NADPH oxidase plays an active role in the changes induced by fructose upon islet function

BORELLI MI; FLORES LE; RASCHIA MA; ROMAN CL; REBOLLEDO OR; GAGLIARDINO JJ

Rio Grande do Norte

Jornada; ISG 2011. Annual Meeting of the EASD Islet Study Group; 2011

EASD Islet Study Group.

Background and Aims: Fructose (F) induces oxidative stress (OE), insulin resistance, impaired glucose tolerance and a decrease in B-cell mass; however, the potential role of islet NADPH oxidase (iNOX) in such changes is still unknown. Thus, we performed this study to answer that question. Methods: Adult normal male Wistar rats received a standard commercial diet without (C) or with the addition of 10% F in the drinking water for 21 days. Another group of C and F rats received a NOX blocker (0.15 mmol/day apocinine [A]; CA and FA, respectively). In all groups we measured: in serum: glucose (G), insulin (1) and triglyceride (TG) levels. In islets: insulin secretion, iNOX activity, RNA (qPCR) and protein concentration (Western Blot [WB]) of antioxidant enzymes. Results: Body weight and G values were similar in all groups. F rats had higher TG and I levels than C rats (TG: 1.93±O.09 vs. 1.18±O.06* g/L; 1: 1.13±O.05 vs.0.76±O.03* ng/mL). A administration prevented such increases, resulting in values similar to those obtained in C rats. F islets released more insulin than C when incubated with 16.7 mM G and values recorded in FA islets were comparable to those of C (F 3.9±0.5 vs.C 2.4±0.2*; FA 3.0±O.3ng/isl/h). iNOX activity had a similar behavior (F 165.6±24.8 vs. C 100.0±3.2* vs. FA 105.7±9.6 arbitrary U/75 isl). Addition of 10 uM DPI to the incu-bation media decreased iNOX activity. F increased iNOX mRNA level of gp91 PHOX (81 %) and p22PHOX (28%). mRNA of superoxide dismutase 1 (SOD1) and glutathione reductase decreased (14 and 13%, respectively), while that of SOD2 and catalase increased (25 and 71%, respectively). The protein concentration of all the enzymes measured decreased significantly. Conclusions: The parallel increase of iNOX activity, of the metabolic parameters measured and of insulin secretion, plus their correction by A, suggests that iNOX actively participates in the endocrine-metabolic dysfunction induced by F. Keywords: Fructose - NADPH oxidase activity -insulin secretion - Financial Support: CONICET (PIP 1211) and National University of La Plata