Methods
Human skeletal muscle cells were isolated from muscle biopsies obtained from RYGB patients (BMI = 48.0 ± 2.1, n = 7) prior to, 1 month and 7 months following surgery and lean control subjects (BMI = 22.4 ± 1.1, n = 7). Complete glucose oxidation, non-oxidized glycolysis rates, mitochondrial respiratory capacity, mitochondrial network morphology, and the regulatory proteins of mitochondrial dynamics were determined in differentiated human myotubes.
Results
Myotubes derived from severely obese humans exhibited enhanced glucose oxidation (13.5%; 95% CI [7.6, 19.4], P = 0.043) and reduced non-oxidized glycolysis (-1.3%; 95% CI [-11.1, 8.6]) in response to insulin stimulation at 7 months after RYGB when compared with the presurgery state (-0.6%; 95% CI [-5.2, 4.0] and 19.5%; 95% CI [4.0, 35.0], P = 0.006), and were not different from the lean controls (16.7%; 95% CI [11.8, 21.5] and 1.9%; 95% CI [-1.6, 5.4], respectively). Further, the number of fragmented mitochondria and Drp1(Ser616) phosphorylation were trended to reduce/reduced (0.0104, 95% CI [0.0085, 0.0126], P = 0.091 and 0.0085, 95% CI [0.0068, 0.0102], P = 0.05) in myotubes derived from severely obese humans at 7 months after RYGB surgery in comparison with the presurgery state. Finally, Drp1(Ser616) phosphorylation was negatively correlated with insulin-stimulated glucose oxidation (r = -0.49, P = 0.037).