Effects of temperature variations on dietary lipid absorption and plasma lipoprotein concentrations in trout (Oncorhynchus mykiss)

In juvenile rainbow trout (Oncorhynchus mykiss) the peak of dietary lipid absorption occurred later at low compared with high temperature. Rapid temperature variations modified plasma concentrations of glucose, lipids and lipoproteins, with no effect on free glycerol. The concentration of these parameters was not affected during the progressive seasonal temperature changes. The plasma concentration of very low density lipoproteins (VLDL) increased by two- to three-fold within two days after the onset of cold acclimation (CA) or warm acclimation, independently of alterations in dietary lipid absorption. The high concentration of VLDL induced an increase in low density lipoproteins (LDL) concentration after several days. CA induced a rapid and transitory decrease in the concentration of high density lipoproteins (HDL) of about 20%. Incomplete successive acclimations resulted in a cumulative effect on the increase of VLDL (10-fold) and of LDL (three-fold). In cold-acclimated trout, the persistent hypertriglyceridemia and high plasma concentration of VLDL observed for several weeks after fasting suggest a long-term increase in the secretion of hepatic VLDL. The results indicated that plasma lipoprotein concentrations appear to be sensitive to the thermal adaptation process in trout exposed to rapid temperature variations.