Genetic background, nutrition and obesity: a review.

OBJECTIVE: To summarize the latest information on the relationship between genes and common forms of obesity, and to review genetic markers (SNPs and miRNA) that play a role in predisposing to common forms of obesity and related disorders. MATERIALS AND METHODS: We searched PubMed with the following keywords: (obesity[Title/Abstract]) AND predisposition[Title/Abstract]) AND miRNA[Title/Abstract]) OR polymorphism[Title/Abstract]. RESULTS: From the search we obtained a total of 44 gene loci and 48 miRNAs associated with common obesity. CONCLUSIONS: It is now widely accepted that obesity involves interactions between environmental risk factors (physical inactivity, excessive calorie intake, chronic stress, taste perception) and a genetic background of risk. Analysis of the genetic background of obese subjects is therefore an important way to determine the molecular mechanisms controlling the link between food intake and obesity, enabling a better understanding of how these interactions may differ from person to person.

Prevalence of mutations in LEP, LEPR, and MC4R genes in individuals with severe obesity.

Obesity is a major public health concern; despite evidence of high heritability, the genetic causes of obesity remain unclear. In this study, we assessed the presence of mutations in three genes involved in the hypothalamic leptin-melanocortin regulation pathway (leptin, LEP; leptin receptor, LEPR; and melanocortin-4 receptor, MC4R), which is important for energy homeostasis in the body, in a group of patients with severe obesity. For this study, we selected 77 patients who had undergone bariatric surgery and had a pre-operative body mass index (BMI) >35 kg/m2, early onset and a family history of being overweight. Candidate genes were screened by direct sequence analysis to search for rare genetic variations. The common LEP -2548 G/A polymorphism was also evaluated for its influence on the BMI (in obesity patients) and for obesity risk, using a case-control study involving 117 healthy individuals. Two different non-synonymous alterations in MC4R were found in two patients: the p.(Thr112Met), previously described in the literature as a probable gene involved in the obesity phenotype, and the novel p.(Tyr302Asp) variant, predicted to be pathogenic by in silico evaluations and family segregation studies. The LEP -2548 G/A polymorphism was not associated with the BMI or obesity risk. In conclusion, we have reported a novel mutation in MC4R in a family of Italian patients with severe obesity. Screening for MC4R could be important for directing the carriers of mutations towards therapy including partial agonists of the MC4R that could normalize their appetite and inhibit compulsive eating. Next-generation sequencing could be used to clarify the genetic basis of obesity in the future.