Breakfast partly restores the anti-inflammatory function of high-density lipoproteins from patients with type 2 diabetes mellitus.

Background and Aims: High-density lipoproteins (HDL) of patients with type 2 diabetes mellitus (T2DM) have impaired anti-inflammatory activities. The anti-inflammatory activity of HDL has been determined ex vivo after isolation by different methods from blood mostly obtained after overnight fasting. We first determined the effect of the HDL isolation method, and subsequently the effect of food intake on the anti-inflammatory function of HDL from T2DM patients.
Methods: Blood was collected from healthy controls and T2DM patients after an overnight fast, and from T2DM patients 3 h after breakfast ( n  = 17 each). HDL was isolated by a two-step density gradient ultracentrifugation in iodixanol (HDL _DGUC2 ), by sequential salt density flotation (HDL _SEQ ) or by PEG precipitation (HDL _PEG ). The anti-inflammatory function of HDL was determined by the reduction of the TNFα-induced expression of VCAM-1 in human coronary artery endothelial cells (HCAEC) and retinal endothelial cells (REC).
Results: HDL isolated by the three different methods from healthy controls inhibited TNFα-induced VCAM-1 expression in HCAEC. With apoA-I at 0.7 μM, HDL _DGUC2 and HDL _SEQ were similarly effective (16% versus 14% reduction; n  = 3; p  > 0.05) but less effective than HDL _PEG (28%, p  < 0.05). Since ultracentrifugation removes most of the unbound plasma proteins, we used HDL _DGUC2 for further experiments. With apoA-I at 3.2 μM, HDL from fasting healthy controls and T2DM patients reduced TNFα-induced VCAM-1 expression in HCAEC by 58 ± 13% and 51 ± 20%, respectively ( p  = 0.35), and in REC by 42 ± 13% and 25 ± 18%, respectively ( p  < 0.05). Compared to preprandial HDL, postprandial HDL from T2DM patients reduced VCAM-1 expression by 56 ± 16% (paired test: p  < 0.001) in HCAEC and by 34 ± 13% (paired test: p  < 0.05) in REC.
Conclusions: The ex vivo anti-inflammatory activity of HDL is affected by the HDL isolation method. Two-step ultracentrifugation in an iodixanol gradient is a suitable method for HDL isolation when testing HDL anti-inflammatory function. The anti-inflammatory activity of HDL from overnight fasted T2DM patients is significantly impaired in REC but not in HCAEC. The anti-inflammatory function of HDL is partly restored by food intake.
Competing Interests: The authors declare that they have no conflict of interest.
(© 2021 The Authors.)