Inulin Improves Postprandial Hypertriglyceridemia by Modulating Gene Expression in the Small Intestine

Lipid metabolism regulation by dietary polysaccharides with different structural properties

Lipid metabolism plays an important role in energy homeostasis maintenance in response to stress. Nowadays, hyperlipidemia-related chronic diseases such as obesity, diabetes, atherosclerosis, and fatty liver pose significant health challenges. Dietary polysaccharides (DPs) have gained attention for their effective lipid-lowering properties. This review examines the multifaceted mechanisms that DPs employ to lower lipid levels in subjects with hyperlipidemia. DPs could directly inhibit lipid intake and absorption, promote lipid excretion, and regulate key enzymes involved in lipid metabolism pathways, including triglyceride and cholesterol anabolism and catabolism, fatty acid oxidation, and bile acid synthesis. Additionally, DPs indirectly improve lipid homeostasis by modulating gut microbiota composition and alleviating oxidative stress. Moreover, the lipid-lowering mechanisms of particular structural DPs (including β-glucan, pectin, glucomannan, inulin, arabinoxylan, and fucoidan) are summarized. The relationship between the structure and lipid-lowering activity of DPs is also discussed based on current researches. Finally, potential breakthroughs and future directions in the development of DPs in lipid-lowering activity are discussed. The paper could provide a reference for further exploring the mechanism of DPs for lipid regulations and utilizing DPs as lipid-lowering dietary ingredients.

Inulin-type fructans with different degrees of polymerization improve insulin resistance, metabolic parameters, and hormonal status in overweight and obese women with polycystic ovary syndrome: A randomized double-blind, placebo-controlled clinical trial

Polycystic ovary syndrome (PCOS) is associated with reproductive disorders and adverse cardiometabolic risk factors that can negatively impact the general health of women. Inulin-type fructans (ITFs) are proposed to beneficially affect risk factors associated with metabolic disorders. Whether ITFs can help with the management of PCOS by modifying insulin resistance (IR) and androgen levels has not yet been explored. The aim of this study was to investigate the effects of ITFs with different degrees of polymerization on insulin resistance, blood lipids, anthropometric measures, and hormonal status in overweight and obese women with PCOS. In a randomized double-blind placebo-controlled trial, seventy-five women with PCOS aged 18-40 years old were randomly assigned to receive 10 g/day of high-performance inulin (HPI) or oligofructose-enriched inulin (OEI) or maltodextrin for 12 weeks. Biochemical and clinical outcomes were measured at baseline and after the intervention. Participants in the HPI and OEI groups experienced improvements in waist circumference, total testosterone, free androgen index, sex hormone-binding globulin, and triglycerides compared to the placebo group. Also, the number of women with irregular menses or oligomenorrhoea decreased significantly in both ITF groups. Participants in the HPI group reported lower body mass, fasting insulin, and HOMA-IR, as well as a higher quantitative insulin sensitivity check index. ITF supplementation, especially with long-chain ITFs, when given for 12 weeks may improve metabolic outcomes, androgen status and clinical manifestations in women with PCOS.

The secondary bile acid isoursodeoxycholate correlates with post-prandial lipemia, inflammation, and appetite and changes post-bariatric surgery

Primary and secondary bile acids (BAs) influence metabolism and inflammation, and the gut microbiome modulates levels of BAs. We systematically explore the host genetic, gut microbial, and habitual dietary contribution to a panel of 19 serum and 15 stool BAs in two population-based cohorts (TwinsUK, n = 2,382; ZOE PREDICT-1, n = 327) and assess changes post-bariatric surgery and after nutritional interventions. We report that BAs have a moderately heritable genetic component, and the gut microbiome accurately predicts their levels in serum and stool. The secondary BA isoursodeoxycholate (isoUDCA) can be explained mostly by gut microbes (area under the receiver operating characteristic curve [AUC] = ∼80%) and associates with post-prandial lipemia and inflammation (GlycA). Furthermore, circulating isoUDCA decreases significantly 1 year after bariatric surgery (β = -0.72, p = 1 × 10-5) and in response to fiber supplementation (β = -0.37, p < 0.03) but not omega-3 supplementation. In healthy individuals, isoUDCA fasting levels correlate with pre-meal appetite (p < 1 × 10-4). Our findings indicate an important role for isoUDCA in lipid metabolism, appetite, and, potentially, cardiometabolic risk.

Inulin: properties and health benefits

Inulin, a soluble dietary fiber, is widely found in more than 36 000 plant species as a reserve polysaccharide. The primary sources of inulin, include Jerusalem artichoke, chicory, onion, garlic, barley, and dahlia, among which Jerusalem artichoke tubers and chicory roots are often used as raw materials for inulin production in the food industry. It is universally acknowledged that inulin as a prebiotic has an outstanding effect on the regulation of intestinal microbiota via stimulating the growth of beneficial bacteria. In addition, inulin also exhibits excellent health benefits in regulating lipid metabolism, weight loss, lowering blood sugar, inhibiting the expression of inflammatory factors, reducing the risk of colon cancer, enhancing mineral absorption, improving constipation, and relieving depression. In this review paper, we attempt to present an exhaustive overview of the function and health benefits of inulin.

Response of gut microbiota and ileal transcriptome to inulin intervention in HFD induced obese mice

Inulin, as a dietary fiber, exerted prominent anti-obesity effects by modulating gut microbiota. However, the possible relationship and interplay of gut microbiome and function of distal intestine is still unclear now. This study aimed to investigate the possible targets of microbes and the related intestinal genes mediated by inulin. C57 BL/6 male mice were randomly allocated to chow diet (Chow) group, high-fat diet (HFD) group, and HFD supplemented with 3 % inulin (Inulin) group. Compared with HFD treatment, inulin supplementation significantly decreased the body weight, fat deposition, and fasting blood glucose level. In addition, mice treated with inulin had a remarkable alteration in the structure of cecal microbiota and transcriptomic profiling of ileum. In particular, inulin supplementation significantly reversed the HFD induced expression of Bacteroides, Allobaculum and nonrank_f_Bacteroidates_S24-7_group, and reversed the expression of genes belonging to phospholipase A2 (PLA2) family and cytochrome P450 (CYP450) family. In summary, inulin might alleviate HFD-induced fat deposition and metabolic disorders via regulating lipid metabolism of ileum, while the interaction between the sPLA2s and gut microbes might play important roles in the process.

The Effect of Microbiome Therapies on Waist Circumference, a Measure of Central Obesity, in Patients with Type 2 Diabetes: A Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND

Microbiome therapies (probiotic, prebiotic, and synbiotics) have been proposed as adjuvants in the control of central obesity; however, their results for patients with type 2 diabetes (T2D) remain inconclusive.

OBJECTIVE

The aim of this systematic review and meta-analysis was to evaluate the effect of microbiome therapies on central obesity as measured by waist circumference (WC), and to evaluate the effect of microbiome therapies for glycemic parameters (fasting glucose [FPG], fasting insulin [FPI], hemoglobin A1c [HbA1c], and insulin resistance [HOMA1-IR]) in patients with T2D.

METHODS

SCOPUS, Pubmed, EBSCO, and LILACS databases were searched for studies that investigated the effect of microbiome therapies on WC up to June 1, 2022. Heterogeneity was determined using Cochran's Q test and quantified using the inconsistency index. The random effects model was used to calculate the pooled difference in means (DM) and 95% confidence intervals (95%CI). Egger's test and Beggs-Muzamar's test were used to assess publication bias.

RESULTS

Fifteen reports were included (443 treated and 387 controls). Overall, a significant decrease in WC was found (DM = -0.97 cm; 95% confidence interval [95%CI] = -1.74 to -0.20; P = 0.014); however, when stratified by type of microbiome therapy, only probiotics significantly decreased WC (DM = -0.62 cm; 95%CI = -1.00 to -0.24; P = 0.002). No effect was observed for prebiotics and synbiotics. With respect to glycemic parameters, HbA1c, FPG, and HOMA1-IR significantly decrease with microbiome therapies (P ≤ 0.001). When stratified by the type of therapy, for probiotic treatments, HbA1c, FPG, and HOMA1-IR scores decrease (P < 0.001). For prebiotic treatments, HbA1c and FPG (P ≤ 0.001) levels decrease, whereas FPI increased (P = 0.012). Synbiotic treatments were only associated with an increase in FPI (P = 0.031).

CONCLUSION

Findings indicate that using probiotics alone improved WC in patients with T2D. Both probiotics and prebiotics decreased HbA1c and FPG; however, prebiotics and synbiotics resulted in an increase in FPI. The formulation of the therapy (single vs multi) had no difference on the effect.

Inulin intake and the incidence of cardiometabolic diseases: a prospective cohort study

Inulin is a prebiotic and has beneficial effects on health, such as improving the immune function, lipid profile, and gut microbiota. Some previous studies have assessed the effects of inulin supplementation on cardiometabolic diseases, but the relationship between dietary inulin and these diseases has not been investigated yet. Thus, this survey was designed to assess the potential association between the dietary intake of inulin and the incidence of cardiometabolic diseases, including cardiovascular disease (CVD), hypertension (HTN), chronic kidney disease (CKD), and type 2 diabetes (T2D) among adults. The present prospective cohort study was conducted on participants in the third wave of the Tehran Lipid and Glucose Study (2006-2008) and was followed up until March 2018. The dietary intake of inulin was estimated using a special database that reports values of inulin and oligofructose in grams per 100 g of each food. Cox proportional hazards regression showed that higher consumption of inulin was associated with a lower risk of HTN (HR: 0.79, 95% CI: 0.63 to 0.99) and T2D (HR: 0.94, 95% CI: 0.89 to 1.00). We found no relationship between higher consumption of dietary inulin and the incidence of CKD and CVD in our population. According to our results, it seems inulin from foods had a preventive effect against HTN and T2D, which are major risk factors for cardiovascular and renal events. However, more investigations are warranted.

Effects of Dried Onion Powder and Quercetin on Obesity-Associated Hepatic Menifestation and Retinopathy

Onion (Allium cepa L.), rich in flavonoids (particularly quercetin), reportedly has anti-obesity properties, but the underlying mechanisms and associated health issues remain unclear. In this study, we compared the effects of dried onion powder (DO) with that of quercetin on high-fat diet (HFD)-induced obesity, nonalcoholic fatty liver disease, and retinal neovascularization. Briefly, rats (n = 9–10 per group) were divided into control, HFD alone (43% fat), HFD + DO (1% DO), HFD + 5DO (5% DO, w/w), and HFD + quercetin (180 mg/kg). After 12 weeks, body fat, markers of metabolism, fatty liver, steatohepatitis, and retinopathy were analyzed. The results revealed that DO and 5DO dose-dependently suppressed body weight, visceral and subcutaneous fat accumulation, and epididymal adipocyte in HFD-fed rats. DO also decreased HFD-induced ALT, AST, free fatty acid, glucose, proinflammatory cytokines, and oxidative stress. DO and 5DO groups had lower triglycerides, total cholesterol, proinflammatory cytokine levels, and ACC-α (a fatty acid synthesis–associated enzyme) expression but higher hepatic antioxidant enzyme activities and fecal lipids. 5DO exhibited better or similar efficacy to quercetin. Both 5DO and quercetin increased fecal levels of acetic acid and butyric acid similarly. They also reduced lipid peroxidation of the eye, retinal adiposity, and neovascularization. However, quercetin resulted in a more apparent decrease in regulation of the Raf/MAPK pathway than DO in eye specimens. Conclusively, DO suppresses visceral, subcutaneous, and liver fat accumulation better than quercetin likely due to higher fecal fat excretion and lower oxidative stress, proinflammatory cytokine levels, and ACC-α expression. Quercetin regulating signal pathways is better than DO at reducing retinal adiposity and neovascularization.

Inulin fructans in diet: Role in gut homeostasis, immunity, health outcomes and potential therapeutics

Inulin consumption in both humans and animal models is recognized for its prebiotic action with the most consistent change that lies in enhancing the growth and functionality of Bifidobacterium bacteria, as well as its effect on host gene expression and metabolism. Further, inulin-type fructans are utilized in the colon by bacterial fermentation to yield short-chain fatty acids (SCFAs), which play important role in its biological effects both locally inside the gut and in systemic actions. The gut symbiosis sustained by inulin supplementation among other dietary fibers exerts preventive and/or therapeutic options for many metabolic disorders including obesity, type 2 diabetes mellitus, cardiometabolic diseases, kidney diseases and hyperuricemia. Although, gastrointestinal negative effects due to inulin consumption were reported, such as gastrointestinal symptoms in humans and exacerbated inflammatory bowel disease (IBD) in mice. This comprehensive review aims to present the whole story of how inulin functions as a prebiotic at cellular levels and the interplay between physiological, functional and immunological responses inside the animal or human gut as influenced by inulin in diets, in context to its structural composition. Such review is of importance to identify management and feed strategies to optimize gut health, for instance, consumption of the tolerated doses to healthy adults of 10 g/day of native inulin or 5 g/day of naturally inulin-rich chicory extract. In addition, inulin-drug interactions should be further clarified particularly if used as a supplement for the treatment of degenerative diseases (e.g., diabetes) over a long period. The combined effect of probiotics and inulin appears more effective, and more research on this synergy is still needed.

Physical activity enhances the improvement of body mass index and metabolism by inulin: a multicenter randomized placebo-controlled trial performed in obese individuals

BACKGROUND

Dietary interventions targeting the gut microbiota have been proposed as innovative strategies to improve obesity-associated metabolic disorders. Increasing physical activity (PA) is considered as a key behavioral change for improving health. We have tested the hypothesis that changing the PA status during a nutritional intervention based on prebiotic supplementation can alter or even change the metabolic response to the prebiotic. We confirm in obese subjects and in high-fat diet fed mice that performing PA in parallel to a prebiotic supplementation is necessary to observe metabolic improvements upon inulin.

METHODS

A randomized, single-blinded, multicentric, placebo-controlled trial was conducted in obese participants who received 16 g/day native inulin versus maltodextrin, coupled to dietary advice to consume inulin-rich versus -poor vegetables for 3 months, respectively, in addition to dietary caloric restriction. Primary outcomes concern the changes on the gut microbiota composition, and secondary outcomes are related to the measures of anthropometric and metabolic parameters, as well as the evaluation of PA. Among the 106 patients who completed the study, 61 patients filled a questionnaire for PA before and after intervention (placebo: n = 31, prebiotic: n = 30). Except the dietitian (who provided dietary advices and recipes book), all participants and research staff were blinded to the treatments and no advices related to PA were given to participants in order to change their habits. In parallel, a preclinical study was designed combining both inulin supplementation and voluntary exercise in a model of diet-induced obesity in mice.

RESULTS

Obese subjects who increased PA during a 3 months intervention with inulin-enriched diet exhibited several clinical improvements such as reduced BMI (- 1.6 kg/m²), decreased liver enzymes and plasma cholesterol, and improved glucose tolerance. Interestingly, the regulations of Bifidobacterium, Dialister, and Catenibacterium genera by inulin were only significant when participants exercised more. In obese mice, we highlighted a greater gut fermentation of inulin and improved glucose homeostasis when PA is combined with prebiotics.

CONCLUSION

We conclude that PA level is an important determinant of the success of a dietary intervention targeting the gut microbiota.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03852069 (February 22, 2019 retrospectively registered).

Microbiota and body weight control: Weight watchers within?

Background

Despite several decades of research, managing body weight remains an unsolved clinical problem. Health problems associated with dysregulated body weight, such as obesity and cachexia, exhibit several gut microbiota alterations. There is an increased interest in utilising the gut microbiota for body weight control, as it responds to intervention and plays an important role in energy extraction from food, as well as biotransformation of nutrients.

Scope of the review

This review provides an overview of the role of the gut microbiota in the physiological and metabolic alterations observed in two body weight dysregulation-related disorders, namely obesity and cachexia. Second, we assess the available evidence for different strategies, including caloric restriction, intermittent fasting, ketogenic diet, bariatric surgery, probiotics, prebiotics, synbiotics, high-fibre diet, and fermented foods – effects on body weight and gut microbiota composition. This approach was used to give insights into the possible link between body weight control and gut microbiota configuration.

Major conclusions

Despite extensive associations between body weight and gut microbiota composition, limited success could be achieved in the translation of microbiota-related interventions for body weight control in humans. Manipulation of the gut microbiota alone is insufficient to alter body weight and future research is needed with a combination of strategies to enhance the effects of lifestyle interventions.

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The gut microbiota is involved in the control of nutrient availability, appetite, and body weight.

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Both obesity and cachexia are associated with altered gut microbiota.

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Specific dietary and surgical approaches positively impact body weight and gut microbiota.

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Manipulation of the gut microbiota alone is insufficient to alter body weight in humans.

Analysis of inulin and fructans in Taraxacum officinale L. roots as the main inulin-containing component of antidiabetic herbal mixture

Herbs and their combinations due to the wide range of biologically active substances can influence on various links of the pathogenetic mechanism of development of diabetes mellitus and its complications. One of such combinations is an antidiabetic herbal mixture with established hypoglycemic, hypolipidemic, antioxidant, hepatoprotective, pancreatoprotective activity in previous pharmacological study in vivo that including an inulin-containing component – Taraxacum officinale L. roots. Thus, the aim of this study was to determine the quantitative content of inulin and fructans in Taraxacum officinale L. Quantity content of inulin was determined by the difference between fructose as a product of enzymatic hydrolysis and D-fructose, a constituent of sucrose and free D-fructose, taking into account the empirical factor for the conversion of D-fructose from inulin. Carbohydrates used in the calculation of inulin were separated by gas chromatography-mass spectrometry after conversion into volatile derivatives as aldononitrile acetate. According to the results, Taraxacum officinale L. roots contain 436.29 mg/g of inulin. Total content of fructans was determined by spectrophotometric analysis as a product of acid hydrolysis of 5-(hydroxymethyl)furfural. The results show that Taraxacum officinale L. roots contain 39.49% of fructans. The obtained results are evidence that this plant component should be included in the herbal antidiabetic mixture, because due to the presence of fructans and inulin causes hypoglycemic, hypolipidemic and detoxification activity.

Inulin ameliorates schizophrenia via modulation of the gut microbiota and anti-inflammation in mice

The microbiome-gut-brain (MGB) axis, which regulates neurological and cognitive functions, plays an essential role in schizophrenia (SCZ) progression. Dietary inulin could be a novel strategy for the treatment of SCZ due to its modulating effects on the gut microbiota. In this study, the effects of inulin on mice with SCZ were studied. As indicated by the behavioural tests, expression of neurotransmitters, inflammatory indicators, and brain morphology, inulin administration ameliorated aberrant behaviours (locomotor hypoactivity, anxiety disorders and depressive behaviours, and impaired learning and spatial recognition memory) and effectively reduced neuroinflammation and neuronal damage. In addition, inulin improved intestinal integrity and permeability, as indicated by the elevated expression of tight junction proteins (p < 0.05). The results of 16S rRNA sequencing and analysis showed that inulin increased the abundance of Lactobacillus and Bifidobacterium, which were negatively correlated with 5-hydroxytryptamine and inflammatory cytokines and positively correlated with brain-derived neurotrophic factor (BDNF). Inulin caused a reduction in Akkermansia that was positively correlated with inflammatory cytokines and negatively correlated with BDNF. These results suggested that dietary inulin modulated the gut microbiota and exerted anti-inflammatory effects in mice though the MGB axis, which further ameliorated SCZ. Therefore, the results of this study provide a potential explanation for inulin intervention in the treatment of SCZ.

Determination of inulin in the herbal mixtures by GC-MS method

The herbal mixtures due to the wide range of biologically active substances can influence on various links of the pathogenetic mechanism of development of diabetes mellitus and its complications. The carbohydrates, especially inulin, deserve the particular attention through their hypoglycemic, hypolipidemic, anticholesterolemic and detoxifying activities. The aim of the study was to investigate the content of inulin in the herbal mixtures No. 3, No. 4, No. 7, No. 13 and No. 19, which are used in folk medicine for the prevention and treatment of diabetes mellitus type 2 in Ukraine. The quantity content of inulin was defined by the difference between fructose as a product of enzymatic hydrolysis and fructose, a constituent of sucrose and free fructose, taking into account the empirical factor for the conversion of fructose from inulin. The carbohydrates were separated by gas chromatography-mass spectrometry after conversion into volatile derivatives as aldononitrile acetate. According to the results, the herbal mixture No. 3 contains 458.97 mg/g of inulin, the herbal mixture No. 4 – 99.21 mg/g, the herbal mixture No. 7 – 139.93 mg/g, the herbal mixture No. 13 – 203.84 mg/g, the herbal mixture No. 19 – 359.65 mg/g. The availability of inulin and its high content in the investigated herbal mixtures due to the presence of inulin-containing medicinal plants, such as Cichorium intubus roots (mixtures No. 3 and No. 13), Taraxacum officinale roots (mixtures No. 3, No. 7 and No. 19), Arctium lappa roots (mixture No. 4), Inula helenium rhizome with roots (mixture No. 7).

Elevated Levels of Apolipoprotein CIII Increase the Risk of Postprandial Hypertriglyceridemia

BACKGROUND

To investigate possible mechanisms of postprandial hypertriglyceridemia (PPT), we analyzed serum lipid and apolipoprotein (Apo) AI, B, CII and CIII levels before and after a high-fat meal.

METHODS

The study has been registered with the China Clinical Trial Registry (registration number:ChiCTR1800019514; URL: http://www.chictr.org.cn/index.aspx). We recruited 143 volunteers with normal fasting triglyceride (TG) levels. All subjects consumed a high-fat test meal. Venous blood samples were obtained during fasting and at 2, 4, and 6 hours after the high-fat meal. PPT was defined as TG ≥2.5 mmol/L any time after the meal. Subjects were divided into two groups according to the high-fat meal test results: postprandial normal triglyceride (PNT) and PPT. We compared the fasting and postprandial lipid and ApoAI, ApoB, ApoCII and ApoCIII levels between the two groups.

RESULTS

Significant differences were found between the groups in fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), TG, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), non-high-density lipoprotein cholesterol (non-HDL-C), TG-rich lipoprotein remnants (TRLRs), ApoB, ApoCIII, ApoAI/ApoB and ApoCII/ApoCIII. The insulin, HOMA-IR, TG, TC, LDL-C, non-HDL-C, TRLRs, ApoB, ApoCIII and ApoCII/ApoCIII values were higher in the PPT group, while the ApoAI/ApoB ratio was higher in the PNT group. The postprandial TG level peaked in the PNT group 2 hours after the meal but was significantly higher in the PPT group and peaked at 4 hours. TRLRs gradually increased within 6 hours after the high-fat meal in both groups. The area under the curve (AUC) of TG and TRLRs and the AUC increment were higher in the PPT group (P < 0.001). ApoCIII peaked in the PNT group 2 hours after the meal and gradually decreased. ApoCIII gradually increased in the PPT group within 6 hours after the meal, exhibiting a greater AUC increment (P < 0.001). Fasting ApoCIII was positively correlated with age, systolic and diastolic blood pressure, body mass index (BMI), waist circumference, TC, TG, LDL-C, non-HDL-C, TRLRs, and ApoB (P<0.05). ApoCIII was an independent risk factor of PPT after adjustment for BMI, waist circumference, TC, LDL-C, and ApoB (P < 0.001, OR=1.188).

CONCLUSIONS

Elevated ApoCIII levels may cause PPT.

Cardiometabolic Syndrome: An Update on Available Mouse Models

Cardiometabolic syndrome (CMS), a disease entity characterized by abdominal obesity, insulin resistance (IR), hypertension, and hyperlipidemia, is a global epidemic with approximately 25% prevalence in adults globally. CMS is associated with increased risk for cardiovascular disease (CVD) and development of diabetes. Due to its multifactorial etiology, the development of several animal models to simulate CMS has contributed significantly to the elucidation of the disease pathophysiology and the design of therapies. In this review we aimed to present the most common mouse models used in the research of CMS. We found that CMS can be induced either by genetic manipulation, leading to dyslipidemia, lipodystrophy, obesity and IR, or obesity and hypertension, or by administration of specific diets and drugs. In the last decade, the ob/ob and db/db mice were the most common obesity and IR models, whereas Ldlr-/- and Apoe-/- were widely used to induce hyperlipidemia. These mice have been used either as a single transgenic or combined with a different background with or without diet treatment. High-fat diet with modifications is the preferred protocol, generally leading to increased body weight, hyperlipidemia, and IR. A plethora of genetically engineered mouse models, diets, drugs, or synthetic compounds that are available have advanced the understanding of CMS. However, each researcher should carefully select the most appropriate model and validate its consistency. It is important to consider the differences between strains of the same animal species, different animals, and most importantly differences to human when translating results.

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

Dietary fibers are fermented by gut bacteria into the major short chain fatty acids (SCFAs) acetate, propionate, and butyrate. Generally, fiber-rich diets are believed to improve metabolic health. However, recent studies suggest that long-term supplementation with fibers causes changes in hepatic bile acid metabolism, hepatocyte damage, and hepatocellular cancer in dysbiotic mice. Alterations in hepatic bile acid metabolism have also been reported after cold-induced activation of brown adipose tissue. Here, we aim to investigate the effects of short-term dietary inulin supplementation on liver cholesterol and bile acid metabolism in control and cold housed specific pathogen free wild type (WT) mice. We found that short-term inulin feeding lowered plasma cholesterol levels and provoked cholestasis and mild liver damage in WT mice. Of note, inulin feeding caused marked perturbations in bile acid metabolism, which were aggravated by cold treatment. Our studies indicate that even relatively short periods of inulin consumption in mice with an intact gut microbiome have detrimental effects on liver metabolism and function.

Evaluating the appropriate oral lipid tolerance test model for investigating plasma triglyceride elevation in mice

The oral lipid tolerance test (OLTT) has been known to assess intestinal fat metabolism and whole-body lipid metabolism, but rodent models for OLTT are not yet established. Differences in OLTT methodology preclude the generation of definitive results, which may cause some confusion about the anti-hypertriglyceridemia effects of the test materials. To standardize and generate more appropriate methodology for the OLTT, we examined the effects of mice strain, dietary lipid sources, fasting period, and gender on lipid-induced hypertriglyceridemia in mice. First, lipid-induced hypertriglyceridemia was more strongly observed in male ddY mice than in C57BL/6N or ICR mice. Second, the administration of olive and soybean oils remarkably represented lipid-induced hypertriglyceridemia. Third, fasting period before the OLTT largely affected the plasma triglyceride elevation. Fasting for 12 h, but less than 48 h, provoked lipid-induced hypertriglyceridemia. Fourth, we explored the suppressive effects of epigallocatechin gallate (EGCG), a green tea polyphenol, on lipid-induced hypertriglyceridemia. The administration of 100 mg/kg of EGCG suppressed lipid-induced hypertriglyceridemia and intestinal lipase activity. Fifth, EGCG-induced suppressive effects were observed after lipid-induced hypertriglyceridemia was observed in male mice, but not in female mice. Lastly, lipid-induced hypertriglyceridemia could be more effectively induced in mice fed a high-fat diet for 1 week before the OLTT. These findings indicate that male ddY mice after 12 h fasting displayed marked lipid-induced hypertriglyceridemia in response to soybean oil. Hence, the defined experiment condition may be a more appropriate OLTT model for evaluating lipid-induced hypertriglyceridemia.

In vitro approach to evaluate the fermentation pattern of inulin-rich food in obese individuals

Alterations of the gut microbiome have been associated with obesity and metabolic disorders. The gut microbiota can be influenced by the intake of dietary fibres with prebiotic properties, such as inulin-type fructans. The present study tested the hypothesis that obese individuals subjected for 12 weeks to an inulin-enriched v. inulin-poor diet have differential faecal fermentation patterns. The fermentation of cellulose and inulin hydrolysates of six different inulin-rich and inulin-poor vegetables of both groups was analysed in vitro on faecal inocula. The results showed that the microbiota from obese patients who received a fructan-rich diet for 3 weeks produces more gas and total SCFA compared with the microbiota taken from the same individuals before the treatment. Obese individuals fed with a low-fructan diet produce less gas and less SCFA compared with the treated group. The present study highlighted profound changes in microbiota fermentation capacity obtained by prebiotic intervention in obese individuals, which favours the production of specific bioactive metabolites.