Botryosphaeran, a water-soluble exopolysaccharide of the ${eta}-(1{ ightarrow}3;1{ ightarrow}6)$-D-glucan type that has been isolated from the culture medium of Botryosphaeria rhodina MAMB-05 grown in submerged fermentation using glucose as the sole carbon source, was previously demonstrated to be non-genotoxic in peripheral blood and bone marrow, and exhibited strong anticlastogenic activity. In the present study, the effects of botryosphaeran were investigated in streptozotocin-induced diabetic rats as well as in high-fat diet-fed hyperlipidemic Wistar rats. The plasma glucose level was reduced by 52% in the diabetic group of rats after administration of 12 mg botryosphaeran/kg body weight of the rats (b.w.)/day by gavage over 15 days. A reduction in the median ration intake was accompanied by an increase in the median body weight gain, as well as the efficiency of food conversion. These results demonstrate that botryosphaeran has protective effects by reducing the symptoms of cachexia in Diabetes mellitus. Botryosphaeran administered by gavage at a concentration of 12 mg botryosphaeran/kg b.w./day over 15 days also reduced the plasma levels of total cholesterol and low density lipoprotein-cholesterol by 18% and 27%, respectively, in hyperlipidemic rats. Based on these findings, we conclude that botryosphaeran possesses hypoglycemic and hypocholesterolemic properties in conditions of diabetes mellitus and hyperlipidemia, respectively, and may be used as an oral anti-diabetic agent.