Are girls more insulin-resistant than boys?

A sex-related mediating effect of uric acid in the association between body composition and blood pressure in children and adolescents

The increase in blood pressure (BP) during somatic growth might have direct determinants but also mediating factors. We investigated whether uric acid (UA) and other metabolic factors would mediate the association between body composition components and BP. A cross-sectional study was conducted in 928 children and adolescents (aged 6-18 years), in which body composition and blood biochemistry were evaluated. Structural equation modeling was performed to test the direct and indirect pathways between systolic blood pressure (SBP) and body composition parameters. Muscle mass (MM) showed a strong direct effect on BP, regardless of sex. In girls, a mediating pathway through UA was not significant, but the association between fat mass (FM) and MM with SBP was mediated by the cluster of metabolic factors. In boys, both MM and FM were associated with SBP through a mediating pathway via UA, but not via the cluster of metabolic factors. The association between body composition and BP in children and adolescents has a complex design and also has a sex-specific mediating component. The increase in the UA levels may affect BP levels early in boys. Also, metabolic changes elicited by FM contribute to the increase in BP at an early age in girls. Novelty: MM showed a strong direct effect on BP, regardless of sex. In girls, the association between FM and MM with SBP was mediated by the cluster of metabolic factors. In boys, both MM and FM were associated with SBP through a mediating pathway via UA.

Insulin resistance is higher in prepubertal girls but switches to become higher in boys at age 16: A Cohort Study (EarlyBird 57)

BACKGROUND

The risk of type 2 diabetes is increasing in teenage girls, and is associated with their greater insulin resistance (IR).

HYPOTHESIS

We hypothesized that the adverse metabolic profile of girls (compared with boys) would persist from childhood through adolescence.

PATIENTS AND METHODS

Community-based longitudinal cohort of 292 children (147 boys) studied annually from 9 to 16 years.

MEASURES

IR (homeostasis-model-assessment-2), high-density lipoprotein-cholesterol (HDL-C), triglycerides, % body-fat (dual-energy x-ray absorptiometry), pubertal stage (age at peak height velocity), physical activity (accelerometry). Multi-level modelling established the age-related trends in IR and lipids and the influence of covariates.

RESULTS

Each year from 9 to 15 years, girls had 21% to 63% higher IR than boys (girls mean IR 0.73-1.33, boys 0.51-0.89, P < .005). At 16 years the gender difference was not significant (girls IR 0.60, boys 0.56, P = .45). Girls had lower HDL-C from 9 to 12 years, higher triglycerides from 9 to 14 years, greater adiposity throughout, and earlier puberty, but boys were more active than girls (all P < .05). After adjustment for %-fat, puberty and activity, the gender difference in IR between girls and boys aged 9 to 15 years became non-significant (IR girls 0.66-1.01, boys 0.65-1.04, P > .07). However, after adjustment at 16 years, girls' IR was 25% lower than boys' (girls 0.44, boys 0.63, P = .001), and they had 22% higher HDL-C (P < .001) and 20% lower triglycerides (P = .003).

CONCLUSIONS

The higher IR of prepubertal and early pubertal girls diminishes during late puberty, and boys begin to exhibit greater metabolic risk. Despite being leaner and more active, boys at 16 years have higher IR than girls, suggesting future higher risk for diabetes, thus we reject our hypothesis.

Sex-gender-related therapeutic approaches for cardiovascular complications associated with diabetes

Diabetes is a chronic disease associated with micro- and macrovascular complications and is a well-established risk factor for cardiovascular disease. Cardiovascular complications associated with diabetes are among the most important causes of death in diabetic patients. Interestingly, several sex-gender differences have been reported to significantly impact in the pathophysiology of diabetes. In particular, sex-gender differences have been reported to affect diabetes epidemiology, risk factors, as well as cardiovascular complications associated with diabetes. This suggests that different therapeutic approaches are needed for managing diabetes-associated cardiovascular complications in men and women. In this review, we will discuss about the sex-gender differences that are known to impact on diabetes, mainly focusing on the cardiovascular complications associated with the disease. We will then discuss the therapeutic approaches for managing diabetes-associated cardiovascular complications and how differences in sex-gender can influence the existing therapeutic approaches.

Cardiometabolic risk factors and insulin resistance in obese children and adolescents: relation to puberty

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

The prevalence of obesity with concomitant increasing risk for having cardiometabolic diseases is rising in the childhood population. Insulin resistance has a key role in metabolic changes in these children. Insulin levels elevate as puberty commences in every individual.

WHAT THIS STUDY ADDS

Children with increased risk for cardiometabolic diseases show significant differences in insulin levels even before the onset of puberty compared with those without risks. The pattern of appearance of dyslipidaemia also varies in children with risk factors even in the pre-pubertal group from those without risk. Children with metabolic syndrome display considerably pronounced changes in their metabolic parameters before the onset of puberty, which become more pronounced as puberty passes.

BACKGROUND

Insulin resistance (IR) has a key role in the metabolic changes in obese children. In commencing puberty, the insulin levels elevate. It is not clear, however, how insulin levels develop if the metabolic syndrome appears.

OBJECTIVES

Metabolic changes were assessed in obese children before, during and after puberty to analyse the relationship between IR and puberty in subjects with and without metabolic syndrome.

METHODS

Three hundred thirty-four obese children (5-19 years) attended the study. The criteria of the International Diabetes Federation were used to assess the presence of cardiometabolic risks (CMRs). Subjects with increased CMR were compared with those without risk (nCMR). Pubertal staging, lipid levels, plasma glucose and insulin levels during oral glucose tolerance test were determined in each participant. IR was expressed by homeostasis model assessment (HOMA-IR) and the ratio of glucose and insulin areas under the curve (AUC-IR).

RESULTS

Significantly higher AUC-IR were found in pre-pubertal CMR children compared with nCMR subjects (11.84 ± 1.03 vs. 8.00 ± 0.69; P < 0.01), but no difference was discovered during and after puberty. HOMA-IR differs between CMR and nCMR only in post-puberty (6.03 ± 1.26 vs. 2.54 ± 0.23; P < 0.01). CMR children have dyslipidaemia before the onset of puberty.

CONCLUSIONS

CMR is associated with increased postprandial IR in pre-pubertal and increased fasting IR in post-pubertal obese children. Dyslipidaemia appeared already in pre-puberty in CMR children.

Population-Based Studies on the Epidemiology of Insulin Resistance in Children

BACKGROUND

In view of the alarming incidence of obesity in children, insight into the epidemiology of the prediabetic state insulin resistance (IR) seems important. Therefore, the aim of this systematic review was to give an overview of all population-based studies reporting on the prevalence and incidence rates of IR in childhood.

METHODS

PubMed, Embase, and Cochrane library were searched in order to find all available population-based studies describing the epidemiology of IR in pediatric populations. Prevalence rates together with methods and cut-off values used to determine IR were extracted and summarized with weight and sex specific prevalence rates of IR if available.

RESULTS

Eighteen population-based studies were identified, describing prevalence rates varying between 3.1 and 44%, partly explained by different definitions for IR. Overweight and obese children had higher prevalence rates than normal weight children. In seven out of thirteen studies reporting sex specific results, girls seemed to be more affected than boys.

CONCLUSION

Prevalence rates of IR reported in children vary widely which is partly due to the variety of definitions used. Overweight and obese children had higher prevalence and girls were more insulin resistant than boys. Consensus on the definition for IR in children is needed to allow for comparisons between different studies.

Importance of android/gynoid fat ratio in predicting metabolic and cardiovascular disease risk in normal weight as well as overweight and obese children

Numerous studies have shown that android or truncal obesity is associated with a risk for metabolic and cardiovascular disease, yet there is evidence that gynoid fat distribution may be protective. However, these studies have focused on adults and obese children. The purpose of our study was to determine if the android/gynoid fat ratio is positively correlated with insulin resistance, HOMA2-IR, and dislipidemia in a child sample of varying body sizes. In 7-13-year-old children with BMI percentiles ranging from 0.1 to 99.6, the android/gynoid ratio was closely associated with insulin resistance and combined LDL + VLDL-cholesterol. When separated by sex, it became clear that these relationships were stronger in boys than in girls. Subjects were stratified into BMI percentile based tertiles. For boys, the android/gynoid ratio was significantly related to insulin resistance regardless of BMI tertile with and LDL + VLDL in tertiles 1 and 3. For girls, only LDL + VLDL showed any significance with android/gynoid ratio and only in tertile 2. We conclude that the android/gynoid fat ratio is closely associated with insulin resistance and LDL + VLDL-, "bad," cholesterol in normal weight boys and may provide a measurement of metabolic and cardiovascular disease risk in that population.

Female sex, small size at birth and low family income increase the likelihood of insulin resistance in late childhood: the Healthy Growth Study

OBJECTIVE

To identify among a wide range of perinatal indices, as well as certain family sociodemographic and parental characteristics, those independently associated with insulin resistance (IR) in late childhood.

METHODS

A representative sample of 2195 Greek schoolchildren, aged 9-13 yr, was examined, and based on the biochemical indices collected IR was estimated using the homeostasis model assessment (HOMA-IR < 3.16). Perinatal data were recorded from children's medical records, retrospectively, while family sociodemographics and parental anthropometrics were reported by parents.

RESULTS

The overall prevalence of IR was 28.4%, with a higher prevalence observed for girls compared with boys (p <0.05). Examination of univariate associations, per se, showed that maternal current and pre-pregnancy overweight/obesity, maternal smoking at early pregnancy, children's small birth weight, and rapid growth at infancy as well as female sex and non-Caucasian race increased the likelihood of IR. In contrast, folate supplementation during pregnancy, as well as higher paternal education and annual family income decreased the likelihood of IR in children. Inclusion of all above variables at a multivariable regression model highlighted female sex [odds ratios (OR): 1.67, 95% confidence intervals (CI): 1.30-2.13], small birth weight (OR: 1.41, 95% CI: 1.03-2.01), and higher annual family income (OR: 0.71, 95% CI: 0.53-0.95 for 12 000-30 000 € and OR: 0.68, 95% CI: 0.48-0.96 for >30 000 €) as the only significant correlates of IR after also controlling for children's body mass index (BMI) and Tanner stage.

CONCLUSIONS

The current study highlighted small birth weight and female sex as the only perinatal factors independently associated with the occurrence of IR in late childhood, when examined at a multivariable level with a wide range of perinatal indices as well as certain family sociodemographic and parental characteristics.

[Correlation between insulin resistance and puberty in children with increased cardiometabolic risk]

Epidemiologic data provide evidence that the frequency of obesity and cardiometabolic risk factors shows an increasing tendency in childhood. Insulin resistance plays a central role in the pathogenesis of cardiovascular and metabolic consequences of obesity. Transient decrease in the insulin sensitivity during puberty is a well-known physiological process; however, the feature of this phenomenon is not clear in obese children with increased cardiometabolic risk.

AIM

The aim of the present study was to assess the effect of puberty on insulin resistance and metabolic parameters in obese children with and without increased cardiometabolic risk.

MATERIALS AND METHODS

Anthropometric data, insulin levels during oral glucose tolerance test and lipid status were analyzed of 161 obese children aged 4-18 years. Σinsulin/Σglucose ratio was obtained during glucose load and HOMA index was used to assess insulin resistance. Children were sorted into prepubertal (T1), pubertal (T2-4) and postpubertal (T5) cohorts according to Tanner staging criteria and metabolic and insulin resistance parameters were evaluated. Increased cardiometabolic risk was defined as the presence of any two risk factors (elevated fasting plasma glucose, blood pressure, triglyceride or decreased HDL-cholesterol) in addition to obesity.

RESULTS

Out of 161 obese subjects, 43 (26.7%) had increased cardiometabolic risk. Decreased HDL-cholesterol and/or elevated triglyceride was observed in 101 (56.5%) cases. Impaired glucose tolerance and/or impaired fasting glucose was found in 23 (14.4%) cases. In subjects without increased cardiometabolic risk, the Σinsulin/Σglucose ratio in T1 stage was significantly lower than in T2-4 and T5 stages (p = 0.01). In children with increased cardiometabolic risk, the insulin/glucose ratio was similar in T1, T2-4 and T5 stages, however, it was significantly higher in T1 stage as compared to subjects without increased cardiometabolic risk (p = 0.04). In T2-4 and T5 stages, Σinsulin/Σglucose ratio did not differ between children with and without increased cardiometabolic risk. No difference was found in HOMA index between groups with and without increased cardiometabolic risk in T1 stage, however significantly higher levels were observed in subjects with increased cardiometabolic risk at T2-4 stages (p = 0.01), indicating the presence of fasting hyperinsulinemia in this cohort. Elevated HbA1c (≥6.0%) was found in 13 (16%) out of the 81 children investigated, of whom only two cases had abnormal oral glucose tolerance test. In cases having normal HbA1c, oral glucose tolerance test showed impaired glucose tolerance in 5 cases, impaired fasting glucose in 2 cases, both impaired glucose tolerance and impaired fasting glucose in 2 cases, and type 2 diabetes in 2 cases.

CONCLUSION

Increased insulin resistance can be observed in obese children without increased cardiometabolic risk. In obese children with increased cardiometabolic risk, substantial insulin resistance occurs in prepuberty and it is present at similar level throughout puberty. Fasting insulin levels are elevated in obese subjects with increased cardiometabolic risk as compared to those without increased cardiometabolic risk. To reveal type 2 diabetes cases, HbA1c and oral glucose tolerance test results should be assessed parallel.

Poor zinc status is associated with increased risk of insulin resistance in Spanish children

Zn plays a key role in the synthesis and action of insulin. The aim of the present work was to determine whether a poorer Zn status was associated with insulin resistance in a group of 357 Spanish schoolchildren. Zn intake was determined by using a 3 d food record (i.e. Sunday to Tuesday). The body weight, height and waist and hip circumferences of all subjects were recorded and fasting plasma glucose, insulin and Zn concentrations were determined. Insulin resistance was determined using the homoeostasis model assessment (HOMA) marker. Children (11·5 %) with Zn deficiency (serum Zn concentration < 10·7 μmol/l) had higher HOMA values than those with a more satisfactory Zn status (1·73 (sd0·93)) compared with 1·38 (sd0·90;P < 0·05). An inverse correlation was found between the HOMA value and the serum Zn concentration (r− 0·149,P < 0·05). The risk of having a greater insulin resistance value (HOMA greater than the 75th percentile) increased with age (OR 1·438; 95 % CI 1·021, 2·027) and BMI (OR 1·448; 95 % CI 1·294, 1·619) and decreased as Zn serum levels increased (OR 0·908; 95 % CI 0·835, 0·987;P < 0·001). Moreover, an inverse relationship was observed between HOMA values and Zn dietary density (r− 0·122), and the Zn intakes of male children with a HOMA value of >3·16 made a significantly smaller contribution to the coverage of those recommended (59·7 (sd14·7) %) than observed in children with lower HOMA values (73·6 (sd18·2) %;P < 0·05). Taking into account that Zn intake was below than that recommended in 89·4 % of the children, it would appear that increasing the intake of Zn could improve the health and nutritional status of these children, and thus contribute to diminish problems of insulin resistance.

Effect of gender on intra-abdominal fat in teenagers and young adults

BACKGROUND

Adult men accumulate greater intra-abdominal fat (IAF) than adult women, a difference closely related to gender differences in cardiometabolic disease risk in the elderly. However, the time when this gender difference appears is a matter of controversy.

OBJECTIVE

We examine the influence of gender on IAF deposition in lean, overweight and obese teenagers and young adults.

MATERIALS AND METHODS

We measured subcutaneous abdominal fat (SAF) and IAF in 505 healthy sexually mature teenagers and young adults (254 males, 251 females; 15-22 years) using a single CT scan at the level of the umbilicus.

RESULTS

Regardless of body size, young females had greater SAF values than young males. Although lean females had higher IAF values than lean males (13.7 ± 7.8 vs. 11.2 ± 5.4; P = 0.001), overweight and obese females and males had strikingly similar IAF values (23.4 ± 11.1 vs. 23.1 ± 9.5; P = 0.88 and 36.5 ± 20.4 vs. 38.8 ± 13.2; P = 0.59, respectively). In contrast, the ratio of IAF/SAF was greater in males than females, except in the very obese. Multiple regression analysis indicated that while gender was a strong predictor of SAF in lean and overweight subjects (P's < 0.0001), it did not influence IAF after adjusting for height and weight (P = 0.35 and 0.65, respectively) in overweight and obese subjects.

CONCLUSION

Overweight and obese young women have similar absolute amounts of IAF as young men.

Preliminary data on the association between waist circumference and insulin resistance in children without a previous diagnosis

The aim of the present work was to study the association between different anthropometric parameters and insulin resistance (IR) in Spanish schoolchildren without a previous diagnosis. A total of 443 Spanish schoolchildren (9-11 years of age) were studied in this cross-sectional study. The anthropometric measurements collected were weight, height, body circumferences and skinfolds. Body mass index (BMI), waist/hip ratio, percentage body fat and fat-free body mass were determined. Overnight-fasted blood lipids, insulin and glucose levels were analysed, and estimation of IR, taking into account the homeostasis model assessment (HOMA), was calculated. The children with IR had higher serum triglycerides and insulin levels, were heavier and taller, and had a higher BMI, a larger waist circumference, a larger hip circumference, a larger waist/hip ratio and thicker bicipital and tricipital skinfolds than those who did not have IR. Age, sex, BMI and waist circumference explained 32.0% of the variance in the HOMA values; only sex, triglycerides and waist circumference independently influenced this variable. A 1-cm increase in waist circumference was associated with approximately a 3.8% increase in the mean HOMA value. The children with a waist circumference of over the p90 for their age and sex were at greater risk of showing IR as measured by the HOMA: odds ratio = 6.94 (2.01-23.91; P < 0.001). In conclusion, according to these results, waist circumference is the best anthropometric parameter associated with IR in children, and those with a waist circumference of over the p90 for their age and sex would appear to be at particular risk.

Is albuminuria associated with obesity in school children?

BACKGROUND

Different studies in adults have shown that obesity is an independent risk factor for end-stage renal disease.

OBJECTIVE

It was to (i) determine the association between albuminuria and age, gender, BMI, waist circumference (WC), and blood pressure (ii) relate albuminuria to gender and age in healthy school children.

METHODS

Over 1564 students (806 males) aged 9.35 +/- 2.00 yr from 9 elementary schools in Buenos Aires, were examined between April and September 2005. BMI, WC, blood pressure, urinary albumin excretion and albumin/creatinine ratio (ACR) were determined.

RESULTS

Over 220 (14.1%) children were obese (OB), and 300 (19.2%) overweight (OW) using centers for disease control (CDC) norms. Median ACR and urinary albumin levels were higher in normal weight children than in OW/OB children (p < 0.01). Median values for ACR were higher in girls than in boys (p < 0.001). OW/OB proved to be a protective factor against ACR [OR, 0.77 (95% CI 0.64-0.92)], whereas female gender [OR, 2.72 (95% CI 2.13-3.47)] was associated with a higher ACR adjusted for age systolic and diastolic blood pressure in the multiple logistic regression analysis. Therefore, children with OW/OB had 23% lower odds of having ACR >or= III quartile and girls had more than two and half times the risk of having high ACR.

CONCLUSIONS

Our results suggest that OW/OB is inversely associated with childhood albuminuria while female gender is positively associated. Whether the results can be explained by the increased physical activity in lean children should be the subject of future investigations. These results suggest that micro-albuminuria in children may not be a useful tool in the early identification of children at risk for future renal and cardiovascular disease (CVD).

Insulin resistance and its association with the components of the metabolic syndrome among obese children and adolescents

Background

Insulin resistance is the primary metabolic disorder associated with obesity; yet little is known about its role as a determinant of the metabolic syndrome in obese children. The aim of this study is to assess the association between the degree of insulin resistance and the different components of the metabolic syndrome among obese children and adolescents.

Methods

An analytical, cross-sectional and population-based study was performed in forty-four public primary schools in Campeche City, Mexico. A total of 466 obese children and adolescents between 11-13 years of age were recruited. Fasting glucose and insulin concentrations, high density lipoprotein cholesterol, triglycerides, waist circumference, systolic and diastolic blood pressures were measured; insulin resistance and metabolic syndrome were also evaluated.

Results

Out of the total population studied, 69% presented low values of high density lipoprotein cholesterol, 49% suffered from abdominal obesity, 29% had hypertriglyceridemia, 8% presented high systolic and 13% high diastolic blood pressure, 4% showed impaired fasting glucose, 51% presented insulin resistance and 20% metabolic syndrome. In spite of being obese, 13% of the investigated population did not present any metabolic disorder. For each one of the components of the metabolic syndrome, when insulin resistance increased so did odds ratios as cardiometabolic risk factors.

Conclusions

Regardless of age and gender an increased degree of insulin resistance is associated with a higher prevalence of disorders in each of the components of the metabolic syndrome and with a heightened risk of suffering metabolic syndrome among obese children and adolescents.

Comparison of various maternal anthropometric indices of obesity for identifying metabolic syndrome in offspring

BACKGROUND

Several maternal anthropometric markers have been associated with the metabolic syndrome (MS) in offspring. The objectives of this study were (1) to determine the association between children's MS and maternal anthropometric markers such as body mass index (BMI), waist circumference (WC), WC/height, weight/sitting height squared, and WC/sitting height and (2) to compare the abilities of these five indices to identify children with MS.

METHODS

Data were collected cross-sectionally from five elementary schools between April 2007 and March 2008. BMI, WC, WC/height, weight/sitting height squared, and WC/sitting height were acquired in mothers and their children. Tanner stage, blood pressure, glucose, lipids, and insulin were measured in children. Criteria analogous to Adult Treatment Panel III for MS were used for children.

RESULTS

Of 624 children (307 boys) 8.96 +/- 1.86 years old, with their mothers being 36.25 +/- 7.14 years old, examined, 107 (17.1%) of children were obese (BMI >95th percentile per Centers for Disease Control and Prevention norms), and 95 (15.2%) were overweight (OW) (85th percentile < or =BMI < 95th percentile). Of the mothers, 109 (30.4%) were obese (BMI > 30 kg/m(2)), and 206 (33.0%) were OW (25 kg/m(2) < BMI < 30 kg/m(2)). Approximately 68% of the children were prepubertal. The prevalence of MS was 3.5% overall: 6.7% in OW and 13.9% in obese children. To determine which marker was a better predictor for MS, a receiver operating characteristics (ROC) curve was generated for the five maternal anthropometric measures, with children's MS as the dichotomous variable. The areas under the ROC curves were 0.697 +/- 0.07 for BMI, 0.698 +/- 0.07 for WC, 0.717 +/- 0.07 for WC/height, 0.725 +/- 0.07 for WC/sitting height, and 0.704 +/- 0.07 for weight/sitting height squared. There was no significant difference between the areas of the five maternal anthropometric markers as predictors of children's MS.

CONCLUSIONS

Measurement of maternal sitting height had no advantages over total height in the prediction of children's MS. All maternal anthropometric measures identified the MS in their children consistent with known familial associations of obesity and type 2 diabetes.