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Aging increases the risk of type 2 diabetes, and this can be prevented by dietary restriction (DR). We have previously shown that DR inhibits the downregulation of miRNAs and their processing enzymes - mainly Dicer - that occurs with aging in mouse white adipose tissue (WAT). Here we used fat-specific Dicer knockout mice (AdicerKO) to understand the contributions of adipose tissue Dicer to the metabolic effects of aging and DR. Metabolomic data uncovered a clear distinction between the serum metabolite profiles of Lox control and AdicerKO mice, with a notable elevation of branched-chain amino acids (BCAA) in AdicerKO. These profiles were associated with reduced oxidative metabolism and increased lactate in WAT of AdicerKO mice and were accompanied by structural and functional changes in mitochondria, particularly under DR. AdicerKO mice displayed increased mTORC1 activation in WAT and skeletal muscle, where Dicer expression is not affected. This was accompanied by accelerated age-associated insulin resistance and premature mortality. Moreover, DR-induced insulin sensitivity was abrogated in AdicerKO mice. This was reverted by rapamycin injection, demonstrating that insulin resistance in AdicerKO mice is caused by mTORC1 hyperactivation. Our study evidences a DR-modulated role for WAT Dicer in controlling metabolism and insulin resistance.

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Metabolic syndrome is a cluster of metabolic risk factors such as obesity, diabetes and cardiovascular diseases. Mitochondria is the main site of ATP production and its dysfunction leads to decreased oxidative phosphorylation, resulting in lipid accumulation and insulin resistance. Our group has demonstrated that kinins can modulate glucose and lipid metabolism as well as skeletal muscle mass. By using B2 receptor knockout mice (B2R-/-) we investigated whether kinin action affects weight gain and physical performance of the animals. Our results show that B2R-/- mice are resistant to high fat diet-induced obesity, have higher glucose tolerance as well as increased mitochondrial mass. These features are accompanied by higher energy expenditure and a lower feed efficiency associated with an increase in the proportion of type I fibers and intermediary fibers characterized by higher mitochondrial content and increased expression of genes related to oxidative metabolism. Additionally, the increased percentage of oxidative skeletal muscle fibers and mitochondrial apparatus in B2R-/- mice is coupled with a higher aerobic exercise performance. Taken together, our data give support to the involvement of kinins in skeletal muscle fiber type distribution and muscle metabolism, which ultimately protects against fat-induced obesity and improves aerobic exercise performance.

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We have investigated early programming of body mass in order to understand the multifactorial etiology of obesity. Considering that the renin-angiotensin system (RAS) is expressed and functional in the white adipose tissue (WAT) and modulates its development, we reasoned whether early transitory inhibition of angiotensin-I converting enzyme activity after birth could modify late body mass development. Therefore, newborn Wistar rats were treated with enalapril (10 mg/kg of body mass) or saline, starting at the first day of life until the age of 16 days. Between days ninetieth and hundred and eightieth, a group of these animals received high fat diet (HFD). Molecular, biochemical, histological, and physiological data were collected. Enalapril treated animals presented hyperphagia, overweight, and increased serum level of triglycerides, total cholesterol and leptin, in adult life. Body composition analyses revealed higher fat mass with increased adipocyte size in these animals. Molecular analyses revealed that enalapril treatment increases neuropeptide Y (NPY) and cocaine- and amphetamine-regulated transcript (CART) gene expression in hypothalamus, fatty acid synthase (FAS), and hormone-sensitive lipase (HSL) gene expression in retroperitoneal WAT, and decreases peroxixome proliferators-activated receptor (PPAR)γ, PPARα, uncoupling protein (UCP)2, and UCP3 gene expression in WAT. The results of the current study indicate that enalapril administration during early postnatal development increases body mass, adiposity and serum lipids in adulthood associated with enhanced food intake and decreased metabolic activity in WAT, predisposing to obesity in adulthood.

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Kinin B(1) and B(2) receptors play an essential role in inflammatory process and cardiovascular homeostasis. The present study investigated the vascular reactivity and nitric oxide (NO) generation in the isolated mesenteric arteriolar bed from B(1) (B(1)(-/-)) and B(2) receptor (B(2)(-/-)) knockout mice. Endothelial-dependent relaxation was significantly decreased in arterioles from both B(1)(-/-) and B(2)(-/-) in comparison to wild type (WT) mice, with no differences for endothelial-independent relaxating or vasoconstrictor agents. Plasmatic and vascular NO production were markedly reduced in both B(1)(-/-) and B(2)(-/-). In contrast, in the presence of l-arginine, Ca(2+) and co-factors for the enzyme, NO synthase activity was higher in homogenates of mesenteric vessels of B(1)(-/-) and B(2)(-/-). The present study demonstrated that targeted deletion of B(1) or B(2) receptor gene in mice induces important alterations in the vascular reactivity of resistance vessels and NO metabolism. The severe impairment in the endothelial-mediated vasodilation accompanied by decreased NO bioavailability, despite the augmented NOS activity, strongly indicates an exacerbation of NO inactivation in B(1)(-/-) and B(2)(-/-) vessels. The present data provide valuable information in order to clarify the relevance of kinin receptors in regulating vascular physiology and may point to new approaches regarding its correlation with endothelial dysfunction, oxidative stress and NO availability.

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Angiotensin I-converting enzyme (ACE), a common element of renin-angiotensin system (RAS) and kallikrein-kinin system (KKS), is involved in myelopoiesis modulation, mainly by cleaving the tetrapeptide N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP). Based on this finding and in our results showing B1 and B2 kinin receptors expression in murine bone marrow (BM) cells, we evaluated the ACE influence on myelopoiesis of kinin B1 receptor knockout mice (B1KO) using long-term bone marrow cultures (LTBMCs). Captopril and AcSDKP were used as controls. Enhanced ACE activity, expressed by non-hematopoietic cells (Ter-199(-) and CD45(-)), was observed in B1KO LTBMCs when compared to wild-type (WT) cells. ACE hyperfunction in B1KO cells was maintained when LTBMCs from B1KO mice were treated with captopril (1.0microM) or AcSDKP (1.0nM). Although no alterations were observed in ACE mRNA and protein levels under these culture conditions, 3.0nM of AcSDKP increased ACE mRNA levels in WT LTBMCs. No alteration in the number of GM-CFC was seen in B1KO mice compared to WT animals, even when the former were treated with AcSDKP (10microg/kg) or captopril (100mg/kg) for 4 consecutive days. Hematological data also revealed no differences between WT and B1KO mice under basal conditions. When the animals received 4 doses of lipopolysaccharide (LPS), a decreased number of blood cells was detected in B1KO mice in relation to WT. We also found a decreased percentage of Gr1(+)/Mac-1(+), Ter119(+), B220(+), CD3(+), and Lin(-)Sca1(+)c-Kit(+) (LSK) cells in the BM of B1KO mice compared to WT animals. Low AcSDKP levels were observed in BM cultures from B1KO in comparison to WT cultures. We conclude that ACE hyperfunction in B1KO mice resulted in faster hydrolysis of AcSDKP peptide, which in turn decreased in BM tissues allowing HSC to enter the S stage of the cell cycle.

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OBJECTIVE: Kinins mediate pathophysiological processes related to hypertension, pain, and inflammation through the activation of two G-protein-coupled receptors, named B(1) and B(2). Although these peptides have been related to glucose homeostasis, their effects on energy balance are still unknown. RESEARCH DESIGN AND METHODS: Using genetic and pharmacological strategies to abrogate the kinin B(1) receptor in different animal models of obesity, here we present evidence of a novel role for kinins in the regulation of satiety and adiposity. RESULTS: Kinin B(1) receptor deficiency in mice (B(1)(-/-)) resulted in less fat content, hypoleptinemia, increased leptin sensitivity, and robust protection against high-fat diet-induced weight gain. Under high-fat diet, B(1)(-/-) also exhibited reduced food intake, improved lipid oxidation, and increased energy expenditure. Surprisingly, B(1) receptor deficiency was not able to decrease food intake and adiposity in obese mice lacking leptin (ob/ob-B(1)(-/-)). However, ob/ob-B(1)(-/-) mice were more responsive to the effects of exogenous leptin on body weight and food intake, suggesting that B(1) receptors may be dependent on leptin to display their metabolic roles. Finally, inhibition of weight gain and food intake by B(1) receptor ablation was pharmacologically confirmed by long-term administration of the kinin B(1) receptor antagonist SSR240612 to mice under high-fat diet. CONCLUSIONS: Our data suggest that kinin B(1) receptors participate in the regulation of the energy balance via a mechanism that could involve the modulation of leptin sensitivity.

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Angiotensin-converting enzyme (ACE) is an ectoprotein able to modulate the activity of a plethora of compounds, among them angiotensin I and bradykinin. Despite several decades of research, new aspects of the mechanism of action of ACE have been elucidated, expanding our understanding of its role not only in cardiovascular regulation but also in different areas. Recent findings have ascribed an important role for ACE/kinin B(2) receptor heterodimerization in the pharmacological properties of the receptor. In this work, we tested the hypothesis that this interaction also affects ACE enzymatic activity. ACE catalytic activity was analyzed in Chinese hamster ovary cell monolayers coexpressing the somatic form of the enzyme and the receptor coding region using as substrate the fluorescence resonance energy transfer peptide Abz-FRK(Dnp)P-OH. Results show that the coexpression of the kinin B(2) receptor leads to an augmentation in ACE activity. In addition, this effect could be blocked by the B(2) receptor antagonist icatibant. The hypothesis was also tested in endothelial cells, a more physiological system, where both proteins are naturally expressed. Endothelial cells from genetically ablated kinin B(2) receptor mice showed a decreased ACE activity when compared with wild-type mice cells. In summary, this is the first report showing that the ACE/kinin B(2) receptor interaction modulates ACE activity. Taking into account the interplay among ACE, ACE inhibitors, and kinin receptors, we believe that these results will shed new light into the arena of the controversial search for the mechanism controlling these interactions.

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Kallikrein-kinin system exerts cardioprotective effects against pathological hypertrophy. These effects are modulated mainly via B2 receptor activation. Chronic physical exercise can induce physiological cardiac hypertrophy characterized by normal organization of cardiac structure. Therefore, the aim of this work was to verify the influence of kinin B2 receptor deletion on physiological hypertrophy to exercise stimulus. Animals were submitted to swimming practice for 5 min or for 60 min, 5 days a week, during 1 month and several cardiac parameters were evaluated. Results showed no significantly difference in heart weight between both groups, however an increased left ventricle weight and myocyte diameter were observed after the 60 min swimming protocol, which was more pronounced in B2(-/-) mice. In addition, sedentary B2(-/-) animals presented higher left ventricle mass when compared to wild-type (WT) mice. An increase in capillary density was observed in exercised animals, however the effect was less pronounced in B2(-/-) mice. Collagen, a marker of pathological hypertrophy, was increased in B2(-/-) mice submitted to swimming protocol, as well as left ventricular thickness, suggesting that these animals do not respond with physiological hypertrophy for this kind of exercise. In conclusion, our data suggest an important role for the kinin B2 receptor in physiological cardiac hypertrophy.

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Post-exercise hypotension is an important event for blood pressure regulation, especially in hypertensive individuals. Although post-exercise hypotension is a well-known phenomenon, the mechanism responsible is still unclear. The kallikrein-kinin system is involved in blood pressure control, but its role in post-exercise hypotension has not yet been investigated. Thus, the purpose of this study was to investigate the involvement of the vasodilators bradykinin and des-Arg(9)-BK and kallikrein activity in post-exercise hypotension promoted by 35 min of cycle ergometer (CE) or circuit weight-training (CWT) bouts in normotensive and hypertensive individuals. A significant decrease in mean arterial pressure at 45 and 60 min after CE and 45 min after CWT was observed in normotensive individuals. Hypertensive values of mean arterial pressure were significantly reduced at 45 and 60 min after CE and at 60 min after CWT. Before exercise, plasma bradykinin concentrations and kallikrein activity were higher in hypertensive compared to normotensive volunteers. Kinin levels increased in the groups evaluated at the end of the training period and 60 min post-exercise. These data suggest that the kallikrein-kinin system may be involved in post-exercise hypotension in normotensive and hypertensive individuals subjected to CE and CWT bouts.

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