Elevated blood lactate is not a primary cause of anorexia in tumor-bearing rats

Tumor-bearing (TB) rats exhibit elevated concentrations of lactate in blood contiguous with the development of anorexia. Continuous intravenous infusion of lactate into non-TB rats reduced food intake at plasma concentrations lower than those observed in anorectic TB rats. Levels of neuropeptide Y (NPY) were elevated in the ventromedial (VMH) and dorsomedial hypothalamic regions of lactate-infused rats. The addition of the enhancer of pyruvate dehydrogenase activity, dichloroacetate (DCA), to the drinking water of TB rats (0.1-0.4%) normalized blood lactate concentration but had no significant effect on anorexia. However, the elevated concentration of NPY in the VMH of anorectic TB rats was also normalized by the DCA treatment. No alterations in regional hypothalamic levels of corticotropin-releasing factor were observed within any treatment conditions. These results suggest that, although hyperlactatemia may be involved in maintaining elevated NPY concentrations in anorectic TB rats, it does not appear t...