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With the improvement of living standards and the change of dietary habits, metabolic syndrome has become a major global public health problem. The gut microbiota is one of the research hotspots in recent years. More and more studies have shown that the gut microbiota can conduct bidirectional signal transduction with different body tissues and organs such as the brain, liver and heart through various pathways, which is closely related to body health. Medium-chain fatty acids (MCFAs) exist in coconut oil, palm kernel oil and dairy products mainly in the form of medium-chain triglycerides (MCTs). MCFAs can be rapidly metabolized for energy in the body, and has good regulatory effects on glucose and lipid metabolism. This article reviews the effects of MCTs on gut microbes and their positive effects on metabolic syndrome in order to provide a reference for future research.

Food preservatives are widely used in the food industry for their broad antibacterial spectrum and strong antibacterial properties. While the effects of dietary food preservatives on the gut microbiota and host health have been studied, a systematic review is lacking. In this paper, the latest research on food preservatives and the gut microbiota is reviewed. It has been found that food preservatives affect lipid metabolism, immunity and intestinal inflammation by altering the diversity of the gut microbiota and regulating the abundance of conditioned pathogens and beneficial bacteria. The future research trends are also discussed. Through this review, we hope that the ‘food preservatives-gut microbiota-host health’ chain can arouse the attention of researchers and readers, and provide a new perspective for the existing safety evaluation system of food preservatives, which may be of guiding significance for the maintenance of human health.

The altered circulating bile acids (BAs) modulate gut microbiota, energy metabolism and various physiological functions. BA profiles in liver, serum, ileum and feces of HFD-fed mice were analyzed with normal chow diet (NCD)-fed mice after 16-week feeding. Furthermore, gut microbiota was analyzed and its correlation analysis with BA was performed. The result showed that long-term HFD feeding significantly decreased hepatic and serum BA levels, mainly attributed to the inhibition of hepatic BA synthesis and the reduced reabsorption efficiency of BAs in enterohepatic circulation. It also significantly impaired glucose and lipid homeostasis and gut microbiota in mice. We found significantly higher bile salt hydrolase activity in ileal microbes and a higher ratio of free BAs to conjugated BA content in ileal contents in HFD groups compared with NCD group mice, which might account for the activated intestinal farnesoid X receptor signaling on liver BA synthesis inhibition and reduced ileal reabsorption. The decreased circulating BAs were associated with the dysregulation of the lipid metabolism according to the decreased TGR5 signaling in the ileum and BAT. In addition, it is astonishing to find extremely high percentages of taurocholate and 12-OH BAs in liver and serum BA profiles of both groups, which was mainly attributed to the high substrate selectivity for 12-OH BAs of the intestinal BAs transporter during the ileal reabsorption of enterohepatic circulation. This study revealed a significant effect of long-term HFD feeding on the decreased circulating BA pool in mice, which impaired lipid homeostasis and gut microbiota, and collectively resulted in metabolic disorders and obesity. [ABSTRACT FROM AUTHOR]

Sodium benzoate (SB) is a common food preservative widely used in the food industry. However, the effects of SB intake on host health at different stages were still unclear. Hence, we investigated the impact of SB with three concentrations (150 mg/kg, 500 mg/kg and 1000 mg/kg) and at three stages (intake for 5-weeks, intake for 10-weeks and removal for 5 weeks) on host health in normal mice. The results showed that SB intake for 5 weeks slightly changed gut microbiota composition, but it significantly increased TG (only 150 mg/kg and 1000 mg/kg) and blood glucose levels (only 500 mg/kg) and promoted the secretion of interleukin (IL)-1β and IL-6 (p < 0.01). However, SB intake for 10 weeks mostly maintained normal glucolipid metabolism; although, IL-1β (p < 0.01) and IL-6 (p < 0.05) levels were also significantly increased and positively regulated the gut microbiota by significantly increasing the relative abundance of Lactobacillus and significantly decreasing the relative abundance of Ileibacterium. Meanwhile, the safety of SB for host metabolism and gut microbiota was also confirmed via a fecal microbiota transplantation experiment. In addition, we found that SB removal after 10 weeks of intake significantly increased the levels of blood glucose, insulin and HOMA-IR index, which might be attributed to gut microbiota dysbiosis. Mechanistically, these positive effects and negative effects had no close relationship with the concentration of short-chain fatty acids in the gut, which might be associated with metabolites of SB or special bacterial strains. In short, this work provided positive evidence for the safety of SB consumption within the recommended range. [ABSTRACT FROM AUTHOR]

With the increase in human mean age, the prevalence of neurodegenerative diseases (NDs) also rises. This negatively affects mental and physiological health. In recent years, evidence has revealed that anthocyanins could regulate the functioning of the central nervous system (CNS) through the microbiome-gut-brain axis, which provides a new perspective for treating NDs. In this review, the protective effects and mechanisms of anthocyanins against NDs are summarized, especially the interaction between anthocyanins and the intestinal microbiota, and the microbial-intestinal-brain axis system is comprehensively discussed. Moreover, anthocyanins achieve the therapeutic purpose of NDs by regulating intestinal microflora and certain metabolites (protocateic acid, vanillic acid, etc.). In particular, the inhibitory effect of tryptophan metabolism on some neurotransmitters and the induction of blood-brain barrier permeability by butyrate production has a preventive effect on NDs. Overall, it is suggested that microbial-intestinal-brain axis may be a novel mechanism for the protective effect of anthocyanins against NDs. [ABSTRACT FROM AUTHOR]

The roles of medium- and long-chain triacylglycerols (MLCT) on health benefits under high fat diet (HFD) conditions remain in dispute. This study was conducted to investigate the effects of novel LaPLa-rich MLCT on the glycolipid metabolism and gut microbiota in HFD-fed mice when pork fat is half replaced with MLCT and palm stearin (PS). The results showed that although MLCT could increase the body weight in the mouse model, it can improve the energy utilization, regulate the glucose and lipid metabolism, and inhibit the occurrence of inflammation. Furthermore, 16S rRNA gene sequencing of gut microbiota indicated that PS and MLCT affected the overall structure of the gut microbiota to a varying extent and specifically changed the abundance of some operational taxonomic units (OTUs). Moreover, several OTUs belonging to the genera Dorea, Streptococcus, and g_Eryipelotrichaceae had a high correlation with obesity and obesity-related metabolic disorders of the host. Therefore, it can be seen that this new MLCT has different properties and functions from the previous traditional MLCT, and it can better combine the advantages of MLCT, lauric acid, and sn-2 palmitate, as well as the advantages of health function and metabolism. In summary, this study explored the effects of LaPLa-enriched lipids on glycolipid metabolism in mice, providing theoretical support for future studies on the efficacy of different types of conjugated lipids, intending to apply them to industrial production and subsequent development of related products. [ABSTRACT FROM AUTHOR]

Hyperuricemia (HUA) is a metabolic disorder caused by abnormal uric acid (UA) metabolism, which is a complex physiological process involving multiple organs (liver, kidney, and intestine). Although UA metabolism in the liver and kidneys has been elucidated, only a few studies have focused on the process in the intestine. With our growing knowledge of the effects of gut microorganisms on health, the gut microbiota has been identified as a new target for HUA treatment. In this review, the relationship between HUA and the gut microbiota is elucidated, and anti-hyperuricemia mechanisms targeting the intestine are discussed, such as the promotion of purine and UA catabolism by the gut microbiota, increases in UA excretion by the gut microbiota and its metabolites, regulation of UA absorption or secretion in the intestinal tract by certain transporters, and the intestinal inflammatory response to the gut microbiota. Additionally, probiotics (Bifidobacteria and Lactobacilli) and prebiotics (polyphenols, peptides, and phytochemicals) with UA-lowering effects targeting the intestinal tract are summarized, providing reference and guidance for further research. [ABSTRACT FROM AUTHOR]

BACKGROUND: Medium‐chain monoglycerides (MGs) are a group of 1‐monoglycerides of medium‐chain fatty acids with strong antibacterial activity, which may influence the gut microbiota in the diet of broilers. The present study evaluated the effects of mixed MGs on the community and function of gut microbiota in broilers. A total of 528 newly hatched male yellow feathered broiler chicks were weighed and randomly assigned into four groups, including a basal diet (CON), a basal diet containing 300 mg kg−1 MG (MG300), 450 mg kg−1 MG (MG450), or 600 mg kg−1 MG (MG600). RESULTS: The cecal acetic acid, propionic acid, butyric acid, isobutyric acid, isovaleric acid and total short‐chain fatty acid of broilers in the MG‐containing groups were notably increased compared with the CON group. Dietary MG selectively increased the relative abundance of Bifidobacteriaceae, Bacteroides and an unclassified genus of Lachnospiraceae family, but decreased the proportion of an unclassified genus of Barnesiellaceae and a norank genus of Flavobacteriaceae family in the cecum of broilers. Functional prediction revealed that MG supplementation enriched the microbial gene abundance of amino acid metabolism and carbohydrate metabolism, while depleted the gene abundance of fat metabolism and energy metabolism. Moreover, the modulation of gut microbiota by MG supplementation was closely correlated with the alteration of muscle amino acids. CONCLUSION: Dietary MGs altered the gut microbiota community structure and metabolites, and modulated the gene abundance of microbial metabolism pathways in the cecum of broilers, which may further influence the growth performance, nutrient utilization and meat quality of the host. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Constipation is a common gastrointestinal problem. This study aimed to identify a combination of prebiotics and wheat peptides (WP) to promote intestinal peristalsis and explore the underlying mechanism. First, we screened four prebiotics (galacto-oligosaccharides (GOS), fructose oligosaccharides (FOS), inulin (IN), and resistant dextrin (RD)) using a zebrafish model and found that GOS was the most synergistic with WP. We then tested the GOS-WP combination in a mouse model of loperamide (Lop)-induced constipation and found that it significantly improved constipation symptoms. Specifically, GOS-WP shortened the first black stool time, increased the number of defecation particles, accelerated small intestinal propulsion rate, and increased fecal water content. GOS-WP also normalized the colonic water transport system by inhibiting colonic AQP4/8 expression. Additionally, GOS-WP reversed Lop-induced morphological damage in the ileum and colon, increased colonic barrier, and reduced inflammation in mice. Furthermore, 16S rRNA gene sequence analysis showed that GOS-WP reversed the gut microbiota structure changes induced by Lop. GOS-WP significantly increased butyric acid and decreased BCFA levels, indicating improved gut health. Our findings suggest that the GOS-WP combination has potential as a novel intervention for constipation relief. This study highlights the potential of combining prebiotics and WP as a therapeutic strategy for constipation. • Among GOS, FOS, IN and RD, GOS and WP had the strongest synergistic effect in promoting intestinal peristalsis. • The GOS to WP ratio of 1:2 was the most effective in promoting intestinal peristalsis in zebrafish model. • The GOS-WP complex (1:2) could relive constipation under mice model. • The GOS-WP complex (1:2) improved the disturbances of intestinal function in constipated mice. • The GOS-WP complex (1:2) recovered the gut microbiota composition in constipated mice. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Intake of GML induced adverse effects on body weight, serum lipids and gut microbiota. • L. plantarum ZJUFT17 could attenuate the adverse effects induced by GML in mice. • Administration of L. plantarum ZJUFT17 could modulate the gut microbiota in mice. • L. plantarum ZJUFT17 may be a candidate for probiotics. Abstract Glycerol monolaurate (GML) is a naturally occurring surfactant and is widely used as a food emulsifier. New evidence, however, has shown that intake of GML could result in metabolic syndrome as well as gut microbiota dysbiosis in mice. In this study, male C57BL/6J mice fed normal chow diet with or without GML supplementation were administered with Lactobacillus plantarum strains isolated from Chinese sourdough for 6 weeks to investigate the influence of GML and the L. plantarum strains on body weight, serum lipid profiles, inflammatory responses and gut microbiota. The results showed that L. plantarum could attenuate the adverse effects induced by GML, especially the strain L. plantarum ZJUFT17, which showed good performance in suppressing body weight gain, lowering total cholesterol, reducing the serum tumor necrosis factor (TNF)-α level and enhancing the α-diversity of gut microbiota in mice supplemented with GML. [ABSTRACT FROM AUTHOR]

Glycerol monocaprylate (GMC) is a glycerol derivative of medium-chain fatty acids (MCFAs) and is widely used as a preservative in food processing. However, GMC and its hydrolytic acid (octylic acid) have antibacterial properties that may affect the physiology and intestinal microecology of the human body. Therefore, in this study, the effects of two different dosages of GMC (150 and 1600 mg kg−1) on glucose, lipid metabolism, inflammation, and intestinal microecology of normal diet-fed C57BL/6 mice were comprehensively investigated. The obtained results showed that the level of triglycerides (TGs) in the low-dose group down-regulated significantly, and the anti-inflammatory cytokine interleukin 10 (IL-10) significantly increased, while the pro-inflammatory cytokines monocyte chemotactic protein 1 (MCP-1) and interleukin 1beta (IL-1β) in the high-dose group were significantly decreased. Importantly, GMC promoted the α-diversity of gut microbiota in normal-diet-fed mice, regardless of dosages. Additionally, it was found that the low-dose treatment of GMC significantly increased the abundance of Lactobacillus, while the high-dose treatment of GMC significantly increased the abundance of SCFA-producers such as Clostridiales, Lachnospiraceae, and Ruminococcus. Moreover, the content of short-chain fatty acids (SCFAs) was significantly increased by GMC supplementation. Thus, our research provides a novel insight into the effects of GMC on gut microbiota and physiological characteristics. [ABSTRACT FROM AUTHOR]

The beneficial effects of ginger polyphenols have been extensively reported. However, their metabolic characteristics and health effects on gut microbiota are poor understood. The purpose of this study was to investigate the digestion stability of ginger polyphenols and their prebiotic effects on gut microbiota by simulating digestion and fermentation in vitro. Following simulated digestion in vitro, 85% of the polyphenols were still detectable, and the main polyphenol constituents identified in ginger extract are 6-, 8-, and 10-gingerols and 6-shogaol in the digestive fluids. After batch fermentation, the changes in microbial populations were measured by 16S rRNA gene Illumina MiSeq sequencing. In mixed-culture fermentation with fecal inoculate, digested ginger extract (GE) significantly modulated the fecal microbiota structure and promoted the growth of some beneficial bacterial populations, such as Bifidobacterium and Enterococcus. Furthermore, incubation with GE could elevate the levels of short-chain fatty acids (SCFAs) accompanied by a decrease in the pH value. Additionally, the quantitative PCR results showed that 6-gingerol (6G), as the main polyphenol in GE, increased the abundance of Bifidobacterium significantly. Therefore, 6G is expected to be a potential prebiotic that improves human health by promoting gut health. [ABSTRACT FROM AUTHOR]

Glycerol monolaurate (GML) has potent antimicrobial and anti-inflammatory activities. The present study aimed to assess the dose-dependent antimicrobial-effects of GML on the gut microbiota, glucose and lipid metabolism and inflammatory response in C57BL/6 mice. Mice were fed on diets supplemented with GML at dose of 400, 800 and 1600 mg kg−1 for 4 months, respectively. Results showed that supplementation of GML, regardless of the dosages, induced modest body weight gain without affecting epididymal/brown fat pad, lipid profiles and glycemic markers. A high dose of GML (1600 mg kg−1) showed positive impacts on the anti-inflammatory TGF-β1 and IL-22. GML modulated the indigenous microbiota in a dose-dependent manner. It was found that 400 and 800 mg kg−1 GML improved the richness of Barnesiella, whereas a high dosage of GML (1600 mg kg−1) significantly increased the relative abundances of Clostridium XIVa, Oscillibacter and Parasutterella. The present work indicated that GML could upregulate the favorable microbial taxa without inducing systemic inflammation and dysfunction of glucose and lipid metabolism. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of antibacterial peptides from Brevibacillus texasporus (BT) on the growth performance, meat quality and gut health of cultured largemouth bass (Micropterus salmoides). Largemouth bass (36.17 ± 1.52 g) were divided into 2 groups and each group was fed with diets supplemented with or without 200 ppm of BT peptides for 130 days. The results showed that BT peptides had no significant influences on growth performance and body indexes, but significantly enhanced total antioxidant capacity and lysozyme content in the serum. Moreover, digestive enzymes activities and intestinal villous height were also prominently increased. From meat quality aspect, no significant differences were found in nutritional components, amino acid composition, fatty acid composition and texture property, except the values of hardness, gumminess and γ-linolenic acid (C18:3n6) were remarkably increased after BT peptides intervention. Finally, the results of gut microbiota and short chain fatty acids revealed that BT peptides significantly decreased the relative abundances of harmful bacteria such as genus Acinetobacter and Pseudomonas , and increased the production of short chain fatty acids. In conclusion, this study confirmed that BT peptides could be used to improve the health of largemouth bass, which provided novel insights into the application of antimicrobial peptides in aquacultures. [Display omitted] • BT peptides enhanced total antioxidant capacity and lysozyme content. • BT peptides increased digestive enzymes activities and intestinal villous height. • Slight changes were found in meat quality after BT peptides intervention. • BT peptides significantly inhibited the relative abundances of harmful gut microbiota. • BT peptides promoted the production of short chain fatty acids. [ABSTRACT FROM AUTHOR]

Potassium sorbate (PS) is a widely used food preservative in the field of food industry. However, the effects of continuous intake and washout period of PS on host health are still unclear. In this study, to investigate long-term effect and after-effect of different concentrations and time points of PS, healthy mice were orally exposed to 150 mg/kg, 500 mg/kg and 1000 mg/kg of PS for 10 weeks, and washout treatment for another 5 weeks, respectively. The results indicated that PS intake for 10 weeks had no obvious effects on organs and adipose tissue, nor did it noteworthily interfere with glucolipid metabolism in the serum. However, it caused inflammatory cell infiltration in the liver, increased serum interleukin (IL)-1β level, changed abundances of gut microbiota but failed to promote the production of short chain fatty acids in the gut. After washout period for 5 weeks, liver inflammation and IL-1β level were decreased, and gut environment developed towards a healthier condition. Specifically, PS washout significantly increased abundance of Lachnospiraceae_NK4A136_group and the production of isobutyric acid. This study confirmed washout period eliminated negative effects from continuous intake of PS, which provided positive evidence for its safety. [Display omitted] • Continuous intake of PS had no significant effect on organic index. • Continuous intake of PS increased IL-1β level in the serum. • PS washout decreased inflammatory cell infiltration in the liver. • PS washout increased the abundance of Lachnospiraceae_NK4A136_group. • PS washout promoted the production of isobutyric acid. [ABSTRACT FROM AUTHOR]

[Display omitted] • GMC significantly ameliorated visceral fat accumulation in HFD-fed mice. • GMC improved systemic inflammation in HFD-fed mice. • GMC modulated gut microbiota dysbiosis with increased beneficial bacteria and promoted SCFAs production. • GMC-induced metabolic improvements were closely related to gut microbiota regulation. • Not all of the food preservatives and emulsifiers would drive gut microbiota dysbiosis. Recent findings imply that great consideration should be given to the potential health risks of food additives on gut microbiota. Glycerol monocaprylate (GMC) is a widely consumed food preservative and emulsifier. Our results indicated that GMC significantly ameliorated visceral fat accumulation and systemic inflammation in high-fat diet (HFD)-fed mice. Furthermore, GMC induced improvements on the composition and function of gut microbiota, resulting in increased beneficial gut bacteria (Bifidobacterium and Lactobacillus) and promoted production of short chain fatty acids. Notably, GMC-induced metabolic amelioration is closely related to the regulation in gut microbiota. Overall, our findings supported that unlike the emulsifiers previously reported to damage intestinal health, GMC performed the potential on attenuating HFD-induced metabolic disorders and gut microbiota dysbiosis, which also refined on the safety evaluation of GMC on gut microbiota. Our findings suggest that when evaluating the safety of food additives with regards to gut microbiota, it is important to take into account the specific characteristics of the additive in question, rather than simply relying on its classification. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fermented sea buckthorn juice (FHJ) displayed better antioxidant and antidiabetic properties in vitro. • FHJ ameliorated diet-induced hyperlipidemia, insulin resistance, oxidative stress, and gut microbiota dysbiosis in vivo. • FHJ could interact with Akkermansia to further attenuate metabolic syndrome. • FHJ increased acetate and butyrate contents in caeca. • Fermentation-triggered metabolomic alterations, especially flavonoids in FHJ, played critical roles in the FHJ-microorganism interactions. To enhance physiological activity and probiotic availability of sea buckthorn juice, sea buckthorn juice pulp (BHJ) went through fermentation to the fermented (FHJ). In vitro , FHJ displayed better antioxidant and antidiabetic capacities. To further study effects of FHJ on diet-induced metabolic syndrome (MS) and possible mechanisms in vivo , C57BL/6 mice were fed on BHJ and FHJ under high fat diet (HFD). FHJ, rather BHJ, displayed better performance on ameliorating hyperlipidemia, insulin resistance, and oxidative stress in MS. Mechanistically, FHJ intervention significantly reversed the microorganism dysbiosis by restoring the microbial diversity, and modulating obesogenic bacteria abundance, like Oscillospira. Furthermore, fermentation altered FHJ's metabolomics, especially flavonoids, contributing to interactions between FHJ and probiotics, like Akkermansia and Lachnospiraceae. Furthermore, short-chain fatty acids, related to ameliorations of MS, were increased by FHJ. This study demonstrated that interactions between metabolomic alterations in FHJ and microorganisms were vital to attenuate MS. [ABSTRACT FROM AUTHOR]

[Display omitted] • LA, GML and GTL ameliorated HFD-induced hyperlipidemia. • GML performed better effects on glucose metabolism and systemic inflammation. • LA and its glycerides-induced improvements were related to gut microbiota regulation. • GML regulated phospholipid metabolism and gut microbe-related metabolites. • GML promoted endogenous unsaturated fatty acids synthesis. The anti-bacterial properties of lauric acid (LA) and its glycerides had been studied. However, their effects on gut microbiota remain unclear. Moreover, LA and its glycerides performed controversial influences on lipid metabolism. This study evaluated the regulation of LA, glycerol monolaurate (GML) and lauric triglyceride (GTL) on metabolic health and gut microbiota in high fat diet-fed mice. Serum metabolomics and lipidomics contributed to elucidate the underlying mechanisms. LA and its glycerides ameliorated hyperlipidemia, while GML performed more pronounced modulation on glucose metabolism and inflammation. LA and its glycerides modulated gut microbiota with increased Bifidobacterium and decreased Desulfovibrio , which closely related with metabolic improvements. Furthermore, the integrative multi-omics analyses identified that the regulation of phospholipid metabolism, intestinal microbial metabolites (bile acids and indole derivatives) and endogenous unsaturated fatty acids synthesis conduced to the more evident modulation of GML. Our findings suggested an effective strategy of GML for improving metabolism and gut health. [ABSTRACT FROM AUTHOR]