Figure 1.

Schematic demonstrating the ¹³C‐labeling of acetyl‐CoA and glutamate with [¹³C₆, ¹⁵N]‐L‐leucine and [2‐¹³C]‐pyruvate as substrates at the end of first turn of the CAC. Filled black circles=¹³C from [¹³C₆, ¹⁵N]‐L‐leucine; filled gray circles=¹³C from [2‐¹³C]‐pyruvate; open circles=¹²C. FC, fraction of acetyl‐CoA enriched in ¹³C. The arrow with a dotted line, sourced from endogenous substrates including fatty acids. CAC indicates citric acid cycle; FC, fractional substrate contribution; KG, ketoglutarate.