Publications by authors named "Omar Bayomy"

5 Publications

  • Page 1 of 1

ACTH Infusion Impairs Baroreflex Sensitivity-Implications for Cardiovascular Hypoglycemia-Associated Autonomic Failure.

J Clin Endocrinol Metab 2020 07;105(7)

Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts.

Context: Hypoglycemia attenuates cardiovascular homeostatic autonomic control. This attenuation, known as the cardiovascular component of hypoglycemia-associated autonomic failure (HAAF), is characterized most notably by decreased baroreflex sensitivity (BRS) that begins during hypoglycemia and persists until at least the next day, despite return to euglycemia. Understanding the mechanisms underlying this reduction in BRS is important because BRS attenuation is associated with increased morbidity and mortality.

Objective: The objective of this work is to investigate the role of the adrenocorticotropin (ACTH)-adrenal axis in decreasing BRS. We tested the hypothesis that infusion of ACTH 1-24 (cosyntropin), as compared to placebo, would acutely suppress BRS, and that this decrease in BRS would be present the next day.

Design: A double-blind, placebo-controlled, random-order, cross-over study was conducted.

Setting: This study took place in a clinical research center.

Participants: Participants included healthy men and women.

Interventions: Interventions included an intravenous infusion of cosyntropin (70 μg/hour for 2.5 hours in the morning and again in the early afternoon) vs normal saline placebo.

Main Outcome Measures: Outcome measures included BRS during and 16 hours after cosyntropin vs placebo infusions.

Results: Cosyntropin infusion attenuated BRS (mm Hg/ms) as compared to placebo (baseline 17.8 ± 1.38 vs 17.0 ± 2.07; during 14.4 ± 1.43 vs 17.3 ± 1.65; and next day 14.8 ± 1.42 vs 18.9 ± 2.04; P < .05, time by treatment, analysis of variance). BRS was decreased during the final 30 minutes of the morning cosyntropin infusion as compared to baseline (P < .01) and remained suppressed the next day (16 hours after afternoon infusion) (P < .025). Placebo infusion did not significantly change BRS. Corrected QT interval was not affected.

Conclusions: ACTH attenuates BRS, raising the possibility that hypoglycemia-induced increases in ACTH may contribute to the cardiovascular component of HAAF.
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July 2020

Disentangling the Relationships Between the Renin-Angiotensin-Aldosterone System, Calcium Physiology, and Risk for Kidney Stones.

J Clin Endocrinol Metab 2020 06;105(6)

Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women's Hospital, Boston, MA, US.

Context: Complex relationships between aldosterone and calcium homeostasis have been proposed.

Objective: To disentangle the influence of aldosterone and intravascular volume on calcium physiology.

Design: Patient-oriented and epidemiology studies.

Setting: Clinical research center and nationwide cohorts.

Participants/interventions: Patient-oriented study (n = 18): Participants were evaluated after completing a sodium-restricted (RES) diet to contract intravascular volume and after a liberalized-sodium (LIB) diet to expand intravascular volume. Cross-sectional studies (n = 3755): the association between 24h urinary sodium and calcium excretion and risk for kidney stones was assessed.

Results: Patient-oriented study: compared to a RES-diet, a LIB-diet suppressed renin activity (LIB: 0.3 [0.1, 0.4] vs. RES: 3.1 [1.7, 5.3] ng/mL/h; P < 0.001) and plasma aldosterone (LIB: 2.0 [2.0, 2.7] vs. RES: 20.0 [16.1, 31.0] vs. ng/dL; P < 0.001), but increased calciuria (LIB: 238.4 ± 112.3 vs. RES: 112.9 ± 60.8 mg/24hr; P < 0.0001) and decreased serum calcium (LIB: 8.9 ± 0.3 vs. RES: 9.8 ± 0.4 mg/dL; P < 0.0001). Epidemiology study: mean urinary calcium excretion was higher with greater urinary sodium excretion. Compared to a urinary sodium excretion of < 120 mEq/day, a urinary sodium excretion of ≥220 mEq/day was associated with a higher risk for having kidney stones in women (risk ratio = 1.79 [95% confidence interval 1.05, 3.04]) and men (risk ratio = 2.06 [95% confidence interval 1.27, 3.32]).

Conclusions: High dietary sodium intake suppresses aldosterone, decreases serum calcium, and increases calciuria and the risk for developing kidney stones. Our findings help disentangle the influences of volume from aldosterone on calcium homeostasis and provide support for the recommendation to restrict dietary sodium for kidney stone prevention.
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June 2020

Identification of Racial Inequities in Access to Specialized Inpatient Heart Failure Care at an Academic Medical Center.

Circ Heart Fail 2019 11 29;12(11):e006214. Epub 2019 Oct 29.

Division of Cardiovascular Medicine, and Department of Medicine (E.F..L.), Brigham and Women's Hospital, Boston, MA.

Background: Racial inequities for patients with heart failure (HF) have been widely documented. HF patients who receive cardiology care during a hospital admission have better outcomes. It is unknown whether there are differences in admission to a cardiology or general medicine service by race. This study examined the relationship between race and admission service, and its effect on 30-day readmission and mortality Methods: We performed a retrospective cohort study from September 2008 to November 2017 at a single large urban academic referral center of all patients self-referred to the emergency department and admitted to either the cardiology or general medicine service with a principal diagnosis of HF, who self-identified as white, black, or Latinx. We used multivariable generalized estimating equation models to assess the relationship between race and admission to the cardiology service. We used Cox regression to assess the association between race, admission service, and 30-day readmission and mortality.

Results: Among 1967 unique patients (66.7% white, 23.6% black, and 9.7% Latinx), black and Latinx patients had lower rates of admission to the cardiology service than white patients (adjusted rate ratio, 0.91; 95% CI, 0.84-0.98, for black; adjusted rate ratio, 0.83; 95% CI, 0.72-0.97 for Latinx). Female sex and age >75 years were also independently associated with lower rates of admission to the cardiology service. Admission to the cardiology service was independently associated with decreased readmission within 30 days, independent of race.

Conclusions: Black and Latinx patients were less likely to be admitted to cardiology for HF care. This inequity may, in part, drive racial inequities in HF outcomes.
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November 2019

Plasminogen Activator Inhibitor-1 and Pericardial Fat in Individuals with Type 2 Diabetes Mellitus.

Metab Syndr Relat Disord 2017 08 15;15(6):269-275. Epub 2017 May 15.

1 Harvard Medical School , Boston, Massachusetts.

Background: Plasminogen activator inhibitor-1 (PAI-1) is implicated in the pathophysiology of cardiovascular disease (CVD) and increased in individuals with type 2 diabetes mellitus (T2DM). Adipose tissue produces PAI-1, and pericardial fat is a CVD risk factor. We sought to determine the relationship between PAI-1 and pericardial fat in males and females with well-controlled T2DM.

Methods: The study population consisted of 32 males and 19 females, aged 35-70 years with T2DM, without clinical evidence of CVD or other active medical problems except for hypertension. Subjects were studied under good cardiometabolic control. Study procedures included fasting blood work and cardiovascular imaging. Cardiac magnetic resonance imaging of the heart was used to identify and quantify pericardial fat from the bifurcation of the pulmonary trunk to the last slice containing cardiac tissue.

Results: PAI-1 was positively correlated with pericardial fat (β = 0.72, r = 0.72, P < 0.001) as well as with homeostatic model assessment of insulin resistance (r = 0.31, P = 0.03) and serum triglycerides (r = 0.27, P = 0.05). In a multivariable regression model, controlling for insulin sensitivity, triglycerides, and body mass index, pericardial fat was independently associated with PAI-1 (β = 0.80, P < 0.001).

Conclusions: PAI-1 is positively associated with pericardial fat in individuals with T2DM.
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August 2017

Brain-specific interleukin-1 receptor accessory protein in sleep regulation.

J Appl Physiol (1985) 2012 Mar 15;112(6):1015-22. Epub 2011 Dec 15.

Sleep and Performance Research Center, WWAMI Medical Education Program, Washington State University, Spokane, WA 99210-1495, USA.

Interleukin (IL)-1β is involved in several brain functions, including sleep regulation. It promotes non-rapid eye movement (NREM) sleep via the IL-1 type I receptor. IL-1β/IL-1 receptor complex signaling requires adaptor proteins, e.g., the IL-1 receptor brain-specific accessory protein (AcPb). We have cloned and characterized rat AcPb, which shares substantial homologies with mouse AcPb and, compared with AcP, is preferentially expressed in the brain. Furthermore, rat somatosensory cortex AcPb mRNA varied across the day with sleep propensity, increased after sleep deprivation, and was induced by somnogenic doses of IL-1β. Duration of NREM sleep was slightly shorter and duration of REM sleep was slightly longer in AcPb knockout than wild-type mice. In response to lipopolysaccharide, which is used to induce IL-1β, sleep responses were exaggerated in AcPb knockout mice, suggesting that, in normal mice, inflammation-mediated sleep responses are attenuated by AcPb. We conclude that AcPb has a role in sleep responses to inflammatory stimuli and, possibly, in physiological sleep regulation.
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March 2012