Influence of acute hyperlipidemia to adipocyte-derived hormones in lean normotensive and subjects with metabolic syndrome.

BACKGROUND: Adipocyte-derived factors and regulators likely contribute to the metabolic syndrome (MetS) in patients with central obesity. This study was undertaken to assess the contribution of leptin, adiponectin, and acylation stimulating protein (ASP-C3ades/ARG) to hemodynamic (blood pressure [BP]) and metabolic (insulin, glucose, lipids) features of MetS. METHODS: In this study, leptin, adiponectin, and C3ades/ARG were measured at baseline and in response to an infusion of Intralipid(®) and heparin in 12 lean healthy controls and 12 patients with MetS. RESULTS: Baseline plasma leptin (27.6 ± 6.2 vs. 10.9 ± 3.8 ng/mL, p < 0.01) and plasma C3ades/ARG (273 ± 79 vs 198 ± 57 mg/dL, p < 0.05) were higher in the MetS than control group, whereas baseline plasma adiponectin was higher in the control than MetS group (9.9 ± 1.9 vs. 5.4 ± 0.6 g/mL). Plasma leptin correlated with body mass index (BMI), systolic and diastolic BP (r = 0.53-0.77, p < 0.01). Conversely, adiponectin correlated inversely with insulin, glucose, waist circumference, and insulin sensitivity (r = 0.48-0.51, p ≤ 0.02). Plasma triglycerides increased similarly in MetS and control groups after 4-hours of Intralipid and heparin. C3ades/ARG increased only in lean volunteers. The decrease in triglycerides 1-hour post-infusion was lower in the MetS than control group (-116 ± 33 vs. -282 ± 81 mg/dL, p = 0.01) and correlated inversely with the change in C3ades/ARG. CONCLUSION: These data suggest that leptin is more closely associated with hemodynamic (BP) aspects of MetS, whereas adiponectin and C3ades/ARG are more closely associated with metabolic components.

Aldosterone and aldosterone: renin ratio associations with insulin resistance and blood pressure in African Americans.

African Americans have more hypertension and hypertension-related morbidity than whites. Aldosterone, in presence of a high salt intake, contributes to hypertension and tissue injury. Inappropriately elevated aldosterone levels could explain this racial disparity. Our study was conducted to determine if aldosterone is associated with elevated blood pressure (BP) or insulin resistance, independent of obesity. A study was conducted on 483 young adult African Americans without cardiovascular or renal disease. Measurements included anthropometrics, BP, lipids, glucose, insulin, aldosterone, and renin. Urine sodium and potassium estimated sodium intake. The cohort was stratified by tertiles of aldosterone and tertiles of aldosterone/renin ratio (ARR). Average urine sodium/potassium ratio was >3.0 in all groups. Insulin resistance, estimated by homeostasis model, was lowest in the low aldosterone group (geometric mean 1.5 [0.6, 2.2]) compared with the high aldosterone group (1.7 [0.9, 2.7], P < .01). Adjusted analyses detected a significant association of aldosterone with insulin resistance, independent of other variables. BP was significantly higher in the high ARR group compared with low and mid ARR groups (P < .01). The significant association of ARR with BP with high dietary sodium suggests that insufficiently suppressed aldosterone may contribute to BP sensitivity to sodium in African Americans.

The human serum metabolome.

Continuing improvements in analytical technology along with an increased interest in performing comprehensive, quantitative metabolic profiling, is leading to increased interest pressures within the metabolomics community to develop centralized metabolite reference resources for certain clinically important biofluids, such as cerebrospinal fluid, urine and blood. As part of an ongoing effort to systematically characterize the human metabolome through the Human Metabolome Project, we have undertaken the task of characterizing the human serum metabolome. In doing so, we have combined targeted and non-targeted NMR, GC-MS and LC-MS methods with computer-aided literature mining to identify and quantify a comprehensive, if not absolutely complete, set of metabolites commonly detected and quantified (with today's technology) in the human serum metabolome. Our use of multiple metabolomics platforms and technologies allowed us to substantially enhance the level of metabolome coverage while critically assessing the relative strengths and weaknesses of these platforms or technologies. Tables containing the complete set of 4229 confirmed and highly probable human serum compounds, their concentrations, related literature references and links to their known disease associations are freely available at http://www.serummetabolome.ca.

Experimentally induced gestational androgen excess disrupts glucoregulation in rhesus monkey dams and their female offspring.

Discrete fetal androgen excess during early gestation in rhesus monkeys (Macaca mulatta) promotes endocrine antecedents of adult polycystic ovary syndrome (PCOS)-like traits in female offspring. Because developmental changes promoting such PCOS-like metabolic dysfunction remain unclear, the present study examined time-mated, gravid rhesus monkeys with female fetuses, of which nine gravid females received 15 mg of testosterone propionate (TP) subcutaneously daily from 40 to 80 days (first to second trimesters) of gestation [term, mean (range): 165 (155-175) days], whereas an additional six such females received oil vehicle injections over the same time interval. During gestation, ultrasonography quantified fetal growth measures and was used as an adjunct for fetal blood collections. At term, all fetuses were delivered by cesarean section for postnatal studies. Blood samples were collected from dams and infants for glucose, insulin, and total free fatty acid (FFA) determinations. TP injections transiently accelerated maternal weight gain in dams, very modestly increased head diameter of prenatally androgenized (PA) fetuses, and modestly increased weight gain in infancy compared with concurrent controls. Mild to moderate glucose intolerance, with increased area-under-the-curve circulating insulin values, occurred in TP-injected dams during an intravenous glucose tolerance test in the early second trimester. Moreover, reduced circulating FFA levels occurred in PA fetuses during a third trimester intravenous glucagon-tolbutamide challenge (140 days gestation), whereas excessive insulin sensitivity and increased insulin secretion relative to insulin sensitivity occurred in PA infants during an intravenous glucose-tolbutamide test at ∼1.5 mo postnatal age. Data from these studies suggest that experimentally induced fetal androgen excess may result in transient hyperglycemic episodes in the intrauterine environment that are sufficient to induce relative increases in pancreatic function in PA infants, suggesting in this nonhuman primate model that differential programming of insulin action and secretion may precede adult metabolic dysfunction.

Activation of the antioxidant response element by specific oxidized metabolites of linoleic acid.

Linoleic acid is required for normal mammalian health and development, but is also prone to oxidation, yielding metabolites with biological effects. We screened linoleic acid, other fatty acids, and some of their derivatives and found that an epoxy-keto derivative of linoleic acid (but neither linoleic acid itself nor others of its oxidation products) strongly activates the antioxidant response element (ARE) in IMR-32 neuroblastoma cells and cerebro-cortical neurons. The active compound, 12,13-epoxy-9-keto-10(trans)-octadecenoic acid (EKODE), induces the expression of ARE-regulated cytoprotective genes such as NQO1 at the transcript and protein levels. EKODE requires transcription factor NRF2 and PI3-kinase for ARE activity. The results suggest that specific oxidation products of linoleic acid may initiate responses that lessen damage caused by oxidative stress.

Obesity, sleep apnea, aldosterone, and hypertension.

The pathogenesis of hypertension associated with obesity is unclear. This review provides evidence supporting excess visceral fat as an early aspect, and obstructive sleep apnea and elevated levels of aldosterone as factors closer to hypertension in the mechanistic chain. Features of visceral obesity and obstructive sleep apnea that may stimulate aldosterone secretion are described here. Possible therapeutic interventions addressing the hypertension associated with obesity are briefly mentioned.

Pioglitazone improves insulin action and normalizes menstrual cycles in a majority of prenatally androgenized female rhesus monkeys.

PURPOSE OF THE STUDY: To determine whether pioglitazone will improve menstrual cyclicity in a fetal programming model for polycystic ovary syndrome. BASIC PROCEDURES: Eight prenatally androgenized (PA) and 5 control female rhesus monkeys of similar age, body weight and body mass index received an oral placebo daily for 6-7 months followed, after at least 90 days, by daily oral dosing with pioglitazone (3mg/kg) for an additional 6-7 months. Blood was sampled thrice weekly to monitor ovulatory function, and a variety of endocrine challenges were performed to quantify changes in ovarian, gonadotropin and glucoregulatory function. MOST IMPORTANT FINDINGS: Pioglitazone normalized menstrual cycles in 5 out of 8 (62%) PA females (pioglitazone responsive; Pio(RESP)). Pioglitazone increased serum 17alpha-hydroxyprogesterone responses to an hCG injection in Pio(RESP) PA females, while diminishing serum progesterone, and increasing DHEA and estradiol responses to hCG in Pio(RESP) PA and all normal females. PRINCIPAL CONCLUSIONS: Insulin resistance plays a mechanistic role in maintaining anovulation in a majority of PA female monkeys.

An oxidized metabolite of linoleic acid increases intracellular calcium in rat adrenal glomerulosa cells.

EKODE, an epoxy-keto derivative of linoleic acid, was previously shown to stimulate aldosterone secretion in rat adrenal glomerulosa cells. In the present study, we investigated the effect of exogenous EKODE on cytosolic [Ca(2+)] increase and aimed to elucidate the mechanism involved in this process. Through the use of the fluorescent Ca(2+)-sensitive dye Fluo-4, EKODE was shown to rapidly increase intracellular [Ca(2+)] ([Ca(2+)](i)) along a bell-shaped dose-response relationship with a maximum peak at 5 microM. Experiments performed in the presence or absence of Ca(2+) revealed that this increase in [Ca(2+)](i) originated exclusively from intracellular pools. EKODE-induced [Ca(2+)](i) increase was blunted by prior application of angiotensin II, Xestospongin C, and cyclopiazonic acid, indicating that inositol trisphosphate (InsP(3))-sensitive Ca(2+) stores can be mobilized by EKODE despite the absence of InsP(3) production. Accordingly, EKODE response was not sensitive to the phospholipase C inhibitor U-73122. EKODE mobilized a Ca(2+) store included in the thapsigargin (TG)-sensitive stores, although the interaction between EKODE and TG appears complex, since EKODE added at the plateau response of TG induced a rapid drop in [Ca(2+)](i). 9-oxo-octadecadienoic acid, another oxidized derivative of linoleic acid, also increases [Ca(2+)](i), with a dose-response curve similar to EKODE. However, arachidonic and linoleic acids at 10 microM failed to increase [Ca(2+)](i) but did reduce the amplitude of the response to EKODE. It is concluded that EKODE mobilizes Ca(2+) from an InsP(3)-sensitive store and that this [Ca(2+)](i) increase is responsible for aldosterone secretion by glomerulosa cells. Similar bell-shaped dose-response curves for aldosterone and [Ca(2+)](i) increases reinforce this hypothesis.

Aldosterone--a hormone of cardiovascular adaptation and maladaptation.

Aldosterone stimulates reabsorption of sodium, sustaining blood volume and pressure in the face of salt deprivation or extracellular fluid depletion. The steroid also stimulates excretion of potassium, protecting extracellular fluid from excessive levels of that ion. These two actions are relatively rapid and clearly adaptive when appropriately initiated and terminated, but maladaptive when prolonged or excessive, causing hypertension and electrolyte imbalance. Aldosterone and other mineralocorticoids exert slower, direct effects on cells in the heart, kidneys, and vessels, leading to hypertrophy, fibrosis, and dysfunction contributing to degenerative cardiovascular diseases. The maladaptive actions of aldosterone are exacerbated by sodium chloride, angiotensin, endothelin, and certain growth factors. Damage can be minimized by antagonists of aldosterone receptors, inhibitors of the renin system, depletion of salt, and repletion of potassium and magnesium. Specific inhibitors of fibrosis and hypertrophy, and more effective inhibitors of the renin system should be useful in the future.

Resistant hypertension, obesity, sleep apnea, and aldosterone: theory and therapy.

Hypertension resistant to 2 antihypertensive drugs is more common among obese patients than among lean patients. The case we describe and the observations we report suggest that refractoriness among obese hypertensives is frequently caused by obstructive sleep apnea and/or inappropriately high plasma aldosterone levels. In other words, obese hypertensives may have sleep apnea, obese hypertensives without sleep apnea may have inappropriately elevated levels of plasma aldosterone, and a surprising number of obese patients with sleep apnea also have elevated levels of aldosterone. The mechanisms by which obesity and obstructive sleep apnea increase aldosterone levels and raise blood pressure are not understood, but sympathetic nervous system activation and production of nonclassical adrenal stimuli are two possibilities. Obstructive sleep apnea can be detected with a careful history and various sleep studies. Inappropriately elevated aldosterone levels can be detected by measuring the ratio of plasma aldosterone concentration to plasma renin activity. Successful treatment of these resistant hypertensives often can be achieved by devices that provide positive pressure to the upper airway to correct obstructive sleep apnea and by incorporating an aldosterone antagonist in the therapeutic regimen.

Epoxy-keto derivative of linoleic acid stimulates aldosterone secretion.

Plasma levels of aldosterone are not always predictable from the activity of renin and the concentration of potassium. Among the unexplained are elevated levels of aldosterone in some obese humans. Obesity is characterized by increased plasma fatty acids and oxidative stress. We postulated that oxidized fatty acids stimulate aldosteronogenesis. The most readily oxidized fatty acids are the polyunsaturated, and the most abundant of those is linoleic acid. We tested oxidized derivatives of linoleic acid for effects on rat adrenal cells. One derivative, 12,13-epoxy-9-keto-10(trans)-octadecenoic acid (EKODE), was particularly potent. EKODE stimulated aldosteronogenesis at concentrations from 0.5 to 5 micromol/L, and inhibited aldosteronogenesis at higher doses. EKODE's stimulatory effect was most prominent when angiotensin and potassium effects were submaximal. The lipid's mechanism of action was on the early pathway leading to pregnenolone; its action was inhibited by atrial natriuretic peptide. Plasma EKODE was measured by liquid chromatography/mass spectrometry. All human plasmas tested contained EKODE in concentrations ranging from 10(-9) to 5x10(-7) mol/L. In samples from 24 adults, levels of EKODE correlated directly with aldosterone (r=0.53, P=0.007). In the 12 blacks in that cohort, EKODE also correlated with body mass index and systolic pressure. Those other correlations were not seen in white subjects. The results suggest that oxidized derivatives of polyunsaturated fatty acids other than arachidonic are biologically active. Compounds like EKODE, derived from linoleic acid, may affect adrenal steroid production in humans and mediate some of the deleterious effects of obesity and oxidative stress, especially in blacks.

Acute hyperlipidemia increases oxidative stress more in African Americans than in white Americans.

Oxidative stress emerges as a potential factor in the pathogenesis of hypertension and a common signal transduction mechanism by which various risk factors mediate cardiovascular and renal disease. A greater level of oxidative stress could contribute to higher rates of hypertension and related cardiovascular and renal complications in African Americans than in white Americans. The objective of this study was to compare oxidative stress induced by a standardized episode of acute hyperlipidemia in the two groups. Fifteen African Americans (37 +/- 1 years, 9 women/6 men, body mass index 30 +/- 2 kg/m(2)) and 15 whites (38 +/- 2 years, 9 women/6 men, body mass index 27 +/- 1 kg/m(2)) were evaluated. Acute hyperlipidemia was induced by a 4-h long infusion of Intralipid and heparin. Blood samples were drawn at baseline and after 2 and 4 h of acute hyperlipidemia for nonesterified fatty acids, triglycerides, and F2-isoprostanes, a biomarker of oxidative stress. Plasma nonesterified fatty acids and triglycerides increased significantly and similarly in African Americans and whites after 2 and 4 h of the Intralipid and heparin infusion. Although baseline plasma F2-isoprostanes did not differ between groups, F2-isoprostanes increased more in African Americans than in whites at 2 h (12.2 +/- 2.6 v 5.0 +/- 2.9 pg/mL, P <.05) and 4 h (13.9 +/- 3.1 v 3.0 +/- 3.0 pg/mL, P <.05) of acute hyperlipidemia. The results indicate that acute hyperlipidemia increases F2-isoprostanes more in African Americans than in whites. The findings may have important implications for ethnic differences in the prevalence of hypertension and cardiovascular and renal disease.

An oxidized metabolite of linoleic acid stimulates corticosterone production by rat adrenal cells.

Oxidized derivatives of linoleic acid have the potential to alter steroidogenesis. One such derivative is 12,13-epoxy-9- keto-10-(trans)-octadecenoic acid (EKODE). To evaluate the effect of EKODE on corticosterone production, dispersed rat zona fasciculata/reticularis (subcapsular) cells were incubated for 2 h with EKODE alone or together with rat ACTH (0, 0.2, or 2.0 ng/ml). In the absence of ACTH, EKODE (26 microM) increased corticosterone production from 5.3 +/- 2.3 to 14.7 +/- 5.0 ng. 10(6) cells. h(-1). The stimulatory effect of ACTH was increased threefold in the presence of EKODE (26.0 microM). Cholesterol transport/P-450scc activity was assessed by measuring basal and cAMP-stimulated pregnenolone production in the presence of cyanoketone (1.1 microM). EKODE (13.1 and 26.0 microM) significantly increased basal and cAMP-stimulated (0.1 mM) pregnenolone production. In contrast, EKODE decreased the effect of 1.0 mM cAMP. EKODE had no effect on early or late-pathway activity in isolated mitochondria. We conclude that EKODE stimulates corticosterone biosynthesis and amplifies the effect of ACTH. Increased levels of fatty acid metabolites may be involved in the increased glucocorticoid production observed in obese humans.

DASH diet lowers blood pressure and lipid-induced oxidative stress in obesity.

Evidence suggests that obesity may raise blood pressure (BP) through oxidative stress-sensitive mechanisms and that the Dietary Approaches to Stop Hypertension combination diet (DASH-CD) may decrease BP by enhancing antioxidant capacity. To address this question, 12 obese patients with high-normal-to-stage 1 hypertension (hypertensives) and 12 lean normotensives were studied on their usual diets and after following the DASH-CD and a low-antioxidant diet in random sequence for 4 weeks each. Acute oxidative stress was induced by a 4-hour infusion of intralipid and heparin. Ferric-reducing activity of plasma (FRAP) and plasma F2-isoprostanes were measured as biomarkers of antioxidant capacity and oxidative stress, respectively. BP was lower in obese hypertensives on the DASH-CD than on the usual and low-antioxidant diets (-8.1+/-1.5/-7.4+/-1.6 mm Hg, P<0.05). BP did not change significantly in lean normotensives after 4 weeks on the DASH-CD but tended to rise on the low-antioxidant diet. FRAP on usual diets was higher in lean subjects than in obese subjects. FRAP increased in obese but not lean volunteers on the DASH-CD compared with usual diet, and the group difference disappeared. F2-isoprostanes increased from baseline during intralipid and heparin in both groups on the low-antioxidant diet but not in obese hypertensives on the DASH-CD. Among free-living obese hypertensives, the DASH-CD raises antioxidant capacity, lowers BP, and reduces oxidative stress induced by acute hyperlipidemia. The findings are consistent with evidence that elevated BP in obese subjects may reflect an imbalance between antioxidant capacity and oxidative stress that is improved by the DASH-CD.

Increasing plasma fatty acids elevates F2-isoprostanes in humans: implications for the cardiovascular risk factor cluster.

OBJECTIVE: To determine whether raised concentrations of non-esterified fatty acids (NEFAs) may contribute to the cardiovascular risk factor cluster by increasing oxidative stress in vivo. DESIGN AND METHODS: Plasma and urine F2-isoprostanes, biomarkers of oxidative stress, were measured after an overnight fast and during a 4 h infusion of Intralipid and heparin to increase NEFAs in 10 obese hypertensive patients with and 12 healthy normotensive individuals without evidence of insulin resistance. A time-control group of nine healthy normotensive individuals received saline and heparin. RESULTS: Plasma F2-isoprostanes increased more in obese hypertensive individuals than in lean normotensive individuals after 2 h (14.9 +/- 2.8 ng/ml compared with 4.6 +/- 2.8 ng/ml; P < 0.05) but not after 4 h (10.3 +/- 2.5 ng/ml compared with 8.1 +/- 4.1 ng/ml; NS) of the Intralipid and heparin infusion. When obese and lean individuals were combined, plasma (+9.1 +/- 2.5 ng/ml; P < 0.05) and urine (+0.7 +/- 0.3 ng/mg creatinine; P < 0.05) F2-isoprostanes increased by about 20% after 4 h of Intralipid and heparin, whereas plasma F2-isoprostanes decreased by approximately 20% (-9.7 +/- 4.5 ng/ml; P < 0.05) after 4 h of saline and heparin. When individuals from both infusions were combined, the correlation between changes in plasma NEFAs and F2-isoprostanes after 4 h persisted after controlling for changes in triglyceride concentrations (partial r = 0.49; P < 0.01), whereas the correlation between changes in triglycerides and F2-isoprostanes did not persist after controlling for changes in NEFA concentrations (partial r = 0.33, NS). CONCLUSIONS: The findings indicate that an acute increase in plasma lipids increases the concentration of F2-isoprostanes, biomarkers of oxidative stress, especially in obese hypertensive individuals. The observations raise the possibility that increased concentrations of NEFAs contribute to the cardiovascular risk factor cluster through oxidative-stress-sensitive mechanisms.