Insulin resistance in human partial lipodystrophy

The common syndrome of insulin resistance is frequently seen in obese individuals, and is characterized by glucose intolerance, dyslipidemia, high blood pressure, and an increased risk of coronary heart disease. A rare genetic form of insulin resistance is Dunnigan-type familial partial lipodystrophy (FPLD; OMIM #151660), which is characterized by loss of subcutaneous fat from extremities, trunk, and gluteal region, and always by insulin resistance and hyperinsulinemia, often with hypertension, dyslipidemia, type-2 diabetes and early endpoints of atherosclerosis. FPLD was recently discovered to result from mutated LMNA (R482Q; OMIM #150330.0010), which is the gene encoding nuclear lamins A and C. Results from extended pedigrees indicate that dyslipidemia precedes the plasma glucose abnormalities in FPLD subjects with mutant LMNA, and that the hyperinsulinemia is present early in the course of the disease. Plasma leptin is also markedly reduced in subjects with FPLD due to mutant LMNA. Thus, rare mutations in a nuclear structural protein can be associated with markedly abnormal qualitative and quantitative phenotypes, indicating that a defect in the structure and function of the nuclear envelope can result in a phenotype that shares many aspects with the common syndrome of insulin resistance.