Plasma human placental lactogen profiles over 24 hours in normal and diabetic pregnancy

Human Placental Lactogen in Relation to Maternal Metabolic Health and Fetal Outcomes: A Systematic Review and Meta-Analysis

Human placental lactogen (hPL) is a placental hormone which appears to have key metabolic functions in pregnancy. Preclinical studies have putatively linked hPL to maternal and fetal outcomes, yet-despite human observational data spanning several decades-evidence on the role and importance of this hormone remains disparate and conflicting. We aimed to explore (via systematic review and meta-analysis) the relationship between hPL levels, maternal pre-existing and gestational metabolic conditions, and fetal growth. MEDLINE via OVID, CINAHL plus, and Embase were searched from inception through 9 May 2022. Eligible studies included women who were pregnant or up to 12 months post-partum, and reported at least one endogenous maternal serum hPL level during pregnancy in relation to pre-specified metabolic outcomes. Two independent reviewers extracted data. Meta-analysis was conducted where possible; for other outcomes narrative synthesis was performed. 35 studies met eligibility criteria. No relationship was noted between hPL and gestational diabetes status. In type 1 diabetes mellitus, hPL levels appeared lower in early pregnancy (possibly reflecting delayed placental development) and higher in late pregnancy (possibly reflecting increased placental mass). Limited data were found in other pre-existing metabolic conditions. Levels of hPL appear to be positively related to placental mass and infant birthweight in pregnancies affected by maternal diabetes. The relationship between hPL, a purported pregnancy metabolic hormone, and maternal metabolism in human pregnancy is complex and remains unclear. This antenatal biomarker may offer value, but future studies in well-defined contemporary populations are required.

Meal Timing and Glycemic Control during Pregnancy-Is There a Link?

Hyperglycemia during pregnancy and gestational diabetes mellitus (GDM) constitute an important public health problem due to their prevalence and long-term health consequences both for the mother and offspring. Results from studies in rodents and some clinical investigations suggest that meal time manipulation may be a potential lifestyle approach against conditions involving perturbations in glucose homeostasis (e.g., hyperglycemia, insulin resistance, diabetes, etc.). The purpose of this review is to summarize and critically evaluate the current literature on the role of meal timing and daily nutrient distribution on glycemic control during pregnancy. Only a small number of mostly observational studies have assessed the role of meal timing in glucose homeostasis during pregnancy. Food consumption earlier in the day and short-term fasting with adequate nutrient intake may improve glycemic control during the second and third trimester of gestation. Considering that the field of chrononutrition is still in its infancy and many questions remain unanswered, future prospective and carefully designed studies are needed to better understand the role of meal timing in metabolic homeostasis and maternal and fetal health outcomes during pregnancy.

Constitutive expression of placental lactogen in pancreatic beta cells: effects on cell morphology, growth, and gene expression

To explore the roles of lactogens in islet function, we generated a stable line of rat insulinoma (INS-1) cells that express rat placental lactogen II (rPLII) constitutively in culture. We used this cell line (Ins-rPLII) to examine the effects of endogenous rPLII on beta-cell growth, islet formation, and the expression of glucose transporter 2 (glut-2) and insulin mRNA. Growth and maturation of Ins-rPLII cells were compared with that of cells transfected stably with an empty expression plasmid (control) and of INS-1 cells treated with exogenous prolactin. The Ins-rPLII cells proliferated more rapidly than control cells in serumfree medium and showed distinct morphologic characteristics in culture. Whereas the control cells flattened readily on plastic and formed a branching monolayer, the Ins-rPLII cells remained more rounded, sent out fewer projections, and formed more numerous (p<0.01) and larger (p<0.01) beta-cell clusters. Larger clusters assumed a spherical form with well-delineated smooth borders and detached more readily from the culture plates. Maturational progression of the Ins-rPLII cells was associated with a 40% increase in preproinsulin mRNA (p<0.05) and a 2-3-fold increase in glut-2 mRNA (p<0.01). Induction of glut-2 mRNA was accompanied by a 1.4-2.4-fold increase (p< 0.01) in the uptake of radiolabeled 2-deoxyglucose. Similar effects were observed in INS-1 cells exposed for 48 h to exogenous prolactin. These findings suggest novel roles for the lactogenic hormones in the maturation and growth of pancreatic islets. Lactogen induction of beta-cell aggregation coupled with localized beta-cell growth may contribute to the expansion of islet mass that occurs in pregnancy and during the perinatal period. The induction of insulin and glut-2 mRNA provides a mechanism by which the lactogens may increase fetal and maternal insulin production and enhance the sensitivity of the pancreas to glucose.

Placental protein distribution in maternal diabetes mellitus: an immunocytochemical study

Placentas associated with maternal diabetes are generally characterized by features of villous immaturity. We correlated the villous histology with the immunocytochemical distribution of four trophoblastic proteins: beta human chorionic gonadotropin (beta HCG), placental alkaline phosphatase (PLAP), pregnancy specific beta-1-glycoprotein (SP1), and human placental lactogen (HPL) in 14 third-trimester placentas associated with diabetes mellitus. Staining was increased for beta HCG and decreased for PLAP, SP1, and HPL in the diabetic placentas compared to control placentas of similar gestational age. This pattern was most prominent in areas of marked architectural villous immaturity within individual placentas and suggests concomitant functional immaturity.

Daily rhythm of serum human chorionic gonadotropin and human chorionic somatomammotropin in normal pregnancy

We have quantified the human chorionic gonadotropin (HCG) and human chorionic somatomammotropin (HCS) serum levels in normal pregnant women at 1-h intervals during 24 h, through radioimmunoassay procedures. The HCG levels were higher during the first trimester, although no circadian variations were detected. Some variations exceeded by ten fold; these variations decreased with advanced periods of gestation. No diurnal fluctuations in serum HCS were apparent; in a case nearly at term, there was an increase from 05:00 h to 09:00 h simulating a circadian pattern, although it was not statistically significant. These data indicate that the placental protein secretion is autonomous and that HCG levels of fluctuation during early stages of pregnancy might be regulated by factors other than the trophoblast.

Plasma unconjugated oestriol in late pregnancy: circadian variation and the effect of meals and a glucose load

Plasma unconjugated oestriol (E3) concentrations were determined by radioimmunoassay in 10 normal subjects in late pregnancy, throughout a normal day and night, and after a 50 g oral glucose load. There was a circadian pattern in E3 concentration characterized by an abrupt increase of 15 per cent at night. There was no significant rhythm during the day or night, taken separately. However there was a 10 to 11 per cent reduction in E3 concentrations soon after some meals and after a glucose load, possibly due to expansion of the plasma volume. Excluding the effect of meals, the fluctuation of E3 concentrations in individuals (median of the coefficients of variation) was 11.5 per cent in the day. Overall, it was 13.2 per cent in the day, 12.1 per cent at night and 15.9 per cent over the whole period studied. Since the variation in plasma unconjugated E3 concentrations through 24 hours was no greater than random fluctuations or day-to-day variation there is no need to restrict the time of blood sampling in clinical practice.