Blood circulating microRNAs (miRNAs) are proposed to be promising biomarkers for many neurodegenerative disorders, including Parkinson’s disease (PD). However, there is a lack of identified differentially expressed miRNAs in PD from different studies. The aim of this study was to evaluate miRNAs expression in PD. We measured plasma circulating miRNA expression in three independent sets with a total of 151 PD patients, 21 multiple system atrophy (MSA) patients and 138 healthy controls using high-throughput RT-PCR. We identified that elevated miR-133b and miR-221-3p discriminated early-stage PD from controls with 94.4% sensitivity and 91.1% specificity. Elevated miR-133b and miR-221-3p distinguished PD from controls with 84.8% sensitivity and 88.9% specificity. In addition, miR-4454 distinguished PD from MSA with 57.1% sensitivity and 82.6% specificity. Hence, elevated miR-133b and miR-221-3p potentially represent good biomarkers for early PD, and a combination of miR-133b, miR-221-3p and miR-4454 has the potential to serve as a non-invasive biomarker for PD diagnosis.

Background and Aims: Sleep is predicted as a key modulator of cognition, but the underlying mechanisms are poorly understood. In this study, we investigated the effects of melatonin on chronic rapid eye movement sleep deprivation (CRSD)‐induced cognitive impairment and circadian dysfunction in rat models.Methods: Thirty‐six Sprague‐Dawley male rats were divided into three groups: CRSD with saline treatment, CRSD with chronic melatonin injection (20 mg/kg/day), and non‐sleep‐deprived control. The cognitive behavioral tests as well as the expression of clocks and HDAC3 were evaluated in all groups.Results: CRSD significantly reduced recognition index in novel object location, increased escape latency and distance traveling in Morris water maze while melatonin treatment attenuated CRSD‐induced hippocampal‐dependent spatial learning and memory deficits. Furthermore, the mRNAs of brain and muscle aryl hydrocarbon receptor nuclear translocator‐like 1(Bmal1) and circadian locomotor output cycles kaput (Clock) were globally down‐regulated by CRSD with constant intrinsic oscillation in both hippocampus and peripheral blood. The protein levels of hippocampal Bmal1, Clock, and HDAC3 were also remarkably down‐regulated following CRSD. Melatonin treatment reversed CRSD‐induced alterations of Bmal1/Clock and HDAC3 on both mRNA levels and protein levels.Conclusions: Our data indicate that melatonin treatment attenuates CRSD‐induced cognitive impairment via regulating HDAC3‐Bmal1/Clock interaction. These findings explore a broader understanding of the relationship between sleep and cognition and provide a potential new therapeutic target for cognitive impairment.