Ebe D’Adamo

Type 2 Diabetes in Youth: Epidemiology and Pathophysiology

The prevalence of type 2 diabetes is significantly increased in the pediatric population, which is affected by obesity worldwide. The progression from normal glucose tolerance (NGT) to type 2 diabetes involves intermediate stages of impaired fasting glucose (IFG) and impaired glucose tolerance (IGT), also known as prediabetes. The pathophysiology underlying the development of these glucose metabolic alterations is multifactorial; however an alteration in the balance between insulin sensitivity and insulin secretion represents the most important player in the development of type 2 diabetes. Obese children and adolescents affected by IGT and type 2 diabetes are characterized by severe insulin resistance, which is associated with an increased lipid accumulation in visceral compartments, liver and muscle tissues and by reduced sensitivity of I²-cell of first and second-phase insulin secretion. The progression in obese children of insulin resistance to type 2 diabetes has been shown to be faster than in adults; in addition, type 2 diabetes is already associated with several metabolic and cardiovascular complications in this age group. In the present review, we summarize the most recent findings concerning the prevalence of type 2 diabetes in youth and in particular we explore the pathophysiology of type 2 diabetes and the natural history of this pathology in obese children and adolescents. Concurrent with the worldwide epidemic increase of childhood obesity, type 2 diabetes and the two prediabetic conditions, IFG and IGT, are becoming increasingly more common in obese children and adolescents (1,2). Until 10 years ago, type 2 diabetes accounted for less than 3% of all cases of new-onset diabetes in adolescents. At present 45% of cases are attributed to it (3,4). Type 2 diabetes occurs in youth more often during the second decade of life, coinciding with the physiological occurrence of pubertal insulin resistance (1). In addition, …

Decreased Transcription of ChREBP-α/β Isoforms in Abdominal Subcutaneous Adipose Tissue of Obese Adolescents With Prediabetes or Early Type 2 Diabetes Associations With Insulin Resistance and Hyperglycemia

Insulin resistance associated with altered fat partitioning in liver and adipose tissues is a prediabetic condition in obese adolescents. We investigated interactions between glucose tolerance, insulin sensitivity, and the expression of lipogenic genes in abdominal subcutaneous adipose and liver tissue in 53 obese adolescents. Based on their 2-h glucose tests they were stratified in the following groups: group 1, 2-h glucose level <120 mg/dL; group 2, 2-h glucose level between 120 and 140 mg/dL; and group 3, 2-h glucose level >140 mg/dL. Liver and adipose tissue insulin sensitivity were greater in group 1 than in group 2 and group 3, and muscle insulin sensitivity progressively decreased from group 1 to group 3. The expression of the carbohydrate-responsive element-binding protein (ChREBP) was decreased in adipose tissue but increased in the liver (eight subjects) in adolescents with impaired glucose tolerance or type 2 diabetes. The expression of adipose ChREBPα and ChREBPβ was inversely related to 2-h glucose level and positively correlated to insulin sensitivity. Improvement of glucose tolerance in four subjects was associated with an increase of ChREBP/GLUT4 expression in the adipose tissue. In conclusion, early in the development of prediabetes/type 2 diabetes in youth, ChREBPβ expression in adipose tissue predicts insulin resistance and, therefore, might play a role in the regulation of glucose tolerance.

Improved oxidative stress and cardio-metabolic status in obese prepubertal children with liver steatosis treated with lifestyle combined with Vitamin E.

Abstract In obese adults with non alcoholic fatty liver disease (NAFLD), treatment with Vitamin E has resulted in an improvement in liver histology, whereas variable and limited results are available in children. Our aim was to assess whether lifestyle combined with supplementation with Vitamin E might reduce oxidative stress and improve cardio-metabolic status in obese children with NAFLD. 24 obese prepubertal children (16M) followed a 6-month lifestyle intervention combined with Vitamin E supplementation (600 mg/day) and they were compared with 21 age and sex-matched obese peers who underwent lifestyle intervention only. At baseline and after 6-month urinary prostaglandin F2α (PGF-2α), endogenous secretory receptor for advanced glycation end products (esRAGE), high sensitivity C-reactive protein (hs-CRP), alanine aminotransferases (ALT), lipid profile, glucose, and insulin were assessed. The two groups were comparable for age (8.3 ± 1.6 vs 8.4 ± 1.3 yr), sex and BMI SDS (2.16 ± 0.29 vs 2.13 ± 0.28). At the beginning of the study, PGF2-α, esRAGE hsCRP, ALT, lipid profile and HOMA-IR levels were similar between the two groups (all p > 0.05). After 6-month treatment, levels of PGF2-α (p < 0.001) significantly decreased and esRAGE significantly increased (p < 0.001) in children treated with Vitamin E. A significant reduction was also found in ALT (p = 0.001), lipid profile and HOMA-IR (p < 0.001). In contrast, no significant change in any of these markers was detected in the lifestyle only group. In conclusion, Vitamin E supplementation was associated with a significant reduction in oxidative stress and improved cardio-metabolic alterations. These data suggest that Vitamin E supplementation could represent a valuable treatment in obese children affected by NAFLD.

The possible role of esRAGE and sRAGE in the natural history of diabetic nephropathy in childhood

The advanced glycation end products/receptor for advanced glycation end products (AGE–RAGE) pathway is a key mediator of glomerular changes in type 1 diabetes. We evaluated endogenous secretory (es)RAGE and soluble (s)RAGE concentrations in 64 pre-pubertal and pubertal normoalbuminuric patients with type 1 diabetes and compared the values with those of 62 controls matched for age, gender and Tanner pubertal stages. We also explored the possible association of their concentrations with early signs of diabetic nephropathy, defined as changes in kidney volume and estimated glomerular filtration rate (eGFR). Significantly lower concentrations of both esRAGE and sRAGE were documented in pre-pubertal (p = 0.003 and p = 0.001) and pubertal (p = 0.002 and p = 0.001) subjects with type 1 diabetes than in the controls. In both groups of patients with type 1 diabetes, the eGFR (pre-pubertal p = 0.01 and pubertal p = 0.01) and the mean value of kidney volume adjusted for body surface (pre-pubertal p = 0.003 and pubertal p = 0.002) were higher than those of the controls. The regression analysis showed an inverse relationship between esRAGE and body surface-adjusted mean kidney volume (p = 0.0004, r = −0.503). esRAGE and sRAGE concentrations were lower in normoalbuminuric youths with type 1 diabetes than in their healthy peers. The inverse association between esRAGE levels and early kidney alterations suggests a potential role of esRAGE in diabetic nephropathy.

Serum Levels of Receptors for Advanced Glycation End Products in Normal-Weight and Obese Children Born Small and Large for Gestational Age

OBJECTIVE To assess potential alterations in soluble and endogenous secretory receptors for advanced glycation end products (sRAGE and esRAGE) in normal-weight (NW) and obese (Ob) children born small (SGA) and large (LGA) compared with appropriate for gestational age (AGA) subjects and to explore if birth weight (BW), insulin resistance (IR), and obesity represent independent risk factors. RESEARCH DESIGN AND METHODS We categorized 130 prepubertal children into six groups according to BW and obesity and evaluated sRAGE, esRAGE, and homeostasis model assessment of IR. RESULTS sRAGE and esRAGE were lower in Ob SGA and LGA children than Ob AGA subjects (all P < 0.05), and in NW SGA and LGA children than NW AGA subjects (all P < 0.05). Interestingly, BW and IR were significantly and independently related to RAGE. CONCLUSIONS sRAGE and esRAGE are decreased in SGA and LGA children, and BW and IR seem to play an important role in the reduction of RAGE.

A Branched-Chain Amino Acid-Related Metabolic Signature Characterizes Obese Adolescents with Non-Alcoholic Fatty Liver Disease

Dysregulation of several metabolite pathways, including branched-chain amino acids (BCAAs), are associated with Non-Alcoholic Fatty Liver Disease (NAFLD) and insulin resistance in adults, while studies in youth reported conflicting results. We explored whether, independently of obesity and insulin resistance, obese adolescents with NAFLD display a metabolomic signature consistent with disturbances in amino acid and lipid metabolism. A total of 180 plasma metabolites were measured by a targeted metabolomic approach in 78 obese adolescents with (n = 30) or without (n = 48) NAFLD assessed by magnetic resonance imaging (MRI). All subjects underwent an oral glucose tolerance test and subsets of patients underwent a two-step hyperinsulinemic-euglycemic clamp and/or a second MRI after a 2.2 ± 0.8-year follow-up. Adolescents with NAFLD had higher plasma levels of valine (p = 0.02), isoleucine (p = 0.03), tryptophan (p = 0.02), and lysine (p = 0.02) after adjustment for confounding factors. Circulating BCAAs were negatively correlated with peripheral and hepatic insulin sensitivity. Furthermore, higher baseline valine levels predicted an increase in hepatic fat content (HFF) at follow-up (p = 0.01). These results indicate that a dysregulation of BCAA metabolism characterizes obese adolescents with NAFLD independently of obesity and insulin resistance and predict an increase in hepatic fat content over time.

Implications of gastrointestinal hormones in the pathogenesis of obesity in prepubertal children.

Abstract Background: There is a worsening high prevalence of global obesity. Special attention has been paid to the gut-endocrine system, represented by the regulators of appetite. In particular, it has been suggested that ghrelin (“hunger” peptide), and obestatin and glucagon-like peptide-1 (GLP-1) (“satiety” peptides) could play important roles in the pathogenesis of obesity. Objectives: The aims of this study were to compare fasting plasma ghrelin, obestatin, and GLP-1 levels between obese and nonobese prepubertal children, and to assess their relations with fatness indexes and insulin resistance (IR). Subjects and methods: Fifty-two prepubertal obese children and 22 controls were enrolled. Fasting levels of gastrointestinal hormones (ghrelin, obestatin, and GLP-1), glucose, and insulin were evaluated. IR was assessed using the homeostasis model assessment of IR (HOMA-IR) index. Analysis was performed by Mann-Whitney U-test, Kruskal-Wallis test, and Spearman’s correlation. Results: Obese prepubertal children and normal-weight controls had similar age distribution. Obese children were more insulin resistant when compared to controls (HOMA-IR: p<0.01). GLP-1 levels were significantly lower in obese children than in controls (p<0.01). Obestatin was significantly higher in obese than normal-weight children (p<0.01), while ghrelin was not different. There was a negative correlation between GLP-1 and standard deviation score-body mass index (r=–0.36, p=0.009) and between GLP-1 and waist circumference (r=–0.45, p=0.001), while no association was observed with HOMA-IR. Conclusions: GLP-1 levels have been shown to be correlated with adiposity indexes, but not with HOMA-IR, suggesting that this hormone could play an important role in the early development of obesity.

Weight Loss in Obese Prepubertal Children: The Influence of Insulin Resistance

Background. Insulin resistance (IR), a link of paramount importance between obesity and cardiovascular/metabolic complications, seems to be implicated in weight changes. Objective. To determine whether IR could influence weight status during a 1-year intervention program in obese prepubertal children. Methods. Forty-four children with IR (IR group) and 42 children without IR (NIR group) were enrolled. Body mass index standard deviation score (BMI-SDS), waist circumference (WC), and homeostasis model assessment (HOMA-IR) were evaluated. Results. NIR children showed a significant reduction of BMI-SDS and WC at final assessment (p = 0.009 and p = 0.001, respectively), whereas IR children presented unchanged values. HOMA-IR decreased after intervention in the NIR group (p = 0.0008), but was exacerbated in IR children (p = 0.004). A positive and significant association between HOMA-IR at baseline and BMI at follow-up was found (B ± SE = 0.87 ± 0.24, p = 0.001). HOMA-IR at baseline was also significantly associated with WC at follow-up (B ± SE = 2.12 ± 0.69, p = 0.003). Conclusions. IR seems to influence adiposity changes in obese prepubertal children. Further longitudinal studies are needed to verify the relationship between IR and weight loss during childhood.

Primary and Secondary Amenorrhea

Puberty represents a particular period of life characterized by hormonal changes and physical and psychological modifications leading children from childhood to adolescence. During this period, menarche represents the most important event in females. Age of menarche is different among populations and has been recognized as an useful marker of socio-economic status, as well as dietary and environmental patterns (Chumlea et al., 2003; Swenson & Havens, 1987; Thomas et al., 2001). Generally, the first menstrual cycle takes place between 12 and 13 years of age, with 98% of girls having menarche by 15 years of age (Diaz, 2006). The normal range for menstrual cycles is between 21 and 45 days, with flow length varying from 2 to 7 days (Flug et al., 1984; World Health Organization Task Force on Adolescent Reproductive Health, 1986). During the first 2 years after menarche, menses length is often abnormal due to immaturity of the hypothalamic-pituitary-ovarian axis (Diaz, 2006); however, cycles range can be regular also in the first gynecologic year (Flug et al., 1984; World Health Organization Task Force on Adolescent Reproductive Health, 1986). Amenorrhea is defined as the complete absence or anomalous cessation of menstrual cycles in females during reproductive years. Just in three situations amenorrhea is considered physiological: during pregnancy, lactation and menopause. In all other situations, amenorrhea can be due to many pathological conditions and merits a careful assessment. Amenorrhea is classified as primary and secondary according to its occurrence before or after menarche, respectively (The Practice Committee of American Society for Reproductive Medicine, 2008). Amenorrhea is defined primary when menarche does not occur by the age of 16 years in a girl with complete secondary sexual development, or by the age of 14 years in a girl without secondary sexual development. Amenorrhea is defined secondary when menstrual cycles disappear for 6 consecutive months in a girl with irregular menses or for 3 consecutive months in a girl with regular menses (Deligeoroglou et al., 2010). According to the American Society for Reproductive Medicine, currently in literature many causes of amenorrhea have been recognized (The Practice Committee of American Society for Reproductive Medicine, 2008), including: • anatomic defects of the genital tract • hypothalamic/pituitary causes • ovary insufficiency • endocrinopathies • chronic oligoor anovulation