Mechanism of Microbiome-induced Insulin Resistance in Humans (Aim 1)

Inclusion Criteria: * Both genders. All races and ethnic groups. * Premenopausal women in the follicular phase, non-lactating, and with a negative pregnancy test. Postmenopausal women on stable dose of or not exposed to hormone replacement for ≥6 months. * Hematocrit (HCT)≥ 34%, serum creatinine ≤ 1.4 mg/dl, and normal serum electrolytes, urinalysis, and coagulation tests. Liver function tests (LFTs) up to 2 times normal. * Stable body weight (±2%) for ≥ 3 months * Two or less sessions of strenuous exercise/wk for last 6 months. Exclusion Criteria: * Presence of diabetes or impaired glucose tolerance based on ADA criteria. * Current treatment with drugs known to affect glucose and lipid homeostasis. If the subject has been on a stable dose for the past 3 months, the following agents will be permitted: calcium channel blockers, β-blockers, ACE inhibitors, angiotensin receptor blockers, and statins * History of allergy to sevelamer. * History of Non-steroidal anti-inflammatory drugs or systemic steroid use for more than a week within 3 months. * Current treatment with anticoagulants (warfarin). Aspirin (up to 325 mg) and clopidogrel will be permitted if these can be held for seven days prior to the biopsy in accordance with the primary physician. * Use of agents that affect gut flora (e.g. antibiotics, colestyramine, lactulose, PEG) within 3 months. * History of heart disease (New York Heart Classification greater than grade II; more than non-specific ST-T wave changes on the ECG), peripheral vascular disease, pulmonary disease, smokers. * Poorly controlled blood pressure (systolic BP\>170, diastolic BP\>95 mmHg). * Active inflammatory, autoimmune, hepatic, gastrointestinal, malignant, and psychiatric disease. * History of gastrointestinal surgery or gastrointestinal obstruction within two years.