Abstract
Interactions between leptin and insulin have been shown previously,
in vitro and in vivo. In this
study, we evaluate the associations of leptin levels with insulin secretion and
insulin sensitivity in type 2 diabetes. Fasting leptin levels,
HbA1c, glucose, insulin, C-peptide, intact and des-31,32-proinsulin
were measured in 100 non-insulin-treated type 2 diabetic patients. Glucose,
insulin and C-peptide were measured 2 hours after an oral glucose load. Insulin
resistance and β-cell function were calculated using HOMA. Leptin levels
were found to be associated with all measures of β-cell secretion: with
fasting and 2 hours insulin and C-peptide, with intact and des-31,32-proinsulin
concentrations, and with β-cell secretion estimated with HOMA. This
association was independent of age and body fat in women, but in men,
associations with insulin and C-peptide weakened after controlling for fat
mass, whereas those with intact and des-31,32-proinsulin disappeared. Fasting
insulin and C-peptide levels were also significant in multiple regression
analyses, besides gender and fat mass. Insulin resistance, as assessed by HOMA,
was strongly correlated with leptin, also after correction for age and fat mass
in both genders. We conclude that, besides fat mass and gender - the main
determinants for leptin levels in type 2 diabetic subjects as in healthy
subjects - insulin secretion and the degree of insulin resistance also
seem to contribute significantly to leptin levels.
Key words
Leptin - Type 2 Diabetes - Insulin Resistance - Proinsulin - β-Cell Function
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Prof. Dr. L. F. Van Gaal
University Hospital Antwerp · Dept. of Diabetology
Wilrijkstraat 10 · 2650 Edegem · Belgium
Telefon: +32 (3) 821 32 66
Fax: +32 (3) 825 49 80
eMail: luc.van.gaal@uza.be