Sodium nitrate co-ingestion with protein does not augment postprandial muscle protein synthesis rates in older, type 2 diabetes patients

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/kg2 body mass index, 7.3 ± 0.4% HbA1C ) received a primed continuous infusion of l-[ring-2H5]phenylalanine and l-[1-13C]leucine and ingested 20 g of intrinsically l-[1-13C]phenylalanine- and l-[1-13C]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-2H5]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-[1-13C]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.