ACLY Facilitates Alanine Flux in the Livers of db/db Mice: A Hyperpolarized [1-13C]pyruvate MRS study

Ho-Taek Song^1*Young-Suk Choi¹Seo-hyun Lim¹Jae Eun Song²

• ¹Yonsei University Collage of Medicine, Department of Radiology, Seoul, Republic of Korea
• ²Seoul National University Hospital, Jongno-gu, Republic of Korea

Non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM) feature paradoxical increases in both gluconeogenesis and lipogenesis. ATP citrate lyase (ACLY) supports both processes by generating cytosolic acetyl-CoA and oxaloacetate from citrate. While ACLY’s role in lipogenesis is well established, its involvement in amino acid–driven gluconeogenesis remains unclear. Using hyperpolarized [1-13C]pyruvate magnetic resonance spectroscopy (MRS), we observed markedly elevated [1-13C]alanine labeling in the livers of db/db mice. Because HP alanine labeling reflects a composite of intracellular pool size and ALT‑mediated pyruvate–alanine exchange, we interpreted this increase as evidence consistent with enhanced transamination capacity rather than a direct proof of flux increase. Based on this finding, we hypothesized that ACLY promotes alanine-driven gluconeogenesis in the diabetic liver. Pharmacologic ACLY inhibition (BMS‑303141) attenuated alanine‑ and glutamine‑induced hyperglycemia and normalized alanine labeling within 2–4 h in db/db mice, without altering aminotransferase gene expression. These in vivo changes correlated with increased hepatic ACLY phosphorylation and with ex vivo ALT assay readouts. Together, these findings support a model in which ACLY facilitate amino acid–driven gluconeogenesis through metabolic control of the ALT-mediated transamination, consistent with increased pyruvate–alanine exchange. HP [1-13C]pyruvate MRS thereby provides a sensitive, translational readout of dynamic hepatic metabolism relevant to NAFLD/T2DM.