Extending the reach of Exendin-4: new pathways in the control of body weight and glucose homeostasis

Exendin-4 shows no effects on the prostatic index in high-fat-diet-fed rat with benign prostatic hyperplasia by improving insulin resistance

Benign prostatic hyperplasia (BPH) is a prevalent disease globally, and accumulating evidence has indicated an association between BPH, insulin resistance (IR) and diabetes. Exendin-4 is widely used in clinics, which could enhance the proliferation of pancreatic β cells. The ability of exendin-4 to promote tumorigenesis has been of concern, and whether exendin-4 would enhance the propagation of BPH is not fully understood. We aimed to determine whether glucagon-like peptide-1 receptors (GLP-1Rs) were expressed in rat prostate and to determine the effect of exendin-4 on prostate of BPH. Male Wistar rats were used and assigned to six groups: normal diet (ND), high-fat diet (HFD), HFD + exendin-4, HFD + BPH, HFD + BPH + exendin-4 and HFD + BPH + rosiglitazone group. After castration, steroids were injected subcutaneously for 4 weeks to induce BPH. Rats were kept on high-fat diet to induce IR. Treatment groups were treated with exendin-4 and rosiglitazone. Prostatic index and HOMA-IR index were used to evaluate the prostatic hyperplasia status and the degree of IR respectively. The expression of GLP-1R was indicated not only by immunohistochemistry, but also by Western blot analysis. The expression of GLP-1R was significantly higher, and HOMA-IR index and body weight significantly decreased after administration of exendin-4. However, no significant differences in the prostatic index were observed between exendin-4 treatment groups and non-exendin-4 treatment groups. Prostatic index was not influenced by exendin-4 maybe by improving IR and weight loss.

Crosstalk between diabetes and brain: glucagon-like peptide-1 mimetics as a promising therapy against neurodegeneration

According to World Health Organization estimates, type 2 diabetes (T2D) is an epidemic (particularly in under development countries) and a socio-economic challenge. This is even more relevant since increasing evidence points T2D as a risk factor for Alzheimer's disease (AD), supporting the hypothesis that AD is a "type 3 diabetes" or "brain insulin resistant state". Despite the limited knowledge on the molecular mechanisms and the etiological complexity of both pathologies, evidence suggests that neurodegeneration/death underlying cognitive dysfunction (and ultimately dementia) upon long-term T2D may arise from a complex interplay between T2D and brain aging. Additionally, decreased brain insulin levels/signaling and glucose metabolism in both pathologies further suggests that an effective treatment strategy for one disorder may be also beneficial in the other. In this regard, one such promising strategy is a novel successful anti-T2D class of drugs, the glucagon-like peptide-1 (GLP-1) mimetics (e.g. exendin-4 or liraglutide), whose potential neuroprotective effects have been increasingly shown in the last years. In fact, several studies showed that, besides improving peripheral (and probably brain) insulin signaling, GLP-1 analogs minimize cell loss and possibly rescue cognitive decline in models of AD, Parkinson's (PD) or Huntington's disease. Interestingly, exendin-4 is undergoing clinical trials to test its potential as an anti-PD therapy. Herewith, we aim to integrate the available data on the metabolic and neuroprotective effects of GLP-1 mimetics in the central nervous system (CNS) with the complex crosstalk between T2D-AD, as well as their potential therapeutic value against T2D-associated cognitive dysfunction.