Obesity is an emerging global health issue with an increasing risk of disease linked to lifestyle choices. Previously, we reported that the hexane extract of Citrus sphaerocarpa (CSHE) suppressed lipid accumulation in differentiated 3T3-L1 adipocytes. In this study, we conducted in vivo experiments to assess whether CSHE suppressed obesity in zebrafish and mouse models. We administered 10 and 20 μg/mL CSHE to obese zebrafish juveniles. CSHE significantly inhibited visceral fat accumulation compared to untreated obese fish. Moreover, the oral administration (100 μg/g body weight/day) of CSHE to high-fat-diet-induced obese mice significantly reduced their body weight, visceral fat volume, and hepatic lipid accumulation. The expression analyses of key regulatory genes involved in lipid metabolism revealed that CSHE upregulated the mRNA expression of lipolysis-related genes in the mouse liver (Pparα and Acox1) and downregulated lipogenesis-related gene (Fasn) expression in epididymal white adipose tissue (eWAT). Fluorescence immunostaining demonstrated the CSHE-mediated enhanced phosphorylation of AKT, AMPK, ACC, and FoxO1, which are crucial factors regulating adipogenesis. CSHE-treated differentiated 3T3L1 adipocytes also exhibited an increased phosphorylation of ACC. Therefore, we propose that CSHE suppresses adipogenesis and enhances lipolysis by regulating the PI3K/AKT/FoxO1 and AMPK/ACC signaling pathways. These findings suggested that CSHE is a promising novel preventive and therapeutic agent for managing obesity.

Ceramides have several well-known biological properties, including anti-pigmentation and anti-melanogenesis, which make them applicable for use in skincare products in cosmetics. However, the efficacy of ceramides is still limited. Dermal or transdermal drug delivery systems can enhance the anti-pigmentation properties of ceramides, although there is currently no systemic evaluation method for the efficacy of these systems. Here we prepared several types of lecithin-based emulsion of maize-derived glucosylceramide, determining PC70-ceramide (phosphatidylcholine-base) to be the safest and most effective anti-pigmentation agent using zebrafish larvae. We also demonstrated the efficacy of PC70 as a drug delivery system by showing that PC70-Nile Red (red fluorescence) promoted Nile Red accumulation in the larval bodies. In addition, PC70-ceramide suppressed melanin in mouse B16 melanoma cells compared to ceramide alone. In conclusion, we developed a lecithin-based dermal delivery method for ceramide using zebrafish larvae with implications for human clinical use.

Ultraviolet B (UVB) irradiation induces epidermal dysregulation characterized by hyperpigmentation, barrier dysfunction, and abnormal keratinocyte differentiation, contributing to photoaging and skin disorders. Ceramides are key structural lipids of the stratum corneum and are widely used as topical agents to support barrier integrity. However, the role of oral ceramide in UVB-induced skin damage remains unclear. In this study, we investigated whether oral ceramide administration attenuates UVB-induced skin alterations in HRM-2 hairless mice. Mice were repeatedly exposed to UVB and orally administered ceramide (2.5 or 7.5 mg/kg/day). UVB exposure increased dorsal skin pigmentation, epidermal thickness, microphthalmia-associated transcription factor (MITF) expression, and melanogenesis-related gene transcription, while tending to reduce skin hydration. Oral ceramide markedly suppressed these changes and enhanced skin moisture content without affecting general health status. Immunofluorescence and reverse transcription-quantitative PCR analyses revealed a reduction in the number of MITF-positive cells and downregulation of Tyrp1, Mc1r, and Mitf. RNA sequencing analysis further demonstrated that ceramide counteracted UVB-induced transcriptional dysregulation by suppressing keratinization pathways and promoting retinoic acid receptor- and wound-healing-associated signaling. These findings indicate that oral ceramide not only reduces melanin synthesis but also promotes the recovery of epidermal homeostasis by modulating melanocyte activity, keratinocyte differentiation, and barrier function. Accordingly, oral ceramide attenuates UVB-induced skin pigmentation by suppressing MITF-dependent melanogenesis and restoring skin homeostasis, highlighting its potential as a therapeutic agent for photodamage-associated skin disorders.