Intracellular Peptide Turnover: Properties and Physiological Significance of the Major Peptide Hydrolases of Brain Cytosol
Gerard O’Cuinn in Metabolism of Brain Peptides, 2020
Recently cloned enzymes have sequence homology to thimet oligopeptidase. A mitochondrial intermediate peptidase which removes an N-terminal octapeptide from a mitochondrial precursor protein has 44% similarity to thimet oligopeptidase113. Similarly an enzyme purified from rabbit liver microsomes with a specificity for peptides containing Arg in the P1 and P4 positions has 60% sequence homology to thimet oligopeptidase114. The latter enzyme is proposed to play a role in prohormone processing. This microsomal processing enzyme is also 91% homologous to angiotensin II binding protein105. Thimet oligopeptidase has 24% amino acid identity to a 565 residue overlap with the metalloproteinase encoding gene opdA from Salmonella typhimurium115. Therefore thimet oligopeptidase is part of a newly recognized family of metalloproteinases.
Human Reproduction Functions: Evaluation with Radiobioassay
Fuad S. Ashkar, Lelio G. Colombetti in Radiobioassays, 2019
Prolactin can be considered a gonadotropic hormone. It is structurally different from LH and FSH in that it consists of only one polypeptide chain containing 198 amino acids in the ovine pituitary.28 It has no carbohydrate content. The structure shows many similar amino acid sequences to the growth hormone and lactogen.29 Some investigators postulate that prolactin is an active hormone stemming from a prohormone.29 Unlike LH and FSH, prolactin physiologically seems to be under the effect of inhibiting as well as releasing factors. Transection of the hypothalamic pituitary channels cause an increase in circulating prolactin levels and a drop in LH, FSH, and growth hormone levels.Dopamine is most likely the major prolactin inhibiting factor.31 Gamma aminobutyric acid (GABA) is another prolactin inhibiting factor.32 Serotonin, on the other hand, is a prolactin-releasing factor.33 It is obvious that prolactin is affected by various neurotransmitter substances, and as a corollary, situations interfering with the neurotransmitter levels will affect prolactin levels in the circulation.
Dietary supplementation
Jay R Hoffman in Dietary Supplementation in Sport and Exercise, 2019
Combination products were reported to be those dietary supplements that contained a number of different ingredients generally seen in weight loss and/or muscle-building supplements. However, the specific ingredients within these supplements were not clearly defined. The authors though did suggest that many of the supplements within this classification contained banned or illegal ingredients such as 1,3 dimethylamylamine or ephedra alkaloids (35). When not including combination products the magnitude of adverse events associated with dietary supplement use dropped to approximately 13%. The use of prohormone supplements resulted in a 9.4% adverse event occurrence, while herbal supplements appeared to be associated with at least one adverse event in 8.9% of users.
The vagina as source and target of androgens: implications for treatment of GSM/VVA, including DHEA
Published in Climacteric, 2023
S. Cipriani, E. Maseroli, S. A. Ravelli, L. Vignozzi
As a steroid prohormone and an intermediate in the synthetic pathway of androgens and estrogens, androstenedione could theoretically represent a therapeutic strategy against GSM. It can be administered as an oral formulation; however, scarce evidence is available regarding its safety and its impact on sexual function. In a small study published in 2002, 30 healthy postmenopausal women randomly took a single oral dose of 50 mg or 100 mg androstenedione or placebo [53]. The authors concluded that both androstenedione doses were able to significantly increase testosterone and estrone, but not estradiol serum levels in the treated groups, with peak testosterone levels higher than the normal upper limit in 4/10 patients in the 50 mg group and 6/10 in the 100 mg group [53]. Consequently, longer-term data, safety and efficacy profiles of androstenedione treatment are needed.
Cardiac biomarkers for risk stratification of arrhythmic death in patients with heart failure and reduced ejection fraction
Published in British Journal of Biomedical Science, 2021
AL Burger, S Stojkovic, A Diedrich, J Wojta, S Demyanets, T Pezawas
Cardiac biomarkers might improve risk stratification for arrhythmic death in HFrEF patients. C-terminal proendothelin-1 (CT-proET-1), midregional pro-atrial natriuretic peptide (MR-proANP) and midregional pro-adrenomedullin (MR-proADM) are released in response to increased cardiovascular stress, pressure and volume overload, increased wall tension and endothelial shear stress [11–13]. Elevated plasma levels of these prohormone fragments are associated with increased all-cause mortality, cardiovascular mortality and adverse outcome in patients with HF [14–20]. However, the role of these biomarkers in the prediction of arrhythmic death alone has not been investigated. The present study tests the null hypothesis that the biomarkers CT-proET-1, MR-proANP and MR-proADM are not associated with an increased risk for arrhythmic death and all-cause mortality in HFrEF patients with ischaemic or non-ischaemic, dilated cardiomyopathy.
Developing mass spectrometry for the quantitative analysis of neuropeptides
Published in Expert Review of Proteomics, 2021
Christopher S. Sauer, Ashley Phetsanthad, Olga L. Riusech, Lingjun Li
This complexity inherent to all neuropeptidomic studies is exacerbated by the difficulties in determining possible neuropeptide sequences. Neuropeptides are produced by the select processing of precursor proteins (i.e. preprohormone) encoded within the genome [19]. These preprohormones contain a signaling sequence and the remaining prohormone. After cleavage of the signaling sequence, the prohormone is selectively and specifically cleaved by endopeptidases, such as various prohormone convertases, to produce several peptide sequences from a single precursor protein [20]. The peptides are then processed further and post-translationally modified to produce the bioactive neuropeptides [20]. The intricate pathways from genome to active neuropeptide, splice variants, and diversity of post-translational modifications lead to many possible peptide forms that are difficult to predict from genomics or even transcriptomics alone. This is compounded by the fact that many model organisms do not have a fully sequenced genome to use as a reliable starting point for predicting a full neuropeptide database, making neuropeptide studies even more challenging.
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