Exposure to per- and polyfluoroalkyl substances and high-throughput proteomics in Hispanic youth

BACKGROUND

Strong epidemiological evidence shows positive associations between exposure to per- and polyfluoroalkyl substances (PFAS) and adverse cardiometabolic outcomes (e.g., diabetes, hypertension, and dyslipidemia). However, the underlying cardiometabolic-relevant biological activities of PFAS in humans remain largely unclear.

AIM

We evaluated the associations of PFAS exposure with high-throughput proteomics in Hispanic youth.

MATERIAL AND METHODS

We included 312 overweight/obese adolescents from the Study of Latino Adolescents at Risk (SOLAR) between 2001 and 2012, along with 137 young adults from the Metabolic and Asthma Incidence Research (Meta-AIR) between 2014 and 2018. Plasma PFAS (i.e., PFOS, PFOA, PFHxS, PFHpS, PFNA) were quantified using liquid-chromatography high-resolution mass spectrometry. Plasma proteins (n = 334) were measured utilizing the proximity extension assay using an Olink Explore Cardiometabolic Panel I. We conducted linear regression with covariate adjustment to identify PFAS-associated proteins. Ingenuity Pathway Analysis, protein-protein interaction network analysis, and protein annotation were used to investigate alterations in biological functions and protein clusters.

RESULTS

Results after adjusting for multiple comparisons showed 13 significant PFAS-associated proteins in SOLAR and six in Meta-AIR, sharing similar functions in inflammation, immunity, and oxidative stress. In SOLAR, PFNA demonstrated significant positive associations with the largest number of proteins, including ACP5, CLEC1A, HMOX1, LRP11, MCAM, SPARCL1, and SSC5D. After considering the mixture effect of PFAS, only SSC5D remained significant. In Meta-AIR, PFAS mixtures showed positive associations with GDF15 and IL6. Exploratory analysis showed similar findings. Specifically, pathway analysis in SOLAR showed PFOA- and PFNA-associated activation of immune-related pathways, and PFNA-associated activation of inflammatory response. In Meta-AIR, PFHxS-associated activation of dendric cell maturation was found. Moreover, PFAS was associated with common protein clusters of immunoregulatory interactions and JAK-STAT signaling in both cohorts.

CONCLUSION

PFAS was associated with broad alterations of the proteomic profiles linked to pro-inflammation and immunoregulation. The biological functions of these proteins provide insight into potential molecular mechanisms of PFAS toxicity.

Cardiometabolic profiles and proteomics associated with obesity phenotypes in a longitudinal cohort of young adults

To assess cardiometabolic profiles and proteomics to identify biomarkers associated with the metabolically healthy and unhealthy obesity. Young adults (N = 156) enrolled were classified as not having obesity, metabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUHO) based on NCEP ATP-III criteria. Plasma proteomics at study entry were measured using Olink Cardiometabolic Explore panel. Linear regression was used to assess associations between proteomics and obesity groups as well as cardiometabolic traits of glucose, insulin, and lipid profiles at baseline and follow-up visits. Enriched biological pathways were further identified based on the significant proteomic features. Among the baseline 95 (61%) and 61 (39%) participants classified as not having obesity and having obesity (8 MHO and 53 MUHO), respectively. Eighty of the participants were followed-up with an average 4.6 years. Forty-one proteins were associated with obesity (FDR < 0.05), 29 of which had strong associations with insulin-related traits and lipid profiles (FDR < 0.05). Inflammation, immunomodulation, extracellular matrix remodeling and endoplasmic reticulum lumen functions were enriched by 40 proteins. In this study population, obesity and MHO were associated with insulin resistance and dysregulated lipid profiles. The underlying mechanism included elevated inflammation and deteriorated extracellular matrix remodeling function.

Associations of dietary intake and longitudinal measures of per- and polyfluoroalkyl substances (PFAS) in predominantly Hispanic young Adults: A multicohort study

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are pollutants linked to adverse health effects. Diet is an important source of PFAS exposure, yet it is unknown how diet impacts longitudinal PFAS levels.

OBJECTIVE

To determine if dietary intake and food sources were associated with changes in blood PFAS concentrations among Hispanic young adults at risk of metabolic diseases.

METHODS

Predominantly Hispanic young adults from the Children's Health Study who underwent two visits (CHS; n = 123) and young adults from NHANES 2013-2018 who underwent one visit (n = 604) were included. Dietary data at baseline was collected using two 24-hour dietary recalls to measure individual foods and where foods were prepared/consumed (home/restaurant/fast-food). PFAS were measured in blood at both visits in CHS and cross-sectionally in NHANES. In CHS, multiple linear regression assessed associations of baseline diet with longitudinal PFAS; in NHANES, linear regression was used.

RESULTS

In CHS, all PFAS except PFDA decreased across visits (all p < 0.05). In CHS, A 1-serving higher tea intake was associated with 24.8 %, 16.17 %, and 12.6 % higher PFHxS, PFHpS, and PFNA at follow-up, respectively (all p < 0.05). A 1-serving higher pork intake was associated with 13.4 % higher PFOA at follow-up (p < 0.05). Associations were similar in NHANES, including unsweetened tea, hot dogs, and processed meats. For food sources, in CHS each 200-gram increase in home-prepared food was associated with 0.90 % and 1.6 % lower PFOS at baseline and follow-up, respectively, and in NHANES was associated with 0.9 % lower PFDA (all p < 0.05).

CONCLUSION

Results suggest that beverage consumption habits and food preparation are associated with differences in PFAS levels in young adults. This highlights the importance of diet in determining PFAS exposure and the necessity of public monitoring of foods and beverages for PFAS contamination.

Exposure to perfluoroalkyl substances and longitudinal changes in bone mineral density in adolescents and young adults: A multi-cohort study

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) may impair bone development in adolescence, which impacts life-long bone health. No previous studies have examined prospective associations of individual PFAS and their mixture with bone mineral density (BMD) changes in Hispanic young persons, a population at high risk of osteoporosis in adulthood.

OBJECTIVES

To examine associations of individual PFAS and PFAS mixtures with longitudinal changes in BMD in an adolescent Hispanic cohort and examine generalizability of findings in a mixed-ethnicity young adult cohort (58.4% Hispanic).

METHODS

Overweight/obese adolescents from the Study of Latino Adolescents at Risk of Type 2 Diabetes (SOLAR; n = 304; mean follow-up = 1.4 years) and young adults from the Southern California Children's Health Study (CHS; n = 137; mean follow-up = 4.1 years) were included in this study. Plasma PFAS were measured at baseline and dual x-ray absorptiometry scans were performed at baseline and follow-up to measure BMD. We estimated longitudinal associations between BMD and five PFAS via separate covariate-adjusted linear mixed effects models, and between BMD and the PFAS mixture via quantile g-computation.

RESULTS

In SOLAR adolescents, baseline plasma perfluorooctanesulfonic acid (PFOS) was associated with longitudinal changes in BMD. Each doubling of PFOS was associated with an average -0.003 g/cm2 difference in change in trunk BMD per year over follow-up (95% CI: -0.005, -0.0002). Associations with PFOS persisted in CHS young adults, where each doubling of plasma PFOS was associated with an average -0.032 g/cm2 difference in total BMD at baseline (95% CI -0.062, -0.003), though longitudinal associations were non-significant. We did not find associations of other PFAS with BMD; associations of the PFAS mixture with BMD outcomes were primarily negative though non-significant.

DISCUSSION

PFOS exposure was associated with lower BMD in adolescence and young adulthood, important periods for bone development, which may have implications on future bone health and risk of osteoporosis in adulthood.

Per- and polyfluoroalkyl substances, polychlorinated biphenyls, organochlorine pesticides, and polybrominated diphenyl ethers and dysregulation of MicroRNA expression in humans and animals-A systematic review

BACKGROUND

Persistent organic pollutants (POPs) are chemicals characterized by their environmental persistence. Evidence suggests that exposure to POPs, which is ubiquitous, is associated with microRNA (miRNA) dysregulation. miRNA are key regulators in many physiological processes. It is thus of public health concern to understand the relationships between POPs and miRNA as related to health outcomes.

OBJECTIVES

This systematic review evaluated the relationship between widely recognized, intentionally manufactured, POPs, including per- and polyfluoroalkyl substances (PFAS), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (dichlorodiphenyltrichloroethane [DDT], dichlorodiphenyldichloroethylene [DDE], hexachlorobenzene [HCB]), with miRNA expression in both human and animal studies.

METHODS

We used PubMed and Embase to systematically search the literature up to September 29th, 2023. Search results for human and animal studies were included if they incorporated at least one POP of interest in relation to at least one miRNA. Data were synthesized to determine the direction and significance of associations between POPs and miRNA. We utilized ingenuity pathway analysis to review disease pathways for miRNA that were associated with POPs.

RESULTS

Our search identified 38 eligible studies: 9 in humans and 29 in model organisms. PFAS were associated with decreased expression of miR-19, miR-193b, and miR-92b, as well as increased expression of miR-128, miR-199a-3p, and miR-26b across species. PCBs were associated with increased expression of miR-15a, miR-1537, miR-21, miR-22-3p, miR-223, miR-30b, and miR-34a, as well as decreased expression of miR-130a and let-7b in both humans and animals. Pathway analysis for POP-associated miRNA identified pathways related to carcinogenesis.

DISCUSSION

This is the first systematic review of the association of POPs with miRNA in humans and model organisms. Large-scale prospective human studies are warranted to examine the role of miRNA as mediators between POPs and health outcomes.

Proteomic and Metabolomic Signatures of Diet Quality in Young Adults

The assessment of "omics" signatures may contribute to personalized medicine and precision nutrition. However, the existing literature is still limited in the homogeneity of participants' characteristics and in limited assessments of integrated omics layers. Our objective was to use post-prandial metabolomics and fasting proteomics to identify biological pathways and functions associated with diet quality in a population of primarily Hispanic young adults. We conducted protein and metabolite-wide association studies and functional pathway analyses to assess the relationships between a priori diet indices, Healthy Eating Index-2015 (HEI) and Dietary Approaches to Stop Hypertension (DASH) diets, and proteins (n = 346) and untargeted metabolites (n = 23,173), using data from the MetaAIR study (n = 154, 61% Hispanic). Analyses were performed for each diet quality index separately, adjusting for demographics and BMI. Five proteins (ACY1, ADH4, AGXT, GSTA1, F7) and six metabolites (undecylenic acid, betaine, hyodeoxycholic acid, stearidonic acid, iprovalicarb, pyracarbolid) were associated with both diets (p < 0.05), though none were significant after adjustment for multiple comparisons. Overlapping proteins are involved in lipid and amino acid metabolism and in hemostasis, while overlapping metabolites include amino acid derivatives, bile acids, fatty acids, and pesticides. Enriched biological pathways were involved in macronutrient metabolism, immune function, and oxidative stress. These findings in young Hispanic adults contribute to efforts to develop precision nutrition and medicine for diverse populations.

Circulating microRNA expression and nonalcoholic fatty liver disease in adolescents with severe obesity

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases in children and adolescents. NAFLD ranges in severity from isolated hepatic steatosis to nonalcoholic steatohepatitis (NASH), wherein hepatocellular inflammation and/or fibrosis coexist with steatosis. Circulating microRNA (miRNA) levels have been suggested to be altered in NAFLD, but the extent to which miRNA are related to NAFLD features remains unknown. This analysis tested the hypothesis that plasma miRNAs are significantly associated with histological features of NAFLD in adolescents.

AIM

To investigate the relationship between plasma miRNA expression and NAFLD features among adolescents with NAFLD.

METHODS

This study included 81 adolescents diagnosed with NAFLD and 54 adolescents without NAFLD from the Teen-Longitudinal Assessment of Bariatric Surgery study. Intra-operative core liver biopsies were collected from participants and used to characterize histological features of NAFLD. Plasma samples were collected during surgery for miRNA profiling. A total of 843 plasma miRNAs were profiled using the HTG EdgeSeq platform. We examined associations of plasma miRNAs and NAFLD features using logistic regression after adjusting for age, sex, race, and other key covariates. Ingenuity Pathways Analysis was used to identify biological functions of miRNAs that were associated with multiple histological features of NAFLD.

RESULTS

We identified 16 upregulated plasma miRNAs, including miR-193a-5p and miR-193b-5p, and 22 downregulated plasma miRNAs, including miR-1282 and miR-6734-5p, in adolescents with NAFLD. Moreover, 52, 16, 15, and 9 plasma miRNAs were associated with NASH, fibrosis, ballooning degeneration, and lobular inflammation, respectively. Collectively, 16 miRNAs were associated with two or more histological features of NAFLD. Among those miRNAs, miR-411-5p was downregulated in NASH, ballooning, and fibrosis, while miR-122-5p, miR-1343-5p, miR-193a-5p, miR-193b-5p, and miR-7845-5p were consistently and positively associated with all histological features of NAFLD. Pathway analysis revealed that most common pathways of miRNAs associated with multiple NAFLD features have been associated with tumor progression, while we also identified linkages between miR-122-5p and hepatitis C virus and between miR-199b-5p and chronic hepatitis B.

CONCLUSION

Plasma miRNAs were associated with NAFLD features in adolescent with severe obesity. Larger studies with more heterogeneous NAFLD phenotypes are needed to evaluate miRNAs as potential biomarkers of NAFLD.

Postprandial Metabolite Profiles and Risk of Prediabetes in Young People: A Longitudinal Multicohort Study

OBJECTIVE

Prediabetes in young people is an emerging epidemic that disproportionately impacts Hispanic populations. We aimed to develop a metabolite-based prediction model for prediabetes in young people with overweight/obesity at risk for type 2 diabetes.

RESEARCH DESIGN AND METHODS

In independent, prospective cohorts of Hispanic youth (discovery; n = 143 without baseline prediabetes) and predominately Hispanic young adults (validation; n = 56 without baseline prediabetes), we assessed prediabetes via 2-h oral glucose tolerance tests. Baseline metabolite levels were measured in plasma from a 2-h postglucose challenge. In the discovery cohort, least absolute shrinkage and selection operator regression with a stability selection procedure was used to identify robust predictive metabolites for prediabetes. Predictive performance was evaluated in the discovery and validation cohorts using logistic regression.

RESULTS

Two metabolites (allylphenol sulfate and caprylic acid) were found to predict prediabetes beyond known risk factors, including sex, BMI, age, ethnicity, fasting/2-h glucose, total cholesterol, and triglycerides. In the discovery cohort, the area under the receiver operator characteristic curve (AUC) of the model with metabolites and known risk factors was 0.80 (95% CI 0.72-0.87), which was higher than the risk factor-only model (AUC 0.63 [0.53-0.73]; P = 0.001). When the predictive models developed in the discovery cohort were applied to the replication cohort, the model with metabolites and risk factors predicted prediabetes more accurately (AUC 0.70 [95% CI 40.55-0.86]) than the same model without metabolites (AUC 0.62 [0.46-0.79]).

CONCLUSIONS

Metabolite profiles may help improve prediabetes prediction compared with traditional risk factors. Findings suggest that medium-chain fatty acids and phytochemicals are early indicators of prediabetes in high-risk youth.

Associations of per- and polyfluoroalkyl substances, polychlorinated biphenyls, organochlorine pesticides, and polybrominated diphenyl ethers with oxidative stress markers: A systematic review and meta-analysis

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs) are intentionally produced persistent organic pollutants (POPs) that are resistant to environmental degradation. Previous in-vitro and in-vivo studies have shown that POPs can induce oxidative stress, which is linked to neurodegenerative diseases, cardiovascular diseases, and cancer. However, findings in epidemiological studies are inconsistent and an evidence synthesis study is lacking to summarize the existing literature and explore research gaps.

OBJECTIVE

We evaluated the effects of PFAS, PCBs, OCPs, and PBDEs, on oxidative stress biomarkers in epidemiological studies.

METHODS

A literature search was conducted in PubMed, Embase, and Cochrane CENTRAL to identify all published studies related to POPs and oxidative stress up to December 7th, 2022. We included human observational studies reporting at least one exposure to POPs and an oxidative stress biomarker of interest. Random-effects meta-analyses on standardized regression coefficients and effect direction plots with one-tailed sign tests were used for quantitative synthesis.

RESULTS

We identified 33 studies on OCPs, 35 on PCBs, 49 on PFAS, and 12 on PBDEs. Meta-analyses revealed significant positive associations of α-HCH with protein carbonyls (0.035 [0.017, 0.054]) and of 4'4-DDE with malondialdehyde (0.121 [0.056, 0.187]), as well as a significant negative association between 2'4-DDE and total antioxidant capacity (TAC) (-0.042 [-0.079, -0.004]), all β [95%CI]. Sign tests showed a significant positive association between PCBs and malondialdehyde (pone-tailed = 0.03). Additionally, we found significant negative associations of OCPs with acetylcholine esterase (pone-tailed = 0.02) and paraoxonase-1 (pone-tailed = 0.03). However, there were inconsistent associations of OCPs with superoxide dismutase, glutathione peroxidase, and catalase.

CONCLUSIONS

Higher levels of OCPs were associated with increased levels of oxidative stress through increased pro-oxidant biomarkers involving protein oxidation, DNA damage, and lipid peroxidation, as well as decreased TAC. These findings have the potential to reveal the underlying mechanisms of POPs toxicity.

Metabolic Signatures of Youth Exposure to Mixtures of Per- and Polyfluoroalkyl Substances: A Multi-Cohort Study

BACKGROUND

Exposure to per- and polyfluoroalkyl substances (PFAS) is ubiquitous and has been associated with an increased risk of several cardiometabolic diseases. However, the metabolic pathways linking PFAS exposure and human disease are unclear.

OBJECTIVE

We examined associations of PFAS mixtures with alterations in metabolic pathways in independent cohorts of adolescents and young adults.

METHODS

Three hundred twelve overweight/obese adolescents from the Study of Latino Adolescents at Risk (SOLAR) and 137 young adults from the Southern California Children's Health Study (CHS) were included in the analysis. Plasma PFAS and the metabolome were determined using liquid-chromatography/high-resolution mass spectrometry. A metabolome-wide association study was performed on log-transformed metabolites using Bayesian regression with a g-prior specification and g-computation for modeling exposure mixtures to estimate the impact of exposure to a mixture of six ubiquitous PFAS (PFOS, PFHxS, PFHpS, PFOA, PFNA, and PFDA). Pathway enrichment analysis was performed using Mummichog and Gene Set Enrichment Analysis. Significance across cohorts was determined using weighted Z -tests.

RESULTS

In the SOLAR and CHS cohorts, PFAS exposure was associated with alterations in tyrosine metabolism (meta-analysis p = 0.00002 ) and de novo fatty acid biosynthesis (p = 0.03 ), among others. For example, when increasing all PFAS in the mixture from low (∼ 30 th percentile) to high (∼ 70 th percentile), thyroxine (T4), a thyroid hormone related to tyrosine metabolism, increased by 0.72 standard deviations (SDs; equivalent to a standardized mean difference) in the SOLAR cohort (95% Bayesian credible interval (BCI): 0.00, 1.20) and 1.60 SD in the CHS cohort (95% BCI: 0.39, 2.80). Similarly, when going from low to high PFAS exposure, arachidonic acid increased by 0.81 SD in the SOLAR cohort (95% BCI: 0.37, 1.30) and 0.67 SD in the CHS cohort (95% BCI: 0.00, 1.50). In general, no individual PFAS appeared to drive the observed associations.

DISCUSSION

Exposure to PFAS is associated with alterations in amino acid metabolism and lipid metabolism in adolescents and young adults. https://doi.org/10.1289/EHP11372.

Exposure to perfluoroalkyl substances and risk of hepatocellular carcinoma in a multiethnic cohort

Background & Aims

Exposure to poly- and perfluoroalkyl substances (PFAS), a class of persistent organic pollutants, is ubiquitous. Animal studies suggest that PFAS may increase risk of fatty liver and hepatocellular carcinoma (HCC) via impacts on hepatic lipid, amino acid, and glucose metabolism, but human data is lacking. We examined associations between PFAS exposure, altered metabolic pathways, and risk of non-viral HCC.

Methods

In this nested case-control study, pre-diagnostic plasma PFAS and metabolomics were measured in 50 incident HCC cases and 50 individually matched controls from the Multiethnic Cohort (MEC) study. Cases/controls were matched by age, sex, race, and study area. PFAS exposure and risk of HCC were examined using conditional logistic regression. A metabolome-wide association study and pathway enrichment analysis was performed for PFAS exposure and HCC risk, and key metabolites/metabolic pathways were identified using a meet in the middle approach.

Results

High perfluorooctane sulfonic acid (PFOS) levels (90^th percentile from NHANES; >55 μg/L) were associated with 4.5-fold increased risk of HCC (odds ratio 4.5, 95% CI 1.2-16.0). Pathway enrichment analysis showed that PFOS exposure was associated with alterations in amino acid and glycan biosynthesis pathways, which were also associated with HCC risk. We identified 4 metabolites linking PFOS exposure with HCC, including glucose, butyric acid (a short-chain fatty acid), α-ketoisovaleric acid (a branched-chain α-keto acid), and 7α-hydroxy-3-oxo-4-cholestenoate (a bile acid), each of which was positively associated with PFOS exposure and risk of HCC.

Conclusion

This proof-of-concept analysis shows that exposure to high PFOS levels was associated with increased risk of non-viral HCC, likely via alterations in glucose, amino acid, and bile acid metabolism. Larger studies are needed to confirm these findings.

Lay summary

Per- and polyfluoroalkyl substances (PFAS), often referred to as “forever chemicals” because they are difficult to break down and stay in the human body for years, are extremely common and can cause liver damage. In a first of its kind study, we found that exposure to high levels of perfluorooctanesulfonic acid, one of the most common PFAS chemicals, was linked to increased risk of hepatocellular carcinoma in humans. Hepatocellular carcinoma is difficult to treat and is one of the most common forms of liver cancer, and these findings may provide new avenues for helping to prevent this disease.

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Associations of PFAS and risk of hepatocellular carcinoma were tested in humans.

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PFAS and untargeted metabolomics were assessed in pre-diagnostic samples.

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Exposure to high PFOS levels was linked to increased hepatocellular carcinoma risk.

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The likely mechanisms were via alterations in glucose, amino acid, and bile acid metabolism.

Plasma concentrations of lipophilic persistent organic pollutants and glucose homeostasis in youth populations

BACKGROUND

Exposure to lipophilic persistent organic pollutants (POPs) is ubiquitous. POPs are metabolic disrupting chemicals and are potentially diabetogenic.

METHODS

Using a multi-cohort study including overweight adolescents from the Study of Latino Adolescents at Risk (SOLAR, N = 301, 2001-2012) and young adults from the Southern California Children's Health Study (CHS, N = 135, 2014-2018), we examined associations of POPs and risk factors for type 2 diabetes. SOLAR participants underwent annual visits for a median of 2.2 years and CHS participants performed a single visit, during which a 2-h oral glucose tolerance test was performed. Linear mixed models were used to examine associations between plasma concentrations of POPs [4,4'-dichlorodiphenyldichloroethylene (4,4'-DDE), hexachlorobenzene (HCB), PCBs-153, 138, 118, 180 and PBDEs-154, 153, 100, 85, 47] and changes in glucose homeostasis across age and pubertal stage.

RESULTS

In SOLAR, exposure to HCB, PCB-118, and PBDE-153 was associated with dysregulated glucose metabolism. For example, each two-fold increase in HCB was associated with approximately 2 mg/dL higher glucose concentrations at 30 min (p = 0.001), 45 min (p = 0.0006), and 60 min (p = 0.03) post glucose challenge. Compared to individuals with low levels of PCB-118, individuals with high levels exhibited a 4.7 mg/dL (p = 0.02) higher glucose concentration at 15 min and a 3.6 mg/dL (p = 0.01) higher glucose concentration at 30 min. The effects observed with exposure to organochlorine compounds were independent of pubertal stages. PBDE-153 was associated with the development of dysregulated glucose metabolism beginning in late puberty. At Tanner stage 4, exposure to PBDE-153 was associated with a 12.7 mg/dL higher 60-min glucose concentration (p = 0.009) and a 16.1 mg*dl-1*hr-1 higher glucose AUC (p = 0.01). These associations persisted at Tanner 5. In CHS, PBDE-153 and total PBDE were associated with similar increases in glucose concentrations.

CONCLUSION

Our results suggest that childhood exposure to lipophilic POPs is associated with dysregulated glucose metabolism.

Exposure to Perfluoroalkyl Substances and Glucose Homeostasis in Youth

BACKGROUND

Exposure to per- and polyfluoroalkyl substances (PFAS), a prevalent class of persistent pollutants, may increase the risk of type 2 diabetes.

OBJECTIVE

We examined associations between PFAS exposure and glucose metabolism in youth.

METHODS

Overweight/obese adolescents from the Study of Latino Adolescents at Risk of Type 2 Diabetes (SOLAR; n=310) participated in annual visits for an average of 3.3±2.9y. Generalizability of findings were tested in young adults from the Southern California Children's Health Study (CHS; n=135) who participated in a clinical visit with a similar protocol. At each visit, oral glucose tolerance tests were performed to estimate glucose metabolism and β-cell function via the insulinogenic index. Four PFAS were measured at baseline using liquid chromatography-high-resolution mass spectrometry; high levels were defined as concentrations >66th percentile.

RESULTS

In females from the SOLAR, high perfluorohexane sulfonate (PFHxS) levels (≥2.0 ng/mL) were associated with the development of dysregulated glucose metabolism beginning in late puberty. The magnitude of these associations increased postpuberty and persisted through 18 years of age. For example, postpuberty, females with high PFHxS levels had 25-mg/dL higher 60-min glucose (95% CI: 12, 39mg/dL; p<0.0001), 15-mg/dL higher 2-h glucose (95% CI: 1, 28mg/dL; p=0.04), and 25% lower β-cell function (p=0.02) compared with females with low levels. Results were largely consistent in the CHS, where females with elevated PFHxS levels had 26-mg/dL higher 60-min glucose (95% CI: 6.0, 46mg/dL; p=0.01) and 19-mg/dL higher 2-h glucose, which did not meet statistical significance (95% CI: -1, 39mg/dL; p=0.08). In males, no consistent associations between PFHxS and glucose metabolism were observed. No consistent associations were observed for other PFAS and glucose metabolism.

DISCUSSION

Youth exposure to PFHxS was associated with dysregulated glucose metabolism in females, which may be due to changes in β-cell function. These associations appeared during puberty and were most pronounced postpuberty. https://doi.org/10.1289/EHP9200.

Platelet-Rich Plasma Versus Hyaluronic Acid for Knee Osteoarthritis: A Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND

Platelet-rich plasma (PRP) and hyaluronic acid (HA) are 2 nonoperative treatment options for knee osteoarthritis (OA) that are supposed to provide symptomatic relief and help delay surgical intervention.

PURPOSE

To systematically review the literature to compare the efficacy and safety of PRP and HA injections for the treatment of knee OA.

STUDY DESIGN

Meta-analysis of level 1 studies.

METHODS

A systematic review was performed by searching PubMed, the Cochrane Library, and Embase to identify level 1 studies that compared the clinical efficacy of PRP and HA injections for knee OA. The search phrase used was platelet-rich plasma hyaluronic acid knee osteoarthritis randomized. Patients were assessed via the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), visual analog scale (VAS) for pain, and Subjective International Knee Documentation Committee (IKDC) scale. A subanalysis was also performed to isolate results from patients who received leukocyte-poor and leukocyte-rich PRP.

RESULTS

A total of 18 studies (all level 1) met inclusion criteria, including 811 patients undergoing intra-articular injection with PRP (mean age, 57.6 years) and 797 patients with HA (mean age, 59.3 years). The mean follow-up was 11.1 months for both groups. Mean improvement was significantly higher in the PRP group (44.7%) than the HA group (12.6%) for WOMAC total scores (P < .01). Of 11 studies based on the VAS, 6 reported PRP patients to have significantly less pain at latest follow-up when compared with HA patients (P < .05). Of 6 studies based on the Subjective IKDC outcome score, 3 reported PRP patients to have significantly better scores at latest follow-up when compared with HA patients (P < .05). Finally, leukocyte-poor PRP was associated with significantly better Subjective IKDC scores versus leukocyte-rich PRP (P < .05).

CONCLUSION

Patients undergoing treatment for knee OA with PRP can be expected to experience improved clinical outcomes when compared with HA. Additionally, leukocyte-poor PRP may be a superior line of treatment for knee OA over leukocyte-rich PRP, although further studies are needed that directly compare leukocyte content in PRP injections for treatment of knee OA.

The importance of lean mass and iron deficiency when comparing hemoglobin mass in male and female athletic groups

Hemoglobin mass (Hbmass) is important for athletes because it helps determine maximal aerobic power. This study examined how lean mass, iron deficiency (ID), and sex influence Hbmass in athletic and nonathletic groups. NCAA Division I student athletes (21 men, 75 women; altitude: 1,625 m) were recruited from six athletic teams; 14 male and 12 female full-time students (non-varsity athletes) served as control subjects. Hbmass, body composition, and iron homeostasis parameters, including ferritin, soluble transferrin receptor (sTfR), hepcidin, erythroferrone, and 10 inflammatory cytokines, were measured two to four times across a competitive/training season. ID was defined as ferritin < 25 ng/mL. Hbmass was more closely related to lean mass (r² = 0.90) than body mass (r² = 0.69, P < 0.01). Compared with female subjects, male subjects had 19.9% higher Hbmass relative to body mass (Hbmass_BM) but only 7.5% higher Hbmass relative to lean mass (Hbmass_LEAN) (both P < 0.001). Prevalence of ID was higher in female than male subjects (47% vs. 9%, P < 0.01) but did not vary between groups. Hbmass_LEAN was 5% lower in ID vs. non-ID female subjects; Hbmass_BM was not different. ID was associated with lower hepcidin, elevated sTfR, and elevated erythroferrone but not with differences in inflammatory cytokines. Hbmass varied significantly between athletic groups and across sex, but the majority of these differences are explained by differences in lean mass. ID was common in female subjects and was associated with lower Hbmass_LEAN and hepcidin but not with differences in Hbmass_BM or inflammatory cytokines. Hbmass relative to lean mass seems advantageous when monitoring iron deficiency.NEW & NOTEWORTHY Differences in hemoglobin mass (Hbmass) between groups and across sex are primarily due to differences in lean mass. Iron deficiency (ID) independently decreases Hbmass; this effect is best characterized with Hbmass relative to lean mass. ID is common in females and is associated with lower hepcidin and elevated erythroferrone but not with differences in inflammatory cytokines. Hbmass relative to lean mass accurately quantifies hematological alterations secondary to iron deficiency.

0231 Sleep Behaviors of Female Collegiate Athletes

Introduction

Sleep is critical to cognitive and physiologic function. It is likely being a female collegiate student athlete places unique demands upon sleep behavior. Therefore, we aimed to study the sleep behavior of female collegiate athletes versus a female collegiate control group.

Methods

Full time female students from the University of Colorado Boulder (Altitude = 1,624 m) were recruited from NCAA Division I athletic teams: Cross Country (XC, n=10), Lacrosse (LAX, n =17), Soccer (SOC, n=15), Golf (GOLF, n=6), Tennis (TENN, n=9). 31 female full-time students were recruited as Controls (CONT). Sleep was monitored with wrist actigraphy (Spectrum Actiwatch, Phillips) for a minimum of one week. Subjects were instructed to wear actigraphs at all times except during competition. Outcome variables included nightly sleep duration, total 24h sleep duration, sleep efficiency, sleep midpoint, social jet lag (SJL) and nap duration/frequency.

Results

On weekdays, XC, LAX and SOC had greater nightly sleep durations ~8.5h compared to TENN, GOLF and CONT (p&lt;0.05). Relative to other groups, XC had the earliest sleep midpoint (3:34 AM ± 1:20 vs. 3:53 AM ± 1:15) while SOC and LAX had the lowest sleep efficiency (~87.3 ± 3.2% vs. ~89.6 ± 3.4%) (all p&lt;0.05). There was significant SJL among CONT, LAX and SOC (difference of sleep midpoints on weekdays and weekends; p&lt;0.05). While nightly sleep duration varied significantly between different groups, there were no significant differences in total daily sleep duration when naps are included. A greater percentage of CONT (87 %) napped compared to athletes (64.2 %) (p&lt;0.05); napping duration/frequency of naps per week were not different between groups.

Conclusion

Variations in sleep behavior exists between collegiate student athletes based upon varsity sport with some sports being similar to controls and others being significantly different. Additional research is needed to determine the significance of these findings to academic and athletic performance.

Support

PAC-12 Student-Athlete Health and Wellbeing Initiative, Grant #1554240

0228 The Impact of Westward Travel Across 9 Time Zones on Sleep Behaviors of Female Collegiate Athletes

Introduction

Jet lag can significantly impact an athlete’s health and performance. However, the effect of ultra long-haul travel (&gt; 12h flying time) westward across nine time zones on the sleep of female collegiate athletes is limited. We therefore studied the sleep behavior of NCAA Division I female volleyball players on an exhibition tour to China.

Methods

For this observational study, eleven females were recruited from a NCAA Division I Volleyball team. During the Tour, sleep behavior was monitored using wrist actigraphy (Actiwatch Spectrum, Phillips) before (5 days) outbound travel (PRE-FLIGHT), during air travel to (1) & from (2) China (FLIGHT-DAY 1 & 2) and during the athletes’ tour while in China (TOUR-DAY 1–8). Athletes were instructed to wear the actigraphs at all times, except during competition. Standard parameters were collected from the actigraph including sleep durations and sleep efficiency and expressed as mean ± sd.

Results

Sleep duration and sleep efficiency were similar for PRE-FLIGHT days (~8.3 hrs ± 1.5, 90.6 ± 3.2%). Sleep duration and efficiency were significantly lower on FLIGHT-DAY 1 & 2 compared to TOUR-DAY and PRE-FLIGHT, but were not significantly different from each other (~5.2 ± 2.4h, 80.5 ± 8.8%). Sleep duration during TOUR-DAY 1–7 followed a quadratic relationship, peaking on TOUR-DAY 1 and reaching a nadir on TOUR-DAY 5, before increasing again through TOUR-DAY 7 (p&lt;0.05). Sleep duration on TOUR-DAY 8 (~5.9 ± 0.9 h) was significantly lower than PRE-FLIGHT and TOUR-DAY 1,2,6 & 7.

Conclusion

During travel female collegiate volleyball players showed sleep disturbance. Implementation of sleep interventions for jet lag are warranted for athletes traveling across multiple time zones.

Support

PAC-12 Student-Athlete Health and Wellbeing Initiative, Grant #1554240

Intermittent low dose carbon monoxide inhalation does not influence glucose regulation in overweight adults: a randomized controlled crossover trial

NEW FINDINGS

What is the central question of this study? Low dose carbon monoxide (CO) inhalation plays a role in regulating proteins involved in glucose metabolism; does low dose CO improve glucose and insulin responses to an oral glucose tolerance test in overweight adults? What is the main finding and its importance? Five days of intermittent CO inhalation does not alter the glucose or insulin responses to ingestion of a glucose bolus in overweight adults. Low dose CO is utilized in various physiological assessment procedures; these findings allow researchers and clinicians to utilize these procedures without concern of altering glucose metabolism.

ABSTRACT

Low dose carbon monoxide (CO) inhalation upregulates several proteins important for glucose metabolism. Such changes could be clinically significant and may be relevant to those who use CO as a research tool. We hypothesized that low dose CO inhalation would improve glucose and insulin responses to an oral glucose bolus in overweight humans. Eleven young adults (5 men, 6 women; body mass index: 25-35 kg m^-2 ) were included in this randomized, placebo-controlled, single-blinded crossover study. Following screening, participants completed two 7-day protocols with a 4-week washout. Twenty-four hours prior to and following five consecutive days of either once daily CO (men: 1.2 ml (kg body mass)^-1 ; women: 1.0 ml (kg body mass)^-1 ) or placebo (room air) inhalation, participants underwent oral glucose tolerance tests (OGTT). For key outcome variables, there were no significant main effects or interactions across condition or time point (mean ± SD), including fasting glucose (mg dl^-1 : pre-placebo: 85.2 ± 10.1; post-placebo: 82.9 ± 10.6; pre-CO: 83.6 ± 7.7; post-CO: 84.0 ± 9.0), 2 h post glucose (mg dl^-1 : pre-placebo: 100.9 ± 20.0; post-placebo: 98.7 ± 13.1; pre-CO: 94.2 ± 23.2; post-CO: 94.4 ± 14.9), or the Matsuda index (pre-placebo: 16.1 ± 11.5; post-placebo: 20.3 ± 24.7; pre-CO: 15.6 ± 15.3; post-CO: 17.5 ± 16.8). In conclusion, 5 days of low dose CO administration did not influence glucose and insulin responses to an OGTT in overweight adults. Low dose CO inhalation is utilized in a variety of physiological assessment procedures; these findings allow researchers to utilize these procedures without concern of altering glucose metabolism.

The "Outside-In" Lesion of Hip Impingement and the "Inside-Out" Lesion of Hip Dysplasia: Two Distinct Patterns of Acetabular Chondral Injury

BACKGROUND

Femoroacetabular impingement (FAI) and acetabular dysplasia lead to acetabular cartilage damage that commonly results in the chondral flaps seen during hip arthroscopy.

PURPOSE

To compare the acetabular chondral flap morphology seen during hip arthroscopy ("outside-in" vs "inside-out") with clinical and radiographic parameters underlying FAI and hip dysplasia.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Patients who underwent hip arthroscopy by the senior author between 2013 and 2017 with a finding of Outerbridge grade IV acetabular chondral flap were included. Each procedure was retrospectively reviewed on video and chondral flaps were categorized as inside-out or outside-in. An inside-out designation was made for flaps exhibiting an intact chondrolabral junction with a detached sleeve of chondrolabral tissue from the central acetabulum, and an outside-in designation was made for centrally anchored flaps exhibiting a break in the chondrolabral junction. Radiographic markers of hip impingement/dysplasia were noted for each patient during assignment into 1 of 2 radiographic groups: group 1, lateral center edge angle (LCEA) >20 with FAI, and group 2, LCEA ≤20 with or without cam FAI. Associations between chondral flap morphology and clinical diagnosis were tested using a chi-square test.

RESULTS

Overall, 95 patients (103 hips) were included (group 1, 78 hips; group 2, 25 hips). Among hips in group 2, 24 had concurrent cam FAI. There was a significant relationship between chondral flap type and radiographic diagnosis (P < .001). Among group 1 hips, 78% exhibited outside-in type chondral flaps, 12% exhibited combined outside-in and inside-out flaps, and 10% exhibited inside-out flaps. Group 2 hips showed 72% inside-out type chondral flaps, 16% combined, and 12% outside-in. Hips exhibiting outside-in type flaps were significantly more likely to be in group 1 (positive predictive value [PPV], 91%; negative predictive value [NPV], 69%). Similarly, hips exhibiting inside-out type flaps were significantly more likely to be in group 2 (PPV, 56%; NPV, 95%). Altogether, 90% of group 1 hips exhibited an outside-in lesion and 88% of group 2 hips exhibited an inside-out lesion.

CONCLUSION

Acetabular chondral flap type visualized during hip arthroscopy correlates with radiographic markers of hip impingement and hip instability. Outside-in flaps are highly predictive of FAI, whereas inside-out flaps are highly predictive of acetabular dysplasia.

Effects of Hip Arthroscopy Without a Perineal Post on Venous Blood Flow, Muscle Damage, Peripheral Nerve Conduction, and Perineal Injury: A Prospective Study

BACKGROUND

Prior reports of hip arthroscopy using a perineal post have established the risks of groin soft tissue injury, sexual dysfunction, and altered lower extremity neurovascular function. These parameters have not been investigated for hip arthroscopy without the use of a perineal post.

PURPOSE

To evaluate the effects of postless hip arthroscopy on lower extremity venous blood flow, nerve conduction, muscle tissue damage, and perineal injury.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Patients between the ages of 18 and 50 years undergoing an elective unilateral or simultaneous bilateral hip arthroscopy were enrolled. Creatine phosphokinase (CPK)-MM levels and D-dimer levels were obtained preoperatively, immediately postoperatively, and 7 to 12 days postoperatively. Bilateral Doppler ultrasonography of the common femoral vein (CFV) and popliteal vein were conducted intraoperatively. Somatosensory evoked potentials (SSEPs) and transcranial motor evoked potentials (TcMEPs) were measured intraoperatively for the lower limbs. Perineal injury was assessed at 7 to 12 days postoperatively.

RESULTS

35 patients underwent a total of 40 hip arthroscopies. No significant differences were found in venous blood flow between the operative and nonoperative legs for either the CFV or popliteal vein. SSEP monitoring of the peroneal nerve showed no significant reduction when traction was applied to the operative leg, 90.8%, compared with final measurement just before it was removed, 72.4% (P = .09). For TcMEPs measured in the muscles outside of the traction boots, no significant changes were seen in the percentage of cases with abnormal measurements throughout the procedure. CPK-MM levels preoperatively, immediately postoperatively, and 7 to 12 days after surgery were on average 112, 190, and 102 IU/L, respectively (normal, <156 IU/L). No significant relationship was found between abnormal venous flow and altered D-dimer levels. No clinical evidence of nerve or vascular injury was encountered, and no groin soft tissue complications were observed during the study period.

CONCLUSION

Postless hip arthroscopy is safe, without a notable reduction of venous blood flow or alteration of nerve function in the operative leg. Muscle tissue damage is subclinical, transient, and reduced compared with distraction with a post. No cases of perineal injury were observed during the study period.

Increased Prevalence of Femoroacetabular Impingement in Patients With Proximal Hamstring Tendon Injuries

PURPOSE

To determine the prevalence of clinically diagnosed femoroacetabular impingement (FAI) in a consecutive series of patients presenting with proximal hamstring tendon injury and to correlate this with pelvic anatomic factors.

METHODS

The prevalence of clinically symptomatic cam-, pincer-, and mixed-type and overall FAI was calculated among a consecutive series of patients presenting to a hip preservation clinic with a confirmed clinical and radiographic diagnosis of proximal hamstring tendon injury between 2012 and 2017. The presence of a cam lesion was determined by an alpha angle > 50° on radiographs and computed tomography radial sequences of the head-neck junction and a femoral head-neck offset ratio < 0.18. Clinical diagnoses of osseous impingement were determined according to accepted pathomorphologic signs and measurements. A diagnosis of FAI was confirmed by imaging findings of acetabular overcoverage for pincer-type FAI and the presence of an anterior or lateral cam lesion for cam-type FAI.

RESULTS

Overall, 120 hips in 97 patients (mean age, 45 years) were included in this study. A clinical diagnosis of FAI was noted in 70.8% of hips (pincer-type 9.2%, cam-type 40.8%, mixed-type 20.8%), an approximate 2- to 7-fold increased prevalence in comparison with the general population from prior studies.

CONCLUSIONS

The prevalence of FAI is high in patients with symptomatic proximal hamstring tendon pathology. Because FAI results in restriction of hip range of motion and altered pelvic tilt, future studies are warranted to investigate whether the presence of FAI acts as a predisposing factor for injury to the hamstring muscle complex.

LEVEL OF EVIDENCE

Level IV, case series.

Combined Lateral Osseolabral Coverage Is Normal in Hips With Acetabular Dysplasia

PURPOSE

To compare the lateral osseolabral coverage between groups of patients with different degrees of acetabular bony coverage using a magnetic resonance imaging parameter known as the combined lateral center-edge angle (cLCEA).

METHODS

The cLCEA was measured among a consecutive series of patients presenting to a dedicated hip preservation surgeon with a magnetic resonance imaging scan. The cLCEA was measured using a coronal T1 or proton density image and was defined as the angle subtended by (1) a line through the center of the femoral head and orthogonal to the transverse line passing through the teardrops of both hips and (2) an oblique line drawn from the center of the femoral head to the free edge of the lateral acetabular labrum. The average difference between the lateral center-edge angle (LCEA) and the cLCEA was calculated and compared between groups based on acetabular bony coverage: dysplasia (LCEA <20°), borderline dysplasia (LCEA 20°-24.9°), normal coverage (LCEA 25°-39.9°), and overcoverage (LCEA ≥40°).

RESULTS

In total, 341 patients (386 hips) were included. There were no significant differences in cLCEA between hips with normal acetabular coverage and dysplasia (P = .10) or borderline dysplasia (P = .46). Despite the large difference in mean LCEA between dysplasia (14.8° ± 3.9°) and acetabular overcoverage (43.1° ± 2.8°), the mean cLCEA values exhibited only a modest difference (44.7° ± 4.9° vs 52.7° ± 4.5°, respectively). Concordantly, hips with dysplasia exhibited the largest difference between mean LCEA and cLCEA (delta = 29.9° ± 4.7°) and hips with acetabular overcoverage had the smallest difference between measures (9.6° ± 5.2°).

CONCLUSIONS

With decreasing acetabular bony coverage, there is increasing labral size such that the total osseolabral coverage, measured by the combined LCEA, remains equivalent between hips with normal acetabular coverage versus dysplasia.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

The Influence of Oxygen Saturation on the Relationship Between Hemoglobin Mass and VO 2 max

Hemoglobin mass (tHb) is a key determinant of maximal oxygen uptake (VO ₂ max). We examined whether oxyhemoglobin desaturation (ΔS _a O ₂ ) at VO ₂ max modifies the relationship between tHb and VO ₂ max at moderate altitude (1,625 m). Seventeen female and 16 male competitive, endurance-trained moderate-altitude residents performed two tHb assessments and two graded exercise tests on a cycle ergometer to determine VO ₂ max and ΔS _a O ₂ . In males and females respectively, VO ₂ max (ml·kg ⁻¹ ·min ⁻¹ ) ranged from 62.5–83.0 and 44.5–67.3; tHb (g·kg ⁻¹ ) ranged from 12.1–17.5 and 9.1–13.0; and S _a O ₂ at VO ₂ max (%) ranged from 81.7–94.0 and 85.7–95.0. tHb was related to VO ₂ max when expressed in absolute terms and after correcting for body mass (r=0.94 and 0.86, respectively); correcting by ΔS _a O ₂ did not improve these relationships (r=0.93 and 0.83). Additionally, there was a negative relationship between tHb and S _a O ₂ at VO ₂ max (r=–0.57). In conclusion, across a range of endurance athletes at moderate altitude, the relationship between tHb and VO ₂ max was found to be similar to that observed at sea level. However, correcting tHb by ΔS _a O ₂ did not explain additional variability in VO ₂ max despite significant variability in ΔS _a O ₂ ; this raises the possibility that tHb and exercise-induced ΔS _a O ₂ are not independent in endurance athletes.

Standardizing the Prearthritic Hip Joint Space Width: An Analysis of 994 Hips

PURPOSE

The purposes of this study were (1) to define a normal prearthritic hip joint space width (JSW) in symptomatic and asymptomatic patients with various degrees of acetabular coverage based on the lateral center edge angle (LCEA) and (2) to determine predictors of JSW using patient-specific variables.

METHODS

In a consecutive series of patients presenting to a hip preservation clinic between July 2012 and April 2016, a standard weight-bearing anteroposterior pelvic view was obtained. JSW was defined as the distance between the bony contour of the acetabular rim and femoral head in 2 locations (lateral and medial weight-bearing zone). Hips with severe anatomic deformity, a Tönnis grade >0, or a lateral or medial JSW <2.5 mm were excluded. A linear mixed model analysis was performed in order to determine which variables (age, sex, side, height, weight, symptomatic/asymptomatic, LCEA, and clinical diagnosis) were significantly related to JSW.

RESULTS

A total of 994 hips were included. LCEA was found to be a significant predictor of both the lateral and medial JSW, with a decreased JSW associated with increasing degrees of acetabular bony coverage (P < .02). A mean 0.9 mm (20%) difference in medial JSW was found between patients with frank dysplasia (LCEA <20°) compared with those with pincer-type FAI (LCEA ≥40°). There was no difference between symptomatic and asymptomatic hips, either for lateral (asymptomatic: 4.51 ± 0.83 mm; symptomatic: 4.52 ± 0.85 mm; P = .58) or medial JSW (asymptomatic: 4.02 ± 0.96 mm; symptomatic: 3.97 ± 0.84 mm; P = .49).

CONCLUSIONS

The LCEA is a significant predictor of hip JSW, with the mean JSW decreasing with increasing degrees of acetabular bony coverage. Joint space is not a major factor in symptomatology in adults with prearthritic hip pain.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Hip Distraction Without a Perineal Post: A Prospective Study of 1000 Hip Arthroscopy Cases

BACKGROUND

Hip arthroscopy has traditionally been performed with a perineal post, resulting in various groin-related complications, including pudendal nerve neurapraxias, vaginal tears, and scrotal necrosis.

PURPOSE

To assess the safety of a technique for hip distraction without the use of a perineal post.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

We prospectively analyzed a consecutive cohort of 1000 hips presenting to a dedicated hip preservation clinic; all patients had hip pain and were subsequently treated with hip arthroscopy. Demographic variables, hip pathology, and lateral center edge angle were recorded for each case. In the operating room, the patient's feet were placed in traction boots in a specifically designed distraction setup, and the operative table was placed in varying degrees of Trendelenburg. With this technique, enough resistance is created by gravity and friction between the patient's body and the bed to allow for successful hip distraction without the need for a perineal post. In a subset of 309 hips (n = 281 patients), the degrees of Trendelenburg as well as the distraction force were analyzed.

RESULTS

The mean ± SD Trendelenburg angle used among the subset of 309 hips was 11° ± 2°. The mean initial distraction force necessary was 90 ± 28 lb, which decreased to 65 ± 24 lb by 30 minutes after traction initiation ( P < .0001). The most important variables in determining initial force for this cohort of patients were, in order of magnitude, sex ( P < .0001), weight ( P < .0001), and lateral center edge angle ( P < .01). No groin-related complications occurred among the entire cohort of patients, including soft tissue or nerve-related complications. The rate of deep venous thrombosis was 2 in 1000.

CONCLUSION

The use of the Trendelenburg position and a specially designed distraction setup during hip arthroscopy allows for safe hip distraction without a perineal post, thereby eliminating groin-related soft tissue and nerve complications. Certain patient variables can be used to estimate the required distraction force and inclination angle with this method.

The Iliofemoral Line: A Radiographic Sign of Acetabular Dysplasia in the Adult Hip

BACKGROUND

Several radiographic parameters utilized for the diagnosis of acetabular dysplasia in adults suffer from poor reproducibility and reliability.

PURPOSE

To define and validate a novel radiographic parameter (the iliofemoral line [IFL]) for the detection of frank and borderline hip dysplasia and to compare the sensitivity and specificity of this radiographic marker to those of previously validated qualitative parameters.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

A consecutive cohort of 222 adult patients (436 hips) undergoing hip preservation surgery was included. The IFL, which extends from the lateral femoral neck through the inner cortical lip of the iliac crest, intersects the femoral head in cases of dysplasia. Percent medialization of the IFL was defined as the horizontal distance of the exposed femoral head lateral to the IFL, relative to the horizontal femoral head width at the center of the femoral head.

RESULTS

Percent medialization of the IFL was strongly correlated to the lateral center edge angle ( P < .0001). Values of percent medialization ranging from 15% to 22% predicted the presence of borderline hip dysplasia with a sensitivity of 62% and specificity of 89%, while values exceeding 22% predicted the presence of frank acetabular dysplasia with a sensitivity of 77% and specificity of 94%. By comparison, abnormality of the Shenton line demonstrated a sensitivity of 3.7% and specificity of 97% for the detection of borderline dysplasia and a sensitivity of 16% and specificity of 99% for the detection of frank acetabular dysplasia. Compared with the Shenton line, percent medialization of the IFL was significantly more sensitive for the detection of both borderline and frank acetabular dysplasia (both P < .0001). The intraobserver and interobserver reproducibility of the horizontal difference outside the IFL were 0.99 and 0.96, respectively.

CONCLUSION

Percent medialization of the IFL is a reliable and accurate radiographic marker of frank acetabular dysplasia and, to a lesser extent, borderline dysplasia. The use of this radiographic parameter as an additional tool may enable the earlier detection of borderline and frank hip dysplasia in young adults presenting with hip pain.

Ten Days of Intermittent, Low-dose Carbon Monoxide Inhalation does not Significantly Alter Hemoglobin Mass, Aerobic Performance Predictors, or Peak-power Exercise Tolerance

Carbon monoxide (CO) rebreathing procedures are used to assess hemoglobin mass (Hbmass) but recent evidence suggests that CO is a signaling molecule that may alter physiological functions. We examined the effects of 10 days of intermittent, low-dose CO inhalation on Hbmass, aerobic performance predictors, and peak-power exercise tolerance. 18 recreationally-active men were randomized to either CO or placebo inhalation groups in a single-blind, pre-post parallel-groups trial. Primary outcomes were assessed before and after an intervention period during which subjects inhaled a bolus of 1.2 ml kg(-1) CO or placebo (room air) for 30 s, once per day on 10 days over a 12-day period. Cycling tests were performed >16 h following CO inhalation to exclude acute effects of CO exposure. CO inhalation elevated carboxyhemoglobin by 4.4±0.4% (mean±SD) following each exposure. Compared to placebo, chronic CO inhalation did not significantly alter Hbmass (p=0.99), peak oxygen uptake (p=0.59), peak power output (p=0.10), submaximal oxygen uptake (p=0.91), submaximal RER (p=0.22), lactate threshold (p=0.65), or peak-power exercise tolerance (p=0.60). In conclusion, our data support the ability to perform repeated measurements of Hbmass using CO rebreathing over a 12-day period without altering physiological responses.

Haemoglobin mass alterations in healthy humans following four-day head-down tilt bed rest

NEW FINDINGS

What is the central question of this study? Is haemoglobin mass (Hbmass) decreased following 4 days of head-down tilt bed rest (HDTBR), and does increased red blood cell (RBC) destruction mediate this adaptation? What is the main finding and its importance? Haemoglobin mass was increased immediately following HDTBR, before decreasing below baseline 5 days after return to normal living conditions. The transient increase in Hbmass might be the result of decreased RBC destruction, but it is also possible that spleen contraction after HDTBR contributed to this adaptation. Our data suggest that the decreased Hbmass 5 days following HDTBR resulted from decreased RBC production, not increased RBC destruction. Rapid decreases in haemoglobin mass (Hbmass) have been reported in healthy humans following spaceflight and descent from high altitude. It has been proposed that a selective increase in the destruction of young red blood cells (RBCs) mediates these decreases, but conclusive evidence demonstrating neocytolysis in humans is lacking. Based on the proposed triggers and time course of adaptation during spaceflight, we hypothesized that Hbmass would be reduced after 4 days of -6 deg head-down tilt bed rest (HDTBR) and that this would be associated with evidence for increased RBC destruction. We assessed Hbmass in seven healthy, recreationally active men before (PRE), 5 h after (POST) and 5 days after (POST5) 4 days of HDTBR. The concentration of erythropoietin decreased from 7.1 ± 1.8 mIU ml(-1) at PRE to 5.2 ± 2.8 mIU ml(-1) at POST (mean ± SD; P = 0.028). Contrary to our hypothesis, Hbmass was increased from 817 ± 135 g at PRE to 849 ± 141 g at POST (P = 0.014) before decreasing below PRE to 789 ± 139 g at POST5 (P = 0.027). From PRE to POST, the concentration of haptoglobin increased from 0.54 ± 0.32 to 0.68 ± 0.28 g l(-1) (P = 0.013) and the concentration of bilirubin decreased from 0.50 ± 0.24 to 0.32 ± 0.11 mg dl(-1) (P = 0.054), suggesting that decreased RBC destruction might have contributed to the increased Hbmass. However, it is possible that spleen contraction following HDTBR also played a role in the increase in Hbmass at POST, but as the transient increase in Hbmass was unexpected, we did not collect data that would provide direct evidence for or against spleen contraction. From PRE to POST5, the concentration of soluble transferrin receptor decreased from 20.7 ± 3.9 to 17.1 ± 3.3 nmol l(-1) (P = 0.018) but the concentrations of ferritin, haptoglobin and bilirubin were not significantly altered, suggesting that the decrease in Hbmass was mediated by decreased RBC production rather than increased RBC destruction. Peak oxygen uptake decreased by 0.31 ± 0.16 l min(-1) from PRE to POST (P = 2 × 10(-4) ) but was not significantly altered at POST5 compared with PRE. Overall, these findings indicate that 4 days of HDTBR does not increase RBC destruction and that re-examination of the time course and mechanisms of Hbmass alterations following short-term spaceflight and simulated microgravity is warranted.

Kinetic and mechanistic analysis of the RNA polymerase II transcrption reaction at the human interleukin-2 promoter

Interleukin-2 (IL-2) is a cytokine critical for the proper stimulation of T-cells during the mammalian immune response. Shortly after T-cell stimulation, transcription of the IL-2 gene is upregulated. Here, we studied the kinetic mechanism of basal transcription at the IL-2 promoter using a human in vitro RNA polymerase II transcription system. We experimentally divided the transcription reaction into discrete steps, including preinitiation complex formation, initiation, escape commitment, and promoter escape. Using pre-steady state approaches, we measured the rate at which each of these steps occurs. We found that the rate of functional preinitiation complex formation limits the overall rate of transcription at the IL-2 promoter under the conditions described here. Furthermore, we found that the recruitment of TFIIF and RNA polymerase II to a TFIID/TFIIA/TFIIB/promoter complex dictates the rate of preinitiation complex formation. The rate of synthesis of 28 nt RNA from preinitiation complexes was rapid compared to the rate of preinitiation complex formation. Moreover, we found that the synthesis of a four nucleotide RNA was necessary and sufficient to rapidly complete the escape commitment step of transcription at the IL-2 promoter. Comparative experiments with the adenovirus major late promoter revealed that, while the overall mechanism of transcription is the same at the two promoters, promoter sequence and/or architecture dictate the rate of promoter escape. We present a kinetic model for a single round of basal transcription at the IL-2 promoter that provides insight into mechanisms by which the IL-2 gene is transcriptionally regulated.

Expression and purification of recombinant human c-Fos/c-Jun that is highly active in DNA binding and transcriptional activation in vitro

c-Fos and c-Jun are members of the AP-1 family of transcriptional activators that regulate the expression of genes during cell proliferation. To facilitate in vitro studies of mechanisms of transcriptional activation by c-Jun and c-Fos we developed a method for obtaining recombinant c-Fos/c-Jun that is highly active in DNA binding and transcriptional activation in vitro. Full-length human c-Fos and c-Jun were expressed in Escherichia coli. The expression of c-Fos was dependent on a helper plasmid that encodes rare (Arg)tRNAs. Both over-expressed c-Fos and c-Jun were recovered from inclusion bodies. A c-Fos/c-Jun complex was generated by co-renaturation and purified via a His-tag on the full-length human c-Fos. The resulting c-Fos/c-Jun bound DNA with high affinity and specificity, and activated transcription in a reconstituted human RNA polymerase II transcription system. The availability of active recombinant human c-Fos/c-Jun will allow future biochemical studies of these important transcriptional activators.

c-Jun binds the N terminus of human TAF(II)250 to derepress RNA polymerase II transcription in vitro

c-Jun is an oncoprotein that activates transcription of many genes involved in cell growth and proliferation. We studied the mechanism of transcriptional activation by human c-Jun in a human RNA polymerase II transcription system composed of highly purified recombinant and native transcription factors. Transcriptional activation by c-Jun depends on the TATA-binding protein (TBP)-associated factor (TAF) subunits of transcription factor IID (TFIID). Protein-protein interaction assays revealed that c-Jun binds with high specificity to the largest subunit of human TFIID, TAF(II)250. The region of TAF(II)250 bound by c-Jun lies in the N-terminal 163 amino acids. This same region of TAF(II)250 binds to TBP and represses its interaction with TATA boxes, thereby decreasing DNA binding by TFIID. We hypothesized that c-Jun is capable of derepressing the effect of the TAF(II)250 N terminus on TFIID-driven transcription. In support of this hypothesis, we found that c-Jun increased levels of TFIID-driven transcription in vitro when added at high concentrations to a DNA template lacking activator protein 1 (AP-1) sites. Moreover, c-Jun blocked the repression of TBP DNA binding caused by the N terminus of TAF(II)250. In addition to revealing a mechanism by which c-Jun activates transcription, our studies provide the first evidence that an activator can bind directly to the N terminus of TAF(II)250 to derepress RNA polymerase II transcription in vitro.

Increased prostacyclin synthesis by atherosclerotic arteries from estrogen-treated monkeys

We hypothesized that the atheroinhibitory and cardioprotective effects of estrogen may be mediated in part through increased prostacyclin formation by the artery wall. Atherosclerotic abdominal aorta was collected at necropsy from ovariectomized female monkeys fed an atherogenic diet alone or with added Premarin. Basal and arachidonate-stimulated prostacyclin and thromboxane synthesis by artery segments was measured by radioimmunoassay. In contrast to no observed differences in basal release of prostacyclin by the control and estrogen-treated arteries, there was a marked increase (approximately 165%) in arachidonate-stimulated formation of prostacyclin by estrogen-treated arteries, and prostacyclin synthesis was inversely correlated with plaque size. No differences were observed in basal or arachidonate-stimulated thromboxane synthesis by the control and estrogen-treated arteries. In light of known antiatherogenic and vasodilatory effects of estrogen, increased prostacyclin synthesis by estrogen-treated arteries may, in part, explain estrogen's beneficial effects on the artery wall.

Human Taf(II)130 is a coactivator for NFATp

NFATp is one member of a family of transcriptional activators that regulate the expression of cytokine genes. To study mechanisms of NFATp transcriptional activation, we established a reconstituted transcription system consisting of human components that is responsive to activation by full-length NFATp. The TATA-associated factor (TAF(II)) subunits of the TFIID complex were required for NFATp-mediated activation in this transcription system, since TATA-binding protein (TBP) alone was insufficient in supporting activated transcription. In vitro interaction assays revealed that human TAF(II)130 (hTAF(II)130) and its Drosophila melanogaster homolog dTAF(II)110 bound specifically and reproducibly to immobilized NFATp. Sequences contained in the C-terminal domain of NFATp (amino acids 688 to 921) were necessary and sufficient for hTAF(II)130 binding. A partial TFIID complex assembled from recombinant hTBP, hTAF(II)250, and hTAF(II)130 supported NFATp-activated transcription, demonstrating the ability of hTAF(II)130 to serve as a coactivator for NFATp in vitro. Overexpression of hTAF(II)130 in Cos-1 cells inhibited NFATp activation of a luciferase reporter. These studies demonstrate that hTAF(II)130 is a coactivator for NFATp and represent the first biochemical characterization of the mechanism of transcriptional activation by the NFAT family of activators.

Non-invasive measurement of blood pressures in the Yucatan micropig (Sus scrofa domestica), with and without midazolam-induced sedation

Current literature suggests that the effects of midazolam, a water-soluble benzodiazepine, on blood pressure in swine are minimal. The hypothesis of the study reported here was that a light sedative dose would induce a decrease in blood pressure in this species. Healthy female Yucatan Micropigs (n = 20), 16 to 30 (mean, 22) kg, aged four six months, were individually placed in a humane restraint sling and allowed to acclimate. Systolic (SBP), diastolic (DBP), and mean (MBP) blood pressures (mmHg) and heart rate (HR; beats per min [bpm]) were measured by use of oscillometry. The pressure cuff was placed at the base of the tail, and five sets of values were recorded at five-min intervals, beginning at 10 and ending 30 min after cuff placement. Following a three- to four-day rest period, this procedure was repeated with the addition of a dose of 0.5 mg of midazolam HCl/kg of body weight given intramuscularly at the time of cuff placement. A paired one-way Student's t-test was used to compare the means of the five measures between control and midazolam treatment. Mean (+/- SD) differences for SBP, DBP, MBP, and HR were 18.9 (+/- 3.97), 17.8 (+/- 5.27), and 18.6 (+/- 5.09) mmHg and 20.7 (+/- 3.73) bpm, respectively. All four parameters were significantly reduced in the midazolam-sedated group (P < 0.001). The maximal decrease in SBP, DBP, and MBP occurred at 15 and 20 min after dosing. Mean values based on the means of the five measures were 128 (+/- 12.6), 80 (+/- 9.4), and 99 (+/- 9.2) mmHg and 135 (+/- 17.4) bpm, and 109 (+/- 15.4), 63 (+/- 12.6), and 80 (+/- 13.6) mmHg and 115 (+/- 15.5) bpm for SBP, DBP, MBP, and HR in the control (n = 20) and midazolam (n = 20) groups, respectively. The control values can serve as normal oscillometric values for this age, sex, and breed of Micropig. We conclude that midazolam, given intramuscularly at a sedative dosage, negatively affects cardiovascular parameters measured by use of a blood pressure cuff, in sexually mature female Micropigs, compared with values in untreated pigs, which is similar to reports for humans.

A kinetic model for the early steps of RNA synthesis by human RNA polymerase II

Eukaryotic mRNA synthesis is a highly regulated process involving numerous proteins acting in concert with RNA polymerase II to set levels of transcription from individual promoters. The transcription reaction consists of multiple steps beginning with preinitiation complex formation and ending in the production of a full-length primary transcript. We used pre-steady-state approaches to study the steps of human mRNA transcription at the adenovirus major late promoter in a minimal in vitro transcription system. These kinetic studies revealed an early transition in RNA polymerase II transcription, termed escape commitment, that occurs after initiation and prior to promoter escape. Escape commitment is rapid and is characterized by sensitivity to competitor DNA. Upon completion of escape commitment, ternary complexes are resistant to challenge by competitor DNA and slowly proceed forward through promoter escape. Escape commitment is stimulated by transcription factors TFIIE and TFIIH. We measured forward and reverse rate constants for discrete steps in transcription and present a kinetic model for the mechanism of RNA polymerase II transcription that describes five distinct steps (preinitiation complex formation, initiation, escape commitment, promoter escape, and transcript elongation) and clearly shows promoter escape is rate-limiting in this system.

Acetyl coenzyme A stimulates RNA polymerase II transcription and promoter binding by transcription factor IID in the absence of histones

Protein acetylation has emerged as a means of controlling levels of mRNA synthesis in eukaryotic cells. Here we report that acetyl coenzyme A (acetyl-CoA) stimulates RNA polymerase II transcription in vitro in the absence of histones. The effect of acetyl-CoA on basal and activated transcription was studied in a human RNA polymerase II transcription system reconstituted from recombinant and highly purified transcription factors. Both basal and activated transcription were stimulated by the addition of acetyl-CoA to transcription reaction mixtures. By varying the concentrations of general transcription factors in the reaction mixtures, we found that acetyl-CoA decreased the concentration of TFIID required to observe transcription. Electrophoretic mobility shift assays and DNase I footprinting revealed that acetyl-CoA increased the affinity of the general transcription factor TFIID for promoter DNA in a TBP-associated factor (TAF)-dependent manner. Interestingly, acetyl-CoA also caused a conformational change in the TFIID-TFIIA-promoter complex as assessed by DNase I footprinting. These results show that acetyl-CoA alters the DNA binding activity of TFIID and indicate that this biologically important cofactor functions at multiple levels to control gene expression.

Use of an internal fixator device to treat comminuted fractures of the distal radius: report of a technique

An internal fixator technique for stabilizing comminuted Colles fractures has been developed in the anatomy laboratory and used in 35 clinical cases. The Colles Fracture Plate (Biomet, Inc, Warsaw, Indiana) can be used to treat any comminuted Colles fracture for which an external fixator is considered proper management. We have determined, based on our surgical experience with both the internal and external fixator techniques, that internal fixation using the Colles Fracture Plate is technically just as simple as external fixation. In addition to requiring a significantly less expensive device, internal fixation using this technique offers the advantages of better patient acceptance and fewer complications. This report will be followed by a more comprehensive analysis of the technical outcome of this procedure to further substantiate the initial results presented here. The process of compiling and analyzing these data is under way.