Decreased hepatic contents of coenzyme A molecular species in mice after subchronic mild social defeat stress

Sub-chronic and mild social defeat stress exposure to C57BL/6J mice increases visceral fat mass and causes accumulation of cholesterol and bile acids in the liver

Major depressive disorder is accompanied by a high metabolic illness comorbidity and patients with atypical depression are a subgroup with particularly high risk of obesity, dyslipidemia, and metabolic syndrome; however, the underlying mechanisms have not been fully elucidated. In this study, we examined visceral fat deposition, lipid profiles in the liver, and gut microbiota in sub-chronic and mild social defeat stress (sCSDS)-exposed C57BL/6J mice, which exhibit atypical depression-like phenotypes, i.e., increased body weight and food and water intake. We found that visceral fat mass and levels of hepatic cholesterol and bile acids in sCSDS-exposed mice were significantly increased compared to those in controls. The expression of hepatic small heterodimer partner, a negative regulator of cholesterol metabolism, was significantly elevated in sCSDS-exposed mice. We also found that gut microbial diversity and composition including lower relative abundance of Bacteroides spp. and Bifidobacterium spp. in sCSDS-exposed mice were different from those in controls. In addition, relative abundance of Bacteroides spp. and Bifidobacterium spp. was significantly and negatively correlated with body weight, visceral fat mass, and hepatic cholesterol and bile acids levels. These results indicate that sCSDS-exposure induces dysbiosis, and thereby contributes to metabolic disorder development.

Metabolomic profiles of 38 acylcarnitines in major depressive episodes before and after treatment

BACKGROUND

Major depression is associated with changes in plasma L-carnitine and acetyl-L-carnitine. But its association with acylcarnitines remains unclear. The aim of this study was to assess metabolomic profiles of 38 acylcarnitines in patients with major depression before and after treatment compared to healthy controls (HCs).

METHODS

Metabolomic profiles of 38 plasma short-, medium-, and long-chain acylcarnitines were performed by liquid chromatography-mass spectrometry in 893 HCs from the VARIETE cohort and 460 depressed patients from the METADAP cohort before and after 6 months of antidepressant treatment.

RESULTS

As compared to HCs, depressed patients had lower levels of medium- and long-chain acylcarnitines. After 6 months of treatment, increased levels of medium- and long-chain acyl-carnitines were observed that no longer differed from those of controls. Accordingly, several medium- and long-chain acylcarnitines were negatively correlated with depression severity.

CONCLUSIONS

These medium- and long-chain acylcarnitine dysregulations argue for mitochondrial dysfunction through fatty acid β-oxidation impairment during major depression.

Impacts of Subchronic and Mild Social Defeat Stress on Plasma Putrefactive Metabolites and Cardiovascular Structure in Male Mice

Psychosocial stress precipitates mental illnesses, such as depression, and increases the risk of other health problems, including cardiovascular diseases. In this study, we observed the effects of psychosocial stress on the histopathological features of systemic organs and tissues in a mouse psychosocial stress model, namely the subchronic and mild social defeat stress (sCSDS) model. There were several pathological findings in the tissues of both sCSDS and control mice. Mild fibrosis of the heart was observed in sCSDS mice but not in control mice. Extramedullary hematopoiesis in the spleen and hemorrhage in the lungs were observed in both the control and sCSDS mice. Focal necrosis of the liver was seen only in control mice. Furthermore, putrefactive substances in the blood plasma were analyzed because these metabolites originating from intestinal fermentation might be linked to heart fibrosis. Among them, plasma p-cresyl glucuronide and p-cresyl sulfate concentrations significantly increased owing to subchronic social defeat stress, which might influence cardiac fibrosis in sCSDS mice. In conclusion, several pathological features such as increased cardiac fibrosis and elevated plasma putrefactive substances were found in sCSDS mice. Thus, sCSDS mice are a potential model for elucidating the pathophysiology of psychosocial stress and heart failure.

The return of malonyl-CoA to the brain: Cognition and other stories

Nutrients, hormones and the energy sensor AMP-activated protein kinase (AMPK) tightly regulate the intracellular levels of the metabolic intermediary malonyl-CoA, which is a precursor of fatty acid synthesis and a negative regulator of fatty acid oxidation. In the brain, the involvement of malonyl-CoA in the control of food intake and energy homeostasis has been known for decades. However, recent data uncover a new role in cognition and brain development. The sensing of malonyl-CoA by carnitine palmitoyltransferase 1 (CPT1) proteins regulates a variety of functions, such as the fate of neuronal stem cell precursors, the motility of lysosomes in developing axons, the trafficking of glutamate receptors to the neuron surface (necessary for proper synaptic function) and the metabolic coupling between astrocytes and neurons. We discuss the relevance of those recent findings evidencing how nutrients and metabolic disorders impact cognition. We also enumerate all nutritional and hormonal conditions that are known to regulate malonyl-CoA levels in the brain, reflect on protein malonylation as a new post-translational modification, and give a reasoned vision of the opportunities and challenges that future research in the field could address.

Effects of Diet Quality and Psychosocial Stress on the Metabolic Profiles of Mice

There has been an increasing interest in relationship between stress and diet. To address this relationship, we evaluated an animal model of depression: male C57BL/6J mice subjected to subchronic mild social defeat stress (sCSDS) for 10 consecutive days using male ICR mice under two different calorie-adjusted diets conditions-nonpurified (MF) and semipurified (AIN) diets made from natural and chemical ingredients mainly, respectively. Our previous study indicates that diet quality and purity affect stress susceptibility in sCSDS mice. We therefore hypothesized that there are some key peripheral metabolites to change stress-susceptible behavior. GC-MS metabolomics of plasma, liver, and cecal content were performed on four test groups: sCSDS + AIN diet (n = 7), sCSDS + MF diet (n = 6), control (no sCSDS) + AIN diet (n = 8), and control + MF diet (n = 8). Metabolome analyses revealed that the number of metabolites changed by food was larger than the number changed by stress in all tissues. Enrichment analysis of the liver metabolite set altered by food implies that stress-susceptible mice show increased glycolysis-related substrates in the liver. We found metabolites that were affected by stress (e.g., plasma and liver 4-hydroxyproline and plasma beta-alanine are higher in sCSDS than in control) and a stress × food interaction (e.g., plasma GABA is lower in sCSDS + AIN than in sCSDS + MF). Because functional compounds were altered by both stress and food, diet may be able to attenuate various stress-induced symptoms by changing metabolites in peripheral tissues.

The acute social defeat stress and nest-building test paradigm: A potential new method to screen drugs for depressive-like symptoms

Psychosocial stress can cause mental conditions such as depression in humans. To develop drug therapies for the treatment of depression, it is necessary to use animal models of depression to screen drug candidates that exhibit anti-depressive effects. Unfortunately, the present methods of drug screening for antidepressants, the forced-swim test and tail-suspension test, are limiting factors in drug discovery because they are not based on the constructive validity of objective phenotypes in depression. Previously, we discovered that the onset of nest building is severely delayed in mice exposed to subchronic mild social defeat stress (sCSDS). Therefore, a novel paradigm combining acute social defeat stress (ASDS) and the nest-building test (SNB) were established for the efficient screening of drugs for depressive-like symptoms. Since ASDS severely delayed the nest-building process as shown in chronically social defeated mice, we sought to rescue the delayed nest-building behavior in ASDS mice. Injecting a specific serotonin 2a receptor antagonist (SR-46349B), the nest-building deficit exhibited by ASDS mice was partially rescued. On the other hand, a selective serotonin reuptake inhibitor (fluoxetine) did not rescue the nest-building deficit in ASDS mice. Therefore, we conclude that the SNB paradigm is an another potential behavioral method for screening drugs for depressive-like symptoms including attention deficit, anxiety, low locomotion, and decreased motivation.

Omics Studies of the Murine Intestinal Ecosystem Exposed to Subchronic and Mild Social Defeat Stress

The microbiota-gut-brain axis plays an important role in the development of stress-induced mental disorders. We previously established the subchronic and mild social defeat stress (sCSDS) model, a murine experimental model of depression, and investigated the metabolomic profiles of plasma and liver. Here we used omics approaches to identify stress-induced changes in the gastrointestinal tract. Mice exposed to sCSDS for 10 days showed the following changes: (1) elevation of cholic acid and reduction of 5-aminovaleric acid among cecal metabolites; (2) downregulation of genes involved in the immune response in the terminal ileum; (3) a shift in the diversity of the microbiota in cecal contents and feces; and (4) fluctuations in the concentrations of cecal metabolites produced by gut microbiota reflected in plasma and hepatic metabolites. Operational taxonomic units within the family Lachnospiraceae showed an inverse correlation with certain metabolites. The social interaction score correlated with cecal metabolites, IgA, and cecal and fecal microbiota, suggesting that sCSDS suppressed the ileal immune response, altering the balance of microbiota, which together with host cells and host enzymes resulted in a pattern of accumulated metabolites in the intestinal ecosystem distinct from that of control mice.