Altered adrenocortical response under the influence of experimentally increased serum very long chain fatty acids in rats

Adrenal Insufficiency in Peroxisomal Disorders: A Single Institution Case Series

INTRODUCTION

There are two major categories of peroxisomal disorders (PDs): peroxisomal biogenesis disorders (PBDs) due to defects in peroxisomal (PEX) genes and deficiency of other peroxisomal enzymes (such as D-bifunctional enzyme deficiency due to HSD17B4). PDs are characterized by abnormal elevations of very-long-chain fatty acids (VLCFA). We aimed to evaluate the clinical phenotype of adrenal insufficiency in patients with PD and to assess any genotype-phenotype correlations with adrenal insufficiency.

CASE PRESENTATION

We performed a retrospective electronic medical record review at a single university medical center, of data over 12 years and identified 7 patients with PD. Of the 7 patients identified, 6 patients had a diagnosis of PBD and one had a single peroxisomal enzyme deficiency, HSD17B4. The average age of the patients at diagnosis were 0.61 ± 0.66 years. Four patients (66.7%) had primary adrenal insufficiency: 3, out of the 4, patients had elevated baseline ACTH. Three patients failed to have increased response after the Cortrosyn™ stimulation test. Three patients were on daily hydrocortisone replacement, and 1 patient was on stress-dose hydrocortisone only as needed. Specific genetic variant analysis revealed that all the 3 patients with PBD and adrenal insufficiency who were on steroid supplementation had the compound heterozygous pathogenic variant in exon 13 of PEX1 c.2097dupT (p.Ile700Tyrfs*42) and c.2528G>A (p.Gly843Asp), while the 1 patient with peroxisomal enzyme deficiency and adrenal insufficiency had compound heterozygous pathogenic variants in HSD17B4 c.1369A>T (p.Asn457Tyr) and c.1210 - 1G>A (splice acceptor). Two of these patients with PEX1 variants also required mineralocorticoid supplementation. The 3 PBD patients without adrenal insufficiency did not have a PEX1 variant.

DISCUSSION/CONCLUSION

Primary adrenal insufficiency is common in patients with PD. Based on our data, patients with the compound heterozygous PEX1 pathogenic variants of exon 13 (c.2097dupT and c.2528G>A) tend to have adrenal insufficiency. Aldosterone deficiency, though rare, can occur in PD.

Biochemical and clinical profiles of 52 Tunisian patients affected by Zellweger syndrome

BACKGROUND

Zellweger syndrome (ZS) is a peroxisome biogenesis disorder attributed to a mutation of the PEX genes family. The incidence of this disease in Africa and the Arab world remains unknown. This contribution is aimed at describing the clinical phenotype and biochemical features in Tunisian patients with ZS in order to improve the detection and management of this severe disorder.

METHODS

A total of 52 patients diagnosed with ZS and 60 age- and sex-matched healthy controls were included in this study. Patients were recruited during the past 21 years, and the diagnosis of ZS was based on clinical and biochemical characteristics. Plasma very long chain fatty acids (VLCFA) were analyzed using capillary gas chromatography. The estimated incidence of ZS was calculated using the Hardy-Weinberg formula.

RESULTS

The estimated incidence of ZS is 1/15,898 in Tunisia. Age at diagnosis varied between 3 days and 18 months. Severe neurological syndrome, polymalformative features, and hepatodigestive signs were observed in 100%, 67.9%, and 32% of patients, respectively. Values for plasma C26:0 and C26:0/C22:0 and C24:0/C22:0 ratios were noticeably higher in ZS patients than in controls. Distributions of values were completely different for C26:0 (0.10-0.37 vs. 0.001-0.009), C26:0/C22:0 ratio (0.11-1.29 vs. 0.003-0.090), and C24:0/C22:0 ratio (1.03-3.18 vs. 0.4-0.90) in ZS patients versus controls, respectively.

CONCLUSIONS

This study highlights the high incidence of ZS in Tunisia and the possibility of simple and reliable biochemical diagnosis, thus permitting early genetic counseling for families at risk.

High prevalence of primary adrenal insufficiency in Zellweger spectrum disorders

Zellweger spectrum disorders are a group of autosomal recessive disorders characterized by impaired peroxisome functions. The clinical spectrum is broad, ranging from the classical most severe Zellweger syndrome to patients with a relatively mild phenotype. Treatment options are limited to symptomatic and supportive therapy. During routine follow-up we discovered patients with asymptomatic primary adrenal insufficiency. It is important to detect impaired adrenal function because it has treatment implications. Primary adrenal insufficiency was found in 7/24 patients examined, with 4/7 being asymptomatic. Systematic evaluation of adrenal function, through a Synacthen test, should be included in the clinical management of these patients.

Human peroxisomal disorders

Peroxisomes are single membrane-bound cell organelles performing numerous metabolic functions. The present article aims to give an overview of our current knowledge about inherited peroxisomal disorders in which these organelles are lacking or one or more of their functions are impaired. They are multiorgan disorders and the nervous system is implicated in most. After a summary of the historical names and categories, each having distinct symptoms and prognosis, microscopic pathology is reviewed in detail. Data from the literature are added to experience in the authors' laboratory with 167 liver biopsy and autopsy samples from peroxisomal patients, and with a smaller number of chorion samples for prenatal diagnosis, adrenal-, kidney-, and brain samples. Various light and electron microscopic methods are used including enzyme- and immunocytochemistry, polarizing microscopy, and morphometry. Together with other laboratory investigations and clinical data, this approach continues to contribute to the diagnosis and further characterization of peroxisomal disorders, and the discovery of novel variants. When liver specimens are examined, three main groups including 9 novel variants (33 patients) are distinguished: (1) absence or (2) presence of peroxisomes, and (3) mosaic distribution of cells with and without peroxisomes (10 patients). Renal microcysts, polarizing trilamellar inclusions, and insoluble lipid in macrophages in liver, adrenal cortex, brain, and in interstitial cells of kidney are also valuable for classification. On a genetic basis, complementation of fibroblasts has classified peroxisome biogenesis disorders into 12 complementation groups. Peroxisome biogenesis genes (PEX), knock-out-mice, and induction of redundant genes are briefly reviewed, including some recent results with 4-phenylbutyrate. Finally, regulation of peroxisome expression during development and in cell cultures, and by physiological factors is discussed.

Inverse expression of peroxisomes and connexin-43 in the granulosa cells of the quail follicle

Studying the regulation of peroxisome (Px) expression could improve our understanding of human peroxisomal disorders. The granulosa of the largest preovulatory quail follicles proved to be a relevant model because (a) Px expression changes according to the follicular maturation stage and (b) Px expression varies regionally according to the distance of the granulosa relative to the germinal disc region containing the female gamete (oocyte). The question was asked whether Px expression is related to the extent of metabolic cell coupling and whether zonal Px variation is causally related to oocytal factors. This was evaluated by the presence of catalase and Cx-43 (marker proteins for peroxisomes and gap junctions, respectively) and by in vitro experiments with granulosa explants. The data obtained show that the expression of Cx-43 and Px is inversely correlated both temporally and spatially. Uncoupling of gap junctions results in an upregulation of alpha-catalase immunofluorescence. This is in agreement with reports that gap junctions are often negatively affected by Px proliferators. The zonal gradient in Px expression appears to be imposed by the oocyte, as is the case for steroidogenesis and proliferative capacity in the granulosa epithelium. (J Histochem Cytochem 48:167-177, 2000)