Basal fat oxidation and after a peak oxygen consumption test in obese women with a beta2 adrenoceptor gene polymorphism

The Glu27Glu genotype in the beta2-adrenergic receptor (ADRB2) has been linked to a higher fat deposition and obesity in females. Also, in our population, it has been described that physically active women carrying the Glu allele had a higher BMI as compared to non-carriers performing the same level of activity. Since exercise may counterbalance a gene predisposition to obesity, we tested the hypothesis of a potential different metabolic response among ADRB2 Gln27Gln versus Glu27Glu obese women when submitted to a peak oxygen consumption test on a treadmill. In our study, 10 obese women with the Gln27Gln genotype were compared to 9 matched obese women bearing the Glu27Glu genotype. The ADRB2 polymorphism was identified by PCR-RFLP, fat oxidation was determined by indirect calorimetry and blood measurements were carried out following conventional procedures. The ADRB2 Glu27Glu subjects had lower plasma glycerol levels (P = 0.026), while plasma triglycerides (P <0.001) and the insulin:glucose ratio were higher (P = 0.046) as compared to the Gln27Gln group along the peak oxygen consumption trial intervention. There was a significantly lower fat oxidation (P = 0.024) in the Glu27Glu obese women during the recovery compared to Gln27Gln obese individuals. These data suggest that exercise would not benefit equally the two ADRB2 polymorphism homozygous groups, since both lipolysis and fat oxidation promoted by a peak oxygen consumption test appear to be blunted in the polymorphic Glu27Glu obese group.     

Role of β2‐Adrenergic Receptor Polymorphisms on Body Weight and Body Composition Response to Energy Restriction in Obese Women: Preliminary Results

We investigated the role of common β2‐adrenergic receptor (ADRB2) rs1042714 (Gln27Glu) and rs1042713 (Arg16Gly) polymorphisms on body weight and body composition response to 12‐week energy‐restricted diet in women. The study comprised 78 Spanish obese (BMI: 34.0 ± 2.8 kg/m²) women (age: 36.7 ± 7 years). We measured (before and after the dietary intervention) weight and height, and BMI calculated. Moreover, body fat mass and lean mass (LM) were measured by dual energy X‐ray absorptiometry. We observed an interaction effect between the Gln27Glu polymorphism and diet‐induced changes on body weight (P = 0.006), BMI (P = 0.004), and LM (P = 0.001). Women carrying the Glu allele had a greater reduction in body weight than non‐Glu allele carriers (9.5 ± 2.9 vs. 7.0 ± 3.5%, respectively, P = 0.002). Moreover, women with the Glu allele lost more LM than the Gln27Gln group (5.9 ± 2.7 vs. 4.0 ± 2.7%, respectively, P = 0.001). We did not find any significant interaction effect between the Arg16Gly polymorphism and diet‐induced changes on the outcome variables (all P > 0.1). The results suggest that the ADRB2 Gln27Glu polymorphism has a modulating effect on diet‐induced changes on body weight and body composition, and should be considered in future obesity treatments. These findings should be taken as preliminary and be replicated in further energy restriction studies with larger sample sizes.     

Different genes and polymorphisms affecting high-density lipoprotein cholesterol levels in Greek familial hypercholesterolemia patients

Familial Hypercholesterolemia (FH) is a genetic disorder characterized by high low-density lipoprotein cholesterol (LDL-C) concentrations that frequently gives rise to premature coronary artery disease. The clinical expression of FH is highly variable, even in patients carrying the same LDL receptor gene mutation. This variability may be due to environmental and other genetic factors. We investigated the effect of APOCIII T1100C, FV Gln506Arg, ADRB2 Glu27Gln, SELE Ser128Arg, SELE Leu554Phe, and ENaCa Ala663Thr polymorphisms on the HDL-C variations in 84 patients with FH. For ApoCIII T1100C, subjects with the TT genotype presented higher HDL-C levels than the other genotype groups (p = 0.046). Similarly the presence of the Gln allele in ADRB2 27 Glu/Gln heterozygotes and ADRB2 27 Gln/Gln homozygotes was associated with higher HDL-C levels (p = 0.014). Among the other polymorphisms tested, none of them were associated with variations in HDL-C levels. The influence of each polymorphism on lipid concentrations was evaluated with linear regression analyses after adjustment for age and sex. Among the variables studied including total cholesterol, LDL-C, high-density lipoprotein (HDL)-C, triglycerides, apolipoprotein A (Apo-A) and B (Apo-B), and lipoprotein alpha (LP alpha), HDL-C concentration was significantly different in models applied for polymorphisms ApoCIII T1100C, FV Gln506Arg, and ADRB2 Glu27Gln (p = 0.01, p = 0.018, p = 0.04, respectively). These results suggest that HDL-C levels in FH heterozygotes may be affected by several different genetic variants.     

ADRB2 Haplotype Is Associated With Glucose Tolerance and Insulin Sensitivity in Obese Postmenopausal Women

The β₂‐adrenergic receptor (ADRB2) mediates obesity, cardiorespiratory fitness, and insulin resistance. We examined the hypothesis that ADRB2 Arg16Gly‐Gln27Glu haplotype is associated with body composition, glucose tolerance, and insulin sensitivity in obese, postmenopausal women. Obese (>35% body fat), postmenopausal (age 45–75 years) women (n = 123) underwent genotyping, dual‐energy X‐ray absorptiometry, and computed tomography scans, exercise testing (VO_2max), 2‐h oral glucose tolerance tests (OGTTs), and hyperinsulinemic‐euglycemic clamps (80 mU/m²/min). Analysis of covariance (ANCOVA) tested for differences among haplotypes, with race, % body fat, and VO_2max as covariates. We found that ADRB2 haplotype was independently associated with % body fat, abdominal fat distribution, VO_2max, insulin sensitivity (M/ΔInsulin), and glucose tolerance (ANOVA, P < 0.05 for all). Women homozygous for Gly16–Gln27 haplotype had the highest % body fat (52.7 ± 1.9%), high abdominal fat, low M/ΔInsulin (0.49 ± 0.08 mg/kg/min/pmol/l/10²), and impaired glucose tolerance (IGT) during an OGTT (G₁₂₀ = 10.2 ± 0.9 mmol/l). Women homozygous for Gly16–Glu27 haplotype also had low M/ΔInsulin (0.51 ± 0.05 mg/kg/min/pmol/l/10²) and IGT (G₁₂₀ = 8.2 ± 0.7 mmol/l). Subjects with Arg16–Gln27/Gly16–Gln27 haplotype combination had the highest VO_2max (1.84 ± 0.07 l/min) and M/ΔInsulin (0.7 ± 0.04 mg/kg/min/pmol/l/10²), and normal glucose tolerance (G₁₂₀ = 6.4 ± 0.4 mmol/l), despite being obese. These data show associations of the ADRB2 Arg16Gly‐Gln27Glu haplotype with VO_2max and body composition, and an independent association with glucose metabolism, which persists after controlling for body composition and fitness. This suggests that ADRB2 haplotypes may mediate insulin action, glucose tolerance, and potentially risk for type 2 diabetes mellitus (T2DM) in obese, postmenopausal women.     

Effects of β2‐Adrenergic Receptor Gene Variants on Adiposity: The HERITAGE Family Study

We investigated whether the Arg16Gly and Gln27Glu polymorphisms of the β2‐adrenergic receptor gene were associated with body‐fat and fat‐distribution phenotypes measured before and in response to a 20‐week endurance‐training program. BMI, fat mass (FAT), percentage of body fat (%FAT), sum of eight skinfolds (SF8), and abdominal fat areas assessed by computed tomography were measured in adult sedentary white and black participants of the HERITAGE Family Study. Evidence of gene‐by‐obesity interaction was found in whites for several adiposity phenotypes measured before training. Analyses performed separately in nonobese and obese subjects revealed that obese men carrying the Glu27 allele have lower fat accumulation (BMI, FAT, and %FAT) than noncarriers. Among white obese women, Gly16Gly homozygotes had a lower fat accumulation (BMI, FAT, and SF8) than Arg16Gly and Arg16Arg carriers. In response to endurance training, white women with the Arg16Arg genotype exhibited a greater reduction in BMI, FAT, and %FAT. Results observed in blacks were mostly negative. These results suggest that polymorphisms in the β2‐adrenergic receptor gene influence the amount of body fat in white obese men (Gln27Glu) and women (Arg16Gly), as well as the changes in adiposity in response to endurance training in white women (Arg16Gly).     

The Gln27Glu beta2-adrenergic receptor variant is associated with obesity due to subcutaneous fat accumulation in Japanese men

The Trp64Arg beta3-adrenergic receptor (AR) variant is associated with visceral obesity probably due to decreased lipolysis in visceral fat (H. Kim-Motoyama et al., Diabetologia 40, 469-472, 1997). Functional alteration of beta2AR may also change fat distribution. We investigated the influence of the Gln27Glu beta2AR variant upon obesity and fat distribution. We screened 278 unrelated Japanese men and detected 249 wild-type Gln27 homozygotes, 28 Gln27/Glu27 heterozygotes, and one mutant Glu27 homozygote. The frequency of mutant Glu27 allele was significantly higher in obese subjects than in nonobese/intermediate subjects (0.11 vs 0.04, P = 0. 004). The Gln27/Glu27 heterozygotes had a significantly higher mean age-adjusted body-mass index (BMI) and mean age-adjusted subcutaneous fat area assessed by CT scan than the wild-type homozygotes but not the mean age-adjusted visceral fat areas. In summary, we have found that in Japanese men the Gln27Glu beta2AR variant is associated with obesity due to subcutaneous fat accumulation.     

Effect of exercise training at different intensities on fat metabolism of obese men.

The present study investigated the effect of exercise training at different intensities on fat oxidation in obese men. Twenty-four healthy male obese subjects were randomly divided in either a low- [40% maximal oxygen consumption (VO(2 max))] or high-intensity exercise training program (70% VO(2 max)) for 12 wk, or a non-exercising control group. Before and after the intervention, measurements of fat metabolism at rest and during exercise were performed by using indirect calorimetry, [U-(13)C]palmitate, and [1,2-(13)C]acetate. Furthermore, body composition and maximal aerobic capacity were measured. Total fat oxidation did not change at rest in any group. During exercise, after low-intensity exercise training, fat oxidation was increased by 40% (P < 0.05) because of an increased non-plasma fatty acid oxidation (P < 0.05). High-intensity exercise training did not affect total fat oxidation during exercise. Changes in fat oxidation were not significantly different among groups. It was concluded that low-intensity exercise training in obese subjects seemed to increase fat oxidation during exercise but not at rest. No effect of high-intensity exercise training on fat oxidation could be shown.     

Obesity-related gene ADRB2, ADRB3 and GHRL polymorphisms and the response to a weight loss diet intervention in adult women

The individual response to diet may be influenced by gene polymorphisms. This study hypothesized that ADRB2 (Gln27Glu, rs1042714 and Arg16Gly, rs1042713), ADRB3 (Trp64Arg, rs4994) and GHRL (Leu72Met, rs696217) polymorphisms moderate weight loss. The study was a seven weeks dietary weight loss intervention with Brazilian adult obese women (n = 109). The body mass index (BMI) was calculated and polymorphisms in these genes were assessed by real-time PCR assays. Two-way repeated-measures ANOVA (2 × 2) were used to analyze the intervention effect between polymorphisms and BMI over the period and after stratification for age and socioeconomic status (SES). The weight loss intervention resulted in decreased BMI over the seven-week period (p < 0.001), for high and low SES (p < 0.05) and mainly for participants with 30–49 y. The intervention did not result in a statistically significant difference in weight loss between polymorphism carriers and non-carriers, and although, the ADRB2, ADRB3 and GHRL polymorphisms did not moderate weight loss, the Gln27Glu polymorphism carriers showed a lower BMI compared to non-carriers in the low SES (p = 0.018) and the 30–39 y (p = 0.036) groups, suggesting a role for this polymorphism related to BMI control.     

Beta2- and beta3-adrenergic receptor polymorphisms and exercise hemodynamics in postmenopausal women.

We sought to determine whether common genetic variations at the beta2 (beta2-AR, Gln27Glu) and beta3 (beta3-AR, Trp64Arg) adrenergic receptor gene loci were associated with cardiovascular (CV) hemodynamics during maximal and submaximal exercise. CV hemodynamics were assessed in 62 healthy postmenopausal women (20 sedentary, 22 physically active, and 20 endurance athletes) during treadmill exercise at 40, 60, 80, and 100% maximal O2 uptake using acetylene rebreathing to quantify cardiac output. The beta2-AR genotype and habitual physical activity (PA) levels interacted to significantly associate with arteriovenous O2 difference (a-vDO2) during submaximal exercise (P = 0.05), with the highest submaximal exercise a-vDO2 in sedentary women homozygous for the beta2-AR Gln allele and no genotype-dependent differences in submaximal exercise a-vDO2 in physically active and athletic women. The beta2-AR genotype also was independently associated with a-vDO2 during submaximal (P = 0.004) and approximately 100% maximal O2 uptake exercise (P = 0.006), with a 1.2-2 ml/100 ml greater a-vDO2 in the Gln/Gln than in the Glu/Glu genotype women. The beta3-AR genotype, independently or interacting with habitual PA levels, was not significantly associated with any CV hemodynamic variables during submaximal or maximal exercise. Thus it appears that the beta2-AR genotype, both independently and interacting with habitual PA levels, is significantly associated with a-vDO2 during exercise in postmenopausal women, whereas the beta3-AR genotype does not appear to be associated with any maximal or submaximal exercise CV hemodynamic responses in postmenopausal women.     

Polymorphisms in ADRB2 gene can modulate the response to bronchodilators and the severity of cystic fibrosis

ABSTRACT: BACKGROUND: The most common cystic fibrosis (CF) manifestation is the progressive chronic obstructive pulmonary disease caused by deficiency, dysfunction, or absence of the CFTR (Cystic Fibrosis Transmembrane Regulator) protein on the apical surface of the cells in the respiratory tract. The use of bronchodilators (BD), and inhaled corticosteroids (IC) have been suggested for the management of airway inflammation in CF. The effectiveness of BD and IC have been verified, proven in laboratory and in the clinical treatment for asthma patients. However, in CF, the effectiveness of these drugs is controversial. The extent of asthma's response to BD depends on the presence of polymorphisms in the ADRB2 gene. In contrast, in CF, little is known about the response to the BD and the association of CF's severity with the different polymorphisms in ADRB2 gene. In this context, our objective was to verify whether the Arg16Gly and Glu27Gln polymorphisms in ADRB2 gene are associated with severity and with the bronchodilator response in CF patients. METHOD: Cross-sectional study of 122 CF patients subjected to analysis of mutations in the CFTR gene, polymorphisms in ADRB2 gene, along with clinical and laboratorial characteristics of severity. Result The Arg16Gly polymorphism in ADRB2 gene was associated with pancreatic insufficiency(p:0.009), Bhalla score(p:0.039), forced expiratory volume in the first second[FEV1(%)](p:0.003), forced expiratory flow between 25 and 75% of the forced vital capacity-FVC[FEF25-75(%)](p:0.008) and lower age at the first isolation of the Pseudomonas aeruginosa(p:0.012). The response to the BD spirometry was associated with clinical severity markers, FEV1(%)(p:0.011) and FEF25-75(%)(p:0.019), for the Arg16Gly polymorphism in the ADRB2 gene. The haplotype analysis showed association with the FEV1/FVC marker from the spirometry test, before and after using the BD, with higher values in the group with Gly/Gly and Glu/Glu, respectively, for the Arg16Gly and Gln27Glu polymorphisms. The analysis by MDR2.0 software, showed association with FEF25-75%; the response to Arg16Gly was respondent by 17.35% and Gln27Glu by 6.8% in variation found. CONCLUSION: There was an association between the Arg16Gly and Gln27Glu polymorphisms in ADRB2 gene with CF's severity and bronchodilator response.     

Cardiopulmonary responses to exercise in obese girls and young women.

A study of exercise performance was carried out in 17 obese girls and young adults. During submaximal steady-state bicycle exercise oxygen intake (Vo2) for a given work output (W) was raised in obese subjects but minute ventilation at a fixed carbon dioxide output, gas exchange, blood gases, and cardiac output at a given VO2 were similar to the values previously found for normals. In obese subjects high levels of VO2 for fixed W were also obtained on the treadmill but when these were standardized for body weight (unlike the bicycle test) it was shown that the obese girls and women exercised within the normal (expected) range of aerobic energy expenditure. During maximal performance the absolute VO2 max was the same in obese and nonobese subjects but for a given body weight, lean body mass, and leg muscle (plus) bone volume, VO2max was reduced by 23.8, 16.3, and 24.5% respectively, in the former group. It was concluded that obesity though having minimal affect on responses to submaximal exercise is nevertheless associated with a marked reduction in physiological performance at or near maximal effort.     

Role ofADRB2 gene polymorphism in asthma and response to β2-agonists in Polish children

The aims of this study were: (1) to find associations of asthma with single-nucleotide polymorphisms (SNPs) within theADRB2 gene: Arg16Gly, Gln27Glu, −1023 G/A, −367 T/C, −47 C/T ; (2) to define linkage disequilibrium in the gene region, basing on the analyzed SNPs; and (3) to analyze the importance ofADRB2 polymorphism for response to bronchodilator drugs in children diagnosed with bronchial asthma. We compared 113 asthmatic children and 123 healthy subjects from the Polish population. Genotyping was performed by PCR-RFLP. We found an association of the A allele of −1023A/GADRB2 polymorphism with asthma (P = 0.024). No significant associations with other SNPs were detected. Moderate linkage was found between Gln27Glu and −47C/T polymorphisms in linkage disequilibrium analysis (D’ = 0.85,r ² = 0.429, LOD = 31.97). No significant differences were found in haplotype frequencies in comparison to the control group, implicating that they are not associated with susceptibility to asthma in the analyzed population. There was no significant correlation between the analyzed SNPs of theADRB2 gene and the response to β₂-agonists. This is the first report providing suggestive evidence for association of —1023A/GADRB2 polymorphism with an increased risk of asthma. The analyzed SNPs may not play a major role in response to β₂-agonists in asthmatic children.     

ADRB2 and LEPR gene polymorphisms: synergistic effects on the risk of obesity in Japanese

The objective of the present study was to validate a recently reported synergistic effect between variants located in the leptin receptor (LEPR) gene and in the β-2 adrenergic receptor (ADRB2) gene on the risk of overweight/obesity. We studied a middle-aged/elderly sample of 4,193 nondiabetic Japanese subjects stratified according gender (1,911 women and 2,282 men). The LEPR Gln223Arg (rs1137101) variant as well as both ADRB2 Arg16Gly (rs1042713) and Gln27Glu (rs1042714) polymorphisms were analyzed. The primary outcome was the risk of overweight/obesity defined as BMI ≥25 kg/m(2), whereas secondary outcomes included the risk of a BMI ≥27 kg/m(2) and BMI as a continuous variable. None of the studied polymorphisms showed statistically significant individual effects, regardless of the group or phenotype studied. Haplotype analysis also did not disclose any associations of ADRB2 polymorphisms with BMI. However, dimensionality reduction-based models confirmed significant interactions among the investigated variants for BMI as a continuous variable as well as for the risk of obesity defined as BMI ≥27 kg/m(2). All disclosed interactions were found in men only. Our results provide external validation for a male specific ADRB2-LEPR interaction effect on the risk of overweight/obesity, but indicate that effect sizes associated with these interactions may be smaller in the population studied.     

Association of Codon 16 and Codon 27 β2‐Adrenergic Receptor Gene Polymorphisms with Obesity: A Meta‐analysis

Objective: To search for an association between the Glu27Gln (rs1042714; B27) and the Arg16Gly (rs1042713; B16) polymorphisms of the β2‐adrenergic receptor (ADRB2) gene and obesity. Methods: Meta‐analysis of published studies, included if subjects were genotyped at either codon 27 (“B27”) or codon 16 (“B16”) of the ADRB2 gene and both obese and nonobese subjects were selected, based on a reported cutoff BMI limit. Initial selection included 14,444 subjects genotyped at B27 (rs1042714) and 6,825 genotyped at B16 (rs1042713). After testing each control group for Hardy‐Weinberg equilibrium, the final selection included 10,404 subjects and 4,328 subjects, respectively. Studies were published before 18 August 2006. Results: The frequency of Glu27 allele carriers, either homozygous or heterozygous, ranged from 6.71% in Aymara American Indians to 78.29% in a Dutch population. The frequency of Arg16 allele carriers varied from 51.4 to 64.6% in Europeans and from 71.1 to 85.6% in East Asians. The summary odds ratio (OR) from overall analyses showed no association between either rs1042714 or rs1042713 and obesity. In race groups with low Glu27 allele frequency (Asians, Pacific Islanders, and American Indians), ORs revealed a significant obesity risk associated with rs1042714. These results were not found in East Asians for rs1042713. Discussion: The presence of the Glu27 allele in the ADRB2 gene appears to be a significant risk factor for obesity in Asians, Pacific Islanders, and American Indians, but not in Europeans. Obesity does not appear to be associated with the Arg16 allele.     

Exercise intensity: effect on postexercise O2 uptake in trained and untrained women

Despite many reports of long-lasting elevation of metabolism after exercise, little is known regarding the effects of exercise intensity and duration on this phenomenon. This study examined the effect of a constant duration (30 min) of cycle ergometer exercise at varied intensity levels [50 and 70% of maximal O2 consumption (VO2max)] on 3-h recovery of oxygen uptake (VO2). VO2 and respiratory exchange ratios were measured by open-circuit spirometry in five trained female cyclists (age 25 +/- 1.7 yr) and five untrained females (age 27 +/- 0.8 yr). Postexercise VO2 measured at intervals for 3 h after exercise was greater (P less than 0.01) after exercise at 50% VO2max in trained (0.40 +/- 0.01 l/min) and untrained subjects (0.39 +/- 0.01 l/min) than after 70% VO2max in (0.31 +/- 0.02 l/min) and untrained subjects (0.29 +/- 0.02 l/min). The lower respiratory exchange ratio values (P less than 0.01) after 50% VO2max in trained (0.78 +/- 0.01) and untrained subjects (0.80 +/- 0.01) compared with 70% VO2max in trained (0.81 +/- 0.01) and untrained subjects (0.83 +/- 0.01) suggest that an increase in fat metabolism may be implicated in the long-term elevation of metabolism after exercise. This was supported by the greater estimated fatty acid oxidation (P less than 0.05) after 50% VO2max in trained (147 +/- 4 mg/min) and untrained subjects (133 +/- 9 mg/min) compared with 70% VO2max in trained (101 +/- 6 mg/min) and untrained subjects (85 +/- 7 mg/min).     

Human-Specific SNP in Obesity Genes, Adrenergic Receptor Beta2 (ADRB2), Beta3 (ADRB3), and PPAR γ2 (PPARG), during Primate Evolution

Adrenergic-receptor beta2 (ADRB2) and beta3 (ADRB3) are obesity genes that play a key role in the regulation of energy balance by increasing lipolysis and thermogenesis. The Glu27 allele in ADRB2 and the Arg64 allele in ADRB3 are associated with abdominal obesity and early onset of non-insulin-dependent diabetes mellitus (NIDDM) in many ethnic groups. Peroxisome proliferator-activated receptor γ (PPARG) is required for adipocyte differentiation. Pro12Ala mutation decreases PPARG activity and resistance to NIDDM. In humans, energy-expense alleles, Gln27 in ADRB2 and Trp64 in ADRB3, are at higher frequencies than Glu27 and Arg64, respectively, but Ala12 in PPARG is at lower frequency than Pro12. Adaptation of humans for lipolysis, thermogenesis, and reduction of fat accumulation could be considered by examining which alleles in these genes are dominant in non-human primates (NHP). All NHP (P. troglodytes, G. gorilla, P. pygmaeus, H. agilis and macaques) had energy-thrifty alleles, Gly16 and Glu27 in ADRB2, and Arg64 in ADRB3, but did not have energy-expense alleles, Arg16, Gln27 and Trp64 alleles. In PPARG gene, all NHP had large adipocyte accumulating type, the Pro12 allele. CONCLUSIONS: These results indicate that a tendency to produce much more heat through the energy-expense alleles developed only in humans, who left tropical rainforests for savanna and developed new features in their heat-regulation systems, such as reduction of body hair and increased evaporation of water, and might have helped the protection of entrails from cold at night, especially in glacial periods.     

Muscle morphological and biochemical adaptations to training in obese Zucker rats

The purposes of the present study were to characterize the histochemical and enzymatic profiles of various hindlimb skeletal muscles, as well as to determine maximal O2 consumption (VO2max) and respiratory exchange ratios (R) during steady-state exercise in the obese Zucker rat. The changes that occurred in these parameters in response to a 6-wk training program were then assessed. Obese rats were randomly assigned to a sedentary or training group. Lean littermates served as a second control. Training consisted of treadmill running at 18 m/min up an 8% grade, 1.5 h/day, 5 day/wk for 6 wk. During week 6, VO2max and R during a steady-state run (74% max) were determined. After 2 days of inactivity, hindlimb muscles were excised, stained for fiber type and capillaries, and assayed for hexokinase, citrate synthase, cytochrome oxidase, and beta-hydroxyacetyl-CoA dehydrogenase. The obese sedentary rats demonstrated greater oxidative enzyme activities per gram of muscle tissue than their lean littermates, greater R values during submaximal exercise of the same relative intensity, and greater absolute VO2max values. Training resulted in a 20-56% increase in oxidative enzymes, a 10% increase in VO2max, and an increase in capillary density in the soleus and plantaris. There was no alteration in R values during exercise at 74% VO2max or in fiber type composition in response to exercise training. Results suggest that the muscle of the obese Zucker rat manifests a greater oxidative capacity than the muscle of its lean littermates. The apparent inability of the obese rat to increase its use of fat during submaximal exercise of the same relative intensity in response to training remains to be elucidated.     

Plasma FFA responses to prolonged walking in untrained men and women

Gender differences in plasma FFA responses to 90 min of treadmill walking at 35% VO2max were investigated in six men and six women following an overnight fast. The subjects represented average values for maximal oxygen uptake and body fat percentage for age and gender. Mean plasma FFA concentration at 45 and 90 min of exercise were significantly (P less than 0.05) higher for women (0.82 mmol X 1(-1), 0.88 mmol X 1(-1)) than men (0.42 mmol X 1(-1), 0.59 mmol X 1(-1)). Lower R values for women throughout the exercise period indicated a greater percentage fat in total metabolism than for men while the FFA/glycerol results supported greater lipolytic activity for women. The uniformity of percent fat in metabolism for women from rest to exercise showed that FFA release from adipose tissue increased rapidly with the onset of exercise which was not the case for men. Comparison of metabolic data as well as a statistical analysis (ANCOVA) controlling for the influence of VO2max and percentage body fat on FFA plasma concentration suggested that gender differences in FFA responses to prolonged submaximal exercise can be expected to occur in untrained subjects.     

Effects of aerobic exercise on serum leptin levels in obese women

It has been demonstrated that leptin concentrations in obese patients may be altered by weight loss. We examined the effects of a 9-week aerobic exercise program on serum leptin concentrations in overweight women (20-50% above ideal body mass) under conditions of weight stability. Sixteen overweight women, mean (SE) age 42.75 (1.64) years, comprised the exercise group which adhered to a supervised aerobic exercise program. A graded exercise treadmill test was conducted before and after the exercise program to determine maximal oxygen uptake (VO2max) using open-circuit spirometry. The women demonstrated improved aerobic fitness (VO2max increased 12.29%), however, body fat and the body mass index did not change significantly [42.27 (1.35)-41.87 (1.33)%]. Fourteen women, age 40.57 (2.80) years, did not exercise over the same time period and served as a control group. Serum leptin levels were not significantly altered for either the exercise [28.00 (2.13)-31.04 (2.71) ng x ml(-1)] or the control group [33.24 (3.78)-34.69 (3.14) ng x mg(-1)]. The data indicate that 9 weeks of aerobic exercise improves aerobic fitness, but does not affect leptin concentrations in overweight women.