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Initial hyperinsulinemia and subsequent beta-cell dysfunction is associated with elevated palmitate levels
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Women's and Children's Health.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry. Uppsala University, Science for Life Laboratory, SciLifeLab.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Cell Biology.
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2016 (English)In: Pediatric Research, ISSN 0031-3998, E-ISSN 1530-0447, Vol. 80, no 2, p. 267-274Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: The prevalence of obesity-related diabetes in childhood is increasing and circulating levels of nonesterified fatty acids may constitute a link. Here, the association between palmitate and insulin secretion was investigated in vivo and in vitro.

METHODS: Obese and lean children and adolescents (n = 80) were included. Palmitate was measured at fasting; insulin and glucose during an oral glucose tolerance test (OGTT). Human islets were cultured for 0 to 7 d in presence of 0.5 mmol/l palmitate. Glucose-stimulated insulin secretion (GSIS), insulin content and apoptosis were measured.

RESULTS: Obese subjects had fasting palmitate levels between 0.10 and 0.33 mmol/l, with higher average levels compared to lean subjects. While obese children with elevated palmitate (>0.20 mmol/l) had accentuated insulin levels during OGTT, obese adolescents with high palmitate had delayed first-phase insulin response. In human islets exposed to palmitate for 2 d GSIS was twofold enhanced, but after 7 d attenuated. Intracellular insulin content decreased time-dependently in islets cultured in the presence of palmitate and cleaved caspase 3 increased.

CONCLUSION: The rapid accentuated and delayed insulin secretory responses observed in obese children and adolescents, respectively, with high palmitate levels may reflect changes in islet secretory activity and integrity induced by extended exposure to the fatty acid.

Place, publisher, year, edition, pages
2016. Vol. 80, no 2, p. 267-274
National Category
Pediatrics
Identifiers
URN: urn:nbn:se:uu:diva-312661DOI: 10.1038/pr.2016.80ISI: 000386719200016PubMedID: 27064244OAI: oai:DiVA.org:uu-312661DiVA, id: diva2:1064392
Funder
EU, FP7, Seventh Framework Programme, 279153Swedish Diabetes Association, DIA 2013-043Swedish Research Council, SRC 621-2011-4423, 2015-4870Available from: 2017-01-12 Created: 2017-01-12 Last updated: 2017-11-29Bibliographically approved
In thesis
1. Childhood Obesity and Islet Function
Open this publication in new window or tab >>Childhood Obesity and Islet Function
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The prevalence of childhood obesity and Type 2 Diabetes Mellitus (T2DM) has increased during recent decades. T2DM is accompanied with functional changes in the islets of Langerhans, which can be identified early in the pathogenesis. The aim of this thesis was to explore how metabolic changes caused by obesity early in life relate to islet function prior to overt T2DM.

To address this, Uppsala Longitudinal Study of Childhood Obesity (ULSCO) was established (paper I). Initially, the association between palmitate and insulin secretion was investigated using a translational approach with obese and lean normoglycemic juveniles and isolated human islets (paper II). Secondly, dynamics of islet-hormones insulin and glucagon, and gut-hormones glucagon like-peptide 1 (GLP-1) and glicentin (paper III) and magnetic resonance imaging of pancreatic fat fraction (PFF) (paper IV) were studied in association to glucose tolerance and beta-cell function. Finally, a novel method of analysing shape features of oral glucose tolerance test (OGTT) curves was introduced and evaluated (paper V).

Obese subjects had high prevalence of prediabetes and metabolic syndrome (MetS) (paper I). In obese pre-pubertal children with elevated palmitate levels, hyperinsulinemia was observed (paper II). In contrast, obese pubertal adolescents with similar palmitate levels showed moderate insulin levels during OGTT with delayed first phase insulin response. To explore mechanisms for these variations, isolated human islets were exposed to palmitate for different time periods in vitro. After 2 days accentuated insulin response was observed. Impaired beta-cell function and apoptosis were evident after 7 days, however. Hyperglucagonemia and disturbed GLP-1 and glicentin levels were associated with obesity and glycaemic status, with fasting glicentin being predictive of prediabetes (paper III). Furthermore, PFF was increased in obese subjects and associated to MetS and visceral adipose tissue, but not to beta-cell function (paper IV). OGTT curves were converted into geometric centres, centroids, which correlated with differences in glucose tolerance (paper V).

In conclusion, the islet function in obese children was associated with elevated levels of palmitate, but not pancreatic fat. Fasting palmitate and glicentin levels, as well as centroid analyses of OGTT curves, could potentially identify obese children at risk of prediabetes and subsequent T2DM.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. p. 54
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1293
Keywords
type 2 diabetes mellitus, Uppsala Longitudinal Study of Childhood Obesity, palmitate, glucose-stimulated insulin secretion, hyperinsulinemia, hyperglucagonemia, GLP-1, glicentin, magnetic resonance imaging, metabolic syndrome, oral glucose tolerance test, centroid
National Category
Medical and Health Sciences
Research subject
Pediatrics
Identifiers
urn:nbn:se:uu:diva-313310 (URN)978-91-554-9801-6 (ISBN)
Public defence
2017-03-10, C2:301, BMC, Husargatan 3, Uppsala, 13:15 (English)
Opponent
Supervisors
Funder
EU, FP7, Seventh Framework Programme, 279153
Available from: 2017-02-15 Created: 2017-01-18 Last updated: 2017-02-27

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Staaf, JohanUbhayasekera, Sarojini J. K. A.Sargsyan, ErnestChowdhury, AzazulKristinsson, HjaltiManell, HannesBergquist, JonasForslund, AndersBergsten, Peter
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