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Fetal proinsulin and birth weight
A Dornhorst1, J S Nicholls, K Ali
1Unit of Metabolic Medicine, St Mary's Hospital Medical School, Imperial College of Science, Technology and Medicine, London, UK.
Insights
Umbilical cord proinsulin is a better indicator of fetal beta-cell activity and infant birth weight than insulin. This finding may be due to proinsulin's longer half-life, making it a more robust marker.
Area of Science:
- Perinatal Medicine
- Endocrinology
- Biochemistry
Background:
- Fetal insulin is a key anabolic hormone influencing fetal growth and birth weight.
- Fetal hyperinsulinism is linked to accelerated growth and higher birth weights.
- Insulin and C-peptide levels in cord blood and amniotic fluid indicate fetal beta-cell function and correlate with birth weight.
Purpose of the Study:
- To compare the efficacy of umbilical venous proinsulin and insulin as markers of fetal beta-cell activity.
- To investigate the correlation between fetal proinsulin/insulin levels and infant birth weight and percentile.
- To assess the utility of proinsulin as a superior marker compared to insulin in pregnancies with mild glucose tolerance disturbances.
Main Methods:
- Measurement of umbilical venous proinsulin and insulin concentrations in 54 term infants.
- Utilized a highly specific immunoradiometric assay for proinsulin.
- Employed a non-specific insulin assay for insulin measurement.
Main Results:
- Umbilical venous proinsulin showed a significant independent correlation with infant birth weight (Rho = 0.53, p < 0.0001) and birth percentile (Rho = 0.65, p < 0.0001).
- The correlation between birth weight/percentile and umbilical venous insulin was diminished after accounting for proinsulin levels.
- Proinsulin demonstrated a stronger association with birth outcomes than non-specifically measured insulin.
Conclusions:
- Umbilical venous proinsulin is a reliable indicator of fetal beta-cell activity.
- Proinsulin is a superior marker for assessing fetal beta-cell function and its impact on birth weight compared to insulin measured by non-specific assays.
- Proinsulin's longer half-life may explain its robustness as a marker of overall fetal beta-cell activity.
Abstract:
In both diabetic and non-diabetic pregnancies fetal insulin is an important anabolic hormone. Fetal hyperinsulinaemia is associated with accelerated fetal growth and increased birth weight. Insulin and C-peptide concentrations in both umbilical cord and amniotic fluid reflect fetal beta-cell secretion and are correlated with birth weight. In the present study umbilical venous proinsulin and insulin concentrations were measured in 54 term infants born to women with and without mild disturbances of glucose tolerance. Umbilical venous cord proinsulin, assayed using a highly specific immunoradiometric assay, was independently correlated with infant birth weight (Rho = 0.53, p < 0.0001) and birth percentile (Rho = 0.65, p < 0.0001). The correlation between birth weight and birth percentile weight with umbilical venous insulin, measured using a non-specific insulin assay, was lost following correction for the influence of proinsulin. Umbilical venous cord proinsulin appears to be a good indicator of fetal beta-cell activity, and in this study, a superior marker to insulin assayed using a non-specific insulin radioimmunoassay. The longer half-life of proinsulin compared with insulin may contribute to proinsulin being a more robust marker of overall fetal beta-cell activity than insulin.