The Role of Branched-chain Amino Acids and Their Metabolism in Cardiovascular Diseases

Leucine enhances the cGAS-STING-NLRP3 pathway in autoimmune thyroiditis

Background

Branched-chain amino acids (BCAAs), including isoleucine (Ile), leucine (Leu), and valine (Val), are substrates for synthesising nitrogenous compounds and signalling molecules involved in regulating immunity. To date, data on the role of BCAAs in autoimmune thyroiditis (AIT) are lacking; therefore, this study aimed to determine the causality using two-sample Mendelian randomisation (MR) and explored the role of BCAAs in the cGAS-STING-NLRP3 pathway in vitro.

Methods

The causal relationship between BCAAs and the pathogenesis of AIT were identified using a two-sample MR study. The anti-inflammatory effects of BCAAs and their role in the cGAS-STING-NLRP3 pathway were investigated in lipopolysaccharide (LPS)- induced thyroid follicular cells (TFCs).

Results

Our findings indicate that BCAAs are a pathogenic factor for AIT (IVW OR = 4.960; 95 % CI = (1.54,15.940); P = 0.007). Leu significantly exacerbated the inflammatory response of thyroid cells, as evidenced by the up-regulation of tumour necrosis factor-alpha (TNF-α) and interleukin (IL)-6 and down-regulation of TGF-β1; simultaneously aggravated cellular injury and oxidative stress; significantly increased the expression of Sestrin2/p-mTOR and cGAS/STING/NLRP3 in AIT cells. Furthermore, the expression of IL-18 and IL-1β was significantly increased. Conversely, Leu deprivation induced cell injury, decreased oxidative stress, and inhibited Sestrin2/p-mTOR and cGAS/STING/NLRP3 pathways.

Conclusion

Our findings suggest a potential causal effect of genetically predicted Leu on AIT; Leu significantly exacerbated the inflammatory response and cellular damage in AIT cells. The mechanism by which Leu induces inflammation involves activating the promoted Sestrin2/mTOR and cGAS-STING-NLRP3 signalling pathways. Our study proposes a novel mechanism for the contributions of Leu in AIT and potential therapeutic strategies involving Leu deprivation in treating AIT.

Exploring the causal impact of body mass index on metabolic biomarkers and cholelithiasis risk: a Mendelian randomization analysis

Obesity is a well-established risk factor for various diseases, but the mechanisms through which it influences disease development remain unclear. Using Mendelian randomization (MR) analysis, we examined the causal relationship between BMI, 249 metabolic traits, and cholelithiasis. BMI data were obtained from four sources, and cholelithiasis data were from two distinct datasets. We analyzed the direct effect of BMI on cholelithiasis and identified key metabolic mediators. BMI was found to be positively associated with the risk of cholelithiasis across all datasets analyzed. A total of 176 metabolites were identified to be significantly associated with BMI, including amino acids, cholesterol esters, free cholesterol, triglycerides, and phospholipids. Among these, 49 metabolites were identified as mediators in the BMI-cholelithiasis relationship. Specifically, fatty acid levels, cholesteryl esters, phospholipids, triglycerides, and free cholesterol were key mediators in this relationship, with mediation proportions ranging from - 2.38-7.14%. This study provides robust evidence that BMI significantly impacts metabolic biomarkers, which in turn affect the risk of cholelithiasis. These findings highlight the importance of managing BMI to mitigate metabolic dysfunction and reduce the risk of gallstone formation. Future research should explore the specific metabolic pathways involved to identify potential therapeutic targets.

Disruption of BCAA degradation is a critical characteristic of diabetic cardiomyopathy revealed by integrated transcriptome and metabolome analysis

In this study, we integrated transcriptomic and metabolomic analyses to achieve a comprehensive understanding of the underlying mechanisms of diabetic cardiomyopathy (DCM) in a diabetic rat model. Functional and molecular characterizations revealed significant cardiac injury, dysfunction, and ventricular remodeling in DCM. A thorough analysis of global changes in genes and metabolites showed that amino acid metabolism, especially the breakdown of branched-chain amino acids (BCAAs) such as valine, leucine, and isoleucine, is highly dysregulated. Furthermore, the study identified the transcription factor Gata3 as a predicted negative regulator of the gene encoding the key enzyme for BCAA degradation. These findings suggest that the disruption of BCAA degradation is a critical characteristic of diabetic myocardial damage and indicate a potential role for Gata3 in the dysregulation of BCAA metabolism in the context of DCM.

Aspartate restrains thermogenesis by inhibiting the AMPK pathway in adipose tissues

Increasing evidence suggests that brown adipose tissue (BAT) plays an important role in obesity and related diseases. Great progress has been made in identifying positive regulators that activate adipocyte thermogenesis, but negative regulatory signaling of thermogenesis remains poorly understood. Here, we evaluated the potential effects of aspartate on the BAT function. We found that the circulating aspartate level is positively associated with metabolic syndrome and obesity in adults. Acute cold exposure significantly increases BAT aspartate as well as other amino acid levels in mice. In this regard, we speculate that aspartate may play a role in regulating the BAT function and systemic energy homeostasis. To verify the hypothesis, we altered aspartate availability to explore the effects on adipose tissue metabolism. Supplementation of aspartate exogenously inhibits the thermogenic gene expression and cold tolerance in mice. Intriguingly, aspartate bioavailability inhibits mitochondrial biosynthesis essentially through the suppression of mechanistic targeting of the AMPK cascade. Therefore, an evaluation of whether a diet deficient in aspartate will increase oxidative phosphorylation in the mitochondria to reestablish aspartate levels and therefore increase the energy expenditure will be interesting because these effects can prevent or ameliorate the development of obesity.

The toxicity of cisplatin derives from effects on renal organic ion transporters expression and serum endogenous substance levels

Acute kidney injury (AKI) is a worldwide public health problem with high morbidity and mortality. Cisplatin is a widely used chemotherapeutic agent for treating solid tumors, but the induction of AKI restricts its clinical application. In this study, the effect of cisplatin on the expression of organic ion transporters was investigated through in vivo and in vitro experiments. Targeted metabolomics techniques were used to measure the levels of selected endogenous substances in serum. Transmission electron microscopy was used to observe the microstructure of renal tubular epithelial cells. Our results show that the toxicity of cisplatin on HK-2 cells or HEK-293 cells was time- and dose-dependent. Administration of cisplatin decreased the expression of OAT1/3 and OCT2 and increased the expression of MRP2/4. Mitochondrial damage induced by cisplatin lead to renal tubular epithelial cell injury. In addition, administration of cisplatin resulted in significant changes in endogenous substance levels in serum, including amino acids, carnitine, and fatty acids. These serum amino acids and metabolites (α-aminobutyric acid, proline, and alanine), carnitines (tradecanoylcarnitine, hexanylcarnitine, octanoylcarnitine, 2-methylbutyroylcarnitine, palmitoylcarnitine, and linoleylcarnitine) and fatty acids (9E-tetradecenoic acid) represent endogenous substances with diagnostic potential for cisplatin-induced AKI.