Muscle and Bone in Patients with Diabetes Mellitus and Neuropathy

The goal of this observational study is to evaluate muscle fiber type composition in people with type 2 diabetes mellitus (T2DM) with a common complication of T2DM: diabetic peripheral neuropathy (DNP), specifically diabetic sensorimotor polyneuropathy. Researchers will also look into factors related to DNP: inflammation, the use of energy in the cell, nerve function and the tiny blood vessels in the muscle. The main question it aims to answer is: Are there differences in muscle fiber type composition between persons with T2DM with and without DNP, in comparison to sex and age-matched healthy peers? Participants will partake in the following tests: * electromyoneurography (EMNG): evaluation of nerve function, damage and repair; for diagnosis of DNP or other diseases of the nerves * blood analysis: researchers will measure insulin, blood sugar, lipid profile, inflammation * muscle biopsy in the calf (m. gastrocnemius): a doctor will take a small sample of muscle to evaluate the muscle shape and structure * mechanography: patients will perform functional tests (e.g. standing up from a chair), researchers will evaluate maximal power and maximal force of the muscles by jumping tests * questionnaires: on food intake, physical activity, smoking history, alcohol use, medical history * measurement of height, weight, and the comparison of the hip and waist circumference * peripheral Quantitative Computed Tomography (pQCT): scan of the calf for muscle density and bone density * electrocardiography (ECG): evaluation of electrical signals of the heart Researchers will compare (1) patients with T2DM with DNP, (2) patients with T2DM without DNP, and (3) healthy persons to see if there are differences in muscle fiber type composition