Oxidative stress and altered lipid homeostasis in the programming of offspring fatty liver by maternal obesity

Abstract

Changes in the maternal nutritional environment during fetal development can influence offspring's metabolic risk in later life. Animal models have demonstrated that offspring of diet-induced obese dams develop metabolic complications, including nonalcoholic fatty liver disease. In this study we investigated the mechanisms in young offspring that lead to the development of nonalcoholic fatty liver disease (NAFLD). Female offspring of C57BL/6J dams fed either a control or obesogenic diet were studied at 8 wk of age. We investigated the roles of oxidative stress and lipid metabolism in contributing to fatty liver in offspring. There were no differences in body weight or adiposity at 8 wk of age; however, offspring of obese dams were hyperinsulinemic. Oxidative damage markers were significantly increased in their livers, with reduced levels of the antioxidant enzyme glutathione peroxidase-1. Mitochondrial complex I and II activities were elevated, while levels of mitochondrial cytochrome c were significantly reduced and glutamate dehydrogenase was significantly increased, suggesting mitochondrial dysfunction. Offspring of obese dams also had significantly greater hepatic lipid content, associated with increased levels of PPARγ and reduced triglyceride lipase. Liver glycogen and protein content were concomitantly reduced in offspring of obese dams. In conclusion, offspring of diet-induced obese dams have disrupted liver metabolism and develop NAFLD prior to any differences in body weight or body composition. Oxidative stress may play a mechanistic role in the progression of fatty liver in these offspring.

Keywords: developmental programming; maternal obesity; metabolism; nonalcoholic fatty liver disease; oxidative stress.

Fig. 1.

Insulin and oxidative stress markers. A: fasting serum insulin concentration. B: serum 8-hydroxy-2-deoxy guanosine (8-OH-dG) concentration. C: liver 3-nitrotyrosine (3NT) concentration. D: liver 4-hydroxynonenal (4HNE) concentration. E: protein levels of liver tumor necrosis factor-α (TNF-α). Data are presented as means ± SE for control (white bar) and maternal obesity (Mat-Ob) (gray bar) offspring. n = 6–8 per group. *P < 0.05, **P < 0.01.

Fig. 2.

Oxidative homeostasis. A: protein levels of oxidative and nitrosative enzymes. eNOS, endothelial nitric oxide synthase; iNOS, inducible nitric oxide synthase; XO, xanthine oxidase; NOX4, NADPH oxidase 4. B: protein levels of antioxidant enzymes. MnSOD, manganese superoxide dismutase; GPx1, glutathione peroxidase-1; GR, glutathione reductase; CuZnSOD, copper/zinc superoxide dismutase; HO1, heme oxygenase-1. C: mitochondrial complex activities. D: protein levels of mitochondrial enzymes. COX4, cytochrome-c oxidase complex IV; Cyt c, cytochrome c; glutamate DH, glutamate dehydrogenase. Data are presented as means ± SE for control (white bar) and Mat-Ob (gray bar) offspring. n = 6–8 per group. *P < 0.05, **P < 0.01, ***P < 0.001.

Fig. 3.

Liver lipid metabolism. A: protein levels of lipogenic enzymes. ACC, acetyl coA carboxylase; PDH, pyruvate dehydrogenase; PPARγ, peroxisome proliferator activator receptor γ; FAS, fatty acid synthase; SREBP1, sterol regulatory element-binding protein 1. B: protein levels of lipolytic enzymes. PPARα, peroxisome proliferator activator receptor α; LPL, lipoprotein lipase; ATGL, adipose triglyceride lipase; 5-LO, 5-lipoxygenase; CYP4A14, cytochrome P-450 4A14. C: total liver lipid content determined from 100 mg liver tissue. D: representative Oil-red-O (ORO) and hematoxylin-and-eosin (H&E) histology images. Scale bar is 50 μm. E: quantification of lipid droplet staining. Data are presented as means ± SE for control (white bar) and Mat-Ob (gray bar) offspring. n = 6–8 per group; *P < 0.05, ***P < 0.001.

Fig. 4.

Liver glycogen metabolism. A: liver glycogen content. B: protein levels of total glycogen synthase kinase-3 isoforms and their phosphorylation levels. C: protein levels of gluconeogenic enzymes. PEPCK, phosphoenolpyruvate carboxykinase; G6Pase, glucose-6 phosphatase. Data are presented as means ± SE for control (white bar) and Mat-Ob (gray bar) offspring. n = 6–8 per group, *P < 0.05.