Obesity can lead to excessive lipid accumulation in non-adipose tissues, such as the liver and skeletal muscles, leading to ectopic lipid deposition and damaging target organ function through lipotoxicity. FGF-21 is a key factor in regulating lipid metabolism, so we aim to explore whether FGF-21 is involved in improving ectopic lipid deposition. We observed the characteristics of ectopic lipid deposition in the liver and skeletal muscles of obesity-resistant mice, detected the expression of FGF-21 and perilipin, and found that obesity-resistant mice showed a decrease in ectopic lipid deposition in the liver and skeletal muscles and increased expression of FGF-21. After inhibiting the expression of FGF-21, a more severe lipid deposition in liver cells and skeletal muscle cells was found. The results indicate that inhibiting FGF-21 can exacerbate ectopic lipid deposition via regulating lipid droplet synthesis and decomposition, as well as free fatty acid translocation and oxidation. In conclusion, FGF-21 is involved in improving ectopic lipid deposition caused by obesity in the liver and skeletal muscles.

Objectives: Obesity precipitates excessive lipid accumulation within the kidney, culminating in ectopic lipid deposition that compromises target organ function through lipotoxicity. Given the pivotal role of GDF15 in lipid metabolism, this study aims to determine whether GDF15 can ameliorate ectopic lipid deposition and mitigate the resulting renal injury. Methods: C57BL/6J mice were used to establish a high-fat diet-induced obesity model. Based on Lee’s index, the mice were categorized into a diet-induced obesity group and an obesity-resistant group. Subsequently, the diet-induced obesity group received an injection of AAV-shGFRAL to knock down the GFRAL receptor. Results: In obesity resistant mice, ectopic lipid deposition in the kidneys was markedly reduced, accompanied by decreased expression of the renal injury marker KIM-1 and significantly elevated levels of GDF15. Modulation of the GDF15-GFRAL axis demonstrated that reduced autophagy levels led to increased lipid accumulation and exacerbated renal injury. Conversely, GDF15 activates the AMPK/SIRT1 signaling pathway to promote cellular autophagy, thereby mitigating renal damage induced by ectopic lipid deposition. Consistent with this mechanism, the suppression of autophagy results in the aggravation of renal injury caused by ectopic lipid accumulation. Conclusions: GDF15 ameliorates renal injury induced by ectopic lipid deposition in the kidney primarily through activation of autophagy via the AMPK/SIRT1 signaling pathway.