OBJECTIVEWe examined the role of butyric acid, a short-chain fatty acid formed by fermentation in the large intestine, in the regulation of insulin sensitivity in mice fed a high-fat diet.RESEARCH DESIGN AND METHODSIn dietary-obese C57BL/6J mice, sodium butyrate was administrated through diet supplementation at 5% wt/wt in the high-fat diet. Insulin sensitivity was examined with insulin tolerance testing and homeostasis model assessment for insulin resistance. Energy metabolism was monitored in a metabolic chamber. Mitochondrial function was investigated in brown adipocytes and skeletal muscle in the mice.RESULTSOn the high-fat diet, supplementation of butyrate prevented development of insulin resistance and obesity in C57BL/6 mice. Fasting blood glucose, fasting insulin, and insulin tolerance were all preserved in the treated mice. Body fat content was maintained at 10% without a reduction in food intake. Adaptive thermogenesis and fatty acid oxidation were enhanced. An increase in mitochondrial function and biogenesis was observed in skeletal muscle and brown fat. The type I fiber was enriched in skeletal muscle. Peroxisome proliferator–activated receptor-γ coactivator-1α expression was elevated at mRNA and protein levels. AMP kinase and p38 activities were elevated. In the obese mice, supplementation of butyrate led to an increase in insulin sensitivity and a reduction in adiposity.CONCLUSIONSDietary supplementation of butyrate can prevent and treat diet-induced insulin resistance in mouse. The mechanism of butyrate action is related to promotion of energy expenditure and induction of mitochondria function.

Oligosaccharides in human milk represent a group of bioactive molecules that have evolved to be an abundant and diverse component of human milk, even though they have no direct nutritive value to the infant. A recent hypothesis proposes that they could be substrates for the development of the intestinal microflora and the mucosal immune system. The inability to determine the exact composition of these oligosaccharides limits research and the ability to understand their biological functions. Oligosaccharides isolated from the lipids and proteins of individual human milk samples were analyzed by a combination of techniques including microchip liquid chromatography mass spectrometry (HPLC-Chip/MS) and matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FT ICR MS). Accurate mass measurements obtained using an orthogonal time-of-flight (o-TOF) mass spectrometry provided oligosaccharide composition for approximately 200 individual molecular species. Comparison of HPLC-Chip/MS profiles from five different women revealed variations in milk oligosaccharide compositions. HPLC-Chip/MS profiling provides a method for routinely identifying milk oligosaccharides. Tandem MS in combination with exoglycosidase digestion provides unambiguous differentiation of structural isomers.

It has been proposed that human milk oligosaccharides (HMO) function as a prebiotic for bifidobacteria, yet this activity has not been adequately investigated. In this study, Bifidobacterium infantis was shown to ferment purified HMO as a sole carbon source, while another gut commensal, Lactobacillus gasseri, did not ferment HMO. Our results support the hypothesis that HMO selectively amplify bacterial populations in the infant intestine.Human milk is unique because of the high concentration and diversity of human milk oligosaccharides (HMO). HMO are the third most abundant component of human milk (9), and at least 130 different masses have been identified (14). In vitro, HMO are resistant to catabolism by host hydrolases (3, 4), and based on the mass balance between consumption and excretion, Chaturvedi et al.(1) calculated that 97% of HMO pass through infants undigested, while Coppa et al. (2) estimated that 40 to 50% of HMO pass through infants undigested.A prebiotic function was attributed to HMO based on studies done in the 1950s with Bifidobacterium bifidus subsp. pennsylvannicus (6, 7), yet the measurements were based on growth enhancement, not fermentability, as the media contained lactose. Direct fermentation of HMO by Bifidobacterium spp. and/or Lactobacillus spp. has not been demonstrated yet, and there are many questions about the metabolic fate of these molecules. Do subpopulations mediate specific functions, such as pathogen binding or prebiotic activity? Are specific bacterial species required for catabolism in the gut? The goals of this investigation were to determine the fermentability of HMO by two representative species of breast-fed infant microbiota, Bifidobacterium infantis and Lactobacillus gasseri (8,10) and to characterize the changes in the HMO after bacterial growth. Determination of the biological basis underlying the HMO abundance in human milk should be of general interest in human nutrition (15).Pooled milk was provided by the Mother's Milk Bank of San Jose, CA, and the Mother's Milk Bank of Austin, TX. Oligosaccharides were extracted as described by Gnoth et al. (5), with modifications. One liter of milk was centrifuged at 5,000 ϫ g for 30 min at 4°C, and the fat was removed. Ethanol (2 liters) was added, and the solution was incubated overnight at 4°C. The precipitate was removed by centrifugation at 5,000 ϫ g for 30 min at 4°C, and the solvent was removed by rotary evaporation. The concentration of the solution was adjusted to 0.05 M with phosphate buffer (pH 6.8), 3,000 U ␤-galactosidase (Kluyveromyces fragilis) was added, and the solution was incubated for 1 h at 37°C. Then the solution was extracted with 4 volumes of chloroform-methanol (2:1, vol/vol), and the aqueous layer was collected.As described by Redmond and Packer (12), monosaccharides and disaccharides were removed by selective adsorption of HMO, using solid-phase extraction with graphitized nonporous graphitized carbon cartridges (Supelco Inc., Bellefonte, PA). The oligosaccharides that were retained were eluted wit...

This study was conducted to investigate the catabolism and fermentation of human milk oligosaccharides (HMO) by individual strains of bifidobacteria. Oligosaccharides were isolated from a pooled sample of human milk using solid-phase extraction, and then added to a growth medium as the sole source of fermentable carbohydrate. Of five strains of bifidobacteria tested (Bifidobacterium longum biovar infantis, Bifidobacterium bifidum, Bifidobacterium longum biovar longum, Bifidobacterium breve, and Bifidobacterium adolescentis), B. longum bv. infantis grew better, achieving triple the cell density then the other strains. B. bifidum did not reach a high cell density, yet generated free sialic acid, fucose and N-acetylglucosamine in the media, suggesting some capacity for HMO degradation. Thin layer chromatography profiles of spent fermentation broth suggests substantial degradation of oligosaccharides by B. longum bv. infantis, moderate degradation by B. bifidum and little degradation by other strains. While all strains were able to individually ferment two monosaccharide constituents of HMO, glucose and galactose, only B. longum bv. infantis and B. breve were able to ferment glucosamine, fucose and sialic acid. These results suggest that as a potential prebiotic, HMO may selectively promote the growth of certain bifidobacteria strains, and their catabolism may result in free monosaccharides in the colonic lumen.