Plasma soluble α-klotho protein levels in premature and term neonates: correlations with growth and metabolic parameters.

OBJECTIVE: α-Klotho (α-KL), a protein with antiaging properties, regulates phosphate, calcium, and bone metabolism, induces resistance to oxidative stress, and may participate in insulin signaling. The role of α-KL in neonates, known to be prone to metabolic disturbances and oxidative stress, is not known. The aim of this study was to evaluate circulating soluble α-KL concentrations in preterm and full-term neonates and unravel possible correlations with growth, metabolism, and indices of oxidative stress. DESIGN: Prospective study. METHODS: Plasma-soluble α-KL levels were determined by specific ELISA in 50 healthy neonates (25 preterm, mean (s.d.) gestational age (GA) 33.7 (1.1) weeks, and 25 full-term infants) at days 14 and 28 of life. Associations of α-KL with anthropometric, metabolic parameters, and indices of oxidative stress were examined. RESULTS: α-KL levels were significantly higher in full-term than in preterm infants at both days 14 (1099 (480) pg/ml vs 884 (239) pg/ml respectively; P<0.05) and 28 (1277 (444) pg/ml vs 983 (264) pg/ml respectively; P<0.01). In both preterm and full-term infants, α-KL levels increased significantly from day 14 to 28 of life (P<0.001). Circulating α-KL concentrations correlated with GA (ß=0.32, P=0.001), body weight (ß=0.34, P=0.001), body length (ß=0.33, P=0.001), 1,25-dihydroxy-vitamin D level (ß=0.24, P<0.05), and malondialdehyde level (ß=0.20, P<0.05) but not with glucose, insulin, or homeostasis model assessment index of insulin resistance values. CONCLUSIONS: Soluble α-KL levels rise as GA and postnatal age advance in neonates and may have an impact on vitamin D metabolism and oxidative stress. Whether α-KL may have a role in the regulation of infants' growth should be further studied.

Disparity in circulating adiponectin multimers between term and preterm infants.

AIMS: To study circulating levels and distribution of adiponectin multimers [low molecular weight (LMW)-, medium molecular weight (MMW)- and high molecular weight (HMW)-adiponectin] in preterm and full-term infants. METHODS: Total serum adiponectin and its multimers were measured in 40 healthy infants at the age of one month and associations with anthropometric parameters [body weight and length, body mass index (BMI)], weight gain and metabolic indices (glucose, insulin) were examined. Twenty of the infants were born preterm (gestational age 33.2+/-1.6 weeks). RESULTS: LMW-adiponectin level and its fractional ratio to total adiponectin were significantly higher in full-term than in preterm infants (P<0.001 and P<0.01, respectively), whereas, MMW-adiponectin level and its ratio were significantly lower (P=0.03 and P=0.01, respectively). HMW-adiponectin did not differ significantly between full-term and preterm infants and accounted for almost 60% of total adiponectin levels in both groups. HMW-adiponectin, but not MMW adiponectin or LMW adiponectin, correlated significantly with anthropometric measurements, similarly to total adiponectin; in addition, HMW adiponectin correlated significantly with weight gain. CONCLUSIONS: HMW adiponectin is the most prevalent form in infants. Circulating levels and distribution of MMW- and LMW-adiponectin differ between full-term and preterm infants, but the role of these adiponectin multimers needs to be studied further.