325

ORIGINAL
Early enteral nutrition with arginine compensates for negative
nitrogen balance in patients undergoing curative total
gastrectomy
Yasuko Okamoto1, 2, Takanori Sakaguchi3, Yoshito Ikematsu4, Toshikazu Kanai4, Kazuhisa Hirayama4, 5,
Hiroaki Tamura4, Tadataka Hayashi4, Yoshiro Nishiwaki4, Hiroyuki Konno6, and Katsunori Aoki6
Faculty of Home Economics, Aichi Gakusen University, Okazaki, Aichi, Japan, 2Clinical Nutritional Management, Hamamatsu Medical
Center, Hamamatsu, Shizuoka, Japan, 3Division of Surgery, Iwata City Hospital, Iwata, Shizuoka, Japan, 4Department of Gastroenterological
Surgery, Hamamatsu Medical Center, Hamamatsu, Shizuoka, Japan, 5Surgery, Shizuoka City Shimizu Hospital, Shizuoka, Japan, 6Department of Emergency Medicine, Hamamatsu University School of Medicine, Hamamatsu, Shizuoka, Japan
1

Abstract : The effects of early enteral arginine-rich nutrition (EAN) were analyzed among patients undergoing
curative-intent total gastrectomy for gastric cancer. There were 19 patients in this prospective study, all randomly assigned to either a parenteral nutrition (PN) group or an EAN group for the first seven days after surgery. The
EAN group received 1.8-fold greater arginine (10.1 g / day) compared with the PN group, which was administeredthrough an enteral tube inserted into the jejunal loop. Both groups were provided almost identical amounts of
total amino acids (54 g / day), and the total energy was set at 65% of the total requirement (25 kcal / kg / day). No
significant differences were observed between the two groups in postoperative complications, length of hospitalstay, oral intake, nutritional status, or body weight. The serum arginine profile was similar in the two groups,
as it decreased significantly on postoperative day (POD) 1, and gradually returned to preoperative levels by
POD 7. The nitrogen balance remained negative until POD 7 in the PN group, but turned neutral at POD 7 in
the EAN group. While we could not confirm body weight loss improvement, these results suggested that earlyarginine-rich enteral nutrition could improve the nitrogen balance after total gastrectomy. J. Med. Invest. 70 :
325-333, August, 2023
Keywords : early enteral nutrition, arginine, nitrogen balance, gastric cancer

INTRODUCTION
Despite advances in surgical techniques and perioperative
management of total gastrectomy for gastric cancer, postoperative complications such as surgical site infection (SSI), anastomotic leakage, and postoperative intestinal paresis cannot
always be avoided, and early postoperative oral or enteral nutritional support has been employed to reduce the incidence and theseverity of these complications (1). Based on the Japanese Guidelines for Nutrition Support Therapy in Adult and Pediatric Critically Ill Patients (2), early enteral nutrition should start within
48 hours after an operation. Enteral nutrition support cannot be
conducted for patients with milk allergies, and is likely to havegastrointestinal complications such as abdominal distensions
and diarrhea. Even considering these disadvantages, enteralnutrition is more acceptable from a physiological standpoint,
has fewer complications, and is less expensive, compared withparenteral nutrition. The European Society of Clinical Nutrition
and Metabolism (ESPEN) guidelines on surgery recommend a
total energy supply of 25 kcal / kg / day (3), but, in actual practice,
it is hard to deliver this amount in the first seven days after
surgery. Furthermore, the Canadian clinical practice guidelines
Abbreviations used :ASPEN, American Society for Parenteral and Enteral Nutrition ; BCA As, branched chain amino acids ; BMI, body massindex ; CRP, C-reactive protein ; DAO, diamine oxidase activity ; EAN,
enteral arginine-rich nutrition ; EN, enteral nutrition ; ESPEN,
European Society for Clinical Nutrition and Metabolism ; IL-6,
interleukin-6 ; iNOS, nitric oxide synthase ; NO, nitric oxide ; PN,
parenteral nutrition ; POD, postoperative day ; PPN, peripheral parenteral nutrition ; RE, retinol equivalents ; SGA, subjective global
assessment ; SSI, surgical site infection

underscore the importance of protein dosage based on the resultsof intentional underfeeding studies of hypocaloric enteral nutrition (4). Arginine is a conditional amino acid, along with cysteine, glutamine, tyrosine, glycine, ornithine, proline, and serine,
and is a precursor for the synthesis of nitric oxide, polyamines
and nucleic acids ; and the latter two are crucial for protein synthesis. It also enhances wound healing and increases hormone
secretion with protein assimilation. In animal models, early
postoperative arginine-rich enteral nutrition promoted woundhealing (5), and suppressed bacterial translocation in the upper
intestinal lumen (6, 7), indicating the clinical usefulness of early
postoperative amino acid-rich enteral nutrition. Several reports
have indicated that arginine is crucial for appropriate nitrogenbalance recovery from starved conditions (8, 9). Based on thesefindings, the ESPEN and American Society for Parenteral andEnteral Nutrition (ASPEN) guidelines recommend arginine as aconstituent of enteral nutrition formulations provided to patientsduring the early postoperative phase after injury or elective
surgery (10, 11). However, only a few reports have assessed theeffects of early postoperative arginine-rich enteral nutrition,
without immunomodulating agents, among patients undergoing
elective gastrointestinal surgery.
Received for publication October 4, 2022 ; accepted March 8, 2023.
Address correspondence and reprint requests to Yasuko Okamoto,
Faculty of Home Economics, Aichi Gakusen University, 28
Kamikawanari, Hegoshi-cho Okazaki, Aichi 444-8520, Japan andFax : +81-0564-34-1270. E-mail : yako.okamoto65@gmail.com

The Journal of Medical Investigation Vol. 70 2023

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Y. Okamoto, et al. Arginine enriched EN after total gastrectomy

Therefore, the aim of this study was to investigate whether ornot, compared to peripheral parental nutrition, early postoperative arginine-rich enteral nutrition improves nitrogen balanceand suppresses weight loss in patients undergoing total gastrectomy in the first seven days after surgery. Specifically, thearginine-rich enteral nutrition (EAN) group was given 1.8-foldgreater arginine, compared with the peripheral parenteral nutrition (PN) group. Due to a limitation in the number of available
injection solutions, we could not match the total amount of aminoacids and total energy of the two groups. Simanuki (12) reported that the nitrogen balance is proportional to total amount of
nitrogen intake, while nitrogen balance does not depend on the
non-protein energy intake. Therefore, the total amount of aminoacids was set so that it was almost identical in both groups (54g / day) at around 90% of the total requirement (60 g / day) (3), andtotal energy was set at around 65% of the total requirement (25kcal / kg / day) in both groups.

MATERIALS AND METHODSPatients and study design

This prospective study included 19 gastric cancer patients who
underwent curative total gastrectomy between January 2010
and December 2011 at the Hamamatsu Medical Center. The
age range of the patients was 56-82 years, with a median age of
71 years. The average values for age, height, and weight of thesubjects were 69.6 ± 7.2 years, 166.2 ± 7.1 cm and 56.7 ± 13.3 kg
for males, and 71.2 ± 10.7 years, 150.7 ± 3.9 cm and 45.0 ± 10.2
kg for females (means ± SD), respectively. The study protocol
was approved by the Ethical Committee of the Hamamatsu
Medical Center (No.21-10), and was registered in the UMINCTR as a clinical trial (UMIN000026770). All of the patientsprovided written informed consent. The inclusion criteria wereas follows : 1) Patients with good performance, who did not haveany other severe disease. 2) Patients who did not suffer from preoperative malnutrition, defined as unintentional weight loss of atleast 10%-15% within the previous 3-6 months and a body massindex (BMI) of < 18 kg / m2. 3) Patients with clinical stages of gastric cancer that were less than Stage Ⅳ. 4) Patients who agreed
to give their informed consent. Patients with milk allergies were
excluded because enteral nutrition support was not appropriate.
All of the patients were randomly assigned using a sealed envelope system to one of 2 groups for the postoperative nutritional
supplementation, specifically, parenteral nutrition (PN) alone(PN group) or those who received early enteral arginine-rich
nutrition (EAN) along with parenteral nutrition (EAN group).
A pair of opaque envelopes were prepared for each patient. The
envelopes contained a sheet of paper with either PN or EAN
written on it. After the patients had consented to the conditionsof the study, each patient chose one of envelopes, and then they
were offered nutritional treatment. We did not adjust the total
number of patients in each group. As a result of the randomization by using the envelope system, 12 and 8 patients wereassigned to the PN group and the EAN group, respectively. Afterthe surgical operation, one of the patients in the EAN group was
diagnosed as Stage IV. This patient was excluded from the EAN
group, and so the total number of patients was 19. As shown in
Table 1, all of the other patients satisfied the inclusion criteria.
The distribution of the clinical stages of gastric cancer among thepatients was as follows : 6 patients in Stage I, 7 in Stage II, and6 in Stage III.
During the gastrectomy operations, perigastric lymph nodes
were dissected and reconstruction was performed using theRoux-en-Y technique after total gastrectomy. In the EAN groupalone, an enteral tube, 140 cm in length, was inserted into thejejunal loop and placed approximately 15-20 cm on the anal sideof the lowest anastomosis. All of the other procedures were similar for the two groups.

Nutrition protocol and treatment schedule
Four types of injection solutions were used for the peripheral
parenteral nutrition (PPN), viz., one pack of Lactec D Injection (100 kcal / 500 mL) (Otsuka Pharmaceutical Factory. Inc.,
Tokushima, Japan) that contained 25 g glucose, 18 mEq lactate,
65 mEq Na, 2 mEq K, 1.5 mEq Ca, and 55 mEq Cl ; one packof Lactec Injection (0 kcal / 500 mL) (Otsuka Pharmaceutical
Factory. Inc., Tokushima, Japan) that included 14 mEq lactate,
65 mEq Na, 2 mEq K, 1.5 mEq Ca, and 55 mEq Cl ; one packof BFLUID Injection (420 kcal / 1,000 mL) (Otsuka Pharmaceutical Factory. Inc., Tokushima, Japan) that included 75 g
glucose, 35 mEq Na, 20 mEq K, 35 mEq Cl, 30.0 g free aminoacids (including 3.15 g of arginine), and 1.5 mg vitamin (Vit)
B1 ; and one pack of SOLDEM 3AG Injection (150 kcal / 500 mL)(TERUMO Inc., Tokyo, Japan) that provided 37.5 g glucose, 17.5
mEq Na, 10 mEq K, and 17.5 mEq Cl. Two types of supplements
were used for the enteral nutrition (EN), specifically, one pack ofarginine-rich nutritional supplement (100 kcal / 125 mL) (Isocal
Arginaid, Nestle Nutrition Company, Tokyo, Japan) that provided 5 g of protein (including 2.5 g L-arginine), 20 g carbohydrate,
500 mg Vit C, 125 μg retinol equivalents (RE) of Vit A, 2.4 μg Vit
D, 5 mg Vit E, 0.9 mg Vit B1, 0.8 mg Vit B2 , 10 mg zinc, and 100
μg folic acid ; and one pack of standard whole protein formula(300 kcal / 300 mL) (Sanette-SA : Sanwa Kagaku Kenkyusho Co.
Ltd., Nagoya. Japan), which contained 16.5 g protein (including
0.744 g L-arginine), 120 g carbohydrate, 45 mg Vit C, 225 μg RE
of Vit A, 0.96 μg Vit D, 6 mg Vit E, 0.45 mg Vit B1, 0.45 mg Vit
B2 , 4.2 mg zinc, and 300 μg folic acid.
The details of the experimental protocols implemented in the
EAN and the PN groups are shown in Fig. 1, and the amounts of
the nutrition provided from POD 1 to POD 7 are summarized inTable 2. The nutrition solutions administered were identical inboth groups on operation day (POD 0) and on POD 1. On POD 0,
1 pack of Lactec D and 1 pack of Lactec (0 kcal / 500 mL) were injected intravenously, which provided 100 kcal of total energy and
1,000 mL of water, respectively. On POD 1, parenteral nutrition
was supplied using 1 pack of BFLUID Injection and 2 packs of
SOLDEM 3AG, which provided 720 kcal, 2,000 mL, and 3.15 gof total energy, water, and arginine, respectively.
In the PN group, only the peripheral parenteral nutritional(PPN) support was provided. As shown in the right column ofFig. 1, on POD1, this group received 1 and 2 packs of BFLUID
Injection and a SOLDEM 3AG Injection, respectively, which
provided 720 kcal, 2,000 mL, 3.15 g and 30.0 g of total energy,
water, arginine and amino acids, respectively. On POD 2,1.5 and1 packs of these solutions were applied, which provided 780 kcal,
2,000 mL, 4.73 g and 45.0 g of total energy, water, arginine andamino acids, respectively. From PODs 3-7, 2 packs of BFLUID
Injection were provided daily, which provided 840 kcal, 2,000mL, 6.30 g and 60.0 g of total energy, water, arginine and aminoacids, respectively.
In the EAN group, water and electrolytes were provided
by the PPN through 1 pack of BFLUID Injection, which was
intravenously administered daily from PODs 2-7 until thepatients could consume sufficient amounts of food orally. The
enteral nutrition (EN) was started on POD 2, which was administered using an enteral feeding pump (Top enteral feeding
TOP6100 ; Fuji Electric F-Tech Co., Ltd., Japan or Kangaroo
Feeding Pump 624 Type ; Covidien Company, Japan). As shownin the left column of Fig. 1, on POD 2, 3 packs of arginine-rich
nutritional supplement were applied, so that the total amounts
were 720 kcal, 10.65 g and 45.0 g of total energy, and arginine

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The Journal of Medical Investigation Vol. 70 August 2023
Table 1. Preoperative patient characteristics.
PN group(n = 12)EAN group(n = 7)

P valueAge median (range)

71.3 (56-82)

67.8 (61-82)

0.37

Gender male or female

9:3

6:1

0.58

3

3

0.71

Gastric cancer UICC-TMN stage
I
II

5

2

III

4

2

IV

0

0

Class I

3

1

ASA physical status
Class II
Prognostic Nutritional Index (PNI)

0.58

9

6

46.7 ± 6.7

48.9 ± 4.5

0.48
0.25

Subjective Global Assessment (SGA)
Normal2

0

Mild malnutrition

10

7

Moderate malnutrition

0

0

0

0

Height (cm)Severe malnutrition

161.6 ± 7.7

165.1 ± 10.6

0.21

Body weight (kg)50.7 ± 11.2

59.8 ± 15.7

0.15

Body Mass Index (BMI) (kg / m2)

19.3 ± 3.5

21.6 ± 2.8

0.17

Serum albumin (g / dL)

3.8 ± 0.4

3.9 ± 0.3

0.92

Serum prealbumin (mg / dL)

19.4 ± 3.8

21.6 ± 5.8

0.33

Fisher ratio

2.8 ± 0.3

3.2 ± 0.4

0.12

Branched chain amino acid (nmol / mL)

363.3 ± 75.9

405.1 ± 78.2

0.27

Serum arginine (nmol / mL)

91.9 ± 23.5

80.2 ± 14.8

0.26

White blood cell (103 / μL)

6.7 ± 2.2

5.2 ± 1.2

0.13

C-reactive protein (mg / dL)

0.6 ± 0.9

0.7 ± 0.9

0.80Interleukin-6 (pg / mL)

3.0 ± 1.5

3.3 ± 1.9

0.66

Total lymphocyte count (TLC) ( / μL)

1508 ± 563

1471 ± 316

0.88

Data are presented as mean ± SD.

and amino acids, respectively. On POD 3, 3 and 2 / 3 packs of arginine-rich nutritional supplement and standard whole protein
formula were applied, respectively, so that the total amounts
were 920 kcal, 11.15 g and 56.0 g of total energy, and arginine
and amino acids, respectively. On PODs 4-7, 3 packs and then1 pack of arginine-rich nutritional supplement and standard
whole protein formula were applied, respectively, so that the
total amounts were 1,020 kcal, 11.39 g and 61.5 g of total energy,
arginine and amino acids, respectively. Total amounts of water
were adjusted as 2,000 mL by administration of water, and injection rates were 20 mL / h, 40 mL / h, 50 mL / h and 60 mL / h in
the PODs 2, 3, 4 and 5-7, respectively.
Oral nutrition was started on POD 7, and the total energy
given was adjusted to 25 kcal / kg / day to avoid unintentional
weight loss and severe Protein-Energy Malnutrition (3).

Evaluation items and nutritional assessment
Nutritional screening was performed using the nutritional
indexes : 1) subjective global assessment (SGA) (13, 14), 2) prognostic nutrition index (PNI) (15), and 3) total lymphocyte count(TLC). The performance status of the patients was evaluatedaccording to the American Society of Anesthesiologists PhysicalStatus (ASA-PS) standard (16). All of these assessments werealso performed perioperatively.

In order to investigate the nitrogen balance, we measured
the urinary excretion of urea nitrogen on PODs 1, 3, and 7. The
nutritional biochemistry assessment used serum levels of albumin, prealbumin, amino acids including arginine, which were
measured preoperatively and on PODs 1, 3, and 7. White blood
cell counts, serum levels of C-reactive protein (CRP) and interleukin-6 (IL-6) as inflammatory markers, and diamine oxidase
activity (DAO) as a marker of small intestinal damage, were alsomeasured. These analyses were performed on routinely drawn
blood samples and the data were retrieved from hospital records.

Statistical analyses
Male to female ratio and cancer stages between the groups
were compared using Fisher’s exact test. For other factors, weused Student’s t-test. A P value less than 0.05 was defined as statistically significant. All statistical analyses used JAMP (SASInstitute Japan, JMP Japan, Tokyo, Japan). Sample sizes were
estimated using Easy R Statistics software (EZR v2.7-1) with R(The R Foundation for Statistical Computing Platform, v.3.6.3)(17, 18). We expected a between group difference of 1.25 SD,
which required a sample size of 8 to discriminate between thetwo groups with a one-sided α error of 0.05 and a power of 0.8.

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Figure 1. Study design and treatment schedule.

The left and right columns represent the contents of the enteral arginine-rich nutrition (EAN) and parenteral nutrition (PN) groups,
respectively. The upper and lower rows represent the quantities of energy and amino acids applied per day, respectively. In the upper row,quantities of energy applied by the enteral nutrition (EN) and peripheral parenteral nutrition (PPN) are presented by white and grey blocks,
respectively. The blocks in the figure represent the applied amounts of energy in kcal / day. In the lower row, the quantities of arginine
applied by the EN and PPN are indicated by white and grey blocks. The blocks in the figure represent the applied amounts of amino acids ing / day. In the EAN group, the daily amounts of arginine were 3.2 g, 10.7 g, 11.1 g, 11.4 g on postoperative days of 1, 2, 3, and 4-7, respectively.
Those values were almost twice that shown in the PN group. The other amino acids (Other a.a.) supplied by the EN and PPN are presented
by upper-left and upper-right diagonal pattern blocks, respectively. For the EAN group, daily total amount of amino acids were 30 g, 45 g, 56 g,
61.5 g on postoperative days of 1, 2, 3, and 4-7, respectively. These values are almost the same as those in the PN group.

Table 2. Nutrition from POD 1 to POD 7
PN group(n = 12)EAN group(n = 7)

5,700

6,440

P value

Total amount for 7 days
Energy (kcal)
Total amino acids (g)

375

377

Arginine (g)

39.38

70.52

Average amount per day
Energy (kcal / day)814 ± 47920 ± 141

Total amino acids (g / day)

53.6 ± 11.8

53.9 ± 12.2

0.09
0.97

Arginine (g / day)

5.63 ± 1.24

10.08 ± 3.07

0.004

16.8 ± 3.9

16.1 ± 3.5

0.70(67.4)(64.5)

Average amount per kg per day
Energy (kcal / kg / day)(% of 25 kcal / kg / day)Total amino acids (g / kg / day)

1.11 ± 0.26

0.94 ± 0.08

0.17

Arginine (g / kg / day)

0.116 ± 0.027

0.177 ± 0.038

0.008

Data are presented as mean ± SD.

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The Journal of Medical Investigation Vol. 70 August 2023
RESULTSAs a result of the randomization using the envelope system, 12
patients and 7 patients were assigned to the PN group and theEAN group, respectively. Using sample size calculations, a pairof sample sizes of 12 and 7 was enough to discriminate 1.25 SD
differences between the two groups with a one-sided α error of
0.05 and a power of 0.8.
There were no significant differences between the PN groupand the EAN group in the preoperative factors, such as age,gender, cancer stage, PNI, SGA, BMI, ASA-PS, and nutritional
and inflammatory markers (Table 1). The PNI were 46.7 ± 6.7 for
the PN group and 48.9 ± 4.5 for the EAN group, so there were no
statistical differences shown between the two groups. The TLC
were 1,508 ± 563 for the PN group and 1,471 ± 316 for the EAN
group, so both patient groups were in the mild malnutrition
range without statistical differences. The SGA values also indicated the mild malnutrition condition in both groups. Averageamounts of nutrition were calculated for 7 days from POD 1 to
POD 7. The results are shown in Table 2. There were no significant differences between the PN group and the EAN group in
the total energy and the total amino acids (P > 0.05), and only theamounts of arginine in the EAN group were significant larger
than those in the PN group (P < 0.01). The lymphadenectomy
scale, the surgical operation time and the blood loss are shownin Table 3, and there were no significant differences between
the PN group and the EAN group. Postoperatively, no adverse
events such as anastomotic leakage or severe infection occurred.
No statistically significant differences were noted between thetwo groups in other factors, such as the occurrence of complications and the number of additional antibiotic treatments, or thelength of the hospital stay. Initiation of oral nutrition tended tobe later in the EAN group. (Table 3).
Postoperatively, inflammation markers, i.e., CRP and IL-6
levels were significantly higher on POD 1 compared to preoperative levels, but were not different between the two groups (Fig. 2
A, B, C). There was no difference in the DAO levels between thegroups during the peri-operative period (Fig. 2D). Prealbumin,
the most convenient nutritional marker, decreased from POD 1
to POD 3, but there was no difference between the two groups.
On POD 1, serum albumin levels fell significantly, comparedwith preoperative values, but there was no difference between
the two groups (Fig. 3A, B). BCAA increased on POD 3 in bothgroups, and while the Fisher ratio remained unchanged on POD
1, it improved on POD 3, but there was no difference between
the two groups (Fig. 3C, D). As shown in Fig. 4A, arginine
concentration decreased significantly on POD 1 in both groups
compared with preoperative levels (P < 0.001), and returned topreoperative levels by POD 3 in both groups. Nitrogen balance
became negative on POD 1 and remained so till POD 7 in the PN
group, indicating protein hypermetabolism. In contrast, in the
EAN group, it turned positive on POD 7 (Fig. 4 B). Regarding
body weight, there was no decrease in body weight or BMI at
POD 7 in either group (P > 0.05), and the balance of body weighttended to be positive in the EAN group, but these differenceswere not statistically significant (Fig. 4C). At the time of discharge, body weight and BMI decreased significantly, but there
were no significant differences between the EAN and PN groups

Table 3. Postoperative factors.
PN group(n = 12)EAN group(n = 7)

P value

Oral nutrition start day (POD) mean ± SD

7.1 ± 0.3

10.1 ± 0.3

0.08

All complications, n (%)

12 (100.0）

7 (100.0)

0.50
0.70

Classification of surgical complications, n (%)
Grade I

7 (58.3)

0 (0.0)

Grade II

2 (16.6)

3 (42.9)

Grade IIIa

2 (16.6)

2 (28.5)

Grade IIIb

0 (0.0)2 (28.5)

Grade IV

1 (8.3)0 (0.0)

Grade V

0 (0.0)0 (0.0)

D1

3

0

D2

9

7

Surgical operation time (h) mean ± SD

4.3 ± 0.5

4.5 ± 0.5

0.41

Lymphadenectomy scale
0.26

Surgical blood loss (mL) mean ± SD

490 ± 281590 ± 353

0.53

Diarrhea, n (%)

5 (41.6)

4 (57.1)

0.54

Surgical site infection (SSI), n (%)

2 (16.7)

2 (28.5)

0.57

Others, n (%)

8 (66.7)

6 (85.6)

0.15

0

7

4

0.14

1

5

1

2

0

1

Number of additional antibiotics

3
Post-operative hospital stay (days) mean ± SD

0132.7 ± 44.1

20.2 ± 8.1*Classification of surgical complications were based on the Clavien-Dindo scale (37).

0.36

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Y. Okamoto, et al. Arginine enriched EN after total gastrectomy

Figure 2. Changes in inflammatory markers.

This figure shows the means and standard error of the means obtained before the operation (Preope), and at postoperative days 1, 3
and 7 (POD 1, POD 3 and POD 7). The bold and dotted lines represent the results of the PN and EAN groups, respectively. A) Numberof white blood cells. B) Serum concentration of C-reactive protein. C) Serum concentration of interleukin-6. D) Serum diamine oxidase
activity. The symbols (†) represent statistically significant difference values between the Preope and POD 1 for the PN and the EAN
groups (P < 0.001).

Figure 3. Changes in nutritional indices.

This figure shows the means and standard error of the means obtained before the operation (Preope), and at postoperative days 1, 3
and 7 (POD 1, POD 3 and POD 7). The bold and dotted lines represent the results obtained for the PN and EAN groups, respectively.
Serum concentrations of A) prealbumin, B) albumin, and C) branched chain amino acid (BCAA). D) Fisher ratio.

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331

Figure 4. Changes in arginine, nitrogen balance, and body weight and body mass index (BMI).

A) Serum arginine concentration. This figure shows the means and standard error of the means obtained before the operation (Preope),
and at postoperative days 1, 3 and 7 (POD 1, POD 3 and POD 7). The symbols (†) represent the statistically significant difference
values between the Preope and POD 1 for the PN and the EAN groups (P < 0.001). B) Nitrogen balance. This shows the means
and standard error of the means of POD 1, POD 3 and POD 7. The symbols (‡) represents statistically significant difference values
between the POD 3 and POD 7 for the EAN group (P < 0.05). C) Changes in body weight and BMI at POD 7, compared with values
obtained before the operation. D) Changes in body weight and BMI at discharge, compared with values obtained before the operation.
The means and standard error of the means of body weight and BMI are shown. The bold and dotted lines in A and B represent theresults for the PN and EAN groups, respectively. The white and black blocks in C and D are values obtained for the PN and EAN
groups, respectively.

(Fig. 4D). Due to faulty communication with the patients, we
could not get body weight or BMI for 1 patient in each group.

DISCUSSION
In this study we investigated whether early postoperative
arginine-rich enteral nutrition improved nitrogen balance andsuppressed weight loss in patients undergoing total gastrectomy. Under normal conditions, 60 g protein and 6 g arginine are
required per day by a 50 kg adult persons (19), and the average
dietary intake of arginine for all ages and genders has been estimated to be around 4.2 g per day (20) . Therefore, we provided
5.6 g / day of arginine on the average from POD1 to POD 7 in the
PN group. Arginine can be synthesized from citrulline, but as its
production is limited, serum concentration of arginine decreases
when demand increases, i.e., such as during surgery, injury, or
infection. Arginine is a precursor for nitric oxide (NO), a signaling molecule for both polyamines and nucleic acids, which areimportant for protein synthesis. It may also indirectly promote
protein synthesis by acting on the pituitary gland to encourage
the secretion of growth hormones and prolactin (21, 22). Arginine
also enhances wound healing and increases hormone secretion
with protein assimilation. Hence, we provided 10.1 g / day of arginine on the average from POD 1 to POD 7 in the EAN group. On
POD 1, 3.15 g / day of arginine was administered to both groups,
but this amount is expected to be too little for the patients.
Indeed, serum arginine on POD 1 decreased to almost 50% of
the preoperative levels in both groups, suggesting an increase inarginine consumption, which was restored after POD 3. Notably,
despite a 1.8-fold enrichment of arginine, no significant differences in serum arginine were seen between the EAN and thePN groups, and this absence of elevated serum arginine levelsin the EAN group indicates that the 10.1 g / day arginine might
have been utilized for protein synthesis, which was necessary
for healing. The early recovery of the nitrogen balance at POD
7 in the EAN group supports this hypothesis. Nitrogen balance,
which represents the difference between administered nitrogenvolume and excreted nitrogen volume, is an index that demonstrates the state of protein metabolism in living organisms. It is
positive in a normal state, but remains negative during protein
hypermetabolism. In animal models, arginine enriched feeding
improved the nitrogen balance and body weight of protein-depleted rats (23), increased muscle creatine and improved the nitrogen balance of the rats after laparotomy (24). It also increased
the protein turnover rate and the nitrogen balance significantly
increased in burned rats (25). Even though only a small numberof studies have been conducted using human patients, high dosesof arginine (30 and 25 g / day) improved nitrogen balance andalso decreased loss of body weight after cholecystectomy (26)
and also in post-operated cancer patients (27). It is crucial that,even though body weight balance did not recover, the 1.8-fold enrichment of arginine recovered the nitrogen balance in the EAN
group at POD 7 after the total gastrectomy. Compared with thehigh dosage of arginine (30-25 g / day), medium dosage (11 g / day)is more suitable to make formula, not only for EAN, but also PN.
During inflammation, NO is produced from arginine by the
enzyme inducible nitric oxide synthase (iNOS) (28, 29). Highly

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Y. Okamoto, et al. Arginine enriched EN after total gastrectomy

intense inflammatory responses have been reported along with
EAN, but these may not have been caused by arginine because
those experiments did not involve the administration of arginine(29, 30). In the present study, no statistically significant differences in the inflammatory response were noted between the twogroups, and similarly, no significant difference was noted in thefrequency of postoperative complications, except diarrhea, which
is a common gastrointestinal complication during enteral nutrition. Bliss et al. have reported that diarrhea occurred in 2%-26%
of cases (31), and in our cohort, it was observed in around 50%of the patients in the EAN and PN groups, with no significant
difference shown between the groups. Enteral nutrition administered via a jejunal fistula should proceed slowly and carefullyusing an enteral feeding pump, because nutrients administereddirectly into the intestines can, in many patients, lead to discomfort. Additionally, as patients may be unable to tolerateenteral nutrition after suffering diarrhea once, adequate caution
is required. Moreover, as many cases of diarrhea are induced bywater-soluble contrast agents used during postoperative gastricfluoroscopy, clinicians must confirm if enteral nutrition was thecause of the diarrhea (32).
As mentioned above, nitrogen balance was restored by POD
7 in the EAN group, whereas it remained negative in the PN
group and nutritional indices tended to improve, but there wasno significant difference between the two groups at POD 7, nor
at discharge. This represents a major limitation of this study. We
attribute the absence of statistical significance to the small sample size. For example, detecting a difference of approximately 0.5
SD in body weight, with a one-sided α error of 0.05 and a powerof 0.8, requires a sample size of 64. Improving the accuracy ofbody weight measurement is also beneficial to reduce sample
size. As far as we found by searching in the literature, there
are only a few studies reporting on the long term effect of arginine-enriched nutrition (33, 34), it might be true that 7-days is
too short to evaluate the body weight recovery, which suggested
conducting a study in the future on the long term effect, for aperiod longer than a month. Despite the identical protein administration (54 g / day ; 1 g / kg / day) in both groups, the poorer recovery of body weight in the EAN group points toward a shortagein protein dosage, potentially due to the higher turnover during
the postoperative period. In healthy elderly subjects consuming
adequate protein (1.0-1.2 g / kg / day), the decrease in lean bodyweight during a period of 3 years was reduced by 40%, comparedwith those consuming less protein (0.8 g / kg·day) (35, 36). Additionally, maintaining identical protein intake probably ensured
no adverse effects on mortality and length of stay between thetwo groups with a calorie intake at 42%-50% and 72%-75% byenteral nutrition. Importantly, the Canadian clinical practiceguidelines agree on the need for maintaining protein intake(4). Despite an extensive literature search, we could not findstudies that have evaluated the effect of protein and arginine
enrichment in postoperative enteral nutrition. Hence, in thenear future, we plan to assess the advantages of high protein andarginine intake to confirm these results.

metabolism in this group. Even though we could not confirm
improvement in the body weight loss, these results suggested
that early arginine-rich enteral nutrition could improve nitrogenbalance after total gastrectomy.

CONFLICTS OF INTEREST
The authors of this research did not receive any specific grants
from funding agencies in the public, commercial, or non-profit
sectors. The authors all hereby declare no conflict of interest.

ACKNOWLEDGEMENTS
The authors would like to express their sincere thanks to thepatients who agreed to participate in this study and also thankthe surgical ward staff. Furthermore, we would also like tothank the companies that provided us with equipment employedin the study (Fuji Electric F-Tech Co., Ltd., and Covidien Company, Japan). We would also like to extend our thanks to Dr. Y.
Seo (National Institute for Physiological Sciences : SEIRIKEN)
for providing helpful comments. Furthermore, we thank Nestle
Nutrition, Japan for supporting our research, and Mr. D. Vancil
for correction of the English language text in the manuscript.

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