IntroductionDiabetic sensorimotor polyneuropathy (DSPN) affects approximately 30% of people with diabetes, while around half of cases are symptomatic. Currently, there are only few pathogenetically oriented pharmacotherapies for DSPN, one of which is benfotiamine, a prodrug of thiamine with a high bioavailability and favourable safety profile. While benfotiamine has shown positive effects in preclinical and short-term clinical studies, no long-term clinical trials are available to demonstrate disease-modifying effects on DSPN using a comprehensive set of disease-related endpoints.Methods and analysisThe benfotiamine on morphometric, neurophysiological and clinical measures in patients with type 2 diabetes trial is a randomised double-blind, placebo-controlled parallel group monocentric phase II clinical trial to assess the effects of treatment with benfotiamine compared with placebo in participants with type 2 diabetes and mild to moderate symptomatic DSPN. Sixty participants will be 1:1 randomised to treatment with benfotiamine 300 mg or placebo two times a day over 12 months. The primary endpoint will be the change in corneal nerve fibre length assessed by corneal confocal microscopy (CCM) after 12 months of benfotiamine treatment compared with placebo. Secondary endpoints will include other CCM measures, skin biopsy and function indices, variables from somatic and autonomic nerve function tests, clinical examination and questionnaires, general health, health-related quality of life, cost, safety and blood tests.Ethics and disseminationThe trial was approved by the competent authority and the local independent ethics committee. Trial results will be published in peer-reviewed journals, conference abstracts, and via online and print media.Trial registration numberDRKS00014832.

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There is increasing evidence for a role of the metabolic syndrome (MetS) during development of distal sensorimotor polyneuropathy (DSPN). We hypothesized that MetS components are differentially associated with measures of DSPN in individuals with normal glucose tolerance (NGT) and early type 2 diabetes (T2D). Electrophysiological and quantitative sensory testing was performed in 180 participants with NGT and 355 with recent-onset T2D (known diabetes duration <1 year) matched for age from the German Diabetes Study (NGT/T2D [mean±SD]: age: 43.9±14.0/45.1±7.7 years; sex: 61/65% male; BMI: 26.8±5.0/32.3±6.5 kg/m²; HbA1c: 5.2±0.3/6.5±1.0%). Intraepidermal nerve fiber density (IENFD) was assessed in 218 individuals (NGT/T2D: n=117/101). Subsets of participants were followed for 5 years (NGT/T2D: n=48/53). MetS was defined according to International Diabetes Federation (2006) and DSPN according to Toronto consensus criteria (2011). After adjustment for age, sex, height, smoking and HbA1c, a lower IENFD was associated with higher weight (β=-0.306), number of MetS components (NMetSC; β=-0.222) and presence of central obesity (β=-0.292), while higher malleolar vibration perception threshold was associated with weight (β=0.219) in NGT (P<0.05), but not in T2D. Median motor nerve conduction velocity and sural sensory nerve action potential were inversely associated with weight (β=-0.182/-0.286), NMetSC (β=-0.127/-0.128), presence of central obesity (β=-0.163/-0.165), and MetS (β=-0.169/-0.203) in T2D (P<0.05). Higher weight predicted the presence of DSPN at 5 years (β=0.652, P=0.001) in NGT, while increasing NMetSC and MetS prevalence predicted a decline in IENFD over 5 years (β=-0.533/-0.388, P=0.001/0.013) in T2D. This suggests that obesity indices can predict DSPN over 5 years in NGT, while MetS and its components are differentially associated with measures of DSPN in early, well-controlled type 2 diabetes compared with NGT. Disclosure G.Sipola: None. A.Strom: None. M.Bombrich: None. R.Wagner: Advisory Panel; Daiichi Sankyo, Speaker's Bureau; Novo Nordisk, Sanofi. D.Ziegler: None. M.Roden: Advisory Panel; Eli Lilly and Company, Consultant; TARGET PharmaSolutions, Inc., Research Support; Boehringer-Ingelheim, Novo Nordisk, Novartis, Sanofi. G.J.Bönhof: None. Gds group: n/a. Funding German Federal Ministry of Health; Ministry of Innovation, Science, Research and Technology of the state North Rhine-Westphalia; German Federal Ministry of Education and Research

There is a lack of evidence on the long-term changes of nerve function in individuals with type 2 diabetes (T2D) compared to those with normal glucose tolerance (NGT). Therefore, we assessed motor and sensory nerve conduction velocities (MNCV, SNCV), sensory nerve action potentials, vibration perception threshold (VPT) and thermal detection threshold of lower extremities in 45 individuals with T2D (known diabetes duration [mean±SD]: 164±95 days) and NGT from the German Diabetes Study (GDS) at baseline (BL) and 5-year follow-up. Individuals were matched pairwise for age (T2D/NGT: 52.9±10.4/52.9±10.3 years) and sex (64/64% male). In addition, 103 individuals with T2D were followed over 10 years. At BL, 1/6 indices was lower in T2D vs NGT (peroneal MNCV: 45.6±4.0 vs 47.2±2.8 m/s; P<0.05). After five years, one index deteriorated in T2D (peroneal MNCV: 45.3±4.1 vs 43.5±3.8 m/s) and one in NGT (malleolar VPT: 1.29±1.88 vs 2.25±3.06 µm) (all P<0.05). After adjustment for BL values and pairwise matching, nerve function similarly declined over the first five years in T2D and NGT (e.g. Δperoneal MNCV; figure). A comparable deterioration was observed in individuals with T2D over 10 years (figure). Parallel decline in small and large fiber function in both NGT and well controlled T2D indicates that the main events leading to impaired nerve function in well controlled T2D might occur earlier than previously assumed. Disclosure A.Strom: None. K.Strassburger: None. G.Sipola: None. D.Ziegler: None. R.Wagner: Advisory Panel; Daiichi Sankyo, Speaker's Bureau; Novo Nordisk, Sanofi. M.Roden: Advisory Panel; Eli Lilly and Company, Consultant; TARGET PharmaSolutions, Inc., Research Support; Boehringer-Ingelheim, Novo Nordisk, Novartis, Sanofi. G.J.Bönhof: None. Gds group: n/a. Funding German Federal Ministry of Health; Ministry of Innovation, Science, Research and Technology of the state North Rhine-Westphalia; German Federal Ministry of Education and Research