Circadian Periodicity of Blood Amino-acids in Adult Men

Feigin, Ralph D.; Klainer, Albert S.; Beisel, William R.

doi:10.1038/215512b0

Cited by 108 publications

(44 citation statements)

References 14 publications

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“…have been redrawn from Fraser et al (1994). (B) Circadian rhythm for amino acids in plasma indicating the location of a highly reproducible nadir around 02:00 -04:00 h. The data, expressed as a percentage of the maximum integrated amino acid level, have been redrawn from Feigin et al (1967). This circadian rhythm is particularly pronounced for the aromatic amino acids L-Phe, L-Trp and L-Tyr 1968), all CaR activators.…”

Section: Discussionmentioning

confidence: 99%

“…Might variations in plasma amino acid level contribute to the circadian rhythm for PTH by altering the Ca 2þ set-point for the CaR? Plasma amino acid levels also exhibit a highly reproducible circadian rhythm (Feigin et al, 1967;Wurtman et al, 1968). Interestingly, the plasma amino acid level reaches a nadir at about 02:00 -04:00 h in individuals on a normal protein diet.…”

Section: Is the Car A Target For The Toxicity Of Aromatic L-amino Acimentioning

confidence: 99%

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L-Amino acid sensing by the calcium-sensing receptor: a general mechanism for coupling protein and calcium metabolism?

et al. 2002

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Cellular sensing of L-amino acids is widespread and controls diverse cellular responses regulating, for example, rates of hormone secretion, amino acid uptake, protein synthesis and protein degradation (autophagy). However, the nature of the sensing mechanisms involved has been elusive. One important sensing mechanism is selective for branched chain amino acids, acts via mTOR (mammalian target of rapamycin) and regulates the rates of insulin and IGF-1 secretion as well as hepatic, and possibly muscle, autophagy. A second sensing mechanism is selective for aromatic L-amino acids and regulates the rate of gastric acid secretion and other responses in the gastro-intestinal tract. Interactions between calcium and protein metabolism, including accelerated urinary calcium excretion in subjects consuming high-protein diets and secondary hyperparathyroidism in subjects consuming low-protein diets, suggest an additional amino acid sensing mechanism linked to the control of urinary calcium excretion and parathyroid hormone (PTH) release.New data demonstrating L-amino acid-dependent activation of the calcium-sensing receptor (CaR), which regulates PTH secretion and urinary calcium excretion, suggests an unexpected explanation for these links between calcium and protein metabolism. Keywords: protein; calcium; free amino acids; amino acid sensing; calcium-sensing receptor; G-protein coupled receptor Roles of amino acids and amino acid sensing mechanisms in human biologyFree L-amino acids are essential molecules in biological systems. This derives, in part, from their fundamental role as the building blocks of proteins, the chief species encoded by DNA. Amino acids are also the metabolic precursors of important biologically active substances that act as the ligands for receptors. These include histamine from L-histidine, 5-hydroxytryptamine (serotonin) from L-tryptophan, and dopamine, catecholamines and thyroid hormone from L-tyrosine. Clearly, cellular amino acid uptake mechanisms are critical for the processes of protein synthesis and amino acid metabolism but how are these processes regulated? Furthermore, to what extent do amino acid sensing mechanisms regulate and coordinate whole body metabolism?It is now clear that amino acid sensors are widely distributed. For example, an amino acid-sensing mechanism couples elevations in branched chain amino acids such as leucine and isoleucine to stimulation of insulin secretion from pancreatic B cells. Branched chain, and other amino acids, also suppress hepatic autophagy, the process by which amino acids are released by activated lysosomal protein degradation at times of amino acid starvation. Although the identities of these amino acid sensors are unclear, similar intracellular signalling pathways are activated that include

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Section: Discussionmentioning

confidence: 99%

Section: Is the Car A Target For The Toxicity Of Aromatic L-amino Acimentioning

confidence: 99%

L-Amino acid sensing by the calcium-sensing receptor: a general mechanism for coupling protein and calcium metabolism?

et al. 2002

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“…Many of our physiological functions are known to exhibit a diurnal variation [2,6,9,11,15, 171 and the change from light to darkness signals a repetitive phenomenon, sleep. A great deal of experimental and clinical evidence has emerged showing that the endocrine system is intimately linked with the sleep rhythm [8, 18,191.…”

Section: Introductionmentioning

confidence: 99%

Sleep Deprivation Reduces Circulating Androgens in Healthy Men

Cortés-Gallegos

Alonso

et al. 1983

Archives of Andrology

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The acute effect of sleep deprivation on the pituitary-testis axis was evaluated in 13 healthy men. To study such association, the circulating levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), Androstenedione (A), Testosterone (T), Dihydrotestosterone (DHT) and Estradiol (E2) were measured along with Cortisol (C) before and after sleep deprivation. Morning (8:OO AM) venous blood samples were obtained prior and after a continuous restless period of 24 hr and the values were analyzed by the paired Student's r test. There was a significant and parallel decrease of each androgen and E2 but not of FSH, LH.PRL, or C, associated with the acute sleep deprivation.

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“…Other studies have confirmed the daily fluctuations, but with slight differences in the concentrations and time of peak/low onset (12,24,25,26,56,99). The most dramatic shift occurred when volunteers were fed a high-protein diet (150 g/day).…”

Section: Diurnal Variationsmentioning

confidence: 79%

Supplemental tyrosine and vigilance performance in a normoxic hypobaric environment

Maresh¹

2001

PsycEXTRA Dataset

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The public re(jortii.g burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection o; rnfo'rnation. including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Exposure to stress results in a decrease in mental performance resulting from a depletion of catecholamines. This decrease can result in an increase in error rates, decreased decision making ability, mental confusion, and an overall decrease in cognitive performance. Previous studies have shown that supplemental tyrosine prevents the normal decrease due to stress.Tyrosine works by increasing the catecholamine precursor.Nine subjects were exposed to a 3-hour protocol for 4 different exposures. During each exposure, the following Stressors were used: 1) hypobaric environment (for two of the four exposures); 2) immobilization; 3) prolonged inactivity; 4) behavioral and psychophysiological testing; 5) cool temperatures and low humidity; and 6) 71 dB(A) chamber environment. Subjects completed computerized vigilance and cognitive tests and a mood questionnaire, each separated by a period of inactivity. Prior to exposure, subjects ingested either 100 mg/kg body weight of a placebo or tyrosine.Supplemental tyrosine improved response time in all of the tests where it was recorded, with all except one being significant. Motor function and overall mood also significantly improved with the use of tyrosine. As expected, no measurement showed a significant improvement in performance with supplemental oxygen alone. The use of supplemental tyrosine did not significantly improve cognitive performance. Results of the contrast sensitivity taskswere not as conclusive and no improvement was found in visual temporal acuity. and physical performance. The less control the individual has over these stresses, the greater the decrement. The decrease in performance, particularly mental performance, results from a depletion of catecholamines within the brain. This decrease, especially in norepinephrine, leads to alterations in normal brain function and an increase in error rates, decreased decision making ability, mental confusion, and an overall decrease in cognitive performance. All of these are compounded the longer the individual is unable to remove the stress. Previous studies involving rats and humans have shown that supplemental tyrosine (levels above normal dietary intake) prevent the normal decrease in performance in stressed individuals. Tyrosine, the initial precursor in catecholamine synthesis, works by increasing the availability of the precursor and thereby slowing the rate of norepinephrine depletion.Nine healthy subjects from the Colorado State University community were exposed to a 3-hour protocol that w...

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Circadian Periodicity of Blood Amino-acids in Adult Men

Cited by 108 publications

References 14 publications

L-Amino acid sensing by the calcium-sensing receptor: a general mechanism for coupling protein and calcium metabolism?

L-Amino acid sensing by the calcium-sensing receptor: a general mechanism for coupling protein and calcium metabolism?

Sleep Deprivation Reduces Circulating Androgens in Healthy Men

Supplemental tyrosine and vigilance performance in a normoxic hypobaric environment

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