Sorbitol Accumulation Research Articles

145-LB: Phase 1/2 Safety and Proof of Biological Activity Study of AT-001, an Aldose Reductase Inhibitor in Development for Diabetic Cardiomyopathy

Hyperactivation of the polyol pathway (PP) contributes to development of diabetic complications. Aldose reductase (AR) is the rate-controlling enzyme in PP that catalyzes NADPH-dependent reduction of glucose to sorbitol. In hyperglycemic and ischemic conditions, PP activation causes intracellular sorbitol accumulation leading to osmotic stress, cell death and diabetic complications. We developed AT-001 based on further characterization of AR and structural changes within the active site of AR following enzymatic activation to design molecular AR inhibitors with enhanced specificity, affinity and selectivity compared with previous AR inhibitors that failed to inhibit redox-activated AR and were associated with off-target effects and/or lack of efficacy. AT-001 safety, pharmacokinetics (PK) and efficacy were assessed in a phase 1/2 study comprised of single oral ascending doses (SAD, n=8 per group) of 5, 10, 20 and 40 mg/kg once daily (QD) and multiple doses (MAD) of placebo (Pbo) or AT-001 5, 20, 40 mg/kg QD or 20 mg/kg twice daily (BID) for 7 d. Subjects with type 2 diabetes, age 18-75 and HbA1c 5.0-8.5% were allocated to each dose cohort (n=8 AT-001, n=2 Pbo). AT-001 was well-tolerated with no drug-related AEs or changes in liver or renal function up to the highest dose tested. Mean half-life (T1/2) and time of maximum concentration (Tmax) ranged from 1.7-3h and 1.75-3h, respectively in both SAD and day 1 MAD with no accumulation at day 7. AR inhibition was confirmed by significant dose-dependent reductions in whole blood sorbitol in SAD and MAD up to approximately -50% change from baseline in SAD and days 1 and 7 of MAD vs. a -3% change in Pbo (p<0.05 for all doses vs. Pbo). Maximum inhibition occurred between 2-4 h. Conclusions: greater selectivity and affinity of AT-001 for AR may endow acceptable safety. These findings support further investigation of the therapeutic potential of AT-001 in subjects with diabetes complications. Disclosure S. Shendelman: Stock/Shareholder; Self; Applied Therapeutics Inc. Other Relationship; Self; Applied Therapeutics Inc. R. Perfetti: Employee; Self; Applied Therapeutics Inc., Sanofi. Stock/Shareholder; Self; Applied Therapeutics Inc., Sanofi.

Response of sugar metabolism in apple leaves subjected to short-term drought stress

For a comprehensive understanding of gene expression, enzyme activity and sugar concentrations in response to short-term water deficit in apple (Greensleeves), sugar-modulated gene expression and enzyme activities were analyzed. Water stress resulted in the accumulation of sorbitol, glucose, fructose, galactose and starch, accompanied by a significant reduction in photosynthesis and sucrose concentration. In response to short-term water deficits, the activities of aldose-6-phosphate reductase (A6PR; EC 1.1.1.200), sorbitol dehydrogenase (SDH; EC 1.1.1.14), neutral invertase (NINV; EC 3.2.1.26), sucrose synthase (SUSY; EC 2.4.1.13), and fructokinase (FK; EC 2.7.1.4) were higher, whereas cell wall invertase (CWINV; EC 3.2.1.26) and hexokinase (HK; EC 2.7.1.1) activities were lower. In addition, sucrose phosphate synthase (SPS; EC 2.4.1.14) activity increased during the initial stages of dehydration and then decreased as the drought strengthened. Transcript levels of MdA6PR, MdSDH1/2, MdNINV1/2, MdSUSY3, MdFK1/2/4, MdSOT1/2, MdSUC1-3, MdTMT2/3, MdvGT1, MdpGlcT1-4 were upregulated, whereas transcript levels of MdCWINV1/2, MdHK1/2/3/5, and MdTMT1 were downregulated after 6 days of water stress. These findings suggest that the sorbitol metabolism pathway is induced and high levels of hexose derived from photosynthetic products are transported into vacuoles for adjustment to the water deficit. Our results provide insights into the relationships between sugar levels and sugar-modulated gene and enzyme activity in response to the imposition of short-term water stress.

Aldose Reductase, Protein Glycation Inhibitory and Antioxidant of Peruvian Medicinal Plants: the Case of Tanacetum parthenium L. and Its Constituents.

Diabetes complications, including peripheral neuropathy, cataracts, impaired wound healing, vascular damage, arterial wall stiffening and retinopathy diseases, are among the most predominant health problems facing the world’s population today. The 22 Peruvian plant extracts were screened for their potential inhibitory activity against rat lens aldose reductase (RLAR) and DPPH radical scavenging. Among them, we have found that Tanacetum parthenium L. (TP) has the RLAR, AGEs and DPPH radical scavenging activities. We used for screening of active components in TP against RLAR and DPPH for the first time by ultrafiltration (UF) and DPPH. Compounds in TP were isolated by Sephadex column chromatography and their structures were established by MS and NMR spectroscopic analyses. Among the isolated compounds, ferulic acid, apigenin, luteolin-7-O-glucoside, luteolin, chrysosplenol, and kaempferol showed potent inhibition with IC50 values of 1.11–3.20 and 6.44–16.23 μM for RLAR and DPPH radical scavenging. Furthermore, these compounds suppressed sorbitol accumulation in rat lenses and ferulic acid, luteolin-7-O-glucoside, and luteolin have AGEs inhibitory activities with IC50 values of 3.43–6.73 μM. In summary, our study provides interesting plants for further study with respect to the treatment and prevention of diabetic complication of Peruvian plant and can provide the scientific base of the traditional uses.

Dynamics of sugars, anaerobic metabolism enzymes and metabolites in apples stored under dynamic controlled atmosphere

Apple storage under extremely low oxygen concentrations, as in dynamic controlled atmosphere, changes both aerobic and anaerobic metabolism. In this work we evaluated the effects of controlled atmosphere (CA) and dynamic controlled atmosphere based on respiratory quotient (DCA – RQ), with RQ 1.3 and RQ 1.5, on the dynamics of pyruvic acid, sugars, anaerobic metabolites and enzymes involved in anaerobic metabolism of ‘Elstar’ and ‘Nicoter’ apples after harvest, 6 and 9 months of storage plus 7 days of shelf life. We also investigated the induction of sorbitol and glycerol biosynthesis, as a response to low oxygen stress in apples stored under DCA – RQ, protecting the cell membrane from leakage. Storage under CA and DCA – RQ had different dynamics of sugars accumulation from harvest up to 9 months of storage, especially for sorbitol, which accumulated more over the storage period when fruit are stored under DCA - RQ. Glycerol was not detected in any of the cultivars or storage conditions. Storage under DCA reduces the membrane permeability even with the accumulation of anaerobic metabolism compounds, like acetaldehyde and ethanol. Perhaps, this is a result of the higher sorbitol accumulation, which acts as osmolyte. For both cultivars, the storage under DCA resulted in an increase of PDC enzyme activity from harvest to 9 months of storage. The dynamics of anaerobic metabolism compounds were different for both cultivars: ‘Elstar’ apples showed an increase from harvest to 9 months storage, but ‘Nicoter’ had an increase until 6 months of storage and a sharp reduction until 9 months of storage. The regulation of anaerobic metabolism is performed by PDC enzyme activity, with little influence of ADH enzyme activity, when apples are stored under DCA – RQ. ‘Nicoter’ apples are much more sensitive to low oxygen stress conditions as compared to ‘Elstar’.

Polyphenols of marine red macroalga Symphyocladia latiuscula ameliorate diabetic peripheral neuropathy in experimental animals

AimsChronic hyperglycaemia activates the polyol pathway of glucose metabolism thereby stimulating the activation aldose reductase enzyme that in turn initiates a cascade of deleterious events, eventually, leading to nerve damage or neuropathy. Marine macroalgae and their isolated chemical constituents have been found to possess potential antidiabetic activity and have proved beneficial in the treatment of diabetes. In this study the neuroprotective effect of polyphenols isolated from the red macroalga Symphyocladia latiuscula was evaluated in experimental diabetic peripheral neuropathy. Main methodsThe polyphenolic fraction from Symphyocladia latiuscula was isolated. Diabetic peripheral neuropathy (DPN) was induced in animals by intraperitoneal injection of streptozotocin (45 mg/kg, b. w) and maintained for 6 weeks followed by treatment with SLPP or epalrestat. Nerve Conduction Velocity (NCV) and Compound Muscle Action Potential (CMAP) were measured using a non-invasive method followed by muscular grip strength test. Sciatic nerve aldose reductase activity, sorbitol accumulation, Na+K+-ATPase activity, production of pro-inflammatory cytokines and expression of AR and PKC were assessed. Key findingsThe Symphyocladia latiuscula polyphenols (SLPP) were found to inhibit aldose reductase activity as well as their expression in diabetic animals thereby improving the NCV, CMAP and muscle grip strength. Improvements in the sciatic nerve Na+K+-ATPase activity and intraneural accumulation of sorbitol, an index of aldose reductase overactivity, were evident with SLPP treatment. The production of pro-inflammatory cytokines (IL-6, IL-1β and TNF-α) and expression of protein kinase C (PKC) were also diminished. SignificanceThe data suggest that the polyphenols of Symphyocladia latiuscula have neuroprotective potential against experimental DPN.

Abnormal oxidative metabolism in a quiet genomic background underlies clear cell papillary renal cell carcinoma.

While genomic sequencing routinely identifies oncogenic alterations for the majority of cancers, many tumors harbor no discernable driver lesion. Here, we describe the exceptional molecular phenotype of a genomically quiet kidney tumor, clear cell papillary renal cell carcinoma (CCPAP). In spite of a largely wild-type nuclear genome, CCPAP tumors exhibit severe depletion of mitochondrial DNA (mtDNA) and RNA and high levels of oxidative stress, reflecting a shift away from respiratory metabolism. Moreover, CCPAP tumors exhibit a distinct metabolic phenotype uniquely characterized by accumulation of the sugar alcohol sorbitol. Immunohistochemical staining of primary CCPAP tumor specimens recapitulates both the depletion of mtDNA-encoded proteins and a lipid-depleted metabolic phenotype, suggesting that the cytoplasmic clarity in CCPAP is primarily related to the presence of glycogen. These results argue for non-genetic profiling as a tool for the study of cancers of unknown driver.

Antioxidant defense against rust infection in the leaf tissue of Malus crabapple

Plant tissues and cells can sense and transmit stress signals, change their morphological structures, alter protein and gene expression, and activate metabolic pathways to adapt to stressful environments. However, the internal and external resistance mechanisms related to antioxidation in local tissues or cells suffering from biotic stress remain unclear. We studied the response of Malus crabapple leaves to cedar-apple rust infection, and the results revealed that significant color changes and flavonoid compound accumulation (especially anthocyanins) occurred in the rust-infected tissue (RIT), whereas no significant color changes and only flavonol and flavanone accumulation occurred in the non-infected tissue (NIT). There was an up-regulation of expression of the key structural genes and MYBs related to anthocyanins biosynthesis in the RIT, while its expression related to flavonol and flavanone biosynthesis was up-regulated in the NIT. Moreover, the accumulation of glucose, sucrose, and sorbitol among the tested carbohydrates was successively induced at higher levels in the RIT and NIT. Importantly, rust infection increased the contents of jasmonate (JA), abscisic acid (ABA), and ethylene (ETH), and significantly up-regulated related key genes in the RIT and NIT during rust spot expansion. Spearman’s correlation and redundancy analyses indicated that ABA and ETH were potentially involved in oxidative defense responses to rust spot expansion by initiating the transcription of key genes, increasing the sugar supply, and adjusting the osmotic balance.

Aqueous leaf extract of Clinacanthus nutans improved metabolic indices and sorbitol-related complications in type II diabetic rats (T2D).

Clinacanthus nutans (Burm. f.) Lindau (C. nutans) has been reported to lower blood glucose level; however, evidence on its efficacy in lowering diabetic complications is limited. The antidiabetic properties of C. nutans aqueous leaf extract on serum metabolic indices, sorbitol production, and aldose reductase enzyme activities in the kidneys, lens, and sciatic nerve of type II diabetic (T2D) rats were evaluated. All rats except normal control rats were fed with a high‐fat diet for 8 weeks to induce obesity and subsequently injected with 35 mg/kg streptozotocin to induce type II diabetes. Aqueous leaf extract of C. nutans (100 and 200 mg kg−1 day−1) and quercetin (10 mg kg−1 day−1) were fed orally for 4 weeks. Diabetic rats administered with C. nutans at 100, 200 mg kg−1 day−1 and quercetin had significantly (p < 0.05) lower fasting blood glucose levels post‐intervention: 14.2, 14.0, and 19.9 mm, respectively, compared with the untreated group (22.1 mm). Total cholesterol was significantly (p < 0.05) lower in the C. nutans groups in comparison with the diabetic control group. Levels of F2‐isoprostane, a marker of oxidative stress, were attenuated in the presence of the extract. Aldose reductase enzyme activity increased by 64, 99, and 0% and total antioxidant activities by 22, 29, and 126%, respectively. Sorbitol levels in the kidney, lens, and nerve were reduced in diabetic rats administered with C. nutans and quercetin group (by 8, 16, and 3%, respectively). The protective effect of the extract to the liver and kidney was confirmed through liver and kidney enzyme markers and histological analyses. The C. nutans has the potential to attenuate T2D‐induced metabolic perturbations and complications related to sorbitol accumulation.

Synthesis of new arylsulfonylspiroimidazolidine-2ʹ,4ʹ-diones and study of their effect on stimulation of insulin release from MIN6 cell line, inhibition of human aldose reductase, sorbitol accumulations in various tissues and oxidative stress

A novel class of spiroimidazolidine-2ʹ,4ʹ-diones substituted with aryl sulfonyl group at different positions was designed and synthesized. The target compounds were evaluated for their potential to release insulin from MIN6 cell line derived from in-vivo immortalized insulin-secreting pancreatic cells. The MIN6 cells represent an important model of beta cells, which as passage numbers increases, lose the first phase but retain partial second phase glucose stimulated insulin secretion (GSIS), similar to patients in early type 2 diabetes onset. Some of the compounds exhibited high potency. Compound 2d and 3f exhibited excellent insulin release activity from MIN6 cells when compared with standard drug, tolbutamide. Some of these compounds had a potent inhibitory activity for human recombinant aldose reductase (ALR2), an enzyme which converts glucose into sorbitol and plays a key role in development of complications arising from diabetes, such as retinopathy, nephropathy, neuropathy and cataract formation. Against human recombinant ALR2, compounds 2a, 3a-d, and 3f-h displayed effective inhibition activities. The results were augmented by the ability of the compounds to prevent sorbitol accumulation in the isolated rat lenses, sciatic nerves and erythrocytes. Some of the compounds were found to possess excellent dual activity, hence they may be promising candidates to modify and evaluate their dual action, i.e., insulin release to combat diabetes and ALR2 inhibition to prevent/treat diabetic complications. The compounds were also found to possess good antioxidant efficacy. Furthermore, most of the compounds lack toxicity as determined on human embryonic kidney cell lines 293 (HEK293).

3-Mercapto-5H-1,2,4-Triazino[5,6-b]Indole-5-Acetic Acid (Cemtirestat) Alleviates Symptoms of Peripheral Diabetic Neuropathy in Zucker Diabetic Fatty (ZDF) Rats: A Role of Aldose Reductase.

Peripheral neuropathy is the most prevalent chronic complication of diabetes mellitus. Good glycemic control can delay the appearance of neuropathic symptoms in diabetic patients but it is not sufficient to prevent or cure the disease. Therefore therapeutic approaches should focus on attenuation of pathogenetic mechanisms responsible for the nerve injury. Considering the role of polyol pathway in the etiology of diabetic neuropathy, we evaluated the effect of a novel efficient and selective aldose reductase inhibitor, 3-mercapto-5H-1,2,4-triazino[5,6-b]indole-5-acetic acid (cemtirestat), on symptoms of diabetic peripheral neuropathy in Zucker Diabetic Fatty (ZDF) rats. Since the age of 5months, male ZDF rats were orally administered cemtirestat, 2.5 and 7.5mg/kg/day, for two following months. Thermal hypoalgesia was evaluated by tail flick and hot plate tests. Tactile allodynia was determined by a von Frey flexible filament test. Two-month treatment of ZDF rats with cemtirestat (i) did not affect physical and glycemic status of the animals; (ii) partially inhibited sorbitol accumulation in red blood cells and the sciatic nerve; (iii) markedly decreased plasma levels of thiobarbituric acid reactive substances; (iv) normalized symptoms of peripheral neuropathy with high significance. The presented findings indicate that inhibition of aldose reductase by cemtirestat is not solely responsible for the recorded improvement of the behavioral responses. In future studies, potential effects of cemtirestat on consequences of diabetes that are not exclusively dependent on glucose metabolism via polyol pathway should be taken into consideration.

Neuroprotective efficacy of polyphenols of marine brown macroalga Ecklonia cava in diabetic peripheral neuropathy

Objectives: In this study, the neuroprotective effect of polyphenols isolated from the brown marine macroalga Ecklonia cava (EC) was evaluated in experimental diabetic peripheral neuropathy (DPN). Materials and Methods: The polyphenolic fraction from EC was isolated. DPN was induced in animals by intraperitoneal injection of streptozotocin (45 mg/kg, b. w) and maintained for 6 weeks followed by treatment with EC polyphenols (ECPP) or epalrestat for 30 days. Nerve conduction velocity (NCV) of sciatic nerves and the compound muscle action potential (CMAP) of the gastrocnemius muscle were measured using a non-invasive method followed by neuropathic thermal analgesia and muscular grip strength. Sciatic nerve aldose reductase (AR) activity, intraneural sorbitol accumulation, Na+K+-ATPase activity, production of proinflammatory cytokines (interleukin-6 [IL-6], IL-1 β, and tumor necrosis factor alpha [TNF-α]), and expression of AR and protein kinase C (PKC) were assessed. Results: The ECPP were found to inhibit AR activity as well as their expression in diabetic animals, thereby improving the NCV, CMAP, muscle grip strength, hot plate, and tail-flick response time. Improvements in the sciatic nerve Na+K+-ATPase activity and intraneural accumulation of sorbitol, an index of AR overactivity, were evident with ECPP treatment. The production of proinflammatory cytokines (IL-6, IL-1 β, and TNF-α) and expression of PKC were also diminished. Conclusion: The data suggest that the polyphenols of EC have neuroprotective potential against experimental DPN.

Changes in sugar metabolism associated to stem bark thickening partially assist young tissues of Eriobotrya japonica seedlings under boron stress

Boron (B) toxicity frequently affects plant performances and productivity, especially in arid and semi-arid environments. In this experiment, loquat seedlings were subjected to 25 μM (control) or 400 μM B (B excess) to test the hypothesis that (i) B alters sugar/polyol metabolism in polyol-producing tree species as loquat and (ii) changes of leaf and stem anatomy assist young tissues against toxic effect of B. Gas exchange was monitored from the beginning of the experiment (FBE) till one week after the first visible symptoms of B toxicity appeared in the upper part of the stems (147 d FBE). At 147 FBE, plant biometric parameters and pattern of B accumulation, leaf and stem anatomy, chlorophyll a fluorescence kinetics as well as biochemical measurements were assessed in top (asymptomatic) leaves and upper stem bark. Boron accumulated principally (in the row) in top leaves > top bark > top wood in B-stressed plants, but no changes in allocation pattern were found between controls and B-stressed plants. Excess B promoted the increase in the spongy layer of top leaves and caused the development of cork and numerous collenchyma cells with increased cell wall thickness. This mechanism, which has never been described before, can be considered an attempt to store excessive B in tissues where B ions are less harmful. The accumulation of sorbitol (B-complexing polyol) in top leaves and stem bark can be considered as a further attempt to detoxify B excess. However, B toxicity drastically affects the photosynthetic rate of top leaves, mainly due to non-stomatal limitations, i.e., reduction of ambient CO2 use efficiency and of photosystem II (PSII) efficiency, modification of the partitioning excess energy dissipation in PSII, thus leading to an increased level of lipid peroxidation. Our results suggest that changes in sugar metabolism associated with leaf and stem bark thickening partially assist (but not totally preserve) young tissues of loquat plants under B stress.

Expression analysis of sorbitol transporters in pear tissues reveals that PbSOT6/20 is associated with sorbitol accumulation in pear fruits

Sorbitol is a primary substrate that is translocated from its source to its sink in pear and apple by sorbitol transporters (SOTs). However, little is known about the expression profiles of SOTs in tree tissues, and their association with sorbitol accumulation. In this study, 64 SOT genes were isolated from the sequenced genomes of six rosaceae trees, which clustered phylogenetically into four groups. Groups I and III contained genes from pome trees, group II those from drupe trees, and group IV those from pome, drupe, and berry trees. A gene duplication analyses showed that the 24 SOT genes of pear arose from tandem, proximal, and dispersed duplications, which differs from their evolution in the other rosaceae fruit trees. A qRT-PCR analysis showed that the PbSOT6/20 gene in group IV is most strongly expressed in the leaf, branch, flower, fruit, and seed of pear. The expression pattern of PbSOT6/20 correlates more strongly with the pattern of sorbitol accumulation in the pear fruits than do those of other SOT genes. A low concentration (100 mg/g) of exogenous sorbitol induced the expression of PbSOT6/20 in the pear fruits, but not in the leaves. These results suggest that PbSOT6/20 is associated with sorbitol accumulation in pear fruits and plays important role in sorbitol translocation from its source to its sink. This study provides new insights into sorbitol translocation mediated by the SOT genes in pear.

Glucotoxicity results in apoptosis in H9c2 cells via alteration in redox homeostasis linked mitochondrial dynamics and polyol pathway and possible reversal with cinnamic acid

Several mechanisms have been proposed for the heart dysfunction during hyperglycemia. The aim of the present in vitro study is to elucidate the role of alterations in redox homeostasis in the induction of apoptosis during hyperglycemia in H9c2 cells via dysfunction in mitochondria and polyol pathway and evaluation of the beneficial effect of cinnamic acid against the same. The H9c2 cells were incubated with 33 mM glucose for 48 h to simulate the diabetic condition. Cell injury was confirmed with a significant increase of atrial natriuretic peptide and lactate dehydrogenase release. Alterations in the innate antioxidant system, polyol pathway, mitochondrial integrity, dynamics and apoptosis were investigated. Hyperglycemic insult has significantly affected redox homeostasis via depletion of superoxide dismutase, glutathione and enhanced reactive oxygen species generation. It also caused dysregulation in mitochondrial dynamics (fusion, fission proteins), dissipation of mitochondrial transmembrane potential and increased sorbitol accumulation. Finally, apoptosis was observed with upregulation of Bax, activation of caspase-3 and downregulation of Bcl-2. Cinnamic acid cotreatment increased the innate antioxidant status, improved mitochondrial function and prevented apoptosis in H9c2 cardiomyoblasts. Moreover, this in vitro model is found to be ideal for the elucidation of mechanisms at the cellular and molecular level of any physiological, pharmacological and toxicological incidents in H9c2 cells.

Pistafolin B is the major aldose reductase inhibitor of the pods of tara [Caesalpinia spinose (Molina) Kuntze

Aldose reductase, the pivotal enzyme in the polyol pathway, has been widely investigated as an enzyme critically involved in the onset and progression of various pathologies associated with diabetes mellitus. Investigation of the inhibitory effect of tara [Caesalpinia spinosa (Molina) Kuntze] pods extract on aldose reductase revealed that its n-butanol fraction exhibits excellent aldose reductase inhibitory activity in vitro and ex vivo. Methyl gallate and pistafolin B were isolated from the n-butanol fraction of the tara pod methanolic extract as the main contributors for its aldose reductase inhibition, guided by affinity-based ultrafiltration-high performance liquid chromatography, with pistafolin B being the more potent inhibitor of the two. In vitro and in silico results demonstrated that pistafolin B is a mixed-type inhibitor that can bind to the aldose reductase active site rapidly, preventing substrate access and product formation (IC50, 0.198 mM; Ki, 0.34 mM). Ex vivo experiments indicated that pistafolin B can penetrate the eye lens and successfully inhibit aldose reductase under hyperglycaemic conditions, thus preventing the accumulation of sorbitol and the subsequent osmotic stress.

The high-energy diet affecting development of diabetes symptoms in Zucker diabetic fatty rats

The appropriate animal model of diabetes mellitus type 2 is Zucker diabetic fatty (ZDF) rats. The goal of this study was to analyse the effect of chronic high-energy diet on diabetes mellitus (DM) complications in ZDF rats. Male ZDF rats (n = 20) and their lean controls (non-diabetic, n = 10) in the age of 3 months were involved in the experiment. Rats were provided with water and diet on ad libitum base. Animals were divided into three groups as follows: lean untreated rats (C) fed by KKZ-P/M (10 MJ/kg), obese rats fed by KKZ-P/M (10 MJ/kg, E1) and obese rats fed by enriched high energy diet (E2, enriched KKZ-P/M, 20 MJ/kg). Glucose, ketones levels, the consumption of feed, water and the live weight was measured weekly during the whole experiment. At the end of the experiment rats were anesthetized and selected haematological parameters were measured. ZDF rats in E1 and E2 group developed obesity, hyperglycaemia, non-insulin dependent diabetes, aggravations in haematological parameters and accumulation of sorbitol in sciatic nerve and lens of rats. High-energy diet immediately induced hyperglycaemia followed by accelerating the secondary symptoms of diabetes complications expressed by disturbed haematology parameters. High-energy diet caused ketoacidosis what meant two cases of death. Extended research on diabetes is needed.

Accumulation of sorbitol in the sciatic nerve modulates circadian properties of diabetes-induced neuropathic pain hypersensitivity in a diabetic mouse model

The intensity of pain in diabetic neuropathy varies in a circadian time-dependent manner. It is well known that diabetes has two distinct types, which are differentiated based on the cause of the disease. Previous studies have yet to compare the circadian properties of the pain intensity of diabetic neuropathy between type I and type II diabetes. In this study, we demonstrated that the pain intensity of diabetic peripheral neuropathy in a db/db mouse model of type II diabetes showed a significant diurnal oscillation, but such time-dependent oscillation was not detected in a streptozotocin (STZ)-induced type I diabetic mouse model. The polyol pathway-induced accumulation of sorbitol in peripheral nerve cells suppresses Na+/K+-ATPase activity, which is associated with the intensity of pain in diabetic neuropathy. In db/db mice, this accumulation of sorbitol in peripheral nerve cells showed significant diurnal oscillation. In addition, pain intensity and Na+/K+-ATPase activity were decreased at the peak time of sorbitol accumulation in these mice. Although STZ-induced diabetic mice also showed sorbitol accumulation and Na+/K+-ATPase dysfunction, these measures did not oscillate in a time-dependent manner. These findings reveal differences in the circadian properties of pain hypersensitivity in mouse models of type I and type II diabetes, and also provide ideas for developing novel approaches to the management of diabetic neuropathy.

A Pharmacological Update of Ellagic Acid.

Ellagic acid is a common metabolite present in many medicinal plants and vegetables. It is present either in free form or as part of more complex molecules (ellagitannins), which can be metabolized to liberate ellagic acid and several of its metabolites, including urolithins. While ellagic acid's antioxidant properties are doubtless responsible for many of its pharmacological activities, other mechanisms have also been implicated in its various effects, including its ability to reduce the lipidemic profile and lipid metabolism, alter pro-inflammatory mediators (tumor necrosis factor-α, interleukin-1β, interleukin-6), and decrease the activity of nuclear factor-κB while increasing nuclear factor erythroid 2-related factor 2 expression. These events play an important role in ellagic acid's anti-atherogenic, anti-inflammatory, and neuroprotective effects. Several of these activities, together with the effect of ellagic acid on insulin, glycogen, phosphatases, aldose reductase, sorbitol accumulation, advanced glycation end-product formation, and resistin secretion, may explain its effects on metabolic syndrome and diabetes. In addition, results from recent research have increased the interest in ellagic acid, both as a potential protective agent of the liver and skin and as a potential anticancer agent, due to the specific mechanisms affecting cell proliferation, apoptosis, DNA damage, and angiogenesis and its aforementioned anti-inflammatory properties. Taken together, these effects make ellagic acid a highly interesting compound that may contribute to different aspects of health; however, more studies are needed, especially on the compound's pharmacokinetic profile. In this review, we selected papers published from 2005 to the present.

Inhibition of C298S mutant of human aldose reductase for antidiabetic applications: Evidence from in silico elementary mode analysis of biological network model.

Human aldose reductase (hAR) is the key enzyme in sorbitol pathway of glucose utilization and is implicated in the etiology of secondary complications of diabetes, such as, cardiovascular complications, neuropathy, nephropathy, retinopathy, and cataract genesis. It reduces glucose to sorbitol in the presence of NADPH and the major cause of diabetes complications could be the change in the osmotic pressure due to the accumulation of sorbitol. An activated form of hAR (activated hAR or ahAR) poses a potential obstacle in the development of diabetes drugs as hAR-inhibitors are ineffective against ahAR. The therapeutic efficacy of such drugs is compromised when a large fraction of the enzyme (hAR) undergoes conversion to the activated ahAR form as has been observed in the diabetic tissues. In the present study, attempts have been made to employ systems biology strategies to identify the elementary nodes of human polyol metabolic pathway, responsible for normal metabolic states, followed by the identification of natural potent inhibitors of the activated form of hAR represented by the mutant C298S for possible antidiabetic applications. Quantum Mechanical Molecular Mechanical docking strategy was used to determine the probable inhibitors of ahAR. Rosmarinic acid was found as the most potent natural ahAR inhibitor and warrants for experimental validation in the near future.

Redox imbalance stress in diabetes mellitus: Role of the polyol pathway.

In diabetes mellitus, the polyol pathway is highly active and consumes approximately 30% glucose in the body. This pathway contains 2 reactions catalyzed by aldose reductase (AR) and sorbitol dehydrogenase, respectively. AR reduces glucose to sorbitol at the expense of NADPH, while sorbitol dehydrogenase converts sorbitol to fructose at the expense of NAD +, leading to NADH production. Consumption of NADPH, accumulation of sorbitol, and generation of fructose and NADH have all been implicated in the pathogenesis of diabetes and its complications. In this review, the roles of this pathway in NADH/NAD + redox imbalance stress and oxidative stress in diabetes are highlighted. A potential intervention using nicotinamide riboside to restore redox balance as an approach to fighting diabetes is also discussed.