Evaluation of urinary hydroxyproline and creatinine level in patients with benign mandibular odontogenic tumor

Background

Odontogenic tumors are relatively common oro‐facial tumors seen in our environment with challenges encountered with management in terms of inadequate infrastructure and high cost of treatment. They are often associated with bone resorption with concomitant collagen degradation and excretion of their by‐products in serum or urine. The aim of this present study was to evaluate urinary hydroxyproline level in patients with benign mandibular odontogenic tumors.

Materials and methods

Twenty‐two consecutive patients with histologically diagnosed mandibular odontogenic tumors were recruited. Twenty‐two controls who matched the study group for sex and age were also recruited. The study group had CT‐Scan of their lesions done. All participants were required to fast 12 hours overnight and their early morning second void urine collected between 7 a.m and 8 a.m. The collected urine samples were stored frozen at −20°C until analysis. Colorimetric method of analysis of urinary hydroxyproline and creatinine were done using Biovision hydroxyproline kit and Randox creatinine kit, respectively. The results were recorded as urinary hydroxyproline alone (μg/μl) and as urinary hydroxyproline/creatinine ratio.

Results

The mean age of the participants was 28.45 ± 6.8 years. The mean duration of the tumors in the study group was 5.9 ± 4.4 years. A mean urinary hydroxyproline/ creatinine ratio of 0.081 ± 0.129 was noted in the study group as compared to 0.016 ± 0.006 that was noted among healthy Nigerian who served as controls in the study.

Conclusion

There was a significant increase in urinary hydroxyproline level in patients with odontogenic tumors when compared with healthy Nigerians.

Optimum conditions of autoclaving for hydrolysis of proteins and urinary peptides of prolyl and hydroxyprolyl residues and HPLC analysis

A method for urinary peptide(s) and protein hydrolysis, involving autoclaving at 15psi (121 degrees C) for 60min, is described. Using three candidate proteins (bovine serum albumin, casein and gelatin) and urine specimens, the effect of autoclaving with respect to the optimum time required for hydrolysis under both acidic (6N HCl) and alkaline (6N KOH) conditions was studied. Recoveries of total amino acids from proteins and urine hydrolysate(s) suggest that complete hydrolysis of proteins and urinary peptides could be achieved by autoclaving for 30-60min instead of 16h of incubation at 110 degrees C. Further, stability of some of the individual amino acids was also studied. The observed differential stability of amino acids under acidic and alkaline conditions, as demonstrated in this study by HPLC analysis, makes it imperative to choose the appropriate hydrolytic condition while studying the composition of any given amino acids in urinary peptide(s)/protein hydrolysates. Further, the finding that both Pro and Hyp were stable under alkaline conditions of hydrolysis by autoclaving renders this method suitable for assaying these two amino acids from urine hydrolysates, hence its utility in the study of urinary peptide derived Hyp and Pro in bone/cartilage disorders.

Evidence for increased pyridinoline concentration in fibrotic tissues in diffuse systemic sclerosis

Systemic sclerosis is a generalized disease characterized mainly by the accumulation of collagen in the skin and internal organs. The aim of our study was to determine the amount of collagen cross-link pyridinoline (Pyd) in a variety of fibrotic tissues (skin, fascia, endocardium, bladder) from an autopsy patient with diffuse systemic sclerosis, and to compare these with normal tissues from the same patient. Mean concentrations of Pyd in the fibrotic skin samples (66 mmol/mol collagen) were more than two-times greater than those in the uninvolved normal samples (27 mmol/mol collagen). The increase of Pyd in the endocardium, fascia, and bladder was also markedly higher (1.41 x, 1.26 x and 2.64 x higher than normal samples). The increased deposition of collagen in systemic sclerosis is accompanied by a significantly increased amount of Pyd in the collagen of fibrotic tissues.

Analysis of 4-hydroxyproline using 4-chloro-7-nitrobenzo-2-oxa-1,3-diazol derivatization and micellar electrokinetic chromatography combined with laser-induced fluorescence detection

Micellar electrokinetic chromatography (MEKC) with laser-induced fluorescence (LIF) detection was used for internal standard (pyrrolidinol) based quantification of 4-hydroxyproline (Hyp) in muscle hydrolysates. Hydrolysates were first derivatized with o-phthaldialdehyde to reduce primary amine interference and then 4-chloro-7-nitrobenzo-2-oxa-1,3-diazol (NBD) to enable selective detection of secondary amines. This method allows for rapid and sensitive detection of hydroxyproline in dilute hydrolysates using commercially available capillary electrophoresis equipment.

Bone biomarkers as tools in osteoporosis management

Biochemical tests that can index bone turnover rate in the patient are increasingly being used in the study and management of osteoporosis. Markers of bone formation and resorption are reviewed here, including their molecular basis, relative strengths and weaknesses in clinical performance, and future potential. A bone mass measurement (e.g., by dual-energy x-ray absorptiometry) and a biochemical index of bone turnover provide different but complementary information that can aid in predicting risk of future bone loss and osteoporotic fracture. A specific and responsive bone resorption marker can also be used to monitor and establish the short-term effectiveness of an antiresorptive therapy in the patient. Bone-specific alkaline phosphatase (an osteoblast enzyme) and osteocalcin (a bone matrix protein) levels in serum are the best markers of bone formation. Collagen degradation products in urine, particularly cross-linked telopeptides and pyridinolines, have the highest specificity to bone resorption activity. The telopeptide markers (NTx and CTx) appear to be the most specific and responsive markers of systemic osteoclast activity.

New marker of bone resorption: hydroxyproline-containing peptide. High-performance liquid chromatographic assay without hydrolysis as an alternative to hydroxyproline determination: a preliminary report

A high-performance liquid chromatographic (HPLC) assay for a urinary hydroxyproline-containing peptide (hydroxy-proline peptide, HypP) is described. This peptide represents about 50% of urinary hydroxyproline-containing peptides. Its concentration and total 4-hydroxyproline (Hyp) concentration evaluated in 325 urine samples have been shown to be closely correlated (r = 0.972; y = 0.499 x -1.5), which may indicate that the two markers provide the same information. The HypP assay, similar to Hyp assay, is carried out without hydrolysis of urine samples. After the blocking of primary amino acids by o-phthaldialdehyde (OPA) and derivatization of secondary amino acids by 9-fluorenylmethyl chloroformate (FMOC-CI), the FMOC derivatives of HypP and 3,4-dehydroproline (internal standard) were separated on a strong anion-exchange column and detected fluorimetrically. HypP concentration was calculated by measurement of peak-area ratios of HypP and the hydroxyproline standard. The HypP/creatinine (mmol/mol) ratio in fasting urine samples from healthy adults was found to be 8.2 (S.D. = 1.6, n = 33) in 27-44-year-old premenopausal women and 6.9 (S.D. = 1.7, n = 21) in 28-49-year-old men.

A simple and automated HPLC method for determination of total hydroxyproline in urine. Comparison with excretion of pyridinolines

An HPLC method for measuring total hydroxyproline in human urine was validated. Hydroxyproline derivatization was achieved with 9-fluorenylmethyl chloroformate after blocking primary amino acids with orthophthaldialdehyde. The derivatives (hydroxyproline and internal standard) were separated by reversed phase high-performance liquid chromatography and detected by absorbance at 254 nm. Duplicate measurements of hydroxyproline have a coefficient of variation of 3.9% and the recovery in spiked urine samples is between 99.5 and 100.8%. We have compared the HPLC procedure with a commercial colorimetric assay. Analytical criteria of these methods are identical. Regression analysis, involving 50 samples, shows an excellent correlation between hydroxyproline chromatographic (y) and colorimetric (x) procedures: y = 0.989x + 2.99 (r = 0.976). Hydroxyproline excretion was determined in urine samples from 76 women more than 5 years post-menopause. The mean hydroxyproline/creatinine ratio in this group was 19.3 +/- 5.6 mumol/mmol (range 10.6-34.7). Finally, we compared in the same urinary samples hydroxyproline excretion with pyridinoline excretion (hydroxylysylpyridinoline and lysylpyridinoline), a new marker of bone resorption. The values show a significant correlation, with r = 0.417 for hydroxylysylpyridinoline and r = 0.443 for lysylpyridinoline.

Derivatization of posttranslationally modified amino acids

After a brief overview of posttranslational modifications of protein amino acids, the use of various derivatizing reagents for amino acid analysis is discussed. Derivatization and chromatographic separation of hydroxyproline, methylhistidine, and phosphorylated amino acids are discussed in detail to illustrate some of the strategies that can be applied to the analysis of posttranslationally modified amino acids.

The effect of low-dose methotrexate on bone metabolism and histomorphometry in rats

OBJECTIVE

To ascertain the effects of low-dose methotrexate (MTX) on bone metabolism and histomorphometry in rats.

METHODS

Female Sprague-Dawley rats (6 months old, n = 42) were divided into the following 4 groups: intraperitoneal (IP) injections of MTX, with and without ovariectomy, and IP saline (controls), with and without ovariectomy. Injections were given for 16 weeks. The MTX dose was equivalent to a standard dose for rheumatoid arthritis in humans that would yield similar serum MTX levels (0.6 +/- 0.1 mumoles).

RESULTS

Bone formation (assessed by serum alkaline phosphatase and osteocalcin levels and histomorphometry) was significantly lower in the MTX groups, and bone resorption (assessed by urinary hydroxyproline levels and histomorphometry) was increased in the MTX groups. Bone mass was significantly diminished in the MTX groups.

CONCLUSION

Prolonged administration of low-dose MTX in rats causes significant osteopenia via suppression of osteoblast activity and stimulation of osteoclast recruitment, which results in increased bone resorption.

Reversed-phase high-performance liquid chromatographic analysis of hydroxyproline and proline from collagen by derivatization with dabsyl chloride

A high-performance liquid chromatographic method for the analysis of hydroxyproline and proline has been developed. The method is based on the derivatization of the secondary amino group with dabsyl-chloride after blocking of the primary amino group with o-phthalaldehyde. Dabsyl-hydroxyproline and dabsyl-proline were separated from other amino acids by high-performance liquid chromatography in the gradient elution mode, and eluted at 10.27 and 16.02 min, respectively. The correlations between the peak areas of dabsyl-hydroxyproline and dabsyl-proline were linear in the range from 20-200 pmol, with equations y = 1.10x - 0.80 (r = 0.999) and y = 1.12x - 0.52 (r = 0.999), respectively. The method was applied to the analysis of rat tail collagen, and the contents of hydroxyproline and proline were 1.55 +/- 0.04 and 2.03 +/- 0.04 nmol/micrograms, respectively.