274 Antioxidant Supplementation Improves Inflammatory Nitrergic Dysfunction in Diabetic Biobreeding Prone Rats

Introduction: Loss of intestinal nitrergic motor control has been reported in Biobreeding diabetes-prone (BBDP) rats (Zandecki 2008). We previously demonstrated that loss of jejunal neuronal nitric oxide synthase (nNOS) mRNA expression occurs in the BBDP, which is related to transient intestinal inflammation (myeloperoxidase: MPO activity) and inducible nitric oxide synthase (iNOS) expression, and which is independent from the development of hyperglycemia (Kindt DDW 2009). Studies in enteric neuron cultures suggest that iNOS overexpression downregulates nNOS expression through oxidative stress (Zandecki 2006). Moreover, aminoguanidine an iNOS inhibitor, counteracts the inflammation-induced nitrergic dysfunction and prevents intestinal elongation and dilatation caused by a 3cm H2O pressure stimulus in normoglycemic BBDP (Masaoka DDW 2011). Aim: To investigate the pathophysiological role of oxidative stress in inflammatory nitrergic dysfunction, we designed a controlled antioxidant supplementation study. Methods: BBDP were fed chow supplemented with 2% vitamin E (α-tocopherol) and 2g/l vitamin C (ascorbic acid) in the drinking water from 21days onwards. After onset of diabetes, 1% vitamin E and 1g/l vitamin C were supplemented to compensate for polyphagia and polydypsia. All rats were sacrificed at 220days. Jejunal inflammation, spontaneous intestinal motility, nitrergic neuron number and nNOS mRNA expression were analyzed respectively by MPO measurements, organ bath (37°C) video analysis, NADPH-diaphorase staining and realtime PCR, both in antioxidant supplemented animals and in a control group of age-matched non-supplemented diabetic animals. Results: Compared with controls (n=7), MPO activity decreased significantly in the antioxidant supplemented group (n=6) (9.9±3.9 vs. 2.1±1.4 U/mg, p 0.05) of a 5-cm jejunum segment in response to intraluminal pressure rise In Vitro. Conclusion: Antioxidant supplementation improves inflammation-induced nitrergic dysfunction and partially prevents intestinal dysmotility in diabetic BBDP.