Time-restricted feeding attenuates age-related cardiac decline in Drosophila

Short-Term, Intermittent Fasting Induces Long-Lasting Gut Health and TOR-Independent Lifespan Extension

Intermittent fasting (IF) can improve function and health during aging in laboratory model organisms, but the mechanisms at work await elucidation. We subjected fruit flies (Drosophila melanogaster) to varying degrees of IF and found that just one month of a 2-day fed:5-day fasted IF regime at the beginning of adulthood was sufficient to extend lifespan. This long-lasting, beneficial effect of early IF was not due to reduced fecundity. Starvation resistance and resistance to oxidative and xenobiotic stress were increased after IF. Early-life IF also led to higher lipid content in 60-day-old flies, a potential explanation for increased longevity. Guts of flies 40 days post-IF showed a significant reduction in age-related pathologies and improved gut barrier function. Improved gut health was also associated with reduced relative bacterial abundance. Early IF thus induced profound long-term changes. Pharmacological and genetic epistasis analysis showed that IF acted independently of the TOR pathway because rapamycin and IF acted additively to extend lifespan, and global expression of a constitutively active S6K did not attenuate the IF-induced lifespan extension. We conclude that short-term IF during early life can induce long-lasting beneficial effects, with robust increase in lifespan in a TOR-independent manner, probably at least in part by preserving gut health.

Increasing autophagy and blocking Nrf2 suppress laminopathy-induced age-dependent cardiac dysfunction and shortened lifespan

Mutations in the human LMNA gene cause a collection of diseases known as laminopathies. These include myocardial diseases that exhibit age-dependent penetrance of dysrhythmias and heart failure. The LMNA gene encodes A-type lamins, intermediate filaments that support nuclear structure and organize the genome. Mechanisms by which mutant lamins cause age-dependent heart defects are not well understood. To address this issue, we modeled human disease-causing mutations in the Drosophila melanogaster Lamin C gene and expressed mutant Lamin C exclusively in the heart. This resulted in progressive cardiac dysfunction, loss of adipose tissue homeostasis, and a shortened adult lifespan. Within cardiac cells, mutant Lamin C aggregated in the cytoplasm, the CncC(Nrf2)/Keap1 redox sensing pathway was activated, mitochondria exhibited abnormal morphology, and the autophagy cargo receptor Ref2(P)/p62 was upregulated. Genetic analyses demonstrated that simultaneous over-expression of the autophagy kinase Atg1 gene and an RNAi against CncC eliminated the cytoplasmic protein aggregates, restored cardiac function, and lengthened lifespan. These data suggest that simultaneously increasing rates of autophagy and blocking the Nrf2/Keap1 pathway are a potential therapeutic strategy for cardiac laminopathies.

Circadian regulation of metabolism and healthspan in Drosophila

Circadian clocks generate daily rhythms in gene expression, cellular functions, physiological processes and behavior. The core clock mechanism consists of transcriptional-translational negative feedback loops that turn over with an endogenous circa 24h period. Classical genetic experiments in the fly Drosophila melanogaster played an essential role in identification of clock genes that turned out to be largely conserved between flies and mammals. Like in mammals, circadian clocks in flies generate transcriptional rhythms in a variety of metabolic pathways related to feeding and detoxification. Given that rhythms pervade metabolism and the loss of metabolic homeostasis is involved in aging and disease, there is increasing interest in understanding how the clocks and the rhythms they control change during aging. The importance of circadian clocks for healthy aging is supported by studies reporting that genetic or environmental clock disruptions are associated with reduced healthspan and lifespan. For example, arrhythmia caused by mutations in core clock genes lead to symptoms of accelerated aging in both flies and mammals, including neurodegenerative phenotypes. Despite the wealth of descriptive data, the mechanisms by which functional clocks confer healthspan and lifespan benefits are poorly understood. Studies in Drosophila discussed here are beginning to unravel causative relationships between the circadian system and aging. In particular, recent data suggest that clocks may be involved in inducing rhythmic expression of specific genes late in life in response to age-related increase in oxidative stress. This review will summarize insights into links between circadian system and aging in Drosophila, which were obtained using powerful genetics tools available for this model organism and taking advantage of the short adult lifespan in flies that is measured in days rather than years.

Redox clocks: Time to rethink redox interventions

Redox interventions have been controversial in the management of chronic disease. The key reason is believed to be a lack of clarity in our understanding of how endogenous dynamics unfold in biochemical redox mechanisms in live cells. Time-resolved, quantitative research strategies combined with high throughput analysis tools may result in realistic characterisation of related in vivo processes. Here we review new evidence about redox dynamics in live cells. We discuss a potential of this line of research to establish new and affordable ways of redox interventions which may efficiently decrease mortality related to largely preventable chronic diseases.

Entrainment of the mouse circadian clock: Effects of stress, exercise, and nutrition

The circadian clock system in mammals plays a fundamental role in maintaining homeostasis. Entrainment is an important characteristic of the internal clock, by which appropriate timing is maintained according to external daily stimuli, such as light, stress, exercise, and/or food. Disorganized entrainment or a misaligned clock time, such as jet lag, increases health disturbances. The central clock in the suprachiasmatic nuclei, located in the hypothalamus, receives information about arousal stimuli, such as physical stress or exercise, and changes the clock time by modifying neural activity or the expression of circadian clock genes. Although feeding stimuli cannot entrain the central clock in a normal light-dark cycle, the central clock can partially detect the metabolic status. Local clocks in the peripheral tissues, including liver and kidney, have a strong direct response to the external stimuli of stress, exercise, and/or food that is independent of the central clock. The mechanism underlying entrainment by stress/exercise is mediated by glucocorticoids, sympathetic nerves, oxidative stress, hypoxia, pH, cytokines, and temperature. Food/nutrition-induced entrainment is mediated by fasting-induced hormonal or metabolic changes and re-feeding-induced insulin or oxyntomodulin secretion. Chrono-nutrition is a clinical application based on chronobiology research. Future studies are required to elucidate the effects of eating and nutrient composition on the human circadian clock. Here, we focus on the central and peripheral clocks mostly in rodents' studies and review the findings of recent investigations of the effects of stress, exercise, and food on the entrainment system.

Aging and Intermittent Fasting Impact on Transcriptional Regulation and Physiological Responses of Adult Drosophila Neuronal and Muscle Tissues

The progressive decline of the nervous system, including protein aggregate formation, reflects the subtle dysregulation of multiple functional pathways. Our previous work has shown intermittent fasting (IF) enhances longevity, maintains adult behaviors and reduces aggregates, in part, by promoting autophagic function in the aging Drosophila brain. To clarify the impact that IF-treatment has upon aging, we used high throughput RNA-sequencing technology to examine the changing transcriptome in adult Drosophila tissues. Principle component analysis (PCA) and other analyses showed ~1200 age-related transcriptional differences in head and muscle tissues, with few genes having matching expression patterns. Pathway components showing age-dependent expression differences were involved with stress response, metabolic, neural and chromatin remodeling functions. Middle-aged tissues also showed a significant increase in transcriptional drift-variance (TD), which in the CNS included multiple proteolytic pathway components. Overall, IF-treatment had a demonstrably positive impact on aged transcriptomes, partly ameliorating both fold and variance changes. Consistent with these findings, aged IF-treated flies displayed more youthful metabolic, behavioral and basal proteolytic profiles that closely correlated with transcriptional alterations to key components. These results indicate that even modest dietary changes can have therapeutic consequences, slowing the progressive decline of multiple cellular systems, including proteostasis in the aging nervous system.

Resistance Training Prevents Muscle Loss Induced by Caloric Restriction in Obese Elderly Individuals: A Systematic Review and Meta-Analysis

It remains unclear as to what extent resistance training (RT) can attenuate muscle loss during caloric restriction (CR) interventions in humans. The objective here is to address if RT could attenuate muscle loss induced by CR in obese elderly individuals, through summarized effects of previous studies. Databases MEDLINE, Embase and Web of Science were used to perform a systematic search between July and August 2017. Were included in the review randomized clinical trials (RCT) comparing the effects of CR with (CRRT) or without RT on lean body mass (LBM), fat body mass (FBM), and total body mass (BM), measured by dual-energy X-ray absorptiometry, on obese elderly individuals. The six RCTs included in the review applied RT three times per week, for 12 to 24 weeks, and most CR interventions followed diets of 55% carbohydrate, 15% protein, and 30% fat. RT reduced 93.5% of CR-induced LBM loss (0.819 kg [0.364 to 1.273]), with similar reduction in FBM and BM, compared with CR. Furthermore, to address muscle quality, the change in strength/LBM ratio tended to be different (p = 0.07) following CRRT (20.9 ± 23.1%) and CR interventions (−7.5 ± 9.9%). Our conclusion is that CRRT is able to prevent almost 100% of CR-induced muscle loss, while resulting in FBM and BM reductions that do not significantly differ from CR.

Gene expression hallmarks of cellular ageing

Ageing leads to dramatic changes in the physiology of many different tissues resulting in a spectrum of pathology. Nonetheless, many lines of evidence suggest that ageing is driven by highly conserved cell intrinsic processes, and a set of unifying hallmarks of ageing has been defined. Here, we survey reports of age-linked changes in basal gene expression across eukaryotes from yeast to human and identify six gene expression hallmarks of cellular ageing: downregulation of genes encoding mitochondrial proteins; downregulation of the protein synthesis machinery; dysregulation of immune system genes; reduced growth factor signalling; constitutive responses to stress and DNA damage; dysregulation of gene expression and mRNA processing. These encompass widely reported features of ageing such as increased senescence and inflammation, reduced electron transport chain activity and reduced ribosome synthesis, but also reveal a surprising lack of gene expression responses to known age-linked cellular stresses. We discuss how the existence of conserved transcriptomic hallmarks relates to genome-wide epigenetic differences underlying ageing clocks, and how the changing transcriptome results in proteomic alterations where data is available and to variations in cell physiology characteristic of ageing. Identification of gene expression events that occur during ageing across distant organisms should be informative as to conserved underlying mechanisms of ageing, and provide additional biomarkers to assess the effects of diet and other environmental factors on the rate of ageing.

Nutritional regimens with periodically recurring phases of dietary restriction extend lifespan in Drosophila

Nutritional interventions such as caloric and dietary restriction increase lifespan in various animal models. To identify alternative and less demanding nutritional interventions that extend lifespan, we subjected fruit flies ( Drosophila melanogaster) to weekly nutritional regimens that involved alternating a conventional diet with dietary restriction. Short periods of dietary restriction (up to 2 d) followed by longer periods of a conventional diet yielded minimal increases in lifespan. We found that 3 or more days of contiguous dietary restriction (DR) was necessary to yield a lifespan extension similar to that observed with persistent DR. Female flies were more responsive to these interventions than males. Physiologic changes known to be associated with prolonged DR, such as reduced metabolic rates, showed the same time course as lifespan extension. Moreover, concurrent transcriptional changes indicative of reduced insulin signaling were identified with DR. These physiologic and transcriptional changes were sustained, as they were detectable several days after switching to conventional diets. Taken together, diets with longer periods of DR extended lifespan concurrently with physiologic and transcriptional changes that may underlie this increase in lifespan.-Romey-Glüsing, R., Li, Y., Hoffmann, J., von Frieling, J., Knop, M., Pfefferkorn, R., Bruchhaus, I., Fink, C., Roeder, T. Nutritional regimens with periodically recurring phases of dietary restriction extend lifespan in Drosophila.

Time-Restricted Feeding Improves Circadian Dysfunction as well as Motor Symptoms in the Q175 Mouse Model of Huntington's Disease

Huntington's disease (HD) patients suffer from a progressive neurodegeneration that results in cognitive, psychiatric, cardiovascular, and motor dysfunction. Disturbances in sleep/wake cycles are common among HD patients with reports of delayed sleep onset, frequent bedtime awakenings, and fatigue during the day. The heterozygous Q175 mouse model of HD has been shown to phenocopy many HD core symptoms including circadian dysfunctions. Because circadian dysfunction manifests early in the disease in both patients and mouse models, we sought to determine if early intervention that improve circadian rhythmicity can benefit HD and delay disease progression. We determined the effects of time-restricted feeding (TRF) on the Q175 mouse model. At six months of age, the animals were divided into two groups: ad libitum (ad lib) and TRF. The TRF-treated Q175 mice were exposed to a 6-h feeding/18-h fasting regimen that was designed to be aligned with the middle of the time when mice are normally active. After three months of treatment (when mice reached the early disease stage), the TRF-treated Q175 mice showed improvements in their locomotor activity rhythm and sleep awakening time. Furthermore, we found improved heart rate variability (HRV), suggesting that their autonomic nervous system dysfunction was improved. Importantly, treated Q175 mice exhibited improved motor performance compared to untreated Q175 controls, and the motor improvements were correlated with improved circadian output. Finally, we found that the expression of several HD-relevant markers was restored to WT levels in the striatum of the treated mice using NanoString gene expression assays.

A new method to characterize function of the Drosophila heart by means of optical flow

The minuteness of Drosophila poses a challenge to quantify performance of its tubular heart and computer-aided analysis of its beating heart has evolved as a resilient compromise between instrumental costs and data robustness. Here, we introduce an optical flow algorithm (OFA) that continuously registers coherent movement within videos of the beating Drosophila heart and uses this information to subscribe the time course of observation with characteristic phases of cardiac contraction or relaxation. We report that the OFA combines high discriminatory power with robustness to characterize the performance of the Drosophila tubular heart using indicators from human cardiology. We provide proof of this concept using the test bed of established cardiac conditions that include the effects of ageing, knockdown of the slow repolarizing potassium channel subunit KCNQ and ras-mediated hypertrophy of the heart tube. Together, this establishes the analysis of coherent movement as a suitable indicator of qualitative changes of the heart's beating characteristics, which improves the usefulness of Drosophila as a model of cardiac diseases.

Myocyte membrane and microdomain modifications in diabetes: determinants of ischemic tolerance and cardioprotection

Cardiovascular disease, predominantly ischemic heart disease (IHD), is the leading cause of death in diabetes mellitus (DM). In addition to eliciting cardiomyopathy, DM induces a ‘wicked triumvirate’: (i) increasing the risk and incidence of IHD and myocardial ischemia; (ii) decreasing myocardial tolerance to ischemia–reperfusion (I–R) injury; and (iii) inhibiting or eliminating responses to cardioprotective stimuli. Changes in ischemic tolerance and cardioprotective signaling may contribute to substantially higher mortality and morbidity following ischemic insult in DM patients. Among the diverse mechanisms implicated in diabetic impairment of ischemic tolerance and cardioprotection, changes in sarcolemmal makeup may play an overarching role and are considered in detail in the current review. Observations predominantly in animal models reveal DM-dependent changes in membrane lipid composition (cholesterol and triglyceride accumulation, fatty acid saturation vs. reduced desaturation, phospholipid remodeling) that contribute to modulation of caveolar domains, gap junctions and T-tubules. These modifications influence sarcolemmal biophysical properties, receptor and phospholipid signaling, ion channel and transporter functions, contributing to contractile and electrophysiological dysfunction, cardiomyopathy, ischemic intolerance and suppression of protective signaling. A better understanding of these sarcolemmal abnormalities in types I and II DM (T1DM, T2DM) can inform approaches to limiting cardiomyopathy, associated IHD and their consequences. Key knowledge gaps include details of sarcolemmal changes in models of T2DM, temporal patterns of lipid, microdomain and T-tubule changes during disease development, and the precise impacts of these diverse sarcolemmal modifications. Importantly, exercise, dietary, pharmacological and gene approaches have potential for improving sarcolemmal makeup, and thus myocyte function and stress-resistance in this ubiquitous metabolic disorder.

Nutrition and fasting mimicking diets in the prevention and treatment of autoimmune diseases and immunosenescence

Complex and coordinated signals are necessary to initiate and sustain the activation, proliferation, and differentiation of lymphocytes. These signals, which are known to determine T-cell fate and function, also depend on the metabolic state of the organism. Recent studies indicate that both the type and levels of nutrients can influence the generation, survival and function of lymphocytes and therefore can affect several autoimmune diseases. Here, we review the dysregulation of lymphocytes during autoimmunity and aging, the mechanisms associated with loss of immune function, and how fasting mimicking diets and other dietary interventions affect autoimmunity and immunosenescence.

TRiC/CCT chaperonins are essential for maintaining myofibril organization, cardiac physiological rhythm, and lifespan

We recently reported that CCT chaperonin subunits are upregulated in a cardiac-specific manner under time-restricted feeding (TRF) [Gill S et al. (2015) Science 347, 1265-1269], suggesting that TRiC/CCT has a heart-specific function. To understand the CCT chaperonin function in cardiomyocytes, we performed its cardiac-specific knock-down in the Drosophila melanogaster model. This resulted in disorganization of cardiac actin- and myosin-containing myofibrils and severe physiological dysfunction, including restricted heart diameters, elevated cardiac dysrhythmia and compromised cardiac performance. We also noted that cardiac-specific knock-down of CCT chaperonin significantly shortens lifespans. Additionally, disruption of circadian rhythm yields further deterioration of cardiac function of hypomorphic CCT mutants. Our analysis reveals that both the orchestration of protein folding and circadian rhythms mediated by CCT chaperonin are critical for maintaining heart contractility.

Impact of intermittent fasting on health and disease processes

Humans in modern societies typically consume food at least three times daily, while laboratory animals are fed ad libitum. Overconsumption of food with such eating patterns often leads to metabolic morbidities (insulin resistance, excessive accumulation of visceral fat, etc.), particularly when associated with a sedentary lifestyle. Because animals, including humans, evolved in environments where food was relatively scarce, they developed numerous adaptations that enabled them to function at a high level, both physically and cognitively, when in a food-deprived/fasted state. Intermittent fasting (IF) encompasses eating patterns in which individuals go extended time periods (e.g., 16-48h) with little or no energy intake, with intervening periods of normal food intake, on a recurring basis. We use the term periodic fasting (PF) to refer to IF with periods of fasting or fasting mimicking diets lasting from 2 to as many as 21 or more days. In laboratory rats and mice IF and PF have profound beneficial effects on many different indices of health and, importantly, can counteract disease processes and improve functional outcome in experimental models of a wide range of age-related disorders including diabetes, cardiovascular disease, cancers and neurological disorders such as Alzheimer's disease Parkinson's disease and stroke. Studies of IF (e.g., 60% energy restriction on 2days per week or every other day), PF (e.g., a 5day diet providing 750-1100kcal) and time-restricted feeding (TRF; limiting the daily period of food intake to 8h or less) in normal and overweight human subjects have demonstrated efficacy for weight loss and improvements in multiple health indicators including insulin resistance and reductions in risk factors for cardiovascular disease. The cellular and molecular mechanisms by which IF improves health and counteracts disease processes involve activation of adaptive cellular stress response signaling pathways that enhance mitochondrial health, DNA repair and autophagy. PF also promotes stem cell-based regeneration as well as long-lasting metabolic effects. Randomized controlled clinical trials of IF versus PF and isoenergetic continuous energy restriction in human subjects will be required to establish the efficacy of IF in improving general health, and preventing and managing major diseases of aging.

Circadian rhythms, time-restricted feeding, and healthy aging

Circadian rhythms optimize physiology and health by temporally coordinating cellular function, tissue function, and behavior. These endogenous rhythms dampen with age and thus compromise temporal coordination. Feeding-fasting patterns are an external cue that profoundly influence the robustness of daily biological rhythms. Erratic eating patterns can disrupt the temporal coordination of metabolism and physiology leading to chronic diseases that are also characteristic of aging. However, sustaining a robust feeding-fasting cycle, even without altering nutrition quality or quantity, can prevent or reverse these chronic diseases in experimental models. In humans, epidemiological studies have shown erratic eating patterns increase the risk of disease, whereas sustained feeding-fasting cycles, or prolonged overnight fasting, is correlated with protection from breast cancer. Therefore, optimizing the timing of external cues with defined eating patterns can sustain a robust circadian clock, which may prevent disease and improve prognosis.

Central and peripheral circadian clocks and their role in Alzheimer's disease

Molecular and cellular oscillations constitute an internal clock that tracks the time of day and permits organisms to optimize their behaviour and metabolism to suit the daily demands they face. The workings of this internal clock become impaired with age. In this review, we discuss whether such age-related impairments in the circadian clock interact with age-related neurodegenerative disorders, such as Alzheimer's disease. Findings from mouse and fly models of Alzheimer's disease have accelerated our understanding of the interaction between neurodegeneration and circadian biology. These models show that neurodegeneration likely impairs circadian rhythms either by damaging the central clock or by blocking its communication with other brain areas and with peripheral tissues. The consequent sleep and metabolic deficits could enhance the susceptibility of the brain to further degenerative processes. Thus, circadian dysfunction might be both a cause and an effect of neurodegeneration. We also discuss the primary role of light in the entrainment of the central clock and describe important, alternative time signals, such as food, that play a role in entraining central and peripheral circadian clocks. Finally, we propose how these recent insights could inform efforts to develop novel therapeutic approaches to re-entrain arrhythmic individuals with neurodegenerative disease.

Circadian Reprogramming in the Liver Identifies Metabolic Pathways of Aging

The process of aging and circadian rhythms are intimately intertwined, but how peripheral clocks involved in metabolic homeostasis contribute to aging remains unknown. Importantly, caloric restriction (CR) extends lifespan in several organisms and rewires circadian metabolism. Using young versus old mice, fed ad libitum or under CR, we reveal reprogramming of the circadian transcriptome in the liver. These age-dependent changes occur in a highly tissue-specific manner, as demonstrated by comparing circadian gene expression in the liver versus epidermal and skeletal muscle stem cells. Moreover, de novo oscillating genes under CR show an enrichment in SIRT1 targets in the liver. This is accompanied by distinct circadian hepatic signatures in NAD+-related metabolites and cyclic global protein acetylation. Strikingly, this oscillation in acetylation is absent in old mice while CR robustly rescues global protein acetylation. Our findings indicate that the clock operates at the crossroad between protein acetylation, liver metabolism, and aging.

Characterization and Expression Pattern Analysis of the T-Complex Protein-1 Zeta Subunit in Musca domestica L (Diptera)

Chaperonins, belonging to the T-complex protein-1 (TCP-1) family, assist in the correct folding of nascent and misfolded proteins. It is well-known that in mammals, the zeta subunit of the TCP-1 complex (TCP-1ζ) plays a vital role in the folding and assembly of cytoskeleta proteins. This study reported for the first time the cloning, characterization and expression pattern analysis of the TCP-1ζ from Musca domestica, which was named as MdTCP-1ζ. The MdTCP-1ζ cDNA is 1,803 bp long with a 1,596 bp open reading frame that encodes a protein with 531 bp amino acids. The analysis of the transcriptional profile of MdTCP-1ζ using qRT-PCR revealed relatively high expression in the salivary glands and trachea at the tissues while among the developmental stages. The highest expression was observed only in the eggs suggesting that the MdTCP-1ζ may play a role in embryonic development. The expression of MdTCP-1ζ was also significantly induced after exposure to short-term heat shock and infection by Escherichia coli, Staphylococcus aureus, or Candida albicans. This suggested that MdTCP-1ζ may take part in the immune responses of housefly and perhaps contribute to the protection against cellular injury.

Time-restricted feeding for prevention and treatment of cardiometabolic disorders

The soaring prevalence of obesity and diabetes is associated with an increase in comorbidities, including elevated risk for cardiovascular diseases (CVDs). CVDs continue to be among the leading causes of death and disability in the United States. While increased nutritional intake from an energy-dense diet is known to disrupt metabolic homeostasis and contributes to the disease risk, circadian rhythm disruption is emerging as a new risk factor for CVD. Circadian rhythms coordinate cardiovascular health via temporal control of organismal metabolism and physiology. Thus, interventions that improve circadian rhythms are prospective entry points to mitigate cardiometabolic disease risk. Although light is a strong modulator of the neural circadian clock, time of food intake is emerging as a dominant agent that affects circadian clocks in metabolic organs. We discovered that imposing a time-restricted feeding (TRF) regimen in which all caloric intakes occur consistently within ≤ 12 h every day exerts many cardiometabolic benefits. TRF prevents excessive body weight gain, improves sleep, and attenuates age- and diet-induced deterioration in cardiac performance. Using an integrative approach that combines Drosophila melanogaster (fruit fly) genetics with transcriptome analyses it was found that the beneficial effects of TRF are mediated by circadian clock, ATP-dependent TCP/TRiC/CCT chaperonin and mitochondrial electron transport chain components. Parallel studies in rodents have shown TRF reduces metabolic disease risks by maintaining metabolic homeostasis. As modern humans continue to live under extended periods of wakefulness and ingestion events, daily eating pattern offers a new potential target for lifestyle intervention to reduce CVD risk.

How we eat may be as important as what we eat: eating behaviour and heart rate variability

Objective Diet exerts a crucial role on cardiovascular health. Evidence is mainly based on the content and the amount of dietary intakes. Some recent reports demonstrated that eating behaviour may also be of significant importance in cardiovascular health. In this study we aimed to investigate the effects of eating behaviour on heart rate variability (HRV) in healthy subjects. Methods and results In total, 521 healthy subjects with 24-hour Holter ECG recordings filled out a special questionnaire about their eating behaviour and lifestyles. From these patients, 425 subjects were healthy and had recordings suitable for analysis. Five types of eating behaviour were assessed in the questionnaire: (1) adherence to the Mediterranean diet (using the MedDietScore), (2) skipping breakfast, (3) late night eating, (4) having snacks, and (5) rapid eating. Physical exercise level and active working status of the subjects were also assessed. The root mean square of successive differences (RMSSD) was used for assessment of HRV. RMSSD values were lower in subjects skipping breakfast compared to subjects having breakfast regularly (26.32 vs 31.52 P = 0.02). Other behavioural patterns did not have any effect on the HRV parameters. Ageing, male sex, sedentary lifestyle and no active working were also found to be associated with reduced HRV in univariate analysis. In multivariate regression analysis, age and skipping breakfast were the only parameters significantly associated with a lower RMSSD (β: -0.222, P: 0.008 and β: -0.191, P: 0.020, respectively) Conclusions The findings of this study showed that skipping breakfast may be a cause of cardiac autonomic dysfunction.

The microRNA machinery regulates fasting-induced changes in gene expression and longevity in Caenorhabditis elegans

Intermittent fasting (IF) is a dietary restriction regimen that extends the lifespans of Caenorhabditis elegans and mammals by inducing changes in gene expression. However, how IF induces these changes and promotes longevity remains unclear. One proposed mechanism involves gene regulation by microRNAs (miRNAs), small non-coding RNAs (∼22 nucleotides) that repress gene expression and whose expression can be altered by fasting. To test this proposition, we examined the role of the miRNA machinery in fasting-induced transcriptional changes and longevity in C. elegans We revealed that fasting up-regulated the expression of the miRNA-induced silencing complex (miRISC) components, including Argonaute and GW182, and the miRNA-processing enzyme DRSH-1 (the ortholog of the Drosophila Drosha enzyme). Our lifespan measurements demonstrated that IF-induced longevity was suppressed by knock-out or knockdown of miRISC components and was completely inhibited by drsh-1 ablation. Remarkably, drsh-1 ablation inhibited the fasting-induced changes in the expression of the target genes of DAF-16, the insulin/IGF-1 signaling effector in C. elegans Fasting-induced transcriptome alterations were substantially and modestly suppressed in the drsh-1 null mutant and the null mutant of ain-1, a gene encoding GW182, respectively. Moreover, miRNA array analyses revealed that the expression levels of numerous miRNAs changed after 2 days of fasting. These results indicate that components of the miRNA machinery, especially the miRNA-processing enzyme DRSH-1, play an important role in mediating IF-induced longevity via the regulation of fasting-induced changes in gene expression.

Membrane Currents, Gene Expression, and Circadian Clocks

Neuronal circadian oscillators in the mammalian and Drosophila brain express a circadian clock comprised of interlocking gene transcription feedback loops. The genetic clock regulates the membrane electrical activity by poorly understood signaling pathways to generate a circadian pattern of action potential firing. During the day, Na⁺ channels contribute an excitatory drive for the spontaneous activity of circadian clock neurons. Multiple types of K⁺ channels regulate the action potential firing pattern and the nightly reduction in neuronal activity. The membrane electrical activity possibly signaling by changes in intracellular Ca²⁺ and cyclic adenosine monophosphate (cAMP) regulates the activity of the gene clock. A decline in the signaling pathways that link the gene clock and neural activity during aging and disease may weaken the circadian output and generate significant impacts on human health.

Clock-Enhancing Small Molecules and Potential Applications in Chronic Diseases and Aging

Normal physiological functions require a robust biological timer called the circadian clock. When clocks are dysregulated, misaligned, or dampened, pathological consequences ensue, leading to chronic diseases and accelerated aging. An emerging research area is the development of clock-targeting compounds that may serve as drug candidates to correct dysregulated rhythms and hence mitigate disease symptoms and age-related decline. In this review, we first present a concise view of the circadian oscillator, physiological networks, and regulatory mechanisms of circadian amplitude. Given a close association of circadian amplitude dampening and disease progression, clock-enhancing small molecules (CEMs) are of particular interest as candidate chronotherapeutics. A recent proof-of-principle study illustrated that the natural polymethoxylated flavonoid nobiletin directly targets the circadian oscillator and elicits robust metabolic improvements in mice. We describe mood disorders and aging as potential therapeutic targets of CEMs. Future studies of CEMs will shed important insight into the regulation and disease relevance of circadian clocks.

A camera-phone based study reveals erratic eating pattern and disrupted daily eating-fasting cycle among adults in India

The daily rhythm of feeding-fasting and meal-timing are emerging as important determinants of health. Circadian rhythm research in animal models and retrospective analyses of human nutrition data have shown that reduced length of overnight fasting or increased late night eating increases risk for metabolic diseases including obesity and diabetes. However, the daily rhythm in eating pattern in humans is rarely measured. Traditional methods to collect nutrition information through food diary and food log pay little attention to the timing of eating which may also change from day to day. We adopted a novel cell-phone based approach to longitudinally record all events of food and beverage intake in adults. In a feasibility study daily food-eating patterns of 93 healthy individuals were recorded for 21 days using camera phones. Analysis of the daily eating patterns of these individuals indicates deviation from conventional assumption that people eat three meals-a-day within a 12 h interval. We found that eating events are widespread throughout the day, with <30% of calories consumed before noon and >30% consumed in evening and late night hours. There was little difference in eating pattern between weekdays and weekends. In this cohort more than 50% of people spread their caloric intake events over 15 h or longer. One decile of the cohort who were spouses of shift-workers or had flexible work schedule spread their caloric intake over 20 h. Although the nutrition quality and diversity of food consumed is different between South-East Asian and Western countries, such overall disruption of daily eating-fasting rhythm is similar. Therefore, in view of hypothesis that disrupted daily eating pattern may contribute to the global increase in metabolic diseases and modification of daily eating pattern is a potential modifiable behavior to contain these diseases, monitoring eating pattern is an important aspect of lifestyle.

Metabolic disturbances: role of the circadian timing system and sleep

The incidence of metabolic disorders such as obesity and diabetes is on the rise, and food quality is not alone to blame. Sleep disturbances, altered feeding time and circadian disruption are linked to metabolic disturbances in many clinical research studies and cross-sectional analyses. This review tried to summarize the role of the circadian timing system and sleep on energy and metabolic homeostasis. We also tried to explain the molecular and endocrine mechanisms behind circadian misalignment and sleep disorders that lead to metabolic disorders.

Different age-dependent performance in Drosophila wild-type Canton-S and the white mutant w1118 flies

Aging has significant effects on the locomotor performance of insects including Drosophila. Using a protocol for the high-throughput analysis of fly locomotion in a circular arena, we examined age-dependent behavioral characteristics in adult flies. There are widely used wild-type and genetically engineered background lines including the Canton-S strain and the w1118 strain, which has a null mutation of the white gene. Under standard rearing conditions, we found similar survival and median lifespans in Canton-S (50days) and w1118 (54days) strains, however, w1118 flies maintained stable body mass for up to 43days, whereas Canton-S flies gained body mass at young age, followed by a gradual decline. We also tested the behavioral performance of young and old flies. Compared with young w1118 flies (5-10days), old w1118 flies (40-45days) had an increased boundary preference during locomotion in small circular arenas, and increased speed of locomotor recovery from anoxia. Old Canton-S files, however, exhibited unchanged boundary preference and reduced recovery speed from anoxia relative to young flies. In addition, old w1118 flies showed decreased path length per minute and reduced 0.2s path increment compared with young flies, whereas old Canton-S flies displayed the same path length per minute and the same 0.2s path increment compared with young flies. We conclude that age-dependent behavioral and physiological changes differ between Canton-S and w1118 flies. These results illustrate that phenotypic differences between strains can change qualitatively, as well as quantitatively, as the animals age.

Age-related circadian disorganization caused by sympathetic dysfunction in peripheral clock regulation

The ability of the circadian clock to adapt to environmental changes is critical for maintaining homeostasis, preventing disease, and limiting the detrimental effects of aging. To date, little is known about age-related changes in the entrainment of peripheral clocks to external cues. We therefore evaluated the ability of the peripheral clocks of the kidney, liver, and submandibular gland to be entrained by external stimuli including light, food, stress, and exercise in young versus aged mice using in vivo bioluminescence monitoring. Despite a decline in locomotor activity, peripheral clocks in aged mice exhibited normal oscillation amplitudes under light–dark, constant darkness, and simulated jet lag conditions, with some abnormal phase alterations. However, age-related impairments were observed in peripheral clock entrainment to stress and exercise stimuli. Conversely, age-related enhancements were observed in peripheral clock entrainment to food stimuli and in the display of food anticipatory behaviors. Finally, we evaluated the hypothesis that deficits in sympathetic input from the central clock located in the suprachiasmatic nucleus of the hypothalamus were in part responsible for age-related differences in the entrainment. Aged animals showed an attenuated entrainment response to noradrenergic stimulation as well as decreased adrenergic receptor mRNA expression in target peripheral organs. Taken together, the present findings indicate that age-related circadian disorganization in entrainment to light, stress, and exercise is due to sympathetic dysfunctions in peripheral organs, while meal timing produces effective entrainment of aged peripheral circadian clocks.

The mammalian circadian clock and its entrainment by stress and exercise

The mammalian circadian clock regulates day-night fluctuations in various physiological processes. The circadian clock consists of the central clock in the suprachiasmatic nucleus of the hypothalamus and peripheral clocks in peripheral tissues. External environmental cues, including light/dark cycles, food intake, stress, and exercise, provide important information for adjusting clock phases. This review focuses on stress and exercise as potent entrainment signals for both central and peripheral clocks, especially in regard to the timing of stimuli, types of stressors/exercises, and differences in the responses of rodents and humans. We suggest that the common signaling pathways of clock entrainment by stress and exercise involve sympathetic nervous activation and glucocorticoid release. Furthermore, we demonstrate that physiological responses to stress and exercise depend on time of day. Therefore, using exercise to maintain the circadian clock at an appropriate phase and amplitude might be effective for preventing obesity, diabetes, and cardiovascular disease.

Time-restricted feeding improves insulin resistance and hepatic steatosis in a mouse model of postmenopausal obesity

BACKGROUND

Menopause is associated with significant hormonal changes that result in increased total body fat and abdominal fat, amplifying the risk for metabolic syndrome and diseases such as diabetes, cardiovascular disease and cancer in postmenopausal women. Intermittent fasting regimens hold significant health benefit promise for obese humans, however, regimens that include extreme daytime calorie restriction or daytime fasting are generally associated with hunger and irritability, hampering long-term compliance and adoption in the clinical setting. Time-restricted feeding (TRF), a regimen allowing eating only during a specific period in the normal circadian feeding cycle, without calorie restriction, may increase compliance and provide a more clinically viable method for reducing the detrimental metabolic consequences associated with obesity.

METHODS

We tested TRF as an intervention in a mouse model of postmenopausal obesity. Metabolic parameters were measured using Clinical Laboratory Animal Monitoring System (CLAMS) and we carried out glucose tolerance tests. We also stained liver sections with oil red O to examine steatosis and measured gene expression related to gluconeogenesis.

RESULTS

Preexisting metabolic disease was significantly attenuated during 7 weeks of TRF. Despite having access to the same high fat diet (HFD) as ad libitum fed (ALF) mice, TRF mice experienced rapid weight loss followed by a delayed improvement in insulin resistance and a reduced severity of hepatic steatosis by having access to the HFD for only 8h during their normal nocturnal feeding period. The lower respiratory exchange ratio in the TRF group compared with the ALF group early in the dark phase suggested that fat was the predominant fuel source in the TRF group and correlated with gene expression analyses that suggested a switch from gluconeogenesis to ketogenesis. In addition, TRF mice were more physically active than ALF fed mice.

CONCLUSIONS

Our data support further analysis of TRF as a clinically viable form of intermittent fasting to improve metabolic health due to obesity.

Circadian physiology of metabolism

A majority of mammalian genes exhibit daily fluctuations in expression levels, making circadian expression rhythms the largest known regulatory network in normal physiology. Cell-autonomous circadian clocks interact with daily light-dark and feeding-fasting cycles to generate approximately 24-hour oscillations in the function of thousands of genes. Circadian expression of secreted molecules and signaling components transmits timing information between cells and tissues. Such intra- and intercellular daily rhythms optimize physiology both by managing energy use and by temporally segregating incompatible processes. Experimental animal models and epidemiological data indicate that chronic circadian rhythm disruption increases the risk of metabolic diseases. Conversely, time-restricted feeding, which imposes daily cycles of feeding and fasting without caloric reduction, sustains robust diurnal rhythms and can alleviate metabolic diseases. These findings highlight an integrative role of circadian rhythms in physiology and offer a new perspective for treating chronic diseases in which metabolic disruption is a hallmark.

Sleep Duration and Diabetes Risk: Population Trends and Potential Mechanisms

Sleep is important for regulating many physiologic functions that relate to metabolism. Because of this, there is substantial evidence to suggest that sleep habits and sleep disorders are related to diabetes risk. In specific, insufficient sleep duration and/or sleep restriction in the laboratory, poor sleep quality, and sleep disorders such as insomnia and sleep apnea have all been associated with diabetes risk. This research spans epidemiologic and laboratory studies. Both physiologic mechanisms such as insulin resistance, decreased leptin, and increased ghrelin and inflammation and behavioral mechanisms such as increased food intake, impaired decision-making, and increased likelihood of other behavioral risk factors such as smoking, sedentary behavior, and alcohol use predispose to both diabetes and obesity, which itself is an important diabetes risk factor. This review describes the evidence linking sleep and diabetes risk at the population and laboratory levels.

Assessing Basal and Acute Autophagic Responses in the Adult Drosophila Nervous System: The Impact of Gender, Genetics and Diet on Endogenous Pathway Profiles

The autophagy pathway is critical for the long-term homeostasis of cells and adult organisms and is often activated during periods of stress. Reduced pathway efficacy plays a central role in several progressive neurological disorders that are associated with the accumulation of cytotoxic peptides and protein aggregates. Previous studies have shown that genetic and transgenic alterations to the autophagy pathway impacts longevity and neural aggregate profiles of adult Drosophila. In this study, we have identified methods to measure the acute in vivo induction of the autophagy pathway in the adult fly CNS. Our findings indicate that the genotype, age, and gender of adult flies can influence pathway responses. Further, we demonstrate that middle-aged male flies exposed to intermittent fasting (IF) had improved neuronal autophagic profiles. IF-treated flies also had lower neural aggregate profiles, maintained more youthful behaviors and longer lifespans, when compared to ad libitum controls. In summary, we present methodology to detect dynamic in vivo changes that occur to the autophagic profiles in the adult Drosophila CNS and that a novel IF-treatment protocol improves pathway response in the aging nervous system.

Daily NO rhythms in peripheral clocks in aging male Wistar rats: protective effects of exogenous melatonin

In mammals suprachiasmatic nucleus (SCN), acts as a light entrainable master clock and by generation of temporal oscillations regulates the peripheral organs acting as autonomous clocks resulting in overt behavioral and physiological rhythms. SCN also controls synthesis and release of melatonin (hormonal message for darkness) from pineal. Nitric Oxide (NO) acts as an important neurotransmitter in generating the phase shifts of circadian rhythms and participates in sleep-wake processes, maintenance of vascular tone as well as signalling and regulating inflammatory processes. Aging is associated with disruption of circadian timing system and decline in endogenous melatonin leading to several physiological disorders. Here we report the effect of aging on NO daily rhythms in various peripheral clocks such as kidney, intestine, liver, heart, lungs and testis. NO levels were measured at zeitgeber time (ZT) 0, 6, 12 and 18 in these tissues using Griess assay in male Wistar rats. Aging resulted in alteration of NO levels as well as phase of NO in both 12 and 24 months groups. Correlation analysis demonstrated loss of stoichiometric interaction between the various peripheral clocks with aging. Age induced alterations in NO daily rhythms were found to be most significant in liver and, interestingly least in lungs. Neurohormone melatonin, an endogenous synchroniser and an antiaging agent decreases with aging. We report further differential restoration with exogenous melatonin administration of age induced alterations in NO daily rhythms and mean levels in kidney, intestine and liver and the stoichiometric interactions between the various peripheral clocks.

The changing microbial landscape of Western society: Diet, dwellings and discordance

BACKGROUND

The last 50-100 years has been marked by a sharp rise in so-called "Western-diseases" in those countries that have experienced major industrial advances and shifts towards urbanized living. These diseases include obesity, type 2 diabetes, inflammatory bowel diseases, and food allergies in which chronic dysregulation of metabolic and/or immune processes appear to be involved, and are likely a byproduct of new environmental influences on our ancient genome. What we now appreciate is that this genome consists of both human and co-evolved microbial genes of the trillions of microbes residing in our body. Together, host-microbe interactions may be determined by the changing diets and behaviors of the Western lifestyle, influencing the etiopathogenesis of "new-age" diseases.

SCOPE OF REVIEW

This review takes an anthropological approach to the potential interplay of the host and its gut microbiome in the post-industrialization rise in chronic inflammatory and metabolic diseases. The discussion highlights both the changes in diet and the physical environment that have co-occurred with these diseases and the latest evidence demonstrating the role of host-microbe interactions in understanding biological responses to the changing environment.

MAJOR CONCLUSIONS

Technological advances that have led to changes in agriculture and engineering have altered our eating and living behaviors in ways never before possible in human history. These changes also have altered the bacterial communities within the human body in ways that are seemingly linked with the rise of many intestinal and systemic metabolic and inflammatory diseases. Insights into the mechanisms of this reciprocal exchange between the environment and the human gut microbiome may offer potential to attenuate the chronic health conditions that derail quality of life. This article is part of a special issue on microbiota.

Fasting, Circadian Rhythms, and Time-Restricted Feeding in Healthy Lifespan

Most animals alternate periods of feeding with periods of fasting often coinciding with sleep. Upon >24 hr of fasting, humans, rodents, and other mammals enter alternative metabolic phases, which rely less on glucose and more on ketone body-like carbon sources. Both intermittent and periodic fasting result in benefits ranging from the prevention to the enhanced treatment of diseases. Similarly, time-restricted feeding (TRF), in which food consumption is restricted to certain hours of the day, allows the daily fasting period to last >12 hr, thus imparting pleiotropic benefits. Understanding the mechanistic link between nutrients and the fasting benefits is leading to the identification of fasting-mimicking diets (FMDs) that achieve changes similar to those caused by fasting. Given the pleiotropic and sustained benefits of TRF and FMDs, both basic science and translational research are warranted to develop fasting-associated interventions into feasible, effective, and inexpensive treatments with the potential to improve healthspan.

Circadian Metabolism: From Mechanisms to Metabolomics and Medicine

The circadian clock directs nearly all aspects of diurnal physiology, including metabolism. Current research identifies several major axes by which it exerts these effects, including systemic signals as well as direct control of cellular processes by local clocks. This redundant network can transmit metabolic and timing information bidirectionally for optimal synchrony of metabolic processes. Recent advances in cellular profiling and metabolomics technologies have yielded unprecedented insights into the mechanisms behind this control. They have also helped to illuminate individual variation in these mechanisms that could prove important in personalized therapy for metabolic disease. Finally, these technologies have provided platforms with which to screen for the first potential drugs affecting clock-modulated metabolic function.

[Cardiac pathologies and aging: lessons from a tiny heart]

The high level of conservation of the cardiogenic gene regulatory network as well as of the cellular and physiological characteristics of the cardiomyocytes between fly and human, makes the small heart of this invertebrate the simplest and most flexible genetic system to dissect the fundamental molecular mechanisms that are brought into play during the development, the establishment and the maintenance of the cardiac function. The recent improvements in techniques of measurements of cardiac function made it possible to validate Drosophila as a model of cardiomyopathies and arrhythmias of genetic and metabolic origin or dependent of ageing. The heart of the fly thus represents a model of choice to identify genes and their interactions implicated in cardiac pathologies.

Daily Rhythms in Mosquitoes and Their Consequences for Malaria Transmission

The 24-h day involves cycles in environmental factors that impact organismal fitness. This is thought to select for organisms to regulate their temporal biology accordingly, through circadian and diel rhythms. In addition to rhythms in abiotic factors (such as light and temperature), biotic factors, including ecological interactions, also follow daily cycles. How daily rhythms shape, and are shaped by, interactions between organisms is poorly understood. Here, we review an emerging area, namely the causes and consequences of daily rhythms in the interactions between vectors, their hosts and the parasites they transmit. We focus on mosquitoes, malaria parasites and vertebrate hosts, because this system offers the opportunity to integrate from genetic and molecular mechanisms to population dynamics and because disrupting rhythms offers a novel avenue for disease control.

Neural clocks and Neuropeptide F/Y regulate circadian gene expression in a peripheral metabolic tissue

Metabolic homeostasis requires coordination between circadian clocks in different tissues. Also, systemic signals appear to be required for some transcriptional rhythms in the mammalian liver and the Drosophila fat body. Here we show that free-running oscillations of the fat body clock require clock function in the PDF-positive cells of the fly brain. Interestingly, rhythmic expression of the cytochrome P450 transcripts, sex-specific enzyme 1 (sxe1) and Cyp6a21, which cycle in the fat body independently of the local clock, depends upon clocks in neurons expressing neuropeptide F (NPF). NPF signaling itself is required to drive cycling of sxe1 and Cyp6a21 in the fat body, and its mammalian ortholog, Npy, functions similarly to regulate cycling of cytochrome P450 genes in the mouse liver. These data highlight the importance of neuronal clocks for peripheral rhythms, particularly in a specific detoxification pathway, and identify a novel and conserved role for NPF/Npy in circadian rhythms.

DOI:http://dx.doi.org/10.7554/eLife.13552.001

Many processes in the body follow rhythms that repeat over 24 hours and are synchronized to the cycle of day and night. Our sleep pattern is a well-known example, but others include daily fluctuations in body temperature and the production of several hormones. Internal clocks located in the brain and other organs drive these rhythms by altering the activity of certain genes depending on the time of day.

Animals have specific organs that contain enzymes needed to break down toxic molecules in the body, and the levels of several of these enzymes rise and fall over each 24-hour period. In mammals, these enzymes are found in the liver, but in insects they are found in an organ called the fat body. Here, Erion, King et al. set out to determine the extent to which the internal clock in the brain influences the daily rhythms of these enzymes.

The experiments show that a hormone released by the nervous system is required for the levels of the detoxifying enzymes to change in 24-hour cycles. This hormone – termed Neuropeptide F in fruit flies and Neuropeptide Y in mice – is also known to stimulate both mice and fruit flies to eat. Since toxic molecules often enter the body during feeding, Erion, King et al. speculate that it may be beneficial to link the detoxification process to feeding by using the same mechanism to control both processes. The next step following on from this work would be to find out exactly how neuropeptide F drives the 24-hour rhythms in the fat body and other organs.

DOI:http://dx.doi.org/10.7554/eLife.13552.002

Circadian rhythms of liver physiology and disease: experimental and clinical evidence

The circadian clock system consists of a central clock located in the suprachiasmatic nucleus in the hypothalamus and peripheral clocks in peripheral tissues. Peripheral clocks in the liver have fundamental roles in maintaining liver homeostasis, including the regulation of energy metabolism and the expression of enzymes controlling the absorption and metabolism of xenobiotics. Over the past two decades, research has investigated the molecular mechanisms linking circadian clock genes with the regulation of hepatic physiological functions, using global clock-gene-knockout mice, or mice with liver-specific knockout of clock genes or clock-controlled genes. Clock dysfunction accelerates the development of liver diseases such as fatty liver diseases, cirrhosis, hepatitis and liver cancer, and these disorders also disrupt clock function. Food is an important regulator of circadian clocks in peripheral tissues. Thus, controlling the timing of food consumption and food composition, a concept known as chrononutrition, is one area of active research to aid recovery from many physiological dysfunctions. In this Review, we focus on the molecular mechanisms of hepatic circadian gene regulation and the relationships between hepatic circadian clock systems and liver physiology and disease. We concentrate on experimental data obtained from cell or mice and rat models and discuss how these findings translate into clinical research, and we highlight the latest developments in chrononutritional studies.

Circadian Rhythms, Metabolism, and Chrononutrition in Rodents and Humans

Chrononutrition is an emerging discipline that builds on the intimate relation between endogenous circadian (24-h) rhythms and metabolism. Circadian regulation of metabolic function can be observed from the level of intracellular biochemistry to whole-organism physiology and even postprandial responses. Recent work has elucidated the metabolic roles of circadian clocks in key metabolic tissues, including liver, pancreas, white adipose, and skeletal muscle. For example, tissue-specific clock disruption in a single peripheral organ can cause obesity or disruption of whole-organism glucose homeostasis. This review explains mechanistic insights gained from transgenic animal studies and how these data are being translated into the study of human genetics and physiology. The principles of chrononutrition have already been demonstrated to improve human weight loss and are likely to benefit the health of individuals with metabolic disease, as well as of the general population.

Drosophila tools and assays for the study of human diseases

Many of the internal organ systems of Drosophila melanogaster are functionally analogous to those in vertebrates, including humans. Although humans and flies differ greatly in terms of their gross morphological and cellular features, many of the molecular mechanisms that govern development and drive cellular and physiological processes are conserved between both organisms. The morphological differences are deceiving and have led researchers to undervalue the study of invertebrate organs in unraveling pathogenic mechanisms of diseases. In this review and accompanying poster, we highlight the physiological and molecular parallels between fly and human organs that validate the use of Drosophila to study the molecular pathogenesis underlying human diseases. We discuss assays that have been developed in flies to study the function of specific genes in the central nervous system, heart, liver and kidney, and provide examples of the use of these assays to address questions related to human diseases. These assays provide us with simple yet powerful tools to study the pathogenic mechanisms associated with human disease-causing genes.

Drosophila in the Heart of Understanding Cardiac Diseases: Modeling Channelopathies and Cardiomyopathies in the Fruitfly

Cardiovascular diseases and, among them, channelopathies and cardiomyopathies are a major cause of death worldwide. The molecular and genetic defects underlying these cardiac disorders are complex, leading to a large range of structural and functional heart phenotypes. Identification of molecular and functional mechanisms disrupted by mutations causing channelopathies and cardiomyopathies is essential to understanding the link between an altered gene and clinical phenotype. The development of animal models has been proven to be efficient for functional studies in channelopathies and cardiomyopathies. In particular, the Drosophila model has been largely applied for deciphering the molecular and cellular pathways affected in these inherited cardiac disorders and for identifying their genetic modifiers. Here we review the utility and the main contributions of the fruitfly models for the better understanding of channelopathies and cardiomyopathies. We also discuss the investigated pathological mechanisms and the discoveries of evolutionarily conserved pathways which reinforce the value of Drosophila in modeling human cardiac diseases.

Circadian clock and the onset of cardiovascular events

The onset of cardiovascular diseases often shows time-of-day variation. Acute myocardial infarction or ventricular arrhythmia such as ventricular tachycardia occurs mainly in the early morning. Multiple biochemical and physiological parameters show circadian rhythm, which may account for the diurnal variation of cardiovascular events. These include the variations in blood pressure, activity of the autonomic nervous system and renin-angiotensin axis, coagulation cascade, vascular tone and the intracellular metabolism of cardiomyocytes. Importantly, the molecular clock system seems to underlie the circadian variation of these parameters. The center of the biological clock, also known as the central clock, exists in the suprachiasmatic nucleus. In contrast, the molecular clock system is also activated in each cell of the peripheral organs and constitute the peripheral clock. The biological clock system is currently considered to have a beneficial role in maintaining the homeostasis of each organ. Discoordination, however, between the peripheral clock and external environment could potentially underlie the development of cardiovascular events. Therefore, understanding the molecular and cellular pathways by which cardiovascular events occur in a diurnal oscillatory pattern will help the establishment of a novel therapeutic approach to the management of cardiovascular disorders.

Daily Eating Patterns and Their Impact on Health and Disease

Cyclical expression of cell-autonomous circadian clock components and key metabolic regulators coordinate often discordant and distant cellular processes for efficient metabolism. Perturbation of these cycles, either by genetic manipulation, disruption of light/dark cycles, or, most relevant to the human population, via eating patterns, contributes to obesity and dysmetabolism. Time-restricted feeding (TRF), during which time of access to food is restricted to a few hours, without caloric restriction, supports robust metabolic cycles and protects against nutritional challenges that predispose to obesity and dysmetabolism. The mechanism by which TRF imparts its benefits is not fully understood but likely involves entrainment of metabolically active organs through gut signaling. Understanding the relationship of feeding pattern and metabolism could yield novel therapies for the obesity pandemic.

Dietary restriction with and without caloric restriction for healthy aging

Caloric restriction is the most effective and reproducible dietary intervention known to regulate aging and increase the healthy lifespan in various model organisms, ranging from the unicellular yeast to worms, flies, rodents, and primates. However, caloric restriction, which in most cases entails a 20–40% reduction of food consumption relative to normal intake, is a severe intervention that results in both beneficial and detrimental effects. Specific types of chronic, intermittent, or periodic dietary restrictions without chronic caloric restriction have instead the potential to provide a significant healthspan increase while minimizing adverse effects. Improved periodic or targeted dietary restriction regimens that uncouple the challenge of food deprivation from the beneficial effects will allow a safe intervention feasible for a major portion of the population. Here we focus on healthspan interventions that are not chronic or do not require calorie restriction.

Glucose modulates Drosophila longevity and immunity independent of the microbiota

The acquisition of nutrients is essential for maintenance of metabolic processes in all organisms. Nutritional imbalance contributes to myriad metabolic disorders that include malnutrition, diabetes and even cancer. Recently, the importance of macronutrient ratio of food has emerged as a critical factor to determine health outcomes. Here we show that individual modifications to a completely defined diet markedly impact multiple aspects of organism wellbeing in Drosophila melanogaster. Through a longitudinal survey of several diets we demonstrate that increased levels of dietary glucose significantly improve longevity and immunity in adult Drosophila. Our metagenomic studies show that relative macronutrient levels not only influence the host, but also have a profound impact on microbiota composition. However, we found that elevated dietary glucose extended the lifespan of adult flies even when raised in a germ-free environment. Furthermore, when challenged with a chronic enteric infection, flies fed a diet with added glucose had increased survival times even in the absence of an intact microbiota. Thus, in contrast to known links between the microbiota and animal health, our findings uncover a novel microbiota-independent response to diet that impacts host wellbeing. As dietary responses are highly conserved in animals, we believe our results offer a general understanding of the association between glucose metabolism and animal health.