Association between allelic variants in the glucagon-like peptide 1 and cholecystokinin receptor genes with gastric emptying and glucose tolerance

Glucagon-like Peptide-1 Receptor Agonists in the Management of Type 2 Diabetes Mellitus and Obesity: The Impact of Pharmacological Properties and Genetic Factors

Glucagon-like peptide-1 (GLP-1) receptor agonists are a new class of antihyperglycemic drugs that enhance appropriate pancreatic β-cell secretion, pancreatic α-cell (glucagon) suppression, decrease liver glucose production, increase satiety through their action on the central nervous system, slow gastric emptying time, and increase insulin action on peripheral tissue. They are effective in the management of type 2 diabetes mellitus and have a favorable effect on weight loss. Their cardiovascular and renal safety has been extensively investigated and confirmed in many clinical trials. Recently, evidence has shown that in addition to the existing approaches for the treatment of obesity, semaglutide in higher doses promotes weight loss and can be used as a drug to treat obesity. However, some T2DM and obese patients do not achieve a desired therapeutic effect of GLP-1 receptor agonists. This could be due to the multifactorial etiologies of T2DM and obesity, but genetic variability in the GLP-1 receptor or signaling pathways also needs to be considered in non-responders to GLP-1 receptor agonists. This review focuses on the pharmacological, clinical, and genetic factors that may influence the response to GLP-1 receptor agonists in the treatment of type 2 diabetes mellitus and obesity.

Gastric Sensory and Motor Functions and Energy Intake in Health and Obesity-Therapeutic Implications

Sensory and motor functions of the stomach, including gastric emptying and accommodation, have significant effects on energy consumption and appetite. Obesity is characterized by energy imbalance; altered gastric functions, such as rapid gastric emptying and large fasting gastric volume in obesity, may result in increased food intake prior to reaching usual fullness and increased appetite. Thus, many different interventions for obesity, including different diets, anti-obesity medications, bariatric endoscopy, and surgery, alter gastric functions and gastrointestinal motility. In this review, we focus on the role of the gastric and intestinal functions in food intake, pathophysiology of obesity, and obesity management.

Duodenal mucosal secretory disturbances in functional dyspepsia

BACKGROUND

There is increased recognition of duodenal disturbances (inflammation, altered mucosal protein expression, and chemosensitivity) in functional dyspepsia (FD). Besides sensorimotor functions, enteric submucosal neurons also regulate epithelial ion transport. We hypothesized that duodenal mucosal ion transport and expression of associated genes are altered in FD.

METHODS

Duodenal mucosal ion transport (basal and acetylcholine- and glucose-evoked changes in short-circuit current [Isc]) and expression of associated genes and regulatory miRNAs were evaluated in 40 FD patients and 24 healthy controls.

RESULTS

Basal Isc (FD: 88.2 [52.6] μA/cm² vs healthy: 20.3 [50.2] μA/cm² ; P ≤ .0001), acetylcholine-evoked Isc (FD: Emax 50.4 [35.8] μA/cm² vs healthy: 16.6 [15] μA/cm² ; P ≤ .001), and glucose-evoked Isc responses (FD: E_max 69.8 [42.1] μA/cm² vs healthy: 40.3 [24.6] μA/cm² ; P = .02) were greater in FD than in controls. The Emax for glucose was greater in FD patients on selective serotonin reuptake inhibitors. In FD, the mRNA expression of SLC4A7 and SLC4A4, which transport bicarbonate into cells at the basolateral surface, and the apical anion exchanger SLC26A3 were reduced (false discovery rate <0.05), the serotonin receptor HTR4 was increased, and the serotonin transporter SLC6A4 was decreased. Selected miRNAs (hsa-miR-590-3p, hsa-miR-32-5p) that target genes associated with ionic transport were upregulated in FD.

CONCLUSIONS

Compared to controls, FD patients had greater baseline and agonist-evoked duodenal mucosal secretory responses. These findings may be explained by reduced gene expression, which would be anticipated to reduce luminal bicarbonate secretion. The upregulated miRNAs may partly explain the downregulation of these genes in FD.

Clinical features and disturbances of gastrointestinal transit in patients with rapid gastric emptying

AIMS

Some patients with upper gastrointestinal symptoms have rapid gastric emptying (GE). We aimed to compare patients with normal and rapid GE and to identify phenotypes among patients with rapid GE.

METHODS

Among 2798 patients who underwent GE scintigraphy, we compared patients with normal and rapid GE and separately, patients with rapid GE at 1 hour (GE1), 2 hours (GE2), or both (GE12).

RESULTS

In 2798 patients, GE was normal (74%), delayed (18%), or rapid (8%). Among 211 patients with rapid GE, patterns were rapid GE1 (48%), 2 hours (17%), or 1 and 2 hours (35%); 42 (20%) had diseases that explain rapid GE. A combination of upper and lower gastrointestinal symptoms (54%) was more common that isolated upper (17%) or lower (28%) gastrointestinal symptoms (P < .001). Constipation was more prevalent in patients with rapid GE 2 (72%) than rapid GE 1 (47%) or rapid GE12 hours (67%) (P < .05). Among 179 diabetes mellitus (DM) patients, 15% had rapid GE, which was not associated with the DM phenotype. By multivariable analysis, insulin therapy (odds ratio [OR], 0.36; 95% confidence interval [CI], 0.15-0.88), and weight loss (OR, 0.10; 95% CI, 0.01-0.78) were associated with a lower risk of rapid than normal GE in DM.

CONCLUSIONS

Eight percent of patients undergoing scintigraphy had rapid GE, which is most frequently associated with upper and lower gastrointestinal symptoms; constipation is common. Insulin therapy and weight loss were associated with a lower risk of rapid than normal GE in DM patients.