Type 2 diabetes mellitus in African-American adolescents: impaired beta-cell function in the face of severe insulin resistance

Challenges and pitfalls of youth-onset type 2 diabetes

The incidence and prevalence of youth-onset type 2 diabetes mellitus (T2DM) are increasing. The rise in frequency and severity of childhood obesity, inclination to sedentary lifestyle, and epigenetic risks related to prenatal hyperglycemia exposure are important drivers of the youth-onset T2DM epidemic and might as well be responsible for the early onset of diabetes complications. Indeed, youth-onset T2DM has a more extreme metabolic phenotype than adult-onset T2DM, with greater insulin resistance and more rapid deterioration of beta cell function. Therefore, intermediate complications such as microalbuminuria develop in late childhood or early adulthood, while end-stage complications develop in mid-life. Due to the lack of efficacy and safety data, several drugs available for the treatment of adults with T2DM have not been approved in youth, reducing the pharmacological treatment options. In this mini review, we will try to address the present challenges and pitfalls related to youth-onset T2DM and summarize the available interventions to mitigate the risk of microvascular and macrovascular complications.

The Prevalence of Obesity Among Children With Type 2 Diabetes: A Systematic Review and Meta-analysis

Importance

The childhood obesity epidemic is presumed to drive pediatric type 2 diabetes (T2D); however, the global scale of obesity in children with T2D is unknown.

Objectives

To evaluate the global prevalence of obesity in pediatric T2D, examine the association of sex and race with obesity risk, and assess the association of obesity with glycemic control and dyslipidemia.

Data Sources

MEDLINE, Embase, CINAHL, Cochrane Library, and Web of Science were searched from database inception to June 16, 2022.

Study Selection

Observational studies with at least 10 participants reporting the prevalence of obesity in patients with pediatric T2D were included.

Data Extraction and Synthesis

Following the Meta-analysis of Observational Studies in Epidemiology reporting guideline, 2 independent reviewers in teams performed data extraction and risk of bias and level of evidence analyses. The meta-analysis was conducted using a random-effects model.

Main Outcomes and Measures

The primary outcomes included the pooled prevalence rates of obesity in children with T2D. The secondary outcomes assessed pooled prevalence rates by sex and race and associations between obesity and glycemic control and dyslipidemia.

Results

Of 57 articles included in the systematic review, 53 articles, with 8942 participants, were included in the meta-analysis. The overall prevalence of obesity among pediatric patients with T2D was 75.27% (95% CI, 70.47%-79.78%), and the prevalence of obesity at diabetes diagnosis among 4688 participants was 77.24% (95% CI, 70.55%-83.34%). While male participants had higher odds of obesity than female participants (odds ratio, 2.10; 95% CI, 1.33-3.31), Asian participants had the lowest prevalence of obesity (64.50%; 95% CI, 53.28%-74.99%), and White participants had the highest prevalence of obesity (89.86%; 95% CI, 71.50%-99.74%) compared with other racial groups. High heterogeneity across studies and varying degrees of glycemic control and dyslipidemia were noted.

Conclusions and Relevance

The findings of this systematic review and meta-analysis suggest that obesity is not a universal phenotype in children with T2D. Further studies are needed to consider the role of obesity and other mechanisms in diabetes genesis in this population.

Type 2 diabetes in adolescents and young adults

The prevalence of type 2 diabetes in adolescents and young adults is dramatically increasing. Similar to older-onset type 2 diabetes, the major predisposing risk factors are obesity, family history, and sedentary lifestyle. Onset of diabetes at a younger age (defined here as up to age 40 years) is associated with longer disease exposure and increased risk for chronic complications. Young-onset type 2 diabetes also affects more individuals of working age, accentuating the adverse societal effects of the disease. Furthermore, evidence is accumulating that young-onset type 2 diabetes has a more aggressive disease phenotype, leading to premature development of complications, with adverse effects on quality of life and unfavourable effects on long-term outcomes, raising the possibility of a future public health catastrophe. In this Review, we describe the epidemiology and existing knowledge regarding pathophysiology, risk factors, complications, and management of type 2 diabetes in adolescents and young adults.

Etiology of insulin resistance in youth with type 2 diabetes

Type 2 diabetes (T2DM), historically an adult disease, is now increasingly prevalent in obese youth. Poor diet and increased sedentary behavior contribute to the increasing rates of obesity in youth, yet not all obese children develop T2DM. In general, T2DM is characterized by both insulin resistance (IR) and pancreatic beta-cell insufficiency. In children, IR is related to elevated body mass index (BMI) and pubertal hormones, along with abnormal fat partitioning, elevated free fatty acids, inflammation, and/or mitochondrial dysfunction. Hyperglycemia and T2DM develop when the pancreas cannot match the increased insulin demands resulting from IR. Unique to youth, IR varies with stage of pubertal development, and some children may have resolution of hyperglycemia post-puberty once the IR of puberty resolves. Further understanding of IR, the progression to T2DM in youth, and later outcomes as adults will help direct future therapies and interventions for youth at risk.

Insulin resistance in type 2 diabetic youth

PURPOSE OF REVIEW

This review focuses on recent literature on insulin resistance in youth with type 2 diabetes mellitus (T2DM). Insulin resistance is associated with a variety of cardiometabolic problems leading to increased morbidity and mortality across the lifespan.

RECENT FINDINGS

Functional pancreatic β-cell changes play a role in the transition from obesity to impaired glucose tolerance (IGT). Insulin resistance drives islet cell upregulation, manifested by elevated glucagon and c-peptide levels, early in the transition to IGT. Surrogate measurements of insulin resistance and insulin secretion exist but their accuracy compared to clamp data is imperfect. Recent large longitudinal studies provide detailed information on the progression from normoglycemia to T2DM and on the phenotype of T2DM youth. Defining prediabetes and T2DM remains a challenge in youth. Lifestyle interventions do not appear as effective in children as in adults. Metformin remains the only oral hypoglycemic agent approved for T2DM in youth.

SUMMARY

New insights exist regarding the conversion from insulin resistance to T2DM, measurement of insulin resistance and phenotypes of insulin resistance youth, but more information is needed. Surrogate measurements of insulin resistance, additional treatment options for insulin resistance and individualization of treatment options for T2DM adolescents in particular require further investigation.

Glycemic control in youth with type 2 diabetes declines as early as two years after diagnosis

OBJECTIVES

To determine the course of glycemic decline in a pediatric cohort with type 2 diabetes mellitus (T2DM) by defining longitudinal changes in hemoglobin A1c (HbA1c) and insulin requirement. We also followed markers of insulin reserve (fasting C-peptide and IGFBP-1) over time.

STUDY DESIGN

Participants included two groups: (1) T2DM Nonacidotic (NA) (n = 46); and (2) T2DM diabetic ketoacidosis (n = 13). HbA1c, insulin dose, and fasting C-peptide and IGFBP-1 were obtained at baseline and every 6 months for 4 years.

RESULTS

At baseline, Mann Whitney tests demonstrated that the diabetic ketoacidosis group had higher HbA1c (P = .002), required more insulin (P = .036), and had lower C-peptide (P = .003) than the NA group. Baseline insulin dose (Spearman r = -0.424, P = .009) and baseline IGFBP-1 (Spearman r = -0.349, P = .046) correlated negatively with C-peptide. Over time, HbA1c, insulin dose, and C-peptide changed significantly in a complex manner, with group differences. HbA1c reached a nadir at 6 to 12 months and began to rise after 1.5 years. Insulin requirements reached a nadir at 1 year and began to rise after 2 years.

CONCLUSIONS

Unlike adults, children with T2DM require increasing insulin doses over a 4-year period, and diabetic ketoacidosis at diagnosis predicts greater β-cell decline over time.

The relationship of insulin secretion and GAD65 antibody levels at diagnosis on glycemic control in type 2 diabetes

OBJECTIVE

To determine if pretreatment insulin and C-peptide levels together with antibody status are predictive of HbAlc levels before and during therapy in obese African-American youth with type 2 diabetes.

METHODS

Records of African-American patients with clinical diagnosis of type 2 diabetes were retrospectively analyzed. Insulin, C-peptide, blood glucose, HbA1c and islet autoantibodies at diagnosis were recorded. These variables were compared with HbA1c levels during therapy.

RESULTS

Eight of 45 patients were islet autoantibody positive. There was no difference in age, Body Mass Index z-score, insulin, C-peptide, glucose or HbAlc levels between antibody positive or negative patients. Insulin (r = -0.45, p < 0.01 n=45) and C-peptide (r = -0.59, p < 0.001, n=36) were correlated with HbA1c at diagnosis but not during therapy.

CONCLUSIONS

Higher insulin levels were associated with lower HbA1c at presentation but not during therapy. Antibody status was not associated with differences in insulin, C-peptide levels or HbAlc level.

Evaluation of beta-cell function in diabetic Taiwanese children using a 6-min glucagon test

This study evaluates the effects of glucagon 30 mug/kg (maximal 1 mg) on beta-cell function in children by C-peptide determined before and 6 min after intravenous administration. From 1990 to 2005, 118 Taiwanese children with newly diagnosed diabetes mellitus (98 children with type 1 and 20 children with type 2) and 29 normal Taiwanese children were enrolled in this study. Fasting and 6-min post-glucagon C-peptide levels were analyzed. In the pre-pubertal group, the median fasting serum C-peptide levels were 0.2 and 0.8 nmol/l in type 1 diabetes and normal children, respectively. These levels rose to 0.3 and 1.9 nmol/l after glucagon stimulation. In the pubertal group, the median fasting serum C-peptide levels were 0.3, 1.0 and 0.9 nmol/l in type 1 diabetes, type 2 diabetes and normal children, respectively. They rose to 0.4, 2.5 and 2.7 nmol/l after glucagon stimulation. Both fasting and post-glucagon C-peptide levels in type 1 diabetes patients were significantly lower than those of normal children and children with type 2 diabetes. The optimal cut-off values to distinguish type 1 diabetes patients from those with type 2 as determined by the receiving operating characteristic curve were 0.7 and 1.1 nmol/l, respectively. The sensitivities of both C-peptide values were 93%. The post-glucagon C-peptide level was more powerful in distinguishing type 1 diabetes from type 2 diabetes with higher specificity (95% vs. 85%). The 6-min glucagon test is valuable in assessing beta-cell function in children and can help pediatricians in the differential diagnoses of diabetes mellitus in children.