Introduction
Obestatin is a 23-amino acid peptide hormone produced in specific epithelial cells of the stomach and small intestine of human. It is present in the gastrointestinal tract, spleen, mammary gland, breast milk and plasma. Obestatin seems to be part of the complex visceral-brain network where hormones and substances in the stomach and intestines send signals of satiety or hunger to the brain. Obestatin also functions as an anorexia hormone that reduces food intake and weight gain. Furthermore, obestatin is effective in memory improvement, sleep regulation, cell proliferation, pancreatic juice enzymes' increase and the inhibition of glucose-induced insulin secretion.
Pharmacologic action
Obestatin is predicted to be a 23-residue peptide with a carboxy-terminal amide function, and it is next to a single base residue in the preproghrelin sequence of a Gly-extended structure.
Endogenous obestatin was subsequently isolated from the stomach extracts, confirming that the prediction was correct. As a trace component, the carboxy-terminal 13-residue peptide of obestatin was isolated too. In the prosotrophin sequence of human, the obestatin is conserved. In addition, the orphan G-protein-coupled receptor GPR39 was identified as a receptor for obestatin. Obestatin is a novel bioactive peptide that was identified using modern techniques in the post-genome era.
Function
Obestatin has a short half-life and a fast degradation rate, so it is recognized to play a wide-ranging pathophysiological role. Obestatin has positive impact both on metabolism and cardiovascular functions. In addition, circulatory compliance levels are usually inversely correlated with obesity and diabetes, and this peptide has been shown to have protective metabolic effects in experimental diabetes, suggesting that it may have therapeutic potential in this environment. Obestatin is also involved in blood pressure regulation and plays a beneficial role in endothelial function. It may also promote cardiovascular protection, such as the treatment of ischemia-reperfusion injury.
Pharmacokinetics and metabolism
In patients with insulin resistance and diabetes mellitus, the concentration of plasma insulinate, but not ghrelin, is reduced. In the multiple linear regression model, obestatin was even considered to be a marker of insulin resistance, but plasma ghrelin was not considered in the analysis. In contrast, patients with type 2 diabetes have reduced or unchanged circulation during fasting. In insulin-resistant patients or type 2 diabetic patients, post-prandial obestatin concentrations remain stable, as opposed to the reduction normally observed in control patients.
References:
1. Ren, A. J., Guo, Z. F., Wang, Y. K., Lin, L., Zheng, X., & Yuan, W. J. (2009). Obestatin, obesity and diabetes. Peptides, 30(2), 439-444.
2. Cowan, E., Burch, K. J., Green, B. D., & Grieve, D. J. (2016). Obestatin as a key regulator of metabolism and cardiovascular function with emerging therapeutic potential for diabetes. British journal of pharmacology, 173(14), 2165-2181.
3. Volante, M., Rosas, R., Ceppi, P., Rapa, I., Cassoni, P., Wiedenmann, B & Papotti, M. (2009). Obestatin in human neuroendocrine tissues and tumours: expression and effect on tumour growth. The Journal of Pathology: A Journal of the Pathological Society of Great Britain and Ireland, 218(4), 458-466.
4. Hassouna, R., Zizzari, P., & Tolle, V. (2010). The ghrelin/obestatin balance in the physiological and pathological control of growth hormone secretion, body composition and food intake. Journal of neuroendocrinology, 22(7), 793-804.
5. Ghanbari-Niaki, A., Saghebjoo, M., Rahbarizadeh, F., Hedayati, M., & Rajabi, H. (2008). A single circuit-resistance exercise has no effect on plasma obestatin levels in female college students. Peptides, 29(3), 487-490.
6. Gourcerol, G. (2013). Obestatin. In Handbook of Biologically Active Peptides (Second Edition) (pp. 1275-1282).
