Abstract

Background

   Gastric cancer is a prevalent malignancy worldwide, with early
   detection and treatment being vital to improving patient outcomes.
   Amino acids (AAs), as essential regulators in cancer cell metabolism,
   are implicated in the progression and response to treatment.

Methods

   This study aimed to investigate the dynamics of plasma AA levels in
   gastric cancer patients preoperatively, postoperatively, and following
   nutritional intervention, comparing them to healthy controls. We
   analyzed 22 AAs in plasma samples from 66 gastric cancer patients and
   55 healthy individuals.

Results

   The results show that significant preoperative elevation of AAs, such
   as threonine (Thr), serine (Ser), proline (Pro), lysine (Lys), arginine
   (Arg), citrulline (Cit), glutamine (Gln), glycine(Gly), and alanine
   (Ala), with reductions in taurine (Tau), phenylalanine (Phe) and
   hydroxylysine (Hylys). Post-surgery, levels of many AAs decreased
   markedly, but were partially restored following nutritional
   intervention, with some exceeding preoperative values. Nevertheless,
   specific AAs, including methionine (Met) and Gln, remained lower than
   in healthy controls, suggesting potential benefit from targeted
   supplementation. Correlations between AA changes and postoperative
   recovery indicators were observed; notably, increased postoperative
   Thr, Ser, Tau, tyrosine (Tyr), glutamic acid (Glu), and Hylys levels
   were associated with quicker gastrointestinal recovery. Additionally,
   several AAs, such as Pro, Lys, Tyr, Met, Cit, and Glu, were linked to
   reduced inflammation, as reflected by C-reactive protein (CRP) and
   white blood cell (WBC) levels, suggesting roles in the postoperative
   immune response. Pathway enrichment analysis highlighted metabolic
   pathways involving Gly, Ser, Phe, Tyr, Lys, and Met as critical in the
   recovery process.

Conclusions

   These findings underscore the potential of AA profiles as biomarkers
   for postoperative recovery and suggest nutritional interventions
   targeting specific AAs may improve outcomes.

Supplementary Information

   The online version contains supplementary material available at
   10.1186/s12957-025-03729-x.

   Keywords: Gastric cancer, Perioperative recovery, Amino acids profiles,
   Biomarker, Nutritional intervention

Introduction

   Gastric cancer is one of the most common malignant tumors of the
   digestive system worldwide, and early diagnosis and treatment are
   critical for improving patient survival rates [[44]1, [45]2]. Metabolic
   changes before and after surgery are key to understanding disease
   progression and assessing treatment efficacy. AAs play a significant
   role in cancer metabolism, and studying changes in amino acid levels
   can provide valuable insights into postoperative recovery and prognosis
   [[46]3].

   AAs, as fundamental metabolites and regulatory molecules, have
   extensive effects on cancer cells. AAs serve as the primary nitrogen
   source for hexosamine, nucleotides, and other nitrogen-containing
   compounds in cancer cells [[47]4, [48]5]. Furthermore, AAs regulate
   gene expression and protein phosphorylation cascades. For example,
   sufficient essential AAs stimulate MYC oncogene mRNA translation by
   inhibiting the GCN2-eIF2A-ATF4 pathway, leading to MYC-dependent
   transcriptional amplification [[49]6]. Gln, Arg and leucine (Leu)
   induce cell-specific phosphorylation of mTORC1, thus regulating
   intracellular protein turnover [[50]7]. Additionally, Gln, Cit and Met
   can activate the mTORC1 signaling pathway by modulating the
   concentration of phosphatidic acids within the late endosome/lysosome
   system and the activity of Ras homologs enriched in the brain [[51]8].
   Conversely, AA metabolism is also tightly regulated and closely
   interconnected with other metabolic networks, such as lipid and glucose
   metabolism [[52]9].

   Although AA concentrations in the circulation remain stable under
   healthy conditions, numerous studies have shown that various cancers,
   including gastric, colorectal, lung, and breast cancers, can alter AA
   levels [[53]10, [54]11]. In recent years, the AminoIndex has garnered
   considerable attention. This index was developed by establishing a
   multivariate profile from the spectrum of free AAs in blood, which aids
   in assessing the likelihood of certain health conditions and diseases
   [[55]12]. Using these indices, researchers have differentiated various
   cancer types, including gastric, lung, colorectal, breast, prostate,
   gynecological, and pancreatic cancers, from healthy controls [[56]13,
   [57]14]. However, the patterns of AA alterations differ across cancer
   types, and further investigation is needed to determine whether changes
   in AA profiles correlate with postoperative prognosis and the risk of
   complications in cancer patients.

   This study included 66 early-stage gastric cancer patients and 55
   healthy controls who were admitted for physical examinations during the
   same period. Plasma samples were collected from gastric cancer patients
   preoperatively, on the first postoperative day, and on the third
   postoperative day, as well as from healthy controls. AAs were profiled
   via mass spectrometry, which measured 22 AAs in total, including 8
   essential and 14 common nonessential AAs. We analyzed differences in
   plasma AA expression profiles between gastric cancer patients and
   healthy controls, as well as changes in amino acid levels in patients
   before and after surgery. Furthermore, we examined the relationship
   between these changes and the clinical prognosis of patients, exploring
   relevant metabolic pathways involving these altered AAs. This study
   also aimed to investigate whether variations in AA profiles could serve
   as potential indicators for assessing postoperative complication risks,
   recovery rates, or long-term prognoses.

Materials and methods

Patient characteristics

   This retrospective study assessed 66 gastric cancer patients enrolled
   in a disease group who underwent cancer surgery at the Department of
   Gastrointestinal Surgery at the Second Affiliated Hospital of Soochow
   University from November 2021 to October 2022 and randomly selected 55
   healthy individuals in the control group who underwent routine health
   examinations at the same hospital during the same period, with no
   history of malignancy.

   The inclusion criteria were as follows: (1) aged 18 or older, (2)
   underwent gastric cancer surgery, (3) had an Nutritional Risk
   Score-2002(NRS-2002) score of ≥ 3, (4) had a plasma amino acid
   concentration of 18 or older, (4) received parenteral nutrition
   treatment (total energy for parenteral nutrition set at 1400 kcal,
   protein intake at 61 ~ 63 g, fluid volume at 1700 ~ 1840 mL), and (5)
   had no prior cancer-related treatments such as radiotherapy or
   chemotherapy.

   The exclusion criteria were as follows: (1) patients who underwent
   prior gastric surgeries for nontumour reasons, (2) had NRS-2002
   scores < 3, (3) weighed less than 46 kg, (4) received radiotherapy and
   chemotherapy before surgery, and (5) had incomplete patient data.

Data collection

   In the disease group, relevant clinical information was gathered,
   including height, weight at admission and discharge, surgical method,
   postoperative time to first flatus, postoperative time to first bowel
   movement, postoperative hospital stay, and preoperative and
   postoperative day 1 and day 3 blood routine and biochemical indicators,
   such as WBC and CRP levels.

   Amino acid profiles were performed for both the disease group and the
   control group. Amino acid concentrations were determined using liquid
   chromatography-tandem mass spectrometry (LC–MS/MS) with a Qlife Lab
   9000 system (Nanjing Pinsheng Medical Technology Co., Ltd., China). A
   total of 22 AAs were detected and analyzed, including 8 essential AAs:
   Phe (Phe), tryptophan (Trp), isoleucine (Ile), Leu, Met, Lys, valine
   (Val), and Thr, as well as 14 nonessential AAs: Gly, Ser, sarcosine
   (Sar), aspartic acid (Asp), cystine (Cys), Glu, Gln, Hylys, Pro, Arg,
   Tyr, Ala, Tau, and Cit.

   This study was approved by the Ethics Committee of the Second
   Affiliated Hospital of Soochow University.

Statistical analyses

   Continuous variables are expressed as medians and interquartile ranges
   (IQRs), whereas categorical variables are presented as counts and
   percentages. The chi-square test was used for between-group comparisons
   of categorical data, and the t test or Mann‒Whitney U test was used for
   between-group comparisons of continuous data. Metabolic pathway
   analysis was performed via MetaboAnalyst 5.0 software. All the
   statistical analyses were conducted via SPSS 22.0 (IBM Corp., Armonk,
   NY, USA) and GraphPad Prism 8.0 (GraphPad, San Diego, CA, USA). A
   two-sided P value less than 0.05 was considered statistically
   significant.

Results

Patient characteristics

   The basic characteristics and clinical information of the 66
   early-stage gastric cancer patients and 55 healthy controls included in
   this study are shown in Table [58]1. Due to the different impacts on
   amino acid absorption patterns among different surgical approaches, two
   main surgical approaches were used to classify the patients: 52
   patients underwent partial gastrectomy, and 14 patients underwent total
   gastrectomy. All patients began receiving parenteral nutritional
   therapy postoperatively. The parenteral nutrition treatment adopts the
   “all-in-one” approach, in which the total energy for parenteral
   nutrition is set at 1400 kcal, the protein intake is 61 ~ 63 g, and the
   fluid volume is 1700–1840 mL.

Table 1.

   Patient characteristics
   Cases (n = 66) Controls(n = 55)
   Age,years (IQR) 64.70 ± 11.34 67.71 ± 8.66
   Gender
   Males 39 35
   Females 27 20
   BMI^a (kg/m^2)
   < 18.5 2 8
   18.5 ~ 24.0 47 26
   24.0 ~ 28.0 13 17
   ≥ 28.0 4 4
   Operation
   Partial gastrectomy 52
   Total gastrectomy 14
   Postoperative time to first flatus 3.22 ± 0.80
   Postoperative time to first bowel movement 3.98 ± 1.29
   Postoperative hospital stays 11.8 ± 8.80
   [59]Open in a new tab

   ^aBMI Body Mass Index

Differences in amino acid changes

   The levels of various AAs in the plasma of healthy controls,
   preoperative gastric cancer patients, and postoperative gastric cancer
   patients on the first and third days are shown in Supplementary
   Table 1S. By comparing the changes in amino acid levels between healthy
   controls and gastric cancer patients before surgery, on the first
   postoperative day, and on the third postoperative day (postnutritional
   intervention), this study revealed that 12 AAs in the serum of gastric
   cancer patients were significantly different from those in the healthy
   control group (P < 0.05). Among these, the levels of Thr, Ser, Pro,
   Lys, Arg, Cit, Gln, Gly and Ala were significantly increased in the
   plasma of gastric cancer patients, whereas the levels of Tau, Phe and
   Hylys were markedly decreased (Fig. [60]1).

Fig. 1.

   [61]Fig. 1
   [62]Open in a new tab

   Differences in plasma amino acid content between preoperative gastric
   cancer patients and healthy subjects

   Comparisons of preoperative and postoperative amino acid levels
   revealed a significant decrease in the levels of most AAs, including
   Ile, MEA, Asp, Thr, Ser, Pro, Tau, Tyr, Lys, Arg, Sar, Cit, Gln, Glu,
   Gly, Ala, and Hylys, after surgery (Fig. [63]2).

Fig. 2.

   [64]Fig. 2
   [65]Open in a new tab

   Difference in plasma amino acid content between preoperative and
   postoperative gastric cancer patients

   By implementing nutritional intervention in postoperative patients, we
   further compared the changes in amino acid levels on the third day
   postsurgery with those before and immediately after surgery. The
   results indicated the following: First, compared with immediately
   postoperative levels, the levels of Ile, MEA, Val, Asp, Thr, Trp, Leu,
   Arg, Cys, Glu, Phe, AAD, and Hylys significantly increased by the third
   day postintervention. Among these, the levels of Ile, Asp, Trp, AAD,
   and Hylys were not different from the preoperative levels. However,
   MEA, Thr, Arg, and Glu remained lower than the preoperative levels,
   with MEA and Glu also below those in healthy individuals, suggesting
   that nutritional supplementation did not fully restore these AAs to
   optimal levels. Second, the levels of Val, Leu, Cys, and Phe exceeded
   the preoperative values, with Val and Cys even surpassing the levels
   observed in healthy controls (Fig. [66]3). In addition, the level of
   Gln remained lower than the preoperative level postintervention but did
   not significantly differ from the level in healthy controls.

Fig. 3.

   [67]Fig. 3
   [68]Open in a new tab

   Changes in amino acid content in gastric cancer patients before and
   after surgery and after nutritional therapy

Correlations between postoperative amino acid content changes and exhaust
time, length of hospital stay, and inflammatory markers

   To investigate whether changes in the amino acid profile can serve as
   potential indicators for assessing postoperative complications,
   recovery speed, or long-term prognosis, we further analyzed the
   relationships between changes in amino acid levels in gastric cancer
   patients before and after surgery and clinical outcome indicators. We
   first examined the correlation between postoperative amino acid changes
   and the time to first flatus (Fig. [69]4). The results revealed a
   negative correlation between the postoperative changes in the Thr, Ser,
   Tau, Tyr, Glu, GABA, and Hylys levels and the time to first flatus in
   gastric cancer patients. These findings indicate that higher
   postoperative amino acid levels are associated with a shorter time to
   first flatus.

Fig. 4.

   [70]Fig. 4
   [71]Open in a new tab

   Correlation between postoperative amino acid changes and exhaust time
   in patients with gastric cancer

   Additionally, we analyzed the correlation between changes in amino acid
   levels before and after surgery and postoperative CRP levels in gastric
   cancer patients. As shown in Fig. [72]5A and B, higher levels of Ser,
   Pro, Leu, Tyr, Lys, Met, Cit, and Glu on the third postoperative day
   were associated with lower CRP levels. Furthermore, changes in Leu,
   Tyr, and Cys levels before and after surgery were negatively correlated
   with changes in CRP levels postoperatively. We also analyzed the
   correlation between changes in amino acid levels before and after
   surgery and postoperative WBC counts. As shown in Fig. [73]5C, changes
   in MEA, Pro, Lys, Tyr, Arg, Met, Gln, and Ala levels before and after
   surgery were negatively correlated with changes in WBC count
   postoperatively. This finding suggests that greater increases in these
   AAs are associated with smaller fluctuations in WBC counts. These
   findings similarly indicate that significant changes in these AAs may
   serve as potential predictors of patient recovery after surgery.

Fig. 5.

   [74]Fig. 5
   [75]Open in a new tab

   Correlation between postoperative amino acid changes and postoperative
   inflammatory markers (CRP and WBC) in patients with gastric cancer. A
   The changes of AAs before and after surgery were correlated with CRP on
   the third day after surgery. B Correlation between preoperative and
   postoperative amino acid changes and preoperative and postoperative CRP
   changes in patients. C Correlation between preoperative and
   postoperative amino acid changes and preoperative and postoperative WBC
   changes in patients

Pathway enrichment analysis of differential AAs

   We analyzed the AAs associated with time to first flatus and
   inflammation levels postsurgery and found that Ser, Tyr, Glu, Pro, Leu,
   Lys, and Met were consistently involved in at least two correlation
   analyses (Fig. [76]6A). Further pathway enrichment analysis revealed
   that these AAs are involved primarily in the following metabolic
   pathways: Gly and Ser metabolism, Phe and Tyr metabolism, Lys
   degradation, ammonia recycling, and Met metabolism (Fig. [77]6B).

Fig. 6.

   [78]Fig. 6
   [79]Open in a new tab

   Enrichment of metabolic Pathways for Differential AAs. A Venn diagram
   of AAs with correlations between changes in content and inflammatory
   markers. B Pathway enrichment of AAs

Discussion

   Numerous studies have demonstrated metabolic dysregulation, including
   disruptions in amino acid metabolism, in cancer patients. As
   fundamental components of proteins, AAs play crucial roles in
   sustaining normal physiological functions and meeting the nutritional
   and energetic demands of tumor cells [[80]9]. Amino acid preparations
   rich in branchedchain amino acids are recommended by many experts for
   cancer patients, and they are helpful for improving muscle loss,
   maintaining liver function, and balancing aromatic amino acids in
   cancer patients. Among them, ESPEN recommends supplementation doses
   ranging from 1 g/(kg·d) to 1.2–2.0 g/(kg·d) for tumor patients
   [[81]15], and the German guidelines for parenteral nutrition for tumor
   patients recommend amino acid supplementation of 1.2–1.5 g/(kg·d)
   [[82]16]. Previous research has shown that AAs undergo significant
   alterations in cancer, leading to the development of indices derived
   from these altered AAs, such as the amino index, which has been used
   for cancer screening and monitoring of cancer therapy [[83]14]. In this
   study, we investigated changes in the plasma amino acid profile of
   gastric cancer patients before and after surgery and following
   nutritional intervention and compared these profiles with those of
   healthy individuals. The results revealed a distinct pattern of amino
   acid changes in gastric cancer patients across these stages. This
   variation is likely the combined result of increased metabolic demands
   of the tumor, surgical trauma, and postoperative stress responses.

   The results of this study indicate that in gastric cancer patients,
   preoperative plasma levels of Thr, Ser, Pro, Lys, Arg, Cit, Gln, Gly,
   and Ala are significantly elevated, whereas Tau, Phe, and Hylys are
   markedly reduced. We believe that these differences are due primarily
   to a combination of factors, including the increased metabolic demands
   of the tumor, impaired digestive function, chronic malnutrition,
   systemic inflammatory response, and abnormal liver function [[84]17].On
   the first day postsurgery, the levels of numerous AAs, including Ile,
   MEA, Asp, Thr, Ser, Pro, Tau, Tyr, Lys, Arg, Sar, Cit, Gln, Glu, Gly,
   Ala, and Hylys, significantly decreased. We hypothesize that the
   postoperative reduction in amino acid levels may result from a
   combination of factors, including the stress response after surgery,
   changes in the metabolic state, alterations in liver function,
   inflammatory responses, and increased protein synthesis [[85]4]. These
   factors collectively lead to an elevated demand for AAs, which is
   reflected as a decrease in their concentrations in the blood. Following
   nutritional intervention, certain AAs (such as Ile, MEA, Val, Asp, Thr,
   Trp, Leu, Arg, Cys, Glu, Phe, AAD, and Hylys) had notably recovered by
   the third postoperative day, with some even surpassing preoperative
   levels. Despite the overall effectiveness of nutritional intervention,
   the levels of certain AAs, such as MEA and Glu, remained below those of
   healthy individuals, suggesting that increasing the content of these
   AAs for nutritional support or extending the intervention period may be
   beneficial, as previously reported [[86]18]. Additionally, the levels
   of Val and Cys exceeded those in the healthy group, indicating a marked
   response to nutritional intervention for these AAs. This could also
   reflect shifts in the patients' postoperative metabolic state.
   Therefore, it may be advisable to moderately reduce the doses of these
   AAs in postoperative supplements or shorten the duration of their
   nutritional intervention.

   To investigate the relationship between amino acid profile changes and
   postoperative recovery, this study further analyzed the correlations
   between amino acid levels and postoperative time to first flatus,
   inflammation levels, and WBC count. The results revealed that
   postoperative increases in Thr, Ser, Tau, Tyr, Glu, GABA, and Hylys
   were negatively correlated with time to first flatus, suggesting that
   elevated amino acid levels may reflect faster recovery of
   gastrointestinal function. This shorter time to first flatus may
   reflect a combination of factors, including recovery rate, protein
   synthesis, gastrointestinal function, nutritional support, the
   inflammatory response, and liver function recovery. These findings
   suggest that changes in amino acid levels may serve as potential
   biomarkers for the speed of postoperative recovery. In addition,
   postoperative levels of Ser, Pro, Leu, Tyr, Lys, Met, Cit and Glu were
   negatively correlated with CRP levels, and the decrease of CRP levels
   was correlated with cancer cell activity and postoperative inflammatory
   response. Therefore, these amino acids negatively correlated with CRP
   levels may help to evaluate the activity of tumor cells and the
   severity of postoperative inflammatory reaction. Similarly, changes in
   MEA, Pro, Lys, Tyr, Arg, Met, Gln, and Ala were negatively correlated
   with WBC changes, suggesting that these AAs may play a significant role
   in the postoperative immune response and could serve as potential
   biomarkers for postoperative recovery.

   Pathway enrichment analysis of AAs associated with both the time to
   first flatus and postoperative inflammation levels revealed that these
   AAs were mainly involved in the following metabolic pathways: Gly and
   Ser metabolism, Phe and Tyr metabolism, Lys degradation, ammonia
   recycling and Met metabolism. These pathways likely play key roles in
   the recovery process following gastric cancer surgery. For example, Ser
   and Gly metabolism is closely related to immune regulation and cell
   proliferation, potentially influencing postoperative recovery by
   modulating inflammatory responses [[87]19, [88]20]. Tyr and Phe
   metabolism is crucial for the production of neurotransmitters such as
   dopamine and adrenaline, and surgery, as a significant stressor, may
   alter gastrointestinal neural function [[89]21, [90]22]. Regulating Phe
   and Tyr metabolism could help restore neurotransmitter balance and
   accelerate gastrointestinal recovery, thus impacting the time to first
   flatus. Additionally, the Lys and Met metabolism pathways are closely
   related to liver function, amino acid metabolism, and antioxidant
   responses [[91]23]. After surgery, the body requires efficient
   clearance of metabolic waste and maintenance of the ammonia balance,
   and adjustments in these amino acid pathways may support these goals.
   Finally, branched-chain AAs (Leu, Ile, and Val) are essential for
   protein synthesis and energy metabolism. Under postoperative stress,
   shifts in the metabolism of these AAs likely reflect the body’s
   adaptation to surgical trauma and its increased metabolic demands
   during recovery [[92]24].

   Postoperative recovery of intestinal function, such as the time to
   first flatus, is a crucial clinical indicator of patient recovery.
   Numerous studies have shown that amino acid metabolism is closely
   related to the gut microenvironment, immune regulation, and the
   gut‒brain axis. Research indicates that specific AAs, such as Glu and
   Pro, play key roles in intestinal mucosal repair and gut barrier
   function and that fluctuations in these AAs may directly affect the
   speed of postoperative gut recovery [[93]25]. Additionally, the
   interplay between amino acid metabolism and the gut microbiome may also
   play a critical role postsurgery. The enrichment or deficiency of
   certain AAs could influence the metabolic activity of the gut
   microbiota, thereby indirectly regulating intestinal function recovery.
   This observation suggests that amino acid metabolism may be a potential
   regulatory factor in the recovery of postoperative intestinal function
   [[94]22, [95]26]. Postoperative inflammation significantly impacts both
   the speed and quality of patient recovery. AAs, in addition to serving
   as essential building blocks for protein synthesis, also regulate
   inflammatory responses through their metabolic byproducts. For example,
   Met metabolism is closely linked to the synthesis of glutathione, an
   important antioxidant that can alleviate oxidative stress induced by
   postoperative inflammation [[96]27]. Moreover, the Arg and Pro
   metabolic pathways are crucial for regulating immune cell function
   [[97]28]. The balance between postoperative inflammation levels and
   alterations in these amino acid pathways may create a dynamic interplay
   influencing recovery. These findings offer new insights into adjusting
   postoperative recovery via amino acid metabolism, suggesting that
   specific AAs or their metabolites could serve as potential targets to
   improve recovery outcomes. Moreover, early postoperative monitoring of
   these AAs may provide valuable biomarkers for predicting patient
   recovery trajectories, shedding light on the mechanisms underlying
   intestinal function recovery, especially in the early stages after
   surgery.

   On the basis of the above analysis, amino acid metabolism may not only
   serve as a biomarker for postoperative recovery but also represent a
   potential new strategy for improving patient recovery through
   nutritional intervention. However, this study has certain limitations.
   First, the sample size is relatively small, and the generalizability of
   the data requires further validation. Second, this study focused
   primarily on early postoperative amino acid changes, lacked long-term
   follow-up data, and thus cannot comprehensively reveal the role of AAs
   in long-term postoperative recovery. Additionally, the need for
   individualized nutritional intervention strategies remains unclear, and
   optimal intervention plans may vary among patients. Future research
   could further investigate the role of specific amino acid
   supplementation in promoting postoperative intestinal function recovery
   and alleviating inflammation. For example, rational supplementation of
   branched-chain AAs and modulation of Met and Lys metabolism may offer
   new approaches for personalized nutritional support.

   In conclusion, this study provides preliminary evidence of the
   relationship between amino acid metabolism and postoperative recovery
   in gastric cancer patients. These findings offer important insights for
   further exploration of the role of metabolic regulation in
   postoperative recovery and lay the foundation for the development of
   personalized postoperative management strategies in the future.

Conclusion

   This study systematically analyzed the changes in plasma amino acid
   profiles before surgery, after surgery, and following nutritional
   intervention in gastric cancer patients and revealed a close
   association between amino acid metabolism and postoperative recovery.
   The results revealed that the amino acid profile of gastric cancer
   patients deviated significantly from normal levels before surgery, with
   certain AAs significantly decreasing postoperatively. Nutritional
   intervention was able to partially restore the levels of specific AAs,
   although some remained lower than those in healthy individuals. Further
   analysis revealed that postoperative amino acid changes were
   significantly negatively correlated with time to first flatus and the
   levels of the inflammatory markers CRP and WBC, suggesting that these
   AAs may play important roles in postoperative intestinal function
   recovery and inflammation regulation. Pathway enrichment analysis
   revealed that amino acid metabolic pathways, such as Gly and Ser
   metabolism, Phe and Tyr metabolism, and Lys and Met metabolism, may
   play critical roles in the postoperative recovery process.

   These findings not only provide new insights into metabolic regulation
   for postoperative recovery but also support the potential application
   of amino acid metabolism as a biomarker. Although this study has
   several limitations, such as a small sample size and a lack of
   long-term follow-up data, it provides a theoretical foundation and
   practical guidance for further exploration of the role of metabolic
   regulation in personalized nutritional support and postoperative
   rehabilitation. Future studies will aim to expand the sample size and
   extend the follow-up time to further validate the potential of specific
   AAs as biomarkers for postoperative recovery. This study is purely
   observational and does not include interventional trials to assess the
   causal effects of amino acid supplementation on postoperative recovery.
   Further research is required to explore the potential benefits of
   targeted amino acid supplementation in this patient population.
   Additionally, exploring precise nutritional intervention strategies on
   the basis of individual amino acid needs may optimize the postoperative
   recovery process and improve patients' long-term prognosis.

Supplementary Information

   [98]Supplementary Material 1.^ (95.8KB, pdf)

Acknowledgements