Oral tributyrin prevents endotoxin-induced lipid metabolism disorder

Tributyrin reverses the deleterious effect of saturated fat on working memory and synaptic plasticity in juvenile mice: differential effects in males and females

Short-chain fatty acids, such as butyric acid, derived from the intestinal fermentation of dietary fiber, have been proposed as a treatment for certain pathologies of the central nervous system. Our research group has shown that tributyrin (TB), a butyric acid prodrug, reverses deficits in spatial memory and modulates hippocampal synaptic plasticity. In the present work, diets enriched in either saturated (SOLF; Saturated OiL-enriched Food) or unsaturated (UOLF; Unsaturated OiL-enriched Food) fat were supplied during either 2 h or 8 weeks to 5-week-old male and female mice undergoing a treatment schedule with TB. After the dietary treatment, spatial learning and memory (SLM) was assessed in both the Y-maze and the eight-arm radial maze (RAM). Hippocampal expression of genes involved in glutamatergic transmission as well as synaptic plasticity (long-term potentiation -LTP- and long-term depression -LTD-) were also analyzed. Our results show that 2 h of SOLF intake impaired LTP as well as the performance in the Y-Maze in juvenile male mice whereas no effect was found in females. Moreover, TB reversed both effects in SLM and LTP in males. In the case of chronic intake, both SOLF and UOLF deteriorated SLM measured in the RAM in both sexes whereas TB only reversed LTP impairment induced by SOLF in male mice. These results suggest that TB may have a potentially beneficial influence on learning and memory processes, contingent upon the type of diet and the sex of the individuals.

Harnessing and delivering microbial metabolites as therapeutics via advanced pharmaceutical approaches

Microbial metabolites have emerged as key players in the interplay between diet, the gut microbiome, and host health. Two major classes, short-chain fatty acids (SCFAs) and tryptophan (Trp) metabolites, are recognized to regulate inflammatory, immune, and metabolic responses within the host. Given that many human diseases are associated with dysbiosis of the gut microbiome and consequent reductions in microbial metabolite production, the administration of these metabolites represents a direct, multi-targeted treatment. While a multitude of preclinical studies showcase the therapeutic potential of both SCFAs and Trp metabolites, they often rely on high doses and frequent dosing regimens to achieve systemic effects, thereby constraining their clinical applicability. To address these limitations, a variety of pharmaceutical formulations approaches that enable targeted, delayed, and/or sustained microbial metabolite delivery have been developed. These approaches, including enteric encapsulations, esterification to dietary fiber, prodrugs, and nanoformulations, pave the way for the next generation of microbial metabolite-based therapeutics. In this review, we first provide an overview of the roles of microbial metabolites in maintaining host homeostasis and outline how compromised metabolite production contributes to the pathogenesis of inflammatory, metabolic, autoimmune, allergic, infectious, and cancerous diseases. Additionally, we explore the therapeutic potential of metabolites in these disease contexts. Then, we provide a comprehensive and up-to-date review of the pharmaceutical strategies that have been employed to enhance the therapeutic efficacy of microbial metabolites, with a focus on SCFAs and Trp metabolites.

Soleus muscle contains a higher concentration of lipid metabolites than extensor digitorum longus in rats with lipopolysaccharide-induced acute muscle atrophy

BACKGROUND & AIMS

Muscle atrophy is one of the most important and frequent problems for critically ill patients. The purpose of this study was to evaluate the effect of lipid mediators on acute muscle atrophy. Skeletal muscle fiber-specific analysis of lipid mediators in endotoxemic rats was therefore performed.

METHODS

Male Wistar rats were intraperitoneally injected with lipopolysaccharide (LPS). Slow-twitch soleus muscle and fast-twitch extensor digitorum longus (EDL) muscle were harvested 0, 6, and 24 h after LPS injection. Lipid mediators were profiled using liquid chromatography-tandem mass spectrometry, and free fatty acid (FFA) concentrations were measured using gas chromatography-mass spectrometry. Muscles were weighed and their cross-sectional areas were evaluated. Expression levels of mRNAs encoding inflammatory cytokines, autophagy-related transcription factors, and members of the ubiquitin-proteasome system were measured using real-time PCR.

RESULTS

Before LPS injection, the concentrations of all FFAs, including arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, and all measured lipid mediators were higher in soleus muscle than in EDL muscle, especially those of pro-inflammatory prostaglandin E2 (PGE2) and leukotriene B4. LPS injection, increased PGE2 and D2 and decreased FFAs in soleus muscle but did not change in EDL muscle. The concentrations of specialized pro-resolving mediators E-series hydroxy-eicosapentaenoic acid and D-series hydroxy-docosahexaenoic acid were higher in soleus muscle. Muscle cross-sectional area decreased and the expression level of atrogin-1 was upregulated in EDL muscle, but both were unchanged in soleus muscle. After LPS injection, a discrepancy involving an increased PGE2 concentration and decreased muscle atrophy was identified in this acute muscle atrophy model of critical illness.

CONCLUSION

Concentrations of FFAs and lipid mediators were higher in soleus muscle than in EDL muscle, and LPS injection rapidly increased concentrations of pro-inflammatory lipid mediators. However, muscle atrophy with upregulation of autophagy-related transcription factors was observed in EDL muscle but not in soleus muscle.

The Role of Gut Microbiome-Derived Short-Chain Fatty Acid Butyrate in Hepatobiliary Diseases

The short-chain fatty acid butyrate, produced from fermentable carbohydrates by gut microbiota in the colon, has multiple beneficial effects on human health. At the intestinal level, butyrate regulates metabolism, helps in the transepithelial transport of fluids, inhibits inflammation, and induces the epithelial defense barrier. The liver receives a large amount of short-chain fatty acids via the blood flowing from the gut via the portal vein. Butyrate helps prevent nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, inflammation, cancer, and liver injuries. It ameliorates metabolic diseases, including insulin resistance and obesity, and plays a direct role in preventing fatty liver diseases. Butyrate has different mechanisms of action, including strong regulatory effects on the expression of many genes by inhibiting the histone deacetylases and modulating cellular metabolism. The present review highlights the wide range of beneficial therapeutic and unfavorable adverse effects of butyrate, with a high potential for clinically important uses in several liver diseases.

Effects of Tributyrin Supplementation on Liver Fat Deposition, Lipid Levels and Lipid Metabolism-Related Gene Expression in Broiler Chickens

The objective of this study was to investigate the effects of tributyrin supplementation on liver fat metabolism in broiler chickens. Two hundred and forty broilers were randomly allocated into two experimental groups (6 replicates per treatment; 20 chickens in each replicate): the control group (CN), which received a basal diet, and the tributyrin group (TB), which received a basal diet supplemented with 1 g/kg of tributyrin. The experimental period lasted 37 days. The results showed that in the liver, broilers supplemented with tributyrin had higher content of high-density lipoprotein cholesterol (HDL-C) (p < 0.05). Liver hepatic lipase (HL), lipoprotein lipase (LPL) and total lipid (TL) activity were significantly lower than in the TB group than that in the NC group. Meanwhile, the diet supplemented with tributyrin had more lipid droplets than the NC group, whereas the TB and NC groups showed no histological abnormalities in the liver. Furthermore, the mRNA expression levels of peroxisome proliferators-activated receptor α (PPARα), proliferators-activated receptor γ (PPARγ), fatty acid synthase (FAS), LPL and adipose triglyceride lipase (ATGL) in the liver were significantly upregulated in the TB group (p < 0.05), while those of the long-chain acyl-CoA-synthetase 1 (ACSL1) mRNA between the TB group and the NC group were not different (p > 0.05). These findings indicated that the diet supplemented with tributyrin could increase fat deposition appropriately by promoting fat synthesis without causing liver tissue damage, which demonstrated that tributyrin can be considered a valid feed additive for broiler chickens.

Butyric Acid Precursor Tributyrin Modulates Hippocampal Synaptic Plasticity and Prevents Spatial Memory Deficits: Role of PPARγ and AMPK

BACKGROUND

Short chain fatty acids (SCFA), such as butyric acid (BA), derived from the intestinal fermentation of dietary fiber and contained in dairy products, are gaining interest in relation to their possible beneficial effects on neuropsychological disorders.

METHODS

C57BL/6J male mice were used to investigate the effect of tributyrin (TB), a prodrug of BA, on hippocampus (HIP)-dependent spatial memory, HIP synaptic transmission and plasticity mechanisms, and the expression of genes and proteins relevant to HIP glutamatergic transmission.

RESULTS

Ex vivo studies, carried out in HIP slices, revealed that TB can transform early-LTP into late-LTP (l-LTP) and to rescue LTP-inhibition induced by scopolamine. The facilitation of l-LTP induced by TB was blocked both by GW9662 (a PPARγ antagonist) and C-Compound (an AMPK inhibitor), suggesting the involvement of both PPARγ and AMPK on TB effects. Moreover, 48-hour intake of a diet containing 1% TB prevented, in adolescent but not in adult mice, scopolamine-induced impairment of HIP-dependent spatial memory. In the adolescent HIP, TB upregulated gene expression levels of Pparg, leptin, and adiponectin receptors, and that of the glutamate receptor subunits AMPA-2, NMDA-1, NMDA-2A, and NMDA-2B.

CONCLUSIONS

Our study shows that TB has a positive influence on LTP and HIP-dependent spatial memory, which suggests that BA may have beneficial effects on memory.

Surfactant Lipidomics of Alveolar Lavage Fluid in Mice Based on Ultra-High-Performance Liquid Chromatography Coupled to Hybrid Quadrupole-Exactive Orbitrap Mass Spectrometry

Surfactant lipid metabolism is closely related to pulmonary diseases. Lipid metabolism disorder can cause lung diseases, vice versa. With this rationale, a useful method was established in this study to determine the lipidome in bronchoalveolar lavage fluid (BALF) of mice. The lipid components in BALF were extracted by liquid-liquid extraction (methanol and methyl tert-butyl ether, and water). Ultra-high-performance liquid chromatography coupled to hybrid Quadrupole-Exactive Orbitrap mass spectrometry was used to analyze the extracted samples, which showed a broad scanning range of 215-1800 m/z. With MS-DIAL software and built-in LipidBlast database, we identified 38 lipids in positive, and 31 lipids in negative, ion mode, including lysophosphatidylcholine (lysoPC), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), etc. Then, the changes of lipids in BALF of mice with acute lung injury (ALI) induced by lipopolysaccharide (LPS) was investigated, which may contribute to further exploration of the pathogenesis of ALI.

Monobutyrin Reduces Liver Cholesterol and Improves Intestinal Barrier Function in Rats Fed High-Fat Diets

Butyric acid has been shown to reduce high-fat diet-related metabolic disturbances and to improve intestinal barrier function due to its potent anti-inflammatory capacity. This study investigates whether a butyric acid ester, monobutyrin (MB) affects lipid profiles and gut barrier function in a dose-response manner in rats fed butter- or lard-based high-fat diets. Four-week-old male Wistar rats were fed butter-based diets containing 0, 0.25, 0.75 and 1.5 MB g/100 g (dry weight basis) or 0.5 glycerol g/100 g, and diets with lard (La) containing 0 and 0.5 MB g/100 g or a low-fat control diet for 3⁻4 weeks. Lipid profiles in blood and liver tissue, intestinal permeability and cecal short-chain fatty acids were examined. The results showed a dose-dependent decrease in liver total cholesterol for 1.5 MB (p < 0.05) and liver triglycerides for 0.75 MB (p < 0.05) and 1.5 MB (p = 0.08) groups compared to the high-fat control group. Furthermore, a lower excretion of mannitol in urine in the 1.5 MB group indicated improved intestinal barrier function. When MB was supplemented in the lard-based diet, serum total cholesterol levels decreased, and total amount of liver high-density lipoprotein-cholesterol increased. Thus, MB dietary supplementation can be effective in counteracting lipid metabolism disturbances and impaired gut barrier function induced by high-fat diets.

Curcumin Attenuates Lipopolysaccharide-Induced Hepatic Lipid Metabolism Disorder by Modification of m6 A RNA Methylation in Piglets

N⁶ -methyladenosine (m⁶ A) regulates gene expression and affects cellular metabolism. In this study, we checked whether the regulation of lipid metabolism by curcumin is associated with m⁶ A RNA methylation. We investigated the effects of dietary curcumin supplementation on lipopolysaccharide (LPS)-induced liver injury and lipid metabolism disorder, and on m⁶ A RNA methylation in weaned piglets. A total of 24 Duroc × Large White × Landrace piglets were randomly assigned to control, LPS, and CurL (LPS challenge and 200 mg/kg dietary curcumin) groups (n = 8/group). The results showed that curcumin reduced the increase in relative liver weight as well as the concentrations of aspartate aminotransferase and lactate dehydrogenase induced by LPS injection in the plasma and liver of weaning piglets (p < 0.05). The amounts of total cholesterol and triacylglycerols were decreased by curcumin compared to that by the LPS injection (p < 0.05). Additionally, curcumin reduced the expression of Bcl-2 and Bax mRNA, whereas it increased the p53 mRNA level in the liver (p < 0.05). Curcumin inhibited the enhancement of SREBP-1c and SCD-1 mRNA levels induced by LPS in the liver. Notably, dietary curcumin affected the expression of METTL3, METTL14, ALKBH5, FTO, and YTHDF2 mRNA, and increased the abundance of m⁶ A in the liver of piglets. In conclusion, the protective effect of curcumin in LPS-induced liver injury and hepatic lipid metabolism disruption might be due to the increase in m⁶ A RNA methylation. Our study provides mechanistic insights into the effect of curcumin in protecting against hepatic injury during inflammation and metabolic diseases.

A lard-rich high-fat diet increases hepatic peroxisome proliferator-activated receptors in endotoxemic rats

BACKGROUND

Diets high in saturated fatty acids activate chronic inflammation. We previously reported that, in even acute inflammation caused by lipopolysaccharide (LPS), liver injury was exacerbated in rats fed a lard-rich diet. Peroxisome proliferator-activated receptors (PPARs) are related to inflammation and are also key regulators of lipid metabolism. In this study, we examined effects of high-fat diet on liver injury and hepatic lipid metabolism during endotoxemia, measuring hepatic PPARs and other markers.

MATERIALS AND METHODS

Male Wistar rats were fed a high-fat diet (HFD, 60 kcal% fat) or control diet (CD, 10 kcal% fat) for 4 or 12 wk, injected with LPS and sacrificed at 0, 1.5, or 6 h. Analyses included plasma aspartate transaminase (AST) and alanine transaminase (ALT) levels, messenger RNA (mRNA) and protein levels of hepatic PPARα and PPARγ, and mRNA levels of enzymes related to fatty acid oxidation and synthesis.

RESULTS

Endotoxemic rats on HFD for 12 wk, but not 4 wk, had higher mRNA and protein levels for hepatic PPARs, than did those on CD (P < 0.01-0.05). Similarly, these rats had increased mRNA expression of hepatic fatty acid oxidation- and synthesis-related enzymes (P < 0.01-0.05). Rats injected with LPS had more severe liver injury, indicated by plasma AST/ALT, if on the HFD for 12 wk, compared with for 4 wk.

CONCLUSIONS

Consumption of a lard-rich diet for 12 wk worsened liver injury and increased hepatic PPARα and PPARγ expression in endotoxemic rats.