Sensitization of endocrine organs to anterior pituitary hormones by the autonomic nervous system

The role of the autonomic nervous system in polycystic ovary syndrome

This article reviewed the relationship between the autonomic nervous system and the development of polycystic ovary syndrome (PCOS). PCOS is the most common reproductive endocrine disorder among women of reproductive age. Its primary characteristics include persistent anovulation, hyperandrogenism, and polycystic ovarian morphology, often accompanied by disturbances in glucose and lipid metabolism. The body's functions are regulated by the autonomic nervous system, which consists mainly of the sympathetic and parasympathetic nervous systems. The autonomic nervous system helps maintain homeostasis in the body. Research indicates that ovarian function in mammals is under autonomic neural control. The ovaries receive central nervous system information through the ovarian plexus nerves and the superior ovarian nerves. Neurotransmitters mediate neural function, with acetylcholine and norepinephrine being the predominant autonomic neurotransmitters. They influence the secretion of ovarian steroids and follicular development. In animal experiments, estrogen, androgens, and stress-induced rat models have been used to explore the relationship between PCOS and the autonomic nervous system. Results have shown that the activation of the autonomic nervous system contributes to the development of PCOS in rat. In clinical practice, assessments of autonomic nervous system function in PCOS patients have been gradually employed. These assessments include heart rate variability testing, measurement of muscle sympathetic nerve activity, skin sympathetic response testing, and post-exercise heart rate recovery evaluation. PCOS patients exhibit autonomic nervous system dysfunction, characterized by increased sympathetic nervous system activity and decreased vagal nerve activity. Abnormal metabolic indicators in PCOS women can also impact autonomic nervous system activity. Clinical studies have shown that various effective methods for managing PCOS regulate patients' autonomic nervous system activity during the treatment process. This suggests that improving autonomic nervous system activity may be an effective approach in treating PCOS.

Systemic Metabolic Alteration Dependent on the Thyroid-Liver Axis in Early PD

OBJECTIVE

Parkinson's disease (PD) is a common neurodegenerative disease characterized by initial involvement of the olfactory bulb/amygdala or autonomic nerves followed by nigral degeneration. Although autonomic innervation strictly regulates multiorgan systems, including endocrine functions, circulation, and digestion, how dysautonomia in PD affects systemic metabolism has not been identified. In this study, we tried to estimate the pathogenic linkage of PD by nuclear medicine techniques, trans-omic analysis of blood samples, and cultured cell experiments.

METHODS

Thyroid mediastinum ratio of ¹²³ I-metaiodobenzylguanidine (MIBG) scintigraphy was measured in 1,158 patients with PD. Furthermore, serum exosome miRNA transcriptome analysis and plasma metabolome analysis followed by trans-omic analysis were performed in patients with de novo PD and age-matched healthy control persons. Additionally, thyroid hormone was administered to skeletal muscle and liver derived cells to evaluate the effect of hypothyroidism for these organs.

RESULTS

Sympathetic denervation of thyroid correlating with its cardiac denervation was confirmed in 1,158 patients with PD by MIBG scintigraphy. Among patients with drug-naïve PD, comprehensive metabolome analysis revealed decreased levels of thyroxine and insufficient fatty acid β-oxidation, which positively correlate with one another. Likewise, both plasma metabolome data and transcriptome data of circulating exosomal miRNAs, revealed specific enrichment of the peroxisome proliferator-activated receptor (PPARα) axis. Finally, association of thyroid hormone with PPARα-dependent β-oxidation regulation was confirmed by in vitro experiments.

INTERPRETATION

Our findings suggest that interorgan communications between the thyroid and liver are disorganized in the early stage of PD, which would be a sensitive diagnostic biomarker for PD. ANN NEUROL 2023;93:303-316.

Microenvironment for spermatogenesis and sperm maturation

The male reproductive system consists of testes, a series of ducts connecting the testes to the external urethral orifice, accessory sex glands, and the penis. Spermatogonial stem cells differentiate and mature in testes and epididymides, and spermatozoa are ejaculated with exocrine fluids secreted by accessory sex glands. Many studies have clarified the detailed structure and function of the male reproductive system, and have shown that various biologic controls, including genomics, epigenetics, and the neuroendocrine-immune system regulate proliferation, differentiation, and maturation of germ cells. In other words (1) genetic deletion or abnormalities, (2) aberration of DNA methylation and histone modifications, as well as small RNA dysfunction, and (3) neuroendocrine-immune disorders are involved in functional failure of the male reproductive system. In this article, we review these three factors for germ cell microcircumstance, especially focused on the immunoendocrine environment. In particular, the relation between factors protecting germ cells with strong auto-immunogenicity and opposite factors compromising this protection are discussed. Reductions in sperm count, concentration, and semen quality are serious problems in developed countries, although the causes are complex and remain unclear. The accumulation of basic knowledge regarding the structure, function, and regulation of the male reproductive system under various experimental conditions will be important to resolve these problems.

Steroidogenic cell microenvironment and adrenal function in physiological and pathophysiological conditions

The human adrenal cortex is a complex organ which is composed of various cell types including not only steroidogenic cells but also mesenchymal cells, immunocompetent cells and neurons. Intermingling of these diverse cell populations favors cell-to-cell communication processes involving local release of numerous bioactive signals such as biogenic amines, cytokines and neuropeptides. The resulting paracrine interactions play an important role in the regulation of adrenocortical cell functions both in physiological and pathophysiological conditions. Especially, recent evidence indicates that adrenocortical cell microenvironment is involved in the pathogenesis of adrenal disorders associated with corticosteroid excess. The paracrine factors involved in these intraadrenal regulatory mechanisms may thus represent valuable targets for future pharmacological treatments of adrenal diseases.

A study of thyroid profile in patients suffering from the first episode of mania: A cross-sectional study

BACKGROUND

Thyroid function is commonly considered in the assessment of mood disorders. Reports of thyroid dysregulation in patients with mania are associated with several confounding factors. To eliminate confounding factors, studies of first-episode mania are desirable. This study tried to find out any relationship between thyroid disorders and mania.

AIM

The aim of this study is to assess and compare the thyroid profile between first-episode mania and healthy controls and to ascertain the correlation between severity and duration of the manic episode with FT3, FT4, and thyroid-stimulating hormone (TSH) levels.

MATERIALS AND METHODS

This was a cross-sectional study conducted in the psychiatry department of a tertiary care hospital. Forty consecutive drug-naïve patients with first-episode mania, diagnosed according to the International Classification of Disease-10 (study group), were matched with 40 healthy controls (control group). Both the groups were compared on the basis of thyroid profile and thyroid levels were correlated with duration and severity of illness in the study group.

RESULTS

Nearly 7.5% of cases in the study group had hyperthyroidism, whereas 5% had subclinical hyperthyroidism. In contrast, normal controls showed 5% and 10% prevalence of hypothyroidism and subclinical hypothyroidism, respectively. A statistically significant lower level of TSH was observed in the study group (P < 0.001), whereas the mean serum levels of FT3 and FT4 were higher in the study group, but the difference was statistically nonsignificant. No significant correlation of thyroid hormones level with duration and severity of illness was noted.

CONCLUSION

Our findings highlight a higher prevalence of hyperthyroidism in patients with mania and suggest the role of thyroid hormones in mania.

ENDOCRINE DISTURBANCES INDUCED BY LOW-DOSE ORGANOPHOSPHATE EXPOSURE IN MALE WISTAR RATS

BACKGROUND

Organophosphate exposure induces many endocrine effects.

AIM

In this study we observed the effects of acute stress induced by cholinesterase inhibition on the main hormonal axes.

MATERIALS AND METHODS

We included thirteen weanling Wistar rats that were subjected to organophosphate exposure. They were first tested for baseline levels of butyrylcholinesterase, cortisol, free triiodothyronine, thyroxine, thyroid-stimulating hormone and prolactin. Secondly, chlorpyrifos was administered. Next samples were taken to determine the level of all the above-mentioned parameters.

RESULTS

Butyrylcholinesterase was significantly decreased after exposure (p<0.001). Cortisol levels were significantly higher after clorpyrifos administration (358.75±43 vs. 241.2±35 nmoL/L)(p<0.01). Although prolactin had a growing trend (450.25±24.65 vs. 423±43.4 uI/mL), the results were not statistically significant. Both free triiodothyronine and thyroxine were significantly higher after exposure. Surprisingly, thyroid-stimulating hormone level almost doubled after exposure with high statistical significance (p<0.001), suggesting a central stimulation of thyroid axis. Butyrylcholinesterase level was proportional with thyroid-stimulating hormone level (p=0.02) and thyroxine level was inversely correlated to the cortisol level (p=0.01). Acute cholinesterase inhibition may induce high levels of cortisol, free triiodothyronine, thyroxine and thyroid-stimulating hormone. From our knowledge this is the first study dedicated to the assessment of acute changes of hormonal status in weanling animals after low-dose organophosphate exposure.Conclusion. Acute cholinesterase inhibition may cause acute phase hormonal disturbances specific to shocked patients.

A retrospective study of pituitary-thyroid interaction in patients with first-episode of bipolar disorder type I in Mania State

ABSTRACT

Bipolar disorder (BD)-mania is related to the dysfunction of anterior pituitary gland, but the pituitary-thyroid interaction on the acute stage of BD has been controversial. In order to rule out the effects of drugs, we aimed to determine the upstream interaction of first-episode of BD type I in mania state, and tried to find the relationship between thyroid-stimulating-hormone (TSH) and Prolactin (PRL)This study included 70 real-world patients diagnosed with first-episode BD-mania recuited and 70 healthy controls (HC) matched for age and sex from 2016 to 2017 in the same district of Shanghai. We compared the levels of thyroid hormones and prolactin between the two groups, and linear regression and curve estimation were used for the correlation analysis of TSH and PRLThere were differences in triiodothyronine (TT3), total thyroxin (TT4), and free thyroxine (FT4) concentrations between the groups (P's < .05). After being grouped by sex, higher PRL in the male and female BD-mania subgroup were observed compared to each isosexual HC [(P's < .01, Cohen's d = 0.82/1.08, 95%CI (0.33, 1.31)/(0.58, 1.58)]. Higher FT4 in the male BD-mania group was observed compared to the HC males [(P's  < .01, Cohen's d = 0.90, 95%CI (0.41, 1.39)] while the female BD-mania group showed lower TT3 and TT4 compared to the HC females [(P's  < .01, Cohen's d = 0.93/0.88, 95%CI (0.43, 1.42)/(0.39, 1.37)]. In the female BD-mania group, correlation analysis established an inverse relationship between PRL and TSH (r2 = 0.25, F = 11.11, P < .01).The findings demonstrate that sex impacts the concentration of hormones secreted by the anterior pituitary of patients with first-episode BD-mania. The increased PRL may be a putative mechanism that underlies the onset in female patients with a moderate inverse relationship between TSH and PRL. Thyroid hormones and prolactin levels may be developed as potential markers for identifying BD-manic.

Rhythmicity matters: Circadian and ultradian patterns of HPA axis activity

Oscillations are a fundamental feature of neural and endocrine systems. The hypothalamic-pituitary-adrenal (HPA) axis dynamically controls corticosteroid secretion in basal conditions and in response to stress. Across the 24-h day, HPA axis activity oscillates with both an ultradian and circadian rhythm. These rhythms have been shown to be important for regulating metabolism, inflammation, mood, cognition and stress responsiveness. Here we will discuss the neural and endocrine mechanisms driving these rhythms, the physiological importance of these rhythms and health consequences when they are disrupted.

Multimodal Regulation of Circadian Glucocorticoid Rhythm by Central and Adrenal Clocks

Adrenal glucocorticoids (GCs) control a wide range of physiological processes, including metabolism, cardiovascular and pulmonary activities, immune and inflammatory responses, and various brain functions. During stress responses, GCs are secreted through activation of the hypothalamic-pituitary-adrenal axis, whereas circulating GC levels in unstressed states follow a robust circadian oscillation with a peak around the onset of the active period of a day. A recent advance in chronobiological research has revealed that multiple regulatory mechanisms, along with classical neuroendocrine regulation, underlie this GC circadian rhythm. The hierarchically organized circadian system, with a central pacemaker in the suprachiasmatic nucleus of the hypothalamus and local oscillators in peripheral tissues, including the adrenal gland, mediates periodicities in physiological processes in mammals. In this review, we primarily focus on our understanding of the circadian regulation of adrenal GC rhythm, with particular attention to the cooperative actions of the suprachiasmatic nucleus central and adrenal local clocks, and the clinical implications of this rhythm in human diseases.

Cooperative roles of the suprachiasmatic nucleus central clock and the adrenal clock in controlling circadian glucocorticoid rhythm

The mammalian circadian timing system consists of the central clock in the hypothalamic suprachiasmatic nucleus (SCN) and subsidiary peripheral clocks in other tissues. Glucocorticoids (GCs) are adrenal steroid hormones with widespread physiological effects that undergo daily oscillations. We previously demonstrated that the adrenal peripheral clock plays a pivotal role in circadian GC rhythm by driving cyclic GC biosynthesis. Here, we show that the daily rhythm in circulating GC levels is controlled by bimodal actions of central and adrenal clockwork. When mice were subjected to daytime restricted feeding to uncouple central and peripheral rhythms, adrenal GC contents and steroidogenic acute regulatory protein expression peaked around zeitgeber time 00 (ZT00), consistent with shifted adrenal clock gene expression. However, restricted feeding produced two distinct peaks in plasma GC levels: one related to adrenal GC content and the other around ZT12, which required an intact SCN. Light pulse-evoked activation of the SCN increased circulating GC levels in both wild-type and adrenal clock-disrupted mutant mice without marked induction of GC biosynthesis. In conclusion, we demonstrate that adrenal clock-dependent steroidogenesis and a SCN-driven central mechanism regulating GC release cooperate to produce daily circulatory GC rhythm.

Stress-Related and Circadian Secretion and Target Tissue Actions of Glucocorticoids: Impact on Health

Living organisms are highly complex systems that must maintain a dynamic equilibrium or homeostasis that requires energy to be sustained. Stress is a state in which several extrinsic or intrinsic disturbing stimuli, the stressors, threaten, or are perceived as threatening, homeostasis. To achieve homeostasis against the stressors, organisms have developed a highly sophisticated system, the stress system, which provides neuroendocrine adaptive responses, to restore homeostasis. These responses must be appropriate in terms of size and/or duration; otherwise, they may sustain life but be associated with detrimental effects on numerous physiologic functions of the organism, leading to a state of disease-causing disturbed homeostasis or cacostasis. In addition to facing a broad spectrum of external and/or internal stressors, organisms are subject to recurring environmental changes associated with the rotation of the planet around itself and its revolution around the sun. To adjust their homeostasis and to synchronize their activities to day/night cycles, organisms have developed an evolutionarily conserved biologic system, the "clock" system, which influences several physiologic functions in a circadian fashion. Accumulating evidence suggests that the stress system is intimately related to the circadian clock system, with dysfunction of the former resulting in dysregulation of the latter and vice versa. In this review, we describe the functional components of the two systems, we discuss their multilevel interactions, and we present how excessive or prolonged activity of the stress system affects the circadian rhythm of glucocorticoid secretion and target tissue effects.

Circadian Clocks, Stress, and Immunity

In mammals, molecular circadian clocks are present in most cells of the body, and this circadian network plays an important role in synchronizing physiological processes and behaviors to the appropriate time of day. The hypothalamic-pituitary-adrenal endocrine axis regulates the response to acute and chronic stress, acting through its final effectors - glucocorticoids - released from the adrenal cortex. Glucocorticoid secretion, characterized by its circadian rhythm, has an important role in synchronizing peripheral clocks and rhythms downstream of the master circadian pacemaker in the suprachiasmatic nucleus. Finally, glucocorticoids are powerfully anti-inflammatory, and recent work has implicated the circadian clock in various aspects and cells of the immune system, suggesting a tight interplay of stress and circadian systems in the regulation of immunity. This mini-review summarizes our current understanding of the role of the circadian clock network in both the HPA axis and the immune system, and discusses their interactions.

Circadian Clocks and the Interaction between Stress Axis and Adipose Function

Many physiological processes and most endocrine functions show fluctuations over the course of the day. These so-called circadian rhythms are governed by an endogenous network of cellular clocks and serve as an adaptation to daily and, thus, predictable changes in the organism's environment. Circadian clocks have been described in several tissues of the stress axis and in adipose cells where they regulate the rhythmic and stimulated release of stress hormones, such as glucocorticoids, and various adipokine factors. Recent work suggests that both adipose and stress axis clock systems reciprocally influence each other and adrenal-adipose rhythms may be key players in the development and therapy of metabolic disorders. In this review, we summarize our current understanding of adrenal and adipose tissue rhythms and clocks and how they might interact to regulate energy homoeostasis and stress responses under physiological conditions. Potential chronotherapeutic strategies for the treatment of metabolic and stress disorders are discussed.

An endocrine hypothesis for the genesis of atrial fibrillation: the hypothalamic-pituitary-adrenal axis response to stress and glycogen accumulation in atrial tissues

Background:

The underlying role of intracellular glycogen in atrial fibrillation is unknown. Experimental models developed in the goat have shown an increase of intracellular glycogen concentration in atrial myocytes resulting from prolonged pacing induced atrial fibrillation (AF). These observed glycogen molecules are as a result of structural remodeling and are known to replace the intracellular myofibrils causing myolysis in studies done in different animal models. The accumulation of glycogen is progressively and directly related to the duration of pacing-induced AF. Similar responses have been seen in clinically derived atrial tissues.

Aims:

We intend to present an endocrine hypothesis supported by published evidence that stress acting through the hypothalamic-pituitary-adrenal axis (HPA) is a contributing metabolic factor responsible for the increase of glucose levels via the hormone cortisol. This excess glucose is then metabolized by the myocytes during each heart beat and stored as glycogen. A literature search was done, and published evidence supporting stress was shown to be the main factor for the formation of glucose leading to glycogen deposition to in the cardiac myocytes.

Results:

Stress on the HPA axis stimulates the adrenal glands to release the hormone cortisol in the blood stream; this in turn increases the cardiac tissue glycogen concentration. It is also known that during each beat, excess glucose is removed by the myocytes and stored as glycogen. As aforementioned, in the cardiac myocytes, dense glycogen content with/without loss of myofibrils has been detected in both human and animal models of AF.

Conclusions:

We hypothesize that the increase of the intrinsic glycogen concentration and distribution is a result of a metabolic disruption caused by stress through the HPA Axis. For example, in atrial myocytes, the glycogen molecules impede the normal intercellular communications leading to areas of slow conduction favoring reentrant-based AF.

Adrenal Clocks and the Role of Adrenal Hormones in the Regulation of Circadian Physiology

The mammalian circadian timing system consists of a master pacemaker in the suprachiasmatic nucleus (SCN) and subordinate clocks that disseminate time information to various central and peripheral tissues. While the function of the SCN in circadian rhythm regulation has been extensively studied, we still have limited understanding of how peripheral tissue clock function contributes to the regulation of physiological processes. The adrenal gland plays a special role in this context as adrenal hormones show strong circadian secretion rhythms affecting downstream physiological processes. At the same time, they have been shown to affect clock gene expression in various other tissues, thus mediating systemic entrainment to external zeitgebers and promoting internal circadian alignment. In this review, we discuss the function of circadian clocks in the adrenal gland, how they are reset by the SCN and may further relay time-of-day information to other tissues. Focusing on glucocorticoids, we conclude by outlining the impact of adrenal rhythm disruption on neuropsychiatric, metabolic, immune, and malignant disorders.

Altered entrainment to the day/night cycle attenuates the daily rise in circulating corticosterone in the mouse

The suprachiasmatic nucleus (SCN) is a circadian oscillator entrained to the day/night cycle via input from the retina. Serotonin (5-HT) afferents to the SCN modulate retinal signals via activation of 5-HT1B receptors, decreasing responsiveness to light. Consequently, 5-HT1B receptor knockout (KO) mice entrain to the day/night cycle with delayed activity onsets. Since circulating corticosterone levels exhibit a robust daily rhythm peaking around activity onset, we asked whether delayed entrainment of activity onsets affects rhythmic corticosterone secretion. Wheel-running activity and plasma corticosterone were monitored in mice housed under several different lighting regimens. Both duration of the light:dark cycle (T cycle) and the duration of light within that cycle was altered. 5-HT1B KO mice that entrained to a 9.5L:13.5D (short day in a T = 23 h) cycle with activity onsets delayed more than 4 h after light offset exhibited a corticosterone rhythm in phase with activity rhythms but reduced 50% in amplitude compared to animals that initiated daily activity <4 h after light offset. Wild type mice in 8L:14D (short day in a T = 22 h) conditions with highly delayed activity onsets also exhibited a 50% reduction in peak plasma corticosterone levels. Exogenous adrenocorticotropin (ACTH) stimulation in animals exhibiting highly delayed entrainment suggested that the endogenous rhythm of adrenal responsiveness to ACTH remained aligned with SCN-driven behavioral activity. Circadian clock gene expression in the adrenal cortex of these same animals suggested that the adrenal circadian clock was also aligned with SCN-driven behavior. Under T cycles <24 h, altered circadian entrainment to short day (winter-like) conditions, manifest as long delays in activity onset after light offset, severely reduces the amplitude of the diurnal rhythm of plasma corticosterone. Such a pronounced reduction in the glucocorticoid rhythm may alter rhythmic gene expression in the central nervous system and in peripheral organs contributing to an array of potential pathophysiologies.