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

Background<p style="padding: 0px; margin: 0px 0px 1em; border: 0px; outline: 0px; font-size: 11px; font-family: Verdana, Arial, Helvetica, sans-serif; vertical-align: baseline; overflow: visible; clear: both; line-height: 17.6px;">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.</p>Methods<p style="padding: 0px; margin: 0px 0px 1em; border: 0px; outline: 0px; font-size: 11px; font-family: Verdana, Arial, Helvetica, sans-serif; vertical-align: baseline; overflow: visible; clear: both; line-height: 17.6px;">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 HDL<sub style="padding: 0px; margin: 0px;">2</sub> and HDL<sub style="padding: 0px; margin: 0px;">3</sub> by rapid ultracentrifugation. Carotenoids were measured in serum, HDL<sub style="padding: 0px; margin: 0px;">2</sub> and HDL<sub style="padding: 0px; margin: 0px;">3</sub> by high performance liquid chromatography. The activity of paraoxonase-1 (PON-1) was measured in serum, HDL<sub style="padding: 0px; margin: 0px;">2</sub> and HDL<sub style="padding: 0px; margin: 0px;">3</sub> by a spectrophotometric assay, while the activity of lecithin cholesterol acyltransferase (LCAT) was measured in serum, HDL<sub style="padding: 0px; margin: 0px;">2</sub> and HDL<sub style="padding: 0px; margin: 0px;">3</sub> by a fluorometric assay.</p>Results<p style="padding: 0px; margin: 0px 0px 1em; border: 0px; outline: 0px; font-size: 11px; font-family: Verdana, Arial, Helvetica, sans-serif; vertical-align: baseline; overflow: visible; clear: both; line-height: 17.6px;">In the ≥6- vs. 1-portion post-intervention comparisons, carotenoids increased in serum, HDL<sub style="padding: 0px; margin: 0px;">2</sub> and particularly HDL<sub style="padding: 0px; margin: 0px;">3</sub>, (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 HDL<sub style="padding: 0px; margin: 0px;">3</sub> (p = 0.006 and 0.044, respectively).</p>Conclusion<p style="padding: 0px; margin: 0px 0px 1em; border: 0px; outline: 0px; font-size: 11px; font-family: Verdana, Arial, Helvetica, sans-serif; vertical-align: baseline; overflow: visible; clear: both; line-height: 17.6px;">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.</p>