Hybrid Closed Loop in Adults With Type 1 Diabetes and Severely Impaired Hypoglycemia Awareness.

BACKGROUND: Benefits of hybrid closed-loop (HCL) systems in a high-risk group with type 1 diabetes and impaired awareness of hypoglycemia (IAH) have not been well-explored. METHODS: Adults with Edmonton HYPO scores ≥1047 were randomized to 26-weeks HCL (MiniMed™ 670G) vs standard therapy (multiple daily injections or insulin pump) without continuous glucose monitoring (CGM) (control). Primary outcome was percentage CGM time-in-range (TIR; 70-180 mg/dL) at 23 to 26 weeks post-randomization. Major secondary endpoints included magnitude of change in counter-regulatory hormones and autonomic symptom responses to hypoglycemia at 26-weeks post-randomization. A post hoc analysis evaluated glycemia risk index (GRI) comparing HCL with control groups at 26 weeks post-randomization. RESULTS: Nine participants (median [interquartile range (IQR)] age 51 [41, 59] years; 44% male; enrolment HYPO score 1183 [1058, 1308]; Clarke score 6 [6, 6]; n = 5 [HCL]; n = 4 [control]) completed the study. Time-in-range was higher using HCL vs control (70% [68, 74%] vs 48% [44, 50%], P = .014). Time <70 mg/dL did not differ (HCL 3.8% [2.7, 3.9] vs control 6.5% [4.3, 8.6], P = .14) although hypoglycemia episode duration was shorter (30 vs 50 minutes, P < .001) with HCL. Glycemia risk index was lower with HCL vs control (38.1 [30.0, 39.2] vs 70.8 [58.5, 72.4], P = .014). Following 6 months of HCL use, greater dopamine (24.0 [12.3, 27.6] vs -18.5 [-36.5, -4.8], P = .014), and growth hormone (6.3 [4.6, 16.8] vs 0.5 [-0.8, 3.0], P = .050) responses to hypoglycemia were observed. CONCLUSIONS: Six months of HCL use in high-risk adults with severe IAH increased glucose TIR and improved GRI without increased hypoglycemia, and partially restored counter-regulatory responses. CLINICAL TRIAL REGISTRATION: ACTRN12617000520336.

Combining an Electrochemical Continuous Glucose Sensor With an Insulin Delivery Cannula: A Feasibility Study.

BACKGROUND: Combining a continuous glucose monitor with an insulin delivery cannula (CGM-IS) could benefit clinical outcomes. We evaluated the feasibility of a single-needle insertion electrochemical investigational CGM-IS (Pacific Diabetes Technologies, Portland, Oregon) in type 1 diabetes adults. METHODS: Following 48 hours run-in using a Medtronic 780G in manual mode with a commercial insulin set, 12 participants commenced insulin delivery using the CGM-IS. A standardized test meal was eaten on the mornings of days 1 and 4. Venous samples were collected every 10 minutes one hour prior to and 15 minutes post-meal for four hours. CGM-IS glucose measurements were post-processed with a single capillary blood calibration during warm-up and benchmarked against YSI. A Dexcom G6 sensor was worn post-consent to study end. RESULTS: Mean absolute relative difference (MARD) for the CGM-IS glucose measurements was 9.2% (484 paired data points). Consensus error grid revealed 88.6% within zone A and 100% in A + B. Mean (SD) % bias was -3.5 (11.7) %. There were 35 paired YSI readings <100 mg/dL cutoff and 449 ≥100 mg/dL with 81.4% within ±15 mg/dL or ±15%, and 89.9% within ±20 mg/dL or ±20%. Two cannula occlusions required discontinuation of insulin delivery: one at 70 hours post insertion and another during the day 4 meal test. Mean (SD) Dexcom glucose measurements during run-in and between meal tests was respectively 161.3 ± 27.3 mg/dL versus 158.0 ± 25.6 mg/dL; P = .39 and corresponding mean total daily insulin delivered by the pump was 58.0 ± 25.4 Units versus 57.1 ± 28.8 Units; P = .47. CONCLUSIONS: Insulin delivery and glucose sensing with the investigational CGM-IS was feasible. Longer duration studies are needed.

A Randomized Crossover Trial Comparing Glucose Control During Moderate-Intensity, High-Intensity, and Resistance Exercise With Hybrid Closed-Loop Insulin Delivery While Profiling Potential Additional Signals in Adults With Type 1 Diabetes.

OBJECTIVE: To compare glucose control with hybrid closed-loop (HCL) when challenged by high intensity exercise (HIE), moderate intensity exercise (MIE), and resistance exercise (RE) while profiling counterregulatory hormones, lactate, ketones, and kinetic data in adults with type 1 diabetes. RESEARCH DESIGN AND METHODS: This study was an open-label multisite randomized crossover trial. Adults with type 1 diabetes undertook 40 min of HIE, MIE, and RE in random order while using HCL (Medtronic MiniMed 670G) with a temporary target set 2 h prior to and during exercise and 15 g carbohydrates if pre-exercise glucose was <126 mg/dL to prevent hypoglycemia. Primary outcome was median (interquartile range) continuous glucose monitoring time-in-range (TIR; 70-180 mg/dL) for 14 h post-exercise commencement. Accelerometer data and venous glucose, ketones, lactate, and counterregulatory hormones were measured for 280 min post-exercise commencement. RESULTS: Median TIR was 81% (67, 93%), 91% (80, 94%), and 80% (73, 89%) for 0-14 h post-exercise commencement for HIE, MIE, and RE, respectively (n = 30), with no difference between exercise types (MIE vs. HIE; P = 0.11, MIE vs. RE, P = 0.11; and HIE vs. RE, P = 0.90). Time-below-range was 0% for all exercise bouts. For HIE and RE compared with MIE, there were greater increases, respectively, in noradrenaline (P = 0.01 and P = 0.004), cortisol (P < 0.001 and P = 0.001), lactate (P ≤ 0.001 and P ≤ 0.001), and heart rate (P = 0.007 and P = 0.015). During HIE compared with MIE, there were greater increases in growth hormone (P = 0.024). CONCLUSIONS: Under controlled conditions, HCL provided satisfactory glucose control with no difference between exercise type. Lactate, counterregulatory hormones, and kinetic data differentiate type and intensity of exercise, and their measurement may help inform insulin needs during exercise. However, their potential utility as modulators of insulin dosing will be limited by the pharmacokinetics of subcutaneous insulin delivery.

Glucose and Counterregulatory Responses to Exercise in Adults With Type 1 Diabetes and Impaired Awareness of Hypoglycemia Using Closed-Loop Insulin Delivery: A Randomized Crossover Study.

OBJECTIVE: To evaluate exercise-related glucose and counterregulatory responses (CRR) in adults with type 1 diabetes with impaired awareness of hypoglycemia (IAH) using hybrid closed-loop (HCL) insulin delivery to maintain glucose homeostasis. RESEARCH DESIGN AND METHODS: Twelve participants undertook 45-min high-intensity intermittent exercise (HIIE) and moderate-intensity exercise (MIE) in random order. The primary outcome was continuous glucose monitoring (CGM) time in range (70-180 mg/dL) for 24-h post-exercise commencement. RESULTS: CGM time in range was similar for HIIE and MIE (median 79.5% [interquartile range 73.2, 87.6] vs. 76.1% [70.3, 83.9], P = 0.37), and time with levels <54mg/dL post-exercise commencement was 0%. HIIE induced greater increases in cortisol (P = 0.002), noradrenaline (P = 0.005), and lactate (P = 0.002), with no differences in adrenaline, dopamine, growth hormone, or glucagon responses. CONCLUSIONS: IAH adults using HCL undertaking HIIE and MIE exhibit heterogeneity in CRR. Novel findings were a preserved cortisol response and variable catecholamine responses to HIIE.

Glucose Control in Adults with Type 1 Diabetes Using a Medtronic Prototype Enhanced-Hybrid Closed-Loop System: A Feasibility Study.

Background: Experience from first-generation closed-loop (CL) systems informs refinements to enhance glucose control and user acceptance. A next-generation prototype enhanced-hybrid CL (E-HCL) system incorporates iterative changes to the Medtronic MiniMed 670G CL system, including automated correction boluses, lower target glucose level, and user enhancements. The aim was to explore safety, system performance, and glucose control using E-HCL in adults with type 1 diabetes. Methods: Twelve adults underwent this first in-human feasibility study. After a 1-week run-in using open-loop (OL), E-HCL was activated at the start of a supervised 1-week hotel phase, followed by 3 weeks free living at home. Supervised challenges included two meal interventions (unannounced and late meal bolus) and a sensor calibration intervention. Primary outcome was sensor glucose time-in-range (TIR); OL run-in and E-HCL at home were compared by Wilcoxon signed-rank test. Results: Twelve adults (seven men; median [interquartile range] age 48 [39, 57] years; HbA1c 6.8 [6.2, 7.2]%, 51 [44, 55] mmol/mol; diabetes duration 31 [13, 41] years) completed the protocol. E-HCL resulted in greater TIR (85.3 [79.4, 88.4]% vs. 75.0 [66.6, 83.7]%, P = 0.003) and lower mean sensor glucose (123.0 [119.3, 129.6] mg/dL vs. 143.5 [135.8, 154.5] mg/dL, P = 0.002) than OL. Time spent <70 mg/dL increased using E-HCL (4.4 [3.3, 6.1]% vs. 3.0 [1.8, 3.8]%, P = 0.02) with no difference in time <54 mg/dL (P = 0.64). Time in CL was 99.98 [99.0, 100.0]%. All participants were satisfied using E-HCL. Conclusions: In adults with well-controlled HbA1c levels, a prototype E-HCL resulted in high TIR, few CL exits, and positive user experiences at the expense of increased hypoglycemia (<70 mg/dL). E-HCL represents a positive step in the journey toward optimizing glucose control in people living with type 1 diabetes.

Changes in soluble tumor necrosis factor receptor type 1 levels and early renal function decline in patients with diabetes.

The relationship between serial changes in soluble tumor necrosis factor receptor type 1 (TNFR1) levels and an early decline in estimated glomerular filtration rate (eGFR) decline remains to be defined. We found that in patients with an early decline in renal function (n = 30), soluble TNFR1 values increased (2,595 ± 683 vs 3,596 ± 1,203 pg/mL, P < 0.001) as eGFR decreased (89 ± 1 vs 51 ± 2 mL/min/1.73m2 , P < 0.001) over an 8-year period. In contrast, there were no significant changes in soluble TNFR1 levels in patients with stable renal function (n = 17). In a multilevel mixed effects regression model, changes in soluble TNFR1 levels were found to be independently associated with eGFR decline (Z = -4.31, P < 0.001). An early decline in eGFR is associated with an increase in soluble TNFR levels; however, the factors driving this increase and the possible pathological role that soluble TNFR1 plays in progressive diabetic kidney disease remain to be determined.

A Prospective Study of Renal Transplant Recipients: A Fall in Insulin Secretion Underpins Dysglycemia After Renal Transplantation.

BACKGROUND: Dysglycemia (encompassing impaired glucose tolerance and diabetes mellitus) arising after renal transplantation is common and confers a significant cardiovascular mortality risk. Nonetheless, the pathophysiology of posttransplant dysglycemia is not well described. The aim of this study was to prospectively and comprehensively assess glucose handling in renal transplant recipients from before to 12 months after transplantation to determine the underpinning pathophysiology. MATERIALS AND METHODS: Intravenous and oral glucose tolerance testing was conducted before and at 3 and 12 months posttransplantation. An intravenous glucose tolerance test was also performed on day 7 posttransplantation. We followed up 16 transplant recipients for 3 months and 14 recipients for 12 months. Insulin secretion, resistance and a disposition index (DI (IV)), a measure of ß cell responsiveness in the context of prevailing insulin resistance, were also determined. RESULTS: At 12 months, 50% of renal transplant recipients had dysglycemia. Dysglycemia was associated with a dramatic fall in DI (IV) and this loss in ß cell function was evident as early as 3 months posttransplantation (23.5 pretransplant; 6.4 at 3 months and 12.2 at 12 months posttransplant). Differences in the ß cell response to oral glucose challenge were evident pretransplant in those destined to develop dysglycemia posttransplant (2-hour blood glucose level 5.6 mmol/L versus 6.8 mmol/L; P < 0.01). CONCLUSIONS: Dysglycemia after renal transplantation is common, and the loss of insulin secretion is a major contributor. Subclinical differences in glucose handling are evident pretransplant in those destined to develop dysglycemia potentially heralding a susceptible ß cell which under the stressors associated with transplantation fails.

Evidence for transcript-specific epigenetic regulation of glucocorticoid-stimulated skeletal muscle 11ß-hydroxysteroid dehydrogenase-1 activity in type 2 diabetes.

BACKGROUND: The enzyme 11ß-hydroxysteroid dehydrogenase type 1 (11ßHSD1) converts inactive cortisone into active cortisol in insulin target tissues. In people with type 2 diabetes, skeletal muscle (SkM) 11ßHSD1 is upregulated by the potent glucocorticoid dexamethasone. The HSD11B1 gene has two promoters designated P1 and P2. CCAAT/enhancer-binding protein beta (C/EBPß) is known to regulate expression of 11ßHSD1 via the P2 promoter. In this study, we investigated the potential role of altered DNA methylation of the P1 and P2 promoters in the observed dexamethasone-induced upregulation of SkM 11ßHSD1 oxoreductase activity in human diabetic subjects. SkM biopsies from 15 people with type 2 diabetes were collected before and after treatment with oral dexamethasone 4 mg/day for 4 days and SkM 11ßHSD1, C/EBPß and P1 and P2 promoter region mRNA levels were measured by quantitative RT-PCR. 11ßHSD1 oxoreductase activity was quantified by measuring the conversion of radiolabeled 3H-cortisone to cortisol by thin layer chromatography. Analysis of HSD11B1 promoter methylation (P1 and P2) was performed using Sequenom MassARRAY EpiTYPER analysis. RESULTS: Dexamethasone treatment resulted in a significant increase in 11ßHSD1 mRNA levels (P = 0.003), oxoreductase activity (P = 0.017) and C/EBPß mRNA (P = 0.015), and increased expression of both the P1 (P = 0.008) and P2 (P = 0.016) promoter regions . The distal P1 promoter region showed a significant reduction in methylation following dexamethasone (P = 0.026). There was a significant negative correlation between the change in methylation at this site and the increment in 11ßHSD1 oxoreductase activity (r = -0.62, P = 0.014). CONCLUSIONS: Our findings of reduced methylation in the HSD11B1 P1 promoter in association with increased 11ßHSD1 oxoreductase activity implicate complex multi-promoter epigenetic mechanisms in the regulation of 11ßHSD1 levels in SkM.

Dexamethasone administration inhibits skeletal muscle expression of the androgen receptor and IGF-1--implications for steroid-induced myopathy.

CONTEXT: Glucocorticoids are a well-recognized cause of muscle weakness. The early effects of glucocorticoids on skeletal muscle (SkM) androgen and IGF-1 pathways have not been previously investigated in human subjects. OBJECTIVE: To determine if administration of the potent glucocorticoid dexamethasone down-regulates SkM androgen receptor and the IGF-1 signalling pathway. METHODS AND SUBJECTS: Twenty-four subjects (12 men and 12 women), including 12 with type 2 diabetes and 12 nondiabetics were enrolled. Venous blood sampling and biopsy of vastus lateralis were performed before and after administration of oral dexamethasone 4 mg/day for 4 days. MAIN OUTCOME MEASURES: Changes in plasma testosterone and IGF-1, SkM androgen receptor mRNA, SkM IGF-1mRNA and SkM IGF-1 receptor mRNA by quantitative RT-PCR after dexamethasone. RESULTS: Relative expression of SkM androgen receptor was similar in male (1.63 +/- 0.37) vs. female (1.57 +/- 0.30) subjects, despite the significant difference in plasma testosterone levels. Plasma IGF-1 and SkM expression of IGF-1 and IGF-1 receptor were also similar between males and females. Following dexamethasone, there was a significant down-regulation of SkM androgen receptor (1.60 +/- 0.23 vs. 1.11 +/- 0.16, P < 0.05) and IGF-1 (1.72 +/- 0.29 vs. 1.06 +/- 0.14, P < 0.05) mRNA, but no change in expression of the IGF-1 receptor. Plasma testosterone fell significantly in both sexes (male: 15.0 +/- 1.3 vs. 11.3 +/- 1.2 nmol/l, P < 0.01, female: 1.8 +/- 0.5 vs. 0.5 +/- 0.1 nmol/l, P < 0.05). CONCLUSIONS: Exogenous steroid excess results in relative androgen deficiency at two levels, reduced circulating testosterone and SkM androgen receptor mRNA, along with reduced SkM IGF-1 mRNA. These defects may contribute to the development of steroid-induced myopathy.

Skeletal muscle 11beta hydroxysteroid dehydrogenase type 1 activity is upregulated following elective abdominal surgery.

OBJECTIVE: Cortisol has been traditionally implicated in the causation of peri-operative skeletal muscle (SkM) insulin resistance, but cortisol levels return to normal within 72 h of surgery. Tissue cortisol bioactivity may be prolonged by local upregulation of the enzyme 11betaHSD1. We aimed to investigate the changes of SkM 11betaHSD1 enzyme activity and mRNA expression, relative to plasma cortisol, insulin and glucose levels following elective abdominal surgery. PATIENTS AND DESIGN: Eight non-diabetic subjects (two male, six female) underwent serial plasma hormone sampling and muscle biopsy of vastus lateralis at baseline and on day 5 following elective laparoscopic cholecystectomy. METHODS: SkM 11betaHSD1 and H6PDH mRNA levels were measured by quantitative RT-PCR and enzyme activity by % conversion of (3)H cortisone to cortisol. Plasma glucose, insulin, free fatty acids (FFA), tumour necrosis factor-alpha and cortisol by standardised assays. RESULTS: Compared with baseline, SkM 11betaHSD1 activity was significantly increased on day 5 after surgery (14.7+/-2.1 vs 20.4+/-3.2%, P=0.005). Neither 11betaHSD1 nor H6PDH mRNA levels were altered after surgery. Plasma cortisol (P=0.027), FFA (P=0.01) and glucose (P=0.004) rose rapidly following surgery and had returned to baseline values by 24 h post-surgery. There was no significant change in plasma insulin. CONCLUSIONS: This is the first study to demonstrate an upregulation of SkM 11betaHSD1 activity in response to a physiological stressor. Sustained activation of this enzyme may increase tissue cortisol bioactivity.

Adiponectin, skeletal muscle adiponectin receptor expression and insulin resistance following dexamethasone.

OBJECTIVE: Skeletal muscle is a major site of adiponectin action and of glucocorticoid-induced insulin resistance. Little human data exist however, regarding the impact of exogenous glucocorticoids on adiponectin receptors in skeletal muscle. DESIGN AND PATIENTS: Twelve subjects with type 2 diabetes and 12 controls underwent blood sampling and muscle biopsy of vastus lateralis before and after 4 days of 4 mg dexamethasone. MEASUREMENTS: (i) Total and high molecular weight (HMW) plasma adiponectin, glucose and insulin; (ii) Skeletal muscle adiponectin receptor AdipoR1 and AdipoR2 mRNA levels by quantitative real time RT-PCR. RESULTS: Baseline total adiponectin (8.0 +/- 0.89 vs. 12.5 +/- 1.46 microg/ml, P = 0.013), HMW adiponectin (2.8 +/- 0.44 vs. 5.9 +/- 1.04 microg/ml, P = 0.014) and AdipoR2 mRNA levels (mean DeltaC(T )14.71 +/- 0.35 vs. 13.37 +/- 0.28, P = 0.017) were significantly lower in diabetic subjects. After dexamethasone, AdipoR2 mRNA fell in the controls but there was no change in the diabetic group, while there was a significant increase in total (P = 0.002) and HMW adiponectin (P < 0.001) across both groups. Total and HMW plasma adiponectin correlated with clinical and biochemical measures of insulin sensitivity. However following dexamethasone which increased insulin resistance, the relationship between adiponectin and the biochemical measures was lost. CONCLUSIONS: Plasma adiponectin and skeletal muscle AdipoR2 mRNA expression are reduced in subjects with diabetes; both are likely to contribute to the observed insulin resistance. Dexamethasone inhibits AdipoR2 mRNA expression in nondiabetic subjects, while there is a small rise in plasma adiponectin levels. The close relationship between plasma adiponectin and biochemical measures of insulin sensitivity is lost in the setting of glucocorticoid-induced insulin resistance.

Altered activity of 11beta-hydroxysteroid dehydrogenase types 1 and 2 in skeletal muscle confers metabolic protection in subjects with type 2 diabetes.

CONTEXT: There is little information regarding the regulation of 11beta-hydroxysteroid dehydrogenase (11beta-HSD) enzymes in skeletal muscle in the setting of type 2 diabetes. OBJECTIVE: Our objective was to investigate whether there is differential mRNA expression and enzyme activity of 11beta-HSD1 and 11beta-HSD2 in the skeletal muscle of diabetic subjects compared with controls at baseline and in response to dexamethasone. DESIGN: Participants underwent muscle biopsy of vastus lateralis at baseline and after dexamethasone. SETTING: The study took place at a university teaching hospital. PARTICIPANTS: Twelve subjects with type 2 diabetes and 12 age- and sex-matched controls participated. INTERVENTION: Subjects were given oral dexamethasone, 4 mg/d for 4 d. MAIN OUTCOME MEASURES: We assessed 11beta-HSD1, 11beta-HSD2, and H6PDH mRNA levels by quantitative RT-PCR and enzyme activity by percent conversion of [(3)H]cortisone and [(3)H]cortisol, respectively. RESULTS: At baseline, mRNA levels were similar in diabetic and control subjects for 11beta-HSD1, 11beta-HSD2, and H6PDH. 11beta-HSD1 activity was reduced in diabetic subjects (percent conversion of [(3)H]cortisone to [(3)H]cortisol was 11.4 +/- 2.5% vs. 18.5 +/- 2.2%; P = 0.041), and 11beta-HSD2 enzyme activity was higher in diabetic subjects (percent conversion of [(3)H]cortisone to [(3)H]cortisol was 17.2 +/- 2.6% vs. 9.2 +/- 1.3%; P = 0.012). After dexamethasone, 11beta-HSD1 mRNA increased in both groups (P < 0.001), whereas 11beta-HSD2 mRNA decreased (P = 0.002). 11beta-HSD1 activity increased in diabetic subjects (P = 0.021) but not in controls, whereas 11beta-HSD2 activity did not change in either group. At baseline, there was a significant negative correlation between 11beta-HSD1 and 11beta-HSD2 enzyme activity (r = -0.463; P = 0.026). CONCLUSIONS: The activities of skeletal muscle 11beta-HSD1 and 11beta-HSD2 are altered in diabetes, which together may reduce intracellular cortisol generation, potentially conferring metabolic protection.

11Beta hydroxysteroid dehydrogenase type 1 is expressed and is biologically active in human skeletal muscle.

OBJECTIVE: No data exist regarding the distribution and oxoreductase enzyme activity of 11beta hydroxysteroid dehydrogenase type 1 (11beta HSD-1) in fresh human skeletal muscle. We aimed to investigate the mRNA and protein expression of 11beta HSD-1 in fresh skeletal muscle, confirm its biological activity and determine its relationship with hexose-6-phosphate dehydrogenase (H6PDH). We also examined the muscle fibre localization of 11beta HSD-1. DESIGN: Eleven non-diabetic community volunteers underwent muscle biopsy of vastus lateralis. MEASUREMENTS: (i) 11beta HSD-1 and H6PDH mRNA expression by quantitative reverse transcription polymerase chain reaction (RT-PCR); (ii) protein localization and fibre type specificity by immunohistochemistry; and (iii) enzyme oxoreductase activity by percentage conversion of 3H cortisone to cortisol. RESULTS: 11beta HSD-1 mRNA was expressed at low levels compared to human liver. Mean DeltaCT of skeletal muscle in 11 subjects was 19.57 (range 18.40-20.79) compared to DeltaCT of 12.75 in human liver, which equates to an approximate 100-fold higher level of expression. H6PDH mRNA was also detected with a mean DeltaCT of 14.46 (range 13.13-16.60), approximately 35-fold more abundant than 11beta HSD-1 in skeletal muscle. There was a significant correlation between 11beta HSD-1 and H6PDH (r = 0.67, P = 0.03). 11beta HSD-1 immunostaining was present in all muscle specimens, with similar distribution among fast and slow twitch fibres. 11beta HSD-1 oxoreductase activity was demonstrated, with mean conversion of cortisone to cortisol of 17.7% per 200 mg of muscle per 24 h (range 7.1-29.5%). CONCLUSIONS: 11beta HSD-1 mRNA and protein is expressed in fresh human skeletal muscle along with readily demonstrable oxoreductase activity. 11beta HSD-1 localization is not muscle fibre type specific. High levels of skeletal muscle H6PDH should ensure that oxoreductase activity predominates in vivo.

Aromatase-deficient (ArKO) mice have reduced blood pressure and baroreflex sensitivity.

Aromatase-deficient (ArKO) mice are deficient in estrogens due to deletion of the aromatase gene. We hypothesized that there may be changes in the cardiovascular system of ArKO mice because of evidence linking estrogens with improved cardiovascular outcomes and the induction of the glucocorticoid-metabolizing enzyme, 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2), gene in the kidney, which is important for the regulation of blood pressure (BP). BP and baroreflex sensitivity (BRS) in female conscious ArKO mice were compared with those in age- and weight-matched wild-type (WT) mice. Power spectral analysis was used to determine cardiovascular variability and BRS. Although systolic BP was similar in the two groups, diastolic and mean BPs were lower in the ArKO mice (-6.3 +/- 1.9 and -4.6 +/- 2.1 mm Hg, respectively). Heart rate (HR) was greater in the ArKO mice (+36 +/- 6 beats/min). The mean BP in WT mice was 105 mm Hg, and the HR was 481 beats/min. In the autonomic frequency range, BP variability was 74% greater, and HR variability was only 26% that in WT mice. The BRS of ArKO mice was 46% of the value observed in WT mice. 11betaHSD2 levels were unaltered in ArKO mice, except in the kidney, where they were only 10% of WT levels. Estradiol administration to ArKO mice restored renal 11betaHSD2 to WT levels. The results show that ArKO mice have lower diastolic BP, but increased BP variability, perhaps due to an impaired BRS. Thus, aromatase activity is critical for normal autonomic control of the heart and, hence, for reducing the deleterious effects of high BP variability.

17 beta-hydroxysteroid dehydrogenase type XI localizes to human steroidogenic cells.

We searched expressed sequence tag databases with conserved domains of the short-chain alcohol dehydrogenase superfamily and identified another isoform of 17 beta-hydroxysteroid dehydrogenase, 17 beta HSDXI. This enzyme converts 5 alpha-androstane-3 alpha, 17 beta-diol to androsterone. The substrate has been implicated in supporting gestation and modulating gamma-aminobutyric acid receptor activity. 17 beta HSDXI is colinear with human retinal short-chain dehydrogenase/reductase retSDR2, a protein with no known biological activity (accession no. AAF06939). Of the proteins with known function, 17 beta HSDXI is most closely related to the retinol-metabolizing enzyme retSDR1, with which it has 30% identity. There is a polymorphic stretch of 15 adenosines in the 5' untranslated region of the cDNA sequence and a silent polymorphism at C719T. A 17 beta HSDXI construct with a stretch of 20 adenosines was found to produce significantly more enzyme activity than constructs containing 15 or less adenosines (43% vs. 26%, P < 0.005). The C719T polymorphism is present in 15% of genomic DNA samples. Northern blot analysis showed high levels of 17 beta HSDXI expression in the pancreas, kidney, liver, lung, adrenal, ovary, and heart. Immunohistochemical staining for 17 beta HSDXI is strong in steroidogenic cells such as syncytiotrophoblasts, sebaceous gland, Leydig cells, and granulosa cells of the dominant follicle and corpus luteum. In the adrenal 17 beta HSDXI, staining colocalized with the distribution of 17 alpha-hydroxylase but was stronger in the mid to outer cortex. 17 beta HSDXI was also found in the fetus and increased after birth. Liver parenchymal cells and epithelium of the endometrium and small intestine also stained. Regulation studies in mouse Y1 cells showed that cAMP down-regulates 17 beta HSDXI enzymatic activity (40% vs. 32%, P < 0.05) and reduces gene expression to undetectable levels. All-trans-retinoic acid did not affect 17 beta HSDXI expression or activity, but addition of the retinoid together with cAMP significantly decreased activity over cAMP alone (32% vs. 23%, P < 0.05). Cloning and sequencing of the 17 beta HSDXI promoter identified the potential nuclear receptor steroidogenic factor-1 half-site TCCAAGGCCGG, and a cluster of three other potential steroidogenic factor-1 half-sites were found in the distal part of intron 1. Collectively, these results suggest a role for 17 beta HSDXI in androgen metabolism during steroidogenesis and a possible role in nonsteroidogenic tissues including paracrine modulation of 5 alpha-androstane-3 alpha, 17 beta-diol levels. 17 beta HSDXI could act by metabolizing compounds that stimulate steroid synthesis and/or by generating metabolites that inhibit it.