Novel effects of the gastrointestinal hormone secretin on cardiac metabolism and renal function

Biomolecules of Adipose Tissue in Atherosclerotic Plaques of Men With Coronary Atherosclerosis

AIM

To study metabolic molecules (adiponectin, adipsin, resistin, glucagon-like peptide-1 (GLP-1), glucagon, secretin) of adipose tissue in atherosclerotic plaques (AP) and their associations with AP instability in men with coronary atherosclerosis.

MATERIAL AND METHODS

Metabolic molecules (adipocytokines and metabolic hormones) of adipose tissue can act as enzymes, hormones or growth factors in modulating insulin resistance and lipid and glucose metabolism and indirectly influence the course of the atherosclerotic process. This study included 48 men from whom 139 coronary artery (CA) samples were collected during coronary artery bypass grafting, after obtaining the informed consent. According to the histological conclusion, 84 (60.4%) CA plaques were stable, 44 (31.7%) were unstable, and 11 histological samples had a conditionally unchanged CA intima (7.9%). The concentrations of adiponectin, adipsin, resistin, GLP-1, glucagon, and secretin were measured in AP homogenates by multiplex analysis using the Human Metabolic Hormone V3 panel (MILLIPLEX, Germany). During the study, demographic and anthropometric characteristics, medical history, and presence of chronic diseases were recorded.

RESULTS

The glucagon concentration in the conditionally unchanged intima was 16.7% lower and in the fragments of unstable atherosclerotic plaques 41.2% lower than in fragments of stable APs. However, the glucagon concentration in stable APs was 28% higher than in unstable APs. The secretin concentration in the conditionally unchanged intima was also lower than in stable APs by 41.2%, while in stable APs, the secretin concentration was 20% higher than in unstable APs. The adiponectin concentrations were directly correlated with serum high-density lipoprotein cholesterol (HDL-C) concentrations (r=0.286; p=0.002), while the secretin concentrations were inversely correlated with serum HDL-C concentrations (r= -0.199; p=0.038). The probability of having an unstable AP (in relation to conditionally unchanged intima) increases by 35.8% with an increase in the AP glucagon concentration by 1 pg/mg protein. The probability of having a stable AP (in relation to unchanged intima) increases by 29.4% with an increase in the AP glucagon concentration by 1 pg/mg protein and by 10.1% with an increase in the AP secretin concentration by 1 pg/mg protein.

CONCLUSION

The AP adiponectin concentration directly correlates and the AP secretin concentration inversely correlates with the serum concentration of HDL-C. The presence of both stable and unstable APs is directly associated with the AP glucagon concentration in men with coronary atherosclerosis. The AP secretin concentration is directly associated with plaque stability in men with coronary atherosclerosis. Further thorough study of the identified markers in atherosclerotic lesions will allow using them as potential targets for therapy.

Secretin: a hormone for HCO3- homeostasis

Secretin is a key hormone of the intestinal phase of digestion which activates pancreatic, bile duct and Brunner gland HCO3- secretion. Recently, the secretin receptor (SCTR) was also found in the basolateral membrane of the beta-intercalated cell (B-IC) of the collecting duct. Experimental addition of secretin triggers a pronounced activation of urinary HCO3- excretion, which is fully dependent on key functional proteins of the B-IC, namely apical pendrin and CFTR and the basolateral SCTR. Recent studies demonstrated that the SCTR knock-out mouse is unable to respond to an acute base load. Here, SCTR KO mice could not rapidly increase urine base excretion, developed prolonged metabolic alkalosis and exhibited marked compensatory hypoventilation. Here, we review the physiological effects of secretin with distinct focus on how secretin activates renal HCO3- excretion. We describe its new function as a hormone for HCO3- homeostasis.

Physiological Appetite Regulation and Bariatric Surgery

Obesity remains a common metabolic disorder and a threat to health as it is associated with numerous complications. Lifestyle modifications and caloric restriction can achieve limited weight loss. Bariatric surgery is an effective way of achieving substantial weight loss as well as glycemic control secondary to weight-related type 2 diabetes mellitus. It has been suggested that an anorexigenic gut hormone response following bariatric surgery contributes to weight loss. Understanding the changes in gut hormones and their contribution to weight loss physiology can lead to new therapeutic treatments for weight loss. Two distinct types of neurons in the arcuate hypothalamic nuclei control food intake: proopiomelanocortin neurons activated by the anorexigenic (satiety) hormones and neurons activated by the orexigenic peptides that release neuropeptide Y and agouti-related peptide (hunger centre). The arcuate nucleus of the hypothalamus integrates hormonal inputs from the gut and adipose tissue (the anorexigenic hormones cholecystokinin, polypeptide YY, glucagon-like peptide-1, oxyntomodulin, leptin, and others) and orexigeneic peptides (ghrelin). Replicating the endocrine response to bariatric surgery through pharmacological mimicry holds promise for medical treatment. Obesity has genetic and environmental factors. New advances in genetic testing have identified both monogenic and polygenic obesity-related genes. Understanding the function of genes contributing to obesity will increase insights into the biology of obesity. This review includes the physiology of appetite control, the influence of genetics on obesity, and the changes that occur following bariatric surgery. This has the potential to lead to the development of more subtle, individualised, treatments for obesity.