Regulation Of Energy Expenditure Research Articles

Nitric Oxide Acts in the Rat Dorsomedial Hypothalamus to Increase High Fat Food Intake and Glutamate Transmission

The dorsomedial nucleus of the hypothalamus (DMH) plays an important role in the regulation of energy intake and expenditure. Numerous appetite-regulatory signals present in the DMH, including nitric oxide (NO) and endogenous cannabinoids (eCBs), act to regulate food intake, but whether these signals are involved in regulating high fat food intake remains unknown. We therefore asked whether NO and eCBs, administered alone or in combination, would influence the consumption of high fat food in rats. We implanted bilateral guide cannulas in the DMH of young, male Sprague-Dawley rats for microinjection of vehicle, NO (via the precursor l-arginine), the eCB 2-arachidonylglycerol (2-AG), or a combination of the two signals. Following the intrahypothalamic injections, both high fat food intake and body weight were measured for two hours at which point brains were removed and sectioned to confirm cannula placement in the DMH. Here we show that l-arginine significantly increases high fat food intake when administered into the DMH. This effect is abolished in the presence of 2-AG, which alone has no effect on high fat food intake or body weight. The l-arginine-induced increase in high fat food intake is dependent on NO synthesis, as it is prevented with the NO synthase inhibitor, l-NAME. We also demonstrate that l-arginine increases glutamate transmission onto DMH neurons, an effect that also requires NO synthesis and is abolished with 2-AG. Together, these data indicate that NO acts in the DMH to regulate the consumption of high fat food, possibly by enhancing glutamate signaling at DMH synapses.

1958-P: Neonatal Il-4 Induces a Persistent Decrease in Adipocyte Maturation

Adipose tissue is a central node for the dynamic regulation of systemic metabolism and energy expenditure. Little is known about adipogenesis in the newborn which is the critical window of adipose tissue development. Emerging data suggest that immune cells, particularly innate immune cells, play an important role in de novo beige adipogenesis and beige fat thermogenesis in mature rodents. In previous studies we showed that administration of low levels of IL-4 in the first week of life to rat pups results in decreased adiposity and improved glucose tolerance in adulthood, suggesting that beige adipogenesis may be enhanced by neonatal IL-4 administration. Developing animals produce higher levels of IL-4 compared to mature animals and use a distinct pre-adipocyte compartment for adipogenesis. In this study, we analyze the effects of IL-4 on adipogenesis in the developing rat. We demonstrate that a short and transient IL-4 exposure in the neonate during postnatal days 1-6 induces acute beige adipogenesis in the inguinal white adipose tissue (iWAT) that is associated with the upregulation of Ucp1 (n=6). Concurrently, adipocyte maturation is decreased with Adipoq downregulated (n=6). Pre-adipocytes from 10 week old mature rats that had been treated with IL-4 as neonates were differentiated in vitro and also show a decrease in Adipoq compared to controls (n=6). These data demonstrate that neonatal IL-4 induces a long term decrease in the maturation potential of pre-adipocytes. Interestingly, these adult differentiated pre-adipocytes show no change in Ucp1 expression after neonatal IL-4 exposure compared to control (n=6). Thus, neonatal IL-4 induces only acute beige adipogenesis, but impairs adipocyte maturation long term. Phenotypically, neonatal IL-4 resulted in decreased iWAT (n=7) and decreased fasting blood glucose in 10 week old animals (n=6) compared to control. Our studies show that the neonatal period is critical for adipocyte development and may influence the later onset of obesity. Disclosure T. Ying: None. P. Seale: None. R.A. Simmons: None. Funding National Institutes of Health (DK114054)

1926-P: Potent Weight Loss Mechanism of a Novel Long-Acting Glucagon Analog, HM15136, in Animal Models of Obesity

Several studies have demonstrated that glucagon plays an essential role in the regulation of body weight via both increase of energy expenditure and suppression of appetite, suggesting its potential application for obesity management. Consistent with this, we previously observed that chronic treatment of the novel long-acting glucagon analog, HM15136, led to efficient body weight loss (BWL) in diet-induced obesity (DIO) mice. To further investigate the therapeutic benefits of HM15136 in obesity, the present study compared the BWL effect with available GLP-1 agonists and investigated the underlying mechanism for efficient BWL by HM15136. In DIO mice, chronic treatment of HM15136 showed greater BWL (-38.5% vs. vehicle) than GLP-1 agonists such as liraglutide, dulaglutide, and semaglutide (-16.8, -2.5, and -11.0% vs. vehicle). Of note, unlike liraglutide, more BWL was observed even under pair-feeding conditions, indicating the appetite regulation-independent BWL by HM15136. As to the responsible mechanism, HM15136 increased the expression of PGC-1α and UCP-1 in white adipose tissue (WAT), leading to enhanced energy expenditure. Together with the reduced respiratory exchange ratio, these results suggest that HM15136 induce WAT browning through which fat utilization and energy expenditure increases. To explore an additional mechanism for BWL by HM15136, oral lipid tolerance test (oLTT) was performed. Interestingly, blood TG level during oLTT was significantly decreased by HM15136 treatment, which coincided with decreased blood bile acid and ApoB48. These results suggest that the inhibition of lipid absorption is involved, at least in part, in efficient BWL by HM15136. Therefore, HM15136 could be a potential option for the management of obesity via favorable regulation of energy expenditure and lipid absorption in addition to appetite inhibition. Efficacy study in obese patients is ongoing to assess the clinical relevance of these findings. Disclosure J. Lee: Employee; Self; Hanmi Pharmaceutical. S. Lee: Employee; Self; Hanmi Pharmaceutical. J. Kim: Employee; Self; Hanmi Pharmaceutical. J. Lee: Employee; Self; Hanmi Pharmaceutical. S. Lee: Employee; Spouse/Partner; Hanmi Pharmaceutical. S. Bae: Employee; Self; Hanmi Pharmaceutical. D. Kim: Board Member; Self; Hanmi Pharmaceutical. I. Choi: Board Member; Self; Hanmi Pharmaceutical.

Dietary Fatty Acid Composition Is Associated with FTO Gene Expression in Human Visceral and Subcutaneous Adipose Tissues

Abstract Objectives The fat mass and obesity-associated gene (FTO) is a functional candidate gene for type 2 diabetes mellitus (T2DM) and metabolic syndrome, based on evidence from genome-wide association studies (GWAS) that linked it to obesity and metabolic disorders. The FTO gene regulates energy expenditure and intake. We aimed to determine how fatty acid species measured in plasma and dietary intake associate with FTO gene expression in subcutaneous and visceral adipose tissues. Methods In this study, 97 participants aged ≥18 years were selected from patients admitted to the hospital for abdominal surgeries. These underlying disorders leading to surgeries were not expected to alter the habitual dietary intake of participants. Participants with diagnosed diabetes or cancer, under treatment of dyslipidemia or dysglycemia, and being on prescribed or any special diets were excluded. Habitual dietary intake of participants was collected using a valid and reliable food frequency questionnaire (FFQ), from which the intake of fatty acids was quantified. Plasma fatty acids were assessed by gas-liquid chromatography. The mRNA expression of the FTO gene in visceral and subcutaneous adipose tissues obtained by biopsy was measured by real-time quantitative PCR. Results After adjusting for age, HOMA-IR and body mass index, total fatty acid intake was significantly associated with FTO gene expression in visceral (STZβ = 0.208, P = 0.037) and subcutaneous (STZβ = 0.236, P = 0.020) adipose tissues. Dietary intake of MUFA and PUFA had positive significant associations with the expression of FTO in visceral (STZβ = 0.227, P = 0.023; STZβ = 0.346, P < 0.001, respectively) and subcutaneous (STZβ = 0.227, P = 0.026; STZβ = 0.274, P = 0.006, respectively) adipose tissues. There were no significant associations between plasma fatty acids and FTO mRNA expression in either subcutaneous or visceral adipose tissues. Conclusions The association of dietary total fatty acids, MUFA, and PUFA with FTO gene expression in both adipose tissues highlight the importance of dietary fatty acids composition along with total fat intake in relation to FTO gene expression. Funding Sources This study was funded by Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.

Physical Exercise and Myokines: Relationships with Sarcopenia and Cardiovascular Complications.

Skeletal muscle is capable of secreting different factors in order to communicate with other tissues. These mediators, the myokines, show potentially far-reaching effects on non-muscle tissues and can provide a molecular interaction between muscle and body physiology. Sarcopenia is a chronic degenerative neuromuscular disease closely related to cardiomyopathy and chronic heart failure, which influences the production and release of myokines. Our objective was to explore the relationship between myokines, sarcopenia, and cardiovascular diseases (CVD). The autocrine, paracrine, and endocrine actions of myokines include regulation of energy expenditure, insulin sensitivity, lipolysis, free fatty acid oxidation, adipocyte browning, glycogenolysis, glycogenesis, and general metabolism. A sedentary lifestyle accelerates the aging process and is a risk factor for developing sarcopenia, metabolic syndrome, and CVD. Increased adipose tissue resulting from the decrease in muscle mass in patients with sarcopenia may also be involved in the pathology of CVD. Myokines are protagonists in the complex condition of sarcopenia, which is associated with adverse clinical outcomes in patients with CVD. The discovery of new pathways and the link between myokines and CVD remain a cornerstone toward multifaceted interventions and perhaps the minimization of the damage resulting from muscle loss induced by factors such as atherosclerosis.

SUN-585 Associations Between UCP1(rs1800592),UCP2(rs6593366) and UCP3(rs1800849) with Fasting Glucose, Body Mass Index, and Energy Expenditure

Background: The uncoupling proteins (UCPs) belong to the mitochondrial inner membrane anion carrier superfamily and play an important role in energy homeostasis. UCP-1 is expressed mostly in brown adipose tissue (BAT) and act in the thermogenesis and regulation of energy expenditure. UCP-2 has a role in the metabolism of fatty acids direct and indirectly path insulin secretion. UCP-3 is specific of skeletal muscle and BAT and may affects the adaptive and translocation of fatty acids. Genetic polymorphisms in these proteins have been associated with obesity, as rs1800592 (-3826 A/G) in UCP-1 gene. The rs659366 (-866GA) UCP-2 has being associated with high expression of its RNAm, decrease of obesity risk, and increase of energy expenditure. The rs1800849 (-55CT) UCP-3 has been associated with low risk of type 2 Diabetes Mellitus, but its association with body mass index is controversial. Objective: To analyze the association of the polymorphisms rs1800592 UCP-1, rs659366 UCP-2, and rs1800849 UCP-3 with BMI and resting energy expenditure (REE). Material and Methods: We included 120 subjects with BMI>30kg/m2 and 100 subjects with BMI between18.5 -24.9 kg/m2, aged 20 to 50 years. Anthropometric data were recorded and the REE was measure for indirect calorimetric. Fasting glucose and lipid profile were assessed. Leptin, insulin and acylated-ghrelin were quantified by ELISA. Genomic DNA was extracted using comercial kit. Genotyping for three polymorphisms was performed by allelic discrimination using Taqman probes. Results: All the three polymorphisms of UCPs showed distribution in accordance with Hardy-Weinberg equilibrium. The weight, BMI, glucose, triglycerides, leptin, insulin, HOMA-IR, and REE levels were signitifcantly higher in obese subjects. There was a strong correlation between REE with BMI (r=0.42, p<0.00001) and with insulin levels (r=0.229, p=0.001) in all group. No differences in genotypic and allelic frequencies of rs1800592 UCP-1, rs659366 UCP-2 and rs180084 UCP-3 polymorphisms between obese and lean subjects. No differences among the genotypes rs1800592 UCP-1 and rs1800849 UCP-3 with metabolic variables. In rs659366 UCP-2 polymorhism, the REE and glucose concentrations were lower in carriers of rs659366AA genotype (F=3.11, p=0.046; F=2.97, p=0.053, respectively) in whole group. In obese subjects with rs659366AA UCP-2 genotype, the REE was significantly low (F=4.15, P=0.017). Conclusion. In this work the obese subjects with rs659366AA genotype had low REE. We found low glucose concentrations in the carries of rs659366 AA genotype.

FGF19 alleviates palmitate-induced atrophy in C2C12 cells by inhibiting mitochondrial overload and insulin resistance

Fibroblast growth factor 19 (FGF19) acts as a novel factor in the regulation of skeletal muscle mass in animal models by regulating energy expenditure. People with obesity have a lower content of FGF19 and lose muscle mass easily. However, as the main energy metabolism organelles, the involvement of mitochondria in the protective effect of FGF19 is still unknown. In this study, the protective effects of FGF19 on palmitate-induced damages in differentiated mouse myoblast cells (C2C12) were studied, including myotube morphology, mitochondrial function and the regulation of pathways and genes. Excessive palmitate resulted in myotube atrophy and activation of the mitochondria-mediated apoptosis pathway in C2C12 cells. Palmitate also inhibited glucose uptake and induced insulin resistance. FGF19 addition during the differentiation of C2C12 cells, returned the palmitate-induced mitochondrial respiration and apoptosis to the control levels and improved the insulin sensitivity. The palmitate-induced upregulation of genes involved in β-oxidation (PPARβ/δ, PPARγ, UCP-1, MCAD) and the downregulation of genes related to myotube atrophy (PPARα, PGC-1α and PGC-1β) were also alleviated by FGF19. In summary, FGF19 prevented excessive palmitate-induced dysfunction of C2C12 cells by protecting mitochondrial overload and apoptosis and maintaining normal insulin signaling.

Dietary carbohydrates modulate metabolic and β-cell adaptation to high-fat diet-induced obesity.

Obesity is associated with several chronic comorbidities, one of which is type 2 diabetes mellitus (T2DM). The pathogenesis of obesity and T2DM is influenced by alterations in diet macronutrient composition, which regulate energy expenditure, metabolic function, glucose homeostasis, and pancreatic islet cell biology. Recent studies suggest that increased intake of dietary carbohydrates plays a previously underappreciated role in the promotion of obesity and consequent metabolic dysfunction. Thus, in this study, we utilized mouse models to test the hypothesis that dietary carbohydrates modulate energetic, metabolic, and islet adaptions to high-fat diets. To address this, we exposed C57BL/6J mice to 12 wk of 3 eucaloric high-fat diets (>60% calories from fat) with varying total carbohydrate (1-20%) and sucrose (0-20%) content. Our results show that severe restriction of dietary carbohydrates characteristic of ketogenic diets reduces body fat accumulation, enhances energy expenditure, and reduces prevailing glycemia and insulin resistance compared with carbohydrate-rich, high-fat diets. Moreover, severe restriction of dietary carbohydrates also results in functional, morphological, and molecular changes in pancreatic islets highlighted by restricted capacity for β-cell mass expansion and alterations in insulin secretory response. These studies support the hypothesis that low-carbohydrate/high-fat diets provide antiobesogenic benefits and suggest further evaluation of the effects of these diets on β-cell biology in humans.

Myeloid-specific Asxl2 deletion limits diet-induced obesity by regulating energy expenditure.

We previously established that global deletion of the enhancer of trithorax and polycomb (ETP) gene, Asxl2, prevents weight gain. Because proinflammatory macrophages recruited to adipose tissue are central to the metabolic complications of obesity, we explored the role of ASXL2 in myeloid lineage cells. Unexpectedly, mice without Asxl2 only in myeloid cells (Asxl2ΔLysM) were completely resistant to diet-induced weight gain and metabolically normal despite increased food intake, comparable activity, and equivalent fecal fat. Asxl2ΔLysM mice resisted HFD-induced adipose tissue macrophage infiltration and inflammatory cytokine gene expression. Energy expenditure and brown adipose tissue metabolism in Asxl2ΔLysM mice were protected from the suppressive effects of HFD, a phenomenon associated with relatively increased catecholamines likely due to their suppressed degradation by macrophages. White adipose tissue of HFD-fed Asxl2ΔLysM mice also exhibited none of the pathological remodeling extant in their control counterparts. Suppression of macrophage Asxl2 expression, via nanoparticle-based siRNA delivery, prevented HFD-induced obesity. Thus, ASXL2 controlled the response of macrophages to dietary factors to regulate metabolic homeostasis, suggesting modulation of the cells' inflammatory phenotype may impact obesity and its complications.

Dynamic of TLQP-peptides upon fasting

BackgroundThe VGF-derived TLQP peptides (TLQPp), a new potential drug target for obesity, are expressed in stomach, pancreas, adrenal gland as well as in adipose tissues, and, when exogenously injected, regulate energy expenditure and food intake. However, it is not clear if these peptides physiologically change in these organs in response to fasting. MethodsRats were subdivided into four groups: (A) fed ad libitum, (B) fed with restrictions (once a day) (C) fast for 48 h and (D) fast for 48 h and then fed 1 h before sacrifice. Immunosorbent assay was used to possibly reveal TLQPp changes upon fasting in plasma as well as in pancreas, adrenal gland, stomach and adipose tissues. In the latter organs, we also measured the levels of the VGF precursor protein while immunohistochemistry was used to investigate the presence of the TLQP-21 receptors. ResultsDuring fasting, TLQPp were down-regulated in the stomach (45 %), pancreas (47 %), adrenal gland (51 %) and WAT (45.2 %) in parallel with a significant increase in the blood (36.6 %), all versus ad libitum group. In the same organs where the TLQPp were decreased upon fasting, the VGF precursor levels were not changed. In ad libitum rats, TLQP-21 receptors were well represented within the same cells that expressed TLQPp, suggesting an autocrine activity to be better investigated. ConclusionsDuring fasting, TLQPp are probably produced and immediately secreted into the blood circulation, until the hypoglycaemia is counteracted.

Tight Regulation of Energy Intake and Expenditure Across a Temperature Spectrum is Disrupted at Thermoneutrality

Energy balance is exquisitely regulated by peripheral and central hormones, brain behavioral centers, and neuronal networks. Under homeostatic conditions, energy intake (EI) is well matched to energy expenditure (EE), presumably via hypothalamic cross‐talk among: peripheral somatosensory afferents, sympathetic nervous system regulators, and feeding sites. The paradigm of closely matched energy balance is not evident during every life stage (e.g., normal growth and development, pregnancy) or in certain diseases (obesity). This highlights a disconnect between systems controlling EI from those controlling EE. We hypothesized that high fat diet (HFD)‐induced obesity (DIO) in mice would disrupt the normal energy intake‐expenditure relationship across a spectrum of temperatures. C57BL/6N male mice were fed a HFD (45% of energy) for ~9 wk, and were split into quartiles (n=8 ea) based on body weight (BWT) to study DIO resistant (Q1) vs. susceptible (Q4) mice compared to low fat (LF) controls. To assess EI and EE during a temperature challenge, 3 d/temperature food intake and indirect calorimetry (IC) measures took place at 10, 20, and 30°C. Despite differences in DIO susceptibility, BWT covariate‐adjusted EE responses to temperature did not differ between Q1 and Q4 mice. As expected, EE increased in all groups transitioning from the TNZ toward 20 and 10°C. EI matched EE at both 20 and 10°C, indicating tight co‐regulation at these temperatures. EI displayed a different pattern at 30°C: calorie consumption was not reduced compared to 20°C, resulting in positive energy balance and BWT gain. Respiratory exchange ratio percent relative cumulative frequency (PRCF) curves at 10 and 20°C indicated more fat combustion in HFD mice vs. LF controls, regardless of DIO status. 30°C led to a rightward shift in the PRCF in all mice, indicative of increased de novo lipogenesis and energy storage.Conclusions1) Countering our hypothesis, obesity did not significantly alter patterns of EI or EE at different temperatures. This suggests that temperature‐sensitive systems that coordinate energy balance in this DIO model remain largely intact. 2) During the fattening period before temperature challenge, hyperphagia only accounted for part of BWT gain in DIO susceptible mice, yet EE calculated from IC did not differ in DIO susceptible‐ vs. resistant mice. Thus, common assumptions related to EE calculation from IC might not be accurate under DIO conditions. 3) Tight co‐regulation of EE and EI was disrupted in mice within the TNZ, leading to hyperphagia and weight gain. The mechanisms behind this EE/EI decoupling remain to be identified. The current experimental paradigm provides a unique system to identify novel temperature‐sensitive factors in the hypothalamic, somatosensory, and sympathetic systems.Support or Funding InformationFunded by USDA‐ARS Project 6026‐51000‐010‐05S, AR Children’s Research Institute, and AR Biosciences Institute. Support in part by NIH grant U24‐DK092993.

The mitochondrial protein PGAM5 suppresses energy consumption in brown adipocytes by repressing expression of uncoupling protein 1

Accumulating evidence suggests that brown adipose tissue (BAT) is a potential therapeutic target for managing obesity and related diseases. PGAM family member 5, mitochondrial serine/threonine protein phosphatase (PGAM5), is a protein phosphatase that resides in the mitochondria and regulates many biological processes, including cell death, mitophagy, and immune responses. Because BAT is a mitochondria-rich tissue, we have hypothesized that PGAM5 has a physiological function in BAT. We previously reported that PGAM5-knockout (KO) mice are resistant to severe metabolic stress. Importantly, lipid accumulation is suppressed in PGAM5-KO BAT, even under unstressed conditions, raising the possibility that PGAM5 deficiency stimulates lipid consumption. However, the mechanism underlying this observation is undetermined. Here, using an array of biochemical approaches, including quantitative RT-PCR, immunoblotting, and oxygen consumption assays, we show that PGAM5 negatively regulates energy expenditure in brown adipocytes. We found that PGAM5-KO brown adipocytes have an enhanced oxygen consumption rate and increased expression of uncoupling protein 1 (UCP1), a protein that increases energy consumption in the mitochondria. Mechanistically, we found that PGAM5 phosphatase activity and intramembrane cleavage are required for suppression of UCP1 activity. Furthermore, utilizing a genome-wide siRNA screen in HeLa cells to search for regulators of PGAM5 cleavage, we identified a set of candidate genes, including phosphatidylserine decarboxylase (PISD), which catalyzes the formation of phosphatidylethanolamine at the mitochondrial membrane. Taken together, these results indicate that PGAM5 suppresses mitochondrial energy expenditure by down-regulating UCP1 expression in brown adipocytes and that its phosphatase activity and intramembrane cleavage are required for UCP1 suppression.

Isoform-selective regulation of mammalian cryptochromes.

CRY1 and CRY2 are essential components of the circadian clock controlling daily physiological rhythms. Accumulating evidences indicate distinct roles of these highly homologous proteins, in addition to redundant functions. Therefore, the development of isoform-selective compounds represents an effective approach towards understanding the similarities and differences of CRY1 and CRY2 by controlling each isoform individually. We conducted phenotypic screenings of circadian clock modulators, and identified KL101 and TH301 that selectively stabilize CRY1 and CRY2, respectively. Crystal structures of CRY-compound complexes revealed conservation of compound-binding sites between CRY1 and CRY2. We further discovered a unique mechanism underlying compound selectivity in which the disordered C-terminal region outside the pocket was required for the differential effects of KL101 and TH301 against CRY isoforms. By using these compounds, we found a new role of CRY1 and CRY2 as enhancers of brown adipocyte differentiation, providing the basis of CRY-mediated regulation of energy expenditure.

Paraventricular, subparaventricular and periventricular hypothalamic IRS4-expressing neurons are required for normal energy balance

Understanding the neural components modulating feeding-related behavior and energy expenditure is crucial to combating obesity and its comorbidities. Neurons within the paraventricular nucleus of the hypothalamus (PVH) are a key component of the satiety response; activation of the PVH decreases feeding and increases energy expenditure, thereby promoting negative energy balance. In contrast, PVH ablation or silencing in both rodents and humans leads to substantial obesity. Recent studies have identified genetically-defined PVH subpopulations that control discrete aspects of energy balance (e.g. oxytocin (OXT), neuronal nitric oxide synthase 1 (NOS1), melanocortin 4-receptor (MC4R), prodynorphin (PDYN)). We previously demonstrated that non-OXT NOS1PVH neurons contribute to PVH-mediated feeding suppression. Here, we identify and characterize a non-OXT, non-NOS1 subpopulation of PVH and peri-PVH neurons expressing insulin-receptor substrate 4 (IRS4PVH) involved in energy balance control. Using Cre-dependent viral tools to activate, trace and silence these neurons, we highlight the sufficiency and necessity of IRS4PVH neurons in normal feeding and energy expenditure regulation. Furthermore, we demonstrate that IRS4PVH neurons lie within a complex hypothalamic circuitry that engages distinct hindbrain regions and is innervated by discrete upstream hypothalamic sites. Overall, we reveal a requisite role for IRS4PVH neurons in PVH-mediated energy balance which raises the possibility of developing novel approaches targeting IRS4PVH neurons for anti-obesity therapies.

A compendium of G-protein-coupled receptors and cyclic nucleotide regulation of adipose tissue metabolism and energy expenditure.

With the ever-increasing burden of obesity and Type 2 diabetes, it is generally acknowledged that there remains a need for developing new therapeutics. One potential mechanism to combat obesity is to raise energy expenditure via increasing the amount of uncoupled respiration from the mitochondria-rich brown and beige adipocytes. With the recent appreciation of thermogenic adipocytes in humans, much effort is being made to elucidate the signaling pathways that regulate the browning of adipose tissue. In this review, we focus on the ligand-receptor signaling pathways that influence the cyclic nucleotides, cAMP and cGMP, in adipocytes. We chose to focus on G-protein-coupled receptor (GPCR), guanylyl cyclase and phosphodiesterase regulation of adipocytes because they are the targets of a large proportion of all currently available therapeutics. Furthermore, there is a large overlap in their signaling pathways, as signaling events that raise cAMP or cGMP generally increase adipocyte lipolysis and cause changes that are commonly referred to as browning: increasing mitochondrial biogenesis, uncoupling protein 1 (UCP1) expression and respiration.

Susceptibility of male wild type mouse strains to antipsychotic-induced weight gain

While both men and women gain weight as a side effect of antipsychotic (AP) treatment, studies in mice have found only female mice are susceptible to weight gain. Therefore, to we set out to identify a strain of male mice that gain significant weight in response to APs which could better model AP-induced weight gain observed in humans. These studies determined that male Balb/c mice developed late onset olanzapine-induced weight gain. Patients often take APs for many years and thus understanding AP-mediated changes in food intake, energy expenditure and body weight regulation is particularly important.

Rare Variants in Genes Linked to Appetite Control and Hypothalamic Development in Early-Onset Severe Obesity.

Context: The hypothalamic circuit has an essential role in the regulation of appetite and energy expenditure. Pathogenic variants in genes involved in the hypothalamic leptin–melanocortin pathway, including melanocortin-4-receptor (MC4R), have been associated with monogenic obesity.Objective: To determine the rate and spectrum of rare variants in genes involved in melanocortin pathway or hypothalamic development in patients with severe early-onset obesity (height-adjusted weight >60% before age 10 years).Methods: We used a custom-made targeted exome sequencing panel to assess peripheral blood DNA samples for rare (minor allele frequency <0.5%), pathogenic/likely pathogenic variants in 24 genes related to the hypothalamic circuit in 92 subjects (51% males, median age 13.7 years) with early-onset severe obesity (median body mass index (BMI) Z-score + 4.0).Results: We identified a novel frameshift deletion in MC4R (p.V103Afs5*) in two unrelated patients and a previously reported MC4R variant (p.T112M) in one patient. In addition, we identified rare heterozygous missense variants in ADCY3 (p.G1110R), MYT1L (p.R807Q), ISL1 (p.I347F), LRP2 (p.R2479I, and p.N3315S) and a hemizygous missense variant in GRPR (p.L87M) (each in one patient), possibly contributing to the obesity phenotype in these patients. Altogether 8 % (7/92) of the subjects had rare pathogenic/likely pathogenic variants in the studied genes.Conclusions: Rare genetic variants within the hypothalamic circuit are prevalent and contribute to the development of severe early-onset obesity. Targeted exome sequencing is useful in identifying affected subjects. Further studies are needed to evaluate the variants' clinical significance and to define optimal treatment.

Dissociation of Adaptive Thermogenesis from Glucose Homeostasis in Microbiome-Deficient Mice

Recent studies suggest that a key mechanism whereby the gut microbiome influences energy balance and glucose homeostasis is through the recruitment of brown and beige adipocytes, primary mediators of the adaptive thermogenic response. To test this, we assessed energy expenditure and glucose metabolism in two complementary mouse models of gut microbial deficiency, which were exposed to a broad range of thermal and dietary stresses. Neither ablation of the gut microbiome, nor the substantial microbial perturbations induced by cold ambient temperatures, influenced energy expenditure during cold exposure or high-fat feeding. Nevertheless, we demonstrated acritical role for gut microbial metabolism in maintaining euglycemia through the production of amino acid metabolites that optimized hepatic TCA (tricarboxylic acid) cycle fluxes in support ofgluconeogenesis. These results distinguish thedispensability of the gut microbiome for the regulation of energy expenditure from its critical contribution to the maintenance ofglucose homeostasis.

Chronic arsenic exposure impairs adaptive thermogenesis in male C57BL/6J mice.

The global prevalence of type 2 diabetes (T2D) has doubled since 1980. Human epidemiological studies support arsenic exposure as a risk factor for T2D, although the precise mechanism is unclear. We hypothesized that chronic arsenic ingestion alters glucose homeostasis by impairing adaptive thermogenesis, i.e., body heat production in cold environments. Arsenic is a pervasive environmental contaminant, with more than 200 million people worldwide currently exposed to arsenic-contaminated drinking water. Male C57BL/6J mice exposed to sodium arsenite in drinking water at 300 μg/L for 9 wk experienced significantly decreased metabolic heat production when acclimated to chronic cold tolerance testing, as evidenced by indirect calorimetry, despite no change in physical activity. Arsenic exposure increased total fat mass and subcutaneous inguinal white adipose tissue (iWAT) mass. RNA sequencing analysis of iWAT indicated that arsenic dysregulated mitochondrial processes, including fatty acid metabolism. Western blotting in WAT confirmed that arsenic significantly decreased TOMM20, a correlate of mitochondrial abundance; PGC1A, a master regulator of mitochondrial biogenesis; and, CPT1B, the rate-limiting step of fatty acid oxidation (FAO). Our findings show that chronic arsenic exposure impacts the mitochondrial proteins of thermogenic tissues involved in energy expenditure and substrate regulation, providing novel mechanistic evidence for arsenic's role in T2D development.

Fasting- and ghrelin-induced food intake is regulated by NAMPT in the hypothalamus.

Neurons in the arcuate nucleus of the hypothalamus are involved in regulation of food intake and energy expenditure, and dysregulation of signalling in these neurons promotes development of obesity. The role of the rate-limiting enzyme in the NAD+ salvage pathway, nicotinamide phosphoribosyltransferase (NAMPT), for regulation energy homeostasis by the hypothalamus has not been extensively studied. We determined whether Nampt mRNA or protein levels in the hypothalamus of mice were affected by diet-induced obesity, by fasting and re-feeding, and by leptin and ghrelin treatment. Primary hypothalamic neurons were treated with FK866, a selective inhibitor of NAMPT, or rAAV carrying shRNA directed against Nampt, and levels of reactive oxygen species (ROS) and mitochondrial respiration were assessed. Fasting and ghrelin-induced food intake was measured in mice in metabolic cages after intracerebroventricular (ICV)-mediated FK866 administration. NAMPT levels in the hypothalamus were elevated by administration of ghrelin and leptin. In diet-induced obese mice, both protein and mRNA levels of NAMPT decreased in the hypothalamus. NAMPT inhibition in primary hypothalamic neurons significantly reduced levels of NAD+ , increased levels of ROS, and affected the expression of Agrp, Pomc and genes related to mitochondrial function. Finally, ICV-induced NAMPT inhibition by FK866 did not cause malaise or anhedonia, but completely ablated fasting- and ghrelin-induced increases in food intake. Our findings indicate that regulation of NAMPT levels in hypothalamic neurons is important for the control of fasting- and ghrelin-induced food intake.