Figure 6. NaCT facilitates growth under nutrient stress and resistance to Zn²⁺ toxicity.

(A) Palmitate synthesis in Huh7 NTC cells grown in high glucose DMEM without glutamine ± 500 μM citrate in hypoxia for 48 h (n = 3).

(B) Mole percent enrichment of metabolites from [U-¹³C₆]glucose in Huh7 SLC13A5 KO cells grown without glutamine in hypoxia ± 500 μM citrate for 48 h, relative to (−) citrate (n = 3).

(C) Mole percent enrichment of TCA intermediates from [2,4-¹³C₂]citrate in Huh7 NTC cells grown in hypoxia ± 4 mM glutamine for 48 h (n = 3).

(D) Growth rates of Huh7 NTC and SLC13A5-KO cells grown in high glucose DMEM ± 4 mM glutamine ± 500 μM citrate in hypoxia for 4 days.

(E) Cell numbers of Huh7 NTC and SLC13A5-KO cells grown in high glucose DMEM ± 5 mM citrate ± 300 μM ZnCl₂ 24 h after Zn²⁺ treatment in hypoxia.

(F) Schematic depicting extracellular citrate utilization during cellular stress. Gray indicates removed metabolites, and pink indicates cytotoxic. Created with Biorender.com.

Cit, citrate; Pyr, pyruvate; Mal, malate; α-KG, α-ketoglutarate; Glu, glutamate; Gln, glutamine. In (A), data are plotted as mean ± 95% CI. Asterisk (*) indicates statistical significance by non-overlapping CIs. In (B)–(E), data are plotted as means ± SD. Statistical significance is determined by two-sided Student’s t test relative to (−) citrate (B), (+) glutamine (C), or determined by two-way ANOVA with Tukey’s method for multiple comparisons relative to (−) citrate (D) or (−) Zn²⁺ (E) conditions with *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001. Unless indicated, all data represent biological triplicates. See also Figure S5. Data shown are from one of at least two separate experiments.