Insulin sensitivity in cystic fibrosis

Area of Science:

• Endocrinology
• Metabolic Research
• Genetics

Background:

• Cystic fibrosis (CF) is linked to pancreatic beta-cell dysfunction.
• CF patients exhibit a spectrum of insulin secretion and glucose metabolism abnormalities.
• Distinct patient groups (NEXO, EXO, EXO-IT) show varying degrees of exocrine insufficiency and diabetes status.

Purpose of the Study:

• To investigate insulin sensitivity and glucose utilization in different cystic fibrosis patient groups.
• To determine if enhanced peripheral insulin sensitivity compensates for impaired insulin secretion in exocrine-insufficient CF patients without diabetes (EXO).

Main Methods:

• Euglycemic-hyperinsulinemic clamp studies with isotope dilution to assess hepatic and peripheral insulin sensitivity.
• Hyperglycemic clamp studies to evaluate glucose-mediated glucose uptake (GMGU).
• Western blotting to analyze skeletal muscle GLUT4 levels in EXO and control patients.

Main Results:

• NEXO patients displayed normal insulin sensitivity.
• EXO patients showed enhanced peripheral insulin sensitivity but hepatic insulin resistance, with no change in GLUT4 abundance.
• Exocrine-insufficient patients with overt diabetes (EXO-IT) exhibited both peripheral and hepatic insulin resistance.
• GMGU was reduced in both EXO and EXO-IT groups.

Conclusions:

• CF patients present distinct patterns of insulin sensitivity related to pancreatic dysfunction.
• The metabolic profile in EXO patients suggests a compensatory adaptation involving increased peripheral glucose utilization and hepatic insulin resistance.
• These findings highlight the complex metabolic alterations in cystic fibrosis beyond simple insulin deficiency.