Modulateurs du métabolisme du cholestérol et avenir du traitement de l’athérosclérose

[A lipid exchange market : vectorial cholesterol transport by the protein OSBP]

Cholesterol is synthesized in the endoplasmic reticulum (RE) and then transported to cellular compartments whose functions require high cholesterol levels. Here, we describe the mechanism by which cholesterol is transported from the RE to the trans-Golgi network (TGN) by the protein OSBP (Oxysterol-Binding Protein). OSBP has two complementary activities. First, it tethers the RE to the TGN by forming a contact site where the two membranes are about twenty nanometers away. Then, it exchanges RE cholesterol for a TGN lipid, phosphatidylinositol 4-phosphate (PI4P). Eventually, PI4P is hydrolyzed at the RE, making the exchange cycle irreversible. Thus, OSBP is at the center of a lipid exchange market where a transported cholesterol "costs" a PI4P. Antiviral or anti-cancer molecules target OSBP, suggesting the importance of the OSBP cycle in different physiopathological contexts. The general principles of this cycle are shared by other lipid-transfer proteins.

[Reactive oxygen species and oxidative stress]

Oxidative stress is defined as an imbalance between the production of reactive oxygen species (ROS) and the antioxidant capacity of the cell. For long, ROS have been considered as harmful by-products of the normal aerobic metabolism process of the mitochondria, implicated in a large variety of diseases. But there are now growing evidences that controlled ROS production also play physiological roles especially in regulating cell redox homeostasis and cell signaling. Biological ROS effects are now well documented. Data show that living organisms have not only adapted themselves to coexist with free radicals but have also developed mechanisms to use them advantageously. However their main sources and mechanisms of action remain poorly described. This review focuses on the main properties of ROS and their paradoxical effects.

Serum cardiovascular risk factors in obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) patients have increased cardiovascular morbidity and mortality. The cardiovascular markers associated with OSA are currently not defined.

OBJECTIVES

The aims of this study were to determine whether OSA is associated with serum cardiac risk markers and to investigate the relationship between them.

METHODS

Sixty-two male patients were classified into two groups with respect to apnea-hypopnea index (AHI): group 1, sleep apnea (n = 30), with AHI > 5; and group 2 (n = 32), with AHI < 5. We compared cardiovascular risk factors in both groups with control subjects (n = 30) without OSA (AHI < 1). Serum cholesterol, triglyceride, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), apolipoprotein A-I, apolipoprotein B, lipoprotein (a), C-reactive protein (CRP), and homocysteine were measured. Statistical significance was assessed with analysis of variance at p < 0.05. In correlation analysis, Pearson correlation was used.

RESULTS

There was no significant difference between group 1 and group 2 in total cholesterol, LDL-C, HDL-C, triglyceride, apolipoprotein A-I, apolipoprotein B, and lipoprotein (a). All of the M-mode echocardiographic parameters were in the normal reference range. Serum homocysteine and CRP levels were significantly increased in group 1 compared to group 2 (p < 0.05). Serum CRP values were increased in both group 1 and group 2 when compared with control subjects (p < 0.05). Serum homocysteine values were higher in group 1 than in control subjects (p < 0.05).

CONCLUSIONS

Our results show that OSA syndrome is associated not only with slight hyperhomocysteinemia but also with increased CRP concentrations. Increased plasma concentrations of homocysteine and CRP can be useful in clinical practice to be predictor of long-term prognosis for cardiovascular disease and the treatment of OSA.