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Pharmacology of p-sitosterol and other Sterols
Published in Amritpal Singh Saroya, Contemporary Phytomedicines, 2017
Sterolins are glucosides, which are molecular structures joined to the sterol. Sterolin is easily destroyed, and without it, the sterol does not have the same immune- enhancing benefits. In nature, plants never contain sterols only. The sterols are always associated with their glucoside sterolin.
Orbital involvement of Sitosterolemia
Published in Orbit, 2022
Linda O. Okafor, Jeremy Bowyer, Caroline Thaung, Elaine Murphy, David H. Verity
Patients with sitosterolemia absorb 15% to 60% of ingested sitosterol, leading to a 50 to 200-fold increase in plasma sitosterol levels compared to unaffected individuals.1,,2,,4 In 1998, the sitosterolemia or (STSL) locus was mapped to the short arm of human chromosome 2 (2p21), and in 2001 the STSL locus was identified as containing the ABCG5 and ABCG8 genes. These encode for the proteins sterolin-1 and −2, which play a key role in sterol absorption and excretion in the liver and intestine. Thus, affected individuals with defects in either ABCG5 or ABCG8 suffer increased intestinal absorption and decreased biliary excretion of plant sterols, leading to extremely high plasma levels of plant sterols.1,2 Our patient’s genetic analysis identified ABCG5 allelic homozygosity; however, heterozygosity is considered by some authors to be partially protective. Finally, it was noted that other family members though suffering mild haematological abnormalities had no history of familial hypercholesterolemia. In such patients, sitosterolemia should always be considered as an alternative diagnosis. Patients with sitosterolemia show extreme phenotypic heterogeneity; some patients are almost asymptomatic, whilst others show severe hypercholesterolemia leading to accelerated atherosclerosis and premature cardiac death.1,2,4Table 2 summarises the full spectrum of the disease. The case reported herein describes xanthomatosis, a feature rarely observed in young children, though in sitosterolemia it can occur very early, and even within the first year of life.6,7
Evaluation of gallstone classification and their diagnosis through serum parameters as emerging tools in treatment: a narrative review
Published in Postgraduate Medicine, 2022
Bhavna Sharma, Shubha Rani Sharma
The genetic polymorphs of genes for Apo B, Apo E Apo A1, CYP7A1, LDL receptor-associated protein LDL receptor and cholesteryl ester transfer are involved in gallstone formation. The variants of hepatic ATP binding cassette transporters are considered to cause gallstone disease and are named genetic susceptibility factors which need to be studied further for risk assessment and prevention. Cholesterol Gallstone susceptibility is conferred by the sterolin locus (ABCG5/ABCG8). In 25% of cases of gallstone formations genetic factors are seen to be involved (ABCG8 cholesterol transporter 11%: UGT1A1 gilbert variant 6%) [18].
ABCG5 and ABCG8 gene variations associated with sitosterolemia and platelet dysfunction
Published in Platelets, 2021
Jose María Bastida, Rocío Benito, José Ramón González-Porras, José Rivera
Sitosterolemia (OMIM 210250) is a rare inherited autosomal recessive disorder of lipid metabolism, characterized by increased levels of plasma plant sterols (PS) such as stigmasterol, campesterol, and sitosterol [1,2]. Only around 100 patients with sitosterolemia have been reported so far, but the exact frequency of this disease is still unknown and maybe as high as 1 in 200,000 general population [1]. It is caused by molecular pathology in two genes named adenosine triphosphate-binding cassette (ABC) subfamily G members 5 and 8 (ABCG5 and ABCG8). These genes encode sterolin-1 or ABCG5 (651aa, UniProtKB-Q9H222) and sterolin-2 or ABCG8 (673aa, UniProtKB-Q9H221), respectively, which regulate the network of absorption and excretion of sitosterol and cholesterol [3]. ABCG5 and ABCG8 are ATP-binding cassette (ABC) half-transporters, which form an obligate heterodimer (ABCG5/ABCG8) able to move to the apical surface of cells and then to mediate Mg2+- and ATP-dependent sterol transport across the cell membrane [4,5]. As other members of the ABC transporter family, its structure consists of an extracellular domain (ECD) that is in intimate contact with a compact transmembrane domain (TMD), which consists of six transmembrane helices (TMHs). The nucleotide-binding domain (NBD) is located N-terminal from the TMD and maintains a tightly closed dimer. At each NBDs, the ABC cassette and the TMD are in close proximity to a triple-helical bundle that consists of the connecting helix (CnH), the coupling helix (CpH) and the E-helix. The conserved Q-loop of ABC proteins is also located in this region. The triple-helical bundle may, therefore, serve as an immediate interface between TMD and NBD. The TMD polar relay is a cluster of polar amino acids located in the transmembrane segments and on the triple-helical bundles [5]. Despite the molecular mechanism by which ABCG5/ABCG8 effluxes sterol from plasma membranes remains to be elucidated, functional abnormalities in these proteins lead to the hyperabsorption and accumulation of PS in plasma [1–5].