Proline metabolism in adult male burned patients and healthy control subjects

Article Abstract:

Amino acids, the building blocks of proteins, are classified as being nonessential or essential, depending on whether the body can manufacture them or must acquire them from the diet, respectively. Proline is technically a nonessential amino acid, but its rate of synthesis is very low compared with other nonessential amino acids. For this reason, and because its structure can undergo reaction to form glucose, levels of proline may be depleted when the body is under great stress, as during infection, surgery, or trauma. Proline is an important constituent of collagen, the predominant protein in skin and related tissues, and both the amino acid and protein are needed during wound healing. To better understand the body's proline requirements during stress, five men (average age 27 years) with severe burns were evaluated and compared with six healthy control men (average age 20 years). Flux (metabolism) of proline and leucine, another nonessential amino acid, was approximately doubled in burned patients compared with healthy subjects. Degradation of proteins was approximately double, while proline oxidation (breakdown for use as fuel) was increased threefold and proline synthesis was not increased. This resulted in a negative proline balance (difference between proline production and excretion) and significantly lower blood proline levels. The report suggests that proline supplementation may be necessary in trauma patients, especially those with burns or other injuries in which wound healing is an important part of recovery. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Wounds and injuries, Injuries, Amino acids

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Metabolic effects of a single administration of growth hormone on lipid and carbohydrate metabolism in normal-weight and obese subjects

Article Abstract:

Human growth hormone (hGH) is being investigated for its effects on lipid (fat) and protein metabolism. Research has shown that hGH promotes the dissolution of lipids and also favors the growth of protein tissue. One study reported that obese subjects retained muscle tissue when treated with diet and a variant of hGH that contained one extra amino acid. In this study the effect of hGH on lipid metabolism was examined. Six normal-weight men and six obese individuals (two men and four women) were each given a single dose of hGH. Following injection of the hormone, a significant increase in circulating free fatty acids was measured in both groups, which indicated fat breakdown. Insulin and glucose concentrations in the blood also increased. After a period of five hours and a 950-calorie meal, the dissolution of lipids continued, but at a slower rate. In conclusion, the hGH injection produced an increase in fat breakdown in both obese and normal-weight adults; this effect was only partially reduced by food consumption and persisted despite an increase in blood insulin levels. Further research on hGH with obese subjects is warranted; the long-term effect of hGH on carbohydrate and lipid metabolism, as well as possible side effects, needs investigation. (Consumer Summary produced by Reliance Medical Information, Inc.)

Obesity, Lipid metabolism, Somatotropin, Fat metabolism, Carbohydrate metabolism, Pituitary hormones

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Menstrual cycle effects on the metabolism of tryptophan loads

Article Abstract:

Tryptophan is an amino acid that functions as a building block for proteins and also regulates the neurotransmitter serotonin. Neurotransmitters are chemicals that carry messages to nerves throughout the human nervous system. A study investigated whether the metabolism of tryptophan changes during the menstrual cycle, since the female sex steroids might influence tryptophan levels. Tryptophan metabolism (synthesis and breakdown) was affected by the stage of the menstrual cycle in eight healthy women. Two parts of the cycle were compared: the seven days before ovulation (follicular phase) and the seven days before the beginning of the menstrual period (luteal phase). Since the menstrual cycle influenced the breakdown of tryptophan, it is suggested that tryptophan may be related to premenstrual changes in women's food intake and mood and that the menstrual cycle's effect on tryptophan may influence both the behavior and physiology of women.

Case studies, Premenstrual syndrome, Amino acid metabolism, Tryptophan metabolism, Serotonin

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