Enteral infusion of sodium 2-ketoisocaproate in endotoxic rats.

OBJECTIVE: In view of our previous finding that the intravenous infusion of 2-ketoisocaproate (KIC) improved survival in septic rats, we endeavored to determine whether the enteral infusion of KIC improves survival in endotoxic rats, and, if so, the mechanism of this effect. SUBJECTS: Eighty-five rats were given 15 mg/kg of Escherichia coli lipopolysaccharide (026:B6). INTERVENTIONS: KIC, sodium pyruvate (PYR), or sodium bicarbonate (HCO3) was infused continuously intragastrically at 18.75 mmol/kg/day. MEASUREMENTS AND MAIN RESULTS: KIC administration increased circulating concentrations of KIC and ketone bodies. Survival rates were: KIC 17/32; PYR 2/22; and HCO3 8/31. The significant improvement in survival with KIC, in contrast with HCO3 (p<.04) or PYR (p<.002), points to an effect specific to KIC rather than to ketoacids generally, and argues against an antioxidant mechanism to explain improved survival with enteral administration. To determine whether altered nitric oxide production was responsible, plasma nitrite plus nitrate concentrations were measured sequentially in rats given a lower dose of lipopolysaccharide plus continuous intragastric KIC, PYR, or HCO3. All rats exhibited pronounced increases in plasma nitrite plus nitrate concentrations, peaking at 8 hrs, but both KIC and PYR caused greater increases than HCO3. Thus, differences in nitric oxide production cannot account for the different effects of PYR and KIC on survival. However, KIC infusion for 8 hrs substantially increased ketone bodies in blood and liver, in comparison with the infusion of HCO3 or PYR. CONCLUSION: Continuous enteral infusion of KIC improves survival in endotoxemia, probably by its conversion to ketone bodies, which serve as an alternative energy substrate.

Effect of a ketoacid-aminoacid-supplemented very low protein diet on the progression of advanced renal disease: a reanalysis of the MDRD feasibility study.

BACKGROUND: We reanalyzed the data of the Modification of Diet in Renal Disease (MDRD) feasibility study to ascertain the effects of ketoacid- and aminoacid-supplemented very low protein diets. METHODS: Sixty-six patients with advanced renal disease (Study B, baseline glomerular filtration rate (GFR) 7.5-24 ml/min/1.73 m2) were randomly assigned to a low protein diet (L, 0.575 g/kg/d), or a very low protein diet (0.28 g/kg/d) supplemented either with a ketoacid-aminoacid mixture (diet K) or with a mixture of essential aminoacids (diet J). Thirty patients with moderate renal disease (Study A, baseline GFR 25-80 ml/min/1.73 m2) were randomly assigned to a usual protein diet (M, 1.2 g/kg/d), diet L, or diet K. Mean follow-up was 14 months. RESULTS: In Study B, GFR decline differed among the three diets (p = 0.028). Pairwise comparisons showed that the mean +/- SE GFR decline in ml/min/mo in diet K [-0.250+/-0.072] was slower than in diet J [-0.533+/-0.074] (p = 0.008) despite similar achieved protein intakes. The mean GFR decline in diet L [-0.394+/-0.068] was intermediate between, and did not differ significantly from the rates of decline in the other two groups. In Study A, consistent with a hemodynamic effect, the mean GFR decline varied directly with the reduction in protein intake in diets M, L and K (p = 0.028) during the first four months of follow-up, but thereafter did not differ among the diet groups (p = 0.76). CONCLUSION: The study suggests that supplementation of a very low protein diet with the ketoacid-aminoacid mixture used in this feasibility study slowed the progression of advanced renal disease more than supplementation with an amino acid mixture.

Nutritional therapy for progressive renal failure.

Results of the Diabetes Control and Complications Trial indicate that intensive insulin treatment of patients with type I diabetes would greatly reduce the incidence of diabetic nephropathy. Another multicenter trial indicates that modest protein restriction is of no value in children with chronic renal failure. The relationship between urea nitrogen excretion and total nitrogen excretion in children differs from that in adults. A repeated crossover study found that ketoacids slow progression of renal failure, in comparison with amino acid supplements to the same diet. Long-term protein restriction does not lead to protein deficiency at the onset of dialysis. When combined with essential amino acid supplements, a low-protein diet may gradually correct hypoalbuminemia in nephrotic subjects.

A crossover comparison of progression of chronic renal failure: ketoacids versus amino acids.

Rates of progression of chronic renal failure were compared in patients receiving alternately an amino acid supplement (AA) and a ketoacid supplement (KA) to a very low protein (0.3 g/kg), low phosphorus (7 to 9 mg/kg) diet. The first supplement was randomly chosen. Bias due to carryover effects was minimized by delaying the regression analysis until one month after starting or changing supplements. In order to minimize possible bias caused by initiating the two supplements at differing levels of severity, a multiple crossover design was used (ABA, BAB, ABAB, or BABA) with at least four GFR's in each treatment period (except for three GFR's in one instance). Sixteen patients completed the protocol; five dropped out. Average starting GFR's were nearly identical for the two supplements (15.4 and 15.9 ml/min). For each patient, mean progression on KA was compared with mean progression on AA. Thirteen out of 16 patients progressed more slowly on KA than AA. On the average, progression on KA was significantly slower (95% confidence limits = -0.36 to 0.09 ml/min/month) than on AA (-0.91 to -0.41 ml/min/month; P = 0.024). There was no significant difference in estimated protein intake, phosphate excretion, or mean arterial pressure between KA and AA periods. Serum triglyceride concentration was significantly lower on KA (P = 0.0026). 17-hydroxycorticosteroid excretion was also lower (P = 0.031). We conclude that KA slow progression, relative to AA, independently of protein or phosphorus intake, in patients on this regimen.

Progression of chronic renal failure on substituting a ketoacid supplement for an amino acid supplement.

Twelve patients with severe chronic renal failure (average initial GFR, 13 mL/min) were monitored for 4 to 23 months while receiving an essential amino acid supplement and were then switched to a ketoacid supplement for 6 to 40 months, while continuously receiving a very low-protein (0.3 g/kg), low-phosphorus (7 to 9 mg/kg) diet. Urinary urea N excretion indicated that actual dietary protein intake averaged 0.46 g/kg. Progression, estimated as the linear regression slope of radioisotopically determined GFR on time, slowed from -0.46 +/- 0.31 (SD) to -0.24 +/- 0.15 mL/min/month (P = 0.029). Serum urea N, creatinine, phosphate, and uric acid rose significantly as GFR fell; blood pressure, plasma lipids, and urinary urea excretion were unchanged. Urinary 17-hydroxy-corticosteroid excretion decreased 18%, but this change was only marginally significant (P = 0.087). There was no change in plasma or urinary cortisol or urinary aldosterone. Viewed in light of previous evidence that progression seldom slows when treatment remains constant, the results suggest that this ketoacid supplement slows progression by approximately half, compared with an essential amino acid supplement, with no change in diet.

Treatment of the anemia of chronic renal failure with subcutaneous recombinant human erythropoietin.

PURPOSE: The purpose of this study was to determine the efficacy of recombinant human erythropoietin (rHuEPO) given subcutaneously three times/week in patients with chronic renal failure and anemia (predialysis). PATIENTS AND METHODS: Eleven patients with predialysis chronic renal failure participated in a double-blind, placebo-controlled study of subcutaneously administered erythropoietin. For 12 weeks, patients received either rHuEPO 100 mu/kg body weight three times/week subcutananeously or a placebo. After 12 weeks of placebo, patients now also received rHuEPO in a dose up to 150 mu/kg three times/week until target hematocrit was achieved. Throughout the study, blood pressure was monitored closely and blood work was obtained regularly for hemoglobin, hematocrit, reticulocyte count, and iron profile determinations. RESULTS: At 12 weeks, the hematocrit of the treated group had risen from 29% +/- 2% to 35% +/- 2% (p less than 0.001). The placebo group baseline hematocrit was 28% +/- 2% and at 12 weeks 26% +/- 2% After 12 weeks of rHuEPO therapy, the hematocrit of the prior placebo group was 32% +/- 2% (p less than 0.001 versus baseline). No significant change in biochemical parameters was noted. Mean blood pressure values were comparable before and after treatment. All protein ultimately required iron supplementation. In two patients, the rate of progression of renal failure appeared to increase as their hematocrit rose and rHuEPO was discontinued. CONCLUSIONS: It is concluded that rHuEPO given subcutaneously is an effective and safe therapy for patients with chronic renal failure who are anemic and who are not receiving dialysis.

Effect of dietary selenium on the development of Fusarium-induced tibial dyschondroplasia in broiler chickens.

A trial was conducted to determine the effects of dietary level of selenium on the pathogenesis of Fusarium-induced tibial dyschondroplasia (FITD) in broiler chicks, and to assess the applicability of FITD as an animal model of Kashin-Beck disease of humans. Day-old female broilers were fed diets that were deficient in selenium (0.02 ppm Se), adequate in selenium (0.15 ppm Se), or generous in selenium (0.50 ppm Se). TDP-1, the toxic component of the fungus, was administered to 15 of 26 chicks in each dietary group starting at 1 week of age and continuing until the chicks were killed at 24-30 days of age. Plasma selenium levels and hepatic glutathione peroxidase activity were significantly lower in the selenium-deficient group than in other dietary groups; these parameters were not affected by treatment with TDP-1. The mortality rate of the TDP-1-treated selenium-generous group was significantly less than that in the other TDP-1-treated groups, but there were no differences in the incidence, severity, or character of the FITD lesions among the groups. Thus, the interaction of selenium and TDP-1 did not include an effect on FITD.

Progression of chronic renal failure in patients given keto acids following amino acids.

Twelve patients with chronic renal failure who exhibited a progressive decline in 24-h creatinine clearance despite being given, for 2-10 months, a diet containing 0.3 g of protein/kg ideal weight and 7-9 mg of phosphorus/kg ideal weight supplemented with vitamins, CaCO3, and 10 g per day of essential amino acids, were changed to a supplement containing predominantly keto acids. In 6 patients whose serum creatinine levels were 7.5 mg/dl or greater at changeover, progression continued unabated. In 6 patients with serum creatinine levels at changeover of 6.5-7.4 mg/dl, one was non-compliant with the diet and progressed to dialysis. In the other 5, progression, measured as the rate of change of a bimonthly radioisotope clearance, has been undetectable during the ensuing 1-2 years.

Progression of chronic renal failure in patients given ketoacids following amino acids.

Twelve patients with chronic renal failure who exhibited a progressive decline in 24-hour creatinine clearance, despite being given for 2 to 10 months a diet containing 0.3 g per kg ideal weight of protein and 7 to 9 g mg per kg ideal weight of phosphorus, supplemented with vitamins, CaCO3, and 10 g per day of essential amino acids, were changed to a supplement containing predominantly ketoacids. In six patients whose serum creatinine was 7.5 mg/dl or greater at changeover, progression continued unabated. In six patients with serum creatinine levels at changeover of 6.6 to 7.4 mg/dl, one was non-compliant with the diet and progressed to dialysis. In the other five, progression, measured as the rate of change of a bimonthly radioisotope clearance, has been undetectable during the ensuing one to two years. There has been no change in urea appearance, blood pressure, phosphaturia or proteinuria. Nutrition has been maintained. Thus this ketoacid supplemented regimen apparently halted the progression of moderately-severe chronic renal failure for at least a year in a small group of patients in whom restriction of protein and phosphate intake without ketoacids failed to halt progression. In more severe renal failure, no effect on progression was seen.

Phosphorus availability bioassay using bone ash and bone densitometry as response criteria.

Two experiments were conducted to examine the relative precision of bone densitometry and bone ash methodologies as response criteria in measurement of bioavailability of phosphorus from various supplements for turkeys. Multivariate analyses of variance were used to analyze data collected. Coefficients of correlation and variation and F ratios were used for evaluation. Bone densitometry with one scan at each of 3 points on the bone was faster than bone ash and as precise as bone ash analysis in measuring phosphorus availability in turkeys. The coefficient of correlation between percentage ash (of dry bone) and scan density (milligrams per centimeter length of bone) measurements for treatment effects was .986. The coefficient of variation was about the same for the bone ash (5.8) and the three-point bone scan (6.9) methods. As indicated by the F ratio for testing treatment effects, bone densitometry was better able to detect differences among phosphorus sources. A technician may scan 50 cleaned bones in 3 hr, but with the bone ash method, drying, ashing, and weighing may require 3 working days. Bone sampling technique, multiple operators, different bone sizes, and decay of iodine source were the major factors affecting precision of the bone densitometry technique. Relative biological availabilities of phosphorus from various supplements were about the same by the two methods.

Nutritional efficiency of alpha-ketoisocaproate relative to leucine, assessed isotopically.

The efficiency of alpha-ketoisocaproate as a dietary substitute for leucine was assessed in rats by two techniques: first, the minimal dose of alpha-ketoisocaproate required, as a supplement to a leucine-free diet, to achieve a growth rate as great as animals receiving leucine was found to be between 2.2 and 4.4 times larger. Therefore the nutritional efficiency of alpha-ketoisocaproate lies between 0.23 and 0.46. Second, alpha-[1-14C]-ketoisocaproate and [3H]leucine were administered orally and the ratio of 14C/3H incorporated into the leucine of whole-body protein and fibrin was measured. This ratio, divided by the ratio 14C/3H injected, was the same in fibrin as in whole-body protein and averaged 0.39. Thus both techniques yield the same value, within the error of measurement, for the relative nutritional efficiency of alpha-ketoisocaproate. We also found that alpha-ketoisocaproate feeding at varying dosage did not alter this ratio in whole-body protein (measured in rats fasted overnight), suggesting that neither wide variations in growth rate nor exposure for 10 days to alpha-ketoisocaproate (in a diet of constant protein content) alters the relative rates of utilization (or oxidation) of alpha-ketoisocaproate vs. leucine.

The effect of a keto acid-amino acid supplement to a restricted diet on the progression of chronic renal failure.

We treated 24 patients who had chronic renal failure with a low-phosphorus diet containing 20 to 30 g of mixed-quality protein, supplemented by amino acids and their keto analogues. Seventeen patients had well-defined rates of progression before treatment, as assessed by serial determinations of serum creatinine levels. By extrapolating these rates of progression, we found that 10 of the 17 (59 per cent) had a clinically important slower rise in creatinine levels during long-term treatment (average, 20 months) than predicted; none had a faster rise than predicted. Seven of the 17 patients began treatment before creatinine reached the level of 8 mg per deciliter; in six of the seven, followed for an average of 22 months, creatinine has remained at or below the level at the start of treatment. Nutrition, as assessed by body weight, nitrogen balance, serum albumin, and serum transferrin, has been well maintained. This regimen slowed or arrested the rise in creatinine levels and thus must have slowed or halted the progression of renal insufficiency in a majority of cases, especially when treatment was initiated before creatinine had reached the level of 8 mg per deciliter. The mechanism underlying this effect remains to be determined.

Bioavailability of phosphorus in commercial phosphate supplements for turkeys.

Forty-seven commercial phosphorus supplements were obtained from feed manufacturers and subjected to biological phosphorus availability assay using the turkey poult. Bone ash was the response criterion. Compared to a reference source of commercial mono/ dicalcium phosphate (assigned 100), 7 other mono/ dicalcium phosphates averaged 97.1 (range 88.6 to 110.0), 20 dicalcium phosphate sources averaged 90.6 (76.3 to 104.8), and 20 defluorinated phosphate sources averaged 78.4% (68.6 to 89.6) availabilities. Combining equal parts of all sources of each type of phosphorus supplement and using purified grade calcium phosphate monobasic monohydrate as a defined standard, the commercial mono/ dicalcium phosphates, dicalcium phosphates, and defluorinated phosphates averaged (with 95% confidence limits) 93.6 +/- 7.6, 88.3 +/- 8.2, and 70.2 +/- 7.2% phosphorus availability in a slope ratio bioassay. Calculating the requirement intercepts utilizing the blended phosphorus supplements indicated apparent requirements using mono/ dicalcium phosphate, dicalcium phosphate, and defluorinated phosphate of .74, .76, and .83% total phosphorus in the diet, respectively. Considering 1) the variability in availability of the sources, 2) variation in feed mixing, 3) the National Research Council requirement of .80%, and 4) that newly hatched poults are completely dependent on one batch of prestarter feed during 0 to 10 days of life, it is suggested that in certain instances field rickets could result from deficiency of dietary phosphorus.

Supplements containing amino acids and keto acids in the treatment of chronic uremia.

Three mixtures containing varying proportions of threonine, tyrosine, and the ornithine, lysine, and histidine salts of branched-chain keto acids have been tested as dietary supplements to a 20- to 25-g mixed-quality protein diet in patients with severe chronic uremia. Two of the three supplements improved the abnormalities of plasma amino acid concentrations, and slowed or arrested progression of renal insufficiency. The second supplement, which contained less threonine and lysine, led to subnormal plasma concentrations of these two amino acids and aggravated hypophosphatemia. The third supplement, which also contained a small amount of the hydroxy analogue of methionine, was the most effective in slowing progression. The results emphasize the importance of optimizing the composition of such supplements.

Effect of dietary sodium fluoride on growth and bone development in growing turkeys.

Large White male turkeys were fed rations containing 0, 12.5, 25, 50, 100, 200, 400, and 800 ppm added fluoride (F) from sodium fluoride in a corn-soybean assay diet containing tricalcium phosphate and 3 to 5 ppm F. The 800 ppm treatment was discontinued at 8 weeks because of low weight gains and a high incidence of leg disorders. Turkeys receiving defluorinated phosphate (32% calcium, 18% phosphorus) had significantly higher 4-week body weights than turkeys receiving tricalcium phosphate. Turkeys fed 0, 400, and 800 ppm F had significantly lower body weights at 8 weeks than turkeys fed 50 ppm F. A similar weight pattern was seen at 18 weeks, although the differences were not statistically significant. Based on growth response in this study, a requirement of 20 ppm F is proposed. Increasing levels of dietary F resulted in large increases in tibia F. Removal of high dietary F in certain groups at 8 weeks resulted in growth recovery and reduction in tibia F by 18 weeks. Elevated plasma alkaline phosphatase activity was observed with added dietary F of 400 and 800 ppm. At 4 weeks, tibiae from turkeys receiving high F had a trend (not statistically significant) toward lower percentage ash and a significantly lower breaking strength than controls. Compared to controls, tibiotarsi from turkeys on high F rations were significantly shorter, had thinner cortices, and had a narrower proliferative zone of proximal growth plates. A high incidence of tibial dyschondroplasia was observed, but it was not correlated with dietary treatment.

Growth of rats with severe renal insufficiency fed a formula designed to minimize urinary solutes.

Experiments were designed to test the hypothesis that growth depression and azotemia in chronic renal failure can be minimized by providing a nutritional formula that is adequate is essential nutrients but minimizes urinary excretion of all solutes. Unrestrained rats were fed exclusively by continuous intragastric infusion with a mixture containing sucrose, essential amino acids, N-free analogues thereof, minerals, corn oil, and vitamins, designed to minimize urinary solute excretion while permitting growth. After 5 days, renal excretory function was reduced to 1/10 by reinfusing 90% of each day's urinary output intragastrically for the next 3 wk. Weight gain (3.6 +/- 0.1 g/day), linear growth and carcass N accretion were the same as in nonreinfused rats receiving substantially the same formula by intragastric catheter. Except for sight acidosis (CO2 18.5 mM) accumulation of electrolytes did not occur. Average final serum urea N was only 42.5 +/- 7.1 mg/dl. The results are considered as supporting the hypothesis.

Long-term effects of a new ketoacid-amino acid supplement in patients with chronic renal failure.

Nine patients with severe chronic renal failure (mean glomerular filtration rate 4.8 ml/min; mean serum creatinine 11.3 mg/dl) who were previously on a protein-restricted diet were treated with a diet containing an average of 33 kcal/kg and 22.5 g/day of mixed quality protein, supplemented by a combination of amino acids and mixed salts formed between basic amino acids and keto-analogues of essential amino acids. The supplement was designed to minimize or reverse the amino acid abnormalities of chronic renal failure rather than to meet the normal requirements for the essential amino acids; it contained tyrosine, ornithine, and a high proportion of branched-chain ketoacids, but no phenylalanine or tryptophan and very little methionine. Within one month, serum urea nitrogen fell and serum albumin and transferrin rose significantly; serum creatinine fell slightly. Hyperphosphatemia (present in three patients) was corrected. Nitrogen balance, measured in seven of the nine patients, on the average was neutral, as it was in a preceding control period on a 40 to 50 g/day protein diet. Plasma tyrosine and threonine, which were subnormal before therapy, rose to normal or high normal levels. Branched-chain amino acids did not change. During a total of 63 patient-months of therapy, no side effects or toxicity were observed, and serum albumin and transferrin did not change further. It is concluded that this specially designed supplement added to a 20 to 25 g/d protein diet is an acceptable regimen which can improve or maintain protein nutrition in patients with severe chronic renal failure who would otherwise require dialysis.

Effects of arginine-free meals on ureagenesis in cats.

Cats given a single arginine-free meal have been reported to develop severe hyperammonemia, attributed to impaired function of ornithine aminotransferase (OAT). We found that cats that developed hyperammonemia following an arginine-free meal had low hepatic ornithine levels. However, the average sum of hepatic ornithine plus arginine plus citrulline rose, indicating that some ornithine synthesis via OAT took place, and hyperammonemia failed to occur in cats with higher hepatic ornithine levels. OAT activity and kinetic constants were comparable to values reported in the rat. Furthermore, dietary supplementation with ornithine caused only occasional and transient hyperornithinemia. Thus, OAT can function in the cat. The Ka of N-acetylglutamate (AGA) synthetase for arginine was 5 times higher in cats than in rats, but AGA content and citrullinogenesis by intact mitochondria were the same following arginine-free or arginine-containing meals. Other kinetic parameters of AGA synthetase and carbamoylphosphate synthetase were similar to values in the rat. We conclude that low levels of hepatic ornithine are probably responsible for making some cats susceptible to hyperammonemia following this stimulus.