Orally administered whole egg demonstrates antidepressant-like effects in the forced swimming test on rats

Relationship between food group-specific intake and depression among local government employees in Japan

BACKGROUND

We aimed to examine the relationship between food group-specific intake and depression among workers in Japan.

METHODS

A questionnaire survey was administered to 568 workers in 2020; 503 workers responded and 423 were included in the study. Information on sex, age, body mass index, overtime hours, sleep duration, marital status, employment position, exercise habits, smoking status, incidence of depression, and intake of energy, proteins, lipids, carbohydrates, alcohol, and specific food groups were collected. The Center for Epidemiologic Studies Depression Scale was used to assess the presence and severity of depression. Food group-specific intake was adjusted for energy intake using the residual method and classified into low, moderate, and high by sex. Logistic regression was used to examine the odds ratios (ORs) and trends according to sex, with the presence/absence of depression as the dependent variable and food group-specific intake as the independent variable.

RESULTS

Men in the eggs low-intake, and women in the other vegetables low- and moderate-intake and eggs moderate-intake groups had significantly higher adjusted ORs (aORs) for depression. Additionally, a dose-response relationship was observed, where the OR for depression was significantly higher in men when the intake of eggs was low (p for trend = 0.024) and in women when the intakes of other vegetables (p for trend = 0.011) and eggs (p for trend = 0.032) were low.

CONCLUSIONS

The intake of eggs in men and eggs and vegetables in women may be related to depression.

The Greater Impact of Paternal, Compared to Maternal, Hereditary Background on Depressive-Like Behavior in Wistar Kyoto Rats with Different Amino Acid Metabolism in the Pup Brain

In the pathogenesis of depression, heredity is believed to be a major factor. However, the mechanism by which heredity contributes to the onset of depression is not fully understood. Wistar Kyoto (WKY) rats have been used as an animal model for depression because of their increased depression-like behavior compared to Wistar (WIS) rats. In the present study, pups crossbred from WKY × WIS rats were used to evaluate locomotor activity in an open field test (OFT) and depression-like behavior in a forced swimming test (FST), with a focus on amino acid metabolism. Pups in the WKY♂ × WKY♀ group showed lower locomotor activity in the OFT and higher depression-like behavior in the FST than those in the WIS♂ × WIS♀ group. In addition, multiple regression analysis showed that the paternal strain had a greater effect than the maternal strain on locomotor activity and depression-like behavior in OFT and FST, respectively. Several amino acids in the brainstem, hippocampus, and striatum were significantly decreased through the influence of the WKY paternal strain, but not the WKY maternal strain. Based on these data from comparing WKY and WIS rats, we hypothesize that the hereditary effects of the WKY paternal strain on behavioral tests are partially caused by dysregulation of the amino acid metabolism in the brain.

Egg consumption reduces the risk of depressive symptoms in the elderly: findings from a 6-year cohort study

BACKGROUND

Accumulating evidence showed that dietary habits might modify the risk of depression. This study aimed to evaluate the longitudinal association of egg consumption with depressive symptoms in the Chinese elderly.

METHODS

We analyzed the data from Zhejiang Ageing and Health Cohort Study including 8289 participants. The Patient Health Questionnaire-9 scale (PHQ-9) was used to assess depressive symptoms at baseline and three waves of follow-up (2015, 2016, and 2019-2020). A PHQ-9 cut-off score ≥ 5 was used to define depressive symptoms. The participants with depressive symptoms at baseline were excluded. Egg consumption was evaluated through the diet habits section of the baseline questionnaire. Self-reported egg consumption was measured as the number of eggs per week and categorized into three categories. Log-binomial regression models with Generalized Estimating Equations were utilized to evaluate the association of egg consumption with depressive symptoms and estimate relative risks (RRs).

RESULTS

The mean age of included participants was 68.6 years. After 6 years of follow-up, 1385 (16.7%) participants were indicated with depressive symptoms by PHQ-9 at least once. Compared with non-consumers or less-than-weekly consumers, participants consuming < 3 eggs/week and ≥ 3 eggs/week had 30% (RR = 0.70, 95%CI 0.62-0.80) and 38% (RR = 0.62, 95%CI 0.54-0.71) lower risks of depressive symptoms, respectively. A linear association was confirmed (P for trend < 0.01), and each egg increment per week was associated with a 4% lower risk of depressive symptoms (RR = 0.96, 95%CI 0.93-0.99). Sensitivity analyses yielded consistent results to the main analyses.

CONCLUSIONS

Egg consumption is prospectively related to a lower risk of depressive symptoms in the Chinese elderly. More prospective studies are needed to verify the association.

Metabolome and microbiome profiling of a stress-sensitive rat model of gut-brain axis dysfunction

Stress negatively impacts gut and brain health. Individual differences in response to stress have been linked to genetic and environmental factors and more recently, a role for the gut microbiota in the regulation of stress-related changes has been demonstrated. However, the mechanisms by which these factors influence each other are poorly understood, and there are currently no established robust biomarkers of stress susceptibility. To determine the metabolic and microbial signatures underpinning physiological stress responses, we compared stress-sensitive Wistar Kyoto (WKY) rats to the normo-anxious Sprague Dawley (SD) strain. Here we report that acute stress-induced strain-specific changes in brain lipid metabolites were a prominent feature in WKY rats. The relative abundance of Lactococcus correlated with the relative proportions of many brain lipids. In contrast, plasma lipids were significantly elevated in response to stress in SD rats, but not in WKY rats. Supporting these findings, we found that the greatest difference between the SD and WKY microbiomes were the predicted relative abundance of microbial genes involved in lipid and energy metabolism. Our results provide potential insights for developing novel biomarkers of stress vulnerability, some of which appear genotype specific.

Differences in free amino acid concentrations in milk between Wistar and Wistar Kyoto rats

Wistar Kyoto (WKY) rats, an animal depression model, display abnormal behaviors such as hypoactivity and depression-like behavior compared with Wistar (WIS) rats as a control. A previous study confirmed a dysfunction of amino acid metabolism in the brain of WKY rats compared with that of WIS rats. At the neonatal stage, free amino acids in milk are important nutrients because they act as immediate nutrients for offspring and may affect later health and behavior of the offspring. Therefore, the present study aimed to investigate free amino acid concentrations in milk and the relationships between free amino acid concentrations in milk and plasma in WIS and WKY rats. The concentrations of ten of the determined free amino acids in milk were significantly higher, but only L-methionine was significantly lower, in WKY rats. Six free amino acids had significantly higher concentrations in colostrum and two free amino acids had higher concentrations in matured milk. Free amino acid concentrations in plasma changed by both genetic background and lactation stage; however, the patterns of change in most free amino acid concentrations except for taurine in plasma were similar between WIS and WKY rats. The transport ratio of free amino acids from plasma to milk was not similar among the free amino acids tested, and each free amino acid was influenced by the genetic background and/or the type of milk.

Egg consumption and prevalence of psychological disorders in adults

PURPOSE

No previous study has examined the associations between egg consumption and prevalence of psychological disorders. The present study was conducted to determine the association between egg consumption and depression in a large sample of Iranian adults.

METHODS

This cross-sectional study was conducted on 3172 adults in Isfahan, Iran. Egg consumption was assessed by using a validated, self-administered, dish-based, semi-quantitative food frequency questionnaire. The Iranian validated version of Hospital Anxiety and Depression Scale was used to screen for anxiety and depression. The Iranian validated version of General Health Questionnaire with 12 items was used to assess psychological distress. Depression, anxiety and psychological distress were defined according to standard criteria.

RESULTS

The mean age of the study participants was 36.5 ± 7.9 years. Depression, anxiety and psychological distress were prevalent among 28.4, 13.6 and 23% of the study subjects, respectively. After controlling for potential confounders, no significant association was observed between egg intake and depression (OR for comparing extreme quartiles: 1.08; 95% CIs 0.80-1.45) and anxiety (OR 0.79; 95% CIs 0.54-1.16), as well as psychological distress (OR 1.03; 95% CIs 0.76-1.41) in the whole population. In men, significant positive associations were observed between egg intake and depression before controlling for BMI (OR 1.68; 95% CIs 1.01-2.80); however, the associations became non-significant after taking BMI into account (OR 1.62; 95% CIs 0.96-2.72).

CONCLUSIONS

We found no significant association between egg intake and psychological disorders. Further studies, in particular of prospective design, are warranted.

Single and chronic L-serine treatments exert antidepressant-like effects in rats possibly by different means

In the present study, the effects of both single (6 mmol L-serine/10 ml/kg orally administrated) and chronic (2% L-serine solution freely given for 28 days) treatments on depression-like behavior were evaluated in Wistar rats, representing the control, and Wistar Kyoto rats, representing an animal model of depression. Both single and chronic L-serine treatments decreased the duration of immobility, which is an index of a depressive-like state, in the forced swimming test in both strains. However, the decreases in the duration of immobility appear to be regulated differently by the different mechanisms involved in single and chronic L-serine treatments. In the prefrontal cortex and hippocampus, single L-serine treatment increased the concentrations of L-serine, but not D-serine, while chronic L-serine treatment increased those of D-serine, but not L-serine. These data suggest that the antidepressant-like effects of single and chronic L-serine treatments may have been induced by the increased L-serine and D-serine concentrations, respectively, in the brain. In addition, chronic L-serine treatment increased cystathionine concentrations in the hippocampus and prefrontal cortex in Wistar rats, but not in Wistar Kyoto rats, suggesting that Wistar Kyoto rats have an abnormality in the serine-cystathionine metabolic pathway. In conclusion, single and chronic L-serine treatments may induce antidepressant-like effects via the different mechanisms related to serine metabolism in the brain.