Sho Kinguchi

Adipocyte‐Specific Enhancement of Angiotensin II Type 1 Receptor‐Associated Protein Ameliorates Diet‐Induced Visceral Obesity and Insulin Resistance

Background The renin–angiotensin system has a pivotal role in the pathophysiology of visceral obesity. Angiotensin II type 1 receptor (AT1R) is a major player in the signal transduction of the renin–angiotensin system, and the overactivation of this signaling contributes to the progression of visceral obesity. We have shown that the AT1R‐associated protein (ATRAP) promotes AT1R internalization from the cell surface into cytoplasm along with the suppression of overactivation of tissue AT1R signaling. In this study, we examined whether the enhancement of adipose ATRAP expression could efficiently prevent diet‐induced visceral obesity and insulin resistance. Methods and Results We generated adipocyte‐specific ATRAP transgenic mice using a 5.4‐kb adiponectin promoter, and transgenic mice and littermate control mice were fed either a low‐ or high‐fat diet for 10 weeks. Although the physiological phenotypes of the transgenic and control mice fed a low‐fat diet were comparable, the transgenic mice exhibited significant protection against high‐fat diet–induced adiposity, adipocyte hypertrophy, and insulin resistance concomitant with an attenuation of adipose inflammation, macrophage infiltration, and adipokine dysregulation. In addition, when mice were fed a high‐fat diet, the adipose expression of glucose transporter type 4 was significantly elevated and the level of adipose phospho‐p38 mitogen‐activated protein kinase was significantly attenuated in the transgenic mice compared with control mice. Conclusions Results presented in this study suggested that the enhancement in adipose ATRAP plays a protective role against the development of diet‐induced visceral obesity and insulin resistance through improvement of adipose inflammation and function via the suppression of overactivation of adipose AT1R signaling. Consequently, adipose tissue ATRAP is suggested to be an effective therapeutic target for the treatment of visceral obesity.

Angiotensin II Type 1 Receptor‐Associated Protein Regulates Kidney Aging and Lifespan Independent of Angiotensin

Background The kidney is easily affected by aging‐associated changes, including glomerulosclerosis, tubular atrophy, and interstitial fibrosis. Particularly, renal tubulointerstitial fibrosis is a final common pathway in most forms of progressive renal disease. Angiotensin II type 1 receptor (AT1R)‐associated protein (ATRAP), which was originally identified as a molecule that binds to AT1R, is highly expressed in the kidney. Previously, we have shown that ATRAP suppresses hyperactivation of AT1R signaling, but does not affect physiological AT1R signaling. Methods and Results We hypothesized that ATRAP has a novel functional role in the physiological age‐degenerative process, independent of modulation of AT1R signaling. ATRAP‐knockout mice were used to study the functional involvement of ATRAP in the aging. ATRAP‐knockout mice exhibit a normal age‐associated appearance without any evident alterations in physiological parameters, including blood pressure and cardiovascular and metabolic phenotypes. However, in ATRAP‐knockout mice compared with wild‐type mice, the following takes place: (1) age‐associated renal function decline and tubulointerstitial fibrosis are more enhanced; (2) renal tubular mitochondrial abnormalities and subsequent increases in the production of reactive oxygen species are more advanced; and (3) life span is 18.4% shorter (median life span, 100.4 versus 123.1 weeks). As a key mechanism, age‐related pathological changes in the kidney of ATRAP‐knockout mice correlated with decreased expression of the prosurvival gene, Sirtuin1. On the other hand, chronic angiotensin II infusion did not affect renal sirtuin1 expression in wild‐type mice. Conclusions These results indicate that ATRAP plays an important role in inhibiting kidney aging, possibly through sirtuin1‐mediated mechanism independent of blocking AT1R signaling, and further protecting normal life span.

ATRAP Expression in Brown Adipose Tissue Does Not Influence the Development of Diet-Induced Metabolic Disorders in Mice

Activation of tissue renin–angiotensin system (RAS), mainly mediated by an angiotensin II (Ang II) type 1 receptor (AT1R), plays an important role in the development of obesity-related metabolic disorders. We have shown that AT1R-associated protein (ATRAP), a specific binding protein of AT1R, functions as an endogenous inhibitor to prevent excessive activation of tissue RAS. In the present study, we newly generated ATRAP/Agtrap-floxed (ATRAPfl/fl) mice and adipose tissue-specific ATRAP downregulated (ATRAPadipoq) mice by the Cre/loxP system using Adipoq-Cre. Using these mice, we examined the functional role of adipose ATRAP in the pathogenesis of obesity-related metabolic disorders. Compared with ATRAPfl/fl mice, ATRAPadipoq mice exhibited a decreased ATRAP expression in visceral white adipose tissue (WAT) and brown adipose tissue (BAT) by approximately 30% and 85%, respectively. When mice were fed a high-fat diet, ATRAPfl/fl mice showed decreased endogenous ATRAP expression in WAT that was equivalent to ATRAPadipoq mice, and there was no difference in the exacerbation of dietary obesity and glucose and lipid metabolism. These results indicate that ATRAP in BAT does not influence the pathogenesis of dietary obesity or metabolic disorders. Future studies that modulate ATRAP in WAT are necessary to assess its in vivo functions in the development of obesity-related metabolic disorders.

Effect of single-pill irbesartan/amlodipine combination-based therapy on clinic and home blood pressure profiles in hypertension with chronic kidney diseases

ABSTRACT We examined the efficacy of single-pill irbesartan/amlodipine combination-based therapy for 12 weeks in 20 hypertensive chronic kidney disease (CKD) patients, by evaluating self-measured home blood pressure (BP) profile. The single-pill irbesartan/amlodipine combination-based therapy decreased clinic BP and home BP (morning, evening, and nighttime BPs), and improved within-visit clinic BP variability, day-by-day home BP variability (morning and evening), and nighttime home BP variability. Furthermore, the single-pill combination-based therapy reduced albuminuria and exerted improved parameters of vascular function. These results indicate that this single-pill combination-based therapy may exert beneficial effects on clinic and home BP profiles as well as on renal and vascular damages, in hypertension with CKD.

Comparison of direct renin inhibitor and angiotensin II receptor blocker on clinic and ambulatory blood pressure profiles in hypertension with chronic kidney disease

ABSTRACT We compared the therapeutic effects of aliskiren (direct renin inhibitor (DRI) group) with angiotensin II (Ang II) type 1 receptor blockers (ARBs) (ARB group) on clinic blood pressure (BP) and ambulatory BP in 36 hypertensive chronic kidney disease (CKD) patients. The baseline clinic BP levels and the after-treatment/baseline (A/B) ratios of clinic BP levels, estimated after 24-week treatment period, were similar in DRI group (n = 18) and ARB group (n = 18). With respect to the effects on ambulatory BP, the A/B ratios of the daytime and nighttime systolic BP in DRI group were significantly higher than those in ARB group. The A/B ratio of ankle-brachial pressure index after the study was higher in the DRI group compared with the ARB group. The results of the present study suggest that DRI therapy is not superior to ARB therapy in lowering ambulatory BP in hypertensive CKD patients, in spite of comparable clinic BP-lowering effects.

Angiotensin receptor-binding molecule in leukocytes in association with the systemic and leukocyte inflammatory profile

BACKGROUND AND AIMS The components of the renin-angiotensin system in leukocytes is involved in the pathophysiology of non-communicable diseases (NCDs), including hypertension, atherosclerosis and chronic kidney disease. Angiotensin II type 1 receptor (AT1R)-associated protein (ATRAP) is an AT1R-specific binding protein, and is able to inhibit the pathological activation of AT1R signaling in certain animal models of NCDs. The aim of the present study was to investigate the expression and regulation of ATRAP in leukocytes. METHODS Human leukocyte ATRAP mRNA was measured with droplet digital polymerase chain reaction system, and analyzed in relation to the clinical variables. We also examined the leukocyte cytokines mRNA in bone-marrow ATRAP-deficient and wild-type chimeric mice after injection of low-dose lipopolysaccharide. RESULTS The ATRAP mRNA was abundantly expressed in leukocytes, predominantly granulocytes and monocytes, of healthy subjects. In 86 outpatients with NCDs, leukocyte ATRAP mRNA levels correlated positively with granulocyte and monocyte counts and serum C-reactive protein levels. These positive relationships remained significant even after adjustment. Furthermore, the leukocyte ATRAP mRNA was significantly associated with the interleukin-1β, tumor necrosis factor-α and monocyte chemotactic protein-1 mRNA levels in leukocytes of NCDs patients. In addition, the leukocyte interleukin-1β mRNA level was significantly upregulated in bone marrow ATRAP-deficient chimeric mice in comparison to wild-type chimeric mice after injection of lipopolysaccharide. CONCLUSIONS These results suggest that leukocyte ATRAP is an emerging marker capable of reflecting the systemic and leukocyte inflammatory profile, and plays a role as an anti-inflammatory factor in the pathophysiology of NCDs.

Angiotensin II Type 1 Receptor-associated Protein Inhibits Angiotensin II-induced Insulin Resistance with Suppression of Oxidative Stress in Skeletal Muscle Tissue

Enhancement of AT1 receptor-associated protein (ATRAP) in adipose tissue improves high fat diet (HFD)-induced visceral obesity and insulin resistance, and suppresses adipose oxidative stress. However, HFD loading is not a direct stimulatory factor for AT1 receptor. In the present study, we investigated the effect of chronic, low-dose angiotensin II (Ang II) stimulation on glucose and lipid metabolism in mice and functional role of ATRAP. ATRAP expression was higher in adipose tissue (5–10-fold) and skeletal muscle tissue (approximately 1.6-fold) in ATRAP transgenic (TG) mice compared with wild-type (WT) mice. After Ang II infusion, insulin sensitivity was impaired in WT mice, but this response was suppressed in TG mice. Unexpectedly, Ang II infusion did not affect the adipose tissue profile in WT or TG mice. However, in skeletal muscle tissue, Ang II stimulus caused an increase in oxidative stress and activation of p38 MAPK, resulting in a decrease in glucose transporter type 4 expression in WT mice. These responses were suppressed in TG mice. Our study suggests that Ang II-induced insulin resistance is suppressed by increased ATRAP expression in skeletal muscle tissue. Hyperactivity of AT1 receptor could be related to formation of insulin resistance related to metabolic syndrome.

Within-visit blood pressure variability and cardiovascular risk factors in hypertensive patients with non-dialysis chronic kidney disease

ABSTRACT As there may be an association between within-visit blood pressure (BP) variability and cardiovascular disease (CVD), we investigated the clinical significance of this BP variability in non-dialysis chronic kidney disease (CKD) patients. Materials and methods: According to the median of coefficient of variation (CV) of three systolic BP (SBP) readings within a single visit, we divided hypertensive patients with stage G1-4 CKD already treated with antihypertensive therapy into the high SBP-CV group and the low SBP-CV group. Univariate and multivariate linear regression analyses were also performed to explore the contributing factors to within-visit BP variability. Results: In the high SBP-CV group, the clinic BP, total cholesterol level, dyslipidemia, and past history of CVD were significantly greater, while α1-blockers and renin-angiotensin system (RAS) inhibitors usage were significantly reduced compared with the lower SBP-CV group. Within-visit BP variability was significantly and positively correlated with total cholesterol (R = 0.392, P < 0.001) and low-density lipoprotein cholesterol (R = 0.284, P = 0.013). Total cholesterol (β = 0.269, P = 0.024), α1-blockers usage (β = −0.260, P = 0.015), and RAS inhibitors usage (β = −0.266, P = 0.017) were shown to independently contribute to the within-visit BP variability after adjustment for age, sex, presence of diabetes, CVD history, statins usage, and clinic SBP. Conclusions: We show that within-visit BP variability may be a clinically relevant factor of CVD risk, and lipid lowering and/or anti-hypertensive therapies using RAS inhibitors and α1-blockers may be associated with the improved within-visit BP variability observed in non-dialysis CKD patients.

PS 13-26 ANGIOTENSIN II TYPE 1 RECEPTOR INTERACTING MOLECULE ATRAP PLAYS A ROLE IN RENAL SODIUM HANDLING AND BLOOD PRESSURE REGULATION

Objective: Exaggerated activation of the renin-angiotensin system via tissue angiotensin II (Ang II) type 1 receptor (AT1R) signaling exerts detrimental effects on cardiovascular, renal and endocrine systems to provoke hypertension and related target organ damage. Design and Method: On the other hand, accumulated research evidence of both basic and clinical studies shows that physiological AT1R signaling also plays an indispensable role for the normal organ development such as the kidney and the maintenance of cardiovascular and renal homeostasis. Such functional diversity of AT1R signaling prompts us to seek a new strategy of selective modulation of AT1R signaling in pathophysiology. Results: In the course of an investigational search for a means to functionally and selectively modulate AT1R signaling for that purpose, a molecule directly interacting with the carboxyl-terminal cytoplasmic domain of AT1R was identified by employing yeast two-hybrid screening of a mouse kidney cDNA library and named AT1R-associated protein (ATRAP). The results of functional analysis showed that ATRAP promotes constitutive AT1R internalization in cultured cells and inhibits Ang II-mediated pathological response in mouse distal convoluted cells. The ATRAP is expressed in a variety of tissues including the kidney where ATRAP is abundantly distributed in epithelial cells along the renal tubules. Conclusions: The results employing genetic engineered mice with modified ATRAP expression showed that ATRAP plays a key role in the regulation of renal sodium handling and the modulation of blood pressure in response to pathological stimuli such as chronic Ang II infusion, and suggest ATRAP to be a target of interest.