Aerobic Exercise, Metabolic Syndrome, and Lipid Profiles: Protocol for a Quantitative Review
Background:
We describe two systematic reviews and univariate meta-analyses of randomized controlled trials to estimate the effect size of aerobic exercise training on the standard lipid profile of adults diagnosed with, and free of, metabolic syndrome; and the determination if study or intervention covariates explain change in lipid outcomes.
Methods:
English language searches of online databases from inception to June 2020. Data will be included from (a) randomized controlled trials of sedentary adult humans with intervention and non-exercising control groups of n ≥ 10; (b) an aerobic exercise training intervention duration ≥12 weeks of at least moderate intensity (>40% VO2MAX); and (c) reporting of pre/post lipid measurements. Subjects with chronic disease (except diabetes mellitus or metabolic syndrome), or pregnant/lactating, or trials testing diet/medication, or resistance/isometric/unconventional training will be excluded.
Results:
We will follow the Preferred Reporting Items for Systematic Reviews and Meta-Analysis statement. Univariate meta-analysis will estimate the effect size of aerobic exercise training on the standard lipid profile, using a random raw mean difference, Knapp-Hartung adjusted, 95% confidence interval, model. Statistical tests and precision and standard error funnel plots will evaluate heterogeneity. Multivariate meta-regression will explore whether study or intervention covariates explain change in lipids. Analyses will be performed in Comprehensive Meta-Analysis 3.0. Study quality will be evaluated using TESTEX.
Conclusion:
We aim to estimate the effect size of aerobic exercise training on the standard lipid profiles of adults with and free of metabolic syndrome, and establish if these changes result in minimal meaningful change to cardiovascular disease risk. We aim to determine if meta-regression covariates might explain change in lipids.
Estimating the Efect of Aerobic Exercise Training on Novel Lipid Biomarkers: A Systematic Review and Multivariate Meta‑Analysis of Randomized Controlled Trials
BackgroundAerobic 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.
Determining the effect size of aerobic exercise training on the standard lipid profile in sedentary adults with three or more metabolic syndrome factors: a systematic review and meta-analysis of randomised controlled trials
Objectives To estimate the change in the standard lipid profile (SLP) of adults diagnosed with ≥3 metabolic syndrome (MetS) factors following aerobic exercise training (AET)" and to investigate whether study/ intervention covariates are associated with this change.
Design Systematic review with univariate meta-analysis and meta-regression.
Data sources English language searches of online databases from inception until July 2020.
Eligibility criteria (1) Published randomised controlled human trials with study population ≥10 per group" (2) sedentary adults with ≥3 MetS factors but otherwise free of chronic disease, not pregnant/lactating" (3) AET-only intervention with duration ≥12 weeks" and (4) reporting pre–post intervention SLP outcomes.
Results Various univariate meta-analyses pooled 48 data sets of 2990 participants. Aerobic exercise training significantly (P<.001) improved all lipids (mmol/L mean difference ranges, 95% CIs): total cholesterol, –0.19 (– 0.26 to –0.12) to –0.29 (−0.36 to –0.21)" triglycerides, −0.17 (–0.19 to –0.14) to –0.18 (−0.24 to –0.13)" high-density lipoprotein-cholesterol (HDL-C), 0.05 (0.03 to 0.07) to 0.10 (0.05 to 0.15)" and low-density lipoprotein-cholesterol (LDL-C), –0.12 (–0.16 to –0.9) to –0.20 (−0.25 to –0.14). Meta-regression showed that intensity may explain change in triglycerides and volume may explain change in HDL-C and LDL-C.
Conclusion Aerobic exercise training positively changes the SLP of sedentary and otherwise healthy adults with ≥3 MetS factors. Adjusting AET intervention training variables may increase the effects of AET on triglycerides and HDL-C.