Effect of gamma-carboxylase inhibition on serum osteocalcin may be partially protective against developing diabetic cardiomyopathy in type 2 diabetic rats

Oxidative Stress and Low-Grade Inflammation in Polycystic Ovary Syndrome: Controversies and New Insights

The pathophysiology of Polycystic Ovary Syndrome (PCOS) is quite complex and different mechanisms could contribute to hyperandrogenism and anovulation, which are the main features of the syndrome. Obesity and insulin-resistance are claimed as the principal factors contributing to the clinical presentation; in normal weight PCOS either, increased visceral adipose tissue has been described. However, their role is still debated, as debated are the biochemical markers linked to obesity per se. Oxidative stress (OS) and low-grade inflammation (LGI) have recently been a matter of researcher attention; they can influence each other in a reciprocal vicious cycle. In this review, we summarize the main mechanism of radical generation and the link with LGI. Furthermore, we discuss papers in favor or against the role of obesity as the first pathogenetic factor, and show how OS itself, on the contrary, can induce obesity and insulin resistance; in particular, the role of GH-IGF-1 axis is highlighted. Finally, the possible consequences on vitamin D synthesis and activation on the immune system are briefly discussed. This review intends to underline the key role of oxidative stress and low-grade inflammation in the physiopathology of PCOS, they can cause or worsen obesity, insulin-resistance, vitamin D deficiency, and immune dyscrasia, suggesting an inverse interaction to what is usually considered.

The Potential Role of Undercarboxylated Osteocalcin Upregulation in Microvascular Insufficiency in a Rat Model of Diabetic Cardiomyopathy

BACKGROUND

Diabetic cardiomyopathy (DCM) is accompanied by microvascular complications that lead to myocardial dysfunction and heart failure. Most conventional therapies cannot ameliorate the microvascular insufficiency in DCM. In this study, we tested the hypothesis that undercarboxylated osteocalcin (ucOC) may be a new adjuvant therapy against the progression of DCM and its underlying microvascular pathology.

MATERIALS AND METHODS

Diabetes was induced in Wistar rats with a high-fat diet combined with streptozotocin injections, and ucOC was upregulated after warfarin administration in the treated group. After 8 weeks, cardiac functions were assessed using a Langendorff apparatus. Cardiac tissue samples were also extracted to assess the ucOC receptor and vascular endothelial growth factor (VEGF) for histopathological studies.

RESULTS

Both the systolic and the diastolic dysfunction observed in the DCM group were significantly improved after the increase in ucOC blood levels. Significant improvement in VEGF and CD31 expression after warfarin injection was associated with increased capillary density, neovascularization, and decreased myocardial fibrosis together with the reestablishment of myocardial structural and ultrastructural patterns.

CONCLUSION

Undercarboxylated osteocalcin may have a promising effect in improving microvascular insufficiency and myocardial dysfunction in DCM.

Low serum osteocalcin levels are correlated with left ventricular systolic dysfunction and cardiac death in Chinese men

Osteocalcin is a newly identified type of cytokine secreted by osteoblasts, which has an endocrine function, mediates energy and glycol-lipid metabolism, and is closely related to cardiovascular diseases. In this study, we investigated the value of serum osteocalcin levels in predicting left ventricular systolic dysfunction and cardiac death. A total of 258 patients in the Department of Cardiology were included. Two-dimensional echocardiography was performed in all the subjects. The cardiac death of subjects occurring with a median follow-up of 4.6 years was informed via phone calls or the electronic medical records. The serum osteocalcin levels were measured using electrochemiluminescent immunoassay. We found that the median left ventricular ejection fractions (LVEFs) were 62% in men and 63% in women. In the men with a LVEF > 62%, the serum osteocalcin levels were significantly higher than in those with LVEF ≤ 62% (P = 0.042), whereas this difference was absent in the women. Both the serum osteocalcin (β = 0.095, P = 0.028) and serum N-terminal pro-brain natriuretic peptide (NT-pro-BNP; β = -0.003, P < 0.01) levels remained independently significantly correlated with LVEF in the men but not in the women. Receiver operating characteristic (ROC) analyses of the men revealed that the serum osteocalcin (P = 0.007), serum NT-pro-BNP (P = 0.018) and serum osteocalcin + NT-pro-BNP (P < 0.01) levels were all significant in identifying left ventricular systolic dysfunction at baseline, but the pairwise comparisons of the three areas under the curves (AUCs) were all non-significant. The men in the lower osteocalcin level group at baseline suffered a greater risk of future cardiac death than those in the higher osteocalcin level group, whereas the result for NT-pro-BNP exhibited the opposite pattern. In conclusion, lower serum osteocalcin levels in the men could identify left ventricular systolic dysfunction and cardiac death in a manner that was not inferior to high serum NT-pro-BNP levels.

Serious Hypoglycemia and Use of Warfarin in Combination With Sulfonylureas or Metformin

Prior research suggests that warfarin, when given concomitantly with some sulfonylureas, may increase the risk of serious hypoglycemia. However, the clinical significance remains unclear. We examined rate ratios (RRs) for the association between serious hypoglycemia and concomitant use of warfarin with either sulfonylureas or metformin using a self-controlled case series design and US Medicaid claims (supplemented with Medicare claims) from 1999 to 2011. Across all risk windows combined, warfarin was associated with an elevated rate of serious hypoglycemia when given concomitantly with glimepiride (RR, 1.47; 95% confidence interval (CI), 1.07-2.02) and metformin (RR, 1.73; 95% CI, 1.38-2.16). Particularly in the late risk window (>120 days since beginning concomitancy), most of the RRs for warfarin were elevated: glipizide (RR, 1.72; 95% CI, 1.29-2.29), glyburide (RR, 1.57; 95% CI, 1.15-2.15), metformin (RR, 2.26; 95% CI, 1.67-3.05), and glimepiride (RR, 1.56; 95% CI, 0.97-2.50). These results are consistent with a previously hypothesized hypoglycemic effect of warfarin in patients with type 2 diabetes through inhibition of the carboxylation of osteocalcin.

GPRC6A: Jack of all metabolism (or master of none)

Background

GPRC6A, a widely expressed G-protein coupled receptor, is proposed to be a master regulator of complex endocrine networks and metabolic processes. GPRC6A is activated by multiple ligands, including osteocalcin (Ocn), testosterone (T), basic amino acids, and various cations.

Scope of Review

We review the controversy surrounding GPRC6A functions. In mice, GPRC6A is proposed to integrate metabolic functions through the coordinated secretion of hormones, including insulin, GLP-1, T, and IL-6, and direct effects of this receptor to control glucose and fat metabolism in the liver, skeletal muscle, and fat. Loss-of-GPRC6A results in metabolic syndrome (MetS), and activation of GPRC6A stimulates proliferation of β-cells, increases peripheral insulin sensitivity, and protects against high fat diet (HFD) induced metabolic abnormalities in most mouse models. Bone, cardiovascular, immune, and skin functions of GPRC6A have also been identified in mice. Expression of GPRC6A is increased in prostate cancer (PCa) cells, and inhibition of GPRC6A attenuates PCa progression in mouse models. The function of GPRC6A in humans, however, is not clear. During evolution, a unique polymorphism of GPRC6A emerged mainly in humans of Asian and European decent that has been proposed to alter membrane trafficking and function. In contrast, the ancestral allele found in all other species is retained in 1%, 15%, and 40% of people of Asian, European and African descent, respectively, suggesting GPRC6A gene variants may contribute to the racial disparities in the risk of developing MetS and PCa.

Major Conclusions

If the regulatory functions of GPRC6A identified in mice translate to humans, and polymorphisms in GPRC6A are found to predict racial disparities in human diseases, GPRC6A may be a new gene target to predict, prevent, and treat MetS, PCa, and other disorders impacted by GPRC6A.