The IGF-I/IGFBP system in congenital partial lipodystrophy

Area of Science:

• Endocrinology
• Metabolic Disorders
• Genetics

Background:

• Congenital partial lipodystrophy is a rare syndrome characterized by insulin resistance, hyperinsulinemia, and fat distribution abnormalities.
• Patients may exhibit acromegaloid features, including thickened skin and enlarged extremities, despite normal growth hormone levels.

Purpose of the Study:

• To investigate the insulin-like growth factor-I/insulin-like growth factor binding protein (IGF-I/IGFBP) system in patients with congenital partial lipodystrophy.
• To explore the relationship between IGF-I/IGFBP levels and the development of acromegaloid features.

Main Methods:

• Assessed IGF-I receptor number and affinity on peripheral blood mononuclear cells (PBMCs) and erythrocytes.
• Measured serum concentrations of insulin, total and free IGF-I, IGFBP-1, and IGFBP-3 in fasting and fed states.
• Evaluated the effect of IGF-I stimulation on thymidine uptake in PBMC cultures in vitro.

Main Results:

• Patients exhibited significantly higher insulin levels and lower serum IGFBP-1 compared to controls.
• The free IGF-I/IGFBP-1 ratio was elevated in lipodystrophy patients in both fasting and fed states.
• IGF-I stimulation of PBMCs showed no significant difference in thymidine uptake, even with low IGFBP-1 concentrations.

Conclusions:

• The study identified hyperinsulinemia and an increased free IGF-I/IGFBP-1 ratio in congenital partial lipodystrophy.
• These alterations suggest unopposed IGF-I activity, potentially contributing to acromegaloid features, acanthosis nigricans, and polycystic ovaries.
• The findings highlight the complex interplay of the IGF system in this rare metabolic disorder.