Changes in Mitochondrial DNA Deletion, Content, and Biogenesis in Folate-Deficient Tissues of Young Rats Depend on Mitochondrial Folate and Oxidative DNA Injuries3

Abstract

We aimed to characterize folate-related changes in mitochondrial (mt) DNA of various tissues of young rats. Weaning Wistar rats were fed folate-deficient (FD) or folate-replete (control) diet for 2 or 4 wk. The mtDNA 4834-bp large deletion (mtDNA(4834) deletion) and mtDNA content were analyzed by quantitative real-time PCR. Compared with pooled 2-wk and 4-wk control groups, 4-wk folate deprivation significantly increased the frequency of the mtDNA(4834) deletion in pancreas, heart, brain, liver, and kidney and reduced mtDNA contents in brain, heart, and liver (P < 0.05). Decreased mt folate levels were correlated with increased mtDNA(4834) deletion frequency in tissues from FD rats after 2 wk (r = -0.380, P = 0.001) and 4 wk FD (r = -0.275, P = 0.033) and with reduced mtDNA content after 4 wk (r = 0.513, P = 0.005). In liver of 4-wk FD rats, the accumulated mtDNA large deletions and decline in mtDNA accompanied increased expressions of messenger RNAs (mRNA) of factors that regulate mtDNA proliferation and transcription, including nuclear respiratory factor 1, mt transcriptional factor A, mt single-strand DNA-binding protein, and mt polymerase r. In parallel, expression of mRNA for nuclear-encoded cytochrome c oxidase subunits (CcOX) IV, V, cytochrome c, and mtDNA-encoded CcOX III increased significantly. This enhanced mt biogenesis in 4-wk FD liver coincided with an elevated ratio of 8 hydroxydeoxyguanosine (8-OHdG):deoxyguanosine (dG) (2.67 +/- 1.41) relative to the controls (0.99 +/- 0.36; P = 0.0002). The 8-OHdG:dG levels in FD liver were correlated with liver mt folate (r = -0.819, P < 0.001), mtDNA deletions (r = 0.580, P = 0.001), and mtDNA contents (r = -0.395, P = 0.045). Thus, folate deprivation induced aberrant changes of mtDNA(4834) deletion and mtDNA content in a manner that was dependent on mt folate and oxidative DNA injuries. The folate-related mt biogenesis provides a molecular mechanism to compensate mtDNA impairment in FD tissues.

Changes in dietary folate intake differentially affect oxidised lipid and mitochondrial DNA damage in various brain regions of rats in the absence/presence of intracerebroventricularly injected amyloid β-peptide challenge

“…1). This finding is in accordance with our previous observation that an FD diet depleted brain folate levels and promoted the accumulation of large mtDNA deletions in whole-brain homogenates of rats (25) . A study has revealed that FD impaired mt antioxidant status, promoted superoxide overproduction and elevated mt protein oxidative damage (46) .…”

“…Consistently, we have previously shown that feeding rats an FD diet for 4 weeks elevated serum homocysteine levels, which were associated with brain oxidative DNA damage as well as increased hepatic lipid peroxidation (25,43) . Although elevated brain homocysteine levels were not measured in the present study, our data showed that 4 weeks of the FD diet significantly promoted higher levels of TBARS in the liver of rats, in parallel with FD-induced hippocampal folate depletion and oxidative lipid damage (Tables 2 and 3).…”

“…The quantity of mtDNA 4834 deletion was determined by co-amplifying the mtDNA displacement loop and mtDNA 4834 deletion in a realtime PCR assay. Primers for each have been previously described (25) . The extent of mtDNA 4834 primer, 50 nmol/l of each displacement loop primer and 100 nmol/l of each mtDNA 4834 deletion and displacement loop probes.…”

Mitochondrial 8-oxoguanine glycosylase decreases mitochondrial fragmentation and improves mitochondrial function in H9C2 cells under oxidative stress conditions

“…Elevated levels of 8-OHdG have been associated with increased mtDNA deletions, mutation, and mtDNA loss (3,6,15,21). For instance, the levels of 8-OHdG and the mtDNA content were 50% higher and 75% lower, respectively, in the left ventricular tissue from end-stage heart failure patients compared with non-heart failure patients (22).…”

Endurance training accelerates exhaustive exercise-induced mitochondrial DNA deletion and apoptosis of left ventricle myocardium in rats

“…The quantiWcation of mtDNA 4834 deletion was determined by coamplifying the mtDNA displacement-loop (D-loop), mtDNA 4834 deletion, and nuclear-encoded -actin gene by real-time PCR (Chou et al 2007;Branda et al 2002). The Xuorescence spectra were monitored by LightCycler (Roche Diagnostics).…”