MicroRNAs (miRNAs) have emerged as important regulators of lipid metabolism. Recent studies have suggested synbiotics may modulate miRNA expression and lipid metabolism. This study aimed to investigate the effects of synbiotic supplementation on circulating miR-27a, miR-33a and lipid parameters in patients with dyslipidaemia. Fifty-six eligible participants were randomly allocated to receive either synbiotic or placebo sachets twice a day for 12 weeks. Each synbiotic sachet contained 3 × 1010 colony forming unit six species of probiotic microorganisms and 5 g of inulin and fructooligosaccharide as prebiotics. Serum miR-27a and miR-33a expression levels, serum lipids and apolipoproteins, the fecal concentration of short-chain fatty acids (SCFA) and Firmicutes and Bacteroidetes phyla were assessed before and after the study. Real-time PCR was used to determine the relative expression levels of miRNAs. The results showed synbiotic supplementation significantly downregulated the expression levels of miR-27a and miR-33a compared with the placebo group (P = 0·008 and P = 0·001, respectively). Furthermore, the intervention group exhibited significant improvements in serum HDL-cholesterol, small dense LDL (sdLDL-cholesterol), apoA-I and apoB-100 (P = 0·008, P = 0·006, P = 0·003, P = 0·001, respectively). The results showed a significant negative correlation between miR-33a expression levels with HDL-cholesterol, butyrate, propionate and a significant positive correlation with total cholesterol, LDL-cholesterol and sdLDL-cholesterol in the intervention group. Fecal bacteria and SCFA were significantly increased in the intervention group. This study provides evidence that synbiotic supplementation can modulate miR-27a and miR-33a expression and improve lipid metabolism in patients with dyslipidaemia.

The synbiotic effect of the oral treatment of Swiss albino mice with milk-based diets supplemented with Lactobacillus helveticus M92 and various kinds of prebiotics was investigated. Survival, competition, adhesion and colonization, as well as, immunomodulating capability of Lb. helveticus M92, in synbiotic combination, in the gastrointestinal tract (GIT) of mice, were monitored. After the mice were fed with synbiotics, the lactic acid bacteria (LAB) counts in faeces were increased and reduction of enterobacteria and sulphite-reducing clostridia was observed. Similar results were obtained in homogenates of small and large intestine of mice on the 1st and 14th day, after feeding with synbiotics. After the mice were orally given viable Lb. helveticus M92 cells, alone or in combination with prebiotic, the concentration of faecal SIgA and total serum IgA antibodies from all immunized mice were higher compared with the control. The specific humoral immune response was not evoked after oral administration, therefore their synbiotic application is suitable. Among inulin, lactulose and raffinose, Lb. helveticus M92 in combination with inulin, has shown the best synbiotic effect on intestinal and faecal microflora and immune system of mice.

Probiotics (PRO) modulate immunity in humans, while the effect of prebiotics (PRE) and synbiotics (SYN) on the human immune system are not well studied yet. The objective of this study was to investigate whether daily intake of a SYN modulates immune functions. In a randomised double-blind, placebo-controlled trial, thirty-four colon cancer patients who had undergone ‘curative resection’ and forty polypectomised patients participated. Subjects of the SYN group daily received encapsulated bacteria (1 × 1010 colony-forming units of Lactobacillus rhamnosus GG (LGG) and 1 × 1010 colony-forming units of Bifidobacterium lactis Bb12 (Bb12)) and 10 g of inulin enriched with oligofructose. Controls received encapsulated maltodextrin and 10 g of maltodextrin. Prior to intervention (T1), and 6 (T2) and 12 weeks after the start of the intervention (T3), phagocytic and respiratory burst activity of neutrophils and monocytes, lytic activity of natural killer cells and production of interleukin (IL)-2, IL-10 and IL-12, as well as tumour necrosis factor-α and interferon-γ (IFN-γ) by activated peripheral blood mononuclear cells (PBMC) were measured. In faeces, the concentrations of transforming growth factor-β1 and prostaglandin E2 were measured. IL-2 secretion by activated PBMC from the polyp group increased significantly between T1 or T2 and T3 (P < 0·05). In the cancer group, SYN treatment resulted in an increased capacity of PBMC to produce IFN-γ at T3 (P < 0·05). Other immunity-related parameters were not affected by SYN treatment, neither in the cancer nor in the polyp group. In conclusion, supplementation with this SYN has minor stimulatory effects on the systemic immune system of the two study groups. Further studies in humans should aim to focus on the gut-associated immune system.

We recently reported that synbiotic Lactobacillus casei subsp. casei together with specific substrate dextran elicited an enhancement in humoral immune response against bovine serum albumin (BSA) as a model antigen in BALB/c mice. The present study was designed to evaluate the oral immunoadjuvant effects of the synbiotic in layer chickens. Using a PCR assay, L. casei subsp. casei was detected specifically in the intestinal chyme of chickens (10d of age, Julia strain) fed ad libitum on a diet supplemented with 75mg dextran/kg (dextran-supplemented diet, DSD) and administered orally with 107 colony-forming units (CFU) L. casei subsp. casei in 0·1ml PBS with the aid of an intubation needle at 1, 2 and 3d of age. Furthermore, oral administration of 107 CFU L. casei subsp. casei at 1–3d of age significantly enhanced the production of anti-BSA antibody in DSD-fed chickens (60d of age) administered orally with 1mg BSA at 32 and 33d of age and subcutaneously with 5μg BSA at 33d of age. In addition, among bacterial numbers tested, 106 CFU L. casei subsp. casei together with dextran induced an effective increase in humoral immune response to mixed inactivated vaccines against Newcastle disease and avian infectious bronchitis, and the treatment may be advantageous in protecting against these infectious diseases in chickens in actual application. These results suggest that dietary supplementation of L. casei subsp. casei with dextran leads to immunomodulation of humoral immune responses.

Probiotics (PRO) are known to modulate immunity in animals and human subjects and to inhibit colon carcinogenesis in experimental models, but the effects of synbiotics (SYN) are not well understood. Therefore, the effects of PRO (Lactobacillus rhamnosus GG and Bifidobacterium lactis Bb12), PRE (inulin-based enriched with oligofructose, 100g/kg) and SYN (combination of PRO and PRE) on the immune system of rats were investigated in the azoxymethane (AOM)-induced colon cancer model. After 33 weeks, rats with and without AOM treatment were killed and immune cells were isolated from spleen, mesenterial lymph nodes (MLN) and Peyer's patches (PP). AOM treatment significantly reduced natural killer (NK) cell-like cytotoxicity in control rats and in PRO- and PRE-supplemented rats. SYN supplementation prevented the AOM-induced suppression of NK cell-like cytotoxicity in PP compared with control rats (P<0·01). SYN and PRE supplementation stimulated IL-10 production in PP in these rats (P<0·01) and in MLN of rats not treated with AOM (P<0·05). Interferon-γ production in PP was decreased by PRO supplementation (PRO and SYN groups combined; P<0·05). Proliferative responsiveness of lymphocytes (PP) from AOM-treated rats was suppressed in SYN-supplemented rats (P<0·01). Overall, SYN supplementation in carcinogen-treated rats primarily modulated immune functions in the PP, coinciding with a reduced number of colon tumours. PRE and PRO provided in combination as SYN may contribute to the suppression of colon carcinogenesis by modulating the gut-associated lymphoid tissue.