CSF hypocretin (Orexin) in neurological and psychiatric conditions

[Neuroendocrine features of the pathogenesis of polycystic ovary syndrome (literature review)]

Polycystic ovary syndrome (PCOS) is one of the most pressing problems in endocrine gynecology. The main signs of the disease are hyperandrogenism, menstrual and/or ovulatory dysfunction, and polycystic ovarian structure according to ultrasound. Women with PCOS are at risk for developing metabolic syndrome, type 2 diabetes, cardiovascular disease, and endometrial cancer. In this connection, the pathogenetic mechanisms of the occurrence of this syndrome are continuously studied and new methods of treatment are being sought. PCOS is characterized by a wide range of various disorders of the neuroendocrine regulation of the reproductive system. The main focus of the review is aimed at summarizing information about the etiological role of neuropeptides and neurotransmitters, such as phoenixin, galanins, orexins, GABA, in the pathophysiology of PCOS and about the possibility of their use for diagnostic and therapeutic purposes. In recent decades, the interest of scientists has been focused on the study of KNDy neurons, because it is the kisspeptin synthesized by them that is one of the main regulators of the hypothalamic-pituitary-ovarian axis. This article discusses data on the significance of KNDy neurons in the pathogenesis of the syndrome. Information is provided on the effect of elevated levels of androgens and anti-Müllerian hormone on GnRH neurons. Also analyzed are studies on functional and structural disorders in the hypothalamus in PCOS. Literature search was carried out in national (eLibrary, CyberLeninka.ru) and international (PubMed, Cochrane Library) databases in Russian and English. The priority was free access to the full text of articles. The choice of sources was prioritized for the period from 2018 to 2023.However, taking into account the insufficient knowledge of the chosen topic, the choice of sources dates back to 1998.

Associations of plasma hypocretin-1 with metabolic and reproductive health: Two systematic reviews of clinical studies

The hypocretin system consists of two peptides hypocretin-1 and hypocretin-2 (HCRT1 and HCRT2). Hypocretin-containing neurons are located in the posterior and lateral hypothalamus, and have widespread projections throughout the brain and spinal cord. In addition to its presence in the cerebrospinal fluid (CSF), peripheral HCRT1 has been detected in plasma. Robust experimental evidence demonstrates functions of hypothalamic-originated HCRT1 in regulation of multiple biological systems related to sleep-wake states, energy homeostasis and endocrine function. In contrast, HCRT1 studies with human participants are limited by the necessarily invasive assessment of CSF HCRT1 to patients with underlying morbidity. Regulation by HCRT1 of energy homeostasis and reproduction in animals suggests similar regulation in humans and prompts these two systematic reviews. These reviews translate prior experimental findings from animal studies to humans and examine associations between HCRT1 and: 1) metabolic risk factors; 2) reproductive function in men, women and children. A total of 21 studies and six studies met the inclusion criteria for the two searches, respectively. Research question, study design, study population, assessments of HCRT1, reproductive, cardiometabolic data and main findings were extracted. Associations between HCRT1, metabolic and reproductive function are inconsistent. Limitations of studies and future research directions are outlined.

Orexin A (hypocretin-1) levels are not reduced while cocaine/amphetamine regulated transcript levels are increased in the cerebrospinal fluid of patients with multiple sclerosis: no correlation with fatigue and sleepiness

BACKGROUND

Fatigue and sleep disturbance are common features of multiple sclerosis (MS). Our objectives were to determine cerebrospinal fluid levels of orexin A (hypocretin-1), a hypothalamic peptide involved in sleep, in patients with MS, and correlate them with fatigue, sleepiness, and levels of cocaine and amphetamine regulated transcript (CART) another neuropeptide regulating metabolism with wider nervous system distribution.

METHODS

Consecutive patients with MS (n=34), other inflammatory (n=24) or non-inflammatory (n=42) neurological diseases, undergoing lumbar puncture were investigated. Orexin and CART were measured by RIA by investigators unaware of the patients' diagnosis.

RESULTS

Orexin A was slightly decreased in the cerebrospinal fluid of patients with inflammatory disease. There was no evidence of orexin A deficiency in MS, although there was a non-significant trend toward a decrease compared to non-inflammatory neurological diseases (p=0.06). CART levels were increased in MS compared to the non-inflammatory disease group (p=0.03). There were no significant correlations between CSF levels of orexin A and CART, fatigue, and hypersomnolence.

CONCLUSIONS

Cerebrospinal fluid orexin A is decreased in CNS inflammatory diseases other than MS, where it shows a trend toward reduction, but does not correlate significantly with CART or with measures of fatigue and hypersomnolence.

Normal hypocretin-1 (orexin-A) levels in the cerebrospinal fluid of patients with Huntington's disease

A significant atrophy and loss of hypocretin neurons in the brains of human patients with Huntington's disease (HD) and in R6/2 mice have been reported. We included 10 patients with HD and 12 patients with chorea-like hyperkinetic movement disorders (non-HD). All patients of the HD group and eleven patients of the non-HD group showed normal hypocretin-1 levels. Thus, hypocretin-1 may not serve as an additional diagnostic marker for HD.

Hypersomnia caused by isolated angiitis of the CNS

A 42-year-old woman presented gradual development of hypersomnia and memory disturbance. T2-weighted and FLAIR MRI scans revealed a high intensity abnormality in the hypothalamus. Stereotactic brain biopsy specimen revealed prominent infiltration of the lymphocytes in the vessel walls. Since there was no evidence of systemic angiitis, the diagnosis of isolated angiitis of the CNS (IAC) was made. Polysomnographic study showed decreased REM sleep and increased stage I sleep. Orexin A in the CSF was decreased. Hypersomnia and a decrease of the CNS orexin A improved after corticosteroid therapy. Hypersomnia can be an initial symptom of IAC if it involves the hypothalamus.