Posted by Larry Hoover on August 24, 2003, at 10:19:45
In reply to I welcome any info----, posted by KellyD on August 24, 2003, at 8:26:14
> I seem to always be saying thanks, but I really mean it. I appreciate all the help I receive.
You're very welcome. And, I want to thank you for stimulating me with your questions. It may seem bizarre, but I'm more likely to immediately and thoroughly investigate a topic in response to e.g. a posted question, than I am to one that arises in my own mind. (This sort of thing is a frequent topic in therapy..... :-/) That's one of the reasons I love questions being tossed my way. Another reason is that I'm a total geek, majorly fascinated by the world around me.
>And Larry, you're my hero (hope you blushed again)
Yaa... major blushage. ;-)
There is a huge amount of new material in Pubmed about glutamine and gut permeability (I've place a few abstracts, below, for those who want to read that sort of thing). What I found was:
Glutamine is a key regulator of the healing process in damaged intestinal membranes. It doesn't matter if the glutamine is supplied from the gut side (i.e. from food/supps), or from the blood side (from body stores), glutamine is required for proteins synthesis, and the restoration of the permeability barrier.
It also doesn't much matter what caused the injury to the intestinal wall. It could be infection, starvation, loss of perfusion (blood flow), celiac sprue, AIDS, other medical stressors (major skin burns, for example)....all of them respond to glutamine.
With respect to celiac, as an example, my impression is that the effect of gluten exposure is in two stages. First, exposure causes injury (one effect is to damage a key glutamine-dependent enzyme), and causes increased permeability (to all sorts of stuff that shouldn't get into the blood so readily). Then, if gluten exposure occurs before healing can take place, you get some real major damage (and the majority of celiac symptoms arise at this point). Cells die.
To support intestinal cell healing, you need not only glutamine, but also omega-3 fatty acids (where have I seen that stuff mentioned before?), gamma-linolenic acid (GLA, from evening primrose or borage), antioxidants, and short-chain fatty acids (coconut oil is a good source). The whole B-vitamin thing (especially B-12), minerals (zinc and selenium, esp.), and all that, too. I guess that's why megadose vitamin therapy may be so important to some people (like me). If your intestines are chronically injured, you need to get the nutrients by passive absorption, rather than by the normal active transport processes.
About the antioxidants. All cell injury increases oxidative stress. Oxidation is the key to our survival (oxidation of carbs or fat in our cells is the identical process you see in fire), but it is very tightly controlled. Injured cells lose control of oxidation, so antioxidants like vitamin C, vitamin E, selenium, alphalipoic acid, glutathione (indirectly dependent on good supplies of methionine....that whole homocysteine thing) become even more important.
Back to glutamine. Glutamine and glutamate are not the same thing. In the gut, they may well be virually interchangeable, but they are not the same thing to your nervous system.
Glutamine is cheap. A very quick check showed you can get a half-pound of pharmaceutical grade glutamine for $20 US.
I'm definitely going to get me some of that.
Lar
Here are the abstracts. BTW, the last one is a review of the subject, written by a major skeptic (His arguments are weak, IMHO. Far too many "may"s, and similar.) Just for balance.
J Nutr Biochem. 2003 Jul;14(7):401-8.
Glutamine supports recovery from loss of transepithelial resistance and increase of permeability induced by media change in Caco-2 cells(1).Li N, DeMarco VG, West CM, Neu J.
Department of Pediatrics, University of Florida, College of Medicine, 32610, Gainesville, Florida, USA
Recent evidence suggests that the conditionally essential amino acid glutamine is important for intestinal barrier function. However, the mechanism remains undefined. To determine the effects of glutamine on permeability of intestinal epithelial cell monolayers, Caco-2 cells were grown on membrane filters and exposed to 4 mmol/L sodium butyrate in order to rapidly achieve high levels of alkaline phosphatase and high transepithelial resistance as seen in functionally mature enterocytes. A standard method of medium exchange consisting of removal and replacement resulted in a catastrophic loss of transepithelial resistance and increase of mannitol and dextran fluxes that required 2-4 hrs and protein synthesis to recover. The effect was attributed to exposure of the upper monolayer surface to atmosphere and could be avoided by refeeding by incremental perfusion. Spontaneously-differentiated Caco-2 monolayers were resistant to this stress. This novel stress test was employed as a sensitive assay for the requirement of glutamine for monolayer transepithelial resistance and mannitol permeability. Pre-stress glutamine availability was more important than Gln-availability during the recovery phase. Thus the transepithelial resistance and permeability of butyrate-induced monolayers is dynamically-regulated in response to atmospheric exposure, by a mechanism that depends on threshold levels of glutamine availability.
J Nutr. 2003 Jul;133(7):2176-9.
Glutamine and barrier function in cultured Caco-2 epithelial cell monolayers.DeMarco VG, Li N, Thomas J, West CM, Neu J.
Department of Pediatrics, University of Florida College of Medicine, Gainesville, FL 32610, USA.
Dietary glutamine (Gln) has been shown to be important for maintenance of the intestinal barrier. To investigate the role of the epithelium in this Gln dependence, Caco-2 cells were raised on semipermeable membranes under conditions that model different regions of the crypt and villus. Gln availability was controlled by addition to the medium and treatment with methionine sulfoximine to inhibit Gln synthetase (GS). Barrier function was assayed by measuring transepithelial electrical resistance and fluxes of [(14)C]mannitol and fluorescein isothiocyanate-dextran. The barrier function of these monolayers was found to require the Gln provided either in the medium at the apical or basal surface or via GS. However, the barrier was no more sensitive to Gln deprivation than it was to accumulation or maintenance of total protein. These results suggest that the in vivo dependence of the gut mucosal barrier on Gln likely involves roles separate from maintenance of the epithelial barrier per se.
Am J Physiol Gastrointest Liver Physiol. 2003 Jul;285(1):G128-36.
Glutamine preserves protein synthesis and paracellular permeability in Caco-2 cells submitted to "luminal fasting".Le Bacquer O, Laboisse C, Darmaun D.
INSERM U.539, Centre de Recherche en Nutrition Humaine Groupe Metabolisme, Hotel-Dieu, 3eme etage aile nord, 44093 Nantes cedex 1, France.
This study used polarized cell line Caco-2 as a model of human enterocytes to determine: 1) whether deprivation of nutrients on the apical (luminal) side of the epithelium (fasting) alters protein synthesis in enterocytes; 2) if so, whether glutamine can attenuate the effects of fasting; and 3) whether the effects of glutamine depend on its route (i.e., apical vs. basolateral) of supply. Caco-2 cells were submitted to nutrient deprivation on the apical side to mimic the effects of fasting, whereas the basolateral side of the epithelium remained exposed to regular medium. Cells were then incubated with [2H3]leucine with or without glutamine, and the fractional synthesis rate (FSR) of total cell protein was determined from [2H3]leucine enrichments in protein-bound and intracellular free leucine measured by gas chromatography/mass spectrometry. A 24-h apical nutrient deprivation (luminal fasting) was associated with a decline in intracellular glutamine, glutamate, and glutathione concentrations (-38, -40, and -40%, respectively), protein FSR (-20%), and a rise in passage of dextran, an index of transepithelial permeability. In fasted cells, basolateral or luminal glutamine supplementation did not alter the glutathione pool, but it restored protein FSR and improved permeability. The effects of glutamine were abolished by 6-diazo-oxo-l-norleucine, an inhibitor of glutaminase, and was mimicked by glutamate. We conclude that in Caco-2 cells, protein synthesis depends on nutrient supply on the apical side, and glutamine regardless of the route of supply corrects some of the deleterious effects of fasting in a model of human enterocytes through its deamidation into glutamate.
Am J Physiol Gastrointest Liver Physiol. 2001 Dec;281(6):G1340-7.
Effects of glutamine deprivation on protein synthesis in a model of human enterocytes in culture.Le Bacquer O, Nazih H, Blottiere H, Meynial-Denis D, Laboisse C, Darmaun D.
INSERM U.539, Centre de Recherche en Nutrition Humaine, 44093 Nantes, France.
To assess the effect of glutamine availability on rates of protein synthesis in human enterocytes, Caco-2 cells were grown until differentiation and then submitted to glutamine deprivation produced by exposure to glutamine-free medium or methionine sulfoximine [L-S-[3-amino-3-carboxypropyl]-S-methylsulfoximine (MSO)], a glutamine synthetase inhibitor. Cells were then incubated with (2)H(3)-labeled leucine with or without glutamine, and the fractional synthesis rate (FSR) of total cell protein was determined from (2)H(3)-labeled enrichments in protein-bound and intracellular free leucine measured by gas chromatography-mass spectrometry. Both protein FSR (28 +/- 1.5%/day) and intracellular glutamine concentration (6.1 +/- 0.6 micromol/g protein) remained unaltered when cells were grown in glutamine-free medium. In contrast, MSO treatment resulted in a dramatic reduction in protein synthesis (4.6 +/- 0.6 vs. 20.2 +/- 0.8%/day, P < 0.01). Supplementation with 0.5-2 mM glutamine for 4 h after MSO incubation, but not with glycine nor glutamate, restored protein FSR to control values (24 +/- 1%/day). These results demonstrate that in Caco-2 cells, 1) de novo glutamine synthesis is highly active, since it can maintain intracellular glutamine pool during glutamine deprivation, 2) inhibition of glutamine synthesis is associated with reduced protein synthesis, and 3) when glutamine synthesis is depressed, exogenous glutamine restores normal intestinal FSR. Due to the limitations intrinsic to the use of a cell line as an experimental model, the physiological relevance of these findings for the human intestine in vivo remains to be determined.
Clin Sci (Lond). 1995 Sep;89(3):311-9.Protein synthesis in isolated enterocytes from septic or endotoxaemic rats: regulation by glutamine.
Higashiguchi T, Noguchi Y, Meyer T, Fischer JE, Hasselgren PO.
Department of Surgery, University of Cincinnati Medical Center, Ohio, USA.
1. We studied the effect of sepsis and the regulation by glutamine of protein synthesis in enterocytes isolated from the small intestine of rats. 2. Sepsis was induced by caecal ligation and puncture; control rats were sham operated. Enterocytes were isolated from the jejunum and incubated in a medium containing [3H]phenylalanine. 3. Sixteen hours after caecal ligation and puncture, protein synthesis, measured as incorporation of radioactivity into protein, was increased by 65%, 89% and 137% respectively in enterocytes from the tips and mid-portions of the villi and from the crypts. 4. Addition of glutamine to incubated enterocytes stimulated protein synthesis in a dose-dependent manner, and this effect was most pronounced in crypt cells from septic rats. The effect of glutamine on protein synthesis was duplicated by equimolar concentrations of acetoacetate or 3-hydroxybutyrate, both of which may serve as fuel for enterocytes, and was blocked by the glutaminase inhibitor 6-diazo-5-oxo-L-norleucine. 5. The results suggest that sepsis stimulates protein synthesis in enterocytes and that glutamine regulates protein synthesis in the same cells, probably by energy provision.
Am J Clin Nutr. 2001 Jul;74(1):25-32.
Glutamine: commercially essential or conditionally essential? A critical appraisal of the human data.Buchman AL.
Division of Gastroenterology and Hepatology, Northwestern University, Chicago, IL 60611, USA. a-buchman@nwu.edu
Glutamine is a nonessential amino acid that can be synthesized from glutamate and glutamic acid by glutamate-ammonia ligase. Glutamine is an important fuel source for the small intestine. It was proposed that glutamine is necessary for the maintenance of normal intestinal morphology and function in the absence of luminal nutrients. However, intestinal morphologic and functional changes related to enteral fasting and parenteral nutrition are less significant in humans than in animal models and may not be clinically significant. Therefore, it is unclear whether glutamine is necessary for the preservation of normal intestinal morphology and function in humans during parenteral nutrition. It was suggested that both glutamine-supplemented parenteral nutrition and enteral diets may pre-vent bacterial translocation via the preservation and augmentation of small bowel villus morphology, intestinal permeability, and intestinal immune function. However, it is unclear whether clinically relevant bacterial translocation even occurs in humans, much less whether there is any value in the prevention of such occurrences. Results of the therapeutic use of glutamine in humans at nonphysiologic doses indicate limited efficacy. Although glutamine is generally recognized to be safe on the basis of relatively small studies, side effects in patients receiving home parenteral nutrition and in those with liver-function abnormalities have been described. Therefore, on the basis of currently available clinical data, it is inappropriate to recommend glutamine for therapeutic use in any condition.
poster:Larry Hoover
thread:252684
URL: http://www.dr-bob.org/babble/20030823/msgs/253570.html