The perception of the human body as a single, self-contained organism is undergoing a paradigm shift. With the advent of 16S rRNA sequencing and metagenomics, it has become clear that humans are perhaps better understood as a supraorganism comprised of both host and microbial cells. Gut microbial populations play key roles in resistance to obesity, insulin sensitivity, glucose intolerance, cardiovascular health, an protection from colon cancer and inflammatory bowel disorders. Additionally, diet is a major modulator of gut microbial community composition and metabolism. Dietary starches and fibers that are not absorbed by the host are a major source of carbon and energy for gut bacteria. These microbes have evolved complex mechanisms to break down and metabolize such substrates, thereby vastly expanding the metabolic repertoire of the host. Gut bacteria produce a number of metabolites that are measureable in host plasma, including the short-chain fatty acids acetate, propionate, and butyrate. Many histone modifying enzyme complexes are known to be exquisitely sensitive to small-molecule metabolite levels and are thought to sense and integrate metabolic signals in response to changes in environment. An octamer of histone proteins forms the core of the eukaryotic nucleosome, a nucleoprotein structure around which ~147bp of DNA wraps to ultimately form highly compacted chromatin. Chromatin can exist in either an open or closed state, depending on the modifications present on histone proteins. Histone acetylation is generally associated with open chromatin and transcriptional activation, whereas Histone H3 lysine 27 trimethylation is associated with closed chromatin and transcriptional silencing. Therefore, is it likely that gut microbial metabolites, as a function of host diet, play a regulatory role at the level of chromatin in a variety of host tissues, not limitd solely to the gut, ultimately affecting host transcriptional programming and overall phenotype. However, the relationship between gut microbial metabolites and host chromatin remains unknown. The primary goal of the proposed work is to establish a link between gut microbial metabolism and host epigenetic programming in a variety of host tissues. A secondary goal of this work is to harness the nutritional sensitivity of gut microbiota to elucidate the effects of det on these microbial metabolite-mediated epigenetic changes, and to determine causal relationships between gut microbial metabolites and host chromatin.
The specific aims are to (1) establish a link between gut microbiota and the host epigenome, (2) determine the effects of diet and microbial community composition on the host epigenome, and (3) determine causal relationships between gut microbial metabolites and host epigenetic changes. The insight gained here will guide follow-up studies to identify specific chromatin complexes that directly respond to bacterial metabolites and alter specific chromatin loci. In light of the global diet-induced obesity epidemic, this work will make key connections between host nutritional status, gut microbial populations, and ultimately host environmental adaptation via epigenetic regulation of transcriptional programs.

Public Health Relevance

In an era of rising global obesity and increasing prevalence of metabolic disorders, understanding complex interactions between diet, gut microbiota, and the host response is essential to guiding dietary and lifestyle practices. This proposal aims to establish a link between gut microbial metabolism and the host epigenetic response, particularly in the setting of host nutritional modulation of gut microbial community composition and metabolism. An important outcome of this research will be identification of and mechanistic insight into the relationship between nutritionally sensitive gut microbial communities and host epigenetic regulation

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Individual Predoctoral NRSA for M.D./Ph.D. Fellowships (ADAMHA) (F30)
Project #
5F30DK108494-02
Application #
9248206
Study Section
Special Emphasis Panel (ZDK1)
Program Officer
Densmore, Christine L
Project Start
2016-04-01
Project End
2018-09-30
Budget Start
2017-04-01
Budget End
2018-03-31
Support Year
2
Fiscal Year
2017
Total Cost
Indirect Cost
Name
University of Wisconsin Madison
Department
Biochemistry
Type
Schools of Medicine
DUNS #
161202122
City
Madison
State
WI
Country
United States
Zip Code
53715
Zhang, Xue-Song; Li, Jackie; Krautkramer, Kimberly A et al. (2018) Antibiotic-induced acceleration of type 1 diabetes alters maturation of innate intestinal immunity. Elife 7:
Kasahara, Kazuyuki; Krautkramer, Kimberly A; Org, Elin et al. (2018) Interactions between Roseburia intestinalis and diet modulate atherogenesis in a murine model. Nat Microbiol 3:1461-1471
Krautkramer, Kimberly A; Rey, Federico E; Denu, John M (2017) Chemical signaling between gut microbiota and host chromatin: What is your gut really saying? J Biol Chem 292:8582-8593
Krautkramer, Kimberly A; Dhillon, Rashpal S; Denu, John M et al. (2017) Metabolic programming of the epigenome: host and gut microbial metabolite interactions with host chromatin. Transl Res 189:30-50
Krautkramer, Kimberly A; Kreznar, Julia H; Romano, Kymberleigh A et al. (2016) Diet-Microbiota Interactions Mediate Global Epigenetic Programming in Multiple Host Tissues. Mol Cell 64:982-992