G protein-coupled receptor 12 deficiency results in dyslipidemia and obesity in mice

Genome-wide association study (GWAS) identified PCOS susceptibility variants and replicates reported risk variants

BACKGROUND

Genetic predisposition and environmental factors are considered risk factors for polycystic ovary syndrome (PCOS). Genome-wide association studies (GWAS) have been reported from various subpopulations to evaluate SNPs associated with PCOS risk. No PCOS-associated GWAS study has been reported from India so far.

PURPOSE

The current study was conducted to identify the PCOS-susceptible loci among the North Indian population and to validate the significant loci reported by previous GWAS studies.

METHODS

A total of 272 participants with 134 PCOS patients and 138 age-matched healthy controls were recruited. Genomic DNA was isolated and genotyped by using Infinium Global Screening Array v3.0 microchip considering HWE 10e-5 statistically significant.

RESULTS

A total of fifteen markers have been identified as candidate PCOS risk factors. Only two SNPs, namely rs17186366 and rs11171739 have been identified through replication analysis while comparing the previously reported PCOS GWAS data. In-silico analysis was performed to study the functional impact of identified significant genes for gene ontology, pathways related to gene set, and cluster analysis to determine protein-protein interaction among genes or gene products.

CONCLUSION

The study suggests that multiple variants play an important role in PCOS pathogenesis and emphasizes the importance of further genetic studies among Indian subpopulations. The study also validates two previously reported SNPs in the Indian population. What this study adds to clinical work Study summarizes the importance of candidate gene markers validated by replication and in-silico functional study, significantly involved in PCOS pathogenesis in the studied population. These markers can be used in the future as diagnostic markers for clinical phenotype identification.

Opportunities and challenges in drug discovery targeting the orphan receptor GPR12

G-protein-coupled receptor 12 (GPR12) is a brain-specific expression orphan G-protein-coupled receptor (oGPCR) that regulates various physiological processes. It is an emerging therapeutic target for central nervous system (CNS) disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), attention deficit hyperactivity disorder (ADHD), and schizophrenia, as well as other human diseases, such as cancer, obesity, and metabolic disorders. GPR12 remains a less extensively investigated oGPCR, particularly in terms of its biological functions, signaling pathways, and ligand discovery. The discovery of drug-like small-molecule modulators to probe the brain functions of GPR12 or to act as a potential drug candidates, as well as the identification of reliable biomarkers, are vital to elucidate the roles of this receptor in various human diseases and develop novel target-based therapeutics.

Calnuc-derived nesfatin-1-like peptide is an activator of tumor cell proliferation and migration

Calnuc (nucleobindin-1, nucb1) is a Ca2+ -binding protein involved in the etiology of many human diseases. To understand the functions of calnuc, we have identified a nesfatin-1-like peptide (NLP) in its N terminus that is proteolyzed by a convertase enzyme in the secretory granules of cells. Mutational studies confirm the presence of a proteolytic cleavage site for proprotein convertase subtilisin/kexin type 1 (PCSK1). We demonstrate that NLP regulates Gαq-mediated intracellular Ca2+ dynamics, likely via a G-protein-coupled receptor. NLP treatment to carcinoma cell lines (SCC131 cells) promotes the expression of regulators of cell cycle, proliferation, and clonogenicity by the AKT/mTOR pathway. NLP is causative of augmented migration and epithelial-mesenchymal transition (EMT), illustrating its metastatic propensity and establishing its tumor promotion ability.

GPR12 Inhibits Apoptosis in Epithelial Ovarian Cancer via the Activation of ERK1/2 Signaling

Epithelial ovarian cancer (EOC) is one of the most lethal gynecological malignancies in women worldwide. G protein–coupled receptor 12 (GPR12) is a member of G protein–coupled receptors (GPCRs) and plays an important role in the regulation of cell proliferation and survival. However, its role in EOC is underappreciated. In this study, we found that GPR12 is highly expressed in the EOC tissues and can be an ideal biomarker to predict the prognosis of patients with EOC. GPR12 knockdown obviously inhibits the proliferation of EOC cells by inducing cellular apoptosis in vitro and in vivo. Meanwhile, bioinformatic analysis showed that the inhibitory effect of GPR12 knockdown on the cell viability is closely related with Extracellular signal-regulated kinases 1/2 (ERK1/2) pathway, which has been confirmed by the fact that the activity of ERK1/2 pathway has been significantly blocked in the GPR12 knockdown cells. LM22B-10, ERK1/2 pathway activator, could reverse the inhibited proliferation caused by GPR12 knockdown in the EOC cells. Our findings suggest that GPR12 is involved in the EOC process and is a potential therapeutic target for EOC.

Stratification of rheumatoid arthritis cohort using Ayurveda based deep phenotyping approach identifies novel genes in a GWAS

Background and aim

Genome wide association studies have scaled up both in terms of sample size and range of complex disorders investigated, but these have explained relatively little phenotypic variance. Of the several reasons, phenotypic heterogeneity seems to be a likely contributor for missing out genetic associations of large effects. Ayurveda, the traditional Indian system of medicine is one such tool which adopts a holistic deep phenotyping approach and classifies individuals based on their body constitution/prakriti. We hypothesized that Ayurveda based phenotypic stratification of healthy and diseased individuals will allow us to achieve much desired homogeneous cohorts which would facilitate detection of genetic association of large effects. In this proof of concept study, we performed a genome wide association testing of clinically diagnosed rheumatoid arthritis patients and healthy controls, who were re-phenotyped into Vata, Pitta and Kapha predominant prakriti sub-groups.

Experimental procedure

Genotypes of rheumatoid arthritis cases (Vata = 49; Pitta = 117; Kapha = 78) and controls (Vata = 33; Pitta = 175; Kapha = 85) were retrieved from the total genotype data, used in a recent genome-wide association study performed in our laboratory. A total of 528461 SNPs were included after quality control. Prakriti-wise genome-wide association analysis was employed.

Results and conclusion

This study identified (i) prakriti-specific novel disease risk genes of high effect sizes; (ii) putative candidates of novel therapeutic potential; and (iii) a good correlation between genetic findings and clinical knowledge in Ayurveda. Adopting Ayurveda based deep phenotyping may facilitate explaining hitherto undiscovered heritability in complex traits and may propel much needed progress in personalized medicine.

Cardiometabolic Syndrome: An Update on Available Mouse Models

Cardiometabolic syndrome (CMS), a disease entity characterized by abdominal obesity, insulin resistance (IR), hypertension, and hyperlipidemia, is a global epidemic with approximately 25% prevalence in adults globally. CMS is associated with increased risk for cardiovascular disease (CVD) and development of diabetes. Due to its multifactorial etiology, the development of several animal models to simulate CMS has contributed significantly to the elucidation of the disease pathophysiology and the design of therapies. In this review we aimed to present the most common mouse models used in the research of CMS. We found that CMS can be induced either by genetic manipulation, leading to dyslipidemia, lipodystrophy, obesity and IR, or obesity and hypertension, or by administration of specific diets and drugs. In the last decade, the ob/ob and db/db mice were the most common obesity and IR models, whereas Ldlr-/- and Apoe-/- were widely used to induce hyperlipidemia. These mice have been used either as a single transgenic or combined with a different background with or without diet treatment. High-fat diet with modifications is the preferred protocol, generally leading to increased body weight, hyperlipidemia, and IR. A plethora of genetically engineered mouse models, diets, drugs, or synthetic compounds that are available have advanced the understanding of CMS. However, each researcher should carefully select the most appropriate model and validate its consistency. It is important to consider the differences between strains of the same animal species, different animals, and most importantly differences to human when translating results.

Advances in Neurobiology and Pharmacology of GPR12

GPR12 is a G protein-coupled orphan receptor genetically related to type 1 and type 2 cannabinoid receptors (CB₁ and CB₂) which are ancient proteins expressed all over the body. Both cannabinoid receptors, but especially CB₁, are involved in neurodevelopment and cognitive processes such as learning, memory, brain reward, coordination, etc. GPR12 shares with CB₁ that both are mainly expressed into the brain. Regrettably, very little is known about physiology of GPR12. Concerning its pharmacology, GPR12 seems to be endogenously activated by the lysophospholipids sphingosine-1-phosphate (S1P) and sphingosyl-phosphorylcholine (SPC). Exogenously, GPR12 is a target for the phytocannabinoid cannabidiol (CBD). Functionally, GPR12 seems to be related to neurogenesis and neural inflammation, but its relationship with cognitive functions remains to be characterized. Although GPR12 was initially suggested to be a cannabinoid receptor, it does not meet the five criteria proposed in 2010 by the International Union of Basic and Clinical Pharmacology (IUPHAR). In this review, we analyze all the direct available information in PubMed database about expression, function, and pharmacology of this receptor in central nervous system (CNS) trying to provide a broad overview of its current and prospective neurophysiology. Moreover, in this mini-review we highlight the need to produce more relevant data about the functions of GPR12 in CNS. Hence, this work should motivate further research in this field.

Effect of vitrification temperature and cryoprotectant concentrations on the mRNA transcriptome of bovine mature oocytes after vitrifying at immature stage

The present study aimed to investigate the effect of vitrification temperature (VT) and cryoprotective agent concentrations (CPAs) on the mRNA transcriptome of bovine mature oocytes after vitrifying at immature stage. Cumulus oocyte complexes (COCs) were randomly divided into the following five groups: fresh oocytes (control), oocytes vitrified in liquid helium (LHe; -269 °C) with 5.6 M CPAs (LHe 5.6 M), oocytes vitrified in LHe with 6.6 M CPAs (LHe 6.6 M), oocytes vitrified in liquid nitrogen (LN; -196 °C) with 5.6 M CPAs (LN 5.6 M), and oocytes vitrified in LN with 6.6 M CPAs (LN 6.6 M). We performed two experiments in this study. In experiment 1, after vitrification and thawing, oocytes of vitrified and control groups were subjected to in vitro maturation (IVM), in vitro fertilization (IVF) and in vitro culture (IVC). The rates of normal morphology, maturation, cleavage, and blastocyst formation in LHe 5.6 M were higher than those in LN 5.6 M (P < 0.05). The rates of normal morphology and cleavage in LHe 6.6 M were higher than those in LN 6.6 M (P < 0.05). However, the maturation and blastocyst rates were similar (P > 0.05) between LHe 6.6 M and LN 6.6 M. The blastocyst rate of 13.31% in LHe 5.6 M was the highest among all vitrified groups (P < 0.05). In experiment 2, the mRNA transcriptome of each sample was analyzed by Smart-Seq4, and the differentially expressed genes (DEGs) were detected by edgeR (P ≤ 0.05; fold-change ≥ 2). A total of 505 DEGs (342 upregulated and 163 downregulated genes) were detected in LHe 5.6 M; 609 DEGs (493 upregulated and 116 downregulated genes) were detected in LHe 6.6 M; 218 DEGs (101 upregulated and 117 downregulated genes) were determined in LN 5.6 M; and 221 DEGs (104 upregulated and 117 downregulated genes) were detected in LN 6.6 M. LHe vitrification affected the mRNA transcriptome of bovine mature oocytes after vitrifying at immature stage mainly by upregulating gene expression. Decreased CPAs (5.6 M) reduced the effect of vitrification on mRNA transcriptome when LHe vitrification was used. Among the DEGs closely related to bovine oocytes, the genes possibly related to VT were ND2, MPV17L2, PIF1, LPIN1, IMP3, BRD1, DCTN3, DERA, ATP7B, NEK5, HVCN1, and MARK2. The gene that may be associated with CPAs is CC2D2A. Genes that may be affected by VT and CPAs included PGK1, SLC7A3, FITM2, NPM3, ISCU, CWC15, and PSAP.

Global transcriptomic analysis of the arcuate nucleus following chronic glucocorticoid treatment

OBJECTIVE

Glucocorticoids (GCs) are widely prescribed medications that are well recognized to cause adverse metabolic effects including hyperphagia, obesity, and hyperglycemia. These effects have been recapitulated in a murine model of GC excess, and we hypothesize that they are mediated, in part, through central mechanisms. This study aimed to identify genes in the hypothalamic arcuate nucleus (ARC) that are altered with GC treatment and evaluate their contribution to GC-induced metabolic abnormalities.

METHODS

Corticosterone (Cort; 75 μg/ml) was administered in the drinking water to male C57Bl/6J mice for 2 days or 4 weeks. Phenotypic analysis of each group was undertaken and central and peripheral tissues were collected for biochemical and mRNA analyses. Arcuate nuclei were isolated by laser capture microdissection and tissue analyzed by RNA-seq.

RESULTS

RNA-seq analysis of ARC tissue from 4 week Cort treated mice revealed 21 upregulated and 22 downregulated genes at a time when mice had increased food intake, expansion of adipose tissue mass, and insulin resistance. In comparison, after 2 days Cort treatment, when the main phenotypic change was increased food intake, RNA-seq identified 30 upregulated and 16 downregulated genes. Within the genes altered at 2 days were a range of novel genes but also those known to be regulated by GCs, including Fkbp5, Mt2, Fam107a, as well as some involved in the control of energy balance, such as Agrp, Sepp1, Dio2, and Nmb. Of the candidate genes identified by RNA-seq, type-II iodothyronine deiodinase (Dio2) was chosen for further investigation as it was increased (2-fold) with Cort, and has been implicated in the control of energy balance via the modulation of hypothalamic thyroid hormone availability. Targeted knockdown of Dio2 in the MBH using AAV-mediated CRISPR-Cas9 produced a mild attenuation in GC-induced brown adipose tissue weight gain, as well as a 56% reduction in the GC-induced increase in Agrp. However, this conferred no protection from GC-induced hyperphagia, obesity, or hyperglycemia.

CONCLUSIONS

This study identified a comprehensive set of genes altered by GCs in the ARC and enabled the selection of key candidate genes. Targeted knockdown of hypothalamic Dio2 revealed that it did not mediate the chronic GC effects on hyperphagia and hyperglycemia.

GPR3, GPR6, and GPR12 as novel molecular targets: their biological functions and interaction with cannabidiol

The G protein-coupled receptors 3, 6, and 12 (GPR3, GPR6, and GPR12) comprise a family of closely related orphan receptors with no confirmed endogenous ligands. These receptors are constitutively active and capable of signaling through G protein-mediated and non-G protein-mediated mechanisms. These orphan receptors have previously been reported to play important roles in many normal physiological functions and to be involved in a variety of pathological conditions. Although they are orphans, GPR3, GPR6, and GPR12 are phylogenetically most closely related to the cannabinoid receptors. Using β-arrestin2 recruitment and cAMP accumulation assays, we recently found that the nonpsychoactive phytocannabinoid cannabidiol (CBD) is an inverse agonist for GPR3, GPR6, and GPR12. This discovery highlights these orphan receptors as potential new molecular targets for CBD, provides novel mechanisms of action, and suggests new therapeutic uses of CBD for illnesses such as Alzheimer's disease, Parkinson's disease, cancer, and infertility. Furthermore, identification of CBD as a new inverse agonist for GPR3, GPR6, and GPR12 provides the initial chemical scaffolds upon which potent and efficacious agents acting on these receptors can be developed, with the goal of developing chemical tools for studying these orphan receptors and ultimately new therapeutic agents.

Towards a better understanding of the cannabinoid-related orphan receptors GPR3, GPR6, and GPR12

GPR3, GPR6, and GPR12 are three orphan receptors that belong to the Class A family of G-protein-coupled receptors (GPCRs). These GPCRs share over 60% of sequence similarity among them. Because of their close phylogenetic relationship, GPR3, GPR6, and GPR12 share a high percentage of homology with other lipid receptors such as the lysophospholipid and the cannabinoid receptors. On the basis of sequence similarities at key structural motifs, these orphan receptors have been related to the cannabinoid family. However, further experimental data are required to confirm this association. GPR3, GPR6, and GPR12 are predominantly expressed in mammalian brain. Their high constitutive activation of adenylyl cyclase triggers increases in cAMP levels similar in amplitude to fully activated GPCRs. This feature defines their physiological role under certain pathological conditions. In this review, we aim to summarize the knowledge attained so far on the understanding of these receptors. Expression patterns, pharmacology, physiopathological relevance, and molecules targeting GPR3, GPR6, and GPR12 will be analyzed herein. Interestingly, certain cannabinoid ligands have been reported to modulate these orphan receptors. The current debate about sphingolipids as putative endogenous ligands will also be addressed. A special focus will be on their potential role in the brain, particularly under neurological conditions such as Parkinson or Alzheimer's disease. Reported physiological roles outside the central nervous system will also be covered. This critical overview may contribute to a further comprehension of the physiopathological role of these orphan GPCRs, hopefully attracting more research towards a future therapeutic exploitation of these promising targets.

Novel differences in renal gene expression in a diet-induced obesity model

Obesity is a significant risk factor for both chronic kidney disease and end-stage renal disease. To better understand disease development, we sought to identify novel genes differentially expressed early in disease progression. We first confirmed that mice fed a high-fat (HF) diet exhibit early signs of renal injury including hyperfiltration. We then performed RNA-Seq using renal cortex RNA from C57BL6/J male mice fed either HF or control (Ctrl) diet. We identified 1,134 genes differentially expressed in the cortex on HF vs. Ctrl, of which 31 genes were selected for follow-up analysis. This included the 9 most upregulated, the 11 most downregulated, and 11 genes of interest (primarily sensory receptors and G proteins). Quantitative (q)RT-PCR for these 31 genes was performed on additional male renal cortex and medulla samples, and 11 genes (including all 9 upregulated genes) were selected for further study based on qRT-PCR. We then examined expression of these 11 genes in Ctrl and HF male heart and liver samples, which demonstrated that these changes are relatively specific to the renal cortex. These 11 genes were also examined in female renal cortex, where we found that the expression changes seen in males on a HF diet are not replicated in females, even when the females are started on the diet sooner to match weight gain of the males. In sum, these data demonstrate that in a HF-diet model of early disease, novel transcriptional changes occur that are both sex specific and specific to the renal cortex.

An Update on Non-CB1, Non-CB2 Cannabinoid Related G-Protein-Coupled Receptors

The endocannabinoid system (ECS) has been shown to be of great importance in the regulation of numerous physiological and pathological processes. To date, two Class A G-protein-coupled receptors (GPCRs) have been discovered and validated as the main therapeutic targets of this system: the cannabinoid receptor type 1 (CB1), which is the most abundant neuromodulatory receptor in the brain, and the cannabinoid receptor type 2 (CB2), predominantly found in the immune system among other organs and tissues. Endogenous cannabinoid receptor ligands (endocannabinoids) and the enzymes involved in their synthesis, cell uptake, and degradation have also been identified as part of the ECS. However, its complex pharmacology suggests that other GPCRs may also play physiologically relevant roles in this therapeutically promising system. In the last years, GPCRs such as GPR18 and GPR55 have emerged as possible missing members of the cannabinoid family. This categorization still stimulates strong debate due to the lack of pharmacological tools to validate it. Because of their close phylogenetic relationship, the Class A orphan GPCRs, GPR3, GPR6, and GPR12, have also been associated with the cannabinoids. Moreover, certain endo-, phyto-, and synthetic cannabinoid ligands have displayed activity at other well-established GPCRs, including the opioid, adenosine, serotonin, and dopamine receptor families. In addition, the cannabinoid receptors have also been shown to form dimers with other GPCRs triggering cross-talk signaling under specific conditions. In this mini review, we aim to provide insight into the non-CB1, non-CB2 cannabinoid-related GPCRs that have been reported thus far. We consider the physiological relevance of these molecular targets in modulating the ECS.

Gene expression profiling in human precision cut liver slices in response to the FXR agonist obeticholic acid

BACKGROUND & AIMS

The bile acid-activated farnesoid X receptor (FXR) is a nuclear receptor regulating bile acid, glucose and cholesterol homeostasis. Obeticholic acid (OCA), a promising drug for the treatment of non-alcoholic steatohepatitis (NASH) and type 2 diabetes, activates FXR. Mouse studies demonstrated that FXR activation by OCA alters hepatic expression of many genes. However, no data are available on the effects of OCA in the human liver. Here we generated gene expression profiles in human precision cut liver slices (hPCLS) after treatment with OCA.

METHODS

hPCLS were incubated with OCA for 24 h. Wild-type or FXR(-/-) mice received OCA or vehicle by oral gavage for 7 days.

RESULTS

Transcriptomic analysis showed that well-known FXR target genes, including NR0B2 (SHP), ABCB11 (BSEP), SLC51A (OSTα) and SLC51B (OSTβ), and ABCB4 (MDR3) are regulated by OCA in hPCLS. Ingenuity pathway analysis confirmed that 'FXR/RXR activation' is the most significantly changed pathway upon OCA treatment. Comparison of gene expression profiles in hPCLS and mouse livers identified 18 common potential FXR targets. ChIP-sequencing in mouse liver confirmed FXR binding to IR1 sequences of Akap13, Cgnl1, Dyrk3, Pdia5, Ppp1r3b and Tbx6.

CONCLUSIONS

Our study shows that hPCLS respond to OCA treatment by upregulating well-known FXR target genes, demonstrating its suitability to study FXR-mediated gene regulation. We identified six novel bona-fide FXR target genes in both mouse and human liver. Finally, we discuss a possible explanation for changes in high or low density lipoprotein observed in NASH and primary biliary cholangitis patients treated with OCA based on the genomic expression profile in hPCLS.

The beneficial effects of n-3 polyunsaturated fatty acids on diet induced obesity and impaired glucose control do not require Gpr120

GPR120 (Ffar4) has been postulated to represent an important receptor mediating the improved metabolic profile seen upon ingestion of a diet enriched in polyunsaturated fatty acids (PUFAs). GPR120 is highly expressed in the digestive system, adipose tissue, lung and macrophages and also present in the endocrine pancreas. A new Gpr120 deficient mouse model on pure C57bl/6N background was developed to investigate the importance of the receptor for long-term feeding with a diet enriched with fish oil. Male Gpr120 deficient mice were fed two different high fat diets (HFDs) for 18 weeks. The diets contained lipids that were mainly saturated (SAT) or mainly n-3 polyunsaturated fatty acids (PUFA). Body composition, as well as glucose, lipid and energy metabolism, was studied. As expected, wild type mice fed the PUFA HFD gained less body weight and had lower body fat mass, hepatic lipid levels, plasma cholesterol and insulin levels and better glucose tolerance as compared to those fed the SAT HFD. Gpr120 deficient mice showed a similar improvement on the PUFA HFD as was observed for wild type mice. If anything, the Gpr120 deficient mice responded better to the PUFA HFD as compared to wild type mice with respect to liver fat content, plasma glucose levels and islet morphology. Gpr120 deficient animals were found to have similar energy, glucose and lipid metabolism when fed HFD PUFA compared to wild type mice. Therefore, GPR120 appears to be dispensable for the improved metabolic profile associated with intake of a diet enriched in n-3 PUFA fatty acids.

The central question of type 2 diabetes

Type 2 diabetes (T2D) represents a significant global epidemic with more than 285 million people affected worldwide. Regulating glycemia in T2D patients can be partially achieved with currently available treatment, but intensive research during the last decades have led to the discovery of modified compounds or new targets that could represent great hope for safe and effective treatment in the future. Among them, targets in the CNS that are known to control feeding and body weight have been also shown to exert glucoregulatory actions, and could be a key in the development of a new generation of drugs in the field of T2D. Such drugs would be of great interest since they can be used both in the treatment of diabetes and obesity. This patent review aims to establish an overview of recent patents disclosing new therapeutic opportunities targeting peripheral, as well as central targets for the treatment of T2D.

Identification of a novel small-molecule agonist for human G protein-coupled receptor 3

G protein-coupled receptor 3 (GPR3) is an orphan G protein-coupled receptor (GPCR) predominantly expressed in mammalian brain and oocytes. GPR3 plays important roles in these two organs and is known as a Gαs-coupled receptor-activated constitutively in cells. However, the signal transduction pathway and pharmacological function of GPR3 remain unclear because of the lack of a specific ligand. By use of a human embryonic kidney 293 cell line stably expressing FLAG-GPR3-green fluorescent protein, a chemical screening for GPR3 ligands was performed using homogeneous time-resolved fluorescence cAMP assay. Diphenyleneiodonium chloride (DPI) was identified as a novel agonist of GPR3 with weak or no cross-reactivity with other GPCRs. DPI was further characterized to activate several GPR3-mediated signal transduction pathways, including Ca(2+) mobilization, cAMP accumulation, membrane recruitment of β-arrestin2, and receptor desensitization. Parallel studies revealed that the activity of DPI is much more pronounced than sphingosine 1-phosphate, a previously reported GPR3 agonist. Our study identified a novel and specific agonist of GPR3, which provides a useful tool for further study of this orphan GPCR.

The Concise Guide to PHARMACOLOGY 2013/14: G protein-coupled receptors

The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. G protein-coupled receptors are one of the seven major pharmacological targets into which the Guide is divided, with the others being G protein-coupled receptors, ligand-gated ion channels, ion channels, catalytic receptors, nuclear hormone receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors and Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and the Guide to Receptors and Channels, providing a permanent, citable, point-in-time record that will survive database updates.

Metabolic parameters and emotionality are little affected in G-protein coupled receptor 12 (Gpr12) mutant mice

Background

G-protein coupled receptors (GPR) bear the potential to serve as yet unidentified drug targets for psychiatric and metabolic disorders. GPR12 is of major interest given its putative role in metabolic function and its unique brain distribution, which suggests a role in emotionality and affect. We tested Gpr12 deficient mice in a series of metabolic and behavioural tests and subjected them to a well-established high-fat diet feeding protocol.

Methodology/Principal Findings

Comparing the mutant mice with wild type littermates, no significant differences were seen in body weight, fatness or weight gain induced by a high-fat diet. The Gpr12 mutant mice displayed a modest but significant lowering of energy expenditure and a trend to lower food intake on a chow diet, but no other metabolic parameters, including respiratory rate, were altered. No emotionality-related behaviours (assessed by light-dark box, tail suspension, and open field tests) were affected by the Gpr12 gene mutation.

Conclusions/Significance

Studying metabolic and emotionality parameters in Gpr12 mutant mice did not reveal a major phenotypic impact of the gene mutation. Compared to previous results showing a metabolic phenotype in Gpr12 mice with a mixed 129 and C57Bl6 background, we suggest that a more pure C57Bl/6 background due to further backcrossing might have reduced the phenotypic penetrance.

Involvement of GPR12 in the regulation of cell proliferation and survival

GPR12, a member of the orphan G-protein-coupled receptor family, constitutively activates the Gs protein and increases intracellular cyclic AMP concentrations. GPR12 can be activated by its known ligand-sphingosylphosphorylcholine, which regulates cellular physiological activities, including proliferation, neurite extension, cell clustering, and maintenance of meiotic arrest. However, signaling pathways involved in the GPR12-mediated physiological and biochemical changes are still not clearly illustrated. In the present study, heterologous GPR12 expression was demonstrated to promote proliferation and survival in human embryonic kidney 293 cells. Immunochemical analysis showed that Ki67, a prototypic cell cycle-related nuclear protein, might participate in the regulation of GPR12-mediated cell proliferation. Activation of extracellular signal-regulated protein kinase signaling and increased total Erk1/2 and B-cell lymphoma/leukemia-2 expression were also observed in HEK293 cells overexpressing human GPR12. In addition, we found that GPR12 promoted cell survival under serum deprivation, indicating that GPR12 may play a role in cell proliferation and survival.

The porcine Gpr3 gene: molecular cloning, characterization and expression level in tissues and cumulus-oocyte complexes during in vitro maturation

G protein-coupled receptor 3 (Gpr3) is a member of G protein-coupled receptor rhodopsin family, which is present throughout the follicle within the ovary and functions as a critical factor for the maintenance of meiotic prophase arrest in oocytes by a Gs protein-mediated pathway. In the current paper, attempts were made to clone and characterize a gene encoding Gpr3 from pigs and investigate its expression pattern in tissues and the whole cumulus-oocyte complexes (COCs) in vitro maturation (IVM). Rapid amplification of cDNA ends and RT-PCR gave rise to the full sequence of Gpr3 gene with its length being 2101 bp nucleotides, including an open reading frame of 993 bp, encoding a 331 amino acid polypeptide with the molecular weight of 35.2 kDa. Homology search and sequence multi-alignment demonstrated that the putative porcine Gpr3 protein sequence shared a high identity with other animal Gpr3 orthologs, including several highly conservative motifs and amino acids. Real-time PCR analysis showed that the Gpr3 gene was expressed in tissues of cerebrum, cerebellum, hypothalamus, pituitary, ovary, oviduct, uterus, heart, liver, spleen, lung, kidney, muscle, fat, testis, thymus and granulosa cell, oocyte and COCs at different expression levels. The expression levels of this gene in oocyte, uterus, liver, fat, pituitary and brain were higher than that in other tissues. Interestingly, the mRNA and protein levels of Gpr3 in the whole COCs were down-regulated, and its mRNA expression levels were significantly and negatively correlated with the degrees of cumulus expansion (r = -0.937, P < 0.01) during IVM, suggesting its important roles in cumulus expansion and oocyte maturation.

International Union of Basic and Clinical Pharmacology. LXXIX. Cannabinoid receptors and their ligands: beyond CB₁ and CB₂

There are at least two types of cannabinoid receptors (CB(1) and CB(2)). Ligands activating these G protein-coupled receptors (GPCRs) include the phytocannabinoid Δ(9)-tetrahydrocannabinol, numerous synthetic compounds, and endogenous compounds known as endocannabinoids. Cannabinoid receptor antagonists have also been developed. Some of these ligands activate or block one type of cannabinoid receptor more potently than the other type. This review summarizes current data indicating the extent to which cannabinoid receptor ligands undergo orthosteric or allosteric interactions with non-CB(1), non-CB(2) established GPCRs, deorphanized receptors such as GPR55, ligand-gated ion channels, transient receptor potential (TRP) channels, and other ion channels or peroxisome proliferator-activated nuclear receptors. From these data, it is clear that some ligands that interact similarly with CB(1) and/or CB(2) receptors are likely to display significantly different pharmacological profiles. The review also lists some criteria that any novel "CB(3)" cannabinoid receptor or channel should fulfil and concludes that these criteria are not currently met by any non-CB(1), non-CB(2) pharmacological receptor or channel. However, it does identify certain pharmacological targets that should be investigated further as potential CB(3) receptors or channels. These include TRP vanilloid 1, which possibly functions as an ionotropic cannabinoid receptor under physiological and/or pathological conditions, and some deorphanized GPCRs. Also discussed are 1) the ability of CB(1) receptors to form heteromeric complexes with certain other GPCRs, 2) phylogenetic relationships that exist between CB(1)/CB(2) receptors and other GPCRs, 3) evidence for the existence of several as-yet-uncharacterized non-CB(1), non-CB(2) cannabinoid receptors; and 4) current cannabinoid receptor nomenclature.

Hypothalamic responses to fasting indicate metabolic reprogramming away from glycolysis toward lipid oxidation

Nutrient-sensitive hypothalamic neurons regulate energy balance and glucose homeostasis, but the molecular mechanisms mediating hypothalamic responses to nutritional state remain incompletely characterized. To address these mechanisms, the present studies used quantitative PCR to characterize the expression of a panel of genes the hypothalamic expression by nutritional status of which had been suggested by DNA microarray studies. Although these genes regulate a variety of function, the most prominent set regulate intermediary metabolism, and the overall pattern clearly indicated that a 48-h fast produced a metabolic reprogramming away from glucose metabolism and toward the utilization of alternative fuels, particularly lipid metabolism. This general reprogramming of intermediary metabolism by fasting was observed both in cortex and hypothalamus but most prominently in hypothalamus. The effect of fasting on the expression of these genes may be mediated by reduction in plasma glucose or glucose metabolism, rather than leptin, because they were generally recapitulated by hypoglycemia even in the presence of elevated insulin and in vitro by low glucose but were not recapitulated in ob/ob mice. These studies suggest that fasting reduces glucose metabolism and thus minimizes the production of hypothalamic malonyl-coenzyme A. However, because the reprogramming of glucose metabolism by fasting was also observed in cortex, this apparent substrate competition may mediate more general responses to nutritional deprivation, including those responsible for the protective effects of dietary restriction. The present studies also provide a large panel of novel glucose-regulated genes that can be used as markers of glucose action to address mechanisms mediating hypothalamic responses to nutritional state.

Two new 5-hydroxy-2-pyrone derivatives isolated from a marine-derived fungus Aspergillus flavus

Two new compounds, 4-(hydroxymethyl)-5-hydroxy-2H-pyran-2-one (1) and (5-hydroxy-2-oxo-2H-pyran-4-yl) methyl acetate (2), have been isolated from a marine-derived fungus Aspergillus flavus. Their structures were determined by spectroscopic data. Compound 1 induced the production of cAMP on GPR12 transfected CHO and HEK293 cells in a dose-dependent manner, which indicated 1 might be a possible ligand for GPR12.

GPR10 deficiency in mice results in altered energy expenditure and obesity

In this study, mice carrying a disrupted gene encoding GPR10 (GPR10 KO) were studied to elucidate the function and importance of this receptor regarding metabolism. Female and male GPR10 KO mice had higher body weight after 11 and 15 weeks of age, respectively. The increased body weight was a result of increased fat mass. The obesity was much more pronounced in female mice, which also had a significant decrease in energy expenditure. In correlation to obesity, higher plasma levels of leptin, total cholesterol, and fractions of LDL and HDL were found in GPR10 KO compared to WT mice. Interestingly, GPR10 KO female mice had decreased relative food intake in correlation to higher hypothalamic expression levels of the anorexic signals CRH and POMC. In conclusion, female mice deficient of the gene encoding GPR10 develop higher body weight and obesity due to lower energy expenditure.

G-protein-coupled receptors and islet function-implications for treatment of type 2 diabetes

Islet function is regulated by a number of different signals. A main signal is generated by glucose, which stimulates insulin secretion and inhibits glucagon secretion. The glucose effects are modulated by many factors, including hormones, neurotransmitters and nutrients. Several of these factors signal through guanine nucleotide-binding protein (G protein)-coupled receptors (GPCR). Examples of islet GPCR are GPR40 and GPR119, which are GPCR with fatty acids as ligands, the receptors for the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), the receptors for the islet hormones glucagon and somatostatin, the receptors for the classical neurotransmittors acetylcholine (ACh; M(3) muscarinic receptors) and noradrenaline (beta(2)- and alpha(2)-adrenoceptors) and for the neuropeptides pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP; PAC(1) and VPAC(2) receptors), cholecystokinin (CCK(A) receptors) and neuropeptide Y (NPY Y1 receptors). Other islet GPCR are the cannabinoid receptor (CB(1) receptors), the vasopressin receptors (V1(B) receptors) and the purinergic receptors (P(2Y) receptors). The islet GPCR couple mainly to adenylate cyclase and to phospholipase C (PLC). Since important pharmacological strategies for treatment of type 2 diabetes are stimulation of insulin secretion and inhibition of glucagon secretion, islet GPCR are potential drug targets. This review summarizes knowledge on islet GPCR.