Traditionally, amber (Succinite) has been used to alleviate all types of pain, skin allergies, and headaches. However, no studies have been conducted on its antidiabetic and antioxidant effects. In this study, differentiated skeletal muscle C2C12 cells were used to demonstrate the protective effects of amber (AMB) against H₂O₂-induced cell death. In addition, the effects of AMB on glucose uptake and ATP production were investigated. Our results showed that AMB at 10, 25, and 50 μg/mL suppressed the elevation of ROS production induced by H₂O₂ in a dose-dependent manner. Moreover, AMB enhanced glucose utilization in C2C12 cells through the improvement of ATP production and an increase in PGC-1α gene expression resulting in an amelioration of mitochondrial activity. On the other hand, AMB significantly increased the gene expression of glucose transporters GLUT4 and GLUT1. Our finding suggests that AMB can be used as a natural supplement for diabetes treatment and for the promotion of skeletal muscle function.

Amber, a plant resin, exhibits an anti-stress effect and is used in traditional medicine. Recently, it has been speculated that amber may possess an anti-depressive effect. However, there is no evidence to support this efficacy. Thus, this study investigated the anti-depressive and oxidative-stress-ameliorating effects of amber extract in mice subjected to restraint stress. Mice were treated with amber extract (25 and 50 mg/kg, p.o.) and bupropion (10 mg/kg, p.o.) as positive control. Mice were then subjected to a tail suspension test, and their immobility time, body weight before and after stress, levels of stress-related hormones and neurotransmitters, and oxidative stress parameters were assessed. Amber supplementation did not affect the body weight of mice in any of the groups. Amber extract (25 and 50 mg/kg) demonstrated an anti-depressive effect by significantly decreasing the immobility time and adrenocorticotropin-hormone and corticosterone-hormone levels. Moreover, amber extract at a dose of 25 mg/kg increased the levels of dopamine and serotonin. Additionally, superoxide dismutase, catalase, and glutathione levels increased, whereas the malondialdehyde content decreased with amber supplementation. These findings confirm that amber may possess an anti-depressive effect and hence can be a useful alternative therapy for preventing and managing depression.

Obesity is a complex metabolic disorder characterized by excessive accumulation of adipose tissue, resulting from an imbalance between energy intake and expenditure. It is associated with an increased risk of chronic diseases such as type 2 diabetes, cardiovascular disease, and cancer. Kefiran is a water-soluble exopolysaccharide produced by lactic acid bacteria, Lactobacillus kefiranofaciens, in kefir grains, composed primarily of glucose and galactose. It has garnered scientific interest due to its antioxidant, anti-inflammatory, and antimicrobial properties. Rice Kefiran (RK) is a functional food made with culturing L. kefiranofaciens in a medium containing rice. It is standardized to contain at least 5 mg/g of kefiran. This study investigated the anti-obesity effect of RK on a high-fat diet (HFD)-induced obese mouse model. HFD-fed mice exhibited marked increases in body weight gain (10.3 g vs. 2.0 g in controls) and adipose tissue mass (2.4 g vs. 0.4 g in controls). RK administration significantly attenuated weight gain to 8.3 g and 6.0 g at doses of 10 and 50 mg/kg, respectively, and reduced adipose tissue mass to 2.2 g (RK10) and 1.7 g (RK50). Oral glucose tolerance testing revealed impaired glucose clearance in HFD-fed mice, with blood glucose levels of 403.5 mg/dL at 15 min and 314.6 mg/dL at 120 min, compared with 348.8 mg/dL and 232.2 mg/dL in controls. RK treatment improved glucose tolerance, particularly at 50 mg/kg, reducing glucose levels to 359.0 mg/dL at 15 min and 263.8 mg/dL at 120 min. Biochemical analyses demonstrated that RK significantly reduced serum total cholesterol (213.6 mg/dL in HFD vs. 178.0 and 184.0 mg/dL in RK10 and RK50), triglycerides (379.0 mg/dL in HFD vs. 228.8 and 234.6 mg/dL), and non-esterified fatty acids (0.89 mEq/mL in HFD vs. 0.54 and 0.35 mEq/mL), while phospholipid levels remained unchanged. Furthermore, RK increased serum nicotinamide phosphoribosyltransferase (NAMPT) levels from 15.8 ng/mL in HFD-fed mice to 30.0 and 50.0 ng/mL in the RK10 and RK50 groups, respectively, and restored hepatic NAD⁺/NADH ratios toward control levels (1.78 µmol/L in HFD vs. 1.90 µmol/L and 2.07 µmol/L in RK10 and RK50). Gene expression analysis showed that RK increased Nampt mRNA expression and decreased the mRNA expression of adipogenic and lipogenic genes, including Srebp-1c, Acc-1, and Fas. These findings suggest that RK may ameliorate obesity-related metabolic disturbances and its associated metabolic dysfunctions by modulating lipid metabolism, glucose tolerance, and NAD⁺ biosynthesis pathways.