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Obesity increases the risk of cancers, including hepatocellular carcinomas (HCC). However, the precise molecular mechanisms through which obesity promotes HCC development are still unclear. Recent studies have shown that gut microbiota may influence liver diseases by transferring its metabolites and components. Here, we show that the hepatic translocation of obesity-induced lipoteichoic acid (LTA), a Gram-positive gut microbial component, promotes HCC development by creating a tumor-promoting microenvironment. LTA enhances the senescenceassociated secretory phenotype (SASP) of hepatic stellate cells (HSC) collaboratively with an obesityinduced gut microbial metabolite, deoxycholic acid, to upregulate the expression of SASP factors and COX2 through Toll-like receptor 2. Interestingly, COX2-mediated prostaglandin E 2 (PGE 2) production suppresses the antitumor immunity through a PTGER4 receptor, thereby contributing to HCC progression. Moreover, COX2 overexpression and excess PGE 2 production were detected in HSCs in human HCCs with noncirrhotic, nonalcoholic steatohepatitis (NASH), indicating that a similar mechanism could function in humans. SIGNIFICANCE: We showed the importance of the gut-liver axis in obesity-associated HCC. The gut microbiota-driven COX2 pathway produced the lipid mediator PGE 2 in senescent HSCs in the tumor microenvironment, which plays a pivotal role in suppressing antitumor immunity, suggesting that PGE 2 and its receptor may be novel therapeutic targets for noncirrhotic NASH-associated HCC.

This review is devoted to the molecular genetics and bioenergetics of human mitochondria related to the mechanism of aging. Morphological and functional changes of mitochondria associated with age and age-related disease are overviewed with special reference to the changes in enzymes encoded by mitochondrial-inherent genome. The somatically acquired mutations and oxidative damage of the genome, which lead an individual to the fragmentation of mitochondrial DNA, cellular energy crisis, naturally occurring cell death (apoptosis), and tissue degeneration and atrophy, are reviewed with relation to the inherited point mutational genotypes and the deletion types of mitochondrial DNA. Theories of aging are discussed with disclosed evidence relevant to them. Some trials to prevent age-related damage in mitochondria are introduced for the development of what may be called mitochondrial medicine.

We examined the substantia nigra of 8 patients with Parkinson's disease immunohistochemically using antisera against complexes I, II, III, and IV of the mitochondrial electron transport system. In the patients with Parkinson's disease, a fair proportion of the nigral neurons showed reduced staining against the complex I antibody. The proportion of the neurons with reduced staining ranged from 12.7 to 74.1% of the melanized nigral neurons. Although neurons with reduced immunostaining for complex I were also observed in control subjects, the proportion among the nigral neurons was significantly smaller than in parkinsonian patients. Staining for complexes III and IV appeared normal. Staining of substantia nigra for complex II was decreased in 3 parkinsonian patients. These results are consistent with our findings that there is a deletion of gene coding for the four subunits in the mitochondrial DNA located in the striata of parkinsonian patients.

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