The role of lipocalin-2 in liver regeneration.

BACKGROUND & AIMS: Various immune mediators such as interleukin-6 (IL-6) have been implicated in the process of liver regeneration. Lipocalin-2 (LCN2) has been recently characterized as a prototypic immune mediator produced by various cell types being involved mainly in host defence. In addition, numerous studies have demonstrated its clinical value as a biomarker. This study aimed at defining the role of LCN2 in liver regeneration. METHODS: We studied LCN2 expression in wild-type mice in a model of partial hepatectomy (PH). Furthermore, we evaluated liver regeneration after PH in LCN-deficient mice compared to littermate controls. Serum levels of LCN2 were assessed in a small group of patients undergoing hepatic resection. RESULTS: LCN2 is dramatically induced in livers and sera of wild-type mice after PH, whereas liver LCN2-receptor expression was decreased. Sham operations did not affect hepatic and serum LCN2 expression. Although LCN2-deficient mice exhibited increased baseline liver expression indices, LCN2-deficient mice did not differ from wild-type mice with respect to hepatic proliferation suggesting that this molecule is not involved in hepatic repair. Only serum IL-1ß levels were slightly lower in LCN(-/-) mice, whereas IL-6 serum levels did not differ between various tested animal groups. In humans undergoing hepatic resection, LCN2 levels increased significantly within 24 h following surgery. CONCLUSIONS: LCN2, although massively induced in mice after PH, is not relevant in murine hepatic regeneration. Further, human studies have to define whether LCN2 could evolve as biomarker after liver surgery.

Adipose tissue and liver expression of SIRT1, 3, and 6 increase after extensive weight loss in morbid obesity.

BACKGROUND & AIMS: Severe obesity is associated with a state of chronic inflammation. Sirtuins (SIRT) are a family of conserved enzymes which are able to affect many metabolic and inflammatory pathways thereby potentially improving health and increasing lifespan. METHODS: We investigated the effect of weight loss on subcutaneous adipose tissue and liver mRNA and immunohistochemical expression of SIRT1, SIRT3, and SIRT6. Twenty-nine severely obese patients undergoing laparoscopic adjustable gastric banding (LAGB) were studied. Tissue samples were collected before and 6months after LAGB surgery. Tissue mRNA expression levels of SIRT1, SIRT3, and SIRT6 were correlated with clinical, biochemical, and histological parameters. In vitro, we studied sirtuin expression in native and stimulated monocytes, adipocytes, and hepatocytes. RESULTS: SIRT1, SIRT3, and SIRT6 mRNA expression was higher in the subcutaneous adipose tissue than in the liver. Weight loss resulted in a significant induction of SIRT1, SIRT3, and SIRT6 expression in the subcutaneous adipose tissue. In the liver, a significant increase after weight loss was observed, particularly for SIRT3 and SIRT6 mRNA expression; immunohistochemically, SIRT1 and SIRT3 expression was upregulated. Endotoxin and tumor necrosis factor-alpha suppressed SIRT1, SIRT3, and SIRT6 expression in human monocytes. The same stimuli suppressed total sirtuin deacetylase activity again, mainly in monocytes and less in adipocytes and hepatocytes. CONCLUSIONS: The relative abundance of adipose tissue mRNA expression of certain sirtuins exceeds its expression in the liver. Extensive weight loss increases sirtuin expression significantly both in adipose tissue and liver, probably as a consequence of reduced inflammation.