Content area
Full Text
International Journal of Obesity (2007) 31, 226235 & 2007 Nature Publishing Group All rights reserved 0307-0565/07 $30.00
www.nature.com/ijo
RM Herman1,2, JB Brower1,2, DG Stoddard1, AR Casano1, JH Targovnik1,3, JH Herman1 and P Tearse1
1Clinical Neurobiology and Bioengineering Research Center, Banner Good Samaritan Medical Center, Phoenix, AZ, USA;
2Harrington Department of Bioengineering, Arizona State University, Tempe, AZ, USA and 3Carl T. Hayden VA Medical Center, Phoenix, AZ, USA
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...