Gastric Sleeve Surgery Alleviates Obesity-Associated Insulin Resistance and Suppresses Endoplasmic Reticulum Stress in Adipose Tissue of db/db Mice

Hydrogen Sulfide Ameliorates Angiotensin II-Induced Atrial Fibrosis Progression to Atrial Fibrillation Through Inhibition of the Warburg Effect and Endoplasmic Reticulum Stress

Atrial fibrosis is the basis for the occurrence and development of atrial fibrillation (AF) and is closely related to the Warburg effect, endoplasmic reticulum stress (ERS) and mitochondrion dysfunctions-induced cardiomyocyte apoptosis. Hydrogen sulfide (H₂S) is a gaseous signalling molecule with cardioprotective, anti-myocardial fibrosis and improved energy metabolism effects. Nevertheless, the specific mechanism by which H₂S improves the progression of atrial fibrosis to AF remains unclear. A case-control study of patients with and without AF was designed to assess changes in H₂S, the Warburg effect, and ERS in AF. The results showed that AF can significantly reduce cystathionine-γ-lyase (CSE) and 3-mercaptopyruvate thiotransferase (3-MST) expression and the H₂S level, induce cystathionine-β-synthase (CBS) expression; increase the Warburg effect, ERS and atrial fibrosis; and promote left atrial dysfunction. In addition, AngII-treated SD rats had an increased Warburg effect and ERS levels and enhanced atrial fibrosis progression to AF compared to wild-type SD rats, and these conditions were reversed by sodium hydrosulfide (NaHS), dichloroacetic acid (DCA) or 4-phenylbutyric acid (4-PBA) supplementation. Finally, low CSE levels in AngII-induced HL-1 cells were concentration- and time-dependent and associated with mitochondrial dysfunction, apoptosis, the Warburg effect and ERS, and these effects were reversed by NaHS, DCA or 4-PBA supplementation. Our research indicates that H₂S can regulate the AngII-induced Warburg effect and ERS and might be a potential therapeutic drug to inhibit atrial fibrosis progression to AF.

Effect of bariatric surgery on in vitro fertilization in infertile men with obesity

BACKGROUND

Obesity has previously been related to reduced female fertility, with prolonged waiting time to pregnancy among women with a body mass index (BMI) >35 kg/m² but there are few studies investigating the relationship between high BMI, bariatric surgery, and male fertility.

OBJECTIVES

The primary objective of this article was to investigate the effect of bariatric surgery on in vitro fertilization (IVF) outcomes in a cohort of men with morbid obesity who underwent sleeve gastrectomy (SG).

SETTING

University hospital, bariatric surgery unit.

METHODS

Pre- and postsurgery data on patient age, body mass index (BMI), and variables related to male fertility (semen volume, concentration, progressively motile sperm count, and sperm morphology) were collected; assisted reproductive technology outcomes before and after bariatric surgery were measured by the number of metaphase II oocytes; the number of top-quality oocytes and embryos; the number of fertilized oocytes; the number of transferred embryo; the implantation rate; the pregnancy rate; the live birth rate and the miscarriage rate.

RESULTS

Thirty-five men with obesity and idiopathic infertility were included in this study. We found a significant increase, after bariatric surgery, in semen volume, total sperm concentration, progressively motile sperm count, and sperm morphology. Considering IVF outcomes, mean number of top-quality oocytes, mean number of fertilized oocytes, mean number of embryos obtained, and top-quality embryos were significantly increased after bariatric procedure.

CONCLUSION

Bariatric surgery is confirmed to be safe and effective in increasing the outcomes of assisted reproductive technology treatment also in case of infertile men with obesity, both in terms of pregnancy and live birth rate.

Prolonged preoperative fasting induces postoperative insulin resistance by ER-stress mediated Glut4 down-regulation in skeletal muscles

Preoperative fasting aims to prevent pulmonary aspiration and improve bowel preparation, but it may induce profound systemic catabolic responses that lead to protein breakdown and insulin-resistant hyperglycemia after operation. However, the molecular mechanisms of catabolic reaction induced by prolonged preoperative fasting and surgical stress are undetermined. In this study, anesthetized rats were randomly assigned to receive a sham operation or laparotomy cecectomy. Fasting groups were restricted from food and water for 12 h before operation, while the feeding group had free access to food throughout the study period. Twenty-four hours after operation, the animals were sacrificed to collect blood samples and soleus muscles for analysis. Postoperative blood glucose level was significantly increased in the fasting group with elevated serum insulin and C-peptide. Continuous feeding reduced serum myoglobin and lactate dehydrogenase concentrations. Preoperative fasting activated inositol-requiring transmembrane kinase/endoribonuclease (IRE)-1α and c-Jun N-terminal kinase (JNK) mediated endoplasmic reticulum (ER)-stress, and reduced glucose transporter type 4 (Glut4) expression in the soleus muscle. Phospholamban phosphorylation was reduced and intracellular calcium levels were increased in the isolated skeletal muscle cells. Similar results were found in ER stress-induced C1C12 myoblasts. The expression of Glut4 was suppressed in the stressed C1C12, but was potentiated following inhibition of ER stress and chelation of intracellular free calcium. This study provides evidence demonstrating that prolonged preoperative fasting induces ER stress and generates insulin resistance in the skeletal muscle through suppression of Glut4 and inactivation of Ca²⁺-ATPase, leading to intracellular calcium homeostasis disruption and peripheral insulin resistance.

Sleeve Gastrectomy Surgery Improves Glucose Metabolism by Downregulating the Intestinal Expression of Sodium-Glucose Cotransporter-3

AIMS

Sleeve gastrectomy (SG) has been proven effective in the treatment of obesity and type 2 diabetes. We hypothesized that SGLT3 may play an important role in the mechanism of glucose control and weight loss after SG.

MATERIALS AND METHODS

Daily body weight and food intake were measured in SG and sham-operated mice. Glucose tolerance test, SGLT3 agonist (αMG), and SGLT1 inhibitor (phlorizin) perfusion experiments were used to detect changes in intestinal SGLT3 and SGLT1 activity following SG. Expression of SGLT3a and SGLT1 was assessed at 2 weeks, 1 month after surgery by quantitative PCR and fluorescence immunoassay. Hematoxylin and eosin staining was used to detect morphological changes in the villi. SGLT3 and SGLT1 expression was measured after stimulation of human intestinal epithelial cells (HIEC).

RESULTS

Both the body weight and daily food intake of the SG-treated mice decreased within 30 days after surgery. Oral glucose absorption was significantly reduced at 30 days. The intestinal stimulation proved that SG can improve glucose metabolism, which can be reversed by αMG and enhanced by phlorizin. Villus height and surface area of the intestine in SG mice decreased after surgery. mRNA expression of SGLT3a and SGLT1 decreased at 2 weeks and 1 month after SG, immunofluorescence also confirmed these changes. HIEC stimulation confirmed that αMG could increase the expression of SGLT3 and SGLT1, but the expression of SGLT1 was down regulated when phlorizin was added to the medium.

CONCLUSION

The results suggest that reducing SGLT3 expression might contribute to lowering blood glucose and controlling body weight after SG.

Activation of α7nAChR via vagus nerve prevents obesity-induced insulin resistance via suppressing endoplasmic reticulum stress-induced inflammation in Kupffer cells

Obesity is a major risk factor for type 2 diabetes mellitus and insulin resistance (IR). In the state of obesity, excess fat accumulates in the liver, a key organ in systemic metabolism, altering the inflammatory and metabolic signals contributing substantially to the development of hepatic IR. Current therapies for these metabolic disorders have not been able to reverse their rapidly rising prevalence. One of the reasons is that the effects of existing drugs are predominantly non-lasting [1,2]. The vagus nerve (VN) is known to play an essential role in maintaining metabolic homeostasis while decreased VN activity has been suggested to contribute to obesity associated metabolic syndrome [3,4]. Several studies have reported that activation of α7 nicotinic acetylcholine receptor (α7nAChR) cholinergic signaling with or without VN intervention has protective effects against obesity-related inflammation and other metabolic complications [5]. However, the molecular mechanisms are still not elucidated. Exaggerated endoplasmic reticulum (ER) stress and consequent dysregulated inflammation has been implicated in the development of lipid accumulation and IR [6]. Whether targeting α7nAChR can regulate IR through these pathways is rarely reported. Accordingly, the present proposal posits that activation of the α7nAChR by VNS attenuates ER stress induced inflammation, thus ameliorating hepatic IR in Kupffer cell. We will focus on the specific interaction between vagal cholinergic activity and the modulation of ER stress induced inflammation via the α7nAChR associated pathway during IR development. Recently, the Endocrine Society has emphasized the absence of specific evidence from basic science, clinical, and epidemiological literature to assess current knowledge regarding underlying mechanisms of obesity [7]. In this proposal, we assign a significant role to α7nAChR in obesity-induced hepatic IR, and suggest a possible therapeutic strategy with VNS intervention.

Regulation of Adipsin Expression by Endoplasmic Reticulum Stress in Adipocytes

Adpsin is an adipokine that stimulates insulin secretion from β-cells and improves glucose tolerance. Its expression has been found to be markedly reduced in obese animals. However, it remains unclear what factors lead to downregulation of adipsin in the context of obesity. Endoplasmic reticulum (ER) stress response is activated in various tissues under obesity-related conditions and can induce transcriptional reprogramming. Therefore, we aimed to investigate the relationship between adipsin expression and ER stress in adipose tissues during obesity. We observed that obese mice exhibited decreased levels of adipsin in adipose tissues and serum and increased ER stress markers in adipose tissues compared to lean mice. We also found that ER stress suppressed adipsin expression via adipocytes-intrinsic mechanisms. Moreover, the ER stress-mediated downregulation of adipsin was at least partially attributed to decreased expression of peroxisome proliferator-activated receptor γ (PPARγ), a key transcription factor in the regulation of adipocyte function. Finally, treatment with chemical chaperones recovered the ER stress-mediated downregulation of adipsin and PPARγ in vivo and in vitro. Our findings suggest that activated ER stress in adipose tissues is an important cause of the suppression of adipsin expression in the context of obesity.