Mitochondrial dysfunction precedes insulin resistance and hepatic steatosis and contributes to the natural history of non-alcoholic fatty liver disease in an obese rodent model

Rector, R. Scott; Thyfault, John P.; Uptergrove, Grace M.; Morris, E. Matthew; Naples, Scott P.; Borengasser, Sarah J.; Mikus, Catherine R.; Laye, Matthew J.; Laughlin, M. Harold; Booth, Frank W.; Ibdah, Jamal A.

doi:10.1016/j.jhep.2009.11.030

« Previous Next »Journal of Hepatology
Volume 52, Issue 5 , Pages 727-736, May 2010

Mitochondrial dysfunction precedes insulin resistance and hepatic steatosis and contributes to the natural history of non-alcoholic fatty liver disease in an obese rodent model

R. Scott Rector
- Division of Gastroenterology and Hepatology, 5 Hospital Drive, CE405 Clinical Support & Education Building, University of Missouri-Columbia, Columbia, MO 65212, USA
John P. Thyfault
- Division of Gastroenterology and Hepatology, 5 Hospital Drive, CE405 Clinical Support & Education Building, University of Missouri-Columbia, Columbia, MO 65212, USA
- Harry S. Truman Memorial Veterans Medical Center, Columbia, MO, USA
- Departments of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO, USA
Grace M. Uptergrove
- Division of Gastroenterology and Hepatology, 5 Hospital Drive, CE405 Clinical Support & Education Building, University of Missouri-Columbia, Columbia, MO 65212, USA
E. Matthew Morris
- Division of Gastroenterology and Hepatology, 5 Hospital Drive, CE405 Clinical Support & Education Building, University of Missouri-Columbia, Columbia, MO 65212, USA
- Departments of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO, USA
Scott P. Naples
- Departments of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO, USA
Sarah J. Borengasser
- Departments of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO, USA
Catherine R. Mikus
- Departments of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO, USA
Matthew J. Laye
- Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, USA
M. Harold Laughlin
- Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, USA
- Biomedical Sciences, University of Missouri, Columbia, MO, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
Frank W. Booth
- Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, USA
- Biomedical Sciences, University of Missouri, Columbia, MO, USA
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, MO, USA
Jamal A. Ibdah
- Division of Gastroenterology and Hepatology, 5 Hospital Drive, CE405 Clinical Support & Education Building, University of Missouri-Columbia, Columbia, MO 65212, USA
- Harry S. Truman Memorial Veterans Medical Center, Columbia, MO, USA
- Medical Pharmacology and Physiology, University of Missouri, Columbia, MO, USA
- Corresponding author. Address: Division of Gastroenterology and Hepatology, 5 Hospital Drive, CE405 Clinical Support & Education Building, University of Missouri-Columbia, Columbia, MO 65212, USA. Tel.: +1 573 882 0482; fax: +1 573 884 4595.

Received 25 August 2009; received in revised form 20 October 2009; accepted 5 November 2009. published online 04 March 2010.

Background & Aims

In this study, we sought to determine the temporal relationship between hepatic mitochondrial dysfunction, hepatic steatosis and insulin resistance, and to examine their potential role in the natural progression of non-alcoholic fatty liver disease (NAFLD) utilising a sedentary, hyperphagic, obese, Otsuka Long–Evans Tokushima Fatty (OLETF) rat model.

Methods

OLETF rats and their non-hyperphagic control Long–Evans Tokushima Otsuka (LETO) rats were sacrificed at 5, 8, 13, 20, and 40weeks of age (n=6–8 per group).

Results

At 5weeks of age, serum insulin and glucose and hepatic triglyceride (TG) concentrations did not differ between animal groups; however, OLETF animals displayed significant (p<0.01) hepatic mitochondrial dysfunction as measured by reduced hepatic carnitine palmitoyl-CoA transferase-1 activity, fatty acid oxidation, and cytochrome c protein content compared with LETO rats. Hepatic TG levels were significantly elevated by 8weeks of age, and insulin resistance developed by 13weeks in the OLETF rats. NAFLD progressively worsened to include hepatocyte ballooning, perivenular fibrosis, 2.5-fold increase in serum ALT, hepatic mitochondrial ultrastructural abnormalities, and increased hepatic oxidative stress in the OLETF animals at later ages. Measures of hepatic mitochondrial content and function including β-hydroxyacyl-CoA dehydrogenase activity, citrate synthase activity, and immunofluorescence staining for mitochondrial carbamoyl phosphate synthetase-1, progressively worsened and were significantly reduced at 40weeks in OLETF rats compared to LETO animals.

Conclusions

Our study documents that hepatic mitochondrial dysfunction precedes the development of NAFLD and insulin resistance in the OLETF rats. This evidence suggests that progressive mitochondrial dysfunction contributes to the natural history of obesity-associated NAFLD.

Keywords: Non-alcoholic fatty liver disease, Fatty acid oxidation, Mitochondrial dysfunction, OLETF rat

Abbreviations: NAFLD, non-alcoholic fatty liver disease, NASH, non-alcoholic steatohepatitis, OLETF, Otsuka Long–Evans Tokushima Fatty rats, ASM, acid soluble metabolite, CPS-1, carbamoylphosphate synthetase-1, H&E, hematoxylin and eosin, TGF-β, transforming growth factor- β, TG, triglycerides, FFA, free fatty acids, ALT, alanine aminotransferase, HbA1c, hemoglobin A1c, GSSG, oxidized glutathione, SOD, superoxide dismutase, β-HAD, beta-hydroxyacyl-CoA dehydrogenase, CPT-1, carnitine palmitoyl-CoA transferase-1, TEM, transmission electron microscopy, SE, standard error of the mean, UCP-2, uncoupling protein-2