Impact of High Fat Dietary Treatment and Nox2-Deficiency on Prooxidant and Antioxidant Enzyme Expression in the Heart

Abstract

Over the last decades obesity has become a major global health problem and its prevalence is still increasing in both western and developing countries [1-3]. Obesity is associated with a state of low-grade systemic inflammation and increased levels of oxidative stress, which both contribute to the development of cardiovascular disease [4-9]. However, up to now little is known about cardiac redox balance and the potential contribution of free radicals to cardiac disease in obesity. In this study, the effects of 15 weeks of dietary treatment with either a low fat diet (LFD), a high fat diet (HFD) or a very high fat diet (VHFD) on steady state messenger RNA (mRNA) expression levels of pro- and antioxidant genes in the heart of C57BL/6 mice were examined. In addition, the impact of nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase subunit Nox2-deficiency combined with a low fat diet (LFD-N) or a high fat diet (HFD-N) were investigated. RNA was isolated from the heart tissue, reverse transcripted and quantified using real-time polymerase chain reaction. While mRNA expression levels of NAD(P)H oxidase subunits Nox2 and Nox4, nitric oxide synthase-2 and - 3, superoxide dismutase-3 and glutathione peroxidase-1 were not affected by 15 weeks of high fat dietary treatment, reduced mRNA expression levels of NAD(P)H oxidase subunit p22phox (P=0.02 vs. LFD, P=0.03 vs. HFD) as well as reduced mRNA expression levels of superoxide dismutase-1 (P=0.01 vs. LFD, P=0.01 vs. HFD) and antioxidant-1 (P=0.004 vs. LFD, P=0.007 vs. HFD) were found in mice fed a VHFD. In Nox2-deficient mice, HFD lowered expression levels of p22phox mRNA (P=0.05 vs. LFD-N) and of superoxide dismutase-3 (P=0.03 vs. HFD). The mRNA expression levels of the other genes investigated were not affected by Nox2-deficiency. In conclusion, the present study demonstrates that in C57BL/6 mice neither high dietary fat intake nor Nox2-deficiency lead to major alterations in cardiac mRNA expression of the redox genes investigated. However, high fat dietary treatment may lead to down-regulation of superoxide dismutase-1 mRNA expression in the heart, thus possibly contributing to impairment of cardiac defense mechanisms against oxidative stress and promoting cardiac disease.