Table 4.

Enrichments of plasma [¹³C]KIC, tissue fluid [¹³C]leucine, and mitochondrial protein-bound [¹³C]leucine measured in the aging study

Subjects	Plasma [13C]KIC, molar % excess	Tissue fluid [13C]leucine, molar % excess	Protein-bound [13C]leucine, atom % excess
Young
Male (n = 6)	5.76 ± 0.19	3.72 ± 0.24	0.020 ± 0.001
Female (n = 6)	6.22 ± 0.23	5.39 ± 0.11	0.028 ± 0.002
Middle-aged
Male (n = 7)	6.87 ± 0.25	4.21 ± 0.16	0.017 ± 0.002
Female (n = 7)	8.11 ± 0.36	5.88 ± 0.52	0.016 ± 0.003
Old
Male (n = 7)	7.40 ± 0.20	5.79 ± 0.16	0.018 ± 0.003
Female (n = 9)	8.20 ± 0.29	6.20 ± 0.46	0.022 ± 0.002
Age effect P	0.0001	0.0003	0.0792
Gender effect P	0.0007	0.0001	0.0116