The objective of this study was to elucidate the protective role of quercetin in atherosclerosis by examining its effect on the phenotypic switch of vascular smooth muscle cells (VSMCs) to macrophage-like cells and the underlying regulatory pathways. Aorta tissues from apolipoprotein E-deficient (ApoE KO) mice fed a high-fat diet (HFD), treated with or without 100 mg/kg/day quercetin, were analyzed for histopathological changes and molecular mechanisms. Quercetin was found to decrease the size of atherosclerotic lesions and mitigate lipid accumulation induced by HFD. Fluorescence co-localization analysis revealed a higher presence of macrophage-like vascular smooth muscle cells (VSMCs) co-localizing with phospho-Janus kinase 2 (p-JAK2), phospho-signal transducer and activator of transcription 3 (p-STAT3), and Krüppel-like factor 4 (KLF4) in regions of foam cell aggregation within aortic plaques. However, this co-localization was reduced following treatment with quercetin. Quercetin treatment effectively inhibited the KLF4-mediated phenotypic switch in oxidized low-density lipoprotein (ox-LDL)-loaded mouse aortic vascular smooth muscle cells (MOVAS), as indicated by decreased expressions of KLF4, LGALS3, CD68, and F4/80, increased expression of alpha smooth muscle actin (α-SMA), reduced intracellular fluorescence Dil-ox-LDL uptake, and decreased lipid accumulation. In contrast, APTO-253, a KLF4 activator, was found to reverse the effects of quercetin. Furthermore, AG490, a JAK2 inhibitor, effectively counteracted the ox-LDL-induced JAK2/STAT3 pathway-dependent switch to a macrophage-like phenotype and lipid accumulation in MOVAS cells. These effects were significantly mitigated by quercetin but exacerbated by coumermycin A1, a JAK2 activator. Our research illustrates that quercetin inhibits the KLF4-mediated phenotypic switch of VSMCs to macrophage-like cells and reduces atherosclerosis by suppressing the JAK2/STAT3 pathway.

As the sole producers of insulin under physiological conditions, the normal functioning of pancreatic β cells is crucial for maintaining glucose homeostasis in the body. Due to the high oxygen and energy demands required for insulin secretion, hypoxia has been shown to play a critical role in pancreatic β-cell dysfunction. Lipid metabolism abnormalities, a common metabolic feature in type 2 diabetic patients, are often accompanied by tissue hypoxia caused by metabolic overload and lead to increased free fatty acid (FFA) levels. However, the specific mechanisms underlying FFA-induced β-cell dysfunction remain unclear. Nicotinamide mononucleotide (NMN), a naturally occurring bioactive nucleotide, has garnered significant attention in recent years for its effectiveness in replenishing NAD⁺ and alleviating various diseases. Nevertheless, studies exploring the mechanisms through which NMN influences β-cell dysfunction remain scarce. In this study, we established an in vitro β-cell dysfunction model by treating INS-1 cells with palmitate (PA), including control, PA-treated, and PA combined with NMN or activator/inhibitor groups. Compared to the control group, cells treated with PA alone showed significantly reduced insulin secretion capacity and decreased expression of proteins related to the NAD⁺/AMPK/SIRT1/HIF-1α pathway. In contrast, NMN supplementation significantly restored the expression of pathway-related proteins by activating NAD⁺ and effectively improved insulin secretion. Results obtained using HIF-1α and AMPK inhibitors/activators further supported these findings. In conclusion, our study demonstrates that NMN reversed the PA-induced downregulation of the NAD⁺/AMPK/SIRT1/HIF-1α pathway, thereby alleviating β-cell dysfunction. Our study investigated the mechanisms underlying PA-induced β-cell dysfunction, examined how NMN mitigates this dysfunction and offered new insights into the therapeutic potential of NMN for treating β-cell dysfunction and T2DM.

Background: Klotho is an aging-related marker closely associated with a number of diseases. A growing body of evidence suggests that dietary factors and lifestyle habits can impact serum Klotho levels. The effect of dietary fiber, a key component of a healthy diet, on the body’s serum Klotho levels has not been fully elucidated. Objective: The aim of this study was to explore the relationship between dietary fiber intake and serum Klotho levels in people aged 40–79 years in the United States. Methods: A total of 11,282 participants were included in this study, all from the National Health and Nutrition Examination Survey from 2007 to 2016. Dietary fiber intake was assessed by uniformly trained interviewers using the 24 h dietary recall method. Serum Klotho was quantified using commercially available ELISA kits manufactured by IBL International, Japan. The relationship between dietary fiber intake and serum Klotho levels was analyzed using a multiple linear regression model. Subsequently, the non-linear dose–response relationship between the two was further explored using a restricted cubic spline (RCS) model. Results: After adjusting for potential confounders, serum Klotho levels increased by 1.9% (95% confidence interval [CI]: 0.8%, 3.0%) for each interquartile range increase in dietary fiber intake in all participants. Considering dietary fiber intake as a categorical variable, serum Klotho levels were found to be 4.7% higher in participants in the highest quartile of dietary fiber intake than in those in the lowest quartile (95% CI: 1.8%, 7.6%). RCS plots depicted a non-linear positive correlation between dietary fiber intake and serum Klotho levels. Subgroup analysis revealed that the relationship between dietary fiber intake and serum Klotho levels was more pronounced in older (percentage change: 7.0%; 95% CI: 2.5%, 11.7%) and overweight and obese participants (percentage change: 4.9%; 95% CI: 1.5%, 8.4%). Conclusions: The results of this study showed that dietary fiber intake was significantly associated with serum Klotho levels in participants. This finding is yet to be further confirmed by prospective studies.

Neutrophil extracellular traps (NETs) are three-dimensional reticular structures that release chromatin and cellular contents extracellularly upon neutrophil activation. As a novel effector mechanism of neutrophils, NETs possess the capacity to amplify localized inflammation and have been demonstrated to contribute to the exacerbation of various inflammatory diseases, including cardiovascular diseases and tumors. It is suggested that lysophosphatidylcholine (LPC), as the primary active component of oxidized low-density lipoprotein, represents a significant risk factor for various inflammatory diseases, such as cardiovascular diseases and neurodegenerative diseases. However, the specific mechanism of NETs formation induced by LPC remains unclear. Quercetin has garnered considerable attention due to its anti-inflammatory properties, serving as a prevalent flavonoid in daily diet. However, little is currently known about the underlying mechanisms by which quercetin inhibits NETs formation and alleviates associated diseases. In our study, we utilized LPC-treated primary rat neutrophils to establish an in vitro model of NETs formation, which was subsequently subjected to treatment with a combination of quercetin or relevant inhibitors/activators. Compared to the control group, the markers of NETs and the expression of P2X7R/P38MAPK/NOX2 pathway-associated proteins were significantly increased in cells treated with LPC alone. Quercetin intervention decreased the LPC-induced upregulation of the P2X7R/P38MAPK/NOX2 pathway and effectively reduced the expression of NETs markers. The results obtained using a P2X7R antagonist/activator and P38MAPK inhibitor/activator support these findings. In summary, quercetin reversed the upregulation of the LPC-induced P2X7R/P38MAPK/NOX2 pathway, further mitigating NETs formation. Our study investigated the potential mechanism of LPC-induced NETs formation, elucidated the inhibitory effect of quercetin on NETs formation, and offered new insights into the anti-inflammatory properties of quercetin.

Background: The relationship between dietary carbohydrate intake and serum Klotho levels, an aging biomarker, remains uncertain. Objective: This study aimed to investigate the association between dietary carbohydrate intake and serum Klotho levels among American adults aged 40–79. Methods: We analyzed data from 10,669 adults aged 40–79 years who participated in the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2016. Trained interviewers assessed dietary carbohydrate intake using a 24 h dietary recall. Serum Klotho concentrations were measured using commercially available ELISA kits provided by IBL International, Japan, which served as the study outcome. Generalized linear models were used to assess the relationship between the carbohydrate energy percentage and serum Klotho concentration, and restricted cubic spline (RCS) analysis was employed to explore any nonlinear associations. Results: After adjusting for multiple variables, we observed a nonlinear inverse J-shaped relationship (p for non-linearity < 0.001) between the carbohydrate energy percentage and serum Klotho levels. Specifically, the highest serum Klotho levels were associated with a total carbohydrate energy percentage ranging from 48.92% to 56.20% (third quartile). When the carbohydrate energy percentage was evaluated in quartiles, serum Klotho levels decreased by 5.37% (95% CI: −7.43%, −3.26%), 2.70% (95% CI: −4.51%, −0.86%), and 2.76% (95% CI: −4.86%, −0.62%) in the first quartile (<41.46%), second quartile (41.46% to 48.92%), and fourth quartile (≥56.20%), respectively, compared to the third quartile. This relationship was more pronounced in male, non-obese and non-diabetic participants under 60 years of age. Conclusion: A non-linear inverse J-shaped relationship exists among the general U.S. middle-aged and older population between the carbohydrate energy percentage and serum Klotho levels, with the highest levels observed at 48.92% to 56.20% carbohydrate intake.