Repeated dose oral toxicological evaluation of concentrated barley beta-glucan in CD-1 mice including a recovery phase

Glucose-lowering effects of a synbiotic combination containing Pediococcus acidilactici in C. elegans and mice

AIMS/HYPOTHESIS

Modulation of gut microbiota has emerged as a promising strategy to treat or prevent the development of different metabolic diseases, including type 2 diabetes and obesity. Previous data from our group suggest that the strain Pediococcus acidilactici CECT9879 (pA1c) could be an effective probiotic for regulating glucose metabolism. Hence, the objectives of this study were to verify the effectiveness of pA1c on glycaemic regulation in diet-induced obese mice and to evaluate whether the combination of pA1c with other normoglycaemic ingredients, such as chromium picolinate (PC) and oat β-glucans (BGC), could increase the efficacy of this probiotic on the regulation of glucose and lipid metabolism.

METHODS

Caenorhabditis elegans was used as a screening model to describe the potential synbiotic activities, together with the underlying mechanisms of action. In addition, 4-week-old male C57BL/6J mice were fed with a high-fat/high-sucrose diet (HFS) for 6 weeks to induce hyperglycaemia and obesity. Mice were then divided into eight groups (n=12 mice/group) according to dietary supplementation: control-diet group; HFS group; pA1c group (1010 colony-forming units/day); PC; BGC; pA1c+PC+BGC; pA1c+PC; and pA1c+BGC. Supplementations were maintained for 10 weeks. Fasting blood glucose was determined and an IPGTT was performed prior to euthanasia. Fat depots, liver and other organs were weighed, and serum biochemical variables were analysed. Gene expression analyses were conducted by real-time quantitative PCR. Sequencing of the V3-V4 region of the 16S rRNA gene from faecal samples of each group was performed, and differential abundance for family, genera and species was analysed by ALDEx2R package.

RESULTS

Supplementation with the synbiotic (pA1c+PC+BGC) counteracted the effect of the high glucose by modulating the insulin-IGF-1 signalling pathway in C. elegans, through the reversal of the glucose nuclear localisation of daf-16. In diet-induced obese mice, all groups supplemented with the probiotic significantly ameliorated glucose tolerance after an IPGTT, demonstrating the glycaemia-regulating effect of pA1c. Further, mice supplemented with pA1c+PC+BGC exhibited lower fasting blood glucose, a reduced proportion of visceral adiposity and a higher proportion of muscle tissue, together with an improvement in the brown adipose tissue in comparison with the HFS group. Besides, the effect of the HFS diet on steatosis and liver damage was normalised by the synbiotic. Gene expression analyses demonstrated that the synbiotic activity was mediated not only by modulation of the insulin-IGF-1 signalling pathway, through the overexpression of GLUT-1 and GLUT-4 mediators, but also by a decreased expression of proinflammatory cytokines such as monocyte chemotactic protein-1. 16S metagenomics demonstrated that the synbiotic combinations allowed an increase in the concentration of P. acidilactici, together with improvements in the intestinal microbiota such as a reduction in Prevotella and an increase in Akkermansia muciniphila.

CONCLUSIONS/INTERPRETATION

Our data suggest that the combination of pA1c with PC and BGC could be a potential synbiotic for blood glucose regulation and may help to fight insulin resistance, diabetes and obesity.

Therapeutic effects of different doses of prebiotic (isolated from Saccharomyces cerevisiae) in comparison to n-3 supplement on glycemic control, lipid profiles and immunological response in diabetic rats

BACKGROUND

The regular intake of fiber generates numerous health benefits. However, the efficacy depends on the duration of consumption and the ingested dose. Studies investigating the optimal dose are of interest to enable the inclusion of fiber in the routine treatment of diabetic patients.

OBJECTIVE

We aimed to evaluate the effects of different doses of β-glucan (BG-isolated from Saccharomyces cerevisiae), in comparison to n-3 supplement, on the inflammatory and metabolic parameters of Wistar rats induced to diabetes by streptozotocin.

METHODS

Forty animals were randomly divided into six groups receiving 0 mg/kg, 10 mg/kg, 20 mg/kg, or 40 mg/kg BG daily for 4 weeks or fish oil derivative [1000 mg/kg of omega-3 fatty acids (n-3)] for the same period. One additional group was composed of healthy controls. Serum metabolic and immunological parameters were evaluated by colorimetric and ELISA assays respectively. Histopathological analysis of the liver, small intestine and pancreas were also conducted. Significant changes due to BG intake were set into regression models with second-degree fit in order to estimate the optimal BG dose to achieve health benefits.

RESULTS

The animals that ingested BG had lower food and water intake (p < 0.05) than the negative control group (0 mg/kg). However, consumption was still elevated in comparison to healthy controls. Blood glucose and serum levels of total cholesterol, LDL-c, and TG (p < 0.05) reduced in comparison to diabetic animals without treatment (better or similar to n-3 group depending on dose), but did not reach normal levels (in comparison to healthy controls). HDL-c was not different (p > 0.05) among all groups. These reductions were already seen with the lowest dose of 10 mg/kg. On average, the serum levels of the hepatic enzymes ALT and AST were 40% and 60% lower in the BG groups in comparison to diabetic animals without treatment (better results than n-3 group). The group receiving 40 mg/kg reached similar values of healthy controls for ALT; whereas the same result occurred from the dose of 10 mg/kg for AST. The ideal dose, estimated from the mean of all metabolic parameters was approximately 30 mg/kg/day. Regarding the immunological profile, TNF-α significantly decreased in the BG groups compared to controls (p < 0.05), reaching better values than n-3 group and similar to healthy controls. No significant differences were found between the groups in IL-1β or IL-10 (p > 0.05). No histological changes were found in the pancreas, liver, or intestine due to treatment among diabetic animals.

CONCLUSIONS

BG significantly reduced blood glucose as well as serum total cholesterol, LDL-c and TG. There was a hepatoprotective effect due to the reduction in ALT and AST and a reduction in TNF-α, indicating a modulation of the immune response. In general, BG effects were better than n-3 supplement (or at least comparable) depending on the dose.

Anti-clastogenic effect of b-glucan extracted from barley towards chemically induced DNA damage in rodent cells

b-Glucan (BG) was tested in vitro to determine its potential clastogenic and/or anti-clastogenic activity, and attempts were made to elucidate its possible mechanism of action by using combinations with an inhibitor of DNA polymerase. The study was carried out on cells deficient (CHO-k1) and cells proficient (HTC) in phases I and II enzymes, and the DNA damage was assessed by the chromosomal aberration assay. BG did not show a clastogenic effect, but was anti-clastogenic in both cell lines used, and at all concentrations tested (2.5, 5 and 10 mg/mL) in combination with damage inducing agents (methylmethane sulfonate in cell line CHO-k1, and methylmethane sulfonate or 2-aminoanthracene in cell line HTC). BG also showed a protective effect in the presence of a DNA polymerase b inhibitor (cytosine arabinoside-3-phosphate, Ara-C), demonstrating that BG does not act through an anti-mutagenic mechanism of action involving DNA polymerase b.

A novel soluble β-1,3-D-glucan salecan reduces adiposity and improves glucose tolerance in high-fat diet-fed mice

Salecan is a recently identified water-soluble viscous extracellular β-1,3-D-glucan polysaccharide from an Agrobacterium species. It is a high-molecular-mass polymer (about 2 × 10⁶ Da) and composed of a linear chain of glucosyl residues linked through a repeat unit of seven β-(1,3) and two α-(1,3) glucosidic bonds. In the present study, we examined the effects of dietary Salecan fed at 2 and 5 % in a high-fat diet (64 % energy) in C57BL/6J mice. After 6 weeks, mice fed 2 and 5 % Salecan had significantly lower body weight, fat mass and percentage of body fat mass compared with those fed a high-fat cellulose (control) diet. Both the Salecan groups significantly and dose-dependently improved glucose tolerance, with a 9 and 26 % reduction of glucose AUC, respectively. Liver and adipose tissue weights were also significantly decreased by the Salecan treatment. Supplementation with 5 % Salecan led to lower serum TAG, total cholesterol (TC) and HDL-cholesterol (52, 18 and 19 %, respectively) and lower hepatic TAG by 56 % and TC by 22 % compared with the high-fat cellulose control group. Dietary Salecan intake caused an obvious elevation of fat in the faeces. Supplementation with Salecan disturbed bile acid-promoted emulsification and reduced the size of emulsion droplets in vitro. These results indicate that Salecan decreases fat absorption, improves glucose tolerance and has biologically important, dose-related effects on reducing high-fat diet-induced obesity.

Immunomodulatory activities and subacute toxicity of a novel β-glucan from Paenibacillus polymyxa JB115 in rats

Subacute toxicity and immunopharmacological activities of β-glucan from P. polymyxa JB115 was evaluated in a 28-day feeding study in rats. The white blood cell count, red blood cell count, hematocrit, hemoglobin, thrombocytes (THR) and thrombocytocrit were significantly higher in male fed with β-glucan than control rats and the insignificant lower eosinophil count, mean corpuscular volume, mean cell hemoglobin and uninfected THR (uTHR) levels were observed in male whereas no marked changes in female rats. No other significant differences in serum chemistry and liver, kidney, and spleen weights were observed. The pathological changes and other abnormal indicators were not detected in urine. Female rats fed with diet supplemented with 0.01% β-glucan also showed marked increase in the percentage of blood cytotoxic T-lymphocytes compared to that of the control group while not significant differences in the percentage of blood B-lymphocytes. No adverse effects on general condition and behavior, growth, feed and water consumption and feed conversion efficiency were found. The results suggest that consumption of the novel β-1, 3/1, 6-glucan from P. polymyxa JB115 was not associated with any obvious toxic effects in rats, indicating its safety as a potential immunostimulant or as an adjuvant of some animal vaccines.

Micronucleus Test of Polycan™, β-Glucan Originated from Aureobasidium, in Bone Marrow Cells of Male ICR Mice

In this research the genotoxic effect of Polycan™ β-glucans originated from Aureobasidium pullulans SM-2001, was evaluated using the mouse micronucleus test. Polycan™ was administered once a day for 2 days by oral gavage to male ICR mice at doses of 1000, 500 and 250 mg/kg. Cyclophosphamide was used as a known genotoxic agent in a positive control group. The appearance of a micronucleus is used as an index for genotoxic potential. The results obtained indicated that Polycan™ shows no genotoxicity effect up to 1000 mg/kg dosing levels. In addition, it is also considered that there were no problems from cytotoxicity of Polycan™ tested in this study because the polychromatic erythrocyte ratio was detected as > 0.47 in all tested groups.

Phosphoinositides Signaling and Epithelial-to-Mesenchymal Transition: Putative Topic for Basic Toxicological Research

Ptdlns(4,5)P₂ is a key cellular phosphoinositide that localizes in separate and distinctive pools in subcellular membrane and vesicular compartments. In membranes, Ptdlns(4,5)P₂ acts as a precursor to second messengers and is itself a main signaling and targeting molecule. Specific subcellular localization of type I PIP kinases directed by interacting with specific targeting module differentiates Ptdlns(4,5)P₂ production in a spatial and temporal manner. Several lines of evidences support the idea that Ptdlns(4,5)P₂ is generated in very specific pools in a spatial and temporal manner or by feeding Ptdlns(4,5)P₂ directly to effectors. In this concept, the interaction of PIPKI isoforms with a specific targeting module to allow precise subcellular targeting modulates highly specific Ptdlns(4,5)P₂ synthesis and channeling overall effectors. For instance, localization of PIPKIγ661 to focal adhesions by an interaction with talin results in spatial and temporal production of Ptdlns(4,5)P₂, which regulates EGF-stimulated directional cell migration. In addition, Type lγ PIPK is targeted to E-cadherin in cell adherence junction and plays a role in controlling dynamics of cell adherence junction and endocytosis of E-cadherin. Characterizing how PIP kinase isoforms are regulated by interactions with their targeting modules, as well as the mechanisms by which their product, Ptdlns(4,5)P₂, exerts its effects on cellular signaling processes, is crucial to understand the harmonized control of numerous cellular signaling pathways. Thus, in this review the roles of the Ptdlns(4)P(5) kinases and Ptdlns(4,5)P₂ were described and critically reviewed in terms of regulation of the E-cadherin trafficking, cell migration, and formation of cell adherence junction which is indispensable and is tightly controlled in epithelial-to-mesenchymal transition process.

Oat-derived beta-glucan significantly improves HDLC and diminishes LDLC and non-HDL cholesterol in overweight individuals with mild hypercholesterolemia

OBJECTIVE

To investigate the effect of bread formulated with 6 g of beta-glucan (oat soluble fiber) on serum lipids in overweight normotensive subjects with mild to moderate hypercholesterolemia.

DESIGN

Thirty-eight male subjects [mean age 59.8 +/- 0.6 yr, mean body mass index (BMI) 28.3 +/- 0.6 kg/m(2)] who were eligible for the study ate an isocaloric diet for a 1-week period. They were then divided into 2 groups: group A (n = 19), who were maintained on American Heart Association (AHA) Step II diet, including whole wheat bread, and group B (n = 19), who were maintained on AHA Step II diet containing high levels of monounsaturated fatty acids plus bread containing 6 g of beta-glucan (Nutrim-OB) for 8 weeks. Plasma lipids and glucose were measured at baseline and after weeks 8 in all subjects. All subjects were advised to walk for 60 minutes every day.

RESULTS

There was a significant increase (upward arrow 27.8%) in plasma high density lipoprotein (HDL) cholesterol in the beta-glucan group (group A) from 39.4 +/- 2.0 to 49.5 +/- 2.1 mg/dL (P < 0.001), but there was no change in group B. There was a significant reduction in total cholesterol in the 2 groups to approximately the same extent: group A, from 232.8 +/- 2.7 mg/dL to 202.7 +/- 6.7 mg/dL; P < 0.001; and group B, from 231.8 +/- 4.3 mg/dL to 194.2 +/- 4.3 mg dL; P < 0.001. Plasma low density lipoprotein (LDL) cholesterol also decreased significantly in the two groups: group A, from 160.3 +/- 2.8 mg/dL to 133.2 +/- 5.4 mg/dL; P < 0.001; group B, from 167.9 +/- 4.3 mg/dL to 120.9 +/- 4.3 mg/dL; P < 0.001; however, the beta-glucan fortified diet was significantly more effective (downward arrow 27.3% vs. downward arrow 16.8%; P < 0.04). There was a small and insignificant reduction in plasma very LDL (VLDL) cholesterol and triglycerides in the two groups. Similarly, non-HDL cholesterol levels were also decreased, with beta-glucan diet producing significantly higher effect (downward arrow 24.5% vs. downward arrow 16.1%; P < 0.04). The beta-glucan diet also produced higher reduction in total cholesterol/HDL cholesterol ratio (downward arrow 33.3% vs. downward arrow 8.4%; P < 0.003) and LDL cholesterol/HDL cholesterol ratio (downward arrow 42.1% vs. downward arrow 13.3%; P < 0.001) than the diet without beta-glucan. The beta-glucan diet also decreased fasting plasma glucose (P < 0.4), whereas the other diet had no effect. Interestingly, both diets reduced body weight and BMI significantly, with beta-glucan diet having a greater effect.

CONCLUSIONS

Six grams of beta-glucan from oats added to the AHA Step II diet and moderate physical activity improved lipid profile and caused a decrease in weight and, thus, reduced the risk of cardiovascular events in overweight male individuals with mild to moderate hypercholesterolemia. The diet with added beta-glucan was well accepted and tolerated.