Bock, Joshua M.

Establishes a robust long-term human adipocyte organoid culture system maintained for over 90 days. Recapitulates key features of OSA-related intermittent hypoxia in human adipocytes in vitro. Demonstrates IH-induced adipocyte aging, including ultrastructural damage and epigenetic reprogramming. Identifies impaired adipogenesis and insulin signaling under intermittent hypoxia. Provides a physiologically relevant platform for mechanistic studies and drug screening.

Abstract Background Obstructive sleep apnea (OSA) is a risk factor for hypertension and some evidence suggests this risk may not be mitigated with positive airway pressure. Low-intensity statin therapy can modestly reduce blood pressure (BP). In this exploratory analysis, we examined if six months of high-intensity statin therapy could lower resting or ambulatory BP in patients with OSA. Methods 39 patients with OSA (13F, age = 49 ± 9yrs, body mass index = 32.9 ± 4.2kg/m2, apnea-hypopnea index = 22.2 ± 12.4 events/hour) were randomized to high-intensity atorvastatin or placebo. BP was assessed using seated, “office” measurements and in 20-minute intervals over 24 consecutive hours at three timepoints (baseline, three- and six-months post-randomization). Participants maintained a diary denoting sleep and wake times for analysis. Changes (Δ) in BP from baseline were assessed and adjusted for adherence to participants’ intervention (atorvastatin or placebo) as well as to their treatment for OSA (yes or no). Results There were no between-group differences in baseline BP variables (P = .09-.96). At three months, the changes in resting (P = .74-.87), 24 hour mean (P = .54-.96), daytime (P = .70-.96), nor nighttime (P = .74-.96) BP did not differ between groups. Similarly, the changes in resting (P = .23-.92), 24 hour mean (P = .51-.82), daytime (P = .17-.78), and nighttime (P = .51-1.00) BP did not differ between groups following six months of their respective intervention. Conclusions Our data suggest that high-intensity atorvastatin does not lower resting or ambulatory BP in patients with OSA relative to a placebo. Thus, it does not appear that atorvastatin is a viable adjunct intervention for BP reduction in patients with OSA. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT03308578.

Obstructive sleep apnea (OSA), a sleep disorder that is associated with exposure to repeated bouts of hypoxia overnight. Evidence suggests that the oxyhemoglobin dissociation curve (ODC) may be shifted rightward with OSA. Nitric oxide (NO) functions as an allosteric regulator of hemoglobin oxygen-binding properties, possibly shifting the ODC curve leftward. Nitrate/nitrite supplementation increases NO bioavailability and attenuates the physiological responses to hypoxia which may be due to changes in the ODC. Therefore, we explored the hypothesis that dietary nitrate supplementation improves oxygen re-saturation following inspiratory hypoxia in subjects with OSA. Fourteen subjects with untreated mild-moderate OSA (53 ± 10yr, 8M/6F; Apnea-hypopnea Index, 17.8 ± 8.1 events) completed two separate study visits. Each visit consisted of two hypoxic bouts separated by ~2 hours and the consumption of one of two beetroot juice beverages (Placebo [BR P ] containing 5-10 mg nitrate, no detectable nitrite, or Active [BR A ] containing 500mg nitrate and 40mg nitrite). For each hypoxia bout, subjects’ pulse oxygen saturation (%SpO 2 ) was titrated to ≤80% over 3-5min by blending a 10% FiO2 gas cylinder with room air. Once ≤80% SpO 2 was achieved, subjects inhaled normoxic room air (~21% FiO2) and oxygen saturation was monitored until SpO 2 returned to baseline (recovery). During recovery, SpO 2 was averaged into 5 sec bins from the end of hypoxia (nadir) up to +15 SpO 2 % above nadir. The ‘hypoxic load’ during recovery was calculated as ( i =1 ∑ n ∣Value i −nadir+15∣) and reflects a total sum of each 5 sec bin ( n ). BR A increased plasma nitrite (248 ± 155 to 738 ± 427nM, P < 0.05), whereas there was no change following BR P (266 ± 153 to 277 ± 164nM, P = 0.87). The level of desaturation (SpO 2 nadir) at the end of hypoxia did not differ within or between trials (BR A : Pre 78 ± 2 vs. 78 ± 3; BR P : Pre 78 ± 2 vs. 78 ± 2, condition x time interaction P = 0.21). Hypoxia load increased following BR P (162.7 ± 36.6 vs. 231.8 ± 65.7, P < 0.001), but was unchanged following BR A (174.3 ± 54.2 vs. 191.2 ± 52, P = 0.32). In summary, our study suggests that acute nitrate supplementation may cause a leftward shift in the ODC in patients with untreated OSA. This is supported by a reduced hypoxic load following a repeat bout of inspiratory hypoxia. These findings may have implications for the health of patients with OSA. Foundation for the National Institutes of Health, K12 AR084222 (Joshua Bock) This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

INTRODUCTION: The increased likelihood of adverse cardiovascular events (CVE) shortly after awakening has been partially attributed to low nitric oxide (NO) production in the early morning. Thus, increasing early morning NO levels to improve vascular function could reduce adverse CVE incidence, especially among older adults as total NO production declines with aging. The increased adverse CVE among post-menopausal women (PMW) are likely due to a steeper decline in their vascular function. As inorganic nitrate increases circulating NO levels for up to 12hrs, our primary hypothesis was to determine if nocturnal inorganic nitrate supplementation improves early morning vascular function relative to a placebo in eight generally healthy adults (6F, 37±5yrs, 26.9±1.8kg/m 2 ). Our secondary hypothesis was that PMW (n=3, 27.1±4.3kg/m 2 ), identified by their age (71±2yrs) and follicle-stimulating hormone levels (72.3±8.0mIU/mL), would show greater improvements in their vascular function compared to younger participants (n=5, 3F, 28±2yrs, 26.8±2.0kg/m 2 ). METHODS: Written informed consent was obtained from all participants before data collection. Participants completed three overnight study visits: Visit 1 was for acclimation with vascular function assessments occurring during Visits 2 and 3. During the latter visits, participants consumed beetroot juice with (6.45mmol) or devoid of (0mmol) inorganic nitrate at 2200 in randomized, cross-over fashion followed by vascular function assessments post-awakening (0630-0800) while participants were supine. Vascular assessments consisted of brachial blood pressure, aortic augmentation index (AIx), carotid-femoral pulse wave velocity (cfPWV), and endothelial function (FMD). Data were compared using a paired-samples t-test (α<0.05). RESULTS: Systolic (125±4 vs. 126±6mmHg, p=0.35) and diastolic (71±2 vs. 72±2mmHg, p=0.32) blood pressure were similar the morning after nitrate and placebo. Additionally, AIx (31±5 vs. 33±6%, p=0.29) and FMD (n=7, 8.8±2.0 vs. 7.6±1.7%, p=0.25) were not different the morning after nitrate and placebo consumption. However, cfPWV was lower the morning following nitrate consumption relative to the placebo (6.3±0.5 vs. 6.9±0.6m/s, p=0.01). A sub-group analysis of PMW showed that both systolic (132±6 vs. 139±9mmHg, p=0.18) and diastolic (70±3 vs. 75±2mmHg, p=0.09) blood pressure tended to be lower following nitrate relative to the placebo whereas AIx (46±1 vs. 50±5%, p=0.31) and FMD (n=2, 8.5±2.7 vs. 6.9±1.6%, p=0.78) did not differ; however, cfPWV was lower the morning after nitrate consumption (7.4±0.9 vs. 8.4±1.1m/s, p=0.02) in PMW but not in the younger participants (5.6±0.4 vs. 6.0±0.3m/s, p=0.23). CONCLUSION: Acute nocturnal inorganic nitrate supplementation lowers aortic stiffness in the early morning, especially among PMW. Although the differences in systolic (7mmHg) and diastolic blood pressure (5mmHg) were not statistically significant, they remain clinically meaningful due to their magnitude. This may suggest a role for nocturnal nitrate supplementation in reducing early-morning adverse CVE among PMW. AHA 24POST1241616 (IMG), NIH K12 AR084222 (JMB), Sleep Research Society 038-JP-23 (JMB), and a grant from Sleep Number Corporation to Mayo Clinic for studies in Aging. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Somali Americans, originating from East Africa, are a fast-growing minority in the United States. Emerging data suggest Somali individuals exhibit increased cardiovascular (CV) risk compared to non-Hispanic White adults. Previous data from our laboratory demonstrated elevated ambulatory arterial stiffness in Somali Americans, as derived from 24-hour blood pressure monitoring. We sought to confirm these vascular stiffness findings via gold-standard applanation tonometry and examine potential sex differences, given that females of African ancestry are at elevated risk of CV disease (CVD). We therefore examined aortic hemodynamics and carotid-femoral pulse wave velocity in male and female Somali Americans. We hypothesized that female Somali Americans would present with greater aortic wave reflection and arterial stiffness compared to males. We further examined the accuracy of prediction of aortic wave reflection from a predominantly White population, when applied to the Somali American population. We utilized applanation tonometry to quantify arterial stiffness in 24 female (age: 27±10 years, BMI: 27±6 kg/m 2 ) and 19 male (age: 22±6 years, BMI: 27±5 kg/m 2 ) Somali Americans without CVD. Each participant arrived in the laboratory at Mayo Clinic, fasted for at least three hours, and did not consume caffeine or exercise for at least 12 hours prior to testing. After 15 minutes of supine rest, duplicate recordings of aortic blood pressure and augmentation index (AIx) were obtained via pulse wave analysis. Similarly, aortic stiffness was quantified via duplicate carotid-femoral pulse wave velocity recordings. Statistical analysis included independent samples t-tests to test for sex differences in aortic hemodynamics, and paired samples t-tests to determine differences between estimated and obtained AIx (α≤0.05). Aortic systolic arterial pressure (111±11 vs. 108±7 mmHg, p=0.295) was similar between female and male Somali Americans. Aortic diastolic arterial pressure (75±7 vs. 67±7 mmHg, p<0.001) and heart rate (67±9 vs. 57±7 beats/min, p<0.001) were higher in female Somali adults. Similarly, AIx (28±14 vs. 19±12%, p=0.045) and AIx normalized to 75 heart beats/minute (24±13 vs. 10±13%, p=0.001) were higher in female Somali Americans. Carotid-femoral pulse wave velocity (5.4±0.9 vs. 5.5±0.8 m/s, p=0.661) was similar between sexes. Estimated AIx (corrected for sex, age, height, and resting heart rate) was markedly lower than observed AIx in both female (13±7 vs. 28±14%, p<0.001) and male (6±5 vs. 19±12%, p<0.001) Somali Americans. These findings, obtained in young, healthy Somali adults are suggestive of elevated CVD risk, evident at an early age. These data are particularly concerning regarding vascular dysfunction in Somali females and suggest that prediction models for arterial stiffness should factor in race to optimize performance. Future work into mechanisms underlying vascular dysfunction in Somali Americans is warranted. Sleep Number Grant to Mayo Clinic and by NIH R01-HL160619, R01-HL169320, T32-DK007013, K12 AR084222, and AHA 24POST1241616. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Abstract Introduction Poor sleep quality is bidirectionally associated with cardiovascular and neurocognitive disorders. Preclinical data implicate nitric oxide (NO) in the onset, and maintenance, of sleep. Acute inorganic nitrate supplementation increases NO bioavailability via serial reduction for &gt;12hrs. We tested if objective (Aim 1) or subjective (Aim 2) sleep quality was better following acute, pre-sleep nitrate supplementation relative to a placebo. Methods Seven non-shift working adults (4F/3M, 40±8yrs, 25.8±1.6kg/m2) with no history of sleep, cardiovascular, or neurocognitive disorders completed three overnight polysomnography (PSG) visits with time in bed standardized to 2200-0600hrs. Visit 1 was for acclimation and screening for sleep-disordered breathing. On Visits 2 and 3, participants consumed beetroot juice containing (6.45mmol) or devoid of (0mmol) inorganic nitrate at 2200 using a randomized, cross-over study design. PSG-derived outcomes included slow-wave (SWS) and rapid eye-movement (REM) sleep, sleep efficiency, and wake after sleep onset (WASO). Subjective sleep quality assessments were administered in-laboratory including a 0-10 scale, the Stanford Sleepiness Scale (SSS), and performance with mental arithmetic shortly after awakening. Results No participant demonstrated evidence for sleep-disordered breathing (apnea-hypopnea index = 1.7±0.9events/hr). Total sleep time (TST, 434±17 vs. 412±19min), sleep efficiency (89±3 vs. 85±4%), as well as SWS duration (75±10 vs. 66±9min) and percent of TST (17±2 vs. 16±2%) were higher after nitrate relative to the placebo (p&lt; 0.05 for all). WASO (47±16 vs. 62±19min, p&lt; 0.05) was lower after nitrate versus placebo and no differences were seen in REM sleep duration (131±23 vs. 117±12min, p=0.45) nor percent of TST (30±5 vs. 29±3%, p=0.80). Neither the 0-10 scale (6.7±0.5 vs. 6.8±0.6units, p=0.84), SSS (2.6±0.4 vs. 2.5±0.3units, p=0.68), or arithmetic performance (82±3 vs. 81±5% correct, p=0.85) differed post-nitrate compared to post-placebo. Conclusion These data suggest that acutely increasing nocturnal NO levels via pre-sleep inorganic nitrate supplementation improves objective indices of sleep quality in healthy adults. However, greater amounts of nitrate or prolonged supplementation (weeks) may be needed to improve perceived sleep quality. Support (if any) The National Institutes of Health (K12 AR084222 to JMB, R01s HL160619 and HL65176 to VKS), Sleep Research Society Foundation (CDA 038-JP-23 to JMB), and the American Heart Association (24POST1241616 to IMG).

Abstract Introduction Cardiovascular disease (CVD) remains the leading cause of death in the United States. We previously showed a high prevalence of obstructive sleep apnea (OSA) among former National Football League (NFL) players. Further, we hypothesized that post-career OSA impacts CVD risk among retired professional athletes, even though these former NFL players are often near peak physical fitness for a significant portion of their lifespan. The Living Heart Foundation Heart-Obesity-Prevention-Education Group aimed to provide an in-depth health assessment for CVD risk factors among former NFL players to examine the role of OSA on blood pressure (BP) and echocardiographic measurements. Methods Forty-three former NFL players completed an at-home sleep study and outpatient health assessment to determine CVD risk including office BP and transthoracic echocardiogram (TTE) measurements. Seated BP readings were made in triplicate, TTE measurements, including ejection fraction, left atrial size, left ventricular size and thickness, and ascending aortic diameter, were obtained in 17 former NFL players without OSA (age: 46±10 years, BMI: 32±5 kg/m2, apnea-hypopnea index: 3±1 events/hour) and 26 with OSA (age: 51±9 years, BMI: 33±5 kg/m2, apnea-hypopnea index: 17±12 events/hour). Independent sample t-tests were utilized to determine differences in blood pressure and TTE measurements between OSA and non-OSA groups (α=0.05). Results Systolic BP was similar in non-OSA vs. OSA groups (131±12 vs. 135±16 mmHg, p=0.443), while diastolic BP was higher in former NFL players with OSA (78±8 vs. 86±9 mmHg, p=0.007). Ejection fraction, left atrial size, left ventricular size, and left ventricular thickness were similar between groups (p&gt;0.05 for all). However, ascending aortic diameter was modestly larger in former NFL players with OSA (3.3±0.19 vs. 3.5±0.40 cm, p=0.048). Conclusion These findings suggest OSA may be a primary driver of increased BP and increased aortic diameter in former NFL players, and impact cardiac structural health, suggesting augmented CVD risk in former NFL players. Future work is warranted to investigate impact of race and player position on OSA-mediated CVD risk in retired NFL players. Support (if any) NFL Players Association, NIH T32-DK007013, and the American Heart Association (24POST1241616)

Abstract Aldosterone, a hormone synthesized by the adrenal glands, plays a pivotal role in regulating both blood pressure and electrolyte balance and may contribute to long term cardiovascular risk. Recent findings suggest that adipose tissue might serve as a source for aldosterone production and secretion. Patients suffering from obstructive sleep apnea (OSA) often exhibit elevated blood pressure levels and increased cardiovascular risk. Therefore, we sought to investigate whether increased aldosterone synthesis in fat tissue could contribute to the increase in hypertension and cardiovascular disease in OSA patients. To address this, we conducted a comparative analysis of adipocyte aldosterone level in OSA patients versus Age and BMI matched healthy individuals. Our data revealed no significant differences in aldosterone content between the two groups. Further examination involved measuring the expression of the key enzyme CYP11B2 responsible for aldosterone synthesis. We observed comparable expression levels of CYP11B2 in both the OSA and control groups. To corroborate these findings, we isolated stromal vascular fraction (SVF) from human fat tissues. The SVF cells were cultured in preadipocyte medium and subjected to normoxia and intermittent hypoxia (IH), mimicking OSA conditions as per established protocol. Subsequent analysis of aldosterone levels in cell lysates and conditioned medium revealed no significant differences. Similarly, in vitro examination of CYBP11B2 expression was not different in normoxic versus IH conditions. In conclusion, our study did not discern significant differences in adipocyte aldosterone production and secretion between patients with OSA and matched control subjects, nor in human preadipocytes under normoxic versus IH conditions.

Inconsistency in the calculation of time spent in moderate to vigorous physical activity (MVPA) limits interstudy comparability and interpretation of surveillance data. This study assesses whether combining multiple individual methods results in a more accurate estimate of MVPA, while considering the influence of device brand and wear location. Participants (n = 30, age = 49.2 ± 19.5 years) wore two accelerometers (GENEActiv, ActiGraph) on each wrist during two laboratory visits. Individual classification methods (11 for left wrist, eight for right wrist) estimated minutes of MVPA using three approaches (cut-point, two-regression, and machine learning), two types of input (count and raw), and five epoch lengths (1, 5, 15, 30, and 60 s). The consensus estimate was calculated as the mean or median (due to skew) across all individual estimates. No individual or consensus estimates were statistically equivalent to direct observation (mean 38.2 min), with 81%–95% of individual methods overestimating MVPA. The best-performing individual methods were raw acceleration cut-points, with a bias of −3.2 to 2.4 min across devices and wrists. Correlation coefficients between individual methods and the criterion were .35–.71 for the left and .12–.67 for the right wrist, compared to .65–.70 and .58–.66 for consensus methods, respectively. Correlations between device brands were .23–.99 for individual methods and .70–.86 for consensus methods, while correlations between locations were .55–.86 and .73–.87, respectively. Better methods are required for estimating MVPA from wrist-worn accelerometers given the consistent overestimation of MVPA observed. While a consensus method for wrist-worn data was not able to fully resolve these issues, it improves interwrist or interbrand comparability.

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.