Altered distribution of adiponectin isoforms in children with Prader-Willi syndrome (PWS): association with insulin sensitivity and circulating satiety peptide hormones.
OBJECTIVE
Prader-Willi syndrome (PWS) is a genetic syndrome characterized by relative hypoinsulinaemia and normal or increased insulin sensitivity despite profound obesity. We hypothesized that this increased insulin sensitivity is mediated by increased levels of total and high molecular weight adiponectin and associated with changes in levels of satiety hormones.


METHODS
We measured total adiponectin and its isoforms [high molecular weight (HMW), middle molecular weight (MMW) and low molecular weight (LMW) adiponectin] and satiety hormones in 14 children with PWS [median age 11.35 years, body mass index (BMI) Z-score 2.15] and 14 BMI-matched controls (median age 11.97 years, BMI Z-score 2.34).


RESULTS
Despite comparable BMI Z-scores and leptin levels, the PWS children exhibited lower fasting insulin and HOMA-IR (homeostasis model assessment of insulin resistance) scores compared to obese controls. For any given BMI Z-score, the PWS children showed higher concentrations of fasting total and HMW adiponectin and higher HMW/total adiponectin ratios. The HMW/total adioponectin ratio was preserved in children with PWS at high degrees of obesity. In PWS children, fasting plasma total adiponectin, HMW adiponectin and HMW/total adiponectin ratio correlated negatively with age (P < 0.05), HOMA-IR (P < 0.01), BMI Z-score (P < 0.05), insulin (P < 0.01) and leptin (P < 0.05). In addition to higher fasting ghrelin concentrations, the PWS children showed significantly higher fasting levels of total peptide YY (PYY) and gastric inhibitory polypeptide (GIP) compared to obese controls.


CONCLUSIONS
Relative to controls of similar age and BMI Z-score, the PWS children had significantly higher levels of total and HMW adiponectin, and increased ratios of HMW/total adiponectin. These findings may explain in part the heightened insulin sensitivity of PWS children relative to BMI-matched controls.
Haqq
Andrea M
AM
Department of Pediatrics, Division of Pediatric Endocrinology, Duke University Medical Center, Durham, NC 27710, USA. haqq0001@mc.duke.edu
Muehlbauer
Michael
M
Svetkey
Laura P
LP
Newgard
Christopher B
CB
Purnell
Jonathan Q
JQ
Grambow
Steven C
SC
Freemark
Michael S
MS
D052242:Adiponectin / Q000097:blood*; D000293:Adolescent; D002648:Child; D005260:Female; D005749:Gastric Inhibitory Polypeptide / Q000097:blood; D054439:Ghrelin / Q000097:blood; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology; D020738:Leptin / Q000097:blood; D008297:Male; D008970:Molecular Weight; D036361:Peptide Hormones / Q000097:blood*; D019894:Peptide YY / Q000097:blood; D011218:Prader-Willi Syndrome / Q000097:blood*; D020033:Protein Isoforms / Q000097:blood*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood
D052242:Adiponectin; D054439:Ghrelin; D007328:Insulin; D020738:Leptin; D036361:Peptide Hormones; D020033:Protein Isoforms; D019894:Peptide YY; D005749:Gastric Inhibitory Polypeptide; D013972:Thyrotropin; D013974:Thyroxine