Improved Muscle Mitochondrial Capacity Following Gastric Bypass Surgery in Obese Subjects
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Weight loss resulting from low-calorie diets is often less than expected. We hypothesized that energy restriction would influence proton leakage and improve mitochondrial efficiency, leading to reduced energy expenditure, partly explaining the difficulties in weight loss maintenance.
Eleven women with a median BMI of 38.5 kg/m2 (q-range 37–40), and referred to gastric bypass surgery participated. Before surgery, and at 6 months of follow-up, muscle biopsies were collected from the vastus lateralis muscle. Mitochondria were isolated and analyzed for coupled (state 3) and uncoupled (state 4) respiration and mitochondrial capacity (P/O ratio).
At follow-up, the participants had a median BMI of 29.6 kg/m2 (28.3–32.0). State 3 increased from 20.6 (17.9–28.9) to 34.9 nmol O2/min/U citrate synthase (CS) (27.0–49.0), p = 0.01, while state 4 increased from 2.8 (1.8–4.2) to 4.2 nmol O2/min/U CS (3.1–6.1), although not statistically significant. The P/O ratio increased from 2.7 (2.5–2.8) to 3.2 (3.0–3.4), p = 0.02, indicating improved mitochondrial efficiency.
Six months after gastric bypass surgery, the mitochondrial capacity for coupled, i.e., ATP-generating, respiration increased, and the P/O ratio improved. Uncoupled respiration was not enhanced to the same extent. This could partly explain the decreased basal metabolism and the reduced inclination for weight loss during energy restriction.
KeywordsEnergy metabolism Mitochondria Muscle Obesity Thermogenesis Weight loss
The authors would like to acknowledge Susanne Rantakyrö at the Bariatric Center for outstanding coordination of the biopsy and blood sampling. Finally, we greatly appreciate the research volunteers who participated in the study.
Compliance with Ethical Standards
All procedures performed in this study were in accordance with the ethical standards of the institutional and national research committee and with the 1964 Helsinki Declaration and later amendments or comparable ethical standards. The study was approved by the ethics committee of Karolinska Institutet, Stockholm, Sweden.
Financial support was provided through grants from the Swedish Transport Administration, the Swedish Nutrition Foundation, the Swedish Research Council (no: 14244), Stiftelsen Serafimerlasarettet, and the regional agreement on medical training and clinical research between Stockholm County Council and Karolinska Institutet. The pedometers were generously provided by Abbott Scandinavia AB.
Conflict of Interest
Maria Fernström, Linda Bakkman, Peter Loogna, Olav Rooyackers, Madeleine Svensson, Towe Jakobsson, and Lena Brandt declare that they have no conflict of interest. Ylva Trolle Lagerros reports receiving consulting fees from Novo Nordisk.
Informed consent was obtained from all individual participants included in the study.
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