Pathological concentrations of fat fuels

The three fat fuels and their metabolism are involved directly or indirectly in diseases such as diabetes mellitus, syndrome X, obesity, atherosclerosis and coronary heart disease, which are discussed in other chapters in this book. This section considers the problems associated with high blood levels of ketone bodies and long-chain fatty acids. 

An elevated plasma ketone body concentration, of about 7-8 mmol/L, occurs in a number of conditions but it causes 

The plasma level of fatty acids in a fed subject is between 0.3 and 0.5 mmol/L. As discussed above, the maximal safe level is about 2 mmol/L. This is not usually exceeded in any physiological condition since, above this concentration, that of the free (not complexed with albumin) fatty acids in the blood increases markedly. This can then lead to the formation of fatty acid micelles which can damage cell membranes the damage can cause aggregation of platelets and interfere with electrical conduction in heart muscle (Chapter 22). The cells particularly at risk are the endothelial cells of arteries and arterioles, since they are directly exposed to the micelles, possibly for long periods of time. Two important roles of endothelial cells are control of the diameter of arterioles of the vascular system and control of blood clotting (Chapter 22). Damage to endothelial cells could be sufficiently severe to interfere with these functions i.e. the arterioles could constrict, and the risk of thrombosis increases. Both of these could contribute to the development of a heart attack (Chapter 22) (Box 7.4). 

In addition, a high intracellular concentration of fatty acids raises that of long-chain acyl-CoA, which can damage 

After the Athens earthquake in 1981 there was a marked increase in deaths due to heart attacks over a period of five days after the quake on the day of the earthquake in Los Angeles, there was an increase in heart attacks. In the first few days after the Iraqi missile attacks on Israel in 1991, there was a sharp increase in heart attacks in Israel compared with control periods. The psychological stress caused by these sudden disasters could have raised the blood fatty acid levels above the safe level in some subjects which could have increased the risk of a heart attack. 

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