Cholesterol enrichment in liver mitochondria impairs oxidative phosphorylation and disrupts the assembly of respiratory supercomplexes

Abstract

Mitochondrial cholesterol accumulation is a hallmark of alcoholic and non-alcoholic fatty liver diseases and impairs the function of specific solute carriers through changes in membrane physical properties. However, its impact on mitochondrial respiration and organization of respiratory supercomplexes has not been determined so far. Here we fed mice a cholesterol-enriched diet (HC) supplemented with sodium cholate to examine the effect of cholesterol in mitochondrial function. HC feeding increased liver cholesterol content, which downregulated Srebp2 and Hmgcr expression, while sodium cholate administration decreased Cyp7a1 and Cyp8b1 mRNA levels, suggesting the downregulation of bile acid synthesis through the classical pathway. HC-fed mice exhibited increased expression of Stard1 and Mln64 and enhanced mitochondrial free cholesterol levels (2–3 fold), leading to decreased membrane fluidity. Mitochondria from HC-fed mice displayed increased cholesterol loading in both outer and inner mitochondrial membranes. Cholesterol loading decreased complex I and complex II-driven state 3 respiration and mitochondrial membrane potential. Decreased respiratory and uncoupling control ratio from complex I was also observed after in situ enrichment of mouse liver mitochondria with cholesterol or enantiomer cholesterol, the mirror image of natural cholesterol. Moreover, in vivo cholesterol loading decreased the level of complex III 2 and the assembly of respiratory supercomplexes I 1 +III 2 +IV and I 1 +III 2 . Moreover, HC feeding caused oxidative stress and mitochondrial GSH (mGSH) depletion, which translated in hepatic steatosis and liver injury, effects that were rescued by replenishing mGSH with GSH ethyl ester. Overall, mitochondrial cholesterol accumulation disrupts mitochondrial functional performance and the organization of respiratory supercomplexes assembly, which can contribute to oxidative stress and liver injury.

Characterization of glutathione proteome in CHO cells and its relationship with productivity and cholesterol synthesis

“…Accumulation of cholesterol in the mitochondria membrane has been shown to impair the activity of some membrane proteins such as the 2‐oxoglutarate carrier that exports 2‐oxoglutarate in the cytosol in exchange of the import of GSH in the mitochondria. Moreover, it has been shown that the accumulation of mitochondrial cholesterol can damage the respiratory chain complexes assembly (Solsona‐Vilarrasa et al, 2019). Under GSH depletion, the cells potentially tried to stabilize the mitochondria membrane and favorize GSH import in the mitochondria matrix by lowering cholesterol.…”

Diabetes Mellitus, Mitochondrial Dysfunction and Ca2+-Dependent Permeability Transition Pore

“…Similar changes were demonstrated in diabetic mice that were fed with a high cholesterol diet. In these animals, the rate of mitochondrial state 3 respiration, the value of the mitochondrial membrane potential, and the assembly of the respiratory supercomplexes in mitochondria of the liver were reduced [ 111 ]. Some studies also revealed that a diabetes-induced decline in the activity of complexes of the respiratory chain can be associated with a decreased content or altered composition (peroxidation) of cardiolipin, a main anionic phospholipid in the inner mitochondrial membrane (see review [ 54 ]).…”

Niemann–Pick type C disease: cellular pathology and pharmacotherapy

“…Perhaps significantly, increased contacts between mitochondria and endosomes, and correspondingly decreased contacts between ER and endosomes, have recently been reported in NPC1‐deficient cells (Höglinger et al ). However, this idea is also problematic as mechanisms for cholesterol‐induced mitochondrial toxicity have been postulated (Torres et al ; Solsona‐Vilarrasa et al ) but not yet proved and an alternate explanation has recently been offered (Yambire et al ). Additionally mitochondria play a role in cellular cholesterol homeostasis for they house Cyp27A1 an enzyme responsible for converting cholesterol to 27‐hydroxycholesterol, a ligand of the liver X receptor (LXR).…”