Abstract
Hypercholesterolemia increases and exacerbates stress signals leading also to liver damage (LD) and failure. Sirtuin1 (SIRT1) is involved in lifespan extension and it plays an essential role in hepatic lipid metabolism. However, its involvement in liver hypercholesterolemic damage is not yet completely defined. This in vivo study evaluated the role of SIRT1 in the hypercholesterolemic-related LD and, then, investigated how oral supplementation of melatonin, pleiotropic indoleamine, may be protective. Control mice and apolipoprotein E-deficient mice (ApoE−/−) of 6 and 15 weeks of age were treated or not treated with melatonin at the dose of 10 mg/kg/day for 9 weeks. In this study, we evaluated serum biochemical markers, liver SIRT1 expression, and oxidative stress markers. We observed that hypercholesterolemia increased significantly serum cholesterol and triglycerides, reduced significantly liver SIRT1, and, in turn, induced hepatic oxidative stress in untreated ApoE−/− mice with respect to control mice. Interestingly, melatonin treatment improved serum biochemical markers and hepatic morphological impairment and inhibited oxidative stress through its antioxidant properties and also by SIRT1 upregulation. In summary, melatonin oral supplementation may represent a new protective approach to block hypercholesterolemic liver alterations involving also a SIRT1-dependent mechanism.
Highlights
Hyperlipidemia, which included hypercholesterolemia (HC), is the most striking risk factor in the development of cardiovascular diseases in occidental population [1]
This disorder has been reported in 20%–80% of cases of nonalcoholic fatty liver disease (NAFLD) [2] and may induce liver inflammatory cell infiltration, fibrosis, and production of chemokines, cytokines, and oxidative factors that, in turn, lead to oxidative stress (OS) and inflammation [3,4,5]
OS characterized by decreased activity of endogenous antioxidant system, with a reduction of superoxide dismutase1 (SOD1) and catalase (CAT), together with an increase in inducible nitric oxide synthase, appears to be responsible for lipid-related liver damage (LD) in different experimental models [10,11,12]
Summary
Hyperlipidemia, which included hypercholesterolemia (HC), is the most striking risk factor in the development of cardiovascular diseases in occidental population [1]. OS characterized by decreased activity of endogenous antioxidant system, with a reduction of superoxide dismutase (SOD1) and catalase (CAT), together with an increase in inducible nitric oxide synthase (iNOS), appears to be responsible for lipid-related LD in different experimental models [10,11,12]. This is consistent with previous findings from our and other research groups showing that hypercholesterolemic mice have important morphological changes at liver level, like disorganization of hepatic parenchyma with widespread cell swelling, congestion of BioMed Research International sinusoids, hepatocytes fatty deposits, polyploidy, and augmented nuclear size [13, 14]
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