Temporal Changes in Serum Cholesterol Levels of Rats Fed Casein and Skim Milk Powdered Diets

Abstract

The temporal cholesterolemic patterns to skim milk powder (SMP) and reprocessed SMP (RSMP) diets were compared to diets containing casein or laboratory rat chow over a 24-day period. SMP was hypocholestetemic relative to casein in rats fed a 1% dietary cholesterol. Reprocessing of SMP resulted in an apparent loss of the relative hypocholesterolemic reponse of native SMP. Amino acid analysis of SMP and RSMP, showed only marginally lower lysine levels than casein; however, the IysineIarginine ratio was higher in SMP than either in casein or RSMP. Available lysine content in SMP was higher than in RSMP, suggesting occurrence of nonenyzmatic browning reactions. Although a similar cholesterolemic response was observed in casein and RSMP, the available lysine content of these two protein sources were markedly different, suggesting that reduced available lysine alone was not totally responsible for the lower cholesterolemic response of SMP, relative to casein.

Redox-Related Cytotoxic Responses to Different Casein Glycation Products in Caco-2 and Int-407 Cells

“…Free lysine and peptide bound lysine residues are actively involved in the MR due to the presence of the lysine -amino group (34). Available lysine content of protein is decreased during the heating process in the presence of reducing sugar (35), and the extent of modification of protein lysine residues depends on MR conditions (36,37). The demonstration in the present study that loss of available lysine was greater for the Rib-casein, as compared to the Glc-casein GP, which in turn was greater than the Fru-casein GP, is additional evidence that casein glycation occurs differently depending on the sugar source.…”

Calcium absorption and bone utilization in spontaneously hypertensive rats fed on native and heat-damaged casein and soya-bean protein

“…The darker colour of the casein protein powder following thermal treatment suggests that a trace amount of lactose (a reducing sugar) was present, indicating the formation of non-enzymic Maillard browning reaction products (MRP). The loss of available lysine (Kanhai et al 1987) combined with the reduced protein digestibility associated with MRP (Lee et al 1977) are additional contributing factors to the reduced growth and nutrient malabsorption noted in this and other studies where animals were fed on HD proteins (Percival & Schneeman, 1979). Lee et al (1980) reported enhanced proteolytic activity and the production of only small amounts of macropeptides devoid of organic P in the intestinal contents of rats given a basal diet containing casein alone.…”