Diet-induced hepatic and mitochondrial lipid remodeling engages one-carbon metabolism under preserved mitochondrial...

Diets rich in saturated fat and sugar drive hepatic steatosis, yet their impact on mitochondrial lipid composition and function remains poorly understood. We investigated how steatotic diets reprogram phospholipid synthesis, remodel the hepatic mitochondrial lipidome, and affect mitochondrial energy metabolism.

Mice were fed a high-fat/high-sucrose (HFHS) diet for 20 weeks alongside controls. Lipidomics, metabolomics and metabolic flux analysis using deuterated water (²H₂O) were performed via high-resolution mass spectrometry in plasma, liver, and isolated hepatic mitochondria. Mitochondrial respiration was assessed via high-resolution respirometry (OROBOROS). A second cohort was fed a methionine choline-deficient (MCD) diet as a model of altered one-carbon metabolism.

HFHS feeding caused marked hepatic lipid accumulation and extensive remodeling of plasma, liver, and mitochondrial lipidomes, including reduced synthesis of select phosphatidylcholines (PCs). Mitochondrial PCs concentrations were tightly linked to dietary modulation of one-carbon metabolism, which governs PC biosynthesis via methylation. Despite these changes, the mitochondrial PC/PE ratio remained stable and mitochondrial respiration and energy metabolism were preserved. To further evaluate the role of one-carbon metabolism in mitochondrial PC, we evaluated changes during MCD feeding. MCD reduced total mitochondrial lipids, particularly PC and PE synthesis and the mitochondrial PC/PE ratio. Remarkably, mitochondrial function remained intact in both dietary conditions.

Steatotic and PC-depleting diets induce substantial remodeling of mitochondrial phospholipids without compromising mitochondrial respiratory capacity. These findings highlight the central role of one-carbon metabolism as a key regulator of mitochondrial membrane homeostasis and underscore the adaptive resilience of mitochondria under dietary and pro-fibrotic stress.