Figure 4.

Dietary sulfur amino acid restriction (SAAR) alters antioxidant responses in liver. (A) Graphical overview of hepatic production of the antioxidants glutathione (GSH) and hydrogen sulfide (H₂S), either via the transsulfuration pathway, involving cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CTH), or through the cystine/glutamate antiporter (comprising SLC7A11 and SLC3A2). (B, C) Serum concentrations (μM) of methionine (left) and cystine (right) in male (B) and female (C) mice without or with liver-specific knockdown of Atf4 (Atf4^fl/fl and lsAtf4KO, respectively), at the end of the 10-wk experimental period. (D, E) Hepatic concentrations of total GSH in male (D) and female (E) mice, relative to the Atf4^fl/fl control (Ctrl)-fed group in each biological sex. (F, G) Hepatic concentrations of endogenous H₂S production capacity in male (F) and female (G) mice, displayed as relative to the Atf4^fl/fl Ctrl-fed group in each biological sex. (H, I) Hepatic mRNA expression levels of Cbs, Cth, Slc7a11, Slc3a2, and Nrf2 in male (H) and female (I) mice, displayed as relative to the Atf4^fl/fl Ctrl-fed group for each gene, in each biological sex. n = 5–12/group. *P < 0.05 with a main effect of diet. ^#P < 0.05 with a main effect of genotype. n.s. indicates no differences at α = 0.05, as determined by two-factor ANOVA. In case of a statistical interaction effect (between diet and genotype), groups not sharing a common letter indicate a statistically significant difference between groups as determined by post hoc analysis using pairwise t tests with Bonferroni correction. Bar chart values are presented as mean ± SEM with individual data points overlaid. Boxplots indicate median values, with upper and lower hinges representing the 25th and 75th percentiles, respectively, and with upper and lower whiskers reaching to the largest and smallest values, respectively, while not extending further than 1.5 times the interquartile range, with individual data points overlaid.