title: Axonal potassium conductance and glycemic control in human diabetic nerves.
abstract: OBJECTIVE
  To investigate the effects of hyperglycemia on axonal excitability and potassium conductance in human diabetic nerves.
  
  
  METHODS
  Threshold tracking was used to measure excitability indices, which depend on potassium channels (supernormality, late subnormality, threshold electrotonus, and a current/threshold relationship) in median motor axons of 96 diabetic patients. The effects of hyperglycemia on these indices were analyzed.
  
  
  RESULTS
  Among diabetic patients, higher serum hemoglobin A1c (HbA1c) levels were significantly associated with greater supernormality (P = 0.04) and smaller late subnormality (P = 0.02), suggestive of reduced nodal/paranodal potassium currents under hyperglycemia. Threshold electrotonus and current/threshold relationships did not correlate with HbA1c levels, but partly related with nerve conduction slowing.
  
  
  CONCLUSIONS
  Hyperglycemia could reduce nodal potassium conductances, possibly due to reduced membranous potassium gradient or suppression of potassium channels. In contrast, internodal potassium conductances may be determined by both metabolic factors and structural changes such as exposure of internodal channels by demyelination.
  
  
  CONCLUSIONS
  Measurements of the excitability indices could provide new insights into nodal and internodal axonal membrane properties in human diabetic neuropathy, whereas multiple factors can affect especially internodal properties.
authors.affiliation: Department of Neurology, Chiba University School of Medicine, Japan. somoko@mb.infoweb.ne.jp
authors.forename: Sonoko
authors.initials: S
authors.lastname: Misawa
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kuwabara
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Kanai
authors.forename: Noriko
authors.initials: N
authors.lastname: Tamura
authors.forename: Akiyuki
authors.initials: A
authors.lastname: Hiraga
authors.forename: Miho
authors.initials: M
authors.lastname: Nakata
authors.forename: Kazue
authors.initials: K
authors.lastname: Ogawara
authors.forename: Takamichi
authors.initials: T
authors.lastname: Hattori
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001369:Axons / Q000502:physiology*; D003920:Diabetes Mellitus / Q000503:physiopathology*; D003929:Diabetic Neuropathies / Q000503:physiopathology; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis; D006801:Humans; D006943:Hyperglycemia / Q000503:physiopathology*; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology*; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*
chemical_list: D006442:Glycated Hemoglobin; D011188:Potassium; D015221:Potassium Channels