Factors influencing sweat gland innervation in diabetes

Using a stereologic approach, the density of nerve fibers innervating sweat gland (SG) fragments in patients with diabetes mellitus (DM) and healthy controls using protein gene product (PGP), tyrosine hydroxylase (TH), and vasoactive intestinal peptide (VIP) was measured to determine which marker best detected differences between the groups. Factors associated with SG nerve fiber (SGNF) innervation were assessed and the change in SG innervation over a 1-year time period was determined.

Ninety-two control subjects and 2 groups of subjects with DM totaling 97 were assessed in this cross-sectional study. Intraepidermal nerve fiber density and SG innervation were determined from leg skin biopsies that were immunohistochemically stained for ubiquitin hydrolase, VIP, and TH. Factors associated with SG innervation were assessed and 15 subjects were longitudinally followed for 1 year.

SGNF innervation was reduced in subjects with DM compared with controls. Lower SG innervation values were associated with increasing glycated hemoglobin A1c, body mass index (BMI), men compared with women, and tobacco use, but not diabetes type or age. Sex, A1c, and BMI remained significant in multivariate modeling. SG innervation measured by VIP+ fibers is a more sensitive marker for neuropathy than either PGP or TH. Fifteen subjects with DM followed for 1 year showed a significant decrease in SGNF innervation but not intraepidermal nerve fiber density.

Stereologic measurement of SG innervation is feasible to assess postganglionic autonomic nerve fiber densities. SG innervation was reduced in subjects with DM compared with control subjects and was associated with sex, A1c, and BMI in multivariate modeling. VIP+ SGNF is more severely reduced in DM than TH+ or PGP9.5+-based assessments. Progression of diabetic polyneuropathy was detected by SGNF over a 1-year time period.