Insulin binding to trophoblast plasma membranes and placental glycogen content in well-controlled gestational diabetic women treated with diet or insulin, in well-controlled overt diabetic patients and in healthy control subjects

Abstract

Insulin binding to trophoblast plasma membranes and the placental glycogen content were measured in twelve healthy women, in eleven well-controlled gestational diabetic women who were treated either with diet alone (n = 4) or with insulin (n = 7) and in 18 women with well-controlled overt diabetes mellitus (six White B; four White C; eight White D). The competitive binding assay was carried out with 22 concentrations of unlabelled insulin. Binding data were analysed by a non-linear direct model fitting procedure assuming one non-cooperative binding site. Maximum specific binding was unchanged in the total collective of gestational diabetic women, but was decreased by 30% in those treated with diet (6.2 +/- 2.2%) and increased by 90% in insulin-treated women (16.4 +/- 10.2%) as compared to the control subjects (8.7 +/- 2.5%). The diet-treated women had only 40% as many and those treated with insulin had more than twice as many receptors compared to control subjects on a per mg protein basis and if expressed per total placenta. In patients with overt diabetes mellitus maximum specific binding (18.5 +/- 10.6%) was higher (p less than 0.05) due to more receptors compared to control subjects but was similar to the insulin-treated gestational diabetic patients. Maximum specific binding and receptor concentrations did not correlate linearly with maternal plasma insulin levels. Receptor affinities were virtually similar in all groups (1.8 x 10(9) l/mol). The placental glycogen content was reduced (p less than 0.05) to about 80% of that of control subjects in the diet-treated collective, whereas it was unchanged compared to control subjects in the insulin-treated gestational diabetic women despite a 40% increase (p less than 0.001) of the maternal-to-cord serum glucose ratio. In overt diabetic patients the maternal-to-cord serum glucose ratio and the placental glycogen content were higher (p less than 0.05) than in the control subjects. We conclude that trophoblast plasma membranes from gestational diabetic women treated with diet alone express less and those from women treated with insulin express more insulin receptors than those from a healthy control group in vitro. These differences could not have been disclosed without consideration of the mode of treatment. Trophoblast plasma membranes from overt diabetic women have more insulin receptors than those from healthy control subjects.

Insulin control of placental gene expression shifts from mother to foetus over the course of pregnancy

“…The 1 nmol/l (167 μU/ml) insulin concentration was chosen as to reflect the higher range of maternal insulin levels seen in response to hyperglycaemia in GDM [21] or in the cord blood of type 1 diabetic pregnancies [22]. It also represents the upper limit of fasting insulin levels in type 1 diabetic mothers [23]. The exposure time of 16 h was chosen in order to allow transcription to occur, but limiting secondary effects.…”

Placental glucose transport and utilisation is altered at term in insulin-treated, gestational-diabetic patients

“…The perfusion of each maternal glucose concentration took 51 min and the entire experiment was completed within 4.5 h. The samples collected for the 4,8,16 or 24 mmol/l maternal glucose concentrations were centrifuged immediately at 3000 rpm for 5 min to remove any trace of blood and assayed fresh for glucose and llactate using a YSI 2300 analyser (YSI, Yellow Springs, Ohio, USA). is the fetal effluent glucose concentration(mmol/ml); V M is the maternal perfusion rate (ml/min); V F is the fetal perfusion rate (ml/min); W is the perfused lobule weight (grams wet weight); G C14 FE is the 14 C-d-glucose activity in the fetal effluent (dpm/mmol); G C14 MP is the 14 C-d-glucose activity in the maternal perfusate (dpm/mmol); L ME is the lactate concentration in the maternal effluent (mmol/ml); L FE is the lactate concentration in the fetal effluent (mmol/ml).…”

“…The direct transfer rate of glucose to the fetal effluent also involves 14 C-d-glucose infusion into the maternal perfusate and its detection in the fetal effluent, providing a measure of the rate of unidirectional glucose transfer from the maternal compartment to fetal compartment.…”

Regulation of Placental Growth Hormone Secretion in a Human Trophoblast Model—The Effects of Hormones and Adipokines

“…If confirmed this would strongly argue for a PI3-kinase-independent insulin effect. In vivo trophoblast insulin receptors are located exclusively at the microvillous membrane of the syncytiotrophoblast (26,27). This location strongly argues for the maternal circulation as the sole insulin source regulating PGH secretion.…”

“…BeWo cells were generously donated by Prof. R Mortimer's laboratory at the Royal Brisbane and Women's Hospital in Brisbane and were originally purchased from the American Tissue Culture Collection (ATCC, Rockville, MD; ATCC no. CCL98; used at passages [25][26][27][28][29][30]. Reagents for cell culture were supplied by Invitrogen Life Technologies (Sydney, Australia).…”