Seasonal variation of vasopressin and its relevance for the winter peak of cardiometabolic disease: A pooled analysis of five cohorts

The neurobiological mechanisms of photoperiod impact on brain functions: a comprehensive review

Variations in day length, or photoperiodism, whether natural or artificial light, significantly impact biological, physiological, and behavioral processes within the brain. Both natural and artificial light sources are environmental factors that significantly influence brain functions and mental well-being. Photoperiodism is a phenomenon, occurring either over a 24 h cycle or seasonally and denotes all biological responses of humans and animals to these fluctuations in day and night length. Conversely, artificial light occurrence refers to the presence of light during nighttime hours and/or its absence during the daytime (unnaturally long and short days, respectively). Light at night, which is a form of light pollution, is prevalent in many societies, especially common in certain emergency occupations. Moreover, individuals with certain mental disorders, such as depression, often exhibit a preference for darkness over daytime light. Nevertheless, disturbances in light patterns can have negative consequences, impacting brain performance through similar mechanisms albeit with varying degrees of severity. Furthermore, changes in day length lead to alterations in the activity of receptors, proteins, ion channels, and molecular signaling pathways, all of which can impact brain health. This review aims to summarize the mechanisms by which day length influences brain functions through neural circuits, hormonal systems, neurochemical processes, cellular activity, and even molecular signaling pathways.

Variability of urinary albumin to creatinine ratio and eGFR are independently associated with eGFR slope in Japanese with type 2 diabetes: a three-year, single-center, retrospective cohort study

BACKGROUND

To evaluate the seasonal variability of urinary albumin to creatinine ratio (UACR) and eGFR and these effects on three-year eGFR slope in persons with type 2 diabetes (T2D).

METHODS

A total of 1135 persons with T2D were analyzed in this single-center, retrospective cohort study in Japan. The standard deviation (SD) of UACR (SD [UACR]) and SD of eGFR (SD [eGFR]) were calculated for each person's 10-point data during the three years, and a multiple linear regression analysis was performed to evaluate associations with eGFR slope. A sensitivity analysis was performed in a group with no medication changes (n = 801).

RESULTS

UACR exhibited seasonal variability, being higher in winter and lower in spring, early summer, and autumn especially in the UACR ≥ 30 mg/g subgroup, while eGFR showed no seasonal variability. The eGFR slope was significantly associated with SD (eGFR) (regression coefficient -0.170 [95% CI -0.189--0.151]) and SD (UACR) (0.000 [-0.001-0.000]). SGLT-2 inhibitors, baseline eGFR, and baseline systolic blood pressure (SBP) were also significantly associated. These associated factors, except baseline SBP, were still significant in the sensitivity analysis.

CONCLUSIONS

The UACR showed clear seasonal variability. Moreover, SD (UACR) and SD (eGFR) were independently associated with a three-year eGFR slope in persons with T2D.

TRIAL REGISTRATION

This study was not registered for clinical trial registration because it was a retrospective observational study.

Seasonality Affects Fluid Intake Behaviors among Young Adults in Hebei, China

BACKGROUND

Evidence on the association between environmental factors and fluid intake behavior remains limited. The current study aims to explore seasonal variations in fluid intake behaviors among young adults in China.

METHODS

A prospective cohort of 79 healthy young adults (43 males and 36 females) aged 19-21 in Hebei, China, was assessed for fluid intake behaviors for four seasons. For each assessment, the participants' anthropometric measurements were collected. Temperature and humidity on survey days were measured. Participants' total drinking fluid (TDF) was recorded using a self-administrative 7 d, 24 h fluid intake questionnaire. To calculate water from food (WFF), we weighed all foods consumed by participants. Duplicates of consumed food samples were collected to measure the water content via the drying method.

RESULTS

The mean total water intake (TWI) was 2761 ± 881, 2551 ± 845, 2210 ± 551, and 1989 ± 579 for spring, summer, fall, and winter, respectively (F(2.37) = 42.29, p < 0.001). The volume and proportion of TWI from TDF and WFF varied across the four seasons. The volume of WFF in spring (1361 ± 281, F(2.61) = 17.21, p < 0.001) and TDF in summer (1218 ± 502, F(2.62) = 9.36, p < 0.001) was among the highest, while participants' fluid intake behaviors in spring and summer were less distinct than the other pairwise comparisons. A moderate association was found between outdoor temperature and TDF (r = 0.53, p < 0.01). Different general estimating equations suggested that gender, seasonality, outdoor temperature, differences in indoor and outdoor temperature, and mean temperature were independent factors of TDF. An interactive effect was found for gender and temperature, showing that the expected TDF of males may increase more as the temperature climbs.

CONCLUSIONS

Gender, seasonality, and air temperature could significantly affect fluid intake behaviors, including the amount and type of fluid intake. However, the independent effect of BMI and humidity remains unclear.

Therapeutic potential of vasopressin in the treatment of neurological disorders

Vasopressin (VP) is a nonapeptide made of nine amino acids synthesized by the hypothalamus and released by the pituitary gland. VP acts as a neurohormone, neuropeptide and neuromodulator and plays an important role in the regulation of water balance, osmolarity, blood pressure, body temperature, stress response, emotional challenges, etc. Traditionally VP is known to regulate the osmolarity and tonicity. VP and its receptors are widely expressed in the various region of the brain including cortex, hippocampus, basal forebrain, amygdala, etc. VP has been shown to modulate the behavior, stress response, circadian rhythm, cerebral blood flow, learning and memory, etc. The potential role of VP in the regulation of these neurological functions have suggested the therapeutic importance of VP and its analogues in the management of neurological disorders. Further, different VP analogues have been developed across the world with different pharmacotherapeutic potential. In the present work authors highlighted the therapeutic potential of VP and its analogues in the treatment and management of various neurological disorders.

Short-term association between outdoor temperature and the hydration-marker copeptin: a pooled analysis in five cohorts

BACKGROUND

Whereas outdoor temperature is linked to both mortality and hydration status, the hormone vasopressin, measured through the surrogate copeptin, is a marker of cardiometabolic risk and hydration. We recently showed that copeptin has a seasonal pattern with higher plasma concentration in winter. Here, we aimed to investigate the association between outdoor temperature and copeptin.

METHODS

Copeptin was analysed in fasting plasma from five cohorts in Malmö, Sweden (n = 26,753, 49.7% men, age 18-86 years). We utilized a multivariable adjusted non-linear spline model with four knots to investigate the association between short-term temperature (24 h mean apparent) and log copeptin z-score.

FINDINGS

We found a distinct non-linear association between temperature and log copeptin z-score, with both moderately low and high temperatures linked to higher copeptin concentration (p < 0.0001). Between 0 °C and nadir at the 75th temperature percentile (corresponding to 14.3 °C), log copeptin decreased 0.13 z-scores (95% CI 0.096; 0.16), which also inversely corresponded to the increase in z-score log copeptin between the nadir and 21.3 °C.

INTERPRETATION

The J-shaped association between short-term temperature and copeptin resembles the J-shaped association between temperature and mortality. Whereas the untangling of temperature from other seasonal effects on hydration warrants further study, moderately increased water intake constitutes a feasible intervention to lower vasopressin and might mitigate adverse health effects of both moderately cold and hot outdoor temperatures.

FUNDING

Swedish Research Council, Å Wiberg, M Stephen, A Påhlsson, Crafoord and Swedish Heart-Lung Foundations, Swedish Society for Medical Research and Swedish Society of Medicine.