Vertical Sleeve Gastrectomy Attenuates the Progression of Non-Alcoholic Steatohepatitis in Mice on a High-Fat High-Cholesterol Diet

Sleeve gastrectomy causes weight-loss independent improvements in hepatic steatosis

BACKGROUND AND AIMS

Sleeve gastrectomy (VSG) leads to improvement in hepatic steatosis, associated with weight loss. The aims of this study were to investigate whether VSG leads to weight-loss independent improvements in liver steatosis in mice with diet-induced obesity (DIO); and to metabolically and transcriptomically profile hepatic changes in mice undergoing VSG.

METHODS

Mice with DIO were treated with VSG, sham surgery with subsequent food restriction to weight-match to the VSG group (Sham-WM), or sham surgery with return to unrestricted diet (Sham-Ad lib). Hepatic steatosis, glucose tolerance, insulin and glucagon resistance, and hepatic transcriptomics were investigated at the end of the study period and treatment groups were compared with mice undergoing sham surgery only (Sham-Ad lib).

RESULTS

VSG led to much greater improvement in liver steatosis than Sham-WM (liver triglyceride mg/mg 2.5 ± 0.1, 2.1 ± 0.2, 1.6 ± 0.1 for Sham-AL, Sham-WM and VSG respectively; p = 0.003). Homeostatic model assessment of insulin resistance was improved following VSG only (51.2 ± 8.8, 36.3 ± 5.3, 22.3 ± 6.1 for Sham-AL, Sham-WM and VSG respectively; p = 0.03). The glucagon-alanine index, a measure of glucagon resistance, fell with VSG but was significantly increased in Sham-WM (9.8 ± 1.7, 25.8 ± 4.6 and 5.2 ± 1.2 in Sham Ad-lib, Sham-WM and VSG respectively; p = 0.0003). Genes downstream of glucagon receptor signalling which govern fatty acid synthesis (Acaca, Acacb, Me1, Acly, Fasn and Elovl6) were downregulated following VSG but upregulated in Sham-WM.

CONCLUSIONS

Changes in glucagon sensitivity may contribute to weight-loss independent improvements in hepatic steatosis following VSG.

Glucose metabolism after bariatric surgery: implications for T2DM remission and hypoglycaemia

Although promising therapeutics are in the pipeline, bariatric surgery (also known as metabolic surgery) remains our most effective strategy for the treatment of obesity and type 2 diabetes mellitus (T2DM). Of the many available options, Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) are currently the most widely used procedures. RYGB and VSG have very different anatomical restructuring but both surgeries are effective, to varying degrees, at inducing weight loss and T2DM remission. Both weight loss-dependent and weight loss-independent alterations in multiple tissues (such as the intestine, liver, pancreas, adipose tissue and skeletal muscle) yield net improvements in insulin resistance, insulin secretion and insulin-independent glucose metabolism. In a subset of patients, post-bariatric hypoglycaemia can develop months to years after surgery, potentially reflecting the extreme effects of potent glucose reduction after surgery. This Review addresses the effects of bariatric surgery on glucose regulation and the potential mechanisms responsible for both the resolution of T2DM and the induction of hypoglycaemia.

RYGB Is More Effective than VSG at Protecting Mice from Prolonged High-Fat Diet Exposure: An Occasion to Roll Up Our Sleeves?

PURPOSE

Understanding the effects of Roux-en-Y gastric bypass (RYGB) and vertical sleeve gastrectomy (VSG) on adipose tissue physiology is important for the treatment of obesity-related metabolic disorders. By using robust mouse models of bariatric surgery that closely resemble those performed in humans, we can compare the effects of RYGB and VSG on adipose physiology in the absence of post-operative confounds such as diet and lifestyle changes.

MATERIALS AND METHODS

RYGB and VSG were compared using a diet-induced mouse model of obesity. High-fat diet (HFD) was administered post-operatively and changes to white and brown adipose tissue were evaluated, along with alterations to weight, glucose homeostasis, dyslipidemia, and insulin sensitivity.

RESULTS

After prolonged exposure to high-fat diet post-operatively, RYGB was effective in achieving sustained weight loss, while VSG unexpectedly accelerated weight gain rates. The resolution of obesity-related comorbidities such as glucose and insulin intolerance, dyslipidemia, and insulin sensitivity was improved after RYGB, but not for VSG. In RYGB, there were improvements to the function and health of white adipose tissue, enhanced brown adipose metabolism, and the browning of subcutaneous white adipose tissue, with no comparable changes seen for these factors after VSG. Some markers of systemic inflammation improved after both RYGB and VSG.

CONCLUSION

There are significantly different effects between RYGB and VSG when HFD is administered post-operatively and robust mouse models of bariatric surgery are used. RYGB resulted in lasting physiological and metabolic changes but VSG showed little difference from that of its sham-operated, DIO counterpart.

Oral administration of trehangelin-A alleviates metabolic disorders caused by a high-fat diet through improvement of lipid metabolism and restored beneficial microbiota

The present study investigated whether or not the oral administration of trehangelin-A (THG-A) is effective for metabolic disorders caused by a high-fat diet, as we previously showed that the intraperitoneal administration of THG-A improved metabolic disorders caused by a high-fat diet. Mice received a control diet or high-fat diet for eight weeks. Concurrently, mice were orally administered 0.2 ml/mouse phosphate-buffered saline (PBS) or 1 or 10 mg/0.2 ml/mouse of THG-A once daily during the experiment. The weight gain caused by a high-fat diet was significantly suppressed by oral THG-A compared to a high-fat diet without THG-A. In addition, at eight weeks after starting the diet, the increased plasma total-cholesterol (T-CHO) and low-density lipoprotein-cholesterol (LDL-C) levels caused by a high-fat diet were significantly reduced by 10 mg/mouse THG-A and tended to attenuated by 1 mg/mouse THG-A. The LDL receptor and CYP7A1 mRNA expression in liver associated with lipid metabolism for reducing plasma LDL-C levels was significantly enhanced by oral THG-A. In contrast, oral THG-A exerted no marked effects on mice fed the control diet. The dysbiosis of a high-fat diet fed mice, which is in the form of an increased Firmicutes-to-Bacteroidetes ratio, also recovered, and the high-fat diet induced decreased levels of Bacteroides and Akkermansia genera, which are beneficial microbiota against metabolic disorders, were also restored by oral THG-A. These results indicate that oral THG-A administration acts on metabolic disorders by improving the lipid metabolism and restoring beneficial microbiota to resolve high-fat diet induced dysbiosis.