Dyslipidemia and atherosclerosis: how much more evidence do we need?

High levels of remnant lipoprotein cholesterol is a risk factor for large artery atherosclerotic stroke

BACKGROUND AND PURPOSE

Remnant lipoproteins (RLPs) are products of partially catabolized chylomicrons and very-low-density lipoprotein, from which some triglycerides have been removed. These particles are smaller and denser than the parent particles and are believed to be strongly atherogenic. We explored the association between RLP cholesterol (RLP-C) and ischemic stroke, including stroke subtypes.

METHODS

A cohort of 142 ischemic stroke patients (90 men and 52 women; age, 65.2±12.8 years, mean±SD) was enrolled; all had acute infarcts confirmed by diffusion-weighted MRI, and had fasting lipograms. A full stroke-related evaluation was conducted on each patient. An outpatient population of 88 subjects without a history of cerebrovascular or cardiovascular disease served as a control group. Serum RLP fractions were isolated using an immunoaffinity gel containing specific antiapolipoprotein (anti-apo)B-100 and anti-apoA-I antibodies. RLP-C values were considered to be high when they were in the highest quartile of all values in the study.

RESULTS

High RLP-C values were more common in stroke patients than in control patients (31.0% vs. 14.8%, p=0.01), when 5.6 mg/dL (>75th percentile) was used as the cutoff value. Multivariable analyses indicated that RLP-C was a risk factor for stroke, with an odds ratio of 2.54 (p=0.045). The RLP-C level was higher in the large artery atherosclerosis subgroup (5.7±3.9 mg/dL) than in any other stroke subgroup (small vessel occlusion, 4.9±5.9 mg/dL; cardioembolism, 1.8±2.3 mg/dL; stroke of undetermined etiology, 3.1±2.9 mg/dL).

CONCLUSIONS

We have found an association between high RLP-C levels and ischemic stroke, and in particular large artery atherosclerotic stroke.

Glucose-oxidized low-density lipoproteins enhance insulin-like growth factor I-stimulated smooth muscle cell proliferation by inhibiting integrin-associated protein cleavage

Prior published reports have demonstrated that glucose-oxidized low-density lipoproteins (g-OxLDL) enhance the proliferative response of vascular smooth muscle cells (SMC) to IGF-I. Our previous studies have determined that the regulation of cleavage of integrin-associated protein (IAP) by matrix-metalloprotease-2 (MMP-2) in diabetic mice in response to hyperglycemia is a key regulator of the response of SMC to IGF-I. Because chronic hyperglycemia enhances glucose-induced LDL oxidation, these studies were conducted to determine whether g-OxLDL modulates the response of SMC to IGF-I by regulating MMP-2-mediated cleavage of IAP. We determined that exposure of SMC to g-OxLDL, but not native LDL, was sufficient to facilitate an increase in cell proliferation in response to IGF-I. Exposure to an anti-CD36 antibody, which has been shown to inhibit g-OxLDL-mediated signaling, inhibited the effects of g-OxLDL on IGF-I-stimulated SMC proliferation. The effect of g-OxLDL could be attributed, in part, to an associated decrease in proteolytic cleavage of IAP leading to increase in the basal association between IAP and Src homology 2 domain-containing protein tyrosine phosphatase substrate-1, which is required for IGF-I-stimulated proliferation. The inhibitory effect of g-OxLDL on IAP cleavage appeared to be due to its ability to decrease the amount of activated MMP-2, the protease responsible for IAP cleavage. In conclusion, these data provide a molecular mechanism to explain previous studies that have reported an enhancing effect of g-OxLDL on IGF-I-stimulated SMC proliferation.

Lipid treatment goals achieved in patients treated with statin drugs in Norwegian general practice

Statin drug treatment has still not achieved complete acceptance, and titration to recommended target goals is still not used by physicians in Norway.