Genetic analyses of the QT interval and its components in over 250K individuals identifies new loci and pathways affecting ventricular depolarization and repolarization

The QT interval is an electrocardiographic measure representing the sum of ventricular depolarization (QRS duration) and repolarization (JT interval). Abnormalities of the QT interval are associated with potentially fatal ventricular arrhythmia. We conducted genome-wide multi-ancestry analyses in >250,000 individuals and identified 177, 156 and 121 independent loci for QT, JT and QRS, respectively, including a male-specific X-chromosome locus. Using gene-based rare-variant methods, we identified associations with Mendelian disease genes. Enrichments were observed in established pathways for QT and JT, with new genes indicated in insulin-receptor signalling and cardiac energy metabolism. In contrast, connective tissue components and processes for cell growth and extracellular matrix interactions were significantly enriched for QRS. We demonstrate polygenic risk score associations with atrial fibrillation, conduction disease and sudden cardiac death. Prioritization of druggable genes highlighted potential therapeutic targets for arrhythmia. Together, these results substantially advance our understanding of the genetic architecture of ventricular depolarization and repolarization.

PHOSPHO1 is a skeletal regulator of insulin resistance and obesity

Background The classical functions of the skeleton encompass locomotion, protection and mineral homeostasis. However, cell-specific gene deletions in the mouse and human genetic studies have identified the skeleton as a key endocrine regulator of metabolism. The bone-specific phosphatase, Phosphatase, Orphan 1 (PHOSPHO1), which is indispensable for bone mineralisation, has been recently implicated in the regulation of energy metabolism in humans, but its role in systemic metabolism remains unclear. Here, we probe the mechanism underlying metabolic regulation by analysing Phospho1 mutant mice. Results Phospho1−/− mice exhibited improved basal glucose homeostasis and resisted high-fat-diet-induced weight gain and diabetes. The metabolic protection in Phospho1−/− mice was manifested in the absence of altered levels of osteocalcin. Osteoblasts isolated from Phospho1−/− mice were enriched for genes associated with energy metabolism and diabetes; Phospho1 both directly and indirectly interacted with genes associated with glucose transport and insulin receptor signalling. Canonical thermogenesis via brown adipose tissue did not underlie the metabolic protection observed in adult Phospho1−/− mice. However, the decreased serum choline levels in Phospho1−/− mice were normalised by feeding a 2% choline rich diet resulting in a normalisation in insulin sensitivity and fat mass. Conclusion We show that mice lacking the bone mineralisation enzyme PHOSPHO1 exhibit improved basal glucose homeostasis and resist high-fat-diet-induced weight gain and diabetes. This study identifies PHOSPHO1 as a potential bone-derived therapeutic target for the treatment of obesity and diabetes.

Phosphorylated and O-GlcNAc Modified IRS-1 (Ser1101) and -2 (Ser1149) Contribute to Human Diabetes type II

Background: The prevalence of the chronic metabolic disorder Type 2 diabetes mellitus (T2DM) is increasing steadily, and has even turned into an epidemic in some countries. T2DM results from defective responses to insulin and obesity is a major factor behind insulin resistance in T2DM. Insulin receptor substrate (IRS) proteins are adaptor proteins in the insulin receptor signalling pathway. The insulin signalling is controlled through tyrosine phosphorylation of IRS-1 and IRS2, and dysregulation of IRS proteins signalling may lead to glucose intolerance and eventually insulin resistance. Objective: In this work, we suggest that both glycosylation (O-GlcNAc modification) and phosphorylation of IRS-1 and -2 are involved in the pathogenesis of T2DM. Methods: Phosphorylation and O-GlcNAc modifications (Ser1101 in IRS-1 and Ser1149 in IRS-2) proteins were determined experimentally by sandwich ELISA with specific antibodies and with bioinformatics tools. Results: When IRS-1 (on Ser1101) and IRS-2 (Ser1149) become glycosylated following an increase in UDP-GlcNAc pools, it may contribute to insulin resistance. Whereas when the same (IRS-1 on Ser1101 and IRS-2 on Ser1149) are phosphorylated, the insulin signalling is inhibited. Discussion: In this work OGlcNAc-modified proteins were specifically detected using O-GlcNAc-specific antibodies, suggesting that elevated levels of O-GlcNAc-modified proteins are found, independently of their possible involvement in AGEs. Conclusion: This study suggests a mechanism, which is controlled by posttranslational modifications, and may contribute to the pathogenesis of type II diabetes.

PHOSPHO1, a novel skeletal regulator of insulin resistance and obesity

The skeleton is recognised as a key endocrine regulator of metabolism. Here we show that mice lacking the bone mineralization enzyme PHOSPHO1 (Phospho1-/-) exhibited improved basal glucose homeostasis and resisted high-fat-diet induced weight gain and diabetes. The metabolic protection in Phospho1-/- mice was manifested in the absence of altered levels of osteocalcin. Osteoblasts isolated from Phospho1-/- mice were enriched for genes associated with energy metabolism and diabetes; Phospho1 both directly and indirectly interacted with genes associated with glucose transport and insulin receptor signalling. Canonical thermogenesis via brown adipose tissue did not underlie the metabolic protection observed in adult Phospho1-/- mice. However, the decreased serum choline levels in Phospho1-/- mice were normalized by feeding a 2% choline rich diet resulting in a normalization in insulin sensitivity and fat mass. This study identifies PHOSPHO1 as a potential therapeutic target for the treatment of obesity and diabetes.

In silico results of ϰ-Opioid receptor antagonists as ligands for the second bromodomain of the Pleckstrin Homology Domain Interacting Protein

Pleckstrin Homology Domain Interacting Protein (PHIP) is a member of the BRWD1-3 Family (Bromodomain and WD repeat-containing proteins). PHIP (BRWD2, WDR11) contains a WD40 repeat (methyl-lysine binder) and 2 bromodomains (acetyl-lysine binder). It was discovered through interactions with the pleckstrin homology domain of Insulin Receptor Signalling (IRS) proteins and has been shown to mediate transcriptional responses in pancreatic islet cells and postnatal growth. An initial hit for the second bromodomain of PHIP (PHIP(2)) was discovered in 2012, with consecutive research yielding a candidate with a binding affinity of 68μM. PHIP(2) is an atypical category III bromodomain with a threonine (THR1396) where an asparagine residue would usually be. In the standard case, this pocket holds four water molecules, but in the case of PHIP(2), there is room for one extra water molecule - also known as “PHIP water”, able to mediate interaction between THR1396 and the typical water network at the back of the binding pocket. We present first ever results of two ϰ-Opioid receptor (KOR) antagonists with distinct pharmacophores having an estimated binding affinity in the nM to μM range, as well as higher binding affinities for every currently discovered PHIP(2) ligand towards KOR. Finally, we also demonstrate selectivity of LY-255582 and LY-2459989 towards PHIP(2) over other bromodomains.

Acupuncture Relieves Motion Sickness via the Irβ-Erk1/2-Dependent Insulin Receptor Signalling Pathway

Objective Acupuncture has been widely used for the treatment of motion sickness (MS), but the underlying mechanisms are unclear. The aim of this research was to study the mechanism of acupuncture in the treatment of MS. Methods To observe the effects of acupuncture in the treatment of MS, 80 rats were randomised into five groups that were subjected to acceleration and either remained untreated (CTRL), or received restraint (REST), scopolamine (SCOP) or acupuncture at SP4 (sham) or PC6+ST36 (verum) acupuncture points. To study the mechanism underlying the effects of acupuncture in the treatment of MS, 48 rats were randomised into three groups: acupuncture+extracellular regulated protein kinases (ERK) 1/2 inhibitor (ERKinh), acupuncture+insulin receptor (IR) antagonist (IRant), and acupuncture+vehicle (VEH). After acceleration, the MS index (MSI) and spontaneous activity (SA) of the rats were recorded. Serum stress hormones, Fos-positive cells, c-fos mRNA in the vestibular nucleus, and IRβ-, p-IRβ-, ERK1/2- and p-ERK1/2-positive cells in the dorsal motor nucleus of the vagus nerve (DMV) were detected. Results After acceleration, MS symptoms in the PC6+ST36 and SCOP groups were reduced compared with the CTRL, REST, and SP4 groups. The number of p-IRβ- and p-ERK1/2-positive cells and insulin levels were higher in the PC6+ST36 group than in the CTRL, REST, and SP4 groups. After ERK1/2 inhibitor and IR antagonist treatment, MS symptoms in the VEH group were lower than in the ERKinh and IRant groups. Conclusions Our study demonstrates that acupuncture significantly alleviates MS through the IRβ-ERK1/2-dependent insulin receptor signalling pathway in the DMV