Hyperhomocysteinemia is a result, rather than a cause, of depression under chronic stress.

BACKGROUND: Although the accumulation of homocysteine (Hcy) has been implicated in the pathogenesis of depression, whether Hcy is directly involved and acts as the primary cause of depressive symptoms remains unclear. The present study was designed to clarify whether increased Hcy plays an important role in stress-induced depression. RESULTS: We employed the chronic unpredictable mild stress model (CUMS) of depression for 8 weeks to observe changes in the plasma Hcy level in the development of depression. The results showed that Wistar rats exposed to a series of mild, unpredictable stressors for 4 weeks displayed depression-like symptoms such as anhedonia (decreased sucrose preferences) and a decreased 5-Hydroxy Tryptophan (5-HT) concentration in the hippocampus. At the end of 8 weeks, the plasma Hcy level increased in the CUMS rats. The anti-depressant sertraline could decrease the plasma Hcy level and improve the depression-like symptoms in the CUMS rats. RhBHMT, an Hcy metabolic enzyme, could decrease the plasma Hcy level significantly, although it could not improve the depressive symptoms in the CUMS rats. CONCLUSIONS: The results obtained from the experiments did not support the hypothesis that the increased Hcy concentration mediated the provocation of depression in CUMS rats, and the findings suggested that the increased Hcy concentration in the plasma might be the result of stress-induced depression

A neuroendocrine mechanism of co-morbidity of depression-like behavior and myocardial injury in rats.

Depression is generally a recurrent psychiatric disorder. Evidence shows that depression and cardiovascular diseases are common comorbid conditions, but the specific pathological mechanisms remain unclear. The purpose of this study is to determine the effects of depression induced by chronic unpredictable mild stress (CUMS) on myocardial injury and to further elucidate the biological mechanism of depression. Rats were used as a model. The CUMS procedure lasted for a total of 8 weeks. After 4 weeks of CUMS, treated rats exhibited a reduced sucrose preference and changes in scores on an open field test, body weight and content of 5-HT in the brain as compared with the values of these variables in controls. These changes indicated depression-like changes in CUMS rats and demonstrated the feasibility of the depression model. In addition, pathological changes in the myocardium and increased cardiomyocyte apoptosis demonstrated that myocardial injury had occurred after 6 weeks of CUMS and had increased significantly by the end of 8 weeks of CUMS. Plasma serotonin (5-HT), norepinephrine (NE) and epinephrine (E), all depression-related neuroendocrine factors, were measured by HPLC-ECD techniques, and the content of plasma corticosterone (GC) was evaluated by an I(125)-cortisol radioactivity immunoassay in control and CUMS rats. The results indicated that 5-HT had decreased, whereas NE, E and GC had increased in CUMS rats, and these factors might be associated with depression-induced myocardial injury. The effects of 5-HT, NE and GC on the survival rate of cultured cardiomyocytes were determined using an orthogonal design. The results showed that 5-HT was a more important factor affecting cell survival than GC or NE. The results suggested that normal blood levels of 5-HT had a cytoprotective effect. The neuroendocrine disorders characterized by decreased 5-HT combined with increased GC and NE mediated the occurrence of depression-induced myocardial injury

Puerarin prevents high-fat diet-induced obesity by enriching Akkermansia muciniphila in the gut microbiota of mice.

Growing evidence indicates that the gut microbiota plays a significant role in the pathophysiological processes of obesity and its related metabolic symptoms in the host. Puerarin, an active ingredient in the root of Pueraria lobate has been suggested to have a potent anti-obesity effect. Herein, we tested whether this effect of puerarin is associated with changes in the gut microbiota. In addition to reducing body weight, inflammation, and insulin resistance, puerarin administration significantly altered the composition of the gut microbiota. Notably, puerarin treatment greatly increased the abundance of Akkermansia muciniphila, a mucin-degrading bacterium known to be beneficial for host metabolism and significantly downregulated in high-fat diet-fed mice. Further experiments revealed that puerarin increased intestinal expression levels of Muc2 and Reg3g and protected intestinal barrier function (normal permeability) by increasing the expression of ZO-1 and occludin in vivo and in vitro. These data suggest that puerarin's enriching effect on A. muciniphila is mediated, at least in part, by a host cellular response to protect the host from diet-induced metabolic disorders and other diseases

Sertraline inhibits depression-like behavior and plasma Hcy content in CUMS rats.

<p>Sucrose preference, open field test scores, 5-HT level in the hippocampus and total plasma Hcy were measured as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0106625#pone-0106625-g001" target="_blank">Figure 1</a>. <b>A.</b> Sertraline inhibited the decline of sucrose preference induced by CUMS. <b>B.</b> Sertraline inhibited the decline of the open field test score induced by CUMS. <b>C.</b> Sertraline decreased the immobility time of the forced swimming test induced by CUMS. <b>D.</b> Sertraline inhibited the decline in the 5-HT level in hippocampus induced by CUMS. <b>E.</b> Sertraline inhibited the increase in the plasma Hcy level induced by CUMS. Values represent the group mean ± structural equation modeling (SEM) (n = 8 rats per group). *<i>P</i><0.05, repeated measures ANOVA followed by Tukey's multiple comparison tests.</p

Unpredictable chronic mild stress induces the comorbidities of depression-like behavior and hyperhomocysteinemia in rats.

<p>The depression-like behavior of CUMS rats was measured at 2, 4, 6 and 8 weeks. <b>A.</b> The rats were weighed weekly, and the weights are shown. <b>B.</b> A 2-bottle sucrose preference test was used to measure the rats' preferences for sweetened solution over water. Preference was calculated as the percentage of sucrose solution consumed compared with the total fluid intake: %sucrose preference = (sucrose intake/total fluid intake)×100. <b>C.</b> Exploratory behavior was evaluated as described in the Materials and Methods section. <b>D.</b> The immobility time was detected by manual measurements. <b>E.</b> 5-HT level in the hippocampus was detected using liquid chromatography (Waters E2695). <b>F.</b> The total plasma Hcy values were determined by high-performance liquid chromatography (HPLC) with fluorimetric detection and isocratic elution. Values represent the group mean ± structural equation modeling (SEM) (n = 8 rats per group). *<i>P</i><0.05 compared with control, repeated measures ANOVA followed by Tukey's multiple comparison tests.</p

Effect of methionine on depression-like behavior in CUMS rats.

<p>Body weight, sucrose preference, open field test scores, immobility time of the forced swimming test, 5-HT level in the hippocampus and total plasma Hcy were measured as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0106625#pone-0106625-g001" target="_blank">Figure 1</a>. Methionine had no effect on the body weight, sucrose preference, open field test scores, immobility time of the forced swimming test and 5-HT level in the hippocampus of CUMS rats. Values represent the group mean ± structural equation modeling (SEM) (n = 8 rats per group). *<i>P</i><0.05, repeated measures ANOVA followed by Tukey's multiple comparison tests.</p

5-HT-induced cardiomyocyte injury required the presence GC or NE <i>in vitro</i>.

<p>An MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay was utilized to detect cell viability. 5-HT (10⁻⁵, 10⁻⁶, 10⁻⁷ and 10⁻⁸ M) was used to treat cultured cardiomyocytes with 10⁻⁶ M GC or 10⁻⁶ M NE. <b>A.</b> The cell viability of cardiomyocytes treated with 10⁻⁸ M 5-HT and 10⁻⁶ M GC decreased significantly compared with the control. <b>B.</b> The cell viability of cardiomyocytes treated with 10⁻⁸ M 5-HT and 10⁻⁶ M NE decreased significantly compared with the control. <b>C.</b> The cell viability of cardiomyocytes treated with only 5-HT was not changed significantly compared with the control. <b>D.</b> The apoptosis rate of cardiomyocytes treated with 5-HT and 10⁻⁶ GC increased significantly compared with the control. <b>E.</b> The apoptosis rate of cardiomyocytes treated with 5-HT and 10⁻⁶ NE increased significantly compared with the control. Values represent the group mean ± structural equation modeling (SEM) (n = 8 rats per group). *P<0.05 compared with control, repeated measures ANOVA followed by Tukey’s multiple comparison test.</p

Effect of RhBHMT on depression-like behavior in CUMS rats.

<p>Body weight, sucrose preference, open field test scores, immobility time of the forced swimming test, 5-HT level in the hippocampus and total plasma Hcy were measured as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0106625#pone-0106625-g001" target="_blank">Figure 1</a>. RhBHMT had no effect on the body weight, sucrose preference, open field test scores, immobility time of the forced swimming test and 5-HT level in the hippocampus of the CUMS rats. Values represent the group mean ± structural equation modeling (SEM) (n = 8 rats per group). *<i>P</i><0.05, repeated measures ANOVA followed by Tukey's multiple comparison test.</p

Unpredictable chronic mild stress induces comorbidity of depression-like behavior and myocardial injury in rats.

<p>The depression-like behavior and myocardial injury of CUMS rats were measured at 2, 4, 6 and 8 weeks. <b>A.</b> The rats were weighed weekly, and the weights are shown. <b>B.</b> Locomotor activity and exploratory behavior were evaluated as described in the Materials and Methods section. Values are the mean ± SD from 3 independent experiments, <i>*P<</i>0.05 compared with the control. <b>C.</b> A 2-bottle sucrose preference test was used to measure rats’ preferences for sweetened solution over water. Preference was calculated as the percentage of sucrose solution consumed compared to the total fluid intake (sucrose/(sucrose+water) x 100). <b>D.</b> Myocardial damage was observed by Nagar Olsen staining. The size and scale of the red-stained range represent the severity of the injury. There was no injury in control group rats (a) or in 2 and 4 week CUMS rats (b, c). Myocardial injury occurred after 6 weeks of CUMS (d) and increased after 8 weeks of CUMS (e). <b>E.</b> An electron microscope was used to detect pathological ultrastructural alteration. A myocardial ultrastructure showing normal cardiac nuclear, myofibril structure and mitochondria (×10000) in control group rats is shown (a). Abnormal ultrastructural changes such as myofibril breakage were observed after 8 weeks of CUMS (×10000) (b). Mitochondrial disarrangement, mitochondrial interrupted inner membrane and cristae and mitochondrial vacuoles (×10000) are shown (c, f). Nuclear membrane shrinkage and chromatin margination (×10000) were also seen in 8-week CUMS rats (d, e, f). <b>F.</b> Restraint stress increased cardiomyocyte apoptosis as measured by TUNEL. Values represent the group mean ± structural equation modeling (SEM) (n = 8 rats per group). *<i>P</i><0.05 compared with control, repeated measures ANOVA followed by Tukey’s multiple comparison test.</p