Serum Lipoproteins in Overweight/Obese Postmenopausal Women

Aerobic Exercise and Weight Loss in Adults: A Systematic Review and Dose-Response Meta-Analysis

Importance

Current guidance on the duration of aerobic exercise recommended in existing guidelines comes primarily from individual trials. Meta-analyses are lacking to examine the dose-response association of aerobic exercise with adiposity measures.

Objective

To clarify the dose-response association of aerobic exercise with adiposity measures.

Data Sources

PubMed, Scopus, the Cochrane Central Register of Controlled Trials, and gray literature sources (ProQuest and ClinicalTrials.gov) from inception to April 30, 2024.

Study Selection

Randomized clinical trials with intervention durations of at least 8 weeks evaluating the effects of supervised aerobic training on adults with overweight or obesity.

Data Extraction and Synthesis

The PRISMA guidelines were followed to report the results of the meta-analysis. Data extraction was conducted by 2 teams of 2 reviewers each, working independently and in duplicate. Random-effects meta-analyses were performed to estimate mean differences and 95% CIs for each 30-minute per week aerobic exercise and to clarify the shape of the curvilinear associations.

Main Outcomes and Measures

Measures of body weight, waist circumference, body fat, adverse events, medication use reduction, and health-related quality of life score. The certainty of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) tool, with a range from very low to high certainty.

Results

In total, 116 randomized clinical trials involving 6880 participants (4199 [61%] female; mean [SD] age, 46 [13] years) with overweight or obesity were included. Each 30 minutes per week of aerobic exercise was associated with reduced body weight by 0.52 kg (95% CI, -0.61 to -0.44 kg; n = 109 trials, GRADE = moderate), waist circumference by 0.56 cm (95% CI, -0.67 to -0.45 cm; n = 62 trials, GRADE = high), body fat percentage by 0.37% (95% CI, -0.43% to -0.31%; n = 65 trials, GRADE = moderate), as well as the areas of visceral (mean difference, -1.60 cm2 [95% CI, -2.12 to -1.07 cm2]; n = 26 trials, GRADE = high) and subcutaneous (mean difference, -1.37 cm2 [95% CI, -1.82 to -0.92 cm2]; n = 27 trials, GRADE = moderate) adipose tissues. Aerobic exercise was associated with modestly increased physical (standardized mean difference, 1.69 SD [95% CI, 1.18-2.20 SD]) and mental (standardized mean difference, 0.74 SD [95% CI, 0.29-1.19 SD]) aspects of quality of life (1 trial with 80 participants, GRADE = low). It was associated with modestly increased mild to moderate adverse events, which were mostly musculoskeletal symptoms (risk difference, 2 more events per 100 participants [95% CI, 1 to 2 more]; GRADE = low). Dose-response meta-analyses indicated that body weight, waist circumference, and body fat measures decreased linearly or monotonically in association with increasing duration of aerobic exercise to 300 minutes per week, with aerobic exercise lasting 150 minutes per week at moderate to vigorous intensities resulting in clinically important reductions in waist circumference and body fat.

Conclusions and Relevance

In this meta-analysis of randomized clinical trials, engaging in 30 minutes of aerobic exercise per week was associated with modest reductions in body weight, waist circumference, and body fat measures among adults with overweight or obesity. However, aerobic training exceeding 150 minutes per week at moderate intensity or greater may be needed to achieve clinically important reductions.

Estimating the Effect of Aerobic Exercise Training on Novel Lipid Biomarkers: A Systematic Review and Multivariate Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Aerobic exercise training (AET) prescribed as lipid management treatment positively affects the standard lipid profile and reduces cardiovascular disease (CVD) risk. Apolipoproteins, lipid and apolipoprotein ratios, and lipoprotein sub-fractions may more effectively predict CVD risk than the standard lipid profile but an AET response in these biomarkers has not been established.

OBJECTIVES

We conducted a quantitative systematic review of randomised controlled trials (RCTs) to (1) determine the effects of AET on lipoprotein sub-fractions, apolipoproteins and relevant ratios; and (2) identify study or intervention covariates associated with change in these biomarkers.

METHODS

We searched PubMed, EMBASE, all Web of Science and EBSCO health and medical online databases from inception to 31 December 2021. We included published RCTs of adult humans with ≥ 10 per group of participants; an AET intervention duration ≥ 12 weeks of at least moderate intensity (> 40% maximum oxygen consumption); and reporting pre/post measurements. Non-sedentary subjects, or those with chronic disease other than Metabolic Syndrome factors, or pregnant/lactating, as well as trials testing diet/medications, or resistance/isometric/unconventional training interventions, were excluded.

RESULTS

Fifty-seven RCTs totalling 3194 participants were analysed. Multivariate meta-analysis showed AET significantly raised antiatherogenic apolipoproteins and lipoprotein sub-fractions (mmol/L mean difference (MD) 0.047 (95% confidence interval (CI) 0.011, 0.082), P = .01); lowered atherogenic apoliproteins and lipoprotein sub-fractions (mmol/L MD - 0.08 (95% CI - 0.161, 0.0003), P = .05); and improved atherogenic lipid ratios (MD - 0.201 (95% CI - 0.291, - 0.111), P < .0001). Multivariate meta-regression showed intervention variables contributed to change in lipid, sub-fraction, and apoliprotein ratios.

CONCLUSION

Aerobic exercise training positively impacts atherogenic lipid and apolipoprotein ratios, alipoproteins, and lipoprotein sub-fractions; and antiatherogenic apolipoproteins and lipoprotein sub-fractions. Cardiovascular disease risk predicted by these biomarkers may be lowered when AET is prescribed as treatment or prevention.

PROSPERO ID

CRD42020151925.

The effect of aerobic exercise on pulse wave velocity in middle-aged and elderly people: A systematic review and meta-analysis of randomized controlled trials

A growing body of research examines the effect of aerobic exercise on pulse wave velocity (PWV) in middle-aged and elderly people, while findings of available studies were conflicting. The aim of this study was to explore the effect of aerobic exercise on PWV in middle-aged and elderly people. Searches were performed in PubMed, Web of Science, and EBSCO databases. Cochrane risk assessment tool was used to evaluate the methodological quality of the included literature. We included studies that satisfied the following criteria: (1) eligible studies should be randomized controlled trials (RCTs); (2) eligible studies should include both an intervention and a control group; (3) eligible studies should use the middle-aged or elderly people as subjects; and (4) eligible studies should use PWV as the outcome measure. From 972 search records initially identified, 11 studies with a total of 12 exercise groups (n = 245) and 11 control groups (n = 239) were eligible for meta-analysis. There was a significant effect of aerobic exercise on reducing PWV in middle-aged and elderly people [weighted mean difference (WMD), -0.75 (95% CI, -1.21 to -0.28), p = 0.002]. Specifically, a higher intensity [vigorous-intensity, -0.74 (-1.34 to -0.14), p = 0.02; moderate-intensity, -0.68 (-1.49 to 0.12), p = 0.10], a younger age [45 years ≤ age < 60 years, -0.57 (-0.78 to -0.37), p < 0.00001; age ≥ 60 years, -0.91 (-2.10 to 0.27), p = 0.13], a better health status [healthy, -1.19 (-2.06 to -0.31), p = 0.008; diseased, -0.32 (-0.64 to -0.01), p = 0.04], and a lower basal body mass index (BMI) [BMI < 25, -1.19 (-2.06 to -0.31), p = 0.008; 25 ≤ BMI < 30, -0.52 (-0.92 to -0.12), p = 0.01; BMI ≥ 30, -0.09 (-0.93 to 0.76), p = 0.84] were associatedwith larger reductions in PWV. Aerobic exercise, especially vigorous-intensity aerobic exercise, contributed to reducing PWV in middle-aged and elderly people. The effect of aerobic exercise on improving PWV was associated with characteristics of the participants. Specifically, a younger age, a better health status, and a lower basal BMI contributed to more significant reductions in PWV.

SYSTEMATIC REVIEW REGISTRATION

[https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022337103], identifier [CRD42022337103].

Comparative Efficacy of 5 Exercise Types on Cardiometabolic Health in Overweight and Obese Adults: A Systematic Review and Network Meta-Analysis of 81 Randomized Controlled Trials

BACKGROUND

Although regular exercise is recommended for preventing and treating overweight/obesity, the most effective exercise type for improving cardiometabolic health in individuals with overweight/obesity remains largely undecided. This network meta-analysis aimed to evaluate and rank the comparative efficacy of 5 exercise modalities on cardiometabolic health measures in individuals with overweight/obesity.

METHODS

A database search was conducted in MEDLINE, Embase, Scopus, and Web of Science from inception up to September 2020. The review focused on randomized controlled trials involving exercise interventions consisting of continuous endurance training, interval training, resistance training, combined aerobic and resistance training (combined training), and hybrid-type training. Exercise interventions aimed to improve somatometric variables, body composition, lipid metabolism, glucose control, blood pressure, cardiorespiratory fitness, and muscular strength. The Cochrane risk of bias tool was used to evaluate eligible studies. A random-effects network meta-analysis was performed within a frequentist framework. The intervention ranking was carried out using a Bayesian model where mean and SD were equal to the respective frequentist estimates.

RESULTS

A total of 4331 participants (59% female; mean age: 38.7±12.3 years) from 81 studies were included. Combined training was the most effective modality and hybrid-type training the second most effective in improving cardiometabolic health-related outcomes in these populations suggesting a higher efficacy for multicomponent exercise interventions compared to single-component modalities, that is, continuous endurance training, interval training, and resistance training. A subgroup analysis revealed that the effects from different exercise types were mediated by gender.

CONCLUSIONS

These findings corroborate the latest guidelines on exercise for individuals with overweight/obesity highlighting the importance of a multicomponent exercise approach to improve cardiometabolic health. Physicians and healthcare professionals should consider prescribing multicomponent exercise interventions to adults with overweight/obesity to maximize clinical outcomes.

REGISTRATION

URL: https://www.crd.york.ac.uk/PROSPERO/; Unique identifier: CRD42020202647.

Comparison of time-matched aerobic, resistance or combined exercise training in women living with obesity: a protocol for a pilot randomised controlled trial-the EXOFFIT (Exercise for Obesity in Females to increase Fitness) study

INTRODUCTION

Obesity in women has more than doubled in the past thirty years. Increasing research suggests that increased cardiorespiratory fitness (CRF) can largely attenuate the negative health risks associated with obesity. Though previous literature suggests that combined training may be the most effective for improving CRF in adults with obesity, there is minimal research investigating the efficacy of combined and resistance programmes in women with obesity. This article outlines a protocol for a parallel pilot study which aims to evaluate the feasibility and efficacy of three exercise modalities in women with obesity for increasing CRF and strength and improving body composition and other health outcomes (i.e. quality of life).

METHODS AND ANALYSIS

Sixty women (aged 18-50) with obesity (body mass index [BMI] ≥ 30 and/or waist circumference ≥ 88 cm) who are physically inactive, have no unstable health conditions and are safe to exercise will be recruited from September 2021 to December 2022. The main outcome will be feasibility and acceptability of the intervention and procedures. Trial feasibility outcomes will be evaluated to determine if a definitive trial should be undertaken. Trial acceptability will be explored through follow-up qualitative interviews with participants. Secondary outcomes will include CRF (predicted VO2 max), anthropometrics (i.e. BMI), strength (5RM bench press, leg dynamometry, grip strength) and other health outcomes (i.e., pain). Participants will be block randomised into one of four trial arms (aerobic exercise, resistance training and combined training groups, non-active control group) and measurements will be completed pre- and post-intervention. The exercise groups will receive an individualised supervised exercise programme for 3× sessions/week for 12 weeks. The change in mean values before and after intervention will be calculated for primary and secondary outcomes. ANOVA and t-tests will be applied to evaluate within-group and between-group differences. If sufficient participants are recruited, the data will be analysed using ANCOVA with the age and BMI as covariates.

DISCUSSION

This pilot will provide data on the feasibility and acceptability of trial procedures and of the programmes' three progressive time-matched exercise interventions (aerobic, resistance and combined) for women living with obesity, which will help inform future research and the potential development of a full-scale randomised clinical trial.

TRIAL REGISTRATION

ISRCTN, ISRCTN13517067 . Registered 16 November 2021-retrospectively registered.

Impact of training modes on fitness and body composition in women with obesity: A systematic review and meta-analysis

OBJECTIVE

This study aimed to assess the effectiveness of different exercise modalities and determine the optimal exercise prescription for improving cardiorespiratory fitness, body composition, and metabolic health of women with obesity.

METHODS

A systematic review of randomized controlled trials (RCTs) published between January 1988 and October 2020 was conducted. The RCTs were screened using the following inclusion criteria: 1) participants: women aged 18 to 65 years with BMI > 30 kg/m² and without comorbidities; 2) intervention: exercise; 3) comparison: non-intervention control; and 4) outcomes measures: cardiorespiratory fitness (maximal oxygen consumption), body composition (i.e., body weight, percentage body fat), and/or metabolic measures (i.e., blood pressure, cholesterol).

RESULTS

A total of 20 RCTs with a total of 2,062 participants were included. Although the results showed that any form of exercise was more effective than control, improvements in fitness and body composition were modest. Aerobic exercise (vigorous and moderate intensity) appeared most promising for improving fitness and body weight, whereas low-load resistance training resulted in the largest improvements in body fatness.

CONCLUSIONS

In women living with obesity, aerobic exercise was consistently effective in improving fitness and body composition. Although both resistance training and combined exercise interventions appear promising, more research is needed to evaluate their efficacy and determine an optimal exercise prescription for this population.

What exercise prescription is optimal to improve body composition and cardiorespiratory fitness in adults living with obesity? A network meta-analysis

Current international guidelines recommend people living with obesity should be prescribed a minimum of 300 min of moderately intense activity per week for weight loss. However, the most efficacious exercise prescription to improve anthropometry, cardiorespiratory fitness (CRF) and metabolic health in this population remains unknown. Thus, this network meta-analysis was conducted to assess and rank comparative efficacy of different exercise interventions on anthropometry, CRF and other metabolic risk factors. Five electronic databases were searched for randomized controlled trials (RCTs) that compared different exercise modalities to improve anthropometry, CRF and/or metabolic health in adults living with obesity. RCTs were evaluated using the Cochrane risk of bias tool. A random effects network meta-analysis was performed within a frequentist framework. Of the 6663 articles retrieved, 45 studies with a total 3566 participants were included. Results reveal that while any type of exercise intervention is more effective than control, weight loss induced is modest. Interventions that combine high-intensity aerobic and high-load resistance training exert beneficial effects that are superior to any other exercise modality at decreasing abdominal adiposity, improving lean body mass and increasing CRF. Clinicians should consider this evidence when prescribing exercise for adults living with obesity, to ensure optimal effectiveness.

Does resistance training have an effect on levels of ferritin and atherogenic lipids in postmenopausal women? - A pilot trial

The objective of this study was to determine if 15 weeks of resistance training (RT) can alter the levels of blood lipids, body iron status, and oxidative stress in postmenopausal women with vasomotor symptoms. Postmenopausal women enrolled in a randomised controlled trial were allocated to either a sedentary control group (n = 29) or a RT group (n = 26). Blood samples were taken at week-0 and week-15 for all participants. Blood lipids and iron status were measured via routine clinical analyses. Immunoassays were used to measure oxidative stress markers. The RT group, with good compliance, was associated with significant reductions in ferritin, total cholesterol, low-density lipoprotein, and non-high-density lipoprotein cholesterol. Moreover, ferritin was positively correlated with atherogenic lipids while negatively correlated with high-density lipoprotein in RT women. This occurred without alterations in serum iron, transferrin, transferrin-saturation, C-reactive protein and oxidative stress markers. No differences were found in control women. This study suggests that RT in postmenopausal women both reduces levels of ferritin and counteracts atherogenic lipid profiles independent of an apparent oxidative mechanism. RT may be a beneficial intervention in postmenopausal women via an interaction between ferritin and lipids; however, further investigation in a larger cohort is essential.

Plasma polychlorinated biphenyl concentrations and immune function in postmenopausal women

BACKGROUND

Polychlorinated biphenyl (PCB) exposure has been associated with non-Hodgkin lymphoma in several studies, and the immune system is a potential mediator.

OBJECTIVES

We analyzed associations of plasma PCBs with immune function measures. We hypothesized that higher plasma PCB concentrations are associated with lower immune function cross-sectionally, and that increases in PCB concentrations over a one year period are associated with decreases in immune function.

METHODS

Plasma PCB concentrations and immune function [natural killer (NK) cell cytotoxicity and PHA-induced T-lymphocyte proliferation (PHA-TLP)] were measured at baseline and one year in 109 postmenopausal overweight women participating in an exercise intervention study in the Seattle, Washington (USA) area. Mixed models, with adjustment for body mass index and other potential confounders, were used to estimate associations of PCBs with immune function cross-sectionally and longitudinally.

RESULTS

Associations of PCBs with immune function measures differed across groups of PCBs (e.g., medium- and high-chlorinated and dioxin-like [mono-ortho-substituted]) and by the time frame for the comparison (cross-sectional vs. longitudinal). Higher concentrations of medium- and high-chlorinated PCBs were associated with higher PHA-TLP cross-sectionally but not longitudinally. The mean decrease in 0.5 µg/mL PHA-TLP/50.0 pmol/g-lipid increase in dioxin-like PCBs over one year was 51.6 (95% confidence interval 2.7, 100.5; P=0.039). There was no association between plasma PCBs and NK cytotoxicity.

CONCLUSIONS

These results do not provide strong evidence of impaired cellular immunity from PCB exposure. Larger longitudinal studies with greater variability in PCB exposures are needed to further examine temporal associations of PCBs with immune function.

Adiposity, body composition, and weight change in relation to organochlorine pollutant plasma concentrations

We investigated cross-sectional associations of body composition and weight change with polychlorinated biphenyls (PCB) and organochlorine pesticides/pesticide metabolites measured in blood collected at the baseline of the Physical Activity for Total Health study of postmenopausal, overweight women living in the Seattle, Washington metropolitan area. Indicators of greater adiposity were associated with lower plasma concentrations of most PCBs with six or more chlorine atoms. This pattern was observed for current weight, body mass index, fat mass percent, subcutaneous abdominal fat, intra-abdominal fat, waist circumference, hip circumference, waist-to-hip ratio, and maximum adult weight. Conversely, PCB 105, PCB 118, and p,p'-DDE were generally increased or showed no association with these variables. Weight gain since age 35 was associated with lower concentrations of almost every organochlorine we studied, and past weight loss episodes of at least 20 pounds (≥9.1 kg) were associated with higher concentrations. Our results have implications for epidemiologic studies of organochlorines in terms of covariates that may be important to consider in statistical analyses, particularly as such considerations may differ importantly by specific analyte. Our finding of increased organochlorine concentrations with past weight loss episodes may have public health significance; however, this association requires confirmation in longitudinal studies.

Metabolic, hormonal and immunological associations with global DNA methylation among postmenopausal women

DNA methylation is an epigenetic modification essential for the regulation of gene expression that has been implicated in many diseases, including cancer. Few studies have investigated the wide range of potential predictors of global DNA methylation, including biomarkers. Here, we investigated associations between DNA methylation and dietary factors, sex-steroid hormones, metabolic, lipid, inflammation, immune and one-carbon biomarkers. Data and baseline biomarker measurements were obtained from 173 overweight/obese postmenopausal women. Global DNA methylation in lymphocyte DNA was measured using the pyrosequencing assay for LINE-1 repeats. We used correlations and linear regression analyses to investigate associations between continuous data and DNA methylation, while t-tests were used for categorical data. Secondary analyses stratified by serum folate levels and multivitamin use were also conducted. There was little variability in LINE-1 methylation (66.3-79.5%). Mean LINE-1 methylation was significantly higher among women with elevated glucose levels. Mean LINE-1 methylation was also higher among women with high CD4+/CD8+ ratio, and lower among women with elevated vitamin B6, but neither reached statistical significance. In analyses stratified by folate status, DNA methylation was negatively associated with sex hormone concentrations (estrone, estradiol, testosterone and sex hormone binding globulin) among women with low serum folate levels (n = 53). Conversely, among women with high serum folate levels (n = 53), DNA methylation was positively associated with several immune markers (CD4/CD8 ratio, NK1656/lymphocytes and IgA). Results from this screening suggest that global DNA methylation is generally stable, with differential associations for sex hormones and immune markers depending on one-carbon status.

Metabolic effects of estrogen substitution in combination with targeted exercise training on the therapy of obesity in ovariectomized Wistar rats

Postmenopausal women tend to have a higher risk in developing obesity and thus metabolic syndrome. Recently we could demonstrate that physical activity and estrogen replacement are effective strategies to prevent the development of nutritional induced obesity in an animal model. The aim of this study was to determine the combined effects of estrogen treatment and exercise training on already established obesity. Therefore ovariectomized (OVX) and sham-operated (SHAM) female Wistar rats were exposed to a high fat diet for ten months. After this induction period obese SHAM and OVX rats either remained sedentary or performed treadmill training for six weeks. In addition OVX rats were treated with 17β-Estradiol (E(2)) alone, or in combination with training. Before and after intervention effects on lipid and glucose metabolism were investigated. Training resulted in SHAM and OVX rats in a significant decrease of body weight, subcutaneous and visceral body fat, size of adipocytes and the serum levels of leptin, cholesterol, low-density lipoprotein and triglycerides. In OVX animals E(2) treatment resulted in similar effects. Often the combination of E(2) treatment and training was most effective. Analysis of the respiratory quotient indicates that SHAM animals had a better fat burning capacity than OVX rats. There was a tendency that training in SHAM animals and E(2) treatment in OVX animals could improve this capacity. Analysis of glucose metabolism revealed that obese SHAM animals had higher glucose tolerance than OVX animals. Training improved glucose tolerance in SHAM and OVX rats, E(2) treatment in OVX rats. The combination of both was most effective. Our results indicate that even after a short intervention period of six weeks E(2) treatment and exercise training improve parameters related to lipid as well as glucose metabolism and energy expenditure in a model of already established obesity. In conclusion a combination of hormone replacement therapy and exercise training could be a very effective strategy to encourage the therapy of diet-induced obesity and its metabolic consequences in postmenopausal women.

Physical activity for obese individuals: a systematic review of effects on chronic disease risk factors

The purpose of this review was to determine the effectiveness of physical activity in improving chronic disease risk factors in obese individuals. A systematic review was conducted to identify randomized physical activity intervention studies reporting changes in risk factors among obese individuals published prior to March 2010. Studies included in the review were randomized trials of at least 10 weeks in duration, with a sample mean body mass index ≥ 30 kg/m(2) at baseline, and reporting a relevant risk factor (blood pressure, blood lipids, glucose/insulin or C-reactive protein). Forty-four studies met the inclusion criteria for this review. Overall, physical activity had no more than a modest effect on chronic disease risk factors in obese individuals. There was great heterogeneity in responses of risk factors across studies. In many studies it was difficult to determine the effect of physical activity, independent of changes in body mass consequent to the intervention. Obese individuals should be encouraged to undertake physical activity following general recommendations for weight loss and health. The degree to which physical activity is effective at lowering risk factor levels among high-risk obese individuals is not known.

Modulation of insulin resistance in ovariectomized rats by endurance exercise training and estrogen replacement

Estrogen is known to play a role in fat metabolism, but its role in carbohydrate metabolism remains controversial. We investigated alterations in carbohydrate and fat metabolism after prolonged estrogen deprivation by determining body weight, food intake, visceral fat content, serum lipids, glucose tolerance, and insulin action on glucose transport activity in isolated soleus and extensor digitorum longus muscles. In addition, effects of endurance exercise training with or without estrogen replacement on metabolic alterations occurring under estrogen deficiency were examined. Female Sprague-Dawley rats were ovariectomized (OVX) or sham-operated (SHAM). The OVX rats remained sedentary, received 5 microg of 17beta-estradiol (E(2)), performed exercise training (ET), or underwent both estrogen treatment and exercise training (E(2) + ET) for 12 weeks. Compared with SHAM, OVX animals had greater final body weights, visceral fat content, and serum levels of total and low-density lipoprotein cholesterol (P < .05). Exercise training and E(2) significantly reduced body weights (6% and 25%), visceral fat (37% and 51%), and low-density lipoprotein cholesterol level (19% and 26%). Exercise training alone improved whole-body glucose tolerance (29%), which was enhanced to the greatest extent (51%) in the ET rats that also received E(2). Insulin-stimulated glucose transport activity in OVX group was lower than that in SHAM by 29% to 44% (P < .05). Exercise training and E(2) corrected the diminished insulin action on skeletal muscle glucose transport in OVX animals, which was partly due to elevated glucose transporter-4 protein expression. These findings indicate that 12 weeks of ovariectomy caused metabolic alterations mimicking features of the insulin resistance syndrome. Furthermore, these metabolic disturbances were attenuated by ET or E(2), whereas the beneficial interactive effects of ET and E(2) on these defects were not apparent.

Effect of obesity on high-density lipoprotein metabolism

Reduced levels of high-density lipoproteins (HDL) in non-obese and obese states are associated with increased risk for the development of coronary artery disease. Therefore, it is imperative to determine the mechanisms responsible for reduced HDL in obese states and, conversely, to examine therapies aimed at increasing HDL levels in these individuals. This paper examines the multiple causes for reduced HDL in obese states and the effect of exercise and diet--two non-pharmacologic therapies--on HDL metabolism in humans. In general, the concentration of HDL-cholesterol is adversely altered in obesity, with HDL-cholesterol levels associated with both the degree and distribution of obesity. More specifically, intra-abdominal visceral fat deposition is an important negative correlate of HDL-cholesterol. The specific subfractions of HDL that are altered in obese states include the HDL2, apolipoprotein A-I, and pre-beta1 subfractions. Decreased HDL levels in obesity have been attributed to both an enhancement in the uptake of HDL2 by adipocytes and an increase in the catabolism of apolipoprotein A-I on HDL particles. In addition, there is a decrease in the conversion of the pre-beta1 subfraction, the initial acceptor of cholesterol from peripheral cells, to pre-beta2 particles. Conversely, as a means of reversing the decrease in HDL levels in obesity, sustained weight loss is an effective method. More specifically, weight loss achieved through exercise is more effective at raising HDL levels than dieting. Exercise mediates positive effects on HDL levels at least partly through changes in enzymes of HDL metabolism. Increased lipid transfer to HDL by lipoprotein lipase and reduced HDL clearance by hepatic triglyceride lipase as a result of endurance training are two important mechanisms for increases in HDL observed from exercise.

A combination of soy isoflavone supplementation and exercise improves lipid profiles and protects antioxidant defense-systems against exercise-induced oxidative stress in ovariectomized rats

Menopause is often accompanied with weight gain, metabolic lipid abnormalities, and oxidative stress. In this study, we investigated the combined effects of exercise and soy isoflavone supplementation on the lipid profiles and antioxidant capacities of ovariectomized rats. Twenty-five female Sprague-Dawley rats were divided into 5 groups: sham-operated, ovariectomized (OVX), OVX with exercise (OVX+EX), OVX with soy isoflavone supplementation (OVX+ISO), and OVX with both soy isoflavones and exercise (OVX+ISO+EX). After 12 weeks of intervention, antioxidant status was evaluated in collected blood samples by the ferric reducing ability of plasma (FRAP), glutathione (GSH) content, and sodium oxide dismutase (SOD) activity. DNA damage in the lymphocytes was determined using alkaline single-cell gel electrophoresis (the Comet assay). Although there were no significant differences in weight gain and food intake, weight gain was lower in OVX+EX, OVX+ISO, and OVX+ISO+EX than in OVX. OVX+EX, OVX+ISO, and OVX+ ISO+EX showed a significant decrease in total cholesterol, triglycerides, and LDL-cholesterol compared to OVX. The soy isoflavone supplemented group had significantly increased FRAP values and GSH contents in contrast to no changes in the exercised group, whereas exercise markedly increased SOD activity and H2O2-induced DNA tail length and tail moment. Exercise with soy isoflavone supplementation significantly increased FRAP values and had no difference on SOD activity, including DNA damage. These results demonstrate that a combined treatment of moderate exercise and soy isoflavone supplementation could exert a beneficial effect on weight control and lipid profiles, and offer protection from exercise-induced oxidative stress in postmenopausal women.