Co-storage and release of insulin-like peptide-5, glucagon-like peptide-1 and peptideYY from murine and human colonic enteroendocrine cells

Abstract

ObjectiveInsulin-like peptide-5 (INSL5) is an orexigenic gut hormone found in a subset of colonic and rectal enteroendocrine L-cells together with the anorexigenic hormones glucagon-like peptide-1 (GLP-1) and peptideYY (PYY). Unlike GLP-1 and PYY, INSL5 levels are elevated by calorie restriction, raising questions about how these hormones respond to different stimuli when they arise from the same cell type. The aim of the current study was to identify whether and how INSL5, GLP-1 and PYY are co-secreted or differentially secreted from colonic L-cells.MethodsAn inducible reporter mouse (Insl5-rtTA) was created to enable selective characterisation of Insl5-expressing cells. Expression profiling and Ca2+-dynamics were assessed using TET-reporter mice. Secretion of INSL5, PYY, and GLP-1 from murine and human colonic crypt cultures was quantified by tandem mass spectrometry. Vesicular co-localisation of the three hormones was analysed in 3D-SIM images of immunofluorescently-labelled murine colonic primary cultures and tissue sections.ResultsINSL5-producing cells expressed a range of G-protein coupled receptors previously identified in GLP-1 expressing L-cells, including Ffar1, Gpbar1, and Agtr1a. Pharmacological or physiological agonists for these receptors triggered Ca2+ transients in INSL5-producing cells and stimulated INSL5 secretion. INSL5 secretory responses strongly correlated with those of PYY and GLP-1 across a range of stimuli. The majority (>80%) of secretory vesicles co-labelled for INSL5, PYY and GLP-1.ConclusionsINSL5 is largely co-stored with PYY and GLP-1 and all three hormones are co-secreted when INSL5-positive cells are stimulated. Opposing hormonal profiles observed in vivo likely reflect differential stimulation of L-cells in the proximal and distal gut.

Important Role of the GLP-1 Axis for Glucose Homeostasis after Bariatric Surgery

“…Steady-state Exendin-9 concentrations ( Figure 1H) were $0.4 mg/mL ($120 nmol/L), $2-fold above the binding affinity of Exendin-9 for GLP1R in human insulinoma cells (Waser and Reubi, 2011). PYY concentrations were higher after Exendin-9 than after placebo ( Figure 1I), mirroring the elevated GLP-1 levels and likely reflecting that PYY and GLP-1 are released from the same EEC type (Billing et al, 2018;Habib et al, 2013). Glucose-dependent insulinotropic polypeptide (GIP) concentrations were reduced by Exendin-9 ( Figure 1J), suggesting that endogenous GLP-1 enhances GIP secretion-a finding not previously reported.…”

Diversity of enteroendocrine cells investigated at cellular and subcellular levels: the need for a new classification scheme

“…Furthermore, electron microscopy demonstrated that in cells coexpressing proglucagon product and PYY in human ileum, nearly all granules were labelled with GLP-1 and glicentin antisera, whereas a minority of vesicles contained PYY immunoreactivity (Eissele et al 1992). In the colon, GLP-1 and PYY are generally in the same vesicles (Billing et al 2018; Fothergill et al 2018). In fact, Billing et al (2018) found that GLP-1, PYY and INSL5 were generally costored in the same vesicles in murine colonic EECs.…”

“…In the colon, GLP-1 and PYY are generally in the same vesicles (Billing et al 2018; Fothergill et al 2018). In fact, Billing et al (2018) found that GLP-1, PYY and INSL5 were generally costored in the same vesicles in murine colonic EECs. This is consistent with an electron microscope study showing that PYY and proglucagon-derived peptides are costored within secretory vesicles in cat colon and human rectum (Böttcher et al 1986).…”

Dissecting the Physiology and Pathophysiology of Glucagon-Like Peptide-1

“…Once translated, the 180 amino acid long GCG protein is processed by two proteases, Psck1 and Psck3, to give GLP-1, GLP-2 but also the less studied and understood glicentin and oxyntomodulin ( 43 ). Other peptide hormones, such as insulin-like peptide 5 (INSL5) ( 44 , 45 ), PYY ( 46 ), GIP and neurotensin ( 17 , 47 ) can be co-expressed with the GCG products depending on the topographical localization of the cell; surprisingly, it appears that GLP-1 and PYY can be excreted independently possibly due to the existence of compartmentalized secretory vesicles ( 48 ).…”