Meal suppression of circulating ghrelin is normalized in obese individuals following gastric bypass surgery

Distinct adaptations of endocrine and cognitive functions may contribute to high variability in long-term weight loss outcome after bariatric surgery

BACKGROUND

Bariatric surgery has been widely recognized as the most efficient long-term treatment method in severe obesity, yet therapy success shows considerable interindividual variability. Postoperative metabolic adaptations, including improved gut hormone secretion (GLP-1, PYY and ghrelin), and restored executive function may play an explanatory role in weight loss, yet causes for poor success in individual patients remain unknown. This study investigates gut-hormonal and cognitive characteristics in extreme weight loss responders to bariatric surgery.

METHODS

Patients (n=47) with high or low excessive weight loss (EWL) at least 2 years after Roux-en-Y-gastric bypass or sleeve gastrectomy were allocated into good responders (GR, EWL 82.4 ± 11.6%) and poor responders (PR, EWL 24.0 ± SD 12.8%) to study differences in postprandial secretion of GLP-1, PYY, ghrelin and in working memory (WM).

RESULTS

Mean BMI was 47.1 ± 6.2 kg/m² in PR (n=21) and 28.9 ± 3.1 kg/m² in GR (n=26, p < 0.001). Fasted GLP-1 and PYY were comparable for GR and PR (p > 0.2) and increased strongly after a standardized test meal (300 kcal liquid meal) with a peak at 15 to 30 minutes. The increase was stronger in GR compared to PR (GLP-1, PYY: Time x Group p < 0.05). Plasma ghrelin levels already differed between groups at fasted state, showing significantly higher levels for GR (p < 0.05). Postprandially, ghrelin secretion was suppressed in both groups, but suppression was higher in GR (Time x Group p < 0.05). GR showed significantly higher WM scores than PR (p < 0.05). Postprandial ghrelin (iAUC), but not GLP-1 or PYY plasma levels, significantly mediated the relationship between EWL and a WM subscore (IS score, CI = 0.07 - 1.68), but not WM main score (MIS score, CI = -0.07 - 1.54), in mediation analyses.

CONCLUSION

Excess weight loss success after bariatric surgical procedures is associated with distinct profiles of gut-hormones at fasted and postprandial state, and differences in working memory. Better working memory performance in GR might be mediated by higher postprandial reduction in ghrelin plasma levels. Future studies need to integrate longitudinal data, larger samples and more sensitive cognitive tests.

Efficacy of liraglutide 3.0 mg treatment on weight loss in patients with weight regain after bariatric surgery

PURPOSE

Bariatric surgery, as Roux-en-Y gastric bypass (RYGB), laparoscopic gastric banding (LGB), and laparoscopic sleeve gastrectomy (LSG), is considered the gold standard treatment to achieve long-term weight loss in severe obesity. In patients who fail to maintain the achieved weight, pharmacological treatment may be required. Here, we reported our real-life experience on the efficacy of liraglutide therapy in 62 patients who regained weight after bariatric surgery.

METHODS

We retrospectively evaluated 62 (60 F-2 M; mean age: 43.6 ± 9.9 years) patients received liraglutide for weight loss after bariatric surgery (17 RYGB, 22 LGB, and 23 LSG). Body mass index (BMI) before and after surgery was, respectively, of 45.4 ± 5.5 kg/m² and 29.5 ± 4.9 kg/m². Patients were followed up from 2016 until 2021. Liraglutide was administered after weight regain once-daily subcutaneously at starting dose of 0.6 mg and with weekly increases up to 3.0 mg. Treatments were administered when a weight regain of 10-15% occurred after reaching a minimum weight loss from bariatric surgery or if weight loss after bariatric surgery was unsatisfactory.

RESULTS

After a mean of 70.7 ± 43.7 months from any bariatric surgery, all patients started liraglutide therapy. At this time, mean BMI was 34.2 ± 4.8 kg/m² (mean increased BMI: 4.7 ± 2.8 kg/m²). After a mean of 10.5 ± 4.4 months from the beginning of liraglutide, 9 patients achieved normal weight (BMI 24.1 ± 0.9 kg/m²), and 28 were overweight (BMI 26.9 ± 1.6 kg/m²). Twenty patients achieved grade I (BMI 32.1 ± 1.5 kg/m²), 5 grade II (BMI 37.3 ± 2.0 kg/m²) obesity, and none had grade III obesity (mean BMI change: - 5.1 ± 2.5 kg/m²). The treatment was well tolerated, and no serious adverse events were recorded.

CONCLUSION

These data confirm the efficacy and safety of liraglutide in patients who experienced weight regain after bariatric surgery. Considering the long-term follow-up, patients should be followed up regularly and the pharmacological treatment should be adapted to the weight fluctuations observed during the clinical history.

LEVEL OF EVIDENCE

V. Opinions of authorities, based on descriptive studies, narrative reviews, clinical experience, or reports of expert committees.

Appetite Changes in Weight Regain and Weight Maintenance After Roux-en-Y Gastric Bypass

PURPOSE

Roux-en-Y gastric bypass (RYGB) surgery produces significant weight loss. However, a number of patients experience weight regain years after surgery. Factors driving weight regain after surgical interventions are currently being explored. Our objective was to investigate appetite-related measures associated with weight regain after RYGB surgery.

MATERIALS AND METHODS

Using a cross-sectional design, 29 participants (49.6 ± 9.1 years of age; current BMI 32.4 ± 4.7 kg/m², 43.6 ± 8.9 months post-RYGB) were stratified into tertiles according to weight regain per month after nadir (weight maintenance (WM), n = 9; low weight regain (LWR), n = 10; and high weight regain (HWR), n = 10). The average weight regain was, by design, significantly different between the groups (WM = 2.2 ± 2.5 kg; LWR = 10.0 ± 3.4 kg; HWR = 14.9 ± 6.3 kg regained, p < 0.05). Appetite (visual analog scales), olfactory performance ("sniffin sticks"), eating behaviors (Three Factor Eating Questionnaire), food reward (Leeds Food Preference Questionnaire), and appetite-related hormones (ghrelin, PYY, GLP-1 and leptin) were measured fasting and in response to a standardized test meal.

RESULTS

Dietary restraint was significantly higher than clinical cutoffs in WM and LWR (p < 0.05). As expected, significant time effects were noted for ghrelin, PYY, and GLP-1, but there were no group differences.

CONCLUSION

The results suggest that appetite-related outcomes are similar across individuals who have maintained weight loss and experienced regain following RYGB.

Jejunal administration of glucose enhances acyl ghrelin suppression in obese humans

Ghrelin is a gastric hormone that stimulates hunger and worsens glucose metabolism. Circulating ghrelin is decreased after Roux-en-Y gastric bypass (RYGB) surgery; however, the mechanism(s) underlying this change is unknown. We tested the hypothesis that jejunal nutrient exposure plays a significant role in ghrelin suppression after RYGB. Feeding tubes were placed in the stomach or jejunum in 13 obese subjects to simulate pre-RYGB or post-RYGB glucose exposure to the gastrointestinal (GI) tract, respectively, without the confounding effects of caloric restriction, weight loss, and surgical stress. On separate study days, the plasma glucose curves obtained with either gastric or jejunal administration of glucose were replicated with intravenous (iv) infusions of glucose. These "isoglycemic clamps" enabled us to determine the contribution of the GI tract and postabsorptive plasma glucose to acyl ghrelin suppression. Plasma acyl ghrelin levels were suppressed to a greater degree with jejunal glucose administration compared with gastric glucose administration (P < 0.05). Jejunal administration of glucose also resulted in a greater suppression of acyl ghrelin than the corresponding isoglycemic glucose infusion (P ≤ 0.01). However, gastric and isoglycemic iv glucose infusions resulted in similar degrees of acyl ghrelin suppression (P > 0.05). Direct exposure of the proximal jejunum to glucose increases acyl ghrelin suppression independent of circulating glucose levels. The enhanced suppression of acyl ghrelin after RYGB may be due to a nutrient-initiated signal in the jejunum that regulates ghrelin secretion.

Perceptual and Brain Response to Odors Is Associated with Body Mass Index and Postprandial Total Ghrelin Reactivity to a Meal

Animal studies have shown that olfactory sensitivity is greater when fasted than when fed. However, human research has generated inconsistent results. One possible explanation for these conflicting findings is metabolic health. Many metabolic peptides, including ghrelin, are moderated by adiposity and influence olfaction and olfactory-guided behaviors. We tested whether the effect of a meal on the perceived intensity of suprathreshold chemosensory stimuli is influenced by body mass index and/or metabolic response to a meal. We found that overweight or obese (n = 13), but not healthy weight (n = 20) subjects perceived odors, but not flavored solutions, as more intense when hungry than when sated. This effect was correlated with reduced postprandial total ghrelin suppression (n = 23) and differential brain response to odors in the cerebellum, as measured with functional magnetic resonance imaging. In contrast, it was unrelated to circulating leptin, glucose, insulin, triglycerides, or free fatty acids; or to odor pleasantness or sniffing (n = 24). These findings demonstrate that the effect of a meal on suprathreshold odor intensity perception is associated with metabolic measures such as body weight and total ghrelin reactivity, supporting endocrine influences on olfactory perception.

Gastrointestinal Hormones and Weight Loss Maintenance Following Roux-en-Y Gastric Bypass

CONTEXT

Factors underlying variable weight loss (WL) after Roux-en-Y gastric bypass (RYGB) are poorly understood.

OBJECTIVE

Our objective was to gain insight on the role of gastrointestinal hormones on poor WL maintenance (P-WLM) following RYGB.

DESIGN AND PATIENTS

First, glucagon-like peptide-1 (GLP-1), peptide YY (PYY), and ghrelin responses to a standardized mixed liquid meal (SMLM) were compared between subjects with good WL (G-WL, n = 32) or P-WLM (n = 22). Second, we evaluated food intake (FI) following blockade of gut hormonal secretion in G-WL (n = 23) or P-WLM (n = 19) subjects. Finally, the impact of dietary-induced WL on the hormonal response in subjects with P-WLM (n = 14) was assessed.

SETTING

This study was undertaken in a tertiary hospital.

MAIN OUTCOME MEASURES

In studies 1 and 3, the outcomes measures were the areas under the curve of gut hormones following a SMLM; in study 2, FI following subcutaneous injection of saline or octreotide were evaluated.

RESULTS

P-WLM associated a blunted GLP-1 (P = .044) and PYY (P = .001) responses and lesser suppression of ghrelin (P = .032) following the SMLM challenge. On saline day, FI in the G-WL (393 ± 143 kcal) group was less than in the P-WLM (519 ± 143 Kcal; P = .014) group. Octreotide injection resulted in enlarged FI in both groups (G-WL: 579 ± 248 kcal, P = .014; P-WLM: 798 ± 284 Kcal, P = .036), but the difference in FI between groups remained (P < .001). In subjects with P-WLM, dietary-induced WL resulted in larger ghrelin suppression (P = .046), but no change in the GLP-1 or PYY responses.

CONCLUSION

Our data show gastrointestinal hormones play a role in the control of FI following RYGB, but do not support that changes in GLP-1, PYY, or ghrelin play a major role as determinants of P-WLM after this type of surgery.

Weight recidivism post-bariatric surgery: a systematic review

Obesity is considered a worldwide health problem of epidemic proportions. Bariatric surgery remains the most effective treatment for patients with severe obesity, resulting in improved obesity-related co-morbidities and increased overall life expectancy. However, weight recidivism has been observed in a subset of patients post-bariatric surgery. Weight recidivism has significant medical, societal and economic ramifications. Unfortunately, there is a very limited understanding of how to predict which bariatric surgical patients are more likely to regain weight following surgery and how to appropriately treat patients who have regained weight. The objective of this paper is to systematically review the existing literature to assess the incidence and causative factors associated with weight regain following bariatric surgery. An electronic literature search was performed of the Medline, Embase and Cochrane library databases along with the PubMed US national library from January 1950 to December 2012 to identify relevant articles. Following an initial screen of 2,204 titles, 1,437 abstracts were reviewed and 1,421 met exclusion criteria. Sixteen studies were included in this analysis: seven case series, five surveys and four non-randomized controlled trials, with a total of 4,864 patients for analysis. Weight regain in these patients appeared to be multi-factorial and overlapping. Aetiologies were categorized as patient specific (psychiatric, physical inactivity, endocrinopathies/metabolic and dietary non-compliance) and operation specific. Weight regain following bariatric surgery varies according to duration of follow-up and the bariatric surgical procedure performed. The underlying causes leading to weight regain are multi-factorial and related to patient- and procedure-specific factors. Addressing post-surgical weight regain requires a systematic approach to patient assessment focusing on contributory dietary, psychologic, medical and surgical factors.

Gastrointestinal hormones and weight loss response after Roux-en-Y gastric bypass

BACKGROUND

Mechanisms underlying variable weight loss (WL) response after Roux-en-Y gastric bypass (RYGB) are poorly understood. The objective of this study was to compare gastrointestinal hormonal responses to meal intake, and fasting plasma concentrations of surrogate markers of enterocyte mass and bile acid effect between patients with failed (F-WL) or successful WL (S-WL) after RYGB.

METHODS

Cross-sectional study including 30 nondiabetic patients, evaluated at≥24 months after RYGB. Cases (F-WL; n = 10) and controls (S-WL; n = 20) were selected based on percent of excess WL (%EWL)<50% or≥50% from 12 months onwards after surgery. Groups were matched for gender, age, presurgical BMI, and length of follow up. Glucagon-like peptide 1 (GLP-1), peptide YY (PYY), GLP-2, and ghrelin responses to a meal challenge, and fasting plasma concentrations of citrulline and serum fibroblast growth factor 19 (FGF-19) were compared.

RESULTS

F-WL patients presented lesser suppression of ghrelin (incremental area under the curve [iAUC]: F-WL -12490±6530 versus S-WL -31196±4536 pg×mL(-1)×min; P<.01), and lesser increase in the GLP-1 (iAUC: F-WL 3354±737 versus S-WL 5629±542 pmol×L(-1)×min; P = .02) but not in the PYY and GLP-2, response to meal intake. Citrulline concentrations were significantly correlated with time after surgery (rho = .537; P<.01). However, citrulline was higher in S-WL compared to F-WL patients (P<.05). Serum FGF-19 concentration was similar between groups.

CONCLUSION

Although limited by the cross-sectional design, our data suggest a role of some gastrointestinal hormones as mediators of successful weight loss but argues against larger enterocyte mass after BS as determinant of failed weight loss after RYGB.

Improved acylated ghrelin suppression at 2 years in obese patients with type 2 diabetes: effects of bariatric surgery vs standard medical therapy

OBJECTIVE

Roux-en-Y gastric bypass (RYGB) produces more durable glycemic control than sleeve gastrectomy (SG) or intensive medical therapy (IMT). However, the contribution of acylated ghrelin (AG), a gluco-regulatory/appetite hormone, to improve glucose metabolism and body composition in patients with type 2 diabetes (T2D) following RYGB is unknown.

DESIGN

STAMPEDE (Surgical Treatment and Medication Potentially Eradicate Diabetes Efficiently) was a prospective, randomized controlled trial.

SUBJECTS

Fifty-three (body mass index: 36±3 kg m(-2), age: 49±9 years) poorly controlled patients with T2D (HbA1c (glycated hemoglobin): 9.7±2%) were randomized to IMT, IMT+RYGB or IMT+SG and underwent a mixed-meal tolerance test at baseline, 12, and 24 months for evaluation of AG suppression (postprandial minus fasting) and beta-cell function (oral disposition index; glucose-stimulated insulin secretion × Matsuda index). Total/android body fat (dual-energy X-ray absorptiometry) was also assessed.

RESULTS

RYGB and SG reduced body fat comparably (15-23 kg) at 12 and 24 months, whereas IMT had no effect. Beta-cell function increased 5.8-fold in RYGB and was greater than IMT at 24 months (P<0.001). However, there was no difference in insulin secretion between SG vs IMT at 24 months (P=0.32). Fasting AG was reduced fourfold following SG (P<0.01) and did not change with RYGB or IMT at 24 months. AG suppression improved more following RYGB than SG or IMT at 24 months (P=0.01 vs SG, P=0.07 vs IMT). At 24 months, AG suppression was associated with increased postprandial glucagon-like peptide-1 (r=-0.32, P<0.02) and decreased android fat (r=0.38; P<0.006).

CONCLUSIONS

Enhanced AG suppression persists for up to 2 years after RYGB, and this effect is associated with decreased android obesity and improved insulin secretion. Together, these findings suggest that AG suppression is partly responsible for the improved glucose control after RYGB surgery.

Effects of laparoscopic gastric band applications on plasma and fundic acylated ghrelin levels in morbidly obese patients

BACKGROUND

It has been proposed that laparoscopic adjustable gastric banding (LAGB) procedure might play a role in modulation of fundic ghrelin production. To test this hypothesis, we examined plasma and tissue concentrations of acylated ghrelin in morbidly obese patients before and 6 months after LAGB. Baseline levels of acylated ghrelin in morbidly obese patients were also compared with those in age-matched, healthy, non-obese controls.

METHODS

We studied 21 patients who had been operated on for morbid obesity (M/F = 9/12, BMI = 49.3 ± 5.3 kg/m(2)) and 16 healthy, non-obese persons (M/F = 7/9, BMI = 23.0 ± 1.7 kg/m(2)). Fasting blood samples were collected once from the non-obese controls as well as the morbidly obese patients before and 6 months after the LAGB. The morbidly obese patients and their respective controls underwent gastroscopy for fundic biopsy. The plasma and fundic acylated ghrelin levels were evaluated in these groups by enzyme-linked immunosorbent assay.

RESULTS

The plasma and fundic acylated ghrelin concentrations were significantly lower in obese patients than in non-obese controls (2.8 ± 1.0 ng/ml, 727 ± 171.7 ng/g tissue, respectively; p = 0.000). These parameters were significantly increased in morbidly obese patients 6 months after LAGB (4.1 ± 1.2 ng/ml and p = 0.001; 999 ± 292.1 ng/g tissue and p = 0.003, respectively).

CONCLUSIONS

We showed that fundic production of acylated ghrelin was significantly increased in morbidly obese patients 6 months after LAGB. Moreover, the weight loss after LAGB occurred in spite of the significant increase in the plasma and fundic acylated ghrelin levels. The potential role of ghrelin as being responsible for the weight loss after bariatric surgery needs to be elucidated in further studies.

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.

Meta-analysis of the relationship between obestatin and ghrelin levels and the ghrelin/obestatin ratio with respect to obesity

INTRODUCTION

The association between gastrointestinal hormones, obestatin and ghrelin, and obesity are controversial. Here, the authors summarize results of published works in this field by using meta-analysis.

METHODS

Studies that evaluated these hormones and were published before December 2009 were collected from PubMed, HighWire Press and ProQuest Health and Medical Complete. Software Review Manager 4.2 was used (Cochrane Collaboration, Oxford, England). Differences between obese and normal weight (NW) groups were compared using fixed or random effects models based on heterogeneity.

RESULTS

In obestatin group, 9 studies with 566 participants were included and had significant heterogeneity (I² = 98.6%, P < 0.01). Obestatin of NW groups was 64.19 pg/mL [95% confidence interval (CI) = 36.11-92.26, P < 0.01] higher than those of obese groups. In total ghrelin group, 21 studies with 1187 participants were included and had significant heterogeneity (I² = 97.9%, P < 0.01). Total ghrelin of NW groups was 145.53 pg/mL (95%CI = 109.59-181.47, P < 0.01) higher than those of obese groups. In active ghrelin group, 6 studies with 265 participants were included and had significant heterogeneity (I² = 98.10%, P < 0.01). Active ghrelin in NW groups was 53.22 pg/mL (95%CI = 25.92-80.53, P < 0.01) higher than those of obese groups. In ghrelin/obestatin group, 5 studies with 259 participants were included and had significant heterogeneity (I² = 94.2, P < 0.01). The ratios in NW groups were 2.49 pg/mL (95%CI = 0.03-4.9, P = 0.05) higher than those of obese groups but without significance.

CONCLUSIONS

Obestatin, total and active ghrelin in NW groups were significantly higher than those of obese groups. Ghrelin/obestatin ratios in NW groups were also higher but without significance.

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.

Ghrelin gene products and the regulation of food intake and gut motility

A breakthrough using "reverse pharmacology" identified and characterized acyl ghrelin from the stomach as the endogenous cognate ligand for the growth hormone (GH) secretagogue receptor (GHS-R) 1a. The unique post-translational modification of O-n-octanoylation at serine 3 is the first in peptide discovery history and is essential for GH-releasing ability. Des-acyl ghrelin, lacking O-n-octanoylation at serine 3, is also produced in the stomach and remains the major molecular form secreted into the circulation. The third ghrelin gene product, obestatin, a novel 23-amino acid peptide identified from rat stomach, was found by comparative genomic analysis. Three ghrelin gene products actively participate in modulating appetite, adipogenesis, gut motility, glucose metabolism, cell proliferation, immune, sleep, memory, anxiety, cognition, and stress. Knockdown or knockout of acyl ghrelin and/or GHS-R1a, and overexpression of des-acyl ghrelin show benefits in the therapy of obesity and metabolic syndrome. By contrast, agonism of acyl ghrelin and/or GHS-R1a could combat human anorexia-cachexia, including anorexia nervosa, chronic heart failure, chronic obstructive pulmonary disease, liver cirrhosis, chronic kidney disease, burn, and postsurgery recovery, as well as restore gut dysmotility, such as diabetic or neurogenic gastroparesis, and postoperative ileus. The ghrelin acyl-modifying enzyme, ghrelin O-Acyltransferase (GOAT), which attaches octanoate to serine-3 of ghrelin, has been identified and characterized also from the stomach. To date, ghrelin is the only protein to be octanylated, and inhibition of GOAT may have effects only on the stomach and is unlikely to affect the synthesis of other proteins. GOAT may provide a critical molecular target in developing novel therapeutics for obesity and type 2 diabetes.

The effect of laparoscopic gastric banding surgery on plasma levels of appetite-control, insulinotropic, and digestive hormones

BACKGROUND

We hypothesized that laparoscopic adjustable gastric banding (LAGB) reduces weight and modulates ghrelin production, but largely spares gastrointestinal endocrine function. To examine this hypothesis, we determined plasma concentrations of appetite-control, insulinotropic, and digestive hormones in relation to LAGB.

METHODS

Twenty-four patients undergoing LAGB were prospectively enrolled. Body mass index (BMI) was measured and blood samples obtained at baseline and 6 and 12 months post-surgery. Plasma concentrations of leptin, acylated and total ghrelin, pancreatic polypeptide (PP), insulin, glucose-dependent insulinotropic peptide (GIP), active glucagon-like peptide-1 (GLP-1), gastrin, and pepsinogens I and II were measured using enzyme-linked immunoassays.

RESULTS

Median percent excess weight loss (%EWL) over 12 months was 45.7% with median BMI decreasing from 43.2 at baseline to 33.8 at 12 months post-surgery (p < 0.001). Median leptin levels decreased from 19.7 ng/ml at baseline to 6.9 ng/ml at 12 months post-surgery (p < 0.001). In contrast, plasma levels of acylated and total ghrelin, PP, insulin, GIP, GLP-1, gastrin, and pepsinogen I did not change in relation to surgery (p > 0.05). Pepsinogen II levels were significantly lower 6 months after LAGB but returned to baseline levels by 12 months.

CONCLUSIONS

LAGB yielded substantial %EWL and a proportional decrease in plasma leptin. Our results support the hypothesis that LAGB works in part by suppressing the rise in ghrelin that normally accompanies weight loss. Unchanged concentrations of insulinotropic and digestive hormones suggest that gastrointestinal endocrine function is largely maintained in the long term.

Circulating peptide YY, weight loss, and glucose homeostasis after gastric bypass surgery in morbidly obese subjects

OBJECTIVE

To prospectively assess the relationship between circulating peptide YY (PYY), body weight, and glucose tolerance in severely obese subjects undergoing Roux-en-Y gastric bypass (RYGBP).

SUMMARY BACKGROUND DATA

The mechanisms accounting for the beneficial effects of RYGBP on body weight and glucose homeostasis are not well understood.

METHODS

Prospective study on the response of PYY to a standardized test meal (STM) and its relationship with weight loss and glucose homeostasis (fasting plasma glucose, HbA1c, HOMA-IR, HOMA-B) in nondiabetic (n = 25) and diabetic (n = 10) severely obese subjects evaluated before, and at 6 and 52 weeks after RYGBP.

RESULTS

The PYY response to a STM significantly increased (P < 0.001) already at 6 weeks at a time when subjects despite presenting a significant weight loss (-14.6% +/- 1.2%) were still markedly obese. Despite massive weight loss (-43.0% +/- 2.3%), no further increase in the area under the curve of PYY was observed at 52 weeks after surgery (P = 0.44). The PYY response to a STM at 6 weeks after surgery significantly correlated (r = 0.489, P < 0.05) with the percent excess weight loss at 32.5 +/- 1.1 months after surgery. In contrast, no significant correlation was found between PYY and glucose homeostasis parameters in nondiabetic and diabetic patients.

CONCLUSION

Our data support the hypothesis that an increased PYY response after meal ingestion is involved in the sustained weight loss observed after RYGBP. In contrast, our data does not support PYY being relevant in the changes in glucose homeostasis occurring after this type of bariatric surgery.

Psychiatric issues in bariatric surgery

WLS is a proven, effective intervention for severely obese patients. There are four broad categories of surgery, but all reduce excess body weight to an extensive extent. Using surgery in the treatment of a disease with a large behavioral component may seem counterintuitive, but numerous studies have shown the ineffectiveness of diet and exercise in the morbidly obese. The ineffectiveness of these methods is the result, in part, of an alteration in hormones and peptides involved with long-term regulation of energy and weight. The WLS procedures have been shown to alter the anatomic and physiologic function of the stomach. In a motivated patient, this change in the gastrointestinal tract results in weight loss and a significant reduction in weight-related health problems. Evaluating a patient for WLS can be challenging, and multiple organizations have suggested that a multidisciplinary approach be used. The mental health professional often is called on to assess many different domains of psychologic function. This evaluation should go beyond the standard interview and should pay attention to the patient's eating behavior, knowledge of surgery, and motivation for surgery. The use of standardized instruments will facilitate accuracy and further research in the field of WLS. Because there are few absolute psychologic contraindications to WLS, the assessment should also focus on risk management, with the goal of improving the patient's postoperative quality of life.

Is a model useful in exploring the catabolic mechanisms of weight loss after gastric bypass in humans?

PURPOSE OF REVIEW

In the USA, approximately 3% of adults are morbidly obese, in whom behavior modification and drug therapy is ineffective in inducing major weight loss. Surgery is their only reliable option. The Roux-en-Y gastric bypass accounts for 90% of all bariatric surgeries because it achieves the best weight loss results. Many studies describe weight loss and changes in metabolic blood parameters after Roux-en-Y gastric bypass. We compare recent human data with the findings in our rats to validate the versatility of using a Roux-en-Y gastric bypass rat model to explore the multifactorial molecular and physiological dimensions of weight loss and weight regain.

RECENT FINDINGS

Not only mechanical factors but also changes in gastrointestinal and adipose hormones and hypothalamic neuropeptides contribute to Roux-en-Y gastric bypass induced weight loss by promoting catabolic processes. Nevertheless, the exact mechanisms of weight loss remain unknown.

SUMMARY

To investigate these catabolic mechanisms we used our Roux-en-Y gastric bypass rat model in diet induced obese rats. We found clear morphometric, physiological and biochemical parallelisms between humans and our rats. It is likely that Roux-en-Y gastric bypass induces similar changes in hypothalamic neuropeptides which can only be studied using the rat model. It therefore provides a useful research tool for exploring and studying the development of adjuvant antiobesity therapies.