Central and peripheral leptin and agouti-related protein during and after pregnancy in relation to weight change

Gestational weight gain, appetite regulating hormones, and metformin treatment in polycystic ovary syndrome: A longitudinal, placebo-controlled study

OBJECTIVE

To explore mechanisms that modulate gestational weight gain (GWG) in women with polycystic ovary syndrome (PCOS) and healthy controls.

DESIGN

Sub-sample of randomised controlled trials (PCOS) combined with a prospective cohort (controls).

SETTING

Eleven Norwegian, Swedish, and Icelandic hospitals.

POPULATION

Pregnant women with PCOS treated with metformin (PCOS-M, n = 36) or placebo (PCOS-P, n = 37), and healthy pregnant women (HC, n = 15).

METHODS

Serum levels of the appetite regulating hormones leptin, ghrelin, allopregnanolone, and soluble leptin receptor (sOB-R) were determined in the first and third trimesters.

MAIN OUTCOME MEASURES

Excessive GWG (eGWG) relative to body mass index according to Institute of Medicine (IOM) guideline. Serum leptin/sOB-R ratio, or free-leptin-index (FLI), as biomarker of leptin sensitivity. Serum ghrelin and allopregnanolone levels.

RESULTS

The overall prevalence of eGWG was 44% (38/86). Women with eGWG had higher first and third trimester FLI (P < 0.001), and lower third trimester allopregnanolone levels (P = 0.003) versus women with non-eGWG. The prevalence of eGWG was lower in PCOS-M versus PCOS-P (28% versus 62%, odds ratio = 0.4, 95% CI 0.2-0.8, P = 0.005). FLI decreased during pregnancy in PCOS-M (P = 0.01), but remained unaltered in PCOS-P and HC. Ghrelin and allopregnanolone levels were comparable in PCOS-M, PCOS-P and HC throughout pregnancy.

CONCLUSION

Excessive GWG is associated with enhanced leptin resistance, and attenuated physiological increase in serum allopregnanolone levels during pregnancy. Metformin reduces the risk for eGWG and improves leptin sensitivity in pregnant women with PCOS.

Pregnancy-specific Adaptations in Leptin and Melanocortin Neuropeptides in Early Human Gestation

INTRODUCTION

Pregnancy is characterized by increased appetitive drive beginning early in gestation, yet the central mechanisms underlying this adaptation are poorly understood in humans. To elucidate central mechanisms underlying appetite regulation in early pregnancy, we examine plasma and cerebrospinal fluid (CSF) leptin and Agouti-related peptide (AgRP) as well as CSF proopiomelanocortin (POMC) as surrogates for brain melanocortin activity.

METHODS

Plasma leptin, soluble leptin receptor, AgRP, and CSF leptin, POMC, and AgRP were collected from pregnant women before cerclage placement (16.6 ± 1.1 weeks; N = 24), scheduled cesarean section (39.2 ± 0.2 weeks; N = 24), and from nonpregnant controls (N = 24), matched for age and body mass index.

RESULTS

Plasma leptin was 1.5 times higher in pregnancy vs controls (P = 0.01), but CSF leptin did not differ. CSF/plasma leptin percentage was lower in early pregnancy vs controls (0.8 ± 0.1 vs 1.7 ± 0.2; P < 0.0001) and remained unchanged at term (0.9 ± 0.1), supporting a decrease in leptin transport into CSF in pregnancy. Plasma AgRP, a peripheral biomarker of the orexigenic hypothalamic neuropeptide, was higher in early pregnancy vs controls (95.0 ± 7.8 vs 67.5 ± 5.3; P = 0.005). In early gestation, CSF AgRP did not differ from controls, but CSF POMC was 25% lower (P = 0.006). In contrast, at term, CSF AgRP was 42% higher vs controls (P = 0.0001), but CSF POMC no longer differed. Overall, the CSF AgRP/POMC ratio was 1.5-fold higher in early pregnancy vs controls, reflecting a decrease in melanocortin tone favoring appetitive drive.

CONCLUSIONS

Pregnancy-specific adaptions in the central regulation of energy balance occur early in human gestation and are consistent with decreased leptin transport into brain and resistance to the effects of leptin on target melanocortin neuropeptides.

Physical activity during pregnancy and association with changes in fat mass and adipokines in women of normal-weight or with obesity

Adipose tissue and adipokine concentrations change markedly during pregnancy, but the effects of physical activity on these changes are rarely studied. We aimed to assess physical activity levels in pregnant women of normal-weight (NW) or with obesity (OB), and to determine the relation with changes in fat mass and adipokines. In each trimester, pregnant women (136 NW, 51 OB) were interviewed about their physical activity and had their body composition, leptin, soluble leptin receptor (sOB-R) and adiponectin determined. NW reported higher activity and more aerobic exercise than OB during early pregnancy. Both groups maintained training frequency but reduced overall activity as pregnancy progressed. NW women reporting aerobic and/or resistance exercise and OB women reporting aerobic exercise had greater sOB-R increases (independent of BMI or gestational weight gain). In NW, exercise also associated with lower fat mass and leptin increases. Higher activity levels associated with lower gestational weight gain in both groups. The relationship between physical activity and adiponectin differed between NW and OB. Maternal exercise may partly mediate its beneficial effects through regulation of leptin bioavailability, by enhancing pregnancy-induced increases in sOB-R. This could be of particular importance in OB with pre-gestational hyperleptinemia and leptin resistance.

Growth differentiation factor 15 increases in both cerebrospinal fluid and serum during pregnancy

Aim

Growth differentiation factor 15 (GDF15) increases in serum during pregnancy to levels not seen in any other physiological state and is suggested to be involved in pregnancy-induced nausea, weight regulation and glucose metabolism. The main action of GDF15 is regulated through a receptor of the brainstem, i.e., through exposure of GDF15 in both blood and cerebrospinal fluid (CSF). The aim of the current study was to measure GDF15 in both CSF and serum during pregnancy, and to compare it longitudinally to non-pregnant levels.

Methods

Women were sampled at elective caesarean section (n = 45, BMI = 28.1±5.0) and were followed up 5 years after pregnancy (n = 25). GDF15, insulin and leptin were measured in CSF and serum. Additional measurements included plasma glucose, and serum adiponectin and Hs-CRP.

Results

GDF15 levels were higher during pregnancy compared with follow-up in both CSF (385±128 vs. 115±32 ng/l, P<0.001) and serum (73789±29198 vs. 404±102 ng/l, P<0.001). CSF levels correlated with serum levels during pregnancy (P<0.001), but not in the non-pregnant state (P = 0.98). Both CSF and serum GDF15 were highest in women carrying a female fetus (P<0.001). Serum GDF15 correlated with the homeostatic model assessment for beta-cell function and placental weight, and CSF GDF15 correlated inversely with CSF insulin levels.

Conclusion

This, the first study to measure CSF GDF15 during pregnancy, demonstrated increased GDF15 levels in both serum and CSF during pregnancy. The results suggest that effects of GDF15 during pregnancy can be mediated by increases in both CSF and serum levels.

Pregnancy-induced adaptation of central sensitivity to leptin and insulin

Pregnancy is a time of increased food intake and fat deposition in the mother, and adaptations of glucose homeostasis to meet the energy demands of the growing fetus. As part of these adaptations, leptin and insulin concentrations increase in the maternal circulation during pregnancy. Central effects of leptin and insulin, however, are counterproductive to pregnancy, as increased action of these hormones in the brain lead to suppression of food intake. To prevent this, it is well documented that pregnancy induces a state of leptin- and insulin-insensitivity in the brain, particularly the hypothalamus, in a range of species. While the mechanisms underlying leptin- or insulin-insensitivity during pregnancy vary between species, there is evidence of reduced transport into the brain, impaired activation of intracellular signalling pathways, including reduced leptin receptor expression, and attenuated activation of downstream neuronal pathways, especially for leptin insensitivity. Pregnancy-induced changes in prolactin, growth hormone and leptin are discussed in terms of their role in mediating this reduced response to leptin and insulin.

Exploring the Relationship Between Maternal Circulating Hormones and Gestational Weight Gain in Women Without Obesity: A Cross-Sectional Study

Background

Central homeostatic regulation of fat stores is attenuated during pregnancy, to allow for adequate fat deposition to support fetal development and lactation. What factors particular to pregnancy facilitate fat accumulation, and why gestational weight gain (GWG) is so variable, are not clear. The aim of this cross-sectional study was to examine the associations between GWG and circulating hormones with known effects on appetite and growth.

Methods

Women without obesity (body mass index, BMI <30 kg/m²), with a healthy singleton pregnancy, were recruited at the time of delivery by elective Caesarean section at a tertiary obstetric hospital. Women with preterm (<37 weeks) delivery and smokers were excluded. Maternal blood was collected at the time of delivery for measurement of fasting oestradiol, progesterone, prolactin, insulin, leptin, insulin-like growth factor 1 and insulin-like growth factor binding protein 3. Comparisons were made between women who gained weight within the range recommended by Institute of Medicine guidelines for normal weight women (11.5–16 kg; n=34) and those who gained excessive weight (>16 kg; n=35) during pregnancy. Analysis of covariance was carried out using multiple linear regression to test the effect of GWG group on biochemical parameters, accounting for pre-pregnancy BMI.

Results

The 69 participants had a mean age of 34.6 ± 4.3 years, and pre-pregnancy BMI of (23.3 ± 1.8 kg/m²), with no significant differences between groups in pre-pregnancy weight, BMI, age, birthweight or parity. Mean GWG was 14.0 ± 1.3 kg in the “recommended” group and 19.6 ± 3.2 kg in the “excessive” group. Leptin was significantly higher (43.4 ± 21.6 vs 33.4 ± 15.0 ng/mL, p=0.03) and prolactin tended to be lower (159.5 ± 66.1 vs 194.0 ± 85.6 ng/mL, p=0.07) at delivery in women with excessive (vs recommended) GWG. No other circulating factors were found to differ between groups. The between-group difference in leptin remained after adjustment for pre-pregnancy BMI in multiple linear regression and quantile regression analyses.

Conclusion

In women without obesity, leptin remains a marker of adiposity during pregnancy. GWG was not associated with other circulating hormones with effects on appetite and growth.

Neurophysiological and cognitive changes in pregnancy

The hormonal fluctuations in pregnancy drive a wide range of adaptive changes in the maternal brain. These range from specific neurophysiological changes in the patterns of activity of individual neuronal populations, through to complete modification of circuit characteristics leading to fundamental changes in behavior. From a neurologic perspective, the key hormone changes are those of the sex steroids, estradiol and progesterone, secreted first from the ovary and then from the placenta, the adrenal glucocorticoid cortisol, as well as the anterior pituitary peptide hormone prolactin and its pregnancy-specific homolog placental lactogen. All of these hormones are markedly elevated during pregnancy and cross the blood-brain barrier to exert actions on neuronal populations through receptors expressed in specific regions. Many of the hormone-induced changes are in autonomic or homeostatic systems. For example, patterns of oxytocin and prolactin secretion are dramatically altered to support novel physiological functions. Appetite is increased and feedback responses to metabolic hormones such as leptin and insulin are suppressed to promote a positive energy balance. Fundamental physiological systems such as glucose homeostasis and thermoregulation are modified to optimize conditions for fetal development. In addition to these largely autonomic changes, there are also changes in mood, behavior, and higher processes such as cognition. This chapter summarizes the hormonal changes associated with pregnancy and reviews how these changes impact on brain function, drawing on examples from animal research, as well as available information about human pregnancy.

Longitudinal changes in adipokines and free leptin index during and after pregnancy in women with obesity

OBJECTIVE

Detailed data on adipokines and body composition during and after pregnancy in women of different BMI categories are lacking. Furthermore, adipokine regulation during pregnancy and the factors contributing to gestational insulin resistance are not completely understood. The objective was to longitudinally determine adipokine levels, body composition, and insulin sensitivity during and after pregnancy in women of healthy weight (HW) and with obesity (OB), and identify factors associated with insulin resistance.

DESIGN

Women (30 HW, 19 OB) underwent blood sampling and body composition examination, by air-displacement plethysmography, longitudinally during pregnancy (trimesters 1, 2, 3) and after pregnancy (6, 12, 18 months postpartum). Serum leptin, soluble leptin receptor (sOB-R), and adiponectin levels were measured and free leptin index (FLI) and homeostatic model assessment of insulin resistance (HOMA-IR) determined.

RESULTS

Fat mass and leptin increased during pregnancy in the HW (p < 0.01) but not in the OB group. sOB-R increased during pregnancy in both groups (p < 0.001). Thus, FLI was unchanged in HW throughout pregnancy but reduced in OB (p = 0.001), although consistently higher in OB. Adiponectin decreased in both groups during pregnancy (p < 0.001 for HW, p = 0.01 for OB). After pregnancy, adiponectin increased in both groups, but more markedly in OB where it reached trimester 1 levels. Multivariable regression identified FLI as the variable most strongly associated with HOMA-IR in all trimesters, but not after pregnancy.

CONCLUSIONS

Leptin, sOB-R, adiponectin, and FLI undergo marked changes during and after pregnancy with differences in women of different BMI. We suggest that leptin activity is regulated by its soluble receptor and that this is an important factor for optimizing fat mass and insulin sensitivity during pregnancy.