Development and performance of an enzyme immunoassay to detect creatine kinase isoenzyme MB activity using anti-mitochondrial creatine kinase monoclonal antibodies

Synthesis of Fluorescent Titanium Nanoclusters at ambient temperature for highly sensitive and selective detection of Creatine Kinase MM in myocardial infarction

Fluorescent-based biosensing in Photoluminescence nanomaterials has emerged as a new sensing platform commonly used for disease diagnosis. However, the synthesis of Titanium nanoclusters is highly challenging since Titanium is easily oxidized into TiO₂ at ambient temperature. To overcome this problem, we used an acidic medium and simple and robust protocol to synthesize the Titanium nanoclusters of 3-4 nm diameter, which could report the first fluorescent Titanium nanoclusters. New approaches for the novel synthesis of TiNCs can be used for rapid sensing of myocardial infarction (cardiac arrest). In converting creatine to phosphocreatine, CK-MM activates the reaction to convert ATP to ADP, thereby releasing the phosphate groups. Titanium nanoclusters bind strongly to the phosphate group and then quench the Fluorescence. Thus, this phenomenon can be further applied for quantification approaches. The quenching of fluorescence intensity with CK-MM concentration is linear with R² = 0.9829. The current approach can be applied for CK-MM sensing for a wide concentration range (0.625 U/L - 10 U/L). The detection limit was 0.2513 ng/ml in aqueous medium and 0.3465 ng/ml in human serum with high sensitivity when compared with the previous reported methods. Also, this is the first fluorescent-based sensing method to detect CK- MM. The fluorescent TiNCs is a novel platform to be widely applied for the phosphopeptide and phosphoprotein analysis due to the strong and covalent bondings between Ti with P atoms in the near future in medicine, biomedicine, and biological fields.

MiR-519b-3p Inhibits the Proliferation and Invasion in Colorectal Cancer via Modulating the uMtCK/Wnt Signaling Pathway

Dysregulation of microRNAs (miRNAs) and their targeted downstream genes is involved in the carcinogenesis and progression of colorectal cancer (CRC). miR-519b-3p has been reported to play an important role in several cancers. However, its function in CRC is unclear. In this study, we detected the expression of miR-519b-3p in CRC tissues and cell lines, and determined the potential role of miR-519b-3p in cell proliferation and invasion in CRC. Also, the downstream gene of miR-519b-3p was determined. Our results showed that miR-519b-3p was notably reduced in CRC specimens and cell lines. Overexpression of miR-519b-3p inhibited the proliferation and invasion of RKO and DLD-1 cells, whereas knockdown of miR-519b-3p had the contrary effect. The ubiquitous mitochondrial creatine kinase (uMtCK) was identified as a direct target of miR-519b-3p in CRC using luciferase assay. Additionally, miR-519b-3p expression was negatively correlated with uMtCK expression in CRC specimens. Notably, the miR-519b-3p suppressed the uMtCK/Wnt signaling pathway in CRC cells, thereby suppressing CRC cell proliferation and invasion. The inhibition of uMtCK by miR-519b-3p may provide a promising option for the treatment of CRC.

Mitochondrial Creatine Kinase is Decreased in the Serum of Idiopathic Parkinson's Disease Patients

Mitochondrial creatine kinase (MtCK) is vital in the process of mitochondrial energy metabolism, and mitochondrial dysfunction has been implicated in the pathogenesis of Parkinson’s disease (PD). Therefore, we speculated that MtCK activity could be altered in the serum of PD patients. However, no studies to date have investigated this specific topic, so we sought to investigate the serum MtCK activities among a cohort of PD patients. 50 patients with PD and 30 age-matched controls were recruited for this study. Serum ubiquitous MtCK (uMtCK) and sarcomeric MtCK (sMtCK) activities were assayed using an immunoinhibition method. Correlations between serum uMtCK/sMtCK activities and clinical features/parameters were explored in the PD group. Our study revealed a significant decrease in the uMtCK activity in the PD group when compared with the control group. No significant difference was found in the serum sMtCK activity between the PD and control groups. There was a significant correlation between serum uMtCK activities and the disease progression rate, duration, and age at onset in PD patients. While no significant relationship was found between the serum uMtCK activities and the Hoehn & Yahr stage or main non-motor symptoms scale. There was a significant decrease in the uMtCK activity in the serum of PD patients, which was associated with the rate of disease progression, duration, and age at onset of disease. Therefore, uMtCK activity in serum offers a useful clue for identification of PD biomarkers.

Mitochondrial Proteolipid Complexes of Creatine Kinase

Isoforms of creatine kinase (CK) generate and use phosphocreatine, a concentrated and highly diffusible cellular "high energy" intermediate, for the main purpose of energy buffering and transfer in order to maintain cellular energy homeostasis. The mitochondrial CK isoform (mtCK) localizes to the mitochondrial intermembrane and cristae space, where it assembles into peripherally membrane-bound, large cuboidal homooctamers. These are part of proteolipid complexes wherein mtCK directly interacts with cardiolipin and other anionic phospholipids, as well as with the VDAC channel in the outer membrane. This leads to a stabilization and cross-linking of inner and outer mitochondrial membrane, forming so-called contact sites. Also the adenine nucleotide translocator of the inner membrane can be recruited into these proteolipid complexes, probably mediated by cardiolipin. The complexes have functions mainly in energy transfer to the cytosol and stimulation of oxidative phosphorylation, but also in restraining formation of reactive oxygen species and apoptosis. In vitro evidence indicates a putative role of mtCK in mitochondrial phospholipid distribution, and most recently a role in thermogenesis has been proposed. This review summarizes the essential structural and functional data of these mtCK complexes and describes in more detail the more recent advances in phospholipid interaction, thermogenesis, cancer and evolution of mtCK.

Determination of total creatine kinase activity in blood serum using an amperometric biosensor based on glucose oxidase and hexokinase

Creatine kinase (CK: adenosine-5-triphosphate-creatine phosphotransferase) is an important enzyme of muscle cells; the presence of a large amount of the enzyme in blood serum is a biomarker of muscular injuries, such as acute myocardial infarction. This work describes a bi-enzyme (glucose oxidase and hexokinase based) biosensor for rapid and convenient determination of CK activity by measuring the rate of ATP production by this enzyme. Simultaneously the biosensor determines glucose concentration in the sample. Platinum disk electrodes were used as amperometric transducers. Glucose oxidase and hexokinase were co-immobilized via cross-linking with BSA by glutaraldehyde and served as a biorecognition element of the biosensor. The biosensor work at different concentrations of CK substrates (ADP and creatine phosphate) was investigated; optimal concentration of ADP was 1mM, and creatine phosphate - 10 mM. The reproducibility of the biosensor responses to glucose, ATP and CK during a day was tested (relative standard deviation of 15 responses to glucose was 2%, to ATP - 6%, to CK - 7-18% depending on concentration of the CK). Total time of CK analysis was 10 min. The measurements of creatine kinase in blood serum samples were carried out (at 20-fold sample dilution). Twentyfold dilution of serum samples was chosen as optimal for CK determination. The biosensor could distinguish healthy and ill people and evaluate the level of CK increase. Thus, the biosensor can be used as a test-system for CK analysis in blood serum or serve as a component of multibiosensors for determination of important blood substances. Determination of activity of other kinases by the developed biosensor is also possible for research purposes.

Comparison of Mass Versus Activity of Creatine Kinase MB and Its Utility in the Early Diagnosis of Re-infarction

Currently employed markers for the detection of acute coronary syndrome are Troponin T, CK (Creatine Kinase) and CKMB activity. CKMB activity measured by immunoinhibition method can give falsely elevated results due to the presence of atypical CK and CKBB and at times lead to the mis-diagnosis of acute coronary syndrome. Hence, CKMB mass (CKMB) measured by electrochemiluminence sandwich principle was employed. In this cross-sectional study 183 samples of 61 patients were analyzed within 6 h of diagnosis of acute coronary syndrome and followed up to 72 h. The correlation coefficient between CKMB activity and CKMBM at 4-6 h was 0.744, while at 12-24 h it was 0.909 and at 48-72 h it was 0.337. Thus there was good association between the two methods at 12-24 h but, statistically for method comparison studies and for replacing one method by another, the two methods need to be in agreement with one another. In this study the two methods are not in agreement with one another and thus analytically not replaceable. Another finding was obtained that CKMBM reached cut off levels prior to CKMB enzyme activity and hence, CKMBM is clinically better than CKMB activity to detect reinfarction.

High ubiquitous mitochondrial creatine kinase expression in hepatocellular carcinoma denotes a poor prognosis with highly malignant potential

We previously reported the increased serum mitochondrial creatine kinase (MtCK) activity in patients with hepatocellular carcinoma (HCC), mostly due to the increase in ubiquitous MtCK (uMtCK), and high uMtCK mRNA expression in HCC cell lines. We explored the mechanism(s) and the relevance of high uMtCK expression in HCC. In hepatitis C virus core gene transgenic mice, known to lose mitochondrial integrity in liver and subsequently develop HCC, uMtCK mRNA and protein levels were increased in HCC tissues but not in non-tumorous liver tissues. Transient overexpression of ankyrin repeat and suppressor of cytokine signaling box protein 9 (ASB9) reduced uMtCK protein levels in HCC cells, suggesting that increased uMtCK levels in HCC cells may be caused by increased gene expression and decreased protein degradation due to reduced ASB9 expression. The reduction of uMtCK expression by siRNA led to increased cell death, and reduced proliferation, migration and invasion in HCC cell lines. Then, consecutive 105 HCC patients, who underwent radiofrequency ablation with curative intent, were enrolled to analyze their prognosis. The patients with serum MtCK activity >19.4 U/L prior to the treatment had significantly shorter survival time than those with serum MtCK activity ≤ 19.4 U/L, where higher serum MtCK activity was retained as an independent risk for HCC-related death on multivariate analysis. In conclusion, high uMtCK expression in HCC may be caused by hepatocarcinogenesis per se but not by loss of mitochondrial integrity, of which ASB9 could be a negative regulator, and associated with highly malignant potential to suggest a poor prognosis.

Increased activity of serum mitochondrial isoenzyme of creatine kinase in hepatocellular carcinoma patients predominantly with recurrence

BACKGROUND & AIMS

Mitochondrial isoenzyme of creatine kinase (MtCK) is reportedly highly expressed in hepatocellular carcinoma (HCC). Clinical relevance of serum MtCK activity in patients with HCC was assessed using a novel immuno-inhibition method.

METHODS

Among patients with cirrhosis caused by hepatitis B or C virus, 147 patients with HCC (12 with the first occurrence and 135 with recurrence) and 92 patients without HCC were enrolled.

RESULTS

Serum MtCK activity was higher in cirrhotic patients with HCC than in those without HCC or healthy subjects. Elevated serum MtCK activity in HCC patients decreased after radiofrequency ablation. In case of prediction of HCC, MtCK had a sensitivity of 62.6% and a specificity of 70.7% at a cut-off point of 8.0 U/L, with an area under the receiver operating curve of 0.722 vs. 0.713 for alpha-fetoprotein (AFP) and 0.764 for des-gamma-carboxy prothrombin (DCP). Among the HCC patients, serum MtCK activity was elevated in 52.9% individuals with serum AFP level < 20 ng/ml and 63.2% individuals with serum DCP level < 40 mAu/ml. Even in patients with a single HCC ≤ 2 cm, the sensitivity of serum MtCK activity for the prediction of HCC was 64.4%, which was comparable to the overall sensitivity. This increased activity was due to an increase in ubiquitous MtCK, not sarcomeric MtCK, and the enhanced mRNA expression of ubiquitous MtCK was observed in cell lines originating from HCCs in contrast to healthy liver tissues.

CONCLUSIONS

Serum MtCK activity merits consideration as a novel marker for HCC to be further tested as for its diagnostic and prognostic power.

Increase in serum mitochondrial creatine kinase levels induced by tenofovir administration

Recently, 2 monoclonal antibodies that specifically inhibit mitochondrial creatine kinase (MtCK) activity have been developed. In this study, we measured the serum MtCK activity in HIV-1-infected individuals (n = 100) by employing a novel method using these antibodies. The mean serum MtCK activity in 44 patients treated with highly active antiretroviral therapy (HAART) including tenofovir disoproxil fumarate (TDF) was 16.0 IU/L. The MtCK activity was significantly higher in patients receiving TDF than in those receiving HAART without TDF (3.4 IU/L) or in naïve patients (6.9 IU/L) (Tukey-Kramer test, p < 0.0001 and p = 0.0029, respectively). The serum MtCK activity reached a plateau at 1 month after the initiation of TDF administration and decreased upon discontinuation. It showed no significant correlation with the trough plasma TDF concentration, serum creatinine level, or red blood cell count. The activity was elevated in 75% of the patients receiving TDF, and this elevation was specific to TDF; it was not observed with other anti-HIV drugs. In addition, our report emphasizes the careful interpretation of creatine kinase-MB (CK-MB) test results in patients receiving TDF because MtCK in serum could cause false-positive results on a conventional CK-MB test, which does not include MtCK-specific inhibitory antibodies.

Anomalous Activity Measurements of Creatine (Phospho) Kinase, CK-MB Isoenzyme in Indian Patients in the Diagnosis of Acute Coronary Syndrome

In the present study, the cause of suspected false-positive (anomalous) values for CK-MB activity, in Indian patients investigated for ACS. Total serum CK and CK-MB activity, serum Troponin I were measured and CK-MB as a percentage of the total CK activity (%CK-MB) calculated. CK-MB was also estimated using densitometry and CK-MB mass assay. Anomalous specimens were tested for the presence of CK isoenzymes. In 22 healthy subjects, 11 male and female, the %CK-MB ranged from 3.6 to 30.2. In 11 male patients, with proven ACS, the %CK-MB was from 4.0 to 17.5. The cut off for anomalous CK-MB activity values was set as >33.0%. In 35 patients with anomalies, total CK values ranged from 39 to 231 U/L, CK-MB from 30 to 161 U/L. Investigation of CK isoenzymes, showed 10 patients had a CK-BB band, 14 an intermediate band between CK-MM and CK-MB (macro-CK type 1), 7 had a cathodal band (macro-CK type 2), and 3 had a band intermediate between CK-MB and CK-BB. This later band does not seem to have been previously reported. Against the CK-MB mass assay, the activity assay showed no correlation, in 43 patients (19 M, 24 F), Pearson coefficient (R(2)) was 0.006. The CK-MB immunoinhibition assay is better described as measuring "non-CK-MM activity." A %CK-MB activity >6% as a marker of ACS is not valid in our patient population. Laboratories should not use only CK-MB activity as a biochemical marker of ACS.