Browsing by Subject "glucose"
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Item Changes in Weight and Glucose Can Protect Against Progression in Early Diabetes Independent of Improvements in β-Cell Function(Oxford University Press, 2016-11) Patel, Y. R.; Kirkman, M. S.; Considine, R. V.; Hannon, T. S.; Mather, K. J.; Medicine, School of MedicineReductions in fasting glucose, via reductions in weight, provided protection from progressive dysglycemia in EDIP. Lifestyle change can contribute importantly to glycemic control in early diabetes.Item Ludwigia octovalvis extract improves glycemic control and memory performance in diabetic mice(Elsevier, 2017-07) Lin, Wei-Sheng; Lo, Jung-Hsin; Yang, Jo-Hsuan; Wang, Hao-Wei; Fan, Shou-Zen; Yen, Jui-Hung; Wang, Pei-Yu; Department of Microbiology and Immunology, IU School of MedicineEthnopharmacological relevance Ludwigia octovalvis (Jacq.) P.H. Raven (Onagraceae) extracts have historically been consumed as a healthful drink for treating various conditions, including edema, nephritis, hypotension and diabetes. Aim of the study We have previously shown that Ludwigia octovalvis extract (LOE) can significantly extend lifespan and improve age-related memory deficits in Drosophila melanogaster through activating AMP-activated protein kinase (AMPK). Since AMPK has become a critical target for treating diabetes, we herein investigate the anti-hyperglycemic potential of LOE. Materials and methods Differentiated C2C12 muscle cells, HepG2 hepatocellular cells, streptozotocin (STZ)-induced diabetic mice and high fat diet (HFD)-induced diabetic mice were used to investigate the anti-hyperglycemic potential of LOE. The open field test and novel object recognition test were used to evaluate spontaneous motor activity and memory performance of HFD-induced diabetic mice. Results In differentiated C2C12 muscle cells and HepG2 hepatocellular cells, treatments with LOE and its active component (β-sitosterol) induced significant AMPK phosphorylation. LOE also enhanced uptake of a fluorescent glucose derivative (2-NBDG) and inhibited glucose production in these cells. The beneficial effects of LOE were completely abolished when an AMPK inhibitor, dorsomorphin, was added to the culture system, suggesting that LOE requires AMPK activation for its action in vitro. In streptozotocin (STZ)-induced diabetic mice, we found that both LOE and β-sitosterol induced an anti-hyperglycemic effect comparable to that of metformin, a drug that is commonly prescribed to treat diabetes. Moreover, LOE also improved glycemic control and memory performance of mice fed a HFD. Conclusions These results indicate that LOE is a potent anti-diabetic intervention that may have potential for future clinical applications.Item New aspects of cellular cholesterol regulation on blood glucose control- review and perspective on the impact of statin medications on metabolic health(2017-01-01) Grice, Brian A.; Elmendorf, Jeffrey S.; Cellular and Integrative Physiology, School of MedicineCholesterol is an essential component of cell membranes, and during the past several years, diabetes researchers have found that membrane cholesterol levels in adipocytes, skeletal muscle fibers and pancreatic beta cells influence insulin action and insulin secretion. Consequently, it is thought that dysregulated cell cholesterol homeostasis could represent a determinant of type 2 diabetes (T2D). Recent clinical findings compellingly add to this notion by finding increased T2D susceptibility in individuals with alterations in a variety of cholesterol metabolism genes. While it remains imperfectly understood how statins influence glucose metabolism, the fact that they display an influence on blood glucose levels and diabetes susceptibility seems to intensify the emerging importance of understanding cellular cholesterol in glucose metabolism. Taking this into account, this review first presents cell system and animal model findings that demonstrate the negative impact of cellular cholesterol accumulation or diminution on insulin action and insulin secretion. With this framework, a description of how changes in cholesterol metabolism genes are associated with T2D susceptibility will be presented. In addition, the connection between statins and T2D risk will be reviewed with expanded information on pitavastatin, a newer statin medication that displays actions favoring metabolic healthItem A Nutrient Network Regulating Cellular Cholesterol and Glucose Metabolism(2014) Pattar, Guruprasad R.; Elmendorf, Jeffrey S.; Considine, Robert V.; Deeg, Mark A.; Herring, B. Paul; Kempson, Stephen A.Insulin resistance, a hallmark of type 2 diabetes (T2D), is associated with accompanying derangements such as hyperinsulinemia that promote the progression of insulin resistance, yet a mechanism(s) is imperfectly understood. Data have demonstrated that hyperinsulinemia promotes insulin resistance as evidenced by diminished ability of insulin to mobilize glucose transporter GLUT4 to the plasma membrane (PM). We found that loss of PM phosphatidylinositol 4,5-bisphosphate (PIP2)-regulated filamentous actin (F-actin) structure contributes to hyperinsulinemia-induced insulin resistance. We tested if increased glucose flux through hexosamine biosynthesis pathway (HBP) causes dysregulation of PM components necessary for GLUT4 translocation. Increased HBP activity was detected in 3T3-L1 adipocytes cultured in hyperinsulinemia (5 nM Ins; 12 h) and also 2 mM glucosamine (GlcN), a distal HBP activator, inducing losses of PM PIP2 and F-actin. In accordance with HBP flux directly weakening PIP2/F-actin structure, inhibition of the rate-limiting HBP enzyme (glutamine:fructose-6-phosphate amidotransferase) restored F-actin and insulin responsiveness. Furthermore, less invasive challenges with glucose led to PIP2/F-actin dysregulation. New findings support a negative correlation between PM cholesterol accrual, PIP2/F-actin structure and GLUT4 regulation. These data stemmed from parallel study aimed at understanding the antidiabetic mechanism of the nutrient chromium (Cr3+). We found that chromium picolinate (CrPic) enhanced insulin-stimulated GLUT4 trafficking via reduction in PM cholesterol. In line with glucose/cholesterol toxicity findings, we demonstrated that therapeutic effects of CrPic occurred solely in adipocytes with increased HBP activity and a concomitant elevation in PM cholesterol. Mechanistically, data are consistent with a role of AMP-activated protein kinase (AMPK) in CrPic action. These data show that CrPic increases AMPK activity and perhaps suppresses cholesterol synthesis via distal phosphorylation and inactivation of 3-hydroxy-3-methylglutaryl CoA reductase (HMGR), a rate-limiting enzyme in cholesterol synthesis. Continued study of the consequence of increased HBP activity revealed alterations in cholesterogenic transcription factors – Sp1, SREBP-1, and NFY – with Sp1 showing a significant increase in O-linked glycosylation. Consistent with Sp1 modification eliciting maximal transcriptional activation of SREBP-1, Hmgr mRNA was significantly enhanced. In conclusion, these data are consistent with a central role of PM cholesterol in glucose transport and suggest perturbations in this lipid have a contributory role in developing insulin resistance.Item The Phosphate/Amide I ratio is Reduced by in vitro Glycation and may Correlate with Fracture Toughness(Office of the Vice Chancellor for Research, 2015-04-17) Hammond, Max A.; Berman, Alycia G.; Wallace, Joseph M.Introduction: Advanced glycation end products (AGEs) form when reducing sugars react with proteins. In bone AGEs can form in type I collagen which results in non-enzymatically derived crosslinks. While enzymatic crosslinks play an important role in strengthening the collagen matrix, non-enzymatic crosslinks are believed to reduce toughness. AGEs accumulate in bone over time and play an important role in reducing bone quality particularly in aging and diabetic patients who accumulate AGEs more rapidly due to increases in circulating glucose. Non-enzymatic glycation of bone can be modeled experimentally by soaking samples in a sugar solution which allows decades worth of AGE accumulation to occur in a short time. AGEs are primarily measured using fluorescence measurements or high performance liquid chromatography (HPLC). Spectroscopic techniques have been developed to determine enzymatic crosslinking maturity by detecting perturbations in collagen structure in the Amide I region and it may be possible to detect similar changes caused by AGEs. We hypothesized that the formation of AGEs in collagen would perturb the Amide I band of Raman spectra causing changes to the mineral to matrix ratio (MMR) which would correlate with AGE-induced mechanical changes in an in vitro ribose soaking experiment. If changes due to non-enzymatic glycation can be detected in the Amide I band, Raman spectroscopic techniques could be developed to assess the presence of AGEs in a non-destructive and widely available manner. Methods: Five femurs were harvested from male hounds from a previous IACUC approved study. From the mid-diaphysis, six beams ~1.4 x 4 x 24 mm were sectioned from each bone. Two beams from each sample were randomly assigned to one of three groups. One of those beams was sanded to 1.4 x 2 x 20 mm for fracture toughness testing while the other was used for Raman spectroscopy and Reference Point Indentation (RPI). All beams were soaked for 14 consecutive days at 37°C in solutions containing 1% Pen-Strep, 1.3mM CaCl2 and either no ribose (Control), 0.2M ribose (Low), or 0.6M ribose (High) in Hank’s Balanced Salt Solution with solutions changed every other day. After soaking, a notch was started in the sanded beam with a diamond wire sectioning saw and then sharpened by hand with a razor using a 1μm diamond suspension. Notched beams were submerged in fluid and loaded in displacement control to 0.03mm, unloaded to 0.015mm, held for 10s, then cycled until failure with a 0.05mm load, a 0.02 unload, and a 10s hold. J-R curves were calculated using ASTM E1820-5a to obtain initiation stress intensity factor (KIc) and maximum stress intensity factor (Kmax). Raman spectra were acquired at five points along the length of the second beam using a LabRAM HR 800 with a 660nm laser focused to a spot size of ~10μm. After baseline correction, OriginPro 8.6 was used to calculate MMR as the area of the PO43- ν1 peak over the area of the Amide I band. Following Raman spectroscopy, co-localized RPI was performed at each Raman location using 10 cycles of a 5N force at 2Hz. One-way ANOVA tested mean differences between samples. Pearson product-moment correlation coefficients were calculated between MMR and parameters from RPI and fracture toughness. All values are presented as mean ± standard deviation and all statistics were carried out using SAS 9.4. Results: Raman spectroscopy and RPI were not performed on one sample from the Low group. Data were not available for one Control sample and Kmax was excluded for one High sample. Neither KIc nor Kmax were significantly different between groups (Control: 6.59 ± 0.42, 13.55 ± 1.38 MPa√m; Low: 6.19 ± 1.98, 14.80 ± 2.00 MPa√m; High: 6.84 ± 1.18, 15.25 ± 2.35 MPa√m). MMR was significantly different between groups (p=0.039). Tukey HSD post-hoc tests revealed that Control (2.45 ± 0.37) was significantly greater than High (1.85 ± 0.20) while Low was intermediate (2.18 ± 0.37) but not significantly different. No significant differences were observed with RPI. A weak positive correlation was observed between average creep indentation increase (CID) and MMR (R2=0.079, p=0.0185) but no other RPI measurements were correlated with MMR. Two influential points, determined by a Cook’s distance > 4/n, were excluded from the regression KIc to MMR. A mild trend was observed between KIc and MMR but the fit did not reach significance (R2=0.334, p=0.0628). Discussion: Because samples were all from the same 5 animals and randomized into groups, any differences between groups arose from the soaking in solutions of different concentrations of ribose. AGEs were not measured to confirm the expected dose-dependent increase, but noticeable browning occurred in the High group which was less pronounced in the Low group and not present in Control. The soaking protocol and ribose concentrations were chosen based on previous literature showing increases in AGEs. Therefore, we are confident changes noted here are due to the presence of AGEs and the resulting non-enzymatic crosslinks. Because soaking was performed in appropriately buffered solutions, decreased MMR in the High group relative to Control are expected to occur due to glycation of collagen rather than changes in mineral content. We suspect that perturbations in collagen structure due to the presence of non-enzymatic crosslinks are causing the differences in the area of the Amide I band between groups. Given the changes in MMR with glycation, future studies investigating models where AGEs are likely present should be cautious in their interpretation of MMR if it is not supported by other measures of mineralization. The lack of significant differences between groups for RPI and fracture toughness parameters may be due to the small sample size (n=4-5 per group) and biological variations associated with mechanical techniques. However, the sample size was adequate to assess correlations between Raman and RPI due to the co-localized measurements in each sample (n=70). The positive correlation between CID and MMR was expected given AGEs have been shown to reduce creep behavior and since MMR is decreased by AGEs. However, the correlation is weak which is likely due to the overall small non-significant effect in CID compared to its variation. The correlation between MMR and initiation toughness similarly suggests that as AGEs reduce MMR, KIc decreases which is known to occur with glycation. While the correlation did not reach significance (p=0.063), the trend is compelling given the small sample size (n=11) and the use of Raman data from an adjacent beam from the same sample rather than the beam used to measure KIc. In conclusion, MMR changes in response to in vitro glycation and these changes are correlated to CID and possibly to KIc. Deconvolution of the Amide I region into sub-peaks to determine which peak(s) are altered in the presence of AGEs is an important next step to developing a spectroscopic technique that can assess the presence of AGEs and is recommended in future work. Significance: Correlations were performed between Raman spectroscopy, Reference Point Indentation, and fracture toughness measurements to evaluate the ability of perturbations in the Amide I band to explain glycation-induced changes in tissue mechanics. Non-enzymatic glycation is an important determinant of bone quality especially in aging and diabetic patients and understanding the specific roles composition and microscale mechanics play in determining how non-enzymatic glycation affects fracture toughness may lead to new therapeutic targets.Item Structural insights into the inhibited state of Glycogen Synthase(Office of the Vice Chancellor for Research, 2016-04-08) Mahalingan, Krishna K.; DePaoli-Roach, Anna A.; Roach, Peter J.; Hurley, Thomas D.Glycogen is an osmotically inert polymer of glucose, synthesized during times of nutritional sufficiency so that it can be rapidly catabolized when there is an energy demand1. Glycogen synthase (GS) is responsible for the bulk of its synthesis by transferring glucose from UDPG to an existing glucose polymer1. Eukaryotic GS is allosterically activated by glucose-6-phosphate (G6P) and negatively regulated by covalent phosphorylation2. A cluster of six arginine residues are conserved across all eukaryotic species which determine the enzyme’s ability to respond to these activating and inhibitory signals2. Prior structural studies from our lab had shed light on the dephosphorylated and activated state of the enzyme3. However, little is known on the phosphorylated state of the enzyme. For structural studies on the inhibited state, we used the yGsy2R589/592A mutant as a surrogate since it has a basal activity state similar to the inhibited phosphorylated state. We solved the structure of the mutant to a resolution of 3.3 Å. While the overall structural arrangement of the tetramer is similar to the basal state enzyme, the interfaces are more closed. In particular, the N-terminal Rossmann-fold domain is rotated toward the interface by 5.9°, limiting access to the active site by the acceptor end of the glycogen chain. Coincident with this domain closure, we also observed that the the distance between the regulatory helices of adjacent monomers are moved closer to one another. Based on this observation, we hypothesized we could develop a reversible redox regulatory feature in the enzyme by substituting cysteine residues for arginines 581 and 592, which lie across from each other at the interface. Consistent with our hypothesis, the yGsy2R581/592C double mutant exhibited very low activity, and could not be activated by G6P. However, normal function of the enzyme could be restored in the presence of reducing agents like DTT, BME and TCEP. Taken together, our mutational work demonstrates that the conserved arginine cluster in the regulatory helix, both regulates the enzyme’s response to signaling inputs and keeps the enzyme in a basal state conformation that is poised to respond to the activating and inhibitory inputs.Item Time spent outside of target glucose range for young children with type 1 diabetes: a continuous glucose monitor study(Wiley, 2020-08) DiMeglio, Linda A.; Kanapka, Lauren G.; DeSalvo, Daniel J.; Anderson, Barbara J.; Harrington, Kara R.; Hilliard, Marisa E.; Laffel, Lori M.; Tamborlane, William V.; Van Name, Michelle A.; Wadwa, R. Paul; Willi, Steven M.; Woerner, Stephanie; Wong, Jenise C.; Miller, Kellee M.; Pediatrics, School of MedicineAim To assess the associations between demographic and clinical characteristics and sensor glucose metrics in young children with type 1 diabetes, using masked, continuous glucose monitoring data from children aged 2 to < 8 years. Research design and methods The analysis included 143 children across 14 sites in the USA, enrolled in a separate clinical trial. Eligibility criteria were: age 2 to <8 years; type 1 diabetes duration ≥3 months; no continuous glucose monitoring use for past 30 days; and HbA1c concentration 53 to <86 mmol/mol (7.0 to <10.0%). All participants wore masked continuous glucose monitors up to 14 days. Results On average, participants spent the majority (13 h) of the day in hyperglycaemia (>10.0 mmol/l) and a median of ~1 h/day in hypoglycaemia (<3.9 mmol/l). Participants with minority race/ethnicity and higher parent education levels spent more time in target range, 3.9–10.0 mmol/l, and less time in hyperglycaemia. More time in hypoglycaemia was associated with minority race/ethnicity and younger age at diagnosis. Continuous glucose monitoring metrics were similar in pump and injection users. Conclusions Given that both hypo- and hyperglycaemia negatively impact neurocognitive development, strategies to increase time in target glucose range for young children are needed.