Effects of medication on methylation of peroxisome proliferator activated receptor-gamma coactivator-1A gene in offspring of gestational diabetes mellitus rat model

Abstract

Objective To determine the epigenetic change in the peroxisome proliferator activated receptor-gamma coactivator-1A (PPARGC1A) gene in offspring of the gestational diabetes mellitus (GDM) rat model treated with insulin and metformin.Methods The GDM model was established by one intraperitoneal injection of streptozotocin on gestational day 6 in pregnant Sprague-Dawley rats.Twenty-four GDM rats were randomly assigned to insulin-treated group,metformin-treated group and non-treated group,eight in each group.GDM rats in the insulin treated group and metformin-treated group were injected 4 U/kg insulin intraperitoneally or intragastric administrated with 300 mg/ (kg · d) metformin to maintain the glucose levels at 2.65 to 7.62 mmol/L,while rats in the non-treated group were administrated with 0.9％ sodium chloride injection.Eight pups from each group were selected and their weight and blood glucose level were monitored at three and eight weeks old.Serum insulin,leptin and triglycerides were measured at eight weeks old.Pancreas PPARGC1A mRNA expression and DNA methylation were analyzed by reverse transcription-polymerase chain reaction.Analysis of variance and the LSD test were used for statistical analysis of the data.Results The birth weight of pups in the insulin-treated and metformin-treated groups were (4.6±0.8) and (4.6±0.9) g,lower than the non treated group [(7.2±0.4) g,LSD test,both P=0.000].Three weeks and eight weeks later,the weight of the pups from the three groups was not statistically different (F=0.616 and 0.904,P=0.550 and 0.420).Fasting blood glucose in three and eight-week-old offspring in the insulin-treated group was (5.58±1.01) and (5.98± 1.47) mmol/L,and was (4.63± 1.16) and (5.65±0.62) mmol/L in the metformin-treated group,which were lower than those in the non-treated group [(8.83±0.73) and (10.54±0.92) mmol/L,respectively].The change in random glucose was consistent with that in fasting glucose (LSD test,P＜0.05).Compared with the non-treated group,eight-week-old offspring in the insulin-treated group and metformin-treated group had higher levels of serum fasting insulin [(8.09± 1.08) and (8.16± 1.42) vs (6.20±0.35) mmol/L] and leptin[(6.51±0.73) and (8.23±1.39) vs (5.14±0.43) mmol/L],but lower triglyceride levels [(1.72±0.29) and (1.41 ±0.21) vs (2.12±0.20) mmol/L,LSD test,P＜0.05respectively].The levels of PPARGC1A mRNA in the insulin-treated group and metformin-treated group were 1.300±0.351 and 0.997±0.389,which were higher than that in the non-treated group (0.485±0.084),but the methylation index was lower (0.025±0.087 and 0.021 ±0.085 vs 0.825±0.334),respectively (LSD test,P＜0.05).Conclusions Insulin and metformin treatment reduces PPARGC1A gene methylation in offspring of the GDM rat model and improve the metabolic disorder. Key words: Diabetes, gestational; Diabetes mellitus, experimental; Transcription Factors; Methylation; Drug therapy; Epigenomics