Investigation of the Locus Near MC4R With Childhood Obesity in Americans of European and African Ancestry

Recently a modest, but consistently, replicated association was demonstrated between obesity and the single‐nucleotide polymorphism (SNP), rs17782313, 3′ of the MC4R locus as a consequence of a meta‐analysis of genome‐wide association (GWA) studies of the disease in white populations. We investigated the association in the context of the childhood form of the disease utilizing data from our ongoing GWA study in a cohort of 728 European‐American (EA) obese children (BMI ≥95th percentile) and 3,960 EA controls (BMI <95th percentile), as well as 1,008 African‐American (AA) obese children and 2,715 AA controls. rs571312, rs10871777, and rs476828 (perfect surrogates for rs17782313) yielded odds ratios in the EA cohort of 1.142 (P = 0.045), 1.137 (P = 0.054), and 1.145 (P = 0.042); however, there was no significant association with these SNPs in the AA cohort. When investigating all 30 SNPs present on the Illumina BeadChip at this locus, again there was no evidence for association in AA cases when correcting for the number of tests employed. As such, variants 3′ to the MC4R locus present on the genotyping platform utilized confer a similar magnitude of risk of obesity in white children as to their adult white counterparts but this observation did not extend to AAs.     

Meta‐analysis Added Power to Identify Variants in FTO Associated With Type 2 Diabetes and Obesity in the Asian Population

Several common variants in the intron 1 of FTO (fat mass and associated obesity) gene have been reliably associated with BMI and obesity in European populations. We analyzed two variants (rs9939609 and rs8050136) in 4,189 Chinese Han individuals and conducted a meta‐analysis of published studies in Asian population to investigate whether these variants are associated with type 2 diabetes (T2D) and obesity in Asian population. In this study, both the minor allele A of rs9939609 and the minor allele A of rs805136 were associated with increased risk of T2D, independent of measures of BMI; the odds ratios (ORs) per copy of the risk allele were 1.19 for rs9939609 (95% confidence interval (CI), 1.04–1.37; P = 0.01) and 1.22 for rs8050136 (95% CI, 1.07–1.40; P = 0.004) after adjusting for age, sex, and BMI. Our results also showed association with risk of obesity (rs9939609: OR = 1.39 (95% CI 1.04–1.85), P = 0.02; rs8050136: OR = 1.45 (95% CI 1.09–1.93), P = 0.01) but no association with overweight. These results were consistent with the pooled results from our meta‐analysis study (for diabetes, rs8050136, P = 1.3 × 10^?3; rs9939609, P = 9.8 × 10^?4; for obesity, rs8050136, P = 2.2 × 10^?7; rs9939609, P = 9.0 × 10^?9). Our findings indicate that the two variants (rs9939609 and rs8050136) in the FTO gene contribute to obesity and T2D in the Asian populations.     

The Impact of Variants in Four Genes: MC4R,FTO, PPARG and PPARGC1A in Overweight and Obesity in a Large Sample of the Brazilian Population

Biochemical Genetics - Obesity and overweight are worldwide public health problems with an evident genetic predisposition that is still poorly understood. In addition, great variability has been...     

FTO and MC4R gene variants are associated with obesity in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the leading cause of anovulatory infertility in women. It is also associated with metabolic disturbances that place women at increased risk for obesity and type 2 diabetes. There is strong evidence for familial clustering of PCOS and a genetic predisposition. However, the gene(s) responsible for the PCOS phenotypes have not been elucidated. This two-phase family-based and case-control genetic study was designed to address the question of whether SNPs identified as susceptibility loci for obesity in genome-wide association studies (GWAS) are also associated with PCOS and elevated BMI. Members of 439 families having at least one offspring with PCOS were genotyped for 15 SNPs previously shown to be associated with obesity. Linkage and association with PCOS was assessed using the transmission/disequilibrium test (TDT). These SNPs were also analyzed in an independent case-control study involving 395 women with PCOS and 176 healthy women with regular menstrual cycles. Only one of these 15 SNPs (rs2815752 in NEGR1) was found to have a nominally significant association with PCOS (χ² = 6.11, P = 0.013), but this association failed to replicate in the case-control study. While not associated with PCOS itself, five SNPs in FTO and two in MC4R were associated with BMI as assessed with a quantitative-TDT analysis, several of which replicated association with BMI in the case-control cohort. These findings demonstrate that certain SNPs associated with obesity contribute to elevated BMI in PCOS, but do not appear to play a major role in PCOS per se. These findings support the notion that PCOS phenotypes are a consequence of an oligogenic/polygenic mechanism.     

Statistical and Biological Gene-Lifestyle Interactions of MC4R and FTO with Diet and Physical Activity on Obesity: New Effects on Alcohol Consumption

Background

Fat mass and obesity (FTO) and melanocortin-4 receptor (MC4R) and are relevant genes associated with obesity. This could be through food intake, but results are contradictory. Modulation by diet or other lifestyle factors is also not well understood.

Objective

To investigate whether MC4R and FTO associations with body-weight are modulated by diet and physical activity (PA), and to study their association with alcohol and food intake.

Methods

Adherence to Mediterranean diet (AdMedDiet) and physical activity (PA) were assessed by validated questionnaires in 7,052 high cardiovascular risk subjects. MC4R rs17782313 and FTO rs9939609 were determined. Independent and joint associations (aggregate genetic score) as well as statistical and biological gene-lifestyle interactions were analyzed.

Results

FTO rs9939609 was associated with higher body mass index (BMI), waist circumference (WC) and obesity (P<0.05 for all). A similar, but not significant trend was found for MC4R rs17782313. Their additive effects (aggregate score) were significant and we observed a 7% per-allele increase of being obese (OR = 1.07; 95%CI 1.01–1.13). We found relevant statistical interactions (P<0.05) with PA. So, in active individuals, the associations with higher BMI, WC or obesity were not detected. A biological (non-statistical) interaction between AdMedDiet and rs9939609 and the aggregate score was found. Greater AdMedDiet in individuals carrying 4 or 3-risk alleles counterbalanced their genetic predisposition, exhibiting similar BMI (P = 0.502) than individuals with no risk alleles and lower AdMedDiet. They also had lower BMI (P = 0.021) than their counterparts with low AdMedDiet. We did not find any consistent association with energy or macronutrients, but found a novel association between these polymorphisms and lower alcohol consumption in variant-allele carriers (B+/−SE: −0.57+/−0.16 g/d per-score-allele; P = 0.001).

Conclusion

Statistical and biological interactions with PA and diet modulate the effects of FTO and MC4R polymorphisms on obesity. The novel association with alcohol consumption seems independent of their effects on BMI.     

The role of common and rare MC4R variants and FTO polymorphisms in extreme form of obesity

Melanocortin 4 receptor (MC4R) is an important regulator of food intake and number of studies report genetic variations influencing the risk of obesity. Here we explored the role of common genetic variation from MC4R locus comparing with SNPs from gene FTO locus, as well as the frequency and functionality of rare MC4R mutations in cohort of 380 severely obese individuals (BMI > 39 kg/m²) and 380 lean subjects from the Genome Database of Latvian Population (LGDB). We found correlation for two SNPs—rs11642015 and rs62048402 in the fat mass and obesity-associated protein (FTO) with obesity but no association was detected for rs17782313 located in the MC4R locus in these severely obese individuals. We sequenced the whole gene MC4R coding region in all study subjects and found five previously known heterozygous non-synonymous substitutions V103I, I121T, S127L, V166I and I251L. Expression in mammalian cells showed that the S127L, V166I and double V103I/S127L mutant receptors had significantly decreased quantity at the cell surface compared to the wild type MC4R. We carried out detailed functional analysis of V166I that demonstrated that, despite low abundance in plasma membrane, the V166I variant has lower EC₅₀ value upon αMSH activation than the wild type receptor, while the level of AGRP inhibition was decreased, implying that V166I cause hyperactive satiety signalling. Overall, this study suggest that S127L may be the most frequent functional MC4R mutation leading to the severe obesity in general population and provides new insight into the functionality of population based variants of the MC4R.     

Relationship of Adipokines and Proinflammatory Cytokines Among Asian Indians With Obesity and Youth Onset Type 2 Diabetes

Objective: It is well known that inflammation is associated with diabetes, but it is unclear whether obesity mediates this association in individuals with youth-onset type 2 diabetes mellitus (T2DM-Y).Methods: We recruited individuals with T2DM-Y (age at onset <25 years) and age-matched normal glucose tolerance (NGT) subjects. Participants were further classified using Asia-Pacific body mass index cut-points for obesity and categorized as: nonobese NGT (n = 100), Obese NGT (n = 50), nonobese T2DM-Y (n = 50), and obese T2DM-Y (n = 50). We compared adipokines (adiponectin and leptin) and proinflammatory cytokines (tumor necrosis factor alpha &lsqb;TNF-α] and monocyte chemotactic protein-1 &lsqb;MCP-1]) across groups.Results: Compared to nonobese NGT, the other 3 groups (obese NGT, nonobese T2DM-Y, and obese T2DM-Y) were found to have lower adiponectin (7.7 vs. 5.7, 4.2, 3.8 μg/mL, P<.01), and higher leptin (3.6 vs. 5.4, 5.7, 7.9 μg/mL, P<.001) and MCP 1 (186 vs. 272, 340, 473 pg/mL, P<.001) respectively. However, TNF-α levels were higher only among nonobese T2DM-Y (112 pg/mL) and obese T2DM-Y (141 pg/mL, P<.01 for each). After adjusting for age, sex, waist, hypertension, homeostatic model assessment of insulin resistance (HOMA-IR), serum cholesterol, triglycerides, and family history of diabetes, adiponectin was associated with 33% and 41% lower odds of being nonobese T2DM and obese T2DM, respectively. However, adjusted for same factors, leptin, TNF-α, and MCP-1 were associated with markedly higher odds (5- to 14-fold) of nonobese and obese T2DM.Conclusion: In young Asian Indians, leptin and proinflammatory cytokines are positively, and adiponectin negatively, associated with both nonobese and obese T2DM-Y compared to nonobese NGT individuals.Abbreviations: BMI = body mass index CI = confidence interval FPG = fasting plasma glucose HOMA-IR = homeostatic model assessment of insulin resistance IGT = impaired glucose tolerance MCP-1 = monocyte chemotactic protein-1 NGT = normal glucose tolerance OGTT = oral glucose tolerance test OR = odds ratio T2DM-Y = youth-onset type 2 diabetes TNF-α = tumor necrosis factor-α     

Common variants in the obesity-associated genes FTO and MC4R are not associated with risk of colorectal cancer

BackgroundObesity is a convincing risk factor for colorectal cancer. Genetic variants in or near FTO and MC4R are consistently associated with body mass index and other body size measures, but whether they are also associated with colorectal cancer risk is unclear.MethodsIn the discovery stage, we tested associations of 677 FTO and 323 MC4R single nucleotide polymorphisms (SNPs) 100 kb upstream and 300 kb downstream from each respective locus with risk of colorectal cancer in data from the Colon Cancer Family Registry (CCFR: 1960 cases; 1777 controls). Next, all SNPs that were nominally statistically significant (p < 0.05) in the discovery stage were included in replication analyses in data from the Genetics and Epidemiology of Colorectal Cancer Consortium (GECCO: 9716 cases; 9844 controls).ResultsIn the discovery stage, 43 FTO variants and 18 MC4R variants were associated with colorectal cancer risk (p < 0.05). No SNPs remained statistically significant in the replication analysis after accounting for multiple comparisons.ConclusionWe found no evidence that individual variants in or near the obesity-related genes FTO and MC4R are associated with risk of colorectal cancer.     

Association of FTO Gene Variants With Adiposity in African‐American Adolescents

The prevalence of obesity continues to increase significantly, with the largest rise in the African‐American adolescents. Genetic contributions to obesity are being identified with the advent of genome‐wide association studies (GWAS). Specifically, variants of the fat mass and obesity associated (FTO) gene have been associated with obesity in populations of European descent. The studies in African Americans have been inconclusive. To further evaluate the association of the FTO gene and adiposity in African Americans, we genotyped 47 single‐nucleotide polymorphisms (SNPs), including seven SNPs previously reported to be significant in the literature in a cohort consisting of 561 non‐Hispanic white and 497 African‐American individuals. Analysis of our data showed 17 SNPs to be associated with BMI Z‐score (BMI‐Z) in our study population. The strongest association was found in the African Americans. The most significant SNP was rs8057044, which was associated with BMI‐Z in the African Americans (P = 0.00054). SNP rs9939609 was found to be significant in the non‐Hispanic white population (P = 0.028). Our data confirm the association between FTO and adiposity suggesting that FTO is a childhood obesity susceptibility gene. Our data also identify a novel SNP of the FTO gene (rs8057044) that is associated with measures of adiposity in the African‐American population.     

Genetic Variants in the Fat and Obesity Associated (FTO) Gene and Risk of Alzheimer's Disease

Background

Recent studies showed that polymorphisms in the Fat and Obesity-Associated (FTO) gene have robust effects on obesity, obesity-related traits and endophenotypes associated with Alzheimer''s disease (AD).

Methods

We used 1,877 Caucasian cases and controls from the NIA-LOAD study and 1,093 Caribbean Hispanics to further explore the association of FTO with AD. Using logistic regression, we assessed 42 SNPs in introns 1 and 2, the region previously reported to be associated with AD endophenotypes, which had been derived by genome-wide screenings. In addition, we performed gene expression analyses of neuropathologically confirmed AD cases and controls of two independent datasets (19 AD cases, 10 controls; 176 AD cases, 188 controls) using within- and between-group factors ANOVA of log₁₀ transformed rank invariant normalized expression data.

Results

In the NIALOAD study, one SNP was significantly associated with AD and three additional markers were close to significance (rs6499640, rs10852521, rs16945088, rs8044769, FDR p-value: 0.05<p<0.09). Two of the SNPs are in strong LD (D′>0.9) with the previously reported SNPs. In the Caribbean Hispanic dataset, we identified three SNPs (rs17219084, rs11075996, rs11075997, FDR p-value: 0.009<p<0.01) that were associated with AD. These results were confirmed by haplotype analyses and in a metaanalysis in which we included the ADNI dataset. FTO had a significantly lower expresssion in AD cases compared to controls in two independent datasets derived from human cortex and amygdala tissue, respectively (p = 2.18×10−5 and p<0.0001).

Conclusions

Our data support the notion that genetic variation in Introns 1 and 2 of the FTO gene may contribute to AD risk.     

Three Novel SNPs in the Coding Region of the Bovine MC3R Gene and Their Associations with Growth Traits

The involvement of melanocortin-3 receptor (MC3R) is well recognized in the regulation of feeding efficiency, body weight, and energy homeostasis. The objective of this study was to investigate the associations between MC3R gene polymorphisms and growth traits. Three novel SNPs (c.24C→T, c.220T→A, c.734G→C) and five haplotypes were identified in 234 Xiangxi cattle. The associations between MC3R gene polymorphisms and growth traits indicated that the individuals with TT and AT genotypes maintained higher body weight than those with the AA genotype at the c.220T→A locus (P < 0.05). The animals with GG and CG genotypes had higher heart girth and body weight than those with the CC genotype at c.734G→C (P < 0.05). The animals with H3H3 and H2H3 haplotype combinations had higher body weight than those with other haplotype combinations (P < 0.05). The results suggest that these SNPs in the MC3R gene might be useful genetic markers for marker-assisted selection and cattle breeding.     

猪资源家系MC4R基因扫描及其与脂肪性状的相关分析

黑素皮质激素受体－4（Melanocortin-4 Receptor,MC4R)是在人类肥胖研究中发现的重要调节因子,它可以与瘦蛋白（Leptin),神经肽Y（Neuropeptide Y,NPY),α－黑素细胞刺激激素（Alpha-melanocyte-stimulating hormone,α-MSH)第一起调节动物体重和采食量。采用PCR－RFLP技术,分析了MC4R基因部分片段在猪资源家系群体中的TaqⅠ酶切片段多态性分析。MC4R基因多态性与生长肥育性状,肉质性状,胴体性状的相关性分析的结果表明,MC4R基因型频率在不同品种群体中的分布不同;MC4R基因与猪胸腰椎间膘厚,臀部膘厚,平均背膘,眼肌宽度,眼肌面积,皮率呈显著性相关。MC4R基因主要以显性作用方式发挥作用,加性作用不显著。     

The missense variation landscape of FTO,MC4R,and TMEM18 in obese children of African Ancestry

Objective:

Common variation at the loci harboring fat mass and obesity (FTO), melanocortin receptor 4 (MC4R), and transmembrane protein 18 (TMEM18) is consistently reported as being statistically most strongly associated with obesity. Investigations if these loci also harbor rarer missense variants that confer substantially higher risk of common childhood obesity in African American (AA) children were conducted.

Design and Methods:

The exons of FTO, MC4R, and TMEM18 in an initial subset of our cohort were sequenced, that is, 200 obese (BMI≥95th percentile) and 200 lean AA children (BMI≤5th percentile). Any missense exonic variants that were uncovered went on to be further genotyped in a further 768 obese and 768 lean (BMI≤50th percentile) children of the same ethnicity.

Results:

A number of exonic variants were observed from our sequencing effort: seven in FTO, of which four were non‐synonymous (A163T, G182A, M400V, and A405V), thirteen in MC4R, of which six were non‐synonymous (V103I, N123S, S136A, F202L, N240S, and I251L), and four in TMEM18, of which two were non‐synonymous (P2S and V113L). Follow‐up genotyping of these missense variants revealed only one significant difference in allele frequency between cases and controls, namely with N240S in MC4R (Fisher's exact P = 0.0001).

Conclusion:

In summary, moderately rare missense variants within the FTO, MC4R, and TMEM18 genes observed in our study did not confer risk of common childhood obesity in African Americans except for a degree of evidence for one known loss‐of‐function variant in MC4R.     

Screening for Coding Variants in FTO and SH2B1 Genes in Chinese Patients with Obesity

Objective

To investigate potential functional variants in FTO and SH2B1 genes among Chinese children with obesity.

Methods

Sanger sequencing of PCR products of all FTO and SH2B1 exons and their flanking regions were performed in 338 Chinese Han children with obesity and 221 age- and sex-matched lean controls.

Results

A total of seven and five rare non-synonymous variants were identified in FTO and SH2B1, respectively. The overall frequencies of FTO and SH2B1 rare non-synonymous variants were similar in obese and lean children (2.37% and 0.90% vs. 1.81% and 1.36%, P>0.05). However, four out of the seven variants in FTO were novel and all were unique to obese children (p>0.05). None of the novel variants was consistently being predicted to be deleterious. Four out of five variants in SH2B1 were novel and one was unique to obese children (p>0.05). One variant (L293R) that was consistently being predicted as deleterious in SH2B1 gene was unique to lean control. While rare missense mutations were more frequently detected in girls from obesity as well as lean control than boys, the difference was not statistically significant. In addition, it''s shown that the prevalence of rare missense mutations of FTO as well as SH2B1 was similar across different ethnic groups.

Conclusion

The rare missense mutations of FTO and SH2B1 did not confer risks of obesity in Chinese Han children in our cohort.     

Interaction between obesity-related genes, FTO and MC4R, associated to an increase of breast cancer risk

Breast cancer (BC) is a complex disease and obesity is a well-known risk factor for its development, especially after menopause. Several studies have shown Single Nucleotide Polymorphisms (SNPs) linked to overweight and obesity, such as: rs1121980 (T/C) and rs9939609 (A/T) in Fat Mass and Obesity Associated gene (FTO) and rs17782313 (T/C) in Melanocortin 4 Receptor gene (MC4R). Thus, we aimed to investigate the association between these obesity-related SNPs and BC risk. One hundred BC patients and 148 healthy women from Santa Catarina, Brazil entered the study. SNPs were genotyped using Taqman assays. For statistical analyses SNPStats and SPSS softwares were used. Association analyses were performed by logistic regression and were adjusted for age and Body mass index (BMI). Multiple SNPs inheritance models (log-additive, dominant, recessive, codominant) were performed to determine odds ratios (ORs), assuming 95 % confidence interval (CI) and P value = 0.05 as the significance limit. When analyzed alone, FTO rs1121980 and rs9939609 did not show significant associations with BC development, however MC4R rs17782313 showed increased risk for BC even after adjustments (P-value = 0.032). Interestingly, the interaction of FTO and MC4R polymorphisms showed a powerful association with BC. We observed a 4.59-fold increased risk for woman who have the allele combination C/T/C (FTO rs1121980/FTO rs9939609/MC4R rs17782313) (P-value = 0.0011, adjusted for age and BMI). We found important and unpublished associations between these obesity-related genes and BC risk. These associations seem to be independent of their effect on BMI, indicating a direct role of the interaction between FTO and MC4R polymorphisms in BC development.     

The obesity-associated polymorphisms FTO rs9939609 and MC4R rs17782313 and endometrial cancer risk in non-Hispanic white women

Overweight and obesity are strongly associated with endometrial cancer. Several independent genome-wide association studies recently identified two common polymorphisms, FTO rs9939609 and MC4R rs17782313, that are linked to increased body weight and obesity. We examined the association of FTO rs9939609 and MC4R rs17782313 with endometrial cancer risk in a pooled analysis of nine case-control studies within the Epidemiology of Endometrial Cancer Consortium (E2C2). This analysis included 3601 non-Hispanic white women with histologically-confirmed endometrial carcinoma and 5275 frequency-matched controls. Unconditional logistic regression models were used to assess the relation of FTO rs9939609 and MC4R rs17782313 genotypes to the risk of endometrial cancer. Among control women, both the FTO rs9939609 A and MC4R rs17782313 C alleles were associated with a 16% increased risk of being overweight (p = 0.001 and p = 0.004, respectively). In case-control analyses, carriers of the FTO rs9939609 AA genotype were at increased risk of endometrial carcinoma compared to women with the TT genotype [odds ratio (OR)  = 1.17; 95% confidence interval (CI): 1.03–1.32, p = 0.01]. However, this association was no longer apparent after adjusting for body mass index (BMI), suggesting mediation of the gene-disease effect through body weight. The MC4R rs17782313 polymorphism was not related to endometrial cancer risk (per allele OR = 0.98; 95% CI: 0.91–1.06; p = 0.68). FTO rs9939609 is a susceptibility marker for white non-Hispanic women at higher risk of endometrial cancer. Although FTO rs9939609 alone might have limited clinical or public health significance for identifying women at high risk for endometrial cancer beyond that of excess body weight, further investigation of obesity-related genetic markers might help to identify the pathways that influence endometrial carcinogenesis.     

Genetic Variants in ADD1 Gene and their Associations with Growth Traits in Cattle

The α-adducin (ADD1) is a subunit of adducin which is a cytoskeleton heterodimeric protein. Adducin participates in oocytes chromosome meiosis of mice, prompting adducin has an effect on embryonic development. Adducin gene mutation has significantly functional change. So the present study was to identify and characterize polymorphisms within the coding region of the bovine ADD1 gene among different cattle breeds. Here, 11 novel single nucleotide polymorphisms (SNPs 1–11) were identified by DNA sequencing and polymerase chain reaction-single stranded conformational polymorphism, there were one synonymous mutation in exon 1 (SNP1); four missense mutations in exons 4, 7, and 8 (SNPs 3–6); and six mutations in introns 4, 12, 13, and 14 (SNPs 2, 7–10). The statistical analyses indicated that the some SNPs are associated with the growth traits (body length, body height, chest circumference, and hucklebone width) in Chinese Jiaxian cattle population. Our results provide evidence that polymorphisms in the ADD1 gene are associated with growth traits, and may be used for marker-assisted selection in beef cattle breeding program.     

Contribution of Common Genetic Variants to Obesity and Obesity-Related Traits in Mexican Children and Adults

Background

Several studies have identified multiple obesity-associated loci mainly in European populations. However, their contribution to obesity in other ethnicities such as Mexicans is largely unknown. The aim of this study was to examine 26 obesity-associated single-nucleotide polymorphisms (SNP) in a sample of Mexican mestizos.

Methods

9 SNPs in biological candidate genes showing replications (PPARG, ADRB3, ADRB2, LEPR, GNB3, UCP3, ADIPOQ, UCP2, and NR3C1), and 17 SNPs in or near genes associated with obesity in first, second and third wave GWAS (INSIG2, FTO, MC4R, TMEM18, FAIM2/BCDIN3, BDNF, SH2B1, GNPDA2, NEGR1, KCTD15, SEC16B/RASAL2, NPC1, SFRF10/ETV5, MAF, PRL, MTCH2, and PTER) were genotyped in 1,156 unrelated Mexican-Mestizos including 683 cases (441 obese class I/II and 242 obese class III) and 473 normal-weight controls. In a second stage we selected 12 of the SNPs showing nominal associations with obesity, to seek associations with quantitative obesity-related traits in 3 cohorts including 1,218 Mexican Mestizo children, 945 Mexican Mestizo adults, and 543 Indigenous Mexican adults.

Results

After adjusting for age, sex and admixture, significant associations with obesity were found for 6 genes in the case-control study (ADIPOQ, FTO, TMEM18, INSIG2, FAIM2/BCDIN3 and BDNF). In addition, SH2B1 was associated only with class I/II obesity and MC4R only with class III obesity. SNPs located at or near FAIM2/BCDIN3, TMEM18, INSIG2, GNPDA2 and SEC16B/RASAL2 were significantly associated with BMI and/or WC in the combined analysis of Mexican-mestizo children and adults, and FTO locus was significantly associated with increased BMI in Indigenous Mexican populations.

Conclusions

Our findings replicate the association of 8 obesity-related SNPs with obesity risk in Mexican adults, and confirm the role of some of these SNPs in BMI in Mexican adults and children.     

Dietary Factors Impact on the Association between CTSS Variants and Obesity Related Traits

Background/Aims

Cathepsin S, a protein coded by the CTSS gene, is implicated in adipose tissue biology–this protein enhances adipose tissue development. Our hypothesis is that common variants in CTSS play a role in body weight regulation and in the development of obesity and that these effects are influenced by dietary factors–increased by high protein, glycemic index and energy diets.

Methods

Four tag SNPs (rs7511673, rs11576175, rs10888390 and rs1136774) were selected to capture all common variation in the CTSS region. Association between these four SNPs and several adiposity measurements (BMI, waist circumference, waist for given BMI and being a weight gainer–experiencing the greatest degree of unexplained annual weight gain during follow-up or not) given, where applicable, both as baseline values and gain during the study period (6–8 years) were tested in 11,091 European individuals (linear or logistic regression models). We also examined the interaction between the CTSS variants and dietary factors–energy density, protein content (in grams or in % of total energy intake) and glycemic index–on these four adiposity phenotypes.

Results

We found several associations between CTSS polymorphisms and anthropometric traits including baseline BMI (rs11576175 (SNP N°2), p = 0.02, β = −0.2446), and waist change over time (rs7511673 (SNP N°1), p = 0.01, β = −0.0433 and rs10888390 (SNP N°3), p = 0.04, β = −0.0342). In interaction with the percentage of proteins contained in the diet, rs11576175 (SNP N°2) was also associated with the risk of being a weight gainer (p_interaction = 0.01, OR = 1.0526)–the risk of being a weight gainer increased with the percentage of proteins contained in the diet.

Conclusion

CTSS variants seem to be nominally associated to obesity related traits and this association may be modified by dietary protein intake.