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Seasonal variations of insulin sensitivity from a euglycemic insulin clamp in elderly men
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, UCR-Uppsala Clinical Research Center. Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences. (Endokrin diabetes och metabolism)
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Family Medicine and Clinical Epidemiology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Medicinska och farmaceutiska vetenskapsområdet, centrumbildningar mm, UCR-Uppsala Clinical Research Center.
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2012 (English)In: Upsala Journal of Medical Sciences, ISSN 0300-9734, E-ISSN 2000-1967, Vol. 117, no 1, 35-40 p.Article in journal (Refereed) Published
Abstract [en]

Introduction

Seasonal variations in hemoglobin-A1c have been reported in diabetic patients, but the underlying mechanisms have not been elucidated.

Aims

To study if insulin sensitivity, insulin secretion, and fasting plasma glucose showed seasonal variations in a Swedish population-based cohort of elderly men.

Methods

Altogether 1117 men were investigated with a euglycemic insulin clamp and measurements of fasting plasma glucose and insulin secretion after an oral glucose tolerance test. Values were analyzed in linear regression models with an indicator variable for winter/summer season and outdoor temperature as predictors.

Results

 During winter, insulin sensitivity (M/I, unit = 100 × mg × min-1 × kg-1/(mU × L-1)) was 11.0% lower (4.84 versus 5.44, P = 0.0003), incremental area under the insulin curve was 16.4% higher (1167 versus 1003 mU/L, P = 0.007). Fasting plasma glucose was, however, not statistically significantly different (5.80 versus 5.71 mmol/L, P = 0.28) compared to the summer season. There was an association between outdoor temperature and M/I (0.57 units increase (95% CI 0.29–0.82, P < 0.0001) per 10°C increase of outdoor temperature) independent of winter/summer season. Adjustment for life-style factors, type 2 diabetes, and medication did not alter these results.Read More:http://informahealthcare.com/doi/abs/10.3109/03009734.2011.628422

Conclusions

Insulin sensitivity showed seasonal variations with lower values during the winter and higher during the summer season. Inverse compensatory variations of insulin secretion resulted in only minor variations of fasting plasma glucose. Insulin sensitivity was associated with outdoor temperature. These phenomena should be further investigated in diabetic patients.

Place, publisher, year, edition, pages
2012. Vol. 117, no 1, 35-40 p.
Keyword [en]
Seasonal variations, insulin sensitivity, clamp, insulin secretion, temperature
National Category
Endocrinology and Diabetes Geriatrics
Identifiers
URN: urn:nbn:se:uu:diva-165044DOI: 10.3109/03009734.2011.628422ISI: 000300304000006PubMedID: 22066936OAI: oai:DiVA.org:uu-165044DiVA: diva2:471452
Available from: 2012-01-02 Created: 2012-01-02 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Measurement Variability Related to Insulin Secretion and Sensitivity: Assessment and Implications in Epidemiological Studies
Open this publication in new window or tab >>Measurement Variability Related to Insulin Secretion and Sensitivity: Assessment and Implications in Epidemiological Studies
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There is a growing interest in random measurement variability of biological variables. In regression models, such variability of the predictors yields biased estimators of coefficients (regression dilution bias). The objectives of this thesis were to develop an efficient method to correct for such bias, to reveal the relative importance of insulin sensitivity and insulin secretion, corrected for regression dilution bias, on glucose tolerance, and to explore the seasonal nature of the variability of insulin sensitivity.

A reliability study is often designed to randomly select subjects from the main study. Our idea was to collect replicates for subjects with extreme values on their first measurement. The extreme selection design, in combination with maximum likelihood estimation, resulted in an efficient estimator of a corrected regression coefficient in a simple linear regression model. Results were presented theoretically and with an application: The relation between insulin sensitivity and fasting insulin in Uppsala Longitudinal Study of Adult Men (ULSAM) where the extreme selection design decreased the standard error of the estimated regression coefficient with 28 per cent compared with the random sampling design.

We estimated the partial longitudinal effects of the predictors insulin sensitivity and insulin secretion, corrected for regression dilution bias, on glucose tolerance in ULSAM. The effects of the predictors, when corrected, were similar.

Insulin sensitivity in ULSAM increased during summer and decreased during winter and insulin secretion exposed opposite variation keeping glucose homeostasis nearly constant. Insulin sensitivity was related to outdoor temperature.

In summary, we developed a cost-efficient reliability design for correction for regression dilution bias. Insulin sensitivity and insulin secretion had similar longitudinal effects on glucose tolerance, which implies that interventions aimed at these targets are equally important. Further, we revealed the seasonal nature of variations of insulin sensitivity and insulin secretion. This result has implications on glycaemic control in diabetic patients.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 67 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 440
National Category
Geriatrics
Research subject
Geriatrics
Identifiers
urn:nbn:se:uu:diva-99636 (URN)978-91-554-7469-0 (ISBN)
Public defence
2009-04-29, Enghoffsalen, Akademiska sjukhuset, Uppsala, 13:15 (Swedish)
Opponent
Supervisors
Available from: 2009-04-07 Created: 2009-03-18 Last updated: 2012-07-26Bibliographically approved

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Berglund, LarsBerne, ChristianSvärdsudd, KurtGarmo, HansMelhus, HåkanZethelius, Björn

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Berglund, LarsBerne, ChristianSvärdsudd, KurtGarmo, HansMelhus, HåkanZethelius, Björn
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Upsala Journal of Medical Sciences
Endocrinology and DiabetesGeriatrics

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