The Alberta FYBER (Feed Your Gut Bacteria morE fibeR) Study
The Alberta FYBER (Feed Your Gut Bacteria morE fibeR) Study
Too much body-fat has been linked to a low-grade inflammation throughout the body. This
 inflammation is thought to then cause different diseases, like heart disease and diabetes. A
 lower amount of inflammation is usually seen in people that follow a high fiber diet. A
 reason for this is the microbes that live in our gut. Fiber is a main food source for these
 microbes. This allows fiber to actually change the type of microbes that live in our gut.
 Also, when fiber gets fermented by these microbes, health-promoting waste products get
 released. We aim to determine how exactly our gut microbes contribute to the health
 properties of fiber.

 We hypothesize that fiber's health properties depend on how the gut microbes respond to the
 fiber. To test this, we plan to add three different fibers to the diets of healthy overweight
 and obese individuals for six weeks. We then will determine how the different fibers affect
 an individuals' health by looking at how established markers of health change from adding the
 fiber. Following this, we will see how an individual's gut microbes respond to the added
 fiber. The response will be decided by looking at changes to the microbe community, as well
 as their ability to ferment the fibers. By connecting health outcomes to the gut microbes'
 response, we can test if the gut microbes' response to the fiber determines the fiber's
 ability to effect health. If we can understand how our gut microbes respond to different
 fibers and the importance of that response. Then we could personalize diets to have a greater
 impact on improving health.
Being overweight and obese significantly increases the risk of developing numerous diseases,
 including cardiovascular disease (CVD), type 2 diabetes (T2D), and certain cancers. The
 microbial community (microbiota) that resides within the gut play a notable role in obesity
 and its associated pathologies (e.g. CVD, T2D), and is therefore a potential therapeutic
 target. Diet is known to determine whether the gut microbiota contributions to host
 metabolism are beneficial or detrimental. A westernized diet high in fat and sugar is
 associated with systemic inflammation, while fat intake increases lipopolysaccharide
 translocation through the gut membrane. In addition, gut microbial metabolism of choline and
 L-carnitine can produce trimethylamine, which has been shown to contribute to atherosclerosis
 after being oxidized in the liver to trimethylamine N-oxide (TMAO). In contrast, diets high
 in dietary fiber from fruits, vegetables, and whole grains are inversely associated with
 inflammation and can potentially reverse effects of a high fat diet. Fermentable fiber types
 can resist host digestion, but are then subsequently fermented by the gut microbiota to
 short-chain fatty acids (SCFAs), which are known to have metabolic and immunologic benefits.
 Accordingly, both epidemiologic associations and human intervention trials suggest an inverse
 association between fiber intake, reduced systemic inflammation, and improved lipid and
 glucose metabolism; however, results remain inconsistent. These discrepancies might be partly
 attributable to (I) the low fiber doses used in most studies, and (II) the high degree of
 inter-individual variation in the response to fiber, which may stem from the individualized
 responses of the microbiome to fiber. The emerging evidence that fiber and the gut microbiota
 interact to influence host physiology warrant human clinical research that investigates the
 capacity of chemically distinct fibers to modulate host metabolism and inflammation, and the
 mechanistic role of the gut microbiota in their physiological effects.

 Our long-term goal is to contribute to such a framework through clinical research that
 applies a holistic approach to examining the effect of fiber on both the host and its gut
 microbiota. We hypothesize that fibers show structure-dependent effects on inflammatory,
 metabolic, and hormonal markers of obesity-associated pathologies that can be predicted
 through compositional, functional, and genetic characteristics of an individual's fecal
 microbiome. We propose the following specific aims:

 AIM 1. Perform a parallel-arm exploratory intervention study in overweight and mildly obese
 individuals to determine the impact of high doses of chemically distinct fibers on host
 inflammatory markers, measures of insulin sensitivity, and other clinical outcomes.

 The effect of two physicochemically distinct fermentable dietary fibers (acacia gum and
 resistant starch type 4) on clinical markers of metabolic disease will be compared against a
 relatively non-fermentable dietary fiber (microcrystalline cellulose - control). We will
 employ a three-arm, parallel-design, single-blind, placebo-controlled, stratified randomized
 exploratory trial. Fibers will be administered in relative pure form daily over six weeks
 without any further lifestyle adjustments. Doses used in the trial will be 25 g/day of fiber
 for women and 35 g/day for men (close to Health Canada's dietary recommendations). Although,
 the first two days of treatment will use half the daily treatment dose of fiber (women: 12.5
 g/day; men: 17.5 g/day), to ease the incorporation of the fiber into the diet. Participants
 will be advised on how to incorporate the fibers into their diet, as to improve tolerance and
 compliance.

 The impact of dietary fiber on a comprehensive set of well-established obesity-related
 biomarkers will be determined via quantification at baseline and post-dietary intervention.
 High sensitive C-reactive protein and other inflammatory markers (e.g. interleukin-6,
 interleukin-10), as well as established markers for metabolic syndrome (e.g. fasting glucose
 and triglycerides) will constitute as key endpoints of the exploratory trial. To gain further
 understanding on the mechanisms that mediate metabolic and inflammatory improvements; five
 primary gut hormones, including satiety/hunger signaling hormones (e.g. glucagon-like
 peptide-1, leptin, and ghrelin), will be included. Lifestyle indicators, compliance with
 treatment, and satiation will be further assessed through self-administered questionnaires.

 AIM 2. Evaluate the short- and long-term impacts of chemically distinct types of dietary
 fiber on gut microbiota composition, genetic characteristics, and production of
 anti-inflammatory (SCFA) and pathogenic (TMAO) metabolites.

 We will utilize Illumina 16S rRNA sequencing and whole metagenomic sequencing to characterize
 the fecal microbiota (that will be enriched for large bowel bacteria) of our exploratory
 trial participants at weeks 0, 1, and 6, to explore fiber-induced changes in gut microbiota
 composition and gene content. These methods will be used as a majority of gut microbiota are
 not currently culturable. To further investigate gut microbiota function, we will quantify
 specific bacterial associated metabolites in plasma (TMAO) and in feces (SCFAs and bile
 acids). In parallel, we will quantify the fecal metabolites after in vitro fermentation, to
 account for absorption in the human gut. This will allow us to gain insight into
 fiber-induced changes in gut microbiota composition, metabolism, and functionality that
 coincide with the physiological effects observed in the host.

 AIM 3. Characterize associations between clinical outcomes and microbiome shifts and
 determine how well individual microbiome configurations predict impacts of dietary fiber.

 With the establishment of a robust human exploratory trial, a well-defined set of host
 phenotypes, and participant microbiome characteristics, Aim 3 will statistically integrate
 these data to specifically test for associations between diet, the gut microbiome, and host
 metabolism, and evaluate if microbiome and host phenotypic signatures at baseline can predict
 clinical outcomes of dietary fibers
Inclusion Criteria:

 -  BMI of 25-35

 -  men and pre-menopausal, non-pregnant or lactating women

 -  weight stability (±3%) for at least 1 month

 -  no diagnosis of gastrointestinal disorders or history of gastrointestinal surgical
 interventions.

 -  no history of diabetes mellitus

 Exclusion Criteria:

 -  vegetarian or vegan

 -  smoking

 -  alcohol intake greater than 7 drinks per week

 -  vigorous exercise more than 3 hours per week

 -  uses supplements (including prebiotics and probiotics)

 -  antibiotic treatment in the last 3 months

 -  allergy or intolerance to treatment fibers (wheat or acacia gum)

 -  use of anti-hypertensive, lipid-lowering, anti-diabetic, anti-inflammatory, or
 laxative medications