Early Brain Development / Gut Microbiota

I am just beginning to look into this subject, so have no comments at this time. Links to related papers available at PNAS site.

USE THIS LINK TO READ FULL TEXT: Proc Natl Acad Sci U S A. 2011 Feb 15; 108(7): 3047–3052. Published online 2011 Jan 31. PMCID: PMC3041077 Neuroscience

Normal gut microbiota modulates brain development and behavior

Rochellys Diaz Heijtz,a,b,1 Shugui Wang,c Farhana Anuar,d Yu Qian,a,b Britta Björkholm,d Annika Samuelsson,d Martin L. Hibberd,c Hans Forssberg,b,e and Sven Pettersson

Abstract

Microbial colonization of mammals is an evolution-driven process that modulate host physiology, many of which are associated with immunity and nutrient intake. Here, we report that colonization by gut microbiota impacts mammalian brain development and subsequent adult behavior. Using measures of motor activity and anxiety-like behavior, we demonstrate that germ free (GF) mice display increased motor activity and reduced anxiety, compared with specific pathogen free (SPF) mice with a normal gut microbiota. This behavioral phenotype is associated with altered expression of genes known to be involved in second messenger pathways and synaptic long-term potentiation in brain regions implicated in motor control and anxiety-like behavior. GF mice exposed to gut microbiota early in life display similar characteristics as SPF mice, including reduced expression of PSD-95 and synaptophysin in the striatum. Hence, our results suggest that the microbial colonization process initiates signaling mechanisms that affect neuronal circuits involved in motor control and anxiety behavior.

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illus. by Benjamin Arthur

Early life environmental influences have a profound impact on the organism’s later development, structure, and function. This phenomenon is called “developmental programming,” a process whereby an environmental factor acting during a sensitive or vulnerable developmental period exerts effects that impact on structure and function of organs that, in some cases, will persist throughout life (1). One such environmental factor is the gut microbiota that, because of an evolutionary process, has adapted to coexist in commensal or symbiotic relationship with mammals (2). Immediately after birth, the newborn organism is rapidly and densely populated with complex forms of indigenous microbes. This process has been shown to contribute to developmental programming of epithelial barrier function, gut homeostasis, and angiogenesis, as well as the innate and host adaptive immune function (3, 4). Recent data indicate that gut microbiota have systemic effects on liver function (57), thus raising the possibility that gut microbiota can have developmental effects in other organs elsewhere in the body.

The functional development of the mammalian brain is of particular interest because it has been shown to be susceptible to both internal and external environmental cues during perinatal life. Epidemiological studies have indicated an association between common neurodevelopmental disorders, such as autism and schizophrenia, and microbial pathogen infections during the perinatal period (8, 9). These findings are supported by experimental studies in rodents, demonstrating that exposure to microbial pathogens during similar developmental periods result in behavioral abnormalities, including anxiety-like behavior and impaired cognitive function (1012). In a recent study, it was shown that the commensal bacteria, Bifidobacteria infantis, could modulate tryptophan metabolism, suggesting that the normal gut microbiota can influence the precursor pool for serotonin (5-HT) (13).

Here, we tested the hypothesis that the “normal” gut microbiota is an integral part of the external environmental signals that modulate brain development and function. : RESULTS: Germ Free (GF) Mice Display Increased Motor Activity and Reduced Anxiety-Like Behavior. ??

 

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Also: From NIH Catalyst Newsletter: Germ-Free Mice, By Julie Wu, NIAID

Some 100 trillion beneficial microorganisms—bacteria, fungi, and viruses—populate your body inside and out. Many species keep us healthy by helping with digestion, producing nutrients, and strengthening the immune system. But what would happen if we didn’t have this assortment of beneficial, or commensal, microbiota living within us? To find out, NIH scientists are studying germ-free mice that have not been naturally colonized by microorganisms.

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BIG claim from the medical side of Autism research, but does it translate to human Autism? “Autism-related Social behavior” – are these actual “Autistic mice” or were they engineered to display “Autistic-like” behavior? It’s a HUGE leap to claim that induced social behavior in mice is a direct corollary to social behavior in Autism. And… do mice have the same microbiota as humans?

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