Substrate Utilization Research Articles

The whole‐body and skeletal muscle metabolic response to 14 days of highly controlled low energy availability in endurance‐trained females

AbstractThis study investigated the effects of 14 days low energy availability (LEA) versus optimal energy availability (OEA) in endurance‐trained females on substrate utilization, insulin sensitivity, and skeletal muscle mitochondrial oxidative capacity; and the impact of metabolic changes on exercise performance. Twelve endurance‐trained females (V̇O2max 55.2 ± 5.1 mL × min−1 × kg−1) completed two 14‐day randomized, blinded, cross‐over, controlled dietary interventions: (1) OEA (51.9 ± 2.0 kcal × kg fat‐free mass (FFM)−1 × day−1) and (2) LEA (22.3 ± 1.5 kcal × kg FFM−1 × day−1), followed by 3 days OEA. Participants maintained their exercise training volume during both interventions (approx. 8 h × week−1 at 79% heart rate max). Skeletal muscle mitochondrial respiratory capacity, glycogen, and maximal activity of CS, HAD, and PFK were unaltered with LEA. 20‐min time trial endurance performance was impaired by 7.8% (Δ −16.8 W, 95% CI: −23.3 to −10.4, p < .001) which persisted following 3 days refueling post‐LEA (p < .001). Fat utilization was increased post‐LEA as evidenced by: (1) 99.4% (p < .001) increase in resting plasma free fatty acids (FFA); (2) 270% (p = .007) larger reduction in FFA in response to acute exercise; and (3) 28.2% (p = .015) increase in resting fat oxidation which persisted during submaximal exercise (p < .001). These responses were reversed with 3 days refueling. Daily glucose control (via CGM), HOMA‐IR, HOMA‐β, were unaffected by LEA. Skeletal muscle O2 utilization and carbohydrate availability were not limiting factors for aerobic exercise capacity and performance; therefore, whether LEA per se affects aspects of training quality/recovery requires investigation.

Carbon preference by Cupriavidus necator for growth and accumulation phases: Heterotrophic vs. autotrophic metabolisms

Cupriavidus necator is a mixotrophic microbe capable of metabolizing both organic carbon (heterotrophic) and CO2 (autotrophic) for cell growth and biodegradable plastic synthesis. This study investigates C. necator's behavior under mixotrophic conditions for cell growth and polyhydroxyalkanoate (PHA) accumulation. Various concentrations of organic substrates (acetate and butyrate from 10 to 1000 mg/L) and gaseous substrates (H2, O2, CO2) were examined to monitor C. necator's substrate preferences. The results indicated a clear preference for organic carbon over CO2 during cell growth. At relatively low organic concentrations (10–100 mg/L), gas utilization began after complete consumption of organic substrates. On the other hand, higher concentrations (500–1000 mg/L) led to a shift from the heterotrophic to mixotrophic metabolism around the 10-h mark due to the abundance of substrates. During PHA accumulation, C. necator initially favored the gaseous substrates (H2 and CO2) before shifting to the organic substrates, with mixotrophic behavior observed immediately at low organic concentrations. Additionally, high CO2 partial pressure (>0.4 atm) inhibited microbial growth in both autotrophic and heterotrophic metabolisms. These findings highlight C. necator's adaptability under mixotrophic conditions and demonstrate the potential for mass-scale applications, such as microbial electrolysis cells to optimize biopolymer production and substrate utilization.

Microbial Cellulase Production: Current Technologies and Future Prospects

Enzymes are biocatalysts, that facilitate chemical reactions by lowering their activation energy. Among these, cellulase emerges as a significant enzyme, consisting of a triad of components that work in synergy to degrade cellulosic biomass. Its significance is mostly pronounced in agricultural contexts, where there is an abundance of lignocellulosic biomass making it pivotal for utilization and conversion of biomass. Utilizing the biomass as a substrate for cellulase production offers dual advantages. Firstly, it simplifies the enzymatic synthesis process by the utilization of naturally occurring precursors. Secondly, it contributes to cost reduction by leveraging readily available resources thereby making it economically viable. Microbial cellulases, sourced from diverse microbes found globally, can aid in efficient enzymatic production. Advances in fermentation processes, coupled with the application of biotechnological tools, have significant impacts in production scalability and cost-effectiveness. Optimizing production strategies is crucial to meet the increasing demands of industrial applications while ensuring sustainability. Emphasizing the utilization of biomass substrates and harnessing the potential of emerging biotechnological advancements are key aspects of enzyme production. This review shall aim to provide an in-depth exploration of current cellulase production technologies and future prospects. By elucidating the underlying principles of cellulase catalysis and the intricacies of production methodologies.

Comparative Ecotoxicity Assessment of highly bioactive Isomeric monoterpenes carvacrol and thymol on aquatic and edaphic indicators and communities

The growing demand for sustainable natural products to replace harmful synthetic ones requires comprehensive ecotoxicity assessments to ensure their eco-friendly nature. This study explored for the first time the changes in microbial community growth and metabolic profiles from river and natural soil samples exposed to the two structural isomers, thymol (THY) and carvacrol (CARV), utilizing Biolog EcoPlate™ assays and 16S rRNA gene sequencing for taxonomic analysis. In addition, we addressed existing ecotoxicity data gaps for these two compounds by using aquatic (Daphnia magna and Vibrio fischeri) and soil (Eisenia fetida and Allium cepa) indicators. Results show acute toxicity of both CARV and THY on all indicators. V. fischeri (LC50=0.59 mg/L) >D. magna (4.75 mg/L) >A. cepa (6.47 mg/L) for CARV, and V. fischeri (LC50=1.71 mg/L) >A. cepa (4.05 mg/L) >D. magna (8.13 mg/L) for THY. E. fetida showed LC50 = 7.68 mg/Kg for THY and 1.04 for CARV. River and soil microbial communities showed resilience, likely because they contain taxa capable of biodegrading these products. No significant growth inhibition effects were observed up to 100 mg/L, though substrate utilization decreased at higher concentrations, particularly for polymers and amines in soil microorganisms and polymers in aquatic communities. Soil microorganisms were more affected than aquatic ones, with CARV being more toxic than THY (EC50120h = THY 94.13 and CARV 29.79 mg/L in soil microorganisms). These findings suggest that an increase in the consumption of these products and their subsequent ecotoxicity effects from environmental discharge should still be monitored before being ruled out. However, long-term effects are unlikely due to microbial degradation of these natural products, potentially reducing risks to other target species and opening the way for their use as substitutes for commercial antibiotics.

Transcriptomics-guided rational engineering in Bacillus licheniformis for enhancing poly-γ-glutamic acid biosynthesis using untreated molasses

The utilization of non-food raw materials for microbial synthesis of poly-γ-glutamic acid (γ-PGA) presents a promising alternative to conventional food-based biosynthesis. However, the complex carbon source and composition of molasses, a prevalent non-food raw material, may impose constraints on its conversion and utilization by microorganisms. This study aimed to enhance the capacity of Bacillus licheniformis to convert untreated molasses into γ-PGA through transcriptomic analysis to guide metabolic modifications. Initial results from the transcriptomic analysis indicated that the strain utilizing molasses exhibited decreased expression of genes associated with substrate utilization (Module 1) and by-product synthesis (Module 2), while upregulating genes related to precursor synthesis (Module 3). Furthermore, we performed a knockout of the acetolactate synthase (AlsS) to reduce the synthesis of metabolic by-products and a knockout of the global regulator (CcpA) to alleviate carbon catabolite repression (CCR) and then promote substrate utilization. Ultimately, following the tandem overexpression of precursor supplying key genes, the titer of γ-PGA reached 48.26 g/L with a productivity of 1.15 g/L/h, using untreated molasses as the sole carbon source, which was 3.12-fold of the starting strain. These findings offer significant insights into the cost-effective synthesis of γ-PGA by bioconversion of untreated molasses during fermentation.

Aging delays the suppression of lipolysis and fatty acid oxidation in the postprandial period.

Plasma glycerol and free fatty acid concentrations decrease following oral glucose consumption, but changes in the rate of lipolysis during an oral glucose tolerance test (OGTT) have not been documented in conjunction with changes in fatty acid (FA) oxidation or reesterification rates in healthy individuals. After a 12-h overnight fast, 15 young (21-35 yr; 7 men and 8 women) and 14 older (60-80 yr; 7 men and 7 women) participants had the forearm vein catheterized for primed continuous infusion of [1,1,2,3,3-2H]glycerol. A contralateral hand vein was catheterized for arterialized blood sampling. Indirect calorimetry was performed simultaneously to determine total FA and carbohydrate (CHO) oxidation rates (Rox). Total FA reesterification rates (Rs) were estimated from tracer-measured lipolytic and FA oxidation rates. After a 90-min equilibration period, participants underwent a 120-min, 75-g OGTT. Glycerol rate of appearance (Ra), an index of lipolysis, decreased significantly from baseline 5 min postchallenge in young participants and 30 min in older participants. At 60 min, FA Rox decreased in both groups, but was significantly higher in older participants. Between 5 and 90 min, CHO Rox was significantly lower in older participants. In addition, FA Rs was significantly lower in older participants at 60 and 90 min. The area under the curve (AUC) for FA Rox was greater than that for FA Rs in older, but not in young participants. Our results indicate that, in aging, the postprandial suppression of lipolysis and FA oxidation are delayed such that FA oxidation is favored over CHO oxidation and FA reesterification.NEW & NOTEWORTHY To our knowledge, our investigation is the first to demonstrate changes in lipolysis during an oral glucose tolerance test (OGTT) in healthy young and older individuals. Plasma glycerol and free fatty acid concentrations changed after glycerol rate of appearance (Ra), indicating that plasma concentrations are incomplete surrogates of the lipolytic rate. Moreover, simultaneous determinations of substrate oxidation rates are interpreted to indicate that metabolic inflexibility in aging is characterized by delayed changes in postprandial substrate utilization related to the lipolytic rate.

Long-term effects of cycle time and volume exchange ratio on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) production from food waste digestate by Haloferax mediterranei cultivated in sequencing batch reactors for 450 days

Food wastedigestatewas fed into a sequencing batch reactor (SBR) forHaloferax mediterranei(HM) to produce poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). This SBR was operated uninterruptedly for 450 days to test its stability, during which the cycle time and volume exchange ratiowere varied to understand their impacts on the PHBV fermentation performance under ranged organic loading rates (OLR). Results showed that 1) PHBV productivity was proportional to OLR of food wastedigestate; 2) substrate and product inhibitions were two limiting factors constraining substrate utilization and PHBV yields; 3) PHBV titer was dependent on the hydraulic retention time of the SBR while a volume exchange ratio lower than 0.5 is unfavorable due to the product inhibitor accumulation. This study for the first time demonstrated that the long-term stability of food waste-fed PHBV production byHMand revealed that inhibition effects could be barriers in SBR limiting the full-scale application of the technology.

Antitumoral Activity and Metabolic Signatures of Dichloroacetate, 6-Aminonicotinamide and Etomoxir in Breast-Tumor-Educated Macrophages.

Pharmacological targeting of metabolic pathways represents an appealing strategy to selectively kill cancer cells while promoting antitumor functions of stromal cells. In this study, we assessed the effectiveness of 13 metabolic drugs (MDs) in steering in vitro generated breast tumor-educated macrophages (TEMs) toward an antitumoral phenotype. For that, the production of vascular endothelial growth factor (VEGF) and tumor necrosis factor α (TNF-α), two important regulators of tumor progression, was evaluated. Notably, dichloroacetate (DCA), 6-aminonicotinamide (6-AN), and etomoxir decreased VEGF production and enhanced TNF-α release. Hence, we further clarified their impact on TEM metabolism using an untargeted NMR-based metabolomics approach. DCA downregulated glycolysis and enhanced the utilization of extracellular substrates like lactate while reconfiguring lipid metabolism. Several DCA-induced changes significantly correlated with heightened TNF-α production in response to pro-inflammatory stimulation. The inhibition of the pentose phosphate pathway by 6-AN was accompanied by enhanced glutaminolysis, which correlated with a decreased level of VEGF production. In etomoxir-treated TEM, inhibition of fatty acid oxidation was compensated through upregulation of glycolysis, catabolism of intracellular amino acids, and consumption of extracellular branched chain alpha-ketoacids (BCKA) and citrate. Overall, our results offer a comprehensive view of the metabolic signature of each MD in breast TEM and highlight putative correlations with phenotypic effects.

Preclinical Multi-Omic Assessment of Pioglitazone in Skeletal Muscles of Mice Implanted with Human HER2/neu Overexpressing Breast Cancer Xenografts

Background/Objectives: Breast cancer (BC) is the second most commonly diagnosed cancer worldwide and is accompanied by fatigue during both active disease and remission in the majority of cases. Our lab has measured fatigue in isolated muscles from treatment-naive BC patient-derived orthotopic xenograft (BC-PDOX) mice. Here, we conducted a preclinical trial of pioglitazone in BC-PDOX mice to determine its efficacy in ameliorating BC-induced muscle fatigue, as well as its effects on transcriptomic, metabolomic, and lipidomic profiles in skeletal muscle. Methods: The pioglitazone and vehicle groups were treated orally for 4 weeks upon reaching a tumor volume of 600 mm3. Whole-animal indirect calorimetry was used to evaluate systemic metabolic states. The transcriptome was profiled using short-read bulk RNA sequencing (RNA-seq). Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to profile the metabolome and lipidome. Fast and slow skeletal muscle function were evaluated using isolated ex vivo testing. Results: Pioglitazone was associated with a 16.634% lower average O2 consumption (mL∙h−1, p = 0.035), 16.309% lower average CO2 production (mL∙h−1, p = 0.022), and 16.4% lower cumulative energy expenditure (EE) (kcal∙h−1, p = 0.035), with no changes in substrate utilization. RNA-seq supported the downstream effects of pioglitazone on target genes and displayed considerable upregulation of mitochondrial bioenergetic pathways. K-means cluster 5 showed enrichment of the PPAR signaling pathway (adj. p < 0.05, Log2FC = 2.58). Skeletal muscle metabolomic and lipidomic profiles exhibited dysregulation in response to BC, which was partially restored in pioglitazone-treated mice compared to vehicle-treated BC-PDOX mice. In particular, the overall abundance of total ceramide levels was significantly lower in the PioTx group (−46.327%, p = 0.048). Despite molecular support for pioglitazone’s efficacy, isolated muscle function was not affected by pioglitazone treatment. No significant difference in the area under the fatigue curve (AUC) was found between the pioglitazone and vehicle groups (p = 0.596). Conclusions: BC induces multi-omic dysregulation in skeletal muscle, which pioglitazone partially ameliorates. Future research should focus on profiling systemic metabolic dysfunction, identifying molecular biomarkers of fatigue, and testing alternative pioglitazone treatment regimens.

SGLT2 inhibitor empagliflozin prevents anthracycline-induced cardiotoxicity in a large-animal model

Abstract Background While the development of cancer therapies has significantly improved the survival of cancer patients, more than 35% of cancer survivors treated with anthracyclines will develop cardiotoxicity. There is currently a lack of preventative therapies against anthracycline-induced cardiotoxicity (AIC). AIC is characterised by a disruption in myocardial metabolism. Sodium-glucose co-transporter (SLGT2) inhibitors represent a potential therapy as they have been shown to modulate myocardial substrate utilisation in other heart-failure contexts. Purpose We developed a highly translational large-animal model to test the ability of SGLT2 inhibitor empagliflozin to prevent AIC at different doses. Methods Female Large-White pigs were randomised (2:1:1) to no treatment (AIC-control group) or empagliflozin at a daily oral dose of 10 mg or 20 mg, beginning at the start of the doxorubicin regimen and continuing to 21 weeks. All pigs received 6 doses of doxorubicin intravenous infusion (25 mg/m2/every 3 weeks) with 2 additional off-dose visits. Pigs were assessed by cardiac magnetic resonance (CMR) and MR spectroscopy (MRS) at baseline and every 3 weeks for 21 weeks. At the end of 21-week follow-up, the LV was collected and processed for analysis by transmission electron microscopy (TEM) and mitochondrial respirometry. Results The primary outcome, final LVEF, was significantly higher in pigs receiving 20 mg empagliflozin than in the AIC-control group (57.5% (IQR=55.5, 60.3) vs 47.0% (40.8, 47.8); p=0.027). Final LVEF in pigs receiving 10 mg empagliflozin was 51% (46.5, 55.5) (p=0.020 vs 20 mg empagliflozin). The 20 mg empagliflozin dose prevented the doxorubicin-induced change in cardiac metabolic substrate utilisation and was associated with preservation of myocardial energetics (ATP/PCr ratio on MRS). TEM revealed disrupted mitochondrial structure and cristae density in AIC-control pigs, while mitochondria respirometry detected deteriorated respiratory function. Both mitochondrial structure and function were preserved in empagliflozin-treated pigs, with the 20 mg dose having the strongest cardioprotective effect. Conclusion The results from our translational large-animal model provide strong evidence that SGLT2 inhibition with empagliflozin prevents AIC by preserving LV systolic function and energetics as well as mitochondrial structural integrity and function. Our results establish the basis for clinical trial testing SGLT2i therapy in patients at high risk of AIC.

Krill oil supplementation in vivo promotes increased fuel metabolism and protein synthesis in cultured human skeletal muscle cells

IntroductionKrill oil is a dietary supplement derived from Antarctic krill; a small crustacean found in the ocean. Krill oil is a rich source of omega-3 fatty acids, specifically eicosapentaenoic acid and docosahexaenoic acid, as well as the antioxidant astaxanthin. The aim of this study was to investigate the effects of krill oil supplementation, compared to placebo oil (high oleic sunflower oil added astaxanthin), in vivo on energy metabolism and substrate turnover in human skeletal muscle cells.MethodsSkeletal muscle cells (myotubes) were obtained before and after a 7-week krill oil or placebo oil intervention, and glucose and oleic acid metabolism and leucine accumulation, as well as effects of different stimuli in vitro, were studied in the myotubes. The functional data were combined with proteomic and transcriptomic analyses.ResultsIn vivo intervention with krill oil increased oleic acid oxidation and leucine accumulation in skeletal muscle cells, however no effects were observed on glucose metabolism. The krill oil-intervention-induced increase in oleic acid oxidation correlated negatively with changes in serum low-density lipoprotein (LDL) concentration. In addition, myotubes were also exposed to krill oil in vitro. The in vitro study revealed that 24 h of krill oil treatment increased both glucose and oleic acid metabolism in myotubes, enhancing energy substrate utilization. Transcriptomic analysis comparing myotubes obtained before and after krill oil supplementation identified differentially expressed genes associated with e.g., glycolysis/gluconeogenesis, metabolic pathways and calcium signaling pathway, while proteomic analysis demonstrated upregulation of e.g., LDL-receptor in myotubes obtained after the krill oil intervention.ConclusionThese findings suggest that krill oil intervention promotes increased fuel metabolism and protein synthesis in human skeletal muscle cells, with potential implications for metabolic health.

Soil viral–host interactions regulate microplastic-dependent carbon storage

Microplastic is globally regarded as an important factor impacting biogeochemical cycles, yet our understanding of such influences is limited by the uncertainties of intricate microbial processes. By multiomics analysis, coupled with soil chemodiversity characterization and microbial carbon use efficiency (CUE), we investigated how microbial responses to microplastics impacted soil carbon cycling in a long-term field experiment. We showed that biodegradable microplastics promoted soil organic carbon accrual by an average of 2.47%, while nondegradable microplastics inhibited it by 17.4%, as a consequence of the virus-bacteria coadaptations to the microplastics disturbance. In the relevant functional pathways, nondegradable microplastics significantly (P < 0.05) enhanced the abundance and transcriptional activity related to complex carbohydrate metabolism, whereas biodegradable microplastics significantly (P < 0.05) promoted functions involved in amino acid metabolism and glycolysis. Accordingly, viral lysis enhanced in nondegradable microplastics treatments to introduce more complex organic compounds to soil dissolved organic matters, thus benefiting the oligotrophs with high carbon metabolic capabilities in exploitation competition. In contrast, biodegradable microplastics enriched viral auxiliary metabolic genes of carbon metabolism through "piggyback-the-winner" strategy, conferring to dominant copiotrophs, enhanced substrate utilization capabilities. These virus-host interactions were also demonstrated in the corresponding soil plastisphere, which would alter microbial resource allocation and metabolism via CUE, affecting carbon storage consequently. Overall, our results underscore the importance of viral-host interactions in understanding the microplastics-dependent carbon storage in the soil ecosystem.

Bacterial functional responses to environmental variability: a case study in three distinct mountain lakes within a single watershed

The utilization of carbon substrates (CSs) is crucial for the functioning of heterotrophic bacterial communities and aquatic ecosystems. This study used the Biolog EcoplateTM technique to explore spatial and temporal community-level physiological profiles (CLPPs) of bacteria in three eutrophic-dystrophic mountain lakes in Bulgaria. Bacterial metabolic activity varied among the lakes, being highest in the lake dominated by phytoplankton and lowest in the lake dominated by macrophyte primary producers. CLPP highlighted specific bacterial metabolic preferences to certain carbon guilds (CGs), showing a higher affinity for carbohydrates and polymers and lower preferences for amino acids and amines. The overall metabolic dissimilarity among the lakes was approximately 32%, primarily driven by the CGs of amino acids and amines. The most preferred CSs included the carbohydrates D-Mannitol and N-Acetyl-D-glucosamine, and the carboxylic acid D-Galacturonic acid. Bacterial functional diversity was high (H′: 3.18 − 3.33) due to the high evenness of CS utilization. Multidimensional analyses revealed significant influences of lake-specific characteristics, sampling month, and the interaction between these factors on CLPP patterns. Nutrients and water temperature were identified as the most influential environmental factors affecting bacterial communities. This study enhances our understanding of bacterial functional responses to changing environments, demonstrating the effectiveness of the Biolog EcoplateTM technique in providing insights into these changes.

Engineering a high-sugar tolerant strain of Saccharomyces cerevisiae for efficient trehalose production using a cell surface display approach

Trehalose production via a one-step enzymatic route using trehalose synthase (TreS) holds significant promise for industrial-scale applications due to its simplicity and utilization of low-cost substrates. However, the development of a robust whole-cell biocatalyst expressing TreS remains crucial for enabling practical and economically viable production. In this study, a high-sugar tolerant strain of S. cerevisiae was screened and employed as a host cell for the cell surface display of TreS from Acidiplasma aeolicum. The resultant strain, S. cerevisiae I3A, exhibited remarkable surface displayed TreS activity of 3358 U/g CDW and achieved approximately 64% trehalose yield (10.8 g/L/h productivity) from maltose. Interestingly, no glucose by-product was observed during trehalose production. The S. cerevisiae I3A cells exhibited reusability for up to 12 cycles leading to potential cost reduction of trehalose products. Therefore, our study demonstrated the development of a high-sugar tolerant S. cerevisiae strain expressing TreS on its surface as a whole-cell biocatalyst for efficient and economical trehalose production with potential applications in the food and pharmaceutical industries.

Greater Excess Post-Exercise Oxygen Consumption and Fat Use Following Calisthenics vs. Oxygen Consumption Matched Steady-State Exercise

ABSTRACT Calisthenics is a form of bodyweight exercise that involves dynamic and rhythmic exercises. The physiological responses during and after calisthenics remain unclear. This study examined whether a bout of full-body calisthenics, a form of circuit resistance exercise that involves bodyweight movements, yields greater excess post-exercise oxygen consumption (EPOC) than steady-state exercise (SSE) at matched oxygen consumption. Twenty-two young adults (age = 22.1 ± 2.4 years; four females) participated in two separate, oxygen consumption ( V ˙ O2) matched exercise sessions: full-body calisthenics (nine body weight exercises, 15 reps × 4 sets) and SSE (running on a treadmill at 60–90% of V ˙ O2max). Energy expenditure, substrate utilization, and EPOC were measured during exercise and 60 min of recovery. SSE showed higher peak V ˙ O2 and heart rate during exercise than those during calisthenics. However, the post-exercise V ˙ O2 and energy expenditure above baseline level during the first 10 min of recovery were significantly higher with calisthenics than with SSE (0–5 min: 1.7 ± 0.5 vs. 1.0 ± 0.6; 6–10 min: 0.5 ± 0.4 vs. 0.1 ± 0.2 kcal/min; 31–60 min recovery: −0.1 ± 0.3 vs. −0.2 ± 0.2; all p < .05). During calisthenics, participants utilized a significantly higher proportion of energy from carbohydrates (85 vs. 73%; p < .01) but after exercise, they used a greater proportion of fat as the energy source (71 vs. 50%; p < .01) compared to SSE. Full-body calisthenics, a circuit-style bodyweight exercise, may be more effective than V ˙ O2 matched SSE in triggering greater EPOC and fat metabolism. Further efforts are warranted to demonstrate whether different amounts of skeletal muscle mass groups indeed lead to varying EPOC responses and energy use.

Multifaceted Impact of SGLT2 Inhibitors in Heart Failure Patients: Exploring Diverse Mechanisms of Action.

Heart failure (HF) is a growing concern due to the aging population and increasing prevalence of comorbidities. Despite advances in treatment, HF remains a significant burden, necessitating novel therapeutic approaches. Sodium-glucose cotransporter 2 inhibitors (SGLT2is) have emerged as a promising treatment option, demonstrating benefits across the entire spectrum of HF, regardless of left ventricular ejection fraction (LVEF). This review explores the multifaceted mechanisms through which SGLT2is exert cardioprotective effects, including modulation of energy metabolism, reduction of oxidative stress, attenuation of inflammation, and promotion of autophagy. SGLT2is shift myocardial energy substrate utilization from carbohydrates to more efficient fatty acids and ketone bodies, enhancing mitochondrial function and reducing insulin resistance. These inhibitors also mitigate oxidative stress by improving mitochondrial biogenesis, reducing reactive oxygen species (ROS) production, and regulating calcium-signaling pathways. Inflammation, a key driver of HF progression, is alleviated through the suppression of proinflammatory cytokines and modulation of immune cell activity. Additionally, SGLT2is promote autophagy, facilitating the clearance of damaged cellular components and preserving myocardial structure and function. Beyond their glucose-lowering effects, SGLT2is provide significant benefits in patients with chronic kidney disease (CKD) and HF, reducing the progression of CKD and improving overall survival. The pleiotropic actions of SGLT2is highlight their potential as a cornerstone in HF management. Further research is needed to fully elucidate their mechanisms and optimize their use in clinical practice.

No evidence of improvements in energy metabolism after 1week of nitrate and citrulline co-supplementation in elite rowers.

Citrulline (CIT) and beetroot extract (BR) supplements positively impacts exercise performance in elite rowers. However, its influence on metabolic outcomes such as whole-body volumes of oxygen consumption (VO2) and carbon dioxide production (VCO2), substrate oxidation, energy expenditure (EE), and gross efficiency remains unknown. We studied the effects of 1week of daily co-supplementation of 3.5g BR (500mg NO3-) plus 6g CIT on VO2 and VCO2 kinetics, substrate utilization, EE, and gross efficiency in elite male rowers compared to a placebo and to a BR supplementation. Twenty elite rowers participated in this randomized, double-blind, placebo-controlled crossover trial completing 1week of supplementation in each group of study: Placebo (PLAG); BRG; and BR-CITG. Efficiency (70% VO2max) and performance (incremental maximal) tests were performed, and gas-exchange data were collected via indirect calorimetry. Analysis of covariance (ANCOVA) showed no mean between-condition differences on respiratory exchange ratio (RER), EE, and gross efficiency in the efficiency test (all P > 0.06), and in the performance test (all P > 0.28). Moreover, in both tests no interaction Time × Supplement effects were observed for VO2, VCO2, RER, EE, substrate oxidation, and, gross efficiency (all P > 0.12). After 1week, no effects on energy metabolism and substrate utilization were observed after the daily co-ingestion of BR extract plus CIT supplement, therefore longer (> 7days) and higher doses of supplementation might be needed to influence metabolism.

Are Changes Occurring in Bacterial Taxa Community and Diversity with the Utilization of Different Substrates within SIR Measurements?

This research explores how the availability of substrates affects the regulation of soil microbial communities and the taxonomical composition of bacteria. The goal is to understand the impact of organic matter and substrate availability and quality on the diversity of soil bacteria. The study observed gradual changes in bacterial diversity in response to the addition of different substrate-induced respiration (SIR) substrates. Understanding the structure, dynamics, and functions of soil microbial communities is essential for assessing soil quality in sustainable agriculture. The preference for carbon sources among bacterial phyla is largely influenced by their life history and trophic strategies. Bacterial phyla like Proteobacteria, Bacteroidetes, and Actinobacteria, which thrive in nutrient-rich environments, preferentially utilize glucose. On the other hand, oligotrophic bacterial phyla such as Acidobacteria or Chloroflexi, which are found in lower numbers, have a lower ability to utilize labile C. The main difference between the two lies in their substrate utilization strategies. Understanding these distinct strategies is crucial for uncovering the bacterial functional traits involved in soil organic carbon turnover. Additionally, adding organic matter can promote the growth of copiotrophic bacteria, thus enhancing soil fertility.

Biohydrogen production from lignocellulosic hydrolysate: Unveiling the synergistic impact of substrate concentration and furfural inhibition.

Lignocellulosic biomass offers substantial potential as an ideal feedstock for dark fermentative hydrogen production due to its sustainability and cost-effectiveness. The current study examined the influence of furfural on fermentative hydrogen production using lignocellulosic hydrolysate in the presence of furfural. Synthetic lignocellulosic hydrolysate, consisting primarily of 76% xylose, 10% glucose, 9% arabinose, and a mixture of other sugars such as galactose and mannose (85% pentose sugars and 15% hexose sugars), was employed as the substrate. Various substrate concentrations ranging from 2 to 32g/L were tested, along with furfural concentrations of 0, 1, and 2g/L. The investigation aimed to assess the effects of initial substrate concentration, initial furfural concentration, furfural-to-biomass ratio (F/B), and furfural-to-substrate ratio (F/S) on biohydrogen production yields. The maximum specific substrate utilization rates at different substrate concentrations were effectively characterized using Haldane's substrate inhibition model. Among the tested concentrations, the 16g/L emerged as the optimal substrate concentration. The initial furfural concentration was identified as the most significant parameter impacting biohydrogen production, with complete inhibition observed at a furfural concentration of 2g/L. Higher F/S ratios at substrate concentrations ranging from 2 to 16g/L resulted in reduced maximum specific hydrogen production rates (MSHPR) and hydrogen yields. Substrate inhibition was observed at 24g/L and 32g/L. Lactate was the predominant metabolite in all batches containing 2-g/L furfural, as well as in batches with 1-g/L furfural and substrate concentrations of 24 and 32g/L. Furfural at a concentration of 1g/L was not inhibitory in any of the batches. Overall, the mixed cultures in this study could efficiently produce hydrogen from lignocellulosic hydrolysates and degrade furfural, providing new insights into fermentative hydrogen-producing bacteria with furfural tolerance.

Comprehensive stable-isotope tracing of glucose and amino acids identifies metabolic by-products and their sources in CHO cell culture

Mammalian cell culture processes are widely utilized for biotherapeutics production, disease diagnostics, and biosensors, and hence, should be optimized to support robust cell growth and viability. However, toxic by-products accumulate in cultures due to inefficiencies in metabolic activities and nutrient utilization. In this study, we applied comprehensive 13C stable-isotope tracing of amino acids and glucose to two Immunoglobulin G (IgG) producing Chinese Hamster Ovary (CHO) cell lines to identify secreted by-products and trace their origins. CHO cells were cultured in media formulations missing a single amino acid or glucose supplemented with a 13C-tracer of the missing substrate, followed by gas chromatography-mass spectrometry (GC-MS) analysis to track labeled carbon flows and identify by-products. We tracked the sources of all secreted by-products and verified the identity of 45 by-products, majority of which were derived from glucose, leucine, isoleucine, valine, tyrosine, tryptophan, methionine, and phenylalanine. In addition to by-products identified previously, we identified several metabolites including 2-hydroxyisovaleric acid, 2-aminobutyric acid, L-alloisoleucine, ketoisoleucine, 2-hydroxy-3-methylvaleric acid, desmeninol, and 2-aminobutyric acid. When added to CHO cell cultures at different concentrations, certain metabolites inhibited cell growth while others including 2-hydroxy acids, surprisingly, reduced lactate accumulation. In vitro enzymatic analysis indicated that 2-hydroxy acids were metabolized by lactate dehydrogenase suggesting a possible mechanism for lowered lactate accumulation, e.g., competitive substrate inhibition. The 13C-labeling assisted metabolomics pipeline developed and the metabolites identified will serve as a springboard to reduce undesirable by-products accumulation and alleviate inefficient substrate utilization in mammalian cultures used for biomanufacturing and other applications through altered media formulations and pathway engineering strategies.