Muscle Isoenzyme Research Articles

Hypoxia-Induced Ephrin-B2 Facilitates Proliferation and Induces Glycolytic Metabolism in Cutaneous Squamous Cell Carcinoma by Modulating PKM2/HIF-1α Axis.

Cutaneous squamous cell carcinoma (cSCC) is a fatal disease characterized by metabolic dysregulation. The role of ephrin type-B receptor 2 (ephrin-B2), a crucial molecule in cancer cell biology, in regulating glycolysis and cell proliferation of cSCC is not well understood. This study aimed to investigate the biological pathways by which ephrin-B2 impacts the glycolysis and cell proliferation of cSCC. Ephrin-B2 expression levels in cSCC were determined using quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and Western blotting. Ephrin-B2 expression in cSCC cells was manipulated using overexpression and knockdown approaches. A series of in vitro assays, such as cell counting kit-8 (CCK-8), Transwell assay, immunofluorescence assay, enzyme-linked immunosorbent assay (ELISA), qRT-PCR, and Western blotting, were employed to delineate the biological roles of ephrin-B2/pyruvate kinase muscle isoenzyme 2 (PKM2)/hypoxia-inducible factor 1 alpha (HIF-1α) in proliferation, migration, invasion, and glucose metabolism of cSCC. This study highlights an upregulation of ephrin-B2 expression in cSCC. Knockdown of ephrin-B2 significantly suppressed the proliferation, migration, invasion, and glucose metabolism of cSCC cells. Moreover, ephrin-B2 expression was upregulated under hypoxic conditions. At the molecular level, ephrin-B2 knockdown resulted in the downregulation of PKM2 and HIF-1α expression. Additionally, the overexpression of PKM2 or HIF-1α successfully rescued the diminished proliferation, migration, invasion and glucose metabolism induced by ephrin-B2 knockdown in cSCC cells. These findings suggest that ephrin-B2 suppression may hinder cSCC cell proliferation and glycolytic metabolism, potentially via the PKM2/HIF-1α axis modulation.

Functional identification of PGM1 in the regulating development and depositing of inosine monophosphate specific for myoblasts.

Inosine monophosphate (IMP) is naturally present in poultry muscle and plays a key role in improving meat flavour. However, IMP deposition is regulated by numerous genes and complex molecular networks. In order to excavate key candidate genes that may regulate IMP synthesis, we performed proteome and metabolome analyses on the leg muscle, compared to the breast muscle control of 180-day-old Jingyuan chickens (hens), which had different IMP content. The key candidate genes identified by a differential analysis were verified to be associated with regulation of IMP-specific deposition. The results showed that the differentially expressed (DE) proteins and metabolites jointly involve 14 metabolic pathways, among which the purine metabolic pathway closely related to IMP synthesis and metabolism is enriched with four DE proteins downregulated (with higher expression in breast muscles than in leg muscles), including adenylate kinase 1 (AK1), adenosine monophosphate deaminase 1 (AMPD1), pyruvate kinase muscle isoenzyme 2 (PKM2) and phosphoglucomutase 1 (PGM1), six DE metabolites, Hypoxanthine, Guanosine, L-Glutamine, AICAR, AMP and Adenylsuccinic acid. Analysis of PGM1 gene showed that the high expression of PGM1 promoted the proliferation and differentiation of myoblasts and inhibited the apoptosis of myoblasts. ELISA tests have shown that PGM1 reduced adenosine triphosphate (ATP) and IMP and uric acid (UA), while enhancing the biosynthesis of hypoxanthine (HX). In addition, up-regulation of PGM1 inhibited the expression of purine metabolism pathway related genes, and promoted the IMP de novo and salvage synthesis pathways. This study preliminarily explored the mechanism of action of PGM1 in regulating the growth and development of myoblasts and specific IMP deposition in Jingyuan chickens, which provided certain theoretical basis for the development and utilization of excellent traits in Jingyuan chickens.

CKM intron: an appropriate marker for the determination of the genetic relationships among horse populations and breeds

To date, the origins, domestication, and genetic structure of Chinese Mongolian horses (CMH) are poorly understood. Furthermore, there have been sparse reports on the genetic differences between CMH and Thoroughbred. In order to determine their genetic structure, understand their genetic relationships, and explore their domestication processes, we performed an extensive survey of creatine kinase (muscle isoenzyme; CKM) variations among six populations of indigenous CMH, cultivated Sanhe horses, and imported Thoroughbred. Twenty-three single-nucleotide polymorphisms were found among the 343 horse sequences. From these, 40 haplotypes were inferred. Haplotype diversity (H) values differed from 0.6424 to 0.7881 and nucleotide diversity (π) values ranged from 0.00150 to 0.00211. The differences between Thoroughbred population and other Chinese horse populations were large, but only small differences were observed among Chinese horse populations with respect to CKM intron sequences suggesting that the domestication history, breeding measures, and origins of these horse populations are completely different. Results suggest that Sanhe and CMH are very closely related and the introgression (interbreeding) between them is serious. Our results suggest that Sanhe and Wushen require prompt and powerful protection. Overall, CKM intron was an appropriate marker for the determination of genetic relationships among horse populations and breeds.

PKM2 Inhibition Enhances the Sensitivity of Doxorubicin in ABC Diffuse Large B-Cell Lymphoma Cells

Background: Pyruvate kinase muscle isoenzyme 2 (PKM2) is a key enzyme in aerobic glycolysis and thought to contribute to cancer cell metabolic reprogramming and regulating the reactive oxygen species (ROS). Doxorubicin has been showed to induced activated-B cell types diffuse large B-cell lymphoma (ABC-DLBCL) cells death by ROS accumulation. Our purpose was to evaluate whether PKM2 inhibition could enhance the sensitivity of doxorubicin in ABC-DLBCL.Methods: MTT assay was used to evaluate the proliferation of 2 ABC-DLBCL cell lines by treated with PKM2 inhibitor, PKM2 shRNA and doxorubicin. Apoptosis were detected by FCM after staining with Annexin V/SYTOX Green. Western Blot was used to evaluated the expression of PARP, Mcl1, Bcl2, Bax, Bim, p38 and JNK in ABC-DLBCL cells treated with PKM2 inhibition, PKM2 shRNA and doxorubicin.Results: PKM2 expression was found in both U2932 and SuDHL2 cell lines. Both PKM2 inhibitor and doxorubicin could inhibit the proliferation and induce apoptosis in ABC-DLBCL cell lines. PKM2 inhibitor could enhance the doxorubicin-induced apoptosis. ShRNA was used to knock down the PKM2 expression in ABC-DLBCL cell lines and PKM2 KD cell lines were more sensitive to doxorubicin. PKM2 inhibition could increase the expression of cleaved PARP, Bax, Bim, p38 and JNK as well as decrease Mcl1 and Bcl2 expressionConclusions: PKM2 inhibition could sensitize ABC-DLBCL cell lines to the cytotoxic effects of doxorubicin.Key words: PKM2, Doxorubicin, Diffuse large B cell lymphoma DisclosuresNo relevant conflicts of interest to declare.

Potential role for pyruvate kinase M2 in the regulation of murine cardiac glycolytic flux during in vivo chronic hypoxia.

Carbohydrate metabolism in heart failure shares similarities to that following hypoxic exposure, and is thought to maintain energy homoeostasis in the face of reduced O2 availability. As part of these in vivo adaptations during sustained hypoxia, the heart up-regulates and maintains a high glycolytic flux, but the underlying mechanism is still elusive. We followed the cardiac glycolytic responses to a chronic hypoxic (CH) intervention using [5-3H]-glucose labelling in combination with detailed and extensive enzymatic and metabolomic approaches to provide evidence of the underlying mechanism that allows heart survivability. Following 3 weeks of in vivo hypoxia (11% oxygen), murine hearts were isolated and perfused in a retrograde mode with function measured via an intraventricular balloon and glycolytic flux quantified using [5-3H]-glucose labelling. At the end of perfusion, hearts were flash-frozen and central carbon intermediates determined via liquid chromatography tandem mass spectrometry (LC-MS/MS). The maximal activity of glycolytic enzymes considered rate-limiting was assessed enzymatically, and protein abundance was determined using Western blotting. Relative to normoxic hearts, CH increased ex vivo cardiac glycolytic flux 1.7-fold with no effect on cardiac function. CH up-regulated cardiac pyruvate kinase (PK) flux 3.1-fold and cardiac pyruvate kinase muscle isoenzyme M2 (PKM2) protein content 1.4-fold compared with normoxic hearts. CH also augmented cardiac pentose phosphate pathway (PPP) flux, reflected by higher ribose-5-phosphate (R5P) content. These findings support an increase in the covalent (protein expression) and allosteric (flux) control of PKM2 as being central to the sustained up-regulation of the glycolytic flux in the chronically hypoxic heart.

PKM2 suppresses osteogenesis and facilitates adipogenesis by regulating β-catenin signaling and mitochondrial fusion and fission.

Bone marrow mesenchymal stem cells (BMSCs) differentiation dysfunction is a common pathological phenotype of several prevalent metabolic and genetic bone diseases. Pyruvate kinase muscle isoenzyme 2 (PKM2) regulates the last step of glycolysis, and its role in BMSCs differentiation is still unknown. In this study, the influence of PKM2 on osteogenesis and adipogenesis was assessed in vitro and in vivo. We found that DASA-58 (the activator of PKM2) reduced the enzymatic activity of ALP, and inhibited the levels of osteogenic marker genes, especially RUNX2, which is a crucial transcription factor for osteogenesis. Besides, we provided evidence that C3k, an inhibitor of PKM2, caused increase in mitochondrial membrane potential and maintained low levels of ROS, and promoted mitochondrial fusion. Furthermore, after treatment with DASA-58, the level of active β-catenin gradually decreased, which also inhibited the transport of active β-catenin into the nucleus, but C3k obviously promoted its nuclear translocation. As for adipogenesis, PKM2 activation increased the expression of adipogenic related genes and decreased active-β-catenin expression, whereas treatment of C3k had the opposite effect. In addition, C3k significantly attenuated ovariectomy-induced trabecular bone loss in vivo. Our findings helped uncover the molecular mechanisms underlying PKM2 regulation of BMSCs differentiation.

Pkm2 Regulates Cardiomyocyte Cell Cycle and Promotes Cardiac Regeneration.

The adult mammalian heart has limited regenerative capacity, mostly attributable to postnatal cardiomyocyte cell cycle arrest. In the last 2 decades, numerous studies have explored cardiomyocyte cell cycle regulatory mechanisms to enhance myocardial regeneration after myocardial infarction. Pkm2 (Pyruvate kinase muscle isoenzyme 2) is an isoenzyme of the glycolytic enzyme pyruvate kinase. The role of Pkm2 in cardiomyocyte proliferation, heart development, and cardiac regeneration is unknown. We investigated the effect of Pkm2 in cardiomyocytes through models of loss (cardiomyocyte-specific Pkm2 deletion during cardiac development) or gain using cardiomyocyte-specific Pkm2 modified mRNA to evaluate Pkm2 function and regenerative affects after acute or chronic myocardial infarction in mice. Here, we identify Pkm2 as an important regulator of the cardiomyocyte cell cycle. We show that Pkm2 is expressed in cardiomyocytes during development and immediately after birth but not during adulthood. Loss of function studies show that cardiomyocyte-specific Pkm2 deletion during cardiac development resulted in significantly reduced cardiomyocyte cell cycle, cardiomyocyte numbers, and myocardial size. In addition, using cardiomyocyte-specific Pkm2 modified RNA, our novel cardiomyocyte-targeted strategy, after acute or chronic myocardial infarction, resulted in increased cardiomyocyte cell division, enhanced cardiac function, and improved long-term survival. We mechanistically show that Pkm2 regulates the cardiomyocyte cell cycle and reduces oxidative stress damage through anabolic pathways and β-catenin. We demonstrate that Pkm2 is an important intrinsic regulator of the cardiomyocyte cell cycle and oxidative stress, and highlight its therapeutic potential using cardiomyocyte-specific Pkm2 modified RNA as a gene delivery platform.

PKM2 regulates angiogenesis of VR-EPCs through modulating glycolysis, mitochondrial fission, and fusion.

Vascular resident endothelial progenitor cells (VR-EPCs) have a certain ability to differentiate into endothelial cells (ECs) and participate in the process of angiogenesis. Glycolysis and mitochondrial fission and fusion play a pivotal role in angiogenesis. Pyruvate kinase muscle isoenzyme 2 (PKM2), which mediates energy metabolism and mitochondrial morphology, is regarded as the focus of VR-EPCs angiogenesis in our study. VR-EPCs were isolated from the hearts of 12-weeks-old Sprague-Dawley rats. The role of PKM2 on angiogenesis was evaluated by tube formation assay, wound healing assay, transwell assay, and chick chorioallantoic membrane assay. Western blot analysis, flow cytometry, mitochondrial membrane potential detection, reactive oxygen species (ROS) detection, immunofluorescence staining, and quantitative real-timepolymerase chain reaction were used to investigate the potential mechanism of PKM2 for regulating VR-EPCs angiogenesis. We explored the function of PKM2 on the angiogenesis of VR-EPCs. DASA-58 (the activator of PKM2) promoted VR-EPCs proliferation and PKM2 activity, it also could promote angiogenic differentiation. At the same time, DASA-58 significantly enhanced glycolysis, mitochondrial fusion, slightly increased mitochondrial membrane potential, and maintained ROS at a low level. C3k, an inhibitor of PKM2, inhibited PKM2 activity, expression of angiogenesis-related genes and tube formation. Besides, C3k drastically reduced glycolysis and mitochondrial membrane potential while significantly promoting mitochondrial fission and ROS level. Activation of PKM2 could promote VR-EPCs angiogenesis through modulating glycolysis, mitochondrial fission and fusion. By contrast, PKM2 inhibitor has opposite effects.

Dietary-phytochemical mediated reversion of cancer-specific splicing inhibits Warburg effect in head and neck cancer

BackgroundThe deregulated alternative splicing of key glycolytic enzyme, Pyruvate Kinase muscle isoenzyme (PKM) is implicated in metabolic adaptation of cancer cells. The splicing switch from normal PKM1 to cancer-specific PKM2 isoform allows the cancer cells to meet their energy and biosynthetic demands, thereby facilitating the cancer cells growth. We have investigated the largely unexplored epigenetic mechanism of PKM splicing switch in head and neck cancer (HNC) cells. Considering the reversible nature of epigenetic marks, we have also examined the utility of dietary-phytochemical in reverting the splicing switch from PKM2 to PKM1 isoform and thereby inhibition of HNC tumorigenesis.MethodsWe present HNC-patients samples, showing the splicing-switch from PKM1-isoform to PKM2-isoform analyzed via immunoblotting and qRT-PCR. We performed methylated-DNA-immunoprecipitation to examine the DNA methylation level and chromatin-immunoprecipitation to assess the BORIS (Brother of Regulator of Imprinted Sites) recruitment and polII enrichment. The effect of dietary-phytochemical on the activity of denovo-DNA-methyltransferase-3b (DNMT3B) was detected by DNA-methyltransferase-activity assay. We also analyzed the Warburg effect and growth inhibition using lactate, glucose uptake assay, invasion assay, cell proliferation, and apoptosis assay. The global change in transcriptome upon dietary-phytochemical treatment was assayed using Human Transcriptome Array 2.0 (HTA2.0).ResultsHere, we report the role of DNA-methylation mediated recruitment of the BORIS at exon-10 of PKM-gene regulating the alternative-splicing to generate the PKM2-splice-isoform in HNC. Notably, the reversal of Warburg effect was achieved by employing a dietary-phytochemical, which inhibits the DNMT3B, resulting in the reduced DNA-methylation at exon-10 and hence, PKM-splicing switch from cancer-specific PKM2 to normal PKM1. Global-transcriptome-analysis of dietary-phytochemical-treated cells revealed its effect on alternative splicing of various genes involved in HNC.ConclusionThis study identifies the epigenetic mechanism of PKM-splicing switch in HNC and reports the role of dietary-phytochemical in reverting the splicing switch from cancer-specific PKM2 to normal PKM1-isoform and hence the reduced Warburg effect and growth inhibition of HNC. We envisage that this approach can provide an effective way to modulate cancer-specific-splicing and thereby aid in the treatment of HNC.

Cachexia Anorexia Syndrome and Associated Metabolic Dysfunction in Peritoneal Metastasis.

Patients with peritoneal metastasis (PM) of gastrointestinal and gynecological origin present with a nutritional deficit characterized by increased resting energy expenditure (REE), loss of muscle mass, and protein catabolism. Progression of peritoneal metastasis, as with other advanced malignancies, is associated with cancer cachexia anorexia syndrome (CAS), involving poor appetite (anorexia), involuntary weight loss, and chronic inflammation. Eventual causes of mortality include dysfunctional metabolism and energy store exhaustion. Etiology of CAS in PM patients is multifactorial including tumor growth, host response, cytokine release, systemic inflammation, proteolysis, lipolysis, malignant small bowel obstruction, ascites, and gastrointestinal side effects of drug therapy (chemotherapy, opioids). Metabolic changes of CAS in PM relate more to a systemic inflammatory response than an adaptation to starvation. Metabolic reprogramming is required for cancer cells shed into the peritoneal cavity to resist anoikis (i.e., programmed cell death). Profound changes in hexokinase metabolism are needed to compensate ineffective oxidative phosphorylation in mitochondria. During the development of PM, hypoxia inducible factor-1α (HIF-1α) plays a key role in activating both aerobic and anaerobic glycolysis, increasing the uptake of glucose, lipid, and glutamine into cancer cells. HIF-1α upregulates hexokinase II, phosphoglycerate kinase 1 (PGK1), pyruvate dehydrogenase kinase (PDK), pyruvate kinase muscle isoenzyme 2 (PKM2), lactate dehydrogenase (LDH) and glucose transporters (GLUT) and promotes cytoplasmic glycolysis. HIF-1α also stimulates the utilization of glutamine and fatty acids as alternative energy substrates. Cancer cells in the peritoneal cavity interact with cancer-associated fibroblasts and adipocytes to meet metabolic demands and incorporate autophagy products for growth. Therapy of CAS in PM is challenging. Optimal nutritional intake alone including total parenteral nutrition is unable to reverse CAS. Pressurized intraperitoneal aerosol chemotherapy (PIPAC) stabilized nutritional status in a significant proportion of PM patients. Agents targeting the mechanisms of CAS are under development.

PKM2 Expression Is Associated with Favorable Outcome in Patients with Diffuse Large B-Cell Lymphoma

Pyruvate kinase muscle isoenzyme 2 (PKM2) is a key enzyme in aerobic glycolysis and thought to contribute to cancer cell metabolic reprogramming. The aim of this study was to evaluate whether PKM2 expression by immunohistochemical was a potential prognostic biomarker in diffuse large B-cell lymphoma (DLBCL) patients. Herein, we explore the expression of PKM2 by immunohistochemistry in all 87 patients diagnosed as de novo DLBCL according to WHO classification. Among all the 87 patients, high expression of PKM2 was observed in 20 cases (23.0%). There was no significant difference in gender, age, B symptoms, performance status, LDH, stage and IPI score between patients with high and low PKM2 expression(P>0.05). Patients with high PKM2 expression showed significant superiorevent-free survival, but only a tendency in overall survival compared with low PKM2 expression patients (p=0.047 and p=0.465, respectively). Multivariate analysis showed that high expression of PKM2, independent of the international prognostic index, implied a favorable event-free survival (HR=0.363; 95% CI=0.109-0.927, p=0.038), but not overall survival (HR=0.646; 95% CI= 0.185-2.254, p=0.493). In conclusion, these data suggest that the expression of PKM2 may implied a good outcome in DLBCL patients treated with R-CHOP. DisclosuresNo relevant conflicts of interest to declare.

Pyruvate Kinase Muscle Isoenzyme 2 (PKM2) Expression Is Associated with Overall Survival in Pancreatic Ductal Adenocarcinoma.

Pyruvate kinase muscle isoenzyme 2 (PKM2) is a key enzyme in aerobic glycolysis and is thought to contribute to cancer cell metabolic reprogramming. The aim of this study was to evaluate PKM2 immunohistochemical expression as a potential prognostic biomarker in pancreatic ductal adenocarcinoma (PDAC). A tissue microarray was constructed using surgical specimens for 115 patients who underwent resections for PDAC, stained with PKM2 antibody, and scored for expression level. Statistical analyses were performed to investigate the association between PKM2 and patient survival, tumor stage, tumor grade, surgical margin status, lymph node ratio, perineural invasion status, or the use of adjuvant chemotherapy. Fifty-three percent of tumors had positive PKM2 expression, and 47 % of tumors had negative PKM2 expression. PKM2 expression was associated with overall survival (HR 0.56, p = 0.007) and CA 19-9 levels (p = 0.035), but was not associated with tumor stage, tumor grade, surgical margin status, lymph node ratio, perineural invasion, or adjuvant chemotherapy use. PKM2 expression is associated with overall survival in PDAC. Further studies are warranted to validate the value of PKM2 as a prognostic biomarker and to examine the potential utility of PKM2 in predicting treatment response, as well as a potential therapeutic target in PDAC.

Evaluation of Acute Cardiac and Chest Wall Damage after Shocks with a Subcutaneous Implantable Cardioverter Defibrillator in Swine

A subcutaneous implantable cardioverter defibrillator (S-ICD) could ease placement and reduce complications of transvenous ICDs, but requires more energy than transvenous ICDs. Therefore we assessed cardiac and chest wall damage caused by the maximum energy shocks delivered by both types of clinical devices. During sinus rhythm, anesthetized pigs (38 ± 6 kg) received an S-ICD (n = 4) and five 80-Joule (J) shocks, or a transvenous ICD (control, n = 4) and five 35-J shocks. An inactive S-ICD electrode was implanted into the same control pigs to study implant trauma. All animals survived 24hours. Troponin I and creatine kinase muscle isoenzyme (CK-MM) were measured as indicators of myocardial and skeletal muscle injury. Histopathological injury of heart, lungs, and chest wall was assessed using semiquantitative scoring. Troponin I was significantly elevated at 4hours and 24hours (22.6± 16.3 ng/mL and 3.1± 1.3 ng/mL; baseline 0.07± 0.09 ng/mL) in control pigs but not in S-ICD pigs (0.12± 0.11 ng/mL and 0.13± 0.13 ng/mL; baseline 0.06± 0.03 ng/mL). CK-MM was significantly elevated in S-ICD pigs after shocks (6,544± 1,496 U/L and 9,705± 6,240 U/L; baseline 704± 398 U/L) but not in controls. Electrocardiogram changes occurred postshock in controls but not in S-ICD pigs. The myocardium and lungs were histologically normal in both groups. Subcutaneous injury was greater in S-ICD compared to controls. Although CK-MM suggested more skeletal muscle injury in S-ICD pigs, significant cardiac, lung, and chest wall histopathological changes were not detected in either group. Troponin I data indicate significantly less cardiac injury from 80-J S-ICD shocks than 35-J transvenous shocks.

Identification of Host Proteins Packaged in H5N1 Avian Influenza Virus Particles Propagated in Embryonated Chicken Eggs by Mass Spectrometry

Abstract In this study, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE) coupled with mass spectrometry was used to perform a comprehensive proteomics analysis of the purified influenza virus particles propagated from embryonated chicken eggs. In addition to the virus-encoded proteins, 12 proteins originated from embryonated chicken eggs were identified in the purified virus particles, such as annexin A2, peptidyl-prolyl cis-trans isomerase B, peroxiredoxin-1, phosphoglycerate kinase, and pyruvate kinase muscle isoenzyme. Two kinds of cytoskeletal proteins, tubulin b-3 and actin, were also detected.

Lactate Dehydrogenase Isozymes in Skeletal Muscle of Patients With Chronic Obstructive Pulmonary Disease

Introduction and Objectives In patients with chronic obstructive pulmonary disease (COPD), lactate dehydrogenase (LDH) levels in skeletal muscles are normal or tend to be elevated; on exercise, these levels increase more rapidly than in individuals without COPD. As it is likely that concentrations of LDH isozymes LDH 4 and LDH 5 are elevated in such patients, we measured those isozymes in peripheral muscle of patients with COPD. Patients and Methods Eighteen patients with COPD and 10 healthy nonsmokers were included in the study. Spirometry and the 6-minute walk test were performed, and a biopsy of the quadriceps muscle was taken to measure levels of both total LDH and LDH isozymes by agarose gel electrophoresis and to classify the types of muscle fibers. Results Controls and patients had similar concentrations of total LDH (mean [SE], 130 [30] μmol/min/g vs 152 [50] μmol/min/g, respectively) and LDH isozymes. A subgroup of 5 patients showed increased levels of isozymes LDH 1, LDH 2, and LDH 3, with decreased LDH 5 levels; these patients were women and had a lower oxygen saturation. The LDH 5 level was directly correlated with the 6-minute walk test and oxygen saturation. The percentage of type IIA fibers correlated directly with LDH 3 and LDH 4 concentrations whereas type IIX fibers were inversely correlated with LDH 3 concentration. Conclusion Measurement of LDH isozyme concentrations enabled a subgroup of patients to be identified with a higher concentration of cardiac isoenzymes and lower concentration of muscle isoenzymes, a situation which might indicate adaptation that favors aerobic metabolism.

Isoenzimas de lactatodeshidrogenasa en el músculo esquelético de pacientes con EPOC

Introduction and Objectives In patients with chronic obstructive pulmonary disease (COPD), lactate dehydrogenase (LDH) levels in skeletal muscles are normal or tend to be elevated; on exercise, these levels increase more rapidly than in individuals without COPD. As it is likely that concentrations of LDH isozymes LDH 4 and LDH 5 are elevated in such patients, we measured those isozymes in peripheral muscle of patients with COPD. Patients and Methods Eighteen patients with COPD and 10 healthy nonsmokers were included in the study. Spirometry and the 6-minute walk test were performed, and a biopsy of the quadriceps muscle was taken to measure levels of both total LDH and LDH isozymes by agarose gel electrophoresis and to classify the types of muscle fibers. Results Controls and patients had similar concentrations of total LDH (mean [SE], 130 [30] μmol/min/g vs 152 [50] μmol/min/g, respectively) and LDH isozymes. A subgroup of 5 patients showed increased levels of isozymes LDH 1, LDH 2, and LDH 3, with decreased LDH 5 levels; these patients were women and had a lower oxygen saturation. The LDH 5 level was directly correlated with the 6-minute walk test and oxygen saturation. The percentage of type IIA fibers correlated directly with LDH 3 and LDH 4 concentrations whereas type IIX fibers were inversely correlated with LDH 3 concentration. Conclusion Measurement of LDH isozyme concentrations enabled a subgroup of patients to be identified with a higher concentration of cardiac isoenzymes and lower concentration of muscle isoenzymes, a situation which might indicate adaptation that favors aerobic metabolism.

Aldolase A is present in smooth muscle cell nuclei.

Previously we have shown that aldolase (ALD; EC 4.1.2.13) is present in cardiomyocyte nuclei. Now, we focused our attention on ALD localization in smooth muscle cells. Immunocytochemical methods were used to study the subcellular localization of ALD. Aldolase was localized in the cytoplasm as well as in the nuclei. Within the nuclei ALD was located in the heterochromatin region. Native polyacrylamide gel electrophoresis followed by aldolase activity staining in gel was used to study the ALD isoenzyme pattern in porcine smooth muscle cells. Two ALD isoenzymes, A and C, were found in these cells but in the nuclei only the muscle isoenzyme was detected. To support the nuclear localization of ALD, measurement of aldolase activity in the smooth muscle cell nuclei isolated from porcine stomach was performed. The ALD activity in the isolated nuclei was detectable only after preincubation of the nuclear fraction with Triton X-100 and high concentration of KCl.

Lactate Dehydrogenase Catalysis: Roles of Keto, Hydrated, and Enol Pyruvate

Many carbonyl substrates of oxidoreductase enzymes undergo hydration and enolization so that these systems are partitioned between keto, hydrated (gem-diol), and enol forms in aqueous solution. Some oxidoreductase enzymes are subject to inhibition by high concentrations of substrate. For such enzymes, two questions arise pertaining to enzyme�substrate interactions: (i) which form of the system serves as the preferential and (ii) which form acts to inhibit the enzyme? Thus the relative concentrations of the forms of these systems (keto, hydrated, enol) may provide a form of metabolic control. In this light, the present article considers the reduction of pyruvate by lactate dehydrogenase in the presence of NADH. This reaction is inhibited by relatively high concentrations of pyruvate and the physiological significance of this inhibition has been a subject of controversy for many years. Summarized in this article are data from the literature pertaining to the interactions of keto, hydrated, and enol pyruvate with lactate dehydrogenase. Biochemistry instructors and their students are invited to review such pertinent articles so that they also may evaluate the possibility that the substrate inhibition of the isoenzymes in the heart muscle may be, under certain conditions, relevant as a form of metabolic control.

Perioperative Creatine Phosphokinase (CPK) and Troponin I Trends After Elective Hip Surgery

Perioperative myocardial infarction (MI) is an important risk factor for cardiac morbidity and mortality after hip surgery. On the basis of the limitations of creatine kinase cardiac muscle isoenzyme (CK-MB) in the perioperative setting, and the high specificity of troponin I, we hypothesized that troponin I would be effective at detecting perioperative MI more frequently than CK-MB would be, after hip surgery. A prospective study of the serum levels of creatine phosphokinase (CPK), its isoenzyme CK-MB, and troponin I, in 90 patients with risk factors for coronary artery disease, undergoing hip surgery is reported. We measured these cardiac markers in the postoperative period for 5 days, after hemiarthroplasty, total hip arthroplasty, and hip intramedullary nailing. We found increased levels of creatine phosphokinase and CK-MB, after all the types of operation, with maximum levels reached on the first postoperative day and the levels were more pronounced after total hip arthroplasty. False-elevated CK-MB index >6% without MI was evidenced in 43.3% of patients. Troponin I levels were elevated >3.1 ng/mL only in the patients who suffered MI postoperatively. All the patients who suffered MI had both CK-MB index and troponin I levels elevated. Also, we found high correlation between maximum CK-MB levels and size of implants, which means that reaming and its heating effect may be responsible for false-elevated CK-MB levels, except direct muscle damage caused by surgical incision. CK-MB index and troponin I have the same sensitivity, but troponin I is more specific than CK-MB index in detecting MI after hip surgery.

Muscle Injury in Organophosphorous Poisoning and Its Role in the Development of Intermediate Syndrome

Muscle injury and its role in the development of Type II paralysis was studied in 25 patients with acute organophosphate poisoning. All patients were assessed for severity of poisoning at admission and through the course of poisoning for the development and duration of intermediate syndrome (IS) (Type II paralysis). Blood levels of acetylcholinesterase, creatine kinase, creatine kinase MM, LDH and LDH 5 were estimated through the course of the poisoning. Of the 25 patients, 22 were severely poisoned and 3 had mild to moderate poisoning. Severely poisoned patients had a significantly greater rate of developing intermediate syndrome (17/22) ( P=0.026). Type I paralysis and fasciculations occurred in 76 and 70.5% of patients who developed intermediate syndrome, in comparison to 38 and 50%, respectively, of those who did not develop intermediate syndrome. Weakness developed in the same groups of muscles in both Types I and II paralysis but was of longer duration in patients who developed Type II paralysis. Acetylcholinesterase was inhibited >90% throughout the course of poisoning with greater inhibition in patients with longer duration intermediate syndrome. Muscle injury was seen in all patients beginning at admission, peaking over the first 5 days and then declining over the next 5 days. Temporal profiles of blood muscle isoenzymes showed significantly greater muscle injury in those patients with greater severity of poisoning at admission, those who developed intermediate syndrome and in patients with longer duration intermediate syndrome. The findings of this study suggest that Types I and II paralysis in organophosphate poisoning are not separate syndromes but a clinical continuum determined by the severity of poisoning. The magnitude of organophosphate exposure and of muscle injury during the cholinergic crises appears to determine the occurrence and severity of intermediate syndrome.