Altered hepatic insulin signalling in male offspring of obese mice

Individuals exposed in utero to maternal obesity have increased risk of developing type 2 diabetes mellitus and obesity in adulthood. The molecular mechanisms underlying this association are unknown. We have therefore used a murine model of maternal obesity, in which the offspring of obese dams develop hyperinsulinaemia by 3 months of age indicative of insulin resistance. Here, we investigate the effects of maternal diet-induced obesity on the expression/phosphorylation of key hepatic insulin signalling proteins and the expression of anti-oxidant enzymes in male offspring. At 3 months of age, offspring of obese dams had decreased levels of insulin receptor substrate (IRS) 1 (P < 0.01), whereas the ratio of phosphorylated IRS1 Ser307 to total IRS1 was significantly increased (P < 0.001), suggesting that it was less active. Protein expression of the PI3K p85α subunit was decreased (P < 0.01) and there was a tendency for phosphorylation of Akt at Ser473 to be reduced (P = 0.08) in the offspring of obese dams. protein kinase Cζ (P < 0.001) and glycogen synthase kinase 3β (P < 0.05) levels were increased in these animals in comparison with controls. Maternal obesity also resulted in increased phosphorylation of p38 mitogen-activated protein kinase at Thr180/Tyr182 (P < 0.01) and raised c-Jun N-terminal kinase 1 expression (P < 0.5) in the offspring. The expression of antioxidant enzymes was also affected by maternal obesity with CuZnSOD (P < 0.001) and glutathione reductase (P < 0.05) being increased, whereas glutathione peroxidase 1 was reduced (P < 0.05) in the offspring. We conclude that maternal obesity leads to alterations in hepatic insulin signalling protein expression and phosphorylation. These molecular changes may contribute to the development of insulin resistance.