Contribution of proteolysis and de novo synthesis to alanine production in diabetic rat skeletal muscle: a 15N/1H nuclear magnetic resonance study.
To assess the role of leucine as a precursor of alanine alpha-amino nitrogen in skeletal muscle during diabetes, extensor digitorum longus muscles from control (n = 7 experiments) and streptozotocin-diabetic rats (n = 8 experiments) were isolated and superfused with [15N]leucine (3 mmol/l) in the presence of glucose (10 mmol/l) for 2 h. Muscle perchloric acid extraction was performed at the end of superfusion in order to quantify newly synthesized alanine by 15N/1H nuclear magnetic resonance. Release of [15N]alanine in the superfusion medium was also measured. The pool of newly synthesized [15N]alanine was significantly increased (approximately 40%) in extensor digitorum longus muscles from streptozotocin-diabetic rats. Whereas a significant enhancement of total alanine release from muscle was induced by diabetes (20%), only a slight increase in [15N]alanine release was detectable under our experimental conditions. Consequently, we conclude that streptozotocin-diabetes in growing rats induces in skeletal muscle: 1) an increase in nitrogen exchange between leucine and alanine leading to newly synthesized [15N]alanine; and 2) an increase of total alanine release from muscle originating from both proteolysis and de novo synthesis.
Meynial-Denis
D
D
Unité d'Etude du Metabolisme Azoté et Centre de Recherches en Nutrition Humaine d'Auvergne, Institut National de la Recherche Agronomique, Clermont-Ferrand-Theix, France.
Chavaroux
A
A
Foucat
L
L
Mignon
M
M
Prugnaud
J
J
Bayle
G
G
Renou
J P
JP
Arnal
M
M
D000409:Alanine / Q000096:biosynthesis*; D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism* / Q000473:pathology; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D007930:Leucine / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology; D009587:Nitrogen Isotopes; D010477:Perfusion; D051381:Rats; D017208:Rats, Wistar; D014316:Tritium
D009587:Nitrogen Isotopes; D014316:Tritium; D007930:Leucine; D000409:Alanine