Hexane Extract of Orthosiphon stamineus Induces Insulin Expression and Prevents Glucotoxicity in INS-1 Cells.
BACKGROUND
Hyperglycemia, a characteristic feature of diabetes, induces glucotoxicity in pancreatic β-cells, resulting in further impairment of insulin secretion and worsening glycemic control. Thus, preservation of insulin secretory capacity is essential for the management of type 2 diabetes. In this study, we evaluated the ability of an Orthosiphon stamineus (OS) extract to prevent glucotoxicity in insulin-producing cells.


METHODS
We measured insulin mRNA expression and glucose-stimulated insulin secretion (GSIS) in OS-treated INS-1 cells after exposure to a high glucose (HG; 30 mM) concentration.


RESULTS
The hexane extract of OS elevated mRNA expression of insulin as well as pancreatic and duodenal homeobox-1 of INS-1 cells in a dose-dependent manner. The hexane OS extract also increased the levels of phosphorylated phosphatidylinositol 3-kinase (PI3K) in a concentration-dependent manner. Additionally, Akt phosphorylation was elevated by treatment with 100 and 200 µmol of the hexane OS extract. Three days of HG exposure suppressed insulin mRNA expression and GSIS; these expressions were restored by treatment with the hexane OS extract. HG elevated peroxide levels in the INS-1 cells. These levels were unaffected by OS treatment under both normal and hyperglycemic conditions.


CONCLUSIONS
Our results suggested that the hexane extract of OS elevates insulin mRNA expression and prevents glucotoxicity induced by a 3-day treatment with HG. This was associated with the activation of PI-3K and Akt.
Department of Pediatrics, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Korea.
Hae-Jung
HJ
Lee
Department of Physiology, Yeungnam University College of Medicine, Daegu, Korea.
Yoon-Jung
YJ
Choi
Department of Physiology, Yeungnam University College of Medicine, Daegu, Korea.
So-Young
SY
Park
Department of Physiology, Yeungnam University College of Medicine, Daegu, Korea.
Jong-Yeon
JY
Kim
Department of Internal Medicine, Yeungnam University College of Medicine, Daegu, Korea.
Kyu-Chang
KC
Won
Yeungnam University College of Pharmacy, Gyeongsan, Korea.
Jong-Keun
JK
Son
Department of Physiology, Yeungnam University College of Medicine, Daegu, Korea.
Yong-Woon
YW
Kim
Glucose-stimulated insulin secretion, Insulin mRNA; Glucotoxicity; Orthosiphon stamineus