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High fat diet induces dysregulation of hepatic oxygen gradients and mitochondrial function in vivo.

Mantena SK, Vaughn DP, Andringa KK, Eccleston HB, King AL, Abrams GA, Doeller JE, Kraus DW, Darley-Usmar VM, Bailey SM - Biochem. J. (2009)

Bottom Line: NAFLD (non-alcoholic fatty liver disease), associated with obesity and the cardiometabolic syndrome, is an important medical problem affecting up to 20% of western populations.Mitochondria from the HFD group showed increased sensitivity to NO-dependent inhibition of respiration compared with controls.These findings indicate that chronic exposure to a HFD negatively affects the bioenergetics of liver mitochondria and this probably contributes to hypoxic stress and deleterious NO-dependent modification of mitochondrial proteins.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Health Sciences, Center for Free Radical Biology, The University of Alabama at Birmingham, Birmingham, AL 35294, USA.

ABSTRACT
NAFLD (non-alcoholic fatty liver disease), associated with obesity and the cardiometabolic syndrome, is an important medical problem affecting up to 20% of western populations. Evidence indicates that mitochondrial dysfunction plays a critical role in NAFLD initiation and progression to the more serious condition of NASH (non-alcoholic steatohepatitis). Herein we hypothesize that mitochondrial defects induced by exposure to a HFD (high fat diet) contribute to a hypoxic state in liver and this is associated with increased protein modification by RNS (reactive nitrogen species). To test this concept, C57BL/6 mice were pair-fed a control diet and HFD containing 35% and 71% total calories (1 cal approximately 4.184 J) from fat respectively, for 8 or 16 weeks and liver hypoxia, mitochondrial bioenergetics, NO (nitric oxide)-dependent control of respiration, and 3-NT (3-nitrotyrosine), a marker of protein modification by RNS, were examined. Feeding a HFD for 16 weeks induced NASH-like pathology accompanied by elevated triacylglycerols, increased CYP2E1 (cytochrome P450 2E1) and iNOS (inducible nitric oxide synthase) protein, and significantly enhanced hypoxia in the pericentral region of the liver. Mitochondria from the HFD group showed increased sensitivity to NO-dependent inhibition of respiration compared with controls. In addition, accumulation of 3-NT paralleled the hypoxia gradient in vivo and 3-NT levels were increased in mitochondrial proteins. Liver mitochondria from mice fed the HFD for 16 weeks exhibited depressed state 3 respiration, uncoupled respiration, cytochrome c oxidase activity, and mitochondrial membrane potential. These findings indicate that chronic exposure to a HFD negatively affects the bioenergetics of liver mitochondria and this probably contributes to hypoxic stress and deleterious NO-dependent modification of mitochondrial proteins.

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Effect of HFD on uncoupler-stimulated respiration and the membrane potential in liver mitochondria(A) Oxygen consumption was measured in freshly isolated mitochondria in the presence of succinate/rotenone (15 mM/5 μM) and the uncoupler FCCP (1 μM). (B) Membrane potential was reported by the red/green fluorescence ratio of JC-1 in freshly isolated coupled (−FCCP) and uncoupled (+FCCP) mitochondria. Both uncoupled respiration and membrane potential are shown for the 16 week feeding time point. Values are expressed as the means±S.E.M. of six pairs of mice. *P<0.05, compared with control. AU, absorbance units.
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Figure 4: Effect of HFD on uncoupler-stimulated respiration and the membrane potential in liver mitochondria(A) Oxygen consumption was measured in freshly isolated mitochondria in the presence of succinate/rotenone (15 mM/5 μM) and the uncoupler FCCP (1 μM). (B) Membrane potential was reported by the red/green fluorescence ratio of JC-1 in freshly isolated coupled (−FCCP) and uncoupled (+FCCP) mitochondria. Both uncoupled respiration and membrane potential are shown for the 16 week feeding time point. Values are expressed as the means±S.E.M. of six pairs of mice. *P<0.05, compared with control. AU, absorbance units.

Mentions: Mitochondrial function was further evaluated by assessing uncoupled respiration and the mitochondrial membrane potential. At 16 weeks, uncoupled respiration, i.e. respiration in the presence of FCCP, was significantly decreased in mitochondria from HFD mice compared with controls (Figure 4A). Feeding a HFD for 16 weeks also decreased the red/green fluorescence ratio of the membrane potential sensitive dye JC-1, indicating impairment in the ability of mitochondria to fully develop a membrane potential (Figure 4B). There was no difference in JC-1 fluorescence between control and HFD groups when mitochondria were uncoupled with FCCP, indicating that the HFD-dependent decrease was not due to inherent differences in mitochondria that would have affected baseline measurements or uptake of JC-1. Taken together, these data suggest that feeding a HFD causes mitochondrial dysfunction at the level of the respiratory chain.


High fat diet induces dysregulation of hepatic oxygen gradients and mitochondrial function in vivo.

Mantena SK, Vaughn DP, Andringa KK, Eccleston HB, King AL, Abrams GA, Doeller JE, Kraus DW, Darley-Usmar VM, Bailey SM - Biochem. J. (2009)

Effect of HFD on uncoupler-stimulated respiration and the membrane potential in liver mitochondria(A) Oxygen consumption was measured in freshly isolated mitochondria in the presence of succinate/rotenone (15 mM/5 μM) and the uncoupler FCCP (1 μM). (B) Membrane potential was reported by the red/green fluorescence ratio of JC-1 in freshly isolated coupled (−FCCP) and uncoupled (+FCCP) mitochondria. Both uncoupled respiration and membrane potential are shown for the 16 week feeding time point. Values are expressed as the means±S.E.M. of six pairs of mice. *P<0.05, compared with control. AU, absorbance units.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2637578&req=5

Figure 4: Effect of HFD on uncoupler-stimulated respiration and the membrane potential in liver mitochondria(A) Oxygen consumption was measured in freshly isolated mitochondria in the presence of succinate/rotenone (15 mM/5 μM) and the uncoupler FCCP (1 μM). (B) Membrane potential was reported by the red/green fluorescence ratio of JC-1 in freshly isolated coupled (−FCCP) and uncoupled (+FCCP) mitochondria. Both uncoupled respiration and membrane potential are shown for the 16 week feeding time point. Values are expressed as the means±S.E.M. of six pairs of mice. *P<0.05, compared with control. AU, absorbance units.
Mentions: Mitochondrial function was further evaluated by assessing uncoupled respiration and the mitochondrial membrane potential. At 16 weeks, uncoupled respiration, i.e. respiration in the presence of FCCP, was significantly decreased in mitochondria from HFD mice compared with controls (Figure 4A). Feeding a HFD for 16 weeks also decreased the red/green fluorescence ratio of the membrane potential sensitive dye JC-1, indicating impairment in the ability of mitochondria to fully develop a membrane potential (Figure 4B). There was no difference in JC-1 fluorescence between control and HFD groups when mitochondria were uncoupled with FCCP, indicating that the HFD-dependent decrease was not due to inherent differences in mitochondria that would have affected baseline measurements or uptake of JC-1. Taken together, these data suggest that feeding a HFD causes mitochondrial dysfunction at the level of the respiratory chain.

Bottom Line: NAFLD (non-alcoholic fatty liver disease), associated with obesity and the cardiometabolic syndrome, is an important medical problem affecting up to 20% of western populations.Mitochondria from the HFD group showed increased sensitivity to NO-dependent inhibition of respiration compared with controls.These findings indicate that chronic exposure to a HFD negatively affects the bioenergetics of liver mitochondria and this probably contributes to hypoxic stress and deleterious NO-dependent modification of mitochondrial proteins.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Health Sciences, Center for Free Radical Biology, The University of Alabama at Birmingham, Birmingham, AL 35294, USA.

ABSTRACT
NAFLD (non-alcoholic fatty liver disease), associated with obesity and the cardiometabolic syndrome, is an important medical problem affecting up to 20% of western populations. Evidence indicates that mitochondrial dysfunction plays a critical role in NAFLD initiation and progression to the more serious condition of NASH (non-alcoholic steatohepatitis). Herein we hypothesize that mitochondrial defects induced by exposure to a HFD (high fat diet) contribute to a hypoxic state in liver and this is associated with increased protein modification by RNS (reactive nitrogen species). To test this concept, C57BL/6 mice were pair-fed a control diet and HFD containing 35% and 71% total calories (1 cal approximately 4.184 J) from fat respectively, for 8 or 16 weeks and liver hypoxia, mitochondrial bioenergetics, NO (nitric oxide)-dependent control of respiration, and 3-NT (3-nitrotyrosine), a marker of protein modification by RNS, were examined. Feeding a HFD for 16 weeks induced NASH-like pathology accompanied by elevated triacylglycerols, increased CYP2E1 (cytochrome P450 2E1) and iNOS (inducible nitric oxide synthase) protein, and significantly enhanced hypoxia in the pericentral region of the liver. Mitochondria from the HFD group showed increased sensitivity to NO-dependent inhibition of respiration compared with controls. In addition, accumulation of 3-NT paralleled the hypoxia gradient in vivo and 3-NT levels were increased in mitochondrial proteins. Liver mitochondria from mice fed the HFD for 16 weeks exhibited depressed state 3 respiration, uncoupled respiration, cytochrome c oxidase activity, and mitochondrial membrane potential. These findings indicate that chronic exposure to a HFD negatively affects the bioenergetics of liver mitochondria and this probably contributes to hypoxic stress and deleterious NO-dependent modification of mitochondrial proteins.

Show MeSH
Related in: MedlinePlus