Long-Term Hyperglycemia Affects the Expression of Diaph1 and Its Cytoskeleton Ligands in the Epidermis of Diabetic Patients—A Quantitative Study

Background/Objectives: Diabetic small fiber neuropathy and related sensory and epidermal problems affect up to 70% of all patients with diabetes. Long-term hyperglycemia disrupts cytoskeletal organization and axonal transport; however, molecular changes within human diabetic epidermis remain understudied. Diaph1 and its cytoskeletal ligands, including β-Actin and Profilin, are key regulators of cytoskeletal dynamics and may be associated with diabetes-related alterations in skin structure and innervation. Methods: Sixteen patients with type 2 diabetes, aged 43.3 ± 9.6 years (disease duration 18.9 ± 8.7 years), and twelve non-diabetic controls, aged 43.9 ± 8.9 years, were enrolled in the study. All participants provided informed consent. Skin punch biopsies were obtained under local anesthesia and processed for staining of PGP 9.5, Diaph1, β-Actin, and Profilin. Quantitative image analysis was performed to assess stained area fraction, signal intensity, and intraepidermal nerve fiber density. Statistical comparisons and Spearman’s rank correlation analyses were used to evaluate group differences and associations between staining parameters. Results: Diabetic skin samples exhibited a significant reduction in PGP 9.5-positive intraepidermal nerve fibers, indicating reduced cutaneous innervation. In contrast, Diaph1 and Profilin showed broader and more diffuse epidermal staining, while β-Actin displayed altered staining patterns and intensity. Significant correlations between Diaph1- and β-Actin-related staining measures indicated an association consistent with altered cytoskeletal organization under chronic hyperglycemic conditions. Conclusions: Long-standing type 2 diabetes was associated with reduced PGP 9.5-positive intraepidermal nerve fibers, together with altered epidermal staining patterns of Diaph1, Profilin and β-Actin. These findings indicate coexisting cutaneous denervation and cytoskeletal alterations in diabetic skin.