Renal and Vascular Effects of Combined SGLT2 and Angiotensin-Converting Enzyme Inhibition.

BACKGROUND: The cardiorenal effects of sodium-glucose cotransporter 2 inhibition (empagliflozin 25 mg QD) combined with angiotensin-converting enzyme inhibition (ramipril 10 mg QD) were assessed in this mechanistic study in patients with type 1 diabetes with potential renal hyperfiltration. METHODS: Thirty patients (out of 31 randomized) completed this double-blind, placebo-controlled, crossover trial. Recruitment was stopped early because of an unexpectedly low proportion of patients with hyperfiltration. Measurements were obtained after each of the 6 treatment phases over 19 weeks: (1) baseline without treatment, (2) 4-week run-in with ramipril treatment alone, (3) 4-week combined empagliflozin-ramipril treatment, (4) a 4-week washout, (5) 4-week combined placebo-ramipril treatment, and (6) 1-week follow-up. The primary end point was glomerular filtration rate (GFR) after combination treatment with empagliflozin-ramipril compared with placebo-ramipril. GFR was corrected for ramipril treatment alone before randomization. At the end of study phase, the following outcomes were measured under clamped euglycemia (4 to 6 mmol/L): inulin (GFR) and para-aminohippurate (effective renal plasma flow) clearances, tubular sodium handling, ambulatory blood pressure, arterial stiffness, heart rate variability, noninvasive cardiac output monitoring, plasma and urine biochemistry, markers of the renin-angiotensin-aldosterone system, and oxidative stress. RESULTS: Combination treatment with empagliflozin-ramipril resulted in an 8 mL/min/1.73 m2 lower GFR compared with placebo-ramipril treatment (P=0.0061) without significant changes to effective renal plasma flow. GFR decrease was accompanied by a 21.3 mL/min lower absolute proximal fluid reabsorption rate (P=0.0092), a 3.1 mmol/min lower absolute proximal sodium reabsorption rate (P=0.0056), and a 194 ng/mmol creatinine lower urinary 8-isoprostane level (P=0.0084) relative to placebo-ramipril combination treatment. Sodium-glucose cotransporter 2 inhibitor/angiotensin-converting enzyme inhibitor combination treatment resulted in additive blood pressure-lowering effects (clinic systolic blood pressure lower by 4 mm Hg [P=0.0112]; diastolic blood pressure lower by 3 mm Hg [P=0.0032]) in conjunction with a 94.5 dynes × sex/cm5 lower total peripheral resistance (P=0.0368). There were no significant changes observed to ambulatory blood pressure, arterial stiffness, heart rate variability, or cardiac output with the addition of empagliflozin. CONCLUSIONS: Adding sodium-glucose cotransporter 2 inhibitor treatment to angiotensin-converting enzyme inhibitor resulted in an expected GFR dip, suppression of oxidative stress markers, additive declines in blood pressure and total peripheral resistance. These changes are consistent with a protective physiologic profile characterized by the lowering of intraglomerular pressure and related cardiorenal risk when adding a sodium-glucose cotransporter 2 inhibitor to conservative therapy. REGISTRATION: URL: https://www. CLINICALTRIALS: gov; Unique identifier: NCT02632747.

Renal Hemodynamics and Renin-Angiotensin-Aldosterone System Profiles in Patients With Heart Failure.

OBJECTIVE: Understanding cardiorenal pathophysiology in heart failure (HF) is of clinical importance. We sought to characterize the renal hemodynamic function and the transrenal gradient of the renin-angiotensin-aldosterone system (RAAS) markers in patients with HF and in controls without HF. METHODS: In this post hoc analysis, the glomerular filtration rate (GFRinulin), effective renal plasma flow (ERPFPAH) and transrenal gradients (arterial-renal vein) of angiotensin converting enzyme (ACE), aldosterone, and plasma renin activity (PRA) were measured in 47 patients with HF and in 24 controls. Gomez equations were used to derive afferent (RA) and efferent (RE) arteriolar resistances. Transrenal RAAS gradients were also collected in patients treated with intravenous dobutamine (HF, n = 11; non-HF, n = 11) or nitroprusside (HF, n = 18; non-HF, n = 5). RESULTS: The concentrations of PRA, aldosterone and ACE were higher in the renal vein vs the artery in patients with HF vs patients without HF (P < 0.01). In patients with HF, a greater ACE gradient was associated with greater renal vascular resistance (r = 0.42; P 0.007) and greater arteriolar resistances (RA: r = 0.39; P = 0.012; RE: r = 0.48; P = 0.002). Similarly, a greater aldosterone gradient was associated with lower GFR (r = -0.51; P = 0.0007) and renal blood flow (RBF), r = -0.32; P = 0.042) whereas greater PRA gradient with lower ERPF (r = -0.33; P = 0.040), GFR (r = -0.36; P = 0.024), and RBF (r = -0.33; P = 0.036). Dobutamine and nitroprusside treatment decreased the transrenal gradient of ACE (P = 0.012, P < 0.0001, respectively), aldosterone (P = 0.005, P = 0.030) and PRA (P = 0.014, P = 0.002) in patients with HF only. CONCLUSIONS: A larger transrenal RAAS marker gradient in patients with HF suggests a renal origin for neurohormonal activation associated with a vasoconstrictive renal profile.

Biologic treatment outcomes in mucous membrane pemphigoid: A systematic review.

BACKGROUND: Mucous membrane pemphigoid (MMP) is an autoimmune disease that can lead to fibrosis of mucous membranes and functional impairment. Biologic agents should be explored as alternative treatment options to improve outcomes. OBJECTIVE: To conduct a systematic review of biologic treatment outcomes in patients with MMP. METHODS: A MEDLINE and Embase search was conducted on July 23, 2020, to include 63 studies using Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. RESULTS: Use of intravenous immunoglobulin (n = 154), rituximab (n = 112), tumor necrosis factor α inhibitors (n = 7), and combination treatments (n = 58) were reported in 331 patients with MMP. Intravenous immunoglobulin led to complete resolution in 61.7% (n = 95/154) of patients within 26.0 months, with a recurrence rate of 22.7% (n = 35/154) and headache as the most common adverse effect (8.4%, n = 13/154). Rituximab led to complete resolution in 70.5% (n = 79/112) of patients within 8.7 months, with a recurrence rate of 35.7% (n = 40/112). The most commonly reported adverse effects were urinary tract infections (4.5%, n = 5/112), leukocytopenia (2.7%, n = 3/112), and death due to severe infections (1.8%, n = 2/112). Tumor necrosis factor α inhibitors led to complete resolution in 71.4% (n = 5/7) of patients within 3.9 months of treatment without reported adverse events. CONCLUSIONS: Randomized clinical trials with long-term follow-up are required to conclude the promising safety and efficacy of biologic agents in patients with MMP.

A Systematic Review Characterizing Psoriatic Arthritis Onset and Exacerbation in Patients Receiving Biologic Therapy.

BACKGROUND: While biologic therapies revolutionized treatment of immune-mediated inflammatory diseases (IMIDs), some adverse effects have been noted. This includes the development and exacerbation of PsA in patients on biologic agents, however the outcomes were not extensively explored. OBJECTIVE: To perform a systematic review to characterize the outcomes of PsA onset or exacerbation secondary to biologic use. METHODS: MEDLINE and EMBASE search conducted on March 23, 2021 resulted in 18 studies comprised of 64 patients. RESULTS: Of the 64 patients, 57 (89.1%) experienced new-onset PsA and 7 (10.9%) experienced exacerbation of preexisting PsA following exposure to a biologic; most commonly a TNF-α inhibitor (42.2%, n = 27/64) and IL-12/23 inhibitors (39.1%, n = 25/64). The mean durations of biologic use before PsA onset and exacerbation were 14.8 months and 5.2 months, respectively. Twenty-four patients (44.4%) subsequently switched to an alternate biologic without further reports of PsA-related adverse events. All 64 patients reported a specific treatment for PsA; most commonly discontinuation of the associated biologic agent (32.8%, n = 21/64). Complete resolution of PsA was reported in 35.9% (n = 23/64) of cases, of which 91.3% (n = 21/23) resulted after discontinuation of biologic. CONCLUSION: Although we characterized outcomes of PsA induction and exacerbation secondary to biologic use, large-scale studies are required.

Treatment Outcomes of IL-17 Inhibitors in Hidradenitis Suppurativa: A Systematic Review.

The IL-17 pathway is a potential therapeutic target shown to be implicated in hidradenitis suppurativa (HS), however, it remains unclear whether evidence from mechanistic studies may translate into clinical practice. This systematic review summarizes available treatment outcomes of IL-17 inhibitors in patients with HS. Embase, MEDLINE, PubMed, and clinicaltrials.gov were comprehensively searched on February 26, 2021 to include 16 original studies representing 128 patients with HS (mean age: 36.5 years; age range: 21-47 years; male: 50.0%). Treatment outcomes were reported for the following biologics: secukinumab (n = 105), brodalumab (n = 22), and ixekizumab (n = 1). Patients were classified as responders or non-responders according to achievement of a positive response/improvement based on criteria established for each included study. For secukinumab 57.1% (n = 60/105) of patients were responders in a mean response period of 16.2 weeks and 42.9% (n = 45/105) were non-responders; for brodalumab, 100.0% (n = 22/22) of patients were responders within 4.4 weeks; and the one patient treated with ixekizumab was a responder within 10 weeks. In conclusion, IL-17 inhibitors may serve as an effective therapeutic target in approximately two-thirds of patients with HS and can be considered in those who are refractory to other treatment modalities. We also stress the importance of consistent outcome measures to enhance evidence synthesis, decrease reporting bias, provide potential for future meta-analysis, and ultimately improve clinical outcomes for patients with HS.

Onset of Pyoderma Gangrenosum in Patients on Biologic Therapies: A Systematic Review.

OBJECTIVE: To summarize clinical outcomes of paradoxical pyoderma gangrenosum (PG) onset in patients on biologic therapy. METHODS: The authors conducted MEDLINE and EMBASE searches using PRISMA guidelines to include 57 patients (23 reports). RESULTS: Of the included patients, 71.9% (n = 41/57) noted PG onset after initiating rituximab, 21.1% (n = 12/57) noted tumor necrosis factor α (TNF-α) inhibitors, 5.3% (n = 3/57) reported interleukin 17A inhibitors, and 1.8% (n = 1/57) reported cytotoxic T-lymphocyte-associated protein 4 antibodies. The majority of patients (94.3%) discontinued biologic use. The most common medications used to resolve rituximab-associated PG were intravenous immunoglobulins, oral corticosteroids, and antibiotics, with an average resolution time of 3.3 months. Complete resolution of PG in TNF-α-associated cases occurred within an average of 2.2 months after switching to another TNF-α inhibitor (n = 1), an interleukin 12/23 inhibitor (n = 2), or treatment with systemic corticosteroids and cyclosporine (n = 3), systemic corticosteroids alone (n = 1), or cyclosporine alone (n = 1). CONCLUSIONS: Further investigations are warranted to determine whether PG onset is associated with underlying comorbidities, the use of biologic agents, or a synergistic effect. Nevertheless, PG may develop in patients on rituximab or TNF-α inhibitors, suggesting the need to monitor and treat such adverse effects.

Changes in plasma and urine metabolites associated with empagliflozin in patients with type 1 diabetes.

AIM: To examine the impact of the sodium-glucose co-transporter-2 inhibitor, empagliflozin, on plasma and urine metabolites in participants with type 1 diabetes. MATERIAL AND METHODS: Participants (n = 40, 50% male, mean age 24.3 years) with type 1 diabetes and without overt evidence of diabetic kidney disease had baseline assessments performed under clamped euglycaemia and hyperglycaemia, on two consecutive days. Participants then proceeded to an 8-week, open-label treatment period with empagliflozin 25 mg/day, followed by repeat assessments under clamped euglycaemia and hyperglycaemia. Plasma and urine metabolites were first grouped into metabolic pathways using MetaboAnalyst software. Principal component analysis was performed to create a representative value for each sufficiently represented metabolic group (false discovery rate ≤ 0.1) for further analysis. RESULTS: Of the plasma metabolite groups, tricarboxylic acid (TCA) cycle (P < .0001), biosynthesis of unsaturated fatty acids (P = .0045), butanoate (P < .0001), propanoate (P = .0053), and alanine, aspartate and glutamate (P < .0050) metabolites were increased after empagliflozin treatment under clamped euglycaemia. Of the urine metabolite groups, only butanoate metabolites (P = .0005) were significantly increased. Empagliflozin treatment also attenuated the increase in a number of urine metabolites observed with acute hyperglycaemia. CONCLUSIONS: Empagliflozin was associated with increased lipid and TCA cycle metabolites in participants with type 1 diabetes, suggesting a shift in metabolic substrate use and improved mitochondrial function. These effects result in more efficient energy production and may contribute to end-organ protection by alleviating local hypoxia and oxidative stress.

Hydroxychloroquine effects on psoriasis: A systematic review and a cautionary note for COVID-19 treatment.

BACKGROUND: While evidence suggests that hydroxychloroquine (HCQ) may decrease the viral load in patients with a COVID-19 infection, a number of case reports indicate adverse dermatologic effects of this potential treatment. OBJECTIVE: To conduct a systematic review of previously reported cases of psoriasis onset, exacerbation, or relapse after HCQ treatment. METHODS: Embase and MEDLINE were comprehensively searched for original studies examining adverse effects of HCQ treatment related to psoriasis. Participant demographics and details of HCQ administration and psoriasis diagnosis were extracted from 15 articles representing 18 patients. RESULTS: Women accounted for a significantly larger number of cases of psoriasis compared with men and unreported sex (14 [77.8%] vs 2 [11.1%] vs 2 [11.1%], respectively). In addition, 50% (n = 9) of the patients did not have a history of psoriasis before taking HCQ. Of the 18 patients, 9 (50.0%) experienced de novo psoriasis, 5 (27.8%) experienced exacerbation of psoriatic symptoms, and 4 (22.2%) had a relapse of psoriasis after HCQ administration. CONCLUSION: HCQ treatment may result in induction, exacerbation, or relapse of psoriasis. Monitoring for adverse effects of HCQ treatment is necessary, and clinical trials are essential in characterizing the safety profile of HCQ use in patients with a COVID-19 infection.

Renal Hemodynamic Function and RAAS Activation Over the Natural History of Type 1 Diabetes.

RATIONALE & OBJECTIVE: The renin-angiotensin-aldosterone system (RAAS) is associated with renal and cardiovascular disease in diabetes. Unfortunately, early RAAS blockade in patients with type 1 diabetes mellitus (T1DM) does not prevent the development of complications. We sought to examine the role of hyperfiltration and RAAS activation across a wide range of T1DM duration to better understand renal hemodynamic status in patients with T1DM. STUDY DESIGN: Post hoc analysis of blood samples. SETTING & PARTICIPANTS: 148 Canadian patients with T1DM: 28 adolescents (aged 16.2±2.0 years), 54 young adults (25.4±5.6 years), and 66 older adults (65.7±7.5 years) studied in a clinical investigation unit. EXPOSURE: Angiotensin II infusion (1ng/kg/min; a measure of RAAS activation) during a euglycemic clamp. OUTCOMES: Glomerular filtration rate measured using inulin clearance, effective renal plasma flow measured using para-aminohippurate, afferent (RA) and efferent (RE) arteriolar resistances, and glomerular hydrostatic pressure estimated using the Gomez equations. RESULTS: In a stepwise fashion, glomerular filtration rate, effective renal plasma flow, and glomerular hydrostatic pressure were higher, while renal vascular resistance and RA were lower in adolescents versus young adults versus older adults. RE was similar in adolescents versus young adults but was higher in older adults. Angiotensin II resulted in blunted renal hemodynamic responses in older adults (renal vascular resistance increase of 3.3% ± 1.6% vs 4.9% ± 1.9% in adolescents; P<0.001), suggesting a state of enhanced RAAS activation. LIMITATIONS: Homogeneous study participants limit the generalizability of findings to other populations. Studying older adult participants with T1DM may be associated with a survivorship bias. CONCLUSIONS: A state of relatively low RAAS activity and predominant afferent dilation rather than efferent constriction characterize early adolescents and young adults with T1DM. This state of endogenous RAAS inactivity in early T1DM may explain why pharmacologic blockade of this neurohormonal system is often ineffective in reducing kidney disease progression in this setting. Older adults with long-standing T1DM who have predominant afferent constriction and RAAS activation may experience renoprotection from therapies that target the afferent arteriole. Further work is required to understand the potential role of non-RAAS pharmacologic agents that target RA in patients with early and long-standing T1DM.

Mineralocorticoid Antagonism and Diabetic Kidney Disease.

PURPOSE OF REVIEW: Type 2 diabetes (T2D) is associated with an increased risk of diabetic kidney disease (DKD), cardiovascular disease, and heart failure, in part through activation of the renin-angiotensin-aldosterone system (RAAS). Although recent cardiovascular outcome trials have identified newer therapeutic agents such as sodium-glucose cotransporter-2 (SGLT-2) inhibitors and glucagon-like peptide-1 (GLP-1)-receptor agonists that reduce the risk of these complications, patients still exhibit residual cardiorenal morbidity and mortality. Accordingly, the identification of pharmacological agents that attenuate micro- and macrovascular complications related to T2D is a major priority. Our aim was to review evidence for the role of novel mineralocorticoid receptor antagonists (MRAs) that are being developed as adjunctive therapies to reduce the risk of DKD and cardiovascular disease in the setting of T2D. RECENT FINDINGS: Dual RAAS blockade with angiotensin-converting enzyme (ACE) inhibitor plus angiotensin receptor blockade (ARB) or ARB plus renin inhibition increases serious adverse events such as acute kidney injury and stroke. Due to the potential for these serious side effects, more recent interest has focused on newer, more selective non-steroidal MRAs such as finerenone as cardiorenal protective therapies. Finerenone reduces albuminuria in the setting of DKD in patients with T2D and has a lower risk of hyperkalemia compared to currently available MRAs. Novel MRAs such as finerenone have the potential to reduce the risk of DKD progression in patients with T2D. The impact of finerenone on hard, long-term cardiorenal endpoints is being examined in the FIGARO and FIDELIO trials in patients with DKD.

Sodium glucose cotransporter (SGLT)-2 inhibitors: Do we need them for glucose-lowering, for cardiorenal protection or both?

Sodium glucose cotransporter (SGLT)-2 inhibitors are the newest addition to our treatment armamentarium for the management of hyperglycemia in type 2 diabetes. Glucose-lowering per se reduces the risk of microvascular complications, but not the risk of cardiovascular disease, including heart failure and cardiovascular mortality. Also, even when embedded in optimal cardiovascular prevention, a large residual risk remains with respect to progression of diabetic kidney disease. SGLT-2 inhibitors lower blood glucose levels by inducing glucosuria. Through various proposed mechanisms, among which diuretic and natriuretic effects, SGLT-2 inhibitors decrease heart failure hospitalization, reduce cardiovascular mortality, and mitigate progression of diabetic kidney disease. In this perspective, we will discuss the glucose-lowering and other protective effects of SGLT-2 inhibitors on the cardiorenal axis, both in primary and secondary prevention. By comparing the glycemic and pleiotropic effects of these agents to other glucose-lowering drugs, we will address questions around whether SGLT-2 inhibitors should be considered primarily as glucose-lowering agents, cardiorenal drugs or both.

Association between uric acid, renal haemodynamics and arterial stiffness over the natural history of type 1 diabetes.

AIMS: To examine the relationship between normal plasma uric acid (PUA) levels, renal haemodynamic function, arterial stiffness and plasma renin and aldosterone over a wide range of type 1 diabetes (T1D) durations in adolescents, young adults and older adults. MATERIALS AND METHODS: PUA, glomerular filtration rate (GFR), effective renal plasma flow (ERPF), vascular stiffness parameters (aortic augmentation index [AIx], carotid AIx, carotid femoral pulse wave velocity [cfPWV]), and plasma renin and aldosterone were measured during a euglycaemic clamp in people with T1D: 27 adolescents (mean ± SD age 16.8 ± 1.9 years), 52 young adults (mean ± SD age 25.6 ± 5.5 years) and 66 older adults (mean ± SD age 65.7 ± 7.5 years). RESULTS: PUA was highest in patients with the longest T1D duration: 197 ± 44 µmol/L in adolescents versus 264 ± 82 µmol/L in older adults (P < 0.001). Higher PUA correlated with lower GFR only in older adults, even after correcting for age, glycated haemoglobin and sex (ß = -2.12 ± 0.56; P = 0.0003), but not in adolescents or young adults. Higher PUA correlated with lower carotid AIx (ß = -1.90, P = 0.02) in adolescents. In contrast, PUA correlated with higher cfPWV (P = 0.02) and higher plasma renin (P = 0.01) in older adults with T1D. CONCLUSIONS: The relationship between higher PUA with lower GFR, increased arterial stiffness and renin angiotensin aldosterone system (RAAS) activation was observed only in older adults with longstanding T1D. T1D duration may modify the association between PUA, renal haemodynamic function and RAAS activation, leading to renal vasoconstriction and ischaemia. Further work must determine whether pharmacological PUA-lowering prevents or reverses injurious haemodynamic and neurohormonal sequelae of longstanding T1D, thereby improving clinical outcomes.

The relationships between markers of tubular injury and intrarenal haemodynamic function in adults with and without type 1 diabetes: Results from the Canadian Study of Longevity in Type 1 Diabetes.

OBJECTIVE: Our aim was to define the relationships between plasma biomarkers of kidney injury and intrarenal haemodynamic function (glomerular filtration rate [GFR], effective renal plasma flow [ERPF], renal vascular resistance [RVR]) in adults with type 1 diabetes (T1D). METHODS: The study sample comprised patients with longstanding T1D (duration ≥50 years), among whom 44 were diabetic kidney disease (DKD) resistors (eGFR >60 mL/min/1.73 m2 and <30 mg/d urine albumin excretion) and 22 had DKD, in addition to 73 control participants. GFRINULIN and ERPFPAH were measured, RVR was calculated, and afferent (RA )/efferent (RE ) areteriolar resistances were derived from Gomez equations. Plasma neutrophil gelatinase-associated lipocalin (NGAL), ß2 microglobulin (B2M), osteopontin (OPN) and uromodulin (UMOD) were measured using immunoassay kits from Meso Scale Discovery. RESULTS: Plasma NGAL, B2M and OPN were higher and UMOD was lower in DKD patients vs DKD resistors and non-diabetic controls. In participants with T1D, plasma NGAL inversely correlated with GFR (r = -0.33; P = 0.006) and ERPF (r = -0.34; P = 0.006), and correlated positively with RA (r = 0.26; P = 0.03) and RVR (r = 0.31; P = 0.01). In participants without T1D, NGAL and B2M inversely correlated with GFR (NGAL r = -0.18; P = 0.13 and B2M r = -0.49; P < 0.0001) and with ERPF (NGAL r = -0.19; P = 0.1 and B2M r = -0.42; P = 0.0003), and correlated positively with RA (NGAL r = 0.19; P = 0.10 and B2M r = 0.3; P = 0.01) and with RVR (NGAL r = 0.20; P = 0.09 and B2M r = 0.34; P = 0.003). Differences were significant after adjusting for age, sex, HbA1c, SBP and LDL. There were statistical interactions between T1D status, B2M and intrarenal haemodynamic function (P < 0.05). CONCLUSIONS: Elevated NGAL relates to intrarenal haemodynamic dysfunction in T1D, whereas elevated NGAL and B2M relate to intrarenal haemodynamic dysfunction in adults without T1D. These data may define a diabetes-specific interplay between tubular injury and intrarenal haemodynamic dysfunction.

Role of Mitochondrial Aldehyde Dehydrogenase in Nitroglycerin-Mediated Vasodilation: Observations Concerning the Dose-Response Relationship.

The mechanism of the bioactivation of nitroglycerin has long been controversial, with a number of suggested enzymatic pathways. More recently, aldehyde dehydrogenase-2 (ALDH-2) has been reported as the important enzyme involved in the bioactivation of nitroglycerin at therapeutically relevant concentrations. Other previously described enzyme systems can also bioactivate nitroglycerin, but only at concentrations, which are significantly higher than achieved in clinical practice. This study investigated the vascular response to nitroglycerin given over a wide range of concentrations in subjects with and without the ALDH-2 Glu504Lys polymorphism, a common genetic variant that greatly reduces the activity of ALDH-2 (n = 10 in both groups). Forearm blood flow (FBF) responses to a brachial artery infusion of nitroglycerin were assessed using venous occlusion plethysmography. Intra-arterial infusion of nitroglycerin caused a significant increase in FBF beginning at 0.464 µg/min with increasing responses seen in both groups at all infusion rates. However, there were no differences in the FBF responses to nitroglycerin in those with and without the ALDH-2 polymorphism, suggesting that ALDH-2 is not solely responsible for the bioactivation of nitroglycerin at either low (therapeutically relevant) or high concentrations of nitroglycerin.