Effect of succinylation, acetylation, and reductive alkylation on substructural properties of three milk protein systems (casein, BSA, and whey proteins) was studied. Three levels of modifications were achieved in each case, and changes in the proteins' spectral properties were determined. Casein attained the highest degree of modification for all of the treatments used. Acylation enhanced denaturation and improved surface hydrophobicity of all of the proteins. Modification of BSA resulted in a red-shifted emission fluorescence peaks; however, its circular dichroic (CD) patterns showed insignificant difference from those of the native. This may imply that acylation has affected only the tertiary structure of BSA. Fluorescence and CD profiles of whey proteins and caseins showed considerable changes in their conformational makeup. It appears that acylation may have a more drastic effect on multicomponent proteins, possibly by means of perturbing their protein-protein mode of interaction.

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Various human trials and pre-clinical studies have suggested that dietary plant sterols possess hypotriacylglycerolaemic properties apart from their cholesterol-lowering properties. We hypothesised that phytosterols (PS) might attenuate triacylglycerolaemia by interfering with the deleterious effects of cholesterol overload in the liver. In the present study, twenty hamsters (Mesocricetus auratus) with dietinduced combined hyperlipidaemia were fed a high-fat diet (HFD, n 10) or a HFD supplemented with soyabean PS (n 10) for 40 d. In parallel, a healthy group was fed a standard diet (n 10). PS normalised fasting plasma cholesterol concentrations completely after 20 d and were also able to normalise serum TAG and NEFA concentrations after 40 d. HFD feeding caused microvesicular steatosis and impaired the expression of key genes related to fatty acid oxidation such as PPARA, carnitine palmitoyltransferase-Ia (CPT1A) and phosphoenolpyruvate carboxykinase 1 (PCK1) in the liver. PS treatment completely protected against HFD-induced steatosis and resulted in a normalised hepatic gene expression profile. The protection of the hepatic function by PS was paralleled by increased faecal cholesterol excretion along with a 2-fold increase in the biliary bile acid (BA):cholesterol ratio. The present study supports the conclusion that long-term consumption of PS can reduce serum TAG and NEFA concentrations and can protect against the development of fatty liver via different mechanisms, including the enhancement of BA synthesis. The results of the present study place these compounds as promising hepatoprotective agents against fatty liver and its derived pathologies.

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