Increased in Vivo Interstitial Hydroxyl Radical Generation in a High-Fat Diet Rat Model of Obesity: A Microdialysis Study in Subcutaneous White Adipose Tissue

Objective: Obesity development associates with oxidative stress imbalance. We monitored in a model of obese rat (high fat fed Sprague Dawley rats) the in vivo interstitial hydroxyl radical (an oxidative stress parameter) measured through microdialysis procedure and trapping techniques in subcutaneous white adipose tissue. Hydroxyl radical generation mainly relates to Haber-Weiss-Fenton chemistry that involves iron oxidation. We also monitored plasma and tissue (through a small adipose tissue biopsy) Ceruloplasmin (CP), an alpha2-glycoprotein that owns antioxidant and ferroxidase properties oxidizing ferrous to ferric iron and preventing hydroxyl generation. Design and method: At 10 weeks of age, two batches for a total of 54 male Sprague Dawley rats started a high fat diet (D12451; Research Diets, New Brunswick, NJ, USA) for 24 weeks. A control group (n=23) was maintained for the same period on standard diet. The high fat diet contained 24 g % fat (45% of total calories), 24 g% protein, (20%); 41 g% carbohydrate (35%). Control diet fat content was 4.25 g%. At the end of the diet period, body weight increase in high fat diet group was in average 14.7% as compared to controls (mean 515 g vs 449 g). Rats underwent a microdialysis procedure of subcutaneous white adipose tissue at the basal time, after 3, 12 and 24 weeks, to evaluate hydroxyl radical generation by trapping this radical through analysis of 2,3-and 2,5-dihydroxybenzoic or 2-hydroxylterephthalic acid. Results: High fat fed rats had a stable rise of hydroxyl radical generated in adipose tissue as compared to control diet rats as well as a higher tissue expression of CP, presumably acting as antioxidant adipokine. CP circulating levels were also elevated. Conclusions: High fat fed rats show an increased in vivo free radical generation in subcutaneous adipose tissue that associates with a presumably compensatory increase in Cp in an attempt to buffer the local excess generation of hydroxyl radical. Even if the observed increase in local and systemic Cp could represent the counter response to the activated inflammatory-oxidative pathway in these high fat diet-treated rats its effectiveness seems quite limited.