Minireview: regulation of steroidogenesis by electron transfer

Examining the Effects of Nutrient Supplementation on Metabolic Pathways via Mitochondrial Ferredoxin in Aging Ovaries

As women age, oocytes are susceptible to a myriad of dysfunctions, including mitochondrial dysfunction, impaired DNA repair mechanisms, epigenetic alterations, and metabolic disturbances, culminating in reduced fertility rates among older individuals. Ferredoxin (FDX) represents a highly conserved iron-sulfur (Fe-S) protein essential for electron transport across multiple metabolic pathways. Mammalian mitochondria house two distinct ferredoxins, FDX1 and FDX2, which share structural similarities and yet perform unique functions. In our investigation into the regulatory mechanisms governing ovarian aging, we employed a comprehensive multi-omics analysis approach, integrating spatial transcriptomics, single-cell RNA sequencing, human ovarian pathology, and clinical biopsy data. Previous studies have highlighted intricate interactions involving excessive lipid peroxide accumulation, redox-induced metal ion buildup, and alterations in cellular energy metabolism observed in aging cells. Through a multi-omics analysis, we observed a notable decline in the expression of the critical gene FDX1 as ovarian age progressed. This observation prompted speculation regarding FDX1's potential as a promising biomarker for ovarian aging. Following this, we initiated a clinical trial involving 70 patients with aging ovaries. These patients were administered oral nutritional supplements consisting of DHEA, ubiquinol CoQ10, and Cleo-20 T3 for a period of two months to evaluate alterations in energy metabolism regulated by FDX1. Our results demonstrated a significant elevation in FDX1 levels among participants receiving nutritional supplementation. We hypothesize that these nutrients potentiate mitochondrial tricarboxylic acid cycle (TCA) activity or electron transport chain (ETC) efficiency, thereby augmenting FDX1 expression, an essential electron carrier in metabolic pathways, while concurrently mitigating lipid peroxide accumulation and cellular apoptosis. In summary, our findings underscore the potential of nutritional intervention to enhance in vitro fertilization outcomes in senescent cells by bolstering electron transport proteins, thus optimizing energy metabolism and improving oocyte quality in aging women.

Identification and functional characterization of compound heterozygous CYP11B1 gene mutations

PURPOSE

11β-Hydroxylase deficiency (11β-OHD) is the second leading cause of congenital adrenal hyperplasia (CAH), a rare autosomal recessive disease caused by mutations in the CYP11B1 gene. We previously reported the case of a male Chinese patient with typical 11β-OHD symptoms. Sanger sequencing revealed that the patient carried a splice-site mutation, c.595+1G>A in the CYP11B1 gene. His mother and sister harbored the heterozygous mutation, c.595+1G>A. Paradoxically, Sanger sequencing did not detect any abnormality in the CYP11B1 gene of his father and brother. Therefore, in this study, we aimed to further explore the exact genetic etiology of 11β-OHD in this pedigree and analyze the functional consequence of the c.595+1G>A mutation.

METHODS

Gemomic DNA was extracted from the peripheral blood leukocytes of the family members and normal control individuals, followed by quantitative real-time polymerase chain reaction (qPCR) to detect the copy number of the target CYP11B1 gene fragment. Mutation analysis was also performed via whole-exome sequencing (WES) followed by Sanger sequencing validation. In vitro minigene assay was also performed to investigate the impact of the c.595+1G>A mutation on pre-mRNA splicing.

RESULTS

qPCR results suggested a heterozygous deletion encompassing position c.595+1 along with flanking exonic and intronic sequences in the CYP11B1 gene of the patient and his father. WES followed by Sanger sequencing verified that the patient carried compound heterozygous mutations in the CYP11B1 gene, including a novel 2840-bp deletion (c.395+661_c.1121+180del) and c.595+1G>A, while his father carried the heterozygous c.395+661_c.1121+180del mutation. No other novel CYP11B1 mutations were found in the rest of the family members. Furthermore, minigene assay revealed that the c.595+1G>A mutation resulted in a 70-bp deletion of exon 3 in the mRNA, and this altered the reading frame at amino acid 176 and created a premature stop codon at amino acid 197.

CONCLUSION

We identified a novel 2840-bp-sized large deletion and confirmed that the c.595+1G>A mutation disrupts normal pre-mRNA splicing. Either mutation could significantly alter the reading frame and abolish CYP11B1 enzyme activity. Therefore, our findings widen the mutation spectrum of CYP11B1 and provide an accurate diagnosis of 11β-OHD at a molecular genetic level.

Activation of Coq6p, a FAD Monooxygenase Involved in Coenzyme Q Biosynthesis, by Adrenodoxin Reductase/Ferredoxin

Adrenodoxin reductase (AdxR) plays a pivotal role in electron transfer, shuttling electrons between NADPH and iron/sulfur adrenodoxin proteins in mitochondria. This electron transport system is essential for P450 enzymes involved in various endogenous biomolecules biosynthesis. Here, we present an in-depth examination of the kinetics governing the reduction of human AdxR by NADH or NADPH. Our results highlight the efficiency of human AdxR when utilizing NADPH as a flavin reducing agent. Nevertheless, akin to related flavoenzymes such as cytochrome P450 reductase, we observe that low NADPH concentrations hinder flavin reduction due to intricate equilibrium reactions between the enzyme and its substrate/product. Remarkably, the presence of MgCl2 suppresses this complex kinetic behavior by decreasing NADPH binding to oxidized AdxR, effectively transforming AdxR into a classical Michaelis-Menten enzyme. We propose that the addition of MgCl2 may be adapted for studying the reductive half-reactions of other flavoenzymes with NADPH. Furthermore, in vitro experiments provide evidence that the reduction of the yeast flavin monooxygenase Coq6p relies on an electron transfer chain comprising NADPH-AdxR-Yah1p-Coq6p, where Yah1p shuttles electrons between AdxR and Coq6p. This discovery explains the previous in vivo observation that Yah1p and the AdxR homolog, Arh1p, are required for the biosynthesis of coenzyme Q in yeast.

Reaction thermodynamics as a constraint on piscine steroidogenesis flux distributions

While a considerable amount is known of the dynamics of piscine steroidogenesis during reproduction, the influence of thermodynamics constraints on its control has not been studied. In this manuscript, Gibbs free energy change of reactions was calculated for piscine steroidogenesis using the in silico eQuilibrator thermodynamics calculator. The analysis identified cytochrome P450 (cyp450) oxidoreductase reactions to have more negative Gibbs free energy changes relative to hydroxysteroid (HSD) and transferase reactions. In addition, a more favorable Gibbs free energy change was predicted for the Δ5 (cyp450 catalyzed) vs. Δ4 (HSD catalyzed) steroidogenesis branch-point, which converts pregnenolone to 17α-hydroxypregnenolone or progesterone respectively. Comparison of in silico predictions with in vivo experimentally measured flux across the Δ5 vs. Δ4 branch-point showed higher flux through the thermodynamically more favorable Δ5 pathway in reproducing or spawning vs. non-spawning fathead minnows (Pimephales promelas). However, the exposure of fish to endocrine stressors such as hypoxia or the synthetic estrogen 17α-ethinylestradiol (EE2), resulted in increased flux through both Δ5 and Δ4 pathways, indicating an adaptive response to increase steroidogenic redundancy. The correspondence of elevated flux through the Δ5 branch-point in spawning fish indicated the use of a thermodynamically favorable pathway to optimize steroid hormone productions during reproduction. We hypothesize that such selective use of a thermodynamically favorable steroidogenesis pathway may conserve reduced equivalents or transcriptional costs for investment to other biosynthetic or catabolic reactions to support reproduction. If generalizable, such an approach can provide novel insights into the structural principles and regulation of steroidogenesis or other metabolic pathways.

Exploring Novel Variants of the Cytochrome P450 Reductase Gene (POR) from the Genome Aggregation Database by Integrating Bioinformatic Tools and Functional Assays

Cytochrome P450 oxidoreductase (POR) is an essential redox partner for steroid and drug-metabolizing cytochromes P450 located in the endoplasmic reticulum. Mutations in POR lead to metabolic disorders, including congenital adrenal hyperplasia, and affect the metabolism of steroids, drugs, and xenobiotics. In this study, we examined approximately 450 missense variants of the POR gene listed in the Genome Aggregation Database (gnomAD) using eleven different in silico prediction tools. We found that 64 novel variants were consistently predicted to be disease-causing by most tools. To validate our findings, we conducted a population analysis and selected two variations in POR for further investigation. The human POR wild type and the R268W and L577P variants were expressed in bacteria and subjected to enzyme kinetic assays using a model substrate. We also examined the activities of several cytochrome P450 proteins in the presence of POR (WT or variants) by combining P450 and reductase proteins in liposomes. We observed a decrease in enzymatic activities (ranging from 35% to 85%) of key drug-metabolizing enzymes, supported by POR variants R288W and L577P compared to WT-POR. These results validate our approach of curating a vast amount of data from genome projects and provide an updated and reliable reference for diagnosing POR deficiency.

Mitochondrial dysfunction as a possible trigger of neuroinflammation at post-traumatic stress disorder (PTSD)

Post-traumatic stress disorder (PTSD) is a neuropsychiatric disorder that occurs in approximately 15% of people as a result of some traumatic events. The main symptoms are re-experiencing and avoidance of everything related to this event and hyperarousal. The main component of the pathophysiology of PTSD is an imbalance in the functioning of the hypothalamic-pituitary-adrenal axis (HPA) and development of neuroinflammation. In parallel with this, mitochondrial dysfunction is observed, as in many other diseases. In this review, we focus on the question how mitochondria may be involved in the development of neuroinflammation and its maintaining at PTSD. First, we describe the differences in the operation of the neuro-endocrine system during stress versus PTSD. We then show changes in the activity/expression of mitochondrial proteins in PTSD and how they can affect the levels of hormones involved in PTSD development, as well as how mitochondrial damage/pathogen-associated molecule patterns (DAMPs/PAMPs) trigger development of inflammation. In addition, we examine the possibility of treating PTSD-related inflammation using mitochondria as a target.

Catalytic and Electrocatalytic Mechanisms of Cytochromes P450 in the Development of Biosensors and Bioreactors

Cytochromes P450 are a unique family of enzymes found in all Kingdoms of living organisms (animals, bacteria, plants, fungi, and archaea), whose main function is biotransformation of exogenous and endogenous compounds. The review discusses approaches to enhancing the efficiency of electrocatalysis by cytochromes P450 for their use in biotechnology and design of biosensors and describes main methods in the development of reconstituted and electrochemical catalytic systems based on the biochemical mechanism of cytochromes P450, as well as and modern trends for their practical application.

FDX1 regulates cellular protein lipoylation through direct binding to LIAS

Ferredoxins are a family of iron-sulfur (Fe-S) cluster proteins that serve as essential electron donors in numerous cellular processes that are conserved through evolution. The promiscuous nature of ferredoxins as electron donors enables them to participate in many metabolic processes including steroid, heme, vitamin D, and Fe-S cluster biosynthesis in different organisms. However, the unique natural function(s) of each of the two human ferredoxins (FDX1 and FDX2) are still poorly characterized. We recently reported that FDX1 is both a crucial regulator of copper ionophore-induced cell death and serves as an upstream regulator of cellular protein lipoylation, a mitochondrial lipid-based post-translational modification naturally occurring on four mitochondrial enzymes that are crucial for TCA cycle function. Here we show that FDX1 directly regulates protein lipoylation by binding the lipoyl synthase (LIAS) enzyme promoting its functional binding to the lipoyl carrier protein GCSH and not through indirect regulation of cellular Fe-S cluster biosynthesis. Metabolite profiling revealed that the predominant cellular metabolic outcome of FDX1 loss of function is manifested through the regulation of the four lipoylation-dependent enzymes ultimately resulting in loss of cellular respiration and sensitivity to mild glucose starvation. Transcriptional profiling established that FDX1 loss-of-function results in the induction of both compensatory metabolism-related genes and the integrated stress response, consistent with our findings that FDX1 loss-of-function is conditionally lethal. Together, our findings establish that FDX1 directly engages with LIAS, promoting its role in cellular protein lipoylation, a process essential in maintaining cell viability under low glucose conditions.

Hepatic transcript profiling in beef cattle: Effects of rumen-protected niacin supplementation

The objective of our study was to assess the effect of rumen-protected niacin supplementation on the transcriptome of liver tissue in growing Angus × Simmental steers and heifers through RNA-seq analysis. Consequently, we wanted to assess the known role of niacin in the physiological processes of vasodilation, detoxification, and immune function in beef hepatic tissue. Normal weaned calves (~8 months old) were provided either a control diet or a diet supplemented with rumen-protected niacin (6 g/hd/d) for a 30-day period, followed by a liver biopsy. We observed a significant list of changes at the transcriptome level due to rumen-protected niacin supplementation. Several metabolic pathways revealed potential positive effects to the animal's liver metabolism due to administration of rumen-protected niacin; for example, a decrease in lipolysis, apoptosis, inflammatory responses, atherosclerosis, oxidative stress, fibrosis, and vasodilation-related pathways. Therefore, results from our study showed that the liver transcriptional machinery switched several metabolic pathways to a condition that could potentially benefit the health status of animals supplemented with rumen-protected niacin. In conclusion, based on the results of our study, we can suggest the utilization of rumen-protected niacin supplementation as a nutritional strategy could improve the health status of growing beef cattle in different beef production stages, such as backgrounding operations or new arrivals to a feedlot.

FDX1 enhances endometriosis cell cuproptosis via G6PD-mediated redox homeostasis

Cuproptosis is a new form of programmed cell death, which is associated with the mitochondrial TCA (tricarboxylic acid) cycle. But the functions of cuproptosis in endometriosis progression are still unknown. Here, we find that cuproptosis suppresses the growth of endometriosis cells and the growth of ectopic endometrial tissues in a mouse model. FDX1 as a key regulator in cuproptosis pathway could promote cuproptosis in endometriosis cells. Interestingly, FDX1 interacts with G6PD, and reduces its protein stability, which predominantly affects the cellular redox-regulating systems. Then, the reduced G6PD activity enhances cuproptosis via down-regulating NADPH and GSH levels. Collectively, our study demonstrates that FDX1 mediates cuproptosis in endometriosis via G6PD pathway, resulting in repression of endometriosis cell proliferation and metastasis.

A Novel Oncogenic Role of FDX1 in Human Melanoma Related to PD-L1 Immune Checkpoint

The aim of this study was to evaluate the association between Ferredoxin 1 (FDX1) expression and the prognostic survival of tumor patients and predict the efficacy of immunotherapy response to antitumor drug sensitivity. FDX1 plays an oncogenic role in thirty-three types of tumors, based on TCGA and GEO databases, and further experimental validation in vitro was provided through multiple cell lines. FDX1 was expressed highly in multiple types of cancer and differently linked to the survival prognosis of tumorous patients. A high phosphorylation level was correlated with the FDX1 site of S177 in lung cancer. FDX1 exhibited a significant association with infiltrated cancer-associated fibroblasts and CD8⁺ T cells. Moreover, FDX1 demonstrated correlations with immune and molecular subtypes, as well as functional enrichments in GO/KEGG pathways. Additionally, FDX1 displayed relationships with the tumor mutational burden (TMB), microsatellite instability (MSI), DNA methylation, and RNA and DNA synthesis (RNAss/DNAss) within the tumor microenvironment. Notably, FDX1 exhibited a strong connection with immune checkpoint genes in the co-expression network. The validity of these findings was further confirmed through Western blotting, RT-qPCR, and flow cytometry experiments conducted on WM115 and A375 tumor cells. Elevated FDX1 expression has been linked to the enhanced effectiveness of PD-L1 blockade immunotherapy in melanoma, as observed in the GSE22155 and GSE172320 cohorts. Autodocking simulations have suggested that FDX1 may influence drug resistance by affecting the binding sites of antitumor drugs. Collectively, these findings propose that FDX1 could serve as a novel and valuable biomarker and represent an immunotherapeutic target for augmenting immune responses in various human cancers when used in combination with immune checkpoint inhibitors.

Non-steroidal CYP17A1 Inhibitors: Discovery and Assessment

CYP17A1 is an enzyme that plays a major role in steroidogenesis and is critically involved in the biosynthesis of steroid hormones. Therefore, it remains an attractive target in several serious hormone-dependent cancer diseases, such as prostate cancer and breast cancer. The medicinal chemistry community has been committed to the discovery and development of CYP17A1 inhibitors for many years, particularly for the treatment of castration-resistant prostate cancer. The current Perspective reflects upon the discovery and evaluation of non-steroidal CYP17A1 inhibitors from a medicinal chemistry angle. Emphasis is placed on the structural aspects of the target, key learnings from the presented chemotypes, and design guidelines for future inhibitors.

FDX1 regulates cellular protein lipoylation through direct binding to LIAS

Ferredoxins are a family of iron-sulfur (Fe-S) cluster proteins that serve as essential electron donors in numerous cellular processes that are conserved through evolution. The promiscuous nature of ferredoxins as electron donors enables them to participate in many metabolic processes including steroid, heme, vitamin D and Fe-S cluster biosynthesis in different organisms. However, the unique natural function(s) of each of the two human ferredoxins (FDX1 and FDX2) are still poorly characterized. We recently reported that FDX1 is both a crucial regulator of copper ionophore induced cell death and serves as an upstream regulator of cellular protein lipoylation, a mitochondrial lipid-based post translational modification naturally occurring on four mitochondrial enzymes that are crucial for TCA cycle function. Here we show that FDX1 regulates protein lipoylation by directly binding to the lipoyl synthase (LIAS) enzyme and not through indirect regulation of cellular Fe-S cluster biosynthesis. Metabolite profiling revealed that the predominant cellular metabolic outcome of FDX1 loss-of-function is manifested through the regulation of the four lipoylation-dependent enzymes ultimately resulting in loss of cellular respiration and sensitivity to mild glucose starvation. Transcriptional profiling of cells growing in either normal or low glucose conditions established that FDX1 loss-of-function results in the induction of both compensatory metabolism related genes and the integrated stress response, consistent with our findings that FDX1 loss-of-functions is conditionally lethal. Together, our findings establish that FDX1 directly engages with LIAS, promoting cellular protein lipoylation, a process essential in maintaining cell viability under low glucose conditions.

Mitochondrial [2Fe-2S] ferredoxins: new functions for old dogs

Ferredoxins (FDXs) comprise a large family of iron-sulfur proteins that shuttle electrons from NADPH and FDX reductases into diverse biological processes. This review focuses on the structure, function and specificity of mitochondrial [2Fe-2S] FDXs that are related to bacterial FDXs due to their endosymbiotic inheritance. Their classical function in cytochrome P450-dependent steroid transformations was identified around 1960, and is exemplified by mammalian FDX1 (aka adrenodoxin). Thirty years later the essential function in cellular Fe/S protein biogenesis was discovered for the yeast mitochondrial FDX Yah1 that is additionally crucial for the formation of haem a and ubiquinone CoQ₆ . In mammals, Fe/S protein biogenesis is exclusively performed by the FDX1 paralog FDX2, despite the high structural similarity of both proteins. Recently, additional and specific roles of human FDX1 in haem a and lipoyl cofactor biosyntheses were described. For lipoyl synthesis, FDX1 transfers electrons to the radical S-adenosyl methionine-dependent lipoyl synthase to kickstart its radical chain reaction. The high target specificity of the two mammalian FDXs is contained within small conserved sequence motifs, that upon swapping change the target selection of these electron donors.

Influence of cytochrome P450 3A4 and membrane lipid composition on doxorubicin activity

Drug resistance is known to depend on the interactions with cell membranes and other molecules such as human cytochromes P450 (CYPs) which are anchored on the endoplasmic reticulum (ER) membrane and involved in the metabolism of anticancer drugs. In this study, we determined the influence from cytochrome P450 3A4 (CYP3A4) on the interaction between the drug doxorubicin (DOX) and Langmuir monolayers mimicking cell membranes. The lipid composition was varied by changing the relative concentrations of cholesterol (Chol), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE), and L-α-phosphatidylinositol (PI). Three compositions were studied in detail which represented a healthy cell membrane and cancerous cell membranes. DOX induced an expansion in the surface pressure isotherms for all monolayers, with stronger effect for the composition of cancerous cell with a high Chol content, thus confirming the relevance of lipid composition. This effect decreased considerably when CYP3A4 was incorporated with the formation of CYP3A4-DOX complexes, according to results from polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS) measurements. Taken together, these results support the hypothesis of CYP3A4 being involved in drug resistance, which may be exploited to design strategies to enhance chemotherapy efficacy.

Congenital lipoid adrenal hyperplasia with Graves' disease: A case report

BACKGROUND

Congenital adrenal hyperplasia (CAH), which is caused by a mutation of the steroidogenic acute regulatory (StAR) gene. Affected patients are usually characterized by adrenal insufficiency in the first year of life, salt loss, glucocorticoid and mineralocorticoid deficiency, and female external genitalia, regardless of chromosomal karyotype. Patients with non-classical lipoid CAH usually develop glucocorticoid deficiency and mild mineralocorticoid deficiency at 2-4 years of age.

CASE SUMMARY

Herein, We report the case of a woman with non-classic lipoid CAH combined with Graves' disease. Her chromosome karyotype was 46, XX, and high-throughput sequencing revealed two missense variants in the StAR gene: c.229C > T (p.Q77X) and c.814C > T (p.R272C), which were inherited from both parents (non-close relatives). The patient was treated for Graves' disease in a timely manner and the dosage of glucocorticoid was adjusted during the treatment of Graves' disease.

CONCLUSION

This is the first case of non-classic lipoid CAH combined with Graves' disease reported in the Chinese population. In addition to conventional glucocorticoid replacement therapy, timely adjustments were made to the dosages of thyroid hormone and glucocorticoid to avoid adrenal crisis as a consequence of the increased demand and accelerated metabolism of glucocorticoids when the patient was diagnosed with Graves' disease.

Getting pregnant with congenital adrenal hyperplasia: Assisted reproduction and pregnancy complications. A systematic review and meta-analysis

Many patients with congenital adrenal hyperplasia (CAH) refrain from seeking pregnancy, suffer from infertility or worry about pregnancy complications, mainly due to genitalia abnormalities, anovulation, unreceptive endometrium and metabolic disturbances. Despite those challenges, many live births have been reported. In this systematic review, we focused on the key to successful assisted reproduction strategies and the potential pregnancy complications. We did a systematic literature search of Pubmed, Medline and Scopus for articles reporting successful pregnancies in CAH other than 21-hydroxylase deficiency, and found 25 studies reporting 39 pregnancies covering deficiency in steroidogenic acute regulatory protein, 17α-hydroxylase/17,20-lyase, 11β-hydroxylase, P450 oxidoreductase, cytochrome b5 and 3β-hydroxysteroid dehydrogenase. We summarized various clinical manifestations and tailored reproduction strategy for each subtype. Furthermore, a meta-analysis was performed to evaluate the pregnancy complications of CAH patients. A total of 19 cross-sectional or cohort studies involving 1311 pregnancies of classic and non-classic CAH patients were included. Surprisingly, as high as 5.5% (95% CI 2.3%-9.7%) of pregnancies were electively aborted, and the risk was significantly higher in those studies with a larger proportion of classic CAH than those with only non-classical patients (8.43% (4.1%-13.81%) VS 3.75%(1.2%-7.49%)), which called for better family planning. Pooled incidence of miscarriage was 18.2% (13.4%-23.4%) with a relative risk (RR) of 1.86 (1.27-2.72) compared to control. Glucocorticoid treatment in non-classical CAH patients significantly lowered the miscarriage rate when compared to the untreated group (RR 0.25 (0.13-0.47)). CAH patients were also more susceptible to gestational diabetes mellitus, with a prevalence of 7.3% (2.4%-14.1%) and a RR 2.57 (1.29-5.12). However, risks of preeclampsia, preterm birth and small for gestational age were not significantly different. 67.8% (50.8%-86.9%) CAH patients underwent Cesarean delivery, 3.86 (1.66-8.97) times the risk of the control group. These results showed that fertility is possible for CAH patients but special care was necessary when planning, seeking and during pregnancy.

Systematic Review Registration

PROSPERO https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=342642, CRD42022342642.

The A'-helix of CYP11A1 remodels mitochondrial cristae

Background

CYP11A1 is a protein located in the inner membrane of mitochondria catalyzing the first step of steroid synthesis. As a marker gene for steroid-producing cells, the abundance of CYP11A1 characterizes the extent of steroidogenic cell differentiation. Besides, the mitochondria of fully differentiated steroidogenic cells are specialized with tubulovesicular cristae. The participation of CYP11A1 in the change of mitochondrial structure and the differentiation of steroid-producing cells, however, has not been investigated.

Methods

We engineered nonsteroidogenic monkey kidney COS1 cells to express CYP11A1 upon doxycycline induction and examined the mitochondrial structure of these cells. We also mapped the CYP11A1 domains that confer structural changes of mitochondria. We searched for CYP11A1-interacting proteins and investigated the role of this interacting protein in shaping mitochondrial structure. Finally, we examined the effect of CYP11A1 overexpression on the amount of mitochondrial contact site and cristae organizing system.

Results

We found that CYP11A1 overexpression led to the formation of tubulovesicular cristae in mitochondria. We also identified the A’-helix located at amino acid #57–68 to be sufficient for membrane insertion and crista remodeling. We identified heat shock protein 60 (Hsp60) as the CYP11A1-interacting protein and showed that Hsp60 is required for CYP11A1 accumulation and crista remodeling. Finally, we found that the small MIC10 subcomplex of the mitochondrial contact site and cristae organizing system was reduced when CYP11A1 was overexpressed.

Conclusions

CYP11A1 participates in the formation of tubulovesicular cristae in the mitochondria of steroidogenic cells. Its A’-helix is sufficient for the formation of tubulovesicular cristae and for protein integration into the membrane. CYP11A1 interacts with Hsp60, which is required for CYP11A1 accumulation. The accumulation of CYP11A1 leads to the reduction of MIC10 complex and changes mitochondrial structure.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12929-022-00846-7.

Classic and backdoor pathways of androgen biosynthesis in human sexual development

Both genes and hormones regulate human sexual development. Although ovarian hormones are not essential for female external genitalia development, male sexual development requires the action of testicular testosterone and dihydrotestosterone (DHT). DHT is the most active endogenous androgen formed by the conversion of testosterone in genital skin. This synthesis route from cholesterol to DHT is called the conventional classic pathway. Recent investigations have reported an alternative ("backdoor") route for DHT formation that bypasses fetal testicular testosterone. This alternative route plays a crucial role in human hyperandrogenic disorders like congenital adrenal hyperplasia caused by P450c21 deficiency, polycystic ovary syndrome, and P450 oxidoreductase deficiency. In addition, mutations in AKR1C2 and AKR1C4, genes encoding 3α-reductases, have been implicated in disorders of sexual development, indicating that both the classic and backdoor routes are required for normal human male sexual development. More recently, androsterone was found to be the primary androgen of the human backdoor route. Androsterone and steroidal substrates specific to the backdoor route are predominantly found in the placenta, liver, and adrenal glands rather than in the testes. These findings are essential to understanding human sexual development.

Identification of a homozygous c.1039C>T (p.R347C) variant in CYP17A1 in a 67-year-old female patient with partial 17α-hydroxylase/17,20-lyase deficiency

17α-Hydroxylase/17,20-lyase deficiency (17OHD) is caused by pathogenic mutations in CYP17A1. Impaired 17α-hydroxylase and 17,20-lyase activities typically induce hypertension, hypokalemia, sexual infantilism, and amenorrhea. Most patients with 17OHD are diagnosed in adolescence. Here, we report a female (46, XX) patient with 17OHD who was diagnosed at the age of 67 years. Genetic analysis was performed using direct DNA sequencing of polymerase chain reaction (PCR) products and multiplex ligation-dependent probe amplification (MLPA) analysis. Direct DNA sequencing revealed a homozygous c.1039C>T in CYP17A1, corresponding to a p.R347C amino acid change. MLPA probe signals showed that the CYP17A1 mutation was present in the homozygous carrier state. The patient's dehydroepiandrosterone sulfate and androstenedione levels were extremely low, despite elevated adrenocorticotropic hormone (ACTH) and normal cortisol levels. A corticotropin-releasing hormone (CRH) test showed no response of cortisol, despite a normal response of ACTH. Rapid ACTH injection resulted in elevations in the deoxycorticosterone, corticosterone, aldosterone, and 17-hydroxypregnenolone levels, but not in the cortisol level. These results suggested that 17α-hydroxylase/17,20-lyase activities were partially impaired. Computed tomography revealed bilateral adrenal hyperplasia and a hypoplastic uterus. A high basal plasma ACTH level and a discrepancy between ACTH and cortisol responses in a CRH test may provide a definitive diagnostic clue for this disease.

A mitochondrial ADXR-ADX-P450 electron transport chain is essential for maternal gametophytic control of embryogenesis in Arabidopsis

Mitochondrial adrenodoxins (ADXs) are small iron–sulfur proteins that function as mobile shuttles transferring electrons. Their function has been largely known in animals, as they transfer electrons between an adrenodoxin reductase (ADXR) and mitochondrial P450s, which is a crucial step that leads to steroidogenesis. Here we show that a functional mitochondrial ADX–ADXR–P450 pathway is essential for steroid biosynthesis and that its function is required for plant sexual reproduction.

Mitochondrial adrenodoxins (ADXs) are small iron–sulfur proteins with electron transfer properties. In animals, ADXs transfer electrons between an adrenodoxin reductase (ADXR) and mitochondrial P450s, which is crucial for steroidogenesis. Here we show that a plant mitochondrial steroidogenic pathway, dependent on an ADXR–ADX–P450 shuttle, is essential for female gametogenesis and early embryogenesis through a maternal effect. The steroid profile of maternal and gametophytic tissues of wild-type (WT) and adxr ovules revealed that homocastasterone is the main steroid present in WT gametophytes and that its levels are reduced in the mutant ovules. The application of exogenous homocastasterone partially rescued adxr and P450 mutant phenotypes, indicating that gametophytic homocastasterone biosynthesis is affected in the mutants and that a deficiency of this hormone causes the phenotypic alterations observed. These findings also suggest not only a remarkable similarity between steroid biosynthetic pathways in plants and animals but also a common function during sexual reproduction.

Congenital Adrenal Hyperplasia-Current Insights in Pathophysiology, Diagnostics, and Management

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive disorders affecting cortisol biosynthesis. Reduced activity of an enzyme required for cortisol production leads to chronic overstimulation of the adrenal cortex and accumulation of precursors proximal to the blocked enzymatic step. The most common form of CAH is caused by steroid 21-hydroxylase deficiency due to mutations in CYP21A2. Since the last publication summarizing CAH in Endocrine Reviews in 2000, there have been numerous new developments. These include more detailed understanding of steroidogenic pathways, refinements in neonatal screening, improved diagnostic measurements utilizing chromatography and mass spectrometry coupled with steroid profiling, and improved genotyping methods. Clinical trials of alternative medications and modes of delivery have been recently completed or are under way. Genetic and cell-based treatments are being explored. A large body of data concerning long-term outcomes in patients affected by CAH, including psychosexual well-being, has been enhanced by the establishment of disease registries. This review provides the reader with current insights in CAH with special attention to these new developments.

Regulation of 17α-Hydroxyprogesterone Production during Induced Oocyte Maturation and Ovulation in Amur Sturgeon (Acipenser schrenckii)

In several teleosts, 17α, 20β-dihydroxy-4-pregnen-3-one (DHP) has been identified as a maturation-inducing steroid. DHP is synthesized from 17α-hydroxyprogesterone (17OHP) by 17β-hydroxysteroid dehydrogenase type 12-like (hsd17b12L). Along with 3β-hydroxysteroid dehydrogenase/Δ5-4 isomerase (3β-HSD), 17α-hydroxylase and C17-20 lyase are associated with 17OHP production. This study aimed to determine the roles of Amur sturgeon hsd3b, P450c17-I (cyp17a1), and P450c17-II (cyp17a2) in 17OHP production and to examine their enzyme activity and mRNA expression pattern during oocyte maturation. In the sturgeons used in this study, hsd3b encoded 3β-HSD, cyp17a1 catalyzed 17α-hydroxylase production with C17-20 lyase activity, and cyp17a2 processed 17α-hydroxylase activity alone. In the ovarian follicles of individuals that underwent induced ovulation, hsd3b mRNA levels increased rapidly, cyp17a1 expression was downregulated, and cyp17a2 expression was upregulated during oocyte maturation. Finally, an in vitro study revealed that salmon pituitary extract (SPE) stimulation rapidly induced hsd3b expression, whereas cyp17a1 expression was downregulated. In vitro, cyp17a2 expression did not rapidly increase with SPE stimulation. This rapid upregulation of hsd3b during oocyte maturation was first observed in teleosts. It was suggested that hsd17b12L expression is upregulated after 17OHP production, which is regulated by hsd3b, cyp17a1, and cyp17a2, resulting in DHP production.

Polycystic ovarian syndrome: signs and feedback effects of hyperandrogenism and insulin resistance

Polycystic ovary syndrome (PCOS) is a disease whose diagnosis is based on the detection of hyperandrogenism (HA) and ovulatory dysfunction. Women with PCOS frequently develop insulin resistance (IR), which generates a metabolic condition that involves a decrease in the action of insulin at the cellular level and is linked to compensatory hyperinsulinemia (HI). In PCOS, the ovary remains sensitive to the action of insulin. Additionally, it has been observed that the main effect of insulin in the ovary is the stimulation of androgen synthesis, resulting in HA, one of the fundamental characteristics of the PCOS. In this sense, the excess of androgens favors the development of IR, thus perpetuating the cycle of IR-HI-HA, and therefore PCOS. Moreover, mitochondrial dysfunction is present in PCOS patients and is a common feature in both IR and HA. This review places electron transfer as a key element in HA and IR development, with emphasis on the relationship between androgen biosynthesis and mitochondrial function. Indeed, metformin has been involved in repair mitochondrial dysfunction, decrease of oxidative stress, reduction of androgens levels and the enhancing of insulin sensitivity. Therefore, we propose that treatment with metformin could decrease HI and consequently HA, restoring, at least in part, the metabolic and hormonal disorders of PCOS.

Estrogens and the Schrödinger's Cat in the Ovarian Tumor Microenvironment

Simple Summary

Ovarian cancer is a complex pathology for which we require effective screening and therapeutical strategies. Apart from the cancer cell portion, there exist plastic immune and non-immune cell populations, jointly constituting the context-adaptive tumor microenvironment, which is pivotal in tumorigenesis. Estrogens might be synthesized in the ovarian tumor tissue and actively contribute to the shaping of an immunosuppressive microenvironment. Current immune therapies have limited effectiveness as a multitude of factors influence the outcome. A thorough understanding of the ovarian cancer biology is crucial in the efforts to reestablish homeostasis.

Abstract

Ovarian cancer is a heterogeneous disease affecting the aging ovary, in concert with a complex network of cells and signals, together representing the ovarian tumor microenvironment. As in the “Schrödinger’s cat” thought experiment, the context-dependent constituents of the—by the time of diagnosis—well-established tumor microenvironment may display a tumor-protective and -destructive role. Systemic and locally synthesized estrogens contribute to the formation of a pro-tumoral microenvironment that enables the sustained tumor growth, invasion and metastasis. Here we focus on the estrogen biosynthetic and metabolic pathways in ovarian cancer and elaborate their actions on phenotypically plastic, estrogen-responsive, aging immune cells of the tumor microenvironment, altogether highlighting the multicomponent-connectedness and complexity of cancer, and contributing to a broader understanding of the ovarian cancer biology.

Steroidogenic electron-transfer factors and their diseases

Most steroidogenesis disorders are caused by mutations in genes encoding the steroidogenic enzymes, but work in the past 20 years has identified related disorders caused by mutations in the genes encoding the cofactors that transport electrons from NADPH to P450 enzymes. Most P450s are microsomal and require electron donation by P450 oxidoreductase (POR); by contrast, mitochondrial P450s require electron donation via ferredoxin reductase (FdxR) and ferredoxin (Fdx). POR deficiency is the most common and best-described of these new forms of congenital adrenal hyperplasia. Severe POR deficiency is characterized by the Antley-Bixler skeletal malformation syndrome and genital ambiguity in both sexes, and hence is easily recognized, but mild forms may present only with infertility and subtle disorders of steroidogenesis. The common POR polymorphism A503V reduces catalysis by P450c17 (17-hydroxylase/17,20-lyase) and the principal drugmetabolizing P450 enzymes. The 17,20-lyase activity of P450c17 requires the allosteric action of cytochrome b5, which promotes interaction of P450c17 with POR, with consequent electron transfer. Rare b5 mutations are one of several causes of 17,20-lyase deficiency. In addition to their roles with steroidogenic mitochondrial P450s, Fdx and FdxR participate in the synthesis of iron-sulfur clusters used by many enzymes. Disruptions in the assembly of Fe-S clusters is associated with Friedreich ataxia and Parkinson disease. Recent work has identified mutations in FdxR in patients with neuropathic hearing loss and visual impairment, somewhat resembling the global neurologic disorders seen with mitochondrial diseases. Impaired steroidogenesis is to be expected in such individuals, but this has not yet been studied.

Substrate-induced modulation of protein-protein interactions within human mitochondrial cytochrome P450-dependent system

Steroidogenesis is strictly regulated at multiple levels, as produced steroid hormones are crucial to maintain physiological functions. Cytochrome P450 enzymes are key players in adrenal steroid hormone biosynthesis and function within short redox-chains in mitochondria and endoplasmic reticulum. However, mechanisms regulating supply of reducing equivalents in the mitochondrial CYP-dependent system are not fully understood. In the present work, we aimed to estimate how the specific steroids, substrates, intermediates and products of multistep reactions modulate protein-protein interactions between adrenodoxin (Adx) and mitochondrial CYP11 s. Using the SPR technology we determined that steroid substrates affect affinity and stability of CYP11s-Adx complexes in an isoform-specific mode. In particular, cholesterol induces a 4-fold increase in the rate of CYP11A1 - Adx complex formation without significant effect on dissociation (koff decreased ∼1.5-fold), overall increasing complex affinity. At the same time steroid substrates decrease the affinity of both CYP11B1 - Adx and CYP11B2 - Adx complexes, predominantly reducing their stability (4-7 fold). This finding reveals differentiation of protein-protein interactions within the mitochondrial pool of CYPs, which have the same electron donor. The regulation of electron supply by the substrates might affect the overall steroid hormones production. Our experimental data provide further insight into protein-protein interactions within CYP-dependent redox chains involved in steroidogenesis.

The mitochondrial localized CISD-3.1/CISD-3.2 proteins are required to maintain normal germline structure and function in Caenorhabditis elegans

Reproductive organs and developing tissues have high energy demands that require metabolic functions primarily supported by mitochondria function. The highly conserved CISD/NEET iron-sulfur (Fe-S) protein family regulates iron and reactive oxygen homeostasis, both of which are important for mitochondrial function. Disruption of iron and reactive oxygen homeostasis typically leads to detrimental effects. In humans, CISD dysfunction is associated with human health issues including Wolfram syndrome 2. Using C. elegans, we previously determined that the cisd-1, cisd-3.1 and cisd-3.2 have an overlapping role in the regulation of physiological germline apoptosis through the canonical programmed cell death pathway. Here, we isolated the cisd-3.2(pnIs68) mutant that resulted in physiological and fitness defects including germline abnormalities that are associated with abnormal stem cell niche and disrupted formation of bivalent chromosomes. The cisd-3.2(pnIs68) mutation led to complete disruption of the cisd-3.2 gene expression and a decrease in expression of genetically intact cisd-1 and cisd-3.1 genes suggesting an indirect impact of the cisd-3.2(pnIs68) allele. The CISD-3.2 and CISD-3.1 proteins localize to the mitochondria in many tissues throughout development. The cisd-3.2(pnIs68) mutant displays phenotypes associated with mitochondrial dysfunction, including disruption of the mitochondrial network within the germline. These results further support the idea that the CISD protein family is required for mitochondrial function that supports important functions in animals including overall fitness and germline viability.

Effects of Osthole on Progesterone Secretion in Chicken Preovulatory Follicles Granulosa Cells

Simple Summary

Progesterone produced by granulosa cells regulates the diverse reproductive events in poultry. Osthole is a natural compound extracted from Cnidium. In this study, we confirmed Osthole up-regulated the progesterone secretion though elevating the expression of key proteins in the process of progesterone synthesis. These results indicate Osthole could be used in the pre-peak phase and (or) the peak phase to maximize the output of egg production in laying hens. Moreover, it provided a new idea that natural compounds may be the target library to screen the potential drugs used in poultry to increase the egg quality and yield.

Abstract

Osthole (Ost) is an active constituent of Cnidium monnieri (L.) Cusson which possesses anti-inflammatory and anti-oxidative properties. It also has estrogen-like activity and can stimulate corticosterone secretion. The present study was aimed to check the role of Ost on progesterone (P4) secretion in cultured granulosa cells obtained from hen preovulatory follicles. Different concentrations (5, 2.5, and 1.25 µg/mL) of Ost was added to granulosa cells for 6, 12, 18, and 24 h to investigate the level of progesterone secretions using enzyme linked immunosorbent assay (ELISA). The results showed that progesterone secretion was significantly increased in cells treated with Ost at 2.5 μg/mL. Also, qRT-PCR showed that mRNA expression of steroidogenic acute regulatory protein (StAR) was significantly up-regulated by Ost at 2.5 μg/mL concentration. Cytochrome P450 side-chain cleavage (P450scc) and 3β-hydroxysteroid dehydrogenase (3β-HSD) was significantly up-regulated by Ost. However, no significant differences were observed for the expression of proliferating cell nuclear antigen (PCNA). The protein expression of StAR, P450scc and 3β-HSD were significantly up-regulated by Ost treatment. The concentration of cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) in cell lysates showed no change with Ost treatment at 2.5 μg/mL by ELISA. An ROS kit showed non-significant difference in the level of reactive oxygen species (ROS). In conclusion, Ost treatment at a concentration of 2.5 μg/mL for 24 h had significantly up-regulated P4 secretion by elevating P450scc, 3β-HSD and StAR at both gene and protein level in granulosa cells obtained from hen preovulatory follicles.

Clinical and genetic analysis of cytochrome P450 oxidoreductase (POR) deficiency in a female and the analysis of a novel POR intron mutation causing alternative mRNA splicing : Overall analysis of a female with POR deficiency

OBJECTIVE

To characterize the clinical features of a female with P450 oxidoreductase (POR) deficiency and to investigate the underlying mechanisms of POR inactivation.

METHODS

The proband was a 35-year-old woman with primary infertility and menstrual irregularity. The reproductive endocrine profile was evaluated. DNA sequencing was conducted for the identification of POR gene mutation. RT-PCR was performed to confirm the impact of the mutation on POR mRNA. A molecular model was built for the structural analysis of mutant POR protein.

RESULTS

The evaluation of reproductive endocrine profile revealed elevation of serum follicle-stimulating hormone (11.48 mIU/ml), progesterone (11.00 ng/ml), 17α-hydroxyprogesterone (24.24 nmol/l), dehydroepiandrosterone (6300 nmol/l), and androstenedione (3.89 nmol/l) and decreased estradiol (36.02 pg/ml). Sequencing of the POR gene showed the female was a compound heterozygote of the paternal P399_E401 deletion and a novel maternal IVS14-1G>C mutation. Functional analysis revealed IVS14-1G>C mutation caused alternative splicing of POR mRNA, with the loss of 12 nucleotides in exon 15 (c.1898_1909delGTCTACGTCCAG). Also, the resulting mutant POR protein had a V603_Q606 deletion, which inactivated the nucleotide-binding domain of NADPH in POR protein (K602_Q606).

CONCLUSION

The mutation IVS14-1G>C of the POR gene could cause alternative splicing of POR mRNA and dysfunction of the resulting POR protein. Under proper IVF strategy with glucocorticoid therapy and endometrial preparation, females with mild POR deficiency still have the opportunity to have a live birth.

Clinical, endocrinological, and molecular features of four Korean cases of cytochrome P450 oxidoreductase deficiency

PURPOSE

Cytochrome P450 oxidoreductase (POR) deficiency is a rare autosomal recessive disorder caused by mutations in the POR gene encoding an electron donor for all microsomal P450 enzymes. It is characterized by adrenal insufficiency, ambiguous genitalia, maternal virilization during pregnancy, and skeletal dysplasia. In this study, we investigated the clinical, hormonal, and molecular characteristics of patients with POR deficiency in Korea.

METHODS

This study included four patients with POR deficiency confirmed by biochemical and molecular analysis of POR. Clinical and biochemical findings were reviewed retrospectively. Mutation analysis of POR was performed by Sanger sequencing after polymerase chain reaction amplification of all coding exons and the exon-intron boundaries.

RESULTS

All patients presented with adrenal insufficiency and ambiguous genitalia regardless of their genetic sex. Two patients harbored homozygous p.R457H mutations in POR and presented with adrenal insufficiency and genital ambiguity without skeletal phenotypes. The other two patients with compound heterozygous mutations of c.[1329_1330insC];[1370G>A] (p.[I444Hfs*6];[R457H]) manifested skeletal abnormalities, such as craniosynostosis and radiohumeral synostosis, suggesting Antley-Bixler syndrome. They also had multiple congenital anomalies involving heart, kidney, and hearing ability. All patients were treated with physiologic doses of oral hydrocortisone.

CONCLUSION

We report the cases of 4 patients with POR deficiency identified by mutation analysis of POR. Although the study involved a small number of patients, the POR p.R457H mutation was the most common, suggesting founder effect in Korea. POR deficiency is rare and can be misdiagnosed as 21-hydroxylase or 17α-hydroxylase/17,20-lyase deficiency. Therefore, molecular analysis is critical for confirmatory diagnosis.

Molecular Basis of CYP19A1 Deficiency in a 46,XX Patient With R550W Mutation in POR: Expanding the PORD Phenotype

CONTEXT

Mutations in cytochrome P450 oxidoreductase (POR) cause a form of congenital adrenal hyperplasia (CAH). We report a novel R550W mutation in POR identified in a 46,XX patient with signs of aromatase deficiency.

OBJECTIVE

Analysis of aromatase deficiency from the R550W mutation in POR.

DESIGN, SETTING, AND PATIENT

Both the child and the mother had signs of virilization. Ultrasound revealed the presence of uterus and ovaries. No defects in CYP19A1 were found, but further analysis with a targeted Disorders of Sexual Development NGS panel (DSDSeq.V1, 111 genes) on a NextSeq (Illumina) platform in Madrid and Barcelona, Spain, revealed compound heterozygous mutations c.73_74delCT/p.L25FfsTer93 and c.1648C > T/p.R550W in POR. Wild-type and R550W POR were produced as recombinant proteins and tested with multiple cytochrome P450 enzymes at University Children's Hospital, Bern, Switzerland.

MAIN OUTCOME MEASURE AND RESULTS

POR-R550W showed 41% of the WT activity in cytochrome c and 7.7% activity for reduction of MTT. Assays of CYP19A1 showed a severe loss of activity, and CYP17A1 as well as CYP21A2 activities were also lost by more than 95%. Loss of CYP2C9, CYP2C19, and CYP3A4 activities was observed for the R550W-POR. Predicted adverse effect on aromatase activity as well as a reduction in binding of NADPH was confirmed.

CONCLUSIONS

Pathological effects due to POR-R550W were identified, expanding the knowledge of molecular pathways associated with aromatase deficiency. Screening of the POR gene may provide a diagnosis in CAH without defects in genes for steroid metabolizing enzymes.

Differential effects of variations in human P450 oxidoreductase on the aromatase activity of CYP19A1 polymorphisms R264C and R264H

Aromatase (CYP19A1) converts androgens into estrogens and is required for female sexual development and growth and development in both sexes. CYP19A1 is a member of cytochrome P450 family of heme-thiolate monooxygenases located in the endoplasmic reticulum and depends on reducing equivalents from the reduced nicotinamide adenine dinucleotide phosphate via the cytochrome P450 oxidoreductase coded by POR. Both the CYP19A1 and POR genes are highly polymorphic, and mutations in both these genes are linked to disorders of steroid biosynthesis. We have previously shown that R264C and R264H mutations in CYP19A1, as well as mutations in POR, reduce CYP19A1 activity. The R264C is a common polymorphic variant of CYP19A1, with high frequency in Asian and African populations. Polymorphic alleles of POR are found in all populations studied so far and, therefore, may influence activities of CYP19A1 allelic variants. So far, the effects of variations in POR on enzymatic activities of allelic variants of CYP19A1 or any other steroid metabolizing cytochrome P450 proteins have not been studied. Here we are reporting the effects of three POR variants on the aromatase activities of two CYP19A1 variants, R264C, and R264H. We used bacterially expressed and purified preparations of WT and variant forms of CYP19A1 and POR and constructed liposomes with embedded CYP19A1 and POR proteins and assayed the CYP19A1 activities using radiolabeled androstenedione as a substrate. With the WT-POR as a redox partner, the R264C-CYP19A1 showed only 15% of aromatase activity, but the R264H had 87% of aromatase activity compared to WT-CYP19A1. With P284L-POR as a redox partner, R264C-CYP19A1 lost all activity but retained 6.7% of activity when P284T-POR was used as a redox partner. The R264H-CYP19A1 showed low activities with both the POR-P284 L as well as the POR-P284 T. When the POR-Y607C was used as a redox partner, the R264C-CYP19A1 retained approximately 5% of CYP19A1 activity. Remarkably, The R264H-CYP19A1 had more than three-fold higher activity compared to WT-CYP19A1 when the POR-Y607C was used as the redox partner, pointing toward a beneficial effect. The slight increase in activity of R264C-CYP19A1 with the P284T-POR and the three-fold increase in activity of the R264H-CYP19A1 with the Y607C-POR point toward a conformational effect and role of protein-protein interaction governed by the R264C and R264H substitutions in the CYP19A1 as well as P284 L, P284 T and Y607C variants of POR. These studies demonstrate that the allelic variants of P450 when present with a variant form of POR may show different activities, and combined effects of variations in the P450 enzymes as well as in the POR should be considered when genetic data are available. Recent trends in the whole-exome and whole-genome sequencing as diagnostic tools will permit combined evaluation of variations in multiple genes that are interdependent and may guide treatment options by adjusting therapeutic interventions based on laboratory analysis.

Dietary Intakes of Vitamin B-2 (Riboflavin), Vitamin B-6, and Vitamin B-12 and Ovarian Cycle Function among Premenopausal Women

BACKGROUND

Riboflavin, vitamin B-6, and vitamin B-12 are key players in one-carbon metabolism as enzymatic cofactors, and deficiency of these nutrients may influence reproductive outcomes possibly through affecting reproductive hormones.

OBJECTIVE

The goal was to investigate associations between dietary intakes of riboflavin, vitamin B-6, and vitamin B-12, and menstrual function among premenopausal women.

DESIGN

This was a secondary analysis of a prospective cohort study conducted at the University at Buffalo during 2005 to 2007.

PARTICIPANTS/SETTING

Participants were 259 healthy, regularly menstruating women (aged 18 to 44 years) with self-reported menstrual cycles between 21 and 35 days, who were not trying to conceive, and who had not used hormonal contraception during the past 3 months.

MAIN OUTCOME MEASURES

Intakes of B vitamins were assessed via 24-hour dietary recalls four times per menstrual cycle for two cycles. Serum reproductive hormones and plasma homocysteine were measured eight and three times, respectively, per cycle for two cycles. Anovulatory cycles were determined by progesterone concentrations ≤5 ng/mL (15.9 nmol/L) and no observed serum luteinizing hormone peak during the mid or late luteal phase visit.

STATISTICAL ANALYSIS

Weighted linear mixed regressions were used to evaluate associations between cycle-averaged B vitamin intakes and hormones and homocysteine, and generalized linear regressions for associations with anovulation. Models were adjusted for age, race, body mass index, physical activity, alternate Mediterranean diet score, intakes of total energy, protein, fiber, and folate, and percentage of energy intake from fat.

RESULTS

Higher intakes of riboflavin (per 0.1 mg increase in intake) were inversely correlated with estradiol (-0.87%, 95% CI -1.67 to -0.06) and homocysteine levels (-0.61%, 95% CI -1.10 to -0.12). Higher vitamin B-6 intakes were suggestive of higher follicle-stimulating hormone, although the results were not statistically significant (0.63% difference, 95% CI -0.03 to 1.29, per 0.1 mg increase in intake; P=0.06). Small increases in testosterone and decreases in homocysteine were found with vitamin B-12 intake. No associations were observed between intake of B vitamins and a risk of sporadic anovulation.

CONCLUSIONS

Higher intakes of riboflavin were associated with a small decrease in serum estradiol among healthy, regularly menstruating women. Higher intakes of riboflavin and vitamin B-12 were associated with lower plasma homocysteine concentrations. Overall, riboflavin, vitamin B-6, and vitamin B-12 that are one-carbon nutrients do not appear to influence the ovarian cycle among premenopausal women.

Association of POR and PPARα polymorphisms with risk of anti-tuberculosis drug-induced liver injury in Western Chinese Han population

OBJECTIVES

Anti-tuberculosis drug-induced liver injury (ATDILI) is a common and sometimes severe adverse drug reaction (ADR). This study was conducted to investigate the relationship between polymorphisms of two genes, cytochrome P450 oxidoreductase (POR) and peroxisome proliferator-activated receptor α (PPARα), and the risk of ATDILI in Western Chinese Han population.

METHODS

A total of 118 tuberculosis (TB) patients with ATDILI and 628 TB patients without ATDILI during anti-TB treatment were recruited from West China Hospital of Sichuan University. DNA was extracted from peripheral blood, and genotypes of the selected 12 single nucleotide polymorphisms (SNPs) (3 SNPs in the POR gene and 9 SNPs in the PPARα gene) were determined. Three genetic models (additive, dominant, and recessive), as well as a haplotype, were used to test the genetic risk of ATDILI. Extended subgroup analysis was conducted according to age, sex and different causality assessments.

RESULTS

The mutant allele, genotype and genetic model of rs3898649 in the POR gene were found to be associated with increased risk of ATDILI, especially in the younger (<50 years old), female and pulmonary tuberculosis subgroup. The other two SNPs rs28737229 and rs4728533 in the POR gene showed only a potential association with susceptibility to ATDILI after Bonferroni correction (P < .05 but P_Bonferroni > .05). The other 9 SNPs loci (rs135549, rs9626730, rs4253712, rs4823613, rs4253730, rs6007662, rs4253728, rs2024929 and rs135561) in the PPARα gene showed no significant differences between ATDILI and non-ATDILI in either allele frequencies or genotype (all P >.05).

CONCLUSIONS

The results demonstrated the strong correlation between POR gene SNP rs3898649 and ATDILI susceptibility, suggesting the importance of POR rs3898649 in the pathogenesis and development of ATDILI. Therefore, our results indicated that POR rs3898649 might be a valuable biomarker potentially involved in ATDILI.

Proteomics Recapitulates Ovarian Proteins Relevant to Puberty and Fertility in Brahman Heifers (Bos indicus L.)

High fertility and early puberty in Bos indicus heifers are desirable and genetically correlated traits in beef production. The hypothalamus-pituitary-ovarian (HPO) axis synthesizes steroid hormones, which contribute to the shift from the pre-pubertal state into the post-pubertal state and influence subsequent fertility. Understanding variations in abundance of proteins that govern steroid synthesis and ovarian signaling pathways remains crucial to understanding puberty and fertility. We used whole ovaries of six pre-pubertal and six post-pubertal Brahman heifers to conduct differential abundance analyses of protein profiles between the two physiological states. Extracted proteins were digested into peptides followed by identification and quantification with massspectrometry (MS) by sequential window acquisition of all instances of theoretical fragment ion mass spectrometry (SWATH-MS). MS and statistical analysis identified 566 significantly differentially abundant (DA) proteins (adjusted p < 0.05), which were then analyzed for gene ontology and pathway enrichment. Our data indicated an up-regulation of steroidogenic proteins contributing to progesterone synthesis at luteal phase post-puberty. Proteins related to progesterone signaling, TGF-β, retinoic acid, extracellular matrix, cytoskeleton, and pleiotrophin signaling were DA in this study. The DA proteins probably relate to the formation and function of the corpus luteum, which is only present after ovulation, post-puberty. Some DA proteins might also be related to granulosa cells signaling, which regulates oocyte maturation or arrest in ovaries prior to ovulation. Ten DA proteins were coded by genes previously associated with reproductive traits according to the animal quantitative trait loci (QTL) database. In conclusion, the DA proteins and their pathways were related to ovarian activity in Bos indicus cattle. The genes that code for these proteins may explain some known QTLs and could be targeted in future genetic studies.

46,XX DSD due to Androgen Excess in Monogenic Disorders of Steroidogenesis: Genetic, Biochemical, and Clinical Features

The term 'differences of sex development' (DSD) refers to a group of congenital conditions that are associated with atypical development of chromosomal, gonadal, or anatomical sex. Disorders of steroidogenesis comprise autosomal recessive conditions that affect adrenal and gonadal enzymes and are responsible for some conditions of 46,XX DSD where hyperandrogenism interferes with chromosomal and gonadal sex development. Congenital adrenal hyperplasias (CAHs) are disorders of steroidogenesis that mainly involve the adrenals (21-hydroxylase and 11-hydroxylase deficiencies) and sometimes the gonads (3-beta-hydroxysteroidodehydrogenase and P450-oxidoreductase); in contrast, aromatase deficiency mainly involves the steroidogenetic activity of the gonads. This review describes the main genetic, biochemical, and clinical features that apply to the abovementioned conditions. The activities of the steroidogenetic enzymes are modulated by post-translational modifications and cofactors, particularly electron-donating redox partners. The incidences of the rare forms of CAH vary with ethnicity and geography. The elucidation of the precise roles of these enzymes and cofactors has been significantly facilitated by the identification of the genetic bases of rare disorders of steroidogenesis. Understanding steroidogenesis is important to our comprehension of differences in sexual development and other processes that are related to human reproduction and fertility, particularly those that involve androgen excess as consequence of their impairment.

The Adrenal Lipid Droplet is a New Site for Steroid Hormone Metabolism

Steroid hormones play essential roles for living organisms. It has been long and well established that the endoplasmic reticulum (ER) and mitochondria are essential sites for steroid hormone biosynthesis because several steroidogenic enzymes are located in these organelles. The adrenal gland lipid droplet (LD) proteomes from human, macaque monkey, and rodent are analyzed, revealing that steroidogenic enzymes are also present in abundance on LDs. The enzymes found include 3β-hydroxysteroid dehydrogenase (HSD3B) and estradiol 17β-dehydrogenase 11 (HSD17B11). Analyses by Western blot and subcellular localization consistently demonstrate that HSD3B2 is localized on LDs. Furthermore, in vitro experiments confirm that the isolated LDs from HeLa cell stably expressing HSD3B2 or from rat adrenal glands have the capacity to convert pregnenolone to progesterone. Collectively, these data suggest that LDs may be important sites of steroid hormone metabolism. These findings may bring novel insights into the biosynthesis and metabolism of steroid hormones and the development of treatments for adrenal disorders.

Sex Differences in Traumatic Brain Injury: What We Know and What We Should Know

There is growing recognition of the problem of male bias in neuroscience research, including in the field of traumatic brain injury (TBI) where fewer women than men are recruited to clinical trials and male rodents have predominantly been used as an experimental injury model. Despite TBI being a leading cause of mortality and disability worldwide, sex differences in pathophysiology and recovery are poorly understood, limiting clinical care and successful drug development. Given growing interest in sex as a biological variable affecting injury outcomes and treatment efficacy, there is a clear need to summarize sex differences in TBI. This scoping review presents an overview of current knowledge of sex differences in TBI and a comparison of human and animal studies. We found that overall, human studies report worse outcomes in women than men, whereas animal studies report better outcomes in females than males. However, closer examination shows that multiple factors including injury severity, sample size, and experimental injury model may differentially interact with sex to affect TBI outcomes. Additionally, we explore how sex differences in mitochondrial structure and function might contribute to possible sex differences in TBI outcomes. We propose recommendations for future investigations of sex differences in TBI, which we hope will lead to improved patient management, prognosis, and translation of therapies from bench to bedside.

Drp1 Phosphorylation Is Indispensable for Steroidogenesis in Leydig Cells

The initial steps of steroidogenesis occur in the mitochondria. Dynamic changes in the mitochondria are associated with their fission and fusion. Therefore, understanding the cellular and molecular relationships between steroidogenesis and mitochondrial dynamics is important. The hypothesis of the current study is that mitochondrial fission and fusion are closely associated with steroid hormone synthesis in testicular Leydig cells. Steroid hormone production, induced by dibutyryl cAMP (dbcAMP) in Leydig cells, was accompanied by increased mitochondrial mass. Mitochondrial elongation increased during the dbcAMP-induced steroid production, whereas mitochondrial fragmentation was reduced. Among the mitochondrial-shaping proteins, the level of dynamin-associated protein 1 (Drp1) was altered in response to dbcAMP stimulation. The increase in Drp1 Ser 637 phosphorylation correlated with steroid hormone production in the MA-10 Leydig cells as well as in the primary adult rat Leydig cells. Drp1 was differentially expressed in the Leydig cells during testicular development. Finally, gonadotropin administration altered the status of Drp1 phosphorylation in the Leydig cells of immature rat testes. Overall, mitochondrial dynamics is directly linked to steroidogenesis, and Drp1 plays an important regulatory role during steroidogenesis. This study shows that Drp1 level is regulated by cAMP and that its phosphorylation via protein kinase A (PKA) activation plays a decisive role in mitochondrial shaping by offering an optimal environment for steroid hormone biosynthesis in Leydig cells. Therefore, it is suggested that PKA-mediated Drp1 Ser 637 phosphorylation is indispensable for steroidogenesis in the Leydig cells, and this phosphorylation results in mitochondrial elongation via the relative attenuation of mitochondrial fission during steroidogenesis.

Transcriptional Regulation of Ovarian Steroidogenic Genes: Recent Findings Obtained from Stem Cell-Derived Steroidogenic Cells

Ovaries represent one of the primary steroidogenic organs, producing estrogen and progesterone under the regulation of gonadotropins during the estrous cycle. Gonadotropins fluctuate the expression of various steroidogenesis-related genes, such as those encoding steroidogenic enzymes, cholesterol deliverer, and electronic transporter. Steroidogenic factor-1 (SF-1)/adrenal 4-binding protein (Ad4BP)/NR5A1 and liver receptor homolog-1 (LRH-1) play important roles in these phenomena via transcriptional regulation. With the aid of cAMP, SF-1/Ad4BP and LRH-1 can induce the differentiation of stem cells into steroidogenic cells. This model is a useful tool for studying the molecular mechanisms of steroidogenesis. In this article, we will provide insight into the transcriptional regulation of steroidogenesis-related genes in ovaries that are revealed from stem cell-derived steroidogenic cells. Using the cells derived from the model, novel SF-1/Ad4BP- and LRH-1-regulated genes were identified by combined DNA microarray and promoter tiling array analyses. The interaction of SF-1/Ad4BP and LRH-1 with transcriptional regulators in the regulation of ovarian steroidogenesis was also revealed.

MECHANISMS IN ENDOCRINOLOGY: Rare defects in adrenal steroidogenesis

Congenital adrenal hyperplasia (CAH) is a group of genetic disorders of adrenal steroidogenesis that impair cortisol synthesis, with compensatory increases in ACTH leading to hyperplastic adrenals. The term 'CAH' is generally used to mean 'steroid 21-hydroxylase deficiency' (21OHD) as 21OHD accounts for about 95% of CAH in most populations; the incidences of the rare forms of CAH vary with ethnicity and geography. These forms of CAH are easily understood on the basis of the biochemistry of steroidogenesis. Defects in the steroidogenic acute regulatory protein, StAR, disrupt all steroidogenesis and are the second-most common form of CAH in Japan and Korea; very rare defects in the cholesterol side-chain cleavage enzyme, P450scc, are clinically indistinguishable from StAR defects. Defects in 3β-hydroxysteroid dehydrogenase, which also causes disordered sexual development, were once thought to be fairly common, but genetic analyses show that steroid measurements are generally unreliable for this disorder. Defects in 17-hydroxylase/17,20-lyase ablate synthesis of sex steroids and also cause mineralocorticoid hypertension; these are common in Brazil and in China. Isolated 17,20-lyase deficiency can be caused by rare mutations in at least three different proteins. P450 oxidoreductase (POR) is a co-factor used by 21-hydroxylase, 17-hydroxylase/17,20-lyase and aromatase; various POR defects, found in different populations, affect these enzymes differently. 11-Hydroxylase deficiency is the second-most common form of CAH in European populations but the retention of aldosterone synthesis distinguishes it from 21OHD. Aldosterone synthase deficiency is a rare salt-losing disorder. Mild, 'non-classic' defects in all of these factors have been described. Both the severe and non-classic disorders can be treated if recognized.

Mutation of HSD3B2 Gene and Fate of Dehydroepiandrosterone

3βHSD2 enzyme is crucial for adrenal and gonad steroid biosynthesis. In enzyme deficiency states, due to recessive loss-of-function HSD3B2 mutations, steroid flux is altered and clinical manifestations result. Deficiency of 3βHSD2 activity in the adrenals precludes normal aldosterone and cortisol synthesis and the alternative backdoor and 11-oxygenated C19 steroid pathways and the flooding of cortisol precursors along the Δ5 pathway with a marked rise in DHEA and DHEAS production. In gonads, it precludes normal T and estrogen synthesis. Here, we review androgen-dependent male differentiation of the external genitalia in humans and link this to female development and steroidogenesis in the developing adrenal cortex. The molecular mechanisms governing postnatal adrenal cortex zonation and ZR development were also revised. This chapter will review relevant clinical, hormonal, and genetic aspects of 3βHSD2 deficiency with emphasis on the significance of alternate fates encountered by steroid hormone precursors in the adrenal gland and gonads. Our current knowledge of the process of steroidogenesis and steroid action is derived from pathological conditions. In humans the 3βHSD2 deficiency represents a model of nature that reinforces our knowledge about the role of the steroidogenic alternative pathway in sex differentiation in both sexes. However, the physiological role of the high serum DHEAS levels in fetal life as well as after adrenarche remains to be elucidated.

Mitochondria, Estrogen and Female Brain Aging

Mitochondria play an essential role in the generation of steroid hormones including the female sex hormones. These hormones are, in turn, able to modulate mitochondrial activities. Mitochondria possess crucial roles in cell maintenance, survival and well-being, because they are the main source of energy as well as of reactive oxygen species (ROS) within the cell. The impairment of these important organelles is one of the central features of aging. In women’s health, estrogen plays an important role during adulthood not only in the estrous cycle, but also in the brain via neuroprotective, neurotrophic and antioxidant modes of action. The hypestrogenic state in the peri- as well as in the prolonged postmenopause might increase the vulnerability of elderly women to brain degeneration and age-related pathologies. However, the underlying mechanisms that affect these processes are not well elucidated. Understanding the relationship between estrogen and mitochondria might therefore provide better insights into the female aging process. Thus, in this review, we first describe mitochondrial dysfunction in the aging brain. Second, we discuss the estrogen-dependent actions on the mitochondrial activity, including recent evidence of the estrogen—brain-derived neurotrophic factor and estrogen—sirtuin 3 (SIRT3) pathways, as well as their potential implications during female aging.

Sequence-Based Analysis of Lipid-Related Metabolites in a Multiethnic Study

Small molecule lipid-related metabolites are important components of fatty acid and steroid metabolism-two important contributors to human health. This study investigated the extent to which rare and common genetic variants spanning the human genome influence the lipid-related metabolome. Sequence data from 1552 European-Americans (EA) and 1872 African-Americans (AA) were analyzed to examine the impact of common and rare variants on the levels of 102 circulating lipid-related metabolites measured by a combination of chromatography and mass spectroscopy. We conducted single variant tests [minor allele frequency (MAF) > 5%, statistical significance P-value ≤ 2.45 × 10^-10] and tests aggregating rare variants (MAF ≤ 5%) across multiple genomic motifs, such as coding regions and regulatory domains, and sliding windows. Multiethnic meta-analyses detected 53 lipid-related metabolites-locus pairs, which were inspected for evidence of consistent signal between the two ethnic groups. Thirty-eight lipid-related metabolite-genomic region associations were consistent across ethnicities, among which seven were novel. The regions contain genes that are related to metabolite transport (SLC10A1) and metabolism (SCD, FDX1, UGT2B15, and FADS2). Six of the seven novel findings lie in expression quantitative trait loci affecting the expression levels of 14 surrounding genes in multiple tissues. Imputed expression levels of 10 of the affected genes were associated with four corresponding lipid-related traits in at least one tissue. Our findings offer valuable insight into circulating lipid-related metabolite regulation in a multiethnic population.

Dehydroepiandrosterone Research: Past, Current, and Future

The discovery of "oestrus-producing" hormones was a major research breakthrough in biochemistry and pharmacology during the early part of the 20th century. The elucidation of the molecular weight and chemical structure of major oxidative metabolites of dehydroepiandrosterone (DHEA) led to the award of the Nobel Prize in 1939 to Adolf Frederick Johann Butenandt and Leopold Ruzicka. Considered a bulk androgen in the circulation, DHEA and its sulfated metabolite DHEA-S can be taken up by most tissues where the sterols are metabolized to active androgenic and estrogenic compounds needed for growth and development. Butenandt's interactions with the German pharmaceutical company Schering led to production of gram quantities of these steroids and other chemically modified compounds of this class. Sharing chemical expertise allowed Butenandt's laboratory at the Kaiser Wilhelm Institute to isolate and synthesize many steroid compounds in the elucidation of the pathway leading from cholesterol to testosterone and estrogen derivatives. As a major pharmaceutical company worldwide, Schering AG sought these new biological sterols as pharmacological agents for endocrine-related diseases, and the European medical community tested these compounds in women for conditions such as postmenopausal depression, and in men for increasing muscle mass. Since it was noted that circulating DHEA-S levels decline as a function of age, experimental pathology experiments in animals were performed to determine how DHEA may protect against cancer, diabetes, aging, obesity, immune function, bone density, depression, adrenal insufficiency, inflammatory bowel disease, diminished sexual function/libido, AIDS/HIV, chronic obstructive pulmonary disease, coronary artery disease, chronic fatigue syndrome, and metabolic syndrome. While the mechanisms by which DHEA ameliorates these conditions in animal models have been elusive to define, even less is known about its role in human disease, other than as a precursor to other sterols, e.g., testosterone and estradiol. Our groups have shown that DHEA and many of its oxidative metabolites serve as a low-affinity ligands for hepatic nuclear receptors, such as the pregnane X receptor, the constitutive androstane receptor, and estrogen receptors α/β (ERα/ERβ) as well as G protein-coupled ER (GPER1). This chapter highlights the founding research on DHEA from a historical perspective, provides an overview of DHEA biosynthesis and metabolism, briefly summarizes the early work on the beneficial effects attributed to DHEA in animals, and summarizes the human trials addressing the action of DHEA as a therapeutic agent. In general, most human studies involve weak correlations of circulating levels of DHEA and disease outcomes. Some support for DHEA as a therapeutic compound has been demonstrated for postmenopausal women, in vitro fertilization, and several autoimmune disorders, and adverse health effects, such as, acne, embryo virilization during pregnancy, and possible endocrine-dependent cancers.

Molecular mechanisms of tributyltin-induced alterations in cholesterol homeostasis and steroidogenesis in hamster testis: In vivo and in vitro studies

Tributyltins (TBT) are ubiquitous and persistent environmental contaminants that disturb normal endocrine function including gonadal function in humans and marine organisms. TBT was administered through oral route to male Syrian hamsters at daily doses of 50, 100, and 150 ppm/kg for 65 days. Changes in testis morphology, immunohistochemistry of iNOS, 3β-HSD, and 17β-HSD, cholesterol transport receptor, nuclear receptors, and transcription factors were analyzed. TBT treatment affected each of these parameters to significant levels in a dose-dependent manner compared to vehicle treated control. Real-time PCR and protein analyses revealed that expression levels of ApoE and LDL-R mRNA were up-regulated in the testis of TBT-treated animals while the expression levels of SR-B1, LXR, PPARs α, β, and γ, SCAP, SREBP 1 and 2, 3β-HSD, 17β-HSD, CYP17A1, and P450_SCC were down-regulated. Leydig cells were isolated and separated adopting percoll gradient centrifugation under aseptic condition. The viability of Leydig cell was affected by TBT treatment in a dose- and time-dependent manner. Further, the mechanism of action of TBT was ascertained by siRNA transfection of ApoE, which was upregulated, and SREBP, which was down-regulated. These observations led us to infer that exposure to TBT hinders intracellular cholesterol transport resulting in abnormal sex steroid biosynthesis and alteration of steroidogenic enzyme activities. Finally, we could recognize ApoE and SREBP as the major factors regulating genes that control cholesterol biosynthesis and steroidogenesis that ultimately inhibit the synthesis of testosterone. Therefore, ApoE is one of the important molecular targets that can be intercepted in context of male infertility/male contraception.

Steroidogenic abnormalities in translocator protein knockout mice and significance in the aging male

The translocator protein (TSPO) has been proposed to act as a key component in a complex important for mitochondrial cholesterol importation, which is the rate-limiting step in steroid hormone synthesis. However, TSPO function in steroidogenesis has recently been challenged by the development of TSPO knockout (TSPO-KO) mice, as they exhibit normal baseline gonadal testosterone and adrenal corticosteroid production. Here, we demonstrate that despite normal androgen levels in young male TSPO-KO mice, TSPO deficiency alters steroidogenic flux and results in reduced total steroidogenic output. Specific reductions in the levels of progesterone and corticosterone as well as age-dependent androgen deficiency were observed in both young and aged male TSPO-KO mice. Collectively, these findings indicate that while TSPO is not critical for achieving baseline testicular and adrenal steroidogenesis, either indirect effects of TSPO on steroidogenic processes, or compensatory mechanisms and functional redundancy, lead to subtle steroidogenic abnormalities which become exacerbated with aging.