The role of the lymphoid system in the regulation of the blood glucose level.

Recent findings have led to a new hypothesis in which it is proposed that the immune system plays a role in regulating the increase in blood glucose levels after a meal. The relevant findings are: (1) the primary lymphoid tissue, the lymph nodes are mostly present within adipose tissue depots throughout the body (there are at least 12 such depots and about 10 (12) lymphocytes, 99% of which are present in lymph nodes); (2) lymphocytes and other immune cells utilize glucose at a high rate but almost all of it is converted to lactate which accumulates in the cells prior to release; (3) glutamine, some of which is synthesized in muscle from glucose, is utilized at a high rate by immune cells, the end-product of which is mainly aspartate, which also accumulates in the cells prior to release; and (4) finally, there is a common blood supply to the lymph node and the adipose tissue depot and the blood flow through the depot and hence the node is increased after a meal. It is proposed that, after a meal, some of the absorbed glucose is taken up from the blood by the lymphocytes and converted to lactate and glutamine is converted to aspartate.

Branched-chain amino acids and central fatigue.

An account of the tryptophan (Trp)-5-hydroxytryptamine (5-HT)-central fatigue theory is provided and an explanation of how oral administration of BCAAs can decrease fatigue on the basis of this theory is given. The rate-limiting step in the synthesis of 5-HT is the transport of Trp across the blood-brain barrier. This transport is influenced by the fraction of Trp available for transport into the brain and the concentration of the other large neutral amino acids, including the BCAAs, which are transported via the same carrier system.

The effect of tryptophan deficiency in the brain on rat fatigue levels: a rat model of fatigue reduction.

The level of tryptophan and 5-hydroxyindoleacetic acid were measured in the brain (striatum) of rats on tryptophan-deficient diet and tryptophan-enriched diet. We measured concentrations of tryptophan and 5-hydroxyindoleacetic acid in striatum by using microdialysis and HPLC methods. The extracellular level of tryptophan and 5-hydroxyindoleacetic acid concentration in the striatum of a tryptophan-reduced rats was decreased by about 50% compared with a tryptophan-enriched diet.

Influence of dietary supplementation with long-chain n-3 or n-6 polyunsaturated fatty acids on blood inflammatory cell populations and functions and on plasma soluble adhesion molecules in healthy adults.

Greatly increasing the amounts of flaxseed oil [rich in alpha-linolenic acid (ALNA)] or fish oil (FO); [rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] in the diet can decrease inflammatory cell functions and so might impair host defense. The objective of this study was to determine the effect of dietary supplementation with moderate levels of ALNA, gamma-linolenic acid (GLA), arachidonic acid (ARA), DHA, or FO on inflammatory cell numbers and functions and on circulating levels of soluble adhesion molecules. Healthy subjects aged 55 to 75 yr consumed nine capsules per day for 12 wk.