-glucan glucanohydrolase, EC 3.2.1.1) as well as concentrations of their corresponding mRNAs were measured in the pancreatic tissue of rats fed isocaloric and isoprotein diets with inverse changes in the amounts of lipids and carbohydrates. A control diet (3% sunflower oil--62% starch) and three lipid-rich diets (10% sunflower oil--46.2% starch, 25% sunflower oil--12.5% starch and 30% sunflower oil--1.25% starch) were fed to rats for 10 days. Ingestion of the 10% lipid diet already resulted in a 1.4-fold increase in lipase activity while a 2.4-fold increase was observed with the other 2 high-lipid low-carbohydrate diets. Similarly, 1.3- and 3.1-fold increases in the total rate of protein synthesis were measured in pancreatic lobules of rats fed 10 and 25% or 30% lipid diets, respectively, as compared with control animals. While absolute lipase synthesis showed an important increase during the dietary manipulation (1.7- and 5.9-fold, respectively), amylase synthesis was significantly lower (1.1- and 1.5-fold, respectively). The level of lipase mRNA, as measured by dot-blot hybridization with the corresponding specific cDNA, showed a 2.2-fold increase (10% lipid diet) and a 3.9-fold increase (25% lipid diet), whereas the level of amylase mRNA showed only 1.1- and 1.3-fold increases under the same experimental conditions. These data demonstrated that protein-specific synthesis rates more accurately reflected pancreatic adaptive states than tissue levels of enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of inverse changes in dietary lipid and carbohydrate on the synthesis of some pancreatic secretory proteins

The effect of ingesting isocaloric and isonitrogenous diets with increasing amounts of lipid (0-30%) and consequently decreasing amounts of carbohydrates (68.7-1.25%) on the exocrine pancreas was studied in adult male Wistar rats. Pancreatic contents of chymotrypsin, lipase and colipase activity, as well as synthesis of amylase, lipase, procarboxypeptidases and individual serine proteases were examined. Lipid-free diets and diets containing 1% lipid were found to have little effect on pancreatic proteins as compared with lipid-rich diets where two distinct patterns of response were observed. Ingestion of diets containing 3-20% lipid resulted in a progressive increase in the activity of lipase, colipase and chymotrypsin up to 2-fold in the first case and 1.6-fold in the two other cases when animals were fed the 20% fat diet. Under the latter conditions, the relative synthesis of secretory proteins, as expressed as percentage of the radioactivity incorporated into individual proteins compared to that incorporated into the total mixture of exocrine proteins, was unchanged for procarboxypeptidases, whereas it was stimulated for lipase (2-fold) and serine proteases (1.6-fold). Amylase relative synthesis progressively decreased as the lipid content of diets increased. Consumption of hyperlipidic diets containing 25% and 30% fat resulted in a further enhancement in the activity of lipase and colipase in the gland in contrast with chymotrypsin activity which was unchanged as compared to the control diet (3% lipid). As far as biosynthesis was concerned, a plateau in the relative synthesis of lipase and serine protease was reached. Amylase relative synthesis further decreased down to 2.2-fold when rats were fed the 30% fat-rich diet whereas that of procarboxypeptidases was markedly increased (about 1.7-fold). Absolute rates of synthesis of total pancreatic secretory proteins, as expressed with regard to the DNA content of the tissue, indicated that biosynthesis of all secretory pancreatic proteins was stimulated by hyperlipidic diets (at least 2-fold with the 30% lipid diet). Consequently, when such an increase was taken into consideration, the absolute synthesis of amylase was found to be unchanged throughout the dietary manipulations, whereas that of lipase, procarboxypeptidases and serine proteases were stimulated by 4.0-fold, 3.4-fold and 3.2-fold, respectively.

Effect of pretreatment with a high fat diet on the gastric inhibitory polypeptide and insulin responses to oral triolein and glucose in rats

Male Wistar rats were pretreated with 3 ml triolein orally for 4 days in addition to their normal diet. A similar control group were allowed free access to normal laboratory food. When given an oral fat load (1 ml triolein) plasma gastric inhibitory polypeptide (GIP) and triglyceride levels were significantly higher in the fat pretreated group. Inhibition of fat-stimulated GIP release by exogenous insulin was demonstrated in the untreated control group (plasma GIP: 663 +/- 49 versus 853 +/- 92 ng/l, mean +/- SEM p less than 0.025), but pretreatment with an oral fat load abolished this effect (plasma GIP: 1008 +/- 95 versus 1116 +/- 100 ng/l, p NS). Plasma glucose levels were significantly higher in fat pretreated rats given oral fat and intraperitoneal insulin compared with untreated controls (plasma glucose nadir 2.6 +/- 0.48 versus 1.6 +/- 0.15 mmol/l, p less than 0.05). Fat-pretreated rats showed significantly higher insulin and glucose levels compared with the untreated rats when given oral glucose (plasma insulin: 6.2 +/- 1.2 versus 2.5 +/- 0.59 micrograms/l, p less than 0.01; plasma glucose: 10.2 +/- 0.39 versus 8.9 +/- 0.41 mmol/l, p less than 0.025). Pretreatment of rats on a high fat diet causes (1) increased GIP secretion in response to an oral fat load, (2) abolition of the feed-back inhibition of exogenous insulin on fat-stimulated GIP release, and (3) some degree of insulin resistance.

Characterization of a mannosyl-lipid compound of microsomal fractions of rat pancreas and influence of diet

1. High-starch diet induces an activation of rat pancreatic microsomal mannosyl-transferase activity as compared with a standard diet or a high-fat diet. 2. This increase is found in a mannose-containing lipid which is identified as a dolichyl-phosphoryl-mannose on the criteria of DEAE-cellulose chromatography, alkaline and acid hydrolysis, thin-layer chromatography and identity of this endogenous product with the [14C]mannose-containing product synthesized in presence of exogenous dolichyl-monophosphate added to the incubation medium. 3. Kinetic parameters (Km and Vmax) of the enzyme versus polyprenic acceptor are not modified by the diet. 4. The results indicate that the activation of the mannose transfer is principally due to an increase of the polyprenic endogenous acceptor by the high-starch diet.

Dietary regulation of pancreatic protein synthesis. I. Rapid and specific modulation of enzyme synthesis by changes in dietary composition

Dietary adaptation of pancreatic protein synthesis and of pancreatic enzyme concentration, was studied over the first 24 h of exposure to a new diet. Rats were adapted to a carbohydrate-rich (G) or to a protein-rich diet (P) and were switched to the opposite regime after a 15 h fast. The evolution of the relative rate of synthesis of amylase, chymotrypsinogen and trypsinogen and of the pancreatic concentration of amylase and chymotrypsinogen were followed. Fasting caused important modifications in the relative rate of synthesis of the three enzymes in rats adapted to a P diet. Adaptative changes in the relative rate of synthesis of amylase, chymotrypsinogen and trypsinogen were seen within 2 h after the beginning of refeeding. These changes were followed by corresponding adaptative modifications in pancreatic contents 4 h after the beginning of refeeding. After 24 h of refeeding, significant adaptative changes had occurred in both the relative rates of synthesis and in enzyme concentrations. Thus exocrine pancreatic protein synthesis can be modulated as early as 2 h after refeeding and this modulation is followed by adaptative changes in pancreatic enzyme content.

Effect of diet composition on the protein synthetic pattern of the rat pancreas after a feeding period of five days

Rats were fed for five days on a protein-rich and on a carbohydrate-rich diet, respectively. One half of the pancreas of these rats was incubated with [3H]leucine and the other half with [14C]leucine and extracts from these pancreas halves were prepared. Mixtures of the differently labeled extracts were subjected to electrophoresis towards the anode as well as towards the cathode on a polyacrylamide gel containing urea at pH 8.5. Several secretory enzymes could be identified on the gels. Along the gels the 3H : 14C ratio was determined in 1 mm slices. The results show that after five days of feeding a diet there is some adaptation to diet composition. Generally rather small changes in synthetic rate occur. Only one component, the cathodic chymotrypsinogen shows an important difference in synthetic rate under the two circumstances.

Rat lingual lipase: factors affecting enzyme activity and secretion

The lingual serous glands of rat tongue secrete a potent lipase that acts in the stomach in which it initiates the digestion of dietary fat. The subcellular localization of the enzyme and factors affecting its activity and secretion were studied in adult male Sprague-Dawley rats. In a fraction rich in secretory granules, 42% of the lipase content of lingual serous glands was recovered after fractionation of homogenates of discontinuous gradients of urografin in 0.3 M sucrose. Lipase secretion was stimulated by isoprenaline: 2 h after isoprenaline administration, the lipase content of lingual serous glands was 73 +/- 5% lower than that of the control group. Accumulation of lipase began 8 h after the injection, reaching 57 +/- 7% of the initial level of the control group after 25 h. Bilateral resection of the glosso-pharyngeal nerves or bilateral sympathectomy led to a 40--50% decrease of enzyme activity in 7 days. Enzyme activity was markedly affected by the fat content of the diet. Feeding a high-fat diet (22% corn oil) for a period of 2 wk led to a 45% increase in the lipase content of lingual serous glands. The exponential rise in the lipase activity of the lingual serous glands immediately after birth could be related to the high-fat content of rat milk. The data suggest that the lingual serous glands are similar to other exocrine glands such as pancreas and parotid gland in the subcellular localization of secretory enzymes and mechanisms of enzyme secretion.

[Effects of diets rich in triglycerides and phospholipids on lipase and phospholipase A activities in rat pancreatic juice and pancreas]

Lipase and phospholipase A activities were increased in the pancreas and pancreatic juice of rats ingesting during two months 20% phospholipids- or triglycerides-rich diets. The activity of lipase is higher with the triglycerides-rich diet and the phospholipase A activity is higher with the phospholipids-rich diet. After seven days of the experiment, these two enzymes activities were less increased with diet containing 40% lipids.

Lack of adaptation of pancreatic colipase in rats and mice

A new automated potentiometric method for the determination of colipase was developed, taking advantage of the reactivation of purified lipase, in the presence of bile salt and at pH 6.5. High-fat and high-starch diets induced an opposite regulation of lipase and amylase in the rat pancreas. At the same time, the level of colipase was not influenced by nutrition. During fasting and in alloxan diabetes, the specific activity of lipase almost doubled, that of amylase decreased sharply, and colipase was not affected in the rat pancreas. In obese-hyperglycemic mice, suffering from obesity, hyperinsulinism, and moderate diabetes, there was also no regulation of pancreatic colipase. Thus, at variance with a number of hydrolases, there was no dietary or hormonal adaptation of colipase. However, this was probably without any bearing on intraluminal lipolysis. Indeed, comparison of lipase and colipase activities in pancreas and in small intestine suggests that colipase concentration is not a limiting factor of intraluminal lipolysis. The molecular mechanism of this assumption is discussed on the basis of in vitro studies.

Esterolytic activities of rat intestinal mucosa. 1. Characterization, cellular distribution and subcellular localization of a glycerol-ester hydrolase

The preferential cellular distribution in the villus tip and the subcellular localization in the endoplasmic reticulum of an intestinal glycerol-ester hydrolase from rat mucosa are described. The enzyme is shown not to be from either pancreatic or bacterial origin; it catalyzes the hydrolysis of short- and medium chain triglycerides and of p-nitrophenylacetate. Contrarily to the specificity found for the pig intestinal lipase (Serrero, Négrel and Ailhaud, 1975), no activity is detectable against acylCoA; a thiolester hydrolase different from the glycerol-ester hydrolase was demonstrated after differential solubilization and chromatographic separation. A high proportion of glycerol-ester hydrolase is present in the intestinal lumen; its possible complementary role in lipid degradation is discussed.

Exocrine pancreas: evidence for topographic partition of secretory function

The pattern of amylase, lipase, and chymotrpsinogen content found in pancreatic exocrine tissue surrounding the islets of Langerhans (periinsular halos) differs from that of the rest, or teleinsular part, of the pancreas. Such a topographic partition of secretory function may play a role in the regulation of pancreatic juice composition.

Multiple forms of tryptophanyl-tRNA synthetase from beef pancreas

Three different forms of tryptophanyl-tRNA synthetase can be isolated from pancreatic extracts. Structural, immunological and catalytic properties of these various forms have been compared. The native enzyme is a dimeric molecule of molecular weight 108000. Two other forms, of molecular weight 85000 and 82000, are composed of two polypeptide chains identical with the carboxyl terminal region of the native subunits. These molecules are supposed to derive from the original protein by removal, from the amino-terminal part of each subunit, of a fragment of 11000 to 13000 molecular weight. Such removal modifies the shape and the stability of the molecule and decreases its specific acitvity. The origin of the derived forms is attributed to proteolysis. In fact, limited proteolysis of purified tryptophanyl-tRNA synthetase, in its native form, by elastase, results in the formation of an active compound, similar to one of the tryptophanyl-tRNA synthetase derived forms. Furthermore, incubation with "elastolytic fractions" prepared from pancreatic extracts presenting a particularly high level of proteolytic activity produces the same cleavage in tryptophanyl-tRNA synthetase polypeptide chain.