Cross-Species Studies Reveal That Dysregulated Mitochondrial Gene Expression and Electron Transport Complex I Activity Are Crucial for Sarcopenia.

The significance of complex I of the electron transport chain (ETC) in the aging process is widely acknowledged; however, its specific impact on the development of sarcopenia in muscle remains poorly understood. This study elucidated the correlation between complex I inhibition and sarcopenia by conducting a comparative analysis of skeletal muscle gene expression in sarcopenia phenotypes from rats, mice, and humans. Our findings reveal a common mechanistic link across species, particularly highlighting the correlation between the suppression of complex I of ETC activity and dysregulated mitochondrial transcription and translation in sarcopenia phenotypes. Additionally, we observed macrophage dysfunction alongside abnormal metabolic processes within skeletal muscle tissues across all species, implicating their pathogenic role in the onset of sarcopenia. These discoveries underscore the importance of understanding the shared mechanisms associated with complex I of ETC in sarcopenia development. The identified correlations provide valuable insights into potential targets for therapeutic interventions aimed at mitigating the impact of sarcopenia, a condition with substantial implications for aging populations.

Wheat seedlings extract ameliorates sarcopenia in aged mice by regulating protein synthesis and degradation with anti-inflammatory and mitochondrial biogenesis effects.

BACKGROUND: Chronic inflammation, which becomes more prevalent during aging, contributes to sarcopenia by reducing muscle mass and strength. PURPOSE: Wheat seedlings extract (WSE) is known for its various physiological activities, including anti-inflammation and antioxidant effects. However, its efficacy against sarcopenia is not well documented. STUDY DESIGN: 8-week-old and 50-week-old C57BL/6 J mice were used as young control (YC group) and aged controls (AC group), respectively. Then, aged mice were randomly divided into 5 groups (WSE100mg/kg, WSE200mg/kg, WSE400mg/kg, and schizandrin as a positive control) and fed each experimental diet for 10 weeks. METHOD: We investigated the effects of WSE on muscle quality and protein homeostasis pathways based on improvements in mitochondrial function and chronic inflammation. We then used TNFα-treated C2C12 to investigate the effects of isoorientin (ISO) and isoschaftoside (ISS), the active substances of WSE, on the myogenic pathway. RESULTS: We administered WSE to aging mice and observed an increase in muscle mass, thickness, protein content, and strength in mice treated with WSE at a dose of 200 mg/kg or 400 mg/kg. Furthermore, the administration of WSE led to a reduction in inflammatory factors (TNFα, IL-1, and IL-6) and an increase in mitochondrial biogenesis (p-AMPK/SIRT3/PGC1α) in muscle. This effect was also observed in TNFα-induced muscle atrophy in C2C12 cells, and we additionally identified the upregulation of myogenic regulatory factors, including Myf5, Myf6, MyoD, and myogenin, by WSE, ISO, and ISS. CONCLUSION: These findings suggest that WSE could function as a dietary anti-inflammatory factor and mitochondrial activator, potentially exerting modulatory effects on the metabolism and mechanical properties of skeletal muscles in the aging population. Furthermore, Our results demonstrate the potential value of ISO and ISS as functional food ingredients for preventing muscle atrophy.

Animal protein hydrolysate reduces visceral fat and inhibits insulin resistance and hepatic steatosis in aged mice.

BACKGROUND/OBJECTIVES: An increasing life expectancy in society has burdened healthcare systems substantially because of the rising prevalence of age-related metabolic diseases. This study compared the effects of animal protein hydrolysate (APH) and casein on metabolic diseases using aged mice. MATERIALS/METHODS: Eight-week-old and 50-week-old C57BL/6J mice were used as the non-aged (YC group) and aged controls (NC group), respectively. The aged mice were divided randomly into 3 groups (NC, low-APH [LP], and high-APH [HP] and fed each experimental diet for 12 weeks. In the LP and HP groups, casein in the AIN-93G diet was substituted with 16 kcal% and 24 kcal% APH, respectively. The mice were sacrificed when they were 63-week-old, and plasma and hepatic lipid, white adipose tissue weight, hepatic glucose, lipid, and antioxidant enzyme activities, immunohistochemistry staining, and mRNA expression related to the glucose metabolism on liver and muscle were analyzed. RESULTS: Supplementation of APH in aging mice resulted in a significant decrease in visceral fat (epididymal, perirenal, retroperitoneal, and mesenteric fat) compared to the negative control (NC) group. The intraperitoneal glucose tolerance test and area under the curve analysis revealed insulin resistance in the NC group, which was alleviated by APH supplementation. APH supplementation reduced hepatic gluconeogenesis and increased glucose utilization in the liver and muscle. Furthermore, APH supplementation improved hepatic steatosis by reducing the hepatic fatty acid and phosphatidate phosphatase activity while increasing the hepatic carnitine palmitoyltransferase activity. Furthermore, in the APH supplementation groups, the red blood cell (RBC) thiobarbituric acid reactive substances and hepatic H2O2 levels decreased, and the RBC glutathione, hepatic catalase, and glutathione peroxidase activities increased. CONCLUSIONS: APH supplementation reduced visceral fat accumulation and alleviated obesity-related metabolic diseases, including insulin resistance and hepatic steatosis, in aged mice. Therefore, high-quality animal protein APH that reduces the molecular weight and enhances the protein digestibility-corrected amino acid score has potential as a dietary supplement for healthy aging.

The animal protein hydrolysate attenuates sarcopenia via the muscle-gut axis in aged mice.

Age-related muscle loss and dysfunction, sarcopenia, is a common condition that results in poor quality of life in the elderly. Protein supplementation is a potential strategy for preventing sarcopenia and increasing muscle synthesis, but the effectiveness of protein type and level in improving sarcopenia is not well understood. In this study, we compared animal protein hydrolysate (APH), which has a high protein digestibility-corrected amino acid score (PDCAAS) and low molecular weight, with casein as a control group to investigate the effects and mechanisms of sarcopenia improvement, with a particular focus on the gut-muscle axis. APH supplementation improved age-related declines in muscle mass, grip strength, hind leg thickness, muscle protein level, muscle fiber size, and myokine levels, compared to the control group. In particular, levels of plasma cortisol, muscle lipids, and muscle collagen were markedly reduced by APH supplements in the aged mice. Furthermore, APH efficiently recovered the concentration of total SCFAs including acetic, propionic, and isovaleric acids decreased in aged mice. Finally, APH induced changes in gut microbiota and increased production of SCFAs, which were positively correlated with muscle protein level and negatively correlated with pro-inflammatory cytokines. In conclusion, APH can help to inhibit age-related sarcopenia by increasing muscle synthesis, inhibiting muscle breakdown, and potentially modulating the gut-muscle axis.

D-Allulose Ameliorates Dysregulated Macrophage Function and Mitochondrial NADH Homeostasis, Mitigating Obesity-Induced Insulin Resistance.

D-allulose, a rare sugar, has been proposed to have potential benefits in addressing metabolic disorders such as obesity and type 2 diabetes (T2D). However, the precise mechanisms underlying these effects remain poorly understood. We aimed to elucidate the mechanisms by which D-allulose influences obesity-induced insulin resistance. We conducted gene set enrichment analysis on the liver and white adipose tissue of mice exposed to a high-fat diet (HFD) along with the white adipose tissue of individuals with obesity. Our study revealed that D-allulose effectively suppressed IFN-γ, restored chemokine signaling, and enhanced macrophage function in the livers of HFD-fed mice. This implies that D-allulose curtails liver inflammation, alleviating insulin resistance and subsequently impacting adipose tissue. Furthermore, D-allulose supplementation improved mitochondrial NADH homeostasis and translation in both the liver and white adipose tissue of HFD-fed mice. Notably, we observed decreased NADH homeostasis and mitochondrial translation in the omental tissue of insulin-resistant obese subjects compared to their insulin-sensitive counterparts. Taken together, these results suggest that supplementation with allulose improves obesity-induced insulin resistance by mitigating the disruptions in macrophage and mitochondrial function. Furthermore, our data reinforce the crucial role that mitochondrial energy expenditure plays in the development of insulin resistance triggered by obesity.

Chronic inflammation in high-fat diet-fed mice: Unveiling the early pathogenic connection between liver and adipose tissue.

Obesity-induced chronic inflammation has been linked to several autoimmune diseases, including rheumatoid arthritis, type 1 diabetes, and multiple sclerosis. The underlying mechanisms are not yet fully understood, but it is believed that chronic inflammation in adipose tissue can lead to the production of pro-inflammatory cytokines and chemokines, which can trigger immune responses and contribute to the development of autoimmune diseases. However, the underlying mechanisms that lead to the infiltration of immune cells into adipose tissue are not fully understood. In this study, we observed a time-dependent response to a high-fat diet in the liver and epididymal white adipose tissue using gene set enrichment analysis. Our findings revealed a correlation between early abnormal innate immune responses in the liver and late inflammatory response in the adipose tissue, that eventually leads to systemic inflammation. Specifically, our data suggest that the dysregulated NADH homeostasis in the mitochondrial matrix, interacting with the mitochondrial translation process, could serve as a sign marking the transition from liver inflammation to adipose tissue inflammation. Taken together, our study provides valuable insights into the molecular mechanisms underlying the development of chronic inflammation and associated autoimmune diseases in obesity.

Circulating immune cell landscape in patients who had mild ischaemic stroke.

INTRODUCTION: Patients who had a mild ischaemic stroke who present with subtle or resolving symptoms sometimes go undiagnosed, are excluded from treatment and in some cases clinically worsen. Circulating immune cells are potential biomarkers that can assist with diagnosis in ischaemic stroke. Understanding the transcriptomic changes of each cell population caused by ischaemic stroke is critical because they work closely in a complicated relationship. In this study, we investigated peripheral blood mononuclear cells (PBMCs) transcriptomics of patients who had a stroke using a single-cell RNA sequencing to understand peripheral immune response after mild stroke based on the gene expression in an unbiased way. METHODS: Transcriptomes of PBMCsfrom 10 patients who had an acute ischaemic stroke within 24 hours after stroke onset were compared with 9 race-matched/age-matched/gender-matched controls. Individual PBMCs were prepared with ddSeqTM (Illumina-BioRad) and sequenced on the Illumina NovaSeq 6000 platform. RESULTS: Notable population changes were observed in patients who had a stroke, especially in NK cells and CD14+ monocytes. The number of NK cells was increased, which was further confirmed by flow cytometry. Functional analysis implied that the activity of NK cells also is enhanced in patients who had a stroke. CD14+ monocytes were clustered into two groups; dendritic cell-related CD14+ monocytes and NK cell-related CD14+ monocytes. We found CD14+ monocyte subclusters were dramatically reduced in patients who had a stroke. DISCUSSION: This is the first study demonstrating the increased number of NK cells and new monocyte subclusters of mild ischaemic stroke based on the transcriptomic analysis. Our findings provide the dynamics of circulating immune response that could assist diagnosis and potential therapeutic development of mild ischaemic stroke.

Myeloid-Derived Suppressive Cell Expansion Promotes Melanoma Growth and Autoimmunity by Inhibiting CD40/IL27 Regulation in Macrophages.

The relationship between cancer and autoimmunity is complex. However, the incidence of solid tumors such as melanoma has increased significantly among patients with previous or newly diagnosed systemic autoimmune disease (AID). At the same time, immune checkpoint blockade (ICB) therapy of cancer induces de novo autoinflammation and exacerbates underlying AID, even without evident antitumor responses. Recently, systemic lupus erythematosus (SLE) activity was found to drive myeloid-derived suppressor cell (MDSC) formation in patients, a known barrier to healthy immune surveillance and successful cancer immunotherapy. Cross-talk between MDSCs and macrophages generally drives immune suppressive activity in the tumor microenvironment. However, it remains unclear how peripheral pregenerated MDSC under chronic inflammatory conditions modulates global macrophage immune functions and the impact it could have on existing tumors and underlying lupus nephritis. Here we show that pathogenic expansion of SLE-generated MDSCs by melanoma drives global macrophage polarization and simultaneously impacts the severity of lupus nephritis and tumor progression in SLE-prone mice. Molecular and functional data showed that MDSCs interact with autoimmune macrophages and inhibit cell surface expression of CD40 and the production of IL27. Moreover, low CD40/IL27 signaling in tumors correlated with high tumor-associated macrophage infiltration and ICB therapy resistance both in murine and human melanoma exhibiting active IFNγ signatures. These results suggest that preventing global macrophage reprogramming induced by MDSC-mediated inhibition of CD40/IL27 signaling provides a precision melanoma immunotherapy strategy, supporting an original and advantageous approach to treat solid tumors within established autoimmune landscapes. SIGNIFICANCE: Myeloid-derived suppressor cells induce macrophage reprogramming by suppressing CD40/IL27 signaling to drive melanoma progression, simultaneously affecting underlying autoimmune disease and facilitating resistance to immunotherapy within preexisting autoimmune landscapes.

IFNγ is a Key Link between Obesity and Th1-Mediated AutoImmune Diseases.

Obesity, a characteristic of metabolic syndrome, is also associated with chronic inflammation and the development of autoimmune diseases. However, the relationship between obesity and autoimmune diseases remains to be investigated in depth. Here, we compared hepatic gene expression profiles among high-fat diet (HFD) mice using the primary biliary cholangitis (PBC) mouse model based on the chronic expression of interferon gamma (IFNγ) (ARE-Del-/- mice). The top differentially expressed genes affected by upstream transcriptional regulators IFNγ, LPS, and TNFα displayed an overlap in HFD and ARE-Del-/- mice, indicating that obesity-induced liver inflammation may be dependent on signaling via IFNγ. The top pathways altered in HFD mice were mostly involved in the innate immune responses, which overlapped with ARE-Del-/- mice. In contrast, T cell-mediated signaling pathways were exclusively altered in ARE-Del-/- mice. We further evaluated the therapeutic effect of luteolin, known as anti-inflammatory flavonoid, in HFD and ARE-Del-/- mice. Luteolin strongly suppressed the MHC I and II antigen presentation pathways, which were highly activated in both HFD and ARE-Del-/- mice. Conversely, luteolin increased metabolic processes of fatty acid oxidation and oxidative phosphorylation in the liver, which were suppressed in ARE-Del-/- mice. Luteolin also strongly induced PPAR signaling, which was downregulated in HFD and ARE-Del-/- mice. Using human GWAS data, we characterized the genetic interaction between significant obesity-related genes and IFNγ signaling and demonstrated that IFNγ is crucial for obesity-mediated inflammatory responses. Collectively, this study improves our mechanistic understanding of the relationship between obesity and autoimmune diseases. Furthermore, it provides new methodological insights into how immune network-based analyses effectively integrate RNA-seq and microarray data.

Multi-omics: Differential expression of IFN-γ results in distinctive mechanistic features linking chronic inflammation, gut dysbiosis, and autoimmune diseases.

Low grade, chronic inflammation is a critical risk factor for immunologic dysfunction including autoimmune diseases. However, the multiplicity of complex mechanisms and lack of relevant murine models limit our understanding of the precise role of chronic inflammation. To address these hurdles, we took advantage of multi-omics data and a unique murine model with a low but chronic expression of IFN-γ, generated by replacement of the AU-rich element (ARE) in the 3' UTR region of IFN-γ mRNA with random nucleotides. Herein, we demonstrate that low but differential expression of IFN-γ in mice by homozygous or heterozygous ARE replacement triggers distinctive gut microbial alterations, of which alteration is female-biased with autoimmune-associated microbiota. Metabolomics data indicates that gut microbiota-dependent metabolites have more robust sex-differences than microbiome profiling, particularly those involved in fatty acid oxidation and nuclear receptor signaling. More importantly, homozygous ARE-Del mice have dramatic changes in tryptophan metabolism, bile acid and long-chain lipid metabolism, which interact with gut microbiota and nuclear receptor signaling similarly with sex-dependent metabolites. Consistent with these findings, nuclear receptor signaling, encompassing molecules such as PPARs, FXR, and LXRs, was detectable as a top canonical pathway in comparison of blood and tissue-specific gene expression between female homozygous vs heterozygous ARE-Del mice. Further analysis implies that dysregulated autophagy in macrophages is critical for breaking self-tolerance and gut homeostasis, while pathways interact with nuclear receptor signaling to regulate inflammatory responses. Overall, pathway-based integration of multi-omics data provides systemic and cellular insights about how chronic inflammation driven by IFN-γ results in the development of autoimmune diseases with specific etiopathological features.

The interplay of type I and type II interferons in murine autoimmune cholangitis as a basis for sex-biased autoimmunity.

We have reported on a murine model of autoimmune cholangitis, generated by altering the AU-rich element (ARE) by deletion of the interferon gamma (IFN-γ) 3' untranslated region (coined ARE-Del-/- ), that has striking similarities to human primary biliary cholangitis (PBC) with female predominance. Previously, we suggested that the sex bias of autoimmune cholangitis was secondary to intense and sustained type I and II IFN signaling. Based on this thesis, and to define the mechanisms that lead to portal inflammation, we specifically addressed the hypothesis that type I IFNs are the driver of this disease. To accomplish these goals, we crossed ARE-Del-/- mice with IFN type I receptor alpha chain (Ifnar1) knockout mice. We report herein that loss of type I IFN receptor signaling in the double construct of ARE-Del-/- Ifnar1-/- mice dramatically reduces liver pathology and abrogated sex bias. More importantly, female ARE-Del-/- mice have an increased number of germinal center (GC) B cells as well as abnormal follicular formation, sites which have been implicated in loss of tolerance. Deletion of type I IFN signaling in ARE-Del-/- Ifnar1-/- mice corrects these GC abnormalities, including abnormal follicular structure. CONCLUSION: Our data implicate type I IFN signaling as a necessary component of the sex bias of this murine model of autoimmune cholangitis. Importantly these data suggest that drugs that target the type I IFN signaling pathway would have potential benefit in the earlier stages of PBC. (Hepatology 2018;67:1408-1419).

Chronic expression of interferon-gamma leads to murine autoimmune cholangitis with a female predominance.

UNLABELLED: In most autoimmune diseases the serologic hallmarks of disease precede clinical pathology by years. Therefore, the use of animal models in defining early disease events becomes critical. We took advantage of a "designer" mouse with dysregulation of interferon gamma (IFNγ) characterized by prolonged and chronic expression of IFNγ through deletion of the IFNγ 3'-untranslated region adenylate uridylate-rich element (ARE). The ARE-Del(-/-) mice develop primary biliary cholangitis (PBC) with a female predominance that mimics human PBC that is characterized by up-regulation of total bile acids, spontaneous production of anti-mitochondrial antibodies, and portal duct inflammation. Transfer of CD4 T cells from ARE-Del(-/-) to B6/Rag1(-/-) mice induced moderate portal inflammation and parenchymal inflammation, and RNA sequencing of liver gene expression revealed that up-regulated genes potentially define early stages of cholangitis. Interestingly, up-regulated genes specifically overlap with the gene expression signature of biliary epithelial cells in PBC, implying that IFNγ may play a pathogenic role in biliary epithelial cells in the initiation stage of PBC. Moreover, differentially expressed genes in female mice have stronger type 1 and type 2 IFN signaling and lymphocyte-mediated immune responses and thus may drive the female bias of the disease. CONCLUSION: Changes in IFNγ expression are critical for the pathogenesis of PBC. (Hepatology 2016;64:1189-1201).