Citations

Key points Theoretical models suggest there is no benefit of high affinity haemoglobin to preserve maximal oxygen uptake in acute hypoxia but the comparative biology literature has many examples of species that are evolutionarily adapted to hypoxia and have high affinity haemoglobin. We studied humans with high affinity haemoglobin and compensatory polycythaemia. These subjects performed maximal exercise tests in normoxia and hypoxia to determine how their altered haemoglobin affinity impacts hypoxic exercise tolerance. The high affinity haemoglobin participants demonstrated an attenuated decline in maximal aerobic capacity in acute hypoxia. Those with high affinity haemoglobin had no worsening of pulmonary gas exchange during hypoxic exercise but had greater lactate and lower pH than controls for all exercise bouts. High affinity haemoglobin and compensatory polycythaemia mitigated the decline in exercise performance in acute hypoxia through a higher arterial oxygen content and an unchanged pulmonary gas exchange. AbstractThe longstanding dogma is that humans exhibit an acute reduction in haemoglobin (Hb) binding affinity for oxygen that facilitates adaptation to moderate hypoxia. However, many animals have adapted to high altitude through enhanced Hb binding affinity for oxygen. The objective of the study was to determine whether high affinity haemoglobin (HAH) affects maximal and submaximal exercise capacity. To accomplish this, we recruited individuals (n = 11, n = 8 females) with HAH (P50 = 16 ± 1 mmHg), had them perform normoxic and acute hypoxic (15% inspired oxygen) maximal exercise tests, and then compared their results to matched controls (P50 = 26 ± 1, n = 14, n = 8 females). Cardiorespiratory and arterial blood gases were collected throughout both exercise tests. Despite no difference in end‐exercise arterial oxygen tension in hypoxia (59 ± 6 vs. 59 ± 9 mmHg for controls and HAH, respectively), the HAH subjects’ oxyhaemoglobin saturation () was ∼7% higher. Those with HAH had an attenuated decline in maximal oxygen uptake () (4 ± 5% vs. 12 ± %, p < 0.001) in hypoxia and the change in between trials was related to the change in (r = −0.75, p < 0.0001). Compared to normoxia, the controls’ alveolar‐to‐arterial oxygen gradient significantly increased during hypoxic exercise, whereas pulmonary gas exchange in HAH subjects was unchanged between the two exercise trials. However, arterial lactate was significantly higher and arterial pH significantly lower in the HAH subjects for both exercise trials. We conclude that HAH attenuates the decline in maximal aerobic capacity and preserves pulmonary gas exchange during acute hypoxic exercise. Our data support the comparative biology literature indicating that HAH is a positive adaptation to acute hypoxia.

New Findings What is the central question of this study? What is the effect of an elevated baseline blood flow, induced by high‐dose intra‐arterial infusion of either adenosine or ATP, on the rapid‐onset vasodilatory response to a single forearm muscle contraction? What is the main finding and its importance? The peak response to a single contraction is unaffected by augmented baseline blood flow, and thus, is likely to be attributable to a feedforward vasodilatory mechanism. AbstractThe hyperaemic responses to single muscle contractions are proportional to exercise intensity, which, in turn, is proportional to tissue metabolic demand. Hence, we tested the hypothesis that the rapid‐onset vasodilatory response after a single muscle contraction would be unaffected when baseline blood flow was increased via high‐dose intra‐arterial infusion of either adenosine (ADO) or ATP. Twenty‐four healthy young participants (28 ± 1 years) performed a single forearm contraction (20% maximal voluntary contraction) 75 min after commencement of a continuous infusion of ADO (n = 6), ATP (n = 8) or saline (control; n = 10). Brachial artery diameter and blood velocity were measured using Doppler ultrasound. Resting forearm vascular conductance (FVC; in millilitres per minute per 100 mmHg per decilitre of forearm volume) was significantly higher during ADO (33 ± 17) and ATP infusion (33 ± 17) compared with the control infusion (8 ± 3; P < 0.05). The peak FVCs post‐contraction during ADO and ATP infusions were significantly greater than during the control infusion (P < 0.05), but not different from one another. The peak change in FVC from baseline was similar in all three conditions (control, 14 ± 1; ADO, 24 ± 2; and ATP, 23 ± 6; P = 0.15). Total FVC (area under the curve) did not differ significantly between ADO and ATP (333 ± 69 and 440 ± 125); however, total FVC during ATP infusion was significantly greater compared with the control value (150 ± 19; P < 0.05). We conclude that the peak response to a single contraction is unaffected by augmented baseline blood flow and is therefore likely to be attributable to a feedforward vasodilatory mechanism.

Abstract Delayed terminal duct lobular unit (TDLU) involution is associated with elevated mammographic breast density (MD). Both are independent breast cancer risk factors among women with benign breast disease (BBD). Prior digital analyses of normal breast tissues revealed that epithelial nuclear density (END) and TDLU involution are inversely correlated. Accordingly, we examined associations of END, TDLU involution, and MD in BBD clinical biopsies. This study included digitized images of 262 representative image-guided hematoxylin and eosin–stained biopsies from 224 women diagnosed with BBD, enrolled within the cross-sectional BREAST-Stamp project that were visually assessed for TDLU involution (TDLU count/100 mm2, median TDLU span and median acini count per TDLU). A digital algorithm estimated nuclei count per unit epithelial area, or END. Single X-ray absorptiometry of prebiopsy ipsilateral craniocaudal digital mammograms measured global and localized MD surrounding the biopsy region. Adjusted ordinal logistic regression models assessed relationships between tertiles of TDLU and END measures. Analysis of covariance examined mean differences in MD across END tertiles. TDLU measures were positively associated with increasing END tertiles [TDLU count/100 mm2, ORT3vsT1: 3.42, 95% confidence interval (CI), 1.87–6.28; acini count/TDLUT3vsT1, OR: 2.40, 95% CI, 1.39–4.15]. END was significantly associated with localized, but not, global MD. Relationships were most apparent among patients with nonproliferative BBD. These findings suggest that quantitative END reflects different but complementary information to the histologic information captured by visual TDLU and radiologic MD measures and merits continued evaluation in assessing cellularity of breast parenchyma to understand the etiology of BBD.

Arterial oxygen tension and oxyhemoglobin saturation ([Formula: see text]) decrease in parallel during hypoxia. Distinguishing between changes in oxygen tension and oxygen content as the relevant physiological stimulus for cardiorespiratory alterations remains challenging. To overcome this, we recruited nine individuals with hemoglobinopathy manifesting as high-affinity hemoglobin [HAH; partial pressure at 50% [Formula: see text] (P50) = 16 ± 0.4 mmHg] causing greater [Formula: see text] at a given oxygen partial pressure compared with control subjects ( n = 12, P50 = 26 ± 0.4 mmHg). We assessed ventilatory and cardiovascular responses to acute isocapnic hypoxia, iso-oxic hypercapnia, and 20 min of isocapnic hypoxia (arterial Po2 = 50 mmHg). Blood gas alterations were achieved with dynamic end-tidal forcing. When expressed as a function of the logarithm of oxygen partial pressure, ventilatory sensitivity to hypoxia was not different between groups. However, there was a significant difference when expressed as a function of [Formula: see text]. Conversely, the rise in heart rate was blunted in HAH subjects when expressed as a function of partial pressure but similar when expressed as a function of [Formula: see text]. Ventilatory sensitivity to hypercapnia was not different between groups. During sustained isocapnic hypoxia, the rise in minute ventilation was similar between groups; however, heart rate was significantly greater in the controls during 3 to 9 min of exposure. Our results support the notion that oxygen tension, not content, alters cellular Po2in the chemosensors and drives the hypoxic ventilatory response. Our study suggests that in addition to oxygen partial pressure, oxygen content may also influence the heart rate response to hypoxia.NEW & NOTEWORTHY We dissociated the effects of oxygen content and pressure of cardiorespiratory regulation studying individuals with high-affinity hemoglobin (HAH). During hypoxia, the ventilatory response, expressed as a function of oxygen tension, was similar between HAH variants and controls; however, the rise in heart rate was blunted in the variants. Our work supports the notion that the hypoxic ventilatory response is regulated by oxygen tension, whereas cardiovascular regulation may be influenced by arterial oxygen content and tension.

Abstract Background: Mammographic breast density (MBD) is a strong breast cancer (BC) risk factor, but its biologic underpinnings are poorly understood. Use of estrogen plus progestin menopausal hormone therapy is linked to increased MBD and BC risk. Experimental data suggest that ratios of tumor promoting (5α-dihydroprogesterone [5αP]) and anti-tumorigenic (3α-dihydroprogesterone [3αP]) progesterone metabolite levels may be related to BC risk. However, relationships of endogenous progesterone and its metabolites with MBD and BC risk have not been established. Accordingly, we assessed levels of circulating progesterone and its metabolites with MBD. Methods: In this cross-sectional study, serum progesterone and its metabolites were quantified using a novel liquid chromatography-tandem mass spectrometry assay in 103 postmenopausal and 52 premenopausal (luteal menstrual cycle phase) women, ages 40-65, undergoing diagnostic image-guided ipsilateral breast biopsy. MBD was measured as percent fibroglandular volume (MBD-V) on pre-biopsy digital mammograms using single X-ray absorptiometry. Square-root transformed MBD-V was examined across tertile categories of progesterone/progesterone metabolites using age and body mass index (BMI)-adjusted linear regression models. Results: Concentrations of the hormones were as follows among postmenopausal women: progesterone [mean: 12.6 pmol/L (range: 5.2-45.8)], 3αP [5.6 pmol/L (1.4-18.8)], 5αP [100 pmol/L (16.7-388)], and 5αP/3αP ratio [26.1 (2.1-150)]; and among luteal phase premenopausal women: progesterone [2063 pmol/L (13.6-7098), 3αP [12.7 pmol/L (2.4-64.4)], 5αP [243 pmol/L (25.3-774)], 5αP/3αP ratio [25.9 (2.3-73.7)]. Among postmenopausal women, progesterone was positively associated with MBD-V (Tertile 3 vs. 1: β=0.68, p-trend=0.02). A similar borderline positive association was observed among premenopausal women (β=0.74, p-trend=0.10). Additional adjustment for circulating estradiol did not substantively alter observed associations. Levels of 3αP, 5αP and the 5αP/3αP ratio were not associated with MBD-V among pre- or postmenopausal women. Conclusions: Concentrations of progesterone and it metabolites show substantial inter-woman variation. We observed a positive association between endogenous progesterone and MBD-V among both postmenopausal and premenopausal luteal phase women. We did not observe an association with the ratio of 5αP to 3αP levels and MBD-V. These findings suggest the need for additional studies to understand the biological basis of the role of progesterone and its metabolites in MBD and BC risk. Citation Format: Manila Hada, Hannah Oh, Sharon Fan, Roni T. Falk, Berta Geller, Pamela Vacek, Donald Weaver, John Shepherd, Jeff Wang, Bo Fan, Amir P. Mahmoudzadeh, Serghei Malkov, Sally Herschorn, Louise A. Brinton, Xia Xu, Mark E. Sherman, Britton Trabert, Gretchen L. Gierach. Relationship of serum progesterone and progesterone metabolites with mammographic density [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 588.

Key points Haemoglobin affinity is an integral concept in exercise physiology that impacts oxygen uptake, delivery and consumption. How chronic alterations in haemoglobin affinity impact physiology is unknown. Using human haemoglobin variants, we demonstrate that the affinity of haemoglobin for oxygen is highly correlated with haemoglobin concentration. Using the Fick equation, we model how altered haemoglobin affinity and the associated haemoglobin concentration influences oxygen consumption at rest and during exercise via alterations in cardiac output and mixed‐venous . The combination of low oxygen affinity haemoglobin and reduced haemoglobin concentration seen in vivo may be unable to support oxygen uptake during moderate or heavy exercise. AbstractThe physiological implications, with regard to exercise, of altered haemoglobin affinity for oxygen are not fully understood. Data from the Mayo Clinic Laboratories database of rare human haemoglobin variants reveal a strong inverse correlation (r = −0.82) between blood haemoglobin concentration and P50, an index of oxygen affinity [Hb = −0.3135(P50) + 23.636]. In the present study, observed P50 values for high, normal and low oxygen‐affinity haemoglobin variants (13, 26 and 39 mmHg) and corresponding haemoglobin concentrations (19.5, 15.5 and 11.4 g dL−1 respectively) are used to model oxygen consumption as a fraction of delivery at rest ( = 0.25 L min−1, cardiac output = 5.70 L min−1) and during exercise ( = 2.75 L min−1, cardiac output = 18.9 l min−1). With high‐affinity haemoglobin, the model shows that normal levels of oxygen consumption can be achieved at rest and during exercise at the assumed cardiac output levels, with reduced oxygen extraction both at rest (16.8% high affinity vs. 21.7% normal) and during exercise (55.8% high affinity vs. 72.2% normal). With low‐affinity haemoglobin, which predicts low haemoglobin concentration, oxygen consumption at rest can be sustained with the assumed cardiac output, with increased oxygen extraction (31.1% low affinity vs. 21.7% normal). However, exercise at 2.75 l min−1 cannot be achieved with the assumed cardiac output, even with 100% oxygen extraction. In conclusion, the model indicates chronic alterations in P50 associate directly with Hb concentration, highlighting that human Hb variants can serve as ‘experiments of nature’ to address fundamental hypotheses on oxygen transport and exercise.

Abstract Background: Mammographic breast density declines during menopause. We assessed changes in volumetric breast density across the menopausal transition and factors that influence these changes. Methods: Women without a history of breast cancer, who had full field digital mammograms during both pre- and postmenopausal periods, at least 2 years apart, were sampled from four facilities within the San Francisco Mammography Registry from 2007 to 2013. Dense breast volume (DV) was assessed using Volpara on mammograms across the time period. Annualized change in DV from pre- to postmenopause was estimated using linear mixed models adjusted for covariates and per-woman random effects. Multiplicative interactions were evaluated between premenopausal risk factors and time to determine whether these covariates modified the annualized changes. Results: Among the 2,586 eligible women, 1,802 had one premenopausal and one postmenopausal mammogram, 628 had an additional perimenopausal mammogram, and 156 had two perimenopausal mammograms. Women experienced an annualized decrease in DV [−2.2 cm3 (95% confidence interval, −2.7 to −1.7)] over the menopausal transition. Declines were greater among women with a premenopausal DV above the median (54 cm3) versus below (DV, −3.5 cm3 vs. −1.0 cm3; P &lt; 0.0001). Other breast cancer risk factors, including race, body mass index, family history, alcohol, and postmenopausal hormone therapy, had no effect on change in DV over the menopausal transition. Conclusions: High premenopausal DV was a strong predictor of greater reductions in DV across the menopausal transition. Impact: We found that few factors other than premenopausal density influence changes in DV across the menopausal transition, limiting targeted prevention efforts.

Abstract Purpose: The evidence on associations of mammographic breast density with breast cancer risk by combination of tumor aggressiveness features is limited. We examined associations of breast density phenotypes with risk of aggressive breast tumor features by menopausal status, and current postmenopausal hormone therapy. Methods: This study included 2,635 invasive breast cancer cases and 4,059 controls from participants of four nested case-control studies within four established cohorts: the Mayo Mammography Health Study, the Nurses Health Study, Nurses Health Study II, and San Francisco Mammography Registry. Percent breast density, absolute dense and non-dense areas were assessed from digitized film-screen mammograms using a computer-assisted threshold technique and standardized across studies. We used polytomous logistic regression to quantify the associations of breast density measures with risk of breast tumor aggressiveness (defined as presence of 2 or more of the following tumor characteristics: size ≥2cm, grade 2 or 3, or positive nodes), stratified by menopausal status and current hormone therapy (i.e., premenopausal, postmenopausal/estrogen therapy, postmenopausal/combined therapy, and postmenopausal/no hormones). We also evaluated differences in the strength of associations across categories. In a secondary analysis, we examined these associations while excluding cases with mammogram date within 2 years of diagnosis. Results: Positive associations of percent density and dense area and inverse associations of non-dense area with breast cancer risk were stronger in aggressive vs. non-aggressive tumors (OR=2.62, 95%CI 2.08-3.31 vs. OR=1.94, 95%CI 1.62-2.33 for percent density≥51% vs. 11-25%, p-heterogeneity=0.001; OR=1.89, 95%CI 1.54-2.31 vs. OR=1.65, 95%CI 1.41-1.93 for dense area 4th vs. 2nd quartile, p-heterogeneity=0.015; OR=0.56, 95%CI 0.44-0.72 vs. OR=0.71, 95%CI 0.59-0.86 for non-dense area 4th vs 2nd quartile, p-heterogeneity=0.007, respectively). These patterns were similar across all menopausal and hormone therapy groups (P-interactions=0.62, 0.76, and 0.23, for percent density, dense area and non-dense area, respectively). Excluding cases diagnosed within 2 years of mammography resulted in similar findings. Conclusion: Mammographic density phenotypes were more strongly associated with aggressive cancer (having two or more of the following: size ≥2cm, grade 2 or 3, or positive nodes) vs. non-aggressive types of breast cancer across categories of menopause and hormone therapy types. Citation Format: Lusine Yaghjyan, Rulla Tamimi, Kimberly Bertrand, Christopher G. Scott, Matthew R. Jensen, Shane Pankratz, Kathleen Brandt, Daniel Visscher, Aaron Norman, Fergus Cough, John Shepherd, Bo Fan, Yunn-Yi Chen, Lin Ma, Andrew H. Beck, Steven R. Cummings, Karla Kerlikowske, Celine Vachon. Interaction of mammographic breast density with menopausal status and postmenopausal hormone use in relation to the risk of aggressive breast cancer subtypes. [abstract]. In: Proceedings of the AACR Special Conference: Improving Cancer Risk Prediction for Prevention and Early Detection; Nov 16-19, 2016; Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(5 Suppl):Abstract nr B27.

OBJECTIVELatent autoimmune diabetes in adults (LADA) shares clinical features with both type 1 and type 2 diabetes; however, there is ongoing debate regarding the precise definition of LADA. Understanding its genetic basis is one potential strategy to gain insight into appropriate classification of this diabetes subtype.RESEARCH DESIGN AND METHODSWe performed the first genome-wide association study of LADA in case subjects of European ancestry versus population control subjects (n = 2,634 vs. 5,947) and compared against both case subjects with type 1 diabetes (n = 2,454 vs. 968) and type 2 diabetes (n = 2,779 vs. 10,396).RESULTSThe leading genetic signals were principally shared with type 1 diabetes, although we observed positive genetic correlations genome-wide with both type 1 and type 2 diabetes. Additionally, we observed a novel independent signal at the known type 1 diabetes locus harboring PFKFB3, encoding a regulator of glycolysis and insulin signaling in type 2 diabetes and inflammation and autophagy in autoimmune disease, as well as an attenuation of key type 1–associated HLA haplotype frequencies in LADA, suggesting that these are factors that distinguish childhood-onset type 1 diabetes from adult autoimmune diabetes.CONCLUSIONSOur results support the need for further investigations of the genetic factors that distinguish forms of autoimmune diabetes as well as more precise classification strategies.