Cerebrospinal fluid levels of insulin, leptin, and agouti-related protein in relation to BMI in pregnant women

Krüppel-like factor 4 in transcriptional control of the three unique isoforms of Agouti-related peptide in mice

Agouti-related peptide (AgRP/Agrp) within the hypothalamic arcuate nucleus (ARC) contributes to the control of energy balance, and dysregulated Agrp may contribute to metabolic adaptation during prolonged obesity. In mice, three isoforms of Agrp are encoded via distinct first exons. Agrp-A (ENSMUST00000005849.11) contributed 95% of total Agrp in mouse ARC, whereas Agrp-B (ENSMUST00000194654.2) dominated in placenta (73%). Conditional deletion of Klf4 from Agrp-expressing cells (Klf4Agrp-KO mice) reduced Agrp mRNA and increased energy expenditure but had no effects on food intake or the relative abundance of Agrp isoforms in the ARC. Chronic high-fat diet feeding masked these effects of Klf4 deletion, highlighting the context-dependent contribution of KLF4 to Agrp control. In the GT1-7 mouse hypothalamic cell culture model, which expresses all three isoforms of Agrp (including Agrp-C, ENSMUST00000194091.6), inhibition of extracellular signal-regulated kinase (ERK) simultaneously increased KLF4 binding to the Agrp promoter and stimulated Agrp expression. In addition, siRNA-mediated knockdown of Klf4 reduced expression of Agrp. We conclude that the expression of individual isoforms of Agrp in the mouse is dependent upon cell type and that KLF4 directly promotes the transcription of Agrp via a mechanism that is superseded during obesity.NEW & NOTEWORTHY In mice, three distinct isoforms of Agouti-related peptide are encoded via distinct first exons. In the arcuate nucleus of the hypothalamus, Krüppel-like factor 4 stimulates transcription of the dominant isoform in lean mice, but this mechanism is altered during diet-induced obesity.

Rescue of obesity-induced infertility in female mice by silencing AgRP neurons

Obesity impacts multiple sites of the hypothalamus-pituitary gland-ovary axis (HPO axis) and has become a leading cause of female infertility. However, the critical hypothalamic neurons that participate in the development of obesity-induced infertility have not been well defined yet. Previous studies suggested that metabolic-sensing agouti-related peptide-expressing (AgRP) neurons in the arcuate nucleus (ARC) are hyperactive in diet-induced obesity (DIO) mice. We hypothesize that these neurons may convey metabolic dysfunction onto the HPO axis and contribute to obesity-induced infertility's pathophysiological process. To determine if AgRP neurons in obesity play a necessary role in the development of reproductive impairment in obesity, we used the chemogenetic method to normalize the neuronal activity of AgRP neurons in DIO female mice and test if their fertility can be restored. Our results indicated that chemogenetic inhibition of AgRP neurons could fully rescue the reproductive performance of DIO female mice, as manifested by recovered sex hormonal levels, ovulation, and fecundity. Moreover, we assayed serum AgRP levels in normal-weight and obese women and found elevated AgRP levels in obese subjects, suggesting the correlation between obesity and AgRP neuronal hyperactivity. Our results indicated that AgRP neurons constitute a central node connecting metabolism and reproduction, and dysfunctions of these neurons play a crucial role in reproductive impairment induced by metabolic abnormalities.

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.

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.

Characterizing the Effects of Diabetes and Obesity on Insulin and Leptin Levels amongst Pregnant Women

OBJECTIVE

In this study, we assess the impact of obesity and diabetes on maternal brain and periphery, as well as fetal exposure to insulin and leptin, and two hormones that play an important role in regulating energy homeostasis.

STUDY DESIGN

Fasting maternal plasma, fetal cord vein and artery plasma, and maternal cerebrospinal fluid (CSF) were collected in 37 women (12 lean, nondiabetic [prepregnancy body mass index (BMI): 22.9 ± 1.7 kg/m²]; 12 overweight/obese nondiabetic [BMI: 37.8 ± 7.3 kg/m²]; 13 gestational/type 2 diabetes mellitus [BMI: 29.8 ± 7.3 kg/m²]) with uncomplicated singleton pregnancies undergoing elective Cesarean delivery. HbA1C, insulin, glucose, and leptin levels were measured.

RESULTS

Compared with lean mothers, mothers with obesity and diabetes mellitus (DM) had significantly lower CSF-to-plasma ratios of insulin. Moreover, mothers with obesity and DM had significantly lower cord arterial and cord venous to maternal plasma ratios of insulin, but not leptin, compared with lean mothers. There were no differences in CSF and cord blood insulin and leptin levels between obese and DM mothers.

CONCLUSION

Compared with lean individuals, mothers with obesity and DM have relative deficiencies in insulin exposure. The patterns observed in mothers with obesity and diabetes were similar highlighting the importance of the maternal metabolic environment in obesity and suggesting obese patients warrant further clinical focus.

Ectopic ACTH Syndrome Emerging 5 Years after the Diagnosis of Neuroendocrine Tumor

Ectopic ACTH syndrome (EAS) arising years after the diagnosis of a neuroendocrine tumor (NET) is exceedingly rare. We describe a case of EAS occurring five years after the diagnosis of a metastatic lung NET in a 61-year-old woman. She presented with severe hypokalemia but was not overtly Cushingoid on exam. Serum cortisol was 61mcg/dL after an overnight 1mg dexamethasone suppression test (<1.8mcg/dL) and urinary free cortisol was 7544 mcg/24h (<45mcg/24h), establishing the diagnosis of Cushing's syndrome. Plasma levels of peptides which have been associated with EAS, Agouti-related peptide (AgRP) and the ACTH precursors POMC (31-kDa) and pro-ACTH (22-kDa), were elevated. Metyrapone was initiated, but hypercortisolism persisted and the patient succumbed to pneumonia shortly after presentation. Retrospective examination of biopsy tissues showed rare ACTH immunoreactivity at the time of initial diagnosis, followed by staining in a greater proportion of cells as the disease progressed, consistent with EAS arising years after the diagnosis of NET. Given the increase in mortality associated with EAS, this unusual case highlights the importance of early detection and raises the possibility that early immunohistochemical stains for ACTH and measurements of ACTH precursors may facilitate the identification of NETs at high risk for EAS.

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

OBJECTIVE

To study changes of neuropeptides and adipokines in cerebrospinal fluid (CSF) and serum from pregnancy to postpregnancy in relation to weight changes, fat mass and glucose metabolism.

CONTEXT

With high postpartum weight retention being a risk factor in future pregnancies and of lifelong obesity, we evaluated neuropeptide and adipokine changes in women who either gained weight or were weight stable.

DESIGN

Women were followed for 5 ± 1 years after pregnancy and divided into two groups, weight stable and weight gain, by weight change from start of pregnancy.

PATIENTS

Twenty-five women (BMI 27 ± 5 kg/m² ) recruited at admission for elective caesarean section.

MEASUREMENTS

CSF and serum levels of agouti-related protein (AgRP), leptin and insulin, and serum levels of adiponectin and soluble leptin receptor were measured during and after pregnancy. These measurements were further related to fat mass and insulin sensitivity (HOMA-IR).

RESULTS

S-AgRP levels during pregnancy were lower in the weight stable group and a 1 unit increase in s-AgRP was associated with 24% higher odds of pertaining to the weight gain group. After pregnancy, s-AgRP increased in the weight stable group but decreased in the weight gain group. Decreased transport of leptin into CSF during pregnancy was reversed by an increased CSF:serum leptin ratio after pregnancy. In women who returned to their prepregnancy weight, serum adiponectin increased after pregnancy and correlated negatively with HOMA-IR.

CONCLUSION

S-AgRP concentration in late pregnancy may be one factor predicting weight change after pregnancy, and circulating AgRP may be physiologically important in the long-term regulation of body weight.