Association of serum adipocyte-specific Fatty Acid binding protein with Fatty liver index as a predictive indicator of nonalcoholic Fatty liver disease

Insulin Resistance, Non-Alcoholic Fatty Liver Disease and Type 2 Diabetes Mellitus: Clinical and Experimental Perspective

It has been generally accepted that insulin resistance (IR) and reduced insulin secretory capacity are the basic pathogenesis of type 2 diabetes mellitus (T2DM). In addition to genetic factors, the persistence of systemic inflammation caused by obesity and the associated threat of lipotoxicity increase the risk of T2DM. In particular, the main cause of IR is obesity and subjects with T2DM have a higher body mass index (BMI) than normal subjects according to recent studies. The prevalence of T2DM with IR has increased with increasing BMI during the past three decades. According to recent studies, homeostatic model assessment of IR was increased compared to that of the 1990s. Rising prevalence of obesity in Korea have contributed to the development of IR, non-alcoholic fatty liver disease and T2DM and cutting this vicious cycle is important. My colleagues and I have investigated this pathogenic mechanism on this theme through clinical and experimental studies over 20 years and herein, I would like to summarize some of our studies with deep gratitude for receiving the prestigious 2023 Sulwon Award.

FABP4 Expression in Subcutaneous Adipose Tissue Is Independently Associated with Circulating Triglycerides in Obesity

Hypertriglyceridemia (HTG) has been associated with an increased risk of pancreatitis and cardiovascular disease. Adipose tissue plays a major role in lipid metabolism, mobilization and distribution. We have compared the histological and transcriptomic profiles of the subcutaneous (SAT) and visceral (VAT) adipose tissues from subjects with severe obesity undergoing bariatric surgery with (Ob-HTG, n = 37) and without HTG (Ob-NTG, n = 67). Mean age and BMI were 51.87 ± 11.21 years, 45.78 ± 6.96 kg/m² and 50.03 ± 10.17 years, 44.04 ± 4.69 kg/m², respectively. The Ob-HTG group showed higher levels of glycosylated hemoglobin, fasting plasma glucose, high-sensitivity C-reactive protein and prevalence of hypertension. The degree of fibrosis was increased by 14% in SAT from the Ob-HTG group (p = 0.028), while adipocyte size distribution was comparable. Twenty genes were found differentially expressed in SAT and VAT between study groups. Among them, only SAT expression of FABP4 resulted significantly associated with circulating triglyceride levels after adjusting for other covariates and independently explained 5% of the variance in triglyceride levels in the combined model. This relationship was not found in the cohort of lean or overweight patients with normotriglyceridemia (non-Ob, n = 21). These results emphasize the contribution of SAT to triglyceride concentrations in obesity and indicate that FABP4 may be a potential drug target for the treatment of HTG.

New Insights into Non-Alcoholic Fatty Liver Disease and Coronary Artery Disease: The Liver-Heart Axis

Non-alcoholic fatty liver disease (NAFLD) represents the hepatic expression of the metabolic syndrome and is the most prevalent liver disease. NAFLD is associated with liver-related and extrahepatic morbi-mortality. Among extrahepatic complications, cardiovascular disease (CVD) is the primary cause of mortality in patients with NAFLD. The most frequent clinical expression of CVD is the coronary artery disease (CAD). Epidemiological data support a link between CAD and NAFLD, underlain by pathogenic factors, such as the exacerbation of insulin resistance, genetic phenotype, oxidative stress, atherogenic dyslipidemia, pro-inflammatory mediators, and gut microbiota. A thorough assessment of cardiovascular risk and identification of all forms of CVD, especially CAD, are needed in all patients with NAFLD regardless of their metabolic status. Therefore, this narrative review aims to examine the available data on CAD seen in patients with NAFLD, to outline the main directions undertaken by the CVD risk assessment and the multiple putative underlying mechanisms implicated in the relationship between CAD and NAFLD, and to raise awareness about this underestimated association between two major, frequent and severe diseases.

Unveiling the Role of the Fatty Acid Binding Protein 4 in the Metabolic-Associated Fatty Liver Disease

Metabolic-associated fatty liver disease (MAFLD), the main cause of chronic liver disease worldwide, is a progressive disease ranging from fatty liver to steatohepatitis (metabolic-associated steatohepatitis; MASH). Nevertheless, it remains underdiagnosed due to the lack of effective non-invasive methods for its diagnosis and staging. Although MAFLD has been found in lean individuals, it is closely associated with obesity-related conditions. Adipose tissue is the main source of liver triglycerides and adipocytes act as endocrine organs releasing a large number of adipokines and pro-inflammatory mediators involved in MAFLD progression into bloodstream. Among the adipocyte-derived molecules, fatty acid binding protein 4 (FABP4) has been recently associated with fatty liver and additional features of advanced stages of MAFLD. Additionally, emerging data from preclinical studies propose FABP4 as a causal actor involved in the disease progression, rather than a mere biomarker for the disease. Therefore, the FABP4 regulation could be considered as a potential therapeutic strategy to MAFLD. Here, we review the current knowledge of FABP4 in MAFLD, as well as its potential role as a therapeutic target for this disease.

Relationship Between Fatty Acid Binding Protein 4 and Liver Fat in Individuals at Increased Cardiometabolic Risk

Background: Liver steatosis is considered the onset of the non-alcoholic fatty liver disease (NAFLD), a major public health challenge. Nevertheless, NAFLD detection and diagnosis remain a difficult task. Fatty acid binding protein 4 (FABP4) has been proposed as potential biomarker for the ectopic fat accumulation in non-adipose tissues, although its role reflecting liver steatosis in metabolic patients is not fully explored. The aim of this study was to assess the relationship between FABP4 and the fatty liver index (FLI) in metabolic patients and to evaluate its potential role in the fatty liver disease.

Methods: A cross-sectional study involving 389 participants at increased cardiometabolic risk was performed. FLI was calculated in order to assess liver fatty disease and a FLI ≥ 60 was considered to define liver steatosis. The serum FABP4 levels were assessed by using a sandwich enzyme-linked immunosorbent assay. Multivariable regression models were used to examine the associations of FABP4 with fatty liver after adjusting for demographic and clinical characteristics.

Results: Both, FLI and serum FABP4 levels were upregulated in diabetic, obese, and metabolic syndrome patients. Serum FABP4 levels were higher in individuals with liver steatosis. Serum FABP4 were robustly associated with FLI in metabolic patients in both linear and logistic regression analyses.

Conclusion: Our findings show that the serum FABP4 is associated to liver steatosis in metabolic patients.

Circulating level of fatty acid-binding protein 4 is an independent predictor of metabolic dysfunction-associated fatty liver disease in middle-aged and elderly individuals

Aims/Introduction

Metabolic dysfunction‐associated fatty liver disease (MAFLD), defined as hepatosteatosis with type 2 diabetes mellitus, overweight/obesity or metabolic dysregulation, has been proposed as a new feature of chronic liver disease. Fatty acid‐binding protein 4 (FABP4) is expressed in adipose tissue, and secreted FABP4 is associated with the development of insulin resistance and atherosclerosis. However, the relationship between MAFLD and FABP4 has not been fully addressed.

Materials and Methods

Associations of MAFLD with metabolic markers, including FABP4, fibroblast growth factor 21 and adiponectin, were investigated in 627 individuals (men/women 292/335) in the Tanno‐Sobetsu Study, a population‐based cohort.

Results

The mean age was 65 years (range 19–98 years, median [interquartile range] 68 [56–76] years). Hepatosteatosis was determined by the fatty liver index (FLI), and FLI ≥35 for men and FLI ≥16 for women were used for detection of fatty liver, as previously reported using 14,471 Japanese individuals. FLI was positively correlated with systolic blood pressure and levels of FABP4 (r = 0.331, P < 0.001), fibroblast growth factor 21, homeostasis model assessment of insulin resistance as an insulin resistance index and uric acid, and was negatively correlated with levels of high‐density lipoprotein cholesterol and adiponectin. FABP4 concentration was independently associated with FLI after adjustment of age, sex, systolic blood pressure and levels of uric acid, high‐density lipoprotein cholesterol, homeostasis model assessment of insulin resistance, adiponectin and fibroblast growth factor 21 in multivariable regression analysis. Logistic regression analysis showed that FABP4 was an independent predictor of MAFLD after adjustment of age, sex, presence of diabetes mellitus, hypertension and dyslipidemia, and levels of uric acid, homeostasis model assessment of insulin resistance, adiponectin and fibroblast growth factor 21.

Conclusions

FABP4 concentration is independently associated with FLI and is an independent predictor of MAFLD in middle‐aged and elderly individuals.

Association between the liver fat score (LFS) and cardiovascular diseases in the national health and nutrition examination survey 1999-2016

BACKGROUND

The liver fat score (LFS) has been proposed to be a simple non-invasive marker of non-alcoholic fatty liver disease (NAFLD), which is highly prevalent in the general population. We tested its association with cardiovascular diseases (CVDs) and prognosis.

METHODS

17,244 adult participants from the National Health and Nutrition Examination Survey 1999-2016 were included. LFS is calculated from variables including serum aspartate transaminase/alanine transaminase (AST/ALT) ratio, fasting serum aspartate transaminase (AST) level, fasting serum insulin level, presence of metabolic syndrome and diabetes mellitus. In cross-sectional analysis, logistic regression was used to examine the association of the LFS with coronary heart disease (CHD), myocardial infarction (MI), congestive heart failure (CHF), stroke and angina pectoris. Mortality during follow-up was analysed using Cox proportional hazard regression.

RESULTS

LFS was associated with CHD (adjusted odds ratio [OR]: 1.09 per standard deviation [SD], 95% confidence interval [95% CI]: 1.03-1.15) (p = .003), CHF (1.11, 1.04-1.18) (p = .003) and angina pectoris (1.08, 1.02-1.13) (p = .005). LFS was not associated with MI or stroke, but was associated with increased all-cause and cardiovascular mortality with hazard ratios (HRs) of 1.10 (95% CI: 1.07-1.13) (p < .001) and 1.12 (95% CI: 1.06-1.17) (p < .001), respectively.

CONCLUSIONS

NAFLD is usually asymptomatic, but this large study of a large general population shows that LFS is associated with CHD, CHF, angina pectoris, cardiovascular and all-cause mortality. Determining the LFS is worthwhile, as it identifies people with NAFLD, who may also be at increased cardiovascular risk.Key MessagesLiver fat score (LFS), a non-invasive marker of non-alcoholic fatty liver disease (NAFLD), is associated with coronary heart disease (CHD), congestive heart failure (CHF) and angina.LFS is also associated with increased cardiovascular and all-cause mortality.Determining the LFS is worthwhile as it identifies people with NAFLD as well as increased cardiovascular risk.

Nonalcoholic Fatty Liver Disease and Diabetes: An Epidemiological Perspective

Nonalcoholic fatty liver disease (NAFLD) is thought to stem from the body's inability to store excess energy in adipocytes; as such, it is commonly viewed as the hepatic manifestation of metabolic syndrome. The pathogenesis of NAFLD involves ectopic fat accumulation, which also takes place in the liver, muscle and visceral fat. NAFLD is rapidly becoming more widespread in Korea, with an estimated prevalence of 30% in adults. Type 2 diabetes mellitus (T2DM) and NAFLD share insulin resistance as a common pathophysiological mechanism, and each of these two diseases affects the development of the other. Recent studies have suggested that NAFLD is often present as a comorbidity in T2DM patients. The mutual interrelationship between these conditions is shown by findings suggesting that T2DM can exacerbate NAFLD by promoting progression to nonalcoholic hepatosteatosis or fibrosis, while NAFLD causes the natural course of diabetic complications to worsen in T2DM patients. It remains unknown whether one disease is the cause of the other or vice versa. In this review, I would like to discuss current epidemiological data on the associations between NAFLD and T2DM, and how each disease affects the course of the other.

The relationship between serum fatty-acid binding protein 4 level and lung function in Korean subjects with normal ventilatory function

Background

The aim of this study was to assess the association of lung function with serum fatty-acid binding protein 4 (FABP4) in apparently healthy Korean adults.

Methods

In 495 participants in a health screening program, Force Exploratory Volume (FEV) 1 and Forced Vital Capacity (FVC) were assessed with standard spirometry. Subjects with obstructive (n = 19) and restrictive (n = 45) lung function were excluded from the analysis. Serum FABP4 level was measured by enzyme-linked immunosorbent assay and transformed into Ln(FABP4). 431 subjects with normal ventilator function (72.4 % men, mean age 41 years) were included in the final analysis.

Results

Mean Ln(FABP4) significantly decreased in subjects from 1^st quartile to 4^th quartile of FVC (p = 0.008). Ln(FABP4) did not show significant differences across the quartile groups of FEV1. The odds ratio (OR) of being in the lowest quartile of FVC was 2.704 in subject with 3^rd tertile of Ln(FABP4) after full adjustment for confounding variables {95 % confidence interval (CI) 1.397 ~ 5.357}. OR of being in the lowest quartile of FEV1 was 1.822 (95 % CI 1.021 ~ 3.298) in subjects with 3^rd tertile of Ln(FABP4) after adjustment of age and sex, which was attenuated after full adjustment for confounding variables.

Conclusion

Increased FABP4 level showed increased risk for reduced lung function in subjects with normal ventilatory function.

Electronic supplementary material

The online version of this article (doi:10.1186/s12890-016-0190-8) contains supplementary material, which is available to authorized users.

Metabolic Health Is More Important than Obesity in the Development of Nonalcoholic Fatty Liver Disease: A 4-Year Retrospective Study

BACKGROUND

The aim of this study is to compare the risk for future development of nonalcoholic fatty liver disease (NAFLD) according to different status of metabolic health and obesity.

METHODS

A total of 3,045 subjects without NAFLD and diabetes at baseline were followed for 4 years. Subjects were categorized into four groups according to the following baseline metabolic health and obesity statuses: metabolically healthy, non-obese (MHNO); metabolically healthy, obese (MHO); metabolically unhealthy, non-obese (MUHNO); and metabolically unhealthy, obese (MUHO). Being metabolically healthy was defined as having fewer than two of the following five components: high blood pressure, high fasting blood glucose, high triglyceride, low high density lipoprotein cholesterol, and being in the highest decile of the homeostasis model assessment-insulin resistance index. Obesity was defined as a body mass index >25 kg/m². The presence of NAFLD was assessed by ultrasonography.

RESULTS

The proportions of subjects included in the MHNO, MHO, MUHNO, and MUHO groups were 71.4%, 9.8%, 13.0%, and 5.8%, respectively. The proportions of subjects who developed NAFLD were 10.5%, 31.4%, 23.2%, and 42% in the MHNO, MHO, MUHNO, and MUHO groups, respectively. The risk for developing NAFLD was highest in subjects who were metabolically unhealthy both at baseline and after 4 years compared with subjects who were consistently metabolically healthy during the follow-up period (odds ratio, 2.862). Using the MHNO group as reference, the odds ratios for the MHO, MUHNO, and MUHO groups were 1.731, 1.877, and 2.501, respectively.

CONCLUSION

The risk for NAFLD was lower in MHO subjects than in MUNO subjects.

Clinical significance of enteral nutrition therapy for elderly patients with nonalcoholic fatty liver disease associated with metabolic syndrome

AIM: To explore the clinical significance of enteral nutrition therapy for elderly patients with nonalcoholic fatty liver disease associated with metabolic syndrome.

METHODS: A total of 120 patients diagnosed with nonalcoholic fatty liver disease with metabolic syndrome between May 2009 and May 2014 were randomly divided into either an enteral nutrition group or a parenteral nutrition group, with 60 cases in each group. The demographic data, such as age, sex and severity of illness, had no statistical difference (P > 0.05).

RESULTS: The body mass index (BMI), fasting plasma glucose (FPG), glycosylated hemoglobin (HbAlc), triglyceride (TG), low density lipoprotein cholesterol (LDL-C), total bilirubin (TBIL), direct bilirubin (DBIL), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were significantly in the enteral nutrition group after treatment (P < 0.05), although the waist-to-hip ratio, triceps skin fold (TSF), cholesterol, and high-density lipoprotein cholesterol (HDL-C) showed no obvious difference (P > 0.05) between before and after the treatment. In the parenteral nutrition group, the BMI, FPG and HbAlc significantly increased after therapy (P > 0.05), while the 2-h postprandial blood glucose level (2-h FBG), TC, HDL-C, and LDL-C had no significant changes (P > 0.05).

CONCLUSION: Enteral nutrition is more effective than parenteral nutrition in protecting liver functions, lowering the BMI and regulating sugar and fat metabolism in elderly patients with nonalcoholic fatty liver disease associated with metabolic syndrome.

Liver fatty acid-binding protein as a diagnostic marker for non-alcoholic fatty liver disease

BACKGROUND AND AIMS

Liver fatty acid-binding protein (L-FABP) is a small cytoplasmic protein. The aim of the current study was to investigate L-FABP levels and to determine their diagnostic value for non-alcoholic fatty liver disease (NAFLD).

METHODS

We enrolled in this study 24 consecutive patients with NAFLD who were diagnosed with elevated transaminases and with steatosis by ultrasonograph. The control group consisted of 22 healthy control subjects matched for age and gender. Serum levels of L-FABP were determined by enzyme-linked immunosorbent assay.

RESULTS

L-FABP levels in NAFLD patients were higher than in the control group (levels were 41,976 ± 18,998 and 17048 ± 5021 pg/mL, respectively). A strong correlation was found between serum L-FABP concentrations and aspartate aminotransferase, alanine aminotransferase, body mass index, glucose and γ-glutamyltransferase levels. A level of 284,000 pg/mL L-FABP had 73% sensitivity and 100% specificity. Positive and negative predictive values for L-FABP were 100  and 79%, respectively.

CONCLUSIONS

Serum L-FABP can be considered as a new diagnostic marker for detecting non-alcoholic fatty liver disease.