Determination of 3 methyl-L-histidine in human urine by ion exchange high performance liquid chromatography. Applications to patients in post-operative surgical care

Effects of dietary soy protein on skeletal muscle volume and strength in humans with various physical activities

BACKGROUND

In recent years, the number of bedridden people is rapidly increasing due to aging or lack of exercise in Japan. This problem is becoming more serious, since there is no countermeasure against it. In the present study, we designed to investigate whether dietary proteins, especially soy, had beneficial effects on skeletal muscle in 59 volunteers with various physical activities.

METHODS

We subjected 59 volunteers with various physical activities to meal intervention examination. Persons with low and high physical activities were divided into two dietary groups, the casein diet group and the soy diet group. They ate daily meals supplemented with 7.8 g of powdered casein or soy protein isolate every day for 30 days. Bedridden patients in hospitals were further divided into three dietary groups: the no supplementation diet group, the casein diet group and the soy diet group. They were also subjected to a blood test, a urinalysis, magnetic resonance imaging analysis and muscle strength test of the knee before and after the meal intervention study.

RESULTS

Thirty-day soy protein supplementation significantly increased skeletal muscle volume in participants with low physical activity, compared with 30-day casein protein supplementation. Both casein and soy protein supplementation increased the volume of quadriceps femoris muscle in bedridden patients. Consistently, soy protein significantly increased their extension power of the knee, compared with casein protein. Although casein protein increased skeletal muscle volume more than soy protein in bedridden patients, their muscle strength changes by soy protein supplementation were bigger than those by casein protein supplementation.

CONCLUSIONS

The supplementation of soy protein would be one of the effective foods which prevent the skeletal muscle atrophy caused by immobilization or unloading.

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.

Reproducibility of urinary 3-methylhistidine excretion in human subjects consuming freely selected diets

Eight males and six females consumed their normal diet for 9 weeks, except for weeks 3 and 9 when they followed a self-selected diet free of 3-methylhistidine (3MH) for five subsequent weekdays (days 1 to 5). Timed 24-hours urine collections were obtained on days 3, 4, and 5 of these 3MH-free dietary periods and on one day during weeks 1 and 7. At the group level, no differences in 3MH excretion (P greater than .05) between days 3, 4, and 5 in weeks 3 and 9 and between these weeks were observed. Reproducibility at the individual level was indicated by the within-subject coefficient of variation (CVw). CVw within weeks 3 and 9 was 2.5% and 5.1% for men and 4.8 and 8.0% for women. CVw between these weeks was highest when more than one measurement per week was performed. Relating 3MH to creatinine decreased the CVw between weeks. If muscle protein breakdown is to be measured at the individual level, a reasonably large biologic variation is to be taken into account and repeated measurements should be done to decrease the CVw.

Analytical determination of methylated histidine in proteins: actin methylation

The methylation of histidine in actin from various muscle and nonmuscle sources has been studied by formation of phenylthiocarbamyl derivatives and subsequent reverse-phase high-pressure liquid chromatographic separation and analysis of actin hydrolyzates. All the actin species examined were found to contain 3-methylhistidine. This method has also been used in assays for the enzyme(s) responsible for methylation of rabbit skeletal muscle actin and to investigate the formation of other methylated residues in vitro. 3-Methyl-histidine is the major methylation product in this in vitro reaction.

Determination of methylated basic, 5-hydroxylysine, elastin crosslinks, other amino acids, and the amino sugars in proteins and tissues

Analytical single-column chromatographic methods have been developed for determining all methylated basic amino acids, isodesmosine, desmosine, the amino sugars glucosamine and galactosamine, the diastereoisomers of 5-hydroxylysine, and related compounds at picomole levels in protein and tissue hydrolysates. Complete resolution of all these unique basic amino acids as discrete peaks was achieved in 5.4 on a 50 X 0.28-cm microcolumn of Dionex type DC-4A spherical resin (9.0 +/- 0.5 micron) using updated instrumentation commonly available for amino acid analysis. The column was operated at 5.65 ml/h with two 0.35 M sodium citrate buffers (pH 5.700 and 4.501), at two temperatures (31.5 and 73 degrees C). Excellent resolution of all omega-N-methylarginines and related compounds was also achieved in 3 h using a 17.5 X 0.28-cm microcolumn of Dionex DC-5A resin (sized to 6.0 +/- 0.5 microns), two citrate buffers (0.21 M Na+, pH 5.125; 0.35 M Na+, pH 5.700), a buffer flow rate of 5.75 ml/h, and a temperature of 52 degrees C. Complete separation of all other amino acids found in protein or tissue hydrolysates including S-carboxymethyl cysteine, 4-hydroxyproline, methionine S,S-dioxide, and the amino sugars was also carried out in 95 min using a 23.5 X 0.28-cm microcolumn of Dionex DC-5A resin. The use of purified microcolumn buffers gave smooth baselines without interference from artifacts or minor hydrolysate components. The major advantages of these methods are: first, their high resolving power; second, their high sensitivity which is comparable and in some aspects superior to the newer instruments; and third, their high reproducibility (100 +/- 2.5%) and low operating costs. These methods should be especially valuable for determining myosin, actin, and elastin in tissue hydrolysates from the amounts of N tau-methylhistidine, desmosine, or isodesmosine present, respectively, and for studying protein methylation, hydroxylation, cross-linking formation, and the turnover rates of contractile and connective tissue proteins in biological systems.