Testing alpha-1 antitrypsin deficiency in black populations

Alpha-1 antitrypsin (AAT) deficiency (AATD) is an under-recognized hereditary disorder and a significant cause of chronic obstructive pulmonary disease (COPD), a disease that contributes to global mortality. AAT is encoded by the SERPINA1 gene, and severe mutation variants of this gene increase the risk of developing COPD. AATD is more frequently screened for in non-Hispanic White populations. However, AATD is also observed in other ethnic groups and very few studies have documented the mutation frequency in these other ethnic populations. Here, we review the current literature on AATD and allele frequency primarily in Black populations and discuss the possible clinical outcomes of low screening rates in a population that experiences poor health outcomes and whether the low frequency of AATD is related to a lack of screening in this population or a truly low frequency of mutations causing AATD. This review also outlines the harmful SERPINA1 variants, the current epidemiology knowledge of AATD, health inequity in Black populations, AATD prevalence in Black populations, the clinical implications of low screening of AATD in this population, and the possible dangers of not diagnosing or treating AATD. </p

Fasting blood glucose and pulmonary function tests of the vehicle and STZ-injected mice.

(A) Fasting blood glucose and glycated hemoglobin (HbA1c) were measured in mice every 4 and 8 weeks, respectively. Pulmonary function testing was performed in mice, (B) 3 months after the onset of hyperglycemia, and (C) 6 months after the onset of hyperglycemia. Data were analyzed by unpaired t-test. N = 7 to 11 animals per group. *p≤0.05; **p≤0.01; ***p≤0.001; ****p≤0.0001. AUC = Area under the curve.</p

Measurement of mean linear intercept for the assessment of emphysematous changes in the lungs of STZ mice.

Mean free distance in the airspace was assessed by mean linear intercept measurements in the upper and lower lobes of the lung in control or STZ mice exposed to RA or CS for 6 months. Data were analyzed by two-way ANOVA using Tukey’s post hoc tests. N = 5/group. (TIF)</p

Quantification of collagen and fibrotic markers in the lung of the vehicle and STZ-injected WT or AAT KO mice.

(A) Representative images of the lung sections stained with Masson’s trichrome were taken at 20x magnification. (B) Blue staining representing collagen was quantified in the upper and lower lobes of the lung sections. Acta2, Ccn2, and Fn1 mRNA expressions in the lung were measured by qRT-PCR. (C) Airspace enlargements were assessed by MLI measurements in the upper and lower lobes of the lung. Data were analyzed by two-way ANOVA using Tukey’s post hoc tests. N = 5 animals per group. *≤0.05; **p≤0.01; ***p≤0.001; ****p≤0.0001.</p

Altered TGFβ signaling observed in STZ animals <i>in vivo</i> and AAT can counter TGFβ-mediated fibroblast signaling <i>in vitro</i>.

qRT-PCR was formed to determine (A) TGF gene expression changes in STZ mice at 3- and 6-months post STZ injects and for TGF and CXCL5 gene expression changes in wild-type and AAT KO mice 3-months post STZ injections. (C) qRT-PCR was performed for CCN2, ACTA2, and FN1 changes in primary human lung fibroblasts exposed to recombinant TGF-β in the presence or absence of AAT. Data were analyzed by two-way ANOVA using Tukey’s post hoc tests. *≤0.05; **p≤0.01; ***p≤0.001; ****p≤0.0001.</p

Plasma AAT concentration and fasting blood glucose of vehicle and STZ-injected WT or AAT KO mice.

(A) Plasma concentration of AAT was measured in control and STZ mice. (B) Schematic showing the timeline of the experiment using vehicle and STZ-injected WT and AAT KO mice. This image was created with BioRender.com. (C) Fasting blood glucose and glycated hemoglobin (HbA1c) were measured in mice every 4 weeks. Data were analyzed by unpaired t-test and two-way ANOVA using Tukey’s post hoc tests. N = 5 to 9 animals per group. *p≤0.05; **p≤0.01; ****p≤0.0001.</p

Measurement of body weight changes and glucose tolerance testing in mice.

(A) Mice were challenged with glucose (2 g/kg, i.p.), and fasting blood glucose was measured at 0, 15, 30, 60, 90 and 120 min after the challenge. Glucose challenge was performed at 2 months and 5 months since STZ or citrate buffer injections. (B) Body weights of the mice were measured weekly and % body weight change was calculated. (A-B) The bar graphs show the area under the curve (AUC) of curves. Data were analyzed by unpaired t-test. N = 8–18. *p≤0.05, **p≤0.01. (TIF)</p

Primer sequences used for qRT-PCR.

Type 1 diabetes (T1D) is a metabolic disease characterized by hyperglycemia and can affect multiple organs, leading to life-threatening complications. Increased prevalence of pulmonary disease is observed in T1D patients, and diabetes is a leading cause of comorbidity in several lung pathologies. A deficiency of alpha-1 antitrypsin (AAT) can lead to the development of emphysema. Decreased AAT plasma concentrations and anti-protease activity are documented in T1D patients. The objective of this study was to determine whether T1D exacerbates the progression of lung damage in AAT deficiency. First, pulmonary function testing (PFT) and histopathological changes in the lungs of C57BL/6J streptozotocin (STZ)-induced T1D mice were investigated 3 and 6 months after the onset of hyperglycemia. PFT demonstrated a restrictive pulmonary pattern in the lungs of STZ-injected mice, along with upregulation of mRNA expression of pro-fibrotic markers Acta2, Ccn2, and Fn1. Increased collagen deposition was observed 6 months after the onset of hyperglycemia. To study the effect of T1D on the progression of lung damage in AAT deficiency background, C57BL/6J AAT knockout (KO) mice were used. Control and STZ-challenged AAT KO mice did not show significant changes in lung function 3 months after the onset of hyperglycemia. However, histological examination of the lung demonstrated increased collagen accumulation and alveolar space enlargement in STZ-induced AAT KO mice. AAT pretreatment on TGF-β-stimulated primary lung fibroblasts reduced mRNA expression of pro-fibrotic markers ACTA2, CCN2, and FN1. Induction of T1D in AAT deficiency leads to a combined pulmonary fibrosis and emphysema (CPFE) phenotype in male mice.</div

PFT in the vehicle and STZ-injected WT or AAT KO mice.

PFT was performed in mice 3 months after the onset of hyperglycemia. (A) FEV0.1 and FVC measurements (B) Pressure-volume curve (AUC = Area under the curve) (C) Inspiratory capacity, compliance, tissue damping, and tissue elastance. Data were analyzed by two-way ANOVA using Tukey’s post hoc tests. N = 5 to 7 animals per group. *p≤0.05; **p≤0.01.</p

Plasma AAT concentration for the screening of AAT KO mice.

(A) Plasma concentration of AAT was measured in control and STZ mice using a commercially available ELISA. The dotted lines denote the limit of detection of the assay. The data are expressed as dot plots with the means ± S.E.M. (TIF)</p