IR and Microvascular Blood Flow in SCI
关键词
抽象
描述
Cutaneous microvascular blood flow is regulated by multiple mechanisms, including that by insulin and by the sympathetic nervous system (SNS). Insulin is the principal hormone responsible for the disposal and storage of glucose in skeletal muscle, in part by the re-direction of blood flow through the rhythmic dilatation or contraction of arterioles. In insulin-sensitive individuals, this "vasomotion" is thought to involve the activation of the vascular smooth muscle, with vasodilatation occurring through nitric oxide and vasoconstriction through the SNS and endothelin-1. A tonic upregulation of SNS activity and increased vasoconstrictor action of insulin may be a contributor to the development of hypertension, decreased peripheral blood flow, and endothelial dysfunction in the general population, especially in individuals with hyperinsulinemia and diabetes mellitus. In persons with spinal cord injury (SCI), a disproportionately high prevalence of insulin resistance and diabetes mellitus has been reported. We postulate that insulin resistance, in combination with the added consequence of SNS impairment below the neurological level of injury, contribute to hemodynamic dysregulation and a variety of medical complications, including pressure ulcer formation and decreased wound healing. Recently, our group demonstrated that the sub-lesional blood perfusion response to iontophoresis with insulin is blunted in euinsulinemic persons with motor-complete SCI compared to demographics-matched neurologically-intact control subjects.
To confirm and extend our preliminary finding and to provide additional insight into its implications, we propose to perform an open-label, non-randomized, placebo-controlled, parallel-group intervention, observational trial to determine the hemodynamic actions of insulin in individuals with complete motor lower extremity paralysis due to SCI and either systemic insulin sensitivity or insulin resistance. Subjects will participate in a screening visit to determine their eligibility and insulin sensitivity (i.e., categorized as being insulin-sensitive or insulin-resistant). Eligible individuals will return for participation in our study to determine skin blood flow by iontophoresis with vasoactive agents or application of heat to the extremities. Measurements will be performed simultaneously with provocation (i.e., with either heat or insulin or acetylcholine iontophoresis) being performed on the ipsilateral extremity and no provocative intervention (i.e., either no heat or placebo iontophoresis) in parallel and simultaneously on the contralateral extremity. On a separate visit, all subjects will repeat the iontophoresis with acetylcholine, which is the gold-standard to induce endothelium-dependent vasodilatation of the microvasculature.
After screening, subjects will participate in 2 study visits where the iontophoresis (i.e., placebo, insulin, and acetylcholine) and heat provocation will be performed one time on the upper and one time on the lower extremity. Each study visit will take no more than 4 hours. The expected enrollment time for a participant to complete the study should be no more than 3 weeks.
The respective outcomes from iontophoresis with insulin will be compared and correlated to systemic insulin sensitivity (as determined by an intravenous glucose tolerance test with insulin administration) (Primary Aim). The peak microvascular perfusion responses to vasodilatation by iontophoresis with acetylcholine to that with insulin will be compared (Secondary Aim). In participants with SCI, the findings from the neurologically intact upper extremity will be compared to those of the neurologically impaired lower extremity (Tertiary Aim). A group of neurologically-intact subjects who are matched for group assignment (i.e., insulin-sensitive or insulin resistant) will serve as age- and gender-matched controls to the participants with SCI.
日期
| 最后验证: | 02/28/2017 |
| 首次提交: | 01/07/2014 |
| 提交的预估入学人数: | 01/09/2014 |
| 首次发布: | 01/12/2014 |
| 上次提交的更新: | 03/05/2017 |
| 最近更新发布: | 03/06/2017 |
| 实际学习开始日期: | 11/30/2012 |
| 预计主要完成日期: | 11/30/2015 |
| 预计完成日期: | 11/30/2016 |
状况或疾病
干预/治疗
Drug: Insulin Iontophoresis
Drug: Placebo Iontophoresis
Drug: Acetylcholine Iontophoresis
Other: Heat Application
相
手臂组
| 臂 | 干预/治疗 |
|---|---|
| Active Comparator: Acetylcholine Iontophoresis For acetylcholine iontophoresis, the anode electrode will contain 0.2 ml of 1% acetylcholine chloride; the cathode electrode will contain a medical grade adhesive for skin placement and last 20 minutes. Preparation, instrumentation and data collection for this intervention are the same as the insulin iontophoresis. | Drug: Acetylcholine Iontophoresis For acetylcholine iontophoresis, the anode electrode will contain 0.2 ml of 1% acetylcholine chloride; the cathode electrode will contain a medical grade adhesive for skin placement and last 20 minutes. Preparation, instrumentation and data collection for this intervention are the same as the insulin iontophoresis. |
| Active Comparator: Heat Application For the provocation with heat, an insulated thermal heat pack (~106°F) will be applied to the exposed arm or leg for 18 minutes. The thermal heat pack is comparable to what is routinely used as a heat therapy in conventional rehabilitation settings. LDF leads and temperature sensors will be placed in the previously specified locations to evaluate the changes. | Other: Heat Application For the provocation with heat, an insulated thermal heat pack (~106°F) will be applied to the exposed arm or leg for 18 minutes. The thermal heat pack is comparable to what is routinely used as a heat therapy in conventional rehabilitation settings. LDF leads and temperature sensors will be placed in the previously specified locations to evaluate the changes. |
| Experimental: Insulin Iontophoresis For insulin iontophoresis, the cathode electrode will contain 0.2 ml of liquid insulin. For preparation and instrumentation, the arms will be uncovered below the elbow; the participant's lower extremities will be uncovered below knee for leg evaluations. The laser Doppler flowmetry (LDF) lead will be placed bilaterally, 2 inches proximal to the lateral malleolus over the peroneus longus muscle. For arm evaluations, a lead will be placed (and secured with dual-sided transparent tape) bilaterally, 2 inches distal to the lateral epicondyle over the flexor carpi ulnaris muscle along the midline with the ulnar process. Baseline and peak cutaneous blood flow responses to application of insulin iontophoresis will be determined for each LDF lead during the evaluation. | Drug: Insulin Iontophoresis For insulin iontophoresis, the cathode electrode will contain 0.2 ml of liquid insulin. For preparation and instrumentation, the arms will be uncovered below the elbow; the participant's lower extremities will be uncovered below knee for leg evaluations. The laser Doppler flowmetry (LDF) lead will be placed bilaterally, 2 inches proximal to the lateral malleolus over the peroneus longus muscle. For arm evaluations, a lead will be placed (and secured with dual-sided transparent tape) bilaterally, 2 inches distal to the lateral epicondyle over the flexor carpi ulnaris muscle along the midline with the ulnar process. Baseline and peak cutaneous blood flow responses to application of insulin iontophoresis will be determined for each LDF lead during the evaluation. |
| Placebo Comparator: Placebo Iontophoresis For placebo iontophoresis, the cathode electrode will contain 0.2 ml of preservative-free normal saline; the anode electrode will contain a medical grade adhesive for skin placement and last 20 minutes. Preparation, instrumentation and data collection for this intervention are the same as the insulin iontophoresis. | Drug: Placebo Iontophoresis For placebo iontophoresis, the cathode electrode will contain 0.2 ml of preservative-free normal saline; the anode electrode will contain a medical grade adhesive for skin placement and last 20 minutes. Preparation, instrumentation and data collection for this intervention are the same as the insulin iontophoresis. |
资格标准
| 有资格学习的年龄 | 20 Years 至 20 Years |
| 有资格学习的性别 | All |
| 接受健康志愿者 | 是 |
| 标准 | Inclusion Criteria: 1. Male or female, age 20 to 69; 2. Chronic (e.g., duration of injury at least 6 months), stable SCI (regardless of level of neurological lesion); 3. American Spinal Injury Association Impairment Scale (AIS) designation of A or B (reflects the level of somato-sensory impairment below the neurological level of injury: AIS A being complete sensory and motor lesion; AIS B being incomplete sensory and complete motor lesion); 4. Neurologically intact, age-matched control subjects 5. insulin-sensitive group: Si ≥ 2.5 min-1 ∙ mU-1 ∙ L x 104; and 6. insulin resistant group: Si < 2.5 min-1 ∙ mU-1 ∙ L x 104 Exclusion Criteria: 1. Diminished mental capacity; 2. Inability or unwillingness of subject to provide informed consent; 3. Acute illness or infection; 4. Current pharmacological treatment for diabetes mellitus or insulin resistance with exogenous insulin (or its synthetic dialogues), insulin-sensitizing agents, or agents that alter pancreatic secretion of insulin; 5. Current pharmacological treatment with sympathomimetic agents demonstrating direct vascular actions or indirect implications (e.g., alpha-1 agonists, cholinesterase inhibitors, norepinephrine, calcium channel blockers, angiotensin converting enzymes); 6. Moderate to high dose glucocorticoid administrations (i.e., ≥ 40mg prednisone or equivalent steroid dose) within the past 3 months; 7. Atherosclerosis, congestive heart failure, or history of myocardial infarction; 8. Previous diagnosis of diabetes mellitus or insulin resistance; and 9. AIS designation of C, D or E (for SCI subjects only). |
结果
主要结果指标
1. Cutaneous microvascular responses to insulin iontophoresis [Single time point]
