Figure 6. Age-Related Differential Methylation Associates with Alterations in Energy Metabolism.

(A) A schematic depicting genes associated with DMRs involved in mitochondrial oxidation. Blue and red represent downregulated and upregulated genes, respectively (absolute fold change [FC] R1.2, FDR % 0.1).

(B) OCR traces from young (3-month-old), middle aged (12-month-old), and old (24-month-old) Nrlp-EGFP mouse retinal punches (n = 11 punches per time point from three individuals). Arrows indicate the injection of a mitochondrial uncoupler (BAM15) or complex I inhibitor (rotenone) in the sample well. Error bars are ± SEM.

(C) A lower basal respiration and a larger mitochondrial reserve capacity can be observed in older mice as defined by 100 × (maximal respiration basal respiration)/maximal respiration. The mitochondrial reserve capacity was compared by one-way ANOVA (post-hoc Tukey 3M vs 24M, p = 0.004). Error bars are ± SEM.

(D) OCR traces from young (4-month-old) and old (20-month-old) Nrlp-EGFP mouse retinal punches after adding etomoxir (8 μM) (n = 7 punches for 4 months; n = 9 punches for 20 months from two individuals each). Error bars are ± SEM.

(E) OCR decrease compared with baseline after adding different concentrations of etomoxir (n = 7–9 punches per condition from two individuals each). OCR decrease was compared by Student’s t test. Error bars are ± SEM. p = 0.8 (vehicle), p = 0.04 (4 μM), p = 0.001 (8 μM), p = 0.07 (20 μM).

BAM15, (2-fluorophenyl) (6-[(2-fluorophenyl) amino] (1,2,5-oxadiazolo[3,4-e] pyrazin-5-yl)) amine; FA, fatty acid; Glu, glucose; OCR, oxygen consumption rate; OXPHOS, oxidative phosphorylation.