Comparison of leptin levels, body composition and insulin sensitivity and secretion by OGTT in healthy, early pubertal girls born at either appropriate- or small-for-gestational age

Abstract

Small for gestational age (SGA) has been associated with decreased insulin sensitivity (IS). A possible mechanism is the postnatal development of a metabolically disadvantageous body composition (BC). To determine whether there are differences between IS and BC in girls in early puberty who were SGA (birth weight < 10th percentile) or appropriate for gestational age (AGA, 10th-90th percentile). Age-matched (SGA/AGA) early pubertal girls (Tanner II) were recruited from local schools. We determined waist circumference (WC), the sum of four skinfolds (S4S), and per cent fat mass (fat %) by impedanciometry. Leptin and OGTT assays were performed. The insulinogenic index (I-In), HOMA-IR (homeostasis model assessment of insulin resistance) and WBISI (whole body insulin sensitivity) were calculated. Median age (interquartile range) for 30 SGA and 35 AGA girls was 10.2 (1.1) vs. 9.8 (0.9), respectively (P = NS). BMI percentiles were 62.6 (56) vs. 67.4 (39); WC 60.5 (9.5) vs. 62.2 (6.5) cm; S4S 52 (30) vs. 52.2 (29.5) cm, and fat %[26.2 (6.7) vs. 28.5 (6.3)] was similar in both groups. SGA girls had higher leptin levels [15.4 (9.7) vs. 9.6 (11) ng/ml; P = 0.01] and I-In [2.05 (1.86) vs. 1.47 (1.27) microU/ml* mg/dl; P = 0.02]. No differences between HOMA-IR [2.07 (1.26) vs. 2.04 (1.4)] and WBISI [5.3 (3.3) vs. 5.1 (3.1)] were found between groups. The higher leptin level and I-In in girls born SGA at the beginning of puberty may be early indicators of an underlying subtle degree of insulin resistance, despite similar BMI and BC to AGA girls.