Introduction
A study of healthy check-up participants found that the prevalence of non-alcoholic fatty liver disease (NAFLD) in Japanese patients was approximately 30% [1]. Furthermore, the incidence of fatty liver is expected to increase rapidly owing to movement restrictions due to the coronavirus pandemic. Non-alcoholic steatohepatitis (NASH) causes fatty liver, hepatitis, liver cirrhosis, and hepatocellular carcinoma in individuals who do not drink alcohol. NAFLD, which also includes nonprogressive fatty liver disease, is a metabolic syndrome phenotype resulting in cardiovascular event-related deaths rather than liver disease-related deaths. Therefore, early management of lifestyle-related diseases associated with cardiovascular events is essential.
Despite intensive efforts, no United States Food and Drug Administration-approved human drug therapy is available for NAFLD/NASH [2]. Development of NASH-improving therapies has focused on preventing fibrosis; however, this is challenging owing to the complexity of NASH pathology. Hence, future treatment strategies for patients with NAFLD/NASH should focus on controlling steatosis in its early stages.
Among Japanese patients with NAFLD, 65.7% have dyslipidemia, while only 43.7% have diabetes mellitus [3]. The American Association for the Study of Liver Disease guidelines suggest that statins can treat dyslipidemia in patients with NAFLD [4]. Furthermore, reports suggest that fibrate protects against NAFLD; however, evidence regarding its effect on liver function is lacking. In general, triglyceride (TG) levels are considerably higher than total cholesterol levels. Thus, high TG levels trigger fatty liver in many cases in clinical practice. Since fatty liver is a pathological condition where TGs are deposited in the liver, therapies that lower blood TG levels and, consequently, fat deposition in the liver are essential.
Peroxisome proliferator-activated receptors (PPARs) contain three isoforms: PPARα, PPARγ, and PPARδ. PPARα was initially identified as the molecular target of xenobiotic-inducing peroxisome proliferation in rodents [5]. It is well established as a critical modulator of lipid transport and metabolism, notably mitochondrial and peroxisomal fatty acid β-oxidation [6]. Activating PPARα promotes fatty acid uptake, utilization, and catabolism [7], potentially benefiting patients with NAFLD. Therefore, PPARα modulation is a key treatment strategy for metabolic diseases, including NAFLD [8]. Moreover, activating PPARα elicits several effects in the liver, such as increased levels of lipoprotein lipase and apolipoprotein, leading to enhanced catabolism of TG-rich lipoproteins and reduced serum TG levels [9]. Furthermore, enhanced mitochondrial β-oxidation decreases fatty acid levels in the liver, reducing hepatic production of very-low-density lipoprotein [10]. Therefore, PPARα might have a protective effect against NAFLD. Notably, patients with NASH have decreased liver PPARα expression [11].
Pemafibrate, a PPARα agonist, may improve fatty liver disease, and reports suggest that it improves liver function in patients with NAFLD [12-14]. However, its effect on fatty liver is unknown. Therefore, in this single-arm study, we evaluated the effect of oral pemafibrate administration for three or six months on fatty liver using the FibroScan, a device that quantitatively measures fat in the liver.
Material and methods
Study population
This retrospective observational study included patients with NAFLD treated with pemafibrate for either three or six months between May 2020 and December 2022. Patients who met the following inclusion criteria were enrolled: 1) those with hypertriglyceridemia and fatty liver; 2) fatty liver was detected using ultrasound B-mode; and 3) those with a TG level of ≥ 150 mg/dl when fasting or ≥ 175 mg/dl at any time, measured at least twice. The exclusion criteria were: 1) changes in drug regimens for dyslipidemia and diabetes during the observation period; 2) patients who started drinking 20 g or more of alcohol during the observation period; and 3) patients with a history of alcoholic liver injury owing to a history of drinking 60 g/day or more of alcohol before the observation period.
Steatosis evaluation
The FibroScan (FibroScan 430 Mini, Echosens, France), the only device covered by health insurance for quantitatively evaluating liver fat content in Japan in April 2022, was used in this study. The controlled attenuation parameter (CAP) was the primary endpoint to assess steatosis. FibroScan measurements were performed with the participant in a fasted state by a single examiner to eliminate operator errors. Moreover, the FibroScan-aspartate aminotransferase (FAST) score [15] was used to predict the severity of NAFLD. The hepatic steatosis index (HSI) [16] was calculated to evaluate steatosis and predict the liver fat content.
Liver evaluations
The secondary endpoints were various liver biomarkers. Alanine transaminase (ALT) levels were used to assess hepatic inflammation. Liver stiffness was measured using FibroScan; liver stiffness is affected by liver inflammation and hepatic congestion. The fibrosis-4 (FIB-4) index and the aspartate aminotransferase-to-platelet ratio index (APRI) were used to assess hepatic fibrosis [17]. The albumin-bilirubin (ALBI) score was used to evaluate hepatic function [18].
Results
Patient backgrounds
In total, 51 and 42 patients were enrolled in the three- and six-month studies, respectively. In the three-month group, three patients were excluded for taking either omega-3-acid ethyl esters (n = 1) or sodium-glucose cotransporter-2 (SGLT-2) inhibitors (n = 2) midway through the study; thus, only 48 patients were included in the three-month analyses. In the six-month group, four patients were excluded for taking either omega-3-acid ethyl esters (n = 1), pravastatin sodium (n = 1), or SGLT-2 inhibitors (n = 2); thus, 38 patients were included in the six-month analyses. Table 1 lists the patients’ baseline characteristics.
Table 1
Baseline patient characteristics
At baseline in the three-month group, 10 patients had dyslipidemia and were taking either rosuvastatin calcium (n = 5), atorvastatin calcium hydrate (n = 3), or pitavastatin calcium hydrate (n = 2). Furthermore, 14 and 17 patients had diabetes and hypertension complications, respectively. At baseline in the six-month group, 8 patients had dyslipidemia and were taking either rosuvastatin calcium (n = 5), atorvastatin calcium hydrate (n = 2), or pitavastatin calcium hydrate (n = 1).
Parameter changes
Table 2 presents the parameter changes after three or six months of pemafibrate administration, which did not significantly affect weight or body mass index. Body composition changes were also not observed in 21 and 15 patients after three and six months, respectively (measured using an InBody body composition meter [InBody470, InBody Co., Korea], data not shown).
Table 2
Clinical parameter changes after three and six months
[i] 3 M – 3 months after administration, 6 M – 6 months after administration SE – standard error, WBC – white blood cells, Hgb – hemoglobin, PLT – platelet, Alb – albumin, TB – total bilirubin, AST – aspartate aminotransferase, ALT – alanine aminotransferase, γ-GTP – γ-glutamyl transpeptidase, ALP – alkaline phosphatase, TG – triglyceride, TC – total cholesterol, HDL-C – high-density lipoprotein cholesterol, LDL-C – low-density lipoprotein cholesterol, FPG – fasting plasma glucose, HbA1c – hemoglobin A1c, LSM – liver stiffness measurement, CAP – controlled attenuation parameter, FAST score – FibroScan-aspartate aminotransferase score, FIB-4 – Fibrosis-4, APRI – aspartate aminotransferase to platelet ratio index, ALBI – albumin-bilirubin, HSI – hepatic steatosis index
The CAP and HSI values significantly improved after three or six months of treatment, indicating fatty liver improvements. The FAST score also significantly improved after three or six months of treatment, suggesting that pemafibrate prevented the progression of fatty liver due to NASH.
Furthermore, the ALT and γ-glutamyl transpeptidase (γ-GTP) levels, FIB-4 index, APRI, and ALBI score values decreased after three or six months, whereas the platelet and serum albumin levels significantly increased. Most significant changes occurred after three months and remained after six months.
Correlation analyses
We performed a correlation analysis between the hepatic markers and other parameters after three months of pemafibrate therapy (Table 3). ALT changes significantly correlated with AST, γ-GTP, ALP, hemoglobin A1c, FAST, and APRI changes. Furthermore, CAP value changes significantly correlated with the changes in fasting plasma glucose (FPG) levels.
Table 3
Association of changes in hepatic markers of inflammation and steatosis with other parameters
[i] ALT – alanine aminotransferase, CAP – controlled attenuation parameter, CC – correlation coefficient, BMI – body mass index, WBC – white blood cells, Hgb – hemoglobin, PLT – platelets, Alb – albumin, TB – total bilirubin AST – aspartate aminotransferase, γ-GTP – gamma-glutamyl transpeptidase, ALP – alkaline phosphatase, TG – triglyceride, TC – total cholesterol, HDL-C – high-density lipoprotein cholesterol, LDL-C – low-density lipoprotein cholesterol, FPG – fasting plasma glucose, HbA1c – hemoglobin A1c, LSM – liver stiffness measurement, FAST score – FibroScan-aspartate aminotransferase score, FIB-4 – Fibrosis-4, APRI – aspartate aminotransferase to platelet ratio index, ALBI – albumin-bilirubin, HSI – hepatic steatosis index.
Discussion
Several reports have demonstrated that pemafibrate improves liver function by improving TG levels. For example, pemafibrate administration improved the histologic findings of the liver, including steatosis, ballooning, and fibrosis, in a NASH mouse model [19]. Pemafibrate treatment also significantly reduced the serum ALT, γ-GTP, and ALP levels in a clinical trial in patients with dyslipidemia [20], which was similar to our results. However, data indicating that pemafibrate improves fatty liver disease are lacking. Therefore, we evaluated fatty liver improvements following pemafibrate treatment.
Seko et al. [13] performed a single-arm prospective study in 20 patients with NAFLD, reporting that the transaminase, γ-GTP, and fasting TG levels were significantly higher, and the high-density lipoprotein cholesterol level and platelet count were significantly lower at baseline than after 12 weeks of pemafibrate treatment. Although these results suggest that pemafibrate may improve fatty liver, no study has assessed CAP values and their association with fatty liver improvement. Thus, we evaluated the CAP values before and after treatment, finding significant differences. Because CAP measurements have an error of approximately 20 dB/m between examiners, the same examiner obtained all measurements in the same treatment center to limit variability [21].
FibroScan is used to measure noninvasive quantified data and probe directly into the liver, providing a more accurate assessment of liver status than blood tests. Three months of oral pemafibrate administration significantly improved the FAST score, NASH progression prediction value derived from FibroScan data, and HSI. These results suggest that pemafibrate improved NAFLD and steatosis.
For patients with NAFLD, reducing ALT is essential for preventing progression to NASH, as inflammation plays a central role in the progression to advanced fibrosis [22]. A three-month retrospective observational study of 38 patients with NAFLD reported that pemafibrate significantly decreased the ALT, γ-GTP, and TG levels and NAFLD fibrosis scores [23]. Another retrospective study [12] reported decreased transaminase and γ-GTP levels in patients with fatty liver disease treated with pemafibrate. These previous results are consistent with our findings. Ikeda et al. [24] reported that pemafibrate significantly improved serum TG levels, liver function, FIB-4 index, APRI, and fatty liver in patients with NAFLD and hypertriglyceridemia. Although similar results were obtained in this study, the FIB-4 and APRI values decreased, possibly owing to the increased platelet count and decreased AST and ALT levels. Specifically, changes in the transaminase level and platelet count, which are used in determining FIB-4 and APRI values, might have resulted in the decreased FIB-4 and APRI values. Similarly, a prospective study by Seko et al. [13] showed a significant increase in the platelet count, supporting our data. Therefore, platelets might be essential for hemostasis, healing inflammation, hepatitis, and progressing from simple lipemia to NASH [25]. Hence, an increased platelet count may indicate the disappearance of liver inflammation, explaining the significant decrease in the APRI and FIB-4 index values.
The significant correlation between changes in CAP values and FPG levels was noteworthy in this study. In patients with hypertriglyceridemia, pemafibrate improves glucose metabolism and liver function while increasing the fibroblast growth factor 21 levels [26]. Matsuba et al. [27] also reported that pemafibrate increased the splanchnic glucose uptake from baseline in patients with hypertriglyceridemia. Improvements in hepatic fat content, liver function, and plasma free fatty acids and adiponectin levels have been postulated to mediate the effects of PPARγ agonists on insulin-stimulated glucose disposal and insulin-mediated hepatic glucose production suppression [28, 29]. Pemafibrate ameliorates NASH by improving lipid turnover, promoting energy metabolism, and reducing insulin resistance and inflammation [19]. Moreover, pemafibrate reportedly improves insulin resistance [30].
This study has some limitations. First, this was a retrospective, observational study, and selection bias was unavoidable owing to the enrollment method, which only registered patients diagnosed with NAFLD based on imaging data. Second, several cases of continuous oral administration of SGLT-2 inhibitors during the study were documented, which also could have improved NAFLD. Body composition changes before and after treatment did not occur for those taking SGLT-2 inhibitors; thus, we suspect that the direct effect of weight loss on fatty liver was minimal. Third, a hepatic histopathological biopsy was not performed. Fourth, dietary remedies and exercise were not evaluated; however, the patients were advised to lose weight at the time of their diagnosis. Finally, the study population was relatively small.
Conclusions
Three months of pemafibrate treatment improved steatohepatitis based on FibroScan measurement data in patients with NAFLD associated with TG. Furthermore, the beneficial effects remained after six months of continuous administration. These results indicate potential effectiveness of pemafibrate for treating NAFLD, which should be investigated further and confirmed in larger prospective trials.
