Trauma fuels

The major role of skeletal muscle is movement, which is described and discussed in Chapter 13). Nevertheless, since muscle comprises 40% of the body it is large enough to play a part in control of the blood concentrations of the major fuels glucose, fatty acids, triacylglycerol and some amino acids. Skeletal muscle contains the largest quantity of protein in the body, which is used as a source of amino acids under various conditions (e.g. starvation, trauma, cancer see above). It plays an important part in the metabolism, in particular, of branched-chain amino acids, glutamine and alanine, which are important in the overall metabolism of amino acids in the body (discussed below). 

Conditions such as malnutrition, starvation, infection or trauma can reduce the fuels available for the colonocytes (glutamine, short chain fatty acids) so that the barrier is less effective. 

In the ebb phase, there is increased activity of the sympathetic nervous system and increased plasma levels of adrenaline and glucocorticoids but a decreased level of insulin. This results in mobilisation of glycogen in the liver and triacylglycerol in adipose tissue, so that the levels of two major fuels in the blood, glucose and long-chain fatty acids, are increased. This is, effectively, the stress response to trauma. These changes continue and are extended into the flow phase as the immune cells are activated and secrete the proinflammatory cytokines that further stimulate the mobilisation of fuel stores (Table 18.2). Thus the sequence is trauma increased endocrine hormone levels increased immune response increased levels of cytokines metabolic responses. 

The increased levels of catecholamines and glucocorticoids, the increased sympathetic activity and the decreased level of insulin increase the activity of hormone-sensitive lipase in adipose tissue that is responsible for the increased rate of lipolysis. Also important are the proinflammatory cytokines, TNFa, interleukins 1 and 6. The significance of fat as a fuel in trauma explains why the cytokines have a... 

One claimed advantage of exercise in the elderly is to maintain an effective cardiovascular system so that a mild trauma or infection does not overload the system and the brain receives its required supply of oxygen and fuel under such conditions i.e. physical fitness allows the elderly person to respond adequately to a mild stress not... 

Amino acids are an important fuel for the intestinal mucosal cells after a protein-containing meal and in catabolic states such as fasting or surgical trauma (Fig. 42.13). During fasting, glutamine is one of the major amino acids used by the gut. The principal fates of glutamine carbon in the gut are oxidation to CO2 and conversion to the carbon... 

The rate and pattern of amino acid utilization by different tissues change with dietary and physiologic state. Two such states, the postprandial period following a high-protein meal and the hypercatabolic state produced by sepsis or surgical trauma, differ from the postabsorptive state with respect to the availability of amino acids and other fuels and the levels of different hormones in the blood. As a result, the pattern of amino acid utilization is somewhat different. 

The demand for the consumption of fuel reserves can be regarded as a form of metabolic stress. This is characterized by a low activity of insulin relative to stress hormones catecholamines, corticotropin, glucocorticoids and glucagon. Such an hormonal balance can occur in starvation, diabetes, trauma and under the influence of certain toxins. As we have seen earlier, it can also be a response to the ingestion of large amounts of ethanol, fructose or fat. 

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