Project Summary, Final Period 3


Project context and main objectives
 

In Europe more than 20% of children are overweight and 5% even obese. Obesity is a strong risk factor for developing complications including type 2 diabetes mellitus (T2DM), which is now seen in growing numbers in children. These high obesity prevalence numbers in children, which do not decline, pose a major health threat for Europe.

High insulin levels are observed in most of the obese children both at fasting and during oral glucose tolerance test (OGTT). The hyperinsulinemia has been interpreted as a result of decreased insulin sensitivity in insulin target tissue.  Although this is probably correct in many obese adults, the situation may be different in children. In some of the obese children hyperinsulinemia was observed despite essentially normal insulin sensitivity. Insulin is the prime hormone promoting storage of calories. Insulin is secreted from the insulin- producing beta-cells in the pancreas. Evidence is accumulating and supporting that high insulin levels in certain subjects could be a primary event leading to development of overweight and obesity. For these subjects it would be essential to normalize the hyperactive beta-cells so that normal insulin levels were attained.

The project Beta-cell function in juvenile type 2 diabetes and obesity (Beta-JUDO) aimed at reducing childhood obesity and obesity-related complications by normalizing insulin hypersecretion. Beta-JUDO was divided into three parts. In the first part of the project the aim was to define factors that contribute to insulin hyeprsecretion in obese children belonging to childhood obesity cohorts. Special focus was on insulin secretory response during an oral glucose tolerance test (OGTT). In addition to insulin also glucose, free fatty acids (FFAs) and incretins were determined. Whereas glucose levels were generally normal in young obese children, lipid levels including circulating fatty acid palmitate were elevated already in these young subjects. Magnetic resonance (MR) images were obtained from the subjects in order to determine percentages of fat in different body parts. Genetic analyses were conducted, where special focus is on identifying genetic variants correlating with the insulin hypersecreting phenotype.

The second part aimed at defining molecular mechanisms responsible for insulin hypersecretion from islets of Langerhans isolated from human organ-donors. When islets were exposed to elevated levels of palmitate, as observed in obese children, for 2 days, they hypersecreted insulin in response to elevated glucose concentrations. Islets with augmented insulin secretory patterns were analyzed for changes in expression patterns at the transcript (transcriptomics), protein (proteomics) and lipid (lipidomics) levels. These omics data sets were analyzed with the aim of identifying novel molecular players and pathways contributing to insulin hypersecretion.

The third aim was to test novel ways of intervening pharmacologically in the obese pediatric population aiming at normalizing insulin hypersecretion. This aim was addressed by investigating how different pharmacological compounds affect insulin hypersecretion in the isolated islets. These results furthermore founded the basis for an interventional trial performed in obese children.



Work performed since the beginning of the project and the main results achieved



The first aim of the project, where underlying mechanisms of insulin hypersecretion in obese children were to be defined, was addressed within the clinical work. Two childhood obesity cohorts, which contained approximately 4000 subjects, formed the basis for the genetic analysis. Two other cohorts containing approximately 650 subjects had the focus on detailed characterization with special emphasis on insulin secretion. Normal-weight children were also recruited, who were characterized in detail. The genetic work was based on deep exome sequencing and genome-wide association studies (GWAS). These approaches identified new genetic variants that were tested for association with insulin hypersecretion. The cohorts with detailed phenotyping centered around the oral glucose tolerance test (OGTT). From the results a definition of insulin hypersecretion has been proposed. Based on the characterization the oral disposition index was decided to define levels for insulin hypersecretion.


The second aim of the project, where underlying mechanisms of insulin hypersecretion in isolated islets were to be defined, was addressed within the pre-clinical part of the project. Isolated islets were cultured in the presence of palmitate for 2 days. After culture, islets were perifused and glucose-stimulated insulin secretion (GSIS) measured dynamically. GSIS was more than doubled in the palmitate-exposed islets. Also, exendine or metformin was included during culture of islets exposed to palmitate. Both compounds normalized insulin hypersecretion. In order to delineate mechanisms by which hypersecretion occured and how the compounds normalized it, islets exposed to palmitate alone and in the presence of exendine or metformin were used to generate large number of transcripts (transcriptomics), proteins (proteomics) and lipids (lipidomics). These expression data sets together with the related changes in islet phenotype were analyzed and differential pathway activation was suggested based on the analyses.

As the third aim of the project, an interventional study aiming at reducing insulin hypersecretion in obese adolescents was undertaken. The study was a 6-month placebo-controlled double-blind study, where 12-18 years old obese adolescents were given the GLP-1 analogue exenatide once weekly in combination with life-style treatment. The study was conducted in two European countries, which enrolled 44 patients in total. The results showed that the drug caused significant reduction in weight. Furthermore, the drug was well tolerated with no difference in adverse events between the treated and un-treated patients.


Expected final results and their potential impacts and use

 

The translational project Beta-JUDO addressed the role of the insulin-producing beta-cell in obesity-related development of type 2 diabetes mellitus in children. The project has generated results, which will have impact in the following areas:

- Clinical area: The characterization of the obesity cohorts including the genetic work is expected to emphasize the importance of maintaining normal insulin levels and also identify situations and foods that elicit accentuated insulin secretion, which are to be avoided. The successful intervention with exenatide is expected to pave the way for further clinical studies, where the drug will be further tested in larger cohorts for its safety and efficacy in combating childhood obesity. To give this patient group a pharmacological alternative would be very important not only for the patients but also for the European health providers.

- Pre-clinical area: The analyses of transcripts, proteins and lipids, associated with islet insulin hypersecretion gave new information about the molecular mechanisms behind insulin hypersecretion and how different compounds associated with the treatment of obesity and T2DM act at the islet level and affect these mechanisms. Several novel, not yet proposed candidates coming form the Beta-JUDO work and operative in the islets of Langerhans are expected to be validated for a role in insulin hypersecretion. Such candidates may be of interest for further development into intervention strategies.

- Societal and economical impact: It is imperative to meet this challenge and to find new ways to attenuate obesity and obesity-related T2DM in the young population, and to identify and evaluate new drugs for this rapidly growing patient group. The results of the project are expected to lead to a reduced number of young individuals with overweight or obesity. The involvement of SMEs in the project will contribute to that therapeutic strategies proposed by the project will lead to new opportunities for European industry strengthening European health economy.