This retrospective study is the first to examine the relationship between MHR and MAFLD in children and adolescents with obesity. In this population, we observed a significant increase in MHR in those with MAFLD compared to those without; this increase correlated significantly with fasting insulin, triglyceride, HOMA-IR, TG/HDL-C, TyG, and the grade of hepatosteatosis. Our study provides evidence that MHR is closely associated with MAFLD, establishing MHR as an independent risk factor for this condition.
The significantly higher MHR value in the MAFLD group suggests an increase in inflammatory biomarkers. Recent studies in adults have shown that MHR is a non-invasive biomarker for predicting NAFLD, aligning with our results (
8,
13-
15). Therefore, high MHR values, which are prognostic markers in atherosclerotic diseases, should be carefully evaluated. An analysis of 409 patients from Turkey revealed that individuals with NAFLD had significantly higher MHR than healthy controls. Additionally, age, ALT, and HOMA-IR values exhibited a positive correlation with MHR (
14). Similarly, our study found a positive correlation between MHR and fasting insulin, triglyceride, HOMA-IR, TG/HDL-C, and TyG. We also demonstrated that MHR correlated positively with the grade of hepatosteatosis.
Our findings indicate a significant relationship between male gender, elevated ALT levels, high MHR, and MAFLD. Huang et al. demonstrated that in a Chinese population of 14,189 individuals, those with high MHR values were significantly more likely to have NAFLD. Their multivariable logistic regression analysis indicated that MHR is significantly and positively associated with NAFLD risk (
15). Furthermore, our study found a link between male gender and an increased risk of NAFLD. A 2015 meta-analysis investigating the incidence of NAFLD in both normal-weight and obese teenagers revealed that the prevalence was twice as high in males, particularly in the obese subgroup. Our findings align with this meta-analysis, indicating that there was a 3.8-fold increase in the risk of NAFLD in males (
3).
In a large-scale study of the American population, there was a positive and independent link between NAFLD, the risk of liver fibrosis, and MHR, as determined using FibroScan. This study found that each unit increase in MHR was associated with a 1.87-fold increase in NAFLD risk (
13). In our study, each incremental unit increase in MHR was associated with a significant 16.166-fold increase in the risk of MAFLD. Zhao et al. found that MHR has good clinical performance in diagnosing NAFLD, with a cut-off value of 3.434 (× 10
8/mmol) (
8). In our study, the cut-off value of MHR for diagnosing MAFLD in children and adolescents was 0.43 (× 10
9/mmol). Additionally, Zhao et al. suggested that a diagnostic model combining MHR with ALT, AST, triglyceride, total cholesterol, creatinine, fasting blood sugar, uric acid, and BMI could better predict NAFLD, with an AUC value of 0.931. They proposed that MHR itself or in combination with other parameters could be used to predict NAFLD (
8).
Yozgat et al. reported a significant relationship between MHR and insulin resistance (
14). Consistent with this, the elevated levels of HOMA-IR, TG/HDL-C, and TyG in our study, which were hypothesized to be predictors of insulin resistance in the NAFLD cohort, validate the association between NAFLD and insulin resistance (
19,
20). Our findings support the positive correlation between MHR and TG/HDL-C, TyG, and HOMA-IR. As reported in previous studies, MHR is an easy, cost-effective, and predictive marker for identifying MAFLD in children and adolescents (
8,
13-
15).
The pathogenesis of obesity involves interactions between adipocytes and other inflammatory cells, including monocytes (
21). It has been demonstrated that inflammatory cytokines and inflammation significantly contribute to the development of hepatosteatosis in this interaction (
6,
7,
9). Hepatosteatosis occurs through metabolic processes and immune phenotypes resulting from interactions between the liver and other organs. Monocyte-derived macrophages are innate immune cells found in all organs (
9). In adipose tissue, the expression of monocyte chemotactic protein 1 (MCP-1) is effective in monocyte recruitment and inflammation stimulation (
22). Through the secretion of inflammatory and non-inflammatory factors, liver macrophages and Kupffer cells contribute to the advancement of steatohepatitis and hepatosteatosis in individuals with obesity (
10,
23). Depending on microenvironmental conditions, different macrophage populations exhibit pro-inflammatory and repair phenotypic characteristics. With simple steatosis, steatohepatitis is the primary indicator of inflammatory phenotype lipotoxicity. Cytokines secreted from active Kupffer cells inhibit genes that play a role in the lipid metabolism of hepatocytes, thereby increasing hepatosteatosis. Macrophages that play a key role in the progression or decline of hepatosteatosis are also being studied as therapeutic targets (
9). Evidence of this is the pharmacological inhibition of monocytes, insulin resistance, liver inflammation, and the alleviation of fibrosis (
24).
On the other hand, HDL-C, recognized for its anti-inflammatory properties, inhibits the activation of monocytes and the growth and specialization of monocyte precursor cells (
10). High-density lipoprotein cholesterol has been demonstrated to inhibit the synthesis of MCP-1, a molecule crucial for monocyte migration (
25). High-density lipoprotein cholesterol inhibits the oxidation of LDL and also opposes the pro-inflammatory and pro-oxidant actions of monocytes. Given the relationship between monocytes and HDL-C in inflammatory processes, MHR is considered an appropriate marker (
10). The association between MHR and conditions such as polycystic ovary syndrome (
26), metabolic syndrome (
27), diabetic retinopathy (
28), diabetic nephropathy (
29), and mortality from cardiovascular disease (
10) has been demonstrated in prior research. Furthermore, our study revealed that children and adolescents diagnosed with MAFLD exhibited elevated concentrations of triglycerides and decreased levels of HDL-C compared to those without MAFLD. This finding provides further evidence that metabolic disorders play a significant role in the development of MAFLD (
6).
In children and adolescents with obesity, while MHR is a good biomarker to distinguish NAFLD, there was no association between NLR, LMR, PLR, and NAFLD. The literature presents conflicting reports about NLR, PLR, and LMR in NAFLD (
7,
8,
30-
33). In a meta-analysis of adult studies, NLR was found to be a promising biomarker in predicting NAFLD and fibrosis (
30). On the other hand, Kara et al. found no association between NLR and hepatic inflammation or the severity of fibrosis, arguing that this could be related to other metabolic disorders present in patients (
31). Kohsari et al. reported that LMR is associated with NAFLD and Fatty Liver Index (
33). Zhou et al. identified a nonlinear correlation among NLR, PLR, and NAFLD (
32). In line with our study, Duan et al. showed that the NLR, PLR, and LMR are not different for people with obesity and NAFLD compared to only obesity. However, within the same investigation, levels of inflammatory cytokines, including IL-1β, IL-17, and IL-6, were notably elevated in comparison to possible biomarkers (
7). In the study of Zhao et al. mentioned earlier, healthy controls showed higher MHR, NLR, and LMR than individuals with NAFLD, while PLR was fairly lower. Moreover, according to ROC analysis, MHR predicted NAFLD above other inflammatory biomarkers (
8). The differences in findings in the literature may be attributed to variations in sample sizes, population age groups, and whether control groups included individuals with obesity.
5.1. Limitation
There were some limitations to our study: (1) we used ultrasound rather than liver biopsy or fibroscan to diagnose hepatosteatosis; (2) since our study is retrospective, a judgment on the cause-and-effect relationship between MHR and MAFLD could not be reached; (3) there was no healthy control group without obesity; and (4) other biomarkers were not considered to assess inflammation. To verify the results of this study, further research is needed, involving larger sample groups with healthy controls, utilizing more accurate diagnostic methods for MAFLD, and evaluating other inflammation markers.
5.2. Conclusions
As a result, MHR significantly increases in pediatric MAFLD and correlates with the grade of hepatosteatosis. The monocyte/HDL-C ratio, as a novel inflammatory biomarker, can be used to predict MAFLD in children and adolescents with obesity.