Prediction Models for Insulin Resistance in Girls with Premature Adrenarche

Association of dehydroepiandrosterone sulfate, birth size, adiposity and cardiometabolic risk factors in 7-year-old children

BACKGROUND

Low birth size (BS) and obesity have been associated with higher dehydroepiandrosterone sulfate (DHEAS) levels in childhood, insulin acting as a mediator, despite contradictory findings. To further explore these issues, we studied the associations between DHEAS, BS, adiposity, maternal characteristics, and cardiometabolic risk indicators, in participants of Generation XXI, a population-based birth cohort.

METHODS

A sample of 700 children (mean age 7.1 yr) was randomly selected. Data on maternal characteristics, BS, body mass index (BMI), waist-to-height ratio, body fat (dual-energy X-ray absorptiometry), insulin, lipid profile, and high-sensitivity C-reactive protein were analyzed in relation to DHEAS.

RESULTS

DHEAS was negatively associated with BS and positively associated with all adiposity indicators, with no sex differences. DHEAS was positively associated with insulinemia independently of the child's BS or BMI. No significant association was found between DHEAS, maternal characteristics, lipid profile, or high-sensitivity C-reactive protein. Including insulin in the model did not affect the association between BS and DHEAS but reduced the magnitude of the BMI effect by 24% for boys and 30% for girls.

CONCLUSION

Higher DHEAS levels at 7 years old were associated with lower BS and higher adiposity. DHEAS levels were positively associated with insulinemia independently of BS or BMI.

IMPACT

Low birth weight and obesity have been associated with higher dehydroepiandrosterone sulfate (DHEAS) levels in prepuberty. Insulin has been suggested as a mediator, despite previous studies failing to show an association between DHEAS and insulin levels. In a randomly selected population of 700 7-year-old children from the Generation XXI birth cohort, higher DHEAS levels were associated with a lower birth size and higher adiposity, with no sex differences. DHEAS was positively related to insulinemia independently of the child's birth size or body mass index. No association was found between DHEAS and other cardiometabolic risk factors.

Associations Between Maternal Pregravid Obesity and Gestational Diabetes and the Timing of Pubarche in Daughters

We investigated whether in utero exposure to maternal pregravid obesity and/or gestational diabetes mellitus (GDM) was associated with early puberty in girls. We used data from a longitudinal study of 421 mother-daughter pairs enrolled in an integrated health services organization, Kaiser Permanente Northern California (2005-2012). Girls aged 6-8 years were followed annually through ages 12-14 years. Onset of puberty was assessed using study clinic-based Tanner staging. We examined associations of self-reported pregravid obesity and maternal GDM with timing of the daughter's transition to pubertal maturation stage 2 or above for development of breasts and pubic hair, using accelerated failure time regression models with interval censoring to estimate time ratios and hazard ratios and corresponding 95% confidence intervals. Maternal obesity (pregravid body mass index (BMI; weight (kg)/height (m)(2)) ≥30) was associated with a daughter's earlier transition to breast and pubic hair stage 2+ in comparison with girls whose mothers had pregravid BMI <25. These associations were attenuated and not statistically significant after adjustment for covariates. Girls whose mothers had both pregravid BMI ≥25 and GDM were at higher risk of an earlier transition to pubic hair stage 2+ than those whose mothers had neither condition (adjusted time ratio = 0.89, 95% confidence interval: 0.83, 0.96; hazard ratio = 2.97, 95% confidence interval: 1.52, 5.83). These findings suggest that exposure to maternal obesity and hyperglycemia places girls at higher risk of earlier pubarche.

The development of a decision analytic model of changes in mean deviation in people with glaucoma: the COA model

PURPOSE

To create and validate a statistical model predicting progression of primary open-angle glaucoma (POAG) assessed by loss of visual field as measured in mean deviation (MD) using 3 landmark studies of glaucoma progression and treatment.

DESIGN

A Markov decision analytic model using patient level data described longitudinal MD changes over 7 years.

PARTICIPANTS

Patient-level data from the Collaborative Initial Glaucoma Treatment Study (n = 607), the Ocular Hypertension Treatment Study (OHTS; n = 148; only those who developed POAG in the first 5 years of OHTS) and Advanced Glaucoma Intervention Study (n = 591), the COA model.

METHODS

We developed a Markov model with transition matrices stratified by current MD, age, race, and intraocular pressure categories and used a microsimulation approach to estimate change in MD over 7 years. Internal validation compared model prediction for 7 years to actual MD for COA participants. External validation used a cohort of glaucoma patients drawn from university clinical practices.

MAIN OUTCOME MEASURES

Change in visual field as measured in MD in decibels (dB).

RESULTS

Regressing the actual MD against the predicted produced an R(2) of 0.68 for the right eye and 0.63 for the left. The model predicted ending MD for right eyes of 65% of participants and for 63% of left eyes within 3 dB of actual results at 7 years. In external validation the model had an R(2) of 0.79 in the right eye and 0.77 in the left at 5 years.

CONCLUSIONS

The COA model is a validated tool for clinicians, patients, and health policy makers seeking to understand longitudinal changes in MD in people with glaucoma.

Body mass index percentile more sensitive than acanthosis nigricans for screening Native American children for diabetes risk

BACKGROUND

Many Native American tribes use acanthosis nigricans to screen for type 2 diabetes risk. We hypothesized that acanthosis nigricans misses many children at risk for type 2 diabetes.

METHODS

We evaluated 5- to 18-year-old Native American children and youth to assess the sensitivity and specificity of acanthosis nigricans as a marker for insulin resistance.

RESULTS

In a cohort of 161 youth (72 males/89 females), mean age was 10.7 years + 3.9. Mean body mass index (BMI) percentile was 76.8 +/- 23.3, and 54% had a BMI at or above the 85th percentile. Acanthosis nigricans was present in 21.7% of the participants and was more common in 12-to 18-year-olds than in 5 to 11-year-olds (p = .02). Of those with acanthosis nigricans, 82.4% had insulin resistance (homeostatic model assessment of insulin resistance >4), but only 48.3% of those with insulin resistance had acanthosis nigricans. In contrast, BMI at or above the 85th percentile had a high sensitivity (74%) for insulin resistance, even though its specificity was lower (58%).

CONCLUSIONS

The presence of acanthosis nigricans alone was a specific, but not a sensitive, screening tool for identifying youth with insulin resistance. BMI at or above the 85th percentile was a more sensitive screening tool than acanthosis nigricans alone, or acanthosis nigricans and BMI together for identifying children and youth with IR who are at increased risk for type 2 diabetes.

Interventional studies for polycystic ovarian syndrome in children and adolescents

Polycystic ovarian syndrome (PCOS) is characterized by chronic anovulation, clinical and/or biochemical hyperandrogenism, which can be associated with altered insulin action. Symptoms usually begin around menarche, but onset after puberty may also occur as a result of environmental modifiers such as weight gain. The consequences of PCOS extend beyond the reproductive axis; there is a substantial risk for development of metabolic and cardiovascular abnormalities similar to the metabolic syndrome. Currently, the treatment is targeted to the patient's primary complaint such as hirsutism, restoration of regular menses or pregnancy. Pharmacological agents available for the treatment of hirsutism include androgen suppressors and peripheral androgen blockers. Recently, our understanding of the role of insulin resistance has led to the use of insulin-sensitizing medications as first-choice therapy. In conjunction with weight reduction and exercise, a pharmacologic reduction in insulin levels by either metformin or thiazolidinediones ameliorates both hyperinsulinemia and hyperandrogenism.