Multisite SUMOylation restrains DNA polymerase η interactions with DNA damage sites.

Translesion DNA synthesis (TLS) mediated by low-fidelity DNA polymerases is an essential cellular mechanism for bypassing DNA lesions that obstruct DNA replication progression. However, the access of TLS polymerases to the replication machinery must be kept tightly in check to avoid excessive mutagenesis. Recruitment of DNA polymerase η (Pol η) and other Y-family TLS polymerases to damaged DNA relies on proliferating cell nuclear antigen (PCNA) monoubiquitylation and is regulated at several levels. Using a microscopy-based RNAi screen, here we identified an important role of the SUMO modification pathway in limiting Pol η interactions with DNA damage sites in human cells. We found that Pol η undergoes DNA damage- and protein inhibitor of activated STAT 1 (PIAS1)-dependent polySUMOylation upon its association with monoubiquitylated PCNA, rendering it susceptible to extraction from DNA damage sites by SUMO-targeted ubiquitin ligase (STUbL) activity. Using proteomic profiling, we demonstrate that Pol η is targeted for multisite SUMOylation, and that collectively these SUMO modifications are essential for PIAS1- and STUbL-mediated displacement of Pol η from DNA damage sites. These findings suggest that a SUMO-driven feedback inhibition mechanism is an intrinsic feature of TLS-mediated lesion bypass functioning to curtail the interaction of Pol η with PCNA at damaged DNA to prevent harmful mutagenesis.

Effects of daily administration of melatonin before bedtime on fasting insulin, glucose and insulin sensitivity in healthy adults and patients with metabolic diseases. A systematic review and meta-analysis.

BACKGROUND: Melatonin is increasingly used as a pharmacological sleep aid but it is also emerging as a regulator of glucose homoeostasis. Yet, previous research has been ambiguous with reports of both positive and negative effects of melatonin on glucose metabolism. OBJECTIVES: To assess the effect of daily treatment with melatonin on fasting glucose, insulin, insulin sensitivity and haemoglobin A1c (HbA1c) levels. DATA SOURCES: MEDLINE, EMBASE, CENTRAL, clinicaltrials.gov and clinicaltrialsregister.eu were systematically searched. ELIGIBILITY CRITERIA, PARTICIPANTS AND INTERVENTIONS: All randomized, placebo-controlled studies with melatonin treatment were assessed. We included studies with daily melatonin treatment (≥2 weeks) of healthy adults or patients with metabolic diseases. METHODS: Hedges' g differences were calculated for the metabolic parameters of the included studies, heterogeneity was assessed with χ2 and I2 tests and meta-analyses were performed with the random-effects model. RESULTS: Long-term treatment with melatonin did not change fasting glucose significantly compared with placebo (g: -0.07 [-0.22 to 0.08], n = 603) but it reduced fasting insulin levels slightly (g: -0.27 [-0.50 to -0.04], n = 278) and trended towards reduced insulin resistance (HOMA-IR) (g: -0.20 [-0.44 to 0.03], n = 278). HbA1c levels were largely unaffected by melatonin treatment compared with placebo (g: 0.14 [-0.19 to 0.46], n = 142). CONCLUSIONS: With the available literature, melatonin seems to be a glucose-metabolic safe sleep aid in patients with metabolic diseases and in healthy adults. It may even have beneficial glucose-metabolic effects as fasting insulin levels were reduced in this meta-analysis, but the confidence intervals of the meta-analyses are wide, underscoring the need for further research within this field.

Protein interaction screening for the ankyrin repeats and suppressor of cytokine signaling (SOCS) box (ASB) family identify Asb11 as a novel endoplasmic reticulum resident ubiquitin ligase.

The ankyrin and SOCS (suppressor of cytokine signaling) box (ASB) family of proteins function as the substrate recognition subunit in a subset of Elongin-Cullin-SOCS (ECS) E3 ubiquitin ligases. Despite counting 18 members in humans, the identity of the physiological targets of the Asb proteins remains largely unexplored. To increase our understanding of the function of ASB proteins, we conducted a family-wide SILAC (stable isotope labeling by amino acids in cell culture)-based protein/protein interaction analysis. This investigation led to the identification of novel as well as known ASB-associated proteins like Cullin 5 and Elongins B/C. We observed that several proteins can be bound by more than one Asb protein. The additional exploration of this phenomenon demonstrated that ASB-Cullin 5 complexes can oligomerize and provides evidence that Cullin 5 forms heterodimeric complexes with the Cullin 4a-DDB1 complex. We also demonstrated that ASB11 is a novel endoplasmic reticulum-associated ubiquitin ligase with the ability to interact and promote the ubiquitination of Ribophorin 1, an integral protein of the oligosaccharyltransferase (OST) glycosylation complex. Moreover, expression of ASB11 can increase Ribophorin 1 protein turnover in vivo. In summary, we provide a comprehensive protein/protein interaction data resource that can aid the biological and functional characterization of ASB ubiquitin ligases.

Whey Protein Premeal Lowers Postprandial Glucose Concentrations in Adults Compared with Water-The Effect of Timing, Dose, and Metabolic Status: a Systematic Review and Meta-analysis.

BACKGROUND: Serving whey protein before a meal in order to lower postprandial blood glucose concentrations is known as a premeal. The underlying mechanisms are only partly understood but may involve stimulation of glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and insulin secretion together with a slower gastric emptying rate. OBJECTIVES: The objective of this systematic review and meta-analysis was to review all randomized clinical trials investigating premeals with whey protein in comparison with a nonactive comparator (control) that evaluated plasma glucose, GLP-1, GIP, insulin, and/or gastric emptying rate. Secondary aims included subgroup analyses on the timing and dose of the premeal together with the metabolic state of the participants [lean, obese, and type 2 diabetes mellitus (T2DM)]. METHODS: We searched EMBASE, CENTRAL, PUBMED, and clinicaltrials.gov and found 16 randomized crossover trials with a total of 244 individuals. The last search was performed on 9 August, 2022. RESULTS: Whey protein premeals lowered peak glucose concentration by -1.4 mmol/L [-1.9 mmol/L; -0.9 mmol/L], and the area under the curve for glucose was -0.9 standard deviation (SD) [-1.2 SD; -0.6 SD] compared with controls (high certainty). In association with these findings, whey protein premeals elevated GLP-1 (low certainty) and peak insulin (high certainty) concentrations and slowed gastric emptying rate (high certainty) compared with controls. Subgroup analyses showed a more pronounced and prolonged glucose-lowering effect in individuals with T2DM compared with participants without T2DM. The available evidence did not elucidate the role of GIP. The protein dose used varied between 4 and 55 g, and meta-regression analysis showed that the protein dose correlated with the glucose-lowering effects. CONCLUSIONS: In conclusion, whey protein premeals lower postprandial blood glucose, reduce gastric emptying rate, and increase peak insulin. In addition, whey protein premeals may elevate plasma concentrations of GLP-1. Whey protein premeals may possess clinical potential, but the long-term effects await future clinical trials.

ß-Lactoglobulin Elevates Insulin and Glucagon Concentrations Compared with Whey Protein-A Randomized Double-Blinded Crossover Trial in Patients with Type Two Diabetes Mellitus.

Whey protein is an insulinotropic fraction of dairy that reduces postprandial glucose levels in patients with type 2 diabetes mellitus (T2DM). We have recently shown that ß-lactoglobulin (BLG), the largest protein fraction of whey, elevates insulin concentrations compared with iso-nitrogenous whey protein isolate (WPI) in healthy individuals. We therefore hypothesized that BLG pre-meals would lower glucose levels compared with WPI in patients with T2DM. We investigated 16 participants with T2DM using a randomized double-blinded cross-over design with two pre-meal interventions, (i) 25 g BLG and (ii) 25 g WPI prior to an oral glucose tolerance test (OGTT), followed by four days of continuous glucose monitoring (CGM) at home. BLG increased concentrations of insulin with 10%, glucagon with 20%, and glucose with 10% compared with WPI after the OGTT (all p < 0.05). Both BLG and WPI reduced the interstitial fluid (ISF) glucose concentrations (using CGM) with 2 mM and lowered glycemic variability with 10-15%, compared with tap-water (p < 0.05), and WPI lowered the ISF glucose with 0.5 mM compared with BLG from 120 min and onwards (p < 0.05). In conclusion, BLG pre-meals resulted in higher insulin, glucagon, and glucose concentrations compared with WPI in participants with T2DM. Pre-meal servings of WPI remains the most potent protein in terms of lowering postprandial glucose excursions.

Subclinical hyperthyroidism and the risk of developing cardiovascular disease - a systematic review.

INTRODUCTION: It is debated whether the presence of subclinical hyperthyroidism (SH) constitutes an increased risk of cardiovascular disease. This review presents a summary of the literature examining the association between SH and atrial fibrillation (AF), heart failure (HF), myocardial infarction (MI) and cardiovascular mortality. METHODS: A systematic literature search of the PubMed database was performed. Studies were included if they were of observational design, about SH in humans, and had AF, HF, MI and/or cardiovascular mortality as outcome, were published in either Danish or English language and included euthyroid controls. RESULTS: A total of 33 papers were suitable for inclusion. Thus, 13 papers on AF and five papers on HF were included for review and supported an association between SH and AF and HF, respectively. In all, 14 papers on MI and 15 papers on cardiovascular mortality were included for review; but, overall, they did not support an association between SH and MI or cardiovascular mortality. CONCLUSIONS: Based on our review, current literature supports an association between SH and AF and HF, respectively; but not between SH and MI or cardiovascular mortality.

Diet and Healthy Lifestyle in the Management of Gestational Diabetes Mellitus.

Gestational diabetes mellitus (GDM) among pregnant women increases the risk of both short-term and long-term complications, such as birth complications, babies large for gestational age (LGA), and type 2 diabetes in both mother and offspring. Lifestyle changes are essential in the management of GDM. In this review, we seek to provide an overview of the lifestyle changes which can be recommended in the management of GDM. The diet recommended for women with GDM should contain sufficient macronutrients and micronutrients to support the growth of the foetus and, at the same time, limit postprandial glucose excursions and encourage appropriate maternal gestational weight gain. Blood glucose excursions and hyperglycaemic episodes depend on carbohydrate-intake. Therefore, nutritional counselling should focus on the type, amount, and distribution of carbohydrates in the diet. Further, physical activity has beneficial effects on glucose and insulin levels and it can contribute to a better glycaemic control.

Licorice induced pseudohyperaldosteronism, severe hypertension, and long QT.

SUMMARY: Excessive intake of licorice may cause pseudohyperaldosteronism which, in turn, may lead to hypertension and hypokalemia. Severe hypokalemia may lead to electrocardiogram (ECG) changes including long QT interval potentially progressing into malignant arrhythmias. Here we present a 43-year-old woman admitted to the hospital with chest pain and a stinging sensation in the upper extremities. Her peak blood pressure was 177/98 mmHg and the blood test revealed low plasma potassium of 1.9 mmol/L. The ECG revealed flattened T-waves and long QT interval. Prior to admission, the patient had increased licorice ingestion to a total of some 70 g daily. The licorice intake was stopped and potassium was administrated orally and intravenously. Plasma potassium normalized and the ECG changes remitted. To our knowledge a few other cases of licorice-induced pseudohyperaldosteronism and long QT interval have previously been reported. This underlines the importance of quantifying licorice intake in younger people with unexplained high blood pressure and low potassium. LEARNING POINTS: Even small amounts of licorice daily may increase the risk of developing hypertension; therefore, licorice should be asked for specifically. Even though licorice intake is very easy to cover in the patient's history, it is often missed. Excessive licorice intake may course severe hypokalemia causing long QT interval in the ECG recording, potentially progressing into arrhythmias and even cardiac arrest/sudden death. Hypokalemia <3 mmol/L and present ECG changes should be treated with potassium intravenously. Licorice-induced hypertension may be associated with syndrome of apparent mineralocorticoid excess (SAME). Plasma renin and aldosterone are both low at diagnosis and normalize when licorice is stopped.

TRAIP is a PCNA-binding ubiquitin ligase that protects genome stability after replication stress.

Cellular genomes are highly vulnerable to perturbations to chromosomal DNA replication. Proliferating cell nuclear antigen (PCNA), the processivity factor for DNA replication, plays a central role as a platform for recruitment of genome surveillance and DNA repair factors to replication forks, allowing cells to mitigate the threats to genome stability posed by replication stress. We identify the E3 ubiquitin ligase TRAIP as a new factor at active and stressed replication forks that directly interacts with PCNA via a conserved PCNA-interacting peptide (PIP) box motif. We show that TRAIP promotes ATR-dependent checkpoint signaling in human cells by facilitating the generation of RPA-bound single-stranded DNA regions upon replication stress in a manner that critically requires its E3 ligase activity and is potentiated by the PIP box. Consequently, loss of TRAIP function leads to enhanced chromosomal instability and decreased cell survival after replication stress. These findings establish TRAIP as a PCNA-binding ubiquitin ligase with an important role in protecting genome integrity after obstacles to DNA replication.

DVC1 (C1orf124) is a DNA damage-targeting p97 adaptor that promotes ubiquitin-dependent responses to replication blocks.

Ubiquitin-mediated processes orchestrate critical DNA-damage signaling and repair pathways. We identify human DVC1 (C1orf124; Spartan) as a cell cycle-regulated anaphase-promoting complex (APC) substrate that accumulates at stalled replication forks. DVC1 recruitment to sites of replication stress requires its ubiquitin-binding UBZ domain and PCNA-binding PIP box motif but is independent of RAD18-mediated PCNA monoubiquitylation. Via a conserved SHP box, DVC1 recruits the ubiquitin-selective chaperone p97 to blocked replication forks, which may facilitate p97-dependent removal of translesion synthesis (TLS) DNA polymerase η (Pol η) from monoubiquitylated PCNA. DVC1 knockdown enhances UV light-induced mutagenesis, and depletion of human DVC1 or the Caenorhabditis elegans ortholog DVC-1 causes hypersensitivity to replication stress-inducing agents. Our findings establish DVC1 as a DNA damage-targeting p97 adaptor that protects cells from deleterious consequences of replication blocks and suggest an important role of p97 in ubiquitin-dependent regulation of TLS.