Amy M. Ahasic

Distinct and replicable genetic risk factors for acute respiratory distress syndrome of pulmonary or extrapulmonary origin

Background The role of genetics in the development of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) from direct or indirect lung injury has not been specifically investigated. The aim of this study was to identify genetic variants contributing to ALI/ARDS from pulmonary or extrapulmonary causes. Methods We conducted a multistage genetic association study. We first performed a large-scale genotyping (50K ITMAT-Broad_CARe Chip) in 1717 critically ill Caucasian patients with either pulmonary or extrapulmonary injury, to identify single nucleotide polymorphisms (SNPs) associated with the development of ARDS from direct or indirect insults to the lung. Identified SNPs (p≤0.0005) were validated in two separated populations (Stage II), with trauma (Population I; n=765) and pneumonia/pulmonary sepsis (Population II; n=838), as causes for ALI/ARDS. Genetic variants replicating their association with trauma related-ALI in Stage II were validated in a second trauma-associated ALI population (n=224, Stage III). Results In Stage I, non-overlapping SNPs were significantly associated with ARDS from direct/indirect lung injury, respectively. The association between rs1190286 (POPDC3) and reduced risk of ARDS from pulmonary injury was validated in Stage II (p<0.003). SNP rs324420 (FAAH) was consistently associated with increased risk of ARDS from extrapulmonary causes in two independent ALI-trauma populations (p<0.006, Stage II; p<0.05, Stage III). Meta-analysis confirmed these associations. Conclusions Different genetic variants may influence ARDS susceptibility depending on direct versus indirect insults. Functional SNPs in POPDC3 and FAAH genes may be driving the association with direct and indirect ALI/ARDS, respectively.

MKK3 regulates mitochondrial biogenesis and mitophagy in sepsis-induced lung injury.

Sepsis is a systemic inflammatory response to infection and a major cause of death worldwide. Because specific therapies to treat sepsis are limited, and underlying pathogenesis is unclear, current medical care remains purely supportive. Therefore targeted therapies to treat sepsis need to be developed. Although an important mediator of sepsis is thought to be mitochondrial dysfunction, the underlying molecular mechanism is unclear. Modulation of mitochondrial processes may be an effective therapeutic strategy in sepsis. Here, we investigated the role of the kinase MKK3 in regulation of mitochondrial function in sepsis. Using clinically relevant animal models, we examined mitochondrial function in primary mouse lung endothelial cells exposed to LPS. MKK3 deficiency reduces lethality of sepsis in mice and by lowering levels of lung and mitochondrial injury as well as reactive oxygen species. Furthermore, MKK3 deficiency appeared to simultaneously increase mitochondrial biogenesis and mitophagy through the actions of Sirt1, Pink1, and Parkin. This led to a more robust mitochondrial network, which we propose provides protection against sepsis. We also detected higher MKK3 activation in isolated peripheral blood mononuclear cells from septic patients compared with nonseptic controls. Our findings demonstrate a critical role for mitochondria in the pathogenesis of sepsis that involves a previously unrecognized function of MKK3 in mitochondrial quality control. This mitochondrial pathway may help reveal new diagnostic markers and therapeutic targets against sepsis.

Adiponectin Gene Polymorphisms and Acute Respiratory Distress Syndrome Susceptibility and Mortality

Rationale Adiponectin is an anti-inflammatory adipokine that is the most abundant gene product of adipose tissue. Lower levels have been observed in obesity, insulin resistance, and in critical illness. However, elevated levels early in acute respiratory failure have been associated with mortality. Polymorphisms in adiponectin-related genes (ADIPOQ, ADIPOR1, ADIPOR2) have been examined for relationships with obesity, insulin resistance and diabetes, cardiovascular disease, and to circulating adipokine levels, but many gaps in knowledge remain. The current study aims to assess the association between potentially functional polymorphisms in adiponectin-related genes with acute respiratory distress syndrome (ARDS) risk and mortality. Methods Consecutive patients with risk factors for ARDS admitted to the ICU were enrolled and followed prospectively for development of ARDS. ARDS cases were followed through day 60 for all-cause mortality. 2067 patients were successfully genotyped using the Illumina CVD BeadChip high-density platform. Of these, 567 patients developed ARDS. Forty-four single nucleotide polymorphisms (SNPs) on ADIPOQ, ADIPOR1 and ADIPOR2 were successfully genotyped. Of these, 9 SNPs were hypothesized to be functional based on their location (promoter, exon, or 3′ untranslated region). These 9 SNPs were analyzed for association with ARDS case status and mortality among ARDS cases. Results After multivariable analysis and adjustment for multiple comparisons, no SNPs were significantly associated with ARDS case status. Among ARDS cases, homozygotes for the minor allele of rs2082940 (ADIPOQ) had increased mortality (hazard ratio 2.61, 95% confidence interval 1.36–5.00, p = 0.0039) after adjustment for significant covariates. The significance of this association persisted after adjustment for multiple comparisons (FDR_q = 0.029). Conclusions A common and potentially functional polymorphism in ADIPOQ may impact survival in ARDS. Further studies are required to replicate these results and to correlate genotype with circulating adiponectin levels.

Functional status after critical illness: agreement between patient and proxy assessments

BACKGROUND assessment of baseline functional status of older patients during and after intensive care unit (ICU) admission is often hampered by challenges related to the critical illness such as cognitive dysfunction, neuropsychological morbidity and pain. To explore the reliability of assessments by carefully chosen proxies, we designed a discriminating selection of proxies and evaluated agreement between patient and proxy responses by assessing activities of daily living (ADLs) at 1 month post-ICU discharge. METHODS patients ≥60 years old admitted to the medical ICU were enrolled in a prospective parent cohort studying delirium. Proxies were carefully screened at ICU admission to choose the best available respondent. Follow-up interviews, including instruments for ADLs, were conducted 1 month after ICU discharge. We examined 179 paired patient-proxy follow-up interviews. Kappa statistics assessed inter-observer agreement, and McNemars exact test assessed response differences. RESULTS patients averaged 73.3 ± 8.1 years old with 29% having evidence of cognitive impairment. Proxies were most commonly spouses (38%) or children (39%). Overall, there was substantial (κ ≥ 0.6) to excellent agreement (κ ≥ 0.8) between patients and proxies on assessment of all but one basic and one instrumental ADL. CONCLUSION proxies carefully chosen at ICU admission show high levels of inter-observer agreement with older patients when assessing current functional status at 1 month post-ICU discharge. This motivates further study of proxy assessments that could be used earlier in critical illness to assess premorbid functional status.

IGF1 and IGFBP3 in acute respiratory distress syndrome

OBJECTIVE IGF1 and its most abundant binding protein, IGF-binding protein 3 (IGFBP3), have been implicated in fibrotic lung diseases and persistent acute respiratory distress syndrome (ARDS) due to profibrogenic and antiapoptotic activity. Whether circulating levels of IGF1 and IGFBP3 are altered in ARDS and whether they predict progression of and survival from ARDS remains unknown. This study aims to characterize the circulating levels of IGF1 and IGFBP3 in patients at risk for ARDS in relation to i) development of ARDS and ii) mortality among ARDS cases. DESIGN In this case-cohort study, consecutive patients with risk factors for ARDS admitted to the intensive care unit were enrolled and followed prospectively for the development of ARDS. Cases were followed for all-cause mortality through day 60. Of the 2397 patients enrolled in the parent study, plasma samples were available in 531 (22%) patients (356 controls and 175 cases) from early in presentation. Total plasma IGF1 and IGFBP3 levels were measured. RESULTS After adjusting for relevant clinical covariates including severity of illness, IGF1 and IGFBP3 levels were significantly lower in ARDS cases than in controls (odds ratio (OR), 0.58; P=0.006; OR, 0.57; P=0.0015 respectively). Among the ARDS cases, IGF1 and IGFBP3 levels were significantly lower in the 78 (45%) non-survivors (hazard ratio (HR), 0.70; P=0.024; HR, 0.69; P=0.021 respectively). CONCLUSIONS Lower circulating levels of IGF1 and IGFBP3 were independently associated with ARDS case status. Furthermore, lower levels were associated with mortality among the ARDS cases. These data support the role of the IGF pathway in ARDS.

Personalized Critical Care Medicine: How Far Away Are We?

Personalized medicine has typically referred to the use of genomics in clinical care. However, the concept more broadly refers to recognizing the heterogeneity of each individual patient, particularly their unique risk factors for developing disease or having poor outcomes, and using this to inform treatment decisions. Pharmacogenomics was perhaps the first major clinical application that came out of the Human Genome Project, but its translation to the critical care arena has been limited by numerous factors. Biomarkers have been widely studied in critical illnesses such as sepsis and acute respiratory distress syndrome in an attempt to aid in accurate diagnostic classification, to predict outcomes, and to assess response to therapy. Clinical use of such biomarkers has remained limited, but multi-biomarker panels have attempted to better reflect the complex physiology of critical illness, and to assist in design and recruitment for clinical trials. Genetic association and gene expression studies have been aimed at classifying risk for and severity in disease, as well as in predicting outcomes. While our understanding of the pathogenesis of critical illness has progressed significantly, the clinical utility of genetic markers remains limited. Novel methods are reaching closer to clinically applicable platforms, both for use in clinical trials and in direct patient care. Although we are not yet living in an era of personalized and precise medical care in the intensive care unit, the future is promising.

Predictors of Circulating Insulin-Like Growth Factor-1 and Insulin-Like Growth Factor Binding Protein-3 in Critical Illness

Objective:To characterize predictors of insulin-like growth factor-1 and insulin-like growth factor–binding protein-3 in acute critical illness with the hypothesis that acute factors associated with critical illness will more strongly predict circulating insulin-like growth factor-1 and insulin-like growth factor–binding protein-3 than chronic clinical or genetic factors. Design:Observational study nested within a large prospective study using multivariable linear regression to model circulating insulin-like growth factor-1 and insulin-like growth factor–binding protein-3 with acute and chronic clinical variables, and genotype from five polymorphisms in insulin-like growth factor pathway genes. Setting:ICUs from two large academic medical centers. Patients:Five hundred forty-three Caucasian patients with risk factors for acute respiratory distress syndrome and available plasma from early in critical illness. Interventions:None. Measurements and Main Results:Total insulin-like growth factor-1 and insulin-like growth factor–binding protein-3 were measured in plasma using IMMULITE assays (Siemens, Malvern, PA). We examined age, gender, body mass index, cirrhosis, and diabetes, as well as Acute Physiology, Age, and Chronic Health Evaluation III score, acute hepatic dysfunction, pneumonia and aspiration, sepsis/septic shock, acute respiratory distress syndrome, and receipt of corticosteroids. Body mass index, cirrhosis, and acute respiratory distress syndrome were strongly associated with insulin-like growth factor-1 and insulin-like growth factor–binding protein-3 levels; Acute Physiology, Age, and Chronic Health Evaluation III was strongly associated with insulin-like growth factor-1 levels; and age was strongly associated with insulin-like growth factor–binding protein-3. Five polymorphisms (IGF1: rs1520220, rs35767, rs2946834; IGFBP1: rs4619; IGFBP3: rs2854746) were analyzed for associations with plasma levels. When genotypes were added to models, rs2854746 was significantly associated with plasma insulin-like growth factor–binding protein-3. Genotype explained an additional 2% of variability with an overall adjusted R-square of 0.18. Conclusions:Despite the acute derangements of critical illness, both acute and chronic health factors significantly influence circulating levels of insulin-like growth factor-1 and insulin-like growth factor–binding protein-3 early in critical illness. rs2854746 is also significantly associated with insulin-like growth factor–binding protein-3 levels in this ICU cohort. Overall, phenotypic and genotypic factors explained only a modest amount of variability in insulin-like growth factor-1 and insulin-like growth factor–binding protein-3. Further research is needed to understand how to apply these findings to patient care.