International Journal of
Molecular Sciences Article
Effects of Late Gestational Fetal Exposure to Dexamethasone Administration on the Postnatal Hypothalamus-Pituitary-Adrenal Axis Response to Hypoglycemia in Pigs René Schiffner 1,2, *, Guadalupe L. Rodríguez-González 3 , Florian Rakers 1 , Marius Nistor 1 Peter W. Nathanielsz 4 , Teodora Daneva 5 ID , Matthias Schwab 1 , Thomas Lehmann 6 and Martin Schmidt 7 ID 1 2 3 4 5 6 7
*
ID
,
Department of Neurology, Jena University Hospital—Friedrich Schiller University, 07747 Jena, Germany;
[email protected] (F.R.);
[email protected] (M.N.);
[email protected] (M.S.) Orthopaedic Department, Jena University Hospital—Friedrich Schiller University, 07747 Jena, Germany Reproductive Biology, National Institute of Medical Science and Nutrition, 14000 Mexico City, Mexico;
[email protected] Department of Animal Science, University of Wyoming, Laramie, 82071 WY, USA;
[email protected] Institute of Biology and Immunology of Reproduction, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria;
[email protected] Institute of Medical Statistics, Computer Sciences and Documentation Science, Jena University Hospital—Friedrich Schiller University, 07743 Jena, Germany;
[email protected] Institute for Biochemistry II, Jena University Hospital—Friedrich Schiller University, 07743 Jena, Germany;
[email protected] Correspondence:
[email protected]; Tel.: +49-36691-81292; Fax: +49-36691-81029
Received: 24 September 2017; Accepted: 21 October 2017; Published: 27 October 2017
Abstract: Background: Prenatal glucocorticoid administration alters the activity of the fetal hypothalamic-pituitary-adrenocortical axis (HPAA), and correspondingly the adenocorticotropic hormone (ACTH) and cortisol levels after birth. The dosages required for these effects are critically discussed. Activation of the HPAA is related to metabolic syndrome and diabetes mellitus. Hypoglycemia is the classic side effect of antidiabetic treatment. We hypothesized that a low dosage of dexamethasone in late pregnancy alters the HPAA response to hypoglycemia in pigs. Methods: 12 pregnant sows were randomly assigned to two groups which received either a low-dose intramuscular injection (99th and 100th day of gestation) of dexamethasone (0.06 µg/kg body weight) or vehicle. Three months after birth, 18 dexamethasone-treated anaesthetized offspring and 12 control offspring underwent a 75 min hypoglycemic clamp (blood glucose below 4 mmol/L) procedure. Heart rate (HR), blood pressure, ACTH and cortisol levels and body weight (at birth and after three months) were recorded. Results: Dexamethasone-treated animals exhibited significantly elevated ACTH (139.9 ± 12.7 pg/mL) and cortisol (483.1 ± 30.3 nmol/L) levels during hypoglycemia as compared to the control group (41.7 ± 6.5 pg/mL and 257.9 ± 26.7 nmol/L, respectively), as well as an elevated HR (205.5 ± 5.7 bpm) and blood pressure (systolic: 128.6 ± 1.5, diastolic: 85.7 ± 0.7 mmHg) response as compared to the control group (153.2 ± 4.5 bpm; systolic: 118.6 ± 1.6, diastolic: 79.5 ± 1.4 mmHg, respectively; p < 0.001). Conclusions: Low-dose prenatal administration of dexamethasone not only exerts effects on the HPAA (ACTH and cortisol concentration) and vital parameters (HR and diastolic blood pressure) under baseline conditions, but also on ACTH, HR and systolic blood pressure during hypoglycemia. Keywords: HPA axis; ACTH; cortisol; stress response; hypoglycemia
Int. J. Mol. Sci. 2017, 18, 2241; doi:10.3390/ijms18112241
www.mdpi.com/journal/ijms
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1. Introduction Endogenous gluconeogenesis is important for the maintenance of a stable blood glucose homeostasis in both humans and pigs [1]. Activation of the sympathetic nervous system may be related to metabolic syndrome and disorders of glucose metabolism, e.g., diabetes mellitus [2–5]. Previous studies have already provided solid evidence that prenatal maternal injection of synthetic glucocorticoids (GCs) [6–8], such as betamethasone and dexamethasone, induces changes in the activity of the hypothalamic-pituitary-adrenocortical axis (HPAA), which is responsible for the distribution of endogenous catecholamines. Therefore, excessive exposure to GCs during gestation may have an adverse impact on stress responsive systems [9]. Changes in the HPAA have an influence on endogenous stress hormones like the adenocorticotropic hormone (ACTH) and cortisol, which stimulate glucose release [10,11], as well as on the autonomous nervous system, which is involved in gluconeogenesis [12,13]. Hypoglycemia, with a resulting increase of the endogenous stress hormones ACTH and cortisol, is a classic side effect of antidiabetic treatment, e.g., inulin or oral antidiabetic drugs (sulfonylureas). Prenatal maternal GC injections in late pregnancy have a direct influence on changes in HPAA in both humans and pigs [14–16]. The exact dosages of injected GCs required for such an alteration remain controversial. We tested the hypothesis that a prenatal maternal low dosage injection of dexamethasone would cause an alteration of the counteregulatory responses of endogenous ACTH and cortisol during hypoglycemia in pigs. Severe hypoglycemia causes a HPAA response that is expressed as enhanced endogenous ACTH and cortisol concentrations. We decided to use the GC dexamethasone since it has a higher affinity for glucocorticoid receptors than betamethasone. The repeated injections of dexamethasone, at the 99th and 100th day of gestation (dGA) in a 12 h interval, were designed to provoke a distinct response [17–21]. The experimental setup allows the experiment to be performed under deep general anesthesia. 2. Results The experimental setup was appropriate to detect differences between offspring of dexamethasone-treated pigs and non-treated pigs with respect to body weight and growth over the course of the observation period (Table 1). No gender-specific differences in body weight and growth were observed during the observation period. Table 1. Weight increase in controls (CON) and prenatally dexamethasone-treated pigs (DEX) over the first three months of life. Timepoint Heading
Control Group (CON) (kg)
Dexamethasone-Treated Group (DEX) (kg)
Birth 28 days of age 67 days of age
1.6 ± 0.02 8.0 ± 0.1 28.6 ± 0.2
1.3 ± 0.01 * 6.8 ± 0.3 * 24.1 ± 0.3 *
Data are given as mean ± SEM, * p < 0.001 vs. controls.
Hypoglycemia was considered to be established at blood glucose concentrations below 4 mmol/L and was maintained for 75 min (Figure 1). Baseline arterial blood glucose concentrations did not differ between both groups and were 8.1 ± 0.4 mmol/L in controls and 8.8 ± 0.4 mmol/L in the dexamethasone-treated group. At the end of the observation period, i.e., after 150 min and the hypoglycemic clamp procedure, the arterial blood glucose concentration was 0.9 ± 0.1 mmol/L in the control group and 1.1 ± 0.2 mmol/L in the dexamethasone-treated group. As the effective time of an established hypoglycemia differed slightly between individual animals and the two groups, all subsequent measurements in each individual animal refer to the first sampling in which the blood glucose was below the threshold of 4 mmol/L. During normoglycemic baseline conditions, heart rate (HR) and systolic and diastolic blood pressures were higher in the dexamethasone-treated group than in the control group (p < 0.05),
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and furthermore, remained higher over the course of the entire hypoglycemic period (p < 0.001, Int. J. Mol. Sci. 2017, 18, 2241 3 of 11 Figure 2). At baseline, the HR of the dexamethasone-treated group was significantly higher than that of the control (mean difference = 10.9 bpm, p = 0.033). the HR of the dexamethasone-treated At group baseline, the HR of the dexamethasone-treated groupOnly was significantly higher than that of the control group (mean difference = 10.9 bpm, p = 0.033). Only theby HR0.3 of the dexamethasone-treated group increased significantly during anesthesia, on average bpm per minute (p < 0.001). group differences increased significantly during anesthesia, average by 0.3 bpm per were minute (p
