Cultivation in Glucose-Deprived Medium Stimulates Mitochondrial Biogenesis and Oxidative Metabolism in HepG2 Hepatoma Cells

Abstract

In order to test the hypothesis that an imbalance between energy requirement and energy supply regulates mitochondrial genes and ultimately mitochondrial biogenesis, energy supply was challenged in HepG2 cells by withdrawal of glucose from the culture medium, making the cells exclusively dependent on mitochondrial ATP production. Such cells showed a 2-fold increase of cytochrome c oxidase activity, elevated levels of mitochondrial DNA, mitochondrial DNA encoded mRNAs and proteins, as well as the nuclear encoded mitochondrial transcription factor A. Lactate production was significantly reduced and glutamine was consumed as an alternative substrate for oxidative metabolism. Long-term adapted cells formed exclusively monolayers, while they normally grow in multilayers forming tumor spheroids. Also, long-term adapted cells proliferated significantly faster. No differences for the ATP/ADP ratio were observed, indicating that this is not the primary signal initiating the adaptative processes. These results show that mitochondrial biogenesis and oxidative metabolism are stimulated in HepG2 cells grown in the absence of fermentable glucose, probably in order to compensate for the diminished supply of glycolytic ATP.

Identification of ataxia‐associated mtDNA mutations (m.4052T>C and m.9035T>C) and evaluation of their pathogenicity in transmitochondrial cybrids

“…This phenomenon has been described for human HepG2 hepatoma cells grown in the absence of glucose for up to 96 h. 46 Thus, the cybrids were placed in glucose-free media for 48 h, and their viability was measured by CFDA assay (Fig. 5A).…”

Molecular-genetic characterization and rescue of a TSFM mutation causing childhood-onset ataxia and nonobstructive cardiomyopathy

“…Compared with wild-type fibroblasts, CI/CII ratios were decreased in mutant fibroblast, both in transfected and untransfected cells. To make cells more dependent on OXPHOS function, 7,8 fibroblasts were grown in DMEM-no glucose supplemented with galactose (5 mM) and fetal bovine serum 10%. In galactose medium, CI/CII ratios were also decreased in mutant cells, but they were partially recovered in transfected cells (Figure 2b).…”

Mitochondrial DNA mutations in human cancer

“…Differences in the ultra structure of mitochondria (Hoberman, 1975;Springer, 1980), and depletion cellular mitochondrial numbers have been reported in liver carcinogenesis (Cuezva et al, 2002). Also, as discussed above, differences in content and composition of all oxidative phosphorylation complexes (Irwin et al, 1978;Cuezva et al, 2002;Simonnet et al, 2002) respiratory chain activity (Boitier et al, 1995;Rossignol et al, 2004) expression of oxidative phosphorylation genes (Weber et al, 2002) and levels of mitochondrial DNA (Simonnet et al, 2002;Meierhofer et al, 2004;Mambo et al, 2005) were reported relative to normal controls.…”