Decision rules, energy metabolism and vigour of hermit-crab fights

Aggressive interactions between animals are often settled by the use of repeated signals that reduce the risk of injury from combat but are expected to be costly. The accumulation of lactic acid and the depletion of energy stores may constrain activity rates during and after fights and thus represent significant costs of signalling. We tested this by analysing the concentrations of lactate and glucose in the haemolymph of hermit crabs following agonistic interactions over the ownership of the gastropod shells that they inhabit. Attackers and defenders play distinct roles of sender and receiver that are fixed for the course of the encounter. Attackers perform bouts of 'shell rapping', which vary in vigour between attackers and during the course of the encounter, and are a key predictor of victory. In contrast to the agonistic behaviour of other species, we can quantify the vigour of fighting. We demonstrate, to our knowledge for the first time, an association between the vigour of aggressive activity and a proximate cost of signalling. We show that the lactate concentration in attackers increases with the amount of shell rapping, and that this appears to constrain the vigour of subsequent rapping. Furthermore, attackers, but not defenders, give up when the concentration of lactate is high. Glucose levels in attackers also increase with the amount of rapping they perform, but do not appear to influence their decision to give up. Defenders are more likely to lose when they have particularly low levels of glucose. We conclude that the two roles use different decision rules during these encounters.

CCAAT/enhancer binding protein α predicts poorer prognosis and prevents energy starvation-induced cell death in hepatocellular carcinoma

CCAAT enhancer binding protein α (C/EBPα) plays an essential role in cellular differentiation, growth, and energy metabolism. Here, we investigate the correlation between C/EBPα and hepatocellular carcinoma (HCC) patient outcomes and how C/EBPα protects cells against energy starvation. Expression of C/EBPα protein was increased in the majority of HCCs examined (191 pairs) compared with adjacent nontumor liver tissues in HCC tissue microarrays. Its upregulation was correlated significantly with poorer overall patient survival in both Kaplan-Meier survival (P = 0.017) and multivariate Cox regression (P = 0.028) analyses. Stable C/EBPα-silenced cells failed to establish xenograft tumors in nude mice due to extensive necrosis, consistent with increased necrosis in human C/EBPα-deficient HCC nodules. Expression of C/EBPα protected HCC cells in vitro from glucose and glutamine starvation-induced cell death through autophagy-involved lipid catabolism. Firstly, C/EBPα promoted lipid catabolism during starvation, while inhibition of fatty acid beta-oxidation significantly sensitized cell death. Secondly, autophagy was activated in C/EBPα-expressing cells, and the inhibition of autophagy by ATG7 knockdown or chloroquine treatment attenuated lipid catabolism and subsequently sensitized cell death. Finally, we identified TMEM166 as a key player in C/EBPα-mediated autophagy induction and protection against starvation.

CONCLUSION: The C/EBPα gene is important in that it links HCC carcinogenesis to autophagy-mediated lipid metabolism and resistance to energy starvation; its expression in HCC predicts poorer patient prognosis.

Lower resting energy expenditure and fat oxidation in Native American and Hispanic infants born to mothers with diabetes

OBJECTIVE: To determine whether exposure to diabetes in utero affects resting energy expenditure (REE) and fuel oxidation in infants.

STUDY DESIGN: At 35 ± 5 days after birth, body composition and REE were measured in full-term offspring of Native American and Hispanic women with either well-controlled diabetes (13 girls, 11 boys) or normal healthy pregnancies (18 girls, 17 boys).

RESULTS: Control of dysglycemia during gestation in the women with diabetes mellitus met current clinical standards, shown by average glycated hemoglobin (5.9 ± 0.2%; 40.6 ± 2.3 mmol/mol). Infant body mass (offspring of women with diabetes: 4.78 ± 0.13, control offspring: 4.56 ± 0.08 kg) and body fatness (offspring of women with diabetes: 25.2 ± 0.6, control offspring: 24.2 ± 0.5 %) did not differ between groups. REE, adjusted for lean body mass, was 14% lower in offspring of women with diabetes (41.7 ± 2.3 kJ/h) than control offspring (48.6 ± 2.0, P = .025). Fat oxidation was 26% lower in offspring of women with diabetes (0.54 ± 0.05 g/h) than control offspring (0.76 ± 0.04, P < .01) but carbohydrate oxidation did not differ. Thus, fat oxidation accounted for a lower fraction of REE in the offspring of women with diabetes (49 ± 4%) than control offspring (60 ± 3%, P = .022). Mothers with diabetes were older and had higher prepregnancy body mass index than control mothers.

CONCLUSIONS: Well-controlled maternal diabetes did not significantly affect body mass or composition of offspring at 1-month old. However, infants with mothers with diabetes had reduced REE and fat oxidation, which could contribute to adiposity and future disease risk. Further studies are needed to assess the impact differences in age and higher prepregnancy body mass index.

Inhibition of O-GlcNAc transferase activity reprograms prostate cancer cell metabolism

Metabolic networks are highly connected and complex, but a single enzyme, O-GlcNAc transferase (OGT) can sense the availability of metabolites and also modify target proteins. We show that inhibition of OGT activity inhibits the proliferation of prostate cancer cells, leads to sustained loss of c-MYC and suppresses the expression of CDK1, elevated expression of which predicts prostate cancer recurrence (p=0.00179). Metabolic profiling revealed decreased glucose consumption and lactate production after OGT inhibition. This decreased glycolytic activity specifically sensitized prostate cancer cells, but not cells representing normal prostate epithelium, to inhibitors of oxidative phosphorylation (rotenone and metformin). Intra-cellular alanine was depleted upon OGT inhibitor treatment. OGT inhibitor increased the expression and activity of alanine aminotransferase (GPT2), an enzyme that can be targeted with a clinically approved drug, cycloserine. Simultaneous inhibition of OGT and GPT2 inhibited cell viability and growth rate, and additionally activated a cell death response. These combinatorial effects were predominantly seen in prostate cancer cells, but not in a cell-line derived from normal prostate epithelium. Combinatorial treatments were confirmed with two inhibitors against both OGT and GPT2. Taken together, here we report the reprogramming of energy metabolism upon inhibition of OGT activity, and identify synergistically lethal combinations that are prostate cancer cell specific.

Ischemic A/D transition of mitochondrial complex I and its role in ROS generation

Mitochondrial complex I (NADH:ubiquinone oxidoreductase) is a key enzyme in cellular energy metabolism and provides approximately 40% of the proton-motive force that is utilized during mitochondrial ATP production. The dysregulation of complex I function – either genetically, pharmacologically, or metabolically induced – has severe pathophysiological consequences that often involve an imbalance in the production of reactive oxygen species (ROS). Slow transition of the active (A) enzyme to the deactive, dormant (D) form takes place during ischemia in metabolically active organs such as the heart and brain. The reactivation of complex I occurs upon reoxygenation of ischemic tissue, a process that is usually accompanied by an increase in cellular ROS production. Complex I in the D-form serves as a protective mechanism preventing the oxidative burst upon reperfusion. Conversely, however, the D-form is more vulnerable to oxidative/nitrosative damage. Understanding the so-called active/deactive (A/D) transition may contribute to the development of new therapeutic interventions for conditions like stroke, cardiac infarction, and other ischemia-associated pathologies. In this review, we summarize current knowledge on the mechanism of A/D transition of mitochondrial complex I considering recently available structural data and site-specific labeling experiments. In addition, this review discusses in detail the impact of the A/D transition on ROS production by complex I and the S-nitrosation of a critical cysteine residue of subunit ND3 as a strategy to prevent oxidative damage and tissue damage during ischemia–reperfusion injury.

A family with erythrocytosis establishes a role for prolyl hydroxylase domain protein 2 in oxygen homeostasis

The number of red blood cells is normally tightly regulated by a classic homeostatic mechanism based on oxygen sensing in the kidney. Decreased oxygen delivery resulting from anemia induces the production of erythropoietin, which increases red cell production and hence oxygen delivery. Investigations of erythropoietin regulation identified the transcription factor hypoxia-inducible factor (HIF). HIF is now recognized as being a key regulator of genes that function in a comprehensive range of processes besides erythropoiesis, including energy metabolism and angiogenesis. HIF itself is regulated through the -subunit, which is hydroxylated in the presence of oxygen by a family of three prolyl hydroxylase domain proteins (PHDs)/HIF prolyl hydroxylases/egg-laying-defective nine enzymes. Hydroxylation allows capture by the von Hippel–Lindau tumor suppressor gene product, ubiquitination, and destruction by the proteasome. Here we describe an inherited mutation in a mammalian PHD enzyme. We show that this mutation in PHD2 results in a marked decrease in enzyme activity and is associated with familial erythrocytosis, identifying a previously unrecognized cause of this condition. Our findings indicate that PHD2 is critical for normal regulation of HIF in humans.

Differences in resting metabolic rates of two southern African tortoises: Psammobates oculiferus and Geochelone pardalis

Energy metabolism varies considerably between different groups of endotherms, yet there is little or no reported variation among extant groups of reptiles. We measured lower resting metabolic rates (RMRs) in Kalahari tent tortoises (Psammobate oculiferus) than in sympatric Leopard tortoises (Geochelone pardalis). G pardalis also had RMR values that were higher than the allometric prediction for reptiles whereas P oculiferus had RMR values that were not significantly different from the prediction. Differences in RMR between the two species may have occurred because of the large differences in body mass, differing body temperatures, differences in growth rates, or because there may have been differences in the heat increment of feeding.

Comparative proteome analysis of triclabendazole response in the liver fluke, Fasciola hepatica.

Control of Fasciola hepatica infections of livestock in the absence of vaccines depends largely on the chemical triclabendazole (TCBZ) because it is effective against immature and adult parasites. Overdependence on a single drug and improper application is considered a significant factor in increasing global reports of fluke resistant to TCBZ. The mode(s) of action and biological target(s) of TCBZ are not confirmed, delaying detection and the monitoring of early TCBZ resistance. In this study, to further understand liver fluke response to TCBZ, the soluble proteomes of TCBZ-resistant and TCBZ-susceptible isolates of F. hepatica were compared with and without in vitro exposure to the metabolically active form of the parent drug triclabendazole sulphoxide (TCBZ-SO), via two-dimensional gel electrophoresis (2-DE). Gel image analysis revealed proteins displaying altered synthesis patterns and responses both between isolates and under TCBZ-SO exposure. These proteins were identified by mass spectrometry supported by a F. hepatica expressed sequence tag (EST) data set. The TCBZ responding proteins were grouped into three categories; structural proteins, energy metabolism proteins, and “stress” response proteins. This single proteomic investigation supported the reductionist experiments from many laboratories that collectively suggest TCBZ has a range of effects on liver fluke metabolism. Proteomics highlighted differences in the innate proteome profile of different fluke isolates that may influence future therapy and diagnostics design. Two of the TCBZ responding proteins, a glutathione transferase and a fatty acid binding protein, were cloned, produced as recombinants, and both found to bind TCBZ-SO at physiologically relevant concentrations, which may indicate a role in TCBZ metabolism and resistance.

Fasciolicides: Efficacy, actions, resistance and its management

The modes of action of fasciolicides are described. Closantel and other salicylanilides interfere with energy metabolism by uncoupling oxidative phosphorylation in the fluke. Other fasciolicides are believed to have a metabolic action-halogenated phenols (via uncoupling) and clorsulon (via inhibition of glycolysis)-but direct evidence is lacking. Benzimidazoles (in particular, riclabendazole) bind to fluke tubulin and disrupt microtubule-based processes. Diamphenethide inhibits protein synthesis in the fluke. Other potential drug actions may contribute to overall drug efficacy. In particular, a number of fasciolicides-salicylanilides, phenols, diamphenethide-induce a rapid paralysis of the fluke, so their action may have a neuromuscular basis, although the actions remain ill-defined. Resistance to salicylanilides and triclabendazole has been detected in the field, although drug resistance does not appear to be a major problem yet. Strategies to minimize the development of resistance include the use of synergistic drug combinations, together with the design of integrated management programmes and the search for alternatives to drugs, in particular, vaccines. (C) 1999 Harcourt Publishers Ltd.

Fructose Chemistry

Fructose is a six-carbon ketose monosaccharide. In aqueous solution and in the crystalline form, the majority of the molecules form ring structures. Of these, the six-membered pyranose form is the most abundant; however, about one-quarter of the molecules are in the five-membered, furanose form. While many of its reactions are similar to those of glucose, the presence of a ketone group in the chain, and the relative ease with which the molecule forms a five-membered furanose ring affects its chemistry and biochemistry. Specific pathways are required to enable organisms to exploit fructose in energy metabolism; these require the enzyme fructokinase and involve the conversion of fructose to glycolytic intermediates. Similarly, specific pathways for the biosynthesis of fructose and fructose-containing polymers, such as inulin, are required. Non-enzymatic glycation (fructation) by fructose has not been as extensively studied as the corresponding reactions with glucose. Nevertheless, especially in diabetic patients and fructose-rich foodstuffs, this reaction is likely to be important.

Determining optimal duration of seed translocation periods for benthic mussel (Mytilus edulis) cultivation using physiological and behavioural measures of stress

During the benthic cultivation process of Mytilus edulis (blue mussels), wild mussel seed is often transplanted from naturally occurring subtidal beds to sheltered in-shore waters to be grown to a commercial size. The survival of these relaid mussels is ultimately a function of their quality and physiological condition upon relaying and it has been recognised that mussels can suffer from a loss in condition following transportation. We investigated whether the process of being transported to ongrowing plots had a negative effect on the physiological health and resultant behaviour of mussels by simulating transportation conditions in a controlled experiment. Mussels were kept, out of water, in plastic piping to recreate translocation conditions and further, we tested if depth held in a ship hold (0, 1.5 and 3 m) and length of time emersed (12, 24 and 48 h) affected mussel condition and behaviour. Physiological condition was assessed by quantifying mussel tissue pH and whole tissue glucose, glycogen, succinate and propionate concentrations. The rate of byssogenesis was also quantified to estimate recovery following a period of re-immersion. The depth at which mussels were held did not affect any of the physiological indicators of mussel stress but short-term byssus production was affected. Mussels held at 3 m produced fewer byssus threads during the first 72 h following re-immersion compared with mussels at 0 m (i.e. not buried) suggesting that depth held can impede recovery following transportation. Duration of emersion affected all stress indicators. Specifically, mussels held out of water for 48 h had a reduced physiological condition compared with those emersed for just 12 h. This work has practical implications for the benthic cultivation industry and based on these results we recommend that mussels are held out of water for less than 24 h prior to relaying to ensure physiological health and resultant condition is preserved.

Genetic studies of body mass index yield new insights for obesity biology

Obesity is heritable and predisposes to many diseases. To understand the genetic basis of obesity better, here we conduct a genome-wide association study and Metabochip meta-analysis of body mass index (BMI), a measure commonly used to define obesity and assess adiposity, in up to 339,224 individuals. This analysis identifies 97 BMI-associated loci (P < 5 × 10(-8)), 56 of which are novel. Five loci demonstrate clear evidence of several independent association signals, and many loci have significant effects on other metabolic phenotypes. The 97 loci account for ∼2.7% of BMI variation, and genome-wide estimates suggest that common variation accounts for >20% of BMI variation. Pathway analyses provide strong support for a role of the central nervous system in obesity susceptibility and implicate new genes and pathways, including those related to synaptic function, glutamate signalling, insulin secretion/action, energy metabolism, lipid biology and adipogenesis.

Effect of monovalent cations on the kinetics of hypoxic conformational change of mitochondrial complex i

Mitochondrial complex I is a large, membrane-bound enzyme central to energy metabolism, and its dysfunction is implicated in cardiovascular and neurodegenerative diseases. An interesting feature of mammalian complex I is the so-called A/D transition, when the idle enzyme spontaneously converts from the active (A) to the de-active, dormant (D) form. The A/D transition plays an important role in tissue response to ischemia and rate of the conversion can be a crucial factor determining outcome of ischemia/reperfusion. Here, we describe the effects of alkali cations on the rate of the D-to-A transition to define whether A/D conversion may be regulated by sodium.At neutral pH (7–7.5) sodium resulted in a clear increase of rates of activation (D-to-A conversion) while other cations had minor effects. The stimulating effect of sodium in this pH range was not caused by an increase in ionic strength. EIPA, an inhibitor of Na+/H+antiporters, decreased the rate of D-to-A conversion and sodium partially eliminated this effect of EIPA. At higher pH (> 8.0), acceleration of the D-to-A conversion by sodium was abolished, and all tested cations decreased the rate of activation, probably due to the effect of ionic strength.The implications of this finding for the mechanism of complex I energy transduction and possible physiological importance of sodium stimulation of the D-to-A conversion at pathophysiological conditions in vivo are discussed.