Daily Rhythm of Fractal Cardiac Dynamics Links to Weight Loss Resistance: Interaction with CLOCK 3111T/C Genetic Variant.
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ABSTRACT:
SUBMITTER: Yang HW
PROVIDER: S-EPMC8308644 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Background/objectivesHumans carrying the genetic risk variant C at the circadian CLOCK (Circadian Locomotor Output Cycles Kaput) 3111T/C have been shown to have more difficulties to achieve desired weight loss than TT carriers. We tested the hypothesis that the daily rhythm of autonomic nervous function differs in CLOCK 3111C carriers, leading to reduced effectiveness in weight control.Subjects/methodsWe recruited 40 overweight/obese Caucasian women (body mass index>25), 20 carrying CLOCK 3111C (CC and TC) and 20 non-carriers with matched age and body mass index who participated in a dietary obesity treatment program of up to 30 weeks. Following the treatment, ambulatory electrocardiography was continuously monitored for up to 3.5 days when subjects underwent their normal daily activities. To assess autonomic function, heart rate variability analysis (HRV) was performed hourly to obtain mean inter-beat interval between two consecutive R waves (mean RR) and s.d. of normal-to-normal heartbeat intervals (SDNN), and two parasympathetic measures, namely, proportion of differences between adjacent NN intervals that are >50 ms (pNN50), and high-frequency (HF: 0.15-0.4 Hz) power.ResultsIn the TT carriers, all tested HRV indices showed significant daily rhythms (all P-values <0.0001) with lower mean RR, SDNN, pNN50, and HF during the daytime as compared with the nighttime. The amplitudes of these rhythms except for SDNN were reduced significantly in the C carriers (mean RR: ~19.7%, P=0.001; pNN50: 58.1%, P=0.001; and HF: 41.1%, P=0.001). In addition, subjects with less weight loss during the treatment program had smaller amplitudes in the rhythms of mean RR (P<0.0001), pNN50 (P=0.007) and HF (P=0.003). Furthermore, the rhythmicity-weight loss associations were much stronger in the C carriers as compared to the TT carriers (mean RR: P=0.028, pNN50: P=0.0002; HF: P=0.015).ConclusionsThe daily rhythm of parasympathetic modulation may play a role in the influence of the CLOCK variation on body weight control.
| S-EPMC5799039 | biostudies-literature
Project description:Suprachiasmatic nuclei (SCN) neurons contain an intracellular molecular circadian clock and the Cryptochromes (CRY1/2), key transcriptional repressors of this molecular apparatus, are subject to post-translational modification through ubiquitination and targeting for proteosomal degradation by the ubiquitin E3 ligase complex. Loss-of-function point mutations in a component of this ligase complex, Fbxl3, delay CRY1/2 degradation, reduce circadian rhythm strength, and lengthen the circadian period by ∼2.5 h. The molecular clock drives circadian changes in the membrane properties of SCN neurons, but it is unclear how alterations in CRY1/2 stability affect SCN neurophysiology. Here we use male and female Afterhours mice which carry the circadian period lengthening loss-of-function Fbxl3Afh mutation and perform patch-clamp recordings from SCN brain slices across the projected day/night cycle. We find that the daily rhythm in membrane excitability in the ventral SCN (vSCN) was enhanced in amplitude and delayed in timing in Fbxl3Afh/Afh mice. At night, vSCN cells from Fbxl3Afh/Afh mice were more hyperpolarized, receiving more GABAergic input than their Fbxl3+/+ counterparts. Unexpectedly, the progression to daytime hyperexcited states was slowed by Afh mutation, whereas the decline to hypoexcited states was accelerated. In long-term bioluminescence recordings, GABAA receptor blockade desynchronized the Fbxl3+/+ but not the Fbxl3Afh/Afh vSCN neuronal network. Further, a neurochemical mimic of the light input pathway evoked larger shifts in molecular clock rhythms in Fbxl3Afh/Afh compared with Fbxl3+/+ SCN slices. These results reveal unanticipated consequences of delaying CRY degradation, indicating that the Afh mutation prolongs nighttime hyperpolarized states of vSCN cells through increased GABAergic synaptic transmission.SIGNIFICANCE STATEMENT The intracellular molecular clock drives changes in SCN neuronal excitability, but it is unclear how mutations affecting post-translational modification of molecular clock proteins influence the temporal expression of SCN neuronal state or intercellular communication within the SCN network. Here we show for the first time, that a mutation that prolongs the stability of key components of the intracellular clock, the cryptochrome proteins, unexpectedly increases in the expression of hypoexcited neuronal state in the ventral SCN at night and enhances hyperpolarization of ventral SCN neurons at this time. This is accompanied by increased GABAergic signaling and by enhanced responsiveness to a neurochemical mimic of the light input pathway to the SCN. Therefore, post-translational modification shapes SCN neuronal state and network properties.
| S-EPMC5559760 | biostudies-other
Project description:Proper function of many physiological processes requires a robust circadian clock. Disruptions of the circadian clock can result in metabolic diseases, mood disorders, and accelerated aging. Therefore, identifying small molecules that specifically modulate regulatory core clock proteins may potentially enable better management of these disorders. In this study, we applied a structure-based molecular-docking approach to find small molecules that specifically bind to the core circadian regulator, the transcription factor circadian locomotor output cycles kaput (CLOCK). We identified 100 candidate molecules by virtual screening of ?2 million small molecules for those predicted to bind closely to the interface in CLOCK that interacts with its transcriptional co-regulator, Brain and muscle Arnt-like protein-1 (BMAL1). Using a mammalian two-hybrid system, real-time monitoring of circadian rhythm in U2OS cells, and various biochemical assays, we tested these compounds experimentally and found one, named CLK8, that specifically bound to and interfered with CLOCK activity. We show that CLK8 disrupts the interaction between CLOCK and BMAL1 and interferes with nuclear translocation of CLOCK both in vivo and in vitro Results from further experiments indicated that CLK8 enhances the amplitude of the cellular circadian rhythm by stabilizing the negative arm of the transcription/translation feedback loop without affecting period length. Our results reveal CLK8 as a tool for further studies of CLOCK's role in circadian rhythm amplitude regulation and as a potential candidate for therapeutic development to manage disorders associated with dampened circadian rhythms.
| S-EPMC7076206 | biostudies-literature
Project description:An oscillator consisting of KaiA, KaiB, and KaiC proteins comprises the core of cyanobacterial circadian clock. While one key reaction in this process--KaiC phosphorylation--has been extensively investigated and modeled, other key processes, such as the interactions among Kai proteins, are not understood well. Specifically, different experimental techniques have yielded inconsistent views about Kai A, B, and C interactions. Here, we first propose a mathematical model of cyanobacterial circadian clock that explains the recently observed dynamics of the four phospho-states of KaiC as well as the interactions among the three Kai proteins. Simulations of the model show that the interaction between KaiB and KaiC oscillates with the same period as the phosphorylation of KaiC, but displays a phase delay of ?8 hr relative to the total phosphorylated KaiC. Secondly, this prediction on KaiB-C interaction are evaluated using a novel FRET (Fluorescence Resonance Energy Transfer)-based assay by tagging fluorescent proteins Cerulean and Venus to KaiC and KaiB, respectively, and reconstituting fluorescent protein-labeled in vitro clock. The data show that the KaiB?KaiC interaction indeed oscillates with ?24 hr periodicity and ?8 hr phase delay relative to KaiC phosphorylation, consistent with model prediction. Moreover, it is noteworthy that our model indicates that the interlinked positive and negative feedback loops are the underlying mechanism for oscillation, with the serine phosphorylated-state (the "S-state") of KaiC being a hub for the feedback loops. Because the kinetics of the KaiB-C interaction faithfully follows that of the S-state, the FRET measurement may provide an important real-time probe in quantitative study of the cyanobacterial circadian clock.
| S-EPMC3416856 | biostudies-literature
Project description:Purpose of reviewThe purpose of this review is to summarize recent advances in investigations of dietary factors, genetic factors, and their interactive effects on obesity and weight loss.Recent findingsEven with a tremendous body of research conducted, controversy still abounds regarding the relative effectiveness of various weight-loss diets. Recent advances in genome-wide association studies have made great strides in unraveling the genetic basis of regulation of body weight. In prospective cohorts, reproducible evidence is emerging to show interactions between genetic factors and dietary factors such as sugar-sweetened beverage on obesity. In randomized clinical trials, individuals' genotypes have also been found to modify diet interventions on weight loss, weight maintenance, and changes in related metabolic traits such as lipids, insulin resistance, and blood pressure. However, replication, functional exploration, and translation of the findings into personalized diet interventions remain the chief challenges.SummaryPreliminary but promising data have emerged to lend support to gene-diet interaction in determining weight loss and maintenance; and studies in the area hold great promise to inform future personalized diet interventions on the reduction of obesity and related health problems.
| S-EPMC5330198 | biostudies-literature
Project description:PurposeObesity is prevalent among participants in cardiac rehabilitation (CR). Establishing a weight loss goal is an important strategy for promoting weight loss. We evaluate the association between a pre-program weight loss goal and change in weight during CR.MethodsBody weight was measured at CR entry and at exit from CR. Overweight/obese participants were categorized as having: (1) established a weight loss goal and attended behavioral weight loss sessions (G + BWL); (2) set a weight loss goal but did not attend BWL (G); (3) and neither set a weight loss goal nor attended BWL (NoG).ResultsThe cohort consisted of 317 overweight/obese participants; 52 of whom set a weight loss goal and attended BWL, 227 patients set a goal but did not attend BWL, and 38 did neither. The G + BWL group lost more weight than the G group (-6.8 + 4.3 vs -1.1 + 3.5) (P < .0001). Both groups that established a weight loss goal lost more weight than the NoG group.ConclusionsFor overweight/obese individuals in CR, participating in BWL classes and setting a weight loss goal leads to more weight loss than G alone. Setting a weight loss goal alone leads to greater weight loss than not setting a weight loss goal.
| S-EPMC7647951 | biostudies-literature
Project description:Biological timekeeping is determined by internal temporal programmes and the resetting of these programmes or clocks by external stimuli. Many of the core genes of the mammalian daily or circadian clock are known, but the factors regulating so-called 'clock' gene proteins are unclear. In this issue of the Biochemical Journal, Gallego and colleagues show for the first time that protein phosphatase 1 plays a major role in the stability of mammalian PER2, a key protein in the core clock works. This contrasts somewhat with circadian rhythm control in the fruitfly Drosophila and the fungus Neurospora where current evidence supports a role for protein phosphatase 2A in core timekeeping. The mechanisms underpinning these actions of phosphatase 1 are unclear, and future investigations will need to identify the regulatory subunit that targets phosphatase 1 to mammalian PER2 (Period 2).
| S-EPMC1570164 | biostudies-other
Project description:One hundred ninety wildtype male C57BL/6J mice age 7-10 weeks were purchased from Jackson Laboratory and entrained to a 12:12 light:dark cycle for 2 weeks. Mice were placed in light-tight boxes on a 12:12 LD cycle for 4 weeks, then released into constant darkness. Starting 30 hours after entry into DD (CT18), tissues from 5 (skeletal muscle) or 10 (liver or SCN) wildtype mice were collected every 4 hours for 48 hours, for a total of 12 timepoints. At timepoints 34 through 58 hours in DD, tissues from age-matched male C57BL/6J Clock/Clock homozygous mutant mice that had been treated with the same light entrainment protocol as the wildtype were collected. Tissues were collected from 5 Clock/Clock mutants at each timepoint except for 34 and 46 hours after the onset of DD, when tissues from 10 Clock/Clock mice were collected and run as independent replicates. Mice were sacrificed by cervical dislocation, and the optic nerves were severed in complete darkness; brain dissection was performed using illumination from an infrared viewer (FJW Industries, Palatine, IL). SCNs were dissected out, pooled at a density of 5 per tube in 100 ul RNAlater (Ambion, Austin, TX), frozen on dry ice, and stored at â80 degrees C until use. Keywords: SuperSeries This reference Series links data in the following related Series: GSE3746 Circadian skeletal muscle_wt and Clock mutants GSE3748 Circadian liver_wt and Clock mutants
2010-06-12 | E-GEOD-3751 | biostudies-arrayexpress
Project description:The growth of telomerase-deficient cancers depends on the alternative lengthening of telomeres (ALT), a homology-directed telomere-maintenance pathway. ALT telomeres exhibit a unique chromatin environment and generally lack the nucleosome remodeler ATRX, pointing to an epigenetic basis for ALT. Recently, we identified a protective role for the ATRX-interacting macroH2A1.2 histone variant during homologous recombination and replication stress (RS). Consistent with an inherent susceptibility to RS, we show that human ALT telomeres are highly enriched for macroH2A1.2. However, in contrast to ATRX-proficient cells, ALT telomeres transiently lose macroH2A1.2 during acute RS to facilitate DNA double-strand break (DSB) formation, a process that is almost completely prevented by ectopic ATRX expression. Telomeric macroH2A1.2 is re-deposited in a DNA damage response (DDR)-dependent manner to promote homologous recombination-associated ALT pathways. Our findings thus identify the dynamic exchange of macroH2A1.2 on chromatin as an epigenetic link among ATRX loss, RS-induced DDR initiation and telomere maintenance via homologous recombination.
| S-EPMC6537592 | biostudies-literature
Project description:One hundred ninety wildtype male C57BL/6J mice age 7-10 weeks were purchased from Jackson Laboratory and entrained to a 12:12 light:dark cycle for 2 weeks. Mice were placed in light-tight boxes on a 12:12 LD cycle for 4 weeks, then released into constant darkness. Starting 30 hours after entry into DD (CT18), tissues from 5 (skeletal muscle) or 10 (liver or SCN) wildtype mice were collected every 4 hours for 48 hours, for a total of 12 timepoints. At timepoints 34 through 58 hours in DD, tissues from age-matched male C57BL/6J Clock/Clock homozygous mutant mice that had been treated with the same light entrainment protocol as the wildtype were collected. Tissues were collected from 5 Clock/Clock mutants at each timepoint except for 34 and 46 hours after the onset of DD, when tissues from 10 Clock/Clock mice were collected and run as independent replicates. Mice were sacrificed by cervical dislocation, and the optic nerves were severed in complete darkness; brain dissection was performed using illumination from an infrared viewer (FJW Industries, Palatine, IL). SCNs were dissected out, pooled at a density of 5 per tube in 100 ul RNAlater (Ambion, Austin, TX), frozen on dry ice, and stored at –80 degrees C until use. This SuperSeries is composed of the SubSeries listed below.
2007-02-07 | GSE3751 | GEO