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.

Effects of Short-Term Metformin Treatment on Gut Microbiota Profile Using Female Obese Zucker Rat Model

Objectives The correlation of short-term metformin treatment and specific alterations to the gut microbiota in obese models is less known. So, the objectives of this experiment was to investigate the effects of short-term metformin treatment on population of gut microbiota profile in obese rat model. Methods Five week old obese (n = 16) female Zucker rats after one week of acclimation, received AIN-93 G diet for 8 weeks and then rats were randomly assigned 8 rats/group): to 1) obese without metformin (ObC), or 2) obese with metformin (ObMet). Metformin were mixed with AIN-93G diet at 1000 mg/kg of diet. Rats were weighed twice per week. All rats were sacrificed 10 weeks post-metformin treatment and fecal samples were collected and kept at − 80c. Total microbial DNA were collected directly from the fecal samples using a PowerSoil® DNA isolation kit. Isolated DNA were used for shotgun-metagenomics data collection using Illumina NextSeq500 and analyzed using MetaPlAn and HUMAnN. DEICODE and Songbird used calculate log-ratios and differential ranks of taxa and functional pathways associated with metformin treatment respectively. The were then visualized using Qurro. Results There was no significant difference between ObC vs. ObMet group body weight (P = 0.20). Overall microbial beta-diversity (DEICODE), showed significant separation between the obese control and metformin samples (P = 0.0007). Differential ranking (Songbird) of Bacteroides dorei and B. massiliensis vs. all other Bacteroides spp., revealed that B. dorei and B. massiliensis were enriched in the obese metformin group, while the remaining Bacteroides spp. where enriched in the obese control group (P = 0.002). The differential ranking of pathway diversity contributed by the Bacteroides were also associated with treatment group (P = 0.008). Conclusions In summary, in the obese zucker rat model, short-term metformin treatment changes the gut microbiota profile. Funding Sources Arkansas Biosciences Institute.

Can Myogenic Tone Protect Endothelial Function? Integrating Myogenic Activation and Dilator Reactivity for Cerebral Resistance Arteries in Metabolic Disease

The obese Zucker rat (OZR) manifests multiple risk factors for impaired cerebrovascular function, including hypertension and insulin resistance although how they combine to produce integrated vascular function is unclear. As studies have suggested that myogenic activation (MA) severity for middle cerebral arteries (MCAs) may be proportional to hypertension severity, we hypothesized that MA will negatively correlate with dilator reactivity in OZR. MA of MCA from OZR was divided into low, medium, and high based on the slope of MA, while MCA reactivity and vascular metabolite bioavailability were assessed in all groups. Endothelium-dependent dilation of MCA in OZR was attenuated and correlated with the MA slope. Treatment of OZR MCA with TEMPOL (antioxidant) improved dilation in low or medium MA groups, but had less impact on high MA. Alternatively, treatment with gadolinium to normalize MA in OZR had reduced impact on dilator reactivity in MCA from low and medium MA groups, but improved responses in the high group. Treatment with both agents resulted in dilator responses that were comparable across all groups. These results suggest that, under conditions with stronger MA, endothelial function may receive some protection despite the environment, potentially from the ability of MCA to reduce wall tension despite increased pressure.

Red raspberry (Rubus idaeus) consumption restores the impaired vasoconstriction and vasorelaxation in the aorta of the obese zucker rat, a model of the metabolic syndrome

Metabolic Syndrome (MetS) increases the risk of cardiovascular disease. Whole red raspberry (WRR) consumption on vascular function was investigated in the obese Zucker rat (OZR), model of MetS. Male OZR and their lean littermates (LZR) were placed on a control (C) or an 8% w/w WRR-enriched diet for 8 weeks. Phenylephrine (Phe)-induced vasoconstriction and acetylcholine (Ach)-induced vasorelaxation were measured in aortic rings in the presence or absence of L-N-monomethyl-arginine (L-NMMA) and mefenamic acid (MFA). Phe-induced vasoconstriction was lower in the OZR-C compared to LZR-C (p < 0.05). The WRR diet partially restored aortic response in the OZR-WRR aorta (p < 0.05) compared to OZR- C. The OZR-WRR group pre-treated with L-NMMA increased compared to OZR-C (p < 0.05). Pre-treatment with L-NMMA, maximal relaxation response was higher in the OZR compared to the LZR (p < 0.05). With L-NMMA, maximal relaxation response in OZR-WRR (p < 0.05) was lower compared to the OZR-C. Prostacyclin I2 concentration was higher in the OZR compared to the LZR (p < 0.05) and was attenuated in the OZR-WRR (p < 0.05). Aortic expression of eNOS and COX-2 were downregulated in the OZR-WRR (p < 0.05). In conclusion, WRR restores the impaired vascular tone of the OZR by enhancing Phe-induced vasoconstriction and attenuating Ach-induced vasorelaxation.

Effects of Obesity and Short-Term Metformin Treatment on Liver Steatosis in Female Zucker Rats

Objectives Non-alcoholic fatty liver disease (NAFLD) is the leading cause of liver disease in adolescents in the US and World, and the risk has increased with the rise in obesity. We reported that obesity increases Fatty liver (steatosis) using an obese Zucker rat model. Metformin is an oral anti-hyperglycemic agent approved by the FDA to treat type 2 diabetes (T2D) in adults and children older than 10 years of age. There is insufficient evidence regarding the effects of metformin in pediatric liver steatosis. The objective of this study was to investigate the effects of short-term metformin treatment on liver steatosis and related serum markers for liver damage. Methods Five week old lean (n = 16) and obese (n = 16) female Zucker rats after one week of acclimation, received AIN-93 G diet for 8 weeks to induce NAFLD. After 8 weeks, lean and obese rats were randomly assigned to the following four groups (8 rats/group): 1) lean without metformin (LC), 2) lean with metformin (LMet), 3) obese without metformin (ObC), and 4) obese with metformin (ObMet). Metformin were mixed with AIN-93 G diet at 1000 mg/kg of diet. Rats were weighed twice per week. All rats were sacrificed 10 weeks post-metformin treatment and serum and livers were collected. Steatosis was semiquantitated as a score of 1 to 4 based upon the relative degree of steatosis within hepatocytes: 1) &lt; 25%, 2) 25–50%, 3) 50–75%, and 4) &gt;75%. Serums were collected to measure the levels of Aspartate Aminotransferase (AST), Alanine Aminotransferase (ALT) on a clinical analyzer. Results Obese rats gained significantly more weight (P &lt; .001) than lean rats for both control and Metformin treatment groups and there was no significant difference between ObC vs. ObMet group (P = 0.20). The mean + SD liver steatosis scores for the LC, LMet, ObC and ObMet groups were 0.13 + o.3, 0.13 + o.3, 3.67 + 0.52 and 3.00 + 0.82. The ObMet treated rats had lower (P &lt; 0.04) liver steatosis than ObC rats. There were no significant differences for the serum ALT and AST levels between groups. However, obesity increased significantly (P &lt; 0.01) serum AST levels compared to LC but not in the metformin group. Conclusions In summary, in the obese zucker rat model, short-term metformin treatment decreased liver steatosis but did not impact serum markers of liver steatosis. Funding Sources Arkansas Children Research Institute/Arkansas Bioscience Institute.

Bladder Dysfunction in an Obese Zucker Rat: The Role of TRPA1 Channels, Oxidative Stress, and Hydrogen Sulfide

Purpose. This study investigates whether functionality and/or expression changes of transient receptor potential vanilloid 1 (TRPV1) and transient receptor potential ankyrin 1 (TRPA1) channels, oxidative stress, and hydrogen sulfide (H2S) are involved in the bladder dysfunction from an insulin-resistant obese Zucker rat (OZR). Materials and Methods. Detrusor smooth muscle (DSM) samples from the OZR and their respective controls, a lean Zucker rat (LZR), were processed for immunohistochemistry for studying the expression of TRPA1 and TRPV1 and the H2S synthase cystathionine beta-synthase (CBS) and cysthathionine-γ-lyase (CSE). Isometric force recordings to assess the effects of TRPA1 agonists and antagonists on DSM contractility and measurement of oxidative stress and H2S production were also performed. Results. Neuronal TRPA1 expression was increased in the OZR bladder. Electrical field stimulation- (EFS-) elicited contraction was reduced in the OZR bladder. In both LZR and OZR, TRPA1 activation failed to modify DSM basal tension but enhanced EFS contraction; this response is inhibited by the TRPA1 blockade. In the OZR bladder, reactive oxygen species, malondialdehyde, and protein carbonyl contents were increased and antioxidant enzyme activities (superoxide dismutase, catalase, GR, and GPx) were diminished. CSE expression and CSE-generated H2S production were also reduced in the OZR. Both TRPV1 and CBS expressions were not changed in the OZR. Conclusions. These results suggest that an increased expression and functionality of TRPA1, an augmented oxidative stress, and a downregulation of the CSE/H2S pathway are involved in the impairment of nerve-evoked DSM contraction from the OZR.