Glucose Tolerance In Obese Adolescents Research Articles

Characteristics of Obstructive Sleep Apnea Across the Spectrum of Glucose Tolerance in Obese Adolescents.

It is not known if dysglycemia and sleep-disordered breathing are linked in adolescents, as in adults. To perform a pilot study evaluating measures of sleep-disordered breathing across the spectrum of glucose tolerance in obese adolescents. We hypothesized that dysglycemia would be associated with sleep-disordered breathing. This was a prospective, cross-sectional clinical pilot study that included 57 adolescents [body mass index (BMI) 38.9 ± 8.4 kg/m2] aged 12-18 years (14.5 ± 1.6) with normal glucose tolerance (NGT), or dysglycemia [impaired glucose tolerance (IGT) or type 2 diabetes (T2D)]. Anthropometrics, overnight polysomnogram, and oral glucose tolerance tests were performed. Participant characteristics and outcome measures were compared by glucose tolerance status. Correlational analyses were conducted to assess the associations between variables of interest. Participants with dysglycemia (n = 21) were not different from those with NGT (n = 36) for BMI, waist circumference, body fat, or sleep characteristics. Nocturnal oxygen desaturation was associated with higher BMI (r = -0.334, p = 0.012). The apnea-hypopnea index (AHI) was not associated with physical and metabolic parameters. Although participants with dysglycemia tended to have higher AHIs (median 3.2, 2.2, and 1.6 events/h for T2D, IGT, and NGT, respectively), there was not a linear relationship between measures of glycemia and AHI. Further study with a larger proportion of youth with prediabetes and T2D is necessary to determine whether evaluation for sleep-disordered breathing is uniformly warranted.

Vitamin D insufficiency and insulin resistance in obese adolescents.

Obese adolescents represent a particularly vulnerable group for vitamin D deficiency which appears to have negative consequences on insulin resistance and glucose homeostasis. Poor vitamin D status is also associated with future risk of type 2 diabetes and metabolic syndrome in the obese. The biological mechanisms by which vitamin D influences glycemic control in obesity are not well understood, but are thought to involve enhancement of peripheral/hepatic uptake of glucose, attenuation of inflammation and/or regulation of insulin synthesis/secretion by pancreatic β cells. Related to the latter, recent data suggest that the active form of vitamin, 1,25-dihydroxyvitamin D, does not impact insulin release in healthy pancreatic islets; instead they require an environmental stressor such as inflammation or vitamin D deficiency to see an effect. To date, a number of observational studies exploring the relationship between the vitamin D status of obese adolescents and markers of glucose homeostasis have been published. Most, although not all, show significant associations between circulating 25-hydroxyvitamn D concentrations and insulin sensitivity/resistance indices. In interpreting the collective findings of these reports, significant considerations surface including the effects of pubertal status, vitamin D status, influence of parathyroid hormone status and the presence of nonalcoholic fatty liver disease. The few published clinical trials using vitamin D supplementation to improve insulin resistance and impaired glucose tolerance in obese adolescents have yielded beneficial effects. However, there is a need for more randomized controlled trials. Future investigations should involve larger sample sizes of obese adolescents with documented vitamin D deficiency, and careful selection of the dose, dosing regimen and achievement of target 25-hydroxyvitamn D serum concentrations. These trials should also include clamp-derived measures of in vivo sensitivity and β-cell function to more fully characterize the effects of vitamin D replenishment on insulin resistance.

Progression of β-Cell Dysfunction in Obese Youth

The epidemic of childhood obesity has led to a remarkable increase in the prevalence of type 2 diabetes (T2D) among youth worldwide. The decreasing age at onset of T2D has alarming public health implications. In particular, the longer duration of the disease, as well as the faster onset and progression of T2D related complications, will present a considerable burden for young adults and a strain on public health. Therefore, it is important to understand the pathophysiology of early phases of disruption of glucose tolerance and identify those critical points in which diabetes may be prevented. β-Cell dysfunction has been shown to represent one of the key pathogenetic defects underlying the progression to diabetes in obese youth. In the present review, we describe longitudinal and cross-sectional studies of changes in insulin sensitivity and secretion across the spectrum of glucose tolerance in obese adolescents. Further, the role of ectopic fat accumulation is discussed in relation to its association with both β-cell dysfunction and insulin resistance.

Primary Defects in β-Cell Function Further Exacerbated by Worsening of Insulin Resistance Mark the Development of Impaired Glucose Tolerance in Obese Adolescents

OBJECTIVE—Impaired glucose tolerance (IGT) is a pre-diabetic state of increasing prevalence among obese adolescents. The purpose of this study was to determine the natural history of progression from normal glucose tolerance (NGT) to IGT in obese adolescents.RESEARCH DESIGN AND METHODS—We determined the evolution of β-cell function, insulin sensitivity (SI), and glucose tolerance in a multiethnic group of 60 obese adolescents over the course of approximately 30 months. Each subject underwent three serial 3-h oral glucose tolerance tests. Dynamic, static, and total β-cell responsivity (Φd, Φs, and Φtot, respectively) and Si were assessed by oral C-peptide and glucose minimal models. The disposition index (DI), which adjusts insulin secretion for Si, was calculated.RESULTS—At baseline, all 60 subjects had NGT. Seventy-seven percent (46 subjects) maintained NGT over the three testing periods (nonprogressors), whereas 23% (14 subjects) developed IGT over time (progressors). At baseline, percent fat and BMI Z score were comparable between the groups. Fasting plasma glucose, 2-h glucose, glucose area under the curve at 180 min, and Φd were significantly different between the two groups at baseline, whereas Si was comparable between the two groups. Over time, although Si remained unchanged in nonprogressors, it steadily worsened by ∼45% (P > 0.04) in progressors. β-Cell responsivity decreased by 20% in progressors, whereas it remained stable in nonprogressors. The DI showed a progressive decline in progressors compared with a modest improvement in nonprogressors (P = 0.02).CONCLUSIONS—Obese adolescents who progress to IGT may manifest primary defects in β-cell function. In addition, progressive decline in Si further aggravates β-cell function, contributing to the worsening of glucose intolerance.