Three steroid-binding globulins, their localization in the brain and nose, and what they might be doing there

Association between vitamin D, depression, and sleep health in the National Health and Nutrition Examination Surveys: a mediation analysis

OBJECTIVE

This study aimed to assess the association between vitamin D and sleep health and to investigate whether depression could mediate this relationship.

METHODS

A cross-sectional analysis was performed using the 2005-2014 US National Health and Nutrition Examination Survey (NHANES) data. The logistic regression models were conducted to evaluate association of serum vitamin D concentrations with sleep health and depression. Mediation analyses were conducted to investigate the mediated effects of depression on the association of vitamin D with sleep health.

RESULTS

In multivariate logistic models, vitamin D was found to be negatively associated with an increased risk of poor sleep health, with an odds ratio (OR) of vitamin D deficiency versus sufficiency was 1.256 (95% CI = 1.084-1.455). Additionally, univariate logistic models showed that vitamin D was also negatively associated with depression risk (vitamin D deficiency vs. sufficiency: OR = 1.699, 95% CI = (1.373-2.103). Further mediation analyses showed that the association of vitamin D with sleep health was mediated by depression, with the mediating effects of depression accounted for 44.56% of the total effects.

CONCLUSION

Vitamin D affects sleep health directly and indirectly through depression. The results suggest that interventions increasing intake of vitamin D should be prioritized to promote sleep health of persons with or at risk of depression.

Sex steroid hormone synthesis, metabolism, and the effects on the mammalian olfactory system

Sex steroid hormones influence olfactory-mediated social behaviors, and it is generally hypothesized that these effects result from circulating hormones and/or neurosteroids synthesized in the brain. However, it is unclear whether sex steroid hormones are synthesized in the olfactory epithelium or the olfactory bulb, and if they can modulate the activity of the olfactory sensory neurons. Here, we review important discoveries related to the metabolism of sex steroids in the mouse olfactory epithelium and olfactory bulb, along with potential areas of future research. We summarize current knowledge regarding the expression, neuroanatomical distribution, and biological activity of the steroidogenic enzymes, sex steroid receptors, and proteins that are important to the metabolism of these hormones and reflect on their potential to influence early olfactory processing. We also review evidence related to the effects of sex steroid hormones on the development and activity of olfactory sensory neurons. By better understanding how these hormones are metabolized and how they act both at the periphery and olfactory bulb level, we can better appreciate the complexity of the olfactory system and discover potential similarities and differences in early olfactory processing between sexes.

Effects of vitamin D supplementation on depression and some selected pro-inflammatory biomarkers: a double-blind randomized clinical trial

BACKGROUND

Both augmented inflammatory reaction and low vitamin D status are associated with depression but the magnitude of their relationships is unclear. This study was, therefore, conducted to evaluate the effects of vitamin D supplementation on serum 25(OH)D concentration, depression severity and some pro-inflammatory biomarkers in patients with mild to moderate depression.

METHODS

An 8-week double-blind randomized clinical trial (RCT) was performed on 56 (18-60 yrs) patients with mild to moderate depression, randomly assigned to intervention (50,000 IU cholecalciferol 2wks^-1) and control (placebo) groups. Serum 25(OH)D, intact parathyroid hormone (iPTH), interlukin (IL)-1β, IL-6, high-sensitivity C-reactive protein (hs-CRP) and depression severity (Beck Depression Inventory-II) (BDI-II)) were initially and finally assessed.

RESULTS

At the end point, statistically significant changes were observed only in intervention group as compared with controls including increased 25(OH)D concentration (+ 40.83 ± 28.57 vs. + 5.14 ± 23.44 nmol L^-1, P < 0.001) and decreased depression severity (-11.75 ± 6.40 vs. -3.61 ± 10.40, P = 0.003). No significant within- or between group differences were observed in serum IL-1β, IL-6 and hs-CRP concentrations.

CONCLUSION

Increased circulating 25(OH)D concentrations following 8-week vitamin D supplementation (50,000 IU 2wks^-1) resulted in a significant decrease in BDI-II scores in patients with mild to moderate depression. However, this effect was independent of the serum concentrations of the studied inflammatory biomarkers.

TRIAL REGISTRATION

The clinical trial registration code was obtained from the Iranian Registry of Clinical Trials (date of registration: 17/09/2018, registration number: IRCT20170926036425N1) and ClinicalTrials.gov (date of registration: 04/12/2018, registration number: NCT03766074).

Association between Ultraviolet B Exposure Levels and Depression in Taiwanese Adults: A Nested Case-Control Study

Depression is a common mental disorder that affects more than 264 million people worldwide. Anxiety, diabetes, Alzheimer’s disease, myocardial infarction, and cancer, among other disorders, are known to increase the risk of depression. Exposure to ultraviolet B (UVB) can cause human serotonin levels to increase. The vitamin D pathway is one mechanism through which ultraviolet light absorbed through the skin can affect mood; however, UVB exposure is known to increase the risk of cancer. In this study, we explored the effects of prolonged exposure to UVB on depression. Data were retrieved from the Taiwan National Health Insurance Research Database for 2008 to 2013. Each patient with depression was matched 1:4 with a comparison patient by sex and age (±5 years); thus, the study included 23,579 patients with depression and 94,316 healthy controls for comparison. The patients had been exposed to UVB for at least 1 year to observe the cumulative effect of UVB exposure. Based on the World Health Organization UV index, we divided the observation period data into five UV levels: low, moderate, high, very high, and extreme. A multivariate Poisson regression model was used to assess the risk of depression according to UVB exposure level, adjusting for sex, age, income, urbanization level, month, and comorbidities. The results revealed that the incidence rate ratio (IRR) for patients with depression was 0.889 for moderate levels (95% CI 0.835–0.947), 1.134 for high levels (95% CI: 1.022–1.260), 1.711 for very high levels (95% CI: 1.505–1.945), and 2.785 for extreme levels (95% CI: 2.439–3.180) when compared to low levels. Moderate levels of UVB lowered the risk of depression, while high levels of UVB gradually increased the risk. We propose that UVB at normal concentrations can effectively improve depression. However, exposure to high concentrations of UVB damage DNA results in physical diseases such as skin cancer, which increase the risk of depression.

Are Multiple Chemosensory Systems Accountable for COVID-19 Outcome?

Chemosensory systems (olfaction, taste, trigeminus nerve, solitary chemoreceptor cells, neuroendocrine pulmonary cells, and carotid body, etc.) detect molecules outside or inside our body and may share common molecular markers. In addition to the impairment of taste and olfaction, the detection of the internal chemical environment may also be incapacitated by COVID-19. If this is the case, different consequences can be expected. (1) In some patients, hypoxia does not trigger distressing dyspnea ("silent" hypoxia): Long-term follow-up may determine whether silent hypoxia is related to malfunctioning of carotid body chemoreceptors. Moreover, taste/olfaction and oxygen chemoreceptors may be hit simultaneously: Testing olfaction, taste, and oxygen chemoreceptor functions in the early stages of COVID-19 allows one to unravel their connections and trace the recovery path. (2) Solitary chemosensory cells are also involved in the regulation of the innate mucosal immune response: If these cells are affected in some COVID-19 patients, the mucosal innate immune response would be dysregulated, opening one up to massive infection, thus explaining why COVID-19 has lethal consequences in some patients. Similar to taste and olfaction, oxygen chemosensory function can be easily tested with a non-invasive procedure in humans, while functional tests for solitary chemosensory or pulmonary neuroendocrine cells are not available, and autoptic investigation is required to ascertain their involvement.

The role of rehabilitation and vitamin D supplementation on motor and psychological outcomes in poststroke patients

Post-Stroke depression affects between 12% and 72% of patients who have suffered a stroke. The association between low serum levels of 25-hydroxyvitamin D (25(OH) D) and increased risk of depression is reported in both stroke and non-stroke patients. Similarly, high 25(OH) D levels might be associated with greater functional improvement during rehabilitation program.We wanted to investigate the effects of an intensive rehabilitation on poststroke outcomes. We wondered if the daily rehabilitation of motor and cognitive functions could also have an effect on mood and functional abilities in addition to or as an alternative to vitamin D supplementation.We conducted a 12-week, randomized trial, double blind, parallel, monocentric clinical trial of 40 patients undergoing intensive neuro-rehabilitation treatment at a specialized care facility for ischemic or hemorrhagic brain stroke. Participants were randomly assigned, in a 1:1 ratio, to 1 of 2 parallel groups: in the experimental group, 2000 IU/day of oral cholecalciferol was administered; in the control group patients were not taking vitamin D supplementation. Patients underwent a text evaluation to investigate psychological and motor outcomes.Significant intra-group difference in outcomes measures was found but not between control group and experimental group. In the vitamin D group, we highlighted significant differences between T0 and T1 in calcium (P < .001), vitamin D (P < .001), in Montgomery Aasberg Depression Rating Scale (P = .001), and in Functional Independent Measures (P < .001). In the health control group, we found a significant difference in calcium (P = .003), vitamin D (P < .001), Montgomery Aasberg Depression Rating Scale (P = 0.006), in general self-efficacy (P = .009), and in Functional Independent Measures (P < .001).Our results show that the beneficial effect on mood and functional recovery is mainly due to neurorehabilitation rather than vitamin D supplementation.

Effects of vitamin D supplementation on depression and some involved neurotransmitters

BACKGROUND

Low vitamin D levels are associated with a dysregulated hypothalamic-pituitary-adrenal (HPA) axis and depression but a causal relationship has not been established. This study aimed to evaluate the effects of vitamin D supplementation on depression severity, serum 25(OH)D, and some neurotransmitters in patients with mild to moderate depression.

METHODS

An 8-week double-blind randomized clinical trial was conducted on 56 subjects with mild to moderate depression, aged 43.0 ± 1.15yrs. The patients were randomly allocated into two groups: intervention (50,000 IU cholecalciferol/2wks) and control (placebo). Biochemical parameters (serum 25(OH)D, iPTH, oxytocin and platelet serotonin), and depression severity (Beck Depression Inventory-II (BDI-II¹)) were initially and finally assessed.

RESULTS

Following intervention, significant changes were observed in the intervention group compared to the controls: 25(OH)D concentrations increased (+40.83±28.57 vs. +5.14±23.44 nmol/L, P<0.001) and BDI scores decreased (-11.75±6.40 vs. -3.61±10.40, P = 0.003). Oxytocin concentrations were significantly reduced in controls (-6.49±13.69 ng/mL, P = 0.01), but between -group differences were insignificant. Within- and between-group differences of platelet serotonin concentrations were not significant; however, the increment in controls was higher (+0.86±10.82 vs. +0.26±9.38 ng/mL, P = 0.83).

LIMITATIONS

Study duration may not reflect the long-term effects of vitamin D on depression. It seems necessary to assess tryptophan-hydroxylasetypes1&2 in relation to vitamin D in serotonin pathways.

CONCLUSIONS

Eight-week supplementation with 50,000 IU/2wks vitamin D, elevated 25(OH)D concentration of subjects with mild to moderate depression and significantly improved their depression severity. However, there was no evidence that the anti-depressive effect of vitamin D supplementation is mediated by the measured neurotransmitters.

Diversity of central oxytocinergic projections

Localization and distribution of hypothalamic neurons expressing the nonapeptide oxytocin has been extensively studied. Their projections to the neurohypophyseal system release oxytocin into the systemic circulation thus controlling endocrine events associated with reproduction in males and females. Oxytocinergic neurons seem to be confined to the ventral hypothalamus in all mammals. Groups of such cells located outside the supraoptic and the paraventricular nuclei are summarized as "accessory neurons." Although evolutionary probably associated with the classical magocellular nuclei, accessory oxytocin neurons seem to consist of rather heterogenous groups: Periventricular oxytocin neurons may gain contact to the third ventricle to secrete the peptide into the cerebrospinal fluid. Perivascular neurons may be involved in control of cerebral blood flow. They may also gain access to the portal circulation of the anterior pituitary lobe. Central projections of oxytocinergic neurons extend to portions of the limbic system, to the mesencephalon and to the brain stem. Such projections have been associated with control of behaviors, central stress response as well as motor and vegetative functions. Activity of the different oxytocinergic systems seems to be malleable to functional status, strongly influenced by systemic levels of steroid hormones.

The role of vasopressin in olfactory and visual processing

Neural vasopressin is a potent modulator of behaviour in vertebrates. It acts at both sensory processing regions and within larger regulatory networks to mediate changes in social recognition, affiliation, aggression, communication and other social behaviours. There are multiple populations of vasopressin neurons within the brain, including groups in olfactory and visual processing regions. Some of these vasopressin neurons, such as those in the main and accessory olfactory bulbs, anterior olfactory nucleus, piriform cortex and retina, were recently identified using an enhanced green fluorescent protein-vasopressin (eGFP-VP) transgenic rat. Based on the interconnectivity of vasopressin-producing and sensitive brain areas and in consideration of autocrine, paracrine and neurohormone-like actions associated with somato-dendritic release, we discuss how these different neuronal populations may interact to impact behaviour.