Metabolic reprogramming in inflammatory microglia indicates a potential way of targeting inflammation in Alzheimer's disease.

Microglia activation drives the pro-inflammatory activity in the early stages of Alzheimer's disease (AD). However, the mechanistic basis is elusive, and the hypothesis of targeting microglia to prevent AD onset is little explored. Here, we demonstrated that upon LPS exposure, microglia shift towards an energetic phenotype characterised by high glycolysis and high mitochondrial respiration with dysfunction. Although the activity of electron transport chain (ETC) complexes is boosted by LPS, this is mostly devoted to the generation of reactive oxygen species. We showed that by inhibiting succinate dehydrogenase (SDH) with dimethyl malonate (DMM), it is possible to modulate the LPS-induced metabolic rewiring, facilitating an anti-inflammatory phenotype. DMM improves mitochondrial function in a direct way and by reducing LPS-induced mitochondrial biogenesis. Moreover, the block of SDH with DMM inhibits the recruitment of hypoxia inducible-factor 1 α (HIF-1α), which mediates the induction of glycolysis and cytokine expression. Similar bioenergetic alterations were observed in the microglia isolated from AD mice (3xTg-AD), which present high levels of circulating LPS and brain toll-like receptor4 (TLR4). Moreover, this well-established model of AD was used to show a potential effect of SDH inhibition in vivo as DMM administration abrogated brain inflammation and modulated the microglia metabolic alterations of 3xTg-AD mice. The RNA-sequencing analysis from a public dataset confirmed the consistent transcription of genes encoding for ETC subunits in the microglia of AD mice (5xFAD). In conclusion, TLR4 activation promotes metabolic changes and the pro-inflammatory activity in microglia, and SDH might represent a promising therapeutic target to prevent AD development.

Eradication of HCV by direct antiviral agents restores mitochondrial function and energy homeostasis in peripheral blood mononuclear cells.

Hepatitis C virus (HCV) adopts several immune evasion mechanisms such as interfering with innate immunity or promoting T-cell exhaustion. However, the recent direct-antiviral agents (DAAs) rapidly eliminate the virus, and the repercussions in terms of immune system balance are unknown. Here we compared the PBMCs transcriptomic profile of patients with HCV chronic infection at baseline (T0) and 12 weeks after the end of the therapy (SVR12) with DAAs. 3862 genes were differently modulated, identifying oxidative phosphorylation as the top canonical pathway differentially activated. Therefore, we dissected PBMCs bioenergetic profile by analyzing mitochondrial respiration and glycolysis at 4 timepoints: T0, 4 weeks of therapy, end of therapy (EoT), and SVR12. Maximal and reserve respiratory capacity considerably increased at EoT, persisting until SVR12. Notably, over time a significant increase was observed in respiratory chain (RC) complexes protein levels and the enzymatic activity of complexes I, II, and IV. Mitochondrial-DNA integrity improved over time, and the expression of mitochondrial biogenesis key regulators such as TFAM, Nrf-1, and PPARGC1A significantly increased at SVR12; hence, RC complexes synthesis and mitochondrial respiration were supported after treatment. HCV clearance with DAAS profoundly changed PBMCs bioenergetic profile, suggesting the immunometabolism study as a new approach to the understanding of viral immune evasion mechanisms and host adaptations during infections and therapies.

Recovery of Bacteroides thetaiotaomicron ameliorates hepatic steatosis in experimental alcohol-related liver disease.

Alcohol-related liver disease (ALD) is a major cause of liver disease and represents a global burden, as treatment options are scarce. Whereas 90% of ethanol abusers develop alcoholic fatty liver disease (AFLD), only a minority evolves to steatohepatitis and cirrhosis. Alcohol increases lipogenesis and suppresses lipid-oxidation implying steatosis, although the key role of intestinal barrier integrity and microbiota in ALD has recently emerged. Bacteroides thetaiotaomicron (Bt) is a prominent member of human and murine intestinal microbiota, and plays important functions in metabolism, gut immunity, and mucosal barrier. We aimed to investigate the role of Bt in the genesis of ethanol-induced liver steatosis. Bt DNA was measured in feces of wild-type mice receiving a Lieber-DeCarli diet supplemented with an increase in alcohol concentration. In a second step, ethanol-fed mice were orally treated with living Bt, followed by analysis of intestinal homeostasis and histological and biochemical alterations in the liver. Alcohol feeding reduced Bt abundance, which was preserved by Bt oral supplementation. Bt-treated mice displayed lower hepatic steatosis and triglyceride content. Bt restored mucosal barrier and reduced LPS translocation by enhancing mucus thickness and production of Mucin2. Furthermore, Bt up-regulated Glucagon-like peptide-1 (GLP-1) expression and restored ethanol-induced Fibroblast growth factor 15 (FGF15) down-regulation. Lipid metabolism was consequently affected as Bt administration reduced fatty acid synthesis (FA) and improved FA oxidation and lipid exportation. Moreover, treatment with Bt preserved the mitochondrial fitness and redox state in alcohol-fed mice. In conclusion, recovery of ethanol-induced Bt depletion by oral supplementation was associated with restored intestinal homeostasis and ameliorated experimental ALD. Bt could serve as a novel probiotic to treat ALD in the future.

Effects of Ultramicronized Palmitoylethanolamide on Mitochondrial Bioenergetics, Cerebral Metabolism, and Glutamatergic Transmission: An Integrated Approach in a Triple Transgenic Mouse Model of Alzheimer's Disease.

The therapeutic potential of ultramicronized palmitoylethanolamide (um-PEA) was investigated in young (6-month-old) and adult (12-month-old) 3 × Tg-AD mice, which received um-PEA for 3 months via a subcutaneous delivery system. Mitochondrial bioenergetics, ATP homeostasis, and magnetic resonance imaging/magnetic resonance spectroscopy were evaluated in the frontal cortex (FC) and hippocampus (HIPP) at the end of um-PEA treatment. Glutamate release was investigated by in vivo microdialysis in the ventral HIPP (vHIPP). We demonstrated that chronic um-PEA treatment ameliorates the decrease in the complex-I respiration rate and the FoF1-ATPase (complex V) activity, as well as ATP content depletion in the cortical mitochondria. Otherwise, the impairment in mitochondrial bioenergetics and the release of glutamate after depolarization was not ameliorated by um-PEA treatment in the HIPP of both young and adult 3 × Tg-AD mice. Moreover, progressive age- and pathology-related changes were observed in the cortical and hippocampal metabolism that closely mimic the alterations observed in the human AD brain; these metabolic alterations were not affected by chronic um-PEA treatment. These findings confirm that the HIPP is the most affected area by AD-like pathology and demonstrate that um-PEA counteracts mitochondrial dysfunctions and helps rescue brain energy metabolism in the FC, but not in the HIPP.

Nuclear factor erythroid 2-related factor 2-mediated signaling and metabolic associated fatty liver disease.

Oxidative stress is a key driver in the development and progression of several diseases, including metabolic associated fatty liver disease (MAFLD). This condition includes a wide spectrum of pathological injuries, extending from simple steatosis to inflammation, fibrosis, cirrhosis, and hepatocellular carcinoma. Excessive buildup of lipids in the liver is strictly related to oxidative stress in MAFLD, progressing to liver fibrosis and cirrhosis. The nuclear factor erythroid 2-related factor 2 (NRF2) is a master regulator of redox homeostasis. NRF2 plays an important role for cellular protection by inducing the expression of genes related to antioxidant, anti-inflammatory, and cytoprotective response. Consistent evidence demonstrates that NRF2 is involved in every step of MAFLD deve-lopment, from simple steatosis to inflammation, advanced fibrosis, and ini-tiation/progression of hepatocellular carcinoma. NRF2 activators regulate lipid metabolism and oxidative stress alleviating the fatty liver disease by inducing the expression of cytoprotective genes. Thus, modulating NRF2 activation is crucial not only in understanding specific mechanisms underlying MAFLD progression but also to characterize effective therapeutic strategies. This review outlined the current knowledge on the effects of NRF2 pathway, modulators, and mechanisms involved in the therapeutic implications of liver steatosis, inflammation, and fibrosis in MAFLD.

A Novel Nutraceuticals Mixture Improves Liver Steatosis by Preventing Oxidative Stress and Mitochondrial Dysfunction in a NAFLD Model.

Non-alcoholic fatty liver disease (NAFLD) is the leading cause of liver disease globally, and represents a health care burden as treatment options are very scarce. The reason behind the NAFLD progression to non-alcoholic steatohepatitis (NASH) is not completely understood. Recently, the deficiency of micronutrients (e.g., vitamins, minerals, and other elements) has been suggested as crucial in NAFLD progression, such that recent studies reported the potential hepatic antioxidant properties of micronutrients supplementation. However, very little is known. Here we have explored the potential beneficial effects of dietary supplementation with FLINAX, a novel mixture of nutraceuticals (i.e., vitamin E, vitamin D3, olive dry-extract, cinnamon dry-extract and fish oil) in a NAFLD model characterized by oxidative stress and mitochondrial function impairment. Steatosis was firstly induced in Wistar rats by feeding with a high-fat/high-cholesterol diet for 4 weeks, and following this the rats were divided into two groups. One group (n = 8) was treated for 2 weeks with a normal chow-diet, while a second group (n = 8) was fed with a chow-diet supplemented with 2% FLINAX. Along with the entire experiment (6 weeks), a third group of rats was fed with a chow-diet only as control. Statistical analysis was performed with Student's T test or one-way ANOVA followed by post-hoc Bonferroni test when appropriate. Steatosis, oxidative stress and mitochondrial respiratory chain (RC) complexes activity were analyzed in liver tissues. The dietary supplementation with FLINAX significantly improved hepatic steatosis and lipid accumulation compared to untreated rats. The mRNA and protein levels analysis showed that CPT1A and CPT2 were up-regulated by FLINAX, suggesting the enhancement of fatty acids oxidation (FAO). Important lipoperoxidation markers (i.e., HNE- and MDA-protein adducts) and the quantity of total mitochondrial oxidized proteins were significantly lower in FLINAX-treated rats. Intriguingly, FLINAX restored the mitochondrial function, stimulating the activity of mitochondrial RC complexes (i.e., I, II, III and ATP-synthase) and counteracting the peroxide production from pyruvate/malate (complex I) and succinate (complex II). Therefore, the supplementation with FLINAX reprogrammed the cellular energy homeostasis by restoring the efficiency of mitochondrial function, with a consequent improvement in steatosis.

Direct-acting antivirals restore systemic redox homeostasis in chronic HCV patients.

Chronic hepatitis C therapy has completely changed in the last years due to the availability of direct-acting antivirals (DAAs). Removing the virus may be not enough since chronic infection deeply modifies immune system and cellular metabolism along decades of inflammation. Oxidative stress plays a significant role in maintaining systemic inflammation during chronic HCV infection. Other than removing the virus, effective therapy could counteract oxidative stress. This study investigated the impact of DAA treatment on circulating markers of oxidative stress and antioxidant defence in a cohort of patients affected by chronic hepatitis C. To this, an observational study on 196 patients who started therapy with DAA for HCV-related hepatitis was performed. Patients were assessed at baseline, 4 weeks after the initiation of therapy (4wks), at the end of treatment (EoT), and 12 weeks after the EoT (SVR12). Circulating oxidative stress was determined by measuring serum hydroxynonenal (HNE)- and malondialdehyde (MDA)-protein adducts, and 8-hydroxydeoxyguanosine (8-OHdG). Antioxidant status was evaluated by measuring the enzymatic activity and mRNA expression of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in peripheral blood mononuclear cells. We observed a reduction of serum 8-OHdG at 4wks, while the circulating level of both HNE- and MDA-protein adducts diminished at EoT; all these markers persisted low at SVR12. On the other side, we reported an increase in the enzymatic activity of all the antioxidant enzymes in PBMC at EoT and SVR12. Taking into account circulating 8-OHdG and antioxidant enzyme activities, patients with high fibrosis stage were those that had the most benefit from DAA therapy. To conclude, this study indicates that treatment with DAAs improves the circulating redox status of patients affected by chronic hepatitis C. This positive impact of DAA therapy may be related to its effectiveness on cutting down viremia and pro-inflammatory markers.