Phosphofructokinase Activity Research Articles

Muscle fiber type and metabolic profiles of four muscles from the African black ostrich

Muscle fiber type, fiber cross-sectional area (CSA), enzyme activities (citrate synthase (CS), 3-hydroxyacetyl Co A dehydrogenase (3HAD), lactate dehydrogenase (LDH) and phosphofructokinase (PFK)) and glycogen content were analyzed in the M. iliotibialis cranialis (ITC), M. iliotibialis lateralis, M. gastrocnemius (G) and M. fibularis longus (FL) muscles from 24 ostriches. Type I and II fiber proportions were similar across the 4 muscles, but the ITC had overall the smallest fibers. CS activity was the highest in the ITC, but similar between the remainder of the muscles. 3HAD activities were very low in all muscles, ranging between 1.9 and 2.7 μmol/min/g protein, indicating poor β-oxidation. The ITC also had the lowest PFK activity. Glycogen content averaged ∼85 mmol/kg dry weight across the muscles with large intramuscular variations. The 4 ostrich muscles present with low fat oxidation capacity and low glycogen content, which could have significant implications on meat quality attributes.

Carbohydrate Utilization and Digestibility by Tilapia, Oreochromis niloticus × O. aureus, Are Affected by Chromic Oxide Inclusion in the Diet

A 12-wk feeding trial was conducted to study the influence of chromic oxide (Cr2O3) on carbohydrate utilization and digestibility by tilapia, Oreochromis niloticus × O. aureus. Two levels of chromic oxide (0.5 and 2%) were each incorporated into diets containing glucose or starch. Chromic oxide was added at 0 or 8 wk. The diets were fed to triplicate groups of fish weighing 1.11 ± 0.05 g. Fish fed the starch diet had greater (P < 0.05) weight gain, feed efficiency ratio, protein efficiency ratio, protein deposition and digestibility of protein, lipid, carbohydrate and dry matter than fish fed the glucose diet irrespective of the time and level of chromic oxide supplementation. Fish fed the glucose diet with 0.5% chromic oxide had higher weight gain, feed efficiency ratio, protein efficiency ratio and protein deposition than fish fed the glucose diet with 2% chromic oxide. The ingredient digestibility estimated using 0.5% chromic oxide as the marker was greater than that estimated with 2% chromic oxide. Higher phosphofructokinase and lower glucose-6-phosphatase activity was found in fish fed the starch diet than in fish fed the glucose diet regardless of the time and level of chromic oxide inclusion. Fish fed the glucose diet with 0.5% chromic oxide had higher phosphofructokinase activity and lower tissue chromium concentration than fish fed the glucose diet with 2% chromic oxide irrespective of chromic oxide inclusion time. These data suggest that the level of chromic oxide in the diet alters glucose utilization by tilapia and affects nutrient digestibility by tilapia. The time of chromic oxide inclusion had no effect on carbohydrate utilization and digestibility.

Metabolic insights into phosphofructokinase inhibition in bloodstream-form trypanosomes.

Previously, we reported the development of novel small molecules that are potent inhibitors of the glycolytic enzyme phosphofructokinase (PFK) of Trypanosoma brucei and related protists responsible for serious diseases in humans and domestic animals. Cultured bloodstream-form trypanosomes, which are fully reliant on glycolysis for their ATP production, are rapidly killed at submicromolar concentrations of these compounds, which have no effect on the activity of human PFKs and human cells. Single-day oral dosing cures stage 1 human trypanosomiasis in an animal model. Here we analyze changes in the metabolome of cultured trypanosomes during the first hour after addition of a selected PFK inhibitor, CTCB405. The ATP level of T. brucei drops quickly followed by a partial increase. Already within the first five minutes after dosing, an increase is observed in the amount of fructose 6-phosphate, the metabolite just upstream of the PFK reaction, while intracellular levels of the downstream glycolytic metabolites phosphoenolpyruvate and pyruvate show an increase and decrease, respectively. Intriguingly, a decrease in the level of O-acetylcarnitine and an increase in the amount of L-carnitine were observed. Likely explanations for these metabolomic changes are provided based on existing knowledge of the trypanosome's compartmentalized metabolic network and kinetic properties of its enzymes. Other major changes in the metabolome concerned glycerophospholipids, however, there was no consistent pattern of increase or decrease upon treatment. CTCB405 treatment caused less prominent changes in the metabolome of bloodstream-form Trypanosoma congolense, a ruminant parasite. This agrees with the fact that it has a more elaborate glucose catabolic network with a considerably lower glucose consumption rate than bloodstream-form T. brucei.

Hydrogen sulfide alleviates chilling injury by modulating respiration and energy metabolisms in cold-stored peach fruit

The respiration and energy metabolisms of refrigerated peach fruit and their relationship to chilling injury (CI) treated with hydrogen sulfide (H2S) were investigated. Results showed that H2S treatment reduced the activities of hexokinase (HK), phosphor-glucose isomerase (PGI), phosphofructokinase (PFK) and pyruvate kinase (PK), and the contents of glucose, pyruvate and nicotinamide adenine dinucleotide (hydrogen) (NAD(H)) in the Embden-Meyerhof-Parnas (EMP) and tricarboxylic acid (TCA)-cycle compared to control and hypotaurine (HT, H2S scavenger) treatment, resulting in a lower respiration rate. Meanwhile, H2S treatment increased the activities of NADK, glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) and NADP(H) contents in the pentose phosphate pathway (PPP), while HT showed the opposite results. Moreover, H2S treatment induced the higher activities of adenosine triphosphatases (ATPases), succinic dehydrogenase (SDH) and cytochrome C oxidase (CCO) along with enhanced levels of ATP and energy charge, whereas HT suppressed energy generation, which increased cell membrane permeability and malondialdehyde content. Therefore, results suggested that H2S could maintain the integrity of the membrane structure by inhibiting the respiration and substance consumption in EMP pathway, increasing the proportion of PPP and energy supply to alleviate CI in peaches.

Changes in gene expression and enzyme activity related to glucose metabolism in the livers of Brandt's voles (Lasiopodomys brandtii) exposed to hypoxia

Brandt's vole (Lasiopodomys brandtii) is a hypoxia-tolerant species, and the metabolic characteristics of hypoxia-tolerant species have become a focus of recent research. However, insights into the anaerobic and aerobic metabolism of the livers of Brandt's voles under hypoxia remain limited. In this study, Brandt's voles and hypoxia-intolerant Kunming mice (Mus musculus, control species) were exposed to hypoxia conditions (Brandt's voles, 10% and 7.5% O2; Kunming mice, 10% O2) for 24 h, and changes in gene expression and enzyme activity related to anaerobic and aerobic metabolism in the livers were evaluated. Phosphofructokinase 1 (PFK1), phosphofructokinase 2 (PFK2), pyruvate kinase muscle (PKM), hexokinase 2 (HK2), and lactate dehydrogenase (LDH) related to anaerobic metabolism in the livers of Brandt's voles were increased under 7.5% O2. Regarding gene expression and enzyme activity for aerobic metabolism in Brandt's voles under 7.5% and 10% O2, pyruvate dehydrogenase kinase 1 (PDK1) expression was up-regulated, and succinate dehydrogenase (SDH) activity was decreased. In the livers of Kunming mice, gene expression related to anaerobic and aerobic metabolism was increased at the late stage of 10% O2, and SDH activity was enhanced at 6 h and reduced at 18 h. In addition, PFK1,PKM, PDK1 expression and SDH activity in Brandt's voles were significantly correlated with HIF-1a expression. PFK1, PKM, LDHand PDK1 expression in Kunming mice were significantly correlated with HIF-1a expression. These findings indicate that the livers of Brandt's voles have a certain tolerance to hypoxia, and metabolic changes play important roles in hypoxia tolerance.

RNAi screening reveals a synthetic chemical-genetic interaction between ATP synthase and PFK1 in cancer cells.

To meet cellular bioenergetic and biosynthetic demands, cancer cells remodel their metabolism to increase glycolytic flux, a phenomenon known as the Warburg effect and believed to contribute to cancer malignancy. Among glycolytic enzymes, phosphofructokinase-1 (PFK1) has been shown to act as a rate-limiting enzyme and to facilitate the Warburg effect in cancer cells. In this study, however, we found that decreased PFK1 activity did not affect cell survival or proliferation in cancer cells. This raised a question regarding the importance of PFK1 in malignancy. To gain insights into the role of PFK1 in cancer metabolism and the possibility of adopting it as a novel anticancer therapeutic target, we screened for genes that caused lethality when they were knocked down in the presence of tryptolinamide (TLAM), a PFK1 inhibitor. The screen revealed a synthetic chemical-genetic interaction between genes encoding subunits of ATP synthase (complex V) and TLAM. Indeed, after TLAM treatment, the sensitivity of HeLa cells to oligomycin A (OMA), an ATP synthase inhibitor, was 13,000 times higher than that of untreated cells. Furthermore, this sensitivity potentiation by TLAM treatment was recapitulated by genetic mutations of PFK1. By contrast, TLAM did not potentiate the sensitivity of normal fibroblast cell lines to OMA, possibly due to their reduced energy demands compared to cancer cells. We also showed that the PFK1-mediated glycolytic pathway can act as an energy reservoir. Selective potentiation of the efficacy of ATP synthase inhibitors by PFK1 inhibition may serve as a foundation for novel anticancer therapeutic strategies.

Effects of soil drought on cottonseed kernel carbohydrate metabolism and kernel biomass accumulation

Cottonseed is the main coproduct of cotton production. The carbohydrate metabolism provides carbon substrate for the accumulation of cottonseed kernel biomass which was the basis of cottonseed kernel development. However, the responses of drought stress on carbohydrate metabolism in kernels are still unclear. To address this, two cotton cultivars (Dexiamian 1 and Yuzaomian 9110) were cultivated under three water treatments including soil relative water content (SRWC) at (75 ± 5)% (control), (60 ± 5)% (mild drought) and (45 ± 5)% (severe drought) to investigate the effects of soil drought on cottonseed kernel carbohydrate metabolism and kernel biomass accumulation. Results suggested that drought restrained the accumulation of cottonseed kernel biomass which eventually decreased cottonseed kernel biomass at maturity. In detail, the down-regulation of sucrose phosphate synthase (SPS) activity led to the inhibition of sucrose synthesis, while the up-regulation of invertase (INV) promoted the sucrose decomposite, which reduced the sucrose content eventually under drought. Though hexose content was increased, phosphoenolpyruvic acid (PEP) content was decreased under drought by downregulating 6-phosphofructokinase (PFK) and pyruvate kinase (PK) activities, which hindered the conversion of hexose to PEP. The large decrease of sucrose and PEP contents hindered the accumulation of kernel biomass. The related substances contents and enzyme activities in carbohydrate metabolism of Yuzaomian 9110 were more susceptible to drought stress than Dexiamian 1.

Alpha-ketoglutarate partially alleviates effects of high-fat high-fructose diet in mouse muscle.

Consumption of high-calorie diets leads to excessive accumulation of storage lipids in adipose tissue. Metabolic changes occur not only in adipose tissue but in other tissues, too, such as liver, heart, muscle, and brain. This study aimed to explore the effects of high-fat high-fructose diet (HFFD) alone and in the combination with alpha-ketoglutarate (AKG), a well-known cellular metabolite, on energy metabolism in the skeletal muscle of C57BL/6J mice. Five-month-old male mice were divided into four groups - the control one fed a standard diet (10 % kcal fat), HFFD group fed a high-fat high-fructose diet (45 % kcal fat, 15 % kcal fructose), AKG group fed a standard diet with 1 % sodium AKG in drinking water, and HFFD + AKG group fed HFFD and water with 1 % sodium AKG. The dietary regimens lasted 8 weeks. Mice fed HFFD had higher levels of storage triacylglycerides, lower levels of glycogen, and total water-soluble protein, and higher activities of key glycolytic enzymes, namely hexokinase, phosphofructokinase, and pyruvate kinase, as compared with the control group. The results suggest that muscles of HFFD mice may suffer from lipotoxicity. In HFFD + AKG mice, levels of the metabolites and activities of glycolytic enzymes did not differ from the respective values in the control group, except for the activity of pyruvate kinase, which was significantly lower in HFFD + AKG group compared with the control. Thus, metabolic changes in mouse skeletal muscles, caused by HFFD, were alleviated by AKG, indicating a protective role of AKG regarding lipotoxicity.

Transcriptomics-based Analysis of the Response of Sugar Content in Litchi Pulp to Foliar Calcium Fertilizer Treatment

Ten 16-year-old trees were used as test materials to investigate the effect of foliar calcium fertilizer on the sugar content of ‘Feizixiao’ litchi (Litchi chinensis Sonn.) pulp. The experiment began 35 days after anthesis (DAA) in 2020 and 2021, and the treatment was a foliar spray application of 0.3% CaCl2 aqueous solution, whereas the control was a foliar spray application of water. The sugar content, sucrose-metabolizing enzymes, and ATP-dependent phosphofructokinase (PFK) activities in pulp were measured in 2020 and 2021. Transcriptome sequencing (RNA-seq) was performed on RNA samples from treatment and control fruit pulps at 35, 63, and 69 DAA (full mature stage) in 2020, and 10 genes were chosen for confirmation by real-time polymerase chain reaction (PCR) in 2020 and 2021. At full maturity, the soluble sugar content in the calcium-treated group was extremely significantly or significantly higher than that in the control group. After 63 DAA, the net sucrose-metabolizing enzyme activity in the calcium-treated group was significantly higher than that in the control group. Furthermore, at full maturity, the calcium-treated group had significantly higher sucrose synthase cleavage activity and significantly lower PFK activity than the control group. Fifty-four highly expressed genes in the glycolytic pathway (EMP) were screened from transcriptome data, including hexokinase, PFK, and pyruvate kinase genes; 87% of these genes were downregulated in the treatment group compared with the control group at 69 DAA in 2020. The linear regression between RNA-seq and real-time PCR results was significant in 2020 (r = 0.9292) and 2021 (r = 0.8889). When the fruit is fully ripe, calcium treatment increases net sucrose-metabolizing enzyme activity by increasing sucrose synthase cleavage activity, promoting the accumulation of reducing sugars, and it downregulates phosphofructokinase gene expression in EMP, promoting sugar accumulation.

Effects of Dietary Carbohydrate Sources on Growth Performance, Glucose Metabolism, and Digestive Enzyme Activity of Litopenaeus vannamei

This study evaluated the effects of different sources of dietary carbohydrates on the growth, antioxidant capacity, and digestive enzyme activity, and carbohydrate metabolic enzyme activity of Litopenaeus vannamei were evaluated. The experimental diets, including glucose, sucrose, potato starch, corn starch, and wheat starch, were fed to L. vannamei for 35 days. We found that shrimp fed on corn starch and wheat starch grew better, whereas shrimp fed on wheat starch showed the highest digestive enzyme activity. In addition, the starch group showed higher total superoxide dismutase (T-SOD) activity and lower malondialdehyde (MDA) content. The glucose, sucrose, starch, and corn starch fed shrimp showed significantly higher levels of hepatopancreatic hexokinase (HK), whereas those fed on glucose and potato starch also showed significantly higher levels of hepatopancreatic phosphofructokinase (PFK) activity. The activities of phosphoenolpyruvate carboxykinase (PEPCK) and glucose 6-phosphatase (G6Pase) were higher in shrimp fed on glucose, whereas higher fructose 1,6-bisphosphatase (FBPase) activity was observed in shrimp fed on wheat starch, glucose, and sucrose. The insulin content of shrimp in the glucose group and potato starch group was higher, whereas that of the glucose group was higher than that of the potato starch group. In brief, the addition of wheat starch to the diet plays a positive role in the growth, glycolysis, gluconeogenesis, and antioxidant activity of shrimp, and is a promising choice for juvenile shrimp culture.

Specificity Protein 1-Mediated Promotion of CXCL12 Advances Endothelial Cell Metabolism and Proliferation in Pulmonary Hypertension.

Pulmonary arterial hypertension (PAH) is a rare yet devastating and incurable disease with few treatment options. The underlying mechanisms of PAH appear to involve substantial cellular proliferation and vascular remodeling, causing right ventricular overload and eventual heart failure. Recent evidence suggests a significant seminal role of the pulmonary endothelium in the initiation and promotion of PAH. Our previous work identified elevated reactive oxygen species (ROS)-producing enzyme NADPH oxidase 1 (NOX1) in human pulmonary artery endothelial cells (HPAECs) of PAH patients promoting endothelial cell proliferation in vitro. In this study, we interrogated chemokine CXCL12's (aka SDF-1) role in EC proliferation under the control of NOX1 and specificity protein 1 (Sp1). We report here that NOX1 can drive hypoxia-induced endothelial CXCL12 expression via the transcription factor Sp1 leading to HPAEC proliferation and migration. Indeed, NOX1 drove hypoxia-induced Sp1 activation, along with an increased capacity of Sp1 to bind cognate promoter regions in the CXCL12 promoter. Sp1 activation induced elevated expression of CXCL12 in hypoxic HPAECs, supporting downstream induction of expression at the CXCL12 promoter via NOX1 activity. Pathological levels of CXCL12 mimicking those reported in human PAH patient serum restored EC proliferation impeded by specific NOX1 inhibitor. The translational relevance of our findings is highlighted by elevated NOX1 activity, Sp1 activation, and CXCL12 expression in explanted lung samples from PAH patients compared to non-PAH controls. Analysis of phosphofructokinase, glucose-6-phosphate dehydrogenase, and glutaminase activity revealed that CXCL12 induces glutamine and glucose metabolism, which are foundational to EC cell proliferation. Indeed, in explanted human PAH lungs, demonstrably higher glutaminase activity was detected compared to healthy controls. Finally, infusion of recombinant CXCL12 into healthy mice amplified pulmonary arterial pressure, right ventricle remodeling, and elevated glucose and glutamine metabolism. Together these data suggest a central role for a novel NOX1-Sp1-CXCL12 pathway in mediating PAH phenotype in the lung endothelium.

Transcriptomics-based analysis of the causes of sugar receding in Feizixiao litchi (Litchi chinensis Sonn.) pulp.

To investigate the causes of the "sugar receding" in 'Feizixiao' litchi (Litchi chinensis Sonn.) pulp, the main sugar contents and sucrose metabolism enzyme activities were measured in pulp obtained in 2020 and 2021. Pulp RNA obtained in 2020 was extracted at 35, 63, and 69 days after anthesis (DAA) for transcriptome sequencing analysis. The differential expression of genes was verified by real-time PCR for both years. The results showed that after 63 DAA, the contents of soluble sugars and sucrose decreased, and the contents of fructose and glucose increased in both years. The dynamic changes in sucrose metabolism enzyme activities were similar in both years. After 63 DAA, except for acid invertase (AI) in 2021, the activities of other enzymes decreased significantly, and the net activity of sucrose metabolism enzymes showed a strong sucrose cleavage activity. There were 18061, 19575, and 985 differentially expressed genes in 35d vs. 63d, 35d vs. 69d, and 63d vs. 69d, respectively. Ninety-one sugar metabolism genes were screened out, including sucrose synthase (SS), sucrose phosphate synthase (SPS), AI, neutral invertase (NI), hexokinase (HK), glucose 6-phosphate dehydrogenase (G6PD), 6-phosphogluconate dehydrogenase (6PGD), phosphofructokinase (PFK), and pyruvate kinase (PK) genes. In 63d vs. 69d, seventy-five percent of sucrose metabolism genes were downregulated, seventy-seven percent of genes in glycolysis (EMP) were upregulated and the PFK genes were significantly upregulated. There was a significant linear correlation between the expression of 15 genes detected by real-time PCR and the transcriptome sequencing results (r2020 = 0.9139, r2021 = 0.8912). These results suggest that the upregulated expression of PFK genes at maturity may enhance PFK activity and promote the degradation of soluble sugar in pulp through the EMP pathway, resulting in decreased soluble sugar and sucrose contents and "sugar receding" in pulp. Moreover, the downregulated expression of sucrose metabolism genes in pulp decreased the activities of these enzymes, but the net activity of these enzymes resulted in cleaved sucrose and replenished levels of reducing sugars, resulting in a stable reducing sugar content.

Dexmedetomidine Alters the Inflammatory Profile of Rat Microglia In Vitro.

Microglia are a primary mediator of the neuroinflammatory response to neurologic injury, such as that in traumatic brain injury. Their response includes changes to their cytokine expression, metabolic profile, and immunophenotype. Dexmedetomidine (DEX) is an α2 adrenergic agonist used as a sedative in critically ill patients, such as those with traumatic brain injury. Given its pharmacologic properties, DEX may alter the phenotype of inflammatory microglia. Primary microglia were isolated from Sprague-Dawley rats and cultured. Microglia were activated using multiple mediators: lipopolysaccharide (LPS), polyinosinic-polycytidylic acid (Poly I:C), and traumatic brain injury damage-associated molecular patterns (DAMP) from a rat that sustained a prior controlled cortical impact injury. After activation, cultures were treated with DEX. At the 24-h interval, the cell supernatant and cells were collected for the following studies: cytokine expression (tumor necrosis factor-α [TNFα], interleukin-10 [IL-10]) via enzyme-linked immunosorbent assay, 6-phosphofructokinase enzyme activity assay, and immunophenotype profiling with flow cytometry. Cytokine expression and metabolic enzyme activity data were analyzed using two-way analysis of variance. Cell surface marker expression was analyzed using FlowJo software. In LPS-treated cultures, DEX treatment decreased the expression of TNFα from microglia (mean difference = 121.5 ± 15.96pg/mL; p < 0.0001). Overall, DEX-treated cultures had a lower expression of IL-10 than nontreated cultures (mean difference = 39.33 ± 14.50pg/mL, p < 0.0001). DEX decreased IL-10 expression in LPS-stimulated microglia (mean difference = 74.93 ± 12.50pg/mL, p = 0.0039) and Poly I:C-stimulated microglia (mean difference = 23.27 ± 6.405pg/mL, p = 0.0221). In DAMP-stimulated microglia, DEX decreased the activity of 6-phosphofructokinase (mean difference = 18.79 ± 6.508 units/mL; p = 0.0421). The microglial immunophenotype was altered to varying degrees with different inflammatory stimuli and DEX treatment. DEX may alter the neuroinflammatory response of microglia. By altering the microglial profile, DEX may affect the progression of neurologic injury.

Polyethylene terephthalate hydrolysate increased bacterial cellulose production

A major challenge to large-scale production and utilization of bacterial cellulose (BC) for various applications is its low yield and productivity by bacterial cells and the high cost of feedstock. A supplementation of the classical expensive Hestrin and Schramm (HS) medium with 1 % polyethylene terephthalate ammonia hydrolysate (PETAH) resulted in 215 % high yield. Although the physicochemical properties of BC were not significantly influenced, the BC produced in 1 % PETAH-supplemented HS medium showed a higher surface area, which showed 1.39 times higher adsorption capacity for tetracycline than BC produced in HS medium. The 1 % PETAH-supplemented HS medium respectively enhanced the activity of α-UDP-glucose pyrophosphorylase and α-phosphoglucomutase by 30.63 % and 135.24 % and decreased the activity of pyruvate kinase and phosphofructokinase by 40.34 % and 52.63 %. The results of this study provide insights into the activation mechanism of Taonella mepensis by PETAH supplementation for high yield and productivity of BC.

Juglone promotes antitumor activity against prostate cancer via suppressing glycolysis and oxidative phosphorylation.

The treatments currently used for prostate cancer (PC) do not meet clinical needs, and thus, new therapies with greater effectiveness are urgently required. Metabolic reprogramming of tumor cells is emerging as an exciting field for cancer therapy. Although the Warburg effect is a common feature of glucose metabolism in many cancers, PC cells have a unique metabolic phenotype. Non-neoplastic prostate cells show reduced oxidative phosphorylation (OXPHOS) because large, accumulated zinc inhibits citrate oxidation. During transformation, there are low levels of zinc in PC cells, and the tricarboxylic acid (TCA) cycle is reactivated. However, metastatic PC exhibits the Warburg effect. Due to metabolic differences in prostate tissue, targeting metabolic alterations in PC cells is an attractive therapeutic strategy. In this study, we investigated the effect of juglone on energy metabolism in PC cells. We found that juglone inhibited cell proliferation and induced apoptosis. Mechanistically, we demonstrated that juglone suppressed OXPHOS and glycolysis due to its inhibition of hexokinase (HK), phosphofructokinase (PFK), and pyruvate kinase (PK) activity. Furthermore, downregulation of PFK and PK, but not HK contributed to the inhibition of these enzyme activities. The current study indicates that further development of juglone for PC treatment would be beneficial.

Effects of nicosulfuron on plant growth and sugar metabolism in sweet maize (Zea mays L.).

The sulfonylurea herbicide nicosulfuron is efficient, harmless and selective at low doses and has been widely used in maize cultivation. In this study, a pair of corn sister lines, HK301 (nicosulfuron-tolerence, NT) and HK320 (nicosulfuron-sensitive, NS), was chosen to study the effect of nicosulfuron on plant growth and sugar metabolism in sweet maize (Zea mays L.) seedlings. All the experimental samples were subjected to treatment with water or 80 mg kg–1 of nicosulfuron when the sweet maize seedlings grew to the four-leaf stage. Nicosulfuron significantly inhibited the growth of NS line. The content of sucrose and the activities of sucrose phosphate synthase and sucrose synthase in the two inbred lines increased differentially under nicosulfuron stress compared with the respective control treatment. After nicosulfuron treatment, the activities of hexokinase and 6-phosphofructokinase and the contents of pyruvic acid and citric acid in NS line decreased significantly compared with those of NT line, while the content of sucrose and activities of sucrose phosphate synthase and sucrose synthase increased significantly. The disruption of sugar metabolism in NS line led to a lower supply of energy for growth. This study showed that the glycolysis pathway and the tricarboxylic acid cycle were enhanced in nicosulfuron-tolerant line under nicosulfuron stress in enhancing the adaptability of sweet maize.

H2O2-induced oxidative stress improves meat tenderness by accelerating glycolysis via hypoxia-inducible factor-1α signaling pathway in postmortem bovine muscle.

Reactive oxygen species (ROS) affect meat quality through multiple biochemical pathways. To investigate the effect of ROS on postmortem glycolysis and tenderness of bovine muscle, ROS content, glycolytic potential, glycolysis rate-limiting enzyme activities, expression of hypoxia-inducible factor-1α (HIF-1α), phosphatidylinositol 3-kinase (PI3K), serine-threonine kinase (AKT), phosphorylated AKT (p-AKT), and tenderness were determined in the H2O2 group and control group. Results showed that the H2O2 group exhibited significantly higher ROS content within 48h, coupled with increased glycolytic potential, pH decline, hexokinase (HK), and phosphofructokinase activities (PFK) early postmortem. These were attributed to ROS-induced PI3K/AKT signaling pathway activation and resultant HIF-1α accumulation. Moreover, shear force in the H2O2 group reached the peak 12h earlier and decreased obviously after 24h, accompanied by a significantly higher myofibril fragmentation index (MFI). These findings suggested that ROS drive HIF-1α accumulation by activating PI3K/AKT signaling pathway, thereby accelerating glycolysis and tenderization of postmortem bovine muscle.

Influence of long-term sodium-glucose cotransporter 2 inhibition on cardiac remodeling in rats with type 1 diabetes mellitus

Abstract Background Sodium-glucose cotransporter 2 (SGLT2) inhibitors have beneficial effects on the cardiovascular system in diabetes mellitus (DM) patients. However, as most clinical trials were performed in type 2 DM, the effects of SGLT2 inhibitors in patients with type 1 DM still need further clarification. In this study, we evaluated the effects of long-term treatment with the SGLT2 inhibitor dapagliflozin on cardiac remodeling, myocardial function, and energy metabolism in rats with type 1 DM. Methods Male Wistar rats were divided into three groups: control (C, n=15); DM (n=15); and DM treated with dapagliflozin (DM+DAPA, n=15) for 30 weeks. DM was induced by streptozotocin; DAPA was added to the rat chow (5 mg/kg/day). Cardiac performance was evaluated by echocardiogram and myocardial function in isolated left ventricular (LV) papillary muscle preparations. Myocardial energy metabolism enzyme activities were evaluated by spectrophotometry. Statistical analyzes: ANOVA and Tukey or Kruskal-Wallis and Dunn. Results DM+DAPA had lower glycemia than DM [C 112 (108–116); DM 531 (522–535)*; DM+DAPA 267 (179–339) mg/dL; p&amp;lt;0.05 vs C and DM+DAPA]. Echocardiogram showed that DM and DM+DAPA had left atrium and left ventricle dilatation with systolic and diastolic dysfunction; in DM+DAPA, the changes were attenuated in relation to DM. Developed tension and +dT/dt were higher in DM+DAPA than DM in basal condition. After inotropic stimulation with post-pause contraction, extracellular calcium concentration elevation, and isoproterenol addition to the nutrient solution, +dT/dt and –dT/dt were higher in DM+DAPA than DM. Hexokinase, phosphofructokinase, and pyruvate kinase activity was lower in DM than the C. Phosphofructokinase and pyruvate kinase activity was higher in DM+DAPA than DM. Conclusion Long-term dapagliflozin treatment attenuates cardiac remodeling and myocardial dysfunction and preserves hexokinase, phosphofructokinase and pyruvate kinase activity in rats with type 1 diabetes mellitus. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): CNPq - National Council for Scientific and Technological Developmentdoctor

Effects of Endurance Training on Metabolic Enzyme Activity and Transporter Proteins in Skeletal Muscle of Ovariectomized Mice.

Estrogen deficiency or insufficiency can occur under several conditions, leading to negative health outcomes. To establish an effective countermeasure against estrogen loss, we investigated the effects of endurance training on ovariectomy (OVX)-induced metabolic disturbances. Female Institute of Cancer Research mice underwent OVX or sham operations. On day 7 of recovery, the mice were randomized to remain either sedentary or undergo 5 wk of treadmill running (15-20 m·min -1 , 60 min, 5 d·wk -1 ). During week 5 of the training, all animals performed a treadmill running test (15 m·min -1 , 60 min). After the experimental period, OVX resulted in greater gains in body mass, fat mass, and triglyceride content in the gastrocnemius muscle. OVX enhanced phosphofructokinase activity in the plantaris muscle and decreased lactate dehydrogenase activity in the plantaris and soleus muscles. OVX decreased the protein content of NDUFB8, a mitochondrial respiratory chain subunit, but did not decrease other mitochondrial proteins or enzyme activities. Endurance training significantly enhanced mitochondrial enzyme activity and protein content in the skeletal muscles. Although OVX increased the respiratory exchange ratio during the treadmill running test, and postexercise blood lactate levels, endurance training normalized these parameters. The present findings suggest that endurance training is a viable strategy to counteract the negative metabolic consequences in hypoestrogenism.

Type 2 polysaccharide storage myopathy in Quarter Horses is a novel glycogen storage disease causing exertional rhabdomyolysis.

Both type 1 (PSSM1) and type 2 polysaccharide storage myopathy (PSSM2) are characterised by aggregates of abnormal polysaccharide in skeletal muscle. Whereas the genetic basis for PSSM1 is known (R309H GYS1), the cause of PSSM2 in Quarter Horses (PSSM2-QH) is unknown and glycogen concentrations not defined. To characterise the histopathological and biochemical features of PSSM2-QH and determine if an associated monogenic variant exists in genes known to cause glycogenosis. Retrospective case control. Sixty-four PSSM2-QH, 30 PSSM1-QH and 185 control-QH were identified from a biopsy repository and clinical data, histopathology scores (0-3), glycogen concentrations and selected glycolytic enzyme activities compared. Coding sequences of 12 genes associated with muscle glycogenoses were identified from whole genome sequences and compared between seven PSSM2-QH and five control-QH. Exertional rhabdomyolysis in PSSM2-QH occurred predominantly in barrel racing and working cow/roping performance types and improved with regular exercise and a low starch/fat-supplemented diet. Histopathological scores, including the amount of amylase-resistant polysaccharide (PSSM2-QH 1.4 ± 0.6, PSSM1-QH 2.1 ± 0.3, control-QH 0 ± 0, p < 0.001), and glycogen concentrations (PSSM2-QH 129 ± 62, PSSM1-QH 175 ± 9, control-QH 80 ± 27 mmol/kg, p < 0.0001) were intermediate in PSSM2-QH with significant differences among groups. In PSSM2-QH, abnormal polysaccharide had a less filamentous ultrastructure than PSSM1-QH and phosphorylase and phosphofructokinase activities were normal. Seventeen of 30 PSSM2-QH with available pedigrees descended from one of three stallions within four generations. Of the 29 predicted high or moderate impact genetic variants identified in candidate genes, none were present in only PSSM2-QH and absent in control-QH. Analyses of PSSM2-QH and PSSM1-QH were performed on shipped samples, controls on frozen samples. PSSM2-QH is a novel glycogen storage disorder that is not the result of a mutation in genes currently known to cause muscle glycogenoses in other species.