Induction of 5-aminolevulinate synthase by activators of steroid biosynthesis

Therapeutic potential of 5-aminolevulinic acid in metabolic disorders: Current insights and future directions

5-Aminolevulinic acid (5-ALA) is an essential compound in the biosynthesis of heme, playing a critical role in various physiological processes within the human body. This review provides the thorough analysis of the latest research on the molecular mechanisms and potential therapeutic benefits of 5-ALA in managing metabolic disorders. The ability of 5-ALA to influence immune response and inflammation, oxidative/nitrosative stress, antioxidant system, mitochondrial functions, as well as carbohydrate and lipid metabolism, is mediated by molecular mechanisms associated with the suppression of the transcription factor NF-κB signaling pathway, activation of the transcription factor Nrf2/heme oxygenase-1 (HO-1) system leading to the formation of heme-derived reaction products (carbon monoxide, ferrous iron, biliverdin, and bilirubin), which may contribute to HO-1-dependent cytoprotection through antioxidant and immunomodulatory effects. Additionally, it regulates the expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha, cytochrome c oxidase subunit IV, uncoupling proteins UCP1 and UCP2, glucose transporters GLUT1 and GLUT2, and sterol regulatory element-binding protein 1c in relevant tissues. Randomized controlled trials have confirmed the effects of 5-ALA on glucose control in both prediabetic and diabetic patients, noting its safety and tolerability, as well as the safety of its combined use with oral hypoglycemic agents. Only minor side effects have been reported. However, the impact of 5-ALA on markers of systemic inflammation, oxidative and nitrosative stress, and dyslipidemia was not evaluated in these studies. At the same time, preparations of 5-ALA may potentially be effective not only in the treatment of prediabetes and type 2 diabetes mellitus (T2DM), but also in other conditions associated with systemic inflammation, oxidative or nitrosative stress, mitochondrial dysfunction, as well as disorders of carbohydrate and lipid metabolism. It has been concluded that the promising advancement of formulations containing 5-ALA may pave the way for new strategies in preventing and treating these diseases, with subsequent preclinical and clinical trials likely to follow.

The CYP11B subfamily

The biosynthesis of steroid hormones is dependent on P450-catalyzed reactions. In mammals, cholesterol is the common precursor of all steroid hormones, and its conversion to pregnenolone is the initial and rate-limiting step in hormone biosynthesis in steroidogenic tissues such as gonads and adrenal glands. The production of glucocorticoids and mineralocorticoids takes place in the adrenal gland and the final steps are catalyzed by 2 mitochondrial cytochromes P450, CYP11B1 (11β-hydroxylase or P45011β) and CYP11B2 (aldosterone synthase or P450aldo). The occurrence and development of these 2 enzymes in different species, their contribution to the biosynthesis of steroid hormones as well as their regulation at different levels (gene expression, cellular regulation, regulation on the level of proteins) is the topic of this chapter.

Drugs and acute porphyrias: reasons for a hazardous relationship

The porphyrias are a group of metabolic diseases caused by inherited or acquired enzymatic deficiency in the metabolic pathway of heme biosynthesis. Simplistically, they can be considered as storage diseases, because the partial enzymatic defect gives rise to a metabolic "bottleneck" in the biosynthetic pathway and hence to an accumulation of different metabolic intermediates, potentially toxic and responsible for the various (cutaneous or neurovisceral) clinical manifestations observed in these diseases. In the acute porphyrias (acute intermittent porphyria, hereditary coproporphyria, variegate porphyria, and the very rare delta-aminolevulinic acid dehydratase ALAD-d porphyria), the characteristic severe neurovisceral involvement is mainly ascribed to a tissue accumulation of delta-aminolevulinic acid, a neurotoxic nonporphyrin precursor. Many different factors, both endogenous and exogenous, may favor the accumulation of this precursor in patients who are carriers of an enzymatic defect consistent with an acute porphyria, thus contributing to trigger the serious (and potentially fatal) clinical manifestations of the disease (acute porphyric attacks). To date, many different drugs are known to be able to precipitate an acute porphyric attack, so that the acute porphyrias are also considered as pharmacogenetic or toxygenetic diseases. This article reviews the different biochemical mechanisms underlying the capacity of many drugs to precipitate a porphyric acute attack (drug porphyrogenicity) in carriers of genetic mutations responsible for acute porphyrias, and addresses the issue of prescribing drugs for patients affected by these rare, but extremely complex, diseases.

Complicity of haem in some adverse drug-reactions

Genetic variants in haem metabolism enzymes can be predisposition factors for adverse reactions in some individuals. New areas of haem biology may also be associated with idiosyncratic effects which are yet to be identified.

Nuclear receptor 5A (NR5A) family regulates 5-aminolevulinic acid synthase 1 (ALAS1) gene expression in steroidogenic cells

5-Aminolevulinic acid synthase 1 (ALAS1) is a rate-limiting enzyme for heme biosynthesis in mammals. Heme is essential for the catalytic activities of P450 enzymes including steroid metabolic enzymes. Nuclear receptor 5A (NR5A) family proteins, steroidogenic factor-1 (SF-1), and liver receptor homolog-1 (LRH-1) play pivotal roles in regulation of steroidogenic enzymes. Recently, we showed that expression of SF-1/LRH-1 induces differentiation of mesenchymal stem cells into steroidogenic cells. In this study, genome-wide analysis revealed that ALAS1 was a novel SF-1-target gene in differentiated mesenchymal stem cells. Chromatin immunoprecipitation and reporter assays revealed that SF-1/LRH-1 up-regulated ALAS1 gene transcription in steroidogenic cells via binding to a 3.5-kb upstream region of ALAS1. The ALAS1 gene was up-regulated by overexpression of SF-1/LRH-1 in steroidogenic cells and down-regulated by knockdown of SF-1 in these cells. Peroxisome proliferator-activated receptor-γ coactivator-1α, a coactivator of nuclear receptors, also strongly coactivated expression of NR5A-target genes. Reporter analysis revealed that peroxisome proliferator-activated receptor-γ coactivator-1α strongly augmented ALAS1 gene transcription caused by SF-1 binding to the 3.5-kb upstream region. Finally knockdown of ALAS1 resulted in reduced progesterone production by steroidogenic cells. These results indicate that ALAS1 is a novel NR5A-target gene and participates in steroid hormone production.