Neuropathy in Minority Populations (Abstract)

Correlation of Autonomic and Peripheral Neuropathies in Minority Populations

Introduction:

The incidence of diabetes has steadily increased over the past 10 years, particularly in certain racial and ethnic groups where the risk of associated complications is dramatically increased (1). Diabetes mellitus is the leading cause of non-traumatic lower-extremity amputations (LEA) in the United States. Increased rates of amputations suggest a higher incidence of both peripheral and autonomic neuropathy in minorities as they may contribute up to 87% of amputations (2). There is more than a 2-fold increase in age-adjusted rates for non-traumatic LEA with diabetes for blacks compared to whites (3-5)(3-5). The impairment of skin blood flow in people with diabetes is well documented, including both impaired peripheral vasoconstriction and vasodilation in cutaneous vessels (6-8). This blood flow impairment is a potentially serious condition because it has recently become apparent that neuro-ischemia is a major contributor to foot ulcers and amputations. Early detection and treatment may prevent the progression to these very disabling complications. These blood vessels are regulated by the autonomic nervous system (9) and the Neuropeptidergic nervous system.

We have shown major defects in the systems regulating blood flow in people with diabetes(10) that relate to small fiber (thin unmyelinated C fibers) that also sub-serve autonomic regulation of the heart, intestines and other organs in the body. We have also shown that autonomic neuropathy involving the heart has dire consequences with a 2-3 fold increase in premature mortality (11,12), but there are no studies determining the relationship between peripheral and cardiac autonomic function. In particular how the different branches of the autonomic nervous system namely the parasympathetic and sympathetic are involved.

Aims and objectives:

Although, the impact of diabetes and its complications are disproportionately represented in Blacks, few studies exist that describe autonomic neuropathy in blacks with diabetes. These facts underscore the need to understand the role of the autonomic nervous system in the etiology of diabetes complications. Previously we have focused studies on the defect in peripheral blood flow and are currently continuing to address the underlying mechanisms behind this microvascular dysfunction. We are also interested, however, in how cardiovascular neuropathy (CAN) correlates with peripheral neuropathy and LEAs among different ethnic groups. The sympathetic branch of the ANS is in control during stress, while the parasympathetic branch is in control during relaxation. An imbalance between these two branches gives an indication of illness or poor health. The Diabetes Institutes currently has a non-invasive devise (Autonomic Nervous System Monitoring (ANSAR)), which measures heart rate variability, respiratory activity, and blood pressure. The analysis from this system can determine the dominant branch of the ANS and whether autonomic neuropathy is present. The specific aim of this study is to correlate these results with epidemiological and skin blood flow data to determine their correlation to peripheral neuropathy and determine if there are any differences among Whites and Blacks. This study will be a subset of another larger ongoing study and will involve patient interaction and data analysis.

Duration:

The duration of this project is estimated to be about 8 to 10 weeks. We anticipate that the outcome of this project will merit presentation and will also be worthy of publication. This project will yield results that could potentially support future grant proposals and from agencies such as ADA to carry out larger studies.

Reference List:

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2. Carter JS, Pugh JA, Monterrosa A: Non-insulin-dependent diabetes mellitus in minorities in the United States. Ann.Intern.Med. 125:221-232, 1996

3. Lavery LA, van Houtum WH, Ashry HR, Armstrong DG, Pugh JA: Diabetes-related lower-extremity amputations disproportionately affect Blacks and Mexican Americans. South.Med J 92:593-599, 1999

4. Ashry HR, Lavery LA, Armstrong DG, Lavery DC, van Houtum WH: Cost of diabetes-related amputations in minorities. J Foot.Ankle.Surg. 37:186-190, 1998

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6. Vinik, A., Erbas, T., Park, T., Stansberry, K., Scanelli, J., and Pittenger, G. Dermal Neurovascular Dysfunction in Type 2 Diabetes. Diabetes Care 24(8), 1468-1475. 2001.

7. McDaid EA, Monaghan B, Parker AI, Hayes JR, Allen JA: Peripheral autonomic impairment in patients newly diagnosed with type II diabetes. Diabetes Care 17:1422-1427, 1994

8. Vinik, A. I., Erbas, T., and Park, T. S. Methods for evaluation of peripheral neurovascular dysfunction. Diabetes Technology and Therapeutics 3, 29-50. 2001.

9. Burnstock G: Integration of factors controlling vascular tone. Overview. Anesthesiology 79:1368-1380, 1993

10. Vinik, A., Erbas, T., Stansberry, K. B., and Pittenger, G. Small fiber neuropathy and neurovascular disturbances in diabetes mellitus. Exp Clin Endocrinol Diabetes 109(Suppl 2), S451-S473. 2001.

11. Maser, R. E., Mitchell, B. D., Vinik, A. I., and Freeman, R. The association between cardiovascular autonomic neuropathy and mortallity in individuals with diabetes: a meta-analysis. Diabetes Care 26(6), 1895-1901. 2003.

12. Vinik, A. I., Maser, R. E., Mitchell, B. D., and Freeman, R. Diabetic Autonomic Neuropathy. Diabetes Care 26(5), 1553-1579. 2003.