Nutmeg extract potentially alters characteristics of white adipose tissue in rats

Background Browning of white adipose tissue (WAT) is a promising approach to obesity treatment. During browning, WAT transforms into beige adipose tissue through stimulation of the peroxisome proliferator activated receptor γ (PPARγ). Nutmeg, one of the Indonesian herbs, reportedly has dual roles as a PPARα/γ partial agonist. Even though nutmeg has been traditionally used in body weight reduction, there is limited information regarding the potential role of nutmeg in browning of WAT. Objectives In this study, we explored the effect of nutmeg seed extract (NuSE) as a potential inductor of WAT browning. Methods Twelve male Wistar rats, 5–6 weeks old, were divided into control and nutmeg groups. The rats in nutmeg group were given NuSE for 12 weeks by oral gavage. After 12 weeks, the rat's inguinal WAT and brown adipose tissue (BAT) were collected, weighed and stored at − 80°C until use. Results We observed that even though NuSE did not reduce the final body weight, it significantly reduced body weight gain. NuSE also increased protein levels of peroxisome proliferator activated receptor γ coactivator 1α (PGC‐1α) and uncoupling protein 3 (UCP3) significantly and tended to increase UCP2 and UCP1 levels. Furthermore, NuSE induced macroscopic and microscopic morphological changes of inguinal WAT, marked by significantly increased adipocyte numbers and decreased adipocyte size. Conclusions Even though NuSE did not increase UCP1 significantly, it potentially alters inguinal WAT characteristics and leads to browning through PGC‐1α and UCP3 induction. However, UCP3’s specific mechanism in WAT browning remains unclear. Our findings could contribute to obesity treatment in the future. White adipose tissue (WAT) browning has been considered as one of the promising approaches in obesity treatment. In WAT browning process, the characteristics of WAT are transformed into brown‐like adipose tissue (known as beige adipose tissue) via stimulation of peroxisome proliferator activated receptors γ (PPARγ) pathway. Interestingly, Indonesian society has been using nutmeg which may mimic browning effect via inducing macroscopic and microscopic morphological changes of iWAT, marked by significant increase of adipocyte number and decrease of adipocyte size. in addition, The increases in UCP1 and PGC‐1α along with histological changes reveal that NuSE may potentially alter the characteristic of iWAT that lead to browning process and contribute to obesity treatment.