Effect of desacyl ghrelin, obestatin and related peptides on triglyceride storage, metabolism and GHSR signaling in 3T3‐L1 adipocytes

Abstract

Acyl-ghrelin (AG), desacyl-ghrelin (DAG) and obestatin are all derived from the same gene transcript; however their plasma levels do not necessarily change in parallel. The influence of these peptides towards the development of obesity and their direct effects on adipocyte physiology has not been thoroughly investigated. This study was designed to evaluate the direct effects of peptides of the ghrelin family on preadipocyte proliferation, differentiation and adipocyte lipid and glucose metabolism in 3T3-L1 cells. 3T3 cells were treated with physiological peptide concentrations for 1 h to 9 days, and the relevant assays measured. In preadipocytes, AG, GHRP-6 and DAG stimulated proliferation, measured as (3)H-thymidine incorporation (up to 200%, P < 0.05), while all peptides stimulated differentiation (up to 300%, P < 0.01) as compared to standard differentiation conditions. In adipocytes, FA uptake was increased in a concentration-dependent manner especially with obestatin (three- to fourfold, P < 0.001) and DAG (three- to fivefold, P < 0.001). By contrast, glucose transport was unchanged. DAG and obestatin significantly decreased lipolysis measured as non-esterified fatty acid and glycerol release by 50%, P < 0.05-0.01 and 51%, P < 0.01, respectively. Interestingly, DAG stimulation of FA uptake was blocked with GHSR1 antagonist (D-lys(3))-GHRP-6 (P < 0.05), phospholipase C inhibitor U73122 and phosphatidylinositol-3-kinase inhibitor wortmannin (P < 0.001). Finally, in omental but not subcutaneous human adipose tissue, GHSR1 correlated with BMI (r = 0.549, P < 0.05) and insulin (r = 0.681, P < 0.01). Taken together, these results suggest that ghrelin-related peptides may directly affect adipose tissue metabolism.

Metabolic effects of overnight continuous infusion of unacylated ghrelin in humans

“…Actually, the observation of decreased FFA levels in our study does not necessarily imply an inhibition of lipolysis but could also suggest an increase in their tissutal uptake or inhibition of gastrointestinal fatty acid uptake and effects on hepatic fat metabolism. Nevertheless, our present findings fit well with the previous report that UAG inhibits isoproterenolinduced lipolysis (23) and stimulates lipid accumulation in human visceral adipocytes (37), as well as in murine preadipocyte cells (38). Interestingly, the inhibitory action on lipolysis seems to be the only common action for nonacylated ghrelin and AG (18,23).…”

Does des-acyl ghrelin improve glycemic control in obese diabetic subjects by decreasing acylated ghrelin levels?

“…Another population to investigate might be patients with the metabolic syndrome, especially since reports suggest that diabetes and obesity are linked with a relative DAG deficiency or an increased AG:DAG ratio (20,21,22,23).…”

Ghrelin Gene Products in Acute and Chronic Inflammation

“…Both peptides promote the differentiation of skeletal myoblasts, preadipocytes, and embryonic stem cells toward cardiomyocytes (Filigheddu et al 2007;Gao et al 2012Gao et al , 2013Giovambattista et al 2008;Miegueu et al 2011). Moreover, they affect, either positively or negatively, proliferation of numerous cell types including osteoblasts, pancreatic b cells, islets and islet microendothelial cells, myoblasts, and adrenocortical tumor cells (Delhanty et al 2006(Delhanty et al , 2007Favaro et al 2012;Filigheddu et al 2007;Granata et al 2007).…”

“…Successive works, however, did not support these assertions (Bassil et al 2007;Chartrel et al 2007;Lauwers et al 2006), and the biological role of obestatin is still debated (Lacquaniti et al 2011). Nevertheless, obestatin has several biological activities, including protective effects on the cardiovascular system (Agnew et al 2012;Alloatti et al 2010;Aragno et al 2012), promotion of adipocytes survival, differentiation, and metabolism Gurriarán-Rodríguez et al 2011;Miegueu et al 2011;Pruszynska-Oszmalek et al 2013), induction of myoblasts differentiation and promotion of skeletal muscle regeneration (Gurriarán-Rodríguez et al 2012), inhibition of pancreatic b-cell and islets apoptosis, stimulation of glucose-stimulated insulin secretion in both normal and diabetic animal models, and enhancement of functional bcell generation from pancreatic precursor cells (Baragli et al 2013;Granata et al 2008Granata et al , 2010. Notably by an evolutionary point of view, while ghrelin is mainly involved in food intake, obestatin has an inhibitory effect on water drinking by acting on mechanisms involved in the thirst (Samson et al 2007) and decreases vasopressin concentration in plasma (Samson et al 2008).…”