Background: The etiology of mild traumatic brain injury (mTBI) remains elusive due to the tissue and cellular heterogeneity of the affected brain regions that underlie cognitive impairments and subsequent neurological disorders. This complexity is further exacerbated by disrupted circuits within and between cell populations across brain regions and the periphery, which occur at different timescales and in spatial domains.Methods: We profiled three tissues (hippocampus, frontal cortex, and blood leukocytes) at the acute (24-h) and subacute (7-day) phases of mTBI at single-cell resolution.Results: We demonstrated that the coordinated gene expression patterns across cell types were disrupted and re-organized by TBI at different timescales with distinct regional and cellular patterns. Gene expression-based network modeling implied astrocytes as a key regulator of the cell–cell coordination following mTBI in both hippocampus and frontal cortex across timepoints, andmt-Rnr2, which encodes the mitochondrial peptide humanin, as a potential target for intervention based on its broad regional and dynamic dysregulation following mTBI. Treatment of a murine mTBI model with humanin reversed cognitive impairment caused by mTBI through the restoration of metabolic pathways within astrocytes.Conclusions: Our results offer a systems-level understanding of the dynamic and spatial regulation of gene programs by mTBI and pinpoint key target genes, pathways, and cell circuits that are amenable to therapeutics.

High fructose consumption has been linked to metabolic syndrome, yet the fructose-induced phenotypes, gene expression, and gut microbiota alterations are distinct between mouse strains. In this study, we aim to investigate how fructose consumption shapes the metabolomic profiles of mice with different genetic background and microbiome. We used fructose-sensitive DBA/2J (DBA) and fructose-resistant C57BL/6J (B6) mice given 8% fructose or regular water for 12 weeks. Plasma and fecal metabolites were profiled using a liquid chromatography-tandem mass spectrometry based global metabolomic approach. We found that the baseline metabolomic profiles were different between DBA and B6 mice, particularly plasma metabolites involved in lipid metabolism and fecal metabolites related to dipeptide/amino acid metabolism. In response to fructose, DBA mice showed a distinct decrease of plasma branched chain fatty acids with concordantly increased branched chain amino acids, which were correlated with adiposity; B6 mice had significantly increased plasma cholesterol and total bile acids, accompanied by decreased fecal levels of farnesoid X receptor antagonist tauro-β-muricholate, which were correlated with fructose-responsive bacteria Dehalobacterium, Magibacteriaceae, and/or Akkermansia. Our results demonstrate that baseline metabolomic profiles differ and respond differentially to fructose between mice with different genetic background and gut microbiota, which may play a role in individualized risks to fructose-induced metabolic syndrome.

Background: It is unclear how high fructose consumption induces disparate metabolic responses in genetically diverse mouse strains. Objective: We aim to investigate whether the gut microbiota contributes to differential metabolic responses to fructose. Methods: Eight-week-old male C57BL/6J (B6), DBA/2J (DBA), and FVB/NJ (FVB) mice were given 8% fructose solution or regular water (control) for 12 weeks. The gut microbiota composition in cecum and feces was analyzed using 16S rDNA sequencing, and PERMANOVA was used to compare community across mouse strains, treatments, and time points. Microbiota abundance was correlated with metabolic phenotypes and host gene expression in hypothalamus, liver and adipose tissues using Biweight midcorrelation. To test the causal role of the gut microbiota in determining fructose response, we conducted fecal transplants from B6 to DBA mice and vice versa for 4 weeks, as well as gavaged antibiotic-treated DBA mice with Akkermansia for 9 weeks, accompanied with or without fructose treatment. Results: Compared to B6 and FVB, DBA mice had significantly higher Firmicutes/Bacteroidetes ratio and lower baseline levels of Akkermansia and S24-7 ( P < 0.05), accompanied by metabolic dysregulation after fructose consumption. Fructose altered specific microbial taxa in individual mouse strains, such as a 7.27-fold increase in Akkermansia in B6 and 0.374-fold change in Rikenellaceae in DBA (FDR < 5%), which demonstrated strain-specific correlations with host metabolic and transcriptomic phenotypes. Fecal transplant experiments indicated that B6 microbes conferred resistance to fructose-induced weight gain in DBA mice ( F = 43.1, P < 0.001), and Akkermansia colonization abrogated the fructose-induced weight gain ( F = 17.8, P <0.001) and glycemic dysfunctions ( F = 11.8, P = 0.004) in DBA mice. Conclusions: Our findings support that differential microbiota composition between mouse strains is partially responsible for host metabolic sensitivity to fructose, and that Akkermansia is a key bacterium that confers resistance to fructose-induced metabolic dysregulation.

Background: Obesity is a prevalent, systemic metabolic disease affecting not only various adipose depots but also the liver, where lipid accumulation results in metabolic dysfunction-associated fatty liver disease, dyslipidemia, and insulin resistance. While estradiol (E2) has been known to be hepatoprotective for glucose and lipid metabolism in females, whether E2’s effects on individual liver cell types are shared between sexes or are sex-specific with obesity remains poorly defined. Methods: We performed single-nucleus RNA sequencing on liver tissue of E2-treated obese, gonadectomized male (XY) and female (XX) mice with diet-induced obesity to evaluate the sex-concordant and discordant effects of chronic E2 treatment. Differential gene expression, pathway analysis, intracellular and intercellular regulatory network modeling, and human metabolic disease/trait association analysis were conducted. Results: E2-induced transcriptional effects among hepatocyte subtypes were largely sex-concordant in both males and females, along with sex-specific E2 changes. In pericentral hepatocytes, E2 concordantly reduced the expression of genes involved in insulin resistance, FOXO signaling, and lipid biosynthesis; in periportal hepatocytes, E2 treatment enhanced cholesterol efflux genes and suppressed oxidative stress response genes. XY-specific effects of E2 included additional suppression of lipid and energy metabolic pathways in pericentral hepatocytes and oxidative phosphorylation in periportal hepatocytes, while in XX mice E2 showed unique regulation of glucose and lipid utilization programs. Network analysis revealed that E2-responsive genes in hepatocyte subtypes in both sexes showed enriched transcription factors associated with estrogen receptor signaling and lipid sensing and metabolism, alongside sex-specific regulators. Intercellular signaling affected by E2 showed more changes in XY mice than in XX mice across hepatocyte subtypes. Lastly, while E2-responsive genes in hepatocyte subtypes of both sexes were enriched for human genetic signals associated with lipid profiles and coronary artery disease, we also identified sex-specific associations, such as the link of E2-downregulated genes in XY hepatocytes to body mass index in men. Conclusions: Our findings revealed that chronic E2 administration remodels gene regulatory programs in individual liver cell types through both shared and sex-specific mechanisms, highlighting the importance of considering sex chromosome-dependent E2 responses when developing therapeutic strategies for obesity and associated hepatic metabolic dysfunction.

Genome-wide association studies (GWAS) have implicated ∼380 genetic loci for plasma lipid regulation. However, these loci only explain 17-27% of the trait variance and a comprehensive understanding of the molecular mechanisms has not been achieved. In this study, we utilized an integrative genomics approach leveraging diverse genomic data from human populations to investigate whether genetic variants associated with various plasma lipid traits, namely total cholesterol (TC), high and low density lipoprotein cholesterol (HDL and LDL), and triglycerides (TG), from GWAS were concentrated on specific parts of tissue-specific gene regulatory networks. In addition to the expected lipid metabolism pathways, gene subnetworks involved in ‘interferon signaling’, ‘autoimmune/immune activation’, ‘visual transduction’, and ‘protein catabolism’ were significantly associated with all lipid traits. Additionally, we detected trait-specific subnetworks, including cadherin-associated subnetworks for LDL, glutathione metabolism for HDL, valine, leucine and isoleucine biosynthesis for TC, and insulin signaling and complement pathways for TG. Finally, utilizing gene-gene relations revealed by tissue-specific gene regulatory networks, we detected both known (e.g. APOH, APOA4 , and ABCA1 ) and novel (e.g. F2 in adipose tissue) key regulator genes in these lipid-associated subnetworks. Knockdown of the F2 gene (Coagulation Factor II, Thrombin) in 3T3-L1 and C3H10T1/2 adipocytes reduced gene expression of Abcb11, Apoa5, Apof, Fabp1, Lipc , and Cd36 , reduced intracellular adipocyte lipid content, and increased extracellular lipid content, supporting a link between adipose thrombin and lipid regulation. Our results shed light on the complex mechanisms underlying lipid metabolism and highlight potential novel targets for lipid regulation and lipid-associated diseases.