title: Extract of lotus leaf ( Nelumbo nucifera ) and its active constituent catechin with insulin secretagogue activity.
abstract: The effect of lotus leaf ( Nelumbo nucifera Gaertn.) on diabetes is unclear. We hypothesized that lotus leaf can regulate insulin secretion and blood glucose levels. The in vitro and in vivo effects of lotus leaf methanolic extract (NNE) on insulin secretion and hyperglycemia were investigated. NNE increased insulin secretion from β cells (HIT-T15) and human islets. NNE enhanced the intracellular calcium levels in β cells. NNE could also enhance phosphorylation of extracellular signal-regulated protein kinases (ERK)1/2 and protein kinase C (PKC), which could be reversed by a PKC inhibitor. The in vivo studies showed that NNE possesses the ability to regulate blood glucose levels in fasted normal mice and high-fat-diet-induced diabetic mice. Furthermore, the in vitro and in vivo effects of the active constituents of NNE, quercetin, and catechin, on glucose-induced insulin secretion and blood glucose regulation were evaluated. Quercetin did not affect insulin secretion, but catechin significantly and dose-dependently enhanced insulin secretion. Orally administered catechin significantly reversed the glucose intolerance in high-fat-diet-induced diabetic mice. These findings suggest that NNE and its active constituent catechin are useful in the control of hyperglycemia in non-insulin-dependent diabetes mellitus through their action as insulin secretagogues.
authors.affiliation: Graduate Institute of Chinese Medical Science, School of Chinese Medicine, College of Chinese Medicine, China.
authors.forename: Chun Fa
authors.initials: CF
authors.lastname: Huang
authors.forename: Ya Wen
authors.initials: YW
authors.lastname: Chen
authors.forename: Ching Yao
authors.initials: CY
authors.lastname: Yang
authors.forename: Hui Yi
authors.initials: HY
authors.lastname: Lin
authors.forename: Tzong Der
authors.initials: TD
authors.lastname: Way
authors.forename: Wenchang
authors.initials: W
authors.lastname: Chiang
authors.forename: Shing Hwa
authors.initials: SH
authors.lastname: Liu
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D002118:Calcium / Q000032:analysis; D002392:Catechin / Q000494:pharmacology*; D002460:Cell Line; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy; D004041:Dietary Fats; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D031653:Nelumbo / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry* / Q000494:pharmacology*; D018515:Plant Leaves / Q000737:chemistry*
chemical_list: D001786:Blood Glucose; D004041:Dietary Fats; D007328:Insulin; D010936:Plant Extracts; D002392:Catechin; D002118:Calcium