Effects of lentinan on abnormal ingestive behaviors induced by tumor necrosis factor.

Lentinan (LNT), a beta-glucan derived from Lentinus edodes (Berk.) Sign., is known to work positively against cachexia in patients with malignant tumors. Because the cachectin/tumor necrosis factor (TNF) is supposed to be one of the factors that mediate cancer cachexia, we tested the effects of LNT on TNF-induced cachexia in rats. First, we analyzed in detail the cachectic actions of TNF (0.2 mg/kg/day, 5 days, IV) on food and water intake, body weight, and locomotor activity. The day after the first administration of TNF (acute phase), food and water intake, as well as body weight, of all rats decreased. However, over the next few days of treatment (chronic phase), the rats gradually developed a tolerance to the cachectic actions of TNF. Specifically, after the third administration, the rats treated with TNF had a higher amount of water intake than the control rats. This was mainly due to an increase in daytime water intake. We also analyzed the effects of LNT (0.1 or 1.0 mg/kg, twice/wk. IV) on TNF-induced cachexia, and compared the data with those from the rats treated with TNF alone. The higher dosage of LNT significantly suppressed TNF-induced daytime polydipsia and increased the amount of nighttime water intake, as well as the meal size of nighttime food intake. These results suggest that LNT partially normalizes TNF-induced cachexia in rats.