Biology subjects

Hastoy, B.

Publications and source records attributed to Hastoy, B..

3 recordsLinked to original sources

bioRxiv2018

Loss of ZnT8 function protects against diabetes by enhanced insulin secretion

A rare loss-of-function variant p.Arg138* in SLC30A8 encoding the zinc transporter 8 (ZnT8) enriched in Western Finland protects against type 2 diabetes (T2D). We recruited relatives of the identified carriers and showed that protection was associated with better insulin secretion due to enhanced glucose responsiveness and proinsulin conversion, especially compared with individuals matched for the genotype of a common T2D risk variant in SLC30A8, p.Arg325. In genome-edited human IPS-derived {beta}-like cells, we establish that the p.Arg138* variant results in reduced SLC30A8 expression due to haploinsufficiency. In human {beta}-cells loss of SLC30A8 leads to increased glucose responsiveness and reduced KATP channel function, which was also seen in isolated islets from carriers of the T2D-protective allele p.Trp325. These data position ZnT8 as an appealing target for treatment aiming at maintaining insulin secretion capacity in T2D.

genetics↗

bioRxiv2017

Electrophysiological properties of human β-cell lines EndoC-βH1 and -βH2 conform with human β-cells

The electrophysiological and secretory properties of the human {beta}-cell lines EndoC-{beta}H1 and EndoC-{beta}H2 were investigated. Both cell lines respond to glucose (6-20mM) with 2-to 3-fold stimulation of insulin secretion, an effect that was mimicked by tolbutamide (0.2mM) and reversed by diazoxide (0.5mM). Glucose-induced insulin release correlated with an elevation of [Ca2+]i, membrane depolarization and increased action potential firing. KATP channel activity at 1mM glucose is low and increasing glucose to 6 or 20mM reduced KATP channel activity to the same extent as application of the KATP channel blocker tolbutamide (0.2mM). The upstroke of the action potentials in EndoC-{beta}H1 and -{beta}H2 cells observed at high glucose principally reflects activation of L- and P/Q-type Ca2+ channels with some small contribution of TTX-sensitive Na+ channels. Action potential repolarization involves activation of voltage-gated Kv2.2 channels and large-conductance Ca2+-activated K+ channels. Exocytosis (measured by measurements of membrane capacitance) was triggered by membrane depolarizations >10ms to membrane potentials above -30mV. Both cell lines were well-granulated (6,000-15,000 granules/cell) and granules consisted of a central insulin core surrounded by a clear halo. We conclude that the EndoC-{beta}H1 and -{beta}H2 cells share many features of primary human {beta}-cells and that they represent a useful experimental model.

cell biology↗

bioRxiv2017

Type 2 Diabetes Risk Alleles Reveal a Role for Peptidylglycine Alpha-amidating Monooxygenase in Beta Cell Function

Molecular mechanisms underpinning the genetic risk for type 2 diabetes (T2D) remain poorly understood, hindering translation into new therapies. Recently, genome-wide studies identified two coding variants in Peptidylglycine Alpha-amidating Monooxygenase (PAM) associated with T2D risk and measures of beta cell dysfunction. Here, we demonstrate that both risk alleles impact negatively on overall PAM activity, but via distinct effects on expression and catalytic function. In a human beta cell model, PAM silencing caused decreased insulin content and altered dynamics of granule exocytosis. Analysis of primary human beta cells from cadaveric donors confirmed an effect on exocytosis in carriers of the p.D563G T2D-risk allele. Finally, we show that the granular packaging protein Chromogranin A is a PAM substrate and a strong candidate for mediating downstream effects on insulin secretion. Taken together, our results establish a role for PAM in beta cell function, and uncover a novel mechanism for T2D-associated PAM alleles.

genetics↗