Mitochondrial Oxidative Activity Research Articles

Nucleophosmin 1 promotes mucosal immunity by supporting mitochondrial oxidative phosphorylation and ILC3 activity.

Nucleophosmin 1 (NPM1) is commonly mutated in myelodysplastic syndrome (MDS) and acute myeloid leukemia. Concurrent inflammatory bowel diseases (IBD) and MDS are common, indicating a close relationship between IBD and MDS. Here we examined the function of NPM1 in IBD and colitis-associated colorectal cancer (CAC). NPM1 expression was reduced in patients with IBD. Npm1+/- mice were more susceptible to acute colitis and experimentally induced CAC than littermate controls. Npm1 deficiency impaired the function of interleukin-22 (IL-22)-producing group three innate lymphoid cells (ILC3s). Mice lacking Npm1 in ILC3s exhibited decreased IL-22 production and accelerated development of colitis. NPM1 was important for mitochondrial biogenesis and metabolism by oxidative phosphorylation in ILC3s. Further experiments revealed that NPM1 cooperates with p65 to promote mitochondrial transcription factor A (TFAM) transcription in ILC3s. Overexpression of Npm1 in mice enhanced ILC3 function and reduced the severity of dextran sulfate sodium-induced colitis. Thus, our findings indicate that NPM1 in ILC3s protects against IBD by regulating mitochondrial metabolism through a p65-TFAM axis.

NAD deficiency contributes to progressive kidney disease in HIV nephropathy mice.

HIV disease remains prevalent in the USA and is particularly prevalent in sub-Saharan Africa. Recent investigations revealed that mitochondrial dysfunction in kidney contributes to HIV-associated nephropathy (HIVAN) in Tg26 transgenic mice. We hypothesized that nicotinamide adenine dinucleotide (NAD) deficiency contributes to energetic dysfunction and progressive tubular injury. We investigated metabolomic mechanisms of HIVAN tubulopathy. Tg26 and wild-type (WT) mice were treated with the farnesoid-X receptor (FXR) agonist INT-747 or nicotinamide riboside (NR) from 6 to 12 weeks of age. Multi-omic approaches were used to characterize kidney tissue transcriptomes and metabolomes. Treatment with INT-747 or NR ameliorated kidney tubular injury, as shown by serum creatinine, the tubular injury marker urinary neutrophil-associated lipocalin and tubular morphometry. Integrated analysis of metabolomic and transcriptomic measurements showed that NAD levels and production were globally downregulated in Tg26 mouse kidney, especially nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the NAD salvage pathway. Further, NAD-dependent deacetylase sirtuin3 activity and mitochondrial oxidative phosphorylation activity were lower in ex vivo proximal tubules from Tg26 mouse kidneys compared to those of WT mice. Restoration of NAD levels in kidney improved these abnormalities. These data suggest that NAD deficiency might be a treatable target for HIVAN.

The Influence of Body Fat Dynamics on Pulmonary Immune Responses in Murine Tuberculosis: Unraveling Sex-Specific Insights.

The World Health Organization (WHO) highlights a greater susceptibility of males to tuberculosis (TB), a vulnerability attributed to sex-specific variations in body fat and dietary factors. Our study delves into the unexplored terrain of how alterations in body fat influence Mycobacterium tuberculosis (Mtb) burden, lung pathology, immune responses, and gene expression, with a focus on sex-specific dynamics. Utilizing a low-dose Mtb-HN878 clinical strain infection model, we employ transgenic FAT-ATTAC mice with modulable body fat to explore the impact of fat loss (via fat ablation) and fat gain (via a medium-fat diet, MFD). Firstly, our investigation unveils that Mtb infection triggers severe pulmonary pathology in males, marked by shifts in metabolic signaling involving heightened lipid hydrolysis and proinflammatory signaling driven by IL-6 and localized pro-inflammatory CD8+ cells. This stands in stark contrast to females on a control regular diet (RD). Secondly, our findings indicate that both fat loss and fat gain in males lead to significantly elevated (1.6-fold (p ≤ 0.01) and 1.7-fold (p ≤ 0.001), respectively) Mtb burden in the lungs compared to females during Mtb infection (where fat loss and gain did not alter Mtb load in the lungs). This upsurge is associated with impaired lung lipid metabolism and intensified mitochondrial oxidative phosphorylation-regulated activity in lung CD8+ cells during Mtb infection. Additionally, our research brings to light that females exhibit a more robust systemic IFNγ (p ≤ 0.001) response than males during Mtb infection. This heightened response may either prevent active disease or contribute to latency in females during Mtb infection. In summary, our comprehensive analysis of the interplay between body fat changes and sex bias in Mtb infection reveals that alterations in body fat critically impact pulmonary pathology in males. Specifically, these changes significantly reduce the levels of pulmonary CD8+ T-cells and increase the Mtb burden in the lungs compared to females. The reduction in CD8+ cells in males is linked to an increase in mitochondrial oxidative phosphorylation and a decrease in TNFα, which are essential for CD8+ cell activation.

Activation of innate immunity selectively compromises mitochondrial complex I, proline oxidation, and flight activity in the major arbovirus vector Aedes aegypti.

Aedes aegypti females are natural vectors of important arboviruses such as dengue, zika, and yellow fever. Mosquitoes activate innate immune response signaling pathways upon infection, as a resistance mechanism to fight pathogens and limit their propagation. Despite the beneficial effects of immune activation for insect vectors, phenotypic costs ultimately affect their fitness. However, the underlying mechanisms that mediate these fitness costs remain poorly understood. Given the high energy required to mount a proper immune response, we hypothesized that systemic activation of innate immunity would impair flight muscle mitochondrial function, compromising tissue energy demand and flight activity. Here, we investigated the dynamic effects of activation of innate immunity by intra-thoracic zymosan injection on A. aegypti flight muscle mitochondrial metabolism. Zymosan injection significantly increased defensin A expression in fat bodies in a time-dependent manner that compromised flight activity. Although oxidant levels in flight muscle were hardly altered, ATP-linked respiratory rates driven by mitochondrial pyruvate+proline oxidation were significantly reduced at 24 h upon zymosan injection. Oxidative phosphorylation coupling was preserved regardless of innate immune response activation along 24 h. Importantly, rotenone-sensitive respiration and complex I-III activity were specifically reduced 24 h upon zymosan injection. Also, loss of complex I activity compromised ATP-linked and maximal respiratory rates mediated by mitochondrial proline oxidation. Finally, the magnitude of innate immune response activation negatively correlated with respiratory rates, regardless of the metabolic states. Collectively, we demonstrate that activation of innate immunity is strongly associated with reduced flight muscle complex I activity with direct consequences to mitochondrial proline oxidation and flight activity. Remarkably, our results indicate a trade-off between dispersal and immunity exists in an insect vector, underscoring the potential consequences of disrupted flight muscle mitochondrial energy metabolism to arbovirus transmission.

Effect of Melatonin and Dehydration on Lipid Peroxidation Level and Respiration of Pea Embryos, Growth of Seedlings, and Oxidative Activity of Mitochondria in Epicotyls

Effect of Melatonin and Dehydration on Lipid Peroxidation Level and Respiration of Pea Embryos, Growth of Seedlings, and Oxidative Activity of Mitochondria in Epicotyls

ACOX1-mediated peroxisomal fatty acid oxidation contributes to metabolic reprogramming and survival in chronic lymphocytic leukemia.

Chronic lymphocytic leukemia (CLL) is still an incurable disease, with many patients developing resistance to conventional and targeted therapies. To better understand the physiology of CLL and facilitate the development of innovative treatment options, we examined specific metabolic features in the tumor CLL B-lymphocytes. We observed metabolic reprogramming, characterized by a high level of mitochondrial oxidative phosphorylation activity, a low glycolytic rate, and the presence of C2- to C6-carnitine end-products revealing an unexpected, essential role for peroxisomal fatty acid beta-oxidation (pFAO). Accordingly, downmodulation of ACOX1 (a rate-limiting pFAO enzyme overexpressed in CLL cells) was enough to shift the CLL cells' metabolism from lipids to a carbon- and amino-acid-based phenotype. Complete blockade of ACOX1 resulted in lipid droplet accumulation and caspase-dependent death in CLL cells, including those from individuals with poor cytogenetic and clinical prognostic factors. In a therapeutic translational approach, ACOX1 inhibition spared non-tumor blood cells from CLL patients but led to the death of circulating, BCR-stimulated CLL B-lymphocytes and CLL B-cells receiving pro-survival stromal signals. Furthermore, a combination of ACOX1 and BTK inhibitors had a synergistic killing effect. Overall, our results highlight a less-studied but essential metabolic pathway in CLL and pave the way towards the development of new, metabolism-based treatment options.

Investigation of mitochondrial oxidative phosforylation enzymes in hematological cancers

It is known that cancerous cells are different from normal cells in their structure and functions. It is aimed to determine whether there is a change in the activities of mitochondrial oxidative phosphorylation (OXPOS) respiratory enzymes, the main energy production site of cells, in various haematological cancers and to use the obtained data for therapeutic purposes. In this study, leukocyte mitochondria were isolated from blood samples obtained from patients with non-hodgkin lymphoma (NHL), hodgkin lemphoma (HL), chronic lymphocytic leukaemia (CLL), acute myelogenic leukaemia (AML), acute lymphocytic leukaemia (ALL), chronic myeloid leukaemia (CML), multiple myeloma and myelodysplastic syndrome (MDS) and controls. The enzyme activities of oxidative phosphorylation complexes I, II and IV were measured by spectrophotometric method. Enzyme activity results were statistically evaluated according to various criteria. Enzyme activities were evaluated according to gender, chemotherapy or not and disease groups. As a result of these statistical evaluations, no correlation was found between the type of haematological cancer and gender (p>0.05). The difference in mitochondrial oxidative complex enzyme activities between patients receiving chemotherapy and those not receiving chemotherapy was insignificant (p>0.05). When the enzyme activities of the control group and all haematological cancer cells studied were compared, the difference was found to be statistically significant (p<0.05). As a result, changes in the activities of OXPOS respiratory enzymes were found in various haematological cancers. The large number of therapies that specifically target mitochondria, the altered metabolic functions and dynamics of mitochondria in cancer cells make it a target for cancer therapeutics.

Cryptotanshinone ameliorates hemorrhagic shock-induced liver injury via activating the Nrf2 signaling pathway.

Hemorrhagic shock (HS) is an important cause of high mortality in traumatized patients. Cryptotanshinone (CTS) is a bioactive compound extracted from Salvia miltiorrhiza Bunge (Danshen). The current study aimed to explore the effect and underlying mechanism of CTS on the liver injury induced by HS. Male Sprague-Dawley rats were used to establish the HS model by hemorrhaging and monitoring mean arterial pressure (MAP). CTS was intravenously administered at concentration of 3.5 mg/kg, 7 mg/kg, or 14 mg/kg 30 minutes before resuscitation. Twenty-four hours after resuscitation, the liver tissue and serum samples were collected for the following examinations. Hematoxylin and eosin (H&E) staining was used to evaluate hepatic morphology changes. The myeloperoxidase (MPO) activity in liver tissue and the serum activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were examined to reveal the extent of liver injury. The protein expression of Bax and Bcl-2 in liver tissue was detected by western blot. The TUNEL assay determined the apoptosis of hepatocytes. Oxidative stress of liver tissue was assessed by the examination of reactive oxygen species (ROS) generation. The content of malondialdehyde (MDA), glutathione (GSH), and adenosine triphosphate (ATP), the activity of superoxide dismutase (SOD) and oxidative chain complexes (complex I, II, III, IV), as well as cytochrome c expression in cytoplasm and mitochondria, were also used to determine the extent of oxidative injury in the liver. Immunofluorescence (IF) was employed to estimate nuclear factor E2-related factor 2 (Nrf2) expression. The mRNA and protein levels of heme oxygenase 1 (HO-1), NAD(P)H: quinone oxidoreductases 1 (NQO1), cyclooxygenase-2 (COX-2), and nitric oxide synthase (iNOS) were assessed by real-time qPCR, western blot to investigate the mechanism of CTS regulating HS-induced liver injury. H&E staining and a histological score of rat liver suggested that HS induced liver injury. The activity of ALT, AST, and MPO was significantly increased by HS treatment. After CTS administration the ALT, AST, and MPO activities were suppressed, which indicates the liver injury was alleviated by CTS. The HS-induced upregulation of the TUNEL-positive cell rate was suppressed by various doses of CTS. HS-induced ROS production was decreased and the protein expression of Bax and Bcl-2 in the HS-induced rat liver was reversed by CTS administration. In the liver of HS-induced rats, the upregulation of MDA content and the downregulation of GSH content and SOD activitywere suppressed by CTS. Additionally, CTS increases ATP content and mitochondrial oxidative complexes activities and suppressed the release of cytochrome c from mitochondria to the cytoplasm. Moreover, IF and western blot demonstrated that the activation of Nrf2 blocked by HS was recovered by different doses of CTS in liver tissue. The expression of downstream enzymes of the Nrf2 pathway, including HO-1, NQO1, COX-2, and iNOS, was reversed by CTS in the HS rat model. The current study for the first time revealed the protective effect of CTS in HS-induced liver injury. CTS effectively recovered hepatocyte apoptosis, oxidative stress, and mitochondria damage induced by HS in the rat liver partly via regulating the Nrf2 signaling pathway.

SIRT3 overexpression in rat muscle does not ameliorate peripheral insulin resistance.

Reduced expression of the NAD+-dependent deacetylase, SIRT3, has been associated with insulin resistance and metabolic dysfunction in humans and rodents. In this study, we investigated whether specific overexpression of SIRT3 in vivo in skeletal muscle could prevent high-fat diet (HFD)-induced muscle insulin resistance. To address this, we used a muscle-specific adeno-associated virus (AAV) to overexpress SIRT3 in rat tibialis and extensor digitorum longus (EDL) muscles. Mitochondrial substrate oxidation, substrate switching and oxidative enzyme activity were assessed in skeletal muscles with and without SIRT3 overexpression. Muscle-specific insulin action was also assessed by hyperinsulinaemic-euglycaemic clamps in rats that underwent a 4-week HFD-feeding protocol. Ex vivo functional assays revealed elevated activity of selected SIRT3-target enzymes including hexokinase, isocitrate dehydrogenase and pyruvate dehydrogenase that was associated with an increase in the ability to switch between fatty acid- and glucose-derived substrates in muscles with SIRT3 overexpression. However, during the clamp, muscles from rats fed an HFD with increased SIRT3 expression displayed equally impaired glucose uptake and insulin-stimulated glycogen synthesis as the contralateral control muscle. Intramuscular triglyceride content was similarly increased in the muscle of high-fat-fed rats, regardless of SIRT3 status. Thus, despite SIRT3 knockout (KO) mouse models indicating many beneficial metabolic roles for SIRT3, our findings show that muscle-specific overexpression of SIRT3 has only minor effects on the acute development of skeletal muscle insulin resistance in high-fat-fed rats.

Abstract 388: Acquired sensitivity to ONC201/TIC10 in ER+ breast cancer progressing on the mTOR inhibitor everolimus

Abstract The mTOR inhibitor everolimus has become an important component for clinical management of metastatic ER+ breast cancer. Despite the improved patient outcomes, progression and resistance will still develop. Therefore, it is important to research strategies that can increase response durability and effectiveness of this therapy. Here we developed everolimus resistance models and performed pre-clinical evaluation of the small molecule ONC201/TIC10, a drug candidate showing promising results in clinical trials with advanced cancer patients. ONC201/TIC10 targets mitochondrial function and metabolism and activates stress response, however its efficacy has not been studied in everolimus resistant breast cancer. Transcriptomic analysis in everolimus resistant tumors identified sustained mitochondrial oxidative phosphorylation activity suggesting increased sensitivity to ONC201/TIC10. Our results show that combination treatment of ONC201/TIC10 with everolimus inhibits the growth of sensitive as well as everolimus resistant cells in 2D and 3D in vitro studies. The increased response to combination therapy was confirmed in primary cells from patients progressing on endocrine and mTOR therapy, supporting clinical relevance. We further show that the mechanism of ONC201/TIC10 anti-proliferative activity involves disruption of mitochondrial function and increased levels of the pro-apoptotic transcription factors CHOP and ATF4. Importantly, several resistant cell lines demonstrated increased dependency on mitochondrial respiration compared to sensitive cells which contributes to a vulnerability to ONC201/TIC10. In conclusion, we used pre-clinical models to characterize acquired sensitivity to mTOR inhibition. Combining patient derived data with resistant cell line driven experiments, our study provides validated findings in various settings strengthening the potential for clinical applications of ONC201/TIC10. We propose that ONC201/TIC10 and modulation of mitochondrial function is effective in drug resistant cancer cells and can enhance the anti-tumor activity of standard of care therapy in progressing patients. Citation Format: Eleni Farmaki, Rena Emond, Aritro Nath, Vince K. Grolmusz, Patrick A. Cosgrove, Andrea H. Bild. Acquired sensitivity to ONC201/TIC10 in ER+ breast cancer progressing on the mTOR inhibitor everolimus [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 388.

Inflammation, Mitochondria and Natural Compounds Together in the Circle of Trust

Human diseases are characterized by the perpetuation of an inflammatory condition in which the levels of Reactive Oxygen Species (ROS) are quite high. Excessive ROS production leads to DNA damage, protein carbonylation and lipid peroxidation, conditions that lead to a worsening of inflammatory disorders. In particular, compromised mitochondria sustain a stressful condition in the cell, such that mitochondrial dysfunctions become pathogenic, causing human disorders related to inflammatory reactions. Indeed, the triggered inflammation loses its beneficial properties and turns harmful if dysregulation and dysfunctions are not addressed. Thus, reducing oxidative stress with ROS scavenger compounds has proven to be a successful approach to reducing inflammation. Among these, natural compounds, in particular, polyphenols, alkaloids and coenzyme Q10, thanks to their antioxidant properties, are capable of inhibiting the activation of NF-κB and the expression of target genes, including those involved in inflammation. Even more, clinical trials, and in vivo and in vitro studies have demonstrated the antioxidant and anti-inflammatory effects of phytosomes, which are capable of increasing the bioavailability and effectiveness of natural compounds, and have long been considered an effective non-pharmacological therapy. Therefore, in this review, we wanted to highlight the relationship between inflammation, altered mitochondrial oxidative activity in pathological conditions, and the beneficial effects of phytosomes. To this end, a PubMed literature search was conducted with a focus on various in vitro and in vivo studies and clinical trials from 2014 to 2022.

Unique fiber phenotype composition and metabolic properties of the stapedius and tensor tympani muscles in the human middle ear.

The middle ear muscles have vital roles, yet their precise function in hearing and protection remains unclear. To better understand the function of these muscles in humans, the morphology, fiber composition, and metabolic properties of nine tensor tympani and eight stapedius muscles were analyzed with immunohistochemical, enzyme-histochemical, biochemical, and morphometric techniques. Human orofacial, jaw, extraocular, and limb muscles were used as references. The immunohistochemical analysis showed that the stapedius and tensor tympani muscles were markedly dominated by fibers expressing fast contracting myosin heavy chain MyHC-2A and MyHC-2X (79 ± 6% vs. 86 ± 9%, respectively, p=0.04). In fact, the middle ear muscles had one of the highest proportions of MyHC-2 fibers ever reported for human muscles. Interestingly, the biochemical analysis revealed a MyHC isoform of unknown identity in both the stapedius and tensor tympani muscles. Muscle fibers containing two or more MyHC isoforms were relatively frequently observed in both muscles. A proportion of these hybrid fibers expressed a developmental MyHC isoform that is normally absent in adult human limb muscles. The middle ear muscles differed from orofacial, jaw, and limb muscles by having significantly smaller fibers (220 vs. 360 μm2 , respectively) and significantly higher variability in fiber size, capillarization per fiber area, mitochondrial oxidative activity, and density of nerve fascicles. Muscle spindles were observed in the tensor tympani muscle but not in the stapedius muscle. We conclude that the middle ear muscles have a highly specialized muscle morphology, fiber composition, and metabolic properties that generally showed more similarities to orofacial than jaw and limb muscles. Although the muscle fiber characteristics in the tensor tympani and stapedius muscles suggest a capacity for fast, fine-tuned, and sustainable contractions, their difference in proprioceptive control reflects different functions in hearing and protection of the inner ear.

Nutmeg Extract Alters Mitochondrial Genes Regulation of Skeletal Muscle Fibers in Aging Rats

Nutmeg as one of Indonesia native plants has already been used widely in herbal treatment. It has been demonstrated that nutmeg presents activities related to mitochondria functions. Nutmeg potentially has the effect of peroxisome proliferator activated receptors Υ (PPAR Υ) which contributes to myogenesis, and may alters mitochondrial homeostasis in respiration and biogenesis. In this study, how nutmeg extract alters oxidative process in skeletal muscle of aging rats was explored. Twenty aging Wistar male rats aged 80 weeks old were divided into two groups (control and nutmeg treatment). Nutmeg extract was administered for 12 weeks using a gavage. After that, the soleus muscles were collected, weighted, frozen, and stored at -800C until used. Nutmeg was observed to increase the COX1 (1.9 folds, p<0.01), COX2 (1.6 folds, p<0.05), and COXIV (2.8 folds, p<0.01) gene expressions, in parallel with increased protein carbonyl levels (1.5 folds, p<0,01). Nutmeg treatment also significantly increased the expressions of antioxidant endogen COQ7 (2 folds, p<0,01) and PDSS2 (2 folds, p<0,01) in the soleus muscle. Taken together, nutmeg extract may improve mitochondrial respiratory oxidative activities in type I aging skeletal muscle.

Vitamin D status modulates mitochondrial oxidative capacities in skeletal muscle: role in sarcopenia

Skeletal muscle mitochondrial function is the biggest component of whole-body energy output. Mitochondrial energy production during exercise is impaired in vitamin D-deficient subjects. In cultured myotubes, loss of vitamin D receptor (VDR) function decreases mitochondrial respiration rate and ATP production from oxidative phosphorylation. We aimed to examine the effects of vitamin D deficiency and supplementation on whole-body energy expenditure and muscle mitochondrial function in old rats, old mice, and human subjects. To gain further insight into the mechanisms involved, we used C2C12 and human muscle cells and transgenic mice with muscle-specific VDR tamoxifen-inducible deficiency. We observed that in vivo and in vitro vitamin D fluctuations changed mitochondrial biogenesis and oxidative activity in skeletal muscle. Vitamin D supplementation initiated in older people improved muscle mass and strength. We hypothesize that vitamin D supplementation is likely to help prevent not only sarcopenia but also sarcopenic obesity in vitamin D-deficient subjects.

Impaired fatigue resistance, sarcoplasmic reticulum function, and mitochondrial activity in soleus muscle of db/db mice.

Type 2 diabetes mellitus (T2DM) is characterized by reduced exercise tolerance due to increased fatigability in skeletal muscle. In this study, we investigated muscle fatigue resistance of soleus (SOL) muscle in obese type 2 diabetic model mice (db/db). No differences in muscle volume, absolute force, or specific force in SOL muscle were observed between db/db mice and control mice (db/+), while fatigue resistance evaluated by repeated tetanic contractions was significantly lower in db/db mice (30th tetani, db/+: 63.7 ± 4.7%, db/db: 51.3 ± 4.8%). The protein abundance related to Ca2+ release from the sarcoplasmic reticulum (SR) in SOL muscle was not different between db/db mice and db/+ mice, while SR Ca2+‐ATPase (Ca2+ reuptake to SR) protein was decreased in db/db mice compared to db/+ mice (db/+: 1.00 ± 0.17, db/db: 0.60 ± 0.04, relative units). In addition, mitochondrial oxidative enzyme activity (succinate dehydrogenase) was decreased in the SOL muscle of db/db mice (p < 0.05). These data suggest that fatigue resistance in slow‐twitch dominant muscle is impaired in mice with T2DM. Decreased mitochondrial oxidative enzyme activity and impairment of Ca2+ uptake to SR, or both might be involved in the mechanisms.

Abstract P3038: Upregulation Of The Mitochondrial Calcium Uniporter Abolishes Mitochondrial Dysfunction Associated With Obesity In Vascular Smooth Muscle Cells

Obesity is a growing national epidemic that is associated with an increased prevalence of arterial disease. We found that aortic medial hypertrophy during obesity was accompanied by upregulation of serum and glucocorticoid-inducible kinase 1 (SGK1) and reduced mitochondrial oxidative capacity of vascular smooth muscle cells (VSMC). Interestingly, VSMC-specific deletion of SGK1 attenuated obesity-related aortic remodeling and restored mitochondrial oxidative capacity in VSMC implicating a mediator role for SGK1 in mitochondrial dysfunction during obesity. The mechanistic basis for impaired mitochondrial respiration during obesity in VSMC is unknown. Thus, due to its fundamental role in stimulation of mitochondrial oxidative phosphorylation, the current study will investigate the mitochondrial calcium uniporter (MCU) in obesity-related mitochondrial dysfunction in VSMC. As SGK1 is known to regulate the expression and/or activity of ion channels, we hypothesize that upregulation of SGK1 during obesity negatively regulates MCU expression, mitochondrial oxidative activity, and ATP production. MCU protein levels were assessed by western blot analysis. Mitochondrial oxidative activity and ATP production rate were measured using the Agilent Seahorse XF Cell Mito Stress Test and the ATP Rate Assay, respectively in cultured wildtype and SGK1 knockout aortic VSMC from low-fat (LF) control and high-fat (HF) obese mice. To assess the importance of MCU, both assays were performed in the presence or absence of the MCU inhibitor, Ru360. Obesity caused a significant decrease in MCU abundance, but SGK1 deletion resulted in enrichment of MCU in VSMC. Ru360 treatment reversed the increase in basal mitochondrial respiration. We found that obesity reduced overall ATP production by diminishing ATP production from glycolysis and mitochondrial respiration. However, SGK1 deletion enhanced ATP production from glycolysis and mitochondrial respiration during obesity and this effect was attenuated by Ru360. These findings demonstrate that SGK1 negatively regulates MCU expression and activity and imply that augmentation of MCU-driven mitochondrial oxidative activity may underlie the protective effects of SGK1 inhibition on the vascular during obesity.

Thermal cum lipopolysaccharide-induced stress challenge downregulates functional response of bovine monocyte-derived macrophages

Macrophages are considered to be key players in innate immunity and inflammatory responses. Domestic cattle with standard body size quickly reach their heat tolerance limit and are prone to heat stress. The combined effects of high temperature and endotoxemia on bovine monocyte-derived macrophages remain almost undisclosed. This study aims to unravel the molecular and functional responses of bovine monocyte-derived macrophages to thermal cum lipopolysaccharide induced stress challenge in vitro. The cells were incubated at 37 °C or 40 °C with lipopolysaccharide (1.0 μg/mL) for 24 h and 48 h. At the end of each treatment, cell viability, apoptotic rate, mitochondrial membrane potential, oxidative activity, phagocytosis, and autophagy functions were assessed and mRNA abundance of genes related to heat shock (HSP 70), inflammation (IL1β, IL6, IL 12, TNF, INF γ), cell signalling (TLR4), cell viability (Bax, Bcl2), nitric oxide synthesis (NOS2) and natural resistant associated macrophage protein were quantified by quantitative polymerase chain reaction (qPCR). The results revealed the increased apoptosis, reduced mitochondrial membrane potential, and cell viability, decreased oxidative and phagocytosis ability in cells co-stimulated with LPS and thermal stimuli. Upregulation of HSP 70 gene and downregulation of natural resistant associated macrophage protein, cell signalling, and inflammation related genes mRNA expressions were also identified due to these stressors. In conclusion, the observed thermal cum LPS stress induced dysregulation in macrophage functionality may be one facet of the increased disease susceptibility in dairy cattle during thermal stress.

Targeting HOTAIRM1 ameliorates glioblastoma by disrupting mitochondrial oxidative phosphorylation and serine metabolism

SummarySerine hydroxymethyltransferase 2 (SHMT2), which catalyzes the conversion of serine to glycine and one-carbon transfer reactions in mitochondria, is significantly upregulated in glioblastoma (GBM). However, the mechanism by which the stability of SHMT2 gene expression is maintained to drive GBM tumorigenesis has not been clarified. Herein, through microarray screening, we identified that HOXA Transcript Antisense RNA, Myeloid-Specific 1 (HOTAIRM1) modulates the SHMT2 level in various GBM cell lines. Serine catabolism and mitochondrial oxidative phosphorylation activities were decreased by HOTAIRM1 inhibition. Mechanistically, according to our mass spectrometry and eCLIP-seq results, HOTAIRM1 can bind to PTBP1 and IGF2BP2. Furthermore, HOTAIRM1 maintains the stability of SHMT2 by promoting the recognition of an m6A site and the interaction of PTBP1/IGF2BP2 with SHMT2 mRNA. The stability of HOTAIRM1 can also be enhanced and results in positive feedback regulation to support the progression of GBM. Thus, targeting HOTAIRM1 could be a promising metabolic therapy for GBM.

NAD + salvage governs mitochondrial metabolism, invigorating natural killer cell antitumor immunity.

Natural killer (NK) cells are key players in tumor immunosurveillance, and metabolic adaptation manipulates their fate and functional state. The nicotinamide adenine dinucleotide (NAD + ) has emerged as a vital factor to link cellular metabolism and signaling transduction. Here, we identified NAD + metabolism as a central hub to determine the homeostasis and function of NK cells. NAD + level was elevated in activated NK cells. NAD + supplementation not only enhanced cytokine production and cytotoxicity but also improved the proliferation and viability of NK cells. Intriguingly, the salvage pathway was involved in maintaining NAD + homeostasis in activated NK cells. Genetic ablation or pharmacological blockade of nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the NAD + salvage pathway, markedly destroyed the viability and function of NK cells. Mechanistically, NAD + salvage dictated the mitochondrial homeostasis and oxidative phosphorylation activity to support the optimal function of NK cells. However, in human HCC tissues, NAMPT expression and NAD + level were significantly down-regulated in tumor-infiltrating NK cells, which negatively correlated with patient survival. And lactate accumulation in the tumor microenvironment was at least partially responsible for the transcriptional repression of NAMPT in NK cells. Further, deficiency of Nampt in NK cells accelerated the growth of HCC and melanoma. Supplementation of the NAD + precursor nicotinamide mononucleotide (NMN) significantly improved NK antitumor response in both mouse and human cell-derived xenografts. These findings reveal NAD + salvage as an essential factor for NK-cell homeostasis and function, suggesting a potential strategy for invigorating NK cell-based immunotherapy.

Mice selected for a high basal metabolic rate evolved larger guts but not more efficient mitochondria.

Intra-specific variation in both the basal metabolic rate (BMR) and mitochondrial efficiency (the amount of ATP produced per unit of oxygen consumed) has profound evolutionary and ecological consequences. However, the functional mechanisms responsible for this variation are not fully understood. Mitochondrial efficiency is negatively correlated with BMR at the interspecific level but it is positively correlated with performance capacity at the intra-specific level. This discrepancy is surprising, as theories explaining the evolution of endothermy assume a positive correlation between BMR and performance capacity. Here, we quantified mitochondrial oxidative phosphorylation activity and efficiency in two lines of laboratory mice divergently selected for either high (H-BMR) or low (L-BMR) levels of BMR. H-BMR mice had larger livers and kidneys (organs that are important predictors of BMR). H-BMR mice also showed higher oxidative phosphorylation activity in liver mitochondria but this difference can be hypothesized to be a direct effect of selection only if the heritability of this trait is low. However, mitochondrial efficiency in all studied organs did not differ between the two lines. We conclude that the rapid evolution of BMR can reflect changes in organ size rather than mitochondrial properties, and does not need to be accompanied obligatorily by changes in mitochondrial efficiency.