Sarcopenia- or cachexia-related muscle atrophy is due to imbalanced energy metabolism and oxidative stress-induced muscle dysfunction. Monoterpenes play biological and pharmacological reactive oxygen species (ROS) scavenging roles. Hence, we explored the effects of camphene, a bicyclic monoterpene, on skeletal muscle atrophy in vitro and in vivo. We treated L6 myoblast cells with camphene and then examined the ROS-related oxidative stress using Mito Tracker^TM Red FM and anti-8-oxoguanine antibody staining. To investigate lipid metabolism, we performed real-time polymerase chain reactions, holotomographic microscopy, and respiratory gas analysis. Rat muscle atrophy in in vivo models was observed using ¹⁸F-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography and immunocytochemistry. Camphene reversed the aberrant cell size and muscle morphology of L6 myoblasts under starvation and in in vivo models. Camphene also attenuated E3 ubiquitin ligase muscle RING-finger protein-1, mitochondrial fission, and 8-oxoguanine nuclear expression in starved myotubes and hydrogen peroxide (H₂O₂)-treated cells. Moreover, camphene significantly regulated lipid metabolism in H₂O₂-treated cells and in vivo models. These findings suggest that camphene may potentially affect skeletal muscle atrophy by regulating oxidative stress and lipid metabolism.

Although aptamers have shown excellent target specificity in preclinical and clinical studies either by themselves or as aptamer‐drug conjugates, their in vivo tissue pharmacokinetic (PK) analysis is still problematic. We aimed to examine the utility of image‐based positron emission tomography (PET) to evaluate in vivo tissue PK, target specificity, and applicability of oligonucleotides. For this, fluorine‐18‐labeled aptamers with erb‐b2 receptor tyrosine kinase 2 (ERBB2)‐specific binding were synthesized by base‐pair hybridization using a complementary oligonucleotide platform. To investigate the PKs and properties of in vivo tissue, usefulness of in vivo PET imaging in the development of an oligonucleotide‐based drug as an assessment tool was evaluated in normal and tumor xenografted mice. ERBB2‐cODN‐idT‐APs‐[¹⁸F]F ([¹⁸F]1), injected intravenously showed significant and rapid uptake in most tissues except for the initial brain and muscle; the uptake was highest in the heart, followed by kidneys, liver, lungs, gall bladder, spleen, and stomach. The main route of excretion was through the renal tract ~77.8%, whereas about 8.3% was through the biliary tract of the total dose. The estimated effective dose for an adult woman was 0.00189 mGy/MBq, which might be safe. ERBB2‐positive tumor could be well visualized in the KPL4 xenograft animal model by in vivo PET imaging. Consequently, the distribution in each organ including ERBB2 expression could be well determined and quantified by PET with fluorine‐18‐labeled aptamers. In vivo PK parameters such as terminal half‐life, time to maximum concentration, area under the curve, and maximum concentration, were also successfully estimated. These results suggest that image‐based PET with radioisotope‐labeled aptamers could be provide valuable information on properties of oligonucleotide‐based drugs in drug discovery of targeted therapeutics against various diseases.

Imaging techniques for diagnosing muscle atrophy and sarcopenia remain insufficient, although various advanced diagnostic methods have been established. We explored the feasibility of ¹⁸F-fluorocholine (¹⁸F-FCH) positron emission tomography/computed tomography (PET/CT) for evaluating skeletal muscle atrophy, as an imaging technique that tracks choline level changes in muscles. Cell uptake in L6 cells by ¹⁸F-FCH was performed in a complete medium containing serum (untreated group, UN) and a serum-free medium (starved group, ST). Small-animal-dedicated PET/CT imaging with ¹⁸F-FCH was examined in in-vivo models with rats that were starved for 2 days to cause muscle atrophy. After the hind limbs were dissected, starvation-induced in-vivo models were anatomically confirmed by reverse-transcription polymerase chain reaction to evaluate the expression levels of the atrophy markers muscle RING-finger protein-1 (MuRF-1) and atrogin-1. ¹⁸F-FCH uptake was lower in the starvation-induced cells than in the untreated group, and in-vivo PET uptake also revealed a similar tendency (the average standardized uptake value (SUV_mean) = 0.26 ± 0.06 versus 0.37 ± 0.07, respectively). Furthermore, the expression levels of MuRF-1 and atrogin-1 mRNA were significantly increased in the starvation-induced muscle atrophy of rats compared to the untreated group. ¹⁸F-FCH PET/CT may be a promising tool for diagnosing skeletal muscle atrophy.

Macrophages are activated during the early phase of paracetamol-induced liver injury (PLI). [¹⁸F]GE180 is a radiolabeled ligand that recognizes the macrophage translocator protein (TSPO). In this study, we evaluated the feasibility of a TSPO-specific radiotracer in a rat model of PLI. A rat model of liver injury was induced by intraperitoneal administration of paracetamol. [¹⁸F]GE180 positron emission tomography (PET) images were obtained after 24 h. The maximal and mean standardized uptake values (SUV_max and SUV_av) of the liver and serum biomarker levels were examined. The TSPO expression level was examined using real-time polymerase chain reaction and Western blot analysis. [¹⁸F]GE180 hepatic uptake in the PLI group was significantly higher than that in the control group (SUV_max p = 0.001; SUV_av p = 0.005). Both mRNA and protein TSPO expression levels were higher in the PLI group. The mRNA expression level of TSPO was significantly correlated with [¹⁸F]GE180 hepatic uptake in both groups (SUV_max p = 0.019; SUV_av p = 0.007). [¹⁸F]GE180 hepatic uptake in the PLI group showed a significant positive correlation with ALT₂₄ and ALT₄₈ (ALT₂₄ p = 0.016; ALT₄₈p = 0.002). [¹⁸F]GE180 enabled visualization of PLI through TSPO overexpression. Our results support the potential utility of hepatic uptake by TSPO-PET as a non-invasive imaging biomarker for the early phase of PLI.