👤 Adan Valladares-Salgado

We investigated the association between the loss-of-function mutation MC4R p.Ile269Asn and T2D risk in the Mexican population. We enrolled 6929 adults [3175 T2D cases and 3754 normal glucose tolerant (NGT) controls] and 994 NGT children in the study. Anthropometric data and T2D-related quantitative traits were studied in 994 NGT children and 3754 NGT adults. The MC4R p.Ile269Asn mutation was genotyped using TaqMan. The MC4R p.Ile269Asn mutation was associated with T2D [OR = 2.00, 95% confidence interval (CI) 1.35-2.97, p = 0.00057] in Mexican adults. Additional adjustment for body-mass index (BMI) attenuated but did not remove the association (OR = 1.70, 95% CI 1.13-2.56, p = 0.011). The MC4R p.Ile269Asn mutation was associated with T2D (OR = 1.88, 95% CI 1.14-3.08, p = 0.013) in a subset of 1269 T2D cases and 1269 NGT controls matched for sex, age, and BMI. A mediation analysis estimated that BMI accounts for 22.7% of the association between MC4R p.Ile269Asn mutation and T2D risk (p = 4.55 × 10 Show less

Studies in mice and humans suggest that melanocortin-4 receptor (MC4R) deficiency affects body weight in a sex-/gender-dependent manner. However, similar evidence for type 2 diabetes (T2D) is scarce. We investigated whether sex/gender modifies the association between the loss-of-function MC4R p.Ile269Asn mutation and T2D in 6929 Mexican adults (3175 T2D cases and 3754 normal glucose tolerance [NGT] controls). The 2003 American Diabetes Association criteria were used to define NGT and T2D. The MC4R p.Ile269Asn mutation was genotyped in all participants using TaqMan technology. The MC4R p.Ile269Asn mutation was associated with T2D in 6929 Mexican adults (Ncontrols = 3754, Ncases = 3175, odds ratio [OR] = 2.00, 95% confidence interval [CI], 1.35-2.97; P = 5.7 × 10-4). The MC4R p.Ile269Asn mutation had a frequency of 0.86 and 1.05% in women with NGT and T2D, and 0.78 and 1.32% in men with NGT and T2D, respectively. We identified a significant interaction between the MC4R p.Ile269Asn mutation and sex/gender on T2D risk (P = 0.049). Although a strong association between the mutation and T2D was observed in men (Ncontrols = 2418, Ncases = 1807, OR = 2.63, 95% CI, 1.62-4.28, P = 9.3 × 10-5), results were not significant in women (Ncontrols = 1336, Ncases = 1368, OR = 1.16, 95% CI, 0.60-2.26, P = 0.65). Further adjustment for body mass index in the logistic regression model did not alter the sex-/gender-specific pattern of association (men: OR = 2.22, 95% CI, 1.34-3.67, P = 0.0019; women: OR = 1.02, 95% CI, 0.51-2.02, P = 0.95). This is the first report of a male-specific association between the MC4R p.Ile269Asn loss-of-function mutation and T2D in the Mexican population. Show less

Rare partial/complete loss-of-function mutations in the melanocortin-4 receptor (MC4R) gene are the most common cause of Mendelian obesity in European populations, but their contribution to obesity in the Mexican population is unclear. We investigated whether deleterious mutations in MC4R contribute to obesity in Mexican children and adults. We provide evidence that the MC4R p.Ile269Asn (rs79783591) mutation may have arisen in modern human populations from a founder event in native Mexicans. The MC4R Isoleucine 269 is perfectly conserved across 184 species, which suggests a critical role for the amino acid in MC4R activity. Four in silico tools (SIFT, PolyPhen-2, CADD, MutPred2) predicted a deleterious impact of the p.Ile269Asn substitution on MC4R function. The MC4R p.Ile269Asn mutation was associated with childhood (Ncontrols = 952, Ncases = 661, odds ratio (OR) = 3.06, 95% confidence interval (95%CI) [1.94-4.85]) and adult obesity (Ncontrols = 1445, Ncases = 2,487, OR = 2.58, 95%CI [1.52-4.39]). The frequency of the MC4R p.Ile269Asn mutation ranged from 0.52 to 0.59% and 1.53 to 1.59% in children and adults with normal weight and obesity, respectively. The MC4R p.Ile269Asn mutation co-segregated perfectly with obesity in 5 multigenerational Mexican pedigrees. While adults with obesity carrying the p.Ile269Asn mutation had higher BMI values than noncarriers, this trend was not observed in children. The MC4R p.Ile269Asn mutation accounted for a population attributable risk of 1.28% and 0.68% for childhood and adult obesity, respectively, in the Mexican population. The MC4R p.Ile269Asn mutation may have emerged as a founder mutation in native Mexicans and is associated with childhood and adult obesity in the modern Mexican population. Show less

Although hundreds of genome-wide association studies-implicated loci have been reported for adult obesity-related traits, less is known about the genetics specific for early-onset obesity and with only a few studies conducted in non-European populations to date. Searching for additional genetic variants associated with childhood obesity, we performed a trans-ancestral meta-analysis of 30 studies consisting of up to 13 005 cases (≥95th percentile of body mass index (BMI) achieved 2-18 years old) and 15 599 controls (consistently <50th percentile of BMI) of European, African, North/South American and East Asian ancestry. Suggestive loci were taken forward for replication in a sample of 1888 cases and 4689 controls from seven cohorts of European and North/South American ancestry. In addition to observing 18 previously implicated BMI or obesity loci, for both early and late onset, we uncovered one completely novel locus in this trans-ancestral analysis (nearest gene, METTL15). The variant was nominally associated with only the European subgroup analysis but had a consistent direction of effect in other ethnicities. We then utilized trans-ancestral Bayesian analysis to narrow down the location of the probable causal variant at each genome-wide significant signal. Of all the fine-mapped loci, we were able to narrow down the causative variant at four known loci to fewer than 10 single nucleotide polymorphisms (SNPs) (FAIM2, GNPDA2, MC4R and SEC16B loci). In conclusion, an ethnically diverse setting has enabled us to both identify an additional pediatric obesity locus and further fine-map existing loci. Show less

Although there is adequate knowledge as to the role of traditional cardiovascular risk factors on stroke incidence, knowledge of other risk factors, particularly genetic ones, is still incomplete. To assess the participation of some polymorphisms, along with other modifiable risk factors, a case-control study was conducted. A total of 253 cases were identified in the emergency room of a general regional hospital, with a clinical trait of stroke confirmed by a skull computerized axial tomography scan. In the surgery ward, 253 controls were identified, gender and age (±5 years) matched. Biochemical parameters were measured, and 4 polymorphisms were genotyped by polymerase chain reaction, rs1801133 (methylenetetrahydrofolate reductase [MTHFR]), rs1498373 (dimethylarginine dimethylaminohydrolase type 1 [DDAH1]), rs662799 (apolipoprotein A5 [APOA5]), and rs1799983 (endothelial nitric oxide). Odds ratios were estimated to assess the strength of association, with 95% confidence intervals, both in a matched case-control analysis and in a conditional regression analysis. Cases had higher mean blood pressure and triglycerides and lower hemoglobin levels. Heterozygous and homozygous subjects to the rs1801133 variant of the MTHFR gene had a 3-fold higher risk of stroke. In the dominant model, those with the polymorphism rs662799 of the promoter region for APOA5 had twice the risk of stroke. Anemia increased the risk of stroke 4-fold. Polymorphisms of the genes MTHFR (rs1801133) and APOA5 (rs662799), as well as anemia, are independent risk factors for stroke in Mexicans, together with traditional cardiovascular risk factors such as high triglycerides and high blood pressure. Show less

We carried out an admixture mapping study of lipid traits in two samples from Mexico City. Native American locus ancestry was significantly associated with triglyceride levels in a broad region of chromosome 11 overlapping the BUD13, ZNF259 and APOA5 genes. In our fine-mapping analysis of this region using dense genome-wide data, rs964184 is the only marker included in the 99% credible set of SNPs, providing strong support for rs964184 as the causal variant within this region. The frequency of the allele associated with increased triglyceride concentrations (rs964184-G) is between 30-40% higher in Native American populations from Mexico than in European populations. The evidence currently available for this variant indicates that it may be exerting its effect through three potential mechanisms: 1) modification of enhancer activity, 2) regulation of the expression of several genes in cis and/or trans, or 3) modification of the methylation patterns of the promoter of the APOA5 gene. Show less

Dyslipidemia is an important risk factor for the development of several diseases. The genetic component of hypertriglyceridemia has been studied in adults, but little is known in children. The objective is to evaluate the association of two variants in APOA5 (rs662799) and APOA1 (rs5072) with triglyceride (TG) levels in Mexican children. Anthropometric parameters were measured in 1559 Mexican children 5-14 years of age. DNA was isolated from blood samples. Lipid profiles and glucose concentrations were determined from serum and genotyping of rs662799, and rs5072 was performed using TaqMan® technology. Additive and dominant models adjusted for age, gender and body mass index were used to evaluate the association of these single nucleotide polymorphisms with TG levels. Children with high TG levels were found to have a higher body mass index and waist circumference as well as a worse lipids profile and glucose levels (p < 0.001). Additive and dominant models demonstrated a significant association between the rs662799 and rs5072 with TG. The dominant model showed the strongest significant association (OR = 1.81; 95% CI 1.46-2.24; p = 5.40 × 10 The minor alleles of rs662799 (APOA5) and rs5072 (APOA1) modulate TG levels in Mexican children. Show less

We performed genome-wide meta-analysis of lipid traits on three samples of Mexican and Mexican American ancestry comprising 4,383 individuals, and followed up significant and highly suggestive associations in three additional Hispanic samples comprising 7,876 individuals. Genome-wide significant signals were observed in or near CELSR2, ZNF259/APOA5, KANK2/DOCK6 and NCAN/MAU2 for total cholesterol, LPL, ABCA1, ZNF259/APOA5, LIPC and CETP for HDL cholesterol, CELSR2, APOB and NCAN/MAU2 for LDL cholesterol, and GCKR, TRIB1, ZNF259/APOA5 and NCAN/MAU2 for triglycerides. Linkage disequilibrium and conditional analyses indicate that signals observed at ABCA1 and LIPC for HDL cholesterol and NCAN/MAU2 for triglycerides are independent of previously reported lead SNP associations. Analyses of lead SNPs from the European Global Lipids Genetics Consortium (GLGC) dataset in our Hispanic samples show remarkable concordance of direction of effects as well as strong correlation in effect sizes. A meta-analysis of the European GLGC and our Hispanic datasets identified five novel regions reaching genome-wide significance: two for total cholesterol (FN1 and SAMM50), two for HDL cholesterol (LOC100996634 and COPB1) and one for LDL cholesterol (LINC00324/CTC1/PFAS). The top meta-analysis signals were found to be enriched for SNPs associated with gene expression in a tissue-specific fashion, suggesting an enrichment of tissue-specific function in lipid-associated loci. Show less