How Genetic and Environmental Factors Influence Cardiometabolic Risk Factors? Findings from the Isfahan Twins Study

Abstract

Background: Disease-discordant twins are excellent subjects for matched case-control studies since the confounding effects of age, sex, genetic background, intrauterine, and early environment factors are perfectly controlled. We aimed to investigate how genetic and environmental factors influence cardiometabolic risk factors in a sample of twins in Iran. Methods: Past medical history and physical examination were collected for all participants. Fasting venous blood samples were taken to measure fasting blood glucose (FBG) and lipids levels. Descriptive statistical analysis was used to present the characteristics of twin pairs. Bivariate correlations between the same age- and gender-corrected parameters were separately analysed in monozygotic and dizygotic pairs. The ACE model i.e., the additive genetic (A) effects, and common (C), and unique (E) environmental influences on the trait was used to assess heritability as a structural equation model. Results: This cross-sectional study included 710 (210 monozygotic and 500 dizygotic) twin pairs (Range age: 2-52 years) (mean age: 11.67 ± 10.71 years) who enrolled in the Isfahan Twin Registry (ITR) in 2017. In early childhood (2-6 years), shared environmental influenced on height (by 76%), weight (by 75%), and body mass index (BMI) (by73%). In late childhood (7-12 years), hip circumference, waist circumference (WC), and LDL-cholesterol are highly heritable, 90%, 76%, and 64%, respectively. In adolescents, the following risk factors were highly or moderately heritable: height (94%), neck circumference (85%), LDL-cholesterol (81%), WC (70%), triglycerides (69%), weight (68%), and BMI (65%). In adult twins, arm circumference (97%), weight (86%), BMI (82%), and neck circumference (81%) were highly heritable. Conclusion: In our study, we observed that various factors, both genetic and environmental, exert an impact on individuals at different stages of their lives. Particularly, we found that certain traits, such as obesity, are highly heritable during childhood but their heritability tends to decline as one progresses into adulthood.