Exercise training increases mitochondria and GLUT4 in skeletal muscles. Recent studies indicate that an increased expression of the transcriptional coactivator peroxisome proliferator-activated receptor ␥ coactivator 1␣ (PGC-1␣) by exercise may promote mitochondrial biogenesis and fatty acid oxidation. To examine whether increased PGC-1␣ expression was also responsible for an increase of GLUT4 expression, transgenic mice that overexpress PGC-1␣ in skeletal muscles driven by a human ␣-skeletal actin promoter were made. PGC-1␣ was overexpresssed in skeletal muscles including type I and II fiber-rich muscles but not in the heart. With an increase of PGC-1␣ mRNA, type II fiber-rich muscles were redder, and genes of mitochondrial oxidative metabolism were up-regulated in skeletal muscles, whereas the expression of GLUT4 mRNA was unexpectedly downregulated. In parallel with a decrease of GLUT4 mRNA, an impairment of glycemic control after intraperitoneal insulin administration was observed. Thus, an increase of PGC-1␣ plays a role in increasing mitochondrial biogenesis and fatty acid oxidation but not in increasing GLUT4 mRNA in skeletal muscles.Endurance exercise training improves physical performance by an enhancement of skeletal muscle respiratory capacity (1) and decreases the incidence rate of diabetes mellitus (2). These effects might be related to increased numbers of mitochondria and the GLUT4 isoform of the glucose transporter in skeletal muscles, respectively. GLUT4, the insulin-responsive glucose transporter, is expressed in skeletal muscles, heart, and adipose tissues, and the number of GLUT4 on plasma membrane becomes a rate-limiting step for whole-body glucose clearance under physiological conditions (3-5). Thus, exercise training modifies the skeletal muscle to metabolize more fatty acids and glucose.As for mitochondrial biogenesis, two transcription factors, nuclear respiratory factor (NRF)-1 1 and NRF-2, were the key transcriptional activators of nuclear genes encoding mitochondrial enzymes (6, 7). NRFs up-regulate mitochondrial transcription factor A, which stimulates mitochondrial DNA transcription and replication (8). Recently, as a regulator of NRFs, peroxisome proliferator-activated receptor ␥ coactivator-1 (PGC-1␣) was found. PGC-1␣ is an inducible coactivator of nuclear receptors cloned from brown fat cell cDNA library because of its interaction with peroxisome proliferator-activated receptor ␥ (PPAR␥) (9). Overexpression of PGC-1␣ increased expression of mitochondrial enzymes in 3T3 adipocytes, stimulated mitochondrial biogenesis in C2C12 myocytes (9, 10), and induced the expression of nuclear and mitochondrial genes involved in multiple mitochondrial energy production pathways, including PPAR␣ target genes encoding the mitochondrial fatty acid ␤-oxidation in neonatal cardiac myocytes (11). In vivo cardiac-specific overexpression of PGC-1␣ in transgenic mice resulted in uncontrolled massive proliferation of mitochondria (11). Also, evidence that PGC-1␣ co-activated PPAR␣ (12) and NRF-1 (10) le...

Although lycopene, a major carotenoid component of tomatoes, has been suggested to attenuate the risk of breast cancer, the underlying preventive mechanism remains to be determined. Moreover, it is not known whether there are any differences in lycopene activity among different subtypes of human breast cancer cells. Using ER/PR positive MCF-7, HER2-positive SK-BR-3 and triple-negative MDA-MB-468 cell lines, we investigated the cellular and molecular mechanism of the anticancer activity of lycopene. Lycopene treatment for 168 consecutive hours exhibited a time-dependent and dose-dependent anti-proliferative activity against these cell lines by arresting the cell cycle at the G0/G1 phase at physiologically achievable concentrations found in human plasma. The greatest growth inhibition was observed in MDA-MB-468 where the sub-G0/G1 apoptotic population was significantly increased, with demonstrable cleavage of PARP. Lycopene induced strong and sustained activation of the ERK1/2, with concomitant cyclin D1 suppression and p21 upregulation in these three cell lines. In triple negative cells, lycopene inhibited the phosphorylation of Akt and its downstream molecule mTOR, followed by subsequent upregulation of proapoptotic Bax without affecting anti-apoptotic Bcl-xL. Taken together, these data indicate that the predominant anticancer activity of lycopene in MDA-MB-468 cells suggests a potential role of lycopene for the prevention of triple negative breast cancer.

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Although pterostilbene, a natural analog of resveratrol, has potent antitumor activity against several human cancer types, the possible inhibitory mechanisms against subtypes of human breast cancer with different hormone receptor and human epidermal growth factor receptor 2 (HER2) status remain unknown. We investigated the anticancer activity of pterostilbene using three subtypes of breast cancer cell lines. Pterostilbene treatment exhibited a dose-dependent antiproliferative activity, with the greatest growth inhibition observed in triple-negative MDA-MB-468 cells. Although pterostilbene arrested cell-cycle progression at the G/G phase regardless of breast cancer subtype, its apoptosis-inducing activity was highly apparent in MDA-MB-468 cells. Pterostilbene induced strong and sustained activation of extracellular signal-regulated kinase (ERK) 1/2, with concomitant cyclin D1 suppression and p21 up-regulation, and inhibited the phosphorylation of AKT and mammalian target of rapamycin (mTOR), followed by subsequent up-regulation of BAX without affecting B-cell lymphoma-extra large (BCL-xL). Oral administration of pterostilbene significantly suppressed tumor growth in nude mice xenotransplanted with MDA-MB-468 cells. These data suggest a potential role of pterostilbene for prevention and treatment of human breast cancer, especially of triple-negative breast cancer.

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