Obesity and diabetes: from genetics to epigenetics.

Obesity is becoming an epidemic health problem. During the last years not only genetic but also, and primarily, environmental factors have been supposed to contribute to the susceptibility to weight gain or to develop complications such as type 2 diabetes. In spite of the intense efforts to identify genetic predisposing variants, progress has been slow and success limited, and the common obesity susceptibility variants identified only explains a small part of the individual variation in risk. Moreover, there is evidence that the current epidemic of obesity and diabetes is environment-driven. Recent studies indicate that normal metabolic regulation during adulthood besides requiring a good balance between energy intake and energy expenditure, can be also affected by pre- and post-natal environments. In fact, maternal nutritional constraint during pregnancy can alter the metabolic phenotype of the offspring by means of epigenetic regulation of specific genes, and this can be passed to the next generations. Studies focused on epigenetic marks in obesity found altered methylation and/or histone acetylation levels in genes involved in specific but also in more general metabolic processes. Recent researches point out the continuous increase of "obesogens", in the environment and food chains, above all endocrine disruptors, chemicals that interfere with many homeostatic mechanisms. Taken into account the already existing data on the effects of obesogens, and the multiple potential targets with which they might interfere daily, it seems likely that the exposure to obesogens can have an important role in the obesity and diabesity pandemic.