Inulin Supplementation Disturbs Hepatic Cholesterol and Bile Acid Metabolism Independent from Housing Temperature

Prebiotic inulin ameliorates SARS-CoV-2 infection in hamsters by modulating the gut microbiome

Current treatment options for COVID-19 are limited, with many antivirals and immunomodulators restricted to the most severe cases and preventative care limited to vaccination. As the SARS-CoV-2 virus and its increasing variants threaten to become a permanent fixture of our lives, this new reality necessitates the development of cost-effective and accessible treatment options for COVID-19. Studies have shown that there are correlations between the gut microbiome and severity of COVID-19, especially with regards to production of physiologically beneficial short-chain fatty acids (SCFAs) by gut microbes. In this study, we used a Syrian hamster model to study how dietary consumption of the prebiotic inulin affected morbidity and mortality resulting from SARS-CoV-2 infection. After two weeks of observation, we discovered that inulin supplementation attenuated morbid weight loss and increased survival rate in hamster subjects. An analysis of microbiome community structure showed significant alterations in 15 genera. Notably, there were also small increases in fecal DCA and a significant increase in serum DCA, perhaps highlighting a role for this secondary bile acid in conferring protection against SARS-CoV-2. In light of these results, inulin and other prebiotics are promising targets for future investigation as preventative treatment options for COVID-19.

Glycocholic acid supplementation improved growth performance and alleviated tissue damage in the liver and intestine in Pelteobagrus fulvidraco fed a high-pectin diet

In a study on the anti-nutritional effect of dietary fiber, it was noticed that a high-pectin diet (PEC diet) caused growth retardation, hepatic cholestasis, steatosis, fibrosis, and enteritis accompanied by decreased glycocholic acid (GCA) in Pelteobagrus fulvidraco. This study was conducted to investigate the potential alleviating effects of supplementation with GCA. A PEC diet and a diet supplemented with 0.6 g kg-1 GCA based on the PEC diet (named the GCA diet) were formulated and randomly fed to juvenile Pelteobagrus fulvidraco. Compared to fish that were fed the PEC diet for 7 days, the GCA content in liver increased significantly in fish fed the GCA diet, the incidence of abnormal liver color, gallbladder somatic index (GBSI), total bile acid concentration in serum and liver, and the expression of arnesoid X receptor gene (fxr) upregulated and genes involved in bile acid (BA) synthesis and uptake in liver decreased significantly. After 56 days, the SGR, the expression of fxr and genes involved in BA synthesis and transportation in the liver, the serum content of total bilirubin, total protein, and globulin were significantly higher, while the hepatosomatic index, GBSI, liver lipid and collagen content, and the incidence of distal intestine tissue damage were lower in fish fed the GCA diet than in those fed the PEC diet. These results suggested that GCA improved growth performance and alleviated hepatic cholestasis and tissue damage to the liver and intestine induced by a high-pectin diet, which might occur through activating FXR.

Prebiotic diet changes neural correlates of food decision-making in overweight adults: a randomised controlled within-subject cross-over trial

OBJECTIVE

Animal studies suggest that prebiotic, plant-derived nutrients could improve homoeostatic and hedonic brain functions through improvements in microbiome-gut-brain communication. However, little is known if these results are applicable to humans. Therefore, we tested the effects of high-dosed prebiotic fibre on reward-related food decision-making in a randomised controlled within-subject cross-over study and assayed potential microbial and metabolic markers.

DESIGN

59 overweight young adults (19 females, 18-42 years, body mass index 25-30 kg/m2) underwent functional task MRI before and after 14 days of supplementary intake of 30 g/day of inulin (prebiotics) and equicaloric placebo, respectively. Short chain fatty acids (SCFA), gastrointestinal hormones, glucose/lipid and inflammatory markers were assayed in fasting blood. Gut microbiota and SCFA were measured in stool.

RESULTS

Compared with placebo, participants showed decreased brain activation towards high-caloric wanted food stimuli in the ventral tegmental area and right orbitofrontal cortex after prebiotics (preregistered, family wise error-corrected p <0.05). While fasting blood levels remained largely unchanged, 16S-rRNA sequencing showed significant shifts in the microbiome towards increased occurrence of, among others, SCFA-producing Bifidobacteriaceae, and changes in >60 predicted functional signalling pathways after prebiotic intake. Changes in brain activation correlated with changes in Actinobacteria microbial abundance and associated activity previously linked with SCFA production, such as ABC transporter metabolism.

CONCLUSIONS

In this proof-of-concept study, a prebiotic intervention attenuated reward-related brain activation during food decision-making, paralleled by shifts in gut microbiota.

TRIAL REGISTRATION NUMBER

NCT03829189.

Maternal inulin supplementation ameliorates prenatal methamphetamine exposure-induced hepatotoxicity and restores gut microbiota in mouse offspring

Prenatal exposure to methamphetamine (METH) is an issue of global concern due to its adverse effects on offspring, particularly its impact on liver health, an area still not fully understood. Inulin, a recognized prebiotic, is thought to potentially ameliorate these developmental disorders and toxic injuries in progeny. To investigate the effects of prenatal METH exposure on the liver and the role of gut microbiota, we established a murine model, the subjects of which were exposed to METH prenatally and subsequently treated with inulin. Our findings indicate that prenatal METH exposure causes liver damage in offspring, as evidenced by a decreased liver index, histopathological changes, diminished glycogen synthesis, hepatic dysfunction, and alterations in mRNA profiles. Furthermore, it impairs the antioxidant system and induces oxidative stress, possibly due to changes in cecal microbiota and dysregulation of bile acid homeostasis. However, maternal inulin supplementation appears to restore the gut microbiota in offspring and mitigate the hepatotoxic effects induced by prenatal METH exposure. Our study provides definitive evidence of METH's transgenerational hepatotoxicity and suggests that maternal inulin supplementation could be an effective preventive strategy.

Energy- and evolution-based design of inulosucrase for enhanced thermostability and inulin production

Inulosucrase from Lactobacillus reuteri 121 (LrInu) exhibits promise in the synthesis of prebiotic inulin and fructooligosaccharides. However, for its use in industry, LrInu's thermostability is a crucial consideration. In this study, the computational program FireProt was used to predict the thermostable variants of LrInu. Using rational criteria, nine variants were selected for protein expression and characterization. The G237P variant was determined to be the greatest designed candidate due to its greatly enhanced stability and activity in comparison to the wild-type enzyme. The optimum temperature of G237P increased from 50 to 60°C, with an over 5-fold increase in the half-life. Spectroscopy studies revealed that the G237P mutation could prevent the structural change in LrInu caused by heat or urea treatment. Molecular dynamics (MD) simulations showed that the enhanced thermostability of the G237P variant resulted from an increase in structural rigidity and the number of native contacts within the protein molecule. In addition, G237P variant synthesizes inulin with greater efficiency than WT. KEY POINTS: • Thermostable inulosucrase variant(s) were designed by Fireprot server. • G237P variant showed significantly improved thermostability compared to the wild type. • Inulin is synthesized more efficiently by G237P variant.

The lipid-lowering effects of fenugreek gum, hawthorn pectin, and burdock inulin

Objective

The present study aimed to investigate the lipid-lowering effects and mechanisms of fenugreek gum (FG), hawthorn pectin (HP), and burdock inulin (BI) on high-fat diet (HFD)-induced hyperlipidemic rats.

Methods

In this study, high-fat diet (HFD) together with fat emulsion administration were used to establish hyperlipidemia model. The biochemical indices were assayed after administration of FG, HP, and BI. Their effects were evaluated by factor analysis. Alterations of gut microbiota and short chain fatty acids (SCFAs) in the cecal were assessed to illustrate the mechanism of lipid lowering.

Results

The supplementation of FG, HP, and BI on HFD-fed rats decreased the levels of serum lipid and reduced the HFD-related liver and testicle damage. In the scatter plot of factor analysis, HP and BI were closer to normal fat diet (NFD) group in restoring the severity of hyperlipidemia, while FG and HP enhanced the excretion of cholesterol and bile acids (BAs). The levels of total SCFAs, especially butyric acid reduced by HFD were increased by HP. The ratio of Firmicutes to Bacteroidetes increased by HFD was reduced by HP and BI. FG, HP, and BI enriched intestinal probiotics, which were related to bile acid excretion or lipid-lowering.

Conclusions

FG inhibited the absorption of cholesterol and enhanced the excretion of it, as well as increased the abundance of beneficial bacteria. While BI restored the imbalance of intestinal microbiota. HP enhanced the excretion of cholesterol and BAs, and restored the imbalance of intestinal microbiota. It was also utilized by intestinal microorganisms to yield SCFAs. This study suggested that FG, HP, and BI possessed the potential to be utilized as dietary supplements for obesity management.

Dietary Inulin Supplementation Affects Specific Plasmalogen Species in the Brain

Plasmalogens (Pls) are glycerophospholipids that play critical roles in the brain. Evidence supports the role of diet and that of the gut microbiota in regulating brain lipids. We investigated the impact of dietary intake of inulin—a soluble fiber used as prebiotic—on the Pl content of the cortex in mice. No global modification in the Pl amounts was observed when evaluated by gas chromatographic analysis of dimethyl acetals (DMAs). However, the analysis of individual molecular species of Pls by liquid chromatography revealed a reduced abundance of major species of ethanolamine Pls (PlsEtn)―PE(P-18:0/22:6) and PE(P-34:1)―in the cortex of mice fed a diet supplemented with inulin. DMA and expression levels of genes (Far-1, Gnpat, Agps, Pla2g6 and Tmem86b) encoding key enzymes of Pl biosynthesis or degradation were not altered in the liver and in the cortex of mice exposed to inulin. In addition, the fatty acid profile and the amount of lyso forms derived from PlsEtn were not modified in the cortex by inulin consumption. To conclude, inulin affects the brain levels of major PlsEtn and further investigation is needed to determine the exact molecular mechanisms involved.

A Gas Chromatography Mass Spectrometry-Based Method for the Quantification of Short Chain Fatty Acids

Short Chain Fatty Acids (SCFAs) are produced by the gut microbiota and are present in varying concentrations in the intestinal lumen, in feces but also in the circulatory system. By interacting with different cell types in the body, they have a great impact on host metabolism and their exact quantification is indispensable. Here, we present a derivatization-free method for the gas chromatography mass spectrometry (GC-MS) based quantification of SCFAs in plasma, feces, cecum, liver and adipose tissue. SCFAs were extracted using ethanol and concentrated by alkaline vacuum centrifugation. To allow volatility for separation by GC, samples were acidified with succinic acid. Analytes were detected in selected ion monitoring (SIM) mode and quantified using deuterated internal standards and external calibration curves. Method validation rendered excellent linearity (R² > 0.99 for most analytes), good recovery rates (95–117%), and good reproducibility (RSD: 1–4.5%). Matrix effects were ruled out in plasma, feces, cecum, liver and fat tissues where most abundant SCFAs were detected and accurately quantified. Finally, applicability of the method was assessed using samples derived from conventionally raised versus germ-free mice or mice treated with antibiotics. Altogether, a reliable, fast, derivatization-free GC-MS method for the quantification of SCFAs in different biological matrices was developed allowing for the study of the (patho)physiological role of SCFAs in metabolic health.

Editorial "Nutrition and Dietary Intake for Liver-Related Diseases"

In this special issue, we focus on the role of nutrition in the therapy of nonalcoholic liver disease (NAFLD) [...].