Fructose-1,6-bisphosphate, a regulator of metabolism

Metabolomics reveals high fructose-1,6-bisphosphate from fluoride-resistant Streptococcus mutans

BACKGROUND

Fluoride-resistant Streptococcus mutans (S. mutans) strains have developed due to the wide use of fluoride in dental caries prevention. However, the metabolomics of fluoride-resistant S. mutans remains unclear.

OBJECTIVE

This study aimed to identify metabolites that discriminate fluoride-resistant from wild-type S. mutans.

MATERIALS AND METHODS

Cell supernatants from fluoride-resistant and wild-type S. mutans were collected and analyzed by liquid chromatography-mass spectrometry. Principal components analysis and partial least-squares discriminant analysis were performed for the statistical analysis by variable influence on projection (VIP > 2.0) and p value (Mann-Whitney test, p < 0.05). Metabolites were assessed qualitatively using the Human Metabolome Database version 2.0 ( http://www.hmdb.ca ), or Kyoto Encyclopedia of Genes and Genomes ( http://www.kegg.jp ), and Metaboanalyst 6.0 ( https://www.metaboanalyst.ca ).

RESULTS

Fourteen metabolites differed significantly between fluoride-resistant and wild-type strains in the early log phase. Among these metabolites, 5 were identified. There were 32 differential metabolites between the two strains in the stationary phase, 13 of which were identified. The pyrimidine metabolism for S. mutans FR was matched with the metabolic pathway.

CONCLUSIONS

The fructose-1,6-bisphosphate concentration increased in fluoride-resistant strains under acidic conditions, suggesting enhanced acidogenicity and acid tolerance. This metabolite may be a promising target for elucidating the cariogenic and fluoride resistant mechanisms of S. mutans.

Cadmium stress dictates central carbon flux and alters membrane composition in Streptococcus pneumoniae

Metal ion homeostasis is essential for all forms of life. However, the breadth of intracellular impacts that arise upon dysregulation of metal ion homeostasis remain to be elucidated. Here, we used cadmium, a non-physiological metal ion, to investigate how the bacterial pathogen, Streptococcus pneumoniae, resists metal ion stress and dyshomeostasis. By combining transcriptomics, metabolomics and metalloproteomics, we reveal that cadmium stress dysregulates numerous essential cellular pathways including central carbon metabolism, lipid membrane biogenesis and homeostasis, and capsule production at the transcriptional and/or functional level. Despite the breadth of cellular pathways susceptible to metal intoxication, we show that S. pneumoniae is able to maintain viability by utilizing cellular pathways that are predominately metal-independent, such as the pentose phosphate pathway to maintain energy production. Collectively, this work provides insight into the cellular processes impacted by cadmium and how resistance to metal ion toxicity is achieved in S. pneumoniae.

Neville et al. investigate how Streptococcus pneumoniae mitigates metal ion stress. Despite cadmium induced dysregulation of central carbon metabolism and lipid membrane homeostasis, they find that S. pneumoniae can remain viable by selectively utilizing predominately metal-independent cellular pathways. This study provides insights into how bacteria overcome metal ion toxicity.

Fructose-1,6-bisphosphate induces generation of reactive oxygen species and activation of p53-dependent cell death in human endometrial cancer cells

Fructose-1,6-bisphosphate (F1,6BP), an intermediate of the glycolytic pathway, has been found to play a promising anticancer effect; nevertheless, the mechanisms involved remain poorly understood. The present study aimed to evaluate the effect and mechanisms of F1,6BP in a human endometrial cancer cell line (Ishikawa). F1,6BP showed an antiproliferative and non-cytotoxic effect on endometrial cancer cells. These effects are related to the increase in reactive oxygen species (ROS) levels and mitochondrial membrane potential (ΔΨm). These harmful stimuli trigger the upregulation of the expression of pro-apoptotic genes (p53 and Bax), leading to the reduction of cell proliferation through inducing programmed cell death by apoptosis. Furthermore, F1,6BP-treated cells had the formation of autophagosomes induced, as well as a decrease in their proliferative capacity after withdrawing the treatment. Our results demonstrate that F1,6BP acts as an anticancer agent through the generation of mitochondrial instability, loss of cell function, and p53-dependent cell death. Thus, F1,6BP proves to be a potential molecule for use in the treatment against endometrial cancer.

Fructose-1,6-Bisphosphate Prevents Bleomycin-Induced Pulmonary Fibrosis in Mice and Inhibits the Proliferation of Lung Fibroblasts

Pulmonary fibrosis is a specific form of interstitial pneumonia. In addition to the idiopathic cause, it may be caused by drugs such as bleomycin (BLM)-used in the treatment of tumors. Fructose-1,6-bisphosphate (FBP) is a high-energy endogenous glycolytic compound that has antifibrotic, anti-inflammatory, and immunomodulatory effects. The aim of this study was to investigate the effects of FBP on both BLM-induced pulmonary fibrosis in mice and in a human embryonic lung fibroblast (MRC-5) culture system. C57BL/6 mice were divided into four groups: control, FBP, BLM, and BLM plus FBP. A single dose of bleomycin (7.5 U/kg) was administered intratracheally, and survival, body weight, Ashcroft score, and histological analysis were evaluated. Pulmonary function and bronchoalveolar lavage fluid (BALF) were also evaluated after a single dose of bleomycin (1.2 U/kg-intratracheally). Treatment with FBP (500 mg/kg) was given on day 0 intraperitoneally. Fibroblasts (MRC-5 cells) were used to access the effect of FBP in vitro. In vivo, FBP increased the survival rate and reduced body weight loss (BLM vs. BLM plus FBP-p < 0.05). FBP also prevented BLM-induced loss of pulmonary function and decreased BALF inflammatory cells, level of fibrosis, and superficial collagen density (p < 0.05). In vitro, FBP (0.62 and 1.25 mM) had inhibitory activity on MRC-5 cells and was able to induce senescence in fibroblasts. These results showed that FBP has the potential of reducing the toxic effects of BLM and may provide supportive therapy for conventional methods used for the treatment of cancer.

Fructose-1,6-bisphosphate preserves glucose metabolism integrity and reduces reactive oxygen species in the brain during experimental sepsis

Sepsis is one of the main causes of hospitalization and mortality in Intensive Care Units. One of the first manifestations of sepsis is encephalopathy, reported in up to 70% of patients, being associated with higher mortality and morbidity. The factors that cause sepsis-associated encephalopathy (SAE) are still not well known, and may be multifactorial, as perfusion changes, neuroinflammation, oxidative stress and glycolytic metabolism alterations. Fructose-1,6-bisphosphate (FBP), a metabolite of the glycolytic route, has been reported as neuroprotective agent. The present study used an experimental sepsis model in C57BL/6 mice. We used in vivo brain imaging to evaluate glycolytic metabolism through microPET scans and the radiopharmaceutical ¹⁸F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG). Brain images were obtained before and 12 h after the induction of sepsis in animals with and without FBP treatment. We also evaluated the treatment effects in the brain oxidative stress by measuring the production of reactive oxygen species (ROS), the activity of catalase (CAT) and glutathione peroxidase (GPx), and the levels of fluorescent marker 2'7'-dichlorofluorescein diacetate (DCF). There was a significant decrease in brain glucose metabolism due to experimental sepsis. A significant protective effect of FBP treatment was observed in the cerebral metabolic outcomes. FBP also modulated the production of ROS, evidenced by reduced CAT activity and lower levels of DCF. Our results suggest that FBP may be a possible candidate in the treatment of SAE.

Fructose 1,6-bisphosphate, a high-energy intermediate of glycolysis, attenuates experimental arthritis by activating anti-inflammatory adenosinergic pathway

Fructose 1,6-bisphosphate (FBP) is an endogenous intermediate of the glycolytic pathway. Exogenous administration of FBP has been shown to exert protective effects in a variety of ischemic injury models, which are attributed to its ability to sustain glycolysis and increase ATP production. Here, we demonstrated that a single treatment with FBP markedly attenuated arthritis, assessed by reduction of articular hyperalgesia, joint swelling, neutrophil infiltration and production of inflammatory cytokines, TNF and IL-6, while enhancing IL-10 production in two mouse models of arthritis. Our mechanistic studies showed that FBP reduces joint inflammation through the systemic generation of extracellular adenosine and subsequent activation of adenosine receptor A2a (A2aR). Moreover, we showed that FBP-induced adenosine generation requires hydrolysis of extracellular ATP through the activity of the ectonucleosides triphosphate diphosphohydrolase-1 (ENTPD1, also known as CD39) and ecto-5'-nucleotidase (E5NT, also known as CD73). In accordance, inhibition of CD39 and CD73 abolished anti-arthritic effects of FBP. Taken together, our findings provide a new insight into the molecular mechanism underlying the anti-inflammatory effect of FBP, showing that it effectively attenuates experimental arthritis by activating the anti-inflammatory adenosinergic pathway. Therefore, FBP may represent a new therapeutic strategy for treatment of rheumatoid arthritis (RA).

Global analysis of protein structural changes in complex proteomes

Changes in protein conformation can affect protein function, but methods to probe these structural changes on a global scale in cells have been lacking. To enable large-scale analyses of protein conformational changes directly in their biological matrices, we present a method that couples limited proteolysis with a targeted proteomics workflow. Using our method, we assessed the structural features of more than 1,000 yeast proteins simultaneously and detected altered conformations for ~300 proteins upon a change of nutrients. We find that some branches of carbon metabolism are transcriptionally regulated whereas others are regulated by enzyme conformational changes. We detect structural changes in aggregation-prone proteins and show the functional relevance of one of these proteins to the metabolic switch. This approach enables probing of both subtle and pronounced structural changes of proteins on a large scale.

Deficiency of nicotinamide mononucleotide adenylyltransferase 3 (nmnat3) causes hemolytic anemia by altering the glycolytic flow in mature erythrocytes

NAD biosynthesis is of substantial interest because of its important roles in regulating various biological processes. Nicotinamide mononucleotide adenylyltransferase 3 (Nmnat3) is considered a mitochondria-localized NAD synthesis enzyme involved in de novo and salvage pathways. Although the biochemical properties of Nmnat3 are well documented, its physiological function in vivo remains unclear. In this study, we demonstrated that Nmnat3 was localized in the cytoplasm of mature erythrocytes and critically regulated their NAD pool. Deficiency of Nmnat3 in mice caused splenomegaly and hemolytic anemia, which was associated with the findings that Nmnat3-deficient erythrocytes had markedly lower ATP levels and shortened lifespans. However, the NAD level in other tissues were not apparently affected by the deficiency of Nmnat3. LC-MS/MS-based metabolomics revealed that the glycolysis pathway in Nmnat3-deficient erythrocytes was blocked at a glyceraldehyde 3-phosphate dehydrogenase (GAPDH) step because of the shortage of the coenzyme NAD. Stable isotope tracer analysis further demonstrated that deficiency of Nmnat3 resulted in glycolysis stall and a shift to the pentose phosphate pathway. Our findings indicate the critical roles of Nmnat3 in maintenance of the NAD pool in mature erythrocytes and the physiological impacts at its absence in mice.

Fructose-1,6-bisphosphate reduces inflammatory pain-like behaviour in mice: role of adenosine acting on A1 receptors

BACKGROUND AND PURPOSE

D-Fructose-1,6-bisphosphate (FBP) is an intermediate in the glycolytic pathway, exerting pharmacological actions on inflammation by inhibiting cytokine production or interfering with adenosine production. Here, the possible antinociceptive effect of FBP and its mechanism of action in the carrageenin paw inflammation model in mice were addressed, focusing on the two mechanisms described above.

EXPERIMENTAL APPROACH

Mechanical hyperalgesia (decrease in the nociceptive threshold) was evaluated by the electronic pressure-metre test; cytokine levels were measured by elisa and adenosine was determined by high performance liquid chromatography.

KEY RESULTS

Pretreatment of mice with FBP reduced hyperalgesia induced by intraplantar injection of carrageenin (up to 54%), tumour necrosis factor alpha (40%), interleukin-1 beta (46%), CXCL1 (33%), prostaglandin E(2) (41%) or dopamine (55%). However, FBP treatment did not alter carrageenin-induced cytokine (tumour necrosis factor alpha and interleukin-1 beta) or chemokine (CXCL1) production. On the other hand, the antinociceptive effect of FBP was prevented by systemic and intraplantar treatment with an adenosine A(1) receptor antagonist (8-cyclopentyl-1,3-dipropylxanthine), suggesting that the FBP effect is mediated by peripheral adenosine acting on A(1) receptors. Giving FBP to mice increased adenosine levels in plasma, and adenosine treatment of paw inflammation presented a similar antinociceptive mechanism to that of FBP.

CONCLUSIONS AND IMPLICATIONS

In addition to anti-inflammatory action, FBP also presents an antinociceptive effect upon inflammatory hyperalgesia. Its mechanism of action seems dependent on adenosine production but not on modulation of hyperalgesic cytokine/chemokine production. In turn, adenosine acts peripherally on its A(1) receptor inhibiting hyperalgesia. FBP may have possible therapeutic applications in reducing inflammatory pain.

Fructose-1,6-diphosphate attenuates acute lung injury induced by lipopolysaccharide in mice

Fructose-1,6-diphosphate (FDP), a high-energy glycolytic pathway intermediate, is reported to have a salutary effect in endotoxic shock and sepsis, but its underlying mechanism of action in inflammation is incompletely understood. In this study, our aim was to examine the function of FDP on acute lung injury (ALI) induced by lipopolysaccharide (LPS). We found that in vitro pretreatment with FDP remarkably repressed the production of TNF-alpha and IL-6 in murine alveolar macrophages MH-S exposed to LPS. In the mouse model of LPS-induced inflammatory lung injury, intravenous precondition of a single 400 mg/kg dose of FDP resulted in a significant reduction in LPS-mediated extravasation of Evans blue dye albumin, bronchoalveolar lavage leucocyte content, and lung tissue myeloperoxidase activity (reflecting phagocyte infiltration). Furthermore, histopathologic examination indicated that alveolitis with inflammatory cells infiltration and alveolar hemorrhage in the alveolar space was less severe in the FDP-treated mice than in the mice treated by LPS alone at 24 h. Additionally, pretreatment with FDP markedly decreased the transcription of TNF-alpha, IL-6 and inducible NO synthase (iNOS), and suppressed the nuclear translocation of NF-kappaB in lung tissues in response to LPS challenge. These results thus suggested that FDP plays an anti-inflammatory role in LPS-mediated acute lung injury, possibly through abrogation of NF-kappaB activation.

Influence of fructose-1,6-diphosphate on endotoxin-induced lung injuries in sheep

BACKGROUND

Fructose-1,6-diphosphate (FDP) is reported to have a salutary effect in endotoxin shock and sepsis. This investigation describes the effect of FDP on pulmonary and systemic hemodynamics, lung lymph protein clearance, and leukocyte count in sheep infused with Escherichia coli endotoxin.

MATERIALS AND METHODS

Anesthetized sheep (n = 18), some of which underwent thoracotomy to cannulate lymphatic nodes, were used in this study. After stabilization, all sheep received E. coli endotoxin, 5 microg/kg i.v. infusion over 30 min. Concomitant with the endotoxin infusion, half of the animals were randomly selected to receive an i.v. bolus of FDP (10%), 50 mg/kg, followed by a continuous infusion of 5 mg.kg(-1).min(-1) for 4 h; the rest were treated in the same manner with glucose (10%) in 0.9% NaCl.

RESULTS

Pulmonary artery pressure (PAP) and resistance in the glucose group increased from 20.8 +/- 1.6 to 36.7 +/- 3.2 mmHg (P < 0.007) and from 531 +/- 114 to 1137 +/- 80 dyn.s(-1).cm(-5), respectively (P < 0.005). Despite an increase during endotoxin infusion, these parameters in the FDP group returned to control values. There were no differences in left ventricular pressures, cardiac output, heart rate, and arterial oxygen tension between the groups. In the glucose group, lymph protein clearance was higher (P < 0.01) and blood leukocyte count was lower (P < 0.02). The wet/dry lung weight ratio (g/g) for the glucose group was 5.57 +/- 0.04 and for the FDP-treated group 4.76 +/- 0.06 (P < 0.0005).

CONCLUSION

FDP treatment attenuated significantly the characteristic pulmonary hypertension, lung lymph protein clearance, and pulmonary vascular leakage seen in sheep infused with endotoxin.

Effect of normothermic perfusion using fructose-1,6-bisphosphate for maintenance of liver function during in situ extended hepatectomy by the total hepatic vascular exclusion technique

BACKGROUND

Recently, hepatic surgery has made remarkable progress, and it is important to use appropriate liver perfusion. We evaluated the effect of normothermic liver perfusion with the addition of fructose-1, 6-bisphosphate (FBP) and oxygenation to maintain liver parenchymal, non-parenchymal, and Kupffer cell function.

MATERIALS AND METHODS

The rats were divided into five groups according to the perfusate and continuous perfusion was performed: Control group = 4 degrees C lactate Ringer with 10% glucose (LRG) solution; normothermic group = 25 degrees C LRG solution; normothermic oxygenated group = 25 degrees C oxygenated LRG solution; normothermic FBP group = 25 degrees C LRG solution with addition of 10 mmol/L FBP; normothermic oxygenated FBP group = 25 degrees C oxygenated LRG solution with addition of 10 mmol/L FBP. Parameters under evaluation were oxygen consumption, liver energy level (adenosine triphosphate, total adenine nucleotide), glutathione, lipid peroxide, hyaluronic acid uptake ratio, apoptosis, and histomorphology. Moreover, we studied the effect of FBP and normothermia on Kupffer cells activation in vitro.

RESULTS

Liver energy level was lower in the normothermic group than the control group. But, it was improved by oxidation or addition of FBP, and it was satisfactorily maintained up to 120 min in the group with normothermic oxygenated FBP. Hyaluronic acid uptake was maintained highly at all times as measured in normothermic oxygenated FBP group. The uptake of lipopolysaccharide was significantly higher as a result of adding FBP, compared with that in the control group and the normothermic group. Moreover, the apoptotic index in the liver was decreased in normothermic FBP group compared to control group.

CONCLUSIONS

The normothermic liver perfusion under additional FBP and oxygenation protects both parenchymal and non-parenchymal cells from reperfusion injury.

Fructose-1,6-diphosphate suppresses T-lymphocyte proliferation, promotes apoptosis and inhibits interleukins-1, 6, beta-actin mRNAs, and transcription factors expression

The overall objective of this study was to determine the role fructose 1,6-diphosphate (FDP), a naturally occurring glycolytic intermediate, plays in activated T-lymphocytes. The hypothesis is twofold. First, we propose that FDP inhibits T cell proliferation to a greater extent than fructose-1-phosphate (F1P), fructose-6-phosphate (F6P) and mannose-6-phosphate (M6P); second, we argue that FDP suppresses immune activation by inhibiting inflammatory cytokine expression, inhibiting expression of key transcription factors, and by inducing apoptosis in immune cells. Rat spleen cells were incubated with concanavalin A (ConA) and increasing concentrations of FDP. Proliferation was determined by tritiated thymidine uptake. FDP inhibited splenocyte proliferation in a dose-related manner while F1P, F6P, M6P demonstrated inhibition only at high concentrations (5000 microg/ml). RNA was harvested from FDP and ConA-treated cells and IL-1 and IL-6 gene expression was analyzed by RT-PCR. IL-1 and IL-6 mRNA expression was completely inhibited at 500-5000 microg/ml FDP. Apoptosis in FDP-treated lymphocytes was determined by DNA fragmentation and flow cytometry. Propidium iodide (PI) staining demonstrated a 39% rate of apoptosis in splenocytes treated with ConA and 5000 microg/ml FDP. Extensive DNA fragmentation was present at 250-5000 microg/ml FDP, and maximal inhibition occurred at 5 microg/ml. F1P, F6P and M6P showed maximal inhibition only at 5000 microg/ml. Nuclear extracts from FDP-treated splenocytes were analyzed by electrophoretic mobility shift assay. ConA activation of NF-kappaB and AP-1 was dramatically inhibited by FDP. Interestingly, beta-actin showed extensive inhibition with FDP and ConA, thus suggesting new possibilities of its being used as a therapeutic modality in arterial injury where the beta-actin, an important cytoskeleton element, plays a very important role. These data indicate that FDP may be a useful immunosuppressive agent. In conclusion, FDP is not only an immunosuppressant but also an anti-inflammatory agent.

Anti-inflammatory effects of fructose-1,6-bisphosphate on carrageenan-induced pleurisy in rat

In the present study, we evaluated the effect of fructose-1,6-bisphosphate (FBP), a high energy intermediate metabolite of glycolysis, in an acute model of lung injury. Injection of carrageenan into the pleural cavity of rats elicited an acute inflammation response characterized by a fluid accumulation in the pleural cavity which contained a large number of polymorphonuclear neutrophils. FBP (500mg/kg) attenuated the inflammation parameters: exudate volume, total leukocytes and the number of polymorphonuclear leukocytes, but the protein concentration in the exudate was not significantly affected by treatment with FBP. The precise site and mechanism of the anti-inflammatory effect was not addressed, considering the diverse pharmacological actions of FBP. This drug has anti-inflammatory actions suggesting that it may represent a novel strategy for the modulation of inflammatory response.

Using fructose-1,6-diphosphate during hypothermic rabbit-heart preservation: a high-energy phosphate study

BACKGROUND

In this study, we evaluated the effects of fructose-1,6-diphosphate (FDP) on high-energy phosphate metabolism during 18-hour hypothermic rabbit-heart preservation.

METHODS

Under general anesthesia and artificial ventilation, hearts from 42 adult New Zealand white rabbits were harvested, flushed, and preserved in St. Thomas solution at 4(o)C for 18 hours. In the study group (n = 15), FDP (5 mmol/liter) was added to the St. Thomas solution, whereas in the control group (n = 17), fructose (5 mmol/liter) was added. Another 10 hearts did not undergo hypothermic storage, but were used as the normal group for high-energy phosphate concentration comparison.

RESULTS

After 18 hours of hypothermic preservation, myocardial high-energy phosphate content decreased in both preservation groups. In the study group, left ventricular adenosine triphosphate (ATP) content was 33% of that in the normal hearts, but in the control group, ATP decreased to 14% of normal. Adenosine diphosphate (ADP) content, energy charge, and ATP-to-ADP ratio showed similar decreases. The high-energy phosphate profile (content in the atria and ventricles and the ratio of ATP to ADP to AMP) was maintained in the study group but not in the control group. High-energy phosphate metabolites such as inosine monophosphate (IMP), inosine, and hypoxanthine increased in both preservation groups, but the increase was more prominent in the control group.

CONCLUSION

Adding FDP to St. Thomas solution attenuated the depletion of high-energy phosphate concentration in the preserved hearts. This difference was especially prominent in the left and right ventricles. The protective effect of FDP during hypothermic heart preservation deserves further study.

Effects of fructose-1,6-bisphosphate on morphological and functional neuronal integrity in rat hippocampal slices during energy deprivation

D-fructose-1,6-bisphosphate, a high energy glycolytic intermediate, attenuates ischemic damage in a variety of tissues, including brain. To determine whether D-fructose-1,6-bisphosphate serves as an alternate energy substrate in the CNS, rat hippocampal slices were treated with D-fructose-1,6-bisphosphate during glucose deprivation. Unlike pyruvate, an endproduct of glycolysis, 10 mM D-fructose-1,6-bisphosphate did not preserve synaptic transmission or morphological integrity of CA1 pyramidal neurons during glucose deprivation. Moreover, during glucose deprivation, 10-mM D-fructose-1,6-bisphosphate failed to maintain adenosine triphosphate levels in slices. D-fructose-1,6-bisphosphate, however, attenuated acute neuronal degeneration produced by 200 microM iodoacetate, an inhibitor of glycolysis downstream of D-fructose-1,6-bisphosphate. Because (5S, 10R)-(+)-5-methyl-10, 11-dihydro-5H-dibenzo [a,d]cyclohepten-5,10-imine, an antagonist of N-methyl-D-aspartate receptors, exhibited similar protection against iodoacetate damage, we examined whether (5S, 10R)-(+)-5-methyl-10, 11-dihydro-5H-dibenzo [a,d]cyclohepten-5,10-imine and D-fructose-1,6-bisphosphate share a common neuroprotective mechanism. Indeed, D-fructose-1,6-bisphosphate diminished N-methyl-D-aspartate receptor-mediated synaptic responses and partially attenuated neuronal degeneration induced by 100-microM N-methyl-D-aspartate. Taken together, these results indicate that D-fructose-1,6-bisphosphate is unlikely to serve as an energy substrate in the hippocampus, and that neuroprotective effects of D-fructose-1,6-bisphosphate are mediated by mechanisms other than anaerobic energy supply.

Physiopathological studies in septic rats and the use of fructose 1,6-bisphosphate as cellular protection

OBJECTIVE

The aim of this research project was to test the ability of fructose 1,6-bisphosphate (FBP), which has anti-inflammatory effects and maintains cellular energy levels, to inhibit the septic process in an experimental model in rats.

DESIGN

Prospective, controlled animal trial.

SETTING

Research laboratory.

SUBJECTS

Fed male Wistar rats.

INTERVENTIONS

Three experimental groups were formed for the test: control group, untreated septic group, and septic group treated with FBP (500 mg/kg).

MEASUREMENTS AND MAIN RESULTS

In the control group, there were no deaths; in the untreated septic group, the mortality rate was 100% within 15 hrs; in the septic group treated with FBP, the mortality rate reached 20% within 15 hrs. The blood cell tests revealed that concentrations of hematocrit, leukocytes, monocytes, and immature cells increased significantly in the untreated septic group compared with both the FBP-treated septic group and the control group. The histologic lesions verified in the heart, lungs, liver, and kidneys of septic animals were smaller and even absent in those treated with FBP.

CONCLUSION

FBP reduced the mortality rate provoked by experimental sepsis and ameliorated hematologic and histologic alterations.

Neuroprotection and intracellular Ca2+ modulation with fructose-1,6-bisphosphate during in vitro hypoxia-ischemia involves phospholipase C-dependent signaling

The neuroprotectant fructose-1,6-bisphosphate (FBP) preserves cellular [ATP] and prevents catastrophic increases in [Ca2+]i during hypoxia. Because FBP does not enter neurons or glia, the mechanism of protection is not clear. In this study, we show that FBP's capacity to protect neurons and stabilize [Ca2+]i during hypoxia derives from signaling by a phospholipase-C-intracellular Ca2+-protein kinases pathway, rather than Ca2+ chelation or glutamate receptor inhibition. FBP reduced [Ca2+]i changes in hypoxic hippocampal neurons, regardless of [Ca2+]e, and preserved cellular integrity as measured by trypan blue or propidium iodide exclusion and [ATP]. FBP also prevented hypoxia-induced increases in [Ca2+]i when glucose was absent and when [Ca2+]e was increased to negate Ca2+ chelation by FBP. These protective effects were observed equally in postnatal day 2 (P2) and P16 neurons. Inhibiting glycolysis with iodoacetate eliminated the protective effects of FBP in P16 neurons. FBP did not alter Ca2+ influx stimulated by brief applications of NMDA or glutamate during normoxia or hypoxia, but did reduce the increase in [Ca2+]i produced by 10 min of glutamate exposure during hypoxia. Because FBP increases basal [Ca2+]i and stimulates membrane lipid hydrolysis, we tested whether FBP's protective action was dependent on phospholipase C signaling. The phospholipase C inhibitor U73122 prevented FBP-induced increases in [Ca2+]i and eliminated FBP's ability to stabilize [Ca2+]i and increase survival during anoxia. Similarly, FBP's protection was eliminated in the presence of the mitogen/extracellular signal protein kinase (MEK) inhibitor U0126. We conclude that FBP may produce neuroprotection via activation of neuroprotective signaling pathways that modulate Ca2+ homeostasis.

Effect of fructose-1, 6-diphosphate versus diphenhydramine on mortality in compound 48/80-induced shock

Fructose-1,6-diphosphate (FDP) has a salutary effect on hemorrhagic, traumatic and endotoxic shock. The role of FDP on compound 48/80-induced shock was therefore investigated. Sprague Dawley aged male rats (448+/-7.4 gm body weight) were randomly assigned into three groups and treated intraperitoneally with diphenhydramine (DPHM) 15 mg/kg (n=11), 12.5 ml of 10% FDP (n=10) and 12.5 ml saline (n=10). The rats were injected with compound 48/80 (5 mg/kg) 30 min later, and monitored every 10 min for 60 min. Arterial pressure was higher in FDP rats than in DPHM (P<0.01) or saline (P<0.005) groups. Plasma potassium (K(+)) was lower in the FDP group (P<0.01). Arterial pO2 and pCO2 were within physiological range in all groups. A profound decrease in arterial pH and bicarbonate (HCO3(-)) was also observed in all groups. Mortality at 48 h in the saline group was 100%, in the DPHM group 91%, and in the FDP group 20% (P<0.001 and P<0.005, respectively). FDP improved survival significantly in this study.

Metabolic responses to fructose-1,6-diphosphate in healthy subjects

Fructose-1,6-diphosphate (FDP) is an important naturally occurring intracellular metabolite with a direct regulatory role in many metabolic pathways. The most important and widely studied of the FDP effects has been its regulation of glycolysis, particularly the enzyme that synthesizes FDP--phosphofructokinase (PFK). Since it was observed experimentally that FDP does indeed modulate carbohydrate metabolism, we investigated whether FDP would similarly enhance carbohydrate utilization in man. The study used indirect calorimetry and was open to healthy adults (N = 45) of either sex and above legal age. After a steady metabolic state was obtained, 5 g of FDP (10%) was infused into a brachial vein. In 10 subjects, glucose (5 g) or FDP (5 g) was sequentially infused. The rapid intravenous infusion of FDP produced a slight but significant decrease in heart and respiration rates (P < .05). A significant increase in the serum concentration of inorganic phosphate (P < .0001) and the intraerythrocytic concentration of adenosine triphosphate (ATP) (P < .01) was also observed. The FDP infusion produced a decrease in plasma cholesterol and triglycerides (P < .001 and P < .01, respectively). The indirect calorimetric data indicate that the infusion produced a highly significant increase in the respiratory quotient ([RQ] P < .0001) and the energy derived from carbohydrates (P < .0001) and a significant decrease in the energy derived from lipids (P < .0001). Glucose infusion did not cause changes in any of the parameters. These data indicate that carbohydrate metabolism is stimulated by FDP.

Regulation of nitric oxide synthesis in the liver

Nitric oxide signalling during the past two decades has been one of the most rapidly growing areas in biology. This simple free radical gas can regulate an ever-growing list of biological processes. Here the regulation of NO synthesis in the liver is reviewed. The biogenesis of nitric oxide (NO) is catalysed by nitric oxide synthases (NOS). These enzymes catalyse the oxidation of one of the guanidino nitrogens of l-arginine by molecular oxygen to form NO and citrulline. Three NOS have been identified: two constitutive (cNOS: type 1 or neuronal and type 3 or endothelial) and one inducible (iNOS: type 2). As to the liver, cNOS activity is normally detectable in Kupffer cells, whereas no cNOS is ever encoded in hepatocytes. However, hepatocytes, Kupffer and stellate cells (the three main types of liver cells) are prompted to express an intense iNOS activity once exposed to effective stimuli such as bacterial lipopolysaccharide and cytokines. This review is focused mainly on two aspects: regulation of NOS activity and expression by endogenous and exogenous compounds. Because NO production has beneficial and detrimental effects, understanding the molecular mechanisms that govern NOS is critical to developing strategies to manipulate NO production in liver diseases.

Fructose-1,6-diphosphate and a glucose-free solution enhances functional recovery in hypothermic heart preservation

BACKGROUND

Fructose-1,6-diphosphate (FDP) has been shown to protect tissue during hypoxia under various ischemic conditions, including isolated heart perfusion. We tested the hypothesis that adding FDP to St. Thomas solution can extend hypothermic heart preservation time.

METHODS

Sixteen adult Sprague-Dawley rats were used. Under general anesthesia, the hearts were removed and preserved at 4 degrees C in St. Thomas solution (30 ml/kg) for 12 hours. FDP (5 mM) was added to the St. Thomas solution in the study group (n = 8), whereas no FDP was used in the control group (n = 10). The hearts were reperfused after 12 hours of preservation using a working heart model.

RESULTS

In the study group, cardiac output ranged from 13.00 +/- 2.34 to 17.66 +/- 1.71 ml/min, maximum aortic flow was 3.40 +/- 1.99 to 9.26 +/- 1.72 ml/min, left ventricular stroke volume ranged from 0.074 +/- 0.014 to 0.092 +/- 0.009 ml, left ventricular stroke work ranged from 6.22 +/- 0.39 to 7.95 +/- 0.44 ml/mmHg, and maximum left ventricular generated power was 14.38 +/- 2.94 to 20.16 +/- 2.49 Joules/min. All of these parameters were higher than those in the control group (p < 0.001). Coronary vascular resistance and myocardial tissue wet/dry weight ratio were lower in the study group than in the control group (p < 0.05).

CONCLUSIONS

Heart function was better preserved when FDP was added to St. Thomas solution during hypothermic rat heart preservation. The mechanism is not totally clear, but enhancement of high-energy phosphate production during ischemia is possible. Key words: heart, procurement, hypothermia, fructose-1,6-diphosphate.

Sodium d-fructose-1,6-diphosphate vs. sodium monohydrogen phosphate in total parenteral nutrition: a comparative in vitro assessment of calcium phosphate compatibility

BACKGROUND

The supply of high amounts of calcium (Ca) and phosphorus (P) during total parenteral nutrition (TPN) is matter of concern because of the risk associated with calcium phosphate precipitation. The in vitro Ca-P compatibility in ready-for-use TPN solutions after the addition of different concentrations of inorganic phosphate or d-fructose-1,6-diphosphate (FDP) and calcium chloride was evaluated.

METHODS

Four series of experiments for each Ca + P couple were carried out by varying amino acid concentrations (2% or 4%), temperature (25 degrees C or 37 degrees C), and pH. The extent of precipitation was estimated by visual inspection and particle count. The areas of maximal compatibility (ie, areas showing the complete absence of precipitates) were drawn from the precipitation curves.

RESULTS

The precipitation extent was considerably higher in conditions mimicking body environment for both Ca + P couples. The compatibility area at 37 degrees C and 2% amino acid for CaCl2 + Na2HPO4 admixtures was included within 2.50 mmol/L CaCl2 and 2.22 mmol/L Na2HPO4, whereas that for CaCl2 + FDP was within 33.3 mmol/L CaCl2 and 10.0 mmol/L FDP (20 mEq/L of P). Unlike inorganic calcium phosphate, FDP dicalcium salt precipitation was kinetically delayed and was only minimally enhanced by decreasing amino acid concentration.

CONCLUSIONS

Our data indicated that the use of FDP as the P source in parenteral nutrition solutions was effective in avoiding the life-threatening calcium phosphate precipitation. Thus, the addition of FDP to TPN admixtures represents a safe choice, allowing the simultaneous administration of high amounts of Ca and P in restricted fluid volumes, even at low amino acid concentrations.

Interaction of neuronal nitric-oxide synthase and phosphofructokinase-M

Neurons that express neuronal nitric-oxide synthase (nNOS) are resistant to NO-induced neurotoxicity; however, the mechanism by which these neurons are protected is not clear. To identify proteins possibly involved in this process, we performed affinity chromatography with the nNOS PDZ domain, a N-terminal motif that mediates protein interactions. Using this method to fractionate soluble tissue extracts, we identified the muscle isoform of phosphofructokinase (PFK-M) as a protein that binds to nNOS both in brain and skeletal muscle. PFK-M interacts with the PDZ domain of nNOS, and nNOS-PFK-M binding can be competed by peptides that bind to the PDZ domain of nNOS. We found that nNOS is significantly associated with PFK-M in skeletal muscle because nNOS can be immunodepleted from cytosolic skeletal muscle extracts using an antibody directed against PFK-M. In brain, nNOS and PFK-M are both enriched in synaptosomes, and specifically, in the synaptic vesicle fraction, where they can interact. At the cellular level, PFK-M is enriched in neurons that express nNOS protein. As fructose-1, 6-bisphosphate, the product of PFK activity, is neuroprotective, the interaction of nNOS and PFK may contribute to neuroprotection of nNOS positive cells.

Impaired growth of an Escherichia coli rpe mutant lacking ribulose-5-phosphate epimerase activity

We present evidence that ribulose-5-phosphate epimerase, a central metabolic enzyme acting in the non-oxidative branch of the pentose-phosphate pathway, is encoded by a gene in the dam containing operon of Escherichia coli. Enzymatic assays confirm that this gene encodes ribulose-5-phosphate epimerase activity. Disruption of the gene (rpe) causes loss of enzymatic activity and renders the rpe mutant unable to utilize single pentose sugars, indicating that rpe supplies the only ribulose-5-phosphate epimerase activity in E. coli. Growth of the rpe mutant is impaired in complex LB medium and severely impaired in minimal medium containing glycolytic carbon sources or gluconate. Enrichment with casamino acids abolishes or strongly relieves growth suppression in minimal medium. Aspartate counteracts the impaired growth in glycolytic carbon sources but not in gluconate. We suggest that the absence of the Rpe enzyme causes changes in the pentose-phosphate levels which alter the regulation of (a) metabolic enzyme(s) and thereby cause growth suppression and that the severity of growth suppression is related to the internal concentration of pentose-phosphates. Target enzymes for negative regulation may be located in the early parts of the Embden-Meyerhof-Parnas pathway and of the Entner-Doudoroff pathway and/or of carbohydrate transport systems feeding sugars into these sections of central metabolic pathways.

Hemodynamic effects of fructose 1,6-diphosphate in patients with normal and impaired left ventricular function

We compared the short-term hemodynamic effects of intravenous fructose 1,6-diphosphate (FDP) administration in patients with coronary artery disease. Hemodynamic measurements were performed before and after administration of FDP in two groups of patients: those with impaired left ventricular (LV) function, elevated LV end-diastolic pressures (LVEDP > or =12 mm Hg, n = 30), and those with normal LV function (LVEDP <12 mm Hg, n = 17). In those with impaired LV function, FDP induced a decrease in LVEDP from 22 +/- 1.31 to 16.73 +/- 1.46 mm Hg (p< 0.0001). The cardiac index increased (2.50 +/- 0.11 to 2.81 +/- 0.13 L/m2 [p < 0.0001]), as did the LV stroke work index (31.7 +/- 2.04 to 40.3 +/- 2.67 gm x m x m2 [p < 0.0001]). FDP induced no significant change in heart rate and mean aortic pressure. Pulmonary pressure and resistance declined (p<0.002 and p< 0.0001, respectively). Systemic vascular resistance decreased because of increased cardiac output and unchanged arterial pressure (p < 0.001). In those patients with normal baseline LVEDP (5.06 +/- 0.27 mm Hg), FDP decreased heart rate (p< 0.0001) and systemic and pulmonary resistance (p < 0.03 and p < 0.004, respectively), whereas LVEDP and mean aortic and pulmonary pressures remained unchanged. FDP moderately increased cardiac output (p < 0.05), stroke volume index, and LV stroke work index (p< 0.002 and p< 0.003, respectively). The observed improvement in LV function in those patients with elevated LV filling pressures is thought to be a result of an increased energy production by the Embden-Meyerhoff pathway and to act as a positive inotrope.

Fructose-1,6-bisphosphate after hypoxic ischemic injury is protective to the neonatal rat brain

Fructose-1,6-bisphosphate (FBP) has been shown to attenuate central nervous system injury in adult animals. We evaluated whether FBP given after an ischemic-hypoxic insult is protective to the developing brain in a neonatal rat model of hypoxia-ischemia. Postnatal day 7 rat pups were subjected to focal ischemia followed by global hypoxia and then administered either FBP or saline intraperitoneally. A dose of 500 mg/kg or greater of FBP significantly reduced the amount of injury such that 55% of FBP- vs. 17% of saline-treated rats had no injury; 6% of FBP- and 47% of saline-treated rats had severe damage (P = 0.004). There was less infarcted brain in FBP-treated rats (12 +/- 11% vs. 37 +/- 32%; P = 0.005); and fewer FBP-treated rats had > 30% ipsilateral cortical injury (12% of FBP- vs. 50% of saline-treated rats; P = 0.002). FBP lowered serum calcium levels during the first 24 h after the insult without significant changes in ionized calcium or osmolarity. These results indicate that FBP treatment administered systemically after hypoxia-ischemia reduces CNS injury in neonatal rats.

Energy metabolism in hypoxic astrocytes: protective mechanism of fructose-1,6-bisphosphate

The protective effects of fructose-1,6-biphosphate (FBP) during hypoxia/ischemia are thought to result from uptake and utilization of FBP as a substrate for glycolysis or from stimulation of glucose metabolism. To test these hypotheses, we measured CO2 and lactate production from [6-14C]glucose, [1-14C]glucose, and [U-14C]FBP in normoxic and hypoxic cultured astrocytes with and without FBP present. FBP had little effect on CO2 production by glycolysis, but increased CO2 production by the pentose phosphate pathway. Labeled FBP produced very small amounts of CO2. Lactate production from [1-, and 6-14C]glucose increased similarly during hypoxic hypoxia; the increase was independent of added FBP. Labeled lactate from [U-14C]FBP was minimal. We conclude that exogenous FBP is not used by astrocytes as a substrate for glycolysis and that FBP alters glucose metabolism.

Fructose 1,6-bisphosphate prevents oxidative stress in the isolated and perfused rat heart

Rat hearts were perfused with the Langendorff technique at constant flux in the presence of the oxidizing agents hydrogen peroxide and diamide. Fructose 1,6-bisphosphate strongly prevented the decline of heart contractility due to the infusion of these oxidizing agents. On the other hand, fructose 1,6-bisphosphate had no effect on the release of total glutathione into the perfusate but prevented the loss of lactate dehydrogenase indicating a protective effect on cell membranes. Comparing the cytosolic and mitochondrial loss of glutathione, fructose 1,6-bisphosphate exerted a beneficial action only on the mitochondrial fraction. Several mechanisms of action have been considered to explain the protective action of fructose 1,6-bisphosphate. In our experimental conditions fructose 1,6-bisphosphate might stimulate its own production giving rise to dihydroxyacetone phosphate, that, after reduction to glycerol 3-phosphate, can permeate the mitochondrial membrane with the final production of energy.

Fructose-1,6-bisphosphate reduces infarct volume after reversible middle cerebral artery occlusion in rats

BACKGROUND AND PURPOSE

We tested the hypothesis that fructose-1,6-bisphosphate, when administered 10 minutes before the end of 2 hours of reversible middle cerebral artery occlusion, reduces ischemia-reperfusion injury and infarct volume measured after a 3-day survival period in rats.

METHODS

After 1 hour and 50 minutes of middle cerebral artery occlusion by the intraluminal suture method, fructose-1,6-bisphosphate, 500 mg/kg in group 1 and 350 mg/kg in group 2 (or an equivalent volume of 1.8% saline as placebo in each group), was given intravenously for a period of 15 minutes to fasted adult Sprague-Dawley rats. After 2 hours of ischemia, the suture was withdrawn and the rats allowed to survive for 3 days. The areas of infarction in 10 hematoxylin-eosin-stained coronal sections of the brain were measured and used to calculate infarct volume.

RESULTS

In group 1, fructose-1,6-bisphosphate decreased total cerebral hemispheric infarct volume by 43% (from 199.6 +/- 11.2 to 114.2 +/- 35.8 mm3, P < .04; mean +/- SEM). Cerebral cortical and subcortical infarct volumes were decreased by 46% (from 137.3 +/- 7.5 to 74.1 +/- 28.6 mm3, P < .04) and 36% (from 62.3 +/- 5.1 to 40.0 +/- 8.3 mm3, P < .04), respectively. In group 2, fructose-1,6-bisphosphate had no effect on infarct volume in rats that developed mild intraischemic hyperthermia, but in rats kept normothermic during ischemia, fructose-1,6-bisphosphate reduced subcortical infarct volume from 53.7 +/- 8.1 to 18.4 +/- 8.0 mm3 (P < .03).

CONCLUSIONS

Fructose-1,6-bisphosphate improves functional neurological outcome and reduces infarct volume after reversible middle cerebral artery occlusion in rats.

Protective effect of fructose 1,6-bisphosphate against carrageenan-induced inflammation

Administration of carrageenan (0.5 mg) to the plantar tissue of rats resulted in reversible inflammatory injury. This damage was monitored as changes in foot volume, using a plethysmometer. Administration of fructose 1,6-bisphosphate at different doses, orally or intraperitoneally, prevented the inflammatory action induced by the simultaneous injection of carrageenan in the rat paw. The effect was dose and time dependent. In contrast, fructose or fructose 6-phosphate afforded no significant protection. In order to extend the average half-life of the drug, we prepared liposomes of fructose 1,6-bisphosphate which, administered orally or intraperitoneally, showed a greater and more prolonged antiinflammatory action. The significance of these findings with respect to the mechanism of the antiinflammatory action of fructose 1,6-bisphosphate is discussed.

Fructose-1,6-diphosphate fails to limit early myocardial infarction size in a canine model

STUDY OBJECTIVE

Fructose-1,6-diphosphate (FDP) appears to improve early post-myocardial infarction hemodynamics and limit early myocardial infarct size in previous canine studies. However, these studies did not account for the effect of collateral blood flow on infarct size. Our objective was to determine the effect of FDP on early infarct size and hemodynamics while measuring regional myocardial blood flow.

DESIGN

A prospective, blinded, placebo-controlled laboratory study using a canine open-chest left anterior descending coronary artery (LAD) occlusion model.

INTERVENTIONS

Twenty-two mongrel dogs were assigned randomly to receive either FDP (175 mg/kg, then 2 mg/kg/min for two hours) or placebo, beginning five minutes after LAD occlusion.

MEASUREMENTS AND MAIN RESULTS

Regional myocardial blood flow, hemodynamics, and myocardial infarct size were determined. Infarct size was assessed using magnetic resonance imaging in a subset of animals. Three of the 22 dogs had no infarct and significantly higher collateral blood flow than the 19 animals with myocardial infarction (P < .001). Four hours after LAD occlusion, cardiac index, dP/dtmax, heart rate, and systolic and mean aortic pressures were not statistically different between groups. Infarct size expressed as area of necrosis/area at risk was similar between groups (FDP, 0.55 +/- 0.28; controls, 0.59 +/- 0.31).

CONCLUSION

FDP given after occlusion of the LAD in this canine model did not limit early myocardial infarct size.

Fructose-1,6-bisphosphate stabilizes brain intracellular calcium during hypoxia in rats

BACKGROUND AND PURPOSE

Exogenously administered fructose-1,6-bisphosphate reduces neuronal injury from hypoxic or ischemic brain insults. To test the hypothesis that fructose-1,6-bisphosphate prevents changes in intracellular calcium ([Ca2+]i) and high-energy phosphate levels, we measured [Ca2+]i, intracellular pH (pHi), and adenosine triphosphate in cultured rat cortical astrocytes and cortical brain slices during hypoxia.

METHODS

The fluorescent indicators fura-2 and bis-carboxyethyl-carboxyfluorescein were used to simultaneously measure [Ca2+]i and pHi with a fluorometer.

RESULTS

Exposure to hypoxia (95% N2, 5% CO2) or 100 microM sodium cyanide produced transient increases in [Ca2+]i in astrocytes and sustained increases in [Ca2+]i in brain slices. Adenosine triphosphate levels fell in slices exposed to hypoxia or cyanide. Fructose-1,6-bisphosphate (3.5 mM) blocked increases in [Ca2+]i and prevented depletion of adenosine triphosphate. Fructose-1,6-bisphosphate also partially prevented adenosine triphosphate depletion in brain slices incubated in glucose-free medium. Iodoacetate (a specific inhibitor of glycolysis) elevated [Ca2+]i and partially prevented these actions of fructose-1,6-bisphosphate. Changes in pHi during hypoxia were not affected by fructose-1,6-bisphosphate.

CONCLUSIONS

Fructose-1,6-bisphosphate supports adenosine triphosphate production via stimulation of glycolysis and results in the maintenance of normal [Ca2+]i during hypoxia or hypoglycemia.

Beneficial effects of fructose-1,6-diphosphate infusion on liver regeneration after ischemic liver injury

The effect of fructose-1,6-diphosphate (FDP) on cellular viability after partial hepatectomy in partial ischemic liver was investigated in rats. The administration of FDP did not increase blood flow in the hepatic tissue; however, it significantly suppressed the elevation of serum liver functions for 24 hours after partial hepatectomy. Levels of DNA synthesis, protein synthesis, and labeling index were significantly higher in the groups administered divided doses of FDP before and after partial hepatic ischemia than in the control group (P less than 0.01). Thus, these findings indicate that FDP has cytoprotective and hepatotrophic effects on liver with ischemic injury and that divided dose administration of FDP is more effective than bolus doses in decreasing damage following ischemic and reperfusion injury.

The effects of fructose-1,6-diphosphate on myocardial damage in acute coronary artery occlusion

Acute myocardial infarction can result from thrombosis of a coronary artery. The purpose of this study was to evaluate the ability of fructose-1,6-diphosphate (FDP; Esafosfina) to reduce myocardial necrosis during acute thrombosis of a coronary artery. A canine model of acute myocardial infarction was used to produce intraluminal thrombosis by placement of a coil of wire in a coronary artery. After developing a coronary thrombosis of the left anterior descending artery, dogs were injected intravenously with 90 mg/kg, 175 mg/kg, or 350 mg/kg of FDP or normal saline (controls). Hemodynamic, biochemical and electrocardiographic parameters were evaluated before, and 30 min and 4 h after occlusion. Four hours after acute coronary occlusion, the animals were sacrificed, and the weights of ischemic and necrotic myocardial tissue were quantified using a histologic-staining method. There were no significant differences between control and treated animals in biochemical or hemodynamic parameters. All animal groups treated with FDP demonstrated significant reductions in the amount of necrotic and ischemic tissue compared to controls (P less than 0.05). However, only the 175 mg/kg group had a significant reduction compared to controls in necrotic tissue weight as a percentage of ischemic myocardium (24 +/- 15% vs. 72 +/- 22%, respectively, P less than 0.01). These data suggest that FDP may have a role in limiting the amount of myocardial damage after an acute coronary artery occlusion.

Protective effects of fructose-1,6-diphosphate on acute and chronic doxorubicin cardiotoxicity in rats

The effects of fructose-1,6-diphosphate, an intermediate metabolite of glycolysis, on acute and chronic cardiotoxicity of doxorubicin were investigated in rats. In the acute study, urethane-anaesthetized Wistar female rats treated with 10 mg/kg i.v. doxorubicin developed a widening of the S alpha T segment, an impairment of +dP/dtmax, and tachycardia. Pretreatment with 375 and 750 mg/kg i.p. fructose-1,6-diphosphate prevented the S alpha T segment from widening, whereas only 750 mg/kg i.p. significantly attenuated the heart rate increase. Chronic cardiomyopathy was induced over a 6-week period by weekly doses of 3 mg/kg i.v. doxorubicin, being characterized in vivo by the progressive enlargement of the S alpha T segment and the occurrence of histological alterations and in vitro by a marked impairment of the inotropic response elicited by adrenaline in isolated hearts from treated rats. Concurrent treatment with 150 and 300 mg/kg i.p. fructose-1,6-diphosphate thrice a week for 6 weeks did not lessen the chronic heart damage, whereas 600 mg/kg given i.p. significantly reduced the widening of the S alpha T segment and the severity of histological damage in vivo, as well as significantly improving the contractile responses of hearts in vitro. These findings suggest that the administration of fructose-1,6-diphosphate plays a protective role in the acute and chronic cardiotoxicity of doxorubicin in the rat.

Prevention of ischemic-hypoxic brain injury and death in rabbits with fructose-1,6-diphosphate

Fructose-1,6-diphosphate has been shown to improve neurologic recovery following resuscitation from cardiac arrest and to restore brain electrical activity during hypoglycemic coma in rabbits. In view of these findings, we determined whether fructose-1,6-diphosphate protects the brain during ischemia-hypoxia. We subjected 16 rabbits to hypotension, hypoxemia, and bilateral common carotid artery occlusion. Five minutes after the onset of isoelectric electroencephalograms, seven randomly selected rabbits received 10% fructose-1,6-diphosphate (350 mg/kg bolus followed by 10 mg/kg/min infusion for 90 minutes) and the remaining nine rabbits (controls) received an equal volume of 1.5% NaCl (3.5 ml/kg bolus followed by 0.1 ml/kg/min infusion for 90 minutes). After isoelectricity lasting 7.86 +/- 0.8 minutes (mean +/- SEM) in the treated group and 6.44 +/- 0.38 minutes in the control group, the rabbits were reinfused with autologous shed blood and reoxygenated and the carotid artery occluders were removed. Treated rabbits recovered electrical activity more rapidly than the controls (p less than 0.005), and all seven treated rabbits survived. Only two controls (22%) survived (p less than 0.001), and they were severely disabled. Histology showed extensive cortical necrosis and focal necrosis in the hippocampi and cerebellum of brains from the two surviving controls. Brains from two treated rabbits exhibited minimal neuronal loss limited to the neocortex, and the brains from the remaining five treated rabbits were normal. This study suggests that fructose-1,6-diphosphate protects the brain from ischemic-hypoxic insults.

Macrophage lysozyme stimulation by fructose-1-6-diphosphate

FDP produces an increase of serum lysozyme concentration which may be related to stimulation of the phagocytic activity. Mice macrophages in vitro produce extracellular and intracellular LSZ (lysozyme) and FDP (fructose-1-6-diphosphate) increases this production. Also in vivo FDP stimulates the macrophages intracellular lysozyme production. The toxic activity in vitro and the protection in vivo against Staphylococcus pyogenes after FDP administration can also be related to macrophage stimulation.

Attenuation of ischemic renal injury with fructose 1,6-diphosphate

Fructose 1,6-diphosphate (FDP) has been shown to attenuate tissue injury associated with ischemia and shock by enhancing the anaerobic carbohydrate utilization and by inhibiting oxygen-free-radical generation by the neutrophils. Previously, we have reported that FDP prevents ischemic renal failure if administered prior to the ischemic insult. The present study was designed to determine whether this agent could prevent renal damage when administered during the postischemic reperfusion period. Rats were subjected to 30 min of bilateral renal artery occlusion and infused with FDP (350 mg/kg body wt) beginning 10 min after release of the renal artery clamps. Control rats received an equal volume of glucose/saline solution. A third group of rats were sham operated. Twenty-four hours after injury, BUN, creatinine, and fractional sodium excretion values were less in FDP-treated rats than in control rats (P less than 0.001, P less than 0.005, and P less than 0.001, respectively) and not different from values observed in sham-operated rats. Inulin clearance was greater (P less than 0.001) in FDP-treated rats than in control rats (665 +/- 38 microliters/min/g kidney wt). Renal histology was also better preserved in the FDP-treated group. These data suggest that FDP infused after the initiation of an acute ischemic insult provides significant, but not complete, functional and histologic protection from renal damage.

Improved brain metabolism with fructose 1-6 diphosphate during insulin-induced hypoglycemic coma

The effect of fructose 1-6 diphosphate (FDP) on brain metabolism and brain function was investigated in hypoglycemic rabbits. The electroencephalogram and differences in oxygen content of arterial and cerebral venous blood were used as indicators for brain metabolic activity. Hypoglycemic coma was induced and maintained for 1 hour by insulin administration. At the onset of isoelectric EEG, six rabbits were treated with FDP and five rabbits received 0.9% saline. The animals were killed by an overdose of barbiturate 60 minutes after hypoglycemic recovery with glucose. FDP-treated rabbits had lower arterial glucose concentration after 40 minutes of treatment (p less than .05) and a significantly greater difference between the oxygen content of arterial and venous blood after 40 minutes (p less than .01), and after 60 minutes (p less than .025) of FDP infusion than saline-treated rabbits. FDP-treated rabbits also had a lower cerebral glucose-oxygen index than did saline-treated rabbits (p less than .005, after 20 and 40 minutes of FDP infusion). FDP administration was followed by a return of EEG activity during hypoglycemia, whereas saline produced no such effect. After glucose infusion, EEG activity was improved in FDP-treated rabbits; in saline-treated rabbits, minimal or no EEG activity was observed. The data suggest the possibility that, at the doses given in this study, FDP is taken up and used as a metabolic substrate by the brain.

Hemodynamics and metabolic effects of fructose 1-6 diphosphate in ischemia and shock--experimental and clinical observations

Numerous interventions have been used to protect organ systems and cellular viability from the lethal injury accompanying hypoperfusion and ischemia. Some measures have been directed toward improving perfusion, while others have attempted to enhance the metabolic processes. Our work has focused for the most part on augmenting the anaerobic carbohydrate utilization in ischemic and hypoperfused tissues with fructose-1,6-diphosphate (FDP). Such an approach is based on the premise that exogenous FDP will restore the activity of glycolysis, which has been inhibited by acidosis, by intervening in the Embden-Meyerhoff pathway both as a metabolic regulator and as a high-energy substrate. We have tested this hypothesis in more than 1,000 animals subjected to shock or regional ischemia, and the results appear to confirm our presumption. In myocardial infarction, FDP improves hemodynamic parameters, attenuates ECG-proven ischemic injury and dysrhythmias, prevents ATP and creatine phosphate depletion from ischemic myocardium, reduces infarct size, and increases survival. In hemorrhagic, traumatic, and endotoxin shock, FDP improves hemodynamics, attenuates organ injury, and increases survival. Recently we demonstrated that FDP attenuates the reperfusion ischemic tissue injury by inhibiting the generation of oxygen free radicals by neutrophils. In normal volunteers, this agent increases carbohydrate utilization, while administration of a like amount of glucose produces no effect. In patients with myocardial infarction, FDP appears to have the same effect as that observed in the animal model. When this agent is administered to patients in traumatic, hemorrhagic, or septic shock, hemodynamic and pulmonary function are significantly improved. In patients with adult respiratory distress syndrome, similar beneficial effects have been observed with FDP administration.(ABSTRACT TRUNCATED AT 250 WORDS)

31P-NMR studies of Mycoplasma gallisepticum cells using a continuous perfusion technique

31P-NMR studies of Mycoplasma gallisepticum cells have been carried out using a continuous perfusion technique; these are the first such studies with this organism. Using this technique, glucose metabolism was monitored in the intact organisms, and cell extracts were prepared to identify the intermediates. Under glycolytic conditions, high levels of fructose-1,6-diphosphate were observed, indicating that this sugar may play a key role in the regulation of metabolism. The level of phosphoenolpyruvate was low under normal glycolytic conditions, and did not increase during starvation. From the position of the internal inorganic phosphate peak, the intracellular pH was estimated. The cells were found to maintain an intracellular pH of approximately 7.1 over an investigated external pH range of 6.6-8.6.