Lipid signals and insulin resistance

The metabolic syndrome, a cluster of metabolic derangements that include obesity, glucose intolerance, dyslipidemia and hypertension, is a major risk factor for cardiovascular disease. Insulin resistance has been proposed to be the common feature that links obesity to the metabolic syndrome, but the mechanism remains obscure. Although the excess content of triacylglycerol in muscle and liver is highly associated with insulin resistance in these tissues, triacylglycerol itself is not causal but merely a marker. Thus, attention has turned to the accumulation of cellular lipids known to have signaling roles. This review will discuss recent progress in understanding how glycerolipids and related lipid intermediates may impair insulin signaling

The prevalence of nurse burnout and its association with telomere length pre and during the COVID-19 pandemic

Background Burnout is a work-related stress syndrome characterized by emotional exhaustion, depersonalization, and reduced personal accomplishment. Nurse burnout is related to nurses’ deteriorating mental health and poorer patient care quality and thus, is a significant concern in healthcare. The Coronavirus Disease 2019 (COVID-19) pandemic has swept the world and distressed the healthcare systems. Because of the body’s stress mechanism, it is vital to examine the current prevalence of nurse burnout and understand it at a biological level, using an epigenetic biomarker, telomere length. Purpose To determine the prevalence of burnout among nurses in the Peri-Operative and Labor & Delivery settings pre and during the COVID-19 pandemic and to examine the effects of burnout on absolute telomere length. Methods This is a cross-sectional study assessing the prevalence of nurses’ burnout and the relationships between nurses’ burnout and telomere length. Due to the COVID-19 pandemic, we had to stop the study during the mid of data collection. Even though the study was not designed to capture changes before and during the pandemic, we analyzed two groups’ data before and during the pandemic. The study took place in a US hospital. Nurses in the hospital’s Operating Room, Post-Anesthesia Care Unit, and Labor & Delivery Unit participated in the study. Maslach Burnout Inventory survey and nurses’ demographics were administered online. Telomere length was measured via finger-prick blood. Results 146 nurses participated in the study, with 120 participants’ blood samples collected. The high-level burnout rate was 70.5%. Correlation analysis did not reveal a direct correlation between nurse burnout and telomere length. However, in a multiple regression analysis, the final model contained the burnout subscale of emotional exhaustion, years as an RN, and work unit’s nursing care quality. There was a low degree of departure from normality of the mean absolute telomere length in the pre-pandemic group and a substantial degree of departure in the during-pandemic group. Conclusions Nurse burnout is a prevalent phenomenon in healthcare, and this study indicates that nurses currently experience high levels of burnout. Nurses’ cellular biomarker, telomere length, is shorter in the group of nurses during the COVID-19 pandemic than before. Appropriate measures should be implemented to decrease nurses’ burnout symptoms and improve nurses’ psychological and physical health. Nurses, especially those younger than 60, report higher burnout symptoms, particularly emotional exhaustion. This study indicates the need for intervention to promote nurses’ health during the pandemic and beyond. If not appropriately managed, nurse burnout may continue to be a significant issue facing the healthcare system

Inhibited Insulin Signaling in Mouse Hepatocytes Is Associated with Increased Phosphatidic Acid but Not Diacylglycerol

Although an elevated triacylglycerol content in non-adipose tissues is often associated with insulin resistance, the mechanistic relationship remains unclear. The data support roles for intermediates in the glycerol-3-phosphate pathway of triacylglycerol synthesis: diacylglycerol (DAG), which may cause insulin resistance in liver by activating PKCϵ, and phosphatidic acid (PA), which inhibits insulin action in hepatocytes by disrupting the assembly of mTOR and rictor. To determine whether increases in DAG and PA impair insulin signaling when produced by pathways other than that of de novo synthesis, we examined primary mouse hepatocytes after enzymatically manipulating the cellular content of DAG or PA. Overexpressing phospholipase D1 or phospholipase D2 inhibited insulin signaling and was accompanied by an elevated cellular content of total PA, without a change in total DAG. Overexpression of diacylglycerol kinase-θ inhibited insulin signaling and was accompanied by an elevated cellular content of total PA and a decreased cellular content of total DAG. Overexpressing glycerol-3-phosphate acyltransferase-1 or -4 inhibited insulin signaling and increased the cellular content of both PA and DAG. Insulin signaling impairment caused by overexpression of phospholipase D1/D2 or diacylglycerol kinase-θ was always accompanied by disassociation of mTOR/rictor and reduction of mTORC2 kinase activity. However, although the protein ratio of membrane to cytosolic PKCϵ increased, PKC activity itself was unaltered. These data suggest that PA, but not DAG, is associated with impaired insulin action in mouse hepatocytes

The Association of Arsenic Exposure and Metabolism With Type 1 and Type 2 Diabetes in Youth: The SEARCH Case-Control Study

Little is known about arsenic and diabetes in youth. We examined the association of arsenic with type 1 and type 2 diabetes in the SEARCH for Diabetes in Youth Case-Control (SEARCH-CC) study. Because one-carbon metabolism can influence arsenic metabolism, we also evaluated the potential interaction of folate and vitamin B12 with arsenic metabolism on the odds of diabetes

Amino acid-sensing mTOR signaling is involved in modulation of lipolysis by chronic insulin treatment in adipocytes

Chronically high insulin levels and increased circulating free fatty acids released from adipose tissue through lipolysis are two features associated with insulin resistance. The relationship between chronic insulin exposure and adipocyte lipolysis has been unclear. In the present study we found that chronic insulin exposure in 3T3-L1 adipocytes, as well as in mouse primary adipocytes, increased basal lipolysis rates. This effect of insulin on lipolysis was only observed when the mammalian target of rapamycin (mTOR) pathway was inhibited by rapamycin in the adipocytes. In addition, amino acid deprivation in adipocytes phenocopied the effect of rapamycin in permitting the stimulation of lipolysis by chronic insulin exposure. The phosphatidylinositol 3-kinase-Akt pathway does not appear to be involved in this insulin effect. Furthermore, we found that triacylglycerol hydrolase (TGH) activity was required for the stimulation of lipolysis by combined exposure to insulin and rapamycin. Therefore, we propose that nutrient sufficiency, mediated by an mTOR pathway, suppresses TGH-dependent lipolysis stimulated by chronic insulin exposure in adipocytes

3D Semantic VSLAM of Indoor Environment Based on Mask Scoring RCNN

In view of existing Visual SLAM (VSLAM) algorithms when constructing semantic map of indoor environment, there are problems with low accuracy and low label classification accuracy when feature points are sparse. This paper proposed a 3D semantic VSLAM algorithm called BMASK-RCNN based on Mask Scoring RCNN. Firstly, feature points of images are extracted by Binary Robust Invariant Scalable Keypoints (BRISK) algorithm. Secondly, map points of reference key frame are projected to current frame for feature matching and pose estimation, and an inverse depth filter is used to estimate scene depth of created key frame to obtain camera pose changes. In order to achieve object detection and semantic segmentation for both static objects and dynamic objects in indoor environments and then construct dense 3D semantic map with VSLAM algorithm, a Mask Scoring RCNN is used to adjust its structure partially, where a TUM RGB-D SLAM dataset for transfer learning is employed. Semantic information of independent targets in scenes provides semantic information including categories, which not only provides high accuracy of localization but also realizes the probability update of semantic estimation by marking movable objects, thereby reducing the impact of moving objects on real-time mapping. Through simulation and actual experimental comparison with other three algorithms, results show the proposed algorithm has better robustness, and semantic information used in 3D semantic mapping can be accurately obtained

Lipid signals and insulin resistance

The metabolic syndrome, a cluster of metabolic derangements that include obesity, glucose intolerance, dyslipidemia and hypertension, is a major risk factor for cardiovascular disease. Insulin resistance has been proposed to be the common feature that links obesity to the metabolic syndrome, but the mechanism remains obscure. Although the excess content of triacylglycerol in muscle and liver is highly associated with insulin resistance in these tissues, triacylglycerol itself is not causal but merely a marker. Thus, attention has turned to the accumulation of cellular lipids known to have signaling roles. This review will discuss recent progress in understanding how glycerolipids and related lipid intermediates may impair insulin signaling

Autophagy is involved in adipogenic differentiation by repressesing proteasome-dependent PPARγ2 degradation

10.1152/ajpendo.00640.2012American Journal of Physiology - Endocrinology and Metabolism3054E530-E539AJPM

Glycerol-3-phosphate acyltransferase-4-deficient mice are protected from diet-induced insulin resistance by the enhanced association of mTOR and rictor

Glycerol-3-phosphate acyltransferase (GPAT) activity is highly induced in obese individuals with insulin resistance, suggesting a correlation between GPAT function, triacylglycerol accumulation, and insulin resistance. We asked whether microsomal GPAT4, an isoform regulated by insulin, might contribute to the development of hepatic insulin resistance. Compared with control mice fed a high fat diet, Gpat4(−/−) mice were more glucose tolerant and were protected from insulin resistance. Overexpression of GPAT4 in mouse hepatocytes impaired insulin-suppressed gluconeogenesis and insulin-stimulated glycogen synthesis. Impaired glucose homeostasis was coupled to inhibited insulin-stimulated phosphorylation of Akt(Ser(473)) and Akt(Thr(308)). GPAT4 overexpression inhibited rictor's association with the mammalian target of rapamycin (mTOR), and mTOR complex 2 (mTORC2) activity. Compared with overexpressed GPAT3 in mouse hepatocytes, GPAT4 overexpression increased phosphatidic acid (PA), especially di16:0-PA. Conversely, in Gpat4(−/−) hepatocytes, both mTOR/rictor association and mTORC2 activity increased, and the content of PA in Gpat4(−/−) hepatocytes was lower than in controls, with the greatest decrease in 16:0-PA species. Compared with controls, liver and skeletal muscle from Gpat4(−/−)-deficient mice fed a high-fat diet were more insulin sensitive and had a lower hepatic content of di16:0-PA. Taken together, these data demonstrate that a GPAT4-derived lipid signal, likely di16:0-PA, impairs insulin signaling in mouse liver and contributes to hepatic insulin resistance