OBJECTIVE: To answer the question of whether onset of insulin resistance (IR) early in life enhances the risk of developing dementia and Alzheimer disease (AD), serum levels of 2 molecules that are likely associated with development of AD, the amyloid b-protein 42 (Ab42) and presenilin 1 (PSEN1), were estimated in 101 preschoolers and 309 adolescents of various BMI.METHODS: Participants (215 boys; 48.8%) were normal weight (n = 176; 40%), overweight (n = 135; 30.7%), and obese (n = 129; 29.3%). The HOmeostasis Model of IR (HOMA-IR), HOMA percent b-cell function (HOMA-b) and QUantitative Insulin-sensitivity Check Index (QUICKI) were calculated.
RESULTS:Obese adolescents had values of Ab42 higher than overweight and normal-weight peers (190.2 6 9.16 vs 125.9 6 7.38 vs 129.5 6 7.65 pg/mL; P , .0001) as well as higher levels of PSEN1 (2.34 6 0.20 vs 1.95 6 0.20 vs 1.65 6 0.26 ng/mL; P , .0001). Concentrations of Ab42 were significantly correlated with BMI (r = 0.262; P , .0001), HOMA-IR (r = 0.261; P , .0001) and QUICKI (r = 20.220; P , .0001). PSEN1 levels were correlated with BMI (r = 0.248; P , .0001), HOMA-IR (r = 0.242; P , .0001), and QUICKI (r = 20.256; P , .0001). Western blot analysis confirmed that PSEN1 assays measured the full-length protein.CONCLUSION: Obese adolescents with IR present higher levels of circulating molecules that might be associated with increased risk of developing later in elderly cognitive impairment, dementia, and AD.
WHAT'S KNOWN ON THIS SUBJECT:Insulin resistance plays a role in obesity. Recently it has been associated with increased risk of AD. Ab42 and PSEN1 are molecules associated with increased risk of later AD. Patients affected by AD show elevated levels of plasma Ab42.WHAT THIS STUDY ADDS: Levels of Ab42 and PSEN1 are significantly elevated in obese adolescents and correlated with the degree of both adiposity and systemic insulin resistance. Dr Manco conceptualized and designed the study, performed assays, analyzed data and interpreted results, contributed to the discussion, and critically revised the manuscript; Ms Luciano and Ms Barraco conceptualized and designed the study, performed assays, analyzed data and interpreted results, and drafted the manuscript; Drs Muraca, Ottino, Sforza, Rustico, and Morino and Ms Spreghini enrolled patients, collected growth data, and revised the manuscript for important intellectual content; and all authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work. This condition has been termed as "brain insulin resistance" and seems to be a constant trait that precedes clinical symptoms of dementia and AD even for decades. Researchers refer to AD also as "type 3 diabetes" by virtue of the analogous brain glucose hypometabolism that characterizes both conditions and the high rate of their co-occurrence. 1,4,5 Patients with T2D exhibit an increased risk of developing cognitive impairment and dementia and, vice versa, impaired fasting glucose and diabetes are highly prevalent among patients...