Molybdate partly mimics insulin-promoted metabolic effects in Drosophila melanogaster

Insights into the biocompatibility of biodegradable metallic molybdenum for cardiovascular applications-a critical review

Atherosclerotic cardiovascular disease (ACD) is the leading cause of death worldwide. The gold standard of treatment is the implantation of a permanent stent implant that is often associated with complications such as thrombus formation, vascular neointimal response, and stent fracture, which altogether decrease the long-term safety and efficacy of the stent. Biodegradable metallic materials have become an attractive alternative because of the ability to facilitate a more physiological healing response while the metal degrades. Recently, Molybdenum (Mo) has been considered as a potential candidate due to its excellent mechanical and medical imaging properties. Moreover, the biomedical research studies performed to date have shown minimal adverse effects in vitro and in vivo. However, there are still concerns of toxicity at high doses, and the impact of the biochemical mechanisms of Mo on material performance especially in pathophysiological environments are yet to be explored. Mo is an essential co factor for enzymes such as xanthine oxidoreductase (XOR) that plays a critical role in vascular homeostasis and ACD progression. Herein, this review will focus on the biochemistry of Mo, its physiological and pathological effects with an emphasis on cardiovascular disease as well as the recent studies on Mo for cardiovascular applications and its advantages over other biodegradable metals. The limitations of Mo research studies will also be discussed and concluded with an outlook to move this revolutionary metallic biomaterial from the bench to the bedside.

Chitosan-Encapsulated Nano-selenium Targeting TCF7L2, PPARγ, and CAPN10 Genes in Diabetic Rats

This study investigates the antidiabetic and antioxidant potential of chitosan-encapsulated selenium nanoparticles in streptozotocin-induced diabetic model. Glibenclamide was used as a reference antidiabetic drug. Forty-eight adult male Wistar rats were used along the study and divided equally into 6 groups of (I) normal control, (II) chitosan-encapsulated selenium nanoparticles (CTS-SeNPs), (III) glibenclamide, (IV) streptozotocin (STZ), (V) STZ + CTS-SeNPs, and (VI) STZ + Glib. The animals were sacrificed on the 35th day of the experiment. Serum glucose, insulin, IGF-1, ALT, AST, CK-MB, oxidative stress, lipid profile, and inflammatory parameters were subsequently assessed. Also, the expression level of TCF7L2, CAPN10, and PPAR-γ genes were evaluated using qPCR. In addition, histopathological studies on pancreatic tissue were carried out. The results revealed that STZ induced both diabetes and oxidative stress in normal rats, manifested by the significant changes in the studied parameters and in the physical structure of pancreatic tissue. Oral administration of CTS-SeNPs or Glib results in a significant amelioration of the levels of serum fasting blood glucose, insulin, IGF-1, AST, ATL, and CK-MB as compared with STZ-induced diabetic rats. CTS-SeNPs and Glib diminished the level of lipid peroxidation, increased total antioxidant capacity level, as well as possessed strong inhibition against serum α-amylase and α-glucosidase activities. Diabetic animals received CTS-SeNPs, or Glib demonstrated a significant (p < 0.05) decrease in the expression level of TCF7L2 and CAPN10 genes with a significant increase in the expression level of PPAR-γ gene, compared to STZ group. The above findings clarify the promising antidiabetic and antioxidant effect of CTS-SeNPs, recommending its inclusion in the currently used protocols for the treatment of diabetes and in the prevention of its related complications.

Dietary Choice Reshapes Metabolism in Drosophila by Affecting Consumption of Macronutrients

The precise regulation of metabolism and feeding behavior is important for preventing the development of metabolic diseases. Here we examine the effects on Drosophila metabolism of dietary choice. These changes are predicted to be dependent on both the quantity and quality of the chosen diet. Using a geometric framework for both no-choice and two-choice conditions, we found that feeding decisions led to higher glucose and trehalose levels but lower triglycerides pools. The feeding regimens had similar strategies for macronutrient balancing, and both maximized hemolymph glucose and glycogen content under low protein intake. In addition, the flies showed significant differences in the way they regulated trehalose and triglyceride levels in response to carbohydrate and protein consumption between choice and no-choice nutrition. Under choice conditions, trehalose and triglyceride levels were maximized at the lowest protein and carbohydrate consumption. Thus, we suggest that these changes in carbohydrate and lipid metabolism are caused by differences in the macronutrients consumed by flies. Food choice elicits rapid metabolic changes to maintain energy homeostasis. These results contribute to our understanding of how metabolism is regulated by the revealed nutrient variation in response to food decisions.

Development of fly tolerance to consuming a high-protein diet requires physiological, metabolic and transcriptional changes

Mortality in insects consuming high-protein-and-low-carbohydrate diets resembles a type III lifespan curve with increased mortality at an early age and few survivors that live a relatively long lifespan. We selected for a Drosophila line able to live for a long time on an imbalanced high-protein-low-carbohydrate diet by carrying out five rounds of breeding to select for the most long-lived survivors. Adaptation to this diet in the selected line was studied at the biochemical, physiological and transcriptomic levels. The selected line of flies consumed less of the imbalanced food but also accumulated more storage metabolites: glycogen, triacylglycerides, and trehalose. Selected flies also had a higher activity of alanine transaminase and a higher urea content. Adaptation of the selected line on the transcriptomic level was characterized by down-regulation of genes encoding serine endopeptidases (Jon25i, Jon25ii, betaTry, and others) but up-regulation of genes encoding proteins related to the immune system, such as antimicrobial peptides, Turandot-family humoral factors, hexamerin isoforms, and vitellogenin. These sets of down- and up-regulated genes were similar to those observed in fruit flies with suppressed juvenile hormone signaling. Our data show that the physiological adaptation of fruit flies to a high-protein-low-carbohydrate diet occurs via intuitive pathways, namely a decrease in food consumption, conversion of amino acids into ketoacids to compensate for the lack of carbohydrate, and accumulation of storage metabolites to eliminate the negative effects of excess amino acids. Nevertheless, transcriptomic adaptation occurs in a counter-intuitive way likely via an influence of gut microbiota on food digestion.

Insulin Signaling in Intestinal Stem and Progenitor Cells as an Important Determinant of Physiological and Metabolic Traits in Drosophila

The insulin–IGF-1 signaling (IIS) pathway is conserved throughout multicellular organisms and regulates many traits, including aging, reproduction, feeding, metabolism, stress resistance, and growth. Here, we present evidence of a survival-sustaining role for IIS in a subset of gut cells in Drosophila melanogaster, namely the intestinal stem cells (ISCs) and progenitor cells. Using RNAi to knockdown the insulin receptor, we found that inhibition of IIS in ISCs statistically shortened the lifespan of experimental flies compared with non-knockdown controls, and also shortened their survival under starvation or malnutrition conditions. These flies also showed decreased reproduction and feeding, and had lower amounts of glycogen and glucose in the body. In addition, increased expression was observed for the Drosophila transcripts for the insulin-like peptides dilp2, dilp5, and dilp6. This may reflect increased insulin signaling in peripheral tissues supported by up-regulation of the target of the brain insulin gene (tobi). In contrast, activation of IIS (via knockdown of the insulin pathway inhibitor PTEN) in intestinal stem and progenitor cells decreased fly resistance to malnutrition, potentially by affecting adipokinetic hormone signaling. Finally, Pten knockdown to enhance IIS also activated JAK–STAT signaling in gut tissue by up-regulation of upd2, upd3, and soc36 genes, as well as genes encoding the EGF receptor ligands spitz and vein. These results clearly demonstrate that manipulating insulin levels may be used to modulate various fly traits, which are important determinants of organismal survival.

Alternative NADH dehydrogenase extends lifespan and increases resistance to xenobiotics in Drosophila

Mitochondrial alternative NADH dehydrogenase (aNDH) was found to extend lifespan when expressed in the fruit fly. We have found that fruit flies expressing aNDH from Ciona intestinalis (NDX) had 17–71% lifespan prolongation on media with different protein-tocarbohydrate ratios except NDX-expressing males that had 19% shorter lifespan than controls on a high protein diet. NDX-expressing flies were more resistant to organic xenobiotics, 2,4-dichlorophenoxyacetic acid and alloxan, and inorganic toxicant potassium iodate, and partially to sodium molybdate treatments. On the other hand, NDX-expressing flies were more sensitive to catechol and sodium chromate. Enzymatic analysis showed that NDX-expressing males had higher glucose 6-phosphate dehydrogenase activity, whilst both sexes showed increased glutathione S-transferase activity.

Metallic Nanoantioxidants as Potential Therapeutics for Type 2 Diabetes: A Hypothetical Background and Translational Perspectives

Hyperglycemia-induced overproduction of reactive oxygen species (ROS) is an important contributor to type 2 diabetes (T2D) pathogenesis. The conventional antioxidant therapy, however, proved to be ineffective for its treatment. This may likely be due to limited absorption profiles and low bioavailability of orally administered antioxidants. Therefore, novel antioxidant agents that may be delivered to specific target organs are actively developed now. Metallic nanoparticles (NPs), nanosized materials with a dimension of 1–100 nm, appear very promising for the treatment of T2D due to their tuned physicochemical properties and ability to modulate the level of oxidative stress. An excessive generation of ROS is considered to be the most common negative outcome related to the application of NPs. Several nanomaterials, however, were shown to exhibit enzyme-like antioxidant properties in animal models. Such NPs are commonly referred to as “nanoantioxidants.” Since NPs can provide specifically targeted or localized therapy, their use is a promising therapeutic option in addition to conventional therapy for T2D. NP-based therapies should certainly be used with caution given their potential toxicity and risk of adverse health outcomes. However, despite these challenges, NP-based therapeutic approaches have a great clinical potential and further translational studies are needed to confirm their safety and efficacy.

Iron Sulfur and Molybdenum Cofactor Enzymes Regulate the Drosophila Life Cycle by Controlling Cell Metabolism

Iron sulfur (Fe-S) clusters and the molybdenum cofactor (Moco) are present at enzyme sites, where the active metal facilitates electron transfer. Such enzyme systems are soluble in the mitochondrial matrix, cytosol and nucleus, or embedded in the inner mitochondrial membrane, but virtually absent from the cell secretory pathway. They are of ancient evolutionary origin supporting respiration, DNA replication, transcription, translation, the biosynthesis of steroids, heme, catabolism of purines, hydroxylation of xenobiotics, and cellular sulfur metabolism. Here, Fe-S cluster and Moco biosynthesis in Drosophila melanogaster is reviewed and the multiple biochemical and physiological functions of known Fe-S and Moco enzymes are described. We show that RNA interference of Mocs3 disrupts Moco biosynthesis and the circadian clock. Fe-S-dependent mitochondrial respiration is discussed in the context of germ line and somatic development, stem cell differentiation and aging. The subcellular compartmentalization of the Fe-S and Moco assembly machinery components and their connections to iron sensing mechanisms and intermediary metabolism are emphasized. A biochemically active Fe-S core complex of heterologously expressed fly Nfs1, Isd11, IscU, and human frataxin is presented. Based on the recent demonstration that copper displaces the Fe-S cluster of yeast and human ferredoxin, an explanation for why high dietary copper leads to cytoplasmic iron deficiency in flies is proposed. Another proposal that exosomes contribute to the transport of xanthine dehydrogenase from peripheral tissues to the eye pigment cells is put forward, where the Vps16a subunit of the HOPS complex may have a specialized role in concentrating this enzyme within pigment granules. Finally, we formulate a hypothesis that (i) mitochondrial superoxide mobilizes iron from the Fe-S clusters in aconitase and succinate dehydrogenase; (ii) increased iron transiently displaces manganese on superoxide dismutase, which may function as a mitochondrial iron sensor since it is inactivated by iron; (iii) with the Krebs cycle thus disrupted, citrate is exported to the cytosol for fatty acid synthesis, while succinyl-CoA and the iron are used for heme biosynthesis; (iv) as iron is used for heme biosynthesis its concentration in the matrix drops allowing for manganese to reactivate superoxide dismutase and Fe-S cluster biosynthesis to reestablish the Krebs cycle.

Longevity and stress resistance are affected by activation of TOR/Myc in progenitor cells of Drosophila gut

Diverse physiological pathways have been shown to regulate longevity, stress resistance, fecundity and feeding rates, and metabolism in Drosophila. Here we tesed physiological traits in flies with Rheb and Myc- Rheb overexpressed in gut progenitor cells, known as enteroblasts (EBs). We found that activation of TOR signaling by overexpression of Rheb in EBs decreases survival and stress resistance. Additionall, we showed that Myc co-expression in EBs reduces fly fecundity and feeding rate. Rheb overexpression enhanced the level of whole body glucose. Higher relative expression of the metabolic genes dilps, akh, tobi and pepck was, however, observed. The role of TOR/Myc in the regulation of genes involved in lipid metabolism and protein synthesis was established. We showed a significant role of TOR/Myc in EBs in the regulation of the JAK/STAT, EGFR and insulin signaling pathways in Drosophila gut. These results highlight the importance of the balance between all different types of cells and confirm previous studies demonstrating that promotion of homeostasis in the intestine of Drosophila may function as a mechanism for the extension of organismal lifespan. Overall, the results demonstrate a role of TOR signaling and its downstream target Myc in EB cells in the regulation of Drosophila physiological processes.

Copper and Zinc Homeostasis: Lessons from Drosophila melanogaster

Maintenance of metal homeostasis is crucial for many different enzymatic activities and in turn for cell function and survival. In addition, cells display detoxification and protective mechanisms against toxic accumulation of metals. Perturbation of any of these processes normally leads to cellular dysfunction and finally to cell death. In the last years, loss of metal regulation has been described as a common pathological feature in many human neurodegenerative diseases. However, in most cases, it is still a matter of debate whether such dyshomeostasis is a primary or a secondary downstream defect. In this review, we will summarize and critically evaluate the contribution of Drosophila to model human diseases that involve altered metabolism of metals or in which metal dyshomeostasis influence their pathobiology. As a prerequisite to use Drosophila as a model, we will recapitulate and describe the main features of core genes involved in copper and zinc metabolism that are conserved between mammals and flies. Drosophila presents some unique strengths to be at the forefront of neurobiological studies. The number of genetic tools, the possibility to easily test genetic interactions in vivo and the feasibility to perform unbiased genetic and pharmacological screens are some of the most prominent advantages of the fruitfly. In this work, we will pay special attention to the most important results reported in fly models to unveil the role of copper and zinc in cellular degeneration and their influence in the development and progression of human neurodegenerative pathologies such as Parkinson's disease, Alzheimer's disease, Huntington's disease, Friedreich's Ataxia or Menkes, and Wilson's diseases. Finally, we show how these studies performed in the fly have allowed to give further insight into the influence of copper and zinc in the molecular and cellular causes and consequences underlying these diseases as well as the discovery of new therapeutic strategies, which had not yet been described in other model systems.

Dietary L-arginine accelerates pupation and promotes high protein levels but induces oxidative stress and reduces fecundity and life span in Drosophila melanogaster

L-Arginine, a precursor of many amino acids and of nitric oxide, plays multiple important roles in nutrient metabolism and regulation of physiological functions. In this study, the effects of L-arginine-enriched diets on selected physiological responses and metabolic processes were assessed in Drosophila melanogaster. Dietary L-arginine at concentrations 5-20 mM accelerated larval development and increased body mass, and total protein concentrations in third instar larvae, but did not affect these parameters when diets contained 100 mM arginine. Young (2 days old) adult flies of both sexes reared on food supplemented with 20 and 100 mM L-arginine possessed higher total protein concentrations and lower glucose and triacylglycerol concentrations than controls. Additionally, flies fed 20 mM L-arginine had higher proline and uric acid concentrations. L-Arginine concentration in the diet also affected oxidative stress intensity in adult flies. Food with 20 mM L-arginine promoted lower protein thiol concentrations and higher catalase activity in flies of both sexes and higher concentrations of low molecular mass thiols in males. When flies were fed on a diet with 100 mM L-arginine, lower catalase activities and concentrations of protein thiols were found in both sexes as well as lower low molecular mass thiols in females. L-Arginine-fed males demonstrated higher climbing activity, whereas females showed higher cold tolerance and lower fecundity, compared with controls. Food containing 20 mM L-arginine shortened life span in both males and females. The results suggest that dietary L-arginine shows certain beneficial effects at the larval stage and in young adults. However, the long-term consumption of L-arginine-enriched food had unfavorable effects on D. melanogaster due to decreasing fecundity and life span.

Exposure to sodium molybdate results in mild oxidative stress in Drosophila melanogaster

OBJECTIVES

The study was conducted to assess the redox status of Drosophila flies upon oral intake of insulin-mimetic salt, sodium molybdate (Na2MoO4).

METHODS

Oxidative stress parameters and activities of antioxidant and associated enzymes were analyzed in two-day-old D. melanogaster insects after exposure of larvae and newly eclosed adults to three molybdate levels (0.025, 0.5, or 10 mM) in the food.

RESULTS

Molybdate increased content of low molecular mass thiols and activities of catalase, superoxide dismutase, glutathione-S-transferase, and glucose-6-phosphate dehydrogenase in males. The activities of these enzymes were not affected in females. Males exposed to molybdate demonstrated lower carbonyl protein levels than the control cohort, whereas females at the same conditions had higher carbonyl protein content and catalase activity than ones in the control cohort. The exposure to 10 mM sodium molybdate decreased the content of protein thiols in adult flies of both sexes. Sodium molybdate did not affect the activities of NADP-dependent malate dehydrogenase and thioredoxin reductase in males or NADP-dependent isocitrate dehydrogenase in either sex at any concentration.

DISCUSSION

Enhanced antioxidant capacity in upon Drosophila flies low molybdate levels in the food suggests that molybdate can be potentially useful for the treatment of certain pathologies associated with oxidative stress.

Alpha-ketoglutarate attenuates toxic effects of sodium nitroprusside and hydrogen peroxide in Drosophila melanogaster

The protective effects of dietary alpha-ketoglutarate (AKG) are described that aid fruit flies, Drosophila melanogaster, to resist sodium nitroprusside (SNP) and hydrogen peroxide toxicity. Food supplementation with 10mM AKG alleviated toxic effects of 1mM SNP added to food and improved fly development. Dietary AKG also prevented the increase in levels of oxidative stress markers seen in SNP-reared adult flies. In vitro AKG did not affect the rate of SNP decomposition and did not bind iron and nitrite ions released in this process. Alpha-ketoglutarate also displayed high H2O2-scavenging activity in vitro and efficiently protected adult flies against this compound in combined treatments. Based on the observed antioxidant activity of AKG, it may be suggested that the antioxidant mode of AKG action (apart from its cyanide-binding capability) may be used to prevent the toxic effects of SNP and improve general physiological state of D. melanogaster and other animals and humans.

Sodium chromate demonstrates some insulin-mimetic properties in the fruit fly Drosophila melanogaster

The effects of food supplementation with sodium chromate at concentrations of 1-500 μM on development of Drosophila melanogaster larvae and food intake, carbohydrate and lipid pools in adult fruit flies were investigated. Food supplementation with hexavalent chromium (Na2CrO4) at high concentrations delayed larval development and decreased the percentage of larvae that pupated which indicated a relatively low toxicity. The supplement decreased glucose levels in fly hemolymph, but at concentrations of 5-25 μM increased fly carbohydrate reserves: hemolymph trehalose and whole body trehalose and glycogen. The data on parameters of carbohydrate metabolism show that chromate possesses some insulin-mimetic properties. The changes in metabolism of carbohydrates under chromate exposure were also accompanied by an increase in total lipid levels and in the portion of triacylglycerides among all lipids. Chromate addition to fly food did not affect male or female body mass, but reduced food consumption by females at all concentrations used, whereas in males only 500 μM chromate decreased food consumption. The data show that: (1) Cr(6+) has many of the same effects as Cr(3+) suggesting that it might be just as effective to treat diabetic states, likely as a result of intracellular reduction of Cr(6+) ions, and (2) the Drosophila model can be used to develop new approaches to investigate the molecular mechanisms of chromium as an insulin-mimetic. Although it is usually believed that hexavalent chromium possesses higher toxicity than the trivalent ion, due to its easier penetration into the cell, application of hexavalent chromium may substantially decrease the chromium doses needed to get the desired effects.

High consumption of fructose rather than glucose promotes a diet-induced obese phenotype in Drosophila melanogaster

During the last 20 years, there has been a considerable scientific debate about the possible mechanisms of induction of metabolic disorders by reducing monosaccharides such as glucose or fructose. In this study, we report the metabolic rearrangement in response to consumption of these monosaccharides at concentrations ranging from 0.25% to 20% in a Drosophila model. Flies raised on high-glucose diet displayed delay in pupation and increased developmental mortality compared with fructose consumers. Both monosaccharides at high concentrations promoted an obese-like phenotype indicated by increased fly body mass, levels of uric acid, and circulating and stored carbohydrates and lipids; and decreased percentage of water in the body. However, flies raised on fructose showed lower levels of circulating glucose and higher concentrations of stored carbohydrates, lipids, and uric acid. The preferential induction of obesity caused by fructose in Drosophila was associated with increased food consumption and reduced mRNA levels of DILP2 and DILP5 in the brain of adult flies. Our data show that glucose and fructose differently affect carbohydrate and lipid metabolism in Drosophila in part by modulation of insulin/insulin-like growth factor signaling. Some reported similarities with effects observed in mammals make Drosophila as a useful model to study carbohydrate influence on metabolism and development of metabolic disorders.