Madlala 2015 Abstract MiPschool Cape Town 2015
|Fructose-induced ROS production: The role of uric acid and transforming growth factor (TGF)-β1.|
Event: MiPschool Cape Town 2015
Fructose has become an important constituent of modern diet particularly in the form of sucrose and high fructose corn syrup (HFCS) which are contained in a variety of commercially available foods and drinks. A growing body of research suggests that excessive intake of fructose ( > 50 g day-1) is linked to the increasing prevalence of obesity and insulin resistance. Fructose induces ROS production and impairs mitochondrial gene expression leading to dysfunctional mitochondrial respiration. In addition, Lanaspa et al reported that fructose-induced hyperurecaemia is responsible for mitochondrial ROS production via activation of NADPH oxidase-4 (NOX4) . Carmona-Cuenca et al further showed that NOX4-mediated ROS production may occur via TGF-β1 activation in hepatocytes . Other studies have also shown that blockade of uric acid inhibits the expression of transforming growth factor (TGF)-β1 in fructose-fed mice . Collectively these studies suggest that fructose-induced ROS production is mediated via both uric acid and TGF-β1. However, Cerillo et al showed that inhibition of uric acid after fructose treatment only partially blocks ROS production , suggesting alternative mechanisms.
The purposes of our study are therefore to investigate whether fructose can: a) activates NOX in the absence of uric acid and/or TGF-β1, b) increase ROS via a NOX4-independent pathway and c) cause mitochondrial dysfunction in the absence of ROS. Hepatocytes will be cultured in medium containing 10 mM fructose, fructose + 10 mM SB431542 (TGF-β1 receptor inhibitor), fructose + 100 M allopurinol (uric acid inhibitor), fructose + SB431542 + allopurinol, fructose + 100 M apocynin + 10 M diphenyleneiodonium (DPI), and fructose + 25 M Mn tetrakis(1-methyl-4-pyridyl) porphyrin (MnTMPyP) + 10 mM N-acetylcysteine (NAC) (ROS scavengers) for 0, 24, 48 and 72 h. Mitochondrial NOX4 content will be assayed by confocal microscopy, NADPH oxidase activity by NADH consumption enzymatic assay, mitochondrial ROS by Mitosox fluorescene, mitochondrial function in permeabilised cell by Oroboros Oxygraph-2k using octanoylcarnitine + malate and pyruvate + malate as substrates.
Labels: MiParea: Exercise physiology;nutrition;life style Pathology: Diabetes, Obesity Stress:Oxidative stress;RONS Organism: Human Tissue;cell: Liver, Other cell lines Preparation: Permeabilized cells
Pathway: N HRR: Oxygraph-2k, O2k-Fluorometer
Inst South Africa Newlands, ESSM UCT Dept Human Biol Sports Sc, Univ Cape Town, South Africa. - [email protected]
- Lanaspa MA, Sanchez-Lozada LG, Choi YJ, Cicerchi C, Kanbay M, Roncal-Jimenez CA, Ishimoto T, Li N, Marek G, Duranay M (2012) Uric acid induces hepatic steatosis by generation of mitochondrial oxidative stress potential role in fructose-dependent and-independent fatty liver. J Biol Chem 287:40732-44.
- Carmona-Cuenca I, Roncero C, Sancho P, Caja L, Fausto N, Fern ez M, Fabregat I (2008) Upregulation of the NADPH oxidase NOX4 by TGFbeta in hepatocytes is required for its pro-apoptotic activity. J Hepatology 49: 965-76.
- Jia G, Habibi J, Bostick BP, Ma L, DeMarco VG, Aroor AR, Hayden MR, Whaley-Connell AT, Sowers JR (2014) Uric acid promotes left ventricular diastolic dysfunction in mice fed a Western diet. Hypertension 114:1-14.
- Cirillo P, Gersch MS, Mu W, Scherer PM, Kim KM, Gesualdo L, Henderson GN, Johnson RJ, Sautin YY (2009) Ketohexokinase-dependent metabolism of fructose induces proinflammatory mediators in proximal tubular cells. J Am Soc Nephrology 20:545-53.