Validation, performance, and reliability of two automated tests for vitamin B12 and folate assay

Background

Deficiency of Vitamin B12 and folate may determine hematological, neurological, and metabolic alterations; therefore, an accurate quantification of their serum levels is required, especially in the presence of symptoms that might suggest a deficiency. CHORUS VIT B12 and CHORUS FOLATE are two automated immunoassays, developed to quantify vitamin B12 and folate, respectively, in human serum.

Design and methods

This single-center, non-pharmacological, diagnostic study described the validation and characterization of CHORUS VIT B12 and CHORUS FOLATE, with a specific focus on performance, precision, and reliability. For each assay, 500 serum samples were analyzed. A comparison between CHORUS assays and commercially available kit was also performed.

Results

For CHORUS VIT B12 the lower limit of quantification (LLoQ) was 165.0 pg/mL and the upper LoQ (ULoQ) was 1846.8 pg/mL. The assay was linear within the calibration range (150-2000 pg/mL) and the accuracy was described with the International Standard Vitamin B12, Serum Folate, HOLO TC (NIBSC code: 03/178), with a mean recovery on two lots of 111%. For CHORUS FOLATE (calibration range of 2.0-20.0 ng/mL), LLoQ was 2.0 ng/mL and ULoQ 19.6 ng/mL. The linearity was demonstrated from 2.4 to 20.0 ng/mL; the accuracy was described with the International Standard mentioned above, achieving a mean recovery on three lots of 92%. The lowest and highest values of both CHORUS and COBAS kits were similar and the median values did not significantly vary.

Conclusion

CHORUS VIT B12 and CHORUS FOLATE performed well, accurately, and reliably in quantifying vitamin B12 and folate in human serum.

Carriers of ADAMTS13 Rare Variants Are at High Risk of Life-Threatening COVID-19

Thrombosis of small and large vessels is reported as a key player in COVID-19 severity. However, host genetic determinants of this susceptibility are still unclear. Congenital Thrombotic Thrombocytopenic Purpura is a severe autosomal recessive disorder characterized by uncleaved ultra-large vWF and thrombotic microangiopathy, frequently triggered by infections. Carriers are reported to be asymptomatic. Exome analysis of about 3000 SARS-CoV-2 infected subjects of different severities, belonging to the GEN-COVID cohort, revealed the specific role of vWF cleaving enzyme ADAMTS13 (A disintegrin-like and metalloprotease with thrombospondin type 1 motif, 13). We report here that ultra-rare variants in a heterozygous state lead to a rare form of COVID-19 characterized by hyper-inflammation signs, which segregates in families as an autosomal dominant disorder conditioned by SARS-CoV-2 infection, sex, and age. This has clinical relevance due to the availability of drugs such as Caplacizumab, which inhibits vWF–platelet interaction, and Crizanlizumab, which, by inhibiting P-selectin binding to its ligands, prevents leukocyte recruitment and platelet aggregation at the site of vascular damage.

Methodology to Evaluate Clinical Impact of 0/3 Hour High-Sensitivity Cardiac Troponin T Protocol on Managing Acute Coronary Syndrome in Daily Emergency Department Practice

OBJECTIVE

Sex-/age-differentiated cutoffs and the magnitude of serial changes in high-sensitivity cardiac troponins (hs-cTn) for acute coronary syndrome (ACS) diagnosis algorithms are still under discussion. This study presents a methodology to evaluate decision-making limits and to assess whether sex-specific cutoffs could improve diagnostic accuracy.

METHODS

A high-sensitivity cardiac troponin T (hs-cTnT) 0-/3-hour protocol was adopted, applying the 2015 European Society of Cardiology Guidelines. Decision-making limits (99th percentile: 14 ng/L; delta change ≥ 30%) were agreed upon with the emergency department (ED) at the University Hospital of Siena in Siena, Italy. One-year requests (5177) for hs-cTnT serial determination were compared with the final International Classification of Diseases, 9th revision, clinical modifications diagnosis (contingency tables; receiver operating characteristic curves).

RESULTS

The algorithm's capability to exclude or confirm ACS was verified by remarkable negative predictive value (97%) and high areas under the curve for the first troponin sampling (0.712), troponin sampling at 3 hours (0.789), and delta (0.744). The clinical utility for the general population-even those with comorbidities-accessing the ED was verified. Our data did not support a sex-differentiated cutoff utility because it would not have affected patient management.

CONCLUSION

This methodology allowed us to confirm the effectiveness of our decision-making limits.

The Appetite-Suppressant and GLP-1-Stimulating Effects of Whey Proteins in Obese Subjects are Associated with Increased Circulating Levels of Specific Amino Acids

The satiating effect of whey proteins depends upon their unique amino acid composition because there is no difference when comparing whey proteins or a mix of amino acids mimicking the amino acid composition of whey proteins. The specific amino acids underlying the satiating effect of whey proteins have not been investigated to date.

AIMS AND METHODS

The aim of the present study was to evaluate the appetite-suppressant effect of an isocaloric drink containing whey proteins or maltodextrins on appetite (satiety/hunger measured by a visual analogue scale or VAS), anorexigenic gastrointestinal peptides (circulating levels of glucagon-like peptide 1 (GLP-1) and peptide tyrosine tyrosine (PYY)) and amino acids (circulating levels of single, total [TAA] and branched-chain amino acids [BCAA]) in a cohort of obese female subjects (n = 8; age: 18.4 ± 3.1 years; body mass index, BMI: 39.2 ± 4.6 kg/m²).

RESULTS

Each drink significantly increased satiety and decreased hunger, the effects being more evident with whey proteins than maltodextrins. Similarly, circulating levels of GLP-1, PYY and amino acids (TAA, BCAA and alanine, arginine, asparagine, citrulline, glutamine, hydroxyproline, isoleucine, histidine, leucine, lysine, methionine, ornithine, phenylalanine, proline, serine, threonine, tyrosine, and valine) were significantly higher with whey proteins than maltodextrins. In subjects administered whey proteins (but not maltodextrins), isoleucine, leucine, lysine, methionine, phenylalanine, proline, tyrosine, and valine were significantly correlated with hunger (negatively), satiety, and GLP-1 (positively).

CONCLUSIONS

Eight specific amino acids (isoleucine, leucine, lysine, methionine, phenylalanine, proline, tyrosine, and valine) were implicated in the appetite-suppressant and GLP-1-stimulating effects of whey proteins, which may be mediated by their binding with nutrient-sensing receptors expressed by L cells within the gastrointestinal wall. The long-term satiating effect of whey proteins and the effectiveness of a supplementation with these amino acids (i.e., as a nutraceutical intervention) administered during body weight reduction programs need to be further investigated.

The Determination of Urinary Oxypurines as Markers of Gastrointestinal Tumors

Plasma levels and urinary excretion of oxypurines – hypoxanthine and xanthine – were evaluated by reverse-phase high-pressure liquid chromatography in 13 patients affected by gastric tumors and in 19 colorectal tumor-bearing patients. Preliminary results indicate higher values of urinary xanthine and an increase in the xanthine/hypoxanthine ratio in cancer patients. The increase was not generalized to all subjects, and did not appear related either to the stage of the disease or to CEA values. The limits within which the determination of urinary oxypurines can be employed as a tumor marker are discussed.

Some Aspects of Purine Nucleotide Metabolism in Lymphocytes of B-CLL

The authors studied the behavior of some enzymes involved in purine nucleotide metabolism in human peripheral blood lymphocytes from normal and B-cell chronic lymphocytic leukemia subjects. Determinations were made with radiochemical methods associated with high performance liquid chromatography. Results indicated a marked increase in de novo purine synthesis enzymes, particularly those of the « inosinic branch point ». The latter were absent in normal lymphocytes, whereas they were well evident in leukemic lymphocytes, with the exception of AMP-S synthetase. Whereas the enzymes of the « salvage pathway » were spared in comparison to other proteins, those of the « catabolic pathway » significantly decreased. The authors discuss the possibility that such enzymes may be used as tumor markers.

Proteomic Investigation of Dermal Fibroblasts Isolated from Affected and Unaffected Skin Samples from Patients with Limited Cutaneous Systemic Sclerosis: 2 Distinct Entities?

Objective.

To identify using proteomic analysis the proteins of altered abundance in the affected and unaffected limited cutaneous systemic sclerosis (lcSSc) skin fibroblasts.

Methods.

Excision biopsies (3 mm) were obtained from the affected and unaffected skin of 5 patients with lcSSc. Dermal fibroblasts were isolated enzymatically. Two-dimensional gel electrophoresis was used to separate and define proteins in affected and unaffected fibroblast lysates. Proteins of altered abundance were identified by mass spectrometry. Differences among skin samples were confirmed also by immunohistochemistry (IHC) and by quantitative real-time PCR (qRT-PCR) for type I collagen (Col-1) and vimentin (VIM).

Results.

Proteomic analysis revealed different expressions of proteins involved in cytoskeleton organization (27%), extracellular matrix remodeling (11%), response to oxidative stress (22%), energy metabolism (19%), protein metabolism (5%), cellular homeostasis (5%), signal transduction (3%), and protein transcription, synthesis, and turnover (8%). IHC analysis showed that SSc-affected epidermis is thickened and the dermis is strongly reactive to Col-1 and VIM (typical markers of activated myofibroblasts) compared to SSc-unaffected skin, whose stainings are comparable to those of control healthy skin. Overexpression of Col-1 and VIM mRNA levels in affected lcSSc fibroblasts compared to unaffected lcSSc ones was confirmed by qRT-PCR.

Conclusion.

Consistent with previous studies, these findings are important for 2 reasons: first, because they reveal the opposite behavior of dermal fibroblasts in the unaffected and affected skin areas of the same patient with lcSSc; second, because they demonstrate the histological/histochemical similarities between unaffected skin from patients with lcSSc and healthy control skin.

Inflammatory protein response in CDKL5-Rett syndrome: evidence of a subclinical smouldering inflammation

BACKGROUND

Mutations in the cyclin-dependent kinase-like 5 gene cause a clinical variant of Rett syndrome (CDKL5-RTT). A role for the acute-phase response (APR) is emerging in typical RTT caused by methyl-CpG-binding protein 2 gene mutations (MECP2-RTT). No information is, to date, available on the inflammatory protein response in CDKL5-RTT. We evaluated, for the first time, the APR protein response in CDKL5-RTT.

METHODS

Protein patterns in albumin- and IgG-depleted plasma proteome from CDKL5-RTT patients were evaluated by two-dimensional gel electrophoresis/mass spectrometry. The resulting data were related to circulating cytokines and compared to healthy controls or MECP2-RTT patients. The effects of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) were evaluated.

RESULTS

CDKL5-RTT mutations resulted in a subclinical attenuated inflammation, specifically characterized by an overexpression of the complement component C3 and CD5 antigen-like, both strictly related to the inflammatory response. Cytokine dysregulation featuring a bulk increase of anti-inflammatory cytokines, predominantly IL-10, could explain the unchanged erythrocyte sedimentation rate and atypical features of inflammation in CDKL5-RTT. Omega-3 PUFAs were able to counterbalance the pro-inflammatory status.

CONCLUSION

For the first time, we revealed a subclinical smouldering inflammation pattern in CDKL5-RTT consisting in the coexistence of an atypical APR coupled with a dysregulated cytokine response.

Expression and oxidative modifications of plasma proteins in autism spectrum disorders: Interplay between inflammatory response and lipid peroxidation

PURPOSE

A role for inflammation and oxidative stress is reported in autism spectrum disorders (ASDs). Here, we tested possible changes in expression and/or oxidative status for plasma proteins in subjects with ASDs.

EXPERIMENTAL DESIGN

To evaluate protein expression and protein adducts of lipid peroxidation-derived aldehyde, analysis of plasma proteins was performed in 30 subjects with ASDs and compared with 30 healthy controls with typical development, using a proteomic approach.

RESULTS

Significant changes were evidenced for a total of 12 proteins. Of these, ten were identified as proteins involved in the acute inflammatory response including alpha-2-macroglobulin, alpha-1-antitrypsin, haptoglobin, fibrinogen, serum transferrin, prealbumin, apolipoprotein A-I apolipoprotein A-IV, apolipoprotein J, and serum albumin. In addition, significant changes occurred for two immunoglobulins alpha and gamma chains.

CONCLUSIONS AND CLINICAL RELEVANCE

Our present data indicate that an inflammatory response, coupled with increased lipid peroxidation, is present in subjects with ASDs. This information can provide new insight into the identification of potential plasma protein biomarkers in autism.

Erectile dysfunction and diabetes: Association with the impairment of lipid metabolism and oxidative stress

OBJECTIVES

To test the hypothesis that exists an association of non-diabetic and diabetic patients suffering from erectile dysfunction (ED) with lipid metabolism and oxidative stress.

DESIGN AND METHODS

Clinical and laboratory characteristics in non-diabetic (n = 30, middle age range: 41–55.5 years; n = 25, old age range: 55.5–73), diabetic ED patients (n = 30, age range: 55.5–75 years) and diabetic patients (n = 25, age range: 56–73.25), were investigated. Proteomic analysis was performed to identify differentially expressed plasma proteins and to evaluate their oxidative posttranslational modifications.

RESULTS

A decreased level of high-density lipoproteins in all ED patients (P < 0.001, C.I. 0.046–0.10), was detected by routine laboratory tests. Proteomic analysis showed a significant decreased expression (P < 0.05) of 5 apolipoproteins (i.e. apolipoprotein H, apolipoprotein A4, apolipoprotein J, apolipoprotein E and apolipoprotein A1) and zinc-alpha-2-glycoprotein, 50% of which are more oxidized proteins. Exclusively for diabetic ED patients, oxidative posttranslational modifications for prealbumin, serum albumin, serum transferrin and haptoglobin markedly increased.

CONCLUSIONS

Showing evidence for decreased expression of apolipoproteins in ED and the remarkable enhancement of oxidative posttranslational modifications in diabetes-associated ED, considering type 2 diabetes mellitus and age as independent risk factors involved in the ED pathogenesis, lipid metabolism and oxidative stress appear to exert a complex interplay in the disease.

Isolation of intraflagellar transport trains

The intraflagellar transport (IFT) system was first identified in situ by electron microscopy in thin sections of plastic-embedded flagella as linear arrays of electrondense particles, located between the B tubules of the outer doublets and the flagellar membrane. These arrays of particles are referred to as IFT trains. Upon membrane rupture, IFT trains are thought to easily dissociate to yield soluble IFT particles, which are commonly purified through sucrose gradients as ∼16-17S complexes. The latters easily dissociate into two subcomplexes, named A and B. We report here the isolation, visualization, and identification by immunolabeling of flexible strings of IFT particles, which are structurally similar to in situ IFT trains and appear to be formed by both complex A and complex B polypeptides. Moreover, the particles forming isolated IFT trains are structurally similar to the individual particles found in the ∼17S gradient peak. Our results provide the first direct evidence that ∼17S particles do indeed compose the IFT trains. The paper also represents the first isolation of the IFT trains, and opens new possibilities for higher resolution studies on their structure and how particles are attached to each other to form the particle trains.

Proteomics of human primary osteoarthritic chondrocytes exposed to extremely low-frequency electromagnetic fields (ELF EMFs) and to therapeutic application of musically modulated electromagnetic fields (TAMMEF)

Osteoarthritis (OA) is the most frequent joint disease, characterized by degradation of extracellular matrix and alterations in chondrocyte metabolism. Some authors reported that electromagnetic fields (EMFs) can positively interfere with patients affected by OA, even though the nature of the interaction is still debated. Human primary osteoarthritic chondrocytes isolated from the femoral heads of OA-patients undergoing to total hip replacement, were cultured in vitro and exposed 30 min/day for two weeks to extremely-low-frequency electromagnetic field (ELF) with fixed frequency (100 Hz) and to therapeutic application of musically modulated electromagnetic fields (TAMMEF) with variable frequencies, intensities and waveforms. Sham-exposed (S.E.) cells served as control group. Cell viability was measured at days 2, 7 and 14. After two weeks, cell lysates were processed using a proteomic approach. Chondrocyte exposed to ELF and TAMMEF system demonstrated different viability compared to untreated chondrocytes (S.E.). Proteome analysis of 2D-Electrophoresis and protein identification by mass spectrometry showed different expression of proteins derived from nucleus, cytoplasm and organelles. Function analysis of the identified proteins showed changes in related-proteins metabolism (glyceraldeyde-3-phosphate-dehydrogenase), stress response (Mn-superoxide-dismutase, heat-shock proteins), cytoskeletal regulation (actin), proteinase inhibition (cystatin-B) and inflammation regulatory functions (S100-A10, S100-A11) among the experimental groups (ELF, TAMMEF and S.E.). In conclusion, EMFs do not cause damage to chondrocytes, besides stimulate safely OA-chondrocytes and are responsible of different protein expression among the three groups. Furthermore, protein analysis of OA-chondrocytes treated with ELF and the new TAMMEF systems could be useful to clarify the pathogenetic mechanisms of OA by identifying biomarkers of the disease.

Human osteoarthritic chondrocytes exposed to extremely low-frequency electromagnetic fields (ELF) and therapeutic application of musically modulated electromagnetic fields (TAMMEF) systems: a comparative study

Osteoarthritis (OA) is the most common joint disease, characterized by matrix degradation and changes in chondrocyte morphology and metabolism. Literature reported that electromagnetic fields (EMFs) can produce benefits in OA patients, even if EMFs mechanism of action is debated. Human osteoarthritic chondrocytes isolated from femoral heads were cultured in vitro in bidimensional (2-D) flasks and in three-dimensional (3-D) alginate beads to mimic closely cartilage environment in vivo. Cells were exposed 30 min/day for 2 weeks to extremely low-frequency electromagnetic field (ELF) with fixed frequency (100 Hz) and to therapeutic application of musically modulated electromagnetic field (TAMMEF) with variable frequencies, intensities, and waveforms. Cell viability was measured at days 7 and 14, while healthy-cell density, heavily vacuolized (hv) cell density, and cluster density were measured by light microscopy only for 3-D cultures after treatments. Cell morphology was observed for 2-D and 3-D cultures by transmission electron microscopy (TEM). Chondrocyte exposure to TAMMEF enhances cell viability at days 7 and 14 compared to ELF. Light microscopy analysis showed that TAMMEF enhances healthy-cell density, reduces hv-cell density and clustering, compared to ELF. Furthermore, TEM analysis showed different morphology for 2-D (fibroblast-like) and 3-D (rounded shape) cultures, confirming light microscopy results. In conclusion, EMFs are effective and safe for OA chondrocytes. TAMMEF can positively interfere with OA chondrocytes representing an innovative non-pharmacological approach to treat OA.

Analysis of aqueous humour proteins in patients with retinoblastoma

BACKGROUND

To investigate aqueous humour protein composition from retinoblastoma patients.

DESIGN

Prospective, hospital-based study.

PARTICIPANTS

Eighteen retinoblastoma patients (Reese-Ellsworth stage V or ABC classification group E RB) undergoing ocular enucleation, and 10 normal subjects undergoing cataract surgery. Five of 18 patients presented with associated secondary glaucoma whereas 13 had no secondary glaucoma; 5 of 13 patients with no secondary glaucoma received chemotherapeutical treatment with melphalan.

METHODS

Aqueous humour samples were collected by limbal paracentesis of the anterior chamber after ocular enucleation in patients and after the stab peripheral corneal incision in controls. Total protein concentration according to Bradford method and sodium dodecyl sulphate-polyacrylamide gel electrophoresis of the samples were performed.

MAIN OUTCOME MEASURE

Aqueous humour protein concentration.

RESULTS

Aqueous humour protein concentration was significantly higher in retinoblastoma patients than controls (P < 0.01); patients with secondary glaucoma presented the highest values (P < 0.05 vs. controls); patients treated with melphalan presented a significant decrease (P < 0.01) versus non-treated; controls did not significantly differ from treated patients. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis pattern in retinoblastoma patients who did not receive any treatment was very different either from treated or from controls.

CONCLUSION

This study represents a preliminary step towards a more accurate two dimensional electrophoresis (2DE) pattern, which will be combined with mass spectrometry analysis to clarify the potential role of specific proteins in tumour development and progression; although these results suggest that aqueous humour protein pattern in retinoblastoma is characteristic, several aspects of the study are still under investigation.

Erythrocyte sedimentation rate measurement by VES Matic Cube 80 in relation to inflammation plasma proteins

Westergren method is considered as the reference procedure to measure Erythrocyte Sedimentation Rate (ESR) by the International Council for Standardization in Haematology. However, a closed automated method, VES Matic Cube 80 (DIESSE S.p.A., Siena, Italy), has been introduced as a new ESR measurement instrument. In this article, we report two different studies: first, we compared the two methods (Westergren and VES Matic Cube 80) and second, we correlated the inflammatory state of 248 patients with their ESR values. Total protein, albumin, C-reactive protein, and other inflammatory proteins were detected in each sample. The results obtained using VES Matic Cube 80 demonstrated a good correlation with those obtained using the Westergren method (Ordinary linear regression: y=0.955x-0.205, r(2) =0.816, P<0.05; Passing-Bablock regression equation: y=0.9153x-0.5763; Bland-Altman analysis: bias 1.2; limits of agreement -17.4-19.9) and with the inflammatory protein levels (CRP: r=0.554 and r=0.498 and Fibrinogen: r=0.699 and r=0.663 for Ves Matic Cube 80 and Westergren, respectively), supporting the hypothesis that VES Matic Cube 80 offers a fast and safe ESR determination, ensuring precision and a very good correlation with the reference method.

In vitro effects of Echis carinatus venom on the human plasma proteome

Echis carinatus venom (EV) is a complex mixture of toxins that contribute to its lethality. EV proteolytic activity was analyzed by zymography, chromogenic assays, and SDS-PAGE. To understand the molecular mechanism of the envenomation, we investigated the in vitro effect of EV on human plasma proteins. We looked for EV protein substrates and their proteolytic fragments. We analyzed EV proteolytic activity on standard proteins such as prothrombin or fibrinogen. To set up the optimal EV:plasma protein ratio conditions, plasma was incubated with EV (treated plasma), depleted of abundant proteins, and subjected to SDS-PAGE. Samples from control and treated plasma were also analyzed by 2-DE/MALDI-TOF MS, leading to the identification of four classes of plasma proteins cleaved by EV: proteases, protease inhibitors, binding proteins, and transporters. EV mainly proteolyzes entire proteins but can also act on physiological fragments. In summary, the physiological effects of EV proteases involve other important processes in addition to blood coagulation; complement activation and hemoglobin metabolism are also affected. In particular, the cleavage of protease inhibitors appears to be the mechanism through which the venom neutralizes the body's defenses.

Ultrastructural and biochemical investigations of protein mobilization of Mucuna pruriens (L.) DC. cotyledons and embryo axis

The mobilization of storage reserves, with particular emphasis on storage proteins of Mucuna pruriens (L.) DC., cotyledons, and embryo was investigated from the ultrastructural and biochemical points of view. Proteins and starch were the two main storage substances in cotyledons, and proteins and lipids were the main ones in the embryo. Embryo protein bodies were smaller and fewer in number than those of cotyledons. Structural and ultrastructural data determined between 24 and 48 h after imbibition and between 48 and 72 h after imbibition, the end of significant embryo and cotyledon protein mobilization, respectively, indicating more precocious storage protein mobilization in the axis than cotyledons. Moreover, storage protein mobilization in embryo and cotyledons occurred before the end of germination. Water soluble proteins were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis, producing 29 bands with molecular weights from 14 to 90 KDa. Embryo extract contained more proteins than cotyledon extract, contained seven characteristic bands, and showed a higher variability of the optical density trend than cotyledon.

Evidence of a new phosphoryl transfer system in nucleotide metabolism

Crude rat liver extract showed AMP-AMP phosphotransferase activity which, on purification, was ascribed to a novel interaction between adenylate kinase, also known as myokinase (EC 2.7.4.3), and adenosine kinase (EC 2.7.1.20). The activity was duplicated using the same enzymes purified from recombinant sources. The reaction requires physical contact between myokinase and adenosine kinase, and the net reaction is aided by the presence of adenosine deaminase (EC 3.5.4.4), which fills the gap in the energy balance of the phosphoryl transfer and shifts the equilibrium towards ADP and inosine synthesis. The proposed mechanism involves the association of adenosine kinase and myokinase through non-covalent, transient interactions that induce slight conformational changes in the active site of myokinase, bringing two already bound molecules of AMP together for phosphoryl transfer to form ADP. The proposed mechanism suggests a physiological role for the enzymes and for the AMP-AMP phosphotransferase reaction under conditions of extreme energy drain (such as hypoxia or temporary anoxia, as in cancer tissues) when the enzymes cannot display their conventional activity because of substrate deficiency.

A kinetic study of the rat liver adenosine kinase reverse reaction

Adenosine kinase is an enzyme catalyzing the reaction: adenosine + ATP --> AMP + ADP. We studied some biochemical properties not hitherto investigated and demonstrated that the reaction can be easily reversed when coupled with adenosine deaminase, which transforms adenosine into inosine and ammonia. The overall reaction is: AMP + ADP --> ATP + inosine + NH(3). The exoergonic ADA reaction shifts the equilibrium and fills the energy gap necessary for synthesis of ATP. This reaction could be used by cells under particular conditions of energy deficiency and, together with myokinase activity, may help to restore physiological ATP levels.

Adenosine kinase gene expression in human colorectal cancer

Real-time reverse transcription polymerase chain reaction (qRT-PCR) was used to evaluate gene expression of adenosine kinase, a key enzyme in adenosine metabolism, in human intestinal biopsy specimens of 10 colorectal cancer patients. Quantitative mRNA expression levels were normalized against the reference gene beta-actin. The results showed that adenosine kinase gene expression was significantly higher in cancer than in normal-appearing tissue, in line with our previous measurements of adenosine kinase enzyme activities in colorectal tumor samples.

Proteomic analysis of the pathophysiological process involved in the antisnake venom effect of Mucuna pruriens extract

Previously, we reported the antisnake venom properties of a Mucuna pruriens seed extract (MPE) and tested its in vivo efficacy against Echis carinatus venom (EV) in short- (1 injection) and long-term (three weekly injections) treatments. The aim of the present study was to investigate plasma proteome changes associated with MPE treatments and identify proteins responsible for survival of envenomated mice (CHALLENGED mice). Six treatment groups were studied. Three control groups: one saline, one short-term and one long-term MPE treatment. One group received EV alone. Two test groups received EV with either a short-term or long-term MPE treatment (CHALLENGED mice). The plasma from each group was analysed by 2-DE/MALDI-TOF MS. The most significant changes with treatment were: albumin, haptoglobin, fibrinogen, serum amyloid A and serum amyloid P. Most of these changes were explained by EV effects on coagulation, inflammation and haemolysis. However, MPE treatments prevented the EV-induced elevation in HPT. Consequently, HPT levels were similar to controls in the plasma of CHALLENGED mice. The plasma of CHALLENGED mice showed substantial proteomic modifications. This suggests the mechanism of MPE protection involves the activation of counterbalancing processes to compensate for the imbalances caused by EV.

Adenosine kinase from rat liver: new biochemical properties

Adenosine kinase is a well-known enzyme which catalyzes the phosphorylation of adenosine to AMP: Its metabolic and kinetic properties are well studied. Here, we report new properties of rat liver enzyme, demonstrating a new reaction: ADP can be a phosphate donor instead ATP, according to the reaction: adenosine + ADP --> 2AMP) demonstrating the efficiency of AdK to phosphorylate adenosine, also starting from ADP. Cells could exploited this property in situations in which ATP levels are strongly decreased and ADP decreases slowly.

Circulating gastrin and ghrelin levels in patients with colorectal cancer: correlation with tumour stage, Helicobacter pylori infection and BMI

Many studies have pointed out a possible role of gut peptides, including gastrin and ghrelin, in the pathogenesis and natural history of gastrointestinal malignancies, one of the most common death cause in the Western world. The objective of this work is to check gastrin and ghrelin serum levels in patients with colorectal cancer according to tumour's location, stage, Helicobacter pylori infection and BMI, in order to understand the two peptides' behaviour through the tumour's natural history and evaluate their assay's use in research and clinical practice. Twenty-nine subjects affected by colorectal cancer and 50 healthy controls were studied. Circulating gastrin and ghrelin levels and H. pylori serum antibodies were assessed by radioimmunologic assay and ELISA method. Gastrin and ghrelin serum levels were respectively slightly higher and significantly lower in colon cancer patients than in controls. Gastrin levels were higher in patients carrying left colon cancer and H. pylori infection while ghrelin levels were lower in both these groups. Both hormones' serum levels decreased from tumour earlier to later stages. Significant differences persisted in the correlation between BMI and ghrelin levels in controls but not in patients. Additional studies are necessary to ascertain the significance of gastrin and ghrelin opposite behaviour in colon cancer probably linked with interferences in endocrine pathways involving other gut peptides in this compromised condition.

Serum folate and vitamin B12 levels in children from Mozambique

In order to investigate the behaviour of biochemical parameters in children from Mozambique, we have determined the serum levels of folic acid and vitamin B12, two well known markers of nutritional anemia. We have correlated their values with other blood parameters and have evidenced potential interesting relationship between folate content and platelets count.

Metabolism of adenosine in human colorectal tumour

The aim of this work is to analyse the activities of the enzymes metabolising adenosine in fragments of neoplastic and normal-appearing mucosa, surrounding the tumour in 20 patients affected by colorectal cancer. The results show that the activities of the enzymes are markedly higher in tumour in comparison to normal mucosa to coope with the accelerated purine metabolism in cancerous tissues.

Enzyme activities controlling adenosine levels in normal and neoplastic tissues

Adenosine is known to be associated with effects such as inhibition of immune response, coronary vasodilation, stimulation of angiogenesis, and inhibition of inflammatory reactions. Some authors suggest that adenosine may also have similar functions in tumor tissues. Tissue levels of adenosine are under close regulation by different enzymes acting at different levels. Adenosine is produced from AMP by the action of 5'-nucleotidase (5'-NT) and is converted back into AMP by adenosine kinase (AK) or into inosine by adenosine deaminase (ADA). Inosine is converted into purine catabolites by purine nucleoside phosphorylase (PNP), whereas AMP is converted into ADP and ATP by adenylate kinase (MK). The aim of this study was to analyze the activities of the above enzymes in fragments of neoplastic and apparently normal mucosa, obtained less than 5 cm and at least 10 cm from tumors, in 40 patients with colorectal cancer. The results showed much higher activities of ADA, AK, 5'-NT, and PNP in tumor tissue than in neighboring mucosa (p > 0.01 for ADA, AK, and PNP; p > 0.05 for 5'-NT), suggesting that the activities of purine metabolizing enzymes increase to cope with accelerated purine metabolism in cancerous tissue. The simultaneous increase in ADA and 5'-NT activities might be a physiological attempt by cancer cells to provide more substrate to accelerate salvage pathway activity.

Effect of testosterone on purine nucleotide metabolism in rat liver

In previous studies, we found that castration induced interesting morphological and biochemical changes in rat liver. For the present study, we have examined the effects of testosterone on the kinetics of purine nucleotide metabolism with the aim of determining the steps affected by testosterone deficiency. A biomathematical model of purine nucleotide metabolism was used to analyze the many reactions involved. The model simplifies purine nucleotide metabolism to four main steps: 1) de novo synthesis from PRPP to IMP; 2) the inosinic branch point from IMP to GMP or AMP; 3) catabolism of IMP, AMP and GMP to uric acid; 4) RNA and DNA formation from AMP and GMP. We evaluated rate constants from each step from variations in specific radioactivity of metabolites labelled with (14)C-formate, a precursor of de novo synthesis. The model was applied to the liver of normal and castrated rats before and after testosterone treatment. All four steps were slowed after castration, and were not completely restored by androgen administration. The model can give a clear representation of the kinetics of the reactions involved in the liver nucleotide metabolism investigated here, and we propose that a similar approach could be useful whenever a quantitative evaluation of the results obtained in vivo after administration of labelled precursors is required.

Structure and function correlations between the rat liver threonine deaminase and aminotransferases

The rat liver threonine deaminase is a cytoplasmic enzyme that catalyses the pyridoxal-phosphate-dependent dehydrative deamination of L-threonine and L-serine to ammonia and alpha-ketobutyrate and pyruvate, respectively, in vivo. During deamination, a molecule of the cofactor is converted to pyridoxamine phosphate. Recently, the ability of this enzyme to accomplish an inverse half-reaction, restoring pyridoxal-phosphate and L-alanine or L-aminobutyrate, respectively, from pyruvate or 2-oxobutyrate, was reported. In order to investigate the molecular mechanisms of this transaminating activity, a molecular model of rat liver threonine deaminase was constructed on the basis of sequence homology with the biosynthetic threonine deaminase of Escherichia coli, the crystal structure of which is known. The model has structural features shared by aminotransferases, suggesting that tertiary structural elements may be responsible for the transaminating activity observed for rat liver threonine deaminase.

Proteins from Mucuna pruriens and enzymes from Echis carinatus venom: characterization and cross-reactions

Mucuna pruriens seeds have been widely used against snakebite in traditional medicine. The antivenin property of a water extract of seeds was assessed in vivo in mice. The serum of mice treated with extract was tested for its immunological properties. Two proteins of Echis carinatus venom with apparent molecular masses of 25 and 16 kDa were detected by Western blot analysis carried out using IgG of mice immunized with extract or its partially purified protein fractions. By enzymatic in-gel digestion and electrospray ionization-mass spectrometry/mass spectrometry analysis of immunoreactive venom proteins, phospholipase A(2,) the most toxic enzyme of snake venom, was identified. These results demonstrate that the observed antivenin activity has an immune mechanism. Antibodies of mice treated with non-lethal doses of venom reacted against some proteins of M. pruriens extract. Proteins of E. carinatus venom and M. pruriens extract have at least one epitope in common as confirmed by immunodiffusion assay.

Inhibition and regulation of rat liver L-threonine dehydrogenase by different fatty acids and their derivatives

Rat liver L-threonine dehydrogenase is a mitochondrial enzyme which transforms L-threonine either into aminoacetone or into acetyl-CoA. We show that it is inhibited by several fatty acids and their derivatives: short chain fatty acids, L-2-hydroxybutyrate and D-3-hydroxybutyrate, long chain fatty acids, such as lauric acid, myristic acid, palmitic and stearic acids, bicarboxylic acids such as malonic acid and its derivatives methyl- and hydroxymalonic acids. The inhibition occurs at low and physiological concentrations of such compounds, which are normally present and metabolized in mitochondria. It presumably plays a role in the physiology of acetyl-CoA-dependent formation of fatty acids and ketobodies, in L-threonine-dependent gluconeogenesis, and in the regulation of L-threonine metabolism by L-threonine dehydrogenase and L-threonine deaminase.

Determination of urinary methylated purine pattern by high-performance liquid chromatography

We describe the group selective separation and quantification of unmodified and modified purines in human urine by high-performance reverse phase liquid chromatography. The pattern of oxypurines and methylated purines: hypoxanthine (Hx), xanthine (X), 1-methyl hypoxanthine (1-MHx), 1-methyl guanine (1-MG), 3-methyl guanine (3-MG), 7-methyl guanine (7-MG), 1-methyl xanthine (1-MX), 3-methyl xanthine (3-MX), 7-methyl xanthine (7-MX), 1,7-dimethyl guanine (1,7-dMG), 1,3-dimethyl xanthine (1,3-dMX), 1,7-dimethyl xanthine (3,7-dMX) and 1,3,7-trimethyl xanthine (1,3,7-tMX) were determined in a single run in urine of a healthy subject and a gout patient before and after treatment with allopurinol. This method may be useful to investigate the urinary pattern of methylated bases in diseases involving purine metabolism.

Restoration of rat liver L-threonine dehydratase activity by pyridoxamine 5'-phosphate: the half-transaminating activity of L-threonine dehydratase and its regulatory role

When a highly purified preparation of rat liver l-threonine deaminase (l-TDH, EC 4.2.1.16) was 99% inactivated by dialysis, removing bound pyridoxal 5'-phosphate (PLP), the apoenzyme was reactivated not only by PLP but also by pyridoxamine 5'-phosphate (PMP). When purified by HPLC, the commercial PMP used in the incubation mixture was found to contain only extremely small amounts of PLP, which could not account for restoration of l-threonine dehydratase activity. HPLC analysis of the assay mixtures showed that during incubation, sufficient PLP had been formed for reactivation of the apoenzyme. The apoenzyme evidently bound PMP and triggered transamination between PMP and the keto acids, which either contaminated, or were formed by the minimal amount of PLP-holoenzyme always present even in the dialyzed preparation. When sufficient PLP was formed, the PLP-holoenzyme and the original 'true' l-threonine dehydratase activity were restored. When PMP was incubated with the apoenzyme in the presence of small quantities of keto acids (pyruvate or 2-oxobutyrate) small amounts of l-alanine or l-aminobutyrate were formed. The reaction was not reversible; l-alanine and l-aminobutyrate did not react with the PLP-holoenzyme. No transaminating activity occurred with other amino acids. These results show that l-threonine dehydratase exists in two forms: the well known stable apoenzyme-PLP (hydrolase deaminating) and the transient apoenzyme-PMP (non-reversible half-transaminating). Half-transamination has the biological role of keeping the activity of the 'true' l-TDH constant and of regulating intracellular levels of pyruvate, alanine, oxobutyric acid, l-aminobutyric acid, l-threonine and l-serine.

Some chemical properties and biological role of thiazolidine compounds

In this study we have investigated some chemical properties and the biological role of thiazolidine compounds, obtained by condensation of aminothiols (L- or D-cysteine, cysteamine) with pyridoxal-5'-phosphate. These products have been tested in presence of rat liver extracts (supernatant and mitochondria); bacterial suspensions and enzymes (L- or D-aminoacid oxidase, xanthine oxidase) with interesting results which gives evidence to a biological role. Their formation in vivo may represent the regulation of intracellular levels of pyridoxal-5'-phosphate and aminothiols. Moreover, we have analysed the two diastereoisomers of the thiazolidine compounds derived from L-cysteine and D-cysteine: we have succeeded to distinguish by NMR analysis the cis and the trans forms, concluding that the interconversion of the free forms is extremely rapid at pH 7: thus, it may be relevant for the protein bound forms.

Biological role of carbamoyl pyridoxal 5'-phosphate

A new compound, carbamoyl-pyridoxal 5'-phosphate (C-PLP), was synthetized by condensation of pyridoxal 5'-phosphate (PLP) with KCNO. It may be obtained under certain physiological conditions of pH, temperature and concentration of reagents. Formation and degradation of C-PLP are readily reversible chemical reactions, not involving enzymes, at least in rat tissues. However, different considerations suggest that synthesis and breakdown of C-PLP play a biological role in the cell, providing 'protective synthesis' and a 'variable reservoir' of PLP and KCNO, which can be trapped by other proteins, apoenzymes and metabolites, to regulate many cell metabolic functions.

Effect of testosterone on purine metabolism and morphometric parameters in the rat liver

The effect of testosterone on the morphology and biochemistry of adult castrated rat liver is described. Castration decreases mean weight and volume of hepatocytes, volume and surface area of sinusoidal lumen, and apparently increases cell number per g of tissue. These variations indicate cell distress. Testosterone administration restored sinusoidal volume and surface area, indicating a true hyperplastic response and improved trophic conditions. Acid soluble nucleotides, RNA and DNA content were lower after castration, being partially restored after testosterone treatment. This restoration, however, was only statistically significant for total guanylate. We concluded that testosterone deficiency and administration exerts a specific effect on the liver in terms of morphological and biochemical changes. Purine nucleotide metabolism is probably the first target of hormonal action, since its changes are the most significant and useful to explain all the other observations.

Purine ribonucleotide content in infected HIV-RT+ and HIV-RT- lymphoblastoid cell lines

We have studied the purine nucleotide metabolism in the following cell lines: a), H9 (continuous human T-cell line) and H9/HTLV-III (H9 cell line, infected with RT+ HIV-I virus); b), A3.01 (human lymphoblastoid cell line CD4+) and 8E51 (line A3.01 permanently transfected with RT-HIV-I virus). Purine metabolism was studied by evaluating the content of the most important ribonucleotides (AMP-GMP-IMP-NAD-ADP-GDP-ATP-GTP) and their ratios. We determined several differences between the cell lines before and after viral infection. All nucleotides except triphosphates were reduced in H9/HTLV-III with respect to H9 cells; in 8E51, however, triphosphates were markedly reduced, while monophosphates increased with respect to A3.01 uninfected cells. Also the ratios exhibited different behaviors, for example the total adenine nucleotides total guanine nucleotides ratio (sigma A/sigma G) was enhanced in H9/HTLV-III cells with respect to H9 and unaltered in 8E51 with respect to A3.01 cells. We may conclude that the HIV-I virus strongly influences the purine nucleotide metabolism of the host cells and that the changes are different when induced either by RT+ or RT- virus.

The influence of testosterone on purine nucleotide metabolism in rat liver

Purine nucleotide metabolism was studied in rat liver by following the incorporation of 14C-formate into soluble nucleotides, uric acid and RNA ribonucleotides. After castration, GMP formation was less than that of AMP, and purine nucleotide catabolism and RNA synthesis decreased. Testosterone administration did not modify GMP or AMP synthesis, but restored purine nucleotide catabolism and RNA production to normal values. These results demonstrate the influence of testosterone on purine nucleotide metabolism in a non-reproductive organ.

Identification of a mitochondrial inhibitor of rat liver L-threonine dehydrogenase

In a previous paper, we showed inhibition of rat liver L-threonine dehydrogenase by a preparation obtained by dialysis and concentration from rat liver mitochondria stored at -20 degrees C for 7-10 days (Pagani, R., Leoncini, R., Guerranti, R. and Marinello, E. (1990) It. J. Biochem. 39, 106-114). The chemical composition of the fraction containing the unknown 'inhibitor' has now been studied and identified as D-3-hydroxybutyrate (D3HB).