Resources
For further information on the human microbiome and prebiotics, see the following resources:
NIH's Human Microbiome Project website contains a great deal of information on the background and current status of the effort.
Gordon JI, et al. A rendezvous with our microbes. Proc Natl Acad Sci U S A. 2011;108 Suppl 1:4513-5. This is an excellent history of the science leading up to the current human microbiome initiative.
De Filippo C, et al. Impact of diet in shaping gut microbiota revealed by a comparative study in children from Europe and rural Africa. Proc Natl Acad Sci U S A. 2010;107(33):14691-6. This study investigates and compares the human intestinal microbiota of children eating a modern European diet to those consuming a traditional rural African diet. The Africans consumed less total calories and less fat than the Europeans, but the greatest difference was that the Africans consumed more fiber. The microbiomes isolated from feces of these children were dramatically different. Africans had significantly more Bacteriodetes than Firmicutes bacteria, while the opposite was true for European children.
Arumugam M, et al. Enterotypes of the human gut microbiome. Nature. 2011;473(7346):174-80. By combining previously published data with newly-sequenced fecal metagenomes of individuals from four countries, the authors were able to identify three distinct core clusters of microbiota that are common in all subjects. While there is much individual variation of most species, the core species cluster into 1 of 3 types, or enterotypes.
Tsukumo DM, Et al. Translational research into gut microbiota: new horizons in obesity treatment. Arq Bras Endocrinol Metabol. 2009;53(2):139-44. This important review discusses evidence that the composition of the gut microbiome is different in lean and obese individuals. Microbiota that belong to the Bacteroidetes group outnumber those of the Firmicutes group in lean individuals and in lean mice when compared to their obese counterparts. The article offers three different hypotheses to explain the relationships between the GI microbiomes and development of obesity.
Blaser MJ. Harnessing the power of the human microbiome. Proc Natl Acad Sci U S A. 2010; 107(14):6125-6. This short review offers an introduction and summary of the latest findings from the Human Microbiome project. It discusses the GI microbiome as well as other microbiota that humans harbor, such as on the skin.
Ley RE, et al. Obesity alters gut microbial ecology. Proc Natl Acad Sci U S A. 2005; 102(31):11070-5. This study assesses the microbiota in lean and obese mice. Compared with lean mice, genetically obese animals have a 50% reduction in the abundance of Bacteroidetes species and a proportional increase in Firmicutes species. Data are provided to demonstrate similarities between the GI microbiome of this mouse model and that of the human GI microbiome. The findings suggest that intentional manipulation of the bacterial community structure may be useful for regulating energy balance in obese individuals.
Goodman AL, et al. Extensive personal human gut microbiota culture collections characterized and manipulated in gnotobiotic mice. Proc Natl Acad Sci U S A. 2011; 108(15):6252-7. This paper demonstrates that the human GI microbiome can be harvested from fresh feces, frozen and banked for later use. The Microbiota can be thawed and individual species can be cloned. Further, either the harvested microbiome or individual cloned species can be transplanted into germ-free mice where they proliferate in the lower GI tract. When the mixture is transplanted, the microbiome reflects that of the human donor. Additionally, the study shows, that an individual's microbiome can be changed by diet.
Heijtz RD, et al. Normal gut microbiota modulates brain development and behavior. Proc Natl Acad Sci U S A. 2011; 108(7):3047-52. This study compared aspects of brain development and behavior between mice that were either both born and maintained in a sterile environment or were born naturally but raised in a sterile environment. The latter group harbored a GI microbiome typical of that characteristic of laboratory mice. However, the germ-free mice were void of any GI microbiota. The data indicate that gut microbiota colonization impacts both mammalian brain development and subsequent adult behavior. The results suggest that the microbial colonization process somehow initiates signaling mechanisms that affect neuronal circuits involved in motor control and anxiety behavior.
Mariat D, et al. The Firmicutes/Bacteroidetes ratio of the human microbiota changes with age. BMC Microbiol. 2009;9:123. This study gives a comparative assessment of human fecal microbiota from three age-groups: infants, adults and the elderly. Five different strains of bacteria that represent microbiota from either the Bacteriodetes group or the Firmicutes group were measured. The data indicate that the human intestinal microbiota population is different for each age examined. The authors suggest that the GI microbiome undergoes change from birth to adulthood through the ageing process.
Kootte RS, et al. The therapeutic potential of manipulating gut microbiota in obesity and type 2 diabetes mellitus. Diabetes Obes Metab. 2011 Aug 3. doi: 10.1111/j.1463-1326.2011.01483.x. [Epub ahead of print]. This review provides insight for the discovery and development of future obesity and diabetes therapeutics based on new knowledge of the GI microbiome.
Rooks MG and Garrett WS. Sharing the Bounty. The Scientist. Aug 2011; 25,8:38. GI microbiota are being linked to obesity, diabetes, bowel diseases, and colon cancer. This review for the non-scientist explains the data associating diet and GI microbiota with these diseases, particularly cancer.
Everard A, et al. Responses of Gut Microbiota and Glucose and Lipid Metabolism to Prebiotics in Genetic Obese and Diet-Induced Leptin-Resistant Mice. Diabetes. 2011 Sep 20. doi: 10.2337/db11-0227. [Epub ahead of print]. Most studies demonstrate that the GI microbiome can be manipulated by changing diet. However, such dramatic lifestyle changes are difficult for many people. This study assessed whether use of a prebiotic could also induce beneficial changes in the microbiome. Obese mice were fed a calorie rich diet and were also given the prebiotic oligofructose for 8 weeks. The mice were observed to have a change in about 100 different species of GI bacteria, with 16 changing more than 10-fold in number. These changes were associated with improved glucose regulation, decreased fat mass and decreased inflammation.