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Altered cellular metabolism in kidney proximal tubule (PT) cells plays a critical role in acute kidney injury (AKI). The transcription factor Krüppel-like factor 6 (KLF6) is rapidly and robustly induced early in the PT after AKI. We found that PT-specific Klf6 knockdown (Klf6PTKD) is protective against AKI and kidney fibrosis in mice. Combined RNA and chromatin immunoprecipitation sequencing analysis demonstrated that expression of genes encoding branched-chain amino acid (BCAA) catabolic enzymes was preserved in Klf6PTKD mice, with KLF6 occupying the promoter region of these genes. Conversely, inducible KLF6 overexpression suppressed expression of BCAA genes and exacerbated kidney injury and fibrosis in mice. In vitro, injured cells overexpressing KLF6 had similar decreases in BCAA catabolic gene expression and were less able to utilize BCAA. Furthermore, knockdown of BCKDHB, which encodes one subunit of the rate-limiting enzyme in BCAA catabolism, resulted in reduced ATP production, while treatment with BCAA catabolism enhancer BT2 increased metabolism. Analysis of kidney function, KLF6, and BCAA gene expression in human chronic kidney disease patients showed significant inverse correlations between KLF6 and both kidney function and BCAA expression. Thus, targeting KLF6-mediated suppression of BCAA catabolism may serve as a key therapeutic target in AKI and kidney fibrosis.

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The relation between interferon-gamma (IFN-γ) levels and the severity of liver diseases through fibrosis, cirrhosis, and hepatocellular carcinoma (HCC) has not been fully clarified. Thus, we aimed to characterize IFN-γ levels in liver-diseased patients. IFN-γ levels were determined by Western-blot and ELISA in sera from 30 healthy individuals, 53 patients with non-significant fibrosis (F0-F1), 47 with moderate/severe fibrosis (F2-F3), 44 cirrhotic patients (F4), and 50 with HCC. Enhanced levels of IFN-γ were associated with the progression of liver disease. The differences were statistically significant (P < 0.0001) when patients with F2-F3, F4, or HCC were compared with F0-F1 or healthy controls. The increase in IFN-γ was associated with HCC (OR = 0.98, 95% CI 0.97-0.99, P = 0.002). There was no statistically significant association between IFN-γ levels and HCV-RNA (IU/ml) (r = 0.1, P = 0.43) or HCV-NS4 (µg/mL) (r = 0.1, P = 0.17). There was significant (P < 0.0001) association between IFN-γ levels and the fibrosis stages and activity, albumin, platelet count, total bilirubin, and international normalized ratio (INR). In conclusion, elevated concentrations of IFN-γ represent a characteristic feature of liver disease severity regardless of underlying disease. Significant correlations with indices of hepatic dysfunction suggest that enhanced IFN-γ levels represent a consequence of liver dysfunction rather than of inflammatory disease.

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