Novel dual-color drug screening model for GLUT4 translocation in adipocytes

Ursolic acid ameliorates adipose tissue insulin resistance in aged rats via activating the Akt-glucose transporter 4 signaling pathway and inhibiting inflammation

Ageing often results in insulin resistance (IR) and chronic inflammation, and adipose is one of the tissues in which inflammation and IR occur earliest during this process. The present study investigated the effect and underlying mechanisms of ursolic acid (UA) on adipose IR and inflammation in ageing rats. Specific pathogen-free male Sprague-Dawley rats were randomly divided into 4 groups: i) Young normal (young); ii) untreated ageing (aged); and groups supplemented with UA either iii) low-UA 10 mg/kg (UA-L) or iv) high-50 mg/kg (UA-H). Animals in the UA-treated groups received 10 or 50 mg/kg UA (suspended in 5% Gum Arabic solution). The rats in the corresponding aged group and young groups received vehicle (5% Gum Arabic) alone. All rats were intragastrically treated once daily by oral gavage for 7 weeks. The day before the experiment terminated, overnight fasting blood (~700 µl) was collected and plasma was prepared to measure biochemical indicators; western blotting was performed to analyze the expression of insulin signaling proteins [(insulin receptor substrate 1 (IRS-1), phosphorylated (p)-IRS-1, PI3K, glucose transporter 4 (GLUT4), Akt and p-Akt)] and inflammatory factors (NF-κB, IL-6 and IL-1β) in the epididymis white adipose tissue (eWAT). The results revealed that treatment with UA-H decreased eWAT weight, the ratio of eWAT weight/body weight, fasted insulin and triglyceride levels, the homeostasis model assessment of insulin resistance and adipose tissue insulin resistance index in ageing rats, indicating the amelioration of systemic and adipose tissue IR, compared with the aged group. Mechanistically, UA-H administration upregulated p-protein kinase B, the ratio of p-Akt to protein kinase B and total and cellular membrane GLUT4 protein levels in eWAT of ageing rats. Conversely, UA inhibited the increase in NF-κB expression and proinflammatory cytokines IL-6 and IL-1β. However, these alterations were not observed in the rats of the aged group. Taken together, the findings of the present study indicated that UA may ameliorate adipose IR, which is associated with activation of the Akt-GLUT4 signaling pathway and inhibition of inflammation in ageing rats. These data provide a basis for the development of effective and safe drugs or functional substances, such as UA, for the prevention and treatment of metabolic diseases.

Depression with Comorbid Diabetes: What Evidence Exists for Treatments Using Traditional Chinese Medicine and Natural Products?

Comorbidity between diabetes mellitus (DM) and depression, two chronic and devastating diseases spreading worldwide, has been confirmed by a large body of epidemiological and clinical studies. Due to the bidirectional relationship between DM and depression, this comorbidity leads to poorer outcomes in both conditions. Given the adverse effects and limited effectiveness of the existing therapies for depression associated with diabetes, the development of novel therapeutic drugs with more potency and fewer side effects is still the most important goal. Hence, many researchers have made great efforts to investigate the potential usefulness of traditional Chinese medicine (TCM) and natural products, including natural extracts and purified compounds, in the treatment of comorbid depression in diabetes. Here, we reviewed the related literature on TCM and natural products that can remedy the comorbidity of diabetes and depression and presented them on the basis of their mechanism of action, focusing on shared risk factors, including insulin resistance, oxidative stress and inflammation, and nervous disturbances. In short, this review suggests that TCM and natural products could expand the therapeutic alternatives to ameliorate the association between DM and depressive disorders.