Effects of physical activity and weight loss on skeletal muscle mitochondria and relationship with glucose control in type 2 diabetes.
Level 4 - case-series / case-control
Single-arm pre-post intervention study without a separate control group
PubMed 17536063 · doi:10.2337/db07-0141
What was done
Type 2 diabetic patients completed a 4-month intervention combining daily moderate-intensity exercise with moderate weight loss. Skeletal muscle biopsies were obtained before and after the intervention to assess mitochondrial morphology, mitochondrial DNA content, cardiolipin content, and oxidative enzyme activities. Investigators also evaluated glucose control, body composition, aerobic fitness (VO2max), and insulin sensitivity.
What was found
Participants achieved a weight loss of 7.1 ± 0.8% and a 12 ± 1.6% increase in VO2max (P < 0.05), alongside a 59 ± 21% improvement in insulin sensitivity (P < 0.05). Skeletal muscle mitochondrial density increased by 67 ± 17% (P < 0.01) and cardiolipin content increased by 55 ± 17% (P < 0.01), accompanied by increases in mitochondrial oxidation enzymes. Physical activity energy expenditure correlated with insulin sensitivity improvements (r = 0.84, P < 0.01), and increases in mitochondrial content correlated with improvements in fasting plasma glucose and HbA1c.
Why it matters
This study demonstrates that skeletal muscle mitochondrial deficits in type 2 diabetes are reversible with lifestyle modifications, linking gains in mitochondrial content directly to improvements in glycemic control.
Limits
The abstract does not report the sample size (n), participant demographics, or baseline characteristics. The study lacks a non-intervention or weight-stable control group, preventing isolation of exercise effects from caloric restriction and weight loss. Long-term durability beyond the 4-month intervention was not evaluated.
Cited by
- supports People with type 2 diabetes have mitochondria that function roughly half as effectively as those in people without type 2 diabetes.