What rate of infusion of intravenous nutrition solution is required to stimulate uptake of amino acids by peripheral tissues in depleted patients?

Early administration of postoperative BCAA-enriched PPN may improve lean body mass loss in gastric cancer patients undergoing gastrectomy

BACKGROUND

It has been reported that weight loss or lean body mass (LBM) loss after gastrectomy for gastric cancer is associated with prognosis and nutritional support alone is insufficient to prevent LBM loss. Branched-chain amino acids (BCAA) play an important role in muscle catabolism, however their clinical effects on suppression of LBM loss in gastric cancer patients undergoing gastrectomy remains elusive. In this current study, we investigated the effect of our original PPN regimen including BCAA (designated to BCAA-regimen) on LBM loss.

METHODS

We conducted a randomized controlled trial (RCT) at a single institution where patients undergoing gastrectomy were assigned to either receive a five-day early postoperative course of the BCAA-regimen (BCAA group) or conventional nutrition. The primary endpoint was the % reduction in LBM at postoperative day 7. The secondary endpoints included the % reduction in LBM at 1 and 3 months postsurgery.

RESULTS

At postoperative day 7, LBM loss in the BCAA group tended to be lower than in the control group (0.16% vs. 1.7%, respectively; P = 0.21), while at 1 month postsurgery, LBM loss in the BCAA group was significantly different to that of the control group (- 0.3% vs. 4.5%, respectively; P = 0.04). At 3 months postgastrectomy, however, LBM loss was similar between the BCAA and the control groups.

CONCLUSION

Our RCT clinical trial clarified that early administration of the postoperative BCAA regimen improved LBM loss at 1 month after surgery in gastric cancer patients undergoing gastrectomy.

Amino acid repletion does not decrease muscle protein catabolism during hemodialysis

Intradialytic protein catabolism is attributed to loss of amino acids in the dialysate. We investigated the effect of amino acid infusion during hemodialysis (HD) on muscle protein turnover and amino acid transport kinetics by using stable isotopes of phenylalanine, leucine, and lysine in eight patients with end-stage renal disease (ESRD). Subjects were studied at baseline (pre-HD), 2 h of HD without amino acid infusion (HD-O), and 2 h of HD with amino acid infusion (HD+AA). Amino acid depletion during HD-O augmented the outward transport of amino acids from muscle into the vein. Increased delivery of amino acids to the leg during HD+AA facilitated the transport of amino acids from the artery into the intracellular compartment. Increase in muscle protein breakdown was more than the increase in synthesis during HD-O (46.7 vs. 22.3%, P < 0.001). Net balance (nmol.min(-1).100 ml (-1)) was more negative during HD-O compared with pre-HD (-33.7 +/- 1.5 vs. -6.0 +/- 2.3, P < 0.001). Despite an abundant supply of amino acids, the net balance (-16.9 +/- 1.8) did not switch from net release to net uptake. HD+AA induced a proportional increase in muscle protein synthesis and catabolism. Branched chain amino acid catabolism increased significantly from baseline during HD-O and did not decrease during HD+AA. Protein synthesis efficiency, the fraction of amino acid in the intracellular pool that is utilized for muscle protein synthesis decreased from 42.1% pre-HD to 33.7 and 32.6% during HD-O and HD+AA, respectively (P < 0.01). Thus amino acid repletion during HD increased muscle protein synthesis but did not decrease muscle protein breakdown.

Parenteral nutrition with lipid or glucose suppresses liver growth and response to GH in adolescent male rats

Our aim was to investigate the effects of modifying the carbohydrate-to-lipid ratio of parenteral nutrition (PN) on body composition and the anabolic actions of insulin-like growth factor I (IGF-I) and growth hormone (GH). Adolescent male Sprague-Dawley rats were randomized to receive 7 days of GH, IGF-I (3.5 mg. kg(-1). day(-1) for both) or placebo while receiving high-carbohydrate PN (CHO-PN), high-lipid PN (L-PN), or an oral diet (chow) (the PN protocols were isonitrogenous and isocaloric). PN impaired muscle growth, which was reversed by GH in the CHO-PN group only (P < 0.03). PN increased carcass lipid (P < 0.02), the effect being greater in the L-PN than in the CHO-PN group (P < 0.001). Visceral lean tissue growth was significantly impaired by PN (P < 0.001). IGF-I reversed this impairment, but GH had no effect. PN impaired the normal increase in hepatic protein and DNA (P < 0.001) and produced liver steatosis (P < 0.001). However, this steatosis was less in L-PN than in CHO-PN (P < 0.001). Serum IGF-I and the acid-labile subunit (ALS) were decreased by PN (P < 0.001) and were not affected by GH during PN treatment. However, GH significantly increased serum ALS concentrations in the chow-fed rats (P = 0.032). In conclusion, modifying the CHO-to-L ratio of PN had no significant effect on IGF-I action, but CHO-PN increased the peripheral effect of GH. L-PN increased carcass lipid significantly and decreased hepatic steatosis. Nevertheless, PN caused significant liver steatosis and profound impairment of hepatic cell growth, which was associated with relative hepatic GH resistance.

Metabolic effects of insulin and insulin-like growth factor-I in endotoxemic rats during total parenteral nutrition feeding

The effects of insulin and insulin-like growth factor-I (IGF-I) on protein, energy, and glucose metabolism were examined in endotoxemic rats receiving total parenteral nutrition (TPN) for 3 days. The endotoxemic model was induced by constant infusion of lipopolysaccharide (1 mg/kg x d) for 3 days. The TPN regimen provided 200 kcal/kg x d and 1.5 g protein/kg x d. The dosage of insulin (5 mU/kg x h) and IGF-I (20 microg/kg x h), either alone or in combination, was chosen to maintain normal levels of leucine and glucose in plasma during feeding. One normal control and 4 endotoxemic groups with different treatments (saline, IGF-I, insulin, or IGF-I and insulin) were included. The effects of endotoxin were compared between the group receiving endotoxin alone and normal controls, and the effects of insulin and IGF-I were compared within the endotoxemic groups. The results show that endotoxin significantly increased the mortality and induced a hypermetabolic state, and nutrition alone could not overcome the catabolism induced by endotoxin. However, administration of insulin and IGF-I enhanced protein preservation in muscle tissue in endotoxemic rats during TPN. This effect was greater for insulin either alone or in combination with IGF-I. Insulin also significantly reduced the mortality. There were no additive effects of these two anabolic hormones on any measured parameter in these experimental conditions.

Addition of tyrosyl-arginine to parenteral nutrition is anabolic in unstressed rats

To determine whether the addition of tyrosine and arginine (Arg), as tyrosyl-arginine (TyrArg), to parenteral nutrition (PN) can promote anabolism, rats were assigned to: 1) PN (1.20 MJ. kg body weight [BW](-1) x d(-1) and 1.22 gN x kgBW(-1) x d(-1); PN control group, n = 5), 2) PN plus TyrArg (2.6 mmol. kgBW(-1) x d(-1); TyrArg group, n = 6), or 3) PN plus Arg (2.6 mmol. kgBW(-1). d(-1); Arg group, n = 5). Results from these three groups were compared with an unoperated chow-fed reference group (chow control group, n = 5). The BW gain during PN and the proportion of lipid in the total body after 14 d of PN was greater for the TyrArg group than for the PN group (P<0.01). Although the differences in weight gain, body water, lipid, and protein between the TyrArg and Arg groups were not significant, the mean weight gain throughout PN was greater in the TyrArg group than in the Arg group. The proportion of protein in the small intestine, colon, and gastrocnemius muscle was greater in the TyrArg and Arg groups than in the PN group (P<0.01). A distinct requirement for tyrosine has not been demonstrated in this model, and additional studies in stressed animals are required. In contrast, arginine had tissue-specific anabolic activity.

Parenteral amino acid intake alters the anabolic actions of insulin-like growth factor I in rats

The anabolic properties of insulin-like growth factor (IGF) I are attenuated by oral diets that are low in protein. However, it is not known whether parenteral nutrition (PN) providing a low amino acid (AA) input will influence IGF-I action. With the use of a rat model, this study examined the interaction between AA input (1.27 and 0.62 g N. kg body wt(-1). 24 h(-1), AA and 1/2AA groups, respectively) and recombinant human IGF-I (rhIGF-I, 2.5 mg. kg body wt(-1). 24 h(-1)) infusion on the composition of the carcass and organs and on plasma insulin, IGF-I, IGF-binding protein 1 (IGFBP-1), and acid-labile subunit (ALS) concentrations. Carcass protein deposition only occurred in the AA groups (P < 0.003) and was not influenced by administration of rhIGF-I. However, visceral protein loss persisted in the AA group but was prevented by rhIGF-I infusion. The changes in water content of the carcass and the organs were generally in the expected proportion of normal lean tissue. The accumulation of lipid that follows the infusion of the AA-deficient PN was prevented by rhIGF-I infusion, which may indicate an improved energy utilization. Neither serum insulin nor ALS concentrations were influenced by the level of AA infusion but were reduced by rhIGF-I administration. However, plasma IGF-I levels were elevated by higher AA infusion and by IGF-I administration. Also, IGFBP-1 concentrations were reduced by the higher AA infusion and increased with rhIGF-I administration. Interestingly, there was a significant interaction effect between both of these influences. It is concluded that free IGF-I concentration, which may be regulated by IGFBP-1 through a direct effect of AAs on the liver, may have an important role in regulating anabolism in visceral and possibly skeletal tissue during PN.

Energy expenditure and substrate utilization in mechanically ventilated children

The objective of the study was to determine the value of indirect calorimetry and nitrogen balance (N balance) in order to evaluate the current feeding protocols of mechanically ventilated children. The study was designed as a cross-sectional prospective study. In 36 mechanically ventilated children energy expenditure was measured by indirect calorimetry, and total urinary nitrogen excretion (TUN) was determined. Substrate utilization and respiratory quotient (RQ) were calculated from the measured values of oxygen consumption (VO2), carbon dioxide production (VCO2), and TUN. The RQ was compared with the RQ of the macronutrients administered (RQmacr) according to the modified criteria of Lusk. In results, the total measured energy expenditure (TMEE) showed a wide variation (range 155-272 kJ.kg-1.d-1). The N balance was positive in 20 and negative in 16 patients. The ratio of caloric intake/TMEE was significantly higher in patients with a positive N balance (1.50 +/- 0.06) as compared with those with a negative N balance (0.8 +/- 0.1, P < 0.001). There was a significant relationship between the difference of RQ-RQmacr versus the ratio caloric intake/TMEE (r = 0.72, P < 0.001). Carbohydrate and fat utilization were not significantly different in patients with a positive or negative N balance. Protein utilization was significantly higher in those patients with a negative N balance. We concluded that measurement of TMEE with indirect calorimetry results in accurate determination of energy needs in critically ill mechanically ventilated children. Feeding according to or in excess of the TMEE is correlated with a positive N balance. A combination of the RQ and the RQmacr can be helpful in differentiating under- or overfeeding.

Role of glutamine in immunologic responses

Glutamine has traditionally been thought of as a nonessential amino acid, but laboratory and clinical data suggests that it may be essential during certain inflammatory conditions, such as infection and injury. Glutamine is a necessary nutrient for cell proliferation, serves as a specific fuel for inflammatory cells and enterocytes, and, when present in appropriate concentrations, enhances cell function. During inflammatory states, glutamine consumption may outstrip endogenous production and a relative glutamine deficiency state may exist. Animal and clinical studies suggest that improved outcome may be possible by providing the appropriate dose of this nutrient by the appropriate route to achieve adequate tissue concentrations. Such an approach prevents patients from being exposed to some of the inadequacies of present day conventional nutrition. The overall benefit of providing an appropriate glutamine-supplemented diet to all metabolically compromised patients arises from the multiple anabolic and host protective effects of this amino acid, of which immunomodulation is only one important facet of glutamine's essential nature.

Luteinizing hormone secretion and hypoandrogenaemia in critically ill men: effect of dopamine

OBJECTIVE

Critical illness has been associated with decreased LH secretion and lowering of testosterone. Dopamine is often used for vasoactive support in these patients. We therefore aimed to investigate LH secretion during severe illness and particularly the effect exerted by dopamine on LH in such patients.

PATIENTS AND DESIGN

In a randomized, controlled study of critically ill adult male polytrauma patients (n = 9), we evaluated the effect of prolonged (83-296 hours) dopamine infusion (5 micrograms/kg/min i.v.) on the dynamics of LH secretion and on serum testosterone concentrations. The effect of brief (15-21 hours) dopamine administration was documented in an additional randomized, controlled, cross-over study involving 6 patients.

MEASUREMENTS

Serum LH concentrations were measured by IRMA. The LH profiles, obtained by blood sampling every 20 minutes for 9 hours during two consecutive nights, were examined by deconvolution analysis. Serum testosterone concentrations were measured by RIA once per study night.

RESULTS

We found that before dopamine initiation and within 24 hours of dopamine withdrawal, the mean serum LH concentrations, the LH secretory amplitude, the amount of LH secreted per burst, the mean LH secretion rate and the number of LH pulses were higher than during dopamine infusion, being increased by a median of 161% (P = 0.006), 98% (P = 0.03), 106% (P = 0.03), 164% (P = 0.01) and 25% (P = 0.008) respectively. However, without dopamine administration the amplitude and mass of the LH secretory bursts still appeared to be low, whereas the pulse frequency remained elevated. After dopamine withdrawal, LH secretion increased significantly within 3 hours. Serum testosterone levels were very low and dopamine infusion appeared not to affect them within 24 hours.

CONCLUSION

We documented decreased LH secretory pulse amplitude and mass with increased pulse frequency, as well as very low serum testosterone concentrations in critically ill men. Dopamine infusion further suppressed LH release by decreasing secretory burst amplitude, mass and frequency, possibly through an inhibitory action at both the pituitary and the hypothalamic level.

Nutrition support in critical illness

Sepsis, shock, multiple trauma, and burns are often associated with altered metabolism characterized by severe catabolism, wasting of the lean body mass, immune dysfunction, and compromised wound healing. Nutrition support is one of the mainstays in the management of these critically ill patients and is aimed at minimizing these complications. The purpose of this article is to compare stress hypermetabolism and starvation metabolism, to review current recommendations for the provision of energy and substrate to the critically ill patient, and to review pertinent literature regarding enteral vs parenteral nutrition. Finally, this article will provide a brief overview of new and future therapies with emphasis on specific substrates and growth factors and the potential for their use in the critically ill patient.

Strategies for attenuating protein-catabolic responses in the critically ill

Specialized enteral and parenteral nutrition are now a standard components of care in critically ill patients. This adjunctive therapy corrects and prevents nutrient deficiencies, attenuates the loss of body protein, and improves clinical outcomes in malnourished patients. Several novel strategies designed to improve the metabolic and clinical effects of specialized nutrition are under vigorous clinical investigation. These new approaches include increased emphasis on enteral feeding to maintain intestinal absorptive, immune, and barrier function; administration of conditionally essential amino acids (glutamine, arginine); use of specialized lipid products and antioxidants; and administration of growth factors such as human growth hormone. Randomized, controlled clinical trials will define the clinical and metabolic efficacy and cost-effectiveness of these therapies in specialized nutrition support.

Organ clearance of tyrosyl-arginine and its effect on amino acid metabolism in young sheep

In a long-term multiple-catheter sheep model (n = 5), organ clearance of the dipeptide tyrosyl-arginine (TyrArg) and its effects on interorgan amino acid metabolism were investigated. Clearance by hindlimb and splanchnic tissues was measured during infusion into the external iliac artery and superior mesenteric artery, respectively. The hindlimb, intestine, and total splanchnic region removed 32% +/- 9.2% (mean +/- SE), 23% +/- 15%, and 33% +/- 24%, respectively, of the amount of TyrArg infused. There was a large release of tyrosine and arginine when TyrArg was infused into either the hindlimb or intestine, which was quantitatively similar to the TyrArg taken up by these organs. However, across the total splanchnic region, the baseline influx of tyrosine and arginine was not altered by infusion of TyrArg. During either clearance study, only trace amounts of TyrArg or its constituent amino acids were excreted in urine. Infusion of TyrArg produced the following effects on interorgan amino acid metabolism: (1) a reduction in the initial efflux of phenylalanine, leucine, isoleucine, and valine from the hindlimb; (2) a reduction in net efflux of citrulline by the intestine and total splanchnic tissues; and (3) a reduction in efflux of arginine and uptake of citrulline from the kidney. In conclusion, we have shown that TyrArg is cleared from the bloodstream by hindlimb (predominantly muscle) and splanchnic tissues. These results indicate that TyrArg taken up by the hindlimb and intestine was hydrolyzed to its constituent amino acids, which were released quantitatively into the circulation. Of the tissues studied, only the liver appeared to use the amino acids liberated from hydrolysis of TyrArg.(ABSTRACT TRUNCATED AT 250 WORDS)

Does portal nutrition benefit liver protein synthesis?

There are only a few experimental investigations on the feasibility and potential advantages of intraportal nutrition in animals and only two uncontrolled studies in humans. The purpose of this study was to compare some metabolic variables in patients who received portal or systemic nutrition after elective surgery for colorectal cancer. Twenty patients were randomized to receive postoperatively for a week a hypocaloric, "protein sparing" standard infusion via the portal (catheter in the gastroepiploic vein) (10 patients) or systemic (10 patients) route. We evaluated the basal concentrations of some visceral and acute-phase proteins and their variations in the first postoperative week and the nitrogen balance. Statistical analysis was performed by the two-tailed Student t test. There was no difference in the daily changes of the visceral and acute-phase proteins after surgery in the two groups of patients, but in the portal group there was a significantly better recovery of the level of total protein, albumin, and cholinesterase at the end of the portal infusion vs the systemic group (p < or = .005, .03, and .02, respectively). In regard to the nitrogen balance, although there was no difference in the overall balance between portal and systemic nutrition, if we separate the acute phase of the injury from the later one we do not see any significant difference in the first period but we do see a highly significant advantage for the portal group during the last 2 days (p < or = .0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Catabolic illness. Strategies for enhancing recovery

After injury, infection, extensive chemotherapy, and other critical illnesses, both protein and fat are lost from the body. Although minor alterations in body composition are probably of little clinical importance, losses of body protein of 10 percent or more contribute to morbidity and debility. This catabolic response can be modified and recovery can be accelerated by a variety of approaches. First, the inflammatory response can be reduced; second, specific nutrients can be provided to support the patient's tissue requirements during catabolic illness; and third, growth factors can be used to enhance protein synthesis and tissue repair. These approaches, whether used alone or in combination, will reduce the loss of body protein, which should accelerate recovery, shorten the length of hospitalization, and reduce convalescence.