Effect of Continuous and Discontinuous Intravenous or Intragastric Total Parenteral Nutrition in Rats on Serum Lipids, Liver Lipids and Liver Lipogenic Rates

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Abstract
Lipogenesis and evidence of fat accumulation in the liver were investigated in adult male rats fed a hypertonic dextrose diet by continuous (C) and discontinuous (D) intravenous (IV) or intragastric (IG) infusion for 14 d. Rats fed by the IV and IG route were infused continuously and discontinuously (2100-0900) with 55 ml/d of a solution containing 30% dextrose and 2.72% amino acids plus vitamins and minerals. An orally (Or) fed group was fed 21.2 g of a solid diet, which provided an equivalent amount of calories and nitrogen as the infusion diet. Serum lipids, glucose, and insulin levels, de novo fatty acid synthesis in adipose tissue and liver, and the content of liver lipids were not altered by feeding the diet IV or IG. De novo lipogenesis was elevated in the livers of the continuously and discontinuously infused IV- or IG-fed rats compared with Or-fed rats. Fat accumulated in the livers of the rats infused continuously but not in the livers of the rats fed DIV, DIG or Or. Discontinuous feeding was associated with the mobilization of fatty acids that are necessary for lipoprotein formation and transport from the liver, which may explain, in part, why discontinuously infused rats do not develop fatty livers. These data indicate that cycling the total parenteral infusion may have clinical importance.