The cytoplasmic protein glutamic acid decarboxylase (GAD) is the rate-limiting enzyme in the synthesis of the major inhibitory neurotransmitter γ-aminobutyric acid (GABA). High serum levels of antibodies (Abs) against the isoform GAD65 have been associated with neurologic syndromes like stiff-person syndrome (SPS), cerebellar ataxia (CA), limbic encephalitis (LE), and temporal lobe epilepsy (TLE) together referred to as GAD65 antibody spectrum disorders (GAD65-Ab SDs) and circulating GAD-reactive B cells in peripheral blood are abundant in these patients
Dickkopf-1 (DKK1) is a soluble inhibitor of Wnt/β-catenin signaling that is required for embryonic head formation in vertebrate development. DKK1 regulates Wnt signaling pathway by binding to lipoprotein-related protein-5/6 (LRP5/6) and Kremen proteins and induces LRP endocytosis, which prevents the formation of Wnt-Frizzled-LRP5/6 receptor complexes. This allows entry of β-catenin into the nucleus where it interacts with members of T cell factor (TCF) family, which regulate Wnt target genes that are essential for embryonic development and tumorigenesis.
DHT is the 5α-reduced metabolite of testosterone (T) that is principally converted from T in target organs such as prostate, skin, and liver. Intracellular DHT is a more potent androgenic agonist than T, and its presence in some tissues such as the prostate is necessary for the full organ development and function.
Erythropoietin (Epo) controls a variety of signal transduction pathways during oxidative stress. The main function of Epo and its receptor (EpoR) is the stimulation of erythropoiesis.
Fibroblast growth factor 21 (FGF21) is a hormone that regulates important metabolic pathways. FGF21 is expressed in several metabolically active organs and interacts with different tissues. Striated muscles have been found to be an important source of FGF21.
Fibroblast growth factor 23 (FGF23) has become the third key player of phosphate/calcium metabolism after PTH and vitamin D. FGF23 is a protein synthesized by osteocytes that acts mainly as a phosphaturic factor and a suppressor of 1α hydroxylase activity in the kidney.
Follistatin is an autocrine glycoprotein. Its primary function is binding and bioneutralization of members of the TGF-β superfamily. Follistatin-like 1 (Fstl1) is a secreted protein of the BMP inhibitor class.
FSTL1 is an extracellular glycoprotein widely expressed in human tissues and induced by ischemic stress and proinflammatory mediators. Follistatin-like protein 1 (FSTL1) is a secreted glycoprotein produced mainly by cells of mesenchymal origin. FSTL1 has been shown to play an important role during embryogenesis. FSTL1 is elevated in various inflammatory conditions and decreased during the course of treatment.
The glial fibrillary acidic protein (GFA protein or GFAP) is the major protein constituent of glial intermediate filaments in differentiated fibrous and protoplasmic astrocytes of the central nervous system. Proteins having similar molecular weights, isoelectric points, and immunoreactivity with GFAP have been found in cells of neural crest and ectodermal origin. A putative function ascribed to glial filaments is its role as a component of the cytoskeleton in defining and maintaining the shape of the astrocyte.