Effect of 12-wk Training in Ovariectomised Rats on PGC-1α, NRF-1 and Energy Substrates.

Metabolic diseases are associated with hypoestrogenism owing to their lower energy expenditure and consequent imbalance. Physical training promotes energy expenditure through PGC-1α and NRF-1, which are muscle proteins of the oxidative metabolism. However, the influence of physical training on protein expression in individuals with hypoestrogenism remains uncertain. Thus, the aim of this study is to determine the effect of 12 weeks of moderate-intensity swimming training on the muscle expression of PGC-1α, NRF-1, glycogen and triglyceride in ovariectomised rats. OVX and OVX+TR rats were subjected to ovariectomy. The trained animals swam for 30 minutes, 5 days/week, at 80% of the critical load intensity. Soleus was collected to quantify PGC-1α and NRF-1 expressions, while gastrocnemius and gluteus maximus were collected to measure glycogen and triglyceride. Blood glucose was also evaluated. Whereas ovariectomy decreased PGC-1α expression (p<0.05) without altering NRF-1 (p=0.48), physical training increased PGC-1α (p<0.01) and NRF-1 (p<0.05). Ovariectomy reduced glycogen (p<0.05) and triglyceride (p<0.05), whereas physical training increased glycogen (p<0.05) but did not change triglyceride (p=0.06). Ovariectomy increased blood glucose (p<0.01), while physical training reduced it (p<0.01). In summary, 12 weeks of individualized and moderate-intensity training were capable of preventing muscle metabolic consequences caused by ovariectomy.

Guarana (Paullinia cupana) Stimulates Mitochondrial Biogenesis in Mice Fed High-Fat Diet.

The aim of this study was to evaluate the effects of guarana on mitochondrial biogenesis in a high-fat diet (HFD)-fed mice. C57BL6J mice were divided in two groups: high-fat diet HFD and high-fat diet + guarana (HFD-GUA). Both groups received HFD and water ad libitum and the HFD-GUA group also received a daily gavage of guarana (1 g/kg weight). Body weight and food intake was measured weekly. Glycemic, triglyceride, and cholesterol levels were determined. VO2 and energy expenditure (EE) were determined by indirect calorimetry. Gene expression was evaluated by real-time PCR and protein content by western blotting. The HFD-GUA group presented lower body weight, subcutaneous, retroperitoneal, visceral, and epididyimal adipose tissue depots, and glycemic and triglyceride levels, with no change in food intake and cholesterol levels. Furthermore, the HFD-GUA group presented an increase in VO2 and basal energy expenditure (EE), as well as Pgc1α, Creb1, Ampka1, Nrf1, Nrf2, and Sirt1 expression in the muscle and brown adipose tissue. In addition, the HFD-GUA group presented an increase in mtDNA (mitochondrial deoxyribonucleic acid) content in the muscle when compared to the HFD group. Thus, our data showed that guarana leads to an increase in energetic metabolism and stimulates mitochondrial biogenesis, contributing to control of weight gain, even when associated with high-fat diet.

A role for focal adhesion kinase in cardiac mitochondrial biogenesis induced by mechanical stress.

We studied the implication of focal adhesion kinase (FAK) in cardiac mitochondrial biogenesis induced by mechanical stress. Prolonged stretching (2-12 h) of neonatal rat ventricular myocytes (NRVM) upregulated the main components of mitochondrial transcription cascade [peroxisome proliferator-activated receptor coactivator-1 (PGC-1α), nuclear respiratory factor (NRF-1), and mitochondrial transcription factor A]. Concomitantly, prolonged stretching enhanced mitochondrial biogenesis [copy number of mitochondrial DNA (mtDNA), content of the subunit IV of cytochrome oxidase, and mitochondrial staining-green fluorescence intensity of Mitotracker green] and induced the hypertrophic growth (cell size and atrial natriuretic peptide transcripts) of NRVM. Furthermore, the stretching of NRVM enhanced phosphorylation, nuclear localization, and association of FAK with PGC-1α. Recombinant FAK COOH-terminal, but not the NH(2)-terminal or kinase domain, precipitated PGC-1α from nuclear extracts of NRVM. Depletion of FAK by RNA interference suppressed the upregulation of PGC-1α and NRF-1 and markedly attenuated the enhanced mitochondrial biogenesis and hypertrophic growth of stretched NRVM. In the context of energy metabolism, FAK depletion became manifest by a reduction of ATP levels in stretched NRVM. Complementary studies in adult mice left ventricle demonstrated that pressure overload upregulated PGC-1α, NRF-1, and mtDNA. In vivo FAK silencing transiently attenuated the upregulation of PGC-1α, NRF-1, and mtDNA, as well as the left ventricular hypertrophy induced by pressure overload. In conclusion, activation of FAK signaling seems to be important for conferring enhanced mitochondrial biogenesis coupled to the hypertrophic growth of cardiomyocytes in response to mechanical stress, via control of mitochondrial transcription cascade.

Oxidative stress and upregulation of mitochondrial biogenesis genes in mitochondrial DNA-depleted HeLa cells.

The signaling mechanism through which deficitary mitochondrial function would activate nuclear genes required for mitochondrial biogenesis, has not been established. To explore the hypothesis that reactive oxygen species (ROS), a mitochondrial product, constitute part of the mitochondria-nuclei signaling pathway, we obtained HeLa cells depleted of mitochondrial DNA (rho0 cells) through exposure to ethidium bromide. We found evidences of oxidative stress in rho0 cells, employing a fluorescent probe and measuring NF-kappaB activation. Nuclear Respiratory Factor-1 (NRF-1) and Mitochondrial Transcription Factor A (Tfam) mRNA were measured by RT-PCR. For both transcription factors, rho0 cells revealed significantly higher levels of mRNA. These results support several hypothesis: that endogenous ROS enhance the expression of nuclear mitochondrial biogenesis genes NRF-1 and Tfam; that DNA deprived mitochondria lead to cellular oxidative stress, probably because of incomplete biogenesis of the mitochondrial electron transport chain, and consequently, that ROS are part of a mitochondria-nuclei regulatory signaling pathway.