Labrador tea (Rhododendron groenlandicum) attenuates insulin resistance in a diet-induced obesity mouse model.
OBJECTIVE
Using a diet-induced obesity (DIO) mouse model, we investigated the antidiabetic effect of Labrador tea [Rhododendron groenlandicum (Oeder) Kron and Judd], a beverage and medicinal tea used by the Cree Nations of northern Quebec.


METHODS
C57BL6 mice were divided into five groups and given standard chow (~4 % of lipids) or high-fat diet (~35 % of lipids) for 8 weeks until they became obese and insulin resistant. Treatment began by adding the plant extract at three doses (125, 250 and 500 mg/kg) to the high-fat diet for another 8 weeks. At the end of the study, insulin-sensitive tissues (liver, skeletal muscle, adipose tissue) were collected to investigate the plant's molecular mechanisms.


RESULTS
Labrador tea significantly reduced blood glucose (13 %), the response to an oral glucose tolerance test (18.2 %) and plasma insulin (65 %) while preventing hepatic steatosis (42 % reduction in hepatic triglyceride levels) in DIO mice. It stimulated insulin-dependent Akt pathway (55 %) and increased the expression of GLUT4 (53 %) in skeletal muscle. In the liver, Labrador tea stimulated the insulin-dependent Akt and the insulin-independent AMP-activated protein kinase pathways. The improvement in hepatic steatosis observed in DIO-treated mice was associated with a reduction in inflammation (through the IKK α/β) and a decrease in the hepatic content of SREBP-1 (39 %).


CONCLUSIONS
Labrador tea exerts potential antidiabetic action by improving insulin sensitivity and mitigating high-fat diet-induced obesity and hyperglycemia. They validate the safety and efficacy of this plant, a promising candidate for culturally relevant complementary treatment in Cree diabetics.
Natural Health Products and Metabolic Diseases Laboratory, Department of Pharmacology, Université de Montréal, P.O. Box 6128, Station Centre-Ville, Montréal, QC, H3C 3J7, Canada.|Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines, Montréal, QC, Canada.|Montreal Diabetes Research Center, Montréal, QC, Canada.
Meriem
M
Ouchfoun
Natural Health Products and Metabolic Diseases Laboratory, Department of Pharmacology, Université de Montréal, P.O. Box 6128, Station Centre-Ville, Montréal, QC, H3C 3J7, Canada.|Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines, Montréal, QC, Canada.|Montreal Diabetes Research Center, Montréal, QC, Canada.|Department of Pharmacognosy, University of Beni-seuf, Beni-Seuf, Egypt.
Hoda M
HM
Eid
Natural Health Products and Metabolic Diseases Laboratory, Department of Pharmacology, Université de Montréal, P.O. Box 6128, Station Centre-Ville, Montréal, QC, H3C 3J7, Canada.|Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines, Montréal, QC, Canada.|Montreal Diabetes Research Center, Montréal, QC, Canada.
Lina
L
Musallam
Natural Health Products and Metabolic Diseases Laboratory, Department of Pharmacology, Université de Montréal, P.O. Box 6128, Station Centre-Ville, Montréal, QC, H3C 3J7, Canada.|Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines, Montréal, QC, Canada.|Montreal Diabetes Research Center, Montréal, QC, Canada.
Antoine
A
Brault
Natural Health Products and Metabolic Diseases Laboratory, Department of Pharmacology, Université de Montréal, P.O. Box 6128, Station Centre-Ville, Montréal, QC, H3C 3J7, Canada.|Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines, Montréal, QC, Canada.|Montreal Diabetes Research Center, Montréal, QC, Canada.
Shilin
S
Li
Natural Health Products and Metabolic Diseases Laboratory, Department of Pharmacology, Université de Montréal, P.O. Box 6128, Station Centre-Ville, Montréal, QC, H3C 3J7, Canada.|Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines, Montréal, QC, Canada.|Montreal Diabetes Research Center, Montréal, QC, Canada.
Diane
D
Vallerand
Centre for Research in Biotechnology and Biopharmaceuticals, Department of Biology, University of Ottawa, Ottawa, ON, Canada.|Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines, Montréal, QC, Canada.|Montreal Diabetes Research Center, Montréal, QC, Canada.
John T
JT
Arnason
Natural Health Products and Metabolic Diseases Laboratory, Department of Pharmacology, Université de Montréal, P.O. Box 6128, Station Centre-Ville, Montréal, QC, H3C 3J7, Canada. pierre.haddad@umontreal.ca.|Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines, Montréal, QC, Canada. pierre.haddad@umontreal.ca.|Montreal Diabetes Research Center, Montréal, QC, Canada. pierre.haddad@umontreal.ca.
Pierre S
PS
Haddad
D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism; D000410:Alanine Transaminase / Q000097:blood; D000469:Alkaline Phosphatase / Q000097:blood; D000818:Animals; D001219:Aspartate Aminotransferases / Q000097:blood; D001786:Blood Glucose / Q000378:metabolism; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D003404:Creatinine / Q000097:blood; D059305:Diet, High-Fat / Q000009:adverse effects; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D005234:Fatty Liver / Q000517:prevention & control; D005951:Glucose Tolerance Test; D051275:Glucose Transporter Type 4 / Q000235:genetics / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D029794:Ledum / Q000737:chemistry*; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D009765:Obesity / Q000097:blood* / Q000188:drug therapy; D010936:Plant Extracts / Q000494:pharmacology*; D029793:Rhododendron / Q000737:chemistry*; D014280:Triglycerides / Q000097:blood
D001786:Blood Glucose; D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D051275:Glucose Transporter Type 4; D007004:Hypoglycemic Agents; D007328:Insulin; D010936:Plant Extracts; C495693:Slc2a4 protein, mouse; D014280:Triglycerides; D003404:Creatinine; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase; D000469:Alkaline Phosphatase
AMPK; Diabetes; GLUT4; Labrador tea; Natural health products; SREBP-1