Plasma amino acids

Facilitates the breakdown of protein in the muscle, leading to increased plasma amino acid levels. Increases activity of enzymes necessary for glucogenesis producing hyperglycemia, which can aggravate diabetes, precipitate latent diabetes, and cause insulin resistance... 

Skeletal muscle utilizes glucose as a fuel, forming both lactate and CO2. It stores glycogen as a fuel for its use in muscular contraction and synthesizes muscle protein from plasma amino acids. Muscle accounts for approximately 50% of body mass and consequently represents a considerable store of protein that can be drawn upon to supply amino acids for gluconeogenesis in starvation. 

R. O., Plasma amino acids in childhood epileptic encephalopathies, Epilepsy Res., 34, 221, 1999. 

Calder, A.G. Garden, K.E. Anderson, S.E. Lobley, G.E. Quantitation of Blood and Plasma Amino Acids Using Isotope Dilution GC-EI-MS with U- C Amino Acids As Internal Standards. Rapid Com-mun. Mass Spectrom. 1999, 13, 2080-2083. 

Plasma amino acid concn (mmol/L) Approx, rate of urea synthesis (g/day)... 

The anorexia suffered by cancer patients is likely to arise from a combination of psychological stress, altered senses of taste and smell and increased levels of cytokines, which influence the appetite and satiety centres in the hypothalamus. There are several consequences micronutrient intake will be diminished and this may contribute to the signs and symptoms of the disease. Plasma amino acid levels will fall, as in starvation (Chapter 16). Synthesis of glutamine (by muscle, adipose and lung), aspartate (by liver), glutathione (by the intestine) and arginine (by the kidney) will all be compromised. The metabolic significance of all of these is discussed in Chapter 18. 

Therapy, in the short term, is with intravenous unfractionated or subcutaneous low molecular weight heparin. Aspirin, given in low doses between 50 and 100 mg per day, is sufficient to diminish platelet-vessel interaction. Alternatives include 100-200 mg of sulphinpyrazone once or twice a day or dipyridamole where 100 mg four times a day can be used on its own or between 25 and 75 mg combined with aspirin three times a day. More recently thiopy-ridines, as a class, has been shown to have equivalence at 250 mg twice a day. In hyperhomocysteinaemia the risk is reduced by 5 mg of folate and 100 mg of vitamin Bg daily, with addition of oral vitamin Bi2 of less clearly defined benefit. The effect of this intervention requires re-assay at 3-monthly intervals, following standard methionine challenge, to ensure that suitable suppression has been achieved in the plasma amino acid level (Table 5). 

Ko GN, Korpi ER, Freed WJ, et al. Effect of valproic acid on behavior and plasma amino acid concentrations in chronic schizophrenia patients. Biol Psychiatry 1985 20 199-228. 

Here we describe a concise method for the analysis of the 20 or so most important plasma amino acids by positive-ion liquid chromatography-(MS/MS). The method is especially useful for the follow-up of dietary treatment. 

National or international quality control schemes for plasma amino acids exist, such as the ERNDIM scheme. Virtually all schemes use consensus values as the most likely target values and an intelligent scheme adds to that information about repro-... 

Amino acids are preferably analyzed in plasma taken after an overnight fast and in a 24-h urine collection. The fasting plasma amino acids levels have a quite narrow range and are somewhat dependent on the general nutritional status of the subject and his/her age (Table 2.1.5)... 

Nutrition may have a considerable effect. A high intake of milk protein in neonates will result in an increase in most plasma amino acids, especially methionine and tyrosine. Canned infant formulae may contain homocitrulline, which may appear in the patient s urine. White meat (chicken ) will contain carnosine, anserine, and... 

Reference values for plasma amino acids in different age groups (p.mol/1)... 

Plasma Amino acid 1 st week 1 week-1 month 1-4 months 4 months-2 years 2-10 years 10-18 years >18 years... 

Gender is not an important determinant of plasma amino acid levels. Females have a tendency toward small changes of their amino acid levels during the menstrual cycle. However these changes are barely distinguishable from the normal diurnal changes and dietary influences. 

Compounds that stimu late insulin secretion One that decreases insulin secretion A rise in blood glucose is the most important signal for increased insulin secretion. Plasma amino acid levels and the intestinal peptide secretin also stimulate insulin secre tion. Its synthesis and release are decreased by epinephrine, which is secreted in response to stress, trauma, or extreme exercise. 

Normal procedures for the qualitative and quantitative evaluation of the chromatograms are employed. Table 10.5 lists normal values for plasma amino acids as determined by this procedure. 

Comparison with in vivo procedures Although the FDNB procedure proved to be a suitable reference method, there is no doubt that all methods should be ultimately compared to in vivo procedures. For this reason selected samples were also analyzed by plasma amino acid and digestibility methods. Preliminary results ( Table II ) show that plasma lysine results correlated very well with results for lysine digestibility and FDNB lysine ( r =0.95 ), reasonably well with those for dansyl chloride lysine, succinic anhydride reactive lysine and dye binding lysine, but poorly with total lysine. Although the absolute values were in many cases very different, it is apparent that all methods except total lysine can be used to at least indicate the extent of lysine damage. 

All enteral feeds were stopped. The baby was given intravenous glucose, L-arginine, sodium benzoate, and sodium phenylacetate. Hemodialysis was initiated. At this time, there were no spontaneous respirations, there was no response to painful stimuli, and brainstem reflexes were absent. The plasma amino acid results revealed a glutamine level of 1500 pmol/L (normal 254-823), and citrulline was undetectable (normal 10-34 pmol/L). Quantitative carnitine, plasma acylcarnitine, and urine organic acid profiles were normal. The urine orotic acid concen-... 

Quantitation of plasma amino acids, especially of citrullinc, is the first step in determining the precise enzyme or transport protein defect in patients with a UCD. If the defect involves N-acetyglutamate synthetase (NAGS), CPSI, or OTC, then plasma citrulline concentration will be low. Marked hypercitrullinemia (>2000 pmol/I.) is seen in argininosuccinate synthetase (AS) deficiency, while moderate increases (>200 pmol/L, normal undetectable) are found in argininosuccinate lyase (AL) and citrin deficiencies. In AL deficiency, the presence of argininosuccinic acid and its anhydrides further distinguishes this disorder. 

Consideration of other plasma amino acids also informs the diagnosis of inborn errors of urea synthesis. The plasma concentrations of glutamine and alanine are often elevated in parallel with or prior to the ammonium concentration as they act as a nitrogen buffer. Plasma arginine concentrations are low since the only synthetic route for arginine in humans is via the urea cycle. In contrast, the arginine concentration is elevated in ARG-1 deficiency. Hyperornithinemia and homocitrullinuria are the characteristic features of the hyperammonemia, hyperornithinemia, and homocitrullinuria (HHH) syndrome caused by a defect in the ornithine transporter (ORNT-1). 

Stuerenburg HJ, Petersen K, Buhmann C, Rosenkranz M, Baeumer T, Thomasius R. Plasma amino acids in ecstasy users. Neuro Endocrinol Lett 2003 24 348-9. 

Marchesini, G., Zoli, M., Dondi, C., Cecchini, L., Angiolini, A., Bian-chi, F.B., Pisi, E. Prevalence of subclinical hepatic encephalopathy in cirrhotics and relationship to plasma amino acid imbalance. Dig. Dis. Sci. 1980 25 763-768... 

Merli, M., Riggio, O., Pieche, U., Ariosto, F., Pinto, G., Romiti, A., Varride, M., Capocaccia, L. The effect of oral BCAA supplement on diurnal variations in plasma amino acid concentrations in cirrhotic patients. Nutrition 1988 4 351 -356... 

Campollo, O., Sprengers, D., McIntyre, N. The BCAA/AAA ratio of plasma amino acids in three different groups of cirrhotics. Rev. Invest. Clin. 1992 44 513-518... 

Staedt, LL, Lewellng, H., Gladisch, R., Kortsick, C., Hagmiiller, E., Holm, E. Effects of ornithine aspartate on plasma ammonia and plasma amino acids in patients with cirrhosis. A double-blind, randomized study using a four-fold crossover design. J. Hepatol. 1993 19 424-430... 

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