Gluconeogenesis: An ancient biochemical pathway with a new twist

Assessment of Amphibola crenata as a bioindicator of estuarine trace element pollution using biochemical and physiological endpoints

To assess its utility as a bioindicator of estuarine contamination, Amphibola crenata, a pulmonate mud snail, was collected from 17 estuaries in New Zealand. Whole-body soft tissue trace element concentrations were measured via quadrupole inductively coupled plasma mass spectrophotometer (Q-ICP-MS) and were found to be significantly positively correlated with sediment trace element profiles for arsenic, copper and lead. Snails from polluted estuaries generally displayed higher ammonia excretion rates, elevated whole-body soft tissue catalase activity and lipid peroxidation compared to snails from reference sites. Across all sites haemolymph glucose was positively correlated with the tissue burdens of arsenic, copper, nickel and zinc, while haemolymph protein was negatively correlated with arsenic, cadmium and zinc soft tissue concentrations, indicative of altered energy metabolism associated with trace element contamination. Overall, sites were distinguishable by application of the array of measures employed. Our findings suggest that gastropods have significant value as bioindicators of estuarine health.

Assessing the potential fasting and postprandial mechanisms involved in the acute hypoglycemic and anti-hyperglycemic effects of four selected plants from Iran used in traditional Persian medicine

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional Persian medicine (TPM), people often use herbal infusions as a dosage form to treat diseases related to hyperglycemia, known as 'dam-kardeh'. Traditionally, herbal preparations of Eryngium bungei Boiss. (E. b), Tragopogon buphthalmoides (DC.) Boiss. (T. b), Salvia hydrangea DC. ex Benth. (S. h), and Juniperus polycarpos K. Koch. (J. p) are used to manage diabetes in Iran. However, there is no evidence of their effectiveness in controlling glucose levels and their mechanisms remain unclear.

AIM OF THE STUDY

This study aimed to investigate whether traditional doses of plant infusions can have hypoglycemic and/or anti-hyperglycemic effects during fasting and/or postprandial states and establish the basis for future research on their potential mechanisms of action.

MATERIALS AND METHODS

The effects of traditional doses of herbal extracts on blood glucose levels in STZ-NA-induced hyperglycemic rats were investigated in 2-h acute tests during fasting and postprandial states (with a glucose load). In addition, the potential inhibitory effect in vitro of enzymes involved in relevant pathways, such as gluconeogenesis (fructose-1,6-bisphosphatase, FBPase and glucose-6-phosphatase, G6Pase), carbohydrate breakdown (intestinal α-glucosidases), and insulin sensitivity (protein tyrosine phosphatase 1B, PTP-1B) was evaluated. Acute toxicity tests were carried out and HPLC-SQ-TOF was used to analyze the chemical profiles of the plant extracts.

RESULTS

In the fasting state, T. b, S. h, and E. b were as effective as glibenclamide in lowering blood glucose levels in hyperglycemic rats. Moreover, all three suppressed G6Pase and FBPase enzymatic activity by 90-97% and 80-91%, respectively. On the other hand, significant postprandial hypoglycemic efficacy was observed for E. b, S. h, and T. b. Based on the AUC values, T. b caused a reduction comparable to the therapeutic efficacy of repaglinide. When investigating the possible mechanisms of action involved in this activity, E. b, S. h, and T. b showed significant inhibition of PTP-1B in vitro (>70%). Finally, all plant extracts showed no signs of acute toxicity. Several compounds that may contribute to biological activities were identified, including phenolic acids and flavonoid glycosides.

CONCLUSIONS

The present study supports the traditional use of T. b, E. b and S. h for the control of diabetes in the fasting and postprandial state. Moreover, these plants were found to be rich in bioactive compounds with hypoglycemic and antihyperglycemic activities. On the other hand, J. p, showed a modest effect only in the fasting state and after 90 min. Further studies are needed to expand these results by analyzing the chemical composition and using complementary experimental models.

Thyroid Hormone and Diabetes Mellitus Interplay: Making Management of Comorbid Disorders Complicated

Insulin and thyroid hormones play important roles in our body. Insulin helps regulate the glucose level while the thyroid hormones affect various cells and tissues, metabolizing protein, lipids, and glucose. Hyperthyroidism and thyrotoxicosis are potential hazards for type 2 diabetes mellitus. There is a high prevalence of hypothyroidism being more common compared to hyperthyroidism coexisting with diabetes mellitus. Thyroid hormones affect glucose metabolism through its action on peripheral tissues (gastrointestinal tract, liver, skeletal muscles, adipose tissue, and pancreas). High-level thyroid hormone causes hyperglycemia, upregulation of glucose transport, and reduction in glycogen storage. The reverse is observed during low levels of thyroid hormone along with insulin clearance. The net result of thyroid disorder is insulin resistance. Type 2 diabetes mellitus can downsize the regulation of thyroid stimulating hormones and impair the conversion of thyroxine to triiodothyronine in peripheral tissues. Furthermore, poorly managed type 2 diabetes mellitus may result in insulin resistance and hyperinsulinemia, contributing to the proliferation of thyroid tissue and an increase in nodule formation and goiter size. Although metformin proves advantageous for both type 2 diabetes mellitus and thyroid disorder patients, other antidiabetics like sulfonylureas, pioglitazone, and thiazolidinediones may have adverse effects on thyroid disorders. Moreover, antithyroid drugs such as methimazole can weaken glycemic control in individuals with diabetes. Thus, an interplay between both endocrinopathies is observed and individualized care and management of the disorder needs to be facilitated.

Trophic guilds differ in blood glucose concentrations: a phylogenetic comparative analysis in birds

Glucose is a central metabolic compound used as an energy source across all animal taxa. There is high interspecific variation in glucose concentration between taxa, the origin and the consequence of which remain largely unknown. Nutrition may affect glucose concentrations because carbohydrate content of different food sources may determine the importance of metabolic pathways in the organism. Birds sustain high glucose concentrations that may entail the risks of oxidative damage. We collected glucose concentration and life-history data from 202 bird species from 171 scientific publications, classified them into seven trophic guilds and analysed the data with a phylogenetically controlled model. We show that glucose concentration is negatively associated with body weight and is significantly associated with trophic guilds with a moderate phylogenetic signal. After controlling for allometry, glucose concentrations were highest in carnivorous birds, which rely on high rates of gluconeogenesis to maintain their glycaemia, and lowest in frugivorous/nectarivorous species, which take in carbohydrates directly. However, trophic guilds with different glucose concentrations did not differ in lifespan. These results link nutritional ecology to physiology and suggest that at the macroevolutionary scale, species requiring constantly elevated glucose concentrations may have additional adaptations to avoid the risks associated with high glycaemia.

Drosophila neuronal Glucose-6-Phosphatase is a modulator of neuropeptide release that regulates muscle glycogen stores via FMRFamide signaling

Neuropeptides (NPs) and their cognate receptors are critical effectors of diverse physiological processes and behaviors. We recently reported of a noncanonical function of the Drosophila Glucose-6-Phosphatase (G6P) gene in a subset of neurosecretory cells in the central nervous system that governs systemic glucose homeostasis in food-deprived flies. Here, we show that G6P-expressing neurons define six groups of NP-secreting cells, four in the brain and two in the thoracic ganglion. Using the glucose homeostasis phenotype as a screening tool, we find that neurons located in the thoracic ganglion expressing FMRFamide NPs (FMRFaG6P neurons) are necessary and sufficient to maintain systemic glucose homeostasis in starved flies. We further show that G6P is essential in FMRFaG6P neurons for attaining a prominent Golgi apparatus and secreting NPs efficiently. Finally, we establish that G6P-dependent FMRFa signaling is essential for the build-up of glycogen stores in the jump muscle which expresses the receptor for FMRFamides. We propose a general model in which the main role of G6P is to counteract glycolysis in peptidergic neurons for the purpose of optimizing the intracellular environment best suited for the expansion of the Golgi apparatus, boosting release of NPs and enhancing signaling to respective target tissues expressing cognate receptors.

Comprehensive review on glucose 6 phosphate dehydrogenase: A critical immunometabolic and redox switch in insects

Mounting an active immune response is energy intensive and demands the reallocation of nutrients to maintain the body's resistance and tolerance against infections. Central to this metabolic adaptation is Glucose-6-phosphate dehydrogenase (G6PDH), a housekeeping enzyme involve in pentose phosphate pathway (PPP). PPP play an essential role in generating ribose, which is critical for nicotinamide adenine dinucleotide phosphate (NADPH). It is vital for physiological and cellular processes such as generating nucleotides, fatty acids and reducing oxidative stress. The G6PDH is extremely conserved enzyme across species in PP shunt. The deficiency of enzymes leads to serious consequences on organism, particularly on adaptation and development. Acute deficiency can lead to impaired cell development, halted embryonic growth, reduce sensitivity to insulin, hypertension and increase inflammation. Historically, research focusing on G6PDH and PPP have primarily targeted diseases on mammalian. However, our review has investigated the unique functions of the G6PDH enzyme in insects and greatly improved mechanistic understanding of its operations. This review explore how G6PDH in insects plays a crucial role in managing the redox balance and immune related metabolism. This study aims to investigate the enzyme's role in different metabolic adaptations.

Drosophila Neuronal Glucose 6 Phosphatase is a Modulator of Neuropeptide Release that Regulates Muscle Glycogen Stores via FMRFamide Signaling

Neuropeptides (NPs) and their cognate receptors are critical effectors of diverse physiological processes and behaviors. We recently reported of a non-canonical function of the Drosophila Glucose-6-Phosphatase ( G6P ) gene in a subset of neurosecretory cells in the CNS that governs systemic glucose homeostasis in food deprived flies. Here, we show that G6P expressing neurons define 6 groups of neuropeptide secreting cells, 4 in the brain and 2 in the thoracic ganglion. Using the glucose homeostasis phenotype as a screening tool, we find that neurons located in the thoracic ganglion expressing FMRFamide neuropeptides ( FMRFa G6P neurons) are necessary and sufficient to maintain systemic glucose homeostasis in starved flies. We further show that G6P is essential in FMRFa G6P neurons for attaining a prominent Golgi apparatus and secreting neuropeptides efficiently. Finally, we establish that G6P dependent FMRFa signaling is essential for the build-up of glycogen stores in the jump muscle which expresses the receptor for FMRFamides. We propose a general model in which the main role of G6P is to counteract glycolysis in peptidergic neurons for the purpose of optimizing the intracellular environment best suited for the expansion of the Golgi apparatus, boosting release of neuropeptides and enhancing signaling to respective target tissues expressing cognate receptors.

SIGNIFICANCE STATEMENT

Glucose-6-phosphtase (G6P) is a critical enzyme in sugar synthesis and catalyzes the final step in glucose production. In Drosophila - and insects in general - where trehalose is the circulating sugar and Trehalose phosphate synthase, and not G6P, is used for sugar production, G6P has adopted a novel and unique role in peptidergic neurons in the CNS. Interestingly, flies lacking G6P show diminished Neuropeptide secretions and have a smaller Golgi apparatus in peptidergic neurons. It is hypothesized that the role of G6P is to counteract glycolysis, thereby creating a cellular environment that is more amenable to efficient neuropeptide secretion.

Architecture, Function, Regulation, and Evolution of α-Glucans Metabolic Enzymes in Prokaryotes

Bacteria have acquired sophisticated mechanisms for assembling and disassembling polysaccharides of different chemistry. α-d-Glucose homopolysaccharides, so-called α-glucans, are the most widespread polymers in nature being key components of microorganisms. Glycogen functions as an intracellular energy storage while some bacteria also produce extracellular assorted α-glucans. The classical bacterial glycogen metabolic pathway comprises the action of ADP-glucose pyrophosphorylase and glycogen synthase, whereas extracellular α-glucans are mostly related to peripheral enzymes dependent on sucrose. An alternative pathway of glycogen biosynthesis, operating via a maltose 1-phosphate polymerizing enzyme, displays an essential wiring with the trehalose metabolism to interconvert disaccharides into polysaccharides. Furthermore, some bacteria show a connection of intracellular glycogen metabolism with the genesis of extracellular capsular α-glucans, revealing a relationship between the storage and structural function of these compounds. Altogether, the current picture shows that bacteria have evolved an intricate α-glucan metabolism that ultimately relies on the evolution of a specific enzymatic machinery. The structural landscape of these enzymes exposes a limited number of core catalytic folds handling many different chemical reactions. In this Review, we present a rationale to explain how the chemical diversity of α-glucans emerged from these systems, highlighting the underlying structural evolution of the enzymes driving α-glucan bacterial metabolism.

PEPCK and glucose metabolism homeostasis in arthropods

The fat body is responsible for a variety of functions related to energy metabolism in arthropods, by controlling the processes of de novo glucose production (gluconeogenesis) and glycogen metabolism. The rate-limiting factor of gluconeogenesis is the enzyme phosphoenolpyruvate carboxykinase (PEPCK), generally considered to be the first committed step in this pathway. Although the study of PEPCK and gluconeogenesis has been for decades restricted to mammalian models, especially focusing on muscle and liver tissue, current research has demonstrated particularities about the regulation of this enzyme in arthropods, and described new functions. This review will focus on arthropod PEPCK, discuss different aspects to PEPCK regulation and function, its general role in the regulation of gluconeogenesis and other pathways. The text also presents our views on potentially important new directions for research involving this enzyme in a variety of metabolic adaptations (e.g. diapause), discussing enzyme isoforms, roles during arthropod embryogenesis, as well as involvement in vector-pathogen interactions, contributing to a better understanding of insect vectors of diseases and their control.

The effect of phenobarbital treatment on behavioral comorbidities and on the composition and function of the fecal microbiome in dogs with idiopathic epilepsy

Phenobarbital (PB) is one of the most important antiseizure drugs (ASDs) to treat canine idiopathic epilepsy (IE). The effect of PB on the taxonomic changes in gastrointestinal microbiota (GIM) and their functions is less known, which may explain parts of its pharmacokinetic and pharmacodynamic properties, especially its antiseizure effect and drug responsiveness or drug resistance as well as its effect on behavioral comorbidities. Fecal samples of 12 dogs with IE were collected prior to the initiation of PB treatment and 90 days after oral PB treatment. The fecal samples were analyzed using shallow DNA shotgun sequencing, real-time polymerase chain reaction (qPCR)-based dysbiosis index (DI), and quantification of short-chain fatty acids (SCFAs). Behavioral comorbidities were evaluated using standardized online questionnaires, namely, a canine behavioral assessment and research questionnaire (cBARQ), canine cognitive dysfunction rating scale (CCDR), and an attention deficit hyperactivity disorder (ADHD) questionnaire. The results revealed no significant changes in alpha and beta diversity or in the DI, whereas only the abundance of Clostridiales was significantly decreased after PB treatment. Fecal SCFA measurement showed a significant increase in total fecal SCFA concentration and the concentrations of propionate and butyrate, while acetate concentrations revealed an upward trend after 90 days of treatment. In addition, the PB-Responder (PB-R) group had significantly higher butyrate levels compared to the PB-Non-Responder (PB-NR) group. Metagenomics of functional pathway genes demonstrated a significant increase in genes in trehalose biosynthesis, ribosomal synthesis, and gluconeogenesis, but a decrease in V-ATPase-related oxidative phosphorylation. For behavioral assessment, cBARQ analysis showed improvement in stranger-directed fear, non-social fear, and trainability, while there were no differences in ADHD-like behavior and canine cognitive dysfunction (CCD) scores after 90 days of PB treatment. While only very minor shifts in bacterial taxonomy were detected, the higher SCFA concentrations after PB treatment could be one of the key differences between PB-R and PB-NR. These results suggest functional changes in GIM in canine IE treatment.

Annotation of glycolysis, gluconeogenesis, and trehaloneogenesis pathways provide insight into carbohydrate metabolism in the Asian citrus psyllid

Citrus greening disease is caused by the pathogen Candidatus Liberibacter asiaticus and transmitted by the Asian citrus psyllid, Diaphorina citri. No curative treatment or significant prevention mechanism exists for this disease, which causes economic losses from reduced citrus production. A high-quality genome of D. citri is being manually annotated to provide accurate gene models to identify novel control targets and increase understanding of this pest. Here, we annotated 25 D. citri genes involved in glycolysis and gluconeogenesis, and seven in trehaloneogenesis. Comparative analysis showed that glycolysis genes in D. citri are highly conserved but copy numbers vary. Analysis of expression levels revealed upregulation of several enzymes in the glycolysis pathway in the thorax, consistent with the primary use of glucose by thoracic flight muscles. Manually annotating these core metabolic pathways provides accurate genomic foundation for developing gene-targeting therapeutics to control D. citri.

The In Vitro Anti-Cancer Activities and Mechanisms of Action of 9-Methoxycanthin-6-one from Eurycoma longifolia in Selected Cancer Cell Lines

An alkaloid compound from the hairy root culture of Eurycoma longifolia has been isolated and characterised as 9-methoxycanthin-6-one. The aims of these studies were to investigate the in vitro anti-cancer activities of 9-methoxycanthin-6-one against ovarian cancer (A2780, SKOV-3), breast cancer (MCF-7), colorectal cancer (HT29), skin cancer (A375) and cervical cancer (HeLa) cell lines by using a Sulphorhodamine B assay, and to evaluate the mechanisms of action of 9-methoxycanthin-6-one via the Hoechst 33342 assay and proteomics approach. The results had shown that 9-methoxycanthin-6-one gave IC₅₀ values of 4.04 ± 0.36 µM, 5.80 ± 0.40 µM, 15.09 ± 0.99 µM, 3.79 ± 0.069 µM, 5.71 ± 0.20 µM and 4.30 ± 0.27 µM when tested in A2780, SKOV-3, MCF-7, HT-29, A375 and HeLa cell lines, respectively. It was found that 9-methoxycanthin-6-one induced apoptosis in a concentration dependent manner when analysed via the Hoechst 33342 assay. 9-methoxycanthine-6-one were found to affect the expressions of apoptotic-related proteins, that were proteins pyruvate kinase (PKM), annexin A2 (ANXA2), galectin 3 (LGAL3), heterogeneous nuclear ribonucleoprotein A1 (HNRNP1A1), peroxiredoxin 3 (PRDX3), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from the differential analysis of 2-DE profiles between treated and non-treated 9-methoxycanthine-6-one. Proteins such as acetyl-CoA acyltransferase 2 (ACAA2), aldehyde dehydrogenase 1 (ALDH1A1), capping protein (CAPG), eukaryotic translation elongation factor 1 (EEF1A1), malate dehydrogenase 2 (MDH2), purine nucleoside phosphorylase (PNP), and triosephosphate isomerase 1 (TPI1) were also identified to be associated with A2780 cell death induced by 9-methoxycanthine-6-one. These findings may provide a new insight on the mechanisms of action of 9-methoxycanthin-6-one in exerting its anti-cancer effects in vitro.

Plants Secondary Metabolites as Blood Glucose-Lowering Molecules

Recently, significant advances in modern medicine and therapeutic agents have been achieved. However, the search for effective antidiabetic drugs is continuous and challenging. Over the past decades, there has been an increasing body of literature related to the effects of secondary metabolites from botanical sources on diabetes. Plants-derived metabolites including alkaloids, phenols, anthocyanins, flavonoids, stilbenoids, saponins, tannins, polysaccharides, coumarins, and terpenes can target cellular and molecular mechanisms involved in carbohydrate metabolism. In addition, they can grant protection to pancreatic beta cells from damage, repairing abnormal insulin signaling, minimizing oxidative stress and inflammation, activating AMP-activated protein kinase (AMPK), and inhibiting carbohydrate digestion and absorption. Studies have highlighted many bioactive naturally occurring plants' secondary metabolites as candidates against diabetes. This review summarizes the current knowledge compiled from the latest studies published during the past decade on the mechanism-based action of plants-derived secondary metabolites that can target various metabolic pathways in humans against diabetes. It is worth mentioning that the compiled data in this review will provide a guide for researchers in the field, to develop candidates into environment-friendly effective, yet safe antidiabetics.

Dense time-course gene expression profiling of the Drosophila melanogaster innate immune response

BACKGROUND

Immune responses need to be initiated rapidly, and maintained as needed, to prevent establishment and growth of infections. At the same time, resources need to be balanced with other physiological processes. On the level of transcription, studies have shown that this balancing act is reflected in tight control of the initiation kinetics and shutdown dynamics of specific immune genes.

RESULTS

To investigate genome-wide expression dynamics and trade-offs after infection at a high temporal resolution, we performed an RNA-seq time course on D. melanogaster with 20 time points post Imd stimulation. A combination of methods, including spline fitting, cluster analysis, and Granger causality inference, allowed detailed dissection of expression profiles, lead-lag interactions, and functional annotation of genes through guilt-by-association. We identified Imd-responsive genes and co-expressed, less well characterized genes, with an immediate-early response and sustained up-regulation up to 5 days after stimulation. In contrast, stress response and Toll-responsive genes, among which were Bomanins, demonstrated early and transient responses. We further observed a strong trade-off with metabolic genes, which strikingly recovered to pre-infection levels before the immune response was fully resolved.

CONCLUSIONS

This high-dimensional dataset enabled the comprehensive study of immune response dynamics through the parallel application of multiple temporal data analysis methods. The well annotated data set should also serve as a useful resource for further investigation of the D. melanogaster innate immune response, and for the development of methods for analysis of a post-stress transcriptional response time-series at whole-genome scale.

Stable Isotope Labeling of Amino Acids in Flies (SILAF) Reveals Differential Phosphorylation of Mitochondrial Proteins Upon Loss of OXPHOS Subunits

Drosophila melanogaster has been a workhorse of genetics and cell biology for more than a century. However, proteomic-based methods have been limited due to the complexity and dynamic range of the fly proteome and the lack of efficient labeling methods. Here, we advanced a chemically defined food source into direct stable-isotope labeling of amino acids in flies (SILAF). It allows for the rapid and cost-efficient generation of a large number of larvae or flies, with full incorporation of lysine-[13C6] after six labeling days. SILAF followed by fractionation and enrichment gave proteomic insights at a depth of 7196 proteins and 8451 phosphorylation sites, which substantiated metabolic regulation on enzymatic level. We applied SILAF to quantify the mitochondrial phosphoproteome of an early-stage leucine-rich PPR motif-containing protein (LRPPRC)-knockdown fly model of mitochondrial disease that almost exclusively affects protein levels of the oxidative phosphorylation (OXPHOS) system. While the mitochondrial compartment was hypo-phosphorylated, two conserved phosphosites on OXPHOS subunits NDUFB10 and NDUFA4 were significantly upregulated upon impaired OXPHOS function. The ease and versatility of the method actuate the fruit fly as an appealing model in proteomic and posttranslational modification studies, and it enlarges potential metabolic applications based on heavy amino acid diets.

Primordial bioenergy sources: The two facets of adenosine triphosphate

Life requires energy to exist, to reproduce and to survive. Two major hypotheses have been put forward concerning the source of this energy at the very early stages of life evolution: (i) abiotic organics either brought to Earth by comets and/or meteorites, or produced at its atmosphere, and (ii) mineral surface-dependent bioinorganic catalytic reactions. Considering the latter possibility, I propose that, besides being a precursor of nucleic acids, adenosine triphosphate (ATP), which probably was used very early to improve the fidelity of nucleic acid polymerization, played an essential role in the transition between mineral-bound protocells and their free counterparts. Indeed, phosphorylation by ATP renders carboxylate groups electrophilic enough to react with nucleophiles such as amines, an effect that, thanks to their Lewis acid character, also have dehydrated metal ions on mineral surfaces. Early ATP synthesis for metabolic processes most likely depended on substrate level phosphorylation. However, the exaptation of a hexameric helicase-like ATPase and a transmembrane H⁺ pump (which evolved to counteract the acidity caused by fermentation reactions within the protocell) generated a much more efficient membrane-bound ATP synthase that uses chemiosmosis to make ATP.

Metabolism and growth adaptation to environmental conditions in Drosophila

Organisms adapt to changing environments by adjusting their development, metabolism, and behavior to improve their chances of survival and reproduction. To achieve such flexibility, organisms must be able to sense and respond to changes in external environmental conditions and their internal state. Metabolic adaptation in response to altered nutrient availability is key to maintaining energy homeostasis and sustaining developmental growth. Furthermore, environmental variables exert major influences on growth and final adult body size in animals. This developmental plasticity depends on adaptive responses to internal state and external cues that are essential for developmental processes. Genetic studies have shown that the fruit fly Drosophila, similarly to mammals, regulates its metabolism, growth, and behavior in response to the environment through several key hormones including insulin, peptides with glucagon-like function, and steroid hormones. Here we review emerging evidence showing that various environmental cues and internal conditions are sensed in different organs that, via inter-organ communication, relay information to neuroendocrine centers that control insulin and steroid signaling. This review focuses on endocrine regulation of development, metabolism, and behavior in Drosophila, highlighting recent advances in the role of the neuroendocrine system as a signaling hub that integrates environmental inputs and drives adaptive responses.

Lactation Ketoacidosis: A Systematic Review of Case Reports

Background and Objective: Lactation ketoacidosis is a rare cause of high anion gap metabolic acidosis affecting breastfeeding mothers. We aim to review and analyze all cases of lactation ketoacidosis reported. Materials and Methods: A systematic search of PubMed/MEDLINE and Cumulative Index to Nursing and Allied Health Literature (CINAHL), identifying relevant case reports published from 1 January 1970 to 31 December 2019. We extracted the following data: the first author, country, year of publication, age of the mother, age of the child, weight/body mass index (BMI) of the mother, precipitating factors, presenting symptoms, biochemical results, treatment, breastfeeding, and time from presentation to the resolution of ketoacidosis. Results: Sixteen case reports and 1 case series reporting 18 cases of lactation ketoacidosis were found. Presenting symptoms were nausea (72%, 13/18), vomiting (67%, 12/18), malaise (56%, 10/18), abdominal pain (44%, 8/18), dyspnea (33%, 6/18), headache (22%, 4/18), and palpitation (11%, 2/18). Dieting and physical exercise to lose weight were reported in 76% (14/18). The treatments included IV dextrose, sodium bicarbonate, insulin, rehydration, monitoring and replacement of electrolytes, and resumption of a balanced diet. The prognoses were good, with no mortalities. Conclusions: lactation ketoacidosis should be suspected in unwell breastfeeding women with high anion gap metabolic acidosis, after excluding other causes.

Gluconeogenesis and glycogen metabolism during development of Pacific abalone, Haliotis discus hannai

In lecithotrophic larvae, egg yolk nutrients are essential for development. Although yolk proteins and lipids are the major nutrient sources for most animal embryos and larvae, the contribution of carbohydrates to development has been less understood. In this study, we assessed glucose and glycogen metabolism in developing Pacific abalone, a marine gastropod mollusc caught and cultured in east Asia. We found that glucose and glycogen content gradually elevated in developing abalone larvae, and coincident expression increases of gluconeogenic genes and glycogen synthase suggested abalone larvae had activated gluconeogenesis and glycogenesis during this stage. At settling, however, glycogen sharply decreased, with concomitant increases in glucose content and expression of Pyg and G6pc, suggesting the settling larvae had enhanced glycogen conversion to glucose. A liquid chromatography-mass spectrometry (LC/MS)-based metabolomic approach that detected intermediates of these pathways further supported active metabolism of glycogen. Immunofluorescence staining and in situ hybridization suggested the digestive gland has an important role as glycogen storage tissue during settlement, while many other tissues also showed a capacity to metabolize glycogen. Finally, inhibition of glycolysis affected survival of the settling veliger larvae, revealing that glucose is, indeed, an important nutrient source in settling larvae. Our results suggest glucose and glycogen are required for proper energy balance in developing abalone and especially impact survival during settling.

Glucose Utilization in the Regulation of Chitin Synthesis in Brown Planthopper

Glucose-6-phosphatase (G6Pase) and hexokinase (HK) are two key enzymes in the glycolysis and gluconeogenesis pathways, which catalyze the synthesis and degradation of glucose in insects, respectively. G6Pase and HK play an important role in insect growth by regulating the metabolism of glucose, leading to the efficient metabolism of other macromolecules. However, it is unclear whether these genes could be investigated for pest control through their actions on chitin metabolism. We studied the potential functions of G6Pase and HK genes in the regulation of chitin metabolism pathways by RNAi technology. Interference with G6Pase expression did not affect trehalose and chitin metabolism pathways in brown planthopper, Nilaparvata lugens (Stål). However, knockdown of the HK gene resulted in a significant decrease of expression of genes associated with the trehalose metabolic pathway but had no significant effect on trehalase activity, trehalose content, or glucogen content. Additionally, HK knockdown resulting in downregulation of the genes involved in chitin metabolism in the brown planthopper. These insects also showed wing deformities and difficulty in molting to varying degrees. We suggest that the silencing of HK expression directly inhibited the decomposition of glucose, leading to impaired chitin synthesis.

Silencing of sucrose hydrolase causes nymph mortality and disturbs adult osmotic homeostasis in Diaphorina citri (Hemiptera: Liviidae)

Plant piercing sucking insects mainly feed on phloem sap containing a high amount of sucrose. To enhance the absorption of sucrose from the midgut, sucrose hydrolase digests sucrose into glucose and fructose. In this study, a sucrose hydrolase homolog (DcSuh) was identified and targeted in Diaphorina citri, the vector of huanglongbing (HLB), by RNA interference (RNAi). In silico analysis revealed the presence of an Aamy domain in the DcSUH protein, which is characteristic of the glycoside hydrolase family 13 (GH13). Phylogenetic analysis showed DcSuh was closely related to the sucrose hydrolase of other Hemiptera members. The highest gene expression levels of DcSuh was found in the 4th and 5th instar nymphs. dsRNA-mediated RNAi of DcSuh was achieved through topical feeding. Our results showed that application of 0.2 μL of 500 ng μL^-1 (100 ng) dsRNA-DcSuh was sufficient to repress the expression of the targeted gene and cause nymph mortality and reduce adult lifespan. The reduction in gene expression, mortality, and lifespan was dose-dependent. In agreement with the gene expression results, treatment with dsRNA-DcSuh significantly reduced sucrose hydrolase activity in treated nymphs and emerged adults from treated nymphs. Interestingly, some emerged adults from treated nymphs showed a swollen abdomen phenotype, indicating that these insects were under osmotic stress. Although the percentage of swollen abdomens was low, their incidence was significantly correlated with the concentration of applied dsRNA-DcSuh. Metabolomic analyses using GC-MS showed an accumulation of sucrose and a reduction in fructose, glucose and trehalose in treated nymphs, confirming the inhibition of sucrose hydrolase activity. Additionally, most of the secondary metabolites were reduced in the treated nymphs, indicating a reduction in the biological activities in D. citri and that they are under stress. Our findings indicate that sucrose hydrolase might be a potential target for effective RNAi control of D. citri.