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

Phase 2

Completed

Interventions: Drug: Synbiotic
Drug: Maltodextrin
Drug: Sevelamer
Other: High Fat diet
Other: Low Fat diet

Brief Summary: The purpose of this study is to determine insulin sensitivity in individuals that are lean normal glucose tolerant subjects after consumption of a normal low fat diet and after a high fat diet and to explore the effects of high fat consumption on the intestinal microbiome, and metabolic endotoxemia.( Aim 1 of the protocol, a separate record is available for Aim 2)

Detailed Description: We will test the hypothesis that a high fat diet given to lean, normal glucose tolerant subjects will impair insulin signaling and sensitivity and modify gut microbiome composition and enhance intestinal permeability, which will increase plasma LPS concentration, induce an inflammatory response in peripheral tissues (skeletal muscle). Also we will test the hypothesis that the inflammatory response and insulin resistance caused by high fat ingestion can be ameliorated by administering

* a synbiotic (Bifidobacterium longum R0175 and oligofructose) which protects the intestinal epithelial barrier and decreases intestinal translocation of LPS; and

* sevelamer, an agent which sequesters lipopolysaccharide (LPS) in the gastrointestinal tract limiting its translocation into the circulation.

All subjects are fed both a low fat diet (considered a normal diet) and high fat diet, first one and then the other in no particular sequence. After a washout period participants are fed the other type of high or low fat diet, depending on which diet they were first assigned to in order to compare the effects of the intervention on insulin sensitivity during each diet.

Recruitment & Eligibility

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.

Arm && Interventions

Group	Intervention	Description
Sevelamer	Low Fat diet	Sevelamer: (1.6 g sevelamer + 4.4 g maltodextrin three times a day)
Placebo	Low Fat diet	Placebo: maltodextrin, 6 g three times a day
Synbiotic	High Fat diet	Synbiotic: 5g Oligofructose + 4x1010 Bifidobacterium longum CFU 3x daily during diet
Placebo	High Fat diet	Placebo: maltodextrin, 6 g three times a day
Sevelamer	High Fat diet	Sevelamer: (1.6 g sevelamer + 4.4 g maltodextrin three times a day)
Synbiotic	Low Fat diet	Synbiotic: 5g Oligofructose + 4x1010 Bifidobacterium longum CFU 3x daily during diet
Synbiotic	Synbiotic	Synbiotic: 5g Oligofructose + 4x1010 Bifidobacterium longum CFU 3x daily during diet
Placebo	Maltodextrin	Placebo: maltodextrin, 6 g three times a day
Sevelamer	Sevelamer	Sevelamer: (1.6 g sevelamer + 4.4 g maltodextrin three times a day)

Primary Outcome Measures

Name	Time	Method
Insulin Sensitivity Low Fat Diet	Day 28	Skeletal muscle insulin sensitivity measured after 28 days of low fat diet and drug intervention. The isocaloric low fat diet will provide 55% energy from carbohydrates, 20% from fat and 25% from protein.
Insulin Sensitivity High Fat Diet	Day 28	Skeletal muscle insulin sensitivity measured after 28 days of high fat diet. The High Fat diet consists of 60% energy from fat (50% saturated), 15% of energy as carbohydrate and 25% from protein consumed while study intervention is being administered.

Secondary Outcome Measures

Name	Time	Method
Gut Permeability	on Day 24 of the intervention.	Gut permeability is measured using a lactulose/mannitol ingestion assay where urine samples are collected to analyse the ratio of excreted lactulose:mannitol.
Plasma Endotoxin Levels	At baseline, on day 3, and 28 of the intervention.	Endotoxin is a bacterially derived product that we hypothesized would impact insulin sensitivity through pro inflammatory pathways.