A spatial map of hepatic mitochondria uncovers functional heterogeneity shaped by nutrient-sensing signaling

Abstract

In the liver, mitochondria are exposed to different concentrations of nutrients due to their spatial positioning across the periportal (PP) and pericentral (PC) axis. How these mitochondria sense and integrate these signals to respond and maintain homeostasis is not known. Here, we combined intravital microscopy, spatial proteomics, and functional assessment to investigate mitochondrial heterogeneity in the context of liver zonation. We found that PP and PC mitochondria are morphologically and functionally distinct; beta-oxidation and mitophagy were elevated in PP regions, while lipid synthesis was predominant in the PC mitochondria. In addition, comparative phosphoproteomics revealed that mitophagy and lipid synthesis are regulated by phosphorylation in a zonated manner. Furthermore, we demonstrated that acute pharmacological modulation of nutrient sensing through AMPK and mTOR shifted mitochondrial phenotypes in the PP and PC regions of the intact liver. This study highlights the role of protein phosphorylation in mitochondrial structure, function, and overall homeostasis in hepatic metabolic zonation. The findings have important implications for liver physiology and disease.

Beyond fission and fusion—Diving into the mysteries of mitochondrial shape

“…Mitochondrial morphology exhibits striking variations across different organisms, various cell types, during different metabolic conditions or circadian times and even within a single cell [ 40 , 41 ]. Mitochondria in hepatic tissue, for instance, exhibit structural diversity influenced by spatial positioning within the hepatic lobule—ranging from short spherical mitochondria to elongated tubules [ 42 ]. In skeletal muscle, mitochondrial subpopulations display differences in morphology, with small round mitochondria close to the sarcolemma and long tubular mitochondria located at the core of myofibers [ 43 ].…”