Prebiotic Effects of Partially Hydrolyzed Guar Gum on the Composition and Function of the Human Microbiota-Results from the PAGODA Trial

Low molecular weight galactomannan alleviates diarrhea induced by senna leaf in mice via intestinal barrier improvement and gut microbiota modulation

Low molecular weight galactomannan (LMGM), a soluble dietary fibre derived from guar gum, is recognized for its prebiotic functions, including promoting the growth of beneficial intestinal bacteria and the production of short-chain fatty acids, but the mechanism of alleviating diarrhea is not fully understood. This study established an acute diarrhea mouse model using senna leaf decoction and evaluated the therapeutic effects of LMGM by monitoring diarrhea scores, loose stool prevalence, intestinal tissue pathology and gene expression, and gut microbiota composition and metabolisms. The results indicated that LMGM significantly reduced diarrhea scores and loose stool prevalence within two hours post-treatment. Hematoxylin and eosin staining and quantitative real-time polymerase chain reaction analysis revealed that LMGM improved intestinal epithelial structure and up-regulated the expression of zonula occludens 1, occludin, mucin 2, aquaporin 3, and aquaporin 4 in ileum, jejunum, and colon tissues. Moreover, LMGM increased the abundance of beneficial bacteria such as Lactobacillaceae and Lachnospiraceae, and decreased Prevotellaceae in the cecum. Furthermore, LMGM promoted short-chain fatty acid production and reduced ammonia nitrogen and skatole concentrations in the intestinal content. The study suggests that LMGM could serve as a functional prebiotic for diarrhea alleviation, potentially by enhancing the intestinal barrier, modulating water transportation, and regulating the microbiota composition.

Partially hydrolyzed guar gum alleviates neurological deficits and gastrointestinal dysfunction in mice with traumatic brain injury

Traumatic brain injury (TBI)-associated neuroinflammation and neurotoxicity can induce gastrointestinal dysfunction through the brain-gut axis. Partially hydrolyzed guar gum (PHGG) was demonstrated to exert beneficial health effects by altering gut microbiota and short-chain fatty acids (SCFAs) production. Our study aimed to explore the effects of PHGG on gastrointestinal dysfunction in TBI mouse models. Controlled cortical impact (CCI)-induced TBI mouse models were administrated with PHGG (600 mg/kg/d) for 21 consecutive days. Behavioral tests (modified neurological severity score and beam walk test) and Y‑maze assay were performed to evaluate neurological functions and cognitive impairment. Enzyme-linked immunosorbent assay, reverse transcription-quantitative polymerase chain reaction, and western blotting examined the levels of inflammatory cytokines, intestinal mucosal damage markers, intestinal tight junction proteins, and NLRP3 inflammasome-related molecules in the serum, cerebral cortex, and colon tissues. The histological changes in the cerebral cortex and colon tissues were observed through hematoxylin and eosin and Nissl staining. Liquid chromatography/mass spectrometry analyzed SCFA amounts in the cecum contents and bile acid levels in the serum. PHGG administration alleviated neurological deficits and cognitive perturbations, reduced neuroinflammation, and attenuated cortical tissue damage and neuron loss in TBI mice. PHGG ameliorated intestinal barrier impairment, upregulated intestinal production of SCFAs, and elevated serum bile acid levels in TBI mice. Besides, PHGG treatment repressed NLRP3 inflammasome activation in TBI mice. Overexpressing NLRP3 reversed the beneficial effects of PHGG against TBI in mice. PHGG ameliorates neuroinflammation and gastrointestinal dysfunction in TBI murine models by inhibiting NLRP3 inflammasome activation.

An Update on Microbial Interventions in Autism Spectrum Disorder with Gastrointestinal Symptoms

In the United States, autism spectrum disorder (ASD) affects 1 in 33 children and is characterized by atypical social interactions, communication difficulties, and intense, restricted interests. Microbial dysbiosis in the gastrointestinal (GI) tract is frequently observed in individuals with ASD, potentially contributing to behavioral manifestations and correlating with worsening severity. Moreover, dysbiosis may contribute to the increased prevalence of GI comorbidities in the ASD population and exacerbate immune dysregulation, further worsening dysbiosis. Over the past 25 years, research on the impact of microbial manipulation on ASD outcomes has gained substantial interest. Various approaches to microbial manipulation have been preclinically and clinically tested, including antibiotic treatment, dietary modifications, prebiotics, probiotics, and fecal microbiota transplantation. Each method has shown varying degrees of success in reducing the severity of ASD behaviors and/or GI symptoms and varying long-term efficacy. In this review, we discuss these microbiome manipulation methods and their outcomes. We also discuss potential microbiome manipulation early in life, as this is a critical period for neurodevelopment.

Enhancing the oral bioavailability of fisetin: polysaccharide-based self nano-emulsifying spheroids for colon-targeted delivery

Fisetin (FS) is a flavonoid that possesses antioxidant and anti-inflammatory properties against ulcerative colitis. FS shows poor dissolution rate and permeability. An attempt has been made to develop colon-targeted solid self-nanoemulsifying drug delivery systems (S-SNEDDS) of FS. Initially, liquid (L) SNEDDS were prepared by loading FS into isotropic mixture of L-SNEDDS was prepared using Labrafil M 1944 CS, Transcutol P, and Tween 80. These L-SNEDDS were further converted into solid (S) SNEDDS by mixing the isotropic mixture with 1:1:1 ratio of guar gum (GG), xanthan gum (XG) and pectin (PC) [GG:XG:PC (1:1:1)]. Aerosil-200 (A-200) was added to enhance their flow characteristics. Further, they were converted into spheroids by extrusion-spheronization technique. The solid-state characterization of S-SNEDDS was done by SEM, DSC, and PXRD, which revealed that the crystalline form of FS was converted into the amorphous form. In the dissolution study, S-SNEDDS spheroids [GG:XG:PC (1:1:1)] exhibited less than 20% drug release within the first 5 h, followed by rapid release of the drug between the 5th and 10th h, indicating its release at colonic site. The site-specific delivery of FS to colon via FS-S-SNEDDS spheroids was confirmed by conducting pharmacokinetic studies on rats. Wherein, results showed delay in absorption of FS loaded in spheroids up to 5 h and achievement of Cmax at 7h, whereas L-SNEDDS showed rapid absorption of FS. Furthermore, FS-L-SNEDDS and FS-S-SNEDDS spheroids [GG:XG:PC (1:1:1)] increased oral bioavailability of FS by 6.86-fold and 4.44-fold, respectively, as compared to unprocessed FS.

The importance of food quality, gut motility, and microbiome in SIBO development and treatment

The prevalence of small intestinal bacterial overgrowth (SIBO) is rising worldwide, particularly in nations with high rates of urbanization. Irritable bowel syndrome, inflammatory bowel illnesses, and nonspecific dysmotility are strongly linked to SIBO. Moreover, repeated antibiotic therapy promotes microorganisms' overgrowth through the development of antibiotic resistance. The primary cause of excessive fermentation in the small intestine is a malfunctioning gastrointestinal motor complex, which results in the gut's longer retention of food residues. There are anatomical and physiological factors affecting the functioning of the myoelectric motor complex. Except for them, diet conditions the activity of gastrointestinal transit. Indisputably, the Western type of nutrition is unfavorable. Some food components have greater importance in the functioning of the gastrointestinal motor complex than others. Tryptophan, an essential amino acid and precursor of the serotonin hormone, accelerates intestinal transit, and gastric emptying, similarly to fiber and polyphenols. Additionally, the effect of food on the microbiome is important, and diet should prevent bacterial overgrowth and exhibit antimicrobial effects against pathogens. Therefore, knowledge about proper nutrition is essential to prevent the development and recurrence of SIBO. Since the scientific world was unsure whether there was a long-term or potential solution for SIBO until quite recently, research on a number of the topics included in the article should be performed. The article aimed to summarize current knowledge about proper nutrition after SIBO eradication and the prevention of recurrent bacterial overgrowth. Moreover, a connection was found between diet, gut dysmotility, and SIBO.

Effects of Pea (Pisum sativum) Prebiotics on Intestinal Iron-Related Proteins and Microbial Populations In Vivo (Gallus gallus)

Iron deficiency remains a public health challenge globally. Prebiotics have the potential to improve iron bioavailability by modulating intestinal bacterial population, increasing SCFA production, and stimulating expression of brush border membrane (BBM) iron transport proteins among iron-deficient populations. This study intended to investigate the potential effects of soluble extracts from the cotyledon and seed coat of three pea (Pisum sativum) varieties (CDC Striker, CDC Dakota, and CDC Meadow) on the expression of BBM iron-related proteins (DCYTB and DMT1) and populations of beneficial intestinal bacteria in vivo using the Gallus gallus model by oral gavage (one day old chicks) with 1 mL of 50 mg/mL pea soluble extract solutions. The seed coat treatment groups increased the relative abundance of Bifidobacterium compared to the cotyledon treatment groups, with CDC Dakota seed coat (dark brown pigmented) recording the highest relative abundance of Bifidobacterium. In contrast, CDC Striker Cotyledon (dark-green-pigmented) significantly increased the relative abundance of Lactobacillus (p < 0.05). Subsequently, the two dark-pigmented treatment groups (CDC Striker Cotyledon and CDC Dakota seed coats) recorded the highest expression of DCYTB. Our study suggests that soluble extracts from the pea seed coat and dark-pigmented pea cotyledon may improve iron bioavailability by affecting intestinal bacterial populations.

Effectiveness of Partially Hydrolyzed Guar Gum on Cognitive Function and Sleep Efficiency in Healthy Elderly Subjects in a Randomized, Double-Blind, Placebo-Controlled, and Parallel-Group Study

The consumption of functional foods in a daily diet is a promising approach for the maintenance of cognitive health. The present study examines the effects of water-soluble prebiotic dietary-fiber, partially hydrolyzed guar gum (PHGG), on cognitive function and mental health in healthy elderly individuals. Participants consumed either 5 g/day of PHGG or a placebo daily for 12 weeks in this randomized, double-blind, placebo-controlled, and parallel-group study. An assessment of cognitive functions, sleep quality, and subjective mood evaluations was performed at baseline and after 8 and 12 weeks of either PHGG or placebo intake. The visual memory scores in cognitive function tests and sleepiness on rising scores related to sleep quality were significantly improved in the PHGG group compared to the placebo group. No significant differences were observed in mood parameters between the groups. Vigor-activity scores were significantly improved, while the scores for Confusion-Bewilderment decreased significantly in the PHGG group when compared to the baseline. In summary, supplementation with PHGG was effective in improving cognitive functions, particularly visual memory, as well as enhancing sleep quality and vitality in healthy elderly individuals (UMIN000049070).

Nutritional and functional roles of β-mannanase on intestinal health and growth of newly weaned pigs fed two different types of feeds

This study aimed to investigate the nutritional and functional roles of β-mannanase on the intestinal health and growth of newly weaned pigs fed a typical or low-cost formulated feeds (LCF). Twenty-four newly weaned pigs at 6.2 kg ± 0.4 body weight (BW) were allotted to three dietary treatments based on a randomized complete block design with sex and initial BW as blocks. Three dietary treatments are as follows: Control, typical nursery feeds including animal protein supplements and enzyme-treated soybean meal; LCF with increased amounts of soybean meal, decreased amounts of animal protein supplements, and no enzyme-treated soybean meal; LCF+, low-cost formulated feed with β-mannanase at 100 g/t, providing 800 thermostable β-mannanase unit (TMU) per kg of feed. Pigs were fed based on a three-phase feeding program for a total of 37 d. On day 37 of feeding, all pigs were euthanized and the gastrointestinal tract was removed for sample collection to analyze intestinal health parameters, mucosa-associated microbiota, and gene expression of tight junction proteins. Pigs fed LCF increased (P < 0.05) the relative abundance of Proteobacteria and Helicobacter in the jejunal mucosa, tended to decrease (P = 0.097; P = 0.098) the concentration of malondialdehyde (MDA) and the expression of zona occluden 1 (ZO-1) gene in the jejunum, tended to decrease average daily gain (ADG; P = 0.084) and final BW (P = 0.090), and decreased (P < 0.05) average daily feed intake. Pigs fed LCF + tended to decrease (P = 0.088) digesta viscosity, decreased (P < 0.05) the relative abundance of Helicobacter, and increased (P < 0.05) Lactobacillus in the jejunal mucosa compared to LCF. Additionally, LCF + tended to increase final BW (P = 0.059) and ADG (P = 0.054), increased (P < 0.05) gain to feed ratio (G:F), and reduced (P < 0.05) fecal score compared to LCF. LCF with decreased amounts of animal protein supplements and increased amounts of soybean meal had negative effects on the composition of the mucosa-associated microbiota, intestinal integrity, and growth performance of nursery pigs. Beta-mannanase supplementation to LCF decreased digesta viscosity, increased the relative abundance of potentially health-benefitting microbiota such as Lactobacillus, and improved growth and fecal score, thus reflecting its efficacy in low-cost formulated feeds with increased amounts of soybean meal.

A dietary intervention for postmenopausal hot flashes: A potential role of gut microbiome. An exploratory analysis

OBJECTIVE

This study examined the role of gut microbiome changes in mediating the effects of a dietary intervention on the frequency and severity of postmenopausal vasomotor symptoms METHODS: Postmenopausal women (n = 84) reporting ≥2 moderate-to-severe hot flashes daily were randomly assigned, in 2 successive cohorts, to an intervention including a low-fat, vegan diet and cooked soybeans (½ cup [86 g] daily) or to stay on their usual diet. Over a 12-week period, frequency and severity of hot flashes were recorded with a mobile application. In a subset of 11 women, gut microbiome was analyzed at baseline and after 12 weeks of the dietary intervention (low-fat vegan diet with soybeans), using deep shotgun metagenomic sequencing. Differences in the microbiome between baseline and 12 weeks were assessed by comparing alpha diversity with Wilcoxon signed rank tests, beta diversity with permanovaFL, and taxon abundance with Wilcoxon signed rank tests. Pearson correlations were used to assess the association between changes in hot flashes and gut bacteria.

RESULTS

In the subset for which microbiome testing was done, total hot flashes decreased by 95 % during the dietary intervention (p = 0.007); severe hot flashes disappeared (from 0.6 to 0.0/day; p = 0.06); and moderate-to-severe hot flashes decreased by 96 % (p = 0.01). Daytime and nighttime hot flashes were reduced by 96 % (p = 0.01) and 94 % (p = 0.004), respectively. Alpha and beta diversity did not significantly differ in the intervention group between baseline and 12 weeks. Two families (Enterobacteriaceae and Veillonellaceae), 5 genera (Erysipelatoclostridium, Fusicatenibacter, Holdemanella, Intestinimonas, and Porphyromonas), and 6 species (Clostridium asparagiforme, Clostridium innocuum, Bacteroides thetaiotaomicron, Fusicatenibacter saccharivorans, Intestinimonas butyriciproducens, Prevotella corporis, and Streptococcus sp.) were differentially abundant, but after correction for multiple comparisons, these differences were no longer significant. Changes in the relative abundance of Porphyromonas and Prevotella corporis were associated with the reduction in severe day hot flashes both unadjusted (r = 0.61; p = 0.047; and r = 0.69; p = 0.02), respectively), and after adjustment for changes in body mass index (r = 0.63; p = 0.049; and r = 0.73; p = 0.02), respectively). Changes in relative abundance of Clostridium asparagiforme were associated with the reduction in total severe hot flashes (r = 0.69; p = 0.019) and severe night hot flashes (r = 0.82; p = 0.002) and the latter association remained significant after adjustment for changes in body mass index (r = 0.75; p = 0.01).

CONCLUSIONS

This exploratory analysis revealed potential associations between changes in vasomotor symptoms in response to a diet change and changes in the gut microbiome. Larger randomized clinical trials are needed to investigate these findings.

Efficacy and Safety of Synbiotics in Patients Undergoing Autologous Hematopoietic Stem Cell Transplantation: A Randomized, Double-blinded, Placebo-controlled Pilot Study

Objective High-dose chemotherapy with autologous hematopoietic stem cell transplantation (auto-HSCT) is an effective treatment option for relapsed and refractory aggressive malignant lymphoma. However, patients frequently experience treatment-induced gastrointestinal symptoms. Synbiotics, including live microorganisms and nondigestible food ingredients, reportedly ameliorate chemotherapy-induced mucosal damage. In this study, we assessed the efficacy and safety of synbiotics in patients undergoing auto-HSCT. Methods This randomized, double-blinded study included patients with malignant lymphoma eligible for auto-HSCT. The patients were randomly assigned to either a synbiotic group receiving Bifidobacterium longum (BB536) and guar gum or a placebo group receiving a placebo containing dextrin. The supplements were administered twice daily from the start of conditioning chemotherapy up to 28 days after auto-HSCT. The primary endpoint was the duration of total parenteral nutrition (TPN). Results In total, 12 patients were included and randomized. The median duration of TPN was 15 (range, 12-33) days in the synbiotic group and 17.5 (range, 0-32) days in the placebo group. The median duration of grade ≥3 diarrhea was shorter in the synbiotic group than in then placebo group (2.5 vs. 6.5 days), as was the duration of hospital stay (31.5 vs. 43 days). The oral intake and quality of life regarding diarrhea and anorexia improved in the synbiotic group after engraftment. Synbiotic infections, including bacteremia, were not observed. Conclusion Synbiotics may reduce gastrointestinal toxicity, thereby reducing nutritional problems and improving the quality of life of patients undergoing auto-HSCT, without severe adverse events.

Partially Hydrolyzed Guar Gum Intake Supports the Gut Microbiota and Attenuates Inflammation during Influenza H1N1 Virus Infection in Mice

Partially hydrolyzed guar gum (PHGG) is a soluble dietary fiber that is effective for defecation control. It influences the gut microbiota, by which it is metabolized to yield short-chain fatty acids (SCFAs), and it was also recently shown to protect against influenza infection in humans. We here investigated the effects of PHGG in a mouse model of influenza H1N1 virus infection. Eight-week-old C57BL/6 mice were fed normal chow with or without PHGG (500 mg/kg per day) for 4 weeks, infected with H1N1 at 10 weeks of age, and analyzed at 12 weeks of age. Administration of PHGG attenuated the decline in body weight induced by H1N1 infection without affecting food intake. It also ameliorated intestinal atrophy and increased the production of SCFAs including acetic acid, propionic acid, and butyric acid in the cecum, thereby preventing the inhibitory effect of H1N1 infection on SCFA production. The H1N1-induced increases in the serum concentrations of inflammatory cytokines including interferon-γ and interleukin-6 and anti-inflammatory cytokine such as interleukin-10 were all inhibited by PHGG intake. In addition, PHGG administration attenuated inflammatory gene expression in the lung and promoted both natural killer cell activity and regulatory T-cell differentiation in the spleen. Our findings suggest that the consumption of PHGG may improve the gut environment and thereby limit the inflammatory response to H1N1 infection. They may thus provide the basis for novel dietary intervention strategies to suppress the excessive inflammation associated with virus infection.

Safety evaluation of rare ginsenosides of stems and leaves from American ginseng: 90-day exposure toxicity study combined with intestinal flora analysis and metabonomics in rats

Rare ginsenosides have already been widely applied in many fields, including health food and bio-medicine. The human being can expose to rare ginsenosides directly or indirectly increasingly. However, there are few studies on the safety assessment of rare ginsenoside mixtures. In the present study, the sub-chronic toxicity of rare ginsenosides for 90 days on SD rats was performed by combining the intestinal flora analysis and urine metabonomics aiming to illustrate the safety of long-term consumption of rare ginsenosides and the potential damage for liver and intestinal. 48 adult rats were divided into four groups: control (0 mg/kg), low-dose (60 mg/kg), medium-dose (200 mg/kg), and high-dose (600 mg/kg). Rats in the high-dose group showed inflammatory changes in their livers and intestines. The strong bactericidal effect of rare ginsenosides caused intestinal flora disorder and changed the structure of intestinal flora in rats, thus inducing intestinal damage in rats. In the high-dose group, levels of alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and alkaline phosphatase (AKP) increased significantly. As a result of the high-dose treatment, certain metabolic pathways were altered, such as vitamin B6 metabolism, methionine metabolism, glutathione metabolism, and others. These results indicated that high doses of rare ginsenosides induced liver injury by affecting the above metabolic pathways. Rare ginsenosides with no observed adverse effect level (NOAEL) were below 200 mg/kg/day in vivo. Thus, this present study provides insight into the rational use of rare ginsenosides.

Gut Dysbiosis in Irritable Bowel Syndrome: A Narrative Review on Correlation with Disease Subtypes and Novel Therapeutic Implications

Irritable bowel syndrome (IBS) is a prevalent functional gastrointestinal disorder characterized by chronic abdominal pain and altered bowel habits. It can be subclassified in different subtypes according to the main clinical manifestation: constipation, diarrhea, mixed, and unclassified. Over the past decade, the role of gut microbiota in IBS has garnered significant attention in the scientific community. Emerging research spotlights the intricate involvement of microbiota dysbiosis in IBS pathogenesis. Studies have demonstrated reduced microbial diversity and stability and specific microbial alterations for each disease subgroup. Microbiota-targeted treatments, such as antibiotics, probiotics, prebiotics, synbiotics, fecal microbiota transplantation, and even diet, offer exciting prospects for managing IBS. However, definitive conclusions are hindered by the heterogeneity of these studies. Further research should focus on elucidating the mechanisms, developing microbiome-based diagnostics, and enabling personalized therapies tailored to an individual's microbiome profile. This review takes a deep dive into the microscopic world inhabiting our guts, and its implications for IBS. Our aim is to elucidate the complex interplay between gut microbiota and each IBS subtype, exploring novel microbiota-targeted treatments and providing a comprehensive overview of the current state of knowledge.

Metabolic response of intestinal microbiota to guar gum consumption

Background

Guar gum is used extensively as a thickening agent in food, but it remains uncertain whether and to what extent it is fermented by colonic microbiota and whether it has microbiota modulatory properties.

Aim

To determine the metabolic response of intestinal microbiota to guar gum consumption, specifically, the extent of initial fermentation and subsequent adaptation.

Methods

Single-center, single arm, open label, proof-of-concept study testing the effect of guar gum on microbiota metabolism and adaptation. Healthy male subjects (n = 12) were administered gum guar (8 g/day) for 18 days. Outcomes were measured before, at initial and late administration: (a) anal gas evacuations (number/day); (b) digestive sensations (daily scales); and (c) fecal gut microbiota taxonomy and metabolic functions by shotgun sequencing.

Results

At initial consumption, guar gum induced a transient increase in anal gas evacuations and digestive sensations; gas evacuation completely reverted upon continuous administration, whereas sensations reverted only in part. Guar gum induced moderate changes in human microbiota composition at both taxonomic and functional levels. Positive associations between effects on microbiota (proliferation of Agathobaculum butyriciproducens and Lachnospira pectinoschiza) and hedonic sensations were detected.

Conclusion

Guar gum is metabolized by intestinal microbiota, and, upon continuous consumption, induces a selective adaptation of microbial taxonomy and function. These data highlight the potential interest of guar gum for novel prebiotic ingredient formulation.

Dietary fiber modulates gut microbiome and metabolome in a host sex-specific manner in a murine model of aging

Emerging evidence reveals the fundamental role of the gut microbiome in human health. Among various factors regulating our gut microbiome, diet is one of the most indispensable and prominent one. Inulin is one of the most widely-studied dietary fiber for its beneficial prebiotic effects by positively modulating the gut microbiome and microbial metabolites. Recent research underscores sexual dimorphism and sex-specific disparities in microbiome and also diet-microbiome interactions. However, whether and how the prebiotic effects of dietary fiber differ among sexes remain underexplored. To this end, we herein examine sex-specific differences in the prebiotic effects of inulin on gut microbiome and metabolome in a humanized murine model of aging i.e., aged mice carrying human fecal microbiota. The findings demonstrate that inulin exerts prebiotic effects, but in a sex-dependent manner. Overall, inulin increases the proportion of Bacteroides, Blautia, and glycine, while decreasing Eggerthella, Lactococcus, Streptococcus, trimethylamine, 3-hydroxyisobutyrate, leucine and methionine in both sexes. However, we note sex-specific effects of inulin including suppression of f_Enteroccaceae:_, Odoribacter, bile acids, malonate, thymine, valine, acetoin, and ethanol while promotion of Dubosiella, pyruvate, and glycine in males. Whereas, suppression of Faecalibaculum, Lachnoclostridium, Schaedlerella, phenylalanine and enhancement of Parasutterella, Phocaeicola, f_Lachnospiraceae;_, Barnesiella, Butyricimonas, glycine, propionate, acetate and glutamate are observed in females. Altogether, the study reveals that prebiotic mechanisms of dietary fiber vary in a sex-dependent manner, underscoring the importance of including both sexes in preclinical/clinical studies to comprehend the mechanisms and functional aspects of dietary interventions for effective extrapolation and translation in precision nutrition milieus.

Complex alpha and beta mannan foraging by the human gut bacteria

The human gut microbiota (HGM), a community of trillions of microbes, underscores its contribution by impacting many facets of host health and disease. In the HGM, Bacteroidota and Bacillota represent dominant bacterial phyla, which mainly rely on the glycans recalcitrant to host digestion to meet their energy requirements. Accordingly, the impact of dietary and host-derived glycans in the assembly and operation of these dominant microbial communities continues to be an area of active research. Among various glycans, mannans represent an integral component of the human diet. Apart from their health effects, the diverse and complex mannan structures bears molecular signatures that alter the expression of specific gene clusters in selected Bacteroidota and Bacillota species. Both the phyla possess variable and sophisticated loci of mannan recognition proteins, hydrolytic enzymes, transporters, and other metabolic proteins to sense, capture and utilize mannans as an energy source. The current review summarizes mannan structural diversity, and strategies adopted by select species of the HGM bacteria to forage mannans by focusing primarily on glycoside hydrolases and their effects on host health and metabolism.

Effects of partially hydrolyzed guar gums of different molecular weights on a human intestinal in vitro fermentation model

Partially hydrolyzed guar gums (PHGGs) are prebiotic soluble dietary fibers. High molecular-weight PHGGs have rapid fermentation and high short-chain fatty acid (SCFA) productivity rates, compared to low molecular-weight PHGGs. Therefore, low molecular-weight PHGGs may have less pronounced prebiotic effects than high molecular-weight PHGGs. However, the effects of PHGGs of different molecular weights on the human intestinal microbiota, as well as their fermentation ability and prebiotic effects, have not been investigated. The aim of this study was to evaluate the effects of two PHGGs of different molecular weights, Sunfiber-R (SF-R; 20 kDa) and Sunfiber-V (SF-V; 5 kDa), on human colonic microbiota and SCFA production. A human intestinal in vitro fermentation model was operated by fecal samples with and without the PHGGs. The addition of 0.2% SF-R or SF-V increased the relative abundance of Bacteroides spp., especially that of Bacteroides uniformis. This increase corresponded to a significant (p = 0.030) and non-significant (p = 0.073) increase in propionate production in response to SF-R and SF-V addition, respectively. Both fibers increased the relative abundance of Faecalibacterium and stimulated an increase in the abundance of unclassified Lachnospiraceae and Bifidobacterium. In conclusion, the low molecular-weight PHGG exerted prebiotic effects on human colonic microbiota to increase SCFA production and bacteria that are beneficial to human health in a manner similar to that of the high molecular-weight forms of PHGG.

Partially hydrolyzed guar gum is associated with improvement in gut health, sleep, and motivation among healthy subjects

Partially hydrolyzed guar gum dietary fiber is well recognized for a number of health benefits. In the present study, we aim to investigate the effects of partially hydrolyzed guar gum on constipation, intestinal microbiota as well as mental health in healthy subjects. In the randomized, parallel, double-blind, and placebo-controlled study the enrolled healthy men and women volunteers took either 3 g/day (T3) or 5 g/day (T5) of dietary fiber intakes for eight consecutive weeks compared to placebo (T0). The fecal characteristics, fecal microbiota, defecation characteristics, and quality of life (QOL) questionnaire were investigated. The results revealed a significant suppression in fecal potent harmful mucolytic bacteria in the T3 and T5 groups compared to the T0 group. The defecation frequency, excretory feeling, and scores of sleep and motivation questionnaire were also improved in the dietary fiber intake groups, showing a significant difference in the T5 group compared to the T0 group. In summary, the consumption of partially hydrolyzed guar gum dietary fiber is found effective in suppressing the potent harmful mucolytic bacteria that could be associated with the improvement of constipation-related symptoms including mental health in terms of sleep and motivation among the healthy subjects.

Dietary Fiber Intake and Gut Microbiota in Human Health

Dietary fiber is fermented by the human gut microbiota, producing beneficial microbial metabolites, such as short-chain fatty acids. Over the last few centuries, dietary fiber intake has decreased tremendously, leading to detrimental alternations in the gut microbiota. Such changes in dietary fiber consumption have contributed to the global epidemic of obesity, type 2 diabetes, and other metabolic disorders. The responses of the gut microbiota to the dietary changes are specific to the type, amount, and duration of dietary fiber intake. The intricate interplay between dietary fiber and the gut microbiota may provide clues for optimal intervention strategies for patients with type 2 diabetes and other noncommunicable diseases. In this review, we summarize current evidence regarding dietary fiber intake, gut microbiota modulation, and modification in human health, highlighting the type-specific cutoff thresholds of dietary fiber for gut microbiota and metabolic outcomes.

Recent advances in developing butyrogenic functional foods to promote gut health

As one of the major short-chain fatty acids produced via microbial fermentation, butyrate serves as not only a preferred energy substrate but also an important signaling molecule. Butyrate concentrations in circulation, tissues, and gut luminal contents have important pathophysiological implications. The genetic capacity of butyrate biosynthesis by the gut microbiota is frequently compromised during aging and various disorders, such as inflammatory bowel disease, metabolic disorders and colorectal cancer. Substantial efforts have been made to identify potent butyrogenic substrates and butyrate-hyperproducing bacteria to compensate for butyrate deficiency. Interindividual butyrogenic responses exist, which are more strongly predicted by heterogeneity in the gut microbiota composition than by ingested prebiotic substrates. In this review, we catalog major food types rich in butyrogenic substrates. We also discuss the potential of butyrogenic foods with proven properties for promoting gut health and disease management using findings from clinical trials. Potential limitations and constraints in the current research are highlighted. We advocate a precise nutrition approach in designing future clinical trials by prescreening individuals for key gut microbial signatures when recruiting study volunteers. The information provided in this review will be conducive to the development of microbiota engineering approaches for enhancing the sustained production of butyrate.

Effect of Resistant Dextrin on Intestinal Gas Homeostasis and Microbiota

Previous studies have shown that a resistant dextrin soluble fibre has prebiotic properties with related health benefits on blood glucose management and satiety. Our aim was to demonstrate the effects of continuous administration of resistant dextrin on intestinal gas production, digestive sensations, and gut microbiota metabolism and composition. Healthy subjects (n = 20) were given resistant dextrin (14 g/d NUTRIOSE^®, Roquette Frères, Lestrem, France) for four weeks. Outcomes were measured before, at the beginning, end, and two weeks after administration: anal evacuations of gas during daytime; digestive perception, girth, and gas production in response to a standard meal; sensory and digestive responses to a comfort meal; volume of colonic biomass by magnetic resonance; taxonomy and metabolic functions of fecal microbiota by shotgun sequencing; metabolomics in urine. Dextrin administration produced an initial increase in intestinal gas production and gas-related sensations, followed by a subsequent decrease, which magnified after discontinuation. Dextrin enlarged the volume of colonic biomass, inducing changes in microbial metabolism and composition with an increase in short chain fatty acids-producing species and modulation of bile acids and biotin metabolism. These data indicate that consumption of a soluble fibre induces an adaptative response of gut microbiota towards fermentative pathways with lower gas production.

Dietary Polysaccharides as Modulators of the Gut Microbiota Ecosystem: An Update on Their Impact on Health

A polysaccharide is a macromolecule composed of more than ten monosaccharides with a wide distribution and high structural diversity and complexity in nature. Certain polysaccharides are immunomodulators and play key roles in the regulation of immune responses during the progression of some diseases. In addition to stimulating the growth of certain intestinal bacteria, polysaccharides may also promote health benefits by modulating the gut microbiota. In the last years, studies about the triad gut microbiota-polysaccharides-health have increased exponentially. In consequence, in the present review, we aim to summarize recent knowledge about the function of dietary polysaccharides on gut microbiota composition and how these effects affect host health.

Efficacy of an Irritable Bowel Syndrome Diet in the Treatment of Small Intestinal Bacterial Overgrowth: A Narrative Review

Small intestinal bacterial overgrowth (SIBO) is highly prevalent in irritable bowel syndrome (IBS). The eradication of bacterial overgrowth with antibiotics is the first-line treatment. However, focusing only on the antimicrobial effects without taking care to improve lifestyle factors, especially dietary patterns, may predispose patients to intestinal microbiota dysfunction. The objective of this study is to determine whether the current recommendations regarding nutrition in IBS are suitable for patients with SIBO. A narrative literature review was carried out using databases, including PubMed, ScienceDirect and Google Scholar. Recent studies indicate that dietary manipulation may have a role in alleviating SIBO gastrointestinal symptoms. A low FODMAP diet proposed for IBS may promote a negative shift in the gut microbiota and deepen the existing state of dysbiosis in SIBO patients. Supplementation with soluble fiber can lessen the symptoms in IBS and SIBO. Targeted probiotic therapy may also increase the effectiveness of antibiotic treatment and regulate bowel movements. Therefore, optimal dietary patterns play a key role in the treatment of SIBO. Based on currently available literature, the potential efficacy of the IBS diet in SIBO is largely hypothetical. Future research is needed to characterize a specific diet for the treatment of SIBO.

Dietary Component-Induced Inflammation and Its Amelioration by Prebiotics, Probiotics, and Synbiotics

A balanced diet with many dietary components maintains immune homeostasis directly by interacting with innate and adaptive immune components or indirectly through gut microbiota and their metabolites. Dietary components may inhibit pro-inflammatory mediators and promote anti-inflammatory functions or vice versa. Western diets with imbalanced dietary components skew the immune balance toward pro-inflammation and induce intestinal inflammation, consequently leading to many intestinal and systemic inflammatory diseases like ulcerative colitis, Crohn's disease, irritable bowel syndrome, cardiovascular problems, obesity, and diabetes. The dietary component-induced inflammation is usually chronic in nature and frequently caused or accompanied by alterations in gut microbiota. Therefore, microbiome-targeted therapies such as probiotics, prebiotics and synbiotics hold great potentials to amend immune dysregulation and gut dysbiosis, preventing and treating intestinal and systemic inflammatory diseases. Probiotics, prebiotics and synbioitcs are progressively being added to foods and beverages, with claims of health benefits. However, the underlining mechanisms of these interventions for preventing and treating dietary component-induced inflammation are still not very clear. In addition, possibly ineffective or negative consequences of some probiotics, prebiotics and synbiotics call for stringent testing and regulation. Here, we will first briefly review inflammation, in terms of its types and the relationship between different dietary components and immune responses. Then, we focus on current knowledge about the direct and indirect effects of probiotics, prebiotics and synbiotics on intestinal and systemic inflammation. Understanding how probiotics, prebiotics and synbiotics modulate the immune system and gut microbiota will improve our strategies for preventing and treating dietary component-induced intestinal inflammation and inflammatory diseases.

Partially Hydrolyzed Guar Gum Suppresses the Development of Sarcopenic Obesity

Partially hydrolyzed guar gum (PHGG) is a soluble dietary fiber derived through controlled enzymatic hydrolysis of guar gum, a highly viscous galactomannan derived from the seeds of Cyamopsis tetragonoloba. Here, we examined the therapeutic potential of dietary supplementation with PHGG against sarcopenic obesity using Db/Db mice. Db/Db mice fed a normal diet alone or a fiber-free diet, or supplemented with a diet containing PHGG (5%), were examined. PHGG increased grip strength and the weight of skeletal muscles. PHGG increased the short-chain fatty acids (SCFAs) concentration in feces and sera. Concerning innate immunity, PHGG decreased the ratio of inflammatory cells, while increasing the ratio of anti-inflammatory cells in the small intestine. The present study demonstrated the preventive effect of PHGG on sarcopenic obesity. Changes in nutrient absorption might be involved through the promotion of an anti-inflammatory shift of innate immunity in the intestine accompanied by an increase in SCFA production by PHGG.

Effects of konjac glucomannan with different molecular weights on gut microflora with antibiotic perturbance in in vitro fecal fermentation

This study investigated the effect of konjac glucomannan (KGM) of different molecular weight on fecal microflora against antibiotic disturbance. KGM (~1.8 × 10⁷ Da) was partially hydrolysed with trifluoroacetic acid (TFA) for 10 and 60 min to KGM1 (~2.1 × 10⁴ Da) and KGM2 (7413 Da), respectively. The acid treatment caused significant reduction of intrinsic viscosity, average molecular weight (MW) and particle size of KGM, but brought limited change to the molecular structure. Low-MW KGM2 showed the most significant effect on fecal microflora in the presence of two common antibiotics (ampicillin and clindamycin), by increasing the relative abundance of Bifidobacteriaceae while decreasing the proportion of Enterobacteriaceae. Additionally, both the native and acid-treated KGM counteracted the adverse influence of antibiotics on the production of short chain fatty acids. The results have demonstrated the effect of KGM on gut microbiota with antibiotic disturbance.

The Short-Term Effects and Tolerability of Low-Viscosity Soluble Fibre on Gastroparesis Patients: A Pilot Clinical Intervention Study

Gastroparesis is a motility disorder that causes severe gastric symptoms and delayed gastric emptying, where the majority of sufferers are females (80%), with 29% of sufferers also diagnosed with Type-1 or Type-2 diabetes. Current clinical recommendations involve stringent dietary restriction and includes the avoidance and minimization of dietary fibre. Dietary fibre lowers the glycaemic index of food, reduces inflammation and provides laxation. Lack of dietary fibre in the diet can affect long-term gastrointestinal health. Our previously published rheological study demonstrated that "low-viscosity" soluble fibres could be a potentially tolerable source of fibre for the gastroparetic population. A randomised controlled crossover pilot clinical study was designed to compare Partially-hydrolysed guar gum or PHGG (test fibre 1), gum Arabic (test fibre 2), psyllium husk (positive control) and water (negative control) in mild-to-moderate symptomatic gastroparesis patients (requiring no enteral tube feeding). The principal aim of the study was to determine the short-term physiological effects and tolerability of the test fibres. In n = 10 female participants, post-prandial blood glucose, gastroparesis symptoms, and breath test measurements were recorded. Normalized clinical data revealed that test fibres PHGG and gum Arabic were able to regulate blood glucose comparable to psyllium husk, while causing far fewer symptoms, equivalent to negative control. The test fibres did not greatly delay mouth-to-caecum transit, though more data is needed. The study data looks promising, and a longer-term study investigating these test fibres is being planned.

Nutraceuticals and Herbal Food Supplements for Weight Loss: Is There a Prebiotic Role in the Mechanism of Action?

Numerous nutraceuticals and botanical food supplements are used with the intention of modulating body weight. A recent review examined the main food supplements used in weight loss, dividing them according to the main effects for which they were investigated. The direct or indirect effects exerted on the intestinal microbiota can also contribute to the effectiveness of these substances. The aim of this review is to evaluate whether any prebiotic effects, which could help to explain their efficacy or ineffectiveness, are documented in the recent literature for the main nutraceuticals and herbal food supplements used for weight loss management. Several prebiotic effects have been reported for various nutraceutical substances, which have shown activity on Bifidobacterium spp., Lactobacillus spp., Akkermansia muciniphila, Faecalibacterium prausnitzi, Roseburia spp., and the Firmicutes/Bacteroidetes ratio. Different prebiotics have beneficial effects on weight and the related metabolic profile, in some cases even acting on the microbiota with mechanisms that are completely independent from those nutraceuticals for which certain products are normally used. Further studies are necessary to clarify the different levels at which a nutraceutical substance can exert its action.

A blend of 3 mushrooms dose-dependently increases butyrate production by the gut microbiota

The gut microbiota has been indicated to play a crucial role in health and disease. Apart from changes in composition between healthy individuals and those with a disease or disorder, it has become clear that also microbial activity is important for health. For instance, butyrate has been proven to be beneficial for health, because, amongst others, it is a substrate for the colonocytes, and modulates the host's immune system and metabolism. Here, we studied the effect of a blend of three mushrooms (Ganoderma lucidum GL AM P-38, Grifola frondosa GF AM P36 and Pleurotus ostreatus PO AM-GP37)) on gut microbiota composition and activity in a validated, dynamic, computer-controlled in vitro model of the colon (TIM-2). Predigested mushroom blend at three doses (0.5, 1.0 and 1.5 g/day of ingested mushroom blend) was fed to a pooled microbiota of healthy adults for 72 h, and samples were taken every day for microbiota composition (sequencing of amplicons of the V3-V4 region of the 16S rRNA gene) and activity (short-chain fatty acid (SCFA) production). The butyrate producing genera Lachnospiraceae UCG-004, Lachnoclostridium, Ruminococcaceae UCG-002 and Ruminococcaceae NK4A214-group are all dose-dependently increased when the mushroom blend was fed. Entirely in line with the increase of these butyrate-producers, the cumulative amount of butyrate also dose-dependently increased, to roughly twice the amount compared to the control (medium without mushroom blend) on the high-dose mushroom blend. Butyrate proportionally made up 53.1% of the total SCFA upon feeding the high-dose mushroom blend, compared to 27% on the control medium. In conclusion, the (polysaccharides in the) mushroom blend led to substantial increase in butyrate by the gut microbiota. These results warrant future mechanistic research on the mushroom blend, as butyrate is considered to be one of the microbial metabolites that contributes to health, by increasing barrier function and modulating inflammation.

Effects of Partially Hydrolyzed Guar Gum Supplementation on the Fecal Microbiotas of Piglets

Probiotics and prebiotics have become viable alternatives of growth-promoting antimicrobials in animal production. Here, we tested partially hydrolyzed guar gum (PHGG) as a possible prebiotic for piglets in the commercial farm. Five hundred and ninety-four piglets were used for the experiments, with 293 given a normal pig feed (control), while the rest the feed plus 0.06% (w/w) of PHGG (PHGG). One and three months post-PHGG supplementation, fecal samples were collected from randomly selected 20 piglets in each group and analyzed for microbiota and organic acid concentrations. Notably, the abundance of Streptococcus, and unclassified Ruminococcaceae were lower (p < 0.05) in PHGG than in control, one-month post-supplementation. Lactobacillus and Prevotella were higher (p < 0.05), while Streptococcus was lower (p < 0.05), in PHGG than in control, three months post-supplementation. The concentrations of acetate, propionate, and butyrate were greater in PHGG than in control, three months post-supplementation. Finally, PHGG grew faster and had fewer deaths until slaughter time (p < 0.05), than control. We concluded that PHGG not only was an effective prebiotic to alter gut microbiota of weanling piglets but also can possibly promote body weight accretion and health.

Partially hydrolyzed guar gum attenuates non-alcoholic fatty liver disease in mice through the gut-liver axis

BACKGROUND

The gut-liver axis has attracted much interest in the context of chronic liver disease pathogenesis. Prebiotics such as dietary fibers were shown to attenuate non-alcoholic fatty liver disease (NAFLD) by modulating gut microbiota. Partially hydrolyzed guar gum (PHGG), a water-soluble dietary fiber, has been reported to alleviate the symptoms of various intestinal diseases and metabolic syndromes. However, its effects on NAFLD remain to be fully elucidated.

AIM

To determine whether treatment with PHGG attenuates NAFLD development in mice through the gut-liver axis.

METHODS

Seven-week-old male C57BL/6J mice with increased intestinal permeability were fed a control or atherogenic (Ath) diet (a mouse model of NAFLD) for 8 wk, with or without 5% PHGG. Increased intestinal permeability was induced through chronic intermittent administration of low-dose dextran sulfate sodium. Body weight, liver weight, macroscopic findings in the liver, blood biochemistry [aspartate aminotransferase (AST) and alanine aminotransferase (ALT), total cholesterol, triglyceride, free fatty acids, and glucose levels], liver histology, myeloperoxidase activity in liver tissue, mRNA expression in the liver and intestine, serum endotoxin levels in the portal vein, intestinal permeability, and microbiota and short-chain fatty acid (SCFA) profiles in the cecal samples were investigated.

RESULTS

Mice with increased intestinal permeability subjected to the Ath diet showed significantly increased serum AST and ALT levels, liver fat accumulation, liver inflammatory (tumor necrosis factor-α and monocyte chemotactic protein-1) and fibrogenic (collagen 1a1 and α smooth muscle actin) marker levels, and liver myeloperoxidase activity, which were significantly attenuated by PHGG treatment. Furthermore, the Ath diet combined with increased intestinal permeability resulted in elevated portal endotoxin levels and activated toll-like receptor (TLR) 4 and TLR9 expression, confirming that intestinal permeability was significantly elevated, as observed by evaluating the lumen-to-blood clearance of fluorescein isothiocyanate-conjugated dextran. PHGG treatment did not affect fatty acid metabolism in the liver. However, it decreased lipopolysaccharide signaling through the gut-liver axis. In addition, it significantly increased the abundance of cecal Bacteroides and Clostridium subcluster XIVa. Treatment with PHGG markedly increased the levels of SCFAs, particularly, butyric acid, acetic acid, propionic acid, and formic acid, in the cecal samples.

CONCLUSION

PHGG partially prevented NAFLD development in mice through the gut-liver axis by modulating microbiota and downstream SCFA profiles.

Plant Prebiotics and Their Role in the Amelioration of Diseases

Prebiotics are either natural or synthetic non-digestible (non-)carbohydrate substances that boost the proliferation of gut microbes. Undigested fructooligosaccharides in the large intestine are utilised by the beneficial microorganisms for the synthesis of short-chain fatty acids for their own growth. Although various food products are now recognized as having prebiotic properties, several others, such as almonds, artichoke, barley, chia seeds, chicory, dandelion greens, flaxseeds, garlic, and oats, are being explored and used as functional foods. Considering the benefits of these prebiotics in mineral absorption, metabolite production, gut microbiota modulation, and in various diseases such as diabetes, allergy, metabolic disorders, and necrotising enterocolitis, increasing attention has been focused on their applications in both food and pharmaceutical industries, although some of these food products are actually used as food supplements. This review aims to highlight the potential and need of these prebiotics in the diet and also discusses data related to the distinct types, sources, modes of action, and health benefits.

Shaping the Future of Probiotics and Prebiotics

Recent and ongoing developments in microbiome science are enabling new frontiers of research for probiotics and prebiotics. Novel types, mechanisms, and applications currently under study have the potential to change scientific understanding as well as nutritional and healthcare applications of these interventions. The expansion of related fields of microbiome-targeted interventions, and an evolving landscape for implementation across regulatory, policy, prescriber, and consumer spheres, portends an era of significant change. In this review we examine recent, emerging, and anticipated trends in probiotic and prebiotic science, and create a vision for broad areas of developing influence in the field.

Functional hydrocolloids, gut microbiota and health: picking food additives for personalized nutrition

The human gut microbiota respond to particular food components, interact with intestinal mucosa and thereby contribute to health and diseases. Key microbiome features are under comprehensive investigation and are likely to be developed as reliable evidences for clinical diagnosis. And the underlying mechanisms lay the foundation of assembling bespoke nutritional ingredients including functional food additives that may lead to favorable outcomes in facilitating amelioration of host dysfunctions. Functional hydrocolloids serve as multiple food additives with promising application prospects and outstanding adjunctive beneficial characteristics. Therefore, in this review, we introduce the latest advances in food additives-gut microbiota-host axis by summarizing the physiochemical and physiological properties of a collection of functional hydrocolloids from various sources, describing the functional hydrocolloids-related intestinal commensal markers, and deciphering the underlying mechanisms of their beneficial effects, and propose the feasibilities and guidelines for further developments of gut microbiota-oriented personalized nutrition.

Potato Preload Mitigated Postprandial Glycemic Excursion in Healthy Subjects: An Acute Randomized Trial

This study investigated the preload effect of the medium and high glycemic index (GI) potato, as well as the combination of partially hydrolyzed guar gum (HG) and potato, when ingested prior to a rice meal, on the iso-carbohydrate basis. In a randomized crossover trial, 17 healthy female subjects consumed (1) rice; (2) co-ingestion of highly cooked potato (HP), and rice (HP + R); (3) co-ingestion of minimally cooked potato (MP) and rice (MP + R); (4) preload HP prior to rice meal (PHP + R); (5) preload MP prior to rice meal (PMP + R); (6) co-ingestion of partially hydrolyzed guar gum (HG), HP and rice (HG + HP + R); (7) preload HG prior to co-ingestion of HP and rice (PHG + HP + R); (8) co-preload of HG and HP prior to rice (PHG + PHP + R); and (9) preload of HP prior to co-ingestion of HG and rice (PHP + HG + R). Postprandial glycemic response (GR) tests and subjective satiety tests were conducted for each test food. Cooked potato as a preload to a rice meal could significantly cut the acute postprandial glycemic excursion by around 1.0 mmol/L, irrespective of the GI of the preload. Co-preload of partial hydrolyzed guar gum and highly cooked potato (PHG + PHP + R) resulted in improved acute GR in terms of peak glucose value and glycemic excursion compared with either HG preload or HP preload. All the meals with preload showed comparable or improved self-reported satiety. Within an equicarbohydrate exchange framework, both high-GI and medium-GI potato preload decreased the postprandial glycemic excursion in young healthy female subjects. The combination of HG and HP as double preload resulted in better GR than both single HG or HP preload did.