Circulating levels of adiponectin in preterm infants

Abstract

Objective: To determine circulating levels of adiponectin in preterm infants and examine possible associations with anthropometric measurements, weight gain, and leptin and insulin levels. Design: Prospective study. Setting: A university hospital neonatal care unit. Study population: 62 preterm (mean (SD) gestational age 32.0 (2.1) weeks) and 15 full-term infants (reference group). Interventions: Blood samples taken at discharge (40.9 (14.8) days of life) from the preterm infants and at a comparable postnatal age in full-term infants. All infants were fed the same commercial formula, but in nine preterms the formula contained long-chain polyunsaturated fatty acids (LCPUFAs). Main outcome measures: Serum levels of adiponectin, leptin and insulin. Associations of adiponectin levels were tested only in the preterm group. Results: Serum levels of adiponectin were lower in preterm (40.9 (14.8) mg/ml) than full-term infants (53.1 (16.0) mg/ml, p,0.01). However, after adjustment for body weight, the influence of prematurity on adiponectin levels was no longer significant. In preterm infants, adiponectin levels independently correlated with being born small for gestational age (SGA) (b = 20.35, p = 0.01), weight gain (b = 0.28, p = 0.03) and LCPUFA-supplemented formula (b = 0.34, p = 0.009). Serum adiponectin levels did not correlate with insulin or leptin levels. However, insulin levels were higher in preterm than in full-term infants after adjustment for body weight. Conclusions: Adiponectin levels are lower in preterm infants at discharge than full-term infants probably due to decreased adiposity. The levels are influenced by being born SGA, weight gain and, possibly, by dietary LCPUFAs. The importance of these findings in the development of insulin or leptin resistance in children born prematurely needs to be further studied. N utrition and growth during fetal life and early infancy have been linked to health and disease in later life.

Peptide YY (3-36) Represents a High Percentage of Total PYY Immunoreactivity in Preterm and Full-Term Infants and Correlates Independently With Markers of Adiposity and Serum Ghrelin Concentrations

“…Although the absence of such a correlation in full term infants may be due to their limited number, it is in accordance with previous studies in older children and adults (16,21). We reported previously that insulin levels tended to be higher in preterm than in full term infants after adjustment for body weight and a negative correlation between insulin levels and the body weight of preterm infants was observed (10). Under hyperinsulinemic conditions, PYY (3-36) reinforces insulin action on glucose disposal in animals, thus exerting an insulin sensitizing effect (22); whether PYY (3-36) increases in our preterm infants to exert such an action is not known.…”

“…Blood was obtained, before feeding, in the morning of the day of discharge in preterm infants [40.9 (14.8) days of life] and at a comparable postnatal age in full term infants [35.1 (15.3) days of life] for routine blood tests, as well as for serum PYY (3-36), total PYY, ghrelin, leptin, insulin and adiponectin level determinations. The anthropometric characteristics of the study population at testing, caloric intake, weight gain and the levels of hormones studied, but not PYY (3-36) values, were reported previously (9,10) and are summarized in Table 1.…”

“…The intraassay and interassay coefficients of variation (CV) were 7.0% and 6.4%, respectively, and the lower limit of detection was 20 ng/L. Serum concentrations of total PYY, ghrelin and adiponectin were also determined by RIA, whereas serum leptin and insulin levels were measured by ELISA and chemiluminescence immunoassay, respectively, as described previously (9,10). Total PYY RIA (Linco Research) recognizes both the 1-36 and 3-36 forms of human PYY, with an interassay CV of 6.5% and intraassay CV of 4.5%.…”

Circulating Adiponectin in Preterm Infants Fed Long-Chain Polyunsaturated Fatty Acids (LCPUFA)-Supplemented Formula—A Randomized Controlled Study

“…The sample size was calculated using our previous report of adiponectin concentrations in preterm infants (5). Assuming an alpha risk of 0.05, a power of 0.80 and a bilateral test, it was estimated that approximately 20 infants were needed in each group to detect a significant difference of 1 SD in mean adiponectin levels between ϩLCPUFA and ϪLCPUFA/control groups.…”

“…Moreover, preterm infants are also at risk for insulin resistance, and possibly for other components of metabolic syndrome, irrespective of whether they were born appropriate or small for gestational age (3,4). Although the underlying mechanism(s) connecting preterm birth and the development of metabolic syndrome risk are not known, circulating concentrations of adiponectin have been shown to be lower in preterm than in full term infants (5). Adiponectin is an adipocyte-derived protein, which has potent insulinsensitizing effects, improves lipid metabolism, and potentially protects against the development of insulin resistance and metabolic syndrome (6).…”