Atherosclerosis in diabetes mellitus: novel mechanisms and mechanism-based therapeutic approaches

Metabolic and vascular insulin resistance: partners in the pathogenesis of cardiovascular disease in diabetes

Vascular insulin resistance has emerged as a pivotal factor in the genesis of cardiovascular disease (CVD) in people with diabetes. It forms a complex pathogenic partnership with metabolic insulin resistance to significantly amplify the CVD risk of diabetes and other affected populations. Metabolic insulin resistance (characterized by quantitatively diminished insulin action on glucose metabolism in skeletal muscle, liver, and adipose tissue) is a hallmark of diabetes, obesity, and related conditions. In contrast, vascular insulin resistance is a less appreciated and not well-quantified complication of these conditions. Importantly, an impaired vascular response to insulin contributes directly to vascular dysfunction and over 40 years of research has convincingly shown that vascular and metabolic insulin resistance synergize to create an environment that predisposes individuals to CVD. In this review, we examine the multifaceted vascular actions of insulin, including its roles in regulating blood pressure, blood flow, endothelial health, and arterial stiffness. We also examine how these processes become disrupted in the setting of vascular insulin resistance, which subsequently undermines endothelial function, compromises tissue microvascular perfusion, and promotes vascular rigidity and atherosclerosis. We then highlight potential therapeutic strategies with demonstrated efficacy to improve vascular insulin sensitivity in people with diabetes and suggest that targeting disordered vascular insulin signaling holds promise not only for refining the functional understanding of vascular insulin resistance but also for developing innovative treatments with potential to reduce CVD risk and improve cardiovascular outcomes in people with diabetes.

Endothelial-Mesenchymal Transition and Possible Role of Cytokines in Streptozotocin-Induced Diabetic Heart

Background: Although endothelial mesenchymal transition (EndMT) has been characterized as a basic process in embryogenesis, EndMT is the mechanism that accelerates the development of cardiovascular diseases, including heart failure, aging, and complications of diabetes or hypertension as well. Endothelial cells lose their distinct markers and take on a mesenchymal phenotype during EndMT, expressing distinct products. Methods: In this study, type 1 Diabetes mellitus (T1DM) was induced in rats with streptozotocin (STZ) by intraperitoneal injection at a 60 mg/kg dose. Diabetic rats were randomly divided into two groups, namely, control and diabetic rats, for 4 weeks. Heart, aorta, and plasma samples were collected at the end of 4 weeks. Sequentially, biochemical parameters, cytokines, reactive oxygen species (ROS), protein expression of EndMT markers (Chemokine C-X-C motif ligand-1 (CXCL-1), vimentin, citrullinated histone H3 (H3Cit), α-smooth muscle actin (α-SMA), and transforming growth factor beta (TGF-β) and versican), components of the extracellular matrix (matrix metalloproteinase 2 (MMP-2), tissue inhibitor of metalloproteinase-1(TIMP-1), and discoidin domain tyrosine kinase receptor 2 (DDR-2)) were detected by ELISA or Western blot, respectively. Results: Cytokines and ROS were increased in diabetic hearts, which induced partial EndMT. Among EndMT markers, histone citrullination, α-SMA, and CXCL-1 were increased; vimentin was decreased in DM. The endothelial marker endothelin-1 was significantly higher in the aortas of DM rats. Interestingly, TGF-β showed a significant decrease in the diabetic heart, plasma, and aorta. Additionally, MMP-2/TIMP-1 levels also decreased in DM. Conclusions: To sum up, the identification of molecules and regulatory pathways involved in EndMT provided novel therapeutic approaches for cardiac pathophysiological conditions.

Peripheral Arterial Disease in Diabetic Foot: One Disease with Multiple Patterns

Peripheral arterial disease (PAD) is a major complication in individuals with diabetes and is increasingly prevalent in those with diabetic foot ulcers (DFUs). Despite this, the characterisation of PAD in diabetic patients remains insufficiently refined, leading to suboptimal management and outcomes. This review underscores the necessity for a more nuanced understanding of PAD's anatomical and biological aspects in diabetic patients. The distribution of atherosclerotic plaques varies significantly among individuals, influencing prognosis and treatment efficacy. We describe three key patterns of PAD in diabetes: pattern 1 PAD-below-the-knee (BTK) disease (with infrageniculate disease where present); pattern 2-below-the-ankle (BTA) disease; and pattern 3-small artery disease (SAD), each presenting unique challenges and require tailored therapeutic approaches. BTK PAD, characterised by occlusions in the anterior tibial, posterior tibial, and peroneal arteries, necessitates targeted revascularisation to improve foot perfusion. BTA PAD, involving the pedal and plantar arteries, is associated with higher risks of amputation and requires advanced revascularisation techniques. SAD, affecting the small arteries of the foot, remains an enigma and is challenging to treat with the current mechanical methods, highlighting the potential of autologous cell therapy as a promising alternative. A refined characterisation of PAD in diabetes is crucial for developing effective, individualised treatment strategies, ultimately improving patient outcomes, and reducing the burden of diabetic foot complications. In light of these complexities, it is incredulous that we often use a single term, "peripheral arterial disease", to describe such a diverse array of disease patterns. This oversimplification can be perilous, as it may lead to inadequate therapeutic approaches and suboptimal patient care.