Diabetes is a primary risk factor for cardiovascular diseases (CVD) and in clinical imaging studies is shown to impair the resolution of CVD, a process termed regression. We have also reported this failure of lesion regression in mouse models of diabetes, despite effective lipid lowering. This, in part, can be attributed to diabetes-driven monocytosis promoting continued monocyte infiltration into plaques. In non-diabetic settings apolipoprotein (apo) A-I and high-density lipoprotein (HDL) suppress leukocytosis and promote lesion regression. As low apoA-I/HDL is a typical feature of diabetic dyslipidemia this study aimed to establish whether raising apoA-I/HDL levels
in vivo
is an effective approach to reduce diabetes-driven leukocytosis and promote lesion regression.
Aortic arches from hyperlipidemic Ldlr
-/-
mice were transplanted into WT, diabetic WT, and diabetic human apoA-I-overexpressing transgenic mice (transgenic mice have a 3-fold increase in HDL-cholesterol), and lesion composition assessed 2 weeks post-surgery. Following aortic transplantation into WT mice (i.e. normal lipid levels) we found regression, as assessed by change in plaque macrophage (mΦ) content relative to baseline control mice was achieved (68% mΦ reduction, P<0.001). Regression was impaired when aortas were transplanted into diabetic WT recipients (50% mΦ reduction, P<0.01). However, raising apoA-I/HDL levels in the setting of diabetes restored regression in diabetic mice (62% mΦ reduction, P<0.001).
In vivo
monocyte/mΦ trafficking analyses revealed that elevating apoA-I/HDL levels in diabetes improves atherosclerosis regression by reducing monocyte entry by 60% (P<0.01), and promoting mΦ egress from lesions (30% increase). We also found that greater apoA-I/HDL reduced blood monocytes by decreasing the proliferation of monocyte progenitors in the bone marrow (15-20% reduction, P<0.05), explaining, in part, how apoA-I/HDL promotes regression.
Raising apoA-I/HDL levels promotes atherosclerotic lesion regression in diabetic mice. This may serve as a therapeutic strategy for patients with diabetes, who unlike WT mice, have reduced HDL levels and remain at an elevated risk for CVD despite effective plasma cholesterol lowering.
Hematopoietic upstream stimulating factor 1 deficiency is associated with increased atherosclerosis susceptibility in LDL receptor knockout mice
