The impact of the first, second and third waves of covid-19 on hepatitis B and C testing in Ontario, Canada.

The COVID-19 pandemic interrupted routine healthcare services. Hepatitis B virus (HBV) and hepatitis C virus (HCV) infections are often asymptomatic, and therefore, screening and on/post-treatment monitoring are required. Our aim was to determine the effect of the first, second and third waves of the pandemic on HBV and HCV testing in Ontario, Canada. We extracted data from Public Health Ontario for HBV and HCV specimens from 1 January 2019 to 31 May 2021. Testing volumes were evaluated and stratified by age, sex and region. Changes in testing volumes were analysed by per cent and absolute change. Testing volumes decreased in April 2020 with the first wave of the pandemic and recovered to 72%-75% of prepandemic volumes by the end of the first wave. HBsAg testing decreased by 33%, 18% and 15%, and HBV DNA testing decreased by 37%, 27% and 20%, in each consecutive wave. Anti-HCV testing decreased by 35%, 21% and 19%, and HCV RNA testing decreased by 44%, 30% and 36% in each consecutive wave. These trends were consistent by age, region and sex. Prenatal HBV testing volumes were stable. In conclusion, significant decreases in HBV and HCV testing occurred during the first three waves of the pandemic and have not recovered. In addition to direct consequences on viral hepatitis elimination efforts, these data provide insight into the impacts of the pandemic on chronic disease screening and management. Strategies to make up for missed testing will be critical to avoid additional consequences of COVID-19 long after the pandemic has resolved.

Reducing Read Time of Point-of-Care Test Does Not Affect Detection of Hepatitis C Virus and Reduces Need for Reflex RNA.

BACKGROUND & AIMS: Global elimination of hepatitis C virus (HCV) will require increases in diagnosis. Point of care (POC) tests that detect antibodies against HCV can be useful for testing large and difficult to reach populations. The most accurate POC test requires a 20 min read time to identify antibody-positive samples. We investigated whether viremic patients could be identified using a shorter read time, to increase efficiency and reduce the need for reflex tests (a follow-up test for HCV RNA on the same specimen to confirm viremia). METHODS: Patients with past or current HCV infections provided samples at 2 clinics in Canada for evaluation by the OraQuick HCV Rapid antibody POC test. A community HCV-screening program in Madrid, Spain (real-world cohort) invited people to be tested for HCV with the same OraQuick test. Patients provided samples of whole blood, via finger prick. Fingerprick samples were tested immediately after collection. In the clinic cohort, photographs of the developing test were taken at 15 second intervals, and blinded readers recorded the time to positivity. In the real-world cohort, readers recorded the OraQuick result at 5 minutes, and each minute after, up to 10 minutes, and then again at 20 minutes; viremia was then evaluated using a POC HCV RNA test (GeneXpert HCV Viral Load Assay). Sera from viremic and non-viremic clinic patients were used to quantify antibody titers to investigate the relationship between the time of band appearance and antibody concentration. Fisher's exact test and exact logistic regression were used to determine factors associated with a positive result at 5 minutes. RESULTS: Blood from all viremic patients produced a positive result in the antibody POC test by 5 min. Median time to a positive result for 171 viremic patients was 2.6 min (range, 1.8-4.6 min), vs 4.1 min (range, 2.3-14.4 min) for 108 patients with resolved infection (P < .001). The 5-min threshold identified all viremic cases among 176 HCV antibody-positive patients in the real-world cohort, confirmed by testing for HCV RNA. In the pooled cohorts, antibody positivity at 5 min identified viremic patients with 100% sensitivity (95% CI, 98.4%-100%); the negative predictive value was 100% (95% CI, 94.9%-100%). The positive predictive value at 5 min was 62.0% (95% CI, 56.7%-67.0%) and therefore insufficient alone to detect viremia; an HCV RNA test would still be necessary to confirm active infection. CONCLUSIONS: The wait time for the OraQuick HCV Rapid antibody POC blood test can be reduced from 20 min to 5 min and continue to reliably identify patients with HCV infection. Shortening the test time could increase high-throughput screening, reduce loss to follow up, and reduce the need for reflex HCV RNA testing.

Prenatal hepatitis B screening, and hepatitis B burden among children, in Ontario: a descriptive study.

BACKGROUND: Ontario is 1 of 5 provinces that immunize adolescents for hepatitis B virus (HBV), despite the World Health Organization recommendation for universal birth dose vaccination. One rationale for not vaccinating at birth is that universal prenatal screening and related interventions prevent vertical transmission. The aims of our study were to evaluate the uptake and epidemiology of prenatal HBV screening, and to determine the number of children in Ontario with a diagnosis of HBV before adolescent vaccination. METHODS: We extracted data from ICES, Public Health Ontario and Better Outcomes & Registry Network (BORN) Ontario databases. We assessed prenatal screening uptake and prevalence of prenatal hepatitis B surface antigen (HBsAg) from 2012 to 2016, as well as subsequent hepatitis B e-antigen (HBeAg) and HBV DNA testing and percent positivity. We used age and region to subcategorize the results. In a separate unlinked analysis, we evaluated the number of children positive for HBV aged 0-11 years who were born in Ontario from 2003 to 2013. RESULTS: From 2012 to 2016, 93% of pregnant women were screened for HBV, with an HBsAg prevalence of 0.6%. Prevalence of HBsAg increased with age, peaking at older than 45 years at 3%. North Toronto had the highest overall prevalence of 1.5%, whereas northern Ontario had the lowest. Of women who were HBsAg positive, HBeAg and HBV DNA tests were subsequently ordered in 13% and 38%, respectively. Of children born in Ontario between 2003 and 2013, 139 of 23 759 tested positive for HBV. INTERPRETATION: Prenatal HBV screening is not universal and subsequent evaluation is poor, limiting optimal intervention and possibly contributing to some Ontario-born children being given a diagnosis of HBV before age 12 years. These findings underscore the limitations of the province's adolescent vaccination strategy.

Tissue Inhibitor of Metalloproteinase 1 Influences Vascular Adaptations to Chronic Alterations in Blood Flow.

Remodeling of the skeletal muscle microvasculature involves the coordinated actions of matrix metalloproteinases (MMPs) and their endogenous inhibitors, tissue inhibitor of metalloproteinases (TIMPs). We hypothesized that the loss of TIMP1 would enhance both ischemia and flow-induced vascular remodeling by increasing MMP activity. TIMP1 deficient (Timp1-/- ) and wild-type (WT) C57BL/6 mice underwent unilateral femoral artery (FA) ligation or were treated with prazosin, an alpha-1 adrenergic receptor antagonist, in order to investigate vascular remodeling to altered flow. Under basal conditions, Timp1-/- mice had reduced microvascular content as compared to WT mice. Furthermore, vascular remodeling was impaired in Timp1-/- mice. Timp1-/- mice displayed reduced blood flow recovery in response to FA ligation and no arteriogenic response to prazosin treatment. Timp1-/- mice failed to undergo angiogenesis in response to ischemia or prazosin, despite maintaining the capacity to increase VEGF-A and eNOS mRNA. Vascular permeability was increased in muscles of Timp1-/- mice in response to both prazosin treatment and FA ligation, but this was not accompanied by greater MMP activity. This study highlights a previously undescribed integral role for TIMP1 in both vascular network maturation and adaptations to ischemia or alterations in flow. J. Cell. Physiol. 232: 831-841, 2017. © 2016 Wiley Periodicals, Inc.

Metabolic effects of prazosin on skeletal muscle insulin resistance in glucocorticoid-treated male rats.

High-dose glucocorticoids (GC) induce skeletal muscle atrophy, insulin resistance, and reduced muscle capillarization. Identification of treatments to prevent or reverse capillary rarefaction and metabolic deterioration caused by prolonged elevations in GCs would be therapeutically beneficial. Chronic administration of prazosin, an α1-adrenergic antagonist, increases skeletal muscle capillarization in healthy rodents and, recently, in a rodent model of elevated GCs and hyperglycemia. The purpose of this study was to determine whether prazosin administration would improve glucose tolerance and insulin sensitivity, through prazosin-mediated sparing of capillary rarefaction, in this rodent model of increased GC exposure. Prazosin was provided in drinking water (50 mg/l) to GC-treated or control rats (400 mg implants of either corticosterone or a wax pellet) for 7 or 14 days (n = 5-14/group). Whole body measures of glucose metabolism were correlated with skeletal muscle capillarization (C:F) at 7 and 14 days in the four groups of rats. Individual C:F was found to be predictive of insulin sensitivity (r2 = 0.4781), but not of glucose tolerance (r2 = 0.1601) and compared with water only, prazosin treatment decreased insulin values during oral glucose challenge by approximately one-third in corticosterone (Cort)-treated animals. Cort treatment, regardless of duration, induced significant glycolytic skeletal muscle atrophy (P < 0.05), decreased IRS-1 protein content (P < 0.05), and caused elevations in FOXO1 protein expression (P < 0.05), which were unaffected with prazosin administration. In summary, it appears that α1-adrenergic antagonism improves Cort-induced skeletal muscle vascular impairments and reduces insulin secretion during an oral glucose tolerance test, but is unable to improve the negative alterations directly affecting the myocyte, including muscle size and muscle signaling protein expression.

Factors associated with knowledge and awareness of Hepatitis B in individuals of Chinese descent: Results from a mass point of care testing and outreach campaign in Toronto, Canada.

Background: Migrants from hepatitis B virus (HBV) endemic regions are at high risk of having chronic infection. Despite this, HBV knowledge and awareness programming, and low-barrier screening methods such as point of care (POC) testing, among this group have yet to become routine. Methods: We conducted a mass HBV POC screening and knowledge and awareness campaign for individuals of Chinese descent in Toronto, Canada. POC screening was administered, then participants completed a knowledge questionnaire. Logistic regression identified associations between demographic factors and participants' level of HBV knowledge. Results: From 2015 to 2018, 33 outreach events resulted in 891 individuals completing testing and the knowledge questionnaire. Individuals averaged 64.4 years old. Most, 62% (N = 552), were female, and 73.6% (N = 656) have been in Canada for <30 years. The average questionnaire score was 70.7% correct, with 65.2% (N = 581) demonstrating a high level of HBV knowledge. Post-secondary education (OR: 2.19, 95% CI: 1.41, 3.39), income of $50,000 to <$75,000 (OR: 2.74, 95% CI: 1.39, 5.43), and having familial history of HBV (OR: 1.72, 95% CI: 1.06, 2.78) were associated with high knowledge. The observed prevalence of HBV was 1.5%, with 13 individuals testing positive on the POC test and confirmatory laboratory testing. Conclusions: Improving knowledge and awareness of HBV is critical to empowering people, especially migrants who experience barriers to care, to pursue vaccination, testing, and treatment. Combining knowledge outreach and POC test campaigns, enabled discussion and screening for HBV with large numbers of people, and can be tailored for optimal effectiveness for specific groups.

Rapid hepatitis C virus point-of-care RNA testing and treatment at an integrated supervised consumption service in Toronto, Canada: a prospective, observational cohort study.

Background: Despite high burden of Hepatitis C (HCV) among people who inject drugs, significant barriers to care persist. The aim of this study was to evaluate the provision of rapid, low-barrier point-of-care (POC) HCV RNA testing and linkage to care among clients of a supervised consumption service (SCS) located within a community health centre in Toronto, Canada. Secondary aims included measuring HCV RNA prevalence at baseline, HCV incidence during follow-up and exploring factors associated with HCV RNA positivity and treatment uptake. Methods: Participants were enrolled in a prospective, observational cohort from August 13, 2018 to September 30, 2021. Those with positive HCV RNA tests were offered immediate referral to onsite treatment. Those with negative results were offered repeat testing every three months for up to four visits. HCV incidence was estimated as the number of incident HCV infections per 100 person-years at risk, among those HCV RNA negative at baseline who returned for ≥1 follow-up visit. Missing data were reported when present. Findings: 128 participants were enrolled with four later removed due to ineligibility. At baseline, 54 of 124 eligible participants (43.5%) tested HCV RNA positive. HCV incidence was 35.1 cases per 100 person-years (95% CI: 18.9-65.3) with a cumulative incidence of 38.3% at 15 months of follow-up. Among participants HCV RNA positive at baseline or follow-up (n = 64), 67.2% (n = 43) were linked to HCV care and treatment was initiated among 67.4% (n = 29/43). Interpretation: High HCV RNA prevalence and incidence demonstrate that the SCS serves a high-risk population for HCV. Testing acceptance was high, as was treatment engagement. POC HCV RNA testing positions SCSs as an important point of HCV care access. Funding: HCV Micro-Elimination Grant, Gilead Sciences Canada; in-kind support from Cepheid.

Evaluation of Hepatitis C Screening and Treatment Among Psychiatry Inpatients.

Objective: To evaluate uptake of hepatitis C virus (HCV) testing and treatment among psychiatry inpatients at Canada's largest mental health institution, the Centre for Addiction and Mental Health (CAMH).Methods: We reviewed medical records for all forensic and long-stay mental health patients from January 2017 to May 2021 to examine rates of HCV testing (antibody and RNA), treatment, and follow-up and completed a logistical regression to identify predictors associated with HCV antibody (Ab) screening among inpatients.Results: Of 1,031 patients, 73% (n = 753) were male, mean age was 44 years (range: 20-92), and mean length of stay was 7.1 months (range: 0 days-24 years). Most, 83% (n = 856), were diagnosed with schizophrenia spectrum disorders. In total, 652/1,031 (63%) of individuals in this cohort received HCV Ab screening. When broken down by admission rather than individual, 570/1,303 (44%) forensic admissions had an associated HCV Ab screening, and 318/1,450 (22%) non-forensic admissions had an associated HCV Ab screening. Individuals admitted to a forensic unit and those diagnosed with schizophrenia or substance use disorders were more likely to undergo HCV Ab screening, while individuals of Asian ethnicity were less likely (all P < .05). HCV Ab positivity was 4.9%, and most (84%, n = 27) HCV Ab-positive individuals had subsequent RNA testing, of whom 56% (n = 15) tested HCV RNA positive. Of 15 RNA-positive individuals, 10 initiated treatments, 7 on-site at CAMH and 3 at a local hepatology center. A total of 7 individuals (1 treated by specialists and 6 on-site) achieved sustained virological response or cure. The remaining 3 were lost to follow-up, 2 of whom were treated at the hepatology clinic.Conclusions: Based on the high prevalence of HCV, mental health inpatients should be included in groups for whom universal screening is recommended. Since on-site treatment was more successful than referral to external hepatology specialists, utilizing inpatient admission as an opportunity for HCV screening and treatment should receive more consideration.

Province-to-province variability in hepatitis C testing, care, and treatment across Canada.

Background: Few countries have implemented the necessary policy changes to reduce the number of steps in the cascade of care to achieve hepatitis C virus (HCV) elimination, including Canada. The aim of this study was to describe and compare legislation, scope of practice, and policy as it relates to the provision of HCV care in each province. Methods: We reviewed grey literature and regulatory and legislative documents which affect various aspects of the HCV cascade of care. Findings were verified by content experts. Results: HCV RNA reflex testing ensures those that are antibody positive get an HCV RNA test; however only 80% of provinces have reflex test. Point-of-care antibody testing can be offered in most community non-health care settings, yet many types of health care providers are unable to do this independently. Following a positive test, it may not be feasible to complete venipuncture; however only a single province processes HCV RNA dried blood spot cards. In many provinces, training and verification are required for novice prescribers, and in some provinces prescribing continues to be restricted to specialists. Only a single province has task-shifted treatment to a non-physician non-nurse practitioner model, where pharmacists can prescribe treatment. Finally, 80% of provinces require authorization forms, and 30% require proof of investigations for treatment. Conclusions: No single province is optimizing the use of diagnostic tools and task shifting and decreasing paperwork to expedite treatment initiation. Collaboration between provinces is needed to streamline practice, update policy, and promote equity in HCV diagnosis, care, and treatment.

Somatostatin Receptor Antagonism Reverses Glucagon Counterregulatory Failure in Recurrently Hypoglycemic Male Rats.

Recent antecedent hypoglycemia is a known source of defective glucose counter-regulation in diabetes; the mechanisms perpetuating the cycle of progressive α-cell failure and recurrent hypoglycemia remain unknown. Somatostatin has been shown to suppress the glucagon response to acute hypoglycemia in rodent models of type 1 diabetes. We hypothesized that somatostatin receptor 2 antagonism (SSTR2a) would restore glucagon counterregulation and delay the onset of insulin-induced hypoglycemia in recurrently hypoglycemic, nondiabetic male rats. Healthy, male, Sprague-Dawley rats (n = 39) received bolus injections of insulin (10 U/kg, 8 U/kg, 5 U/kg) on 3 consecutive days to induce hypoglycemia. On day 4, animals were then treated with SSTR2a (10 mg/kg; n = 17) or vehicle (n = 12) 1 hour prior to the induction of hypoglycemia using insulin (5 U/kg). Plasma glucagon level during hypoglycemia was ~30% lower on day 3 (150 ± 75 pg/mL; P < .01), and 68% lower on day 4 in the vehicle group (70 ± 52 pg/mL; P < .001) compared with day 1 (219 ± 99 pg/mL). On day 4, SSTR2a prolonged euglycemia by 25 ± 5 minutes (P < .05) and restored the plasma glucagon response to hypoglycemia. Hepatic glycogen content of SSTR2a-treated rats was 35% lower than vehicle controls after hypoglycemia induction on day 4 (vehicle: 20 ± 7.0 vs SSTR2a: 13 ± 4.4 µmol/g; P < .01). SSTR2a treatment reverses the cumulative glucagon deficit resulting from 3 days of antecedent hypoglycemia in healthy rats. This reversal is associated with decreased hepatic glycogen content and delayed time to hypoglycemic onset. We conclude that recurrent hypoglycemia produces glucagon counterregulatory deficiency in healthy male rats, which can be improved by SSTR2a.

Impact of comprehensive care on health care use among a cohort of marginalized people living with hepatitis C in Toronto.

Background: The majority of new hepatitis C (HCV) cases occur among people who inject drugs. In recent years, multidisciplinary models of HCV treatment have emerged that demonstrate successful treatment outcomes for this population, as well as broad positive individual- and system-level impacts. Our objective was to evaluate changes in health care use among a cohort of people living with HCV before and after engagement with one such program. Methods: Program data were uniquely linked to provincial health administrative databases. Rates of emergency department (ED) visits and hospital admissions of clients from 2011 through 2015 (N = 103) were evaluated using linkages with administrative data for the 2 years before and after program initiation. Data were evaluated using negative binomial regression models with a covariance structure to account for within-individual correlations. Results: Of participants, 72.8% were men (mean age 47 years), and 38% experienced high rates of physical and mental health comorbidity (Aggregated Diagnosis Group score ≥10). Female clients had significantly fewer ED visits 2 years after program initiation (5.04 versus 3.12; risk ratio [RR] 0.61 [95% CI 0.44% to 0.86%]). ED visits for infectious diseases and soft tissue injury were significantly lower for the cohort overall (RRs 0.58 0.51 [95% CIs 0.35% to 0.95% and 0.29% to 0.90%], respectively). Conclusion: Co-locating HCV treatment within comprehensive primary care and harm reduction services appears to have benefits beyond HCV, including a reduction in ED visits among women and a decrease in ED visits for soft tissue infections for all participants.

Hyperglycaemia correlates with skeletal muscle capillary regression and is associated with alterations in the murine double minute-2/forkhead box O1/thrombospondin-1 pathway in type 1 diabetic BioBreeding rats.

Type 1 diabetes can have deleterious effects on skeletal muscle and its microvasculature. Our laboratory has recently identified murine double minute-2 as a master regulator of muscle microvasculature by controlling expression levels of two key molecular actors of the angio-adaptive process: the pro-angiogenic vascular endothelial growth factor-A and the anti-angiogenic thrombospondin-1. Here, we show for the first time that in the soleus and plantaris muscles of the diabetes-prone BioBreeding rats, a rodent model of autoimmune type 1 diabetes, murine double minute-2 protein levels are significantly decreased, coinciding with elevated protein levels of thrombospondin-1 and its transcription factor forkhead box O1. Significant capillary regression was observed to similar extent in soleus and plantaris muscles of type 1 diabetic rats. Elevated blood glucose levels were correlated with the loss of capillaries, the reduction in murine double minute-2 expression and with the elevations in thrombospondin-1. Vascular endothelial growth factor-A protein levels were unaltered or even increased in diabetic animals, yet type 1 diabetic animals had less vascular endothelial growth factor receptor-2 abundance. The vascular endothelial growth factor-A/thrombospondin-1 ratio, a good indicator of skeletal muscle angio-adaptive environment, was decreased in type 1 diabetic muscle. Our results suggest that the murine double minute-2-forkhead box O1-thrombospondin-1 pathway plays an important role in angio-regulation of the skeletal muscle in the pathophysiological context of type 1 diabetes.

Hepatitis C Core-Antigen Testing from Dried Blood Spots.

In order to expand hepatitis C virus (HCV) screening, a change in the diagnostic paradigm is warranted to improve accessibility and decrease costs, such as utilizing dried blood spot (DBS) collection. In our study, blood from 68 patients with chronic HCV infection was spotted onto DBS cards and stored at the following temperatures for one week: -80 °C, 4 °C, 21 °C, 37 °C, and alternating 37 °C and 4 °C; to assess whether temperature change during transportation would affect sensitivity. Sample was eluted from the DBS cards and tested for HCV antibodies (HCV-Ab) and HCV core antigen (core-Ag). HCV-Abs were detected from 68/68 DBS samples at -80 °C, 4 °C, 21 °C, and 67/68 at 37 °C and alternating 37 °C and 4 °C. Sensitivity of core-Ag was as follows: 94% (-80 °C), 94% (4 °C), 91% (21 °C), 93% (37 °C), and 93% (37 °C/4 °C). Not only did temperature not greatly affect sensitivity, but sensitivities are higher than previously reported, and support the use of this assay as an alternative to HCV RNA. We then completed a head-to-head comparison (n = 49) of venous versus capillary samples, and one versus two DBS. No difference in core-Ag sensitivity was observed by sample type, but there was an improvement when using two spots. We conclude that HCV-Abs and core-Ag testing from DBS cards has high diagnostic accuracy and could be considered as an alternative to HCV RNA in certain settings.

The effects of voluntary exercise and prazosin on capillary rarefaction and metabolism in streptozotocin-induced diabetic male rats.

Type-1 diabetes mellitus (T1D) causes impairments within the skeletal muscle microvasculature. Both regular exercise and prazosin have been shown to improve skeletal muscle capillarization and metabolism in healthy rats through distinct angiogenic mechanisms. The aim of this study was to evaluate the independent and additive effects of voluntary exercise and prazosin treatment on capillary-to-fiber ratio (C:F) in streptozotocin (STZ)-treated diabetic rats. STZ (65 mg/kg) was intraperitoneally administered to male Sprague-Dawley rats (n = 36) to induce diabetes, with healthy, nondiabetic, sedentary rats (n = 10) as controls. The STZ-treated rats were then divided into sedentary (SED) or exercising (EX; 24-h access to running wheels) groups and then further subdivided into prazosin (Praz) or water (H2O) treatment groups: nondiabetic-SED-H2O, STZ-SED-H2O, STZ-EX-H2O, STZ-SED-Praz, and STZ-EX-Praz. After 3 wk, untreated diabetes significantly reduced the C:F in tibialis anterior (TA) and soleus muscles in the STZ-SED-H2O animals (both P < 0.05). Voluntary exercise and prazosin treatment independently resulted in a normalization of C:F within the TA (1.86 ± 0.12 and 2.04 ± 0.03 vs 1.71 ± 0.09, P < 0.05) and the soleus (2.36 ± 0.07 and 2.68 ± 0.14 vs 2.13 ± 0.12, P < 0.05). The combined STZ-EX-Praz group resulted in the highest C:F within the TA (2.26 ± 0.07, P < 0.05). Voluntary exercise volume was negatively correlated with fed blood glucose levels (r2 = -0.7015, P < 0.01) and, when combined with prazosin, caused further enhanced nonfasted glucose (P < 0.01). Exercise and prazosin reduced circulating nonesterified fatty acids more than either stimulus alone (P < 0.05). These results suggest that the distinct stimulation of angiogenesis, with both regular exercise and prazosin treatment, causes a cooperative improvement in the microvascular complications associated with T1D.NEW & NOTEWORTHY It is currently well established that poorly controlled diabetes reduces both skeletal muscle mass and muscle capillarization. These muscle-specific features of diabetes may, in turn, compromise insulin sensitivity and glucose control. Using a model of streptozotocin-induced diabetes, we show the vascular complications linked with disease and how chronic exposure to exercise and prazosin (an α1-adrenergic antagonist) can reduce these complications and improve glycemic control.

The superoxide dismutase mimetic tempol does not alleviate glucocorticoid-mediated rarefaction of rat skeletal muscle capillaries.

Sustained elevations in circulating glucocorticoids elicit reductions in skeletal muscle microvascular content, but little is known of the underlying mechanisms. We hypothesized that glucocorticoid-induced oxidative stress contributes to this phenomenon. In rats that were implanted with corticosterone (CORT) or control pellets, CORT caused a significant decrease in muscle glutathione levels and a corresponding increase in protein carbonylation, an irreversible oxidative modification of proteins. Decreased endothelial nitric oxide synthase and increased endothelin-1 mRNA levels were detected after 9 days of CORT, and blood flow to glycolytic muscles was diminished. Control and CORT rats were treated concurrently with drinking water containing the superoxide dismutase mimetic tempol (172 mg/L) or the α-1 adrenergic receptor antagonist prazosin (50 mg/L) for 6 or 16 days. Both tempol and prazosin alleviated skeletal muscle protein carbonylation. Tempol failed to prevent CORT-mediated capillary rarefaction and was ineffective in restoring skeletal muscle blood flow. In contrast, prazosin blocked capillary rarefaction and restored skeletal muscle blood flow to control levels. The failure of tempol to prevent CORT-induced skeletal muscle microvascular rarefaction does not support a dominant role of superoxide-induced oxidative stress in this process. Although a decrease in protein carbonylation was observed with prazosin treatment, our data suggest that the maintenance of skeletal muscle microvascular content is related more closely with counteracting the CORT-mediated influence on skeletal muscle vascular tone.

Prazosin Can Prevent Glucocorticoid Mediated Capillary Rarefaction.

Glucocorticoids (GC) elicit skeletal muscle capillary rarefaction, which can subsequently impair blood distribution and muscle function; however, the mechanisms have not been established. We hypothesized that CORT would inhibit endothelial cell survival signals but that treatment with the alpha-1 adrenergic receptor inhibitor prazosin, which leads to angiogenesis in skeletal muscle of healthy rats, would reverse these effects and induce angiogenesis within the skeletal muscle of corticosterone (CORT)-treated rats. Male Sprague Dawley rats were implanted subcutaneously with CORT pellets (400 mg/rat), with or without concurrent prazosin treatment (50mg/L in drinking water), for 1 or 2 weeks. Skeletal muscle capillary rarefaction, as indicated by a significant reduction in capillary-to-fiber ratio (C:F), occurred after 2 weeks of CORT treatment. Concurrent prazosin administration prevented this capillary rarefaction in CORT-treated animals but did not induce angiogenesis or arteriogenesis as was observed with prazosin treatment in control rats. CORT treatment reduced the mRNA level of Angiopoietin-1 (Ang-1), which was partially offset in the muscles of rats that received 2 weeks of co-treatment with prazosin. In 2W CORT animals, prazosin treatment elicited a significant increase in vascular endothelial growth factor-A (VEGF-A) mRNA and protein. Conversely prazosin did not rescue CORT-induced reductions in transforming growth factor beta-1 (TGFß1 and matrix metalloproteinase-2 (MMP-2) mRNA. To determine if CORT impaired shear stress dependent signaling, cultured rat skeletal muscle endothelial cells were pre-treated with CORT (600nM) for 48 hours, then exposed to 15 dynes/cm2 shear stress or maintained with no flow. CORT blunted the shear stress-induced increase in pSer473 Akt, while pThr308 Akt, ERK1/2 and p38 phosphorylation and nitric oxide (NO) production were unaffected. This study demonstrates that GC-mediated capillary rarefaction is associated with a reduction in Ang-1 mRNA within the skeletal muscle microenvironment and that concurrent prazosin treatment effectively increases VEGF-A levels and prevents capillary loss.

Voluntary exercise improves metabolic profile in high-fat fed glucocorticoid-treated rats.

Diabetes is rapidly induced in young male Sprague-Dawley rats following treatment with exogenous corticosterone (CORT) and a high-fat diet (HFD). Regular exercise alleviates insulin insensitivity and improves pancreatic ß-cell function in insulin-resistant/diabetic rodents, but its effect in an animal model of elevated glucocorticoids is unknown. We examined the effect of voluntary exercise (EX) on diabetes development in CORT-HFD-treated male Sprague-Dawley rats (∼6 wk old). Animals were acclimatized to running wheels for 2 wk, then given a HFD, either wax (placebo) or CORT pellets, and split into 4 groups: placebo-sedentary (SED) or -EX and CORT-SED or -EX. After 2 wk of running combined with treatment, CORT-EX animals had reduced visceral adiposity, and increased skeletal muscle type IIb/x fiber area, oxidative capacity, capillary-to-fiber ratio and insulin sensitivity compared with CORT-SED animals (all P < 0.05). Although CORT-EX animals still had fasting hyperglycemia, these values were significantly improved compared with CORT-SED animals (14.3 ± 1.6 vs. 18.8 ± 0.9 mM). In addition, acute in vivo insulin response to an oral glucose challenge was enhanced ∼2-fold in CORT-EX vs. CORT-SED (P < 0.05) which was further demonstrated ex vivo in isolated islets. We conclude that voluntary wheel running in rats improves, but does not fully normalize, the metabolic profile and skeletal muscle composition of animals administered CORT and HFD.

Inhibition of proliferation, migration and proteolysis contribute to corticosterone-mediated inhibition of angiogenesis.

The angiostatic nature of pharmacological doses of glucocorticoid steroids is well known. However, the consequences of pathophysiological elevation of endogenous glucocorticoids are not well established. In the current study, we hypothesized that the angiostatic effect of corticosterone, an endogenous glucocorticoid in rodents, occurs through multi-faceted alterations in skeletal muscle microvascular endothelial cell proliferation, migration, and proteolysis. Chronic corticosterone treatment significantly reduced the capillary to fiber ratio in the tibialis anterior muscle compared to that of placebo-treated rats. Corticosterone inhibited endothelial cell sprouting from capillary segments ex vivo. Similarly, 3-dimensional endothelial cell spheroids treated with corticosterone for 48 hours showed evidence of sprout regression and reduced sprout length. Endothelial cell proliferation was reduced in corticosterone treated cells, coinciding with elevated FoxO1 and reduced VEGF production. Corticosterone treated endothelial cells exhibited reduced migration, which correlated with a reduction in RhoA activity. Furthermore, corticosterone treated endothelial cells in both 3-dimensional and monolayer cultures had decreased MMP-2 production and activation resulting in decreased proteolysis by endothelial cells, limiting their angiogenic potential. Promoter assays revealed that corticosterone treatment transcriptionally repressed MMP-2, which may map to a predicted GRE between -1510 and -1386 bp of the MMP-2 promoter. Additionally, Sp1, a known transcriptional activator of MMP-2 was decreased following corticosterone treatment. This study provides new insights into the mechanisms by which pathophysiological levels of endogenous glucocorticoids may exert angiostatic effects.