WDTC1, the ortholog of Drosophila adipose gene, associates with human obesity, modulated by MUFA intake

Abstract

Adipose (adp) is an obesity gene in Drosophila and mice with crucial functions in fat metabolism. We investigated the correlation between genetic variation of the WDTC1 locus, the ortholog of adp, and human obesity. Five WDTC1 single-nucleotide polymorphisms (SNPs) were genotyped in 935 and 1,115 adults of two ethnically diverse US populations. In the Boston Puerto Rican population, we demonstrated that two WDTC1 SNPs strongly associated with obesity. Homozygote and heterozygote carriers of the major allele i22835A, representing approximately 96% of the population, had significantly higher mean BMI (31.5 and 31.0 kg/m(2), respectively) than noncarriers (28.6 kg/m(2)). Conversely, homozygotes of the minor allele i22835G were leaner and were 74% less likely to be overweight or obese (odds ratio (OR) = 0.26, P = 0.003) compared to homozygote carriers of the major allele. Haplotype analyses based on two SNPs further supported these findings. In addition, we found a strong interaction of monounsaturated fatty acid (MUFA) intake by genotype in this population. As dietary MUFA intake increased, minor allele carriers of SNP i22835A>G had higher BMIs, whereas major allele carriers had lower BMIs. A white population also exhibited a pattern of association between WDTC1 genotypes and obesity although of a different nature. Those WDTC1 variants which associated with obesity likely have experienced strong positive selection in human history, when food supply was unpredictable. Given the high frequency of the major alleles in both populations, we suggest that WDTC1 variation may be an important risk factor contributing to obesity in these populations.

Figures

Fig.1

Interaction between WDTC1- i22835A>G genotype and sex in the GOLDN population. The open bar depicts the mean BMI (in kg/m2) of the major allele i22835A homozygotes (AA) and the solid bar represents those of the minor allele i22835G carriers (GG+GA). Means were adjusted for age, familial relationships, smoking, alcohol use, hormone use, medications for hypertension and dyslipidemia.

Fig. 2

Strong interaction between WDTC1- i22835A>G genotype and dietary MUFA intake in the BPRHS population. Open circles represent the major allele i22835A homozygotes (AA), open squares the heterozygotes (GA), and open triangles the minor allele i22835G homozygotes (GG). Predicted BMI values for all subjects were plotted against their dietary MUFA intake expressed as the percentage of total energy intake. BMI values were calculated based on the regression model containing MUFA intake, i22835A>G genotypes, their interaction term, and the potential confounders including age, gender, smoking, alcohol use, physical activity, total energy, population admixture, medications for depression.