Nocturnal urinary dopamine excretion is reduced in otherwise healthy subjects with periodic leg movements in sleep

Dopamine levels determined in synthetic urine using an electrochemical tyrosinase biosensor based on ZnO@Au core-shell

This work presents a biosensor based on core-shell nanostructure formed by zinc oxide (ZnO) nanoparticles coated with gold (Au). The core-shell nanostructure served as a support for the immobilisation of tyrosinase on screen-printed carbon electrodes to measure dopamine using differential pulse voltammetry. While ZnO is a semiconductor with good electrical conductivity, Au offers high stability and biocompatibility, which is beneficial for maintaining enzyme activity. Atomic force microscopy (ATM), ultraviolet (UV) and infrared (IR) spectroscopy measurements confirmed that the core-shell was successfully formed. The biosensor comprising of ZnO@Au core-shell nanostructures with immobilised tyrosinase allowed the detection of dopamine in real samples with remarkable selectivity and accuracy with a relative error of 3.8%. The limit of detection and dynamic range of the biosensor for dopamine in real samples were 86 nmol L-1 and 0.1 to 500 μmol L-1, respectively. Thus, the results indicate that the proposed miniaturized biosensor device is promising for the monitoring of dopamine in real samples and can be used for disease diagnosis and prognosis. Furthermore, the reported electrochemical biosensor is of low-cost when compared to conventional techniques.

Towards using high-performance liquid chromatography at home

In order to make high-performance liquid chromatography (HPLC) more widely available at home and in small-scale settings, we have simplified two of its most costly modules, namely the pump and the detector. This should make the setup affordable for home or small laboratory use. A manual HPLC pump was constructed so as to fit into a caulk gun from a local hardware store enabling the generation of 100-150 bar of pressure. In order to limit the pressure drop during the running of a chromatogram, a pulse dampener was developed. We further modified the electrochemical detection (ECD) system so as to use a cheap boron-doped diamond electrode with an overlay of thin filter paper, causing an eluent flow over the electrode by wicking and gravity. Both the pump and the detector are at least ten times cheaper than conventional HPLC modules. Using a home-packed Jupiter^Ⓡ Proteo reversed phase capillary column we show how this low-cost HPLC system generates well resolving chromatograms after direct injection of fresh urine. The ECD did not lose its sensitivity during regular use over more than half a year. For homovanillic acid (HVA), which is of medical interest, we measured a linear dynamic range of two orders of magnitude, a detection limit of HVA in the injected sample of 3 μM and a coefficient of variation <10%. The contribution to peak broadening by the detector was much smaller than the contributions by the injector and by the column. After consumption of table olives containing hydroxytyrosol (HT), its metabolite HVA in the corresponding urine could be measured quantitatively. An approach to quantify HT in table olives is presented, as well. This method provides a new tool for investigating physiology of oneself or of dear ones at home.

COMT Val158Met Polymorphism, Cardiometabolic Risk, and Nadir CD4 Synergistically Increase Risk of Neurocognitive Impairment in Men Living With HIV

OBJECTIVE

The Val allele of the Val158Met single-nucleotide polymorphism of the catechol-o-methyltransferase gene (COMT) results in faster metabolism and reduced bioavailability of dopamine (DA). Among persons living with HIV, Val carriers display neurocognitive deficits relative to Met carriers, presumably due to exacerbation of HIV-related depletion of DA. COMT may also impact neurocognition by modulating cardiometabolic function, which is often dysregulated among persons living with HIV. We examined the interaction of COMT, cardiometabolic risk, and nadir CD4 on neurocognitive impairment (NCI) among HIV+ men.

METHODS

Three hundred twenty-nine HIV+ men underwent COMT genotyping and neurocognitive and neuromedical assessments. Cohort-standardized z scores for body mass index, systolic blood pressure, glucose, triglycerides, and high-density lipoprotein cholesterol were averaged to derive a cardiometabolic risk score (CMRS). NCI was defined as demographically adjusted global deficit score of ≥0.5. Logistic regression modeled NCI as a function of COMT, CMRS, and their interaction, covarying for estimated premorbid function, race/ethnicity, and HIV-specific characteristics. Follow-up analysis included the 3-way interaction of COMT, CMRS, and nadir CD4.

RESULTS

Genotypes were 81 (24.6%) Met/Met, 147 (44.7%) Val/Met, and 101 (30.7%) Val/Val. COMT interacted with CMRS (P = 0.02) such that higher CMRS increased risk of NCI among Val/Val [odds ratio (OR) = 2.13, P < 0.01], but not Val/Met (OR = 0.93, P > 0.05) or Met/Met (OR = 0.92, P > 0.05) carriers. Among Val/Val, nadir CD4 moderated the effect of CMRS (P < 0.01) such that higher CMRS increased likelihood of NCI only when nadir CD4 <180.

DISCUSSION

Results suggest a tripartite model by which genetically driven low DA reserve, cardiometabolic dysfunction, and historical immunosuppression synergistically enhance risk of NCI among HIV+ men, possibly due to neuroinflammation and oxidative stress.

Single dose pharmacokinetics of intravenous 3,4-dihydroxyphenylacetic acid and 3-hydroxyphenylacetic acid in rats

3,4-Dihydroxyphenylacetic acid (DOPAC) and 3-hydroxyphenylacetic acid (3-HPAA) are intestinal metabolites of the dietary flavonoid quercetin. DOPAC reportedly showed anxiolytic activity after i.p. administration in rats. The fate of these metabolites after consumption, and the pharmacological properties of 3-HPAA in the body are largely unknown. The aim of the current study was to characterize pharmacokinetic properties of DOPAC and 3-HPAA after intravenous bolus application in rats. UHPLC-MS/MS methods for quantification of DOPAC and 3-HPAA levels in lithium heparin Sprague Dawley rat plasma were developed and validated according to international regulatory guidelines. Non-compartmental and compartmental analyses were performed. Pharmacokinetic profiles of DOPAC and 3-HPAA followed a two-compartment body model, with a fast distribution into peripheral tissues (half-lives of 3.27-5.26 min) and rapid elimination from the body (half-lives of 18.4-33.3 min).

Restless Legs Syndrome: Would You Like That with Movements or Without?

The restless legs syndrome (RLS) is a common sensorimotor condition that often results in discomfort and sleep disturbance. Diagnosis of RLS is entirely clinical and based upon a patient's description of subjective symptoms, and thus when considering RLS diagnosis non-specificity is a real problem. RLS is associated with periodic limb movements during sleep (PLMS) in up to 90% of RLS sufferers; however, their presence is neither sufficient nor necessary for the diagnosis of RLS. The disease RLS and the motor phenomenon of PLMS share similarities in various areas, which include pathophysiology, pharmacology, genetics, and epidemiology. The purpose of this opinion piece is to outline the many similarities between RLS and PLMS in order to make an argument for the inclusion of PLMS as a supplementary diagnostic criterion of RLS, termed electro-clinical RLS, which would consist of the current clinical RLS diagnosis plus PLMS. This additional criterion could be used in cases where diagnosis is unclear to increase specificity or in research projects where proper diagnosis is desired at the investigational level.

Self-reported sleep disturbance is associated with lower CD4 count and 24-h urinary dopamine levels in ethnic minority women living with HIV

BACKGROUND

Sleep disturbance is associated with dopamine dysregulation, which can negatively impact immune status. Individuals living with HIV experience more sleep difficulties, and poor sleep may compound immune decrements associated with HIV infection. Little research has examined associations between sleep, dopamine, and immune status (CD4 count) in individuals with HIV. As ethnic minority women living with HIV (WLWH) are at heightened risk for HIV disease progression, we related sleep reports to both CD4 count and dopamine levels in a cohort of ethnic minority WLWH.

METHODS

Participants were 139 low-income WLWH (ages 20-62; 78.3% African-American or Caribbean) who reported both overall sleep quality and sleep disturbance on the Pittsburgh sleep quality index (PSQI). CD4 count and HIV viral load were measured via morning peripheral venous blood samples, and concentrations of dopamine were measured via 24-h urine collection. Covariates included HIV viral load, length of time since HIV diagnosis, HAART adherence, perceived stress and depression.

RESULTS

After controlling for all covariates, greater sleep disturbance was associated with significantly lower CD4 count (β=-.20, p=.03) and lower levels of dopamine (β=-.25, p=.04). Poorer overall sleep quality was marginally associated with lower CD4 count (β=-.16, p=.08), and was not associated with dopamine.

CONCLUSION

Our analyses suggest that sleep disturbance is independently related with immune status and dopamine levels in WLWH. Lower levels of dopamine may indicate neuroendocrine dysregulation and may impact immune and health status. Results highlight sleep disturbance rather than overall sleep quality as potentially salient to neuroendocrine and immune status in ethnic minority WLWH.

Emotional states of love moderate the association between catecholamines and female sexual responses in the laboratory

INTRODUCTION

Research suggests that there are three interrelated, yet distinct, emotion-motivation brain systems for human love (lust, romantic love, and attachment), each associated with a unique catecholaminergic and hormonal profile. Of interest for the current study are norepinephrine (NE) and dopamine (DA), which have a hypothesized connection with romantic love. As NE and DA are also known to facilitate sexual arousal, it is plausible that NE and DA may have a greater positive association with the sexual arousal responses of women in romantic love compared with women in lust.

AIM

This study investigated if the effects of NE and DA activity on sexual arousal responses would differ depending on emotion-motivation state (Lust or Romantic).

MAIN OUTCOME MEASURES

Physiological sexual arousal was assessed by photoplethysmography and subjective sexual arousal was assessed with a participant-controlled lever.

METHODS

Seventeen women were included in the Lust group and 29 in the Romantic group. All participants provided a urine sample (to assess NE and DA) and completed a psychophysiological assessment.

RESULTS

Elevated NE was positively and significantly associated with greater subjective and physiological sexual arousal for the Lust group, but not for the Romantic group. Similarly, elevated DA was positively and significantly associated with greater subjective sexual arousal for the Lust group, but not for the Romantic group.

CONCLUSIONS

The sexual arousal responses of women in the Lust group, but not in the Romantic group, were positively and significantly associated with elevated NE and DA. It is feasible that, when women are seeking a partner (Lust), NE and DA may facilitate attention toward sexually relevant stimuli.

Update on the management of restless legs syndrome: existing and emerging treatment options

Restless legs syndrome (RLS) is a sensorimotor disorder, characterized by a circadian variation of symptoms involving an urge to move the limbs (usually the legs) as well as paresthesias. There is a primary (familial) and a secondary (acquired) form, which affects a wide variety of individuals, such as pregnant women, patients with end-stage renal disease, iron deficiency, rheumatic disease, and persons taking medications. The symptoms reflect a circadian fluctuation of dopamine in the substantia nigra. RLS patients have lower dopamine and iron levels in the substantia nigra and respond to both dopaminergic therapy and iron administration. Iron, as a cofactor of dopamine production and a regulator of the expression of dopamine type 2-receptor, has an important role in the RLS etiology. In the management of the disease, the first step is to investigate possible secondary causes and their treatment. Dopaminergic agents are considered as the first-line therapy for moderate to severe RLS. If dopaminergic drugs are contraindicated or not efficacious, or if symptoms are resistant and unremitting, gabapentin or other antiepileptic agents, benzodiazepines, or opioids can be used for RLS therapy. Undiagnosed, wrongly diagnosed, and untreated RLS is associated with a significant impairment of the quality of life.

Antidepressants and periodic leg movements of sleep

BACKGROUND

Frequent electroencephalographic arousals or awakenings associated with periodic leg movements (PLM) might be responsible in part for the complaints of sleep disturbances made by patients treated with antidepressants. Past studies, however, have determined the effects of only certain limited antidepressants, generally in small numbers of subjects, and never in a head-to-head study.

METHODS

A total of 274 consecutive patients taking antidepressants and 69 control subjects not taking antidepressants met criteria among patients referred for overnight diagnostic polysomnography. Periodic leg movements were visually counted and the PLM index (PLMI) was calculated.

RESULTS

The venlafaxine and selective serotonin reuptake inhibitor (SSRI) groups had significantly higher mean PLMIs than control and bupropion groups. Periodic leg movement indexes at thresholds considered to be of potential clinical significance were more statistically prevalent in the SSRI and venlafaxine groups compared with the control and bupropion groups. The odds ratio of having a PLMI greater than 20 was 5.15 for the SSRI group and 5.24 for the venlafaxine group compared with the control group.

CONCLUSIONS

Venlafaxine and SSRI-induced PLM are likely to be the result of enhanced serotonergic availability and secondarily decreased dopaminergic effects. The results of this study might assist in the selection of antidepressants, especially in patients with pronounced sleep complaints.

Restless legs syndrome

PURPOSE OF REVIEW

In the review period since February 2004 a number of papers have been published that make significant contributions to the current understanding of the epidemiology, clinical assessment, pathophysiology and treatment of restless legs syndrome. Those with the most significant findings were selected and will be reviewed.

RECENT FINDINGS

Several epidemiological studies about restless legs syndrome have become available in the review period. A new susceptibility locus for restless legs syndrome has been reported. Neuropathological studies have provided profound insights into the key role of iron regulation in the pathophysiology of restless legs syndrome. Several randomized, double-blind, placebo-controlled studies have demonstrated that dopamine agonists are efficacious in the treatment of restless legs syndrome. A few pilot treatment studies with intravenous iron have been performed.

SUMMARY

In this paper, recent advances in the field of restless legs syndrome are reviewed. Special emphasis is placed on pathophysiology and treatment. Restless legs syndrome is still an underdiagnosed disorder. The evidence basis for its treatment has been considerably increased in the review period.