Hypoglycemia Associated Autonomic Failure in Type 1 Diabetes Mellitus (DM)

Hypoglycemia Associated Autonomic Failure in Type 1 DM, SSRI and Exercise

Exercise is a cornerstone of diabetes management. It helps reduce blood pressure, promote weight loss, lower insulin resistance and improve glucose and lipid (triglyceride and HDL-cholesterol) profiles. Unfortunately, the benefits of exercise are often not embraced by diabetic individuals because of the fear of low blood sugar (hypoglycemia). My laboratory has demonstrated that Autonomic nervous system (ANS) counterregulatory failure plays an important role in exercise associated hypoglycemia in Type 1 DM. ANS responses are significantly reduced in Type 1 DM and are further blunted by antecedent episodes of hypoglycemia. Furthermore, there is a large sexual dimorphism of reduced ANS responses during submaximal exercise in both Type 1 DM and healthy individuals that is unexplained. Accumulating data are demonstrating that serotonergic pathways can regulate ANS discharge. Generally, serotonergic pathways are inhibitory but both single and longer term administration of selective serotonin reuptake inhibitors (SSRI's) such as Prozac has been demonstrated to increase basal epinephrine levels and enhance baroreflex control of Sympathetic nervous system (SNS) activity. What is unknown is whether fluoxetine can also enhance SNS responses and also override the large ANS sexual dimorphism present during sub maximal exercise. Therefore, the purpose of this study is to determine if the SSRI fluoxetine (Prozac) can improve SNS responses during exercise.

Inclusion Criteria:

• 32 (16 males, 16 females) Healthy controls aged 18-45 yr.
• 32 (16 males, 16 females) Type 1 diabetic patients aged 18-45 yr.
• HbA1c 6-10.0%
• Has been diagnosed Type 1 DM
• No clinically diagnosed diabetic tissue complications (i.e. history of retinopathy, neuropathy, stasis ulcers, etc)
• Body mass index < 40kg • m-2

Exclusion Criteria:

• Pregnant women
• Subjects unable to give voluntary informed consent
• Subjects on anticoagulant drugs, anemic or with known bleeding diatheses
• Subjects taking any of the following medications will be excluded: Non-selective Beta Blockers, Sedative-Hypnotics, Anticonvulsants, Antiparkinsonian drugs, Antipsychotics, Antidepressants, Mood stabilizers, CNS Stimulants, Opioids, Hallucinogens
• Subjects with a recent medical illness
• Subjects with a history of hypertension, heart disease, cerebrovascular incidents
• Current tobacco use