A nucleotide is regarded as the basic building block of nucleic acid polymers (. DNA and RNA ). It is an organic compound made up of three subunits: a nitrogenous base , a five-carbon sugar , and a phosphate group . The sugar component may either be ribose or deoxyribose. The ribose sugar is the sugar component of the nucleotides that make up RNA. The deoxyribose sugar is the sugar component of DNA. The most common nucleotides are divided into purines and pyrimidines based on the structure of the nitrogenous base . In DNA , the purine bases include adenine and guanine while the pyrimidine bases are thymine and cytosine . RNA includes adenine , guanine , cytosine , and uracil instead of thymine ( thymine is produced by adding a methyl to uracil ).
GLP-1 is produced from the proglucagon gene in L-cells of the small intestine and is secreted in response to nutrients ( figure 1 ) [ 3 ]. GLP-1 binds to a specific GLP-1 receptor, which is expressed in various tissues, including pancreatic beta cells, pancreatic ducts, gastric mucosa, kidney, lung, heart, skin, immune cells, and the hypothalamus [ 2,4 ]. GLP-1 exerts its main effect by stimulating glucose-dependent insulin release from the pancreatic islets [ 2 ]. It has also been shown to slow gastric emptying [ 5 ], inhibit inappropriate post-meal glucagon release [ 3,6 ], and reduce food intake ( table 1 ) [ 3 ]. Owing in part to the effects of GLP-1 on slowed gastric emptying and appetite centers in the brain, therapy with GLP-1 and its receptor agonists is associated with weight loss, even among patients without significant nausea and vomiting. (See 'Weight loss' below.)