Enhancement of Cerebral Vasoreactivity and Cognition by Intranasal Insulin in Type 2 Diabetes

Phase 2

Completed

Brief Summary: Our goal is to determine the acute effects of intranasal insulin on regional perfusion and cognition of older adults. We propose a pilot study to examine the effect of a single dose of intranasal insulin on regional vasoreactivity and cognitive functions in 30 subjects with T2DM and 30 healthy controls \>50 years old using a double blinded, placebo-controlled, cross-over design.

Hypothesis 1: Intranasal insulin improves acutely regional perfusion and vasoreactivity in older patients with T2DM as compared with placebo and compared with the control group.

Hypothesis 2: Intranasal insulin improves cognitive functioning including attention, memory and executive function in diabetic patients as compared with placebo and compared with control group.

Detailed Description: Type 2 diabetes mellitus (T2DM) is a major risk factor for vascular dementia. DM alters insulin transport across blood-brain barrier affecting perfusion and neuronal function. Intranasal administration enables effective delivery of insulin to the brain. Clinical studies demonstrated improvement of cognitive function and memory in healthy and cognitively impaired people.

Aim 1: To determine the acute effects of a single 40-IU dose of intranasal insulin vs. placebo on regional perfusion and vasoreactivity to CO2 challenge measured by 3-D continuous arterial spin labeling (CASL) MRI at 3 Tesla in the control and diabetic groups. We will use transcranial Doppler to determine the effects on intranasal insulin vs. placebo on cerebral autoregulation based on measurements of beat-to-beat pressure flow velocity relationship.

Aim 2: To determine whether intranasal insulin improves cognitive functioning in older T2DM patients as compared with placebo and the control group.

This translational study will address an important area about the effects of intranasal insulin on cerebral blood flow regulation and cognition in older diabetics that has not been studied. Intranasal insulin administration may provide a novel therapeutic target for prevention and treatment of microvascular disease and cerebrovascular complications of T2DM. If successful, this approach may have significant impact on the clinical management of large population of older adults with T2DM.

Recruitment & Eligibility

Inclusion Criteria

Diabetes group:

30 men and women aged >50 years old diagnosed with T2DM and treated > 5 years with oral agents
Diabetes severity will be assessed from diabetes duration, hemoglobin A1C, and fasting glucose levels.

Control group:

30 healthy men and women aged >50 years selected to have the same age and sex distributions as the diabetic subjects
Normotensive, not treated for any systemic disease, and have normal fasting blood glucose.

Exclusion Criteria

Type 1 Diabetes Mellitus
History of severe hypoglycemia or hypoglycemic episode during home baseline monitoring
Positive stress test for CAD or other ischemic conditions
Carotid stenosis > 50% by medical history
History of a clinically documented stroke
Treatment with any medications administered intranasally including intranasal steroids
Any previous adverse or allergic reactions to insulin
Acute or unstable medical condition including Myocardial infarction or major illness and surgery within six months
Liver or renal failure or transplant
Uncontrolled hypertension (systolic BP >180 and/or diastolic BP >100 mm Hg or subjects taking more than 3 antihypertensive medications)
Seizure disorders
Malignant tumors
Clinical dementia (by history) or inability to follow details of the protocol(MMSE (Mini Mental Status Exam) score (≥3 points below the Comparative Normal Value for the subject's age group and education level, or ≤ 24)
Current recreational drug or alcohol abuse
Morbid obesity (BMI >40)
Inability to obtain permission for participation from the primary care physician
Transcranial Doppler (TCD) exclusion criterion - poor insonation window and TCD signal
MR exclusion criteria - any metal or bioimplants not compatible with 3 Tesla MRI and claustrophobia
Clinically significant and movement limiting hip, knee and/or back disorders or injury, and rheumatoid arthritis

Arm && Interventions

Group	Intervention	Description
Insulin vs. placebo	Intranasal insulin	Comparisons of acute effects of intranasal insulin or placebo (saline) on cerebral blood flow and cognition in healthy controls and type 2 diabetes.
Insulin vs. placebo	Placebo	Comparisons of acute effects of intranasal insulin or placebo (saline) on cerebral blood flow and cognition in healthy controls and type 2 diabetes.
Healthy vs. Diabetic	Intranasal insulin	Comparisons of acute effects of intranasal insulin or placebo (saline) on cerebral blood flow and cognition in healthy controls and type 2 diabetes.
Healthy vs. Diabetic	Placebo	Comparisons of acute effects of intranasal insulin or placebo (saline) on cerebral blood flow and cognition in healthy controls and type 2 diabetes.

Primary Outcome Measures

Name	Time	Method
Cognitive Outcome: Brief Visuospatial Spatial Memory Test -Total Recall (Unit T Score)	Acute changes within 2 hours	To determine the acute effects of a single 40-IU dose of intranasal insulin vs. placebo on cognition and regional perfusion and vasoreactivity to CO2 challenge measured by 3-D continuous arterial spin labeling (CASL) MRI at 3 Tesla in the control and diabetic groups. Cognitive outcome: Brief Visuospatial Spatial Memory test -Total Recall (unit T Score). Perfusion outcome: Regional vasoreactivity (ml/100g/min/mmHg). Each participant received a single dose of intranasal insulin (INI) or placebo on day 2 and a single dose dose of insulin or placebo on day 3 in a random order. Acute effects on baseline perfusion, regional vasoreactivity and cognition were determined within 2 hours after administration of insulin or placebo.
Perfusion Outcome: Right Insular Cortex Perfusion (ml/100g/Min/mmHg)	Acute changes within 2 hours	To determine the acute effects of a single 40-IU dose of intranasal insulin vs. placebo on cognition and regional perfusion and vasoreactivity to CO2 challenge measured by 3-D continuous arterial spin labeling (CASL) MRI at 3 Tesla in the control and diabetic groups. Cognitive outcome: Brief Visuospatial Spatial Memory test -Total Recall (unit T Score). Perfusion outcome: Regional vasoreactivity (ml/100g/min/mmHg).