Characteristic, synthesis, and non-photic regulation of endogenous melatonin

Several researchers have confirmed that the melatonin hormone is significant to the body’s circadian rhythm, hence, the need to explore the connection between the two aspects. The circadian rhythm is a natural endogenous process that controls essential body functions as it affects hormone release, body temperature, sleep patterns, and eating habits. In that view, the circadian rhythm relies on melatonin to synchronize the night and day cycles. Melatonin plays a significant role in controlling the circadian rhythm by facilitating quality sleep at night and alertness during the day. In effect, understanding the acute non-image-forming visual effects of melatonin will help derive ways to ensure the circadian rhythms operate efficiently for healthy body functions

Interaction between Melatonin, Sleepiness-Alertness and Body Temperature

Circadian rhythms confer a biological clock of all living beings, comprising oscillations in a range of physiological variables, including body temperature and melatonin, that regulate the sleep/wake cycle rhythmically. Both variables have been marked to influence the sleep/wake cycle; even so, the interrelationship among the triad (body temperature, melatonin & sleepiness/alertness) is still unknown. The current literature review is envisioned to examine the contemporary details regarding the interaction between melatonin, body temperature, and sleepiness/alertness. All the included information is procured from the latest review articles, systematic & meta-analytical literature reviews, and original research reports. Findings revealed that melatonin and body temperature collectively contribute to the formation of sleep. An increase in melatonin induces fluctuations in body temperature. Both physiologic variables serve as close indicators of sleepiness/alertness. However, modulating factors such as light, environmental temperature, and timing of melatonin administration (with the circadian clock) may impact the overall outcomes. A significant number of studies are required to infer the underlying processes by which these factors influence the circadian clock

The effects of light at night and/or melatonin on hormones, metabo- lites, appetite control, vascular function, and behavioural responses.

Light at night (LAN) is a major factor in disruption of SCN function, including melatonin suppression. Melatonin has been linked to a variety of biological processes such as lipid and glucose metabolism, vascular parameters, appetite, and behaviour. However, few human studies have investigated the effect of LAN and suppressed melatonin prior to and after an evening meal. The current thesis aims to investigate the impact of light at night and/or mela- tonin on hormones, metabolites, appetite, vascular function, and behaviour prior to and after an evening test meal in healthy participants. The first study investigated the effect of dim or bright light conditions on hor- mones, metabolites, appetite, vascular function and behavioural responses. Glucose tolerance and insulin sensitivity were reduced, lipid profiles altered and salivary melatonin suppressed under bright light compared to dim light conditions. Subjec- tive mood was improved and appetite scores increased in bright light. No differences were seen in vascular parameters. Although clear differences were apparent it could not be determined whether the effects were due to the light at night, the absence of melatonin or a combination of the two. The second study involved three conditions with the administration of exogenous melatonin 90 mins before the evening test meal under bright and dim light conditions compared to bright light alone with the consequent melatonin suppression. Glucose tolerance and insulin sensitivity were reduced and lipid profile altered in bright light when melatonin was suppressed compared to the two conditions with exogenous melatonin. Mood was improved and appetite increased with lower leptin levels and elevated wrist temperature with bright light and suppressed melatonin. Statistical analysis showed that the major effects were due to melatonin. These studies demonstrate a possible role for melatonin in glucose tolerance, insulin sensitivity and lipid metabolism when eating late at night which may have implications for shift-workers

A single night light exposure acutely alters hormonal and metabolic responses in healthy participants

Many animal studies have reported an association between melatonin suppression and the disturbance of metabolic responses; yet, few human studies have investigated bright light effects on metabolic and hormonal responses at night. This study investigated the impact of light on plasma hormones and metabolites prior to, and after, an evening meal in healthy participants. Seventeen healthy participants, 8 females (22.2 ± 2.59 years, mean ± s.d.) and 9 males (22.8 ± 3.5 years) were randomised to a two-way cross-over design protocol; dim light (DL) (500 lux) sessions, separated by at least seven days. Saliva and plasma samples were collected prior to and after a standard evening meal at specific intervals. Plasma non-esterified fatty acid (NEFA) levels were significantly higher pre-meal in DL compared to BL (P < 0.01). Plasma glucose and insulin levels were significantly greater post-meal in the BL compared to DL session (P = 0.02, P = 0.001), respectively. Salivary melatonin levels were significantly higher in the DL compared to those in BL session (P = 0.005). BL at night was associated with significant increases in plasma glucose and insulin suggestive of glucose intolerance and insulin insensitivity. Raised pre-prandial NEFA levels may be due to changes in insulin sensitivity or the presence of melatonin and/or light at night. Plasma triglyceride (TAG) levels were the same in both sessions. These results may explain some of the health issues reported in shift workers; however, further studies are needed to elucidate the cause of these metabolic changes

A single night light exposure acutely alters hormonal and metabolic responses in healthy participants

Many animal studies have reported an association between melatonin suppression and the disturbance of metabolic responses; yet, few human studies have investigated bright light effects on metabolic and hormonal responses at night. This study investigated the impact of light on plasma hormones and metabolites prior to, and after, an evening meal in healthy participants. Seventeen healthy participants, 8 females (22.2 ± 2.59 years, mean ± s.d.) and 9 males (22.8 ± 3.5 years) were randomised to a two-way cross-over design protocol; dim light (DL) (500 lux) sessions, separated by at least seven days. Saliva and plasma samples were collected prior to and after a standard evening meal at specific intervals. Plasma non-esterified fatty acid (NEFA) levels were significantly higher pre-meal in DL compared to BL (P < 0.01). Plasma glucose and insulin levels were significantly greater post-meal in the BL compared to DL session (P = 0.02, P = 0.001), respectively. Salivary melatonin levels were significantly higher in the DL compared to those in BL session (P = 0.005). BL at night was associated with significant increases in plasma glucose and insulin suggestive of glucose intolerance and insulin insensitivity. Raised pre-prandial NEFA levels may be due to changes in insulin sensitivity or the presence of melatonin and/or light at night. Plasma triglyceride (TAG) levels were the same in both sessions. These results may explain some of the health issues reported in shift workers; however, further studies are needed to elucidate the cause of these metabolic changes

Effects of antidepressants on body weight in patients treated in a naturalistic setting in Oman

Abstract Background The rising use of antidepressants is critical for managing mental health disorders, but weight gain is a concerning side effect, particularly with certain classes like TCAs and SSRIs. This study aims to investigate weight changes in Omani patients prescribed paroxetine, fluoxetine, mirtazapine, or venlafaxine. Method A cross-sectional study conducted from January to June 2023 at Sultan Qaboos University Hospital recruited adults with mental disorders on these medications. Weight measurements were taken at baseline and follow-up, with clinically significant weight gain defined as a ≥ 7% increase. Results A total of 135 participants were analyzed, showing a mean weight gain of 5.54 kg, with 60.7% experiencing significant weight gain. Mirtazapine and paroxetine exhibited the highest average weight increases (7.51 kg and 8.05 kg, respectively) compared to fluoxetine (0.69 kg) and venlafaxine (4.32 kg). No significant demographic factors influenced weight changes (p = 0.213). Conclusion The study highlights significant weight gain among Omani patients on antidepressants, particularly mirtazapine and paroxetine. This underscores the importance of monitoring weight in clinical practice and necessitates further investigations into individualized treatment strategies to manage both mental health and weight-related concerns

Similar effectiveness of the inactivated vaccine BBIBP-CorV (Sinopharm) and the mRNA vaccine BNT162b2 (Pfizer-BioNTech) against COVID-19 related hospitalizations during the Delta outbreak in the UAE

Inactivated vaccine BBIBP-CorV {Sinopharm; 95% [95% confidence interval (CI): 94, 97%]} and the mRNA vaccine BNT162b2 [Pfizer-BioNTech; 98% (95% CI: 86, 99%)] demonstrated protection against COVID-19 related hospitalizations from the Delta (B.1.617.2) variant. Ongoing efforts are necessary to target vaccine hesitancy and to promote booster shots for protection against severe COVID-19 disease and arising variants of concern.</jats:p

A genome-wide association study identifies a possible role for cannabinoid signalling in the pathogenesis of diabetic kidney disease

Diabetic kidney disease (DKD), also known as diabetic nephropathy, is the leading cause of renal impairment and end-stage renal disease. Patients with diabetes are at risk for DKD because of poor control of their blood glucose, as well as nonmodifable risk factors including age, ethnicity, and genetics. This genome-wide association study (GWAS) was conducted for the frst time in the Emirati population to investigate possible genetic factors associated with the development and progression of DKD. We included data on 7,921,925 single nucleotide polymorphism (SNPs) in 258 cases of type 2 diabetes mellitus (T2DM) who developed DKD and 938 control subjects with T2DM who did not develop DKD. GWAS suggestive results (P&lt; 1 × ­10–5) were further replicated using summary statistics from three cohorts with T2DM-induced DKD (Bio Bank Japan data, UK Biobank, and FinnGen Project data) and T1DM-induced DKD (UK-ROI cohort data from Belfast, UK). When conducting a multiple linear regression model for gene-set analyses, the CNR2 gene demonstrated genome-wide signifcance at 1.46 × ­10–6. SNPs in CNR2 gene, encodes cannabinoid receptor 2 or CB2, were replicated in Japanese samples with the leading SNP rs2501391 showing a Pcombined = 9.3 × ­10–7, and odds ratio= 0.67 in association with DKD associated with T2DM, but not with T1DM, without any signifcant association with T2DM itself. The allele frequencies of our cohort and those of the replication cohorts were in most cases markedly diferent. In addition, we replicated the association between rs1564939 in the GLRA3 gene and DKD in T2DM (P= 0.016, odds ratio= 0.54 per allele C). Our fndings suggest evidence that cannabinoid signalling may be involved in the development of DKD through CB2, which is expressed in diferent kidney regions and known to be involved in insulin resistance, infammation, and the development of kidney fbrosis.</sup