ROSMOND, ROLAND, YVON C. CHAGNON, GÖ RAN HOLM, MONIQUE CHAGNON, LOUIS PÉ RUSSE, KAJSA LINDELL, BJÖ RN CARLSSON, CLAUDE BOUCHARD, AND PER BJÖ RNTORP.A glucocorticoid receptor gene marker is associated with abdominal obesity, leptin, and dysregulation of the hypothalamic-pituitaryadrenal axis. Obes Res. 2000;8:211-218. Objective: Abdominal obesity has a key role in the pathogenesis of prevalent and serious diseases and has been shown to be associated with an altered hypothalamic-pituitary-adrenal (HPA) axis function, which is regulated by endocrine feedback mediated via hippocampal glucocorticoid receptors (GR). Research Methods and Procedures:We examined the HPA axis function by repeated salivary samples for the assessment of cortisol, as well as other endocrine, anthropometric, metabolic, and circulatory variables in middle-aged Swedish men (n ϭ 284). With the restriction enzyme BclI, variants of the GR gene (GRL) locus were identified and two alleles with fragment lengths of 4.5 and 2.3 kilobases (kb) were detected. Results: The observed frequencies were 40.1% for the 2.3-and 2.3-kb, 46.2% for the 4.5-and 2.3-kb, and 13.7% for the 4.5-and 4.5-kb genotypes. The larger allele (4.5 and 4.5 kb) was associated with elevated body mass index (BMI; p Ͻ 0.001), waist-to-hip circumference ratio (p ϭ 0.015), abdominal sagittal diameter (p ϭ 0.002), leptin (p Ͻ 0.001), and systolic blood pressure (borderline, p ϭ 0.058). The 4.5-and 4.5-kb allele was associated with leptin after adjustment for BMI. Moreover, salivary cortisol values, particularly after stimulation by a standardized lunch (p ϭ 0.040 to 0.086), were elevated in the men with the larger allele. Discussion: These results indicate that there is an association between a deficient GR function, defined as a poor feedback regulation of the HPA axis activity, and a polymorphic restriction site at the GR gene locus. An abnormal control of HPA axis function due to genetic alterations may contribute to the pathogenesis of abdominal obesity.

. Abdominal visceral fat is associated with a BclI restriction fragment length polymorphism at the glucocorticoid receptor gene locus. Obes Res. 1997;5: 186-192. Several investigations have suggested that body fat distribution is influenced by nonpathologic variations in the responsiveness to cortisol. Genetic variations in the glucocorticoid receptor (GRL) could therefore potentially have an impact on the level of abdominal fat. A restriction fragment length polymorphism (RFLP) has previously been detected with the BcZI restriction enzyme in the GRL gene identifying two alleles with fragment lengths of 4.5 and 2.3 kb. This study investigates whether abdominal fat areas measured by computerized tomography (CT) are associated with this polymorphism in 152 middle-aged men and women. The less frequent 4.5-kb allele was found to be associated with a higher abdominal visceral fat (AVF) area independently of total body fat mass (4.514.5 vs. 2.312.3 kb genotype; men: 190.7 f 30.1 vs. 150.7 2 33.3 cm', p=0.04; women: 132.7 f 37.3 vs. 101.3 34.5 cm' , p=0.06). However, the association with AVF was seen only in subjects of the lower tertile of the percent body fat level. In these subjects, the polymorphism was found to account for 41% @=0.003) and 35% @=0.007), in men and women, respectively, of the total variance in AVF area. The consistent association between the GRL polymorphism detected with BcZI and AVF area suggests that this gene or a locus in linkage disequilibrium with the BcZI restriction site may contribute to the accumulation of AVF.

To identify chromosomal regions harboring genes influencing the propensity to store fat in the abdominal area, a genome-wide scan for abdominal fat was performed in the Qué bec Family Study. Cross-sectional areas of the amount of abdominal total fat (ATF) and abdominal visceral fat (AVF) were assessed from a computed tomography scan taken at L4-L5 in 521 adult subjects. Abdominal subcutaneous fat (ASF) was obtained by computing the difference between ATF and AVF. The abdominal fat phenotypes were adjusted for age and sex effects as well as for total amount of body fat (kilogram of fat mass) measured by underwater weighing, and the adjusted phenotypes were used in linkage analyses. A total of 293 microsatellite markers spanning the 22 autosomal chromosomes were typed. The average intermarker distance was 11.9 cM. A maximum of 271 sib-pairs were available for single-point ( A n elevated body fat content, as commonly seen in overweight or obese individuals, and particularly excess abdominal fat (1) are recognized as risk factors for type 2 diabetes and cardiovascular disease. The evidence suggesting that the amount of abdominal visceral fat is influenced by genetic factors has been recently reviewed (2). Two family studies have provided heritability estimates for abdominal total fat (ATF), abdominal subcutaneous fat (ASF), and abdominal visceral fat (AVF) areas measured by computed tomography (CT). In the first study based on 366 adult subjects from the Qué bec Family Study (QFS), age-and sexadjusted heritability estimates of 70, 68, and 68% were obtained for ATF, ASF, and AVF, respectively (3). After adjustment for fat mass measured by hydrodensitometry, heritability estimates were slightly reduced for ASF (42%) and AVF (56%). For ATF, there were sex differences in the heritabilities with higher values in male (76%) than in female (69%) and cross-sex (57%) pairs. In the second study based on 483 subjects from the HERITAGE Family Study, heritability estimates of 47 and 48% were obtained for AVF before and after adjustment for fat mass, respectively (4). Segregation analyses of these two study samples have also provided tentative evidence for the role of a single gene with a major effect on AVF (5,6). The results of these family studies indicate that the amount of fat stored in the abdomen, independent of overall body fatness, is strongly influenced by genetic factors.Despite evidence of a strong genetic component determining the amount of abdominal fat, very little is known about the nature of the genes involved. Only a few candidate genes, including the glucocorticoid receptor gene (7), the ␤ 3 -adrenergic receptor gene (8,9), and the fatty acid binding protein 2 gene (10), were found to be associated with abdominal fat. The identification of genes associated with complex phenotypes such as abdominal fat is limited when based on the candidate gene approach only. A genome-wide scan allows the identification of chromosomal regions that may harbor novel genes affecting a phenotype. Here we report the results of the f...

MC4R and MC5R exhibit evidence of linkage or association with obesity phenotypes, but this evidence is strongest for MC5R.

OBJECTIVE: To investigate linkage and association between the leptin receptor (LEPR) gene and body composition variables in the Que  bec Family Study (QFS). DESIGN: Single-point linkage analysis using families, and covariance and chi-square analyses using normal weight and obese unrelated subjects from QFS. SUBJECTS: 169 nuclear families were used for linkage study. 308 unrelated subjects (146 males; 162 females) from these families were used for chi-square testing of genotype and allele distributions between subjects with body mass index (BMI)`27 kgam 2 (n 167) and those with BMI ! 27 kgam 2 (n 141), and for a series of covariance analyses using age, plus height for fat mass (FM) and fat free mass (FFM), as covariates. A corrected P value (P*) for multiple tests has been calculated according to P* 1-(1-P) number of phenotypes . MEASUREMENTS: Variables were BMI (in kgam 2 ), sum of six skinfolds (SF6 in mm), FM (in kg), percent body fat (%FAT) and FFM (in kg). Polymerase chain react restricted fragment length polymorphisms PCR-RFLP) was used to identi®ed a K109R substitution in exon 4, a Q223R in exon 6, a K656N in exon 14 and an automatic DNA sequencer for a CA microsatellite repeat in intron 3, and heteroduplex pattern on non-denaturing gel for a CTTT repeat in intron 16. RESULTS: Good evidence of linkage was observed for Q223R with FM (P 0.005; P* 0.02), and for the CTTT repeat with FFM (P 0.007; P* 0.03). Weaker linkages (0.02 P 0.05) were also observed between Q223R and BMI, SF6 and FFM, between the CA repeat and BMI, SF6 and FM, and between the CTTT repeat and FM. Moreover, FFM values were found to be different among genotypes for the CTTT repeat polymorphism with heavier females, carriers of the 123* allele at the CTTT repeat, showing 4 kg less of FFM (43.6 AE 1.0, n 21 vs 47.7 AE 0.8, n 30; P 0.005; P* 0.02) than non-carriers. Also, at the Q223R polymorphism, in lower BMI males, carriers of the Q223 allele were 4 kg lighter in FFM (53.4 AE 0.6, n 47 vs 56.6 AE 0.9, n 18; P 0.005; P* 0.02) than non-carriers. No signi®cant differences were observed between lower and higher BMI subjects in genotype and allele frequency distributions for any of the polymorphisms. CONCLUSIONS: These results indicate that the LEPR gene is involved in the regulation of the body composition in human particularly of FFM in the QFS.

Ghrelin and preproghrelin sequences were determined in 96 unrelated female subjects with severe obesity (mean body mass index (BMI) 42.3 +/- 3.4 kg/m(2)) and in 96 non-obese female controls (mean BMI 23.0 +/- 1.4 (kg/m2) of the Swedish Obese Subjects cohort. A mutation at amino acid position 51 (Arg51Gln) of the preproghrelin sequence that corresponds to the last amino acid in mature ghrelin product was identified in six (all heterozygotes) obese subjects (6.3%) but not among controls (p < 0.05). The self-reported weight at 20, 30, and 40 years of age tended to be 7.5, 4.7 and 6.4 kg lower, respectively, among obese Gln allele carriers versus obese non-carriers. In addition, a mutation at codon 72 of the preproghrelin gene (Leu72Met) was detected in 15 obese (12 hetero- and 3 homozygotes) and 12 control (all heterozygotes) subjects. This mutation outside the coding region of the mature ghrelin product tended to be associated with lower age of self-reported onset of obesity (15.6 +/- 7.9 vs. 20.5 +/- 10.5 years; p = 0.09). In addition to these two mutations in coding regions, a G274A base change in a non-coding region between exons one and two was found only in two obese individuals. The Arg51Gln amino acid substitution may alter the cleavage site of endoproteases and the length of the mature ghrelin product. The functional significance of the Leu72Met mutation and a G274A base change remains to be determined. In conclusion, the data provide evidence that a low frequency sequence variation in the ghrelin gene could play a role in the etiology of obesity.

This study explores the associations between polymorphisms in two candidate genes-myostatin gene (MSTN or GDF8) and angiotensin-converting enzyme (ACE) gene-with interindividual differences in human muscle mass and strength responses to strength training. The MSTN AluI A55T (exon 1), BanII K153R, TaqI E164 K and BstNI P198A (all in exon 2) markers and the ACE insertion (I)/deletion (D) polymorphism were typed in 57 males [22.4 (3.7) years] who participated in a 10-week, high-resistance training program for the elbow flexors. Maximal strength, and maximal isometric and concentric elbow flexor torques were measured at baseline and after training. Information on muscle cross-sectional area of the upper arm was obtained by computer tomography scans. Only one individual was heterozygous for the MSTN BanII K153R variant. No allelic variant was detected at the other MSTN sites in this population. For the ACE I/D polymorphism, no evidence was found for an association of the D or I allele with baseline strength, isometric and concentric torque or arm muscle cross-sectional area [analysis of covariance (ANCOVA) 0.25< P<0.97]. Responses to the strength-training program were not associated with the ACE I/D genotype (ANCOVA 0.057< P<0.70). Borderline significance was found for larger strength gains in dynamic flexion torques for I/I genotypes. This study therefore does not support the hypothesis that an increased muscle fiber hypertrophic effect of strength training is present in D-allele carriers.

OBJECTIVE:Leptin is an adipocyte-secreted hormone involved in body weight regulation, acting through the leptin receptor, localised centrally in the hypothalamus as well as peripherally, amongst others on adipose tissue. The aim of this study was to evaluate whether polymorphisms in the leptin receptor (LEPR) gene were related to obesity and body fat distribution phenotypes, such as waist and hip circumferences and the amount of visceral and subcutaneous fat. METHODS: Three known LEPR polymorphisms, Lys109Arg, Gln223Arg and Lys656Asn, were typed on genomic DNA of 280 overweight and obese women (body mass index (BMI) b 25), aged 18 ± 60 y. General linear model (GLM) analyses were performed in 198 pre-and 82 postmenopausal women, adjusting the data for age and menopausal state, plus fat mass for the fat distribution phenotypes. RESULTS: No associations were found between the LEPR polymorphisms and BMI or fat mass. In postmenopausal women, carriers of the Asn656 allele had increased hip circumference (P 0.03), total abdominal fat (P 0.03) and subcutaneous fat (P 0.04) measured by CT scan. Total abdominal fat was also higher in Gln223Gln homozygotes (P 0.04). Also in postmenopausal women, leptin levels were higher in Lys109Lys homozygotes (P 0.02). CONCLUSION: In conclusion, polymorphisms in the leptin receptor gene are associated with levels of abdominal fat in postmenopausal overweight women. Since body fat distribution variables were adjusted for fat mass, these results suggest that DNA sequence variations in the leptin receptor gene play a role in fat topography and may be involved in the predisposition to abdominal obesity.