Genome-wide association study of morbid obesity in Han Chinese

Polycystic Ovary Syndrome, Insulin Resistance, and Cardiovascular Disease

PURPOSE OF REVIEW

Polycystic ovary syndrome (PCOS) is a prevalent endocrine disorder in women of reproductive age. It has been associated with metabolic, reproductive, and psychiatric disorders. Despite its association with insulin resistance (IR) and cardiovascular disease (CVD) risk factors, the association between PCOS and CVD outcomes has been conflicting. This review reports the updated evidence between PCOS, insulin resistance, and CVD events.

RECENT FINDINGS

IR is highly prevalent occurring in 50 to 95% of general and obese PCOS women. The etiology of PCOS involves IR and hyperandrogenism, which lead to CVD risk factors, subclinical CVD, and CVD outcomes. Multiple studies including meta-analysis confirmed a strong association between PCOS and CVD events including ischemic heart disease, stroke, atrial fibrillation, and diabetes, particularly among premenopausal women, and these associations were mediated by metabolic abnormalities. PCOS is highly familial and has substantial CVD risk and transgenerational effects regardless of obesity. A personalized approach to the CVD risk assessment and management of symptom manifestations should be conducted according to its phenotypes. Lifestyle modifications and reduction in environmental stressors should be encouraged for CVD prevention among PCOS women.

Whole genome sequencing of mouse lines divergently selected for fatness (FLI) and leanness (FHI) revealed several genetic variants as candidates for novel obesity genes

BACKGROUND

Analysing genomes of animal model organisms is widely used for understanding the genetic basis of complex traits and diseases, such as obesity, for which only a few mouse models exist, however, without their lean counterparts.

OBJECTIVE

To analyse genetic differences in the unique mouse models of polygenic obesity (Fat line) and leanness (Lean line) originating from the same base population and established by divergent selection over more than 60 generations.

METHODS

Genetic variability was analysed using WGS. Variants were identified with GATK and annotated with Ensembl VEP. g.Profiler, WebGestalt, and KEGG were used for GO and pathway enrichment analysis. miRNA seed regions were obtained with miRPathDB 2.0, LncRRIsearch was used to predict targets of identified lncRNAs, and genes influencing adipose tissue amount were searched using the IMPC database.

RESULTS

WGS analysis revealed 6.3 million SNPs, 1.3 million were new. Thousands of potentially impactful SNPs were identified, including within 24 genes related to adipose tissue amount. SNP density was highest in pseudogenes and regulatory RNAs. The Lean line carries SNP rs248726381 in the seed region of mmu-miR-3086-3p, which may affect fatty acid metabolism. KEGG analysis showed deleterious missense variants in immune response and diabetes genes, with food perception pathways being most enriched. Gene prioritisation considering SNP GERP scores, variant consequences, and allele comparison with other mouse lines identified seven novel obesity candidate genes: 4930441H08Rik, Aff3, Fam237b, Gm36633, Pced1a, Tecrl, and Zfp536.

CONCLUSION

WGS revealed many genetic differences between the lines that accumulated over the selection period, including variants with potential negative impacts on gene function. Given the increasing availability of mouse strains and genetic polymorphism catalogues, the study is a valuable resource for researchers to study obesity.

Energy Expenditure Homeostasis Requires ErbB4, an Obesity Risk Gene, in the Paraventricular Nucleus

Obesity affects more than a third adult population in the United States; the prevalence is even higher in patients with major depression disorders. GWAS studies identify the receptor tyrosine kinase ErbB4 as a risk gene for obesity and for major depression disorders. We found that ErbB4 was enriched in the paraventricular nucleus of the hypothalamus (PVH). To investigate its role in metabolism, we deleted ErbB4 by injecting a Cre-expressing virus into the PVH of ErbB4-floxed male mice and found that PVH ErbB4 deletion increased weight gain without altering food intake. ErbB4 PVH deletion also reduced nighttime activity and decreased intrascapular brown adipose tissue (iBAT) thermogenesis. Analysis of covariance (ANCOVA) revealed that ErbB4 PVH deletion reduced O2 consumption, CO2 production and heat generation in a manner independent of body weight. Immunostaining experiments show that ErbB4+ neurons in the PVH were positive for oxytocin (OXT); ErbB4 PVH deletion reduces serum levels of OXT. We characterized mice where ErbB4 was specifically mutated in OXT+ neurons and found reduction in energy expenditure, phenotypes similar to PVH ErbB4 deletion. Taken together, our data indicate that ErbB4 in the PVH regulates metabolism likely through regulation of OXT expressing neurons, reveal a novel function of ErbB4 and provide insight into pathophysiological mechanisms of depression-associated obesity.

Effect of Body Weight and Obesity on Esophageal Function

The incidence of obesity in the population is gradually increasing. Obesity can cause a variety of complications in the digestive system such as gastroesophageal reflux disease, and impacts the integrity of the esophageal mucosal barrier and esophageal motility. However, not many studies have focused on the effect of varying degrees of obesity on the esophagus. A total of 611 participants were included in this study. We divided them into three groups according to their body mass index (BMI): the normal weight group, the overweight group, and the obesity group. We performed a retrospective comparison between groups based on indicators from high resolution esophageal manometry (HREM) and 24-hour pH impedance monitoring, and did a correlation analysis on multiple indicators such as esophageal mucosal barrier, esophageal motility, and acid reflux. The mean nocturnal baseline impedance (MNBI) in the overweight and obesity groups was lower than that in the normal group. The MNBI of the subjects in Z5-Z6 channels in the overweight group was significantly lower than that in the normal group. With respect to Z3-Z6 channels, MNBI values in the obesity group were significantly lower than those in the normal group. 'The acid exposure time (AET), the DeMeester scores (DMS) and 24-hour total reflux episodes was significantly higher in the obesity group than those in the normal and overweight groups. The upper esophageal sphincter (UES) residual pressure, and intrabolus pressure (IBP) in the overweight and obesity groups were significantly higher than those in the normal group. In addition, lower esophageal sphincter (LES) resting pressure, and esophagogastric junction contractile integral (EGJ-CI) in the obesity group were significantly higher than those in the normal group. We found that increase in body weight affected the integrity of esophageal mucosa, and different degrees of increase associated with different degrees and different aspects of changes in esophageal motility.

LRP5-/6 gene polymorphisms and its association with risk of abnormal bone mass in postmenopausal women

OBJECTIVES

To assess LRP5-/6 gene polymorphisms and its association with risk of abnormal bone mass (ABM) in postmenopausal women.

METHODS

The study recruited 166 patients with ABM (case group) and 106 patients with normal bone mass (control group) based on bone mineral density (BMD) results. Multi-factor dimensionality reduction (MDR) was used to analyze the interaction between the Low-density lipoprotein receptor-related protein 5 (LRP5) gene (rs41494349, rs2306862) and the Low-density lipoprotein receptor-related protein 6 (LRP6) gene (rs10743980, rs2302685) and the subjects' clinical characteristics of age and menopausal years.

RESULTS

(1) Logistic regression analysis showed that the subjects with the CT or TT genotype at rs2306862 had a higher risk of ABM than those with the CC genotype (OR = 2.353, 95%CI = 1.039-6.186; OR = 2.434, 95%CI = 1.071, 5.531; P < 0.05). The subjects with the TC genotype at rs2302685 had a higher risk of ABM than those with the TT genotype (OR = 2.951, 95%CI = 1.030-8.457, P < 0.05). (2) When taking the three Single-nucleotide polymorphisms (SNPs) together, the accuracy was the highest with the cross-validation consistency of 10/10 (OR = 1.504, 95%CI:1.092-2.073, P < 0.05), indicating that the LRP5 rs41494349 and LRP6 rs10743980, rs2302685 were interactively associated with the risk of ABM. (3) Linkage disequilibrium (LD) results revealed that the LRP5 (rs41494349,rs2306862) were in strong LD (D' > 0.9, r² > 0.3). AC and AT haplotypes were significantly more frequently distributed in the ABM group than in the control group, indicating that subjects carrying the AC and AT haplotypes were associated with an increased risk of ABM (P < 0.01). (4) MDR showed that rs41494349 & rs2302685 & rs10743980 & age were the best model for ABM prediction. The risk of ABM in "high-risk combination" was 1.00 times that of "low-risk combination"(OR = 1.005, 95%CI: 1.002-1.008, P < 0.05). (5) MDR showed that there was no significant association between any of the SNPs and menopausal years and ABM susceptibility.

CONCLUSION

These findings indicate that LRP5-rs2306862 and LRP6-rs2302685 polymorphisms and gene-gene and gene-age interactions may increase the risk of ABM in postmenopausal women. There was no significant association between any of the SNPs and menopausal years and ABM susceptibility.

Integration of Genomic and Clinical Retrospective Data to Predict Endometrioid Endometrial Cancer Recurrence

Endometrial cancer (EC) incidence and mortality continues to rise. Molecular profiling of EC promises improvement of risk assessment and treatment selection. However, we still lack robust and accurate models to predict those at risk of failing treatment. The objective of this pilot study is to create models with clinical and genomic data that will discriminate patients with EC at risk of disease recurrence. We performed a pilot, retrospective, case−control study evaluating patients with EC, endometrioid type: 7 with recurrence of disease (cases), and 55 without (controls). RNA was extracted from frozen specimens and sequenced (RNAseq). Genomic features from RNAseq included transcriptome expression, genomic, and structural variation. Feature selection for variable reduction was performed with univariate ANOVA with cross-validation. Selected variables, informative for EC recurrence, were introduced in multivariate lasso regression models. Validation of models was performed in machine-learning platforms (ML) and independent datasets (TCGA). The best performing prediction models (out of >170) contained the same lncRNA features (AUC of 0.9, and 95% CI: 0.75, 1.0). Models were validated with excellent performance in ML platforms and good performance in an independent dataset. Prediction models of EC recurrence containing lncRNA features have better performance than models with clinical data alone.

Effectiveness and safety of different academic schools of traditional Chinese medicine in the treatment of obesity: A protocol for systematic review and meta-analysis

BACKGROUND

Obesity is a global epidemic. Since 1975, the global obesity rate has almost tripled. Although many systematic reviews and clinical trials have shown that traditional Chinese medicine (TCM) can effectively treat obesity, the effectiveness and safety of different academic schools of TCM in treating obesity have not been systematically evaluated.

METHODS

The retrieval language of this study was Chinese and English. From the date of creation of the following data to June 2023, the data of Medline, PubMed, Embase, Cochrane Science Network, China Biomedical Literature Database, Central Controlled Trial Registration Center, and China Science Journal Database were retrieved, respectively. This study included clinical randomized controlled trials related to the treatment of obesity by different academic schools of TCM. The main outcome measures were body mass index, waist circumference, hip circumference, waist hip ratio, body fat content, fasting blood glucose, glycosylated hemoglobin, and blood lipid level. In addition, we manually searched other resources, including reference lists of identified publications, conference articles, and gray literature.

RESULTS

This study will provide a more diverse choice of treatment options.

CONCLUSION

The purpose of this study is to summarize and evaluate the effectiveness and safety of different academic schools of TCM in improving and treating obese patients from clinical trials, so as to provide more options for obesity treatment.

Deconstructing a Syndrome: Genomic Insights Into PCOS Causal Mechanisms and Classification

Polycystic ovary syndrome (PCOS) is among the most common disorders in women of reproductive age, affecting up to 15% worldwide, depending on the diagnostic criteria. PCOS is characterized by a constellation of interrelated reproductive abnormalities, including disordered gonadotropin secretion, increased androgen production, chronic anovulation, and polycystic ovarian morphology. It is frequently associated with insulin resistance and obesity. These reproductive and metabolic derangements cause major morbidities across the lifespan, including anovulatory infertility and type 2 diabetes (T2D). Despite decades of investigative effort, the etiology of PCOS remains unknown. Familial clustering of PCOS cases has indicated a genetic contribution to PCOS. There are rare Mendelian forms of PCOS associated with extreme phenotypes, but PCOS typically follows a non-Mendelian pattern of inheritance consistent with a complex genetic architecture, analogous to T2D and obesity, that reflects the interaction of susceptibility genes and environmental factors. Genomic studies of PCOS have provided important insights into disease pathways and have indicated that current diagnostic criteria do not capture underlying differences in biology associated with different forms of PCOS. We provide a state-of-the-science review of genetic analyses of PCOS, including an overview of genomic methodologies aimed at a general audience of non-geneticists and clinicians. Applications in PCOS will be discussed, including strengths and limitations of each study. The contributions of environmental factors, including developmental origins, will be reviewed. Insights into the pathogenesis and genetic architecture of PCOS will be summarized. Future directions for PCOS genetic studies will be outlined.

Chronic non-communicable diseases: Hainan prospective cohort study

PURPOSE

The Hainan Cohort was established to investigate the incidence, morbidity and mortality of non-communicable diseases and their risk factors in the community population.

PARTICIPANTS

The baseline investigation of the Hainan Cohort study was initiated in five main areas of Hainan, China, from June 2018 to October 2020. A multistage cluster random-sampling method was used to obtain samples from the general population. Baseline assessments included a questionnaire survey, physical examination, blood and urine sample collection, and laboratory measurements, and outdoor environmental data were obtained.

FINDINGS TO DATA

A total of 14 443 participants aged 35-74 years were recruited at baseline, with a participation rate of 90.1%. The mean age of the participants was 48.8 years; 51.8% were men, and 83.7% had a secondary school or higher education. The crude prevalence of diabetes, coronary heart disease, stroke, hypertension, hyperuricaemia, chronic bronchitis, pulmonary tuberculosis, asthma, cancer, chronic hepatitis and metabolic syndrome were 8.6%, 9.2%, 2.0%, 37.1%, 7.1%, 2.3%, 1.4%, 2.1%, 4.1%, 2.2% and 14.5%, respectively.

FUTURE PLANS

The Hainan Cohort is a dynamic cohort with no end date. All participants will be monitored annually for cause-specific mortality and morbidity until death. Long-term follow-up will be conducted every 5 years. The baseline population is considered to expand in the next wave of follow-up, depending on the availability of funding support.

Gut microbiota modulates differential lipid metabolism outcomes associated with FTO gene polymorphisms in response to personalized nutrition intervention

Background

Interindividual differences in response to personalized nutrition (PN) intervention were affected by multiple factors, including genetic backgrounds and gut microbiota. The fat mass and obesity associated (FTO) gene is an important factor related to hyperlipidemia and occurrence of cardiovascular diseases. However, few studies have explored the differences in response to intervention among subjects with different genotypes of FTO, and the associations between gut microbiota and individual responses.

Objective

To explore the differential lipid metabolism outcomes associated with FTO gene polymorphisms in response to PN intervention, the altered taxonomic features of gut microbiota caused by the intervention, and the associations between gut microbiota and lipid metabolism outcomes.

Methods

A total of 400 overweight or obese adults were recruited in the study and randomly divided into the PN group and control group, of whom 318 completed the 12-week intervention. The single nucleotide polymorphism (SNP) of rs1121980 in FTO was genotyped. Gut microbiota and blood lipids were determined at baseline and week 12. Functional property of microbiota was predicted using Tax4Fun functional prediction analysis.

Results

Subjects with the risk genotype of FTO had significantly higher weight and waist circumference (WC) at baseline. Generalized linear regression models showed that the reduction in weight, body mass index (BMI), WC, body fat percentage, total cholesterol (TCHO), and low-density lipoprotein (LDL) was greater in subjects with the risk genotype of FTO and in the PN group. Significant interaction effects between genotype and intervention on weight, BMI, WC, TCHO, and LDL were found after stratifying for specific genotype of FTO. All subjects showed significant increasement in α diversity of gut microbiota after intervention except for those with the non-risk genotype in the control group. Gut microbiota, including Blautia and Firmicutes, might be involved in lipid metabolism in response to interventions. The predicted functions of the microbiota in subjects with different genotypes were related to lipid metabolism-related pathways, including fatty acid biosynthesis and degradation.

Conclusion

Subjects with the risk genotype of FTO had better response to nutrition intervention, and PN intervention showed better amelioration in anthropometric parameters and blood lipids than the control. Gut microbiota might be involved in modulating differential lipid metabolism responses to intervention in subjects with different genotypes.

Trial registration

[Chictr.org.cn], identifier [ChiCTR1900026226].

Association Between Body Mass Index and All-Cause Mortality in a Prospective Cohort of Southern Chinese Adults Without Morbid Obesity

Objective: This prospective study examined the relationship between body mass index (BMI) and all-cause mortality in Chinese adults without morbid obesity.

Methods: We prospectively examined the relationship between BMI and all-cause mortality in 12,608 Southern Chinese adults with age ≥35 years who participated in the National Key R&D Program from 2013–2014 to 2019–2020. Cox proportional hazards models were used to examine the association between BMI and all-cause mortality.

Results: The prevalence of being underweight, normal weight, overweight and having moderate obesity was 7.36%, 55.83%, 28.51% and 8.31%, respectively. A total of 683 (5.65%) deaths occurred during a median follow-up period of 5.61 years. The Cox proportional hazards models indicated that a continuous BMI level was negatively associated with all-cause mortality [adjusted-hazard ratio (HR) per 1 kg/m² increase: 0.96, 95% CI 0.93 to 0.98, p < 0.001]. Furthermore, the HRs of all-cause mortality in the underweight, overweight and moderate obesity groups were 1.31 (1.05, 1.64), 0.89 (0.73, 1.08) and 0.64 (0.44, 0.92), respectively in the confounder model relative to the normal weight group. Survival analysis further confirmed this inverse association of the four BMI categories with mortality.

Conclusion: BMI was negatively associated with all-cause mortality in southern Chinese adults without morbid obesity. Compared to the normal weight category, adults in the moderate obesity category had lower all-cause mortality, whereas being underweight was associated with increased all-cause mortality.

The Statin Target Hmgcr Regulates Energy Metabolism and Food Intake through Central Mechanisms

The statin drug target, 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), is strongly linked to body mass index (BMI), yet how HMGCR influences BMI is not understood. In mammals, studies of peripheral HMGCR have not clearly identified a role in BMI maintenance and, despite considerable central nervous system expression, a function for central HMGCR has not been determined. Similar to mammals, Hmgcr is highly expressed in the Drosophila melanogaster brain. Therefore, genetic and pharmacological studies were performed to identify how central Hmgcr regulates Drosophila energy metabolism and feeding behavior. We found that inhibiting Hmgcr, in insulin-producing cells of the Drosophila pars intercerebralis (PI), the fly hypothalamic equivalent, significantly reduces the expression of insulin-like peptides, severely decreasing insulin signaling. In fact, reducing Hmgcr expression throughout development causes decreased body size, increased lipid storage, hyperglycemia, and hyperphagia. Furthermore, the Hmgcr induced hyperphagia phenotype requires a conserved insulin-regulated α-glucosidase, target of brain insulin (tobi). In rats and mice, acute inhibition of hypothalamic Hmgcr activity stimulates food intake. This study presents evidence of how central Hmgcr regulation of metabolism and food intake could influence BMI.

Association of FTO rs1421085 single nucleotide polymorphism with fat and fatty acid intake in Indonesian adults

Objective

Recent studies showed that genetic polymorphisms in the fat mass and obesity-associated gene (FTO) were associated with obesity and dietary intake. In this study of 71 adults in Jakarta, Indonesia, we investigated FTO rs1421085 association with body mass index (BMI), macronutrient intake, and fatty acid intake. The association was evaluated using linear regression analyses assuming co-dominant, dominant, recessive, over-dominant, and additive genetic models.

Results

Only individuals with the CC genotype had a considerably higher BMI (p < 0.001), which indicates a recessive genetic trait, but the incidence for this genotype is low (68 TT + TC vs. 3 CC). Individuals with the minor C allele had an estimated increase of fat intake by 3.45–4.06% across various genetic models (dominant: p < 0.010, over-dominant: p < 0.030, additive: p < 0.010). Subjects with TC/CC genotypes had increased dietary monounsaturated fatty acid (MUFA; 1.14%, p = 0.046) and saturated fatty acid (SAFA; 2.06%, p = 0.023) intakes, compared to those with the TT genotype. In conclusion, our study provided evidence for the association between FTO rs1421085 risk allele with higher BMI and individual preferences for consuming more fat, MUFA, and SAFA. This study highlights the important role of FTO gene in food preference, and its influence on body weight.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-021-05823-1.

Race/ethnicity-associated blood DNA methylation differences between Japanese and European American women: an exploratory study

BACKGROUND

Racial/ethnic disparities in health reflect a combination of genetic and environmental causes, and DNA methylation may be an important mediator. We compared in an exploratory manner the blood DNA methylome of Japanese Americans (JPA) versus European Americans (EUA).

METHODS

Genome-wide buffy coat DNA methylation was profiled among healthy Multiethnic Cohort participant women who were Japanese (JPA; n = 30) or European (EUA; n = 28) Americans aged 60-65. Differentially methylated CpGs by race/ethnicity (DM-CpGs) were identified by linear regression (Bonferroni-corrected P < 0.1) and analyzed in relation to corresponding gene expression, a priori selected single nucleotide polymorphisms (SNPs), and blood biomarkers of inflammation and metabolism using Pearson or Spearman correlations (FDR < 0.1).

RESULTS

We identified 174 DM-CpGs with the majority of hypermethylated in JPA compared to EUA (n = 133), often in promoter regions (n = 48). Half (51%) of the genes corresponding to the DM-CpGs were involved in liver function and liver disease, and the methylation in nine genes was significantly correlated with gene expression for DM-CpGs. A total of 156 DM-CpGs were associated with rs7489665 (SH2B1). Methylation of DM-CpGs was correlated with blood levels of the cytokine MIP1B (n = 146). We confirmed some of the DM-CpGs in the TCGA adjacent non-tumor liver tissue of Asians versus EUA.

CONCLUSION

We found a number of differentially methylated CpGs in blood DNA between JPA and EUA women with a potential link to liver disease, specific SNPs, and systemic inflammation. These findings may support further research on the role of DNA methylation in mediating some of the higher risk of liver disease among JPA.

FTO Obesity Variant-Exercise Interaction on Changes in Body Weight and BMI: The Taiwan Biobank Study

CONTEXT

Gene-exercise interaction on cross-sectional body mass index (BMI) has been extensively studied and is well established. However, gene-exercise interaction on changes in body weight/BMI remains controversial.

OBJECTIVE

To examine the interaction between the FTO obesity variant and regular exercise on changes in body weight/BMI.

PARTICIPANTS

Taiwan Biobank participants aged 30-70 years (N = 20 906) were examined at both baseline and follow-up visit (mean follow-up duration: 3.7 years).

MAIN OUTCOME MEASURES

The interaction between the FTO obesity variant rs1421085 and regular exercise habit (no exercise, ≤20 metabolic equivalent of tasks (METs)/week exercise, >20 METs/week exercise) on changes in body weight/BMI.

RESULTS

Individuals with the risk allele of rs1421085 gained more weight and increased BMI than those without the risk allele if they did not exercise. In contrast, individuals with the risk allele gained less weight and BMI if they exercised regularly, indicating an interaction between rs1421085 and regular exercise habit (P = .030 for Δbody weight and P = .034 for ΔBMI). The effect of exercise on maintaining body weight was larger in those with the risk allele of rs1421085. When we focused on individuals without regular exercise at baseline, individuals with the risk allele again tended to lose more weight than those with a nonrisk allele if they had acquired an exercise habit by the follow-up visit.

CONCLUSION

The beneficial effect of exercise is greater in individuals genetically prone to obesity due to the interaction between the FTO obesity variant rs1421085 and regular exercise on changes in body weight and BMI.

Omics Approaches in Adipose Tissue and Skeletal Muscle Addressing the Role of Extracellular Matrix in Obesity and Metabolic Dysfunction

Extracellular matrix (ECM) remodeling plays important roles in both white adipose tissue (WAT) and the skeletal muscle (SM) metabolism. Excessive adipocyte hypertrophy causes fibrosis, inflammation, and metabolic dysfunction in adipose tissue, as well as impaired adipogenesis. Similarly, disturbed ECM remodeling in SM has metabolic consequences such as decreased insulin sensitivity. Most of described ECM molecular alterations have been associated with DNA sequence variation, alterations in gene expression patterns, and epigenetic modifications. Among others, the most important epigenetic mechanism by which cells are able to modulate their gene expression is DNA methylation. Epigenome-Wide Association Studies (EWAS) have become a powerful approach to identify DNA methylation variation associated with biological traits in humans. Likewise, Genome-Wide Association Studies (GWAS) and gene expression microarrays have allowed the study of whole-genome genetics and transcriptomics patterns in obesity and metabolic diseases. The aim of this review is to explore the molecular basis of ECM in WAT and SM remodeling in obesity and the consequences of metabolic complications. For that purpose, we reviewed scientific literature including all omics approaches reporting genetic, epigenetic, and transcriptomic (GWAS, EWAS, and RNA-seq or cDNA arrays) ECM-related alterations in WAT and SM as associated with metabolic dysfunction and obesity.

Conserved sequence motifs in human TMTC1, TMTC2, TMTC3, and TMTC4, new O-mannosyltransferases from the GT-C/PMT clan, are rationalized as ligand binding sites

BACKGROUND

The human proteins TMTC1, TMTC2, TMTC3 and TMTC4 have been experimentally shown to be components of a new O-mannosylation pathway. Their own mannosyl-transferase activity has been suspected but their actual enzymatic potential has not been demonstrated yet. So far, sequence analysis of TMTCs has been compromised by evolutionary sequence divergence within their membrane-embedded N-terminal region, sequence inaccuracies in the protein databases and the difficulty to interpret the large functional variety of known homologous proteins (mostly sugar transferases and some with known 3D structure).

RESULTS

Evolutionary conserved molecular function among TMTCs is only possible with conserved membrane topology within their membrane-embedded N-terminal regions leading to the placement of homologous long intermittent loops at the same membrane side. Using this criterion, we demonstrate that all TMTCs have 11 transmembrane regions. The sequence segment homologous to Pfam model DUF1736 is actually just a loop between TM7 and TM8 that is located in the ER lumen and that contains a small hydrophobic, but not membrane-embedded helix. Not only do the membrane-embedded N-terminal regions of TMTCs share a common fold and 3D structural similarity with subgroups of GT-C sugar transferases. The conservation of residues critical for catalysis, for binding of a divalent metal ion and of the phosphate group of a lipid-linked sugar moiety throughout enzymatically and structurally well-studied GT-Cs and sequences of TMTCs indicates that TMTCs are actually sugar-transferring enzymes. We present credible 3D structural models of all four TMTCs (derived from their closest known homologues 5ezm/5f15) and find observed conserved sequence motifs rationalized as binding sites for a metal ion and for a dolichyl-phosphate-mannose moiety.

CONCLUSIONS

With the results from both careful sequence analysis and structural modelling, we can conclusively say that the TMTCs are enzymatically active sugar transferases belonging to the GT-C/PMT superfamily. The DUF1736 segment, the loop between TM7 and TM8, is critical for catalysis and lipid-linked sugar moiety binding. Together with the available indirect experimental data, we conclude that the TMTCs are not only part of an O-mannosylation pathway in the endoplasmic reticulum of upper eukaryotes but, actually, they are the sought mannosyl-transferases.

Genetics of early growth traits

In recent years, genome-wide association studies have shed light on the genetics of early growth and its links with later-life health outcomes. Large-scale datasets and meta-analyses, combined with recently developed analytical methods, have enabled dissection of the maternal and fetal genetic contributions to variation in birth weight. Additionally, longitudinal approaches have shown differences between the genetic contributions to infant, childhood and adult adiposity. In contrast, studies of adult height loci have shown strong associations with early body length and childhood height. Early growth-associated loci provide useful tools for causal analyses: Mendelian randomization (MR) studies have provided evidence that early BMI and height are causally related to a number of adult health outcomes. We advise caution in the design and interpretation of MR studies of birth weight investigating effects of fetal growth on later-life cardiometabolic disease because birth weight is only a crude indicator of fetal growth, and the choice of genetic instrument (maternal or fetal) will greatly influence the interpretation of the results. Most genetic studies of early growth have to date centered on European-ancestry participants and outcomes measured at a single time-point, so key priorities for future studies of early growth genetics are aggregation of large samples of diverse ancestries and longitudinal studies of growth trajectories.

Implication of genetic variants in overweight and obesity susceptibility among the young Arab population of the United Arab Emirates

OBJECTIVE

Overweight and obesity are major risk factors for Type 2 Diabetes Mellitus (T2DM), cardiovascular disease (CVD) and cancer. Genetic predisposition has been shown to play a key role in obesity, and genome-wide association studies (GWAS) have identified multiple loci linked with obesity in various ethnic groups. The aim of this study was to validate the reported genetic variants associated with obesity and overweight in a young UAE Arab population.

METHODS

Twenty-two associated single nucleotide polymorphisms (SNPs) at 11 loci (FTO, MC4R, TMEM18, KCTD15, MTCH2, SH2B1, TFAP2B, GNPDA2, NEGR1, PCSK1 and BDNF) were studied in 392 controls and 318 overweight/obese young Emiratis (aged 18-35 years).

RESULTS

After adjusting for age and smoking, rs3751812 of the FTO gene was associated with overweight/obesity in male participants (p-value < 0.016), while SNPs rs17782313, rs571312 of the MC4R gene and rs12463617 of the TMEM18 gene were significantly associated with overweight/obesity in female participants (p-value = 0.001, 0.028, 0.044, respectively). Follow-up association tests and logistic regression revealed the contribution of the FTO rs3751812 and MC4R rs571213 SNPs to the risk of overweight/obesity after adjusting for age, sex and smoking (p-value = 0.044, 0.049, respectively). In addition, the FTO rs3751812 was associated with the risk of overweight/obesity after adjusting for the effect of other markers (rs17782313, rs571312, rs2867125, rs6548238 and rs12463617) (p-value = 0.035). A significant gene-gene interaction was seen between FTO, MCR4 and TMEM18 (p-value = 0.013).

CONCLUSIONS

Our data demonstrates that rs3751812 of the FTO gene is the key SNP associated with risk of overweight/obesity among the young UAE Arab population, in alignment with previous findings. Our results also indicate that the identified genes stratify with sex and risk of overweight/obesity. In addition to their direct association with overweight/obesity, rs17782313 and rs571312, as well as rs2867125 and rs6548238, may have a modifying effect on the risk of overweight/obesity caused by the rs3751812. Population-specific, sex-specific genetic profiling is important in understanding the heritability of obesity.