ABSTRACT
Epidemiológica! methods are increasingly used to assess the role of genetic factors and their interaction with environmental factors, in the occurrence of diseases in populations. Nutrition is one of the most relevant components of the interaction between the human being and the environment. Therefore, the interaction between susceptibility genotypes and nutritional risk factors has a great importance in the study of several chronic diseases. The aim of this article is to review different epidemiologic study designs and basic methods of analysis commonly used in the evaluation of the interaction between nutritional and genetic factors. These study designs and analytical methods are equally valid for the assessment of genotype-environment or genotype-genotype interaction.
Subject(s)
Humans , Environment , Epidemiologic Methods , Genetic Predisposition to Disease , Nutritional Physiological Phenomena , Chronic Disease , Environmental Exposure/adverse effects , Genotype , Nutritional Physiological Phenomena/genetics , Odds Ratio , Research Design/standards , Risk FactorsABSTRACT
Background : Tumor necrosis factor-alpha (TNF-alpha) has an increased expression in the adipose tissue of obese subjects and is involved in insulin resistance. Aim: To screen for associations between -308G/A, -238G/A, -376G/A and -163G/A genetic variants of the TNF-alpha gene, diabetes and obesity-related variables. Material and methods: A group of 263 elderly women aged 60-90 years were recruited. Among them, an oral glucose tolerance test was performed and serum lipids measured in 100 women. TNF-alpha genotypes were determined by polymerase chain reaction (PCR) and analysis of restriction fragment lenght polymorphisms. Results: No significant differences were found when comparing allele frequencies in TNF-alpha polymorphisms of normal subjects with those having impaired glucose tolerance or type 2 diabetes. After excluding patients with previous diagnosis of diabetes, no significant differences by polymorphism carrier status were found for plasma levels of lipids, glucose and insulin. Additionally, no significant differences were found for the association between variables related to adiposity and the ¡308G/A polymorphisms. Conclusions: It is unlikely that polymorphisms in the promoter region of the TNF-alpha gene have a major influence in obesity and diabetes phenotypes in Chilean elderly women.
Subject(s)
Adult , Aged , Female , Humans , Middle Aged , Promoter Regions, Genetic , /genetics , Obesity/genetics , Polymorphism, Genetic/genetics , Tumor Necrosis Factor-alpha/genetics , Blood Glucose , Body Mass Index , Chile , Cross-Sectional Studies , Gene Frequency , Genotype , Glucose Tolerance Test , Insulin Resistance , Lipids/blood , Polymerase Chain Reaction , Polymorphism, Restriction Fragment LengthABSTRACT
This review focuses on methodological aspects and main results of different family studies that have been conducted to assess the existence of a genetic contribution in human obesity. A genetic component in the etiology of obesity has been elucidated through specific study designs answering different research questions such as: a) Do obesity aggregate in families? b) Is there a genetic contribution to familial clustering? c) Is it possible to localize chromosomal regions that contain susceptibility genes to obesity? d) Is it possible to estimate the risk for developing obesity depending on the genotype profile in candidate genes? There are sufficient evidences indicating the existence of a moderate familial clustering of obesity defined as body mass index 30 with a stronger aggregation with more extreme values of body mass index. Twin studies have demonstrated that the familial aggregation of obesity has a genetic component and is not only due to cultural or environmental factors clustered in families. Linkage studies have identified markers and genes related to obesity in virtually all human chromosomes. However, some of these linkage studies have produced conflicting results. Discordant results are even more pronounced in case-control studies that evaluate the association between alleles at candidate genes and obesity. Topics related to study design will acquire increasing importance in order to avoid methodological problems related to trait definition, sample sizes, population stratification by ethnicity and other confounding factors.