Introduction: Previously, we reported that the tyrosine kinase inhibitor (TKI) sorafenib decreases serum levels of carnitine and reduces skeletal muscle volume. Moreover, others reported that TKIs might lead to cardiomyopathy or heart failure. Therefore, this study aimed to evaluate the effects of lenvatinib (LEN) on skeletal muscle volume and cardiac function in patients with hepatocellular carcinoma (HCC). Methods: This retrospective study included 58 adult Japanese patients with chronic liver diseases and HCC treated with LEN. Blood samples were collected before and after 4 weeks of treatment, and serum carnitine fraction and myostatin levels were measured. Before and after 4–6 weeks of treatment, the skeletal muscle index (SMI) was evaluated from computed tomography images and cardiac function was assessed by ultrasound cardiography. Results: After treatment, SMI, serum levels of total carnitine, and global longitudinal strain were significantly lower, but serum levels of myostatin were significantly higher. Left ventricular ejection fraction showed no significant change. Conclusion: In patients with HCC, LEN decreases serum levels of carnitine, skeletal muscle volume, and worsens cardiac function.

At the American Association for the Study of Liver Diseases consensus conference in 2021, systemic combination chemotherapy with atezolizumab plus bevacizumab was recommended as a new first-line treatment for advanced hepatocellular carcinoma (HCC), and the tyrosine kinase inhibitors (TKIs) sorafenib and lenvatinib were recommended as second-line treatment [1]. Sorafenib, an oral multi-kinase inhibitor, improves the median survival and radiologic progression of patients with HCC and metastatic breast cancer [2‒4]. Previously, we reported that sorafenib decreases serum levels of carnitine and leads to pre-sarcopenia. We indicated that these phenomena might be induced by inhibition of carnitine absorption [5]. In patients with HCC and good liver function at the time of introduction of lenvatinib, treatment was associated with good prognosis [6, 7] and a higher likelihood of successful treatment after progression [8].

Sarcopenia frequently occurs in patients with liver cirrhosis (LC), and in liver diseases, it is reported to be associated with a lower survival rate. In LC, sarcopenia has an estimated prevalence of 40%–70%, and after liver transplant it leads to a lower quality of life, shorter survival, and worse outcomes [9‒11]. Lower skeletal muscle mass is also associated with severe adverse events, shorter time to treatment failure, and worse overall survival in patients with HCC treated with lenvatinib [12]. Finally, loss of skeletal muscle is a significant prognostic factor in patients treated with lenvatinib for unresectable HCC [13].

Carnitine (β-hydroxy-γ-N-trimethyl aminobutyric acid) is an important biological factor in fatty acid and energy metabolism. It is found in many foods, and humans obtain 75% of carnitine from animal products [14]. In particular, carnitine plays a central role in the transport of long-chain fatty acids from the cytosol to the mitochondrial matrix. It binds to long-chain acyl-coenzyme A to form acylcarnitine, which is then transported to the mitochondria and degraded by β-oxidation [15]. Patients with LC have secondary carnitine deficiency with sarcopenia and malnutrition, and supplementation with carnitine is beneficial in case of complications such as hepatic encephalopathy, sarcopenia, and muscle cramp [16, 17]. Carnitine is retained in the body by the human organic cationic transporter OCTN2, a sodium-dependent, high-affinity carnitine carrier. Sorafenib has been reported to inhibit OCTN2 function by approximately 24% [18]. Furthermore, lenvatinib was reported to cause reduced OCTN2 expression and carnitine deficiency in the skeletal muscle of rats [19]. Lenvatinib may also decrease serum levels of carnitine in patients with HCC, although one study found significantly higher serum levels of free carnitine at days 3 and 7 than at baseline [20].

Rates of cardiotoxicity associated with TKIs may be unknown or underestimated [21]. TKI-induced myocyte damage was evaluated by assessing lactate dehydrogenase release from cultured neonatal rat cardiac myocytes, and the TKIs lapatinib, erlotinib, gefitinib, imatinib, sorafenib, sunitinib, and dasatinib were all shown to increase lactate dehydrogenase release from damaged myocytes [22]. However, the detailed effects of lenvatinib on cardiac function remain unknown.

A phase Ib study evaluated lenvatinib plus pembrolizumab treatment in patients with unresectable HCC [23]. Because this drug combination may become a first-line treatment for unresectable HCC in the future, it is important to evaluate the effects of lenvatinib on sarcopenia. Therefore, the present retrospective study aimed to determine whether lenvatinib decreases carnitine levels and thus reduces skeletal muscle volume and worsens cardiac function in patients with HCC.

Patients

We retrospectively enrolled 58 patients with chronic hepatitis (CH) or LC who received lenvatinib therapy for advanced HCC at our hospital between April 2018 and February 2021. Lenvatinib (Eisai Co., Ltd., Tokyo, Japan) was administered once daily after breakfast at a dose based on body weight (8 mg/day for body weight <60 kg and 12 mg/day for body weight ≥60 kg). Before and after 4 weeks of treatment, skeletal muscle volume was measured in all 58 patients and serum levels of carnitine were measured in 43 patients, and before and after 4–6 weeks of treatment, cardiac function was evaluated in 7 patients (Fig. 1).

Fig. 1.

Study population. Evaluations performed in 58 retrospectively enrolled patients with advanced hepatocellular carcinoma and chronic hepatitis or liver cirrhosis who received lenvatinib therapy. Serum levels of carnitine were measured before and after 4 weeks of treatment, and cardiac function was evaluated before and after 4–6 weeks treatment.

Fig. 1.

Study population. Evaluations performed in 58 retrospectively enrolled patients with advanced hepatocellular carcinoma and chronic hepatitis or liver cirrhosis who received lenvatinib therapy. Serum levels of carnitine were measured before and after 4 weeks of treatment, and cardiac function was evaluated before and after 4–6 weeks treatment.

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Evaluation of Efficacy

Dynamic computed tomography (CT) scans were obtained at baseline and 4 weeks after starting lenvatinib treatment. Tumor response was assessed with the modified Response Evaluation Criteria in Solid Tumors [24, 25].

Measurement of Skeletal Muscle Volume

Skeletal muscle volume was also assessed from the CT scans obtained at baseline and after 4 weeks of treatment. In the CT images, the tissue Hounsfield unit (HU) limit for skeletal muscles was −29 HU to +150 HU. The third lumbar vertebra (L3) was used as the standard landmark; skeletal muscles at this level include the erector spinae, transverse abdominis, psoas, quadratus lumborum, internal and external oblique muscles, and the rectus abdominis muscle. The muscles were manually traced on the CT images, their cross-sectional areas (cm2) were measured, and their sum was calculated [26]. Finally, the skeletal muscle index (SMI) was calculated by normalizing the cross-sectional areas for patient height (cm2/m2).

Measurement of Serum Levels of Carnitine and Myostatin

Serum levels of total carnitine (TC), free carnitine (FC), and acylcarnitine (AC) were determined by an enzymatic cycling method [27], and serum levels of myostatin were determined with a commercially available enzyme-linked immunosorbent assay kit (KAMIYA BIOMEDICAL COMPANY, Seattle, WA, USA) according to the manufacturer's protocol [28]. The ratio of AC to FC was calculated before and after 4 weeks of treatment.

Evaluation of Cardiac Function

With the patients at rest in the left lateral decubitus position, transthoracic echocardiography was performed with commercially available ultrasound equipment (GE E95, GE- Healthcare Japan Corporation, Tokyo, Japan). All images were digitally stored on hard disks for offline analysis (EchoPAC version 204, GE- Healthcare Japan). Left ventricular (LV) end-diastolic volume and end-systolic volume were calculated with the Simpson biplane method of discs. LV ejection fraction (LVEF) was calculated and expressed as a percentage.

In the present evaluation, global systolic LV myocardial function was determined with two-dimensional speckle-tracking strain analysis [29, 30]. The speckle-tracking software tracks the frame-to-frame movement of natural myocardial acoustic markers, or speckles, on standard gray-scale images. Speckle-tracking analysis is angle-independent and allows accurate evaluation of myocardial deformation in all the LV segments [31, 32]. The change in length/initial length of the speckle pattern over the cardiac cycle is used to calculate global longitudinal strain (GLS), with myocardial lengthening or stretching represented as positive strain, and myocardial shortening as negative strain (Fig. 2).

Fig. 2.

Evaluation of cardiac function. Change in length of the speckle pattern over the cardiac cycle is used to calculate global longitudinal strain, with myocardial lengthening or stretching represented as positive strain, and myocardial shortening as negative strain. a Left ventricle, b lateral direction, c longitudinal direction, d ejection fraction, e global longitudinal strain.

Fig. 2.

Evaluation of cardiac function. Change in length of the speckle pattern over the cardiac cycle is used to calculate global longitudinal strain, with myocardial lengthening or stretching represented as positive strain, and myocardial shortening as negative strain. a Left ventricle, b lateral direction, c longitudinal direction, d ejection fraction, e global longitudinal strain.

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Statistical Analysis

The Statistical Package for the Social Sciences (SPSS version 11.0; SPSS, Chicago, IL, USA) was used for statistical analyses. Results are expressed as the mean ± SD. Patient characteristics were compared by Wilcoxon’s signed-rank sum test. p < 0.05 was considered statistically significant.

Ethics and Participants

The Ethics Committee of Toho University Omori Medical Center approved the present study (number M22044) and was conducted according to the Declaration of Helsinki and current legal regulations in Japan. Written informed consent was obtained from all patients for using of serum preservation. Details about this study were disclosed in our institutional website and the potential participants were given the opportunity to decline to be further enrolled in the study (opt out).

Clinical Characteristics of Patients with CH or LC and HCC

A total of 58 patients were included. Patients comprised 48 men and 10 women aged 31–87 years (mean ± SD, 71.4 ± 11 years). Ten patients had CH, and 48 had LC (42 patients, Child-Pugh class A; 6 patients, Child-Pugh class B). Eleven patients had liver diseases related to hepatitis B virus (HBV); 18 patients, liver diseases related to hepatitis C virus (HCV); and 29 patients, non-HBV- and non-HCV-related LC (non-HBV non-HCV-LC). Two patients had stage II HCC, 21 patients had stage III, 28 patients had stage IVA, and 7 patients had stage IVB. Three patients had portal vein tumor thrombosis (PVTT) of the secondary branch of the portal vein (Vp2); 16, PVTT of the primary branch of the portal vein (Vp3); and 11, PVTT of the portal trunk (Vp4). Thirty-one patients showed a partial response to treatment, 21 had stable disease, and 6 patients had progressive disease; no patients showed a complete response to treatment. The objective response rate was 53.4%. Thirty-six patients received a branched chain amino acid (Table 1).

Table 1.

Clinical characteristics of patients with hepatocellular carcinoma treated with lenvatinib (N = 58)

Age (mean ± SD), y 71.4±11 
Sex (male/female), n 48/10 
Etiology, HBV/HCV/non-HBV-non-HCV, n 11/18/29 
Chronic hepatitis/liver cirrhosis, n 10/48 
Child-Pugh class, A/B, n 42/6 
Stage of tumor, II/III/IVA/IVB, n 2/21/28/7 
PVTT, Vp2/Vp3/Vp4, n 3/16/11 
CR/PR/SD/PD, n 0/31/21/6 
Objective response rate, % 53.4 
BCAA, with/without, n 36/22 
Age (mean ± SD), y 71.4±11 
Sex (male/female), n 48/10 
Etiology, HBV/HCV/non-HBV-non-HCV, n 11/18/29 
Chronic hepatitis/liver cirrhosis, n 10/48 
Child-Pugh class, A/B, n 42/6 
Stage of tumor, II/III/IVA/IVB, n 2/21/28/7 
PVTT, Vp2/Vp3/Vp4, n 3/16/11 
CR/PR/SD/PD, n 0/31/21/6 
Objective response rate, % 53.4 
BCAA, with/without, n 36/22 

BCAA, branched-chain amino acid; CR, complete response; HBV, hepatitis B virus; HCV, hepatitis C virus; non-HBV non-HCV, non-hepatitis B non-hepatitis C virus; PD, progressive disease; PR, partial response; PVTT, portal vein tumor thrombosis; SD, stable disease; Vp2, PVTT of the secondary branch of the portal vein; Vp3, PVTT of the primary branch of the portal vein; Vp4, PVTT of the portal trunk.

Comparison of Characteristics

Serum levels of ammonia, total bilirubin, direct bilirubin, and des-gamma-carboxy-prothrombin increased after treatment. In contrast, serum levels of albumin, creatinine, the platelet count, prothrombin time, and alpha-fetoprotein decreased after treatment (Table 2).

Table 2.

Comparison of clinical characteristics of patients with hepatocellular carcinoma treated with lenvatinib (N = 58)

Before treatmentAfter treatmentp value
Ammonia, mg/dL 41.8±24 57.6±47 0.005 
Total bilirubin, g/dL 0.8±0.5 1.1±0.7 0.001** 
Direct bilirubin, g/dL 0.3±0.2 0.4±0.4 0.002** 
Albumin, mg/dL 3.5±0.4 3.3±0.6 0.035* 
ALT, IU/L 41.3±33 42.9±36 0.580 
Total cholesterol, mg/dL 169.0±45 169.4±65 0.956 
BUN, mg/dL 17.7±7 19.7±10 0.470 
Creatine, mg/dL 0.9±0.7 0.9±0.5 0.017* 
WBC, n/mm3 5,610.7±2,116 5,596.4±2,302 0.989 
Platelets, ×104/mm3 19.5±10 15.5±8 0.001** 
Prothrombin time, % 93.4±17 88.3±20 0.045* 
AFP, ng/mL 14,677.0±13,564 12,764.7±63,237 0.001** 
AFP-L3, % 24.4±25 24.9±28 0.251 
DCP, AU/mL 35,094.5±78,155 40,202.7±111,242 0.025* 
Before treatmentAfter treatmentp value
Ammonia, mg/dL 41.8±24 57.6±47 0.005 
Total bilirubin, g/dL 0.8±0.5 1.1±0.7 0.001** 
Direct bilirubin, g/dL 0.3±0.2 0.4±0.4 0.002** 
Albumin, mg/dL 3.5±0.4 3.3±0.6 0.035* 
ALT, IU/L 41.3±33 42.9±36 0.580 
Total cholesterol, mg/dL 169.0±45 169.4±65 0.956 
BUN, mg/dL 17.7±7 19.7±10 0.470 
Creatine, mg/dL 0.9±0.7 0.9±0.5 0.017* 
WBC, n/mm3 5,610.7±2,116 5,596.4±2,302 0.989 
Platelets, ×104/mm3 19.5±10 15.5±8 0.001** 
Prothrombin time, % 93.4±17 88.3±20 0.045* 
AFP, ng/mL 14,677.0±13,564 12,764.7±63,237 0.001** 
AFP-L3, % 24.4±25 24.9±28 0.251 
DCP, AU/mL 35,094.5±78,155 40,202.7±111,242 0.025* 

All data are shown as mean ± standard deviation, the Mann-Whitney test was used for comparisons.

ALT, alanine aminotransferase; AFP, alpha-fetoprotein; AFP-L3, alpha-fetoprotein-L3; BUN, blood urea nitrogen; DCP, des-gamma-carboxy-prothrombin; WBC, white blood cells.

SMI and Serum Levels of Myostatin

SMI decreased significantly from baseline to after treatment (50.2 ± 5 cm2/m2 vs. 48.3 ± 5 cm2/m2; p = 0.0001) (Fig. 3a), but serum levels of myostatin increased significantly (35.8 ± 7 ng/mL vs. 36.8 ± 11 ng/mL; p = 0.0475) (Fig. 3b).

Fig. 3.

Changes in skeletal muscle index and serum levels of myostatin in patients with hepatocellular carcinoma treated by lenvatinib. The skeletal muscle index decreased significantly from before to after treatment (50.2 ± 5 cm2/m2 vs. 48.3 ± 5 cm2/m2; p = 0.0001) (a), and serum levels of myostatin increased significantly from before to after treatment (35.8 ± 7 ng/mL vs. 36.8 ± 11 ng/mL; p = 0.0475) (b). *p < 0.05, **p < 0.01. SMI, skeletal muscle index.

Fig. 3.

Changes in skeletal muscle index and serum levels of myostatin in patients with hepatocellular carcinoma treated by lenvatinib. The skeletal muscle index decreased significantly from before to after treatment (50.2 ± 5 cm2/m2 vs. 48.3 ± 5 cm2/m2; p = 0.0001) (a), and serum levels of myostatin increased significantly from before to after treatment (35.8 ± 7 ng/mL vs. 36.8 ± 11 ng/mL; p = 0.0475) (b). *p < 0.05, **p < 0.01. SMI, skeletal muscle index.

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Serum Levels of Carnitine Fractions

Serum levels of TC decreased significantly from baseline to after treatment (62.6 ± 13 μmol/L vs. 59.4 ± 12 μmol/L; p = 0.0268), as did serum levels of FC (49.9 ± 11 μmol/L vs. 46.9 ± 11 μmol/L; p = 0.0100). However, no significant changes were found in serum levels of AC (12.7 ± 4 μmol/L vs. 12.5 ± 5 μmol/L) (Fig. 4a) or the ratio of AC to FC (0.26 ± 0.1% vs. 0.28 ± 0.1%) (Fig. 4b).

Fig. 4.

Changes in serum levels of carnitine fraction and the acylcarnitine to free carnitine ratio in patients with hepatocellular carcinoma treated by lenvatinib (N = 58). Serum levels of total carnitine decreased significantly from before to after treatment (total carnitine, 62.6 ± 13 μmol/L vs. 59.4 ± 12 μmol/L, p = 0.0268; free carnitine, 49.9 ± 11 μmol/L vs. 46.9 ± 11 μmol/L, p = 0.0100), but serum levels of acylcarnitine showed no significant change (12.7 ± 4 μmol/L vs. 12.5 ± 5 μmol/L) (a). No significant change in the ratio of acylcarnitine to free carnitine was observed from before to after treatment (0.26 ± 0.1% vs. 0.28 ± 0.1%) (b). *p < 0.05. AC, acylcarnitine; FC, free carnitine.

Fig. 4.

Changes in serum levels of carnitine fraction and the acylcarnitine to free carnitine ratio in patients with hepatocellular carcinoma treated by lenvatinib (N = 58). Serum levels of total carnitine decreased significantly from before to after treatment (total carnitine, 62.6 ± 13 μmol/L vs. 59.4 ± 12 μmol/L, p = 0.0268; free carnitine, 49.9 ± 11 μmol/L vs. 46.9 ± 11 μmol/L, p = 0.0100), but serum levels of acylcarnitine showed no significant change (12.7 ± 4 μmol/L vs. 12.5 ± 5 μmol/L) (a). No significant change in the ratio of acylcarnitine to free carnitine was observed from before to after treatment (0.26 ± 0.1% vs. 0.28 ± 0.1%) (b). *p < 0.05. AC, acylcarnitine; FC, free carnitine.

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Evaluation of Cardiac Function

GLS decreased significantly from before to after treatment (21.6% ± 3% vs. 18.5% ± 3%; p = 0.0280), but there was no significant change in LVEF (Fig. 5) or the other parameters (Table 3).

Fig. 5.

Evaluation of cardiac function. Left ventricular ejection fraction showed no significant change from before and after treatment (67.1% ± 5% vs. 68.0% ± 9%) (a) but global longitudinal strain decreased significantly (21.6% ± 3% vs. 18.5% ± 3%; p = 0.0280) (b). *p < 0.05.

Fig. 5.

Evaluation of cardiac function. Left ventricular ejection fraction showed no significant change from before and after treatment (67.1% ± 5% vs. 68.0% ± 9%) (a) but global longitudinal strain decreased significantly (21.6% ± 3% vs. 18.5% ± 3%; p = 0.0280) (b). *p < 0.05.

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Table 3.

Changes in cardiac function in patients with liver cirrhosis and hepatocellular carcinoma treated by lenvatinib (N = 58)

Before treatmentAfter treatmentp value
Systolic blood pressure, mm Hg 125.2±12 120.2±7 0.144 
Diastolic blood pressure, mm Hg 69.0±10 64.4±7 0.225 
Aortic dimension, cm 3.5±0.2 3.5±0.3 1.000 
Left atrial dimension, cm 4.3±0.9 3.9±0.8 0.116 
Inter ventricular septum thickness/diastole, cm 1.0±0.3 1.0±0.2 0.599 
Left ventricular posterior wall thickness/diastole, cm 0.9±0.1 0.9±0.2 0.596 
Ventricular mass, g 171.9±73 156.4±53 0.345 
Heart rate/min 79.6±9 86.1±17 0.446 
Left ventricular dimension/diastole, cm 4.9±0.6 4.6±0.8 0.128 
Left ventricular dimension/systole, cm 3.1±0.4 2.9±0.7 0.345 
Fractional shortening, % 37.4±4 38.3±7 0.866 
Cardiac output, L/min 6.1±1 5.7±2 0.248 
End-diastolic volume, mL 116.8±35 100.5±41 0.128 
End-systolic volume, mL 37.2±13 33.8±19 0.463 
Stroke volume, mL 78.2±24 66.7±25 0.063 
Left ventricular ejection fraction, % 67.1±5 68.0±9 0.866 
Global longitudinal strain, % 21.6±3 18.5±3 0.028* 
Before treatmentAfter treatmentp value
Systolic blood pressure, mm Hg 125.2±12 120.2±7 0.144 
Diastolic blood pressure, mm Hg 69.0±10 64.4±7 0.225 
Aortic dimension, cm 3.5±0.2 3.5±0.3 1.000 
Left atrial dimension, cm 4.3±0.9 3.9±0.8 0.116 
Inter ventricular septum thickness/diastole, cm 1.0±0.3 1.0±0.2 0.599 
Left ventricular posterior wall thickness/diastole, cm 0.9±0.1 0.9±0.2 0.596 
Ventricular mass, g 171.9±73 156.4±53 0.345 
Heart rate/min 79.6±9 86.1±17 0.446 
Left ventricular dimension/diastole, cm 4.9±0.6 4.6±0.8 0.128 
Left ventricular dimension/systole, cm 3.1±0.4 2.9±0.7 0.345 
Fractional shortening, % 37.4±4 38.3±7 0.866 
Cardiac output, L/min 6.1±1 5.7±2 0.248 
End-diastolic volume, mL 116.8±35 100.5±41 0.128 
End-systolic volume, mL 37.2±13 33.8±19 0.463 
Stroke volume, mL 78.2±24 66.7±25 0.063 
Left ventricular ejection fraction, % 67.1±5 68.0±9 0.866 
Global longitudinal strain, % 21.6±3 18.5±3 0.028* 

ALL data are shown as mean ± standard deviation.

The Mann-Whitney test was used for comparisons.

The present retrospective study in patients with HCC was performed to clarify whether lenvatinib causes low carnitine levels and thus induces a reduction in skeletal muscle volume and worsening of cardiac function. Sarcopenia is characterized by a reduction in skeletal muscle mass [9, 33]. Specifically, in secondary sarcopenia, skeletal muscle mass and strength or physical function are impaired secondary to underlying diseases [34]. The present study considered changes in skeletal muscle volume without loss of muscle strength. The results showed that TC, FC, and SMI significantly decreased with lenvatinib, but the AC-to-FC ratio did not change significantly from before to after treatment. Lenvatinib is hypothesized to decrease carnitine serum levels by impairing absorption of carnitine through inhibition of human organic cationic transporter OCTN2 and also by causing loss of appetite. Hara et al. reported that loss of appetite as a complication of lenvatinib was seen in 45.5% of patients with HCC with low median plasma lenvatinib trough levels and in 100.0% of patients with high trough levels [35]. Moreover, cancer-related fatigue was reported to involve adenosine triphosphate synthesis abnormalities resulting from carnitine deficiency [36]; however, in the present study we did not assess the presence of anorexia or fatigue.

Myostatin is a cytokine of the transforming growth factor beta family and suppresses skeletal muscle synthesis, resulting in a loss of muscle mass [37]. In the present study, serum levels of ammonia and myostatin increased after treatment with lenvatinib. Some research has indicated that sarcopenia can be caused by hyperammonemia [38]. Hyperammonemia is seen in LC and plays a sizable role in the pathogenesis of hepatic encephalopathy, for which sarcopenia is the main risk factor [39, 40]. These phenomena might indicate that in our study, the decrease in FC induced downregulation of β-oxidation in mitochondria and increased levels of ammonia (Fig. 6). Furthermore, they also might indicate that downregulation of β-oxidation in mitochondria induces upregulation of protein catabolism and consequently a decrease in the amount of skeletal muscle induced by higher serum levels of myostatin. A decrease in skeletal muscle and increase in serum levels of myostatin might lead to decreased ammonia metabolism (Fig. 7).

Fig. 6.

β-Oxidation in carnitine metabolism representation in patients with hepatocellular carcinoma treated by lenvatinib. The human organic cationic transporter OCTN2 is inhibited by lenvatinib in the cell membrane, which in turn inhibits carnitine absorption. Lenvatinib is responsible for causing anorexia as a complication, and anorexia results in low carnitine serum levels. The decrease in free carnitine might induce downregulation of β-oxidation of mitochondria and increased ammonia. CPT, carnitine palmitoyltransferase; hOCTN2, human organic cationic transporter OCTN2; TCA, tricarboxylic acid.

Fig. 6.

β-Oxidation in carnitine metabolism representation in patients with hepatocellular carcinoma treated by lenvatinib. The human organic cationic transporter OCTN2 is inhibited by lenvatinib in the cell membrane, which in turn inhibits carnitine absorption. Lenvatinib is responsible for causing anorexia as a complication, and anorexia results in low carnitine serum levels. The decrease in free carnitine might induce downregulation of β-oxidation of mitochondria and increased ammonia. CPT, carnitine palmitoyltransferase; hOCTN2, human organic cationic transporter OCTN2; TCA, tricarboxylic acid.

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Fig. 7.

Schematic showing the role of carnitine (as acylcarnitine) in protein catabolism in patients with hepatocellular carcinoma treated by lenvatinib. A decrease in serum carnitine levels caused by lenvatinib blocks glycolysis and the tricarboxylic acid and urea cycles. In turn, lipid metabolism is blocked and protein catabolism induced. In addition, the declining muscle mass increases myostatin, which suppresses muscle protein synthesis. These phenomena also lead to an increase in ammonia levels.

Fig. 7.

Schematic showing the role of carnitine (as acylcarnitine) in protein catabolism in patients with hepatocellular carcinoma treated by lenvatinib. A decrease in serum carnitine levels caused by lenvatinib blocks glycolysis and the tricarboxylic acid and urea cycles. In turn, lipid metabolism is blocked and protein catabolism induced. In addition, the declining muscle mass increases myostatin, which suppresses muscle protein synthesis. These phenomena also lead to an increase in ammonia levels.

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Stanton et al. [41] reported that GLS was stronger predictor of all-cause mortality than LVEF and a composite of cardiac death, heart failure hospitalization, and malignant arrhythmias. Our study found that GLS decreased significantly after treatment, although we found no significant change in LVEF. Vascular endothelial growth factor signaling inhibitors are expected to cause an imbalance between vasodilators and vasoconstrictors, loss of capillary circulation, and altered glomerular function [42, 43]. The TKI sunitinib was reported to cause a clinically significant decrease in cardiac function and the development of congestive heart failure in 8% of patients [44]. Furthermore, OCTN2 was reported to be functionally expressed on the plasma membrane of muscle cells and to be involved in the distribution of carnitine to the heart [45]. Our study found a significant decrease in TC, FC, and GLS in patients with HCC treated with lenvatinib but no significant change in the AC to FC ratio. Lenvatinib may reduce carnitine in heart muscle and lower GLS by suppressing the function of OCTN2. Moreover, previous studies suggested that the TKI imatinib induces cardiomyocyte dysfunction by disruptin autophagy and inducing endoplasmic reticulum stress [46]. Lenvatinib might also reduce cardiac function by directly impairing cardiomyocytes without affecting carnitine metabolism because we found no significant co-relation between changes in GLS and TC or FC values from before to after treatment (data were not shown).

In patients with LC, levocarnitine supplementation is reported to improve hyperammonemia and symptoms of muscle cramp [17] and reduces the loss of skeletal muscle mass [47]. In addition, Hiramatsu et al. [48] reported that in patients with LC, levocarnitine supplementation suppresses the progression of sarcopenia in a dose-dependent manner and is associated with an improvement in hyperammonemia. Sarcopenia worsens the prognosis of patients with unresectable HCC treated with lenvatinib [12]. Further research is needed to assess whether replenishment of carnitine not only improves the prognosis of patients treated with lenvatinib but also prevents the decrease in skeletal muscle and deterioration of cardiac function.

In patients with HCC, lenvatinib decreases skeletal muscle volume, worsens cardiac function, and inhibits carnitine absorption. TKIs are becoming increasingly important as anticancer agents in HCC treatment, and further study is needed to determine whether replenishment of carnitine to treat the TKI-induced decrease in carnitine levels not only prevents a reduction in skeletal muscle volume and cardiac function but also inhibits hyperammonemia.

The Ethics Committee of Toho University Omori Medical Center approved the present study (number M22044) and was conducted according to the Declaration of Helsinki and current legal regulations in Japan. Written informed consent was obtained from all patients for using of serum preservation. Details about this study were disclosed in our institutional website and the potential participants were given the opportunity to decline to be further enrolled in the study (opt out).

Hidenari Nagai has received research funding from Eisai, Otsuka Pharma, Sumitomo Pharma, and AbbVie.

The authors declare no fundings regarding the publication on this paper.

Hidenari Nagai and Takanori Mukozu performed all the experiments and the data analysis and finalized the article. Hidenari Nagai drafted the manuscript. Takanori Mukozu, Kojiro Kobayashi, Hideki Nagumo, Kunihide Mohri, Go Watanabe, Makoto Amanuma, Naoyuki Yosjimine, Yu Ogino, Daigo Matsui, Yasuko Daido, Yasushi Matsukiyo, Teppei Matsui, Noritaka Wakui, and Koichi Momiyama collected blood samples and performed the data analysis. Hidenari Nagai, Koji Higai, Takahisa Matsuda, and Yoshinori Igarashi reviewed and provided feedback on the manuscript. All authors approved the final version of the manuscript.

All data generated or analyzed during this study are included in this article. Further inquiries can be directed to the corresponding author.

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