Does Class of Dietary Fat Affect Insulin Resistance?
Condition: Insulin Resistance
MeSH terms: Insulin Resistance
Study type: Interventional

Summary: 
      It has been shown that intravenous fatty acids given to normal volunteers in the form of
      heparin and lipid emulsions will cause insulin resistance in a matter of a few hours. It is
      not known if this same phenomenon can be demonstrated with oral fat. The investigators are
      specifically interested in whether or not there are differences in the induction of insulin
      resistance between the 3 main classes of fatty acids (saturated, monounsaturated and
      polyunsaturated).

      The investigators also plan to evaluate endothelial dysfunction and blood pressure; both of
      which frequently accompany insulin resistance.
    

Detailed description: 
      Type 2 Diabetes and cardiovascular disease are closely linked. A common abnormality in both
      conditions is insulin resistance. The primary cause of insulin resistance in not known. A
      significant question is what dietary components contribute to the development of insulin
      resistance. Based on epidemiologic data, it seems that the type of dietary fat is a
      significant contributor to the development of insulin resistance. However, some researchers
      argue that the main determinant is total amount of fat, not the composition.

      This study is intended to determine if the main types of fat (saturated, monounsaturated and
      polyunsaturated) ingested over a short time can cause insulin resistance in lean, healthy
      people. It has been demonstrated that 6 hours of intravenous fat infused into lean, healthy
      subjects can result in insulin resistance, as well as blood pressure elevation and
      endothelial dysfunction. Whether this is so with oral fat is not known. The question is
      important because there is debate about whether the type of fat is as important as the
      quantity of fat in a person's daily diet. Settling this debate will enhance the ability of
      health care personnel to determine the optimal dietary recommendations.

      This study will make use of a high fat diet consisting of vegetable oils high in the 3 main
      fatty acids in plasma (palmitate, oleate and linoleate). Because large fat loads can cause
      intestinal discomfort, a feeding tube will be used to bypass the stomach. The 3 oils will be
      assigned randomly following a base line study with saline 2 weeks prior to the intervention.
      Our primary endpoint is insulin resistance, which will be measured by a euglycemic,
      hyperinsulinemic clamp. Secondary measures will include changes in blood pressure and in
      vascular reactivity as measured by ultrasound after brief occlusion of a forearm vessel. The
      changes will be compared to baseline and to the other 2 groups.
    

Intervention name(s): Dietary fat
Intervention type(s): Other
Intervention description(s): On the study day, each participant will receive 100 grams of a randomly assigned fat via a nasoduodenal tube. The oil will be infused at a rate of ~1 tablespoon per hour so that the total infusion time will be 6 hours.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Insulin resistance; Endothelial dysfunction; saturated fat; monounsaturated fat; polyunsaturated fat