OC 09.3 - CD36-dependent metabolic rewiring and mitochondrial dysfunction in platelets in response to hyperlipidaemia – new mechanisms of platelet hyperactivity

Background: Atherogenic hyperlipidaemia leads to the accumulation of oxidised low-density lipoproteins (oxLDL) particles in the plasma. The scavenger receptor CD36 translates this oxidised lipid stress to platelet hyperactivity through the binding of oxLDL. When activated by haemostatic agonists, platelet transition to an overtly glycolytic phenotype to produce ATP. The effects of oxLDL on platelet metabolism is unknown.

Aims: We investigated the effects of oxLDL on platelet glucose metabolism and mitochondrial function.

Methods: We used platelets from mice with a platelet specific deletion of CD36 (CD36fl/fl/PF4cre) and whole-body CD36 knockout (CD36-/-). Hyperlipidaemia was induced by feeding the mice with high fat diet (HFD) for 12 weeks. In vitro, washed platelets were treated with oxLDL or native-LDL (nLDL).

Results: Under whole-body hyperlipidaemic stress, CD36fl/fl platelets, but not CD36fl/fl/PF4cre platelets, had elevated glucose uptake and glycolysis when tested ex vivo. In vitro oxLDL, but not nLDL, induced similar effects on glucose metabolism and was associated with elevated mitochondrial superoxide generation upstream of mitochondrial hyperpolarisation. In contrast to thrombin which cause a rapid and reversible activation of glycolysis, oxLDL caused a sustained and irreversible increase in glucose catabolism.
To understand the mechanisms underpinning these effects we focussed on hexokinase (HK) the enzyme catalysing the first-rate limiting step in glycolysis. HK inhibitors, 2-deoxyglucose and 3-bromopyruvate, inhibited oxLDL-induced glycolysis and mitochondrial dysfunction, suggesting that HK is a key node in the CD36-induced metabolic response. Further, we discovered that oxLDL activated HK activity via a CD36-dependent pathway that included Syk and phosphoinositide 3-kinase. Critically oxLDL-induced shape change was blocked by pharmacological inhibitors of both CD36 and HK.

Conclusion(s): We identify HK as a novel target for CD36 signalling in platelets. OxLDL induces CD36-dependent hyperglycolysis and mitochondrial dysfunction in a HK-dependent manner, and represents a new maladaptive metabolic response that promotes platelet hyperactivity.
This work was funded by the British Heart Foundation (RG/16/5/32250).