The effects of insulin on the endothelium

The genetic causal relationship between type 2 diabetes, glycemic traits and venous thromboembolism, deep vein thrombosis, pulmonary embolism: a two-sample Mendelian randomization study

OBJECTIVE

To investigate the genetic underpinnings of the association between type 2 diabetes (T2D), glycemic indicators such as fasting glucose (FG), fasting insulin (FI), and glycated hemoglobin (GH), and venous thromboembolism (VTE), encompassing deep vein thrombosis (DVT) and pulmonary embolism (PE), thereby contributing novel insights to the scholarly discourse within this domain.

METHODS

Genome-wide association study (GWAS) summary data pertaining to exposures (T2D, FG, FI, GH) and outcomes (VTE, DVT, PE) were acquired from the IEU Open GWAS database, encompassing participants of European descent, including both male and female individuals. Two-sample Mendelian randomization (MR) analyses were conducted utilizing the TwoSampleMR and MRPRESSO packages within the R programming environment. The primary analytical approach employed was the random-effects inverse variance weighted (IVW) method. Heterogeneity was assessed via Cochran's Q statistic for MR-IVW and Rucker's Q statistic for MR-Egger. Horizontal pleiotropy was evaluated using the intercept test of MR Egger and MR pleiotropy residual sum and outlier (MR-PRESSO) analysis, with the latter also employed for outlier detection. Additionally, a "Leave one out" analysis was conducted to ascertain the influence of individual single nucleotide polymorphisms (SNPs) on MR results.

RESULTS

The random-effects IVW analysis revealed a negative genetic causal association between T2D) and VTE (P = 0.008, Odds Ratio [OR] 95% confidence interval [CI] = 0.896 [0.827-0.972]), as well as between FG and VTE (P = 0.002, OR 95% CI = 0.655 [0.503-0.853]), GH and VTE (P = 0.010, OR 95% CI = 0.604 [0.412-0.884]), and GH and DVT (P = 0.002, OR 95% CI = 0.413 [0.235-0.725]). Conversely, the random-effects IVW analysis did not detect a genetic causal relationship between FI and VTE (P > 0.05), nor between T2D, FG, or FI and DVT (P > 0.05), or between T2D, FG, FI, or GH and PE (P > 0.05). Both the Cochran's Q statistic for MR-IVW and Rucker's Q statistic for MR-Egger indicated no significant heterogeneity (P > 0.05). Moreover, the intercept tests of MR Egger and MR-PRESSO suggested the absence of horizontal pleiotropy (P > 0.05). MR-PRESSO analysis identified no outliers, while the "Leave one out" analysis underscored that the MR analysis was not influenced by any single SNP.

CONCLUSION

Our investigation revealed that T2D, FG, and GH exhibit negative genetic causal relationships with VTE at the genetic level, while GH demonstrates a negative genetic causal relationship with DVT at the genetic level. These findings furnish genetic-level evidence warranting further examination of VTE, DVT, and PE, thereby making a contribution to the advancement of related research domains.

Glycemic and metabolic sub-classification of prediabetes and risk factors for cardiovascular disease in the D2d cohort

Objectives

Prediabetes represents a spectrum of metabolic abnormalities, including insulin resistance and secretory impairment, that carries increased cardiovascular disease (CVD) risk. It is unclear whether specific glycemic and metabolic sub-classifications are associated with CVD risk. This cross-sectional analysis of 3946 participants from the Vitamin D and Type 2 Diabetes (D2d) study cohort aimed to determine the associations between various baseline CVD risk factors, glycemic sub-classifications of prediabetes (FPG, 2hPG, and HbA1c), and measures of insulin sensitivity and secretion from an OGTT.

Methods

The metabolic syndrome and atherosclerotic cardiovascular disease (ASCVD) risk scores were determined for tertiles of insulin sensitivity (HOMA2S) and insulinogenic index (IGI). Unadjusted analyses showed elevated CVD risk factors in the lowest tertile for both IGI and HOMA2S.

Results

After adjustment for age, gender, race, obesity, and smoking status, the association remained between HOMA2S and ASCVD score (r = -0.11, p< 0.001) but not for IGI. Those who met at least 2 diagnosic criteria for prediabetes had the largest proportion (> 40%) of participants with high ASCVD risk score >20. A higher percentage of individuals that met all 3 criteria for prediabetes had metabolic syndrome and ASCVD risk score >20 (87.2% and 15.3%, respectively) than those who only met 1 prediabetes criterion (51.6% and 7.1%, respectively).

Conclusions

In conclusion, multiple metabolic (HOMA2S, IGI) and glycemic criteria of prediabetes (FPG, 2hPG, & HbA1c) are needed to fully recognize the elevated CVD risk profile that can manifest in prediabetes.

Insulin Receptors and Insulin Action in the Heart: The Effects of Left Ventricular Assist Devices

This year, 2022, marks the 100th anniversary of the isolation of human insulin and its administration to patients suffering from diabetes mellitus (DM). Insulin exerts many effects on the human body, including the cardiac tissue. The pathways implicated include the PKB/Akt signaling pathway, the Janus kinase, and the mitogen-activated protein kinase pathway and lead to normal cardiac growth, vascular smooth muscle regulation, and cardiac contractility. This review aims to summarize the existing knowledge and provide new insights on insulin pathways of cardiac tissue, along with the role of left ventricular assist devices on insulin regulation and cardiac function.

Endothelium as a Therapeutic Target in Diabetes Mellitus: From Basic Mechanisms to Clinical Practice

Endothelium plays an essential role in human homeostasis by regulating arterial blood pressure, distributing nutrients and hormones as well as providing a smooth surface that modulates coagulation, fibrinolysis and inflammation. Endothelial dysfunction is present in Diabetes Mellitus (DM) and contributes to the development and progression of macrovascular disease, while it is also associated with most of the microvascular complications such as diabetic retinopathy, nephropathy and neuropathy. Hyperglycemia, insulin resistance, hyperinsulinemia and dyslipidemia are the main factors involved in the pathogenesis of endothelial dysfunction. Regarding antidiabetic medication, metformin, gliclazide, pioglitazone, exenatide and dapagliflozin exert a beneficial effect on Endothelial Function (EF); glimepiride and glibenclamide, dipeptidyl peptidase-4 inhibitors and liraglutide have a neutral effect, while studies examining the effect of insulin analogues, empagliflozin and canagliflozin on EF are limited. In terms of lipid-lowering medication, statins improve EF in subjects with DM, while data from short-term trials suggest that fenofibrate improves EF; ezetimibe also improves EF but further studies are required in people with DM. The effect of acetylsalicylic acid on EF is dose-dependent and lower doses improve EF while higher ones do not. Clopidogrel improves EF, but more studies in subjects with DM are required. Furthermore, angiotensin- converting-enzyme inhibitors /angiotensin II receptor blockers improve EF. Phosphodiesterase type 5 inhibitors improve EF locally in the corpus cavernosum. Finally, cilostazol exerts favorable effect on EF, nevertheless, more data in people with DM are required.

The transcriptional response in human umbilical vein endothelial cells exposed to insulin: a dynamic gene expression approach

Background

In diabetes chronic hyperinsulinemia contributes to the instability of the atherosclerotic plaque and stimulates cellular proliferation through the activation of the MAP kinases, which in turn regulate cellular proliferation. However, it is not known whether insulin itself could increase the transcription of specific genes for cellular proliferation in the endothelium. Hence, the characterization of transcriptional modifications in endothelium is an important step for a better understanding of the mechanism of insulin action and the relationship between endothelial cell dysfunction and insulin resistance.

Methodology and principal findings

The transcriptional response of endothelial cells in the 440 minutes following insulin stimulation was monitored using microarrays and compared to a control condition. About 1700 genes were selected as differentially expressed based on their treated minus control profile, thus allowing the detection of even small but systematic changes in gene expression. Genes were clustered in 7 groups according to their time expression profile and classified into 15 functional categories that can support the biological effects of insulin, based on Gene Ontology enrichment analysis. In terms of endothelial function, the most prominent processes affected were NADH dehydrogenase activity, N-terminal myristoylation domain binding, nitric-oxide synthase regulator activity and growth factor binding. Pathway-based enrichment analysis revealed “Electron Transport Chain” significantly enriched.

Results were validated on genes belonging to “Electron Transport Chain” pathway, using quantitative RT-PCR.

Conclusions

As far as we know, this is the first systematic study in the literature monitoring transcriptional response to insulin in endothelial cells, in a time series microarray experiment. Since chronic hyperinsulinemia contributes to the instability of the atherosclerotic plaque and stimulates cellular proliferation, some of the genes identified in the present work are potential novel candidates in diabetes complications related to endothelial dysfunction.

Ethanol potentiates the acute fatty infiltration of liver caused by burn injury: prevention by insulin treatment

Burn injury is a significant and severe representation of critical illness. Nearly, 50% of patients admitted to hospitals for burn injuries have detectable levels of ethanol in their circulations and these patients have poorer clinical outcomes than burned individuals without measurable circulating ethanol. We report here data on a clinically relevant form of hepatic injury, the development of microvesicular steatosis, in a murine model wherein animals were either given ethanol or saline, and were subjected to burn or sham injury. Because better glycemic control with insulin has been shown in clinical studies to impart major clinical benefit, an additional group of burn ethanol animals were treated with insulin. Insulin significantly reduced blood glucose in injured animals to levels no different from those seen in animals that were neither ethanol exposed nor burned. A single intraperitoneal injection of ethanol was insufficient to raise blood alanine aminotransferase (ALT), measured as an index of liver injury. However, burn injury led to significant increases in ALT at 24 and 48 hours, which had returned to preinjury levels by 7 days. This ALT rise was completely prevented with insulin treatment. A single injection of ethanol did not evoke increased microvesicular steatosis but did potentiate the ability of burn to do so at 24 hours after injury. The burn induced increase in microvesicular steatosis was also seen at 48 hours, but had subsided by 7 days. The increased microvesicular steatosis was prevented by insulin therapy. Thus, ethanol potentiates the ability of burn to cause acute liver injury, which is completely preventable by insulin therapy. These findings may have substantial clinical significance and suggest this model may be useful for the study of the mechanisms of hepatic injury as well as the mechanisms, probably multiple, of insulin action in this setting.