title: Sodium nitrate co-ingestion with protein does not augment postprandial muscle protein synthesis rates in older, type 2 diabetes patients.
abstract: The age-related anabolic resistance to protein ingestion is suggested to be associated with impairments in insulin-mediated capillary recruitment and postprandial muscle tissue perfusion. The present study investigated whether dietary nitrate co-ingestion with protein improves muscle protein synthesis in older, type 2 diabetes patients. Twenty-four men with type 2 diabetes (72 ± 1 yr, 26.7 ± 1.4 m/kg(2) body mass index, 7.3 ± 0.4% HbA1C) received a primed continuous infusion of l-[ring-(2)H5]phenylalanine and l-[1-(13)C]leucine and ingested 20 g of intrinsically l-[1-(13)C]phenylalanine- and l-[1-(13)C]leucine-labeled protein with (PRONO3) or without (PRO) sodium nitrate (0.15 mmol/kg). Blood and muscle samples were collected to assess protein digestion and absorption kinetics and postprandial muscle protein synthesis rates. Upon protein ingestion, exogenous phenylalanine appearance rates increased in both groups (P < 0.001), resulting in 55 ± 2% and 53 ± 2% of dietary protein-derived amino acids becoming available in the circulation over the 5h postprandial period in the PRO and PRONO3 groups, respectively. Postprandial myofibrillar protein synthesis rates based on l-[ring-(2)H5]phenylalanine did not differ between groups (0.025 ± 0.004 and 0.021 ± 0.007%/h over 0-2 h and 0.032 ± 0.004 and 0.030 ± 0.003%/h over 2-5 h in PRO and PRONO3, respectively, P = 0.7). No differences in incorporation of dietary protein-derived l-[1-(13)C]phenylalanine into de novo myofibrillar protein were observed at 5 h (0.016 ± 0.002 and 0.014 ± 0.002 mole percent excess in PRO and PRONO3, respectively, P = 0.8). Dietary nitrate co-ingestion with protein does not modulate protein digestion and absorption kinetics, nor does it further increase postprandial muscle protein synthesis rates or the incorporation of dietary protein-derived amino acids into de novo myofibrillar protein in older, type 2 diabetes patients.
authors.affiliation: NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: Imre W K
authors.initials: IW
authors.lastname: Kouw
authors.affiliation: NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: Naomi M
authors.initials: NM
authors.lastname: Cermak
authors.affiliation: NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Burd
authors.affiliation: NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: Tyler A
authors.initials: TA
authors.lastname: Churchward-Venne
authors.affiliation: NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: Joan M
authors.initials: JM
authors.lastname: Senden
authors.affiliation: NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands.
authors.forename: Annemarie P
authors.initials: AP
authors.lastname: Gijsen
authors.affiliation: NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre, Maastricht, The Netherlands l.vanloon@maastrichtuniversity.nl.
authors.forename: Luc J C
authors.initials: LJ
authors.lastname: van Loon
mesh_terms: D000368:Aged; D001786:Blood Glucose / Q000378:metabolism; D002247:Carbon Isotopes; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D004044:Dietary Proteins / Q000494:pharmacology*; D004435:Eating; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects; D007930:Leucine / Q000494:pharmacology; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000378:metabolism; D009210:Myofibrils / Q000187:drug effects* / Q000378:metabolism; D009566:Nitrates / Q000494:pharmacology*; D010649:Phenylalanine / Q000494:pharmacology; D019518:Postprandial Period / Q000187:drug effects; D014176:Protein Biosynthesis / Q000187:drug effects*
chemical_list: D001786:Blood Glucose; D002247:Carbon Isotopes; D004044:Dietary Proteins; D006442:Glycated Hemoglobin; D007930:Leucine; D009124:Muscle Proteins; D009566:Nitrates; D010649:Phenylalanine; C517652:hemoglobin A1c protein, human; C031618:sodium nitrate
keywords: aging; anabolic resistance; dietary nitrate; protein ingestion; type 2 diabetes