Duodenal-jejunal exclusion improves insulin resistance in type 2 diabetic rats by upregulating the hepatic insulin signaling pathway

Duodenal mucosal resurfacing with photodynamic therapy using methylene blue in a mouse model

BACKGROUND

The duodenum has emerged as a key player in metabolic diseases. The objective was to evaluate the safety and efficacy of intra-duodenal PDT using methylene blue in managing glycemic control and weight reduction.

METHODS

Optimal concentration of methylene blue and conditions for intra-duodenal PDT were determined through in vitro experiments. After injecting methylene blue into the duodenum, we performed intra-duodenal PDT. High-fat diet rats were used to assess the efficacy of intra-duodenal PDT through measures of oral glucose tolerance, insulin sensitivity, and weight change. Immunohistochemical staining was also conducted to examine GLP-1 and GIP-producing cells in the ileum and duodenum, respectively.

RESULTS

Introduodenal PDT reduced villous height of duodenum at 48 h, which was fully recovered at 30 days without complications. Rats treated with PDT showed significantly lower blood glucose levels with glucose loading and improved insulin sensitivity than rats in the sham-treatment group. The PDT group also had a significant reduction in body weight compared to the sham-treatment group at 30 days after intervention, although food intake was not significantly different between the two groups. Numbers of GLP-1 and GIP producing cells in the ileum and irradiated area were significantly higher in the PDT group than in the sham-treatment group.

CONCLUSIONS

Intra-duodenal PDT using methylene blue showed a feasible therapeutic modality in improving metabolic parameters. However, large animal experiments and mechanism studies are needed to determine the clinical relevance. The possibility of repeating this treatment every 30 days and its accompanying complications should be further studied.

Duodenal Mucosa: A New Target for the Treatment of Type 2 Diabetes

OBJECTIVE

After a high-fat and high-sugar diet, the duodenal mucosa of rodents proliferate and trigger the signal of insulin resistance, which may be the cause of type 2 diabetes (T2D). In response to this phenomenon, researchers have designed the duodenal mucosal resurfacing (DMR) procedure, mainly through the hydrothermal ablation procedure, to restore the normal mucosal surface, thereby correcting this abnormal metabolic signal. This article aims to understand the changes in duodenum before and after the onset or treatment of T2D, and the potential mechanisms of DMR procedure.

METHODS

A literature search of PubMed and Web of Science was conducted using appropriate keywords.

RESULTS

Both animal and clinical studies have shown that the villus thickness, intestinal cells, glucose transporters, enteric nerves, and gut microbiota and their metabolites in the duodenum undergo corresponding changes before and after the onset or treatment of T2D. These changes may be related to the pathogenesis of T2D. DMR procedure may produce beneficial glycemic and hepatic metabolic effects by regulating these changes.

CONCLUSION

The duodenum is an important metabolic signaling center, and limiting nutrient exposure to this critical region will have powerful metabolic benefits. The DMR procedure may regulate glycemic and hepatic parameters through various mechanisms, which needs to be further confirmed by a large number of animal and clinical studies.

Glucose Tolerance after Pancreatectomy: A Prospective Observational Follow-Up Study of Pancreaticoduodenectomy and Distal Pancreatectomy

BACKGROUND

Effects of pancreatectomy on glucose tolerance have not been clarified, and evidence regarding the difference in postoperative glucose tolerance between pancreaticoduodenectomy (PD) and distal pancreatectomy (DP) is lacking.

STUDY DESIGN

This prospective, single-center observational study analyzed 40 patients undergoing PD and 29 patients undergoing DP (Clinical trial registry number UMIN000008122). Glucose tolerance, including insulin secretion (Δ C-peptide immunoreactivity, ΔCPR) and insulin resistance (homeostasis model assessment of insulin resistance, HOMA-IR) were assessed before and 1 month after pancreatectomy using the oral glucose tolerance test (OGTT) and glucagon stimulation test. We assessed long-term hemoglobin A1c (HbA1c) levels in patients, with a follow-up time of 3 years.

RESULTS

Percentages of patients diagnosed with abnormal OGTT decreased after PD (from 12 [30%] to 7 [17.5%] of 40 patients, p = 0.096); however, they increased after DP (from 4 [13.8%] to 8 [27.6%] of 29 patients, p = 0.103), although the changes were not statistically significant. ΔCPR decreased after both PD (from 3.2 to 1.0 ng/mL, p < 0.001) and DP (from 3.3 to 1.8 ng/mL, p < 0.001). HOMA-IR decreased after PD (from 1.10 to 0.68, p < 0.001), but did not change after DP (1.10 and 1.07, p = 0.42). Median HbA1c level was higher after DP than after PD for up to 3 years, but the differences were not statistically significant.

CONCLUSIONS

In comparisons of pre- and 1 month post-pancreatectomy data, glucose tolerance showed improvement after PD, whereas it worsened after DP. Insulin secretion decreased after both PD and DP. Insulin resistance improved after PD, but did not change after DP. Further studies are warranted to clarify mechanisms of improved insulin resistance after PD.

Metabolic endoscopy by duodenal mucosal resurfacing: expert review with critical appraisal of the current technique and results

INTRODUCTION

Duodenal mucosal resurfacing (DMR) is an endoscopic procedure for type 2 diabetes (T2D) consisting of circumferential hydrothermal ablation of the duodenal mucosa.

AREAS COVERED

A review was conducted on the reports available up to March-2020. On a total of 79 patients, DMR induced a significant mean HbA1c, FPG and HOMA-IR reduction at 6 months (0.9 ± 0.2%, 1.7 ± 0.5 mmol/L and 2.9 ± 1.1 mUI/L respectively - P < 0.001). DMR metabolic efficacy directly correlates with the length of the ablated mucosa (mean 3 months HbA1c reduction 1.2% vs 2.5% after short and long ablation respectively - P < 0.05), while it is independent of weight-loss. Severe AEs were registered in 3.7% of the cases.

EXPERT OPINION

DMR plays a promising role in metabolic impairment improvement inducing a morpho-functional duodenal alteration not necessarily depending on weight-loss. Technical-functional improvements of the device and appropriate training aimed at its correct use are needed to lower the rate of severe AEs and technical failure. The current role of DMR needs to be clarified, but it might be proposed for poorly controlled T2D in accurately selected patients. Evidence on DMR is still scanty and further research is mandatory to standardize the endoscopic technique and its indications.

Duodenal-Jejunal Exclusion Surgery Improves Type 2 Diabetes in a Rat Model Through Regulation of Early Glucose Metabolism

OBJECTIVES

Metabolic surgery has been proven to be widely effective for the control of glucose and weight in patients with type 2 diabetes and obesity. However, the effects of bariatric surgery on nonobesity type 2 diabetes and its metabolism are still unclear. This study aimed to measure the effects of duodenal-jejunal exclusion on glycometabolism in nonobese rats with type 2 diabetes and to investigate its mechanisms.

METHODS

Goto-Kakizaki rats and Sprague-Dawley rats were divided into duodenal-jejunal exclusion operation groups and sham operation groups, respectively. The glucose-relative parameters were measured before and after operation. Eight weeks postoperation, the levels of the key regulators of intestinal gluconeogenesis and the crucial proteins of hepatic insulin signalling were evaluated.

RESULTS

Postoperatively, the concentrations of blood glucose declined, and the insulin sensitivity increased significantly in rats with diabetes. However, there was no obvious reduction in weight. Eight weeks postoperatively, the mRNA levels of glucose-6-phosphatase and phosphoenolpyruvate pyruvate kinase in the jejunum and the levels of insulin receptor substrate-2 and glucose transporter-2 in the liver were significantly increased compared with the rats that had undergone the sham operation.

CONCLUSIONS

Duodenal-jejunal exclusion surgery is an effective procedure for improving glucose metabolism independent of weight loss in nonobese rats with diabetes. The molecular mechanisms might be associated with a series of processes, including intestinal gluconeogenesis and the hepatic insulin signaling pathway.

Beneficial effects of Aronia melanocarpa berry extract on hepatic insulin resistance in type 2 diabetes mellitus rats

We aimed to investigate) the effects of Aronia melanocarpa berry extract (AMBE) on hepatic insulin resistance and its mechanism at the molecular level in high-fat diet (HFD)- and streptozotocin (STZ)-induced type 2 diabetes mellitus (T2DM) rats. The rats were supplemented with AMBE at doses of 100 and 400 mg/kg body weight (bw) daily for 8 weeks. AMBE significantly reduced blood glucose and serum insulin levels and the homeostatic model assessment for insulin resistance score; improved glucose tolerance; increased hepatic glycogen content; and regulated glucose metabolism enzyme activity, including glucokinase, pyruvate kinase, phosphoenolpyruvate carboxykinase, and glucose-6-phosphatase in the liver. AMBE also reduced lipid accumulation and oxidative stress along with inflammation in the hepatic tissue of T2DM rats and improved hepatic function. The phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway was activated by AMBE through the elevation of insulin receptor substrate-2, PI3K, Akt, and glycogen synthase kinase-3β phosphorylation and glucose transporter 2, which might contribute to the promotion of glycogen synthesis and improvement of hepatic insulin resistance. AMBE shows promise as an ingredient of functional foods for alleviating hepatic insulin resistance in T2DM. PRACTICAL APPLICATION: The extract from the berries of Aronia melanocarpa (Michx.) Elliott (AMBE), with its relatively high content of polyphenolic compounds, has been shown to exert hypoglycemic effects in animal models of diabetes. Our findings support the use of A. melanocarpa as a functional food additive for the alleviation of hepatic insulin resistance and the management of glucose homeostasis in T2DM.

Cajanonic acid A regulates the ratio of Th17/Treg via inhibition of expression of IL-6 and TGF-β in insulin-resistant HepG2 cells

BACKGROUND

The objectives of the present study are to investigate whether cajanonic acid A (CAA) can reduce insulin resistance (IR) in HepG2 cells and to gain a preliminary understanding of the mechanisms underlying this effect.

METHODS

Following induction of IR in HepG2 cells, we tested the regulatory effect of CAA on glucose consumption and evaluated hepatocyte production of IL-6, TGF-β, and key molecules in the insulin transduction pathway. A transwell co-culturing system was used to assess the effect of CAA on IR in HepG2 cells during the differentiation of CD4+ T cells by calculating the ratio of (Th17)/regulatory T cell (Treg). We evaluated the effect of CAA on the expression of IL-17RC cells and HepG2 cell apoptosis by immunofluorescence and flow cytometry assay.

RESULTS

CAA improved dexamethasone-induced reduction in glucose consumption in HepG2 cells, inhibited hepatocyte production of IL-6 and TGF-β, increased the expression of IL-17RC cell, and increased cellular apoptosis in insulin-resistant HepG2 cells. When co-cultured with CD4+ T cells, insulin-resistant HepG2 cells induced a decrease in the ratio of Th17/Treg, but CAA dampened the effect. Application of IL-6 and TGF-β, together with CAA, reversed the effect of CAA on insulin-resistant HepG2 cells. Overexpression of IL17R, however, counteracted the effect of IL-6 neutralizing antibody within the culture system.

CONCLUSION

CAA can regulate the ratio of Th17/Treg by mediating the expression of IL-6 and TGF-β in insulin-resistant HepG2 cells.

Duodenal mucosal resurfacing: proof-of-concept, procedural development, and initial implementation in the clinical setting

BACKGROUND AND AIMS

We aimed to develop duodenal mucosal resurfacing (DMR), a minimally invasive upper endoscopic hydrothermal ablation procedure, to treat insulin-resistant metabolic diseases.

METHODS

We completed a sham-controlled, rodent proof-of-concept study and longitudinal safety study in pigs to demonstrate feasibility to test DMR in humans. Subsequently, the DMR procedure was implemented in an open-label first-in-human (FIH) study of safety and efficacy in patients with type 2 diabetes (T2D).

RESULTS

In rats, duodenal abrasion reduced hyperglycemia by 59 mg/dL on average, compared with no change from baseline in the sham treatment arm (P < .05). In pigs, the balloon catheter successfully and safely delivered hydrothermal ablation to the duodenal mucosa and superficial submucosa. Complete mucosal healing was demonstrated by week 6. In the FIH study, hydrothermal ablation was successfully administered with no evidence of perforation, pancreatitis, or hemorrhage. Duodenal biopsy specimens obtained 3 months postprocedure demonstrated full mucosal regrowth. No inflammation was observed, and there was minimal-to-mild collagen banding deposition observed in a proportion of ablation site biopsy specimens with no evidence of fibrotic scarring. Glycemic and hepatic measures improved through 6 months of follow-up.

CONCLUSIONS

DMR shows potential as an endoscopic intervention that improves glycemic and hepatic parameters in patients with T2D. Further mechanistic and clinical studies are underway to further explore DMR as a treatment for metabolic disease.

Changes of serum lipopolysaccharide, inflammatory factors, and cecal microbiota in obese rats with type 2 diabetes induced by Roux-en-Y gastric bypass

OBJECTIVES

Previous studies have shown that Roux-en-Y gastric bypass (RYGB) leads to rapid regression of obesity and type 2 diabetes (T2D). However, the underlying mechanism remains unclear. This study aimed to investigate the effect of RYGB on serum lipopolysaccharide (LPS), interleukin (IL)-1, IL-6, tumor necrosis factor alpha (TNF-α), and cecal microbiota in obese rats with T2D.

METHODS

Obese Sprague-Dawley rats with T2D were randomly divided into RYGB diabetes operation (DO; n = 8), diabetes sham operation (DS; n = 8), and diabetic control (DC; n = 8) groups. Healthy Sprague-Dawley rats were grouped as normal control (NC; n = 8). Fasting plasma glucose and body weight were measured. The levels of peripheral serum LPS, IL-1, IL-6, and TNF-α were measured by enzyme-linked immunosorbent assay. The rats were sacrificed 12 wk after operation. Subsequently, a superior mesenteric venous blood sample was taken to measure serum LPS levels by enzyme-linked immunosorbent assay. The cecal contents of the DO and DS groups were taken to extract metagenomic DNA per the genomic DNA standardization procedure. The V4 region of the 16 S rRNA was sequenced with the Illumina Hiseq sequencing platform to compare the structure and relative abundance of cecal microbiota between the DO and DS groups.

RESULTS

Twelve weeks after operation in the DO group, fasting plasma glucose and body weight showed a significant decrease (P < 0.05). Moreover, the levels of peripheral serum LPS, IL-1, IL-6, and TNF-α were obviously decreased (P < 0.05). A change in the LPS level of superior mesenteric venous blood also revealed a dramatic decrease (P < 0.05). Additionally, RYGB resulted in a shift of cecal microbiota in obese rats with T2D.

CONCLUSIONS

Hypoglycemic effects after RYGB may be associated with improved levels of LPS, IL-1, IL-6, and TNF-α. Changes in the structure of cecal microbiota may also play an important role.

Modulatory Effects of Berberine Chloride on Lipid Profile, Oxidant Status and Insulin Signaling Molecules in Streptozotocin Induced Diabetic Rats

The goal of the present study was to evaluate the effect of Berberine chloride (BC) on lipid profile, oxidant status and insulin signaling molecules in Streptozotocin (STZ) induced diabetic rat model. Diabetes was induced in rats by a single dose of intraperitoneal administration of STZ (40 mg/kg b.w). Diabetic rats were treated with BC (50 mg/kg b.w) and glibenclamide (6 mg/kg b.w) for 45 days. BC treated diabetic rats showed significant (p <0.05) decrease in the levels of TC, TG, phospholipids, LDL, VLDL and lipid peroxidation markers such as LOOH and TBARS. An increase in enzymatic antioxidant (SOD, CAT and GPx), non-enzymatic antioxidant (GSH, vitamin C and E) and insulin signaling molecules expression, like Insulin receptor substrate-1 (IRS-1), Protein kinase B (PKB or Akt) and glucose transporter-4 (GLUT-4) were found to be significantly raised in BC treated STZ induced diabetic rats. Thus, the results of the current study demonstrated that BC significantly reversed the abnormal levels of lipids, oxidant status and insulin signaling molecules in the diabetic rat model, which may be contributed to its anti-diabetic and antioxidant activities.

Duodeno-jejunal bypass restores β-cell hypersecretion and islet hypertrophy in western diet obese rats

PURPOSE

Duodeno-jejunal bypass (DJB) operation improves glucose homeostasis in morbid obesity, independently of weight loss or reductions in adiposity, through mechanisms not yet fully elucidated. Herein, we evaluated the effects of DJB upon glucose homeostasis, endocrine pancreatic morphology, and β-cell responsiveness to potentiating agents of cholinergic and cAMP pathways, in western diet (WD) obese rats, at 2 months after operation.

METHODS

From 8 to 18 weeks of age male Wistar rats fed on a WD. After this period, a sham (WD Sham group) or DJB (WD DJB) operations were performed. At 2 months after operation glucose homeostasis was verified.

RESULTS

Body weight was similar between WD DJB and WD Sham rats, but WD DJB rats showed a decrease in Lee index, retroperitoneal and perigonadal fat pads. Also, WD DJB rats displayed reduced fasting glycemia and insulinemia, and increased insulin-induced Akt activation in the gastrocnemius. Islets from WD DJB rats secreted less amounts of insulin, in response to activators of the cholinergic (carbachol and phorbol 12-myristate 13-acetate) and cAMP (forskolin and 3-isobutyl-1-methyl-xantine) pathways. Islets of WD DJB rats had higher sintaxin-1 protein content than WD Sham, but without modification in muscarinic-3 receptor, protein kinase (PK)-Cα, and (PK)-Aα protein amounts. In addition, islets of WD DJB animals showed reduction in islets and β-cell masses.

CONCLUSION

DJB surgery improves fasting glycemia and insulin action in skeletal muscle. Better endocrine pancreatic morphofunction was associated, at least in part, with the regulation of the cholinergic and cAMP pathways, and improvements in syntaxin-1 islet protein content induced by DJB.

Comparison of consumption behavior and appetite sensations among patients with type 2 diabetes mellitus after bariatric surgery

BACKGROUND

The promising postsurgical weight loss and remission of type 2 diabetes (T2D) from bariatric surgery can be attributed to modified eating physiology after surgical procedures. We sought to investigate the changes in the parameters of consumption behaviors and appetite sensations induced by a mixed meal tolerance test, and to correlate these alterations with age, body mass index, C-peptide levels, and duration of T2D 1 year after bariatric surgery.

METHODS

A total of 16 obese patients with T2D who underwent mini-gastric bypass (GB) and 16 patients who underwent sleeve gastrectomy (SG) were enrolled in this study and evaluated using a mixed meal tolerance test one year after surgery. A visual analogue scale was used for scoring appetite sensation at different time points. The area under the curve (AUC) and the incremental or decremental AUC (ΔAUC) were compared between the two groups.

RESULTS

One year after surgery, a decreasing trend in the consumption time was observed in the GB group compared to the SG group, while the duration of T2D before surgery was negatively correlated with the post-operative consumed time in those after GB. Patients who underwent GB had significantly higher fasting scores for fullness and desire to eat, higher AUC_0'-180' of scores for desire to eat, as well as more effective post-meal suppression of hunger and desire to eat compared with those undergoing SG one year after surgery. Post-operative C-peptide levels were negatively correlated with ΔAUC_0'-180' for hunger and ΔAUC_0'-180' for desire to eat in the GB group, while negatively correlated with ΔAUC_0'-180' for fullness in the SG group.

DISCUSSION

Patients with T2D after either GB or SG exhibit distinct nutrient-induced consumption behaviors and appetite sensations post-operatively, which may account for the differential effects on weight loss and glycemic control after different surgery.

Common Channel Length in Bypass Surgery Does Not Impact T2DM in Diabetic Zucker Rats

INTRODUCTION

Metabolic surgery is known to impact glucose tolerance but the exact mechanism is still unclear. Based on recently-published data, especially the role of the hindgut may require redefinition.

METHODS

Either a loop duodeno-jejunostomy (DJOS) with exclusion of one third of total intestinal length, a loop duodeno-ileostomy (DiOS, exclusion of two thirds), or SHAM operation was performed in 9-week-old Zucker diabetic fatty rats. One, 3, and 6 months after surgery, an oral glucose tolerance test (OGTT) and glucose-stimulated hormone analyses were conducted. Body weight was documented weekly.

RESULTS

DJOS and DiOS animals showed significantly better glucose control in all OGTTs than the SHAM group (two-way ANOVA p < 0.0001). Body weight developed largely parallel in both intervention groups; SHAM animals had gained significantly less weight after 6 months (Mann-Whitney DJOS/DiOS vs. SHAM p < 0.05, DJOS vs. DiOS p > 0.05). Operative interventions had no impact on GLP-1 and GIP levels at any time point (Mann-Whitney p > 0.05 for all). DJOS/DiOS operations could preserve insulin production up to 6 months, while there was already a sharp decline of insulin levels in the SHAM group (Mann-Whitney: DJOS/DiOS vs. SHAM p < 0.05 for all time points). Additionally, insulin sensitivity was improved significantly 1 month postoperative in both intervention groups compared to SHAM (Mann-Whitney DJOS/DiOS vs. SHAM p < 0.05).

CONCLUSION

The data of the current study demonstrate a sharp amelioration of glucose control after duodenal exclusion with unchanged levels of GLP-1 and GIP. Direct or delayed hindgut stimulation had no impact on glucose control in our model.

Schisandra polysaccharide increased glucose consumption by up-regulating the expression of GLUT-4

In our previous study, a polysaccharide was extracted from Schisandra Chinensis (Trucz.) Baill and found with anti-diabetic effects. The aim of this study was to investigate the anti-diabetic effects of the low weight molecular polysaccharide (SCPP11) purified from crude Schisandra polysaccharide and illustrate the underlying mechanism in buffalo rat liver cells. The insulin resistance model of BRL cells was established by incubating with insulin solution for 24h. The effects of SCPP11 on regulating related protein and mRNA expression in an insulin and AMPK signal pathway were investigated by western blot and RT-PCR analysis. SCPP11 showed no cytotoxicity to BRL cells and could improve the glucose consumption in BRL cells. SCPP11 increased the protein expression of Akt, p-AMPK and GLUT-4 in BRL cells. Moreover, SCPP11 could enhance the mRNA expression levels of IRS-1, PI3K, Akt, GLUT-4, AMPKα and PPAR-γ in BRL cells at the same time. In conclusion, SCPP11 possessed effects in improving glucose consumption by up-regulating the expression of GLUT-4 which might occur via insulin and AMPK signal pathway and could be a potential functional food to prevent and mitigate the insulin resistance condition.

Antioxidant Drug Tempol Promotes Functional Metabolic Changes in the Gut Microbiota

Recent studies have identified the important role of the gut microbiota in the pathogenesis and progression of obesity and related metabolic disorders. The antioxidant tempol was shown to prevent or reduce weight gain and modulate the gut microbiota community in mice; however, the mechanism by which tempol modulates weight gain/loss with respect to the host and gut microbiota has not been clearly established. Here we show that tempol (0, 1, 10, and 50 mg/kg p.o. for 5 days) decreased cecal bacterial fermentation and increased fecal energy excretion in a dose-dependent manner. Liver (1)H NMR-based metabolomics identified a dose-dependent decrease in glycogen and glucose, enhanced glucogenic and ketogenic activity (tyrosine and phenylalanine), and increased activation of the glycolysis pathway. Serum (1)H NMR-based metabolomics indicated that tempol promotes enhanced glucose catabolism. Hepatic gene expression was significantly altered as demonstrated by an increase in Pepck and G6pase and a decrease in Hnf4a, ChREBP, Fabp1, and Cd36 mRNAs. No significant change in the liver and serum metabolomic profiles was observed in germ-free mice, thus establishing a significant role for the gut microbiota in mediating the beneficial metabolic effects of tempol. These results demonstrate that tempol modulates the gut microbial community and its function, resulting in reduced host energy availability and a significant shift in liver metabolism toward a more catabolic state.