Abstract
Background: Parenteral multivitamin preparation (MVP) induces fatty liver in neonatal guinea pig pups; this is prevented by photoprotection. Photo-excited riboflavin present in MVP generates H2O2 and molecules with masses of 136 and 208. We hypothesized that H2O2 initiates the peroxidation of ascorbic acid (AA), producing biologically active byproducts affecting hepatic lipid metabolism.
Methods: Mass spectrometry (MS) documented the participation of H2O2 and photo-excited riboflavin (Ribo) in the formation of AA byproducts. Sixteen 3-day-old guinea pig pups received an intravenous solution (50 g/L dextrose + 4.5 g/L NaCl + 1 kIU/L heparin) at 240 mL · kg−1 · day−1, enriched with control or test mixtures, for 4 days. The control mixture was photo-protected AA + Ribo (without byproducts or H2O2), and the test mixture was AA + Ribo treated to generate AA byproducts without H2O2. Hepatic acetyl-CoA carboxylase (ACC) activity was determined after 4 days. Fourth-day urine samples were analyzed by MS. Data were treated by ANOVA (α = 0.05).
Results: H2O2 did not influence the classic degradation of AA, as the generation of 2,3-diketogulonic acid was not affected. In contrast, the formation of molecules with masses of 136 and 208 was H2O2 and time dependent. ACC activity was higher (P <0.01) in animals receiving high concentration of these molecules; its hepatic activation correlated (P <0.01) with the urinary concentration of molecule-208.
Conclusions: H2O2 at concentrations found in the clinical setting of total parenteral nutrition induce the transformation of dehydroascorbic acid into compounds that have the potential to affect lipid metabolism. These molecules have peroxide and aldehyde functions.
METABOLISM OF l-ASCORBIC ACID, DEHYDRO-l-ASCORBIC ACID, AND DIKETO-l-GULONIC ACID IN THE GUINEA PIG
