Cardiovascular disease is the leading cause of death in patients with type 2 diabetes (T2D). Recent evidence indicates that T2D also increases cardiac mortality via inducing coronary microvascular dysfunction (CMD); however, its molecular mechanisms are understudied. The objective of this study was to characterize the sex differences in diabetes-induced CMD using two different T2D mouse models, identify key genes altered in both sexes, and evaluate whether the most significantly altered gene serves as a potential therapeutic target for diabetes-induced CMD. Inducible T2D (iT2D) mice were generated using a single low-dose injection of streptozotocin (75 mg/kg, i.p.) and a high-fat diet. TALLYHO (TH) mice, a spontaneous polygenic T2D mouse model, were purchased from Jackson Laboratory. iT2D mice and age-matched control mice were used for the experiments 16 weeks after diabetes induction. TH mice and age-matched wild-type (Wt) mice were used at 16 weeks old. Coronary flow velocity reserve (CFVR) was used as a surrogate measure of coronary microvascular function. Coronary endothelial function was evaluated by 1) isometric tension experiments in small coronary arteries (3rd order) and 2) assessment of capillary density and cell apoptosis in the left ventricle. Cardiac endothelial cells (CECs) were isolated using CD31-coated magnetic beads for bulk RNA sequencing (RNA-seq). Male and female iT2D and TH mice exhibited abnormal glucose tolerance; however, fasting glucose levels did not differ between female Wt and female TH mice, suggesting that female TH mice have insulin resistance but not diabetes. All diabetic groups showed a significant decrease in CFVR regardless of sex. Male iT2D mice, male TH mice, and female TH mice exhibited a significant decrease in endothelium-dependent relaxation (EDR) compared to their controls, while there was no difference between female iT2D and female controls. Endothelium-independent relaxation did not differ among groups. There was a significant reduction in capillary density and an increase in apoptotic ECs in diabetic mice regardless of sex. To further understand the molecular mechanisms, RNA-seq was conducted. We identified 15 downregulated and 113 upregulated genes that are commonly altered in male and female iT2D mice, and Gja5 was most significantly downregulated among 15 genes. GJA5 (connexin 40) is a gap junction protein, and the activity of gap junction intracellular communication is a critical regulatory factor of endothelium-dependent hyperpolarization-mediated vascular relaxation. Therefore, we generated endothelial cell–specific doxycycline-inducible Gja5 overexpressing (Tie2-Gja5 TG) mice to examine the role of Gja5 in diabetes-induced CMD. Mice were induced to T2D, and doxycycline was administered at 2 g/L in drinking water for 6 weeks from 10 weeks after diabetic induction. There was no difference in glucose tolerance between diabetic Wt mice and diabetic Tie2-Gja5 TG mice; however, diabetic Tie2-Gja5 TG mice exhibited a significant increase in CFVR compared to diabetic Wt mice. These data suggest that diabetic mice develop CMD regardless of sex and model. The cause was, however, different in female TH mice, which was led by reduced capillary density, while other diabetic mice were induced to CMD via capillary rarefaction and attenuated EDR. Gja5 overexpression in diabetic mice successfully restores CMD, suggesting that GJA5 is a potential therapeutic target for CMD in diabetic patients. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Ramirez et al. (Fri,) studied this question.