OBJECTIVE:This study aimed to assess iron oxide magnetic nanoparticles (MNPs) for adipose tissue-targeted therapeutics to restore adipose tissue function and insulin sensitivity in obesity. METHODS:The insulin-sensitizing effects of rosiglitazone and known adverse effects were leveraged for this proof-of-concept assessment of adipose tissue drug targeting. Rosiglitazone was adsorbed to alendronic acid-coated MNPs (rosiMNPs) and a biocompatible magnet implanted in the right inguinal white adipose tissue (ingWAT) of obese, insulin resistant male mice. Following rosiMNP treatment (1.5 mg/kg/day, 18 days), insulin sensitivity and adipose tissue health were assessed. RESULTS:RosiMNPs restored insulin sensitivity as well as systemic rosiglitazone (1.5 mg/kg/day, 18 days), with a shift in adipocyte size compatible with PPARγ-induced adipocyte hyperplasia and no increase in circulating adiponectin. PPARγ target genes were induced in ingWAT with rosiMNPs or systemic rosiglitazone, but only in liver and gonadal WAT of systemically treated mice. Additionally, iron accumulation was shown in the right, targeted ingWAT depot, but not in the left, untargeted ingWAT, kidney, or liver, suggesting targeting was achieved. Unfortunately, the dose and duration of systemic treatment were ineffective at inducing changes in kidney. CONCLUSIONS:Results demonstrate the potential benefits of adipose tissue-targeted therapeutics to improve adipose tissue function to restore insulin sensitivity to prevent the metabolic complications of obesity.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is an important regulator of the stress response in mammals, influencing both the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system (SNS). PACAP has been reported to influence energy homeostasis, including adaptive thermogenesis, an energy burning process in adipose tissue regulated by the SNS in response to cold stress and overfeeding. While research suggests PACAP acts centrally at the level of the hypothalamus, knowledge of PACAP's role within the sympathetic nerves innervating adipose tissues in response to metabolic stressors is limited. This work shows, for the first time, gene expression of PACAP receptors in stellate ganglia and highlights some differential expression with housing temperature. Additionally, we present our dissection protocol, analysis of tyrosine hydroxylase gene expression as a molecular biomarker for catecholamine producing tissue and recommend three stable reference genes for the normalization of quantitative real time-polymerase chain reaction (qRT-PCR) data when working with this tissue. This study adds to information about neuropeptide receptor expression in peripheral ganglia of the sympathetic nervous system innervating adipose tissue and provides insight into PACAP's role in the regulation of energy metabolism.

Abstract One of the many pathophysiological changes associated with obesity is the build up of structural and physiochemical extracellular matrix components in adipose depots, known as adipose tissue fibrosis. Like liver fibrosis, adipose tissue fibrosis occurs as a response to chronic injury and inflammation and can perpetuate inflammation and impede proper tissue functioning. Key adipose tissue fibrosis markers have been identified in obese adipose tissue, including collagen VI and its cleavage product endotrophin, however, adipose tissue fibrosis remains poorly characterized, particularly in its initiating phases. We have developed and characterized a murine model of diet-induced obesity (12 weeks of high fat feeding), insulin resistance, and early fibrotic development in both sexes. While diagnosable fibrosis was absent, as determined by picrosirius red staining, we detected elevated collagen VI, TGF-β, TNF-α, and TIMP-1 mRNA in gonadal white adipose of both sexes. TIMP-4 was decreased in males but elevated in females. Immunohistochemical analysis revealed pericellular build up of collagen VI immunoreactivity in males only, co-localized with immunoreactivity of its protease MMP-14, which is known to generate the pro-fibrotic fragment endotrophin. This work identifies key sex differences and fibrosis markers present during the initiation of adipose tissue fibrosis, earlier than diagnosable fibrosis can be detected, highlighting their potential as therapeutic targets for prevention or reversal of fibrosis in the treatment of obesity and insulin resistance. Presentation: No date and time listed

Abstract   In obesity, energy intake exceeds energy expenditure and concomitantly increases risk of chronic diseases, including metabolic diseases such as diabetes. Therapeutics to correct dysregulations in energy balance are needed and one notable neuropeptide being studied is pituitary adenylate cyclase-activating polypeptide (PACAP), an overarching regulator of the stress response1,2. In the context of metabolism, PACAP has been shown to regulate adaptive thermogenesis, an energy burning process regulated by the sympathetic nervous system (SNS) in response to cold stress and overfeeding. While research suggests PACAP acts centrally at the level of the hypothalamus to regulate energy balance3-5, PACAP is also known to be expressed in the SNS. In preganglionic neurons innervating the adrenal medulla6, PACAP is co-localized with acetylcholine and regulates catecholamine synthesis and release. Recent neuronal tracing studies have shown that postganglionic fibres of the stellate ganglia innervate intrascapular brown adipose tissue (BAT), the main thermogenic tissue in mammals7. However, PACAP's role within the sympathetic nerves innervating and regulating energy metabolism in adipose tissues is not known. As such, our group is interested in characterizing PACAP and PACAP receptor expression in sympathetic nerves innervating and regulating energy metabolism in BAT (via the stellate ganglia) in response to metabolic stressors, such as cold stress. We hypothesize that PACAP is released from preganglionic nerves which binds PACAP receptors (PAC1, VPAC1, VPAC2) expressed in postganglionic nerves of the stellate ganglia. Here we report, for the first time, PAC1 and VPAC1 expression in the stellate ganglia with sex-specific differential gene expression based on housing temperature. Analysis of PAC1 splice variant expression identified at least two variants in tissues of the SNS (adrenal gland, superior cervical ganglia and the stellate ganglia). These results will support future functional studies characterizing PACAP regulation of catecholamine production in peripheral ganglia which will contribute to assessing G-protein coupled receptors (GPCRs) as potential therapeutic targets for obesity and metabolic disease. References 1. Gray SL, Cline DL. 2019. Fink G, Ed. Elsevier: London UK. p.279-91. 2. Mustafa T. 2013. Adv Pharmacol. San Diego, Calif. p.445-57. 3. Banki E, Pakai E, Gaszner B, et al. 2014. J Mol Neurosci 54(3): 543-54. 4. Contreras C, Gonzalez F, Fernø J et al. 2015. Ann Med. 47(2): 150-68. 5. Resch JM, Maunze B, Gerhardt AK, et al. 2013. Am J Physiol-Endoc M. 305(12): E1452-E1463. 6. Eiden LE, Emery AC, Zhang L, et al. 2018. Pflügers Arch. 470(1): 79-88. 7.François M, Torres H, Huesing C, et al. 2019. Ann N T Acad Sci. 1454(1): 3-13. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

Abstract The sympathetic branch of the autonomic nervous system (ANS) regulates the body’s response to psychogenic and systemic stress. In response to stress, endocrine pathways are activated to rebalance physiological changes and restore homeostasis. Gene expression analysis through quantitative real-time PCR (qPCR) is a key method to assess differential gene expression in tissue and cell samples, with high sensitivity and specificity. To assess differential gene expression between samples, qPCR data must be normalized to two or more reference genes to account for technical variation in nucleic acid loading between samples, ensuring data represents target gene expression due to experimental treatments (1). Reference genes must be selected and tested for each experimental paradigm, showing stability of expression between samples and treatments. Reference genes are usually constitutively expressed genes required for cellular maintenance, such as well known “housekeeping” genes or genes encoding ribosomal RNAs. Ganglia of the sympathetic nervous system (SNS) are small in size, and thus total yields of RNA for qPCR experiments are limited. Our group has established a protocol for the isolation of adrenal glands, superior cervical, celiac, and stellate ganglia using a dissecting scope and anatomical landmarks in mice. Here we present optimization data assessing five commonly used reference genes for normalization of qPCR data in three ganglia of the SNS (superior cervical, stellate, and celiac) and adrenal glands. We have evaluated their suitability as reference genes in these tissues after acclimation to cold (4°C) stress compared to the same tissues from animals housed at thermoneutrality (30°C). Through qPCR reaction optimization and subsequent calculations of geNorm stability-measure M, we present optimized primer sequences and reaction conditions, and provide recommendations for combinations of three or more reference genes to use for normalization in gene expression analysis experiments in adrenal gland, superior cervical, stellate or celiac ganglia from male and female mice exposed to thermoneutrality or cold. This research will be valuable to groups interested in SNS physiology and facilitate a streamlined approach to gene expression analysis given the low RNA availability from these minute tissue samples, saving valuable sample, costs and time in carrying out qPCR experiments. Reference: (1) Bustin et al., Clin Chem. 2009 Jan 27;55(4):611-622.

Adaptive thermogenesis in brown adipose tissue is stimulated by the sympathetic nervous system (SNS) in response to cold stress. Using retrograde viral transneuronal tract tracers, previous studies have identified that the paraventricular nucleus (PVN), ventromedial hypothalamus (VMH), and median preoptic nucleus (MnPO) contain neurons that are part of sympathetic outflow tracts to brown adipose tissue, presumptively involved in SNS stimulation of interscapular brown adipose tissue (iBAT). Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) is a peptide hormone known to regulate energy homeostasis, acting in both the central (CNS) and peripheral nervous system (PNS). Mice lacking PACAP have impaired adrenergic-induced thermogenesis and a cold-sensitive phenotype. In the CNS, PACAP is highly expressed in the VMH, MnPO, and PVN of the hypothalamus. Injection of PACAP into the VMN increased core body temperature and sympathetic nerve activity to brown adipose tissue. While these studies show exogenous PACAP can activate sympathetic outflow tracts to brown adipose tissue, they do not confirm that endogenously expressed PACAP induces sympathetic nerve activity as an adaptive mechanism to cold stress, or if sympathetic outflow tracts originating in the hypothalamus express PACAP. We hypothesize that PACAP is expressed in neurons of sympathetic outflow tracts originating in the hypothalamus. To test this hypothesis, PACAP-eGFP transgenic mice were injected with the retrograde neural tracer, pseudorabies virus tagged with β-galactosidase (β-gal, PRV-BaBlu), in iBAT where postganglionic nerves innervate the tissue. Five-days post-infection, animals were culled, brains removed and cryosectioned. Neurons positive for green fluorescent protein (eGFP) and/or β-gal immunoreactivity (ir) were identified by immunohistochemistry in serial coronal and sagittal brain cryo-sections. Co-occurrence of eGFP-ir and β-gal-ir, inferred PACAP expressing neurons present in sympathetic outflow tracts (ImageJ). Co-occurrence was identified in several structures in the hypothalamus and thalamus. In conclusion, this study presents neuroanatomical evidence for populations of PACAPinergic neurons in the hypothalamus that are part of sympathetic outflow tracts to brown adipose tissue, providing further evidence of a central role for PACAP in regulating energy homeostasis.

GIPR activity in α cells is required for the complete metabolic response to a meal.

The association of obesity with cardiovascular disease is well established. However, the interplay of obesity and vascular dysfunction in peripheral tissues such as skeletal muscle, which plays a key in role metabolic homeostasis, requires further study. In particular, there is a paucity of data with regard to sex-differences. Therefore, using a murine model (C57BL/6) of high-fat diet-induced obesity and insulin resistance, we investigated changes in vascular function in gluteus maximus muscle of female and male mice. Diet-induced obesity resulted in alterations in microvascular function. Obese male mice displayed impaired vasoconstriction in second order arterioles compared to lean, male mice, whereas arterioles of obese, female mice displayed significant impairments of both vasodilation and vasoconstrictor responses compared to lean, female mice. Overall, this study identifies distinct differences in how obesity impacts the female and male murine response to skeletal muscle vascular function. This work advances our understanding of sex-specific risk of metabolic complications of obesity and indicates the need for expansion of this study as well as detailed investigation of sex-specific differences in obesity pathology in the future.

New Findings What is the central question of this study? Can chronic treatment of pituitary adenylate cyclase-activating polypeptide (PACAP) deficient mice with the melanocortin agonist melanotan II during cold acclimation rescue the impaired thermogenic capacity previously observed in PACAP deficient mice? What is the main finding and its importance? Using a genetic model of PACAP deficiency, this study provides evidence that PACAP acts upstream of the melanocortin system in regulating sympathetic nerve activity to brown adipose tissue in mice. Impaired adipose tissue function in obesity, including reduced thermogenic potential, has detrimental consequences for metabolic health. Hormonal regulation of adaptive thermogenesis is being explored as a potential therapeutic target for human obesity. Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide expressed in nuclei of the hypothalamus known to regulate energy expenditure, and functional studies reveal a role for PACAP in the central regulation of thermogenesis, although mechanisms are not well understood. We hypothesized that PACAP acts upstream of the melanocortin system to regulate sympathetic nerve activity to stimulate thermogenesis. To assess this, female PACAP(-/-) and PACAP(+/+) mice were given daily peripheral injections of a melanocortin receptor agonist, melanotan II (MTII), for 3 weeks during cold acclimation, and the effect of MTII on thermogenic capacity and adipose tissue remodelling was examined by physiological and histological analyses. MTII partially rescued the impaired thermogenic capacity in PACAP(-/-) mice as compared to PACAP(+/+) mice as determined by measuring noradrenaline-induced metabolic rate. In addition, MTII treatment during cold acclimation corrected the previously identified deficit in lipid utilization in response to adrenergic stimulation in PACAP(-/-) null mice, suggesting impaired lipid mobilization may contribute to the impaired thermogenic capacity of PACAP(-/-) mice. Results presented here provide physiological evidence to suggest that PACAP acts upstream of melanocortin receptors to facilitate sympathetically induced mechanisms of adaptive thermogenesis in response to cold acclimation.

Abstract Pituitary adenylate cyclase-activating polypeptide (PACAP) is being studied to understand the endocrine regulation of energy balance and has been shown to be important in the regulation of the stress response (1,2). Specifically, PACAP has been shown to regulate thermogenesis, an energy burning process regulated by the sympathetic nervous system that contributes to achieving energy homeostasis in response to cold stress and overfeeding. PACAP is expressed in the sympathetic nervous system and is required at the adrenomedullary synapse to maintain epinephrine secretion from the adrenal medulla in response to physiological stress (3). Across the branches of the sympathetic nervous system, PACAP receptor expression is most well characterized in the superior cervical ganglia (SCG) (4). However, a detailed characterization of PACAP and its receptors has not been performed in ganglia whose postganglionic fibres innervate adipose tissues (stellate and celiac ganglia) in response to thermogenic stress. We hypothesized that PACAP is produced by preganglionic neurons innervating the stellate and celiac ganglia, and act on PACAP receptors expressed on the post-ganglionic neurons, and this expression will be upregulated in response to chronic cold stress. Due to their small and amorphous shape, we have developed a protocol to reliably isolate the stellate and celiac ganglia and validate their identity through the presence of tyrosine hydroxylase mRNA, using adrenal and SCG samples as positive controls. PACAP receptor expression (VPAC1, VPAC2, PAC1) was examined in the ganglia utilizing real-time PCR, and PACAP protein was visualized in the ganglia of transgenic mice that express eGFP under the control of the PACAP promoter (PACAP-eGFP mice) (5). This research demonstrates the expression of PACAP receptors in ganglia whose postganglionic fibres innervate adipose tissue, enhancing our understanding of PACAP’s role in the SNS, and its contribution to the regulation of adaptive thermogenesis. References: (1) Gray et al., Pacap: Regulator of the stress response. In: Fink G, ed. Stress: Physiology, biochemistry, and pathology. 2019:279-291. (2) Mustafa, Adv Pharmacol. San Diego, Calif:445-457. (3) Eiden et al., Pflungers Arch. 2018 Jan;470(1):79-88. (4) Braas et al., J Biol Chem. 1999 Sep 24;274(39):27702-27710. (5) Condro et al., J Comp Neurol. 2016 Dec 15; 524(18):3827-3848.

Abstract Pituitary Adenylate Cyclase Activating Polypetptide (PACAP) is a peptide hormone known to regulate energy homeostasis1. Mice lacking PACAP are cold sensitive and have impaired adrenergic-induced thermogenesis2-4. Interestingly, Pacap null mice can survive cold housing if acclimated slowly, similar to what was observed in UCP1 deficient mice4,5. We hypothesized that Pacap-/- mice employ alternate thermogenic pathways to compensate for impaired adaptive thermogenesis and assessed shivering thermogenesis and UCP1-dependent and UCP1-independent adaptive thermogenesis in male and female Pacap-/- and Pacap+/+ with cold acclimation (4°C). Assessment of oxidative fibres in skeletal muscles and behavioural observations did not show evidence of prolonged shivering in male or female Pacap-/- mice during cold acclimation compared to Pacap+/+ mice. We did however observe morphological and molecular differences in adipose tissues of Pacap-/- mice compared to Pacap+/+ mice that were distinct in males and females. Cold-acclimated, female Pacap-/- mice had decreased induction of UCP1 protein in intrascapular brown fat (iBAT), yet had a significantly higher beiging and UCP1 immunoreactivity (ir) in gonadal white fat (gWAT) compared to female Pacap+/+ mice. Furthermore, beiging was observed in inguinal white fat (ingWAT) and gWAT of female Pacap-/- mice housed at thermoneutrality (30°C), a finding not observed in Pacap+/+ control mice. Unlike female mice, we did not observe impaired UCP1 induction in iBAT of male Pacap-/- mice compared to Pacap+/+ mice, and this was associated with negligible UCP1-ir in male gWAT similar to wildtype controls. Despite previous work that has established impaired adaptive thermogenesis in Pacap-/- mice4, we show here that UCP1 protein can be induced in adipose tissues of Pacap-/- mice during cold acclimation, although to a lesser degree or in a different pattern compared to Pacap+/+ control mice. Taken together, this work suggests that while PACAP is clearly involved in regulating thermoregulation, it is not required for cold-induced UCP1 expression. In addition, this work highlights sexual dimorphism in adipose tissue remodeling and induction of thermogenesis with cold acclimation. References: (1) Rudecki AP, et al. Trends Endocrinol Metab. 2016;27(9), 620–632. (2) Gray SL, et al. J Mol Endocrinol. 2001;15(10), 1739–1747. (3) Gray SL, et al. J Endocrinol. 2002;143(10), 3946–3954. (4) Diané A, et al. J Endocrinol. 2014;222, 327–339. (5) Golozoubova V, et al. FASEB J. 2001;15, 2048–2050.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide critical to the regulation of the stress response, including having a role in energy homeostasis. Mice lacking PACAP are cold-sensitive and have impaired adrenergic-induced thermogenesis. Interestingly, Pacap null mice can survive cold housing if acclimated slowly, similar to observations in uncoupling protein 1 (UCP1)-deficient mice. We hypothesized that Pacap null mice use alternate thermogenic pathways to compensate for impaired adaptive thermogenesis when acclimated to cold. Observations of behavior and assessment of fiber type in skeletal muscles did not show evidence of prolonged burst shivering or changes in oxidative metabolism in male or female Pacap(-/-) mice during cold acclimation compared with Pacap(+/+) mice. Despite previous work that has established impaired capacity for adaptive thermogenesis in Pacap null mice, adaptive thermogenesis can be induced in mice lacking PACAP to support survival with cold housing. Interestingly, sex-specific morphological and molecular differences in adipose tissue remodeling were observed in Pacap null mice compared with controls. Thus, sexual dimorphisms are highlighted in adipose tissue remodeling and thermogenesis with cold acclimation in the absence of PACAP. NEW & NOTEWORTHY This manuscript adds to the literature of endocrine regulation of adaptive thermogenesis and energy balance. It specifically describes the role of pituitary adenylate cyclase-activating polypeptide on the regulation of brown adipose tissue via the sympathetic nervous system with a focus on compensatory mechanisms of thermogenesis. We highlight sex-specific differences in energy metabolism.

In vivo genetic manipulation is used to study the impact of gene deletion or re-expression on β-cell function and organism physiology. Cre-LoxP is a system wherein LoxP sites flanking a gene are recognized by Cre recombinase. Cre transgenic mice are the most prevalent technology used to deliver Cre but many models have caveats of off-target recombination, impaired β-cell function, and high cost of animal production. Inducible estrogen receptor conjugated Cre models face leaky recombination and confounding effects of tamoxifen. As an alternative, we characterize an adeno associated virus (AAV) with a rat insulin 1 promoter driving Cre recombinase (AAV8 Ins1-Cre) that is economical and rapid to implement, and has limited caveats. Intraperitoneal AAV8 Ins1-Cre produced efficient β-cell recombination, alongside some hepatic, exocrine pancreas, α-cell, δ-cell, and hypothalamic recombination. Delivery of lower doses via the pancreatic duct retained good rates of β-cell recombination and limited rates of off-target recombination. Unlike inducible Cre in transgenic mice, AAV8 Ins1-Cre required no tamoxifen and premature recombination was avoided. We demonstrate the utility of this technology by inducing hyperglycemia in inducible insulin knockout mice ( Ins1 −/− ; Ins2 f/f ). AAV-mediated expression of Cre in β-cells provides an effective alternative to transgenic approaches for inducible knockout studies.

Ghrelin is a 28-peptide hormone that was originally discovered as a ligand for the growth hormone secretagogue receptor (GHSR) and noted for its roles in food intake and feeding behavior. Beyond this, ghrelin may also regulate glucose tolerance and insulin secretion. In times of starvation, ghrelin defends against hypoglycemia. Contrastingly, ghrelin removal increases insulin secretion and improves glucose tolerance in metabolically-stressed mice. Though ghrelin is predominantly produced by stomach X/A cells, it is also made in the pancreas. Within the pancreatic islet, ghrelin is produced by ε-cells and GHSR is predominantly expressed in somatostatin-secreting δ-cells. This positioning suggests that, locally, islet ghrelin could reach interstitial levels that are higher than detected in circulation and act in a paracrine manner to inhibit insulin secretion. Additionally, GHSR has high constitutive activity and may act in the absence of ghrelin. We hypothesized that a ghrelin-GHSR paracrine axis within the islet modulates insulin secretion and tested this using parallel in vivo and ex vivo approaches in genetic rodent models lacking ghrelin (Ghrl-/-) or GHSR (GHSR-/-). Glycemic responses in GHSR-/- and GHSR+/+male mice did not differ after i.p. glucose tolerance tests (IPGTT) after a 6- or 16-hr fast, oral mixed meal tolerance test (MMTT), or insulin sensitivity during insulin tolerance test (ITT). Female GHSR-/- mice had impaired glucose tolerance after 6-hr fast IPGTT compared to GHSR+/+ (glucose AUC, p=0.01) but did not differ from controls during 16-hr fasted IPGTT, MMTT, or ITT. These data suggest constitutive GHSR activity does not mediate in vivo glucose tolerance. Ghrl-/- and Ghrl+/+ male mice did not differ in glycemia in response to IPGTTs, MMTT, or ITT. Female Ghrl-/- mice showed a slight improvement compared to Ghrl+/+ during MMTT (glucose AUC, p=0.04) but did not differ in other tests. Thus, endogenous ghrelin does not substantially alter glucose tolerance. Given that many factors can affect in vivo glucose tolerance, we perifused isolated islets. Here, exogenous ghrelin robustly decreased glucose-stimulated insulin secretion (GSIS, p<0.001 at 16.7 mM glucose) in a GHSR-dependent manner. Insulin secretion from Ghrl-/- or GHSR-/- islets did not differ from their wild type controls during a glucose ramp or in response to alanine or GLP-1 stimulation. Ex vivo, islet ghrelin and constitutive GHSR activity do not appear to mediate insulin secretion in the paradigms we tested. Collectively, our data provide strong evidence against a paracrine ghrelin-GHSR axis in mediating insulin secretion in lean, chow-fed adult mice. Islet ghrelin and GHSR may impact insulin secretion at earlier stages of development, during times of extreme nutritional stress (e.g., starvation or overnutrition), or in the transition from fasting to fed state.

Objective: The blood-brain barrier (BBB) regulates the entry of substrates and peptides into the brain. Ghrelin is mainly produced in the stomach but exerts its actions in the central nervous system (CNS) by crossing the BBB. Once present in the CNS, ghrelin can act in the hypothalamus to regulate food intake, in the hippocampus to regulate neurogenesis, and in the olfactory bulb to regulate food-seeking behavior. The goal of this study was to determine whether the primary signaling receptor for ghrelin, the growth hormone secretagogue receptor (GHSR), mediates the transport of ghrelin from blood to brain. Methods: We utilized the sensitive and quantitative multiple-time regression analysis technique to determine the transport rate of mouse and human acyl ghrelin (AG) and desacyl ghrelin (DAG) in wildtype and Ghsr null mice. We also measured the regional distribution of these ghrelin peptides throughout the brain. Lastly, we characterized the transport characteristics of human DAG by measuring the stability in serum and brain, saturability of transport, and the complete transfer across the brain endothelial cell. Results: We found the transport rate across the BBB of both forms of ghrelin, AG, and DAG, were not affected by the loss of GHSR. We did find differences in the transport rate between the two isoforms, with DAG being faster than AG; this was dependent on the species of ghrelin, human being faster than mouse. Lastly, based on the ubiquitous properties of ghrelin throughout the CNS, we looked at regional distribution of ghrelin uptake and found the highest levels of uptake in the olfactory bulb. Conclusions: The data presented here suggest that ghrelin transport can occur independently of the GHSR, and ghrelin uptake varies regionally throughout the brain. These findings better our understanding of the gut-brain communication and may lead to new understandings of ghrelin physiology. (C) 2018 Published by Elsevier GmbH.

Obesity arises from disrupted energy balance and is caused by chronically higher energy intake compared to expenditure via basal metabolic rate, exercise, and thermogenesis. The brown adipose tissue (BAT), the primary thermogenic organ, has received considerable attention as a potential therapeutic target due to its ability to burn lipids in the production of heat. Pituitary adenylate cyclase-activating polypeptide (PACAP) has been identified as a key regulator of the physiological stress response both centrally and peripherally. While PACAP has been shown to increase thermogenesis by acting at the hypothalamus to increase sympathetic output to BAT, a peripheral role for PACAP-activated thermogenesis has not been studied. We identified PACAP receptor (PAC1, VPAC1/2) expression for the first time in murine BAT and confirmed their expression in white adipose tissues. PAC1 receptor expression was significantly altered in all three adipose tissues studied in response to 3.5-week cold acclimation, with expression patterns differing by depot type. In primary cell culture, VPAC1 was increased in differentiated compared to non-differentiated brown adipocytes, and the same trend was observed for the PACAP-specific receptor PAC1 in gonadal white fat primary cultures. The primary PAC1R mRNA splice variant in interscapular BAT was determined as isoform 2 by RNA-Seq. These results show that PACAP receptors are present in adipose tissues and may have important functional roles in adipocyte differentiation, lipid metabolism, or adipose sensitization to sympathetic signaling in response to thermogenic stimuli.

AimsFamilial partial lipodystrophic syndrome 3 (FPLD3) is associated with mutations in the transcription factor PPARγ. One of these mutations, the P467L, confers a dominant negative effect. We and others have previously investigated the pathophysiology associated with this mutation using a humanized mouse model that recapitulates most of the clinical symptoms observed in patients who have been phenotyped under different experimental conditions. One of the key clinical manifestations observed, both in humans and mouse models, is the ectopic accumulation of fat in the liver. With this study we aim to dissect the molecular mechanisms that contribute to the excessive accumulation of lipids in the liver and characterize the negative effect of this PPARγ mutation on the activity of PPARα in vivo when activated by fibrates.Material and MethodsP465L‐PPAR mutant and wild‐type mice were divided into 8 experimental groups, 4 different conditions per genotype. Briefly, mice were fed a chow diet or a high‐fat diet (HFD 45% Kcal from fat) for a period of 28 days and treated with WY14643 or vehicle for five days before culling. At the end of the experiment, tissues and plasma were collected. We performed extensive gene expression, fatty acid composition and histological analysis in the livers. The serum collected was used to measure several metabolites and to perform basic lipoprotein profile.ResultsP465L mice showed increased levels of insulin and free fatty acids (FFA) as well as increased liver steatosis. They also exhibit decreased levels of very low density lipoproteins (VLDL) when fed an HFD. We also provide evidence of impaired expression of a number of well‐established PPARα target genes in the P465L mutant livers.ConclusionOur data demonstrate that P465L confers partial resistance to the hypolipidemic action of fibrates. These results show that the fatty liver phenotype observed in P465L mutant mice is not only the consequence of dysfunctional adipose tissue, but also involves defective liver metabolism. All in all, the deleterious effects of P465L‐PPARγ mutation may be magnified by their collateral negative effect on PPARα function.

Obesity is a state of positive energy balance where excess white adipose tissue accumulates to the detriment of metabolic health. Improving adipocyte function with systemic administration of thiazolidinediones (TZDs) improves metabolic outcomes in obesity, however TZD use is limited clinically due to undesirable side effects. Here we evaluate magnetic nanoparticles (MNPs) as a tool to target rosiglitazone (Rosi) specifically to adipose tissue. Results show Rosi can be adsorbed to MNPs (Rosi-MNPs) with hydrophobic coatings for which we present binding and release kinetics. Rosi adsorbed to MNPs retained the ability to induce PPARγ target gene expression in cells. Biodistribution analysis of radiolabeled Rosi-MNPs revealed a fat-implanted magnet significantly enhanced localization of Rosi to the targeted adipose tissue when administered by subcutaneous injection to obese mice. We propose MNPs for targeted delivery of anti-diabetic agents to superficially located subcutaneous adipose tissue.

The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) mediates diverse physiology from neuroprotection to thermoregulation. PACAP is well established as a master regulator of the stress response, regulating psychological and physiological equilibrium via the autonomic nervous system. Neuroanatomical and functional evidence support a role for PACAP in energy metabolism, including thermogenesis, activity, mobilization of energy stores, and appetite. Through integration of this evidence we suggest PACAP be included in the growing list of neuropeptides that mediate energy homeostasis. Future work to uncover the intricacies of PACAP expression and the molecular pathways responsible for PACAP signaling may show potential for this neuropeptide as a therapeutic target as well as further elucidate the complex neuroanatomical networks involved in defending energy balance.