Glutamine supplementation further enhances exercise-induced plasma IL-6
Exercise stimulates the production and release of interleukin-6 (IL-6) from skeletal muscle. Glutamine is also synthesized in skeletal muscle and is involved in protein synthesis within this tissue. During exercise, plasma levels of glutamine decline, and this may affect the concentration of plasma IL-6 via a decrease in IL-6 synthesis and release from muscle. We hypothesized that glutamine supplementation would attenuate the exercise-induced decrease in plasma glutamine concentration and, thus, further enhance levels of plasma IL-6.
Eight healthy men participated in a randomized, double-blind, crossover study in which they performed 2 h of cycle ergometry at 75% of peak O2 uptake. They received glutamine, glutamine-rich protein, or placebo supplementation at intervals during and 2 h after exercise.
Exercise induced an 11-fold increase in plasma IL-6, which was further enhanced by glutamine (18-fold) and glutamine-rich protein (14-fold) supplementation, administered at doses that attenuated the exercise-induced decrease in plasma glutamine concentration. [Source]
Glutamine attenuates post-traumatic glutathione depletion in human muscle
Glutathione is quantitatively the most important endogenous scavenger system. Glutathione depletion in skeletal muscle is pronounced following major trauma and sepsis in intensive care unit patients. Also, following elective surgery, glutathione depletion occurs in parallel with a progressive decline in muscle glutamine concentration. The present study was designed to test the hypothesis that glutamine supplementation may counteract glutathione depletion in a human trauma model.
In the control (unsupplemented) subjects, total muscle glutathione had decreased by 47±8% and 37±11% and reduced glutathione had decreased by 53±10% and 45±16% respectively at 24 and 72h after surgery (P<0.05). In contrast, in the glutamine-supplemented group, no significant post-operative decreases in total or reduced glutathione were seen following surgery. Muscle free glutamine had decreased at 72h after surgery in both groups, by 41.4±14.8% (P<0.05) in the glutamine-supplemented group and by 46.0±14.3% (P<0.05) in the control group.
In conclusion, the present study demonstrates that intravenous glutamine supplementation attenuates glutathione depletion in skeletal muscle in humans following standardized surgical trauma. [Source]
Glutamine-enriched diets support muscle glutamine metabolism without stimulating tumor growth
Glutamine is a principal fuel utilized by rapidly growing tumors. Advanced malignant disease results in muscle glutamine depletion and weight loss. Concern exists about providing dietary glutamine to the host with cancer since it may stimulate tumor growth. This study examined the effects of oral glutamine on muscle glutamine metabolism and tumor growth.
There was no difference in arterial glutamine between the two groups, but provision of a glutamine-enriched diet increased muscle glutamine content by 60% (2.31 ± 0.21 μmole/g tissue vs 1.44 ± 0.22 μmol/g tissue, P < 0.05), which supported muscle glutamine release. There were no differences among tumor DNA content, tumor glutaminase activity, or tumor weight and there was no difference histologically in the number of metaphase mitoses/HPF.
Glutamine-enriched oral diets may replete host glutamine stores and support muscle glutamine metabolism without stimulating tumor growth. [Source]