Gut hormones: a weight off your mind

Molecular Mechanism Contributing to Malnutrition and Sarcopenia in Patients with Liver Cirrhosis

Liver cirrhosis is frequently accompanied by disease-related malnutrition (DRM) and sarcopenia, defined as loss of skeletal muscle mass and function. DRM and sarcopenia often coexist in cirrhotic patients and are associated with increased morbidity and mortality. The clinical manifestation of both comorbidities are triggered by multifactorial mechanisms including reduced nutrient and energy intake caused by dietary restrictions, anorexia, neuroendocrine deregulation, olfactory and gustatory deficits. Maldigestion and malabsorption due to small intestinal bacterial overgrowth, pancreatic insufficiency or cholestasis may also contribute to DRM and sarcopenia. Decreased protein synthesis and increased protein degradation is the cornerstone mechanism to muscle loss, among others mediated by disease- and inflammation-mediated metabolic changes, hyperammonemia, increased myostatin and reduced human growth hormone. The concise pathophysiological mechanisms and interactions of DRM and sarcopenia in liver cirrhosis are not completely understood. Furthermore, most knowledge in this field are based on experimental models, but only few data in humans exist. This review summarizes known and proposed molecular mechanisms contributing to malnutrition and sarcopenia in liver cirrhosis and highlights remaining knowledge gaps. Since, in the prevention and treatment of DRM and sarcopenia in cirrhotic patients, more research is needed to identify potential biomarkers for diagnosis and development of targeted therapeutic strategies.

Recent advances in clinical practice challenges and opportunities in the management of obesity

Despite advances in understanding the roles of adiposity, food intake, GI and adipocyte-related hormones, inflammatory mediators, the gut-brain axis and the hypothalamic nervous system in the pathophysiology of obesity, the effects of different therapeutic interventions on those pathophysiological mechanisms are controversial. There are still no low-cost, safe, effective treatments for obesity and its complications. Currently, bariatric surgical approaches targeting the GI tract are more effective than non-surgical approaches in inducing weight reduction and resolving obesity-related comorbidities. However, current guidelines emphasise non-surgical approaches through lifestyle modification and medications to achieve slow weight loss, which is not usually sustained and may be associated with medication-related side effects. This review analyses current central, peripheral or hormonal targets to treat obesity and addresses challenges and opportunities to develop novel approaches for obesity.

Hypoxia, energy balance and obesity: from pathophysiological mechanisms to new treatment strategies

High altitude exposure is often accompanied by weight loss. Postulated mechanisms are a reduction of nutritional energy intake, a reduction of intestinal energy uptake from impaired intestinal function and increased energy expenditure. Beyond the field of altitude, there are good reasons for renewed interest in the relationship between hypoxia and energy balance. The increasing prevalence of obesity and associated comorbidities represent a major health concern. Obesity is frequently associated with sleep disorders leading to intermittent systemic hypoxia with deleterious cardiovascular and metabolic consequences. Hypoxic regions may be present within hypertrophic white adipose tissue leading to chronic systemic inflammation. Among the increasing number of people commuting to altitude for work or leisure, obesity is a risk factor for acute mountain sickness. Paradoxically, exposure to intermittent hypoxia might be considered as a means to lose body mass and to improve metabolic risk factors. Daytime exposure to intermittent hypoxia has been used to treat hypertension in former Soviet Union countries and is now being experimented elsewhere. Such intermittent hypoxic exposure at rest or during exercise may lead to improvement in body composition and health status with improved exercise tolerance, metabolism and systemic arterial pressure. Future research should confirm whether hypoxic training could be a new treatment strategy for weight loss and comorbidities in obese subjects and elucidate the underlying mechanisms and signalling pathways.

Vitamin D receptor activation induces peptide YY transcription in pancreatic islets

Peptide YY (PYY) is a peptide hormone secreted from L cells in the intestine after food intake and regulates appetite and intestinal function. PYY is also expressed in the pancreas, but the mechanisms of regulation of pancreatic PYY expression have not been elucidated. The vitamin D receptor (VDR) is a nuclear receptor for the active form of vitamin D(3) and regulates numerous physiological processes. Because VDR is expressed in the pancreas, we investigated the role of pancreatic VDR activation and found that Pyy is a VDR target gene in the mouse pancreas. Treatment of mice with 1α-hydroxyvitamin D(3) increased plasma PYY levels. VDR activation increased mRNA and protein expression of PYY in the pancreatic islets of mice and pancreatic endocrine cell lines but did not change intestinal PYY expression. 1α-Hydroxyvitamin D(3)-dependent induction of pancreatic and plasma PYY was abolished in VDR-null mice. We identified a functional vitamin D-responsive element in the mouse Pyy promoter using chromatin immunoprecipitation assay, EMSA, and luciferase promoter assay. Thus, Pyy is a tissue-specific VDR target gene. The pancreatic VDR-PYY pathway may mediate a regulatory function of vitamin D in the neuroendocrine system.

Effects of JNJ-38431055, a novel GPR119 receptor agonist, in randomized, double-blind, placebo-controlled studies in subjects with type 2 diabetes

AIM

G-protein coupled receptor agonists are currently under investigation for their potential utility in patients with type 2 diabetes mellitus (T2DM). The objective was to determine the pharmacokinetics, pharmacodynamics, safety and tolerability of GPR119 agonist, JNJ-38431055 in T2DM subjects.

METHODS

This was a randomized, double-blind, placebo- and positive-controled, single-dose cross-over study and a randomized, double-blind, placebo-controled multiple-dose parallel design study. The study was conducted at 4 US research centres. Two different experiments involving 25 and 32 different subjects were performed in male and female subjects, aged 25-60 years, mean body mass index between 22 and 39.9 kg/m2 who had T2DM diagnosed 6 months to 10 years before screening. JNJ-38431055 (100 and 500 mg) or sitagliptin (100 mg) as a single-dose or JNJ-38431055 (500 mg) once daily for 14 consecutive days were tested. Effects on stimulated plasma glucose, insulin, C-peptide and incretin concentrations were pre-specified outcomes.

RESULTS

JNJ-38431055 was well tolerated and not associated with hypoglycaemia. Plasma systemic exposure of JNJ-38431055 increased as the dose increased, was approximately two-fold greater after multiple-dose administration, and attained steady-state after approximately 8 days. Compared with placebo, single-dose administration of oral JNJ-38431055 decreased glucose excursion during an oral glucose tolerance test, but multiple-dose administration did not alter 24-h weighted mean glucose. Multiple dosing of JNJ-38431055 increased post-meal total glucagon-like peptide 1 and gastric insulinotropic peptide concentrations compared to baseline.

CONCLUSIONS

These studies provide evidence of limited glucose lowering and incretin activity for JNJ-38431055 in subjects with T2DM.

Correlations of circulating peptide YY and ghrelin with body weight, rate of weight gain, and time required to achieve the recommended daily intake in preterm infants

The objective was to elucidate the relationships between serum concentrations of the gut hormone peptide YY (PYY) and ghrelin and growth development in infants for potential application to the clinical observation index. Serum concentrations of PYY and ghrelin were measured using radioimmunoassay from samples collected at the clinic. For each patient, gestational age, birth weight, time required to return to birth weight, rate of weight gain, time required to achieve recommended daily intake (RDI) standards, time required for full-gastric feeding, duration of hospitalization, and time of administration of total parenteral nutrition were recorded. Serum PYY and ghrelin concentrations were significantly higher in the preterm group (N = 20) than in the full-term group (N = 20; P < 0.01). Within the preterm infant group, the serum concentrations of PYY and ghrelin on postnatal day (PND) 7 (ghrelin = 1485.38 ± 409.24; PYY = 812.37 ± 153.77 ng/L) were significantly higher than on PND 1 (ghrelin = 956.85 ± 223.09; PYY = 545.27 ± 204.51 ng/L) or PND 3 (ghrelin = 1108.44 ± 351.36; PYY = 628.96 ± 235.63 ng/L; P < 0.01). Both serum PYY and ghrelin concentrations were negatively correlated with body weight, and the degree of correlation varied with age. Serum ghrelin concentration correlated negatively with birth weight and positively with the time required to achieve RDI (P < 0.05). In conclusion, serum PYY and ghrelin concentrations reflect a negative energy balance, predict postnatal growth, and enable compensation. Further studies are required to elucidate the precise concentration and roles of PYY and ghrelin in newborns and to determine the usefulness of measuring these hormones in clinical practice.

Circulating ghrelin and GLP-1 are not affected by habitual diet

BACKGROUND

Ghrelin and glucagon-like peptide-1 (GLP-1) are gut hormones known to induce hunger and satiety, respectively. Current knowledge about the effects of different macronutrients on circulating ghrelin and GLP-1 comes mainly from acute test meals, whereas little is known about the effects of chronic dietary intake on gut hormone secretion. This study was designed to examine whether 8-week habituation to diets with different percentages of carbohydrate and fat would affect serum ghrelin, GLP-1, and subjective hunger in a postabsorptive state and in response to a standard liquid mixed meal.

METHODS

Sixty-one overweight men and women were provided all food for 8 weeks of either a higher-carbohydrate/lower-fat diet (High-CHO/Low-FAT; 55% CHO, 18% PRO, 27% FAT) or a lower-carbohydrate/higher-fat diet (Low-CHO/High-FAT; 43% CHO, 18% PRO, 39% FAT). After overnight fasts at baseline and week 8, participants consumed a standard liquid meal (7 kcals/kg, 58.6% CHO, 17.4% PRO, 24% FAT). Blood was sampled before the meal and at 15, 60, 90, 120, 180, and 240 min to determine total serum ghrelin and active GLP-1. Hunger was assessed by a visual analog scale. Mixed models were used to evaluate whether the temporal patterns of total serum ghrelin and active GLP-1 differed with diet.

RESULTS

Although both diet groups reported greater hunger after 8 weeks (p=0.03), circulating ghrelin and GLP-1 were not affected by acclimation to different macronutrients.

CONCLUSION

Habituation to different diets does not appear to influence fasting ghrelin, fasting GLP-1, or responses of these gut hormones to a standard meal.

Duration of lactation and maternal adipokines at 3 years postpartum

OBJECTIVE

Lactation has been associated with reduced maternal risk of type 2 diabetes, the metabolic syndrome, and cardiovascular disease. We examined the relationship between breastfeeding duration and maternal adipokines at 3 years postpartum.

RESEARCH DESIGN AND METHODS

We used linear regression to relate the duration of lactation to maternal leptin, adiponectin, ghrelin, and peptide YY (PYY) at 3 years postpartum among 570 participants with 3-year postpartum blood samples (178 fasting), prospectively collected lactation history, and no intervening pregnancy in Project Viva, a cohort study of mothers and children.

RESULTS

A total of 88% of mothers had initiated breastfeeding, 26% had breastfed ≥ 12 months, and 42% had exclusively breastfed for ≥ 3 months. In multivariate analyses, we found that duration of total breastfeeding was directly related to PYY and ghrelin, and exclusive breastfeeding duration was directly related to ghrelin (predicted mean for never exclusively breastfeeding: 790.6 pg/mL vs. ≥ 6 months of exclusive breastfeeding: 1,008.1 pg/mL; P < 0.01) at 3 years postpartum, adjusting for pregravid BMI, gestational weight gain, family history of diabetes, parity, smoking status, and age. We found a nonlinear pattern of association between exclusive breastfeeding duration and adiponectin in multivariate-adjusted models.

CONCLUSIONS

In this prospective cohort study, we found a direct relationship between the duration of lactation and both ghrelin and PYY at 3 years postpartum.

Nesfatin-1: a novel inhibitory regulator of food intake and body weight

The protein nucleobindin 2 (NUCB2) or NEFA (DNA binding/EF-hand/acidic amino acid rich region) was identified over a decade ago and implicated in intracellular processes. New developments came with the report that post-translational processing of hypothalamic NUCB2 may result in nesfatin-1, nesfatin-2 and nesfatin-3 and convergent studies showing that nesfatin-1 and full length NUCB2 injected in the brain potently inhibit the dark phase food intake in rodents including leptin receptor deficient Zucker rats. Nesfatin-1 also reduces body weight gain, suggesting a role as a new anorexigenic factor and modulator of energy balance. In light of the obesity epidemic and its associated diseases, underlying new mechanisms regulating food intake may be promising targets in the drug treatment of obese patients particularly as the vast majority of them display reduced leptin sensitivity or leptin resistance while nesfatin-1's mechanism of action is leptin independent. Although much progress on the localization of NUCB2/nesfatin-1 in the brain and periphery as well as on the understanding of nesfatin-1's anorexic effect have been achieved during the past three years, several important mechanisms have yet to be unraveled such as the identification of the nesfatin-1 receptor and the regulation of NUCB2 processing and nesfatin-1 release.

Therapeutic potential of neuropeptide Y (NPY) receptor ligands

Neuropeptide Y (NPY) is widely distributed in the human body and contributes to a vast number of physiological processes. Since its discovery, NPY has been implicated in metabolic regulation and, although interest in its role in central mechanisms related to food intake and obesity has somewhat diminished, the topic remains a strong focus of research concerning NPY signalling. In addition, a number of other uses for modulators of NPY receptors have been implied in a range of diseases, although the development of NPY receptor ligands has been slow, with no clinically approved receptor therapeutics currently available. Nevertheless, several interesting small molecule compounds, notably Y2 receptor antagonists, have been published recently, fueling optimism in the field. Herein we review the role of NPY in the pathophysiology of a number of diseases and highlight instances where NPY receptor signalling systems are attractive therapeutic targets.

Peptide hormones regulating appetite--focus on neuroimaging studies in humans

In recent years, knowledge about hormonal feedback from the gastrointestinal tract and adipose tissue has increased tremendously. Peptide hormones modulating hunger have been intensively studied, mostly in animals but increasingly also in humans. The first therapeutic agents, such as GLP-1 analogues, are in successful clinical use for T2D and may beneficially affect hunger and reduce weight. Data from in vitro studies and animals provide detailed insight into regulatory mechanisms leading to peptide secretion and receptor bindings, as well as to the distribution of receptors involved in different parts of the body. With neuroimaging techniques human brain structures have been identified that play a role in hunger, satiety and eating behaviour. These include the primary gustatory (insular) and olfactory (pyriform) cortex and regions with a highly permeable blood-brain barrier (hypothalamus, brain stem), which facilitates humoral input via gut peptides and leptin. In addition, cerebral networks involved in higher cognitive functions, especially those relevant to reward, pleasure and also addiction (ventral and dorsal striatum, amygdala, orbitofrontal cortex (OFC), prefrontal cortex (PFC)) were shown to be involved. First indications of direct influences of peptide hormones on these networks have become available from neuroimaging studies administrating synthetic PYY, ghrelin and leptin. Insulin also appears to play an important role as a central satiety hormone, and evidence indicating the possibility of central insulin resistance in obesity is available.

Gut-brain cross-talk in appetite regulation

PURPOSE OF REVIEW

To review the role of gut hormones involved in appetite regulation and their potential in the treatment of obesity.

RECENT FINDINGS

The medical treatment of obesity has been fraught with challenges. With two centrally acting agents having been recently withdrawn from the market, new therapies are required. The gut hormones are especially promising therapeutic targets. This article looks at the interplay between gut and brain which mediates the regulation of appetite and energy expenditure. Some recent developments that point the way towards the future development of gut hormone analogues as treatments for obesity are reviewed.

SUMMARY

Our understanding of the interaction between gut hormones and the neuronal circuits controlling appetite regulation has made great advances over recent years. This knowledge is essential if these peptides are to become potential obesity therapies, both from an efficacy and safety perspective.

Metabolic signals in human puberty: effects of over and undernutrition

Puberty in mammals is associated with important physical and psychological changes due to the increase in sex steroids and growth hormone (GH). Indeed, an increase in growth velocity and the attainment of sexual maturity for future reproductive function are the hallmark changes during this stage of life. Both growth and reproduction consume high levels of energy, requiring suitable energy stores to face these physiological functions. During the last two decades our knowledge concerning how peptides produced in the digestive tract (in charge of energy intake) and in adipose tissue (in charge of energy storage) provide information regarding metabolic status to the central nervous system (CNS) has increased dramatically. Moreover, these peptides have been shown to play an important role in modulating the gonadotropic axis with their absence or an imbalance in their secretion being able to disturb pubertal onset or progression. In this article we will review the current knowledge concerning the role played by leptin, the key adipokine in energy homeostasis, and ghrelin, the only orexigenic and growth-promoting peptide produced by the digestive tract, on sexual development. The normal evolutionary pattern of these peripherally produced metabolic signals throughout human puberty will be summarized. The effect of two opposite situations of chronic malnutrition, obesity and anorexia, on these signals and how they influence the course of puberty will also be discussed. Finally, we will briefly mention other peptides derived from the digestive tract (such as PYY) that may be involved in the regulatory link between energy homeostasis and sexual development.

Taspoglutide, a novel human once-weekly analogue of glucagon-like peptide-1, improves glucose homeostasis and body weight in the Zucker diabetic fatty rat

AIM

Glucagon-like peptide-1 (GLP-1) receptor agonists are a novel class of pharmacotherapy for type 2 diabetes. We investigated the effects of a novel, long-acting human GLP-1 analogue, taspoglutide, in the Zucker diabetic fatty (ZDF) rat, an animal model of type 2 diabetes.

METHODS

Blood glucose and plasma levels of insulin, peptide YY (PYY), glucose-dependent insulinotropic polypeptide (GIP) and triglycerides were measured during oral glucose tolerance tests (oGTT) conducted in ZDF rats treated acutely or chronically with a single long-acting dose of taspoglutide. Pioglitazone was used as a positive control in the chronic study. Postprandial glucose, body weight, glycaemic control and insulin sensitivity were assessed over 21 days in chronically treated animals.

RESULTS

Acute treatment with taspoglutide reduced glucose excursion and increased insulin response during oGTT. In chronically treated rats, glucose excursion and levels of GIP, PYY and triglycerides during oGTT on day 21 were significantly reduced. Postprandial glucose levels were significantly lower than vehicle controls by day 15. A significant reduction in body weight gain was noticed by day 8, and continued until the end of the study when body weight was approximately 7% lower in rats treated with taspoglutide compared to vehicle. Glycaemic control (increased levels of 1,5-anhydroglucitol) and insulin sensitivity (Matsuda index) were improved by taspoglutide treatment.

CONCLUSIONS

Taspoglutide showed typical effects of native GLP-1, with improvement in glucose tolerance, postprandial glucose, body weight, glycaemic control and insulin sensitivity.

Peptide YY is critical for acylethanolamine receptor Gpr119-induced activation of gastrointestinal mucosal responses

Peptide YY (PYY) is released following food intake and regulates intestinal function and glucose homeostasis, but the mechanisms underpinning these processes are unclear. Enteroendocrine L cells contain PYY and express the acylethanolamine receptor, Gpr119. Here, we show that Gpr119 activation inhibited epithelial electrolyte secretion in human and mouse colon in a glucose-sensitive manner. Endogenous PYY selectively mediated these effects, since PYY(-/-) mice showed no Gpr119 response, but responses were observed in NPY(-/-) mice. Importantly, Gpr119 responses in wild-type (WT) mouse tissue and human colon were abolished by Y(1) receptor antagonism, but were not enhanced by dipeptidylpeptidase IV blockade, indicating that PYY processing to PYY(3-36) was not important. In addition, Gpr119 agonism reduced glycemic excursions after oral glucose delivery to WT mice but not PYY(-/-) mice. Taken together, these data demonstrate a previously unrecognized role of PYY in mediating intestinal Gpr119 activity and an associated function in controlling glucose tolerance.

Nesfatin-1--role as possible new potent regulator of food intake

Nesfatin-1 is an 82 amino acid peptide recently discovered in the brain which is derived from nucleobindin2 (NUCB2), a protein that is highly conserved across mammalian species. Nesfatin-1 has received much attention over the past two years due to its reproducible food intake-reducing effect that is linked with recruitment of other hypothalamic peptides regulating feeding behavior. A growing amount of evidence also supports that various stressors activate fore- and hindbrain NUCB2/nesfatin-1 circuitries. In this review, we outline the central nervous system distribution of NUCB2/nesfatin-1, and recent developments on the peripheral expression of NUCB2/nesfatin-1, in particular its co-localization with ghrelin in gastric X/A-like cells and insulin in ss-cells of the endocrine pancreas. Functional studies related to the characteristics of nesfatin-1's inhibitory effects on dark phase food intake are detailed as well as the central activation of NUCB2/nesfatin-1 immunopositive neurons in the response to psychological, immune and visceral stressors. Lastly, potential clinical implications of targeting NUCB2/nesfatin-1 signaling and existing gaps in knowledge to ascertain the role and mechanisms of action of nesfatin-1 are presented.

Targeting intermediary metabolism in the hypothalamus as a mechanism to regulate appetite

The central nervous system mediates energy balance (energy intake and energy expenditure) in the body; the hypothalamus has a key role in this process. Recent evidence has demonstrated an important role for hypothalamic malonyl CoA in mediating energy balance. Malonyl CoA is generated by the carboxylation of acetyl CoA by acetyl CoA carboxylase and is then either incorporated into long-chain fatty acids by fatty acid synthase, or converted back to acetyl-CoA by malonyl CoA decarboxylase. Increased hypothalamic malonyl CoA is an indicator of energy surplus, resulting in a decrease in food intake and an increase in energy expenditure. In contrast, a decrease in hypothalamic malonyl CoA signals an energy deficit, resulting in an increased appetite and a decrease in body energy expenditure. A number of hormonal and neural orexigenic and anorexigenic signaling pathways have now been shown to be associated with changes in malonyl CoA levels in the arcuate nucleus (ARC) of the hypothalamus. Despite compelling evidence that malonyl CoA is an important mediator in the hypothalamic ARC control of food intake and regulation of energy balance, the mechanism(s) by which this occurs has not been established. Malonyl CoA inhibits carnitine palmitoyltransferase-1 (CPT-1), and it has been proposed that the substrate of CPT-1, long-chain acyl CoA(s), may act as a mediator(s) of appetite and energy balance. However, recent evidence has challenged the role of long-chain acyl CoA(s) in this process, as well as the involvement of CPT-1 in hypothalamic malonyl CoA signaling. A better understanding of how malonyl CoA regulates energy balance should provide novel approaches to targeting intermediary metabolism in the hypothalamus as a mechanism to control appetite and body weight. Here, we review the data supporting an important role for malonyl CoA in mediating hypothalamic control of energy balance, and recent evidence suggesting that targeting malonyl CoA synthesis or degradation may be a novel approach to favorably modify appetite and weight gain.

Secretin: Should we revisit its metabolic outcomes?

Metabolic pathologies such as Type 2 Diabetes have become a major health problem for worldwide populations. Unfortunately, efforts to cure and especially to prevent these significant global problems have so far been met with disappointment. Recently, the involvement of the gut-derived hormonal dysregulation in the development of obesity-related disturbances has been intensively studied. For instance, studies of gut-derived peptides such as peptide YY 3-36, glucagon-like peptide-1, oxyntomodulin and, more recently, ghrelin have significantly improved our understanding of mechanisms underlying weight and metabolic regulation. Even though early reports of the existence of secretin, the first peptide hormone to be described, date back as far as 1825, so much and yet so little is still known about its physiological role in mammals, including humans. However, recent years have provided a better understanding of how the release of secretin is regulated by enteral secretagogues. On the other hand, most basic questions about its role in the post-prandial regulation of metabolic functions in normal and pathophysiological conditions remain to be elucidated. The present work intends to review the physiology of secretin along with its central and peripheral outcomes on metabolic functions.

Expression of neuropeptide Y and agouti-related peptide in the hypothalamic arcuate nucleus of newborn neurogenin3 null mutant mice

Mice deficient in neurogenin 3 (Ngn3) fail to generate pancreatic endocrine cells and intestinal endocrine cells. Hypothalamic neuropeptides implicated in the control of energy homeostasis might also be affected in Ngn3 homozygous null mutant mice. We investigated the expression of two prominent orexigenic neuropeptides, neuropeptide Y (NPY) and agouti-related protein (AgRP), in the hypothalamic arcuate nucleus of newborn wild-type and Ngn3 null mutant mice. Immunohistochemical analysis demonstrated that, in Ngn3 null mutants, the number of NPY-immunoreactive neurons and nerve fibers was markedly increased in the arcuate nucleus, and the nerve fibers were widely distributed in the hypothalamic area, including the paraventricular and dorsomedial nuclei. Little increase of AgRP immunoreactivity was detected in the arcuate nucleus of mutant mice. In situ hybridization analysis confirmed the increased population of the NPY neurons in the arcuate nucleus of the mutants. The NPY mRNA level, as estimated by laser capture microdissection and real-time quantitative polymerase chain reaction, was 371% higher in Ngn3 null mutants than in wild-type mice. AgRP mRNA levels did not differ significantly between the null mutants and wild-type mice. Thus, up-regulation of the hypothalamic NPY system is probably a feature characteristic of Ngn3 null mice.

Resistin-like molecule alpha decreases glucose tolerance during intestinal inflammation

Resistin-like molecule alpha (Relm-alpha) is a secreted cysteine-rich protein belonging to a newly defined family of proteins, including resistin, Relm-beta, and Relm-gamma. Resistin was initially defined based on its insulin resistance activity, but the family members are highly up-regulated in various inflammatory states, especially those involving intestinal inflammation. In this study, we report the role of Relm-alpha at baseline and following an experimental model of colitis. Relm-alpha was readily detected in the serum at baseline (4-5 ng/ml), and its level was regulated by energy uptake. Retnla(-/-) mice had decreased baseline circulating leptin levels, but displayed normal glucose, glucose clearance, and insulin levels. Following exposure to the oral innate trigger dextran sodium sulfate (DSS), a nonredundant proinflammatory role for Relm-alpha was uncovered as Retnla(-/-) mice were markedly protected from DSS-induced disease activity and histopathological features. Relm-alpha regulated eosinophil-directed cytokines (e.g., IL-5, CCL11/eotaxin-1, and CCL5/RANTES) and IL-17 ex vivo. Consistently, DSS-treated Retnla(-/-) mice displayed substantially decreased eosinophil accumulation and decreased phosphorylation of NF-kappaB, ERK1/2, and p38 in macrophages and eosinophils. Following DSS exposure, serum level of Relm-alpha was up-regulated, and DSS-treated Retnla(-/-) mice were markedly protected from hyperglycemia induced by glucose injection independent of changes in insulin levels. Retnla(-/-) mice were protected from increases in gut hormone serum levels of gastric inhibitory polypeptide and peptide YY that were induced following DSS treatment. These findings demonstrate a central proinflammatory role for Relm-alpha in the regulation of colonic inflammation and a novel link between colonic injury, glucose tolerance, and energy intake.

Cross-talk in the gut

Modification of host signaling by the gut microbiota can influence weight gain and fat deposition.

Modulation of host signaling by the products of microbial activity in the gut may affect weight gain and fat formation.