Association of serum leptin levels with homeostasis model assessment-estimated insulin resistance and metabolic syndrome: the key role of central obesity.
BACKGROUND
Leptin is correlated with several features of metabolic syndrome; however, possible confounders (eg, obesity) of this association are not known. This study evaluated the relationship between leptin, metabolic syndrome, and insulin resistance in an Iranian population and further investigated whether this relationship is confounded by obesity or central obesity.


METHODS
A total of 387 participants (18-65 years old) who referred to a large university general hospital for routine health examinations were categorized into 2 groups with (n = 130) and without (n = 257) metabolic syndrome. Fasting plasma glucose, insulin, lipids, and leptin levels were measured and the homeostasis model assessment of insulin resistance (HOMA-IR) was calculated. Metabolic syndrome was defined according to the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) criteria.


RESULTS
Age- and sex-adjusted leptin levels were significantly higher in patients with than those without metabolic syndrome (29.62 +/- 1.67 vs. 18.50 +/- 1.21 ng/mL, P < 0.001). After adjustment for age, sex, and body mass index (BMI), leptin values were significantly correlated with HOMA-IR (P < 0.001), metabolic syndrome, and its components (P < 0.05). After adjustment for waist circumference, however, these associations were no longer statistically significant.


CONCLUSIONS
We demonstrated that high leptin levels are associated with insulin resistance and metabolic syndrome independent of BMI but these associations are significantly mediated through the effects of central obesity.
Endocrinology and Metabolism Research Center (EMRC), Vali-Asr hospital, Tehran University of Medical Sciences, Tehran, Iran. esteghamati@tums.ac.ir
Alireza
A
Esteghamati
Omid
O
Khalilzadeh
Mehdi
M
Anvari
Armin
A
Rashidi
Mohammad
M
Mokhtari
Manouchehr
M
Nakhjavani
D000293:Adolescent; D000328:Adult; D000368:Aged; D044466:Asian People; D015415:Biomarkers / Q000097:blood; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D015986:Confounding Factors, Epidemiologic; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000208:ethnology; D007492:Iran / Q000453:epidemiology; D020738:Leptin / Q000097:blood*; D008055:Lipids / Q000097:blood; D016015:Logistic Models; D008297:Male; D024821:Metabolic Syndrome / Q000097:blood* / Q000208:ethnology / Q000503:physiopathology; D008875:Middle Aged; D008954:Models, Biological; D056128:Obesity, Abdominal / Q000097:blood* / Q000208:ethnology / Q000503:physiopathology; D018570:Risk Assessment; D012307:Risk Factors; D055105:Waist Circumference; D055815:Young Adult
D015415:Biomarkers; D001786:Blood Glucose; D007328:Insulin; D020738:Leptin; D008055:Lipids