Melanocortin-4 receptor gene and physical activity in the Québec Family Study

Physical inactivity is a risk factor for numerous chronic diseases. Low compliance with interventions to increase activity suggests involvement of biological systems.

OBJECTIVE

To examine whether sequence variants in genes encoding neuropeptides and receptors in the arcuate and paraventricular nucleus of the hypothalamus contribute to variations in physical activity level in the Québec Family Study.

METHODS

We genotyped polymorphisms in the melanocortin-4 receptor (MC4R), melanocortin-3 receptor (MC3R), neuropeptide-Y (NPY), neuropeptide-Y Y1 receptor (NPY Y1R), cocaine- and amphetamine-regulated transcript (CART), agouti-related protein (AGRP), and pro-opiomelanocortin (POMC) genes in 669 subjects (age (X+/-s.d.): parents: 52+/-3.4 y; offspring: 28+/-8.7 y). Total physical activity, moderate-to-strenuous activity, and inactivity phenotypes were estimated from a three-day record. The past year's physical activity level was assessed from a questionnaire. Associations between the physical activity phenotypes and the polymorphisms were analyzed using the MIXED model (SAS).

RESULTS

The MC4R-C-2745T variant showed significant associations with physical activity phenotypes. The lowest moderate-to-strenuous activity scores (P = 0.005) and the highest inactivity scores (P = 0.01) emerged in the T/T genotype. Exclusion of obese subjects increased the association. For inactivity, the association of the MC4R-C-2745T variant was strongest in the offspring (P = 0.002). The T/T offspring had both the highest inactivity score and the lowest body mass index. The CART-A1475G variant modified the associations with MC4R-C-2745T; T/T homozygotes had the lowest activity scores when they also had the A/A CART-A1475G genotype. No significant associations were observed with polymorphisms in the other neuropeptides.

CONCLUSION

These findings suggest that DNA sequence variation at the MC4R gene locus may contribute to the propensity to be sedentary.

Haplotypes in the phospholipid transfer protein gene are associated with obesity-related phenotypes: the Québec Family Study

BACKGROUND

The phospholipid transfer protein (PLTP) may play a role in body fat regulation.

OBJECTIVE

To investigate the association between PLTP genetic variants and obesity-related phenotypes.

METHODS

Two intronic variants, one in intron 1 (c.-87G>A) and the other in intron 12 (c.1175+68T>G), were genotyped in 811 participants of the Québec Family Study. Nine obesity-related phenotypes were investigated, including body mass index (BMI), obesity (BMI> or =30 kg/m(2)), and waist circumference, percentage of fat, fat mass and fat-free mass measured by hydrostatic weighing as well as total, visceral and subcutaneous abdominal adipose tissue areas assessed by computed tomography. Single markers and haplotypes were tested for associations in family-based designs using the FBAT program.

RESULTS

The SNP located in intron 1 showed significant associations with obesity, BMI, waist circumference and fat-free mass (P<0.05). The low-frequency allele (A allele) was associated with higher trait values, suggesting that the transmission of this allele is associated with an increased risk of being obese. Significant associations were observed between haplotypes and obesity, waist circumference, percentage of fat and fat-free mass (P<0.05). The transmission of the AT haplotype (frequency=0.180) was positively associated with obesity-related phenotypes. After sequencing the promoter and the coding regions of the PLTP gene, we were unable to identify a mutation that could replicate these results.

CONCLUSION

Intronic variants of the PLTP gene are significantly associated with obesity-related phenotypes. Considering the number and the relevance of candidate genes surrounding the PLTP locus and the absence of missense polymorphisms in the coding region, the associations could be mediated by a second gene allele in linkage disequilibrium with the marker locus.

Genome-wide linkage scans for prediabetes phenotypes in response to 20 weeks of endurance exercise training in non-diabetic whites and blacks: the HERITAGE Family Study

AIMS/HYPOTHESIS

Impaired insulin secretion, insulin action, insulin-independent glucose effectiveness, glucose tolerance and the associated abnormalities in insulin and glucose metabolism phenotypes are precursors of type 2 diabetes. Genome-wide multipoint variance component linkage scans were carried out using 654 markers to identify quantitative trait loci for insulin sensitivity, acute insulin response to glucose, disposition index and glucose effectiveness training responses in whites and blacks in the HERITAGE Family Study.

METHODS

These phenotypes were obtained from an IVGTT with the minimal model. The distributions of insulin sensitivity, acute insulin response to glucose and disposition index training responses (post-training minus baseline) were approximately normalised using a square-root transformation. All phenotypes were adjusted for the effects of age, BMI and their respective baseline values within sex and generation by race prior to linkage scans.

RESULTS

In blacks, a promising linkage with a maximum lod score of 3.1 on 19q (54-62 Mb) for glucose effectiveness training response was found. Six interesting linkages with lod scores of at least 1.0 were found for disposition index training response in whites. They included 1p (30 Mb), 3q (152 Mb), 6p (23-42 Mb), 7q (95-96 Mb), 10p (15 Mb) and 12q (119-126 Mb).

CONCLUSIONS/INTERPRETATION

Quantitative trait loci for 20 weeks of endurance exercise training responses in insulin action and glucose metabolism phenotypes were found on chromosome 19q as well as 6p and 7q, with nominal (6p, 7q) but consistent (6p) linkages across the races.

A cell forin situdynamic X-ray diffraction studies: application to the dehydration of zeolite SrX

A new compact cell forin situsynchrotron X-ray diffraction studies of adsorption or catalysis reactions has been designed to enable high performance whilst minimizing difficulties in use. It includes a system for simple insertion and alignment of capillary samples and an original miniaturized furnace providing excellent temperature homogeneity along the sample (temperature gradient less than 1 K over a 6 mm zone at 530 K). The efficiency of this setup is illustrated byin situcharacterization of a zeolite (SrX) at four hydration levels.

Physical activity, obesity and cardiovascular diseases

Sedentary lifestyle and overweight are major public health, clinical, and economical problems in modern societies. The worldwide epidemic of excess weight is due to imbalance between physical activity and dietary energy intake. Sedentary lifestyle, unhealthy diet, and consequent overweight and obesity markedly increase the risk of cardiovascular diseases. Regular physical activity 45-60 min per day prevents unhealthy weight gain and obesity, whereas sedentary behaviors such as watching television promote them. Regular exercise can markedly reduce body weight and fat mass without dietary caloric restriction in overweight individuals. An increase in total energy expenditure appears to be the most important determinant of successful exercise-induced weight loss. The best long-term results may be achieved when physical activity produces an energy expenditure of at least 2,500 kcal/week. Yet, the optimal approach in weight reduction programs appears to be a combination of regular physical activity and caloric restriction. A minimum of 60 min, but most likely 80-90 min of moderate-intensity physical activity per day may be needed to avoid or limit weight regain in formerly overweight or obese individuals. Regular moderate intensity physical activity, a healthy diet, and avoiding unhealthy weight gain are effective and safe ways to prevent and treat cardiovascular diseases and to reduce premature mortality in all population groups. Although the efforts to promote cardiovascular health concern the whole population, particular attention should be paid to individuals who are physically inactive, have unhealthy diets or are prone to weight gain. They have the highest risk for worsening of the cardiovascular risk factor profile and for cardiovascular disease. To combat the epidemic of overweight and to improve cardiovascular health at a population level, it is important to develop strategies to increase habitual physical activity and to prevent overweight and obesity in collaboration with communities, families, schools, work sites, health care professionals, media and policymakers.

Human resistin gene polymorphism is associated with visceral obesity and fasting and oral glucose stimulated C-peptide in the Québec Family Study

Obesity and insulin resistance are common features of Type 2 Diabetes. A new protein called resistin has been shown to be secreted by adipocytes in mice and to influence insulin sensitivity. The goal of the present study was to investigate the associations between one polymorphism (g-420C>G) of the human resistin gene and phenotypes related to adiposity and glucose metabolism. We genotyped 725 (including 42 diabetics) adult subjects participating in the Quebec Family Study (QFS) by a minisequencing method. Forty-two were diabetic subjects. Phenotypes measured were: body mass index (BMI) and waist circumference (WC), % body fat (PFAT) and fat mass (FM) assessed by under water weighing, abdominal total, subcutaneous and visceral fat assessed by computed tomography and fasting plasma glucose, insulin and C-peptide and their responses to an oral glucose tolerance test (OGTT). Comparisons between genotypes were performed in non-diabetic men (no.=280) and women (no.=403) separately by analyses of covariance (ANCOVA). Among men, g-420 G homozygotes had less visceral fat (p < 0.05), lower levels of acute insulin responses to an OGTT and lower levels of C-peptide in a fasting state and in responses to an OGTT than carriers of the C allele (p < 0.01). These associations were independent of age and adiposity but were not observed in women. These results suggest that in men, the human resistin gene is associated with reduced amount of visceral obesity and lower insulin secretory responses to a glucose load.

Post-heparin lipolytic enzyme activities, sex hormones and sex hormone-binding globulin (SHBG) in men and women: The HERITAGE Family Study

We tested the hypothesis that androgen, estrogen, and sex hormone-binding globulin (SHBG) levels would be significantly related to post-heparin hepatic lipase (HL) and lipoprotein lipase (LPL) activities in a sample of Caucasian men (n = 233) and women (n = 235) aged 17-64 years from the HERITAGE Family Study. Body composition (hydrostatic weighing), abdominal adipose tissue distribution (computed tomography), plasma lipid-lipoprotein and hormone levels, and post-heparin lipases activities were measured. HL activity was significantly higher in males, whereas LPL activity was higher in women (P < 0.005). In women only, HL activity was positively associated with body fat mass (r = 0.17, P < 0.05) and intra-abdominal adipose tissue area (r = 0.18, P < 0.05). Significant associations were also found between fasting insulin and LPL activity (r = -0.16, P < 0.05 and r = -0.18, P < 0.005) as well as HL activity (r = 0.22, P < 0.005, and r = 0.27, P < 0.0001) in men and women, respectively. A positive association between total testosterone and HL activity was noted in men (r = 0.13, P = 0.05). In women, plasma SHBG levels were negatively associated with HL activity (r = -0.48, P < 0.0001), and statistical adjustment for body fat mass, visceral adipose tissue area, and fasting insulin did not attenuate this correlation. In multivariate analyses with models including adiposity variables and measurements of the hormonal profile, insulin, and testosterone levels were both independent positive predictors of HL activity in men. In women, hormone use was a significant positive predictor, and SHBG level a strong negative predictor of HL activity, independent of plasma estradiol and testosterone concentrations. Fasting insulin was the only significant predictor of LPL activity in men (negative association), whereas menstrual status, fasting insulin (negative associations), and plasma SHBG levels (positive association) were all independent predictors of LPL activity in women. These results suggest that the postulated sensitivity of lipolytic enzymes to androgens and estrogens is reflected by a strong negative association between SHBG levels and HL, and a lower magnitude positive association of this hormonal parameter to LPL activity in women. These associations appear to be independent from concomitant variation in total adiposity or body fat distribution.

Two variants in the resistin gene and the response to long-term overfeeding

OBJECTIVE AND SUBJECTS

To investigate the role of resistin gene variants on the adiposity and metabolic changes observed in response to a 100-day overfeeding protocol conducted with 12 pairs of monozygotic twins.

MEASUREMENTS

Body-fat measurements included hydrodensitometry and abdominal fat from computed tomography. Plasma glucose and insulin during fasting and in response to an oral glucose tolerance test (OGTT) were assayed. A 4.2 MJ test meal was consumed, after which calorimetric measurements were performed for 240 min.

RESULTS

Respiratory quotient (RQ) decreased (P=0.001) more in AA/AG than in GG subjects of the IVS2+181G>A polymorphism after the caloric surplus and the significance persisted when correction for multiple testing was performed. Total abdominal (P=0.027) and visceral (P=0.004) fat increased more in TC than in TT subjects of the IVS2+39C>T polymorphism. In response to overfeeding, glucose area under the curve during the OGTT showed a slight decrease (P=0.031) in the TC while it increased in TT subjects. OGTT insulin area tended to increase less (P=0.055) in TC than in TT subjects. After overfeeding, fasting insulin was lower in TC than in TT subjects (P=0.010). In addition, TC subjects experienced more decrease in RQ than TT subjects (P=0.034).

CONCLUSION

The IVS2+181G>A variant was associated with the changes in RQ in response to overfeeding. The IVS2+39C>T polymorphism was associated with overfeeding-induced changes in abdominal visceral fat, OGTT glucose area and RQ. The results suggest that sequence variation in the resistin gene is involved in the adaptation to chronic positive energy balance.

Functional dimorphism of two hAgRP promoter SNPs in linkage disequilibrium

The agouti related protein (AgRP) exerts its anabolic effects on food intake by antagonising the alpha-melanocyte stimulating hormone (alpha-MSH) at its receptors, melanocortin receptors 3 and 4 (MC3R and MC4R). A single nucleotide polymorphism (SNP) in the promoter of the human AgRP (hAgRP), -38C>T, was associated with low body fatness. The -38T allele that was associated with low body fatness also resulted in lower promoter activity. Here we report a novel SNP, -3019G>A, again in the promoter of hAgRP, which is in complete linkage disequilibrium (LD) with the -38C>T SNP (linked alleles: -3019A/-38T and -3019G/-38C). Functional analyses in a human adrenal and two mouse hypothalamus cell lines showed that the -3019A allele had significantly higher promoter activity. Hence, the two linked alleles (-3019A and -38T) had opposite effects on promoter function and yet they were both associated with low body fatness. The region encompassing the -38C>T SNP had approximately 1000-fold higher activity than the region encompassing the -3019G>A SNP, potentially determining the net functional effect between these two SNPs.

Generalized abdominal visceral fat prediction models for black and white adults aged 17–65 y: the HERITAGE Family Study

OBJECTIVE

To determine if the relationship between abdominal visceral fat (AVF) and measures of adiposity are different between Black and White subjects and to develop valid field prediction models that accurately identify those individuals with AVF levels associated with high risk for chronic disease.

DESIGN

Cross-sectional measurements obtained from 91 Black men, 137 Black women, 227 White men, and 237 White women subjects, ages 17-65 y, who were participants in the HERITAGE Family Study, both at baseline and following 20 weeks of endurance training.

MEASUREMENTS

AVF, abdominal subcutaneous fat (ASF), abdominal total fat (ATF), and sagittal diameter (SagD) were measured by computed tomography (CT). Body density was determined by hydrostatic weighing and was used to estimate relative body fat. Arm, waist (WC), and hip circumferences and skinfold thickness measures were taken, and BMI was calculated from weight (kg) and height (m(2)). Since CT abdominal fat variables were skewed, a natural log transformation (Ln) was used to produce a normal distribution. The General Linear Model (GLM) procedure was used to test the relationship between AVF and two different groups of variables-CT and anthropometric.

RESULTS

The AVF of White men and women was significantly higher than that of Black men and women, independent of BMI, WHR, WC, and age, and was greater for men than for women. The CT model showed that the combination of SagD, Ln (ASF), age, and race accounted for 84 and 75% of the variance in AVF in men and women, respectively. The anthropometric model provided two valid generalized field AVF prediction equations. The Field-I equation, which included BMI, WHR, age and race, had an r(2) of 0.78 and 0.73 for men and women, respectively. The Field-II equation, which included BMI (women only), WC, age, and race, had an r(2) of 0.78 and 0.72 for men and women, respectively. The field model equations became less accurate as the estimated AVF increased.

CONCLUSIONS

(1) At the same age and level of adiposity, Black men and women have less AVF than White men and women. These differences are greater in men than in women. (2) The field regression equations can be generalized to the diverse group of adults studied, both in an untrained and trained state. However, their accuracy decreases with increasing levels of AVF.

Estimation of daily energy needs with the FAO/WHO/UNU 1985 procedures in adults: comparison to whole-body indirect calorimetry measurements

OBJECTIVES

To measure daily energy expenditure (DEE) with indirect calorimetric facilities in sedentary and active subjects. To estimate daily energy needs with the FAO/WHO/UNU (1985) procedures (EDEE) and estimated energy requirement (EER) with the dietary reference intakes 2002 (DRI) in healthy adults with sedentary or high-activity conditions. To compare estimated daily energy needs with their measured values.

DESIGN

Two groups of healthy subjects were tested under sedentary or high-activity conditions. In both groups, resting energy expenditure was measured after a 12-h overnight fast. DEE and basal metabolic rate (BMR) values were also measured with indirect calorimetry and compared to the relevant predicted values. Physical activity level and BMR were also estimated.

SUBJECTS

A total of 45 sedentary (26 men and 19 women) and 69 active subjects (43 men and 26 women) aged 18-30 and 30-60 y.

RESULTS

Measured daily energy expenditure (MDEE) was significantly lower than EDEE in sedentary men and women and in active men for the two age groups considered (P<0.05). EER was significantly lower than EDEE in both sedentary and active subjects of each subgroup (P<0.05).

CONCLUSIONS

The FAO/WHO/UNU (1985) procedures may overestimate daily energy needs, particularly in sedentary individuals. However, DRI (2002) are probably more adapted to estimate real daily energy needs in sedentary and active subjects in comparison to the FAO/WHO/UNU (1985) procedures.

Is the SOGS an accurate measure of pathological gambling among children, adolescents and adults?

The South Oaks Gambling Screen (SOGS) is widely used to assess the prevalence of pathological gambling. For a variety of reasons, this instrument may not provide an accurate rate of the prevalence of pathological gambling. In this paper, one source of error in data provided by the SOGS is investigated. It is argued that individuals may not fully understand the meaning of some items, and that clarification of the meaning of misunderstood items may in some cases lead to a changed score on the scale. The present study evaluates respondents' understanding of the SOGS items. The results from three studies are reported, each using a different sample: grade school children, adolescents and adults. It was hypothesised that (1) participants would not understand some items of the SOGS, (2) problem gamblers and probable pathological gamblers would be more inclined to interpret items incorrectly than would non-problem gamblers and, (3) consistent with the first two hypotheses, clarification of items would decrease the number of participants identified as problem gamblers or probable pathological gamblers. The data obtained supported hypotheses 1 and 3. Furthermore, hypothesis 2 was supported for grade school children, but not for adolescents or adults. These results are consistent with recent literature on endorsement and acquiescence phenomena, and have implications for prevalence studies of probable pathological gambling.

Role of candidate genes in the responses to long-term overfeeding: review of findings

An overfeeding experiment conducted with 12 pairs of young male identical twins revealed that genetic factors were likely to play an important role in the response to caloric affluence. Significant intrapair resemblance was observed for the overfeeding-induced changes in body weight, fat mass, abdominal fat, fasting insulin, fasting cholesterol and triglycerides. In an attempt to define the molecular basis of these genotype-energy balance interaction effects, a panel of candidate genes has been investigated. Among the most significant findings, an adipsin polymorphism was associated with increases in body weight, total fat mass and subcutaneous fat in response to overfeeding. In addition, the beta2 adrenergic receptor gene Gln27Glu polymorphism showed a strong association with the gains in body weight and subcutaneous fat. Only a few markers were related to abdominal fat changes and, among them, the adipsin Hinc II polymorphism was associated with both computed tomography (CT)-measured abdominal visceral and total fat. The changes in insulin parameters brought about by long-term overfeeding were influenced most consistently by leptin receptor (LEPR) Gln223Arg and insulin-like growth factor-II Apa I polymorphisms. The LEPR Gln223Arg variant was also associated with the changes in plasma total triglycerides and high-density lipoprotein cholesterol concentrations. Further research with larger sample sizes should make it possible to identify the specific contributions of DNA sequence variations at multiple candidate gene loci in the complex response to chronic positive energy balance.

Quantitative trait loci for maximal exercise capacity phenotypes and their responses to training in the HERITAGE Family Study

The purpose of this study was to identify regions of the human genome linked to maximal oxygen uptake (V̇o2 max) and maximal power output (MPO), and their response to a standardized 20-wk endurance-training program in sedentary black and white subjects. A total of 509 polymorphic markers covering the 22 autosomes were used in the genome-wide linkage scan. Baseline phenotypes were adjusted for age, sex, and body mass, whereas the training responses were adjusted for age, sex, and the baseline values. Regression-based single- and multipoint linkage analyses were used. In the sedentary state, a total of 351 and 102 sibling pairs were available for whites and blacks, respectively, and 329 and 90 sibling pairs, respectively, for the training response phenotypes. Baseline V̇o2 maxshowed promising linkage ( P < 0.0023) with 11p15.1 (whites), and suggestive evidence of linkage (0.01 > P > 0.0023) was found on 1p31, 7q32, and 7q36 (blacks). Baseline MPO exhibited promising linkage on 10q23 and suggestive evidence of linkage on 13q33 and 18q11-q12 (whites). V̇o2 maxtraining response yielded promising linkages with markers on 1p31 (blacks) and suggestive on 4q27, 7q34, and 13q12 (whites) and on 16q22 and 20q13.1 (blacks). Training-induced changes in MPO showed promising linkages on 5q23 (whites) and suggestive on 1q21, 4p15.1, and 4p13 (whites) and on 1q22 and 13q11 (blacks). In conclusion, the strongest evidence of linkage was found on chromosomal regions 11p15 and 10q23 for V̇o2 maxand MPO in the sedentary state and on chromosomes 1p31 and 5q23 for their responsiveness to training. These chromosomal regions harbor several candidate genes that deserve further investigation.

Genome-wide linkage scan reveals multiple susceptibility loci influencing lipid and lipoprotein levels in the Quebec Family Study

A genome-wide linkage study was performed to identify chromosomal regions harboring genes influencing lipid and lipoprotein levels. Linkage analyses were conducted for four quantitative lipoprotein/lipid traits, i.e., total cholesterol, triglyceride, HDL-cholesterol (HDL-C), and LDL-C concentrations, in 930 subjects enrolled in the Québec Family Study. A maximum of 534 pairs of siblings from 292 nuclear families were available. Linkage was tested using both allele-sharing and variance-component linkage methods. The strongest evidence of linkage was found on chromosome 12q14.1 at marker D12S334 for HDL-C, with a logarithm of the odds (LOD) score of 4.06. Chromosomal regions harboring quantitative trait loci (QTLs) for LDL-C included 1q43 (LOD = 2.50), 11q23.2 (LOD = 3.22), 15q26.1 (LOD = 3.11), and 19q13.32 (LOD = 3.59). In the case of triglycerides, three markers located on 2p14, 11p13, and 11q24.1 provided suggestive evidence of linkage (LOD > 1.75). Tests for total cholesterol levels yielded significant evidence of linkage at 15q26.1 and 18q22.3 with the allele-sharing linkage method, but the results were nonsignificant with the variance-component method. In conclusion, this genome scan provides evidence for several QTLs influencing lipid and lipoprotein levels. Promising candidate genes were located in the vicinity of the genomic regions showing evidence of linkage.

Sex differences in the relationships of abdominal fat to cardiovascular disease risk among normal-weight white subjects

The objectives of this study are to investigate the relationships between abdominal fat and risk factors for cardiovascular disease (CVD) among normal-weight (NW) white subjects and to determine how these relationships differ by sex. NW adults (177 males and 258 females) and overweight adults (133 males and 111 females) from the Québec Family Study and the HERITAGE Family Study were retained for this study. Risk factors included systolic and diastolic blood pressures, low-density lipoprotein and high-density lipoprotein cholesterols, triglycerides, and fasting glucose. Only in NW female adults, abdominal visceral fat (AVF) area assessed by computed tomography was significantly correlated with all risk factors, except for fasting glucose, even after age, study cohort, and fat mass were taken into account. NW female subjects with at least one risk factor had a significantly higher AVF than those without risk factors, although the difference was small. Thus, only NW female adults with more AVF tended to have a more adverse CVD risk factor profile.

Obesity--is it a genetic disorder?

Obesity is one of the most pressing problems in the industrialized world. Twin, adoption and family studies have shown that genetic factors play a significant role in the pathogenesis of obesity. Rare mutations in humans and model organisms have provided insights into the pathways involved in body weight regulation. Studies of candidate genes indicate that some of the genes involved in pathways regulating energy expenditure and food intake may play a role in the predisposition to obesity. Amongst these genes, sequence variations in the adrenergic receptors, uncoupling proteins, peroxisome proliferator-activated receptor, and the leptin receptor genes are of particular relevance. Results that have been replicated in at least three genome-wide scans suggest that key genes are located on chromosomes 2p, 3q, 5p, 6p, 7q, 10p, 11q, 17p and 20q. We conclude that the currently available evidence suggests four levels of genetic determination of obesity: genetic obesity, strong genetic predisposition, slight genetic predisposition, and genetically resistant. This growing body of research may help in the development of anti-obesity agents and perhaps genetic tests to predict the risk for obesity.

Test-retest errors and the apparent heterogeneity of training response

Published reports have shown large apparent inter-individual differences of gains in maximal oxygen intake (VO(2max)) in response to a standard 20-week programme of aerobic conditioning that progressed to 75% of the individual's initial VO(2max). The observed gains of VO(2max) ranged from 0 to 1,000 ml min(-1), with a coefficient of variation (CV) of 8.4%. The present analysis evaluates the potential contribution of test-retest errors to these apparent large inter-individual differences in training response. The 2-day test-retest CV for VO(2max) readings in 742 healthy adults was initially 5.0%, dropping to 4.1% after training. Published training responses were estimated from the mean of paired measurements obtained before and after training if readings agreed by <5%, but from the highest of paired values if these differed by >5%. Taking account of the relative proportions of single and paired observations, the weighted VO(2max) data for the entire sample had an effective 2-day CV of 4.3% before and 3.4% after training. Assumption 1: if the 20-week test-retest error remained similar to the 2-day figure, measurement error would contribute a CV of 5.5% to apparent training responses, or (for the stated initial mean VO(2max) of 2,409 ml min(-1)) an SD of 132 ml min(-1). Assumption 2: if the 20-week CV was similar to that in other long-term studies (~5%), measurement error would contribute a CV of 6.1%, or a SD of 146 ml min(-1). The published data show a total SD of 202 ml min(-1) for apparent inter-individual differences in training response, with age, gender, race and baseline VO(2max) accounting for only 11% of this variance. After estimating the likely effect of test-retest measurement errors, the SD due to inter-individual differences would decrease to 138 ml min VO(2max) (assumption 1) or 123 ml min(-1) (assumption 2). We conclude that when estimating the extent of inter-individual differences in training response, allowance must be made not only for the minor effects of recognized covariates (age, gender, race and initial fitness), but also for the larger influence of test-retest measurement errors. Nevertheless, substantial inter-individual differences persist after making such adjustments. The most likely explanation of these differences is a familial aggregation of training responses.

Evidence of major genes for exercise heart rate and blood pressure at baseline and in response to 20 weeks of endurance training: the HERITAGE family study

Major gene effects on exercise heart rate (HR) and blood pressure (BP) measured at 50 W and 80 % maximal oxygen uptake (VO (2)max) were assessed in 99 White families in the HERITAGE Family Study. Exercise HR and BP were measured both before and after 20 weeks of endurance training. The baseline phenotypes were adjusted for the effects of age and BMI, whereas the training responses (post-training minus baseline) were adjusted for the effects of age, BMI and the corresponding baseline values, within four sex-by-generation groups. Baseline exercise HR at 50 W was under the influence of a major recessive gene and a multifactorial component, which accounted for 30 % and 27 % of the variance, respectively. The training response was found to be under the influence of a major dominant gene, which accounted for 27 % of the variance. These significant major gene effects were independent of the effects of cigarette smoking, baseline VO (2)max, and the resting HR levels. No significant interactions were found between genotype and age, sex, or BMI. No major gene effect was found for exercise BP. Instead, we found the baseline exercise BP at 50 W and 80 % VO (2)max and the training response at 50 W were solely influenced by multifactorial effects, which accounted for about 50 %, 40 % and 20 % of the variance, respectively. No familial resemblance was found for training responses in exercise HR or BP at 80 % VO (2)max. Segregation analysis also was carried out for exercise HR in Whites pooled with a small sample of Blacks in HERITAGE. Similar major effects were found, but the transmission from parents to offspring did not follow Mendelian expectations, suggesting sample heterogeneity. In conclusion, submaximal exercise HR at baseline and in response to endurance training was influenced by putative major genes, with no evidence of interactions with sex, age or BMI, in contrast to a multifactorial etiology for exercise BP.

Genetic variation at the adipsin locus and response to long-term overfeeding

OBJECTIVES

The role of adipsin and adipsin Hinc II polymorphisms on the metabolic and body composition changes in response to overfeeding was studied.

SUBJECTS

A total of 12 pairs of male monozygotic twins ate a 4.2 MJ/day energy surplus, 6 days a week, during a period of 100 days.

RESULTS

The preoverfeeding plasma adipsin concentration correlated positively with the change in CT-measured abdominal total and subcutaneous (P<0.05) fat. The changes in abdominal total fat and abdominal subcutaneous fat correlated negatively with changes in plasma adipsin concentrations (P<0.005). Overfeeding induced greater increases in body weight, fat mass, abdominal total and subcutaneous fat (P<0.05) in 6.1 kb noncarriers (n=10) than in 6.1 kb carriers (n=14) of the adipsin Hinc II polymorphism. The 6.1 kb noncarriers had a greater increase in plasma leptin levels (P<0.01). Also the total (P<0.01) and very-low-density lipoprotein (VLDL)-triglycerides (P<0.05), apolipoprotein B (P<0.05) and VLDL-cholesterol (P<0.05) levels increased more in the 6.1 kb noncarriers than in the 6.1 kb carriers.

CONCLUSIONS

Adipsin plasma level could be a predictor of the changes in abdominal subcutaneous fat during times of increased energy intake. However, a greater increase in the abdominal subcutaneous fat was related to a lower increase in the plasma adipsin level. The adipsin Hinc II 6.1 kb allele noncarriers gained more abdominal subcutaneous fat and had a greater increase in plasma levels of leptin- and triglyceride-rich lipoproteins when exposed to a long-term positive energy balance. These findings provide new information on the role of adipsin on individual differences in response to chronically elevated food intake.

Effect of malnutrition during the first year of life on adult plasma insulin and glucose tolerance

There is evidence linking intrauterine growth retardation with increased cardiovascular risk and diabetes mellitus (DM) later in life. However, little is known about the association between malnutrition during the first year of life and metabolic abnormalities in adulthood. The objective of this study was to assess the effect of documented malnutrition during the first year of life on glucose tolerance, plasma insulin, lipid profile, and blood pressure in early adulthood, as well as to assess the interaction between body mass index (BMI) and malnutrition on these variables. A study group of young men with a documented history of malnutrition during their first year of life was recruited from 4 pediatric hospitals in Mexico City and compared with a control group. Subjects included were 52 men, aged 20.2 +/- 3.6 years, with a mean birth weight of 3.0 +/- 0.7 kg and documented malnutrition in their first year of life; controls were 50 men, aged 23.3 +/- 1.8 years, with a mean birth weight of 3.2 +/- 0.5 kg. Insulin and glucose concentrations, fasting and in response to an oral glucose load, plasma lipids, blood pressure, and an insulin sensitivity index (ISI) were measured. The areas under the curves of glucose (AUCG) and insulin (AUCI) were significantly higher in cases (P =.012 and <.002, respectively), independent of birth weight, BMI, or age. BMI was significantly associated with fasting plasma insulin (FPI), AUCI, ISI, triglyceride, and high-density lipoprotein (HDL)-cholesterol concentrations in cases, but not in controls. These data suggest that early malnutrition in extrauterine life, independently of birth weight, has an adverse effect on insulin metabolism and glucose tolerance in young men, and it worsens as body mass increases even within the normal range of BMI. Therefore, it is advisable to prevent obesity in individuals exposed to early malnutrition.

Associations between cardiorespiratory responses to exercise and the C34T AMPD1 gene polymorphism in the HERITAGE Family Study

The associations of the C34T polymorphism of the adenosine monophosphate deaminase 1 (AMPD1) gene with cardiorespiratory phenotypes were tested during cycling exercise at absolute and relative power outputs progressing to exhaustion before and after endurance training for 20 wk in the HERITAGE Family Study cohort (n = 779). Since no blacks were mutant homozygotes (TT), only whites were considered for analysis (400 normal homozygotes, CC; 97 heterozygotes, CT; and 6 TT). For sedentary state, cycling at the absolute power output of 50 W resulted in a higher rating of perceived exertion in TT (P < 0.0001). At the relative intensity of 60% of Vo(2 max), stroke volume was lower in TT (P < 0.05). Maximal values for power output, systolic blood pressure, heart rate, Vco(2), and respiratory exchange ratio were lower in TT (P < 0.05). The cardiorespiratory training response at 50 W and at 60% of Vo(2 max) was similar across C34T-AMPD1 genotypes. However, the maximal values for ventilation, Vo(2), and Vco(2) during exercise increased less in TT (P < 0.01). The results indicate that subjects with the TT genotype at the C34T AMPD1 gene have diminished exercise capacity and cardiorespiratory responses to exercise in the sedentary state. Furthermore, the training response of ventilatory phenotypes during maximal exercise is more limited in TT.

Cardiorespiratory fitness modifies the association between dietary fat intake and plasma fatty acids

OBJECTIVES

To investigate the relation between (1) cardiorespiratory fitness and plasma saturated, monounsaturated and polyunsaturated fatty acids and (2) the interactions between cardiorespiratory fitness, dietary fat intake and plasma fatty acid composition.

DESIGN

Cross-sectional analysis.

SETTING AND SUBJECTS

The subjects were randomly selected, 127 middle-aged Finnish men participating in the DNASCO exercise intervention study.

INTERVENTIONS

Cardiorespiratory fitness was determined spiroergometrically, dietary intake of macro- and micronutrients by 4-day food records and plasma fatty acids by gas chromatography. The subjects were divided into tertiles of aerobic fitness.

RESULTS

Differences between fitness tertiles were not observed for dietary intake of total fat, and saturated, monounsaturated or polyunsaturated fatty acids (percent of total energy). In contrast, plasma saturated fatty acids were significantly lower (P <0.01) and polyunsaturated fatty acids significantly higher (P <0.05) in the highest fitness tertile compared to the lowest tertile. Dietary saturated fat intake was positively associated with plasma saturated fatty acids (r=0.342; P <0.05) and inversely with plasma polyunsaturated fatty acids (r=-0.453; P <0.01) only in the lowest fitness tertile. In addition, a positive correlation between body mass index and plasma saturated fatty acids (r=0.516; P <0.01) as well as a negative correlation between body mass index and plasma polyunsaturated fatty acids (r=-0.516; P <0.01) was observed in the lowest tertile solely.

CONCLUSION

Different levels in cardiorespiratory fitness are associated with different levels in plasma saturated and polyunsaturated fatty acids and lead to modifications in the association between dietary and plasma fatty acids. These findings can perhaps be explained by a reduced hepatic fatty acid and lipoprotein synthesis as well as by an enhanced muscular lipid utilization, which are commonly seen in those who are physically active and who exhibit a higher level of fitness.

Do 6-y changes in eating behaviors predict changes in body weight? Results from the Québec Family Study

OBJECTIVE

This study was performed to examine changes in eating behaviors as assessed by the three-factor eating questionnaire (TFEQ) and to quantify the potential associations between these eating behaviors and body weight changes in a 6-follow-up study.

DESIGN AND SUBJECTS

Prospective study performed in men and women who were tested twice (Visit 1=1989-1995 and Visit 2=6 y later) in the Québec Family Study (QFS).

RESULTS

Women were more restrained and less hungry than men. To reduce food intake, women relied more on strategic dieting behavior and avoided more fattening food. However, they had higher emotional and situational susceptibility to eat than men. Significant decreases in the disinhibition score were noted over time in women (P<0.01), which resulted from a decrease in habitual susceptibility behavior to increase food intake. In men, we observed an increase in the avoidance of fattening food (P<0.05). In both genders, we found that the 6-y change in restraint behavior was negatively correlated with body weight changes (P<0.05). In women, a high restraint behavior seems to promote weight gain, whereas in men, it is associated with the opposite trend.

CONCLUSION

These results suggest that variables reflecting some eating behaviors are associated with body weight changes in a free-living context. However, these behaviors are expressed differently between men and women. These behaviors should be considered in clinical interventions for individuals seeking a better body weight control.

Correlation between culture testing of swabs and ligase chain reaction of first void urine from patients recently treated for Chlamydia trachomatis

We assessed the correlation between ligase chain reaction (LCR) on first void urine (FVU) and cultures of urethral and cervical swabs to detect chlamydia during three post-treatment follow up visits for 10 men and 19 women with genital chlamydial infections who had been treated with azithromycin or doxcycline.