Experimental, double-blind, randomized, prospective, placebo-controlled study. Patients aged
4-17 years old are selected from the endocrine outpatient clinic of the Hospital de Pediatria
del CMN "Siglo XXI", and both patients and parents sign informed consent. They are scheduled
for a fasting oral glucose tolerance test (OGTT) with 1.75 mg/kg of oral glucose. A blood
sample is taken from antecubital vein at baseline and 120 minutes.
A high carbohydrate diet is indicated for 3 days prior to the test. All patients diagnosed
with glucose intolerance are invited to participate. All followed an aerobic program of 30 to
45 minutes every day, an isocaloric diet from the moment of inclusion throughout the study
period, in order to decrease the effect of nutrition modification in the metabolic and
vascular parameters. A complete medical history is taken, recording family background of
diabetes plus blood pressure, heart rate and Tanner stage13. Age, body weight, height, waist
circumference are measured and recorded in percentile according to age and gender, and the
body mass index is calculated (kg/m2), and recorded in percentile according to reference
values of the Center for the Disease Control, Atlanta, GA14. Subjects are randomized for
metformin or placebo. Both metformin and placebo are placed in capsules with gelatin to blind
their aspect. Treatments are administered during 3 months. Children are evaluated monthly,
measuring transaminases, glucose, creatinine, and uric acid. Measurements of C reactive
protein, cytokines, adipokines, insulin concentrations, HbA1c levels and lipid profile are
made at the beginning and end of the study. Insulin resistance was assayed by HOMA-IR index.
Beta cell function is determined by using HOMA-β. These are complemented with an evaluation
of diet, physical activity, and physical examination.
Treatment assignment: Two groups are formed, randomly assigned using a table of random
numbers previously designed with the Epistat statistic package (Round Rock, Texas). When the
screening finished, every child receives a consecutive number. This number corresponds to an
envelope with a card identifying his/her medication flasks, containing 60 tablets of 850 mg
or placebo. The content of the capsules is not identified, so both the physician and the
patient are blinded. A blinded member of the study prepared the flasks and labeled them.
Participants take the capsules twice daily, at breakfast and dinner. They are instructed to
take medication with meals in order to decrease the possibility of adverse effects (nausea,
meteorism, diarrhea), which are checked during every visit. Hepatic function is monitored
during the study.
FPG, total cholesterol, HDL-cholesterol, triglycerides, liver function tests and creatinine
are measured using the Synchron CX analyzer (Beckman Systems, Fullerton CA), according to the
standard protocols. The coefficients of variation for cholesterol and HDL-cholesterol are
3.3% and 2.5% respectively. Plasma leptin, adiponectin and insulin concentrations are
measured in duplicate by radioinmmunoassay (Linco Research Inc, St Charles, MO). HbA1c is
determined in whole blood using ion exchange high performance liquid chromatography (normal
range 4-6). Plasma resistin is measured using Human Resistin Elisa Kit (PeproTech, Rock Hill,
NJ, USA) read by Multiscan EX, Lab Systems, USA). Plasma IL-6, IL1-b, TNF-α concentrations
are determined by ELISA using Quantike HS Human Immunoassay Kits (R&D Systems, Minneapolis,
MN, USA), plasma C-reactive protein (hs-CRP) is measured using a highly sensitive human CRP
ELISA Kit (Alpha diagnostic international, San Antonio, TX, USA ) according to the
manufacturer's instructions and are read by an ELISA reader (Sunrise, Tecan USA, Durham
NC,USA).