Somers, Kiran R.

Introduction: Adderall, the brand name for a combination of dextroamphetamine and amphetamine salts, is used to treat attention deficit disorder and narcolepsy, but is widely abused for improving cognitive function and alertness in absence of a medical indication. While little is known of its acute cardiovascular (CV) physiologic effects, Adderall has been linked to acute CV events (myocardial infarction, tachyarrhythmias, heart failure, Takotsubo cardiomyopathy and sudden death) and to long term CV consequences including hypertension and arterial disease. Aim: To examine the acute CV responses to Adderall in healthy subjects not on stimulant therapy in a randomized double-blind placebo-controlled crossover study. (CT.gov NCT02979327) Methods: Thirty subjects were randomized to 25 mg Adderall versus placebo. We measured supine resting blood pressure (BP), heart rate (HR), and plasma catecholamines, before and 3 hours after consuming Adderall or placebo. Results: Twenty-nine subjects (16 females; aged 25±5 yrs) completed both Adderall and placebo conditions, with a median of 10 days between visits. Systolic BP (SBP) increased from 112±10 mmHg to 127±11 mmHg after use of Adderall but was unchanged before vs after placebo drug intake (112±8 mmHg and 112±9 mmHg respectively; group by time interaction p<0.01). Diastolic BP and mean BP increased by 6.8 mmHg and 8.5 mmHg respectively and HR increased by 7.3 beats/min with Adderall, but they did not change with placebo (p<0.01). Plasma norepinephrine increased from 217±79 pg/ml before to 323±105 pg/ml after Adderall but was unchanged after placebo (p<0.05) (Figure 1). Conclusions: Healthy subjects consuming a modest dose of Adderall manifest striking increases in BP, HR and sympathetic activation, even during supine rest. These findings may have important mechanistic implications for understanding acute CV events and long-term risk of CV disease associated with stimulant medications.

Introduction: The popularity of energy drinks among young adults is rising. Warnings have been issued regarding potential health risks including adverse cardiovascular complications. We and others have previously shown that energy drink consumption increases blood pressure. The mechanisms are not fully understood. Hypothesis: We hypothesized that increase in blood pressure after drinking a commercially available energy drink, compared to a placebo, is secondary to increased sympathetic activation. Methods: In a randomized, double-blind, placebo-controlled, cross-over study, we studied 25 healthy subjects, age 29±1 years, who were free of known disease, had no known cardiovascular risk factors, and were not on any medications. Each subject consumed a can, 16-fluid ounces, of Rockstar energy drink or a placebo drink in random order on two separate days. Blood pressure (n=25) and plasma norepinephrine levels (n=23) were measured before and 30-minutes after drink consumption. Results: Despite the increase in blood pressure after drinking Rockstar energy drink, which would be expected to elicit reflex reductions in central sympathetic outflow, plasma norepinephrine levels increased markedly after energy drink consumption vs placebo (73.6±9.7% vs 30.9±9.7%, respectively, P=0.003; Figure). Specifically, plasma norepinephrine levels increased from 149.8±11.7pg/ml to 249.8±17.3pg/ml after the energy drink consumption and from 139.9±11.7pg/ml to 178.6±17.3pg/ml after placebo (P=0.0007 for timeхtreatment comparison). Conclusions: Increased blood pressure after consumption of commercially available energy drink is associated with significantly increased catecholamine levels in young healthy adults. These acute hemodynamic and adrenergic changes may predispose to increased cardiovascular risk by triggering arrhythmias or ischemia, particularly in individuals with a vulnerable cardiovascular substrate.

Background Caveolin‐1 is a structural protein of caveolae which forms a signaling platform for several cell surface receptors including leptin and insulin receptor. Caveolin‐1 expression is increased with obesity which is implicated in impaired adipose tissue leptin signaling. Considering the overlap between insulin and leptin cellular signaling pathways, we investigated known insulin‐sensitizing drugs which may reduce caveolin‐1 expression in adipose tissue and consequently improve leptin signaling. Methods We used an in‐vitro approach to identify insulin‐sensitizing drugs which may reduce caveolin‐1 expression. Differentiated human white preadipocytes (dHWP) were treated with pioglitazone (5–30 μM), troglitazone (10–30 μM), metformin (1–5 mM), or glimepiride (20–100 μM) for 24 hours. Caveolin‐1 expression was determined by Western blot. We further tested the responses in human adipose tissue from obese individuals (n=12, age: 45.4 ± 9.2 years, BMI: 48.9 ± 7.3 kg/m 2 ) undergoing surgery. Tissue was incubated with drugs for 24 h and caveolin‐1 expression was determined. Furthermore, the effect of drugs on leptin‐dependent activation of ERK and STAT3 was examined by western blot. Results Among the drugs investigated, only treatment with increasing concentrations of metformin resulted in a dose‐dependent decease in caveolin‐1 protein (p=0.01) expression in dHWP. Treatment with increasing concentrations of troglitazone upregulated caveolin‐1 (p=0.01), while pioglitazone (p=0.50) and glimepiride (p=0.09) had no effect of caveolin‐1 protein expression. Given these findings, only metformin was tested in human adipose tissue. Overall, metformin did not alter caveolin‐1 expression in adipose tissue from obese individuals (n=12, control: 0.040 ± 0.056, metformin: 0.024 ± 0.030, p=0.57), although a metformin dependent decrease in caveolin‐1 was evident in adipose tissue from 7 of the 12 obese subjects (control: 0.062 ± 0.066, metformin: 0.014 ± 0.013, p=0.02). Notably, changes in caveolin‐1 expression induced by metformin treatment were positively correlated with BMI (p=0.05, r 2 =0.33, n=12). Also, leptin dependent activation of ERK (control: 0.26 ± .098, leptin: 0.28 ± .08) and STAT3 (control: 0.028 ± 0.027, leptin: 0.032 ± 0.023) was impaired in obese adipose tissue and did not change with metformin treatment even in the 7 individuals with metformin associated decreases in caveolin‐1. Conclusions Metformin reduces caveolin‐1 expression in differentiated HWP. However, metformin decreases caveolin‐1 expression in adipose tissue of some but not all obese subjects, and does not have any effects on leptin signaling. The heterogeneous effects of metformin on caveolin‐1 expression in adipose tissue from obese individuals may be related to BMI and needs further investigation. Support or Funding Information MAP and KRS were supported by the American Physiological Society Stride Summer Undergraduate Research Fellowship NHLBI 1 R25 HL115473‐01. PS was supported by AHA scientist development grant 11SDG7260046.

Background Obesity‐associated metabolic disorders have been shown to be related to body fat distribution. Specifically, increases in visceral fat are more detrimental than increases in subcutaneous fat depots. However, the underlying mechanisms through which visceral fat potentiates cardiometabolic dysregulation are not completely understood. In recent years, the presence of localized renin angiotensin system (RAS) in adipose tissue and its role in regulating blood pressure and metabolism has been recognized. Therefore, we investigated if differential expression of RAS components in visceral versus subcutaneous adipose tissue may help explain pathological effects of visceral fat. Hypothesis We hypothesized that compared to subcutaneous adipose tissue, visceral adipose tissue has increased expression of RAS proteins involved in the pro‐inflammatory and pro‐fibrotic ANGII‐AT1R pathway but attenuated expression of proteins mediating the anti‐inflammatory and anti‐fibrotic ANG1‐7‐MASR pathway. Methods We determined the expression of RAS proteins in paired subcutaneous and visceral (omental) adipose tissue samples from obese individuals undergoing surgery (n = 30, BMI: 46.1 ± 7.3 kg/m 2 , age: 46.5 ± 14.4 years) by Western blot. We examined proteins involved in 1) Ang II generation: angiotensinogen (AGT), angiotensin converting enzyme (ACE), chymase; 2) Ang1‐7 generation: ACE‐2; and 3) cellular receptors: angiotensin I receptor (AT1R), MAS receptor (MASR), and aldosterone receptor. Results Comparison of protein expression between subcutaneous and visceral adipose tissue samples showed no changes in proteins involved in generation of angiotensin peptides, namely AGT (0.64 ± 0.57 vs. 0.33 ± 0.28, p = 0.11, n = 12), chymase (0.27 ± 0.23 vs. 0.36 ± 0.41, p = 0.77, n = 22), and ACE‐2 (0.23 ± 0.41 vs. 0.08 ± 0.09, p = 0.21, n = 15). However, ACE expression tended to be higher in subcutaneous vs. visceral fat (0.10 ± 0.06 vs. 0.06 ± 0.03, p = 0.052, n = 12). Furthermore, expression of cellular receptor AT1R was higher in subcutaneous fat (0.24 ± 0.34 vs. 0.07 ± 0.09, p = 0.03, n = 12), and MASR was lower in subcutaneous fat (0.22 ± 0.26 vs. 0.88 ± 0.99, p = 0.01, n = 20). Aldosterone receptor expression (0.21 ± 0.22 vs. 0.14 ± 0.13, p = 0.52, n = 11) was not altered in subcutaneous and visceral depots. Conclusions Proteins involved in the generation of angiotensin peptides are not differentially expressed in subcutaneous versus visceral fat depots. However, expression of cellular receptors is different such that inflammatory and fibrotic effects of RAS may be more predominant in subcutaneous fat. Therefore, RAS is likely to play a role in limiting subcutaneous fat expansion thereby leading to increased visceral fat depots. Furthermore, our findings do not support the role of visceral RAS in development and progression of cardiovascular pathology associated with increased visceral fat depots. Support or Funding Information MAP and KRS were supported by the American Physiological Society Stride Summer Undergraduate Research Fellowship NHLBI 1 R25 HL115473‐01.

Background Obstructive sleep apnea (OSA) patients have elevated levels of plasma leptin and are exposed to repeated nocturnal intermittent hypoxia (IH). Leptin induces increased adiponectin expression, suggesting that adiponectin should be increased in OSA. However, levels of plasma adiponectin, an anti‐atherogenic and insulin‐sensitizing adipokine, are inconsistent in OSA, and adiponectin levels are often low. Both increases in leptin and decreases in adiponectin may contribute to increased cardiometabolic risk in OSA. In this study we sought to examine the interactions between IH, leptin, and adiponectin. Using an in‐vitro approach in differentiated human white preadipocytes (dHWP), we tested the hypothesis that adiponectin expression in response to acute IH‐mediated increases in leptin may be modulated in the presence of hypoxia. Methods dHWP were exposed to 24 cycles of IH (30 min 0.1% O2 followed by 30 min exposure to 21% O2), continuous hypoxia (0.1% O2) or continuous normoxia (21% O2, control). Secretion of leptin and adiponectin in the 24h conditioned media was determined by ELISA and intracellular changes in adiponectin were determined by Western blot analysis. Results We show that acute 24 hour exposure to IH or sustained hypoxia increased leptin secretion (p = 0.013) but did not alter adiponectin secretion (p = 0.48). In fact, the intracellular expression of adiponectin actually decreased during the acute exposure to both IH and to continuous hypoxia (p = 0.02). Also, while leptin increased intracellular adiponectin expression in normoxic conditions (p = 0.03), it was unable to do so in the presence of IH and hypoxia (p = 0.36). Conclusions Acute IH and continuous hypoxia mediate increases in leptin, but not in adiponectin secretion. Furthermore, although leptin increases adiponectin in normoxic conditions, IH and continuous hypoxia cause decreases in intra‐cellular adiponectin expression and also attenuate leptin‐mediated increases in adiponectin expression. These hypoxia‐effects on adiponectin expression may help explain the low adiponectin levels in OSA, which may contribute to increased cardiovascular and diabetes risk. Support or Funding Information Christiane Becari was supported by a grant from CNPq Brazil (# 203802/2014‐4); Michaela Pfeifer was supported by the APS STRIDE summer undergraduate research fellowship (NHLBI 1R25HL115473‐01); Prachi Singh was supported by AHA scientist development grant 11SDG7260046.

There is an increasing consumption of energy drinks both in the United States and worldwide. The components of these beverages are sometimes unclear but commonly include caffeine, sugars, taurine, and B-vitamins. Young people, particularly those engaged in sports, studying, and in the military are especially likely to be consumers of energy drinks. While limited data are available regarding their autonomic and hemodynamic effects, current literature suggests that energy drink consumption is accompanied by increases in blood pressure, sympathetic drive, and also in QT prolongation. There are no systematic long term studies identifying consequences of frequent energy drink consumption. However, multiple anecdotal reports implicate energy drinks in adverse cardiovascular events including atrial fibrillation, ventricular arrhythmia, myocardial infarction, and sudden death. Events such as atrial fibrillation may even occur in otherwise healthy subjects with structurally normal hearts. It is likely that these cardiovascular outcomes are triggered by the hemodynamic, autonomic, and electrocardiographic responses to energy drink consumption. What remains unclear is how concomitant use of other stimulants such as amphetamines and nicotine may interact to potentiate neural and circulatory responses and cardiovascular consequences when combined with energy drinks.