Variants of the peroxisome proliferator-activated receptor gamma- and beta-adrenergic receptor genes are associated with measures of compensatory eating behaviors in young children

Synergizing Mouse and Human Studies to Understand the Heterogeneity of Obesity

Obesity is routinely considered as a single disease state, which drives a "one-size-fits-all" approach to treatment. We recently convened the first annual University of North Carolina Interdisciplinary Nutrition Sciences Symposium to discuss the heterogeneity of obesity and the need for translational science to advance understanding of this heterogeneity. The symposium aimed to advance scientific rigor in translational studies from animal to human models with the goal of identifying underlying mechanisms and treatments. In this review, we discuss fundamental gaps in knowledge of the heterogeneity of obesity ranging from cellular to population perspectives. We also advocate approaches to overcoming limitations in the field. Examples include the use of contemporary mouse genetic reference population models such as the Collaborative Cross and Diversity Outbred mice that effectively model human genetic diversity and the use of translational models that integrate -omics and computational approaches from pre-clinical to clinical models of obesity. Finally, we suggest best scientific practices to ensure strong rigor that will allow investigators to delineate the sources of heterogeneity in the population with obesity. Collectively, we propose that it is critical to think of obesity as a heterogeneous disease with complex mechanisms and etiologies, requiring unique prevention and treatment strategies tailored to the individual.

Converging Relationships of Obesity and Hyperuricemia with Special Reference to Metabolic Disorders and Plausible Therapeutic Implications

BACKGROUND

Obesity and hyperuricemia mutually influence metabolic syndrome. This study discusses the metabolic relationships between obesity and hyperuricemia in terms of pathophysiology, complications, and treatments.

METHODS

We searched for preclinical or clinical studies on the pathophysiology, complications, and therapy of obesity and hyperuricemia on the PubMed database.

RESULTS

In this systemic review, we summarized our searching results on topics of pathophysiology, complications and therapeutic strategy. In pathophysiology, we firstly introduce genetic variations for obesity, hyperuricemia and their relationships by genetic studies. Secondly, we talk about the epigenetic influences on obesity and hyperuricemia. Thirdly, we describe the central metabolic regulation and the role of hyperuricemia. Then, we refer to the character of adipose tissue inflammation and oxidative stress in the obesity and hyperuricemia. In the last part of this topic, we reviewed the critical links of gut microbiota in the obesity and hyperuricemia. In the following part, we review the pathophysiology of major complications in obesity and hyperuricemia including insulin resistance and type 2 diabetes mellitus, chronic kidney disease, cardiovascular diseases, and cancers. Finally, we recapitulate the therapeutic strategies especially the novel pharmaceutic interventions for obesity and hyperuricemia, which concurrently show the mutual metabolic influences between two diseases.

CONCLUSION

The data reviewed here delineate the metabolic relationships between obesity and hyperuricemia, and provide a comprehensive overview of the therapeutic targets for the management of metabolic syndromes.

Formalising recall by genotype as an efficient approach to detailed phenotyping and causal inference

Detailed phenotyping is required to deepen our understanding of the biological mechanisms behind genetic associations. In addition, the impact of potentially modifiable risk factors on disease requires analytical frameworks that allow causal inference. Here, we discuss the characteristics of Recall-by-Genotype (RbG) as a study design aimed at addressing both these needs. We describe two broad scenarios for the application of RbG: studies using single variants and those using multiple variants. We consider the efficacy and practicality of the RbG approach, provide a catalogue of UK-based resources for such studies and present an online RbG study planner.

Variability in children's eating response to portion size. A biobehavioral perspective

The portion size of foods and beverages offered at meals has been shown to significantly affect human food intake. While portion size effects appear to be fairly robust across studies in adults, findings from studies in children are generally more variable and do not reliably predict a significant portion size effect. Eating behaviors are still forming at a young age and individual differences in children's response to portion size will depend upon genetic predisposition interacting with the child's environment. The aim of this review is to present and discuss evidence that innate controls of appetite and eating, which involve genes that encode key hormones and neuropeptides implicated in processes of satiety and satiation, may differentially affect meal size. We also present evidence that children's response to portion size is learned and this is in turn shaped by upbringing, the early family and home environment. The review will conclude with a conceptual model that illustrates how biological and environmental factors may interact to shape child eating traits including a behavioral susceptibility to overeating when large portion sizes are available.

Polymorphisms in LEPR, PPARG and APM1 genes: associations with energy intake and metabolic traits in young children

OBJECTIVE: To assess the association of single nucleotide polymorphisms (SNPs) in five genes - leptin, leptin receptor (LEPR), adiponectin (APM1), peroxisome proliferator-activated receptor gamma (PPARG) and uncoupling protein 1 - with anthropometric, metabolic, and dietary parameters in a Southern Brazilian cohort of 325 children followed up from birth to 4 years old. MATERIALS AND METHODS: SNPs were analyzed using polymerase chain reaction-based procedures, and their association with phenotypes was evaluated by t-test, analysis of variance, and general linear models. RESULTS: LEPR223Arg allele (rs1137101) was associated with higher daily energy intake at 4 years of age (P = 0.002; Pcorrected = 0.024). PPARG 12Ala-carriers (rs1801282) presented higher glucose levels than Pro/Pro homozygotes (P = 0.007; Pcorrected = 0.042). CONCLUSIONS: Two of the six studied SNPs presented consistent associations, showing that it is already possible to detect the influences of genetic variants on susceptibility to overweight in 4-year-old children.

ADRB3 and PPARγ2 gene polymorphisms and their association with cardiovascular disease risk in postmenopausal women

OBJECTIVES

The contribution of heritability to the development of cardiovascular disease (CVD) is of interest as the identification of genes enhancing the susceptibility of individuals to CVD may help the design of clinical interventions optimized for the individual's genome.

METHODS

We studied the associations of polymorphism of ADRB3 and PPARγ2 genes with obesity indices, unfavorable lipid profile parameters and insulin resistance index HOMA in 343 postmenopausal women.

RESULTS

No association was found between tested polymorphisms and CVD risk factors such as total cholesterol ≥ 5.0 mmol/l, high density lipoprotein cholesterol < 1.2 mmol/l, low density lipoprotein cholesterol > 3.0 mmol/l and triacylglycerols > 1.7 mmol/l. The presence of arterial hypertension and HOMA value ≥ 1.95 were also not related to these polymorphisms. A significant association between PPARγ2 gene polymorphism and total body fat mass (odds ratio = 1.90 at p = 0.037) as well as android fat deposit mass (odds ratio = 1.82 at p = 0.048) was found.

CONCLUSIONS

CVD risk factors in postmenopausal women are not directly associated with the polymorphisms of PPARγ2 and ADRB3 genes. We suggest that some indirect link between PPARγ2 gene polymorphism and susceptibility of postmenopausal women to CVD may exist. This suggestion is based on our finding that high total body fat mass and high android fat deposits are associated with the presence of the Pro12Ala allele of the PPARγ2 gene.

Caloric compensation and eating in the absence of hunger in 5- to 12-y-old weight-discordant siblings

BACKGROUND

An impaired ability to compensate for calories and increased eating in the absence of hunger (EAH) has been associated with increased energy intake and weight gain in unrelated children.

OBJECTIVE

The aims of this study were to compare caloric compensation [the percentage compensation index (%COMPX)] and EAH in weight-discordant siblings aged 5-12 y.

DESIGN

In a crossover, behavioral genetics design, 47 same-sex sibling pairs (53% female, 55% full siblings) were served dinner once a week for 3 wk. Across conditions, siblings were served the same dinner, but 25 min before dinner, they either consumed in full or did not consume 1 of 2 preloads that varied in energy density (ED; 0.57 or 0.97 kcal/g). On the day when no preload was consumed, EAH was assessed after dinner and defined as the number of calories consumed from snacks.

RESULTS

Overweight/obese siblings undercompensated [%COMPX: -48.8 ± 56.3 (mean ± SEM)] and therefore overate after the high-ED preload, whereas normal-weight siblings showed accurate compensation (%COMPX: 101.3 ± 51.9; P = 0.03). Furthermore, overweight/obese siblings consumed 34% more calories (93 kcal) in the absence of hunger than did normal-weight siblings (P = 0.01). Within-pair resemblances for %COMPX and EAH were stronger for full siblings (P < 0.049) than for half siblings (P > 0.23).

CONCLUSIONS

An impaired ability to regulate short-term energy intake, which includes incomplete adjustment for calorie differences in a preload and eating when satiated, may represent a behavioral phenotype for obesity in children. Future studies should test whether teaching children to focus on internal satiety cues may prevent at-risk children from overeating.

Obesity and eating behaviour in children and adolescents: contribution of common gene polymorphisms

The prevalence of childhood obesity is increasing in many countries and confers risks for early type 2 diabetes, cardiovascular disease and metabolic syndrome. In the presence of potent 'obesogenic' environments not all children become obese, indicating the presence of susceptibility and resistance. Taking an energy balance approach, susceptibility could be mediated through a failure of appetite regulation leading to increased energy intake or via diminished energy expenditure. Evidence shows that heritability estimates for BMI and body fat are paralleled by similar coefficients for energy intake and preferences for dietary fat. Twin studies implicate weak satiety and enhanced food responsiveness as factors determining an increase in BMI. Single gene mutations, for example in the leptin receptor gene, that lead to extreme obesity appear to operate through appetite regulating mechanisms and the phenotypic response involves overconsumption and a failure to inhibit eating. Investigations of robustly characterized common gene variants of fat mass and obesity associated (FTO), peroxisome proliferator-activated receptor (PPARG) and melanocortin 4 receptor (MC4R) which contribute to variance in BMI also influence the variance in appetite factors such as measured energy intake, satiety responsiveness and the intake of palatable energy-dense food. A review of the evidence suggests that susceptibility to childhood obesity involving specific allelic variants of certain genes is mediated primarily through food consumption (appetite regulation) rather than through a decrease in activity-related energy expenditure. This conclusion has implications for early detection of susceptibility, and for prevention and management of childhood obesity.

Association of PPAR-γ gene polymorphisms with obesity and obesity-associated phenotypes in North Indian population

OBJECTIVES

The worldwide increasing prevalence of obesity is considered as a major health problem. Peroxisome proliferator-activated receptor gamma (PPAR-γ) controls adipocyte differentiation and regulates a number of genes associated with energy homeostasis. In this study, we investigated the association of PPAR-γ gene Pro12Ala (rs1801282) and C1431T (rs3856806) polymorphisms with morbid obesity and related phenotypes, in north Indian population.

METHODS

A total of 6,42 subjects, 309, obese and 333 nonobese individuals were included in this case-control study. Insulin, adiponectin, glucose, and lipid levels were estimated using standard protocols. All subjects were genotyped by PCR restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

The ProAla+AlaAla genotypes of PPAR-γ Pro12Ala were significantly associated with higher risk of obesity while C1431T polymorphism did not show any significant association. None of the haplotypes showed association with morbid obesity. However, a strong association of variant genotypes was observed with higher levels of insulin, HOMA-IR, and lower serum adiponectin concentrations.

CONCLUSION

PPAR-γ gene polymorphisms influence obesity and obesity phenotype in a complex manner, probably involving insulin resistance in north Indian population.

HTR1B, ADIPOR1, PPARGC1A, and CYP19A1 and obesity in a cohort of Caucasians and African Americans: an evaluation of gene-environment interactions and candidate genes

The World Health Organization estimates that the number of obese and overweight adults has increased to 1.6 billion, with concomitant increases in comorbidity. While genetic factors for obesity have been extensively studied in Caucasians, fewer studies have investigated genetic determinants of body mass index (BMI; weight (kg)/height (m)(2)) in African Americans. A total of 38 genes and 1,086 single nucleotide polymorphisms (SNPs) in African Americans (n = 1,173) and 897 SNPs in Caucasians (n = 1,165) were examined in the Southern Community Cohort Study (2002-2009) for associations with BMI and gene × environment interactions. A statistically significant association with BMI survived correction for multiple testing at rs4140535 (β = -0.04, 95% confidence interval: -0.06, -0.02; P = 5.76 × 10(-5)) in African Americans but not in Caucasians. Gene-environment interactions were observed with cigarette smoking and a SNP in ADIPOR1 in African Americans, as well as between a different SNP in ADIPOR1 and physical activity in Caucasians. A SNP in PPARGC1A interacted with alcohol consumption in African Americans, and a different SNP in PPARGC1A was nominally associated in Caucasians. A SNP in CYP19A1 interacted with dietary energy intake in African Americans, and another SNP in CYP191A had an independent association with BMI in Caucasians.

Maternal perception of the causes and consequences of sibling differences in eating behaviour

Objective

To explore mothers’ perceptions of differences between their children in the eating behaviour domain.

Methods

Twelve semi-structured interviews were carried out with mothers who had at least two children aged between 6 and 15 years, to discuss feeding experiences, particularly around healthy eating. Interviews were recorded and transcribed verbatim and analysed using Framework Analysis.

Results

Mothers frequently identified differences in appetite and food preferences between their children, which they attributed largely to genetic factors. These sibling differences meant that although feeding goals might be common, the pathways to the goals varied depending on each child’s appetitive characteristics. The overall pattern was one of flexible responsiveness to each child. In contrast to perceptions of their own children’s eating behaviours, feeding difficulties in other families were usually attributed to lack of parental control.

Conclusion

The feeding relationship is complex and interactive, resulting in parents modulating their feeding strategies to match each child’s eating behaviour. Guidance to parents on healthy feeding needs to acknowledge the nuanced and interactive nature of feeding practices.

A single nucleotide polymorphism on exon-4 of the gene encoding PPARdelta is associated with reduced height in adults and children

CONTEXT

Peroxisome proliferator-activated receptor (PPAR)-delta is a nuclear transcription factor that plays a key role in many metabolic processes, including energy metabolism, and lipid and glucose metabolism. Candidate gene studies have identified a putative functional variant, rs2016520, in the gene encoding PPARdelta (PPARD), which is associated in some studies with metabolic traits. In addition, this single-nucleotide polymorphism was associated with adult height in several whole-genome scans, but this association did not achieve whole genome significance.

OBJECTIVE

This study sought to determine whether PPARD variation influenced height.

DESIGN

Haplotype tagging analysis across PPARD was performed in about 11,000 individuals from the Wellcome Trust U.K. Type 2 Diabetes Case Control Collection (Go-DARTS2).

RESULTS

There was an association between rs2016520 and height in both patients with type 2 diabetes and controls without diabetes (combined P = 5 x 10(-5)). In a metaanalysis using published data from Caucasian cohorts totaling more than 38,000 participants, compelling evidence was found for this locus and its association with height (P = 10(-8)) with an overall effect size of about 0.5 cm per allele. A similar analysis in a group of 2700 prepubescent children also displayed a similar effect size to that seen in the adults.

CONCLUSION

PPARD variation is clearly associated with a phenotype of reduced stature in both adults and children. Because height is an important indicator of metabolic and nutritional status, this provides additional support for a key role for PPARdelta in critical metabolic functions. PPARdelta may affect height through a variety of mechanisms including altered metabolic efficiency or effects on osteoclast function.

Genetic influences on blood lipids and cardiovascular disease risk: tools for primary prevention

Genetic polymorphism in human populations is part of the evolutionary process that results from the interaction between the environment and the human genome. Recent changes in diet have upset this equilibrium, potentially influencing the risk of most common morbidities such as cardiovascular diseases, obesity, diabetes, and cancer. Reduction of these conditions is a major public health concern, and such a reduction could be achieved by improving our ability to detect disease predisposition early in life and by providing more personalized behavioral recommendations for successful primary prevention. In terms of cardiovascular diseases, polymorphisms at multiple genes have been associated with differential effects in terms of lipid metabolism; however, the connection with cardiovascular disease has been more elusive, and considerable heterogeneity exists among studies regarding the predictive value of genetic markers. This may be because of experimental limitations, the intrinsic complexity of the phenotypes, and the aforementioned interactions with environmental factors. The integration of genetic and environmental complexity into current and future research will drive the field toward the implementation of clinical tools aimed at providing dietary advice optimized for the individual's genome. This may imply that dietary changes are implemented early in life to gain maximum benefit. However, it is important to highlight that most reported studies have focused on adult populations and to extrapolate these findings to children and adolescents may not be justified until proper studies have been carried out in these populations and until the ethical and legal issues associated with this new field are adequately addressed.

An obesity-associated FTO gene variant and increased energy intake in children

BACKGROUND

Variation in the fat mass and obesity-associated (FTO) gene has provided the most robust associations with common obesity to date. However, the role of FTO variants in modulating specific components of energy balance is unknown.

METHODS

We studied 2726 Scottish children, 4 to 10 years of age, who underwent genotyping for FTO variant rs9939609 and were measured for height and weight. A subsample of 97 children was examined for possible association of the FTO variant with adiposity, energy expenditure, and food intake.

RESULTS

In the total study group and the subsample, the A allele of rs9939609 was associated with increased weight (P=0.003 and P=0.049, respectively) and body-mass index (P=0.003 and P=0.03, respectively). In the intensively phenotyped subsample, the A allele was also associated with increased fat mass (P=0.01) but not with lean mass. Although total and resting energy expenditures were increased in children with the A allele (P=0.009 and P=0.03, respectively), resting energy expenditure was identical to that predicted for the age and weight of the child, indicating that there is no defect in metabolic adaptation to obesity in persons bearing the risk-associated allele. The A allele was associated with increased energy intake (P=0.006) independently of body weight. In contrast, the weight of food ingested by children who had the allele was similar to that in children who did not have the allele (P=0.82).

CONCLUSIONS

The FTO variant that confers a predisposition to obesity does not appear to be involved in the regulation of energy expenditure but may have a role in the control of food intake and food choice, suggesting a link to a hyperphagic phenotype or a preference for energy-dense foods.

PPAR-alpha L162V and PGC-1 G482S gene polymorphisms, but not PPAR-gamma P12A, are associated with alcohol consumption in a Spanish Mediterranean population

BACKGROUND

Peroxisome Proliferator-Activated Receptors (PPARs) and its co-activators are regulatory elements of the cellular lipid homeostasis and have been associated with feeding behavior modulation. Animal models suggest that these genes may be involved in alcohol consumption regulation. However, no studies in humans exist. Our aim is to estimate the possible association between polymorphisms in the PPAR-alpha, PPAR-gamma and PPAR-gamma co-activator 1A (PGC-1A) genes and alcohol consumption in humans.

METHODS

We have conducted a cross-sectional study between the PPAR-alpha L162V, PPAR-gamma P12A and PGC-1A G482S polymorphisms, and alcohol consumption in a general Mediterranean Spanish population (303 men and 443 women).

RESULTS

We have found an association between the L162V polymorphism and alcohol consumption in which, carriers of the V allele were more prevalent among alcohol consumers (19.4% vs. 9.8%; OR 2.69; 95% CI: 1.31-5.54, p=0.007). The G482S polymorphism showed a significantly higher frequency in the group of high alcohol drinkers than in non-high alcohol drinkers (33.4% vs. 20.6%; OR 2.28; 95% CI: 1.07-4.88, p=0.034). Mean alcohol consumption was higher as the number of G alleles increased (GG 8.6+/-12.8 g/day, GS 6.6+/-9.2 g/day, SS 5.6+/-7.8 g/day, p=0.003). These results remained statistically significant after covariate adjustment.

CONCLUSIONS

PPAR-alpha L162V and PGC-1A G482S polymorphisms are associated with alcohol consumption in the Mediterranean population.

Central and peripheral neuroendocrine peptides and signalling in appetite regulation: considerations for obesity pharmacotherapy

Appetite and satiety are mediated by complex neuroendocrine signalling pathways involving over 40 hormones, neuropeptides, enzymes, other chemical messengers and their receptors. Research efforts continue to expand understanding of the role of signalling molecules between central hypothalamic nuclei and peripheral enteroendocrine cells; and discoveries of novel networks and messengers provide new biological insights on how to manipulate appetite-satiety pathways. Despite the vast array of peptides that are potentially useful for anti-obesity drug development, only four classes of agents are approved: (i) catecholamine stimulants; (ii) serotonin and noradrenaline reuptake inhibitors; (iii) lipase inhibitors; and (iv) more recently cannabinoid-1 receptor antagonists. Clinical effects of these drugs confer modest improvements, and side effects negatively impact long-term treatment course. This paper suggests single target pharmacological interventions are possibly hampered by the myriad of alternate orexigenic peptidic signals that drive hyperphagia, hence a multiple target model or combination treatment approach is proposed to offer greater therapeutic potential in modulating appetite and managing weight.