Oxidative stress rather than triglyceride accumulation is a determinant of mitochondrial dysfunction in in vitro models of hepatic cellular steatosis
Article first published online: 19 MAR 2012
© 2012 John Wiley & Sons A/S
Volume 32, Issue 7, pages 1079–1092, August 2012
How to Cite
Lockman, K. A., Baren, J. P., Pemberton, C. J., Baghdadi, H., Burgess, K. E., Plevris-Papaioannou, N., Lee, P., Howie, F., Beckett, G., Pryde, A., Jaap, A. J., Hayes, P. C., Filippi, C. and Plevris, J. N. (2012), Oxidative stress rather than triglyceride accumulation is a determinant of mitochondrial dysfunction in in vitro models of hepatic cellular steatosis. Liver International, 32: 1079–1092. doi: 10.1111/j.1478-3231.2012.02775.x
- Issue published online: 2 JUL 2012
- Article first published online: 19 MAR 2012
- Manuscript Accepted: 1 FEB 2012
- Manuscript Received: 8 JUN 2011
- mitochondrial dysfunction;
- nonalcoholic fatty liver disease;
- oxidative stress;
- reactive oxygen species;
There is still debate about the relationship between fat accumulation and mitochondrial function in nonalcoholic fatty liver disease. It is a critical question as only a small proportion of individuals with steatosis progress to steatohepatitis. In this study, we focused on defining (i) the effects of triglyceride accumulation and reactive oxygen species (ROS) on mitochondrial function (ii) the contributions of triglyceride, ROS and subsequent mitochondrial impairment on the metabolism of energy substrates.
Human hepatoblastoma C3A cells, were treated with various combinations of oleate, octanoate, lactate (L), pyruvate (P) and ammonia (N) acutely or for 72 h, before measurements of triglyceride concentration, cell respiration, ROS production, mitochondrial membrane potential, ketogenesis and gluconeogenesis, TCA cycle metabolite analysis and electron microscopy.
Acutely, LPON treatment enhanced mitochondrial respiration and ROS formation. After 72 h, despite the similarities in triglyceride accumulation, LPON treatment, but not oleate, dramatically affected mitochondrial function as evidenced by decreased respiration, increased mitochondrial membrane potential and ROS formation with concomitant enhanced ketogenesis. By comparison, respiration and ROS formation remained unperturbed with oleate. Importantly, this was accompanied by an increased gluconeogenesis and ketogenesis. The addition of the antioxidant N-acetyl-L-cysteine prevented mitochondrial dysfunction and reversed metabolic changes seen with LPON, strongly suggesting ROS involvement in mediating mitochondrial impairment.
Our data indicate that ROS formation, rather than cellular steatosis per se, impairs mitochondrial function. Thus, reduction in cellular steatosis may not always be the desired outcome without concomitant improvement in mitochondrial function and/or reducing of ROS formation.