Prevalence of somatic small fiber neuropathy in obesity

• Published in: International Journal of Obesity 2007-02, Vol.31 (2), p.226-235
• Main Authors: Herman, R.M, Brower, J.B, Stoddard, D.G, Casano, A.R, Targovnik, J.H, Herman, J.H, Tearse, P
• Format: Article
• Language: English
• Subjects: Adult; age; age differences; Age Factors; Aging; animal injuries; Asymptomatic; Bioengineering; Biological and medical sciences; blood glucose; Body Mass Index; Capsaicin; central nervous system; Complications and side effects; Cross-Sectional Studies; Diabetes; diabetes mellitus; Diabetic neuropathies; Diagnosis; Epidemiology; Feeding. Feeding behavior; Female; Fibers; Fundamental and applied biological sciences. Psychology; Glucose; glucose tolerance; Glucose Tolerance Test; Good samaritans; Health aspects; Health Promotion and Disease Prevention; Hot Temperature; Humans; Hyperglycemia; Hyperglycemia - complications; Hyperinsulinism - etiology; insulin; Insulin resistance; Internal Medicine; Male; Medical sciences; Medicine; Medicine & Public Health; Mental depression; Metabolic Diseases; Middle Aged; Nerve Fibers - physiology; Neurobiology; Neurons; neuropathy; Neurosciences; Obesity; Obesity, Morbid - complications; original-article; Pain; patients; Peripheral Nervous System Diseases - etiology; Probes; Public Health; Reaction Time; Regional Blood Flow; Risk factors; Sensation Disorders - etiology; sensory neurons; signs and symptoms (animals and humans); Skin - blood supply; Skin - innervation; skin diseases; small sensory fiber neuropathy; somatic small fiber neuropathy; tissue repair; Transcutaneous Electric Nerve Stimulation; vasodilation; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Wound healing
• ISSN: 0307-0565; 1476-5497
• DOI: 10.1038/sj.ijo.0803418

Background: Somatic cutaneous small sensory fiber neuropathy (SSFN) can be an early manifestation of impaired glucose tolerance and diabetes mellitus and/or insulin resistance among obese subjects and is often associated with pain, wound occurrence and impaired wound healing. It is yet unclear as to whether SSFN is prevalent among obese individuals without glucose and/or insulin dysregulation despite abundant evidence of delayed wound healing. Objective: To observe whether there is hypofunctioning of stimulated capsaicin-sensitive cutaneous nerves (small sensory fibers) in obese subjects with/without hyperglycemia and hyperinsulinemia. Design, setting and participants: Fifty-eight morbidly obese and 15 lean subjects were recruited for small fiber testing of the forearm in a cross-sectional study. Hyperglycemia was observed in 35 obese subjects. Of 25 obese subjects, hyperinsulinemia was noted in 15, 14 of which were hyperglycemic. No subjects demonstrated symptoms/signs of neuropathy over the hairy skin of the forearm. In fact, a neurological examination revealed that 37 subjects were asymptomatic in the legs and only four complained of a neuropathic pain in the foot. Virtually all subjects were exposed to a set of capsaicin-sensitive tests and measures which were identified by capsaicin desensitization procedures. These tests, conducted while in a supine position in bed at the Banner Good Samaritan Medical Center, Phoenix, examined the two principle roles of cutaneous SSFs, namely conveying pain signals to the CNS and controlling local neurogenic vasodilatation (flare; axon-reflex). Main outcome measures: Heat-induced pain was assessed by verbal reports of sensation after accommodation and heat-, capsaicin-, and transcutneous stimulation- induced blood flow was measured by laser Doppler flowmetry with probes placed at the site of stimulation and 1 cm remote from the site, the latter to evaluate flare latency and intensity of flare. Results: Significant depression of pain and flare responses were observed in the obese subjects in all but one test. Decreased pain and flare responses were noted in all subjects without hyperglycemia and hyperinsulinemia. Age negatively correlated with capsaicin-induced flare in both the obese and normal groups. Conclusion: SSFN was prevalent in the cohort of morbidly obese subjects in a skin area without neurological symptoms or signs and in subjects with/without hyperglycemia and hyperinsulinemia. SSFN may be a serious facto