Oxidative Stress and Neutrophil Function in Cats with Diabetes Mellitus Compared to Controls: Assessing the Impact of Nutrition
Oxidative stress is a key component in the pathophysiology of Type 2 diabetes mellitus (DM) in humans, and an estimated 85% of cats with DM are Type 2 diabetics. Accordingly, the use of high protein-low carbohydrate diets in diabetic cats may lead to a significant reduction in oxidative stress as the production of free radicals is driven by the metabolism of excess carbohydrates. Neutrophil function may be impaired by oxidative stress in patients with DM, resulting in a decreased ability to prevent or eliminate infections. This study was designed to test the hypothesis that cats with DM have increased oxidative stress and decreased neutrophil function that will improve with consumption of a diabetes-specific diet.
Body weight, serum fructosamine level, complete blood count, and parameters of oxidative stress and neutrophil (PMN) function were measured in 15 cats with DM and in 20 healthy control cats before and after being fed a commercially available diet designed specifically for feline diabetics (Purina Veterinary Diets® DM®) for 8 weeks. Erythrocyte superoxide dismutase (SOD), blood glutathione peroxidase (GPx), malondialdehyde, and reduced glutathione:oxidized glutathione ratios were evaluated spectrophotometrically. PMN phagocytosis and subsequent respiratory burst activity was evaluated using flow cytometry. Results were compared both between groups and within groups over time.
The diabetic cats were significantly older and heavier than the control group. Prior to the diet change, cats with DM had significantly less plasma SOD (211 U/ml ± 143) than control cats (352 U/ml ± 200)(P=0.02). Other oxidative stress parameters and measures of neutrophil function were not significantly different between the two groups. Following 8 weeks of consuming a diabetes-specific diet, the control group gained a significant amount of weight (5.2 to 5.4 kg; P=0.005), the mean fructosamine value was significantly decreased in both groups (control, 273 to 245 μmol/L, P=0.004; DM, 416 to 353 μmol/L, P=0.03), and GPx increased significantly in both groups (control, 37K to 68K U/L, P<0.005; DM, 29K to 67K U/L, P<0.005). PMN function did not change significantly in either group.
Diabetes mellitus may be associated with an increase in oxidative stress in cats. Diet appears to significantly impact some parameters of oxidative stress in both affected and healthy cats, supporting the continued development and evaluation of targeted antioxidant dietary supplementation. A diabetes-specific diet may be beneficial in cats predisposed to developing DM, although the potential for weight gain needs to be considered.