Molecular mechanisms of Charcot-Marie-Tooth neuropathy linked to mutations in human myelin protein P2

Charcot-Marie-Tooth (CMT) disease is one of the most common inherited neuropathies. Recently, three CMT1-associated point mutations (I43N, T51P, and I52T) were discovered in the abundant peripheral myelin protein P2. These mutations trigger abnormal myelin structure, leading to reduced nerve conduction velocity, muscle weakness, and distal limb atrophy. P2 is a myelin-specific protein expressed by Schwann cells that binds to fatty acids and membranes, contributing to peripheral myelin lipid homeostasis. We studied the molecular basis of the P2 patient mutations. None of the CMT1-associated mutations alter the overall folding of P2 in the crystal state. P2 disease variants show increased aggregation tendency and remarkably reduced stability, T51P being most severe. In addition, P2 disease mutations affect protein dynamics. Both fatty acid binding by P2 and the kinetics of its membrane interactions are affected by the mutations. Experiments and simulations suggest opening of the β barrel in T51P, possibly representing a general mechanism in fatty acid-binding proteins. Our findings demonstrate that altered biophysical properties and functional dynamics of P2 may cause myelin defects in CMT1 patients. At the molecular level, a few malformed hydrogen bonds lead to structural instability and misregulation of conformational changes related to ligand exchange and membrane binding.

Improving quality of care in people with Type 2 diabetes through the Associazione Medici Diabetologi-annals initiative: a long-term cost-effectiveness analysis

AIMS

The Associazione Medici Diabetologi-annals initiative is a physician-led quality-of-care improvement scheme that has been shown to improve HbA1c concentration, blood pressure, lipid profiles and BMI in enrolled people with Type 2 diabetes. The present analysis investigated the long-term cost-effectiveness of enrolling people with Type 2 diabetes in the Associazione Medici Diabetologi-annals initiative compared with conventional management.

METHODS

Long-term projections of clinical outcomes and direct costs (in 2010 Euros) were made using a published and validated model of Type 2 diabetes in people with Type 2 diabetes who were either enrolled in the Associazione Medici Diabetologi-annals initiative or who were receiving conventional management. Treatment effects were based on mean changes from baseline seen at 5 years after enrolment in the scheme. Costs and clinical outcomes were discounted at 3% per annum.

RESULTS

The Associazione Medici Diabetologi-annals initiative was associated with improvements in mean discounted life expectancy and quality-adjusted life expectancy of 0.55 years (95% CI 0.54-0.57) years and 0.48 quality-adjusted life years (95% CI 0.46-0.49), respectively, compared with conventional management. Whilst treatment costs were higher in the Associazione Medici Diabetologi-annals arm, this was offset by savings as a result of the reduced incidence and treatment of diabetes-related complications. The Associazione Medici Diabetologi-annals initiative was found to be cost-saving over patient lifetimes compared with conventional management [€ 37,289 (95% CI 37,205-37,372) vs € 41,075 (95% CI 40,956-41,155)].

CONCLUSIONS

Long-term projections indicate that the physician-led Associazione Medici Diabetologi-annals initiative represents a cost-saving method of improving long-term clinical outcomes compared with conventional management of people with Type 2 diabetes in Italy.