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AMP-activated protein kinase activation and NADPH oxidase inhibition by inorganic nitrate and nitrite prevent liver steatosis.

ABSTRACT: Advanced age and unhealthy dietary habits contribute to the increasing incidence of obesity and type 2 diabetes. These metabolic disorders, which are often accompanied by oxidative stress and compromised nitric oxide (NO) signaling, increase the risk of adverse cardiovascular complications and development of fatty liver disease. Here, we investigated the therapeutic effects of dietary nitrate, which is found in high levels in green leafy vegetables, on liver steatosis associated with metabolic syndrome. Dietary nitrate fuels a nitrate-nitrite-NO signaling pathway, which prevented many features of metabolic syndrome and liver steatosis that developed in mice fed a high-fat diet, with or without combination with an inhibitor of NOS (l-NAME). These favorable effects of nitrate were absent in germ-free mice, demonstrating the central importance of host microbiota in bioactivation of nitrate. In a human liver cell line (HepG2) and in a validated hepatic 3D model with primary human hepatocyte spheroids, nitrite treatment reduced the degree of metabolically induced steatosis (i.e., high glucose, insulin, and free fatty acids), as well as drug-induced steatosis (i.e., amiodarone). Mechanistically, the salutary metabolic effects of nitrate and nitrite can be ascribed to nitrite-derived formation of NO species and activation of soluble guanylyl cyclase, where xanthine oxidoreductase is proposed to mediate the reduction of nitrite. Boosting this nitrate-nitrite-NO pathway results in attenuation of NADPH oxidase-derived oxidative stress and stimulation of AMP-activated protein kinase and downstream signaling pathways regulating lipogenesis, fatty acid oxidation, and glucose homeostasis. These findings may have implications for novel nutrition-based preventive and therapeutic strategies against liver steatosis associated with metabolic dysfunction.

SUBMITTER: Cordero-Herrera I

PROVIDER: S-EPMC6320503 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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AMP-activated protein kinase activation and NADPH oxidase inhibition by inorganic nitrate and nitrite prevent liver steatosis.

Cordero-Herrera Isabel I Kozyra Mikael M Zhuge Zhengbing Z McCann Haworth Sarah S Moretti Chiara C Peleli Maria M Caldeira-Dias Mayara M Jahandideh Arghavan A Huirong Han H Cruz Josiane de Campos JC Kleschyov Andrei L AL Montenegro Marcelo F MF Ingelman-Sundberg Magnus M Weitzberg Eddie E Lundberg Jon O JO Carlstrom Mattias M

Proceedings of the National Academy of Sciences of the United States of America 20181217 1

Advanced age and unhealthy dietary habits contribute to the increasing incidence of obesity and type 2 diabetes. These metabolic disorders, which are often accompanied by oxidative stress and compromised nitric oxide (NO) signaling, increase the risk of adverse cardiovascular complications and development of fatty liver disease. Here, we investigated the therapeutic effects of dietary nitrate, which is found in high levels in green leafy vegetables, on liver steatosis associated with metabolic s ...[more]

PMID: 30559212

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Project description:BackgroundRenal fibrosis, associated with oxidative stress and nitric oxide (NO) deficiency, contributes to the development of chronic kidney disease and renal failure. As major energy source in maintaining renal physiological functions, tubular epithelial cells with decreased fatty acid oxidation play a key role in renal fibrosis development. Inorganic nitrate, found in high levels in certain vegetables, can increase the formation and signaling by bioactive nitrogen species, including NO, and dampen oxidative stress. In this study, we evaluated the therapeutic value of inorganic nitrate treatment on development of kidney fibrosis and investigated underlying mechanisms including regulation of lipid metabolism in tubular epithelial cells.MethodsInorganic nitrate was supplemented in a mouse model of complete unilateral ureteral obstruction (UUO)-induced fibrosis. Inorganic nitrite was applied in transforming growth factor β-induced pro-fibrotic cells in vitro. Metformin was administrated as a positive control. Fibrosis, oxidative stress and lipid metabolism were evaluated.ResultsNitrate treatment boosted the nitrate-nitrite-NO pathway, which ameliorated UUO-induced renal dysfunction and fibrosis in mice, represented by improved glomerular filtration and morphological structure and decreased renal collagen deposition, pro-fibrotic marker expression, and inflammation. In human proximal tubule epithelial cells (HK-2), inorganic nitrite treatment prevented transforming growth factor β-induced pro-fibrotic changes. Mechanistically, boosting the nitrate-nitrite-NO pathway promoted AMP-activated protein kinase (AMPK) phosphorylation, improved AKT-mediated peroxisome proliferator-activated receptor-γ coactivator 1-α (PGC1α) activity and restored mitochondrial function. Accordingly, treatment with nitrate (in vivo) or nitrite (in vitro) decreased lipid accumulation, which was associated with dampened NADPH oxidase activity and mitochondria-derived oxidative stress.ConclusionsOur findings indicate that inorganic nitrate and nitrite treatment attenuates the development of kidney fibrosis by targeting oxidative stress and lipid metabolism. Underlying mechanisms include modulation of AMPK and AKT-PGC1α pathways.

Project description:Fatty liver hemorrhagic syndrome (FLHS) in laying hens, a nutritional metabolic disorder disease, can lead to the decline of laying rate, shortening of laying peak period and increase of mortality, which seriously constrain the sustainable development of layer industry. Until now, there is no effective strategies can prevent and control the occurrence of fatty liver hemorrhagic syndrome in laying hens. The AMP-activated protein kinase (AMPK), a major sensor of cellular energy status, acts a crucial role in regulating lipid metabolism, oxidative stress and inflammatory responses in body. However, the potential molecular mechanisms about AMP-activated protein kinase signal in controlling the occurrence of fatty liver hemorrhagic syndrome are remain unclear. In present study, we found that the phosphorylated AMP-activated protein kinase (Thr172) protein level was markedly reduced in palmitic acid plus oleic acid (PO)-induced primary chicken hepatocytes. Moreover, blocked AMP-activated protein kinase signal by AMP-activated protein kinase inhibitor compound C obviously exacerbated lipid metabolism disorders, oxidative stress and inflammatory response triggered by palmitic acid plus oleic acid in primary chicken hepatocytes. Nevertheless, the lipid metabolism disorders, oxidative stress and inflammatory response challenged by palmitic acid plus oleic acid were obviously alleviated through activation of AMP-activated protein kinase signal with AMP-activated protein kinase activator AICAR in hepatocytes. In addition, we found that the beneficial effects of AMP-activated protein kinase signal in relieving lipid metabolism disorders, oxidative stress and inflammatory response are achieved by activating the nuclear factor erythroid 2-related factor 2 (NRF-2)/kelch-like ECH-associated protein 1 (KEAP1) pathway and inhibiting the NF-κB pathway in PO-stimulated primary chicken hepatocytes. Collectively, our data demonstrated that AMP-activated protein kinase acts as a potential target for the prevention of fatty liver hemorrhagic syndrome occurrence in laying hens.

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AMP-activated protein kinase activation and NADPH oxidase inhibition by inorganic nitrate and nitrite prevent liver steatosis.

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AMP-activated protein kinase activation and NADPH oxidase inhibition by inorganic nitrate and nitrite prevent liver steatosis.

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