A Study to Evaluate the Effect of Lipid Infusion on Toll Like Receptor 4 (TLR4) Signaling

Not Applicable

Completed

Conditions: Diabetes
Obesity

Interventions: Drug: Intralipid 20%
Drug: Saline

Registration Number: NCT01740817

Lead Sponsor: The University of Texas Health Science Center at San Antonio

Brief Summary: The purpose of this study is to determine whether a lipid infusion can up-regulate toll-like receptor 4 (TLR4) signaling in human subjects

Detailed Description: The investigators plan to examine the effect of a lipid infusion on TLR4 expression and insulin sensitivity. A group of 30 subjects aged 18-60 years old, lean (BMI \< 26 kg/m2) normal glucose tolerant subjects without a family history of type 2 diabetes will receive a lipid or saline infusion. The subjects will be randomly assigned to first receive either a 48 hour long lipid or saline infusion. Approximately 4-6 weeks later subjects will return to undergo another study (if, in the first study they received lipid, on the second study they will receive saline, and vice versa). A near-equal number of women and men will be included in each group.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 12

Inclusion Criteria

Subjects must have the following laboratory values: Hematocrit ≥ 35%, serum creatinine ≤ 1.5 mg/dl, aspartate aminotransferase (AST) < 2 X upper limit of normal, Alanine aminotransferase (ALT) < 2 X upper limit of normal, alkaline phosphatase < 2 X upper limit of normal, normal urinalysis [no glucose, trace protein, trace ketones, lipase < 50 IU/L, no bacteria, up to 1-3 white blood cells (WBC) and red blood cells (RBC) per hpf], and normal platelets, prothrombin time (PT) and partial thromboplastin time (PTT).
Female subjects must be non-lactating. Female patients are eligible only if they have a negative pregnancy test throughout the study period (or postmenopausal). Postmenopausal women taking hormone replacement will be included if they have been on a stable dose for ≥6 months.
Subjects whose body weight has been stable (within 2%) for at least three months.

Exclusion Criteria

Subjects with impaired glucose tolerance based on American Diabetes Association criteria.
Subjects taking drugs known to affect glucose and lipid homeostasis will be excluded. Statins will be permitted if the subject has been on a stable dose for at least three months. Subjects who have taken for more than a week non-steroidal anti inflammatory drugs (NSAIDS) within two months or systemic steroids, anabolic steroids, growth hormone or immunosuppressants within 12 months will be excluded. Subjects taking low-dose (81 mg/day or less) aspirin will be allowed.
Patients with a history of clinically significant heart disease (New York Heart Classification greater than grade II; more than non-specific ST-T wave changes on the EKG), peripheral vascular disease (history of claudication), or pulmonary disease (dyspnea on exertion of one flight or less; abnormal breath sounds on auscultation) will not be studied.
Recent systemic or pulmonary embolus, impaired renal function, poorly controlled blood pressure (systolic BP>170, diastolic BP>95), resting heart rate >100, electrolyte abnormalities, neuromuscular or musculoskeletal disease.
Subjects who smoke.
Subjects who engage in a regular exercise program (zero or one exercise sessions per week are allowed).
Any subject who has donated blood in the previous two months.
Any subject with a hematocrit of less than 35.
Subjects who are claustrophobic.
Women taking oral contraceptives.
alcohol consumption greater than 30 grams daily.
baseline plasma triglyceride levels over 200 mg/dl

Study & Design

Study Type: INTERVENTIONAL

Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Saline, then Intralipid	Intralipid 20%	Participants first received saline infusion of 30ml/h x48h. After a washout period of 4-6 weeks, they then received lipid infusion of 30ml/h x48h.
Intralipid 20%, then saline	Intralipid 20%	Participants first received lipid infusion of 30ml/h x48h. After a washout period of 4-6 weeks, they then received saline infusion of 30ml/h x48h.
Saline, then Intralipid	Saline	Participants first received saline infusion of 30ml/h x48h. After a washout period of 4-6 weeks, they then received lipid infusion of 30ml/h x48h.
Intralipid 20%, then saline	Saline	Participants first received lipid infusion of 30ml/h x48h. After a washout period of 4-6 weeks, they then received saline infusion of 30ml/h x48h.

Primary Outcome Measures

Name	Time	Method
Muscle Insulin Sensitivity-M Value	48 hr after lipid/saline infusion	Forty eight hrs after lipid or saline infusion, muscle insulin sensitivity will be measured by insulin clamp. The results are compared to determine whether lipid infusion reduces muscle insulin sensitivity compared to saline infusion.. The M value is defined as the exogenous glucose infusion rate at steady state (i.e, when the exogenous glucose infusion rate is equal to the rate of whole body glucose disposal).

Secondary Outcome Measures

Name	Time	Method
Extracellular Signal-regulated Kinase (ERK) Phosphorylation in Muscle	48 hr following lipid or saline infusion, pre-clamp	Forty eight hrs after lipid or saline infusion, muscle ERK phosphorylation will be measured by western blot. The results are compared to determine whether lipid infusion increases muscle ERK phosphorylation compared to saline infusion. Saline mean was used to normalize the data for both arms.
TLR4 Messenger Ribonucleic Acid (mRNA) in Muscle	48 hr following lipid/saline infusion, pre-clamp	Forty eight hrs after lipid or saline infusion, muscle TLR4 mRNA levels will be measured by RT-PCR. The results are compared to determine whether lipid infusion increases muscle TLR4 mRNA expression compared to saline infusion. Saline mean was used to normalize the data for both arms.