CLINICAL SIGNIFICANCE OF A HYDROXYPROLINE-CONTAINING PROTEIN IN HUMAN PLASMA

Plasma α-Actin as an Early Marker of Muscle Damage After Repeated Bouts of Eccentric Cycling

Purpose: This study aimed to examine the changes in skeletal muscle (SM) α-actin, myoglobin (Mb) and hydroxyproline (HP) in plasma and other indirect markers of muscle damage after repeated bouts of eccentric cycling. Methods: Ten healthy men (23.3 ± 2.8 years) performed two 30-min eccentric cycling bouts at 100% of maximal concentric power output (230.7 ± 36.9 W) separated by 2 weeks (ECC1 and ECC2). Maximal voluntary isometric contraction (MVIC) peak force of the knee extensor muscles, muscle soreness (SOR), pain pressure threshold (PPT) and plasma levels of SM α-actin, Mb, and HP were measured before, 0.5, 3, 24-168 h after each cycling bout. Results: MVIC peak force decreased on average 10.7 ± 13.1% more after ECC1 than ECC2. SOR was 80% greater and PPT was 12-14% lower after ECC1 than ECC2. Plasma SM α-actin levels increased at 0.5, 3, and 24-72 h after ECC1 (26.1-47.9%), and SM α-actin levels at 24 h after ECC1 were associated with muscle strength loss (r = -0.56, P = .04) and SOR (r = 0.88, P = .001). Mb levels increased at 0.5, 3, and 24 h after ECC1 (200-502%). However, Mb levels at 24 h after ECC1were not associated with muscle strength loss and SOR. HP levels remained unchanged after ECC1. ECC2 did not increase SM α-actin, Mb and HP levels. Conclusion: Our results indicate that α-actin could be used as a potential marker for the early identification of SM damage due to its early appearance in plasma and its association with other indirect markers of muscle damage.

Evaluation of Serum and Urine Amino Acids in Dogs with Chronic Kidney Disease and Healthy Dogs Fed a Renal Diet

This observational study aimed to evaluate serum and urinary amino acid (AA) concentrations in healthy dogs and dogs with chronic kidney disease (CKD) fed a commercial therapeutic renal diet with reduced protein and phosphorus levels. Ten dogs with CKD stages 3 or 4 composed the study group and received the renal diet for 180 days (RG T180). A control group (CG T30) composed of seven healthy dogs was fed a renal diet for 30 days. When comparing serum AA between RG T180 and CG T30, histidine, isoleucine, leucine, lysine, phenylalanine, tryptophan, cysteine, citrulline, ornithine, taurine, branched-chain amino acids (BCAA), and total essential amino acids (EAA) were higher in RG T180. Meanwhile, arginine, asparagine, aspartate, glutamine, serine, and tyrosine were higher in CG T30. Serum phenylalanine, tryptophan, and hydroxyproline were higher in RG T0 (dogs with CKD before consuming a renal diet) when compared to RG T180. In addition, the serum ratios of arginine/citrulline, tyrosine/phenylalanine, and serine/glycine were higher in CG T30 than in RG T180. Concerning urinary AA concentrations in CKD dogs, isoleucine, phenylalanine, tryptophan, aspartate, cysteine, and BCAA were higher in RG T180. In urine, the total EAA/total non-essential AA ratio in RG T180 was higher than in CG T30 as well as tyrosine/phenylalanine ratio higher in CG T30. In conclusion, the combination of renal diet and conservative treatment over 6 months in dogs with CKD stages 3 or 4 affected the AAs metabolism when compared to healthy adult dogs.

Development, validation, and application of a liquid chromatography-tandem mass spectrometry method for quantitative determination of trans-4-hydroxy-l-proline concentration in the serum of dogs with chronic hepatitis

OBJECTIVE

To develop and analytically validate a liquid chromatography-tandem mass spectrometry method for measurement of endogenous trans-4-hydroxy-l-proline concentrations in canine serum and to assess serum trans-4-hydroxy-l-proline concentrations in dogs with chronic hepatitis.

SAMPLE

Serum samples obtained from 20 dogs with histopathologically confirmed chronic hepatitis and 20 healthy control dogs.

PROCEDURES

A liquid chromatography-tandem mass spectrometry method for quantification of trans-4-hydroxy-l-proline concentration was developed and assessed for analytic sensitivity, linearity, accuracy, precision, and reproducibility. Serum concentration of trans-4-hydroxy-l-proline in dogs with chronic hepatitis and healthy control dogs was measured.

RESULTS

Observed-to-expected ratios for dilutional parallelism ranged from 72.7% to 111.5% (mean ± SD, 91.3 ± 19.6%). Intra-assay and interassay coefficients of variation ranged from 2.1% to 3.0% and 3.2% to 5.3%, respectively. Relative error ranged from -2.3% to 7.8%. Trans-4-hydroxy-l-proline concentrations were significantly lower in serum obtained from dogs with chronic hepatitis (median, 0.24 ng/mL; range, 0.06 to 1.84 ng/mL) than in serum obtained from healthy control dogs (median, 0.78 ng/mL; range, 0.14 to 4.90 ng/mL).

CONCLUSIONS AND CLINICAL RELEVANCE

The method described here for the quantification of trans-4-hydroxy-l-proline concentration in canine serum was found to be sensitive, specific, precise, accurate, and reproducible. Dogs with chronic hepatitis had significantly lower serum trans-4-hydroxy-l-proline concentrations than did healthy control dogs, possibly as a result of altered hepatic metabolism of amino acids.

Untargeted metabolomic profiling of serum from dogs with chronic hepatic disease

Background

Chronic hepatopathies present a diagnostic challenge, with different diseases being associated with similar clinical and laboratory findings. Characterization of dogs with chronic hepatopathies can be difficult and require costly diagnostic procedures such as acquisition of a liver biopsy specimen. Noninvasive and inexpensive biomarkers that reliably characterize chronic hepatopathies such as chronic hepatitis or a congenital portosystemic vascular anomaly may decrease the need for costly or invasive diagnostic testing and guide novel therapeutic interventions.

Objective

To investigate differences in the serum metabolome among healthy dogs, dogs with congenital portosystemic shunts, and dogs with chronic hepatitis.

Animals

Stored serum samples from 12 healthy dogs, 10 dogs with congenital portosystemic shunts, and 6 dogs with chronic hepatitis were analyzed.

Methods

The serum metabolome was analyzed with an untargeted metabolomics approach using gas chromatography–quadrupole time of flight mass spectrometry.

Results

Principal component analysis and heat dendrogram plots of the metabolomics data showed clustering among individuals in each group. Random forest analysis showed differences in the abundance of various metabolites including increased aromatic amino acids and xylitol in dogs with congenital portosystemic shunts. Based on the univariate statistics, 50 metabolites were significantly different among groups.

Conclusions and Clinical Importance

The serum metabolome varies among healthy dogs, dogs with congenital portosystemic shunts, and dogs with chronic hepatitis. Statistical analysis identified several metabolites that differentiated healthy dogs from dogs with vascular or parenchymal liver disease. Further targeted assessment of these metabolites is needed to confirm their diagnostic reliability.

Vitamin B6 deficiency experimentally-induced bone and joint disorder: microscopic, radiographic and biochemical evidence

In the present study the effect of pyridoxine deficiency on the ultrastructure and morphology of bone and its metabolism was examined in the rapidly growing chick. Pyridoxine-deficient animals had tibias of reduced dry weight and cortical thickness. Histomorphometry demonstrated a disproportionately high eroded surface, lower amount of osteoid tissue and reduced mineralized trabecular width. Anterior-posterior radiographs of the tibiotarsometatarsal joint showed reduced secondary ossification centres and coarse trabeculation. Decalcified metaphyseal cartilage showed irregular trabeculas and a markedly reduced amount of Fast-green counterstain matrix suggesting that there is less collagen present and in turn less availability for matrix to be laid down for later calcification. Plasma activity of the bone alkaline phosphatase isoenzyme (EC 3.1.3.1) was decreased. Plasma Ca and PO4 levels did not vary. The present bone study referring to a pseudo-lathyritic state in which collagen maturation is not completely achieved supports the hypothesis that pyridoxine is an essential nutrient for the connective tissue matrix.

Increased amount of serum type IV collagen peptide in human liver fibrosis as determined by enzyme-immunoassay with monoclonal antibodies

Chronic liver injury by various toxic agents causes an increase in collagen biosynthetic activity, resulting in deposition of excessive amounts of collagen and rearrangement of the lobular architecture leading to hepatocellular dysfunction and portal hypertension. The authors have developed sandwich enzyme-immunoassay for human serum type IV collagen peptide using monoclonal antibody as a marker of fibrogenesis and examined the relationship between the amount of this collagen peptide and hepatic disorders including chronic active hepatitis and liver cirrhosis. Sera from patients with chronic active hepatitis or liver cirrhosis were used after confirmation of the histopathological diagnosis. Control sera were obtained from healthy subjects without any serological abnormality in liver function tests. Serum type IV collagen peptide levels were significantly higher in patients with chronic hepatic disorders associated with fibrosis than in healthy subjects. This non-invasive enzyme-immunoassay gave reproducible quantitation, and serum type IV collagen peptide was concluded to be a useful, and reproducible marker for the early detection of fibrogenesis in the liver.

Clinical significance of serum hydroxyproline-containing peptides with special reference to hyproprotein

Serum hydroxyproline-containing peptides were separated into three fractions, i.e. large protein, polypeptide and smaller peptides, by gel filtration on Sephadex G-200. The large protein was presumed to be the C1q subunit of the first component of complement by an immunological analysis. The polypeptide had an electrophoretic mobility corresponding to beta-globulin and its molecular weight was estimated between 35000 and 45000 by gel filtration analysis. The polypeptide might well be defined as hyproprotein. The molecular weight of smaller peptides was estimated between 1400 and 3000. As compared with the control value, hyproprotein levels were significantly increased in rheumatoid arthritis, systemic lupus erythematosus and chronic liver disease. C1q levels were slightly lowered in rheumatoid arthritis and systemic lupus erythematosus, and were slightly increased in chronic liver disease but were not significant. In all patient groups smaller peptides levels remained in the normal range. These results suggest that serum hyproprotein levels are raised in some fibroproliferative disorders, probably reflecting collagen metabolism.

Chemical and immunological features of pleural effusions: comparison between rheumatoid arthritis and other diseases

The value of determination of pleural fluid glucose, pH, lactic dehydrogenase, IgG, IgA, IgM, C3, C4, anti-IgG antibody, and hydroxyproline in distinguishing between pleural effusions caused by rheumatoid arthritis (RA) and those resulting from other diseases was studied. The series comprised seven patients with RA and 115 patients with other diseases including systemic lupus erythematosus, tuberculosis, malignant disease, empyema, pneumonia, congestive heart failure, and nonspecific pleural effusion. The low glucose concentration, the low pH and the low C4 level in rheumatoid pleural effusion were the most valuable diagnostic findings. The presence of anti-IgG antibody in pleural fluid was not specific for RA. The concentration of hydroxyproline in pleural fluid and the pleural fluid-to-plasma hydroxyproline ratio were significantly higher in RA than in tuberculosis and malignant disease. The results support the view that local metabolic and immunological phenomena as well as a high turnover of collagen occur in the pleural cavity in RA.

Plasma hydroxyproline fractions in patients with dialysis osteodystrophy

Plasma hydroxyproline fractions were measured in 17 normal subjects and in 54 patients on maintenance haemodialysis therapy (MHT) with various degrees of dialysis osteodystrophy. On the basis of both radiological and histological findings these patients were divided into three groups: radiologically normal, histologically normal and those with osteitis fibrosa. The mean total plasma hydroxyproline concentrations were significantly elevated in all groups of MHT patients. However, these increases were mainly due to peptide-bound and free hydroxyproline fractions. The highest values for these two fractions were found in patients with osteitis fibrosa. The free to peptide-bound hydroxyproline ratio was not significantly altered in the majority of patients on dialysis; the mean ratio was significantly lower in patients with osteitis fibrosa when compared with patients with no histological evidence of bone disease. This finding would suggest that there is no inhibition of hydroxyproline catabolism in patients on haemodialysis and the measurements of both free and peptide-bound hydroxyproline were equally sensitive in identifying patients with osteitis fibrosa.

Distribution of plasma-bound hydroxyproline in breast cancer, benign breast disease and healthy females

In normal adult females, patients with benign breast disease and patients with breast cancer, hydroxyproline (OHPro) was found in the plasma attached to the protein fractions which were separated by Sephadex gel filtration. In addition, a distinct moiety, probably a protein sub-unit, containing substantial amounts of this imino acid, occurred in between gel filtration fractions III and IV. Quantitative differences in the OHPro content of these various fractions were observed in the groups of patients studied. Significant elevations in the peptide-bound OHPro (fraction IV) were found only in patients with breast cancer and the level appeared to correlate with the degree of advancement of the disease. Similar findings relate to the OHPro content of the sub-protein moiety which is found between gel filtration fractions III and IV. A reduced level of high molecular weight hyproprotein (fraction I) was found in the breast cancer group.

[Parameters of collagen biosynthesis in cotton pellet granuloma of rats on iron deficiency (author's transl)]

Rats of Wistar strain, of same age, were kept on iron free diet up to nearly absolute iron deficiency in iron depots. Afterwards granuloma was produced by implantation of cotton pellets subcutaneously. For characterization of the collagen biosynthesis in the granuloma the neutral salt soluble collagen and the activity of the prolyl hydroxylase were measured in the granuloma 4, 8 and 12 days after cotton pellet implantation. At the same time "collagen-like" protein was determined in the serum of the animals. The enzyme activity was statistically significant lower in the granuloma of animals on iron deficiency than in the granuloma of the comparable groups on normal diet. Statistically significant higher concentration of neutral salt soluble collagen was found 8 and 12 days after cotton pellet implantation in the group on iron free diet. There was no significant difference as to the serum levels of "collagen-like" protein in serum.

Determination of hydroxyproline polypeptides in urine and blood serum by gel filtration

Hydroxyproline-containing polypeptides were isolated from urine by filtration on polyacrylamide gel Bio-Gel P-2. This fraction was quantitatively and qualitatively similar to the nondialysable hydroxyproline in urines of normal adult subjects, patients with chronic uremia, and with primary or secondary hyperparathyroidism. Hydroxyproline polypeptides isolated from urines of patients with extensive Paget's disease or from normal growing subjects contained a group of smaller polypeptides slightly retarded on Bio-Gel P-2 which were not retained by the dialysis membrane Spectrapor-TM. In these two groups of subjects the values of hydroxyproline polypeptides were 35-45 percent higher than those of dialysable hydroxyproline. Increased excretion of hydroxyproline polypeptides was found in chronic uremia, primary and secondary hyperparathyroidism, Paget's bone disease and in normal growing subjects. With the notable exception of chronic uremia the excretion of hydroxyproline polypeptides paralleled that of total and oligopeptidic hydroxyproline. In some cases of chronic uremia the polypeptidic hydroxyproline represented the predominant fraction. On long columns of Bio-Gel P-6 hydroxyproline polypeptides separated into several peaks. The chromatographic pattern was rather characteristic for chronic uremia, secondary hyperparathyroidism, Paget's bone disease and physiological growth. Ahydroxyproline fraction of similar chromatographic properties was isolated from blood serum after deproteinisation with heat or ethanol at pH 4.8. High serum levels of this hydroxyproline fraction were observed in pathological conditions with increased urinary excretion of polypeptidic and nondialysable hydroxyproline.

High-molecular-weight hydroxyproline-protein in relation to immunoglobulins M (IgM) in human blood serum

The content of the high-molecular-weight protein-bound hydroxyproline (Hyp) and IgM level in the sera of 30 healthy persons and 29 patients showing changes in gamma and/or beta globulin levels was determined. Statistically significant correlations between quantities of these components have been found. On the base of the present results as well as the results of previous studies authors suggest that the high-molecular-weight Hyp-protein contains immunoglobulin of the IgM class.