Figure 5.

Improvements in mitochondrial function driven by NAD⁺ and UPR^mt induction and UPR^er attenuation in vivo. (A) Mitochondrial abundance was higher in livers from mice treated with NR. Results are expressed as mtDNA amount (Cox2) relative to nDNA (Hk2) (n = 6). (B) This was matched by increases in mitochondrial complexes and supercomplexes, as evidenced by blue native PAGE of isolated liver mitochondria. (C) NR induced a mitonuclear protein imbalance, indicated by the reduced ratio between SDHB (nuclear encoded complex II protein) and MTCO1 (mtDNA encoded complex IV protein) expression, from whole‐liver extracts. (D) Activation of UPR^mt by NR is demonstrated by increases in hepatic gene transcripts for Clpp and Hspe1 (HSP10), but not Hspd1 (HSP60) (n = 6). These are matched by elevations in CLPP and HSP10 protein levels and the mitochondrial proteins, ATP5A and UQCRC2, from isolated liver mitochondria, indicating higher expression of oxidative phosphorylation proteins per amount of mitochondria. (E) HFHS diet‐induced transcripts involved in the UPR^er, including atf4, chop, and grp78, were mostly reduced after NR treatments, as confirmed with ATF4 and GRP78 protein expression analysis. *P < 0.05; **P < 0.001, compared to the HFHS cohort, and ^ϵ P < 0.05 compared to the CD cohort. Data are expressed as mean ± SEM. One‐way ANOVA with a post‐hoc Bonferroni test was used for all statistical analyses. Male mice were used for these experiments.