Magnetic Resonance Imaging of Vascular Function

Magnetic Resonance Imaging of Vascular Function

A major function of blood vessels is to control blood flow by dilating or constricting depending on the demand. Vascular dysfunction is a state in which blood vessels fail to carry out its normal roles such as regulating blood flow. Diabetes is a risk factor for vascular dysfunction. Dysfunction may involve the smaller and/or larger blood vessels. Failure in the ability of large (conduit) blood vessels to control blood flow may be an early feature of atherosclerosis, a leading cause of stroke and heart attack. Measures of blood vessel dilation give an indication of the health of the vessel. Ultrasound and MRI can assess vascular function by measuring changes in blood vessel dilation. Diabetes may also affect tiny vessels in the kidney. These vessels become porous allowing albumin (a protein in the blood) to leak into the urine. The investigators can easily measure the presence of albumin in the urine.

This study aims to explore if MRI can demonstrate an association between vascular health in tiny and larger (conduit) blood vessels, by testing for an association between blood flow regulatory capacity of large vessels and presence of albumin in the urine.

Inclusion Criteria:

• Men and women with type 2 diabetes who:

  • are treated with oral hypoglycemic agents at a stable dose for at least 8 weeks
  • have diabetes diagnosed >6 months
  • have maintained stable weight for 2 months (within 3%)
  • have a valid Ontario Health Insurance Plan (OHIP) card and a family physician
  • if prescribed lipid medication, have taken a stable dose for at least 2 weeks
  • if prescribed blood pressure medication, have taken a stable dose for at least 1 week
  • can keep written food records
  • carotid intima-media thickness (cIMT) < 1.2 mm and ankle brachial index (ABI) of >0.9.

Exclusion Criteria:

• Individuals who

  • take insulin
  • take steroids
  • have GI disease (gastroparesis, celiac disease, ulcerative colitis, Crohn's Disease, IBS)
  • have had a major cardiovascular event (stroke or myocardial infarction) in the past 6 months
  • take warfarin (Coumadin)
  • have had major surgery in the past 6 months
  • have a major debilitating disorder
  • have clinically significant liver disease ( liver transaminase levels > 130 U/L), excluding Nonalcoholic fatty liver (NAFL) disease or NASH
  • have hepatitis B or C
  • have renal failure (high creatinine > 150 mmol/L)
  • have serum triglycerides ≥ 6.0 mmol/L
  • have a history of cancer, except non-melanoma skin cancer (basal cell, squamous cell)
  • have food allergies to study food components
  • have acute or chronic infections (bacterial or viral)
  • have chronic inflammatory diseases (e.g. rheumatoid arthritis, lupus; ulcerative colitis)
  • have other conditions which in the opinion of any of the investigators would make them unsuitable for the study
  • Any condition or circumstance which would prevent an individual from having an MRI (e.g. individuals with prostheses or metal implants, or those who are excessively claustrophobic)