Επίπεδα αντιπονεκτίνης και πολυμορφισμοί του γονιδίου της στον ορό παιδιών και εφήβων με παχυσαρκία και υποθρεψία. Συσχέτιση με τη σύσταση του σώματος και την αντίσταση στην ινσουλίνη

Abstract

Obesity is one of the major public health problems and has become an epidemic in developed countries. Its complications such as Type 2 Diabetes Mellitus DM-2 are some of the main morbidity and mortality causes. Adipose tissue and adipokines produced by it play a crucial role in the pathogenesis of these complications. Among them, adiponectin is of particular importance. Its levels are decreased in obese subjects, increased in patients with negatives energy balance and are related to single nucleotide polymorphisms of the adiponectin gene. In addition, it is related to conditions such as visceral adiposity, insulin resistance, DM-2, cardiovascular disease for which it has been suggested as a prognostic biomarker. Little is known about the function of adiponectin during childhood while its levels have not been studied in the Greek population. The aims of the present study were to investigate adiponectin levels and the factors that affect them in children and adolescents of Greek ethnic background with obesity and malnutrition. More specifically, the study involved the investigation of: 1) adiponectin levels in the serum of obese children and adolescents and their association with body composition and insulin resistance, 2) adiponectin levels in patients with malnutrition 3) certain single nucleotide polymorphisms of the adiponectin gene and their association with its concentration, body composition, and insulin resistance. This was a prospective study, and was carried out at the 4th Department of Pediatrics, Aristotle University of Thessaloniki, Papageorgiou General Hospital. Obese patients were recruited from the Pediatric Endocrinology Outpatient Clinic and patients with malnutrition were recruited from the Cystic Fibrosis (CF) Special Unit of the Department. Three groups of patients were included in the study: 1) Obese children and adolescents, 2) Children, adolescents and adults with cystic fibrosis with and without malnutrition, 3) Age and sex-matched healthy children, adolescents and adults with normal BMI as control groups. Obese patients were divided according to their age, puberty stage and gender. Cystic fibrosis patients were divided according to their age and nutritional status. The study protocol included the assessment of body composition with Bioelectrical Impedance Analysis (BIA), measurement of blood lipids, assessment of insulin resistance with oral glucose tolerance testing (OGTT). For CF patients and control groups that did not undergo OGTT, fasting insulin resistance indices (FGIR and HOMA-IR) were used. Blood samples for the measurement of adiponectin and genetic analysis were collected. Adiponectin levels were measured with ELISA. In a subset of obese patients genetic analysis was performed PCR-RFLP with for the detection of the SNP45T→G and SNP276G→T polymorphisms. The results of the study were: Obese children and adolescents had significantly higher insulin resistance and lower adiponectin levels in comparison to control groups. Obese adolescent males had the lowest adiponectin concentrations. This is in agreement with other studies that involve subjects of different ethnic and racial background. The study did not reveal a strong association with percentage of body fat. Other studies had conflicting results. Adiponectin levels have been associated mainly to the amount of visceral adipose tissue. This difference can be explained by the fact that in the present study total and not visceral fat was measured. In all 123 subjects (except CF patients), an important correlation between adiponectin and insulin resistance (HOMA-IR, FGIR) was observed. This finding is in agreement with adult studies. In obese patients, adiponectin correlated significantly with indices of hyperinsulinemia and insulin sensitivity derived from the OGTT (Insulin at 30′, Mean Insulin during OGTT, AUC insulin, WBISI). Similar studies in children are scarce and yielded similar conclusions. With regard to CF patients, young patients with malnutrition had the lowest adiponectin levels while young patients with normal nutritional status had higher adiponectin levels in comparison to malnourished patients and healthy controls. There are only two published studies that concern adiponectin levels in CF patients with conflicting results. In the present study, low adiponectin concentration in young malnourished patients can be attributed to a mechanism similar to lipodystrophy that is also associated with low adiponectin levels because of body fat reduction and redistribution. On the contrary, increased adiponectin levels in young CF patients with normal nutrition can be attributed to their increased energy needs, because of growth, and the negative energy balance related to the disease. To further explore this finding, data from other patient groups with energy intake restriction (e.g. anorexia nervosa) can be taken into consideration. Additionally, high adiponectin levels in CF patients were associated with the presence of nodular biliary cirrhosis. This is a novel finding since it has never been studied in the past. Studies in patients with cirrhosis of different etiology however, also showed increased adiponectin levels. Finally, adiponectin gene polymorphisms SNP45T→G and SNP276G→T are common in the population that was examined. They are associated with higher adiponectin levels (not significantly). Their presence does not affect the degree of obesity, body composition, and the degree of insulin resistance. SNP + 276 specifically, is associated with lower risk for insulin resistance and lower total and LDL-cholesterol. Haplotype TG/X was associated with lower adiponectin concentrations in comparison to the other two haplotypes (TG/TG and X/X).

Η αντιπονεκτίνη είναι μια λιποκυτταροκίνη η οποία παράγεται αποκλειστικά από τα λιποκύτταρα και έχει ιδιότητες αντιφλεγμονώδεις, αντι-διαβητικές και αντιαθηρογενετικές. Σκοπός: η μέτρηση των επιπέδων αντιπονεκτίνης (ΑΝΤ) στον ορό παιδιών και εφήβων με παχυσαρκία και υποθρεψία και ο συσχετισμός τους με την αντίσταση στην ινσουλίνη (ΑΙ), το % λίπους σώματος (%ΛΣ), και τους πολυμορφισμούς του γονιδίου της. Υλικό-Μέθοδοι: Συμπεριλήφθησαν: 80 παχύσαρκα παιδιά και έφηβοι (44Θ) ηλικίας 11,09±2,54 ετών, 17 παιδιά, έφηβοι και ενήλικες με υποθρεψία εξαιτίας Κυστικής Ίνωσης (ΚΙ), 26 παιδιά, έφηβοι και ενήλικες με ΚΙ και φυσιολογική θρέψη και 43 μη-παχύσαρκα παιδιά και έφηβοι αντίστοιχης ηλικίας και φύλου. Μετρήθηκαν: Δείκτης Μάζας Σώματος (BMI) και σταθερή απόκλιση (ΒΜΙ-SDS), %ΛΣ, (Ανάλυση Βιοηλεκτρικής Εμπέδησης), δείκτες ΑΙ (HOMA-IR, FGIR). Οι παχύσαρκοι υποβλήθηκαν σε από του στόματος δοκιμασία ανοχής στη γλυκόζη (OGTT). Οι συγκεντρώσεις ΑΝΤ μετρήθηκαν με ELISA. Σε 48 παχύσαρκα παιδιά αναζητήθηκαν οι πολυμορφισμοί μιας βάσης (SNP) του γονιδίου της ΑΝΤ (SNP45T→G, SNP276G→T) με PCR-RFLP (Polymerase Chain Reaction-Restriction Fragment Length Polymorphism). Αποτελέσματα: (ΜΟ±ΣΑ): Τα επίπεδα της AD ήταν χαμηλότερα στα παχύσαρκα άτομα (8.11±3.80 έναντι 11.81±4.98 g/ml, p<0.001) και στους παχύσαρκους έφηβους σε σχέση με τα κορίτσια (5.87±3.52 έναντι 8.31±3.16g/ml, p=0.042). Βρέθηκε σημαντική συσχέτιση της ΑΝΤ με: ηλικία, ΒΜΙ, BMI-SDS, HOMA-IR και FGIR. Στους παχύσαρκους η ΑΝΤ παρουσίαζε συσχέτιση με τις παραμέτρους: AUCγλυκόζη, AUCινσουλίνη, WBISI, Γλυκόζη120, και Ινσουλίνη 30 αλλά όχι με το %ΛΣ. Όσον αφορά τους ασθενείς με ΚΙ τα χαμηλότερα επίπεδα διαπιστώθηκαν στους νέους ασθενείς και υποθρεψία ενώ τα υψηλότερα στους ασθενείς με φυσιολογική θρέψη. Από τον γονοτυπικό έλεγχο βρέθηκαν οι εξής γονότυποι: 45T/T(69%), 45T/G(27%), 45G/G(4%) και 276G/G(41%), 276G/T(51%) και 276T/T(8%), όλοι σε ισορροπία Hardy-Weinberg. Σε σύγκριση με το γονότυπο 45T/T, ένα ή δύο G-αλλήλια στη θέση 45 δε συσχετίζονταν με ΑΙ ή χαμηλότερη ΑΝΤ. Σε σύγκριση με τον γονότυπο 276G/G, ένα ή δύο Τ-αλλήλια στη θέση 276 συσχετίζονταν με μειωμένο κίνδυνο για ΑΙ. Συμπέρασμα: Η ΑΝΤ είναι χαμηλότερη στα παχύσαρκα άτομα, παρουσιάζει συσχέτιση με την ΑΙ και αξίζει να διερευνηθεί η χρήση της ως δείκτη ΑΙ. Επίσης είναι μειωμένη στα παιδιά και τους εφήβους με ΚΙ και υποθρεψία ενώ είναι αυξημένη στα παιδιά και εφήβους με ΚΙ και φυσιολογική θρέψη καθώς και σε ασθενείς με ΚΙ και ηπατική νόσο. Οι πολυμορφισμοί 45T/G και 276G/T είναι συχνοί. Ο SNP276G-T συσχετίζεται με χαμηλότερο κίνδυνο για ΑΙ και η μελέτη του σε παχύσαρκα Ελληνόπουλα μπορεί να δώσει πληροφορίες για τον κίνδυνο ΑΙ.