Lifestyle traits a strong factor in obesity
Scientific studies of twins can throw light on many fascinating aspects of the genes versus environment debate. In a study just published by EU-funded researchers, lifestyle factors came out more strongly responsible for obesity and insulin resistance than hereditary ones. The study, entitled 'Acquired obesity and poor physical fitness impair expression of genes of mitochondrial oxidative phosphorylation in monozygotic twins discordant for obesity' is published in the American Journal of Physiology-Endocrinology and Metabolism. It involved 14 pairs of identical twins, eight male and six female, all born in Finland between 1975 and 1979. One twin in each pair was obese (called discordant pairs). The control group consisted of five male and five female identical twin pairs who were not obese and had similar body weights (called concordant pairs). Recent studies have suggested that defects in the genes that are responsible for the body's conversion of food to energy can cause insulin resistance. Researchers were interested to find out if this was caused by hereditary or environmental factors. The study found that the lifestyle led by the identical twins in the study impaired their gene expression much more than hereditary factors. For example, it was found that acquired obesity and lack of exercise contributed to insulin resistance. During the study, the researchers measured the insulin sensitivity of the subjects' whole bodies, and how fit they were. They also took needle biopsies of abdominal subcutaneous fat tissue. The results found that among the discordant pairs the obese twins had lower insulin sensitivity which means it is harder for their bodies to produce energy. They also found that the genes responsible for helping cells to convert food to energy were less active in the obese twins, suggesting that the faulty expression of these genes could make it harder to control weight and easier to gain it. 'These data suggest that physical inactivity may have contributed to the defects in mitochondrial oxidative phosphorylation described in type 2 diabetic patients and prediabetic subjects,' said Linda Mustelin of the University of Helsinki, author of the report. 'Although we found that the reduced transcript levels of genes encoding mitochondrial oxidative phosphorylation in obesity is influenced by environmental and acquired factors, it does not exclude the possibility that genetic factors may contribute to regulation of mitochondrial oxidative metabolism.' The researchers now want to do a further study to see if exercise and other positive lifestyle changes can increase gene expression. EU support for the research came from the 'Quality of life and management of living resources' Thematic Area of the Fifth Framework Programme (FP5).
Countries
Finland