A retrospective observational study of osteoporosis management after a fragility fracture in primary care.

In many countries, osteoporosis is predominantly managed by primary care physicians; however, management after a fragility fracture has not been widely investigated. We describe osteoporosis care gaps in a real-world patient cohort. Our findings help inform initiatives to identify and overcome obstacles to effective management of patients after fragility fracture. PURPOSE: A fragility fracture is a major risk factor for subsequent fracture in adults aged ≥ 50 years. This retrospective observational study aimed to characterize post-fracture management in Canadian primary care. METHODS: A total of 778 patients with an index fragility fracture (low-trauma, excluding small bones) occurring between 2014 and 2016 were identified from medical records at 76 primary care centers in Canada, with follow-up until January 2018. RESULTS: Of 778 patients (80.5% female, median age [IQR] 73 [64-80]), 215 were on osteoporosis treatment and 269 had osteoporosis diagnosis recorded prior to their index fracture. The median follow-up was 363 (IQR 91-808) days. Of patients not on osteoporosis treatment at their index fracture, 60.2% (n = 339/563) remained untreated after their index fracture and 62.2% (n = 23/37) continued untreated after their subsequent fracture. After their index fracture, fracture risk assessment (FRAX or CAROC) was not performed in 83.2% (n = 647/778) of patients, and 59.9% (n = 466/778) of patients did not receive bone mineral density testing. Of patients without osteoporosis diagnosis recorded prior to their index date, 61.3% (n = 300/489) remained undiagnosed after their index fracture. At least one subsequent fracture occurred in 11.5% (n = 86/778) of patients. CONCLUSION: In the primary care setting, fragility fracture infrequently resulted in osteoporosis treatment or fracture risk assessment, even after multiple fragility fractures. These results suggest a fragility fracture is not recognized as a major risk factor for subsequent fracture and its occurrence does not prompt primary care physicians to intervene. These data urge initiatives to identify and overcome obstacles to primary care physicians' effective management of patients after fragility fractures.

Treatment and Low-Density Lipoprotein Cholesterol Management in Patients Diagnosed With Clinical Atherosclerotic Cardiovascular Disease in Alberta.

BACKGROUND: Low-density lipoprotein cholesterol (LDL-C) is an important indicator in the development and management of atherosclerotic cardiovascular disease (ASCVD). Herein, we describe the management of LDL-C with lipid-lowering therapy, among patients diagnosed with clinical ASCVD in Alberta, Canada. METHODS: A retrospective study was conducted by linking multiple health system databases to examine clinical characteristics, treatments, and LDL-C assessments. Patients with ASCVD were identified using a specific case definition on the basis of International Classification of Diseases, Ninth Revision, Clinical Modification/International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Canada codes between 2011 and 2015. LDL-C was assessed at the first measurement (index test) and second measurement (follow-up test) during the study period. LDL-C levels were evaluated on the basis of the 2016 Canadian Cardiovascular Society guideline recommendations for achieving < 2.0 mmol/L or a 50% reduction. Statin therapies were categorized as low-, moderate-, and high-intensity. RESULTS: Among the 281,665 individuals identified with ASCVD during the study period, 219,488 (77.9%) had an index LDL-C test, whereas 120,906 (55.1%) and 144,607 (65.9%) were prescribed lipid-lowering therapy before and after their index test, respectively. Most patients who received any lipid-lowering therapy were receiving moderate-/high-intensity statins (n = 133,029; 60.6%). Among the study cohort who had 2 LDL-C tests (n = 91,841; 32.6%), 48.5% of patients who received any lipid-lowering therapy did not achieve LDL-C levels < 2.0 at index date, whereas 36.6% did not achieve LDL-C levels < 2.0 or a 50% reduction at the follow-up test. CONCLUSIONS: The current study revealed that only two-thirds of patients with ASCVD were receiving pharmacotherapy and of those, a significant proportion did not reach recommended LDL-C levels. A remarkable treatment gap was identified for at-risk ASCVD patients. Further implementation strategies are required to address this undermanagement.

ER stress contributes to renal proximal tubule injury by increasing SREBP-2-mediated lipid accumulation and apoptotic cell death.

Renal proximal tubule injury is induced by agents/conditions known to cause endoplasmic reticulum (ER) stress, including cyclosporine A (CsA), an immunosuppressant drug with nephrotoxic effects. However, the underlying mechanism by which ER stress contributes to proximal tubule cell injury is not well understood. In this study, we report lipid accumulation, sterol regulatory element-binding protein-2 (SREBP-2) expression, and ER stress in proximal tubules of kidneys from mice treated with the classic ER stressor tunicamycin (Tm) or in human renal biopsy specimens showing CsA-induced nephrotoxicity. Colocalization of ER stress markers [78-kDa glucose regulated protein (GRP78), CHOP] with SREBP-2 expression and lipid accumulation was prominent within the proximal tubule cells exposed to Tm or CsA. Prolonged ER stress resulted in increased apoptotic cell death of lipid-enriched proximal tubule cells with colocalization of GRP78, SREBP-2, and Ca(2+)-independent phospholipase A(2) (iPLA(2)ß), an SREBP-2 inducible gene with proapoptotic characteristics. In cultured HK-2 human proximal tubule cells, CsA- and Tm-induced ER stress caused lipid accumulation and SREBP-2 activation. Furthermore, overexpression of SREBP-2 or activation of endogenous SREBP-2 in HK-2 cells stimulated apoptosis. Inhibition of SREBP-2 activation with the site-1-serine protease inhibitor AEBSF prevented ER stress-induced lipid accumulation and apoptosis. Overexpression of the ER-resident chaperone GRP78 attenuated ER stress and inhibited CsA-induced SREBP-2 expression and lipid accumulation. In summary, our findings suggest that ER stress-induced SREBP-2 activation contributes to renal proximal tubule cell injury by dysregulating lipid homeostasis.

Endoplasmic reticulum stress and lipid dysregulation.

Cellular cholesterol homeostasis is a fundamental and highly regulated process. Transcription factors known as sterol regulatory element binding proteins (SREBPs) coordinate the expression of many genes involved in the biosynthesis and uptake of cholesterol. Dysregulation of SREBP activation and cellular lipid accumulation has been associated with endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR). This review will provide an overview of ER stress and the UPR as well as cholesterol homeostasis and SREBP regulation, with an emphasis on their interaction and biological relevance.

Induction of the unfolded protein response after monocyte to macrophage differentiation augments cell survival in early atherosclerotic lesions.

Endoplasmic reticulum (ER) stress causes macrophage cell death within advanced atherosclerotic lesions, thereby contributing to necrotic core formation and increasing the risk of atherothrombotic disease. However, unlike in advanced lesions, the appearance of dead/apoptotic macrophages in early lesions is less prominent. Given that activation of the unfolded protein response (UPR) is detected in early lesion-resident macrophages and can enhance cell survival against ER stress, we investigated whether UPR activation occurs after monocyte to macrophage differentiation and confers a cytoprotective advantage to the macrophage. Human peripheral blood monocytes were treated with monocyte colony-stimulating factor to induce macrophage differentiation, as assessed by changes in ultrastructure and scavenger receptor expression. UPR markers, including GRP78, GRP94, and spliced XBP-1, were induced after macrophage differentiation and occurred after a significant increase in de novo protein synthesis. UPR activation after differentiation reduced macrophage cell death by ER stress-inducing agents. Further, GRP78 overexpression in macrophages was sufficient to reduce ER stress-induced cell death. Consistent with these in vitro findings, UPR activation was observed in viable lesion-resident macrophages from human carotid arteries and from the aortas of apoE(-/-) mice. However, no evidence of apoptosis was observed in early lesion-resident macrophages from the aortas of apoE(-/-) mice. Thus, our findings that UPR activation occurs during macrophage differentiation and is cytoprotective against ER stress-inducing agents suggest an important cellular mechanism for macrophage survival within early atherosclerotic lesions.

Endoplasmic reticulum stress causes the activation of sterol regulatory element binding protein-2.

BACKGROUND: Sterol regulatory element binding protein-2 (SREBP-2) is a membrane-bound transcription factor that upon proteolytic processing can activate the expression of genes involved in cholesterol biosynthesis and uptake. We as well as others have demonstrated that the accumulation of misfolded proteins within the endoplasmic reticulum (ER), a condition known as ER stress, can dysregulate lipid metabolism by activating the SREBPs. The purpose of this study was to determine the mechanism by which ER stress induces SREBP-2 activation. METHODS AND RESULTS: HeLa and MCF7 cells were treated with ER stress-inducing agents to determine the effect of ER stress on SREBP-2 cleavage and subsequent cholesterol accumulation. Cells treated with thapsigargin (Tg) exhibit proteolytic cleavage of SREBP-2. Proteolytic cleavage of SREBP-2 induced by Tg occurred independently of caspase activation and was inhibited by the site-1 protease inhibitor AEBSF, suggesting that Tg-induced SREBP-2 cleavage occurs through the conventional site-1/-2 pathway. Treatment of HeLa cells with Tg also led to the accumulation of free cholesterol as measured by Filipin staining. CONCLUSIONS: These results imply that ER stress-induced SREBP-2 activation occurs through the conventional pathway that normally regulates SREBP in accordance with intracellular sterol concentration.

Hypoxia-induced lactate dehydrogenase expression and tumor angiogenesis.

The aim of this review is to discuss the basic science of tumor angiogenesis and recent clinical trial results with angiogenic inhibitors. Colorectal cancer (CRC) continues to be a major cause of all new cancer cases and cancer-related deaths in North America. Although advances in chemotherapy have increased overall survival for patients suffering from metastatic CRC, the survival rate continues to be poor. In order to develop new and more effective therapies for advanced CRC, it is important to understand the basic biologic processes that govern tumor growth. This review will focus on pathways involved in stimulating tumor growth and angiogenesis. Recent excitement has been generated by the clinical efficacy of targeted antiangiogenic therapy against growth factors important in angiogenesis and tumor proliferation. By presenting the basic biology of tumor growth and angiogenesis, we will attempt to explain the therapeutic effects of different angiogenesis inhibitors and speculate how combination treatments with these agents might be beneficial.