FIGURE 3.

Mitochondrial phenotype develops with age in GAMT^–/– mice (A,B) Representative electron micrographs at 50 week age; 10000× magnification. (C) Stereological analysis shows lower mitochondrial volume density in GAMT^–/– compared to WT (n = 3). (D) Mitochondrial DNA copy number in a separate group of mice (WT n = 6, GAMT^–/– n = 5). (E) Citrate synthase activity inversely correlates with age in KO, but not in WT mice (n = 14/group 6F/8M). (F,G) Protein carbonylation in LV homogenates from >1 year old mice was not different (n = 7–8) nor were there differences in superoxide production (n = 8). (H) Activity (AUC) of purified monoamine oxidase (MAO) in presence of preferential substrate, tyramine (Tyr), is inhibited by monoamine oxidase inhibitor (MAOI). Creatine (Cr) and guanidinoacetate (GA) are equally good substrates for MAO, but only in the absence of primary amines (n = 30/group). (I) mRNA expression of PGC-1α and its upstream and downstream regulated genes by real-time quantitative PCR in LV from GAMT^–/– and WT mice >1 year age (n = 4/group). Fold change normalized to control concentration (WT levels = 1) with propagated errors (SEM). (J) Uncoupling protein 3 (UCP3) expression and representative western blot (n = 4/group 2F/2M). ^∗Denotes P < 0.05, ^∗∗P < 0.01, ^∗∗∗P < 0.001 versus WT by unpaired t-test. Pearson’s correlation coefficient was used to assess the relationship between the variables. Mouse mean age 84 weeks (C–J). All values are mean ± SEM.