Implications of Abdominal Adipose Tissue Distribution on Nonalcoholic Fatty Liver Disease and Metabolic Syndrome: A Chinese General Population Study

The association between the visceral to subcutaneous abdominal fat ratio and the risk of cardiovascular diseases: a systematic review

BACKGROUND

Cardiovascular diseases (CVDs) are the primary cause of mortality globally. The prevalence of obesity is rising worldwide; there seems to be a significant positive association between obesity and CVDs. The distribution of fat in the abdominal area in the form of visceral (VAT) or subcutaneous adipose tissue (SAT) affects the risk of CVDs. The aim of the present study was to conduct a systematic review of the available literature regarding the association between the VAT-to-SAT ratio and CVDs.

METHODS

A comprehensive search strategy was used to retrieve all human observational studies indexed in PubMed, Scopus and Google Scholar databases/search engines (from Jan 2000 up to Oct 2023). The VAT-to-SAT or SAT-to-VAT ratio was an independent variable and various cardiovascular diseases, including hypertension, atherosclerosis, coronary heart disease, cerebrovascular disease and heart failure, were considered as outcomes of interest.

RESULTS

Out of 1173 initial studies, 910 papers were screened. Based on the inclusion criteria, 883 papers were excluded. Finally, 27 papers (18 cross-sectional and 9 cohort studies) published between 2010 and 2023 which met the inclusion criteria were reviewed.

CONCLUSIONS

The distribution of abdominal fat seems to be associated with the risk of CVDs; the majority of the evidence suggests that a higher abdominal VAT-to-SAT ratio is associated with the development of CVDs. Therefore, this ratio can be used as a prognostic indicator for CVDs.

TRIAL REGISTRATION

Not applicable.

Predictive Value of the Chinese Visceral Adiposity Index for Metabolic Dysfunction-Associated Fatty Liver Disease and Elevated Alanine Aminotransferase Levels in Nonobese Chinese Adults: A Cross-Sectional Study

Purpose

It is unclear how the Chinese Visceral Adiposity Index (cVAI) relates to metabolic dysfunction-associated fatty liver disease (MAFLD) and alanine aminotransferase (ALT) in nonobese individuals. In this study, we evaluated the ability of the cVAI to predict MAFLD and elevated ALT in nonobese participants.

Methods

This cross-sectional study recruited 541 nonobese subjects from March 2019 to January 2022 with the age range of 18-80 years. Hepatic steatosis was diagnosed by ultrasound. Participants were divided into four groups according to cVAI quartiles. To assess the associations between cVAI and MAFLD and elevated ALT, multivariate logistic regression was used. Receiver operating characteristic (ROC) curves were generated to evaluate the ability of the cVAI to predict MAFLD and elevated ALT.

Results

Compared to the group with the lowest cVAI, the group with the highest cVAI was positively associated with nonobese MAFLD [16.173 (4.082-64.073), P < 0.001] and elevated ALT [8.463 (2.859-25.049), P < 0.001]. The area under the ROC curve (AUC) of the cVAI was greater than that of WC, waist-to-height ratio, or BMI for predicting nonobese MAFLD in the male, female, > 38 and ≤ 38 years old subgroups (P < 0.05), respectively. In addition, the ability of the cVAI to predict MAFLD was better in females, young individuals, and individuals with a higher education level (P < 0.05). The cVAI also had good predictive ability for elevated ALT levels [0.655 (0.602-0.708)], particularly in females, young people, and highly educated participants. Furthermore, the cVAI was strongly positively correlated with the liver fibrosis score (P < 0.05) and was also a strong indicator of concomitant metabolic syndrome in nonobese MAFLD patients [AUC = 0.688 (0.612-0.763)].

Conclusion

The cVAI was strongly related to nonobese MAFLD and elevated ALT. The cVAI may be a reliable and accessible predictor of nonobese MAFLD and elevated ALT.

Sex- and age-specific associations between abdominal fat and non-alcoholic fatty liver disease: a prospective cohort study

Obesity is closely related to non-alcoholic fatty liver disease (NAFLD). Although sex differences in body fat distribution have been well demonstrated, little is known about the sex-specific associations between adipose tissue and the development of NAFLD. Using community-based cohort data, we evaluated the associations between magnetic resonance imaging quantified areas of abdominal adipose tissue, including visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT), and incident NAFLD in 2830 participants (1205 males and 1625 females) aged 55-70 years. During a 4.6-year median follow-up, the cumulative incidence rates of NAFLD increased with areas of VAT and SAT both in males and in females. Further analyses showed that the above-mentioned positive associations were stronger in males than in females, especially in participants under 60 years old. In contrast, these sex differences disappeared in those over 60 years old. Furthermore, the risk of developing NAFLD increased non-linearly with increasing fat area in a sex-specific pattern. Additionally, sex-specific potential mediators, such as insulin resistance, lipid metabolism, inflammation, and adipokines, may exist in the associations between adipose tissue and NAFLD. This study showed that the associations between abdominal fat and the risk of NAFLD were stratified by sex and age, highlighting the potential need for sex- and age-specific management of NAFLD.

Changes in mesenteric fat thickness and its clinical impact in bariatric surgery

Obesity, especially central obesity is associated with increased risk of metabolic syndrome, non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus. The study aimed to investigate the associations of the changes of abdominal fat thicknesses with changes of anthropometric indexes and improvements of metabolic phenotypes in patients with obesity and T2DM before and after bariatric surgery. Between April 2016 and January 2017, 34 adult patients with concurrent obesity and T2DM scheduled for different bariatric surgeries were prospectively evaluated by ultrasound before and 1-year after bariatric surgery to determine abdominal fat thicknesses (mesenteric fat, preperitoneal fat and subcutaneous fat) and NAFLD. At 1 year, of the 25 patients that finished the study, significant decrease in mesenteric-fat-thickness was associated with significant reduction of obesity, that is, BMI (-24%, p < .001), remission of metabolic syndrome (32%, p = .008), NAFLD (60%, p < .001) and T2DM (44%, p < .001). Lower baseline mesenteric fat thickness was associated with remission of metabolic syndrome. Lower baseline mesenteric-fat-thickness may have the potential to predict metabolic syndrome remission after bariatric surgery.

Associations between abdominal obesity indices and pathological features of non-alcoholic fatty liver disease: Chinese visceral adiposity index

BACKGROUND AND AIM

Many abdominal obesity indices such as waist circumference (WC), lipid accumulation product (LAP), visceral obesity index (VAI), and Chinese VAI (CVAI) have been considered to be associated with the risk of non-alcoholic fatty liver disease (NAFLD), but the association between abdominal obesity indices and the pathological features of NAFLD is uncertain. This study aims to explore the associations between these indices and the pathological features of NAFLD.

METHODS

A total of 147 patients with biopsy-confirmed NAFLD were enrolled in the final analysis. General information, biochemical tests, and pathological information of patients were collected. VAI, LAP, and CVAI were calculated. Spearman's correlation analysis and logistics regression analysis were applied to assess the relationship between abdominal obesity indices and the pathological features of NAFLD. Receiver operating characteristic curve analyses were used to assess the value of abdominal obesity indices in predicting liver fibrosis and non-alcoholic steatohepatitis.

RESULTS

Non-alcoholic fatty liver disease activity score (NAS) ≥ 5 significantly correlated with WC, LAP, VAI, and CVAI both in univariate and multivariate analyses (P < 0.05). Fibrosis was significantly and positively correlated with WC, LAP, and CVAI (P < 0.05). After adjustment for potential confounders, fibrosis remained associated with CVAI (P < 0.05).

CONCLUSION

CVAI is significantly associated with the pathological features of NAFLD, and CVAI shows the most superior efficacy in diagnosing fibrosis among these indices.

The Role of Olfactomedin 2 in the Adipose Tissue–Liver Axis and Its Implication in Obesity-Associated Nonalcoholic Fatty Liver Disease

This study’s objective was to assess the involvement of olfactomedin 2 (OLFM2), a secreted glycoprotein related to lipid metabolism regulation, in nonalcoholic fatty liver disease (NAFLD) mediated by the adipose-tissue–liver axis. OLFM2 mRNA expression was analyzed in subcutaneous (SAT) and visceral (VAT) adipose tissue by RT–qPCR. The cohort included women with normal weight (n = 16) or morbid obesity (MO, n = 60) who were subclassified into normal liver (n = 20), simple steatosis (n = 21), and nonalcoholic steatohepatitis (NASH, n = 19) groups. The results showed that OLFM2 expression in SAT was enhanced in MO individuals and in the presence of NAFLD. Specifically, OLFM2 expression in SAT was increased in mild and moderate degrees of steatosis in comparison to the absence of it. Moreover, OLFM2 expression in SAT was negatively correlated with interleukin-6 levels. On the other hand, OLFM2 expression in VAT decreased in the presence of NASH and exhibited a positive correlation with adiponectin levels. In conclusion, OLFM2 in SAT seems to be implicated in hepatic lipid accumulation. Additionally, since we previously suggested the possible implication of hepatic OLFM2 in NAFLD progression, now we propose a possible interaction between the liver and SAT, reinforcing the potential implication of this tissue in NAFLD development.

Positive Association Between the Chinese Visceral Adiposity Index and Nonalcoholic Fatty Liver Disease in Lean Adults

BACKGROUND

Chinese visceral adiposity index (CVAI) is a novel indicator that precisely evaluates visceral obesity and has been shown to be significantly associated with nonalcoholic fatty liver disease (NAFLD) in the general population. However, the relationship between CVAI and NAFLD in lean adults remains unclear.

AIMS

This study aimed to explore the association of CVAI with NAFLD in a lean population and evaluate the diagnostic capability of CVAI for lean NAFLD.

METHODS

A cross-sectional study was conducted among 9,607 lean adults (body mass index < 24 kg/m²), who underwent their annual health examinations at the First Affiliated Hospital, Zhejiang University School of Medicine in 2021. NAFLD was determined by ultrasonography to the exclusion of other known etiologies.

RESULTS

The prevalence of NAFLD was 16.4% in this lean population. CVAI values were significantly higher in participants with NAFLD than those without NAFLD and the CVAI quartile was positively associated with the prevalence of NAFLD, which was 0.4%, 6.0%, 19.4%, and 39.8% among the participants with CVAI in quartile 1 to 4, respectively (P for trend < 0.001). Logistic regression analysis found that CVAI was positively associated with the risk of NAFLD (adjusted odds ratio: 1.025, 95% confidence interval: 1.021-1.028; P < 0.001). Furthermore, CVAI had a significantly higher area under curve value for detecting NAFLD than other visceral obesity indices.

CONCLUSION

Our study showed that CVAI was positively associated with the prevalence and risk of NAFLD in lean adults, and CVAI showed the highest diagnostic ability for lean NAFLD.

Sex-specific Cutoff Values of Visceral Fat Area for Lean vs. Overweight/Obese Nonalcoholic Fatty Liver Disease in Asians

BACKGROUND AND AIMS

Visceral obesity is a risk factor for nonalcoholic fatty liver disease (NAFLD). We investigated sex-specific optimal cutoff values for visceral fat area (VFA) associated with lean and overweight/obese NAFLD in an Asian population.

METHODS

This retrospective study included 678 potential living liver donors (mean age, 30.8±9.4 years; 434 men and 244 women) who had undergone abdominal computed tomography (CT) imaging and liver biopsy between November 2016 and October 2017. VFA was measured using single-slice abdominal CT. NAFLD was evaluated by liver biopsy (≥5% hepatic steatosis). Receiver operating characteristic curve analysis was used to determine cutoff values for VFA associated with lean (body mass index [BMI] <23 kg/m²) and overweight/obese (BMI ≥23 kg/m²) NAFLD.

RESULTS

Area under the curve (AUC) values with 95% confidence intervals (CI) for VFA were 0.82 (95% CI, 0.75-0.88) for lean and 0.74 (95% CI, 0.69-0.79) for overweight/obese men with NAFLD. The AUC values were 0.67 (95% CI, 0.58-0.75) for lean and 0.71 (95% CI, 0.62-0.80) for overweight/obese women with NAFLD. The cutoff values for VFA associated with lean NAFLD were 50.2 cm² in men and 40.5 cm² in women. The optimal cutoff values for VFA associated with overweight/obese NAFLD were 100.6 cm² in men and 68.0 cm² in women.

CONCLUSIONS

Sex-specific cutoff values for VFA may be useful for identifying subjects at risk of lean and overweight/obese NAFLD.

The association of pericardial fat and peri-aortic fat with severity of nonalcoholic fatty liver disease

Visceral adipose tissue (VAT) is associated with central obesity, insulin resistance and metabolic syndrome. However, the association of body-site specific adiposity and non-alcoholic fatty liver disease (NAFLD) has not been well characterized. We studies 704 consecutive subjects who underwent annual health survey in Taiwan. All subjects have been divided into three groups including normal (341), mild (227) and moderate and severe (136) NAFLD according to ultrasound finding. Pericardial (PCF) and thoracic peri-aortic adipose tissue (TAT) burden was assessed using a non-contrast 16-slice multi-detector computed tomography (MDCT) dataset with off-line measurement (Aquarius 3DWorkstation, TeraRecon, SanMateo, CA, USA). We explored the relationship between PCF/TAT, NAFLD and cardiometabolic risk profiles. Patients with moderate and mild NAFLD have greater volume of PCF (100.7 ± 26.3vs. 77.1 ± 21.3 vs. 61.7 ± 21.6 ml, P < 0.001) and TAT (11.2 ± 4.1 vs. 7.6 ± 2.6 vs. 5.5 ± 2.6 ml, P < 0.001) when compared to the normal groups. Both PCF and TAT remained independently associated with NAFLD after counting for age, sex, triglyceride, cholesterol and other cardiometabolic risk factors. In addition, both PCF and TAT provided incremental prediction value for NAFLD diagnosis. (AUROC: 0.85 and 0.87, 95%, confidence interval: 0.82-0.89 and 0.84-0.90). Both visceral adipose tissues strongly correlated with the severity of NAFLD. Compared to PCF, TAT is more tightly associated with NAFLD diagnosis in a large Asian population.

The Perirenal Fat Thickness Was Associated with Nonalcoholic Fatty Liver Disease in Patients with Type 2 Diabetes Mellitus

PURPOSE

Obesity is an important risk factor for nonalcoholic fatty liver disease (NAFLD). Perirenal fat and paranephric fat were seldom studied in NAFLD. We aimed to explore the relationship between perirenal fat thickness (PrFT) and paranephric fat thickness (PnFT) and NAFLD in patients with type 2 diabetes mellitus (T2DM).

PATIENTS AND METHODS

A total of 493 diabetic patients including 231 NAFLD patients were enrolled in our study from September 2019 to December 2020. Patients with NAFLD were categorized into three subgroups according to the severity and fibrosis risk of NAFLD. Anthropometric indices and clinical characteristics were collected from clinical records. PrFT and PnFT were measured via ultrasound. Multivariate logistic regression analysis was used to assess the association between PrFT, PnFT and presence, severity and advanced fibrosis risk of NAFLD.

RESULTS

Compared with non-NAFLD patients, those with NAFLD had significantly higher PrFT and PnFT. The PrFT and PnFT were independently associated with presence of NAFLD and the PrFT was independently associated with the advanced fibrosis risk of NAFLD after adjusting confounding factors.

CONCLUSION

The PrFT was independently associated with the presence and advanced fibrosis risk of NAFLD in patients with T2DM.

The Interplay between Insulin Resistance, Inflammation, Oxidative Stress, Base Excision Repair and Metabolic Syndrome in Nonalcoholic Fatty Liver Disease

One of the most common chronic liver disorders, affecting mainly people in Western countries, is nonalcoholic fatty liver disease (NAFLD). Unfortunately, its pathophysiological mechanism is not fully understood, and no dedicated treatment is available. Simple steatosis can lead to nonalcoholic steatohepatitis and even to fibrosis, cancer, and cirrhosis of the liver. NAFLD very often occurs in parallel with type 2 diabetes mellitus and in obese people. Furthermore, it is much more likely to develop in patients with metabolic syndrome (MS), whose criteria include abdominal obesity, elevated blood triacylglycerol level, reduced high-density lipoprotein cholesterol level, increased blood pressure, and high fasting glucose. An important phenomenon in MS is also insulin resistance (IR), which is very common in NAFLD. Liver IR and NAFLD development are linked through an interaction between the accumulation of free fatty acids, hepatic inflammation, and increased oxidative stress. The liver is particularly exposed to elevated levels of reactive oxygen species due to a large number of mitochondria in hepatocytes. In these organelles, the main DNA repair pathway is base excision repair (BER). The present article will illustrate how impairment of BER may be related to the development of NAFLD.