Fractional catabolic rates of myosin and actin estimated by urinary excretion of<i>N<sup>T</sup></i>-methylhistidine: the effect of dietary protein level on catabolic rates under conditions of restricted food intake

Nishizawa, Naoyuki; Shimbo, Mamoru; Hareyama, Shin-ichi; Funabiki, Ryuhei

doi:10.1079/bjn19770038

Cited by 81 publications

(36 citation statements)

References 23 publications

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“…7 Skeletal muscle turnover was estimated by urinary 3-methylhistidine excretion, which reflects myofibrillar turnover. 35 As illustrated in Fig. 3, urinary 3-methylhistidine excretion by BDL rats was either not different from control rats (weeks 1-3) or increased (28% increase in comparison with control rats in the fourth week after BDL).…”

Section: Resultsmentioning

confidence: 83%

“…7,8 Because skeletal muscle contains the largest reservoir of peptidelinked trimethyllysine (this study and Davis 10,11 ), myofibrillar turnover is a critical factor in carnitine biosynthesis. 7 Urinary 3-methylhistidine excretion, a measure for myofibrillar turnover, 35 was not different between BDL and control rats up to 3 weeks after BDL, and showed a 28% increase in BDL rats 4 weeks after BDL (Fig. 3).…”

Section: Discussionmentioning

confidence: 99%

“…Muscular mass was estimated by measuring the 24-hour creatinine excretion (in weekly intervals starting the first week after surgery) and by using the 3-methylhistidine concentrations determined in skeletal muscle and carcass. Using the assumption that 75% of the total body 3-methylhistidine content is located in skeletal muscle, 35 the muscular mass was calculated as follows (in grams per 100 grams of body weight):…”

Section: Materials and Equipmentmentioning

confidence: 99%

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Decreased carnitine biosynthesis in rats with secondary biliary cirrhosis

2000

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Carnitine biosynthesis was investigated in rats with secondary biliary cirrhosis induced by bile duct ligation (BDL) for 4 weeks (n ‫؍‬ 5) and in pair-fed, sham-operated control rats (n ‫؍‬ 4). Control rats were pair-fed to BDL rats, and all rats were fed an artificial diet with negligible contents of carnitine, butyrobetaine, or trimethyllysine. Biosynthesis of carnitine and its precursors was determined by measuring their excretion in urine and accumulation in the body of the animals. Four weeks after BDL, total carnitine content was increased by 33% in livers from BDL rats when compared with control rats, but was unchanged in skeletal muscle and whole carcass. The plasma total carnitine concentration averaged 29.0 ؎ 4.1 vs. 46.4 ؎ 7.3 mol/L in BDL rats and control rats, respectively. Urinary total carnitine excretion was reduced by 56% in BDL rats as compared with control rats. Carnitine biosynthesis was significantly decreased in BDL rats (0.45 ؎ 0.19 vs. 0.93 ؎ 0.08 mol/100 g body weight/d in BDL and control rats, respectively). The tissue content of free and protein-linked trimethyllysine, a carnitine precursor, and trimethyllysine plasma concentrations were not different between BDL and control rats. However, urinary trimethyllysine excretion was increased 5-fold in BDL rats and approximated glomerular filtration. In contrast, urinary excretion of butyrobetaine, the direct carnitine precursor, was decreased by 40% in BDL rats as compared with control rats. Trimethyllysine biosynthesis was not different, but butyrobetaine biosynthesis was decreased by 51% in BDL as compared with control rats. In conclusion, carnitine biosynthesis is decreased in BDL rats as a result of a defect in the conversion of trimethyllysine to butyrobetaine.

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Section: Resultsmentioning

confidence: 83%

Section: Discussionmentioning

confidence: 99%

Section: Materials and Equipmentmentioning

confidence: 99%

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Decreased carnitine biosynthesis in rats with secondary biliary cirrhosis

2000

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“…Svanberg et al noted that alterations in MeHis release from human arm and leg muscle tissues in response to increasing doses of AA mixture infusion showed an increasing trend (20). Furthermore, urinary MeHis output was elevated in response to increased dietary protein levels in rats under conditions of restricted food intake (21). Conversely, AAs, particularly branched chain AAs, are well known to inhibit myofibrillar proteolysis (22)(23)(24).…”

Section: Discussionmentioning

confidence: 99%

Enhancement of Myofibrillar Proteolysis Following Infusion of Amino Acid Mixture Correlates Positively with Elevation of Core Body Temperature in Rats

Yamaoka

Mikura

Nishimura

et al. 2008

J Nutr Sci Vitaminol

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Summary Administration of an amino acid (AA) mixture stimulates muscle protein synthesis and elevates core body temperature (T b ), as characteristically found under anesthetic conditions. We tested the hypothesis that not only AA given, but also AA produced by degradation of endogenous muscular protein are provided for muscle protein synthesis, which is further reflected in T b modifications. Rats were intravenously administered an AA mixture or saline in combination with the anesthetic propofol or lipid emulsion. We measured plasma 3-methylhistidine (MeHis) concentrations as an index of myofibrillar protein degradation, rectal temperature and mRNA expression of atrogin-1, MuRF-1 and ubiquitin in gastrocnemius and soleus muscles of rats following 3 h infusion of test solutions. T b did not differ significantly between conscious groups, but was higher in the AA group than in the saline group among anesthetized rats. Plasma MeHis concentrations were higher in the AA group than in the saline group under both conditions. Plasma MeHis levels correlated positively with T b of rats under both conditions. AA administration decreased mRNA levels of atrogin-1 and ubiquitin in gastrocnemius muscle and all mRNA levels in soleus muscle. These results suggest that AA administration enhances myofibrillar protein degradation and that the change is a determinant of T b modification by AA administration. However, the mechanisms underlying AA administration-associated enhancement of myofibrillar proteolysis remains yet to be determined.

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“…In rats, the total amount of 3MH in the whole body was analyzed, 10) but this is impossible with large animals. Taking this and the data for cattle 9 ) into account, most of the 3MH in the goat body, probably about 93%, is found in the skeletal muscle.…”

mentioning

confidence: 99%