Human cystic echinococcosis (CE) is a zoonotic disorder triggered by the larval stage of Echinococcus granulosus (E. granulosus) and predominantly occurred in the liver and lungs. The M2 macrophage level is considerably elevated among the liver of patients with hepatic CE and performs an integral function in liver fibrosis. However, the mechanism of CE inducing polarisation of macrophage to an M2 phenotype is unknown. In this study, macrophage was treated with E. granulosus cyst fluid (EgCF) to explore the mechanism of macrophage polarisation. Consequently, the expression of the M2 macrophage and production of anti-inflammatory cytokines increased after 48 h treatment by EgCF. In addition, EgCF promoted polarisation of macrophage to an M2 phenotype by inhibiting the expression of transcriptional factor hypoxia-inducible factor 1-alpha (HIF-1α), which increased the expression of glycolysis-associated genes, including hexokinase 2 (HK2) and pyruvate kinase 2 (PKM2). The HIF-1α agonist ML228 also inhibited the induction of macrophage to an M2 phenotype by EgCF in vitro. Our findings indicate that E. granulosus inhibits glycolysis by suppressing the expression of HIF-1α.

An 8-week experiment was performed to investigate the influence on growth performance, plasma biochemistry, glucose metabolism and the insulin pathway of supplementation of dietary taurine to a high-carbohydrate diet for grass carp. In this study, fish were fed diets at one of two carbohydrate levels, 31·49 % (positive control) or 38·61 % (T00). The high-carbohydrate basal diet (T00), without taurine, was supplemented with 0·05 % (T05), 0·10 % (T10), 0·15 % (T15) or 0·20 % (T20) taurine, resulting in six isonitrogenous (30·37 %) and isolipidic (2·37 %) experimental diets. The experimental results showed that optimal taurine level improved significantly weight gain, specific growth rate (SGR), feed utilisation, reduced plasma total cholesterol levels, TAG and promoted insulin-like growth factor level. Glucokinase, pyruvate kinase and phosphoenolpyruvate carboxykinase activities showed a quadratic function model with increasing dietary taurine level, while hexokinase, fatty acid synthetase activities exhibited a positive linear trend. Optimal taurine supplementation in high-carbohydrate diet upregulated insulin receptor (Ir), insulin receptor substrate (Irs1), phosphatidylinositol 3-kinase (pi3k), protein kinase B (akt1), glycogen synthase kinase 3 β (gs3kβ) mRNA level and downregulated insulin-like growth factor (igf-1), insulin-like growth factor 1 receptor (igf-1R) and Fork head transcription factor 1 (foxo1) mRNA level. The above results suggested that optimal taurine level could improve growth performance, hepatic capacity for glycolipid metabolism and insulin sensitivity, thus enhancing the utilisation of carbohydrates in grass carp. Based on SGR, dietary optimal tributyrin taurine supplementation in grass carp was estimated to be 0·08 %.

To unveil the adaptation of Litopenaeus vannamei to elevated ambient ammonia-N, crustacean hyperglycaemic hormone (CHH) was knocked down to investigate its function in glucose metabolism pathway under ammonia-N exposure. When CHH was silenced, haemolymph glucose increased significantly during 3–6 h, decreased significantly during 12–48 h and recovered to the control groups’ level at 72 h. After CHH knock-down, dopamine (DA) contents reduced significantly during 3–24 h, which recovered after 48 h. Besides, the expressions of guanylyl cyclase (GC) and DA1R in the hepatopancreas decreased significantly, while DA4R increased significantly. Correspondingly, the contents of cyclic AMP (cAMP), cyclic GMP (cGMP) and diacylglycerol (DAG) and the expressions of protein kinase A (PKA), protein kinase G (PKG), AMP active protein kinase α (AMPKα) and AMPKγ were significantly down-regulated, while the levels of protein kinase C (PKC) and AMPKβ were significantly up-regulated. The expressions of cyclic AMP response element-binding protein (CREB) and GLUT2 decreased significantly, while GLUT1 increased significantly. Moreover, glycogen content, glycogen synthase and glycogen phosphorylase activities in hepatopancreas and muscle were significantly increased. Furthermore, the levels of key enzymes hexokinase, pyruvate kinase and phosphofructokinase in glycolysis (GLY), rate-limiting enzymes citrate synthase in tricarboxylic acid and critical enzymes phosphoenolpyruvate carboxykinase, fructose diphosphate and glucose-6-phosphatase in gluconeogenesis (GNG) were significantly decreased in hepatopancreas. These results suggest that CHH affects DA and then they affect their receptors to transmit glucose metabolism signals into the hepatopancreas of L. vannamei under ammonia-N stress. CHH acts on the cGMP-PKG-AMPKα-CREB pathway through GC, and CHH affects DA to influence cAMP-PKA-AMPKγ-CREB and DAG-PKC-AMPKβ-CREB pathways, thereby regulating GLUT, inhibiting glycogen metabolism and promoting GLY and GNG. This study contributes to further understand glucose metabolism mechanism of crustacean in response to environmental stress.

An oral starch administration trial was used to evaluate glucose homoeostasis in grass carp (Ctenopharyngodon idella) and Chinese longsnout catfish (Leiocassis longirostris Günther). Fish were administered with 3 g of a water and starch mixture (with 3:2 ratio) per 100 g body weight after fasting for 48 h. Fish were sampled at 0, 1, 3, 6, 12, 24 and 48 h after oral starch administration. In grass carp, plasma levels of glucose peaked at 3 h but returned to baseline at 6 h. However, in Chinese longsnout catfish, plasma glucose levels peaked at 6 h and returned to baseline at 48 h. The activity of intestinal amylase was increased in grass carp at 1 and 3 h, but no significant change in Chinese longsnout catfish was observed. The activity of hepatic glucose-6-phosphatase fell significantly in grass carp but change was not evident in Chinese longsnout catfish. The expression levels and enzymic activity of hepatic pyruvate kinase increased in grass carp, but no significant changes were observed in the Chinese longsnout catfish. Glycogen synthase (gys) and glycogen phosphorylase (gp) were induced in grass carp. However, there was no significant change in gys and a clear down-regulation of gp in Chinese longsnout catfish. In brief, compared with Chinese longsnout catfish, grass carp exhibited a rapid increase and faster clearance rate of plasma glucose. This effect was closely related to significantly enhanced levels of digestion, glycolysis, glycogen metabolism and glucose-induced lipogenesis in grass carp, as well as the inhibition of gluconeogenesis.

Despite sperm mitochondrial relevance to the fertilization capacity, the processes involved in the production of ATP and functional dynamics of sperm mitochondria are not fully understood. One of these processes is the paradox involved between function and formation of reactive oxygen species performed by the organelle. Therefore, this review aimed to provide data on the role of sperm mitochondria in oxidative homeostasis and functionality as well the tools to assess sperm mitochondrial function.

Most previous studies on the effects of lipopolysaccharide (LPS) in pigs focused on the body’s immune response, and few reports paid attention to body metabolism changes. To better understand the glucose metabolism changes in skeletal muscle following LPS challenge and to clarify the possible mechanism, 12 growing pigs were employed. Animals were treated with either 2 ml of saline or 15 µg/kg BW LPS, and samples were collected 6 h later. The glycolysis status and mitochondrial function in the longissimus dorsi (LD) muscle of pigs were analyzed. The results showed that serum lactate content and NADH content in LD muscle significantly increased compared with the control group. Most glycolysis-related genes expression, as well as hexokinase, pyruvate kinase and lactic dehydrogenase activity, in LD muscle was significantly higher compared with the control group. Mitochondrial complexes I and IV significantly increased, while mitochondrial ATP concentration markedly decreased. Significantly increased calcium content in the mitochondria was observed, and endoplasm reticulum (ER) stress has been demonstrated in the present study. The results showed that LPS treatment markedly changes glucose metabolism and mitochondrial function in the LD muscle of pigs, and increased calcium content induced by ER stress was possibly involved. The results provide new clues for clarifying metabolic diseases in muscle induced by LPS.

The antimalarial drug mefloquine has promising antischistosomal properties killing haematophagous adult schistosomes as well as schistosomula. The mode of action and involved drug targets of mefloquine in Schistosoma mansoni schistosomula are unknown. In order to identify mefloquine-binding proteins and thus potential drug targets, mefloquine affinity chromatography with S. mansoni schistosomula crude extracts was performed. We found one specific mefloquine-binding protein that was identified by mass spectrometry as the glycolytic enzyme enolase (Q27877). Enolase activity assays were performed on schistosomula crude extracts and on the recombinant enolase Q27877 expressed in Escherichia coli. In schistosomula crude extracts enolase activity was inhibited by mefloquine and by the enolase inhibitor sodium fluoride, while activity of the recombinant enolase was not affected. In contrast to enolase from crude extracts, recombinant Q27877 did not bind to mefloquine-agarose. Using isothermal microcalorimetry, we next investigated the metabolic inhibition of mefloquine and 3 known glycolytic inhibitors in Schistosoma spp., namely sodium fluoride, 3-bromopyruvate and menadione on schistosomula in the presence or absence of glucose. We found that in the presence of glucose, schistosomula were less affected by mefloquine, sodium fluoride and 3-bromopyruvate, whereas glucose had no protective effect when schistosomula had been exposed to menadione. These results suggest a potential role of mefloquine as an inhibitor of glycolysis, at least in stages where other targets like haem degradation are not relevant.

Enzymes moonlight in a non-enzymatic capacity in a diverse variety of cellular processes. The discovery of these non-enzymatic functions is generally unexpected, and moonlighting enzymes are known in both prokaryotes and eukaryotes. Importantly, this unexpected multi-functionality indicates that caution might be needed on some occasions in interpreting phenotypes that result from the deletion or gene-silencing of some enzymes, including some of the best known enzymes from classic intermediary metabolism. Here, we provide an overview of enzyme moonlighting in parasitic protists. Unequivocal and putative examples of moonlighting are discussed, together with the possibility that the unusual biological characteristics of some parasites either limit opportunities for moonlighting to arise or perhaps contribute to the evolution of novel proteins with clear metabolic ancestry.

Comparison of glycolysis in Brugia pahangi and Onchocerca volvulus by C nuclear magnetic resonance (NMR) spectroscopy showed that the former organism is predominantly a lactate fermenter and the latter resembles more closely the metabolism of a mixed acid fermenter producing lactate, succinate, acetate, ethanol, formate and carbon dioxide. Both organisms synthesize glycogen as a storage carbohydrate. Glutaminolysis in both organisms proceeds by the δ-aminobutyrate shunt to produce succinate which is then further metabolized to acetate and carbon dioxide as end-products.

Throughout evolution, enzymes and their metabolites have been highly conserved. Parasites are no exception to this and differ most markedly by the absence of metabolic pathways that are present in the mammalian host. In general, parasites are metabolically lazy and rely on the metabolism of the host both for a supply of prefabricated components such as purines, fatty acids, sterols and amino acids and for the removal of end-products. Nonetheless, parasites are metabolically highly sophisticated in that (1) they retain the genetic capacity to induce many pathways, when needed, and (2) they have developed complex mechanisms for their survival in the host. Certain unique features of the metabolism of trypanosomes, leishmania, malaria and anaerobic protozoa will be discussed. This will include (1) glycolysis and electron transport with reference to the unique organelles: the glycosome and the hydrogenosome, (2) purine salvage, pyrimidine biosynthesis and folic acid metabolism and (3) polyamine and thiol metabolism with special reference to the role of the unique metabolite of trypanosomes and leishmanias, trypanothione.

The aim of the present study is to investigate the effect of acetic acid feeding on the circadian changes in glycogen concentration in liver and skeletal muscle. Rats were provided meal once daily (09.00–13.00 hours) for 10d. On the 11th day, they were either killed immediately or given 9g diet containing either 0 (control) or 0·7g/kg-diet acetic acid beginning at 09.00 hours for 4h, as in the previous regimen. Rats in the fed group were killed at 4, 8 or 24h after the start of feeding. At 4h after the start of feeding, the acetic acid group had significantly greater liver and gastrocnemius muscle glycogen concentrations (P<0·05). Also, at this same point, liver xylulose-5-phosphate, a key stimulator of glycolysis, the ratio of fructose-1,6-bisphosphate to fructose-6-phosphate in skeletal muscle, which reflects phosphofructokinase-1 activity, and liver malonyl-CoA, an allosteric inhibitor of carnitine palmitoyl-transferase, were significantly lower in the acetic acid group than in the control group (P<0·05). In addition, the acetic acid group had a significantly lower serum lactate concentration and lower ratio of insulin to glucagon than the control group at the same point (P<0·05). We conclude that a diet containing acetic acid may enhance glycogen repletion but not induce supercompensation, a large increase in the glycogen level that is beneficial in improving performance, in liver and skeletal muscle by transitory inhibition of glycolysis. Further, we indicate the possibility of a transient enhancement of fatty acid oxidation in liver by acetic acid feeding.

Retinal ischemia, a major cause of visual loss, is believed to result from overexcitation of glutamate receptors. However, under euglycemic and normoxic conditions, exogenously applied glutamate is not neurotoxic in the retina. Under such conditions, exogenous glutamate typically causes glia swelling and requires very high concentrations to produce neurotoxicity. To determine whether ischemic conditions enhance the neurotoxicity of endogenous and exogenous glutamate, we examined the effects of simulated ischemia (deprivation of both glucose and oxygen) on retinal morphology and lactate dehydrogenase (LDH) release. In an ex vivo rat retinal preparation, glutamate was administered during simulated ischemia in the presence of riluzole, an inhibitor of glutamate release. Deprivation of both glucose and oxygen for 60 min at 30°C produced severe acute neurodegeneration. This neurodegeneration, characterized by bull's eye formation in the inner nuclear layer and spongy appearance in the inner plexiform layer, was prevented by the combination of MK-801 and DNQX, antagonists of N-methyl-D-aspartate (NMDA) and non-NMDA receptors, indicating that the damage results from activation of both glutamate receptors. We also found that administration of glutamate pyruvate transaminase (alanine aminotransaminase) with pyruvate diminished the neurodegeneration during simulated ischemia. Furthermore, riluzole, an inhibitor of glutamate release, attenuated the neurodegeneration, suggesting the importance of endogenous glutamate in ischemic damage. In the presence of riluzole and simulated ischemia, exogenously applied glutamate failed to cause Müller cell swelling but was extremely neurotoxic. These results suggest that simulated ischemia enhances glutamate-mediated neurotoxicity in part by depressing glutamate uptake. When glutamate transport is impaired, sub-millimolar glutamate concentrations become profoundly neurotoxic.

We examined intraretinal [H+] in the intact retina of anesthetized cats using H+-sensitive microelectrodes to obtain spatial profiles of extracellular [H+]. One H+ is produced when an anaerobically generated ATP is utilized. We theorized that H+ production directly reflects anaerobic glucose consumption. From the choroid (pH ∼7.40), [H+]o steadily increased to a maximum concentration in the proximal portion of the outer nuclear layer (pH∼7.20). The shape of the profile was always concave down, indicating that a net production of H+ occurred across the avascular outer retina. A three-layer diffusion model of the outer retina was developed and fitted to the data to quantify photoreceptor H+ extrusion into the extracellular space (QOR-H+). It was determined that the outer segment (OS) layer had negligible H+ extrusion. The data were then refitted to a special three-layer model in which the OS layer QH+ was set equal to zero, but in which the inner segments and outer nuclear layer produced H+. The resulting QOR-H+ was several orders of magnitude lower than previous measurements of QOR-lactate, which were based on choroidal mass balances of lactate.

Background and objective: Myocardial ischaemic preconditioning is characterized by a reduction in the rate of glycolysis. Brief myocardial ischaemia also reduces the glycogen content of the heart. The first objective was to determine whether augmenting glucose oxidation by activation of the pyruvate dehydrogenase complex would prevent the infarct limitation of ischaemic preconditioning. The second part of the study evaluates whether glycogen depletion before ischaemia mimics the infarct-limiting effect of ischaemic preconditioning.

Methods: Dichloroacetate (300 + 150 mg kg−1), an activator of the pyruvate dehydrogenase complex, was administered intravenously in the anaesthetized open-chest rabbit. All animals underwent 45 min of regional ischaemia and 3 h of reperfusion. Ischaemic preconditiong was elicited by 5 min of coronary occlusion. Control rabbits, those with ischaemic preconditioning with no dichloroacetate, received a saline vehicle. An isolated perfused rabbit heart model was employed to test the second hypothesis. Hearts were depleted of glycogen by perfusing them with a substrate-free buffer. Infarction was assessed by triphenyl tetrazolium chloride and area at risk determined with fluorescent particles.

Results: (a) Pyruvate dehydrogenase complex activation experiments. Treatment with dichloroacetate alone did not alter infarct size (58 ± 7% control vs. 60 ± 5% dichloroacetate). Addition of dichloroacetate did not attenuate the infarct-limiting effect of ischaemic preconditioning as evidenced by a similar reduction in infarct size in the ischaemic preconditioning group (22 ± 5%) and in the ischaemic preconditioning + dichloroacetate group (27 ± 7%). (b) Glycogen depletion experiments. Compared with control hearts with a normal glycogen content (4.84 ± 0.15 mg g−1 wet weight), glycogen depleted and ischaemic preconditioning hearts had reduced glycogen content before ischaemia (2.15 ± 0.26, 1.62 ± 0.17 mg g−1 wet weight, respectively; P < 0.01). Glycogen depletion did not reduce infarct size: 25.0 ± 4.5% cf. 27.9 ± 3.4% in the control group. However, ischaemic preconditioning resulted in a significant reduction of infarct size (11.5 ± 2.3% vs. 27.9 ± 3.4% control; P < 0.01).

Conclusions: Augmentation of oxidative glycolysis by dichloroacetate in in situ rabbit hearts does not alter the effect of ischaemic preconditioning, and glycogen depletion in the isolated rabbit heart does not influence infarct size after subsequent coronary occlusion.

The effects of diet composition and ration size on the activities of key enzymes involved in intermediary metabolism were studied in the liver of gilthead sea bream (Sparus aurata). High-carbohydrate, low-protein diets stimulated 6-phosphofructo 1-kinase (EC 2.7.1.11), pyruvate kinase (EC 2.7.1.40), glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (EC 1.1.1.44) enzyme activities, while they decreased alanine aminotransferase (EC 2.6.1.2) activity. A high degree of correlation was found between food ration size and the activity of the enzymes 6-phosphofructo 1-kinase, pyruvate kinase, glucose-6-phosphate dehydrogenase (positive correlations) and fructose-1,6-bisphosphatase (EC 3.1.3.11) (negative correlation). These correlations matched well with the high correlation also found between ration size and growth rate in starved fish refed for 22 d. Limited feeding (5 g/kg body weight) for 22 d decreased the activities of the key enzymes for glycolysis and lipogenesis, and alanine aminotransferase activity. The findings presented here indicate a high level of metabolic adaptation to both diet type and ration size. In particular, adaptation of enzyme activities to the consumption of a diet with a high carbohydrate level suggests that a carnivorous fish like Sparus aurata can tolerate partial replacement of protein by carbohydrate in the commercial diets supplied in culture. The relationship between enzyme activities, ration size and fish growth indicates that the enzymes quickly respond to dietary manipulations of cultured fish.