Further evidence for the role of ENPP1 in obesity: association with morbid obesity in Finns

Genetic architecture and selection of Anhui autochthonous pig population revealed by whole genome resequencing

The genetic resources among pigs in Anhui Province are diverse, but their value and potential have yet to be discovered. To illustrate the genetic diversity and population structure of the Anhui pigs population, we resequenced the genome of 150 pigs from six representative Anhui pigs populations and analyzed this data together with the sequencing data from 40 Asian wild boars and commercial pigs. Our results showed that Anhui pigs were divided into two distinct types based on ancestral descent: Wannan Spotted pig (WSP) and Wannan Black pig (WBP) origins from the same ancestor and the other four populations origins from another ancestor. We also identified several potential selective sweep regions associated with domestication characteristics among Anhui pigs, including reproduction-associated genes (CABS1, INSL6, MAP3K12, IGF1R, INSR, LIMK2, PATZ1, MAPK1), lipid- and meat-related genes (SNX19, MSTN, MC5R, PRKG1, CREBBP, ADCY9), and ear size genes (MSRB3 and SOX5). Therefore, these findings expand the catalogue and how these genetic differences among pigs and this newly generated data will be a valuable resource for future genetic studies and for improving genome-assisted breeding of pigs and other domesticated animals.

Melanocortin-5 Receptor: Pharmacology and Its Regulation of Energy Metabolism

As the most recent melanocortin receptor (MCR) identified, melanocortin-5 receptor (MC5R) has unique tissue expression patterns, pharmacological properties, and physiological functions. Different from the other four MCR subtypes, MC5R is widely distributed in both the central nervous system and peripheral tissues and is associated with multiple functions. MC5R in sebaceous and preputial glands regulates lipid production and sexual behavior, respectively. MC5R expressed in immune cells is involved in immunomodulation. Among the five MCRs, MC5R is the predominant subtype expressed in skeletal muscle and white adipose tissue, tissues critical for energy metabolism. Activated MC5R triggers lipid mobilization in adipocytes and glucose uptake in skeletal muscle. Therefore, MC5R is a potential target for treating patients with obesity and diabetes mellitus. Melanocortin-2 receptor accessory proteins can modulate the cell surface expression, dimerization, and pharmacology of MC5R. This minireview summarizes the molecular and pharmacological properties of MC5R and highlights the progress made on MC5R in energy metabolism. We poInt. out knowledge gaps that need to be explored in the future.

Implication of Melanocortin Receptor Genes in the Familial Comorbidity of Type 2 Diabetes and Depression

The melanocortin receptors are G-protein-coupled receptors, which are essential components of the hypothalamic–pituitary–adrenal axis, and they mediate the actions of melanocortins (melanocyte-stimulating hormones: α-MSH, β-MSH, and γ-MSH) as well as the adrenocorticotropin hormone (ACTH) in skin pigmentation, adrenal steroidogenesis, and stress response. Three melanocortin receptor genes (MC1R, MC2R, and MC5R) contribute to the risk of major depressive disorder (MDD), and one melanocortin receptor gene (MC4R) contributes to the risk of type 2 diabetes (T2D). MDD increases T2D risk in drug-naïve patients; thus, MDD and T2D commonly coexist. The five melanocortin receptor genes might confer risk for both disorders. However, they have never been investigated jointly to evaluate their potential contributing roles in the MDD-T2D comorbidity, specifically within families. In 212 Italian families with T2D and MDD, we tested 11 single nucleotide polymorphisms (SNPs) in the MC1R gene, 9 SNPs in MC2R, 3 SNPs in MC3R, 4 SNPs in MC4R, and 2 SNPs in MC5R. The testing used 2-point parametric linkage and linkage disequilibrium (LD) (i.e., association) analysis with four models (dominant with complete penetrance (D1), dominant with incomplete penetrance (D2), recessive with complete penetrance (R1), and recessive with incomplete penetrance (R2)). We detected significant (p ≤ 0.05) linkage and/or LD (i.e., association) to/with MDD for one SNP in MC2R (rs111734014) and one SNP in MC5R (rs2236700), and to/with T2D for three SNPs in MC1R (rs1805007 and rs201192930, and rs2228479), one SNP in MC2R (rs104894660), two SNPs in MC3R (rs3746619 and rs3827103), and one SNP in MC4R genes (Chr18-60372302). The linkage/LD/association was significant across different linkage patterns and different modes of inheritance. All reported variants are novel in MDD and T2D. This is the first study to report risk variants in MC1R, MC2R, and MC3R genes in T2D. MC2R and MC5R genes are replicated in MDD, with one novel variant each. Within our dataset, only the MC2R gene appears to confer risk for both MDD and T2D, albeit with different risk variants. To further clarity the role of the melanocortin receptor genes in MDD-T2D, these findings should be sought among other ethnicities as well.

ARPE-19-derived VEGF-containing exosomes promote neovascularization in HUVEC: the role of the melanocortin receptor 5

ARPE-19 retinal pigment epithelial cells cultured in a medium containing 35 mM D-glucose led to an augmented ROS formation and release of vascular endothelial factor (VEGF)-containing exosomes compared to ARPE-19 cells cultured in a medium containing 5 mM D-glucose (standard medium). Exposing these cells to the melanocortin 5 receptor agonist (MCR₅) PG-901 (10^-10M), for 9 d reduced ROS generation, the number of exosomes released and their VEGF content. In contrast, incubating the cells with the melanocortin receptor MCR₁ agonist BMS-470539 (10^-5 M) or with the mixed MCR_3/4 agonist MTII (0.30 nmol) did not produce any significant decrease in ROS levels. ARPE-19-derived VEGF-containing exosomes promoted neovascularization in human umbilical vein endothelial cells (HUVEC), an effect that was markedly reduced by PG-901 (10^-10M) but not by the MCR_3/4 agonist MTII (0.30 nmol) or the MCR₁ agonist BMS-470539 (10^-5 M). The MCR₅-related action in the ARPE-19 cells was accompanied by the increased expression of two coupled factors, cytochrome p4502E1 (CYP2E1) and nuclear factor kappa b (Nf-κB). These are both involved in high glucose signalling, in ROS generation and, interestingly, were reduced by the MCR₅ agonist in the ARPE-19 cells. Altogether, these data suggest that MCR₅ is a modulator of the responses stimulated by glucose in ARPE-19 cells, which might possibly be translated into a modulation of the retinal pigment epithelium response to diabetes in vivo.

The Melanocortin MC5R as a New Target for Treatment of High Glucose-Induced Hypertrophy of the Cardiac H9c2 Cells

The study explored the anti-hypertrophic effect of the melanocortin MC5R stimulation in H9c2 cardiac myocytes exposed to high glucose. This has been done by using α-MSH and selective MC5R agonists and assessing the expression of GLUT4 and GLUT1 transporters, miR-133 and urotensin receptor levels as a marker of cardiac hypertrophy. The study shows for the first time an up-regulation of MC5R expression levels in H9c2 cardiomyocytes exposed to high glucose medium (33 mM D-glucose) for 48 h, compared to cells grown in normal glucose medium (5.5 mM D-glucose). Moreover, H9c2 cells exposed to high glucose showed a significant reduction in cell viability (-40%), a significant increase in total protein per cell number (+109%), and an increase of the urotensin receptor expression levels as an evidence of cells hypertrophy. The pharmacological stimulation of MC5R with α-MSH (90 pM)of the high glucose exposed H9c2 cells increased the cell survival (+50,8%) and reduced the total protein per cell number (-28,2%) with respect to high glucose alone, confirming a reduction of the hypertrophic state as per cell area measurement. Similarly, PG-901 (selective agonist, 10^-10 M) significantly increased cell viability (+61,0 %) and reduced total protein per cell number (-40,2%), compared to cells exposed to high glucose alone. Interestingly, the MC5R agonist reduced the GLUT1/GLUT4 glucose transporters ratio on the cell membranes exhibited by the hypertrophic H9c2 cells and increased the intracellular PI3K activity, mediated by a decrease of the levels of the miRNA miR-133a. The beneficial effects of MC5R agonism on the cardiac hypertrophy caused by high glucose was also observed also by echocardiographic evaluations of rats made diabetics with streptozotocin (65 mg/kg i.p.). Therefore, the melanocortin MC5R could be a new target for the treatment of high glucose-induced hypertrophy of the cardiac H9c2 cells.

Melanocortins, Melanocortin Receptors and Multiple Sclerosis

The melanocortins and their receptors have been extensively investigated for their roles in the hypothalamo-pituitary-adrenal axis, but to a lesser extent in immune cells and in the nervous system outside the hypothalamic axis. This review discusses corticosteroid dependent and independent effects of melanocortins on the peripheral immune system, central nervous system (CNS) effects mediated through neuronal regulation of immune system function, and direct effects on endogenous cells in the CNS. We have focused on the expression and function of melanocortin receptors in oligodendroglia (OL), the myelin producing cells of the CNS, with the goal of identifying new therapeutic approaches to decrease CNS damage in multiple sclerosis as well as to promote repair. It is clear that melanocortin signaling through their receptors in the CNS has potential for neuroprotection and repair in diseases like MS. Effects of melanocortins on the immune system by direct effects on the circulating cells (lymphocytes and monocytes) and by signaling through CNS cells in regions lacking a mature blood brain barrier are clear. However, additional studies are needed to develop highly effective MCR targeted therapies that directly affect endogenous cells of the CNS, particularly OL, their progenitors and neurons.

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.

•

Glucose stimulates α-MSH release from the pituitary.

•

Systemic α-MSH drives glucose disposal and thermogenesis in skeletal muscles.

•

α-MSH acts on MC5R expressed on skeletal muscles and activate cAMP-PKA pathway.

•

The combined treatment of nonselective or selective PDE 4 inhibitor and α-MSH ameliorates glucose intolerance in obese mice.

Common genetic variation in and near the melanocortin 4 receptor gene (MC4R) is associated with body mass index in American Indian adults and children

Six rare functional coding mutations were previously identified in melanocortin 4 receptor (MC4R) in 6,760 American Indians. Individuals heterozygous for one of these mutations become obese while young. We now investigate whether common non-coding variation near MC4R also contributes to obesity. Fifty-six tag single-nucleotide polymorphisms (SNPs) were genotyped in 3,229 full-heritage Pima Indians, and nine of these SNPs which showed evidence for association were genotyped in additional 3,852 mixed-heritage American Indians. Associations of SNPs with maximum body mass index (BMI) in adulthood (n = 5,918), BMI z score in childhood (n = 5,350), percent body fat (n = 864), energy expenditure (n = 358) and ad libitum food intake (n = 178) were assessed. Conditional analyses demonstrated that SNPs, rs74861148 and rs483125, were independently associated with BMI in adulthood (β = 0.68 kg/m² per risk allele, p = 5 × 10⁻⁵; β = 0.58 kg/m², p = 0.002, respectively) and BMI z score in childhood (β = 0.05, p = 0.02; β = 0.07, p = 0.01, respectively). One haplotype (frequency = 0.35) of the G allele at rs74861148 and the A allele at rs483125 provided the strongest evidence for association with adult BMI (β = 0.89 kg/m², p = 5.5 × 10⁻⁷), and was also associated with childhood BMI z score (β = 0.08, p = 0.001). In addition, a promoter SNP rs11872992 was nominally associated with adult BMI (β = 0.61 kg/m², p = 0.05) and childhood BMI z score (β = 0.11, p = 0.01), where the risk allele also modestly decreased transcription in vitro by 12 % (p = 0.005). This risk allele was further associated with increased percent body fat (β = 2.2 %, p = 0.002), increased food intake (β = 676 kcal/day, p = 0.007) and decreased energy expenditure (β = −53.4 kcal/day, p = 0.054). Common and rare variation in MC4R contributes to obesity in American Indians.

Hypothesis of the neuroendocrine cortisol pathway gene role in the comorbidity of depression, type 2 diabetes, and metabolic syndrome

Depression, type 2 diabetes (T2D), and metabolic syndrome (MetS) are often comorbid. Depression per se increases the risk for T2D by 60%. This risk is not accounted for by the use of antidepressant therapy. Stress causes hyperactivation of the hypothalamic–pituitary–adrenal (HPA) axis, by triggering the hypothalamic corticotropin-releasing hormone (CRH) secretion, which stimulates the anterior pituitary to release the adrenocorticotropin hormone (ACTH), which causes the adrenal secretion of cortisol. Depression is associated with an increased level of cortisol, and CRH and ACTH at inappropriately “normal” levels, that is too high compared to their expected lower levels due to cortisol negative feedback. T2D and MetS are also associated with hypercortisolism. High levels of cortisol can impair mood as well as cause hyperglycemia and insulin resistance and other traits typical of T2D and MetS. We hypothesize that HPA axis hyperactivation may be due to variants in the genes of the CRH receptors (CRHR1, CRHR2), corticotropin receptors (or melanocortin receptors, MC1R-MC5R), glucocorticoid receptor (NR3C1), mineralocorticoid receptor (NR3C2), and of the FK506 binding protein 51 (FKBP5), and that these variants may be partially responsible for the clinical association of depression, T2D and MetS. In this review, we will focus on the correlation of stress, HPA axis hyperactivation, and the possible genetic role of the CRHR1, CRHR2, MCR1–5, NR3C1, and NR3C2 receptors and FKBP5 in the susceptibility to the comorbidity of depression, T2D, and MetS. New studies are needed to confirm the hypothesized role of these genes in the clinical association of depression, T2D, and MetS.

The association between ANKH promoter polymorphism and chondrocalcinosis is independent of age and osteoarthritis: results of a case-control study

Introduction

Chondrocalcinosis (CC) most commonly results from calcium pyrophosphate crystal deposition (CPPD). The objective of this study is to examine the association between candidate single-nucleotide polymorphisms (SNPs) and radiographic CC.

Methods

SNPs in ankylosis human (ANKH), high ferritin (HFE), tissue non-specific alkaline phosphatase (TNAP), ecto-neucleotide pyrophosphatase 1 (ENPP1), and transferrin (TE) genes were genotyped in participants of the Genetics of Osteoarthritis and Lifestyle (GOAL) and Nottingham Osteoarthritis Case-Control studies. Adjusted genotype odds ratio (aOR_GENOTYPE), the OR for association between one additional minor allele and CC, was calculated and adjusted for age, gender, body mass index (BMI), and osteoarthritis (OA) by using binary logistic regression. Statistical significance was set at P ≤0.003 after Bonferroni correction for multiple tests.

Results

The -4bpG > A polymorphism in the 5′ untranslated region (5′ UTR) of ANKH associated with CC after Bonferroni correction. This was independent of age, gender, OA, and BMI; aOR_GENOTYPE (95% confidence interval, or CI) was 1.39 (1.14-1.69) (P = 0.001). rs3045 and rs875525, two other SNPs in ANKH, associated with CC; aOR_GENOTYPE (95% CI) values were 1.31 (1.09-1.58) (P = 0.005) and 1.18 (1.03-1.35) (P = 0.015), respectively; however, this was non-significant after Bonferroni correction.

Conclusions

This study validates the association between a functional polymorphism in the 5′ UTR of ANKH and CC and shows for the first time that this is independent of age and OA – the two key risk factors for CC. It shows that other SNPs in ANKH may also associate with CC. This supports the role of extracellular inorganic pyrophosphate in the pathogenesis of CC. The findings of this hospital-based study require replication in a community-based population.

Family of melanocortin receptor (MCR) genes in mammals-mutations, polymorphisms and phenotypic effects

The melanocortin receptor gene family consists of five single-exon members, which are located on autosomes. Three genes (MC2R, MC4R and MC5R) are syntenic in the human, mouse, cattle and dog genomes, while in the pig, the syntenic group comprises MC1R, MC2R and MC5R. Two genes (MC1R and MC4R) have been extensively studied due to their function in melanogenesis (MC1R) and energy control (MC4R). Conservative organisation of these genes in five mammalian species (human, mouse, cattle, pig and dog), in terms of the encoded amino acid sequence, is higher in the case of MC4R compared to MC1R. Polymorphisms of these two genes are responsible or associated with variation of pigmentation (MC1R) and adipose tissue deposition (MC4R). Polymorphic variants in MC1R, causing coat colour variation, were described in humans and domestic mammals (cattle, horse, pig, sheep, dog), as well as farm red and arctic foxes. The MC4R gene is very polymorphic in humans and it is well known that some variants cause monogenic obesity or significantly contribute to the development of polygenic obesity. Such relationships are not so evident in domestic mammals; however, at least one missense substitution (298Asp > Asn) in the porcine MC4R significantly contributes, at least in some breeds, to fat tissue accumulation, feed conversion ratio and daily weight gain. Knowledge on the phenotypic effects of polymorphisms of MC2R, MC3R and MC5R in domestic mammals is scarce, probably due to the small number of reports addressing these genes. Thus, further studies focused on these genes should be undertaken.

Identification of shared genetic susceptibility locus for coronary artery disease, type 2 diabetes and obesity: a meta-analysis of genome-wide studies

Type 2 diabetes (2DM), obesity, and coronary artery disease (CAD) are frequently coexisted being as key components of metabolic syndrome. Whether there is shared genetic background underlying these diseases remained unclear. We performed a meta-analysis of 35 genome screens for 2DM, 36 for obesity or body mass index (BMI)-defined obesity, and 21 for CAD using genome search meta-analysis (GSMA), which combines linkage results to identify regions with only weak evidence and provide genetic interactions among different diseases. For each study, 120 genomic bins of approximately 30 cM were defined and ranked according to the best linkage evidence within each bin. For each disease, bin 6.2 achieved genomic significanct evidence, and bin 9.3, 10.5, 16.3 reached suggestive level for 2DM. Bin 11.2 and 16.3, and bin 10.5 and 9.3, reached suggestive evidence for obesity and CAD respectively. In pooled all three diseases, bin 9.3 and 6.5 reached genomic significant and suggestive evidence respectively, being relatively much weaker for 2DM/CAD or 2DM/obesity or CAD/obesity. Further, genomewide significant evidence was observed of bin 16.3 and 4.5 for 2DM/obesity, which is decreased when CAD was added. These findings indicated that bin 9.3 and 6.5 are most likely to be shared by 2DM, obesity and CAD. And bin 16.3 and 4.5 are potentially common regions to 2DM and obesity only. The observed shared susceptibility regions imply a partly overlapping genetic aspects of disease development. Fine scanning of these regions will definitely identify more susceptibility genes and causal variants.

ATP acts as a survival signal and prevents the mineralization of aortic valve

Calcific aortic valve disease (CAVD) is a disorder related to progressive mineralization of valvular tissue that is a leading cause of heart disease. Thus far, there is no medical treatment to prevent the mineralization of aortic valves. It is generally thought that pathologic mineralization is linked to apoptosis of vascular cells. However, the role of apoptosis during mineralization as well as the survival signals for valvular interstitial cells (VICs), the main cellular component of aortic valves, remains to be identified. Here, through several lines of evidence, we show that bioavailability of extracellular ATP is a signal which determines survival or apoptosis of VICs and, in doing so, plays a major role in the development of CAVD. Specifically, in CAVD and in VIC cultures undergoing mineralization, we found a high level of the ectonucleotidase ENPP1. In addition, a genetic polymorphism in the intron 9 of the ENPP1 gene was associated with CAVD in a case-control cohort as well as with mRNA expression levels of ENPP1 in aortic valves. A high level of ENPP1 in CAVD promoted apoptosis-mediated mineralization of VICs by depleting the extracellular pool of ATP. We then documented that release of ATP by VICs promoted cell survival via the P2Y(2) receptor and the PI3K/Akt signaling pathway. Hence, our results show that level of ENPP1 modulates extracellular concentration of ATP, which is an important survival signal for VICs. These findings may help to develop novel pharmacological treatment for CAVD.

Possible role for ENPP1 polymorphism in obesity but not for INSIG2 and PLIN variants

Previous studies have suggested that ENPP1, INSIG2, and PLIN may be linked with a higher risk for obesity or with increased phenotypic measures of obesity. We selected polymorphisms in these candidate genes based on their prior associations with obesity risk or obesity parameters. K121Q (rs1044498) in ENPP1, rs7566605 in INSIG2, and rs894160 in PLIN were genotyped by Taqman assays in a Belgian sample of 1,078 obese subjects (body mass index (BMI) > 30 kg/m(2)) and 323 lean controls (18.5 < BMI < 25 kg/m(2)). BMI, waist circumference, and waist-to-hip ratio (WHR) were assessed by standard methods while a computerized tomography-scan was used to measure visceral (VFA), subcutaneous (SFA), and total (TFA) abdominal fat areas. Presence of the rare allele was not significantly different between cases and controls for the three variants that were tested, while only WHR was associated with ENPP1 in obese subjects. Our data thus indicate that K121Q, rs7566605, and rs894160 are not major contributing factors for obesity.