Time-Restricted Feeding Reduces the Detrimental Effects of a High-Fat Diet, Possibly by Modulating the Circadian Rhythm of Hepatic Lipid Metabolism and Gut Microbiota

Time-restricted eating, the clock ticking behind the scenes

Introduction

Maintaining metabolic balance relies on accumulating nutrients during feeding periods and their subsequent release during fasting. In obesity and metabolic disorders, strategies aimed at reducing food intake while simulating fasting have garnered significant attention for weight loss. Caloric restriction (CR) diets and intermittent fasting (IF) interventions have emerged as effective approaches to improving cardiometabolic health. Although the comparative metabolic benefits of CR versus IF remain inconclusive, this review focuses on various forms of IF, particularly time-restricted eating (TRE).

Methods

This study employs a narrative review methodology, systematically collecting, synthesizing, and interpreting the existing literature on TRE and its metabolic effects. A comprehensive and unbiased search of relevant databases was conducted to identify pertinent studies, including pre-clinical animal studies and clinical trials in humans. Keywords such as "Obesity," "Intermittent Fasting," "Time-restricted eating," "Chronotype," and "Circadian rhythms" guided the search. The selected studies were critically appraised based on predefined inclusion and exclusion criteria, allowing for a thorough exploration and synthesis of current knowledge.

Results

This article synthesizes pre-clinical and clinical studies on TRE and its metabolic effects, providing a comprehensive overview of the current knowledge and identifying gaps for future research. It explores the metabolic outcomes of recent clinical trials employing different TRE protocols in individuals with overweight, obesity, or type II diabetes, emphasizing the significance of individual chronotype, which is often overlooked in practice. In contrast to human studies, animal models underscore the role of the circadian clock in mitigating metabolic disturbances induced by obesity through time-restricted feeding (TRF) interventions. Consequently, we examine pre-clinical evidence supporting the interplay between the circadian clock and TRF interventions. Additionally, we provide insights into the role of the microbiota, which TRE can modulate and its influence on circadian rhythms.

Gut microbiota and eating behaviour in circadian syndrome

Eating behaviour and circadian rhythms are closely related. The type, timing, and quantity of food consumed, and host circadian rhythms, directly influence the intestinal microbiota, which in turn impacts host circadian rhythms and regulates food intake beyond homeostatic eating. This Opinion discusses the impact of food intake and circadian disruptions induced by an obesogenic environment on gut-brain axis signalling. We also explore potential mechanisms underlying the effects of altered gut microbiota on food intake behaviour and circadian rhythmicity. Understanding the crosstalk between gut microbiota, circadian rhythms, and unhealthy eating behaviour is crucial to addressing the obesity epidemic, which remains one of the biggest societal challenges of our time.

Counting hours or calories? Metabolic regulatory role of time-restricted eating in adults with overweight and obesity: a systematic review and meta-analysis

Time-restricted eating (TRE) effectively improves healthspan, including controlling obesity and improving metabolic health. To date, few meta-analyses have been conducted to explore the effects of various protocols of TRE in participants with overweight/obesity. PubMed, Embase and the Cochrane Central Register of Controlled Trials were searched up until October 15, 2022. Randomized and non-randomized clinical trials that investigated the effect of TRE on body weight, body composition and cardiometabolic parameters in participants with overweight/obesity were included. Mean differences of changes from the baseline were used for all analyses between the two groups. Prespecified subgroup analyses based on different protocols of TRE were performed. Twenty-three studies were included in the meta-analysis with 1867 participants. TRE interventions led to significant changes in body weight. When energy restriction strategies were conducted in both the TRE and control groups, the weight-loss effect of TRE remained significant. TRE with 4 ∼ 8h feeding window, morning or late eating strategies, led to reduction in body weight and fat mass for at least 8 wk. Hence TRE is a potential and effective approach for weight loss for participants with overweight/obesity. An 8h-TRE intervention with a morning eating strategy for at least eight weeks might be the optimum TRE intervention mode.

Health Benefits of Intermittent Fasting

We propose that intermittent fasting (time-restricted eating), in agreement with the conclusions of other biologists, as revealed in recent publications, promotes the achievement of numerous health benefits including the extension of human and animal lifespans. Background: There is evidence, obtained both with animal model systems and with humans, that intermittent fasting has health benefits. These benefits include extended longevity, weight loss, and counteracting various disease conditions. Such procedures positively influence the benefits of human tissue-specific microbiomes and minimize the consequences of organellar apoptosis. Key Messages: In this review, we attempt to summarize the predominant evidence, published in the scientific literature, relevant to the conclusions that in general, and in many specific instances, intermittent fasting has long-term benefits to animals, including humans, with respect to overall and specific organismal health and longevity.

Diurnal expression of Dgat2 induced by time-restricted feeding maintains cardiac health in the Drosophila model of circadian disruption

Circadian disruption is associated with an increased risk of cardiometabolic disorders and cardiac diseases. Time-restricted feeding/eating (TRF/TRE), restricting food intake within a consistent window of the day, has shown improvements in heart function from flies and mice to humans. However, whether and how TRF still conveys cardiac benefits in the context of circadian disruption remains unclear. Here, we demonstrate that TRF sustains cardiac performance, myofibrillar organization, and regulates cardiac lipid accumulation in Drosophila when the circadian rhythm is disrupted by constant light. TRF induces oscillations in the expression of genes associated with triglyceride metabolism. In particular, TRF induces diurnal expression of diacylglycerol O-acyltransferase 2 (Dgat2), peaking during the feeding period. Heart-specific manipulation of Dgat2 modulates cardiac function and lipid droplet accumulation. Strikingly, heart-specific overexpression of human Dgat2 at ZT 0-10 significantly improves cardiac performance in flies exposed to constant light. We have demonstrated that TRF effectively attenuates cardiac decline induced by circadian disruption. Moreover, our data suggests that diurnal expression of Dgat2 induced by TRF is beneficial for heart health under circadian disruption. Overall, our findings have underscored the relevance of TRF in preserving heart health under circadian disruptions and provided potential targets, such as Dgat2, and strategies for therapeutic interventions in mitigating cardiac aging, metabolic disorders, and cardiac diseases in humans.

A detective story of intermittent fasting effect on immunity

Intermittent fasting (IF) refers to periodic fasting routines, that caloric intake is minimized not by meal portion size reduction but by intermittently eliminating ingestion of one or several consecutive meals. IF can instigate comprehensive and multifaceted alterations in energy metabolism, these metabolic channels may aboundingly function as primordial mechanisms that interface with the immune system, instigating intricate immune transformations. This review delivers a comprehensive understanding of IF, paying particular attention to its influence on the immune system, thus seeking to bridge these two research domains. We explore how IF effects lipid metabolism, hormonal levels, circadian rhythm, autophagy, oxidative stress, gut microbiota, and intestinal barrier integrity, and conjecture about the mechanisms orchestrating the intersect between these factors and the immune system. Moreover, the review includes research findings on the implications of IF on the immune system and patients burdened with autoimmune diseases.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Effect of time restricted feeding on anthropometric measures, eating behavior, stress, serum levels of BDNF and LBP in overweight/obese women with food addiction: a randomized clinical trial

BACKGROUND & AIM

Food addiction (FA) as a specific food-related behavior may play an essential role in the pathogenesis of obesity. Brain-derived neurotrophic factor (BDNF) and gut microbiota (GM) alterations probably through fasting are closely related to brain function, affecting eating behaviors and body weight management. This study aimed to evaluate the effect of time-restricted feeding (TRF) on serum BDNF levels and eating behaviors in overweight and obese women with FA.

METHODS AND DESIGN

This clinical trial was performed with a 2-month follow-up on 56 obese and overweight women with FA. Participants were randomly divided into two groups receiving a low-calorie diet (n = 27) and a group receiving a low-calorie diet with TRF (n = 29). Anthropometric measurements, biochemical markers, eating behavior, and stress were assessed during the study period.

RESULTS

The reductions in weight, body mass index (BMI), waist circumference, and body fat mass were significantly higher in the TRF group compared to the control group at week 8 (P = 0.018, P = 0.015. P = 0.03, and P = 0.036, respectively). The cognitive restriction score was higher in the TRF as compared with the control group (P = 0.002). The food addiction criteria score was significantly reduced in both groups (P < 0.001). Serum levels of BDNF were significantly increased in the TRF group (P < 0.001). In addition, BDNF levels had a positive and significant correlation with the cognitive restriction score (r = 0.468 and P < 0.001), While the correlation with FA was not significant (β = 0.588 and P = 0.618). Lipopolysaccharide binding protein decreased significantly in both groups, but this decrease was significantly higher in the TRF group than in the control group (P < 0.001).

CONCLUSION

The results of this study showed that a low-calorie diet with TRF is more effective in weight management than a low-calorie diet alone, probably through further modulating the GM and improving BDNF levels. More effective weight loss in the TRF is probably related to better management of eating behavior than FA.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials identifier: IRCT20131228015968N7.

The effects of time-restricted eating and Ramadan fasting on gut microbiota composition: a systematic review of human and animal studies

CONTEXT

It is well known that the microbiome undergoes cyclical diurnal rhythms. It has thus been hypothesized that meal timing may affect gut microbial composition, function, and host health.

OBJECTIVE

This review aims to examine the effects of time-restricted eating (TRE) and Ramadan fasting (RF) on the composition of the gut microbiota in animal and human studies. The associations between composition of microbiota and host metabolic parameters are also examined.

DATA SOURCES

A search was performed on the PubMed, Cochrane, Scopus, and Web of Science databases up to December 31, 2022. The search strategy was performed using the Medical Subject Heading (MeSH) terms "intermittent fasting" and "gastrointestinal microbiome" and the key words "Ramadan fasting" and "microbes."

DATA EXTRACTION

Seven human studies (4 TRE and 3 RF) and 9 animal studies (7 TRE, 2 RF-like) were retrieved.

DATA ANALYSIS

TRE and RF in human studies lead to an increase in gut microbial community alpha-diversity. In animal studies (both TRE and RF-like), fasting is not associated with improved alpha-diversity, but enhancement of microbial fluctuation is observed, compared with high-fat diet ad libitum groups. Within Firmicutes and Bacteroidetes phyla, no specific direction of changes resulting from fasting are observed in both animals and human. After TRE or RF, a greater abundance of the Faecalibacterium genus is observed in human studies; changes in Lactobacillus abundance are found in animal studies; and increases in Akkermansia are seen both in humans and in animals fed a feed-pellet diet. Only 2 human studies show a beneficial correlation between microbiota changes and host metabolic (HDL cholesterol) or anthropometric parameters (body mass index).

CONCLUSIONS

These findings support the importance of both regimens in improving the gut microbiota composition. However, based on results of animal studies, it can be suggested that diet remains the essential factor in forming the microbiota's environment.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42021278918.

Circadian Regulation of Endocrine Fibroblast Growth Factors on Systemic Energy Metabolism

The circadian clock is an endogenous biochemical timing system that coordinates the physiology and behavior of organisms to earth's ∼24-hour circadian day/night cycle. The central circadian clock synchronized by environmental cues hierarchically entrains peripheral clocks throughout the body. The circadian system modulates a wide variety of metabolic signaling pathways to maintain whole-body metabolic homeostasis in mammals under changing environmental conditions. Endocrine fibroblast growth factors (FGFs), namely FGF15/19, FGF21, and FGF23, play an important role in regulating systemic metabolism of bile acids, lipids, glucose, proteins, and minerals. Recent evidence indicates that endocrine FGFs function as nutrient sensors that mediate multifactorial interactions between peripheral clocks and energy homeostasis by regulating the expression of metabolic enzymes and hormones. Circadian disruption induced by environmental stressors or genetic ablation is associated with metabolic dysfunction and diurnal disturbances in FGF signaling pathways that contribute to the pathogenesis of metabolic diseases. Time-restricted feeding strengthens the circadian pattern of metabolic signals to improve metabolic health and prevent against metabolic diseases. Chronotherapy, the strategic timing of medication administration to maximize beneficial effects and minimize toxic effects, can provide novel insights into linking biologic rhythms to drug metabolism and toxicity within the therapeutical regimens of diseases. Here we review the circadian regulation of endocrine FGF signaling in whole-body metabolism and the potential effect of circadian dysfunction on the pathogenesis and development of metabolic diseases. We also discuss the potential of chrononutrition and chronotherapy for informing the development of timing interventions with endocrine FGFs to optimize whole-body metabolism in humans. SIGNIFICANCE STATEMENT: The circadian timing system governs physiological, metabolic, and behavioral functions in living organisms. The endocrine fibroblast growth factor (FGF) family (FGF15/19, FGF21, and FGF23) plays an important role in regulating energy and mineral metabolism. Endocrine FGFs function as nutrient sensors that mediate multifactorial interactions between circadian clocks and metabolic homeostasis. Chronic disruption of circadian rhythms increases the risk of metabolic diseases. Chronological interventions such as chrononutrition and chronotherapy provide insights into linking biological rhythms to disease prevention and treatment.

The Diurnal Transcriptome Reveals the Reprogramming of Lung Adenocarcinoma Cells Under a Time-Restricted Feeding-Mimicking Regimen

BACKGROUND

The processes of tumor growth and circadian rhythm are intimately intertwined; thus, rewiring circadian metabolism by time-restricted feeding (TRF) may contribute to delaying carcinogenesis. However, research on the effect of a TRF cellular regimen on cancer is lacking.

OBJECTIVE

Investigate the circadian signatures of TRF in lung cancer in vitro.

METHODS

We first developed a cellular paradigm mimicking in vivo TRF and collected cells for transcriptome analysis. We further confirmed the effect on tumor cells upon 6-h TRF-mimicking (6-h TRFM) by real-time PCR, Lumicycle experiments, CCK-8, and flow cytometry assays.

RESULTS

We found that A549 lung adenocarcinoma cells treated with 6-h TRFM conditions displayed robust diurnal rhythms of transcriptomes, as well as modulation of the core clock genes relative to other different cellular regimens used in this study, including the fasting-mimicking conditions (ie, short-term starvation) and the serum-free regime. Notably, pathway analysis of oscillating genes exclusively in 6-h TRFM showed that some circadian genes were enriched in tumor-related pathways, such as the oxytocin signaling pathway, HIF-1 signaling pathway, and pentose and glucuronate interconversions. Moreover, in line with the circadian pathway enrichment results, 6-h TRFM robustly inhibited cell proliferation and induced cell apoptosis and cell cycle arrest in lung adenocarcinoma A549 cells, lung adenocarcinoma H460 cells, esophageal carcinoma Eca-109 cells, and breast adenocarcinoma MCF-7 cells.

CONCLUSIONS

Our findings provide the first in vitro mimicking medium for TRF intervention and indicate that 6-h TRFM is sufficient to reprogram the circadian signatures of lung adenocarcinoma cells and inhibit the progression of multiple tumors.

Does early time-restricted eating reduce body weight and preserve fat-free mass in adults? A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

This meta-analysis evaluated whether weight loss caused by early time-restricted eating could promote fat mass loss while preserving fat-free mass, thereby leading to improvements in inflammation and metabolic health.

METHODS

Relevant randomized controlled trials (RCTs) published up to March 28, 2023, were identified in six databases, including PubMed, Web of Science, and Embase.

RESULTS

We initially screened 1279 articles, thirteen RCTs with 859 patients were ultimately included. Compared with nontime-restricted eating, early time-restricted eating significantly reduced body weight (-1.84 kg [-2.28, -1.41]; I2 = 56 %; P < 0.00001), fat mass (-1.10 kg [-1.47, -0.74]; I2 = 42 %; P < 0.00001), waist circumstance (-3.21 cm [-3.90, -2.51]; I2 = 43 %; P < 0.00001), visceral fat area (-9.76 cm2 [-13.76, -5.75]; I2 = 2 %; P < 0.00001), and inflammation as measured by tumour necrosis factor-α (-1.36 pg/mL [-2.12, -0.60]; I2 = 42 %; P < 0.001). However, early time-restricted eating did not lead to a significant change in fat-free mass (-0.56 kg [-1.16, 0.03]; I2 = 59 %; P = 0.06). Subgroup analysis showed that the early time-restricted eating of the 16:08 (fasting-time versus eating-time) strategy had a superior effect on preserving fat-free mass (-0.25 kg [-0.68, 0.18]; I2 = 0 %; P = 0.25) while significantly reducing body weight (-1.60 kg [-2.09, -1.11]; I2 = 0 %; P < 0.001) and improving metabolic outcomes.

CONCLUSIONS

Early time-restricted eating, especially 16:08 strategy, appears to be an effective strategy to decrease body weight, fat mass, abdominal obesity and inflammation, but less likely to decrease fat-free mass.

Various types of fasting diet and possible benefits in nonalcoholic fatty liver: Mechanism of actions and literature update

Non-alcoholic fatty liver disease (NAFLD) is one of the major causes of chronic liver injury, affecting around one-fourth of the general population across the world. Several important pathophysiological mechanisms underlying NAFLD include oxidative stress, inflammation, liver fibrosis, and apoptosis. Currently, therapeutic approaches are not ideal for managing NAFLD, thus new approaches and treatments are still needed. Over the last two decades, various fasting protocols have been explored to reduce body weight and improve metabolic disorders. In this review, we provide updated literature that supports fasting regimens for subjects with NAFLD and describes underlying mechanisms of action. We suggest that fasting regimens may modulate NAFLD via several mechanisms, including changes in gut microbiota, hepatic arginase, hepatic autophagy, inflammatory responses, liver functional enzymes and hepatic steatosis, fibroblast growth factors signaling, white adipose tissue browning, adipokines, circadian rhythms, lipid profiles, and body composition.

SIRT1/SREBPs-mediated regulation of lipid metabolism

Sirtuins, also called silent information regulator 2, are enzymes that rely on nicotinamide adenine dinucleotide (NAD+) to function as histone deacetylases. Further investigation is warranted to explore the advantageous impacts of Sirtuin 1 (SIRT1), a constituent of the sirtuin group, on lipid metabolism, in addition to its well-researched involvement in extending lifespan. The regulation of gene expression has been extensively linked to SIRT1. Sterol regulatory element-binding protein (SREBP) is a substrate of SIRT1 that has attracted significant interest due to its role in multiple cellular processes including cell cycle regulation, DNA damage repair, and metabolic functions. Hence, the objective of this analysis was to investigate and elucidate the correlation between SIRT1 and SREBPs, as well as assess the contribution of SIRT1/SREBPs in mitigating lipid metabolism dysfunction. The objective of this research was to investigate whether SIRT1 and SREBPs could be utilized as viable targets for therapeutic intervention in managing complications associated with diabetes.

Chronic jet lag alters gut microbiome and mycobiome and promotes the progression of MAFLD in HFHFD-fed mice

Metabolic dysfunction-associated fatty liver disease (MAFLD) is the most common chronic liver disease worldwide. Circadian disruptors, such as chronic jet lag (CJ), may be new risk factors for MAFLD development. However, the roles of CJ on MAFLD are insufficiently understood, with mechanisms remaining elusive. Studies suggest a link between gut microbiome dysbiosis and MAFLD, but most of the studies are mainly focused on gut bacteria, ignoring other components of gut microbes, such as gut fungi (mycobiome), and few studies have addressed the rhythm of the gut fungi. This study explored the effects of CJ on MAFLD and its related microbiotic and mycobiotic mechanisms in mice fed a high fat and high fructose diet (HFHFD). Forty-eight C57BL6J male mice were divided into four groups: mice on a normal diet exposed to a normal circadian cycle (ND-NC), mice on a normal diet subjected to CJ (ND-CJ), mice on a HFHFD exposed to a normal circadian cycle (HFHFD-NC), and mice on a HFHFD subjected to CJ (HFHFD-CJ). After 16 weeks, the composition and rhythm of microbiota and mycobiome in colon contents were compared among groups. The results showed that CJ exacerbated hepatic steatohepatitis in the HFHFD-fed mice. Compared with HFHFD-NC mice, HFHFD-CJ mice had increases in Aspergillus, Blumeria and lower abundances of Akkermansia, Lactococcus, Prevotella, Clostridium, Bifidobacterium, Wickerhamomyces, and Saccharomycopsis genera. The fungi-bacterial interaction network became more complex after HFHFD and/or CJ interventions. The study revealed that CJ altered the composition and structure of the gut bacteria and fungi, disrupted the rhythmic oscillation of the gut microbiota and mycobiome, affected interactions among the gut microbiome, and promoted the progression of MAFLD in HFHFD mice.

Intermittent Fasting on Neurologic Diseases: Potential Role of Gut Microbiota

As the global population ages, the prevalence of neurodegenerative diseases is surging. These disorders have a multifaceted pathogenesis, entwined with genetic and environmental factors. Emerging research underscores the profound influence of diet on the development and progression of health conditions. Intermittent fasting (IF), a dietary pattern that is increasingly embraced and recommended, has demonstrated potential in improving neurophysiological functions and mitigating pathological injuries with few adverse effects. Although the precise mechanisms of IF's beneficial impact are not yet completely understood, gut microbiota and their metabolites are believed to be pivotal in mediating these effects. This review endeavors to thoroughly examine current studies on the shifts in gut microbiota and metabolite profiles prompted by IF, and their possible consequences for neural health. It also highlights the significance of dietary strategies as a clinical consideration for those with neurological conditions.

Time-restricted feeding affects the fecal microbiome metabolome and its diurnal oscillations in lung cancer mice

The homeostasis of the gut microbiota and circadian rhythm is critical to host health, and both are inextricably intertwined with lung cancer. Although time-restricted feeding (TRF) can maintain circadian synchronization and improve metabolic disorders, the effects of TRF on the fecal microbiome, metabolome and their diurnal oscillations in lung cancer have not been discussed. We performed 16S rRNA sequencing and untargeted metabonomic sequencing of the feces prepared from models of tumor-bearing BALB/c nude mice and urethane-induced lung cancer. We demonstrated for the first time that TRF significantly delayed the growth of lung tumors. Moreover, TRF altered the abundances of the fecal microbiome, metabolome and circadian clocks, as well as their rhythmicity, in lung cancer models of tumor-bearing BALB/c nude mice and/or urethane-induced lung cancer C57BL/6J mice. The results of fecal microbiota transplantation proved that the antitumor effects of TRF occur by regulating the fecal microbiota. Notably, Lactobacillus and Bacillus were increased upon TRF and were correlated with most differential metabolites. Pathway enrichment analysis of metabolites revealed that TRF mainly affected immune and inflammatory processes, which might further explain how TRF exerted its anticancer benefits. These findings underscore the possibility that the fecal microbiome/metabolome regulates lung cancer following a TRF paradigm.

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.

Circadian rhythms, gut microbiota, and diet: Possible implications for health

AIMS

Over the past years, interest in chrono-nutrition has grown enormously as the fundamental role of circadian rhythms in regulating most physiological and metabolic processes has become clearer. Recently, the influence of circadian rhythms on the gut microbiota (GM) composition has also emerged, as more than half of the total microbial composition fluctuates rhythmically throughout the day. At the same time, other studies have observed that the GM itself synchronises the host's circadian biological clock through signals of a different nature. Therefore, it has been hypothesised that there is a two-way communication between the circadian rhythms of the host and the GM, but researchers have only just begun to identify some of its action mechanisms. The manuscript aim is, therefore, to gather and combine the latest evidence in the field of chrono-nutrition with the more recent research on the GM, in order to investigate their relationship and their potential impact on human health.

DATA SYNTHESIS

Considering current evidence, a desynchronization of circadian rhythms is closely associated with an alteration in the abundance and functionality of the gut microbiota with consequent deleterious effects on health, such as increased risk of numerous pathologies, including cardiovascular disease, cancer, irritable bowel disease, and depression. A key role in maintaining the balance between circadian rhythms and GM seems to be attributed to meal-timing and diet quality, as well as to certain microbial metabolites, in particular short-chain fatty acids.

CONCLUSIONS

Future studies are needed to decipher the link between the circadian rhythms and specific microbial patterns in relation to different disease frameworks.

Post-Effects of Time-Restricted Feeding against Adipose Tissue Inflammation and Insulin Resistance in Obese Mice

Time-restricted feeding (TRF) has been shown to improve the disordered metabolic and immunologic functions associated with obesity, however little is known about its post-effects after the cessation of TRF practice. In the current study, we determined how long the effects of TRF persist, and whether the effects are tissue-dependent. There were four groups of mice in this study: overweight and obese mice were randomized into (1) TRF group (TRF for 6 weeks), (2) post-TRF group (TRF for 4 weeks and later ad libitum), (3) continuous ad libitum of high-fat diet (HFD-AL), and (4) the lean control-fed low-fat diet ad libitum. Blood, liver, and adipose tissues were collected to measure the metabolic, inflammatory, and immune cell parameters. The results showed that TRF withdrawal quickly led to increased body weight/adiposity and reversed fasting blood glucose. However, fasting insulin and insulin resistance index HOMA-IR remained lower in the post-TRF than in the HFD-AL group. In addition, TRF-induced reduction in blood monocytes waned in the post-TRF group, but the TRF effects on mRNA levels of proinflammatory immune cells (macrophages Adgre1 and Itgax) and cytokine (Tnf) in adipose tissue remained lower in the post-TRF group than in the HFD-AL group. Furthermore, the TRF group was protected from the down-regulation of Pparg mRNA expression in adipose tissue, which was also observed in the post-TRF group to a lesser extent. The post-TRF animals displayed liver mass similar to those in the TRF group, but the TRF effects on the mRNA of inflammation markers in the liver vanished completely. Together, these results indicate that, although the lasting effects of TRF may differ by tissues and genes, the impact of TRF on adipose tissue inflammation and immune cell infiltration could last a couple of weeks, which may, in part, contribute to the maintenance of insulin sensitivity even after the cessation of TRF.

Epilepsy, gut microbiota, and circadian rhythm

In recent years, relevant studies have found changes in gut microbiota (GM) in patients with epilepsy. In addition, impaired sleep and circadian patterns are common symptoms of epilepsy. Moreover, the types of seizures have a circadian rhythm. Numerous reports have indicated that the GM and its metabolites have circadian rhythms. This review will describe changes in the GM in clinical and animal studies under epilepsy and circadian rhythm disorder, respectively. The aim is to determine the commonalities and specificities of alterations in GM and their impact on disease occurrence in the context of epilepsy and circadian disruption. Although clinical studies are influenced by many factors, the results suggest that there are some commonalities in the changes of GM. Finally, we discuss the links among epilepsy, gut microbiome, and circadian rhythms, as well as future research that needs to be conducted.

A nexus of dietary restriction and gut microbiota: Recent insights into metabolic health

In recent times, dietary restriction (DR) has received considerable attention for its promising effects on metabolism and longevity. Previous studies on DR have mainly focused on the health benefits produced by different restriction patterns, whereas comprehensive reviews of the role of gut microbiota during DR are limited. In this review, we discuss the effects of caloric restriction, fasting, protein restriction, and amino acid restriction from a microbiome perspective. Furthermore, the underlying mechanisms by which DR affects metabolic health by regulating intestinal homeostasis are summarized. Specifically, we reviewed the impacts of different DRs on specific gut microbiota. Additionally, we put forward the limitations of the current research and suggest the development of personalized microbes-directed DR for different populations and corresponding next-generation sequencing technologies for accurate microbiological analysis. DR effectively modulates the composition of the gut microbiota and microbial metabolites. In particular, DR markedly affects the rhythmic oscillation of microbes which may be related to the circadian clock system. Moreover, increasing evidence supports that DR profoundly improves metabolic syndrome, inflammatory bowel disease, and cognitive impairment. To summarize, DR may be an effective and executable dietary manipulation strategy for maintaining metabolic health, however, further investigation is needed to elucidate the underlying mechanisms.

Fasting: From Physiology to Pathology

Overnutrition is a risk factor for various human diseases, including neurodegenerative diseases, metabolic disorders, and cancers. Therefore, targeting overnutrition represents a simple but attractive strategy for the treatment of these increasing public health threats. Fasting as a dietary intervention for combating overnutrition has been extensively studied. Fasting has been practiced for millennia, but only recently have its roles in the molecular clock, gut microbiome, and tissue homeostasis and function emerged. Fasting can slow aging in most species and protect against various human diseases, including neurodegenerative diseases, metabolic disorders, and cancers. These centuried and unfading adventures and explorations suggest that fasting has the potential to delay aging and help prevent and treat diseases while minimizing side effects caused by chronic dietary interventions. In this review, recent animal and human studies concerning the role and underlying mechanism of fasting in physiology and pathology are summarized, the therapeutic potential of fasting is highlighted, and the combination of pharmacological intervention and fasting is discussed as a new treatment regimen for human diseases.

Capsaicin ameliorates diet-induced disturbances of glucose homeostasis and gut microbiota in mice associated with the circadian clock

Glucose metabolism disorder triggered by a high-energy diet is associated with circadian disruption in the brain, peripheral tissues and gut microbiota. The present study aims to investigate the regulating effects of capsaicin (CAP) on the diet-induced disturbances of glucose homeostasis and gut microbiota in respect of circadian rhythm-related mechanisms. Our results indicated that CAP significantly ameliorated glucose metabolism disorder in mice induced by a high-fat and high-fructose diet (HFFD). The rhythmic expressions of circadian clock genes (Bmal1, Clock, and others) and glucose metabolism-related genes (Pgc-1α, Glut2, G6pc, and Pepck) in the liver disrupted by an abnormal diet were also recovered by CAP. Microbial studies using 16S rDNA sequencing revealed that CAP modulated the structure and composition of gut microbiota and improved the circadian oscillations of Firmicutes and Bacteroidetes at the phylum level and Allobaculum, Bacteroides, Bifidobacterium, and Alistipes at the genus level. Correlation analysis indicated that a close correlation existed between intestinal microbiota, hepatic circadian gene expressions and the level of glucose metabolism-related factors, indicating that CAP could alleviate HFFD-induced disturbances of glucose metabolism and gut microbiota associated with circadian clock related mechanisms.

Gut Microbiota and Time-Restricted Feeding/Eating: A Targeted Biomarker and Approach in Precision Nutrition

Each individual has a unique gut microbiota; therefore, the genes in our microbiome outnumber the genes in our genome by about 150 to 1. Perturbation in host nutritional status influences gut microbiome composition and vice versa. The gut microbiome can help in producing vitamins, hormones, and other active metabolites that support the immune system; harvest energy from food; aid in digestion; protect against pathogens; improve gut transit and function; send signals to the brain and other organs; oscillate the circadian rhythm; and coordinate with the host metabolism through multiple cellular pathways. Gut microbiota can be influenced by host genetics, medications, diet, and lifestyle factors from preterm to aging. Aligning with precision nutrition, identifying a personalized microbiome mandates the provision of the right nutrients at the right time to the right patient. Thus, before prescribing a personalized treatment, it is crucial to monitor and count the gut flora as a focused biomarker. Many nutritional approaches that have been developed help in maintaining and restoring an optimal microbiome such as specific diet therapy, nutrition interventions, and customized eating patterns. One of these approaches is time-restricted feeding/eating (TRF/E), a type of intermittent fasting (IF) in which a subject abstains from food intake for a specific time window. Such a dietary modification might alter and restore the gut microbiome for proper alignment of cellular and molecular pathways throughout the lifespan. In this review, we have highlighted that the gut microbiota would be a targeted biomarker and TRF/E would be a targeted approach for restoring the gut-microbiome-associated molecular pathways such as hormonal signaling, the circadian system, metabolic regulators, neural responses, and immune-inflammatory pathways. Consequently, modulation of the gut microbiota through TRF/E could contribute to proper utilization and availability of the nutrients and in this way confer protection against diseases for harnessing personalized nutrition approaches to improve human health.

Time-restricted feeding's effect on overweight and obese patients with chronic kidney disease stages 3-4: A prospective non-randomized control pilot study

Background

Time-restricted feeding (TRF) has become a popular weight loss method in recent years. It is widely used in the nutritional treatment of normal obese people and obese people with chronic diseases such as diabetes mellitus and hypertension, and has shown many benefits. However, most TRF studies have excluded chronic kidney disease (CKD) patients, resulting in a lack of sufficient evidence-based practice for the efficacy and safety of TRF therapy for CKD. Therefore, we explore the efficacy and safety of TRF in overweight and obese patients with moderate-to-severe stage CKD through this pilot study, and observe patient compliance to assess the feasibility of the therapy.

Methods

This is a prospective, non-randomized controlled short-term clinical trial. We recruited overweight and obese patients with CKD stages 3-4 from an outpatient clinic and assigned them to either a TRF group or a control diet (CD) group according to their preferences. Changes in renal function, other biochemical data, anthropometric parameters, gut microbiota, and adverse events were measured before the intervention and after 12 weeks.

Results

The change in estimated glomerular filtration rate (eGFR) before and after intervention in the TRF group (Δ = 3.1 ± 5.3 ml/min/1.73m²) showed significant improvement compared with the CD group (Δ = -0.8 ± 4.4 ml/min/1.73m²). Furthermore, the TRF group had a significant decrease in uric acid (Δ = -70.8 ± 124.2 μmol/L), but an increase in total protein (Δ = 1.7 ± 2.5 g/L), while the changes were inconsistent for inflammatory factors. In addition, the TRF group showed a significant decrease in body weight (Δ = -2.8 ± 2.9 kg) compared to the CD group, and body composition indicated the same decrease in body fat mass, fat free mass and body water. Additionally, TRF shifted the gut microbiota in a positive direction.

Conclusion

Preliminary studies suggest that overweight and obese patients with moderate-to-severe CKD with weight loss needs, and who were under strict medical supervision by healthcare professionals, performed TRF with good compliance. They did so without apparent adverse events, and showed efficacy in protecting renal function. These results may be due to changes in body composition and alterations in gut microbiota.

Time-restricted feeding rescues circadian disruption-aggravated progression of Alzheimer's disease in diabetic mice

Circadian rhythms, type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) are closely related and interacted with each other. We have previously showed circadian disruption aggravated progression of AD in T2DM mice. Time-restricted feeding (TRF) is shown to be a potential synchronizer. This study aims to determine whether TRF has a protective effect against the circadian disruption-aggravated progression of AD in T2DM. 6-week-old male diabetic (db/db) mice and wildtype (wt/wt) mice were kept under normal 12:12 light/dark cycles or altered 6:18 light/dark cycles (dark extended to 18 h) with or without TRF (food restricted to 8 h during the active (dark) period). After 8 weeks, three behavioral tests (open field test, novel object recognition test, barnes maze test) were performed and the circadian gene expression, body weight, lipid levels and AD-associated tau phosphorylation were evaluated. We found altered light/dark cycles contributed to disruptive circadian rhythms in the hippocampus of db/db mice, while TRF prevented this effect. TRF also ameliorated circadian disruption-aggravated increased body weight and lipid accumulation in db/db mice. Importantly, the db/db mice under circadian disruption showed impaired cognition accompanied by increased tau phosphorylation, whereas TRF reversed these changes. The altered light/dark cycles only affected circadian rhythms but not other indicators like plasma/liver lipids, cognition and tau phosphorylation in the wt/wt mice. Collectively, TRF has a protective effect against altered light/dark cycles-aggravated AD progression in diabetic mice.

Chrononutrition-When We Eat Is of the Essence in Tackling Obesity

Obesity is a chronic and relapsing public health problem with an extensive list of associated comorbidities. The worldwide prevalence of obesity has nearly tripled over the last five decades and continues to pose a serious threat to wider society and the wellbeing of future generations. The pathogenesis of obesity is complex but diet plays a key role in the onset and progression of the disease. The human diet has changed drastically across the globe, with an estimate that approximately 72% of the calories consumed today come from foods that were not part of our ancestral diets and are not compatible with our metabolism. Additionally, multiple nutrient-independent factors, e.g., cost, accessibility, behaviours, culture, education, work commitments, knowledge and societal set-up, influence our food choices and eating patterns. Much research has been focused on 'what to eat' or 'how much to eat' to reduce the obesity burden, but increasingly evidence indicates that 'when to eat' is fundamental to human metabolism. Aligning feeding patterns to the 24-h circadian clock that regulates a wide range of physiological and behavioural processes has multiple health-promoting effects with anti-obesity being a major part. This article explores the current understanding of the interactions between the body clocks, bioactive dietary components and the less appreciated role of meal timings in energy homeostasis and obesity.

Efficacy and mechanism of intermittent fasting in metabolic associated fatty liver disease based on ultraperformance liquid chromatography-tandem mass spectrometry

OBJECTIVES

Drug treatment of metabolic associated fatty liver disease (MAFLD) remains lacking. This study analyzes the efficacy and mechanism underlying intermittent fasting combined with lipidomics.

METHODS

Thirty-two male rats were randomly divided into three groups: Normal group, administered a standard diet; MAFLD group, administered a 60% high-fat diet; time-restricted feeding (TRF) group, administered a 60% high-fat diet. Eating was allowed for 6 h per day (16:00-22:00). After 15 weeks, liver lipidomics and other indicators were compared.

RESULTS

A total of 1,062 metabolites were detected. Compared with the Normal group, the weight, body fat ratio, aspartate aminotransferase, total cholesterol, low-density cholesterol, fasting blood glucose, uric acid, and levels of 317 lipids including triglycerides (TG) (17:0_-18:1_-20:4) were upregulated, whereas the levels of 265 lipids including phosphatidyl ethanolamine (PE) (17:0_-20:5) were downregulated in the MAFLD group (P < 0.05). Compared with the MAFLD group, the weight, body fat ratio, daily food intake, and levels of 253 lipids including TG (17:0_-18:1_-22:5) were lower in the TRF group. Furthermore, the levels of 82 lipids including phosphatidylcholine (PC) (20:4_-22:6) were upregulated in the TRF group (P < 0.05), while serum TG level was increased; however, the increase was not significant (P > 0.05). Enrichment analysis of differential metabolites showed that the pathways associated with the observed changes mainly included metabolic pathways, regulation of lipolysis in adipocytes, and fat digestion and absorption, while reverse-transcription polymerase chain reaction showed that TRF improved the abnormal expression of FAS and PPARα genes in the MAFLD group (P < 0.05).

CONCLUSION

Our results suggest that 6 h of TRF can improve MAFLD via reducing food intake by 13% and improving the expression of genes in the PPARα/FAS pathway, thereby providing insights into the prevention and treatment of MAFLD.

The effects of fasting diets on nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease in the world. There is no confirmed treatment for NAFLD as yet. Recently, fasting regimens and their relationship to NAFLD have drawn a great deal of attention in the literature. We review the current evidence that supports fasting diets as an adjunctive therapeutic strategy for patients with NAFLD and address potential action mechanisms. We reason that the fasting diets might be a promising approach for modulating hepatic steatosis, fibroblast growth factors 19 and 21 signaling, lipophagy, and the metabolic profile.

Time-Restricted Feeding Could Not Reduce Rainbow Trout Lipid Deposition Induced by Artificial Night Light

Artificial night light (ALAN) could lead to circadian rhythm disorders and disrupt normal lipid metabolism, while time-restricted feeding (TRF) could maintain metabolic homeostasis. In mammals, TRF has been demonstrated to have extraordinary effects on the metabolic regulation caused by circadian rhythm disorders, but studies in lower vertebrates such as fish are still scarce. In this study, the impacts of ALAN on the body composition and lipid metabolism of juvenile rainbow trout were investigated by continuous light (LL) exposure as well as whether TRF could alleviate the negative effects of LL. The results showed that LL upregulated the expression of lipid synthesis (fas and srebp-1c) genes and suppressed the expression of lipid lipolysis (pparβ, cpt-1a, and lpl) genes in the liver, finally promoting lipid accumulation in juvenile rainbow trout. However, LL downregulated the expression of genes (Δ6-fad, Δ9-fad, elovl2, and elovl5) related to long-chain polyunsaturated fatty acid (LC-PUFA) synthesis, resulting in a significant decrease in the proportion of LC-PUFA in the dorsal muscle. In serum, LL led to a decrease in glucose (Glu) levels and an increase in triglyceride (TG) and high-density lipoprotein cholesterol (H-DLC) levels. On the other hand, TRF (mid-dark stage feeding (D)) and mid-light stage feeding (L)) upregulated the expression of both the lipid synthesis (srebp-1c and pparγ), lipolysis (pparα, pparβ, and cpt-1a), and lipid transport (cd36/fat and fatp-1) genes, finally increasing the whole-body lipid, liver protein, and lipid content. Meanwhile, TRF (D and L groups) increased the proportion of polyunsaturated fatty acid (PUFA) and LC-PUFA in serum. In contrast, random feeding (R group) increased the serum Glu levels and decreased TG, total cholesterol (T-CHO), and H-DLC levels, suggesting stress and poor nutritional status. In conclusion, ALAN led to lipid accumulation and a significant decrease in muscle LC-PUFA proportion, and TRF failed to rescue these negative effects.

Multi-Tissue Time-Domain NMR Metabolomics Investigation of Time-Restricted Feeding in Male and Female Nile Grass Rats

Metabolic disease resulting from overnutrition is prevalent and rapidly increasing in incidence in modern society. Time restricted feeding (TRF) dietary regimens have recently shown promise in attenuating some of the negative metabolic effects associated with chronic nutrient stress. The purpose of this study is to utilize a multi-tissue metabolomics approach using nuclear magnetic resonance (NMR) spectroscopy to investigate TRF and sex-specific effects of high-fat diet in a diurnal Nile grass rat model. Animals followed a six-week dietary protocol on one of four diets: chow ad libitum, high-fat ad libitum (HF-AD), high-fat early TRF (HF-AM), or high-fat late TRF (HF-PM), and their liver, heart, and white adipose tissues were harvested at the end of the study and were analyzed by NMR. Time-domain complete reduction to amplitude–frequency table (CRAFT) was used to semi-automate and systematically quantify metabolites in liver, heart, and adipose tissues while minimizing operator bias. Metabolite profiling and statistical analysis revealed lipid remodeling in all three tissues and ectopic accumulation of cardiac and hepatic lipids for HF-AD feeding compared to a standard chow diet. Animals on TRF high-fat diet had lower lipid levels in the heart and liver compared to the ad libitum group; however, no significant differences were noted for adipose tissue. Regardless of diet, females exhibited greater amounts of hepatic lipids compared to males, while no consistent differences were shown in adipose and heart. In conclusion, this study demonstrates the feasibility of performing systematic and time-efficient multi-tissue NMR metabolomics to elucidate metabolites involved in the crosstalk between different metabolic tissues and provides a more holistic approach to better understand the etiology of metabolic disease and the effects of TRF on metabolic profiles.

Valuing the Diversity of Research Methods to Advance Nutrition Science

The ASN Board of Directors appointed the Nutrition Research Task Force to develop a report on scientific methods used in nutrition science to advance discovery, interpretation, and application of knowledge in the field. The genesis of this report was growing concern about the tone of discourse among nutrition professionals and the implications of acrimony on the productive study and translation of nutrition science. Too often, honest differences of opinion are cast as conflicts instead of areas of needed collaboration. Recognition of the value (and limitations) of contributions from well-executed nutrition science derived from the various approaches used in the discipline, as well as appreciation of how their layering will yield the strongest evidence base, will provide a basis for greater productivity and impact. Greater collaborative efforts within the field of nutrition science will require an understanding that each method or approach has a place and function that should be valued and used together to create the nutrition evidence base. Precision nutrition was identified as an important emerging nutrition topic by the preponderance of task force members, and this theme was adopted for the report because it lent itself to integration of many approaches in nutrition science. Although the primary audience for this report is nutrition researchers and other nutrition professionals, a secondary aim is to develop a document useful for the various audiences that translate nutrition research, including journalists, clinicians, and policymakers. The intent is to promote accurate, transparent, verifiable evidence-based communication about nutrition science. This will facilitate reasoned interpretation and application of emerging findings and, thereby, improve understanding and trust in nutrition science and appropriate characterization, development, and adoption of recommendations.

Integrated Bacteria-Fungi Diversity Analysis Reveals the Gut Microbial Changes in Buffalo With Mastitis

The gut microbial community is closely related to mastitis, but studies regarding the influences of mastitis on gut microbiota in buffalo remain scarce. Herein, we characterized the differences in gut bacterial and fungal communities between mastitis-affected and healthy buffalos. Interestingly, although mastitis had no effect on gut bacterial and fungal diversities in the buffalos, some bacterial and fungal taxa were significantly altered. Bacterial and fungal taxonomic analysis showed that the preponderant bacterial phyla (Firmicutes and Bacteroidetes) and fungal phyla (Ascomycota and Basidiomycota) in buffalo were the same regardless of health status. At the level of genus, the changes in some gut bacterial and fungal abundances between both groups were gradually observed. Compared with healthy buffalos, the proportions of 3 bacterial genera (uncultured_bacterium_f_Muribaculaceae, Eubacterium_nodatum_group, and Lachnoclostridium_10) and 1 fungal genus (Pichia) in the mastitis-affected buffalo were significantly increased, whereas 4 bacterial genera (Ruminococcus_2, Candidatus_Stoquefichus, Turicibacter, and Cellulosilyticum) and 4 fungal genera (Cladosporium, Thermothelomyces, Ganoderma and Aspergillus) were significantly decreased. Taken together, this research revealed that there was significant difference in the compositions of the gut microbial community between the healthy and mastitis-affected buffalos. To our knowledge, this is the first insight into the characteristics of the gut microbiota in buffalos with mastitis, which is beneficial to understand the gut microbial information of buffalo in different health states and elucidate the pathogenesis of mastitis from the gut microbial perspective.

The Effects of Time-Restricted Eating on Metabolism and Gut Microbiota: A Real-Life Study

The metabolic benefits of time-restricted eating (TRE) in humans are statistically significant but not clinically relevant. Few data are available about the effects of TRE on the gut microbiota. We compared the effects of a TRE regimen (<12 h feeding; n = 25) with a time-unrestricted (TUE) regimen (>12 h feeding; n = 24), on the clinical and dietary variables and gut-microbiota composition in patients with obesity, who were subjected for 12 weeks to the same caloric restriction. Median weight loss was 4.0 kg and 2.2 kg in the TRE and TUE groups, respectively, with a between-group borderline difference (p = 0.049). No significant between-group difference was found in other dietary, anthropometric, or laboratory variables. There were no substantial between-group differences in alpha and beta diversity or gut-microbiota composition. The TRE group showed a significant increase in the frequency of Lachnospiraceae, Parasutterella, and Romboutsia at the study’s end. A TRE regimen induced small changes both in metabolic/dietary variables and in the gut-microbiota composition, with respect to the TUE. The microbial changes we have found were of uncertain clinical significance.

Chronic circadian disruption on a high-fat diet impairs glucose tolerance

BACKGROUND

Nearly 14% of Americans experience chronic circadian disruption due to shift work, increasing their risk of obesity, diabetes, and other cardiometabolic disorders. These disorders are also exacerbated by modern eating habits such as frequent snacking and consumption of high-fat foods.

METHODS

We investigated the effects of recurrent circadian disruption (RCD) on glucose metabolism in C57BL/6 mice and in human participants exposed to non-24-h light-dark (LD) schedules vs. those on standard 24-h LD schedules. These LD schedules were designed to induce circadian misalignment between behaviors including rest/activity and fasting/eating with the output of the near-24-h central circadian pacemaker, while minimizing sleep loss, and were maintained for 12 weeks in mice and 3 weeks in humans. We examined interactions of these circadian-disrupted schedules compared to control 24-h schedules with a lower-fat diet (LFD, 13% in mouse and 25-27% in humans) and high-fat diet (HFD, 45% in mouse and 45-50% in humans). We also used young vs. older mice to determine whether they would respond differently to RCD.

RESULTS

When combined with a HFD, we found that RCD caused significant weight gain in mice and increased body fat in humans, and significantly impaired glucose tolerance and insulin sensitivity in both mice and humans, but this did not occur when RCD was combined with a LFD. This effect was similar in both young and older mice.

CONCLUSION

These results in both humans and a model organism indicate that circadian disruption has an adverse effect on metabolism among individuals eating a high-fat Western-style diet, even in the absence of significant sleep loss, and suggest that reducing dietary fat may protect against the metabolic consequences of a lifestyle (such as shift work) that involves chronic circadian disruption.

Early Time-Restricted Feeding Amends Circadian Clock Function and Improves Metabolic Health in Male and Female Nile Grass Rats

Lengthening the daily eating period contributes to the onset of obesity and metabolic syndrome. Dietary approaches, including energy restriction and time-restricted feeding, are promising methods to combat metabolic disorders. This study explored the effect of early and late time-restricted feeding (TRF) on weight and adiposity, food consumption, glycemic control, clock gene expression, and liver metabolite composition in diurnal Nile grass rats (NGRs). Adult male and female Nile grass rats were randomly assigned to one of three groups: (1) access to a 60% high-fat (HF) diet ad-libitum (HF-AD), (2) time-restricted access to the HF diet for the first 6 h of the 12 h light/active phase (HF-AM) or (3) the second 6 h of the 12 h light/active phase (HF-PM). Animals remained on their respective protocols for six weeks. TRF reduced total energy consumption and weight gain, and early TRF (HF-AM) reduced fasting blood glucose, restored Per1 expression, and reduced liver lipid levels. Although sex-dependent differences were observed for fat storage and lipid composition, TRF improved metabolic parameters in both male and female NGRs. In conclusion, this study demonstrated that early TRF protocol benefits weight management, improves lipid and glycemic control, and restores clock gene expression in NGRs.

Repercussions of intermittent fasting on the intestinal microbiota community and body composition: a systematic review

CONTEXT

Several therapies have been tested for combating weight gain and obesity-related metabolic diseases, and among these therapies, intermittent fasting (IF) has gained a great deal of interest.

OBJECTIVE

The aim of this study was to provide the reader with a current survey of IF protocols and an understanding of the outcomes found to date in terms of the profile of the intestinal microbiota (IM) in obese organisms.

DATA SOURCES

Data were obtained from 4 databases: PubMed, SCOPUS, LILACs, and Web of Science.

DATA EXTRACTION

Data from studies relating IF protocols to the microbiota and weight loss were extracted using a protocol in START program.

DATA ANALYSIS

Of the 82 original articles identified from the databases, 35 were eliminated due to duplication, and 32 were excluded due to not meeting the inclusion criteria. Two additional articles found in a new search were added, yielding a total of 17 studies to be included in this review. Among the protocols, alternate-day fasting (ADF) and time-restricted feeding (TRF) were the most common, and they were shown to have different mechanisms of metabolic signaling. TRF influences weight control and biochemical parameters by regulating the circadian system, and improving satiety control systems by acting on leptin secretion. On the other hand, ADF leads to a reduction of ±75% of all energy consumption regardless of dietary composition in addition to promoting hormonal adjustments that promote weight control. Furthermore, both protocols showed the ability to remodel the IM by changing the Firmicutes/Bacteroidetes ratio and increasing the abundance of strains such as Lactobacillus spp. and Akkermansia m. that have a protective effect on metabolism against the effects of weight gain.

CONCLUSION

In short, the ADF and TRF protocols have a positive effect on the remodeling of the IM and can possibly be used to control body adiposity, improve insulin sensitivity, and achieve other obesity-related metabolic changes.

Benefits, mechanisms, and risks of intermittent fasting in metabolic syndrome and type 2 diabetes

One of the emergent nutritional strategies for improving multiple features of cardiometabolic diseases is the practice of intermittent fasting (IF), which consists of alternating periods of eating and fasting. IF can reduce circulating glucose and insulin levels, fat mass, and the risk of developing age-related pathologies. IF appears to upregulate evolution-conserved adaptive cellular responses, such as stress-response pathways, autophagy, and mitochondrial function. IF was also observed to modulate the circadian rhythms of hormones like insulin or leptin, among others, which levels change in conditions of food abundance and deficit. However, some contradictory results regarding the duration of the interventions and the anterior metabolic status of the participants suggest that more and longer studies are needed in order to draw conclusions. This review summarizes the current knowledge regarding the role of IF in the modulation of mechanisms involved in type 2 diabetes, as well as the risks.

Night-Restricted Feeding Improves Gut Health by Synchronizing Microbe-Driven Serotonin Rhythm and Eating Activity-Driven Body Temperature Oscillations in Growing Rabbits

The circadian misalignment of the gut microbiota caused by unusual eating times in adult animals is related to disease development. However, whether the composition and diurnal rhythm of gut microbiota can be optimized by synchronizing the window period of eating with natural eating habits to reduce the risk of diarrhea remains unclear, especially in growing animals. In this study, 108 5-week-old weaned rabbits (nocturnal animals) were randomly subjected to daytime feeding (DF) and night-restricted feeding (NRF). At age 12 weeks, six rabbits were selected from each group, and caecum and cecal contents, as well as serum samples were collected at 4-h intervals during 24 h. Overall, NRF was found to reduce the risk of diarrhea in growing rabbits, improved the diurnal rhythm and abundance of beneficial microorganisms, along with the production of beneficial metabolites, whereas reduced the abundance of potential pathogens (Synergistes, Desulfovibrio, and Alistipes). Moreover, NRF improved diurnal rhythm of tryptophan hydroxylase isoform 1 and serotonin. Furthermore, NRF strengthened the diurnal amplitude of body core temperature, and promoted the diurnal expression of intestinal clock genes (BMAL1, CLOCK, REV-ERBα, and PER1), and genes related to the regulation of the intestinal barrier (CLAUDIN-1), and intestinal epithelial cell self-proliferation and renewal (BMI1). In vitro simulation experiments further revealed that synchronization of microbial-driven serotonin rhythm and eating activity-driven body temperature oscillations, which are important zeitgebers, could promote the diurnal expression of clock genes and CLAUDIN-1 in rabbit intestinal epithelial cells (RIEC), and enhance RIEC proliferation. This is the first study to reveal that NRF reprograms the diurnal rhythm of the gut microbiome, promotes the diurnal expression of clock genes and tight junction genes via synchronization of microbial-driven serotonin rhythm and eating activity-driven body temperature oscillations, thereby improving intestinal health and reducing the risk of diarrhea in growing rabbits. Collectively, these results provide a new perspective for the healthy feeding and management of growing animals.

Dissociation between Corneal and Cardiometabolic Changes in Response to a Time-Restricted Feeding of a High Fat Diet

Mice fed a high fat diet (HFD) ab libitum show corneal dysregulation, as evidenced by decreased sensitivity and impaired wound healing. Time-restricted (TR) feeding can effectively mitigate the cardiometabolic effects of an HFD. To determine if TR feeding attenuates HFD-induced corneal dysregulation, this study evaluated 6-week-old C57BL/6 mice fed an ad libitum normal diet (ND), an ad libitum HFD, or a time-restricted (TR) HFD for 10 days. Corneal sensitivity was measured using a Cochet-Bonnet aesthesiometer. A corneal epithelial abrasion wound was created, and wound closure was monitored for 30 h. Neutrophil and platelet recruitment were assessed by immunofluorescence microscopy. TR HFD fed mice gained less weight (p < 0.0001), had less visceral fat (p = 0.015), and had reduced numbers of adipose tissue macrophages and T cells (p < 0.05) compared to ad libitum HFD fed mice. Corneal sensitivity was reduced in ad libitum HFD and TR HFD fed mice compared to ad libitum ND fed mice (p < 0.0001). Following epithelial abrasion, corneal wound closure was delayed (~6 h), and neutrophil and platelet recruitment was dysregulated similarly in ad libitum and TR HFD fed mice. TR HFD feeding appears to mitigate adipose tissue inflammation and adiposity, while the cornea remains sensitive to the pathologic effects of HFD feeding.

Gut microbiota modulation as a possible mediating mechanism for fasting-induced alleviation of metabolic complications: a systematic review

BACKGROUND

Intermittent fasting has been reported to have positive effects on obesity, diabetes, cardiovascular diseases, hypertension, and several neurodegenerative diseases through different mechanisms such as alteration in the gut microbiota. This systematic review was conducted with the aim of providing an overview of the existing animal and human literature regarding the gut microbiota alterations in various fasting regimens.

METHOD

A systematic literature search was conducted on PubMed, Scopus and Web of Science databases up to May 2021 to find all relevant studies examining the gut microbiota alteration during the fasting. Original researches on animal models or human patients were included in this study.

RESULTS

The search fulfilled 3072 documents from which 31 studies (20 animal and 11 human studies) were included. Upon fasting, abundance of several beneficial bacteria including Lactobacillus and Bifidobacterium shifted significantly. Moreover, some taxa, including Odoribacter which negatively associated with blood pressure bloomed during fasting. Ramadan fasting, as a kind of intermittent fasting, improves health parameters through positive changes in gut microbiota including upregulation of A. muciniphila, B. fragilis, Bacteroides and butyric acid-producing Lachnospiraceae.

CONCLUSION

The findings suggest that different fasting regimens including alternate-day fasting, calorie- and time-restricted fasting programs and Ramadan fasting could promote health maybe through the modulation of gut microbiome. However, further studies are needed to explore properly the connection between gut microbiota and meal frequency and timing.

Circadian Rhythms, Disease and Chronotherapy

Circadian clocks are biological timing mechanisms that generate 24-h rhythms of physiology and behavior, exemplified by cycles of sleep/wake, hormone release, and metabolism. The adaptive value of clocks is evident when internal body clocks and daily environmental cycles are mismatched, such as in the case of shift work and jet lag or even mistimed eating, all of which are associated with physiological disruption and disease. Studies with animal and human models have also unraveled an important role of functional circadian clocks in modulating cellular and organismal responses to physiological cues (ex., food intake, exercise), pathological insults (e.g. virus and parasite infections), and medical interventions (e.g. medication). With growing knowledge of the molecular and cellular mechanisms underlying circadian physiology and pathophysiology, it is becoming possible to target circadian rhythms for disease prevention and treatment. In this review, we discuss recent advances in circadian research and the potential for therapeutic applications that take patient circadian rhythms into account in treating disease.

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.

Gut microbiota in obesity

Obesity is a major global health problem determined by heredity and environment, and its incidence is increasing yearly. In recent years, increasing evidence linking obesity to the gut microbiota has been reported. Gut microbiota management has become a new method of obesity treatment. However, the complex interactions among genetics, environment, the gut microbiota, and obesity remain poorly understood. In this review, we summarize the characteristics of the gut microbiota in obesity, the mechanism of obesity induced by the gut microbiota, and the influence of genetic and environmental factors on the gut microbiota and obesity to provide support for understanding the complex relationship between obesity and microbiota. At the same time, the prospect of obesity research related to the gut microbiota is proposed.

Circadian Rhythm Disruption Influenced Hepatic Lipid Metabolism, Gut Microbiota and Promoted Cholesterol Gallstone Formation in Mice

BACKGROUND

Hepatic lipid metabolism regulates biliary composition and influences the formation of cholesterol gallstones. The genes Hmgcr and Cyp7a1, which encode key liver enzymes, are regulated by circadian rhythm-related transcription factors. We aimed to investigate the effect of circadian rhythm disruption on hepatic cholesterol and bile acid metabolism and the incidence of cholesterol stone formation.

METHODS

Adult male C57BL/6J mice were fed either a lithogenic diet (LD) only during the sleep phase (time-restricted lithogenic diet feeding, TRF) or an LD ad libitum (non-time-restricted lithogenic diet feeding, nTRF) for 4 weeks. Food consumption, body mass gain, and the incidence of gallstones were assessed. Circulating metabolic parameters, lipid accumulation in the liver, the circadian expression of hepatic clock and metabolic genes, and the gut microbiota were analyzed.

RESULTS

TRF caused a dysregulation of the circadian rhythm in the mice, characterized by significant differences in the circadian expression patterns of clock-related genes. In TRF mice, the circadian rhythms in the expression of genes involved in bile acid and cholesterol metabolism were disrupted, as was the circadian rhythm of the gut microbiota. These changes were associated with high biliary cholesterol content, which promoted gallstone formation in the TRF mice.

CONCLUSION

Disordered circadian rhythm is associated with abnormal hepatic bile acid and cholesterol metabolism in mice, which promotes gallstone formation.