Night-time feeding of Bmal1-/- mice restores SCFA rhythms and their effect on ghrelin

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.

Chronobiotics, satiety signaling, and clock gene expression interplay

The biological clock regulates the way our body works throughout the day, including releasing hormones and food intake. Disruption of the biological clock (chronodisruption) may deregulate satiety, which is strictly regulated by hormones and neurotransmitters, leading to health problems like obesity. Nowadays, using bioactive compounds as a coadjutant for several pathologies is a common practice. Phenolic compounds and short-chain fatty acids, called "chronobiotics," can modulate diverse mechanisms along the body to exert beneficial effects, including satiety regulation and circadian clock resynchronization; however, the evidence of the interplay between those processes is limited. This review compiles the evidence of natural chronobiotics, mainly polyphenols and short-chain fatty acids that affect the circadian clock mechanism and process modifications in genes or proteins resulting in a signaling chain that modulates satiety hormones or hunger pathways.

Time-restricted eating for chronodisruption-related chronic diseases

The circadian timing system enables organisms to adapt their physiology and behavior to the cyclic environmental changes including light-dark cycle or food availability. Misalignment between the endogenous circadian rhythms and external cues is known as chronodisruption and is closely associated with the development of metabolic and gastrointestinal disorders, cardiovascular diseases, and cancer. Time-restricted eating (TRE, in human) is an emerging dietary approach for weight management. Recent studies have shown that TRE or time-restricted feeding (TRF, when referring to animals) has several beneficial health effects, which, however, are not limited to weight management. This review summarizes the effects of TRE/TRF on regulating energy metabolism, gut microbiota and homeostasis, development of cardiovascular diseases and cancer. Furthermore, we will address the role of circadian clocks in TRE/TRF and propose ways to optimize TRE as a dietary strategy to obtain maximal health benefits.

Age-Related Changes in Circadian Rhythm and Association with Nutrition

PURPOSE OF REVIEW

Considering the increase in life expectancy, there is a time-related decline in biological functions. Age-related changes are also observed in the circadian clock which directly leads to appropriate rhythms in the endocrine and metabolic pathways required for organism homeostasis. Circadian rhythms are affected by the sleep/wake cycle, environmental changes, and nutrition. The aim of this review is to show the relationship between age-related changes in circadian rhythms of physiological and molecular processes and nutritional differences in the elderly.

RECENT FINDINGS

Nutrition is an environmental factor that is particularly effective on peripheral clocks. Age-related physiological changes have an impact on nutrient intake and circadian processes. Considering the known effects of amino acid and energy intakes on peripheral and circadian clocks, it is thought that the change in circadian clocks in aging may occur due to anorexia due to physiological changes.

Circadian rhythms in colonic function

A rhythmic expression of clock genes occurs within the cells of multiple organs and tissues throughout the body, termed "peripheral clocks." Peripheral clocks are subject to entrainment by a multitude of factors, many of which are directly or indirectly controlled by the light-entrainable clock located in the suprachiasmatic nucleus of the hypothalamus. Peripheral clocks occur in the gastrointestinal tract, notably the epithelia whose functions include regulation of absorption, permeability, and secretion of hormones; and in the myenteric plexus, which is the intrinsic neural network principally responsible for the coordination of muscular activity in the gut. This review focuses on the physiological circadian variation of major colonic functions and their entraining mechanisms, including colonic motility, absorption, hormone secretion, permeability, and pain signalling. Pathophysiological states such as irritable bowel syndrome and ulcerative colitis and their interactions with circadian rhythmicity are also described. Finally, the classic circadian hormone melatonin is discussed, which is expressed in the gut in greater quantities than the pineal gland, and whose exogenous use has been of therapeutic interest in treating colonic pathophysiological states, including those exacerbated by chronic circadian disruption.

Time-restricted feeding affects colonic nutrient substrates and modulates the diurnal fluctuation of microbiota in pigs

Introduction

Studies demonstrate that time-restricted feeding (TRF) can regulate gut microbiota composition. However, it is unclear whether TRF could affect the gut microbial rhythmicity in growing pigs. Therefore, the present study aimed to explore the effects of TRF on the dynamic fluctuation of the gut microbiota.

Methods

A total of 10 healthy growing pigs equipped with T cannula were employed. Pigs were randomly allotted to the free access (FA) and the TRF groups with 5 replicates (1 pig/replicates). Pigs in the FA group were fed free access during the whole experimental period, whereas pigs in the TRF group were fed free access three times per day within limited times (7:00-8:00, 12:00-13:00, 17:00-18:00). The experiment lasted for 15 days, at 06:00 a.m. of the day 16, colonic digesta were collected at a 6-h interval for consecutive 24 h marked as T06 (06:00), T12 (12:00), T18 (18:00), T24 (24:00), T30 (06:00), respectively.

Results

Results showed that TRF altered the distribution of feed intake without changing the total feed intake within a day (p = 0.870). TRF decreased the overall concentration of colonic cellulose and altered their oscillating patterns. All alpha-diversity indexes of different time points showed significant differences regardless of feeding pattern with a trough at T18 or T24. TRF shifted the trough of the alpha-diversity index Simpson and Invsimpson. TRF lost the rhythmicity of Prevotellaceae, Ruminococcaceae, Bacteroidales_S24-7_group, and Peptococcaceae and gained the rhythmicity of Pasteurellaceae, Clostridiaceae_1, Veillonellaceae, and Peptostreptococcaceae. Also, TRF altered the interaction pattern by increasing the microbes involved in the co-occurrence network and their crosstalk, especially at T24. Interestingly, the microbial variation at T24 could largely explained by colonic substrates starch (R² = 0.369; p = 0.001), cellulose (R² = 0.235; p = 0.009) and NH4-N (R² = 0.489; p = 0.001).

Conclusion

In conclusion, TRF has changed the concentrates of cellulose and the relative abundance of specific microbes and certain microbial metabolites. In addition, TRF has more powerful effects on the fluctuation modes of these nutrient substrates, microbes, and metabolites by shifting their peaks or troughs. This knowledge facilitates the development of precision regulation targeting gut microbial rhythmicity.

Controlled light exposure and intermittent fasting as treatment strategies for metabolic syndrome and gut microbiome dysregulation in night shift workers

The mammalian circadian clocks are entrained by environmental time cues, such as the light-dark cycle and the feeding-fasting cycle. In modern society, circadian misalignment is increasingly more common under the guise of shift work. Shift workers, accounting for roughly 20% of the workforce population, are more susceptible to metabolic disease. Exposure to artificial light at night and eating at inappropriate times of the day uncouples the central and peripheral circadian clocks. This internal circadian desynchrony is believed to be one of the culprits leading to metabolic disease. In this review, we discuss how alterations in the rhythm of gut microbiota and their metabolites during chronodisruption send conflicting signals to the host, which may ultimately contribute to disturbed metabolic processes. We propose two behavioral interventions to improve health in shift workers. Firstly, by carefully timing the moments of exposure to blue light, and hence shifting the melatonin peak, to improve sleep quality of daytime sleeping episodes. Secondly, by timing the daily time window of caloric intake to the biological morning, to properly align the feeding-fasting cycle with the light-dark cycle and to reduce the risk of metabolic disease. These interventions can be a first step in reducing the worldwide burden of health problems associated with shift work.

Effects of prebiotics on intestinal physiology, neuropsychological function, and exercise capacity of mice with sleep deprivation

People suffered from insufficient or disrupted sleep due to night shifts, work pressure, and irregular lifestyles. Sleep deprivation caused by inadequate quantity or quality of sleep has been associated with not only increased risk of metabolic diseases, gut dysbiosis, and emotional disorders but also decreased work and exercise performance. In this study, we used the modified multiple platform method (MMPM) to induce pathological and psychological characteristics of sleep deprivation with C57BL/6J male mice, and investigated whether supplementing a prebiotics mixture of short-chain galactooligosaccharides (scGOS) and long-chain fructooligosaccharides (lcFOS) (9:1 ratio) could improve the impacts of sleep deprivation on intestinal physiology, neuropsychological function, inflammation, circadian rhythm, and exercise capacity. Results showed that sleep deprivation caused intestinal inflammation (increased TNFA and IL1B) and decreased intestinal permeability with a significant decrease in the tight junction genes (OCLN, CLDN1, TJP1, and TJP2) of intestine and brain. The prebiotics significantly increased the content of metabolite short-chain fatty acids (acetate and butyrate) while recovering the expression of indicated tight junction genes. In hypothalamus and hippocampus, clock (BMAL1 and CLOCK) and tight junction (OCLN and TJP2) genes were improved by prebiotics, and corticotropin-releasing hormone receptor genes, CRF1 and CRF2, were also significantly regulated for mitigation of depression and anxiety caused by sleep deprivation. Also, prebiotics brought significant benefits on blood sugar homeostasis and improvement of exercise performance. Functional prebiotics could improve physiological modulation, neuropsychological behaviors, and exercise performance caused by sleep deprivation, possibly through regulation of inflammation and circadian rhythm for health maintenance. However, the microbiota affected by prebiotics and sleep deprivation should warrant further investigation.

Consequences of collagen induced inflammatory arthritis on circadian regulation of the gut microbiome

The gut microbiota is important for host health and immune system function. Moreover autoimmune diseases, such as rheumatoid arthritis, are associated with significant gut microbiota dysbiosis, although the causes and consequences of this are not fully understood. It has become clear that the composition and metabolic outputs of the microbiome exhibit robust 24 h oscillations, a result of daily variation in timing of food intake as well as rhythmic circadian clock function in the gut. Here, we report that experimental inflammatory arthritis leads to a re-organization of circadian rhythmicity in both the gut and associated microbiome. Mice with collagen induced arthritis exhibited extensive changes in rhythmic gene expression in the colon, and reduced barrier integrity. Re-modeling of the host gut circadian transcriptome was accompanied by significant alteration of the microbiota, including widespread loss of rhythmicity in symbiont species of Lactobacillus, and alteration in circulating microbial derived factors, such as tryptophan metabolites, which are associated with maintenance of barrier function and immune cell populations within the gut. These findings highlight that altered circadian rhythmicity during inflammatory disease contributes to dysregulation of gut integrity and microbiome function.

Chronic jetlag reprograms gene expression in the colonic smooth muscle layer inducing diurnal rhythmicity in the effect of bile acids on colonic contractility

BACKGROUND

Secondary bile acids entrain peripheral circadian clocks and inhibit colonic motility via the bile acid receptor GPBAR1. We aimed to investigate whether chronodisruption affected the rhythm in serum bile acid levels and whether this was associated with alterations in clock gene and Gpbar1 mRNA expression in the colonic smooth muscle layer. We hypothesized that this in turn may affect the rhythm in the inhibitory effect of secondary bile acids on colonic contractility.

METHODS

Mice were exposed to 4 weeks of chronic jetlag induction. The expression of Gpbar1 and clock genes was measured in colonic smooth muscle tissue using RT-qPCR over 24 h (4 h time interval). The effect of secondary bile acids on electrical field-induced neural contractions was measured isometrically in colonic smooth muscle strips.

KEY RESULTS

Chronic jetlag abolished the rhythmicity in serum bile acid levels. This was associated with a phase-shift in diurnal clock gene mRNA fluctuations in smooth muscle tissue. Chronic jetlag induced a rhythm in Gpbar1 expression in the colonic smooth muscle layer. In parallel, a rhythm was induced in the inhibitory effect of taurodeoxycholic acid (TDCA), but not deoxycholic acid, on neural colonic contractions that peaked together with Gpbar1 expression.

CONCLUSIONS & INFERENCES

Chronodisruption abolished the rhythm in bile acid levels which might contribute to a shift in smooth muscle clock gene expression. Our findings suggest that chronodisruption caused a transcriptional reprogramming in the colonic smooth layer thereby inducing a rhythm in the expression of Gpbar1 and in the inhibitory effect of TDCA on colonic contractility.

New Insights into the Diurnal Rhythmicity of Gut Microbiota and Its Crosstalk with Host Circadian Rhythm

Simple Summary

There is a growing consensus that the gut microbiota exhibits diurnal oscillation. The rhythmicity of gut microbiota has fundamental implications for host physiology, metabolism, and health. Further, the gut microbiota rhythmicity can regulate the host’s circadian rhythm. Therefore, in this review, we aimed to highlight the rhythmic phenomenon of the gut microbiota and elucidate its fundamental roles in host physiology, metabolism, and health, and illuminate the possible interactions between the gut microbiota rhythmicity and host circadian rhythm. Insights into these questions facilitate the development of chronotherapy.

Abstract

Unlike the strictly hierarchical organization in the circadian clock system, the gut microbiota rhythmicity has a more complex multilayer network of all taxonomic levels of microbial taxa and their metabolites. However, it is worth noting that the functionality of the gut microbiota rhythmicity is highly dependent on the host circadian clock and host physiological status. Here, we discussed the diurnal rhythmicity of the gut microbiota; its crucial role in host physiology, health, and metabolism; and the crosstalk between the gut microbial rhythmicity and host circadian rhythm. This knowledge lays the foundation for the development of chronotherapies targeting the gut microbiota. However, the formation mechanism, its beneficial effects on the host of gut microbial rhythmicity, and the dynamic microbial–host crosstalk are not yet clear and warrant further research.

The Oscillating Gut Microbiome and Its Effects on Host Circadian Biology

The microbial community colonizing the gastrointestinal tract, collectively termed the gut microbiota, is an important element of the host organism due to its impact on multiple aspects of health. The digestion of food, secretion of immunostimulatory molecules, performance of chemical reactions in the intestine, and production of metabolites by the microbiota contribute to host homeostasis and disease. Recent discoveries indicate that these major functions are not constantly performed over the course of a day, but rather undergo diurnal fluctuations due to compositional and biogeographical oscillations in the microbiota. Here, we summarize the characteristics and origins of diurnal microbiome rhythms as well as their functional consequences for the circadian biology of the host. We describe the major known pathways of circadian host-microbiome communication and discuss possible implications of altered diurnal microbiome rhythms for human disease. Expected final online publication date for the Annual Review of Nutrition, Volume 42 is August 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Oat Fiber Modulates Hepatic Circadian Clock via Promoting Gut Microbiota-Derived Short Chain Fatty Acids

The biological alteration of circadian rhythm was found to be related to the development of metabolic disorders. Our previous studies reported that impaired lipid metabolism caused by a high-fat diet was improved by oat fiber, but did not attempt to answer whether the improvement is mechanistically linked to circadian rhythm. By focusing on circadian alteration, the present study aimed to elucidate the effect of gut microbiota-derived short chain fatty acids (SCFAs) on circadian rhythm in a high-fat diet experimental paradigm with and without dietary oat fiber feeding. The results showed that oat fiber prevented the production of obesity and dyslipidemia caused by a high-fat diet in C57BL/6 mice. From a circadian perspective specifically, a high-fat diet disrupted the hepatic circadian protein expressions of the liver clock genes, which were in parallel with the altered oscillation of serum triglycerides, low-density lipoprotein cholesterol, fasting insulin, and the homeostasis model assessment-insulin resistance index. Oat fiber, by contrast, reversed these disrupted diurnal oscillations. Most interestingly, what a high-fat diet induced and what oat fiber prevented were dictated in a close oscillation pattern resembling that of SCFA production facilitated by the intestinal microbiome. Given the results from the present study and from others that demonstrated the role played by SCFAs in regulating circadian rhythm, we conclude that the beneficial effects of oat fiber are likely mediated by complex processes involving multiple mechanisms including a signal transduction pathway of gut microbiota-derived SCFAs to hepatic circadian protein expression to lipid and other metabolic oscillations. The latter warrants more investigation to further determine whether the circadian rhythm pathway has any major and causal significance for the outcome measures in the prevention and treatment of metabolic disorders in humans.

Chronodisruption by chronic jetlag impacts metabolic and gastrointestinal homeostasis in male mice

AIM

Chronodisruption desynchronizes peripheral clocks and leads to metabolic diseases. Feeding cues are important synchronizers of peripheral clocks and influence rhythmic oscillations in intestinal microbiota and their metabolites. We investigated whether chronic jetlag, mimicking frequent time zone travelling, affected the diurnal fluctuations in faecal short-chain fatty acid (SCFA) levels, that feed back to the gut clock to regulate rhythmicity in gut function.

METHODS

Rhythms in faecal SCFAs levels and in the expression of clock genes and epithelial markers were measured in the colonic mucosa of control and jetlagged mice. The entraining effect of SCFAs on the rhythm in clock gene mRNA expression was studied in primary colonic crypts. The role of the circadian clock in epithelial marker expression was studied in Arntl^-/- mice.

RESULTS

Chronic jetlag increased body weight gain and abolished the day/night food intake pattern which resulted in a phase-delay in the rhythm of faecal SCFAs that paralleled the shift in the expression of mucosal clock genes. This effect was mimicked by stimulation of primary colonic crypts from control mice with SCFAs. Jetlag abolished the rhythm in Tnfα, proglucagon and ghrelin expression but not in the expression of tight junction markers. Only a dampening in plasma glucagon-like peptide-1 but not in ghrelin levels was observed. Rhythms in ghrelin but not proglucagon mRNA expression were abolished in Arntl^-/- mice.

CONCLUSION

The altered food intake pattern during chronodisruption corresponds with the changes in rhythmicity of SCFA levels that entrain clock genes to affect rhythms in mRNA expression of gut epithelial markers.

Time-Restricted Feeding in Mice Prevents the Disruption of the Peripheral Circadian Clocks and Its Metabolic Impact during Chronic Jetlag

We used time-restricted feeding (TRF) to investigate whether microbial metabolites and the hunger hormone ghrelin can become the dominant entraining factor during chronic jetlag to prevent disruption of the master and peripheral clocks, in order to promote health. Therefore, hypothalamic clock gene and Agrp/Npy mRNA expression were measured in mice that were either chronically jetlagged and fed ad libitum, jetlagged and fed a TRF diet, or not jetlagged and fed a TRF diet. Fecal short-chain fatty acid (SCFA) concentrations, plasma ghrelin and corticosterone levels, and colonic clock gene mRNA expression were measured. Preventing the disruption of the food intake pattern during chronic jetlag using TRF restored the rhythmicity in hypothalamic clock gene mRNA expression of Reverbα but not of Arntl. TRF countered the changes in plasma ghrelin levels and in hypothalamic Npy mRNA expression induced by chronic jetlag, thereby reestablishing the food intake pattern. Increase in body mass induced by chronic jetlag was prevented. Alterations in diurnal fluctuations in fecal SCFAs during chronic jetlag were prevented thereby re-entraining the rhythmic expression of peripheral clock genes. In conclusion, TRF during chronodisruption re-entrains the rhythms in clock gene expression and signals from the gut that regulate food intake to normalize body homeostasis.

THE ROLE OF CIRCADIAN REGULATION OF GHRELIN LEVELS IN PARKINSON’S DISEASE (LITERATURE REVIEW)

The paper is aimed at the analysis of the role of the circadian regulation of ghrelin levels in patients with Parkinson’s disease. Based on the literature data, patients with Parkinson’s disease have clinical fluctuations in the symptoms of the disease, manifested by the diurnal changes in motor activity, autonomic functions, sleep-wake cycle, visual function, and the efficacy of dopaminergic therapy. Biological rhythms are controlled by central and peripheral oscillators which links with dopaminergic neurotransmission – core of the pathogenesis of Parkinson`s disease. Circadian system is altered in Parkinson`s disease due to that ghrelin fluctuations may be changed. Ghrelin is potential food-entrainable oscillator because it is linked with clock genes expression. In Parkinson`s disease this hormone may induce eating behavior changing and as a result metabolic disorder. The “hunger hormone” ghrelin can be a biomarker of the Parkinson’s disease, and the study of its role in the pathogenesis, as well as its dependence on the period of the day, intake of levodopa medications to improve the effectiveness of treatment is promising.

Circadian clocks in the digestive system

Many molecular, physiological and behavioural processes display distinct 24-hour rhythms that are directed by the circadian system. The master clock, located in the suprachiasmatic nucleus region of the hypothalamus, is synchronized or entrained by the light-dark cycle and, in turn, synchronizes clocks present in peripheral tissues and organs. Other environmental cues, most importantly feeding time, also synchronize peripheral clocks. In this way, the circadian system can prepare the body for predictable environmental changes such as the availability of nutrients during the normal feeding period. This Review summarizes existing knowledge about the diurnal regulation of gastrointestinal processes by circadian clocks present in the digestive tract and its accessory organs. The circadian control of gastrointestinal digestion, motility, hormones and barrier function as well as of the gut microbiota are discussed. An overview is given of the interplay between different circadian clocks in the digestive system that regulate glucose homeostasis and lipid and bile acid metabolism. Additionally, the bidirectional interaction between the master clock and peripheral clocks in the digestive system, encompassing different entraining factors, is described. Finally, the possible behavioural adjustments or pharmacological strategies for the prevention and treatment of the adverse effects of chronodisruption are outlined.

Diurnal Rhythmicity Programs of Microbiota and Transcriptional Oscillation of Circadian Regulator, NFIL3

Circadian rhythms are a very exquisite mechanism to influence on transcriptional levels and physiological activities of various molecules that affect cell metabolic pathways. Long-term alteration of circadian rhythms increases the risk of cardiovascular diseases, hypertension, hypertriglyceridemia, and metabolic syndrome. A drastic change in dietary patterns can affect synchronizing the circadian clock within the metabolic system. Therefore, the interaction between the host and the bacterial community colonizing the mammalian gastrointestinal tract has a great impact on the circadian clock in diurnal programs. Here, we propose that the microbiota regulates body composition through the transcriptional oscillation of circadian regulators. The transcriptional regulator, NFIL3 (also called E4BP4) is a good example. Compositional change of the commensal bacteria influences the rhythmic expression of NFIL3 in the epithelium, which subsequently controls obesity and insulin resistance. Therefore, control of circadian regulators would be a promising therapeutic target for metabolic diseases.

Circadian Host-Microbiome Interactions in Immunity

The gut microbiome plays a critical role in regulating host immunity and can no longer be regarded as a bystander in human health and disease. In recent years, circadian (24 h) oscillations have been identified in the composition of the microbiota, its biophysical localization within the intestinal tract and its metabolic outputs. The gut microbiome and its key metabolic outputs, such as short chain fatty acids and tryptophan metabolites contribute to maintenance of intestinal immunity by promoting barrier function, regulating the host mucosal immune system and maintaining the function of gut-associated immune cell populations. Loss of rhythmic host-microbiome interactions disrupts host immunity and increases risk of inflammation and metabolic complications. Here we review factors that drive circadian variation in the microbiome, including meal timing, dietary composition and host circadian clocks. We also consider how host-microbiome interactions impact the core molecular clock and its rhythmic outputs in addition to the potential impact of this relationship on circadian control of immunity.