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Mytilus coruscus is a dominant shellfish in the Yangtze estuary and its adjacent sea area. Food deprivation often occurs during their growth due to fluctuations in algal abundance caused by seasonal freshwater flushing and high-density aquaculture mode. To investigate the coping strategies of M. coruscus to starvation stress, electron microscopy and differential proteomic analysis were performed on the critical feeding organ gill of the mussels after 9 days of starvation. The electron microscopy results showed that the cilia of the mussel gills were dissolved, and the gaps between gill filaments widened under starvation. Differential proteomic analysis revealed that phagocytosis-related proteins such as ATPeV1E, ATPeV1C, LAMP1_2 and CTSL were significantly upregulated, and the phagocytosis pathway was significantly enriched (p < 0.05). In addition, the corin content in gill and myeloperoxidase level as well as the number of dead cells in blood were both significantly increased (p < 0.05). What’s more, proteomic data suggested that immune maintenance, cellular transport and metabolism related pathways were significantly enriched, which illustrated an immune and metabolism responses under starvation. This study reveals for the first time that phagocytosis functions as an essential strategy for M. coruscus to cope with starvation, which provides new scientific knowledge and a theoretical basis for understanding the adaptation mechanisms of mussel to starvation and for rational optimization of mussel culture patterns.

Being an industrially valuable species of bivalve, Mytilus is widespread in the area around the eastern coast of China. Starvation is an environmental stress that mussels often encounter in their growth. However, few report carried out on the physiological and biochemical response and molecular regulation and adaptation mechanism of mussels under starvation. To illustrate the molecular mechanism of hosts of Mytilus to starvation, the gill transcriptome was used for analysis before and after 9 days of starvation in Mytilus using the Illumina/HiSeq-2000 deep sequencing platform, accompanied by the study of differentially expressed genes (DEGs). In total, 42.137 GB of clean data were obtained from six sample libraries, the average amount of clean data of each sample is 7.023 GB, and 58,540 unigenes that average 780 bp in length were assembled. Unigenes were illustrated by commenting them against the NR, Swiss-Prot, Pfam, String, GO and KEGG databases. After 9 days of starvation, 2,188 and 2,672 genes were determined to be significantly up- or down-regulated expression genes, separately. Amongst, 4,860 genes were associated with 260 pathways, contains vital enrichment pathways, such as “Metabolic”, “PI3K-Akt signaling pathway”, “Phagosome”, “Apoptosis” and “Lysosome”. In inclusion, autophagy cells were investigated by an electron microscopy, alongside further observations of the expression of autophagy-related genes in gill tissue before and after starvation. The data indicates that the amount of autophagosomes increased and found that atg2, atg6 and atg13 were significantly up-regulated. These results indicated that Mytilus may use autophagy to cope with their damage after starvation. With our research results, we have contributed to a deeper understanding of the role of the molecular mechanisms of immune defence in Mytilus under environmental stress, which has given insights into mussel breeding and the understanding of the molecular mechanisms of Mytilus immune system.

Background: The diagnosis, treatment, and prevention of atherosclerosis co-depression are poor, so it is urgent to explore new targets. Based on the “microbiota-gut-brain axis,” this study aimed to investigate the changes of lipid metabolites in the prefrontal cortex and hippocampus regions and the characteristics of the gut microbiota in ApoE−/− mice with atherosclerosis co-depression.Methods: ApoE−/− mice (hyperlipid feeding combined with binding, HFB group, n = 14, male) fed a high-fat diet for 16 weeks with binding stimulation were used as an animal model for atherosclerosis co-depression. The depression degree of mice was evaluated by body weight, sucrose preference test, open field test, and tail suspension test. Oil-red O staining, HE staining, and biochemical parameters were used to evaluate the damage degree of atherosclerosis in mice. LC-MS/MS technique for non-targeted lipidomics analysis was used to analyze the differential lipid metabolites in the prefrontal cortex and hippocampus regions of mice. 16S rDNA amplification sequencing was used to screen the differential gut microbial, and association analysis was performed with the differential lipid metabolites.Results: Compared with the normal control group (NC group), the HFB group showed depression-like behaviors and atherosclerosis-related pathological indicators. The differential lipid metabolites in the prefrontal cortex and hippocampus regions were mainly LPC, LPE, LPS, PC, PE, PS, PI, and GD1a, and were mainly enriched in the glycerophospholipid metabolism pathway and the retrograde endocannabinoid signaling pathway. At the same time, there were significant differences in the structure of the gut microbial community between the two groups. The abundance of Deferribacteres and Proteobacteria in the HFB group increased, while the abundance of Verrucomicrobia and Actinobacteria decreased at the phylum level; the abundance of Desulfovibrio, Clostridium_IV, Helicobacter and Pseudoflavonifractor increased, while the abundance of Akkermansia decreased at the genus level.Conclusion: Atherosclerosis co-depression of ApoE−/− mice of the prefrontal cortex and hippocampus lipid metabolism pathways of disorder and the changes of to the gut microbiota, which leads to abnormal white matter and synaptic dysfunction, increased gut inflammation, and decreased gut permeability, leading to the release of inflammatory cytokines, there is a strong correlation between both, it further confirmed the existence of the “microbiota-gut-brain axis.”