Lipid Update

I was trained a s a lipid chemist and have always enjoyed this aspect of biochemistry, along with the analytical techniques and function studies. A series of reviews in Nature Reviews Molecular Cell Biology are hence very interesting to me. The place of nutrition in these stories is through the building blocks which is so important.

Mark A. Lemmon 2008, Membrane recognition by phospholipid-binding domain Nature Reviews Molecular Cell Biology vol 9 pp99-111

Many different globular domains bind to the surfaces of cellular membranes, or to specific phospholipid components in these membranes. This binding is often tightly regulated. Examples include pleckstrin homology and C2 domains, which are among the largest domain families in the human proteome. Crystal structures, binding studies and analyses of sub cellular localization have provided much insight into how members of this diverse group of domains bind to membranes, what features they recognize and how binding is controlled. A full appreciation of these processes is crucial for understanding how protein localization and membrane topography and trafficking are regulated in cells-

Hannun and Obeid 2008 Principles of bioactive lipid signalling: lessons from sphingolipids Nature Reviews Molecular Cell Biology vol 9 pp 139-50

It has become increasingly difficult to find an area of cell biology in which lipids do not have important, if not key, roles as signalling and regulatory molecules. The rapidly expanding field of bioactive lipids is exemplified by many sphingolipids, such as ceramidc, sphingosine, sphingosine-1-phosphatc (Si P). ceramide-1-phosphate and lyso-sphingomyelin, which have roles in the regulation of cell growth, death, senescence, adhesion, migration, inflammation, angiogenesis and intraccllular trafficking. Deciphering the mechanisms of these varied cell functions necessitates an understanding of the complex pathways of sphingolipid metabolism and the mechanisms that regulate lipid generation and lipid action.

Michell 2008 Inositol derivatives: evolution and functions. Nature Reviews Molecular Cell Biology vol 9, 151-161

Current research on inositols mainly focuses on myo-inositol derivatives in cuka ryotic cells, and in particular on the many roles of myo-inositol phospholipids and polyphosphorylated myo-inositol derivatives. However, inositols, and their derivatives are more versatile than this — they have acquired diverse functions over the course of evolution. Given the central involvement of primordial bacteria and archaea in the emergence of eukaryotes, what is the status of inositol derivatives ini these groups of organisms, and how might inositol, inositol lipids and inositol phosphates have become ubiquitous constituents of eukaryotes? And how, later, might the multifarious functions of inositol derivatives have emerged during eukaryotc diversification?

See what I mean?

Long Chain Fatty Acids

In the December 2008 British Journal of Nutrition Chapkin et al ( Bioactive dietary long chain fatty acids: emerging mechanisms of action BJN vol 100 pp 1152-57) discuss the role of dietary long chain fatty acids.

They describe the plasma membrane of eukaryotic cells as containing self organising intrinsically unstable liquid ordered domains or lipid assemblies in which key transduction proteins are localised.

These are lipid rafts ( 10-200 nm ) and consist of cholesterol and sphingolipid microdomains which do not integrate readily with the phospholipid biolayers. They suggest that dietary long chain polyunsaturated fatty acids . especially n-3 long chain polyunsaturated fatty acids and maybe conjugated fatty acids alter the basic properties of cell membrane, lipid raft behaviour and protein function. And hence cell signalling, protein trafficking and cell cytokinetics and apoptosis. The balance between cell proliferation and apoptosis is critical to the maintenance of steady state cell populations in the body.

Transfats

Abstract

A review of trans fats by D Mozaffarian, A Aro and W C Willett indicating that these ar not too good for out health.

Growing evidence indicates that trans-fatty acids (TFA) adversely affect cardiovascular health. As part of the World Health Organization (WHO) Scientific Update on TFA, we reviewed the evidence for effects of TFA consumption on coronary heart disease (CHD).

The effects of TFA consumption on risk factors most consistently seen in both controlled trials and observational studies included adverse lipid effects (for example low-density lipoprotein cholesterol, high-density lipoprotein cholesterol (HDL-C), total/HDL-C ratio), proinflammatory effects (for example tumor necrosis factor-activity, interleukin-6, C-reactive protein) and endothelial dysfunction. These effects were most prominent in comparison with cis unsaturated fats; adverse effects on total/HDL-C and endothelial function were also seen in comparison with saturated fatty acids (SFA). TFA may also worsen insulin sensitivity, particularly among individuals predisposed to insulin resistance; possible effects on weight gain and diabetes incidence require further confirmation. Five retrospective case–control studies and four prospective cohort studies demonstrated positive associations between TFA consumption and CHD events. A meta-analysis of prospective studies indicated 24, 20, 27 and 32% higher risk of myocardial infarction (MI) or CHD death for every 2% energy of TFA consumption isocalorically replacing carbohydrate, SFA, cis monounsaturated fatty acids and cis polyunsaturated fatty acids, respectively. The differential effects of specific TFA isomers may be important but are less well established. The available evidence indicates that trans-18:1 and particularly trans-18:2 isomers have stronger CHD effects than trans-16:1 isomers. The limited data suggest that the experimental effects of ruminant and industrial TFA are similar when consumed in similar quantities, but very few persons consume such high levels of ruminant TFA, and observational studies do not support adverse CHD effects of ruminant TFA in amounts actually consumed.

Conclusions:

Controlled trials and observational studies provide concordant evidence that consumption of TFA from partially hydrogenated oils adversely affects multiple cardiovascular risk factors and contributes significantly to increased risk of CHD events. The public health implications of ruminant TFA consumption appear much more limited. The effects of specific TFA isomers require further investigation.

trans-fatty acids, coronary heart disease, randomized controlled trials, epidemiology, review

D Mozaffarian, A Aro and W C Willett (2009)Health effects of trans-fatty acids: experimental and observational evidence European Journal of Clinical Nutrition 63, S5–S21;