Tumor Suppressor Par-4 Regulates Complement Factor C3 and Obesity

Prostate apoptosis response-4 (Par-4) is a tumor suppressor that induces apoptosis in cancer cells. However, the physiological function of Par-4 remains unknown. Here we show that conventional Par-4 knockout (Par-4^-/-) mice and adipocyte-specific Par-4 knockout (AKO) mice, but not hepatocyte-specific Par-4 knockout mice, are obese with standard chow diet. Par-4^-/- and AKO mice exhibit increased absorption and storage of fat in adipocytes. Mechanistically, Par-4 loss is associated with mdm2 downregulation and activation of p53. We identified complement factor c3 as a p53-regulated gene linked to fat storage in adipocytes. Par-4 re-expression in adipocytes or c3 deletion reversed the obese mouse phenotype. Moreover, obese human subjects showed lower expression of Par-4 relative to lean subjects, and in longitudinal studies, low baseline Par-4 levels denoted an increased risk of developing obesity later in life. These findings indicate that Par-4 suppresses p53 and its target c3 to regulate obesity.

Healthy Gut, Healthy Bones: Targeting the Gut Microbiome to Promote Bone Health

Over the past decade, the use of probiotics to modify the gut microbiome has become a public spotlight in reducing the severity of a number of chronic diseases such as autoimmune disease, diabetes, cancer and cardiovascular disease. Recently, the gut microbiome has been shown to play an important role in regulating bone mass. Therefore, targeting the gut microbiome may be a potential alternative avenue for those with osteopenia or osteoporosis. In this mini-review, we take the opportunity to delve into how the different components of the gut work together and how the gut-related diseases impact on bone health.

Inhibition of matrix metalloproteinase-2 improves endothelial function and prevents hypertension in insulin-resistant rats

BACKGROUND AND PURPOSE

Insulin resistance is often found to be associated with high blood pressure. We propose that in insulin-resistant hypertension, endothelial dysfunction is the consequence of increased activity of vascular MMP-2. As MMP-2 proteolytically cleaves a number of extracellular matrix proteins, we hypothesized that MMP-2 impairs endothelial function by proteolytic degradation of endothelial NOS (eNOS) or its cofactor, heat shock protein 90 (HSP90).

EXPERIMENTAL APPROACH

We tested our hypothesis in bovine coronary artery endothelial cells and fructose-fed hypertensive rats (FHR), a model of acquired systolic hypertension and insulin resistance.

KEY RESULTS

Treatment of FHRs with the MMP inhibitor doxycycline, preserved endothelial function as well as prevented the development of hypertension, suggesting that MMPs impair endothelial function. Furthermore, incubating endothelial cells in vitro with a recombinant MMP-2 decreased NO production in a dose-dependent manner. Using substrate cleavage assays and immunofluorescence microscopy studies, we found that MMP-2 not only cleaves and degrades HSP90, an eNOS cofactor but also co-localizes with both eNOS and HSP90 in endothelial cells, suggesting that MMPs functionally interact with the eNOS system. Treatment of FHRs with doxycycline attenuated the decrease in eNOS and HSP90 expression but did not improve insulin sensitivity.

CONCLUSIONS AND IMPLICATIONS

Our data suggest that increased activity of MMP-2 in FHRs impairs endothelial function and promotes hypertension. Inhibition of MMP-2 could be a potential therapeutic strategy for the management of hypertension.