Surgical ablation of whitened interscapular brown fat ameliorates cardiac pathology in salt-loaded metabolic syndrome rats.

Brown adipose tissue (BAT) is an endocrine organ that contributes to thermogenesis and energy consumption. We investigated the effects of salt loading and surgical removal of whitened interscapular BAT (iBAT) on cardiac and adipose tissue pathology in DahlS.Z-Leprfa /Leprfa (DS/obese) rats, an animal model of metabolic syndrome (MetS). DS/obese rats were subjected to surgical removal of iBAT or sham surgery at 8 weeks of age and were provided with drinking water containing or not containing 0.3% NaCl for 4 weeks beginning at 9 weeks of age. Removal of iBAT suppressed the salt-induced exacerbation of left ventricular inflammation, fibrosis, and diastolic dysfunction, but not that of hypertension development, in DS/obese rats. Salt loading attenuated adipocyte hypertrophy but enhanced inflammation in both visceral white adipose tissue (WAT) and iBAT. Although iBAT removal did not affect visceral WAT pathology in salt-loaded DS/obese rats, it attenuated the elevation of circulating interleukin-6 levels in these animals. Downregulation of uncoupling protein-1 expression in iBAT of DS/obese rats was not affected by salt loading. Our results suggest that the conversion of iBAT to WAT-like tissue contributes to a salt-induced elevation of circulating proinflammatory cytokine levels that leads to exacerbation of cardiac pathology in this model of MetS.

The prebiotic fiber inulin ameliorates cardiac, adipose tissue, and hepatic pathology, but exacerbates hypertriglyceridemia in rats with metabolic syndrome.

Prebiotics ameliorate dysbiosis and influence metabolism and the immune system, but their effects on cardiovascular complications in metabolic disorders remain largely unknown. We here investigated the effects of the soluble fiber inulin on cardiac, adipose tissue, and hepatic pathology as well as on metabolic disorders in DahlS.Z-Leprfa/Leprfa (DS/obese) rats, an animal model of metabolic syndrome (MetS). DS/obese rats and their homozygous lean (DahlS.Z-Lepr+/Lepr+, or DS/lean) littermate controls were fed a purified diet containing 5% or 20% inulin from 9 to 13 wk of age. The high-fiber diet ameliorated hypertension, left ventricular inflammation, fibrosis and diastolic dysfunction; attenuated adipose tissue inflammation and fibrosis; and alleviated the elevation of interleukin-6 levels, without affecting insulin resistance, in DS/obese rats. In addition, high fiber intake ameliorated lipid accumulation, inflammation, and fibrosis; attenuated the reduction in AMPK activity; upregulated sterol regulatory element-binding protein-1c gene expression; and increased the expression of microsomal triglyceride transfer protein gene in the liver of DS/obese rats. It also mitigated increases in total and non-high-density lipoprotein cholesterol levels but increased the triglyceride concentration in serum in these rats. None of these parameters were affected by high dietary fiber in DS/lean rats. The proportion of regulatory T cells in adipose tissue was influenced by dietary fiber but not by genotype. Our results indicate that inulin exacerbates hypertriglyceridemia but alleviates hypertension and cardiac injury as well as adipose tissue and hepatic pathology in MetS rats.NEW & NOTEWORTHY Prebiotics ameliorate dysbiosis and influence metabolism and the immune system, but their effects on cardiovascular complications in metabolic disorders remain largely unknown. Inulin ameliorated hypertension, cardiac injury, and diastolic dysfunction without affecting obesity or insulin resistance in a rat model of metabolic syndrome. The favorable cardiac effects of inulin may be related to inhibition of systemic inflammation associated with a reduction in circulating interleukin-6 levels. Additionally, inulin exacerbated hypertriglyceridemia but alleviates adipose tissue and hepatic pathology in these animals, as well as increased the number of regulatory T cells in adipose tissue.

Alleviation of salt-induced exacerbation of cardiac, renal, and visceral fat pathology in rats with metabolic syndrome by surgical removal of subcutaneous fat.

OBJECTIVES: Evidence suggests that visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) should be considered as distinct types of white fat. Although VAT plays a key role in metabolic syndrome (MetS), the role of subcutaneous adipose tissue (SAT) has been unclear. DahlS.Z-Leprfa/Leprfa (DS/obese) rats, an animal model of MetS, develop adipocyte hypertrophy and inflammation to similar extents in SAT and VAT. We have now investigated the effects of salt loading and SAT removal on cardiac, renal, and VAT pathology in DS/obese rats. METHODS: DS/obese rats were subjected to surgical removal of inguinal SAT or sham surgery at 8 weeks of age. They were provided with a 0.3% NaCl solution as drinking water or water alone for 4 weeks from 9 weeks of age. RESULTS: Salt loading exacerbated hypertension, insulin resistance, as well as left ventricular (LV) hypertrophy, inflammation, fibrosis, and diastolic dysfunction in DS/obese rats. It also reduced both SAT and VAT mass but aggravated inflammation only in VAT. Although SAT removal did not affect LV hypertrophy in salt-loaded DS/obese rats, it attenuated hypertension, insulin resistance, and LV injury as well as restored fat mass and alleviated inflammation and the downregulation of adiponectin gene expression in VAT. In addition, whereas salt loading worsened renal injury as well as upregulated the expression of renin-angiotensin-aldosterone system-related genes in the kidney, these effects were suppressed by removal of SAT. CONCLUSIONS: SAT removal attenuated salt-induced exacerbation of MetS and LV and renal pathology in DS/obese rats. These beneficial effects of SAT removal are likely attributable, at least in part, to inhibition of both VAT and systemic inflammation.

Anti-inflammatory effects of heat-killed Lactobacillus plantarum L-137 on cardiac and adipose tissue in rats with metabolic syndrome.

The effects of heat-killed Lactobacillus plantarum L-137 (HK L-137) on chronic inflammation associated with metabolic disorders have remained unknown. We examined the effects of HK L-137 on cardiac and adipose tissue pathophysiology in DahlS.Z-Lepr fa /Lepr fa (DS/obese) rats as a model of metabolic syndrome. DS/obese rats were treated orally with HK L-137 (2 or 75 mg kg-1 day-1) from 9 to 13 weeks of age. HK L-137 attenuated left ventricular (LV) inflammation and fibrosis as well as adipocyte hypertrophy, inflammation, and up-regulation of sterol regulatory element-binding protein-1c (SREBP-1c) gene expression in visceral and subcutaneous adipose tissue, without affecting body weight gain or hypertension. The low dose of HK L-137 also ameliorated LV diastolic dysfunction, the increase in subcutaneous fat mass, and insulin resistance as well as attenuated the down-regulation of Akt phosphorylation in visceral and subcutaneous adipose tissue, and the elevation of the circulating interleukin-6 concentration. Furthermore, the proportion of regulatory T (Treg) cells among CD4+ T cells in the spleen was increased by HK L-137. These results suggest that the anti-inflammatory effects of HK L-137 on the heart and adipose tissue are related, at least partly, to suppression of systemic inflammation associated with an increase in splenic Treg cell.

Effects of ramelteon on cardiac injury and adipose tissue pathology in rats with metabolic syndrome.

Melatonin regulates circadian rhythms but also has antioxidative and anti-inflammatory effects that ameliorate metabolic disorders. We investigated the effects of the selective melatonin agonist ramelteon on cardiac and adipose tissue pathology in the DahlS.Z-Leprfa /Leprfa (DS/obese) rat, a model of metabolic syndrome (MetS). Rats were treated with a low (0.3 mg/kg per day) or high (8 mg/kg per day) dose of ramelteon from 9 to 13 weeks of age. Ramelteon treatment at either dose attenuated body weight gain, left ventricular fibrosis, and diastolic dysfunction, as well as cardiac oxidative stress and inflammation, without affecting hypertension or insulin resistance. Although ramelteon did not affect visceral white adipose tissue (WAT) mass, it attenuated inflammation and downregulated insulin signaling in this tissue. In contrast, ramelteon reduced fat mass, adipocyte hypertrophy, and inflammation, and ameliorated impaired insulin signaling in subcutaneous WAT. In addition, ramelteon attenuated adipocyte hypertrophy, downregulated mitochondrial uncoupling protein 1, and upregulated 11ß-hydroxysteroid dehydrogenase type 1 expression in interscapular brown adipose tissue (BAT). In summary, ramelteon treatment attenuated obesity and cardiac injury, improved insulin signaling in visceral and subcutaneous WAT, and inhibited the whitening of BAT in rats with MetS.

Effects of mTOR inhibition on cardiac and adipose tissue pathology and glucose metabolism in rats with metabolic syndrome.

The mammalian target of rapamycin (mTOR) is a regulator of metabolism and is implicated in pathological conditions such as obesity and diabetes. We aimed to investigate the role of mTOR in obesity. A new animal model of metabolic syndrome (MetS), named DahlS.Z-Leprfa /Leprfa (DS/obese) rats was established previously in our laboratory. In this study, we used this model to evaluate the effects of mTOR inhibition on cardiac and adipose tissue pathology and glucose metabolism. DS/obese rats were treated with the mTOR inhibitor, everolimus, (0.83 mg/kg per day, per os) for 4 weeks at 9 weeks of age. Age-matched homozygous lean (DahlS.Z-Lepr+ /Lepr+ or DS/lean) littermates of DS/obese rats were used as controls. Treatment with everolimus ameliorated hypertension, left ventricular (LV) hypertrophy and fibrosis, and LV diastolic dysfunction, and attenuated cardiac oxidative stress and inflammation in DS/obese rats, but had no effect on these parameters in DS/lean rats. Treatment with everolimus reduced Akt Thr308 phosphorylation in the heart of DS/obese rats. It also alleviated obesity, hyperphagia, adipocyte hypertrophy, and adipose tissue inflammation in DS/obese rats. Everolimus treatment exacerbated glucose intolerance, but did not affect Akt phosphorylation levels in the fat or liver in these rats. Pancreatic ß-cell mass was increased in DS/obese rats compared with that in DS/lean rats and this effect was attenuated by everolimus. Activation of mTOR signaling contributes to the pathophysiology of MetS and its associated complications. And mTOR inhibition with everolimus ameliorated obesity as well as cardiac and adipose tissue pathology, but exacerbated glucose metabolism in rats with MetS.

Atorvastatin reduces cardiac and adipose tissue inflammation in rats with metabolic syndrome.

BACKGROUND: Statins are strong inhibitors of cholesterol biosynthesis and help to prevent cardiovascular disease. They also exert additional pleiotropic effects that include an anti-inflammatory action and are independent of cholesterol, but the molecular mechanisms underlying these additional effects have remained unclear. We have now examined the effects of atorvastatin on cardiac and adipose tissue inflammation in DahlS.Z-Leprfa/Leprfa (DS/obese) rats, which we previously established as a model of metabolic syndrome (MetS). METHODS AND RESULTS: DS/obese rats were treated with atorvastatin (6 or 20mgkg-1day-1) from 9 to 13weeks of age. Atorvastatin ameliorated cardiac fibrosis, diastolic dysfunction, oxidative stress, and inflammation as well as adipose tissue inflammation in these animals at both doses. The high dose of atorvastatin reduced adipocyte hypertrophy to a greater extent than did the low dose. Atorvastatin inhibited the up-regulation of peroxisome proliferator-activated receptor γ gene expression in adipose tissue as well as decreased the serum adiponectin concentration in DS/obese rats. It also activated AMP-activated protein kinase (AMPK) as well as inactivated nuclear factor-κB (NF-κB) in the heart of these animals. The down-regulation of AMPK and NF-κB activities in adipose tissue of DS/obese rats was attenuated and further enhanced, respectively, by atorvastatin treatment. CONCLUSIONS: The present results suggest that the anti-inflammatory effects of atorvastatin on the heart and adipose tissue are attributable at least partly to increased AMPK activity and decreased NF-κB activity in this rat model of MetS.

Effects of various types of anesthesia on hemodynamics, cardiac function, and glucose and lipid metabolism in rats.

Anesthesia can affect respiratory, circulatory, and endocrine systems but is necessary for certain experimental procedures such as echocardiography and blood sampling in small animals. We have now investigated the effects of four types of anesthesia [pentobarbital sodium (PENT), ketamine-xylazine (K/X), and low- or high-dose isoflurane (ISO)] on hemodynamics, cardiac function, and glucose and lipid metabolism in Sprague-Dawley rats. Aortic pressure, heart rate, and echocardiographic parameters were measured at various time points up to 45 min after the induction of anesthesia, and blood was then collected for measurement of parameters of glucose and lipid metabolism. Systolic aortic pressure remained constant in the PENT group, whereas it showed a biphasic pattern in the K/X group and a gradual decline in the ISO groups. Marked bradycardia was observed in the K/X group. The serum glucose concentration was increased and the plasma insulin level was reduced in the K/X and ISO groups compared with the PENT group. The concentrations of free fatty acids and norepinephrine in plasma were increased in the K/X group. Despite the metabolic effects of K/X and ISO, our results suggest that the marked bradycardic effect of K-X renders this combination appropriate for measurement of Doppler-derived indexes of left ventricular diastolic function, whereas the relative ease with which the depth of anesthesia can be controlled with ISO makes it suitable for manipulations or data collection over long time periods. On the other hand, PENT may be best suited for experiments that focus on measurement of cardiac function by M-mode echocardiography and metabolic parameters.