We have demonstrated previously that a diet containing skimmed milk (SM) fermented by Lactobacillus gasseri SBT2055 (LGSP) reduces adipocyte size in Sprague–Dawley rats. Two experiments were conducted to extend these observations in order to elucidate the mechanism involved. In experiment 1, lean and obese Zucker rats were fed a diet containing SM or LGSP for 4 weeks. The LGSP diet, compared with the SM diet, resulted in lowering of the mesenteric adipose tissue weight (23 %; P < 0·05), adipocyte sizes (28 %; P < 0·001) and serum leptin concentration (36 %; P < 0·05) in lean rats. Obese Zucker rats did not display such dietary effects. Only the number of smaller adipocytes was increased (P < 0·05) by the LGSP diet in the subcutaneous adipose tissue of obese rats. The LGSP diet significantly reduced the serum and hepatic cholesterol in rats. In addition, the LGSP diet led to an increased excretion of faecal fatty acids and total neutral faecal sterols in both rat strains. In experiment 2, Sprague–Dawley rats with permanent cannulation of the thoracic duct were fed either the SM or LGSP diets and their lymph was collected. The LGSP diet lowered the maximum transport rate of TAG and phospholipids. These results indicate that fermented milk regulates adipose tissue growth through inhibition at the stage of dietary fat absorption in lean Zucker rats.

The aim was to investigate how blueberry husks and/or mixtures of probiotic strains (Lactobacillus crispatus DSM16743, L. gasseri DSM16737 and L. plantarum DSM15313 (LABmix), or Bifidobacterium infantis DSM15159 and DSM15161 (BIFmix)) affect colonic fermentation, caecal counts of lactobacilli, bifidobacteria and Enterobacteriaceae, body weight gain, and blood concentrations of carboxylic acids (CA) and ammonia in rats. Dietary fibres in blueberry husks were fermented to 61 % in colon, and the elevated faecal excretion of fibre and protein contributed to the high faecal bulking capacity (1·3). The caecal pool of CA was higher in rats fed blueberry husks than the fibre-free control (P < 0·05), and the propionic acid proportion was higher in the distal colon than in the control group (P < 0·05). Probiotics lowered the caecal amount of CA when added to blueberry husks (P < 0·001), while the propionic acid proportion was higher with LABmix (P < 0·01) than blueberry husks only. The propionic acid and butyric acid concentrations in blood were higher in rats fed blueberry husks and probiotics than those fed blueberry husks only (P < 0·01), implying that the absorption of these acids was facilitated by the bacteria. The caecal counts of lactobacilli, bifidobacteria and Enterobacteriaceae were lower in rats fed blueberry husks than the control diet (P < 0·05). The body weight gain was partly influenced by the caecal tissue and contents weights, and BIFmix decreased the ammonia concentration in blood (P < 0·05). We conclude that colonic fermentation is differentially affected by dietary fibre and probiotics, which may be of importance when developing foods with certain health effects.

Despite adequate scientific evidence of the potential benefits of probiotics to human health or disease prevention, their contribution to the growth of adipose tissue remains to be established. Four-week-old male Sprague-Dawley rats were fed a diet containing skim milk (control diet) or skim milk fermented by Lactobacillus gasseri SBT2055 (LGSP diet) for 4 weeks. Their body weight gain, adipose tissue weight, adipocyte size distribution profile, blood and hepatic lipids, and serum leptin, glucose and adiponectin levels were determined. There was a significant reduction in average adipocyte size in mesenteric white adipose tissue (P = 0·004). Moreover, the rats fed the LGSP diet displayed greater numbers of small adipocytes from mesenteric and retroperitoneal adipose tissues than did those on the control diet. Whereas adiponectin concentrations did not differ between the groups, serum leptin concentrations were decreased to 32 % in the LGSP diet group compared with the control group. Concentrations of serum glucose and lipids, and liver lipids, except for the liver TAG level, were similar in the two groups. These results indicate a possible role for a fermented milk product in the regulation of adipose tissue growth.

In in vivo study on 24 weaned piglets (8 per group), the survival rates of human isolates Lactobacillus gasseri K7 and LF221 were quantified by selective enumeration on MRS agar with rifampicin, and the presence of both strains in intestinal mucosa was examined. Faeces from individual animals were analysed for the number (cfu/g) of coliforms, lactobacilli, clostridia and both of the two probiotic strains during 2-weeks probiotic application period (5×1010 cfu of individual strain/day) and 1 week after the probiotic treatment was ceased. Samples of duodenum, jejunum and ileum of sacrificed animals (5th or 20th day) were also examined microbiologically. A great variability in the microflora of faeces and mucosa was observed even between equally treated animals. The survival of both Lb. gasseri strains was established by their detection in the faeces (2·5×105 to 3·3×105 cfu of K7 strain/g faeces; 4·5×105 to 5×105 cfu of LF221 strain/g). In two animals, the LF221 or K7 viable cells were found in the faeces 6 d after ceasing probiotic application. In both animals from the group fed with Lb. gasseri K7 that were sacrificed 5 d after weaning, the presence of K7 strain was found either in the mucosa of duodenum (140 cfu/10 cm2) and jejunum (170 cfu/10 cm2) or in the ileum (1600 cfu/10 cm2). LF221 cells were detected in the ileal mucosa of one piglet (820 cfu/10 cm2). The results demonstrated the capability of both tested strains of in vivo adhesion to intestinal mucosa and of temporary colonisation of the piglets' intestine.

The effects of Lactobacillus gasseri JCM 1131T on isoflavonoid levels within the caecum and plasma were assessed in adult mice. Male 5-week-old mice were fed an AIN 93M diet for 30 d. Two groups of mice were administered either L. gasseri JCM 1131T (the LGI group) or physiological saline solution (the control (CI) group) daily for 5 d before dissection. The plasma daidzein concentration was significantly higher in the LGI group, however, their plasma equol concentration was significantly less than in the CI group. The total amount of equol present as aglycone in the caecum was significantly greater in the CI group, but there was no significant difference in the total daidzein present as caecal aglycone. In an in vitro incubation of daidzin with the faecal flora of mice, the equol concentration was significantly higher in the CI group. The numbers of lactobacilli present were significantly higher in the LGI group. The present data suggest that the administration of L. gasseri is likely to influence the effect of isoflavonoids on the host via changes in the gastrointestinal environment.

The production of similar or even identical bacteriocins by different lactic acid bacteria is not a rare event. To take advantage of this finding, genetic determinants of the Lactobacillus K7 bacteriocins were tested for putative homologies with previously described bacteriocins of the Lactobacillus acidophilus group through polymerase chain reaction (PCR). Among specific primer pairs of seven known bacteriocins, derived from their respective sequences, only acidocin LF221 A and B primers amplified fragments in chromosomal DNA of K7 strain that revealed strong similarity over small regions of LF221 bacteriocins. Treatment of Lactobacillus K7 with ethidium bromide and mitomycin C was ineffective in generating non-bacteriocinogenic derivatives and had no impact on plasmid loss either. Classification studies elucidated Lactobacillus K7 as a member of the Lactobacillus gasseri species.

The effects of administration of Lactobacillus gasseri SBT0270 on serum lipids and bile acids, faecal bile acids and microflora were estimated in hypercholesterolemic rats. An effective dose of strain SBT0270 to exert its hypocholesterolemic effect was 109 viable cells/d. The dose of 109 cells/d did not affect the faecal coliform counts, but the number of faecal lactobacilli in rats fed this dose was significantly higher than that in the control group observed at the end of feeding period. Hypocholesterolemic effect of Lb. gasseri SBT0270 was attributed to its ability to suppress the reabsorption of bile acids into the enterohepatic circulation and to enhance the excretion of acidic steroids in faeces of hypercholesterolemic rats.