RESUMEN
To determine the optimal fat intake and source in nutritional support, we measured the protein-sparing effects of a structured lipid (SL) derived from 60% medium-chain triglyceride (MCT) and 40% fish oil and a 50:50 soybean to safflower oil emulsion (long-chain triglyceride, LCT). Male Sprague-Dawley rats received an enteral diet for 7 d with either all nonprotein energy as dextrose (control diet) or 10% or 35% nonprotein energy as SL or LCT. The rats were burned on day 3. Indirect calorimetry and nitrogen balance were measured on day 2 (preburn) and days 4 and 6 (postburn). Respiratory quotient decreased postburn. There was a significant increase in total energy expenditure postburn, particularly with 35% LCT. Nitrogen balance was best without fat and 10% fat compared with 35% fat and with SL compared with LCT. These results confirm previous studies that fish oil-containing SLs possess protein-sparing effects in burn injury and that 10% SL seems optimal for nutritional support in burn injury.
Asunto(s)
Quemaduras/metabolismo , Grasas de la Dieta/administración & dosificación , Nutrición Enteral , Aceites de Pescado/administración & dosificación , Proteínas/metabolismo , Análisis de Varianza , Animales , Peso Corporal , Metabolismo Energético , Ácidos Grasos/análisis , Masculino , Nitrógeno/metabolismo , Distribución Aleatoria , Ratas , Ratas Sprague-Dawley , Triglicéridos/administración & dosificación , Triglicéridos/sangre , Triglicéridos/químicaRESUMEN
This report investigates the effect of various levels of medium-chain/fish oil structured triglycerides on protein and energy metabolism in hypermetabolic rats. Male Sprague-Dawley rats (192 to 226 g) were continuously infused with isovolemic diets that provided 200 kcal/kg per day and 2 g of amino acid nitrogen per kilogram per day. The percentage of nonnitrogen calories as structured triglyceride was varied: no fat, 5%, 15%, or 30%. A 30% long-chain triglyceride diet was also provided as a control to compare the protein-sparing abilities of these two types of fat. Nitrogen excretion, plasma albumin, plasma triglycerides, and whole-body and liver and muscle protein kinetics were determined after 3 days of feeding. Whole-body protein breakdown, flux, and oxidation were similar in all groups. The 15% structured triglyceride diet maximized whole-body protein synthesis (p < .05). Liver fractional synthetic rate was significantly greater in animals receiving 5% of nonprotein calories as structured triglyceride (p < .05). Muscle fractional synthetic rate was unchanged. Plasma triglycerides were markedly elevated in the 30% structured triglyceride-fed rats. The 30% structured triglyceride diet maintained plasma albumin levels better than those diets containing no fat, 5% medium-chain triglyceride/fish oil structured triglyceride, or 30% long-chain triglycerides. Nitrogen excretion was lower in animals receiving 30% of nonnitrogen calories as a structured triglyceride than in those receiving 30% as long-chain triglycerides, but this difference did not reach statistical significance (p = .1). These data suggest that protein metabolism is optimized when structured triglyceride is provided at relatively low dietary fat intakes.
Asunto(s)
Quemaduras/complicaciones , Proteínas en la Dieta/metabolismo , Endotoxinas/toxicidad , Aceites de Pescado/farmacología , Nutrición Parenteral , Estrés Fisiológico/etiología , Triglicéridos/farmacología , Animales , Peso Corporal/efectos de los fármacos , Quemaduras/metabolismo , Proteínas en la Dieta/efectos de los fármacos , Metabolismo Energético/efectos de los fármacos , Aceites de Pescado/química , Leucina/sangre , Hígado/metabolismo , Masculino , Nitrógeno/metabolismo , Ratas , Ratas Sprague-Dawley , Estrés Fisiológico/metabolismo , Triglicéridos/químicaRESUMEN
This study assessed the effects of total parenteral nutrition (TPN) containing long-chain triglycerides (LCTs), an equimolar physical mixture of LCT and medium-chain triglycerides (MCTs), and a structured triglyceride synthesized from equimolar amounts of MCT and LCT on energy and protein metabolism after thermal injury (25% body surface area full-thickness scald burn). Male Sprague-Dawley rats (245-271 g) received isovolemic diets intravenously that supplied 250 kcal.kg-1.day-1, 2 g amino acid nitrogen.kg-1.day-1, and 50% of nonprotein calories as lipid and 50% as dextrose for 3 days. Whole-body and tissue leucine kinetics were estimated by a 4-h continuous infusion of L-[1-14C]leucine on day 3. Nitrogen balance, plasma albumin, plasma glucose, energy expenditure, and whole-body and liver and rectus muscle protein kinetic parameters were determined. No significant differences were noted in any of the parameters measured. This study suggests that the unique protein-sparing actions usually associated with structured triglyceride administration are not seen when they are provided as 50% of nonprotein calories. In addition, the ratio of MCT to LCT in the starting mixture from which the structured triglycerides are synthesized may be an important determinant of the protein-sparing actions attributed to these lipids.
Asunto(s)
Emulsiones Grasas Intravenosas/administración & dosificación , Nutrición Parenteral Total , Triglicéridos/administración & dosificación , Animales , Glucemia/metabolismo , Ingestión de Energía , Metabolismo Energético/efectos de los fármacos , Cinética , Hígado/metabolismo , Masculino , Músculos/metabolismo , Nitrógeno/administración & dosificación , Nitrógeno/metabolismo , Proteínas/metabolismo , Ratas , Ratas Sprague-Dawley , Albúmina Sérica/metabolismo , Triglicéridos/farmacologíaRESUMEN
Degradation of serum amyloid A (SAA) was studied in isolated perfused livers of mice treated with either a single injection of casein to induce an acute phase response or with 14 daily casein injections to maintain chronic inflammation. Littermates administered sterile saline served as controls. Radioiodinated SAA and apolipoprotein A-I, reconstituted with high-density lipoproteins in vivo, were studied in parallel. Degradation was monitored by appearance of acid-soluble radioactivity in the perfusate. Induction of an acute phase response reduced hepatic catabolism of SAA by 14% (from 8.6 +/- 1.2% to 7.4 +/- 1.1%/g liver in 3 hr, P less than 0.05, n = 16). The acute phase response had no effect on apolipoprotein A-I degradation or bile production. Livers from animals receiving 14 daily injections of casein were 31% less active than control livers at degrading SAA (8.1 +/- 1.6%/g/3 hr for treated group vs. 11.7 +/- 2.3%/g/3 hr for control group, P less than 0.025). Apolipoprotein A-I degradation was decreased but differences were not statistically significant and bile production was the same in both treatment groups. However, livers from treated animals were larger (mean weight 1.8 g) than those from controls (1.5 g) (P less than 0.05), although amyloid fibrils were not detected by Congo red stain. The size of the degradation products was analyzed by column chromatography. Elution profiles of perfusates from livers of chronically inflamed animals contained a peak corresponding to the molecular weight of amyloid A which was not present in perfusates from control liver. We conclude that hepatic catabolism of SAA is decreased both early and late in an inflammatory response and intermediate degradation products corresponding in size to amyloid A are released into the circulation following prolonged inflammation.
Asunto(s)
Reacción de Fase Aguda/metabolismo , Inflamación/metabolismo , Hígado/metabolismo , Proteína Amiloide A Sérica/metabolismo , Animales , Caseínas , Cromatografía en Gel , Enfermedad Crónica , Ratones , Técnicas de Cultivo de ÓrganosRESUMEN
Degradation of serum amyloid A (SAA) was studied in the isolated perfused rat liver. Radioiodinated SAA was reconstituted with high density lipoproteins (HDL) and administered to rats. Plasma was taken 1 h later, and the HDL were isolated for use as tracer. HDL-bound 125I-SAA was cleared from the plasma of intact animals at a rate similar to SAA in native human HDL. Catabolism of SAA and HDL apoproteins was studied in parallel in the perfused liver. In a 3-h perfusion, 21% of SAA was degraded in contrast to 13% of apoC-III, 7% of apoA-I, and 6% of apoA-II. SAA1 (47% in 3 h) was degraded more rapidly than SAA5 (37%) although their in vivo clearance rates were similar. Degradation of SAA was inhibited when lipoproteins were added to the perfusate. At a protein concentration of 0.15 mg/ml, low density lipoproteins inhibited 47%, HDL 62%, and SAA-rich HDL 75%. Lipid-free normal HDL (0.3 mg/ml perfusate) did not appreciably affect SAA degradation; however, delipidated SAA-rich HDL (0.3 mg of protein/ml; 0.02 mg of SAA/ml) inhibited SAA degradation by 40%. Isolated perfused mouse liver proved more effective than rat liver in degrading SAA (5.3% versus 2.8%/g of liver/h). Degradation appeared to be mediated by cell-associated enzymes since perfusate, which had been recirculated through the liver for 3 h, accounted for less than 15% of the total degradation. Partial (38%) hepatectomy did not significantly reduce apoA-I clearance but reduced that of SAA by 16%, providing additional evidence for hepatic SAA catabolism. We conclude from these studies that SAA is catabolized independently of other HDL proteins, that association with lipoproteins retards SAA clearance, and that SAA catabolism is, in part, a specific process.
Asunto(s)
Hígado/metabolismo , Proteína Amiloide A Sérica/metabolismo , Animales , Humanos , Lipoproteínas HDL/metabolismo , Lipoproteínas LDL/metabolismo , Ratones , Péptido Hidrolasas/metabolismo , Perfusión , RatasRESUMEN
In previous studies we have demonstrated that the reduced renal reabsorption of calcium and hypercalciuria resulting from protein consumption are associated with serum insulin levels. Arginine stimulation of insulin secretion also results in hypercalciuria. The present study was designed to test whether the calciuria associated with arginine-stimulated insulin secretion is mediated by insulin inhibition of parathyroid hormone (PTH) activity. Parathyroidectomized (PTX) and sham-operated rats were infused with physiological saline, or with 12 mmol X kg-1 X hour-1 arginine in saline at 1.2 ml/hour. Analysis of data from clearance periods 90-150 minutes after infusions commenced show that arginine infusion increased urine volume, and calcium excretion (nanograms/minute and nanograms/milliliter glomerular filtration rate), to the same extent in PTX and sham-operated animals. PTH does not, therefore, appear to be involved in the calciuretic response to amino acid infusion.