Extracts of Eastern Nigeria Mistletoe, Tapinanthus globiferus (A. Rich.) Tiegh. Modulate Dexamethasone-induced Insulin Resistance and Exhibit Potent osteogenic Activity in Animal Experimental Model

Ethnopharmacological Relevance: Scientific evidence for the traditional use of eastern Nigeria mistletoe as an anti-diabetic and anti-osteoporotic agent has been documented. In our continued efforts to provide further evidence towards eventual approval of the medicinal usage of the eastern Nigeria mistletoes, the present study was undertaken to evaluate its effects on steroid induced insulin-resistance and in-vivo bone health parameters in rodent model.

Materials and Methods: Twelve-weeks (12) old Sprague-Dawley (SD) rats of both sexes and weighing 200±20 g were administered with dexamethasone (200 mgkg-1) for minimum of 14 days and with or without 100-400 mgkg-1 of crude aqueous extract of mistletoe harvested from Kola acuminata, in this paper referred to as Kola-mistletoe (KM). The basal glucose levels were established and animals were later exposed to oral glucose tolerance test (OGTT). Blood samples were collected from ketamine-anesthetized animals via cardiac puncture for measurement of biochemical parameters. The femur and vertebrae bones were neatly excised and stored in 70% isopropanol at 4°C until further analysis. µCT determination of excised bones was carried out using the Sky Scan 1076 µCT scanner (Aartselaar, Belgium) as described in our previously published protocols.

Results: The extracts significantly preserved the animals from the effects of dexamethasone mostly at 400 mg/kg dose in terms of weight loss and blood glycaemia. The extract (either alone or in combination with dexamethasone and within the duration of treatments showed better bone quality (higher BV/TV (Bone volume to Trabecular volume ratio), lower Tb.Sp (Trabecular separation) and SMI (Structure model index) indices at the dose of 400 mg/kg compared with vehicle and metformin groups.

Conclusion: The present data show that the Nigeria mistletoes are potent in reversing the adverse effects of prolonged exposure to dexamethasone in rodents and evidently protected the bones from impairment.