Stensløkken KO, Ellefsen S, Stecyk JAW, Dahl MB, Nilsson GE, Vaage J. Differential regulation of AMP-activated kinase and AKT kinase in response to oxygen availability in crucian carp (Carassius carassius). Am J Physiol Regul Integr Comp Physiol 295: R1803-R1814, 2008. First published October 15, 2008 doi:10.1152/ajpregu.90590.2008.-We investigated whether two kinases critical for survival during periods of energy deficiency in anoxia-intolerant mammalian species, AMP-activated kinase (AMPK), and protein kinase B (AKT), are equally important for hypoxic/anoxic survival in the extremely anoxia-tolerant crucian carp (Carassius carassius). We report that phosphorylation of AMPK and AKT in heart and brain showed small changes after 10 days of severe hypoxia (0.3 mg O 2/l at 9°C). In contrast, anoxia exposure (0.01 mg O2/l at 8°C) substantially increased AMPK phosphorylation but decreased AKT phosphorylation in carp heart and brain, indicating activation of AMPK and deactivation of AKT. In agreement, blocking the activity of AMPK in anoxic fish in vivo with 20 mg/kg Compound C resulted in an elevated metabolic rate (as indicated by increased ethanol production) and tended to reduce energy charge. This is the first in vivo experiment with Compound C in a nonmammalian vertebrate, and it appears that AMPK plays a role in mediating anoxic metabolic depression in crucian carp. Real-time RT-PCR analysis of the investigated AMPK subunit revealed that the most likely composition of subunits in the carp heart is ␣ 2, ␤1B, ␥2a, whereas a more even expression of subunits was found in the brain. In the heart, expression of the regulatory ␥ 2-subunit increased in the heart during anoxia. In the brain, expression of the ␣ 1-, ␣2-, and ␥1-subunits decreased with anoxia exposure, but expression of the ␥ 2-subunit remained constant. Combined, our findings suggest that AMPK and AKT may play important, but opposing roles for hypoxic/anoxic survival in the anoxia-tolerant crucian carp. metabolism; hypoxia; ATP; ADP; ethanol ANOXIA TOLERANCE IN VERTEBRATES is limited to a few species, the most extreme being the crucian carp (Carassius carassius) and the freshwater turtles (genera Trachemys, Chrysemys, and Chelydra). These ectothermic animals can survive for months without oxygen at temperatures near 0°C (43,50). A key to survival in prolonged anoxia is the successful matching of ATP demand to the limited ATP production from anaerobic glycolysis. The anoxia-tolerant species appear to have evolved different strategies to meet this challenge (32). The turtle is strongly metabolically depressed during anoxia, with a drastically suppressed rate of ATP-turnover. Anoxic Carassius also decreases metabolic rate, but to a more moderate extent (62).The anoxic carp also upregulates glycolysis to match ATP supply and demand (33), but has evolved a unique strategy of producing ethanol as the major end product of anaerobic glycolysis (56). Ethanol is released to the surrounding water to avoid severe acidosis (42), and liver glycogen content is likely...

BackgroundSeveral beneficial effects have been demonstrated for secretogranin II (SgII) in non-cardiac tissue. As cardiac production of chromogranin A and B, two related proteins, is increased in heart failure (HF), we hypothesized that SgII could play a role in cardiovascular pathophysiology.Methodology/Principal FindingsSgII production was characterized in a post-myocardial infarction heart failure (HF) mouse model, functional properties explored in experimental models, and circulating levels measured in mice and patients with stable HF of moderate severity. SgII mRNA levels were 10.5 fold upregulated in the left ventricle (LV) of animals with myocardial infarction and HF (p<0.001 vs. sham-operated animals). SgII protein levels were also increased in the LV, but not in other organs investigated. SgII was produced in several cell types in the myocardium and cardiomyocyte synthesis of SgII was potently induced by transforming growth factor-β and norepinephrine stimulation in vitro. Processing of SgII to shorter peptides was enhanced in the failing myocardium due to increased levels of the proteases PC1/3 and PC2 and circulating SgII levels were increased in mice with HF. Examining a pathophysiological role of SgII in the initial phase of post-infarction HF, the SgII fragment secretoneurin reduced myocardial ischemia-reperfusion injury and cardiomyocyte apoptosis by 30% and rapidly increased cardiomyocyte Erk1/2 and Stat3 phosphorylation. SgII levels were also higher in patients with stable, chronic HF compared to age- and gender-matched control subjects: median 0.16 (Q1–3 0.14–0.18) vs. 0.12 (0.10–0.14) nmol/L, p<0.001.ConclusionsWe demonstrate increased myocardial SgII production and processing in the LV in animals with myocardial infarction and HF, which could be beneficial as the SgII fragment secretoneurin protects from ischemia-reperfusion injury and cardiomyocyte apoptosis. Circulating SgII levels are also increased in patients with chronic, stable HF and may represent a new cardiac biomarker.

BACKGROUND The N-terminal part of pro–B-type natriuretic peptide (NT-proBNP) is glycosylated, but whether glycosylation influences the diagnostic and prognostic accuracy of NT-proBNP measurements is not known. METHODS We measured NT-proBNP concentrations of 309 patients with acute dyspnea by use of standard EDTA tubes and EDTA tubes pretreated with deglycosylation enzymes. The primary cause of dyspnea was classified as heart failure (HF) or non-HF, and the diagnosis was adjudicated by 2 independent physicians. We collected information on all-cause mortality during follow-up. RESULTS In all, 142 patients (46%) were diagnosed with HF. NT-proBNP concentrations in nondeglycosylated samples distinguished HF patients from patients with non-HF related dyspnea [median 3588 (quartiles 1–3 1578–8404) vs 360 (126–1139) ng/L, P &lt; 0.001], but concentrations were markedly higher in samples pretreated with deglycosylation enzymes (total NT-proBNP) [7497 (3374–14 915) vs 798 (332–2296) ng/L, P &lt; 0.001]. The AUC to separate HF patients from patients with non-HF related dyspnea was 0.871 (95% CI 0.829–0.907) for total NT-proBNP compared with 0.852 (0.807–0.890) for NT-proBNP measurements in standard EDTA plasma. During a median follow-up of 816 days, 112 patients (36%) died. Both NT-proBNP and total NT-proBNP concentrations were associated with mortality in separate multivariate models, but only total NT-proBNP concentrations provided added value to the basic risk model of our dataset as assessed by the net reclassification index: 0.24 (95% CI 0.003–0.384). There was a graded increase in risk across total NT-proBNP quartiles, in contrast with the results for NT-proBNP measurements. CONCLUSIONS NT-proBNP concentrations were higher, and diagnostic and prognostic accuracy was improved, by pretreating tubes with deglycosylation enzymes.