Effect of non-digestible fermentable carbohydrates on hepatic fatty acid metabolism

Obesity and Its Multiple Clinical Implications between Inflammatory States and Gut Microbiotic Alterations

Obesity is a chronic multifactorial disease that has become a serious health problem and is currently widespread over the world. It is, in fact, strongly associated with many other conditions, including insulin resistance, type 2 diabetes, cardiovascular and neurodegenerative diseases, the onset of different types of malignant tumors and alterations in reproductive function. According to the literature, obesity is characterized by a state of low-grade chronic inflammation, with a substantial increase in immune cells, specifically macrophage infiltrates in the adipose tissue which, in turn, secrete a succession of pro-inflammatory mediators. Furthermore, recent studies on microbiota have postulated new possible mechanisms of interaction between obesity and unbalanced nutrition with inflammation. This intestinal "superorganism" complex seems to influence not only the metabolic balance of the host but also the immune response, favoring a state of systemic inflammation and insulin resistance. This review summarizes the major evidence on the interactions between the gut microbiota, energetic metabolism and host immune system, all leading to a convergence of the fields of immunology, nutrients physiology and microbiota in the context of obesity and its possible clinical complications. Finally, possible therapeutic approaches aiming to rebalance the intestinal microbial ecosystem are evaluated to improve the alteration of inflammatory and metabolic states in obesity and related diseases.

Effects of Agave Fructans, Inulin, and Starch on Metabolic Syndrome Aspects in Healthy Wistar Rats

Healthy Wistar rats were supplemented during 20 weeks with commercial inulin (I) and Agave tequilana fructans (CAT), experimental fructans from A. tequilana (EAT) and A. salmiana (AS) mature stems, rice starch 10% (RS), and standard feed for rodents (C). Feed intake was kept steady, but with I, body weight and abdominal adipose tissue (6.01 g) decreased at the end. Glucose (mg/dL) (C, 120.52; I, 110.69; CAT, 105.75; EAT, 115.48; AS, 101.63; and RS, 121.82), total cholesterol (C, 89.89; I, 64.48; CAT, 68.04; EAT, 68.74; AS, 68.04; and RS, 82), and triglycerides (C, 84.03; I, 59.52; CAT, 68.56; EAT, 59.08; AS, 75.27; and RS, 81.8) kept being normal and without differences between fructans. At the end, there was a significant increase in lactic acid bacteria when the I and AS groups were compared to the C group (C, 9.18; I, 10.64; CAT, 10.34; EAT, 10.36; AS, 10.49; and RS, 9.62 log 10 CFU/g of feces). In addition, with fructans, there was an accelerated process in feces emptiness, Lieberkühn crypts kept their morphology, and there was an increment of goblet cells.

Cereal fructan extracts alter intestinal fermentation to reduce adiposity and increase mineral retention compared to oligofructose

PURPOSE

Intestinal fermentation of inulin-type fructans, including oligofructose, can modulate adiposity, improve energy regulation, and increase mineral absorption. We aimed to determine whether cereal fructans had greater effects on reducing adiposity and improving mineral absorption compared with oligofructose.

METHODS

Thirty-two male Sprague-Dawley rats were randomly assigned to one of four dietary treatments that contained 0% fructan (control), or 5% fructan provided by oligofructose (OF), a barley grain fraction (BGF), or a wheat stem fraction (WSF). After 1 week on the diets, mineral absorption and retention was assessed. At 4 weeks, blood samples were collected for gut hormone analysis, adipose depots were removed and weighed, and caecal digesta was analyzed for pH and short-chain fatty acids (SCFA).

RESULTS

The BGF and WSF, but not OF, had lower total visceral fat weights than the Control (p < 0.05). The fructan diets all lowered caecal pH and raised caecal digesta weight and total SCFA content, in comparison to the Control. Caecal propionate levels for OF were similar to the Control and higher for WSF (p < 0.05). Plasma peptide YY and glucagon-like peptide-1 levels were elevated for all fructan groups when compared to Control (p < 0.001) and gastric inhibitory peptide was lower for the WSF compared to the other groups (p < 0.05). The fructan diets improved calcium and magnesium retention, which was highest for WSF (p < 0.05). BGF and WSF in comparison to OF showed differential effects on fermentation, gut hormone levels, and adiposity.

CONCLUSIONS

Cereal fructan sources have favorable metabolic effects that suggest greater improvements in energy regulation and mineral status to those reported for oligofructose.

Gut microbiome and liver diseases

The gut microbiota has recently evolved as a new important player in the pathophysiology of many intestinal and extraintestinal diseases. The liver is the organ which is in closest contact with the intestinal tract, and is exposed to a substantial amount of bacterial components and metabolites. Various liver disorders such as alcoholic liver disease, non-alcoholic liver disease and primary sclerosing cholangitis have been associated with an altered microbiome. This dysbiosis may influence the degree of hepatic steatosis, inflammation and fibrosis through multiple interactions with the host's immune system and other cell types. Whereas few results from clinical metagenomic studies in liver disease are available, evidence is accumulating that in liver cirrhosis an oral microbiome is overrepresented in the lower intestinal tract, potentially contributing to disease process and severity. A major role for the gut microbiota in liver disorders is also supported by the accumulating evidence that several complications of severe liver disease such as hepatic encephalopathy are efficiently treated by various prebiotics, probiotics and antibiotics. A better understanding of the gut microbiota and its components in liver diseases might provide a more complete picture of these complex disorders and also form the basis for novel therapies.

Impact of the gut microbiota on inflammation, obesity, and metabolic disease

The human gut harbors more than 100 trillion microbial cells, which have an essential role in human metabolic regulation via their symbiotic interactions with the host. Altered gut microbial ecosystems have been associated with increased metabolic and immune disorders in animals and humans. Molecular interactions linking the gut microbiota with host energy metabolism, lipid accumulation, and immunity have also been identified. However, the exact mechanisms that link specific variations in the composition of the gut microbiota with the development of obesity and metabolic diseases in humans remain obscure owing to the complex etiology of these pathologies. In this review, we discuss current knowledge about the mechanistic interactions between the gut microbiota, host energy metabolism, and the host immune system in the context of obesity and metabolic disease, with a focus on the importance of the axis that links gut microbes and host metabolic inflammation. Finally, we discuss therapeutic approaches aimed at reshaping the gut microbial ecosystem to regulate obesity and related pathologies, as well as the challenges that remain in this area.

Fermentation of purple Jerusalem artichoke extract to improve the α-glucosidase inhibitory effect in vitro and ameliorate blood glucose in db/db mice

BACKGROUND/OBJECTIVES

Jerusalem artichoke has inhibitory activity against α-glucosidase and decreases fasting serum glucose levels, which may be related to its fructan content. The biological activity of fructan can be influenced by the degree of polymerization. Thus, in this study, the inhibitory effects of original and fermented purple Jerusalem artichoke (PJA) on α-glucosidase were compared in vitro. Additionally, the anti-diabetes effect of Lactobacillus plantarum-fermented PJA (LJA) was studied in a non-insulin-dependent diabetes mellitus animal model (C57BIKsJ db/db).

MATERIALS/METHODS

The water extract of PJA was fermented by L. plantarum, and two strains of Bacillus subtilis to compare their anti-α-glucosidase activities in vitro by α-glucosidase assays. The anti-diabetes effect of LJA was studied in a non-insulin-dependent diabetes mellitus animal model (C57BIKsJ db/db) for seven weeks. During the experiment, food intake, body weight, and fasting blood glucose were measured every week. At the end of the treatment period, several diabetic parameters and the intestinal α-glucosidase activity were measured.

RESULTS

The LJA showed the highest α-glucosidase inhibitory activity in vitro. In the in vivo study, it resulted in a significantly lower blood glucose concentration than the control. Serum insulin and HDL cholesterol levels were significantly higher and the concentrations of triglycerides, non-esterified fatty acids, and total cholesterol were significant lower in mice treated with LJA after seven weeks. In addition, the intestinal α-glucosidase activity was partially inhibited.

CONCLUSIONS

These results suggested that LJA regulates blood glucose and has potential use as a dietary supplement.

Prebiotics as functional food ingredients preventing diet-related diseases

This paper reviews the potential of prebiotic-containing foods in the prevention or postponement of certain diet-related diseases, such as cardiovascular diseases with hypercholesterolemia, osteoporosis, diabetes, gastrointestinal infections and gut inflammation.

Prebiotic Effects of Agave salmiana Fructans in Lactobacillus acidophilus and Bifidobacterium lactis Cultures

Agave salmiana is a fructan rich species that is widely distributed in Mexico. The aim of this investigation was to extract the fructans of A. salmiana and evaluate their prebiotic effect in 48 hours in vitro cultures of Bifidobacterium lactis and Lactobacillus acidophilus and to compare this effect with other available fructan sources. A significant difference in pH, optical density and biomass was found in the cultures depending on the source of fructans and the type of bacteria. It was possible to determine a dose-response effect of the A. salmiana fructans and the growth of the studied strains.

Soluble polysaccharide composition and myo-inositol content help differentiate the antioxidative and hypolipidemic capacity of peeled apples

Many people prefer to eat peeled apples. The present study investigated the composition of soluble polysaccharides (SP) in peeled apples and its antioxidative and hypolipidemic activity. The yield of SP ranged 0.43-0.88%, having MW ranging 223-848 kDa. All belonged to peptidoglycans. Among the fourteen amino acids found, seven were essential amino acids. In addition, sugar analysis indicated that 50% of apple samples consisted of glucoarabinan, 37.5% comprising taloarabinan and the remaining 12.5% containing alloglucan. Moreover, SP consisted of a huge amount of myo-inositol (>5.61%) and uronic acid (>11.7%), which may play a synergistic role in the hypolipidemic effect. Worth noting, we are the first who reported the presence of talose, allose and fucose in the apple SP. Conclusively, the biological value of SP is attributable to the differential effect of SP and the synergistic effect exerted by its unique SP pattern, high myo-inositol and uronic acid contents.

Effect of prebiotic fibre supplementation on hepatic gene expression and serum lipids: a dose-response study in JCR:LA-cp rats

Prebiotic fibres have been proposed to promote weight loss and lower serum cholesterol; however, the mechanisms are not fully understood. The aim of the present research was to identify possible mechanisms through which prebiotic fibres improve serum lipids. Lean and obese JCR:La-cp rats aged 8 weeks consumed one of three diets supplemented with 0, 10 or 20 % prebiotic fibre for 10 weeks. Rats were anaesthetised and a fasting blood sample was taken for lipid analysis. Real-time PCR was used to determine gene expression for cholesterol and fatty acid regulatory genes in liver tissue. Liver and caecal digesta cholesterol and TAG content were quantified. Both doses of prebiotic fibre lowered serum cholesterol levels by 24 % in the obese hyperlipidaemic rats (P < 0.05). This change was associated with an increase in caecal digesta as well as an up-regulation of genes involved in cholesterol synthesis and bile production. Additionally, there was a 42 % reduction in TAG accumulation in the liver of the obese rats with 10 % prebiotic diet (P < 0.05); however, no change in liver fatty acid synthase (FAS). Prebiotic fibres appear to lower cholesterol levels through increased cholesterol excretion in the form of bile and inhibit the accumulation of TAG in the liver through a mechanism unrelated to FAS. These effects appear to be limited to the obese model and particularly the 10 % dose. The present work is significant as it provides insight into the mechanisms of action for prebiotic fibres on lipid metabolism and furthers the development of dietary treatments for hypercholesterolaemia.

Panorganismal gut microbiome-host metabolic crosstalk

Coevolution shapes interorganismal crosstalk leading to profound and diverse cellular and metabolic changes as observed in gut dysbiosis in human diseases. Here, we modulated a simplified gut microbiota using pro-, pre-, and synbiotics to assess the depth of systemic metabolic exchanges in mice, using a multicompartmental modeling approach with metabolic signatures from 10 tissue/fluid compartments. The nutritionally induced microbial changes modulated host lipid, carbohydrate, and amino acid metabolism at a panorganismal scale. Galactosyl-oligosaccharides reduced lipogenesis, triacylglycerol incorporation into lipoproteins and triglyceride concentration in the liver and the kidney. Those changes were not correlated with decreased plasma lipoproteins that were specifically induced by L. rhamnosus supplementation. Additional alteration of transmethylation metabolic pathways (homocysteine-betaine) was observed in the liver and the pancreas following pre- and synbiotic microbial modulation, which may be of interest for control of glucose metabolism and insulin sensitivity. Probiotics also reduced hepatic glycogen and glutamine and adrenal ascorbate with inferred effects on energy homeostasis, antioxidation, and steroidogenesis. These studies show the breadth and the depth of gut microbiome modulations of host biochemistry and reveal that major mammalian metabolic processes are under symbiotic homeostatic control.

Effects of lifelong intervention with an oligofructose-enriched inulin in rats on general health and lifespan

Ageing is associated with changes in physiology and morphology; nutritional strategies to decrease morbidity and to prolong life are of high interest. The aim of the study was to investigate the effects of lifelong supplementation with an oligofructose-enriched inulin on morphological and biological markers and lifespan in male and female rats. Male and female rats, age 3 months, were randomised into two groups to receive either a diet with 10 % of an oligofructose-enriched inulin (Synergy1) or a standard diet (control) for 27 months. The rats were weighed every 2 weeks and their food intake was evaluated on four successive days every 4–6 weeks. Samples were taken at 12, 18 and 24 months of age. During the whole intervention period, male rats receiving Synergy1 (SYN1-M) displayed lower body weight, cholesterol and plasma triacylglycerolaemia compared with the controls (Cont-M). The survival rate at 24 months of age of SYN1-M rats was 35·3 % greater than that of Cont-M rats. In female rats, the Synergy1 supplementation (SYN1-F) group also reduced body weight, cholesterol and triacylglycerolaemia levels, but results were less consistent over the experiment. The survival rate at 24 months of age in SYN1-F rats was 33·3 % greater compared with that of the control (Cont-F) group. To conclude, lifelong intervention with Synergy1 improved biological markers during ageing and survival rate (lifespan) of rats.

Hypolipidemic effect in cholesterol-fed rats of a soluble fiber-rich product obtained from cocoa husks

A new soluble cocoa fiber product (SCFP), obtained after enzymatic treatment of cocoa husks, was characterized and its potential health effects studied in an animal model of dietary-induced hypercholesterolemia. The SCFP was rich in soluble dietary fiber (DF) and antioxidant polyphenols. Consumption of a cholesterol-rich diet containing the SCFP as a source of DF resulted in lower food intake and body weight gain in comparison with control groups consuming cholesterol-free or cholesterol-rich diets with cellulose as DF. The cholesterol-rich diet caused remarkable hypercholesterolemia. However, the SCFP diminished the negative impact of the cholesterol-rich diet, buffering the decrease of high density lipoprotein-cholesterol, and the increase of total and low density lipoprotein-cholesterol levels, and lipid peroxidation (malondialdehyde levels) induced by the fatty diet. The SCFP also decreased triglyceride levels to values lower than those in the group fed the cholesterol-free diet. These results put forward the potential application of the SCFP as a dietary supplement or functional food ingredient.

Top-down systems biology integration of conditional prebiotic modulated transgenomic interactions in a humanized microbiome mouse model

Gut microbiome-host metabolic interactions affect human health and can be modified by probiotic and prebiotic supplementation. Here, we have assessed the effects of consumption of a combination of probiotics (Lactobacillus paracasei or L. rhamnosus) and two galactosyl-oligosaccharide prebiotics on the symbiotic microbiome-mammalian supersystem using integrative metabolic profiling and modeling of multiple compartments in germ-free mice inoculated with a model of human baby microbiota. We have shown specific impacts of two prebiotics on the microbial populations of HBM mice when co-administered with two probiotics. We observed an increase in the populations of Bifidobacterium longum and B. breve, and a reduction in Clostridium perfringens, which were more marked when combining prebiotics with L. rhamnosus. In turn, these microbial effects were associated with modulation of a range of host metabolic pathways observed via changes in lipid profiles, gluconeogenesis, and amino-acid and methylamine metabolism associated to fermentation of carbohydrates by different bacterial strains. These results provide evidence for the potential use of prebiotics for beneficially modifying the gut microbial balance as well as host energy and lipid homeostasis.

Inulin and oligofructose modulate lipid metabolism in animals: review of biochemical events and future prospects

Inulin and oligofructose, besides their effect on the gastro-intestinal tract, are also able to exert ‘systemic’ effect, namely by modifying the hepatic metabolism of lipids in several animal models. Feeding male Wistar rats on a carbohydrate-rich diet containing 10 % inulin or oligofructose significantly lowers serum triacylglycerol (TAG) and phospholipid concentrations. A lower hepatic lipogenesis, through a coordinate reduction of the activity and mRNA of lipogenic enzymes is a key event in the reduction of very low-density lipoprotein-TAG secretion by oligofructose. Oligofructose is also able to counteract triglyceride metabolism disorder occurring through dietary manipulation in animals, and sometimes independently on lipogenesis modulation: oligofructose reduces post-prandial triglyceridemia by 50 % and avoids the increase in serum free cholesterol level occurring in rats fed a Western-type high fat diet. Oligofructose protects rats against liver TAG accumulation (steatosis) induced by fructose, or occurring in obese Zucker fa/fa rats. The protective effect of dietary inulin and oligofructose on steatosis in animals, would be interesting, if confirmed in humans, since steatosis is one of the most frequent liver disorders, occurring together with the plurimetabolic syndrome, in overweight people. The panel of putative mediators of the systemic effects of inulin and oligofructose consists in either modifications in glucose/insulin homeostasis, the end-products of their colonic fermentation (i.e. propionate) reaching the liver by the portal vein, incretins and/or the availability of other nutrients. The identification of the key mediators of the systemic effects of inulin and oligofructose is the key to identify target function(s) (or dysfunction(s)), and finally individuals who would take an advantage of increasing their dietary intake.

Prebiotics and other microbial substrates for gut functionality

The intestinal microbiota is of great importance to our health and wellbeing. Modulation of the intestinal microbiota by exogenous and endogenous substrates can be expected to improve various physiological functions of our body, not just those in the intestine. Recently, new targets such as immune function and areas outside the colon have been considered to be influenced by the intestinal microbiota. Novel approaches might include the application of prebiotics in different combinations or the provision of nutrients to different bacterial groups and to different parts of the intestine.

Applications of inulin and oligofructose in health and nutrition

Inulin and oligofructose belong to a class of carbohydrates known as fructans. The main sources of inulin and oligofructose that are used in the food industry are chicory and Jerusalem artichoke. Inulin and oligofructose are considered as functional food ingredients since they affect the physiological and biochemical processes in rats and human beings, resulting in better health and reduction in the risk of many diseases. Experimental studies have shown their use as bifidogenic agents, stimulating the immune system of the body, decreasing the pathogenic bacteria in the intestine, relieving constipation, decreasing the risk of osteoporosis by increasing mineral absorption, especially of calcium, reducing the risk of atherosclerosis by lowering the synthesis of triglycerides and fatty acids in the liver and decreasing their level in serum. These fructans modulate the hormonal level of insulin and glucagon, thereby regulating carbohydrate and lipid metabolism by lowering the blood glucose levels; they are also effective in lowering the blood urea and uric acid levels, thereby maintaining the nitrogen balance. Inulin and oligofructose also reduce the incidence of colon cancer. The biochemical basis of these beneficial effects of inulin and oligofructose have been discussed. Oligofructose are non cariogenic as they are not used by Streptococcus mutans to form acids and insoluble glucans that are the main culprits in dental caries. Because of the large number of health promoting functions of inulin and oligofructose, these have wide applications in various types of foods like confectionery, fruit preparations, milk desserts, yogurt and fresh cheese, baked goods, chocolate, ice cream and sauces. Inulin can also be used for the preparation of fructose syrups.

Dietary oligofructose lessens hepatic steatosis, but does not prevent hypertriglyceridemia in obese zucker rats

We studied the influence of oligofructose (OFS), a nondigestible fructan, on lipid metabolism in obese fa/fa Zucker rats. The addition of 10 g/100 g OFS to the diet slowed the increase in body weight without modifying serum triglycerides or glucose concentrations after 7 wk of treatment. However, an oral load of 2 g glucose and 5 g corn oil/kg body weight increased triglyceridemia more in OFS-fed rats than in control rats. After 10 wk, OFS decreased the hepatic concentration of triglycerides 57% relative to controls. The less severe steatosis was confirmed by histologic analysis. Among the key enzymes involved in fatty acid synthesis and esterification, only malic enzyme activity was significantly lower in OFS-fed rats than in controls. The epididymal fat mass was significantly lower in OFS-fed rats. In conclusion, dietary enrichment with OFS can counteract both the fat mass development and the hepatic steatosis that occur in obese Zucker rats. Future studies will be designed to clarify in obese animals the influence of dietary OFS on postprandial triglyceridemia, which is an important variable associated with the development of atherosclerosis in humans, and to analyze the biochemical mechanism underlying the "hepatoprotective" effect of OFS.

The effect of the daily intake of inulin on fasting lipid, insulin and glucose concentrations in middle-aged men and women

The present study was carried out to examine the effect of the daily intake of 10 g inulin on fasting blood lipid, glucose and insulin levels in healthy middle-aged men and women with moderately raised total plasma cholesterol (TC) and triacylglycerol (TAG) levels. This study was a double-blind randomized placebo-controlled parallel study in which fifty-four middle-aged subjects received either inulin or placebo for a period of 8 weeks. Fasting blood samples were collected before the supplementation period (baseline samples 1 and 2, separated by 1 week) and at weeks 4 and 8, with a follow-up at week 12. Compared with baseline values, insulin concentrations were significantly lower at 4 weeks (P < 0.01) in the inulin group. There was a trend for TAG values, compared with baseline, to be lower in the inulin group at 8 weeks (P < 0.08) returning to baseline concentrations at week 12. On comparison of the inulin and placebo groups, the fasting TAG responses over the 8-week test period were shown to be significantly different (P < 0.05, repeated measures ANOVA), which was largely due to lower plasma TAG levels in the inulin group at week 8. The percentage change in TAG levels in the inulin group during the 8-week study was shown to correlate with the initial TAG level of the subjects (rs -0.499, P = 0.004). We therefore conclude that the daily addition of 10 g inulin to the diet significantly reduced fasting insulin concentrations during the 8-week test period and resulted in lower plasma TAG levels, particularly in subjects in whom fasting TAG levels were greater than 1.5 mmol/l. These data support findings from animal studies that fructans influence the formation and/or degradation of TAG-rich lipoprotein particles, and the insulin data are also consistent with recent studies showing attenuation of insulin levels in fructan-treated rats.