The Direct Economic Burden of Gout in an Elderly Canadian Population.

OBJECTIVE: To estimate the direct healthcare cost and resource use from the public payer perspective between patients with incident gout and matched gout-free patients in Ontario. METHODS: Patients with incident gout aged ≥ 66 with uninterrupted Ontario Health Insurance Plan (OHIP) coverage in the 1-year baseline period were included in the study. Patients with gout were indexed at first gout diagnosis or prescription over the study period April 1, 2008, to March 31, 2014. Gout-free patients with no gout diagnosis within history were matched (up to 5:1) to each patient with gout. Linked medical records were analyzed until end of study, death, or OHIP ineligibility. Bang and Tsiatis adjusted healthcare costs and resource use were compared using bootstrap p-values and 95% CI. RESULTS: A total of 29,894 patients with gout and 148,231 gout-free patients were included in the study. Patients were 56% male, had a median Adjusted Clinical Group healthcare resource use band of moderate morbidity, and had a median age of 75-79 years. Baseline comorbidities were similar between groups except for renal disease. Analyzing 5-year total healthcare costs, patients with gout ($44,297) incurred a significantly higher average healthcare cost compared to gout-free patients ($33,965), for an incremental cost of $10,332 (95% CI $9617-$11,039; p < 0.01). Similar trends were observed in all individual healthcare component cost and use metrics. CONCLUSION: Following onset of gout, patients in Ontario incur significantly greater healthcare costs and resource use compared to matched gout-free patients. Alternative gout management strategies should be investigated to reduce the incremental burden of gout borne by the Ontario healthcare system.

Exploring the Distribution of Prescription for Sulfonylureas in Patients with Type 2 Diabetes According to Cardiovascular Risk Factors Within a Canadian Primary Care Setting.

BACKGROUND: A growing body of evidence generated from observational studies and meta-analyses has begun to illustrate the potential adverse cardiovascular (CV) risk profile associated with sulfonylurea (SU) use. Specifically, the use of an SU has been demonstrated to be associated with increased mortality and a higher risk of stroke with more CV events associated with SU use having been reported in subgroups of patients with a history of CV disease, elderly and a higher body mass index. OBJECTIVE: The objective of the current study was to explore the distribution of established atherosclerotic CV disease and CV risk factors amongst patients with diabetes on an SU using a Canadian primary care dataset for the 2013 calendar year. METHODS: The Canadian Primary Care Sentinel Surveillance Network (CPCSSN), which is a multi-disease surveillance system based on primary care electronic medical record data, was utilized for this research study. Patients with a diagnosis of diabetes and exposure to an SU were identified. Distribution/prevalence of CV risk profile amongst this sub-cohort was explored. RESULTS: In analyzing the CPCSSN database for the 2013 calendar year, 6150 patients were identified as having diabetes, at least one visit with their family doctor, and on an SU. For this sub-cohort, demographic data was as follows: age [mean (SD)] 65.4(12.8) years-old; 56.4% male and mean BMI 31.3(10.0). Established atherosclerotic CV disease was observed in 16.8% of the patients with the following distribution: 13.2% had ischemic heart disease/myocardial infarction or coronary artery disease; 2.4% had stroke; and 2.3% had peripheral vascular disease. Regarding the aggregation of CV risk factors, a large proportion (65%) of patients without established atherosclerotic CV disease presented with 2 or more CV risk factors including: hypertension (62%), dyslipidemia (33%), active smoking (13%), and obesity (43%). Almost half of the cohort (45%) were males older than 55 years of age or females older than 60 years of age with at least one of the following risk factors: dyslipidemia, hypertension or current smoking, but without established cardiovascular disease. A large proportion of patients (19.5%) had a diagnosis of cardiac-specific issues including ischemic heart disease/myocardial infarction/coronary artery disease, heart failure (not due to ischemic heart disease/myocardial infarction/coronary artery disease), or arrhythmia. Almost 82% of patients had either established atherosclerotic CV disease or 2 or more CV risk factors without established atherosclerotic CV disease. CONCLUSION: This study illustrated that in this dataset of Canadian patients with diabetes in a primary care setting, a substantial proportion of patients treated with an SU in 2013 had established CV disease and/or an aggregation of multiple CV risk factors. In light of recent data reporting on an association between SU utilization and CV events and increased mortality, pharmacovigilance programs should actively monitor SU utilization in patients with diabetes and a high risk CV profile in real world clinical settings.

Canonical WNT signaling during kidney development.

The canonical WNT signaling pathway plays a crucial role in patterning of the embryo during development, but little is known about the specific developmental events which are under WNT control. To understand more about how the WNT pathway orchestrates mammalian organogenesis, we studied the canonical beta-catenin-mediated WNT signaling pathway in kidneys of mice bearing a beta-catenin-responsive TCF/betaGal reporter transgene. In metanephric kidney, intense canonical WNT signaling was evident in epithelia of the branching ureteric bud and in nephrogenic mesenchyme during its transition into renal tubules. WNT signaling activity is rapidly downregulated in maturing nephrons and becomes undetectable in postnatal kidney. Sites of TCF/betaGal activity are in proximity to the known sites of renal WNT2b and WNT4 expression, and these WNTs stimulate TCF reporter activity in kidney cell lines derived from ureteric bud and metanephric mesenchyme lineages. When fetal kidney explants from HoxB7/GFP mice were exposed to the canonical WNT signaling pathway inhibitor, Dickkopf-1, arborization of the ureteric bud was significantly reduced. We conclude that restricted zones of intense canonical WNT signaling drive branching nephrogenesis in fetal kidney.

Neuronal apoptosis inhibitory protein is expressed in developing kidney and is regulated by PAX2.

During fetal kidney development, the extent of ureteric bud (UB) branching will determine final nephron endowment for life. Nephron number varies widely among normal humans and those who are born at the low end of the nephron number spectrum may be at risk for essential hypertension in adulthood. Little is known about how nephron number is set. However, we previously showed that the transcription factor, Pax2, suppresses apoptosis in UB cells during kidney development and optimizes branching morphogenesis. Here, we report that PAX2 directly binds to a specific recognition motif in the human neuronal apoptosis inhibitory protein (NAIP) gene promoter. NAIP is an endogenous inhibitor of apoptosis, inactivating caspase-3 and caspase-7 in neuronal tissues. PAX2 activates NAIP gene transcription (7-fold) in vitro and NAIP transcript level is increased fourfold in HEK293 cells stably transfected with PAX2. We show that Naip is expressed in embryonic day 15 (E15) fetal kidney tissue (RT-PCR) and NAIP protein is demonstrated by immunohistochemistry in E15 mouse kidney collecting ducts and P1 proximal tubules. Naip mRNA is significantly reduced (50%) in heterozygous Pax2 mutant mice. Finally, we show that an antisense Naip1 cDNA transfected into murine collecting duct cells doubles caspase-3/7 activity induced by Baxalpha. These observations suggest that the powerful effects of PAX2 on renal branching morphogenesis and final nephron number may be mediated by activation of Naip which then suppresses apoptosis in UB cells.

Suppression of ureteric bud apoptosis rescues nephron endowment and adult renal function in Pax2 mutant mice.

The molecular mechanisms that set congenital nephron number are unknown. However, humans with modest suboptimal nephron number may be at increased risk for essential hypertension, and those with more severe nephron deficits at birth may develop progressive renal insufficiency. A model of branching morphogenesis during fetal kidney development in which the extent of ureteric bud arborization is dependent on suppression of programmed cell death has been proposed. This study shows that the increased apoptosis and reduced ureteric bud branching of heterozygous Pax2 mutant mice is associated with 40% decrease in nephron number at birth. This leads to postnatal glomerular hypertrophy and long-term renal insufficiency in the absence of glomerulosclerosis. To determine whether restoration of antiapoptotic factors alone is sufficient to rescue the nephron deficit in these mice, a BCL2 transgene that is under the control of the PAX2 promoter was targeted to the ureteric bud. The transgene suppressed programmed cell death in the ureteric bud lineage, increased nephron number to 90% of that of wild-type littermates at birth, and normalized renal function at 1 yr. These observations lend strong support to the hypothesis that factors that control ureteric bud apoptosis are powerful determinants of congenital nephron endowment.

PAX2 activates WNT4 expression during mammalian kidney development.

The transcription factor PAX2 is expressed during normal kidney development and is thought to influence outgrowth and branching of the ureteric bud. Mice with homozygous null Pax2 mutations have developmental defects of the midbrain-hindbrain region, optic nerve, and ear and are anephric. During nephrogenesis, PAX2 is also expressed by mesenchymal cells as they cluster and reorganize to form proximal elements of each nephron, but the function of PAX2 in these cells is unknown. In this study we hypothesized that PAX2 activates expression of WNT4, a secreted glycoprotein known to be critical for successful nephrogenesis. PAX2 protein was identified in distal portions of the "S-shaped" body, and the protein persists in the emerging proximal tubules of murine fetal kidney. PAX2 activated WNT4 promoter activity 5-fold in co-transfection assays with JTC12 cells derived from the proximal tubule. Inspection of the 5'-flanking sequence of the human WNT4 gene identified three novel PAX2 recognition motifs; each exhibited specific PAX2 protein binding in electromobility shift assays. Two motifs were contained within a completely duplicated 0.66-kb cassette. Transfection of JTC12 cells with a PAX2 expression vector was associated with a 7-fold increase in endogenous WNT4 mRNA. In contrast, Wnt4 mRNA was decreased by 60% in mesenchymal cell condensates of fetal kidney from mice with a heterozygous Pax2 mutation. We speculated that a key function of PAX2 is to activate WNT4 gene expression in metanephric mesenchymal cells as they differentiate to form elements of the renal tubules.

Renal hypoplasia: lessons from Pax2.

The functions of Pax2 during renal development are many. It organizes caudal descent of the nephric duct, emergence of the ureteric bud, branching morphogenesis, and sustained arborization of the collecting system. In this review, we use lessons from the study of Pax2 as organizing principles to focus on the developmental processes which, if disrupted, might lead to renal hypoplasia in humans. We consider the problem of renal hypoplasia as a continuum, ranging from renal agenesis to subtle congenital nephron deficits. Early failure in the first two developmental stages (e.g. homozygous inactivation of Pax2) should preclude formation of metanephric kidneys and cause bilateral renal agenesis, incompatible with life. Interference with the later stages affects the extent of branching morphogenesis (e.g. heterozygous Pax2 mutations). Although the resulting nephron deficits are compatible with life, they may be moderately severe and account for up to 40% of the children in dialysis and transplant units around the world. Finally, the effect of Pax2 on apoptosis in the branching ureteric bud seems to imply a quantitative process which is finely tuned. Modest changes in this program could account for subtle nephron deficits in "normal" humans and increased risk of hypertension or susceptibility to acquired renal disease later in life.

Rescue of defective branching nephrogenesis in renal-coloboma syndrome by the caspase inhibitor, Z-VAD-fmk.

In renal-coloboma syndrome (RCS), null mutations of the PAX2 gene cause renal hypoplasia due to a congenital deficit of nephrons; affected individuals may develop renal insufficiency in childhood. During normal kidney development, PAX2, is expressed at high levels throughout the arborizing ureteric bud (UB); recent observations suggest that one of its key roles is to suppress apoptosis in this collecting duct lineage. The authors hypothesized that increased UB cell apoptosis due to PAX2 haploinsufficiency must directly influence the rate of branching morphogenesis in developing kidney and the number of nephrons that can be formed before birth, when nephrogenesis in humans comes to an end. If so, the authors reasoned that caspase inhibitors might be used to suppress unwanted UB cell apoptosis during kidney development in Pax2(1Neu) mutant mice and rescue the genetic UB branching defect. E17.5 kidneys from Pax2(1Neu) mutant mice had smaller (-25%) longitudinal cross-sectional area and 3.5-fold increase in collecting duct cell apoptosis versus wild-type littermates; mutant E13.5 kidney explants allowed to arborize for 50 h in vitro had 18% fewer terminal branches than wild-types. However, exposure to the caspase inhibitor, Z-VAD-fmk (25 micro M), significantly increased terminal branch number in mutant explants (23%). It also increased branching in wild-type explants, apparently reflecting an effect of Z-VAD-fmk on basal apoptosis induced by ex vivo culture conditions. Similarly, when pregnant mice were injected daily with Z-VAD-fmk (10 micro g/g weight from E10.5 to E17.5), apoptosis of Pax2(1Neu) fetal collecting duct cells was suppressed to 40% of untreated mutants; by E14, terminal branch number was increased to 152% that of untreated litters. These studies support the hypothesis that PAX2 normally optimizes the rate of branching morphogenesis in fetal kidney by suppressing UB apoptosis. Furthermore, it suggests that caspase inhibitors can rescue the branching defect caused by PAX2 mutations.

Ureteric bud apoptosis and renal hypoplasia in transgenic PAX2-Bax fetal mice mimics the renal-coloboma syndrome.

In humans, PAX2 haploinsufficiency causes renal-coloboma syndrome (RCS) involving eye abnormalities, renal hypoplasia, and renal failure in early life. The authors previously showed that heterozygous mutant Pax2 mice have smaller kidneys with fewer nephrons, associated with elevated apoptosis in the ureteric bud (UB). However, PAX2 may have a variety of developmental functions such as effects on cell fate and differentiation. To determine whether apoptosis alone is sufficient to cause a UB branching deficit, the authors targeted a pro-apoptotic gene (Baxalpha) to the embryonic kidney under the control of human PAX2 regulatory elements. The exogenous PAX2 promoter directed Baxalpha gene expression specifically to the developing kidney UB, eye, and mid/hindbrain. At E15.5 PAX2Promoter-Baxalpha fetal mice exhibited renal hypoplasia, elevated UB apoptosis, and retinal defects, mimicking the phenotype observed in RCS. The kidneys of E15.5 PAX2Promoter-Baxalpha fetal mice were 55% smaller than those of wild-type fetal mice, and they contained 70% of the normal level of UB branching. The data indicate that loss of Pax2 anti-apoptotic activity is sufficient to account for the reduced UB branching observed in RCS and suggest that elevated UB apoptosis may be a key process responsible for renal hypoplasia. The authors propose a morphogenic unit model in which cell survival influences the rate of UB branching and determines final nephron endowment.