A comparison of four methods to estimate dim light melatonin onset: a repeatability and agreement study

Dim light melatonin onset (DLMO) is considered the most reliable circadian phase marker in humans. However, the methods to calculate it are diverse, which limits the comparability between studies. Given the key role of DLMO to diagnose circadian rhythm sleep-wake disorders and determine the optimal timing of chronotherapies, the establishment of clear and validated guidelines on the methodology to assess DLMO is very important. We performed a repeatability study (n = 31) and an agreement study (n = 62) in healthy young adults with hourly blood samples collected under dim light conditions (<8 lux) during a chronobiological protocol. We assessed the repeatability of DLMO with three different methods (fixed threshold, dynamic threshold and hockey stick) across two nights and assessed agreement of each method with the mean visual estimation made by four chronobiologists. Analyses included Bland-Altman diagrams, intraclass correlation coefficients and equivalence tests. The repeatability of the four methods across two nights ranged from good to perfect. The agreement study highlighted that the hockey stick showed equivalent or superior performance (ICC: 0.95, mean difference with visual estimation: 5 min) in healthy subjects compared to the dynamic and fixed thresholds. Thanks to its objective nature, the hockey stick method may provide better estimates than the mean of the visual estimations of several raters. These findings suggest that the hockey stick method provides the most reliable estimate of DLMO within the tested methods and should be considered for use in future studies.</p

Lithium response in bipolar disorders and core clock genes expression

<p><b>Objectives:</b> We examine whether the lithium response is associated with changes in the expression of core clock genes.</p> <p><b>Methods:</b> The effect of a therapeutic concentration of lithium (1 mM) on the expression levels of 17 circadian genes was examined in lymphoblastoid cell lines (LCLs) derived from two well-characterized groups of bipolar disorder patients, defined as lithium non-responders (NR, <i>n</i> = 20) or excellent responders (ER, <i>n</i> = 16). Quantitative real-time PCR (qRT-PCR) was conducted at 2, 4 and 8 days (d2, d4 and d8) with and without lithium exposure.</p> <p><b>Results:</b> At d2, in ER only, <i>BHLHE41</i>, <i>RORA</i>, <i>PER1</i>, <i>ARNTL</i>, <i>CRY2</i>, <i>BHLHE40</i> and <i>CSNK1D</i> were upregulated, whereas <i>NR1D1</i> was downregulated. At d4, in ER only, <i>CRY1</i> was downregulated. At d8, in NR only, <i>GSK3β</i> was upregulated and <i>DBP</i>, <i>TIMELESS</i> and <i>CRY1</i> were downregulated. Significant Group × Lithium interactions existed for <i>NR1D1</i> at d2 (<i>P</i> = 0.02), and <i>CRY1</i> at d4 (<i>P</i> = 0.02). Longitudinal analyses showed differential temporal evolutions between NR and ER (significant Time × Group interaction) for <i>PER3</i>, <i>NR1D1</i>, <i>DBP</i>, <i>RORA</i>, <i>CSNK1D and TIMELESS</i>; and a significant Time × Lithium interaction for <i>NR1D1</i>. Coexpression data analyses suggested distinct groups of circadian genes concurrently modulated by lithium.</p> <p><b>Conclusions:</b> In LCLs, lithium influences expression of circadian genes with differences in amplitude and kinetics according to the patient’s lithium response status.</p

Lithium effects on serine-threonine kinases activity: High throughput kinomic profiling of lymphoblastoid cell lines from excellent-responders and non-responders bipolar patients

<p><b>Objectives:</b> Lithium is the leading mood stabiliser for maintenance treatment in bipolar disorder (BD). However, response to lithium is heterogeneous with more than 60% of patients experiencing partial or no response. <i>In vitro</i> and <i>in vivo</i> molecular studies have reported the implication of kinases in the pathophysiology of BD.</p> <p><b>Methods:</b> Since kinases are putative targets for lithium therapeutic action, we conducted the first pilot study using kinase array technology to evaluate the global serine/threonine kinases (STK) profiles in cell lines from BD I subtype patients classified as lithium excellent-responders (ER) and non-responder (NR) to lithium treatment.</p> <p><b>Results:</b> We found significant differences in the basal STK profiles between ER and NR to lithium. We also tested lithium influence on the global STK profile and found no significant difference between ER vs NR cell lines.</p> <p><b>Conclusions:</b> The results obtained in this exploratory study suggest that multiplex kinase activity profiling could provide a complementary approach in the study of biomarkers of therapeutic response in BD.</p