Phenotypic linkage between single-nucleotide polymorphisms of beta3-adrenergic receptor gene and NADH dehydrogenase subunit-2 gene, with special reference to eating behavior

Longevity-associated mitochondrial DNA 5178 C/A polymorphism modifies effect of aging on renal function in male Japanese health checkup examinees: an exploratory cross-sectional study

Background

Mitochondrial DNA 5178 (Mt5178) C/A polymorphism is reportedly associated with longevity in the Japanese population. The objective of this study was to investigate whether Mt5178 C/A polymorphism influences the effect of physiological aging on renal function in male Japanese health checkup examinees.

Methods

A total of 404 male subjects (mean age ± SD, 53.9 ± 7.8 years; range, 29–76 years) were selected from among individuals visiting the hospital for regular medical checkups. After Mt5178 C/A genotyping, a cross-sectional study assessing the joint effects of Mt5178 C/A polymorphism and aging on renal function was then conducted. Renal function was evaluated by estimated glomerular filtration rate (eGFR). Subjects were divided into three age groups (< 50, 50–59, ≥ 60 years).

Results

In simple linear regression analysis, a significant negative association between aging and eGFR was observed in both Mt5178C and Mt5178A genotypic men (P < 0.001 and P = 0.003, respectively). However, in multiple linear regression analysis, a significant effect of aging on reduced eGFR was observed only in Mt5178C genotypic men (P < 0.001). Logistic regression analysis showed that, in the case of reduced eGFR defined as < 75 mL/min/1.73 m², reduced eGFR was dependent on aging in both Mt5178C and Mt5178A genotypic men (P for trend < 0.001 and P for trend = 0.002, respectively). After adjusting for smoking status and alcohol consumption, reduced eGFR was also dependent on aging in both Mt5178C and Mt5178A genotypic men (P for trend < 0.001 and P for trend = 0.014, respectively). However, in reduced eGFR defined as < 90 mL/min/1.73 m², reduced eGFR was dependent on aging only in Mt5178C genotypic men (P for trend < 0.001).

Conclusions

This cross-sectional study suggests that Mt5178 C/A polymorphism modulates the effects of physiological aging on kidney function in Japanese men.

Physiology and pathophysiology of the β3-adrenergic receptor

The β₃-adrenergic receptor (β₃-AR) is an important regulator of various physiological functions, such as thermogenesis in brown adipose tissue, lipolysis in white adipose tissue, negative inotropic effect in cardiomyocyte, and relaxation in blood vessel. The activation of β₃-AR by its agonists is shown to have metabolic (antiobesity and antidiabetic) and cardiovascular effects in animal models, highlighting β₃-AR as a potential therapeutic target in the treatment of several human diseases. Moreover, a substantial number of studies performed on different populations have identified some β₃-AR polymorphic variants associated with obesity, diabetes, cardiovascular diseases, and other disorders. The clinical phenotypes and functional characteristics of these variants provide insights into potential pathophysiological roles of β₃-AR in the development of these diseases.

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.

Influence of mitochondrial DNA 5178 C/A polymorphism on serum cholesterol changes: a short-term follow-up in middle-aged Japanese men

OBJECTIVE

The mitochondrial DNA 5178 cytosine/adenine (Mt5178 C/A) polymorphism is reportedly associated with longevity in the Japanese population, and the Mt5178A genotype may exert anti-atherogenic effects. The aim of this study was to determine whether there were longitudinal differences in serum lipid levels between carriers of the Mt5178C genotype and those of the Mt5178A genotype and to assess the impact of these genotypes on serum cholesterol levels.

METHODS

The serum levels of total cholesterol (TC), high-density lipoprotein cholesterol (HDLC), and low-density lipoprotein cholesterol (LDLC) were measured and the Mt5178 C/A genotypes determined in 110 Japanese men aged 41-66 (mean 52.3) years who had received medical checkups twice in the period 1999-2005. The longitudinal changes of TC, HDLC, and LDLC were calculated according to genotype.

RESULTS

The serum levels of TC at baseline and follow-up were significantly different, whereas those of HDLC and LDLC were not. The changes in HDLC differed significantly between the two Mt5178 C/A genotype groups, with the changes in HDLC level being significantly greater in the Mt5178A genotype group than in the Mt5178C group (p = 0.015).

CONCLUSIONS

The Mt5178 C/A genotype may modify longitudinal changes in serum TC and HDLC levels in middle-aged Japanese men.

The ADRB3 Trp64Arg variant and BMI: a meta-analysis of 44 833 individuals

BACKGROUND

The beta-3 adrenergic receptor gene (ADRB3) is part of the adrenergic system, which is known to play a key role in energy metabolism. The association between the Trp64Arg variant in the ADRB3 and body mass index (BMI) has been widely examined, but previous studies have been small and results have been inconsistent.

METHODS

We assessed the association between the ADRB3 Trp64Arg variant and BMI in a large UK population-based cohort of 4854 middle-aged men and women. We also performed a meta-analysis of 97 studies, involving 44 833 individuals, to place our findings in context.

RESULTS

Although we found no significant difference in BMI (0.20 kg/m(2), P=0.40) between the Trp64Trp homozygotes and Arg64 allele carriers in our UK population-based cohort, the meta-analysis showed significant association between the Arg64Trp variant and BMI, with Arg64-allele carriers having a 0.24 kg/m(2) (P=0.0002) higher BMI compared with noncarriers. However, we also found substantial heterogeneity among the studies (P=2.2 x 10(-14)). The difference in East Asians (0.31 kg/m(2), P=0.001) was 3.9 times larger than that in Europeans in whom no significant association was observed (0.08 kg/m(2), P=0.36). This was consistent with the chronological cumulative decrease in the effect size, which decreased steadily in Europeans and reached nonsignificance after 11 studies in 1996. In East Asians, the cumulative effect size decreased after the first reports, but reached a steady state at a significant effect size of 0.24 kg/m(2) in 2000. Although the funnel plot indicated no apparent publication bias, smaller studies tended to report greater differences in BMI, compared with larger studies.

CONCLUSIONS

Collectively, these data suggest that the Trp64Arg ADRB3 genetic variant might be associated with BMI in East Asians, but not Europeans. More generally, our study shows the importance of meta-analyses in the field of genetic association studies for common traits. Each genetic variant makes only a small contribution to variation in BMI, and large sample sizes are needed to reliably assess and interpret gene-phenotype associations.

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

BACKGROUND

Young children can regulate energy precisely in the short term, showing the potential for an innate compensation mechanism of eating behavior. However, data suggest that precise compensation is attenuated as a function of increasing adiposity, parental feeding style, and age. Common variation in candidate obesity genes may account for some of the individual variation observed in short-term energy compensation. Polymorphisms in the peroxisome proliferator-activated receptor gamma (PPARG) and beta-adrenergic receptor (ADRB3) genes have been linked to increased body mass index (BMI; in kg/m(2)), obesity, and more recently dietary nutrients and preferences. In addition, common variation in ADRB3 interacts with PPARG to modulate adult body weight.

OBJECTIVE

This study investigated whether variants in these genes were associated with measurable effects on child eating behavior.

DESIGN

Children (n=84) aged 4-10 y were prospectively selected for variants of the PPARG locus (Pro12Ala, C1431T). Heights and weights were measured. Energy intake from a test meal was measured 90 min after ingestion of a no-energy (NE), low-energy (LE), or high-energy (HE) preload, and the compensation index (COMPX) was calculated.

RESULTS

BMI differed significantly by gene model, whereby Pro12Ala was associated with a lower BMI. Poor COMPX was associated with the PPARG T1431 allele (P=0.009). There was a significant interaction between COMPX and the ADRB3 Trp64Arg variant in modulating compensation (P=0.003), whereas the Arg64 allele was associated with good compensation (P=0.001).

CONCLUSIONS

This is the first study to suggest that a genetic interaction involving ADRB3 and PPARG variants influences eating behavior in children.

Genetic epidemiological studies of longevity-associated mitochondrial DNA 5178 C/A polymorphism

Mitochondrial DNA 5178 cytosine/adenine (Mt5178 C/A) polymorphism is associated with longevity in the Japanese population, and the Mt5178A genotype may confer antiatherogenic advantages. Individuals with the Mt5178A genotype may be more resistant to adult-onset diseases, such as myocardial infarction, cerebrovascular diseases and type 2 diabetes, than those with the Mt5178C genotype. Moreover, Mt5178 C/A polymorphism has been reported to be associated with blood pressure, serum lipid levels, hematological parameters, intraocular pressure, serum protein fraction levels and serum electrolyte levels in healthy Japanese individuals. Differences in the influence of habitual drinking or habitual smoking on health status between the Mt5178C genotype and the Mt5178A genotype have been reported. The individual modification of drinking habits or smoking habits based on the genotyping of Mt5178 C/A may promote improved health and lead to the establishment of personalized prevention strategies for adult-onset diseases.

Nonshivering thermogenesis capacity associated to mitochondrial DNA haplotypes and gender in the greater white-toothed shrew, Crocidura russula

A selection gradient was recently suggested as one possible cause for a clinal distribution of mitochondrial DNA (mtDNA) haplotypes along an altitudinal transect in the greater white-toothed shrew, Crocidura russula (Ehinger et al. 2002). One mtDNA haplotype (H1) rare in lowland, became widespread when approaching the altitudinal margin of the distribution. As H1 differs from the main lowland haplotype by several nonsynonymous mutations (including on ATP6), and as mitochondria play a crucial role in metabolism and thermogenesis, distribution patterns might stem from differences in the thermogenic capacity of different mtDNA haplotypes. In order to test this hypothesis, we measured the nonshivering thermogenesis (NST) associated with different mtDNA haplotypes. Sixty-two shrews, half of which had the H1 haplotype, were acclimated in November at semioutdoor conditions and measured for NST throughout winter. Our results showed the crucial role of NST for winter survival in C. russula. The individuals that survived winter displayed a higher significant increase in NST during acclimation, associated with a significant gain in body mass, presumably from brown fat accumulation. The NST capacity (ratio of NST to basal metabolic rate) was exceptionally high for such a small species. NST was significantly affected by a gender x haplotype interaction after winter-acclimation: females bearing the H1 haplotype displayed a better thermogenesis at the onset of the breeding season, while the reverse was true for males. Altogether, our results suggest a sexually antagonistic cyto-nuclear selection on thermogenesis.

Longevity-associated NADH dehydrogenase subunit-2 polymorphism and serum electrolyte levels in middle-aged obese Japanese men

Mitochondrial DNA 5178 cytosine/adenine polymorphism, which is also called NADH dehydrogenase subunit-2 237 leucine/methionine (ND2-237 Leu/Met) polymorphism is associated with Japanese longevity. This polymorphism is widely associated with blood pressure, serum lipid levels, hematological parameters, intraocular pressure, and serum protein fraction levels. However, there have been no reports on the association between ND2-237 Leu/Met polymorphism and serum electrolyte levels. To investigate this relationship, we performed an association study in 321 healthy middle-aged Japanese men. Crude data showed that serum sodium levels and serum chloride levels were significantly lower in men with ND2-237 Met than in those with ND2-237 Leu (P = 0.021 and 0.003, respectively). Cigarette consumption and body mass index were significantly and positively associated with serum chloride levels (P = 0.002 and 0.008, respectively) and hemoglobin levels were significantly and negatively associated with them (P = 0.007) in ND2-237 Leu genotypic men. In men with ND2-237 Met, only hemoglobin levels were significantly and negatively associated with serum chloride levels (P = 0.025). After adjusting for covariates, only in male obese (body mass index> or =25) subjects, serum sodium and chloride levels remained significantly lower, and serum calcium levels appeared to be significantly higher in ND2-237 Met than in ND2-237 Leu (P = 0.013, <0.001, and 0.046, respectively). Longevity-associated NADH dehydrogenase subunit-2 polymorphism may influence serum electrolyte levels in middle-aged obese Japanese men.