title: Effects of stevioside on glucose transport activity in insulin-sensitive and insulin-resistant rat skeletal muscle.
abstract: Stevioside (SVS), a natural sweetener extracted from Stevia rebaudiana, has been used as an antihyperglycemic agent. However, little is known regarding its potential action on skeletal muscle, the major site of glucose disposal. Therefore, the purpose of the present study was to determine the effect of SVS treatment on skeletal muscle glucose transport activity in both insulin-sensitive lean (Fa/-) and insulin-resistant obese (fa/fa) Zucker rats. SVS was administered (500 mg/kg body weight by gavage) 2 hours before an oral glucose tolerance test (OGTT). Whereas the glucose incremental area under the curve (IAUC(glucose)) was not affected by SVS in lean Zucker rats, the insulin incremental area under the curve (IAUC(insulin)) and the glucose-insulin index (product of glucose and insulin IAUCs and inversely related to whole-body insulin sensitivity) were decreased (P<.05) by 42% and 45%, respectively. Interestingly, in the obese Zucker rat, SVS also reduced the IAUC(insulin) by 44%, and significantly decreased the IAUC(glucose) (30%) and the glucose-insulin index (57%). Muscle glucose transport was assessed following in vitro SVS treatment. In lean Zucker rats, basal glucose transport in type I soleus and type IIb epitrochlearis muscles was not altered by 0.01 to 0.1 mmol/L SVS. In contrast, 0.1 mmol/L SVS enhanced insulin-stimulated (2 mU/mL) glucose transport in both epitrochlearis (15%) and soleus (48%). At 0.5 mmol/L or higher, the SVS effect was reversed. Similarly, basal glucose transport in soleus and epitrochlearis muscles in obese Zucker rats was not changed by lower doses of SVS (0.01 to 0.1 mmol/L). However, these lower doses of SVS significantly increased insulin-stimulated glucose transport in both obese epitrochlearis and soleus (15% to 20%). In conclusion, acute oral SVS increased whole-body insulin sensitivity, and low concentrations of SVS (0.01 to 0.1 mmol/L) modestly improved in vitro insulin action on skeletal muscle glucose transport in both lean and obese Zucker rats. These results indicate that one potential site of action of SVS is the skeletal muscle glucose transport system.
authors.affiliation: Muscle Metabolism Laboratory, Department of Physiology, University of Arizona College of Medicine, Tuscon, USA.
authors.forename: Narissara
authors.initials: N
authors.lastname: Lailerd
authors.forename: Vitoon
authors.initials: V
authors.lastname: Saengsirisuwan
authors.forename: Julie A
authors.initials: JA
authors.lastname: Sloniger
authors.forename: Chaivat
authors.initials: C
authors.lastname: Toskulkao
authors.forename: Erik J
authors.initials: EJ
authors.lastname: Henriksen
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001786:Blood Glucose / Q000032:analysis; D003847:Deoxyglucose / Q000378:metabolism; D004224:Diterpenes / Q000494:pharmacology*; D045786:Diterpenes, Kaurane; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005947:Glucose / Q000378:metabolism*; D005951:Glucose Tolerance Test; D005960:Glucosides / Q000494:pharmacology*; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000097:blood / Q000494:pharmacology*; D007333:Insulin Resistance; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D009765:Obesity / Q000378:metabolism; D051381:Rats; D011924:Rats, Zucker
chemical_list: D001786:Blood Glucose; D004224:Diterpenes; D045786:Diterpenes, Kaurane; D005230:Fatty Acids, Nonesterified; D005960:Glucosides; D007004:Hypoglycemic Agents; D007328:Insulin; C012043:stevioside; D003847:Deoxyglucose; D005947:Glucose