Meal cysteine improves postprandial glucose control in rats fed a high-sucrose meal.
Whey protein, particularly the alpha-lactalbumin fraction, are rich in cysteine (cys) and could therefore favor postprandial glucose homeostasis by a glutathione-mediated effect. This work investigates the effects of the ingestion of an alpha-lactalbumin-rich whey concentrate (alpha-LAC) during a high-sucrose (HS) meal on postprandial glucose homeostasis in healthy rats. In the first experiment, rats received an HS meal containing 14% protein, in which the protein source was either alpha-LAC (HS(a)) or total milk proteins, alone (HS(0)) or supplemented with 17 mg (HS(1)) or 59 mg (HS(2)) of N-acetylcysteine (NAC). This resulted in a total cys content 3.6-fold higher in the HS(1) and HS(a) meals and 12-fold higher in the HS(2) meal, when compared to the HS(0) meal. Postprandial parameters were monitored for 3 h after ingestion of the meal. The same measurements were performed on rats injected with 4 mmol/kg of buthionine sulfoximine (BSO), a specific inhibitor of glutathione synthesis. Increasing the meal's cys content dose-dependently reduced both postprandial glucose and insulin (P<.05). The inhibition of glutathione synthesis with BSO injection abrogated the beneficial effects of NAC supplementation on postprandial glucose response but did not affect those of alpha-LAC. These results show that (1) the substitution of alpha-LAC for total milk protein reduces glucose response, as does the addition of a cys donor to the meal, (2) but contrary to those of a simple cys donor, the beneficial effects of alpha-LAC are not entirely mediated by glutathione synthesis, suggesting additional mechanisms.
Blouet
Clemence
C
UMR 914 INRA, INAPG, Nutrition Physiology and ingestive behavior, Institut National Agronomique, Paris 75005, France.
Mariotti
François
F
Mikogami
Takashi
T
Tome
Daniel
D
Huneau
Jean-François
JF
D000818:Animals; D019540:Area Under Curve; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism*; D019328:Buthionine Sulfoximine / Q000097:blood / Q000494:pharmacology; D003545:Cysteine / Q000008:administration & dosage / Q000494:pharmacology*; D004040:Dietary Carbohydrates; D007328:Insulin / Q000097:blood; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008297:Male; D019518:Postprandial Period; D051381:Rats; D017208:Rats, Wistar; D013395:Sucrose / Q000494:pharmacology*
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D007328:Insulin; D019328:Buthionine Sulfoximine; D013395:Sucrose; D003545:Cysteine