Abstract
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.
Key words
Cyclopia maculata
- Fabaceae - mangiferin - diabetes - streptozotocin -
β-cell - glucose tolerance
