Demonstration of a day-night rhythm in human skeletal muscle oxidative capacity.

Five consecutive skeletal muscle biopsies were taken from a young healthy male research volunteer under controlled living conditions consisting of 3 meals and normal sleeping time. Samples were obtained with five hour-intervals, always at least 4 hours after the last meal at 8AM, 1PM, 6PM, 11PM and 4AM the next day. Biopsies were taken according to the Bergström method under local anesthesia from the m. vastus lateralis. The first biopsy was taken from the left leg and each consecutive biopsie was taken from the other leg. RNAs were extracted from SKM biopsies. RNA integrity was assessed using a Bioanalyzer 2100 (Agilent) and RIN were above 9.0. RNAs were then processed to generate labeled ssDNA using the Whole Transcript cDNA synthesis and amplification and the Terminal Labeling kit as suggested by the manufacturer (Affymetrix). Samples were hybridized to HuGene 2.0 arrays and native .CEL files imported into GeneSpring (v13,1,1, Agilent) after quality controls using the Affymetrix Expression Console.