Inhibition of the mitochondrial citrate carrier, Slc25a1, reverts steatosis, glucose intolerance, and inflammation in preclinical models of NAFLD/NASH

Abstract

Nonalcoholic fatty liver disease (NAFLD) and its evolution to inflammatory steatohepatitis (NASH) are the most common causes of chronic liver damage and transplantation that are reaching epidemic proportions due to the upraising incidence of metabolic syndrome, obesity, and diabetes. Currently, there is no approved treatment for NASH. The mitochondrial citrate carrier, Slc25a1, has been proposed to play an important role in lipid metabolism, suggesting a potential role for this protein in the pathogenesis of this disease. Here, we show that Slc25a1 inhibition with a specific inhibitor compound, CTPI-2, halts salient alterations of NASH reverting steatosis, preventing the evolution to steatohepatitis, reducing inflammatory macrophage infiltration in the liver and adipose tissue, while starkly mitigating obesity induced by a high-fat diet. These effects are differentially recapitulated by a global ablation of one copy of the Slc25a1 gene or by a liver-targeted Slc25a1 knockout, which unravel dose-dependent and tissue-specific functions of this protein. Mechanistically, through citrate-dependent activities, Slc25a1 inhibition rewires the lipogenic program, blunts signaling from peroxisome proliferator-activated receptor gamma, a key regulator of glucose and lipid metabolism, and inhibits the expression of gluconeogenic genes. The combination of these activities leads not only to inhibition of lipid anabolic processes, but also to a normalization of hyperglycemia and glucose intolerance as well. In summary, our data show for the first time that Slc25a1 serves as an important player in the pathogenesis of fatty liver disease and thus, provides a potentially exploitable and novel therapeutic target.

Liver Pyruvate Kinase Promotes NAFLD/NASH in Both Mice and Humans in a Sex-Specific Manner

“… 38 Citrate also allosterically activates the enzyme acetyl-CoA carboxylase that converts acetyl-coA into malonyl-coA, the committed step in DNL. 39 Indeed, inhibiting mitochondrial pyruvate import 40 , 41 or mitochondrial citrate export 42 has been shown to reduce DNL and/or revert NAFLD/NASH. In addition, several investigators have shown that increased DNL is a hallmark of NAFLD in both mouse 43 , 44 and human studies.…”

Angiotensin‐(1‐7), the product of ACE2 ameliorates NAFLD by acting through its receptor Mas to regulate hepatic mitochondrial function and glycolipid metabolism

“…29 The development of NASH or simple steatosis in certain patients and rodent models has been reported to be partly due to hepatic mitochondrial dysfunction and impaired β-oxidation, as well as hepatic ATP-content reduction. 30,31 Moreover, ATP synthesis is impaired because of OXPHOS uncoupling or suppressed activity of different electron-transport-chain complexes. 4 Notably, the activity of citrate synthase, a rate-limiting enzyme in the tricarboxylic acid cycle, is also the key marker of mitochondrial condition.…”

“…The initial TG formation in hepatocytes might act as an adaptive response to supply FFAs, but excessive FFA disposal leads to metabolic abnormalities 29 . The development of NASH or simple steatosis in certain patients and rodent models has been reported to be partly due to hepatic mitochondrial dysfunction and impaired β‐oxidation, as well as hepatic ATP‐content reduction 30,31 . Moreover, ATP synthesis is impaired because of OXPHOS uncoupling or suppressed activity of different electron‐transport‐chain complexes 4 .…”

NASH, Fibrosis and Hepatocellular Carcinoma: Lipid Synthesis and Glutamine/Acetate Signaling

“…The liver-specific deletion of Slc25a1 ( Alb-Cre; Slc25a1 lox/lox ) leads to attenuation of HFD-induced steatosis. Inhibition of CiC/SLC25A1 with a specific inhibitor compound CTPI-2 (2-((4-chloro-3-nitrophenyl)sulfonamido)benzoic acid) ( Figure 2 ) reverses steatosis, glucose intolerance, and inflammation in HFD-fed mice [ 87 ].…”