Diabetes and the Stomach

Mfge8 is expressed by pericytes in gastric antrum submucosa from patients with obesity

The main function of the stomach is to digest ingested food. Gastric antrum muscular contractions mix ingested food with digestive enzymes and stomach acid and propel the chyme through the pyloric sphincter at a rate in which the small intestine can process the chyme for optimal nutrient absorption. Mfge8 binding to α8β1 integrins helps regulate gastric emptying by reducing the force of antral smooth muscle contractions. The source of Mfge8 within gastric muscles is unclear. Since Mfge8 is a secreted protein, Mfge8 could be delivered via the circulation, or be locally secreted by cells within the muscle layers. In this study, we identify a source of Mfge8 within human gastric antrum muscles using spatial transcriptomic analysis. We show that Mfge8 is expressed in subpopulations of Mef2c+ perivascular cells within the submucosa layer of the gastric antrum. Mef2c is expressed in subpopulations of NG2+ and PDGFRB+ pericytes. Mfge8 is expressed in NG2+/Mef2c+ pericytes, but not in NG2+/Mef2c-, PDGFRB+/Mef2c-, or PDGFRB+/Mef2c+ pericytes. Mfge8 is absent from CD34+ endothelial cells but is expressed in a small population of perivascular ACTA2+ cells. We also show that α8 integrin is not expressed by interstitial cells of Cajal (ICC), supporting the findings that Mfge8 attenuates gastric antrum smooth muscle contractions by binding to α8β1 integrins on enteric smooth muscle cells. These findings suggest a novel, supplementary mechanism of regulation of gastric antrum motility by cellular regulators of capillary blood flow, in addition to the regulation of gastric antrum motility by the enteric nervous system and the SMC, ICC, and PDGFRα+ cell (SIP) syncytium.

Influence of Gender in Diabetes Mellitus and Its Complication

In medicine, there is growing evidence that gender differences are important and lead to variations in the pathophysiology and treatment of many diseases with traits that appear to be particularly relevant in influencing the outcomes of many morbid forms. Today, the inclusion of gender in biomedical research, to improve the scientific quality and scientific relevance of knowledge, of technology is an increasingly present element precisely due to the practical implications that derive from it. Gender differences describe the biological variability between women and men, which is, in turn, related to differences in the information contained in sex chromosomes, the specific gene expression of autosomes linked to sex, the different number and quality of sex hormones, and their different effects on systems and organs, without neglecting the fact that each of the sexes has different target organs on which these hormones act. Additionally, both genders undergo metabolic changes throughout their lives, and this is especially true for women who show more dramatic changes due to their role in reproduction. Gender differences are not only the result of our genetic makeup but are also mixed with socio-cultural habits, behaviors, and lifestyles, differences between women and men, exposure to specific environmental influences, different food and lifestyle styles or stress, or different attitude in compliance with treatments and disease prevention campaigns. Gender differences also affect behavior throughout life, and physical changes can have implications for lifestyle, social roles, and mental health. Therefore, determinism and therapeutic outcome in chronic diseases are influenced by a complex combination of biological and environmental factors, not forgetting that there are many interactions of social and biological factors in women and men. This review will address the role of gender differences in the management of various forms of diabetes and its complications considering the different biological functions of hormones, the difference in body composition, physiological differences in glucose and fat metabolism, also considering the role of the microbiota. intestinal, as well as the description of gestational diabetes linked to possible pathophysiological events typical of reproduction.

Nitric oxide and its role as a non-adrenergic, non-cholinergic inhibitory neurotransmitter in the gastrointestinal tract

NO is a neurotransmitter released from enteric inhibitory neurons and responsible for modulating gastrointestinal (GI) motor behaviour. Enteric neurons express nNOS (NOS1) that associates with membranes of nerve varicosities. NO released from neurons binds to soluble guanylate cyclase in post-junctional cells to generate cGMP. cGMP-dependent protein kinase type 1 (PKG1) is a major mediator but perhaps not the only pathway involved in cGMP-mediated effects in GI muscles based on gene deletion studies. NOS1+ neurons form close contacts with smooth muscle cells (SMCs), interstitial cells of Cajal (ICC) and PDGFRα+ cells, and these cells are electrically coupled (SIP syncytium). Cell-specific gene deletion studies have shown that nitrergic responses are due to mechanisms in SMCs and ICC. Controversy exists about the ion channels and other post-junctional mechanisms that mediate nitrergic responses in GI muscles. Reduced nNOS expression in enteric inhibitory motor neurons and/or reduced connectivity between nNOS+ neurons and the SIP syncytium appear to be responsible for motor defects that develop in diabetes. An overproduction of NO in some inflammatory conditions also impairs normal GI motor activity. This review summarizes recent findings regarding the role of NO as an enteric inhibitory neurotransmitter. LINKED ARTICLES: This article is part of a themed section on Nitric Oxide 20 Years from the 1998 Nobel Prize. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.2/issuetoc.

MicroRNA 375 modulates hyperglycemia-induced enteric glial cell apoptosis and Diabetes-induced gastrointestinal dysfunction by targeting Pdk1 and repressing PI3K/Akt pathway

Diabetic neuropathy can damage systemic nervous system, including alteration of enteric nervous system and subsequent gastrointestinal dysfunction. The effect of diabetes on enteric glia cell (EGC) is not clear. We investigated the effect of diabetes and hyperglycemia on EGC, and the role of microRNA375 in modulating EGC survival in vivo and in vitro. Streptozotocin-induced diabetic mice were intraperitoneally injected with microRNA375 inhibitor or its negative control. EGC was transfected with microRNA375 inhibitor or its mimic. Diabetes mice with gastrointestinal dysfunction showed increased apoptosis of EGC (no difference in cell numbers) and gene expression of micorRNA375 in the myenteric plexus. Hyperglycemia triggered apoptosis of EGC in vitro with decreased expression of Pdk1 and p-Akt, but increased expression of micorRNA375. MicorRNA375 mimic induced apoptosis of EGC in vitro with repressed Pdk1and p-Akt. MicorRNA375 inhibitor could both prevent hyperglycemia-induced apoptosis of EGC in vitro and diabetes-induced gastrointestinal dysfunction in vivo. Our results suggest that diabetes-induced gastrointestinal dysfunction is related to increased apoptosis of EGC in the myenteric plexus. Hyperglycemia can increase the expression of microRNA375 and damage EGC survival through PI3K/Akt pathway. MicroRNA375 specific inhibition can prevent hyperglycemia induced EGC damage and diabetes-induced gastrointestinal dysfunction.

Bidirectional Relationship between Gastric Emptying and Plasma Glucose Control in Normoglycemic Individuals and Diabetic Patients

Gastric emptying and glycemic control pathways are closely interrelated processes. Gastric chyme is transferred into the duodenum with velocities depending on its solid or liquid state, as well as on its caloric and nutritional composition. Once nutrients enter the intestine, the secretion of incretins (hormonal products of intestinal cells) is stimulated. Among incretins, glucagon-like peptide-1 (GLP-1) has multiple glycemic-regulatory effects that include delayed gastric emptying, thus triggering a feedback loop lowering postprandial serum glucose levels. Glycemic values also influence gastric emptying; hyperglycemia slows it down, and hypoglycemia accelerates it, both limiting glycemic fluctuations. Disordered gastric emptying in diabetes mellitus is understood today as a complex pathophysiological condition, with both irreversible and reversible components and high intra- and interindividual variability of time span and clinical features. While limited delays may be useful for reducing postprandial hyperglycemias, severely hindered gastric emptying may be associated with higher glycemic variability and worsened long-term glycemic control. Therapeutic approaches for both gastric emptying and glycemic control include dietary modifications of meal structure or content and drugs acting as GLP-1 receptor agonists. In the foreseeable future, we will probably witness a wider range of dietary interventions and more incretin-based medications used for restoring both gastric emptying and glycemic levels to nearly physiological levels.