Protective effects of epicatechin against the toxic effects of streptozotocin on rat pancreatic islets: in vivo and in vitro.
BACKGROUND
Green tea catechins have diverse pharmacological effects such as anticarcinogenic and antioxidant activities.


OBJECTIVE
To study the protective effects of green tea (-)-epicatechin (EC) against the toxic effects of streptozotocin (STZ), a selective beta cell toxin, on pancreatic islets in vivo and in vitro.


METHODS
Rats were randomly divided into four groups: control, EC (30 mg/kg)-treated, STZ (60 mg/kg)-treated, and EC plus STZ (same doses; EC+STZ)-treated rats. EC was administered twice a day for 6 days, and a single injection of STZ was used. In EC+STZ-treated rats, EC was administered 6 hours prior to STZ since posttreatment with EC had no beneficial effects on fully developed diabetes in our unpublished study. Insulin and insulin mRNA were detected by immunohistochemical analysis and in situ hybridization, respectively, and physiologic parameters including blood glucose concentration were measured daily. Following isolation of the islets, insulin release, nitrite levels, and islet morphology were observed in the four groups: control, EC (0.8 mM)-treated, STZ (5 mM)-treated, and EC+STZ (same doses)-treated islets.


RESULTS
In EC+STZ-treated rats, hyperglycemia and weight loss were not observed and islet morphology was well preserved compared with STZ-treated rats. Compared with STZ treatment alone, insulin release was increased and nitrite production was decreased in EC+STZ-treated islets.


CONCLUSIONS
EC appears to be helpful in protecting pancreatic islets against exposure to STZ in both in vivo and in vitro systems.
Kim
Myung-Jun
MJ
Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul, Korea.
Ryu
Gyeong Ryul
GR
Chung
Ji-Sung
JS
Sim
Sang Soo
SS
Min
Do Sik
DS
Rhie
Duck-Joo
DJ
Yoon
Shin Hee
SH
Hahn
Sang June
SJ
Kim
Myung-Suk
MS
Jo
Yang-Hyeok
YH
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D002392:Catechin / Q000627:therapeutic use*; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007328:Insulin / Q000096:biosynthesis; D008297:Male; D009573:Nitrites / Q000032:analysis; D010179:Pancreas / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D001786:Blood Glucose; D007328:Insulin; D009573:Nitrites; D012333:RNA, Messenger; D002392:Catechin