The major urinary protein gene cluster knockout mouse as a novel model for translational metabolism research

Sappanone A alleviates metabolic dysfunction-associated steatohepatitis by decreasing hepatocyte lipotoxicity via targeting Mup3 in mice

BACKGROUND AND PURPOSE

Metabolic dysfunction-associated steatohepatitis (MASH) is an inflammatory lipotoxic disorder marked by hepatic steatosis, hepatocyte damage, inflammation, and varying stages of fibrosis. Sappanone A (SA), a flavonoid, exhibits anti-inflammatory and hepatoprotection activities. Nevertheless, the effects of SA on MASH remain ambiguous. We evaluated the effects of SA on hepatocyte lipotoxicity, inflammation, and fibrosis conditions in MASH mice, as well as the underlying mechanisms.

METHODS

A conventional murine MASH model fed a methionine-choline-deficient (MCD) diet was utilized to assess the role of SA on MASH in vivo. Drug target prediction and liver transcriptomics were employed to elucidate the potential actions of SA. AML12 cells were applied to further explore the effects and mechanisms of SA in vitro.

RESULTS

The in silico prediction indicated that SA could modulate inflammation, insulin resistance, lipid metabolism, and collagen catabolic process. Treating with SA dose-dependently lessened the elevated levels of serum ALT and AST in mice with diet-triggered MASH, and high-dose SA treatment exhibited a similar effect to silymarin. Additionally, SA treatment significantly reduced lipid deposition, inflammation, and fibrosis subjected to metabolic stress in a dose-dependent manner. Besides, SA mitigated palmitate-triggered lipotoxicity in hepatocytes. Liver transcriptomics further confirmed the aforementioned findings. Of note, mRNA-sequencing analysis and molecular biology experiments demonstrated that SA statistically up-regulated the hepatic expression of major urinary protein 3 (Mup3), thereby facilitating lipid transportation and inhibiting lipotoxicity. Furthermore, Mup3 knockdown in hepatocytes significantly abolished the hepatoprotection provided by SA.

CONCLUSION

SA alleviates MASH by decreasing lipid accumulation and lipotoxicity in hepatocytes, at least partially by targeting Mup3, and subsequently blocks MASH process. Therefore, SA could be a promising hepatoprotective agent in the context of MASH.

Multi-layered metabolic effects of trehalose on the liver proteome in apoE-knockout mice model of liver steatosis

BACKGROUND

Metabolic dysfunction-associated fatty liver disease has been well documented as a key independent risk factor for the development of atherosclerosis. A growing body of evidence suggests that due to its numerous favorable molecular effects, trehalose may exert beneficial effects in counteracting liver steatosis. In our previous study, we described the antiatherosclerotic and antisteatotic properties of trehalose, which we attributed to the induction of autophagy. Considering the pleiotropic activities of trehalose, our present study aimed to extend our preliminary results with the comprehensive examination of proteome-wide changes in the livers of high-fat-fed apoE-/- mice.

METHODS

Thus, we applied modern, next-generation proteomic methodology to comprehensively analyze the effects of trehalose on the alterations of liver proteins in apoE-/- mice.

RESULTS

Our proteomic analysis showed that the administration of trehalose elicited profound changes in the liver proteome of apoE-/- mice. The collected data allowed the identification and quantitation of 3 681 protein groups of which 129 were significantly regulated in the livers of trehalose-treated apoE-/- mice.

CONCLUSIONS

The presented results are the first to highlight the effects of disaccharide on the induction of proteins mainly related to the metabolism and elimination of lipids, especially by peroxisomal β-oxidation. Our study provides evidence for the pleiotropic activity of trehalose, extending our initial observations of its potential mechanisms responsible for mitigating of liver steatosis, which paves the way for new pharmacological strategies in fatty liver disease.

Macrophage activation and inflammatory priming by anti-MAA antibodies in rheumatoid arthritis

We studied the effects of rheumatoid arthritis (RA) autoantibodies that target malondialdehyde-acetaldehyde protein adducts (anti-MAA) on inflammation and macrophage functions. We detected a profound reprogramming of gene expressions and the production of chemokines, such as CCL22 and CCL24, in anti-MAA exposed macrophages. Moreover, anti-MAA pretreatment promoted a more inflammatory cytokine profile upon TLR activation. Although anti-MAA are typically multi-reactive, we observed a prominent clonal diversity in inducing macrophage activation. Anti-MAA antibodies were not arthritogenic in mice, but altered a set of cytokine and growth factor encoding genes in the joints. In individuals at risk of RA anti-MAA IgG levels correlated with circulating inflammatory mediators prior to and at arthritis onset. Certain IgG anti-MAA clones may thus contribute to an inflammatory priming of the joint prior to the onset of systemic inflammation via inducing FcγR-mediated macrophage pre-activation and setting the stage for augmented responses to subsequent inflammatory stimuli.

Diverse genetic alteration dysregulates neuropeptide and intracellular signalling in the suprachiasmatic nuclei

In mammals, intrinsic 24 h or circadian rhythms are primarily generated by the suprachiasmatic nuclei (SCN). Rhythmic daily changes in the transcriptome and proteome of SCN cells are controlled by interlocking transcription-translation feedback loops (TTFLs) of core clock genes and their proteins. SCN cells function as autonomous circadian oscillators, which synchronize through intercellular neuropeptide signalling. Physiological and behavioural rhythms can be severely disrupted by genetic modification of a diverse range of genes and proteins in the SCN. With the advent of next generation sequencing, there is unprecedented information on the molecular profile of the SCN and how it is affected by genetically targeted alteration. However, whether the expression of some genes is more readily affected by genetic alteration of the SCN is unclear. Here, using publicly available datasets from recent RNA-seq assessments of the SCN from genetically altered and control mice, we evaluated whether there are commonalities in transcriptome dysregulation. This was completed for four different phases across the 24 h cycle and was augmented by Gene Ontology Molecular Function (GO:MF) and promoter analysis. Common differentially expressed genes (DEGs) and/or enriched GO:MF terms included signalling molecules, their receptors, and core clock components. Finally, examination of the JASPAR database indicated that E-box and CRE elements in the promoter regions of several commonly dysregulated genes. From this analysis, we identify differential expression of genes coding for molecules involved in SCN intra- and intercellular signalling as a potential cause of abnormal circadian rhythms.

Integrated transcriptome and metabolome study reveal the therapeutic effects of nicotinamide riboside and nicotinamide mononucleotide on nonalcoholic fatty liver disease

Nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) have received considerable attention as anti-aging and anti-metabolic disease nutraceuticals. However, few studies have focused on their role in ameliorating hepatic metabolic disturbances. In the present study, the effects of NMN and NR on the liver of mice with nonalcoholic fatty liver disease (NAFLD) were investigated via transcriptome and metabolome analyses. NMN and NR reduced body weight gain, improved glucose homeostasis, regulated plasma lipid levels, and ameliorated liver injury, oxidative stress, and lipid accumulation in mice with HFD-induced NAFLD. Integrated transcriptome and metabolome analyses indicated that NMN and NR altered the biosynthesis of unsaturated fatty acids, arachidonic acid metabolism, and linoleic acid metabolism pathways, increased saturated fatty acid (palmitic acid, stearate, and arachidic acid) content, and increased polyunsaturated fatty acid (linoleic acid and eicosapentaenoic acid) content. Quantitative reverse transcription PCR (qRT-PCR) showed that NMN and NR primarily promoted arachidonic acid and linoleic acid catabolism via cytochrome P450 (CYP450) enzymes. This study established a theoretical foundation for the potential use of NMN and NR in future clinical settings.

Transplantation of committed pre-adipocytes from brown adipose tissue improves whole-body glucose homeostasis

Obesity and its co-morbidities including type 2 diabetes are increasing at epidemic rates in the U.S. and worldwide. Brown adipose tissue (BAT) is a potential therapeutic to combat obesity and type 2 diabetes. Increasing BAT mass by transplantation improves metabolic health in rodents, but its clinical translation remains a challenge. Here, we investigated if transplantation of 2-4 million differentiated brown pre-adipocytes from mouse BAT stromal fraction (SVF) or human pluripotent stem cells (hPSCs) could improve metabolic health. Transplantation of differentiated brown pre-adipocytes, termed "committed pre-adipocytes" from BAT SVF from mice or derived from hPSCs improves glucose homeostasis and insulin sensitivity in recipient mice under conditions of diet-induced obesity, and this improvement is mediated through the collaborative actions of the liver transcriptome, tissue AKT signaling, and FGF21. These data demonstrate that transplantation of a small number of brown adipocytes has significant long-term translational and therapeutic potential to improve glucose metabolism.

Major urinary protein (Mup) gene family deletion drives sex-specific alterations in the house-mouse gut microbiota

The gut microbiota is shaped by host metabolism. In house mice (Mus musculus), major urinary protein (MUP) pheromone production represents a considerable energy investment, particularly in sexually mature males. Deletion of the Mup gene family shifts mouse metabolism toward an anabolic state, marked by lipogenesis, lipid accumulation, and body mass increases. Given the metabolic implications of MUPs, they may also influence the gut microbiota. Here, we investigated the effect of a deletion of the Mup gene family on the gut microbiota of sexually mature mice. Shotgun metagenomics revealed distinct taxonomic and functional profiles between wild-type and knockout males but not females. Deletion of the Mup gene cluster significantly reduced diversity in microbial families and functions in male mice. Additionally, a species of Ruminococcaceae and several microbial functions, such as transporters involved in vitamin B5 acquisition, were significantly depleted in the microbiota of Mup knockout males. Altogether, these results show that MUPs significantly affect the gut microbiota of house mouse in a sex-specific manner.IMPORTANCEThe community of microorganisms that inhabits the gastrointestinal tract can have profound effects on host phenotypes. The gut microbiota is in turn shaped by host genes, including those involved with host metabolism. In adult male house mice, expression of the major urinary protein (Mup) gene cluster represents a substantial energy investment, and deletion of the Mup gene family leads to fat accumulation and weight gain in males. We show that deleting Mup genes also alters the gut microbiota of male, but not female, mice in terms of both taxonomic and functional compositions. Male mice without Mup genes harbored fewer gut bacterial families and reduced abundance of a species of Ruminococcaceae, a family that has been previously shown to reduce obesity risk. Studying the impact of the Mup gene family on the gut microbiota has the potential to reveal the ways in which these genes affect host phenotypes.

The admixed brushtail possum genome reveals invasion history in New Zealand and novel imprinted genes

Combining genome assembly with population and functional genomics can provide valuable insights to development and evolution, as well as tools for species management. Here, we present a chromosome-level genome assembly of the common brushtail possum (Trichosurus vulpecula), a model marsupial threatened in parts of their native range in Australia, but also a major introduced pest in New Zealand. Functional genomics reveals post-natal activation of chemosensory and metabolic genes, reflecting unique adaptations to altricial birth and delayed weaning, a hallmark of marsupial development. Nuclear and mitochondrial analyses trace New Zealand possums to distinct Australian subspecies, which have subsequently hybridised. This admixture allowed phasing of parental alleles genome-wide, ultimately revealing at least four genes with imprinted, parent-specific expression not yet detected in other species (MLH1, EPM2AIP1, UBP1 and GPX7). We find that reprogramming of possum germline imprints, and the wider epigenome, is similar to eutherian mammals except onset occurs after birth. Together, this work is useful for genetic-based control and conservation of possums, and contributes to understanding of the evolution of novel mammalian epigenetic traits.

Metabolic changes and propensity for inflammation, fibrosis, and cancer in livers of mice lacking lysosomal acid lipase

Lysosomal acid lipase (LAL) is the sole lysosomal enzyme responsible for the degradation of cholesteryl esters and triacylglycerols at acidic pH. Impaired LAL activity leads to LAL deficiency (LAL-D), a severe and fatal disease characterized by ectopic lysosomal lipid accumulation. Reduced LAL activity also contributes to the development and progression of non-alcoholic fatty liver disease (NAFLD). To advance our understanding of LAL-related liver pathologies, we performed comprehensive proteomic profiling of livers from mice with systemic genetic loss of LAL (Lal-/-) and from mice with hepatocyte-specific LAL-D (hepLal-/-). Lal-/- mice exhibited drastic proteome alterations, including dysregulation of multiple proteins related to metabolism, inflammation, liver fibrosis, and cancer. Global loss of LAL activity impaired both acidic and neutral lipase activities and resulted in hepatic lipid accumulation, indicating a complete metabolic shift in Lal-/- livers. Hepatic inflammation and immune cell infiltration were evident, with numerous upregulated inflammation-related gene ontology biological process terms. In contrast, both young and mature hepLal-/- mice displayed only minor changes in the liver proteome, suggesting that loss of LAL solely in hepatocytes does not phenocopy metabolic alterations observed in mice globally lacking LAL. These findings provide valuable insights into the mechanisms underlying liver dysfunction in LAL-D and may help in understanding why decreased LAL activity contributes to NAFLD. Our study highlights the importance of LAL in maintaining liver homeostasis and demonstrates the drastic consequences of its global deficiency on the liver proteome and liver function.

Major urinary protein (Mup) gene family deletion drives sex-specific alterations on the house mouse gut microbiota

The gut microbiota is shaped by host metabolism. In house mice (Mus musculus), major urinary protein (MUP) pheromone production represents a considerable energy investment, particularly in sexually mature males. Deletion of the Mup gene family shifts mouse metabolism towards an anabolic state, marked by lipogenesis, lipid accumulation, and body mass increases. Given the metabolic implications of MUPs, they may also influence the gut microbiota. Here, we investigated the effect of deletion of the Mup gene family on the gut microbiota of sexually mature mice. Shotgun metagenomics revealed distinct taxonomic and functional profiles between wildtype and knockout males, but not females. Deletion of the Mup gene cluster significantly reduced diversity in microbial families and functions in male mice. Additionally, specific taxa of the Ruminococcaceae family, which is associated with gut health and reduced risk of developing metabolic syndrome, and several microbial functions, such as transporters involved in vitamin B5 acquisition, were significantly depleted in the microbiota of Mup-knockout males. Altogether these results show that major urinary proteins significantly affect the gut microbiota of house mouse in a sex-specific manner.