DeLany 2013 TOS

Skeletal muscle mitochondrial respiration is lower in African American compared to Caucasian women and is associated with resting metabolic rate and cardiorespiratory fitness.

Link: Open Access

DeLany JP, Distefano G, Coen PM, Toledo FGS, Dube JJ, Stefanovic-Racic M, Goodpaster BH (2013)

Event: The Obesity Society

The prevalence of obesity is greater in African American women (AAW) compared to Caucasian women (CW). Lower energy expenditure, particularly lower resting metabolic rate (RMR) is observed in AAW. This low RMR may play a role in the greater obesity in AAW, but reasons for this difference are not known.

We examined skeletal muscle mitochondrial respiration, cardiorespiratory fitness (VO₂ peak), and RMR in young (23.8±4.8 y) healthy women. We present data from 20 AAW (22.7±4.0 kg/m₂, 62±9 kg) and 22 CW (22.7±3.1 kg/m₂; 63±9 kg) matched for BMI and weight. Percutaneous biopsies of the vastus lateralis were obtained following an overnight fast. Mitochondrial respiratory properties were determined in permeabilized muscle fiber bundles by high-resolution respirometry. RMR was measured by indirect calorimetry, and VO₂ peak was determined during a graded exercise test.

Basal (State 4; 67±16 vs. 82±18 pmol O₂/sec/mg; p<0.015), maximal coupled (State 3; 320±68 vs. 422±65 pmol O₂/sec/mg; p<0.001) and uncoupled (State U; 354±76 vs. 483±69 pmol O₂/sec/mg; p<0.001) respiration were lower in AAW compared to CW. This corresponded with lower RMR (1259±185 vs 1383±178 kcal/day; p<0.01) and VO₂ peak (2007±428 vs 2320±491 ml/min; p< 0.03) in AAW. When combining groups, State 4, State 3 and State U respiration correlated positively with RMR (r=0.44, p<0.01; r=0.39, p<0.03; r=0.40, p<0.02) and VO₂ peak (r=0.54, p<0.001; r=0.48, p<0.002; r=0.48, p<0.003).

In summary, RMR and VO₂ peak were lower in these young, lean AWW compared with matched CW. Skeletal muscle mitochondrial respiration was also lower in AWW and was associated with RMR and VO₂ peak. These data suggest that differences in skeletal muscle mitochondrial respiration are related to the lower metabolic rate in AAW and may be related to the increased risk of weight gain in AA women.

• Bioblast editor: Kandolf G • O2k-Network Lab: US PA Pittsburgh DeLany JP, US FL Orlando Goodpaster BH

Labels: MiParea: Respiration  Pathology: Obesity 

Organism: Human  Tissue;cell: Skeletal muscle  Preparation: Permeabilized tissue 

Coupling state: LEAK, OXPHOS 

HRR: Oxygraph-2k