Gastric bypass does not normalize obesity-related changes in ghrelin profile and leads to higher acylated ghrelin fraction

Bariatric Surgery and Gut-Brain-Axis Driven Alterations in Cognition and Inflammation

Obesity is associated with systemic inflammation, comorbidities like diabetes, cardiovascular disease and several cancers, cognitive decline and structural and functional brain changes. To treat, or potentially prevent these related comorbidities, individuals with obesity must achieve long-term sustainable weight loss. Often life style interventions, such as dieting and increased physical activity are not successful in achieving long-term weight loss. Meanwhile bariatric surgery has emerged as a safe and effective procedure to treat obesity. Bariatric surgery causes changes in physiological processes, but it is still not fully understood which exact mechanisms are involved. The successful weight loss after bariatric surgery might depend on changes in various energy regulating hormones, such as ghrelin, glucagon-like peptide-1 and peptide YY. Moreover, changes in microbiota composition and white adipose tissue functionality might play a role. Here, we review the effect of obesity on neuroendocrine effects, microbiota composition and adipose tissue and how these may affect inflammation, brain structure and cognition. Finally, we will discuss how these obesity-related changes may improve after bariatric surgery.

Gastrointestinal hormones and appetite ratings after weight loss induced by diet or bariatric surgery

OBJECTIVE

The aim of this study was to compare changes in gastrointestinal hormones and appetite ratings after a similar weight loss induced by a very low-energy diet alone or in combination with sleeve gastrectomy (SG) or Roux-en-Y gastric bypass (RYGB).

METHODS

Patients with severe obesity scheduled for SG (n = 15) and RYGB (n = 14) and 15 controls (very low-energy diet alone) were recruited. Body weight/composition, plasma concentrations of ß-hydroxybutyric acid, acylated ghrelin, total glucagon-like peptide-1, total peptide YY, cholecystokinin, and ratings of hunger, fullness, desire to eat, and prospective food consumption were measured pre- and postprandially, before and after 10 weeks of intervention.

RESULTS

Changes in body weight/composition and level of ketosis were similar across groups. In SG and RYGB, basal and postprandial acylated ghrelin declined, and postprandial glucagon-like peptide-1 increased, both significantly more compared with controls. Postprandial peptide YY increased in all groups. Overall, postprandial hunger decreased, and postprandial fullness increased. But ratings of desire to eat and prospective food consumption were more favorable after both surgeries compared with controls.

CONCLUSIONS

Weight loss with SG and RYGB leads to more favorable changes in gastrointestinal hormones compared with diet alone, although ratings of appetite were reduced across all groups.

Differences in gastrointestinal hormones and appetite ratings between individuals with and without obesity-A systematic review and meta-analysis

Determining if gastrointestinal (GI) hormone response to food intake differs between individuals with, and without, obesity may improve our understanding of obesity pathophysiology. A systematic review and meta-analysis of studies assessing the concentrations of GI hormones, as well as appetite ratings, following a test meal, in individuals with and without obesity was undertaken. Systematic searches were conducted in the databases MEDLINE, Embase, Cochrane Library, PsycINFO, Web of Science, and ClinicalTrials.gov. A total of 7514 unique articles were retrieved, 115 included in the systematic review, and 70 in the meta-analysis. The meta-analysis compared estimated standardized mean difference in GI hormones' concentration, as well as appetite ratings, between individuals with and without obesity. Basal and postprandial total ghrelin concentrations were lower in individuals with obesity compared with controls, and this was reflected by lower postprandial hunger ratings in the former. Individuals with obesity had a lower postprandial concentration of total peptide YY compared with controls, but no significant differences were found for glucagon-like peptide 1, cholecystokinin, or other appetite ratings. A large methodological and statistical heterogeneity among studies was found. More comprehensive studies are needed to understand if the differences observed are a cause or a consequence of obesity.

Neurohormonal Changes in the Gut–Brain Axis and Underlying Neuroendocrine Mechanisms following Bariatric Surgery

Obesity is a complex, multifactorial disease that is a major public health issue worldwide. Currently approved anti-obesity medications and lifestyle interventions lack the efficacy and durability needed to combat obesity, especially in individuals with more severe forms or coexisting metabolic disorders, such as poorly controlled type 2 diabetes. Bariatric surgery is considered an effective therapeutic modality with sustained weight loss and metabolic benefits. Numerous genetic and environmental factors have been associated with the pathogenesis of obesity, while cumulative evidence has highlighted the gut–brain axis as a complex bidirectional communication axis that plays a crucial role in energy homeostasis. This has led to increased research on the roles of neuroendocrine signaling pathways and various gastrointestinal peptides as key mediators of the beneficial effects following weight-loss surgery. The accumulate evidence suggests that the development of gut-peptide-based agents can mimic the effects of bariatric surgery and thus is a highly promising treatment strategy that could be explored in future research. This article aims to elucidate the potential underlying neuroendocrine mechanisms of the gut–brain axis and comprehensively review the observed changes of gut hormones associated with bariatric surgery. Moreover, the emerging role of post-bariatric gut microbiota modulation is briefly discussed.

Expression of adipokine ghrelin and ghrelin receptor in human colorectal adenoma and correlation with the grade of dysplasia

BACKGROUND

Ghrelin is an adipokine that plays an important role in energy balance. Expression of ghrelin and ghrelin receptor has been investigated in different tissues and tumors. Studies regarding expression of ghrelin and ghrelin receptor in colorectal tumors are scarce and no data on expression of ghrelin and its receptor in colorectal adenomas has been published. Ghrelin and ghrelin receptor were highly expressed in colon carcinoma cells while expression was decreased in less differentiated tumors, presuming that ghrelin might be important in early phases of tumorigenesis.

AIM

To investigate the expression of ghrelin and ghrelin receptor in human colorectal adenomas and adjacent colorectal tissue.

METHODS

In this prospective study (conducted from June 2015 until May 2019) we included 92 patients (64 male and 28 female) who underwent polypectomy for colorectal adenomas in the Department of Gastroenterology and Hepatology, “Sestre milosrdnice” Clinical Hospital Center in Zagreb, Croatia. After endoscopic removal of colorectal adenoma, an additional sample of colon mucosa in the proximity of the adenoma was collected for pathohistological analysis. Adenomas were graded according to the stage of dysplasia, and ghrelin and ghrelin receptor expression were determined immunohistochemically in both adenoma and adjacent colon tissue using the polyclonal antibody for ghrelin (ab150514, ABCAM Inc, Cambridge, United States) and ghrelin receptor (ab48285, ABCAM Inc, Cambridge, United States). Categorical and nominal variables were described through frequencies and proportions and the difference between specific groups were analyzed with Fisher’s and Fisher-Freeman-Halton’s method respectively. Spearman's rank correlation coefficient was determined for correlation of expression of ghrelin and ghrelin receptor in adenoma and adjacent colon tissue with the grade of adenoma dysplasia.

RESULTS

Among 92 patients with colorectal adenoma 43 had adenomas with high-grade dysplasia (46.7%). High expression of ghrelin was 7 times more common in high-grade adenoma compared to low-grade adenomas (13.95% to 2.04%, P = 0.048), while the expression of ghrelin in adjacent colon tissue was low. We found no correlation between ghrelin receptor expression in adenoma and adjacent colon tissue and the grade of colorectal adenoma dysplasia. The most significant correlation was found between ghrelin and ghrelin receptor expression in adenomas with high-grade dysplasia (rho = 0.519, P < 0.001).

CONCLUSION

Ghrelin and ghrelin receptor are expressed in colorectal adenoma and adjacent tissue with ghrelin expression being more pronounced in high grade dysplasia as a possible consequence of increased local synthesis.

Do Gut Hormones Contribute to Weight Loss and Glycaemic Outcomes after Bariatric Surgery?

Bariatric surgery is an effective intervention for management of obesity through treating dysregulated appetite and achieving long-term weight loss maintenance. Moreover, significant changes in glucose homeostasis are observed after bariatric surgery including, in some cases, type 2 diabetes remission from the early postoperative period and postprandial hypoglycaemia. Levels of a number of gut hormones are dramatically increased from the early period after Roux-en-Y gastric bypass and sleeve gastrectomy—the two most commonly performed bariatric procedures—and they have been suggested as important mediators of the observed changes in eating behaviour and glucose homeostasis postoperatively. In this review, we summarise the current evidence from human studies on the alterations of gut hormones after bariatric surgery and their impact on clinical outcomes postoperatively. Studies which assess the role of gut hormones after bariatric surgery on food intake, hunger, satiety and glucose homeostasis through octreotide use (a non-specific inhibitor of gut hormone secretion) as well as with exendin 9–39 (a specific glucagon-like peptide-1 receptor antagonist) are reviewed. The potential use of gut hormones as biomarkers of successful outcomes of bariatric surgery is also evaluated.

Higher unacylated ghrelin and insulin sensitivity following dietary restriction and weight loss in obese humans

BACKGROUND & AIMS

Unacylated ghrelin (UnAG) modulates insulin sensitivity. Low plasma UnAG occurs in obesity and potentially contributes to obesity-associated insulin resistance. We hypothesized that improvements in insulin sensitivity in obese people induced by moderate caloric restriction (CR) may be paralleled and at least in part explained by concurrent increases in UnAG levels.

METHODS

20 general community obese people were randomly assigned to 16-week CR (n = 11) or control diet (n = 9). We investigated the impact of CR on the interaction between insulin sensitivity changes [area under the curve (AUCg) of glucose infusion to maintain euglycemia during hyperinsulinemic-euglycemic clamp] and plasma total (TotalG), acylated (AG) and Unacylated ghrelin (UnAG). Plasma pro-inflammatory tumor necrosis factor alpha (TNFα) and anti-inflammatory interleukin-10 (IL-10) were also measured since changes in inflammation may contribute to UnAG activities.

RESULTS

CR reduced BMI and increased insulin sensitivity (p < 0.05). TotalG and UnAG but not AG increased in CR but not in Control (p < 0.05). Il-10 and IL-10/TNFα ratio also increased in CR (p < 0.05). Changes in UnAG were positively associated with changes in AUCg in all subjects (n = 20; p < 0.01) also after adjustment for treatment and changes in BMI and cytokines.

CONCLUSIONS

Caloric restriction modifies circulating ghrelin profile with selective increase in unacylated hormone in obese individuals. The current study supports the hypothesis that higher unacylated ghrelin contributes to improvements in insulin sensitivity following diet-induced weight loss in human obesity.

Revisiting the Ghrelin Changes Following Bariatric and Metabolic Surgery

Since the description of ghrelin in 1999, several studies have dug into the effects of this hormone and its relationship with bariatric surgery. While some aspects are still unresolved, a clear connection between ghrelin and the changes after metabolic surgery have been established. Besides weight loss, a significant amelioration in obesity-related comorbidities following surgery has also been reported. These changes in patients occur in the early postoperative period, before the weight loss appears, so that amelioration may be mainly due to hormonal changes. The purpose of this review is to go through the current body of knowledge of ghrelin's physiology, as well as to update and clarify the changes that take place in ghrelin concentrations following bariatric/metabolic surgery together with their potential consolidation to outcomes.

Ghrelin forms in the modulation of energy balance and metabolism

Ghrelin is a gastric hormone circulating in acylated (AG) and unacylated (UnAG) forms. This narrative review aims at presenting current emerging knowledge on the impact of ghrelin forms on energy balance and metabolism. AG represents ~ 10% of total plasma ghrelin, has an appetite-stimulating effect and is the only form for which a receptor has been identified. Moreover, other metabolic AG-induced effects have been reported, including the modulation of glucose homeostasis with stimulation of liver gluconeogenesis, the increase of fat mass and the improvement of skeletal muscle mitochondrial function. On the other hand, UnAG has no orexigenic effects, however recent reports have shown that it is directly involved in the modulation of skeletal muscle energy metabolism by improving a cluster of interlinked functions including mitochondrial redox activities, tissue inflammation and insulin signalling and action. These findings are in agreement with human studies which show that UnAG circulating levels are positively associated with insulin sensitivity both in metabolic syndrome patients and in a large cohort from the general population. Moreover, ghrelin acylation is regulated by a nutrient sensor mechanism, specifically set on fatty acids availability. These recent findings consistently point towards a novel independent role of UnAG as a regulator of muscle metabolic pathways maintaining energy status and tissue anabolism. While a specific receptor for UnAG still needs to be identified, recent evidence strongly supports the hypothesis that the modulation of ghrelin-related molecular pathways, including those involved in its acylation, may be a potential novel target in the treatment of metabolic derangements in disease states characterized by metabolic and nutritional complications.Level of evidence Level V, narrative review.

Effect of different bariatric surgeries on dietary protein bioavailability in rats

Bariatric surgery may induce protein malabsorption, although data are scarce. This study aims at evaluating dietary protein bioavailability after different bariatric surgeries in rats. Diet-induced obese Wistar rats were operated for vertical sleeve gastrectomy (VSG) or Roux-en-Y gastric bypass (RYGB). The control group was composed of pair-fed, sham-operated rats (Sham). Two weeks after surgery, rats were fed a ¹⁵N protein meal. Protein bioavailability was assessed by determination of ¹⁵N recovery in the gastrointestinal tract and organs 6 h after the meal. Fractional protein synthesis rate (FSR) was assessed using a flooding dose of ¹³C valine. Weight loss was the highest in RYGB rats and the lowest in Sham rats. Surprisingly, RYGB (95.6 ± 0.7%) improved protein digestibility (P = 0.045) compared with Sham (93.5 ± 0.5%) and VSG (93.8 ± 0.6%). In contrast, ¹⁵N retained in the liver (P = 0.001) and plasma protein (P = 0.037) was lower than in Sham, with a similar trend in muscle (P = 0.052). FSR was little altered by bariatric surgery, except for a decrease in the kidney of RYGB (P = 0.02). The ¹⁵N distribution along the small intestinal tissue suggests that dietary nitrogen was considerably retained in the remodeled mucosa of RYGB compared with Sham. This study revealed that in contrast to VSG, RYGB slightly improved protein digestibility but altered peripheral protein bioavailability. This effect may be ascribed to a higher uptake of dietary amino acids by the remodeled intestine.NEW & NOTEWORTHY Using a sensitive ¹⁵N meal test, we found that gastric bypass slightly improved protein digestibility compared with sleeve gastrectomy or control but, in contrast, lowered protein retention in the liver and muscles. This paradox can be due to a higher uptake of dietary nitrogen by the intestinal mucosa that was hypertrophied. This study provides new insight on the digestive and metabolic fate of dietary protein in different models of bariatric surgery in rats.

Role of ghrelin isoforms in the mitigation of hepatic inflammation, mitochondrial dysfunction, and endoplasmic reticulum stress after bariatric surgery in rats

BACKGROUND/OBJECTIVES

Bariatric surgery improves nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH), but the underlying mechanisms remain elusive. We evaluated the potential role of ghrelin isoforms in the amelioration of hepatic inflammation after sleeve gastrectomy and Roux-en-Y gastric bypass (RYGB).

SUBJECTS/METHODS

Plasma ghrelin isoforms were measured in male Wistar rats (n = 129) subjected to surgical (sham operation, sleeve gastrectomy, or RYGB) or dietary interventions [fed ad libitum a normal (ND) or a high-fat diet (HFD) or pair-fed diet]. The effect of acylated and desacyl ghrelin on markers of inflammation, mitochondrial dysfunction, and endoplasmic reticulum (ER) stress in primary rat hepatocytes under palmitate-induced lipotoxic conditions was assessed.

RESULTS

Plasma desacyl ghrelin was decreased after sleeve gastrectomy and RYGB, whereas the acylated/desacyl ghrelin ratio was augmented. Both surgeries diminished obesity-associated hepatic steatosis, CD68⁺- and apoptotic cells, proinflammatory JNK activation, and Crp, Tnf, and Il6 transcripts. Moreover, a postsurgical amelioration in the mitochondrial DNA content, oxidative phosphorylation (OXPHOS) complexes I and II, and ER stress markers was observed. Specifically, following bariatric surgery GRP78, spliced XBP-1, ATF4, and CHOP levels were reduced, as were phosphorylated eIF2α. Interestingly, acylated and desacyl ghrelin inhibited steatosis and inflammation of palmitate-treated hepatocytes in parallel to an upregulation of OXPHOS complexes II, III, and V, and a downregulation of ER stress transducers IRE1α, PERK, ATF6, their downstream effectors, ATF4 and CHOP, as well as chaperone GRP78.

CONCLUSIONS

Our data suggest that the increased relative acylated ghrelin levels after bariatric surgery might contribute to mitigate obesity-associated hepatic inflammation, mitochondrial dysfunction, and ER stress.

Fasting and postprandial acyl and desacyl ghrelin and the acyl/desacyl ratio in obese patients before and after different types of bariatric surgery

Introduction

The mechanism underlying beneficial outcomes of bariatric surgery still remains unclear. Especially little is known about hormonal and metabolic changes induced by the novel bariatric procedure mini gastric bypass (MGB).

Aim

To evaluate pre- and post-prandial changes in both ghrelin isoforms in obese patients without diabetes and cardiovascular complications treated with MGB, sleeve gastrectomy (SG) or Roux-en-Y gastric bypass (RYGB) surgery.

Material and methods

From 45 patients initially enrolled in the study, 23 persons completed a one-year follow-up period. Venous blood for acyl and desacyl ghrelin (AG and DAG) as well as other metabolic assays was collected 3 months before and 6 and 12 months after bariatric surgery (MGB, RYGB, SG) – in the fasting state and 2 h after the consumption of a standard 300 kcal-mixed meal (Nutridrink standard, Nutricia).

Results

AG and DAG levels (both fasting and prandial) as well as AG/DAG ratio did not change after 6 and 12 months in MGB and RYGB groups. In the SG group we observed a significant decrease in fasting and postprandial DAG levels and consecutively an increase in the fasting AG/DAG ratio after 6 and 12 months. Six months after surgery we observed some differences between carbohydrate metabolism measures in the MGB group (lower HbA_1c, HOMA-IR and fasting insulinaemia) in comparison to the rest of the participants, but 12 months after each type of surgery body mass index and indices of carbohydrate and lipid metabolism did not differ.

Conclusions

The results of our study demonstrate that all studied bariatric procedures can successfully reduce overall body weight and suggest also that the mechanisms of weight loss and improvement in carbohydrate and lipid metabolism after all three types of surgery are independent of ghrelin and the acyl/desacyl ghrelin ratio.

Effect of vertical sleeve gastrectomy on alcohol consumption and preferences in dietary obese rats and mice: A plausible role for altered ghrelin signaling

Vertical sleeve gastrectomy (VSG) and Roux-en-Y gastric bypass (RYGB) are the most common surgical options for the treatment of obesity and metabolic disorder. Whereas RYGB may result in greater and more durable weight loss, recent clinical and pre-clinical studies in rats have raised concerns that RYGB surgery may increase risk for alcohol use disorder (AUD). In contrast, recent clinical reports suggest a lesser risk for AUD following VSG, although no preclinical studies have been done to confirm that. Therefore, the present study sought to determine the effects of VSG on ethanol intake and preferences in rodent models using protocols similar to those previously used in animal studies for RYGB. Male Sprague Dawley rats and male C57B6 mice were made obese on a high fat diet (60%kcal from fat) and received VSG or no surgery (controls). All animals then were given access to increasing concentrations of ethanol (2%, 4%, 6%, and 8%), presented for few days each. Compared to controls, VSG rats consumed significantly less of 2, 6 and 8% ethanol and showed significantly reduced preferences to 6 and 8% ethanol over water. VSG mice also displayed reduced intake and preference for 6 and 8% ethanol solutions. After a two-week period of forced abstinence, 8% ethanol was reintroduced and the VSG rats and mice continued to exhibit reduced consumption and less preference for ethanol. Regarding the underlying mechanism, we hypothesized that the removal of the ghrelin producing part of the stomach in the VSG surgery is a possible contributor to the observed reduced ethanol preference. To test for functional changes at the ghrelin receptors, the VSG and control rats were given IP injections of acyl-ghrelin (2.5nmol and 5nmol) prior to ethanol access. Neither concentration of ghrelin resulted in a significant increase in 8% ethanol consumption of VSG or control subjects. Next, the rats were given IP injections of the ghrelin receptor antagonist, JMV (2.5mg/kg body weight). This dose induced a significant reduction in 8% ethanol consumption in the VSG group, but no effect on ethanol intake in the controls. While ghrelin injection was uninformative, increased sensitivity to subthreshold doses of the ghrelin receptor antagonist may indicate reduced ghrelin signaling following VSG. Overall, these findings suggest that bariatric patients with increased susceptibility to AUD may benefit from receiving VSG instead of RYGB surgery, and that changes in ghrelin signaling, at least in part, may play a role in the differential AUD risks between the two most commonly performed bariatric surgical procedures.

Insulin resistance in obesity: an overview of fundamental alterations

Obesity is a major health risk factor, and obesity-induced morbidity and complications account for huge costs for affected individuals, families, healthcare systems, and society at large. In particular, obesity is strongly associated with the development of insulin resistance, which in turn plays a key role in the pathogenesis of obesity-associated cardiometabolic complications, including metabolic syndrome components, type 2 diabetes, and cardiovascular diseases. Insulin sensitive tissues, including adipose tissue, skeletal muscle, and liver, are profoundly affected by obesity both at biomolecular and functional levels. Altered adipose organ function may play a fundamental pathogenetic role once fat accumulation has ensued. Modulation of insulin sensitivity appears to be, at least in part, related to changes in redox balance and oxidative stress as well as inflammation, with a relevant underlying role for mitochondrial dysfunction that may exacerbate these alterations. Nutrients and substrates as well as systems involved in host-nutrient interactions, including gut microbiota, have been also identified as modulators of metabolic pathways controlling insulin action. This review aims at providing an overview of these concepts and their potential inter-relationships in the development of insulin resistance, with particular regard to changes in adipose organ and skeletal muscle.

Neuroendocrine regulation of energy balance: Implications on the development and surgical treatment of obesity

INTRODUCTION

Obesity, a serious public health problem, occurs mainly when food consumption exceeds energy expenditure. Therefore, energy balance depends on the regulation of the hunger-satiety mechanism, which involves interconnection of the central nervous system and peripheral signals from the adipose tissue, pancreas and gastrointestinal tract, generating responses in short-term food intake and long-term energy balance. Increased body fat alters the gut- and adipose-tissue-derived hormone signaling, which promotes modifications in appetite-regulating hormones, decreasing satiety and increasing hunger senses. With the failure of conventional weight loss interventions (dietary treatment, exercise, drugs and lifestyle modifications), bariatric surgeries are well-accepted tools for the treatment of severe obesity, with long-term and sustained weight loss. Bariatric surgeries may cause weight loss due to restriction/malabsorption of nutrients from the anatomical alteration of the gastrointestinal tract that decreases energy intake, but also by other physiological factors associated with better results of the surgical procedure.

OBJECTIVE

This review discusses the neuroendocrine regulation of energy balance, with description of the predominant hormones and peptides involved in the control of energy balance in obesity and all currently available bariatric surgeries.

CONCLUSIONS

According to the findings of our review, bariatric surgeries promote effective and sustained weight loss not only by reducing calorie intake, but also by precipitating changes in appetite control, satiation and satiety, and physiological changes in gut-, neuro- and adipose-tissue-derived hormone signaling.

Acylated and desacyl ghrelin are associated with hepatic lipogenesis, β-oxidation and autophagy: role in NAFLD amelioration after sleeve gastrectomy in obese rats

Bariatric surgery improves non-alcoholic fatty liver disease (NAFLD). Our aim was to investigate the potential role of ghrelin isoforms in the resolution of hepatic steatosis after sleeve gastrectomy, a restrictive bariatric surgery procedure, in diet-induced obese rats. Male Wistar rats (n = 161) were subjected to surgical (sham operation and sleeve gastrectomy) or dietary interventions [fed ad libitum a normal (ND) or a high-fat (HFD) diet or pair-fed]. Obese rats developed hepatosteatosis and showed decreased circulating desacyl ghrelin without changes in acylated ghrelin. Sleeve gastrectomy induced a dramatic decrease of desacyl ghrelin, but increased the acylated/desacyl ghrelin ratio. Moreover, sleeve gastrectomy reduced hepatic triglyceride content and lipogenic enzymes Mogat2 and Dgat1, increased mitochondrial DNA amount and induced AMPK-activated mitochondrial FFA β-oxidation and autophagy to a higher extent than caloric restriction. In primary rat hepatocytes, the incubation with both acylated and desacyl ghrelin (10, 100 and 1,000 pmol/L) significantly increased TG content, triggered AMPK-activated mitochondrial FFA β-oxidation and autophagy. Our data suggest that the decrease in the most abundant isoform, desacyl ghrelin, after sleeve gastrectomy contributes to the reduction of lipogenesis, whereas the increased relative acylated ghrelin levels activate factors involved in mitochondrial FFA β-oxidation and autophagy in obese rats, thereby ameliorating NAFLD.

Preoperative Predictive Factors of Successful Weight Loss and Glycaemic Control 1 Year After Gastric Bypass for Morbid Obesity

BACKGROUND

Gastric bypass (GBP) is one of the most effective surgical procedures to treat morbid obesity and the related comorbidities. This study aimed at identifying preoperative predictors of successful weight loss and type 2 diabetes mellitus (T2DM) remission 1 year after GBP.

METHODS

Prospective longitudinal study of 771 patients who underwent GBP was performed at four Italian centres between November 2011 and May 2013 with 1-year follow-up. Preoperative anthropometric, metabolic and social parameters, the surgical technique and the previous failed bariatric procedures were analyzed. Weight, the body mass index (BMI), the percentage of excess weight lost (% EWL), the percentage of excess BMI lost (% BMIL) and glycated haemoglobin (HbA1c) were recorded at follow-up.

RESULTS

Univariate and multivariate analysis showed that BMI <50 kg/m(2) (p = 0.006) and dyslipidaemia (p = 0.05) were predictive factors of successful weight loss. Multivariate analysis of surgical technique showed significant weight loss in patients with a small gastric pouch (p < 0.001); the lengths of alimentary and biliary loops showed no statistical significance. All diabetic patients had a significant reduction of HbA1c (p < 0.001) after surgery. BMI ≥ 50 kg/m(2) (p = 0.02) and low level of preoperative HbA1c (p < 0.01) were independent risk factors of T2DM remission after surgery.

CONCLUSIONS

This study provides a useful tool for making more accurate predictions of best results in terms of weight loss and metabolic improvement.

The effect of bariatric surgery on gastrointestinal and pancreatic peptide hormones

Bariatric surgery for obesity has proved to be an extremely effective method of promoting long-term weight reduction with additional beneficial metabolic effects, such as improved glucose tolerance and remission of type 2 diabetes. A range of bariatric procedures are in common use, including gastric banding, sleeve gastrectomy and the Roux-en-Y gastric bypass. Although the mechanisms underlying the efficacy of bariatric surgery are unclear, gastrointestinal and pancreatic peptides are thought to play an important role. The aim of this review is to summarise the effects of different bariatric surgery procedures upon gastrointestinal and pancreatic peptides, including ghrelin, gastrin, cholecystokinin (CCK), glucose-dependent insulinotropic hormone (GIP), glucagon-like peptide 1 (GLP-1), peptide YY (PYY), oxyntomodulin, insulin, glucagon and somatostatin.

Plasma total and unacylated ghrelin predict 5-year changes in insulin resistance

BACKGROUND & AIMS

Ghrelin is a gastric hormone circulating in acylated (AG) and unacylated (UG) forms, and higher plasma total ghrelin (TG) and UG may be cross-sectionally associated with lower insulin resistance in metabolic syndrome patients. The potential value of ghrelin forms in predicting insulin resistance and its time-related changes in community-based population cohorts remains unknown.

METHODS

We measured TG, AG and calculated UG (TG-AG) in 716 individuals from the North-East-Italy MoMa study (age: 55 ± 9 years, BMI: 29 ± 5 kg/m(2), M/F:349/367) to test the hypothesis that circulating TG and UG, but not AG are negatively associated with insulin resistance (HOMA). We further hypothesized that baseline TG and UG negatively predict 5-year HOMA changes in a 350-individual subgroup.

RESULTS

Baseline TG and UG were associated negatively with HOMA after adjusting for gender and body mass index (BMI). Baseline gender- and BMI-adjusted TG and UG were also negatively associated with HOMA at 5-year follow-up (n = 350), and changes in TG and UG were negatively associated with changes in HOMA (P < 0.05) after adjustment for anthropometric and metabolic confounders. No statistically significant correlations were observed between AG and baseline or 5-year HOMA.

CONCLUSIONS

In a North-East Italy community-based population cohort, plasma TG and UG but not AG are negatively associated with HOMA. TG and UG and their changes also independently predict 5-year HOMA changes. TG and UG are therefore novel potential modulators of insulin resistance and may contribute to predict its time-related changes in humans.

What is the Mechanism Behind Weight Loss Maintenance with Gastric Bypass?

Obesity is an epidemic on the rise. With the failure of non-surgical strategies, bariatric surgery has emerged as the most effective therapeutic option for the treatment of severe obesity. Among various surgical options, Roux-en-Y gastric bypass (RYGB) results in sustained weight loss and profound metabolic improvements. The traditional view that gastric bypass and bariatric surgery in general works primarily through restriction/malabsorption of nutrients has become obsolete. It is now increasingly recognised that its mechanisms of action are primarily physiologic, not mechanic. In fact, clinical and translational studies over the last decade have shown that a number of gastrointestinal mechanisms, including changes in gut hormones, neural signalling, intestinal flora, bile acid and lipid metabolism can play a significant role in the effects of this procedure on energy homeostasis. The clinical efficacy and mechanisms of action of RYGB provide a compelling evidence for the role of the gastrointestinal tract in the regulation of appetite and satiety, body weight and glucose metabolism. This review discusses the physiologic changes that occur after RYGB and that contribute to its mechanisms of action.

Effect of oral glucose administration on rebound growth hormone release in normal and obese women: the role of adiposity, insulin sensitivity and ghrelin

Context

Metabolic substrates and nutritional status play a major role in growth hormone (GH) secretion. Uncovering the mechanisms involved in GH secretion following oral glucose (OG) administration in normal and obese patients is a pending issue.

Objective

The aim of this study was to investigate GH after OG in relation with adiposity, insulin secretion and action, and ghrelin secretion in obese and healthy women, to further elucidate the mechanism of GH secretion after OG and the altered GH secretion in obesity.

Participants and Methods

We included 64 healthy and obese women. After an overnight fast, 75 g of OG were administered; GH, glucose, insulin and ghrelin were obtained during 300 minutes. Insulin secretion and action indices and the area under the curve (AUC) were calculated for GH, glucose, insulin and ghrelin. Univariate and multivariate linear regression analyses were employed.

Results

The AUC of GH (μg/L•min) was lower in obese (249.8±41.8) than in healthy women (490.4±74.6), P=0.001. The AUC of total ghrelin (pg/mL•min) was lower in obese (240995.5±11094.2) than in healthy women (340797.5±37757.5), P=0.042. There were significant correlations between GH secretion and the different adiposity, insulin secretion and action, and ghrelin secretion indices. After multivariate analysis only ghrelin AUC remained a significant predictor for fasting and peak GH.

Roux-en-Y gastric bypass: effects on feeding behavior and underlying mechanisms

Bariatric surgery is the most effective treatment for severe obesity, producing marked sustained weight loss with associated reduced morbidity and mortality. Roux-en-Y gastric bypass surgery (RYGBP), the most commonly performed procedure, was initially viewed as a hybrid restrictive-malabsorptive procedure. However, over the last decade, it has become apparent that alternative physiologic mechanisms underlie its beneficial effects. RYGBP-induced altered feeding behavior, including reduced appetite and changes in taste/food preferences, is now recognized as a key driver of the sustained postoperative weight loss. The brain ultimately determines feeding behavior, and here we review the mechanisms by which RYGBP may affect central appetite-regulating pathways.

Roux en Y gastric bypass increases ethanol intake in the rat

Roux en Y gastric bypass (RYGB) surgery is currently the most effective therapy employed to treat obesity and its associated complications. In addition to weight loss and resolution of metabolic syndromes, such as diabetes, the RYGB procedure has been reported to increase alcohol consumption in humans. Using an outbred rodent model, we demonstrate that RYGB increases postsurgical ethanol consumption, that this effect cannot be explained solely by postsurgical weight loss and that it is independent of presurgical body weight or dietary composition. Altered ethanol metabolism and postsurgical shifts in release of ghrelin were also unable to account for changes in alcohol intake. Further investigation of the potential physiological factors underlying this behavioral effect identified altered patterns of gene expression in brain regions associated with reward following RYGB surgery. These findings have important clinical implications as they demonstrate that RYGB surgery leads directly to increased alcohol intake in otherwise alcohol nonpreferring rat and induces neurobiological changes in brain circuits that mediate a variety of appetitive behaviors.

Novel molecular aspects of ghrelin and leptin in the control of adipobiology and the cardiovascular system

Ghrelin and leptin show opposite effects on energy balance. Ghrelin constitutes a gut hormone that is secreted to the bloodstream in two major forms, acylated and desacyl ghrelin. The isoforms of ghrelin not only promote adiposity by the activation of hypothalamic orexigenic neurons but also directly stimulate the expression of several fat storage-related proteins in adipocytes, including ACC, FAS, LPL and perilipin, thereby stimulating intracytoplasmic lipid accumulation. Moreover, both acylated and desacyl ghrelin reduce TNF-α-induced apoptosis and autophagy in adipocytes, suggesting an anti-inflammatory role of ghrelin in human adipose tissue. On the other hand, leptin is an adipokine with lipolytic effects. In this sense, leptin modulates via PI3K/Akt/mTOR the expression of aquaglyceroporins such as AQP3 and AQP7 that facilitate glycerol efflux from adipocytes in response to the lipolytic stimuli via its translocation from the cytosolic fraction (AQP3) or lipid droplets (AQP7) to the plasma membrane. Ghrelin and leptin also participate in the homeostasis of the cardiovascular system. Ghrelin operates as a cardioprotective factor with increased circulating acylated ghrelin concentrations in patients with left ventricular hypertrophy (LVH) causally related to LV remodeling during the progression to LVH. Additionally, leptin induces vasodilation by inducible NO synthase expression (iNOS) in the vascular wall. In this sense, leptin inhibits the angiotensin II-induced Ca(2+) increase, contraction and proliferation of VSMC through NO-dependent mechanisms. Together, dysregulation of circulating ghrelin isoforms and leptin resistance associated to obesity, type 2 diabetes, or the metabolic syndrome contribute to cardiometabolic derangements observed in these pathologies.

Clinical biomarkers in metabolic syndrome

A biomarker can be defined as a measurable variable that may be used as an indicator of a given biological state or condition. Biomarkers have been used in health and disease for diagnostic purposes, as tools to assess effectiveness of nutritional or drug intervention, or as risk markers to predict the development of certain diseases. In nutrition studies, selecting appropriate biomarkers is important to assess compliance, or incidence of a particular dietary component in the biochemistry of the organism, and in the diagnosis and prognosis of nutrition-related diseases. Metabolic syndrome is a cluster of cardiovascular risk factors that occur simultaneously in the same individual, and it is associated with systemic alterations that may involve several organs and tissues. Given its close association with obesity and the increasing prevalence of obesity worldwide, identifying obese individuals at risk for metabolic syndrome is a major clinical priority. Biomarkers for metabolic syndrome are therefore potential important tools to maximize the effectiveness of treatment in subjects who would likely benefit the most. Choice of biomarkers may be challenging due to the complexity of the syndrome, and this article will mainly focus on nutrition biomarkers related to the diagnosis and prognosis of the metabolic syndrome.

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.