AbstractDuringthe past three decades alteration in gut microbiota grown to be an issue of interestby literature due to their impact on human health, which have been establishedto be altered by diet. Prebiotics are the main effectors on it. Someoligosaccharides can demonstrate a prebiotic effect. Bifidobacteria is apredominant part of human gut microbiota which decreased by age. Prebioticmixture of galacto-oligosaccharides (GOS) and fructo-oligosaccharides (FOS)found to mimics the molecular size distribution of human milk oligosaccharides.
Commercially existing prebiotics also encourage the growth of pathogenic, gramnegative anaerobes and E.coli.which came with the necessity of developing an innovative selective prebiotics.
In human studies GOSs support the growth of bifidobacteria in well-being young,older, and overweight, and in patients with metabolic syndrome, type 2 diabetes,and irritable bowel syndrome. GOSs fermentationand its bifidogenic effect lead to the production of short chain fatty acids (SCFAs),which may sustain positive health effects. Bifidobacterium spp. producemainly the short chain fatty acid acetate and lactate.
SCFAs found to promotehuman health by enhancing immune system, delay metabolic diseases, supportwell-being in mature population, and reduce the risk factors associated withshifts in the colonic microbiota and fermentation resultant of ageing. Abbreviation Full term CFU Colony Forming Unit DP Degree of Polarization FOSs Fructo-oligosaccharides GOSs Galacto-oligosaccharides IL Interleukin LPS Lipopolysaccharides NK Natural Killer SCFAs Short Chain Fatty Acids Keywords: Prebiotics, Galacto-oligosaccharides (GOSs),Bifidobacteria, Intestine, Gut, MicrobioticaBifidogenicEffect of Galacto-Oligosaccharides IntroductionDuring the past three decades alterationin gut microbiota grown to be an issue of interest by literature due to theirimpact on human health, which have been found to be altered by diet. These microbiotaferment undigested dietary sources of carbohydrates and proteins in the humanintestine (Walton et al., 2012). Prebiotics are the mainsupplements used to alter the composition of the intestinal microbiota by thought-provokingthe growth of beneficial microorganisms and inhibition the growth of gramnegative and pathogenic bacteria (Musilova et al., 2014). Commerciallyavailable prebiotics also promote the growth of pathogenic gut bacteria such asgram negative anaerobes and E.
coli.which came with the necessity of developing an innovative selective prebiotics.Anumber of oligosaccharides established to demonstrate a prebiotic effectincluding inulin, fructo-oligosaccharides (FOSs) and galacto-oligosaccharides(GOSs). Prebiotic mixture of GOS and FOS canmimics the molecular size distribution of human milk oligosaccharides (Musilovaet al., 2014). Over and over again GOSs found to target Bifidobacteriumspp. due to the size and structure of these oligosaccharides and inhibit thegrowth of pathogenic gut bacteria such as gram negative anaerobes and E.
coli. (Morel et al., 2015; Vulevic et la., 2008;Vulevic et al.
, 2015; Walton et al., 2012). Bifidobacteria had defined as abeneficial bacterial specieses that enhance human health (Musilova et al.
,2014). Galacto-oligosaccharidePrebioticdefined as “a selectively fermented ingredient that allows specificchanges, both in the composition and/or activity in the gastrointestinalmicrobiota that confers benefits upon host well-being and health” (Musilovaet al., 2014). The previous concept can be applicated on the GOSs asinnovative prebiotics.
In human studies GOSs promote the growth ofbifidobacteria in healthy young, older, and overweight, and among patients withirritable bowel syndrome, type 2 diabetes, and metabolic syndrome (Morel et al., 2015; Vulevic et la., 2008;Vulevic et al.
, 2015; Walton etal., 2012).Together degree of polymerization (DP) and the dose of non-digestibleoligosaccharides can alter their effect on the gut microbial composition andactivity, and the subsequent associated physiologic and health effects (Morel etal., 2015; Vulevic et la., 2008). DP in manufactured GOSs productsdepend on the reverse ?-Galactosidase that used in the synthesis (Vulevic etal., 2015). Bifidobacteriumspp.
Bifidobacteria found to be a predominantpart of neonates and infants gut microbiota which decreased with age whichpromoted by human oligosaccharides. Though, bifidobacteria still characterizedas an important part of the adult gut microbiota. Bifidobacterium spp.produce mainly the short chain fatty acids acetate and lactate depending on the substrate and identified to enhancebutyrate production via cross-feeding with butyrogenic microorganisms (Musilova et al., 2014). Galacto-oligosaccharideand Bifidobacterium spp. InteractionVulevicet al. (2015), double blind, placebo (matodextrin)-controlled study, foundthat 5.
5 g GOSs daily supplementation for 10 weeks in elderly group led to asignificant increase in bifidobacteria and its related lactic acid in feces. Musilovaet al., 2014 also found that consumption of a mixture of 9 g GOSs and 1 gmaltodextrin daily for 5 days had significantly increased bifidobacteria countin feces from 9.45 to 9.83 log colony-forming units (CFU)/g and decreased the E.
coli count from 7.23 to 6.28 log CFU/g. Another study by Walton et al.(2012), 4 g supplement of GOSs twicedaily led to significantly more fecal bifidobacteria 9·16±1·09 log10 CFU/g ascompared to the placebo: 8·64±0·95 log10 CFU/g (P =0·024) in women above 50years of age. In a double-blind,placebo-controlled, crossover study, 44 elderly subjects were randomly allocatedto receive 5.5 g/d B-GOS or placebo for 10 wk, then went through a 4-wk washoutperiod, and after that switched to the other treatment for the final 10 wk (Vulevicet la., 2008).
The group supplemented with B-GOS showed a significantly increase in thenumbers of beneficial bacteria, mainly bifidobacteria and decreased the numbersof pathogenic bacteria including E.coli and Desulfovibrio spp. comparedwith the baseline and placebo (Vulevic etla., 2008).
Health impact of bifidogenic effect ofGOSs Thecontrol of intestinal microbial composition by the use of prebiotics have thehealth effect by prevention of constipation or diarrehea, modulation of the metabolismof gut microorganisms, cancer prevention, enhanced mineral adsorption, enhancedlipid metabolism, and immunomodulatory properties (Musilova et al.,2014). These health effect associated with microbiota actionsthat related to the improved expression of binding proteins, short-chain fattyacids (SCFAs) production and the related decrease in colon PH (Musilovaet al., 2014). UP to 95% ofSCFAs produced of carbohydrate fermentation by microbiota may be absorbed and metabolizedby human body (Musilova et al., 2014).
Another supposed mechanism that increasedin SCFAs promote gut peptide secretionand as a consequence control appetite and food intake (Morel et al.,2015). Morel et al. 2015, found that subjectssupplemented either with a mix of ?-GOSs of different degrees of polymerization or with aformula rich in DP2, DP3, or DP4 for 15day compared with control group showed a significant decrease in hunger, desireto eat, and prospective consumption, while greater satiety and fullness wereobserved. Bifidobacteriais known to improve barrier function which may reduce inflammatory compoundssuch as intestinal lipopolysaccharides (LPS). In Morel et al. (2015), LPSlevels was significantly lower after ?-GOSintake for 15 days.
This study found a significant (P < 0.001) negativecorrelation (r = –0.57) between GOSs dose and changes in plasma LPS. Alsobifidobacteria can promote immune response by its effect on the regulation ofT-cell.
Adding to that the SCFA acetate produced by bifidobacteria has reportedto activate natural killer (NK) cells and enhance the capability of gutepithelial cells (Vulevic et al., 2015). Also supplementation with GOSsin elderly have showed a significant increase in phagocytosis, NK cellactivity, and the production of anti-inflammatory cytokine interleukin-10(IL-10) and significant reduction in proinflammatory cytokines (IL-6, IL-1?,and tumor necrosis factor-?) production (Vulevic et la., 2008). ConclusionConsumptionof GOSs from natural sources or as prebiotics can be used as a selective ingredientto beneficially alter gut microbiota by its bifidogenic effect which in turncan inhibit the growth of pathogenic and gram negative bacteria such as E.
coli. The alteration in the gut microbiota mainly the increase ofbifidobacteria and other beneficial microorganisms can promote human health, supportwell-being in mature population, and reduce the risk factors associated withshifts in the colonic microbiota and fermentation resultant of ageing.