Prolonged breastfeeding protects from obesity by hypothalamic action of hepatic FGF21.

Early-life determinants are thought to be a major factor in the rapid increase of obesity. However, while maternal nutrition has been extensively studied, the effects of breastfeeding by the infant on the reprogramming of energy balance in childhood and throughout adulthood remain largely unknown. Here we show that delayed weaning in rat pups protects them against diet-induced obesity in adulthood, through enhanced brown adipose tissue thermogenesis and energy expenditure. In-depth metabolic phenotyping in this rat model as well as in transgenic mice reveals that the effects of prolonged suckling are mediated by increased hepatic fibroblast growth factor 21 (FGF21) production and tanycyte-controlled access to the hypothalamus in adulthood. Specifically, FGF21 activates GABA-containing neurons expressing dopamine receptor 2 in the lateral hypothalamic area and zona incerta. Prolonged breastfeeding thus constitutes a protective mechanism against obesity by affecting long-lasting physiological changes in liver-to-hypothalamus communication and hypothalamic metabolic regulation.

Circulating LEAP-2 is associated with puberty in girls.

BACKGROUND/OBJECTIVES: Liver-expressed antimicrobial peptide 2 (LEAP-2) was recently identified as an endogenous non-competitive allosteric antagonist of the growth hormone secretagogue receptor 1a (GHSR1a). LEAP-2 blunts ghrelin-induced feeding and its plasma levels are modulated in response to nutritional status in humans. Despite the relevant role of ghrelin in childhood, puberty, and childhood obesity, the potential implication of LEAP-2 in these aspects remains totally unknown. We aimed to investigate the regulation of circulating plasma LEAP-2 in childhood and adolescent either lean or obese. METHODS AND RESULTS: Plasma levels of LEAP-2 were analyzed in a cross-sectional study with lean and obese children and adolescents (n = 150). Circulating LEAP-2 levels were significantly higher in girls than in boys independently of whether they were obese or lean. In addition, LEAP-2 was significantly increased (p < 0.001) in pubertal than in prepubertal girls, while no changes were found in boys between both developmental stages. Moreover, in girls LEAP-2 was positively correlated with insulin, IGF-1, HOMA-IR and triglycerides and negatively with ghrelin. In boys, LEAP-2 was positively correlated with leptin and negatively with vitamin D levels. CONCLUSION: This study reveals a sexual dimorphism in LEAP-2 levels in children and adolescents. These changes and the higher levels during puberty imply that LEAP-2 may contribute to some of the biological adaptations occurring during pubertal development in terms of food intake, energy balance, growth rate, and puberty onset. Future studies assessing LEAP-2 levels in longitudinal studies and its implications in growth rate, puberty onset, and reproductive hormones will help to understand the relevance of this hormone in this stage of life.

Hypothalamic dopamine signaling regulates brown fat thermogenesis.

Dopamine signaling is a crucial part of the brain reward system and can affect feeding behavior. Dopamine receptors are also expressed in the hypothalamus, which is known to control energy metabolism in peripheral tissues. Here we show that pharmacological or chemogenetic stimulation of dopamine receptor 2 (D2R) expressing cells in the lateral hypothalamic area (LHA) and the zona incerta (ZI) decreases body weight and stimulates brown fat activity in rodents in a feeding-independent manner. LHA/ZI D2R stimulation requires an intact sympathetic nervous system and orexin system to exert its action and involves inhibition of PI3K in the LHA/ZI. We further demonstrate that, as early as 3 months after onset of treatment, patients treated with the D2R agonist cabergoline experience an increase in energy expenditure that persists for one year, leading to total body weight and fat loss through a prolactin-independent mechanism. Our results may provide a mechanistic explanation for how clinically used D2R agonists act in the CNS to regulate energy balance.

ANGPTL-4 is Associated with Obesity and Lipid Profile in Children and Adolescents.

Angiopoietin-like protein 4 (ANGPTL-4) regulates lipidic metabolism and affects energy homeostasis. However, its function in children with obesity remains unknown. We investigated plasma ANGPTL-4 levels in children and its relationship with body mass index (BMI) and different lipidic parameters such as free fatty acids (FFA). Plasma ANGPTL-4 levels were analyzed in two different cohorts. In the first cohort (n = 150, age 3-17 years), which included children with normal weight or obesity, we performed a cross-sectional study. In the second cohort, which included only children with obesity (n = 20, age 5-18 years) followed up for two years after an intervention for weight loss, in which we performed a longitudinal study measuring ANGPTL-4 before and after BMI-loss. In the cross-sectional study, circulating ANGPTL-4 levels were lower in children with obesity than in those with normal weight. Moreover, ANGPTL-4 presented a negative correlation with BMI, waist circumference, weight, insulin, homeostasis model assessment of insulin resistance index (HOMA index), triglycerides, and leptin, and a positive correlation with FFA and vitamin-D. In the longitudinal study, the percent change in plasma ANGPTL-4 was correlated with the percent change in FFA, total-cholesterol and high-density lipoprotein cholesterol. This study reveals a significant association of ANGPTL-4 with pediatric obesity and plasma lipid profile.

Uroguanylin Improves Leptin Responsiveness in Diet-Induced Obese Mice.

The gastrointestinal-brain axis is a key mediator of the body weight and energy homeostasis regulation. Uroguanylin (UGN) has been recently proposed to be a part of this gut-brain axis regulating food intake, body weight and energy expenditure. Expression of UGN is regulated by the nutritional status and dependent on leptin levels. However, the exact molecular mechanisms underlying this UGN-leptin metabolic regulation at a hypothalamic level still remains unclear. Using leptin resistant diet-induced obese (DIO) mice, we aimed to determine whether UGN could improve hypothalamic leptin sensitivity. The present work demonstrates that the central co-administration of UGN and leptin potentiates leptin's ability to decrease the food intake and body weight in DIO mice, and that UGN activates the hypothalamic signal transducer and activator of transcription 3 (STAT3) and phosphatidylinositide 3-kinases (PI3K) pathways. At a functional level, the blockade of PI3K, but not STAT3, blunted UGN-mediated leptin responsiveness in DIO mice. Overall, these findings indicate that UGN improves leptin sensitivity in DIO mice.

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.

Plasma ANGPTL-4 is Associated with Obesity and Glucose Tolerance: Cross-Sectional and Longitudinal Findings.

SCOPE: Angiopoietin-like protein 4 (ANGPTL-4) regulates plasma lipoprotein levels, but its relevance in human obesity and type 2 diabetes (T2D) is largely unknown. We aim to investigate the regulation of circulating ANGPTL-4 levels in obesity, T2D, and after changes in body weight. METHODS AND RESULTS: Circulating ANGPTL-4 levels were measured in two different cohorts. First, in a cross-sectional study, we evaluated ANGPTL-4 levels in lean and obese patients with normoglycemia or with altered glucose tolerance (AGT; n = 282). Second, in a longitudinal intervention study, 51 obese participants were evaluated. A hypocaloric diet was prescribed, with follow-up 2 years later. ANGPTL-4 levels were significantly increased in obese patients with AGT compared to lean participants. Moreover, ANGPTL-4 was positively correlated with BMI, waist circumference, fat mass, HbA1c, HOMA-IR, fasting triglycerides, and with inflammatory markers. Participants gaining weight after the follow-up showed increased ANGPTL-4 levels in parallel to increased BMI, fat mass, and fasting glucose, while ANGPTL-4 levels were reduced in participants losing weight. CONCLUSION: Our data support a relevant role of ANGPTL-4 in human obesity and its involvement in long-term body weight changes.

Pharmacological inhibition of cannabinoid receptor 1 stimulates gastric release of nesfatin-1 via the mTOR pathway.

AIM: To determine whether Nucb2/nesfatin1 production is regulated by the cannabinoid system through the intracellular mTOR pathway in the stomach. METHODS: Sprague Dawley rats were treated with vehicle, rimonabant, rapamycin or rapamycin+rimonabant. Gastric tissue obtained from the animals was used for biochemical assays: Nucb2 mRNA measurement by real time PCR, gastric Nucb2/nesfatin protein content by western blot, and gastric explants to obtain gastric secretomes. Nucb2/nesfatin levels were measured in gastric secretomes and plasma using enzyme-linked immunosorbent assay. RESULTS: The inhibition of cannabinoid receptor 1 (CB1) by the peripheral injection of an inverse agonist, namely rimonabant, decreases food intake and increases the gastric secretion and circulating levels of Nucb2/nesfatin-1. In addition, rimonabant treatment activates mTOR pathway in the stomach as showed by the increase in pmTOR/mTOR expression in gastric tissue obtained from rimonabant treated animals. These effects were confirmed by the use of a CB1 antagonist, AM281. When the intracellular pathway mTOR/S6k was inactivated by chronic treatment with rapamycin, rimonabant treatment was no longer able to stimulate the gastric secretion of Nucb2/nesfatin-1. CONCLUSION: The peripheral cannabinoid system regulates food intake through a mechanism that implies gastric production and release of Nucb2/Nesfatin-1, which is mediated by the mTOR/S6k pathway.

Visceral and subcutaneous adipose tissue express and secrete functional alpha2hsglycoprotein (fetuin a) especially in obesity.

The secretion of the hepatokine alpha-2-Heremans-Schmid glycoprotein/Fetuin A, implicated in pathological processes including systemic insulin resistance, by adipose tissue has been recently described. Thus, we have recently identified its presence in white adipose tissue secretomes by mass spectrometry. However, the secretion pattern and function of adipose-derived alpha-2-Heremans-Schmid glycoprotein are poorly understood. The aim of this study is to evaluate the expression and secretion of total and active phosphorylated alpha-2-Heremans-Schmid glycoprotein by adipose tissue from visceral and subcutaneous localizations in animals at different physiological and nutritional status including anorexia and obesity. Alpha-2-Heremans-Schmid glycoprotein expression and secretion in visceral adipose tissue and subcutaneous adipose tissue explants from animals under fasting and exercise training, at pathological situations such as anorexia and obesity, and from human obese individuals were assayed by immunoblotting, quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay. We reveal that visceral adipose tissue expresses and secretes more alpha-2-Heremans-Schmid glycoprotein than subcutaneous adipose tissue, and that this secretion is diminished after fasting and exercise training. Visceral adipose tissue from anorectic animals showed reduced alpha-2-Heremans-Schmid glycoprotein secretion; on the contrary, alpha-2-Heremans-Schmid glycoprotein is over-secreted by visceral adipose tissue in the occurrence of obesity. While secretion of active-PhophoSer321α2HSG by visceral adipose tissue is independent of body mass index, we found that the fraction of active-alpha-2-Heremans-Schmid glycoprotein secreted by subcutaneous adipose tissue increments significantly in situations of obesity. Functional studies show that the inhibition of adipose-derived alpha-2-Heremans-Schmid glycoprotein increases insulin sensitivity in differentiated adipocytes. In conclusion, visceral adipose tissue secretes more alpha-2-Heremans-Schmid glycoprotein than subcutaneous adipose tissue and this secretion is more sensitive to nutritional and physiological changes. The over-secretion of alpha-2-Heremans-Schmid glycoprotein by visceral adipose tissue, the increased secretion of the active phosphorylated form by subcutaneous adipose tissuein obese animals, and the adipose-derived alpha-2-Heremans-Schmid glycoprotein capacity to inhibit the insulin pathway suggest the participation of adipose-derived alpha-2-Heremans-Schmid glycoprotein in the deleterious effects of obesity.

Regulation of Growth Hormone by the Splanchnic Area.

The regulation of growth hormone (GH) was traditionally thought to be under the control of two main hypothalamic neuropeptides; GH-releasing hormone and somatostatin. In 1999, with the isolation of ghrelin, as a gastric-derived peptide with potent GH-releasing activity, concept of regulation of the somatotropic axis completely changed. In addition to its GH-releasing activity, ghrelin exhibited the capacity to modulate food intake and body weight. The role of this splanchnic factor in regulating GH as a nexus of energy balance control and GH are explored in this chapter. From a physiological standpoint, a novel mechanism of GH regulation mediated by ghrelin exists, implicating the peripheral modulation of the cannabinoid receptor.

Comparative secretome analysis of rat stomach under different nutritional status.

The fact that gastric surgery is at the moment the most effective treatment to fight against obesity highlights the relevance of gastric derived proteins as potential targets to treat this pathology. Taking advantage of a previously established gastric explant model for endocrine studies, the proteomic analysis of gastric secretome was performed. To validate this gastric explant system for proteomic analysis, the identification of ghrelin, a classical gastric derived peptide, was performed by MS. In addition, the differential analysis of gastric secretomes under differential nutritional status (control feeding vs fasting vs re-feeding) was performed. The MS identified proteins are showed in the present manuscript. The data supplied in this article is related to the research article entitled "Comparative secretome analysis of rat stomach under different nutritional status" [1].

Circulating Betatrophin Levels Are Increased in Anorexia and Decreased in Morbidly Obese Women.

CONTEXT: Betatrophin is produced primarily by liver and adipose tissue and has been recently reported as a novel hormone promoting ß-cell proliferation and ß-cell mass and improving glucose tolerance. OBJECTIVE: Because it is markedly regulated by nutritional status, we hypothesized that circulating betatrophin levels might be affected by pathophysiological conditions altering body weight. SETTING AND PATIENTS: We analyzed circulating betatrophin levels in 149 female patients, including 99 with extreme body mass index (30 anorexia nervosa, 24 obese, 45 morbid obese, and 50 healthy eating/weight controls). OUTCOME MEASUREMENTS: Serum betatrophin levels and its correlations with different anthropometric and biochemical parameters were measured. RESULTS: Plasma betatrophin levels were significantly elevated in anorexic patients, whereas its levels were reduced in morbidly obese women when compared with normal-weight women. Plasma betatrophin correlated negatively with weight, body mass index, fat percentage, glucose, insulin, and homeostatic model assessment index and positively correlated with high-density lipoprotein. CONCLUSIONS: These results suggest that metabolic status is an important regulator of circulating betatrophin levels.

Peripheral signals mediate the beneficial effects of gastric surgery in obesity.

Obesity is nowadays a public health problem both in the industrialized world and developing countries. The different treatments to fight against obesity are not very successful with the exception of gastric surgery. The mechanism behind the achievement of this procedure remains unclear although the modifications in the pattern of gastrointestinal hormones production appear to be responsible for the beneficial effect. The gastrointestinal tract has emerged in the last time as an endocrine organ in charge of response to the different stimulus related to nutritional status by the modulation of more than 30 signals acting at central level to modulate food intake and body weight. The production of some of these gastric derived signals has been proved to be altered in obesity (ghrelin, CCK, and GLP-1). In fact, bariatric surgery modifies the production of both gastrointestinal and adipose tissue peripheral signals beyond the gut microbiota composition. Through this paper the main peripheral signals altered in obesity will be reviewed together with their modifications after bariatric surgery.

Regulation of NUCB2/nesfatin-1 production in rat's stomach and adipose tissue is dependent on age, testosterone levels and lactating status.

Nesfatin-1, which is derived from the NEFA/nucleobindin 2 (NUCB2) precursor, was recently identified as an anorexigenic peptide that is produced in several tissues including the hypothalamus. Currently, no data exist regarding the regulation of NUCB2/nesfatin-1 production in peripheral tissues, such as gastric mucosa and adipose tissue, through different periods of development. The aim of the present work was to study the variations on circulating levels, mRNA expression and tissue content in gastric mucosa and adipose tissue of NUCB2/nesfatin-1 with age and specially in two clue periods of maturation, weaning and puberty. The weaning period affected NUCB2/nesfatin-1 production in gastric tissue. The testosterone changes associated with the initiation of puberty regulated NUCB2/nesfatin-1 production via adipose tissue and gastric NUCB2/nesfatin-1 production. In conclusion, the production of NUCB2/nesfatin-1 by the stomach and adipose tissue fluctuates with age to regulate energy homeostasis during different states of development.

Comparative secretome analysis of rat stomach under different nutritional status.

Obesity is a major public health threat for many industrialised countries. Bariatric surgery is the most effective treatment against obesity, suggesting that gut derived signals are crucial for energy balance regulation. Several descriptive studies have proven the presence of gastric endogenous systems that modulate energy homeostasis; however, these systems and the interactions between them are still not well known. In the present study, we show for the first time the comparative 2-DE gastric secretome analysis under different nutritional status. We have identified 38 differently secreted proteins by comparing stomach secretomes from tissue explant cultures of rats under feeding, fasting and re-feeding conditions. Among the proteins identified, glyceraldehyde-3-phosphate dehydrogenase was found to be more abundant in gastric secretome and plasma after re-feeding, and downregulated in obesity. Additionally, two calponin-1 species were decreased in feeding state, and other were modulated by nutritional and metabolic conditions. These and other secreted proteins identified in this work may be considered as potential gastrokines implicated in food intake regulation. BIOLOGICAL SIGNIFICANCE: The present work has an important impact in the field of obesity, especially in the regulation of body weight maintenance by the stomach. Nowadays, the most effective treatment in the fight against obesity is bariatric surgery, which suggests that stomach derived signals might be crucial for the regulation of the energy homeostasis. However, until now, the knowledge about the gastrokines and its mechanism of action has been poorly elucidated. In the present work, we had updated a previously validated explant secretion model for proteomic studies; this analysis allowed us, for the first time, to study the gastric secretome without interferences from other organs. We had identified 38 differently secreted proteins comparing ex vivo cultured stomachs from rats under feeding, fasting and re-feeding regimes. The results in the present article provide novel targets to study the role of the stomach in body weight and appetite regulation, and suggest new potential therapeutic targets for treating obesity.

The gastric CB1 receptor modulates ghrelin production through the mTOR pathway to regulate food intake.

Over the years, the knowledge regarding the relevance of the cannabinoid system to the regulation of metabolism has grown steadily. A central interaction between the cannabinoid system and ghrelin has been suggested to regulate food intake. Although the stomach is the main source of ghrelin and CB1 receptor expression in the stomach has been described, little information is available regarding the possible interaction between the gastric cannabinoid and ghrelin systems in the integrated control of energy homeostasis. The main objective of the present work was to assess the functional interaction between these two systems in terms of food intake using a combination of in vivo and in vitro approaches. The present work demonstrates that the peripheral blockade of the CB1 receptor by rimonabant treatment decreased food intake but only in food-deprived animals. This anorexigenic effect is likely a consequence of decreases in gastric ghrelin secretion induced by the activation of the mTOR/S6K1 intracellular pathway in the stomach following treatment with rimonabant. In support of this supposition, animals in which the mTOR/S6K1 intracellular pathway was blocked by chronic rapamycin treatment, rimonabant had no effect on ghrelin secretion. Vagal communication may also be involved because rimonabant treatment was no longer effective when administered to animals that had undergone surgical vagotomy. In conclusion, to the best of our knowledge, the present work is the first to describe a CB1 receptor-mediated mechanism that influences gastric ghrelin secretion and food intake through the mTOR pathway.

FNDC5/irisin is not only a myokine but also an adipokine.

Exercise provides clear beneficial effects for the prevention of numerous diseases. However, many of the molecular events responsible for the curative and protective role of exercise remain elusive. The recent discovery of FNDC5/irisin protein that is liberated by muscle tissue in response to exercise might be an important finding with regard to this unsolved mechanism. The most striking aspect of this myokine is its alleged capacity to drive brown-fat development of white fat and thermogenesis. However, the nature and secretion form of this new protein is controversial. The present study reveals that rat skeletal muscle secretes a 25 kDa form of FNDC5, while the 12 kDa/irisin theoretical peptide was not detected. More importantly, this study is the first to reveal that white adipose tissue (WAT) also secretes FNDC5; hence, it may also behave as an adipokine. Our data using rat adipose tissue explants secretomes proves that visceral adipose tissue (VAT), and especially subcutaneous adipose tissue (SAT), express and secrete FNDC5. We also show that short-term periods of endurance exercise training induced FNDC5 secretion by SAT and VAT. Moreover, we observed that WAT significantly reduced FNDC5 secretion in fasting animals. Interestingly, WAT of obese animals over-secreted this hormone, which might suggest a type of resistance. Because 72% of circulating FNDC5/irisin was previously attributed to muscle secretion, our findings suggest a muscle-adipose tissue crosstalk through a regulatory feedback mechanism.

Muscle tissue as an endocrine organ: comparative secretome profiling of slow-oxidative and fast-glycolytic rat muscle explants and its variation with exercise.

The notion that skeletal muscle is a secretory organ capable to release proteins that can act locally in an autocrine/paracrine manner or even in an endocrine manner to communicate with distant tissues has now been recognized. Under this context, a new paradigm has arisen implicating the muscle in metabolism regulation. Considering the evidences that give exercise a protective role against illnesses associated to physical inactivity, it becomes of especial relevance to characterize muscle secreted proteins. In the present study we show for the first time the secretome characterization and the comparative 2-DE secretome analysis among fast-glycolytic (gastrocnemius) and slow-oxidative (soleus) rat muscle explants and its variation after exercise intervention. We have identified 19 differently secreted proteins when comparing soleus and gastrocnemius secretomes, and 10 in gastrocnemius and 17 in soleus distinctive secreted proteins after 1 week of endurance exercise training. Among identified proteins, DJ-1 was found to be more abundant in fast-glycolytic fiber secretomes. On the contrary, FABP-3 was elevated in slow-oxidative fiber secretomes, although its secretion from gastrocnemius muscle increased in exercised animals. These and other secreted proteins identified in this work may be considered as potential myokines.

Secretome analysis of rat adipose tissues shows location-specific roles for each depot type.

Obesity prevalence is reaching pandemic proportions becoming a major public health threat for many industrialized nations. It is especially worrying as it causes a higher risk of premature death due to associated diseases such as type 2 diabetes, cardiovascular disease, and some cancers. Current evidence shows biological and genetic differences between adipose tissues depending on its anatomical location. Particularly, upper body/visceral fat distribution in obesity is closely linked to metabolic complications. In this report, we characterize for the first time the secretome of rat adipose tissue explants from different anatomical localizations and its differential analysis. Visceral, subcutaneous, and gonadal fat specific secretomes and differentially secreted proteins among the three fat depots were analyzed by 2-DE and MS. Reference maps for location-specific adipose tissue secretomes are shown and the 45 most significant differences are listed. Identified proteins include classical adipokines and novel secreted proteins. Interestingly, our results show that the type of proteins and their role in different biological processes diverge significantly when comparing the set of proteins identified from visceral, subcutaneous and gonadal fat explants. This study emphasizes and supports the differential role of adipose tissue in accordance to its anatomical localization.