Effects of duodenal-jejunal exclusion on beta cell function and hormonal regulation in Goto-Kakizaki rats

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.

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.

Improved glycemic control with proximal intestinal bypass and weight loss following gastrectomy in non-obese diabetic gastric cancer patients

PURPOSE

The aim of this study was to assess whether gastrectomy influences glycemic control in non-obese diabetic gastric cancer patients and to identify factors related to glucose metabolism after gastrectomy.

MATERIALS AND METHODS

We retrospectively analyzed changes in glucose metabolism in 238 non-obese (body mass index < 30 kg/m2) patients with type II diabetes who underwent distal gastrectomy with either gastroduodenostomy (n = 91) or gastrojejunostomy (n = 147) for stage I gastric cancer. We collected demographics, diabetes-related features, surgery-related features, and changes in glucose metabolism during follow-up. The effect of surgery on the course of diabetes was evaluated at different time points according to fasting blood glucose levels and use of diabetes-related medication.

RESULTS

Preoperatively, the mean body mass index was 24.3 ± 2.3. Weight, body mass index and fasting blood glucose of all patients were significantly lower compared to preoperative levels at all time points. Weight loss after 6 months and the percentage of patients whose weight loss ratio was higher than 10% after one year were greater in the gastrojejunostomy group than the gastroduodenostomy group. Overall, 88 (37%) patients showed improvement in their diabetes course at one month after surgery; 152 (64%) showed improvement after 2 years. Duration of diabetes, weight loss, and reconstruction type were associated with improvement in diabetes at different time points. At 6 months and thereafter, the percentage of patients with an improved diabetes course was highest in the gastrojejunostomy plus higher than 10% weight loss group.

CONCLUSIONS

Although weight loss may be associated with adverse effects of gastrectomy, postoperative weight loss in an acceptable range is a useful measure of the better glycemic control for the group of diabetic patients. Selecting gastrojejunostomy during gastrectomy and inducing acceptable weight loss after gastrectomy could be beneficial to the non-obese diabetic gastric cancer patients for improved glycemic control.

Gut: A key player in the pathogenesis of type 2 diabetes?

The gut regulates glucose and energy homeostasis; thus, the presence of ingested nutrients into the gut activates sensing mechanisms that affect both glucose homeostasis and regulate food intake. Increasing evidence suggest that gut may also play a key role in the pathogenesis of type 2 diabetes which may be related to both the intestinal microbiological profile and patterns of gut hormones secretion. Intestinal microbiota includes trillions of microorganisms but its composition and function may be adversely affected in type 2 diabetes. The intestinal microbiota may be responsible of the secretion of molecules that may impair insulin secretion/action. At the same time, intestinal milieu regulates the secretion of hormones such as GLP-1, GIP, ghrelin, gastrin, somatostatin, CCK, serotonin, peptide YY, GLP-2, all of which importantly influence metabolism in general and in particular glucose metabolism. Thus, the aim of this paper is to review the current evidence on the role of the gut in the pathogenesis of type 2 diabetes, taking into account both hormonal and microbiological aspects.

Bariatric surgery: beta cells in type 2 diabetes remission

Bariatric surgery is a new emerging treatment that demonstrates a favourable effect on type 2 diabetes, although its underlying mechanisms still remain unknown. After receiving bariatric surgery, beta cells undergo the process of rebirth, which involves apoptosis evasion, regeneration and improved beta-cell function. Therefore, further studies are necessary to elucidate how bariatric surgery can resolve type 2 diabetes. Here, our review focuses mainly on beta cells, the insulin-generating cells, whose biological features change dramatically after bariatric surgery. Copyright © 2015 John Wiley & Sons, Ltd.

Amelioration of glycemic control by sleeve gastrectomy and gastric bypass in a lean animal model of type 2 diabetes: restoration of gut hormone profile

BACKGROUND

In obese diabetic patients, bariatric surgery has been shown to induce remission of type 2 diabetes. Along with weight loss itself, changes in gut hormone profiles after surgery play an important role in the amelioration of glycemic control. However, the potential of gastrointestinal surgery regarding diabetes remission in non-severely obese diabetic patients has yet to be defined. In the present experimental study, we explored the effect of established bariatric procedures with and without duodenal exclusion on glycemic control and gut hormone profile in a lean animal model of type 2 diabetes.

METHODS

Forty 12- to 14-week-old non-obese diabetic Goto-Kakizaki (GK) rats were randomly assigned to four groups: control group (GKC), sham surgery (GKSS), sleeve gastrectomy (GKSG), and gastric bypass (GKGB). Age-matched Wistar rats served as a non-diabetic control group (WIC). Glycemic control and plasma lipids were assessed at the beginning of the observation period and 4 weeks after surgery. Fasting and mixed meal-induced plasma levels of ghrelin, glucagon-like peptide-17-36 (GLP-1), and peptide tyrosine-tyrosine (PYY) were measured.

RESULTS

In GK rats, glycemic control improved after sleeve gastrectomy (SG) and gastric bypass (GB). Mixed meal-induced gut hormone profiles in Wistar rats (WIC) were significantly different from those of sham-operated or control group GK rats. After SG and GB, GK rats showed a similar postprandial decrease in ghrelin as observed in non-diabetic WIC. Following both surgical procedures, a significant meal-induced increase in PYY and GLP-1 could be demonstrated.

CONCLUSIONS

SG and GB induce a similar improvement in overall glycemic control in lean diabetic rodents. Meal-induced profiles of ghrelin, GLP-1, and PYY in GK rats are significantly modified by SG and GB and become similar to those of non-diabetic Wistar rats. Our data do not support the hypothesis that duodenal exclusion and early contact of food with the ileal mucosa alone explain changes in gut hormone profile in GK rats after gastrointestinal surgery.

Preserve common limb in duodenal-jejunal bypass surgery benefits rats with type 2-like diabetes

BACKGROUND

In order to understand the underlying mechanisms by which weight loss surgeries improve metabolic profiles in type 2 diabetes mellitus (T2DM) patients and to evaluate the relevance of the length of the common limb in modulating various aspects of metabolism, we performed regular duodenal-jejunal bypass (DJB) and long-limb DJB (LL-DJB) surgeries in Goto-Kakizaki (GK) rats and compared their effects on glycemic control.

METHODS

Male GK rats at 12 weeks of age were used for this study. Body weight, food intake, fasting glucose, glucagon-like peptide-1 (GLP-1) level, glucose tolerance, insulin sensitivity, cholesterol and triglycerides levels, and fecal energy content were monitored for 26 weeks after the two types of surgeries.

RESULTS

We performed systematic analyses on GK rats after DJB or long-limb surgeries. Both procedures prevented body weight gain, reduced blood glucose and lipid levels, increased GLP-1 levels, and led to better insulin sensitivity. In general, LL-DJB displayed better effects than DJB, except that both surgeries caused similar increase in GLP-1 levels.

CONCLUSIONS

Both DJB and LL-DJB surgeries triggered beneficial effects in GK rats. LL-DJB showed better outcomes than DJB, which may be due to reduced food intake and higher fecal energy content. This indicates that the length of the common limb could influence metabolic profiles of surgery recipients.

Duodenal-jejunal bypass and jejunectomy improve insulin sensitivity in Goto-Kakizaki diabetic rats without changes in incretins or insulin secretion

Gastric bypass surgery can dramatically improve type 2 diabetes. It has been hypothesized that by excluding duodenum and jejunum from nutrient transit, this procedure may reduce putative signals from the proximal intestine that negatively influence insulin sensitivity (SI). To test this hypothesis, resection or bypass of different intestinal segments were performed in diabetic Goto-Kakizaki and Wistar rats. Rats were randomly assigned to five groups: duodenal-jejunal bypass (DJB), jejunal resection (jejunectomy), ileal resection (ileectomy), pair-fed sham-operated, and nonoperated controls. Oral glucose tolerance test was performed within 2 weeks after surgery. Baseline and poststimulation levels of glucose, insulin, glucagon-like peptide 1 (GLP-1), and glucose-dependent insulinotropic polypeptide (GIP) were measured. Minimal model analysis was used to assess SI. SI improved after DJB (SI = 1.14 ± 0.32 × 10(-4) min(-1) ⋅ pM(-1)) and jejunectomy (SI = 0.80 ± 0.14 × 10(-4) min(-1) ⋅ pM(-1)), but not after ileectomy or sham operation/pair feeding in diabetic rats. Both DJB and jejunal resection normalized SI in diabetic rats as shown by SI levels equivalent to those of Wistar rats (SI = 1.01 ± 0.06 × 10(-4) min(-1) ⋅ pM(-1); P = NS). Glucose effectiveness did not change after operations in any group. While ileectomy increased plasma GIP levels, no changes in GIP or GLP-1 were observed after DJB and jejunectomy. These findings support the hypothesis that anatomic alterations of the proximal small bowel may reduce factors associated with negative influence on SI, therefore contributing to the control of diabetes after gastric bypass surgery.

Effects of bariatric surgery on adipokine-induced inflammation and insulin resistance

Over a third of the US population is obese and at high risk for developing type 2 diabetes, insulin resistance, and other metabolic disorders. Obesity is considered a chronic low-grade inflammatory condition that is primarily attributed to expansion and inflammation of adipose tissues. Indeed, adipocytes produce and secrete numerous proinflammatory and anti-inflammatory cytokines known as adipokines. When the balance of these adipokines is shifted toward higher production of proinflammatory factors, local inflammation within adipose tissues and subsequently systemic inflammation occur. These adipokines including leptin, visfatin, resistin, apelin, vaspin, and retinol binding protein-4 can regulate inflammatory responses and contribute to the pathogenesis of diabetes. These effects are mediated by key inflammatory signaling molecules including activated serine kinases such as c-Jun N-terminal kinase and serine kinases inhibitor κB kinase and insulin signaling molecules including insulin receptor substrates, protein kinase B (PKB, also known as Akt), and nuclear factor kappa B. Bariatric surgery can decrease body weight and improve insulin resistance in morbidly obese subjects. However, despite reports suggesting reduced inflammation and weight-independent effects of bariatric surgery on glucose metabolism, mechanisms behind such improvements are not yet well understood. This review article focuses on some of these novel adipokines and discusses their changes after bariatric surgery and their relationship to insulin resistance, fat mass, inflammation, and glucose homeostasis.

Effects of bariatric surgery on glucose homeostasis and type 2 diabetes

Obesity is an important risk factor for type 2 diabetes mellitus (T2DM). Weight loss improves the major factors involved in the pathogenesis of T2DM, namely insulin action and beta cell function, and is considered a primary therapy for obese patients who have T2DM. Unfortunately, most patients with T2DM fail to achieve successful weight loss and adequate glycemic control from medical therapy. In contrast, bariatric surgery causes marked weight loss and complete remission of T2DM in most patients. Moreover, bariatric surgical procedures that divert nutrients away from the upper gastrointestinal tract are more successful in producing weight loss and remission of T2DM than those that simply restrict stomach capacity. Although upper gastrointestinal tract bypass procedures alter the metabolic response to meal ingestion, by increasing early postprandial plasma concentrations of glucagon-like peptide 1 and insulin, it is not clear whether these effects make an important contribution to long-term control of glycemia and T2DM once substantial surgery-induced weight loss has occurred. Nonetheless, the effects of surgery on body weight and metabolic function indicate that bariatric surgery should be part of the standard therapy for T2DM. More research is needed to advance our understanding of the physiological effects of different bariatric surgical procedures and possible weight loss-independent factors that improve metabolic function and contribute to the resolution of T2DM.

New clues to bariatric surgery's benefits

Bariatric surgery to treat obesity can also be effective against type 2 diabetes, but it is unclear how such surgical procedures improve glucose metabolism. A new study in rats suggests that nutrient sensing in the jejunum contributes to the antidiabetic effects of duodenal-jejeunal bypass (pages 950–955).