Insulin sensitivity in prepubertal Caucasian normal weight children

Insulin resistance and lung function in obese asthmatic pre-pubertal children

BACKGROUND

Recent findings have supposed that the underlying association between the increased prevalence of both asthma and obesity may be insulin resistance (IR).

METHODS

Insulin and glucose serum levels were analyzed to calculate the homeostatic model assessment of insulin resistance (HOMA-IR) for IR in 98 pre-pubertal children. Lung function and allergy status evaluation were performed. The study population was divided into four groups: (1) obese asthmatic children (ObA); (2) normal-weight asthmatic children (NwA); (3) normal-weight non-asthmatic children (Nw) and (4) obese non-asthmatic children (Ob).

RESULTS

Forced expiratory volume in 1 s (FEV1) was slightly lower in obese subjects compared with normal-weight subjects and forced vital capacity (FVC) appeared lower in asthmatics, whereas between non-asthmatics subjects, it was lower in the obese group than in the normal-weight one. The post hoc analysis revealed a statistically significant reduction in FEV1, peak expiratory flow (PEF), forced expiratory flows (FEF) between 50% and 25% of the FVC (FEF50 and FEF25) between ObA and Nw and in FEV1, FVC, PEF, FEF50 and FEF25 between NwA and Nw, but no statistically significant differences of lung function parameters were observed between ObA and NwA. We found an inverse relationship between HOMA-IR and all spirometric parameters, although without any statistical significance. We also observed a significantly lower FVC in insulin-resistant children (HOMA-IR>95th percentile) (p=0.03).

CONCLUSIONS

This study suggests that lung function could be early altered in obese children, already in pre-pubertal age. Although IR should not manifest its effects on lungs in pre-pubertal obese children, the prevention or treatment of obesity in the pre-pubertal period may prevent definitive negative effects on lungs.

Metabolic Outcomes, Bone Health, and Risk of Polycystic Ovary Syndrome in Girls with Idiopathic Central Precocious Puberty Treated with Gonadotropin-Releasing Hormone Analogues

BACKGROUND/AIMS

Gonadotropin-releasing hormone analogues (GnRHa) represent the gold standard treatment for central precocious puberty (CPP). We aimed to assess the effects of GnRHa treatment on metabolic outcomes, bone status, and polycystic ovary syndrome (PCOS) prevalence in young girls with idiopathic CPP (ICPP).

METHODS

We enrolled 94 ICPP girls who were at least 2 years after menarche and had already attained adult height at the time of the study: 56 previously treated with depot triptorelin (3.4 ± 0.6 years) and 38 untreated. Auxological parameters, lipid profile, homeostatic model assessment of insulin resistance (HOMA-IR), bone state, and prevalence of PCOS were assessed.

RESULTS

The 2 groups were similar for body mass index (BMI) and waist circumference. HOMA-IR, dehydroepi-androsterone sulfate, and Δ4-androstenedione were higher in the treated than in the untreated subjects (p < 0.001). Significant differences were found for amplitude-dependent speed of sound (p < 0.03) and bone transmission time z-scores (p < 0.01). The prevalence of PCOS was higher in the treated than in the untreated subjects (p < 0.04).

CONCLUSION

GnRHa therapy is associated with hyperandrogenism and an increase in insulin resistance and PCOS prevalence, but not with increased BMI or lipid profile alterations. Long-term evaluations at the time of expected peak bone mass achievement are needed to understand the persistent or transient nature of subtle bone abnormalities.

DEPTOR promoter genetic variants and insulin resistance in obese children and adolescents

BACKGROUND

Insulin resistance (IR) is one of the major metabolic complications of obesity in children and adolescents. DEP domain-containing mammalian target of rapamycin interacting protein (DEPTOR) is involved in downstream insulin signaling and DEPTOR's effects are regulated by its level of expression.

OBJECTIVES

To analyze promoter region of DEPTOR for genetic variants associated with altered IR in obese children and adolescents.

SUBJECTS AND METHODS

IR was determined in 322 normoglycemic obese subjects [173 females, 149 males; mean age 13.3 ± 3.5 yr, mean BMI-SDS 2.85 ± 0.83, HbA1C 5.2 ± 0.2% (33 ± 2.5 mmol/mol)] using homeostatic model assessment - insulin resistance [HOMA-IR (>2 prepubertal and >3 pubertal)] and whole body insulin sensitivity index [WBISI (<6.5 prepubertal and <4.5 pubertal)]. Genetic variants, determined by high resolution melting analysis, were confirmed by Sanger sequencing, whereas population allele distribution was determined by TaqMan genotyping probes.

RESULTS

Genetic variant c.-143T>C (rs7840156) was associated with a significant 2-fold decreased risk to present with IR, determined by HOMA-IR [odds ratio (OR) = 0.614, 95% confidence interval (CI) = 0.435-0.867, p = 0.0057) and WBISI (OR = 0.582, 95% CI = 0.414-0.817, p = 0.0018). The CC genotype had lower mean HOMA-IR value (2.47 ± 0.44 vs. 3.04 ± 0.14, p = 0.0177) and higher mean WBISI value (7.00 ± 0.71 vs. 5.27 ± 0.33, p = 0.0235) than TT genotype. Variant c.-143T>C was located in evolutionary highly conserved region in DEPTOR promoter region.

CONCLUSION

Presented results on association between insulin sensitivity and genetic variants in DEPTOR gene suggest DEPTOR and mammalian target of rapamycin signaling pathway to be potential target for future research and pharmacological interventions.

FKBP5 polymorphism is associated with insulin resistance in children and adolescents with obesity

OBJECTIVE

Since metabolic syndrome shares several clinical features with hypercortisolism, it was hypothesised that genes altering individual glucocorticoid (GC) sensitivity might be implicated in pathogenesis of obesity and its adverse outcomes. FKBP5 gene encodes a chaperon protein in the GC receptor (GR) complex, which modulates steroid action upon target genes. Its functional variant, rs1360780, may enhance FKBP5 gene transcription, affect GR signalling and thereby influence the hypothalamo-pituitary-adrenal axis. We investigated the association of rs1360780 with obesity and metabolic characteristics in 250 obese children and adolescents (mean age 12.3±3.6years, BMI ≥95th percentile).

METHODS

Anthropometric measurements, body composition, biochemical and hormonal results were analysed. Genotyping of rs1360780 was compared with 568 lean controls.

RESULTS

Impaired fasting glucose was present in 8.8%, glucose intolerance in 10.4%, diabetes in 2.8% and dyslipidemia in 28.8% obese individuals. Hypertension was diagnosed in 34 out of 143 patients. No difference was found in FKBP5 polymorphism distribution between subjects with obesity and controls (p>0.05). Stratification by rs1360780 revealed no differences in body mass and composition. However, carriers of the minor allele displayed enhanced insulin resistance (p=0.009) and elevated serum triglyceride (p=0.006), whereas cholesterol, HbA1c, and oral glucose challenge results were similar for all genotypes. Morning ACTH and cortisol did not differ but evening cortisol was higher in minor allele carriers (p=0.039), although this association was lost in logistic regression analysis.

CONCLUSION

This study does not support the association of FKBP5 with obesity but demonstrates plausible implication of its variant in susceptibility to obesity-related insulin resistance and hypertriglyceridemia.

Socioeconomic status is positively associated with measures of adiposity and insulin resistance, but inversely associated with dyslipidaemia in Colombian children

BACKGROUND

Low socioeconomic status (SES) has been associated with higher risk of cardiometabolic diseases in developed societies, but investigation of SES and cardiometabolic risk in children in less economically developed populations is sparse. We aimed to examine associations among SES and cardiometabolic risk factors in Colombian children.

METHODS

We used data from a population-based study of 1282 children aged 6-10 years from Bucaramanga, Colombia. SES was classified according to household wealth, living conditions and access to public utilities. Anthropometric and biochemical parameters were measured at a clinic visit. Cardiometabolic risk factors were analysed continuously using linear regression and as binary outcomes-according to established paediatric cut points-using logistic regression to calculate OR and 95% CIs.

RESULTS

Mean age of the children was 8.4 (SD 1.4) and 51.1% of the sample were boys. Odds of overweight/obesity, abdominal obesity and insulin resistance were greater among higher SES. Compared with the lowest SES stratum, children in the highest SES had higher odds of overweight/obesity (OR=3.25, 95% CI 1.89 to 5.57), abdominal obesity (OR=2.74, 95% CI 1.41 to 5.31) and insulin resistance (OR=2.60, 95% CI 1.81 to 3.71). In contrast, children in the highest SES had lower odds of hypertriglyceridaemia (triglycerides ≥90th centile; OR=0.28, 95% CI 0.14 to 0.54) and low (≤10th centile) high-density lipoprotein (HDL) cholesterol (OR=0.35, 95% CI 0.15 to 0.78).

CONCLUSIONS

In Colombian children, SES is directly associated with obesity and insulin resistance, but inversely associated with dyslipidaemia (hypertriglyceridaemia and low HDL cholesterol). Our findings highlight the need to analyse cardiometabolic risk factors separately in children and to carefully consider a population's level of economic development when studying their social determinants of cardiometabolic disease.

Weight loss in obese prepubertal children: the influence of insulin resistance

BACKGROUND

Insulin resistance (IR), a link of paramount importance between obesity and cardiovascular/metabolic complications, seems to be implicated in weight changes.

OBJECTIVE

To determine whether IR could influence weight status during a 1-year intervention program in obese prepubertal children.

METHODS

Forty-four children with IR (IR group) and 42 children without IR (NIR group) were enrolled. Body mass index standard deviation score (BMI-SDS), waist circumference (WC), and homeostasis model assessment (HOMA-IR) were evaluated.

RESULTS

NIR children showed a significant reduction of BMI-SDS and WC at final assessment (p = 0.009 and p = 0.001, respectively), whereas IR children presented unchanged values. HOMA-IR decreased after intervention in the NIR group (p = 0.0008), but was exacerbated in IR children (p = 0.004). A positive and significant association between HOMA-IR at baseline and BMI at follow-up was found (B ± SE = 0.87 ± 0.24, p = 0.001). HOMA-IR at baseline was also significantly associated with WC at follow-up (B ± SE = 2.12 ± 0.69, p = 0.003).

CONCLUSIONS

IR seems to influence adiposity changes in obese prepubertal children. Further longitudinal studies are needed to verify the relationship between IR and weight loss during childhood.

Adiposity indices in the prediction of insulin resistance in prepubertal Colombian children

OBJECTIVE

To compare BMI with abdominal skinfold thickness (ASF), waist circumference and waist-to-height ratio in the prediction of insulin resistance (IR) in prepubertal Colombian children.

DESIGN

We calculated age- and sex-specific Z-scores for BMI, ASF, waist circumference, waist-to-height ratio and three other skinfold-thickness sites. Logistic regression with stepwise selection (P = 0·80 for entry and P = 0·05 for retention) was performed to identify predictors of IR and extreme IR, which were determined by age- and sex-specific Z-scores to identify the ≥ 90th and ≥ 95th percentile of homeostasis model assessment (HOMAIR), respectively. We used receiver operating characteristic curves to compare the area under the curve between models.

SETTING

Bucaramanga, Colombia.

SUBJECTS

Children (n 1261) aged 6-10 years in Tanner stage 1 from a population-based study.

RESULTS

A total of 127 children (seventy girls and fifty-seven boys) were classified with IR, including sixty-three children (thirty-three girls and thirty boys) classified with extreme IR. Only ASF and BMI Z-scores were retained as predictors of IR by stepwise selection. Adding ASF Z-score to BMI Z-score improved the area under the curve from 0·794 (95 % CI 0·752, 0·837) to 0·811 (95 % CI 0·770, 0·851; P for contrast = 0·01). In predicting extreme IR, the addition of ASF Z-score to BMI Z-score improved the area under the curve from 0·837 (95 % CI 0·790, 0·884) to 0·864 (95 % CI 0·823, 0·905; P for contrast = 0·01).

CONCLUSIONS

ASF Z-score predicted IR independent of BMI Z-score in our population of prepubertal children. ASF and BMI Z-scores together improved IR risk stratification compared with BMI Z-score alone, opening new perspectives in the prediction of cardiometabolic risk in prepubertal children.

Impaired insulin sensitivity and elevated ectopic fat in healthy obese vs. nonobese prepubertal children

Insulin sensitivity is impaired and ectopic fat (accretion of lipids outside of typical adipose tissue depots) increased in obese adults and adolescents. It is unknown how early in life this occurs; thus, it is important to evaluate young children to identify potential factors leading to the development of metabolic syndrome. We examined an ethnically diverse cohort of healthy, exclusively prepubertal children (N = 123; F = 57, M = 66; age 8.04 ± 0.77 years) to examine differences in insulin sensitivity and ectopic and visceral fat deposition between obese and nonobese youth. Obesity was categorized by age- and sex-adjusted BMI z-scores (nonobese = z-score <2 (N = 94) and obese = z-score ≥2 (N = 29)). Insulin sensitivity was assessed by both a frequently sampled intravenous glucose tolerance test (S(i)) and the homeostatic model assessment of insulin resistance (HOMA(IR)). Intramyocellular lipids (IMCLs) from soleus and intrahepatic lipids (IHLs) were assessed by magnetic resonance spectroscopy, visceral adipose tissue (VAT) by magnetic resonance imaging, and total body fat by dual-energy X-ray absorptiometry. We also examined serum lipids (total cholesterol, triglycerides, high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol) and blood pressure (diastolic and systolic). Obese children exhibited significantly lower S(i) (5.9 ± 5.98 vs. 13.43 ± 8.18 (mµ/l)(-1)·min(-1), P = 0.01) and HDL-C and higher HOMA(IR) (1.68 ± 1.49 vs. 0.63 ± 0.47, P < 0.0001), IMCL (0.74 ± 0.39 vs. 0.44 ± 0.21% water peak, P < 0.0001), IHL (1.49 ± 1.13 vs. 0.54 ± 0.42% water peak, P < 0.0001), VAT (20.16 ± 8.01 vs. 10.62 ± 5.44 cm(2), P < 0.0001), total cholesterol, triglycerides, low-density lipoprotein cholesterol, and systolic blood pressure relative to nonobese children. These results confirm significantly increased ectopic fat and insulin resistance in healthy obese vs. nonobese children prior to puberty. Excessive adiposity during early development appears concomitant with precursors of type 2 diabetes and the metabolic syndrome.

Metabolic, inflammatory, endothelial and haemostatic markers in a group of Italian obese children and adolescents

Childhood obesity and its related comorbidities are increasingly recognised in children, predisposing them to early cardiovascular disease and metabolic syndrome. The objective of the study was to investigate markers of metabolism, inflammation and haemostasis in a group of Italian obese children and adolescents. Fifty-nine obese and 40 non-obese subjects were recruited. Fasting glucose and insulin, total cholesterol, HDL and LDL cholesterol, triglycerides, high-sensitivity C-reactive protein (hsCRP), tumour necrosis factor alpha (TNF-α), and adiponectin were measured. Hypercoagulability was assessed by measuring the circulating levels of thrombin-antithrombin complex (TAT), D: -dimer, fibrinogen, plasminogen activator inhibitor 1 (PAI-1) and von Willebrand Factor (vWF). A significant degree of insulin resistance was present in obese subjects compared with controls (p < 0.0001). The obese showed higher levels of total cholesterol, LDL cholesterol and triglycerides, and lower levels of HDL cholesterol than controls (p < 0.0001). Circulating levels of hsCRP and TNF-α were significantly higher in obese than in controls while serum adiponectin levels were significantly lower in obese than non-obese subjects (p < 0.001; p = 0.031; p < 0.0001, respectively). vWF, TAT, D-dimer, fibrinogen and PAI-1 levels were significant higher in obese subjects compared with control group (p = 0.02; p < 0.0001; p = 0.0037; p < 0.0001; p = 0.017, respectively). In conclusion, our results suggest that childhood obesity per se is associated with a proinflammatory and prothrombotic state.