Anti-Diabetic Effect of a Shihunine-Rich Extract of Dendrobium loddigesii on 3T3-L1 Cells and db/db Mice by Up-Regulating AMPK–GLUT4–PPARα

Abstract

The stems of Dendrobium loddigesii, a Chinese herb, are often used to treat diabetes and its polar extract is rich in shihunine, a water-soluble Orchidaceae alkaloid, but little is known about the anti-diabetes effects and mechanism of shihunine. This study investigated the anti-diabetic effect of a shihunine-rich extract of D. loddigesii (DLS) based on 3T3-L1 cells and db/db mice. The underlying mechanisms were primarily explored using Western blot analysis and immunohistochemical staining. The 3T3-L1 cell experiments showed that DLS can reduce the intracellular accumulation of oil droplets as well as triglycerides (p < 0.001) and promote the 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2deoxyglucose (2-NBDG) uptake of 3T3-L1 cells (p < 0.001). The animal experiments confirmed that after 8 weeks of DLS treatment, the body weight, fasting blood sugar, and serum lipid levels of mice were significantly lowered, and the oral glucose tolerance test and serum insulin level were significantly improved compared to the no-treatment diabetes mellitus group. Further histomorphology observation led to the conclusion that the quantities of islet cells were significantly increased and the increase in adipose cell size was significantly suppressed. The immunohistochemical test of pancreatic tissue revealed that DLS inhibited the expression of cleaved cysteine aspartic acid-specific protease 3 (cleaved caspase-3). Western blot experiments showed that DLS had agonistic effects on adenosine monophosphate (AMP)-activated protein kinase phosphorylation (p-AMPK) and increased the expression levels of peroxisome proliferator-activated receptor α (PPARα) and glucose transporter 4 (GLUT4) in liver or adipose tissues. These data suggest that the shihunine-rich extract of D. loddigesii is an anti-diabetic fraction of D. loddigesii. Under our experimental condition, DLS at a dose of 50 mg/kg has good anti-diabetic efficacy.

Identification, Biological Activities and Biosynthetic Pathway of Dendrobium Alkaloids

“…For instance, shihunidine (2) and shihunine (1) isolated from Dendrobium loddigesii Rolfe displayed inhibitory effects on Na + /K + -ATPase of the rat kidney ( Li et al, 1991 ). Li et al (2019) recently reported that DNLA showed vital hypoglycemic effects in diabetic rats. The shihunine (1) extracts from Dendrobium loddigesii Rolfe at the dose of 50 mg/kg decreased the triglycerides level by 43.7%, compared with the non-treated db/db mice, and inhibited the expression of cleaved cysteine aspartic acid-specific protease 3.…”

Transcriptome Analysis Reveals Biosynthesis of Important Bioactive Constituents and Mechanism of Stem Formation of Dendrobium huoshanense

“…Modern pharmacological researches have confirmed that polysaccharides can activate immune cells, modulate the immune responses in the intestines, spleen, and liver, and inhibit cell proliferation in tumors [10][11][12][13] . Alkaloids possessed the functions of anti-inflammatory, anti-diabetic effect and anticancer activity 14,15 . Flavonoids also possesses biological functions including anti-oxidant, anti-cancer, anti-aging, cardiovascular protection, and building of immunity [16][17][18][19] .…”

Study on the Potential Mechanism of Tonifying Kidney and Removing Dampness Formula in the Treatment of Postmenopausal Dyslipidemia Based on Network Pharmacology, Molecular Docking and Experimental Evidence

“…Total protein from either hepatocytes or liver tissues was extracted using RIPA buffer (Cell Signaling Technology Inc., Danvers, MA, USA), and the protein contents was determined using a BCA protein assay kit (Beyotime Biotech Inc., Shanghai, China). After the proteins were quantified, western blot analysis was performed, as described in the literature ( 26 ). Densitometry values for the western blot analysis were analyzed by ImageJ Software 1.6 (National Institutes of Health, Bethesda, MD, USA).…”