Diagnosis of Smith-Lemli-Opitz syndrome from stored filter paper blood specimens

Newborn screening for lipid disorders

PURPOSE OF REVIEW

Newborn screening is one of the most successful public health programs of the last century and offers unparalleled access to universal screening for a variety of metabolic and other disorders. Interest in development of newborn screening for lipid disorders has intensified in recent years. Screening newborns for lipid disorders has important implications for the health of the newborn as well as their relatives, and in the case of more common lipid disorders like familial hypercholesterolemia, could have important public health implications.

RECENT FINDINGS

Recent studies have demonstrated feasibility of measuring biomarkers for heterozygous familial hypercholesterolemia from newborn screening dried blood spot specimens. Another lipid disorder, cerebrotendinous xanthomatosis, is currently amenable to newborn screening utilizing currently available assays. New research in next-generation sequencing as a primary screen in newborns will also identify both common and rare lipid disorders in newborns.

SUMMARY

Historically, newborn screening for lipid disorders was not done for many reasons, but new research has developed testing methods that may successfully identify common and rare lipid disorders. This will impact the health of the newborn but could also impact family members and public health.

The role of cholesterol metabolism and various steroid abnormalities in autism spectrum disorders: A hypothesis paper

Based on evidence from the relevant research literature, we present a hypothesis that there may be a link between cholesterol, vitamin D, and steroid hormones which subsequently impacts on the development of at least some of the "autisms" [Coleman & Gillberg]. Our hypothesis, driven by the peer reviewed literature, posits that there may be links between cholesterol metabolism, which we will refer to as "steroid metabolism" and findings of steroid abnormalities of various kinds (cortisol, testosterone, estrogens, progesterone, vitamin D) in autism spectrum disorder (ASD). Further research investigating these potential links is warranted to further our understanding of the biological mechanisms underlying ASD. Autism Res 2017. © 2017 The Authors Autism Research published by Wiley Periodicals, Inc. on behalf of International Society for Autism Research. Autism Res 2017, 10: 1022-1044. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

A routine method for cholesterol and 7-dehydrocholesterol analysis in dried blood spot by GC-FID to diagnose the Smith-Lemli-Opitz syndrome

This work was aimed to implement a fast and simple method to quantify cholesterol (CHOL) and 7-dehydrocholesterol (7-DHC) in dried blood spot (DBS) to diagnose the Smith-Lemli-Opitz syndrome (SLOS), an inborn error of CHOL biosynthesis. We developed and validated a GC-FID method for separation and quantification of underivatized CHOL and 7-DHC using a DBS disc of 6mm with a run time of 9 min. Correlation coefficients (r) of calibration curves ranged from 0.998 to 0.999 for CHOL and from 0.997 to 0.998 for 7-DHC. Within-day and between-day imprecision (CV%), accuracy (%), carry-over, and extraction efficacy (%) were also evaluated for validation. CHOL and 7-DHC were analyzed in DBS and plasma samples from 8 SLOS patients and 30 unaffected subjects. In SLOS patients, 7-DHC/CHOL ratios in DBS and plasma samples ranged from 0.035 to 1.448 and from 0.012 to 0.926, respectively. Results from calibration curves, quality controls and patient samples reveal that the method is suitable to analyze DBS to screen patients affected by SLOS.

Utility of dried blood spots for measurement of cholesterol and triglycerides in a surveillance study

BACKGROUND

Developing countries are facing a rise in noncommunicable diseases (NCD), which is a cause for concern. The World Health Organization has recommended a stepwise approach for NCD risk factor surveillance. Screening for risk factors in remote populations is difficult due to lack of resources and technical expertise, including standardized laboratory facilities. The collection of samples on filter paper for the assessment of risk factors circumvents the need for blood processing, storage, and shipment at ultralow temperatures.

METHOD

Samples were collected on 3-mm Whatman filter paper from one industry (National Thermal Power Corporation) located in the periphery of Delhi as part of a surveillance carried out in industries from different parts of India. Total cholesterol was measured in serum and dried blood by the cholesterol oxidase/p-aminophenazone method and triglycerides by the glycerophosphate oxidase-peroxidase/aminophenazone method. Values obtained by the two methods were compared using Pearson correlation, and Bland-Altman plots were prepared to assess bias.

RESULTS

The correlation coefficient "r" was 0.78 for cholesterol and 0.94 for triglycerides between dried blood spots and serum. Bland-Altman plots suggest that differences in values obtained by the two methods were within two standard deviations for most of the samples.

CONCLUSIONS

Blood samples dried on filter paper can be a successful option for population screening in remote areas, provided preanalytical variations arising due to the method of blood spot preparation and storage are well controlled.

Potential of sterol analysis by liquid chromatography-tandem mass spectrometry for the prenatal diagnosis of Smith-Lemli-Opitz syndrome

BACKGROUND

Smith-Lemli-Opitz syndrome (SLOS), a severe disorder of cholesterol synthesis, is classically diagnosed prenatally by GC-MS analysis of sterols in amniotic fluid. Considering the current trend toward tandem mass spectrometry (MS/MS) methodologies, we developed prototype LC-MS/MS methods for accurate diagnosis of the disorder.

METHODS

3beta-Hydroxysterols in amniotic fluid are oxidized with cholesterol oxidase to their corresponding 3-ketones, which are then derivatized with Girard P (GP) hydrazine in a "one-pot" reaction. The resulting GP-hydrazones give an improved response in electrospray (ES)-MS/MS owing to the presence of a charged quaternary nitrogen and are analyzed by reversed-phase LC-ES-MS/MS. Both capillary and conventional LC-MS/MS formats are suitable, and the method is also applicable to paper-absorbed blood spots.

RESULTS

In a double-blind analysis of 18 amniotic fluid samples comprising 6 SLOS and 12 controls, the ratio of 7 + 8-dehydrocholesterol (7 + 8-DHC) to cholesterol was <0.02 [range 0.00-0.02, mean (SD) 0.01 (0.007)] in all control samples (intraassay variation 5.91%) and >0.20 [0.20-1.13, 0.79 (0.35)] in SLOS (intraassay variation 4.56%), corresponding to a difference in ratios between the 2 groups of at least a factor of 10. The limit of quantification was equivalent to that of 2 nL amniotic fluid injected on-column.

CONCLUSIONS

We describe a proof-of-concept for the prenatal diagnosis of SLOS. Further developments will be necessary to automate sample handling and reduce chromatographic time for the methodology to be used in pre- and postnatal diagnosis.

Molecular studies in Portuguese patients with Smith-Lemli-Opitz syndrome and report of three new mutations in DHCR7

Smith-Lemli-Opitz syndrome (SLO) is an autosomal recessive disorder characterised by craniofacial dysmorphism, mental retardation, multiple congenital anomalies, and increased levels of 7-dehydrocholesterol (7-DHC) in body tissues and fluids. SLO is caused by mutations in the DHCR7 gene which encodes 7-dehydrocholesterol reductase, the last enzyme of cholesterol biosynthesis pathway. In our investigation, we screened 682 dysmorphic/mentally retarded Portuguese patients for abnormal levels of 7-DHC in blood by UV spectrometry. We identified six unrelated patients with SLO (0.87% of total). Mutational analysis of the DHCR7 gene led to the identification of seven distinct mutations, three of which are new (F174S, H301R, and Q98X). The common IVS8-1G > C and T93M variants together with the H301R accounted for 70% of the all SLO alleles in our population. Our findings contribute to the variegate array of pathological changes in the DHCR7 gene among different European populations.

Simvastatin treatment in the SLO syndrome: a safe approach?

Soon after the discovery of reduced cholesterol synthesis in the Smith-Lemli-Opitz syndrome (SLOS), several trials with dietary supplementation were initiated with the aim of increasing cholesterol and reducing the de novo synthesis and accumulation of 7- and 8-dehydrocholesterol (DHC). Dietary cholesterol raises cholesterol levels in the circulation with only marginal effects on levels of DHC. Photosensitivity and polyneuropathy have been reported to be improved by the treatment, but other effects have been difficult to evaluate. In order to see whether inhibition of hydroxymethylglutaryl CoA reductase is of benefit, two of our patients have been treated with simvastatin in addition to the long-term treatment with cholesterol and bile acids. Absolute as well as relative levels of DHC were reduced. In one patient, creatine kinase increased moderately after 2 months of treatment. In the other patient, the treatment had to be interrupted because of hepatotoxic side effects with a marked increase in alanine aminotransferase and aggravation of the hypocholesterolemia and photosensitivity. We conclude that even if the levels of accumulated intermediates can be reduced, treatment with a statin may be harmful in some patients with SLOS.

A colorimetric assay for 7-dehydrocholesterol with potential application to screening for Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS; MIM 270400) is a genetic disorder characterized by hypocholesterolemia and elevated 7-dehydrocholesterol (7DHC) levels resulting from mutations affecting 7-dehydrocholesterol reductase. We describe a colorimetric assay for 7DHC with potential application to large-scale screening for SLOS. Reaction of 7DHC and its esters with the Liebermann-Burchard reagent resulted in a brief initial absorbance at 510 nm (pink color) followed by an absorbance at 620 nm (blue color) after 2 min, while cholesterol samples were essentially colorless. The assay could identify typical SLOS blood samples by their pink color and increased absorbance at 620 nm after 2 min. Colorimetric identification of mild SLOS cases requires monitoring of the transient absorbance at 510 nm, which must be detected immediately after rapid, consistent mixing of the reagents. The need for special mixing devices and rigorous validation precludes sporadic use of the assay for diagnosing suspected SLOS cases. We also studied the stability of 7DHC in dried SLOS blood spots on Guthrie cards, which are widely used for archiving neonatal blood. Decomposition of 7DHC was effectively retarded by storage at low temperature and by precoating of the cards with antioxidants. The combined results provide a foundation for development of a simple, automated test for SLOS screening.