TRIB1 constitutes a molecular link between regulation of sleep and lipid metabolism in humans

Integrative metabolomics and transcriptomics analysis of hippocampus reveals taurine metabolism and sphingolipid metabolism dysregulation associated with sleep deprivation-induced memory impairment

Sleep plays a crucial role in restoring and repairing the body, consolidating memory, regulating emotions, maintaining metabolic and so on. Sleep deprivation is known to impair cognitive functions. In this study, we investigated the mechanisms underlying memory impairment induced by sleep deprivation through a combined metabolomic and transcriptomic analysis of hippocampus. Eight-week-old mice were selected as the study subjects and the sleep deprivation chamber was used to establish a sleep deprivation (SD) model. Novel object recognition tests (NOR), and Y-maze tests were used to assess the behavioral outcomes in mice. The hippocampus were extracted and studied using the untargeted metabolomics or transcriptomics high-throughput sequencing method. An integrative analysis was conducted to elucidate the metabolic and genetic changes. Behavioral tests showed that SD group exhibited memory impairment. Metabolomic analysis identified 84 differentially expressed metabolites (DEMs), including 12 under the positive ion mode and 72 under the negative ion mode. The analysis revealed that sleep deprivation caused abnormalities in several metabolic pathways, with particularly pronounced effects observed in glycerophospholipid metabolism, linoieic acid metabolism, alanine, aspartate, glutamate metabolism, taurine and hypotaurine metabolism, and purine metabolism. While transcriptomic analysis releaved 97 differentially expressed genes (DEGs) (51 were down-regulated and 46 were up-regulated DEGs). Integrative analysis of the metabolomic and transcriptomic identified profiles showed that sleep deprivation may regulate taurine and hypotaurine metabolism and sphingolipid metabolism, there by influencing memory. Our results prompt severe metabolic disturbances occur in the hippocampus with SD in mice, which can provide a basis for the mechanism research.

Association of Insomnia, Lipid Profile, and Lipid-Lowering Medications: A Narrative Review

Sleep is a fundamental phenomenon that helps maintain normal physiological processes. Conversely, sleep disorders, usually presented as insomnia, are a common public health problem that can lead to multiple pathophysiological changes in humans, including lipid metabolic abnormality. Interestingly, several previous studies have examined the potential relation of insomnia to metabolic syndrome and hyperlipidemia and found that insomnia was associated with elevated plasma cholesterol and triglyceride concentrations. This review summarizes evidence regarding the linkage between insomnia and lipid abnormalities. Moreover, the underlying physiologic mechanisms linking insomnia to lipid abnormalities are systemically discussed. Finally, issues with lipid-lowering drugs and the risk of insomnia are also presented. This knowledge can improve our understanding of the pathophysiological features of insomnia, which may help to prevent and treat insomnia-induced dyslipidemia clinically.

PON1 rs662, rs854560 and TRIB1 rs17321515, rs2954029 Gene Polymorphisms Are Associated with Lipid Parameters in Patients with Unstable Angina

Acute coronary heart disease (CHD) is mainly caused by the rupture of an unstable atherosclerotic plaque. Many different factors can cause stenosis or even occlusion of the coronary artery lumen, such as vasculitis and platelet aggregation. Our study was performed to assess the association between PON1 rs662, rs854560 and TRIB1 rs17321515, rs2954029 polymorphisms and the risk of CHD, as well as the association between studied polymorphisms and selected clinical parameters affecting the risk of developing ischemic heart disease. A total of 232 patients with unstable angina were enrolled in this study. There were no statistically significant differences in the PON1 rs662, rs854560 and TRIB1 rs17321515, rs2954029 polymorphism distributions between the total study and control groups. Total cholesterol plasma levels were significantly higher in patients with the PON1 rs662 TT genotype compared to those with the CC+TC genotypes, as well as in patients with the PON1 rs854560 TT genotype compared to those with the AA+AT genotypes. LDL plasma levels were significantly increased in patients with the PON1 rs854560 TT genotype compared to those with the AA+AT genotypes. Plasma levels of HDL were significantly decreased in patients with the TRIB1 rs17321515 AA+AG genotypes compared to those with the GG genotype, as well as in patients with the TRIB1 rs2954029 AA+AT genotypes compared to those with the TT genotype. Our results suggest that the analysed polymorphisms are not risk factors for unstable angina in the Polish population. However, the results of this study indicate an association between the PON1 rs662, rs854560 and TRIB1 rs17321515, rs2954029 polymorphisms with lipid parameters in patients with coronary artery disease.

Genetic study of the causal effect of lipid profiles on insomnia risk: a Mendelian randomization trial

OBJECTIVES

In response to the controversy surrounding observational studies of the association between lipid profiles and the risk of insomnia, the aim of this study was to analyze lipid profiles, including triglycerides (TG), apolipoprotein A-1 (ApoA-1), apolipoprotein B (ApoB) and lipoprotein A (LPA), in a European population to further assess the causal relationship between these lipid types and insomnia.

MATERIALS AND METHODS

This study explores the causal effect of lipid profiles on insomnia based on a genome-wide association study (GWAS)-derived public dataset using two-sample and multivariate Mendelian randomization (MVMR) analysis. The main MR analyses used inverse variance weighting (IVW) odds ratio (OR), and the sensitivity analyses included weighted median (WM) and MR‒Egger.

RESULTS

Both MR and MVMR showed that lowering ApoA-1 and LPA levels had causal effects on the risk of insomnia [MR: per 10 units, ApoA-1: OR: 0.7546, 95% CI: 0.6075-0.9372, P = 0.011; LPA: OR: 0.8392, 95% CI: 0.7202-0.9778, P = 0.025; MVMR: per 10 units, ApoA-1: OR: 0.7600, 95% CI: 0.6362-0.9079, P = 0.002; LPA, OR: 0.903, 95% CI: 0.8283-0.9845, P = 0.021]. There were no causal effects of TG or ApoB on insomnia (all P > 0.05). The MR‒Egger intercept test, funnel plot, and IVW methods all suggested an absence of strong directional pleiotropy, and leave-one-out permutation analysis did not detect any single single-nucleotide polymorphism that had a strong influence on the results.

CONCLUSION

Elevated levels of ApoA-1 and LPA were independently and causally associated with the risk of insomnia, suggesting that elevated ApoA-1 and LPA levels may contribute to a reduced risk of insomnia.

Circadian Clocks, Sleep, and Metabolism

A molecular circadian clock exists not only in the brain, but also in most cells of the body. Research over the past two decades has demonstrated that it directs daily rhythmicity of nearly every aspect of metabolism. It also consolidates sleep-wake behavior each day into an activity/feeding period and a sleep/fasting period. Otherwise, sleep-wake states are mostly controlled by hypothalamic and thalamic regulatory circuits in the brain that direct overall brain state. Recent evidence suggests that hypothalamic control of appetite and metabolism may be concomitant with sleep-wake regulation, and even share the same control centers. Thus, circadian control of metabolic pathways might be overlaid by sleep-wake control of the same pathways, providing a flexible and redundant system to modify metabolism according to both activity and environment.

Current Progress in Delineating the Roles of Pseudokinase TRIB1 in Controlling Human Diseases

Tribbles homolog 1 (TRIB1) is a member of the tribbles family of pseudoprotein kinases and is widely expressed in numerous tissues, such as bone marrow, skeletal muscle, liver, heart, and adipose tissue. It is closely associated with acute myeloid leukemia, prostate cancer, and tumor drug resistance, and can interfere with the hematopoietic stem cell cycle, promote tumor cell proliferation, and inhibit apoptosis. Recent studies have shown that TRIB1 can regulate acute and chronic inflammation by affecting the secretion of inflammatory factors, which is closely related to the occurrence of hyperlipidemia and cardiovascular diseases. Given the important biological functions of TRIB1, the reviews published till now are not sufficiently comprehensive. Therefore, this paper reviews the progress in TRIB1 research aimed at exploring its roles in cancer, hyperlipidemia, and cardiovascular disease, and providing a theoretical basis for further studies on the biological roles of TRIB1.

TRIB1 rs17321515 gene polymorphism increases the risk of coronary heart disease in general population and non-alcoholic fatty liver disease patients in Chinese Han population

Background

Present evidences suggested that TRIB1 rs17321515 polymorphism was tightly associated with the increased risk of NAFLD and CHD. CHD is one of the main complications of NAFLD, whether TRIB1 rs17321515 polymorphism could affect the risk of CHD in general population and NAFLD patients in Chinese Han population was remain unknown. The present study was designed to investigate the association between TRIB1 rs17321515 polymorphism and the risk of CHD in general population and NAFLD patients in Chinese Han population, and investigate the effect of TRIB1 rs17321515 polymorphism on serum lipid levels.

Patients and methods

TRIB1 rs17321515 gene polymorphism was genotyped using the polymerase chain reaction (PCR) in healthy controls (n = 175), CHD patients (n = 155), NAFLD patients (n = 146), and NAFLD+CHD patients (n = 156). Serum lipid profiles were determined using biochemical methods. Statistical analyses were performed using SPSS 24.0 statistical software.

Results

The TRIB1 rs17321515 AA+GA genotypes were the significant risk factors for the CHD in general population (OR = 1.788; 95% CI: 1.104–2.897; P = 0.018) and in the NAFLD patients (OR = 1.760; 95% CI: 1.071–2.891; P = 0.026). After adjusted for age, gender, and body mass index, the risk for CHD in general population (OR = 1.857; 95% CI: 1.116–3.089; P = 0.017) and NAFLD patients was still significant (OR = 1.723; 95% CI: 1.033–2.873; P = 0.037). In addition, TRIB1 rs17321515 A carriers possess the higher lipid profiles in the included subjects.

Conclusions

TRIB1 rs17321515 AA+GA genotypes were significant associated with the risk of CHD in general population and in NAFLD patients in Chinese Han population. The rs17321515 A allele increases the serum lipid profiles in included subjects.

The acyl-CoA Synthetase, pudgy, Promotes Sleep and Is Required for the Homeostatic Response to Sleep Deprivation

The regulation of sleep and the response to sleep deprivation rely on multiple biochemical pathways. A critical connection is the link between sleep and metabolism. Metabolic changes can disrupt sleep, and conversely decreased sleep can alter the metabolic environment. There is building evidence that lipid metabolism, in particular, is a critical part of mounting the homeostatic response to sleep deprivation. We have evaluated an acyl-CoA synthetase, pudgy (pdgy), for its role in sleep and response to sleep deprivation. When pdgy transcript levels are decreased through transposable element disruption of the gene, mutant flies showed lower total sleep times and increased sleep fragmentation at night compared to genetic controls. Consistent with disrupted sleep, mutant flies had a decreased lifespan compared to controls. pdgy disrupted fatty acid handling as pdgy mutants showed increased sensitivity to starvation and exhibited lower fat stores. Moreover, the response to sleep deprivation is reduced when compared to a control flies. When we decreased the transcript levels for pdgy using RNAi, the response to sleep deprivation was decreased compared to background controls. In addition, when the pdgy transcription is rescued throughout the fly, the response to sleep deprivation is restored. These data demonstrate that the regulation and function of acyl-CoA synthetase plays a critical role in regulating sleep and the response to sleep deprivation. Endocrine and metabolic signals that alter transcript levels of pdgy impact sleep regulation or interfere with the homeostatic response to sleep deprivation.

A genetic risk score for CAD, psychological stress, and their interaction as predictors of CAD, fatal MI, non-fatal MI and cardiovascular death

Background

Psychological stress is an independent risk factor for cardiovascular disease (CVD), but the mechanism by which stress is associated with CVD is not entirely understood. Although genetic factors are implied in both stress responsivity and cardiovascular reactivity, no studies to date have investigated their interactions with stress for cardiovascular end points. The objective was to elucidate the association and interactions between a genetic risk score (GRS), individual genetic variants and stress for three cardiovascular end points: coronary artery disease (CAD), fatal myocardial infarction (MI), non-fatal MI, and cardiovascular death.

Methods and findings

18,559 participants from the Malmö Diet Cancer Study, a population-based prospective study, were included in the analyses. Cox proportional hazards regression models were used and adjusted for a large number of known predictors of cardiovascular end points. Mean follow-up time in years was 14.6 (CAD; n = 1938), 14.8 (fatal MI; n = 436), 14.8 (non-fatal MI; n = 1108), and 15.1 (cardiovascular death; n = 1071) respectively. GRS was significantly associated with increased risks of CAD (top quartile hazard ratio [HR], 1.72; 95% confidence interval [CI], 1.51–1.96), fatal MI (top quartile HR, 1.62; 95%CI, 1.23–2.15), non-fatal MI (top quartile HR, 1.55; 95%CI, 1.31–1.84), and cardiovascular death (top quartile HR, 1.29; 95%CI, 1.08–1.53). Stress was not independently associated with any end point and did not interact with GRS. Four individual genetic variants interacted unfavorably with stress for end points with mortality outcomes.

Conclusion

A GRS composed of 50 SNPs and predictive of CAD was found for the first time to also strongly predict fatal MI, non-fatal MI and cardiovascular death. A stress-sensitive component of the GRS was isolated on the basis of individual genetic variants that interacted unfavorably with stress.

Common variants in DRD2 are associated with sleep duration: the CARe consortium

Sleep duration is implicated in the etiologies of chronic diseases and premature mortality. However, the genetic basis for sleep duration is poorly defined. We sought to identify novel genetic components influencing sleep duration in a multi-ethnic sample. Meta-analyses were conducted of genetic associations with self-reported, habitual sleep duration from seven Candidate Gene Association Resource (CARe) cohorts of over 25 000 individuals of African, Asian, European and Hispanic American ancestry. All individuals were genotyped for ∼50 000 SNPs from 2000 candidate heart, lung, blood and sleep genes. African-Americans had additional genome-wide genotypes. Four cohorts provided replication. A SNP (rs17601612) in the dopamine D2 receptor gene (DRD2) was significantly associated with sleep duration (P = 9.8 × 10(-7)). Conditional analysis identified a second DRD2 signal with opposite effects on sleep duration. In exploratory analysis, suggestive association was observed for rs17601612 with polysomnographically determined sleep latency (P = 0.002). The lead DRD2 signal was recently identified in a schizophrenia GWAS, and a genetic risk score of 11 additional schizophrenia GWAS loci genotyped on the IBC array was also associated with longer sleep duration (P = 0.03). These findings support a role for DRD2 in influencing sleep duration. Our work motivates future pharmocogenetics research on alerting agents such as caffeine and modafinil that interact with the dopaminergic pathway and further investigation of genetic overlap between sleep and neuro-psychiatric traits.

Short sleep duration and dietary intake: epidemiologic evidence, mechanisms, and health implications

Links between short sleep duration and obesity, type 2 diabetes, hypertension, and cardiovascular disease may be mediated through changes in dietary intake. This review provides an overview of recent epidemiologic studies on the relations between habitual short sleep duration and dietary intake in adults from 16 cross-sectional studies. The studies have observed consistent associations between short sleep duration and higher total energy intake and higher total fat intake, and limited evidence for lower fruit intake, and lower quality diets. Evidence also suggests that short sleepers may have irregular eating behavior deviating from the traditional 3 meals/d to fewer main meals and more frequent, smaller, energy-dense, and highly palatable snacks at night. Although the impact of short sleep duration on dietary intake tends to be small, if chronic, it may contribute to an increased risk of obesity and related chronic disease. Mechanisms mediating the associations between sleep duration and dietary intake are likely to be multifactorial and include differences in the appetite-related hormones leptin and ghrelin, hedonic pathways, extended hours for intake, and altered time of intake. Taking into account these epidemiologic relations and the evidence for causal relations between sleep loss and metabolism and cardiovascular function, health promotion strategies should emphasize improved sleep as an additional factor in health and weight management. Moreover, future sleep interventions in controlled studies and sleep extension trials in chronic short sleepers are imperative for establishing whether there is a causal relation between short sleep duration and changes in dietary intake.

Dissecting Daily and Circadian Expression Rhythms of Clock-Controlled Genes in Human Blood

The identification and investigation of novel clock-controlled genes (CCGs) has been conducted thus far mainly in model organisms such as nocturnal rodents, with limited information in humans. Here, we aimed to characterize daily and circadian expression rhythms of CCGs in human peripheral blood during a sleep/sleep deprivation (S/SD) study and a constant routine (CR) study. Blood expression levels of 9 candidate CCGs ( SREBF1, TRIB1, USF1, THRA1, SIRT1, STAT3, CAPRIN1, MKNK2, and ROCK2), were measured across 48 h in 12 participants in the S/SD study and across 33 h in 12 participants in the CR study. Statistically significant rhythms in expression were observed for STAT3, SREBF1, TRIB1, and THRA1 in samples from both the S/SD and the CR studies, indicating that their rhythmicity is driven by the endogenous clock. The MKNK2 gene was significantly rhythmic in the S/SD but not the CR study, which implies its exogenously driven rhythmic expression. In addition, we confirmed the circadian expression of PER1, PER3, and REV-ERBα in the CR study samples, while BMAL1 and HSPA1B were not significantly rhythmic in the CR samples; all 5 genes previously showed significant expression in the S/SD study samples. Overall, our results demonstrate that rhythmic expression patterns of clock and selected clock-controlled genes in human blood cells are in part determined by exogenous factors (sleep and fasting state) and in part by the endogenous circadian timing system. Knowledge of the exogenous and endogenous regulation of gene expression rhythms is needed prior to the selection of potential candidate marker genes for future applications in medical and forensic settings.

Diurnal Variation of Hormonal and Lipid Biomarkers in a Molecular Epidemiology-Like Setting

Introduction

Many molecular epidemiology studies focusing on high prevalent diseases, such as metabolic disorders and cancer, investigate metabolic and hormonal markers. In general, sampling for these markers can occur at any time-point during the day or after an overnight fast. However, environmental factors, such as light exposure and food intake might affect the levels of these markers, since they provide input for the internal time-keeping system. When diurnal variation is larger than the inter-individual variation, time of day should be taken into account. Importantly, heterogeneity in diurnal variation and disturbance of circadian rhythms among a study population might increasingly occur as a result of our increasing 24/7 economy and related variation in exposure to environmental factors (such as light and food).

Aim

The aim of the present study was to determine whether a set of often used biomarkers shows diurnal variation in a setting resembling large molecular epidemiology studies, i.e., non-fasted and limited control possibilities for other environmental influences.

Results

We show that markers for which diurnal variation is not an issue are adrenocorticotropic hormone, follicle stimulating hormone, estradiol and high-density lipoprotein. For all other tested markers diurnal variation was observed in at least one gender (cholesterol, cortisol, dehydroepiandrosterone sulfate, free fatty acids, low-density lipoprotein, luteinizing hormone, prolactin, progesterone, testosterone, triglycerides, total triiodothyronine and thyroid-stimulating hormone) or could not reliably be detected (human growth hormone).

Discussion

Thus, studies investigating these markers should take diurnal variation into account, for which we provide some options. Furthermore, our study indicates the need for investigating diurnal variation (in literature or experimentally) before setting up studies measuring markers in routine and controlled settings, especially since time-of-day likely matters for many more markers than the ones investigated in the present study.

Modulators of hepatic lipoprotein metabolism identified in a search for small-molecule inducers of tribbles pseudokinase 1 expression

Recent genome wide association studies have linked tribbles pseudokinase 1 (TRIB1) to the risk of coronary artery disease (CAD). Based on the observations that increased expression of TRIB1 reduces secretion of VLDL and is associated with lower plasma levels of LDL cholesterol and triglycerides, higher plasma levels of HDL cholesterol and reduced risk for myocardial infarction, we carried out a high throughput phenotypic screen based on quantitative RT-PCR assay to identify compounds that induce TRIB1 expression in human HepG2 hepatoma cells. In a screen of a collection of diversity-oriented synthesis (DOS)-derived compounds, we identified a series of benzofuran-based compounds that upregulate TRIB1 expression and phenocopy the effects of TRIB1 cDNA overexpression, as they inhibit triglyceride synthesis and apoB secretion in cells. In addition, the compounds downregulate expression of MTTP and APOC3, key components of the lipoprotein assembly pathway. However, CRISPR-Cas9 induced chromosomal disruption of the TRIB1 locus in HepG2 cells, while confirming its regulatory role in lipoprotein metabolism, demonstrated that the effects of benzofurans persist in TRIB1-null cells indicating that TRIB1 is sufficient but not necessary to transmit the effects of the drug. Remarkably, active benzofurans, as well as natural products capable of TRIB1 upregulation, also modulate hepatic cell cholesterol metabolism by elevating the expression of LDLR transcript and LDL receptor protein, while reducing the levels of PCSK9 transcript and secreted PCSK9 protein and stimulating LDL uptake. The effects of benzofurans are not masked by cholesterol depletion and are independent of the SREBP-2 regulatory circuit, indicating that these compounds represent a novel class of chemically tractable small-molecule modulators that shift cellular lipoprotein metabolism in HepG2 cells from lipogenesis to scavenging.

An epigenetic map of age-associated autosomal loci in northern European families at high risk for the metabolic syndrome

BACKGROUND

The prevalence of chronic diseases such as cancer, type 2 diabetes, metabolic syndrome (MetS), and cardiovascular disease increases with age in all populations. Epigenetic features are hypothesized to play important roles in the pathophysiology of age-associated diseases, but a map of these markers is lacking. We searched for genome-wide age-associated methylation signatures in peripheral blood of individuals at high risks for MetS by profiling 485,000 CpG sites in 192 individuals of Northern European ancestry using the Illumina HM450 array. Subjects (ages 6-85 years) were part of seven extended families, and 73% of adults and 32% of children were overweight or obese.

RESULTS

We found 22,122 genome-wide significant age-associated CpG sites (P α=0.05 = 3.65 × 10(-7) after correction for multiple testing) of which 14,155 are positively associated with age while 7,967 are negatively associated. By applying a positional density-based clustering algorithm, we generated a map of epigenetic 'hot-spots' of age-associated genomic segments, which include 290 age-associated differentially methylated CpG clusters (aDMCs), of which 207 are positively associated with age. Gene/pathway enrichment analyses were performed on these clusters using FatiGO. Genes localized to both the positively (n = 241) and negatively (n = 16) age-associated clusters are significantly enriched in specific KEGG pathways and GO terms. The most significantly enriched pathways are the hedgehog signaling pathway (adjusted P = 3.96 × 10(-3)) and maturity-onset diabetes of the young (MODY) (adjusted P = 6.26 × 10(-3)) in the positive aDMCs and type I diabetes mellitus (adjusted P = 3.69 × 10(-7)) in the negative aDMCs. We also identified several epigenetic loci whose age-associated change rates differ between subjects diagnosed with MetS and those without.

CONCLUSION

We conclude that in a family cohort at high risk for MetS, age-associated epigenetic features enrich in biological pathways important for determining the fate of fat cells and for insulin production. We also observe that several genes known to be related to MetS show differential epigenetic response to age in individuals with and without MetS.

A genome-wide linkage scan of bipolar disorder in Latino families identifies susceptibility loci at 8q24 and 14q32

A genome-wide nonparametric linkage screen was performed to localize Bipolar Disorder (BP) susceptibility loci in a sample of 3757 individuals of Latino ancestry. The sample included 963 individuals with BP phenotype (704 relative pairs) from 686 families recruited from the US, Mexico, Costa Rica, and Guatemala. Non-parametric analyses were performed over a 5 cM grid with an average genetic coverage of 0.67 cM. Multipoint analyses were conducted across the genome using non-parametric Kong & Cox LOD scores along with Sall statistics for all relative pairs. Suggestive and significant genome-wide thresholds were calculated based on 1000 simulations. Single-marker association tests in the presence of linkage were performed assuming a multiplicative model with a population prevalence of 2%. We identified two genome-wide significant susceptibly loci for BP at 8q24 and 14q32, and a third suggestive locus at 2q13-q14. Within these three linkage regions, the top associated single marker (rs1847694, P = 2.40 × 10(-5)) is located 195 Kb upstream of DPP10 in Chromosome 2. DPP10 is prominently expressed in brain neuronal populations, where it has been shown to bind and regulate Kv4-mediated A-type potassium channels. Taken together, these results provide additional evidence that 8q24, 14q32, and 2q13-q14 are susceptibly loci for BP and these regions may be involved in the pathogenesis of BP in the Latino population.

Genetic and Environmental Influences on Individual Differences in Sleep Duration During Adolescence

This study assessed to what extent genetic and environmental factors contributed to individual differences in adolescent sleep duration, and whether genetic and environmental contributions to sleep duration changed throughout adolescence. A twin-family design was used to gain insight into the genetic and environmental contributions to variation in sleep duration. The study sample consisted of 6,319 adolescent twins (44% males) and 1,359 non-twin siblings (44% males) in the age range of 12 to 20 years (mean age = 16.85,SD= 1.40). The participants self-reported usual sleep duration, which was categorized as less than 8 hours per night, 8–9 hours per night, and more than 9 hours per night. Results showed that the prevalence of shorter than optimum sleep duration, that is, less than 8 hours per night, was high, with the highest prevalence rates in later adolescence. The contribution of genetic and environmental factors to individual differences in sleep duration was dependent on age. Variation in sleep duration at the age of 12 years was accounted for by genetic (boys: 34%, girls: 36%), shared environmental (boys: 28%, girls: 45%), and non-shared environmental factors (boys: 38%, girls: 19%). At the age of 20 years, the role of genetic (boys: 47%, girls: 33%) and non-shared environmental factors (boys: 53%, girls: 67%) was more pronounced. It can be concluded from the results that individual differences in sleep duration were accounted for by genetic and non-shared environmental factors throughout adolescence, whereas shared environmental factors account for a substantial part of variation during early adolescence only.

Genetic factors in evolution of sleep length--a longitudinal twin study in Finnish adults

Genetic factors affect many aspects of sleep, such as sleep length. We investigated the contribution of genetic factors to stability and change of sleep length among adults over a 15-year period. In this representative follow-up study we used the Finnish Twin Cohort as the study population. Questionnaire surveys were performed in 1975 (response rate 89%, 11,041 twin pairs; age ≥18 years), 1981 (84%, 9323; ≥24 years) and 1990 (77%, 4507; 33-60 years). Sleep was categorized as short (<7 h), average or long (>8 h). Pairwise similarity in monozygotic and dizygotic pairs was examined at each survey by age group and sex. Quantitative genetic modelling was used to estimate cross-sectional and longitudinal genetic effects. The proportion of variance in sleep length at one point in time that was accounted for by genetic effects was very stable over the study period, being 0.31 in 1975, 0.32 in 1981 and 0.30 in 1990. Longitudinal genetic modelling indicated that the correlations of genetic effects between the three measurement points were high: 0.85 between 1975 and 1981; 0.93 between 1981 and 1990; and 0.76 between 1975 and 1990. Despite a high contribution of environmental effects, their correlations over time were modest: 0.31 between 1975 and 1981; 0.33 between 1981 and 1990; and 0.18 between 1975 and 1990. In conclusion, genetic factors have a modest but stable effect on the evolution of sleep length over a long time span in adults. Multiple measures are a more robust basis for genetic analyses than a single cross-sectional measure.

Mammalian tribbles homologs at the crossroads of endoplasmic reticulum stress and Mammalian target of rapamycin pathways

In 2000, investigators discovered Tribbles, a Drosophila protein that coordinates morphogenesis by inhibiting mitosis. Further work has delineated Xenopus (Xtrb2), Nematode (Nipi-3), and mammalian homologs of Drosophila tribbles, which include TRB1, TRB2, and TRB3. The sequences of tribbles homologs are highly conserved, and despite their protein kinase structure, to date they have not been shown to have kinase activity. TRB family members play a role in the differentiation of macrophages, lymphocytes, muscle cells, adipocytes, and osteoblasts. TRB isoforms also coordinate a number of critical cellular processes including glucose and lipid metabolism, inflammation, cellular stress, survival, apoptosis, and tumorigenesis. TRB family members modulate multiple complex signaling networks including mitogen activated protein kinase cascades, protein kinase B/AKT signaling, mammalian target of rapamycin, and inflammatory pathways. The following review will discuss metazoan homologs of Drosophila tribbles, their structure, expression patterns, and functions. In particular, we will focus on TRB3 function in the kidney in podocytes. This review will also discuss the key signaling pathways with which tribbles proteins interact and provide a rationale for developing novel therapeutics that exploit these interactions to provide better treatment options for both acute and chronic kidney disease.