Long-lasting partnership between insulin resistance and endothelial dysfunction: role of metabolic memory

Screening of natural epigenetic modifiers for managing glycemic memory and diabetic nephropathy

Short hyperglycaemic episodes trigger metabolic memory (MM) in which managing hyperglycaemia alone is not enough to tackle the progression of Diabetic nephropathy on the epigenetic axis. We used a structural similarity search approach to identify phytochemicals similar to natural epigenetic modifiers and docked with SIRT1 protein and did ADME studies. We found that UMB was 84.3% similar to esculetin. Upon docking, we found that UMB had a binding energy of -9.2 kcal/mol while the standard ligand had -11.8 kcal/mol. ADME showed UMB to be a good lead. 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay showed it to be a good antioxidant with IC50 of 107 µg/mL and MTT stands for 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) showed that it does not promote cell death. Oxidative biomarkers in vitro showed UMB was able to ameliorate glycemic memory induced by high glucose. Western blot revealed decreased histone acetylation under hyperglycaemic conditions and upon treatment with UMB along with DR, its levels increased. This led us to check our hypothesis of whether concomitant diet reversal (DR) together with UMB can alleviate high-fat diet-induced metabolic memory and diabetic nephropathy (DN) in SD rats. UMB was able to decrease blood glucose, lipid, renal, and liver profile concluding UMB was able to ameliorate DN and MM by increasing the histone acetylation level.

Association of triglyceride-glucose index with cardiovascular disease among a general population: a prospective cohort study

BACKGROUND

The impact of triglyceride-glucose (TyG) index, a surrogate marker for insulin resistance, on the risk of cardiovascular disease (CVD) in general populations remains controversial. We aimed to comprehensively study the relationship between TyG index with the risk of incident CVD events in the general population in Shanghai.

METHODS

A total of 42,651 participants without previous history of CVD events from Shanghai Suburban Adult Cohort and Biobank (SSACB) were included. SSACB was a community-based natural population cohort study using multistage cluster sampling method. TyG index was calculated as Ln [fasting serum triglyceride (mg/dL) * fasting blood glucose (mg/dL)/2]. Kaplan-Meier curves, log-rank test and cox proportional hazards model were used to calculate the association between TyG index and incident CVD, including stroke and coronary heart disease (CHD). Restricted cubic spline analyses were used to determine whether there was a non-linear relationship between TyG index and CVD events.

RESULTS

During a median follow-up of 4.7 years, 1,422 (3.3%) individuals developed CVD, including 674 (1.6%) cases of stroke and 732 (1.7%) cases of CHD. A one unit increment higher TyG index was associated with [HR(95%CI)] 1.16(1.04-1.29) in CVD and with 1.39(1.19-1.61) in stroke. Only linear relationships between TyG and CVD/stroke were observed, while no relationship was observed with CHD after adjustments for confounders. In subgroup analyses, younger (< 50y) and diabetic participants had higher risk of CVD than their counterpart groups, while hypertensive and dyslipidemic participants depicted lower risks than their counterparts.

CONCLUSION

Elevated TyG index was associated with a higher risk of incident CVD and stroke. TyG index may help in the early stage of identifying people at high risk of CVD.

Triglyceride-glucose index trajectory and stroke incidence in patients with hypertension: a prospective cohort study

Background

It has been suggested that the baseline triglyceride-glucose (TyG) index, a simple surrogate measure for insulin resistance, is significantly associated with the occurrence of stroke. Nevertheless, the impact of longitudinal patterns of TyG on the stroke risk in hypertensive patients is still unknown. Hence, this study aimed to investigate the association between TyG index trajectory and stroke risk among hypertensive patients.

Methods

This prospective study included 19,924 hypertensive patients from the Kailuan Study who underwent three waves survey and were free of myocardial infarction, cancer and stroke before or during 2010. The TyG index was calculated as ln [fasting triglyceride (mg/dL) × fasting plasma glucose (mg/dL)/2], and latent mixed modelling was used to identify the trajectory of TyG during the exposure period (2006–2010). Furthermore, the Cox proportional hazard models were applied to estimate the hazard ratio (HR) and 95% confidence interval (CI) for incident stroke of different trajectory groups.

Results

Five distinct TyG trajectory were identified during 2006–2010: low-stable (n = 2483; range, 8.03–8.06), moderate low-stable (n = 9666; range, 8.58–8.57), moderate high-stable (n = 5759; range, 9.16–9.09), elevated-stable (n = 1741; range, 9.79–9.75), and elevated-increasing (n = 275; range, 10.38–10.81). During the median follow-up of 9.97 years, 1,519 cases of incident stroke were identified, including 1,351 with ischemic stroke and 215 with hemorrhage stroke. After adjusting for confounding variables, the HR and 95% CI of stroke were 2.21 (1.49,3.28) for the elevated-increasing group, 1.43 (1.13,1.83) for the elevated-stable group, 1.35 (1.10,1.64) for the moderate high-stable group, 1.26 (1.06,1.52) for the moderate low-stable group, respectively, when compare with the low-stable group. Similar results were observed in ischemic stroke, but a significant association was not found between TyG trajectory and risk of hemorrhage stroke.

Conclusion

A long-term elevated TyG index in hypertensive patients is associated with an increased risk of stroke, especially ischemic stroke. This finding implies that regular monitoring of TyG index may assist in identifying individuals at a higher risk of stroke among patients with hypertension.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01577-7.

Old and New Biomarkers Associated with Endothelial Dysfunction in Chronic Hyperglycemia

Chronic hyperglycemia and vascular damage are strictly related. Biomarkers of vascular damage have been intensively studied in the recent years in the quest of reliable cardiovascular risk assessment tools able to facilitate risk stratification and early detection of vascular impairment. The present study is a narrative review with the aim of revising the available evidence on current and novel markers of hyperglycemia-induced vascular damage. After a discussion of classic tools used to investigate endothelial dysfunction, we provide an in-depth description of novel circulating biomarkers (chemokines, extracellular vesicles, and epigenetic and metabolomic biomarkers). Appropriate use of a single as well as a cluster of the discussed biomarkers might enable in a near future (a) the prompt identification of targeted and customized treatment strategies and (b) the follow-up of cardiovascular treatment efficacy over time in clinical research and/or in clinical practice.

Metformin in cardiovascular diabetology: a focused review of its impact on endothelial function

As a first-line treatment for diabetes, the insulin-sensitizing biguanide, metformin, regulates glucose levels and positively affects cardiovascular function in patients with diabetes and cardiovascular complications. Endothelial dysfunction (ED) represents the primary pathological change of multiple vascular diseases, because it causes decreased arterial plasticity, increased vascular resistance, reduced tissue perfusion and atherosclerosis. Caused by “biochemical injury”, ED is also an independent predictor of cardiovascular events. Accumulating evidence shows that metformin improves ED through liver kinase B1 (LKB1)/5'-adenosine monophosphat-activated protein kinase (AMPK) and AMPK-independent targets, including nuclear factor-kappa B (NF-κB), phosphatidylinositol 3 kinase-protein kinase B (PI3K-Akt), endothelial nitric oxide synthase (eNOS), sirtuin 1 (SIRT1), forkhead box O1 (FOXO1), krüppel-like factor 4 (KLF4) and krüppel-like factor 2 (KLF2). Evaluating the effects of metformin on endothelial cell functions would facilitate our understanding of the therapeutic potential of metformin in cardiovascular diabetology (including diabetes and its cardiovascular complications). This article reviews the physiological and pathological functions of endothelial cells and the intact endothelium, reviews the latest research of metformin in the treatment of diabetes and related cardiovascular complications, and focuses on the mechanism of action of metformin in regulating endothelial cell functions.

CXCL2 Impairs Functions of Bone Marrow Mesenchymal Stem Cells and Can Serve as a Serum Marker in High-Fat Diet-Fed Rats

In modern society excessive consumption of a high-fat diet (HFD) is a significant risk factor for many diseases such as diabetes, osteoarthritis and certain cancers. Resolving cellular and molecular mechanisms underlying HFD-associated disorders is of great importance to human health. Mesenchymal stem cells (MSCs) are key players in tissue homeostasis and adversely affected by prolonged HFD feeding. Low-grade systemic inflammation induced by HFD is characterized by increased levels of pro-inflammatory cytokines and alters homeostasis in many organs. However, whether, which and how HFD associated inflammatory cytokines impair MSCs remain unclear. Here we demonstrated that HFD induced serum cytokines disturbances, especially a continuous elevation of serum CXCL2 level in rats. Coincidentally, the differentially expressed genes (DEGs) of bone marrow MSCs (BMSCs) which functions were impaired in HFD rats were enriched in cytokine signaling. Further mechanism analysis revealed that CXCL2 treatment in vitro suppresses the adipogenic potential of BMSCs via Rac1 activation, and promoted BMSC migration and senescence by inducing over-production of ELMO1 and reactive oxygen species (ROS) respectively. Moreover, we found that although glycolipid metabolism indicators can be corrected, the CXCL2 elevation and BMSC dysfunctions cannot be fully rescued by diet correction and anti-inflammatory aspirin treatment, indicating the long-lasting deleterious effects of HFD on serum CXCL2 levels and BMSC functions. Altogether, our findings identify CXCL2 as an important regulator in BMSCs functions and may serve as a serum marker to indicate the BMSC dysfunctions induced by HFD. In addition, our findings underscore the intricate link among high-fat intake, chronic inflammation and BMSC dysfunction which may facilitate development of protective strategies for HFD associated diseases.

Triglyceride-glucose index and the risk of stroke and its subtypes in the general population: an 11-year follow-up

Background

Triglyceride-glucose (TyG) index was recently suggested to be a reliable surrogate marker of insulin resistance. We aim to investigate the associations between baseline and long-term TyG index with subsequent stroke and its subtypes in a community-based cohort.

Methods

A total of 97,653 participants free of history of stroke in the Kailuan Study were included. TyG index was calculated as ln (fasting triglyceride [mg/dL] × fasting glucose [mg/dL]/2). Baseline TyG index was measured during 2006–2007. Updated cumulative average TyG index used all available TyG index from baseline to the outcome events of interest or the end of follow up. The outcome was the first occurrence of stroke, including ischemic stroke, intracerebral hemorrhage and subarachnoid hemorrhage. The associations of TyG index with outcomes were explored with Cox regression.

Results

During a median of 11.02 years of follow-up, 5122 participants developed stroke of whom 4277 were ischemic stroke, 880 intracerebral hemorrhage, and 144 subarachnoid hemorrhage. After adjusting for confounding variables, compared with participants in the lowest quartile of baseline TyG index, those in the third and fourth quartile were associated with an increased risk of stroke (adjusted hazard ratio [HR] 1.22, 95% confidence interval [CI] 1.12–1.33, and adjusted HR 1.32, 95% CI 1.21–1.44, respectively, P for trend < 0.001). We also found a linear association between baseline TyG index with stroke. Similar results were found for ischemic stroke. However, no significant associations were observed between baseline TyG index and risk of intracranial hemorrhage. Parallel results were observed for the associations of updated cumulative average TyG index with outcomes.

Conclusions

Elevated levels of both baseline and long-term updated cumulative average TyG index can independently predict stroke and ischemic stroke but not intracerebral hemorrhage in the general population during an 11-year follow-up.

The Legacy Effect in the Prevention of Cardiovascular Disease

The "legacy effect" describes the long-term benefits that may persist for many years after the end of an intervention period, involving different biological processes. The legacy effect in cardiovascular disease (CVD) prevention has been evaluated by a limited number of studies, mostly based on pharmacological interventions, while few manuscripts on dietary interventions have been published. Most of these studies are focused on intensive treatment regimens, whose main goal is to achieve tight control of one or more cardiovascular risk factors. This review aims to summarise the legacy effect-related results obtained in those studies and to determine the existence of this effect in CVD prevention. There is sufficient data to suggest the existence of a legacy effect after intensive intervention on cardiovascular risk factors; however, this effect is not equivalent for all risk factors and could be influenced by patient characteristics, disease duration, and the type of intervention performed. Currently, available evidence suggests that the legacy effect is greater in subjects with moderately-high cardiovascular risk but without CVD, especially in those patients with recent-onset diabetes. However, preventive treatment for CVD should not be discontinued in high-risk subjects, as the level of existing evidence on the legacy effect is low to moderate.

Metformin Improves Metabolic Memory in High Fat Diet (HFD)-induced Renal Dysfunction

Recently, we have shown that high fat diet (HFD) in vivo and in vitro generates metabolic memory by altering H3K36me2 and H3K27me3 on the promoter of FOXO1 (transcription factor of gluconeogenic genes) (Kumar, S., Pamulapati, H., and Tikoo, K. (2016) Mol. Cell. Endocrinol. 422, 233-242). Here we checked the hypothesis whether concomitant diet reversal and metformin could overcome HFD-induced metabolic memory and renal damage. Male adult Sprague-Dawley rats were rendered insulin-resistant by feeding high fat diet for 16 weeks. Then the rats were subjected to diet reversal alone and along with metformin for 8 weeks. Biochemical and histological markers of insulin resistance and kidney function were measured. Blood pressure and in vivo vascular reactivity to angiotensin II (200 ng kg^-1) were also checked. Diet reversal could improve lipid profile but could not prevent renal complications induced by HFD. Interestingly, metformin along with diet reversal restored the levels of blood glucose, triglycerides, cholesterol, blood urea nitrogen, and creatinine. In kidney, metformin increased the activation of AMP-activated protein kinase (AMPK) and decreased inflammatory markers (COX-2 and IL-1β) and apoptotic markers (poly(ADP-ribose) polymerase (PARP) and caspase 3). Metformin was effective in lowering elevated basal blood pressure and acute change in mean arterial pressure in response to angiotensin II (Ang II). It also attenuated tubulointerstitial fibrosis and glomerulosclerosis induced by HFD feeding in kidney. Here we report, for the first time, that metformin treatment overcomes metabolic memory and prevents HFD-induced renal damage.