Physiological and pathological variations in saliva cortisol

Direct vs Mediated Coupling of Antibodies to Gold Nanoparticles: The Case of Salivary Cortisol Detection by Lateral Flow Immunoassay

Stable and efficient conjugates between antibodies and gold nanoparticles (GNP-Ab) are sought to develop highly sensitive and robust biosensors with applications in medicine, toxicology, food safety controls, and targeted drug delivery. Several strategies have been proposed for directing the antibody attachment to GNPs thus preserving antibody activity, including covalently coupling the antibody to a polymer grafted on GNP surface and exploiting the high affinity of bioreceptors as mediators for the binding. Both approaches also allow for shielding GNPs with a protective layer that guarantees the robustness of the conjugate. Notwithstanding, antibodies freely adsorb to GNP with high binding efficiency. The nonspecific adsorption is far more simple, fast, and inexpensive than any mediated coupling. Therefore, it is preferred for most applications, although it is considered to produce GNP-Ab with a limited activity. In this work, we compared three strategies for producing GNP-Ab, such as (i) covalent coupling mediated by a chemical layer, (ii) affinity-based binding mediated by a biomolecular layer composed of Staphylococcal protein A, and (iii) direct attachment via adsorption. The so-prepared GNP-Ab were employed as probes in a colorimetric lateral flow immunoassay (LFIA) for measuring salivary cortisol as a model biosensor that relies on the use of active GNP-Ab conjugates. Unexpectedly, the biosensors fabricated using the three probes were completely comparable in terms of their ability to measure salivary cortisol. Furthermore, we observed that the sensitivity of the LFIA primarily depended on the amount of the antibody bound to GNPs rather than on the method by which it was bound. The probes prepared using both the direct adsorption approach and mediated coupling via the biochemical mediator enabled development of point-of-care devices for the fast, sensitive, and reliable measurement of human salivary cortisol.

Chemical analysis in saliva and the search for salivary biomarkers – a tutorial review

A review of the uses of saliva biomarkers, detection methods and requirements for new biomarkers.

Cushing’s disease: the clinical features, diagnostics, differential diagnostics, and methods of treatment

The present guidelines on diagnostics, differential diagnostics, and methods of treatment of Cushing’s disease have been developed by a group of Russian specialists.

Dysregulation of the Autonomic Nervous System Can Be a Link between Visceral Adiposity and Insulin Resistance

OBJECTIVE

To evaluate the interplay among abdominal adipose tissue distribution, the cortisol axis, the autonomic nervous system, and insulin resistance.

RESEARCH METHODS AND PROCEDURES

Two age-, sex-, and BMI-matched groups were studied. Fifteen subjects were first-degree relatives of patients with type 2 diabetes (R), and 15 had no family history of diabetes (controls, C). A hyperinsulinemic euglycemic clamp, cortisol measurements, and analysis of heart rate variability (HRV) were performed. Computed tomography was performed in a subgroup (n = 9 + 9) to determine abdominal adipose tissue distribution.

RESULTS

R tended to be less insulin-sensitive than C (M value 9.2 +/- 1.0 vs 10.3 +/- 0.7 mg/kg per minute, not significant). Stimulation with tetracosactin or corticotropin releasing hormone yielded lower peak serum cortisol levels in R (p = 0.03 and p = 0.06, respectively). The amount of visceral abdominal fat (VAT) tended to be greater in R. In all subjects, VAT was negatively correlated to insulin sensitivity (r = -0.93, p < 0.001). There was a positive association between VAT and resting heart rate (r = 0.70, p = 0.003) and sympathetic/parasympathetic ratio in HRV assessment after tilt (r = 0.53, p = 0.03). Subcutaneous abdominal tissue was not associated with insulin sensitivity or any of the hormonal or HRV assessments.

DISCUSSION

Subjects genetically predisposed for type 2 diabetes had a tendency toward a larger amount of VAT and to lower insulin sensitivity compared with control subjects. The amount of visceral fat was strongly associated with insulin resistance and signs of a high ratio of sympathetic vs. parasympathetic reactivity. A large amount of visceral fat may act in concert with sympathetic/parasympathetic imbalance to promote the development of insulin resistance, and this may be partly independent of genetic background.

Diagnostic performance of late-night salivary cortisol measured by automated electrochemiluminescence immunoassay in obese and overweight patients referred to exclude Cushing's syndrome

This study estimates diagnostic performance of late-night salivary cortisol (LNSC) as measured by automated electrochemiluminescence immunoassay (ECLIA), evaluates the clinical implication of two consecutive LNSC measurements, and compares its accuracy with enzyme-linked immunosorbent assay (ELISA) and serum cortisol after low-dose dexamethasone suppression test (DST) in obese and overweight patients referred for suspected Cushing's syndrome (CS). One hundred twenty three consecutive obese and overweight referred patients and 98 healthy volunteers provided two saliva samples collected at 23:00 using a Salivette (Sarstedt, Germany), assayed by ECLIA (Cobas e601) and ELISA. The patients underwent DST and were further evaluated until CS was pathologically confirmed (n = 45) or excluded. Diagnostic performance of LNSC was evaluated by receiver operating characteristic (ROC) analysis. The total areas under the curve (AUC) were calculated to compare the different tests. We found that a cut-off value of 9.4 nmol/l can differentiate CS among obese and overweight patients with sensitivity of 84.4 % (95% CI 71.2-92.2), specificity of 92.3 % (95% CI 84.2-96.4), and diagnostic odds ratio of 65.1 (95% CI 20.4-207.6). No difference was found between AUCs from the first, second, and the mean from the two LNSC measurements (ECLIA), LNSC (ELISA), or DST. The single LNSC (ECLIA) and DST improved the sensitivity and specificity for concordant results up to 100 and 97.4 %, respectively. In conclusion, due to its automation and its comparable diagnostic performance, ECLIA is preferable as a first-line LNSC screening test for CS. The initial use of single LNSC followed by DST provides better diagnostic performance for concordant results.

Can non-invasive glucocorticoid measures be used as reliable indicators of stress in animals?

Refinement techniques are being increasingly employed in all fields of animal research to try to ensure that the highest standards of welfare are upheld. This review concerns one of the main emerging techniques for the assessment of welfare itself, namely the non-invasive measurement of glucocorticoids (GCs) as indicators of stress. The paper is divided into three sections. The first discusses the relationship between GCs and stress. The second section considers whether factors other than stress are linked to rises in GCs, eg exercise, oestrus cycle and diet. The final part examines the reliability of the non-invasive techniques that measure GCs from samples of saliva and faeces. Although it is important to take into account some caveats associated with the methodologies employed, it is concluded, nevertheless, that these techniques can give accurate and reliable information regarding the welfare status of an individual or group of animals without the procedures themselves causing any kind of distress to the subjects.

Insulin resistance, endocrine function and adipokines in type 2 diabetes patients at different glycaemic levels: potential impact for glucotoxicity in vivo

OBJECTIVE

To evaluate the interplay between hyperglycaemia, insulin resistance, hormones and adipokines in patients with type 2 diabetes mellitus (T2DM).

DESIGN AND METHODS

Ten patients with T2DM with good glycaemic control (G), 10 with poor control (P) and 10 nondiabetic control subjects (C) were matched for sex (M/F 6/4), age and body mass index. A hyperinsulinaemic, euglycaemic clamp was performed and cytokines and endocrine functions, including cortisol axis activity were assessed.

RESULTS

Patients with diabetes were more insulin resistant than group C, and group P exhibited the highest degree of insulin resistance (P = 0.01, P vs C). Tumour necrosis factor (TNF)-alpha levels were elevated in patients with diabetes (P = 0.05) and group P had the highest levels of fasting serum cortisol (P = 0.05), nonesterified fatty acids (NEFA; P = 0.06) and C-reactive protein (CRP; P = 0.01). Adiponectin levels were lower in the P group. In partial correlation analyses, significant associations were found: glycaemic level (HbA1c) with insulin resistance, TNF-alpha, CRP and basal and ACTH-stimulated cortisol levels, insulin resistance with plasma NEFA, TNF-alpha and stimulated cortisol levels.

CONCLUSION

Poor glycaemic control in patients with T2DM was associated with insulin resistance and with elevated TNF-alpha, CRP and basal as well as stimulated cortisol levels. Inflammatory mediators, e.g. TNF-alpha, may contribute to insulin resistance in hyperglycaemic patients with T2DM and this might be a partial explanation for glucotoxicity.

Bioluminescence immunoassay for cortisol using recombinant aequorin as a label

The analysis of hormones in saliva is a powerful tool in the assessment of a patient's endocrine function, since it allows multiple noninvasive samplings. Since salivary levels of most hormones are 10 to 50 times lower than plasma levels, accurate and highly sensitive assays are needed for saliva measurements. Herein, we describe the development of a solid-phase competitive immunoassay for cortisol in saliva, in which a mutant of the photoprotein aequorin has been used as a label. We have chemically conjugated cortisol to aequorin at different molar ratios. The various cortisol-aequorin conjugates were characterized in terms of bioluminescent activity and affinity for the anti-cortisol antibody. The conjugate that gave the best analytical performance was used for the development of the immunoassay and the analysis of cortisol in saliva samples. The conjugates were stable for at least 6 months when stored at 4 degrees C. The method fulfilled all the standard requirements of precision and accuracy. The optimized immunoassay gave a detection limit of 300 fmol/tube, corresponding to 3 nmol/L, with a linear dynamic range of 10-1000 nmol/L. Therefore, cortisol can be detected down to 0.1 ng in 100 microl of saliva sample using this assay, without any sample pretreatment. This detection limit is almost one order of magnitude lower than the physiological levels of salivary cortisol, which are reported to be 10-25 nmol/L. This allows the quantification of salivary cortisol to be performed in the linear range of the calibration curve, which is most reliable for quantification purposes.

Self-reported dietary restraint is associated with elevated levels of salivary cortisol

Previous studies have found inconsistent relationships between restrained eating, dieting, and cortisol. The present study was designed to clarify the relationship between self-reported restrained eating and cortisol using multiple measures of dietary restraint. Eighty-five college-age women completed the Restraint Scale (RS) and the Cognitive Restraint Scale of the Three Factor Eating Questionnaire (TFEQ-R) and provided a saliva sample for analysis of cortisol. Both measures of restraint were positively associated with elevated levels of salivary cortisol, although the TFEQ-R was more strongly associated than the RS. Restrained eating, characterized by largely unsuccessful efforts to control eating, may lead to elevated cortisol levels.

Anxiety and cortisol excretion correlate prior to dental treatment

The aim of this study was to investigate the possible relationship between dental anxiety and cortisol excretion prior to dental treatment. Trait and state dental anxiety of male subjects were determined using the Dental Anxiety Scale (DAS) and a visual analogue scale (VAS), respectively. Urine and stimulated parotid saliva were collected immediately before dental treatment sessions. Cortisol levels were determined by radioimmunoassay. The self-reported trait dental anxiety (= DAS score) showed a significant relation to the urinary cortisol excretion. The salivary cortisol concentration did not correlate with either VAS or DAS score. The data suggest that dental anxiety has a long-term effect on cortisol metabolism of patients. Therefore, measurement of the cortisol concentration in urine, which reflects a longer term response to stress, seems a promising parameter in the investigation of dental anxiety.

Corticotroph axis sensitivity after exercise in endurance-trained athletes

OBJECTIVE

The present study was conducted in order to describe human hypothalamo-pituitary adrenal (HPA) axis adaptation in a model of repeated physical stress (endurance training) that causes a moderate increase in cortisol levels.

SUBJECTS

We performed the same stimulation tests (adrenal stimulation with ACTH or pituitary stimulation with combined CRH/LVP) in a population of 8 endurance-trained athletes in two distinct situations: resting (baseline cortisol values) and 2 h after the end of strenuous exercise (increased cortisol values) to evaluate the HPA axis sensitivity to endogenous sustained increases in cortisol concentrations.

MEASUREMENTS

During these tests, saliva and plasma cortisol (Fs and Fp, respectively) were assessed and compared.

RESULT

Cortisol values in both plasma and saliva at the end of 2 h of exercise were significantly higher than in rested controls: Fs 11.5 +/- 1.3 vs 6.5 +/- 0.8 nmol.l-1 and Fp 428 +/- 36 vs 279 +/- 27 nmol.l-1 (post exercise vs post rest sessions, respectively, P < 0.001 for both). After either hormone test (CRH/LVP or ACTH), cortisol levels in plasma and saliva increased similarly when rest was compared to post exercise. Saliva variations (delta %) under exogenous hormone stimulation were dramatically greater than plasma variations. For example, under ACTH stimulation, the relative increments in cortisol were on control day: delta Fs 980 +/- 139 vs delta Fp 218 +/- 43% (saliva vs plasma, respectively, P < 0.05) and on exercise day: delta Fs 605 +/- 89 vs delta Fp 102 +/- 14% (saliva vs plasma, respectively, P < 0.05).

CONCLUSIONS

In endurance-trained athletes, displaying a moderate but sustained endogenous cortisol increase: (1) ACTH responses following pituitary stimulation are not blunted, (2) cortisol responses following maximal adrenal stimulation are not blunted. Our results favour the hypothesis of a decreased pituitary sensitivity to cortisol negative feedback whereas the hypothesis of a major decreased adrenal sensitivity to ACTH was discarded. The greater ability of saliva assays to detect a cortisol increase strongly supports its use in the study of HPA physiology, whether under basal or dynamic conditions.

Salivary cortisol testing in children

Biological markers can identify links between human biology and human behavior. Cortisol, a marker of hypothalamic-pituitary-adrenocortical axis function, is a useful measure in research. Newer technology involving the measurement of cortisol in saliva is being utilized in research studies. Salivary cortisol measurement is inexpensive and noninvasive and offers many advantages over serum testing. Although there are various methods of saliva collection, it is relatively easy to perform in both infants and children. Salivary cortisol testing may offer a significant measure for pediatric stress, coping, and health research.

Saliva cortisol and testosterone in the guinea pig: measures for the endocrine function of adrenals and testes?

For collection of saliva, cotton buds (Q-tips) were inserted into the guinea pig's cheek pouch, parallel with the cheek teeth. Within 5 min, sufficient fluid was collected for cortisol and testosterone measurements. In saline-treated animals, saliva cortisol and testosterone were about 15 ng/mL and 1.5 ng/mL, corresponding to plasma levels of 52 ng/mL and 5.9 ng/mL. Within 2-4 h after administration of 20 IU ACTH, saliva and plasma cortisol concentrations were strikingly elevated: saliva: 125 ng/mL (2 h), 157 ng/mL (4 h); plasma: 458 ng/mL (2 h), 736 ng/mL (4 h). This treatment did not influence testosterone in saliva, but reduced it in plasma (2.4 ng/mL (4 h)). In animals receiving 100 IU HCG, saliva testosterone remained unchanged, whereas its plasma levels were markedly raised (9.6 ng/mL (2 h), 12.5 ng/mL (4 h)). These results show that saliva cortisol offers promise as a noninvasive method of monitoring changes in guinea pig adrenocortical function. Saliva testosterone, on the other hand, does not correlate with plasma values; hence it cannot be used to assess testicular function in the guinea pig.

Comparison of time-integrated measurement of salivary corticosteroids by oral diffusion sink technology to plasma cortisol

We report preliminary data on the standardization of a device used in the recently developed "Oral Diffusion Sink" (ODS) technology for the time-integrated measurement of salivary corticosteroids. The concentrations of corticosteroids collected with the ODS devices were compared to plasma cortisol and saliva corticosteroid levels measured simultaneously. Six volunteers installed the ODS devices into their mouths during unstimulated and ACTH (250 micrograms) stimulated periods. Blood and saliva samples were also collected during these periods. The integrated plasma cortisol response and saliva corticosteroid levels were strongly correlated with the time-integrated total corticosteroid measurement of the ODS devices as well as with the cortisol and cortisone fractions. This preliminary data suggests that the accuracy of assessing adrenocortical activity by the measurement of salivary corticosteroids collected with the ODS device is high in both normal and stimulated conditions in normal volunteers. Continued standardization and studies in the practical use of this technology could lead to an important tool in assessing adrenocortical abnormalities. The use of such technology would increase the convenience while reducing the cost and invasiveness of current provocative testing of adrenal functioning.

Assessment of adrenocortical activity in term newborn infants using salivary cortisol determinations

Salivary cortisol concentrations were collected every 2 hours over a 24-hour period in eight healthy 2-day-old term neonates. Two maxima in cortisol output were noted, neither being related to the time of day or time since birth. Salivary cortisol concentrations ranged from 2.5 to 57.4 nmol/L (0.09 to 2.08 micrograms/dL), and throughout the 24 hours showed considerable variation (21% to 42%) not related to the state of arousal. The validity of the method was confirmed by collecting matched plasma and saliva samples from another group of 36 neonates. The correlation between plasma and saliva cortisol was r = 0.83. We suggest that salivary cortisol is a useful, noninvasive method of studying adrenocortical status in the newborn infant.

The effect of oral contraceptives on plasma-free and salivary cortisol and cortisone

The effect of a low estrogen oral contraceptive (OC) on glucocorticoid levels in plasma and saliva as well as glucocorticoid binding was studied in 23 healthy women using 30 micrograms ethinyl estradiol (EE2) + 150 micrograms desogestrel (Marvelon) (II). Fifteen healthy females with normal menses served as controls (I). Blood and salivary samples were taken between 9.00 and 9.30 a.m. on the 18th day of menstrual or pill cycle. Assay accuracy had been optimised by applying extraction and chromatographic purification before radioimmunoassay (RIA) of cortisol and cortisone in both plasma and salivary samples. Free steroid assays were performed by applying the same procedure to equilibrium dialysates obtained after dialysing plasma against an equal volume of buffer, instead of measuring tracer distribution. Corticosteroid Binding Globulin (CBG) was measured by a commercial RIA. As expected, CBG as well as plasma total cortisol were elevated in the pill group. Interestingly both plasma free and salivary cortisol were higher than in controls (free cortisol I: 18.0 +/- 7.95 nmol/l; II: 32.3 +/- 9.03 nmol/l; salivary cortisol I: 9.2 +/- 3.88 nmol/l; II: 18.8 +/- 6.92 nmol/l. Salivary cortisol closely parallelled plasma free cortisol both within and between the groups, though at a much lower level (about 50%). Free cortisone was slightly lower in the pill group (I: 10.8 +/- 2.55 nmol/l; II 8.5 +/- 1.86 nmol/l) whereas salivary cortisone was 2.3 (I) and 4.4 (II) times higher than plasma free cortisone and tended to follow the plasma free and salivary cortisol pattern, both within and between the study groups.(ABSTRACT TRUNCATED AT 250 WORDS)

The diurnal variation and response to dexamethasone suppression test of saliva cortisol level in autistic children

In order to examine the function of hypothalamic-pituitary-adrenal axis (HPA-axis) in autistic children, the diurnal rhythm of saliva cortisol and the response of cortisol to the DST was investigated using saliva samples. 1) The plasma and saliva cortisol levels showed a positive correlation in normal healthy adults. Moreover, the saliva cortisol level exhibited a similar diurnal rhythm and DST response as did the plasma cortisol level. 2) The saliva cortisol level in normal children showed a similar diurnal rhythm and DST response as that in normal healthy adults. 3) Some children with infantile autism showed an abnormal diurnal rhythm or DST response for saliva cortisol. Moreover, the latter abnormality was observed more frequently in poorly-developed cases than in highly-developed cases. 4) These results suggest that the negative feedback mechanism of the HPA-axis may be disturbed in autistic children, especially the poorly-developed cases, owing to a disorder in the regulation by serotonin metabolism.

The measurement of hormones in saliva: possibilities and pitfalls

The easy stress-free, non-invasive nature of saliva collection makes it one of the most accessible body fluids and it is potentially of value in studying normal human physiology as well as pathology. Measurements of salivary hormone levels will usually only be of value if they reflect the plasma level of the hormone and the relationship between the saliva and plasma levels of many hormones have been studied by a number of groups. The measurement of the salivary level is a valuable clinical tool for some hormones (e.g. cortisol, oestriol, progesterone), is of little value for others (e.g. cortisone, dehydroepiandrosterone sulphate, thyroxine, pituitary hormones) and for many others the saliva/plasma relationship is not yet sufficiently understood to assess the value of the salivary measurement. As well as reviewing the state of our knowledge of the salivary concentration of many hormones this review outlines a number of "rules of thumb" concerning the presence of hormones in saliva, their saliva/plasma relationship and the potential usefulness of assays of their salivary concentration.

Hormonal responses to a graded mental workload

Three mental arithmetic tests of graded difficulty were presented to eight young male volunteers on consecutive days. The effort compensation patterns were investigated using urinary catecholamines and salivary cortisol. A significant increase in adrenaline excretion was found in response to all three tests. Urinary adrenaline was partially graded according to the level of difficulty of the tests. The response patterns to mental workload also included a significantly lower noradrenaline/adrenaline ratio and a higher adrenaline/dopamine ratio after the tests. No significant increase was found after the tests for noradrenaline and dopamine. Changes in salivary cortisol concentration during the tests were graded with respect to test difficulty between the easiest and both of the more difficult tests. Salivary cortisol concentration changes are proposed as the basis for field observations involving mental workload. It is concluded that mental workload causes distinguishable effort compensation patterns and that under certain conditions urinary adrenaline and salivary cortisol allow one to distinguish different mental workload levels.

Hormones in saliva

Since the collection of saliva is noninvasive, nonstressful and usually very convenient there have been many recent studies examining the clinical relevance of measuring various hormones in saliva. It now appears that the measurement of most unconjugated steroids in saliva will provide clinically useful data whereas the measurement of conjugated steroids, thyroid hormones, and protein hormones is unlikely to be clinically relevant. The key factors determining whether the salivary concentration of a hormone or drug is likely to be clinically relevant are the mechanisms by which the material enters the saliva; the "free to protein bound" ratio for the material; and the structure of the material, i.e., its molecular weight, polarity and the presence of ionizable groups.

Adrenocorticosteroids: chemistry, synthesis and disturbances in disease

The biosynthesis of adrenocortical steroids is now a reasonably well understood process, which proceeds by discrete, enzyme directed steps from cholesterol to the various hormonal steroids. However, much of our knowledge derives from studies of animal tissues and there is a need for further studies of human glands. In particular, the details of individual enzyme systems, and the extent and significance of compartmentalization of steroid intermediates requires further exploration. The adrenal metabolic errors also merit further study, to clarify some aspects of congenital adrenal hyperplasia and to explain the relationship between biochemical and clinical observations. The advent of immunoassay methods for the measurement of steroid hormone levels in plasma has changed the approach to diagnostic steroid endocrinology, with less emphasis now on the measurement of urinary steroid metabolites, particularly in regard to androgens. The newer and sensitive methods available also allow the assay of steroid hormones in saliva, and the ready availability of this fluid, and the fact that sampling is a non-invasive technique makes salivary steroid assay an attractive alternative to other, traditional methods of investigation requiring blood or urine collection. Inhibitors of steroid biosynthesis and of steroid action have been used with considerable success in diagnostic techniques and to a limited extent in the treatment of steroid disorders. As our understanding of the details of steroid biosynthesis, mechanism of steroid action, and control of steroid secretion improve, further progress in designing clinically useful inhibitors should be possible.