
==== Front
Sci Rep
Sci Rep
Scientific Reports
2045-2322
Nature Publishing Group UK London

39261554
72482
10.1038/s41598-024-72482-0
Article
Effects of MAFLD defined by fatty liver index or ultrasonography on kidney function decline in the general population
Lee Yu-Ji yuji.lee@samsung.com

1
Kim Kwang Min 2
Ko Nak Gyeong 3
Jin Mihyeon 3
Na Jin Hee 1
Park In Ho 1
1 grid.264381.a 0000 0001 2181 989X Division of Nephrology, Department of Internal Medicine, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, 158, Paryong-ro, Masanhoewon-gu, Changwon, 51353 Republic of Korea
2 grid.264381.a 0000 0001 2181 989X Division of Gastroenterology, Department of Medicine, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Republic of Korea
3 grid.264381.a 0000 0001 2181 989X Department of Research and Support, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Republic of Korea
11 9 2024
11 9 2024
2024
14 2118931 5 2024
9 9 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
This study aimed to investigate whether metabolic dysfunction-associated fatty liver disease (MAFLD) defined by the fatty liver index (FLI) affects the decline in kidney function and whether this relationship is still observed in MAFLD defined by ultrasonography (USG). A retrospective cohort study was conducted using de-identified data from participants who received health checkups at Samsung Changwon Hospital between 2002 and 2018. The primary and secondary exposures were the presence of FLI- and USG-defined MAFLD, respectively. The primary outcome was 5-years slope of eGFR. The secondary outcome was a rapid decline in kidney function, defined as a 5-years slope of estimated glomerular filtration rate (eGFR) of less than − 3 mL/min/1.73 m2 per year. A total of 37,500 participants were included in the analysis. Participants with FLI-defined MAFLD had a larger decline in 5-year eGFR slope than those without FLI-defined MAFLD (beta coefficients − 0.11; 95% CI − 0.14 to − 0.08). Participants with FLI-defined MAFLD had a higher risk of rapid kidney function decline than those without FLI-defined MAFLD (odds ratio 1.33; 95% confidence intervals (CIs) 1.05–1.69). However, USG-defined MAFLD was less related to kidney function decline. In conclusion, the presence of FLI-defined MAFLD was associated with larger and faster kidney function decline.

Keywords

Fatty liver index
General population
Kidney
Metabolic dysfunction-associated fatty liver disease
Ultrasonography
Subject terms

Gastroenterology
Nephrology
issue-copyright-statement© Springer Nature Limited 2024
==== Body
pmcIntroduction

In 2020, metabolic dysfunction-associated fatty liver disease (MAFLD) was proposed as an alternative terminology to nonalcoholic FLD (NAFLD), focusing on metabolic abnormalities that play important roles in the pathophysiology of FLD1. The prevalence of MAFLD has been steadily rising, with estimates suggesting that up to 25% of the global population may be affected, and has emerged as a significant public health concern2,3. Recently, studies have evaluated the effect of newly defined MAFLD on the prevalence and incidence of extrahepatic complications such as cardiovascular diseases or chronic kidney disease (CKD)4–7.

MAFLD is defined as the presence of hepatic steatosis along with one of the following three criteria, namely overweight or obesity, presence of type 2 diabetes mellitus, or presence of at least two metabolic risk abnormalities1. Liver biopsy is the gold standard for evaluating hepatic steatosis in MAFLD; however, it is an invasive test associated with a risk of complications, which limits its use as a diagnostic method for MAFLD in the general population8,9. Ultrasonography (USG) is commonly used as a diagnostic method for MAFLD because of its noninvasiveness and cost-effectiveness; however, it has limitations in detecting mild hepatic steatosis10. The fatty liver index (FLI), another diagnostic method for MAFLD, is a simple algorithm based on anthropometric and laboratory parameters and offers another approach for detecting hepatic steatosis, demonstrating good sensitivity and specificity in various populations11–13.

Kidney function decline has garnered epidemiological importance as a major public health issue because of its association with adverse outcomes such as cardiovascular events, end-stage renal disease, and mortality14. Previous studies have elucidated various risk factors for CKD, including diabetes, hypertension, and obesity, which are commonly associated with MAFLD14,15. Recently, several cross-sectional or cohort studies have explored the relationship between MAFLD defined using USG or FLI and CKD4,5,7. These studies have compared MAFLD and NAFLD mainly in their associations with CKD.

Despite the growing recognition of both MAFLD and CKD as public health issues, existing literature has not comprehensively explored the association between MAFLD and the degree and rate of kidney function decline in the general population. Although diagnostic methods for MAFLD, such as USG and FLI, have been extensively validated, their respective effects on the association between MAFLD and kidney function decline have not been systematically investigated. It may be necessary to address the lack of knowledge in implementing preventive strategies and clinical management approaches to reduce the burden of both MAFLD and kidney disease in the general population. In this study, we aimed to investigate whether FLI-defined MAFLD affects kidney function decline, and whether this relationship is still observed in USG-defined MAFLD.

Methods

Study participants and data collection

A retrospective cohort study was performed using de-identified data from participants who received a comprehensive health checkup at Samsung Changwon Hospital between January 2002 and December 2018. The study included participants aged ≥ 18 years who underwent abdominal USG at baseline and measured serum creatinine at least twice during a 5-year follow-up period after initial assessment of creatinine. The participants who had missing data for MAFLD diagnosis were excluded from the analysis.

The following data were collected at baseline: age, sex, comorbidities (diabetes mellitus, hypertension, dyslipidemia, stroke, and coronary artery disease), smoking status, binge drinking, hepatitis B, hepatitis C, systolic blood pressure (SBP), diastolic blood pressure (DBP), body mass index (BMI), waist circumference (WC), and laboratory parameters including serum hemoglobin, serum albumin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl-transferase (GGT), total cholesterol, triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), fasting glucose, fasting insulin, glycated hemoglobin A1c (HbA1c), C-reactive protein (CRP), serum creatinine, and the presence of proteinuria. BMI was calculated as body weight in kilograms divided by the square of height in meters (kg/m2). The homeostasis model assessment of insulin resistance (HOMA-IR) value was calculated using the formula: HOMA-IR = [fasting plasma glucose (mg/dL) × fasting insulin (μU/mL)]/405. Proteinuria was defined as 1 + or more protein on a urine dipstick test. Binge drinking was defined as consuming ≥ 5 and ≥ 4 drinks on an occasion for male and female participants, respectively. The eGFR was estimated by an equation developed by the CKD Epidemiology Collaboration16.

The study was approved by the Institutional Review Board of Samsung Changwon Hospital that waived the requirement for informed consent from the participants because only de-identified datasets from the health screening cohort of the epidemiological research center at Samsung Changwon Hospital were retrospectively accessed for analyses (SCMC 2024-02-005). The study protocol conformed to the provisions of the Declaration of Helsinki.

Definition of MAFLD

MAFLD was diagnosed based on the presence of hepatic steatosis (detected by FLI or abdominal USG) and at least one of the following three metabolic conditions: (a) overweight or obesity (BMI ≥ 23 kg/m2), (b) type 2 diabetes mellitus, and (c) at least two metabolic dysregulations among increased WC (≥ 90 and 80 cm in men and women, respectively), hypertension (blood pressure ≥ 130/85 mmHg or specific drug treatment), hypertriglyceridemia (TG ≥ 150 mg/dL or specific drug treatment), low serum HDL-C (< 40 mg/dL for men and < 50 mg/dL for women), impaired fasting glucose (fasting glucose levels 100–125 mg/dL or HbA1c 5.7%–6.4%), insulin resistance (HOMA-IR ≥ 2.5), or subclinical inflammation (CRP ≥ 2 mg/dL)1. The FLI was calculated using the following formula: FLI = [e(0.953*ln(TG) +0.139*BMI+0.718*ln(GGT) +0.053*WC-15.745) ]/[1 + e(0.953*ln(TG) +0.139*BMI+0.718*ln(GGT) +0.053*WC-15.745)]× 10011.

Exposures and outcomes

The primary and secondary exposures of interest were the presence of FLI- and USG-defined MAFLDs, respectively. The primary outcome of interest was a 5-year slope of eGFR measured in mL/min/1.73 m2 per year. The secondary outcome of interest was a rapid kidney function decline, defined as a 5-years eGFR slope of less than − 3 mL/min/1.73 m2 per year.

Statistical analysis

Baseline characteristics were expressed according to the presence of FLI-defined MFALD. The Wilcoxon rank-sum and the χ2 tests were used to compare the baseline variables of participants, as appropriate. Linear regression analyses were performed to assess the association between FLI- or USG-defined MAFLD and 5-year slope of eGFR. The analyses were adjusted for age, sex, diabetes mellitus, hypertension, dyslipidemia, stroke, and coronary artery disease, smoking status, binge drinking, hepatitis B, hepatitis C, hemoglobin, albumin, total cholesterol, baseline eGFR, and proteinuria. Logistic regression analyses were performed to evaluate the association between FLI- or USG-defined MAFLD and a rapid kidney function decline with the aforementioned adjustments. The 5-year eGFR slope was estimated with at least two follow-up eGFR measurement taken during a 5-year follow-up period, in addition to eGFR assessment at the baseline, using a linear mixed-effects model, which allows for a random intercept and slope using an unstructured covariance matrix. A likelihood ratio test was conducted by adding interaction term between FLI-defined MAFLD and each of the covariates to the linear regression model and then subgroup analyses according to each of the covariates were performed. For sensitivity analysis, propensity score matching analysis was performed to balance the baseline characteristics between FLI-defined MAFLD groups.

Missing data were noted in some baseline variables, including alcohol drinking, hepatitis B, hepatitis C, proteinuria, smoking status, and levels of albumin, ALT, HbA1c, and CRP. The rate of missing data was < 1.0% for albumin (0.6%), ALT (0.1%), HbA1c (0.9%), CRP (0.8%), hepatitis B (0.8%), and hepatitis C (0.9%), except for smoking status (2.4%) and proteinuria (3.2%). To address this issue, multiple imputation methods using a multivariate normal model incorporating all variables in a fully adjusted model were employed, using 10 imputed datasets. All statistical analyses were performed using STATA, version 14.2 (StataCorp P, College Station, TX, USA).

Results

Baseline characteristics of participants

Data of 93,038 participants aged ≥ 18 years who underwent abdominal USG at baseline health checkup were extracted for analysis. Of these participants, data of 38,663 participants who measured serum creatinine at least twice during follow-up after initial assessment of creatinine were included. Participants without data on anthropometric measurements or laboratory variables for diagnosing FLI- or USG-defined MAFLD (n = 1163) were excluded. Data from 37,500 participants were finally included in the analysis (Supplemental Fig. 1).

Of the total number of participants, 11,822 (31.5%) had FLI-defined MAFLD. USG-defined MAFLD was found in 8741 (23.3%) participants. The baseline characteristics of the participants overall and by FLI-defined MAFLD status are shown in Table 1. The median [interquartile range (IQR)] age of the overall participants was 41 (35–47), and 60% were men. The proportion of men was higher in the participants with FLI-defined MAFLD compared to those without FLI-defined MAFLD (86% vs 48%, respectively). The median (IQR) level of eGFR for all participants was 99 (88–109) mL/min/1.73 m2. Supplemental Table 1 also shows the baseline characteristics of the participants by USG-defined MAFLD status.Table 1 Baseline characteristics of the participants according to the presence or absence of MAFLD defined by the fatty liver index.

	Total	Non-MAFLD	MAFLD	P	
n = 37,500	n = 25,678	n = 11,822	
Age, yr	41 (35–47)	41 (34–47)	42 (36–48)	 < 0.001	
Male, %	60	48	86	 < 0.001	
Comorbidities, %	
 Diabetes	2.8	1.8	4.9	 < 0.001	
 Hypertension	10.6	6.9	18.7	 < 0.001	
 Dyslipidemia	11.9	8.3	19.8	 < 0.001	
 Coronary artery disease	0.9	0.7	1.4	 < 0.001	
 Stroke	0.6	0.6	0.8	0.002	
 Hepatitis B	3.9	4.2	3.2	 < 0.001	
 Hepatitis C	0.4	0.4	0.4	0.402	
Current smoking, %	24	18	39	 < 0.001	
Binge drinking, %	51	42	69	 < 0.001	
SBP, mmHg	118 (110–125)	115 (108–122)	121 (116–130)	 < 0.001	
DBP, mmHg	70 (65–80)	70 (63–76)	76 (70–80)	 < 0.001	
BMI, kg/m2	23 (21–26)	22 (21–24)	26 (25–28)	 < 0.001	
WC, cm	82 (76–88)	79 (74–83)	90 (87–95)	 < 0.001	
Laboratory findings	
 Hemoglobin, g/dL	15 (14–16)	14 (13–15)	16 (15–16)	 < 0.001	
 Albumin, g/dL	4.6 (4.5–4.8)	4.6 (4.4–4.8)	4.7 (4.5–4.9)	 < 0.001	
 AST, IU/L	21 (17–26)	19 (16–23)	25 (20–32)	 < 0.001	
 AST, IU/L	19 (13–28)	16 (12–21)	29 (21–43)	 < 0.001	
 GGT, IU/L	19 (12–34)	15 (11–21)	41 (27–66)	 < 0.001	
 Total cholesterol, mg/dL	193 (171–216)	187 (167–209)	207 (184–230)	 < 0.001	
 TG, mg/dL	90 (63–136)	73 (55–99)	155 (114–212)	 < 0.001	
 HDL-C, mg/dL	58 (48–68)	62 (53–72)	49 (42–57)	 < 0.001	
 Glucose, mg/dL	88 (82–94)	86 (81–92)	92 (86–100)	 < 0.001	
 HbA1c, %	5.4 (5.2–5.6)	5.4 (5.2–5.6)	5.5 (5.3–5.8)	 < 0.001	
 Serum creatinine, mg/dL	0.9 (0.7–1.0)	0.8 (0.7–1.0)	1.0 (0.9–1.1)	 < 0.001	
 eGFR, mL/min/1.73 m2	99 (88–109)	101 (90–110)	95 (85–105)	 < 0.001	
 Proteinuria, %	2.9	2.6	3.7	 < 0.001	
 CRP, mg/dL	0.4 (0.2–0.9)	0.2 (0.2–0.7)	0.8 (0.4–1.6)	 < 0.001	
ALT alanine aminotransferase, AST aspartate aminotransferase, BMI body mass index, DBP diastolic blood pressure, eGFR estimated glomerular filtration rate, GGT gamma-glutamyl transferase, HbA1c hemoglobin A1c, HDL-C high-density lipoprotein cholesterol, CRP C-reactive protein, SBP systolic blood pressure, TG triglyceride, WC waist circumference.

Association between FLI-defined MAFLD and 5-year slope of eGFR

The median (IQR) value of 5-year slope of eGFR was 0.17 (− 0.60 to 0.98) mL/min/1.73 m2 per year. Crude and adjusted beta (β) coefficients and 95% confidence intervals (CIs) for the association between FLI-defined MAFLD and 5-year slope of eGFR were − 0.03 (− 0.06 to 0.003) and − 0.11 (− 0.14 to − 0.08), respectively. In the subgroup analyses, the association between FLI-defined MAFLD and 5-year slope of eGFR was not modified by age (Pinteraction = 0.946), sex (Pinteraction = 0.107), diabetes (Pinteraction = 0.787), hypertension (Pinteraction = 0.321), coronary artery disease (Pinteraction = 0.997), stroke (Pinteraction = 0.694), dyslipidemia (Pinteraction = 0.924), smoking status (Pinteraction = 0.775), binge drinking (Pinteraction = 0.218), hepatitis B (Pinteraction = 0.054), hepatitis C (Pinteraction = 0.869), hemoglobin (Pinteraction = 0.393), total cholesterol (Pinteraction = 0.051), serum albumin (Pinteraction = 0.375), and proteinuria (Pinteraction = 0.675) (Supplemental Fig. 2). In contrast, the association between FLI-defined MAFLD and 5-year slope of eGFR was modified by eGFR (Pinteraction < 0.001); the association was more evident in participants with an eGFR < 90 mL/min/1.73 m2 than in those with an eGFR ≥ 90 mL/min/1.73 m2. BMI also modified the association between FLI-defined MAFLD and 5-year slope of eGFR ((Pinteraction < 0.001) but the trends were similar (Fig. 1).Fig. 1 The association between FLI-defined MAFLD and 5-year slope of eGFR in subgroup analyses according to BMI and eGFR. Abbreviations: BMI, body mass index; eGFR, estimated glomerular filtration rate; FLI, fatty liver index; MAFLD, metabolic dysfunction-associated fatty liver disease. Points and bars represent adjusted beta coefficients and 95% confidence intervals.

Association between FLI-defined MAFLD and rapid kidney function decline

Of all the participants, 427 (1.1%) met the criteria for rapid kidney function decline, including 283 (1.1%) and 144 (1.2%) participants without and with FLI-defined MAFLD, respectively. Adjusted logistic regression analysis revealed a higher risk of rapid kidney function decline in participants with FLI-defined MAFLD than in those without FLI-defined MAFLD [odds ratio (OR), 1.33; 95% confidence intervals (CIs), 1.05–1.69] (Table 2).Table 2 The association between FLI-defined MAFLD and rapid kidney function decline in FLI-defined MAFLD and USG-defined MAFLD.

Models	FLI-defined MAFLD	USG-defined MAFLD	
Odds ratio	95% Confidence intervals	P value	Odds ratio	95% Confidence intervals	P value	
Unadjusted	1.11	0.90–1.35	0.326	0.88	0.69–1.11	0.273	
Adjusted	1.33	1.05–1.69	0.017	0.94	0.73–1.22	0.644	
Adjusted logistic regression model included age, sex, diabetes mellitus, hypertension, dyslipidemia, stroke, and coronary artery disease, smoking status, binge drinking, hepatitis B, hepatitis C, hemoglobin, albumin, total cholesterol, baseline eGFR, and proteinuria.

FLI fatty liver index, MAFLD metabolic dysfunction-associated fatty liver disease, USG ultrasonography.

Association between USG-defined MAFLD and kidney function

No clear association was found between USG-defined MAFLD and kidney function decline. Crude and adjusted β coefficients (95% CIs) for the association between USG-defined MAFLD and 5-year slope of eGFR were 0.02 (− 0.02 to 0.05) and − 0.03 (− 0.06 to 0.001), respectively. Adjusted OR (95% CIs) for the association between USG-defined MAFLD and rapid kidney function decline were 0.94 (0.73–1.22) (Table 2).

Sensitivity analysis

Propensity score matching was performed to balance the covariates distribution including age, sex, diabetes, hypertension, coronary artery disease, stroke, dyslipidemia, smoking status, BMI, binge drinking, hepatitis B, hepatitis C, hemoglobin, serum albumin, proteinuria, and eGFR between the presence and absence of FLI-defined MAFLD. In 14,355 individuals after propensity score matching, FLI-defined MAFLD was still associated with a 5-year eGFR slope and a risk of rapid kidney function decline; adjusted β coefficients (95% CIs) and OR (95% CIs) were − 0.09 (− 0.15, − 0.04) and 1.76 (1.15–2.69), respectively. On the other hand, USG-defined MAFLD was not associated with a 5-year eGFR slope and a risk of rapid kidney function decline; adjusted β coefficients (95% CIs) and OR (95% CIs) were 0.01 (− 0.04, 0.05) and 0.99 (0.71–1.39), respectively. In subgroup analyses after propensity score matching, the association between FLI-defined MAFLD and 5-year slope of eGFR was modified by age (Pinteraction = 0.031), eGFR (Pinteraction < 0.001), and total cholesterol (Pinteraction = 0.007); the degree of association was stronger in participants over 45 years of age than in those under 45 years of age, in participants with an eGFR < 90 ml/min/1.73 m2 than in those with eGFR > 90 ml/min/1.73 m2, and in participants with cholesterol levels > 200 mg/dL than in those with cholesterol levels < 200 mg/dL but all the trends were similar. Other covariates did not modify the association between FLI-defined MAFLD and 5-year slope of eGFR (all Ps for interaction > 0.05) (Fig. 2).Fig. 2 The association between FLI-defined MAFLD and 5-year slope of eGFR in subgroup analyses after propensity score matching. Abbreviations: estimated glomerular filtration rate; FLI, fatty liver index; MAFLD, metabolic dysfunction-associated fatty liver disease. Points and bars represent adjusted beta coefficients and 95% confidence intervals.

Discussion

In this retrospective cohort study, we investigated the effect of MAFLD on changes in kidney function. Specifically, two different definitions of MAFLD were examined: one based on the FLI and the other on USG. Our findings revealed intriguing associations, i.e., participants with FLI-defined MAFLD experienced a rapid kidney function decline. On the other hand, the association between USG-defined MAFLD and kidney function decline was not observed in this study. After adjusting for balanced covariates, the results for the association between FLI-defined MAFLD or USG-defined MAFLD and kidney function decline remained similar.

Several cross-sectional or cohort studies have reported a higher prevalence and incidence of CKD in patients with MAFLD than in those without MAFLD4,5,7. All these studies have addressed the association of MAFLD with CKD, defined as eGFR < 60 mL/min/1.73 m2 and/or proteinuria. Our results were similar to the findings of previous studies. However, the present study focused not only on the association of MAFLD with the rate and extent of eGFR changes but also on the assessment of the difference in effect of using FLI and USG as tools to detect the presence of hepatic steatosis. In this study, the weakening association between USG-defined MAFLD and kidney function decline may be explained by operator dependence on ultrasound image quality and interpretation of results, differences in sensitivity and specificity for diagnosing FLD, and limitations in capturing the full spectrum of liver inflammation17–20. Moreover, FLI is calculated by combining metabolic factors such as BMI, WC, and TG, so it is a tool for quantitatively evaluating metabolic abnormalities and thus can help identify patient populations with more severe metabolic abnormalities. In addition, there are reports that GGT included in FLI may be also associated with the risk of CKD21. Therefore, FLI-defined MAFLD may better reflect the patient's overall metabolic status and long-term metabolic burden compared to USG-defined MAFLD.

The observed association between MAFLD, particularly when defined by FLI, and the rapid kidney function decline suggests a potential interplay between hepatic and renal pathophysiology and metabolic dysregulation22. Previous studies have implicated various shared mechanisms that link hepatic dysfunction to kidney dysfunction, such as visceral adiposity, systemic inflammation, oxidative stress, insulin resistance, and dyslipidemia6,22–24. These factors may contribute to endothelial dysfunction, glomerular injury, and tubulointerstitial fibrosis, leading to progressive kidney function decline22,23. Another concept proposed as an underlying pathomechanism is the gut–liver–kidney axis, which indicates that the imbalance in the gut microbiota and disrupted intestinal barrier integrity can contribute to the pathogenesis of both FLD and CKD25.

The strength of this study is that eGFR change was used as an outcome. The findings indicated the potential of using eGFR slope as an outcome to investigate the relationship between MAFLD and kidney dysfunction in a population at a low risk of CKD. In addition, this study showed that FLI- and USG-defined MAFLDs differed in their abilities to predict kidney function decline. This finding suggests that FLI-defined MAFLD, which uses only blood tests and anthropometric measurements, may be simpler and more helpful in identifying individuals at high risk of kidney function decline than USG-defined MAFLD. However, this study has several limitations. First, the retrospective study design inherently carries the risk of selection bias and cannot establish causality. Second, despite adjustments for potential confounders such as age, sex, comorbidities, and laboratory variables, residual confounding cannot be entirely ruled out. In particular, the lack of data on certain important variables, such as lifestyle factors, medication use, and socioeconomic status26,27, which can affect FLD or kidney function, may limit the ability to fully explore potential confounders or effect modifiers. Lastly, the generalizability of our findings may be limited because the study was conducted in a specific geographic area or healthcare setting. Future prospective studies with larger sample sizes and more comprehensive assessments of both MAFLD and kidney function parameters are warranted to confirm and expand upon our findings while addressing these limitations.

In conclusion, the presence of FLI-defined MAFLD was associated with a faster and greater kidney function decline, but USG-defined MAFLD was not. Interventions targeting FLI-defined MAFLD may help slow down kidney function decline. This study confirms and extends previous findings regarding the adverse effects of MAFLD on kidney function, highlighting the need for further prospective research and targeted interventions to mitigate the effect of MAFLD on kidney health.

Statement of ethics

The study was approved by the Institutional Review Board of Samsung Changwon Hospital that waived the requirement for informed consent from the participants because only de-identified datasets from the health screening cohort of the epidemiological research center at Samsung Changwon Hospital were retrospectively accessed for analyses (IRB No. SCMC 2024-02-005).

Supplementary Information

Supplementary Information.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-024-72482-0.

Author contributions

Concept and design (Y.J.L., K.M.K.), analysis and/or interpretation of data (N.G.K., M.J., K.M.K., Y.J.L.), drafting the article (K.M.K., I.H.P., J.H.N., Y.J.L.), reviewing critical version of the article (Y.J.L., K.M.K., I.H.P., J.H.N.). All authors approved the final version of the manuscript.

Funding

This study was not supported by any sponsor or funder.

Data availability

All data generated or analyzed during this study are included in this article and its supplementary material files. Further enquiries can be directed to the corresponding author.

Competing interests

The authors declare no competing interests.

Publisher's note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
==== Refs
References

1. Eslam M A new definition for metabolic dysfunction-associated fatty liver disease: An international expert consensus statement J. Hepatol. 2020 73 202 209 10.1016/j.jhep.2020.03.039 32278004
Eslam, M. et al. A new definition for metabolic dysfunction-associated fatty liver disease: An international expert consensus statement. J. Hepatol. 73, 202–209. 10.1016/j.jhep.2020.03.039 (2020).32278004 10.1016/j.jhep.2020.03.039
2. Yuan Q Prevalence and risk factors of metabolic-associated fatty liver disease among 73,566 individuals in Beijing, China Int. J. Environ. Res. Public Health 2022 10.3390/ijerph19042096 36612889
Yuan, Q. et al. Prevalence and risk factors of metabolic-associated fatty liver disease among 73,566 individuals in Beijing, China. Int. J. Environ. Res. Public Health10.3390/ijerph19042096 (2022).36612889 10.3390/ijerph19042096
3. Wong VW Impact of the new definition of metabolic associated fatty liver disease on the epidemiology of the disease Clin. Gastroenterol. Hepatol. 2021 19 2161 2171e2165 10.1016/j.cgh.2020.10.046 33137486
Wong, V. W. et al. Impact of the new definition of metabolic associated fatty liver disease on the epidemiology of the disease. Clin. Gastroenterol. Hepatol. 19, 2161-2171e2165. 10.1016/j.cgh.2020.10.046 (2021).33137486 10.1016/j.cgh.2020.10.046
4. Kwon SY MAFLD and NAFLD in the prediction of incident chronic kidney disease Sci. Rep. 2023 13 1796 10.1038/s41598-023-27762-6 36720976
Kwon, S. Y. et al. MAFLD and NAFLD in the prediction of incident chronic kidney disease. Sci. Rep. 13, 1796. 10.1038/s41598-023-27762-6 (2023).36720976 10.1038/s41598-023-27762-6
5. Sun DQ MAFLD and risk of CKD Metabolism 2021 115 154433 10.1016/j.metabol.2020.154433 33212070
Sun, D. Q. et al. MAFLD and risk of CKD. Metabolism 115, 154433. 10.1016/j.metabol.2020.154433 (2021).33212070 10.1016/j.metabol.2020.154433
6. Targher G Byrne CD Lonardo A Zoppini G Barbui C Non-alcoholic fatty liver disease and risk of incident cardiovascular disease: A meta-analysis J. Hepatol. 2016 65 589 600 10.1016/j.jhep.2016.05.013 27212244
Targher, G., Byrne, C. D., Lonardo, A., Zoppini, G. & Barbui, C. Non-alcoholic fatty liver disease and risk of incident cardiovascular disease: A meta-analysis. J. Hepatol. 65, 589–600. 10.1016/j.jhep.2016.05.013 (2016).27212244 10.1016/j.jhep.2016.05.013
7. Mantovani A MAFLD and CKD: An updated narrative review Int. J. Mol. Sci. 2022 10.3390/ijms23137007 36362108
Mantovani, A. et al. MAFLD and CKD: An updated narrative review. Int. J. Mol. Sci.10.3390/ijms23137007 (2022).36362108 10.3390/ijms23137007
8. Nalbantoglu IL Brunt EM Role of liver biopsy in nonalcoholic fatty liver disease World J. Gastroenterol. 2014 20 9026 9037 10.3748/wjg.v20.i27.9026 25083076
Nalbantoglu, I. L. & Brunt, E. M. Role of liver biopsy in nonalcoholic fatty liver disease. World J. Gastroenterol. 20, 9026–9037. 10.3748/wjg.v20.i27.9026 (2014).25083076 10.3748/wjg.v20.i27.9026
9. Tsai E Lee TP Diagnosis and evaluation of nonalcoholic fatty liver disease/nonalcoholic steatohepatitis, including noninvasive biomarkers and transient elastography Clin. Liver Dis. 2018 22 73 92 10.1016/j.cld.2017.08.004 29128062
Tsai, E. & Lee, T. P. Diagnosis and evaluation of nonalcoholic fatty liver disease/nonalcoholic steatohepatitis, including noninvasive biomarkers and transient elastography. Clin. Liver Dis. 22, 73–92. 10.1016/j.cld.2017.08.004 (2018).29128062 10.1016/j.cld.2017.08.004
10. Liao YY Multifeature analysis of an ultrasound quantitative diagnostic index for classifying nonalcoholic fatty liver disease Sci. Rep. 2016 6 35083 10.1038/srep35083 27734972
Liao, Y. Y. et al. Multifeature analysis of an ultrasound quantitative diagnostic index for classifying nonalcoholic fatty liver disease. Sci. Rep. 6, 35083. 10.1038/srep35083 (2016).27734972 10.1038/srep35083
11. Bedogni G The Fatty Liver Index: a simple and accurate predictor of hepatic steatosis in the general population BMC Gastroenterol. 2006 6 33 10.1186/1471-230X-6-33 17081293
Bedogni, G. et al. The Fatty Liver Index: a simple and accurate predictor of hepatic steatosis in the general population. BMC Gastroenterol. 6, 33. 10.1186/1471-230X-6-33 (2006).17081293 10.1186/1471-230X-6-33
12. Cho EJ Fatty liver index for predicting nonalcoholic fatty liver disease in an asymptomatic Korean population Diagnostics 2021 10.3390/diagnostics11122233 35054251
Cho, E. J. et al. Fatty liver index for predicting nonalcoholic fatty liver disease in an asymptomatic Korean population. Diagnostics10.3390/diagnostics11122233 (2021).35054251 10.3390/diagnostics11122233
13. Huang X Validation of the fatty liver index for nonalcoholic fatty liver disease in middle-aged and elderly Chinese Medicine 2015 94 e1682 10.1097/MD.0000000000001682 26448014
Huang, X. et al. Validation of the fatty liver index for nonalcoholic fatty liver disease in middle-aged and elderly Chinese. Medicine 94, e1682. 10.1097/MD.0000000000001682 (2015).26448014 10.1097/MD.0000000000001682
14. Jha V Chronic kidney disease: global dimension and perspectives Lancet 2013 382 260 272 10.1016/S0140-6736(13)60687-X 23727169
Jha, V. et al. Chronic kidney disease: global dimension and perspectives. Lancet 382, 260–272. 10.1016/S0140-6736(13)60687-X (2013).23727169 10.1016/S0140-6736(13)60687-X
15. Zhou XD Metabolic dysfunction-associated fatty liver disease and implications for cardiovascular risk and disease prevention Cardiovasc. Diabetol. 2022 21 270 10.1186/s12933-022-01697-0 36463192
Zhou, X. D. et al. Metabolic dysfunction-associated fatty liver disease and implications for cardiovascular risk and disease prevention. Cardiovasc. Diabetol. 21, 270. 10.1186/s12933-022-01697-0 (2022).36463192 10.1186/s12933-022-01697-0
16. Levey AS A new equation to estimate glomerular filtration rate Ann. Intern. Med. 2009 150 604 612 10.7326/0003-4819-150-9-200905050-00006 19414839
Levey, A. S. et al. A new equation to estimate glomerular filtration rate. Ann. Intern. Med. 150, 604–612. 10.7326/0003-4819-150-9-200905050-00006 (2009).19414839 10.7326/0003-4819-150-9-200905050-00006
17. Guajardo-Salinas GE Hilmy A Prevalence of nonalcoholic fatty liver disease (NAFLD) and utility of FIBROspect II to detect liver fibrosis in morbidly obese Hispano-American patients undergoing gastric bypass Obes. Surg. 2010 20 1647 1653 10.1007/s11695-009-0027-0 19957049
Guajardo-Salinas, G. E. & Hilmy, A. Prevalence of nonalcoholic fatty liver disease (NAFLD) and utility of FIBROspect II to detect liver fibrosis in morbidly obese Hispano-American patients undergoing gastric bypass. Obes. Surg. 20, 1647–1653. 10.1007/s11695-009-0027-0 (2010).19957049 10.1007/s11695-009-0027-0
18. Perez NE Ultrasound diagnosis of fatty liver in patients with chronic liver disease: A retrospective observational study J. Clin. Gastroenterol. 2007 41 624 629 10.1097/01.mcg.0000225680.45088.01 17577120
Perez, N. E. et al. Ultrasound diagnosis of fatty liver in patients with chronic liver disease: A retrospective observational study. J. Clin. Gastroenterol. 41, 624–629. 10.1097/01.mcg.0000225680.45088.01 (2007).17577120 10.1097/01.mcg.0000225680.45088.01
19. Mishra P Younossi ZM Abdominal ultrasound for diagnosis of nonalcoholic fatty liver disease (NAFLD) Am. J. Gastroenterol. 2007 102 2716 2717 10.1111/j.1572-0241.2007.01520.x 18042105
Mishra, P. & Younossi, Z. M. Abdominal ultrasound for diagnosis of nonalcoholic fatty liver disease (NAFLD). Am. J. Gastroenterol. 102, 2716–2717. 10.1111/j.1572-0241.2007.01520.x (2007).18042105 10.1111/j.1572-0241.2007.01520.x
20. Khov N Sharma A Riley TR Bedside ultrasound in the diagnosis of nonalcoholic fatty liver disease World J. Gastroenterol. 2014 20 6821 6825 10.3748/wjg.v20.i22.6821 24944472
Khov, N., Sharma, A. & Riley, T. R. Bedside ultrasound in the diagnosis of nonalcoholic fatty liver disease. World J. Gastroenterol. 20, 6821–6825. 10.3748/wjg.v20.i22.6821 (2014).24944472 10.3748/wjg.v20.i22.6821
21. Ryu S Chang Y Kim DI Kim WS Suh BS gamma-Glutamyltransferase as a predictor of chronic kidney disease in nonhypertensive and nondiabetic Korean men Clin. Chem. 2007 53 71 77 10.1373/clinchem.2006.078980 17110470
Ryu, S., Chang, Y., Kim, D. I., Kim, W. S. & Suh, B. S. gamma-Glutamyltransferase as a predictor of chronic kidney disease in nonhypertensive and nondiabetic Korean men. Clin. Chem. 53, 71–77. 10.1373/clinchem.2006.078980 (2007).17110470 10.1373/clinchem.2006.078980
22. Pan Z Alqahtani SA Eslam M MAFLD and chronic kidney disease: two sides of the same coin? Hepatol. Int. 2023 17 519 521 10.1007/s12072-023-10526-9 37069420
Pan, Z., Alqahtani, S. A. & Eslam, M. MAFLD and chronic kidney disease: two sides of the same coin?. Hepatol. Int. 17, 519–521. 10.1007/s12072-023-10526-9 (2023).37069420 10.1007/s12072-023-10526-9
23. Kadatane SP Satariano M Massey M Mongan K Raina R The Role of Inflammation in CKD Cells 2023 10.3390/cells12121581 37371050
Kadatane, S. P., Satariano, M., Massey, M., Mongan, K. & Raina, R. The Role of Inflammation in CKD. Cells10.3390/cells12121581 (2023).37371050 10.3390/cells12121581
24. Popolo A Autore G Pinto A Marzocco S Oxidative stress in patients with cardiovascular disease and chronic renal failure Free Radic. Res. 2013 47 346 356 10.3109/10715762.2013.779373 23438723
Popolo, A., Autore, G., Pinto, A. & Marzocco, S. Oxidative stress in patients with cardiovascular disease and chronic renal failure. Free Radic. Res. 47, 346–356. 10.3109/10715762.2013.779373 (2013).23438723 10.3109/10715762.2013.779373
25. Raj D Tomar B Lahiri A Mulay SR The gut-liver-kidney axis: Novel regulator of fatty liver associated chronic kidney disease Pharmacol. Res. 2020 152 104617 10.1016/j.phrs.2019.104617 31881272
Raj, D., Tomar, B., Lahiri, A. & Mulay, S. R. The gut-liver-kidney axis: Novel regulator of fatty liver associated chronic kidney disease. Pharmacol. Res. 152, 104617. 10.1016/j.phrs.2019.104617 (2020).31881272 10.1016/j.phrs.2019.104617
26. Chen W Prevalence and risk factors associated with chronic kidney disease in an adult population from southern China Nephrol Dial Transpl. 2009 24 1205 1212 10.1093/ndt/gfn604
Chen, W. et al. Prevalence and risk factors associated with chronic kidney disease in an adult population from southern China. Nephrol Dial Transpl. 24, 1205–1212. 10.1093/ndt/gfn604 (2009).10.1093/ndt/gfn604
27. Ingsathit A Prevalence and risk factors of chronic kidney disease in the Thai adult population: Thai SEEK study Nephrol Dial Transpl. 2010 25 1567 1575 10.1093/ndt/gfp669
Ingsathit, A. et al. Prevalence and risk factors of chronic kidney disease in the Thai adult population: Thai SEEK study. Nephrol Dial Transpl. 25, 1567–1575. 10.1093/ndt/gfp669 (2010).10.1093/ndt/gfp669
