Optimization and validation of direct gas chromatography-mass spectrometry method for simultaneous quantification of ten short-chain fatty acids in rat feces

Research Progress on the Mechanism of Action and Screening Methods of Probiotics for Lowering Blood Lipid Levels

Hyperlipidemia is one of the most prevalent metabolic disorders worldwide. It is a significant risk factor for a range of cardiovascular diseases, including acute pancreatitis, fatty liver disease, atherosclerosis, and coronary heart disease. In clinical practice, the management of hyperlipidemia is hindered by numerous challenges. One of the critical issues is that traditional lipid-lowering drugs often require long-term or even lifelong administration, potentially inducing a range of adverse effects that compromise patient compliance and therapeutic efficacy. Therefore, there is an urgent need to develop safer and more effective strategies for the prevention and adjunctive treatment of hyperlipidemia with the aim of reducing the risk of disease and over-reliance on medication. Recent studies have revealed a close relationship between hyperlipidemia and related metabolic disorders involving gut microbiota dysbiosis, and the administration of probiotics has been shown to improve lipid metabolism homeostasis. This review summarizes the molecular mechanisms of probiotics in hyperlipidemia treatment and the latest advances in probiotic research on lipid metabolism, enumerates the experimental and clinical applications of probiotic-based therapies, introduces methods for screening and identifying probiotics with lipid-lowering functions, and, for the first time, summarizes the roles of emerging technologies such as functional genomics and in vivo zebrafish-on-a-chip models in studying the lipid-lowering efficacy of probiotics, providing insights for researchers. By facilitating a deeper understanding of the mechanisms whereby probiotics reduce blood lipid levels and furthering the development of multifaceted screening methods, we hope that we can achieve high-throughput and efficient screening of probiotics with lipid-lowering functions, thereby promoting the sustainable, high-quality, and rapid development of the probiotics industry.

Integrated anti-fatigue effects of polysaccharides and small molecules coexisting in water extracts of ginseng: Gut microbiota-mediated mechanisms

ETHNOPHARMACOLOGICAL RELEVANCE

Both clinical and animal studies have demonstrated that ginseng has curative effects on fatigue. Our previous study found that water extracts of ginseng (WEG) could significantly mitigate exercise-induced fatigue (EF). Notably, polysaccharides (GP) and small molecules (GS, mainly ginsenosides) coexist in WEG. Whether and how GP and GS contribute to the anti-EF effects of WEG remains unknown.

AIM OF THE STUDY

To evaluate the contribution of GP and GS to the anti-EF effects of WEG and clarify the potential gut microbiota-mediated mechanisms.

MATERIALS AND METHODS

Firstly, the anti-EF effects of WEG, GP and GS were comparatively investigated by determining fatigue phenotypes (energy metabolism and oxidative stress parameters), gut microbiota composition as well as exogenous and endogenous metabolites in EF modeling rats. Then, the gut microbiota mediated mechanisms were verified by antibiotics (ABX) intervention and fecal microbial transplantation (FMT).

RESULTS

GP, GS and WEG each exhibited distinct anti-EF effects in differentially improving EF-induced energy metabolism abnormality and oxidative stress, reshaping gut microbiota composition, and elevating systemic metabolites. Notably, WEG showed stronger anti-EF effects than both GP and GS, characterized by better alleviation of disturbances in energy metabolism (e.g. Glc) and oxidative stress parameters (e.g. SOD), regulation of gut microbiota homeostasis (e.g. enriching the genus Coprococcus and species Collinsella provencensis etc.), as well as increases in exogenous secondary ginsenosides (e.g. 20(S)-Rg3, 20(R)-Rg3, CK), endogenous bile acids (BAs) (e.g. CA, DCA, LCA), and short chain fatty acids (SCFAs) (e.g. butyric acid). The stronger anti-EF effects of WEG compared to GP and GS could be abolished by ABX intervention, and transferred by FMT.

CONCLUSION

GP and GS could collectively contribute to the anti-EF effects of WEG through integrated actions. Gut microbiota mediate the integrated anti-EF effects of GP and GS in WEG, potentially by regulating the levels of exogenous bioactive secondary ginsenosides, as well as endogenous BAs and SCFAs, thereby alleviating fatigue-related energy metabolic abnormalities and oxidative stress.

Gut Microbiome in Impulsively Violent Female Convicts

INTRODUCTION

Impulsivity and aggression are often interlinked behavioral traits that have major implications for our society. Therefore, the study of this phenomenon and derivative interventions that could lead to better control of impulsive aggression are of interest.

METHODS

We analyzed the composition and diversity of the gut bacterial microbiome of 33 impulsively violent female convicts with dissocial personality disorder and 20 non-impulsive age-matched women. Further, levels of assorted neurotransmitters and short-chain fatty acids (SCFAs) were analyzed in serum and stool samples. We also assessed all participants using a battery of psychological questionnaires and tested possible correlations between the collected clinical data and the composition and diversity of their microbiomes and metabolites.

RESULTS

We identified four bacterial amplicon sequencing variants that were differentially abundant in non-impulsive versus impulsive women - the genera Bacteroides, Barnesiella, and the order Rhodospirillales were more abundant in impulsive women. In contrast, the genus Catenisphaera was more abundant in non-impulsive women. Fecal tryptophan levels were significantly higher in impulsive women. Association analysis revealed a strong positive intercorrelation between most fecal SCFAs in the entire dataset.

CONCLUSIONS

Our study demonstrated possible associations between gut microbiomes and their metabolites and impulsive behavior in a unique cohort of prisoners convicted of violent assaults and a matched group of non-impulsive women from the same prison. Genus Bacteroides, which was differentially abundant in the two groups, encoded enzymes that affect serotonin pathways and could contribute to this maladaptive behavior. Similarly, increased fecal tryptophan levels in impulsive individuals could affect neuronal circuits in the brain.

INTRODUCTION

Impulsivity and aggression are often interlinked behavioral traits that have major implications for our society. Therefore, the study of this phenomenon and derivative interventions that could lead to better control of impulsive aggression are of interest.

METHODS

We analyzed the composition and diversity of the gut bacterial microbiome of 33 impulsively violent female convicts with dissocial personality disorder and 20 non-impulsive age-matched women. Further, levels of assorted neurotransmitters and short-chain fatty acids (SCFAs) were analyzed in serum and stool samples. We also assessed all participants using a battery of psychological questionnaires and tested possible correlations between the collected clinical data and the composition and diversity of their microbiomes and metabolites.

RESULTS

We identified four bacterial amplicon sequencing variants that were differentially abundant in non-impulsive versus impulsive women - the genera Bacteroides, Barnesiella, and the order Rhodospirillales were more abundant in impulsive women. In contrast, the genus Catenisphaera was more abundant in non-impulsive women. Fecal tryptophan levels were significantly higher in impulsive women. Association analysis revealed a strong positive intercorrelation between most fecal SCFAs in the entire dataset.

CONCLUSIONS

Our study demonstrated possible associations between gut microbiomes and their metabolites and impulsive behavior in a unique cohort of prisoners convicted of violent assaults and a matched group of non-impulsive women from the same prison. Genus Bacteroides, which was differentially abundant in the two groups, encoded enzymes that affect serotonin pathways and could contribute to this maladaptive behavior. Similarly, increased fecal tryptophan levels in impulsive individuals could affect neuronal circuits in the brain.

Recent progress on media for biological sample preparation

The analysis of biological samples is highly valuable for disease diagnosis and treatment, forensic examination, and public safety. However, the serious matrix interference effect generated by biological samples severely affects the analysis of trace analytes. Sample preparation methods are introduced to address the limitation by extracting, separating, enriching, purifying trace target analytes from biological samples. With the raising demand of biological sample analysis, a review focuses on media for biological sample preparation and analysis over the last 5 years is presented. High-performance media in biological sample preparation are first reviewed, including porous organic frameworks, imprinted polymers, hydrogels, ionic liquids, and bioactive media. Then, application of media for different biological sample preparation and analysis is briefly introduced, including liquid samples of body fluids, solid samples (hair, feces, and tissues), and gas samples of exhale breath gas. Finally, conclusions and outlooks on media promoting biological sample preparation are presented.

Fructus Jujubae cooperated with water-expelling members in Shizao decoction alleviated intestinal injury and malignant ascites by modulating gut microbiota and metabolic homeostasis

BACKGROUND

Shizao decoction (SZD) consisted of Euphorbia kansui (EK), Euphorbia pekinensis (EP), Daphne genkwa (DG), and Fructus Jujubae (FJ) is a classic Chinese herbal medicine formula for treating malignant ascites, which is closely related to the modulation of gut microbiota by our previous study. For water-expelling members (WEM) including EK, EP, and DG may have side effects on the intestine, FJ is employed for detoxification and effectivity enhancement of WEM. However, the underlying mechanism for the compatibility of WEM and FJ is still unknown.

PURPOSE

To investigate the effect of the compatibility of WEM with FJ in SZD on malignant ascites and elucidate the potential mechanism from the perspective of the modulation of gut microbiota and related metabolic function.

METHODS

Qualitative and quantitative evaluation of main components was conducted for comprehensive characterization of SZD and WEM. The effect of WEM and SZD was compared on malignant ascites effusion (MAE) rats. The intestinal injury was evaluated by HE staining and oxidative damage. Ascites weight, urine amount, fecal water content, the expression of aquaporins, and cytokines in ascites (IL-6, VEGF, and TNF-α) were measured to estimate the water-expelling activity. The intestinal flora was detected by 16S rDNA sequencing and the content of fecal short-chain fatty acids (SCFAs) was analyzed using gas chromatography-mass spectrometry. Pseudo-germ-free (PGF) and fecal bacteria transplantation animal experiments were subsequently employed to validate this finding. The fecal metabolomics and correlation analysis were finally conducted to explore the related metabolic changes.

RESULTS

51 and 33 components were identified in SZD and WEM, respectively. Compared to WEM alone, the compatibility with FJ remarkably reduced intestinal oxidative damage in MAE rats. Ascites was also relieved by downregulating the expression of AQP3 in the colon and decreasing the levels of IL-6, TNF-α and VEGF in ascites. The diversity of gut microbiota was reversed with an increase in Lactobacillus and Clostridia_UCG-014 while a decrease in Colidextribacter. Under the PGF condition, compatibility of WEM with FJ failed to reduce intestinal injury and alleviate MA significantly, but this effect was further enhanced after FMT. 23 potential fecal metabolites were finally identified. Correlation analysis further showed that Lactobacillus and Clostridia_UCG-014 were positively correlated with SCFAs and l-tryptophan. Colidextribacter was negatively correlated with thymidine but positively correlated with ursodeoxycholic acid and deoxycholic acid.

CONCLUSION

FJ cooperated with WEM reduced intestinal injury and alleviated malignant ascites by modulating gut microbiota, short-chain fatty and tryptophan metabolism. These findings provide a scientific basis for the clinical application of FJ from SZD and the safe usage of SZD.

Solanum nigrum L. berries extract ameliorated the alcoholic liver injury by regulating gut microbiota, lipid metabolism, inflammation, and oxidative stress

Solanum nigrum L. (SN) berry is an edible berry containing abundant polyphenols and bioactive compounds, which possess antioxidant and antiinflammatory properties. However, the effects of SN on alcohol-induced biochemical changes in the enterohepatic axis remain unclear. In the current study, a chronic ethanol-fed mice ALD model was used to test the protective mechanisms of SN berries. Microbiota composition was determined via 16S rRNA sequencing, we found that SN berries extract (SNE) improved intestinal imbalance by reducing the Firmicutes to Bacteroides ratio, restoring the abundance of Akkermansia microbiota, and reducing the abundance of Allobaculum and Shigella. SNE restored the intestinal short-chain fatty acids content. In addition, liver transcriptome data analysis revealed that SNE primarily affected the genes involved in lipid metabolism and inflammatory responses. Furthermore, SNE ameliorated hepatic steatosis in alcohol-fed mice by activating AMP-activated protein kinase (AMPK), acetyl-CoA carboxylase (ACC), peroxisome proliferator-activated receptor α (PPAR-α). SNE reduced the expression of toll-like receptor 4 (TLR4), myeloid differentiation factor-88 (MyD88) nuclear factor kappa-B (NF-κB), which can indicate that SNE mainly adjusted LPS/TLR4/MyD88/NF-κB pathway to reduce liver inflammation. SNE enhanced hepatic antioxidant capacity by regulating NRF2-related protein expression. SNE alleviates alcoholic liver injury by regulating of gut microbiota, lipid metabolism, inflammation, and oxidative stress. This study may provide a reference for the development and utilization of SN resources.

Short-chain fatty acid levels in stools of patients with inflammatory bowel disease are lower than those in healthy subjects

OBJECTIVE

Short-chain fatty acids (SCFAs) are produced when the microbiota in the large intestine cause fermentation of dietary carbohydrates and fibers. These fatty acids constitute the primary energy source of colon mucosa cells and have a protective effect in patients suffering from inflammatory bowel disease (IBD). This study aimed to compare the SCFA levels in the stools of patients with IBD and healthy controls.

METHOD

Healthy controls and patients with IBD aged 18 and over were included in the study. Stool samples from all patients and healthy controls were collected, and stool acetic acid, propionic acid, and butyric acid levels were measured using a gas chromatography-mass spectrometry measurement method.

RESULTS

In this study, 64 participants were divided into two groups: 34 were in IBD (Crohn disease and ulcerative colitis) and 30 were in healthy control group. When fecal SCFA concentrations of IBD and healthy control groups were compared, a statistically significant difference was observed between them. When the fecal SCFA concentrations of Crohn's disease and ulcerative colitis patients in the IBD group were compared, however, no statistically significant difference was observed between them. Furthermore, when the participants' diet type (carbohydrate-based, vegetable-protein-based and mixed diet) and the number of meals were compared with fecal SCFA concentrations, no statistically significant difference was observed between them.

CONCLUSION

In general, fecal SCFA levels in patients with IBD were lower than those in healthy controls. Moreover, diet type and the number of meals had no effect on stool SCFA levels in patients with IBD and healthy individuals.

Determination of six short-chain fatty acids in rat feces using headspace solid-phase dynamic extraction coupled with GC-MS

Short-chain fatty acids (SCFAs) are organic acids with carbon atoms less than six, released through fermentation products by intestinal microbiome, having multiple physiological activities. Considering weak acidity and high volatility, derivatization or liquid-liquid extraction is essential, which is time consuming. Headspace-solid-phase dynamic extraction (HS-SPDE) coupled with gas chromatography-mass spectrometry is automated and effortless to determine SCFAs in rat feces. The extraction procedure is performed by aspirating and discharging the headspace cyclically through a steel needle, coated with an inner polyethylene glycol sorbent. The key parameters of SPDE were optimized including coating type, incubation time and temperature, and number of extraction strokes. Besides, salting-out was conducted. Then, a method by HS-SPDE-GC-MS was established and validated. It only took 3-min incubation time, 4.5 min extraction time, and 13 min chromatographic separation in a run. The recovery, linearity, limit of quantification, and stability were evaluated. Then, the proposed method was applied to analyze rat feces including 18 rats with liver injury and 23 normal controls. Mann-Whitney U test indicated that the concentrations of six SCFAs in normal rat feces were higher than those with liver injury. This method provides a choice for fast, solvent-free, automated, and high-throughput analysis of SCFAs.

Sample preparation for fatty acid analysis in biological samples with mass spectrometry-based strategies

Fatty acids (FAs) have attracted many interests for their pivotal roles in many biological processes. Imbalance of FAs is related to a variety of diseases, which makes the measurement of them important in biological samples. Over the past two decades, mass spectrometry (MS) has become an indispensable technique for the analysis of FAs owing to its high sensitivity and precision. Due to complex matrix effect of biological samples and inherent poor ionization efficiency of FAs in MS, sample preparation including extraction and chemical derivatization prior to analysis are often employed. Here, we describe an updated overview of FA extraction techniques, as well as representative derivatization methods utilized in different MS platforms including gas chromatography-MS, liquid chromatography-MS, and mass spectrometry imaging based on different chain lengths of FAs. Derivatization strategies for the identification of double bond location in unsaturated FAs are also summarized and highlighted. The advantages, disadvantages, and prospects of these methods are compared and discussed. This review provides the development and valuable information for sample pretreatment approaches and qualitative and quantitative analysis of interested FAs using different MS-based platforms in complex biological matrices. Finally, the challenges of FA analysis are summarized and the future perspectives are prospected.

Microbiome metabolite quantification methods enabling insights into human health and disease

Many of the health-associated impacts of the microbiome are mediated by its chemical activity, producing and modifying small molecules (metabolites). Thus, microbiome metabolite quantification has a central role in efforts to elucidate and measure microbiome function. In this review, we cover general considerations when designing experiments to quantify microbiome metabolites, including sample preparation, data acquisition and data processing, since these are critical to downstream data quality. We then discuss data analysis and experimental steps to demonstrate that a given metabolite feature is of microbial origin. We further discuss techniques used to quantify common microbial metabolites, including short-chain fatty acids (SCFA), secondary bile acids (BAs), tryptophan derivatives, N-acyl amides and trimethylamine N-oxide (TMAO). Lastly, we conclude with challenges and future directions for the field.

HiSorb sorptive extraction for determining salivary short chain fatty acids and hydroxy acids in heart failure patients

Variations in salivary short-chain fatty acids and hydroxy acids (e.g., lactic acid, and 3-hydroxybutyric acid) levels have been suggested to reflect the dysbiosis of human gut microbiota, which represents an additional factor involved in the onset of heart failure (HF) disease. The physical-chemical properties of these metabolites combined with the complex composition of biological matrices mean that sample pre-treatment procedures are almost unavoidable. This work describes a reliable, simple, and organic solvent free protocol for determining short-chain fatty acids and hydroxy acids in stimulated saliva samples collected from heart failure, obese, and hypertensive patients. The procedure is based on in-situ pentafluorobenzyl bromide (PFB-Br) derivatization and HiSorb sorptive extraction coupled to thermal desorption and gas chromatography-tandem mass spectrometry. The HiSorb extraction device is completely compatible with aqueous matrices, thus saving on time and materials associated with organic solvent-extraction methods. A Central Composite Face-Centred experimental design was used for the optimization of the molar ratio between PFB-Br and target analytes, the derivatization temperature, and the reaction time which were 100, 60 °C, and 180 min, respectively. Detection limits in the range 0.1-100 µM were reached using a small amount of saliva (20 µL). The use of sodium acetate-1-13C as an internal standard improved the intra- and inter-day precision of the method which ranged from 10 to 23%. The optimized protocol was successfully applied for what we believe is the first time to evaluate the salivary levels of short chain fatty acids and hydroxy acids in saliva samples of four groups of patients: i) patients admitted to hospital with acute HF symptoms, ii) patients with chronic HF symptoms, iii) patients without HF symptoms but with obesity, and iv) patients without HF symptoms but with hypertension. The first group of patients showed significantly higher levels of salivary acetic acid and lactic acid at hospital admission as well as the lowest values of hexanoic acid and heptanoic acid. Moreover, the significant high levels of acetic acid, propionic acid, and butyric acid observed in HF respect to the other patients suggest the potential link between oral bacteria and gut dysbiosis.

Structure-specific antitumor effects and potential gut microbiota-involved mechanisms of ginseng polysaccharides on B16F10 melanoma-bearing mice

Ginseng polysaccharides (GPs) have shown gut microbiota-related antitumor effects. However, the relation between their structures and antitumor functions remains unknown. Here, crude polysaccharide (GP-c) and its fractions neutral polysaccharide (GP-n) and pectin (GP-a) were prepared for structure characterization and anti-B16F10 melanoma effect evaluation, and their influence on gut microbiota diversities and short-chain fatty acids (SCFAs) were also analyzed. Spearman correlations among the altered gut microbiota, SCFAs, and antitumor effects were conducted to elucidate the structure-function relationships. It was shown that the structures of GP-c, GP-n, and GP-a varied in monosaccharide composition and molecular weight distribution. GP-n and GP-c showed anti-melanoma effects, whereas GP-a promoted its growth slightly. GP-n and GP-c restored SCFAs levels such as acetic acid and butyric acid; moreover, it improved the gut microbiota ecosystem by upregulating the abundance of Allobaculum and Bifidobacterium. However, the restoration effect of GP-a was weak, or even worse. In addition, these two bacteria were negatively correlated with the tumor weight and related with the altered SCFAs. In conclusion, GP-n is essential for the anti-melanoma effects of GP, and the potential mechanisms might be related with its specific regulation of Allobaculum and Bifidobacterium abundance, and tumor-associated SCFAs levels. The outcomes highlighted here enable a deeper insight into the structure-function relationship of GP and propose new opinions on its antitumor effect.

Comparative effects of different enzymatic hydrolysates of konjac glucomannan on gut flora and constipation rats

This study aimed to compare the effects of different hydrolysates (named GKOS and MKOS) on constipated rats, which were degraded to obtain from konjac glucomannan by β-glucanase and β-mannanase, respectively....