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Open Access Original investigation

A randomised controlled trial of increasing fruit and vegetable intake and how this influences the carotenoid concentration and activities of PON-1 and LCAT in HDL from subjects with type 2 diabetes

Jane-Ann Daniels1, Ciara Mulligan2, David McCance2, Jayne V Woodside1, Christopher Patterson1, Ian S Young1 and Jane McEneny1*

Author Affiliations

1 Centre for Public Health, Queen’s University Belfast, Pathology Building, Grosvenor Road, Belfast BT12 6BJ, UK

2 Regional Centre for Endocrinology and Diabetes, Royal Victoria Hospital, Belfast BT12 6BA, UK

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Cardiovascular Diabetology 2014, 13:16  doi:10.1186/1475-2840-13-16

Published: 14 January 2014

Abstract

Background

High density lipoproteins (HDL) have many cardioprotective roles; however, in subjects with type 2 diabetes (T2D) these cardioprotective properties are diminished. Conversely, increased fruit and vegetable (F&V) intake may reduce cardiovascular disease risk, although direct trial evidence of a mechanism by which this occurs in subjects with T2D is lacking. Therefore, the aim of this study was to examine if increased F&V consumption influenced the carotenoid content and enzymes associated with the antioxidant properties of HDL in subjects with T2D.

Methods

Eighty obese subjects with T2D were randomised to a 1- or ≥6-portion/day F&V diet for 8-weeks. Fasting serum was collected pre- and post-intervention. HDL was subfractionated into HDL2 and HDL3 by rapid ultracentrifugation. Carotenoids were measured in serum, HDL2 and HDL3 by high performance liquid chromatography. The activity of paraoxonase-1 (PON-1) was measured in serum, HDL2 and HDL3 by a spectrophotometric assay, while the activity of lecithin cholesterol acyltransferase (LCAT) was measured in serum, HDL2 and HDL3 by a fluorometric assay.

Results

In the ≥6- vs. 1-portion post-intervention comparisons, carotenoids increased in serum, HDL2 and particularly HDL3, (α-carotene, p = 0.008; β-cryptoxanthin, p = 0.042; lutein, p = 0.012; lycopene, p = 0.016), as did the activities of PON-1 and LCAT in HDL3 (p = 0.006 and 0.044, respectively).

Conclusion

To our knowledge, this is the first study in subjects with T2D to demonstrate that increased F&V intake augmented the carotenoid content and influenced enzymes associated with the antioxidant properties of HDL. We suggest that these changes would enhance the cardioprotective properties of this lipoprotein.

Clinical trial registration

ISRCTN21676269

Keywords:
Type-2 diabetes; Fruit and vegetables; High density lipoprotein; Carotenoids; Paraoxonase-1; Lecithin cholesterol acyltransferase