Day-night variations in pro-oxidant reactions of hypothalamic, hepatic and pancreatic tissue in mice with spontaneous obesity (Neotomodon alstoni)

Abstract

Objectives: The present work compares the pro-oxidant properties in hypothalamic, hepatic, and pancreatic tissue of spontaneously obese and lean Neotomodon alstoni during day and night. Methods: Lipid peroxidation from hypothalamus, liver, and pancreas from lean and obese mice were quantified by the two-thiobarbituric acid method. Lipid peroxidation in vivo was also determined by means of detection of conjugated dienes in lipid extracts. Results: Hypothalamic tissue from obese Neotomodon showed a notorious increase (nearly 700%) in the production of thiobarbituric acid-reactive substances (TBARS) at day, either in basal as well as in an assay supplemented with Fe2+; the presence of conjugated dienes was also notably greater (76%) at day. Hypothalamus of lean mice presented an increase (170%) in assay supplemented with Fe2+. Hepatic tissue in obese mice showed diurnal increasing in TBARS + Fe2+ (34%) and in conjugated dienes (38%), while lean mice showed only a diurnal increase (45%) in TBARS + Fe2+. Pancreatic tissue from obese mice presented a diurnal increasing in basal TBARS (130%) but a decrease (72%) in TBARS + Fe2+. Presence of conjugated dienes was also decreased during the day in lean (60%) and in obese (40%) mice. Conclusions: In the obese Neotomodon, there is a larger day–night change in pro-oxidant status in the hypothalamus and in pancreas than the one observed in the liver, suggesting a differential equilibrium between oxidative reactions and antioxidant defenses in the different tissues during the day–night cycle.