Whey And Casein In Non‐Fat Dairy Milk Protect Against Postprandial Hyperglycemia‐Mediated Dysregulated Arginine Metabolism In Prediabetic Adults

Greater intakes of dairy are associated with a lower risk of cardiovascular disease (CVD). Ingestion of low‐fat milk compared with carbohydrate‐rich rice milk limits postprandial hyperglycemia (PPH), a predictor of CVD‐related mortality. We hypothesized that acute ingestion of dairy milk proteins would protect against PPH‐mediated increases in lipid peroxidation and dysregulated arginine metabolism. A randomized, cross‐over study was conducted in prediabetic adults (n = 23) who ingested isovolumetric beverages (473 mL) of glucose (75 g; GLU), or glucose with non‐fat milk (MILK), whey protein isolate (WHEY), or sodium caseinate (CASEIN; 16.5 g). Plasma glucose, insulin, malondialdehyde (MDA), arginine (ARG) and its related metabolites [asymmetric dimethylarginine (ADMA); symmetric dimethylarginine (SDMA), homoarginine (hARG)] that regulate nitric oxide (NO • ) biosynthesis were measured to calculate postprandial AUC 0–180 min . Glucose AUC was lower (P<0.05) in MILK, WHEY, and CASEIN compared with GLU, whereas insulin AUC was unaffected (P>0.05). Compared with GLU, MDA AUC was lower in MILK only. Each dairy‐based beverage similarly increased ARG AUC while similarly decreasing ADMA/ARG AUC , SDMA/ARG AUC , and hARG/ARG AUC (P<0.01). Glucose AUC correlated with MDA AUC (r = 0.36, P<0.01) and each correlated with ADMA/ARG AUC (r = 0.24–0.79 P<0.05) whereas only glucose AUC correlated with SDMA/ARG AUC (r = 0.24, P<0.05). Whey and casein protect against PPH‐mediated dysregulated ARG metabolism independent of lipid peroxidation. These findings would be expected to decrease NO • bioavailability by competitively inhibiting NO • synthase and ARG availability, transport, and its binding to NO • synthase. Support or Funding Information Supported by the National Dairy Council.