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Open Access Research

Lipoprotein metabolism in patients with type 1 diabetes under intensive insulin treatment

Alina C R Feitosa12, Gilson S Feitosa-Filho1, Fatima R Freitas1, Bernardo L Wajchenberg2 and Raul C Maranhão13*

Author Affiliations

1 Heart Institute (InCor) of the Medical School Hospital, University of Sao Paulo, São Paulo, Brazil

2 Endocrinology Service of the Medical School Hospital, University of Sao Paulo, São Paulo, Brazil

3 Faculty of Pharmaceutic Sciences, University of Sao Paulo, São Paulo, Brazil

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Lipids in Health and Disease 2013, 12:15  doi:10.1186/1476-511X-12-15

Published: 11 February 2013

Abstract

Background

Type 1 diabetes (T1DM) is frequently accompanied by dyslipidemia related with insulin-dependent steps of the intravascular lipoprotein metabolism. T1DM dyslipidemia may predispose to precocious cardiovascular disease and the lipid status in T1DM under intensive insulin treatment has not been sufficiently explored. The aim was to investigate the plasma lipids and the metabolism of LDL and HDL in insulin-treated T1DM patients with high glycemic levels.

Methods

Sixteen male patients with T1DM (26 ± 7 yrs) with glycated hemoglobin >7%, and 15 control subjects (28 ± 6 yrs) were injected with a lipid nanoemulsion (LDE) resembling LDL and labeled with 14C-cholesteryl ester and 3H-free-cholesterol for determination of fractional clearance rates (FCR, in h-1) and cholesterol esterification kinetics. Transfer of labeled lipids from LDE to HDL was assayed in vitro.

Results

LDL-cholesterol (83 ± 15 vs 100 ± 29 mg/dl, p=0.08) tended to be lower in T1DM than in controls; HDL-cholesterol and triglycerides were equal. LDE marker 14C-cholesteryl ester was removed faster from plasma in T1DM patients than in controls (FCR=0.059 ± 0.022 vs 0.039 ± 0.022h-1, p=0.019), which may account for their lower LDL-cholesterol levels. Cholesterol esterification kinetics and transfer of non-esterified and esterified cholesterol, phospholipids and triglycerides from LDE to HDL were also equal.

Conclusion

T1DM patients under intensive insulin treatment but with poor glycemic control had lower LDL-cholesterol with higher LDE plasma clearance, indicating that LDL plasma removal was even more efficient than in controls. Furthermore, HDL-cholesterol and triglycerides, cholesterol esterification and transfer of lipids to HDL, an important step in reverse cholesterol transport, were all normal. Coexistence of high glycemia levels with normal intravascular lipid metabolism may be related to differences in exogenous insulin bioavailabity and different insulin mechanisms of action on glucose and lipids. Those findings may have important implications for prevention of macrovascular disease by intensive insulin treatment.

Keywords:
Type 1 diabetes mellitus; Insulin treatment; Glycemia; Lipoprotein; Cholesterol metabolism; Lipids transfer; Cardiovascular disease