Antidiabetic effects of duodenojejunal bypass in an experimental model of diabetes induced by a high-fat diet

Intestinal gluconeogenesis shapes gut microbiota, fecal and urine metabolome in mice with gastric bypass surgery

Intestinal gluconeogenesis (IGN), gastric bypass (GBP) and gut microbiota positively regulate glucose homeostasis and diet-induced dysmetabolism. GBP modulates gut microbiota, whether IGN could shape it has not been investigated. We studied gut microbiota and microbiome in wild type and IGN-deficient mice, undergoing GBP or not, and fed on either a normal chow (NC) or a high-fat/high-sucrose (HFHS) diet. We also studied fecal and urine metabolome in NC-fed mice. IGN and GBP had a different effect on the gut microbiota of mice fed with NC and HFHS diet. IGN inactivation increased abundance of Deltaproteobacteria on NC and of Proteobacteria such as Helicobacter on HFHS diet. GBP increased abundance of Firmicutes and Proteobacteria on NC-fed WT mice and of Firmicutes, Bacteroidetes and Proteobacteria on HFHS-fed WT mice. The combined effect of IGN inactivation and GBP increased abundance of Actinobacteria on NC and the abundance of Enterococcaceae and Enterobacteriaceae on HFHS diet. A reduction was observed in the amounf of short-chain fatty acids in fecal (by GBP) and in both fecal and urine (by IGN inactivation) metabolome. IGN and GBP, separately or combined, shape gut microbiota and microbiome on NC- and HFHS-fed mice, and modify fecal and urine metabolome.

Ileal interposition improves metabolic syndrome parameters in a rat model of metabolic syndrome induced by monosodium glutamate

AIMS

Metabolic syndrome (MetS) is a cluster of metabolic abnormalities. Anatomically restructuring of the gastrointestinal system has recently been an important subject of research in the treatment of MetS and closely related diseases. The aim of this study is to ensure the remission of parameters that define MetS by ileal interposition (IT) and to examine the effect of IT on plasma total GLP-1 and pancreatic GLP-1R expression.

MAIN METHODS

To induce MetS, newborn male Wistar albino rats were given MSG (4 g/mg) on days 0, 2, 4, 6, 8, and 10. The control group was injected with saline. In the 5th month, IT or sham surgery was performed on the MetS rats. The lipid levels, abdominal obesity, insulin level, OGTT, Lee index, HOMA-IR, plasma GLP-1 and pancreas GLP-1R expression were evaluated 2 months after surgery.

KEY FINDINGS

The results showed that IT significantly improved hyperinsulinemia (p = 0.013) and lipid profile (TG p = 0.0001; TCHOL p = 0.018; HDL p = 0.001). Furthermore, it normalized the Lee index (p = 0.006) and insulin resistance. The IT did not affect the secretion of the GLP-1, but the expression levels of pancreas GLP-1R were increased (p = 0.006).

SIGNIFICANCE

IT surgery corrected the MetS parameters in this rat model. The healing effects of IT surgery could be caused by mechanisms in the target tissues of insulin. The decrease in pancreatic GLP-1R levels in the MetS groups might be a compensatory response to the harmful effects of hyperinsulinemia in these groups. These results show that IT can be useful in the treatment of MetS.

Metabolic benefits of gastric bypass surgery in the mouse: The role of fecal losses

Objective

Roux-en-Y gastric surgery (RYGB) promotes a rapid and sustained weight loss and amelioration of glucose control in obese patients. A high number of molecular hypotheses were previously tested using duodenal-jejunal bypass (DJB) performed in various genetic models of mice with knockouts for various hormones or receptors. The data were globally negative or inconsistent. Therefore, the mechanisms remained elusive. Intestinal gluconeogenesis is a gut function that has been suggested to contribute to the metabolic benefits of RYGB in obese patients.

Methods

We studied the effects of DJB on body weight and glucose control in obese mice fed a high fat-high sucrose diet. Wild type mice and mice with a genetic suppression of intestinal gluconeogenesis were studied in parallel using glucose- and insulin-tolerance tests. Fecal losses, including excretion of lipids, were studied from the feces recovered in metabolic cages.

Results

DJB induced a dramatic decrease in body weight and improvement in glucose control (glucose- and insulin-tolerance) in obese wild type mice fed a high calorie diet, for 25 days after the surgery. The DJB-induced decrease in food intake was transient and resumed to normal in 7–8 days, suggesting that decreased food intake could not account for the benefits. Total fecal losses were about 5 times and lipid losses 7 times higher in DJB-mice than in control (sham-operated and pair-fed) mice, and could account for the weight loss of mice. The results were comparable in mice with suppression of intestinal gluconeogenesis. There was no effect of DJB on food intake, body weight or fecal loss in lean mice fed a normal chow diet.

Conclusions

DJB in obese mice fed a high calorie diet promotes dramatic fecal loss, which could account for the dramatic weight loss and metabolic benefits observed. This could dominate the effects of the mouse genotype/phenotype. Thus, fecal energy loss should be considered as an essential process contributing to the metabolic benefits of DJB in obese mice.

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Duodenal-jejunal bypass (DJB) promotes weight loss in mice fed a high calorie diet.

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DJB induces dramatic fecal energy losses in mice fed a high calorie diet.

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DJB has no effect in mice fed a control (starch-based) diet.

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There is no fecal losses in DJB-mice fed a control diet.

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Fecal energy loss is a cause of body weight loss in DJB-mice fed high calorie diet.

Meal patterns after bariatric surgery in mice and rats

With behavioral and pharmacological interventions continuously failing to tackle the obesity epidemic, bariatric surgery has been hailed as the most effective treatment strategy. Current literature suggests that bariatric surgery successfully decreases body weight and excess fat mass through targeting both variables of the energy homeostasis - energy intake and energy expenditure. Here we review current knowledge on changes in caloric consumption, an important arm in the energy balance equation, in rodent models of bariatric surgery. In particular, circadian feeding dynamics, post-surgical caloric intake at both "rapid weight loss" phase and "weight maintenance" phase, as well as meal pattern analysis will be the subject of this review. Considering that different types of bariatric surgery may trigger differential energy intake dynamics resulting in variable weight loss outcomes, the effects of most popular surgeries - vertical sleeve gastrectomy (VSG), Roux-en-Y gastric bypass (RYGB), and gastric banding (GB) - are elaborated. Potential candidate mechanisms underlying alterations in food intake and meal patterns following different bariatric procedures are briefly discussed at the end.

Three-year result of efficacy for type 2 diabetes mellitus control between laparoscopic duodenojejunal bypass compared with laparoscopic Roux-en-Y gastric bypass

Purpose

The mechanism by which bariatric surgery facilitates diabetic control is still unknown. Duodenojejunal bypass supports the foregut theory; however, its efficacy when used alone is not yet established.

Methods

During the period from January 2008 to December 2009, patients who underwent laparoscopic duodenojejunal bypass (LDJB) or laparoscopic Roux-en-Y gastric bypass (LRYGB) for type 2 diabetes mellitus (T2DM) with or without morbid obesity were included. Patients who had a follow-up for less than 3 years were excluded. Patient baseline characteristics, change of body weight, body mass index (BMI), glycosylated hemoglobin (HbA_1c), and diabetic treatments were analyzed.

Results

In total, 8 LDJB and 20 LRYGB patients were analyzed. The LDJB group had more number of male patients than the LRYGB group (LDJB 75% vs. LRYGB 30%, P = 0.030). Baseline BMI in the LRYGB group was higher than in the LDJB group (LDJB 27.0 ± 2.5 vs. LRYGB 32.6 ± 3.4, P < 0.001). Age, DM duration, baseline HbA_1c, and C-peptide levels were similar. Longer operation time was needed to perform LDJB (LDJB 367.5 ± 120.2 vs. LRYGB 232.9 ± 41.1, P < 0.001), but no differences were observed in the hospital stay and complication rate between the 2 groups. At the third year of follow-up, the T2DM remission rate was observed in 40% of patients in the LRYGB group and 12.5% of patients in the LDJB group.

Conclusion

LDJB is not an effective method for controlling T2DM compared with LRYGB. Foregut theory may not be the main mechanism of diabetic control during bariatric surgery.

Duodenal-jejunal bypass normalizes pancreatic islet proliferation rate and function but not hepatic steatosis in hypothalamic obese rats

Modifications in life-style and/or pharmacotherapies contribute to weight loss and ameliorate the metabolic profile of diet-induced obese humans and rodents. Since these strategies fail to treat hypothalamic obesity, we have assessed the possible mechanisms by which duodenal-jejunal bypass (DJB) surgery regulates hepatic lipid metabolism and the morphophysiology of pancreatic islets, in hypothalamic obese (HyO) rats. During the first 5 days of life, male Wistar rats received subcutaneous injections of monosodium glutamate (4 g/kg body weight, HyO group), or saline (CTL). At 90 days of age, HyO rats were randomly subjected to DJB (HyO DJB group) or sham surgery (HyO Sham group). HyO Sham rats were morbidly obese, insulin resistant, hypertriglyceridemic and displayed higher serum concentrations of non-esterified fatty acids (NEFA) and hepatic triglyceride (TG). These effects were associated with higher expressions of the lipogenic genes and fatty acid synthase (FASN) protein content in the liver. Furthermore, hepatic genes involved in β-oxidation and TG export were down-regulated in HyO rats. In addition, these rats exhibited hyperinsulinemia, β-cell hypersecretion, a higher percentage of islets and β-cell area/pancreas section, and enhanced nuclear content of Ki67 protein in islet-cells. At 2 months after DJB surgery, serum concentrations of TG and NEFA, but not hepatic TG accumulation and gene and protein expressions, were normalized in HyO rats. Insulin release and Ki67 positive cells were also normalized in HyO DJB islets. In conclusion, DJB decreased islet-cell proliferation, normalized insulinemia, and ameliorated insulin sensitivity and plasma lipid profile, independently of changes in hepatic metabolism.

Absence of Role of Dietary Protein Sensing in the Metabolic Benefits of Duodenal-Jejunal Bypass in the Mouse

Roux-en-Y gastric bypass (RYGB) induces remission or substantial improvement of type 2 diabetes mellitus (T2D) but underlying mechanisms are still unclear. The beneficial effects of dietary proteins on energy and glucose homeostasis are mediated by the antagonist effects of peptides toward mu-opioid receptors (MORs), which are highly expressed in the distal gut. We hypothesized that the beneficial effects of RYGB could depend at least in part on the interaction of peptides from food with intestinal MORs. Duodenal-jejunal bypass (DJB) was performed in obese and lean wild-type (WT) or MOR deficient (MOR^−/−) mice. Food intake and body weight was monitored daily during 3 weeks. Glucose homeostasis was assessed from glucose and insulin tolerance tests. In obese WT and MOR^−/− mice, DJB induced a rapid and sustained weight loss partly independent of food intake, and a rapid improvement in glycaemic parameters. Weight loss was a major determinant of the improvements observed. In lean WT and MOR^−/− mice, DJB had no effect on weight loss but significantly enhanced glucose tolerance. We found that MORs are not essential in the metabolic beneficial effects of DJB, suggesting that protein sensing in the distal gut is not a link in the metabolic benefits of gastric surgery.

High-fat diet ingestion correlates with neuropathy in the duodenum myenteric plexus of obese mice with symptoms of type 2 diabetes

Obesity and type 2 diabetes are increasing in prevalence at an alarming rate in developed and developing nations and over 50% of patients with prolonged stages of disease experience forms of autonomic neuropathy. These patients have symptoms indicating disrupted enteric nervous system function including gastric discomfort, gastroparesis and intestinal dysmotility. Previous assessments have examined enteric neuronal injury within either type 1 diabetic or transgenic type 2 diabetic context. This study aims to assess damage to myenteric neurons within the duodenum of high-fat diet ingesting mice experiencing symptoms of type 2 diabetes, as this disease context is most parallel to the human condition and disrupted duodenal motility underlies negative gastrointestinal symptoms. Mice fed a high-fat diet developed symptoms of obesity and diabetes by 4 weeks. After 8 weeks, the total number of duodenal myenteric neurons and the synaptophysin density index were reduced and transmission electron microscopy showed axonal swelling and loss of neurofilaments and microtubules, suggesting compromised neuronal health. High-fat diet ingestion correlated with a loss of neurons expressing VIP and nNOS but did not affect the expression of ChAT, substance P, calbindin and CGRP. These results correlate high-fat diet ingestion, obesity and type 2 diabetes symptoms with a loss of duodenal neurons, biasing towards those with inhibitory nature. This pathology may underlie dysmotility and other negative GI symptoms experienced by human type 2 diabetic and obese patients.

Intestinal adaptation and Reg gene expression induced by antidiabetic duodenal-jejunal bypass surgery in Zucker fatty rats

The antidiabetic mechanism of bariatric surgery includes specific changes in the secretion of incretins. To identify additional players originating from the gut, we evaluated the effects of duodenal-jejunal bypass (DJB) in morbidly obese Zucker fatty rats. A fast relief of hyperglycemia and hyperinsulinemia was achieved even before a significant weight loss occurred. Fourteen days after DJB, we characterized the changes in intestinal histochemistry in the bypassed duodenum and shortcut jejunum that was reanastomosed directly to the starting point of the duodenum and compared with the corresponding regions of sham-operated rats. The bypassed duodenum exhibited mucosal atrophy and apoptosis and decreased proliferative renewal. In shortcut jejunum, DJB resulted in 40% significantly enlarged intestinal circumference and increased epithelial proliferation, especially in putative transit-amplifying (TA) cells and the crypt. Because Reg family proteins promote cell growth and survival, we explored their expression in the intestine. With the use of immunohistochemistry, Reg1, -3α, and -3β were normally expressed in intestinal mucosa. After DJB, the level of Reg1 protein was reduced, whereas Reg3α and -3β were not changed in bypassed duodenum. Downstream in shortcut jejunum, the levels of Reg1 and -3β were greatly induced and especially concentrated in the putative TA cells. Our results revealed significant changes in the integrity and proliferation of the intestinal mucosa as a consequence of DJB, and in cell- and isoform-specific expression of Reg proteins within the replicating mucosal epithelium, and provide evidence indicating that the activation of Reg proteins may contribute to intestinal compensation against increased load and/or to improving insulin sensitivity.

Phenotype of entero-endocrine L cells becomes restricted during development

BACKGROUND

Glucagon-like peptide (GLP)-1 and glucose-dependent insulinotropic polypeptide (GIP) are hormones secreted by L and K cells, respectively, and by LK cells. To characterize L and K cells during development, we examined ileum from embryonic (e)- 12 to e-17.

RESULTS

GLP-1 cells were first seen at e-15 and their number increased at e-17. At e-17, most GLP-1 cells co-expressed GIP. The transcription factors Pax6 and Pdx-1 are required for GIP expression, while Pax6 activates the expression of GLP-1. At e-17, the mucosa has GIP+ Pax6+, GIP+ Pdx-1+, GLP-1+ Pax6+, and GLP-1+ Pdx-1+ cells. Unlike ileal L cells of postnatal and adult mice, a subset of ileal L cells of e-17 embryos co-expressed GLP-1 and glucagon (Glu). Glu-positive cells contain proprotein-convertase 2 (PC2) and PC3/1, the enzymes responsible for Glu and GLP-1 synthesis, respectively.

CONCLUSIONS

Our findings indicate that most GLP-1+ cells of ileum of e-17 embryos co-express GIP and, therefore, are LK cells. In addition, a subset of GLP-1+ cells of embryos but not of neonates co-express glucagon, indicating that the expression of Glu in GLP-1+ cells disappears after birth.

Duodenal-jejunal bypass surgery enhances glucose tolerance and beta-cell function in Western diet obese rats

BACKGROUND

The aim of this study was to investigate the effect of the duodenal-jejunal bypass (DJB) on glucose homeostasis and islet insulin secretion in Western diet (WD) obese rats.

METHODS

Male Wistar rats received a standard rodent chow diet (CTL group) or WD ad libitum. After 32 weeks of diet, WD rats were submitted to duodenal-jejunal bypass (WD DJB) or sham (WD S-DJB) operation. Intraperitoneal (ip) glucose tolerance test was performed 1 week after surgery. Body weight, fat pad depots, glycemia, insulinemia, HOMA-IR, and glucose-induced insulin secretion were evaluated 1 month after surgery.

RESULTS

Body weight and fat pads of the WD group were higher than those of the CTL group. Sham and DJB surgeries did not alter these parameters. WD and WD S-DJB rats were glucose intolerant, insulin resistant, and hyperinsulinemic. WD DJB rats showed similar glucose tolerance, insulin sensitivity, and plasma insulin levels to those of CTL rats. WD rats presented higher fat and glycogen contents in the liver. DJB surgery normalized fat and glycogen stores in the liver of the WD DJB group. Insulin release at 11.1-mM glucose, in isolated islets from WD and WD S-DJB rats, was higher than from islets of CTL rats. In contrast, DJB surgery improves the beta-cell secretory capacity with increased glucose-induced secretion at 5.6-, 11.1-, and 22.2-mM glucose in WD DJB islets, compared with CTL islets.

CONCLUSIONS

DJB surgery improves glucose homeostasis and enhances beta-cell glucose responsiveness in rats submitted to the WD diet without any modification in adiposity.