Effects of intermittent and constant exposure to high concentration of blood glucose on adiponectin and resistin expression in 3T3-L1 adipocytes

Abstract

Objective To investigate the effects of intermittent and constant high blood glucose on the expressions of adiponectin and resistin in cultured 3T3-L1 adipocytes, nitrotyrosine formation and 8-hydroxydeoxyguanosine (8-OHdG), either in the presence or in the absence of MnTBAP or TTFA. Methods In vitro cultured 3T3-L1 preadipocytes were used for the intermittent high blood glucose or oxidative model. The cultured cells were then divided into two groups: group A to study changes of adiponectin and resistin mRNA and protein expression, nitrotyrosine and 8-OHdG level after intermittent or continuing exposure to 25 mmol/L glucose, MnTBAP or TTFA; group B to test adiponectin and resistin mRNA expression when intermittently or constantly exposed to H2O2. The adiponectin and resistin mRNA and protein expression was determined by reverse transcript polymerase chain reaction (RT-PCR) and ELISA, respectively. The production of nitrotyrosine and 8-OHdG as the oxidative stress parameter were measured.Student′s t test or analysis of variance was used for data analysis. Results Compared to constant high blood glucose group, the adiponectin proteins concentration and mRNA expression level of the intermittent high blood glucose group were lower(t=7.29 or 7.13, both P<0.01), while resistin protein concentration and mRNA expression level(t=6.85 or 6.94, both P<0.01), nitrotyrosine and 8-OHdG(t=4.74 or 6.93, both P<0.01) were higher. On the other hand, the antioxidants MnTBAP and TTFA could reverse high-glucose-induced dysregulation of adiponectin(t=7.47, P<0.01) and resistin(t=6.91, P<0.01), as well as overproduction of nitrotyrosine and 8-OhdG(t=4.87 or 6.90, both P<0.01). Compared to constant exposure to H2O2, the adiponectin mRNA expression level with intermittent exposure to H2O2 was lower(t=7.21, P<0.01), and the resistin mRNA expression level with intermittent exposure to H2O2 was higher(t=6.79, P<0.01). Conclusion These findings suggest that intermittent high blood glucose significantly decrease adiponectin and augment resistin expression and secretion from adipocytes through reactive oxygen species overproduction at the mitochondria transport chain level. Key words: Blood glucose, intermittent; Oxidative stress; Adipokine; Mitochondria