BACKGROUND:Dysfunction of δ-aminolevulinic acid dehydratase (ALAD), the second enzyme involved in heme biosynthesis, leads to two pathologies: genetic and acquired. The genetic form is an ultrarare, severe childhood-onset disease inherited in an autosomal recessive manner, whereas the acquired form usually affects adults due to enzyme inhibition by specific chemicals. AIMS AND PATIENT COHORT:This study reports the molecular characterization of three pediatric patients with genetic ALAD deficiency porphyria (ADP), including two siblings, and five adults who exhibited features suggestive of heavy metal poisoning. Furthermore, using an innovative mouse liver model, we performed in vivo functional analysis of the pathogenic variants and lead susceptibility alleles identified in the ALAD gene. RESULTS:Siblings (one female) were found to carry the c440_441delinsTT (p.Arg147Leu) variant in homozygosis. However, the vector expression system confirmed a pathogenic role only for the c.440C > T substitution. The third patient exhibited compound heterozygosity, with a c.839G > A (p.Gly280Glu) dominant variant and a hypomorphic c.724G > A (p.Val242Ile) allele. The rs1805313 and rs8177800 common intron variants were most prevalent in patients with acquired ADP. However, increased ALAD activity for the rs1139488 synonymous variant and a hexameric ALAD conformation for the rs1800435 missense variant have been established. CONCLUSION:These findings underscore the molecular heterogeneity of the ALAD gene and present the first reported case of ADP in a female patient.

RNA-based therapeutics have rapidly emerged over the past decade, offering a new class of medicines that differ significantly from conventional drugs. These therapies can be programmed to target or restore defective genes, allowing for more personalised treatments and reducing side effects. Notably, RNA therapies have made significant progress in the treatment of genetic liver diseases, exemplified by small interfering RNA treatments for hereditary transthyretin amyloidosis, which use liver-targeting strategies such as GalNAc conjugation to improve efficacy and safety. RNA-based gene-editing technologies, such as base editor and prime editor clustered regularly interspaced short palindromic repeats systems, also show promise with their ability to minimise genomic rearrangements and cancer risk. While RNA therapies offer high precision, challenges remain in optimising delivery methods and ensuring long-term safety and efficacy. Lipid nanoparticle-mRNA therapeutics, particularly for protein replacement in rare diseases, have gained support from preclinical successes. Compared with viral gene therapies, mRNA therapies present a safer profile with reduced risks of genomic integration and oncogene activation. However, clinical trials, especially for rare diseases, face limitations such as small sample sizes and short observation periods. Further preclinical studies, including non-human primates, will be essential for refining trial designs. Despite their potential, the high costs of RNA therapies pose a challenge that will require cost-utility models to guide pricing and accessibility. Here, we discuss the fundamental aspects of RNA-based therapeutics and showcase the most relevant preclinical and clinical developments in genetic liver metabolic diseases.

Acute intermittent porphyria (AIP) is a genetic metabolic disorder characterized by neurovisceral attacks. Although high-carbohydrate diets or intravenous glucose administration can help alleviate incipient attacks in patients, these interventions may also promote insulin resistance and increase metabolic risk. This study explored targeted dietary interventions to manage hyperinsulinemia and to enhance glucose uptake in insulin-sensitive organs under high-carbohydrate diet. Body composition and fecal microbiota profile were also investigated in a murine model of the disease. Wild-type and AIP mice (n = 6/group) were supplemented with tapioca maltodextrin in drinking water for 12 weeks, alongside heat-treated Bifidobacterium animalis subsp. lactis CECT-8145 (BPL1®HT), its by-product lipoteichoic acid (LTA), or the insulin-sensitizing agent α-lipoic acid (α-LA). Liver-targeted therapies, previously assessed in AIP mice, were also included in this study. AIP mice on a high-carbohydrate diet exhibited hyperinsulinemia and tissue-specific differences in glucose uptake compared to wild-type mice. Dysbiosis, marked by reduced fecal Dorea spp. and Adlercreutzia muris, alongside higher abundance of Escherichia coli, was also showed. Supplementation with α-LA and LTA revealed superior ability to improve glucose tolerance test and skeletal muscle glucose uptake, reduce hyperinsulinemia, and enhance body composition by increasing lean mass relative to fat, compared to gene therapy or liver-targeted insulin administration. Notably, LTA restored fecal microbiota profiles resembling those of wild-type mice. In conclusion, supplementation with LTA from BPL1®HT and α-LA may represent promising dietary interventions to manage glucose tolerance, improve insulin sensitivity in muscle and adipose tissues, and potentially ameliorate body composition in AIP patients under a high-carbohydrate diet.

Objective Acute intermittent porphyria (AIP) is a rare metabolic disorder caused by haploinsufficiency of hepatic porphobilinogen deaminase (PBGD), the third enzyme of the heme biosynthesis. Individuals with AIP experience neurovisceral attacks closely associated with hepatic overproduction of potentially neurotoxic heme precursors. Design We replicated AIP in non-human primates (NHPs) through selective knockdown of the hepatic PBGD gene and evaluated the safety and therapeutic efficacy of human PBGD (hPBGD) mRNA rescue. Results Intrahepatic administration of a recombinant adeno-associated viral vector containing short hairpin RNA against endogenous PBGD mRNA resulted in sustained PBGD activity inhibition in liver tissue for up to 7 months postinjection. The administration of porphyrinogenic drugs to NHPs induced hepatic heme synthesis, elevated urinary porphyrin precursors and reproduced acute attack symptoms in patients with AIP, including pain, motor disturbances and increased brain GABAergic activity. The model also recapitulated functional anomalies associated with AIP, such as reduced brain perfusion and cerebral glucose uptake, disturbances in hepatic TCA cycle, one-carbon metabolism, drug biotransformation, lipidomic profile and abnormal mitochondrial respiratory chain activity. Additionally, repeated systemic administrations of hPBGD mRNA in this AIP NHP model restored hepatic PBGD levels and activity, providing successful protection against acute attacks, metabolic changes in the liver and CNS disturbances. This approach demonstrated better efficacy than the current standards of care for AIP. Conclusion This novel model significantly expands our understanding of AIP at the molecular, biochemical and clinical levels and confirms the safety and translatability of multiple systemic administration of hPBGD mRNA as a potential aetiological AIP treatment.

Porphyrias are rare, mostly inherited disorders resulting from altered activity of specific enzymes in the haem synthesis pathway that lead to accumulation of pathway intermediates. Photocutaneous symptoms occur when excess amounts of photoreactive porphyrins circulate in the blood to the skin, whereas increases in potentially neurotoxic porphyrin precursors are associated with neurovisceral symptoms. Current therapies are suboptimal and their mechanisms are not well established. As described here, emerging therapies address underlying disease mechanisms by introducing a gene, RNA or other specific molecule with the potential to cure or slow progression of the disease. Recent progress in nanotechnology and nanoscience, particularly regarding particle design and formulation, is expanding disease targets. More secure and efficient drug delivery systems have extended our toolbox for transferring specific molecules, especially into hepatocytes, and led to proof-of-concept studies in animal models. Repurposing existing drugs as molecular chaperones or haem synthesis inhibitors is also promising. This review summarizes key examples of these emerging therapeutic approaches and their application for hepatic and erythropoietic porphyrias.

Computational electromagnetics (CEM) has become an indispensable tool for engineers in a wide range of applications in the aerospace and naval industries. The complexity of these industries, with challenges such as advanced antenna design, Electromagnetic Environmental Effects (E3), and radar cross section (RCS) control, demands the use of powerful simulation tools. However, new times bring new advances to the industry and, with them, new challenges to the computational electromagnetic field. Seeking cutting-edge advances in very low observability (VLO) techniques and E3 in modern platforms further underscores the need for these tools, capable of dealing with multiple scales and all kinds of novel modern materials (metamaterials).

Non-conformal surface integral equation (SIE) methods have received considerable attention from the research community in recent years, in search of procedures to simplify the generation of computer-aided-design (CAD) and mesh models for electromagnetic solution of complex problems or in the context of collaborative projects.

The electromagnetic behavior of periodic structures has gained great interest in recent years due to their fundamental role in the development of scattering networks, plasmonic crystals and many other fields related to nanophotonics, including nanoscale and metasurface devices. Linked to this interest is an increasing demand for the development of tools capable of modelling the electromagnetic behaviour of periodic structures as efficiently as possible. In the context of surface integral equation (SIE) methods based on the method of moments (MoM), most of the existing literature has focused on the development of techniques based on the Ewald method, which requires modelling the system with an infinite periodic structure or dealing with complex physical issues to correctly model the edge effects or the standing waves, whose accurate prediction can be critical in some applications.

Acute intermittent porphyria (AIP) is a metabolic disorder caused by mutations in the porphobilinogen deaminase (PBGD) gene, encoding the third enzyme of the heme synthesis pathway. Although AIP is characterized by low clinical penetrance (~1% of PBGD mutation carriers), patients with clinically stable disease report chronic symptoms and frequently show insulin resistance. This study aimed to evaluate the beneficial impact of nutritional interventions on correct carbohydrate dysfunctions in a mouse model of AIP that reproduces insulin resistance and altered glucose metabolism. The addition of spores of Bacillus coagulans in drinking water for 12 weeks modified the gut microbiome composition in AIP mice, ameliorated glucose tolerance and hyperinsulinemia, and stimulated fat disposal in adipose tissue. Lipid breakdown may be mediated by muscles burning energy and heat dissipation by brown adipose tissue, resulting in a loss of fatty tissue and improved lean/fat tissue ratio. Probiotic supplementation also improved muscle glucose uptake, as measured using Positron Emission Tomography (PET) analysis. In conclusion, these data provide a proof of concept that probiotics, as a dietary intervention in AIP, induce relevant changes in intestinal bacteria composition and improve glucose uptake and muscular energy utilization. Probiotics may offer a safe, efficient, and cost-effective option to manage people with insulin resistance associated with AIP.

Porphobilinogen deaminase (PBGD) haploinsufficiency (acute intermittent porphyria, AIP) is characterized by neurovisceral attacks associated with high production, accumulation and urinary excretion of heme precursors, δ-aminolevulinic acid (ALA) and porphobilinogen (PBG). The estimated clinical penetrance for AIP is extremely low (<1%), therefore it is likely that other factors may play an important role in the predisposition to developing attacks. Fasting is a known triggering factor. Given the increased prevalence of insulin resistance in patients and the large urinary loss of succinyl-CoA to produce ALA and PBG, we explore the impact of reduced availability of energy metabolites in the severity of AIP pathophysiology. Classic studies found clinical improvement in patients affected by AIP associated with the administration of glucose and concomitant insulin secretion, or after hyperinsulinemia associated with diabetes. Molecular studies have confirmed that glucose and insulin administration induces a repressive effect on hepatic ALA Synthase, the first and regulatory step of the heme pathway. More recently, the insulin-mimicking α-lipoic acid has been shown to improve glucose metabolism and mitochondrial dysfunction in a hepatocyte cell line transfected with interfering RNA targeting PBGD. In AIP mice, preventive treatment with an experimental fusion protein of insulin and apolipoprotein A-I improved the disease by promoting fat mobilization in adipose tissue, increasing the metabolite bioavailability for the TCA cycle and inducing mitochondrial biogenesis in the liver. In this review, we analyze the possible mechanisms underlying abnormal hepatocellular carbohydrate homeostasis in AIP.

Acute intermittent porphyria (AIP) is a rare disease caused by a genetic mutation in the hepatic activity of the porphobilinogen‐deaminase. We aimed to develop a mechanistic model of the enzymatic restoration effects of a novel therapy based on the administration of different formulations of recombinant human‐PBGD (rhPBGD) linked to the ApoAI lipoprotein. This fusion protein circulates in blood, incorporating into HDL and penetrating hepatocytes.

Rare diseases, especially monogenic diseases, which usually affect a single target protein, have attracted growing interest in drug research by encouraging pharmaceutical companies to design and develop therapeutic products to be tested in the clinical arena. Acute intermittent porphyria (AIP) is one of these rare diseases. AIP is characterized by haploinsufficiency in the third enzyme of the heme biosynthesis pathway. Identification of the liver as the target organ and a detailed molecular characterization have enabled the development and approval of several therapies to manage this disease, such as glucose infusions, heme replenishment, and, more recently, an siRNA strategy that aims to down-regulate the key limiting enzyme of heme synthesis. Given the involvement of hepatic hemoproteins in essential metabolic functions, important questions regarding energy supply, antioxidant and detoxifying responses, and glucose homeostasis remain to be elucidated. This review reports recent insights into the pathogenesis of acute attacks and provides an update on emerging treatments aimed at increasing the activity of the deficient enzyme in the liver and restoring the physiological regulation of the pathway. While further studies are needed to optimize gene therapy vectors or large-scale production of liver-targeted PBGD proteins, effective protection of PBGD mRNA against the acute attacks has already been successfully confirmed in mice and large animals, and mRNA transfer technology is being tested in several clinical trials for metabolic diseases.

Inborn errors of metabolism (IEM) encompass a group of monogenic diseases affecting both pediatric and adult populations and currently lack effective treatments. Some IEM such as familial hypercholesterolemia or X-linked protoporphyria are caused by gain of function mutations, while others are characterized by an impaired protein function, causing a metabolic pathway blockage. Pathophysiology classification includes intoxication, storage and energy-related metabolic disorders. Factors specific to each disease trigger acute metabolic decompensations. IEM require prompt and effective care, since therapeutic delay has been associated with the development of fatal events including severe metabolic acidosis, hyperammonemia, cerebral edema, and death. Rapid expression of therapeutic proteins can be achieved hours after the administration of messenger RNAs (mRNA), representing an etiological solution for acute decompensations. mRNA-based therapy relies on modified RNAs with enhanced stability and translatability into therapeutic proteins. The proteins produced in the ribosomes can be targeted to specific intracellular compartments, the cell membrane, or be secreted. Non-immunogenic lipid nanoparticle formulations have been optimized to prevent RNA degradation and to allow safe repetitive administrations depending on the disease physiopathology and clinical status of the patients, thus, mRNA could be also an effective chronic treatment for IEM. Given that the liver plays a key role in most of metabolic pathways or can be used as bioreactor for excretable proteins, this review focuses on the preclinical and clinical evidence that supports the implementation of mRNA technology as a promising personalized strategy for liver metabolic disorders such as acute intermittent porphyria, ornithine transcarbamylase deficiency or glycogen storage disease.