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.

Feeding of cuticles from Tenebrio molitor larvae modulates the gut microbiota and attenuates hepatic steatosis in obese Zucker rats

an alternative and sustainable source of food and feed. A byproduct from mass-rearing of insect larvae are the shed cuticles - the most external components of insects which are a...

Renoprotection Induced by Aerobic Training Is Dependent on Nitric Oxide Bioavailability in Obese Zucker Rats

Aerobic training (AT) promotes several health benefits that may attenuate the progression of obesity associated diabetes. Since AT is an important nitric oxide (NO-) inducer mediating kidney-healthy phenotype, the present study is aimed at investigating the effects of AT on metabolic parameters, morphological, redox balance, inflammatory profile, and vasoactive peptides in the kidney of obese-diabetic Zucker rats receiving L-NAME (N(omega)-nitro-L-arginine methyl ester). Forty male Zucker rats (6 wk old) were assigned into four groups ( n = 10 , each): sedentary lean rats (CTL-Lean), sedentary obese rats (CTL-Obese), AT trained obese rats without blocking nitric oxide synthase (NOS) (Obese+AT), and obese-trained with NOS block (Obese+AT+L-NAME). AT groups ran 60 min in the maximal lactate steady state (MLSS), five days/wk/8 wk. Obese+AT rats improved glycemic homeostasis, SBP, aerobic capacity, renal mitochondria integrity, redox balance, inflammatory profile (e.g., TNF-α, CRP, IL-10, IL-4, and IL-17a), and molecules related to renal NO- metabolism (klotho/FGF23 axis, vasoactive peptides, renal histology, and reduced proteinuria). However, none of these positive outcomes were observed in CTL-Obese and Obese+AT+L-NAME ( p < 0.0001 ) groups. Although Obese+AT+L-NAME lowered BP (compared with CTL-Obese; p < 0.0001 ), renal damage was observed after AT intervention. Furthermore, AT training under conditions of low NO- concentration increased signaling pathways associated with ACE-2/ANG1-7/MASr. We conclude that AT represents an important nonpharmacological intervention to improve kidney function in obese Zucker rats. However, these renal and metabolic benefits promoted by AT are dependent on NO- bioavailability and its underlying regulatory mechanisms.

Altered Brain Cholinergic and Synaptic Markers in Obese Zucker Rats

The association between obesity and loss of cognitive performance has been recognized. Although there are data regarding the metabolic alterations in obese conditions and the development of neuroinflammation, no clear evidence concerning obesity-related cholinergic and synaptic impairments in the frontal cortex and hippocampus has been reported yet. Here, we investigate different cholinergic and synaptic markers in 12-, 16-, and 20-week-old obese Zucker rats (OZRs) compared with lean littermate rats (LZRs), using immunochemical and immunohistochemical analysis. Consequently, OZRs showed body weight gain, hypertension, and dysmetabolism. In 20-week-old OZRs, the reduction of vesicular acetylcholine transporter (VAChT) and alpha7 nicotinic acetylcholine receptors (α7nAChR) occurred both in the frontal cortex and in the hippocampus, suggesting a cognitive dysfunction due to obesity and aging. Among the muscarinic receptors analyzed, the level of expression of type 1 (mAChR1) was lower in the hippocampus of the older OZRs. Finally, we showed synaptic dysfunctions in OZRs, with a reduction of synaptophysin (SYP) and synaptic vesicle glycoprotein 2B (SV2B) in 20-week-old OZRs, both in the frontal cortex and in the hippocampus. Taken together, our data suggest specific alterations of cholinergic and synaptic markers that can be targeted to prevent cognitive deficits related to obesity and aging.

Antioxidant Effect of Lonicera caerulea L. in the Cardiovascular System of Obese Zucker Rats

Background: Lonicera caerulea L. (Loni) represents a promising source of beneficial polyphenols with therapeutical potential in cardiovascular diseases. We aimed to study the effects of Loni and coenzyme Q10 (CoQ10) on selected cardiometabolic parameters and NO/ROS balance in obese Zucker rats. Methods: Male Zucker rats were divided into the control group and groups treated with CoQ10 (30 mg/kg/day) or Loni (5 g/kg/day) for 6 weeks. Blood pressure, body weight, heart weight, and plasma lipid profile were determined. NOS activity and protein expressions of eNOS, SOD, NADPH oxidase, and NF-kappa B were measured in the heart and aorta. Results: Neither body weight nor blood pressure were significantly changed after six weeks of Loni or CoQ10 treatment. Both Loni and CoQ10 decreased the plasma LDL level. Moreover, Loni decreased the total cholesterol level. The total NOS activity did not change in the heart after the treatments. However, in the aorta, Loni treatment increased NOS activity and protein expression of SOD and decreased expressions of NADPH oxidase and NF-kappa B compared to both the control and CoQ10 groups. There were no changes in the eNOS protein expression within the groups. In conclusion, it seems that the antioxidant effect of Loni was responsible for both the decrease of plasma LDL and the total cholesterol levels and the increase of vascular NOS activity.

Leptin resistant Zucker rats with trinitrobenzene sulfonic acid colitis present a reduced inflammatory response but enhanced epithelial damage

The role of leptin in the development of intestinal inflammation remains controversial, since proinflammatory and anti-inflammatory effects have been described. This study describes the effect of the absence of leptin signaling in intestinal inflammation. Experimental colitis was induced by intrarectal administration of trinitrobenzene sulfonic acid (TNBS) to lean and obese Zucker rats (n=10). Effects on inflammation and mucosal barrier were studied. Bacterial translocation and LPS concentration were evaluated together with colonic permeability to 4 kDa FITC-dextran. Obese Zucker rats showed a lower intestinal myeloperoxidase and alkaline phosphatase activity, reduced alkaline phosphatase sensitivity to levamisole, and diminished colonic expression of Nos2, Tnf and Il6, indicating attenuated intestinal inflammation, associated with attenuated STAT3, AKT and ERK signaling in the colonic tissue. S100a8 and Cxcl1 mRNA levels were maintained, suggesting that in the absence of leptin signaling neutrophil activation rather than infiltration is hampered. In spite of the lower inflammatory response, leptin resistance enhanced intestinal permeability, reflecting an increased epithelial damage. This was shown by augmented LPS presence in the portal vein of colitic obese Zucker rats, associated with induction of tissue non-specific alkaline phosphatase, LPS-binding protein and CD14 hepatic expression (involved in LPS handling). This was linked to decreased ZO-1 immunoreactivity in tight junctions and lower occludin expression. Our results indicate that obese Zucker rats present an attenuated inflammatory response to TNBS, but increased intestinal epithelial damage allowing the passage of bacterial antigens.

Effects of Short and Long-Term Soy Protein Isolate Intake on Hepatic Cytochrome P450 Expression in Obese Zucker Rats

Objectives To determine the effects feeding for 8 (short-term) and 16 weeks (long-term) soy protein isolate on hepatic CYP gene expression. Methods 7-weeks old rats were randomly assigned to either a casein (CAS) or a soy protein isolate (SPI) diet. They were provided the diets ad libitum for 8 and 16 weeks. Rats were euthanized and livers were stored at − 80°C. RNA was extracted from liver samples, and sequenced to obtain transcriptomic data (RNAseq). Ingenuity Pathway Analysis software (IPA, Qiagen, CA) was used in the analysis of global gene expression data. This analysis includes predictions of activation or inhibition of molecules or upstream regulators and functions based on a generated z-score and p-value of overlap (P = 0.05). Z-scores were consider significant when &gt; 2 (activation) and &lt; −2 (inhibition). Results Comparing short- vs long-term feeding revealed an increase in the number of down-regulated CYP genes from only 3 at 8 weeks of SPI diet to 10 at 16 weeks of same diet (P &lt; 0.05). In contrast, upregulated CYP gene numbers showed a small increase in long-term SPI diet compared to short-term, from 14 genes at 8 weeks to 17 genes at 16 weeks (P &lt; 0.05). In addition, we present a predicted activation of the transcription factor Aryl hydrocarbon receptor (AHR, activation z-score = 2.146, P = 4.20E-11), linked to the subsequent activation or up-regulation of various CYPs genes, indirectly leading to the activation and inhibition of two main metabolic functions under SPI feeding: conversion of lipid (lipid metabolism) –predicted to be activated (z-score = 2.089, P = 2.77E-08), and recruitment of phagocytes (inflammatory response) –predicted to be inhibited (z-score = −2.311, P = 2.10E-05). Conclusions Through global gene expression analysis we showed that gene expression of drug-metabolizing cytochrome P450 genes was modified in genetically obese Zucker rats after being fed a soy-based diet for short- and long-term, and that this change could have an important role in attenuation of liver steatosis. Further research is needed to corroborate these results. Funding Sources This study was supported in part by the College of Medicine's University Medical Group (RH) and the Arkansas Biosciences Institute (WB, RH).

Effect of Ecdysterone on the Hepatic Transcriptome and Lipid Metabolism in Lean and Obese Zucker Rats

Conflicting reports exist with regard to the effect of ecdysterone, the predominating representative of steroid hormones in insects and plants, on hepatic and plasma lipid concentrations in different rodent models of obesity, fatty liver, and diabetes, indicating that the effect is dependent on the rodent model used. Here, the hypothesis was tested for the first time that ecdysterone causes lipid-lowering effects in genetically obese Zucker rats. To test this hypothesis, two groups of male obese Zucker rats (n = 8) were fed a nutrient-adequate diet supplemented without or with 0.5 g ecdysterone per kg diet. To study further if ecdysterone is capable of alleviating the strong lipid-synthetic activity in the liver of obese Zucker rats, the study included also two groups of male lean Zucker rats (n = 8) which also received either the ecdysterone-supplemented or the non-supplemented diet. While hepatic and plasma concentrations of triglycerides and cholesterol were markedly higher in the obese compared to the lean rats (p < 0.05), hepatic and plasma triglyceride and cholesterol concentrations did not differ between rats of the same genotype fed the diets without or with ecdysterone. In conclusion, the present study clearly shows that ecdysterone supplementation does not exhibit lipid-lowering actions in the liver and plasma of lean and obese Zucker rats.

Preserved glycemic control and baroreflex efficacy in young adult hypertensive female obese Zucker rats

Obese Zucker rats (OZRs) develop hypertension and hyperinsulinemia by 3 months of age. Male OZRs also have diminished baroreflex-mediated activation of nucleus tractus solitarius (NTS) and bradycardia, which are improved by correcting their hyperglycemia. Conversely, 3-month-old female OZRs and lean Zucker rats (LZRs) have equivalent baroreflex-mediated bradycardia that is impaired in 6-month-old OZRs. We hypothesized that 3-month-old female OZRs maintain NTS activation and baroreflexes coincident with glycemic control. We also hypothesized that 6-month-old female OZRs develop impaired baroreflexes with hyperglycemia and diminished NTS activation. In 12-16-week-old females, sympathetic nerve activity (SNA) and arterial pressure (AP) were higher in OZRs than LZRs. However, baroreflex-mediated inhibition of SNA and bradycardia were equivalent in female OZRs and LZRs. Unlike deficits in male OZRs, female OZRs and LZRs had no differences in phenylephrine-induced c-Fos expression in NTS or decreases in SNA and AP evoked by glutamate into NTS. Compared to hyperglycemia in male OZRs (217.9±34.4mg/dl), female OZRs had normal fed blood glucose levels (108.2±1.6mg/dl in LZRs and 113.6±3.5mg/dl in OZRs) with emerging glucose intolerance. Conscious 24-27-week-old female OZRs had impaired baroreflex-mediated bradycardia, but fed blood glucose was modestly elevated (124.2±5.2mg/dl) and phenylephrine-induced c-Fos expression in NTS was comparable to LZRs. These data suggest better glycemic control in 3-month-old female OZRs prevents diminished NTS activation and baroreflexes, supporting the notion that hyperglycemia impairs these responses in male OZRs. However, 6-month-old female OZRs had impaired baroreflex efficacy without diminished NTS activation or pronounced hyperglycemia, suggesting baroreflex deficits develop by different mechanisms in female and male OZRs.