Aqueous extract of unfermented honeybush (Cyclopia maculata) attenuates STZ-induced diabetes and β-cell cytotoxicity.
New strategies, which include β-cell protection, are required in the treatment of T2D, as current drugs demonstrate little or no capacity to directly protect the vulnerable β-cell against diabetes-induced cytotoxicity. In this study we investigated the ameliorative effect of pre-treatment with an aqueous extract of unfermented Cyclopia maculata (honeybush) on STZ-induced diabetes and pancreatic β-cell cytotoxicity in Wistar rats after demonstrating a protective effect in vitro in RIN-5F cells. The amelioration of STZ-induced diabetes was seen in the reduction of the area under the curve, determined by the oral glucose tolerance test, as well as fasting glucose levels in extract-treated rats. Pre-treatment with extract also improved serum triglyceride levels and the glucose-to-insulin ratio. Pre-treatment with the extract or the drug, metformin, increased the β-cell area in islets, with a concomitant increase in β-cell proliferation at the higher extract dose (300 mg/kg/d), but not the lower dose (30 mg/kg/d). Subsequently, the in vitro tritiated thymidine incorporation assay showed that the extract was not mitogenic in RIN-5F cells. STZ-induced elevation of plasma nitrite levels was reduced in extract-treated rats, but no changes were observed in their serum catalase, serum glutathione, liver lipid peroxidation and liver nitrotyrosine levels. Pre-treating the rats with extract ameliorated the diabetic effect of STZ in Wistar rats, with evidence of pancreatic β-cells protection, attributed to the presence of high levels of antioxidants such as the xanthones, mangiferin and isomangiferin.
Diabetes Discovery Platform, Medical Research Council, Tygerberg, South Africa.
Nireshni
N
Chellan
Post-Harvest and Wine Technology Division, Agricultural Research Council (ARC) Infruitec-Nietvoorbij, Stellenbosch, South Africa.
Elizabeth
E
Joubert
Division of Medical Physiology, Faculty of Medicine and Health Sciences, Stellenbosch University, Matieland, South Africa.
Hans
H
Strijdom
Diabetes Discovery Platform, Medical Research Council, Tygerberg, South Africa.
Candice
C
Roux
Diabetes Discovery Platform, Medical Research Council, Tygerberg, South Africa.
Johan
J
Louw
Diabetes Discovery Platform, Medical Research Council, Tygerberg, South Africa.
Christo J F
CJ
Muller
D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D001786:Blood Glucose / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D053998:Cyclopia Plant / Q000737:chemistry*; D003921:Diabetes Mellitus, Experimental / Q000139:chemically induced / Q000188:drug therapy*; D005951:Glucose Tolerance Test; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000097:blood; D050417:Insulin-Secreting Cells / Q000187:drug effects*; D008297:Male; D008687:Metformin / Q000627:therapeutic use; D009573:Nitrites / Q000097:blood; D018384:Oxidative Stress / Q000187:drug effects; D010936:Plant Extracts / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013311:Streptozocin / Q000009:adverse effects; D044004:Xanthones / Q000378:metabolism*
D000975:Antioxidants; D001786:Blood Glucose; D007004:Hypoglycemic Agents; D007328:Insulin; D009573:Nitrites; D010936:Plant Extracts; D044004:Xanthones; C013592:mangiferin; C061492:isomangiferin; D013311:Streptozocin; D008687:Metformin