ZINC ATTENUATION OF GDP BINDING TO BROWN ADIPOCYTES MITOCHONDRIA IN GENETICALLY-OBESE (OB OB) MICE/

In this study, we investigate the in vitro effect of zinc addition on guanosine diphosphate (GDP:I binding to mitochondria in brown adipocyt es of genetically obese (ob/ob) mice. Interscapular brown adipocytes o f male mice (obese; lean) at 4 and 3.2 wk of age were incubated with 0 , 50, 100, or 200 mu M zinc sulfate. Mitochondria were then isolated a nd their GDP binding capacities were measured. The GDP-binding capacit ies of ob/ob mice were lower than lean mice, with or without zinc addi tion, in both age groups (p < 0.05). Zinc addition did not have any si gnificant effect on GDP binding in lean mice. GDP binding decreased wi th increasing zinc addition in ob/ob mice, and this attenuation was mo re predominant in 12-wk old ob/ob mice. Moreover, we found that high m agnesium addition (5 mM) increased GDP binding in lean mice, but this effect was not significant in ob/ob mice. This study reveals that brow n adipose tissue thermogenesis in ob/ob mice could be greatly attenuat ed by zinc addition, suggesting that zinc may play a regulatory role i n obesity.