α-Galactosidase

Galactosidases are enzymes that metabolize saccharides. One of these, a-galactosidase, acts on the a-galactosidic linkage of the globotriaosylceramide (Gb3) receptor, a tumor-associated carbohydrate antigen. In response to toxins, such as Shiga toxin, a-galactosidase activity can be decreased. This increases Gb3 receptor content, increasing a cytotoxic response.

Gallic acid

Gallic acid is a tannin that is thought to exert antioxidant activity. It has been proposed that the presence of gallic acid in red wine has beneficial antioxidant effects.

GAMT knock out mice

Creatine is an important molecule involved in energy storage and in transmission of phosphatebound energy substrates. One of the creatine synthetic enzymes is S-adenosyl-L-methionine:Nguanidinoacetate methyltransferase (GAMT). GAMT knockout mice lack GAMT, and therefore have a defect in creatine synthesis. They are therefore useful in looking at the role of creatine deficiency in energy homeostasis.

Geranylgeranyl-pyrophosphate

Geranylgeranyl pyrophosphate (GGPP) is an isoprenoid that is a precursor for numerous molecules essential for cellular function. GGPP also acts as a substrate in isoprenylation reactions. GGPP is produced from farnesyl-PP, which is produced from geranyl-PP, an intermediate in the cholesterol synthetic pathway. Inhibition of GGPP production, using a geranylgernayl transferase inhibitor can inhibit vascular smooth muscle proliferation. A similar effect can be observed by HMG-CoA reductase inhibition, which inhibits the production of mevalonate, which eventually can go on to produce geranyl-PP.

Globotriaosylceramide (Gb3)

Globotriaosylceramide (Gb3) is a membranous lipidic receptor. Cytokines and binding of toxins, such as Shiga toxin and verotoxin, increase Gb3 expression. This can lead to the import of peptides and the initiation of cell toxicity and injury.

Glucocorticoids

Glucocorticoids are steroids produced by the adrenal gland that have diverse actions on the body, including control of glucose metabolism, and control gene expression. Glucocorticoids regulate the transcription of a large number of genes, including a number of gluconeogenic genes in the liver.

Glutathione

Glutathione is an amino acid that acts as a substrate for glutathione peroxidase. Increasing glutathione levels are thought to increase the antioxidant actions of glutathione peroxidase.

Glutathione peroxidase

Glutathione peroxidase is a peroxidase found in cells that helps to prevent lipid peroxidation of the cell membrane. The function of glutathione peroxidase is to reduce lipid hydroperoxides to their corresponding alcohols and to reduce free hydrogen peroxide to water.

GLUT-1

GLUT-1 is a protein that transports glucose across cell membranes. GLUT-1 primarily resided in the plasma membrane, and unlike GLUT-4 it is not responsive to insulin.

GLUT-4

GLUT-4 is a protein that transports glucose across cell membranes. In insulin-responsive tissues (such as the heart), insulin will cause GLUT-4 to be translocated from inside the cell to the plasma membrane, thereby stimulating glucose uptake.

Glyceraldehyde 3-phosphate (GA3PDH)

Glyceraldehyde 3-phosphate (GA3PDH) is a key enzyme of glycolysis. During myocardial ischemia, GA3PDH can become rate-limiting for glycolysis. GA3PDH mRNA expression levels are often used as a control in many Northern blot experiments in order to ensure that equal amounts of mRNA have been loaded on the gel.

Glycogen synthase kinase 3 (GSK3)

GSK3 is an unusual protein serine/threonine kinase that, as the name implies phosphorylates glycogen synthase. The two mammalian isoforms, GSK-3a and b, play largely overlapping roles and have been implicated in a variety of human pathologies, including type 2 diabetes, Alzheimer's disease, bipolar disorder and cancer. Inhibition of ccglycogen synthase kinase-3 has been shown to prevent caspase-dependent apoptosis.

Glycolysis

Glycolysis is the first part of the pathway by which glucose is metabolized in cells. It is a highly regulated pathway that converts glucose to pyruvate. In the process of doing this, two ATP molecules are produced. This occurs without the requirement for oxygen.

Glycophosphatidylinositol-linked lipoprotein lipase

One type of post-translational modification of protein involves the addition of a glycophosphatidylinositol (GPI) anchor that facilitates anchoring of proteins to cell membrane. A glycophosphatidylinositol-linkage on lipoprotein lipase is one way of linking lipoprotein lipase to the cell membrane.

Glycosphingolipid metabolism

Sphingolipids are a type of phospholipid. Glycosphingolipids are sphingolipids that are glycosylated. Globotriaosylceramide is an example of a glycosphingolipid.

Glycosylation end products

Glycosylation is the process of adding oligosaccharide moieties to proteins or other molecules. In diabetes, chronically high glucose levels will increase the level of protein glycosylation. Therefore, by measuring glycosylation end products, the longer term degree of glucose control can be determined.

G-proteins

G-proteins refer to a group of guanylate triphosphate (GTP) binding proteins that are crucial in linking numerous types of receptor to their subcellular signalling pathways. An example of this is the b-adrenergic receptor, which is coupled to adenylate cyclase via a G-protein. Receptors that are coupled to the G-protein family are called Gprotein coupled receptors.

Gpx1

Gpx1 is an abbreviation for glutathione peroxidase.

Growth factor

Growth factors are usually proteins that regulate cell growth. One such growth factor is vascular endothelial growth factor (VEGF), which is an endothelial-derived growth factor that stimulates vascular growth. VEGF is also an important determinant of vascular permeability.

Guanylate cyclase

Guanylate cyclase is an enzyme that catalyzes the formation of cGMP from guanosine triphosphate. Guanylate cyclase is a target of nitric oxide (NO), and is primarily responsible for NO mediated vasodilation.

Hemoproteins

Hemoproteins are proteins that contain a heme molecule, which is an iron-containing protophorphyrin. Cytochrome P-450 and hemoglobin are two examples of hemoproteins.

Heptadecanoic acid (IHDA)

Heptadecanoic is a 16-carbon fatty acid that can be radiolabeled and used as a tracer for fatty acid uptake into the heart. One of the radiolabels that can be attached to heptadecanoic acid is a 123I group, which produces 123Iheptadecanoic acid (IHDA). A gamma camera can then be used to measure 123I-heptadecanoic acid uptake into the heart. This approach is used to assess fatty acid metabolism in the heart.

Heterodimeric

The term heterodimeric refers to two different proteins that combine to form a complex.

Hexokinase

Hexokinase is an important enzyme that phosphorylates glucose to glucose-6-P in the cytoplasm of cells. This allows glucose to be further metabolized. The glucose-6-P can be used as a substrate for glycolysis, a substrate for glycogen synthesis, or as a substrate for the pentose phosphate pathway. However, all of these pathways require that hexokinase first phosphorylate glucose.

5-HT(1D)-serotonin receptor

Serotonin (5-hydroxytryptamine or 5-HT) is a transmitter in the central nervous system, and also functions in the periphery as a ubiquitous hormone involved in vasocontriction and platelet function. Serotonin acts on a variety of serotonin receptors, one of these being the 5- HT1D receptors.

Human menopausal gonadotropin (hMG)-coenzyme A reductase inhibitors

Human menopausal gonadotropin (hMG)-coenzyme A reductase is important in the production of gonadal steroid hormones. There has been concern that the commonly used hMG reductase inhibitors used to lower cholesterol may also inhibit gonadotropincoenzyme. A reductase, therefore altering gonadal steroid hormone production.

Hydrobiopterin

Tetra-hydrobiopterin is produced by the reduction of dihydrobiopterin, catalyzed by the enzyme, dihydrofolate reductase. Tetra-hydrobiopterin is an essential cofactor for nitric oxide (NO) formation.

Hydrogen peroxide

Hydrogen peroxide is an intermediate between two free radicals. Superoxide radicals can be acted upon by superoxide dismutase to produce hydrogen peroxide. However, if hydrogen peroxide is not subsequently removed from the cell (usually by catalase), a nonenzymatic reaction can occur in which highly reactive hydroxyl radicals are produced.

Hydroperoxides

Hydroperoxides contain the O–O–H– unit. Hydrogen peroxide is therefore also an example of a hydroperoxide. Another hydroperoxide, lipid hydroperoxides, are also a marker of free radical injury. Free oxygen radicals can react with membrane lipids to form lipid hydroperoxides, a destructive process known as lipid peroxidation. Lipid peroxidation leads to oxidative injury of biologic membranes in vivo.

3-Hydroxyacyl-CoA dehydrogenase

3-hydroxyacyl-CoA dehydrogenase is the third enzyme in the intramitochondrial pathway that is involved in the metabolism of fatty acids (fatty acid b-oxidation). Recent interest has focused on inhibition of fatty acid oxidation as a way to protect the ischemic heart.

7Β-Hydroxycholesterol

7Β-Hydroxycholesterol is a cholesterol ester. Since free radicals can produce 7Β-hydroxycholesterol, the levels of plasma 7Β-hydroxycholesterol are sometimes used as a marker of free radical injury.

Hydroxyl

A hydroxyl free radical is a hydroxyl group with an unpaired electron. It is a highly reactive free radical that can cause serious damage to a cell by reacting with lipids, proteins, or DNA.

Hyperinsulinemic-euglycemic clamp

During a hyperinsulinemic-euglycemic clamp, high insulin levels are infused into a patient (or animal) and glucose is subsequently infused at a rate which maintains normal blood glucose levels. This procedure is used to determine the insulin sensitivity of the muscle. The more glucose infused under conditions of hyperinsulinemia the more insulin-sensitive is the muscle.

Hypoxia-inducible factor-1α(HIF-1-α)

Hypoxia-inducible factor-1α (HIF-1-α) is a transcriptional factor that is activated by stresses such as hypoxia. HIF- 1α then modifies the transcription of a number of genes, including glycolytic enzymes.

I-123 β–methyl-phenyl pentadecanoic acid (BMIPPA)

I-123 β–methyl-phenyl pentadecanoic acid (BMIPPA) is a radiolabeled fatty acid analog that can be used as an imaging agent to assess fatty acid uptake into tissues. It is often used to determine whether fatty acid uptake is altered in the hearts of patients. This is established by using a gamma-camera to determine the amount of BMIPPA taken up by the heart.

If current

If is the abbreviation for a current that actively hyperpolarizes cells. The “f” stands for “funny” because this unusual current hyperpolarizes cells. If current is primarily present in the autonomic tissue of the heart (i.e sinoatrial and AV node). It contributes to the phase 4 depolarization of the cell.

Inducible nitric oxide synthase (iNOS)

Nitric oxide synthase (NOS) is the enzyme responsible for synthesizing nitric oxide (NO). NO has received considerable research attention, since it is not only a vasodilator but is also important in numerous other processes, including apoptosis. Inducible NOS (iNOS) is an isoform of NOS that can be dramatically induced under a variety of conditions. One example of this is the dramatic expression of iNOS in muscle following sepsis.

Insulin receptor substrate (IRS)-1

Insulin receptor substrate (IRS)-1 is a key protein in the insulin-signaling pathway. Binding of insulin to the receptor results in activation of IRS-1. IRS-1 then alters the activity of a number of downstream signaling pathways to mediate the diverse effects of insulin.

Interleukin-6 (IL-6)

Interleukin-6 (IL-6) is a proinflammatory cytokine involved in many immune responses, including physiological stress reactions. IL-6 is also involved in several diseases, including lymphoid malignancies. This cytokine binds to soluble IL-6 receptor circulating in blood, leading to signal transduction. A significant correlation between circulating IL-6 level and insulin sensitivity has recently been found in humans.

Interleukin (IL)-1

Interleukin (IL)-1 is a proinflammatory cytokine which is involved in many immune responses, including physiological stress reactions. IL-1 has a diverse number of biological actions, part of which occur through ceramide signaling.

IP3-sensitive

IP3 is an important intracellular signaling molecule that is released from phosphatidylinositol present in the phospholipid cell membrane. IP3-sensitive refers to any signalling pathway that involves IP3.