31P MR spectroscopy and in vitro markers of oxidative capacity in type 2 diabetes patients
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Background: Skeletal muscle mitochondrial function in type 2 diabetes (T2D) is currently being studied intensively. In vivo 31P magnetic resonance spectroscopy (31P MRS) is a noninvasive tool used to measure mitochondrial respiratory function (MIFU) in skeletal muscle tissue. However, microvascular co-morbidity in long-standing T2D can interfere with the 31P MRS methodology.
Aim: To compare 31P MRS-derived parameters describing in vivo MIFU with an in vitro assessment of muscle respiratory capacity and muscle fiber-type composition in T2D patients.
Methods: 31P MRS was applied in long-standing, insulin-treated T2D patients. 31P MRS markers of MIFU were measured in the M. vastus lateralis. Muscle biopsy samples were collected from the same muscle and analyzed for succinate dehydrogenase activity (SDH) and fiber-type distribution.
Results: Several 31P MRS parameters of MIFU showed moderate to good correlations with the percentage of type I fibers and type I fiber-specific SDH activity (Pearson’s R between 0.70 and 0.75). In vivo and in vitro parameters of local mitochondrial respiration also correlated well with whole-body fitness levels (VO2peak) in these patients (Pearson’s R between 0.62 and 0.90).
Conclusion: Good correlations exist between in vivo and in vitro measurements of MIFU in long-standing insulin-treated T2D subjects, which are qualitatively and quantitatively consistent with previous results measured in healthy subjects. This justifies the use of 31P MRS to measure MIFU in relation to T2D.
Keywords31P MRS VO2peak Muscle biopsy Fiber-type Oxidative enzymes Type 2 diabetes Mitochondrial dysfunction
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