Resistant Starch Insulin Sensitivity Trial
Resistant Starch Insulin Sensitivity Trial
The alarming increase in the prevalence of obesity is a cause of great concern given its
 association with many adverse health conditions, including insulin resistance and type 2
 diabetes, which are associated with increased cardiovascular disease (CVD) risk. The primary
 objective of this project is to identify effective dietary strategies, focused on
 carbohydrate quantity and starch digestibility, to improve outcome variables associated with
 CVD risk in insulin resistant individuals who express components of the atherogenic
 lipoprotein phenotype (ALP). Current dietary guidelines emphasize substitution of
 carbohydrate calories for total and saturated fat calories for prevention and management of
 chronic disease. Yet, we and others have shown that high-carbohydrate diets increase the
 expression of the ALP, characterized by increased plasma triglycerides, reduced HDL
 cholesterol, and increased levels of small, dense LDL particles, and that this phenotype is
 reversed by moderate carbohydrate restriction. We have also shown that expression of stearoyl
 coenzymeA desaturase (SCD), an enzyme involved in triglyceride synthesis, is reduced with
 carbohydrate restriction and that this change is correlated with plasma triglyceride
 response. While carbohydrate restriction is effective for management of ALP, the role of
 starch quality has not been addressed. Furthermore, there has been no study of the effects of
 resistant vs. digestible starches incorporated into high- vs. lower carbohydrate diets. Since
 isolated reports suggest that increased intake of resistant starch lowers plasma
 triglycerides and postprandial insulinemia, we hypothesize that starch quality is an
 important determinant of components of ALP, and that this may be mediated in part by reduced
 adipose tissue SCD expression. Aim 1 and of this proposal will address this hypothesis by a
 controlled dietary intervention in 52 insulin resistant men and women in which changes in
 plasma lipids, lipoproteins and lipogenic gene expression will be determined after
 substituting resistant starch for digestible starch in a high- vs. lower-carbohydrate diet.
 In Aim 2, the fasting and postprandial glucose and insulin responses to a resistant vs.
 digestible starch meal will be measured to test the hypothesis that starch digestibility
 improves glycemic and insulinemic control in a way that relates to diet-induced changes in
 plasma lipids and lipoproteins.
Clinic Visits:

 Participants will visit the clinic a total of 11 times from screen to completion of the
 study. This will include weekly visits with a dietician and 7 visits requiring blood draws
 (screen and twice following each diet period). At each visit, participants will be weighed,
 waist and hip circumferences will be measured, and blood pressure will be monitored. The
 total amount of blood collected is 450ml.

 Screening visit (V1: 1 hour):

 Recruiters will initially determine eligibility through review of a screening questionnaire
 and a telephone or personal interview. If a potential subject is eligible and interested, an
 orientation package will be mailed that will include written information about the study
 requirements. Interested subjects will be scheduled for a screening visit to determine final
 eligibility by the Clinical staff. At the screening visit (V1), informed consent will be
 obtained, anthropometric measurements obtained (height, weight, waist circumference, blood
 pressure), and blood (30ml) will be drawn to assess laboratory criteria for enrollment (total
 cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides, glucose, and insulin for
 determination of HOMA-IR). Screening blood samples from individuals who are either not
 eligible or unwilling to proceed with the intervention will be destroyed. We will screen for
 pregnancy, and repeat pregnancy tests after all "A" visits (V2a, v3a, v4a). Menstruating
 women will be given a calendar to record their menstrual cycle for the duration of the study.
 Eligible individuals will be contacted within 2 weeks of this screen visit and invited to
 participate in the study. We are prepared to enroll up to 64 participants in this study to
 yield a target of 52 completed participants (20% dropout).

 Dietitian Visits (Initial: 1 hr, Subsequent: 15 min):

 Participants will meet weekly with a dietitian or dietitian aide to receive counseling
 including weight management and diet review. At these meetings, participants will receive a
 week's worth of frozen entrees, standardized menus with check lists, and itemized grocery
 lists. Baked goods and products containing the test starches will also be provided at this
 time. The form in which they will be provided (frozen or fresh) will depend on the nature of
 the product and its capacity to withstand refrigerated vs. frozen storage. During the washout
 period (days 28-42), subjects will continue to refrain from alcohol but will consume their
 usual home diet for 7 days, followed by the baseline diet for an additional 7 days. We
 anticipate that giving participants permission to eat what they want for 7 days during the
 washout will improve their compliance during the remainder of the dietary protocol.

 Participants will bring grocery store receipts from the previous week so that the dietitians
 may ensure purchase of prescribed foods not provided by the Bionutrition Unit.

 Post-diet Visits Requiring Blood Draws (A visits: 2.5 hr, B visits: 5 hr):

 Participants will visit the clinic on two separate days following completion of each diet to
 provide blood samples. Duplicate sampling reduces biological variability, and hence improves
 the power of the study to detect significant diet-induced changes in measurement. On the
 penultimate day of each diet (Visits 2A, 3A, 4A) participants will visit the clinic in the
 fasting state and provide a fasting blood sample (30ml) for measurement of total, LDL- and
 HDL-cholesterol, triglycerides, apolipoproteins A1 and B, and lipoprotein subfraction
 analysis by ion mobility. Lipoprotein lipase and hepatic lipase activities will also be
 measured in plasma (20ml) obtained 15 minutes after IV heparin (75 units/kg). On the final
 day of each diet (Visits 2B, 3B, 4B), participants will provide a second fasting blood sample
 (for lipids and lipoproteins as above) and an adipose tissue aspiration to measure lipogenic
 gene expression. In addition a 3 hour starch tolerance meal will be performed at visits 3B
 and 4B, with blood samples for measuring glucose and insulin drawn in the fasting state and
 30, 60, 120, and 180 minutes after a starch meal (60ml total).

 Clinical Procedures:

 Clinical measurements: Blood pressure will be measured 3 times in a sitting position and the
 last 2 values averaged. Anthropometric measurements include height, weight, waist and hip
 circumference, and % body fat by bioimpedance (Tanita scale). Waist circumference is measured
 two times at the iliac crest and hip circumference is measured at the widest point of the
 hips.

 Standard Blood sampling: Using standard blood collection procedures, blood samples will be
 collected from participants after a 12-14 hour fast. The blood will be collected into tubes
 containing the following preservative solution: 3.0 gms EDTA (dipotassium), 1.7 mg P-Pack,
 0.15 gms gentamycin sulfate, 0.15 gms chloramphenicol, 5.96 mls aprotinin (Sigma A-6279), and
 0.30 gms sodium azide all of which are diluted to 20mls with doubly deionized water. Plasma
 is separated by immediate centrifugation at 4°C. Lipid and lipoprotein measurements are
 performed and aliquots of plasma are frozen for future analyses.

 Post-heparin Blood Sampling:

 A blood sample (20ml) will be drawn 15 minutes after intravenous administration of a heparin
 bolus (75U/kg, see Risk section for justification) for the analysis of plasma lipase
 activity. Prior to administration, participants will be interviewed for family history of
 clotting disorders or personal contraindications including use of anticoagulants, history of
 bleeding or bruising abnormalities or other diseases, allergies, or recent dental work.
 Following administration, participants will remain in clinic for 2 hours under observation.
 They will also be provided with an information sheet regarding heparin and the procedure.

 Adipose Tissue Biopsy:

 Adipose biopsies will be collected from the subcutaneous flanking region by an R.N. using a
 standardized, sterile procedure. Participants will be instructed not to take any drugs within
 2 days of the procedure that would impair clotting. This procedure will take place at least
 24 hours after post-heparin lipase analysis. Because the half-life of heparin is 2 hours,
 this is sufficient time to ensure clearance. After cleaning the area above the participant's
 buttock with betadine, Lidocaine hydrochloride 1% (10mg/ml) will be injected into the
 subcutaneous skin. Using a number 14G needle, 1-1.5 c.c.'s of fat will be aspirated. Cold
 pressure will be held on site and then the wound will be bandaged. Participants will be
 instructed to change the bandage once daily for two days. They will be provided with two
 bandages, instructions for keeping the wound clean, and a telephone number where clinical
 staff can be reached.

 Starch Meal Test:

 Immediately following adipose tissue biopsy and fasting blood draw, participants will be
 given a starch meal that provides 1/3 of the daily calories to be consumed in 15 minutes. It
 will be similar in macronutrient composition to the test diet to which the participant is
 assigned and will either be high in amylose or amylopectin. Blood will be drawn 30, 60, 120,
 and 180 minutes after meal consumption through an IV. For this procedure, an intravenous
 cannula or needle will be placed in the antecubital vein. A normal saline solution will be
 run at a keep open rate at the antecubital site.
Inclusion Criteria:

 -  Men and women ≥ 20 years

 -  Blood pressure less than 150/90. If on three separate clinic visits blood pressure
 remains above this level, a subject will be referred to his or her physician for
 treatment.

 -  Body mass index (BMI) ≥ 20 and ≤ 35 kg/m2.

 -  Non-smoking and does not use nicotine products or recreational drugs.

 -  Agrees to consume no alcohol or dietary supplements during the study.

 -  Total cholesterol and LDL cholesterol <95th percentile for sex and age.

 -  Fasting triglycerides <500mg/dl.

 -  HOMA-IR ≥ 50th percentile for sex.

 -  Fasting blood sugar (FBS) < 126 mg/dl.

 -  Hematocrit ≥ 36%.

 -  At least 3 months of a weight stable state. During the study, subjects will be
 required to maintain their body weight within ± 3% (up to a maximum change of 5 lbs)
 of their initial weight over the course of any consecutive two weeks.

 -  For women of childbearing potential, two barrier methods of contraception must be used
 throughout the study and urine pregnancy B-hCG will be done at screen (v1) and at all
 "A" visits (v2a, 3a, 4a). Subjects who become pregnant will no longer be allowed to
 continue the study.

 -  Women will be considered post-menopausal if ≥ 3 years since last menses or no menses
 for 1-3 years and plasma FSH elevated into postmenopausal range.

 -  Subjects who cannot complete the requirements of the study for reasons determined by
 the investigator (i.e. non-accessible veins for blood drawing, inability to keep
 clinic appointments) will not be able to participate in the study.

 Exclusion Criteria:

 -  History of coronary heart disease, cerebrovascular disease, peripheral vascular
 disease, bleeding disorder, liver or renal disease, diabetes, lung disease, HIV, or
 cancer (other than skin cancer) in the last 5 years.

 -  Taking drugs known to affect lipid metabolism, blood thinning agents or hormones

 -  Abnormal thyroid stimulating hormone (TSH) levels