Diurnal regulation of lipid metabolism and applications of circadian lipidomics

Regulation of metabolism by circadian rhythms: Support from time-restricted eating, intestinal microbiota & omics analysis

Circadian oscillatory system plays a key role in coordinating the metabolism of most organisms. Perturbation of genetic effects and misalignment of circadian rhythms result in circadian dysfunction and signs of metabolic disorders. The eating-fasting cycle can act on the peripheral circadian clocks, bypassing the photoperiod. Therefore, time-restricted eating (TRE) can improve metabolic health by adjusting eating rhythms, a process achieved through reprogramming of circadian genomes and metabolic programs at different tissue levels or remodeling of the intestinal microbiota, with omics technology allowing visualization of the regulatory processes. Here, we review recent advances in circadian regulation of metabolism, focus on the potential application of TRE for rescuing circadian dysfunction and metabolic disorders with the contribution of intestinal microbiota in between, and summarize the significance of omics technology.

Oncogenic fatty acid oxidation senses circadian disruption in sleep-deficiency-enhanced tumorigenesis

Circadian disruption predicts poor cancer prognosis, yet how circadian disruption is sensed in sleep-deficiency (SD)-enhanced tumorigenesis remains obscure. Here, we show fatty acid oxidation (FAO) as a circadian sensor relaying from clock disruption to oncogenic metabolic signal in SD-enhanced lung tumorigenesis. Both unbiased transcriptomic and metabolomic analyses reveal that FAO senses SD-induced circadian disruption, as illustrated by continuously increased palmitoyl-coenzyme A (PA-CoA) catalyzed by long-chain fatty acyl-CoA synthetase 1 (ACSL1). Mechanistically, SD-dysregulated CLOCK hypertransactivates ACSL1 to produce PA-CoA, which facilitates CLOCK-Cys194 S-palmitoylation in a ZDHHC5-dependent manner. This positive transcription-palmitoylation feedback loop prevents ubiquitin-proteasomal degradation of CLOCK, causing FAO-sensed circadian disruption to maintain SD-enhanced cancer stemness. Intriguingly, timed β-endorphin resets rhythmic Clock and Acsl1 expression to alleviate SD-enhanced tumorigenesis. Sleep quality and serum β-endorphin are negatively associated with both cancer development and CLOCK/ACSL1 expression in patients with cancer, suggesting dawn-supplemented β-endorphin as a potential chronotherapeutic strategy for SD-related cancer.

Day and Night Reversed Feeding Aggravates High-Fat Diet-Induced Abnormalities in Intestinal Flora and Lipid Metabolism in Adipose Tissue of Mice

BACKGROUND

The incongruity between dietary patterns and the circadian clock poses an elevated risk for metabolic health issues, particularly obesity and associated metabolic disorders. The intestinal microflora engages in regulating various physiological functions of the host through its metabolites.

OBJECTIVES

This study aimed to investigate the impact of reversed feeding schedules during the day and night on intestinal flora and lipid metabolism in high-fat diet-induced obese mice.

METHODS

Mice aged 8-10 wk were subjected to either daytime or nighttime feeding and were administered a control or high-fat diet for 18 wk. At the end of the experiment, various assessments were conducted, including analysis of serum biochemic indices, histologic examination, evaluation of gene and protein expression in adipose tissue, and scrutiny of changes in intestinal microbial composition.

RESULTS

The results showed that day-night reversed feeding caused an increase in fasting blood glucose and exacerbated the high-fat diet-induced weight gain and lipid abnormalities. The mRNA expression levels of Leptin and Dgat1 were increased by day-night reversed feeding, which also reduced the expression level of adiponectin under the high-fat diet. Additionally, there was a significant increase in the protein concentrations of PPARγ, SREBP1c, and CD36. Inverted feeding schedules led to a reduction in intestinal microbial diversity, an increase in the abundance of inflammation-related bacteria, such as Coriobacteriaceae_UCG-002, and a suppression of beneficial bacteria, including Akkermansia, Candidatus_Saccharimonas, Anaeroplasma, Bifidobacterium, Carnobacterium, and Odoribacter. Acinetobacter exhibited a significant negative correlation with Leptin and Fasn, suggesting potential involvement in the regulation of lipid metabolism.

CONCLUSIONS

The results elucidated the abnormalities of lipid metabolism and intestinal flora caused by day-night reversed feeding, which exacerbates the adverse effects of a high-fat diet on lipid metabolism and intestinal microflora. This reversal in feeding patterns may disrupt both intestinal and lipid metabolism homeostasis by altering the composition and abundance of intestinal microflora in mice.

Assessing the Feasibility and Efficacy of Pre-Sleep Dim Light Therapy for Adults with Insomnia: A Pilot Study

Background: Insomnia is increasingly recognized for its marked impact on public health and is often associated with various adverse health outcomes, including cardiovascular diseases and mental health disorders. The aim of this study was to investigate the efficacy of pre-sleep dim light therapy (LT) as a non-pharmacological intervention for insomnia in adults, assessing its influence on sleep parameters and circadian rhythms. Methods: A randomized, open-label, two-arm clinical trial was conducted over two weeks with 40 participants aged 20-60 years, all of whom had sleep disorders (CRIS, KCT0008501). They were allocated into control and LT groups. The LT group received exposure to warm-colored light, minimizing the blue spectrum, before bedtime. The study combined subjective evaluation via validated, sleep-related questionnaires, objective sleep assessments via actigraphy, and molecular analyses of circadian clock gene expression in peripheral blood mononuclear cells. Baseline characteristics between the two groups were compared using an independent t-test for continuous variables and the chi-squared test for categorical variables. Within-group differences were assessed using the paired t-test. Changes between groups were analyzed using linear regression, adjusting for each baseline value and body mass index. The patterns of changes in sleep parameters were calculated using a linear mixed model. Results: The LT group exhibited significant improvements in sleep quality (difference in difference [95% CI]; -2.00 [-3.58, -0.43], and sleep efficiency (LT: 84.98 vs. control: 82.11, p = 0.032), and an advanced Dim Light Melatonin Onset compared to the control group (approximately 30 min). Molecular analysis indicated a significant reduction in CRY1 gene expression after LT, suggesting an influence on circadian signals for sleep regulation. Conclusions: This study provides evidence for the efficacy of LT in improving sleep quality and circadian rhythm alignment in adults with insomnia. Despite limitations, such as a small sample size and short study duration, the results underscore the potential of LT as a viable non-pharmacological approach for insomnia. Future research should expand on these results with larger and more diverse cohorts followed over a longer period to validate and further elucidate the value of LT in sleep medicine. Trial registration: The trial was registered with the Clinical Research Information Service (KCT0008501).

Cord blood lipid correlation network profiles are associated with subsequent attention-deficit/hyperactivity disorder and autism spectrum disorder symptoms at 2 years: a prospective birth cohort study

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) are neurodevelopmental conditions with early life origins. Alterations in blood lipids have been linked to ADHD and ASD; however, prospective early life data are limited. This study examined (i) associations between the cord blood lipidome and ADHD/ASD symptoms at 2 years of age, (ii) associations between prenatal and perinatal predictors of ADHD/ASD symptoms and cord blood lipidome, and (iii) mediation by the cord blood lipidome.

METHODS

From the Barwon Infant Study cohort (1074 mother-child pairs, 52.3% male children), child circulating lipid levels at birth were analysed using ultra-high-performance liquid chromatography-tandem mass spectrometry. These were clustered into lipid network modules via Weighted Gene Correlation Network Analysis. Associations between lipid modules and ADHD/ASD symptoms at 2 years, assessed with the Child Behavior Checklist, were explored via linear regression analyses. Mediation analysis identified indirect effects of prenatal and perinatal risk factors on ADHD/ASD symptoms through lipid modules.

FINDINGS

The acylcarnitine lipid module is associated with both ADHD and ASD symptoms at 2 years of age. Risk factors of these outcomes such as low income, Apgar score, and maternal inflammation were partly mediated by higher birth acylcarnitine levels. Other cord blood lipid profiles were also associated with ADHD and ASD symptoms.

INTERPRETATION

This study highlights that elevated cord blood birth acylcarnitine levels, either directly or as a possible marker of disrupted cell energy metabolism, are on the causal pathway of prenatal and perinatal risk factors for ADHD and ASD symptoms in early life.

FUNDING

The foundational work and infrastructure for the BIS was sponsored by the Murdoch Children's Research Institute, Deakin University, and Barwon Health. Subsequent funding was secured from the Minderoo Foundation, the European Union's Horizon 2020 research and innovation programme (ENDpoiNTs: No 825759), National Health and Medical Research Council of Australia (NHMRC) and Agency for Science, Technology and Research Singapore [APP1149047], The William and Vera Ellen Houston Memorial Trust Fund (via HOMER Hack), The Shepherd Foundation, The Jack Brockhoff Foundation, the Scobie & Claire McKinnon Trust, the Shane O'Brien Memorial Asthma Foundation, the Our Women Our Children's Fund Raising Committee Barwon Health, the Rotary Club of Geelong, the Ilhan Food Allergy Foundation, Geelong Medical and Hospital Benefits Association, Vanguard Investments Australia Ltd, the Percy Baxter Charitable Trust, and Perpetual Trustees.

Circadian clock and lipid metabolism disorders: a potential therapeutic strategy for cancer

Recent research has emphasized the interaction between the circadian clock and lipid metabolism, particularly in relation to tumors. This review aims to explore how the circadian clock regulates lipid metabolism and its impact on carcinogenesis. Specifically, targeting key enzymes involved in fatty acid synthesis (SREBP, ACLY, ACC, FASN, and SCD) has been identified as a potential strategy for cancer therapy. By disrupting these enzymes, it may be possible to inhibit tumor growth by interfering with lipid metabolism. Transcription factors, like SREBP play a significant role in regulating fatty acid synthesis which is influenced by circadian clock genes such as BMAL1, REV-ERB and DEC. This suggests a strong connection between fatty acid synthesis and the circadian clock. Therefore, successful combination therapy should target fatty acid synthesis in addition to considering the timing and duration of drug use. Ultimately, personalized chronotherapy can enhance drug efficacy in cancer treatment and achieve treatment goals.

Serum metabolic alterations in peritoneal dialysis patients with excessive daytime sleepiness

Excessive daytime sleepiness (EDS) is associated with quality of life and all-cause mortality in the end-stage renal disease population. This study aims to identify biomarkers and reveal the underlying mechanisms of EDS in peritoneal dialysis (PD) patients. A total of 48 nondiabetic continuous ambulatory peritoneal dialysis patients were assigned to the EDS group and the non-EDS group according to the Epworth Sleepiness Scale (ESS). Ultra-high-performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry (UHPLC-Q-TOF/MS) was used to identify the differential metabolites. Twenty-seven (male/female, 15/12; age, 60.1 ± 16.2 years) PD patients with ESS ≥ 10 were assigned to the EDS group, while twenty-one (male/female, 13/8; age, 57.9 ± 10.1 years) PD patients with ESS < 10 were defined as the non-EDS group. With UHPLC-Q-TOF/MS, 39 metabolites with significant differences between the two groups were found, 9 of which had good correlations with disease severity and were further classified into amino acid, lipid and organic acid metabolism. A total of 103 overlapping target proteins of the differential metabolites and EDS were found. Then, the EDS-metabolite-target network and the protein-protein interaction network were constructed. The metabolomics approach integrated with network pharmacology provides new insights into the early diagnosis and mechanisms of EDS in PD patients.

Age-related changes in circadian regulation of the human plasma lipidome

Aging alters the amplitude and phase of centrally regulated circadian rhythms. Here we evaluate whether peripheral circadian rhythmicity in the plasma lipidome is altered by aging through retrospective lipidomics analysis on plasma samples collected in 24 healthy individuals (9 females; mean ± SD age: 40.9 ± 18.2 years) including 12 younger (4 females, 23.5 ± 3.9 years) and 12 middle-aged older, (5 females, 58.3 ± 4.2 years) individuals every 3 h throughout a 27-h constant routine (CR) protocol, which allows separating evoked changes from endogenously generated oscillations in physiology. Cosinor regression shows circadian rhythmicity in 25% of lipids in both groups. On average, the older group has a ~14% lower amplitude and a ~2.1 h earlier acrophase of the lipid circadian rhythms (both, p ≤ 0.001). Additionally, more rhythmic circadian lipids have a significant linear component in addition to the sinusoidal across the 27-h CR in the older group (44/56) compared to the younger group (18/58, p < 0.0001). Results from individual-level data are consistent with group-average results. Results indicate that prevalence of endogenous circadian rhythms of the human plasma lipidome is preserved with healthy aging into middle-age, but significant changes in rhythmicity include a reduction in amplitude, earlier acrophase, and an altered temporal relationship between central and lipid rhythms.

The circadian rhythm: an influential soundtrack in the diabetes story

Type 2 Diabetes Mellitus (T2DM) has been the main category of metabolic diseases in recent years due to changes in lifestyle and environmental conditions such as diet and physical activity. On the other hand, the circadian rhythm is one of the most significant biological pathways in humans and other mammals, which is affected by light, sleep, and human activity. However, this cycle is controlled via complicated cellular pathways with feedback loops. It is widely known that changes in the circadian rhythm can alter some metabolic pathways of body cells and could affect the treatment process, particularly for metabolic diseases like T2DM. The aim of this study is to explore the importance of the circadian rhythm in the occurrence of T2DM via reviewing the metabolic pathways involved, their relationship with the circadian rhythm from two perspectives, lifestyle and molecular pathways, and their effect on T2DM pathophysiology. These impacts have been demonstrated in a variety of studies and led to the development of approaches such as time-restricted feeding, chronotherapy (time-specific therapies), and circadian molecule stabilizers.

Spatiotemporal Metabolic Liver Zonation and Consequences on Pathophysiology

Hepatocytes are the main workers in the hepatic factory, managing metabolism of nutrients and xenobiotics, production and recycling of proteins, and glucose and lipid homeostasis. Division of labor between hepatocytes is critical to coordinate complex complementary or opposing multistep processes, similar to distributed tasks at an assembly line. This so-called metabolic zonation has both spatial and temporal components. Spatial distribution of metabolic function in hepatocytes of different lobular zones is necessary to perform complex sequential multistep metabolic processes and to assign metabolic tasks to the right environment. Moreover, temporal control of metabolic processes is critical to align required metabolic processes to the feeding and fasting cycles. Disruption of this complex spatiotemporal hepatic organization impairs key metabolic processes with both local and systemic consequences. Many metabolic diseases, such as nonalcoholic steatohepatitis and diabetes, are associated with impaired metabolic liver zonation. Recent technological advances shed new light on the spatiotemporal gene expression networks controlling liver function and how their deregulation may be involved in a large variety of diseases. We summarize the current knowledge about spatiotemporal metabolic liver zonation and consequences on liver pathobiology.

Genome-Wide Expression Profiling and Networking Reveals an Imperative Role of IMF-Associated Novel CircRNAs as ceRNA in Pigs

Intramuscular fat (IMF) deposition is a biological process that has a strong impact on the nutritional and sensorial properties of meat, with relevant consequences on human health. Pork loins determine the effects of marbling on the sensory attributes and meat quality properties, which differ among various pig breeds. This study explores the crosstalk of non-coding RNAs with mRNAs and analyzes the potential pathogenic role of IMF-associated competing endogenous RNA (ceRNA) in IMF tissues, which offer a framework for the functional validation of key/potential genes. A high-throughput whole-genome transcriptome analysis of IMF tissues from longissimus dorsi muscles of Large White (D_JN) and Laiwu (L_JN) pigs resulted in the identification of 283 differentially expressed circRNAs (DECs), including two key circRNAs (circRNA-23437, circRNA-08840) with potential binding sites for multiple miRNAs regulating the whole network. The potential ceRNA mechanism identified the DEC target miRNAs-mRNAs involved in lipid metabolism, fat deposition, meat quality, and metabolic syndrome via the circRNA-miRNA-mRNA network, concluding that ssc-mir-370 is the most important target miRNA shared by both key circRNAs. TGM2, SLC5A6, ECI1, FASN, PER1, SLC25A34, SOD1, and COL5A3 were identified as hub genes through an intensive protein-protein interaction (PPI) network analysis of target genes acquired from the ceRNA regulatory network. Functional enrichments, pathway examinations, and qRT-PCR analyses infer their implications in fat/cholesterol metabolism, insulin secretion, and fatty acid biosynthesis. Here, circRNAs and miRNA sequencing accompanied by computational techniques were performed to analyze their expressions in IMF tissues from the longissimus dorsi muscles of two pig breeds. Their target gene evolutionary trajectories, expression profiling, functional enrichments, subcellular localizations, and structural advances with high-throughput protein modeling, following genomic organizations, will provide new insights into the underlying molecular mechanisms of adipocyte differentiation and IMF deposition and a much-needed qualitative framework for future research to improve meat quality and its role as a biomarker to treat lipid metabolic syndromes.

The Circadian Regulation of Nutrient Metabolism in Diet-Induced Obesity and Metabolic Disease

Obesity and other metabolic diseases are major public health issues that are particularly prevalent in industrialized societies where circadian rhythmicity is disturbed by shift work, jet lag, and/or social obligations. In mammals, daylight entrains the hypothalamic suprachiasmatic nucleus (SCN) to a ≈24 h cycle by initiating a transcription/translation feedback loop (TTFL) of molecular clock genes. The downstream impacts of the TTFL on clock-controlled genes allow the SCN to set the rhythm for the majority of physiological, metabolic, and behavioral processes. The TTFL, however, is ubiquitous and oscillates in tissues throughout the body. Tissues outside of the SCN are entrained to other signals, such as fed/fasting state, rather than light input. This system requires a considerable amount of biological flexibility as it functions to maintain homeostasis across varying conditions contained within a 24 h day. In the face of either circadian disruption (e.g., jet lag and shift work) or an obesity-induced decrease in metabolic flexibility, this finely tuned mechanism breaks down. Indeed, both human and rodent studies have found that obesity and metabolic disease develop when endogenous circadian pacing is at odds with the external cues. In the following review, we will delve into what is known on the circadian rhythmicity of nutrient metabolism and discuss obesity as a circadian disease.

Emerging Insight Into the Role of Circadian Clock Gene BMAL1 in Cellular Senescence

Cell senescence is a crucial process in cell fate determination and is involved in an extensive array of aging-associated diseases. General perceptions and experimental evidence point out that the decline of physical function as well as aging-associated diseases are often initiated by cell senescence and organ ageing. Therefore, regulation of cell senescence process can be a promising way to handle aging-associated diseases such as osteoporosis. The circadian clock regulates a wide range of cellular and physiological activities, and many age-linked degenerative disorders are associated with the dysregulation of clock genes. BMAL1 is a core circadian transcription factor and governs downstream genes by binding to the E-box elements in their promoters. Compelling evidence has proposed the role of BMAL1 in cellular senescence and aging-associated diseases. In this review, we summarize the linkage between BMAL1 and factors of cell senescence including oxidative stress, metabolism, and the genotoxic stress response. Dysregulated and dampened BMAL1 may serve as a potential therapeutic target against aging- associated diseases.

Effects of fatty acid metabolites on nocturia

Dysregulation of circadian rhythm can cause nocturia. Levels of fatty acid metabolites, such as palmitoylethanolamide (PEA), 9-hydroxy-10E,12Z-octadecadienoic acid (9-HODE), and 4-hydroxy-5E,7Z,10Z,13Z,16Z,19Z-docosahexaenoic acid (4-HDoHE), are higher in the serum of patients with nocturia; however, the reason remains unknown. Here, we investigated the circadian rhythm of fatty acid metabolites and their effect on voiding in mice. WT and Clock mutant (ClockΔ19/Δ19) mice, a model for nocturia with circadian rhythm disorder, were used. Levels of serum PEA, 9-HODE, and 4-HDoHEl were measured every 8 h using LC/MS. Voiding pattern was recorded using metabolic cages after administration of PEA, 9-HODE, and 4-HDoHE to WT mice. Levels of serum PEA and 9-HODE fluctuated with circadian rhythm in WT mice, which were lower during the light phase. In contrast, circadian PEA and 9-HODE level deteriorated or retreated in ClockΔ19/Δ19 mice. Levels of serum PEA, 9-HODE, and 4-HDoHE were higher in ClockΔ19/Δ19 than in WT mice. Voiding frequency increased in PEA- and 4-HDoHE-administered mice. Bladder capacity decreased in PEA-administered mice. The changes of these bladder functions in mice were similar to those in elderly humans with nocturia. These findings highlighted the novel effect of lipids on the pathology of nocturia. These may be used for development of biomarkers and better therapies for nocturia.

CircadiOmic medicine and aging

The earth displays daily, seasonal and annual environmental cycles that have led to evolutionarily adapted ultradian, circadian and infradian rhythmicities in the entire biosphere. All biological organisms must adapt to these cycles that synchronize the function of their circadiome. The objective of this review is to discuss the latest knowledge regarding the role of circadiomics in health and aging. The biological timekeepers are responsive to the environmental cues at microsecond to seasonal time-scales and act with precision of a clock machinery. The robustness of these rhythms is essential to normal daily function of cells, tissues and organs. Mis-alignment of circadian rhythms makes the individual prone to aging, sleep disorders, cancer, diabetes, and neuro-degenerative diseases. Circadian and CircadiOmic medicine are emerging fields that leverage our in-depth understanding of health issues, that arise as a result of disturbances in circadian rhythms, towards establishing better therapeutic approaches in personalized medicine and for geroprotection.

Circadian Regulation and Clock-Controlled Mechanisms of Glycerophospholipid Metabolism from Neuronal Cells and Tissues to Fibroblasts

Along evolution, living organisms developed a precise timekeeping system, circadian clocks, to adapt life to the 24-h light/dark cycle and temporally regulate physiology and behavior. The transcriptional molecular circadian clock and metabolic/redox oscillator conforming these clocks are present in organs, tissues, and even in individual cells, where they exert circadian control over cellular metabolism. Disruption of the molecular clock may cause metabolic disorders and higher cancer risk. The synthesis and degradation of glycerophospholipids (GPLs) is one of the most highly regulated metabolisms across the 24-h cycle in terms of total lipid content and enzyme expression and activity in the nervous system and individual cells. Lipids play a plethora of roles (membrane biogenesis, energy sourcing, signaling, and the regulation of protein-chromatin interaction, among others), making control of their metabolism a vital checkpoint in the cellular organization of physiology. An increasing body of evidence clearly demonstrates an orchestrated and sequential series of events occurring in GPL metabolism across the 24-h day in diverse retinal cell layers, immortalized fibroblasts, and glioma cells. Moreover, the clock gene Per1 and other circadian-related genes are tightly involved in the regulation of GPL synthesis in quiescent cells. However, under proliferation, the metabolic oscillator continues to control GPL metabolism of brain cancer cells even after molecular circadian clock disruption, reflecting the crucial role of the temporal metabolism organization in cell preservation. The aim of this review is to examine the control exerted by circadian clocks over GPL metabolism, their synthesizing enzyme expression and activities in normal and tumorous cells of the nervous system and in immortalized fibroblasts.

Advances in Unhealthy Nutrition and Circadian Dysregulation in Pathophysiology of NAFLD

Unhealthy diets and lifestyle result in various metabolic conditions including metabolic syndrome and non-alcoholic fatty liver disease (NAFLD). Much evidence indicates that disruption of circadian rhythms contributes to the development and progression of excessive hepatic fat deposition and inflammation, as well as liver fibrosis, a key characteristic of non-steatohepatitis (NASH) or the advanced form of NAFLD. In this review, we emphasize the importance of nutrition as a critical factor in the regulation of circadian clock in the liver. We also focus on the roles of the rhythms of nutrient intake and the composition of diets in the regulation of circadian clocks in the context of controlling hepatic glucose and fat metabolism. We then summarize the effects of unhealthy nutrition and circadian dysregulation on the development of hepatic steatosis and inflammation. A better understanding of how the interplay among nutrition, circadian rhythms, and dysregulated metabolism result in hepatic steatosis and inflammation can help develop improved preventive and/or therapeutic strategies for managing NAFLD.

Diurnal regulation of oxidative phosphorylation restricts hepatocyte proliferation and inflammation

The principles guiding the diurnal organization of biological pathways remain to be fully elucidated. Here, we perturb the hepatic transcriptome through nutrient regulators (high-fat diet and mTOR signaling components) to identify enduring properties of pathway organization. Temporal separation and counter-regulation between pathways of energy metabolism and inflammation/proliferation emerge as persistent transcriptome features across animal models, and network analysis identifies the G0s2 and Rgs16 genes as potential mediators at the metabolism-inflammation interface. Mechanistically, G0s2 and Rgs16 are sequentially induced during the light phase, promoting amino acid oxidation and suppressing overall mitochondrial respiration. In their absence, sphingolipids and diacylglycerides accumulate, accompanied by hepatic inflammation and hepatocyte proliferation. Notably, the expression of G0s2 and Rgs16 is further induced in obese mouse livers, and silencing of their expression accentuates hepatic fibrosis. Therefore, diurnal regulation of energy metabolism alleviates inflammatory and proliferative stresses under physiological and pathological conditions.

Identification of a Preliminary Plasma Metabolome-based Biomarker for Circadian Phase in Humans

Measuring individual circadian phase is important to diagnose and treat circadian rhythm sleep-wake disorders and circadian misalignment, inform chronotherapy, and advance circadian science. Initial findings using blood transcriptomics to predict the circadian phase marker dim-light melatonin onset (DLMO) show promise. Alternatively, there are limited attempts using metabolomics to predict DLMO and no known omics-based biomarkers predict dim-light melatonin offset (DLMOff). We analyzed the human plasma metabolome during adequate and insufficient sleep to predict DLMO and DLMOff using one blood sample. Sixteen (8 male/8 female) healthy participants aged 22.4 ± 4.8 years (mean ± SD) completed an in-laboratory study with 3 baseline days (9 h sleep opportunity/night), followed by a randomized cross-over protocol with 9-h adequate sleep and 5-h insufficient sleep conditions, each lasting 5 days. Blood was collected hourly during the final 24 h of each condition to independently determine DLMO and DLMOff. Blood samples collected every 4 h were analyzed by untargeted metabolomics and were randomly split into training (68%) and test (32%) sets for biomarker analyses. DLMO and DLMOff biomarker models were developed using partial least squares regression in the training set followed by performance assessments using the test set. At baseline, the DLMOff model showed the highest performance (0.91 R2 and 1.1 ± 1.1 h median absolute error ± interquartile range [MdAE ± IQR]), with significantly (p < 0.01) lower prediction error versus the DLMO model. When all conditions (baseline, 9 h, and 5 h) were included in performance analyses, the DLMO (0.60 R2; 2.2 ± 2.8 h MdAE; 44% of the samples with an error under 2 h) and DLMOff (0.62 R2; 1.8 ± 2.6 h MdAE; 51% of the samples with an error under 2 h) models were not statistically different. These findings show promise for metabolomics-based biomarkers of circadian phase and highlight the need to test biomarkers that predict multiple circadian phase markers under different physiological conditions.

The transcriptional repressor Rev-erbα regulates circadian expression of the astrocyte Fabp7 mRNA

The astrocyte brain-type fatty-acid binding protein (Fabp7) circadian gene expression is synchronized in the same temporal phase throughout mammalian brain. Cellular and molecular mechanisms that contribute to this coordinated expression are not completely understood, but likely involve the nuclear receptor Rev-erbα (NR1D1), a transcriptional repressor. We performed ChIP-seq on ventral tegmental area (VTA) and identified gene targets of Rev-erbα, including Fabp7. We confirmed that Rev-erbα binds to the Fabp7 promoter in multiple brain areas, including hippocampus, hypothalamus, and VTA, and showed that Fabp7 gene expression is upregulated in Rev-erbα knock-out mice. Compared to Fabp7 mRNA levels, Fabp3 and Fabp5 mRNA were unaffected by Rev-erbα depletion in hippocampus, suggesting that these effects are specific to Fabp7. To determine whether these effects of Rev-erbα depletion occur broadly throughout the brain, we also evaluated Fabp mRNA expression levels in multiple brain areas, including cerebellum, cortex, hypothalamus, striatum, and VTA in Rev-erbα knock-out mice. While small but significant changes in Fabp5 mRNA expression exist in some of these areas, the magnitude of these effects are minimal to that of Fabp7 mRNA expression, which was over 6-fold across all brain regions. These studies suggest that Rev-erbα is a transcriptional repressor of Fabp7 gene expression throughout mammalian brain.

•

The transcriptional repressor Rev-erbα binds to the Fabp7 promoter across brain areas.

•

Multiple Rev-erbα response element binding sites exist on the Fabp7 promoter.

•

Rev-erbα is required for Fabp7 transcriptional repression and circadian expression.

•

Rev-erbα depletion does not affect other Fabp-type gene expression in brain.

Circadian rhythms and the gut microbiome synchronize the host's metabolic response to diet

The molecular circadian clock and symbiotic host-microbe relationships both evolved as mechanisms that enhance metabolic responses to environmental challenges. The gut microbiome benefits the host by breaking down diet-derived nutrients indigestible by the host and generating microbiota-derived metabolites that support host metabolism. Similarly, cellular circadian clocks optimize organismal physiology to the environment by influencing the timing and coordination of metabolic processes. Host-microbe interactions are influenced by dietary quality and timing, as well as daily light/dark cycles that entrain circadian rhythms in the host. Together, the gut microbiome and the molecular circadian clock play a coordinated role in neural processing, metabolism, adipogenesis, inflammation, and disease initiation and progression. This review examines the bidirectional interactions between the circadian clock, gut microbiota, and host metabolic systems and their effects on obesity and energy homeostasis. Directions for future research and the development of therapies that leverage these systems to address metabolic disease are highlighted.

Sympathetic Nervous System Mediates Cardiac Remodeling After Myocardial Infarction in a Circadian Disruption Model

Background: Circadian rhythms have a considerable impact on the daily physiology of the heart, and their disruption causes pathology. Several studies have revealed that circadian disruption impaired cardiac remodeling after myocardial infarction (MI); however, the underlying brain-heart mechanisms remain unknown. We aim to discuss whether circadian disruption facilitates cardiac remodeling after MI by activating sympathetic nervous system.

Methods: Rats were randomly divided into three groups: Sham group (Sham), MI group (MI), and MI+ circadian disruption group (MI+Dis); rats were treated with pseudorabies virus (PRV) injections for trans-synaptic retrograde tracing; rats were randomly divided into two groups: MI+ circadian disruption + Empty Vector+ clozapine N-oxide (CNO) (Empty Vector), and MI+ circadian disruption + hM4D(Gi)+ CNO [hM4D(Gi)].

Results: Circadian disruption significantly facilitated cardiac remodeling after MI with lower systolic function, larger left ventricular volume, and aggravated cardiac fibrosis. Cardiac sympathetic remodeling makers and serum norepinephrine levels were also significantly increased by circadian disruption. PRV virus-labeled neurons were identified in the superior cervical ganglion (SCG), paraventricular nucleus (PVN), and suprachiasmatic nucleus (SCN) regions. Ganglionic blockade via designer receptors exclusively activated by designer drugs (DREADD) technique suppressed the activity of sympathetic nervous system and significantly alleviated the disruption-related cardiac dysfunction.

Conclusion: Circadian disruption adversely affected cardiac remodeling after MI possibly by activating sympathetic nervous system, and suppressing sympathetic activity can attenuate this disruption-related cardiac dysfunction.

Variability of Lipids in Human Milk

Lipids in breastmilk play a critical role in infant growth and development. However, few studies have investigated sources of variability of both high- and low-abundant milk lipids. The objective of our study was to investigate individual and morning-evening differences in the human milk lipidome. In this study, a modified two-phase method (MTBE: Methanol 7:2) was validated for the extraction of lipids from human breastmilk. This method was then applied to samples from a group of 20 healthy women to measure inter- and intra-individual (morning versus evening) variability of the breastmilk lipidome. We report here the levels of 237 lipid species from 13 sub-classes using reversed-phase liquid chromatography mass spectrometry (RP-LCMS) and direct-infusion mass spectrometry (DI-MS). About 85% of lipid species showed stable inter-individual differences across time points. Half of lipid species showed higher concentrations in the evening compared with the morning, with phosphatidylethanolamines (PEs) and triacylglycerols (TAGs) exhibiting the largest changes. In morning and evening samples, the biological variation was greater for diacylglycerols (DAGs) and TAGs compared with phospholipids and sphingolipids, and the variation in DAGs and TAGs was greater in evening samples compared with morning samples. These results demonstrate that variation in the milk lipidome is strongly influenced by individual differences and time of day.

Temporal regulation of tumor growth in nocturnal mammals: In vivo studies and chemotherapeutical potential

Tumors of the nervous system including glioblastoma multiforme (GBM) are the most frequent and aggressive form of brain tumors; however, little is known about the impact of the circadian timing system on the formation, growth, and treatment of these tumors. We investigated day/night differences in tumor growth after injection of A530 glioma cells isolated from malignant peripheral nerve sheath tumor (MPNSTs) of NPcis (Trp53+/- ; Nf1+/- ) mice. Synchronized A530 cell cultures expressing typical glial markers were injected at the beginning of the day or night into the sciatic nerve zone of C57BL/6 mice subject to a 12:12 hours light/dark (LD) cycle or after being released to constant darkness (DD). Tumors generated in animals injected early at night in the LD cycle or in DD showed higher growth rates than in animals injected diurnally. No differences were found when animals were injected at the same time with cultures synchronized 12 hours apart. Similar experiments performed with B16 melanoma cells showed higher tumor growth rates in animals injected at the beginning of the night compared to those injected in the daytime. A higher tumor growth rate than that in controls was observed when mice were injected with knocked-down clock gene Bmal1 cells. Finally, when we compared day/night administration of different doses of the proteasome inhibitor Bortezomib (0.5-1.5 mg/kg) in tumor-bearing animals, we found that low-dose chemotherapy displayed higher efficacy when administered at night. Results suggest the existence of a precise temporal control of tumor growth and of drug efficacy in which the host state and susceptibility are critical.

Suppressing postcollection lysophosphatidic acid metabolism improves the precision of plasma LPA quantification

Lysophosphatidic acid (LPA) is a potent signaling lipid, and state-dependent alterations in plasma LPA make it a promising diagnostic marker for various diseases. However, plasma LPA concentrations vary widely among reports, even under normal conditions. These variations can be attributed, at least in part, to the artificial metabolism of LPA after blood collection. Here, we aimed to develop an optimized plasma preparation method that reflects the concentration of LPA in the circulating blood. The main features of the devised method were suppression of both LPA production and degradation after blood collection by keeping whole blood samples at low temperature followed by the addition of an autotaxin inhibitor to plasma samples. Using this devised method, the LPA level did not change for 30 min after blood collection. Also, human and mouse LPA levels were found to be much lower than those previously reported, ranging from 40 to 50 nM with minimal variation across the individual. Finally, the increased accuracy made it possible to detect circadian rhythms in the levels of certain LPA species in mouse plasma. These results demonstrate the usefulness of the devised plasma preparation method to determine accurate plasma LPA concentrations.

PPARs in liver physiology

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors and transcriptional modulators with crucial functions in hepatic and whole-body energy homeostasis. Besides their well-documented roles in lipid and glucose metabolism, emerging evidence also implicate PPARs in the control of other processes such as inflammatory responses. Recent technological advances, such as single-cell RNA sequencing, have allowed to unravel an unexpected complexity in the regulation of PPAR expression, activity and downstream signaling. Here we provide an overview of the latest advances in the study of PPARs in liver physiology, with a specific focus on formerly neglected aspects of PPAR regulation, such as tissular zonation, cellular heterogeneity, circadian rhythms, sexual dimorphism and species-specific features.

A Lipidomics View of Circadian Biology

Lipidomics approaches provide quantitative characterization of hundreds of lipid species from biological samples. Recent studies highlight the value of these methods in studying circadian biology, and their potential goes far beyond studying lipid metabolism per se. For example, lipidomics analyses of subcellular compartments can be used to determine daily rhythmicity of different organelles and their intracellular dynamics. In this chapter we describe in detail the procedure for around the clock shotgun lipidomics, from sample preparation to bioinformatics analyses. Sample preparation includes biochemical fractionation of nuclei and mitochondria from mouse liver harvested throughout the day. Lipid content is determined and quantified, in unbiased manner and with wide coverage, using multidimensional mass spectrometry shotgun lipidomics (MDMS-SL). Circadian parameters are then determined with nonparametric statistical tests. Overall, the approach described herein is applicable for various animal models, tissues, and organelles, and is expected to yield new insight on various aspects of circadian biology and lipid metabolism.

A Role for Exercise to Counter Skeletal Muscle Clock Disruption

Disruption of the skeletal muscle circadian clock leads to a preferential shift toward lipid oxidation while reducing carbohydrate oxidation. These effects are apparent at the whole-body level, including glucose intolerance, increased energy expenditure, and fasting hyperglycemia. We hypothesize that exercise counters these metabolic disturbances by modifying the skeletal muscle clock and reverting substrate metabolism back toward an optimal substrate balance.

An evidence map of actigraphy studies exploring longitudinal associations between rest-activity rhythms and course and outcome of bipolar disorders

BACKGROUND

Evidence mapping is a structured approach used to synthesize the state-of-the-art in an emerging field of research when systematic reviews or meta-analyses are deemed inappropriate. We employed this strategy to summarise knowledge regarding longitudinal ecological monitoring of rest-activity rhythms (RAR) and disease modifiers, course of illness, treatment response or outcome in bipolar disorders (BD).

STRUCTURE

We had two key aims: (1) to determine the number and type of actigraphy studies of in BD that explored data regarding: outcome over time (e.g. relapse/recurrence according to polarity, or recovery/remission), treatment response or illness trajectories and (2) to examine the range of actigraphy metrics that can be used to estimate disruptions of RAR and describe which individual circadian rhythm or sleep-wake cycle parameters are most consistently associated with outcome over time in BD. The mapping process incorporated four steps: clarifying the project focus, describing boundaries and 'coordinates' for mapping, searching the literature and producing a brief synopsis with summary charts of the key outputs. Twenty-seven independent studies (reported in 29 publications) were eligible for inclusion in the map. Most were small-scale, with the median sample size being 15 per study and median duration of actigraphy being about 7 days (range 1-210). Interestingly, 17 studies comprised wholly or partly of inpatients (63%). The available evidence indicated that a discrete number of RAR metrics are more consistently associated with transition between different phases of BD and/or may be predictive of longitudinal course of illness or treatment response. The metrics that show the most frequent associations represent markers of the amount, timing, or variability of RAR rather than the sleep quality metrics that are frequently targeted in contemporary studies of BD.

CONCLUSIONS

Despite 50 years of research, use of actigraphy to assess RAR in longitudinal studies and examination of these metrics and treatment response, course and outcome of BD is under-investigated. This is in marked contrast to the extensive literature on case-control or cross-sectional studies of actigraphy, especially typical sleep analysis metrics in BD. However, given the encouraging findings on putative RAR markers, we recommend increased study of putative circadian phenotypes of BD.

The Association of Energy and Macronutrient Intake at Dinner Versus Breakfast With Disease-Specific and All-Cause Mortality Among People With Diabetes: The U.S. National Health and Nutrition Examination Survey, 2003-2014

OBJECTIVE

This study aims to evaluate the association of energy and macronutrient intake at dinner versus breakfast with disease-specific and all-cause mortality in people with diabetes.

RESEARCH DESIGN AND METHODS

A total of 4,699 people with diabetes who enrolled in the National Health and Nutrition Examination Survey from 2003 to 2014 were recruited for this study. Energy and macronutrient intake was measured by a 24-h dietary recall. The differences (Δ) in energy and macronutrient intake between dinner and breakfast (Δ = dinner - breakfast) were categorized into quintiles. Death information was obtained from the National Death Index until 2015. Cox proportional hazards regression models were developed to evaluate the survival relationship between Δ and diabetes, cardiovascular disease (CVD), and all-cause mortality.

RESULTS

Among the 4,699 participants, 913 deaths, including 269 deaths due to diabetes and 314 deaths due to CVD, were documented. After adjustment for potential confounders, compared with participants in the lowest quintile of Δ in terms of total energy and protein, participants in the highest quintile were more likely to die due to diabetes (hazard ratio [HR]_Δenergy 1.92, 99% CI 1.08-3.42; HR_Δprotein 1.92, 99% CI 1.06-3.49) and CVD (HR_Δenergy 1.69, 99% CI 1.02-2.80; HR_Δprotein 1.96, 99% CI 1.14-3.39). The highest quintile of Δtotal fat was related to CVD mortality (HR 1.67, 99% CI 1.01-2.76). Isocalorically replacing 5% of total energy at dinner with breakfast was associated with 4% and 5% lower risk of diabetes (HR 0.96, 95% CI 0.94-0.98) and CVD (HR 0.95, 95% CI 0.93-0.97) mortality, respectively.

CONCLUSIONS

Higher intake of energy, total fat, and protein from dinner than breakfast was associated with greater diabetes, CVD, and all-cause mortality in people with diabetes.

Shotgun Lipidomics Discovered Diurnal Regulation of Lipid Metabolism Linked to Insulin Sensitivity in Nondiabetic Men

CONTEXT

Meal timing affects metabolic homeostasis and body weight, but how composition and timing of meals affect plasma lipidomics in humans is not well studied.

OBJECTIVE

We used high throughput shotgun plasma lipidomics to investigate effects of timing of carbohydrate and fat intake on lipid metabolism and its relation to glycemic control.

DESIGN

29 nondiabetic men consumed (1) a high-carb test meal (MTT-HC) at 09.00 and a high-fat meal (MTT-HF) at 15.40; or (2) MTT-HF at 09.00 and MTT-HC at 15.40. Blood was sampled before and 180 minutes after completion of each MTT. Subcutaneous adipose tissue (SAT) was collected after overnight fast and both MTTs. Prior to each investigation day, participants consumed a 4-week isocaloric diet of the same composition: (1) high-carb meals until 13.30 and high-fat meals between 16.30 and 22:00 or (2) the inverse order.

RESULTS

12 hour daily lipid patterns showed a complex regulation by both the time of day (67.8%) and meal composition (55.4%). A third of lipids showed a diurnal variation in postprandial responses to the same meal with mostly higher responses in the morning than in the afternoon. Triacylglycerols containing shorter and more saturated fatty acids were enriched in the morning. SAT transcripts involved in fatty acid synthesis and desaturation showed no diurnal variation. Diurnal changes of 7 lipid classes were negatively associated with insulin sensitivity, but not with glucose and insulin response or insulin secretion.

CONCLUSIONS

This study identified postprandial plasma lipid profiles as being strongly affected by meal timing and associated with insulin sensitivity.

Photoperiod Manipulation Affects Transcriptional Profile of Genes Related to Lipid Metabolism and Apoptosis in Zebrafish (Danio rerio) Larvae: Potential Roles of Gut Microbiota

Gut microbiota plays a fundamental role in maintaining host's health by controlling a wide range of physiological processes. Administration of probiotics and manipulation of photoperiod have been suggested as modulators of microbial composition and are currently undergoing an extensive research in aquaculture as a way to improve health and quality of harvested fish. However, our understanding regarding their effects on physiological processes is still limited. In the present study we investigated whether manipulation of photoperiod and/or probiotic administration was able to alter microbial composition in zebrafish larvae at hatching stage. Our findings show that probiotic does not elicit effects while photoperiod manipulation has a significant impact on microbiota composition. Moreover, we successfully predicted lipid biosynthesis and apoptosis to be modulated by microbial communities undergoing continuous darkness. Interestingly, expression levels of caspase 3 gene (casp3) and lipid-related genes (hnf4a, npc1l1, pparγ, srebf1, agpat4 and fitm2) were found to be significantly overexpressed in dark-exposed larvae, suggesting an increase in the occurrence of apoptotic processes and a lipid metabolism impairment, respectively (p < 0.05). Our results provide the evidence that microbial communities in zebrafish at early life stages are not modulated by a short administration of probiotics and highlight the significant effect that dark photoperiod elicits on zebrafish microbiota and potentially on health.

A circadian rhythm-related MTNR1B genetic variant (rs10830963) modulate body weight change and insulin resistance after 9 months of a high protein/low carbohydrate vs a standard hypocaloric diet

BACKGROUND & AIMS

The risk allele (G) of rs10830963 in the melatonin receptor 1 B (MTNR1B) gene presents an association with biochemical parameters and obesity. We study the effect of this SNP on insulin resistance and weight loss secondary to two hypocaloric diets.

METHODS

270 obese subjects were randomly allocated during 9 months (Diet HP: a high protein/low carbohydrate vs. Diet S: a standard severe hypocaloric diets). Anthropometric parameters, fasting blood glucose, C-reactive protein (CRP), insulin concentration, insulin resistance (HOMA-IR), lipid profile and adipocytokines levels were measured. Genotype of MTNR1B gene polymorphism (rs10830963) was evaluated.

RESULTS

All adiposity parameters, systolic blood pressure and leptin levels decreased in all subjects after both diets. This improvement of adiposity parameters was higher in non-G allele carriers than G allele carriers. After weight loss with Diet HP, (CC vs. CG + GG at 9 months); total cholesterol (delta: -9.9 ± 2.4 mg/dl vs. -4.8 ± 2.2 mg/dl:p < 0.05), LDL-cholesterol (delta: -8.3 ± 1.9 mg/dl vs. -5.1 ± 2.2 mg/dl: p < 0.05), insulin (delta: -4.7 ± 0.8 UI/L vs. -0.9 ± 1.0 UI/L: p < 0.05), triglycerides (delta: -17.7 ± 3.9 mg/dl vs. -6.1 ± 2.8 mg/dl: p < 0.05) and HOMA IR (delta: -0.8 ± 0.2 units vs. -0.2 ± 0.1 units: p < 0.05) improved only in no G allele carriers. After weight loss with Diet S in non G allele carriers, insulin levels (delta (CC vs. CG + GG): -3.4 ± 0.6 UI/L vs. -1.2 ± 0.4 UI/L: p < 0.05), triglycerides (delta: -29.2 ± 3.4 mg/dl vs. -8.2 ± 3.8 mg/dl: p < 0.05), HOMA-IR (delta (CC vs. CG + GG): -1.1 ± 0.2 units vs. -0.1 ± 0.1 units: p < 0.05), total cholesterol (delta: -15.9 ± 7.4 mg/dl vs. -5.8 ± 2.9 mg/dl:ns) and LDL-cholesterol (delta: -13.7 ± 5.9 mg/dl vs. -6.0 ± 2.9 mg/dl: ns) decreased, too.

CONCLUSIONS

our study detected a relationship of rs10830963 variant of MTNR1B gene with adiposity changes, cholesterol changes and insulin resistance modification induced by two different hypocaloric during 9 months.

Diurnal rhythm of plasma EPA and DHA in healthy adults

Knowledge of the diurnal variation in circulating omega-3 polyunsaturated fatty acids (n-3 PUFAs) may be an important consideration for the development of dosing protocols designed to optimise tissue delivery of these fatty acids. The objective of the current study was to examine the variation in plasma concentrations of eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) over a 24-h period in healthy adults under eating and sleeping conditions generally approximate to a free-living environment. Twenty-one healthy participants aged 25-44 years took part in a single laboratory visit encompassing an overnight stay. EPA and DHA were measured in plasma samples collected every two hours from 22:00 until 22:00 the following day, with all meals being provided at conventional times. Cosinor analysis was used to estimate the diurnal variation in each fatty acid from pooled data across all participants. A significant diurnal variation in the pooled plasma concentrations of both fatty acids was detected. However, evidence of distinct rhythmicity was strongest for DHA. The timing of the peak concentration of DHA was 17:43 with a corresponding nadir at 05:43. In comparison, the observed acrophase for EPA was delayed by three hours, occurring at 20:41, with a nadir at 08:41. This is the first time that the diurnal variation in these important bioactive fatty acids has been described in a sample of healthy adults following a normal pattern of eating and sleeping. In the absence of any dietary intake of EPA and DHA, circulating levels of these fatty acids fall during the overnight period and reach their lowest point in the morning. Consumption of n-3 PUFAs at night time, which counteracts this pattern, may have functional significance.

Circadian Clock Regulation on Lipid Metabolism and Metabolic Diseases

The basic helix-loop-helix-PAS transcription factor (CLOCK, Circadian locomotor output cycles protein kaput) was discovered in 1994 as a circadian clock. Soon after its discovery, the circadian clock, Aryl hydrocarbon receptor nuclear translocator-like protein 1 (ARNTL, also call BMAL1), was shown to regulate adiposity and body weight by controlling on the brain hypothalamic suprachiasmatic nucleus (SCN). Farther, circadian clock genes were determined to exert several of lipid metabolic and diabetes effects, overall indicating that CLOCK and BMAL1 act as a central master circadian clock. A master circadian clock acts through the neurons and hormones, with expression in the intestine, liver, kidney, lung, heart, SCN of brain, and other various cell types of the organization. Among circadian clock genes, numerous metabolic syndromes are the most important in the regulation of food intake (via regulation of circadian clock genes or clock-controlled genes in peripheral tissue), which lead to a variation in plasma phospholipids and tissue phospholipids. Circadian clock genes affect the regulation of transporters and proteins included in the regulation of phospholipid metabolism. These genes have recently received increasing recognition because a pharmacological target of circadian clock genes may be of therapeutic worth to make better resistance against insulin, diabetes, obesity, metabolism syndrome, atherosclerosis, and brain diseases. In this book chapter, we focus on the regulation of circadian clock and summarize its phospholipid effect as well as discuss the chemical, physiology, and molecular value of circadian clock pathway regulation for the treatment of plasma lipids and atherosclerosis.

MS-based targeted metabolomics of eicosanoids and other oxylipins: Analytical and inter-individual variabilities

Oxylipins, including the well-known eicosanoids, are potent lipid mediators involved in numerous physiological and pathological processes. Therefore, their quantitative profiling has gained a lot of attention during the last years notably in the active field of health biomarker discovery. Oxylipins include hundreds of structurally and stereochemically distinct lipid species which today are most commonly analyzed by (ultra) high performance liquid chromatography-mass spectrometry based ((U)HPLC-MS) methods. To maximize the utility of oxylipin profiling in clinical research, it is crucial to understand and assess the factors contributing to the analytical and biological variability of oxylipin profiles in humans. In this review, these factors and their impacts are summarized and discussed, providing a framework for recommendations expected to enhance the interlaboratory comparability and biological interpretation of oxylipin profiling in clinical research.

The Association of Polymorphisms in Circadian Clock and Lipid Metabolism Genes With 2nd Trimester Lipid Levels and Preterm Birth

Deregulation of the circadian system in humans and animals can lead to various adverse reproductive outcomes due to genetic mutations and environmental factors. In addition to the clock, lipid metabolism may also play an important role in influencing reproductive outcomes. Despite the importance of the circadian clock and lipid metabolism in regulating birth timing few studies have examined the relationship between circadian genetics with lipid levels during pregnancy and their relationship with preterm birth (PTB). In this study we aimed to determine if single nucleotide polymorphisms (SNPs) in genes from the circadian clock and lipid metabolism influence 2^nd trimester maternal lipid levels and if this is associated with an increased risk for PTB. We genotyped 72 SNPs across 40 genes previously associated with various metabolic abnormalities on 930 women with 2^nd trimester serum lipid measurements. SNPs were analyzed for their relationship to levels of total cholesterol, high density lipoprotein (HDL), low density lipoprotein (LDL) and triglycerides (TG) using linear regression. SNPs were also evaluated for their relationship to PTB using logistic regression. Five SNPs in four genes met statistical significance after Bonferroni correction (p < 1.8 × 10^-4) with one or more lipid levels. Of these, four SNPs were in lipid related metabolism genes: rs7412 in APOE with total cholesterol, HDL and LDL, rs646776 and rs599839 in CELSR2-PSRC1-SORT1 gene cluster with total cholesterol, HDL and LDL and rs738409 in PNPLA3 with HDL and TG and one was in a circadian clock gene: rs228669 in PER3 with TG. Of these SNPs only PER3 rs228669 was marginally associated with PTB (p = 0.02). In addition, PER3 rs228669 acts as an effect modifier on the relationship between TG and PTB.

Chronic intermittent electronic cigarette exposure induces cardiac dysfunction and atherosclerosis in apolipoprotein-E knockout mice

Electronic cigarettes (e-cigarettes), also known as electronic nicotine delivery systems, are a popular alternative to conventional nicotine cigarettes, both among smokers and those who have never smoked. In spite of the widespread use of e-cigarettes and the proposed detrimental cardiac and atherosclerotic effects of nicotine, the effects of e-cigarettes on these systems are not known. In this study, we investigated the cardiovascular and cardiac effects of e-cigarettes with and without nicotine in apolipoprotein-E knockout (ApoE^-/-) mice. We developed an e-cigarette exposure model that delivers nicotine in a manner similar to that of human e-cigarettes users. Using commercially available e-cigarettes, bluCig PLUS, ApoE^-/- mice were exposed to saline, e-cigarette without nicotine [e-cigarette (0%)], and e-cigarette with 2.4% nicotine [e-cigarette (2.4%)] aerosol for 12 wk. Echocardiographic data show that mice treated with e-cigarette (2.4%) had decreased left ventricular fractional shortening and ejection fraction compared with e-cigarette (0%) and saline. Ventricular transcriptomic analysis revealed changes in genes associated with metabolism, circadian rhythm, and inflammation in e-cigarette (2.4%)-treated ApoE^-/- mice. Transmission electron microscopy revealed that cardiomyocytes of mice treated with e-cigarette (2.4%) exhibited ultrastructural abnormalities indicative of cardiomyopathy. Additionally, we observed increased oxidative stress and mitochondrial DNA mutations in mice treated with e-cigarette (2.4%). ApoE^-/- mice on e-cigarette (2.4%) had also increased atherosclerotic lesions compared with saline aerosol-treated mice. These results demonstrate adverse effects of e-cigarettes on cardiac function in mice.NEW & NOTEWORTHY The present study is the first to show that mice exposed to nicotine electronic cigarettes (e-cigarettes) have decreased cardiac fractional shortening and ejection fraction in comparison with controls. RNA-seq analysis reveals a proinflammatory phenotype induced by e-cigarettes with nicotine. We also found increased atherosclerosis in the aortic root of mice treated with e-cigarettes with nicotine. Our results show that e-cigarettes with nicotine lead to detrimental effects on the heart that should serve as a warning to e-cigarette users and agencies that regulate them.

Atlas of Circadian Metabolism Reveals System-wide Coordination and Communication between Clocks

Metabolic diseases are often characterized by circadian misalignment in different tissues, yet how altered coordination and communication among tissue clocks relate to specific pathogenic mechanisms remains largely unknown. Applying an integrated systems biology approach, we performed 24-hr metabolomics profiling of eight mouse tissues simultaneously. We present a temporal and spatial atlas of circadian metabolism in the context of systemic energy balance and under chronic nutrient stress (high-fat diet [HFD]). Comparative analysis reveals how the repertoires of tissue metabolism are linked and gated to specific temporal windows and how this highly specialized communication and coherence among tissue clocks is rewired by nutrient challenge. Overall, we illustrate how dynamic metabolic relationships can be reconstructed across time and space and how integration of circadian metabolomics data from multiple tissues can improve our understanding of health and disease.

Systems Biology Approaches and Precision Oral Health: A Circadian Clock Perspective

A vast majority of the pathophysiological and metabolic processes in humans are temporally controlled by a master circadian clock located centrally in the hypothalamic suprachiasmatic nucleus of the brain, as well as by specialized peripheral oscillators located in other body tissues. This circadian clock system generates a rhythmical diurnal transcriptional-translational cycle in clock genes and protein expression and activities regulating numerous downstream target genes. Clock genes as key regulators of physiological function and dysfunction of the circadian clock have been linked to various diseases and multiple morbidities. Emerging omics technologies permits largescale multi-dimensional investigations of the molecular landscape of a given disease and the comprehensive characterization of its underlying cellular components (e.g., proteins, genes, lipids, metabolites), their mechanism of actions, functional networks and regulatory systems. Ultimately, they can be used to better understand disease and interpatient heterogeneity, individual profile, identify personalized targetable key molecules and pathways, discover novel biomarkers and genetic alterations, which collectively can allow for a better patient stratification into clinically relevant subgroups to improve disease prediction and prevention, early diagnostic, clinical outcomes, therapeutic benefits, patient's quality of life and survival. The use of “omics” technologies has allowed for recent breakthroughs in several scientific domains, including in the field of circadian clock biology. Although studies have explored the role of clock genes using circadiOmics (which integrates circadian omics, such as genomics, transcriptomics, proteomics and metabolomics) in human disease, no such studies have investigated the implications of circadian disruption in oral, head and neck pathologies using multi-omics approaches and linking the omics data to patient-specific circadian profiles. There is a burgeoning body of evidence that circadian clock controls the development and homeostasis of oral and maxillofacial structures, such as salivary glands, teeth and oral epithelium. Hence, in the current era of precision medicine and dentistry and patient-centered health care, it is becoming evident that a multi-omics approach is needed to improve our understanding of the role of circadian clock-controlled key players in the regulation of head and neck pathologies. This review discusses current knowledge on the role of the circadian clock and the contribution of omics-based approaches toward a novel precision health era for diagnosing and treating head and neck pathologies, with an emphasis on oral, head and neck cancer and Sjögren's syndrome.

Dietary-fat effect of the rs10830963 polymorphism in MTNR1B on insulin resistance in response to 3 months weight-loss diets

BACKGROUND & AIMS

The risk allele (G) of rs10830963 in the melatonin receptor 1 B (MTNR1B) gene presents an association with obesity. We study the effect of this SNP on cardiovascular risk factors and weight loss secondary to 2hypocaloric diets.

METHODS

361 obese subjects were randomly allocated during 3 months (Diet M - high monounsaturated fat hypocaloric diet vs. Diet P - high polyunsaturated fat hypocaloric diet). Anthropometric parameters, fasting blood glucose, C-reactive protein (CRP), insulin concentration, insulin resistance (HOMA-IR), lipid profile and adipocytokines levels were measured. Genotype of MTNR1B gene polymorphism (rs10830963) was evaluated.

RESULTS

All anthropometric parameters, systolic blood pressure and leptin levels decreased in all subjects after both diets. This improvement of anthropometric parameters was higher in non G allele carriers than G allele carriers. After dietary intervention with Diet M, (CC vs. CG + GG); total cholesterol (delta: -10.4 ± 2.1mg/dl vs. -6.4 ± 1.2mg/dl: P <.05), LDL-cholesterol (delta:-7.1 ± 0.9mg/dl vs. -2.8 ± 0.8mg/dl: P <.05), insulin (delta:-3.0 ± 0.8 UI/L vs. -2.0 ± 1.0 UI/L: P<.05) and HOMA-IR (delta:-3.4 ± 1.0 units vs. -2.9 ± 0.9 units: P<.05) improved in no G allele carriers. After Diet P, in the group of subjects without G allele CC, insulin levels (delta: -2.9 ± 1.0 UI/L vs. -0.6 ± 0.2 UI/L: P <.05) and HOMA-IR (delta (CC vs. CG + GG): -0.8 ± 0.2 units vs. -0.4 ± 0.3 units: P <.05) decreased, too.

CONCLUSIONS

Our study detected a relationship of rs10830963 MTNR1B SNP with body weight loss and insulin resistance modification induced by 2different hypocaloric. Only monounsaturated enriched hypocaloric diet and in no-G allele carriers showed a significant effect on lipoproteins.

Circadian clocks and insulin resistance

Insulin resistance is a main determinant in the development of type 2 diabetes mellitus and a major cause of morbidity and mortality. The circadian timing system consists of a central brain clock in the hypothalamic suprachiasmatic nucleus and various peripheral tissue clocks. The circadian timing system is responsible for the coordination of many daily processes, including the daily rhythm in human glucose metabolism. The central clock regulates food intake, energy expenditure and whole-body insulin sensitivity, and these actions are further fine-tuned by local peripheral clocks. For instance, the peripheral clock in the gut regulates glucose absorption, peripheral clocks in muscle, adipose tissue and liver regulate local insulin sensitivity, and the peripheral clock in the pancreas regulates insulin secretion. Misalignment between different components of the circadian timing system and daily rhythms of sleep-wake behaviour or food intake as a result of genetic, environmental or behavioural factors might be an important contributor to the development of insulin resistance. Specifically, clock gene mutations, exposure to artificial light-dark cycles, disturbed sleep, shift work and social jet lag are factors that might contribute to circadian disruption. Here, we review the physiological links between circadian clocks, glucose metabolism and insulin sensitivity, and present current evidence for a relationship between circadian disruption and insulin resistance. We conclude by proposing several strategies that aim to use chronobiological knowledge to improve human metabolic health.

OnPLS-Based Multi-Block Data Integration: A Multivariate Approach to Interrogating Biological Interactions in Asthma

Integration of multiomics data remains a key challenge in fulfilling the potential of comprehensive systems biology. Multiple-block orthogonal projections to latent structures (OnPLS) is a projection method that simultaneously models multiple data matrices, reducing feature space without relying on a priori biological knowledge. In order to improve the interpretability of OnPLS models, the associated multi-block variable influence on orthogonal projections (MB-VIOP) method is used to identify variables with the highest contribution to the model. This study combined OnPLS and MB-VIOP with interactive visualization methods to interrogate an exemplar multiomics study, using a subset of 22 individuals from an asthma cohort. Joint data structure in six data blocks was assessed: transcriptomics; metabolomics; targeted assays for sphingolipids, oxylipins, and fatty acids; and a clinical block including lung function, immune cell differentials, and cytokines. The model identified seven components, two of which had contributions from all blocks (globally joint structure) and five that had contributions from two to five blocks (locally joint structure). Components 1 and 2 were the most informative, identifying differences between healthy controls and asthmatics and a disease–sex interaction, respectively. The interactions between features selected by MB-VIOP were visualized using chord plots, yielding putative novel insights into asthma disease pathogenesis, the effects of asthma treatment, and biological roles of uncharacterized genes. For example, the gene ATP6 V1G1, which has been implicated in osteoporosis, correlated with metabolites that are dysregulated by inhaled corticoid steroids (ICS), providing insight into the mechanisms underlying bone density loss in asthma patients taking ICS. These results show the potential for OnPLS, combined with MB-VIOP variable selection and interaction visualization techniques, to generate hypotheses from multiomics studies and inform biology.

Analysing the Expression of Eight Clock Genes in Five Tissues From Fasting and Fed Sows

In a previous study, we observed that circadian clock genes are differentially expressed in the skeletal muscle of fasting and fed sows. The goal of the current work was to investigate if these genes are also differentially expressed in tissues containing the central (hypothalamus) and peripheral (duodenum, dorsal fat, muscle, and liver) clocks. As animal material, we used 12 sows that fasted 12 h before slaughtering (T0) and 12 sows that were fed ad libitum 7 h prior slaughtering (T2). Tissue samples were collected immediately after slaughter and total RNA was subsequently extracted. The expression of the ARNTL, BHLHE40, CRY2, NPAS2, NR1D1, PER1, PER2, and SIK1 genes was measured by quantitative reverse transcription PCR. The numbers of clock genes showing differential expression before and after feeding varied depending on the tissue i.e., four in dorsal fat and duodenum, six in skeletal muscle, and seven in the liver. In contrast, none of the eight analysed genes displayed a significant differential expression in hypothalamus, the tissue where the central clock resides. This result supports that the differential expression of clock genes in the four tissues mentioned above is probably induced by nutrition and not by the central clock entrained by light. Moreover, we have observed that the NPAS2 and ARNTL genes display positive log2(FC) values in the five tissues under analysis, whilst the CRY2, PER1 (except dorsal fat) and PER2 (except hypothalamus) genes generally show negative log2(FC) values. Such result might be explained by the existence of a negative feedback loop between the ARNTL/NPAS2 and CRY/PER genes. Collectively, these results support that nutrition plays an important role in modulating the timing of porcine peripheral circadian clocks. Such regulation could be essential for coordinating the subsequent metabolic response to nutrient supply.

Intestinal barrier tightening by a cell-penetrating antibody to Bin1, a candidate target for immunotherapy of ulcerative colitis

Patients afflicted with ulcerative colitis (UC) are at increased risk of colorectal cancer. While its causes are not fully understood, UC is associated with defects in colonic epithelial barriers that sustain inflammation of the colon mucosa caused by recruitment of lymphocytes and neutrophils into the lamina propria. Based on genetic evidence that attenuation of the bridging integrator 1 (Bin1) gene can limit UC pathogenicity in animals, we have explored Bin1 targeting as a therapeutic option. Early feasibility studies in the dextran sodium sulfate mouse model of experimental colitis showed that administration of a cell-penetrating Bin1 monoclonal antibody (Bin1 mAb 99D) could prevent lesion formation in the colon mucosa in part by preventing rupture of lymphoid follicles. In vivo administration of Bin1 mAb altered tight junction protein expression and cecal barrier function. Strikingly, electrophysiology studies in organ cultures showed that Bin1 mAb could elevate resistance and lower ¹⁴ C-mannitol leakage across the cecal mucosa, consistent with a direct strengthening of colonic barrier function. Transcriptomic analyses of colitis tissues highlighted altered expression of genes involved in circadian rhythm, lipid metabolism, and inflammation, with a correction of the alterations by Bin1 mAb treatment to patterns characteristic of normal tissues. Overall, our results suggest that Bin1 mAb protects against UC by directly improving colonic epithelial barrier function to limit gene expression and cytokine programs associated with colonic inflammation.