Mechanistic insights into the pleiotropic effects of butyrate as a potential therapeutic agent on NAFLD management: A systematic review

Expression of PGC-1α, PPAR-α and UCP1 genes, metabolic and anthropometric factors in response to sodium butyrate supplementation in patients with obesity: a triple-blind, randomized placebo-controlled clinical trial

OBJECTIVES

There is increasing evidence that gut metabolites have a role in the etiology of obesity. This study aimed to investigate the effects of sodium butyrate (NaB) supplementation on the expression of peroxisome proliferator-activated receptor (PPAR) gamma coactivator-1α (PGC-1α), PPAR-α, and uncoupling protein-1 (UCP-1) genes, as well as on the metabolic parameters and anthropometric indices in persons with obesity.

METHODS

In this triple-blind placebo-controlled randomized clinical trial, 50 individuals with obesity were randomly assigned to NaB (600 mg/day) + hypo-caloric diet or placebo group + hypo-caloric diet for 8 weeks. The study measured the participants' anthropometric characteristics, food consumption, and feelings of hunger in addition to the serum levels of metabolic indices and the mRNA expression of the PGC-1α, PPAR-α, and UCP-1 genes in peripheral blood mononuclear cells (PBMCs).

RESULTS

PGC-1α and UCP-1 genes expression significantly increased in NaB group compared to the placebo at the endpoint. A significant decrease in weight, BMI, and waist circumference (WC) was observed in NaB group. Among the metabolic factors, NaB significantly decreased fasting blood sugar (FBS) (P = 0.04), low-density lipoprotein cholesterol (LDL-C) (P = 0.038) and increased high-density lipoprotein cholesterol (HDL-C) (P = 0.016). NaB could not significantly change serum GLP-1 level.

CONCLUSIONS

This study unveiled NaB supplementation alone cannot have significant beneficial effects on anthropometric, and biochemical factors. NaB could affect anthropometric and metabolic risk variables associated with obesity only when prescribed, along with calorie restriction.

CLINICAL TRIAL REGISTRATION

This study was registered in the Iranian Registry of Clinical Trials ( https://en.irct.ir/trial/53968 ) on 31 January 2021 (registry number IRCT20190303042905N2).

Preclinical Evaluation of Sodium Butyrate's Potential to Reduce Alcohol Consumption: A Dose-Escalation Study in C57BL/6J Mice in Antibiotic-Enhanced Binge-Like Drinking Model

INTRODUCTION

In our earlier efforts to establish gut-brain axis during alcohol use disorder (AUD), we have demonstrated that supplementation of C57BL/6J male mice with 8 mg/mL sodium butyrate, a major short-chain fatty acid, in drinking water reduced ethanol intake and neuroinflammatory response in antibiotic (ABX)-enhanced voluntary binge-like alcohol consumption model, drinking in the dark (DID).

METHODS

To further evaluate the preclinical potential of SB, we have set a dose-escalation study in C57BL/6J male mice to test effects of ad libitum 20 mg/mL SB and 50 mg/mL SB and their combinations with ABX in the DID procedure for 4 weeks. Effects of these SB concentrations on ethanol consumption and bodily parameters were determined for the duration of the treatments. At the end of study, blood, liver, and intestinal tissues were collected to study any potential adverse effects ad to measure blood ethanol concentrations.

RESULTS

Increasing SB concentrations in the drinking water caused a loss in the protective effect against ethanol consumption and produced adverse effects on body and liver weights, reduced overall liquid intake. The hypothesis that these effects were due to aversion to SB smell/taste at these high concentrations were further tested in a follow up proof-of-concept study with intragastric gavage administration of SB. The higher gavage dose (320 mg/kg) caused reduction in ethanol consumption without any adverse effects.

CONCLUSION

Overall, these findings added more support for the therapeutic potential of SB in management of AUD, given a proper form of administration.

Effect of Supplementation of a Butyrate-Based Formula in Individuals with Liver Steatosis and Metabolic Syndrome: A Randomized Double-Blind Placebo-Controlled Clinical Trial

Postbiotics could exert different metabolic activities in animal models of non-alcoholic fatty liver disease (NAFLD) and in humans affected by metabolic syndrome. This is a randomized, double-blind, placebo-controlled, parallel-group clinical trial that enrolled a sample of 50 Caucasian healthy individuals with NAFLD, defined as liver steatosis, and metabolic syndrome. After a 4-week run-in, the enrolled individuals were randomized to take a food for special medical purposes with functional release, one tablet a day, containing calcium butyrate (500 mg/tablet), zinc gluconate (zinc 5 mg/tablet), and vitamin D3 (500 IU/tablet), or an identical placebo for 3 months. Liver and metabolic parameters were measured at baseline and at the end of the study. No subject experienced any adverse events during the trial. In both groups, a significant decrease in total cholesterol (TC) and triglycerides (TG) plasma levels was observed at the randomization visit vs. pre-run-in visit (p < 0.05). Regarding liver parameters, after treatment, the fatty liver index (FLI) improved significantly vs. baseline values (p < 0.05) and vs. placebo group (p < 0.05) in the active treatment group, and the hepatic steatosis index (HSI) improved significantly vs. baseline values (p < 0.05). Moreover, after active treatment, TC, TG, and gamma-glutamyl transferase (gGT) improved significantly vs. baseline values (p < 0.05), and TC and TG improved vs. placebo group (p < 0.05), as well. In the placebo group, liver parameters remained unchanged after treatment; only TG improved significantly vs. baseline values (p < 0.05). In our study, we observed that the butyrate-based formula improved FLI and plasma lipid patterns in individuals affected by liver steatosis and metabolic syndrome.

Digestive dynamics: Unveiling interplay between the gut microbiota and the liver in macronutrient metabolism and hepatic metabolic health

Although the liver is the largest metabolic organ in the body, it is not alone in functionality and is assisted by "an organ inside an organ," the gut microbiota. This review attempts to shed light on the partnership between the liver and the gut microbiota in the metabolism of macronutrients (i.e., proteins, carbohydrates, and lipids). All nutrients absorbed by the small intestines are delivered to the liver for further metabolism. Undigested food that enters the colon is metabolized further by the gut microbiota that produces secondary metabolites, which are absorbed into portal circulation and reach the liver. These microbiota-derived metabolites and co-metabolites include ammonia, hydrogen sulfide, short-chain fatty acids, secondary bile acids, and trimethylamine N-oxide. Further, the liver produces several compounds, such as bile acids that can alter the gut microbial composition, which can in turn influence liver health. This review focuses on the metabolism of these microbiota metabolites and their influence on host physiology. Furthermore, the review briefly delineates the effect of the portosystemic shunt on the gut microbiota-liver axis, and current understanding of the treatments to target the gut microbiota-liver axis.

Antioxidant supplementation for sickle cell disease

BACKGROUND

Sickle cell disease (SCD) refers to a group of genetic disorders characterized by the presence of an abnormal haemoglobin molecule called haemoglobin S (HbS). When subjected to oxidative stress from low oxygen concentrations, HbS molecules form rigid polymers, giving the red cell the typical sickle shape. Antioxidants have been shown to reduce oxidative stress and improve outcomes in other diseases associated with oxidative stress. Therefore, it is important to review and synthesize the available evidence on the effect of antioxidants on the clinical outcomes of people with SCD.

OBJECTIVES

To assess the effectiveness and safety of antioxidant supplementation for improving health outcomes in people with SCD.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was 15 August 2023.

SELECTION CRITERIA

We included randomized and quasi-randomized controlled trials comparing antioxidant supplementation to placebo, other antioxidants, or different doses of antioxidants, in people with SCD.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data, assessed the risk of bias and certainty of the evidence, and reported according to Cochrane methodological procedures.

MAIN RESULTS

The review included 1609 participants in 26 studies, with 17 comparisons. We rated 13 studies as having a high risk of bias overall, and 13 studies as having an unclear risk of bias overall due to study limitations. We used GRADE to rate the certainty of evidence. Only eight studies reported on our important outcomes at six months. Vitamin C (1400 mg) plus vitamin E (800 mg) versus placebo Based on evidence from one study in 83 participants, vitamin C (1400 mg) plus vitamin E (800 mg) may not be better than placebo at reducing the frequency of crisis (risk ratio (RR) 1.18, 95% confidence interval (CI) 0.64 to 2.18), the severity of pain (RR 1.33, 95% CI 0.40 to 4.37), or adverse effects (AE), of which the most common were headache, nausea, fatigue, diarrhoea, and epigastric pain (RR 0.56, 95% CI 0.31 to 1.00). Vitamin C plus vitamin E may increase the risk of SCD-related complications (acute chest syndrome: RR 2.66, 95% CI 0.77 to 9.13; 1 study, 83 participants), and increase haemoglobin level (median (interquartile range) 90 (81 to 96) g/L versus 93.5 (84 to 105) g/L) (1 study, 83 participants) compared to placebo. However, the evidence for all the above effects is very uncertain. The study did not report on quality of life (QoL) of participants and their caregivers, nor on frequency of hospitalization. Zinc versus placebo Zinc may not be better than placebo at reducing the frequency of crisis at six months (rate ratio 0.62, 95% CI 0.17 to 2.29; 1 study, 36 participants; low-certainty evidence). We are uncertain whether zinc is better than placebo at improving sickle cell-related complications (complete healing of leg ulcers at six months: RR 2.00, 95% CI 0.60 to 6.72; 1 study, 34 participants; very low-certainty evidence). Zinc may be better than placebo at increasing haemoglobin level (g/dL) (MD 1.26, 95% CI 0.44 to 1.26; 1 study, 36 participants; low-certainty evidence). The study did not report on severity of pain, QoL, AE, and frequency of hospitalization. N-acetylcysteine versus placebo N-acetylcysteine (NAC) 1200 mg may not be better than placebo at reducing the frequency of crisis in SCD, reported as pain days (rate ratio 0.99 days, 95% CI 0.53 to 1.84; 1 study, 96 participants; low-certainty evidence). Low-certainty evidence from one study (96 participants) suggests NAC (1200 mg) may not be better than placebo at reducing the severity of pain (MD 0.17, 95% CI -0.53 to 0.87). Compared to placebo, NAC (1200 mg) may not be better at improving physical QoL (MD -1.80, 95% CI -5.01 to 1.41) and mental QoL (MD 2.00, 95% CI -1.45 to 5.45; very low-certainty evidence), reducing the risk of adverse effects (gastrointestinal complaints, pruritus, or rash) (RR 0.92, 95% CI 0.75 to 1.14; low-certainty evidence), reducing the frequency of hospitalizations (rate ratio 0.98, 95% CI 0.41 to 2.38; low-certainty evidence), and sickle cell-related complications (RR 5.00, 95% CI 0.25 to 101.48; very low-certainty evidence), or increasing haemoglobin level (MD -0.18 g/dL, 95% CI -0.40 to 0.04; low-certainty evidence). L-arginine versus placebo L-arginine may not be better than placebo at reducing the frequency of crisis (monthly pain) (RR 0.71, 95% CI 0.26 to 1.95; 1 study, 50 participants; low-certainty evidence). However, L-arginine may be better than placebo at reducing the severity of pain (MD -1.41, 95% CI -1.65 to -1.18; 2 studies, 125 participants; low-certainty evidence). One participant allocated to L-arginine developed hives during infusion of L-arginine, another experienced acute clinical deterioration, and a participant in the placebo group had clinically relevant increases in liver function enzymes. The evidence is very uncertain whether L-arginine is better at reducing the mean number of days in hospital compared to placebo (MD -0.85 days, 95% CI -1.87 to 0.17; 2 studies, 125 participants; very low-certainty evidence). Also, L-arginine may not be better than placebo at increasing haemoglobin level (MD 0.4 g/dL, 95% CI -0.50 to 1.3; 2 studies, 106 participants; low-certainty evidence). No study in this comparison reported on QoL and sickle cell-related complications. Omega-3 versus placebo Very low-certainty evidence shows no evidence of a difference in the risk of adverse effects of omega-3 compared to placebo (RR 1.05, 95% CI 0.74 to 1.48; 1 study, 67 participants). Very low-certainty evidence suggests that omega-3 may not be better than placebo at increasing haemoglobin level (MD 0.36 g/L, 95% CI -0.21 to 0.93; 1 study, 67 participants). The study did not report on frequency of crisis, severity of pain, QoL, frequency of hospitalization, and sickle cell-related complications.

AUTHORS' CONCLUSIONS

There was inconsistent evidence on all outcomes to draw conclusions on the beneficial and harmful effects of antioxidants. However, L-arginine may be better than placebo at reducing the severity of pain at six months, and zinc may be better than placebo at increasing haemoglobin level. We are uncertain whether other antioxidants are beneficial for SCD. Larger studies conducted on each comparison would reduce the current uncertainties.

Bacteroides and NAFLD: pathophysiology and therapy

Non-alcoholic fatty liver disease (NAFLD) is a prevalent chronic liver condition observed globally, with the potential to progress to non-alcoholic steatohepatitis (NASH), cirrhosis, and even hepatocellular carcinoma. Currently, the US Food and Drug Administration (FDA) has not approved any drugs for the treatment of NAFLD. NAFLD is characterized by histopathological abnormalities in the liver, such as lipid accumulation, steatosis, hepatic balloon degeneration, and inflammation. Dysbiosis of the gut microbiota and its metabolites significantly contribute to the initiation and advancement of NAFLD. Bacteroides, a potential probiotic, has shown strong potential in preventing the onset and progression of NAFLD. However, the precise mechanism by which Bacteroides treats NAFLD remains uncertain. In this review, we explore the current understanding of the role of Bacteroides and its metabolites in the treatment of NAFLD, focusing on their ability to reduce liver inflammation, mitigate hepatic steatosis, and enhance intestinal barrier function. Additionally, we summarize how Bacteroides alleviates pathological changes by restoring the metabolism, improving insulin resistance, regulating cytokines, and promoting tight-junctions. A deeper comprehension of the mechanisms through which Bacteroides is involved in the pathogenesis of NAFLD should aid the development of innovative drugs targeting NAFLD.

Short-chain fatty acids in nonalcoholic fatty liver disease: New prospects for short-chain fatty acids as therapeutic targets

Nonalcoholic fatty liver disease (NAFLD) is a stress-induced liver injury related to heredity, environmental exposure and the gut microbiome metabolism. Short-chain fatty acids (SCFAs), the metabolites of gut microbiota (GM), participate in the regulation of hepatic steatosis and inflammation through the gut-liver axis, which play an important role in the alleviation of NAFLD. However, little progress has been made in systematically elucidating the mechanism of how SCFAs improve NAFLD, especially the epigenetic mechanisms and the potential therapeutic application as clinical treatment for NAFLD. Herein, we adopted PubMed and Medline to search relevant keywords such as 'SCFAs', 'NAFLD', 'gut microbiota', 'Epigenetic', 'diet', and 'prebiotic effect' to review the latest research on SCFAs in NAFLD up to November 2023. In this review, firstly, we specifically discussed the production and function of SCFAs, as well as their crosstalk coordination in the gut liver axis. Secondly, we provided an updated summary and intensive discussion of how SCFAs affect hepatic steatosis to alleviate NAFLD from the perspective of genetic and epigenetic. Thirdly, we paid attention to the pharmacological and physiological characteristics of SCFAs, and proposed a promising future direction to adopt SCFAs alone or in combination with prebiotics and related clinical drugs to prevent and treat NAFLD. Together, this review aimed to elucidate the function of SCFAs and provide new insights to the prospects of SCFAs as a therapeutic target for NAFLD.

The connection between epigenetics and gut microbiota-current perspective

Both the epigenetic changes and gut microbiota (GM) have attracted a growing interest in establishing effective diagnostics and potential therapeutic strategies for a number of diseases. These disorders include metabolic, central nervous system-related diseases, autoimmune, and gastrointestinal infections (GI). Despite the number of studies, there is no extensive review that connects the epigenetics modifications and GM as biomarkers that could confer effective diagnostics and confer treatment options. To this end, this review hopes to give detailed information on connecting the modifications in epigenetic and GM. An updated and detailed information on the connection between the epigenetics factors and GM that influence diseases are given. In addition, the review showed some associations between the epigenetics to the maternal GM and offspring health. Finally, the limitations of the concept and prospects into this new emerging discipline were also looked into. Although this review elucidated on the maternal diet and response to offspring health with respect to GM and epigenetic modifications, there still exist various limitations to this newly emerging discipline. In addition to integrating complementary multi-omics data, longitudinal sampling will aid with the identification of functional mechanisms that may serve as therapeutic targets. To this end, this review gave a detailed perspective into harnessing disease diagnostics, prevention and treatment options through epigenetics and GM.

Deciphering the molecular mediators of triclosan-induced lipid accumulation: Intervention via short-chain fatty acids and miR-101a

As a potential environmental obesogen, triclosan (TCS) carries inherent risks of inducing obesity and metabolic disorders. However, the underlying molecular mechanisms behind the lipid metabolism disorder induced by TCS have remained elusive. Through a fusion of transcriptomics and microRNA target prediction, we hypothesize that miR-101a as a responsive miRNA to TCS exposure in zebrafish, playing a central role in disturbing lipid homeostasis. As an evidence, TCS exposure triggers a reduction in miR-10a expression that accompanied by elevation of genes linked to regulation of lipid homeostasis. Through precision-controlled interventions involving miRNA expression modulation, we discovered that inhibition of miR-101a enhanced expression of its target genes implicated in lipid homeostasis, subsequently triggering excessive fat accumulation. Meanwhile, the overexpression of miR-101a acts as a protective mechanism, counteracting the lipid metabolism disorder induced by TCS in the larvae. Notably, the combination of short-chain fatty acids (SCFAs) emerged as a potential remedy to alleviate TCS-induced lipid accumulation partially by counteracting the decline in miR-101a expression induced by TCS. These revelations provide insight into a prospective molecular framework underlying TCS-triggered lipid metabolism disorders, thereby paving the way for pre-emptive strategies in combating the ramifications of TCS pollution.

Targeting the Adipose Tissue-Liver-Gut Microbiota Crosstalk to Cure MASLD

The gut microbiota is a complex system, playing a peculiar role in regulating innate and systemic immunity. Increasing evidence links dysfunctional gut microbiota to metabolic dysfunction-associated steatotic liver disease (MASLD) due to the activation of multiple pathways in the gut and in the liver, including those mediated by Toll-like receptors (TLRs), that sustain hepatic inflammation. Thus, many efforts have been made to unravel the role of microbiota-associated dysfunction in MASLD, with the final aim of finding novel strategies to improve liver steatosis and function. Moreover, recent evidence underlines the role of adipose tissue in sustaining hepatic inflammation during MASLD development. In this review, we focus on the recently discovered strategies proposed to improve the alteration of gut microbiota observed in MASLD patients, with a particular insight into those known to modulate gut microbiota-associated dysfunction and to affect the complex crosstalk between the gut, the adipose tissue, and the liver.

Microbiota-Accessible Boron-Containing Compounds in Complex Regional Pain Syndrome

The microbiota-gut-brain axis has garnered increasing attention in recent years for its role in various health conditions, including neuroinflammatory disorders like complex regional pain syndrome (CRPS). CRPS is a debilitating condition characterized by chronic neuropathic pain, and its etiology and pathophysiology remain elusive. Emerging research suggests that alterations in the gut microbiota composition and function could play a significant role in CRPS development and progression. Our paper explores the implications of microbiota in CRPS and the potential therapeutic role of boron (B). Studies have demonstrated that individuals with CRPS often exhibit dysbiosis, with imbalances in beneficial and pathogenic gut bacteria. Dysbiosis can lead to increased gut permeability and systemic inflammation, contributing to the chronic pain experienced in CRPS. B, an essential trace element, has shown promise in modulating the gut microbiome positively and exerting anti-inflammatory effects. Recent preclinical and clinical studies suggest that B supplementation may alleviate neuropathic pain and improve CRPS symptoms by restoring microbiota balance and reducing inflammation. Our review highlights the complex interplay between microbiota, inflammation, and neuropathic pain in CRPS and underscores the potential of B as a novel therapeutic approach to target the microbiota-gut-brain axis, offering hope for improved management of this challenging condition.

Akkermansia muciniphila Ameliorates Alcoholic Liver Disease in Experimental Mice by Regulating Serum Metabolism and Improving Gut Dysbiosis

Alcoholic liver disease (ALD) represents a significant global health concern, yet the available treatment options remain limited. Numerous studies have shown that gut microbiota is a critical target for the treatment of ALD. Additionally, there is increasing evidence that host metabolism also plays a crucial role in the development of ALD. Akkermansia muciniphila has been demonstrated to ameliorate experimental ALD through its modulatory effects on the intestinal vascular barrier, enhancement of mucus layer thickness, and promotion of intestinal tight junction proteins. Nevertheless, there is a dearth of studies investigating the impact of A. muciniphila on host metabolism and gut microbiota. Here, C57BL/6 mice were utilized to establish a modified NIAAA model in order to investigate the impact of the oral administration of A. muciniphila during the development of ALD. Furthermore, we employed targeted metabolomics to analyze the serum metabolomic profiles of the mice and 2bRAD-M sequencing to comprehensively examine the underlying mechanisms of the efficacy of A. muciniphila on ALD. Our results illustrated that the oral administration of A. muciniphila alleviated alcohol-induced liver injury in conjunction with encouraged serum levels of ornithine and diminished the elevation of oxalic acid levels induced by alcohol intake. In addition, A. muciniphila also inhibited the proliferation of harmful bacteria, such as Escherichia coli and Helicobacter hepaticus, induced by alcohol consumption while promoting the growth of butyrate-producing and commensal bacteria, including Paramuribaculum intestinale and Bacteroides ovatus. In conclusion, this study suggests that A. muciniphila restores ALD by regulating the gut microbiota, and this corrective effect is associated with alterations in the serum metabolism. Our research supplies a theoretical basis for developing A. muciniphila as an innovative generation of probiotic for preventing and managing ALD.

The effects of sodium butyrate supplementation on the expression levels of PGC-1α, PPARα, and UCP-1 genes, serum level of GLP-1, metabolic parameters, and anthropometric indices in obese individuals on weight loss diet: a study protocol for a triple-blind, randomized, placebo-controlled clinical trial

BACKGROUND

Obesity is a multifaceted disease characterized by an abnormal accumulation of adipose tissue. Growing evidence has proposed microbiota-derived metabolites as a potential factor in the pathophysiology of obesity and related metabolic conditions over the last decade. As one of the essential metabolites, butyrate affects several host cellular mechanisms related to appetite sensations and weight control. However, the effects of butyrate on obesity in humans have yet to be studied. Thus, the present study was aimed to evaluate the effects of sodium butyrate (SB) supplementation on the expression levels of peroxisome proliferator activated-receptor (PPAR) gamma coactivator-1α (PGC-1α), PPARα and uncoupling protein 1 (UCP1) genes, serum level of glucagon-like peptide (GLP1), and metabolic parameters, as well as anthropometric indices in obese individuals on a weight loss diet.

METHODS

This triple-blind randomized controlled trial (RCT) will include 50 eligible obese subjects aged between 18 and 60 years. Participants will be randomly assigned into two groups: 8 weeks of SB (600 mg/day) + hypo-caloric diet or placebo (600 mg/day) + hypo-caloric diet. At weeks 0 and 8, distinct objectives will be pursued: (1) PGC-1α, PPARα, and UCP1 genes expression will be evaluated by real-time polymerase chain reaction; (2) biochemical parameters will be assayed using enzymatic methods; and (3) insulin and GLP1 serum level will be assessed by enzyme-linked immunosorbent assay kit.

DISCUSSION

New evidence from this trial may help fill the knowledge gap in this realm and facilitate multi-center clinical trials with a substantially larger sample size.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials: IRCT20190303042905N2 . Registered on 31 January 2021.