L. Perrone

Low frequency of melanocortin-4 receptor (MC4R) mutations in a Mediterranean population with early-onset obesity.

Background: Melanocortin-4 receptor (MC4R) mutations have been reported as the most common single genetic cause of obesity in some populations and it has been suggested that they may be responsible for more than 4% of early-onset obesity.Objectives: To verify the presence of mutations of the MC4R coding region in children from southern Italy with early-onset obesity.Subjects and Methods: Two-hundred and eight unrelated obese children and adolescents were included in the study. The average age at obesity onset was 4.5±2.6u2005y. MC4R coding region was screened using both single-strand conformation polymorphism (SSCP) analysis and denaturing high-performance liquid chromatography (DHPLC). Automatic sequencing of PCR products of all individuals that showed an aberrant SSCP and/or DHPLC pattern was performed.Results: One novel missense mutation and one previously described polymorphism (Vall03Ile) were identified. The missense mutation C142T, resulting in the substitution of proline with serine at codon 48, within the first MC4R transmembrane domain, was detected at the heterozygous state in a 15-y-old obese girl (body mass index (BMI)=35u2005kg/m2) who has been obese since she was 8u2005y old. The mutation co-segregated with the obesity phenotype for over three generations and was not found in the control population.Conclusions: Our data show MC4R obesity causing mutations in less than 0.5% of the patients (ie 1 out of 208 patients) and therefore indicate a low prevalence of MC4R variants in the obese population from southern Italy. The specific genetic background of the Mediterranean population could make it difficult for MC4R mutations to produce an essentially polygenic trait such as common obesity, at least during childhood.

Molecular screening of the ghrelin gene in Italian obese children: the Leu72Met variant is associated with an earlier onset of obesity

OBJECTIVE: To test whether ghrelin variants could play a role in modulating some aspects of the obese phenotype during childhood.DESIGN: We screened the ghrelin gene in 300 Italian obese children and adolescents (mean age 10.5±3.2u2009y; range 4–19u2009y) and 200 controls by using the single-strand conformation polymorphism and the restriction fragment length polymoprhism analysis.RESULTS: No mutations were detected with the exception of two previously described polymorphisms, Arg51Gln and Leu72Met. For both variations, allelic frequencies were similar between patients and controls. Interestingly, we showed that the Leu72Met polymorphism was associated with differences in the age at obesity onset. Patients with the Met72 allele became obese earlier than homozygous patients for the wild Leu72 allele. The logrank test comparing the plots of the complement of Kaplan–Meier estimates between the two groups of patients was statistically significant (P<0.0001).CONCLUSION: It is unlikely that ghrelin variations cause the obesity due to single-gene mutations. The Leu72Met polymorphism of the ghrelin gene seems to play a role in anticipating the onset of obesity among children suggesting, therefore, that ghrelin may be involved in the pathophysiology of human adiposity.

Effect of body mass index reduction on serum hepcidin levels and iron status in obese children.

Iron deficiency has been linked to obesity. Hepcidin is the main regulator of iron homeostasis and is higher in obese children compared to controls. To gain insight into the link between obesity and hepcidin, we performed an intervention study in 15 obese children. These children were subjected to a 6-month weight loss program and underwent physical examination and iron status and absorption as well as hepcidin, interleukin-6 and leptin serum levels evaluation at baseline and after the weight loss program. After the program all children reduced their body mass index standard deviation score (BMI SDS) of at least 0.5. We observed a significant decrease in hepcidin (P=0.003) and leptin levels (P=0.005), and a significant increase in iron absorption (P=0.02). A direct correlation between the measure of hepcidin and leptin reduction was observed and this correlation appeared significant (r2=0.33, P=0.003) when adjusted for interleukin-6 and BMI SDS variations. In conclusion, we have shown that, in obese children, BMI reduction is associated with hepcidin reduction, potentially improving iron status and absorption. Implications of these findings could be considered in the management of obese children with poor iron status.

Molecular screening of the proopiomelanocortin ( POMC ) gene in Italian obese children: report of three new mutations

BACKGROUND: Although linkage studies strongly suggest that proopiomelanocortin (POMC) alterations could play a role in the genetic predisposition to obesity, systematic POMC mutational analysis did not completely confirm this hypothesis.OBJECTIVES: To verify the presence of mutations of the POMC coding region in Italian children with very early onset obesity.SUBJECTS AND METHODS: Eighty seven unrelated Italian obese children and adolescents were studied. Mean age at obesity onset was 4.7±2.5u2005y. The POMC gene coding region was screened using single-strand conformation polymorphism (SSCP) analysis. Bi-directional automatic sequencing of PCR products was performed for all individuals who showed an aberrant SSCP pattern.RESULTS: Three new mutations have been identified in the heterozygous state in three patients: (a) G3834C, resulting in the substitution of Ser with Thr at codon 7 within the POMC signal peptide; (b) C3840T, resulting in the substitution of Ser with Leu at codon 9 of the pre-proopiomelanocortin signal peptide; and (c) C7406G, producing the substitution of Arg with Gly at codon 236 within the β-endorphin peptide. A polymorphism consisting of a 9u2005bp insertion, AGC AGC CGC, between position 6997 and 6998 has been found at the heterozygous state in nine patients. They showed leptin levels adjusted for BMI, gender and pubertal stage significantly higher than obese subjects homozyous for the POMC wild-type allele.CONCLUSIONS: Mutations in codons 7 and 9 of the signal peptide may alter the translocation of the pre-proopiomelanocortin into the endoplasmic reticulum and, therefore, can be implicated in obesity. Although further studies are required, the polymorphism between position 6997 and 6998 may represent one of the genetic variations that explain the linkage between obesity and POMC.

Could the savory taste of snacks be a further risk factor for overweight in children

Introduction: The quantity, type and composition of snack foods may play a role in the development and maintenance of obesity in children. A high consumption of energy-dense snacks may promote fat gain. Aims: To assess the type and number of snacks consumed weekly by a large sample of 8- to 10-year-old children, as well as to assess its relationship with body size. Results: The children consumed on average 4 snacks per day. There was no statistical difference in the number of servings per day between obese and nonobese children. However, the mean energy density of the foods consumed was significantly higher for obese and overweight children than for normal weight children [6.8 (0.3) kJ/g, 6.8 (0.16) kJ/g, and 6.3 (0.08) kJ/g, respectively; P < 0.05]. Logistic regression analysis showed that the energy density of the snacks (kJ/g), their savory taste (servings/week), television viewing (hours/day) and sports activity (hours/week) independently contributed to predict obesity in children. However, when the parents body mass index was included among the independent variables of the regression, only salty foods and sports activity showed an independent association with childhood obesity. Conclusions: Parents eating habits and lifestyle influence those of their children, as suggested by the association between parents obesity and their childrens energy-dense food intake at snacktime, the savory taste of snacks and sedentary behavior. However, regardless of parents body mass index, the preference for savory snacks seems to be associated with overweight in prepubertal children.

CIRCANNUAL RHYTHMS OF PLASMA LUTEINIZING HORMONE, FOLLICLE‐STIMULATING HORMONE, TESTOSTERONE, PROLACTIN AND CORTISOL IN PREPUBERTY

For a period of four years we have been studying 106 healthy males and 66 healthy females, aged 6–10, by cross‐sectional design, to look for evidence of a circannual rhythm in LH, FSH, testosterone, PRL, and cortisol secretion. Plasma samples were taken at 0800 h and all hormones were measured by RIA. A cosine function was fitted to the single data to indicate any significant circannual (about 1 year) rhythm and to estimate its parameters: mesor, amplitude, and acrophase. Annual changes were validated in the secretion of: LH (annual crest time in January in both sexes), testosterone (studied only in males, annual crest time in July), and PRL (significant rhythm only in females with annual crest time in March). FSH and cortisol did not show an annual rhythm in both sexes. Our data suggest that sex influences the circannual hormonal rhythms from prepuberty onwards.

TM6SF2 Glu167Lys polymorphism is associated with low levels of LDL-cholesterol and increased liver injury in obese children.

The Glu167Lys (E167K) transmembrane 6 superfamily member 2 (TM6SF2) variant has been associated with liver steatosis, high alanine transaminase (ALT) levels and reduced plasma levels of liver‐derived triglyceride‐rich lipoproteins.

Variations of retinol binding protein 4 levels are not associated with changes in insulin resistance during puberty.

Retinol binding protein 4 (RBP4) is an adipokine involved in the pathogenesis of insulin resistance in obese adults and children. Since insulin resistance occurs during puberty, independently of adiposity, a role for RBP4 in the onset of this phenomenon may be hypothesized. In order to verify our hypothesis, we studied 90 subjects (45 obese and 45 lean controls). A complete physical examination was assessed, the z-score body mass index (BMI) was calculated, fat mass was assessed by bioelectric impedance analysis, and pubertal stage was assessed according to Tanner. Serum insulin and serum RBP4 levels were assayed. Obese and lean children differed for z-score BMI, fat mass, homeostasis model assessment of insulin resistance (HOMA-IR) and RBP4 levels. z-score BMI and HOMA-IR showed a direct correlation with RBP4 in the total population. When the subjects were divided in lean and obese, this correlation was evident only in obese (r2: 0.2; p=0.009 and r2: 0.2; p=0.01), but not in lean subjects (r2: 0.09; p=0.1 and r2: 0.03; p=0.4). Both in obese and lean HOMA-IR values were higher in pubertal subjects than in pre-pubertal (p<0.001), while serum RBP4 levels were similar in pubertal and in pre-pubertal subjects (>0.1). We conclude that RBP4 is correlated with adiposity and insulin resistance in obese children, but it is not involved in the insulin resistance occurring during puberty.

Long-term Zinc and Iron Supplementation in Children of Short Stature: Effect of Growth and on Trace Element Content in Tissues

We evaluated the effect of one year of supplementation with iron plus zinc (12 mg/day of Fe+++ and 12.5 mg/day of Zn++), zinc alone (12.5 mg/day of Zn++) and placebo on growth and on the iron, zinc, copper and selenium tissue contents in 30 well-selected children of short stature (16 M and 14 F; 4-11 years old). Before and after supplementation, we measured the concentrations of iron, transferrin, ferritin, zinc and copper in serum, of zinc in erythrocytes and leukocytes, and of zinc, copper and selenium in hair, as well as glutathione peroxidase activity in erythrocytes. Before supplementation, ferritin and serum, erythrocyte and hair zinc contents were significantly lower than in age-matched controls, while the other measured indices were in the normal range. Iron plus zinc supplementation caused an improvement in growth rate in all subjects, i.e., the median Z-score increased from -2.22 +/- 0.45 to -0.64 +/- 0.55; (p < 0.01). In the zinc-supplemented group, only the subjects whose ferritin levels were higher than 20 ng/L before supplementation showed a similar improvement of growth rate. Iron plus zinc supplementation could be a reasonable treatment in short, prepubertal children affected by marginal zinc and iron deficiency.

High-normal fasting glucose levels are associated with increased prevalence of impaired glucose tolerance in obese children.

The natural history of impaired glucose tolerance (IGT) and Type 2 diabetes among obese children is not clear. Although the cut-off for impaired fasting glucose (IFG) has recently been changed from 110 (6.1 mmol/l) to 100 mg/dl (5.6 mmol/l), it does not seem a reliable way to find all subjects with impaired glucose homeostasis. The aim of our study was to determine whether high-normal fasting glucose level could predict the occurrence of IGT and metabolic syndrome. Three hundred and twenty-three Italian obese children and adolescents were included in the study (176 females, mean age 11±2.9 yr; mean body mass index z-score: 3±0.6). Waist circumference, serum glucose, insulin, triglyceride, cholesterol HDL, blood pressure were evaluated and an oral glucose tolerance test (OGTT) was performed. The prevalence of IFG and IGT were respectively 1.5% (5 subjects) and 5% (18 patients); no diabetic patients were found. Metabolic syndrome was diagnosed in 20% of patients. Fasting glycemia values <100 mg/dl (5.6 mmol/l) have been divided in quintiles. Metabolic syndrome prevalence increased across quintiles, although not in a statistically significantly manner, but it could depend on the selected diagnostic criteria as no univocal definition exists for metabolic syndrome in youths. Interestingly high-normal fasting plasma glucose levels constitute an independent risk factor for IGT among obese children and adolescents; therefore, this very easy-to-use parameter may help to identify obese patients at increased risk of diabetes or at least could suggest in which subjects to perform an OGTT.