Pancreatic Hypertrophy Research Articles

The Effects of Long-Term Soy Protein and Milk Protein Feeding on the Pancreas of Cebus albifrons Monkeys

Twenty-seven 2- to 4-yr-old cebus monkeys (Cebus albifrons) were fed from infancy purified diets containing lactalbumin, soy isolate, casein or soy concentrate as the sole protein source. hematologic and clinical chemistry values were similar for all groups. Head and tail portions of each pancreas were surgically removed for histopathologic evaluation and determination of protein, RNA and DNA content, and for trypsin and chymotrypsin activity. Hematoxylin and eosin-stained sections from 26 of 27 monkeys showed normal pancreatic tissue with occasional acinar vacuolation in all diet groups. The remaining animal, one of only two fed soy concentrate, had diffuse interstitial fibrosis of the pancreas associated with mild to moderate atrophy of acinar tissue. Biochemical analyses of the pancreatic biopsies indicated no group differences among animals fed lactalbumin, soy isolate or casein. One of two monkeys in the soy concentrate group showed decreased pancreatic protein, RNA and trypsin concentrations; this was probably due to the fibrosis in this animal. No evidence of pancreatic hypertrophy or hyperplasia, as measured by RNA/DNA and protein/DNA ratios, respectively, was seen in any diet group.

Caerulein and secretin induced pancreatic growth: a possible control by endogenous pancreatic somatostatin

Pancreatic hypertrophy and hyperplasia following chronic joint (CA + SE), or separate, caerulein (CA: 1 μg·kg −1) and secretin (SE: 75 μg·kg −1) administration were studied in parallel with pancreatic somatostatin (SRIF) contents following 2, 4, 7 and 10 days of treatment. Parameters indicative of pancreatic growth (tissue weight, DNA and protein contents, cellular protein concentrations) increased significantly after 2 days of CA or CA + SE and reached a plateau between days 4 and 10. SE merely induced a mild hypertrophy after 4 days. Endogenous pancreatic SRIF contents varied upon treatment, differently so with each peptide regimen. Indeed, CA and CA + SE treatments decreased total SRIF contents after 2 days with no effect thereafter. SE also decreased the latter after 2 days while significant increases were observed after 7 and 10 days. The inverse relationship seemingly existing between SRIF contents and the amplitude of hormonally-induced pancreatic growth supports the hypothesis that endogenous pancreatic SRIF, operating as an ‘antigrowth’ factor, may participate in the exogenous CA, SE and CA + SE stimulated pancreatic growth phenomena.

Reversal of α-difluoromethylornithine inhibition of caerulein-induced pancreatic growth by putrescine

The role of ornithine decarboxylase and of polyamines was investigated on caerulein-induced pancreatic growth through the use of α-difluoromethylornithine (DFMO) and putrescine. Caerulein, the cholecystokinin analog, given at a dose of 1 μg · kg −1 three times a day was associated with pancreatic hyperplasia and hypertrophy after 2 and 4 days of treatment. The present study shows that putrescine, given once daily i.p. at a dose of 300 μmol · kg −1, can reverse the previously observed DFMO inhibition on pancreatic DNA content increments stimulated by caerulein. It was also observed that putrescine inhibits severely the 2-day caerulein-induced pancreatic hypertrophy, yet interferes only moderately with 4 days of caerulein treatment. These data lend further support to the involvement of ornithine decarboxylase and polyamines in induced pancreatic growth.

Modulation of rat pancreatic muscarinic cholinergic receptors by caerulein

To evaluate the modulation of pancreatic muscarinic receptors in two states of pancreatic growth, hypertrophy and hyperpasia, caerulein, a cholecystokinin analog, (1 μg/kg) was administered thrice daily for 2 and 4 days to adult rats. After 2 days of treatment, pancreatic hypertrophy was well established as evidenced by increases in pancreatic weight, cellular mass and protein content. Using an increase in DNA content as an index of hyperplsia, we demonstrated that pancreatic hyperplasia occurred only after 4 days of caerulein treatment. Caerulein increased the concentration of muscarinic receptors per DNA in pancreatic homogenate by 57% over control value after 2 days of treatment without modification of the receptor affinity for the ligand QNB. This increase involved mainly receptors in the low affinity state for carbamylcholine and their concentration returned to control levels after 4 days of treatment. The functional capacity of the acini was significantly increased after 2 days of caerulein as amylase release (U/mg DNA) was significantly increased but the sensitivity of these acini to carbamylcholine was significantly decreased. After 4 days of caerulein, the functional capacity has returned towards control values but the sensitivity to carbamylcholine remained decreased. The increase in muscarinic receptor concentration could be ascribed to a general increase in cellular proteins, as part of the hypertrophic effect of caerulein. This specific effect would also explain the increased functional secretory capacity of the caerulein-treated acini but the decreased sensitivity to carbamylcholine probably resulted in changes at a postreceptor loci since the affinities of the muscarinic receptors for carbamylcholine remained unaffected.

Trophic effect of bombesin on the rat pancreas: Is it mediated by the release of gastrin or cholecystokinin?

This work investigates the effect, on the rat pancreas, of a chronic administration of bombesin in function of the dose and duration of treatment and examines whether this effect may be mediated by the release of endogenous gastrin or cholecystokinin. Bombesin, administered three times daily for 5 or 15 days, induced a marked increase in pancreatic weight, its protein, RNA and enzyme contents with the dose of 10 μg/kg body weight: the ratios of pancreatic weight, protein and RNA contents to DNA contents increased significantly after a 5 day treatment, suggesting cellular hypertrophy. Pancreatic DNA content was markedly enhanced after a 15 day treatment, suggesting cellular hyperplasia. Antrectomy decreased plasma gastrin levels, but did not alter the pancreatico-trophic action of a 10 μg/kg bombesin treatment for 5 days. Proglumide, an inhibitor of cholecystokinin and gastrin receptors in the pancreas, did not affect the growth of the pancreas induced by a 10 μg/kg bombesin treatment for 5 days. It is concluded that chronic bombesin induces, in the rat pancreas, cellular hypertrophy or hyperplasia depending on the duration of treatment. Pancreatic hypertrophy is not mediated by the release of endogenous gastrin or cholecystokinin.

The USDA trypsin inhibitor study. I. Background, objectives, and procedural details

Short-term feeding studies have shown that raw soy flour and purified trypsin inhibitors (TI) cause pancreatic hypertrophy and hyperplasia in certain monogastric animals. Prolonged exposure to high levels of TI in raw soy ultimately leads to pancreatic nodular hyperplasia and acinar cell adenoma in rats exposed to low levels of pancreatic carcinogens. Such change has been observed even in the absence of any exposure to known carcinogens. These results emphasized the need for chronic (2 yr) feeding trials which would clearly reveal dose response relationships of alterations in pancreatic pathology to dietary TI and possible interactions with dietary protein and fat. Here we report on the objectives and designs of the first phase of the USDA TI Study, including composition of diets, preparation, and analyses of test substances. To provide the requisite TI and protein levels, raw and heated defatted soy flours, soy protein isolates, and lactic casein were used. The interrelationship of dietary level of TI (93–1270 mg/100 g diet) and that of protein (10%, 20%, and 30%) to pancreatic function and pathology will be reported in the following three papers. Both serial and chronic sacrifice regimes, respectively, were employed with 26 diets and 40 weaning male Wistar rats per dietary group.

Alteration of the rat exocrine pancreas after chronic scopolamine administration.

N-Methyl scopolamine (NMS) 25 mg kg-1 was given to rats for 14 days as a single daily intraperitoneal injection or by constant infusion through osmotic minipumps placed in the abdominal cavity. The anticholinergic drug reduced significantly body and pancreatic weights, and total pancreatic DNA contents, an indication of tissue growth inhibition. Total enzyme and protein contents were however significantly increased with the drug infusion more efficiently than by the daily injection. It is suggested that pancreatic hypertrophy observed after NMS treatment can be ascribed partially to inhibition of enzyme release elicited by blocking the enteropancreatic reflex causing over a long period enzyme accumulation in the gland. In conclusion, chronic anticholinergic treatment resulted in pancreatic aplasia and hypertrophy and could serve as a good model to study muscarinic receptor modulation in the pancreas.

Folyamines and pancreatic growth induced by caerulein

Activation of polyamine metabolism may be important to initiation of pancreatic cell growth. We are reporting that such activation did occur during pancreatic growth initiation by caerulein, a cholecystokinin analog. Maximal increases in total putrescine (319%), spermidine (63%) and spermine (50%) were observed 12, 96 and 96 hr respectively after the beginning of the caerulein treatment. This time period coincides with pancreatic hypertrophy and hyperplasia as characterized by increased cell mass and DNA content. Rates of pancreatic weight and DNA content increases were significantly correlated with total spermidine and spermine contents. These data suggest that polyamine biosynthesis is closely associated with pancreatic growth.

Short-term effects of feeding raw soya flour on pancreatic cell turnover in the rat.

Pancreatic acinar cell turnover was studied after a 48-h fast and in rats fed raw soya flour (RSF) for up to 28 days. Feeding RSF for 2 days resulted in a significant increase in pancreatic weight and RNA content while protein was increased by the 4th day compared with rats fasted for 48 h. RSF also resulted in a significant increase in RNA by the 4th day and weight and protein by the 7th day compared with rats fed heated soya flour (HSF). This pancreatic hypertrophy was maintained for the rest of the study period. Two days after starting RSF, pancreatic DNA synthesis, measured by the rate of incorporation of [3H]thymidine into pancreatic DNA, had increased sixfold compared with that in animals fed HSF but returned to control values again by the 4th day on the diet. Autoradiography showed that this increase in DNA synthesis occurred in both acinar and duct cells, with turnover in acinar cells preceding that in duct cells. A second more gradual rise in DNA synthesis was seen from the 7th to 28th day. This peak in DNA synthesis was associated with an increased total pancreatic DNA content and occurred predominately in duct cells with a smaller contribution from acinar cells. Histological studies of the pancreas during the 1st wk showed cell damage and tissue necrosis, possibly due to exposure to high levels of cholecystokinin released by RSF. The first peak in DNA synthesis may be a regenerative response to this damage. The second more delayed peak appears to be hyperplasia in response to a trophic stimulus, again possibly mediated by cholecystokinin.

Nutritional studies of a carboxypeptidase inhibitor from potato tubers.

Carboxypeptidase inhibitor from potato tubers was fed to newly hatched chicks at a level equal to that present in diet containing 50% raw potato, which caused severe growth depression and 20% mortality. At this level the effects of the inhibitor on growth was small but the following effects were noted: (a) increased fecal protein (the increase mainly consisting of low molecular weight proteins); (b) poorer feed efficiency; and (c) a significant decrease in pancreatic digestive proenzyme levels, although no hypertrophy was noted. In addition, the inhibitor was not digested readily in the intestinal tract and it increased in concentration in intestinal contents as it progressed down the tract. Potato Inhibitor II, a potent trypsin inhibitor, when fed to chicks, also at the level found in a 50% raw potato diet, was severely growth depressing. It significantly increased fecal protein and caused pancreatic hypertrophy. The trypsin inhibitor may be a major growth depressing agent in raw potatoes whereas the carboxypeptidase inhibitor probably contributes little to the growth depression.

The effect of oral synthetic protease inhibitor (FOY 305) on endocrine pancreas and carbohydrate and lipid metabolism in normal and streptozotocin-induced diabetic rats

The effect of long-term oral synthetic protease inhibitor (FOY 305) administration on fasting blood sugar (FBS), body weight, glucose tolerance, plasma insulin and glucagon levels, pancreatic insulin and glucagon contents, hepatic enzyme activities, and plasma lipids in normal and streptozotocin (STZ)-induced diabetic rats was studied. Normal rats treated with oral FOY 305 for 9 weeks were found to have pancreatic hypertrophy and decreased body weight gain as compared with the untreated normal controls. FBS, glucose tolerance, plasma insulin and glucagon levels, pancreatic insulin and glucagon contents, and plasma lipids were uninfluenced in FOY 305 treated normal rats. STZ-induced diabetic rats treated with oral FOY 305 were found to have decreased FBS for 5 weeks after the beginning of FOY 305 administration as compared with the untreated diabetic controls, whereas at the 7th and 9th week after treatment there was no difference in FBS between FOY 305 treated and untreated diabetic rats. In the metabolic balance observed at the 4th week after treatment, a slight improvement of the diabetic state was found in FOY 305 treated diabetic rats. There was no apparent difference in the blood sugar curve and insulin response following oral glucose load between diabetic rats treated for 7 weeks and untreated diabetic rats. All the rats were sacrificed after 9 weeks of treatment. Diabetic rats treated with oral FOY 305 for 9 weeks showed pancreatic hypertrophy and decreased plasma glucagon level and decreased pancreatic glucagon content as compared with the untreated diabetic controls, whereas there was no difference in body weight, plasma insulin level and pancreatic insulin content between FOY 305 treated and untreated diabetic rats. Furthermore, oral FOY 305 treatment improved hyperlipidemia in STZ-induced diabetic rats and also significantly improved the hepatic pyruvate kinase and phosphoenlpyruvate carboxykinase activities of diabetic rats. These improvements might partly be due to a decreased pancreatic content and secretion of glucagon and/or a direct action of the synthetic PI, FOY 305 to tissues.

Effects of feeding a carboxypeptidase inhibitor from potatoes to newly hatched chicks.

For the first time, the effects on animal growth and protein digestion of a specific inhibitor of the pancreatic digestive exopeptidases carboxypeptidases A and B were studied. Carboxypeptidase inhibitor from potato tubers was fed to newly hatched chicks at a level equal to that present in a diet containing 50% raw potato solids, which was severely growth depressing. At this level the effect of the carboxypeptidase inhibitor on growth was insignificant but the following effects were noted: (1) increased fecal protein (the increase mainly consisting of low-molecular weight proteins); (b) poorer feed efficiency; and (c) a significant decrease in pancreatic digestive proenzyme levels, although no hypertrophy was noted. In addition, the inhibitor was not digested readily in the intestinal tract and increased in concentration in intestinal contents as it progressed down the tract. Potato Inhibitor II, a potent trypsin inhibitor, when fed to chicks, also at the level found in the diet containing 50% raw potato, was severely growth depressing. The inhibitor produced significantly increased fecal protein and caused pronounced pancreatic hypertrophy. Thus, the growth depressing effects of raw potato tubers is probably due in part to the trypsin inhibitor, with only a small contribution originating from the carboxypeptidase inhibitor.

Amylase secretion by isolated pancreatic acini after chronic cholecystokinin treatment in vivo.

Rats were given subcutaneous injections of synthetic cholecystokinin octapeptide (CCK8, 5 micrograms/kg) in a depot carrier twice daily for 7-14 days. The pancreatic wet weight increased by 20.6 and 30.9% in the rats treated with CCK8 for 7 and 14 days, respectively. The increase in pancreatic weight was associated with an increase in the amount of protein per DNA, indicating hypertrophy of the acinar cells, and with an increase in the total amount of pancreatic DNA. Moreover, CCK administration also increased the amylase content per DNA. In acini prepared from CCK8-treated rats, responsiveness to CCK8 was increased when amylase release was expressed relative to DNA but was decreased when calculated as the percentage of the initial content in the acini. The dose-response curves for CCK8 were similarly shaped in both CCK8-treated and control rats, but they were shifted 3- to 10-fold toward higher concentrations of CCK8 after 7 and 14 days of CCK8 treatment. There were no major changes in the affinity and capacity of CCK receptors determined by studying the binding of radioiodinated CCK, suggesting that alterations in pancreatic amylase release were due to changes at a postreceptor loci. In support of this hypothesis, the secretory response to carbachol, known to act on a different receptor but by a common intracellular mechanism, was altered in a manner identical to the response to CCK8. Thus chronic stimulation with CCK sufficient to induce pancreatic hypertrophy does not greatly alter CCK receptors and induces only moderate postreceptor desensitization.

Hypocholesterolemia and Growth-Depression in Chicks Fed Guar Gum and Konjac Mannan

Two mannans (guar gum and konjac mannan) were fed to growing chicks at a level of 2% in a semipurified diet containing 0.5% cholesterol for 4 weeks. The mannans were nearly identical in producing growth depression, pancreatic hypertrophy and reduction in plasma and hepatic cholesterol when compared to controls fed corn starch or the sugars D-galactose or D-mannose. Hepatic triglyceride levels were higher for chicks fed konjac mannan, but no significant differences in fasting plasma glucose were observed. Apparent metabolizable energy levels for the mannan diets were significantly less than those of the other diets. The effects of the mannans in this study were not correlated with viscosity measurements made in vitro.

Nutritional significance of a rice bran concentrate with trypsin inhibitor activity.

A rice bran protein concentrate (RBPC) was prepared from de-fatted rice bran by extraction with a 1% sodium chloride solution and by acetone-precipitation. This protein concentrate contained 45% protein, which was as good as casein in terms of protein quality being judged from the results of amino acid analysis. On the other hand, RBPC possessed the trypsin inhibitor activity corresponding to the complete inhibition of about 6 mg of bovine trypsin per 1 g of dry material. The activity was, however, completely destroyed by autoclaving RBPC for 30 min at 121 degrees C. In vitro digestion tests showed that RBPC was easily digested by pepsin but was resistant to the attack by trypsin, compared with autoclaved RBPC. Concerning in vivo digestion, however, there was no significant difference in apparent nitrogen digestibility between RBPC and the heated RBPC. In growth experiments with weanling rats fed a 10% level of protein diet, growth depression and the tendency of slight pancreatic hypertrophy were observed in rats receiving a RBPC diet. It is presumed that one of the reasons which explains these phenomena is the presence of trypsin inhibitor in RBPC.

Interaction of hydrocortisone and caerulein on pancreatic size and composition in the rat.

To determine the effects of hydrocortisone and caerulein (separately and in combination) on the exocrine pancreas of suckling, recently weaned, growing, and adult rats, we administered hydrocortisone (0.5 mg/100 g body wt), caerulein (1 microgram/kg), and a combination of these two hormones for 3 days. The rats were killed, and the pancreas was weighed and analyzed for DNA, protein, amylase, and chymotrypsinogen. Caerulein alone was associated with significant decreases in amylase, chymotrypsinogen, and protein concentration in suckling rats; after weaning, it produced significant increases of these same parameters, representative of pancreatic hypertrophy. Hydrocortisone caused significant increases in DNA content and enzyme and protein concentrations in suckling rats; after weaning, the steroid significantly decreased DNA content in 26-day-old rats, but increases in enzyme and protein concentration were observed. Using an increase in DNA content as an index of hyperplasia and cellular mass and enzyme and protein concentrations as indices of hypertrophy, we conclude that over a 3-day period 1) caerulein produced pancreatic hypertrophy after weaning while potentiating the hyperplastic and hypertrophic action of hydrocortisone in suckling rats; and 2) hydrocortisone potentiated the hypertrophic effect of caerulein after weaning. The data suggest that these two hormones may regulate acinar cell proliferation and enzyme synthesis of the exocrine pancreas.

621 TROPHIC EFFECTS OF BOMBESIN AND SECRETIN ON NEONATAL RAT PANCREAS

Secretin(SEC) and Bombesin(BNP) produce pancreatic hyperplasia and hypertrophy in adult rats. Their effects in newborn animals have not been studied. We investigated the effects of SEC and BNP on pancreatic growth at 2 postnatal ages. Neonatal rats were injected subcutaneously with BNP,5μg/kg,or SEC,100μg/kg,or saline, every 12 hours for 7 days beginning at 6 or 13 days of age. Pups remained with their mothers until 12 hours after their last injection, when they were weighed and sacrificed. Weight gain did not differ among groups. Pancreatic weight, total DNA and protein (PRO) were measured and are shown below as ratios of treatment group values to control group.*p<0.05, **p<0.01;E=number in treatment group;+=content per 100 gms. body weight;†E=4.1)SEC and BNP caused significant pancreatic hypertrophy at 13-20 days. Only SEC caused hypertrophy, and possibly hyperplasia at 6-13 days,(2)Trophic effects of GI peptides may vary as a function of postnatal age,(3)BNP and SEC may play an important role in early pancreatic growth and development.

Significance of soya trypsin inhibitors in nutrition

AbstractAlthough recent evidence clearly indicates that trypsin inhibitors (TI) and low protein digestibility are the major factors responsible for the pancreatic hypertrophic and growth inhibitory effects of raw soybeans, there was uncertainty regarding the biological threshold level of TI at which these biological effects occur. To obtain such data, dehulled defatted flakes (10% dietary protein) containing graded levels of TI were fed to weanling rats for 4 weeks in two feeding trials. Normal pancreas weights were obtained in rats fed samples in which only 54 to 68% of the original TI of raw soya flour was inactivated. In partially toasted flakes with a nitrogen digestibility value of 77%, the average tolerance level of dietary TI activity that did not cause pancreatic hypertrophy was calculated to be 385 mg TI/100 g diet. TI tolerance level at maximum nitrogen digestibility of 85%, which did not significantly lower weight gain and reduce protein efficiencey ratios, was 260 mg TI/100 g diet. Continuous ingestion of high levels of TI (459 mg TI/100 g diet) in a 20% protein diet for 215 days did not inhibit growth nor cause pancreatic hypertrophy when compared to rats fed toasted soya flour diets. Pancreatic hypertrophy that occurs in rats fed raw soya diets containing up to about 1300 mg TI/100 g diet for 35 days was reversed by switching the rats to control diets or to 30% toasted flour. In long‐term feeding studies, no pancreatic hypertrophy occurred in rats fed commercial edible‐grade soya flour, concentrate, or isolate from time of weaning to adulthood (ca. 300 to 330 days). TI content of the diets ranged from 178 to 310 mg/100 g diet. Microscopic examination of the pancreas revealed no abnormalities. Gross appearances of heart, kidney, spleen and liver were normal. In long‐term feeding, vitamin B‐12 supplements were needed to provide optimum growth and to maintain body weight. Results of numerous chemical analyses, relatively short‐term human tests and long‐term animal feeding studies indicate that with proper control of manufacturing processes, soya protein products can be produced that, in mixed diets, have protein nutritional value approaching that of animal protein.

Progress and future needs for research in soya protein utilization and nutrition

AbstractAlthough soya protein was clearly recognized as an essential part of the diet in the Orient centuries ago, its acceptance in the western world has been slow and recent. Progress in utilization has revolved around solving problems of flavor, nutrition and functionality, and has resulted in commercial development of flours and grits, concentrates, isolates, textured products, cereal‐soya blends and beef‐soya blends. Among the latter two developments, cereal‐soya blends established the principle of using soya to increase protein content and quality of cereal diets consumed in many countries, and beef‐soya blends demonstrated the usefulness of soya in extending expensive meat supplies. Governmental actions such as approval of soya in school lunches and in military diets in the U.S. have also contributed to progress in utilizing soya protein in foods. Future research needed to increase food uses of soya protein includes: further improvement in flavor, greater versatility in functional properties, development of new foods rather than simulation of traditional items, and elaboration of adequate methods for determining soya proteins in regulated products. Highlights in soya protein nutrition research include: discovery of the need for moist heat treatment to develop maximal nutritive value; establishment of methionine as the first limiting amino acid; isolation and characterization of trypsin inhibitors; determination that trypsin inhibitor retards growth and causes pancreatic hypertrophy; discovery of negative feedback control of pancreatic enzyme secretion; and demonstration of apparent adequacy of soya proteins in meeting protein requirements of young children and adults. Further nutritional research is needed in the following areas: long‐term studies with humans to determine protein quality as well as possible needs for fortification with vitamins and minerals; establishment of need or lack of need for supplementation with methionine; mechanism of action trypsin inhibitors when ingested from soya and other sources; and development of rapid methods for measuring protein quality.

The effects of long-term feeding of soya flour on the rat pancreas.

Rats were fed raw and heated soya flour for up to 2 years. The rats fed raw soya flour all developed pancreatic hypertrophy and hyperplastic and adenomatous nodules. Four of 26 rats fed raw soya flour continuously and 1 of 5 rats fed raw soya flour for 2 days each week developed pancreatic cancer. Preheating the soya flour seemed to protect against the pancreatic hyperplastic and neoplastic changes.