Cyclocarya paliurus tea leaves enhances pancreatic β cell preservation through inhibition of apoptosis

Leaves of Cyclocarya paliurus are a sweet tea traditionally used to treat obesity and diabetes in China. However, its protective mechanisms against hyperglycemia remains unclear. Here, we demonstrate that the extract of C. paliurus leaves significantly decreased body loss, food intake and blood glucose level, and increased blood insulin level, β-cell number and insulin-producing β cells in high-fat diet-low dose STZ-induced diabetic mice. In vivo and in vitro studies also showed the extract of C. paliurus leaves significantly inhibited pancreatic β cell apoptosis by suppressing the expression of caspase 8, caspase 9 and cleaved caspase-3, as well as Bax/Bcl-2 ratio, down-regulating p38, ERK and JNK phosphorylation, and up-regulating Akt phosphorylation. These effects were significantly enhanced by inhibitor p-38 or ERK or JNK, and counteracted by inhibitor of PI3K. In addition, the extract of C. paliurus leaves also significantly improved hepatic steatosis, nephropathy and cardiac hypertrophy of diabetic mice. Taken together, these results provide the insight into the effects of C. paliurus leaves on pancreatic β cell preservation in standing glucolipotoxicity. Therefore, C. paliurus tea leaves may be used as a new remedy for diabetes through enhancing pancreatic β cell preservation by inhibiting β cell apoptosis.