Effect of dietary amino acid composition on the accumulation of lipids in the liver of growing rats

The effect of the rate and route of nutrient delivery on total body and organ composition in rats

To assess the effects of administering increasing rates of total parenteral nutrition (TPN) on total-body and organ composition, infusion catheters were implanted aseptically into the right jugular vein of Sprague-Dawley rats. Animals received 14 d of either a high (H), medium (M), or low (L) rate of TPN infusion (1.22, 1.49, 1.74 MJ.kg-1BW.d-1 and 1.74, 1.48, 1.22 gN.kg-1BW.d-1, respectively: 1:1 lipid:glucose energy), or the TPN solution orally (O TPN group). Weight-matched (w) chow-fed (c) animals were sacrificed at the same final weight as the L TPN and O TPN groups (190 g, LWC group), or the M and H TPN groups (250 g, HWC group). There were 5 animals in each group. The rates of body weight increase of the M TPN, H TPN, and HWC groups were similar (p > 0.05) and greater than the L TPN and O TPN groups (p < 0.001). The L TPN and O TPN groups who received similar amounts of nutrients had similar rates of weight gain. Total body lipid expressed as a percentage of body weight was significantly greater (P < 0.01) in the L, M, and H TPN groups compared to the orally fed groups. The proportion of water and protein in the fat-free wet weight were similar for all groups (p > 0.05). The lipid content of the liver as a percentage of its weight was greater (P < 0.05) in the orally fed groups. There was no significant difference in the percentage of water or protein of individual organs or the total viscera between any group. These finding indicate that: (a) TPN administration can maintain similar rates of protein and water deposition compared to normal growth-maintaining oral diets; (b) there is an effect of route of TPN administration on lipid deposition in adipose tissues; and (c) infusion of a glucose/lipid TPN regimen at rates in excess of requirements for growth in rats promotes lipid deposition in adipose tissues rather than visceral tissues.

Effect of dietary protein level on platelet aggregation in rat

In order to investigate the effects of dietary protein level on the development of atherosclerosis and arterial thrombosis, studies were made on platelet function, plasma lipids and aortic prostaglandin I2 biosynthesis in rats. Under the same calorie intake, the group consuming a low level of protein (10% casein) increased plasma triglycerides and platelet aggregability in comparison with control (20% casein) and high protein groups (60% casein). Moreover, the low protein group produced more thromboxane A2 and less prostaglandin I2 compared with the high protein one. These data suggest that high protein diets may have beneficial effects on arterial thrombosis.

The effect of protein deficiency on some rat liver lipid metabolic enzymes and CoA

Two groups of male Wistar rats were fed normal (i.e., 18%) and protein-free diets, respectively, for 7 weeks. In vivo incorporation of [1-14C] acetate into palmitic, stearic, oleic, and arachidonic acids by the liver was reduced in the protein-deficient rats. In vitro incubation of liver microsomes with labeled palmitate or linoleate revealed no change in the specific activities of chain elongating or desaturating enzymes. Protein deficiency resulted in a decrease in specific activity of short chain acyl-CoA synthetase and in total CoA, accompanied by the virtual disappearance of acyl-CoA and an increase in free CoA. Furthermore, there was less microsomal fatty acid synthetase and mitochondrial beta-hydroxybutyrate dehydrogenase activity. These results are discussed in relation to fatty acid synthesis and the changes in liver fatty acid composition.