Gut and adipocyte peptides

Gut motility and hormone changes after bariatric procedures

PURPOSE OF REVIEW

Metabolic and bariatric surgery (MBS) and endoscopic bariatric therapies (EBT) are being increasingly utilized for the management of obesity. They work through multiple mechanisms, including restriction, malabsorption, and changes in the gastrointestinal hormonal and motility.

RECENT FINDINGS

Roux-en-Y gastric bypass (RYGB) and laparoscopic sleeve gastrectomy (LSG) cause decrease in leptin, increase in GLP-1 and PYY, and variable changes in ghrelin (generally thought to decrease). RYGB and LSG lead to rapid gastric emptying, increase in small bowel motility, and possible decrease in colonic motility. Endoscopic sleeve gastroplasty (ESG) causes decrease in leptin and increase in GLP-1, ghrelin, and PYY; and delayed gastric motility.

SUMMARY

Understanding mechanisms of action for MBS and EBT is critical for optimal care of patients and will help in further refinement of these interventions.

Impact of biliopancreatic diversion with duodenal switch on glucose homeostasis and gut hormones and their correlations with appetite

BACKGROUND

Biliopancreatic diversion with duodenal switch (BPD/DS) results in lifelong changes in gastrointestinal physiology with unclear associations with appetite perception.

OBJECTIVE

To explore mixed meal-induced changes in glucose homeostasis and gut hormones and their correlations with appetite perception.

SETTING

University hospital.

METHODS

Of 28 patients studied preoperatively (age: 38.4 ± 11.3 years; body mass index [BMI]: 56.5 ± 5.1 kg/m²; 14 women), 19 (68%) returned for postoperative follow-up. Plasma was sampled for 180 minutes during a 260-kcal standardized mixed meal. Concentrations of leptin, glucose, insulin, triglycerides, active acyl-ghrelin, motilin, total glucose-dependent insulinotropic polypeptide (GIP), active glucagon-like peptide 1 (GLP-1), and total peptide YY (PYY) were measured. Subjective appetite sensations were scored.

RESULTS

BPD/DS resulted in 66.1% ± 23.3% excess BMI loss. Leptin was halved. Glucose and insulin levels were reduced, blunting a preoperative peak at 30 minutes, giving a lower homeostasis model assessment for insulin resistance (HOMA-IR; 13.9 versus 4.8). In contrast, reduced ghrelin and motilin concentrations were accompanied by pronounced peaks 20-30 minutes prior to meal responses. GIP was reduced, whereas GLP-1 and PYY responses were markedly increased, with an early postprandial peak (P < .05, for all). HOMA-IR correlated with insulin (r = .72) and GIP (r = .57). Postoperatively, satiety correlated with GLP-1 (r = .56), whereas the gastric motility index correlated with the desire to eat (r = .60), percentage excess BMI loss (r = -.55), and percentage total weight loss (r = -.49). Delta insulin, GLP-1, and leptin correlated positively with percentage total weight loss (r = .51, r = .48, and r = .58, respectively).

CONCLUSIONS

BPD/DS reduces leptin, HOMA-IR, and GIP while markedly increasing GLP-1 and PYY. This study marks the magnitude change in GLP-1 with additional effects of PYY as important factors for weight loss.

Time course metabolome of Roux-en-Y gastric bypass confirms correlation between leptin, body weight and the microbiome

Roux-en-Y gastric bypass (RYGB) is an effective way to lose weight and reverse type 2 diabetes. We profiled the metabolome of 18 obese patients (nine euglycemic and nine diabetics) that underwent RYGB surgery and seven lean subjects. Plasma samples from the obese patients were collected before the surgery and one week and three months after the surgery. We analyzed the metabolome in association to five hormones (Adiponectin, Insulin, Ghrelin, Leptin, and Resistin), four peptide hormones (GIP, Glucagon, GLP1, and PYY), and two cytokines (IL-6 and TNF). PCA showed samples cluster by surgery time and many microbially driven metabolites (indoles in particular) correlated with the three months after the surgery. Network analysis of metabolites revealed a connection between carbohydrate (mannosamine and glucosamine) and glyoxylate and confirms glyoxylate association to diabetes. Only leptin and IL-6 had a significant association with the measured metabolites. Leptin decreased immediately after RYGB (before significant weight loss), whereas IL-6 showed no consistent response to RYGB. Moreover, leptin associated with tryptophan in support of the possible role of leptin in the regulation of serotonin synthesis pathways in the gut. These results suggest a potential link between gastric leptin and microbial-derived metabolites in the context of obesity and diabetes.

Changes in gastrointestinal hormones and leptin after Roux-en-Y gastric bypass surgery

BACKGROUND

Roux-en-Y gastric bypass (RYGB) imparts long-term weight loss, the mechanisms for which are not well understood. Changes in leptin and gastrointestinal (GI) hormones, including glucagon-like peptide 1 (GLP-1), peptide YY (PYY), and ghrelin, may contribute to the relative success of RYGB compared with conventional weight loss methods. This study evaluated changes in GI hormones and leptin post-RYGB. The study also evaluated whether GI hormones differed after a short-term dose of protein or fat.

METHODS

GLP-1, PYY, ghrelin, and leptin were assessed in 16 women before RYGB and up to 1 year after RYGB. Plasma was collected before and at several times after a short-term equicaloric dose of protein or fat.

RESULTS

GLP-1 area under the curve (AUC) increased at week 6 and 1 year in the fat beverage (FAT-BEV) group compared with baseline. PYY AUC remained elevated at 1 year in the FAT-BEV group. Ghrelin AUC decreased at week 2, week 6, and 1 year in the protein beverage (PRO-BEV) group compared with baseline. Ghrelin AUC was lower in the PRO-BEV group compared with the FAT-BEV group at week 6. Fasted leptin decreased at all visits in both groups and was lower in the FAT-BEV group compared with the PRO-BEV group at 1 year.

CONCLUSIONS

Changes from baseline were evident for all GI hormones and leptin; some differences were evident soon after surgery (ghrelin, leptin), whereas others were maintained long term (GLP-1, PYY, ghrelin, leptin). In response to a short-term stimulus, protein suppressed ghrelin and fat potently stimulated GLP-1 and PYY. Future work in this area is warranted.

Metabolic surgery-principles and current concepts

INTRODUCTION

In the almost six decades of bariatric surgery, a variety of surgical approaches to treating morbid obesity have been developed.

HISTORY AND EVOLUTION

Rather than prior techniques being continually superseded by new ones, a broad choice of surgical solutions based on restrictive, malabsorptive, humoral effects, or combinations thereof, is now available. In fact, in recent years, the advent of surgically modifying human metabolism promises new approaches to ameliorate traditionally medically treated metabolic entities, i.e., diabetes, even in the non-obese. The understanding of the various metabolic effects have led to a paradigm shift from bariatric surgery as a solely weight-reducing procedure to metabolic surgery affecting whole body metabolism.

CONCLUSION

The bariatric surgeon now faces the challenge and opportunity of selecting the most suitable technique for each individual case. To assist in such decision-making, this review, Metabolic surgery-principles and current concepts, is presented, tracing the historical development; describing the various surgical techniques; elucidating the mechanisms by which glycemic control can be achieved that involve favorable changes in insulin secretion and insulin sensitivity, gut hormones, adipokines, energy expenditure, appetite, and preference for low glycemic index foods; as well as exploring the fascinating future potential of this new interdisciplinary field.

Changes in gastrointestinal hormones and leptin after Roux-en-Y gastric bypass procedure: a review

Roux-en-Y gastric bypass is a well-accepted tool for the treatment of obesity and, compared to conventional weight loss methods (eg, diet and exercise) and other weight loss surgeries (eg, gastric banding), it results in considerable weight loss that is maintained long term. Although successful, the mechanisms for weight loss are not completely understood and it is thought that gastrointestinal hormones play a role. Several gastrointestinal hormones have been identified for their effects on appetite, including glucagon-like peptide-1 (GLP-1), peptide tyrosine-tyrosine (PYY), leptin, and ghrelin. This review encompasses a literature search that included 45 primary articles and shows that there are alterations in GLP-1, PYY, leptin, and ghrelin postoperatively. GLP-1 and PYY concentrations were usually found to be higher, whereas ghrelin levels were typically lower post- Roux-en-Y gastric bypass than in individuals with obesity, those who were overweight or of normal weight, and in those who underwent procedures other than Roux-en-Y gastric bypass or who achieved weight loss by lifestyle modification. An understanding of how gastrointestinal hormones change after Roux-en-Y gastric bypass may help dietetics practitioners optimize nutrition care for this patient population. A review of the literature also highlighted some research gaps that should be taken into consideration when designing future studies.