Metabolism of round spermatids in the rat: effect of gossypol on the glucose transport

Antimetabolic Effects of Polyphenols in Breast Cancer Cells: Focus on Glucose Uptake and Metabolism

In the last years, metabolic reprogramming became a new key hallmark of tumor cells. One of its components is a deviant energetic metabolism, known as Warburg effect—an aerobic lactatogenesis—characterized by elevated rates of glucose uptake and consumption with high-lactate production even in the presence of oxygen. Because many cancer cells display a greater sensitivity to glucose deprivation-induced cytotoxicity than normal cells, inhibitors of glucose cellular uptake (facilitative glucose transporter 1 inhibitors) and oxidative metabolism (glycolysis inhibitors) are potential therapeutic targets in cancer treatment. Polyphenols, abundantly contained in fruits and vegetables, are dietary components with an established protective role against cancer. Several molecular mechanisms are involved in the anticancer effect of polyphenols, including effects on apoptosis, cell cycle regulation, plasma membrane receptors, signaling pathways, and epigenetic mechanisms. Additionally, inhibition of glucose cellular uptake and metabolism in cancer cell lines has been described for several polyphenols, and this effect was shown to be associated with their anticarcinogenic effect. This work will review data showing an antimetabolic effect of polyphenols and its involvement in the chemopreventive/chemotherapeutic potential of these dietary compounds, in relation to breast cancer.

Effect of polyphenols on glucose and lactate transport by breast cancer cells

One of the cancer molecular hallmarks is a deviant energetic metabolism, known as the Warburg effect, whereby the rate of glucose uptake is significantly increased and a high rate of glycolysis and lactic acid production occurs even when oxygen is present-"aerobic lactatogenesis". Accordingly, GLUT1 and MCT1, which are the main glucose and lactate transporters in cancer cells, respectively, have been proposed as oncogenes and are currently seen as potential therapeutic targets in cancer treatment. Polyphenols, commonly contained in fruits and vegetables, have long been associated with a protective role against cancer. Generally considered as nontoxic, dietary polyphenols are considered ideal chemopreventive and possibly chemotherapeutic agents. Several mechanisms of action of polyphenols in breast cancer cells have been proposed including modulation of intracellular signaling, induction of apoptosis through redox regulation or modulation of epigenetic alterations. Additionally, in vitro studies have shown that several polyphenols act as specific inhibitors of glucose transport in breast cancer cell lines and an association between their anticarcinogenic effect and inhibition of glucose cellular uptake has been described. Also, some polyphenols were found to inhibit lactate transport. Importantly, some polyphenols behave as inhibitors of both glucose and lactate cellular uptake by breast cancer cells and these compounds are thus very interesting in the context of a chemopreventive effect, because they deplete breast cancer cells of their two most important energy suppliers. So, the antimetabolic effect of polyphenols should be regarded as a mechanism of action contributing to their chemopreventive/chemotherapeutic potential in relation to breast cancer.

The antifertility agent, gossypol, changes several mitochondrial functions in the presence of Mg2+

1. The effect of gossypol in the presence of K+ or Mg2+, or both, was studied on ATPase activity and respiration of rat liver mitochondria. 2. Respiration was uncoupled in the presence of gossypol, Mg2+, and K+, whereas in the presence of gossypol and Mg2+ a partial inhibition was observed. 3. Gossypol stimulated ATPase activity in the presence of K+ or Mg2+, but maximal activity was observed when both cations were in the incubation medium. 4. Stimulation of ATPase activity in the presence of Mg2+ was dose related. 5. EDTA reverted the stimulation produced by gossypol on ATPase activity. 6. Gossypol had no effect on the ATPase activity of submitochondrial particles, which suggests an indirect action of gossypol on the enzyme. 7. Mitochondrial membrane potential showed a higher collapse in the presence of gossypol and 1 mM MgCl2. 8. The observed effects of gossypol could be explained by the collapse of the mitochondrial membrane potential.