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Objectives: Metabolic syndrome is a leading cause for vascular dysfunction and cardiovascular diseases. We have previously shown that vascular functional responses in metabolic syndrome exhibit exaggerated vasocontractility and impaired endothelium-dependent relaxation. However, it remains unclear if a correlation between vascular abnormalities and metabolic disturbances exists. Accordingly, we aimed to explore the association between vascular dysfunction and changes in metabolic parameters in a rodent model of metabolic syndrome, the high fat diet (HFD)-streptozotocin (STZ)-induced diabetes mellitus rat (HFD-D).Design and method: Five weeks old male Wistar albino rats (n = 24) were fed with either HFD (45 kcal% fat) or control diet (10 kcal% fat) for 10 weeks. On week 6, 40 mg/kg STZ and saline were injected intraperitoneally into the HFD and control groups, respectively. At the end of the treatment, metabolic data were collected then rats were euthanized for blood and kidney collection and to measure maximal vasoconstrictor and vasodilator responses of the abdominal aortic rings. Recorded measures also included fasting blood glucose (FBG), plasma total cholesterol (TC), plasma triglyceride (TG), plasma high density lipoprotein (HDL), plasma creatinine (Cr), urinary protein: urinary creatinine (UPC) and kidney index (KI).Results: HFD-D rats had higher FBG, TG, Cr, UPC, and KI compared with controls. HDL was lower in HFD-D while TC remained unchanged. Maximal vasoconstriction to norepinephrine (NE Rmax) was greater in the HFD group compared with controls. Maximal endothelium-dependent vasorelaxation to acetylcholine (ACh Rmax) was blunted in the HFD group relative to controls. A positive correlation between NE Rmax and FBG was found, whereas ACh Rmax was negatively correlated with FBG, KI, UPC and TG.Conclusions: Impaired glucose metabolism, lipid profile and renal function are likely key contributors to vascular dysfunction in metabolic syndrome; however, further mechanistic investigations are required to verify these assumptions.

Objective:Proximal tubule angiotensin II type 1 receptor (AT1R) is involved in blood pressure (BP) regulation (Li XC, et al. Hypertension, 77:1285-1298, 2021). AT1 receptor-associated protein (ATRAP) interacts with AT1R and promotes constitutive internalization of AT1R, to inhibit pathological activation of its downstream signaling (Tamura K, et al. Hypertens Res, 45:32–39, 2022). Endogenous ATRAP is abundantly expressed along kidney tubules in the kidney, and our previous investigations using systemic ATRAP knockout and distal tubule-dominant ATRAP transgenic mice revealed that ATRAP suppressed Ang II-induced hypertension mainly through a distal tubule-mediated mechanism (Wakui H, et al. Hypertension, 61:1203–10, 2013; Ohsawa M, et al. Kidney Int, 86:570–81, 2014). On the other hand, proximal tubule-specific ATRAP knockout mice exhibited similar baseline BP and pressor response to Ang II compared with wild-type mice (Kinguchi S, et al. J Am Heart Assoc, 8(8):e012395, 2019). The present study was performed to investigate the effects of enhancement of proximal tubule ATRAP on Ang II-mediated hypertension, using proximal tubule-specific ATRAP transgenic mice.Design and method:[Experiment 1] Using mouse ATRAP cDNA linked to the type II sodium-dependent phosphate cotransporters (NPT2) promoter, we generated transgenic mice (NPT2-Tg mice) with proximal tubule-specific overexpression of ATRAP. ATRAP mRNA expression in the proximal tubule was quantified by a laser capture microdissection and quantitative reverse transcription-polymerase chain reaction analysis.[Experiment 2] Male NPT2-Tg and wild-type littermate control (LC) mice were divided into Ang II (1000 ng/kg/min) and vehicle groups. BP was measured using a tail-cuff method before and 14 days after treatment, and then mice were sacrificed and their organs were collected.Results:[Experiment 1] 5 of 12 lines of ATRAP Tg mice exhibited kidney overexpression of the ATRAP-transgene in comparison with LC mice. Kidney ATRAP expression at the protein level revealed the highest expression level of ATRAP in lines 23, approximately 10-fold higher compared to LC mice. Therefore, we chose line 23 (NPT2-Tg23) for further analysis. ATRAP mRNA expression was increased approximately 9-fold in the proximal tubules of NPT2-Tg23 mice compared with LC mice. On the other hand, ATRAP mRNA expression in the distal tubules was comparable between NPT2-Tg23 and LC mice.[Experiment 2] We are currently conducting the experiments and will present our findings at this conference.Conclusions:We succeeded in generating transgenic mice with proximal tubule-specific overexpression of ATRAP. We plan to present the results of the impact of enhancement of proximal tubular ATRAP on Ang II-dependent hypertension at this conference.