Insulin resistance and abdominal adiposity in young men with documented malnutrition during the first year of life

OBJECTIVE

The main objective of the study was to examine the effect of early life malnutrition on the relation between insulin sensitivity and abdominal adiposity in adulthood. It was hypothesised that participants with early life malnutrition would display a more pronounced deterioration of insulin sensitivity in association with a gain in abdominal fat.

DESIGN

As a first attempt to investigate this issue, we studied the effect of body fat gains in a cross-sectional context.

SUBJECTS

A total of 26 young adult men with evidence of malnutrition during the first year of life and 27 control subjects were recruited for this study. Malnutrition status was determined from medical files of paediatric hospitals in the Mexico City metropolitan area.

MEASUREMENTS

Insulin sensitivity was measured by hyperinsulinaemic euglycaemic clamp, and body composition was measured by anthropometrics, bioelectrical impedance and computed tomography.

RESULTS

There was a negative correlation between total abdominal adipose tissue area and insulin sensitivity in the previously malnourished and control groups (r(2)=0.65 and 0.35, P<0.01, respectively). When matched for low amounts of abdominal fat (114 cm(2)), participants with and without early life malnutrition had similar insulin sensitivity (9.03 vs 8.88 mg kg(-1) x min(-1)). However, when matched for high amounts of abdominal fat (310 cm(2)) participants who were malnourished during the first year of life had lower insulin sensitivity (4.74 vs 6.85 mg kg(-1) x min(-1), P<0.05).

CONCLUSION

Higher levels of abdominal adipose tissue are more detrimental to insulin sensitivity in previously malnourished individuals.

Interactions among the beta2- and beta3- adrenergic receptor genes and total body fat and abdominal fat level in the HERITAGE Family Study

OBJECTIVE AND SUBJECTS

Interactions between markers in the beta2- and beta3-adrenergic receptor (ADR) genes and total body fat and computerized tomography-measured abdominal fat phenotypes were studied in the HERITAGE Family Study cohort of Black (n=205; 81 males and 124 females) and White (n=415; 198 males and 217 females) subjects before and after an endurance training program.

RESULTS

In Black subjects, beta2- and beta3-ADR gene variants showed evidence of interactions on changes in total body fat mass and abdominal fat area (P<0.005 and =0.010, respectively). Black subjects who were carriers of both beta2-ADR Arg16 and beta3-ADR Arg64 alleles had a greater decrease in total fat mass as well as abdominal total and subcutaneous, but not visceral fat areas in response to endurance training than subjects with other genotype combinations (P from 0.011 to 0.047). After correction for multiple tests, the findings remained essentially unchanged for total body fat mass and abdominal fat area, but became nonsignificant for subcutaneous fat area. The changes in abdominal fat correlated positively with the changes in fat mass (P<0.0001). The interactions between beta2 and beta3-ADR gene markers accounted for a maximum of 3% of the variances in the response of total fat mass and abdominal fat area to endurance training in Black subjects but it was not significant in White subjects.

CONCLUSION

Interactions between sequence variants in the beta2-beta3-ADR gene contributed to the changes in fat mass and abdominal adiposity in response to endurance training in Black subjects.

The agouti-related protein and body fatness in humans

OBJECTIVE

The objective of this study was to examine the impact of a single nucleotide polymorphism (SNP) (-38C>T) in the promoter of the human agouti-related protein (hAgRP) gene on promoter affinity for transcription factors (TFs) and its possible association with body composition phenotypes.

DESIGN

Electrophoretic mobility shift assays for the functional studies and association analyses for the population studies.

SUBJECTS AND METHODS

Nuclear extracts were isolated from the mouse hypothalamus cell line GT1-7 and subjected to binding assays using oligonucleotide probes corresponding to the -38C>T region and an antibody for the E12/E47 TFs. Individuals (n = 259) from the HERITAGE Family Study were genotyped for the -38C>T SNP and used in the association studies.

RESULTS

Electrophoretic mobility shift and supershift assays confirmed binding of the E12/E47 TF to the -38C>T site in a genotype-dependent manner. The T allele was found exclusively in the black subjects while the genotype with the higher binding affinity, CC, was significantly associated with high BMI, fat mass, and percent body fat in the black subjects of the HERITAGE Family Study.

CONCLUSIONS

The E12/E47 TF could play a role in the regulation of hAgRP expression while the population studies suggest that the TT genotype of the -38C>T SNP could play a protective role against the development of obesity in the black population of the HERITAGE Family Study.

Familial aggregation of exercise heart rate and blood pressure in response to 20 weeks of endurance training: the HERITAGE family study

Changes of heart rate (HR) and blood pressure (BP) relative to baseline levels in response to an extended period of endurance training are indices of cardiovascular adaptability. Familial influences were investigated for HR and BP at work rates of 50 W and 60 % of the maximal oxygen uptake (VO2max) in response to 20 weeks of endurance training. A total of 481 participants from 99 sedentary White nuclear families in the HERITAGE Family Study (HERITAGE) were analyzed using a familial correlation model. Each of these training response phenotypes was adjusted for the effects of age, BMI, cigarette smoking, baseline VO2max, and its baseline values in fathers, mothers, sons and daughters, respectively. We found that maximal heritabilities reached 34 % and 29 % for HR training responses at 50 W and 60 % of VO2 max, respectively. The heritability was 22 % for systolic BP (SBP) training response at 50 W, but negligible at 60 % of VO2max. No significant heritabilities were found for diastolic BP (DBP) training responses at either 50 W or 60 % of VO2max. Familial influences for exercise HR and BP training responses were also assessed in a total of 257 participants from 113 Black family units in HERITAGE. However, there was no significant familial resemblance, which may be attributable to the small sample size. In conclusion, HR and SBP training responses during submaximal exercise in Whites were influenced by a modest, but significant, familial component. These observations are therefore in contrast to substantial familial effects (heritability estimates of about 50 %) previously reported for these variables measured at baseline.

The genetics of human obesity: recent progress

The risk of becoming obese is higher in some families than in others. The risk (the lambda coefficient) is two to three fold for moderate obesity, but up to five to eight fold for severe obesity. Several genes exhibit mutations that can cause early onset severe obesity. These mutations are rare and account for only a small fraction of the cases of obesity. At this time, more than fifty genes have been shown in various studies to influence the energy balance, nutrient partitioning, or the age of onset of obesity. The results of these studies are generally disappointing and often contradictory. One approach is to scan the genome with a high number of polymorphic markers to identify chromosomal regions harboring genes implicated in the development of obesity. Such studies can be helpful in defining new targets to explore.

Genetics and blood pressure response to exercise, and its interactions with adiposity

Regular aerobic exercise has the potential to induce several beneficial health effects, including a decrease in blood pressure level, especially in hypertensive patients and in subjects with high-normal blood pressure. However, it is also well documented that some people show more pronounced blood pressure responses to endurance training than others, despite identical training programs and similar initial blood pressure levels. This kind of variation is an example of normal biologic diversity and most likely originates from interactions with genetic factors. Data from genetic epidemiologic studies indicate that there is a genetic component that affects both resting blood pressure and blood pressure responses to acute exercise. Evidence from molecular genetic studies is scarce, but the first reports suggest that DNA sequence variation in the hypertension candidate genes, such as angiotensinogen, also modify blood pressure responses to endurance training. The current knowledge regarding the role of genetic factors in the modification of blood pressure responses to endurance training will be summarized and discussed.

Adiposity, adipose tissue distribution and mortality rates in the Canada Fitness Survey follow-up study

OBJECTIVE

To compare mortality rates across indicators of adiposity and relative adipose tissue distribution in the Canadian population.

SUBJECTS

The sample included 10,323 adult participants 20-69 y of age from the Canada Fitness Survey who were monitored for all-cause mortality over 13 y.

METHODS

BMI, waist circumference (WC) and the sum of five skinfolds (SF5) were indicators of adiposity, and the first principal component of skinfold residuals (PC1) represented subcutaneous adipose tissue distribution. Proportional hazards regression was used to estimate relative mortality risk from mortality rates across levels of adiposity and adipose tissue distribution, controlling for the confounding effects of age, smoking status and alcohol consumption.

RESULTS

:Significant curvilinear (J-shaped) relationships in men and linear relationships in women were observed between BMI, WC and SF5 and all-cause mortality rates. PC1 was not related to mortality rates in either men or women. In women, the inclusion of the other indicators of adiposity and adipose tissue distribution did not significantly add to the prediction of mortality rates beyond BMI; however, combinations of BMI and both WC and SF5 produced significant models in men.

CONCLUSION

The results support the hypothesis that overall level of adiposity is an important predictor of all-cause mortality, more so than the relative distribution of subcutaneous body fat, once overall level of body fatness has been accounted for.

Allelic variants in the GABA(A)alpha6 receptor subunit gene (GABRA6) is associated with abdominal obesity and cortisol secretion

INTRODUCTION

Cortisol is involved in the regulation of adipose-tissue differentiation, function and distribution, and in excess causes abdominal obesity. At the level of the brain, cortisol secretion is partly controlled by gamma-aminobutyric acid (GABA), which is the major inhibitory neurotransmitter in the vertebrate brain, and acts by binding to GABA(A) receptors.

METHOD

We examined the potential impact of a 1519T>C polymorphism in the GABA(A)alpha6 receptor subunit (GABRA6) gene on obesity and obesity-related phenotypes as well as circulating hormones, including salivary cortisol in 284 unrelated Swedish men born in 1944. The subjects were genotyped by using PCR amplification of the 3' non-coding region of the GABRA6 gene followed by digestion with the restriction enzyme AlwNI.

RESULTS

The frequency of allele T was 0.54 and 0.46 for allele C. Carriers for the T allele (n=211) had borderline significantly higher waist-to-hip ratio (P=0.094) and abdominal sagittal diameter (P=0.084) compared to homozygotes for the C allele (n=56). The homozygotes for the T allele had, in comparison to heterozygotes, significantly (P=0.004-0.024) higher mean cortisol levels at 11:45 am, and 30, 45 and 60 min after a standardized lunch and, finally, at 5:00 pm. In addition, T/T subjects had significantly (P=0.031) higher diurnal cortisol secretion compared to T/C subjects. Other hormones, glucose and serum lipids were not different across the genotype groups.

CONCLUSION

These findings suggest a role of the 1519T>C polymorphism in GABRA6 in the predisposition to hypercortisolism and perhaps abdominal obesity. The pathophysiology may involve various environmental factors, particularly stress, that destabilize the GABA-hypothalamic-pituitary-adrenal systems in those with genetic vulnerability.

A 12-year follow-up study of treated obese children in Japan

OBJECTIVE

To assess tracking for body weight from childhood to adulthood in obese Japanese children who were treated for obesity, investigate the relation between the changes in body weight status and morbidity, and identify correlates of the changes in body weight status.

STUDY DESIGN

Twelve-year retrospective cohort study.

SUBJECTS

A sample of 276 subjects (age 23.9+/-4.1, 176 males and 100 females) who responded to a questionnaire mailed in 1998 to 1047 children (age 10.6+/-2.2) treated for obesity at Mie National Hospital in Japan between 1976 and 1992.

MEASUREMENTS

Based on height and weight from medical records during childhood, the relative weight (RW; weight expressed as a percentage of the standard body weight for age, height, and sex) was calculated. Degrees of childhood obesity were based on RW: slight obesity (120% < or = RW<130%; n=17), moderate obesity (130% < or = RW <150%; n=131), and severe obesity (RW > or = 150%; n=128). Adult body mass index (BMI), which was obtained from the mailed questionnaires, was classified as normal, overweight and obese according to the WHO/NIH criteria. Body weight tracking by degree of obesity was evaluated. Subjects with severe obesity during childhood (n=128) were examined for their weight status in adulthood, prevalence of chronic diseases in adulthood, and factors such as parental obesity, dietary and exercise habits and obesity treatment during childhood.

RESULTS

Childhood obesity tracked into adulthood obesity or overweight in 54.7% of all cases. Severely obese children (36.7%) were more likely to be obese as an adult than moderately obese children (16.8%). The prevalence of adult obesity tended to be greater in boys with moderate childhood obesity than in girls (29.7% in boys vs 14.9% in girls, P=0.058). Among the severely obese children who became normal-weight adults, the prevalence of chronic diseases was about one-fifth of those who remained obese in adulthood (P=0.041). Four factors were associated with changes in body weight status: maternal BMI at entry (P=0.044), the changes in dietary and exercise habits after treatment (P=0.014, P=0.030, respectively), and satisfaction with obesity treatment in childhood (P=0.035).

CONCLUSIONS

Severely obese children have a higher risk of becoming obese adults even when they received obesity treatment in childhood. The risk of adulthood obesity was twice as high in moderately obese boys than in girls. On the other hand, many cases of childhood obesity can be corrected with obesity treatment, which in turn can decrease the risk for adult chronic diseases.

The effect of sex, age and race on estimating percentage body fat from body mass index: The Heritage Family Study

OBJECTIVE

To study the effects of sex, age and race on the relation between body mass index (BMI) and measured percent body fat (%fat).

DESIGN

Cross-sectional validation study of sedentary individuals.

SUBJECTS

The Heritage Family Study cohort of 665 black and white men and women who ranged in age from 17 to 65 y.

MEASUREMENTS

Body density determined from hydrostatic weighing. Percentage body fat determined with gender and race-specific, two-compartment models. BMI determined from height and weight, and sex and race in dummy coded form.

RESULTS

Polynomial regression showed that the relationship between %fat and BMI was quadratic for both men and women. A natural log transformation of BMI adjusted for the non-linearity. Test for homogeneity of log transformed BMI and gender showed that the male-female slopes were within random variance, but the intercepts differed. For the same BMI, the %fat of females was 10.4% higher than that of males. General linear models analysis of the women's data showed that age, race and race-by-BMI interaction were independently related to %fat. The same analysis applied to the men's data showed that %fat was not just a function of BMI, but also age and age-by-BMI interaction. Multiple regression analyses provided models that defined the bias.

CONCLUSIONS

These data and results published in the literature show that BMI and %fat relationship are not independent of age and gender. These data showed a race effect for women, but not men. The failure to adjust for these sources of bias resulted in substantial differences in the proportion of subjects defined as obese by measured %fat.

A meta-analytic investigation of linkage and association of common leptin receptor (LEPR) polymorphisms with body mass index and waist circumference

METHODS

We analyzed data pooled from nine studies on the human leptin receptor (LEPR) gene for the association of three alleles (K109R, Q223R and K656N) of LEPR with body mass index (BMI; kg/m(2)) and waist circumference (WC). A total of 3263 related and unrelated subjects from diverse ethnic backgrounds including African-American, Caucasian, Danish, Finnish, French Canadian and Nigerian were studied. We tested effects of individual alleles, joint effects of alleles at multiple loci, epistatic effects among alleles at different loci, effect modification by age, sex, diabetes and ethnicity, and pleiotropic genotype effects on BMI and WC.

RESULTS

We found that none of the effects were significant at the 0.05 level. Heterogeneity tests showed that the variations of the non-significant effects are within the range of sampling variation.

CONCLUSIONS

We conclude that, although certain genotypic effects could be population-specific, there was no statistically compelling evidence that any of the three LEPR alleles is associated with BMI or WC in the overall population.

Lipoprotein lipase polymorphisms and responses to long-term overfeeding

OBJECTIVES

The role of the lipoprotein lipase (LPL) gene Hind III, S447X, Bam HI and Pvu II polymorphisms on body composition and lipid and lipoprotein changes in response to long-term overfeeding was studied.

SUBJECTS

Twelve pairs of male monozygotic twins ate a 4.2 MJ day-1 energy surplus, 6 days a week, during a period of 100 days.

RESULTS

Overfeeding induced a decrease in high-density lipoprotein 2 cholesterol (HDL2-C) and HDL2-C to HDL3-C ratio in the H2H2 (n = 12) subjects of the LPL Hind III polymorphism. In contrast, the H1H1/H1H2 (n = 12) subjects experienced increases both in the HDL2-C and HDL2-C to HDL3-C ratio (P = 0.009 and 0.007, respectively, for differences in percentage changes between H2H2 and H1H1/H1H2). In addition, the H2H2 genotype was associated with higher levels of very-low-density lipoprotein triglyceride (VLDL-TG) (P < 0.03) and VLDL-C (P < 0.05) before and after overfeeding and higher HDL-TG levels (P < 0.003) after overfeeding. Postheparin lipoprotein lipase (PH-LPL) activity tended to increase in H1H1/H1H2 and decrease in H2H2 subjects. The H2H2 subjects had lower total HDL-C than those with the genotype H1H1/H1H2 4 months and 5 years after overfeeding (P = 0.04 and 0.10, respectively). The plasma lipid differences were similar amongst subjects with the S447S (n = 4) genotype of the S447X and H2H2 genotype of the Hind III polymorphisms. Body composition changes in response to overfeeding were not different between the Hind III genotypes. LPL Pvu II and Hind III polymorphisms were associated weakly with body weight gain (P = 0.015-0.039) but strongly with adipose tissue LPL activity (P < 0.01) after the caloric surplus.

CONCLUSIONS

We conclude that the H2H2 subjects of the LPL gene Hind III polymorphism experience a decrease in the concentration of antiaterogenic lipoproteins when they are exposed to long-term positive energy balance. This may have been partly caused by a diminished catabolism of TG-rich particles in H2H2 subjects. LPL Pvu II and Bam HI polymorphisms were associated with body weight gain and adipose tissue LPL activity. Genetic variation at the LPL locus could thus be one of the factors responsible for the inter-individual differences observed in plasma lipid and lipoprotein responses to chronic positive energy balance. It must be kept in mind that the sample size for this study was small. Nonetheless, it provides useful information on the genes and pathways that should be further explored.

Genetic factors as predictors of weight gain in young adult Dutch men and women

OBJECTIVE

To investigate the association between DNA polymorphisms in several candidate genes for obesity and weight gain. Polymorphisms in these genes may contribute to weight gain through effects on energy intake, energy expenditure or adipogenesis.

DESIGN AND METHODS

From two large cohorts in The Netherlands (total 17,500 adult men and women), we compared 286 subjects aged 20-40 y who gained an average of 12.8 kg (range 5.5-47 kg) during a mean follow-up of 6.8 y with 296 subjects who remained relatively constant over the same period with respect to occurrence of several polymorphisms in candidate genes of obesity and some lifestyle factors. Subjects who were dieting, were high alcohol consumers, were pregnant, changed their smoking status recently, or those who suffered from serious illnesses were excluded. Polymorphisms were determined in the LEPR-gene (LEPR Lys109Arg, LEPR Gln223Arg, LEPR Lys656Asn), in the UCP1 gene (A-G mutation at position-3826 5' region), in the UCP2 gene (Ala55Val, 45 bp Ins/Del), in the PPARG2 gene (Pro12Ala) and in the ADRB2 gene (Gly16Arg and Gln27Glu).

RESULTS

With the exception of the Gly16Arg polymorphism in the ADRB2 gene in men (P = 0.04) and women (P = 0.05), and the Lys109Arg polymorphism in the LEPR gene in women, no statistically significant differences in the genotype and allele frequencies were observed between weight gainers and non-weight gainers. Weight gainers differed in some aspects of dietary habits and physical activity patterns: weight gainers consumed relatively more savory snacks and were less active during leisure time compared with non-weight gainers.

CONCLUSION

Only variations in the ADRB2 gene and LEPR gene, may contribute to susceptibility to weight gain. None of the other studied genetic markers were clearly associated with weight gain. Further research is necessary to establish the role of lifestyle factors, or interactions between genes or between genes and lifestyle factors on weight gain with age.

A C-1291G polymorphism in the alpha2A-adrenergic receptor gene (ADRA2A) promoter is associated with cortisol escape from dexamethasone and elevated glucose levels

OBJECTIVES

The objective of the current study was to examine the potential impact of a C right arrow G substitution at position -1291 of the alpha2A-adrenergic receptor gene (ADRA2A) promoter on obesity and estimates of insulin, glucose, and lipid metabolism as well as circulating hormones, including salivary cortisol in 284 unrelated Swedish men born in 1944.

MAIN OUTCOME MEASURES

The subjects were genotyped by using PCR amplification of the promoter region of the ADRA2A gene followed by digestion with the restriction enzyme MspI.

RESULTS

The frequencies were 0.23 for allele C and 0.77 for allele G. The observed genotype frequencies were 45.8 and 54.2% for C/G and G/G, respectively. Heterozygotes (n=121) had significantly (P=0.009) higher salivary cortisol levels after 0.5 mg dexamethasone compared with G/G homozygotes (n=143). Fasting glucose was found to be significantly (P=0.017) higher in heterozygotes than in G/G homozygotes. The latter group had also a borderline significantly (P=0.080) higher mean diastolic blood pressure. These results were all adjusted for the potential confounding effect of body mass index (BMI) and waist-to-hip ratio (WHR). Other measurements such as BMI, WHR, abdominal sagittal diameter, total testosterone, insulin-like growth factor I, serum leptin, fasting insulin and serum lipids were not different across the ADRA2A genotype groups.

CONCLUSIONS

In conclusion, we have shown that an C --> G polymorphism at position -1291 of the ADRA2A gene is associated with a subnormal cortisol response to dexamethasone, elevated glucose levels and perhaps increased diastolic blood pressure. The pathophysiology could involve an altered density of the alpha2A-AR that destabilizes the sympathetic-hypothalamic-pituitary-adrenal systems in those with genetic vulnerability in the alpha2A-adrenergic receptor gene promoter.

A +2138InsCAGACC polymorphism of the melanocortin receptor 3 gene is associated in human with fat level and partitioning in interaction with body corpulence

BACKGROUND

The melanocortin system includes five receptors (MC1R to MC5R), and mouse and human MC4R has been shown to be involved in the regulation of feeding, and mouse MC3R in body composition. To verify a possible similar effect of MC3R in humans, we analyzed one insertion and one single nucleotide polymorphism by restriction fragment length polymorphisms (RFLP), and a microsatellite (D20S32e) in relation to body composition and glucose metabolism.

METHODS

Eight hundred twelve subjects of the Québec Family Study (QFS) cohort were analyzed for body composition, food intake, and energy metabolism phenotypes. Southern Blot with the complete MC3R cDNA was used to detect a new +2138InsCAGACC variant by Pst1 restriction. PCR-RFLP with BsaJ1 was used to type amino acid polymorphism V81I arising from a G241A nucleotide change. PCR and automatic DNA sequencers were used for the analysis of the TG dinucleotide repeat D20S32e located between -1933/-1892 of MC3R. In a covariance analysis among genotypes, phenotypes were adjusted for age and sex as covariates. Food intake and energy metabolism phenotypes were also adjusted for body mass index (BMI), and leptin and abdominal fat, as assessed by a computed tomography scan, for fatness using six skinfold thicknesses.

RESULTS

An association between the +2138InsCAGACC MC3R polymorphism was observed with fat mass (FM), percent body fat (%FAT), and total abdominal fat (ATF). Homozygote subjects for the +2138 insertion variant allele in normal weight (BMI < 25 kg/m(2)) and overweight (25 < or = BMI < 30 kg/m(2)) subjects showed a similar level of fatness despite the overall difference in BMI. In normal weight, homozygotes for the insertion allele showed higher mean values than heterozygotes and homozygotes for wild-type allele without insertion (%FAT: 24.0 +/- 1.1 versus 19.3 +/- 0.9 and 20.5 +/- 0.8, p = 0.0005; FM: 15.7 +/- 0.9 kg versus 11.7 +/- 0.7 kg and 12.6 +/- 0.6 kg, p = 0.0003). In contrast, overweight subjects homozygote for the variant allele showed lower mean values (%FAT: 27.0 +/- 1.2 versus 31.4 +/- 0.8 and 30.9 +/- 0.7, p = 0.002; FM: 18.3 +/- 1.0 kg versus 22.8 +/- 0.8 kg and 22.0 +/- 0.6 kg, p = 0.0001). This resulted in a similar level of body fat between both BMI groups for subjects homozygote for the insertion allele versus wild-type allele carriers (%FAT: +/-2-3% versus +/-10-12%; FM: +/-2 kg versus +/-9-11 kg). In obese subjects (BMI > or = 30 kg/m(2) ), a lower level of ATF was seen (-15%, p = 0.002). Other polymorphisms and phenotypes tested showed no association.

CONCLUSION

A new 12138InsCAGACC MC3R polymorphism is associated with the level of adiposity and with body fat partitioning in interaction with corpulence in humans.

Is adiposity at normal body weight relevant for cardiovascular disease risk?

OBJECTIVE

To examine the relation between adiposity and risk factors for cardiovascular disease (CVD) in normal weight (NW) individuals.

METHODS

Cross-sectional study using the sample of white people, aged from 17 to 60 y from the Québec Family Study and the Heritage Family Study. NW subjects with a body mass index (BMI) between 18.5 and 25 kg/m(2) (181 males and 265 females) and overweight (OW) subjects with a BMI between 25 and 30 kg/m(2) (133 males and 114 females) were retained for this study. NW subjects were divided into quintiles of each adiposity variable, then the quintiles and the OW group were evaluated for the presence of CVD risk factors. Using logistic regression analysis, the odds ratio (OR) for the prevalence of risk factors for each quintile of each adiposity variable and the OW group was estimated relative to the first quintile in NW subjects. Mean values of adiposity variables were compared between the subjects with and without risk factors. In these analyses, age and study cohort effects were taken into account.

MEASUREMENTS

Percentage body fat (%fat) and fat mass (FM) measured by underwater weighing were available as adiposity variables. Risk factors included systolic and diastolic blood pressure, LDL and HDL cholesterol, triglycerides and fasting glucose.

RESULTS

Wide ranges of values were observed for adiposity variables. HDL cholesterol, triglycerides and fasting glucose in NW males and HDL cholesterol in NW females were significantly correlated with all adiposity variables. For males, higher quintiles of adiposity variables in the NW group and the OW group tended to have higher ORs compared to the first quintiles for the risk factor variables. The fifth quintiles of all adiposity variables had the highest ORs (3.15 for %fat and 3.77 for FM) and they were significantly different from the first quintiles. OW males had ORs similar to those of the fifth quintiles for the risk factor variables. On the other hand, for females, the relatively linear associations were less clear in the NW group. In NW males, the subjects with at least one risk factor had significantly higher %fat and FM than the subjects without risk factors. In NW females, no significant difference was observed for these adiposity variables between the subjects with and without risk factors.

CONCLUSION

NW males with elevated adiposity had higher prevalence of risk factors than NW males with less adiposity and the prevalence in the former was rather similar to that seen in OW males. On the other hand, measures of adiposity added little additional information to the BMI classification of NW on CVD risk factors in females.

Spousal resemblance in the Canadian population: implications for the obesity epidemic

OBJECTIVE

To determine the extent of the spousal resemblance for adiposity and leanness in the Canadian population.

DESIGN

Cross-sectional population survey.

METHODS

The sample comprised parents and offspring from 1341 families (n=4023) of the Canada Fitness Survey. Indicators of adiposity included the body mass index (BMI) and the sum of five skinfolds (SF5). Both offspring and parents were ranked by their BMI and SF5 percentile position in the population using the entire Canada Fitness Survey database (n=15 818).

RESULTS

Pearson correlations indicated significant spousal resemblance for both BMI (r=0.14; P<0.0001) and SF5 (r=0.13; P<0.0001). However, the magnitude of the spousal correlations varied by the adiposity status of the offspring, with spousal correlations tending to be stronger in parents of lean or obese children and lower among parents of 'average' children. Bivariate histograms indicated that among lean (<or=5th percentile) and obese offspring (>or=95th percentile), the parental pairs tended to cluster among the lower and higher percentiles of adiposity, respectively.

CONCLUSIONS

There are spousal similarities in adiposity, particularly among parents of lean or obese offspring in the Canadian population. The degree to which these similarities are due to a loading of spouses with genes predisposing to obesity or a shared household environment cannot be determined from the present study. However, these results are compatible with the notion that genes and mutations predisposing to obesity are more prevalent among obese parents while those for pronounced leanness are more prevalent among lean parents.

The hormone-sensitive lipase gene and body composition: the HERITAGE Family Study

OBJECTIVE

To investigate whether the C-60G polymorphism and other markers in the hormone-sensitive lipase (LIPE) gene are associated with baseline body composition and free-fatty acid (FFA) concentrations measured at rest and during low-intensity exercise in white and black subjects participating in the HERITAGE Family Study.

SUBJECTS

Adult sedentary white (245 men and 258 women) and black (91 men and 185 women) subjects.

MEASUREMENTS

body mass index (BMI); fat mass (FAT); percentage body fat (%FAT); fat-free mass (FATFR); sum of eight skinfolds (SF8); subcutaneous (ASF), visceral (AVF) and total (ATF) abdominal fat areas assessed by CT scan; plasma FFA concentrations measured at rest (FFAR), at a power output of 50 W (FFA50) and at a relative power output of 60% of VO(2max) (FFA60%); and fasting insulin (INS).

STATISTICAL ANALYSIS

Association between the C-60G polymorphism of the LIPE gene and each phenotype was tested separately in men and women using ANCOVA with the effects of age and race as covariates and with further adjustment for FAT for ASF, AVF, ATF, FFAR, FFA50 and FFA60%. Secondly, owing to significant gene-by-race interaction, associations were investigated separately in each of the two race groups. Linkage was tested with the C-60G polymorphism, a dinucleotide repeat polymorphism in the intron 7 of the LIPE gene and two microsatellites markers (D19S178 and D19S903) flanking the LIPE gene.

RESULTS

There were no race differences in the allele frequencies of the C-60G polymorphism of the LIPE gene. No association or gene-by-race interaction was observed in men. However, in women, strong gene-by-race interactions were observed for BMI (P=0.0005), FAT (P=0.0007), %FAT (P=0.0003), SF8 (P=0.0001), ASF (P=0.03) and ATF (P=0.01). When the analysis was performed separately in each race, white women carriers of the -60G allele exhibited lower %FAT (P=0.005) and SF8 (P=0.01) than non-carriers, while in black women, the -60G allele was associated with higher BMI (P=0.004), FAT (P=0.009), %FAT (P=0.01) and SF8 (P=0.0009). These associations were no longer significant after adjusting for INS. Evidence of linkage was observed in whites with ATF, FFAR, FFA50 and FFA60%.

CONCLUSION

These results suggest that the C-60G polymorphism in the LIPE gene plays a role in determining body composition and that its effect is sex-, race- and insulin-dependent.

Variability in the response of HDL cholesterol to exercise training in the HERITAGE Family Study

In the HERITAGE Family Study, 675 sedentary, healthy, white and black men and women, aged 17 to 65 years, performed 20 weeks of supervised cycle ergometer exercise at the same relative intensity and weekly volume. As a group, subjects had normal mean baseline lipid levels for North Americans with the exception of below average high density lipoprotein cholesterol (HDL-C) levels. A significant mean increase in plasma HDL-C of 3.6 % was observed; however, there was marked variability in responsiveness to training, ranging from a mean 9.3 % decrease in Quartile 1 of HDL-C response to a mean 18 % increase in Quartile 4 (P < 0.0001 by ANOVA). Parallel changes in HDL(2)-C and HDL(3)-C, apolipoprotein A-I levels, and lipoprotein lipase activity were noted across quartiles. The change in HDL-C across quartiles was inversely related to baseline HDL-C (p < 0.0001) and to changes with training in plasma triglycerides (p = 0.0007). No significant differences in HDL-C response were observed across quartiles by sex, race, age, or increase in VO(2)max with training; however, weak positive associations were observed with age-adjusted education level and with reduction in abdominal fat and increase in VO(2)max at the ventilatory threshold following training. Multivariate regression analysis including baseline variables and training responses only accounted for 15.5 % of the variability in the HDL-C response to training. Thus, marked variability was found in the HDL-C response to the same endurance exercise training stimulus with only a modest amount of the response predictable by identified nongenetic factors.

Polymorphisms in the leptin receptor gene, body composition and fat distribution in overweight and obese women

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)>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.

Insulin-like growth factor 2 (IGF2 ) and IGF-binding protein 1 (IGFBP1) gene variants are associated with overfeeding-induced metabolic changes

AIMS/HYPOTHESIS

The aim of this study was to investigate the role of insulin-like growth factor 1 (IGF1), IGF2, IGF binding protein 1 (IGFBP1) and IGFBP3 gene variants on the metabolic changes observed in response to a 100-day overfeeding protocol conducted with 12 pairs of monozygotic twins.

METHODS

Genotyping was done by PCR-RFLP and DNA sequencer methods. Body fat measurements included hydrodensitometry and abdominal fat from computed tomography. Plasma glucose and insulin during fasting and in response to an OGTT were assayed. Plasma lipids were measured enzymatically.

RESULTS

In response to caloric surplus, fasting plasma insulin (p < 0.05) and OGTT insulin (p = 0.004) but not glucose area, increased more among the subjects with IGF2 Apa I GG (n = 12) than those with AA + AG (n = 12). The changes were independent of changes in total fatness. The subjects with IGFBP1 Bgl II AA (n = 8) showed greater increases in abdominal visceral fat (p < 0.01), OGTT insulin area (p = 0.05) and total cholesterol (p < 0.03) with overfeeding than the subjects with AG + GG (n = 16). IGFBP3 Nde I and the IGF1 (CT)n markers were not associated with responsiveness to overfeeding.

CONCLUSION/INTERPRETATION

Insulin sensitivity decreased in the subjects with IGF2 Apa I GG and the subjects with IGFBP1 Bgl II AA showed an accumulation of abdominal visceral fat and the early symptoms of the metabolic syndrome after long-term caloric surplus. Genetic variation at the IGF2 and IGFBP1 loci could be among the factors responsible for the inter-individual differences observed in the response to long-term alterations in energy balance and should be further investigated in larger cohorts.

Race differences in the response of postheparin plasma lipoprotein lipase and hepatic lipase activities to endurance exercise training in men: results from the HERITAGE Family Study

Endurance exercise training is known to produce favorable changes in the metabolic profile including reduced plasma triglyceride (TG) and increased high-density lipoprotein (HDL) cholesterol concentrations. These metabolic improvements are likely to contribute to the reduced coronary heart disease (CHD) risk often observed in physically active individuals. However, the physiological mechanisms responsible for such improvements in TG and HDL cholesterol concentrations with endurance exercise are not fully understood. The effect of a 20-week endurance exercise training program on plasma lipoproteins as well as on post-heparin plasma lipoprotein lipase (PH-LPL) and hepatic lipase (PH-HL) activities were therefore examined in a sample of 200 White and 69 Black men who were part of the HERITAGE Family Study. As expected, there were decreases in adiposity and in abdominal fat accumulation following training in both White and Black men. We also found that exercise training was associated with decreases in plasma cholesterol, TG and apolipoprotein B levels, as well as with an increase in HDL cholesterol concentrations in White men. In contrast, Black men showed an increase only in HDL(2) cholesterol over the 20-week period. Higher PH-LPL and lower PH-HL activities were noted in both ethnic groups at follow-up. Whereas in White men improvement of the lipoprotein-lipid profile was related to increased PH-LPL activity, no association between PH-LPL (or PH-HL) and lipoprotein-lipid variables was observed in Black men. Results of the present study suggest that in Whites, the increase in PH-LPL activity in response to endurance exercise training is associated with a better lipoprotein-lipid profile, therefore reducing CHD risk. However, the generally better metabolic profile of Black individuals may minimize further improvement of lipoprotein-lipid concentrations by exercise training.

Familial aggregation of 7-year changes in musculoskeletal fitness

The purpose of this study was to determine the degree of familial resemblance in baseline and 7-year changes in musculoskeletal fitness. Data from the 1981 Canada Fitness Survey and the Campbell's Survey 7-year follow-up were used. The sample consisted of 1264 people (635 males and 629 females) between the ages of 7 and 69 years for whom measurements of musculoskeletal fitness were available at baseline. A subsample of 834 people had measurements at both baseline and 7-year follow-up. Sit-and-reach trunk flexibility, number of push-ups without time limit, number of sit-ups in 60 seconds, and hand-grip strength were used as indicators of musculoskeletal fitness. The data were adjusted for the effects of age and body mass index (and baseline level of the variable for changes) by using regression procedures, and they were standardized to zero mean and unit variance within each of the four sex-by-generation groups (fathers, mothers, sons, and daughters). Familial correlation models were fitted to the data by using the computer software SEGPATH. The results indicate significant familial resemblance for all indicators of musculoskeletal fitness for baseline measures and 7-year changes. The heritabilities, or the percentages of the total variance attributable to heredity, were 64% for trunk flexibility, 37% for push-ups, 59% for sit-ups, and 48% for grip strength. Similarly, heritabilities for the change scores were 48% for trunk flexibility, 52% for push-ups, 41% for sit-ups, and 32% for grip strength. The results suggest that familial, and perhaps genetic, factors are important in explaining the variance in musculoskeletal fitness not only cross-sectionally but also for changes over time.

Familial aggregation of seven-year changes in blood pressure in Canada

OBJECTIVE

To determine the familial resemblance for baseline and seven-year changes in blood pressure in the Canadian population.

METHODS

The study participants were 857 people from 348 families in the 1988 Campbell's Survey, which was a seven-year follow-up of the Canada Fitness Survey. Systolic and diastolic blood pressures were measured at baseline and at follow-up, and were adjusted for age and body mass index by using regression analysis. Familial correlation models were fit to the data by using path analysis, and maximal heritabilities were calculated from the most parsimonious models.

RESULTS

There was significant familial resemblance for baseline blood pressure and changes in blood pressure. In general, all classes of familial correlations (spousal, parent-offspring and sibling) were significant and were of comparable magnitude. The maximal heritabilities, which are influenced to an unknown degree by genes and shared environmental factors, were 50% and 70% for diastolic and systolic blood pressures, respectively, and 66% and 41% for seven-year changes in diastolic and systolic blood pressures, respectively.

CONCLUSIONS

There is significant familial aggregation for blood pressure and for natural changes in blood pressure in the Canadian population. Genes may be important in explaining the familial resemblance for blood pressure; however, the presence of significant spousal correlations suggests that shared lifestyle and family environments are also important factors in the familial aggregation.

Genetic variation at the uncoupling protein 1, 2 and 3 loci and the response to long-term overfeeding

OBJECTIVE

To evaluate the effects of uncoupling protein (UCP) 1, UCP2 and UCP3 gene variants on body composition and metabolic changes in response to chronic overfeeding and the recovery after the period of overfeeding.

SUBJECTS AND DESIGN

Twenty-four normal weight men (21+/-2 y), who constituted 12 pairs of identical twins, ate a 4.2 MJ/day energy surplus, 6 days a week, during a period of 100 days. The subjects were asked to return to the laboratory for testing at 4 months and for a final examination 5 y after completion of the overfeeding protocol.

METHODS

Resting metabolic rate (RMR) measurements were performed before and after overfeeding. A 4.2 MJ test meal was consumed, after which calorimetric measurements were continued for 240 min. Total body fat was assessed by hydrodensitometry and total subcutaneous fat by the sum of eight skinfolds. Polymorphisms were typed by PCR and PCR-RFLP-techniques. Thyroid stimulating hormone (TSH) concentrations after a thyrotropin releasing hormone (TRH) injection were measured by radioimmunoassay (RIA).

RESULTS

The changes in body weight and adiposity were not different between UCP1 Bcl I, UCP2 alanine to valine (A55V), UCP2 insertion/deletion (I/D) or UCP3 Rsa I genotypes. However, the recovery from overfeeding was worse among G-allele carriers of the UCP1 Bcl I, I allele non-carriers of the UCP2 I/D, AV heterozygote subjects of the UCP2 A55V and CC subjects of the UCP3 Rsa I polymorphisms. RMR was lower both before (P=0.01) and after (P=0.001) overfeeding in subjects with the CC genotype of the UCP3 Rsa I polymorphism. Moreover, after overfeeding, the UCP2 A55V heterozygote and UCP3 Rsa I CC homozygote subjects had significantly higher respiratory quotient (RQ) values at rest (P<0.01) and during the meal test (P from<0.01 to<0.05). Also mean plasma TSH concentrations 20, 30 and 45 min after the TRH injection increased more with overfeeding among UCP2 A55V (P<0.005) and UCP3 Rsa I CC (P=0.017) subjects.

CONCLUSIONS

These data suggest that UCP polymorphisms may play a role in the recovery from the overfeeding by regulating substrate oxidation in response to long-term caloric surplus. The association of the UCP2 A55V and UCP3 Rsa I CC genotypes with a greater increase in the TSH response to TRH load could reflect a compensatory mechanism counteracting the effects of overfeeding. A longer period of exposure to chronic positive energy balance conditions may be necessary before sequence variation in UCP2 and UCP3 makes an impact on thyroid metabolism to influence body mass and composition changes.