Nutritional regulation of genome-wide association obesity genes in a tissue-dependent manner

Targeting E3 ubiquitin ligases and their adaptors as a therapeutic strategy for metabolic diseases

Posttranslational modification of proteins via ubiquitination determines their activation, translocation, dysregulation, or degradation. This process targets a large number of cellular proteins, affecting all biological pathways involved in the cell cycle, development, growth, and differentiation. Thus, aberrant regulation of ubiquitination is likely associated with several diseases, including various types of metabolic diseases. Among the ubiquitin enzymes, E3 ubiquitin ligases are regarded as the most influential ubiquitin enzymes due to their ability to selectively bind and recruit target substrates for ubiquitination. Continued research on the regulatory mechanisms of E3 ligases and their adaptors in metabolic diseases will further stimulate the discovery of new targets and accelerate the development of therapeutic options for metabolic diseases. In this review, based on recent discoveries, we summarize new insights into the roles of E3 ubiquitin ligases and their adaptors in the pathogenesis of metabolic diseases by highlighting recent evidence obtained in both human and animal model studies.

The Hexosamine Biosynthesis Pathway: Regulation and Function

The hexosamine biosynthesis pathway (HBP) produces uridine diphosphate-N-acetyl glucosamine, UDP-GlcNAc, which is a key metabolite that is used for N- or O-linked glycosylation, a co- or post-translational modification, respectively, that modulates protein activity and expression. The production of hexosamines can occur via de novo or salvage mechanisms that are catalyzed by metabolic enzymes. Nutrients including glutamine, glucose, acetyl-CoA, and UTP are utilized by the HBP. Together with availability of these nutrients, signaling molecules that respond to environmental signals, such as mTOR, AMPK, and stress-regulated transcription factors, modulate the HBP. This review discusses the regulation of GFAT, the key enzyme of the de novo HBP, as well as other metabolic enzymes that catalyze the reactions to produce UDP-GlcNAc. We also examine the contribution of the salvage mechanisms in the HBP and how dietary supplementation of the salvage metabolites glucosamine and N-acetylglucosamine could reprogram metabolism and have therapeutic potential. We elaborate on how UDP-GlcNAc is utilized for N-glycosylation of membrane and secretory proteins and how the HBP is reprogrammed during nutrient fluctuations to maintain proteostasis. We also consider how O-GlcNAcylation is coupled to nutrient availability and how this modification modulates cell signaling. We summarize how deregulation of protein N-glycosylation and O-GlcNAcylation can lead to diseases including cancer, diabetes, immunodeficiencies, and congenital disorders of glycosylation. We review the current pharmacological strategies to inhibit GFAT and other enzymes involved in the HBP or glycosylation and how engineered prodrugs could have better therapeutic efficacy for the treatment of diseases related to HBP deregulation.

Obesity-Related Genes Expression in Testes and Sperm Parameters Respond to GLP-1 and Caloric Restriction

Aim: Calorie restriction (CR) diets and glucagon-Like Peptide-1 (GLP-1) analogs are known to alter energy homeostasis with the potential to affect the expression of obesity-related genes (ORGs). We hypothesized that CR and GLP-1 administration can alter ORGs expression in spermatozoa and testes, as well as the sperm parameters implicated in male fertility. Materials and Methods: Six-week-old adult male Wistar rats (n = 16) were divided into three groups, submitted either to CR (n = 6, fed with 30% less chow diet than the control rats), GLP-1 administration (n = 5, 3.5 pmol/min/kg intraperitoneal) for 28 days, or used as controls (n = 5, fed ad libitum). Selected ORGs expression, namely the fat mass and obesity-associated (FTO), melanocortin-4 receptor (MC4R), glucosamine-6-phosphate deaminase 2 (GNPDA2), and transmembrane protein 18 (TMEM18) were evaluated in testes and spermatozoa by a quantitative polymerase chain reaction (qPCR). Results: CR resulted in lower body weight gain and insulin resistance, but a higher percentage of sperm head defects. GLP-1 administration, despite showing no influence on body weight or glucose homeostasis, resulted in a lower percentage of sperm head defects. CR and GLP-1 administration were associated with a higher expression of all ORGs in the testes. Under CR conditions, the genes FTO and TMEM18 expression in the testes and the MC4R and TMEM18 transcripts abundance in sperm were positively correlated with the spermatozoa oxidative status. The abundance of FTO and TMEM18 in the spermatozoa of rats under CR were positively correlated with sperm concentration, while the testes’ TMEM18 expression was also positively correlated with sperm vitality and negatively correlated with insulin resistance. Testes GNPDA2 expression was negatively correlated with sperm head defects. Conclusions: CR and GLP-1 administration results in higher ORGs expression in testes, and these were correlated with several alterations in sperm fertility parameters.

Relationships between the expression of adipose genes and profiles of hospitalized dogs

Obesity is one of the risk factors for the onset of various metabolic diseases in dogs. Energy expenditure in brown/beige adipocytes, which is partially regulated by the bone morphogenetic protein (BMP) pathway, is a key factor determining systemic energy balance. Here, we examined gene expression in the fat depots of 129 hospitalized dogs, and the relationship between the relative levels of gene expression and profiles of dogs. We evaluated the expression levels of 23 genes such as regulatory genes of adipocyte differentiation and function, adipokines, genes related to brown adipogenesis and uncoupling protein (Ucp), and genes involved in BMP signaling. A reliable equation of multiple regression was not obtained to explain the body condition score (BCS), which is an index of adiposity. Positive relationships were detected between the expression levels of many genes, except for Ucp1 or Ucp3. BCS was found to increase with age. BCS was negatively correlated to the expression levels of Pparγ and Fasn, and positively correlated to Leptin and Opn3 expression. Aging decreased the expression levels of genes related to adipocyte differentiation and function (Pparγ, Fabp4, Fasn, Hsl, and Insr) and Adipoq. In addition, age was negatively correlated with the expression of genes involved in brown adipogenesis and BMP signaling components (Prdm16, Bmp4, Alk3, Actr2a, and Actr2b). In contrast, the expression levels of Leptin and Ucp2 were found to increase with age. The present study clarifies BCS- and age-related gene expressions in the adipose tissue, which potentially contribute to elucidating the etiology of canine obesity.

CNS GNPDA2 Does Not Control Appetite, but Regulates Glucose Homeostasis

GNPDA2 has been associated with human obesity and type-2 diabetes by using a GWAS approach. GNPDA2 is an enzyme involved in the hexosamine biosynthesis pathway, which is known to be important for nutrient sensing in various organism. Its counter enzyme, GFAT, has previously been shown to be important to the development of insulin resistance in diabetes. The implication of GNPDA2 and GFAT in metabolism is scarce and the effect of both enzymes over appetite and glucose homeostasis is unknown. Aim: Identify the role of GNPDA2 and GFAT in nutrient sensing circuits of the CNS that are important for the regulation of both appetite and glucose homeostasis. Methods: Using Long Evans rats, we administered either a GNPDA2 or GFAT antagonist or vehicle in i3vt. Key Findings: GNPDA2 is highly expressed in hypothalamus and adipose tissue, followed by muscle and liver. GNPDA2 is expressed in different hypothalamic nuclei (ARC, DMH, LHA, PVN). GNPDA2 is downregulated in hypothalamus under diet-induced obesity (as previously described), but GFAT expression does not change. Moreover, i3vt infusion of GNPDA2 or GFAT inhibitor resulted in increased c-Fos in areas related to appetite and glucose homeostasis control as PVN and DMH and to a lesser extent in the LHA and ARC. Central inhibition of GNPDA2 does not alter either acute food intake or body weight; however, GFAT inhibition diminished appetite and body weight due to visceral illness. In addition, central administration of the GNPDA2 antagonist, prior to an intraperitoneal glucose tolerance test, resulted in glucose intolerance in comparison to vehicle without altering insulin levels. Significance: These results suggest that central GNPDA2 does not control appetite, but regulates glucose homeostasis.

Dissecting genome-wide studies for microbiome-related metabolic diseases

Despite the meteoric rise in genome-wide association studies for metabolic diseases (MetD) over the last few years, our understanding of the pathogenesis of these diseases is still far from complete. Recent developments have established that MetD arises from complex interactions between host genetics, the gut microbiome and the environment. However, our knowledge of the genetic and microbiome components involved and the underlying molecular mechanisms remains limited. Here, we review and summarize recent studies investigating the genetic and microbiome basis of MetD. Then, given the critical importance of study-individual's ancestry in these studies, we leverage 4932 whole-genome sequence samples from 18 worldwide ethnic groups to examine genetic diversity in currently reported variants associated with MetD. The analyses show marked differences in gene-specific proportion of pathogenic single-nucleotide polymorphisms (SNPs) and gene-specific SNPs MAFs across ethnic groups, highlighting the importance of population- and ethnic-specific investigations in pinpointing the causative factors for MetD. We conclude with a discussion of research areas where further investigation on interactions between host genetics, microbiome and the environment is needed.

Association of KCTD15 gene with fat deposition in pigs

KCTD15 is associated with body mass index and fat deposition in humans, mice and chickens. However, the function of KCTD15 in pig fat deposition remains unclear. In this study, we cloned and analysed the cDNA sequence of porcine KCTD15. The full length of the mRNA sequence of KCTD15 is 4,091 bp, encoding 283 amino acids. The protein is hydrophilic, it has a relative molecular mass of about 31.9 kDa and an isoelectric point of 7.09 with no signal peptide sequence or transmembrane structure. Expression analysis showed that KCTD15 expression level was significantly higher in the tissues of Large White pigs (LW) than in those of Tibetan pigs (TP) and Diannan Small-ear pigs (DN) at 6 months of age, whereas its expression level in embryonic tissues of LW at 60 days was lower than that in tissues of TP and Wujin pigs (WJ). In pig primary adipocytes, the expression level of KCTD15 is high in the early stage of differentiation and gradually decreases in later stages. Additionally, the single-nucleotide polymorphism (SNP) site T-2030C (T/C mutation, located 2,030 bp upstream of the start codon) showed a dominant allele T with high promoter activity in the LW population and a dominant allele C in the TP and WJ populations. Our results indicate that KCTD15 is involved in pig fat deposition and that T-2030C is an important regulatory site for transcriptional activity, affecting fat deposition.

Differential response to a 6-month energy-restricted treatment depending on SH2B1 rs7359397 variant in NAFLD subjects: Fatty Liver in Obesity (FLiO) Study

PURPOSE

Non-alcoholic fatty liver disease (NAFLD) is worldwide recognized as the most common cause of chronic liver disease. Current NAFLD clinical management relies on lifestyle change, nevertheless, the importance of the genetic make-up on liver damage and the possible interactions with diet are still poorly understood. The aim of the study was to evaluate the influence of the SH2B1 rs7359397 genetic variant on changes in body composition, metabolic status and liver health after 6-month energy-restricted treatment in overweight/obese subjects with NAFLD. In addition, gene-treatment interactions over the course of the intervention were examined.

METHODS

The SH2B1 genetic variant was genotyped in 86 overweight/obese subjects with NAFLD from the FLiO study (Fatty Liver in Obesity study). Subjects were metabolically evaluated at baseline and at 6-months. Liver assessment included ultrasonography, Magnetic Resonance Imaging, elastography, a lipidomic test (OWL^®-test) and specific blood liver biomarkers. Additionally, body composition, general biochemical markers and dietary intake were determined.

RESULTS

Both genotypes significantly improved their body composition, general metabolic status and liver health after following an energy-restricted strategy. Liver imaging techniques showed a greater decrease in liver fat content (- 44.3%, p < 0.001) and in serum ferritin levels (p < 0.001) in the carriers of the T allele after the intervention. Moreover, lipidomic analysis, revealed a higher improvement in liver status when comparing risk vs. no-risk genotype (p = 0.006 vs. p = 0.926, respectively). Gene-treatment interactions showed an increase in fiber intake and omega-3 fatty acid in risk genotype (p interaction = 0.056 and p interaction = 0.053, respectively), while a significant increase in MedDiet score was observed in both genotype groups (p = 0.020). Moreover, no-risk genotype presented a relevant decrease in hepatic iron as well as in MUFA intake (p = 0.047 and p = 0.034, respectively).

CONCLUSION

Subjects carrying the T allele of the rs7359397 polymorphism may benefit more in terms of hepatic health and liver status when prescribed an energy-restricted treatment, where a Mediterranean dietary pattern rich in fiber and other components such as omega-3 fatty acids might boost the benefits.

TRIAL REGISTRATION

The Fatty Liver in Obesity was approved by the Research Ethics Committee of the University of Navarra and retrospectively registered (NCT03183193; www.clinicaltrials.gov ); June 2017.

Identification of biomarkers and pathways in hypertensive nephropathy based on the ceRNA regulatory network

BACKGROUND

Hypertensive nephropathy (HTN) is a kind of renal injury caused by chronic hypertension, which seriously affect people's life. The purpose of this study was to identify the potential biomarkers of HTN and understand its possible mechanisms.

METHODS

The dataset numbered GSE28260 related to hypertensive and normotensive was downloaded from NCBI Gene Expression Omnibus. Then, the differentially expressed RNAs (DERs) were screened using R limma package, and functional analyses of DE-mRNA were performed by DAVID. Afterwards, a ceRNA network was established and KEGG pathway was analyzed based on the Gene Set Enrichment Analysis (GSEA) database. Finally, a ceRNA regulatory network directly associated with HTN was proposed.

RESULTS

A total of 947 DERs were identified, including 900 DE-mRNAs, 20 DE-lncRNAs and 27 DE-miRNAs. Based on these DE-mRNAs, they were involved in biological processes such as fatty acid beta-oxidation, IRE1-mediated unfolded protein response, and transmembrane transport, and many KEGG pathways like glycine, serine and threonine metabolism, carbon metabolism. Subsequently, lncRNAs KCTD21-AS1, LINC00470 and SNHG14 were found to be hub nodes in the ceRNA regulatory network. KEGG analysis showed that insulin signaling pathway, glycine, serine and threonine metabolism, pathways in cancer, lysosome, and apoptosis was associated with hypertensive. Finally, insulin signaling pathway was screened to directly associate with HTN and was regulated by mRNAs PPP1R3C, PPKAR2B and AKT3, miRNA has-miR-107, and lncRNAs SNHG14, TUG1, ZNF252P-AS1 and MIR503HG.

CONCLUSIONS

Insulin signaling pathway was directly associated with HTN, and miRNA has-miR-107 and lncRNAs SNHG14, TUG1, ZNF252P-AS1 and MIR503HG were the biomarkers of HTN. These results would improve our understanding of the occurrence and development of HTN.

The Obesity-Susceptibility Gene TMEM18 Promotes Adipogenesis through Activation of PPARG

TMEM18 is the strongest candidate for childhood obesity identified from GWASs, yet as for most GWAS-derived obesity-susceptibility genes, the functional mechanism remains elusive. We here investigate the relevance of TMEM18 for adipose tissue development and obesity. We demonstrate that adipocyte TMEM18 expression is downregulated in children with obesity. Functionally, downregulation of TMEM18 impairs adipocyte formation in zebrafish and in human preadipocytes, indicating that TMEM18 is important for adipocyte differentiation in vivo and in vitro. On the molecular level, TMEM18 activates PPARG, particularly upregulating PPARG1 promoter activity, and this activation is repressed by inflammatory stimuli. The relationship between TMEM18 and PPARG1 is also evident in adipocytes of children and is clinically associated with obesity and adipocyte hypertrophy, inflammation, and insulin resistance. Our findings indicate a role of TMEM18 as an upstream regulator of PPARG signaling driving healthy adipogenesis, which is dysregulated with adipose tissue dysfunction and obesity.

KCTD15 inhibits the Hedgehog pathway in Medulloblastoma cells by increasing protein levels of the oncosuppressor KCASH2

Medulloblastoma (MB) is the most common malignant childhood brain tumor. About 30% of all MBs belong to the I molecular subgroup, characterized by constitutive activation of the Sonic Hedgehog (Hh) pathway. The Hh pathway is involved in several fundamental processes during embryogenesis and in adult life and its deregulation may lead to cerebellar tumorigenesis. Indeed, Hh activity must be maintained via a complex network of activating and repressor signals. One of these repressor signals is KCASH2, belonging to the KCASH family of protein, which acts as negative regulators of the Hedgehog signaling pathway during cerebellar development and differentiation. KCASH2 leads HDAC1 to degradation, allowing hyperacetylation and inhibition of transcriptional activity of Gli1, the main effector of the Hh pathway. In turn, the KCASH2 loss leads to persistent Hh activity and eventually tumorigenesis. In order to better characterize the physiologic role and modulation mechanisms of KCASH2, we have searched through a proteomic approach for new KCASH2 interactors, identifying Potassium Channel Tetramerization Domain Containing 15 (KCTD15). KCTD15 is able to directly interact with KCASH2, through its BTB/POZ domain. This interaction leads to increase KCASH2 stability which implies a reduction of the Hh pathway activity and a reduction of Hh-dependent MB cells proliferation. Here we report the identification of KCTD15 as a novel player in the complex network of regulatory proteins, which modulate Hh pathway, this could be a promising new target for therapeutic approach against MB.

Incorporating methylation genome information improves prediction accuracy for drug treatment responses

BACKGROUND

An accumulation of evidence has revealed the important role of epigenetic factors in explaining the etiopathogenesis of human diseases. Several empirical studies have successfully incorporated methylation data into models for disease prediction. However, it is still a challenge to integrate different types of omics data into prediction models, and the contribution of methylation information to prediction remains to be fully clarified.

RESULTS

A stratified drug-response prediction model was built based on an artificial neural network to predict the change in the circulating triglyceride level after fenofibrate intervention. Associated single-nucleotide polymorphisms (SNPs), methylation of selected cytosine-phosphate-guanine (CpG) sites, age, sex, and smoking status, were included as predictors. The model with selected SNPs achieved a mean 5-fold cross-validation prediction error rate of 43.65%. After adding methylation information into the model, the error rate dropped to 41.92%. The combination of significant SNPs, CpG sites, age, sex, and smoking status, achieved the lowest prediction error rate of 41.54%.

CONCLUSIONS

Compared to using SNP data only, adding methylation data in prediction models slightly improved the error rate; further prediction error reduction is achieved by a combination of genome, methylation genome, and environmental factors.

Generation and characterization of Kctd15 mutations in zebrafish

Potassium channel tetramerization domain containing 15 (Kctd15) was previously found to have a role in early neural crest (NC) patterning, specifically delimiting the region where NC markers are expressed via repression of transcription factor AP-2a and inhibition of Wnt signaling. We used transcription activator-like effector nucleases (TALENs) to generate null mutations in zebrafish kctd15a and kctd15b paralogs to study the in vivo role of Kctd15. We found that while deletions producing frame-shift mutations in each paralog showed no apparent phenotype, kctd15a/b double mutant zebrafish are smaller in size and show several phenotypes including some affecting the NC, such as expansion of the early NC domain, increased pigmentation, and craniofacial defects. Both melanophore and xanthophore pigment cell numbers and early markers are up-regulated in the double mutants. While we find no embryonic craniofacial defects, adult mutants have a deformed maxillary segment and missing barbels. By confocal imaging of mutant larval brains we found that the torus lateralis (TLa), a region implicated in gustatory networks in other fish, is absent. Ablation of this brain tissue in wild type larvae mimics some aspects of the mutant growth phenotype. Thus kctd15 mutants show deficits in the development of both neural crest derivatives, and specific regions within the central nervous system, leading to a strong reduction in normal growth rates.

Obesity-associated gene TMEM18 has a role in the central control of appetite and body weight regulation

An intergenic region of human chromosome 2 (2p25.3) harbors genetic variants which are among those most strongly and reproducibly associated with obesity. The gene closest to these variants is TMEM18, although the molecular mechanisms mediating these effects remain entirely unknown. Tmem18 expression in the murine hypothalamic paraventricular nucleus (PVN) was altered by changes in nutritional state. Germline loss of Tmem18 in mice resulted in increased body weight, which was exacerbated by high fat diet and driven by increased food intake. Selective overexpression of Tmem18 in the PVN of wild-type mice reduced food intake and also increased energy expenditure. We provide evidence that TMEM18 has four, not three, transmembrane domains and that it physically interacts with key components of the nuclear pore complex. Our data support the hypothesis that TMEM18 itself, acting within the central nervous system, is a plausible mediator of the impact of adjacent genetic variation on human adiposity.

lncRNA-SNHG7 promotes the proliferation, migration and invasion and inhibits apoptosis of lung cancer cells by enhancing the FAIM2 expression

There is growing evidence that long non-coding RNAs (lncRNAs) are related to cancer development. In the present study, we found that the expression levels of lncRNA-SNHG7 mRNA and protein obviously increased in lung cancer tissues compared to adjacent non-cancerous tissues. Simultaneously, the expression levels of Fas apoptotic inhibitory molecule 2 (FAIM2) also increased in lung cancer tissues. In addition, lncRNA-SNHG7 was of positive relevance with FAIM2 in human lung cancer tissues. Silence of lncRNA‑SNHG7 by siRNA repressed the level of FAIM2 protein and suppressed cell proliferation, migration and invasion and accelerated apoptosis of A594 cells in vitro. Furthermore, silence of FAIM2 by siRNA generated a phenotype similar to silence of lncRNA-SNHG7 by siRNA. Therefore, our research showed that lncRNA-SNHG7 promotes the proliferation, migration and invasion, and inhibits apoptosis of lung cancer cells by enhancing the FAIM2 expression, suggesting that lncRNA-SNHG7 as a key regulator of gene expression, may be a promising therapeutic strategy for the treatment of lung cancer. It may improve the understanding of their biogenesis and function of lung cancer and further provide the theoretical fundamental basis for cancer pathogenesis and treatment.

Birth weight modifies the association between central nervous system gene variation and adult body mass index

Genome wide association studies have identified ~100 loci associated with body mass index (BMI). Persons with low birth weight have an increased risk of metabolic disorders. We postulate that normal mechanisms of body weight regulation are disrupted in subjects with low birth weight. The present analyses included 2215 African American women from the Black Women's Health Study, and were based on genotype data on 20 BMI-associated loci and self-reported data on birth weight, weight at age 18 and adult weight. We used general linear models to assess the association of individual single-nucleotide polymorphisms (SNPs) with BMI at age 18 and later in adulthood within strata of birth weight (above and below the median, 3200 g). Three SNPs (rs1320330 near TMEM18, rs261967 near PCSK1 and rs17817964 in FTO), and a genetic score combining these three variants, showed significant interactions with birth weight in relation to BMI. Among women with birth weight <3200 g, there was an inverse association between genetic score and BMI; beta-coefficient=-0.045 (95% confidence intervals (CI) -0.104, 0.013) for BMI at age 18, and -0.055 (95% CI -0.112, 0.002) for adult BMI. Among women with birth weight ⩾3200 g, genetic score was positively associated with BMI: beta-coefficient=0.110 (95% CI 0.051, 0.169) for BMI at age 18 (P for interaction=0.0002), and 0.112 (95% CI 0.054, 0.170) for adult BMI (P for interaction<0.0001). Because TMEM18, PCSK1 and FTO are highly expressed in the central nervous system (CNS), our results suggest that low-birth weight may disrupt mechanisms of CNS body weight regulation.

Dissecting diabetes/metabolic disease mechanisms using pluripotent stem cells and genome editing tools

BACKGROUND

Diabetes and metabolic syndromes are chronic, devastating diseases with increasing prevalence. Human pluripotent stem cells are gaining popularity in their usage for human in vitro disease modeling. With recent rapid advances in genome editing tools, these cells can now be genetically manipulated with relative ease to study how genes and gene variants contribute to diabetes and metabolic syndromes.

SCOPE OF REVIEW

We highlight the diabetes and metabolic genes and gene variants, which could potentially be studied, using two powerful technologies - human pluripotent stem cells (hPSCs) and genome editing tools - to aid the elucidation of yet elusive mechanisms underlying these complex diseases.

MAJOR CONCLUSIONS

hPSCs and the advancing genome editing tools appear to be a timely and potent combination for probing molecular mechanism(s) underlying diseases such as diabetes and metabolic syndromes. The knowledge gained from these hiPSC-based disease modeling studies can potentially be translated into the clinics by guiding clinicians on the appropriate type of medication to use for each condition based on the mechanism of action of the disease.

SH2B1 is critical for the regulation of cardiac remodelling in response to pressure overload

AIMS

Src homology 2 (SH2) B adaptor protein 1 (SH2B1) is expressed in various tissues, including the heart. Previous studies have demonstrated that SH2B1 is involved in a variety of biological process, such as maintaining neuronal differentiation, regulating energy and glucose homeostasis, and promoting cell proliferation and motility. However, the role of SH2B1 in cardiac hypertrophy remains unclear. This study aimed at identifying the effects and the underlying mechanisms of SH2B1 in cardiac hypertrophy.

METHODS AND RESULTS

We performed gain- and loss-of-function studies using genetic approaches, and cardiac hypertrophy was evaluated through pathological, echocardiographic, haemodynamic, and molecular analyses. We found that SH2B1 expression was significantly increased in both failing human hearts and hypertrophic murine hearts. Mice overexpressing SH2B1 specifically in the heart displayed increased aortic banding (AB)-induced cardiac hypertrophy, fibrosis, ventricular dilation, and dysfunction compared with controls, whereas loss of SH2B1 produced the opposite phenotype. Consistently, similar results were observed in a global SH2B1-knockout rat model. Mechanistically, the pro-hypertrophic effects elicited by SH2B1 were associated with activation of the Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signalling cascade. Furthermore, rescue experiments revealed that pharmacological inactivation of JAK2 rescued pressure overload-induced cardiac abnormalities in transgenic mice with cardiac-specific SH2B1 overexpression.

CONCLUSION

Taken together, our data demonstrate, for the first time, that SH2B1 is a key positive mediator of pathological cardiac hypertrophy, and that it primarily acts by regulating JAK2/STAT3 signalling.

Fine Mapping of a GWAS-Derived Obesity Candidate Region on Chromosome 16p11.2

INTRODUCTION

Large-scale genome-wide association studies (GWASs) have identified 97 chromosomal loci associated with increased body mass index in population-based studies on adults. One of these SNPs, rs7359397, tags a large region (approx. 1MB) with high linkage disequilibrium (r2>0.7), which comprises five genes (SH2B1, APOBR, sulfotransferases: SULT1A1 and SULT1A2, TUFM). We had previously described a rare mutation in SH2B1 solely identified in extremely obese individuals but not in lean controls.

METHODS

The coding regions of the genes APOBR, SULT1A1, SULT1A2, and TUFM were screened for mutations (dHPLC, SSCP, Sanger re-sequencing) in 95 extremely obese children and adolescents. Detected non-synonymous variants were genotyped (TaqMan SNP Genotyping, MALDI TOF, PCR-RFLP) in independent large study groups (up to 3,210 extremely obese/overweight cases, 485 lean controls and 615 obesity trios). In silico tools were used for the prediction of potential functional effects of detected variants.

RESULTS

Except for TUFM we detected non-synonymous variants in all screened genes. Two polymorphisms rs180743 (APOBR p.Pro428Ala) and rs3833080 (APOBR p.Gly369_Asp370del9) showed nominal association to (extreme) obesity (uncorrected p = 0.003 and p = 0.002, respectively). In silico analyses predicted a functional implication for rs180743 (APOBR p.Pro428Ala). Both APOBR variants are located in the repetitive region with unknown function.

CONCLUSION

Variants in APOBR contributed as strongly as variants in SH2B1 to the association with extreme obesity in the chromosomal region chr16p11.2. In silico analyses implied no functional effect of several of the detected variants. Further in vitro or in vivo analyses on the functional implications of the obesity associated variants are warranted.

Influence of lifestyle on the FAIM2 promoter methylation between obese and lean children: a cohort study

OBJECTIVE

An obesity-related gene, Fas apoptotic inhibitory molecule 2 (FAIM2), is regulated by nutritional state and the methylation levels of the FAIM2 promoter are significantly associated with obesity. Lifestyle factors, such as sedentary behaviour and physical activity, might modify epigenetic patterns that have been related to obesity. Whether the molecular mechanisms by which FAIM2 affects obesity are involved in lifestyle is unclear. This study investigates the potential differences of the FAIM2 promoter methylation with sedentary behaviour and physical activity in obese and lean children.

DESIGN

Cohort study.

SETTING

Institute of Pediatrics in China.

PARTICIPANTS

59 obese cases and 39 lean controls aged 8-18 years recruited from a cross-sectional survey of children from Beijing in 2013.

PRIMARY AND SECONDARY OUTCOME MEASURES

The FAIM2 promoter methylation was quantified using the Sequenom MassARRAY platform. Sedentary behaviour and physical activity were investigated using a questionnaire. The influences of different lifestyles on methylation variations in obese and lean children were examined by multiple linear regression.

RESULTS

The methylation levels at seven CpG sites of the FAIM2 promoter were significantly associated with sedentary behaviour, especially the methylation levels at site -975, site -413, sites -362 and -360, and sites -353 and -349 (p=0.00004, 0.00009, 0.0006 and 0.00005, respectively). There were significant differences between the methylation levels at four CpG sites in obese and lean participants with high or moderate physical activity level <150 min/week.

CONCLUSIONS

This study provides the first evidence that there are significant differences in the associations of the FAIM2 promoter methylation with sedentary behaviour and physical activity between obese and lean children. Our results suggest that lifestyle may possibly be mediating the process of the FAIM2 involved in obesity.

Obesity genetics in mouse and human: back and forth, and back again

Obesity is a major public health concern. This condition results from a constant and complex interplay between predisposing genes and environmental stimuli. Current attempts to manage obesity have been moderately effective and a better understanding of the etiology of obesity is required for the development of more successful and personalized prevention and treatment options. To that effect, mouse models have been an essential tool in expanding our understanding of obesity, due to the availability of their complete genome sequence, genetically identified and defined strains, various tools for genetic manipulation and the accessibility of target tissues for obesity that are not easily attainable from humans. Our knowledge of monogenic obesity in humans greatly benefited from the mouse obesity genetics field. Genes underlying highly penetrant forms of monogenic obesity are part of the leptin-melanocortin pathway in the hypothalamus. Recently, hypothesis-generating genome-wide association studies for polygenic obesity traits in humans have led to the identification of 119 common gene variants with modest effect, most of them having an unknown function. These discoveries have led to novel animal models and have illuminated new biologic pathways. Integrated mouse-human genetic approaches have firmly established new obesity candidate genes. Innovative strategies recently developed by scientists are described in this review to accelerate the identification of causal genes and deepen our understanding of obesity etiology. An exhaustive dissection of the molecular roots of obesity may ultimately help to tackle the growing obesity epidemic worldwide.

Extreme obesity is associated with variation in genes related to the circadian rhythm of food intake and hypothalamic signaling

The hypothalamus is important for regulation of energy intake. Mutations in genes involved in the function of the hypothalamus can lead to early-onset severe obesity. To look further into this, we have followed a strategy that allowed us to identify rare and common gene variants as candidates for the background of extreme obesity from a relatively small cohort. For that we focused on subjects with a well-selected phenotype and on a defined gene set and used a rich source of genetic data with stringent cut-off values. A list of 166 genes functionally related to the hypothalamus was generated. In those genes complete exome sequence data from 30 extreme obese subjects (60 genomes) were screened for novel rare indel, nonsense, and missense variants with a predicted negative impact on protein function. In addition, (moderately) common variants in those genes were analyzed for allelic association using the general population as reference (false discovery rate<0.05). Six novel rare deleterious missense variants were found in the genes for BAIAP3, NBEA, PRRC2A, RYR1, SIM1, and TRH, and a novel indel variant in LEPR. Common variants in the six genes for MBOAT4, NPC1, NPW, NUCB2, PER1, and PRRC2A showed significant allelic association with extreme obesity. Our findings underscore the complexity of the genetic background of extreme obesity involving rare and common variants of genes from defined metabolic and physiologic processes, in particular regulation of the circadian rhythm of food intake and hypothalamic signaling.

Expression of variant transcripts of the potassium channel tetramerization domain-containing 15 (KCTD15) gene and their association with fatness traits in chickens

The aim of this study was to characterize the structure, expression, and biological functions of potassium channel tetramerization domain containing 15 (KCTD15) in chickens. We compared the KCTD15 expression level in samples of hypothalamic, adipose, and liver tissue of Xinghua chickens that were maintained on different dietary status. An association analysis of KCTD15 gene variant transcripts with fatness traits in a F2 resource population of chickens was performed. Three KCTD15 transcripts were identified in which the complete transcript was predominantly expressed in adipose tissue and the hypothalamus. The chicken KCTD15 gene was regulated by both feeding and fasting and consumption of a high-fat diet. The expression level of KCTD15 gene was markedly decreased in hypothalamus and liver of fasted and refed chickens (P < 0.05) and significantly downregulated in adipose tissue by the high-fat diet (P < 0.05). Three single-nucleotide polymorphisms of the KCTD15 gene were significantly associated with a number of fatness traits in chicken (P < 0.05). These results suggest that KCTD15 have a potential role regulation of obesity and fat metabolism in chickens.

SH2B1 regulation of energy balance, body weight, and glucose metabolism

The Src homology 2B (SH2B) family members (SH2B1, SH2B2 and SH2B3) are adaptor signaling proteins containing characteristic SH2 and PH domains. SH2B1 (also called SH2-B and PSM) and SH2B2 (also called APS) are able to form homo- or hetero-dimers via their N-terminal dimerization domains. Their C-terminal SH2 domains bind to tyrosyl phosphorylated proteins, including Janus kinase 2 (JAK2), TrkA, insulin receptors, insulin-like growth factor-1 receptors, insulin receptor substrate-1 (IRS1), and IRS2. SH2B1 enhances leptin signaling by both stimulating JAK2 activity and assembling a JAK2/IRS1/2 signaling complex. SH2B1 promotes insulin signaling by both enhancing insulin receptor catalytic activity and protecting against dephosphorylation of IRS proteins. Accordingly, genetic deletion of SH2B1 results in severe leptin resistance, insulin resistance, hyperphagia, obesity, and type 2 diabetes in mice. Neuron-specific overexpression of SH2B1β transgenes protects against diet-induced obesity and insulin resistance. SH2B1 in pancreatic β cells promotes β cell expansion and insulin secretion to counteract insulin resistance in obesity. Moreover, numerous SH2B1 mutations are genetically linked to leptin resistance, insulin resistance, obesity, and type 2 diabetes in humans. Unlike SH2B1, SH2B2 and SH2B3 are not required for the maintenance of normal energy and glucose homeostasis. The metabolic function of the SH2B family is conserved from insects to humans.

Supplementation based on protein or energy ingredients to beef cattle consuming low-quality cool-season forages: II. Performance, reproductive, and metabolic responses of replacement heifers

This experiment evaluated the influence of supplement composition on performance, reproductive, and metabolic responses of Angus × Hereford heifers consuming a low-quality cool-season forage (8.7% CP and 57% TDN). Sixty heifers (initial age = 226 ± 3 d) were allocated into 15 drylot pens (4 heifers/pen and 5 pens/treatment) and assigned to 1) supplementation with soybean meal (PROT), 2) supplementation with a mixture of cracked corn, soybean meal, and urea (68:22:10 ratio, DM basis; ENER), or 3) no supplementation (CON). Heifers were offered meadow foxtail (Alopecurus pratensis L.) hay for ad libitum consumption during the experiment (d -10 to 160). Beginning on d 0, PROT and ENER were provided daily at a rate of 1.30 and 1.40 kg of DM/heifer to ensure that PROT and ENER intakes were isocaloric and isonitrogenous. Hay and total DMI were recorded for 5 consecutive days during each month of the experiment. Blood was collected every 10 d for analysis of plasma progesterone to evaluate puberty attainment. Blood samples collected on d -10, 60, 120, and 150 were also analyzed for plasma concentrations of plasma urea N (PUN), glucose, insulin, IGF-I, NEFA, and leptin. Liver samples were collected on d 100 from 2 heifers/pen and analyzed for mRNA expression of genes associated with nutritional metabolism. No treatment effect was detected (P = 0.33) on forage DMI. Total DMI, ADG, and mean concentrations of glucose, insulin, and IGF-I as well as hepatic mRNA expression of IGF-I and IGFBP-3 were greater (P ≤ 0.02) for PROT and ENER compared with CON and similar between PROT and ENER (P ≥ 0.13). Mean PUN concentrations were also greater (P < 0.01) for PROT and ENER compared with CON, whereas PROT heifers had greater (P < 0.01) PUN compared with ENER. Plasma leptin concentrations were similar between ENER and PROT (P ≥ 0.19) and greater (P ≤ 0.03) for ENER and PROT compared with CON on d 120 and 150 (treatment × day interaction, P = 0.03). Hepatic mRNA expression of mitochondrial phosphoenolpyruvate carboxykinase was greater (P = 0.05) in PROT compared with CON and ENER and similar between CON and ENER (P = 0.98). The proportion of heifers pubertal on d 160 was greater (P < 0.01) in ENER compared with PROT and CON and similar between PROT and CON (P = 0.38). In conclusion, beef heifers consuming a low-quality cool-season forage had a similar increase in DMI, growth, and overall metabolic status if offered supplements based on soybean meal or corn at 0.5% of BW.

Effects of calcium salts of soybean oil on factors that influence pregnancy establishment in Bos indicus beef cows

The objective of this experiment was to compare fatty acid (FA) concentrations in plasma and reproductive tissues as well as hormones and expression of genes associated with pregnancy establishment in beef cows supplemented or not with Ca salts of soybean oil (CSSO) beginning after timed AI. Ninety nonlactating multiparous Nelore (Bos indicus) cows were timed inseminated on d 0 of the experiment and divided into 18 groups of 5 cows/group. Groups were randomly assigned to receive (as-fed basis) 100 g of a protein-mineral mix plus 100 g of ground corn per cow daily in addition to 1) 100 g/cow daily of CSSO (n = 9) or 2) 100 g/cow daily of kaolin (CON; rumen-inert indigestible substance; n = 9). All groups were maintained in a single Brachiaria brizanta pasture (24 ha) with ad libitum access to forage and water. However, groups were segregated daily and offered treatments individually at the working facility during the experimental period (d 0 to 18). Blood samples were collected and transrectal ultrasonography was performed to verify ovulation and estimate corpus luteum (CL) volume immediately before AI (d 0) and on d 7 and 18 of the experiment. On d 19, 36 cows (18 cows/treatment; 2 cows/group) diagnosed without the presence of a CL on d 0 but with a CL greater than 0.38 cm(3) in volume on d 7 and 18 were slaughtered for collection of conceptus, uterine luminal flushing, and tissue samples from the CL and endometrium. Cows receiving CSSO had greater concentrations of linoleic and other ω-6 FA in plasma (P < 0.01), endometrium (P ≤ 0.05), CL (P ≤ 0.05), and conceptus (P ≤ 0.08) compared to CON. On d 7 of the experiment, CSSO-supplemented cows had greater plasma progesterone concentrations (P < 0.01) and CL volume (P = 0.02) compared to CON, whereas no treatment effects were detected (P ≥ 0.15) for these parameters on d 18 (treatment × day interaction; P < 0.01). Cows receiving CSSO tended (P = 0.09) to have greater concentrations of interferon-tau in the uterine flushing media compared with CON. However, no treatment effects were detected for mRNA expression genes associated with pregnancy establishment in endometrial, CL, and conceptus samples (P ≥ 0.12). In summary, supplementing beef cows with 100 g of CSSO beginning after AI favored incorporation of ω-6 FA into their circulation, reproductive tissues, and conceptus, without impacting expression of genes associated with pregnancy establishment on d 19 of gestation.

The KCTD family of proteins: structure, function, disease relevance

The family of potassium channel tetramerizationdomain (KCTD) proteins consists of 26 members with mostly unknown functions. The name of the protein family is due to the sequence similarity between the conserved N-terminal region of KCTD proteins and the tetramerization domain in some voltage-gated potassium channels. Dozens of publications suggest that KCTD proteins have roles in various biological processes and diseases. In this review, we summarize the character of Bric-a-brack,Tram-track, Broad complex(BTB) of KCTD proteins, their roles in the ubiquitination pathway, and the roles of KCTD mutants in diseases. Furthermore, we review potential downstream signaling pathways and discuss future studies that should be performed.

Functional analysis of seven genes linked to body mass index and adiposity by genome-wide association studies: a review

Genome-wide association studies (GWAS) have identified a total of about 40 single nucleotide polymorphisms (SNPs) that show significant linkage to body mass index, a widely utilised surrogate measure of adiposity. However, only 8 of these associations have been confirmed by follow-up GWAS using more sophisticated measures of adiposity (computed tomography). Among these 8, there is a SNP close to the gene FTO which has been the subject of considerable work to diagnose its function. The remaining 7 SNPs are adjacent to, or within, the genes NEGR1, TMEM18, ETV5, FLJ35779, LINGO2, SH2B1 and GIPR, most of which are less well studied than FTO, particularly in the context of obesity. This article reviews the available data on the functions of these genes, including information gleaned from studies in humans and animal models. At present, we have virtually no information on the putative mechanism associating the genes FLJ35779 and LINGO2 to obesity. All of these genes are expressed in the brain, and for 2 of them (SH2B1 and GIPR), a direct link to the appetite regulation system is known. SH2B1 is an enhancer of intracellular signalling in the JAK-STAT pathway, and GIPR is the receptor for an appetite-linked hormone (GIP) produced by the alimentary tract. NEGR1, ETV5 and SH2B1 all have suggested roles in neurite outgrowth, and hence SNPs adjacent to these genes may affect development of the energy balance circuitry. Although the genes have central patterns of gene expression, implying a central neuronal connection to energy balance, for at least 4 of them (NEGR1, TMEM18, SH2B1 and GIPR), there are also significant peripheral functions related to adipose tissue biology. These functions may contribute to their effects on the obese phenotype.

Association of the FTO obesity risk variant rs8050136 with percentage of energy intake from fat in multiple racial/ethnic populations: the PAGE study

Common obesity risk variants have been associated with macronutrient intake; however, these associations' generalizability across populations has not been demonstrated. We investigated the associations between 6 obesity risk variants in (or near) the NEGR1, TMEM18, BDNF, FTO, MC4R, and KCTD15 genes and macronutrient intake (carbohydrate, protein, ethanol, and fat) in 3 Population Architecture using Genomics and Epidemiology (PAGE) studies: the Multiethnic Cohort Study (1993-2006) (n = 19,529), the Atherosclerosis Risk in Communities Study (1987-1989) (n = 11,114), and the Epidemiologic Architecture for Genes Linked to Environment (EAGLE) Study, which accesses data from the Third National Health and Nutrition Examination Survey (1991-1994) (n = 6,347). We used linear regression, with adjustment for age, sex, and ethnicity, to estimate the associations between obesity risk genotypes and macronutrient intake. A fixed-effects meta-analysis model showed that the FTO rs8050136 A allele (n = 36,973) was positively associated with percentage of calories derived from fat (βmeta = 0.2244 (standard error, 0.0548); P = 4 × 10(-5)) and inversely associated with percentage of calories derived from carbohydrate (βmeta = -0.2796 (standard error, 0.0709); P = 8 × 10(-5)). In the Multiethnic Cohort Study, percentage of calories from fat assessed at baseline was a partial mediator of the rs8050136 effect on body mass index (weight (kg)/height (m)(2)) obtained at 10 years of follow-up (mediation of effect = 0.0823 kg/m(2), 95% confidence interval: 0.0559, 0.1128). Our data provide additional evidence that the association of FTO with obesity is partially mediated by dietary intake.

Diabetes genes identified by genome-wide association studies are regulated in mice by nutritional factors in metabolically relevant tissues and by glucose concentrations in islets

Background

Genome-wide association studies (GWAS) have recently identified many new genetic variants associated with the development of type 2 diabetes. Many of these variants are in introns of known genes or between known genes, suggesting they affect the expression of these genes. The regulation of gene expression is often tissue and context dependent, for example occurring in response to dietary changes, hormone levels, or many other factors. Thus, to understand how these new genetic variants associated with diabetes risk may act, it is necessary to understand the regulation of their cognate genes.

Results

We identified fourteen type 2 diabetes-associated genes discovered by the first waves of GWAS for which there was little prior evidence of their potential role in diabetes (Adam30, Adamts9, Camk1d, Cdc123, Cdkal1, Cdkn2a, Cdkn2b, Ext2, Hhex, Ide, Jazf1, Lgr5, Thada and Tspan8). We examined their expression in metabolically relevant tissues including liver, adipose tissue, brain, and hypothalamus obtained from mice under fasted, non-fasted and high fat diet-fed conditions. In addition, we examined their expression in pancreatic islets from these mice cultured in low and high glucose. We found that the expression of Jazf1 was reduced by high fat feeding in liver, with similar tendencies in adipose tissue and the hypothalamus. Adamts9 expression was decreased in the hypothalamus of high fat fed mice. In contrast, the expression of Camk1d, Ext2, Jazf1 and Lgr5 were increased in the brain of non-fasted animals compared to fasted mice. Most notably, the expression levels of most of the genes were decreased in islets cultured in high glucose.

Conclusions

These data provide insight into the metabolic regulation of these new type 2 diabetes genes that will be important for determining how the GWAS variants affect gene expression and ultimately the development of type 2 diabetes.

Moo1 obesity quantitative trait locus in BTBR T+ Itpr3tf/J mice increases food intake

The rising prevalence of obesity is one of the greatest health challenges facing the world today. Discovery of genetic factors affecting obesity risk will provide important insight to its etiology that could suggest new therapeutic approaches. We have previously identified the Modifier of obese 1 (Moo1) quantitative trait locus (QTL) in a cross between leptin-deficient BTBR T(+) Itpr3(tf)/J (BTBR) and C57BL/6J (B6) mice. Understanding the mechanism by which this locus acts will aid in the identification of candidate genes. Here we refined the location of this QTL and sought to determine the mechanism by which Moo1 affects body weight. We found that the effects of Moo1 also alter high fat diet-induced obesity in mice having functional leptin. In detailed metabolic analyses we determined that this locus acts by increasing food intake in BTBR mice, without affecting energy expenditure. The expression levels of the main molecular mediators of food intake in the hypothalamus were not altered, suggesting this locus affects an independent pathway, consistent with its identification in mice lacking functional leptin. Finally, we show that the increased adiposity resulting from Moo1 is sufficient to affect glucose tolerance. These studies show that the Moo1 obesity QTL affects food intake, likely through a novel mechanism, and indicate that modulation of the underlying pathway may not only ameliorate obesity but also its clinical consequences.

Mutation screen in the GWAS derived obesity gene SH2B1 including functional analyses of detected variants

Background

The SH2B1 gene (Src-homology 2B adaptor protein 1 gene) is a solid candidate gene for obesity. Large scale GWAS studies depicted markers in the vicinity of the gene; animal models suggest a potential relevance for human body weight regulation.

Methods

We performed a mutation screen for variants in the SH2B1 coding sequence in 95 extremely obese children and adolescents. Detected variants were genotyped in independent childhood and adult study groups (up to 11,406 obese or overweight individuals and 4,568 controls). Functional implications on STAT3 mediated leptin signalling of the detected variants were analyzed in vitro.

Results

We identified two new rare mutations and five known SNPs (rs147094247, rs7498665, rs60604881, rs62037368 and rs62037369) in SH2B1. Mutation g.9483C/T leads to a non-synonymous, non-conservative exchange in the beta (βThr656Ile) and gamma (γPro674Ser) splice variants of SH2B1. It was additionally detected in two of 11,206 (extremely) obese or overweight children, adolescents and adults, but not in 4,506 population-based normal-weight or lean controls. The non-coding mutation g.10182C/A at the 3’ end of SH2B1 was only detected in three obese individuals. For the non-synonymous SNP rs7498665 (Thr484Ala) we observed nominal over-transmission of the previously described risk allele in 705 obesity trios (nominal p = 0.009, OR = 1.23) and an increased frequency of the same allele in 359 cases compared to 429 controls (nominal p = 0.042, OR = 1.23). The obesity risk-alleles at Thr484Ala and βThr656Ile/γPro674Ser had no effect on STAT3 mediated leptin receptor signalling in splice variants β and γ.

Conclusion

The rare coding mutation βThr656Ile/γPro674Ser (g.9483C/T) in SH2B1 was exclusively detected in overweight or obese individuals. Functional analyzes did not reveal impairments in leptin signalling for the mutated SH2B1.