Periplogenin, isolated from Lagenaria siceraria, ameliorates L-T₄-induced hyperthyroidism and associated...

The importance of glycoside in the regulation of thyroid dysfunction is not well understood. In the present investigation, effects of periplogenin-3- O-D-glucopyranosyl (1→6)(1→4)-D-cymaropyranoside, isolated from the vegetable, LAGENARIA SICERARIA, in L-thyroxine (L-T₄)-induced hyperthyroidism and in related cardiovascular abnormalities have been revealed in Wistar albino rats. L-T₄ (500 μg/kg, s. c./d) administration for 12 days significantly increased serum concentrations of thyroxine (T₄), triidothyronine (T₃), and hepatic 5'-deiodinase I (5'-DI) activity with a parallel increase in lipid peroxidation (LPO) in different organs such as heart, liver and kidney; serum glucose and insulin concentrations and a decrease in cardiac Na (+)-K (+)-ATPase activity as well as serum total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol and triglycerides. Most of these adverse effects were reversed following the administration of isolated periplogenin. However, out of its 3 different concentrations (5.0, 10, and 25 mg/kg), 5 mg/kg appeared to be the most effective one as it could nearly normalize the level of T₃, glucose, insulin, Na (+)-K (+)-ATPase activity, tissue LPO and different serum lipids suggesting the protective role of periplogenin against thyrotoxicosis and associated cardiovascular problems. It appears that the periplogenin actions are mediated through its direct antithyroidal and/or LPO inhibiting properties.