Atorvastatin ameliorates endothelium-specific insulin resistance induced by high glucose combined with high insulin

Renal denervation improves vascular endothelial dysfunction by inducing autophagy via AMPK/mTOR signaling activation in a rat model of type 2 diabetes mellitus with insulin resistance

BACKGROUND

Recent clinical and animal studies have shown that renal denervation (RDN) improves insulin sensitivity and endothelial dysfunction. However, the specific mechanism remains incompletely understood. The purpose of this study is to investigate the effects of RDN on endothelial dysfunction of type 2 diabetes mellitus (T₂DM) rat models with insulin resistance and to explore the underlying molecular mechanisms.

METHODS

Male Sprague-Dawley rats were fed with or without high-fat diet allocated in different groups, combined with low-dose streptozotocin which induces a rat model to develop T₂DM with insulin resistance. RDN was conducted 1 week after the rat models fully developed T₂DM. The animals were sub-divided into four groups randomly: control group (CON, n = 6), diabetic group (T₂DM, n = 6), diabetic with sham surgery group (Sham, n = 6) and diabetic with RDN group (RDN, n = 6). Rats in all groups were studied at baseline, both preoperatively and 4 weeks after RDN, respectively. Western blot was used to detect the expression of angiotensin-converting enzyme 2 (ACE2) protein and the expression of autophagy-related proteins Beclin1, LC3 and p62 and autophagy signaling pathway AMPK/mTOR proteins and apoptosis-related protein caspase-3 in the aorta endothelial cells. In addition, the effects of ACE2 on autophagy of human umbilical vein insulin resistance endothelial cell culture in vitro were also studied.

RESULTS

RDN decreased plasma and renal tissue norepinephrine levels. The Von Willebrand factor level was also decreased, while the plasma level of nitric oxide (NO) was significantly increased after RDN. Compared with the T₂DM group and the Sham group, the endothelium-dependent and endothelium-independent diastolic function of the RDN group was improved significantly, the expression of Beclin1, LC3, ACE2 and eNOS proteins was higher, and the level of p62 protein was decreased. Furthermore, we found that RDN can activate the expression of p-AMPK and inhibit the expression of p-mTOR. In cell culture experiment, ACE2 activated p-AMPK and inhibited p-mTOR, thus promoting autophagy.

CONCLUSIONS

RDN may not only increase the expression of ACE2 in the vascular endothelium, but also can via ACE2 activate p-AMPK and inhibit p-mTOR, thus promoting autophagy and improving endothelial dysfunction.

Atorvastatin attenuates obese-induced kidney injury and impaired renal organic anion transporter 3 function through inhibition of oxidative stress and inflammation

An excessive consumption of high-fat diet can lead to the alterations of glucose and lipid metabolism, impaired insulin signaling and increased ectopic lipid accumulation resulting in renal lipotoxicity and subsequent renal dysfunction. Atorvastatin is a lipid-lowering drug in clinical treatment. Several studies have reported that atorvastatin has several significant pleiotropic effects including anti-inflammatory, antioxidant, and anti-apoptotic effects. However, the effects of atorvastatin on metabolic disturbance and renal lipotoxicity in obesity are not fully understood. In this study, obesity in rat was developed by high-fat diet (HFD) feeding for 16 weeks. After that, the HFD-fed rats were received either a vehicle (HF), atorvastatin (HFA) or vildagliptin (HFVIL), by oral gavage for 4 weeks. We found that HF rats showed insulin resistance, visceral fat expansion and renal lipid accumulation. Impaired renal function and renal organic anion transporter 3 (Oat3) function and expression were also observed in HF rats. The marked increases in MDA level, renal injury and NF-κB, TGF-β, NOX-4, PKC-α expression were demonstrated in HF rats. Atorvastatin or vildagliptin treatment attenuated insulin resistance and renal lipid accumulation-induced lipotoxicity in HFA and HFVIL rats. Moreover, the proteins involved in renal inflammation, fibrosis, oxidative stress and apoptosis were attenuated leading to improved renal Oat3 function and renal function in the treated groups. Interestingly, atorvastatin showed higher efficacy than vildagliptin in improving insulin resistance, renal lipid accumulation and in exerting renoprotective effects in obesity-induced renal injury and impaired renal Oat3 function.

Mevastatin promotes neuronal survival against Aβ-induced neurotoxicity through AMPK activation

Statins or HMG-CoA reductase inhibitors have been shown to be effective at lowering cholesterol levels, and the application of these molecules has gradually emerged as an attractive therapeutic strategy for neurodegenerative diseases. Epidemiological studies suggest that statin use is associated with a decreased incidence of Alzheimer's disease (AD). Thus, statins may play a beneficial role in reducing amyloid β (Aβ) toxicity, the most relevant pathological feature and pathogenesis of AD. However, the precise mechanisms involved in statin-inhibited Aβ toxicity remain unclear. In the present study, we report that mevastatin significantly protects against Aβ-induced neurotoxicity in SK-N-MC neuronal cells by restoring impaired insulin signaling. This protection appears to be associated with the activation of AMP-activated protein kinase (AMPK), which has long been known to increase insulin sensitivity. Our results also indicate that high levels of cholesterol likely underlie Aβ-induced neurotoxicity and that activation of AMPK by mevastatin alleviates insulin resistance. Signaling through the insulin receptor substrate-1/Akt pathway appears to lead to cell survival. These findings demonstrate that mevastatin plays a potential therapeutic role in targeting Aβ-mediated neurotoxicity. The molecule presents a novel therapeutic strategy for further studies in AD prevention and therapeutics.

A natural compound jaceosidin ameliorates endoplasmic reticulum stress and insulin resistance via upregulation of SERCA2b

Increased endoplasmic reticulum (ER) stress has emerged as a vital contributor to dysregulated glucose homeostasis, and impaired function of sarco-endoplasmic reticulum Ca²⁺-ATPase 2b (SERCA2b) is one of the central mechanisms underlying ER stress. In this study, we reported that SERCA2b upregulation contributed to the amelioration of ER stress and insulin resistance by a small natural compound jaceosidin. In a model of differentiated C2C12 myotubes, jaceosidin-triggered SERCA2b upregulation enhanced insulin sensitivity and decreased ER stress. Moreover, the activity of Ca²⁺-ATPase in thapsigargin-treated myotubes was also augmented by jaceosidin. Furthermore, jaceosidin significantly suppressed blood glucose levels, improved glucose tolerance and lowered body weight, but did not alter food intake in insulin-resistant obese mice. In addition, this compound markedly reduced lipid accumulation, suppressed the expression of lipogenic genes in liver and ameliorated liver injury. The ameliorative effects of jaceosidin were due to its ability to reduce ER stress via increasing the expression of SERCA2b in the muscles of obese mice. Taken together, jaceosidin could improve ER stress and attenuate insulin resistance via SERCA2b upregulation in mice skeletal muscles.