Inhibition of Fatty Acid ß-Oxidation by Fatty Acid Binding Protein 4 Induces Ferroptosis in HK2 Cells Under High Glucose Conditions.

BACKGRUOUND: Ferroptosis, which is caused by an iron-dependent accumulation of lipid hydroperoxides, is a type of cell death linked to diabetic kidney disease (DKD). Previous research has shown that fatty acid binding protein 4 (FABP4) is involved in the regulation of ferroptosis in diabetic retinopathy. The present study was constructed to explore the role of FABP4 in the regulation of ferroptosis in DKD. METHODS: We first detected the expression of FABP4 and proteins related to ferroptosis in renal biopsies of patients with DKD. Then, we used a FABP4 inhibitor and small interfering RNA to investigate the role of FABP4 in ferroptosis induced by high glucose in human renal proximal tubular epithelial (HG-HK2) cells. RESULTS: In kidney biopsies of DKD patients, the expression of FABP4 was elevated, whereas carnitine palmitoyltransferase-1A (CP-T1A), glutathione peroxidase 4, ferritin heavy chain, and ferritin light chain showed reduced expression. In HG-HK2 cells, the induction of ferroptosis was accompanied by an increase in FABP4. Inhibition of FABP4 in HG-HK2 cells changed the redox state, sup-pressing the production of reactive oxygen species, ferrous iron (Fe2+), and malondialdehyde, increasing superoxide dismutase, and reversing ferroptosis-associated mitochondrial damage. The inhibition of FABP4 also increased the expression of CPT1A, reversed lipid deposition, and restored impaired fatty acid ß-oxidation. In addition, the inhibition of CPT1A could induce ferroptosis in HK2 cells. CONCLUSION: Our results suggest that FABP4 mediates ferroptosis in HG-HK2 cells by inhibiting fatty acid ß-oxidation.

Dietary betaine intake and risk of mortality in patients with coronary artery disease: the prospective Guangdong Coronary Artery Disease Cohort.

This study is designed to explore the association between dietary betaine intake and risk of all-cause and cardiovascular death in patients with coronary artery diseases (CAD). In this cohort study, 1292 patients with CAD were followed up for a median of 9·2 years. Baseline dietary betaine intake was collected using a paper-based semi-quantitative FFQ and assessed according to the US Department of Agriculture (USDA) database and the data of betaine in common foods. Cox proportional hazards regression models were used to analyse the association between dietary betaine intake and risks of all-cause and cardiovascular mortality. During the follow-up periods, 259 deaths recorded in 1292 participants, of which 167 died of CVD. Patients in the highest tertile of dietary betaine intake had a lower risk of all-cause (P = 0·007) and cardiovascular death (P < 0·001) than those in the lowest tertile after adjusting for age and sex, traditional cardiovascular risk factors and other potential confounders. After further adjusting for plasma methionine metabolites and vitamins, hazard ratio across tertiles of dietary betaine intake were 1·00, 0·84 and 0·72 for all-cause mortality (Pfor trend = 0·124), and 1·00, 0·77 and 0·55 for cardiovascular mortality (Pfor trend = 0·021). Higher dietary betaine intake was associated with a decreased risk of cardiovascular death after fully adjustment for cardiovascular risk factors, other potential confounders and plasma methionine metabolites and vitamins. However, the association between dietary betaine intake and risk of all-cause mortality was not statistically significant after further adjusting for plasma methionine metabolites and vitamins.

Epigenetic Upregulation of H19 and AMPK Inhibition Concurrently Contribute to S-Adenosylhomocysteine Hydrolase Deficiency-Promoted Atherosclerotic Calcification.

BACKGROUND: S-adenosylhomocysteine (SAH) is a risk factor of cardiovascular disease; inhibition of SAH hydrolase (SAHH) results in SAH accumulation and induces endothelial dysfunction and atherosclerosis. However, the effect and mechanism of SAHH in atherosclerotic calcification is still unclear. We aimed to explore the role and mechanism of SAHH in atherosclerotic calcification. METHODS: The relationship between SAHH and atherosclerotic calcification was investigated in patients with coronary atherosclerotic calcification. Different in vivo genetic models were used to examine the effect of SAHH deficiency on atherosclerotic calcification. Human aortic and murine vascular smooth muscle cells (VSMCs) were cultured to explore the underlying mechanism of SAHH on osteoblastic differentiation of VSMCs. RESULTS: The expression and activity of SAHH were decreased in calcified human coronary arteries and inversely associated with coronary atherosclerotic calcification severity, whereas plasma SAH and total homocysteine levels were positively associated with coronary atherosclerotic calcification severity. Heterozygote knockout of SAHH promoted atherosclerotic calcification. Specifically, VSMC-deficient but not endothelial cell-deficient or macrophage-deficient SAHH promoted atherosclerotic calcification. Mechanistically, SAHH deficiency accumulated SAH levels and induced H19-mediated Runx2 (runt-related transcription factor 2)-dependent osteoblastic differentiation of VSMCs by inhibiting DNMT3b (DNA methyltransferase 3b) and leading to hypomethylation of the H19 promoter. On the contrary, SAHH deficiency resulted in lower intracellular levels of adenosine and reduced AMPK (AMP-activated protein kinase) activation. Adenosine supplementation activated AMPK and abolished SAHH deficiency-induced expression of H19 and Runx2 and osteoblastic differentiation of VSMCs. Finally, AMPK activation by adenosine inhibited H19 expression by inducing Sirt1 (sirtuin-1)-mediated histone H3 hypoacetylation and DNMT3b-mediated hypermethylation of the H19 promoter in SAHH deficiency VSMCs. CONCLUSIONS: We have confirmed a novel correlation between SAHH deficiency and atherosclerotic calcification and clarified a new mechanism that epigenetic upregulation of H19 and AMPK inhibition concurrently contribute to SAHH deficiency-promoted Runx2-dependent atherosclerotic calcification.

Betaine Supplementation Attenuates S-Adenosylhomocysteine Hydrolase-Deficiency-Accelerated Atherosclerosis in Apolipoprotein E-Deficient Mice.

S-adenosylhomocysteine (SAH) is a risk factor of cardiovascular diseases and atherosclerosis. However, the causal association between SAH and atherosclerosis is still uncertain. In the present study, heterozygous SAH hydrolase (SAHH+/-) knockout mice were bred with apolipoprotein E-deficient mice to produce ApoE-/-/SAHH+/- mice. At 8 weeks of age, these mice were fed on AIN-93G diets added with or without betaine (4 g betaine/100 g diet) for 8 weeks. Compared with ApoE-/-/SAHHWT mice, SAHH deficiency caused an accumulation of plasma SAH concentration and a decrease in S-adenosylmethionine (SAM)/SAH ratio as well as plasma homocysteine levels. Betaine supplementation lowered SAH levels and increased SAM/SAH ratio and homocysteine levels in ApoE-/-/SAHH+/- mice. Furthermore, SAHH deficiency promoted the development of atherosclerosis, which was reduced by betaine supplementation. The atheroprotective effects of betaine on SAHH-deficiency-promoted atherosclerosis were associated with inhibition of NFκB inflammation signaling pathway and inhibition of proliferation and migration of smooth muscle cells. In conclusion, our results suggest that betaine supplementation lowered plasma SAH levels and protected against SAHH-deficiency-promoted atherosclerosis through repressing inflammation and proliferation and migration of smooth muscle cells.