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Glutamine promotes triglyceride absorption in a dose-dependent .pdf


									Glutamine promotes triglyceride absorption in a
dose-dependent manner
Jeffrey B. Schwimmer, Looi Ee, Shuqin Zheng and Patrick Tso
Am J Physiol Gastrointest Liver Physiol 282:G317-G323, 2002.

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          Fasting and postprandial concentrations of GLP-1 in intestinal lymph and portal plasma:
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          Am J Physiol Regul Integr Comp Physiol 2007; 293 (6): R2163-R2169.
          [Abstract] [Full Text] [PDF]

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                                                                                                      Am J Physiol Gastrointest Liver Physiol
                                                                                                                     282: G317–G323, 2002.

Glutamine promotes triglyceride absorption in a
dose-dependent manner

               Division of Pediatric Gastroenterology and Nutrition, Children’s Hospital Medical Center and
               Department of Pathology, College of Medicine, University of Cincinnati, Cincinnati, Ohio 45267
             Received 21 August 2000; accepted in final form 14 August 2001

   Schwimmer, Jeffrey B., Looi Ee, Shuqin Zheng, and                      burns, oral L-Gln was shown (23) to improve intestinal
Patrick Tso. Glutamine promotes triglyceride absorption in                absorption of macronutrients including fats. The ben-
a dose-dependent manner. Am J Physiol Gastrointest Liver                  efit of Gln when used in conjunction with growth hor-
Physiol 282: G317–G323, 2002.—Dietary proteins may play                   mone for patients with short bowel syndrome is con-
a role in lipid absorption. Whether amino acids are specifi-               troversial (3, 4, 18). In one study (18), however, half of
cally involved is unknown. We hypothesized that enterally
                                                                          the patients had improved fat balance.
administered L-glutamine (L-Gln) given with a lipid meal
increases triglyceride (TG) absorption in rats. Mesenteric                   Under normal conditions, the efficiency of fat absorp-
                                                                          tion is 96%. However, in diseased states such as

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lymph fistulae and gastroduodenal feeding tubes were placed
in adult male Sprague-Dawley rats. The animals received an                burns, trauma, sepsis, and prematurity, lipid absorp-
enteral bolus of Intralipid (5 ml) followed by enteral infusion           tion is impaired; therefore, affected patients may ben-
of increasing concentrations of L-Gln in saline (0, 85, 170, or           efit from a Gln supplement. We decided to test whether
340 mM) or equimolar concentrations of the inactive isomer                Gln affects intestinal lipid absorption. This informa-
D-Gln or an essential amino acid mixture without Gln.                     tion is important to gastrointestinal physiology and is
Lymph was collected continuously for 6 h and analyzed for                 clinically relevant.
TG content. Animals infused with 85 mM L-Gln had a 64%                       The lymph fistula rat exploits the process of fat
increase in total TG output vs. controls (P 0.05) despite no              absorption to capture the lipid before it enters the
difference in lymph flow rate. Total TG output for animals                 circulation (1). Furthermore, lymph can be collected in
infused with 340 mM L-Gln declined by 43% vs. controls (P
                                                                          a conscious animal without the confounding effect of
0.05). The effect of Gln in promoting lymphatic fat transport
is specific to L-Gln and not shared by D-Gln or an equivalent
                                                                          anesthesia. Therefore, we chose the conscious lymph
amino acid mixture. L-Gln is capable of either promoting or               fistula rat model to test our hypothesis that enterally
impairing lymphatic TG transport in a dose-dependent man-                 administered L-Gln given with a lipid meal enhances
ner.                                                                      the total absorption of TG. We further hypothesize that
                                                                          this effect of L-Gln on fat absorption is dose specific.
enteral nutrition; intestinal lymph; lipid absorption
                                                                          MATERIALS AND METHODS

THE PROCESS OF LIPID ABSORPTION  has largely been studied                 Animals
without accounting for the potential effects of other                        Adult male Sprague-Dawley rats weighing 250–275 g were
macronutrients. However, several studies (16) suggest                     purchased from Harlan Industries (Indianapolis, IN). All
a role for dietary protein in lipid absorption. Luminal                   animals were quarantined for 1 wk to allow them to adjust to
proteins are capable of stabilizing triglyceride (TG)                     laboratory conditions. The rats had free access to standard
emulsions in vivo. Moreover, protein-stabilized emul-                     chow and water. The room lighting was set for a 12:12-h
sions are able to largely restore lymphatic TG output in                  light-dark cycle. The Institutional Animal Care and Use
bile duct-ligated rats. Fecal fat excretion is greater in                 Committee of the University of Cincinnati (Cincinnati, OH)
                                                                          approved all procedures.
infants fed a protein-free diet (15). Low birth weight
infants fed a formula with an identical fat blend but                     Operative Procedure and Recovery
different protein constituents have different fat ab-
                                                                             The animals were fasted overnight but had free access to
sorption (2). Weber and Ehrlein (21) demonstrated that
                                                                          water. The rats were anesthetized with 2% halothane (Halo-
meal macronutrient composition alters the length of                       carbon Laboratories, River Edge, NJ) in an air-O2 mixture.
small intestine required for the complete absorption                      The abdomen was prepped and shaved. A midline vertical
of fat.                                                                   incision was made from the xyphoid process to the suprapu-
   L-Glutamine (L-Gln), the major source of fuel for                      bic region. The intestines were retracted to the left onto
enterocytes (8, 13), is one amino acid (AA) that may                      sterile saline-soaked gauze. The lymph tubing [polyvinyl
impact lipid absorption. In miniswine with severe
                                                                            The costs of publication of this article were defrayed in part by the
   Address for reprint requests and other correspondence: P. Tso, Dept.   payment of page charges. The article must therefore be hereby
of Pathology, Univ. of Cincinnati Medical Center, 231 Albert Sabin Way    marked ‘‘advertisement’’ in accordance with 18 U.S.C. Section 1734
(ML 0529), Cincinnati, OH 45267 (E-mail:             solely to indicate this fact.              0193-1857/01 $5.00 Copyright © 2002 the American Physiological Society                                   G317
G318                                   GLUTAMINE AND TRIGLYCERIDE ABSORPTION

chloride (0.5 mm ID, 0.8 mm OD), Critchley Products, Silver-         using a standard kit (procedure no. 334-UV, Sigma Diagnos-
water BC, New South Wales, Australia] was flushed with a              tics, St. Louis, MO).
heparin-saline solution (1,000 U/ml). The duodenal feeding
tube [silicone (1.02 mm ID, 2.16 mm OD), Helix Medical,              Statistical Analysis
Carpinteria, CA] was flushed with saline. The lymph cannula              Statistical analysis was performed using statistical soft-
and the duodenal tubing were introduced into the peritoneal          ware (SAS Institute, Cary, NC). The overall differences in
cavity through two punctures made with a 16-gauge needle.            lymph flow rate over a 6-h period were evaluated with a
The mesenteric lymphatic duct was opened with ophthalmic             repeated-measures ANCOVA with an of 0.05. The repeated
iris scissors, and the tubing was placed into the lumen. The         measure was time. We measured total lymphatic TG output
tube was secured with one drop of cyanoacrylate glue. The            continuously for 6 h after the ingestion of a lipid bolus. The
intestines were returned to the peritoneal cavity, and the           overall differences in total TG output among the experimen-
stomach was retracted. A purse-string ligature was made in           tal and control groups were evaluated by a covariance test
the fundus of the stomach. The stomach was punctured with            with an      of 0.05. Individual relationships between the
a 16-gauge needle, and the catheter was introduced into the          groups for total TG output were evaluated using Tukey’s
stomach and advanced 1 cm beyond the pylorus into the                honest significant difference test. Individual relationships
duodenum. The purse string was tied, fixing the tube in               between the groups for hourly lymphatic TG output were
place. The abdominal musculature and skin were closed in             evaluated via a priori nonorthogonal contrasts with a re-
two layers with 4-0 silk suture (Ethicon, Somerville, NJ).           stricted Bonferroni       0.0028.
Postoperatively, a glucose-saline solution containing 145 mM
NaCl, 4 mM KCl, and 280 mM glucose was infused into the              Chemicals
duodenum at 3 ml/h. The animals were placed in restraint
cages and allowed to recover overnight (18–22 h) in a tem-             All chemicals and reagents, unless otherwise specified,
perature-regulated box maintained at 30°C.                           were obtained from Sigma Chemical (St. Louis, MO) and

                                                                                                                                              Downloaded from on May 19, 2012
                                                                     were of analytical grade.
Experimental Plan
   To test the absorption of TG, we provided the total daily
TG intake as a single lipid meal. We delivered an emulsified          Lymph Flow
solution to the duodenum with Intralipid (Clintec Nutrition,
Deerfield, IL) as the TG source. A bolus of 5 ml of 20%                 Increasing L-Gln concentrations. There was no sig-
Intralipid was chosen because this provides 1 g of TG, which         nificant difference in mean baseline lymph flow among
is approximately the 24-h fat intake of an adult rat. The lipid      the four L-Gln groups (0, 85, 170, and 340 mM L-Gln;
bolus was then followed by a continuous intraduodenal infu-          Fig. 1). In all groups, the lymph flow rate increased in
sion of a control (saline only) or experimental solution (sa-        response to lipid feeding. With 0, 8, or 170 mM L-Gln,
line Gln). Experimental solutions contained 145 mM NaCl              the lymph flow rate increased and peaked during the
and increasing concentration of L-Gln (85, 170, or 340 mM).          third hour. After the fourth hour, the rate returned to
Continuous infusion with 145 mM NaCl and 0 mM L-Gln was              baseline. In contrast, the lymph flow rate in the group
chosen as a control solution to ensure adequate hydration
                                                                     infused with 340 mM L-Gln increased in the first hour
and lymph flow. The Gln concentrations used were based on
both clinical trials and saturability. We chose 85 mM L-Gln          but declined thereafter. The lymph flow rates in the
because it is in the range of solutions of supplemental Gln          groups infused with 0 or 85 mM L-Gln were not differ-
used in clinical trials. We also used two additional controls        ent from each other. Animals infused with 170 mM
for 85 mM L-Gln. To test whether an effect was due to                L-Gln had a numerically greater volume of lymph flow
physiological activity, we used a solution with an equimolar         over the 6 h, but this was not significantly different
concentration of the inactive isomer D-Gln. To assess whether
an effect of 85 mM L-Gln is common to other AA, we mixed an
equimolar concentration of an essential AA mixture without
Gln (MEM essential AA 50 solution, BioWhittaker, Walk-
ersville, MD) with water and NaCl to make a solution con-
taining 145 mM NaCl and 85 mM of essential AA (85 mM
AA). We chose 340 mM L-Gln because it is a maximally
saturated solution. To assess whether the result with 340
mM L-Gln was physiological, we used an equimolar solution
of D-Gln that also controlled for the high osmolarity of the
saturated solution. Finally, we chose to test the intermediate
concentration, 170 mM L-Gln.

Experimental Procedure
  Lymph was collected into conical graduated centrifuge
tubes on ice for 1 h to assess baseline (fasting) lymph flow and
TG output. Animals with a baseline lymph flow rate 2 ml/h
were excluded. The animals (n 7/group) were then given a
5 ml duodenal bolus of Intralipid over 2 min. The lipid bolus        Fig. 1. The mean lymph flow rate is shown (in ml/h) at baseline and
was followed by a 3 ml/h continuous duodenal infusion of             hourly over 6 h following an intraduodenal bolus of triglyceride (TG).
control or test solution for 6 h. Lymph was collected contin-        After the bolus, each group (n      7/group) received a continuous
uously on ice for 6 h and analyzed for TG content. TG                infusion of a solution containing L-glutamine (L-Gln; 0, 85, 170, or
concentrations were determined by the enzymatic method               340 mM). Values are means SE.

                              AJP-Gastrointest Liver Physiol • VOL   282 • FEBRUARY 2002 •
                                          GLUTAMINE AND TRIGLYCERIDE ABSORPTION                                                    G319

from the 0 or 85 mM L-Gln groups. The lymph flow rate
in the 170 mM L-Gln group was significantly different
from the group infused with 340 mM L-Gln (P 0.05).
When the individual hourly lymph flow rates were
compared, 340 mM L-Gln led to a significantly (P
0.0028) lower lymph flow rate than did 0, 85, and 170
mM L-Gln for the third and fourth hour.
  Controls and 85 mM L-Gln. The effects of 85 mM
L-Gln were further evaluated by using the initial con-
trol, 0 mM L-Gln, and two additional controls, 85 mM
D-Gln and 85 mM essential AA. Among these groups,
baseline lymph flow was not significantly different
(Fig. 2). The individual differences between the groups
for each hour of the experiment were not significant,
except for the 85 mM L-Gln and D-Gln groups during
the fourth hour (P 0.001).
                                                                       Fig. 3. The mean lymph flow rate is shown (in ml/h) at baseline and
  Controls and 340 mM L-Gln. Using the initial con-                    hourly over 6 h following an intraduodenal bolus of TG. After the
trol, 0 mM L-Gln, and an additional control, 340 mM                    bolus, each group (n   7/group) received a continuous infusion of a
D-Gln, the effects of 340 mM L-Gln were further eval-                  solution containing no Gln or a solution of 340 mM L-Gln or the
uated. Fasting lymph flow was not significantly differ-                  stereoisomer D-Gln. Values are means SE.
ent between these groups (Fig. 3). Over time, however,

                                                                                                                                             Downloaded from on May 19, 2012
a significant difference in the change of lymph flow rate
                                                                       infused with 0 and 170 mM L-Gln, lymphatic TG con-
between these groups (P       0.01) was observed. When
                                                                       tent peaked during the third hour. Lymphatic TG con-
the individual relationships for lymph flow rate be-
                                                                       tent in the group infused with 85 mM L-Gln had a
tween these groups for each hour were evaluated, the
                                                                       higher and longer increase that peaked during the
lymph flow rate for the group infused with 340 mM
                                                                       fourth hour. The group infused with 340 mM L-Gln had
L-Gln was significantly lower than that of the 0 mM
                                                                       an earlier and much lower peak during the second hour
L-Gln group during the third and fourth hour (P
                                                                       and a decline in TG output thereafter. There was a
0.0028). Lymph flow in the group infused with 340 mM
                                                                       significant difference in the change of TG output over
D-Gln was not significantly different from that of the 0
                                                                       time between the four groups of rats studied (0, 85,
or 340 mM L-Gln group at any time point.
                                                                       170, and 340 mM L-Gln) (P        0.05). There was also a
Lymphatic TG Output                                                    significant overall difference between the groups when
                                                                       levels were collapsed across time (P 0.0001).
  Increasing L-Gln concentrations. The fasting lym-                      The hourly lymphatic TG output was summed to
phatic TG output was not significantly different among                  obtain total TG absorption (Fig. 5). The total TG ab-
the four L-Gln groups (0, 85, 170, and 340 mM L-Gln;                   sorption over the 6-h period for each group ( mol SE)
Fig. 4). After lipid feeding, there was a rapid rise in TG             in ascending order was 101       9, 178    21, 253   23,
within the intestinal lymph in all groups. In the groups               and 292     17 mol for 340, 0, 170, and 85 mM L-Gln,
                                                                       respectively. The overall difference between the groups

Fig. 2. The mean lymph flow rate is shown (in ml/h) at baseline and
hourly over 6 h following an intraduodenal bolus of TG. After the      Fig. 4. The mean lymphatic TG output is shown (in mol) at baseline
bolus, each group (n    7/group) received a continuous infusion of a   and hourly over 6 h following an intraduodenal bolus of 1 g of TG.
solution containing no Gln or a solution of 85 mM L-Gln, the stereo-   After the bolus, each group (n     7/group) received a continuous
isomer D-Gln, or a mixture of essential amino acids without L-Gln      infusion of a solution containing L-Gln (0, 85, 170, or 340 mM).
(AA). Values are means SE.                                             Values are means SE.

                                AJP-Gastrointest Liver Physiol • VOL   282 • FEBRUARY 2002 •
G320                                         GLUTAMINE AND TRIGLYCERIDE ABSORPTION

Fig. 5. The total lymphatic TG output (in mol) for
experimental and control groups (n 7/group) is shown
over the 6-h period following a bolus of 1 g of TG. Values
are means SE.

was significant (P     0.01). The group infused with 85                   a lipid meal. When individual relationships between

                                                                                                                                                  Downloaded from on May 19, 2012
mM L-Gln and the group infused with 170 mM L-Gln                         the groups for hourly TG absorption were compared,
were each significantly different from the 0 mM L-Gln                     the group infused with 85 mM L-Gln had a significantly
group, but were not significantly different from each                     higher TG output than the other three groups for the
other. To test whether concentrations of L-Gln lower                     fourth, fifth, and sixth hours (P 0.0028). The overall
than 85 mM would also promote lymphatic TG trans-                        difference in total TG output between the group in-
port we studied five additional animals receiving 42.5                    fused with 85 mM L-Gln and its three control groups
mM L-Gln supplemented in the infusate. Lymphatic                         was significant (P      0. 001) (Fig. 5). There was no
TG output in these animals was superimposable with                       significant difference in total TG output among the
the output observed in the animals infused with saline                   groups infused with 0 mM L-Gln, 85 mM D-Gln, or 85
only (0 mM L-Gln; data not shown). We therefore con-                     mM AA (Fig. 5).
cluded that the 42.5 mM dose of supplemented L-Gln                         Controls and 340 mM L-Gln. The difference in fast-
had no effect on lymphatic TG output with the infused                    ing lymphatic TG output between groups at baseline
Intralipid. Thus it appears that promotion of lymphatic                  was not significant (Fig. 7). After lipid feeding, the
TG transport by 85 mM L-Gln is dose specific. Support-                    group infused with 340 mM D-Gln had a similar pat-
ing this conclusion is the fact that the 340 mM L-Gln                    tern as the group infused with 0 mM L-Gln, with a
group had significantly lower TG output than the other                    rapid rise in TG within the intestinal lymph that
three groups.                                                            peaked during the third hour. The overall difference in
  Controls and 85 mM L-Gln. Figure 6 shows the lym-                      total TG output between the group infused with 340
phatic TG output during the first 6 h after ingestion of

Fig. 6. The mean lymphatic TG output is shown (in mol) at baseline       Fig. 7. The mean lymphatic TG output is shown (in mol) at baseline
and hourly over 6 h following an intraduodenal bolus of 1 g of TG.       and hourly over 6 h following an intraduodenal bolus of 1 g of TG.
After the bolus, each group (n        7/group) received a continuous     After the bolus, each group (n        7/group) received a continuous
infusion of a solution containing no Gln or a solution of 85 mM L-Gln,   infusion of a solution containing no Gln or a solution of 340 mM L-Gln
the stereoisomer D-Gln, or AA. Values are means SE.                      or the stereoisomer D-Gln. Values are means SE.

                                  AJP-Gastrointest Liver Physiol • VOL   282 • FEBRUARY 2002 •
                                        GLUTAMINE AND TRIGLYCERIDE ABSORPTION                                                          G321

mM L-Gln and the two control groups was significant                   Table 2. Mucosal recoveries of radioactive triolein
(P     0.001) (Fig. 7). The groups infused with 0 mM
                                                                                         Group                     Triolein Recovery
L-Gln and 340 mM D-Gln were not different from each
other.                                                                      Intralipid   saline                       4.10   0.27
   In a separate study, we compared the luminal recov-                      Intralipid   85 mM L-Gln                  3.75   0.60
eries of radioactive triolein incorporated in the 5 ml of                   Intralipid   340 mM L-Gln                 4.15   0.67
Intralipid emulsion (i.e., 6 h after the introduction of                 Values are means     SE given as %dose incorporated in Intralipid;
Intralipid    saline, Intralipid    85 mM L-Gln, or In-              n      4/group.
tralipid 340 mM L-Gln) (Table 1). As shown in Table
1, there was significant inhibition of the uptake of the
radioactive fatty acids (FA) derived from the radioac-               promotes TG output. Because 42.5 mM L-Gln failed to
tive triolein when a high concentration of L-Gln was                 stimulate lymphatic TG transport, we can infer that 85
present in the intestinal lumen vs. a low concentration              mM is probably the optimal dose for maximum stimu-
of L-Gln (85 mM) (P 0.05) or saline (P 0.05). There                  lation of lymphatic TG transport. This observation
was no significant difference between 85 mM L-Gln and                 supports our first hypothesis that the absorption of
the saline controls.                                                 L-Gln promotes intestinal absorption of lipid into
   We also determined the mucosal recoveries of the                  lymph.
radioactive triolein incorporated in Intralipid at the                  Next, we addressed the question of whether the
end of the study. Mucosal lipids were extracted accord-              enhancement of lymphatic TG transport is a specific
ing to the method described by Folch et al. (7). As                  action of L-Gln. Interestingly, infusion of an 85 mM
shown in Table 2, there was no significant difference in              solution of the stereoisomer D-Gln did not change the

                                                                                                                                              Downloaded from on May 19, 2012
the amount of radioactive lipid recovered from the                   lymph flow or the TG output compared with 0 mM
intestinal mucosa among the three groups of rats.                    L-Gln. Therefore, the effect of 85 mM L-Gln is due to a
   Additionally, we performed TLC analyses of the ra-                cellular action of L-Gln and not to only the physical
dioactive lipid in both the intestinal lumen and the                 presence of Gln. To further test this specific action of
intestinal mucosa. At the end of the infusion period,                L-Gln on intestinal lipid absorption into lymph, we
  10% of the radioactive triolein remained as TG in the              infused 85 mM AA. As expected, TG output was signif-
intestinal lumen in all three groups of rats and there               icantly greater in rats infused with 85 mM L-Gln than
was no difference between them. Therefore, L-Gln in                  in those infused with 85 mM AA (P        0.001). The AA
different concentrations has no effect on the lipolysis of           mixture did result in TG output that was 30% higher
TG ingested. Next, we analyzed the distribution of                   than with 0 mM L-Gln; this difference, however, did not
radioactive FA in the intestinal mucosa of the three                 reach significance. Therefore, the effect of 85 mM L-Gln
groups of rats. Most of the radioactive FA (60–70%)                  on TG output by enterocytes is specific to L-Gln and
was in the TG fraction in all three groups and there                 cannot be generalized to mixed AA. These experiments
was no difference between them. Thus the presence of                 do not exclude, however, the possibility that other AA
different concentrations of L-Gln in the intestinal lu-              may play a similar role in enhancing TG absorption.
men has no effect on the reesterification of absorbed                 Actually, these data (30% stimulation of lymphatic TG
monoglyceride and FA to form TG.                                     transport) suggest that there are other AA that stim-
                                                                     ulate lymphatic TG transport.
DISCUSSION                                                              In contrast to the intraduodenal infusion of 85 or
   We chose to study Gln because of its diverse effects              170 mM L-Gln, intraduodenal infusion of 340 mM
on the intestine. Using the intestinal lymph fistula rat              L-Gln led to a 43% decrease in TG output compared

model, we found that intraduodenal infusion of a solu-               with the Gln-free control. This data implies that
tion containing 85 mM L-Gln led to a 64% increase in                 higher doses of intraduodenally infused L-Gln actu-
total lymphatic TG output after a lipid meal. This                   ally decrease rather than increase intestinal lipid
dramatic rise in TG output was not caused by a change                absorption into lymph. Analysis of radioactive tri-
in lymph flow, since the change in the lymph flow rate                 olein given with the Intralipid indicated that more
was comparable between the groups. We also observed                  radioactive FA remained in the intestinal lumen of
a significant increase (42%) in TG output with 170 mM                 animals infused with 340 mM L-Gln than in animals
L-Gln, indicating that there is a range of L-Gln that                infused with either 85 mM L-Gln or saline. Although
                                                                     not conclusive, decreased uptake of FA by the small
                                                                     intestine in the presence of a high concentration of
Table 1. Luminal recoveries of radioactive triolein                  L-Gln was partially responsible for the decreased
                                                                     transport of lipid into lymph. Given the high osmo-
                   Group                  Triolein Recovery          larity of the solution and the decrease in lymph flow,
      Intralipid   saline                   22.2   2.2               it is possible that these findings were a result of the
      Intralipid   85 mM L-Gln              23.3   1.6               hypertonicity of the solution. However, no change in
      Intralipid   340 mM L-Gln             37.3   5.2*              TG output compared with 0 mM L-Gln was observed
  Values are means SE given as %dose incorporated in Intralipid;     when using a solution with the same osmolarity
n    4/groups. L-Gln, L-glutamine. * P 0.05 vs. saline and 85 mM     containing 340 mM D-Gln. If the decreased TG out-
L-Gln groups.                                                        put was due to an osmotic effect, then 340 mM D-Gln
                              AJP-Gastrointest Liver Physiol • VOL   282 • FEBRUARY 2002 •
G322                                 GLUTAMINE AND TRIGLYCERIDE ABSORPTION

should have demonstrated the same effect. There-                   possibility of dose-specific L-Gln playing a therapeu-
fore, the decline in TG output cannot be attributed to             tic role in fat malabsorption.
hypertonicity but instead is probably caused by the
                                                                      We thank Drs. W. Balistreri, M. Cohen, and J. Heubi for the
high concentration of L-Gln.                                       thoughtful manuscript reviews.
   We also examined the mucosal radioactive FA recov-                 This work was supported by National Institute of Diabetes and
ery of animals given Intralipid incorporated with ra-              Digestive and Kidney Diseases Grants DK-54504, DK-56910, and
dioactive triolein (Table 2). We found no difference in            DK-56863.
                                                                      J. Schwimmer was the recipient of National Research Service
the amounts of radioactive FA between the three                    Award DK-07727.
groups (Intralipid saline, Intralipid 85 mM L-Gln,
and Intralipid 340 mM L-Gln). Additionally, despite                REFERENCES
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