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DNA damage in pregnant women

Researchers from the Universidade Estadual Paulista and Instituto Dante Pazzanese de Cardiologia (both São Paulo, Brazil) decided to investigate oxidative DNA damage in pregnant women.  The women in the study were either ‘normal’, suffering with diabetes or had mild gestational hyperglycemia.

Hyperglycemia, or high blood sugar, is a condition in which an excessive amount of glucose circulates in the blood plasma.  The researchers believe that pregnant women with mild gestational hyperglycemia present high risk for hypertension (also known as high blood pressure), obesity and hyperglycemia, and appear to suffer with insulin resistance and hyperinsulinemia (a condition in which there are excess levels of insulin circulating in the blood than expected relative to the level of glucose) during pregnancy.

The scientists’ previous clinical studies showed that mild gestational hyperglycemia or gestational diabetes were related to similar adverse maternal and perinatal outcomes. They believed that hyperglycemia and other factors associated with diabetes generate reactive oxygen species that increase DNA damage levels.

“The aim of this study was to evaluate oxidative DNA damage in lymphocytes of pregnant women with diabetes or mild gestational hyperglycemia” said the investigators. 

This particular study included 111 pregnant women distributed into three groups based on oral glucose tolerance test (OGTT) and glycemic profiles (GP), as follows:

1.       Normal OGTT and normal GP (control group);
2.       Normal OGTT and abnormal GP (mild gestational hyperglycemia group);
3.       Abnormal OGTT and abnormal GP (diabetic group).

From 34 weeks of gestation and before the onset of labor, maternal blood samples (5 to 10 mL) and urine samples were collected. The blood samples were collected in Vacutainer tubes with EDTA and the urine samples in collector tubes. The collected blood samples were immediately processed for determination of oxidative DNA damage by the comet assay using Fpg and Endo III digestion enzymes.  The urine samples were stored in a freezer at -80°C for the measurement of 8-hidroxy-2-deoxi guanosina (8-OHdG) and creatinine levels.

For full experimental details of the comet assay method and other scientific details from this investigation, please refer to the original publication.   The comets were analysed in a fluorescence microscope connected to a computer-based analysis system (Comet Assay IV, Perceptive Instruments, UK) to determine the extent of DNA damage. Results were expressed as tail intensity (% DNA in the comet tail). One hundred randomly selected nucleoids (50 from each of two replicate slides) were scored per blood sample. Positive controls consisted of lymphocytes treated with H2O2 (200 μM, 30 minutes). 

The scientists reported that when using the restriction enzyme Endo III, women in the mild hyperglycemic group with hypertension had higher values of oxidative DNA damage compared to those in the mild hyperglycemic group without hypertension.  Ultimately, they concluded that gestational, overt diabetes and mild gestational hyperglycemia, were all related to increased oxidative DNA damage.

This study indicated that diabetic pregnant women showed increased level of oxidative DNA damage, possibly mainly due to hyperglycemia. However, oxidative DNA damage detected in women with mild gestational hyperglycemia might be associated with repercussions from obesity, hypertension and/or insulin resistance.

For more information, please refer to the original publication:

Oxidative DNA damage in diabetic and mild gestational hyperglycemic pregnant women
Rafael Bottaro Gelaleti, Débora Cristina Damasceno, Paula Helena Ortiz Lima, Daisy Maria Favero Salvadori, Iracema de Mattos Paranhos Calderon, José Carlos Peraçoli and Marilza Vieira Cunha Rudge.
Diabetology & Metabolic Syndrome 2015, 7:1