5-aminolevulinic acid (ALA) deficiency causes impaired glucose tolerance and insulin resistance coincident with an attenuation of mitochondrial function in aged mice

Unearthing FLVCR1a: tracing the path to a vital cellular transporter

The Feline Leukemia Virus Subgroup C Receptor 1a (FLVCR1a) is a member of the SLC49 Major Facilitator Superfamily of transporters. Initially recognized as the receptor for the retrovirus responsible of pure red cell aplasia in cats, nearly two decades since its discovery, FLVCR1a remains a puzzling transporter, with ongoing discussions regarding what it transports and how its expression is regulated. Nonetheless, despite this, the substantial body of evidence accumulated over the years has provided insights into several critical processes in which this transporter plays a complex role, and the health implications stemming from its malfunction. The present review intends to offer a comprehensive overview and a critical analysis of the existing literature on FLVCR1a, with the goal of emphasising the vital importance of this transporter for the organism and elucidating the interconnections among the various functions attributed to this transporter.

Heme metabolism in nonerythroid cells

Heme is an iron-containing prosthetic group necessary for the function of several proteins termed "hemoproteins." Erythrocytes contain most of the body's heme in the form of hemoglobin and contain high concentrations of free heme. In nonerythroid cells, where cytosolic heme concentrations are 2 to 3 orders of magnitude lower, heme plays an essential and often overlooked role in a variety of cellular processes. Indeed, hemoproteins are found in almost every subcellular compartment and are integral in cellular operations such as oxidative phosphorylation, amino acid metabolism, xenobiotic metabolism, and transcriptional regulation. Growing evidence reveals the participation of heme in dynamic processes such as circadian rhythms, NO signaling, and the modulation of enzyme activity. This dynamic view of heme biology uncovers exciting possibilities as to how hemoproteins may participate in a range of physiologic systems. Here, we discuss how heme is regulated at the level of its synthesis, availability, redox state, transport, and degradation and highlight the implications for cellular function and whole organism physiology.

Heme biosynthesis regulates BCAA catabolism and thermogenesis in brown adipose tissue

With age, people tend to accumulate body fat and reduce energy expenditure 1 . Brown (BAT) and beige adipose tissue dissipate heat and increase energy expenditure via the activity of the uncoupling protein UCP1 and other thermogenic futile cycles 2,3 . The activity of brown and beige depots inversely correlates with BMI and age 4-11 , suggesting that promoting thermogenesis may be an effective approach for combating age-related metabolic disease 12-15 . Heme is an enzyme cofactor and signaling molecule that we recently showed to regulate BAT function 16 . Here, we show that heme biosynthesis is the primary contributor to intracellular heme levels in brown adipocytes. Inhibition of heme biosynthesis leads to mitochondrial dysfunction and reduction in UCP1. Although supplementing heme can restore mitochondrial function in heme-synthesis-deficient cells, the downregulation of UCP1 persists due to the accumulation of the heme precursors, particularly propionyl-CoA, which is a product of branched-chain amino acids (BCAA) catabolism. Cold exposure promotes BCAA uptake in BAT, and defects in BCAA catabolism in this tissue hinder thermogenesis 17 . However, BCAAs' contribution to the TCA cycle in BAT and WAT never exceeds 2% of total TCA flux 18 . Our work offers a way to integrate current literature by describing heme biosynthesis as an important metabolic sink for BCAAs.

Synergy of 5-aminolevulinate supplement and CX3CR1 suppression promotes liver regeneration via elevated IGF-1 signaling

Inadequate remnant volume and regenerative ability of the liver pose life-threatening risks to patients after partial liver transplantation (PLT) or partial hepatectomy (PHx), while few clinical treatments focus on safely accelerating regeneration. Recently, we discovered that supplementing 5-aminolevulinate (5-ALA) improves liver cold adaptation and functional recovery, leading us to uncover a correlation between 5-ALA metabolic activities and post-PLT recovery. In a mouse 2/3 PHx model, 5-ALA supplements enhanced liver regeneration, promoting infiltration and polarization of anti-inflammatory macrophages via P53 signaling. Intriguingly, chemokine receptor CX3CR1 functions to counterbalance these effects. Genetic ablation or pharmacological inhibition of CX3CR1 (AZD8797; phase II trial candidate) augmented the macrophagic production of insulin-like growth factor 1 (IGF-1) and subsequent hepatocyte growth factor (HGF) production by hepatic stellate cells. Thus, short-term treatments with both 5-ALA and AZD8797 demonstrated pro-regeneration outcomes superior to 5-ALA-only treatments in mice after PHx. Overall, our findings may inspire safe and effective strategies to better treat PLT and PHx patients.

Sodium ferrous citrate and 5-aminolevulinic acid improve type 2 diabetes by maintaining muscle and mitochondrial health

OBJECTIVE

Improving mitochondrial function is a promising strategy for intervention in type 2 diabetes mellitus. This study investigated the preventive effects of sodium ferrous citrate (SFC) and 5-aminolevulinic acid phosphate (ALA) on several metabolic dysfunctions associated with obesity because they have been shown to alleviate abnormal glucose metabolism in humans.

METHODS

Six-week-old male C57BL/6J mice were fed with a normal diet, a high-fat diet, or a high-fat diet supplemented with SFC and ALA for 15 weeks.

RESULTS

The simultaneous supplementation of SFC + ALA to high-fat diet-fed mice prevented loss of muscle mass, improved muscle strength, and reduced obesity and insulin resistance. SFC + ALA prevented abnormalities in mitochondrial morphology and reverted the diet effect on the skeletal muscle transcriptome, including the expression of glucose uptake and mitochondrial oxidative phosphorylation-related genes. In addition, SFC + ALA prevented the decline in mitochondrial DNA copy number by enhancing mitochondrial DNA maintenance and antioxidant transcription activity, both of which are impaired in high-fat diet-fed mice during long-term fasting.

CONCLUSIONS

These findings suggest that SFC + ALA supplementation exerts its preventive effects in type 2 diabetes mellitus via improved skeletal muscle and mitochondrial health, further validating its application as a promising strategy for the prevention of obesity-induced metabolic disorders.

Antagonism of ALAS1 by the Measles Virus V protein contributes to degradation of the mitochondrial network and promotes interferon response

Viruses have evolved countless mechanisms to subvert and impair the host innate immune response. Measles virus (MeV), an enveloped, non-segmented, negative-strand RNA virus, alters the interferon response through different mechanisms, yet no viral protein has been described as directly targeting mitochondria. Among the crucial mitochondrial enzymes, 5'-aminolevulinate synthase (ALAS) is an enzyme that catalyzes the first step in heme biosynthesis, generating 5'-aminolevulinate from glycine and succinyl-CoA. In this work, we demonstrate that MeV impairs the mitochondrial network through the V protein, which antagonizes the mitochondrial enzyme ALAS1 and sequesters it to the cytosol. This re-localization of ALAS1 leads to a decrease in mitochondrial volume and impairment of its metabolic potential, a phenomenon not observed in MeV deficient for the V gene. This perturbation of the mitochondrial dynamics demonstrated both in culture and in infected IFNAR-/- hCD46 transgenic mice, causes the release of mitochondrial double-stranded DNA (mtDNA) in the cytosol. By performing subcellular fractionation post infection, we demonstrate that the most significant source of DNA in the cytosol is of mitochondrial origin. Released mtDNA is then recognized and transcribed by the DNA-dependent RNA polymerase III. The resulting double-stranded RNA intermediates will be captured by RIG-I, ultimately initiating type I interferon production. Deep sequencing analysis of cytosolic mtDNA editing divulged an APOBEC3A signature, primarily analyzed in the 5'TpCpG context. Finally, in a negative feedback loop, APOBEC3A an interferon inducible enzyme will orchestrate the catabolism of mitochondrial DNA, decrease cellular inflammation, and dampen the innate immune response.

Pilot Trial on the Effect of 5-Aminolevulinic Acid on Glucose Tolerance in Patients with Maternally Inherited Diabetes and Deafness

INTRODUCTION

The amino acid 5-aminolevulinic acid (5-ALA) is the first heme biosynthetic precursor. The combination of 5-ALA with sodium ferrous citrate (SFC) enhances heme production, leading to increased adenosine triphosphate (ATP) production in mitochondria. We investigated whether administering 5-ALA/SFC improves glucose tolerance with an increase in insulin secretion in patients with maternally inherited diabetes and deafness (MIDD), which is characterized by an insulin secretory disorder due to impaired mitochondrial ATP production.

METHODS

This was a single-arm, open-label, interventional study. We prospectively administered the oral glucose tolerance test (OGTT) twice in five patients with MIDD who had received intensive insulin therapy: before and 24 weeks after an administration of 5-ALA/SFC (200/232 mg per day). We measured the concentrations of glucose, insulin, C-peptide, and proinsulin at fasting, and 30, 60, and 120 min after glucose load in each OGTT. The primary endpoint was the changes in the area under the curve (AUC) of serum insulin from 0 to 120 min during OGTT from baseline to 24 weeks.

RESULTS

The serum insulin AUC (µU/mL) during the 120-min OGTT tended to increase from baseline to 24 weeks but not significantly (17.1 ± 13.7 versus 22.3 ± 13.4, p = 0.077). The plasma glucose AUC (mg/dL) during the 120-min OGTT at 24 weeks was not significantly decreased; the late phase of glucose excursion from 60 to 120 min was significantly decreased compared with baseline (357 ± 42 versus 391 ± 50, p = 0.041). The mean level of glycated hemoglobin (HbA1c) decreased from 8.3 ± 1.2% at baseline to 7.9 ± 0.3% at 24 weeks (p = 0.36) without increasing the daily dose of insulin injections.

CONCLUSION

The 24-week administration of 5-ALA/SFC did not demonstrate a significant improvement in insulin secretion in patients with MIDD. Further investigations with a larger number of patients and a placebo control group are required to clarify the potential efficacy of 5-ALA/SFC for ameliorating mitochondrial dysfunctions in MIDD.

TRIAL REGISTRATION

UMIN-CTR000040581 and jRCT071200025.

Age-Related Changes in Skeletal Muscle Iron Homeostasis

Sarcopenia is an age-related condition of slow, progressive loss of muscle mass and strength, which contributes to frailty, increased risk of hospitalization and mortality, and increased health care costs. The incidence of sarcopenia is predicted to increase to >200 million affected older adults worldwide over the next 40 years, highlighting the urgency for understanding biological mechanisms and developing effective interventions. An understanding of the mechanisms underlying sarcopenia remains incomplete. Iron in the muscle is important for various metabolic functions, including oxygen supply and electron transfer during energy production, yet these same chemical properties of iron may be deleterious to the muscle when either in excess or when biochemically unshackled (eg, in ferroptosis), it can promote oxidative stress and induce inflammation. This review outlines the mechanisms leading to iron overload in muscle with aging and evaluates the evidence for the iron overload hypothesis of sarcopenia. Based on current evidence, studies are needed to (a) determine the mechanisms leading to iron overload in skeletal muscle during aging; and (b) investigate whether skeletal muscles are functionally deficient in iron during aging leading to impairments in oxidative metabolism.

Understanding Carbohydrate Metabolism and Insulin Resistance in Acute Intermittent Porphyria

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.

Adverse Effect of Blue Light on DNA Integrity Is Accelerated by 5-Aminolevulinic Acid in HaCaT Human Keratinocyte Cells and B16F1 Murine Melanoma Cells

Several studies have suggested the potential benefits of 5-aminolevulinic acid (5-ALA)-based photodynamic therapy (PDT). 5-ALA is a precursor of heme, which generates reactive oxygen species (ROS) following photoirradiation. Some reports indicate that blue light induces intracellular ROS production. In the present study, we elucidated the effects of blue light and 5-ALA on DNA integrity in B16F1 murine melanoma and human keratinocyte HaCaT cells using a variety of comet assay techniques. Co-treatment with blue light and 5-ALA significantly decreased cell viability in both cell lines. A neutral comet assay was performed to assess DNA double-strand break (DSB) formation and blue light and 5-ALA caused DSBs. We also performed an alkali comet assay to detect single-strand breaks (SSB) and alkali labile sites (ALS). The results indicated that 5-ALA accelerated blue light-induced SSB formation. In addition, modified comet assays were done using two types of enzymes to evaluate oxidative DNA damages. The results indicated that blue light and 5-ALA generated oxidized purine and pyrimidines in both cell lines. In summary, co-treatment with 5-ALA and photoirradiation may cause unexpected DNA damage in cells and tissues.

Evolutionary Trend Analysis of Research on 5-ALA Delivery and Theranostic Applications Based on a Scientometrics Study

5-aminolevulinic acid (5-ALA) has been extensively studied for its sustainability and broad-spectrum applications in medical research and theranostics, as well as other areas. It’s a precursor of protoporphyrin IX (PpIX), a sustainable endogenous and naturally-existing photosensitizer. However, to the best of our knowledge, a scientometrics study based on the scientific knowledge assay of the overall situation on 5-ALA research has not been reported so far, which would be of major importance to the relevant researchers. In this study, we collected all the research articles published in the last two decades from the Web of Science Core Collection database and employed bibliometric methods to comprehensively analyze the dataset from different perspectives using CiteSpace. A total of 1595 articles were identified. The analysis results showed that China published the largest number of articles, and SBI Pharmaceuticals Co., Ltd. was the most productive institution that sponsored several of the most productive authors. The cluster analysis and burst detections indicated that the improvement of photodynamic efficacy theranostics is the up-to-date key direction in 5-ALA research. Furthermore, we emphatically studied nanotechnology involvement in 5-ALA delivery and theranostics research. We envision that our results will be beneficial for researchers to have a panorama of and deep insights into this area, thus inspiring further exploitations, especially of the nanomaterial-based systems for 5-ALA delivery and theranostic applications.

Therapy Follows Diagnosis: Old and New Approaches for the Treatment of Acute Porphyrias, What We Know and What We Should Know

Heme, iron protoporphyrin IX, is one of life’s most central molecules. Hence, availability of the enzymatic machinery necessary for its synthesis is crucial for every cell. Consequently, inborn errors of porphyrin metabolism that compromise normal synthesis, namely the family of porphyrias, undermine normal cellular metabolism given that heme has functions in catalytic centers, signal transduction and functional regulation and its synthesis is fully integrated into the center of intermediary metabolism. Very often, diagnosis of porphyrias is difficult and therefore delayed. Therapy can be as complicated. Over the last 50 years, several strategies have been developed: because of its integration with other parts of intermediary metabolism, the infusion of glucose (glucose effect) was one of the first attempts to counterbalance the dysregulation of porphyrin synthesis in porphyrias. Since heme synthesis is impaired, infusional replacement of heme was the next important therapeutic step. Recently, siRNA technology has been introduced in order to downregulate 5-ALA-synthase 1, which contributes to the patho-physiology of these diseases. Moreover, other novel therapies using enzyme protein replacement, mRNA techniques or proteostasis regulators are being developed.

Assessment of porphyrogenicity of drugs and chemicals in selected hepatic cell culture models through a fluorescence-based screening assay

Compounds that induce 5-aminolevulinic acid [ALA] synthase-1 and/or cytochromes P-450 may induce acute porphyric attacks in patients with the acute hepatic porphyrias [AHPs]. Currently, there is no simple, robust model used to assess and predict the porphyrogenicity of drugs and chemicals. Our aim was to develop a fluorescence-based in vitro assay for this purpose. We studied four different hepatic cell culture models: HepG2 cells, LMH cells, 3D HepG2 organoids, and 3D organoids of primary liver cells from people without known disease [normal human controls]. We took advantage of the fluorescent properties of protoporphyrin IX [PP], the last intermediate of the heme biosynthesis pathway, performing fluorescence spectrometry to measure the intensity of fluorescence emitted by these cells treated with selected compounds of importance to patients with AHPs. Among the four cell culture models, the LMH cells produced the highest fluorescence readings, suggesting that these cells retain more robust heme biosynthesis enzymes or that the other cell models may have lost their inducibility of ALA synthase-1 [ALAS-1]. Allyl isopropyl acetamide [AIA], a known potent porphyrogen and inducer of ALAS-1, was used as a positive control to help predict porphyrogenicity for tested compounds. Among the tested compounds (acetaminophen, acetylsalicylic acid, β-estradiol, hydroxychloroquine sulfate, alpha-methyldopa, D (-) norgestrel, phenobarbital, phenytoin, sulfamethoxazole, sulfisoxazole, sodium valproate, and valsartan), concentrations greater than 0.314 mM for norgestrel, phenobarbital, phenytoin, and sodium valproate produced fluorescence readings higher than the reading produced by the positive AIA control. Porphyrin accumulation was also measured by HPLC to confirm the validity of the assay. We conclude that LMH cell cultures in multi-well plates are an inexpensive, robust, and simple system to predict the porphyrogenicity of existing or novel compounds that may exacerbate the AHPs.

Complex response to physiological and drug-induced hepatic heme demand in monoallelic ALAS1 mice

Regulation of 5-aminolevulinate synthase 1 (ALAS1) for nonerythroid heme is critical for respiration, cell signaling mechanisms and steroid/drug metabolism. ALAS1 is induced in some genetic disorders but unlike other genes in the heme pathway, a gene variant of ALAS1 associated with inherited disease has not been reported. BALB/c mice carrying a null ALAS1 allele caused by a βGEO insert were developed and used to determine the consequences of heme demand of a semi gene copy number. Homozygous disruption of ALAS1 (−/−) was lethal for embryo development post day 6.5 but expression in heterozygotes (+/−) was sufficient for the number of offspring and survival. In both wild type (WT +/+) and +/− mice expression of ALAS1 RNA was greatest in liver and harderian gland and much lower in kidney, lung, heart, brain and spleen. The effects of one WT ALAS1 allele in +/− mice on mRNA levels in liver and harderian gland were less marked compared to brain and other organs that were examined. Many other genes were up-regulated by heterozygosity in liver and brain but to a minimal extent. Hepatic heme oxygenase 1 (HMOX1) mRNA expression was significantly lower in +/− mice but not in brain. No elevated translation of WT allele ALAS1 mRNA was detected in +/− liver as a compensatory mechanism for the disabled allele. Fasting induced ALAS1 mRNA in both WT and +/− mice but only in +/− was this manifest as increased ALAS1 protein. The hepatic protoporphyria-inducing drug 4-ethyl-DDC caused induction of hepatic ALAS1 mRNA and protein levels in both WT and +/− mice but markedly less in the mice with only one intact allele. The findings illustrate the complex response of ALAS1 expression for heme demand but limited evidence that upregulation of a wild type allele can compensate for a null allele.

Crosstalk between Metabolic Disorders and Immune Cells

Metabolic syndrome results from multiple risk factors that arise from insulin resistance induced by abnormal fat deposition. Chronic inflammation owing to obesity primarily results from the recruitment of pro-inflammatory M1 macrophages into the adipose tissue stroma, as the adipocytes within become hypertrophied. During obesity-induced inflammation in adipose tissue, pro-inflammatory cytokines are produced by macrophages and recruit further pro-inflammatory immune cells into the adipose tissue to boost the immune response. Here, we provide an overview of the biology of macrophages in adipose tissue and the relationship between other immune cells, such as CD4+ T cells, natural killer cells, and innate lymphoid cells, and obesity and type 2 diabetes. Finally, we discuss the link between the human pathology and immune response and metabolism and further highlight potential therapeutic targets for the treatment of metabolic disorders.

An Analysis of the Multifaceted Roles of Heme in the Pathogenesis of Cancer and Related Diseases

Heme is an essential prosthetic group in proteins and enzymes involved in oxygen utilization and metabolism. Heme also plays versatile and fascinating roles in regulating fundamental biological processes, ranging from aerobic respiration to drug metabolism. Increasing experimental and epidemiological data have shown that altered heme homeostasis accelerates the development and progression of common diseases, including various cancers, diabetes, vascular diseases, and Alzheimer's disease. The effects of heme on the pathogenesis of these diseases may be mediated via its action on various cellular signaling and regulatory proteins, as well as its function in cellular bioenergetics, specifically, oxidative phosphorylation (OXPHOS). Elevated heme levels in cancer cells intensify OXPHOS, leading to higher ATP generation and fueling tumorigenic functions. In contrast, lowered heme levels in neurons may reduce OXPHOS, leading to defects in bioenergetics and causing neurological deficits. Further, heme has been shown to modulate the activities of diverse cellular proteins influencing disease pathogenesis. These include BTB and CNC homology 1 (BACH1), tumor suppressor P53 protein, progesterone receptor membrane component 1 protein (PGRMC1), cystathionine-β-synthase (CBS), soluble guanylate cyclase (sGC), and nitric oxide synthases (NOS). This review provides an in-depth analysis of heme function in influencing diverse molecular and cellular processes germane to disease pathogenesis and the modes by which heme modulates the activities of cellular proteins involved in the development of cancer and other common diseases.

Multiple roles of haem in cystathionine β-synthase activity: implications for hemin and other therapies of acute hepatic porphyria

The role of haem in the activity of cystathionine β-synthase (CBS) is reviewed and a hypothesis postulating multiple effects of haem on enzyme activity under conditions of haem excess or deficiency is proposed, with implications for some therapies of acute hepatic porphyrias. CBS utilises both haem and pyridoxal 5′-phosphate (PLP) as cofactors. Although haem does not participate directly in the catalytic process, it is vital for PLP binding to the enzyme and potentially also for CBS stability. Haem deficiency can therefore undermine CBS activity by impairing PLP binding and facilitating CBS degradation. Excess haem can also impair CBS activity by inhibiting it via CO resulting from haem induction of haem oxygenase 1 (HO 1), and by induction of a functional vitamin B₆ deficiency following activation of hepatic tryptophan 2,3-dioxygenase (TDO) and subsequent utilisation of PLP by enhanced kynurenine aminotransferase (KAT) and kynureninase (Kynase) activities. CBS inhibition results in accumulation of the cardiovascular risk factor homocysteine (Hcy) and evidence is emerging for plasma Hcy elevation in patients with acute hepatic porphyrias. Decreased CBS activity may also induce a proinflammatory state, inhibit expression of haem oxygenase and activate the extrahepatic kynurenine pathway (KP) thereby further contributing to the Hcy elevation. The hypothesis predicts likely changes in CBS activity and plasma Hcy levels in untreated hepatic porphyria patients and in those receiving hemin or certain gene-based therapies. In the present review, these aspects are discussed, means of testing the hypothesis in preclinical experimental settings and porphyric patients are suggested and potential nutritional and other therapies are proposed.

Iron supplementation regulates the progression of high fat diet induced obesity and hepatic steatosis via mitochondrial signaling pathways

Disruption of iron metabolism is closely related to metabolic diseases. Iron deficiency is frequently associated with obesity and hepatic steatosis. However, the effects of iron supplementation on obesity and energy metabolism remain unclear. Here we show that a high-fat diet supplemented with iron reduces body weight gain and hepatic lipid accumulation in mice. Iron supplementation was found to reduce mitochondrial morphological abnormalities and upregulate gene transcription involved in mitochondrial function and beta oxidation in the liver and skeletal muscle. In both these tissues, iron supplementation increased the expression of genes involved in heme or iron–sulfur (Fe–S) cluster synthesis. Heme and Fe–S cluster, which are iron prosthetic groups contained in electron transport chain complex subunits, are essential for mitochondrial respiration. The findings of this study demonstrated that iron regulates mitochondrial signaling pathways—gene transcription of mitochondrial component molecules synthesis and their energy metabolism. Overall, the study elucidates the molecular basis underlying the relationship between iron supplementation and obesity and hepatic steatosis progression, and the role of iron as a signaling molecule.

Heterozygous disruption of ALAS1 in mice causes an accelerated age-dependent reduction in free heme, but not total heme, in skeletal muscle and liver

5-Aminolevulinic acid (ALA) is the rate-limiting intermediate in heme biosynthesis in vertebrate species; a reaction catalyzed by the mitochondrial ALA synthase 1 (ALAS1) enzyme. Previously we reported that knockdown of the ubiquitously expressed ALAS1 gene in mice disrupts normal glucose metabolism, attenuates mitochondrial function and results in a prediabetic like phenotype when animals pass 20-weeks of age (Saitoh et al., 2018). Contrary to our expectations, the cytosolic and mitochondrial heme content of ALAS1 heterozygous (A1+/-) mice were similar to WT animals. Therefore, we speculated that regulatory "free heme" may be reduced in an age dependent manner in A1+/- mice, but not total heme. Here, we examine free and total heme from the skeletal muscle and liver of WT and A1+/- mice using a modified acetone extraction method and examine the effects of aging on free heme by comparing the amounts at 8-12 weeks and 30-36 weeks of age, in addition to the mRNA abundance of ALAS1. We found an age-dependent reduction in free heme in the skeletal muscle and liver of A1+/- mice, while WT mice showed only a slight decrease in the liver. Total heme levels showed no significant difference between young and aged WT and A1+/- mice. ALAS1 mRNA levels showed an age-dependent reduction similar to that of free heme levels, indicating that ALAS1 mRNA expression levels are a major determinant for free heme levels. The free heme pools in skeletal muscle tissue were almost 2-fold larger than that of liver tissue, suggesting that the heme pool varies across different tissue types. The expression of heme oxygenase 1 (HO-1) mRNA, which is expressed proportionally to the amount of free heme, were similar to those of free heme levels. Taken together, this study demonstrates that the free heme pool differs across tissues, and that an age-dependent reduction in free heme levels is accelerated in mice heterozygous for ALAS1, which could account for the prediabetic phenotype and mitochondrial abnormality observed in these animals.

Regulation of Skeletal Muscle Function by Amino Acids

Amino acids are components of proteins that also exist free-form in the body; their functions can be divided into (1) nutritional, (2) sensory, and (3) biological regulatory roles. The skeletal muscle, which is the largest organ in the human body, representing ~40% of the total body weight, plays important roles in exercise, energy expenditure, and glucose/amino acid usage—processes that are modulated by various amino acids and their metabolites. In this review, we address the metabolism and function of amino acids in the skeletal muscle. The expression of PGC1α, a transcriptional coactivator, is increased in the skeletal muscle during exercise. PGC1α activates branched-chain amino acid (BCAA) metabolism and is used for energy in the tricarboxylic acid (TCA) cycle. Leucine, a BCAA, and its metabolite, β-hydroxy-β-methylbutyrate (HMB), both activate mammalian target of rapamycin complex 1 (mTORC1) and increase protein synthesis, but the mechanisms of activation appear to be different. The metabolite of valine (another BCAA), β-aminoisobutyric acid (BAIBA), is increased by exercise, is secreted by the skeletal muscle, and acts on other tissues, such as white adipose tissue, to increase energy expenditure. In addition, several amino acid-related molecules reportedly activate skeletal muscle function. Oral 5-aminolevulinic acid (ALA) supplementation can protect against mild hyperglycemia and help prevent type 2 diabetes. β-alanine levels are decreased in the skeletal muscles of aged mice. β-alanine supplementation increased the physical performance and improved the executive function induced by endurance exercise in middle-aged individuals. Further studies focusing on the effects of amino acids and their metabolites on skeletal muscle function will provide data essential for the production of food supplements for older adults, athletes, and individuals with metabolic diseases.

Safety and Mode of Action of Diabetes Medications in comparison with 5-Aminolevulinic Acid (5-ALA)

5-Aminolevulinic acid (5-ALA) is a delta amino acid naturally present in every living cell of the human body. 5-ALA is produced in the mitochondria as the first product of the porphyrin synthesis pathway and composes heme; exogenously supplemented 5-ALA helps in upregulating mitochondrial functions. Mitochondrial dysfunction has been associated with the pathophysiology of diabetes mellitus. Thus, in this review, we evaluate the mechanisms of action and adverse effects of common medications used to treat type 2 diabetes mellitus as well as 5-ALA including its mechanism and possible use in diabetes management.

The Relationship of 5-Aminolevulinic Acid on Mood and Coping Ability in Prediabetic Middle Aged and Older Adults

In 2010, approximately 79 million Americans had prediabetes and about 50 percent of those individuals were 65 years and older. The most effective diabetes prevention method in prediabetic adults is lifestyle modification. However, despite the benefits of lifestyle change, diabetes prevalence continues to increase. Maintaining a regular exercise routine and a healthy eating plan may be difficult because of the negative emotional barriers (i.e., stress, mood) that a prediabetic individual faces. This is particularly evident in older individuals when you combine that with decreases in mobility and geriatric syndromes. A potential treatment for these emotional barriers is a natural supplement called 5-aminolevulinic acid (5-ALA). In the current study, the group included 154 participants, both men and women, ranging between the ages of 41 to 71 years old. The study design was a double-blind, randomized parallel-group study. The Psychosocial Depressive Symptoms Questionnaire (PDS) and the Perceived Stress Scale (PSS) were used to examine the effect of two doses of 5-ALA (15 mg and 50 mg) on various components of mood (i.e., hopefulness, loneliness, and motivation) and coping ability. Using SAS software, an ordered logistic regression model was used to analyze the association between the dose groups (control, 15 mg, and 50 mg) and the responses to the two questionnaires, the PDS and PSS, used in this study. An integrative literature review, using the PubMed database, searched for studies on the relationship between 5-ALA administration and mood and coping ability. Our literature review resulted in zero published articles. Next, we found that the intake of 5-ALA was significantly associated with improved coping ability (p = 0.004) and improved self-perception of effort spent (p = 0.002). Finally, we found a significant dose-dependent relationship for the association of 5-ALA intake on measures of effort (p = 0.003), loneliness (p = 0.006), and coping ability (p = 0.003). The 50 mg dose was more effective than the 15 mg dose in improving these measures. In conclusion, after 12 weeks of taking 5-ALA, we found significant improvements in self-perception of effort spent, loneliness, and coping ability in prediabetic middle age and older adults. Improved mood and coping ability may allow prediabetic individuals to overcome the emotional obstacles preventing them from maintaining a healthy lifestyle and ultimately, help them to avoid the development of diabetes.