Experimental rat models to study the metabolic syndrome

Early elevations in arterial pressure: a contributor to rapid depressive symptom emergence in female Zucker rats with metabolic disease?

One of the growing challenges to public health and clinical outcomes is the emergence of cognitive impairments, particularly depressive symptom severity, because of chronic elevations in metabolic disease and cerebrovascular disease risk. To more clearly delineate these relationships and to assess the potential for sexual dimorphism, we used lean (LZR) and obese Zucker rats (OZR) of increasing age to determine relationships between internal carotid artery (ICA) hemodynamics, cerebral vasculopathies, and the emergence of depressive symptoms. Male OZR exhibited progressive elevations in perfusion pressure within the ICA, which were paralleled by endothelial dysfunction, increased cerebral arterial myogenic activation, and reduced cerebral cortex microvessel density. In contrast, female OZR exhibited a greater degree of ICA hypertension than male OZR but maintained normal endothelial function, myogenic activation, and microvessel density to an older age range than did males. Although both male and female OZR exhibited significant and progressive elevations in depressive symptom severity, these were significantly worse in females. Finally, plasma cortisol concentration was elevated higher and at a younger age in female OZR as compared with males, and this difference was maintained to final animal usage at ∼17 wk of age. These results suggest that an increased severity of blood pressure waves may penetrate the cerebral circulation more deeply in female OZR than in males, which may predispose the females to a more severe emergence of depressive symptoms with chronic metabolic disease, whereas males may be more predisposed to more direct cerebral vasculopathies (e.g., stroke, transient ischemic attack).NEW & NOTEWORTHY We provide novel insight that the superior maintenance of cerebrovascular endothelial function in female versus male rats with chronic metabolic disease buffers myogenic activation of cerebral resistance arteries/arterioles despite worsening hypertension. As hypertension development is earlier and more severe in females, potentially due to an elevated stress response, the blunted myogenic activation allows greater arterial pressure wave penetrance into the cerebral microcirculation and is associated with accelerated emergence/severity of depressive symptoms in obese female rats.

Preventive effects of a nutraceutical mixture of berberine, citrus and apple extracts on metabolic disturbances in Zucker fatty rats

BACKGROUND

The prevention of obesity represents a major health and socio-economic challenge. Nutraceuticals are regularly highlighted for their beneficial effects in preventing the metabolic disturbances associated with obesity. However, few studies have described the combined action of nutraceutical mixtures combining polyphenols with alkaloids.

OBJECTIVE

The aim of this study was to evaluate the effects of long-term dietary supplementation with a mixture of Berberine, Citrus and Apple extracts (BCA) in the primary prevention of obesity and its metabolic and vascular complications in the obese Zucker rat, a spontaneous model of genetic obesity and insulin resistance.

METHODS

Sixteen 8-week-old obese Zucker male rats were randomly divided into two groups: all rats received oral gavage daily either with water, untreated obese (U-ObZ) or BCA (BCA-ObZ) mixture for thirteen weeks. Morphological and metabolic parameters were measured along the study. Cumulative concentration-response curves to insulin, acetylcholine and phenylephrine were determined on isolated thoracic aorta. Colon permeability measurements were performed using the Ussing chamber technique. Fecal samples collected at the beginning and the end of the protocol were used as a template for amplification of the V3-V4 region of the 16S rDNA genes.

RESULTS

BCA supplementation reduced weight gain (p<0.05) and food intake (p<0.05) in the BCA-ObZ group rats compared to the U-ObZ group rats. It also improved glucose tolerance (p<0.001) and decreased fasting insulin and Homeostasis model assessment index (p<0.05). Through ex vivo experiments, the BCA mixture enhanced significantly aortic insulin relaxation (p<0.01), reduced α1-adrenoceptor-mediated vasoconstriction (p<0.01), and decreased distal colon permeability. Moreover, short-chain fatty acid producers such as Bacteroides, Blautia, and Akkermansia were found to be increased by the BCA mixture supplementation.

CONCLUSION

The results showed that a 13-week-supplementation with BCA mixture prevented weight gain and improved glucose metabolism in obese Zucker rats. We also demonstrated that BCA supplementation improved vascular function, colonic barrier permeability and gut microbiota profile.

Glutathione Levels and Lipid Oxidative Damage in Selected Organs of Obese Koletsky and Lean Spontaneously Hypertensive Rats

Koletsky rats, the genetically obese strain of spontaneously hypertensive rats (SHROB), are the well-accepted animal model of human metabolic syndrome. They are characterized by early onset obesity, spontaneous hypertension, hyperinsulinemia, hyperlipidemia, proteinuria and shortened life-span. One of the factors in the pathogenesis of metabolic syndrome is oxidative stress. The aim of the present study was to compare two parameters related to oxidative stress: the levels of the main intracellular antioxidant, reduced glutathione as well as the indirect indicator of lipid peroxidation damage, thiobarbituric acid-reactive substances (TBARS) in heart, renal cortex and medulla and liver in male lean spontaneously hypertensive rats (SHR) and obese Koletsky rats. We did not find any significant differences in these markers in heart and kidneys. However, we found significantly lower glutathione level in Koletsky rat liver compared with SHR (5.03+/-0.23 vs. 5.83+/-0.14 µmol/g tissue, respectively). On the contrary, we observed significantly higher TBARS levels in Koletsky rat liver compared with SHR (28.56+/-2.15 vs. 21.83+/-1.60 nmol/mg protein, respectively). We conclude that the liver is the most sensitive tissue to oxidative damage with the significantly decreased concentration of glutathione and the significantly increased concentration of TBARS in obese Koletsky rats in comparison with lean control SHR.

Comparison of Metabolic Changes after 6 Months of High-Carbohydrate Diet or High-Fat Diet with Low Dose Streptozotocin Injection in Rats

We compared 2 models of metabolic syndrome in rats: high-fat diet (58% calories) with single streptozotocin injection at a dose of 25 mg/kg and replacement of water with 20% fructose solution. The model with fructose solution did not cause the main signs of metabolic syndrome over 24 weeks: concentrations of glucose, triglycerides, cholesterol, weight, and BP did not significantly differ from the control group (standard diet). At the same time, single streptozotocin administration was followed by the development of persistent hyperglycemia, hypertriglyceridemia, hypercholesterolemia, and signs of visceral obesity. High-fat diet combined with injection of streptozotocin in a low dose can be considered a more representative model of metabolic syndrome in humans.

Synthesis and Anti-Diabetic Activity of an 8-Purine Derivative as a Novel DPP-4 Inhibitor in Obese Diabetic Zücker Rats

Type 2 diabetes mellitus (T2DM) is one of the world's principal metabolic diseases characterized by chronic hyperglycemia. The gut incretin hormones, glucagon-like peptide 1 (GLP-1) and gastric inhibitory polypeptide (GIP), which has been proposed as a new treatment for T2DM, are extensively metabolized by Dipeptidyl peptidase 4 (DPP-4). Inhibitors of DPP-4 block the degradation of GLP-1 and GIP and may increase their natural circulating levels, favoring glycemic control in T2DM. A novel and potent selective inhibitor of DPP-4 with an 8-purine derived structure (1) has been developed and tested in vitro and in vivo in Zücker obese diabetic fatty (ZDF) rats, an experimental model of the metabolic syndrome and T2DM to assess the inhibitory activity using vildagliptin as reference standard. ZDF rats were subdivided into three groups (n = 7/group), control (C-ZDF), and those treated with compound 1 (Compound1-ZDF) and with vildagliptin (V-ZDF), both at 10 mg/kg/d rat body weight, in their drinking water for 12 weeks, and a group of lean littermates (ZL) was used. ZDF rats developed DM (fasting hyperglycemia, 425 ± 14.8 mg/dL; chronic hyperglycemia, HbA1c 8.5 ± 0.4%), compared to ZL rats. Compound 1 and vildagliptin reduced sustained HbAl1c (14% and 10.6%, P < 0.05, respectively) and fasting hyperglycemia values (24% and 19%, P < 0.05, respectively) compared to C-ZDF group (P < 0.001). Compound 1 and vildagliptin have shown a potent activity with an IC50 value of 4.92 and 3.21 µM, respectively. These data demonstrate that oral compound 1 administration improves diabetes in ZDF rats by the inhibitory effect on DPP-4, and the potential to be a novel, efficient and tolerable approach for treating diabetes of obesity-related T2DM, in ZDF rats.

Effect of Gracilaria vermiculophylla Macroalga on Non-Alcoholic Fatty Liver Disease in Obese Rats

Marine algae are valuable sources of bioactive compounds that have the potential to be used in the management of various pathologies. Despite the increasing prevalence of NAFLD, the absence of an approved effective pharmacological treatment with demonstrable effectiveness persists. In this context, the aim of the present study is to assess the effect of Gracilaria vermiculophylla red seaweed dietary supplementation on hepatic lipid accumulation, as well as on oxidative stress, inflammation and fibrosis- related markers on obese fa/fa Zucker rats fed with a standard diet, supplemented or not with 2.5% or 5% dehydrated Gracilaria vermiculophylla. After a six-week supplementation with the macroalga, no significant reduction in hepatic total lipid content or hepatic triglyceride content was observed. However, both doses were able to diminish hepatic NEFA concentration by reducing de novo lipogenesis and increasing mitochondrial biogenesis. Moreover, supplementation with the dose of 2.5% improved some oxidative stress and inflammation-related markers. Supplementation with the dose of 5% did not exert these clear beneficial effects. Thus, this study demonstrates that while Gracilaria vermiculophylla may not mitigate hepatic steatosis, it could exert protective effects on the liver by reducing NEFA content and enhancing oxidative stress and inflammation parameters.

Chronic melatonin treatment improves obesity by inducing uncoupling of skeletal muscle SERCA-SLN mediated by CaMKII/AMPK/PGC1α pathway and mitochondrial biogenesis in female and male Zücker diabetic fatty rats

Melatonin acute treatment limits obesity of young Zücker diabetic fatty (ZDF) rats by non-shivering thermogenesis (NST). We recently showed melatonin chronically increases the oxidative status of vastus lateralis (VL) in both obese and lean adult male animals. The identification of VL skeletal muscle-based NST by uncoupling of sarcoendoplasmic reticulum Ca2+-ATPase (SERCA)- sarcolipin (SLN) prompted us to investigate whether melatonin is a SERCA-SLN calcium futile cycle uncoupling and mitochondrial biogenesis enhancer. Obese ZDF rats and lean littermates (ZL) of both sexes were subdivided into two subgroups: control (C) and 12 weeks orally melatonin treated (M) (10 mg/kg/day). Compared to the control groups, melatonin decreased the body weight gain and visceral fat in ZDF rats of both sexes. Melatonin treatment in both sex obese rats restored the VL muscle skin temperature and sensitized the thermogenic effect of acute cold exposure. Moreover, melatonin not only raised SLN protein levels in the VL of obese and lean rats of both sexes; also, the SERCA activity. Melatonin treatment increased the SERCA2 expression in obese and lean rats (both sexes), with no effects on SERCA1 expression. Melatonin increased the expression of thermogenic genes and proteins (PGC1-α, PPARγ, and NRF1). Furthermore, melatonin treatment enhanced the expression ratio of P-CaMKII/CaMKII and P-AMPK/AMPK. In addition, it rose mitochondrial biogenesis. These results provided the initial evidence that chronic oral melatonin treatment triggers the CaMKII/AMPK/PGC1α axis by upregulating SERCA2-SLN-mediated NST in ZDF diabetic rats of both sexes. This may further contribute to the body weight control and metabolic benefits of melatonin.

J147 affects cognition and anxiety after surgery in Zucker rats

Vulnerable patients are at risk for neuroinflammation-mediated post-operative complications, including depression (POD) and cognitive dysfunction (POCD). Zucker rats, expressing multiple risk factors for post-operative complications in humans, may provide a clinically relevant model to study pathophysiology and explore potential interventions. J147, a newly developed anti-dementia drug, was shown to prevent POCD in young healthy rats, and improved early post-surgical recovery in Zucker rats. Aim of the present study was to investigate POCD and the therapeutic potential of J147 in male Zucker rats. Risk factors in the Zucker rat strain were evaluated by comparison with lean littermates. Zucker rats were subjected to major abdominal surgery. Acute J147 treatment was provided by a single iv injection (10 mg/kg) at the start of surgery, while chronic J147 treatment was provided in the food (aimed at 30 mg/kg/day), starting one week before surgery and up to end of protocol. Effects on behavior were assessed, and plasma, urine and brain tissue were collected and processed for immunohistochemistry and molecular analyses. Indeed, Zucker rats displayed increased risk factors for POCD, including obesity, high plasma triglycerides, low grade systemic inflammation, impaired spatial learning and decreased neurogenesis. Surgery in Zucker rats reduced exploration and increased anxiety in the Open Field test, impaired short-term spatial memory, induced a shift in circadian rhythm and increased plasma neutrophil gelatinase-associated lipocalin (NGAL), microglia activity in the CA1 and blood brain barrier leakage. Chronic, but not acute J147 treatment reduced anxiety in the Open Field test and protected against the spatial memory decline. Moreover, chronic J147 increased glucose sensitivity. Acute J147 treatment improved long-term spatial memory and reversed the circadian rhythm shift. No anti-inflammatory effects were seen for J147. Although Zucker rats displayed risk factors, surgery did not induce extensive POCD. However, increased anxiety may indicate POD. Treatment with J147 showed positive effects on behavioral and metabolic parameters, but did not affect (neuro)inflammation. The mixed effect of acute and chronic treatment may suggest a combination for optimal treatment.

A diet containing cod backbone proteins attenuated the development of mesangial sclerosis and tubular dysfunction in male obese BTBR ob/ob mice

PURPOSE

The obese black and tan, brachyuric (BTBR) ob/ob mouse spontaneously develops features comparable to human diabetic nephropathy. The primary aim of the present study was to investigate if a diet containing fish proteins would attenuate or delay the development of glomerular hypertrophy (glomerulomegaly), mesangial sclerosis and albuminuria in obese BTBR ob/ob mice.

METHODS

Obese BTBR.CgLepob/WiscJ male mice were fed diets containing 25% of protein from Atlantic cod backbones and 75% of protein from casein (Cod-BB group), or casein as the sole protein source (control group). Kidneys were analysed morphologically, and markers for renal dysfunction were analysed biochemically in urine and serum.

RESULTS

The Cod-BB diet attenuated the development of mesangial sclerosis (P 0.040) without affecting the development of glomerular hypertrophy and albuminuria. The urine concentration of cystatin C (relative to creatinine) was lower in mice fed the Cod-BB diet (P 0.0044).

CONCLUSION

A diet containing cod backbone protein powder attenuated the development of mesangial sclerosis and tubular dysfunction in obese BTBR ob/ob mice, but did not prevent the development of glomerular hypertrophy and albuminuria in these mice.

Effect of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol and benzo[a]pyrene exposure on the development of metabolic syndrome in mice

AIM

The prevalence of metabolic syndrome (MetS), a cluster of serious medical conditions that raise the risk of lung cancer, has increased worldwide. Tobacco smoking (TS) potentially increases the risk of developing MetS. Despite the potential association of MetS with lung cancer, preclinical models that mimic human diseases, including TS-induced MetS, are limited. Here we evaluated the impact of exposure to tobacco smoke condensate (TSC) and two representative tobacco carcinogens, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNK) and benzo[a]pyrene (BaP), on MetS development in mice.

MATERIALS AND METHODS

FVB/N or C57BL/6 mice were exposed to vehicle, TSC, or NNK and BaP (NB) twice weekly for 5 months. The serum levels of total cholesterol (TCHO), triglycerides, high-density lipoprotein (HDL), blood glucose, and metabolites, along with glucose tolerance and body weight, were measured.

KEY FINDINGS

Compared with those of vehicle-treated mice, mice with TSC or NB exposure displayed major phenotypes associated with MetS, including increased serum levels of TCHO, triglycerides, and fasting and basal blood glucose and decreased glucose tolerance, and serum levels of HDL. These MetS-associated changes were found in both FVB/N and C57BL/6 mice that were susceptible or resistant to carcinogen-induced tumorigenesis, respectively, indicating that tumor formation is not involved in the TSC- or NB-mediated MetS. Moreover, oleic acid and palmitoleic acid, which are known to be associated with MetS, were significantly upregulated in the serum of TSC- or NB-treated mice compared with those in vehicle-treated mice.

SIGNIFICANCE

Both TSC and NB caused detrimental health problems, leading to the development of MetS in experimental mice.

Neuroprotection from protein misfolding in cerebral hypoperfusion concurrent with metabolic syndrome. A translational perspective

Based on clinical and experimental evidence, metabolic syndrome (MetS) and type 2 diabetes (T2D) are considered risk factors for chronic cerebral hypoperfusion (CCH) and neurodegeneration. Scientific evidence suggests that protein misfolding is a potential mechanism that explains how CCH can lead to either Alzheimer's disease (AD) or vascular cognitive impairment and dementia (VCID). Over the last decade, there has been a significant increase in the number of experimental studies regarding this issue. Using several animal paradigms and different markers of CCH, scientists have discussed the extent to which MetSor T2D causes a decrease in cerebral blood flow (CBF). In addition, different models of CCH have explored how long-term reductions in oxygen and energy supply can trigger AD or VCID via protein misfolding and aggregation. Research that combines two or three animal models could broaden knowledge of the links between these pathological conditions. Recent experimental studies suggest novel neuroprotective properties of protein-remodeling factors. In this review, we present a summarized updated revision of preclinical findings, discussing clinical implications and proposing new experimental approaches from a translational perspective. We are confident that research studies, both clinical and experimental, may find new diagnostic and therapeutic tools to prevent neurodegeneration associated with MetS, diabetes, and any other chronic non-communicable disease (NCD) associated with diet and lifestyle risk factors.

The role of exercise intensity on fatty liver in rats

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and is often caused by obesity. Currently, moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) are two effective treatments for reducing fat mass in patients with obesity and NAFLD. However, the comparative fat-reducing effects and underlying molecular mechanisms of MICT and HIIT remain unclear. This comprehensive study was performed on male Wistar rats treated with standard diet, high-fat diet, MICT, and HIIT to explore their comparative fat-reducing effects and corresponding molecular mechanisms. HIIT had a greater effect on hepatic vacuolation density and lipid content reduction than MICT, and triglyceride and total cholesterol levels in the serum and the liver demonstrated different sensitivities to different exercise training programs. At the molecular level, both MICT and HIIT altered the processes of fatty acid synthesis, fatty acid transport, fatty acid β-oxidation, and cholesterol synthesis, wherein the transcriptional and translational levels of signaling molecules peroxisome proliferator-activated receptors (PPARs) regulating fatty acid and cholesterol synthesis were strongly changed. Moreover, the metabolic pathways of amino acids, bile acids, and carbohydrates were also affected according to transcriptome analysis, and the changes in the above-mentioned processes in the HIIT group were greater than those in the MICT group. In combination with the search tool for the retrieval of interacting genes/proteins (STRING) analysis and the role of PPARs in lipid metabolism, as well as the expression pattern of PPARs in the MICT and HIIT groups, the MICT-and HIIT-induced fat loss was mediated by the PPAR pathway, causing feedback responses in fatty acid, steroid, amino acid, bile acid, and carbohydrate metabolism, and HIIT had a better fat-reducing effect, which may be initiated by PPAR-α. This study provides a theoretical basis for targeted therapy of patients with obesity and NAFLD.

Effects of diets containing proteins from fish muscles or fish by-products on the circulating cholesterol concentration in rodents: a systematic review and meta-analysis

A high circulating cholesterol concentration is considered an important risk factor for the development of CVD. Since lean fish intake and fish protein supplementation have been associated with lower cholesterol concentration in some but not all clinical studies, the main aim of this study was to investigate the effect of diets containing proteins from fish muscles and fish by-products on the serum/plasma total cholesterol (TC) concentration in rodents. A systematic literature search was performed using the databases PubMed, Web of Science and Embase, structured around the population (rodents), intervention (type of fish and fraction, protein dose and duration), comparator (casein) and the primary outcome (circulating TC). Articles were assessed for risk of bias using the SYRCLE's tool. A meta-analysis was conducted in Review Manager v. 5·4·1 (the Cochrane Collaboration) to determine the effectiveness of proteins from fish on the circulating TC concentration. Thirty-nine articles were included in the systematic review and meta-analysis, with data from 935 rodents. The risk of bias is unclear since few of the entries in the SYRCLE's tool were addressed. Consumption of proteins from fish resulted in a significantly lower circulating TC concentration when compared with control groups (mean difference -0·24 mmol/l, 95 % CI - 0·34, -0·15, P < 0·00001), with high statistical heterogeneity (I² = 71 %). To conclude, proteins from fish muscles and by-products show promise as a functional dietary ingredient or supplement by preventing high cholesterol concentration in rodents, thus reducing one of the most important risk factors for developing CVD.

Morphological changes in the heart and aorta of rats with diet-induced metabolic syndrome

Aim. To identify early morphological changes in the heart and aorta of rats with experimental metabolic syndrome induced by a high-fat and high-carbohydrate diet (HFHCD).

Materials and methods. The study was carried out on male Wistar rats. The animals were divided into two groups: a control group (n = 10) and an experimental group (n = 10). The rats from the control group were fed with a standard laboratory diet. The rats from the experimental group received HFHCD for 12 weeks. Body weight, blood pressure (BP), and individual parameters of carbohydrate and lipid metabolism were assessed in the rats.   A histologic examination of the heart and aorta in the animals was performed.

Results. Feeding rats with HFHCD led to an increase in body weight, elevation of BP, obesity, hyperglycemia, and triglyceridemia. The histologic examination of the heart in the rats of the experimental group showed signs of vascular disease, lipomatosis, and focal myocardial degeneration. Lipid accumulation in the cells of the media, hyperplasia of adipocytes in the adventitia, and depletion and fragmentation of the elastic lamina were revealed in the aortic wall of the rats receiving HFHCD.

Conclusion. The study indicated that HFHCD is an effective way to model metabolic syndrome. Structural disorders in the heart and aorta may be the mainstay for the development of cardiomyopathy and arterial hypertension in diet-induced metabolic syndrome.

Diet Containing Soy Protein Concentrate With Low and High Isoflavones for 9 Weeks Protects Against Non-alcoholic Fatty Liver Steatosis Using Obese Zucker Rats

Non-alcoholic fatty liver disease (NAFLD), is one of the main liver diseases in the US and the world which often is related to obesity. Previously, we reported short- and long-term consumption of soy protein isolate diet with high isoflavones can reduce liver steatosis in the male and female obese Zucker rat model. However, the effects of high vs. low soy isoflavones on NAFLD is less known. The objectives of the present study were to examine the role of isoflavones levels in soy protein concentrate diets on protection against NAFLD in an obese rat model. Forty-two 6-week old lean (L, n = 21) and obese (O, n = 21) Zucker rats were randomly assigned to 1 of 3 dietary groups: casein diet (C = control), soy protein concentrate with low isoflavones (LIF), or soy protein concentrate with high isoflavones (HIF) for 9 weeks. Rats were weighed twice weekly. After 9 weeks, rats were sacrificed and samples of livers were taken for histopathological analysis. Serums were collected to measure ALT and AST levels. Results indicate that obese rats gained significantly more weight than lean rats for all three diet groups (P < 0.001). No significant difference in body weight between LC, LLIF and LHIF was noted. However, the OLIF and OHIF rats gained significantly more weight than OC rats (P < 0.001). Liver steatosis scores were significantly greater in obese rats compared to lean rats (P < 0.001). The OLIF and OHIF-fed rats had significantly reduced steatosis scores than OC rats (P = 0.013 and P < 0.001, respectively). The serum ALT levels were significantly greater in OC, OLIF and OHIF compared to LC, LLIF and LHIF, respectively (P < 0.001, P < 0.001, and P = 0.011). AST serum levels were greater in OC and OLIF compared to LC and LLIF, respectively (P = 0.001 and P = 0.022). In summary, we found that soy protein concentrate with isoflavones protects against liver steatosis and the protection is greater with a higher concentration of isoflavones.

Aerobic exercise training combined or not with okra consumption as a strategy to prevent kidney changes caused by metabolic syndrome in Zucker rats

The complications of Metabolic Syndrome (MetS) include kidney disease, and most dialysis patients are diagnosed with MetS. The benefit of exercise training (ET) for MetS treatment is already well defined in the literature, but the antidiabetic and antihyperlipidemic benefits of okra (O) have been discovered only recently. The aim of this study was to evaluate the effects of O and/or ET supplementation on renal function and histology; serum urea and creatinine value; inflammation (IL-6, IL-10, TNF-α) and oxidative stress in renal tissue. For this, 32 Zucker rats (fa/fa) were randomly separated into four groups of 8 animals each: Metabolic Syndrome (MetS), MetS + Okra (MetS + O), MetS + Exercise Training (MetS + ET), and MetS + Exercise Training and Okra (MetS + ET + O), and 8 Zucker lean (fa/+) rats comprised the Control group (CTL). Okra was administered by orogastric gavage 2x/day (morning and night, 100 mg/kg) and ET performed on the treadmill, at moderate intensity, 1h/day, 5x/week for 6 weeks. Although the renal function was not altered, the animals with MetS showed greater fibrotic deposition accompanied by a worse stage of renal injury, in addition to increased kidney weight. Although all interventions were beneficial in reducing fibrosis, only ET combined with O was able to improve the degree of renal tissue impairment. ET improved the anti-inflammatory status and reduced nitrite levels, but the combination of ET and O was more beneficial as regards catalase activity. Okra consumption alone did not promote changes in inflammatory cytokines and oxidative stress in the kidney. In conclusion, ET combined or not with O seems to be beneficial in preventing the progression of renal disease when renal function is not yet altered.

Rapeseed (canola) oil aggravates metabolic syndrome-like conditions in male but not in female stroke-prone spontaneously hypertensive rats (SHRSP)

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Canola oil shortens life of male SHRSP.

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Testis is the target of canola oil toxicity.

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Inhibition of negative regulation by testosterone of aldosterone production may be a trigger of canola oil toxicity.

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Facilitation of hypertension by aldosterone may lead to life-shortening.

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Increased plasma lipids by canola oil have no relevance to life-shortening.

This study was conducted to investigate whether or not there are sex differences in canola oil (CAN)-induced adverse events in the rat and to understand the involvement and the role of testosterone in those events, including life-shortening. Stroke-prone spontaneously hypertensive rats (SHRSP) of both sexes were fed a diet containing 10 wt/wt% soybean oil (SOY, control) or CAN as the sole dietary fat. The survival of the males fed the CAN diet was significantly shorter than that of those fed the SOY diet. In contrast, the survival of the females was not affected by CAN. The males fed the CAN diet showed elevated blood pressure, thrombopenia and insulin-tolerance, which are major symptoms of metabolic syndrome, whereas such changes by the CAN diet were not found in the females. Plasma testosterone was significantly lower in animals of both sexes fed the CAN diet than in those fed the SOY diet, but interestingly, the lowered testosterone was accompanied by a marked increase in plasma aldosterone only in the males. These results demonstrate significant sex differences in CAN-toxicity and suggest that those sex differences may be attributable to the increased aldosterone level, which triggers aggravation of the genetic diseases specific to SHRSP, that is, metabolic syndrome-like conditions, but only in the males. The present results also suggest that testosterone may negatively regulate aldosterone production in the physiology of the males, and the inhibition of that negative regulation caused by the CAN diet is one of the possible causes of the adverse events.

Metabolic Status of Lean and Obese Zucker Rats Based on Untargeted and Targeted Metabolomics Analysis of Serum

Obesity is growing worldwide epidemic. Animal models can provide some clues about the etiology, development, prevention, and treatment of obesity. We examined and compared serum metabolites between seven lean (L) and seven obese (O) female Zucker rats to investigate the individual serum metabolic profile. A combination of HPLC-UV, HPLC-ECD, and LC-MS revealed more than 400 peaks. The 50 highest quality peaks were selected as the focus of our study. Untargeted metabolomics analysis showed significantly higher mean peak heights for 20 peaks in L rats, generally distributed randomly, except for a cluster (peaks 44–50) where L showed stable dominancy over O. Only eight peaks were significantly higher in O rats. Peak height ratios between pairs of L and O rats were significantly higher at 199 positions in L rats and at 123 positions in O rats. Targeted metabolomics analysis showed significantly higher levels of methionine, cysteine, tryptophan, kynurenic acid, and cysteine/cystine ratio in L rats and significantly higher levels of cystine and tyrosine in O rats. These results contribute to a better understanding of systemic metabolic perturbations in the obese Zucker rat model, emphasizing the value of both whole metabolome and individual metabolic profiles in the design and interpretation of studies using animal models.

High-fat western diet-consumption alters crystalline silica-induced serum adipokines, inflammatory cytokines and arterial blood flow in the F344 rat

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Silica reduced serum leptin and adiponectin, no effects on body or fat pad weight.

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HFWD-consumption altered pro-inflammatory cytokines in silica-exposed animals.

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Silica altered pulse frequency; HFWD increased mean blood flow; effects additive.

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HFWD affected silica-induced metabolic effects.

Adipose tissue (AT) plays a central role in the maintenance of whole-body energy homeostasis through release of adipokines. High-fat Western diet (HFWD)-consumption contributes to obesity, disruption of adipocyte metabolism, chronic systemic inflammation, and metabolic dysfunction (MetDys). MetDys is associated with impaired lung function, pulmonary hypertension, and asthma. Thirty-five percent of adults in the U.S. have MetDys, yet the impact of MetDys on susceptibility to occupational hazards is unknown. The aim of this study was to determine the potential of HFWD-consumption to alter inhaled crystalline silica dust-induced metabolic responses. Six-wk old male F344 rats were fed a HFWD (45 kcal % fat, sucrose 22.2 % by weight) or standard rat chow (STD, controls), and exposed to silica-inhalation (6 h/d, 5 d/wk, 39 d; Min-U-Sil 5®, 15 mg/m³) or filtered air. Indices of MetDys and systemic inflammation were measured at 0, 4, and 8 wk following cessation of silica exposure. At 8 wk post-exposure, silica reduced serum leptin and adiponectin levels, and increased arterial pulse frequency. HFWD-consumption induced weight gain, altered adipokines, liver, kidney, and pancreatic function, and increased tail artery blood flow. At 8 wk in HFWD + SIL-treated animals, the levels of serum pro-inflammatory cytokines (IFN-γ, CXCL-1, TNF-α, IL-1β, IL-4, IL-5, IL-6, IL-10 and IL-13) were increased compared to STD + SIL but were less than HFWD + AIR-induced levels. In conclusion, consumption of a HFWD altered silica-induced metabolic responses and silica exposure disrupted AT endocrine function. These findings demonstrate previously unknown interactions between HFWD-consumption and occupational silica exposure.

Whey proteins inhibit food intake and tend to improve oxidative balance in obese zucker rats

BACKGROUND/AIMS

Whey proteins (WP), obtained from milk after casein precipitation, represent a heterogeneous group of proteins. WP are reported to inhibit food intake in diet-induced experimental obesity; WP have been proposed as adjuvant therapy in oxidative stress-correlated pathologies. This work evaluates the effects of WP in comparison with casein, as a source of alimentary proteins, on food intake, weight growth and some indexes of oxidative equilibrium in Zucker Rats, genetically prone to obesity.

METHODS

We monitored food intake and weight of Zucker Rats during the experiment, and some markers of oxidative equilibrium.

RESULTS

WP induced significant decrease of food intake in comparison to casein (WP 80.41 ± 1.069 ml/day; CAS: 88.95 ± 1.084 ml/day; p < 0.0005). Body weight growth was slightly reduced, and the difference was just significant (WP 128.2 ± 6.56 g/day; CAS 145.2 ± 3.29 g/day; p = 0.049), while plasma HNE level was significantly lower in WP than in CAS (WP 41.2 ± 6.3 vs CAS 69.61 ± 4.69 pmol/ml, p = 0.007). Mild amelioration of oxidative equilibrium was indicated by a slight increase of total glutathione both in the liver and in the blood and a significant decrease of plasma 4-hydroxynonenal in the group receiving WP.

CONCLUSIONS

The effect of WP on food intake and weight growth in Zucker Rats is particularly noteworthy since the nature of their predisposition to obesity is genetic; the possible parallel amelioration of the oxidative balance may constitute a further advantage of WP since oxidative stress is believed to be interwoven to obesity, metabolic syndrome and their complications.

Intestinal, liver and lipid disorders in genetically obese rats are more efficiently reduced by dietary milk thistle seeds than their oil

We hypothesized that milk thistle seed or seed oil dietary supplementation reduces intestinal, liver and lipid disorders specific to genetic obesity, and the seeds can be more efficient in doing so. Lean and obese male Zucker rats were allocated to 4 groups: the lean (LC) and obese control (OC) groups fed a standard diet and the other 2 obese groups fed a diet supplemented with milk thistle seed oil (O + MTO) or milk thistle seeds (O + MTS). After 5 weeks of feeding, the cecal SCFA pool was slightly and significantly lower in OC and O + MTO compared with LC and O + MTS. The liver fat content was greater in OC, O + MTO and O + MTS compared with LC; however, it was significantly lower in O + MTS than in OC and O + MTO. The plasma cholesterol was greater in OC compared with LC, O + MTO and O + MTS; however, it was significantly greater in O + MTO and O + MTS compared with LC. The plasma bilirubin was detected in OC and O + MTO, whereas it was not present in LC and O + MTS. Milk thistle seeds can improve fermentation events in the distal intestine and reduce other disorders specific to genetically obese rats, and the seed PUFAs are responsible for that to a lesser extent.

Oxygen in Metabolic Dysfunction and Its Therapeutic Relevance

Significance: In recent years, a number of studies have shown altered oxygen partial pressure at a tissue level in metabolic disorders, and some researchers have considered oxygen to be a (macro) nutrient. Oxygen availability may be compromised in obesity and several other metabolism-related pathological conditions, including sleep apnea-hypopnea syndrome, the metabolic syndrome (which is a set of conditions), type 2 diabetes, cardiovascular disease, and cancer. Recent Advances: Strategies designed to reduce adiposity and its accompanying disorders have been mainly centered on nutritional interventions and physical activity programs. However, novel therapies are needed since these approaches have not been sufficient to counteract the worldwide increasing rates of metabolic disorders. In this regard, intermittent hypoxia training and hyperoxia could be potential treatments through oxygen-related adaptations. Moreover, living at a high altitude may have a protective effect against the development of abnormal metabolic conditions. In addition, oxygen delivery systems may be of therapeutic value for supplying the tissue-specific oxygen requirements. Critical Issues: Precise in vivo methods to measure oxygenation are vital to disentangle some of the controversies related to this research area. Further, it is evident that there is a growing need for novel in vitro models to study the potential pathways involved in metabolic dysfunction to find appropriate therapeutic targets. Future Directions: Based on the existing evidence, it is suggested that oxygen availability has a key role in obesity and its related comorbidities. Oxygen should be considered in relation to potential therapeutic strategies in the treatment and prevention of metabolic disorders. Antioxid. Redox Signal. 35, 642-687.

Rodent models of hypertension

Elevated blood pressure (BP), or hypertension, is the main risk factor for cardiovascular disease. As a multifactorial and systemic disease that involves multiple organs and systems, hypertension remains a challenging disease to study. Models of hypertension are invaluable to support the discovery of the specific genetic, cellular and molecular mechanisms underlying essential hypertension, as well as to test new possible treatments to lower BP. Rodent models have proven to be an invaluable tool for advancing the field. In this review, we discuss the strengths and weaknesses of rodent models of hypertension through a systems approach. We highlight the ways how target organs and systems including the kidneys, vasculature, the sympathetic nervous system (SNS), immune system and the gut microbiota influence BP in each rodent model. We also discuss often overlooked hypertensive conditions such as pulmonary hypertension and hypertensive-pregnancy disorders, providing an important resource for researchers.

Baked cod consumption delayed the development of kidney and liver dysfunction and affected plasma amino acid concentrations, but did not affect blood pressure, blood glucose or liver triacylglycerol concentrations in obese fa/fa Zucker rats

Obesity is associated with changes in amino acid metabolism, and studies show that ingestion of fish proteins influence amino acid composition in plasma and urine, in addition to affecting risk factors for metabolic syndrome. Since the majority of fish proteins consumed by humans are as fish fillet, it is of interest to investigate if cod fillet intake affects amino acid composition and metabolic disorders. We hypothesized that a modified AIN-93G diet containing cod fillet would affect amino acid compositions in plasma and urine in obese rats, and also affect risk factors for metabolic syndrome when compared to rats fed a regular AIN-93G diet with casein as the protein source. Obese Zucker fa/fa rats, a rat model of metabolic syndrome, received diets containing 25% protein from lyophilized baked cod fillet and 75% protein from casein (Baked cod diet), or a Control diet with casein for four weeks. The Baked cod diet affected the amino acid composition in plasma, with e.g., lower glycine, histidine, homoarginine, homocysteine, methionine, proline and tyrosine concentrations, but did not affect amino acid concentrations in urine. The concentrations of markers for kidney and liver dysfunction were lower in the Baked cod group, however blood pressure development, fasting and postprandial glucose, and hepatic triacylglycerol concentrations were similar to the Control group. To conclude, substituting 25% of dietary protein with baked cod fillet affected concentrations of some amino acids in plasma and delayed development of kidney and liver dysfunction, but did not affect blood pressure, glucose concentration or fatty liver.

Diet, body weight and pain susceptibility - A systematic review of preclinical studies

Obesity has been associated with increased chronic pain susceptibility but causes are unclear. In this review, we systematize and analyze pain outcomes in rodent models of obesity as these can be important tools for mechanistic studies. Studies were identified using MEDLINE/PubMed and Scopus databases using the following search query: (((pain) OR (nociception)) AND (obesity)) AND (rat OR (mouse) OR (rodent))). From each eligible record we extracted the following data: species, strain, sex, pain/obesity model and main behavioral readouts. Out of 695 records 33 were selected for inclusion. 27 studies assessed nociception/acute pain and 17 studies assessed subacute or chronic pain. Overall genetic and dietary models overlapped in pain-related outcomes. Most acute pain studies reported either decreased or unaltered responses to noxious painful stimuli. However, decreased thresholds to mechanical innocuous stimuli, i.e. allodynia, were frequently reported. In most studies using subacute and chronic pain models, namely of subcutaneous inflammation, arthritis and perineural inflammation, decreased thresholds and/or prolonged pain manifestations were reported in obesity models. Strain comparisons and longitudinal observations indicate that genetic factors and the time course of the pathology might account for some of the discrepancies observed across studies. Two studies reported increased pain in animals subjected to high fat diet in the absence of weight gain. Pain-related outcomes in experimental models and clinical obesity are aligned indicating that the rodent can be an useful tool to study the interplay between diet, obesity and pain. In both cases weight gain might represent only a minor contribution to abnormal pain manifestation.

The Effect of Hemp (Cannabis sativa L.) Seeds and Hemp Seed Oil on Vascular Dysfunction in Obese Male Zucker Rats

Seeds of industrial hemp (Cannabis sativa L.) contain a large amount of protein (26.3%), dietary fiber (27.5%), and fatty acids (33.2%), including linoleic, α-linolenic, and some amount of γ-linolenic acid. In our study, obese male Zucker rats (n = 6) at 8 weeks of age were supplemented for a further 4 weeks with either ground hemp seeds (12% diet) or lipid fractions in the form of hemp seed oil (4% diet). Hemp oil decreased blood plasma HDL-cholesterol (x0.76, p ≤ 0.0001), triglycerides (x0.55, p = 0.01), and calculated atherogenic parameters. Meanwhile, hemp seeds decreased HDL-cholesterol (x0.71, p ≤ 0.0001) and total cholesterol (x0.81, p = 0.006) but not the atherogenic index. The plasma antioxidant capacity of water-soluble compounds was decreased by the seeds (x0.30, p = 0.0015), which in turn was associated with a decrease in plasma uric acid (x0.18, p = 0.03). Dietary hemp seeds also decreased plasma urea (x0.80, p = 0.02), while the oil decreased the plasma total protein (x0.90, p = 0.05). Hemp seeds and the oil decreased lipid peroxidation in the blood plasma and in the heart (reflected as malondialdehyde content), improved contraction to noradrenaline, and up-regulated the sensitivity of potassium channels dependent on ATP and Ca²⁺. Meanwhile, acetylcholine-induced vasodilation was improved by hemp seeds exclusively. Dietary supplementation with ground hemp seeds was much more beneficial than the oil, which suggests that the lipid fractions are only partially responsible for this effect.

Time-of-Day-Dependent Effects of Bromocriptine to Ameliorate Vascular Pathology and Metabolic Syndrome in SHR Rats Held on High Fat Diet

The treatment of type 2 diabetes patients with bromocriptine-QR, a unique, quick release micronized formulation of bromocriptine, improves glycemic control and reduces adverse cardiovascular events. While the improvement of glycemic control is largely the result of improved postprandial hepatic glucose metabolism and insulin action, the mechanisms underlying the drug's cardioprotective effects are less well defined. Bromocriptine is a sympatholytic dopamine agonist and reduces the elevated sympathetic tone, characteristic of metabolic syndrome and type 2 diabetes, which potentiates elevations of vascular oxidative/nitrosative stress, known to precipitate cardiovascular disease. Therefore, this study investigated the impact of bromocriptine treatment upon biomarkers of vascular oxidative/nitrosative stress (including the pro-oxidative/nitrosative stress enzymes of NADPH oxidase 4, inducible nitric oxide (iNOS), uncoupled endothelial nitric oxide synthase (eNOS), the pro-inflammatory/pro-oxidative marker GTP cyclohydrolase 1 (GTPCH 1), and the pro-vascular health enzyme, soluble guanylate cyclase (sGC) as well as the plasma level of thiobarbituric acid reactive substances (TBARS), a circulating marker of systemic oxidative stress), in hypertensive SHR rats held on a high fat diet to induce metabolic syndrome. Inasmuch as the central nervous system (CNS) dopaminergic activities both regulate and are regulated by CNS circadian pacemaker circuitry, this study also investigated the time-of-day-dependent effects of bromocriptine treatment (10 mg/kg/day at either 13 or 19 h after the onset of light (at the natural waking time or late during the activity period, respectively) among animals held on 14 h daily photoperiods for 16 days upon such vascular biomarkers of vascular redox state, several metabolic syndrome parameters, and mediobasal hypothalamic (MBH) mRNA expression levels of neuropeptides neuropeptide Y (NPY) and agouti-related protein (AgRP) which regulate the peripheral fuel metabolism and of mRNA expression of other MBH glial and neuronal cell genes that support such metabolism regulating neurons in this model system. Such bromocriptine treatment at ZT 13 improved (reduced) biomarkers of vascular oxidative/nitrosative stress including plasma TBARS level, aortic NADPH oxidase 4, iNOS and GTPCH 1 levels, and improved other markers of coupled eNOS function, including increased sGC protein level, relative to controls. However, bromocriptine treatment at ZT 19 produced no improvement in either coupled eNOS function or sGC protein level. Moreover, such ZT 13 bromocriptine treatment reduced several metabolic syndrome parameters including fasting insulin and leptin levels, as well as elevated systolic and diastolic blood pressure, insulin resistance, body fat store levels and liver fat content, however, such effects of ZT 19 bromocriptine treatment were largely absent versus control. Finally, ZT 13 bromocriptine treatment reduced MBH NPY and AgRP mRNA levels and mRNA levels of several MBH glial cell/neuronal genes that code for neuronal support/plasticity proteins (suggesting a shift in neuronal structure/function to a new metabolic control state) while ZT 19 treatment reduced only AgRP, not NPY, and was with very little effect on such MBH glial cell genes expression. These findings indicate that circadian-timed bromocriptine administration at the natural circadian peak of CNS dopaminergic activity (that is diminished in insulin resistant states), but not outside this daily time window when such CNS dopaminergic activity is naturally low, produces widespread improvements in biomarkers of vascular oxidative stress that are associated with the amelioration of metabolic syndrome and reductions in MBH neuropeptides and gene expressions known to facilitate metabolic syndrome. These results of such circadian-timed bromocriptine treatment upon vascular pathology provide potential mechanisms for the observed marked reductions in adverse cardiovascular events with circadian-timed bromocriptine-QR therapy (similarly timed to the onset of daily waking as in this study) of type 2 diabetes subjects and warrant further investigations into related mechanisms and the potential application of such intervention to prediabetes and metabolic syndrome patients as well.

Addiction-like response in brain and behavior in a rat experimental model of night-eating syndrome

STUDY OBJECTIVES

Individuals ailing from night eating syndrome (NES) consume more than 25% of their daily food intake during the normal sleep time, delaying their sleep or waking up in the middle of the night to eat. This study explored two experimental conditions resembling NES in Wistar rats by offering palatable food during the sleep phase, alone or combined with sleep delay. Also we explored their impact on addiction-like changes in the brain and behavior.

METHODS

Experiment 1 explored the brain response after a first NES-like event; experiment 2 and 3 explored addiction-like behaviors c-Fos and FosB/ΔFosB in corticolimbic regions after 4 weeks exposition to NES-like conditions and after one week of withdrawal, respectively. For all 3 experiments 6 experimental groups were used: 1. Control; 2. Restricted access (1 h) to high-sugar diet (HSD) or to 3. high-fat diet (HFD); 4., Sleep delay for 4 h (SD) (from ZT0-ZT4, rats using slow rotating wheels); 5. SD + HSD; 6. SD + HFD.

RESULTS

A first event of eating a palatable diet with or without SD was sufficient to stimulate c-Fos and ΔFosB. Along 4 weeks of exposure to the palatable diets rats exhibited escalation and binge eating, which was highest for the HFD. At this stage, SD did not influence behavioral changes nor the neuronal response. After one-week in withdrawal, rats exhibited craving and effort to obtain their palatable diet. The brains of rats previously exposed to sleep delay maintained high levels of FosB/ΔFosB in the accumbens shell and high c-Fos activation in the insular cortex.

CONCLUSIONS

In our experimental models of NES-like a HFD in the sleep phase and SD are risk factors to develop binge eating and addiction-like behaviors.

Prolonged lifespan in a spontaneously hypertensive rat (stroke prone) model following intravenous infusion of mesenchymal stem cells

Intravenous infusion of mesenchymal stem cells (MSCs) has been reported to provide therapeutic efficacy via microvascular remodeling in a spontaneously hypertensive rat. In this study, we demonstrate that intravenous infusion of MSCs increased the survival rate in a spontaneously hypertensive (stroke prone) rat model in which organs including kidney, brain, heart and liver are damaged during aging due to spontaneous hypertension. Gene expression analysis indicated that infused MSCs activates transforming growth factor-β1-smad3/forkhead box O1 signaling pathway. Renal dysfunction was recovered after MSC infusion. Collectively, intravenous infusion of MSC may extend lifespan in this model system.

Whole Red Raspberry (Rubus idaeus)-Enriched Diet Is Hepatoprotective in the Obese Zucker Rat, a Model of the Metabolic Syndrome

Non-alcoholic fatty liver disease is a major risk factor of the metabolic syndrome (MetS). The effect of whole red raspberry (WRR) consumption on lipid metabolism was investigated in the obese Zucker rat (OZR), a model for the MetS. Male OZRs (n = 16) and their lean littermates (lean Zucker rat) (n = 16) at 8 weeks of age were placed on a control or an 8% WRR-enriched diet for 8 weeks. Plasma triglycerides (TGs), total cholesterol, high-density lipoprotein cholesterol (HDL-C), and non-HDL-C levels, and hepatic concentration of TG were measured. The expression of nine genes related to lipid metabolism was evaluated, both in liver and adipose tissue. A WRR-enriched diet reduced plasma cholesterol and HDL-C and increased plasma TG, while it decreased hepatic TG accumulation in the OZR. The OZR assigned to a WRR exhibited upregulation of microsomal triglyceride transfer protein (Mttp) and downregulation of fatty acid synthase (Fas) expression in the liver. Results showed a decrease in accumulation of liver TG and gene expression modulation of enzymes and transcription factors associated with lipid metabolism, suggesting a possible hepatoprotective role of a WRR-enriched diet.

Green tea polyphenols ameliorate metabolic abnormalities and insulin resistance by enhancing insulin signalling in skeletal muscle of Zucker fatty rats

In the present study, we evaluated the metabolic effects of green tea polyphenols (GTPs) in high-fat diet (HFD) fed Zucker fatty (ZF) rats, in particular the effects of GTP on skeletal muscle insulin sensitivity. Body weight, visceral fat, glucose tolerance, lipid profiles and whole-body insulin sensitivity were measured in HFD-fed ZF rats after 8-week-treatment with GTP (200 mg/kg of body weight) or saline (5 ml/kg of body weight). Zucker lean rats were studied as controls. Ex vivo insulin-mediated muscle glucose uptake was assessed. Immunoblotting was used to evaluate the expression of key insulin signalling proteins in skeletal muscle. GTP treatment attenuated weight gain (P<0.05) and visceral fat accumulation (27.6%, P<0.05), and significantly reduced fasting serum glucose (P<0.05) and insulin (P<0.01) levels. Homoeostasis model assessment of insulin resistance (HOMA-IR), a measure of insulin resistance, was lower (P<0.01) in GTP-treated animals compared with ZF controls. Moreover, insulin-stimulated glucose uptake by isolated soleus muscle was increased (P<0.05) in GTP-ZF rats compared with ZF-controls. GTP treatment attenuated the accumulation of ectopic lipids (triacyl- and diacyl-glycerols), enhanced the expression and translocation of glucose transporter-4, and decreased pSer612IRS-1 and increased pSer473Akt2 expression in skeletal muscle. These molecular changes were also associated with significantly decreased activation of the inhibitory (muscle-specific) protein kinase (PKC) isoform, PKC-θ. Taken together, the present study has shown that regular ingestion of GTP exerts a number of favourable metabolic and molecular effects in an established animal model of obesity and insulin resistance. The benefits of GTP are mediated in part by inhibiting PKC-θ and improving muscle insulin sensitivity.

Plasma Leptin Reflects Progression of Neurofibrillary Pathology in Animal Model of Tauopathy

The close relationship between Alzheimer's disease (AD) and obesity was recognized many years ago. However, complete understanding of the pathological mechanisms underlying the interactions between degeneration of CNS and fat metabolism is still missing. The leptin a key adipokine of white adipose tissue has been suggested as one of the major mediators linking the obesity and AD. Here we investigated the association between peripheral levels of leptin, general metabolic status and stage of the pathogenesis in rat transgenic model of AD. We demonstrate significantly decreased levels of plasma leptin in animals with experimentally induced progressive neurofibrillary pathology, which represents only 62.3% (P = 0.0015) of those observed in normal wild type control animals. More detailed analysis showed a strong and statistically significant inverse correlation between the load of neurofibrillary pathology and peripheral levels of leptin (r = - 0.7248, P = 0.0177). We also observed a loss of body weight during development of neurodegeneration (about 14% less than control animals, P = 0.0004) and decrease in several metabolic parameters such as glucose, insulin, triglycerides and VLDL in plasma of the transgenic animals. Our data suggest that plasma leptin could serve as a convenient peripheral biomarker for tauopathies and Alzheimer's disease. Decrease in gene expression of leptin in fat tissue and its plasma level was found as one of the consequences of experimentally induced neurodegeneration. Our data may help to design rational diagnostic and therapeutic strategies for patients suffering from Alzheimer's disease or other forms of tauopathy.

Effects of Anthocyanin Extracts from Bilberry (Vaccinium myrtillus L.) and Purple Potato (Solanum tuberosum L. var. 'Synkeä Sakari') on the Plasma Metabolomic Profile of Zucker Diabetic Fatty Rats

This study compared the effects of the nonacylated and acylated anthocyanin-rich extracts on plasma metabolic profiles of Zucker diabetic fatty rats. The rats were fed with the nonacylated anthocyanin extract from bilberries (NAAB) or the acylated anthocyanin extract from purple potatoes (AAPP) at daily doses of 25 and 50 mg/kg body weight for 8 weeks. ¹H NMR metabolomics was used to study the changes in plasma metabolites. A reduced fasting plasma glucose level was seen in all anthocyanin-fed groups, especially in the groups fed with NAAB. Both NAAB and AAPP decreased the levels of branched-chain amino acids and improved lipid profiles. AAPP increased the glutamine/glutamate ratio and decreased the levels of glycerol and metabolites involved in glycolysis, suggesting improved insulin sensitivity, gluconeogenesis, and glycolysis. AAPP decreased the hepatic TBC1D1 and G6PC messenger RNA level, suggesting regulation of gluconeogenesis and lipogenesis. This study indicated that AAPP and NAAB affected the plasma metabolic profile of diabetic rats differently.

Aminopeptidases in Cardiovascular and Renal Function. Role as Predictive Renal Injury Biomarkers

Aminopeptidases (APs) are metalloenzymes that hydrolyze peptides and polypeptides by scission of the N-terminus amino acid and that also participate in the intracellular final digestion of proteins. APs play an important role in protein maturation, signal transduction, and cell-cycle control, among other processes. These enzymes are especially relevant in the control of cardiovascular and renal functions. APs participate in the regulation of the systemic and local renin-angiotensin system and also modulate the activity of neuropeptides, kinins, immunomodulatory peptides, and cytokines, even contributing to cholesterol uptake and angiogenesis. This review focuses on the role of four key APs, aspartyl-, alanyl-, glutamyl-, and leucyl-cystinyl-aminopeptidases, in the control of blood pressure (BP) and renal function and on their association with different cardiovascular and renal diseases. In this context, the effects of AP inhibitors are analyzed as therapeutic tools for BP control and renal diseases. Their role as urinary biomarkers of renal injury is also explored. The enzymatic activities of urinary APs, which act as hydrolyzing peptides on the luminal surface of the renal tubule, have emerged as early predictive renal injury biomarkers in both acute and chronic renal nephropathies, including those induced by nephrotoxic agents, obesity, hypertension, or diabetes. Hence, the analysis of urinary AP appears to be a promising diagnostic and prognostic approach to renal disease in both research and clinical settings.

Effect of waterpipe tobacco smoke exposure on the development of metabolic syndrome in adult male rats

The prevalence of metabolic syndrome is increased worldwide. Tobacco smoking increases the risk of developing metabolic syndrome. Waterpipe tobacco smoking has become a global trend of tobacco consumption and is as common as cigarette smoking. In this study, the effect of waterpipe tobacco smoke (WTS) on the development of metabolic syndrome in rats was evaluated. Adult Wistar rats were exposed for 19 weeks to either fresh air (control) or WTS for 1 hour daily/ 5 days per week (WTS). Central obesity, systolic blood pressure, lipid profile, glucose hemostasis and levels of leptin and adiponectin were evaluated. The WTS exposure increased body weight, abdominal circumference, systolic blood pressure and fasting glucose compared to control animals (P<0.05), consistent with inducing metabolic syndrome. The retroperitoneal fat, lipid profile and levels of insulin, leptin and adiponectin were not affected by WTS exposure (P>0.05). In conclusion, exposure to WTS has detrimental health effects leading to the development of metabolic syndrome in experimental animals.

Dietary Hemp Seeds More Effectively Attenuate Disorders in Genetically Obese Rats than Their Lipid Fraction

BACKGROUND

Hemp seeds are rich in PUFAs and other bioactives that can attenuate the development of obesity-related disorders; however, the extent to which their lipid fraction is responsible for this effect is unknown.

OBJECTIVE

We hypothesized that hemp seed or hemp oil supplementation can attenuate genetically determined disorders and that the former are more effective in doing so.

METHODS

Lean and obese male Zucker rats, aged 8 wk, weighing 174 ± 4.2 g and 223 ± 3.8 g, respectively, were allocated to 4 groups. The lean (LC) and obese controls (OC) were fed a standard diet, whereas the other 2 obese groups were fed a modified diet in which hemp oil (4% diet; O + HO) or hemp seeds (12% diet; O + HS) were included. All diets had the same proportions of protein (18%), fat (8%), and fiber (5%) and a similar carbohydrate proportion (∼52%). Diets fed to O + HO and O + HS had similar fatty acid profiles. After 4 wk, markers of gut and liver function, antioxidant status, and lipid metabolism were measured.

RESULTS

The total SCFA concentration in the cecal digesta was lower in OC (64.8 ± 4.21 µmol/g) compared with LC (78.1 ± 2.83 µmol/g) (P ≤ 0.05), whereas it was greater in O + HS (89 ± 4.41 µmol/g) compared with LC, OC, and O + HO (69.7 ± 2.68 µmol/g) (P ≤ 0.05). Plasma total cholesterol was greater in OC (6.20 ± 0.198 mmol/L) and O + HO (5.60 ± 0.084 mmol/L) compared with LC (2.71 ± 0.094 mmol/L) (P ≤ 0.05); in O + HS, the concentration did not differ from the other groups (5.16 ± 0.278 mmol/L). The liver cholesterol concentration was greater in OC (1.79 ± 0.379 mg/g) compared with the other groups (1.28-1.43 mg/g) (P ≤ 0.05). Hepatic expression of peroxisome proliferator-activated receptor γ was lower in OC (11.9 ± 0.93 units) compared with LC (17.3 ± 1.3 units) (P ≤ 0.05), whereas it was greater in O + HS (19.2 ± 1.04 units) compared with OC and O + HO (14.0 ± 1.33 units) (P ≤ 0.05).

CONCLUSIONS

Dietary hemp seeds more effectively attenuate metabolic disorders in genetically obese rats than the oil extracted from them, which suggests that the lipid fraction is only partly responsible for these effects.

Effects of intact and hydrolysed blue whiting proteins on blood pressure and markers of kidney function in obese Zucker fa/fa rats

PURPOSE

To investigate the effects of diets containing intact or hydrolysed proteins from blue whiting (Micromesistius poutassou) on the development of high blood pressure and markers of kidney function in obese Zucker fa/fa rats which are prone to develop hypertension and renal failure.

METHODS

Male rats were fed isocaloric diets containing either intact blue whiting whole meal (BW-WM), blue whiting protein hydrolysate prepared with Alcalase^® (BW-HA) or blue whiting protein hydrolysate prepared with Protamex^® (BW-HP) as 1/3 of total protein with the remaining 2/3 as casein, or casein as sole protein source (control group). Blood pressure was measured at Day 0 and Day 32. Rats were housed in metabolic cages for 24 h for collection of urine in week 4. After 5 weeks, rats were euthanized and blood was drawn from the heart. The renin and angiotensin-converting enzyme (ACE) inhibition capacities for casein and blue whiting proteins were measured in vitro.

RESULTS

The blood pressure increase was lower in rats fed diets containing blue whiting proteins when compared to the control group, whereas markers of kidney function were similar between all groups. The three blue whiting proteins inhibited renin activity in vitro, whereas casein had no effect. The in vitro ACE inhibition was similar for casein, BW-WM and BW-HP proteins, whereas BW-HA protein was less potent.

CONCLUSION

Blue whiting protein feeding attenuated the blood pressure increase in obese Zucker fa/fa rats, possibly mediated through the renin-angiotensin system and without affecting markers of kidney function.

Obesity and Age-Related Changes in the Brain of the Zucker Lepr fa/fa Rats

Metabolic syndrome (MetS) is an association between obesity, dyslipidemia, hyperglycemia, hypertension, and insulin resistance. A relationship between MetS and vascular dementia was hypothesized. The purpose of this work is to investigate brain microanatomy alterations in obese Zucker rats (OZRs), as a model of MetS, compared to their counterparts lean Zucker rats (LZRs). 12-, 16-, and 20-weeks-old male OZRs and LZRs were studied. General physiological parameters and blood values were measured. Immunochemical and immunohistochemical techniques were applied to analyze the brain alterations. The morphology of nerve cells and axons, astrocytes and microglia were investigated. The blood-brain barrier (BBB) changes occurring in OZRs were assessed as well using aquaporin-4 (AQP4) and glucose transporter protein-1 (GLUT1) as markers. Body weight gain, hypertension, hyperglycemia, and hyperlipidemia were found in OZRs compared to LZRs. In the frontal cortex and hippocampus, a decrease of neurons was noticeable in the older obese rats in comparison to their age-matched lean counterparts. In OZRs, a reduction of neurofilament immunoreaction and gliosis was observed. The BBB of older OZRs revealed an increased expression of AQP4 likely related to the development of edema. A down-regulation of GLUT1 was found in OZRs of 12 weeks of age, whereas it increased in older OZRs. The behavioral analysis revealed cognitive alterations in 20-week-old OZRs. Based on these results, the OZRs may be useful for understanding the mechanisms through which obesity and related metabolic alterations induce neurodegeneration.

Cardiovascular Changes Related to Metabolic Syndrome: Evidence in Obese Zucker Rats

Metabolic syndrome (MetS) is a predictor of cardiovascular diseases, commonly associated with oxidative stress and inflammation. However, the pathogenic mechanisms are not yet fully elucidated. The aim of the study is to evaluate the oxidative status and inflammation in the heart of obese Zucker rats (OZRs) and lean Zucker rats (LZRs) at different ages. Morphological and morphometric analyses were performed in the heart. To study the oxidative status, the malondialdehyde (MDA), 4-hydroxynonenal (4-HNE), protein oxidation, and antioxidant enzymes were measured in plasma and heart. To elucidate the inflammatory markers involved, immunohistochemistry and Western blot were performed for cellular adhesion molecules and proinflammatory cytokines. OZRs were characterized by hypertension, hyperlipidemia, hyperglycemia, and insulin resistance. The obesity increased MDA and decreased the activities of superoxide dismutase (SOD) in plasma as well as in the heart, associated with cardiomyocytes hypertrophy. OxyBlot in plasma and in heart showed an increase of oxidativestate proteins in OZRs. Vascular cell adhesion molecule-1, interleukin-6, and tumor necrosis factor-α expressions in OZRs were higher than those of LZRs. However, these processes did not induce apoptosis or necrosis of cardiomyocytes. Thus, MetS induces the lipid peroxidation and decreased antioxidant defense that leads to heart tissue changes and coronary inflammation.

The Vascular Consequences of Metabolic Syndrome: Rodent Models, Endothelial Dysfunction, and Current Therapies

Metabolic syndrome is characterized by visceral obesity, dyslipidemia, hyperglycemia and hypertension, and affects over one billion people. Independently, the components of metabolic syndrome each have the potential to affect the endothelium to cause vascular dysfunction and disrupt vascular homeostasis. Rodent models of metabolic syndrome have significantly advanced our understanding of this multifactorial condition. In this mini-review we compare the currently available rodent models of metabolic syndrome and consider their limitations. We also discuss the numerous mechanisms by which metabolic abnormalities cause endothelial dysfunction and highlight some common pathophysiologies including reduced nitric oxide production, increased reactive oxygen species and increased production of vasoconstrictors. Additionally, we explore some of the current therapeutics for the comorbidities of metabolic syndrome and consider how these benefit the vasculature.

Effects of liraglutide on metabolic syndrome in WBN/Kob diabetic fatty rats supplemented with a high-fat diet

BACKGROUND

Liraglutide, a GLP-1 receptor agonist, has recently been used to treat metabolic syndrome (MS) because of its anti-diabetic and anti-obesity effects. We have previously shown that Wistar Bonn Kobori diabetic and fatty (WBN/Kob-Lepr fa , WBKDF) rats fed a high-fat diet (HFD) developed MS including marked obesity, hyperglycemia, and dyslipidemia. To obtain further information on WBKDF-HFD rats as a severe MS model, we performed a pharmacological investigation into the anti-MS effects of liraglutide in this model.

METHODS

Seven-week-old male WBKDF-HFD rats were allocated to three groups (N = 8 in each group): a vehicle group, a low-dose liraglutide group, and a high-dose liraglutide group. They received subcutaneous injections of either saline or liraglutide at doses of 75 or 300 μg/kg body weight once daily for 4 weeks.

RESULTS

Results showed that liraglutide treatment reduced body weight gain and food intake in a dose-dependent manner. The marked hyperglycemia and the glucose tolerance were also significantly ameliorated in the liraglutide-treated groups. Moreover, liraglutide also reduced the plasma triglyceride concentration and liver fat accumulation.

CONCLUSIONS

The present study demonstrated that liraglutide could significantly alleviate MS in WBKDF-HFD rats, and the reaction to liraglutide is similar to human patients with MS. WBKDF-HFD rats are therefore considered to be a useful model for research on severe human MS.

Ameliorative activity of Adansonia digitata fruit on high sugar/high fat diet-simulated Metabolic Syndrome model in male Wistar rats

Metabolic syndrome is a complex of metabolic disorders characterized by oxidative stress which compromises cell functions and entails multiple organs pathologies. We investigated the therapeutic and protective potential of Adansonia digitata fruit -a potent antioxidant- in high sugar/high fat diet-simulated metabolic syndrome in Wistar rats. 42 male rats (140-200 g) were randomly divided into 7 groups. G1 was kept on standard laboratory diet (SLD) for all 9 weeks (negative control). 5 groups were fed high Sugar/high fat diet for 6 weeks then switched to SLD for another 3 weeks + oral treatment as follows: G2+ no treatment (positive control), G3-G5 + 200, 400 and 800 mg/kg/day aqueous A. digitata fruit respectively, G6 + 10 mg/kg/day Simvastatin. G7 + HS/HFD + 400 mg/kg/day A. digitata fruit simultaneously and was terminated at W6. Our results showed that G2-G6 develops dyslipidemia, hyperglycaemia, weight gain, elevated hepatic biomarkers, elevated creatinine and urea plus pathological derangements in the heart, liver and kidney tissues compared to negative control at W6. 200 mg/kg/day A. digitata fruit significantly ameliorated the induced dyslipidemia (P ≤ 0.001), hyperglycaemia (P ≤ 0.001) with a significant reduction in the Atherogenic Index of Plasma (P ≤ 0.000) after 3 weeks treatment. The fruit normalized the elevated hepatic biomarkers as well as creatinine and urea. A dose dependent partial reduction in lesion intensity was observed in the hepatic tissue while the heart and kidney showed mostly reversed to normal histology. The inflammatory infiltration was eliminated. Relevant results were observed for the two higher doses. The simultaneous treatment showed significant lower levels in all biomarkers investigated compared to positive control which could be interpreted as protective activity. A reduction of 4-11% in whole body weight was achieved. CONCLUSION: MetS was successfully simulated with a HS/HFD formula in male Wistar rats. Treatment with aqueous A. digitata fruit showed anti-Metabolic Syndrome potential reflected by weight loss, anti-inflammatory, hypolipidemic, hypoglycaemic, renal, hepatic and cardio-protective activities.

Characterization of Rat ILCs Reveals ILC2 as the Dominant Intestinal Subset

Innate lymphoid cells (ILCs) are tissue-resident lymphocytes that lack antigen-specific receptors and exhibit innate effector functions such as cytokine production that play an important role in immediate responses to pathogens especially at mucosal sites. Mouse and human ILC subsets have been extensively characterized in various tissues and in blood. In this study, we present the first characterization of ILCs and ILC subsets in rat gut and secondary lymphoid organs using flow cytometry and single cell RNA sequencing. Our results show that phenotype and function of rat ILC subsets are conserved as compared to human and mouse ILCs. However, and in contrast to human and mouse, our study unexpectedly revealed that ILC2 and not ILC3 was the dominant ILC subset in the rat intestinal lamina propria. ILC2 predominance in the gut was independent of rat strain, sex or housing facility. In contrast, ILC3 was the predominant ILC subset in mesenteric lymph nodes and Peyer patches. In conclusion, our study demonstrates that in spite of highly conserved phenotype and function between mice, rat and humans, the distribution of ILC subsets in the intestinal mucosa is dependent on the species likely in response to both genetic and environmental factors.

Shifted vascular optimization: the emergence of a new arteriolar behaviour with chronic metabolic disease

NEW FINDINGS

What is the topic of this review? Altered perfusion distribution at skeletal muscle arteriolar bifurcations and how this is modified by development of chronic metabolic disease. What advances does it highlight? The outcome created is a distribution of erythrocytes in the distal microcirculation that is characterized by increased spatial heterogeneity and reduced flexibility such that mass transport/exchange within the network is impaired, with limited ability to respond to imposed challenges. This advances our understanding of how altered vascular structure and function with metabolic disease impairs perfusion to skeletal muscle at a level of resolution that would not be identified through bulk flow responses.

ABSTRACT

This review is based on the presentation 'Shifted vascular optimization: the emergence of a new arteriolar behaviour with chronic metabolic disease', given at the Symposium 'Understanding Complex Behaviours in the Microcirculation: from Blood Flow to Oxygenation' during the Annual Meeting of the Physiological Society at the Aberdeen Exhibition and Conference Centre in Aberdeen, UK in July 2019. The past years of dedicated investigation on linkages between vascular (dys)function under conditions of elevated cardiovascular disease risk and tissue/organ performance have produced results and insights that frequently suffer from limited correlation and causation. Reaching out from this challenge, it was proposed that this may reflect a 'level of resolution' argument and that altered haemodynamic behaviour in vascular networks could be a stronger predictor of functional outcomes than higher resolution measures. Using this approach, we have determined that an attractor that describes the spatial and temporal shift in perfusion distribution at successive arteriolar bifurcations within the skeletal muscle is a strong predictor of functional outcomes within animals and provides novel insight into fundamental mechanistic contributors to altered patterns of intra-muscular perfusion. This article focuses on the applicability and utility of the attractor in models of cardiovascular and metabolic disease risk of increasing severity. We will also discuss the utility of the attractor in terms of understanding the effectiveness of aggressive interventions for reversing established vasculopathy and perfusion impairments.

Coenzyme A and Its Thioester Pools in Obese Zucker and Zucker Diabetic Fatty Rats

Feeding behavior is closely related to hypothalamic malonyl-CoA level in the brain and diet-induced obesity affects total CoA pools in liver. Herein, we performed a comprehensive analysis of the CoA pools formed in thirteen tissues of Zucker and Zucker diabetic fatty (ZDF) rats. Hypothalamic malonyl-CoA levels in obese rats remained low and were almost the same as those of lean rats, despite obese rats having much higher content of leptin, insulin, and glucose in their sera. Regardless of the fa-genotypes, larger total CoA pools were formed in the livers of ZDF rats and the size of hepatic total CoA pools in Zucker rats showed almost one tenth of the size of ZDF rats. The decreased total CoA pool sizes in Zucker rats was observed in the brown adipose tissues, while ZDF-fatty rats possessed 6% of total CoA pool in the lean rats in response to fa deficiency. This substantially lower CoA content in the obese rats would be disadvantageous to non-shivering thermogenesis. Thus, comparing the intracellular CoA behaviors between Zucker and ZDF rats, as well as the lean and fatty rats of each strain would help to elucidate features of obesity and type 2 diabetes in combination with result (s) of differential gene expression analysis and/or comparative genomics.

Molecular changes in hepatic metabolism in ZDSD rats-A new polygenic rodent model of obesity, metabolic syndrome, and diabetes

In recent years, the prevalence of obesity, metabolic syndrome and type 2 diabetes is increasing dramatically. They share pathophysiological mechanisms and often lead to cardiovascular diseases. The ZDSD rat was suggested as a new animal model to study diabetes and the metabolic syndrome. In the current study, we have further characterized metabolic and hepatic gene expression changes in ZDSD rats. Immuno-histochemical staining of insulin and glucagon on pancreas sections of ZDSD and control SD rats revealed that ZDSD rats have severe damage to their islet structures as early as 15 weeks of age. Animals were followed till they were 26 weeks old, where they exhibited obesity, hypertension, hyperglycemia, dyslipidemia, insulin resistance and diabetes. We found that gene expressions involved in glucose metabolism, lipid metabolism and amino acid metabolism were changed significantly in ZDSD rats. Elevated levels of ER stress markers correlated with the dysregulation of hepatic lipid metabolism in ZDSD rats. Key proteins participating in unfolded protein response pathways were also upregulated and likely contribute to the pathogenesis of dyslipidemia and insulin resistance. Based on its intact leptin system, its insulin deficiency, as well as its timeline of disease development without diet manipulation, this insulin resistant, dyslipidemic, hypertensive, and diabetic rat represents an additional, unique polygenic animal model that could be very useful to study human diabetes.

Rodent models of obesity

Obese or overweight people exceed one-third of the global population and obesity along with diabetes mellitus consist basic components of metabolic syndrome, both of which are known cardio-cerebrovascular risk factors with detrimental consequences. These data signify the pandemic character of obesity and the necessity for effective treatments. Substantial advances have been accomplished in preclinical research of obesity by using animal models, which mimic the human disease. In particular, rodent models have been widely used for many decades with success for the elucidation of the pathophysiology of obesity, since they share physiological and genetic components with humans and appear advantageous in their husbandry. The most representative rodents include the laboratory mouse and rat. Within this review, we attempted to consolidate the most widely used mice and rat models of obesity and highlight their strengths as well as weaknesses in a critical way. Our aim was to bridge the gap between laboratory facilities and patient's bed and help the researcher find the appropriate animal model for his/her obesity research. This tactful selection of the appropriate model of obesity may offer more translational derived results. In this regard, we included, the main diet induced models, the chemical/mechanical ones, as well as a selection of monogenic or polygenic models.

Western Diet-Induced Metabolic Alterations Affect Circulating Markers of Liver Function before the Development of Steatosis

Since nutrition might have a significant impact on liver function, we analyzed the early effect of Western-type diet on hepatic tissue and lipid and drug metabolism in Wistar–Kyoto rats (n = 8); eight rats fed with a standard diet were used as controls. Histological analysis of liver tissue was performed, and plasma biochemical parameters were measured. Plasma concentration of six bile acids was determined by ultra-liquid chromatography-tandem mass spectrometry UHPLC-MS/MS. Hepatic gene expressions of enzymes involved in drug and lipid metabolism were assessed by means of real-time reverse transcription (qRT)-PCR. Liver of rats fed with a Western diet did not show macroscopic histological alterations, but number and diameter of lipid droplets increased, as well as DGAT1, GPAT4, SCD, FASN and SREBP2 expression. Furthermore, Western diet-fed animals showed an increase in the activation of hepatic stellate cells and macrophage number in liver tissue, as well as a significant increase in AST and bilirubin levels (p < 0.01), and in the LDL:HDL cholesterol ratio (p < 0.001). Plasma chenodeoxycholic acid concentration increased significantly, whereas cholic acid decreased (p < 0.05), and cytochrome P450 genes were generally downregulated. Significant changes in hepatic lipid and drug metabolism are early induced by the Western diet, prior to steatosis development. Such changes are associated with a peculiar alteration in circulating bile acids, which could represent an early marker of non-alcoholic fatty liver disease (NAFLD) development.

Metabolic Syndrome Exacerbates Pulmonary Hypertension due to Left Heart Disease

RATIONALE

Pulmonary hypertension (PH) due to left heart disease (LHD), or group 2 PH, is the most prevalent form of PH worldwide. PH due to LHD is often associated with metabolic syndrome (MetS). In 12% to 13% of cases, patients with PH due to LHD display vascular remodeling of pulmonary arteries (PAs) associated with poor prognosis. Unfortunately, the underlying mechanisms remain unknown; PH-targeted therapies for this group are nonexistent, and the development of a new preclinical model is crucial. Among the numerous pathways dysregulated in MetS, inflammation plays also a critical role in both PH and vascular remodeling.

OBJECTIVE

We hypothesized that MetS and inflammation may trigger the development of vascular remodeling in group 2 PH.

METHODS AND RESULTS

Using supracoronary aortic banding, we induced diastolic dysfunction in rats. Then we induced MetS by a combination of high-fat diet and olanzapine treatment. We used metformin treatment and anti-IL-6 (interleukin-6) antibodies to inhibit the IL-6 pathway. Compared with sham conditions, only supracoronary aortic banding+MetS rats developed precapillary PH, as measured by both echocardiography and right/left heart catheterization. PH in supracoronary aortic banding+MetS was associated with macrophage accumulation and increased IL-6 production in lung. PH was also associated with STAT3 (signal transducer and activator of transcription 3) activation and increased proliferation of PA smooth muscle cells, which contributes to remodeling of distal PA. We reported macrophage accumulation, increased IL-6 levels, and STAT3 activation in the lung of group 2 PH patients. In vitro, IL-6 activates STAT3 and induces human PA smooth muscle cell proliferation. Metformin treatment decreased inflammation, IL-6 levels, STAT3 activation, and human PA smooth muscle cell proliferation. In vivo, in the supracoronary aortic banding+MetS animals, reducing IL-6, either by anti-IL-6 antibody or metformin treatment, reversed pulmonary vascular remodeling and improve PH due to LHD.

CONCLUSIONS

We developed a new preclinical model of group 2 PH by combining MetS with LHD. We showed that MetS exacerbates group 2 PH. We provided evidence for the importance of the IL-6-STAT3 pathway in our experimental model of group 2 PH and human patients.

Obesity and Cage Environment Modulate Metabolism in the Zucker Rat: A Multiple Biological Matrix Approach to Characterizing Metabolic Phenomena

Obesity and its comorbidities are increasing worldwide imposing a heavy socioeconomic burden. The effects of obesity on the metabolic profiles of tissues (liver, kidney, pancreas), urine, and the systemic circulation were investigated in the Zucker rat model using ¹H NMR spectroscopy coupled to multivariate statistical analysis. The metabolic profiles of the obese ( fa/ fa) animals were clearly differentiated from the two phenotypically lean phenotypes, ((+/+) and ( fa/+)) within each biological compartment studied, and across all matrices combined. No significant differences were observed between the metabolic profiles of the genotypically distinct lean strains. Obese Zucker rats were characterized by higher relative concentrations of blood lipid species, cross-compartmental amino acids (particularly BCAAs), urinary and liver metabolites relating to the TCA cycle and glucose metabolism; and lower amounts of urinary gut microbial-host cometabolites, and intermatrix metabolites associated with creatine metabolism. Further to this, the obese Zucker rat metabotype was defined by significant metabolic alterations relating to disruptions in the metabolism of choline across all compartments analyzed. The cage environment was found to have a significant effect on urinary metabolites related to gut-microbial metabolism, with additional cage-microenvironment trends also observed in liver, kidney, and pancreas. This study emphasizes the value in metabotyping multiple biological matrices simultaneously to gain a better understanding of systemic perturbations in metabolism, and also underscores the need for control or evaluation of cage environment when designing and interpreting data from metabonomic studies in animal models.