Pharmacokinetics, cardiovascular and metabolic actions of cyclohexylamine in man

Diagnosis and prognosis of COVID-19 employing analysis of patients' plasma and serum via LC-MS and machine learning

OBJECTIVE

To implement and evaluate machine learning (ML) algorithms for the prediction of COVID-19 diagnosis, severity, and fatality and to assess biomarkers potentially associated with these outcomes.

MATERIAL AND METHODS

Serum (n = 96) and plasma (n = 96) samples from patients with COVID-19 (acute, severe and fatal illness) from two independent hospitals in China were analyzed by LC-MS. Samples from healthy volunteers and from patients with pneumonia caused by other viruses (i.e. negative RT-PCR for COVID-19) were used as controls. Seven different ML-based models were built: PLS-DA, ANNDA, XGBoostDA, SIMCA, SVM, LREG and KNN.

RESULTS

The PLS-DA model presented the best performance for both datasets, with accuracy rates to predict the diagnosis, severity and fatality of COVID-19 of 93%, 94% and 97%, respectively. Low levels of the metabolites ribothymidine, 4-hydroxyphenylacetoylcarnitine and uridine were associated with COVID-19 positivity, whereas high levels of N-acetyl-glucosamine-1-phosphate, cysteinylglycine, methyl isobutyrate, l-ornithine and 5,6-dihydro-5-methyluracil were significantly related to greater severity and fatality from COVID-19.

CONCLUSION

The PLS-DA model can help to predict SARS-CoV-2 diagnosis, severity and fatality in daily practice. Some biomarkers typically increased in COVID-19 patients' serum or plasma (i.e. ribothymidine, N-acetyl-glucosamine-1-phosphate, l-ornithine, 5,6-dihydro-5-methyluracil) should be further evaluated as prognostic indicators of the disease.

Toxicity of food sweetener-sodium cyclamate on osteoblasts cells

In this paper, the effect of commonly used food sweetener (sodium cyclamate) on the proliferation and differentiation of osteoblasts has been researched. The morophology change of osteoblasts was investigated by confocal laser scanning microscopy. Cell viability was studied by MTT analysis. BMP2 expression was analyzed by western blot and immunofluorescence. Mineralization ability of osteoblasts was researched by using alizarin red staining method. The results indicate that a very low concentration (0.06 μM) of sodium cyclamate can curle and fold microfilament and microtubule of osteoblasts. The increase addition of sodium cyclamate resulted significantly decrease of cells viability. The expression of bone morphogenetic protein-2 (BMP2) was seriously suppressed by sodium cyclamate. Alizarin Red staining experiment revealed that sodium cyclamate decreased the mineralization ability of osteoblasts. The present results suggest that sodium cyclamate can seriously inhibit the proliferation and differentiation of osteoblasts.

Cyclamate intake and cyclohexylamine excretion are not related to male fertility in humans

Cyclamate and its metabolite cyclohexylamine affect male fertility in high dose animal studies, but this affect has not been investigated in epidemiological studies. This paper reports the first epidemiological study designed to investigate the possibility of a relationship between cyclamate and cyclohexylamine and male fertility in humans, in which 405 cases of clinically defined infertility in men and 379 controls were surveyed. Semen evaluation, urine analysis for cyclamate and cyclohexylamine and dietary questionnaires were compared between cases and controls. No evidence was found of a significant association between cyclamate intake and male infertility; neither high cyclamate nor high cyclohexylamine excretion were associated with elevated risk. The lack of association remained after adjusting by age, area of residence, education, total energy intake and other variables. No significant correlations were observed between cyclamate intake, metabolism or excretion, and sperm count and motility. The results demonstrate no effect of cyclamate or cyclohexylamine on male fertility at the present levels of cyclamate consumption.

Cyclohexylamine inhibits the adhesion of lymphocytic cells to human syncytiotrophoblast

We have previously shown that lymphocytic cells adhere to cultured syncytiotrophoblast and that this may be important in the lymphocyte-mediated infection of trophoblast with the human immunodeficiency virus (HIV). During the course of studies aimed at investigating the role of cell surface carbohydrates in adhesion, it was discovered that a contaminant of commercial fucose-1-phosphate, dicyclohexylamine, inhibited MOLT-trophoblast adhesion. Dicyclohexylamine and the related compounds, cyclohexylamine and hexylamine, inhibited adhesion in a dose-responsive manner with half-maximal inhibition seen at about 4 mM. While the pressor effects of cyclohexylamine, the principal metabolite of cyclamate, are well known, this is the first report of an effect of this and related compounds on cell adhesion activity. The inhibitory effect was reversible and, at concentrations less than 25 mM, did not result in loss of cell viability. Several possible mechanisms of action of cyclohexylamine were examined in an attempt to explain the effect on adhesion. No evidence was found to suggest that the effects of cyclohexylamine were due to inhibition of polyamine synthesis, increase in intracellular Ca2+ concentration or to a lysosomotropic effect. The concentrations of cyclohexylamine used are within the range of plasma concentrations attainable in humans, raising the possibility that the in vitro effects described here may also occur in vivo. The results also suggest that caution should be used in the interpretation of results obtained from experiments where cell adhesion is blocked using exogenous monosaccharides that are in the form of dicyclohexylammonium salts. Appropriate controls must be included or, if possible, sodium, potassium or barium salts should be chosen.

The metabolism of cyclamate to cyclohexylamine and its cardiovascular consequences in human volunteers

A group of 194 diabetic patients were given calcium cyclamate (1 g/day as cyclamic acid equivalents) for a period of 7 days. Blood and urine samples were collected to determine the formation of cyclohexylamine, which is an indirectly acting sympathomimetic amine. Blood pressure and heart rate were recorded before and after treatment. Urine samples were collected each day and analyzed for cyclamate (to check compliance) and cyclohexylamine (to monitor the development of metabolizing activity). After 7 days intake most individuals (78%) did not excrete significant amounts of cyclohexylamine (less than 0.1% of the daily dose of cyclamate) but a small number (8; 4% of the group) excreted more than 20% of the daily dose as cyclohexylamine in the urine. Similar interindividual variations were found in the plasma concentrations of cyclohexylamine after 7 days intake of cyclamate, with 8 individuals having concentrations of 300-1942 ng/ml. The changes in cardiovascular parameters in these 8 subjects between pre- and postdosing were similar to those found in 150 subjects with plasma cyclohexylamine concentrations less than 10 ng/ml. Twenty of the subjects were restudied after receiving calcium cyclamate for 2 weeks at a daily dose equivalent to 2 g of cyclamic acid (0.66 g tds). Plasma concentrations of cyclohexylamine, heart rate, and blood pressure were measured every 30 min for a period of 8 hr (one dose interval) after the final dose. Twelve patients had plasma concentrations of cyclohexylamine greater than 10 ng/ml (89-2043 ng/ml) at the start of the dose-interval investigations. There were no transient increases or decreases in plasma concentrations of cyclohexylamine which might have resulted in a transient change in blood pressure or heart rate. These data indicate that the metabolism of cyclamate (2 g/day) to cyclohexylamine would not affect blood pressure or heart rate even in individuals with high metabolizing ability.

Blood pressure changes and sympathetic function in rats given cyclohexylamine by intravenous infusion

Intravenous infusion of cyclohexylamine (30-120 mg/kg) caused a dose-dependent increase in blood pressure in urethane-anesthetized rats. The increase in blood pressure was inversely related to the duration of the infusion. The blood pressure returned to baseline values (+/- 5 mm Hg) within 60 min of the end of the infusion after doses of 30 and 60 mg/kg were administered over 20 and 40 min. The plasma concentrations of cyclohexylamine were related linearly to the administered dose and decreased only 27% between the end of the infusion and 60 min later. The concentration-effect relationship showed clockwise hysteresis, indicative of tachyphylaxis, as has been reported in humans (Eichelbaum et al., 1974). Administration of bolus doses of tyramine at the end of the infusion or 60 min later demonstrated the presence of an indirect sympathomimetic response, although this was attenuated to a greater extent by high doses and more rapid infusions of cyclohexylamine. An almost complete loss of response to tyramine was found only in animals given 120 mg/kg over 40 min. The presence of a tyramine response 60 min after the infusion of 60 mg/kg occurred when there was an essentially complete reversal of the hypertensive effect of cyclohexylamine. These data indicate that the hypertensive effect of the indirectly acting sympathomimetic amine cyclohexylamine occurs primarily during rapid increases in plasma concentrations. Tachyphylaxis develops rapidly after the cessation of the infusion which is probably due largely to reuptake of released noradrenaline at low doses and depletion of releasable noradrenaline at high doses.

Safety factors and establishment of acceptable daily intakes

The acceptable daily intake (ADI) of food additives and other foreign compounds is derived usually by the application of a 100-fold safety factor to the 'no observable adverse effect' level in animal experiments. This safety factor is recognized as comprising two 10-fold factors to allow for possible differences between animals and humans, and for possible differences between individual humans. This paper reviews the adequacy of these safety factors in relation to published data on inter-species and inter-individual differences in both the kinetics and dynamics of foreign compounds. Although the 100-fold factor is reasonable, situations can be envisaged where the scientific data base indicates that considerably higher or lower factors would be more appropriate. A scheme is proposed that would allow structured flexibility to be available in the choice of safety factor to be used in the regulation of foreign compounds.

Organic acids and bases: review of toxicological studies

Organic acids and bases are among the most frequently used chemicals in the manufacturing industries. However, the toxicology of only a number of them has been fully characterized, and for fewer still have occupational exposure limits been established. This paper reviews the acute and chronic toxicity data of the organic acids and bases, and considers the mechanism by which these chemicals produce their effects. A methodology for establishing preliminary occupational exposure limits based on the physicochemical properties of these chemicals is presented. Workplace exposure limits for 20 organic acids and bases which currently have no exposure guidelines are suggested. Advice regarding appropriate medical treatment of exposure to these materials is discussed.

The pharmacokinetics and tissue concentrations of cyclohexylamine in rats and mice

Cyclohexylamine showed dose-dependent kinetics after administration of single oral doses up to 500 mg/kg in rats, with a reduction in plasma clearance, an increase in apparent half-life, and an increased area under the testicular concentration-time curve. Cyclohexylamine was absorbed and eliminated more rapidly by mice. Saturation of cyclohexylamine uptake by rat renal cortical slices in vitro and of renal tubular secretion in vivo occurred at concentrations and doses comparable to the oral dose studies. During chronic dietary administration the concentrations of cyclohexylamine in the plasma and testes showed a pronounced diurnal variation in rats which was not detected in mice. The steady-state plasma clearance in rats was approximately one-half that in mice. The concentrations of cyclohexylamine in the plasma and testes of rats, but not mice, showed a nonlinear relationship to dietary intake. Elevated concentrations were found at intakes greater than 200 mg/kg/day. The pharmacokinetics of cyclohexylamine make an important contribution to the difference in sensitivity to testicular atrophy in rats and mice and the dose-response relationship for this toxicity in rats.

Toxicological aspects of cyclamate and cyclohexylamine

In the late 1960s the artificial sweetener cyclamate was implicated as a bladder carcinogen in rats. This finding and other concerns about its safety ultimately led to a ban on cyclamate in the U.S. and restrictions on its use in many other countries. Since that time, the carcinogenic potential of cyclamate and cyclohexylamine, its principal metabolite, has been reevaluated in a group of well-controlled, well-designed bioassays that have failed to substantiate the earlier findings. This review of the published and unpublished literature on cyclamate attempts to evaluate the carcinogenicity question and other important aspects of the toxicity of cyclamate and cyclohexylamine, including their effects on various organ systems, their genotoxic potential, and their effects on reproduction. In addition, the physiological disposition of cyclamate is reviewed, with particular attention directed toward the site and extent of its conversion to cyclohexylamine.