The renin-angiotensin system (RAS) is an important therapeutic target in the treatment of hypertension. Obesity has emerged as a primary contributor to essential hypertension in the United States and clusters with other metabolic disorders (hyperglycemia, hypertension, high triglycerides, low HDL cholesterol) defined within the metabolic syndrome. In addition to hypertension, RAS blockade may also serve as an effective treatment strategy to control impaired glucose and insulin tolerance and dyslipidemias in patients with the metabolic syndrome. Hyperglycemia, insulin resistance, and/or specific cholesterol metabolites have been demonstrated to activate components required for the synthesis [angiotensinogen, renin, angiotensin-converting enzyme (ACE)], degradation (ACE2), or responsiveness (angiotensin II type 1 receptors, Mas receptors) to angiotensin peptides in cell types (e.g., pancreatic islet cells, adipocytes, macrophages) that mediate specific disorders of the metabolic syndrome. An activated local RAS in these cell types may contribute to dysregulated function by promoting oxidative stress, apoptosis, and inflammation. This review will discuss data demonstrating the regulation of components of the RAS by cholesterol and its metabolites, glucose, and/or insulin in cell types implicated in disorders of the metabolic syndrome. In addition, we discuss data supporting a role for an activated local RAS in dyslipidemias and glucose intolerance/insulin resistance and the development of hypertension in the metabolic syndrome. Identification of an activated RAS as a common thread contributing to several disorders of the metabolic syndrome makes the use of angiotensin receptor blockers and ACE inhibitors an intriguing and novel option for multisymptom treatment.

Previous studies demonstrated that diet-induced obesity increased plasma angiotensin II concentrations and elevated systolic blood pressures in male mice. Adipocytes express angiotensinogen and secrete angiotensin peptides. We hypothesize that adipocyte-derived angiotensin II mediates obesity-induced increases in systolic blood pressure in male high fat-fed C57BL/6 mice. Systolic blood pressure was measured by radiotelemetry during week 16 of low fat or high fat feeding in Agtfl/fl and adipocyte-angiotensinogen deficient mice (AgtaP2). Adipocyte angiotensinogen deficiency had no effect on diet-induced obesity. Basal 24 hour systolic blood pressure was not different in low fat-fed Agtfl/fl compared to AgtaP2 mice (124 ± 3 vs. 128 ± 3 mmHg, respectively). In Agtfl/fl mice, high fat feeding significantly increased systolic blood pressure (24 hr; 134 ± 2 mmHg; P<0.05). In contrast, high fat-fed AgtaP2 mice did not exhibit an increase in systolic blood pressure (126 ± 2 mmHg). Plasma angiotensin II concentrations were increased by high fat-feeding in Agtfl/fl mice (low fat, 32 ± 14; high fat, 219 ± 58 pg/ml, P<0.05). In contrast, high fat-fed AgtaP2 mice did not exhibit elevated plasma angiotensin II concentrations (high fat, 18 ± 7 pg/ml). Similarly, adipose tissue concentrations of angiotensin II were significantly decreased in low fat and high fat-fed AgtaP2 mice compared to controls. In conclusion, adipocyte angiotensinogen deficiency prevented high fat-induced elevations in plasma angiotensin II concentrations and systolic blood pressure. These results suggest that adipose tissue serves as a major source of angiotensin II in the development of obesity-hypertension.

Purpose of review In contrast to previous understanding, adipocytes are now known to produce an array of factors collectively termed “adipokines”, several of which have effects on the cardiovascular system. The marked rise in prevalence of obesity warrants investigation into the role of adipocyte-derived factors in the regulation of blood pressure. For example, dysregulated production of specific adipokines in the setting of obesity may contribute to hypertension commonly experienced in obese subjects. This editorial highlights current concepts for regulation of adipokine production by adipocytes and their potential role in blood pressure regulation. Recent findings Adipocytes synthesize and release several factors that have been linked to blood pressure control, including adiponectin, leptin, angiotensin, perivascular relaxation factors and resistin. Increasing evidence suggests that aberrant production and release of these factors from adipocytes may contribute to the high prevalence of hypertension in the obese population. However, additional studies are warranted to define precise mechanisms for blood pressure regulation by these factors, and to delineate their role in obesity-related hypertension. Summary Studies aimed at determining the role of adipocyte-derived factors in blood pressure regulation during normal physiology and in the setting of obesity are needed.

Schiedea adamantis is a rare, perennial shrub endemic to the Hawaiian island of Oahu where it consists of a single population. Using a nonradioactive protocol, 12 microsatellite primers were developed that consisted of di-, tri-, penta- and hexanucleotide repeats. Using multiplexed reactions, all but two primers exhibited polymorphism with an average of 3.67 alleles per primer. Most primers also amplified in 28 additional Schiedea species, revealing wide applicability across the genus; eight and nine primers also amplified in Honckenya peploides and Silene lanceolata, respectively, related genera in the Caryophyllaceae. This is the first known report of microsatellite primers developed in Schiedea.