Lactose Glycation of the Maillard-Type Impairs the Benefits of Caseinate Digest to the Weaned Rats for Intestinal Morphology and Serum Biochemistry

Abstract

The Maillard reaction between the lactose and milk proteins unavoidably occurs during the thermal treatment of milk. Although the impact of this reaction on protein nutrition and safety has been well-studied, whether a lactose glycation of milk proteins of the Maillard-type might affect the rats in their growth and intestinal morphology needs an investigation. In this study, caseinate and lactose-glycated caseinate were digested using pepsin and trypsin. Afterward, the resultant caseinate digest and glycated caseinate digest (lactose content of 13.5 g/kg of protein) at 100, 200, and 400 mg/kg body weight (BW)/d were assessed for their effects on the female weaned Wistar rats in terms of daily body weight gain, intestinal morphology, digestive and brush-border enzyme activities, as well as serum chemical indices. The results showed that glycated caseinate digest always showed a weaker effect on rat than caseinate digest either at the 0–7 or 0–28 d feeding stage, and more importantly, at the highest dose of 400 mg/kg BW/d, it caused obvious adverse effect on the rats, reflected by lower values of these indices. Compared with caseinate digest, glycated caseinate digest in the rats caused 0.9–15.4% and 10.6–49.7% decreases in average daily gain of BW and small intestinal length, 1.1–21.5% and 2.3–33.3% decreases in villus height and the ratio of villus height to crypt depth of the small intestine, or 0.3–57.6% and 0.2–55.7% decreases in digestive and critical brush-border enzyme activities, respectively. In addition, when the rats were fed with glycated caseinate digest, some serum indices related to oxidative stress status were enhanced dose-dependently. Lactose glycation of the Maillard-type is thus considered as a negative event of the Maillard reaction on milk proteins because this reaction might impair protein benefits to the body.

Casein Lactose-Glycation of the Maillard-Type Attenuates the Anti-Inflammatory Potential of Casein Hydrolysate to IEC-6 Cells with Lipopolysaccharide Stimulation

“…It was also proven in the previous three studies of our group that casein lactose-glycation of Maillard-type was detrimental to the in vitro activities of the resultant casein hydrolysate, because this hydrolysate exerted a decreased barrier enhancement on IEC-6 cells [ 27 ], a lower growth proliferation and anti-apoptotic effect on IEC-6 cells [ 32 ], and a reduced immunomodulatory effect on the targeted immune cells [ 45 ]. Furthermore, the in vivo results from weaned rats also demonstrated that the casein lactose-glycation of the Maillard-type impaired the ability of casein hydrolysates to promote the development of small intestine and secretion of three digestive enzymes or three brush-border enzymes [ 46 ]. Our daily diets usually contain various products generated from Maillard reactions (especially AGEs).…”