Different processed milk with residual xanthine oxidase activity and risk of increasing serum uric acid level

Abstract

Xanthine oxidase (XO), the main enzyme responsible for the formation of uric acid, is abundant on milk fat globule membrane (MFGM), which might be associated with the increasing risk of hyperuricemia from high-fat compared to the low-fat dairy product. In our study, we hypothesized that XO activity could be maintained after hydrolysis under conditions simulating digestion and produce uric acid either in blood or intestine. First, protein levels of XO in different types of processed milk (ultra-high temperature treatment (UHT), pasteurization and skim) were examined by Western Blot, and XO activity was measured by the level of uric acid production. In conclusion, residual XO activity in pasteurized whole milk could be retained after in vitro hydrolysis, and increased uric acid levels in vitro and in vivo. Although whole milk is highly nutritious, XO in milk can be a risk factor for acute increase of uric acid. This study elaborated the different digestive characteristics of milk after different processes, and provides a theoretical basis of milk selection in controlling gout.