Genetics of Obesity: Gene × Nutrient Interactions

Healthy human aging: intrinsic and environmental factors

Abstract This review is an attempt to compile current knowledge on concepts and transformations that occur naturally in the human body and that characterize what is defined today as biological aging with quality of life and longevity. Many authors define natural aging as a continuous and uninterrupted process, which occurs in the human body causing structural and functional changes, classified as: cumulative, progressive, intrinsic and deleterious (CUPID). Usually these changes begin early in life and culminate in physical death. Genetic, chemical and biochemical changes lead to progressive degeneration of cells, tissues and organs, body systems and the organism as a whole, leading to loss of structures and functions due to aging. All these changes were discussed in some detail in the review here presented. We concluded that aging is not genetically determined, resulting in the accumulation of cellular and tissue damage, particularly in chromatin and DNA within cells, in addition to structural and bioactive proteins that command the general metabolism. Environmental factors such as feeding (nutrition) and lifestyle were also discussed.

Obesity susceptibility loci on body mass index and weight loss in Spanish adolescents after a lifestyle intervention

OBJECTIVE

To estimate the contribution of 9 obesity-related polymorphisms and a genetic predisposition score (GPS) on anthropometric and biochemical variables before and after a weight loss intervention program in overweight/obese Spanish adolescents.

STUDY DESIGN

Overweight/obese adolescents (n = 168; 12-16 years) participating in the EVASYON program were genotyped for 9 obesity-related single nucleotide polymorphisms in the FTO, MC4R, TMEM18, IL6, PPARG, and ADIPQ genes.

RESULTS

At baseline, the GPS showed a significant association with body mass index-standard deviation score (BMI-SDS) and fat mass. After 3 months of intervention, this GPS also showed a relationship with the variation of both anthropometric measurements. After adjusting for baseline BMI-SDS, subjects with a lower GPS had a greater improvement on metabolic profile, as well as a better response to physical activity, compared with those subjects with a higher GPS.

CONCLUSIONS

The GPS seems to have an important relationship with BMI-SDS and fat mass both at baseline and after a 3-month weight loss lifestyle intervention. Obese and overweight adolescents with a lower GPS have a greater benefit of weight loss after 3 months of a multidisciplinary lifestyle intervention.

The profile of the Greek ‘XXL’ family

Objective

To identify Greek families in which all members were overweight or obese (XXL families) and to describe their profile with regard to their socio-economic status and their eating behaviours and practices.

Design

A prospective cohort study.

Setting

The metropolitan area of Kavala.

Subjects

We recruited children aged 11 and 12 years from twelve primary schools, and their parents, from volunteers. Auxologic measurements of the children included height and weight. A structured questionnaire pertaining to information on the socio-economic status of the family, anthropometric values and educational status of parents, dietary habits and the availability of various food products and beverages at home, as well as dietary intake, physical activity, time spent sleeping and time spent watching television, was filled in by one of the parents of each child. A total of 331 families finally participated.

Results

In sixty-one families (18·43 %) both parents and child were either overweight or obese (XXL family), and in seven of these families all members were obese. Only twenty-eight families (8·46 %) had all members with a normal BMI. The XXL family was associated with lower educational status of both parents, whereas a higher percentage of XXL families resided in rural areas and had lower income. Skipping breakfast and spending more than 3 h in front of a screen every day were more frequently observed in XXL families. With regard to the availability of various food products and beverages at home, no significant differences were observed between XXL families and the rest of the studied families.

Conclusions

Greek XXL families have lower educational status and lower annual income.

Interaction between genes and lifestyle factors on obesity

Obesity originates from a failure of the body-weight control systems, which may be affected by changing environmental influences. Basically, the obesity risk depends on two important mutually-interacting factors: (1) genetic variants (single-nucleotide polymorphisms, haplotypes); (2) exposure to environmental risks (diet, physical activity etc.). Common single-nucleotide polymorphisms at candidate genes for obesity may act as effect modifiers for environmental factors. More than 127 candidate genes for obesity have been reported and there is evidence to support the role of twenty-two genes in at least five different populations. Gene-environment interactions imply that the synergy between genotype and environment deviates from either the additive or multiplicative effect (the underlying model needs to be specified to appraise the nature of the interaction). Unravelling the details of these interactions is a complex task. Emphasis should be placed on the accuracy of the assessment methods for both genotype and lifestyle factors. Appropriate study design (sample size) is crucial in avoiding false positives and ensuring that studies have enough power to detect significant interactions, the ideal design being a nested case-control study within a cohort. A growing number of studies are examining the influence of gene-environmental interactions on obesity in either epidemiological observational or intervention studies. Positive evidence has been obtained for genes involved in adiposity, lipid metabolism or energy regulation such as PPARgamma2 (Pro12Ala), beta-adrenoceptor 2 (Gln27Glu) or uncoupling proteins 1, 2 and 3. Variants on other genes relating to appetite regulation such as melanocortin and leptin receptors have also been investigated. Examples of some recently-identified interactions are discussed.

Genetics of obesity

Objective

The aim was to review and update advances in genetics of obesity.

Design

Analysis and interpretation of recent investigations about regulating the energy balance as well as about gene-nutrient interactions and current nutrigenomic research methods.

Background and main statements

Obesity results from a long-term positive energy balance. However, its rising prevalence in developed and developing societies must reflect lifestyle changes, since genetic susceptibility remains stable over many generations. Like most complex diseases, obesity derives from a failure of adequate homoeostasis within the physiological system controlling body weight. The identification of genes that are involved in syndromic, monogenic and polygenic obesity has seriously improved our knowledge of body weight regulation. This disorder may arise from a deregulation at the genetic level (e.g. gene transcription or altered protein function) or environmental exposure (e.g. diet, physical activity, etc.).

Conclusions

In practice, obesity involves the interaction between genetic and environmental factors.