Peptide YY is a regulator of energy homeostasis in obese children before and after weight loss

CONTEXT

The gut hormone peptide YY(3-36) (PYY) reduces food intake via hypothalamic Y2 receptors in the brain. There is not much known about PYY in obese children.

OBJECTIVE

The objective of this study was to investigate the role of PYY in the metabolic changes in obese children and its change during weight loss.

SETTING

The study was performed at a university medical center.

PARTICIPANTS

We studied 73 obese children and 45 age-matched normal-weight children.

INTERVENTIONS

We determined fasting serum total PYY and leptin by RIA in obese and normal-weight children. Fasting PYY was also measured in 28 obese children before and after completion of a 1-yr outpatient weight reduction program.

MAIN OUTCOME MEASURES

PYY, insulin, and body mass index were the main outcome measures.

RESULTS

Obese children demonstrated significantly lower PYY levels than lean children (median, 67 vs. 124 pg/ml; P < 0.001). Fasting PYY correlated negatively to the degree of overweight. PYY levels did not differ significantly between boys and girls, nor between prepubertal and pubertal children. The group of patients participating in the outpatient weight reduction program was divided into four quartiles according to their changes in body mass index SD score over a 1-yr period. PYY increased significantly in patients with the most effective weight loss, but decreased in the subgroup of children with weight gain.

CONCLUSIONS

PYY is negatively correlated to the degree of overweight, with reduced values in obese compared with normal-weight children. Decreased PYY levels could predispose subjects to develop obesity. Our results indicate that low pretreatment PYY levels that increase during weight loss may be a predictor of maintained weight loss.

Genes involved in the neuroendocrine control of normal puberty and abnormal puberty of central origin

There is now compelling evidence that both normal puberty and disturbed pubertal development of central origin are, to a significant extent, determined by genetic factors. Although delayed sexual development can result from a deficient pituitary responsiveness to GnRH caused by mutations in the GnRH receptor gene, until recently the only genetically determined hypothalamic defects known to affect puberty were those caused by mutations in genes required for the migration of gonadotropin releasing hormone (GnRH) neurons, such as KAL1, FGFR1, and NELF. Recently, mutations in a gene termed GPR54 were identified as causing isolated hypogonadotrophic hypogonadism (IHH), due to a functional, instead of a structural hypothalamic defect. Studies in nonhuman primates and rodent models suggest that the functional integrity of the hypothalamic mechanism controlling puberty requires a gene network that includes GPR54. Altogether, these findings indicate that the genetic underpinnings of disturbed pubertal development of central origin are polygenic, rather than specified by a single gene.

Rate of hypoglycaemia and insulin dosage in children during the initial therapy of type 1 diabetes mellitus

Hypoglycaemia is a major side-effect of insulin treatment. It is known that young children with type 1 diabetes mellitus (T1DM) show a higher risk of hypoglycaemia than older children. This study was performed to analyse the incidence of hypoglycaemia within the first 14 days (day 1-day 14) of insulin treatment in children at the onset of T1DM and to evaluate the influence of age and insulin dosage. The Paediatric Quality Initiative (DPV), including data from 121 centres in Germany and Austria, provided anonymous data of 1,680 patients (age 0.7-18.8 years; 799 girls) at the onset of T1DM. Hypoglycaemia was defined as a blood glucose level (BG) <2.8 mmol/l (50 mg/dl). The hypoglycaemia rate rose continuously from day 2 (4.8%) to day 5 (11.2%) and then remained stable between 8.7%-11.2% until day 14. The hypoglycaemia rate was higher in younger than in older children (P <0.0001). Multiple regression analysis revealed an influence of age (P <0.0001), insulin dosage (P = 0.0034), and route of initial treatment (P = 0.0052) on the hypoglycaemia rate. From day 2 to day 14, the insulin dosage itself was higher in females than in males (P = 0.0147), in patients with high HbA1c (P = 0.0001), high BG (P <0.0001), or low pH (P <0.0001). There was no influence of age on the insulin dosage.

CONCLUSION

During the first 14 days after onset of type 1 diabetes mellitus, young children, intravenous-treated patients and patients receiving a high insulin dosage are at particular risk of developing hypoglycaemia. In order to avoid hypoglycaemia, blood glucose should be measured frequently and the insulin dosage should be carefully adjusted. Low blood glucose levels should be treated promptly.

High-sensitive C-reactive protein, tumor necrosis factor alpha, and cardiovascular risk factors before and after weight loss in obese children

To confirm the existence of obesity-induced inflammation and to clarify the association between such inflammation and other cardiovascular risk factors, we investigated the relationships between high-sensitive C-reactive protein (hsCRP), tumor necrosis factor alpha (TNF-alpha), obesity, blood pressure, lipids, and insulin resistance in a long-term follow-up of obese children. We compared the serum concentrations of hsCRP, TNF-alpha, high-density lipoprotein cholesterol, and triglycerides as well as blood pressure and the insulin resistance index (homeostasis model assessment [HOMA]) of 14 nonobese and 31 obese children. Furthermore, we studied the changes in these parameters in 16 obese children who lost weight and in 15 obese children without weight change over a 1-year period. In the obese children, blood pressure (P=.003), HOMA (P=.034), and triglyceride (P=.011), TNF-alpha (P=.015), and hsCRP (P<.001) levels were significantly higher, whereas high-density lipoprotein cholesterol concentrations were significantly (P=.015) lower compared with the nonobese children. Weight loss was associated with a significant decrease in hsCRP (P=.008) and triglyceride (P=.048) levels, HOMA (P<.001), and blood pressure (P=.019), whereas there were no significant changes in the children with stable weight status. The changes in hsCRP and TNF-alpha levels over the 1-year period were not significantly correlated to the changes in lipids, blood pressure, and HOMA. Obese children demonstrated significantly higher levels of hsCRP and TNF-alpha compared with nonobese children. The chronic inflammation markers TNF-alpha and hsCRP were independent of lipids, blood pressure, and insulin resistance index. Weight loss was associated with the significant decrease of hsCRP and triglyceride levels, and blood pressure.

Antagonistic and Agonistic GnRH Analogue Treatment of Precocious Puberty: Tracking Gonadotropin Concentrations in Urine

BACKGROUND

The pharmacodynamics of gonadotropin-releasing hormone (GnRH) agonists includes an initial 'flare-up' of the pituitary-gonadal axis, followed by reduced luteinizing hormone (LH) secretion. The question is if combining a short-acting antagonist with a long-acting agonist can diminish gonadotropin flare-up.

METHODS

To achieve quick downregulation in patients with recently diagnosed central precocious puberty (CPP, 7 patients) or short stature with short predicted final height (3 patients), we combined the GnRH antagonist cetrorelix (3 subcutaneous injections every 72 h) at the beginning of GnRH agonist treatment (leuprorelin or triptorelin) in 6 patients and compared the effect to 4 patients treated solely with GnRH agonist. To monitor effects, we measured LH and FSH concentrations in urine collected from initial morning urination during the first month of treatment.

RESULTS

In both treatment groups, gonadotropin flare-up could be detected in urine levels increased due to the flare-up phenomenon which was of short duration (<5 days) in the majority (5 of 6) of combined-treated patients and in the minority (1 of 4) of patients treated by agonist alone. During the first 10 days of treatment, mean LH concentration measured in urine was significantly lower in 4 CPP patients treated by the combined therapy compared to 3 CPP patients treated by the agonist only (mean LH combined therapy: 10.4 +/- 2.8 vs. 20.1 +/- 11.0 mU/ml in the agonist-only group, mean +/- SEM, p < 0.05). Significant correlations between stimulated serum LH in GnRH test prior to treatment and maximum urine LH after initiating GnRH analogue treatment (r = 0.547, p = 0.043), as well as basal serum LH and basal urine LH (r = 0.685, p = 0.014) were found.

CONCLUSION

Combined GnRH agonist and antagonist treatment led to rapid gonadotropin suppression. Also, urine measurements of LH and FSH seemed suitable for monitoring gonadotropin-inhibiting or -stimulating properties of GnRH analogues in individual patients. However, a controlled trial of a larger patient cohort is required to decide which treatment is the most effective.

Ghrelin levels before and after reduction of overweight due to a low-fat high-carbohydrate diet in obese children and adolescents

BACKGROUND

There are conflicting results for ghrelin changes in reduction of overweight. Increasing ghrelin levels in weight reduction are considered to be responsible for compensatory mechanisms that make the reduction of overweight unlikely to be sustained.

METHODS

We have analyzed fasting serum ghrelin levels, weighed dietary record and, as biochemical markers of clinically relevant reduction of overweight, leptin, adiponectin and insulin levels and insulin resistance measured by homeostasis model assessment (HOMA) at baseline and after a 1-y outpatient weight reduction program based on a high-carbohydrate and low-fat diet in 37 obese children (median age 10 y). We divided these children into two subgroups according to their degree of weight loss (substantial reduction of overweight: decrease in SDS-BMI > or = 0.5). Furthermore, we analyzed ghrelin levels in 16 normal-weight children.

RESULTS

Obese children demonstrated significant (P<0.001) lower ghrelin levels compared to normal-weight children. Daily caloric intake (P = 0.004) and percentage fat content decreased significantly (P<0.001), while percentage carbohydrate content increased significantly (P = 0.003) between baseline and 1-y follow-up in the obese children. The substantial reduction of overweight in 16 children (median SDS-BMI = -0.7) was associated with significant changes in insulin resistance (median decrease of HOMA 27%; P = 0.013), insulin (median decrease 25%, P = 0.036), adiponectin (median increase 15%; P = 0.003), and leptin levels (median decrease 19%; P = 0.023), while there were no significant changes in ghrelin levels (median increase 4%; P = 0.326). In the 21 children without substantial reduction of overweight (median SDS-BMI = -0.3), there were no significant changes in insulin resistance and in insulin, adiponectin, leptin and ghrelin levels.

CONCLUSIONS

We conclude that in obese children, low-fat high-carbohydrate diet-induced weight loss does not change ghrelin secretion, but significantly decreases leptin levels, increases adiponectin levels and improves insulin resistance determined by significantly decreased insulin resistance indices as well as lowered serum insulin levels.

Fetal insulin-like growth factor (IGF)-I, IGF-II, and ghrelin in association with birth weight and postnatal growth in monozygotic twins with discordant growth

OBJECTIVE

To investigate the relative contribution of genetic (fetal) vs. environmental (maternal/placental) factors on growth, we studied monozygotic twins with intertwin birth weight difference.

PATIENTS AND METHODS

Twenty-seven twins (15 with discordant growth) who have been treated for severe twin-to-twin transfusion syndrome by laser coagulation were studied. Cord blood samples were analyzed for IGF-I, IGF-II, IGF-binding protein-2, and ghrelin. Intertwin difference (Delta) of birth weight was correlated to Delta of the parameters analyzed. The Delta weight after 1 yr was correlated with Delta birth weight and all hormones.

RESULTS

The Delta birth weight was positively correlated with Delta IGF-I (r = 0.66; P < 0.0002) and negatively correlated with Delta IGF-binding protein-2 levels (r = -0.68; P < 0.001) but with neither Delta IGF-II nor Delta ghrelin. There was a strong intertwin correlation for all hormones. By comparing the growth in the first year, we found an overall reduction of the relative weight difference between the twins of 57%. ANOVA was used to calculate factors for prediction of postnatal catch-up growth. Besides the birth weight difference (R2= 0.84; P < 0.0001), only ghrelin was of prognostic value for postnatal catch-up growth (R2= 0.94; P = 0.0035).

CONCLUSION

These data confirm the importance of IGF-I in contrast to IGF-II for fetal weight. Additionally, ghrelin seems to be involved in fetal and probably postnatal growth.

Insulin resistance in children and adolescents with type 1 diabetes mellitus: relation to obesity

BACKGROUND

Insulin resistance is well recognized both in type 1 diabetes mellitus (T1DM) and in obesity. Studies concerning the relation between insulin resistance and overweight in T1DM have not yet been carried out.

METHODS

Degree of overweight [standard deviation score-body mass index (SDS-BMI)] and daily insulin doses per weight (ID/kg), per body surface (ID/m2), and per ideal body weight (ID/IW) were recorded in 4124 children aged between 5 and 20 yr with a duration of T1DM of 4-5 yr and an adequate metabolic control [hemoglobin A1c (HbA1c) <8.0%]. SDS-BMI was compared between insulin-resistant (ID/kg > or = 1.0) and insulin-sensitive (ID/kg <1.0) children. The ID/kg, ID/m2, and ID/IW were compared between obese (SDS-BMI >1.9) and non-obese children. Multivariate linear regression analysis was conducted for the dependent variables ID/kg, ID/m2, and ID/IW, including age, gender, SDS-BMI, and HbA1c as independent variables.

RESULTS

The 882 insulin-resistant children did not differ significantly (p = 0.447) with respect to SDS-BMI (median +0.38) compared to the 3242 insulin-sensitive children (median SDS-BMI +0.42). The ID/kg was significantly (p = 0.031) lower in the obese children compared to the non-obese children (median 0.80 vs. 0.83), while ID/m2 (median 31.0 vs. 26.2) and ID/IW (median 1.17 vs. 0.85) were significantly (p < 0.001) increased in the obese children. In multivariate linear regression analysis, SDS-BMI was significantly (p < 0.001) associated with an increase in ID/m2 and ID/IW and a decrease in ID/kg.

CONCLUSIONS

T1DM children with insulin resistance based on ID/kg are not more overweight than insulin-sensitive children with T1DM. ID/m2 and ID/IW seem to reflect a better tool than ID/kg to describe the influence of overweight on insulin resistance in T1DM.