Inhibition of beta-glucuronidase by casein hydrolysate formula.
BACKGROUND
A casein hydrolysate infant formula has been shown to be associated with lower levels of neonatal jaundice than are standard infant formulas. Because beta-glucuronidase is related to neonatal jaundice, this study examined the effect of a casein hydrolysate formula on beta-glucuronidase.


METHODS
Beta-glucuronidase activity was measured with or without added dietary components. The beta-glucuronidase sources used were meconium, breast milk, and the purified bovine liver enzyme. The dietary components assayed for their effect on beta-glucuronidase activity included casein hydrolysate formula (Nutramigen), whey-predominant formula (Enfamil), breast milk; enzymatically hydrolyzed casein, and other constituents of the casein hydrolysate formula. Stool samples of 6-day-old infants, who were exclusively fed one of the two formulas or breast milk, were also assayed for inhibition of beta-glucuronidase.


RESULTS
Only Nutramigen, enzymatically hydrolyzed casein, and stool from Nutramigen-fed infants consistently demonstrated significant inhibition of beta-glucuronidase activity, ranging from 45% to 85% of that in controls. The inhibition of beta-glucuronidase in purified bovine liver demonstrates a dose response in a pH range from 4 to 7.3.


CONCLUSIONS
Hydrolyzed casein contains a beta-glucuronidase inhibitor that, in casein hydrolysate-fed infants, persists after passage through the digestive tract. These data are consistent with the possibility that inhibition of beta-glucuronidase is a mechanism by which infants fed casein hydrolysate have lower jaundice levels than infants fed routine formulas or breast milk. Further study of this mechanism is needed.
Gourley
G R
GR
Department of Pediatrics, University of Wisconsin Medical School, Madison, USA.
Kreamer
B L
BL
Cohnen
M
M
D000818:Animals; D002364:Caseins / Q000494:pharmacology*; D002417:Cattle; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005243:Feces / Q000737:chemistry; D005966:Glucuronidase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007225:Infant Food; D007231:Infant, Newborn; D008099:Liver / Q000201:enzymology; D008470:Meconium / Q000201:enzymology; D008895:Milk, Human / Q000201:enzymology; D011492:Protein Hydrolysates / Q000494:pharmacology*
D002364:Caseins; D004791:Enzyme Inhibitors; D011492:Protein Hydrolysates; C026375:trypticase-soy broth; D005966:Glucuronidase