This study reveals a positive correlation between PHR and the risk of diabetes and prediabetes, which remains significant after accounting for various confounding factors. After full adjustment, the OR for diabetes and prediabetes per unit increase in PHR was 1.14 (95% CI: 1.00–1.29, P < 0.05). Participants in the highest PHR quartile had an OR of 2.46 (95% CI: 1.34–4.51, P < 0.05) compared to those in the lowest quartile. Subgroup analyses and interaction tests suggest that this positive correlation is consistent across different demographic groups. Additionally, the RCS analysis revealed a non-linear relationship. The two-piecewise regression identified an inflection point at PHR = 4.55, and showing a stronger positive association when PHR is below this threshold.
In recent years, PHR has attracted extensive attention as a new biomarker in the study of metabolic diseases[21–23]. PHR not only reflects platelet activity but also integrates an individual's lipid metabolic status. One study has found that PHR is significantly elevated in patients with metabolic syndrome (MetS) and increases with MetS severity[7]. Another study has reported a positive correlation between PHR and the risk of hyperuricemia[18]. MetS is characterized by a constellation of metabolic disorders centered on insulin resistance, including abdominal obesity, dyslipidemia, and hypertension, which are closely associated with the development of diabetes[24, 25]. In addition to being a component of MetS, hyperuricemia is also an independent risk factor for the development of insulin resistance and diabetes[26–28]. Large-scale prospective cohort studies have confirmed that MetS and hyperuricemia significantly increase the risk of developing diabetes[29, 30]. Therefore, it is logical to suggest that PHR is closely related to diabetes or prediabetes.
The relationship between PHR and diabetes involves complex pathophysiological mechanisms that are not yet fully understood. In this paper, we attempt to explore the pathophysiological links by focusing on three aspects: chronic inflammation, oxidative stress, and lipid metabolism disorders.
Chronic low-grade inflammation is a key characteristic in the development of diabetes and prediabetes. Studies have shown that the pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) can inhibit the expression and translocation of glucose transporter 4 (GLUT4) through the nuclear factor-kappa B (NF-κB) and c-Jun N-terminal kinase (JNK) pathways, leading to a decrease in insulin sensitivity[31, 32]. Platelets promote the spread of systemic inflammation and contribute to chronic inflammatory responses by releasing various pro-inflammatory mediators, such as platelet factor 4 (PF4), transforming growth factor-β (TGF-β), and platelet-activating factor (PAF)[33–35]. Study has shown that elevated levels of PF4 are closely associated with insulin resistance. PF4 binds to chemokine receptors, activating monocytes and macrophages, which then promote the release of additional pro-inflammatory cytokines[36]. Platelets also interact directly with neutrophils and monocytes, forming platelet-leukocyte aggregates that activate leukocytes and enhance their pro-inflammatory activity[37]. HDL-C is considered to have anti-inflammatory properties, and can reduce inflammatory responses by promoting reverse cholesterol transport, inhibiting the oxidation of LDL-C, and clearing circulating pro-inflammatory factors[38, 39]. When PHR is elevated, it may indicate an increase in the pro-inflammatory effects of platelets and a reduction in the anti-inflammatory effects of HDL-C. This imbalance exacerbates chronic inflammation, may lead to increased insulin resistance and the development of diabetes.
Pancreatic β cells are more susceptible to damage by reactive oxygen species (ROS) due to their relatively weak antioxidant capacity. Excessive platelet activation can increase oxidative stress by producing ROS, which can damage not only vascular endothelial cells but also pancreatic β cells and weaken the ability to secrete insulin[40–42]. Platelets in diabetic patients are often in a highly activated state, which is closely linked to heightened oxidative stress[43]. HDL-C has antioxidant properties and can protect pancreatic β-cells by scavenging excess ROS[44]. Therefore, this imbalance between oxidative stress and the antioxidant system could be one of the key mechanisms underlying the association between PHR and diabetes.
Lipid metabolism disorders affect the secretion and function of insulin, and have a significant impact on platelet activity. HDL-C plays a crucial role in maintaining lipid metabolic balance, and low levels of HDL-C are often associated with high triglycerides and elevated LDL-C levels[45]. These lipid abnormalities can exacerbate insulin resistance[46, 47]. Hyperlipidemia is a major feature of diabetes and prediabetes, usually manifested as an abnormal combination of high TG, low HDL-C levels, and elevated LDL-C levels[48, 49]. Research indicates that HDL-C facilitates the reverse transport of cholesterol, transporting excess cholesterol from peripheral tissues to the liver for metabolism, thereby reducing the formation of atherosclerotic plaques. HDL-C inhibits the progression of atherosclerosis by reducing the generation of lipid peroxidation products. In addition, platelet function is affected by lipid metabolism, and hyperlipidemia is often accompanied by increased platelet reactivity and thrombotic tendency[50]. PHR reflects the lipid metabolism status of an individual, and its increase usually indicates abnormal lipid metabolism, especially low HDL-C levels. These lipid metabolism disorders will further promote the development of insulin resistance, leading to the progression of diabetes.
The major strengths of this study are as follows. First, it is the first study to use a nationally representative sample to examine the associations of the PHR with diabetes and prediabetes. Second, a wide array of potential confounding variables was accounted for in the analysis. Third, the accuracy and reliability of the data were bolstered by employing trained staff who adhered to standardized protocols for collecting key information and conducting participant interviews.
Our study also has some limitations. First, as a cross-sectional study, this study cannot establish causal relationships. Additionally, the study's capacity to explore and test etiological hypotheses is limited, and its findings may not be fully generalizable. Therefore, further prospective longitudinal studies are needed to confirm these findings. Second, potential confounding from unknown or unmeasurable factors cannot be entirely excluded. Third, due to the presence of randomly missing data and the large sample size, we did not use multiple imputation methods to address the missing data, which may impact the precision of the results.