Serum markers for early detection of patients with mesenteric ischemia after cardiac surgery.

OBJECTIVE: Mesenteric ischemia (MESI) is a rare but often fatal complication in patients after cardiac surgery. Non-specific clinical symptoms and lack of specific laboratory parameters complicate the diagnosis. We evaluated potential serum markers for MESI in cardiac surgery patients. METHODS: Between March and October 2012, serial serum samples of 567 elective cardiac surgery patients were collected 1, 24, and 48 h after the operation, and concentrations of potential markers for MESI [α-glutathione-S-transferase (αGST), intestinal fatty-acid-binding protein (iFABP), and D-lactate] were measured retrospectively. In patients requiring laparotomy, blood samples obtained 72, 48, 24, and 12 h before the laparotomy were additionally measured and compared to all other patients (control group). RESULTS: Laparotomy was performed in 18 patients at 11±7 days after cardiac surgery. MESI was found in 9/18 patients. Already 1 h after cardiac surgery, the serum concentrations of D-lactate (37±18 vs. 25±20 nmol/mL, p<0.01) and αGST (82±126 vs. 727±1382 µg/L, p<0.01) in patients undergoing laparotomy were increased compared to the control group. Between patients with and without MESI, differences were only found for iFABP 24 h after cardiac surgery (1.1±0.4 vs. 2.9±0.6 ng/mL, p=0.04) and up to 72 h before laparotomy (0.56±0.72 vs. 2.51±1.96 ng/mL, p=0.01). CONCLUSIONS: D-lactate and αGST were early markers for gastrointestinal complications after cardiac surgery. Before laparotomy, lowered iFABP levels indicated MESI. Routinely used, these markers can help identify patients with gastrointestinal complications after cardiac surgery early, and might be useful for the evaluation of new therapeutic or preventive strategies.

Accelerated progression of coronary artery calcification in hypertension but also prehypertension.

OBJECTIVE: To determine the role of hypertension for coronary artery calcification (CAC) progression. METHODS: The population-based Heinz Nixdorf Recall study recruited 4814 participants from a German urban population in 2000-2003. CAC was measured using electron-beam computed tomography at baseline and after 5 years. The present analyses refer to 3481 participants with repeat scan (coronary heart disease until 5 years excluded, age at baseline 45-74 years, and 53.1% women). Blood pressure (BP), Framingham risk factors, and antihypertensive medication were recorded at baseline. BP was staged according to Joint National Committee 7 guidelines. Participants under antihypertensive medication were classified as stage 2. CAC at 5 years was predicted from baseline using our dedicated, publicly available algorithm. CAC progression was accordingly classified as slow, expected, or rapid. RESULTS: Normotension was found in 20.5%, prehypertension in 27.2%, stage 1 hypertension in 15.8%, and stage 2 (ST2) in 36.5%. The frequency of rapid progression increases with BP stage (normotension: 16.7% to ST2: 21.1%, P = 0.004). Risk factor adjusted relative risk [RR (95% confidence interval), reference: normotension] of rapid progression was for prehypertension: 1.22 (0.98;1.51), stage 1: 1.29 (1.01;1.65), and ST2: 1.45 (1.17;1.79). Risk factor adjusted measures of CAC progression per 10 mmHg SBP were already elevated in women with BP below 140/90 mmHg: CAC onset, RR = 1.22 (1.07;1.40), rapid progression, RR = 1.17 (1.05;1.31), 5-year CAC progression, 6.7% (0.5;13.4). In men below 140/90 mmHg, only RR of rapid progression was considerably increased [RR = 1.11 (0.96;1.29)]. CONCLUSION: CAC progression, a sign of ongoing target organ damage, is already accelerated in prehypertensive patients, a substantial proportion of our urban population.

Associations among sleep disturbances, nocturnal sleep duration, daytime napping, and incident prediabetes and type 2 diabetes: the Heinz Nixdorf Recall Study.

OBJECTIVE: Poor sleep quality as well as short and long sleep duration has been linked to type 2 diabetes. In addition to confirmational analyses, we examined the impact of daytime napping on incident diabetes, and we assessed associations between sleep characteristics and incident prediabetes. METHODS: In a subgroup of the Heinz Nixdorf Recall Study, a population-based cohort study in Germany (N = 2962; age 45-75 years, without history of cancer, stroke, or cardiovascular diseases), diabetes at baseline and at 5-year follow-up was assessed by self-report and measurement of serum glucose levels. Prediabetes was defined as impaired fasting glucose (6.1-6.9 mmol/L). A sleep questionnaire was used to assess difficulties falling asleep, difficulties maintaining sleep, early morning arousal, and duration of nocturnal and daytime sleep. RESULTS: In adjusted regression models, short (≤5 hours) and long (≥7.5 hours) sleepers were at greater risk for diabetes (relative risk [RR] = 1.56, 95% confidence interval [CI] = 1.02-2.39, and 1.40, 95% CI = 1.01-1.96, respectively [reference: 7 hours]). Moreover, the prevalence of any regular sleep disorder was associated with incident diabetes (RR = 1.30, 95% CI = 1.01-1.68), and with incident prediabetes (RR = 1.31, 95% CI = 1.00-1.72). Regular daytime nappers had no increased risk of incident diabetes (RR = 1.00, 95% CI = 0.70-1.41). CONCLUSION: This study shows that people with regular sleep disorders, people with short and long sleep duration, but not regular daytime nappers are at increased risk of diabetes. Furthermore, regular sleep disorders are associated with an increased risk of prediabetes.

Mutant p97 exhibits species-specific changes of its ATPase activity and compromises the UBXD9-mediated monomerisation of p97 hexamers.

p97 (VCP) is a homo-hexameric triple-A ATPase that exerts a plethora of cellular processes. Heterozygous missense mutations of p97 cause at least five human neurodegenerative disorders. However, the specific molecular consequences of p97 mutations are hitherto widely unknown. Our in silico structural models of human and Dictyostelium p97 showed that the disease-causing human R93C, R155H, and R155C as well as Dictyostelium R154C, E219K, R154C/E219K p97 mutations constitute variations in surface-exposed locations. In-gel ATPase activity measurements of p97 monomers and hexamers revealed significant mutation- and species-specific differences. While all human p97 mutations led to an increase in ATPase activity, no changes could be detected for the Dictyostelium R154C mutant, which is orthologous to human R155C. The E219K mutation led to an almost complete loss of activity, which was partially recuperated in the R154C/E219K double-mutant indicating p97 inter-domain communication. By means of co-immunoprecipitation experiments we identified an UBX-domain containing Dictyostelium protein as a novel p97 interaction partner. We categorized all UBX-domain containing Dictyostelium proteins and named the interaction partner UBXD9. Pull-down assays and surface plasmon resonance analyses of Dictyostelium UBXD9 or the human orthologue TUG/ASPL/UBXD9 demonstrated direct interactions with p97 as well as species-, mutation- and ATP-dependent differences in the binding affinities. Sucrose density gradient assays revealed that both human and Dictyostelium UBXD9 proteins very efficiently disassembled wild-type, but to a lesser extent mutant p97 hexamers into monomers. Our results are consistent with a scenario in which p97 point mutations lead to differences in enzymatic activities and molecular interactions, which in the long-term result in a late-onset and progressive multisystem disease.

VCP and PSMF1: Antagonistic regulators of proteasome activity.

Protein turnover and quality control by the proteasome is of paramount importance for cell homeostasis. Dysfunction of the proteasome is associated with aging processes and human diseases such as neurodegeneration, cardiomyopathy, and cancer. The regulation, i.e. activation and inhibition of this fundamentally important protein degradation system, is still widely unexplored. We demonstrate here that the evolutionarily highly conserved type II triple-A ATPase VCP and the proteasome inhibitor PSMF1/PI31 interact directly, and antagonistically regulate proteasomal activity. Our data provide novel insights into the regulation of proteasomal activity.

Heteromeric p97/p97R155C complexes induce dominant negative changes in wild-type and autophagy 9-deficient Dictyostelium strains.

Heterozygous mutations in the human VCP (p97) gene cause autosomal-dominant IBMPFD (inclusion body myopathy with early onset Paget's disease of bone and frontotemporal dementia), ALS14 (amyotrophic lateral sclerosis with or without frontotemporal dementia) and HSP (hereditary spastic paraplegia). Most prevalent is the R155C point mutation. We studied the function of p97 in the social amoeba Dictyostelium discoideum and have generated strains that ectopically express wild-type (p97) or mutant p97 (p97(R155C)) fused to RFP in AX2 wild-type and autophagy 9 knock-out (ATG9(KO)) cells. Native gel electrophoresis showed that both p97 and p97(R155C) assemble into hexamers. Co-immunoprecipitation studies revealed that endogenous p97 and p97(R155C)-RFP form heteromers. The mutant strains displayed changes in cell growth, phototaxis, development, proteasomal activity, ubiquitinylated proteins, and ATG8(LC3) indicating mis-regulation of multiple essential cellular processes. Additionally, immunofluorescence analysis revealed an increase of protein aggregates in ATG9(KO)/p97(R155C)-RFP and ATG9(KO) cells. They were positive for ubiquitin in both strains, however, solely immunoreactive for p97 in the ATG9(KO) mutant. A major finding is that the expression of p97(R155C)-RFP in the ATG9(KO) strain partially or fully rescued the pleiotropic phenotype. We also observed dose-dependent effects of p97 on several cellular processes. Based on findings in the single versus the double mutants we propose a novel mode of p97 interaction with the core autophagy protein ATG9 which is based on mutual inhibition.

Strumpellin is a novel valosin-containing protein binding partner linking hereditary spastic paraplegia to protein aggregation diseases.

Mutations of the human valosin-containing protein gene cause autosomal-dominant inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia. We identified strumpellin as a novel valosin-containing protein binding partner. Strumpellin mutations have been shown to cause hereditary spastic paraplegia. We demonstrate that strumpellin is a ubiquitously expressed protein present in cytosolic and endoplasmic reticulum cell fractions. Overexpression or ablation of wild-type strumpellin caused significantly reduced wound closure velocities in wound healing assays, whereas overexpression of the disease-causing strumpellin N471D mutant showed no functional effect. Strumpellin knockdown experiments in human neuroblastoma cells resulted in a dramatic reduction of axonal outgrowth. Knockdown studies in zebrafish revealed severe cardiac contractile dysfunction, tail curvature and impaired motility. The latter phenotype is due to a loss of central and peripheral motoneuron formation. These data imply a strumpellin loss-of-function pathogenesis in hereditary spastic paraplegia. In the human central nervous system strumpellin shows a presynaptic localization. We further identified strumpellin in pathological protein aggregates in inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia, various myofibrillar myopathies and in cortical neurons of a Huntington's disease mouse model. Beyond hereditary spastic paraplegia, our findings imply that mutant forms of strumpellin and valosin-containing protein may have a concerted pathogenic role in various protein aggregate diseases.