Molecular biology of apolipoprotein E

The common polymorphism of apolipoprotein E: geographical aspects and new pathophysiological relations

Apolipoprotein E (apoE) has important functions in systemic and local lipid transport, but also has other functions. The gene (APOE) shows a common polymorphism with three alleles--APOE*2, APOE*3, and APOE*4. Their frequencies vary substantially around the world, but APOE*3 is the most common almost everywhere and is often considered to be the ancestral or "wild-type" allele for that reason. However, there are several arguments for APOE*4 being the ancestral allele. But then, why has APOE*3 become so frequent? And why has APOE*4 not become extinct? The proportion of APOE*4 carriers increases from only 10-15% in southern Europe to 40-50% in the north. The gradient may be a trace of the demic expansion of agriculture that began about 10,000 years ago, but it may also reflect the possibility that APOE*4 carriers are less likely to develop vitamin D deficiency. The common APOE polymorphism is associated with varying risk of cardiovascular disease and Alzheimer's disease, but other interesting aspects may emerge in the future.

Role of cholesterol in synapse formation and function

Cholesterol is a multifaceted molecule, which serves as essential membrane component, as cofactor for signaling molecules and as precursor for steroid hormones. Consequently, defects in cholesterol metabolism cause devastating diseases. So far, the role of cholesterol in the nervous system is less well understood. Recent studies showed that cultured neurons from the mammalian central nervous system (CNS) require glia-derived cholesterol to form numerous and efficient synapses. This suggests that the availability of cholesterol in neurons limits the extent of synaptogenesis. Here, I will summarize the experimental evidence for this hypothesis, describe what is known about the structural and functional role of cholesterol at synapses, and discuss how cholesterol may influence synapse development and stability.

Apolipoprotein and apolipoprotein receptor genes, blood lipids and disease

PURPOSE OF REVIEW

Apolipoproteins and their receptors are the main controllers of lipid metabolism and, as such, have a major impact not only on the risk of cardiovascular disease but also on the development and degeneration of the central nervous system. Variations in the genes coding for these apolipoproteins and their receptors and the interaction with the environment determine individual susceptibility to metabolic disturbances, the response to dietary or pharmacological intervention and, finally, to disease.

RECENT FINDINGS

This review will focus on recent findings, such as the latest concepts regarding apolipoprotein E in neurodevelopment, the newly identified apolipoprotein A-V and its influence in triglyceride metabolism, and the improved understanding of apolipoprotein A-I and HDL metabolism in the light of the discovery of the ABC family of transporters. Other key aspects of lipoprotein metabolism and cardiovascular disease risk such as apolipoprotein B-100, the LDL receptor, apolipoprotein C-III or apolipoprotein (a) will be updated.

SUMMARY

Variations in these genes will be analysed in relation to plasma lipid levels, their interactions with diet, treatment or other environmental stimuli, and their influence on the risk of cardiovascular disease and neurological disorders.

Renal dysfunction after vascular surgery

PURPOSE OF REVIEW

The purpose of this review is to focus on the static incidence of renal dysfunction, the lack of evidence of benefit of traditional renoprotective strategies, and newer techniques that may provide an insight into the mechanisms of acute perioperative renal injury associated with vascular surgery.

RECENT FINDINGS

Recent studies that have investigated the long-term results of aortic surgery still report a significant incidence of postoperative renal dysfunction. This finding remains consistent in several reports. However, less invasive techniques such as endovascular repair seem to be associated with reduced inflammation and postoperative renal dysfunction. The possible association between genetic heterogeneity and renal dysfunction in vascular surgical patients is an exciting new area of research.

SUMMARY

Renal dysfunction after major vascular surgery remains a significant problem. New insights into the mechanisms of acute renal injury and less invasive techniques of vascular repair may help reduce the incidence of renal dysfunction in this patient population. The lack of a truly 'renoprotective' agent has hampered our efforts in preventing this major complication of vascular surgery.