Protein sparing therapy during periods of starvation with sepsis of trauma

Changes in protein synthesis after trauma: importance of nutrition

The effect of trauma (femur fracture) on protein synthesis in rats given four different parenterally administered nutrient formulations ("diets") was investigated. Diet I was a maintenance formulation. It contained sufficient amino acids and glucose to keep the rats in nitrogen balance but was inadequate to support growth. Diet II was amino acids only, diet III was severely hypocaloric glucose, and diet IV was diet I minus the amino acids. The rats received parenterally all nutrients for the duration of the 4-5 day study. Twenty-four hours posttrauma, the fractional synthesis rates of liver, lung, heart, kidney, and muscle were estimated by infusing [15N]glycine for 17.5-19 h. (T.P. Stein, J.C. Oram-Smith, M.J. Leskiw, H.W. Wallace, L.C. Long, and J.M. Leonard. The effects of protein and calorie restriction on protein synthesis in the rat. Am. J. Physiol. 230: 1321-1326, 1976.) Two trends were found: i) on the amino acid-containing diets (I and II), most protein synthesis rates were increased posttrauma. Lung was the exception: no change was found; ii) rats on the amino acid deficient diets (III and IV) showed a decrease in the fractional muscle and lung synthesis rates posttrauma. We concluded that in this rat trauma model the requirement is mostly for amino acid nitrogen posttrauma.

Intravenous glucose, aminoacids, and fat in the postoperative period. A controlled evaluation of each substrate

The metabolic effects of hypocaloric (2-51 MJ), equicalorific quantities of intravenous glucose, crystalline aminoacids, and soyabean emulsion were comapred with those of fasting in 4 groups of male patients (closely matched for age, weight, and fat-free mass) on the day of vagotomy and pylorplasty and on the fast 3 postoperative day. Patients given glucose alone excreted less nitrogen than the fasting patients but nitrogen sparing was greatest in the group given aminoacids alone. There was no evidence of any nitrogen sparing when intravenous fat was the source of energy. There was no difference in blood glucose, free fatty acids, and insulin concentrations among the groups. Ketone-body concentrations rose in the fasting and fat-fed groups but remained low in the groups who received glucose or aminoacids. This study indicates that, in the short term, the increased preservation of protein achieved by the infusion of aminoacids compared with that produced by the traditional infusion of glucose does not warrant the extra cost involved.

Specific muscle protein-sparing postoperative dextrose-free amino acid infusions

The protein-sparing and ketogenic effect of postoperative infusion of maintenance solutions containing either 3.5% amino acids or 5% dextrose in 0.33 normal (N) saline was compared by nitrogen balance and urinary acetone determination in 31 patients. A specific muscle protein sparing effect was determined by quantitation of excretion of 3-methylhistidine in seven patients of the amino acid group and eight patients in the dextrose group. In addition, an extensive hormone and substrate profile was determined. It was found that amino acid infusions not only produce a less negative nitrogen balance but also significantly reduce excretion of 3-methylhistidine indicating specific preservation of the muscle compartment.

Metabolic aspects of a protein-sparing modified fast in the dietary management of Prader-Willi obesity

Four adolescents or young adults with the Prader-Willi syndrome (hypotonia, mental retardation, hypogonadism and obesity) received a protein-sparing modified fast consisting of 1.5 g of meat protein per kilogram of ideal body weight and meeting vitamin, mineral and fluid requirements. Evaluation of nitrogen and energy metabolism revealed the development of starvation ketosis and a positive nitrogen balance. Serial whole-body potassium measurements in two patients confirmed preservation of lean tissue despite continuing loss of weight. Clinical diabetes mellitus in two subjects was rapidly ameliorated by the regimen. Short-term weight loss greater than 18 kg occurred in three of the four subjects, and reduced weight persisted during observation periods of 26 to 44 months. This degree of outpatient diet adherence by mentally deficient subjects, who do not normally experience satiety, suggests that hunger is eliminated or at least reduced by modified, protein-sparing fasting.

Human splanchnic metabolism during diabetic ketoacidosis

Splanchnic exchange rates of glucose, acetoacetate, beta-hydroxybutyrate, lactate, pyruvate, glycerol, alanine, glutamine, glutamate, free fatty acids, and triglycerides were measured in eight patients during moderate to severe diabetic ketoacidosis. Their arterial glucose concentration was 20.68 (9.80-52.79) mumole/liter and tic glucose release was 0.77 (0.09-2.44) mmole/min. Gluconeogenesis accounted for about one-half of net splanchnic glucose release, assuming quantitative conversion of net splanchnic extracted lactate, pyruvate, glycerol, alanine, and alpha-ketoglutarate equivalents to glucose. Net splanchnic free fatty acid extraction was 0.24 (0.09-0.52) mmole/min. There was a positive correlation between free fatty acid uptake and ketone-body release. Net splanchnic acetoacetate release was 0.50 (0.05-0.92) mmole/min and beta-hydroxybutyrate release was 0.35 (-0.16 to 0.84) mmole/min. Total ketone-body release was 0.84 (0.37-1.61) mmole/min. The wide ranges of net splanchnic glucose and ketone-body production rates show the heterogeneous characteristics of the diabetic patient in ketoacidosis. It is concluded that the hyperglycemia and hyperketonemia of diabetic ketoacidosis is due to the lack of reciprocity among rates of hepatic glycogenlysis, gluconeogenesis, and ketogenesis resulting in inappropriate net splanchnic release of glucose and ketone bodies.

Nitrogen retention in rats fed on diets enriched with arginine and glycine. 1. Improved N retention after trauma

1. Nitrogen retention was measured in adult rats (250-350 g) subjected to the trauma of hind-leg fracture and given diets with or without arginine plus glycine supplementation. Observations were also recorded on excretion of creatine, creatinine, allantoin, and orotic acid. Liver and skeletal muscle transaminase activities were also determined. 2. When traumatized rats weighing approximately 250 g were given a diet with 200 g casein/kg, supplemented with 20 g arginine and 10 g glycine/kg (EC diet) or a casein diet made isonitrogenous with the EC diet by addition of aspartic acid (C diet), a 60-70% increase in N retention was observed for the first 5 d post-injury for animals consuming the EC diet. A soya-bean (S) diet, isonitrogenous to the diet containing 20% casein, supplemented with arginine and glycine was as effective as the EC diet in promoting significantly better N retention of traumatized rats (350 g) in comparison to rats given the C diet. 3. When the dietary casein content was reduced to 100 g/kg, supplements of 10 g arginine and 5 g glycine or 20 g arginine and 10 g glycine/kg did not improve N retention. It is suggested that both protein quality and protein quantity are important following injury. 4. An increased excretion of creatine was observed in traumatized rats given the high-protein diets supplemented with arginine and glycine. No consistent changes were noted for urine creatinine. 5. 5. Urine allantoin levels remained stable after leg-fracture in rats consuming either the C or EC diets. Differences in the levels of urine orotic acid were found during both the pre- and post-injury periods in rats given the C, EC or S diets. 6. The mechanisms responsible for the improved N retention of traumatized rats consuming the high-protein diets with supplements of arginine and glycine may be related to the role of arginine both as a constituent of muscle tissue and as an intermediate in the urea cycle. 7. In traumatized rats fed the C or EC diets, liver transaminase activity increased whereas the transaminase activity in skeletal muscle decreased. These results support the recent concept that the increased excretion of N following injury arises from diminished reutilization of amino acids by muscle tissue without an acute increase in the rate of muscle catabolism.

Improved albumin synthesis in postoperative patients by amino acid infusion

To determine whether intravenous 3.5 per cent amino acid solution enhanced the rate of albumin synthesis in postoperative patients, we measured the albumin synthesis rate by the (14C) carbonate technic in 10 patients on the fourth day after elective gastrointestinal-tract operations. Five patients were randomized to receive a 3.5 per cent solution of essential and non-essential amino acids, and five to receive 5 per cent glucose. A mean (+/-S.E.M.) of 75.0+/-2.0 per day of amino acids or 111.0+/-12.4 glucose was given. In the amino acid group the mean (+/-S.E.M.) albumin synthesis rate was 237+/-24 mg per kilogram per day, in comparison to 157+/-23 in the glucose group (P less than 0.05). The infused amino acids were apparently more effective than plain glucose in promoting albumin synthesis.

Total body potassium and nutritional status

A method for the indirect measurement of Ke is described. It is accurate, safe, and simple to perform in the clinical setting, and provides quantitative information regarding both the extracellular supporting component of body composition and the body cell. As a result, this technique was applied to quantitatively assess the nutritional status of several groups of surgical patients. A marked contraction of the body cell mass, as indicated by a significant decrease in Ke, was recorded in a group of patients in a chronic catabolic state. The decrease in Ke was accompanied by a reciprocal expansion of the extracellular supporting component of body composition. Thus, in these patients, there was a large increase in the Nae/Ke ratio. Similar changes, which however were much smaller in magnitude, were also observed following a major abdominal operation in a group of patients whose postoperative intravenous fluids contained glucose. In contrast, in a second similar group of patients, the above changes in Nae/Ke were avoided, and postoperative protein sparing was achieved, by avoiding intravenous glucose in the postoperativeperiod and infusing instead solutions containing amino acids. Finally, data were presented which indicates that the effect of a chronic catabolic state on both Nae and Ke can be prevented by administering intravenous hyperalimentation, provided that the total calories infused exceeded 50 cal per kg per day.

Composition of weight lost during short-term weight reduction. Metabolic responses of obese subjects to starvation and low-calorie ketogenic and nonketogenic diets

The effects of starvation, an 800-kcal mixed diet and an 800-kcal ketogenic (low carbohydrate-high fat) diet on the composition of weight lost were determined in each of six obese subjects during three 10-day periods. The energy-nitrogen balance method was used to quantify the three measurable components of weight loss; protein, fat, and water. On the 800-kcal ketogenic diet, subjects lost (mean +/- SE) 466.6 +/-51.3 g/day; on the isocaloric mixed diet, which provided carbohydrate and fat in conventional proportions, they lost 277.9+/- 32.1 g/day. Composition of weight lost (percentage) during the ketogenic diet was water 61.2, fat 35.0, protein 3.8. During the mixed diet, composition of loss was water 37.1, fat 59.5, protein 3.4...

Protein-sparing therapy in postoperative patients. Effects of added hypocaloric glucose or lipid

In patients receiving hypocaloric total parenteral nutrition, protein sparing with infusions of amino acids alone is alleged to occur because low insulin levels allow mobilization of endogenous fat. Four groups of patients studied for their first four postoperative days received all their nutrition parenterally as: 150 g per day of glucose, protein (as amino acids, 1 g per kilogram per day) alone, protein plus 50 g per day of soybean-oil emulsion or protein plus 150 g per day of glucose. All groups of patients receiving protein had lesser negative nitrogen balance than patients receiving glucose alone. The addition of glucose to protein did not increase negative nitrogen balance. The protein-sparing effect of amino acids appears to be a function of the infused amino acids alone and is not related to the degree of endogenous fat mobilization.

Organic acidaemia in intensive care unit patients

Forty ICU patients were studied as to the prevalence and importance of organic acidaemia. It was observed that organic acidaemia was extremely common, secondly that a persistence of such an acidaemia heralded a poor prognosis and finally that the acidaemia rarely needed treatment in its own right.

Metabolic studies in total parenteral nutrition with lipid in man. Comparison with glucose

A study was undertaken of patients on a regimen of total parenteral nutrition comparing the nitrogen balance, energy substrates, blood amino acids, immunoreactive insulin, and immunoreactive glucagon levels during the sequential infusion of nonprotein calories as either glucose alone (glucose system) or 83% as Intralipid (Pharmacia Fine Chemicals, Montreal, Canada) and 17% glucose (lipid system). These nonprotein calories were administered with a constant background of amino acids (1 g/kg per day), vitamins, and minerals. Each system was infused for a week at a time and the order of infusion randomized. In some patients whole blood arteriovenous (A-V) levels of amino acids were measured across forearm muscle. During the glucose system there was a significantly higher level of pyruvate, lactate, alanine, and immunoreactive insulin, consistent with glucose being the principal source of energy. In contrast, during the lipid system there was a rise in free fatty acids and ketone bodies with a fall in insulin, suggesting that lipid was now the principal source of energy. Despite these two very diverse metabolic situations the nitrogen balance with both systems was positive to a comparable degree after the establishment of equilibrium. Correspondingly, A-V differences of whole blood amino acid nitrogen showed uptake by muscle to an equivalent degree with both systems. Clinical studies indicated that the lipid system as defined herein could be infused by peripheral vein for up to 43 days with resultant weight gain, elevation of serum proteins, and healing of fistulae. Our studies suggest that for both metabolic and clinical reasons exogenously infused lipid is a suitable source of nonprotein calories.

Leucine. A possible regulator of protein turnover in muscle

Incorporation of radiolabeled precursors into muscle proteins was studied in isolated rat hemidiaphragms. A mixture of three branched-chain amino acids (0.3 mM each) added to media containing glucose stimulated the incorporation of [14C]lysine into proteins. When tested separately, valine was ineffective, isoleucine was inhibitory, but 0.5 mM leucine increased the specific activity of muscle proteins during incubation with [14C]lysine or [14C]acetate in hemidiaphragms from fed or fasted rats incubated with or without insulin. Preincubation with 0.5 mM leucine increased the specific activity of muscle proteins during a subsequent 30- or 60-min incubation with [14C]lysine or [14C]pyruvate without leucine. Preincubation with other amino acids (glutamate, histidine, methionine, phenylalanine, or tryptophan) did not exert this effect. When hemidiaphragms were incubated with a mixture of amino acids at concentrations found in rat serum and a [14C]lysine tracer, the specific activity of muscle proteins increased when leucine in the medium was raised from 0.1 to 0.5 mM. Experiments with actinomycin D and cycloheximide suggested that neither RNA synthesis nor protein synthesis are required for the initiation of the leucine effect. Leucine was not effective when added after 1 h preincubation without leucine. The concentration of lysine in the tissue water of diaphragms decreased during incubation with 0.5 mM leucine in the presence or absence of cycloheximide, suggesting that leucine inhibited protein degradation. During incubation with [3h]tyrosine (0.35 mM) the addition of 0.5 mM leucine increased the specific activity of muscle proteins, while the specific activity of intracellular tyrosine remained constant and its concentration decreased, suggesting that leucine also promoted protein synthesis. The concentration of leucine in muscle cells or a compartment thereof may play a role in regulating the turnover of muscle proteins and influence the transition to negative nitrogen balance during fasting, uncontrolled diabetes, and the posttraumatic state. Leucine may play a pivotal role in the protein-sparing effect of amino aicds.

Optimizing results of gastric bypass

Gastric bypass is an extensive gastric exclusion operation used in patients who are more than twice their ideal weight. Most of the early postoperative deaths observed in 3% of 442 patients during the initial 9 years, could have been prevented by more attention to operative technique and early recognition and correction of leaks when they occurred. The best weight loss can be produced by adherence to three components of the operation: 1) Bypass of stomach and duodenum, 2) a small fundic segment and 3) a small (12 mm diameter) gastroenterostomy stoma. The average patient of 142 kg can expect to have a weight of around 107 kg at 1 year 103 kg at 5 years. Revision of a large stoma to a smaller (9 mm) diameter can induce further weight loss in some patients whose loss has been inadequate. The 1.8% incidence of stoma ulceration may be lowered with the present emphasis on a smaller fundic pouch, but could increase with longer observation. Presently stoma ulcers occur once in every 140 patient years at risk.

Nitrogen balance in patients receiving either fat or carbohydrate for total intravenous nutrition

Eighteen pre and/or postoperative patients underwent TIN using either fat or carbohydrate as a caloric substrate source for a similar period. Positive nitrogen balance was achieved with either solution for an equal number of days when balance studies were complete. Both groups demonstrated weight gain but it was more marked in the carbohydrate TIN group. One patient in the carbohydrate TIN group was changed to Intralipid because of a catheter related complication. This patient continued to show positive nitrogen balance while on Intralipid. There were 4 deaths in the 18 patients unrelated to TIN. It is concluded that Intralipid, when given through a peripheral vein with a nitrogen source, can produce positive nitrogen balance and is a safe and effective means for doing this.

Nitrogen-sparing intravenous fluids in postoperative patients

Improved nitrogen sparing was demonstrated in 20 patients undergoing either head-and-neck operations or abdominal explorations, who were randomized to receive intravenously either 3 per cent amino acids or 5 per cent dextrose. Infusions were started immediately after operation and continued for a minimum of six days. In patients receiving amino acids, as compared with those receiving dextrose, mean cumulative six-day nitrogen losses were significantly lower (42 plus or minus 5 g [S.E.M.] and 74 plus or minus 7 g, respectively--P smaller 0.005), as were serum glucose and insulin levels, but beta-hydroxybutyrate, acetoacetate and blood urea nitrogen were significantly elevated. No adverse effects of the amino acid solution were observed. The presumed mechanism for improved nitrogen sparing is a decrease in serum glucose and insulin levels, allowing greater endogenous fat mobilization and utilization, thus sparing lean body mass.

Nutritional aspects of body water dislocations in postoperative and depleted patients

Measurements of plasma volume with 125I human serum albumin, extracellular water (ECW) with 82Br-minus, and total body water (TBW) with 3-H2O were made on 16 postoperative patients, 15 depleted patients, and three control subjects. Intracellular water (ICW) was calculated as the difference between TBW and ECW. The observed findings for the series as a whole showed no change in blood volume, an increase of 3.7 I in ECW, and a decrease of 1.5 I in ICW as compared to predicted values based on current weight. Compared to predicted values based on normal (pre-illness) weight, the observed body weight decreased 16% and ICW decreased 22%; this suggests that body weight consistently under-estimates the extent of nutritional depletion. Severe depletion seen in postoperative patients indicates that frequently earlier use of total parenteral nutrition would be beneficial. ICW was found to be the most reliable single index of moderate or severe nutritional depletion; errors in estimating normal values interfere with its use in mild depletion. The ratio of ECW:TBW best reflects distortion of body water composition; it is largely independent of weight, and is a more sensitive index than absolute values of ICW. Repeat measurements of body composition were made on 9 patients given total parenteral nutrition for an average period of 18 days. On the average, there was an ECW decrease of 1.8 I, a body weight increase of 2 kg, and an ICW increase of 3.2 I after parenteral nutrition. The increased ICW represents the repletion of half of the average initial deficit of 6.1 The initial ratio of ECW:TBW of 0.58 was reduced to 0.50, returning it about three-quarters of the way to the expected normal value of 0.48. Intravenous administration of 5% glucose as sole source of calories may be a factor in distortion of body water compartments.

Initial effect of injury on ketone bodies and other blood metabolites

The arterial and venous concentrations of ketone bodies and other metabolites were measured in twelve adults, from 2 to 24 hours after injury. Two groups could be distinguished, with or without hyperketonaemia (defined as more than 0.2 mmol per litre) in the 2-hour blood-sample. In the hyperdetonaemic group the concentrations of alanine, pyruvate, and lactate and the urinary nitrogen excretion were lower throughout the first 24 hours than in the non-hyperdetonaemic group. These preliminary results indicate that hyperketonaemia after trauma is associated with decreased protein breakdown.

The control of plasma glucose in the surgical patient

In a controlled merabolic study of 18 surgical patients alterations in the relationship of plasma glucose to insulin and non-esterified fatty acids could be divided into two phases. In the immediate postoperative period insulin resistance allowed a simultaneous increase in glucose and fatty acids, a situation which does not occur in the normal subject. On subsequent days resistance subsided and the reciprocal relationship of glucose to fatty acids was restored. It is suggested that insulin resistance is an adaptive feature which permits an augmented supply of energy substrate to meet the demands of injury. In adequate amounts intravenous carbohydrate spares tissue protein and fat during recovery. This is mediated by a long term change in the relationship of insulin to the more stable plasma glucose.