Peripheral signals mediate the beneficial effects of gastric surgery in obesity

Gastric GDF15 levels are regulated by age, sex, and nutritional status in rodents and humans

AIM

Growth differentiation factor 15 (GDF15) is a stress response cytokine that has been proposed as a relevant metabolic hormone. Descriptive studies have shown that plasma GDF15 levels are regulated by short term changes in nutritional status, such as fasting, or in obesity. However, few data exist regarding how GDF15 levels are regulated in peripheral tissues. The aim of the present work was to study the variations on gastric levels of GDF15 and its precursor under different physiological conditions, such as short-term changes in nutritional status or overfeeding achieved by HFD. Moreover, we also address the sex- and age-dependent alterations in GDF15 physiology.

METHODS

The levels of gastric and plasma GDF15 and its precursor were measured in lean and obese mice, rats and humans by western blot, RT-PCR, ELISA, immunohistochemistry and by an in vitro organ culture system.

RESULTS

Our results show a robust regulation of gastric GDF15 production by fasting in rodents. In obesity an increase in GDF15 secretion from the stomach is reflected with an increase in circulating levels of GDF15 in rats and humans. Moreover, gastric GDF15 levels increase with age in both rats and humans. Finally, gastric GDF15 levels display sexual dimorphism, which could explain the difference in circulating GFD15 levels between males and females, observed in both humans and rodents.

CONCLUSIONS

Our results provide clear evidence that gastric GDF15 is a critical contributor of circulating GDF15 levels and can explain some of the metabolic effects induced by GDF15.

[Evaluation of food habits and physical activity in Galician students]

Introduction

Introduction: obesity causes millions of deaths each year. Its high prevalence in children and adolescents from southern European countries, including Spain, is associated with the new food preferences and decreased physical activity. Objective: to evaluate diet quality and physical activity in Galician schoolchildren in order to assess if modifying the current intervention strategies in lifestyles is required. Methods: in the present study, 662 students from the south of Galicia were studied (9-17 years). Body mass index (BMI) was calculated as adiposity indicator. The dietary pattern was evaluated through the Kidmed test and physical activity with PAQ-C. The sample was stratified by BMI according to Cole international standards. Data were analysed with the SPPS software. Results: fifty-six per cent of children are at high risk of overnutrition or need to improve their nutrition. The average adherence to the Mediterranean diet was low (7.64 ± 2.28), worsening with age and adiposity significantly. The average level of physical activity was moderate (3.02 ± 0.74) and it was lower in girls and adolescents; 58% showed a low-moderate level of physical activity. Quality diet was positively correlated with physical activity and negatively with BMI. Conclusions: Galician students showed a diet and physical activity risky pattern according to international/national recommendations. After several years of awareness campaigns and lifestyle interventions, improving their diet and increasing physical activity is still necessary.

Importance of the gastrointestinal tract in type 2 diabetes. Metabolic surgery is more than just incretin effect

Bariatric and metabolic surgery is creating new concepts about how the intestine assimilates food. Recent studies highlight the role of the gastrointestinal tract in the genesis and evolution of type 2 diabetes. This article has been written to answer frequent questions about metabolic surgery results and the mechanisms of action. For this purpose, a non-systematic search of different databases was carried out, identifying articles published in the last decade referring to the mechanisms of action of metabolic techniques. Understanding these mechanisms will help grasp why some surgeries are more effective than others and why the results can be so disparate among patients undergoing the same surgical approach.

Circulating Pro-Uroguanylin Levels In Children And Their Relation To Obesity, Sex And Puberty

Uroguanylin is a 16 amino acid peptide that constitutes a key component of the gut- brain axis with special relevance in body weight regulation. In childhood and adolescence, periods of life with notable metabolic changes; limited data exist, with measurements of pro-uroguanylin in adolescence but not in prepubertal children. This study investigates pro-uroguanylin circulating levels in children with obesity and its relationship with obesity, sex and pubertal development. We analyzed circulating prouroguanylin levels in 117 children (62) and adolescents (55), including 73 with obesity and 44 with normal weight. The pro-uroguanylin concentration is higher in lean girls during pre-puberty versus lean boys (1111 vs 635, p < 0.001). During puberty, pro-uroguanylin levels are higher in lean males with respect to lean females (1060 vs 698, p < 0.01). In girls, a negative correlation exists between pro-uroguanylin and age, Tanner stage, weight, height, BMI (body mass index), waist circumference and plasma levels of leptin and testosterone; a positive correlation was found between pro-uroguanylin and free triiodothyronine. In boys, a positive correlation was found between pro-uroguanylin and BMI and waist circumference and a negative correlation was found with high density lipoprotein-cholesterol. We conclude that a sexual dimorphism exists in circulating pro-uroguanylin levels with respect to BMI. Uroguanylin presents also an opposed circulating pattern during puberty in both sexes.

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.

Changes in metabolic hormones after bariatric surgery and their predictive impact on weight loss

BACKGROUND

Although various metabolic hormones have been implicated in bariatric-related weight loss, their use as predictors of weight loss is unknown. Our study evaluates changes in metabolic hormones after bariatric surgery, and their role as predictors of weight loss.

METHODS

This nonrandomized study included 51 patients, 21 underwent laporascopic adjustable gastric banding (LAGB), 15 laparoscopic sleeve gastrectomy (LSG) and 15 Roux-en Y gastric bypass (RYGB). Serum ghrelin, leptin, insulin, growth hormone, HOMA-IR and HOMA-β was recorded at baseline and 1, 3, 6 and 12 months, and correlated with weight loss. Successful weight loss was defined as excess weight loss >50% at 12 months for all groups.

RESULTS

Weight loss pattern was similar in all groups. Ghrelin increased only in the LAGB group (P = 0·016). However, baseline ghrelin concentrations >664·6 pg/mL in the LSG group predicted successful weight loss with 81·8% sensitivity and 100·0% specificity, and ghrelin >969·8 pg/mL in the 1st postoperative month predicted success with 83·3% sensitivity and 83·3% specificity in the LAGB group. Insulin and HOMA-IR decreased significantly in the LSG and RYGB group, HOMA-β increased in the LAGB and LSG group. Serum leptin decreased and GH increased in all groups (P < 0·001 for all changes). Changes in insulin, leptin and growth hormone were not predictors, but a consequence of weight loss.

CONCLUSIONS

LSG is the most effective procedure for improvement of beta-cell function. High baseline ghrelin in the LSG group and an adequate 1st month increase in the LAGB group are associated with greater weight loss. Validation studies are required to confirm the role of ghrelin in predicting weight loss after bariatric surgery, but also in selecting candidates for specific bariatric procedures.

FNDC5 is produced in the stomach and associated to body composition

The fibronectin type III domain-containing protein 5 (FNDC5) discovered in 2002 has recently gained attention due to its potential role in protecting against obesity. In rat, no data exist regarding FNDC5 production and regulation in the stomach. The aim of the present work was to determine the expression of FNDC5 in the rat stomach and its potential regulation by body composition. The present data shows FNDC5 gene expression in the gastric mucosa. Immunohistochemical studies found FNDC5 immunopositivity in chief cells of gastric tissue. By the use of three different antibodies FNDC5 was found expressed in gastric mucosa and secreted by the stomach. The rate of gastric FNDC5 secretion parallels the circulating levels of FNDC5. The body fat mass increase after intervention with high fat diet coincided with a decrease in the secretion of FNDC5 from the stomach and a diminution in the FNDC5 circulating levels. In summary, the present data shows, for the first time, the expression of FNDC5 in the stomach of rats and its regulation by body composition, suggesting a potential role of gastric FNDC5 in energy homeostasis.

The Gustatory Signaling Pathway and Bitter Taste Receptors Affect the Development of Obesity and Adipocyte Metabolism in Mice

Intestinal chemosensory signaling pathways involving the gustatory G-protein, gustducin, and bitter taste receptors (TAS2R) have been implicated in gut hormone release. Alterations in gut hormone profiles may contribute to the success of bariatric surgery. This study investigated the involvement of the gustatory signaling pathway in the development of diet-induced obesity and the therapeutic potential of targeting TAS2Rs to induce body weight loss. α-gustducin-deficient (α-gust^-/-) mice became less obese than wild type (WT) mice when fed a high-fat diet (HFD). White adipose tissue (WAT) mass was lower in α-gust^-/- mice due to increased heat production as a result of increases in brown adipose tissue (BAT) thermogenic activity, involving increased protein expression of uncoupling protein 1. Intra-gastric treatment of obese WT and α-gust^-/- mice with the bitter agonists denatonium benzoate (DB) or quinine (Q) during 4 weeks resulted in an α-gustducin-dependent decrease in body weight gain associated with a decrease in food intake (DB), but not involving major changes in gut peptide release. Both WAT and 3T3-F442A pre-adipocytes express TAS2Rs. Treatment of pre-adipocytes with DB or Q decreased differentiation into mature adipocytes. In conclusion, interfering with the gustatory signaling pathway protects against the development of HFD-induced obesity presumably through promoting BAT activity. Intra-gastric bitter treatment inhibits weight gain, possibly by directly affecting adipocyte metabolism.