Gut microbiota

Backhed et al. (2004) reported that gut microbiota regulates fat storage. Fourteen days postconventionalization with normal microbiota, germfree mice developed more body fat and insulin resistance, with surprisingly lower food intake. These effects were seen in male and females in two different mouse strains (B6 and NMRI) (Backhed et al., 2004). 

Eight- to ten-week-old male germfree mice, which experience colonization for 14 days, showed 57% increase in total body fat with 61% increase in epididymal fat and 7% decrease in lean mass with no difference in body weight. Lipid profile did not change after colonization. A similar change was determined by colonization of germfree animals at birth or for different amount of time however, increasing colonization time did not amplify the effect on adipose tissue (Backhed et al., 2004). 

Subsequently, germfree mice were colonized only with Bacteroides theta-iotaomicron, which is predominant in gut microbiota and has the ability to degrade plant polysaccharides (Hooper et al., 2001). B. thetaiotaomicron is 

Ley et al. (2005) reported that obesity correlates with a shift in microbiota composition. Obese mice showed 50% decrease in Bacteroides and significant increase in Firmicutes (p 0.05), independent on kinship or gender. Offspring shared cecal microbiota with their mothers, independent of their ob phenotype. The authors suggest that changes in microbiota of ob/ob animals may represent an unheralded contributing factor to their fuel partitioning (Ley et al., 2005). 

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Fuller R. and Perdigon G. (eds.) (2000). Probiotics 3. Immunomodulation by the Gut Microbiota and Probiotics, Kluwer Academic Publishers, Dordrecht. 

A very importaut case is the productiou of viruleuce factors, structures that are responsible for disease in humans and other species. Take Escherichia coli for example. Most strains of this bacterium are quite harmless and, indeed, we have E. coli as a normal member of our gut microbiota. However, equipped with a set of virulence factors, we can get the E. coli strain known as H157 07, which can cause afatal infection. 

The authors proposed that butyrate producers may be protective in diseases such as type II diabetes, a fact that was supported in a study using gut microbiota transplantation from lean donors to patients with metabolic syndrome that demonstrated improved insulin sensitivity in conjunction with a rise in known butyrate producing bacteria, such as those related to Roseburia... 

The gut microbiome is also being investigated for its role in severe malnutrition states such as kwashiorkor (156,157). Indeed, a complex interplay exists between the gut microbiota and host metabolism, and likely has far-ranging implications on normal metabolic homeostasis as well as several disease states, the mechanisms of which we are just beginning to elucidate. 

The gut microbiota of termites synthesize and secrete the enzyme cellulase, which hydrolyzes the cellulose. 

LAP also appears to play several critical functions. LAP plays an important role in fatty acid absorption. LAP is able to dephosphor-ylate the phosphorylated fatty acid translocase FAT/CD36, which is thought to play a role in facilitating the transport of long-chain fatty acids into cells. In addition, Uke TNAP, LAP is able to dephos-phorylate LPS. The locahzation of the active site of LAP into the gut lumen allows LAP to protect gut barrier function and determine the composition of the gut microbiota. These functions of LAP, Uke those of TNAP, may have very important therapeutic appUcations. 

Malo MS, Alam SN, Mostafa G et al (2010) Intestinal alkaline phosphatase preserves the normal homeostasis of gut microbiota. Gut 59 1476-1484... 

Rinne MM, Gueimonde M, Kalliomaki M, Hoppu U, Salminen SJ, Isolauri E. Similar bifidogenic effects of prebiotic-supplemented partially hydrolyzed infant formula and breastfeeding on infant gut microbiota. FEMS Immunol Med Microbiol 2005 43 59-65. 

Bates, J. M., Akerlund, J., Mittge, E., and Guillemin, K. (2007) Intestinal alkaline phosphatase detoxifies lipopolysaccharide and prevents inflammation in zebrafish in response to the gut microbiota. Cell Host Microbe 2, 371-382. 

Gut microbiota Human gut (Xu and Gordon, 2003) Increased processing of polysaccharides Increased calories Increased inefficient metabolism (Backhed et al., 2004)... 

Hemarajata, P Versalovic, J., Effects of probiotics on gut microbiota Mechanisms of intestinal immu-nomodulation and neuromodulation. Therapeutic Advances in Gastroenterology (2013) 6, 39-51. 

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