Long-term lipid-based total parenteral nutrition activates mononuclear cells and modulates membrane lipid composition in pigs

Pulmonary function in rats dying from long‐term parenteral nutrition

Infusion of Vamin or Intralipid causes death in a rat model of continuous parenteral nutrition. Morphological investigations have shown vascular injury and thrombus formation in the lungs. In this study, lung function in rats was examined before death due to parenteral nutrition. The rats were fed saline intravenously (group I); 100 mL kg(-1) day(-1) (controls); a 7% amino acid-glucose solution (Vamin-Glukos) (group II); 100 mL kg(-1) day(-1), or 20% fat emulsion (Intralipid) (group III); 40 mL kg(-1) day(-1). The infusion was stopped when the condition of the rats deteriorated. In a saline-perfused, isolated lung model, pulmonary arterial pressure (Ppa), transpulmonary pressure (Ptp), endothelial function, measured as inactivation of serotonin (bioassay), and the capillary filtration coefficient (CFC) were determined. Haematological parameters were also evaluated. Constant findings in group II and III were central thrombus formation, anaemia and thrombocytopenia. Ppa increased from 0.7 (0.04) kPa in group I to 1.4 (0.1) kPa and 1.7 (0.1) kPa in groups II and III, respectively (p<0.001). Inactivation of serotonin was reduced to 36% (2) in group II and 37% (2) in group III compared with 74% (5) in group I (p<0.002). CFC increased to 25 mg min(-1) (5) (group II) and 30 mg min(-1) (6) (group III) compared with 13 mg min(-1) (2) in controls (p=0.01). The study shows that major pulmonary hypertension and severe reduction of the endothelial function are present when rats deteriorate after infusion of parenteral nutrition substrates.

Massive macrophage lipid accumulation presenting as hepatosplenomegaly and lymphadenopathy associated with long-term total parenteral nutrition therapy for short bowel syndrome

We present a unique case of massive splenomegaly, hepatomegaly, and lymphadenopathy caused by lipid-laden macrophages in a 50 year old white female with short-bowel syndrome treated with long-term total parenteral nutrition. Using transmission electron microscopy and special stains we were able to show that the total parenteral nutrition lipid component was composed of lipid droplets and micelles morphologically identical to those found in lipid-laden macrophages which had accumulated in the patient's reticuloendothelial system leading to massive splenomegaly, hepatomegaly (without evidence of steatosis) and lymphadenopathy. While this phenomenon has been reported in animal models, no human cases have been previously reported.

Modification of mononuclear cell function after incubation with albumin-bound unsaturated fatty acids or soybean oil emulsion

Administration of total parenteral nutrition (TPN) with soybean oil emulsion leads to a linoleic acid enrichment of the plasma membrane that may explain an in vivo activation of mononuclear cells (MNC) seen in our previous studies. Fatty acids from the lipid emulsion may have been accessible to MNC after endocytosis of lipid particles, or by direct uptake of fatty acids after lipoprotein lipase hydrolyzation of the emulsion triglycerides. To resemble the incorporation of fatty acids in vivo, we have modified MNC membrane lipid composition by incubation with different albumin-bound unsaturated fatty acids (UFA) or soybean oil emulsion. After incubation with albumin-bound linoleic and oleic acid, the unstimulated release of superoxide anion was unchanged, while zymosan-stimulated release was 140% (n.s) and 112% (p < 0.05) and phorbol-myristate-acetate (PMA)-stimulated release 148% (p < 0.05) and 124% (p < 0.05) of controls, respectively. Incubation with other UFAs or emulsion did not change superoxide anion release. Unstimulated lymphocyte proliferation increased 3 to 13-fold (p < 0.05) after incubation with all UFAs compared to controls, while UFA incubation did not change phytohemagglutinin (PHA) or PMA-stimulated proliferation. Unstimulated lymphocyte proliferation was decreased after incubation with emulsion, while PHA/PMA-stimulated proliferation was unchanged. Increase in membrane fluidity was detectable only after incubation with emulsion. The increased reactivity may have been caused by changes in the lipid environment surrounding membrane-bound enzymes important for signal transduction through the plasma membrane.