Sustained inhibition of NPY/AgRP neuronal activity by FGF1.

In rodent models of type 2 diabetes (T2D), central administration of FGF1 normalizes elevated blood glucose levels in a manner that is sustained for weeks or months. Increased activity of NPY/AgRP neurons in the hypothalamic arcuate nucleus (ARC) is implicated in the pathogenesis of hyperglycemia in these animals, and the ARC is a key brain area for the antidiabetic action of FGF1. We therefore sought to determine whether FGF1 inhibits NPY/AgRP neurons and, if so, whether this inhibitory effect is sufficiently durable to offer a feasible explanation for sustained diabetes remission induced by central administration of FGF1. Here, we show that FGF1 inhibited ARC NPY/AgRP neuron activity, both after intracerebroventricular injection in vivo and when applied ex vivo in a slice preparation; we also showed that the underlying mechanism involved increased input from presynaptic GABAergic neurons. Following central administration, the inhibitory effect of FGF1 on NPY/AgRP neurons was also highly durable, lasting for at least 2 weeks. To our knowledge, no precedent for such a prolonged inhibitory effect exists. Future studies are warranted to determine whether NPY/AgRP neuron inhibition contributes to the sustained antidiabetic action elicited by intracerebroventricular FGF1 injection in rodent models of T2D.

Evaluation of VGF peptides as potential anti-obesity candidates in pre-clinical animal models.

VGF is a peptide precursor expressed in neuroendocrine cells that is suggested to play a role in the regulation of energy homeostasis. VGF is proteolytically cleaved to yield multiple bioactive peptides. However, the specific actions of VGF-derived peptides on energy homeostasis remain unclear. The aim of the present work was to investigate the role of VGF-derived peptides in energy homeostasis and explore the pharmacological actions of VGF-derived peptides on body weight in preclinical animal models. VGF-derived peptides (NERP-1, NERP-2, PGH-NH2, PGH-OH, NERP-4, TLQP-21, TLQP-30, TLQP-62, HHPD-41, AQEE-30, and LQEQ-19) were synthesized and screened for their ability to affect neuronal activity in vitro on hypothalamic brain slices and modulate food intake and energy expenditure after acute central administration in vivo. In addition, the effects of NERP-1, NERP-2, PGH-NH2, TLQP-21, TLQP-62, and HHPD-41 on energy homeostasis were studied after chronic central infusion. NERP-1, PGH-NH2, HHPD-41, and TLQP-62 increased the functional activity of hypothalamic neuronal networks. However, none of the peptides altered energy homeostasis after either acute or chronic ICV administration. The present data do not support the potential use of the tested VGF-derived peptides as novel anti-obesity drug candidates.

Transcriptomic analysis links diverse hypothalamic cell types to fibroblast growth factor 1-induced sustained diabetes remission.

In rodent models of type 2 diabetes (T2D), sustained remission of hyperglycemia can be induced by a single intracerebroventricular (icv) injection of fibroblast growth factor 1 (FGF1), and the mediobasal hypothalamus (MBH) was recently implicated as the brain area responsible for this effect. To better understand the cellular response to FGF1 in the MBH, we sequenced >79,000 single-cell transcriptomes from the hypothalamus of diabetic Lepob/ob mice obtained on Days 1 and 5 after icv injection of either FGF1 or vehicle. A wide range of transcriptional responses to FGF1 was observed across diverse hypothalamic cell types, with glial cell types responding much more robustly than neurons at both time points. Tanycytes and ependymal cells were the most FGF1-responsive cell type at Day 1, but astrocytes and oligodendrocyte lineage cells subsequently became more responsive. Based on histochemical and ultrastructural evidence of enhanced cell-cell interactions between astrocytes and Agrp neurons (key components of the melanocortin system), we performed a series of studies showing that intact melanocortin signaling is required for the sustained antidiabetic action of FGF1. These data collectively suggest that hypothalamic glial cells are leading targets for the effects of FGF1 and that sustained diabetes remission is dependent on intact melanocortin signaling.

Whole transcriptome analysis and validation of metabolic pathways in subcutaneous adipose tissues during FGF21-induced weight loss in non-human primates.

Fibroblast growth factor 21 (FGF21) induces weight loss in mouse, monkey, and human studies. In mice, FGF21 is thought to cause weight loss by stimulating thermogenesis, but whether FGF21 increases energy expenditure (EE) in primates is unclear. Here, we explore the transcriptional response and gene networks active in adipose tissue of rhesus macaques following FGF21-induced weight loss. Genes related to thermogenesis responded inconsistently to FGF21 treatment and weight loss. However, expression of gene modules involved in triglyceride (TG) synthesis and adipogenesis decreased, and this was associated with greater weight loss. Conversely, expression of innate immune cell markers was increased post-treatment and was associated with greater weight loss. A lipogenesis gene module associated with weight loss was evaluated by testing the function of member genes in mice. Overexpression of NRG4 reduced weight gain in diet-induced obese mice, while overexpression of ANGPTL8 resulted in elevated TG levels in lean mice. These observations provide evidence for a shifting balance of lipid storage and metabolism due to FGF21-induced weight loss in the non-human primate model, and do not fully recapitulate increased EE seen in rodent and in vitro studies. These discrepancies may reflect inter-species differences or complex interplay of FGF21 activity and counter-regulatory mechanisms.

Reelin is modulated by diet-induced obesity and has direct actions on arcuate proopiomelanocortin neurons.

OBJECTIVE: Reelin (RELN) is a large glycoprotein involved in synapse maturation and neuronal organization throughout development. Deficits in RELN signaling contribute to multiple psychological disorders, such as autism spectrum disorder, schizophrenia, and bipolar disorder. Nutritional stress alters RELN expression in brain regions associated with these disorders; however, the involvement of RELN in the neural circuits involved in energy metabolism is unknown. The RELN receptors apolipoprotein E receptor 2 (ApoER2) and very low-density lipoprotein receptor (VLDLR) are involved in lipid metabolism and expressed in the hypothalamus. Here we explored the involvement of RELN in hypothalamic signaling and the impact of diet-induced obesity (DIO) on this system. METHODS: Adult male mice were fed a chow diet or maintained on a high-fat diet (HFD) for 12-16 weeks. HFD-fed DIO mice exhibited decreased ApoER2 and VLDLR expression and increased RELN protein in the hypothalamus. Electrophysiology was used to determine the mechanism by which the central fragment of RELN (CF-RELN) acts on arcuate nucleus (ARH) satiety-promoting proopiomelanocortin (POMC) neurons and the impact of DIO on this circuitry. RESULTS: CF-RELN exhibited heterogeneous presynaptic actions on inhibitory inputs onto ARH-POMC-EGFP neurons and consistent postsynaptic actions. Additionally, central administration of CF-RELN caused a significant increase in ARH c-Fos expression and an acute decrease in food intake and body weight. CONCLUSIONS: We conclude that RELN signaling is modulated by diet, that RELN is involved in synaptic signaling onto ARH-POMC neurons, and that altering central CF-RELN levels can impact food intake and body weight.

The central fibroblast growth factor receptor/beta klotho system: Comprehensive mapping in Mus musculus and comparisons to nonhuman primate and human samples using an automated in situ hybridization platform.

Central activation of fibroblast growth factor (FGF) receptors regulates peripheral glucose homeostasis and reduces food intake in preclinical models of obesity and diabetes. The current work was undertaken to advance our understanding of the receptor expression, as sites of ligand action by FGF19, FGF21, and FGF1 in the mammalian brain remains unresolved. Recent advances in automated RNAscope in situ hybridization and droplet digital PCR (ddPCR) technology allowed us to interrogate central FGFR/beta klotho (Klb) system at the cellular level in the mouse, with relevant comparisons to nonhuman primate and human brain. FGFR1-3 gene expression was broadly distributed throughout the CNS in Mus musculus, with FGFR1 exhibiting the greatest heterogeneity. FGFR4 expression localized only in the medial habenula and subcommissural organ of mice. Likewise, Klb mRNA was restricted to the suprachiasmatic nucleus (SCh) and select midbrain and hindbrain nuclei. ddPCR in the rodent hypothalamus confirmed that, although expression levels are indeed low for Klb, there is nonetheless a bonafide subpopulation of Klb+ cells in the hypothalamus. In NHP and human midbrain and hindbrain, Klb + cells are quite rare, as is expression of FGFR4. Collectively, these data provide the most robust central map of the FGFR/Klb system to date and highlight central regions that may be of critical importance to assess central ligand effects with pharmacological dosing, such as the putative interactions between the endocrine FGFs and FGFR1/Klb, or FGF19 with FGFR4.

Determining the Effects of Combined Liraglutide and Phentermine on Metabolic Parameters, Blood Pressure, and Heart Rate in Lean and Obese Male Mice.

Liraglutide, a glucagon-like peptide 1 (GLP-1) receptor agonist, and phentermine, a psychostimulant structurally related to amphetamine, are drugs approved for the treatment of obesity and hyperphagia. There is significant interest in combination use of liraglutide and phentermine for weight loss; however, both drugs have been reported to induce systemic hemodynamic changes, and as such the therapeutic window for this drug combination needs to be determined. To understand their impact on metabolic and cardiovascular physiology, we tested the effects of these drugs alone and in combination for 21 days in lean and obese male mice. The combination of liraglutide and phentermine, at 100 µg/kg/day and 10 mg/kg/day, respectively, produced the largest reduction in body weight in both lean and diet-induced obese (DIO) mice, when compared with both vehicle and monotherapy-treated mice. In lean mice, combination treatment at the aforementioned doses significantly increased heart rate and reduced blood pressure, whereas in DIO mice, combination therapy induced a transient increase in heart rate and decreased blood pressure. These studies demonstrate that in obese mice, the combination of liraglutide and phentermine may reduce body weight but only induce modest improvements in cardiovascular functions. Conversely, in lean mice, the additional weight loss from combination therapy does not improve cardiovascular parameters.

Maternal high-fat diet reversal improves placental hemodynamics in a nonhuman primate model of diet-induced obesity.

BACKGROUND: In a Japanese macaque model of diet-induced obesity, we have previously demonstrated that consumption of a high-fat, "Western-style" diet (WSD) is associated with placental dysfunction and adverse pregnancy outcomes, independent of an obese maternal phenotype. Specifically, we have reported decreased uterine placental blood flow and increased inflammation with maternal WSD consumption. We also previously investigated the use of a promising therapeutic intervention that mitigated the adverse placental effects of a WSD but had unexpected detrimental effects on fetal pancreatic development. Thus, the objective of the current study was to determine whether simple preconception diet reversal (REV) would improve placental function. METHODS: Female Japanese macaques were divided into three groups: REV animals (n = 5) were switched from a chronic WSD (36% fat) to a low fat, CON diet (14% fat) prior to conception and throughout pregnancy. The CON (n = 6) and WSD (n = 6) cohorts were maintained on their respective diets throughout pregnancy. Maternal body weight and composition were regularly assessed and advanced noninvasive imaging was performed at midgestation (gestational day 90, G90, or 0.5 of gestation, where full term is G175), and G129, 1 day prior to C-section delivery at G130 (0.75 of gestation). Imaging studies comprised Doppler ultrasound (US), contrast-enhanced US, and dynamic contrast-enhanced magnetic resonance imaging to assess uteroplacental hemodynamics and maternal-side placental perfusion. RESULTS: Dietary intervention resulted in significant maternal weight loss prior to pregnancy, and improved lean to fat mass ratio. By advanced imaging we demonstrated that a chronic WSD led to decreased blood flow velocity in the intervillous space, delayed blood flow transfer through the maternal spiral arteries, and reduced total placental blood flow compared to CON fed animals. Dietary reversal ameliorated these concerning derangements, restoring these hemodynamic parameters to CON levels. CONCLUSIONS: Preconception dietary modification has beneficial effects on the maternal metabolic phenotype, and results in improved placental hemodynamics.

FGF21 decreases body weight without reducing food intake or bone mineral density in high-fat fed obese rhesus macaque monkeys.

OBJECTIVE: Administration of FGF21 and FGF21 analogues reduce body weight; improve insulin sensitivity and dyslipidemia in animal models of obesity and in short term clinical trials. However potential adverse effects identified in mice have raised concerns for the development of FGF21 therapeutics. Therefore, this study was designed to address the actions of FGF21 on body weight, glucose and lipid metabolism and importantly its effects on bone mineral density (BMD), bone markers, and plasma cortisol in high-fat fed obese rhesus macaque monkeys. METHODS: Obese non-diabetic rhesus macaque monkeys (five males and five ovariectomized (OVX) females) were maintained on a high-fat diet and treated for 12 weeks with escalating doses of FGF21. Food intake was assessed daily and body weight weekly. Bone mineral content (BMC) and BMD were measured by DEXA scanning prior to the study and on several occasions throughout the treatment period as well as during washout. Plasma glucose, glucose tolerance, insulin, lipids, cortisol, and bone markers were likewise measured throughout the study. RESULTS: On average, FGF21 decreased body weight by 17.6 ± 1.6% after 12 weeks of treatment. No significant effect on food intake was observed. No change in BMC or BMD was observed, while a 2-fold increase in CTX-1, a marker of bone resorption, was seen. Overall glucose tolerance was improved with a small but significant decrease in HbA1C. Furthermore, FGF21 reduced concentrations of plasma triglycerides and very low density lipoprotein cholesterol. No adverse changes in clinical chemistry markers were demonstrated, and no alterations in plasma cortisol were observed during the study. CONCLUSION: In conclusion, FGF21 reduced body weight in obese rhesus macaque monkeys without reducing food intake. Furthermore, FGF21 had beneficial effects on body composition, insulin sensitivity, and plasma triglycerides. No adverse effects on bone density or plasma cortisol were observed after 12 weeks of treatment.

Adverse Placental Perfusion and Pregnancy Outcomes in a New Nonhuman Primate Model of Gestational Protein Restriction.

Maternal malnutrition during pregnancy impacts fetal growth, with developmental consequences that extend to later life outcomes. In underdeveloped countries, this malnutrition typically takes the form of poor dietary protein content and quality, even if adequate calories are consumed. Here, we report the establishment of a nonhuman primate model of gestational protein restriction (PR) in order to understand how placental function and pregnancy outcomes are affected by protein deficiency. Rhesus macaques were assigned to either a control diet containing 26% protein or switched to a 13% PR diet prior to conception and maintained on this PR diet throughout pregnancy. Standard fetal biometry, Doppler ultrasound of uteroplacental blood flow, ultrasound-guided amniocentesis, and contrast-enhanced ultrasound (CE-US) to assess placental perfusion were performed mid-gestation (gestational day 85 [G85] where term is G168) and in the early third trimester (G135). Our data demonstrate that a 50% reduction in dietary protein throughout gestation results in reduced placental perfusion, fetal growth restriction, and a 50% rate of pregnancy loss. In addition, we demonstrate reduced total protein content and evidence of fetal hypoxia in the amniotic fluid. This report highlights the use of CE-US for in vivo assessment of placental vascular function. The ability to detect placental dysfunction, and thus a compromised pregnancy, early in gestation, may facilitate the development of interventional strategies to optimize clinical care and improve long-term offspring outcomes, which are future areas of study in this new model.

Maternal and postnatal high-fat diet consumption programs energy balance and hypothalamic melanocortin signaling in nonhuman primate offspring.

Maternal high-fat-diet (HFD) consumption during pregnancy decreased fetal body weight and impacted development of hypothalamic melanocortin neural circuitry in nonhuman primate offspring. We investigated whether these impairments during gestation persisted in juvenile offspring and examined the interaction between maternal and early postnatal HFD consumption. Adult dams consumed either a control diet (CTR; 15% calories from fat) or a high-saturated-fat diet (HFD; 37% calories from fat) during pregnancy. Offspring were weaned onto a CTR or HFD at ~8 mo of age. Offspring from HFD-fed dams displayed early catch-up growth and elevated body weight at 6 and 13 mo of age. Maternal and postnatal HFD exposure reduced the amount of agouti-related peptide fibers in the paraventricular nucleus of the hypothalamus. Postnatal HFD consumption also decreased the amount of agouti-related peptide fibers in the arcuate nucleus of the hypothalamus. Postnatal HFD was associated with decreased food intake and increased activity. These results support and extend our previous findings of maternal diet effects on fetal development and reveal, for the first time in a nonhuman primate model, that maternal HFD-induced disturbances in offspring body weight regulation extended past gestation into the juvenile period. Maternal HFD consumption increases the risk for offspring developing obesity, with the developmental timing of HFD exposure differentially impacting the melanocortin system and energy balance regulation. The present findings provide translational insight into human clinical populations, suggesting that profound health consequences may await individuals later in life following intrauterine and postnatal HFD exposure.

GLP-1R Signaling Directly Activates Arcuate Nucleus Kisspeptin Action in Brain Slices but Does not Rescue Luteinizing Hormone Inhibition in Ovariectomized Mice During Negative Energy Balance.

Kisspeptin (Kiss1) neurons in the hypothalamic arcuate nucleus (ARC) are key components of the hypothalamic-pituitary-gonadal axis, as they regulate the basal pulsatile release of gonadotropin releasing hormone (GnRH). ARC Kiss1 action is dependent on energy status, and unmasking metabolic factors responsible for modulating ARC Kiss1 neurons is of great importance. One possible factor is glucagon-like peptide 1 (GLP-1), an anorexigenic neuropeptide produced by brainstem preproglucagon neurons. Because GLP fiber projections and the GLP-1 receptor (GLP-1R) are abundant in the ARC, we hypothesized that GLP-1R signaling could modulate ARC Kiss1 action. Using ovariectomized mice, we found that GLP-producing fibers come in close apposition with ARC Kiss1 neurons; these neurons also contain Glp1r mRNA. Electrophysiological recordings revealed that liraglutide (a long-acting GLP-1R agonist) increased action potential firing and caused a direct membrane depolarization of ARC Kiss1 cells in brain slices. We determined that brainstem preproglucagon mRNA is decreased after a 48-h fast in mice, a negative energy state in which ARC Kiss1 expression and downstream GnRH/luteinizing hormone (LH) release are potently suppressed. However, activation of GLP-1R signaling in fasted mice with liraglutide was not sufficient to prevent LH inhibition. Furthermore, chronic central infusions of the GLP-1R antagonist, exendin(9-39), in ad libitum-fed mice did not alter ARC Kiss1 mRNA or plasma LH. As a whole, these data identify a novel interaction of the GLP-1 system with ARC Kiss1 neurons but indicate that CNS GLP-1R signaling alone is not critical for the maintenance of LH during fasting or normal feeding.

Genomic Variants Associated with Resistance to High Fat Diet Induced Obesity in a Primate Model.

Maternal obesity contributes to an increased risk of lifelong morbidity and mortality for both the mother and her offspring. In order to better understand the molecular mechanisms underlying these risks, we previously established and extensively characterized a primate model in Macaca fuscata (Japanese macaque). In prior studies we have demonstrated that a high fat, caloric dense maternal diet structures the offspring's epigenome, metabolome, and intestinal microbiome. During the course of this work we have consistently observed that a 36% fat diet leads to obesity in the majority, but not all, of exposed dams. In the current study, we sought to identify the genomic loci rendering resistance to obesity despite chronic consumption of a high fat diet in macaque dams. Through extensive phenotyping together with exon capture array and targeted resequencing, we identified three novel single nucleotide polymorphisms (SNPs), two in apolipoprotein B (APOB) and one in phospholipase A2 (PLA2G4A) that significantly associated with persistent weight stability and insulin sensitivity in lean macaques. By application of explicit orthogonal modeling (NOIA), we estimated the polygenic and interactive nature of these loci against multiple metabolic traits and their measures (i.e., serum LDL levels) which collectively render an obesity resistant phenotype in our adult female dams.

α-Melanocyte stimulating hormone promotes muscle glucose uptake via melanocortin 5 receptors.

OBJECTIVE: Central melanocortin pathways are well-established regulators of energy balance. However, scant data exist about the role of systemic melanocortin peptides. We set out to determine if peripheral α-melanocyte stimulating hormone (α-MSH) plays a role in glucose homeostasis and tested the hypothesis that the pituitary is able to sense a physiological increase in circulating glucose and responds by secreting α-MSH. METHODS: We established glucose-stimulated α-MSH secretion using humans, non-human primates, and mouse models. Continuous α-MSH infusions were performed during glucose tolerance tests and hyperinsulinemic-euglycemic clamps to evaluate the systemic effect of α-MSH in glucose regulation. Complementary ex vivo and in vitro techniques were employed to delineate the direct action of α-MSH via the melanocortin 5 receptor (MC5R)-PKA axis in skeletal muscles. Combined treatment of non-selective/selective phosphodiesterase inhibitor and α-MSH was adopted to restore glucose tolerance in obese mice. RESULTS: Here we demonstrate that pituitary secretion of α-MSH is increased by glucose. Peripheral α-MSH increases temperature in skeletal muscles, acts directly on soleus and gastrocnemius muscles to significantly increase glucose uptake, and enhances whole-body glucose clearance via the activation of muscle MC5R and protein kinase A. These actions are absent in obese mice, accompanied by a blunting of α-MSH-induced cAMP levels in skeletal muscles of obese mice. Both selective and non-selective phosphodiesterase inhibition restores α-MSH induced skeletal muscle glucose uptake and improves glucose disposal in obese mice. CONCLUSION: These data describe a novel endocrine circuit that modulates glucose homeostasis by pituitary α-MSH, which increases muscle glucose uptake and thermogenesis through the activation of a MC5R-PKA-pathway, which is disrupted in obesity.

Maternal obesity reduces oxidative capacity in fetal skeletal muscle of Japanese macaques.

Maternal obesity is proposed to alter the programming of metabolic systems in the offspring, increasing the risk for developing metabolic diseases; however, the cellular mechanisms remain poorly understood. Here, we used a nonhuman primate model to examine the impact of a maternal Western-style diet (WSD) alone, or in combination with obesity (Ob/WSD), on fetal skeletal muscle metabolism studied in the early third trimester. We find that fetal muscle responds to Ob/WSD by upregulating fatty acid metabolism, mitochondrial complex activity, and metabolic switches (CPT-1, PDK4) that promote lipid utilization over glucose oxidation. Ob/WSD fetuses also had reduced mitochondrial content, diminished oxidative capacity, and lower mitochondrial efficiency in muscle. The decrease in oxidative capacity and glucose metabolism was persistent in primary myotubes from Ob/WSD fetuses despite no additional lipid-induced stress. Switching obese mothers to a healthy diet prior to pregnancy did not improve fetal muscle mitochondrial function. Lastly, while maternal WSD alone led only to intermediary changes in fetal muscle metabolism, it was sufficient to increase oxidative damage and cellular stress. Our findings suggest that maternal obesity or WSD, alone or in combination, leads to programmed decreases in oxidative metabolism in offspring muscle. These alterations may have important implications for future health.

Temporal Changes in Skeletal Muscle Capillary Responses and Endothelial-Derived Vasodilators in Obesity-Related Insulin Resistance.

The inability of insulin to increase skeletal muscle capillary blood volume (CBV) reduces glucose uptake in insulin resistance (IR). We hypothesized that abnormalities in endothelial-derived vasodilator pathways are temporally associated with the development of IR and an impaired ability to increase skeletal muscle CBV. A comprehensive metabolic and vascular screening assessment was performed on 10 adult rhesus macaques at baseline and every 4-6 months for 2 years after starting a high-fat diet supplemented with fructose. Diet changes resulted in an 80% increase in truncal fat by 4 months. Hyperinsulinemia and decreased glucose utilization were observed from 4 to 18 months. At 24 months, pancreatic secretory function and the glucose utilization rate declined. CBV at rest and during an intravenous glucose tolerance test demonstrated a sustained increase from 4 to 18 months and then abruptly fell at 24 months. Nitric oxide bioavailability progressively decreased over 2 years. Conversely, endothelial-derived vasodilators progressively increased over 18 months and then abruptly decreased at 24 months in concert with the CBV. The increase in basal and glucose-mediated CBV early in IR may represent a compensatory response through endothelial-derived vasodilator pathways. The inability to sustain a vascular compensatory response limits glucose-mediated increases in CBV, which correlates with the severity of IR.

Postnatal undernutrition delays a key step in the maturation of hypothalamic feeding circuits.

OBJECTIVE: Humans and animals exposed to undernutrition (UN) during development often experience accelerated "catch-up" growth when food supplies are plentiful. Little is known about the mechanisms regulating early growth rates. We previously reported that actions of leptin and presynaptic inputs to orexigenic NPY/AgRP/GABA (NAG) neurons in the arcuate nucleus of the hypothalamus are almost exclusively excitatory during the lactation period, since neuronal and humoral inhibitory systems do not develop until after weaning. Moreover, we identified a critical step that regulates the maturation of electrophysiological responses of NAG neurons at weaning - the onset of genes encoding ATP-dependent potassium (KATP) channel subunits. We explored the possibility that UN promotes subsequent catch-up growth, in part, by delaying the maturation of negative feedback systems to neuronal circuits driving food intake. METHODS: We used the large litter (LL) size model to study the impacts of postnatal UN followed by catch-up growth. We evaluated the maturation of presynaptic and postsynaptic inhibitory systems in NAG neurons using a combination of electrophysiological and molecular criteria, in conjunction with leptin's ability to suppress fasting-induced hyperphagia. RESULTS: The onset of KATP channel subunit expression and function, the switch in leptin's effect on NAG neurons, the ingrowth of inhibitory inputs to NAG neurons, and the development of homeostatic feedback to feeding circuits were delayed in LL offspring relative to controls. The development of functional KATP channels and the establishment of leptin-mediated suppression of food intake in the peri-weaning period were tightly linked and were not initiated until growth and adiposity of LL offspring caught up to controls. CONCLUSIONS: Our data support the idea that initiation of KATP channel subunit expression in NAG neurons serves as a molecular gatekeeper for the maturation of homeostatic feeding circuits.

The MAFB transcription factor impacts islet α-cell function in rodents and represents a unique signature of primate islet ß-cells.

Analysis of MafB(-/-) mice has suggested that the MAFB transcription factor was essential to islet α- and ß-cell formation during development, although the postnatal physiological impact could not be studied here because these mutants died due to problems in neural development. Pancreas-wide mutant mice were generated to compare the postnatal significance of MafB (MafB(Δpanc)) and MafA/B (MafAB(Δpanc)) with deficiencies associated with the related ß-cell-enriched MafA mutant (MafA(Δpanc)). Insulin(+) cell production and ß-cell activity were merely delayed in MafB(Δpanc) islets until MafA was comprehensively expressed in this cell population. We propose that MafA compensates for the absence of MafB in MafB(Δpanc) mice, which is supported by the death of MafAB(Δpanc) mice soon after birth from hyperglycemia. However, glucose-induced glucagon secretion was compromised in adult MafB(Δpanc) islet α-cells. Based upon these results, we conclude that MafB is only essential to islet α-cell activity and not ß-cell. Interestingly, a notable difference between mice and humans is that MAFB is coexpressed with MAFA in adult human islet ß-cells. Here, we show that nonhuman primate (NHP) islet α- and ß-cells also produce MAFB, implying that MAFB represents a unique signature and likely important regulator of the primate islet ß-cell.

Maternal high-fat diet and obesity impact palatable food intake and dopamine signaling in nonhuman primate offspring.

OBJECTIVE: To utilize a nonhuman primate model to examine the impact of maternal high-fat diet (HFD) consumption and pre-pregnancy obesity on offspring intake of palatable food and to examine whether maternal HFD consumption impaired development of the dopamine system, critical for the regulation of hedonic feeding. METHODS: The impact of exposure to maternal HFD and obesity on offspring consumption of diets of varying composition was assessed after weaning. The influence of maternal HFD consumption on the development of the prefrontal cortex-dopaminergic system at 13 months of age was also examined. RESULTS: During a preference test, offspring exposed to maternal HFD consumption and obesity displayed increased intake of food high in fat and sugar content relative to offspring from lean control mothers. Maternal HFD consumption suppressed offspring dopamine signaling (as assessed by immunohistochemistry) relative to control offspring. Specifically, there was decreased abundance of dopamine fibers and of dopamine receptor 1 and 2 proteins. CONCLUSIONS: This study reveals that offspring exposed to both maternal HFD consumption and maternal obesity during early development are at increased risk for obesity due to overconsumption of palatable energy-dense food, a behavior that may be related to reduced central dopamine signaling.

Melanocortin agonists stimulate lipolysis in human adipose tissue explants but not in adipocytes.

BACKGROUND: The central melanocortin system is broadly involved in the regulation of mammalian nutrient utilization. However, the function of melanocortin receptors (MCRs) expressed directly in peripheral metabolic tissues is still unclear. The objective of this study was to investigate the lipolytic capacity of MC1-5R in differentiated adipocytes versus intact white adipose tissue. RESULTS: Non-selective MCR agonist α-MSH, MC5R-selective agonist PG-901 and MC4R-selective agonist LY2112688 significantly stimulated lipolysis in intact white adipose tissue, whereas stimulation of MCRs in differentiated adipocytes failed to do so. The lipolytic response of MC5R was decreased in intact human white adipose tissue when co-treating with ß-adrenergic antagonist propranolol, suggesting that the effect may be dependent on neuronal innervation via noradrenalin release. CONCLUSION: When developing an anti-obesity therapeutic drug with selective MC4R/MC5R properties, effects on lipolysis in white adipose tissue may be physiologically relevant.