TET3 boosts hepatocyte autophagy and impairs non-alcoholic fatty liver disease by increasing ENPP1 promoter hypomethylation

BACKGROUND

Dysregulated ecto-nucleotide pyrophosphatase/phosphodiesterase (ENPP) family occurs in metabolic reprogramming pathological processes. Nonetheless, the epigenetic mechanisms by which ENPP family impacts NAFLD, also known as metabolic dysfunction-associated steatotic liver disease (MASLD), is poorly appreciated.

METHODS

We investigated the causes and consequences of ENPP1 promoter hypomethylation may boost NAFLD using NAFLD clinical samples, as well as revealed the underlying mechanisms using high-fat diet (HFD) + carbon tetrachloride (CCl4) induced mouse model of NAFLD and FFA treatment of cultured hepatocyte.

RESULTS

Herein, we report that the expression level of ENPP1 are increased in patients with NAFLD liver tissue and in mouse model of NAFLD. Hypomethylation of ENPP1, is associated with the perpetuation of hepatocyte autophagy and liver fibrosis in the NAFLD. ENPP1 hypomethylation is mediated by the DNA demethylase TET3 in NAFLD liver fibrosis and hepatocyte autophagy. Additionally, knockdown of TET3 methylated ENPP1 promoter, reduced the ENPP1 expression, ameliorated the experimental NAFLD. Mechanistically, TET3 epigenetically promoted ENPP1 expression via hypomethylation of the promoter. Knocking down TET3 can inhibit the hepatocyte autophagy but an overexpression of ENPP1 showing rescue effect.

CONCLUSIONS

We describe a novel epigenetic mechanism wherein TET3 promoted ENPP1 expression through promoter hypomethylation is a critical mediator of NAFLD. Our findings provide new insight into the development of preventative measures for NAFLD.

Current Data Regarding the Relationship between Type 2 Diabetes Mellitus and Cardiovascular Risk Factors

Reducing cardiovascular risk (CVR) is the main focus of diabetes mellitus (DM) management nowadays. Complex pathogenic mechanisms that are the subject of this review lead to early and severe atherosclerosis in DM patients. Although it is not a cardiovascular disease equivalent at the moment of diagnosis, DM subjects are affected by numerous cardiovascular complications, such as acute coronary syndrome, stroke, or peripheral artery disease, as the disease duration increases. Therefore, early therapeutic intervention is mandatory and recent guidelines focus on intensive CVR factor management: hyperglycaemia, hypertension, and dyslipidaemia. Most important, the appearance of oral or injectable antidiabetic medication such as SGLT-2 inhibitors or GLP-1 agonists has proven that an antidiabetic drug not only reduces glycaemia, but also reduces CVR by complex mechanisms. A profound understanding of intimate mechanisms that generate atherosclerosis in DM and ways to inhibit or delay them are of the utmost importance in a society where cardiovascular morbidity and mortality are predominant.

The sirtuin1 gene associates with left ventricular myocardial hypertrophy and remodeling in two chronic kidney disease cohorts: a longitudinal study

BACKGROUND

Oxidative stress and inflammation are major drivers of myocardial hypertrophy in chronic kidney disease (CKD). The silent information regulator gene 1 (Sirt1) is a fundamental mediator of the response to oxidative stress and inflammation and promotes myocardial growth under stress conditions; therefore, it may contribute to myocardial hypertrophy and concentric remodeling of the left ventricle (LV) in CKD.

METHODS

We investigated the cross-sectional and longitudinal relationship between three candidate polymorphisms in the Sirt1 gene and LV parameters in two cohorts of CKD patients including 235 stage G5D patients and 179 stages G1-5 patients, respectively.

RESULTS

In both cohorts, the C allele of the Sirt1 rs7069102 polymorphism associated with the posterior wall thickness in separate and combined analyses (beta = 0.15, P = 2 × 10) but was unrelated with the LV volume and the LV mass index indicating a peculiar association of this allele with LV concentric remodeling. Accordingly, the same allele was linked with the LV mass-to-volume ratio in separate and combined (beta = 0.14, P = 2 × 10) analyses in the same cohorts. Furthermore, in longitudinal analyses patients harboring the C allele showed a more pronounced increase in LV mass-to-volume ratio over time than patients without such an allele (regression coefficient = 0.14, 95% confidence interval: 0.05-0.23; P = 3 × 10 in the combined analysis).

CONCLUSION

The rs7069102 polymorphism in the Sirt1 gene is associated with LV concentric remodeling in two independent cohorts of stages G5D and G1-5 CKD patients. These results offer a genetic basis to the hypothesis that the Sirt1 gene plays a causal role in myocardial hypertrophy and LV concentric remodeling in these patients.

Insulin resistance in chronic kidney disease: a systematic review

Insulin resistance (IR) is an early metabolic alteration in chronic kidney disease (CKD) patients, being apparent when the glomerular filtration rate is still within the normal range and becoming almost universal in those who reach the end stage of kidney failure. The skeletal muscle represents the primary site of IR in CKD, and alterations at sites beyond the insulin receptor are recognized as the main defect underlying IR in this condition. Estimates of IR based on fasting insulin concentration are easier and faster but may not be adequate in patients with CKD because renal insufficiency reduces insulin catabolism. The hyperinsulinemic euglycemic clamp is the gold standard for the assessment of insulin sensitivity because this technique allows a direct measure of skeletal muscle sensitivity to insulin. The etiology of IR in CKD is multifactorial in nature and may be secondary to disturbances that are prominent in renal diseases, including physical inactivity, chronic inflammation, oxidative stress, vitamin D deficiency, metabolic acidosis, anemia, adipokine derangement, and altered gut microbiome. IR contributes to the progression of renal disease by worsening renal hemodynamics by various mechanisms, including activation of the sympathetic nervous system, sodium retention, and downregulation of the natriuretic peptide system. IR has been solidly associated with intermediate mechanisms leading to cardiovascular (CV) disease in CKD including left ventricular hypertrophy, vascular dysfunction, and atherosclerosis. However, it remains unclear whether IR is an independent predictor of mortality and CV complications in CKD. Because IR is a modifiable risk factor and its reduction may lower CV morbidity and mortality, unveiling the molecular mechanisms responsible for the pathogenesis of CKD-related insulin resistance is of importance for the identification of novel therapeutic targets aimed at reducing the high CV risk of this condition.

ATP acts as a survival signal and prevents the mineralization of aortic valve

Calcific aortic valve disease (CAVD) is a disorder related to progressive mineralization of valvular tissue that is a leading cause of heart disease. Thus far, there is no medical treatment to prevent the mineralization of aortic valves. It is generally thought that pathologic mineralization is linked to apoptosis of vascular cells. However, the role of apoptosis during mineralization as well as the survival signals for valvular interstitial cells (VICs), the main cellular component of aortic valves, remains to be identified. Here, through several lines of evidence, we show that bioavailability of extracellular ATP is a signal which determines survival or apoptosis of VICs and, in doing so, plays a major role in the development of CAVD. Specifically, in CAVD and in VIC cultures undergoing mineralization, we found a high level of the ectonucleotidase ENPP1. In addition, a genetic polymorphism in the intron 9 of the ENPP1 gene was associated with CAVD in a case-control cohort as well as with mRNA expression levels of ENPP1 in aortic valves. A high level of ENPP1 in CAVD promoted apoptosis-mediated mineralization of VICs by depleting the extracellular pool of ATP. We then documented that release of ATP by VICs promoted cell survival via the P2Y(2) receptor and the PI3K/Akt signaling pathway. Hence, our results show that level of ENPP1 modulates extracellular concentration of ATP, which is an important survival signal for VICs. These findings may help to develop novel pharmacological treatment for CAVD.