Effects of Exercise on Type 2 Diabetes: A Systematic Review and Meta-Analysis
Introduction
Researchers have conducted a systematic review and meta-analysis to evaluate the impact of exercise on individuals with type 2 diabetes. This condition significantly increases the risk of cardiovascular disease, primarily due to impaired vascular endothelial function. Previous studies have indicated that a combination of exercise, a balanced diet, and medication may enhance endothelial function in type 2 diabetes patients, potentially reducing the risk of cardiovascular complications. However, findings in this area have been inconsistent.
Research Overview
In a recent investigation led by Jung-Hoon and colleagues, the team aimed to assess the effects of exercise on adults diagnosed with type 2 diabetes through a systematic review and meta-analysis. They analyzed research articles published since June 2017, utilizing two independent reviewers to determine the eligibility of studies for inclusion. A third reviewer assisted in resolving any disputes regarding the selected papers.
Inclusion Criteria
To qualify for the meta-analysis, studies had to meet specific criteria: they needed to be randomized controlled trials involving diabetic participants aged 18 and older, assess endothelial function via brachial artery flow-mediated dilation, and feature an exercise regimen lasting at least eight weeks.
Understanding Flow-Mediated Dilation
Flow-mediated dilation (FMD) is the expansion of an artery in response to blood flow, serving as a reliable indicator of cardiovascular health. Higher FMD values signify better cardiovascular function, while lower values indicate poorer health.
Study Findings
The researchers refined their results from an initial pool of 7,870 studies down to 13 exercise trials across eight studies, following the established criteria. The average participant age in the meta-analysis was 59 years. They evaluated the FMD results from the selected studies, which were subsequently published in the Journal of Diabetology and Metabolic Syndrome.
Impact of Exercise on Flow-Mediated Dilation
The analysis revealed an increase in flow-mediated dilation associated with the 13 exercise regimens, indicating a positive correlation with exercise. Interestingly, low to moderate exercise yielded significantly greater improvements in dilation than high-intensity exercise. Additionally, groups engaging in aerobic exercise alone demonstrated higher dilation values than those combining aerobic and resistance training. The differences in exercise effects on FMD between the eight-week and 12-week periods were not statistically significant. Moreover, the effects of exercise on the body mass index (BMI) of participants in 11 of the exercise groups were largely negligible.
Conclusion
In conclusion, flow-mediated dilation appeared to improve more significantly in the low to moderate exercise group compared to the high-intensity group. The authors proposed that this improvement in endothelial function might be partially linked to increased levels of nitric oxide (NO), a molecule known for its protective roles against inflammation and oxidative stress. However, the research team acknowledged the possibility of other contributing factors. They noted that individuals with type 2 diabetes may display decreased sensitivity to nitric oxide in vascular smooth muscle. Further studies are essential to explore the physiological pathways and mechanisms behind these findings.
Study Limitations
Several limitations were noted in the study. Variability in other treatments, such as meditation, across different studies may have introduced bias in the flow-mediated dilation results. The studies focused on low to moderate exercise primarily included aerobic activities, while high-intensity exercises incorporated a mix of aerobic and resistance training, potentially skewing conclusions. Furthermore, the measurement methods for flow-mediated dilation were inconsistent among groups, and the quality of studies varied, with a limited number included in the analysis.
Final Thoughts
Despite these limitations, the study suggests that high-intensity exercise may not provide additional benefits compared to moderate exercise for individuals with type 2 diabetes, warranting further research to validate these findings.
Reference
Jung-Hoon L, Ruda L, Moon-Hyon H, Marc TH, Yoonjung P. The effects of exercise on vascular endothelial function in type 2 diabetes: A systematic review and meta‑analysis. Diabetol Metab Syndr. 2018;10:15. doi:10.1186/s13098-018-0316-7.