Sex differences in the development of coronary microvascular diseases in type-2 diabetes: possible role of gap junction protein connexin-40
Authors: Razan Md Rahatullah , Si Rui , Gao Lei , Cabrera Jody , Ramirez Francisco , Yuan Jason X.-J. , Makino Ayako 
Published: May 2023

Type-2 diabetes (T2D) increases the risk of cardiovascular diseases 2-4 folds in both sexes compared to non-diabetic individuals. However, more than 50% of female patients who experience chest pain have coronary microvascular disease (CMD) instead of obstructive CAD. On the other hand, 20% of men with chest pain have CMD. CMD is characterized by reduced coronary flow reserve, and coronary flow is regulated by the change in capillary density and vessel diameter. Gap junction protein connexin-40 (Cx40) plays a significant role in coronary microvascular function by controlling endothelium-dependent relaxation (EDR), cardiac endothelial cell (CEC) migration and capillary density. We hypothesized that T2D differentially affects the CX-40 expression and function in male and female coronary artery (CA) and causes CMD. The objective of this study is to identify the molecular mechanisms underlining the development of T2D-induced CMD in male and female mice.T2D mice were generated by a combination of high-fat diet feeding and a low-dose of streptozotocin (75 mg/kg, i.p.). The oral glucose tolerance was conducted at 4-, 8-, 12-, and 16 weeks after diabetes induction. Coronary flow velocity reserve (CFVR) was used to assess coronary microvascular function in mice. Coronary endothelial function was determined by 1) capillary density measurement in the left ventricle and 2) isometric tension experiment in small CAs (3rd order). CECs from male and female mice were isolated to conduct molecular biological experiments.There was no significant difference in CFVR and capillary density between control male and female mice. However, T2D mice of both sexes showed significant differences in the properties of EDR, CFVR and capillary density. T2D male mice exhibited a significant attenuation of EDR accompanied by impaired endothelium-derived nitric oxide(EDNO)-dependent relaxation and endothelium-dependent hyperpolarization (EDH)-mediated relaxation. On the contrary, there is no difference in EDR between control and diabetic female mice. Capillary density was reduced in T2D mice of both sexes compared to the respective controls. Our RNA sequencing data in CECs revealed that Cx40 is one of the genes which contributes to diabetes-mediated CMD. Systemic Cx40-KO male mice showed reduced EDR, EDH-mediated relaxation and capillary density compared to wild type control. T2D reduced the expression of Cx40 and overexpression of Cx40 restored EDR in CAs and increased capillary density in T2D male mice.T2D impaired coronary microvascular function in both sexes. However, the cause of reduced CFVR was different between diabetic male and female mice. In T2D females, capillary rarefaction was a primary cause of reduced CFVR. In contrast, attenuated EDNO- and EDH-mediated relaxation, reduced capillary density and downregulation of Cx40 contributed to decreased CFVR in T2D male mice. Future studies are required to establish the role of Cx40 in the development of CMD in T2D females. Supported by NIH R01HL142214 and DOD W81XWH2110472 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.