Dietary supplementation of Mortis nigra L. leaves decrease fat mass partially through elevating leptin-stimulated lipolysis in pig model

Ethnopharmacological relevance: Mulberry leaves are the dry leaves of Morus nigra L. trees, which are widely cultivated in central and southern China. Mulberry has a long history of medicinal use, such as anti-stress, lowering blood glucose and anti-obesity. Aim of the study: Explore the effects of mulberry leaves on fat deposition as well as the underlying mechanisms. Materials and methods: Total of 48 fattening pigs weighing about 70 kg were randomly allotted to normal diet or die supplemented with 5% (w/w) mulberry leave powder. Changes of fat mass, indicated by backfat thickness was measured with Piggyback tester, blood triglyceride and cholesterol were tested using commercial biochemical kits, serum hormones were estimated by ELISA, and leptin-related signaling activity were assessed using western-blot. Results: Supplementation with Mulberry leaf feed (MF) significantly reduced serum triglyceride and free cholesterol concentrations and increased the ratio of high-density lipoprotein cholesterol (HDL-c) to low-density lipoprotein cholesterol (LDL-c), while serum glucose and free fatty acids remained unchanged. Dietary MF resulted in a significant reduction in the size of adipocytes and backfat thickness (P < 0.05). Accordingly, hormone-sensitive lipase (HSL) in backfat was significantly up-regulated and fatty acid synthase (FAS) was down-regulated by MF supplementation (both P < 0.05). Furthermore, MF supplementation significantly elevated circulating leptin and adiponectin without influencing serum insulin and glucocorticoid. Moreover, significantly higher leptin receptor (Leptin-R) and phosphorylated signal transducer and activator of transcription 3 (p-STAT3) were detected in MF-supplemented pigs, suggesting an enhanced leptin signaling induced by MF in the subcutaneous fat. Conclusions: Mulberry leaves have obvious anti-obesity effects, providing a theoretical basis for the development of mulberry leaves as a drug against obesity.