Figure 4. Aged rats have impaired metabolic parameters when fed ad libitum. Aged rats had significantly elevated (A) insulin, (B) leptin, (C) C-peptide and (D) HOMA levels relative to young rats when fed standard rodent chow ad libitum. Data are represented as group mean ± 1 SEM. * = p < 0.05. For panel A: ad libitum n = 15 young, n = 18 aged. For panel B: n = 27 young, n = 24 aged. For panel C: n = 27 young, n = 23 aged. For panel D: n = 9 young, n = 13 aged.