Pancreatic Digestive Enzymes Research Articles

Alcoholic pancreatitis: New insights into the pathogenesis and treatment.

Acute pancreatitis is a necro-inflammatory disease of the exocrine pancreas that is characterized by inappropriate activation of zymogens, infiltration of the pancreas by inflammatory cells, and destruction of the pancreatic exocrine cells. Acute pancreatitis can progress to a severe life-threatening disease. Currently there is no pharmacotherapy to prevent or treat acute pancreatitis. One of the more common factors associated with acute pancreatitis is alcohol abuse. Although commonly associated with pancreatitis alcohol alone is unable to cause pancreatitis. Instead, it appears that alcohol and its metabolic by-products predispose the pancreas to damage from agents that normally do not cause pancreatitis, or to more severe disease from agents that normally cause mild pancreatic damage. Over the last 10 to 20 years, a tremendous amount of work has defined a number of alcohol-mediated biochemical changes in pancreatic cells. Among these changes are: Sustained levels of intracellular calcium, activation of the mitochondrial permeability transition pore, endoplasmic reticulum stress, impairment in autophagy, alteration in the activity of transcriptional activators, and colocalization of lysosomal and pancreatic digestive enzymes. Elucidation of these changes has led to a deeper understanding of the mechanisms by which ethanol predisposes acinar cells to damage. This greater understanding has revealed a number of promising targets for therapeutic intervention. It is hoped that further investigation of these targets will lead to the development of pharmacotherapy that is effective in treating and preventing the progression of acute pancreatitis.

Influence of nutrient restriction and melatonin supplementation of pregnant ewes on maternal and fetal pancreatic digestive enzymes and insulin-containing clusters

Primiparous ewes (n=32) were assigned to dietary treatments in a 2×2 factorial arrangement to determine effects of nutrient restriction and melatonin supplementation on maternal and fetal pancreatic weight, digestive enzyme activity, concentration of insulin-containing clusters and plasma insulin concentrations. Treatments consisted of nutrient intake with 60% (RES) or 100% (ADQ) of requirements and melatonin supplementation at 0 (CON) or 5 mg/day (MEL). Treatments began on day 50 of gestation and continued until day 130. On day 130, blood was collected under general anesthesia from the uterine artery, uterine vein, umbilical artery and umbilical vein for plasma insulin analysis. Ewes were then euthanized and the pancreas removed from the ewe and fetus, trimmed of mesentery and fat, weighed and snap-frozen until enzyme analysis. In addition, samples of pancreatic tissue were fixed in 10% formalin solution for histological examination including quantitative characterization of size and distribution of insulin-containing cell clusters. Nutrient restriction decreased (P⩽0.001) maternal pancreatic mass (g) and α-amylase activity (U/g, kU/pancreas, U/kg BW). Ewes supplemented with melatonin had increased pancreatic mass (P=0.03) and α-amylase content (kU/pancreas and U/kg BW). Melatonin supplementation decreased (P=0.002) maternal pancreatic insulin-positive tissue area (relative to section of tissue), and size of the largest insulin-containing cell cluster (P=0.04). Nutrient restriction decreased pancreatic insulin-positive tissue area (P=0.03) and percent of large (32 001 to 512 000 µm2) and giant (⩾512 001 µm2) insulin-containing cell clusters (P=0.04) in the fetus. Insulin concentrations in plasma from the uterine vein, umbilical artery and umbilical vein were greater (P⩽0.01) in animals receiving 100% requirements. When comparing ewes to fetuses, ewes had a greater percentage of medium insulin-containing cell clusters (2001 to 32 000 µm2) while fetuses had more (P<0.001) pancreatic insulin-positive area (relative to section of tissue) and a greater percent of small, large and giant insulin-containing cell clusters (P⩽0.02). Larger insulin-containing clusters were observed in fetuses (P<0.001) compared with ewes. In summary, the maternal pancreas responded to nutrient restriction by decreasing pancreatic weight and activity of digestive enzymes while melatonin supplementation increased α-amylase content. Nutrient restriction decreased the number of pancreatic insulin-containing clusters in fetuses while melatonin supplementation did not influence insulin concentration. This indicated using melatonin as a therapeutic agent to mitigate reduced pancreatic function in the fetus due to maternal nutrient restriction may not be beneficial.

Differential expression of pancreatic protein and chemosensing receptor mRNAs in NKCC1-null intestine.

To investigate the intestinal functions of the NKCC1 Na(+)-K(+)-2Cl cotransporter (SLC12a2 gene), differential mRNA expression changes in NKCC1-null intestine were analyzed. Microarray analysis of mRNA from intestines of adult wild-type mice and gene-targeted NKCC1-null mice (n = 6 of each genotype) was performed to identify patterns of differential gene expression changes. Differential expression patterns were further examined by Gene Ontology analysis using the online Gorilla program, and expression changes of selected genes were verified using northern blot analysis and quantitative real time-polymerase chain reaction. Histological staining and immunofluorescence were performed to identify cell types in which upregulated pancreatic digestive enzymes were expressed. Genes typically associated with pancreatic function were upregulated. These included lipase, amylase, elastase, and serine proteases indicative of pancreatic exocrine function, as well as insulin and regenerating islet genes, representative of endocrine function. Northern blot analysis and immunohistochemistry showed that differential expression of exocrine pancreas mRNAs was specific to the duodenum and localized to a subset of goblet cells. In addition, a major pattern of changes involving differential expression of olfactory receptors that function in chemical sensing, as well as other chemosensing G-protein coupled receptors, was observed. These changes in chemosensory receptor expression may be related to the failure of intestinal function and dependency on parenteral nutrition observed in humans with SLC12a2 mutations. The results suggest that loss of NKCC1 affects not only secretion, but also goblet cell function and chemosensing of intestinal contents via G-protein coupled chemosensory receptors.

Temporal expression analyses of pancreatic and gastric digestive enzymes during early development of the olive flounder (Paralichthys olivaceus)

The olive flounder (Paralichthys olivaceus) is one of the most important aquaculture species in Korea. Previous studies focused on the morphological changes and only analysed digestive enzyme expression patterns of certain digestive systems. A comprehensive analysis of the pancreatic and gastric digestive enzymes of the olive flounder in its early developmental stages has not been performed. In this study, we determined the mRNA expression levels of pancreas and stomach digestive enzymes by extracting total RNA from the whole body of olive flounders from hatching to post-metamorphosis and conducting real-time PCR analysis with gene-specific primers for each isoform. The pancreatic digestive enzymes were initially and strongly expressed from the first feeding period to pre-metamorphosis. The expression of trypsinogen 3 was detected from the early stage of development to metamorphosis, whereas trypsinogen 2 was significantly increased only in the post-metamorphosis period. The mRNA expression of pepsinogen was only detected at metamorphosis and corresponded to stomach differentiation. The lipid digestive-related enzymes had already reached a certain level at the beginning of hatching, then increased during the early developmental stage and gradually decreased before metamorphosis. These results suggest that food ingestion is exclusively digested by pancreatic digestive enzymes and trypsinogen 3 during the early developmental stage until pre-metamorphosis, and it then fully switches to digestion by pepsinogen and trypsinogen 2 in mid-metamorphosis. In conclusion, understanding the expression profiles of digestive enzymes in the pancreas and stomach during the early developmental stages is an important consideration when developing formulated larval diets for aquacultured olive flounder.

Serum-Derived Bovine Immunoglobulin/Protein Isolate for the Management of Diarrhea Associated with Chronic Pancreatitis and Pancreatic Insufficiency: A Novel Approach

Chronic pancreatitis (CP) is a debilitating disorder that ultimately leads to pancreatic insufficiency (PI) and its sequelae. Patients with CP often experience abdominal pain, bloating, nausea, vomiting, weight loss, and steatorrhea. The dearth of pancreatic enzyme secretion in these patients leads to maldigestion, excess fat in the stool, and compromised nutritional status. A typical treatment for management of CP is pancreatic digestive enzyme therapy with pancrelipase, but it is usually ineffective in controlling pain and clinical symptoms, with potential risk of intestinal strictures. Serum-derived bovine immunoglobulin/protein isolate (SBI) is a prescription medical food that has been shown to manage chronic loose and frequent stools in patients with IBS-D, IBD, and HIV enteropathy. SBI has a multifaceted mode of action that through binding of microbial components, results in a downstream reduction in inflammatory markers and up-regulation of tight junction proteins, thus increasing barrier function. This results in improved nutrient utilization, as reported in non-clinical and clinical studies. For this reason, SBI was added to the therapy regimen of a CP/PI patient. The patient is a 73 year old female diagnosed with idiopathic CP and PI in 2012. She has a history of papillary stenosis diagnosed by ERCP with sphincterotomy. She also had chronic pancreatic steatorrhea that was managed with 5-6 doses of pancrelipase per day (at meals and snacks). This patient developed persistent bloating, distension, abdominal pain, and constipation, secondary to pancrelipase therapy. SBI 5g BID was added to her therapy regimen. Upon follow-up 7 weeks later, the patient reported improved discomfort, bloating and regularity of bowel movements to 1 every 2-3 days. The dosing of pacrealipase therapy was reduced due to this favorable response to SBI. She continues on SBI and is doing remarkably well in managing her condition, including her steatorrhea. Three other patients with CP/PI have also responded well to SBI therapy. For this patient, SBI proved to be a novel, safe option for the management of gastrointestinal issues associated with CP/PI. The ability of SBI to return the gut to homeostasis, restore barrier function, and thus allow for the proper absorption of nutrients from the diet may be the reason for its efficacy in this patient. A larger, well-controlled study in CP/PI patients is recommended.

Lack Of PRSS1 And SPINK1 Polymorphisms In Serbian Acute Pancreatitis Patients

Abstract Acute pancreatitis represents an acute nonbacterial inflammation of the pancreas caused by a premature and ectopic activation of pancreatic digestive enzymes. Two of the most important genes in pancreatic autodigestion, PRSS1 and SPINK1, were implicated in the earliest discoveries of the genetic background of pancreatitis. However, the distribution of their variations displays interethnic variability, which could significantly affect the magnitude of their proposed effects on this disease worldwide. The aim of the present study was to investigate the distribution of the most important functional variations of PRSS1 (86A&gt;T and 365G&gt;A) and SPINK1 (101A&gt;G), and their influence on the clinical course of acute pancreatitis in Serbian patients. The study enrolled 81 subjects, the severity of disease course was determined using the Atlanta Classification system, and the genotyping was conducted using a PCR-RFLP method. PRSS1 86A&gt;T and 365G&gt;A SNPs were not observed in the study population, while SPINK1 101A&gt;G was present with the frequency of 0.62% (95% CI: 0.00, 3.83%). Due to extremely low frequencies or absences of examined variations, the proposed effect of these SNPs on the severity of acute pancreatitis could not be confirmed. The results do not support routine genotyping of either PRSS1 or SPINK1 in Serbs.

English

Biochemical and feeding assays were performed in order to assess the bioactivity of trypsin inhibitors from sesame seeds to control Plodia interpunctella larvae. The biochemical assays were based on the ability of protease inhibitors (PI) present in sesame seeds to inhibit bovine pancreatic trypsin and digestive enzymes of insect larvae. The stability of the inhibitors was also assessed at different pH and temperature. The feeding bioassays were carried out in plates containing second instar larvae fed on diet with sesame protein extract. It was observed that all genotypes presented inhibition when tested with BPT, ranging from 51 to 90%, among them BRS Seda, CNPA G3 and CNPA G4 showed average of 69% of inhibitory activity for intestinal homogenate. The FII-fractions in these three genotypes showed thermal and pH stabilities at 40°C and 8.5, respectively. In feeding bioassay, P. interpunctella larvae were susceptible to SPCE of all three genotypes, revealing average mortality of 74% to SPCE and 45% to FII-fractions. Among all genotypes, BRS Seda was more effective to inhibition of digestive enzymes of insects and considered the more suitable genotype for further using in sesame breeding program to resistance to P. interpunctella. Key words: Sesamum indicum L., serine protease, stored grain pest, Lepidoptera.

Role of Endogenous Peptides and Enzymes in the Pathogenesis of Acute Pancreatitis: A Review

Acute pancreatitis is an inflammatory disease with the clinical manifestation of acute abdominal pain. Several factors are involved in the pathogenesis of acute pancreatitis. The exact mechanism(s) by which diverse etiological factors induce an attack are still unclear. However, one of the proposed mechanisms for induction of acute pancreatitis is auto-digestion of pancreatic tissues by unwanted activation of pancreatic digestive enzymes. The main objective of this review is to describe the pathogenesis mechanism of acute pancreatitis that are related to various inflammatory and proinflammatory mediators.Keywords: Acute Pancreatitis, Pancreatic Injury, Cytokines, Chemokines, Inflammation

Lysosome associated membrane proteins maintain pancreatic acinar cell homeostasis: LAMP-2 deficient mice develop pancreatitis.

Background & AimsThe pathogenic mechanism of pancreatitis is poorly understood. Recent evidence implicates defective autophagy in pancreatitis responses; however, the pathways mediating impaired autophagy in pancreas remain largely unknown. Here, we investigate the role of lysosome associated membrane proteins (LAMPs) in pancreatitis.MethodsWe analyzed changes in LAMPs in experimental models and human pancreatitis, and the underlying mechanisms: LAMP deglycosylation and degradation. LAMP cleavage by cathepsin B (CatB) was analyzed by mass spectrometry. We used mice deficient in LAMP-2 to assess its role in pancreatitis.ResultsPancreatic levels of LAMP-1 and LAMP-2 greatly decrease across various pancreatitis models and in human disease. Pancreatitis does not trigger the LAMPs’ bulk deglycosylation but induces their degradation via CatB-mediated cleavage of the LAMP molecule close to the boundary between luminal and transmembrane domains. LAMP-2 null mice spontaneously develop pancreatitis that begins with acinar cell vacuolization due to impaired autophagic flux, and progresses to severe pancreas damage characterized by trypsinogen activation, macrophage-driven inflammation, and acinar cell death. LAMP-2 deficiency causes a decrease in pancreatic digestive enzymes content, and stimulates the basal and inhibits cholecystokinin-induced amylase secretion by acinar cells. The effects of LAMP-2 knockout and acute cerulein pancreatitis overlap, which corroborates the pathogenic role of LAMP decrease in experimental pancreatitis models.ConclusionsThe results indicate a critical role for LAMPs, particularly LAMP-2, in maintaining pancreatic acinar cell homeostasis and provide evidence that defective lysosomal function, resulting in impaired autophagy, leads to pancreatitis. Mice with LAMP-2 deficiency present a novel genetic model of human pancreatitis caused by lysosomal/autophagic dysfunction.

Lipid transport in cholecystokinin knockout mice

Cholecystokinin (CCK) is released in response to lipid feeding and regulates pancreatic digestive enzymes vital to the absorption of nutrients. Our previous reports demonstrated that cholecystokinin knockout (CCK-KO) mice fed for 10weeks of HFD had reduced body fat mass, but comparable glucose uptake by white adipose tissues and skeletal muscles. We hypothesized that CCK is involved in energy homeostasis and lipid transport from the small intestine to tissues in response to acute treatment with dietary lipids. CCK-KO mice with comparable fat absorption had increased energy expenditure and were resistant to HFD-induced obesity. Using intraduodenal infusion of butter fat and intravenous infusion using Liposyn III, we determined the mechanism of lipid transport from the small intestine to deposition in lymph and adipocytes in CCK-KO mice. CCK-KO mice had delayed secretion of Apo B48-chylomicrons, lipid transport to the lymphatic system, and triglyceride (TG)-derived fatty acid uptake by epididymal fat in response to acute treatment of intraduodenal lipids. In contrast, CCK-KO mice had comparable TG clearance and lipid uptake by white adipocytes in response to TGs in chylomicron-like emulsion. Thus, we concluded that CCK is important for lipid transport and energy expenditure to control body weight in response to dietary lipid feeding.

Chronic metabolic acidosis destroys pancreas.

One primary reason for the current epidemic of digestive disorders might be chronic metabolic acidosis, which is extremely common in the modern population. Chronic metabolic acidosis primarily affects two alkaline digestive glands, the liver, and the pancreas, which produce alkaline bile and pancreatic juice with a large amount of bicarbonate. Even small acidic alterations in the bile and pancreatic juice pH can lead to serious biochemical/biomechanical changes. The pancreatic digestive enzymes require an alkaline milieu for proper function, and lowering the pH disables their activity. It can be the primary cause of indigestion. Acidification of the pancreatic juice decreases its antimicrobial activity, which can lead to intestinal dysbiosis. Lowering the pH of the pancreatic juice can cause premature activation of the proteases inside the pancreas with the potential development of pancreatitis. The acidification of bile causes precipitation of the bile acids, which irritate the entire biliary system and create bile stone formation. Aggressive mixture of the acidic bile and the pancreatic juice can cause erratic contractions of the duodenum's walls and subsequent bile reflux into the stomach and the esophagus. Normal exocrine pancreatic function is the core of proper digestion. Currently, there is no effective and safe treatment for enhancing the exocrine pancreatic function. Restoring normal acid-base homeostasis can be a useful tool for pathophysiological therapeutic approaches for various gastrointestinal disorders. There is strong research and practical evidence that restoring the HCO3(-) capacity in the blood can improve digestion.

Venom-related transcripts from Bothrops jararaca tissues provide novel molecular insights into the production and evolution of snake venom.

Attempts to reconstruct the evolutionary history of snake toxins in the context of their co-option to the venom gland rarely account for nonvenom snake genes that are paralogous to toxins, and which therefore represent important connectors to ancestral genes. In order to reevaluate this process, we conducted a comparative transcriptomic survey on body tissues from a venomous snake. A nonredundant set of 33,000 unigenes (assembled transcripts of reference genes) was independently assembled from six organs of the medically important viperid snake Bothrops jararaca, providing a reference list of 82 full-length toxins from the venom gland and specific products from other tissues, such as pancreatic digestive enzymes. Unigenes were then screened for nontoxin transcripts paralogous to toxins revealing 1) low level coexpression of approximately 20% of toxin genes (e.g., bradykinin-potentiating peptide, C-type lectin, snake venom metalloproteinase, snake venom nerve growth factor) in body tissues, 2) the identity of the closest paralogs to toxin genes in eight classes of toxins, 3) the location and level of paralog expression, indicating that, in general, co-expression occurs in a higher number of tissues and at lower levels than observed for toxin genes, and 4) strong evidence of a toxin gene reverting back to selective expression in a body tissue. In addition, our differential gene expression analyses identify specific cellular processes that make the venom gland a highly specialized secretory tissue. Our results demonstrate that the evolution and production of venom in snakes is a complex process that can only be understood in the context of comparative data from other snake tissues, including the identification of genes paralogous to venom toxins.

Feeding habits and ontogenic changes in digestive enzyme patterns in five freshwater teleosts.

Feeding habits and the activity of digestive enzymes (total alkaline proteases, α-amylase and lipase) from dace Leuciscus leuciscus, roach Rutilus rutilus, Prussian carp Carassius auratus gibelio, perch Perca fluviatilis and pikeperch Sander lucioperca fry were studied in the Malye Chany Lake-Kargat Estuary (western Siberia, Russia). The diet of fry from all studied species was mainly composed of chironomid larvae and zooplanktonic organisms (i.e. cladocera and copepoda), whereas carnivorous species such as P. fluviatilis and S. lucioperca also preyed on fry from other fishes while detritus and microalgae were also important in the diet of ommivorous species. When comparing diet similarity (Sørensen-Dice index, Q(S)) among fry at different stages of development, both omnivorous and carnivorous species showed a high level of similarity (0.67 < Q(S) < 0.89 and 0.73 < Q(S)< 0.89, respectively). Diet similarity values were in agreement with the overall digestive activity profile analysed by cluster analysis. Diet similarity suggested potential trophic competition when zooplanktonic and benthic prey began to decline towards autumn. The analysis of pancreatic digestive enzymes revealed a correlation among their activities and fry feeding habits with α-amylase:total proteases (A:P) values higher than 1 in omnivorous species and lower (A:P ≤ 1) in carnivorous species.

Meal timing affects protein-sparing effect by carbohydrates in sea bream: Effects on digestive and absorptive processes

Abstract A commercial diet (C) (48% protein and 20% lipids) and a high-digestible carbohydrate diet (CH) (37% protein, 12.5% lipids and 40% high-digestible carbohydrates) were used to feed sea bream juveniles for an 8-week period. In the commercial diet, more than 60% of ingredients were of plant origin from various sources, whereas the only component of plant origin in the CH diet was wheat. To determine the best time to administer carbohydrates and the possible protein-sparing effect, three different dietary regimes were established: C, CH-M and CH-A, and the corresponding diet was fed to sea bream in the morning (1.6% of bw) and in the afternoon (1% of bw), calculating quantities according to the amount of feed that fish ate during the acclimatization period. After the growth trial, specific growth rate (SGR), relative intestinal length, intestinal pH content, gastric and pancreatic digestive enzyme activities and nutrient absorption capacities were studied 5 h post-feeding after each meal (morning and afternoon). The acid protease activity measured was anticipatory and was higher when the next meal would have more protein. No differences in relative intestinal length or feed buffering capacity were found. The smaller ration given to sea bream in the afternoon led to a lower pancreatic release of alkaline protease and α-amylase and an up-regulation of D-Glc and L-Ala absorption capacity. A higher transit rate was measured when sea bream were fed the CH diet. When high-digestible carbohydrates were administered in the morning and the commercial diet in the afternoon, we observed a better assimilation of both diets due to compensatory mechanisms such as an increase in L-Lys, D-Glc and L-Ala absorption capacity after the morning feed, and a higher pancreatic release of alkaline protease and amylase after the afternoon feed. In contrast, when high-digestible carbohydrates were given in the afternoon, only a significant up-regulation of the capacity to absorb L-Lys was detected. Thus, the inclusion of high-digestible carbohydrates in the diet improved digestion and absorption processes when administered in the morning, leading to a protein-sparing effect that yielded growth comparable to that of fish fed an exclusively commercial diet.

Characterization and ontogenetic development of digestive enzymes in Pacific bluefin tuna Thunnus orientalis larvae.

The major digestive enzymes in Pacific bluefin tuna Thunnus orientalis larvae were characterized, and the physiological characteristics of the enzymes during early ontogeny were clarified using biochemical and molecular approaches. The maximum activity of trypsin (Try), chymotrypsin (Ct) and amylase (Amy) was observed at pH 6-11, 8-11 and 6-9, respectively. Maximum activity of Try, Ct and Amy occurred at 50 °C, that of lipase (Lip) was at 60 °C and that of pepsin (Pep) was at 40-50 °C. These pH and thermal profiles were similar to those for other fish species but differed from those previously reported for adult bluefin tuna. Enzyme activity for all enzymes assayed was found to decrease at high temperatures (Try, Ct, Amy and Pep: 50 °C; Lip: 40 °C), which is similar to findings for other fish species with one marked exception-increased Try activity was observed at 40 °C. Lip activity appeared to be dependent on bile salts under our assay conditions, resulting in a significant increase in activity in the presence of bile salts. Ontogenetic changes in pancreatic digestive enzymes showed similar gene expression patterns to those of other fish species, whereas marked temporal increases in enzyme activities were observed at 10-12 days post hatching (dph), coinciding with previously reported timing of the development of the pyloric caeca in bluefin tuna larvae. However, complete development of digestive function was indicated by the high pep gene expression from 19 dph, which contradicts the profile of Pep activity and previously reported development timing of the gastric gland. These findings contribute to the general knowledge of bluefin tuna larval digestive system development.

Differential regulation of pancreatic digestive enzymes during chronic high-fat diet-induced obesity in C57BL/6J mice

Exocrine pancreatic digestive enzymes are essential for the digestion of dietary components and are regulated by them. Chronic excess dietary high fat (HF) consumption is a contributing factor of diet-induced obesity (DIO) and associated chronic diseases and requires adaptation by the pancreas. The aim of the present study was to investigate the effects of chronic HF diet feeding on exocrine pancreatic digestive enzyme transcript levels in DIO C57BL/6J mice. C57BL/6J mice were fed diets containing either 10 or 45% energy (E%) derived from fat for 12 weeks (n 10 mice per diet group). Pancreatic tissue and blood samples were collected at 0, 4 and 12 weeks. The expression of a panel of exocrine pancreatic digestive enzymes was analysed using quantitative RT-PCR and Western blot analysis. The HF (45 E%) diet-fed C57BL/6J mice developed obesity, hyperleptinaemia, hyperglycaemia and hyperinsulinaemia. The transcript levels of pancreatic lipase (PL), pancreatic lipase-related protein 2 (PLRP2) and pancreatic phospholipase A2 (PLA2) were initially elevated; however, they were down-regulated to basal control levels at week 12. The transcript levels of colipase were significantly affected by diet and time. The protein levels of PL and PLRP2 responded to HF diet feeding. The transcript levels of amylase and proteases were not significantly affected by diet and time. The transcript levels of specific lipases in hyperinsulinaemic, hyperleptinaemic and hyperglycaemic DIO C57BL/6J mice are down-regulated. However, these mice compensate for this by the post-transcriptional regulation of the levels of proteins that respond to dietary fat. This suggests a complex regulatory mechanism involved in the modulation of fat digestion.

Novel Exenatide Analogs with Peptidic Albumin Binding Domains: Potent Anti-Diabetic Agents with Extended Duration of Action

The design, synthesis and pharmacology of novel long-acting exenatide analogs for the treatment of metabolic diseases are described. These molecules display enhanced pharmacokinetic profile and potent glucoregulatory and weight lowering actions compared to native exenatide. [Leu14]exenatide-ABD is an 88 residue peptide amide incorporating an Albumin Binding Domain (ABD) scaffold. [Leu14]exenatide-ABP is a 53 residue peptide incorporating a short Albumin Binding Peptide (ABP). [Leu14]exenatide-ABD and [Leu14]exenatide-ABP exhibited nanomolar functional GLP-1 receptor potency and were metabolically stable in vitro in human plasma and in a pancreatic digestive enzyme mixture. Both molecules displayed picomolar and nanomolar binding association with albumin across multiple species and circulating half lives of 16 and 11 hours, respectively, post a single IV dose in rats. Unlike exenatide, both molecules elicited robust glucose lowering when injected 1 day prior to an oral glucose tolerance test, indicative of their extended duration of action. [Leu14]exenatide-ABD was compared to exenatide in a Lep ob/ob mouse model of diabetes. Twice-weekly subcutaneously dosed [Leu14]exenatide-ABD displayed superior glucose lowering and weight loss in diabetic mice when compared to continuously infused exenatide at the same total weekly dose. A single oral administration of each molecule via an enteric coated capsule to cynomolgus monkeys showed superior pharmacokinetics for [Leu14]exenatide-ABD as compared to [Leu14]exenatide-ABP with detectable exposure longer than 14 days. These studies support the potential use of these novel long acting exenatide analogs with different routes of administration for the treatment of type 2 diabetes.

Pancreatic Digestive Enzyme Blockade in the Small Intestine Prevents Insulin Resistance in Hemorrhagic Shock

Hemorrhagic shock is associated with metabolic defects, including hyperglycemia and insulin resistance, but the mechanisms are unknown. We recently demonstrated that reduction of the extracellular domain of the insulin receptor by degrading proteases may lead to a reduced ability to maintain normal plasma glucose values. In shock, transfer of digestive enzymes from the lumen of the intestine into the systemic circulation after breakdown of the intestinal mucosal barrier causes inflammation and organ dysfunction. Suppression of the digestive enzymes in the lumen of the intestine with protease inhibitors is effective in reducing the level of the inflammatory reactions. To determine the degree to which blockade of digestive enzymes affects insulin resistance in shock, rats were exposed to acute hemorrhagic shock (mean arterial pressure of 30 mmHg for 2 h) at which time all shed blood volume was returned. Digestive proteases in the intestine were blocked with a serine protease inhibitor (tranexamic acid in polyethylene glycol and physiological electrolyte solution), and the density of the insulin receptor was measured with immunohistochemistry in the mesentery microcirculation. The untreated rat without enzyme blockade had significantly attenuated levels of insulin receptor density as compared with control and treated rats. Blockade of the digestive proteases after 60 min of hypotension in the lumen of the small intestine led to a lesser decrease in insulin receptor density compared with controls without protease blockade. Glucose tolerance test indicates a significant increase in plasma glucose levels 2 h after hemorrhagic shock, which are reduced to control values in the presence of protease inhibition in the lumen of the intestine. The transient reduction of the plasma glucose levels after an insulin bolus is significantly attenuated after shock but is restored when digestive enzymes in the lumen of the intestine are blocked. These results suggest that in hemorrhagic shock elevated microvascular extracellular digestive enzyme activity causes insulin receptor dysfunction, hyperglycemia, and reduced ability to regulate blood glucose values.

Cholecystokinin and pancreatic cancer: the chicken or the egg?

The gastrointestinal peptide cholecystokinin (CCK) causes the release of pancreatic digestive enzymes and growth of the normal pancreas. Exogenous CCK administration has been used in animal models to study pancreatitis and also as a promoter of carcinogen-induced or Kras-driven pancreatic cancer. Defining CCK receptors in normal human pancreas has been problematic because of its retroperitoneal location, high concentrations of pancreatic proteases, and endogenous RNase. Most studies indicate that the predominant receptor in human pancreas is the CCK-B type, and CCK-A is the predominant form in rodent pancreas. In pancreatic cancer cells and tumors, the role of CCK is better established because receptors are often overexpressed by these cancer cells and stimulation of such receptors promotes growth. Furthermore, in established cancer, endogenous production of CCK and/or gastrin occurs and their actions stimulate the synthesis of more receptors plus growth by an autocrine mechanism. Initially it was thought that the mechanism by which CCK served to potentiate carcinogenesis was by interplay with inflammation in the pancreatic microenvironment. But with the recent findings of CCK receptors on early PanIN (pancreatic intraepithelial neoplasia) lesions and on stellate cells, the question has been raised that perhaps CCK actions are not the result of cancer but an early driving promoter of cancer. This review will summarize what is known regarding CCK, its receptors, and pancreatic cancer, and also what is unknown and requires further investigation to determine which comes first, the chicken or the egg, "CCK or the cancer."

Removal of luminal content protects the small intestine during hemorrhagic shock but is not sufficient to prevent lung injury

The small intestine plays a key role in the pathogenesis of multiple organ failure following circulatory shock. Current results show that reduced perfusion of the small intestine compromises the mucosal epithelial barrier, and the intestinal contents (including pancreatic digestive enzymes and partially digested food) can enter the intestinal wall and transport through the circulation or mesenteric lymph to other organs such as the lung. The extent to which the luminal contents of the small intestine mediate tissue damage in the intestine and lung is poorly understood in shock. Therefore, rats were assigned to three groups: No-hemorrhagic shock (HS) control and HS with or without a flushed intestine. HS was induced by reducing the mean arterial pressure (30 mmHg; 90 min) followed by return of shed blood and observation (3 h). The small intestine and lung were analyzed for hemorrhage, neutrophil accumulation, and cellular membrane protein degradation. After HS, animals with luminal contents had increased neutrophil accumulation, bleeding, and destruction of E-cadherin in the intestine. Serine protease activity was elevated in mesenteric lymph fluid collected from a separate group of animals subjected to intestinal ischemia/reperfusion. Serine protease activity was elevated in the plasma after HS but was detected in lungs only in animals with nonflushed lumens. Despite removal of the luminal contents, lung injury occurred in both groups as determined by elevated neutrophil accumulation, permeability, and lung protein destruction. In conclusion, luminal contents significantly increase intestinal damage during experimental HS, suggesting transport of luminal contents across the intestinal wall should be minimized.