Catabolic Activity Research Articles

Mechanical Loading Promotes the Migration of Endogenous Stem Cells and Chondrogenic Differentiation in a Mouse Model of Osteoarthritis.

Osteoarthritis (OA) is a major health problem, characterized by progressive cartilage degeneration. Previous works have shown that mechanical loading can alleviate OA symptoms by suppressing catabolic activities. This study evaluated whether mechanical loading can enhance anabolic activities by facilitating the recruitment of stem cells for chondrogenesis. We evaluated cartilage degradation in a mouse model of OA through histology with H&E and safranin O staining. We also evaluated the migration and chondrogenic ability of stem cells using in vitro assays, including immunohistochemistry, immunofluorescence, and Western blot analysis. The result showed that the OA mice that received mechanical loading exhibited resilience to cartilage damage. Compared to the OA group, mechanical loading promoted the expression of Piezo1 and the migration of stem cells was promoted via the SDF-1/CXCR4 axis. Also, the chondrogenic differentiation was enhanced by the upregulation of SOX9, a transcription factor important for chondrogenesis. Collectively, the results revealed that mechanical loading facilitated cartilage repair by promoting the migration and chondrogenic differentiation of endogenous stem cells. This study provided new insights into the loading-driven engagement of endogenous stem cells and the enhancement of anabolic responses for the treatment of OA.

Assembly between wheat cultivars and soil microorganisms modulates phosphorus and water use efficiency

The current scientific evidence shows a synergistic role between phosphorus use efficiency (PUE) and water use efficiency (WUE). However, the interactions between plants and soil microorganisms that stimulate phosphorus (P) and water uptake could exhibit variation at the cultivar level. This manuscript aims to evaluate the influence of different wheat cultivars on soil microbial activities and functional diversity and how their interaction could affect plant performance in terms of PUE and WUE.Three wheat cultivars (Fritz, Chevignon, and Rancofén) differing in their ability to use P and water were grown under controlled conditions on an Andisol with background soil P-concentration of 4 mg P kg−1 (-P), which was enriched to 30 mg P kg−1 (+P). Water management was applied at two levels: well-watered (+W) and 30% of the water applied to + W (water stress, -W). Soil microbial activities were assayed at the anthesis stage, but wheat was harvested at the end of its phenological cycle.Phosphorus scarcity and water deficit stress negatively affected growth traits, P acquisition, and grain yield of wheat cultivars. The P concentration affected the acid phosphatase (APs) and dehydrogenase activity (DHA) more than water management.The community-level physiological profile (CLPP) was modulated by the cultivar, water management, and P concentration. The main drivers determining microorganisms' catabolic activity were water deficit stress and high P concentration in the soil. The P addition to plants facing water limitation increased by about 84% the CO2 production by soil microorganisms.Finally, the differences observed among cultivars and the soil microbial activities affected PUE and WUE performance, being Fritz the most efficient cultivar in both components in all conditions evaluated.Our data suggest that an assembly between cultivars and microorganisms affects the plant performance in terms of PUE and WUE.

Proteomic analysis of spinal cord tissue in a rat model of cancer-induced bone pain.

Cancer-induced bone pain (CIBP) is a moderate to severe pain and seriously affects patients' quality of life. Spinal cord plays critical roles in pain generation and maintenance. Identifying differentially expressed proteins (DEPs) in spinal cord is essential to elucidate the mechanisms of cancer pain. CIBP rat model was established by the intratibial inoculation of MRMT-1 cells. Positron emission tomography (PET) scan and transmission electron microscopy (TEM) were used to measure the stats of spinal cord in rats. Label free Liquid Chromatography with tandem mass spectrometry (LC-MS-MS) were used to analyze the whole proteins from the lumbar spinal cord. Differentially expressed proteins (DEPs) were performed using Gene Ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis, and verified using Western blot and immunofluorescence assay. In the current study, CIBP rats exhibited bone damage, spontaneous pain, mechanical hyperalgesia, and impaired motor ability. In spinal cord, an hypermetabolism and functional abnormality were revealed on CIBP rats. An increase of synaptic vesicles density in active zone and a disruption of mitochondrial structure in spinal cord of CIBP rats were observed. Meanwhile, 422 DEPs, consisting of 167 up-regulated and 255 down-regulated proteins, were identified among total 1539 proteins. GO enrichment analysis indicated that the DEPs were mainly involved in catabolic process, synaptic function, and enzymic activity. KEGG pathway enrichment analysis indicated a series of pathways, including nervous system disease, hormonal signaling pathways and amino acid metabolism, were involved. Expression change of synaptic and mitochondrial related protein, such as complexin 1 (CPLX1), synaptosomal-associated protein 25 (SNAP25), synaptotagmin 1 (SYT1), aldehyde dehydrogenase isoform 1B1 (ALDH1B1), Glycine amidinotransferase (GATM) and NADH:ubiquinone oxidoreductase subunit A11 (NDUFA11), were further validated using immunofluorescence and Western blot analysis. This study provides valuable information for understanding the mechanisms of CIBP, and supplies potential therapeutic targets for cancer pain.

Altered PLD3 exonuclease activity impacts on lysosomal and mitochondrial homeostasis

AbstractBackgroundPhospholipase D3 (PLD3) is a single‐pass type II membrane protein that is majorly localized to late endosomes/lysosomes (LE/Lys) where it functions as a 5'‐3' exonuclease that degrades ssDNA. Whereas PLD3 has been identified as risk factor for late‐onset Alzheimer’s disease (LOAD), knockout studies have resulted in conflicting data regarding its impact on the amyloid precursor protein metabolism. Moreover, the substrates for PLD3 in LE/Lys remain unexploredMethodCRISPR/Cas9 gene editing was used to generate PLD3 knockout (KO) SH‐SY5Y cells that were subsequently stably rescued with wild‐type PLD3 and coding‐variants (M6R & V232M). All cell lines were evaluated for morphological and functional alterations of the LE/Lys compartment, including lipid profiling and analysis of the nucleotide content of LE/Lys magnetically isolated from the different cell lines. We optimized a PLD3 activity assay and analyzed the LE/Lys nucleotide content as a means to identify PLD3 substrates.ResultWe report that a PLD3 KO and LOAD‐associated risk variants lead to a significant lysosomal pathology, comprising an increase in the size of LE/Lys, more LAMP1 immunoreactivity, a reduced catabolic activity, an increased propensity for leakage and a marked increase in cholesterol content and in storage lipids. At the ultrastructural level, this is accompanied with the appearance of multilamellar bodies, sometimes including mitochondrial remnants. This is suggestive for a defective mitophagy, which we confirm on the light microscopy level using mKeima assays. Furthermore, we provide support for a role of PLD3 in the homeostatic degradation of mtDNA. We argue that when PLD3’s role is compromised, this leads to a build‐up of the lysosomal nucleotide content, impacting on the normal functioning of LE/Lys. We are currently analysing alterations in downstream cellular signaling pathways, including the TLR9 cascade.ConclusionCollectively, our findings subscribe a key role for PLD3 exonuclease activity in lysosomal homeostasis. Its dysfunction, as occurs in LOAD, leads to the co‐occurrence of lysosomal and mitochondrial defects.

Parkin deficiency exacerbates fasting-induced skeletal muscle wasting in mice

Parkinson’s Disease (PD) is a chronic and progressive neurodegenerative disease manifesting itself with tremors, muscle stiffness, bradykinesia, dementia, and depression. Mutations of mitochondrial E3 ligase, PARKIN, have been associated with juvenile PD. Previous studies have characterized muscle atrophy and motor deficits upon loss of functional Parkin in fly and rodent models. However, the mechanisms behind pathophysiology of Parkin deficient muscle remains to be elusive. Here, results suggested that knock down of Parkin significantly increases proteolytic activities in skeletal muscle cell line, the C2C12 myotubes. However, the atrogene levels increase moderately in Parkin deficient cell line. To further investigate the role of Parkin in skeletal muscle atrophy, Parkin knock out (KO) and wild type mice were subjected to 48 h starvation. After 48 h fasting, a greater reduction in skeletal muscle weights was observed in Parkin KO mice as compared to age matched wild type control, suggesting elevated proteolytic activity in the absence of Parkin. Subsequent microarray analyses revealed further enhanced expression of FOXO and ubiquitin pathway in fasted Parkin KO mice. Furthermore, a greater reduction in the expression of cytoskeleton genes was observed in Parkin KO mice following 48 h fasting. Collectively, these results suggest that Parkin deficiency exacerbates fasting-induced skeletal muscle wasting, through upregulating genes involved in catabolic activities in skeletal muscle.

CsGDH2.1 negatively regulates theanine accumulation in late-spring tea plants (Camellia sinensis var. sinensis).

Theanine, a unique and the most abundant non-proteinogenic amino acid in tea plants, endows tea infusion with the umami taste and anti-stress effects. Its content in tea correlates highly with green tea quality. Theanine content in new shoots of tea plants is high in mid-spring and greatly decreases in late spring. However, how the decrease is regulated is largely unknown. In a genetic screening, we observed that a yeast mutant, glutamate dehydrolase 2 (gdh2), was hypersensitive to 40mM theanine and accumulated more theanine. This result implied a role of CsGDH2s in theanine accumulation in tea plants. Therefore, we identified the two homologs of GDH2, CsGDH2.1 and CsGDH2.2, in tea plants. Yeast complementation assay showed that the expression of CsGDH2.1 in yeast gdh2 mutant rescued the theanine hypersensitivity and hyperaccumulation of this mutant. Subcellular localization and tissue-specific expression showed CsGDH2.1 localized in the mitochondria and highly expressed in young tissues. Importantly, CsGDH2.1 expression was low in early spring, and increased significantly in late spring, in the new shoots of tea plants. These results all support the idea that CsGDH2.1 regulates theanine accumulation in the new shoots. Moreover, the in vitro enzyme assay showed that CsGDH2.1 had glutamate catabolic activity, and knockdown of CsGDH2.1 expression increased glutamate and theanine accumulation in the new shoots of tea plants. These findings suggested that CsGDH2.1-mediated glutamate catabolism negatively regulates theanine accumulation in the new shoots in late spring, and provides a functional gene for improving late-spring green tea quality.

Extra-cardiac BCAA catabolism lowers blood pressure and protects from heart failure

Pharmacologic activation of branched-chain amino acid (BCAA) catabolism is protective in models of heart failure (HF). How protection occurs remains unclear, although a causative block in cardiac BCAA oxidation is widely assumed. Here, we use invivo isotope infusions to show that cardiac BCAA oxidation in fact increases, rather than decreases, in HF. Moreover, cardiac-specific activation of BCAA oxidation does not protect from HF even though systemic activation does. Lowering plasma and cardiac BCAAs also fails to confer significant protection, suggesting alternative mechanisms of protection. Surprisingly, activation of BCAA catabolism lowers blood pressure (BP), a known cardioprotective mechanism. BP lowering occurred independently of nitric oxide and reflected vascular resistance to adrenergic constriction. Mendelian randomization studies revealed that elevated plasma BCAAs portend higher BP in humans. Together, these data indicate that BCAA oxidation lowers vascular resistance, perhaps in part explaining cardioprotection in HF that is not mediated directly in cardiomyocytes.

Cartilage-penetrating hyaluronic acid hydrogel preserves tissue content and reduces chondrocyte catabolism.

Articular cartilage injuries have a limited healing capacity and, due to inflammatory and catabolic activities, often experience progressive degeneration towards osteoarthritis. Current repair techniques generally provide short-term symptomatic relief; however, the regeneration of hyaline cartilage remains elusive, leaving both the repair tissue and surrounding healthy tissue susceptible to long-term wear. Therefore, methods to preserve cartilage following injury, especially from matrix loss and catabolism, are needed to delay, or even prevent, the deteriorative process. The goal of this study was to develop and evaluate a cartilage-penetrating hyaluronic-acid (HA) hydrogel to improve damaged cartilage biomechanics and prevent tissue degeneration. At time zero, the HA-based hydrogel provided a 46.5% increase in compressive modulus and a decrease in permeability after simulated degeneration of explants (collagenase application). Next, in a degenerative culture model (interleukin-1β [IL-1β] for 2weeks), hydrogel application prior to or midway through the culture mitigated detrimental changes to compressive modulus and permeability observed in non-treated explants. Furthermore, localized loss of proteoglycan was observed in degenerative culture conditions alone (non-treated), but hydrogel administration significantly improved the retention of matrix elements. Finally, NITEGE staining and gene expression analysis showed the ability of the HA gel to decrease chondrocyte catabolic activity. These results highlight the importance of reinforcing damaged cartilage with a biomaterial system to both preserve tissue content and reduce catabolism associated with injury and inflammation.

201 Forage Biodegradation: Advances in Ruminal Microbial Ecology

Abstract The rumen microbial ecosystem provides ruminant animals a selective advantage, the ability to utilize forages, which allows ruminant animals to flourish around the world in a wide variety of environments. The ability of the microbial population to convert sunlight captured in forages to high quality meat, milk, and fiber has been recognized for many years. However, the rumen microbial population composition and degradative activity has remained a “black box” with only the most active (and most amenable to laboratory growth) cellulolytic and hemicellulolytic organisms being recognized and understood. The limitation of reliance upon growth of forage degrading organisms in a test tube in order to measure the catabolic activity, severely limited the development of knowledge of the microbial ecology of ruminal forage degradation. The past 15 years has seen the development and implementation of numerous Next-Generation Sequencing (NGS) approaches, which have greatly contributed to a better understanding of the microbial ecology of ruminants fed a variety of forages. NGS has provided new insights into changes in the microbial population of ruminants fed different diets, or undergoing dietary changes. The ability to take a “snapshot” of the composition of the ruminal microbial population has furthered our understanding of the impacts of forage maturity, forage type, and phytochemicals on the degradation and fermentation of forages. We now better understand the microbial pathways that are enriched by feeding of forages and are impacted by forage quality or composition, which can further our understanding of metabolomics of the rumen. As NGS data continues to accumulate on ruminants fed forage, our understanding of the ruminal microbial ecosystem will grow both deeper and broader, allowing us to build predictive models of rumen function during forage degradation and fermentation.

Efficient degradation of hydroquinone by a metabolically engineered Pseudarthrobacter sulfonivorans strain.

Pseudarthrobacter sulfonivorans strain Ar51 can degrade crude oil and multi-substituted benzene compounds efficiently at low temperatures. However, it cannot degrade hydroquinone, which is a key intermediate in the degradation of several other compounds of environmental importance, such as 4-nitrophenol, g-hexachlorocyclohexane, 4-hydroxyacetophenone and 4-aminophenol. Here we co-expressed the two subunits of hydroquinone dioxygenase from Sphingomonas sp. strain TTNP3 with different promoters in the strain Ar51. The strain with 2 hdnO promoters exhibited the strongest hydroquinone catabolic activity. However, in the absence of antibiotic selection this ability to degrade hydroquinone was lost due to plasmid instability. Consequently, we constructed a hisD knockout strain, which was unable to synthesise histidine. By introducing the hisD gene onto the plasmid, the ability to degrade hydroquinone in the absence of antibiotic selection was stabilised. In addition, to make the strain more stable for industrial applications, we knocked out the recA gene and integrated the hydroquinone dioxygenase genes at this chromosomal locus. This strain exhibited the strongest activity in catabolizing hydroquinone, up to 470mg/L in 16h without antibiotic selection. In addition, this activity was shown to be stable when the strain has cultured in medium without antibiotic selection after 20 passages.

A Review on Peripheral Tinnitus, Causes, and Treatments from the Perspective of Autophagy.

Tinnitus is the perception of phantom noise without any external auditory sources. The degeneration of the function or activity of the peripheral or central auditory nervous systems is one of the causes of tinnitus. This damage has numerous causes, such as loud noise, aging, and ototoxicity. All these sources excite the cells of the auditory pathway, producing reactive oxygen species that leads to the death of sensory neural hair cells. This causes involuntary movement of the tectorial membrane, resulting in the buzzing noise characteristic of tinnitus. Autophagy is an evolutionarily conserved catabolic scavenging activity inside a cell that has evolved as a cell survival mechanism. Numerous studies have demonstrated the effect of autophagy against oxidative stress, which is one of the reasons for cell excitation. This review compiles several studies that highlight the role of autophagy in protecting sensory neural hair cells against oxidative stress-induced damage. This could facilitate the development of strategies to treat tinnitus by activating autophagy.

Metabolic Pathways and Ion Channels Involved in Skeletal Muscle Atrophy: A Starting Point for Potential Therapeutic Strategies.

Skeletal muscle tissue has the important function of supporting and defending the organism. It is the largest apparatus in the human body, and its function is important for contraction and movements. In addition, it is involved in the regulation of protein synthesis and degradation. In fact, inhibition of protein synthesis and/or activation of catabolism determines a pathological condition called muscle atrophy. Muscle atrophy is a reduction in muscle mass resulting in a partial or complete loss of function. It has been established that many physiopathological conditions can cause a reduction in muscle mass. Nevertheless, it is not well known the molecular mechanisms and signaling processes causing this dramatic event. There are multiple concomitant processes involved in muscle atrophy. In fact, the gene transcription of some factors, oxidative stress mechanisms, and the alteration of ion transport through specific ion channels may contribute to muscle function impairment. In this review, we focused on the molecular mechanisms responsible for muscle damage and potential drugs to be used to alleviate this disabling condition.

Direct control of lysosomal catabolic activity by mTORC1 through regulation of V-ATPase assembly

Mammalian cells can acquire exogenous amino acids through endocytosis and lysosomal catabolism of extracellular proteins. In amino acid-replete environments, nutritional utilization of extracellular proteins is suppressed by the amino acid sensor mechanistic target of rapamycin complex 1 (mTORC1) through an unknown process. Here, we show that mTORC1 blocks lysosomal degradation of extracellular proteins by suppressing V-ATPase-mediated acidification of lysosomes. When mTORC1 is active, peripheral V-ATPase V1 domains reside in the cytosol where they are stabilized by association with the chaperonin TRiC. Consequently, most lysosomes display low catabolic activity. When mTORC1 activity declines, V-ATPase V1 domains move to membrane-integral V-ATPase Vo domains at lysosomes to assemble active proton pumps. The resulting drop in luminal pH increases protease activity and degradation of protein contents throughout the lysosomal population. These results uncover a principle by which cells rapidly respond to changes in their nutrient environment by mobilizing the latent catabolic capacity of lysosomes.

Ketogenic Diet Promotes Epithelial Ovarian Cancer Progression and Alters Tumor Gene Expression in-vivo (104)

<b>Objectives:</b> The ketogenic diet (KD) is hypothesized to impact tumor progression indirectly through altering the immune system as well as directly at the cellular level. Our studies were designed to assess changes in tumor resident immune cells and tumor gene expression in relation to epithelial ovarian cancer (EOC) progression in KD-fed mice. <b>Methods:</b> ID8 EOC cells, syngeneic with C57Bl/6J mouse strain, transfected with luciferase (ID8-Luc), were injected and monitored for tumor development via imaging with an <i>in vivo</i> Imaging System (IVIS) intraperitoneal D-luciferin. Tumor-bearing mice were fed a KD (10% protein, 0% carbohydrates, 90% fat), high fat diet (HFD) (10% protein, 15% carbohydrates, 75% fat), or control diet (CD) (10% protein, 77% carbohydrates, and 13% fat) (<i>n</i>=10 mice per group). EOC tumor growth was monitored weekly, and tumor burden was determined based on total flux recorded in photons/second measured. At the endpoint, tumors were collected and processed for flow cytometry and RNAseq analysis. Single-cell dissociated tumors (Papain System) were stained with an immune targeted antibody panel and analyzed on the BD Cytek Aurora. RNA was isolated (Qiagen), and sequencing was performed. Statistical tests included analysis of variance (ANOVA), permutational multivariate analysis (PERMANOVA), linear regression, and Wilcoxon test; a p-value of <0.05 was considered statistically significant. <b>Results:</b> Throughout the study, KD-fed mice exhibited a statistically significant increase in tumor progression. We observed a 9.1-fold increase in tumor volume from baseline in the KD-fed group compared to HFD and CD-fed groups (9.1 vs 2.0 vs 3.1-fold, respectively, p<0.001). At the endpoint, tumor-associated macrophages (TAM) were significantly enriched and activated lymphoid cells (NK cells) were significantly diminished in the KD group (p<0.001). There was a trend toward increased M2:M1 polarization in KD-fed mice. However, there was no significant difference in Treg cells or activated CD8+ cells among diet groups. EOC tumors in KD-fed mice exhibited a significant decrease in differential gene expression on RNA seq compared to CD- and HFD-fed tumors, with no significant difference between CD- and HFD-fed groups at the gene expression level. Gene set enrichment analysis (GSEA) demonstrated that EOC tumors from KD-fed mice had enhanced angiogenesis, inflammatory response, and epithelial to mesenchymal transition (EMT) phenotype, as well as altered lipid metabolism. Specifically, an increase in lipid catalytic activity and catabolism and decrease in lipid synthesis were noted among KD-fed mice versus HFD-fed mice. <b>Conclusions:</b> KD induced tumor progression in our murine EOC model compared to HFD and CD. KD was associated with an increase in TAM and a decrease in activated NK cells consistent with a protumorigenic immune environment. KD-fed mice exhibited markedly increased alterations in angiogenesis, inflammation, and EMT pathways with enhanced lipid catabolic activity. Further testing of KD in human EOC cells is needed to clarify the <i>in-vivo</i> effect of KD on EOC growth.Fig. 1

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.

Increased Chondroprotective Effect of Combining Hyaluronic Acid with a Glucocorticoid Compared to Separate Administration on Cytokine-Treated Osteoarthritic Chondrocytes in a 2D Culture

Intra-articular injections of glucocorticoids (GC) or hyaluronic acid (HA) are commonly used interventions for patients suffering from knee osteoarthritis (OA). Both substances are combined to achieve a chondroprotective and anti-inflammatory effect. Clinical studies have shown benefits, but data on the cellular level are still lacking. This study aimed to investigate the effect of the GC triamcinolone hexacetonide, HA, and a mix of both substances on cytokine-treated chondrocytes in vitro. Chondrocytes isolated from human articular cartilage were seeded on 6- and 24-well plates. Mimicking OA’s inflammatory state, cells were treated with IL-1β and IL-17 for six days, whereby, after three days, test substances (10%) were added to the culture medium. Chondrocytes were analyzed on days three and six concerning their actin polymerization, expression of anabolic and catabolic genes, metabolic activity, cytokine release, and reactive oxygen species (ROS). Adding HA or GC/HA to the inflammatory culture medium increased the metabolic activity of chondrocytes, while groups containing GC reduced catabolic gene expression and the release of TNF-α. In addition, enhanced F-actin content was shown supplementing HA or GC/HA to the culture medium. Supplementing GC with HA leads to an anti-inflammatory and chondroprotective effect by diminishing the side effects of GC supplementation alone.

Growth rate-dependent coordination of catabolism and anabolism in the archaeon Methanococcus maripaludis under phosphate limitation.

Catabolic and anabolic processes are finely coordinated in microorganisms to provide optimized fitness under varying environmental conditions. Understanding this coordination and the resulting physiological traits reveals fundamental strategies of microbial acclimation. Here, we characterized the system-level physiology of Methanococcus maripaludis, a niche-specialized methanogenic archaeon, at different dilution rates ranging from 0.09 to 0.003 h-1 in chemostat experiments under phosphate (i.e., anabolic) limitation. Phosphate was supplied as the limiting nutrient, while formate was supplied in excess as the catabolic substrate and carbon source. We observed a decoupling of catabolism and anabolism resulting in lower biomass yield relative to catabolically limited cells at the same dilution rates. In addition, the mass abundance of several coarse-grained proteome sectors (i.e., combined abundance of proteins grouped based on their function) exhibited a linear relationship with growth rate, mostly ribosomes and their biogenesis. Accordingly, cellular RNA content also correlated with growth rate. Although the methanogenesis proteome sector was invariant, the metabolic capacity for methanogenesis, measured as methane production rates immediately after transfer to batch culture, correlated with growth rate suggesting translationally independent regulation that allows cells to only increase catabolic activity under growth-permissible conditions. These observations are in stark contrast to the physiology of M. maripaludis under formate (i.e., catabolic) limitation, where cells keep an invariant proteome including ribosomal content and a high methanogenesis capacity across a wide range of growth rates. Our findings reveal that M. maripaludis employs fundamentally different strategies to coordinate global physiology during anabolic phosphate and catabolic formate limitation.

The new metabolic needs of hematopoietic stem cells.

Hematopoietic stem cells (HSCs) are endowed with high regenerative potential to supply mature blood cells throughout life, under steady state or stress conditions. HSCs are thought to rely on glycolysis when in a quiescent state and to switch to oxidative phosphorylation to meet their metabolic needs during activation. Recently, a series of important studies reveals a higher degree of complexity that goes well beyond the dichotomy between glycolysis and oxidative phosphorylation. The purpose of this review is to summarize the recent findings highlighting the multifaceted metabolic requirements of HSC homeostasis. Emerging evidence points to the importance of lysosomal catabolic activity and noncanonical retinoic acid pathway in maintaining HSC quiescence and stemness. HSC activation into cycle seems to be accompanied by a switch to glycolysis-mitochondrial coupling and to anabolic pathways, including Myc, aspartate-mediated purine synthesis. Knowledge of metabolism of HSCs has dramatically increased in the past 2 years and reveals unexpected needs of HSCs during both their quiescent and activated state. Understanding how HSCs use metabolism for their functions will offer new opportunity for HSC-based therapies.

Improved Hydrogen Peroxide Stress Resistance of Zymomonas mobilis NADH Dehydrogenase (ndh) and Alcohol Dehydrogenase (adhB) Mutants

Unintended shifts in stress resistance of microbial strains with engineered central metabolism may impact their growth and production performance under oxidative, lignocellulosic, solvent, and other stress conditions, and as such, must be taken into account in bioprocess design. In the present work, we studied oxidative stress resistance in mutant strains of the facultatively anaerobic, ethanologenic bacterium Zymomonas mobilis with modified respiratory (inactivated NADH dehydrogenase Ndh, by disruption of ndh) and ethanologenic (inactivated iron-containing alcohol dehydrogenase isoenzyme ADH II, by disruption of adhB) catabolism, using exogenously added H2O2 in the concentration range of 2–6 mM as the oxidative stressor. Both mutations improved H2O2 resistance and enhanced catalase activity by a factor of 2–5, while the overexpression of Ndh had an opposite effect. Strains with a catalase-negative background were unable to grow already at 1 mM hydrogen peroxide, and their H2O2 resistance did not depend on AdhB or Ndh expression levels. Hence, the improved resistance of the ndh and adhB mutants to H2O2 resulted from their elevated catalase activity. The interrelation between these mutations, the catabolic redox balance, catalase activity, and oxidative stress defense in Z. mobilis is discussed.

A randomized placebo-controlled clinical trial for pharmacological activation of BCAA catabolism in patients with type 2 diabetes

Elevations in plasma branched-chain amino acid (BCAA) levels associate with insulin resistance and type 2 diabetes (T2D). Pre-clinical models suggest that lowering BCAA levels improve glucose tolerance, but data in humans are lacking. Here, we used sodium phenylbutyrate (NaPB), an accelerator of BCAA catabolism, as tool to lower plasma BCAA levels in patients with T2D, and evaluate its effect on metabolic health. This trial (NetherlandsTrialRegister: NTR7426) had a randomized, placebo-controlled, double-blind cross-over design and was performed in the Maastricht University Medical Center (MUMC+), the Netherlands, between February 2019 and February 2020. Patients were eligible for the trial if they were 40–75years, BMI of 25–38 kg/m², relatively well-controlled T2D (HbA1C < 8.5%) and treated with oral glucose-lowering medication. Eighteen participants were randomly assigned to receive either NaPB 4.8 g/m²/day and placebo for 2 weeks via controlled randomization and sixteen participants completed the study. The primary outcome was peripheral insulin sensitivity. Secondary outcomes were ex vivo muscle mitochondrial oxidative capacity, substrate oxidation and ectopic fat accumulation. Fasting blood samples were collected to determine levels of BCAA, their catabolic intermediates, insulin, triglycerides, free fatty acids (FFA) and glucose. NaPB led to a robust 27% improvement in peripheral insulin sensitivity compared to placebo (ΔRd:13.2 ± 1.8 vs. 9.6 ± 1.8 µmol/kg/min, p = 0.02). This was paralleled by an improvement in pyruvate-driven muscle mitochondrial oxidative capacity and whole-body insulin-stimulated carbohydrate oxidation, and a reduction in plasma BCAA and glucose levels. No effects were observed on levels of insulin, triglycerides and FFA, neither did fat accumulation in muscle and liver change. No adverse events were reported. These data establish the proof-of-concept in humans that modulating the BCAA oxidative pathway may represent a potential treatment strategy for patients with T2D.