Recombinant human insulin-like growth factor-I (IGF-I) therapy decreases plasma leptin concentration in patients with chronic renal insufficiency

OBJECTIVE: To determine the relationship between plasma leptin and insulin-like growth factor-I (IGF-I) levels in healthy subjects and patients with chronic renal insufficiency at baseline, and during administration of recombinant human IGF-I in the renal impaired patients. SUBJECTS: 20 healthy subjects (six men, 14 women, age: 42.7 ± 3.2 y) and nine subjects with chronic renal insufficiency (five men, four women, age: 53.6 ± 3.7 y). INTERVENTION: Daily sc injection of recombinant human IGF-I (50 μg/kg) for 24 d. MEASUREMEMTS: Fasting plasma levels of leptin, IGF-I, growth hormone, C-peptide, glucagon and IGF binding proteins by specific radioimmunoassays at baseline in all subjects and serially during IGF-I therapy in the renal impaired subjects. RESULTS: Baseline leptin levels were correlated with body mass index (BMI, R = 0.72, P = 0.0001) but not IGF-I levels (R = 0.02). During IGF-I therapy, plasma IGF-I levels increased from 128 ± 17.4 ng/ml at baseline to 250 ± 36.8 ng/ml on day 3 (P = 0.003) and 323 ± 61.6 ng/ml on day 24 (P = 0.01), whereas leptin levels declined: 24.4 ± 10.3 ng/ml (baseline), 19.5 ± 6.2 ng/ml (day 3, P = 0.028), and 17.2 ± 4.9 ng/ml (day 24, P = 0.05). CONCLUSION: Basal plasma leptin and IGF-I levels are not correlated; however, chronic administration of recombinant IGF-I is associated with an early and sustained decrease in plasma leptin levels. IGF-I may have an inhibitory effect on leptin secretion in humans.