Negative control of human pancreatic secretion: physiological mechanisms and factors

Interactions between the Exocrine and the Endocrine Pancreas

The pancreas has two main functions: to produce and secrete digestive enzymes (exocrine function) and to produce hormones that regulate blood glucose and splanchnic secretion (endocrine function). The endocrine and exocrine portions of the pancreas are central regulators in digestion and metabolism, with continuous crosstalk between their deeply interconnected components, which plays a role in disease. Pancreatic neoplasms, inflammation, trauma, and surgery can lead to the development of type 3c diabetes when an insult simultaneously damages both acini and islets, leading to exocrine and endocrine dysfunction. In diabetes mellitus patients, pancreatic exocrine insufficiency is highly prevalent, yet little is known about the associations between diabetes mellitus and pancreatic exocrine function. This review aims to provide an overview of the physiology of the pancreas, summarize the pathophysiology and diagnostic work-up of pancreatic exocrine insufficiency, and explore the relationships between exocrine pancreatic insufficiency and diabetes mellitus.

Diverse role of phytic acid in plants and approaches to develop low-phytate grains to enhance bioavailability of micronutrients

Natural or synthetic compounds that interfere with the bioavailability of nutrients are called antinutrients. Phytic acid (PA) is one of the major antinutrients present in the grains and acts as a chelator of micronutrients. The presence of six reactive phosphate groups in PA hinders the absorption of micronutrients in the gut of non-ruminants. Consumption of PA-rich diet leads to deficiency of minerals such as iron and zinc among human population. On the contrary, PA is a natural antioxidant, and PA-derived molecules function in various signal transduction pathways. Therefore, optimal concentration of PA needs to be maintained in plants to avoid adverse pleiotropic effects, as well as to ensure micronutrient bioavailability in the diets. Given this, the chapter enumerates the structure, biosynthesis, and accumulation of PA in food grains followed by their roles in growth, development, and stress responses. Further, the chapter elaborates on the antinutritional properties of PA and explains the conventional breeding and transgene-based approaches deployed to develop low-PA varieties. Studies have shown that conventional breeding methods could develop low-PA lines; however, the pleiotropic effects of these methods viz. reduced yield, embryo abnormalities, and poor seed quality hinder the use of breeding strategies. Overexpression of phytase in the endosperm and RNAi-mediated silencing of genes involved in myo-inositol biosynthesis overcome these constraints. Next-generation genome editing approaches, including CRISPR-Cas9 enable the manipulation of more than one gene involved in PA biosynthesis pathway through multiplex editing, and scope exists to deploy such tools in developing varieties with optimal PA levels.

Life with the pancreas: A personal experience

This review article has primary objective to summarize pancreatic research which has been done in our laboratory since 1965, the first year of the author's registration in the Ph.D. program at the University of Sherbrooke (Canada). It covers the following major topics of pancreatic physiology: controls of pancreatic adaptation to diet, control of pancreatic enzyme secretion, control of pancreatic enzyme synthesis, control of pancreatic growth, intracellular events stimulated during pancreatic growth, pancreas regeneration after pancreatitis and pancreatectomy, the pancreatic cholecystokinin receptor types 1 and 2, growth control and cell signaling in pancreatic cancer cells and finally, cystic fibrosis.

Asymmetrical distribution of δ and PP cells in human pancreatic islets

The aim of this study was to evaluate the location of PP and δ cells in relation to the vascularization within human pancreatic islets. To this end, pancreas sections were analysed by immunofluorescence using antibodies against endocrine islet and endothelial cells. Staining in different islet areas corresponding to islet cells adjacent or not to peripheral or central vascular channels was quantified by computerized morphometry. As results, α, PP and δ cells were preferentially found adjacent to vessels. In contrast to α cells, which were evenly distributed between islet periphery and intraislet vascular channels, PP and δ cells had asymmetric and opposite distributions: PP staining was higher and somatostatin staining was lower in the islet periphery than in the area around intraislet vascular channels. Additionally, frequencies of PP and δ cells were negatively correlated in the islets. No difference was observed between islets from the head and the tail of the pancreas, and from type 2 diabetic and non-diabetic donors. In conclusion, the distribution of δ cells differs from that of PP cells in human islets, suggesting that vessels at the periphery and at the centre of islets drain different hormonal cocktails.

Oral Food Intake Versus Fasting on Postoperative Pancreatic Fistula After Distal Pancreatectomy: A Multi-Institutional Randomized Controlled Trial

The usefulness of enteral nutrition via a nasointestinal tube for patients who develop postoperative pancreatic fistula (POPF) after miscellaneous pancreatectomy procedures has been reported. However, no clear evidence regarding whether oral intake is beneficial or harmful during management of POPF after distal pancreatectomy (DP) is currently available.To investigate the effects of oral food intake on the healing process of POPF after DP.Multi-institutional randomized controlled trial in Nagoya University Hospital and 4 affiliated hospitals.Patients who developed POPF were randomly assigned to the dietary intake (DI) group (n = 15) or the fasted group (no dietary intake [NDI] group) (n = 15). The primary endpoint was the length of drain placement.No significant differences were found in the length of drain placement between the DI and NDI groups (12 [6-58] and 12 [7-112] days, respectively; P = 0.786). POPF progressed to a clinically relevant status (grade B/C) in 5 patients in the DI group and 4 patients in the NDI group (P = 0.690). POPF-related intra-abdominal hemorrhage was found in 1 patient in the NDI group but in no patients in the DI group (P = 0.309). There were no significant differences in POPF-related intra-abdominal hemorrhage, the incidence of other complications, or the length of the postoperative hospital stay between the 2 groups.Food intake did not aggravate POPF and did not prolong drain placement or hospital stay after DP. There may be no need to avoid oral DI in patients with POPF.

Influence of Food Intake on the Healing Process of Postoperative Pancreatic Fistula After Pancreatoduodenectomy: A Multi-institutional Randomized Controlled Trial

BACKGROUND

The usefulness of enteral nutrition via a nasointestinal tube for patients who develop postoperative pancreatic fistula (POPF) after miscellaneous pancreatectomy procedures has been reported. However, no clear evidence regarding whether oral intake is possible during management of POPF after pancreatoduodenectomy (PD) is currently available. We investigated the effects of oral food intake on the healing process of POPF after PD by a multi-institutional randomized controlled trial.

METHODS

Patients who developed POPF were randomly assigned to the dietary intake (DI) group (n = 30) or the fasted group [no dietary intake (NDI) group] (n = 29). The primary endpoint was the length of drain placement.

RESULTS

No significant differences were found in the length of drain placement between the DI and NDI groups [27 (7-80) vs. 26 (7-70) days, respectively; p = .8858]. POPF progressed to a clinically relevant status (grade B/C) in 20 patients in the DI group and 19 patients in the NDI group (p = .9257). POPF-related intra-abdominal hemorrhage was found in 2 patients in the NDI group, but in no patients in the DI group (p = .1434). There were no significant differences in POPF-related intra-abdominal hemorrhage, the incidence of other complications, or the length of the postoperative hospital stay between the 2 groups.

CONCLUSION

Food intake did not aggravate POPF and did not prolong the length of drain placement or hospital stay after PD. There may be no need to avoid oral dietary intake in patients with POPF.

An update on pancreatic pathophysiology (do we have to rewrite pancreatic pathophysiology?)

This review focuses on seven aspects of physiology and pathophysiology of the exocrine pancreas that have been intensively discussed and studied within the past few years: (1) the role of neurohormonal mechanisms like melatonin, leptin, or ghrelin in the stimulation of pancreatic enzyme secretion; (2) the initiation processes of acute pancreatitis, like fusion of zymogen granules with lysosomes leading to intracellular activation of trypsinogen by the lysosomal enzyme cathepsin B, or autoactivation of trypsinogen; (3) the role of genes in the pathogenesis of acute pancreatitis; (4) the role of alcohol and constituents of alcoholic beverages in the pathogenesis of acute pancreatitis; (5) the role of pancreatic hypertension, neuropathy, and central mechanisms for the pathogenesis of pain in chronic pancreatitis; (6) the relation between exocrine pancreatic function and diabetes mellitus; and (7) pathophysiology, diagnosis and treatment of pancreatic steatorrhea.

Principles of endocrinology

The endocrine system plays a major role in human survival. Endocrine glands secrete chemical messengers or hormones that affect every tissue of the body, including the periodontium, during the life of the individual. As the endocrine system influences a broad assortment of biological activities necessary for life, a general understanding of the principal components and functions of this system is essential. A fundamental assessment of hormone structure, mechanism of action and hormone transport, as well as influence on homeostasis is reviewed. A concise evaluation of the functions of the central endocrine glands, the functions of the major peripheral endocrine glands (other than gonadal tissues) and the known relationships of these hormones to the periodontium is examined.

Review: Anti-nutritional effects of phytic acid in diets for pigs and poultry – current knowledge and directions for future research

Woyengo, T. A. and Nyachoti, C. M. 2013. Review: Anti-nutritional effects of phytic acid in diets for pigs and poultry – current knowledge and directions for future research. Can. J. Anim. Sci. 93: 9–21. Plant feedstuffs contain phytic acid (PA), which is a storage form of phosphorus. Phytic acid is, however, poorly hydrolyzed by pigs and poultry, and it has a capacity to complex dietary nutrients, thereby reducing nutrient digestibility. Reduced nutrient digestibility by PA implies reduced efficiency of utilization of the nutrients and increased discharge of the unabsorbed nutrients to the environment. Phytic acid has also recently been shown to increase the endogenous nutrient losses (ENL) in pigs and poultry. Because the increased ENL in the gastrointestinal tract are associated with increased maintenance requirement for the lost nutrients and of energy spent on their secretion, an increase in ENL due to PA implies that there are other adverse effects of PA on nutrient utilization in addition to reducing nutrient digestibility. In this review, the effects of PA on performance of pigs and poultry, and on the digestibility and ENL in these animals are discussed in detail. Also, the mechanisms by which PA reduces nutrient digestibility and increases gastrointestinal ENL in pigs and poultry are discussed, and areas that need further research to gain more insight into these mechanisms are suggested.

Ileal digestibility of amino acids for zero-tannin faba bean (Vicia faba L.) fed to broiler chicks

An experiment was conducted to determine the apparent ileal digestibility (AID) of amino acids (AA) in zero-tannin faba beans (ZFB; Vicia faba L.) fed to broiler chicks. In total, 120 broiler chicks were divided into 24 groups of 5 birds that were balanced for BW and fed 1 of 3 diets in a completely randomized design (8 groups/diet) from d 14 to 21 of age. The diets were a soybean meal-cornstarch-based basal diet or the basal diet with soybean meal and cornstarch replaced by 50% of either conventional (tannin-containing) faba beans (CFB) or ZFB. The CFB were fed for comparison with ZFB. All of the 3 diets contained chromic oxide (0.3%) as an indigestible marker, and nutrient digestibilities were determined by the difference method. On d 21, the birds were killed by cervical dislocation and contents of the lower-half of the ileum were obtained for determination of apparent AA digestibility. The CFB and ZFB were similar in CP, AA, neutral detergent fiber, and acid detergent fiber contents. The ZFB did not contain tannins, whereas the CFB contained 0.82% tannins. The ZFB had greater (P < 0.05) AID for all AA (except Met) compared with that of the CFB by an average of 12.6 percentage points. The 2 faba-bean types were similar in AID of Met. The results show that the ZFB evaluated in the current study had greater AID of AA than CFB, and hence, it may be a better source of protein for broiler chicks than CFB.

Enteral and parenteral nutrition in the conservative treatment of pancreatic fistula: a randomized clinical trial

BACKGROUND & AIMS

Postoperative pancreatic fistula is the most common and potentially life-threatening complication after pancreatic surgery. Although nutritional support is a key component of conservative therapy in such cases, there have been no well-designed clinical trials substantiating the superiority of either total parenteral nutrition or enteral nutrition. This study was conducted to compare the efficacy and safety of both routes of nutritional intervention.

METHODS

A randomized clinical trial was conducted in a tertiary surgical center of pancreatic and gastrointestinal surgery. Seventy-eight patients with postoperative pancreatic fistula were treated conservatively and randomly assigned to groups receiving for 30 days either enteral nutrition or total parenteral nutrition. The primary end point was the 30-day fistula closure rate.

RESULTS

After 30 days, closure rates in patients receiving enteral and parenteral nutrition were 60% (24 of 40) and 37% (14 of 38), respectively (P=.043). The odds ratio for the probability that fistula closes on enteral nutrition compared to total parenteral nutrition was 2.571 (95% confidence interval [CI]: 1.031-6.411). Median time to closure was 27 days (95% CI: 21-33) for enteral nutrition, and no median time was reached in total parenteral nutrition (P=.047). A logistic regression analysis identified only 2 factors significantly associated with fistula closure, ie, enteral nutrition (odds ratio=6.136; 95% CI: 1.204-41.623; P=.043) and initial fistula output of ≤200 mL/day (odds ratio=12.701; 95% CI: 9.102-47.241; P<.001).

CONCLUSIONS

Enteral nutrition is associated with significantly higher closure rates and shorter time to closure of postoperative pancreatic fistula.

26. Pain in chronic pancreatitis

Chronic pancreatitis is defined as a progressive inflammatory response of the pancreas that has lead to irreversible morphological changes of the parenchyma (fibrosis, loss of acini and islets of Langerhans, and formation of pancreatic stones) as well as of the pancreatic duct (stenosis and pancreatic stones). Pain is one of the most important symptoms of chronic pancreatitis. The pathogenesis of this pain can only partly be explained and it is therefore often difficult to treat this symptom. The management of pain induced by chronic pancreatitis starts with lifestyle changes and analgesics. For the pharmacological management, the three-step ladder of the World Health Organization extended with the use of co-analgesics is followed. Interventional pain management may consist of radiofrequency treatment of the nervi splanchnici, spinal cord stimulation, endoscopic stenting or stone extraction possibly in combination with lithotripsy, and surgery. To date, there are no randomized controlled trials supporting the efficacy of radiofrequency and spinal cord stimulation. The large published series reports justify a recommendation to consider these treatment options. Radiofrequency treatment, being less invasive than spinal cord stimulation, could be tested prior to considering spinal cord stimulation. There are several other treatment possibilities such as endoscopic or surgical treatment, pancreatic enzyme supplementation and administration of octreotide and antioxidants. All may have a role in the management of pain induced by chronic pancreatitis.

Hormonal control of pancreatic growth during fetal, neonatal and adult life

This review article has for major objective to summarize the old and latest developments on the hormonal controls of pancreatic growth. The article deals with hormonal controls during the fetal, neonatal and adult periods of pancreas development, growth and regeneration. During the fetal period, comparisons were made between studies performed with pancreatic explants and those designed in vivo. After birth, the effects of glucocorticoids, thyroxine, gastrin, bombesin, secretin, cholecystokinin alone or with secretin are reported. In the adults, similar studies were reported on hormones with addition of the effects of neuropeptides, the cell types targeted by hormones and the hormonal control after pancreatectomy and pancreatitis.

Encapsulated porcine islet transplantation: an evolving therapy for the treatment of type I diabetes

BACKGROUND

Allogeneic tissue-based therapies for Type I diabetes have demonstrated efficacy but are limited due to tissue-sourcing constraints, as the number of patients exceeds that of tissue donors. Porcine islets derived from designated pathogen-free sources could be an alternative, particularly if delivered in a way that evades the host immune system's rejection.

METHODS

This review focuses on approaches designed to protect xenogeneic islets from immune rejection by provision of perm-selective barriers.

RESULTS

Designated pathogen-free herds could provide a supply of wild-type porcine islets that are well tolerated when administered in a suitable protective delivery vehicle. Such barrier systems have enabled amelioration of diabetes in a variety of animal models and preliminary evidence suggests that similar results could be attained in humans.

CONCLUSION

With advances in biomaterial design, source tissue selection, and the evolution of critical cell processing techniques, contemporary encapsulated porcine islet therapies offer a new level of clinical promise.