|Year : 2022 | Volume
| Issue : 2 | Page : 72-76
Impact of bariatric surgery on non-alcoholic fatty liver disease - Role of non-invasive tests
Kiran Kumar Yelkur, Mahidhar Valeti, Sumanth Kankanala, Sahithi Jekkyreddy, Mithila Gade
Department of Bariatric and Metabolic Surgery, Continental Hospitals, Hyderabad, Telangana, India
|Date of Submission||13-Dec-2021|
|Date of Acceptance||15-Apr-2022|
|Date of Web Publication||17-Jun-2022|
Dr. Mahidhar Valeti
Department of Bariatric and Metabolic Surgery, Continental Hospitals, Gachibowli, Hyderabad - 500 032, Telangana
Source of Support: None, Conflict of Interest: None
Background: Nonalcoholic fatty liver disease (NAFLD) is present in the majority of the patients undergoing bariatric surgery. Weight loss induced by bariatric surgery has been shown to improve clinical measurements and liver histology of NAFLD. The present study aims to evaluate the impact of bariatric surgery on NAFLD in Indian patients with severe obesity using noninvasive parameters. Materials and Methods: This prospective study was conducted on 67 patients who underwent bariatric surgery (laparoscopic sleeve gastrectomy and laparoscopic Roux-en-Y gastric bypass). The Asia-Pacific Metabolic and Bariatric Surgery Society guidelines were followed to ensure the indications for bariatric surgery. Data collected included anthropometrics, biochemical parameters, and other noninvasive parameters. Results: Fifty-four patients were included in the final analysis, with the majority being males (54.2%). The mean age was 44.77 ± 12.64 years old. One-year follow-up postsurgery demonstrated a statistically significant improvement in total weight loss and body mass index (BMI) reduction (P < 0.00001). Mean NAFLD fibrosis scores improved from −1.70 to −1.95; however, the improvement was not statistically significant (P = 0.4295). Biochemical improvement was found in the serum levels of alanine aminotransferase (P = 0.0169) and aspartate aminotransferase (P = 0.0004). Concomitantly, significant improvements in AST to Platelet Ratio Index score, BMI, AST/alanine aminotransferase ratio, diabetes score, and liver stiffness measurement on Fibroscan (8.9 ± 1.01 pka [initial] to 7.2 ± 0.40 pka [follow-up]) were observed. Conclusions: Our findings suggest a beneficial association of bariatric surgery in NAFLD patients. Bariatric surgery is found to induce weight loss significantly and improve liver functions as measured by noninvasive parameters. Further, long-term studies are needed to consolidate these results.
Keywords: Bariatric surgery, FibroScan, morbid obesity, nonalcoholic fatty liver disease, weight loss
|How to cite this article:|
Yelkur KK, Valeti M, Kankanala S, Jekkyreddy S, Gade M. Impact of bariatric surgery on non-alcoholic fatty liver disease - Role of non-invasive tests. J Bariatr Surg 2022;1:72-6
|How to cite this URL:|
Yelkur KK, Valeti M, Kankanala S, Jekkyreddy S, Gade M. Impact of bariatric surgery on non-alcoholic fatty liver disease - Role of non-invasive tests. J Bariatr Surg [serial online] 2022 [cited 2023 Jun 6];1:72-6. Available from: http://www.jbsonline.org/text.asp?2022/1/2/72/347747
| Introduction|| |
Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide., It is frequently recognized as the hepatic manifestation of metabolic syndrome and is commonly observed among populations with obesity, Type 2 diabetes mellitus (T2DM), and dyslipidemia.,,, NAFLD manifestation includes fatty liver and nonalcoholic steatohepatitis (NASH) which is found to be associated with liver cirrhosis, end-stage liver disease, and mortality. NAFLD has been shown to be prevalent in up to 75% of individuals living with obesity. Evidence suggests that NAFLD or NASH was found to be diagnosed in over 80% of patients undergoing bariatric surgery., In addition, NAFLD rates are found to be as high as 90% in patients with severe obesity undergoing bariatric surgery.
The most effective treatments for NAFLD, NASH, and liver fibrosis are weight loss as well as the management of the metabolic syndrome. Strong evidence suggested that a 5%–10% loss of the initial body weight led to a recovery in the histological findings of NAFLD. Bariatric surgery is a reliable intervention for attaining significant and sustained weight loss and decreasing obesity-related comorbidities. Bariatric surgery is likely to have potential benefits in bettering the factors relating to NAFLD development and helps to reduce the grade of hepatic steatosis, inflammation, and fibrosis. Furthermore, a biopsy study has provided convincing evidence of significant improvements in steatosis and NASH in postbariatric surgery NAFLD patients. In light of this evidence, improvement in fibrosis after bariatric surgery is frequently reported; however, progression and new onset of fibrosis have also been documented.,
Liver biopsy is considered the gold standard for diagnosing and characterizing NAFLD, but it is not always convenient due to its invasive nature and high cost. Noninvasive measures, such as metabolomics assays, have been recently developed to accurately distinguish NASH from simple steatosis, whereas fibrosis can be diagnosed noninvasively using imaging or blood-based biomarkers. Despite the high prevalence of NAFLD in bariatric patients, the effects of bariatric surgery on NAFLD using multiple noninvasive measures have received little attention, with only a limited number of studies have been conducted in the Indian cohorts. Although the available evidence is mixed, we hypothesize that the surgical intervention through bariatric surgery (Roux-en-Y Gastric Bypass [RYGBP] [or] sleeve gastrectomy [SG]) would have a positive impact on the management of NAFLD and/or NASH. Consequently, more studies are needed to derive the outcomes of bariatric surgery among patients with NAFLD and liver fibrosis, particularly using noninvasive measures. With this context, the aim of this prospective study is to evaluate the impact of bariatric surgery on NAFLD, NASH, and liver fibrosis stage in patients with NAFLD, using noninvasive measures.
| Materials and Methods|| |
This was a single-center, prospective study performed at the Continental hospital in Hyderabad. Sixty-seven patients who underwent bariatric surgery (RYGBP [or] SG) in compliance with the indications for bariatric surgery (in accordance with Asia-Pacific Metabolic and Bariatric Surgery Society guidelines) from December 2018 to July 2019 were included in this study. The exclusion criteria include patients who lost to follow-up, patients who had a redo bariatric surgery and those with concomitant gastric pathologies. Written informed consent was provided by all participants, and an Institutional Review Board approval was obtained before the commencement of the study.
Preoperative and postoperative parameters
Anthropometric measurements, including height, weight, and body mass index (BMI), were measured for all patients preoperatively. Standard laboratory assessments and clinical features were prospectively assessed before surgery. Preoperatively, liver function test (LFT) and ultrasonography were performed, and levels of complete blood picture (including platelet count), serum albumin, aspartate aminotransferase (AST, U/l), alanine aminotransferase (ALT, U/l), and blood glucose were determined in all patients. Postoperative data were collected 6 months after bariatric surgery, and all the patients included in the study were followed up for 1 year.
At 1-year follow-up, BMI, weight, LFT, and FibroScan were measured for comparative analysis. Other noninvasive markers of liver fibrosis, such as AST to Platelet Ratio Index (APRI), BMI, AST/ALT ratio, Diabetes (BARD) score, and NAFLD fibrosis score, were calculated for each patient. BARD score was calculated with consideration of parameters, such as BMI, aspartate aminotransferase/ALT (AST) ratio, and presence of diabetes. The NAFLD fibrosis score – first developed in 2007 by Angulo et al. and based on standard laboratory assessments – was established using the following formula: −1.675 + 0.037 − age (years) + 0.094 − BMI (kg/m2) + 1.13 × IFG/diabetes (yes = 1, no = 0) + 0.99 × AST/ALT ratio – 0.013 × platelet count (×109/l) − 0.66 × albumin (g/dl)., To improve the reliability of FibroScan method, a minimum of 10 valid readings were taken with at least a 60% success rate, and the results are expressed in kilopascals (kPa).
Statistical analysis was performed using the SPPS © software version 23.0 (2014, IBM Corp; Armonk, NY, USA) using the Chi-square test or the Mann–Whitney test as appropriate. The continuous data are presented as mean and standard deviation. The categorical data are presented as frequencies (percent). The independent variables in the model included weight, height, laboratory, and liver tests. P < 0.05 was considered statistically significant.
| Results|| |
Baseline characteristics of the study cohort
In total, 67 patients took part in the study. With 13 patients lost to follow-up, a final of 54 patients were considered for the analysis. The majority of the study participants were male (54.2%), and the mean age was 44.77 ± 12.60 years. Preoperative mean weight and BMI were 104.96 ± 17.22 and 44.15 ± 5.60 kg/m2, respectively. Baseline characteristics and clinical features of the patients are summarized in [Table 1].
At 12-month follow-up, the mean BMI was found to be 33.52 ± 4.32 kg/m2. There was a statistically significant (P ≤ 0.00001) reduction in BMI values, a decrease of 24.09%, at postsurgery follow-up. Preoperative average weight loss was 9.53% of the initial weight (P < 0.0103), and the average total weight loss was statistically significant at follow-up, with a 24.13% reduction in weight compared to the initial weight (P < 0.00001) [Table 2].
|Table 2: Comparative analysis of body mass index, weight loss, and total weight loss|
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Clinical and biochemical assessments
The parameters which are evaluated to find the efficiency of bariatric surgery in NAFLD are summarized in [Table 3]. Preoperatively, the mean NAFLD score was −1.70. There was an improvement in mean NAFLD scores from −1.70 to − 1.95 at 1-year follow-up; however, the improvement is not statistically significant (P = 0.4295). According to the Angulo et al. classification, 36 participants in our analysis had scores in the indeterminate category (−1.455 and 0.675), while 18 patients had scores of F0-F2 score (<−1.455), which signified the predictor of the absence of significant fibrosis. The number of patients who had scores in the indeterminate category for liver fibrosis are dropped during the postoperative follow-up period from 36 to 10, and 44 patients had an F0-F2 score (mean NAFLD fibrosis score: −1.95; P < 0.0001).
There was also a statistically significant decline in mean aspartate transaminase (AST) and ALT (P = 0.0004 and P = 0.0169, respectively). The preoperative values were 22.25 ± 8.44 and 24.96 ± 10.49 U/l, which were reduced to 14.38 ± 4.52 and 18.88 ± 5.89 U/l, respectively, at final follow-up. In particular, a statistically significant decrease was noted in the following variables: APRI (P = 0.03), and FibroScan – Liver stiffness measurement (P = 0.002). Correspondingly, though AST: ALT ratio decreased from 0.91 ± 0.17 preoperatively to 0.81 ± 0.22 at 1-year follow-up, the change was not statistically significant (P = 0.0621).
Preoperatively, 18 patients had a BARD score of <2, while 36 had a score >2. At the final follow-up, the BARD scores demonstrated 36 patients with <2 scores, and 18 with >2 scores. This change in mean BARD score was observed from 2.63 ± 1.01 (preoperative) to 1.67 ± 1.09 (postoperative) (P = 0.0011) which is a statistically significant improvement (P = 0.02).
| Discussion|| |
In this study, we have demonstrated the use of noninvasive examinations to assess NAFLD following bariatric surgery. NAFLD is often asymptomatic and comprises a spectrum of diseases ranging from simple steatosis, NASH with inflammation and fibrosis. Bariatric surgery affects metabolic pathways and has been shown to provide a regression of steatosis, NASH, and fibrosis., Considering the strong correlation between obesity with NAFLD, weight loss is beneficial for patients with NAFLD, especially in patients who are not responding to dietary manipulation and weight reduction exercise programs.,,,,,
The available evidence showed that all types of bariatric surgeries (both laparoscopic SG and RYGB) were proven to be safe, effective, and efficient. In a meta-analysis, the authors assessed the impact of bariatric surgery on metabolic outcomes and reported an excessive weight loss of almost 60% and a complete resolution of T2DM in more than 75% of diabetic patients. In another meta-analysis, bariatric surgery was found to decrease the mean BMI to 28.6–39 kg/m2 at follow-up from 43.9 to 56 kg/m2 preoperatively. The percentage decrease in mean BMI values is reported to be in the range of 19.11–41.76 kg/m2. These results are incongruent with the findings of our study where preoperative weight loss of 9.53% (P < 0.010394), total weight loss of 24.13% (P < 0.00001), and 24.09% reduction in BMI (P < 0.00001) were observed.
Liver biopsy is the current gold standard for the diagnosis and assessment of the severity of liver fibrosis; however, this invasive procedure is considered not feasible due to its high cost and associated complications. These limitations have led to the emergence of newer, noninvasive methods for the assessment of liver fibrosis. However, evidence derived from studies using noninvasive methods is limited and the effect of bariatric surgery on NAFLD using noninvasive methods has been mildly explored. From the limited published data available, we assume that the role of noninvasive measures to assess hepatic effects provides a suitable approach in patients undergoing bariatric surgery. Vargas et al. and Major et al. revealed that the RYGBS leads to bodyweight reduction and improves liver function through regression of liver steatosis., In a meta-analysis, authors reported favorable outcomes demonstrating a positive impact of bariatric surgery on the levels of AST and ALT concentrations. Our study findings are in compliance with this evidence, where a preoperative APRI score of 0.08 ± 0.03 was improved to 0.06 ± 0.02 at the final follow-up visit, and the levels of AST and ALT liver enzymes were statistically significantly reduced postoperatively (P = 0.0004; P = 0.0169).
Existing evidence suggests a favorable outcome of bariatric surgery on NAFLD., In the BariScan study by Nickel et al., a significant decrease in NAFLD fibrosis score was reported at the end of 12 months (P < 0.001). In addition, there were significant improvements of AST/ALT ratio (P < 0.001), APRI score (P = 0.009), and BARD score (P = 0.008) 1 year after surgery. Similar results were shown by Nascimento et al. indicating a statistically significant improvement in NAFLD fibrosis score at 12 months postbariatric surgery (P = 0.0002). In line with these findings, bariatric surgery is associated with improving NAFLD scores at 1-year follow-up in our cohort. However, despite an observed reduction in the mean NAFLD score, the change was not statistically significant. Interestingly, in our study, the FibroScan results were significantly improved. Moreover, the BARD scoring system for evaluating advanced fibrosis in NAFLD showed a statistically significant improvement (P = 0.0011). The previous studies have demonstrated a significant improvement in liver stiffness measured by Fibroscan or transient elastography postbariatric surgery., In a study by Garg et al., the authors reported a decline in liver stiffness from 8.6 kPa at baseline to 6.0 kPa at 1 year after surgery. Naveau et al. have also reported a similar reduction from 6.95 to 5.37 kPa. In the present study, liver stiffness improved from a preoperative mean value of 8.9 ± 1.01 kPa to a mean liver stiffness of 7.2 ± 0.40 kPa after bariatric surgery which is consistent with the above findings.
| Conclusions|| |
Utilizing noninvasive tests, we have demonstrated a significant improvement in weight loss, BMI, BARD scores, APRI values, liver enzymes (AST and ALT), and FibroScan values in an Indian cohort of patients with severe obesity postbariatric surgery. Our comparison of changes between pre-operative and 1-year follow-up adds to the growing body of evidence that indicates that bariatric surgery is associated with improvement in NAFLD fibrosis scores. Our study needs to be viewed with limitations, such as a moderate sample size with a follow-up period of only 1 year. The effectiveness of bariatric surgery in estimating NAFLD was not measured by liver biopsy as we wished to do noninvasive tests during the follow-up. We recommend randomized clinical trials using noninvasive tests with long-term follow-up to be carried out to reinforce the results of this study.
Patient declaration of consent statement
Written consent was obtained from the study participants. Further, all participants were informed of the research and that the data would be used for research purposes, giving patients the right to decline participation.
Data availability statement
The data set used in the current study is available on request from Dr. Mahidhar Valeti/Email: [email protected].
The authors would like to acknowledge the Department of Radiology, Continental Hospitals, Gachibowli, Hyderabad, India.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]