Delayed lung maturation in the macrosomic offspring of genetically determined diabetic (db/+) mice

We studied a genetically determined diabetes in pregnancy, the heterozygous diabetes (db/+) mouse. We found that fetal mice from these pregnancies are macrosomic with increased body, lung, and placenta wt, have altered organ protein, DNA and phospholipid content, and exhibit abnormal carbohydrate metabolism with increased liver and glycogen content. We further studied the effect of increased substrate availability and utilization on lung growth and maturation in (db/+) fetal mice, by measuring lung phospholipid synthesis as represented by the incorporation of the radiolabeled precursors, [3H]choline and [14C]glycerol, in fetal lung at 18 days' gestation (term = 19). Diabetic fetuses incorporated significantly more [3H]choline into disaturated phosphatidylcholine than controls (1.32 +/- 0.10 X 10(-2) versus 0.78 +/- 0.05 X 10(-2) nmol/g protein/min, mean +/- SE; p less than 0.001), but significantly less [14C]glycerol into phosphatidylglycerol than controls (3.18 +/- 0.38 versus 4.91 +/- 0.53 nmol/g protein/min, mean +/- SE; p less than 0.002), and their phosphatidylglycerol/phosphatidylinositol synthesis ratios were decreased (1.81 +/- 0.18 versus 3.17 +/- 0.14; mean +/- SE; p less than 0.001). Diabetic fetal lungs appeared morphologically less mature than controls at 18 days' gestation, as shown by a significantly decreased air space density (0.27 +/- 0.01 versus 0.43 +/- 0.02, mean +/- SE; p less than 0.001) and alveolar epithelial cell/total tissue ratio (0.54 +/- 0.02 versus 0.66 +/- 0.03, mean +/- SE; p less than 0.01). The increased synthesis of lung disaturated phosphatidylcholine in diabetic fetal mice may reflect the enhancement of body and lung growth in these macrosomic fetuses.(ABSTRACT TRUNCATED AT 250 WORDS)