A longitudinal study of serum insulin and insulin resistance as predictors of weight and body fat gain in African American and Caucasian children

Factors associated with body weight gain and insulin-resistance: a longitudinal study

BACKGROUND

Obesity is the result of energy intake (EI) chronically exceeding energy expenditure. However, the potential metabolic factors, including insulin resistance, remain unclear. This study longitudinally investigated factors associated with changes in body weight.

SUBJECTS

A cohort of 707 adults without diabetes were investigated at the 4-year follow-up visit. The habitual intake of energy and macronutrients during the past 12 months was assessed using a validated Food Frequency Questionnaire for the local population. Homeostatic model assessment of β-cell function and insulin resistance (HOMA-IR) was used as a surrogate measure of insulin resistance. Additionally, PNPLA3 was genotyped.

RESULTS

Eighty-seven participants were weight gainers (G; cutoff value = 5 kg), and 620 were non-gainers (NG). Initial anthropometric (G vs. NG: age, 44 ± 13 vs 51 ± 13 years, P < 0.001; body mass index, 27.8 ± 6.5 vs 28.1 ± 5.1 kg/m2, P = ns; body weight, 76.7 ± 22.1 vs 74.2 ± 14.7 kg, P = ns; final body weight, 86.3 ± 23.7 vs 72.9 ± 14.2 kg, P < 0.001) and diet characteristics, as well as insulin concentrations and HOMA-IR values, were similar in both groups. Four years later, G showed significantly increased EI, insulin concentrations, and HOMA-IR values. G had a higher prevalence of the PNPLA3 CG and GG alleles than NG (P < 0.05). The presence of G was independently associated with age (OR = 1.031), EI change (OR = 2.257), and unfavorable alleles of PNPLA3 gene (OR = 1.700). Final body mass index, waist circumference, and EI were independently associated with final HOMA-IR (P < 0.001).

CONCLUSIONS

EI is associated with body weight gain, and genetic factors may influence the energy balance. Insulin resistance is a consequence of weight gain, suggesting a possible intracellular protective mechanism against substrate overflow.

CLINICAL TRIAL REGISTRATION

ISRCTN15840340.

Adipose Tissue Insulin Resistance Is Not Associated With Changes in the Degree of Obesity in Children and Adolescents

CONTEXT

The "carbohydrate-insulin model" claims that adipose tissue insulin sensitivity explains development of obesity via adipocyte energy storage and/or low postprandial metabolic fuel levels.

OBJECTIVE

We tested whether adipose tissue insulin sensitivity predicts changes in the degree of obesity over time.

METHODS

This secondary analysis of an observational study of youth with obesity included 213 youths at a pediatric weight management clinic. Adipose tissue insulin sensitivity/resistance and whole-body insulin sensitivity were evaluated using oral glucose tolerance test (OGTT)-derived surrogates in the face of changes in the degree of obesity over time. The main outcome measure was change in body mass index (BMI) z score.

RESULTS

Mean BMI z change was 0.05 ± 0.28 (range, -1.15 to 1.19), representing a broad distribution of changes in the degree of obesity over a follow-up period of 1.88 ± 1.27 years. Adipose tissue insulin resistance was not associated with changes in the degree of obesity in univariate or multivariate analyses (adjusted for baseline age, BMI z score, sex, ethnicity, and time of follow-up). Low postprandial free fatty acid concentrations or their suppression during the OGTT were not associated with changes in the degree of obesity in univariate or multivariate analyses. Whole-body insulin sensitivity was not associated with changes in the degree of obesity in univariate or multivariate analyses.

CONCLUSION

In this secondary analysis, in youth with obesity, adipose tissue insulin resistance is not protective from increases of the degree of obesity and skeletal muscle insulin resistance is not associated with increases of the degree of obesity.The analysis was performed using data derived from NCT00000112 and NCT00536250.

Insulin sensitivity as a predictor of longitudinal changes on body mass index in Brazilian adolescents

OBJECTIVES

We aimed to investigate the effect of insulin sensitivity and insulin resistance status at baseline on longitudinal body mass index, and the possible effect modification by sex.

METHODS

This is a secondary analysis of a randomized intervention community trial, in which a subgroup of 84 adolescents, aged between 10 and 12 years, were analyzed. Body weight, height, and body mass index (BMI) were determined before and after 8 months of follow-up. Glucose and serum insulin were examined at baseline and IR was defined based on the homeostasis model assessment-insulin resistance (HOMA-IR), with a cutoff >2.5 for both genders. Linear mixed-effects models were performed to evaluate the influence of HOMA-IR at baseline on BMI changes over time. Models were adjusted for age, pubertal stage, and stratified by sex.

RESULTS

The sample comprised 65.4% of girls and the prevalence of overweight/obesity was 54.7% among girls and 50.0% among boys. The overall prevalence of IR was 75.3%, of which 60.7% for boys and 83.0% for girls. We found an interaction effect by sex (p = .004) for HOMA-IR as a continuous variable, with a decreased BMI rate of change among boys (β = -0.13; p = .03) but not for girls (β = +0.03; p = .36). Longitudinal BMI changes considering IR status at baseline (IR vs. non-IR) did not demonstrate any statistically significant difference for both boys (-0.1 vs. +0.4; p = .28) and girls (+0.7 vs. +1.0; p = .44).

CONCLUSION

Increased HOMA-IR values at baseline were associated with greater BMI reduction over time among boys but not girls, with no influence of IR status.

Predictive Markers of Early Cardiovascular Impairment and Insulin Resistance in Obese Pediatric Patients

BACKGROUND

The increased prevalence of obesity among children determined the rising number of its comorbidities in children and adults, too. This study aimed to evaluate certain markers of inflammation and insulin resistance in obese pediatric patients, identifying those who are more likely to develop further complications.

METHODS

We included 115 obese pediatric patients: 85 overweight and obese patients in the study group and 30 normal-weight patients in the control group. We calculated the body mass index (BMI) and we evaluated markers (biological, inflammatory) and the hormones profile.

RESULTS

Low-threshold inflammation was assessed by measuring interleukin 6 IL-6 and Intercellular Adhesion Molecules (ICAM). The analysis showed that IL-6 is significantly correlated with glucose (p = 0.001) and BMI value (p = 0.031). ICAM correlates significantly with triglycerides (p = 0.001), glucose (p = 0.044) and BMI percentile (p = 0.037). For pediatric obese patients, endotoxemia has been significantly correlated only with BMI percentile (p = 0.001). Plasma cortisol did not show significant correlations with total cholesterol, triglycerides, glucose or BMI percentile. The results indicated a significant predictive power of BMI percentile on inflammatory markers: IL-6 (AUC = 0.803, p < 0.001), ICAM (AUC = 0.806, p < 0.001) and endotoxemia (AUC = 0.762, p = 0.019). Additionally, BMI percentile has a significant predictive power for metabolic markers of insulin resistance (insulin value: AUC = 0.72, p < 0.001 and HOMA index: AUC = 0.68, p = 0.003).

CONCLUSIONS

The study highlighted the importance of early markers of cardiovascular risk in obese pediatric patients represented by IL-6, ICAM, endotoxemia and their correlation with metabolic markers of insulin resistance represented by insulinemia, HOMA index and plasma cortisol. It can clearly be considered that the BMI percentile has significant predictive power for metabolic markers of insulin resistance.

Associations between sleep duration and insulin resistance in European children and adolescents considering the mediating role of abdominal obesity

Background

Short sleep duration has been suggested to lead to insulin resistance both directly by altering glucose metabolism and indirectly through obesity. This study aims to investigate associations between nocturnal sleep duration and insulin resistance considering abdominal obesity as a mediator.

Methods

We analysed data of 3 900 children aged 2–15 years participating in the second (2009/10) and third (2013/14) examination wave of the European IDEFICS/I.Family study (hereafter referred to as baseline and follow-up). Information on nocturnal sleep duration was collected by questionnaires and age-standardised (SLEEP z-score). The homeostasis model assessment (HOMA) was calculated from fasting insulin and fasting glucose obtained from blood samples; waist circumference (WAIST) was measured with an inelastic tape. HOMA and WAIST were used as indicators for insulin resistance and abdominal obesity, respectively, and transformed to age- and sex-specific z-scores. Cross-sectional and longitudinal associations between SLEEP z-score and HOMA z-score were investigated based on a path model considering WAIST z-score as a mediator adjusting for relevant confounders.

Results

Cross-sectionally, baseline SLEEP z-score was negatively associated with baseline WAIST z-score (unstandardised effect estimate -0.120, 95% confidence interval [-0.167; -0.073]). We observed no direct effect of baseline SLEEP z-score on baseline HOMA z-score but a negative indirect effect through baseline WAIST z-score (-0.042 [-0.058; -0.025]). Longitudinally, there was no direct effect of baseline SLEEP z-score on HOMA z-score at follow-up but a negative indirect effect through both baseline WAIST z-score and WAIST z-score at follow-up (-0.028 [-0.040; -0.016]).

Conclusions

Our results do not support the hypothesis of an association between short sleep duration and insulin resistance independent of abdominal obesity. However, longer sleep duration may exert short and long term beneficial effects on insulin resistance through its beneficial effects on abdominal obesity.

Insulin translates unfavourable lifestyle into obesity

Lifestyle factors conferring increased diabetes risk are associated with elevated basal insulin levels (hyperinsulinaemia). The latter predicts later obesity in children and adolescents.A causal role of hyperinsulinaemia for adipose tissue growth is probable because pharmacological reduction of insulin secretion lowers body weight in people who are obese. Genetic inactivation of insulin gene alleles in mice also lowers their systemic insulin levels and prevents or ameliorates high-fat diet-induced obesity. Hyperinsulinaemia causes weight gain because of a physiological property of insulin. Insulin levels that are on the high side of normal, or which are slightly elevated, are sufficient to suppress lipolysis and promote lipogenesis in adipocytes. The effect of insulin on glucose transport or hepatic glucose production requires six or two times higher hormone levels, respectively.It seems justified to suggest a lifestyle that avoids high insulin levels in order to limit anabolic fat tissue activity.