An Osteoblastic Redox Model Simulating Insulin Resistance in Periodontal Patients

Objectives: Insulin resistance is linked to the actions of glucose oxidised low-density lipoprotein (GLDL) and tumour necrosis factor alpha (TNF). The aim of this investigation is to study the yield of 5 alpha dihydrotestosterone (DHT) as a marker of wound healing in osteoblasts in response to GLDL, TNF and the antioxidant effects of minocycline (M). Methods: Confluent monolayer cultures of a well characterised line of osteoblasts were incubated with radiolabelled testosterone as substrate and optimal concentrations of GLDL, TNF and minocycline (previously established) in multiwell plates for 24h, with 8 replicates for each incubation. The controls were set up with the radiolabelled substrate in the absence of any agents. At the end of a 24h incubation period the medium was eluted, metabolites isolated by solvent extraction with ethyl acetate and separated using thin layer chromatography in a benzene acetone solvent system (4:1 v/v). The plates were then scanned in a radioisotope scanner to quantify separated metabolites for each experimental set-up. Results: The main metabolites formed were DHT, diols and 4-androstenedione. There were significantly reduced yields of DHT in response to GLDL and TNF of 3.4- and 2.8- fold respectively, compared with controls. There was a 50% increase in yields of DHT over controls, in response to M. The depressed yields of DHT in response to the combined incubation of GLDL with TNF were overcome by M to values similar to those of M alone. All results were significant (n=8; p<0.002). The other metabolites diols and 4-androstenedione showed similar and inverse trends to those of DHT respectively. Conclusion: Oxidative responses to glucose oxidised low density lipoproteins and tumour necrosis factor alpha in osteoblasts were overcome by the antioxidant effects of minocycline. Adjunctive use of minocycline in the management of periodontal patients with insulin resistance is likely to benefit healing responses.