Changes in rat plasma apolipoproteins and lipoproteins during moderate protein deficiency: potential use in the assessment of nutritional status

To test apolipoprotein sensitivity as protein deficiency markers, concomitant evolution of plasma apolipoproteins (apo) and usual nutritional markers (transthyretin, albumin, transferrin) were followed during a 28-d protein restriction in young male Wistar rats. In addition, plasma lipids and chemical composition of lipoproteins were assayed by d 28. The control and the deficient groups were fed 18% and 6% casein diets, respectively. By d 28 the protein-deficient group exhibited hypotriglyceridemia resulting from the decrease in VLDL triacylglycerols; free cholesterol and phospholipids were increased, reflecting the increment in LDL-HLDL1. In plasma total lipoproteins, apo BH, AI and E were not different than controls in the deficient group. Apolipoprotein AIV decreased after d 14 and was significantly less than in controls at d 28. Apolipoprotein BI was considerably reduced by d 14 (43% less) and d 28 (52% less) compared with the control group. Apolipoproteins C + AII were significantly lower in the protein-deficient group by d 14 (43%). By d 28, VLDL apo C were decreased 60% by protein restriction. Transthyretin level was 20% lower in the protein-deficient group by d 7 but returned to control values by d 14. A moderately lower value was observed for albumin by d 7 and d 14 and for transferrin by d 28. These results indicate that, in this model, apo BI and C are more sensitive to protein depletion than usual nutritional markers.