Autonomous and self-sustained circadian oscillators displayed in human islet cells

Abstract

Aims/hypothesisFollowing on from the emerging importance of the pancreas circadian clock on islet function and the development of type 2 diabetes in rodent models, we aimed to examine circadian gene expression in human islets. The oscillator properties were assessed in intact islets as well as in beta cells.MethodsWe established a system for long-term bioluminescence recording in cultured human islets, employing lentivector gene delivery of the core clock gene Bmal1 (also known as Arntl)-luciferase reporter. Beta cells were stably labelled using a rat insulin2 promoter fluorescent construct. Single-islet/cell oscillation profiles were measured by combined bioluminescence–fluorescence time-lapse microscopy.ResultsHuman islets synchronised in vitro exhibited self-sustained circadian oscillations of Bmal1-luciferase expression at both the population and single-islet levels, with period lengths of 23.6 and 23.9 h, respectively. Endogenous BMAL1 and CRY1 transcript expression was circadian in synchronised islets over 48 h, and antiphasic to REV-ERBα (also known as NR1D1), PER1, PER2, PER3 and DBP transcript circadian profiles. HNF1A and PDX1 exhibited weak circadian oscillations, in phase with the REV-ERBα transcript. Dispersed islet cells were strongly oscillating as well, at population and single-cell levels. Importantly, beta and non-beta cells revealed oscillatory profiles that were well synchronised with each other.Conclusions/interpretationWe provide for the first time compelling evidence for high-amplitude cell-autonomous circadian oscillators displayed in human pancreatic islets and in dispersed human islet cells. Moreover, these clocks are synchronised between beta and non-beta cells in primary human islet cell cultures.Electronic supplementary materialThe online version of this article (doi:10.1007/s00125-012-2779-7) contains peer-reviewed but unedited supplementary material, which is available to authorised users.

Circadian Mechanisms in Bioenergetics and Cell Metabolism

“…Subsequent studies in three other groups have corroborated our observation that local function of the clock transcription factor in islets is crucial for normal glucose homeostasis (Sadacca et al 2011;Lee et al 2013;Pulimeno et al 2013). Importantly, work from the Dibner laboratory has been the first to manipulate and monitor clock function in isolated human islet cells, raising the possibility that future investigation into circadian cell physiology will yield new understanding of beta cell failure in man (Pulimeno et al 2013). In recently published work, we have developed tamoxifen-inducible Cre-LoxP technology to conditionally eliminate clock gene function in pancreas (PMID 26542580).…”

“…Against this backdrop, work from our laboratory using circadian clock mutant mice first revealed an essential role for the intrinsic beta cell clock in insulin secretion, beta cell development, and diabetes mellitus (Marcheva et al 2010). Subsequent studies in three other groups have corroborated our observation that local function of the clock transcription factor in islets is crucial for normal glucose homeostasis (Sadacca et al 2011;Lee et al 2013;Pulimeno et al 2013). Importantly, work from the Dibner laboratory has been the first to manipulate and monitor clock function in isolated human islet cells, raising the possibility that future investigation into circadian cell physiology will yield new understanding of beta cell failure in man (Pulimeno et al 2013).…”

The role of melatonin in diabetes: therapeutic implications

“…Deregulation of the circadian system is associated with the instance of metabolic syndrome, including diabetes and obesity (36). The transcription factors that maintains rhythmic functions consist of the clock regulators including the clock circadian regulator (Clock) and Aryl hydrocarbon receptor nuclear translocator-like (Arntl, also known as Bmal1) that heterodimerize and activate transcription of target genes, including Period (Per1, 2, and 3) and Cryptochrome (Cry 1 and 2) (37).…”

Pancreatic α- and β-cellular clocks have distinct molecular properties and impact on islet hormone secretion and gene expression

“…Circadian oscillators in the endocrine pancreas have been demonstrated recently to play an essential role in driving transcription and function of the pancreatic islet in mice and humans (Marcheva et al 2010;Sadacca et al 2011;Pulimeno et al 2013;Qian et al 2013;Perelis et al 2015a;Saini et al 2016). Moreover, ablation of the islet clock in mouse models, including islet clock perturbation induced at an adult age, directly triggers the onset of type 2 diabetes (T2D) (Marcheva et al 2010;Sadacca et al 2011;Perelis et al 2015a).…”