Intermittent Calorie Restriction, Insulin Resistance, and Biomarkers of Brain Function

Being overweight or obese can cause insulin resistance (IR), which is defined as reduced
responsiveness to insulin by the cells of various tissues or organs. IR at midlife increases
the risk of developing Alzheimer s disease (AD). We recently discovered novel biomarkers of
brain IR (altered Tyr and Ser phosphorylated forms of insulin receptor substrate 1; IRS-1) in
plasma exosomes enriched for neuronal origin. Moreover, IR is associated with AD biomarkers
including deficits in resting state brain activity and cognitive performance. Calorie
restriction is defined as consuming fewer calories than what is considered normal without a
lack of nutrients. A certain type of calorie restriction, in which one consumes 500-600
calories a day for two consecutive days, followed by non-restricted eating for 5 days (5-2
CR), has been shown to lower peripheral insulin resistance effectively. Effects of CR and
lowering peripheral IR on brain IR and cognition are unknown. The goal of this exploratory
pilot study is to provide proof-of-concept that 5-2 CR at midlife can reverse brain IR, lower
peripheral IR, improve cognitive performance, and increase brain activation at rest and
during tasks. Specifically, we will study the effects of 8 weeks of 5-2 CR versus a control
dietary intervention on brain and peripheral IR, memory and executive function, resting state
default mode network activity, brain metabolism, and AD biomarkers. Forty overweight to obese
women and men (between 55 and 70 years of age) will be randomized 1:1 into 5-2 CR and control
groups. In the 5-2 CR group, participants will be offered healthy living dietary counseling
at baseline, which they will be instructed to implement for five days/week. For each of the
other two consecutive days/week, they will consume two shakes (Boost , CWI Medical),
providing a total of 480 Kcal/day. In the control group, participants will be offered healthy
living dietary counseling at baseline, which they will be asked to implement for every day of
the week. Participants will undergo screening including a history and physical examination,
calculation of Body Mass Index (BMI, which must be greater than or equal to 27) and a blood
draw for insulin and glucose to determine whether they have insulin resistance. If
participants meet eligibility criteria, they will continue with a baseline visit involving
anthropometric measures, questionnaires, tests of cognitive function, brain MRI, blood draws
for plasma and peripheral blood mononuclear cells, and lumbar puncture for cerebrospinal
fluid biomarkers of AD. After 8 weeks, we will collect the same measures. To assess and
reinforce compliance with their respective diet, participants will come into the clinic every
2 weeks to discuss compliance, measure their body weight and perform blood draws for
measurement of ketones to objectively confirm energy restriction for the 5-2 CR group. We
will also contact participants every week to further ensure compliance. To assess the effects
of the diets on physical activity, participants will be asked to wear an accelerometer for 96
hours before and after they are on the diet.

- INCLUSION CRITERIA:

- BMI greater than or equal to 27; in addition, weight less than or equal to 350 lbs
(weight limit for MRI scanner);

- Age of 55-70 years;

- HOMA-IR greater than or equal to 1.8;

- MMSE greater than or equal to 26

EXCLUSION CRITEIRA:

- History of clinically significant cardiovascular disease for the purpose of this
study, such as chronic heart failure, coronary disease, cardiomyopathy, clinically
significant cardiac valvular disease or clinically significant peripheral vascular
disease. Cardiovascular conditions that are clinically non-significant for the purpose
of this study, such as controlled hypertension, minor EKG abnormalities, mitral valve
prolapse or benign murmurs are permissible;

- History of clinically significant stroke or other neurological disease of the central
nervous system;

- History of substance abuse in the past 6 months or positive urine drug screen;

- History of clinically significant endocrine disorders (common mild endocrine
disorders, such as untreated subclinical hypothyroidism with TSH < 10 mU/l or
successfully treated hypothyroidism may be allowed);

- History of eating disorders, significant GI disorders or malabsorption disorders;

- History of type 2 diabetes; and/or use of anti-diabetes medications or insulin; and/or
type 2 diabetes diagnosed during the screening visit based on fasting glucose > 125
mg/dL;

- History of hypoglycemia; and/or a fasting glucose < 70 mg/dL during the screening
visit.

- Current use of systemic corticosteroids;

- Positive screening tests for HIV, HCV or HBV;

- Hematocrit less than 35% or hemoglobin less than 11 mg/dL;

- ALT or AST > 1.5 times the upper normal limit;

- Contraindications for MRI (pacemakers, ferrous metal implants or shrapnel in or around
the head, etc.).

- Contraindications to LP, such as Coumadin, coagulopathy (international normalized
ratio, or INR > 1.5; prothrombin time (PT), partial prothrombin time (PTT) > 1.5 x
upper normal limit). Aspirin 81 mg qd is allowed. Aspirin up to 325 mg qd is allowed,
if withheld for 7 days prior to the LP.

- Pregnancy or nursing.

- Refusal to consent to genetic testing for APOE.