Metabolic and thermogenic response to continuous and cyclic total parenteral nutrition in traumatised and infected patients

16 traumatised or infected patients on mechanical ventilation were randomised to continuous TPN or to cyclic TPN after a 24-h period of glucose infusion (1.25 kJ x kg BW(-1) x h(-1)). Energy supply was equivalent to 1.3 x baseline energy expenditure. Glucose, fat and amino acids were administered at a constant rate over 24 h in the continuous TPN group and over 12 h, followed by glucose (1.25 kJ x kg BW(-1) x h(-1)), in the cyclic TPN group. Nutrient-induced thermogenesis was lower during continuous than during cyclic TPN (5 +/- 4 vs. 12 +/- 7%, mean +/- SD, p < 0.05), as was the increase in CO(2) elimination (13 +/- 11 vs. 30 +/- 7%, respectively, p < 0.01). Energy balance was more positive during continuous TPN. In both groups, energy expenditure reached a plateau during the first 12 h of TPN infusion. The lower nutrient-induced thermogenesis and more positive energy balance, indicates a more efficient utilisation of nutrients during continuous than during cyclic TPN. The lower CO(2) production during continuous TPN, may be advantageous when respiratory function is compromised. The plateau in energy expenditure in response to TPN infusion may be useful as a guideline for nutritional therapy.     

Calciuretic effect of cyclic versus continuous total parenteral nutrition

Metabolic bone disease has been reported in patients receiving long-term cyclic administration of total parenteral nutrition (TPN). The exact etiology of this disturbance in mineral homeostasis has not been identified, however many of these patients are markedly hypercalciuric and in negative calcium balance. We have studied the effects of cyclical versus continuous infusion of nutrients on urinary calcium losses in a group of patients beginning a program of long-term home TPN. Cyclic TPN, when administered over either 18 or 12 hours, significantly increased daily urinary calcium excretion compared to continuous 24-h TPN infusion by 19 and 28%, respectively. During cyclic TPN, frank negative calcium balance was observed in 3 of 5 patients studied compared to 2 of 5 patients during continuous TPN. The pattern of urinary calcium loss during cyclic TPN was such that approximately 80% of the daily urinary calcium losses occurred during the 12 hours of TPN infusion. Cyclic administration of TPN increased the urinary calcium losses in all patients suggesting that an intermittent TPN infusion schedule, as typically utilized in home TPN programs, increases the risk of developing negative calcium balance, at least during the early phase of cyclic TPN administration.     

Effect of starvation and total parenteral nutrition on electrolyte homeostasis in normal man

Elemental balances, and skeletal muscle membrane potential (Em) and biopsy were utilized to evaluate electrolyte homeostasis and body composition in 11 healthy adult volunteers after 10 days of starvation. This controlled, acute malnutrition was followed by refeeding for 10 days with two different, commonly used, total parenteral nutrition (TPN) solutions. Six subjects were refed with crystalline amino acids and dextrose (dextrose group), while five subjects received amino acids, dextrose, and lipid (lipid group). During starvation, negative balances for potassium, phosphorous, magnesium, and nitrogen were observed in both groups. When compared to starvation, total parenteral nutrition produced statistically significant (p less than 0.05) equilibrium or positive electrolyte and nitrogen balances for both, the dextrose and lipid groups. During TPN, there was a significantly (p less than 0.001) positive chloride balance in the lipid group when compared to the dextrose group. At the conclusion of the 10-day period of TPN, there was a decrease (p less than 0.05) in skeletal muscle Em. This change, in concert with the electrolyte balance data obtained during parenteral repletion, lead us to postulate that restoration of lean tissue protein and cellular function does not occur at a rate which might be inferred from the positive nitrogen balance observed in this model. A persistent defect in cellular function which was evident after starvation, suggests that a brief period of TPN is insufficient to restore skeletal muscle integrity.     

Effect of age on substrate oxidation during total parenteral nutrition

OBJECTIVE: Parenteral nutrition is increasingly used in the elderly. Aging is accompanied by metabolic changes that can modify substrate use. We compared substrate oxidation during cyclic total parenteral nutrition (TPN) in elderly and middle-aged patients. METHODS: Twelve elderly patients (eight women, four men; 72 +/- 5 y) and 12 middle-aged patients (nine women, three men; 39 +/- 13 y) who were on cyclic TPN for intestinal failure were investigated while in stable condition after at least 15 d of TPN. No patient was diabetic. Indirect calorimetry was performed during fasting and every 30 min during the 3 h of TPN infusion and 3 h after infusion, allowing the measurement of nutrient oxidation. Blood samples were obtained every hour for the measurement of glucose, insulin, triacylglycerols, and free fatty acids. RESULTS: In the fasting state, resting energy expenditure was significantly higher in the elderly patients than in the middle-aged patients (39.3 +/- 8.1 versus 31.9 +/- 4.3 kcal/kg of fat-free mass per day, P = 0.008). During TPN, lipid oxidation was significantly higher in the elderly patients than in the middle-aged patients (1.09 +/- 0.17 versus 0.84 +/- 0.27 mg x kg(-1) x min(-1), P = 0.011); glucose oxidation was significantly lower in the elderly patients than in the middle-aged patients (2.19 +/- 0.93 versus 3.22 +/- 1.54 mg x kg(-1) x min(-1), P = 0.038). Areas under the curves of glycemia and free fatty acids were significantly higher in the elderly patients. CONCLUSION: In the elderly, TPN was associated with significantly higher lipid oxidation and lower glucose oxidation than in younger patients. TPN formulas and flow rates should therefore be adapted in the elderly.     

Relative importance of amino acid infusion as a means of sparing protein in surgical patients

We performed isotopic infusions in 51 surgical patients to investigate the effectiveness of different substrates to conserve protein. All patients were initially studied in the basal state and then the effects of glucose infusion (GL, N = 13), lipid infusion (LIP, N = 11), or amino acid infusion (AA, N = 17) were determined. Ten patients receiving total parenteral nutrition (TPN) were also studied. The basal value for net protein catabolism (NPC) in GL patients was 1.53 +/- 0.4 (SEM) g/kg/day decreasing to 1.39 +/- 0.4 g/kg/day during glucose infusion (p less than 0.01). The basal NPC in the LIP group was 2.04 +/- 0.4 g/kg/day decreasing to 1.72 +/- 0.3 g/kg/day during lipid infusion (p less than 0.01). In the TPN patients the NPC was 0.79 +/- 0.46 g/kg/day whereas in the AA patients the basal value for NPC was 1.37 +/- 0.14 g/kg/day decreasing to -0.77 +/- 0.11 g/kg/day during amino acid infusion (p less than 0.0005). From our study we conclude that: (1) All substrates commonly used in intravenous feeding have the capacity to spare protein. (2) Protein sparing was more pronounced when a balanced amino acid infusion was used than with either glucose or lipid infusion alone. (3) This effect is not solely due to insulin secretion as larger insulin responses were seen with both GL and TPN patients. (4) These results may have implications for peripheral vein feeding with amino acid solutions where there is a contraindication for full TPN or the lack of resources for administering it.     

Microbial growth patterns in a total parenteral nutrition formulation containing lipid emulsion

Microbial growth of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans was evaluated in a standard amino acid-dextrose-based total parenteral nutrition (TPN) solution, 10% lipid emulsion, and a combined TPN formulation containing amino acids, dextrose, and lipid emulsion. At an initial inoculum of 10(4) CFU/ml, all three bacterial organisms grew well in 10% lipid emulsion, died in the standard solution and grew only minimally or died in the combined formulation. C. albicans grew in all three formulations at an initial inoculum of 10(4) CFU/ml; however, at an initial inoculum of 10(2) CFU/ml, which approximates touch contamination, growth of Candida in the standard and combined formulations was less than 1 log at 24 hr in contrast to the 10% lipid emulsion which showed significant growth greater than 2 log at 24 hr. It is concluded that a 24-hr infusion time is safe for the combined TPN formulation used in this study. This should result in significant cost savings compared to the previously recommended 12-hr infusion time.     

Endotoxemia affects organ protein metabolism differently during prolonged feeding in pigs

The metabolic response after sepsis is characterized by net protein loss. Nutritional intervention often is applied to sustain whole body protein mass under such circumstances. The manner in which protein metabolism of the different organs is affected under nutrition-supported and postseptic circumstances remains ambiguous. Therefore, we explored the changes in in vivo organ and whole body protein turnover after endotoxin-induced sepsis during enteral nutrition in pigs. The use of isotopes enabled simultaneous measurements of protein synthesis, breakdown and amino acid degradation across the portal-drained viscera (PDV; approximately intestine), liver and hindquarter ( approximately 50% skeletal muscle). All pigs received a continuous enteral infusion of a liquid meal equivalent to 0.3 g protein. kg bw(-1). h(-1) 3 d before and 4 d after a 24-h endotoxemia period. Measurements were performed 1 d before and 1 and 4 d after endotoxemia that was induced by a 24-h endotoxin (3 microg. kg bw(-1). h(-1) lipopolysaccharide, n = 7) infusion. Controls received NaCl (n = 7). At 4 d after endotoxemia, hindquarter protein turnover was increased, resulting in net synthesis. The amino acid output by the PDV was increased 1 and 4 d after endotoxemia. In the liver, net protein synthesis was enhanced 1 d after endotoxemia. Increased amino acid transamination in hindquarter and PDV led to glutamine and alanine effluxes that serve as substrates for liver and, possibly, the immune system. By providing substrate, enteral nutrition can sustain elevated amino acid demand in the postendotoxemic state by hindquarter, PDV and liver for protein synthesis and transamination processes.     

Parenteral nutrition in septic patients: effect of increasing nitrogen intake

Metabolic effects of increasing nitrogen intake during total parenteral nutrition (TPN) were studied in nine septic patients. The patients were given 5% dextrose (D5W) for 1 d. For the next 6 d they received total parenteral nutrition (TPN), at 1.35 times resting energy expenditure (REE), containing either 191 or 366 mg N/(kg.d) Non-protein calories were divided equally between glucose and lipid emulsion. Three patients were studied on both diets (n = 6 for each diet). On the high- but not the low-N diet were significant increases in protein oxidation, blood urea N, O2 consumption, and CO2 production. TPN normalized most plasma amino acid levels but intramuscular amino acids remained unchanged. Transient positive N balance occurred during days 1-3 on the high- but not the low-N intake; on days 5-6 N balance did not differ significantly from zero on either diet and the improvement (165 mg N/[kg.d]) was the same for both diets.     

Serum Amino Acid Concentrations in Patients Receiving Total Parenteral Nutrition with an Amino Acid Plus Dextrose Mixture

The results of monitoring the serum amino acid concentrations during three infusion regimens using a 5:4 mixture of 70% glucose and the synthetic L-amino acid solution, Synthamin 17 (Travasol) are reported. Twelve stabilized patients received continuous total parenteral nutrition (TPN), eight of whom were subsequently placed on a second regimen of cyclical feeding. A separate group of five patients was infused with amino acids, both with and without simultaneous glucose. The serum amino acid concentrations indicated that the supply of valine, leucine, isoleucine, lysine, and histidine, and the synthesis of taurine from the infused methionine was suboptimal, particularly if the period of TPN was prolonged. The synthesis of tyrosine from phenylalanine appeared to be inversely proportional to the infusion rate of the TPN mixture, in particular the glucose component, resulting in depressed tyrosine and increased phenylalanine concentrations in serum during continuous iv nutrition. Cyclical infusions, on the other hand, permitted the tyrosine and phenylalanine concentrations to return to normal during the noninfusion stage of the cycle. Amino acid measurements enabled us to design an amino acids additive mixture which normalized the serum concentrations in three long-term home parenteral nutrition patients. As a result of these investigations serum amino acid measurements are used routinely to monitor the efficacy of TPN and accommodate any specific amino acid requirements of individual patients. (Journal of Parenteral and Enteral Nutrition 8: 535–541, 1984)     

Glucose versus glucose-fat mixture in the course of total parenteral nutrition: effects on substrate utilisation and energy metabolism in malnourished children

Energy substrate utilisation was evaluated over 21 days in two groups of malnourished children on total parenteral nutrition (TPN). Non-protein energy was infused as glucose (Group A; n = 7) or as a glucose/fat (1:1 v/v) mixture (Group B; n = 10). Results indicated that: 1) net glucose oxidation was related to glucose intake; 2) glucose storage was elevated in group A; 3) net fat synthesis occurred earlier in group B together with constant net fat oxidation which was inversely related to glucose intake (r = -0.89, p < 0.001); 4) lipogenesis from glucose occurred only when glucose intake exceeded 19.3g/kg/d; 5) energy expenditure increased by 36% (group A) and 18% (group B) during renutrition; 6) 73% and 82% of the energy administered in excess of energy required was stored in group A and B respectively. Hence, glucose/fat infusion appears to be more energy-efficient than glucose-alone in TPN of malnourished children.     

Effect of DL-3-hydroxybutyrate infusions on leucine and glucose kinetics in burned rats receiving TPN

Whole-body leucine and plasma glucose kinetics were simultaneously measured in burned rats after 2 d of total parenteral nutrition (TPN) containing sodium DL-3-hydroxybutyrate or sodium acetate to evaluate the ketone bodies as energy substrates during stress. TPN solutions consisted of dextrose and amino acids [200 kcal/(kg . d); 13 g amino acids/(kg . d)] and contained 34.3 mEq/(kg . d) either as sodium DL-3-hydroxybutyrate (n = 8) or sodium acetate (n = 7). Whole-body leucine appearance, incorporation into protein, release from protein breakdown and oxidation rates, as measured after a constant infusion of L-[1-14C]leucine did not significantly differ between the groups. In contrast, D-[6-3H]glucose appearance rates after constant infusion of this tracer were significantly higher in rats given sodium DL-3-hydroxybutyrate [209.3 +/- 3.8 mumol/(kg body weight . min)] than in those given sodium acetate [162.4 +/- 9.7 mumol/(kg body weight . min)] (P less than 0.01). Since leucine kinetics did not differ, the results suggest that sodium DL-3-hydroxybutyrate infusions increase endogenous glucose production [61.0 +/- 4.6 mumol/(100 kg body weight . min)] by enhancing glucose recycling. However, there was no unique protein-sparing effect of ketone bodies identified during injury.     

Long-term parenteral nutrition in unrestrained nonhuman primates: an experimental model

A freely mobile jacket and tether system was developed for the investigation of total parenteral nutrition (TPN)-induced metabolic bone disease and complications of prolonged TPN in 12 Macaca fascicularis nonhuman primates. The animals received TPN for 49 +/- 7 d (means +/- SEM), providing 82 +/- 2 kcal.kg-1.d-1. Serum glucose increased from 3.6 +/- 0.2 mmol/L at baseline to 8.3 +/- 1.9 mmol/L (p less than 0.01) during TPN, and serum albumin decreased from 38 +/- 1 g/L at baseline to 29 +/- 1 g/L (p less than 0.001) during 2.75% amino acid TPN and 30 +/- 2 g/L (p less than 0.01) during 5% amino acid TPN infusion. No significant changes were seen in serum prealbumin, total protein, bilirubin, alanine aminotransferase, and 5'-nucleotidase during TPN infusion. Major complications included catheter sepsis, hyperglycemia, diarrhea, and premature death in six animals. Thus, metabolic complications of prolonged TPN support may be investigated in a freely mobile nonhuman primate.     

Intravenously infused 13C-leucine is retained in fasting healthy adult men

We have proposed a leucine requirement of 40 mg/(kg. d) in adults, based on 24-h direct amino acid balance (24-h DAAB) studies in which leucine intake is calculated as the sum of diet and tracer intake. However, it is possible that the tracer intake that is given during the fasting state in the 24-h studies is oxidized, thereby not contributing to the effective daily leucine intake and thus lowering the intake and, consequently, the requirement estimate. We assessed the fasting state leucine oxidation with different leucine infusion rates ( approximately 2.5-5% of the leucine flux rate) in well-nourished Indian men. Healthy subjects (n = 10) in a fasting state were studied during three randomly administered infusions of different, known amounts of leucine, supplying 4.1, 6.6 or 8.3 mg/(kg. 12 h) during the 12-h fast. Mean 12-h leucine oxidation rate and leucine flux for the different levels of leucine infused did not change significantly (P > 0.1) for the three leucine infusion rates. The plasma leucine concentrations increased significantly after 12 h of leucine infusion, rising from between 20 and 50 micromol/L by the end of the infusions over the range of tracer input. We conclude that tracer leucine infused in the fasting state does not measurably increase leucine oxidation at the doses studied. Thus, tracer intake during the 12-h fast contributes to the effective leucine intake in 24-h DAAB studies.     

Comparison of the effects of continuous and cyclic nocturnal parenteral nutrition on energy expenditure and protein metabolism

Although cyclic nocturnal total parenteral nutrition is a widely used technique, its metabolic consequences have not been fully investigated. During two successive 7-day periods, 12 patients received randomly either standard continuous (infusion 24 hr/day) or cyclic (infusion between 5 pm and 9 am) total parenteral nutrition (TPN). Calorie and nitrogen intakes were identical during both periods. Energy expenditure was investigated by indirect calorimetry and showed practically no difference between continuous standard (1383 +/- 41 kcal/day-1) and cyclic total parenteral nutrition (1428 +/- 46 kcal/day-1). However, in the cyclic regimen, when compared with continuous infusion, energy expenditure was higher between 5 pm and 9 am and lower between 9 am and 5 pm. At the end of the noninfusion period, the 24-hr profile of the nonprotein respiratory quotient showed a slight decrease in patients receiving the cyclic infusion, in contrast with the stability of the quotient in the standard regimen. However, the nitrogen balance and variations in nutritional status did not differ significantly. In conclusion cyclic TPN is efficient for achieving a positive energy and nitrogen balance and in addition it induces a metabolic profile closer to physiological conditions.     

Thermogenesis from intravenous medium-chain triglycerides

Eighteen hospitalized patients dependent on total parenteral nutrition (TPN) were randomly enrolled into a prospective study comparing intravenous long-chain triglycerides (LCT) with a physical mixture of 75% medium-chain triglycerides (MCT) and 25% LCT. The TPN was given continuously as amino acids and glucose over 5 days with the respective lipid emulsion given intermittently during each day for 10 hr. Indirect calorimetry was measured on each patient before the lipid emulsion was administered in the morning and again 10 hr later near the end of the lipid infusion, on days 1, 3, and 5. Resting energy expenditure, VO2, VCO2, and calculated fat oxidation were shown to increase during MCT infusion but not during LCT administration, (resting energy expenditure 899 +/- 37 to 1085 +/- 40, compared with 978 +/- 23 to 976 +/- 39, kcal/m2 body surface area [BSA]/day, respectively, p less than 0.0002; VO2: 129.9 +/- 5.2 to 157.2 +/- 5.9, compared with 140.9 +/- 3.6 to 141.2 +/- 5.9 ml O2/min/m2 BSA, respectively, p less than 0.0005; and VCO2: 110.7 +/- 4.4 to 127.5 +/- 4.3, compared with 118.3 +/- 2.8 to 118.0 +/- 5.3, ml CO2/min/m2 BSA, respectively, p less than 0.0076; calculated fat oxidation 10.7 +/- 1.5 to 19.3 +/- 2.4, compared with 20.0 +/- 2.7 to 20.0 +/- 3.6, kcal/m2 BSA/hr, respectively, p less than 0.014). Respiratory quotient tended to fall with lipid infusion but did not change statistically. Body temperatures were unaltered by either fat infusion. It is concluded that TPN consisting of MCT causes an increased thermogenesis, most likely through increased fat oxidation, reflective of MCT's property as an obligate fuel. The increased thermogenesis occurs without an increase in body temperature.     

Effect of the continuous administration of fat emulsion on the infiltration of intravenous lines in infants receiving peripheral parenteral nutrition solutions

Animal data and anecdotal human experience suggest that vascular damage induced by the infusion of dextrose/amino acid solutions may be ameliorated by the concomitant administration of fat emulsion. We prospectively evaluated the effect of the continuous infusion of peripheral nutrition solutions with and without fat emulsion on the incidence of, probability of, and time to infiltration of peripheral venous lines in infants (median age: 1.0 month; range 1 day-11.9 months). Ninety-seven peripheral venous lines were studied in 53 infants who received 10% dextrose (n = 34), 10% dextrose/2% amino acids (n = 30), or 10% dextrose/2% amino acids/fat emulsion (n = 33). Solutions were administered by positive pressure infusion devices through Teflon catheters with similar gauge. Dextrose, amino acid, electrolyte, and mineral content was standardized for the dextrose/amino acid and dextrose/amino acid/fat emulsion groups. The three groups were similar with respect to age, race, gender, weight, administration of intravenous medications, and catheter site (p greater than 0.05). Patients receiving dextrose/amino acid or dextrose/amino acid/fat emulsion had greater rates of solution administration than those receiving dextrose alone (p less than 0.002). Infiltration occurred in 71% of dextrose, 66% of dextrose/amino acid, and 67% of dextrose/amino acid/fat emulsion solutions (p greater than 0.05). The probability of infiltration was greater for infants receiving dextrose/amino acid than for those receiving either dextrose or dextrose/amino acid/fat emulsion (p = 0.01). The mean +/- SEM length of time the intravenous sites were viable was significantly shorter for the dextrose/amino acid solutions (26.3 +/- 3.3 hr) compared to the dextrose (54.9 +/- 7.8 hr) and dextrose/amino acid/fat emulsion (43.6 +/- 4.2 hr) groups. No site complications were associated with the infiltration of any solution. We conclude that the incidence of infiltration among the three solution groups studied is not different. However, the time to infiltration is prolonged and the probability of infiltration is decreased following the infusion of either dextrose alone or dextrose/amino acid/fat emulsion solutions when compared to the administration of dextrose/amino acid solutions without concomitant fat emulsion infusion.     

Response of glutamine metabolism to glutamine-supplemented parenteral nutrition

BACKGROUND: Increasing evidence suggests that glutamine is important for the function of many organ systems and supports the use of glutamine-enriched total parenteral nutrition (TPN) during severe illness. However, the effect of prolonged glutamine supplementation on glutamine kinetics has not been studied. OBJECTIVE: We investigated the effect of 8-10 d of TPN enriched with glutamine dipeptides on glutamine kinetics. DESIGN: Twenty-three preoperative patients were randomly allocated to receive either TPN enriched with glutamine dipeptides (60 micromol glutamine*kg body wt(-1)*h(-1)) or isonitrogenous, isoenergetic, glutamine-free TPN. A primed, continuous, 6-h intravenous infusion of L-[5-(15)N]glutamine and L-[1-(13)C]leucine was given before (baseline) and 8-10 d after the TPN solutions were administered. Baseline measurements were performed after a 40-h administration of a standard solution of glucose and amino acids (no glutamine). RESULTS: Glutamine-enriched TPN increased the total appearance rate of glutamine (P: < 0.05) but did not inhibit or increase the endogenous appearance rate. The standard TPN solution also increased the glutamine appearance rate (P: < 0.05), but the change was much smaller than in the glutamine-supplemented group (P: < 0.01). The plasma glutamine concentration did not rise significantly during either treatment, suggesting increased tissue glutamine utilization, especially in the glutamine-supplemented group. CONCLUSION: In view of the enhanced glutamine requirements in response to trauma and disease by tissues such as those of the gut, the immune system, and the liver, increased glutamine availability during glutamine-enriched TPN may be beneficial preoperatively in patients with gastrointestinal disease.     

The Henry M. Vars Award. The effect of lipid emulsions on reticuloendothelial system function in the injured animal

Use of intravenous lipid emulsions in trauma and sepsis still remains controversial. In order to examine the impact lipid emulsions have on host defense against bacterial infection during total parenteral nutrition (TPN), 56 male Sprague-Dawley rats underwent jugular cannulation and were randomly divided into three groups, each receiving one of three TPN regimens. All regimens delivered approximately 250 kcal/kg X body weight/day, of which 12.5 g were as amino acids. Group 1 received 100% of the nonprotein calories as glucose (AA + G). Group 2 was given 50% of the nonprotein calories as a longchain triglyceride emulsion (100% LCT). Group 3 received 50% of nonprotein calories as a mixed lipid system, composed of medium- and long-chain triglycerides (75% MCT/25% LCT). After 24 hr on intravenous nutrition, all animals received bilateral septic femur fractures and were continued on TPN for 3 days. On the last day, the level of bacteremia and the in vivo response to an intravenous challenge of 59Fe-labeled Escherichia coli were examined. Three days following the septic injury, animals given MCT as part of their lipid calories were not bacteremic, whereas the other groups had greater than 10(2) cfu/ml of blood. Animals receiving TPN with MCT sequestered a greater percentage of exogenously administered bacteria in the liver and sequestered less in the lung compared to animals given 100% LCT (p less than 0.05). From these data, we conclude that parenteral nutrition formulas where LCT has been partially replaced with MCT may better support host bactericidal capacity than similar regimens comprised of LCT as the sole lipid source.     

The mode of delivery of parenteral multivitamins influences nutrient handling in an animal model of total parenteral nutrition

BACKGROUND: Very low birthweight preterm infants receive early total parenteral nutrition (TPN) to optimize protein balance. Adding multivitamins (MVP) to the lipid emulsion (MVP+LIP) rather than to the amino acid+dextrose moiety of TPN (AA+MVP) limits the effects of light exposure on lipid peroxidation and vitamin loss. AIM: Compare the effects of the mode of delivery of MVP on nutrient handling and indices of oxidant stress. METHODS: Three-day old guinea pig pups were assigned to TPN containing MVP+amino acids+dextrose+heparin and electrolytes, with lipids provided separately (AA+MVP). Solutions were light exposed (LE, n = 8) or light protected (LP, n = 9). In a further group (n = 7), MVP was co-administered with the lipid moiety and light exposed (LIP+MVP). Variables measured in urine (creatinine, nitrogen, vitamin C) and in liver (protein, glutathione, isoprostane, vitamins A, E, C) were compared by ANOVA. RESULTS: Urinary nitrogen and vitamin C were higher (P<0.05) during LE, while hepatic levels of vitamin C were higher (P<0.05) with LIP+MVP. These results were not related to total peroxide levels in TPN or to markers of oxidant stress. CONCLUSION. Co-administration of MVP with lipid or light protected amino acids offers comparable beneficial effects on nitrogen and vitamin C metabolism.     

Threonine requirements of healthy Indian men,measured by a 24-h indicator amino acid oxidation and balance technique

BACKGROUND: We previously questioned the validity of the 1985 FAO/WHO/UNU upper requirement value for threonine (7 mg x kg(-1) x d(-1)) and proposed a tentative mean requirement of 15 mg x kg(-1) x d(-1). OBJECTIVE: In this study we used a 24-h indicator amino acid oxidation and balance technique, with [1-(13)C]leucine as the indicator amino acid, to assess threonine adequacy at 6 test intakes (7, 11, 15, 19, 22, and 27 mg x kg(-1) x d(-1)) with a 6-d dietary adaptation phase in healthy, well-nourished Indian men. DESIGN: Sixteen men were randomly allocated to 3 of 6 test intakes and were studied after 6 d of adaptation to the experimental diets. Diets were based on an L-amino acid mixture in which the threonine content was varied. At 1800 on day 6, a 24-h intravenous [(13)C]leucine tracer infusion protocol was conducted to assess 24-h leucine oxidation and daily leucine balances. RESULTS: Leucine balances differed significantly (P = 0.02) between the different intakes of threonine. Two-phase linear regression analysis from 12-h and 24-h leucine oxidation and 24-h leucine balance gave a breakpoint at a threonine intake of 15 mg x kg(-1) x d(-1), with 95% CIs ranging from 11 to 27 mg x kg(-1) x d(-1). There was no significant effect of threonine intake on 24-h leucine flux. CONCLUSION: The results of the 24-h indicator amino acid oxidation and balance experiments indicate that the current FAO/WHO/UNU threonine recommendation of 7 mg x kg(-1) x d(-1) is inadequate. A mean threonine intake of 15 mg x kg(-1) x d(-1) is sufficient to achieve the indicator (leucine) amino acid balance in healthy Indian men.