High sucrose intake in rats is associated with increased ACE2 and angiotensin-(1–7) levels in the adipose tissue

Abstract

Sucrose-fed rats, a model of metabolic syndrome, are characterized by insulin resistance, obesity, hypertension, and high plasma levels of triacylglycerols and angiotensin II (Ang II). However, whether tissue renin-angiotensin system (RAS) is altered in metabolic syndrome is unclear. To study this issue, food ad libitum and water (C) or 20% sucrose solution (SC) were given to adult male Wistar rats, for 30 days. Body weight (BW), blood pressure (BP), epididymal adipose tissue (EPI) mass, rate of in vivo fatty acid (FA) synthesis in EPI, circulating glucose, insulin, leptin, angiotensins I and II, triacylglycerols, and plasma renin (PRA) and angiotensin-converting enzyme (ACE) activities were evaluated. In kidneys and EPI, gene and protein expression of type 1 (AT(1)) and 2 (AT(2)) Ang II receptors, ACE, angiotensinogen (AGT) as well as protein expression of angiotensin-converting enzyme 2 (ACE2) were determined. In both tissues, Ang I, Ang II and Ang-(1-7) contents were also measured by HPLC. In SC rats higher BP, EPI mass, circulating triacylglycerols, insulin, leptin, PRA and, Ang II were found. In EPI, the rate of in vivo FA synthesis was associated with increased Ang-(1-7), protein expression of AT(1) and AT(2) receptors, ACE2, AGT, and gene expression of AGT although a reduction in ACE activity and in adipose Ang I and Ang II contents was observed. In kidneys, AT(1) and AT(2), ACE and AGT gene and protein expression as well as protein expression of ACE2 were unaltered while Ang II, Ang-(1-7) and ACE activity increased. These RAS component changes seem to be tissue specific and possibly are related to enhancement of FA synthesis, EPI mass and hypertension.

Estimation of angiotensin peptides in biological samples by LC–MS method

“…Moreover, we also observed similar levels of Ang II in the eWAT which was again much higher than the reported value available in the literature. 15 The existing method employs time-consuming peptide extraction procedure by HPLC and its detection by RIA is lengthy, costly and poses health risk. Although mass spectrometry is an expensive instrument, it is automated and time-efficient; cost of running samples is low.…”

Biochemical evaluation of the renin-angiotensin system: the good, bad, and absolute?

“…Typically regarded as the enzyme that initiates the RAS cascade, renin is an aspartyl-type protease (30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40) that cleaves angiotensinogen to form the inactive peptide ANG I (Fig. 1).…”

“…ANG II and ANG-(1-7) values derived from these methods are typically far higher in plasma (26,33,51,135), kidney (33,110,114), vasculature (48), adipose tissue (33,115), and heart (42) than by RIA, HPLC-RIA, or HPLC-MS methods (Table 1). Indeed, two recent studies quantified mouse renal ANG-(1-7) at Ͼ1,000,000 fmol/g tissue (110) and rat plasma ANG II at Ͼ300,000 pM by HPLC analysis alone (33). Rubio-Ruiz et al (115) reported an ANG-(1-7) concentration of 6,000 pM in serum and Ͼ500,000 fmol/g in adipose tissue from male Wistar rats by capillary electrophoresis.…”

The intricacies of the renin-angiotensin-system in metabolic regulation

“…Additional studies investigating the ACE2 component of this ‘protective arm’ in adipose tissue have revealed that the expression and activity of this enzyme are regulated by energy status [23, 88, 89]. For example, Gupte et al .…”