Four Gene Variants Stack the Odds of Metabolic Syndrome in Brazilian Adults

Metabolic syndrome is the quiet accelerant behind many of the world’s most serious chronic diseases. Defined by a cluster of abnormalities—abdominal obesity, elevated triglycerides, low HDL cholesterol, high blood pressure and disturbed blood sugar—it multiplies the risk of type 2 diabetes and cardiovascular disease. A new study from researchers at the University of Sao Paulo, published in the International Journal of Obesity, adds a crucial genetic dimension to the picture: in a cohort of 420 Brazilian adults, inherited variants in four genes involved in energy balance and fat metabolism were independently linked to the syndrome and to the metabolic and inflammatory disturbances that accompany it.

The research team, led by Tamiris Invencioni Moraes Stefani, Thiago Dominguez Crespo Hirata and Alvaro Cerda, set out to test whether variants in ten candidate genes—FTO, LEP, LEPR, ADRB3, ADIPOQ, TCF7L2, ENPP1, APOA5, PPARG and CYP11B2—were associated with metabolic syndrome and obesity-related traits. These genes were chosen because genome-wide association studies and candidate gene analyses had previously implicated them in obesity, diabetes, dyslipidemia and blood pressure regulation. The participants, aged 18 to 83, were randomly selected from a Brazilian observational cohort, with 179 diagnosed with metabolic syndrome under International Diabetes Federation criteria and 241 serving as controls. Individuals with kidney, liver, thyroid or adrenal disease, gonadal dysfunction, secondary obesity or pregnancy were excluded.

The methodological rigor of the study deserves attention. Each participant underwent a detailed clinical and anthropometric evaluation, including body mass index, waist circumference, waist-to-hip ratio, body fat percentage and basal metabolic rate. Fasting blood samples yielded an extensive laboratory panel: glucose, glycated hemoglobin, insulin, a full lipid profile, apolipoproteins, adipokines such as leptin and adiponectin, and a battery of inflammatory markers including high-sensitivity C-reactive protein, interleukin-6, interleukin-1 beta, tumor necrosis factor alpha and plasminogen activator inhibitor 1. Insulin resistance was quantified both by the HOMA-IR index and by the triglyceride-glucose index. Genomic DNA was extracted from leukocytes and variants were genotyped using TaqMan assays, with control samples in every run and twenty percent of samples re-analyzed with complete concordance.

When the researchers applied multivariate logistic regression—adjusting for age, ethnicity, sex, alcohol consumption, tobacco smoking, physical activity and family history of cardiovascular disease—two variants stood out as independent predictors of metabolic syndrome. The G allele of ADRB3 rs4994, a missense change known as Trp64Arg, more than tripled the odds of the syndrome, with an odds ratio of 3.71. The G allele of LEPR rs1137100, the Lys109Arg variant in the leptin receptor, nearly doubled the risk, with an odds ratio of 2.52. Both variants were also associated with hypertension, and the ADRB3 risk allele additionally predicted dyslipidemia, insulin resistance and obesity.

The biological logic behind these associations is compelling. The ADRB3 gene encodes the beta-3 adrenergic receptor, which sits on the surface of adipose tissue cells and drives lipolysis, thermogenesis and energy expenditure. The Trp64Arg substitution lies in the intracellular tail of the receptor and is thought to impair its signaling, effectively dampening the body’s ability to burn fat. Carriers of the risk allele in this study showed higher body mass index, larger waist circumference in women, greater body fat, elevated glucose, insulin, triglycerides and HOMA-IR, and a strikingly pro-inflammatory profile, with increased leptin, PAI-1, hsCRP, IL-1 beta, IL-6 and TNF-alpha. The leptin receptor variant, meanwhile, alters the stability of the receptor’s ligand-binding domain, potentially weakening the leptin-melanocortin pathway that governs satiety and body weight.

Beyond the two strongest hits, variants in FTO and PPARG shaped the anthropometric, metabolic and inflammatory landscape of the cohort. The FTO rs17817449-G allele predicted higher waist-to-hip ratio in women along with lower apolipoprotein AI and resistin concentrations, echoing earlier findings in Chinese adults and in Brazilians with severe obesity. FTO is an intronic risk locus whose variants are believed to disrupt regulatory interactions that control energy homeostasis. The PPARG rs1801282 variant, Pro12Ala in the nuclear receptor that orchestrates adipogenesis and insulin sensitivity, predicted higher body fat in women and higher leptin in men—a gender-dependent effect that underscores how genetic risk can be expressed differently across sexes.

The study’s most forward-looking contribution is its polygenic risk score. Rather than treating each variant in isolation, the team built a weighted score in which each individual’s risk alleles were summed using adjusted odds ratios derived from their own regression models. Because genotyping success varied across participants, the researchers also computed a normalized score, dividing each person’s total by the number of successfully genotyped variants. Both versions of the score told the same story: values were significantly higher in people with metabolic syndrome, and they climbed steadily as the number of metabolic syndrome components increased from zero to five. Quartile analysis revealed a dose-response relationship, with syndrome prevalence rising progressively from the lowest to the highest genetic burden category.

The discriminatory power of the score, however, was modest. Receiver operating characteristic analysis yielded an area under the curve of 0.598 for the raw score and 0.616 for the normalized version—statistically significant but far from a stand-alone diagnostic test. The authors are candid about why: the score was built from a restricted set of candidate genes rather than genome-wide data, and the cohort, while carefully phenotyped, was relatively small and cross-sectional. Large genome-wide polygenic models, such as a recent multivariate analysis of nearly five million people of European and East Asian ancestry, achieve better discrimination by leveraging hundreds of loci. Yet those models transfer poorly to admixed populations like Brazil’s, which is precisely where a biologically informed candidate gene approach offers complementary value.

The limitations of the study are acknowledged with unusual transparency. The cross-sectional design precludes causal inference. Multiple comparisons were corrected using the Benjamini-Hochberg method at a ten percent false discovery rate, but some associations may still be influenced by the sheer number of tests. Deviations from Hardy-Weinberg equilibrium were observed for several polymorphisms, notably in the two variants most strongly associated with the syndrome, where deviations appeared only in the control group—a pattern the authors interpret as consistent with differential selective pressure rather than genotyping error. Many participants, particularly those with metabolic syndrome, were taking antidiabetic, antihypertensive or lipid-lowering medications, which may have blunted some genotype-phenotype associations. Self-reported ethnicity, without ancestry-informative markers, limits full control of population stratification in this admixed cohort.

Even with these caveats, the findings carry real weight for precision medicine in underrepresented populations. They confirm that variants governing energy homeostasis—ADRB3, LEPR and FTO—and lipid metabolism through PPARG are not merely statistical signals but are reflected in measurable differences in body composition, insulin resistance, lipid transport and systemic inflammation. The clear gradient of polygenic risk across the number of metabolic syndrome components supports the idea that common variants with individually modest effects accumulate into meaningful susceptibility. As the authors conclude, further studies in diverse populations will be essential before such scores can enter clinical practice, but this work marks an important step toward genetically informed assessment of metabolic and cardiovascular risk in a population that genome-wide resources have long overlooked.

Subject of Research: Genetic variants and polygenic risk scores associated with obesity-related metabolic syndrome in Brazilian adults

Article Title: ADRB3, LEPR, FTO and PPARG variants contribute to obesity-related metabolic syndrome in Brazilian adults: a polygenic risk score approach

Article References: Stefani, T. I. M., Hirata, T. D. C., Cerda, A., de Oliveira, R., dos Santos, M. A., Fajardo, C. M., Dorea, E. L., Bernik, M. M. S., Hirata, M. H., & Hirata, R. D. C. (2026). ADRB3, LEPR, FTO and PPARG variants contribute to obesity-related metabolic syndrome in Brazilian adults: a polygenic risk score approach. International Journal of Obesity. https://doi.org/10.1038/s41366-026-02218-9

Image Credits: AI Generated

DOI: 10.1038/s41366-026-02218-9

Keywords: metabolic syndrome, obesity, polygenic risk score, ADRB3, LEPR, FTO, PPARG, genetic variants, insulin resistance, inflammation, Brazilian cohort, cardiovascular risk