Duodenal–Jejunal Bypass Improves Glucose Homeostasis in Association with Decreased Proinflammatory Response and Activation of JNK in the Liver and Adipose Tissue in a T2DM Rat Model

Baicalin suppresses macrophage JNK-mediated adipose tissue inflammation to mitigate insulin resistance in obesity

ETHNOPHARMACOLOGICAL RELEVANCE

Radix scutellariae (the root of Scutellaria baicalensis Georgi) is a traditional Chinese medicine (TCM) used to treat a wide range of inflammation-related diseases, such as obesity, diabetes, diabetic kidney disease, and COVID-19-associated inflammatory states in the lung and kidney. Baicalin is the major anti-inflammatory component of Radix scutellariae and has shown the potential to inhibit inflammation in metabolic disorders. In this study, we explored the ability and underlying mechanisms of baicalin to modulate the macrophage to mitigate insulin resistance in obesity.

MATERIALS AND METHODS

Obese mice were administered baicalin (50 mg/kg/day) intraperitoneally for 3 weeks. RAW264.7 and BMDM cells were stimulated with LPS and treated with baicalin for 24 h, while 3T3-L1 and primary white adipocytes were treated with the supernatants from baicalin-treated RAW264.7 cells for 24 h.

RESULTS

The results showed that baicalin significantly improved glucose and insulin tolerance as well as decreased fat and adipose tissue macrophage levels in obese mice. Besides, baicalin significantly reduced serum and adipose tissue IL-1β, TNF-α and IL-6 levels in obese mice, as well as suppressed LPS-induced IL-1β, TNF-α and IL-6 expression and release in macrophages. Furthermore, treatment with the supernatant from baicalin-treated RAW264.7 cells increased the levels of PGC-1α, SIRT1, p-IRS-1 and p-AKT in adipocytes. Moreover, baicalin treatment dramatically downregulated macrophage p-p38, p-JNK, and Ac-p65Lys310 levels while increasing SIRT1 both in vivo and in vitro. Importantly, JNK inhibitor SP600125 blocked most of the effects of baicalin on SIRT1, Ac-p65Lys310 and pro-inflammatory factors in macrophages.

CONCLUSION

Therefore, these results demonstrated for the first time that baicalin exerts its anti-inflammatory effects in obese adipose tissue macrophages mainly through suppressing JNK/SIRT1/p65 signaling. These findings amplified the mechanisms of baicalin and its potential to attenuate insulin resistance.

Transcriptome Changes and Metabolic Outcomes After Bariatric Surgery in Adults With Obesity and Type 2 Diabetes

Context

Bariatric surgery has been shown to be effective in inducing complete remission of type 2 diabetes in adults with obesity. However, its efficacy in achieving complete diabetes remission remains variable and difficult to predict before surgery.

Objective

We aimed to characterize bariatric surgery-induced transcriptome changes associated with diabetes remission and the predictive role of the baseline transcriptome.

Methods

We performed a whole-genome microarray in peripheral mononuclear cells at baseline (before surgery) and 2 and 12 months after bariatric surgery in a prospective cohort of 26 adults with obesity and type 2 diabetes. We applied machine learning to the baseline transcriptome to identify genes that predict metabolic outcomes. We validated the microarray expression profile using a real-time polymerase chain reaction.

Results

Sixteen patients entered diabetes remission at 12 months and 10 did not. The gene-expression analysis showed similarities and differences between responders and nonresponders. The difference included the expression of critical genes (SKT4, SIRT1, and TNF superfamily), metabolic and signaling pathways (Hippo, Sirtuin, ARE-mediated messenger RNA degradation, MSP-RON, and Huntington), and predicted biological functions (β-cell growth and proliferation, insulin and glucose metabolism, energy balance, inflammation, and neurodegeneration). Modeling the baseline transcriptome identified 10 genes that could hypothetically predict the metabolic outcome before bariatric surgery.

Conclusion

The changes in the transcriptome after bariatric surgery distinguish patients in whom diabetes enters complete remission from those who do not. The baseline transcriptome can contribute to the prediction of bariatric surgery-induced diabetes remission preoperatively.

Role of JNK, TGF-β1, Akt, IL-1β and INSL-3 in proanthocyanidin protection against apoptosis in diabetic rat testis

We investigated how proanthocyanidin treatment altered c-Jun N-terminal kinases, transforming growth factor beta 1, serine/threonine-specific protein kinase, interleukin 1 beta and insulin-like 3 expression in the testis of diabetic rats. We used 24 Wistar albino male rats divided into four groups. Group 1 was untreated control. Group 2 was treated with 40 mg/kg streptozotocin (STZ) for 5 days. Group 3 was treated with 40 mg/kg STZ + 250 mg/kg proanthocyanidin once daily for six weeks. Group 4 was treated with 40 mg/kg STZ + 250 mg/kg proanthocyanidin. Superoxide dismutase activity was reduced in groups 3 and 4 compared to group 2. Glutathione peroxidase activity was increased significantly in groups 3 and 4 compared to groups 1 and 2. Catalase activity was decreased in group 4 compared to group 2. We found that proanthocyanidin increased cell proliferation in diabetic testis. Phospho-JNK and TGF-β1 immunostaining was decreased groups 3 and 4 compared to group 2, while p-Akt immunostaining was increased in groups 3 and 4. The number of IL-1β immunostained cells in groups 3 and 4 was decreased compared to group 2. INSL-3 immunostaining was increased significantly in group 3 compared to group 2. Our findings indicate that proanthocyanidin ameliorated diabetes related testicular dysfunction. Proanthocyanidin contributes to a balanced oxidant-antioxidant status, and balanced proliferation and apoptosis activity in the germinal cells.

Effect of Sleeve Gastrectomy on Glycometabolism via Forkhead Box O1 (FoxO1)/Lipocalin-2 (LCN2) Pathway

BACKGROUND The mechanism by which sleeve gastrectomy (SG) improves glycometabolism has remained unclear so far. Increasing evidence has demonstrated that bone is a regulator of glucose metabolism, and osteoblast-derived forkhead box O1 (FoxO1) and lipocalin-2 (LCN2) are regulators of energy metabolism. The aim of this study was to investigate whether the FOXO1/LCN2 signaling pathway is involved in the anti-diabetic effect of SG. MATERIAL AND METHODS Insulin resistance was induced in Wistar rats, which were then intraperitoneally injected with streptozotocin to induce a type 2 diabetic state. Levels of fasting blood glucose, serum insulin, HbA1c, and LCN2 were analyzed at corresponding time points after SG and sham surgeries. The expressions of FOXO1, LCN2, and the melanocortin 4 receptor (MC4R) in bone and hypothalamus were detected by immunofluorescence. FOXO1 siRNA was applied to downregulate FOXO1 expression in osteoblasts of rats. The influence of FOXO1 gene on expression of LCN2 was investigated in cultured osteoblasts by western blot and PCR. RESULTS Glucose metabolism in the SG group was significantly improved. The LCN2 expression in bone in the SG group was higher than that in the sham group, whereas FOXO1 expression in the SG group was lower than that in the sham group. The binding rate of LCN2 and MC4R in the hypothalamus was also higher in the SG group compared with that in the sham group. The downregulation of FOXO1 expression in osteoblasts was accompanied by upregulation of LCN2 expression. CONCLUSIONS These results suggest that the FOXO1/LCN2 signaling pathway participates in the anti-diabetic effect of SG.

Establishing a successful rat model of duodenal- jejunal bypass: A detailed guide

Gastric bypass surgery, an operation that restricts the stomach and bypasses the duodenum and part of the jejunum, results in major improvement or remission of type 2 diabetes. Duodenual-jejunal bypass was developed by one of the authors (FR) as an experimental, stomach-sparing variant of gastric bypass surgery to investigate weight-independent mechanisms of surgical control of diabetes. Duodenual-jejunal bypass has been shown to improve various aspects of glucose homeostasis in rodents and in humans, thus providing an experimental model for investigating mechanisms of action of surgery and elusive aspects of gastrointestinal physiology. Performing duodenual-jejunal bypass in rodents, however, is associated with a steep learning curve. Here we report our experience with duodenual-jejunal bypass and provide practical tips for successful surgery in rats. Duodenual-jejunal bypass was performed on 50 lean rats as part of a study aimed at investigating the effect of the procedure on the physiologic mechanisms of glucose homeostasis. During the study, we have progressively refined details of anatomic exposure, technical aspects of duodeno-jejunostomy and peri-operative care. We analysed the role of such refinements in improving operative time and post-operative mortality. We found that refinement of exposure methods of the gastro-duodenal junction aimed at minimizing tension on small visceral vasculature, technical aspects of duodeno-jejunal anastomosis and peri-operative management played a major role in improving the survival rate and operative time. Overall, an experimental model of duodenual-jejunal bypass was successfully reproduced. Based on this experience, we describe here what we believe are the most important technical tips to reduce the learning curve for the procedure.

The effect of distal-ileal exclusion after Roux-en-Y gastric bypass on glucose tolerance and GLP-1 response in type-2 diabetes Sprague-Dawley rat model

BACKGROUND

An increase in glucagon-like peptide-1 (GLP-1) mediating early diabetes remission after Roux-en-Y gastric bypass (RYGB) is believed to be associated with distal-ileal stimulation.

OBJECTIVE

To observe the effect of distal-ileal exclusion on glucose tolerance and GLP-1 response after RYGB.

SETTING

Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China.

METHODS

A type 2 diabetes model was created in 40 Sprague-Dawley rats that were randomly assigned to a RYGB group (n = 32) and a sham group (n = 8). Four weeks after surgery, the RYGB group was further divided into the RYGB control group (n = 8) and the distal-ileal exclusion group (RYGB-IEx, n = 24). Rats in the RYGB-IEx group underwent laparotomy, and the last 20 cm of ileum was excluded. An oral glucose tolerance test, insulin tolerance test, and mixed-meal tolerance test conducted preoperatively were repeated in all groups at 4 and 8 weeks postoperatively.

RESULTS

Compared with preoperative level, GLP-1 was significantly increased after RYGB. GLP-1 area under the curve recorded after oral gavage at week 4 postoperatively was significantly higher than the preoperative level (P < .05). GLP-1, insulin area under the curve, and improved glucose-excursion on oral glucose tolerance test 4 weeks after gastric bypass were not reversed at week 8 after distal-ileal exclusion in the RYGB-IEx group. Food intake increased significantly after distal-ileal exclusion in the RYGB-IEx group.

CONCLUSION

These findings suggest that distal-ileal stimulation might not be required for incretin response and diabetes remission after gastric bypass in the type 2 diabetes Sprague-Dawley rat model.

Duodenal-Jejunal Bypass Surgery Ameliorates Glucose Homeostasis and Reduces Endoplasmic Reticulum Stress in the Liver Tissue in a Diabetic Rat Model

BACKGROUND

Duodenal-jejunal bypass (DJB) has been shown to be an effective surgical treatment for type 2 diabetes mellitus (T2DM). However, the underlying mechanisms are poorly understood. Recently, accumulating evidences suggest that endoplasmic reticulum (ER) stress plays an important role in the development of insulin resistance in T2DM. The present study was designed to investigate the effect of DJB on glucose homeostasis, the ER stress state in the liver tissue, and the involving signaling independently of weight loss.

METHODS

Thirty adult male T2DM Sprague-Dawley (SD) rats induced by high-fat diet and low dose of streptozotocin (STZ) were randomly divided into DJB and sham groups. Ten age-matched male SD rats were assigned as the control group. The parameters of body weight and calorie intake were measured at indicated time points. The glucose tolerance and insulin resistance were detected to evaluate the glucose homeostasis. Serum insulin was determined by enzyme-linked immunosorbent assay (ELISA). The markers of ER stress, the activity of c-Jun N-terminal kinase (JNK) and serine phosphorylation of insulin receptor substrate 1 (IRS-1) in the liver tissue, were determined by Western blotting.

RESULTS

DJB induced significant improvements in glucose homeostasis and insulin sensitivity, but without weight loss. DJB improved the ER stress state indicated by decreased protein kinase RNA (PKR)-like ER protein kinase (PERK) and inositol-requiring enzyme 1 (IRE-1) phosphorylation in the liver tissue. The JNK activity and serine phosphorylation of IRS-1 in the liver tissue were significantly reduced after DJB.

CONCLUSIONS

DJB ameliorates glucose homeostasis. Meanwhile, our study helps to reveal that the reduced hepatic ER stress and the decreased JNK activity may contribute to the improved glucose homeostasis after DJB.

Glucoregulatory Relevance of Small Intestinal Nutrient Sensing in Physiology, Bariatric Surgery, and Pharmacology

Emerging evidence suggests the gastrointestinal tract plays an important glucoregulatory role. In this perspective, we first review how the intestine senses ingested nutrients, initiating crucial negative feedback mechanisms through a gut-brain neuronal axis to regulate glycemia, mainly via reduction in hepatic glucose production. We then highlight how intestinal energy sensory mechanisms are responsible for the glucose-lowering effects of bariatric surgery, specifically duodenal-jejunal bypass, and the antidiabetic agents metformin and resveratrol. A better understanding of these pathways lays the groundwork for intestinally targeted drug therapy for the treatment of diabetes.