The alpha 2-adrenergic receptor gene and body fat content and distribution: the HERITAGE Family Study

BACKGROUND: Among adrenergic receptor subtypes that regulate lipid mobilization, the alpha2-adrenergic receptor is involved in the inhibition of fatty acid mobilization from adipose tissue. A C-1291G polymorphism is located in the alpha2-adrenergic receptor gene (ADRA2A) but no association with body fat accumulation has been reported yet. MATERIALS AND METHODS: Body mass index (BMI), fat mass (FAT), percentage body fat (%FAT), trunk-to-extremity skinfold ratio (TER), sum of eight skinfolds (SF8), and abdominal subcutaneous (ASF), visceral (AVF), and total (ATF) fat areas assessed by CT scan have been measured in adult sedentary white (n = 503) and black (n = 276) subjects participating in the HERITAGE Family Study. Association between the C-1291G polymorphism and each phenotype was tested separately in men and women of each race using ANCOVA with the effects of age as covariate in addition to the effects of BMI for TER and of FAT for AVF, ASF, and ATF. RESULTS: The allele frequencies of the ADRA2A C-1291G polymorphism differed between races. No association was observed in white subjects, except for a moderate effect of the polymorphism accounting for less than 1% of the variance in AVF and ATF in women. In black subjects, however, the G-1291 allele was found to be associated with an increase of TER in men (3.8% of variance accounted for by the polymorphism), while in black women it was associated with a decrease in TER (2.9%) and in AVF (2.5%). CONCLUSION: These results suggest a role for the ADRA2A gene in determining the propensity to store fat in the abdominal area, independently of total body fatness.     

Angiogenin gene-race interaction for resting and exercise BP phenotypes: the HERITAGE Family Study.

We examined the association between an angiogenin gene polymorphism and blood pressure (BP) at rest and in response to acute exercise before and after a 20-wk endurance-training program. Subjects were 737 normotensive and borderline hypertensive subjects (257 black and 480 white). The polymorphism was detected by PCR and digestion with AvaII, yielding an allele of 253 bp or a rare allele of 194 + 59 bp. Resting and exercise [50 W; 60, 80, and 100% of maximal O2 consumption (VO2 max)] systolic (SBP) and diastolic BP were determined before and after training. Among blacks, adjusted SBP in the sedentary state was significantly lower in carriers of the rare allele at rest and exercise intensities of 60, 80, and 100% of VO2 max. In the trained state, carriers of the rare allele had a significantly (P < 0.05) lower SBP than did noncarriers at rest and at 80 and 100% of VO2 max. The genotypic effect observed among blacks was not evident among whites. Furthermore, change in BP (after--before) was not significantly associated with the genotype. In conclusion, the angiogenin gene AvaII polymorphism is associated with a lower SBP at rest and in response to acute high-intensity exercise in blacks but not in whites.     

Major gene effects on exercise ventilatory threshold: the HERITAGE Family Study.

This study investigates whether there are major gene effects on oxygen uptake at the ventilatory threshold (VO(2VT)) and the VO(2VT) maximal oxygen uptake (VT%VO(2 max)), at baseline and in response to 20 wk of exercise training by using data on 336 whites and 160 blacks. Segregation analysis was performed on the residuals of VO(2VT) and VT%VO(2 max). In whites, there was strong evidence of a major gene, with 3 and 2% of the sample in the upper distribution, that accounted for 52 and 43% of the variance in baseline VO(2VT) and VT%VO(2 max), respectively. There were no genotype-specific covariate effects (sex, age, weight, fat mass, and fat-free mass). The segregation results were inconclusive for the training response in whites, and for the baseline and training response in blacks, probably due to insufficient power because of reduced sample sizes or smaller gene effect or both. The strength of the genetic evidence for VO(2VT) and VT%VO(2 max) suggests that these traits should be further investigated for potential relations with specific candidate genes, if they can be identified, and explored through a genome-wide scan.     

Angiotensin-converting enzyme ID polymorphism and fitness phenotype in the HERITAGE Family Study.

It has been suggested that genetic variation in the angiotensin-converting enzyme (ACE) gene is associated with physical performance. We studied the association between the ACE insertion (I)/deletion (D) polymorphism and several fitness phenotypes measured before and after 20 wk of a standardized endurance training program in sedentary Caucasian (n = 476) and black (n = 248) subjects. Phenotypes measured were oxygen uptake (VO(2)), work rate, heart rate, minute ventilation, tidal volume, and blood lactate levels during maximal and submaximal [50 W and at 60 and 80% of maximal VO(2) (VO(2 max))] exercise and stroke volume and cardiac output during submaximal exercise (50 W and at 60% VO(2 max)). The ACE ID polymorphism was typed with the three-primer PCR method. Out of 216 association tests performed on 54 phenotypes in 4 groups of participants, only 11 showed significant (P values from 0.042 to 0. 0001) associations with the ACE ID polymorphism. In contrast to previous claims, in Caucasian offspring, the DD homozygotes showed a 14-38% greater increase with training in VO(2 max), VO(2) at 80% of VO(2 max), and all work rate phenotypes and a 36% greater decrease in heart rate at 50 W than did the II homozygotes. No associations were evident in Caucasian parents or black parents or offspring. Thus these data do not support the hypothesis that the ACE ID polymorphism plays a major role in cardiorespiratory endurance.     

Segregation Analysis of Abdominal Visceral Fat: The HERITAGE Family Study

RICE, TREVA, JP DESPRÉS, LOUIS PÉRUSSE, JACQUES GAGNON, ARTHUR S LEON, JAMES S SKINNER, JACK H WILMORE, DC RAO, CLAUDE BOUCHARD. Segregation analysis of abdominal visceral fat: The HERITAGE Family Study. A major gene hypothesis for abdominal visceral fat (AVF) level, both before and after adjustment for total body fat mass, was investigated in 86 white families who participated in the HERITAGE Family Study. In this study, sedentary families were tested for a battery of measures (baseline), endurance exercise trained for 20 weeks, and then remeasured again. The baseline measures reported here are unique in that the variance due to a potentially important environmental factor (activity level) was limited. AVF area was assessed at L4 to L5 by the use of computerized tomography scan, and total body fat mass was assessed with underwater weighing. For fat mass, a putative locus accounted for 64% of the variance, but there was no evidence of a multifactorial component (i.e., no polygenic and/or common familial environmental effects). For AVF area, both a major gene effect accounting for 54% of the variance and a multifactorial component accounting for 17% of the variance were significant. However, after AVF area was adjusted for the effects of total level of body fat, the support for a major gene was reduced. In particular, there was a major effect for fat mass-adjusted AVF area, but it was not transmitted from parents to offspring (i.e., the three transmission probabilities were equal). The importance of this study is twofold. First, these results confirm a previous study that suggested that there is a putative major locus for AVF and for total body fat mass. Second, the findings from the HERITAGE Family Study suggest that the factors underlying AVF area in sedentary families may be similar to those in the population at large, which includes both sedentary and active families. Whether the gene(s) responsible for the high levels of AVF area is the same as that which influences total body fat content remains to be further investigated.     

Genomic scan for maximal oxygen uptake and its response to training in the HERITAGE Family Study.

This study aimed to identify human genomic regions that are linked to maximal oxygen uptake (VO(2 max)) in sedentary individuals or to the responsiveness of VO(2 max) to a standardized endurance training program. The results of a genomic scan based on 289 polymorphic markers covering all 22 pairs of autosomes performed on the Caucasian families of the HERITAGE Family Study are presented. The mean spacing of the markers was 11 cM, and a total of 99 families and 415 pairs of siblings were available for the study. VO(2 max) in the sedentary state was adjusted for the effects of age, sex, body mass, fat mass, and fat-free mass, whereas the VO(2 max) response was adjusted for age and baseline level of the phenotype. Two analytic strategies were used: a single-point linkage procedure using all available pairs of siblings (SIBPAL) and a multipoint variance components approach using all the family data (SEGPATH). Results indicate that linkages at P values of 0.01 and better are observed with markers on 4q, 8q, 11p, and 14q for VO(2 max) before training and with markers on 1p, 2p, 4q, 6p, and 11p for the change in VO(2 max) in response to a 20-wk standardized endurance training program. These chromosomal regions harbor many genes that may qualify as candidate genes for these quantitative traits. They should be investigated in this and other cohorts.     

Pleiotropic Relationships between Cortisol Levels and Adiposity: The HERITAGE Family Study

Objective: To investigate familial basis for the relationship between cortisol adiposity at baseline and their training responses. Research Methods and Procedures: Bivariate correlation and segregation analyses were employed between cortisol and several adiposity measures [body mass index, fat mass (FM), fat-free mass, percentage of body fat (% BF), abdominal visceral fat (AVF), abdominal subcutaneous fat (ASF), and abdominal total fat (ATF)] from 99 white families and 105 black families. Results: In both races, significant inverse phenotypic correlations were generally observed between cortisol and adiposity measures at baseline but not for training responses. Significant cross-trait familial correlations were found for cortisol with abdominal fat (ASF, AVF, ATF) and overall body adiposity (FM, % BF) measures at baseline, which accounted for 14% to 20% of the phenotypic variance in whites. The cross-trait correlations were not significant for baseline phenotypes in blacks, perhaps because of the small sample size. A bivariate segregation analysis showed evidence of polygenic pleiotropy for cortisol with both abdominal fat and overall adiposity measures that accounted for 14% to 17% of the phenotypic covariance, but major gene pleiotropy was not suggested in whites. However, when ASF, AVF, and ATF were additionally adjusted for FM, no familial cross-trait correlations or polygenic pleiotropy between cortisol and the abdominal fat measures remained. Discussion: Evidence was found for polygenic pleiotropy but not for pleiotropic major gene effects between cortisol and overall adiposity in whites. However, the covariation of cortisol with abdominal fat phenotypes is dependent on concomitant polygenic factors for total-body fat.     

Cross-trait familial resemblance for body fat and blood pressure: familial correlations in the Québec Family Study.

Cross-trait resemblance between body fat and blood pressure (BP) was examined among families in the Québec Family Study by using a bivariate familial correlation model assessing both intraindividual (e.g., comparison of father's body fat with his own BP) and interindividual (e.g., comparison of father's body fat with son's BP) cross-trait correlations. Each of six body-fat measures-(i) percent body fat, (ii) body-mass index, (iii) the sum of six skinfolds, (iv) the ratio of the sum of six skinfolds to total fat mass, (v) the ratio of the trunk skinfold sum to the extremity skinfold sum, and (vi) the regression of the trunk-extremity skinfold ratio on the sum of six skinfolds--was analyzed separately with systolic BP and with diastolic BP. Results showed that (1) upper-body fat was the strongest interindividual correlate of BP (especially the correlation of trunk-extremity ratio with diastolic BP), suggesting shared pleiotropic genetic and/or common familial environmental effects; (2) summary body-fat measures either were inconsistent (in the case of both percent body fat and sum of six skinfolds) or gave no evidence of interindividual cross-trait resemblance with BP (in the case of body-mass index); and (3) intraindividual resemblance between the sum of six skinfolds and BP largely vanished once the skinfold sum was adjusted for fat mass, suggesting that the intraindividual association may be mediated largely by the absolute amount of subcutaneous fat rather than by the subcutaneous proportion. Finally, the magnitude of the spouse resemblance for the trunk-extremity ratio with diastolic BP suggests that a significant proportion of the resemblance may be due to environmental influences. In summary, our investigation confirms a heritable link between BP and truncal-abdominal fat as predicted by the metabolic-syndrome hypothesis. That this result is obtained in primarily normotensive, nonobese families, suggests the connection involves normal metabolic paths.     

TGF-beta(1) gene-race interactions for resting and exercise blood pressure in the HERITAGE Family Study.

We examined the possible association between a transforming growth factor (TGF)-beta(1) gene polymorphism in codon 10 and blood pressure (BP) at rest, in acute response to exercise in the pretrained (sedentary) and trained states, as well as in its training response (Delta) to 20 wk of endurance exercise. Subjects were 257 black and 480 white, healthy sedentary normotensive subjects from the HERITAGE Family Study. The polymorphism was detected by polymerase chain reaction and digestion with the Msp A1 I endonuclease yielding a wild (leucine-10) and a mutant (proline-10) allele. Resting and exercise [50 W plus 60, 80, and 100% maximal oxygen consumption (VO(2)(max))] BP were determined before and after training. Significant (P < 0.05) race-genotype interactions were found for systolic (S) BP in both the sedentary and trained states. Among whites but not in blacks, the TGF-beta(1) genotypes were significantly (P < 0.05) associated with sedentary-state SBP at rest, at 50 W, and at 60 and 100% VO(2)(max)as well as with trained-state SBP at rest and at 80 and 100% VO(2)(max). The leucine-10 homozygotes had significantly (P < 0.05) lower SBP than proline-10 homozygotes. DeltaBP was not significantly associated with genotype. These results support the hypothesis of an association between the TGF-beta(1) marker in codon 10 and SBP at rest and in response to acute exercise in whites but not in blacks.     

Age, sex, race, initial fitness, and response to training: the HERITAGE Family Study.

Effects of age, sex, race, and initial fitness on training responses of maximal O(2) uptake (VO(2 max)) are unclear. Data were available on 435 whites and 198 blacks (287 men and 346 women), aged 17-65 yr, before and after standardized cycle ergometer training. Individual responses varied widely, but VO(2 max) increased significantly for all groups. Responses by men and women and by blacks and whites of all ages varied widely. There was no sex difference for change (Delta) in VO(2 max) (ml. kg(-1). min(-1)); women had lower initial values and greater relative (%) increases. Blacks began with lower values but had similar responses. Older subjects had a lower Delta but a similar percent change. Baseline VO(2 max) correlated nonsignificantly with DeltaVO(2 max) but significantly with percent change. There were high, medium, and low responders in all age groups, both sexes, both races, and all levels of initial fitness. Age, sex, race, and initial fitness have little influence on VO(2 max) response to standardized training in a large heterogeneous sample of sedentary black and white men and women.     

Evidence of Pleiotropic Loci for Fasting Insulin,Total Fat Mass,and Abdominal Visceral Fat in a Sedentary Population: The HERITAGE Family Study

Objective: To examine whether there is a major gene effect on fasting insulin and pleiotropic loci for fasting insulin, total fat mass (FM), and abdominal visceral fat (AVF). Research Methods and Procedures: A major gene hypothesis for fasting plasma insulin levels was assessed using segregation analyses of data on 495 members in 98 normolipidemic sedentary families of white descent who participated in the HERITAGE Family Study. Results: Segregation analyses were performed on insulin adjusted for age, on insulin adjusted for age and FM, and on insulin adjusted for age and AVF. Before adjustment for AVF and FM, a major gene effect on fasting insulin levels was indicated. The putative locus accounted for 54% of the variance under a recessive inheritance pattern, affecting 11% of the sample (i.e., allele frequency = 0.33). However, after adjusting for the effects of AVF or FM, neither a major effect alone nor a multifactorial component alone could be rejected, and support for a major gene was equivocal, i.e., neither the hypothesis of Mendelian τ values or that of the equal τs were rejected and the equal τ model fit the data better than the Mendelian τ model. This pattern (i.e., major gene evidence for insulin before but not after adjustment for AVF or FM) suggests that there is a putative locus with pleiotropic effects on both insulin and FM and another pleiotropic locus for both insulin and AVF. Discussion: Although these data do not directly support an additional major gene for insulin independent of AVF and FM, such support cannot be ruled out because there is still a significant major effect on FM‐ or AVF‐adjusted insulin (albeit the Mendelian nature of this effect is ambiguous).     

Peroxisome proliferator-activated receptor-delta polymorphisms are associated with physical performance and plasma lipids: the HERITAGE Family Study

We tested the hypothesis that peroxisome proliferator-activated receptor-delta (PPARdelta) gene polymorphisms are associated with cardiorespiratory fitness and plasma lipid responses to endurance training. Associations between the PPARdelta exon 4 +15 C/T and exon 7 +65 A/G polymorphisms and maximal exercise capacity and plasma lipid responses to 20 wk of endurance training were investigated in healthy white (n = 477) and black (n = 264) subjects. In black subjects, the exon 4 +15 C/C homozygotes showed a smaller training-induced increase in maximal oxygen consumption (P = 0.028) than the C/T and T/T genotypes. Similarly, a lower training response in maximal power output was observed in the exon 4 +15 C/C homozygotes (P = 0.005) compared with the heterozygotes and the T/T homozygotes in black subjects, and a similar trend was evident in white subjects (P = 0.087). In white subjects, baseline apolipoprotein A-1 (Apo A-1)levels were higher in the exon 4 +15 C/C (P = 0.011) and exon 7 +65 G/G (P = 0.05) genotypes compared with those in the other genotypes. In white subjects, exon 4 +15 C/C (P = 0.0025) and exon 7 +65 G/G (P = 0.011) genotypes showed significantly greater increases in plasma high-density lipoprotein-cholesterol (HDL-C) levels with endurance training than in the other genotypes, whereas in black subjects the exon 4 +15 CC homozygotes tended to increase (P = 0.057) their Apo A-1 levels more than the T allele carriers. DNA sequence variation in the PPARdelta locus is a potential modifier of changes in cardiorespiratory fitness and plasma HDL-C in healthy individuals in response to regular exercise.     

Sub-chronic administration of stable GIP analog in mice decreases serum LPL activity and body weight

GIP receptor knockout mice were shown to be protected from the development of obesity on a high fat diet, suggesting a role of GIP in the development of obesity. In our study we aimed to test the hypothesis if excess of GIP could accelerate development of obesity and to identify GIP gene targets in adipose tissue. Therefore, mice were kept on a chow or a high fat diet and during the last 2 weeks D-Ala²-GIP or PBS injections were performed. Afterwards, serum LPL activity and several biochemical parameters (TG, FFA, cholesterol, glucose, insulin, resistin, IL-6, IL-1β, TNFα, GIP) were measured. Fat tissue was isolated and QPCR was performed for a set of genes involved in energy metabolism and inflammation. A DNA-microarray was used to identify GIP gene targets in adipose tissue of the chow diet group. We found that the D-Ala²-GIP injections caused a significant decrease in both body weight and LPL activity compared to controls. Serum biochemical parameters were not affected by D-Ala²-GIP, with an exception for resistin and insulin. The set of inflammatory genes were significantly decreased in adipose tissue in the D-Ala²-GIP injected animals on a chow diet. A DNA-microarray revealed that APO-genes and CYP-genes were affected by D-Ala²-GIP treatment in adipose tissue. These results suggest that the body weight-reducing effect of D-Ala²-GIP may be explained by lower LPL activity and insulin serum level. Moreover, the identified GIP candidate gene targets in adipose tissue link GIP action to lipid metabolism exerted by APO and CYP genes.     

Familial aggregation of VO(2max) response to exercise training: results from the HERITAGE Family Study.

The aim of this study was to test the hypothesis that individual differences in the response of maximal O(2) uptake (VO(2max)) to a standardized training program are characterized by familial aggregation. A total of 481 sedentary adult Caucasians from 98 two-generation families was exercise trained for 20 wk and was tested for VO(2max) on a cycle ergometer twice before and twice after the training program. The mean increase in VO(2max) reached approximately 400 ml/min, but there was considerable heterogeneity in responsiveness, with some individuals experiencing little or no gain, whereas others gained >1.0 l/min. An ANOVA revealed that there was 2.5 times more variance between families than within families in the VO(2max) response variance. With the use of a model-fitting procedure, the most parsimonious models yielded a maximal heritability estimate of 47% for the VO(2max) response, which was adjusted for age and sex with a maternal transmission of 28% in one of the models. We conclude that the trainability of VO(2max) is highly familial and includes a significant genetic component.     

The relationship between aromatase activity and body fat distribution

The metabolism of androstenedione (A) to estrone (E1) and 5 alpha-reduced androgens was studied in stromal cells derived from human adipose tissue from different body sites. The tissue was obtained from non-obese patients undergoing cosmetic liposuction or at the time of surgery for reduction mammoplasty. The conversion of A to E1 per 1x 10(6) cells was between 6- and 30-fold greater in the upper thigh, buttock, and flank than in the abdomen. These differences were present in primary culture and persisted to at least the third subculture. Estrogen formation in breast adipose tissue was similar to that found in cells from abdominal fat. The formation of 5 alpha-reduced metabolites (5 alpha-androstenedione, androsterone, and dihydrotestosterone) varied from patient to patient but was similar in cells from different body sites. These studies show that the regional distribution of fat may influence the metabolism of androgens in adipose tissue, with upper body fat tending to form a lower ratio of estrogens to 5 alpha-reduced androgens than lower body fat.     

Calmodulin activity in whole body and fat body tissue extracts of Heliothis virescens larvae

Calmodulin is an activator of many enzymatic activities. Total calmodulin activity in tissue extracts of Heliothis virescens larvae (5th instar), assayed by cyclic phosphodiesterase activation, was 0.48 unit/gm for whole body and 22.2 units/gm for fat body. Specific calmodulin activity was 0.1 unit/mg protein for whole body and 3.0 units/mg protein for fat body. The larval fat body is therefore the main site of calmodulin activity in this lepidopterous larva.     

Evidence of genetic influence on central body fat in middle-aged twins

The heritability of centrally and peripherally deposited subcutaneous body fat, as measured by thickness of subscapular and triceps skinfolds respectively, was examined in 173 monozygotic and 178 dizygotic pairs of white male twins, ages 54 to 65 years, who participated in the second examination of the National Heart, Lung, and Blood Institute's Twin Study. The heritability of two indices of body fat distribution (subscapular/triceps ratio and subscapular-triceps difference) and two indices of overall obesity (body mass index and sum of skinfolds) were also assessed. Evidence for a genetic influence on central deposition of body fat was suggested in that the classical estimate of heritability for subscapular skinfold thickness was 0.77 (p less than 0.0001). After adjusting subscapular skinfold for the overall level of obesity, heritability was reduced but remained highly significant (0.40, p = 0.003). Heritability estimates for triceps skinfold thickness and for the two fat distribution indices were substantially lower and were not statistically significant after adjustment for overall obesity. High classical estimates of heritability were also observed for both measures of overall obesity: 0.70 for BMI and 0.73 for sum of skinfolds. However, these two estimates were biased upward because of lower total variances among monozygotic compared to dizygotic twins in this sample. The more conservative and unbiased among-component estimates also suggested substantial heritability for each measure (0.35, p = 0.08 and 0.53, p = 0.01, respectively). The heritability of overall obesity emphasizes the importance of adjusting measures of fat distribution for overall obesity before assessing its heritability.     

Sodium-lithium countertransport and body fat distribution.

The relationship between erythrocyte sodium-lithium countertransport (Na-Li CT) and body fat distribution is analyzed in a sample (n = 101) of normotensive and untreated hypertensive men participating in an epidemiological study of coronary heart disease risk factors. Na-Li CT is significantly and positively associated with both subscapular skinfold and waist to hip ratio, but not with triceps skinfold. The univariate correlation between Na-Li CT and blood pressure is diminished when adjusted for body mass index and waist to hip ratio. These findings support the existence of an association between Na-Li CT and central body fat distribution and suggest that the metabolic abnormalities associated with centrally distributed body fat could explain, at least in part, the association between Na-Li CT and blood pressure. The maximal velocity of the sodium-lithium countertransport (Na-Li CT) in erythrocytes has been reported to be directly associated with blood pressure and hypertension in numerous reports from both clinical and epidemiological studies. In most of these studies, indices of weight and/or adiposity (body mass index, in particular) have been shown to be among the most important correlates of Na-Li CT. Adiposity is an important determinant of blood pressure, and there is evidence suggesting that the patterning of the fat cells in the body is linked to a number of metabolic disturbances that could lead to hypertension and an increase in other CHD risk factors. The present report analyses the relationship between Na-Li CT and body fat distribution in a sample of normotensive and untreated hypertensive men participating in an epidemiological study.