Gluconeogenesis: Biosynthesis of GLUCOSE from nonhexose or non-carbohydrate precursors, such as LACTATE; PYRUVATE; ALANINE; and GLYCEROL.Lactates: Salts or esters of LACTIC ACID containing the general formula CH3CHOHCOOR.Liver: A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.Phosphoenolpyruvate Carboxykinase (GTP): An enzyme of the lyase class that catalyzes the conversion of GTP and oxaloacetate to GDP, phosphoenolpyruvate, and carbon dioxide. This reaction is part of gluconeogenesis in the liver. The enzyme occurs in both the mitochondria and cytosol of mammalian liver. (From Dorland, 27th ed) EC Carboxykinase (ATP): An enzyme of the lyase class that catalyzes the conversion of ATP and oxaloacetate to ADP, phosphoenolpyruvate, and carbon dioxide. The enzyme is found in some bacteria, yeast, and Trypanosoma, and is important for the photosynthetic assimilation of carbon dioxide in some plants. EC An enzyme that catalyzes the conversion of D-glucose 6-phosphate and water to D-glucose and orthophosphate. EC A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement.Glucagon: A 29-amino acid pancreatic peptide derived from proglucagon which is also the precursor of intestinal GLUCAGON-LIKE PEPTIDES. Glucagon is secreted by PANCREATIC ALPHA CELLS and plays an important role in regulation of BLOOD GLUCOSE concentration, ketone metabolism, and several other biochemical and physiological processes. (From Gilman et al., Goodman and Gilman's The Pharmacological Basis of Therapeutics, 9th ed, p1511)Dihydroxyacetone: A ketotriose compound. Its addition to blood preservation solutions results in better maintenance of 2,3-diphosphoglycerate levels during storage. It is readily phosphorylated to dihydroxyacetone phosphate by triokinase in erythrocytes. In combination with naphthoquinones it acts as a sunscreening agent.Glycogenolysis: The release of GLUCOSE from GLYCOGEN by GLYCOGEN PHOSPHORYLASE (phosphorolysis). The released glucose-1-phosphate is then converted to GLUCOSE-6-PHOSPHATE by PHOSPHOGLUCOMUTASE before entering GLYCOLYSIS. Glycogenolysis is stimulated by GLUCAGON or EPINEPHRINE via the activation of PHOSPHORYLASE KINASE.Pyruvic Acid: An intermediate compound in the metabolism of carbohydrates, proteins, and fats. In thiamine deficiency, its oxidation is retarded and it accumulates in the tissues, especially in nervous structures. (From Stedman, 26th ed)Ketone Bodies: The metabolic substances ACETONE; 3-HYDROXYBUTYRIC ACID; and acetoacetic acid (ACETOACETATES). They are produced in the liver and kidney during FATTY ACIDS oxidation and used as a source of energy by the heart, muscle and brain.Lactic Acid: A normal intermediate in the fermentation (oxidation, metabolism) of sugar. The concentrated form is used internally to prevent gastrointestinal fermentation. (From Stedman, 26th ed)Liver Glycogen: Glycogen stored in the liver. (Dorland, 28th ed)Deuterium Oxide: The isotopic compound of hydrogen of mass 2 (deuterium) with oxygen. (From Grant & Hackh's Chemical Dictionary, 5th ed) It is used to study mechanisms and rates of chemical or nuclear reactions, as well as biological processes.Glycerol: A trihydroxy sugar alcohol that is an intermediate in carbohydrate and lipid metabolism. It is used as a solvent, emollient, pharmaceutical agent, and sweetening agent.Fructose-Bisphosphatase: An enzyme that catalyzes the conversion of D-fructose 1,6-bisphosphate and water to D-fructose 6-phosphate and orthophosphate. EC Kinase: ATP:pyruvate 2-O-phosphotransferase. A phosphotransferase that catalyzes reversibly the phosphorylation of pyruvate to phosphoenolpyruvate in the presence of ATP. It has four isozymes (L, R, M1, and M2). Deficiency of the enzyme results in hemolytic anemia. EC Derivatives of OXALOACETIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that include a 2-keto-1,4-carboxy aliphatic structure.Pyruvate Carboxylase: A biotin-dependent enzyme belonging to the ligase family that catalyzes the addition of CARBON DIOXIDE to pyruvate. It is occurs in both plants and animals. Deficiency of this enzyme causes severe psychomotor retardation and ACIDOSIS, LACTIC in infants. EC Lengthy and continuous deprivation of food. (Stedman, 25th ed)GlycogenMethenamine: An anti-infective agent most commonly used in the treatment of urinary tract infections. Its anti-infective action derives from the slow release of formaldehyde by hydrolysis at acidic pH. (From Martindale, The Extra Pharmacopoeia, 30th ed, p173)Blood Glucose: Glucose in blood.Fasting: Abstaining from all food.Picolinic AcidsGlycolysis: A metabolic process that converts GLUCOSE into two molecules of PYRUVIC ACID through a series of enzymatic reactions. Energy generated by this process is conserved in two molecules of ATP. Glycolysis is the universal catabolic pathway for glucose, free glucose, or glucose derived from complex CARBOHYDRATES, such as GLYCOGEN and STARCH.Alanine: A non-essential amino acid that occurs in high levels in its free state in plasma. It is produced from pyruvate by transamination. It is involved in sugar and acid metabolism, increases IMMUNITY, and provides energy for muscle tissue, BRAIN, and the CENTRAL NERVOUS SYSTEM.Citric Acid Cycle: A series of oxidative reactions in the breakdown of acetyl units derived from GLUCOSE; FATTY ACIDS; or AMINO ACIDS by means of tricarboxylic acid intermediates. The end products are CARBON DIOXIDE, water, and energy in the form of phosphate bonds.Acetoacetates: Salts and derivatives of acetoacetic acid.Hydroxybutyrates: Salts and esters of hydroxybutyric acid.Insulin: A 51-amino acid pancreatic hormone that plays a major role in the regulation of glucose metabolism, directly by suppressing endogenous glucose production (GLYCOGENOLYSIS; GLUCONEOGENESIS) and indirectly by suppressing GLUCAGON secretion and LIPOLYSIS. Native insulin is a globular protein comprised of a zinc-coordinated hexamer. Each insulin monomer containing two chains, A (21 residues) and B (30 residues), linked by two disulfide bonds. Insulin is used as a drug to control insulin-dependent diabetes mellitus (DIABETES MELLITUS, TYPE 1).Quinolinic AcidsAminooxyacetic Acid: A compound that inhibits aminobutyrate aminotransferase activity in vivo, thereby raising the level of gamma-aminobutyric acid in tissues.PhosphoenolpyruvateMalatesHepatocytes: The main structural component of the LIVER. They are specialized EPITHELIAL CELLS that are organized into interconnected plates called lobules.Perfusion: Treatment process involving the injection of fluid into an organ or tissue.Glutamine: A non-essential amino acid present abundantly throughout the body and is involved in many metabolic processes. It is synthesized from GLUTAMIC ACID and AMMONIA. It is the principal carrier of NITROGEN in the body and is an important energy source for many cells.Carbon Isotopes: Stable carbon atoms that have the same atomic number as the element carbon, but differ in atomic weight. C-13 is a stable carbon isotope.3-Hydroxybutyric Acid: BUTYRIC ACID substituted in the beta or 3 position. It is one of the ketone bodies produced in the liver.Rats, Inbred Strains: Genetically identical individuals developed from brother and sister matings which have been carried out for twenty or more generations or by parent x offspring matings carried out with certain restrictions. This also includes animals with a long history of closed colony breeding.Hypoglycins: Methylene cyclopropyl alanine and congeners isolated from the unripe edible fruit of the AKEE plant (BLIGHIA SAPIDA). Hypoglycin B is the gamma-glutamyl congener of hypoglycin A. They are very toxic and teratogenic, causing a syndrome called Jamaican vomiting sickness that includes a fall in blood glucose due to the interference of FATTY ACIDS and LEUCINE metabolism which leads to VOMITING, liver damage, CONVULSIONS and DEATH.Fatty Acids, Nonesterified: FATTY ACIDS found in the plasma that are complexed with SERUM ALBUMIN for transport. These fatty acids are not in glycerol ester form.Transaldolase: An enzyme of the transferase class that catalyzes the reaction sedoheptulose 7-phosphate and D-glyceraldehyde 3-phosphate to yield D-erythrose 4-phosphate and D-fructose phosphate in the PENTOSE PHOSPHATE PATHWAY. (Dorland, 27th ed) EC Derivatives of propionic acid. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain the carboxyethane structure.Deuterium: Deuterium. The stable isotope of hydrogen. It has one neutron and one proton in the nucleus.Fructosediphosphates: Diphosphoric acid esters of fructose. The fructose-1,6- diphosphate isomer is most prevalent. It is an important intermediate in the glycolysis process.Carbohydrate Metabolism: Cellular processes in biosynthesis (anabolism) and degradation (catabolism) of CARBOHYDRATES.Radioisotope Dilution Technique: Method for assessing flow through a system by injection of a known quantity of radionuclide into the system and monitoring its concentration over time at a specific point in the system. (From Dorland, 28th ed)Glyceraldehyde 3-Phosphate: An aldotriose which is an important intermediate in glycolysis and in tryptophan biosynthesis.Fructose: A monosaccharide in sweet fruits and honey that is soluble in water, alcohol, or ether. It is used as a preservative and an intravenous infusion in parenteral feeding.Mitochondria, Liver: Mitochondria in hepatocytes. As in all mitochondria, there are an outer membrane and an inner membrane, together creating two separate mitochondrial compartments: the internal matrix space and a much narrower intermembrane space. In the liver mitochondrion, an estimated 67% of the total mitochondrial proteins is located in the matrix. (From Alberts et al., Molecular Biology of the Cell, 2d ed, p343-4)Phosphofructokinase-1: An allosteric enzyme that regulates glycolysis by catalyzing the transfer of a phosphate group from ATP to fructose-6-phosphate to yield fructose-1,6-bisphosphate. D-tagatose- 6-phosphate and sedoheptulose-7-phosphate also are acceptors. UTP, CTP, and ITP also are donors. In human phosphofructokinase-1, three types of subunits have been identified. They are PHOSPHOFRUCTOKINASE-1, MUSCLE TYPE; PHOSPHOFRUCTOKINASE-1, LIVER TYPE; and PHOSPHOFRUCTOKINASE-1, TYPE C; found in platelets, brain, and other tissues.Glucokinase: A group of enzymes that catalyzes the conversion of ATP and D-glucose to ADP and D-glucose 6-phosphate. They are found in invertebrates and microorganisms, and are highly specific for glucose. (Enzyme Nomenclature, 1992) EC NucleotidesCarbon Radioisotopes: Unstable isotopes of carbon that decay or disintegrate emitting radiation. C atoms with atomic weights 10, 11, and 14-16 are radioactive carbon isotopes.Hyperglycemia: Abnormally high BLOOD GLUCOSE level.Glucose-6-Phosphate: An ester of glucose with phosphoric acid, made in the course of glucose metabolism by mammalian and other cells. It is a normal constituent of resting muscle and probably is in constant equilibrium with fructose-6-phosphate. (Stedman, 26th ed)Ketoglutaric Acids: A family of compounds containing an oxo group with the general structure of 1,5-pentanedioic acid. (From Lehninger, Principles of Biochemistry, 1982, p442)Oleic Acids: A group of fatty acids that contain 18 carbon atoms and a double bond at the omega 9 carbon.Epinephrine: The active sympathomimetic hormone from the ADRENAL MEDULLA. It stimulates both the alpha- and beta- adrenergic systems, causes systemic VASOCONSTRICTION and gastrointestinal relaxation, stimulates the HEART, and dilates BRONCHI and cerebral vessels. It is used in ASTHMA and CARDIAC FAILURE and to delay absorption of local ANESTHETICS.Radioactive Tracers: Radioactive substances added in minute amounts to the reacting elements or compounds in a chemical process and traced through the process by appropriate detection methods, e.g., Geiger counter. Compounds containing tracers are often said to be tagged or labeled. (Hawley's Condensed Chemical Dictionary, 12th ed)Hypoglycemia: A syndrome of abnormally low BLOOD GLUCOSE level. Clinical hypoglycemia has diverse etiologies. Severe hypoglycemia eventually lead to glucose deprivation of the CENTRAL NERVOUS SYSTEM resulting in HUNGER; SWEATING; PARESTHESIA; impaired mental function; SEIZURES; COMA; and even DEATH.Metformin: A biguanide hypoglycemic agent used in the treatment of non-insulin-dependent diabetes mellitus not responding to dietary modification. Metformin improves glycemic control by improving insulin sensitivity and decreasing intestinal absorption of glucose. (From Martindale, The Extra Pharmacopoeia, 30th ed, p289)Caprylates: Derivatives of caprylic acid. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain a carboxy terminated eight carbon aliphatic structure.Amino Acids: Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins.Kinetics: The rate dynamics in chemical or physical systems.Glutamates: Derivatives of GLUTAMIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain the 2-aminopentanedioic acid structure.Carbon Dioxide: A colorless, odorless gas that can be formed by the body and is necessary for the respiration cycle of plants and animals.Energy Metabolism: The chemical reactions involved in the production and utilization of various forms of energy in cells.Hypoglycemic Agents: Substances which lower blood glucose levels.Food Deprivation: The withholding of food in a structured experimental situation.Oxidation-Reduction: A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).Urea: A compound formed in the liver from ammonia produced by the deamination of amino acids. It is the principal end product of protein catabolism and constitutes about one half of the total urinary solids.Fatty Acids: Organic, monobasic acids derived from hydrocarbons by the equivalent of oxidation of a methyl group to an alcohol, aldehyde, and then acid. Fatty acids are saturated and unsaturated (FATTY ACIDS, UNSATURATED). (Grant & Hackh's Chemical Dictionary, 5th ed)CitratesKidney Cortex: The outer zone of the KIDNEY, beneath the capsule, consisting of KIDNEY GLOMERULUS; KIDNEY TUBULES, DISTAL; and KIDNEY TUBULES, PROXIMAL.Ammonia: A colorless alkaline gas. It is formed in the body during decomposition of organic materials during a large number of metabolically important reactions. Note that the aqueous form of ammonia is referred to as AMMONIUM HYDROXIDE.Fructose-Bisphosphate Aldolase: An enzyme of the lyase class that catalyzes the cleavage of fructose 1,6-biphosphate to form dihydroxyacetone phosphate and glyceraldehyde 3-phosphate. The enzyme also acts on (3S,4R)-ketose 1-phosphates. The yeast and bacterial enzymes are zinc proteins. (Enzyme Nomenclature, 1992) E.C. G2 Cells: A human liver tumor cell line used to study a variety of liver-specific metabolic functions.Oxymetazoline: A direct acting sympathomimetic used as a vasoconstrictor to relieve nasal congestion. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1251)Glycerol Kinase: An enzyme that catalyzes the formation of glycerol 3-phosphate from ATP and glycerol. Dihydroxyacetone and L-glyceraldehyde can also act as acceptors; UTP and, in the case of the yeast enzyme, ITP and GTP can act as donors. It provides a way for glycerol derived from fats or glycerides to enter the glycolytic pathway. EC Resistance: Diminished effectiveness of INSULIN in lowering blood sugar levels: requiring the use of 200 units or more of insulin per day to prevent HYPERGLYCEMIA or KETOSIS.Oxygen Consumption: The rate at which oxygen is used by a tissue; microliters of oxygen STPD used per milligram of tissue per hour; the rate at which oxygen enters the blood from alveolar gas, equal in the steady state to the consumption of oxygen by tissue metabolism throughout the body. (Stedman, 25th ed, p346)KetonesAcetates: Derivatives of ACETIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that contain the carboxymethane structure.Carbon: A nonmetallic element with atomic symbol C, atomic number 6, and atomic weight [12.0096; 12.0116]. It may occur as several different allotropes including DIAMOND; CHARCOAL; and GRAPHITE; and as SOOT from incompletely burned fuel.Glycogen Phosphorylase: An enzyme that catalyzes the degradation of GLYCOGEN in animals by releasing glucose-1-phosphate from the terminal alpha-1,4-glycosidic bond. This enzyme exists in two forms: an active phosphorylated form ( PHOSPHORYLASE A) and an inactive un-phosphorylated form (PHOSPHORYLASE B). Both a and b forms of phosphorylase exist as homodimers. In mammals, the major isozymes of glycogen phosphorylase are found in muscle, liver and brain tissue.C-Peptide: The middle segment of proinsulin that is between the N-terminal B-chain and the C-terminal A-chain. It is a pancreatic peptide of about 31 residues, depending on the species. Upon proteolytic cleavage of proinsulin, equimolar INSULIN and C-peptide are released. C-peptide immunoassay has been used to assess pancreatic beta cell function in diabetic patients with circulating insulin antibodies or exogenous insulin. Half-life of C-peptide is 30 min, almost 8 times that of insulin.Diabetes Mellitus, Type 2: A subclass of DIABETES MELLITUS that is not INSULIN-responsive or dependent (NIDDM). It is characterized initially by INSULIN RESISTANCE and HYPERINSULINEMIA; and eventually by GLUCOSE INTOLERANCE; HYPERGLYCEMIA; and overt diabetes. Type II diabetes mellitus is no longer considered a disease exclusively found in adults. Patients seldom develop KETOSIS but often exhibit OBESITY.Magnetic Resonance Spectroscopy: Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING).Aspartic Acid: One of the non-essential amino acids commonly occurring in the L-form. It is found in animals and plants, especially in sugar cane and sugar beets. It may be a neurotransmitter.