Rapid enzyme assays investigating the variation in the glycolytic pathway in field-caught populations of Fundulus heteroclitus

Baked Bread Enhances the Immune Response and the Catabolism in the Human Body in Comparison with Steamed Bread

It is unclear whether different processing methods change the biological functions of foods and how these functions are evaluated in the human body. Here, steamed bread and baked bread, the traditional staple foods in China and many Western countries, were made by steaming and baking, respectively, using one piece of fermented wheat dough and then consumed by 16 healthy young volunteers. By detecting 38 cytokines, 12 metabolic enzymes, glucose, lactate, and nicotinamide adenine dinucleotide (NADH) in the serum, the cytokine network and central metabolic pathway network were investigated to compare the effects of the two staple foods on immunity and metabolism. Compared with steamed bread, baked bread increased (p < 0.05) concentrations of fractalkine and macrophage-derived chemokine, decreased (p < 0.05) the concentration of interleukin-1RA, increased (p < 0.05) the expression level of phosphofructokinase, and decreased (p < 0.05) the expression level of glucose-6-phosphate dehydrogenase in the serum. Two network analyses indicated that baked bread, as compared to the steamed bread, enhanced communication between immune cells, increased catabolism, and decreased anabolism. Further, a correlation analysis of cytokines and metabolic enzymes suggested that the two staple foods may affect metabolism by regulating the secretion of cytokines. These findings highlight how the same raw food material processed by different methods may have different impacts on immunity and metabolism in humans.

Interindividual variation in Complex I activity in Fundulus heteroclitus along a steep thermocline

The first enzyme in the oxidative phosphorylation pathway is Complex I (EC 1.6.5.3). Complex I is a large heteromeric enzyme complex with 45 protein subunits that translocates H(+) ions across the mitochondrial inner membrane. Among northern and southern populations of the teleost fish Fundulus heteroclitus, Complex I subunits have fixed amino acid substitutions. Additionally, there are differences in oxidative phosphorylation activity among populations of F. heteroclitus. To investigate whether these differences are related to Complex I, enzyme activity was measured in 121 individuals from five populations of F. heteroclitus and its sister species Fundulus grandis acclimated to a constant 20°C temperature. Within each population, Complex I activity is highly variable among individuals of F. heteroclitus (coefficient of variation percentage among individuals has a mean of 90% in the five F. heteroclitus populations), and the mean Complex I activity among populations is significantly different at the latitudinal extremes of the range. Importantly, Complex I activity is more similar between F. heteroclitus from the southernmost population and its sister species F. grandis than to the northern populations of F. heteroclitus, suggesting important evolutionary differences. Unexpectedly, the activity is nearly fourfold higher in southern populations than northern populations. Mitochondrial density appears to compensate partially for decreased activity in northern individuals; activity per wet weight is only twofold higher in southern populations. We suggest that some of the variation in Complex I activity is genetically based and thus is being influenced by directional selection. However, this conclusion presents a conundrum: there should not be so much variation in Complex I activity within a population if this variation is biologically important.

Natural variation in enzyme activity of the African cichlid Pseudocrenilabrus multicolor victoriae

This study describes the metabolic capacities of the African cichlid Pseudocrenilabrus multicolor victoriae from four sites in Uganda, East Africa. Fish were captured during the dry season, from two aquatic systems in different regions (Lake Nabugabo and Mpanga River). Within the Lake Nabugabo region, individuals were sampled from Lake Kayanja (normoxic) and Lwamunda Swamp (hypoxic); within the Mpanga River system, individuals were sampled from Bunoga and Kahunge (characterized by seasonal variation in dissolved oxygen (D.O.)). Enzyme activity levels of pyruvate kinase, lactate dehydrogenase, citrate synthase, and cytochrome C oxidase were measured in four tissues: white skeletal muscle, heart, brain, and liver. Two additional enzymes were measured in the liver, malate dehydrogenase and fructose 1,6-bisphosphatase. Regional differences between enzyme activities in most tissues were evident; however, little variation was observed between two sites within a region despite differences in D.O. In general, P. multicolor from the Mpanga River system displayed greater anaerobic enzyme activity in white skeletal muscle, lower gluconeogenic enzyme activity in the liver, and an overall higher enzyme activity in the heart and brain tissues than fish from the Nabugabo region. The latter may reflect a long-term adaptation to low-oxygen conditions at the metapopulation level in the Nabugabo region.

Oxygen limitation and tissue metabolic potential of the African fish Barbus neumayeri: roles of native habitat and acclimatization

Background

Oxygen availability in aquatic habitats is a major environmental factor influencing the ecology, behaviour, and physiology of fishes. This study evaluates the contribution of source population and hypoxic acclimatization of the African fish, Barbus neumayeri, in determining growth and tissue metabolic enzyme activities. Individuals were collected from two sites differing dramatically in concentration of dissolved oxygen (DO), Rwembaita Swamp (annual average DO 1.35 mgO₂ L^-1) and Inlet Stream West (annual average DO 5.58 mgO₂ L^-1) in Kibale National Park, Uganda, and reciprocally transplanted using a cage experiment in the field, allowing us to maintain individuals under natural conditions of oxygen, food availability, and flow. Fish were maintained under these conditions for four weeks and sampled for growth rate and the activities of phosphofructokinase (PFK), lactate dehydrogenase (LDH), citrate synthase (CS), and cytochrome c oxidase (CCO) in four tissues, liver, heart, brain, and skeletal muscle.

Results

Acclimatization to the low DO site resulted in lower growth rates, lower activities of the aerobic enzyme CCO in heart, and higher activities of the glycolytic enzyme PFK in heart and skeletal muscle. The activity of LDH in liver tissue was correlated with site of origin, being higher in fish collected from a hypoxic habitat, regardless of acclimatization treatment.

Conclusions

Our results suggest that the influence of site of origin and hypoxic acclimatization in determining enzyme activity differs among enzymes and tissues, but both factors contribute to higher glycolytic capacity and lower aerobic capacity in B. neumayeri under naturally-occurring conditions of oxygen limitation.

Fundulus as the premier teleost model in environmental biology: opportunities for new insights using genomics

A strong foundation of basic and applied research documents that the estuarine fish Fundulus heteroclitus and related species are unique laboratory and field models for understanding how individuals and populations interact with their environment. In this paper we summarize an extensive body of work examining the adaptive responses of Fundulus species to environmental conditions, and describe how this research has contributed importantly to our understanding of physiology, gene regulation, toxicology, and ecological and evolutionary genetics of teleosts and other vertebrates. These explorations have reached a critical juncture at which advancement is hindered by the lack of genomic resources for these species. We suggest that a more complete genomics toolbox for F. heteroclitus and related species will permit researchers to exploit the power of this model organism to rapidly advance our understanding of fundamental biological and pathological mechanisms among vertebrates, as well as ecological strategies and evolutionary processes common to all living organisms.

Effects of long-term hypoxia on enzymes of carbohydrate metabolism in the Gulf killifish, Fundulus grandis

The goal of the current study was to generate a comprehensive, multi-tissue perspective of the effects of chronic hypoxic exposure on carbohydrate metabolism in the Gulf killifish Fundulus grandis. Fish were held at approximately 1.3 mg l(-1) dissolved oxygen (approximately 3.6 kPa) for 4 weeks, after which maximal activities were measured for all glycolytic enzymes in four tissues (white skeletal muscle, liver, heart and brain), as well as for enzymes of glycogen metabolism (in muscle and liver) and gluconeogenesis (in liver). The specific activities of enzymes of glycolysis and glycogen metabolism were strongly suppressed by hypoxia in white skeletal muscle, which may reflect decreased energy demand in this tissue during chronic hypoxia. In contrast, several enzyme specific activities were higher in liver tissue after hypoxic exposure, suggesting increased capacity for carbohydrate metabolism. Hypoxic exposure affected fewer enzymes in heart and brain than in skeletal muscle and liver, and the changes were smaller in magnitude, perhaps due to preferential perfusion of heart and brain during hypoxia. The specific activities of some gluconeogenic enzymes increased in liver during long-term hypoxic exposure, which may be coupled to increased protein catabolism in skeletal muscle. These results demonstrate that when intact fish are subjected to prolonged hypoxia, enzyme activities respond in a tissue-specific fashion reflecting the balance of energetic demands, metabolic role and oxygen supply of particular tissues. Furthermore, within glycolysis, the effects of hypoxia varied among enzymes, rather than being uniformly distributed among pathway enzymes.

Flight muscles polymorphism in a flightless bug, Pyrrhocoris apterus (L.): developmental pattern, biochemical profile and endocrine control

The flightless bug Pyrrhocoris apterus (L.) is polymorphic for both wing length and flight muscle development. The developed flight muscles of macropterous adults of both sexes first enlarge their volume during the first 5 days after adult emergence, but are then histolyzed in all males and females older than 10 and 14 days, respectively. The flight muscles of brachypterous adult males and females are underdeveloped due to their arrested growth. The total protein content of histolyzed dorsolongitudinal flight muscles from 21-day-old macropterous adults of both sexes is lower than that of developed dorsolongitudinal flight muscles in 5-10-days-old macropterous bugs, but substantially higher than the protein content of underdeveloped dorsolongitudinal flight muscles from adult brachypters. Histolyzed dorsolongitudinal flight muscles differ from the developed ones by decreased quantities of 18 electrophoretically separated proteins. Histolysis of developed dorsolongitudinal flight muscles is accompanied by significant decreases in citrate synthase, glyceraldehyde-3-phosphate dehydrogenase and beta-hydroxyacyl-CoA dehydrogenase enzyme activities and an increase in alanine aminotransferase activity, and can be precociously induced by application of a juvenile hormone analogue. This is the first report of flight muscle polymorphism, histolysis of developed flight muscles and its endocrine control in insects displaying non-functional wing polymorphism.

Prior PCB exposure suppresses hypoxia-induced up-regulation of glycolytic enzymes in Fundulus heteroclitus

Increased activity of the glycolytic enzymes is a conserved feature of the cellular response to hypoxia, and may represent a protective mechanism by which cells can survive short-term hypoxic exposure. Gene induction by hypoxia involves a dimer of the hypoxia inducible factor (HIF)-1 alpha and the nuclear cofactor HIF-1 beta, also called the aryl hydrocarbon receptor nuclear translocator (ARNT), which is also involved in induction of genes in response to aryl hydrocarbon exposure. To assess the possibility of interaction between these pathways, we examined changes in the activity of the glycolytic enzymes in response to hypoxia and polychlorinated biphenyl (PCB) exposure in the liver of a teleost fish, Fundulus heteroclitus. After 3 days of hypoxic exposure (dissolved oxygen levels between 1.5 and 2.0 mg/L), there were significant increases in the activity of six glycolytic enzymes (PGI, ALD, TPI, PGK, PGM and LDH). In contrast, intraperitoneal injection of 1 microg/g body weight of PCB #77 (3,3',4,4'-tetrachlorobiphenyl) caused significant decreases in glycolytic enzyme activity after 7 days of exposure. When fish were injected with PCB #77 and then (4 days later) exposed to hypoxia for 3 days as before, we observed no induction of the glycolytic enzymes. This suggests that there is an antagonistic interaction between exposure to PCBs and hypoxia in F. heteroclitus. Prior PCB exposure could make these fish less tolerant of environmental hypoxia.

Stress and interpopulation variation in glycolytic enzyme activity and expression in a teleost fish Fundulus heteroclitus

Northern populations of Fundulus heteroclitus have twofold greater activity of lactate dehydrogenase-B (LDH-B) than southern populations, but exposure to stress increases LDH-B in southern populations, abolishing this difference. To test whether differences in the activity of other hepatic glycolytic enzymes between populations are sensitive to stress, we injected fish with a pharmacological dose of cortisol in coconut oil (400 microg g(-1)) or exposed them to handling stress and measured the activities of all the glycolytic enzymes. At rest, liver phosphofructokinase (PFK) and aldolase (ALD) activities were greater in southern fish, whereas LDH-B activity was greater in northern fish. No other glycolytic enzymes differed in activity between populations in control fish. Cortisol injection and handling stress decreased PFK and ALD and increased LDH activities in the southern but not the northern population, such that the populations no longer differed in the activity of any enzyme following treatment. Unlike Ldh-B mRNA, Pfk and Ald mRNA levels did not parallel enzyme activity, suggesting complex kinetics or regulation at multiple levels. Plasma cortisol did not differ between populations at rest but was significantly different between populations in treated fish. These data suggest that differences in liver enzyme activity may be related to differences in stress hormone physiology between populations.

Heritabilities and additive genetic variances of the activities of some enzymes in Drosophila melanogaster populations living in different habitats

Drosophila melanogaster samples were collected from a large population in two habitats: farmyards and distilleries. Samples were taken from two villages in each habitat. Three isofemale lines were established from all four samples and full-sib crosses were set in each isofemale line. Activities of four enzymes (ADH, alpha GPDH, IDH and 6PGDH) were measured in the offspring of each cross on starch gel after electrophoresis. Broad sense heritabilities and additive genetic variances were estimated in all four samples. Most of the activity variation was observed within the isofemale lines. The isofemale lines tended to be more different in the distilleries than in the farmyards. There was no significant difference in the average activities between the two habitats for any of the enzymes investigated. The additive genetic variance of the enzyme activities did not exhibit a consistent habitat pattern. In the farmyard habitat, we detected a higher activity variation in Tiszafüred than in the other village. Strong correlation was observed among the activities of the enzymes investigated. Correlation coefficients indicated higher level of correlation in the samples collected in Tiszafüred than in those originating from Tiszaszolos. The heritability values were rather high and they had a considerable variation both between the habitats and across the enzymes.

Variation of enzyme activities at a branched pathway involved in the utilization of gluconate in Escherichia coli

Twenty-four strains of Escherichia coli from the ECOR collection were characterized for growth rate in gluconate minimal salts medium and for Vmax and Km of the three enzymes (gluconokinase, 6-phosphogluconate dehydrogenase, and 6-phosphogluconate dehydratase) that form a branch point for the utilization of gluconate. A total of 11 characters--growth rate, three Vmax values, four Km values, and three Vmax/Km values--were determined for these 24 ECOR strains. Most of the characters were normally distributed. Statistical tests showed that growth rate is significantly less variable than enzyme activities. Also, analyses of variance showed significant differences among strains and among the extant five genetic groups of E. coli for the characters measured. A Mantel test showed that, for some characters, closely related strains shared similar character values. Two hypotheses regarding the relationships between growth rate and enzyme activity and between various enzyme activities were tested. None of the expected correlations between growth rate and enzyme activity or between enzyme activities was detected. The results were discussed in terms of metabolic control analysis and neutral theory.

Intraspecific variation in aerobic metabolism and glycolytic enzyme expression in heart ventricles

A previous phylogenetic analysis among 15 taxa of the teleost fish Fundulus suggested that there should be thermal-adaptive differences in heart metabolism among populations. To test this hypothesis, the rate of oxygen consumption and the activities of all 11 glycolytic enzymes were measured in isolated heart ventricle from two populations of Fundulus heteroclitus. Heart ventricular metabolism is greater in a northern population versus a southern population of these fish. Analysis of the amount of glycolytic enzymes indicates that 87% of the variation in cardiac metabolism within and between populations is explained by the variation in three enzymes (pyruvate kinase, glyceraldehyde-3-phosphate dehydrogenase, and lactate dehydrogenase). These enzymes are the same three enzymes that were predicted to be important based on previously determined phylogenetic patterns of expression. Our data indicate that near-equilibrium enzymes, as well as classically defined rate-limiting enzymes, can also influence metabolism.

Metabolic enzyme activities in fish gills as biomarkers of exposure to petroleum hydrocarbons

Metabolic effects of low-level exposure of Atlantic salmon (Salmo salar) to the water accommodated fraction (WAF) of crude oil and to dispersed crude oil were studied. Aerobic enzymes citrate synthase and cytochrome C oxidase, and anaerobic enzyme lactate dehydrogenase were measured in gills during a 4-day exposure to low concentrations of dispersed Bass Strait crude oil and WAF, and during the following 8 days of depuration in clean seawater. Relative to pre-exposure levels, citrate synthase and lactate dehydrogenase exhibited a significant inhibition of activity during exposure to the WAF of crude oil, and to dispersed crude oil, while activity of cytochrome C oxidase remained unchanged. Citrate synthase activities returned to preexposure levels after 4 days following termination of exposure for the WAF-exposed fish, and after 2 days for the dispersed-oil-exposed fish. After the termination of exposure to both treatments, lactate dehydrogenase activity remained low relative to levels measured prior to exposure, which indicated that the activity of this enzyme may be a sensitive medium to long-term biomarker of exposure to petroleum-contaminated water bodies.

Detection of individual variation in enzyme activity in natural populations of Drosophila melanogaster

The method allows the determination of the activity level of enzymes in a single fly and assessing the genetic composition of the given individual at these enzyme loci. Three isofemale lines were constructed which were monomorphic at several enzyme loci. Samples were prepared in two different ways: (i) individual samples--individuals were homogenised separately; (ii) collective samples--a common homogenate was prepared from several individuals. Oregon-R strain was also used to prepare a standard homogenate. The activities of alcohol dehydrogenase (ADH), alpha-glycerophosphate dehydrogenase (alpha GPDH), isocitrate dehydrogenase (IDH), and 6-phosphogluconate dehydrogenase (6PGDH), were measured in each sample on starch gel after the proteins were separated by electrophoresis. Enzyme activities were assessed by the optical density of the bands. Gel and position weights were estimated on the basis of the statistical analyses of the activities measured in the standard samples. Gel weights were then used to account for the activity differences among the gels while position weights were applied to correct for the general tendencies in the activities observed within the gels. The gel and position weighted activities of individual and collective samples were compared in the isofemale lines. The individual samples had approximately two times as much variation as the collective samples for all four enzymes. The electrophoretic method is sensitive enough to study the structure of the phenotypic variation in enzyme activity in the natural populations. The total variation among the standard samples was close to the within subline component of variation obtained for the collective samples (measurement error). This shows that the standard samples can be used to estimate the size of the measurement error.

Phylogenetic analysis of glycolytic enzyme expression

Although differences among species in enzyme maximal activity or concentration are often interpreted as adaptive and important for regulating metabolism, these differences may simply reflect phylogenetic divergence. Phylogenetic analysis of the expression of the glycolytic enzymes among 15 taxa of a North American fish genus (Fundulus) indicated that most variation in enzyme concentration is due to evolutionary distance and may be nonadaptive. However, three enzymes' maximal activities covary with environmental temperature and have adaptive value. Additionally, two pairs of enzymes covary, indicating coevolution. Thus, metabolic flux may be modulated by many different enzymes rather than by a single rate-limiting enzyme.