Lean Zucker Rats Research Articles

Perspectives on obesity imaging: [18F]2FNQ1P a specific 5-HT6 brain PET radiotracer.

Estimates suggest that approximatively 25% of the world population will be overweight in 2025. Better understanding of the pathophysiology of obesity will help to develop future therapeutics. Serotonin subtype 6 receptors (5-HT6) have been shown to be critically involved in appetite reduction and weight loss. However, it is not known if the pathological cascade triggered by obesity modifies the density of 5-HT6 receptors in the brain. Influence of diet-induced obesity (DIO) in Wistar rats was explored using MRI (whole-body fat) and PET ([18F]2FNQ1P as a specific 5-HT6 radiotracer). The primary goal was to monitor the 5-HT6 receptor density before and after a 10-week diet (DIO group). The secondary goal was to compare 5-HT6 receptor densities between DIO group, Wistar control diet group, Zucker rats (with genetic obesity) and Zucker lean strain rats. Wistar rats fed with high-fat diet showed higher body fat gain than Wistar control diet rats on MRI. [18F]2FNQ1P PET analysis highlighted significant clusters of voxels (located in hippocampus, striatum, cingulate, temporal cortex and brainstem) with increased binding after high-fat diet (p < 0.05, FWE corrected). This study sheds a new light on the influence of high-fat diet on 5-HT6 receptors. This study also positions [18F]2FNQ1P PET as an innovative tool to explore neuronal consequences of obesity or eating disorder pathophysiology.

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 was 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. While 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 to males and this difference was maintained to final animal usage at ~17 weeks 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 while males may be more predisposed to more direct cerebral vasculopathies (e.g., stroke, transient ischemic attack).

Expression of FAM159B in Humans, Rats, and Mice: A Cross-species Examination.

Little is known about the adaptor protein FAM159B. To determine whether FAM159B expression findings in rats or mice can be extrapolated to humans, we compared FAM159B expression in healthy tissue samples from all three species using immunohistochemistry. Despite variations in expression intensity, similar FAM159B expression patterns were observed in most organs across species. The most prominent species difference was noted in pancreatic islets; while FAM159B expression was limited to single cells on the outer edges in mice and rats, it was detectable across entire islets in humans. Double-labeling immunohistochemistry revealed partial overlap of FAM159B expression with that of insulin, glucagon, and somatostatin in human islets. By contrast, FAM159B showed complete colocalization with only somatostatin in rats and mice. An additional analysis of FAM159B expression in lean and obese Zucker rats revealed larger islet areas due to increased β-cell mass in obese rats, which was accompanied by a smaller percentage of FAM159B-positive δ-cells per islet area. Beyond the known differences in islet architecture across species, our results point to larger dissimilarities in blood glucose regulation between rodents and humans than generally assumed. Moreover, findings regarding FAM159B expression (and function) cannot be directly transferred between rodents and humans.

Marginal Zinc Deficiency Promotes Pancreatic Islet Enlargement While Zinc Supplementation Improves the Pancreatic Insulin Response in Zucker Diabetic Fatty Rats.

Zinc deficiency has been associated with the worsening of diabetes while zinc supplementation has been proposed to ameliorate diabetes. This study examined the effects of marginal zinc deficiency (MZD) and zinc supplementation (ZS) on obesity, glycemic control, pancreatic islets, hepatic steatosis and renal function of Zucker diabetic fatty (ZDF) rats. Male ZDF rats were fed an MZD, zinc control (ZC) or ZS diet (4, 30 and 300 mg Zn/kg diet, respectively), and lean Zucker rats were fed a ZC diet for 8 weeks. MZD and ZS did not alter body weight or whole-body composition in ZDF rats. MZD ZDF rats had reduced zinc concentrations in the femur and pancreas, a greater number of enlarged pancreatic islets and a diminished response to an oral glucose load based on a 1.8-fold greater incremental area-under-the-curve (AUC) for glucose compared to ZC ZDF. ZS ZDF rats had elevated serum, femur and pancreatic zinc concentrations, unchanged pancreatic parameters and a 50% reduction in the AUC for insulin compared to ZC ZDF rats, suggesting greater insulin sensitivity. Dietary zinc intake did not alter hepatic steatosis, creatinine clearance, or levels of proteins that contribute to insulin signaling, inflammation or zinc transport in epididymal fat. Potential adverse effects of ZS were suggested by reduced hepatic copper concentrations and elevated serum urea compared to ZC ZDF rats. In summary, ZS improved the pancreatic insulin response but not the glucose handling. In contrast, reduced zinc status in ZDF rats led to impaired glucose tolerance and a compensatory increase in the number and size of pancreatic islets which could lead to β-cell exhaustion.

Adherence of Candida albicans to fibrin-clot matrices in a rat model for type 2 diabetes

Individuals with type 2 diabetes are at increased risk for the development of infective endocarditis and septic thrombosis. Adherence to fibrin clot matrices by Candida albicans is the initial step in initiation of the infective processes. Clots made from lean (Fa/fa) and obese (fa/fa) Zucker rat plasma were used to measure adherence of yeast grown at environmental temperature and human body temperature. Adherence to clots by C. albicans was influenced both by source of plasma and temperature of yeast growth. Amphotericin B was effective in diminishing the candidal binding to lean but not obese clots. The degree of fungal surface hydrophobicity did not correlate with adherence to clots. However, Candida adherence to clots from both lean and obese Zucker rats was inhibited by the pretreatment of cells with mannose. These findings indicate that treatment of thrombi-associated candidal infections with ergosterol-targeting drugs e.g., amphotericin B alone in hypercholesterolemic individuals may have decreased clinically efficacy.

Evaluation of glomerular hemodynamic changes by sodium-glucose-transporter 2 inhibition in type 2 diabetic rats using in vivo imaging

The mechanisms responsible for glomerular hemodynamic regulation with sodium-glucose co-transporter 2 (SGLT2) inhibitors in kidney disease due to type 2 diabetes remain unclear. Therefore, we investigated changes in glomerular hemodynamic function using an animal model of type 2 diabetes, treated with an SGLT2 inhibitor alone or in combination with a renin-angiotensin-aldosterone system inhibitor using male Zucker lean (ZL) and Zucker diabetic fatty (ZDF) rats. Afferent and efferent arteriolar diameter and single-nephron glomerular filtration rate (SNGFR) were evaluated in ZDF rats measured at 0, 30, 60, 90, or 120 minutes after the administration of a SGLT2 inhibitor (luseogliflozin). Additionally, we assessed these changes under the administration of the adenosine A1 receptor (A1aR) antagonist (8-cyclopentyl-1,3-dipropylxanthine), along with coadministration of luseogliflozin and an angiotensin II receptor blocker (ARB), telmisartan. ZDF rats had significantly increased SNGFR, and afferent and efferent arteriolar diameters compared to ZL rats, indicating glomerular hyperfiltration. Administration of luseogliflozin significantly reduced afferent vasodilatation and glomerular hyperfiltration, with no impact on efferent arteriolar diameter. Urinary adenosine levels were increased significantly in the SGLT2 inhibitor group compared to the vehicle group. A1aR antagonism blocked the effect of luseogliflozin on kidney function. Co-administration of the SGLT2 inhibitor and ARB decreased the abnormal expansion of glomerular afferent arterioles, whereas the efferent arteriolar diameter was not affected. Thus, regulation of afferent arteriolar vascular tone via the A1aR pathway is associated with glomerular hyperfiltration in type 2 diabetic kidney disease.

Low to moderate doses of dietary resistant starch and a renin-angiotensin system inhibitor exhibit nephroprotective effects through similar mechanisms in a preclinical model of diabetes

The investigative goal of our study was to determine the molecular mechanisms of nephroprotection of a drug-diet intervention for type II diabetes in a pre-clinical model. Our working hypothesis proposed that a combination of moderate doses of dietary resistant starch and a low-dose renin-angiotensin system (RAS) inhibitor would decrease renal biomarkers associated with the progression and complications of type II diabetes through the modulation of the renal renin-angiotensin system. Four weeks old Zucker Diabetic Fatty rats ( fa/fa) ( ZDF, n=48) and Zucker lean rats (n=7) were obtained from Charles River Laboratories and acclimated for one week. ZDF rats were then randomly assigned to one of three diets: AIN-93G diet with 0% resistant starch (RS), which served as the control diet, AIN-93G diet with 5% RS, or AIN-93 with 10% resistant starch, which were adjusted at the expense of cornstarch in the diet composition, for a total of eight weeks. At six weeks old, they were randomly assigned to daily intraperitoneal (IP) injections of either captopril (at a dose of 0.5 g/kg of body weight) in saline water and ascorbic acid solution or placebo solution, which consisted of just the vehicle, until the end of the 8-weeks. Zucker lean rats were assigned to an AIN-93G diet with 0% RS and administered daily IP placebo injections at the same timeline as the ZDF counterparts. Rats were placed in metabolic cages 12 hours before euthanization by exsanguination to collect urine and feces. Samples and tissues were aliquoted and frozen, respectively, until further analyses. Enzyme-linked immunosorbent assays were used to quantify different renal biomarkers in the urine and serum samples (i.e., 25-hydroxy-vitamin D, albumin, creatinine). Protein was extracted from kidney samples for Western Blot analyses. ZDF 10% RS and captopril group (ZDF 10% cap) had a decrease of 62.5% in urinary protein creatinine ratio, 29% of urinary albumin levels, and 18% of 25-hydroxy vitamin D (25D) levels, compared to the diabetic control group (ZDF 0% RS placebo). The ZDF 10% RS cap group also exhibited a 62% increase in serum 25D levels, while the 5% RS and captopril group had an 8.7% increase in 1,25-dihydroxy-vitamin D levels compared to the diabetic control. The ZDF 10% RS cap group also presented a 5.5% increase in relative abundance of nephrin and a decrease of 5.9% and 33.3% in angiotensin II receptor I and aldosterone synthase relative abundance, respectively, compared to the diabetic control group. Our results suggest that a combination of dietary resistant starch and a RAS inhibitor help to protect kidney integrity in type II diabetic rats, evidenced by a decrease of biomarkers in the urine and expression of proteins that play a part in the RAS, and increase in serum biomarkers and expression of glomerular structural proteins. Our work was funded by a USDA-NIFA grant. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Is the Zucker Diabetic Fat Rat an Appropriate Model of Diabetic Kidney Disease: A Discussion on Hydronephrosis

Introduction: Kidney disease is a significant concern for global healthcare, particularly in individuals with diabetes. Experimental research into the pathology of diabetes is dependent on the utilisation of appropriate animal models. The Zucker Diabetic Fat (ZDF) rat has a Leptin receptor deficiency and is a commonly used model of type 2 diabetes. Here, we examine the relevance of this model for the investigation of diabetic kidney disease, with a particular focus on vascular imaging. The Zucker Lean (ZL) rat is a non-diabetic strain of the same rat lineage and will be used as a control. Method: This dataset used the ZDF rat (n=13) and the Zucker Lean (ZL) rat (n=16). Individuals were scanned at ages of 12 weeks (ZDF n=4, ZL n=4), 22 weeks (ZDF n=4, ZL n=5), and 40 weeks (ZDF n=5, ZL n=7). During open laparotomy, rats were maintained on a respirator under general anaesthesia via isoflurane and blood pressure was monitored via a central catheter. During surgery, a blood glucose measurement was taken from the tail vein and samples of arterial blood and urine were collected. The contrast medium Microfil (MV122, Flow Tech Inc., Carver, MA) was injected post-mortem via the renal artery and excised kidneys were scanned for 11 hours in a ZEISS XRadia 410 Versa μCT scanner (Carl Zeiss Microscopy GmbH, Jena, Germany). Results: As expected, the ZDF rats developed significant hyperglycaemia from 12 weeks, significant increases in albumin creatinine ratio (ACR) from 22 weeks, and a significant decrease in glomerular filtration rate (GFR) from 40 weeks. Concurrent hydronephrosis affecting more than 10% of total kidney volume was detected in 51% of all rats (group prevalence rates were ZDF=69% and ZL=38%). The percent of the kidney mass affected by hydronephrosis was significantly higher in ZDF than ZL (ANOVA row factor p=0,029*). Age had no significant impact on the size of the hydronephrotic cavity. There was a significant correlation between the degree of hyperglycaemia and the size of the hydronephrotic cavity (mm) (r=0.57, p=0,0014**). ACR, GFR and urine excretion rate were unaffected by hydronephrosis. Hydronephrosis did not have a significant impact on vascular density in the remaining kidney tissue (p=0.53). Conclusion: The high prevalence of hydronephrosis development in the ZDF rat questions its appropriateness to model human diabetic kidney disease, as hydronephrosis is not commonly seen in diabetic patients. While vascular density was preserved in the remaining kidney tissue, the huge loss of vascular tissue caused by hydronephrotic erosion means this model is limited for all renal imaging applications. Both ZDF and ZL rats develop hydronephrosis suggesting this may be a genetic condition of their common lineage. However, the conditions' increased severity in the ZDF rat indicates that the deficit in the leptin receptor contributes to disease pathology. The significant relationship between hyperglycaemia and hydronephrosis size suggests the two conditions are interacting, raising questions about whether the underlying molecular mechanisms of this model of diabetic kidney disease have any relevance for translational research. Funded by European Research Council Synergy grant SURE, project no. 854796. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Feeding Status Transiently Alters the Phosphorylation of Enzymes in the PI3K/Akt/GSK3β Pathway but not Phosphorylated Tau in the Cortex of Male Obese Zucker Rats

Metabolic syndrome (MetS) fosters pathological brain markers such as excess phosphorylated tau (ptau) to produce neuronal dysfunction. Activation of the PI3K/Akt/GSK3β pathway by increasing pAkt-Ser473 and pGSK3β-Tyr216 promotes phosphorylation of tau at residues such as Ser396. Insulin also increases pGSK3β-Ser9 to limit phosphorylation of tau. Deficient insulin signaling has been proposed to reduce pGSK3β-Ser9 and promote pathological excess ptau-Ser396. However, studies of these pathways in rodent models of MetS report both elevated and reduced expression of pAkt-Ser473 and pGSK3β-Ser9, raising the question of the predictive value and role of altered pGSK3β-Ser9 expression in producing excess ptau. Studies reporting reduced pGSK3β-Ser9 in insulin resistant and diabetic rodents often used fasted animals for tissue collection, but other studies without reported fasting showed increased pGSK3β-Ser9. However, elevated ptau was consistently observed under both conditions. Because short-term changes in insulin and glucose alter pAkt-Ser473 and pGSK3β-Ser9 expression, we hypothesized that phosphorylation was related to the feeding status at time of tissue collection rather than the chronic disease state, and excess ptau was resistant to these short-term changes. We examined whether fasting altered pAkt-Ser473, pGSK3β-Tyr216, and pGSK3β-Ser9, and ptau-Ser396 levels in 18-week-old male obese (OZR) and lean (LZR) Zucker rats. After measurement of blood glucose by tail sample in their home cage, fasted (16 hours) and non-fasted rats were euthanized for tissue collection. Though baseline glucose was higher in OZRs vs. LZRs in the fed state (202.4±21.9 vs. 115.9±2.7 mg/dl, t-test) and fasted state (169.4±5.8 vs. 95.3±3.8 mg/dl, t-test), fasting significantly reduced glucose in OZRs but not LZRs (2-way ANOVA with Tukey’s post hoc, P=0.023 for OZRs and P=0.143 for LZRs, n=5-8/group). Protein expression in the cerebral cortex was measured by Western blotting and normalized to actin (n=3-5 for all groups). Expression of ptau-Ser396/total tau was significantly elevated in OZRs vs. LZRs in both feeding conditions (p&lt;0.001) and was not altered by fasting in either phenotype. Expression of pAkt-Ser476 was elevated in non-fasted OZRs vs. LZRs (p&lt;0.001). Fasting greatly reduced pAkt-Ser476 in OZRs (p&lt;0.001) but not LZRs (P=0.741), making expression in fasted OZRs and LZRs comparable (P=0.674). Expression of pGSK3β-Ser9 was significantly elevated in fed OZRs vs. LZRs (p&lt;0.001). Fasting reduced expression of pGSK3β-Ser9 only in OZRs (p&lt;0.001 in OZRs, P=0.952 in LZRs), but expression of was still elevated in fasted OZRs vs. LZRs (P=0.009). Expression of pGSK3β-Tyr216 was significantly elevated in fed OZRs vs. LZRs (p&lt;0.001) but significantly lower in fasted OZRs vs. LZRs (p&lt;0.001). These data show that feeding status does not alter the ptau-Ser396 in the cerebral cortex of OZRs vs. LZRs, but phosphorylation of the enzymes of the PI3K/Akt/GSK3β signaling pathway are greatly affected by MetS and feeding status at time of tissue collection. Thus, when OZRs have access to food, elevated pGSK3β-Tyr216 may contribute to the GSK3β-mediated rise in ptau-Ser396 despite elevated pGSK3β-Ser9. Supported by R01Hl132568S1, JES Edwards Foundation, and Summerfield G. Roberts Foundation. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Differential Modulation by Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) of Mesenteric Fat and Macrophages and T Cells in Adipose Tissue of Obese fa/fa Zucker Rats.

Polyunsaturated fatty acids (PUFAs) can alter adipose tissue function; however, the relative effects of plant and marine n3-PUFAs are less clear. Our objective was to directly compare the n3-PUFAs, plant-based α-linolenic acid (ALA) in flaxseed oil, and marine-based eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) in high-purity oils versus n6-PUFA containing linoleic acid (LA) for their effects on the adipose tissue and oral glucose tolerance of obese rats. Male fa/fa Zucker rats were assigned to faALA, faEPA, faDHA, and faLA groups and compared to baseline fa/fa rats (faBASE) and lean Zucker rats (lnLA). After 8 weeks, faEPA and faDHA had 11-14% lower body weight than faLA. The oral glucose tolerance and total body fat were unchanged, but faEPA had less mesenteric fat. faEPA and faDHA had fewer large adipocytes compared to faLA and faALA. EPA reduced macrophages in the adipose tissue of fa/fa rats compared to ALA and DHA, while faLA had the greatest macrophage infiltration. DHA decreased (~10-fold) T-cell infiltration compared to faBASE and faEPA, whereas faALA and faLA had an ~40% increase. The n3-PUFA diets attenuated tumour necrosis factor-α in adipose tissue compared to faBASE, while it was increased by LA in both genotypes. In conclusion, EPA and DHA target different aspects of inflammation in adipose tissue.

Hydroxytyrosol Linoleoyl Ether Ameliorates Metabolic-Associated Fatty Liver Disease Symptoms in Obese Zucker Rats.

A main hepatic consequence of obesity is metabolic-associated fatty liver disease (MAFLD), currently treated by improving eating habits and administrating fibrates yet often yielding suboptimal outcomes. Searching for a new therapeutic approach, we aimed to evaluate the efficacy of hydroxytyrosol linoleoyl ether (HTLE), a dual Ppar-α agonist/Cb1 antagonist with inherent antioxidant properties, as an antisteatotic agent. Using lean and obese Zucker rats, they were administrated daily doses of HTLE (3 mg/kg) over a 15-day period, evaluating its safety profile, pharmacokinetics, impact on body weight, hepatic fat content, expression of key enzymes involved in lipogenesis/fatty acid oxidation, and antioxidant capacity. HTLE decreased the body weight and food intake in both rat genotypes. Biochemical analysis demonstrated a favorable safety profile for HTLE along with decreased concentrations of urea, total cholesterol, and aspartate aminotransferase AST transaminases in plasma. Notably, HTLE exhibited potent antisteatotic effects in obese rats, evidenced by a decrease in liver fat content and downregulation of lipogenesis-related enzymes, alongside increased expression of proteins controlling lipid oxidation. Moreover, HTLE successfully counteracted the redox imbalance associated with MAFLD in obese rats, attenuating lipid peroxidation and replenishing both glutathione levels and the overall antioxidant. Our findings highlight the effectiveness of triple-action strategies in managing MAFLD effectively. Based on our results in the Zucker rat model, HTLE emerges as a promising candidate with triple functionality as an anorexigenic, antisteatotic, and antioxidant agent, offering potential relief from MAFLD symptoms associated with obesity while exhibiting minimal side effects. In conclusion, our study positions HTLE as a highly promising compound for therapeutic intervention in MAFLD treatment, warranting further exploration in clinical trials.

Genetic analysis of impaired healing responses after periodontal therapy in type 2 diabetes: Clinical and invivo studies.

This study aims to investigate the mechanisms underlying the impaired healing response by diabetes after periodontal therapy. Outcomes of periodontal therapy in patients with diabetes are impaired compared with those in patients without diabetes. However, the mechanisms underlying impaired healing response to periodontal therapy have not been sufficiently investigated. Zucker diabetic fatty (ZDF) and lean (ZL) rats underwent experimental periodontitis by ligating the mandibular molars for one week. The gingiva at the ligated sites was harvested one day after ligature removal, and gene expression was comprehensively analyzed using RNA-Seq. In patients with and without type 2 diabetes (T2D), the corresponding gene expression was quantified in the gingiva of the shallow sulcus and residual periodontal pocket after non-surgical periodontal therapy. Ligation-induced bone resorption and its recovery after ligature removal were significantly impaired in the ZDF group than in the ZL group. The RNA-Seq analysis revealed 252 differentially expressed genes. Pathway analysis demonstrated the enrichment of downregulated genes involved in the peroxisome proliferator-activated receptor (PPAR) signaling pathway. PPARα and PPARγ were decreased in mRNA level and immunohistochemistry in the ZDF group than in the ZL group. In clinical, probing depth reduction was significantly less in the T2D group than control. Significantly downregulated expression of PPARα and PPARγ were detected in the residual periodontal pocket of the T2D group compared with those of the control group, but not in the shallow sulcus between the groups. Downregulated PPAR subtypes expression may involve the impaired healing of periodontal tissues by diabetes.

Chronic exercise improves renal AT1 and ETB receptor functions via modulating GRK4 expression in obese Zucker rats

ABSTRACT Background Physical activity has profound benefits on health, especially in patients with cardiovascular and metabolic disease. Exercise training can reduce oxidative stress, improve renal function, and thus lower blood pressure. However, the effect of exercise training on angiotensin II type 1 receptors (AT1R) and endothelin subtype B receptors (ETBR)-mediated diuresis and natriuresis in obese Zucker rats is unclear. Methods Lean and obese Zucker rats were exercised or placed on a nonmoving treadmill for 8 weeks. Blood pressure was measured by tail-cuff plethysmography, and functions of AT1R and ETBR in the kidney were measured by natriuresis, respectively. Results Our data showed that exercise training improved glucose and lipid metabolism, renal function and sodium excretion in obese Zucker rats, accompanied by decreased oxidative stress and GRK4 expression in obese Zucker rats. Moreover, exercise training reduced the Candesartan-induced an increase in diuresis and natriuresis and increased ETBR agonists (BQ3020)-mediated diuresis and natriuresis in obese Zucker rats, which were associated with decreased renal AT1R expression and ETBR phosphorylation levels. Conclusions The results demonstrate that exercise training lowers blood pressure via improving renal AT1R and ETBR function through modulating GRK4 expression in Obese Zucker Rats and provides potentially effective targets for obesity-related hypertension.

Temporal and region-specific tau hyperphosphorylation in the medulla and forebrain coincides with development of functional changes in male obese Zucker rats.

Metabolic syndrome (MetS) is associated with development of tauopathies that contribute to cognitive decline. Without functional leptin receptors, male obese Zucker rats (OZRs) develop MetS, and they have increased phosphorylated tau (ptau) with impaired cognitive function. In addition to regulating energy balance, leptin enhances activation of the hippocampus, which is essential for spatial learning and memory. Whether spatial learning and memory are always impaired in OZRs or develop with MetS is unknown. We hypothesized that male OZRs develop MetS traits that promote regional increases in ptau and functional deficits associated with those brain regions. In the medulla and cortex, tau-pSer199,202 and tau-pSer396 were comparable in juvenile (7-8 wk old) lean Zucker rats (LZRs) and OZRs but increased in 18- to 19-wk-old OZRs. Elevated tau-pSer396 was concentrated in the dorsal vagal complex of the medulla, and by this age OZRs had hypertension with increased arterial pressure variability. In the hippocampus, tau-pSer199,202 and tau-pSer396 were still comparable in 18- to 19-wk-old OZRs and LZRs but elevated in 28- to 29-wk-old OZRs, with emergence of deficits in Morris water maze performance. Comparable escape latencies observed during acquisition in 18- to 19-wk-old OZRs and LZRs were increased in 28- to 29-wk-old OZRs, with greater use of nonspatial search strategies. Increased ptau developed with changes in the insulin/phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway in the hippocampus and cortex but not medulla, suggesting different underlying mechanisms. These data demonstrate that leptin is not required for spatial learning and memory in male OZRs. Furthermore, early development of MetS-associated autonomic dysfunction by the medulla may be predictive of later hippocampal dysfunction and cognitive impairment.NEW & NOTEWORTHY Male obese Zucker rats (OZRs) lack functional leptin receptors and develop metabolic syndrome (MetS). At 16-19 wk, OZRs are insulin resistant, with increased ptau in dorsal medulla and impaired autonomic regulation of AP. At 28-29 wk OZRs develop increased ptau in hippocampus with deficits in spatial learning and memory. Juvenile OZRs lack elevated ptau and these deficits, demonstrating that leptin is not essential for normal function. Elevated ptau and deficits emerge before the onset of diabetes in insulin-resistant OZRs.

Intestinal Effects of Filtered Alkalinized Water in Lean and Obese Zucker Rats.

This study evaluated the intestinal effects of alkalinized filtered water in lean and obese adult Zucker rats. For 3 months, 12-week-old rats consumed either tap water or filtered alkalinized tap water from Madrid city. Weight gain was monitored, changes in metabolism were evaluated by indirect calorimetry, and total antioxidant capacity and levels of inflammatory mediators were measured in plasma. Feces were collected, their microbial composition was analyzed and histological analysis of the small and large intestine was performed, assessing the general state of the mucosa (MUC2), the inflammatory state (F4/80) and the presence of oxidative modifications in protein 4-Hydroxynonenal (4-HNE) by immunofluorescence (IF) and immunohistochemistry (IHC). The results obtained showed that the consumption of alkalinized filtered water improved the composition of the intestinal microbiome and the state of the intestinal mucosa, reducing both local and systemic inflammation and the level of oxidative stress. These changes were accompanied by a better maintenance of the oxidative status in rats. No differences were observed in antioxidant capacity nor in weight gain. The incorporation of probiotics in the diet had a significant impact on the microbiome. These effects were indicative of an improvement in general metabolic, oxidative and inflammatory status.

Lipidomics and biodistribution of extracellular vesicles‐secreted by hepatocytes from Zucker lean and fatty rats

AbstractExtracellular vesicles (EVs) have been involved in metabolic syndrome, although their specific role in the development of the pathology is still unknown. To further study the role of EVs, we have analysed by Raman tweezers microspectroscopy and mass spectrometry‐based lipidomics the small EVs population secreted by fatty (ZF) and lean (ZL) hepatocytes obtained from Zucker rats. We have also explored in vivo and ex vivo biodistribution of these EVs through fluorine‐18‐radiolabelling using a positron emission tomography imaging. Based on the proportion of proteins to lipids and the types of lipids, our results indicate that within the range of small EVs, primary hepatocytes secrete different subpopulations of particles. These differences were observed in the enrichment of triglyceride species in EVs secreted by ZF hepatocytes. Biodistribution experiments showed accumulation in the brain, heart, lungs, kidney and specially in bladder after intravenous administration. In summary, we show that EVs released by a fatty hepatocytes carry a different lipid signature compared to their lean counterpart. Biodistribution experiment has shown no difference in the distribution of EVs secreted by ZF and ZL hepatocytes but has given us a first view of possible target organs for these particles. Our results might open a door to both pathology studies and therapeutic interventions.

High-Density Lipoprotein Is Located Alongside Insulin in the Islets of Langerhans of Normal and Rodent Models of Diabetes.

Recent studies have implicated pre-beta and beta lipoproteins (VLDL and LDL) in the etiopathogenesis of complications of diabetes mellitus (DM). In contrast, alpha lipoprotein (HDL) is protective of the beta cells of the pancreas. This study examined the distribution of HDL in the islets of Langerhans of murine models of type 1 diabetic rats (streptozotocin (STZ)-induced DM in Wistar rats) and type 2 models of DM rats (Goto-Kakizaki (GK), non-diabetic Zucker lean (ZL), and Zucker diabetic and fatty (ZDF)). The extent by which HDL co-localizes with insulin or glucagon in the islets of the pancreas was also investigated. Pancreatic tissues of Wistar non-diabetic, diabetic Wistar, GK, ZL, and ZDF rats were processed for immunohistochemistry. Pancreatic samples of GK rats fed with either a low-fat or a high-fat diet were prepared for transmission immune-electron microscopy (TIEM) to establish the cytoplasmic localization of HDL in islet cells. HDL was detected in the core and periphery of pancreatic islets of Wistar non-diabetic and diabetic, GK, ZL, and ZDF rats. The average total of islet cells immune positive for HDL was markedly (<0.05) reduced in GK and ZDF rats in comparison to Wistar controls. The number of islet cells containing HDL was also remarkably (p < 0.05) reduced in Wistar diabetic rats and GK models fed on high-fat food. The co-localization study using immunofluorescence and TIEM techniques showed that HDL is detected alongside insulin within the secretory granules of β-cells. HDL did not co-localize with glucagon. This observation implies that HDL may contribute to the metabolism of insulin.

Leptin-dependent differential remodeling of visceral and pericardial adipose tissue following chronic exercise and psychosocial stress.

Obesity is driven by an imbalance between caloric intake and energy expenditure, causing excessive storage of triglycerides in adipose tissue at different sites around the body. Increased visceral adipose tissue (VAT) is associated with diabetes, while pericardial adipose tissue (PAT) is associated with cardiac pathology. Adipose tissue can expand either through cellular hypertrophy or hyperplasia, with the former correlating with decreased metabolic health in obesity. The aim of this study was to determine how VAT and PAT remodel in response to obesity, stress, and exercise. Here we have used the male obese Zucker rats, which carries two recessive fa alleles that result in the development of hyperphagia with reduced energy expenditure, resulting in morbid obesity and leptin resistance. At 9 weeks of age, a group of lean (Fa/Fa or Fa/fa) Zucker rats (LZR) and obese (fa/fa) Zucker rats (OZR) were treated with unpredictable chronic mild stress or exercise for 8 weeks. To determine the phenotype for PAT and VAT, tissue cellularity and gene expression were analyzed. Finally, leptin signaling was investigated further using cultured 3T3-derived adipocytes. Tissue cellularity was determined following hematoxylin and eosin (H&E) staining, while qPCR was used to examine gene expression. PAT adipocytes were significantly smaller than those from VAT and had a more beige-like appearance in both LZR and OZR. In the OZR group, VAT adipocyte cell size increased significantly compared with LZR, while PAT showed no difference. Exercise and stress resulted in a significant reduction in VAT cellularity in OZR, while PAT showed no change. This suggests that PAT cellularity does not remodel significantly compared with VAT. These data indicate that the extracellular matrix of PAT is able to remodel more readily than in VAT. In the LZR group, exercise increased insulin receptor substrate 1 (IRS1) in PAT but was decreased in the OZR group. In VAT, exercise decreased IRS1 in LZR, while increasing it in OZR. This suggests that in obesity, VAT is more responsive to exercise and subsequently becomes less insulin resistant compared with PAT. Stress increased PPAR-γ expression in the VAT but decreased it in the PAT in the OZR group. This suggests that in obesity, stress increases adipogenesis more significantly in the VAT compared with PAT. To understand the role of leptin signaling in adipose tissue remodeling mechanistically, JAK2 autophosphorylation was inhibited using 5 μM 1,2,3,4,5,6-hexabromocyclohexane (Hex) in cultured 3T3-derived adipocytes. Palmitate treatment was used to induce cellular hypertrophy. Hex blocked adipocyte hypertrophy in response to palmitate treatment but not the increase in lipid droplet size. These data suggest that leptin signaling is necessary for adipocyte cell remodeling, and its absence induces whitening. Taken together, our data suggest that leptin signaling is necessary for adipocyte remodeling in response to obesity, exercise, and psychosocial stress.

Female and male obese Zucker rats display differential inflammatory mediator and long non-coding RNA profiles

AimsThe goal of this study was to identify mediators in peri-lymphatic adipose tissue (PLAT) that are altered in obese versus lean Zucker rats, with focus on potential sex differences Main methodsMesenteric PLAT was analyzed with protein and lncRNA arrays. Additional RT-PCR confirmation was performed with epididymal/ovarian fat. Key findingsMCP-1, TCK-1, Galectin-1, Galectin-3, and neuropilin-1 were elevated in PLAT from obese rats of both sexes. However, 11 additional proteins were elevated only in obese males while 24 different proteins were elevated in obese females. Profiling of lncRNAs revealed lean males have elevated levels of NEAT1, MALAT1 and GAS5 compared to lean females. NEAT1, MALAT1, and GAS5 were significantly reduced with obesity in males but not in females. Another lncRNA, HOTAIR, was higher in lean females compared to males, and its levels in females were reduced with obesity. Obese rats of both sexes had similar histologic findings of mesenteric macrophage crown-like structures and hepatocyte fat accumulation. SignificanceWhile obese male and female Zucker rats both have increased inflammation, they have distinct signals. Future studies of the proteome and lncRNA landscape of obese males vs. females in various animal models and in human subjects are warranted to better guide development of therapeutics for obesity-induced inflammation.

Feeding soy protein concentrates with low or high isoflavone decreases liver inflammation by reducing lipopolysaccharide translocation

Lipopolysaccharide (LPS) translocation and inflammation contribute to the increased risk of chronic diseases, including non-alcoholic fatty liver disease (NAFLD), associated with obesity. Previously, we reported that feeding soy protein with high or low (negligible) isoflavone reduces liver steatosis in obese Zucker rats, and the reduced steatosis is accompanied by decreased serum C-reactive protein levels. The current study investigated the effect of feeding soy protein concentrate (SPC) with high or low isoflavone (HIF or LIF) on liver inflammation and LPS translocation in obese Zucker rats. Six-week-old male lean (L, n = 21) and obese (O, n = 21) Zucker rats were fed casein control, SPC-LIF, or SPC-HIF diets for 18 weeks. At the end of 18 weeks, the expression levels of tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), inducible nitric oxide synthase (iNOS), arginase 1 (ARG1), lipopolysaccharide binding protein (LBP), myeloperoxidase (MPO), and sterol regulatory element-binding protein 1 (SREBP-1) were significantly higher in obese rats compared to lean rats. Compared to the casein control diet, both the SPC-LIF and SPC-HIF diets significantly decreased TNF-α, MCP-1, iNOS, and LBP expression in obese rats, which is accompanied by significantly less LPS staining in liver slides from SPC-LIF-and SPC-HIF-fed obese rats compared to the casein control diet-fed obese rats. Taken together, the SPC-LIF and SPC-HIF diets attenuated liver inflammation in obese Zucker rats, likely by decreasing LPS translocation.