Stewart A. Laidlaw

The taurine content of common foodstuffs

There is growing evidence that taurine is a biologically valuable nutrient. However, there are few published data concerning the taurine content of different foods. We measured the taurine content of 29 meats, including both cooked and uncooked samples, nine dairy products, 17 infant or adult-feeding solutions and 48 plant foods (including vegetables, nuts or seeds, fruits and legumes. Taurine was detected in meats, dairy products, and infant feeding solutions but not in plant products or adult feeding solutions. Using these data, we compared calculated and measured daily taurine intakes in six defined diets. We present sample daily diets for omnivores, lacto-ovovegetarians and vegans (strict vegetarians), together with calculated taurine intakes.

Patterns of Fasting Plasma Amino Acid Levels in Chronic Renal Insufficiency: Results From the Feasibility Phase of the Modification of Diet in Renal Disease Study

Fasting plasma amino acid levels were measured in 78 patients with chronic renal insufficiency (glomerular filtration rate [GFR], 8.0 to 56.0 mL/min), who had been enrolled in phase II of the Modification of Diet in Renal Disease study, prior to their beginning the experimental portion of the protocol. Alterations in many plasma amino acid levels were observed in the patients with the mildest degrees of renal insufficiency, and the number and severity of abnormalities tended to be greater in the patients with more severe renal failure. In patients with GFRs greater than 24.5 mL/min, 15 to 24.5 mL/min, and less than 15 mL/min, statistically significant abnormalities were observed in the concentrations or ratios of 9, 14, and 18 amino acids, respectively. The following correlations of amino acid levels or ratios with GFR were observed (all P < 0.001): citrulline, r = -0.41; citrulline to arginine ratio, r = -0.42; glycine to serine ratio, r = -0.37; N-tau methylhistidine, r = -0.65; and cystine, r = -0.37. Other weaker correlations observed were valine, r = 0.26 (P < 0.025); valine to glycine ratio, r = 0.32 (P = 0.004); and sum of isoleucine, leucine, and valine, r = 0.21 (P = 0.061). N-tau methylhistidine and the essential to nonessential amino acid ratio became altered with declining GFR in a nonlinear fashion. Thus, many of the characteristic alterations in the plasma amino acid profile that are observed in chronic end-stage renal disease are already present in mild renal insufficiency. Progressive loss of renal function generally results in increasing abnormalities; these changes in plasma amino acid concentrations with reduction in GFR were usually linear.

Plasma amino acid concentrations in children receiving long-term parenteral nutrition

Plasma amino acid concentrations were measured in 15 children aged 4–65 months who received home parenteral nutrition (PN) and in 10 normal controls. In seven patients (Group I). PN was the only source of nutrition. Eight patients (Group II) ingested 30%–70% of their total energy requirements and received the remainder intravenously. Group I and Group II patients received PN for 25.6 × 14.4 (SD) and 25.7 × 19.1 months, respectively. In comparison to controls. Group I had significantly decreased plasma concentrations of total essential amino acids, the three branched chain amino acids. cystine, tyrosine, and the three major urea cycle amino acids. Group II children displayed decreased plasma concentrations of two branched chain amino acids. leucine and valine, as well as cystine and tyrosine. Taurine was decreased in both groups. The presence of liver disease did not have a major effect on amino acid levels. These data indicate that children receiving long-term parenteral nutrition will develop abnormalities in their plasma amino acid concentrations even though they appear to receive adequate amounts of amino acids in their intravenous solutions. Further studies will be necessary to assess whether modifying the intravenous intake of amino acids will normalize plasma amino acid concentrations in these children.

Lipoproteins in children treated with continuous peritoneal dialysis

ABSTRACT: Total lipids, lipoprotein-lipids, and apolipo-proteins were studied in plasma of 20 patients, aged 13.9 ± 3.4 y (mean ± SD, range 7.4 to 19 y), who were treated with continuous peritoneal dialysis for a period of 2.1 ± 1.2 (range 0.5 to 4.9) y. Measurements included total plasma cholesterol and triglycerides, triglycerides in the very low density fraction, and cholesterol in the very low density, low density, and high density fractions, as well as apo A-I and apo B. The results were compared with values in 17 healthy control subjects, aged 13.0 ± 5.1 (range 5.1 to 19) y. The patients had significantly elevated levels of total plasma triglycerides, triglycerides in the very low density fraction, total plasma cholesterol, cholesterol in the very low density fraction, and cholesterol in the low density fraction, whereas levels of cholesterol in the high density fraction were normal. Plasma apo B levels were elevated, but apo A-I levels were not different from controls. In addition, the nutritional status of the patients was assessed and apo A-I and apo B concentrations were measured in the dialysate of 10 patients. The losses of apo A-I and apo B in dialysate averaged 13.4 ± 7.4 and 2.1 ± 3.1 mg/kg/d, respectively. Lipoprotein profiles were not correlated with nutritional status. We conclude that pediatric patients treated with continuous peritoneal dialysis have atherogenic lipoprotein profiles, cholesterol ratios, and apolipoprotein ratios, but normal cholesterol in the high density fraction and apo A-I levels despite considerable apo A-I losses in the dialysate.

Taurine Levels in Plasma and Blood Cells in Patients Undergoing Routine Maintenance Hemodialysis

We compared taurine levels in plasma, erythrocytes, platelets, lymphocytes, and granulocytes from 11 normal adults and 11 maintenance hemodialysis (MHD) patients immediately before and following a routine hemodialysis treatment. Taurine concentrations were elevated in plasma predialysis, as compared with normal subjects (90 +/- 16 [SEM] v 54 +/- 2 mumol/L [1.1 +/- 0.2 v 0.7 +/- 0.03, mg/dL]), but decreased with a dialysis treatment (to 34 +/- 3 mumol/L [0.4 +/- 0.04 mg/dL]). Erythrocyte taurine levels tended to be higher in MHD patients predialysis (1.2 +/- 0.2 v 0.7 +/- 0.1 nmol/10(9) cells, P less than 0.05 where P less than 0.025 is significant) as compared with controls; erythrocyte taurine was increased after dialysis (to 1.8 +/- 0.3 nmol/10(9) cells, P less than 0.006). In contrast, platelet taurine concentrations in MHD patients were lower than normal predialysis (18 +/- 2 v 27 +/- 2 nmol/10(9) cells) and declined further during the dialysis procedure (to 14 +/- 1). Granulocyte and lymphocyte taurine levels were not different in MHD patients, as compared with normal adults, either before or after dialysis. The observed differences in blood cell taurine content (expressed per 10(9) cells) could not be explained by variation in cell volumes among the groups examined. Thus, both chronic renal failure and a routine hemodialysis treatment produce changes in cell and plasma taurine levels that tend to be specific for the individual cell type.

Fingernail Creatinine as a Predictor of Prior Renal Function

When a patient presents with renal failure, it is often difficult to ascertain whether the individual is suffering from acute or chronic renal failure. Fingernail creatinine might help to differentiate between the two. To test this possibility, the relationship between the fingernail creatinine and the serum creatinine obtained concurrently or 1 or more months previously was examined in 22 normal adults, nine patients with acute renal failure, seven patients with chronic renal failure not undergoing dialysis, 16 maintenance hemodialysis patients, and 33 patients with a functioning renal transplant who had been transplanted 0.2 to 3.9 months (n = 21) or 4.3 to 33 months previously (n = 12). Fingernail creatinine was significantly greater than normal in the patients with chronic renal failure, patients undergoing maintenance hemodialysis, and patients who had a functioning renal transplant implanted 0.2 to 3.9 months previously. In contrast, fingernail creatinine was not different from normal in the patients with acute renal failure and in patients who had a functioning renal transplant placed 4.3 to 33 months previously. In the maintenance hemodialysis patients, fingernail creatinine showed the strongest correlation with the serum creatinine obtained between 5 and 10 months previously, with the highest correlation at 9 months. In the renal transplant recipients, the fingernail creatinine decreased to normal or near normal values within approximately 90 to 120 days after transplantation. These findings indicate that fingernail creatinine may reflect the serum creatinine values several months previously. The fingernail creatinine may help to identify whether patients have recent onset as compared with longstanding renal failure.