Fig. 1: SDH deficiency stimulates glutamate-pyruvate transamination in cells.

A Measurement of intracellular alanine levels in Sdhb^fl/fl and Sdhb^Δ/Δ cells. Data were presented as mean ± s.e.m. of n = 4 replicates; ***P < 0.001 (two-tailed Student’s t-test). B Determination of intracellular alanine to pyruvate ratio in Sdhb^fl/fl and Sdhb^Δ/Δ cells. Data were presented as mean ± s.e.m. of n = 4 replicates; ***P < 0.001 (two-tailed Student’s t-test). C Labeling pattern of the indicated metabolites in cells incubated either with U-¹³C₆-glucose or α-¹⁵N-glutamine. Red and white circles indicate ¹³C and ¹²C units, respectively. Blue squares indicate ¹⁵N units. AGXT alanine-glyoxylate aminotransferase, GPT glutamate-pyruvic transaminase. D Levels of ¹³C₃-alanine measured in Sdhb^fl/fl and Sdhb^Δ/Δ cells cultured for 24 h in a medium containing U-¹³C₆-glucose. Data were presented as mean ± s.e.m. of n = 3 replicates. *P < 0.05 (two-tailed Student’s t-test). E Determination of intracellular alanine to glutamate ratio in Sdhb^fl/fl and Sdhb^Δ/Δ cells. Data were presented as mean ± s.e.m. of n = 4 replicates. ***P < 0.001 (two-tailed Student’s t-test. F Intracellular ¹⁵N-alanine levels in Sdhb^fl/fl and Sdhb^Δ/Δ cells incubated with α-¹⁵N-glutamine for the indicated time. Data were presented as mean ± s.e.m. of n = 4 replicates. *P < 0.05 (two-way ANOVA).