title: Reduced respiratory capacity in muscle mitochondria of obese subjects.
abstract: OBJECTIVE
  The extent of weight gain varies among individuals despite equal calorie overconsumption. Furthermore, weight gain is often less than expected from energy excess. This suggests differences in metabolic efficiency and basal metabolism. Since mitochondrial uncoupling accounts for a substantial portion of the basal metabolic rate, we compared skeletal muscle mitochondrial respiration in obese subjects to normal-weight reference groups with various degrees of physical activity.
  
  
  METHODS
  Muscle biopsies were taken from the vastus lateralis muscle of 9 healthy obese subjects (BMI 40 ± 3). Mitochondria were isolated and analyzed for coupled (state 3) and uncoupled (state 4) respirations as well as mitochondrial efficiency (P/O ratio) using pyruvate as a substrate. Respiratory data were compared to reference groups A, normal-weight untrained (BMI 24 ± 0.7), and B, normal-weight trained (BMI 24 ± 0.6).
  
  
  RESULTS
  Obese subjects had a decreased respiratory capacity per mitochondrial volume compared to the reference groups: this was evident in state 4 (65% and 35% of reference group A and B, respectively) and state 3 (53% and 29% of A and B, respectively) (p < 0.05).
  
  
  CONCLUSIONS
  Obese subjects had a low capacity for fuel oxidation, which may play a role in the predisposition of obesity. However, whether lower mitochondrial capacity is a cause or a consequence of obesity requires further research.
authors.affiliation: Department of Medicine, Karolinska Institutet Solna, Stockholm, Sweden. linda.bakkman@ki.se
authors.forename: Linda
authors.initials: L
authors.lastname: Bakkman
authors.forename: Maria
authors.initials: M
authors.lastname: Fernström
authors.forename: Peter
authors.initials: P
authors.lastname: Loogna
authors.forename: Olav
authors.initials: O
authors.lastname: Rooyackers
authors.forename: Lena
authors.initials: L
authors.lastname: Brandt
authors.forename: Ylva Trolle
authors.initials: YT
authors.lastname: Lagerros
mesh_terms: D000328:Adult; D001706:Biopsy; D015992:Body Mass Index; D016022:Case-Control Studies; D019069:Cell Respiration; D004734:Energy Metabolism; D015444:Exercise; D005260:Female; D015390:Gastric Bypass; D006801:Humans; D008297:Male; D008931:Mitochondria, Muscle / Q000378:metabolism*; D009765:Obesity / Q000378:metabolism* / Q000503:physiopathology / Q000601:surgery; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D019289:Pyruvic Acid / Q000378:metabolism; D052097:Quadriceps Muscle / Q000378:metabolism* / Q000503:physiopathology; D055815:Young Adult
chemical_list: D019289:Pyruvic Acid