Aspects Of Glucose Metabolism Research Articles

Magnetic Resonance Imaging and Spectroscopy Methods to Study Hepatic Glucose Metabolism and Their Applications in the Healthy and Diabetic Liver.

The liver plays an important role in whole-body glucose homeostasis by taking up glucose from and releasing glucose into the blood circulation. In the postprandial state, excess glucose in the blood circulation is stored in hepatocytes as glycogen. In the postabsorptive state, the liver produces glucose by breaking down glycogen and from noncarbohydrate precursors such as lactate. In metabolic diseases such as diabetes, these processes are dysregulated, resulting in abnormal blood glucose levels. Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) are noninvasive techniques that give unique insight into different aspects of glucose metabolism, such as glycogenesis, glycogenolysis, and gluconeogenesis, in the liver in vivo. Using these techniques, liver glucose metabolism has been studied in regard to a variety of interventions, such as fasting, meal intake, and exercise. Moreover, deviations from normal hepatic glucose metabolism have been investigated in both patients with type 1 and 2 diabetes, as well as the effects of antidiabetic medications. This review provides an overview of current MR techniques to measure hepatic glucose metabolism and the insights obtained by the application of these techniques in the healthy and diabetic liver.

Gluclas: A software for computer-aided modulation of glucose infusion in glucose clamp experiments

Background and ObjectiveThe glucose clamp (GC) is an experimental technique for assessing several aspects of glucose metabolism. In these experiments, investigators face the non-trivial challenge of accurately adjusting the rate of intravenous glucose infusion to drive subjects’ blood glucose (BG) concentration towards a desired plateau level. In this work we present Gluclas, an open-source software to support researchers in the modulation of glucose infusion rate (GIR) during GC experiments. MethodsGluclas uses a proportional-integrative-derivative controller to provide GIR suggestions based on BG measurements. The controller embeds an anti-wind-up scheme to account for actuator physical limits and suitable corrections of control action to accommodate for possible sampling jitter due to manual measurement and actuation. The software also provides a graphic user interface to increase its usability. A preliminary validation of the controller is performed for different clamp scenarios (hyperglycemic, euglycemic, hypoglycemic) on a simulator of glucose metabolism in healthy subjects, which also includes models of measurement error and sampling delay for increased realism. In silico trials are performed on 50 virtual subjects. We also report the results of the first in-vivo application of the software in three subjects undergoing a hypoglycemic clamp. ResultsIn silico, during the plateau period, the coefficient of variation (CV) is in median below 5% for every protocol, with 5% being considered the threshold for sufficient quality. In terms of median [5th percentile, 95th percentile], average BG level during the plateau period is 12.18 [11.58 - 12.53] mmol/l in the hyperglycemic clamp (target: 12.4 mmol/), 4.92 [4.51 – 5.14] mmol/l in the euglycemic clamp (target: 5.5 mmol/) and 2.38 [2.33 – 2.64] in the hypoglycemic clamp (target: 2.5 mmol/). Results in vivo are consistent with those obtained in silico during the plateau period: average BG levels are between 2.56 and 2.68 mmol/l (target: 2.5 mmol/l); CV is below 5% for all three experiments. ConclusionsGluclas offered satisfactory control for tested GC protocols. Although its safety and efficacy need to be further validated in vivo, this preliminary validation suggest that Gluclas offers a reliable and non-expensive solution for reducing investigator bias and improving the quality of GC experiments.

No deleterious effect of an additional pregnancy on glucose metabolism in women with previous gestational diabetes mellitus

ObjectiveWomen with gestational diabetes mellitus (GDM) often develop type 2 diabetes later in life. It remains unclear whether this results solely from a common underlying predisposition or, whether a pregnancy itself persistently impairs glucose metabolism in predisposed women. We therefore examined how an additional pregnancy affected different aspects of glucose metabolism in women with previous GDM. Research design and methodsNested case-control study within the prospective cohort study PPSDiab, recruited in Munich, Germany from 2011-16. Cases (n = 41): women with previous GDM who completed an additional pregnancy; controls: no additional pregnancy, pairwise matching. Endpoints: change of the area under the glucose curve (AUGC) of an oral glucose tolerance, of plasma glucose at 60′ of the test (PG 60′), of the insulin sensitivity index (ISI) and of the disposition index (DI), all between before and after the additional pregnancy in cases/the corresponding observation period in controls. ResultsWe observed no significant difference between cases and controls in the primary [ratio AUGC 1.05(0.92–1.15) vs. 0.97(0.85–1.14); p = 0.21] and in the secondary endpoints [difference PG 60′, ratio ISI and ratio DI. ConclusionWe did not find a deleterious effect of an additional pregnancy on glucose metabolism in women with previous GDM.

Differential Effects of Rapamycin on Glucose Metabolism in Nine Inbred Strains.

Studies in mice suggest that rapamycin has a negative impact on glucose homeostasis by inducing insulin resistance. However, results have been inconsistent and difficult to assess because the strains, methods of treatment, and analysis vary among studies. Using a consistent protocol, we surveyed nine inbred strains of mice for the effect of rapamycin on various aspects of glucose metabolism. Across all strains, rapamycin significantly delayed glucose clearance after challenge. However, rapamycin showed no main effect on systemic insulin sensitivity. Analysis of individual strains shows that rapamycin induced higher glucose values at 15 minutes post-challenge in 7/9 strains. However, only three strains show rapamycin-induced reduction in glucose clearance from 15 to 120 minutes. Although pancreatic insulin content was reduced by rapamycin in seven strains, none showed reduced serum insulin values. Although one strain showed no effects of rapamycin on glucose metabolism (129), another showed increased systemic insulin sensitivity (B6). We suggest that rapamycin likely inhibits insulin production and secretion in most strains while having strain-specific effects on glucose clearance without altering systemic insulin sensitivity. This strain survey indicates that genetic differences greatly influence the metabolic response to rapamycin.

The Emerging Role of Glucose Metabolism in Cartilage Development.

Proper cartilage development is critical to bone formation during endochondral ossification. This review highlights the current understanding of various aspects of glucose metabolism in chondrocytes during cartilage development. Recent studies indicate that chondrocytes transdifferentiate into osteoblasts and bone marrow stromal cells during endochondral ossification. In cartilage development, signaling molecules, including IGF2 and BMP2, tightly control glucose uptake and utilization in a stage-specific manner. Perturbation of glucose metabolism alters the course of chondrocyte maturation, suggesting a key role for glucose metabolism during endochondral ossification. During prenatal and postnatal growth, chondrocytes experience bursts of nutrient availability and energy expenditure, which demand sophisticated control of the glucose-dependent processes of cartilage matrix production, cell proliferation, and hypertrophy. Investigating the regulation of glucose metabolism may therefore lead to a unifying mechanism for signaling events in cartilage development and provide insight into causes of skeletal growth abnormalities.

Dichloroacetic acid upregulates apoptosis of ovarian cancer cells by regulating mitochondrial function.

BackgroundMetabolic reprogramming is a characteristic of tumor cells and is considered a potential therapeutic target. Even under aerobic conditions, tumor cells use glycolysis to produce energy, a phenomenon called the “Warburg effect”. Pyruvate dehydrogenase kinase 1 (PDK1) is a key factor linking glycolysis and the tricarboxylic acid cycle. Dichloroacetic acid (DCA) reverses the Warburg effect by inhibition of PDK1 to switch cytoplasmic glucose metabolism to mitochondrial oxidative phosphorylation (OXPHOS).MethodsCell viability was examined using a standard MTT assay. Glucose consumption and l-lactate production were measured using commercial colorimetric kits, and intracellular lactate dehydrogenase (LDH) activity was evaluated using cell lysates and an LDH Quantification Kit. Real-time PCR was used to detect the expression of related genes. The production of total ROS was evaluated by staining with dichlorofluorescin diacetate.ResultsComparison of various aspects of glucose metabolism, such as expression of key enzymes in glycolysis, lactate production, glucose consumption, mitochondrial oxygen consumption rate, and citric acid production, revealed that A2780/DDP cells were primarily dependent on glycolysis whereas A2780 cells were primarily dependent on mitochondrial OXPHOS. Mitochondrial uncoupling protein 2 (UCP2) protects against mitochondrial ROS while allowing energy metabolism to switch to glycolysis. Treatment of A2780 cells with various concentrations of DCA resulted in decreased expression of UCP2, a metabolic switch from glycolysis to mitochondrial OXPHOS, and an increase in oxidative stress induced by ROS. These effects were not observed in A2780/DDP cells with higher UCP2 expression suggesting that UCP2 might induce changes in mitochondrial functions that result in different sensitivities to DCA.ConclusionOur results show that a drug targeting tumor metabolic changes affects almost the entire process of glucose metabolism. Thus, it is necessary to comprehensively determine tumor metabolic functions to facilitate individualized antitumor therapy.

A randomized clinical trial to evaluate the single-dose pharmacokinetics, pharmacodynamics, and safety of sitagliptin in pediatric patients with type 2 diabetes.

To evaluate the single-dose pharmacokinetics (PK), pharmacodynamics (PD), and safety of sitagliptin in pediatric patients with type 2 diabetes mellitus (T2DM). This was a randomized, placebo-controlled, double-blind evaluation of sitagliptin in 35 patients 10 to 17 years old with T2DM at 7 clinical research sites. The safety, tolerability, PK, and PD (dipeptidyl peptidase-4 [DPP-4] inhibition and aspects of glucose metabolism) of single doses of 50, 100, and 200 mg were assessed. Appropriate transformations on the PK parameters were used and back-transformed summary statistics are reported. Adverse experiences were reported by eight study participants; all were of mild intensity except one (intravenous site pain of moderate intensity). PK characteristics in the young patients were comparable to reference adult data, with geometric mean ratios (youths/adults) for AUC0-∞ , Cmax , and C24hr of 0.82, 1.04, and 0.74, respectively. Single doses of 50, 100, and 200 mg sitagliptin inhibited 67.2%, 73.8%, and 81.2% of plasma DPP-4 activity over 24 hours, respectively. Least squares (LS) mean glucose concentrations 2 hours after an oral glucose tolerance test or a meal tolerance test decreased in study participants treated with sitagliptin, compared to placebo, while active LS mean glucagon-like peptide 1 concentrations increased significantly at all sitagliptin doses in both tests. Single doses of sitagliptin as high as 200 mg were generally well tolerated in 10- to 17-year-old male and female study participants with T2DM, and a daily sitagliptin dose of 100 mg is appropriate for evaluation in Phase III safety and efficacy studies in pediatric patients with T2DM. (ClinicalTrials.gov: NCT00730275).

Adiposity and family history of type 2 diabetes in an admixed population of adolescents: Associations with insulin sensitivity, beta-cell function, and hepatic insulin extraction in BRAMS study

AimsInsulin resistance and beta-cell dysfunction manifest differently across racial/ethnic groups, and there is a lack of knowledge regarding the pathophysiology of type 2 diabetes mellitus (T2DM) for ethnically admixed adolescents. This study aimed to investigate the influence of adiposity and family history (FH) of T2DM on aspects of insulin sensitivity, beta-cell function, and hepatic insulin extraction in Brazilian adolescents. MethodsA total of 82 normoglycemic adolescents were assessed. The positive FH of T2DM was defined as the presence of at least one known family member with T2DM. The hyperglycemic clamp test consisted of a 120-min protocol. Insulin secretion and beta-cell function were obtained from C-peptide deconvolution. Analysis of covariance considered pubertal stage as a covariate. ResultsBoth lean and overweight/obese adolescents had similar glycemic profiles and disposition indexes. Overweight/obese adolescents had about 1/3 the insulin sensitivity of lean adolescents (1.1 ± 0.2 vs. 3.4 ± 0.3 mg·kg·min·pmol ∗ 1000), which was compensated by an increase around 2.5 times in basal (130 ± 7 vs. 52 ± 10 pmol·l·min) and total insulin secretion (130,091 ± 12,230 vs. 59,010 ± 17,522 pmol·l·min), and in the first and second phases of insulin secretion; respectively (p < 0.001). This increase was accompanied by a mean reduction in hepatic insulin extraction of 35%, and a 2.7-time increase in beta-cell glucose sensitivity (p < 0.05). The positive FH of T2DM was not associated with derangements in insulin sensitivity, beta-cell function, and hepatic insulin extraction. ConclusionsIn an admixed sample of adolescents, the hyperglycemic clamp test demonstrated that adiposity had a strong influence, and FH of T2DM had no direct influence, in different aspects of glucose metabolism.

Relationship between postprandial hyperglycaemia and Progression of Diabetic Nephropathy

Measurement of glycosylated hemoglobin (HbA1C) remains the gold standard for the assessment of glycemic control in patients with type 2 diabetes. Recent investigations have studied the correlation between HbA1C levels and other aspects of glucose metabolism, specifically, postprandial glucose (PPG). The results suggest that PPG is also important to overall glycemic control and may be a better index of glucose regulation than no effect on FPG. Thus, all aspects of glucose metabolism appear to be clinically relevant and should be monitored for effective diabetes management. This study defines the clinical significance of postprandial hyperglycaemia regarding the development of diabetic nephropathy.

MED28 Mediates Glucose Metabolism in Human Colorectal Cancer Cells

Most normal cells mainly rely on mitochondrial oxidative phosphorylation to generate energy, whereas cancer cells preferentially rely on aerobic glycolysis or so‐called “Warburg effect” even in the presence of sufficient oxygen. Albeit inefficient energy production, cancer cells compensate for this disadvantage by accelerating the uptake of glucose and increasing the rate of glycolysis. To increase the rate of glycolysis also provides the glycolytic intermediates for the synthesis of macromolecules, DNA, protein, and lipid, to keep up with the rapid proliferation mode. Recent studies have shown that Mediator Complex is involved in human diseases, including cancer, cardiovascular disease, metabolic disorder, and neurological disease. MED28, a Mediator subunit for transcriptional activation, is also an interactor with multiple proteins including Grb2, Src kinases, actin cytoskeleton, and merlin. MED28 was found highly expressed in colorectal cancer. In addition, our laboratory has previously reported that MED28 mediates Wnt/β‐catenin signaling in human colorectal cancer cells. This study is to investigate if MED28 plays a role in cell growth in the aspect of glucose metabolism in colorectal cancer. Expression profiling upon MED28 knockdown in SW480 colorectal cancer cells showed that MED28 suppression down‐regulated genes involved in glucose metabolism including glucose transporters and glycolytic enzymes, and the effect on several proteins and enzymes have been confirmed at both transcriptional and translational levels by RT‐PCR and Western blotting, respectively. The underlying mechanism is currently under investigation. In summary, MED28 regulates cell growth, at least in part, by mediating Warburg effect in colorectal cancer.Support or Funding InformationThis work was supported by the grants NSC102‐2320‐B‐309‐001‐MY3 and MOST105‐2320‐B‐309‐001 to M‐F Lee.

Clinical Aspects of Glucose Metabolism and Chronic Disease.

The burden of chronic disease is an emerging world health problem. Advances made in the treatment of individual disease states often fail to consider multimorbidity patterns in clinical research models. Adjusting for age as a confounder ignores its contribution as a powerful risk factor for most chronic diseases. Sarcopenia is an age-related loss of skeletal muscle mass, which is accelerated by chronic inflammation and its resulting cascade of cytokines. Skeletal muscle loss results in insulin resistance, hyperglycemia, and altered mitochondrial glucose signaling pathways. Vascular disease in the brain may alter blood-brain barrier function, allowing transport of substances into the brain which adversely affect the "astrocyte-centric" subunit. Neurogenesis that provides neuronal plasticity is impaired in the diabetic brain, while insulin resistance markers such as insulin-like growth factor (IGF-1) and insulin receptor substrate (IRS-1) are associated with poor cognitive performance. Advanced glycation end products generated by chronic hyperglycemia are found in postmortem AD brain. Intranasal insulin administration, a preferential route for CNS delivery, improved cognitive function in healthy adults, without affecting circulating levels of insulin or glucose. Exercise has demonstrated a neuroprotective effect through induction of antioxidative enzymes, neurotrophic, and vascular endothelial growth factors. Sarcopenia appears to be a dynamic process and is potentially reversible with attention to nutrition and cardiovascular fitness. Early detection and intervention may slow the progression of multimortality disease states and should be a focus of worldwide health systems.

Novel Strategies to Discover Effective Drug Targets in Metabolic and Immune Therapy for Glioblastoma.

Glioblastoma multiforme is a common primary brain tumor, which exhibits an imbalance between glioma cell growth and glucose metabolism. Recent discoveries have found that the multiple pathways and downstream genes involved in the dysregulated metabolic pathway allow tumor to manifest and progress, which is critical to patients with glioblastoma associated with significant systemic and immunosuppression. Moreover, immune microenvironment is considered a major obstacle to generating an effective antitumor immune response. Therefore, identification of patient-specific tumor antigens through highly personalized approach, and effective combination with other therapeutic modalities such as molecular agents targeting tumor metabolic oncogene addiction and potent host immune modulators, may provide targets for more effective therapeutic strategies for glioblastoma. In this review, we aim to highlight the most recent findings regarding glucose uptake and proliferation, cell mobility and to expand our investigations and more comprehensively examine different aspects of glucose metabolism in glioblastoma, such as pentose phosphate pathway (PPP) and its enzymes, metabolic modulation of genetics and epigenetics and key metabolic regulators, importantly, tumor cell-induced glucose deprivation inhibits T-cell glycolysis and immunogenic functions. Furthermore, this review will concentrate on how to discover effective drug targets to regulate glucose metabolism in tumor and T cell growth for future glioblastoma therapies, and the challenges faced by the field of metabolism in tumor immune microenviroment.

Metabolic reprogramming through fatty acid transport protein 1 (FATP1) regulates macrophage inflammatory potential and adipose inflammation.

ObjectiveA novel approach to regulate obesity-associated adipose inflammation may be through metabolic reprogramming of macrophages (MΦs). Broadly speaking, MΦs dependent on glucose are pro-inflammatory, classically activated MΦs (CAM), which contribute to adipose inflammation and insulin resistance. In contrast, MΦs that primarily metabolize fatty acids are alternatively activated MΦs (AAM) and maintain tissue insulin sensitivity. In actuality, there is much flexibility and overlap in the CAM-AAM spectrum in vivo dependent upon various stimuli in the microenvironment. We hypothesized that specific lipid trafficking proteins, e.g. fatty acid transport protein 1 (FATP1), would direct MΦ fatty acid transport and metabolism to limit inflammation and contribute to the maintenance of adipose tissue homeostasis.MethodsBone marrow derived MΦs (BMDMs) from Fatp1−/− and Fatp1+/+ mice were used to investigate FATP1-dependent substrate metabolism, bioenergetics, metabolomics, and inflammatory responses. We also generated C57BL/6J chimeric mice by bone marrow transplant specifically lacking hematopoetic FATP1 (Fatp1B−/−) and controls Fatp1B+/+. Mice were challenged by high fat diet (HFD) or low fat diet (LFD) and analyses including MRI, glucose and insulin tolerance tests, flow cytometric, histologic, and protein quantification assays were conducted. Finally, an FATP1-overexpressing RAW 264.7 MΦ cell line (FATP1-OE) and empty vector control (FATP1-EV) were developed as a gain of function model to test effects on substrate metabolism, bioenergetics, metabolomics, and inflammatory responses.ResultsFatp1 is downregulated with pro-inflammatory stimulation of MΦs. Fatp1−/− BMDMs and FATP1-OE RAW 264.7 MΦs demonstrated that FATP1 reciprocally controled metabolic flexibility, i.e. lipid and glucose metabolism, which was associated with inflammatory response. Supporting our previous work demonstrating the positive relationship between glucose metabolism and inflammation, loss of FATP1 enhanced glucose metabolism and exaggerated the pro-inflammatory CAM phenotype. Fatp1B−/− chimeras fed a HFD gained more epididymal white adipose mass, which was inflamed and oxidatively stressed, compared to HFD-fed Fatp1B+/+ controls. Adipose tissue macrophages displayed a CAM-like phenotype in the absence of Fatp1. Conversely, functional overexpression of FATP1 decreased many aspects of glucose metabolism and diminished CAM-stimulated inflammation in vitro. FATP1 displayed acyl-CoA synthetase activity for long chain fatty acids in MΦs and modulated lipid mediator metabolism in MΦs.ConclusionOur findings provide evidence that FATP1 is a novel regulator of MΦ activation through control of substrate metabolism. Absence of FATP1 exacerbated pro-inflammatory activation in vitro and increased local and systemic components of the metabolic syndrome in HFD-fed Fatp1B−/− mice. In contrast, gain of FATP1 activity in MΦs suggested that Fatp1-mediated activation of fatty acids, substrate switch to glucose, oxidative stress, and lipid mediator synthesis are potential mechanisms. We demonstrate for the first time that FATP1 provides a unique mechanism by which the inflammatory tone of adipose and systemic metabolism may be regulated.

Lessons learned from metabolomics in cystic fibrosis.

Cystic fibrosis is a mono-genetic multi-system disease; however, respiratory manifestations cause the main morbidity and mortality where chronic bacterial infections lead to bronchiectasis and ultimately respiratory failure. Metabolomics allows a relatively complete snapshot of metabolic processes in a sample using different mass spectrometry methods. Sample types used for discovery of biomarkers or pathomechanisms in cystic fibrosis (CF) have included blood, respiratory secretions, and exhaled breath to date. Metabolomics has shown distinction of CF vs. non-CF for matrices of blood, exhaled breath, and respiratory epithelial cultures, each showing different pathways. Severity of lung disease has been addressed by studies in bronchoalveolar lavage and exhaled breath condensate showing separation by metabolites that the authors of each study related to inflammation; e.g., ethanol, acetone, purines. Lipidomics has been applied to blood and sputum samples showing associations with lung function and Pseudomonas aeruginosa infection status. Finally, studies of bacteria grown in vitro showed differences of bacterial metabolites to be associated with clinical parameters. Metabolomics, in the sense of global metabolomic profiling, is a powerful technique that has allowed discovery of pathways that had not previously been implicated in CF. These may include purines, mitochondrial pathways, and different aspects of glucose metabolism besides the known differences in lipid metabolism in CF. However, targeted studies to validate such potential metabolites and pathways of interest are necessary. Studies evaluating metabolites of bacterial origin are in their early stages. Thus further well-designed studies could be envisioned.

Evaluation of liver perfusion in diabetic patients using 99mTc-sestamibi

The liver is an important organ for various aspects of glucose metabolism, including glucose uptake, storage, and synthesis. It is a major organ in the metabolic process with perfusion provided by both the portal vein and hepatic artery. In diabetic patients organ perfusion is reduced and this is linked to atherosclerosis, and as a result complications occur. In this study, we aimed to evaluate liver perfusion by scintigraphic methods in diabetic patients. We retrospectively investigated 1,100 myocardial perfusion scintigraphies taken between January 2011 and December 2012 at Canakkale Onsekiz Mart University Medical Faculty Nuclear Medicine Department. A total of 66 patients who were diagnosed with diabetes mellitus and had myocardial perfusion scintigraphies were included in the study. The control subjects included 127 patients without diabetes mellitus who were chosen at random. Patients with chronic liver disease were not included in the study. The values from liver regions of interest (liver-ROI) rates and heart regions of interest (heart-ROI) rates were compared between the patients and controls. Patients were grouped according to the presence of diabetes. In the diabetes mellitus group, the liver-ROI average was lower (p = 0.66) than in the controls. In the control group, the average liver-ROI/heart-ROI ratios were higher than the ratio in the diabetes mellitus group (p = 0.019). Multivariate variance analysis showed that the diabetes mellitus liver-ROI/heart-ROI ratio was independent of other risk factors (p = 0.003; F: 9.6). Powered by Editorial Manager(®) and ProduXion Manager(®) from Aries Systems Corporation. This study shows that liver perfusion in diabetic patients is reduced compared with those without diabetes. Prospective studies with larger patient groups are required.

Glucose metabolism in Alzheimer's disease: It's not just about energy

Normally, glucose is the only substrate used by the brain for energy production. Given the prodigious energy consumption of the brain (i.e., 20% of the total energy consumption of adult humans) disruptions of glucose metabolism have serious consequences for brain function. Thus, presymptomatic changes in glucose metabolism in patients with AD have important implications with regard to the pathophysiology of AD. Pursuit of this hypothesis requires a more comprehensive view of glucose metabolism and brain function. In vivo imaging of glucose metabolism and plaques has provided new insight about the dependence of the brain on different aspects of glucose metabolism and their relation to AD. Upon entry into the brain, glucose is phosphorylated. From this point on approximately 85% of the resulting glucose-6-phosphate passes through glycolysis, enters the Kreb's cycle on its way to oxidative phosphorylation and the production of ATP. In the adult, this leaves 15% of the metabolized glucose, usually referred to as aerobic glycolysis (AG). In the first decade of life, there is a burst in AG which parallels an explosive period of synaptogenesis. In addition, AG plays a critical role in neuroprotection through its involvement in managing reactive oxygen species via the pentose phosphate shunt and adjudicating apoptosis. Finally, AG is critical for the fueling of membrane pumps. AD has a predilection for specific areas of the cerebral cortex which exhibit early reductions in glucose metabolism and accumulate β-amyloid plaques. This constellation of brain areas constitute what has become known as the brain's default mode network (DMN). One of the interesting features of this network is its reliance on AG in the normal adult human brain. Pairing images of AG with images of plaque deposition documents the remarkable correspondence between the unique metabolism of the DMN and its involvement in AD. Collaborative work with David Holtzman at Washington University in transgenic mice has further elucidated the relationship between regional levels of AG, soluble Aβ and plaque deposition. Understanding the full role of glucose metabolism in the human brain will reveal new ways of thinking about pathophysiology of AD and its treatment.

Monitoring states of altered carbohydrate metabolism via breath analysis

To introduce the potential of breath analysis as a diagnostic or monitoring tool in diabetes. Blood testing for plasma glucose and other metabolic variables is the base for the diagnosis and management of diabetes, whose two main types (type 1 and type 2, T1DM, T2DM) are projected to affect 450 million by 2030. As blood testing is often uncomfortable, painful, costly, and in some situations unreliable, the quest for alternative, noninvasive methods has been ongoing for decades. Breath analysis has emerged as an ideal alternative as sample collection is easy, painless, flexible, noninvasive, practical, and inexpensive. No single exhaled gas can reflect systemic glucose concentrations. Multiple gases, however, have been linked to various aspects of glucose metabolism, and integrated analysis of their simultaneous profiles during prolonged glycemic fluctuations has yielded accurate predictions of plasma values, building expectation that a clinically usable breath-based glucometer may be developed within a few years. While prototypes of hand-held breath testing glucometers may still be several years away, current research shows the imminent promise of this methodology and the widening support for its development.

Abstract 3866: The KISS1 metastasis suppressor appears to reverse the Warburg effect by enhancing mitochondria biogenesis.

Abstract Cancer cells tend to utilize aerobic glycolysis even under normoxic conditions, which is commonly called the “Warburg Effect.” Aerobic glycolysis often directly correlates with malignant potential. Though its purpose remains unclear, the “Warburg Effect” is thought to confer advantages to proliferation, survival and dissemination to cancer cells by increasing uptake of nutrients into biomass. KISS1 protein is secreted and proteolytically cleaved into kisspeptins (KP) that block the colonization of disseminated metastatic C8161.9 human melanoma cells at secondary sites. In this study, we hypothesized that KISS1 metastasis suppression occurs via regulation of aerobic glycolysis. Comparison of bioenergetic and metabolic aspects of glucose metabolism showed that all KISS1-secreting clones were less invasive, took up less glucose, produced less lactate which corresponds to higher pH[Ex], effects which were reversed when cells were transduced with shRNA to KISS1. The metabolism, invasion, and metastasis changes did not occur when KISS1 was missing the signal peptide (ΔSS). Utilizing a Seahorse bioanalyzer, KISS1, but not ΔSS cells showed significantly decreased extracellular acidification rates, increased O2 consumption and elevated mitochondria reserve capacity, an indicator of mitochondrial condition and a parameter thought to improve the cells’ ability to cope with oxidative stress. KISS1-expressing cells have 30-50% more mitochondria compared to vector or ΔSS-expressing cells. Increased mitochondrial mass was accompanied by significantly increased expression of mitochondrial genes involved in apoptosis and mitophagy, protein processing and trafficking. Increased mitochondrial mass correlated with higher PGC1α considered to be a master co-activator that regulates mitochondrial mass and metabolism. Interestingly, KISS1 differentially affects PGC1α-mediated downstream pathways, i.e. fatty acid synthesis and β-oxidation. KISS1-mediated up-regulation of mitochondria biogenesis appears to rely on KISS1 interaction with NRF1, a major transcription factor of mitochondria biogenesis. KP10 (which can activate the KISS1 receptor) does not alter pH[Ex] since the metastatic tumor cells do not express KISS1R. This paradox - metastasis and metabolic changes require secretion, but responding cells do not have the receptor - raises questions regarding the mechanism. Nonetheless, these data appear to directly connect changes in mitochondria mass, cellular glucose metabolism and metastasis. [Support: CA134581, Natl. Fndn. Cancer Res., Komen SAC110037]. Citation Format: Wen Liu, Benjamin H. Beck, Kedar S. Vaidya, Kevin T. Nash, Anne R. Diers, Kyle P. Feeley, Aimee Landar, Scott W. Ballinger, Danny R. Welch. The KISS1 metastasis suppressor appears to reverse the Warburg effect by enhancing mitochondria biogenesis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3866. doi:10.1158/1538-7445.AM2013-3866

CLA prevents alterations in glycolytic metabolites induced by a high fat diet

CLA has been reported to have beneficial and controversial effects on glucose and lipid metabolism. Besides, high fat (HF) diets induce alterations in liver and muscle lipid deposition, which could be associated with anomalous glucose utilization. Therefore, our aim was to evaluate whether the intake of CLA could prevent alterations in glycolytic intermediate metabolites and glycogen deposition induced by a HF diet. For this purpose, growing mice were fed a control diet (7% corn oil), a HF diet (20% corn oil), or a HF diet containing 17% corn oil + 3% CLA for 30 days. Liver and muscle glucose intermediate metabolites and glycogen were assessed. Liver glycolysis was inhibited by HF, reflected by a decreased flow of substrates through phosphofructokinase-1α linked to elevated citrate. CLA at HF diet prevented these alterations while increasing the lactate and glycogen synthesis. In the muscle, the HF diet emphasized the reduction of the flux through phosphofructokinase-1α, without additional changes in total glycogen levels. In conclusion, dietary CLA partially prevented glycolytic pathway alterations in the liver but not in the muscle of mice fed a HF diet, associated with adverse effects as sustained hyperglycemia and hepatic lactate accumulation. Practical applications: The present study evaluates the potential use of CLA and its consequences on several aspects of glucose metabolism. Considering that the FDA has recently approved CLA as a Generally Recognized as Safe (GRAS) category, a measure that will foster the commercial production of food and beverages with CLA supplementation, we believe it is relevant to study its potential functional properties on glucose metabolism in an experimental animal model characterized by alterations in liver and muscle lipid deposition.

Abstract 965: The KISS1 metastasis suppressor appears to reverse the ‘Warburg Effect’

Abstract In 1924, Otto Warburg described the preference of cancer cells for glycolytic metabolism, even under normoxic conditions and that these metabolic changes directly correlate with malignant potential of several cancers. Although its purpose remains unclear, the “Warburg Effect” is thought to confer proliferative and survival advantages by increasing uptake of nutrients into biomass. The KISS1 metastasis suppressor protein is secreted and proteolytically cleaved into so-called kisspeptins (KP) that block the colonization of metastatic C8161.9 human melanoma cells at secondary sites. We asked whether secreted KISS1 mediates its inhibitory effects on metastatic growth through regulation of the “Warburg Effect.” Comparing multiple bioenergetic and metabolic aspects of glucose metabolism in C8161.9 ± KISS1 showed that all KISS1-secreting clones had significantly (P&amp;lt;0.05) reduced invasion (60%) and reduced lactate production (100 mg/dL vs. 128 mg/dL). Irrespective of cell density, KISS1-expressing cells had a significantly higher extracellular pH (pHe=7.2) compared to cells transfected with empty vector or cells transfected with KISS1 harboring a deleted signal sequence (ΔSS; pHe=6.7). Utilizing a Seahorse® bioanalyzer, reduced extracellular acidification by KISS1 cells was verified concomitant with increased O2 consumption. Interestingly, mitochondrial reserve capacity, an indicator thought to reflect a cell's ability to cope with oxidative stresses, was also elevated in KISS1-expressing cells. Using mitochondrial-selective fluorescent probes, C8161.9KISS1 melanoma and MDA-MB-435KISS1 breast carcinoma cells have ∼30% more mitochondria compared to empty vector or KISS1ΔSS-expressing cells. Increased mitochondrial number in KISS1-expressing cells was correlated with higher levels of PGC-1α, a major mitochondrial biogenesis regulatory molecule, which was confirmed using siRNA to KISS1. Expression of KISS1 also protected C8161.9 cells from dichloroacetate-induced cell death. Unexpectedly, addition of KP10 to C8161.9 cells did not alter pHe, raising questions regarding the mechanism by which KISS1/KP alter PGC-1α in the absence of KISS1 receptor expression in the tumor cells. Nonetheless, these data appear to directly connect changes in mitochondrial number, metabolic pathway regulation and the metastatic process. Future studies will determine whether the increase in mitochondrial number is directly responsible for the change in glycolytic metabolism and whether these changes are necessary for KISS1's effects on metastatic growth. Support: RO1-CA134981, the National Foundation for Cancer Research, METAvivor, and UAB Med-into-Grad Fellowship. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 965. doi:10.1158/1538-7445.AM2011-965