The objective of this study was to investigate the activation of natural killer (NK) cells and anticancer effects of exo-biopolymer from rice bran cultured with Lentinus edodes [rice bran exo-biopolymer (RBEP)]. Oral administration of RBEP induced the activation of NK cells in a dose-dependent manner. RBEP also prolonged the life spans of mice transplanted with Sarcoma-180 cells and inhibited growing Sarcoma-180 cells in intraperitoneum. Solid tumor growth was also suppressed by oral administration of RBEP in C57/Bl6 mice transplanted with B16/Bl6 melanoma. Intraperitoneal injection of RBEP was more effective than oral administration at the same dosage in mice with transplanted tumor cells. According to this result, when RBEP directly contacts immune cells, the anticancer activity is higher than by indirectly inducing an immune response through oral administration. Therefore, we suggest that the administration of RBEP may be effective for preventing and/or treating cancer through NK cell activation. However, further studies are needed to elucidate the possible mechanisms of the anticancer activity and to investigate the other beneficial effects of RBEP for the development of a new biological response modifier.
Saengshik is a Korean "non-cooked food" that is commercially produced and marketed. Ingredients in commercial Saengshik include grains, vegetables, fruits, mushrooms, sea plants, and various functional botanicals. This study investigated the effects of Saengshik on the survival rate of streptozotocin (STZ)-induced diabetic rats. Male Sprague-Dawley rats weighing around 190 g were randomly assigned to one of the three experimental groups: a healthy normal group (NC) and two groups with STZ-induced diabetes and fed either control diet (DC) or Saengshik diet (DS). Rats in all groups were supplied with a diet of equal energy. The animals were maintained on an experimental diet for 168 days in experiment I and for 42 days in experiment II. The body weight in the DS rats decreased less than in the DC rats in both experiments I and II. There was a trend for blood glucose level in the DS group to decrease during the experimental period in both experiments I and II. A survival rate of 50% was reached on day 49 in the DC group and on day 118 in the DS group. All rats in the DC group died by day 140, while 50% of the rats in the DS group were still alive on day 168, when experiment I was terminated. In experiment II, 50% of the DC group and 90% of the DS group survived at day 42. Saengshik did not have any influence on cholesterol levels, thiobarbituric acid-reactive substances, and activities of superoxide dismutase and glutathione peroxidase. These results suggest that blood glucose concentrations and the survival rate are positively affected by Saengshik feeding in diabetic rats.
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