Effects of supramaximal exercise on blood glucose levels during a subsequent exercise

The purpose of the present investigation was to examine the effects of hyperglycemia induced by supramaximal exercise on blood glucose homeostasis during submaximal exercise following immediately after. Six men were subjected to three experimental situations; in two of these situations, 3 min of high-intensity exercise (corresponding to 112, SD 1% VO2max) was immediately followed by either a 60-min period of submaximal exercise (68, SD 2% VO2max) or a 60-min resting period. In the third situation, subjects performed a 63-min period of submaximal exercise only. There were no significant differences between the heart rates, oxygen uptakes, and respiratory exchange ratios during the two submaximal exercise bouts (greater than 15 min) whether or not preceded by supramaximal exercise. The supramaximal exercise was associated within 10 min of the start increases (P less than 0.05) in blood glucose, insulin, and lactate concentrations. This hyperglycemia was more pronounced when subjects continued to exercise submaximally than when they rested (at 7.5 min; P less than 0.05). There was a more rapid return to normal exercise blood glucose and insulin values during submaximal exercise compared with rest. The data show that the hyperinsulinemia following supramaximal exercise is corrected in between 10-30 min during submaximal exercise following immediately, suggesting that this exercise combination does not lead to premature hypoglycemia.     

Hypoglycemic potency of novel trivalent chromium in hyperglycemic insulin-deficient rats

Two sources of chromium III, "chromium 454" and "chromium picolinate," were tested in insulin-deficient Streptozocin-treated diabetic rats. This model was selected in order to evaluate the possibility of any hypoglycemic potency of chromium in a relative absence of blood insulin concentration. Three weeks of the treatment with CRC454 and CrP resulted in a 38% and 11% reduction of blood glucose levels, respectively. Body weight gains were equally improved by both treatments. Blood levels of CK, ALT and AST were significantly reduced by CRC454 and CrP. These results might suggest that any hypoglycemic effect of trivalent chromium under insulin-deficient conditions could be largely dependent upon the type of chromium agent and associated characteristics such as solubility and bioavalibility. In contrast, improvement of body weight gains and blood levels of CK, AST and ALT seems to be less dependent on the type of chromium compound under these experimental conditions. In conclusion, CRC454 showed significant reduction of hyperglycemia under insulin-deficient conditions.     

Synthesis, characterization, electrochemical studies and antitumor activity of some new chalcone analogues containing ferrocenyl pyrazole moiety

A series of new α,β-unsaturated conjugated ketones containing ferrocenyl pyrazole unit were synthesized and fully characterized by IR and NMR spectroscopy. Electrochemical characterization of subject compounds was performed by means of cyclic voltametry. The in vitro cytotoxic activity of all the synthesized compounds was studied against cervix adenocarcinoma HeLa, melanoma Fem-x and myelogenous leukemia K562 cell lines by the MTT method. Derivative 1l containing 3-pyridyl moiety exhibited a better cytotoxic activity in the cell growth inhibition of K562 cell lines in comparison with cisplatin as a reference compound.     

Antisense chalcone synthase genes in petunia: Visualization of variable transgene expression

Summary The constitutive expression of an antisense chalcone synthase (CHS) gene in transgenic petunia plants results with high frequency in a reduced flower pigmentation due to a reduction in the CHS mRNA steady-state level in floral tissue. Here we show that this reduction is specific for CHS mRNA; chalcone flavanone isomerase (CHI) and dihydroflavonol reductase (DFR) mRNA steady-state levels are unaffected. However, in white floral tissue a severe reduction in CHI specific activity is found, accompanied by an altered signal for CHI protein on western blots. We find no correlation between the phenotypic effect of the antisense CHS gene and its chromosomal position. For some of the antisense CHS transformants the flower phenotype is highly variable. We demonstrate that pigmentation in these plants can be influenced by gibberellic acid and light, suggesting that the variable flower phenotype is caused by changes in physiological conditions during flower development. The results not only indicate that flower pigmentation in these plants reveals the variable expression of the antisense transgene, but also show that genomic sequences flanking the transgene may render its expression extremely susceptible to physiological conditions.     

Beta-endorphin infusion alters pancreatic hormone and glucose levels during exercise in rats

β-Endorphin (BE) infusion at rest can influence insulin and glucagon levels and thus may affect glucose availability during exercise. To clarify the effect of BE on levels of insulin, glucagon and glucose during exercise, 72 untrained male Sprague-Dawley rats were infused i.v. with either: (1) BE (bolus 0.05 mg · kg⁻¹ +0.05 mg · kg⁻¹ · h⁻¹, n = 24); (2) naloxone (N, bolus 0.8 mg · kg⁻¹ + 0.4 mg · kg⁻¹, n = 24); or (3) volume-matched saline (S, n = 24). Six rats from each group were killed after 0, 60, 90 or 120 min of running at 22 m · min⁻¹, at 0% gradient. BE infusion resulted in higher plasma glucose levels at 60 min [5.93 (0.32) mM] and 90 min [4.16 (0.29) mM] of exercise compared to S [4.62 (0.27) and 3.41 (0.26 mM] and N [4.97 (0.38) and 3.44 (0.25) mM]. Insulin levels decreased to a greater extent with BE [21.5 (0.9) and 18.3 (0.6) uIU · ml⁻¹] at 60 and 90 min compared to S [24.5 (0.5) and 20.6 (0.6) uIU · ml⁻¹] and N [24.5 (0.4) and 21.6 (0.7) uIU · ml⁻¹] groups. Plasma C-peptide declined to a greater extent at 60 and 90 min of exercise with BE infusion compared to both S and N. BE infusion increased glucagon at all times during exercise compared to S and N. These data suggest that BE infusion during exercise influences plasma glucose by augmenting glucagon levels and attenuating insulin release. Accepted: 26 February 1997     

High extracellular glucose inhibits exocytosis through disruption of syntaxin 1A-containing lipid rafts

Diabetes is characterized by high blood glucose which eventually impairs the secretion of insulin. Glucose directly affects cholesterol biosynthesis and may in turn affect cellular structures that depend on the sterol, including lipid rafts that help organize the secretory apparatus. Here, we investigated the long-term effects of glucose upon lipid rafts and secretory granule dynamics in pancreatic β-cells. Raft fractions, identified by the presence of GM1 and flotillin, contained characteristically high levels of cholesterol and syntaxin 1A, the t-SNARE which tethers granules to the plasma membrane. Seventy-two hours exposure to 28 mM glucose resulted in ∼30% reduction in membrane cholesterol, with consequent redistribution of raft markers and syntaxin 1A throughout the plasma membrane. Live cell imaging indicated loss of syntaxin 1A from granule docking sites, and fewer docked granules. In conclusion, glucose-mediated inhibition of cholesterol biosynthesis perturbs lipid raft stability, resulting in a loss of syntaxin 1A from granule docking sites and inhibition of insulin secretion.     

IGF alters jejunal glucose transporter expression and serum glucose levels in immature rats

Milk-borne insulin-like growth factors (IGFs) enhance nutrient absorption in the immature intestine, which is characterized by low levels of glucose oxidation. We therefore hypothesized that feeding a rat milk substitute (RMS) devoid of growth factors to rat pups would lower serum glucose levels relative to dam-fed control rats and that supplementation of RMS with physiological doses of either IGF-I or IGF-II would normalize serum glucose levels via increased jejunal glucose transporter 2 (GLUT2) and high-affinity Na(+)-glucose cotransporter (SGLT1) expression. We found lower serum glucose concentrations in RMS-fed pups; in contrast, serum glucose levels in the IGF-supplemented pups were similar to those of dam-fed controls. RT-PCR and laser scanning confocal microscopy similarly demonstrated that IGF supplementation increased expression of jejunal glucose transporters. Further experiments demonstrated that IGF supplementation altered mRNA levels of key mitochondrial enzymes without altering jejunal lactase activity. We conclude that IGF-I and IGF-II supplementation increases serum glucose levels in the immature rat pup fed artificial formula and alters gene expression of the jejunal glucose transporters.     

Synthesis of chalcone derivatives on steroidal framework and their anticancer activities

Chalcone derivatives on estradiol framework have been synthesized. Some of the derivatives showed potent anticancer activity against some human cancer cell lines. Compounds 9 and 19 showed potent activity against MCF-7, a hormone dependent breast cancer cell line. Chalcone 7 was further modified to the corresponding indanone derivative (19) using the Nazarov reaction, which showed better activity than the parent compound against the MCF-7 breast cancer cell line. Active anticancer derivatives were also evaluated for osmotic hemolysis using the erythrocyte as a model system. It was observed that chalcone derivatives showing cytotoxicity against cancer cell lines did not affect the fragility of erythrocytes and hence may be considered as non-toxic to normal cells.     

A novel plastid localization of chalcone synthase in developing grape berry

Chalcone synthase (CHS, E.C. 2.3.1.74) is an entrance enzyme of flavonoid metabolism and a critical point to regulation of biosynthesis of different flavonoid compounds that directly contribute to color and monthfeel of grape and wine. In the present experiment, subcellular localization of CHS in developing grape berry was performed via immunogold electron microscopy technique. The result showed that CHS was localized in rough endoplasmic reticulum (ER) and cytoplasm of the skin cells, while few gold particles representing CHS were found on the cell wall. Besides, two novel localized sites of CHS were observed within a cell of developing grape berry, one being the plastid-distributed throughout developmental stages and the other being vacuole-distributed at late developmental stage. It is speculated that these novel localized patterns may relate to abundant and multi-branch flavonoid metabolism in grape berry. This work will provide new insight for the regulation of different branch pathways leading to diverse flavonoid compounds.     

Altered O-GlcNAc modification and phosphorylation of mitochondrial proteins in myoblast cells exposed to high glucose

Hyperglycemia induced increased posttranslational modification of proteins by O-linked-β-N-acetyl glucosamine (O-GlcNAcylation) and mitochondrial dysfunction has been independently implicated in the development of insulin resistance. It is not known whether repertoire of O-GlcNAcylated proteins includes mitochondrial proteins and their altered O-GlcNAcylation impinges on their phosphorylation mediated normal functioning thus contribute to mitochondrial dysfunction and insulin resistance. We have explored the O-GlcNAcylation of mitochondrial proteins from myoblast cells under basal (4 mM) and high glucose (30 mM) conditions using a combination of proteomic approaches. Furthermore, we have assessed the accompanied changes in the phosphorylation of mitochondrial proteins. We report that a number of mitochondrial proteins are O-GlcNAcylated under basal condition which is altered under high glucose condition. In addition, we report that exposure to high glucose not only changes the O-GlcNAcylation of mitochondrial proteins but also changes their phosphorylation profiles. The dynamic and complex interplay between O-GlcNAcylation and phosphorylation of mitochondrial proteins was further validated by immunoblot analysis of HSP60, prohibitin, and voltage-dependent anion channel 1 as candidate proteins. O-GlcNAcylation of mitochondrial proteins may play a role in normal functioning of mitochondria. High glucose induced changes in O-GlcNAcylation and phosphorylation of mitochondrial proteins may be associated with mitochondrial dysfunction and insulin resistance.     

Calorie restriction improves whole-body glucose disposal and insulin resistance in association with the increased adipocyte-specific GLUT4 expression in Otsuka Long-Evans Tokushima fatty rats

Calorie restriction (CR) has been shown to improve peripheral insulin resistance and type 2 diabetes in animal models. However, the exact mechanism of CR on GLUT4 expression and translocation in insulin-sensitive tissues has not been well elucidated. In the present study, we examine the effect of CR on the expression of glucose transporter 4 (GLUT4), GLUT4 translocation, and glucose transport activity in adipose tissue from Otsuka Long-Evans Tokushima Fatty (OLETF) rat and control (LETO) rats. CR (70% of satiated group) ameliorated hyperglycemia and improved impaired glucose tolerance (IGT) in OLETF rats. In skeletal muscle, the expression levels of GLUT4 and GLUT1 were not significantly different between LETO and OLETF rats, and were not affected by CR. By contrast, the expression level of GLUT4 was markedly decreased in the adipose tissue of OLETF rats, but was dramatically increased by CR. The GLUT4 recruitment stimulated by insulin was also improved in OLETF rat adipocytes by CR. The insulin-stimulated 2-deoxyglucose (2DG) uptake was significantly increased in adipocytes from the CR OLETF rats, as compared with the satiated OLETF rats. Taken together, these results suggest that CR improves whole body glucose disposal and insulin resistance in OLETF rats, and that these effects may associate with the increased adipocyte-specific GLUT4 expression.     

强化胰岛素治疗对脓毒症患者 血清D-乳酸及前降钙素水平的影响及疗效观察

目的探讨强化胰岛素治疗对脓毒症患者血清D-乳酸及前降钙素水平的影响及疗效观察。方法选取脓毒症患者72例,随机分为强化组和对照组,每组36例。两组患者均予以抗生素抗感染、能量支持及治疗基础疾病等常规治疗,必要时行机械通气或血管活性药物。强化组患者将50 U胰岛素加入50 mL生理盐水中微量泵控制血糖5.0~7.0 mmol/L;对照组患者血糖控制在10.0~11.9 mmol/L,当血糖超过时才加用胰岛素治疗。观察两组患者治疗前和治疗7 d后血清D-乳酸及前降钙素水平的变化,并比较其临床疗效。结果治疗7 d后,两组患者血清D-乳酸及前降钙素水平均较前明显下降（P〈0.01或P〈0.05）,且强化组下降值明显大于对照组（P〈0.05）;强化组患者的临床总有效率明显高于对照组（94.44%vs.77.78%）（χ2=4.18,P〈0.05）。结论强化胰岛素治疗脓毒症患者具有较好的临床疗效,能明显降低血清D-乳酸及前降钙素水平的影响,改善肠黏膜屏障功能。     

Conglutin gamma, a lupin seed protein, binds insulin in vitro and reduces plasma glucose levels of hyperglycemic rats

This work describes the in vitro interaction between a lupin seed protein, namely, conglutin gamma, and insulin. The binding to an insulin-immobilized matrix occurs in the pH range from 7.5 to 4.2 and is strongly affected by ionic strength, suggesting that it is driven primarily by electrostatic interactions. The quantitative parameters of the binding were determined by surface plasmon resonance. On the basis of the conditions required for the interaction to take place and the quantitative binding parameters, it appeared that the interaction is specific, despite the fact that the origin of the two protein molecules is completely different. The effect of the oral administration of conglutin gamma on the glycemic levels of rats subjected to glucose overloading was a statistically significant reduction in glycemia comparable to that of metformin, a well-known glucose lowering drug. These findings represent the first molecular evidence of the possible use of a legume protein in the control of glycemia.     

Molecular genetic analysis of chalcone synthase in Lycopersicon esculentum and an anthocyanin-deficient mutant

Summary Twelve loci have previously been identified in tomato (Lycopersicon esculentum) that control the intensity and distribution of anthocyanin pigmentation; these are useful genetic markers because they encode phenotypes that are readily visualized in the hypocotyls of emerging seedlings. In order to obtain molecular probes for tomato anthocyanin biosynthesis genes, we isolated two cDNAs which encode chalcone synthase (CHS), one of the key enzymes in anthocyanin biosynthesis, from a tomato hypocotyl cDNA library. By comparing their nucleic acid sequences, we determined that the two CHS cDNAs have an overall similarity of 76% at the nucleotide level and 88% at the amino acid level. We identified hybridization conditions that would distinguish the two clones and by Northern analysis showed that 1.5 kb mRNA species corresponding to each cDNA were expressed in cotyledons, hypocotyls and leaves of wild-type seedlings. Hybridization of the cDNAs at low stringency to genomic blots indicated that in tomato, CHS genes comprise a family of at least three individual members. The two genes that encode the CHS cDNAs were then placed onto the tomato genetic map at unique loci by restriction fragment length polymorphism mapping. We also assayed the activity of CHS and another enzyme in the anthocyanin pathway, flavone 3-hydroxylase, in hypocotyl extracts of wild-type tomato and a number of anthocyanin-deficient mutants. Five mutants had reduced CHS activity when compared to the wildtype controls. Of these, three were also reduce in flavone 3-hydroxylase activity, suggesting a regulatory role for these loci. The other two mutants were preferentially reduced in CHS activity, suggesting a more specific role for these loci in CHS expression.     

Sequence variation of chalcone synthase gene in a spontaneous white-flower mutant of Chinese cabbage-pak-choi

A spontaneous white-flower mutant of Chinese cabbage-pak-choi (Brassica campestris ssp. chinenesis, syn. B. rapa ssp. chinenesis) was found in our test fields, and all the plant characters except flower color were identical with wild type ones. We hypothesized that a mutational event had occurred in the gene coding for chalcone synthase (CHS), the key enzyme of flavonoid biosynthesis pathway. Two genes, later designated BcCHS and BcCHS-wf, were isolated from wild type and mutant Chinese cabbage-pak-choi, respectively, using gene-specific primer pairs. Comparison of the genomic sequences revealed two mutations in BcCHS-wf, both with A to G transitions, one at position +37 bp and the other at +970 bp. Both nucleotide substitutions occurred in AGA codes for arginine into GGA for glycin at residue +13 and into AGC coding for serine at residue +229, respectively. Homologous genes of BcCHS were isolated from another four cruciferous plants, though there were some differences among the genomic and deduced amino acid sequences, the mutation locus of the mutant, as we called it, were identical to the wild type Chinese cabbage-pak-choi.     

Influence of lithium and exercise on serum levels of copper and zinc in rats

The variations in serum levels of Cu and Zn induced by exercise in rats undergoing Li therapy are determined. The results show that exercise until exhaustion leads to a reduction in the Li concentration, which is more pronounced in rats subjected to training (to 50% maximum capacity) in the week before the test. The serum levels of Zn and Cu increased significantly with exhaustion in untrained rats, while there were no significant alterations in trained rats, except for serum Zn in those not treated with Li. The modifications in serum induced by exhaustion are lower in rats treated with Li. It is likely that Li and exercise have opposite effects on the tissue distribution of the two ions studied.     

Injection of the insulin receptor alpha subunit increases blood glucose levels in mice

Using the expression vector of the truncated human insulin receptor (hIR), we have constructed a stable Chinese hamster ovary (CHO) cell line which secretes the His-tagged alpha subunit (insulin-binding domain) of hIR into medium. To examine characteristics of the His-tagged hIRalpha, we purified the protein secreted from the CHO cells. The His-tagged hIRalpha was glycosylated and processed a dimer. The molecule bound insulin with an affinity similar to that of the intact hIR. The His-tagged full length of hIR was autophosphorylated by insulin stimulation in CHO cells. Injection of the purified His-tagged hIRalpha into veins of mice increased in the concentration of blood glucose within 30 min. The intraperitoneal glucose tolerance test (ipGTT) done after injection of the purified His-tagged hIRalpha showed evidence of a marked hyperglycemia. These findings provide direct evidence that the presence of hIRalpha in the blood stream inhibits insulin actions by binding with plasma insulin.     

Influence of zinc depletion and zinc status on serum growth hormone levels in rats

In a preceding trial, the growth hormone concentrations in the serum of zinc-deficient rats were greatly reduced compared to thead libitum- fed control animals. The same reduction, however, was also noted in the case of the pair-fed control animals with strongly diminished feed intake. Therefore, it was not possible to distinguish between the effects of zinc deficiencyper se and the effects resulting from restricted feed intake. A new study with 136 young male Sprague-Dawley rats showed again that zinc deficiency as well as strongly restricted feed intake reduced the growth hormone content in the serum. But in a marginal zinc deficiency status, when feed intake was only slightly or not reduced, there were lowered serum growth hormone levels in comparison to pair-fed control rats. A 1-wk zinc repletion did not increase the serum growth hormone content of the rats to a normal level, although the serum zinc concentration was normalized.     

In vivo insulin responsiveness for glucose uptake and production at eu- and hyperglycemic levels in normal and diabetic rats.

Whole body glucose uptake (BGU) and hepatic glucose production (HGP) at maximal plasma insulin concentrations (+/- 5000 microU/ml) were determined by eu- (EC) (6 mM) and hyperglycemic (HC) (20 mM) clamps (120 min), combined with [3-3H]glucose infusion, in normal and streptozotocin-treated (65 mg/kg) 3-day diabetic, conscious rats. In normal rats, during EC, BGU was 12.4 +/- 0.4 mg/min and during HC, when urinary glucose loss was 0.54 +/- 0.09 mg/min, BGU was 25.5 +/- 1.6 mg/min. However, throughout the final 60 min of HC, glucose infusion rate (GIR) was not constant but a linear decline in time (r = -0.99) of 17%, P less than 0.0001, was observed indicating a hyperglycemia-induced desensitization process. In diabetic rats, during EC, BGU was 7.7 +/- 0.3 mg/min and during HC, BGU was 15.5 +/- 1.4 mg/min. Throughout the final 60 min of HC, GIR was constant, suggesting that the hyperglycemia-induced desensitization process was already completed. In normal and diabetic rats, HGP was similar: during EC 0.2 +/- 0.5 mg/min and 0.1 +/- 0.5 mg/min, and during HC 0.4 +/- 0.4 mg/min and 0.5 +/- 0.6 mg/min, respectively. In vitro adipocyte and muscle insulin receptor studies showed normal to increased receptor number and increased receptor autophosphorylation in diabetic compared to normal rats. In conclusion: (i) 3-day diabetic rats show, at maximal plasma insulin concentrations, insulin resistance to BGU, but not to HGP. The resistance to BGU is equally present (reduction of 38%) at eu- and hyperglycemic levels as compared to normal rats. (ii) 3-day diabetic rats reveal no defect in adipocyte and muscle insulin receptor function. These data indicate that the diabetes induced insulin resistance for BGU is at the post-receptor level and due to a decreased maximal capacity (Vmax) for glucose uptake, with no change in affinity, or Km.