Pathways Of Glucose Utilization Research Articles

Multiple pathways for glucose phosphate transport and utilization support growth of Cryptosporidium parvum

Cryptosporidium parvum is an obligate intracellular parasite with a highly reduced mitochondrion that lacks the tricarboxylic acid cycle and the ability to generate ATP, making the parasite reliant on glycolysis. Genetic ablation experiments demonstrated that neither of the two putative glucose transporters CpGT1 and CpGT2 were essential for growth. Surprisingly, hexokinase was also dispensable for parasite growth while the downstream enzyme aldolase was required, suggesting the parasite has an alternative way of obtaining phosphorylated hexose. Complementation studies in E. coli support a role for direct transport of glucose-6-phosphate from the host cell by the parasite transporters CpGT1 and CpGT2, thus bypassing a requirement for hexokinase. Additionally, the parasite obtains phosphorylated glucose from amylopectin stores that are released by the action of the essential enzyme glycogen phosphorylase. Collectively, these findings reveal that C. parvum relies on multiple pathways to obtain phosphorylated glucose both for glycolysis and to restore carbohydrate reserves.

#2999 APABETALONE REDUCES CARDIAC EVENTS IN CKD PATIENTS BY DOWNREGULATING FIBROTIC AND INFLAMMATORY PROCESSES

Abstract Background and Aims Major adverse cardiac events (MACE) are a leading cause of mortality in patients with chronic kidney disease (CKD). Apabetalone is an orally available inhibitor of bromodomain & extraterminal (BET) proteins – epigenetic readers that modulate gene expression involved in fibrosis & inflammation. In the phase 3 BETonMACE trial in patients with CVD & diabetes mellitus (NCT02586155), apabetalone reduced MACE by 50% in the subpopulation with CKD (eGFR < 60 mL/min/1.73 m2; HR 0.50 95% CI 0.26,0.96 p = 0.04) indicating favorable response along the kidney-heart axis. This study examines effects of apabetalone in human renal mesangial cells (HRMCs) on fibrotic & inflammatory pathways. In the clinic, we assess plasma levels of fibrotic factors in CKD patients & matched controls after receiving apabetalone. Method TGF-β1 is a pro-fibrotic cytokine that activates HRMCs to over-produce extracellular matrix (ECM). HRMCs were stimulated with TGF-β1 or LPS ± 1-25 µM apabetalone, 0.15-0.5 µM JQ1 or 0.1 µM MZ1 - BET inhibitors (BETi) with chemical scaffolds different than apabetalone. Gene expression was measured by RNA-seq & real-time PCR. RNA-seq was evaluated by Gene Ontology (GO) & Ingenuity Pathway Analysis (IPA). Proteins were measured by immunofluorescence microscopy or ELISA. Collagen gel contraction was assessed in 3D culture. In human subjects, proteomic analysis of plasma was performed via SOMAscan 1.3k 12 hours after 100 mg of apabetalone in CKD patients (n = 8 eGFR < 30 stage 4 or 5) and matched controls (n = 8 eGFR > 60). Results GO analysis of RNA-seq from TGF-β1 stimulated HRMCs showed multiple gene sets associated with ECM production & remodeling in the top 20 affected by BETi. IPA predicted NfkB-RelA and NFkB (complex) were inhibited by apabetalone, consistent with suppressed inflammation. IPA also predicted apabetalone activated pathways of glucose utilization & tolerance of ROS production, including Oxidative Phosphorylation (z-score 5.7, p = 2.95 × 10−3 at 25 µM) & NRF2-Mediated Oxidative Stress Response (z score 2.3, p = 7.9 × 10−12 at 25 µM; z-score 1.6, p = 1.5 × 10−5 at 5 µM). Predicted changes may allow tolerance of elevated glucose. Mechanistically, apabetalone suppressed TGF-β1 induced α-smooth muscle actin (α-SMA) gene expression, a marker of activation, up to 89% (p = 2.8 × 10−6 at 25 µM), and abolished α-SMA filament formation. Consequently, apabetalone opposed TGF-β1 induced collagen gel contraction up to 24% (p = 0.031 at 25 µM). Further, apabetalone countered TGF-β1 induced expression & protein production of key drivers of fibrosis including (a) thrombospondin, an activator of latent TGF-β1 (b) fibronectin, a key ECM component (c) periostin, a promoter of ECM production (d) osteonectin, a regulator of TGF-β1 expression and (e) IL6, a pro-inflammatory cytokine (Table 1). In addition, apabetalone dose dependently opposed LPS stimulated expression of inflammatory genes: IL6 up to 94%, IL1B up to 95% and PTGS2 up to 94% (p<0.001 for each). In all studies, JQ1 or MZ1 had similar activity as apabetalone, confirming on-target BETi effects. In humans, plasma levels of profibrotic and inflammatory markers were reduced 12 hours after receiving apabetalone specifically in those with CKD. Only periostin was reduced in subjects without renal impairment (Table 1). Conclusion Through epigenetic regulation of transcription in HRMCs, apabetalone reduces production of fibrotic & inflammatory factors known to signal along the kidney-heart axis & exacerbate kidney dysfunction. Predicted changes in energy metabolism suggest apabetalone facilitates adaptation to high glucose in kidneys. In a clinical trial, plasma levels of fibrotic & inflammatory factors were reduced specifically in CKD patients receiving apabetalone. Our results provide mechanistic insights into reduced MACE in CKD patients receiving apabetalone in the phase 3 BETonMACE trial & will be further evaluated in an upcoming Phase 3 trial.

Does flux through the hexosamine biosynthesis pathway differ between endothelial cells from African American and Caucasian donors?

People with Type 2 Diabetes (T2D) often exhibit endothelial dysfunction (EndoDys), which underlies the initiation of many diseases. African Americans (AA) have a greater prevalence of T2D and EndoDys than their Caucasian (CA) counterparts. To understand these differences, we examined glucose metabolism within the endothelium. Specifically, we sought to determine whether there are differences between AAs and CAs in the Hexosamine Biosynthesis Pathway (HBP), a route of glucose utilization that is upregulated in T2D. We hypothesized that endothelial cells (EC) from AA donors will show a greater flux through the HBP and express higher markers of EndoDys compared to CA donors. Human umbilical vein ECs (HUVECs), n=2-3/group, were incubated for 24hrs with high (HG, 30mM) or normal (5.5mM) glucose. Protein expression was measured via western blot for the: 1) HBP rate-limiting enzyme (Glutamine: fructose-6-phosphate amidotransferase, GFAT); 2) enzyme catalyzing the addition of HBP end-products to various proteins (O-GlcNAc transferase, OGT); and 3) attachment of O-linked N-acetylglucosamine moieties to various proteins (O-GlcNAcylation, O-GlcNAc), in addition to markers of EndoDys. Hyperglycemia did not differentially impact the expression of HBP markers GFAT or OGT between ECs from CA and AA donors (glycemic status [GS], p=0.6723; race, p=0.3807 and GS, p=0.8695; race, p=0.3536, respectively). Although total O-GlcNAc did not significantly increase with HG, there was a trend toward higher O-GlcNAcylation in AA ECs (p=0.0897). Upon further examination of O-GlcNAcylation, there were 3 prominent bands of highly O-GlcNAcylated proteins at >220kDa (band 1), ~150-200kDa (band 2), and ~85kDa (band 3). There was significantly higher O-GlcNAcylation of protein in band 2 for AA donors compared to CA donors (p=0.0362). The apoptotic marker, Caspase-3, did not change with HG (p=0.9219) nor differ in expression between races (p=0.2060). The inflammatory marker, VCAM, was significantly higher in cells from AA donors (p=0.002) but did not differ with GS (p=0.3468). There was no GS by race interaction found. EndoDys links T2D and other pathologies. We examined the HBP pathway of glucose utilization in ECs from CA and AA donors. There was a main effect of race related to inflammation and total O-GlcNAcylation, without differences in the expression of key proteins within the pathway. Our results suggest that the HBP may contribute to the racial differences in EndoDys, however, this relationship is not straightforward and does not seem to be exacerbated in the context of HG. Future research is needed to examine these unexpected discrepancies and interrogate the link between HBP flux within the endothelium, along with its connection to various pathologies This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Microglial metabolic reconfiguration provides a new strategy for the treatment of Alzheimer's disease.

Microglial metabolic reconfiguration provides a new strategy for the treatment of Alzheimer's disease.

The Antiviral Effects of 2-Deoxy-D-glucose (2-DG), a Dual D-Glucose and D-Mannose Mimetic, against SARS-CoV-2 and Other Highly Pathogenic Viruses.

Viral infection almost invariably causes metabolic changes in the infected cell and several types of host cells that respond to the infection. Among metabolic changes, the most prominent is the upregulated glycolysis process as the main pathway of glucose utilization. Glycolysis activation is a common mechanism of cell adaptation to several viral infections, including noroviruses, rhinoviruses, influenza virus, Zika virus, cytomegalovirus, coronaviruses and others. Such metabolic changes provide potential targets for therapeutic approaches that could reduce the impact of infection. Glycolysis inhibitors, especially 2-deoxy-D-glucose (2-DG), have been intensively studied as antiviral agents. However, 2-DG’s poor pharmacokinetic properties limit its wide clinical application. Herein, we discuss the potential of 2-DG and its novel analogs as potent promising antiviral drugs with special emphasis on targeted intracellular processes.

Нові, генетично детерміновані, фактори ризику діабетичної ретинопатії при цукровому діабеті 2-го типу: заключне повідомлення

Актуальність. За прогнозами Міжнародної федерації діабету (IDF), до 2030 року кількість хворих на цукровий діабет (ЦД) зросте з 366 до 552 мільйонів. В Україні зареєстровано понад 1,5 мільйона хворих на цукровий діабет, із яких 84–95 % — хворі на діабет 2-го типу (ЦД2). Одним із важливих ускладнень цукрового діабету є діабетична ретинопатія (ДР), що залишається однією з причин сліпоти і слабкозорості, в тому числі в осіб працездатного віку. В патогенезі ДР важлива роль належить метаболічним порушенням, в тому числі активації поліолового шляху утилізації глюкози, ключову роль у чому відіграє альдозоредуктаза, активність якої пов’язують з поліморфізмом її гена — AKR1B1. Вивчення нових метаболічних і генетичних механізмів розвитку і прогресування ДР при ЦД2 у пацієнтів української популяції є актуальним завданням сучасної офтальмології. Мета: дослідити та узагальнити нові дані про генетично детерміновані фактори ризику діабетичної ретинопатії при цукровому діабеті 2-го типу. Матеріали та методи. У дослідження було залучено 409 осіб, які були розподілені на чотири групи: 1-ша — пацієнти когорти порівняння (98 осіб без ЦД2); 2-га — 76 пацієнтів (I стадія ДР, без змін на очному дні); 3-тя — 64 пацієнти (непроліферативна ДР (НПДР)); 4-та — 64 пацієнти (проліферативна ДР); контрольну групу для генетичних досліджень становили 107 офтальмологічно здорових обстежених пацієнтів. Всім пацієнтам виконували забір крові для молекулярно-генетичних досліджень шляхом пункції ліктьової вени і забору 2,5 мл крові через одноразовий шприц (Hemoplast, Etalon+, Україна) об’ємом 5,0 мл із голкою діаметром 23G з подальшим випусканням до контейнера (Vacuette K3E K3EDTA, Greiner bio-one, Австрія) об’ємом 3,0 мл. Досліджували розподіл поліморфних алелей і генотипів rs759853 та rs9640883 гена AKR1B1 у пацієнтів з НПДР та ПДР і ЦД2 та в контрольній групі та їх асоціацію з захворюванням і впливом на виникнення, механізми розвитку і прогресування ДР. На підставі проведених досліджень було розроблено модель прогнозування розвитку ДР шляхом побудови множинної регресії з достатньою надійністю ступеня впливу незалежних змінних на розрахунковий показник. Результати. В результаті проведених нами досліджень були встановлені нові, генетично детерміновані, фактори ризику розвитку та прогресування різних стадій ДР у пацієнтів із ЦД2, а саме роль поліморфних алелей і генотипів rs759853 та rs9640883 гена AKR1B1. Розроблені логістичні моделі регресії встановили, що ризик розвитку ДР у п’ять разів менший у носіїв генотипів G/G і G/A порівняно з носіями генотипу A/A поліморфізму rs759853 (p < 0,001). Встановлено, що ризик у два рази більший (p = 0,01) у носіїв генотипу G/G rs9640883 порівняно з генотипами A/A + G/A. Ризик розвитку ПДР у 3,3 раза менший у носіїв генотипу G/G та в 2,5 раза — у носіїв генотипу G/A порівняно з носіями генотипу А/А rs759853. Висновки. Отже, на підставі проведених нами клінічних, офтальмологічних і молекулярно-генетичних та статистичних досліджень були встановлені нові фактори ризику розвитку та прогресування різних стадій ДР у пацієнтів із ЦД2. Були побудовані математичні моделі розвитку та прогресування різних стадій ДР у пацієнтів із ЦД2.

Exploring the Obesity Paradox in A Murine Model of Sepsis: Improved Survival Despite Increased Organ Injury in Obese Mice.

Despite the known deleterious effects of obesity, clinical data indicate that overweight or obese patients experience higher rates of sepsis survival compared to normal and underweight patients; a phenomenon called the obesity paradox. Results from preclinical sepsis studies have not been able to replicate these findings. The objective of this study was to test the existence of the obesity paradox in a murine model of cecal slurry (CS)-induced sepsis with insulin-resistant diet-induced obese mice. Male C57BL/6 mice were provided high-fat (HFD) or low-fat (LFD) diets for 20 weeks. HFD-fed mice experienced higher rates of survival compared to LFD-fed mice after septic challenge induced by CS injection (66% vs. 25%, P = 0.01, survival assessed for 14 days). Despite the survival advantage, HFD-fed mice had higher rates of positive bacterial cultures and increased markers of kidney injury. Circulating levels of IL-6, IL-1β, TNFα, and IL-23 were equivalent 24 h after CS-injection; however, IL-17A was uniquely increased in HFD-fed mice. While LFD-fed mice maintained euglycemia, HFD-fed mice were hyperglycemic 6 and 12 h after CS-injection. Stable isotope resolved metabolomics analysis of liver tissue showed diverging pathways of glucose utilization during sepsis, with LFD-fed mice significantly upregulating glycolytic activity and HFD-fed mice decreasing glucose entry into the TCA cycle. This murine study corroborates clinical data that obesity confers a survival benefit in sepsis, albeit at the expense of more significant organ injury. The mechanisms promoting survival in the obese remain unknown; however, this model appears to be well-poised to begin answering this question. Differences in glucose utilization are a novel target to investigate this paradox.

MiR-183 and miR-96 orchestrate both glucose and fat utilization in skeletal muscle.

Our knowledge of the coordination of fuel usage in skeletal muscle is incomplete. Whether and how microRNAs are involved in the substrate selection for oxidation is largely unknown. Here we show that mice lacking miR-183 and miR-96 have enhanced muscle oxidative phenotype and altered glucose/lipid homeostasis. Moreover, loss of miR-183 and miR-96 results in a shift in substrate utilization toward fat relative to carbohydrates in mice. Mechanistically, loss of miR-183 and miR-96 suppresses glucose utilization in skeletal muscle by increasing PDHA1 phosphorylation via targeting FoxO1 and PDK4. On the other hand, loss of miR-183 and miR-96 promotes fat usage in skeletal muscle by enhancing intramuscular lipolysis via targeting FoxO1 and ATGL. Thus, our study establishes miR-183 and miR-96 as master coordinators of fuel selection and metabolic homeostasis owing to their capability of modulating both glucose utilization and fat catabolism. Lastly, weshow that loss of miR-183 and miR-96 can alleviate obesity andimprove glucose metabolism in high-fat diet-induced mice, suggesting that miR-183 and miR-96 may serve as therapeutic targets for metabolic diseases.

Thermodynamic and Kinetic Modeling of Co-utilization of Glucose and Xylose for 2,3-BDO Production by Zymomonas mobilis.

Prior engineering of the ethanologen Zymomonas mobilis has enabled it to metabolize xylose and to produce 2,3-butanediol (2,3-BDO) as a dominant fermentation product. When co-fermenting with xylose, glucose is preferentially utilized, even though xylose metabolism generates ATP more efficiently during 2,3-BDO production on a BDO-mol basis. To gain a deeper understanding of Z. mobilis metabolism, we first estimated the kinetic parameters of the glucose facilitator protein of Z. mobilis by fitting a kinetic uptake model, which shows that the maximum transport capacity of glucose is seven times higher than that of xylose, and glucose is six times more affinitive to the transporter than xylose. With these estimated kinetic parameters, we further compared the thermodynamic driving force and enzyme protein cost of glucose and xylose metabolism. It is found that, although 20% more ATP can be yielded stoichiometrically during xylose utilization, glucose metabolism is thermodynamically more favorable with 6% greater cumulative Gibbs free energy change, more economical with 37% less enzyme cost required at the initial stage and sustains the advantage of the thermodynamic driving force and protein cost through the fermentation process until glucose is exhausted. Glucose-6-phosphate dehydrogenase (g6pdh), glyceraldehyde-3-phosphate dehydrogenase (gapdh) and phosphoglycerate mutase (pgm) are identified as thermodynamic bottlenecks in glucose utilization pathway, as well as two more enzymes of xylose isomerase and ribulose-5-phosphate epimerase in xylose metabolism. Acetolactate synthase is found as potential engineering target for optimized protein cost supporting unit metabolic flux. Pathway analysis was then extended to the core stoichiometric matrix of Z. mobilis metabolism. Growth was simulated by dynamic flux balance analysis and the model was validated showing good agreement with experimental data. Dynamic FBA simulations suggest that a high agitation is preferable to increase 2,3-BDO productivity while a moderate agitation will benefit the 2,3-BDO titer. Taken together, this work provides thermodynamic and kinetic insights of Z. mobilis metabolism on dual substrates, and guidance of bioengineering efforts to increase hydrocarbon fuel production.

Metabolic pathway analysis of walnut endophytic bacterium Bacillus subtilis HB1310 related to lipid production from fermentation of cotton stalk hydrolysate based on genome sequencing

In this study, genome sequencing and metabolic analysis were used to identify and verify the key metabolic pathways for glucose and xylose utilization and fatty acid synthesis in the walnut endophytic bacterium (WEB) Bacillus subtilis HB1310. The genome sequence of WEB HB1310 was generated with a size of 4.1Mb and GC content of 43.5%. Genome annotation indicated that the Embden-Meyerhof-Parnas, pentose phosphate, and fatty acid synthesis pathways were mainly involved in mixed sugar utilization and lipid production. In particular, diverse and abundant fatty acid synthesis genes were observed in a higher number than in other Bacillus strains. The tricarboxylic acid cycle competitively shared the carbon flux flowing before 48h, and the acetic acid fermentation competed after 72h. Moreover, fatty acid synthase activity was highly correlated with lipid titer with a correlation coefficient of 0.9626, and NADPH might be more utilized for the lipid synthesis within 48h. This study is the first attempt to explain the metabolic mechanism of mixed sugar utilization and lipid production based on genomic information, which provides a theoretical basis for the metabolic regulation of bacterial lipid production from lignocellulosic hydrolysates.

MO072APABETALONE DOWNREGULATES FIBROTIC, INFLAMMATORY AND CALCIFIC PROCESSES IN RENAL MESANGIAL CELLS WHICH MAY CONTRIBUTE TO REDUCED CARDIAC EVENTS OBSERVED IN CKD PATIENTS

Abstract Background and Aims Major adverse cardiac events (MACE) remain a leading cause of mortality in chronic kidney disease (CKD). Apabetalone is an orally available inhibitor of bromodomain & extraterminal (BET) proteins – epigenetic readers that modulate gene expression involved in fibrosis, inflammation and calcification. In the phase 3 BETonMACE trial, apabetalone treatment was associated with reduction in MACE in the subpopulation with CKD (eGFR < 60 mL/min/1.73m2; HR 0.50 95% CI 0.26,0.96 p=0.04]) implying favorable effects of apabetalone on cellular responses along the kidney-heart axis. This study examines effects of apabetalone on primary human renal mesangial cells (HRMCs) in culture on fibrosis, inflammation, reactive oxygen species (ROS) and calcification pathways that contribute to renal pathology. Method HRMCs from donors without kidney dysfunction were stimulated with TGF-β1 or lipopolysaccharide (LPS) ± 1-25µM apabetalone, 0.15-0.5µM JQ1 or 0.1µM MZ1 (BET inhibitors [BETi] with chemical scaffolds different than apabetalone). Gene expression was measured by real-time PCR and RNA-seq. Smooth muscle actin (α-SMA) was examined by immunofluorescence microscopy, and alkaline phosphatase enzyme activity in a biochemical assay. RNA-seq from TGF-β1 treated HRMC ± BETi was evaluated by Gene Ontology (GO) Enrichment and Ingenuity Pathway Analysis (IPA). Results TGF-β1 is a pro-fibrotic cytokine that activates HRMC to a fibroblast-like state which over-produces extracellular matrix (ECM). Apabetalone dose dependently suppressed TGF-β1 induced gene expression of (a) α-SMA, a marker of fibrotic activation, up to 90% p<0.001 and de novo α-SMA protein production (b) fibronectin, a key ECM component, up to 44% p<0.001 (c) NADPH oxidase 4 (NOX4), involved in production of pro-fibrotic ROS, up to 82% p<0.001 (d) tissue non-specific alkaline phosphatase (TNALP), associated with reduced glomerular function & extracellular calcification, up to 96% as well as TNALP enzyme activity up to 96% p<0.001. An inhibitor of TGF-β receptors reduced or abolished TGF-β1 responses, indicating the expected signal transduction pathways mediated its downstream effects. Apabetalone dose dependently opposed LPS stimulated expression of inflammatory genes: IL6 up to 94%, IL1B up to 95% & PTGS2 (COX2) up to 94% p<0.001, suggesting downregulation of inflammatory processes. In all studies, JQ1 and / or MZ1 had similar activity as apabetalone, confirming on-target BETi effects. In GO Enrichment analysis of RNA-seq from TGF-β1 stimulated HRMCs, multiple gene sets associated with ECM were in the top 20 affected by BETi, supporting anti-fibrotic properties. IPA predicted NfkB-RelA and NFkB (complex) were upstream regulators inhibited by apabetalone, indicating suppression of NF-kB mediated inflammation. IPA also predicted apabetalone activated canonical pathways of glucose utilization & tolerance of ROS production, including Oxidative Phosphorylation (z-score 5.7, p<0.01 at 25µM; z-score 3.5, p>0.05 at 5µM) and NRF2-Mediated Oxidative Stress Response (z score 2.3, p<0.001 at 25µM; z-score 1.6, p<0.001 at 5µM). PGC-1α, a key upstream regulator of the Oxidative Phosphorylation pathway, was also predicted to be activated by apabetalone (z score 4.2, p<0.001 at 25µM; z-score 2.3, p<0.001 at 5µM). These changes in energy metabolism pathways may allow HRMC to cope with elevated glucose. Conclusion Apabetalone downregulated responses to TGF-β1 or LPS in HRMCs that promote fibrotic, inflammatory and calcific processes which exacerbate kidney dysfunction. Changes in energy metabolism pathways predicted apabetalone facilitates adaptation to high glucose in the kidney. Together, our results provide mechanistic insight into reductions in MACE in CKD patients receiving apabetalone in the phase 3 BETonMACE trial. The effect of apabetalone on MACE in patients with diabetes and CKD will be further evaluated in the upcoming BETonMACE2 trial.

Exogenous bovine somatotropin and mist-fan cooling synergistically promote the intramammary glucose transport for lactose synthesis in crossbred Holstein cows in the tropics.

Background and Aim:Milk synthesis by the mammary gland is negatively influenced in part by high ambient temperature (AT). This study aimed to clarify the pathway of intramammary glucose utilization involved in mediating lactose synthesis during treatment with somatotropin under housing with misters and fans.Materials and Methods:A single subcutaneous injection of 500 mg of recombinant bovine somatotropin (rbST) was administered 3 times once every 14 days to 87.5% crossbred Holstein cattle in early-/mid-/late lactation, under housing in a normal shaded barn and in a shaded barn with a mist-fan cooling system.Results:The milk yields of the cooled cows tended to increase compared with those of uncooled cows and exhibited more potentiated effects in response to rbST treatment, coinciding with increases in mammary plasma flow and glucose uptake, but not in the mammary extraction of glucose. Treatment with rbST in the cooled cows resulted in a greater increase in the milk glucose concentration and a greater decrease in the milk glucose-6-phosphate concentration at all stages of lactation.Conclusion:rbST treatment exerted its galactopoietic action more by local intramammary factors than by other extramammary factors at a low AT and the synergistic effect between rbST treatment and low AT increased the availability of intramammary glucose transport in activating the process of lactose synthesis.

Pathogenesis and Molecular Treatment Strategies of Diabetic Neuropathy Collateral Glucose-Utilizing Pathways in Diabetic Polyneuropathy.

Diabetic polyneuropathy (DPN) is the most common neuropathy manifested in diabetes. Symptoms include allodynia, pain, paralysis, and ulcer formation. There is currently no established radical treatment, although new mechanisms of DPN are being vigorously explored. A pathophysiological feature of DPN is abnormal glucose metabolism induced by chronic hyperglycemia in the peripheral nerves. Particularly, activation of collateral glucose-utilizing pathways such as the polyol pathway, protein kinase C, advanced glycation end-product formation, hexosamine biosynthetic pathway, pentose phosphate pathway, and anaerobic glycolytic pathway are reported to contribute to the onset and progression of DPN. Inhibitors of aldose reductase, a rate-limiting enzyme involved in the polyol pathway, are the only compounds clinically permitted for DPN treatment in Japan, although their efficacies are limited. This may indicate that multiple pathways can contribute to the pathophysiology of DPN. Comprehensive metabolic analysis may help to elucidate global changes in the collateral glucose-utilizing pathways during the development of DPN, and highlight therapeutic targets in these pathways.

Okra Modulates Regulatory Enzymes and Metabolites of Glucose-Utilizing Pathways in Diabetic Rats

Objective Using a rat diabetes model, the authors examined how substrates and products of glycolysis and key regulatory enzymes for glycolysis, gluconeogenesis, Kreb’s cycle, and glycogen metabolism react to treatment with okra diet therapy, relative to glibenclamide treatment. Method The animal grouping involved normoglycemic rats, untreated diabetic rats, and diabetic rats treated with glibenclamide, 50% w/w okra sauce, exclusive okra sauce diet, or sauce without okra. Alloxan monohydrate was the diabetogenic agent. Insulin and adiponectin were assayed with enzyme-linked immunosorbent assay (ELISA) while the metabolites and enzymes were assed using standard spectrophotometric methods. Results The exclusive diet therapy significantly (p < 0.05) improved insulin activities after 60 days and reversed the altered adiponectin activities. Glucose-6-phosphate, fructose-6-phosphate, and fructose-1,6-bisphosphate levels were depleted during diabetes, but phosphoenolpyruvate and pyruvate accumulated during the first short phase of diabetes. Rats in the glibenclamide and 100% okra diet groups showed comparable hexokinase, phosphofructokinase, and pyruvate kinase activities relative to the normoglycemic rats, while the gluconeogenic enzymes, glucose-6-phosphatase, and fructose-1,6-bisphosphatase remained altered. The authors observed that extended treatment with glibenclamide restored the activities of all the Kreb’s cycle enzymes, while succinate dehydrogenase and α-ketoglutarate dehydrogenase were nonresponsive to the okra diet therapy relative to their control levels. The glycogen stores were normalized by the exclusive diet therapy, but glycogen synthase and phosphorylase activities were unresponsive. Conclusions Okra diet has shown insulin-sensitizing potentials with prolonged intake during diabetes as well as the potential to reverse alterations in the major carbohydrate-metabolizing enzyme.

The role of diabetes in the onset and development of endothelial dysfunction

The vascular endothelium performs many functions. It is a key regulator of vascular homeostasis, maintains a balance between vasodilation and vasoconstriction, inhibition and stimulation of smooth muscle cell migration and proliferation, fibrinolysis and thrombosis, and is involved to regulation of platelet adhesion and aggregation. Endothelial dysfunction (ED) plays the critical role in pathogenesis of diabetes mellitus (DM) vascular complications. The purpose of this review was to consider the mechanisms leading to the occurrence of ED in DM. The paper discusses current literature data concerning the role of hyperglycemia, oxidative stress, advanced glycation end products in endothelial alteration. A separate section is devoted to the particularities of the functioning of the antioxidant system and their significance in the development of ED in DM. The analysis of the literature allows to conclude that pathological activation of glucose utilization pathways causes damage of endothelial cells, which is accompanied by disorders of all their basic functions. Metabolic disorders in DM cause a pronounced imbalance of free radical processes and antioxidant defense, accompanied by oxidative stress of endotheliocytes, which contributes to the progression of ED and the development of vascular complications. Many aspects of multicomponent regulatory reactions in the pathogenesis of the development of ED in DM have not been sufficiently studied.

Modulation of glucose-related metabolic pathways controls glucose level in airway surface liquid and fight oxidative stress in cystic fibrosis cells.

Direct and indirect evidences show that elevated glucose concentrations in airway surface liquid (ASL) promote lung infection by pathogens, playing a role in the progression of the Cystic Fibrosis (CF) disease. The joint action of transporter/s for glucose and of the cellular enzymes is essential in order to try to lower ASL glucose level. Inside the cell, the glycolysis and the pentose phosphate pathway (PPP) compete for the utilization of glucose-6-phosphate (G6P), the product in which glucose, after entry within the cell and phosphorylation, is trapped. The study aims to clarify whether, modulating the activity of enzymatic proteins and/or the level of metabolites/cofactors, involved in intracellular glucose utilization, a lowering of the extracellular glucose level in CF occurs. Biochemical approaches have enabled us to understand i) how G6P is shunted between glycolysis and PPP and ii) that mitochondria, more than enzymes/cofactors participating to the two cell glucose utilization pathways, are protagonists of the scene in counteracting the high ASL glucose level as well as oxidative stress in CF.

Phloretin inhibits Zika virus infection by interfering with cellular glucose utilisation

Zika virus (ZIKV) is a re-emerging Flavivirus that has been linked to microcephaly and other neurological pathologies. In this study, phloretin, a glucose transporter inhibitor naturally derived from plants, was used to investigate the glucose dependence of ZIKV replication in host cells. The results showed that phloretin significantly decreased infectious titres of two ZIKV strains, namely MR766 (African genotype) and PRVABC59 (Puerto Rico genotype). The 50% effective concentration (EC50) of phloretin against MR766 and PRVABC59 was 22.85 µM and 9.31 µM, respectively. Further analyses demonstrated that decreased viral production was due to host-targeted inhibition, including decreased apoptotic caspase-3 and -7 activities and reduced phosphorylation of Akt/mTOR pathways. In addition, upon disruption of cellular glucose availability within host cells using 2-deoxy-d-glucose, ZIKV propagation was inhibited. Collectively, we demonstrate phloretin inhibition of ZIKV propagation and provide evidence of glucose utilization pathways as being important for ZIKV propagation. The activity of phloretin and its role in inhibiting glucose uptake could provide a useful foundation for the development of ZIKV antivirals.

Soluble curcumin prevents cadmium cytotoxicity in primary rat astrocytes by improving a lack of GFAP and glucose-6-phosphate-dehydrogenase

Cadmium (Cd) is a heavy metal which is widespread in various environmental components. Moreover several occupational diseases have the complications that are related to Cd cytotoxicity. Low doses of Cd exposure could induce pathogenetic disturbances in several sensitive cells as result of its long biological half-life and accumulation in vital tissue types. Prolonged Cd exposure was determined as main factor in accumulation of this metal ion over time in the liver, kidneys and neural tissue cells. The neurotoxic effect of Cd was presented in several articles which reported both in vivo and in vitro study. One of the main causes of Cd neurotoxicity is the ability of this ion to increase the permeability of the blood brain barrier. Despite a focus of attention on Cd cytotoxicity over the last few decades, the effect of Cd in neural tissue cells has been presented in a limited number of articles. The neurotoxic effect of Cd is accompanied by biochemical changes as well as a lack of functional activity of the central nervous system. Taking into account that the cytotoxic effect of Cd is associated with oxidative stress, inflammation and selective cell death, antioxidants could be used to protect neural tissue cells against both chronic and acute Cd exposure. Antioxidants protect diverse cell types against metal induced cytotoxicity. Curcumin is a natural polyphenol which exhibits antioxidant and anti-inflammatory effect. Soluble forms of cucrcumin can penetrate the blood brain barrier and protect neural tissue cells against detrimental effects of cytotoxic compounds. Glial cells are the most numerous cell population in CNS. Astrocytes possess the ability to protect the neuronal cells against cytotoxicity and maintain CNS functions. The cytoskeleton of astrocytes is constructed with glial fibrillary acidic protein (GFAP). GFAP is involved in essential functions of astrocytes and reflects astrocyte reactivity. The molecular mechanisms of the neurotoxic effect of Cd on glial cytoskeleton remain unknown. Primary astrocyte cell culture was used as model to assess the gliotoxic effect of Cd as well as the potency of low doses of soluble curcumin to ameliorate the neurotoxic effect of Cd. The obtained results demonstrated depletion of GFAP and glucose-6-phosphate-dehydrogenase (G6PD) in astrocytes treated with 10 µM Cd. The exposure to 5 µM curcumin ameliorated the expression both of GFAP and G6PD in Cd suppressed astrocytes. Moreover, low doses of soluble curcumin significantly prevented the detrimental effects of Cd on cell viability and indices of oxidative stress. The obtained results are evidence that soluble forms of curcumin improve astrocyte viability, cytoskeleton depletion and glucose utilization pathway. Thus, soluble curcumin possesses a neuroprotective effect directed on astrocyte cytoskeleton and metabolic energy production.

Metabolomic Approaches Reveal the Role of CAR in Energy Metabolism.

The constitutive androstane receptor (CAR; NR1I3) contributes important regulatory roles in biotransformation, xenobiotic transport function, energy metabolism and lipid homeostasis. In this investigation, global serum and liver tissue metabolomes were assessed analytically in wild type and CAR-null transgenic mice using NMR, GC–MS and UPLC–MS/MS-based metabolomics. Significantly, CAR activation increased serum levels of fatty acids, lactate, ketone bodies and tricarboxylic acid cycle products, whereas levels of phosphatidylcholine, sphingomyelin, amino acids and liver glucose were decreased following short-term activation of CAR. Mechanistically, quantitative mRNA analysis demonstrated significantly decreased expression of key gluconeogenic pathways, and increased expression of glucose utilization pathways, changes likely resulting from down-regulation of the hepatic glucose sensor and bidirectional transporter, Glut2. Short-term CAR activation also resulted in enhanced fatty acid synthesis and impaired β-oxidation. In summary, CAR contributes an expansive role regulating energy metabolism, significantly impacting glucose and monocarboxylic acid utilization, fatty acid metabolism and lipid homeostasis, through receptor-mediated regulation of several genes in multiple associated pathways.

Glucose metabolism mediates disease tolerance in cerebral malaria

Sickness behaviors are a conserved set of stereotypic responses to inflammatory diseases. We recently demonstrated that interfering with inflammation-induced anorexia led to metabolic changes that had profound effects on survival of acute inflammatory conditions. We found that different inflammatory states needed to be coordinated with corresponding metabolic programs to actuate tissue-protective mechanisms. Survival of viral inflammation required intact glucose utilization pathways, whereas survival of bacterial inflammation required alternative fuel substrates and ketogenic programs. We thus hypothesized that organismal metabolism would be important in other classes of infectious inflammation and sought to understand its role in the prototypic parasitic disease malaria. Utilizing the cerebral malaria model, Plasmodium berghei ANKA (PbA) infection in C57BL/6J male mice, we unexpectedly found that inhibition of glycolysis using 2-deoxy glucose (2DG) conferred protection from cerebral malaria. Unlike vehicle-treated animals, 2DG-treated animals did not develop cerebral malaria and survived until ultimately succumbing to fatal anemia. We did not find any differences in parasitemia or pathogen load in affected tissues. There were no differences in the kinetics of anemia. We also did not detect differences in immune infiltration in the brain or in blood-brain barrier permeability. Rather, on pathological analyses performed on the entire brain, we found that 2DG prevented the formation of thrombi and thrombotic complications. Using thromboelastography (TEG), we found that 2DG-treated animals formed clots that were significantly less strong and stable. Together, these data suggest that glucose metabolism is involved in inflammation-induced hemostasis and provide a potential therapeutic target in treatment of cerebral malaria.