title: Effect of zinc supplementation on serum leptin levels and insulin resistance of obese women.
abstract: Leptin is thought to be a lipostatic signal that contributes to body weight regulation. Zinc might play an important role in appetite regulation and its administration stimulates leptin production. However, there are few reports in the literature on its role on leptin levels in the obese population. The present work assesses the effect of zinc supplementation on serum leptin levels in insulin resistance (IR). A prospective double-blind, randomized, clinical, placebo-controlled study was conducted. Fifty-six normal glucose-tolerant obese women (age: 25-45 yr, body mass index [BMI] = 36.2 +/- 2.3 kg/m2) were randomized for treatment with 30 mg zinc daily for 4 wk. Baseline values of both groups were similar for age, BMI, caloric intake, insulin concentration, insulin resistance, and zinc concentration in diet, plasma, urine, and erythrocytes. Insulin and leptin were measured by radioimmunoassay and IR was estimated by the homeostasis model assessment (HOMA). The determinations of zinc in plasma, erythrocytes, and 24- h urine were performed by using atomic absorption spectrophotometry. After 4 wk, BMI, fasting glucose, and zinc concentration in plasma and erythrocyte did not change in either group, although zinc concentration in the urine increased from 385.9 +/- 259.3 to 470.2 +/- 241.2 +/- microg/24 h in the group with zinc supplementation (p < 0.05). Insulin did not change in the placebo group, whereas there was a significant decrease of this hormone in the supplemented group. HOMA also decreased from 5.8 +/- 2.6 to 4.3 +/- 1.7 (p < 0.05) in the zinc-supplemented group but did not change in the placebo group. Leptin did not change in the placebo group. In the zinc group, leptin was 23.6 +/- 12.3 microg/L and did not change. More human data from a unique population of obese individuals with documented insulin resistance would be useful in guiding future studies on zinc supplementation (with higher doses or longer intervals) or different measures.
authors.affiliation: Department of Food Science and Experimental Nutrition, School of Pharmacy, University of São Paulo, São Paulo, Brazil.
authors.forename: Dilina do Nascimento
authors.initials: DN
authors.lastname: Marreiro
authors.forename: Bruno
authors.initials: B
authors.lastname: Geloneze
authors.forename: Marcos A
authors.initials: MA
authors.lastname: Tambascia
authors.forename: Antonio C
authors.initials: AC
authors.lastname: Lerário
authors.forename: Alfredo
authors.initials: A
authors.lastname: Halpern
authors.forename: Silvia Maria Franciscato
authors.initials: SM
authors.lastname: Cozzolino
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D019587:Dietary Supplements; D004311:Double-Blind Method; D006801:Humans; D007333:Insulin Resistance; D020738:Leptin / Q000097:blood*; D008875:Middle Aged; D009765:Obesity / Q000097:blood* / Q000503:physiopathology; D010919:Placebos; D011446:Prospective Studies; D013054:Spectrophotometry, Atomic; D015032:Zinc / Q000008:administration & dosage* / Q000097:blood / Q000652:urine
chemical_list: D001786:Blood Glucose; D020738:Leptin; D010919:Placebos; D015032:Zinc