Female Zucker Fatty Rats Research Articles

Myristolated Serotonin 2A Receptor Peptide Promotes Long-Lasting Blood Pressure-Lowering and Reno protection in Hypertensive Rat Species.

The aim of the present study was to test whether conjugation of a synthetic peptide corresponding to a fragment of the second extracellular domain of the human serotonin 2A receptor substantially alters the in vivo pharmacodynamic blood pressure-lowering profile of the peptide in different hypertensive rat strains. Sertuercept (SCLLADDN) was synthesized and modified using pegylation or myristolation. The two different peptide conjugates were tested in male Zucker diabetic fatty rats for acute and long-lasting blood pressure-lowering effects following single intraperitoneal administration. The myristolated Sertuercept was administered intraperitoneally to female Zucker fatty and male spontaneously hypertensive rats (SHR) and blood pressure was monitored either using tail cuff measurement (female Zucker) or by telemetry (SHR) rats. Plasma immunoglobulin G obtained by Protein G affinity chromatography in 25-week-old female Zucker or male spontaneously hypertensive rats was tested for binding to a linear synthetic peptide corresponding to the second extracellular loop of the serotonin 2A receptor. A cohort of male Zucker diabetic fatty rats was randomized to seven weeks of once-weekly myristolated Sertuercept or scrambled peptide (injections) and the kidneys were examined histologically for differences in total kidney lesions or fibrosis. Pegylated Sertuercept promoted substantial blood pressure-lowering lasting approximately 30-48 hours in male Zucker diabetic fatty rats. Blood pressure-lowering following a single injection of Myristolated Sertuercept was much longer-lasting (6-11 days) and it was effective in male Zucker diabetic fatty rats, male spontaneously hypertensive rats and in a subset of hypertensive female Zucker fatty rats. Seven weeks' treatment with once-weekly Myristolated Sertuercept (2mg/kg) was associated with significantly fewer kidney lesions and less interstitial fibrosis compared to scrambled peptide in 25-week-old male Zucker diabetic fatty rats. Male spontaneously hypertensive rats (4 of 4 tested) harbored plasma IgG which bound significantly to serotonin 2A receptor peptide, and a subset of female Zucker fatty rats harboring IgG were responsive to blood pressure-lowering from the myristolated Sertuercept peptide. Myristolated-Sertuercept, an epitope-specific peptide comprised of a portion of second extracellular loop of the human serotonin 2A receptor was safe, well-tolerated and effectively lowered blood pressure for one week or longer in two different strains of male hypertensive rats. These data provide proof-of-concept that once-weekly systemic drug administration is feasible to achieve not only long-lasting hypertension control, but also substantial renoprotection.

Expression of hypothalamic kisspeptin, neurokinin B, and dynorphin A neurons attenuates in female Zucker fatty rats.

Zucker fatty (ZF) rats are considered to be an obese model due to leptin receptor abnormality and such rats show infertility. Pulsatile gonadotropin-releasing hormone/luteinizing hormone (LH) secretion, which is important for follicular development in females, is considered to be controlled by KNDy neurons coexpressing kisspeptin, neurokinin B (NKB), and dynorphin A (DynA), encoded by Kiss1, Tac3, and Pdyn, respectively, in the hypothalamic arcuate nucleus (ARC). The purpose of this study is to examine the expression of KNDy neurons in female ZF rats by histochemical approach because pulsatile LH secretion is suppressed. Zucker lean (ZL) rats served as a control group. Animals were ovariectomized and subcutaneously implanted with a silicon tube containing estradiol to produce plasma level of estradiol during diestrus. Plasma LH levels decreased in ZF rats compared with ZL rats. The expressions of each mRNA (Kiss1, Tac3, and Pdyn) and each peptide (kisspeptin, NKB, and DynA) in the ARC significantly decreased in ZF rats compared with ZL rats. However, the number of Kiss1 neurons in the anterior ventral periventricular nucleus did not significantly differ between the two groups. These results suggest that dysfunction of leptin signaling negatively affects KNDy neurons in the ARC, resulting in reproductive dysfunction caused by suppression of the LH pulse.

Obesity-induced discrepancy between contractile and metabolic phenotypes in slow- and fast-twitch skeletal muscles of female obese Zucker rats.

A clear picture of skeletal muscle adaptations to obesity and related comorbidities remains elusive. This study describes fiber-type characteristics (size, proportions, and oxidative enzyme activity) in two typical hindlimb muscles with opposite structure and function in an animal model of genetic obesity. Lesser fiber diameter, fiber-type composition, and histochemical succinic dehydrogenase activity (an oxidative marker) of muscle fiber types were assessed in slow (soleus)- and fast (tibialis cranialis)-twitch muscles of obese Zucker rats and compared with age (16 wk)- and sex (females)-matched lean Zucker rats (n = 16/group). Muscle mass and lesser fiber diameter were lower in both muscle types of obese compared with lean animals even though body weights were increased in the obese cohort. A faster fiber-type phenotype also occurred in slow- and fast-twitch muscles of obese rats compared with lean rats. These adaptations were accompanied by a significant increment in histochemical succinic dehydrogenase activity of slow-twitch fibers in the soleus muscle and fast-twitch fiber types in the tibialis cranialis muscle. Obesity significantly increased plasma levels of proinflammatory cytokines but did not significantly affect protein levels of peroxisome proliferator-activated receptors PPARγ or PGC1α in either muscle. These data demonstrate that, in female Zucker rats, obesity induces a reduction of muscle mass in which skeletal muscles show a diminished fiber size and a faster and more oxidative phenotype. It was noteworthy that this discrepancy in muscle's contractile and metabolic features was of comparable nature and extent in muscles with different fiber-type composition and antagonist functions.NEW & NOTEWORTHY This study demonstrates a discrepancy between morphological (reduced muscle mass), contractile (shift toward a faster phenotype), and metabolic (increased mitochondrial oxidative enzyme activity) characteristics in skeletal muscles of female Zucker fatty rats. It is noteworthy that this inconsistency was comparable (in nature and extent) in muscles with different structure and function.

Impaired contractility of the circular striated urethral sphincter muscle may contribute to stress urinary incontinence in female zucker fatty rats.

Obesity has been an independent risk factor for female stress urinary incontinence (SUI), the mechanism of this association remains unknown. The aim of this study is to validate the hypothesis that urethral dysfunction is a possible contributor to SUI in obese women. Ten Zucker Fatty (ZF) (ZUC-Leprfa 185) and 10 Zucker Lean (ZL) (ZUC-Leprfa 186) female rats at 12-week-old were used in this experiment. The urethral sphincter rings were harvested from the bladder neck through to the most proximal 2/3 regions. In the organ bath study, single pulses of electrical field stimulation (EFS) were applied. For the fatiguing stimulation, repeated multi-pulse EFS with 70 mA were applied at frequency of 5 Hz for 5 min. Caffeine-containing Krebs' solution was administrated to contract the urethra until the contraction began to reach a plateau for 10 min. We performed immunofluorescence staining of the urethra after the experiment was finished. Compared to ZL controls, ZF rats had significantly impaired muscle contractile activity (MCA) (P < 0.05). Also, ZF rats presented early fatiguing of MCA and had a significantly greater percentage of MCA decline from baseline in the fatiguing test (37.7% vs 25.6%, P < 0.05). The plateau of maximal MCA induced by caffeine in ZF rats was significantly lower than ZL controls (0.22 vs 0.36, P < 0.05). This novel study showed that obese female rats had significantly impaired contractile properties of striated urethral sphincter, suggesting urethral dysfunction could be an important contributor to SUI in obesity.

Transgenic animal model for studying the mechanism of obesity-associated stress urinary incontinence.

To study and compare the function and structure of the urethral sphincter in female Zucker lean (ZL) and Zucker fatty (ZF) rats and to assess the viability of ZF fats as a model for female obesity-associated stress urinary incontinence (SUI). Two study arms were created: a ZL arm including 16-week-old female ZL rats (ZUC-Leprfa 186; n = 12) and a ZF arm including 16-week-old female ZF rats (ZUC-Leprfa 185; n = 12). I.p. insulin tolerance testing was carried out before functional study. Metabolic cages, conscious cystometry and leak point pressure (LPP) assessments were conducted. Urethral tissues were harvested for immunofluorescence staining to check intramyocellular lipid (IMCL) and sphincter muscle (smooth muscle and striated muscle) composition. The ZF rats had insulin resistance, a greater voiding frequency and lower LPP compared with ZL rats (P < 0.05), with more IMCL deposition localized in the urethral striated muscle fibres of the ZF rats (P < 0.05). The thickness of the striated muscle layer and the ratio of striated muscle to smooth muscle were lower in ZF than in ZL rats. Obesity impairs urethral sphincter function via IMCL deposition and leads to atrophy and distortion of urethral striated muscle. The ZF rats could be a consistent and reliable animal model in which to study obesity-associated SUI.

Soluble fiber-enriched diets improve inflammation and oxidative stress biomarkers in Zucker fatty rats

In this study we evaluated the effect of the administration of different soluble fiber enriched-diets on inflammatory and redox state of Zucker fatty rats. Four groups of ten 8 week-old female Zucker fatty rats were used. The four groups were respectively fed the following diets until the 15th week of life: standard diet (obese control), 10% high methoxylated apple pectin (HMAP)-, 5% soluble cocoa fiber (SCF)-, and 10% β-glucan-enriched diets. A group of Zucker lean rats fed the standard diet was also used as control for normal values of this rat strain. The plasma levels of tumoral necrosis factor-α (TNF-α), adiponectin, and malondialdehyde (MDA) were measured at the end of treatment. The reduced glutathione liver levels were also obtained at that moment. TNF-α plasma levels decreased somewhat in Zucker fatty rats fed the different fibers, and MDA plasma levels significantly decreased in these animals. Nevertheless, adiponectin plasma levels increased in the Zucker fatty rats fed the SCF enriched diet, but did not change in the HMAP and the β-glucan group. The Zucker fatty rats fed the different fiber showed a trend towards increased the reduced glutathione liver levels, but significant differences with obese control rats were only obtained in the β-glucan group. The results obtained in this study suggest that the intake of the different soluble fiber-enriched diets that we have evaluated could prevent and/or attenuate the inflammatory and/or the prooxidative state of the metabolic syndrome.

Effects of Salsalate Therapy on Recovery From Vascular Injury in Female Zucker Fatty Rats

OBJECTIVESalsalate is a dimeric form of salicylic acid that has been shown to have anti-inflammatory activity and to reduce glucose levels, insulin resistance, and cytokine expression. However, the effect of salsalate on vascular injury has not been determined. The objective of this study is to investigate the effect of salsalate on vascular injury and repair in a rat model of carotid artery balloon catheter injury.RESEARCH DESIGN AND METHODSSalsalate treatment was started in female Zucker fatty rats (insulin resistant) 1 week before carotid artery balloon catheter injury and continued for 21 days, at which time the animals were killed and studied.RESULTSTreatment with salsalate significantly decreased the intima-to-media ratio and upregulated the expression of aortic endothelial nitric oxide synthase (eNOS), phosphorylated eNOS (p-eNOS) (ser 1177), and manganese superoxide dismutase (MnSOD) and reduced serum interleukin (IL)-6 with concomitant downregulation of nuclear factor (NF) κB subunit p65 and vascular endothelial growth factor (VEGF) expression in the balloon-injured carotid artery of female Zucker fatty rats.CONCLUSIONSThe present study shows that salsalate treatment decreases vascular damage caused by balloon catheter injury in female Zucker fatty rats. The beneficial effect of salsalate on vascular injury was associated with upregulation of eNOS, p-eNOS, and MnSOD, which reduce oxidative stress and have anti-inflammatory properties, as evidenced by reduction in serum IL-6 and the downregulation of VEGF and NFκB, which promote inflammation without changing glucose levels. These results suggest that salsalate may be useful in reducing vascular injury and restenosis following interventional revascularization procedures.

Influence of Various Central Moieties on the Hypolipidemic Properties of Long Hydrocarbon Chain Diols and Diacids

A series of long (11-15) hydrocarbon chain diols and diacids with various central functional groups and terminal gem-dimethyl or -methyl/aryl substituents was synthesized and evaluated in both in vivo and in vitro assays for its potential to favorably alter lipid disorders including metabolic syndrome. Compounds were assessed for their effects on the de novo incorporation of radiolabeled acetate into lipids in primary cultures of rat hepatocytes, as well as for their effects on lipid and glycemic variables in obese female Zucker fatty rats, Crl:(ZUC)-faBR. The most active compounds were hydroxyl-substituted symmetrical diacids and diols with a 13-atom chain and terminal gem-dimethyl substituents. Furthermore, biological activity was enhanced by central substitution with O, C=O, S, S=O compared to the methylene analogues and was diminished for compounds with central functional groups such as carbamate, ester, urea, acetylmethylene, and hydroxymethylene.

Long Hydrocarbon Chain Keto Diols and Diacids that Favorably Alter Lipid Disorders in Vivo

Keto-substituted hydrocarbons with 11-19 methylene and bis-terminal hydroxyl and carboxyl groups have been synthesized and evaluated in both in vivo and in vitro assays for their potential to favorably alter lipid disorders including metabolic syndrome. Compounds were assessed for their effects on the de novo incorporation of radiolabeled acetate into lipids in primary cultures of rat hepatocytes as well as for their effects on lipid and glycemic variables in obese female Zucker fatty rats [Crl:(ZUC)-faBR] following 1 and 2 weeks of oral administration. The most active compounds were found to be symmetrical with four to five methylene groups separating the central ketone functionality and the gem dimethyl or methyl/aryl substituents. Furthermore, biological activity was found to be greatest in both in vivo and in vitro assays for the tetramethyl-substituted keto diacids and diols (e.g., 10c, 10g, 14c), and the least active were shown to be the bis(arylmethyl) derivatives (e.g., 10e, 10f, 14f). Compound 14c dose-dependently elevated HDL-cholesterol, reduced triglycerides, and reduced NEFA, with a minimum effective dose of 30 mg/kg/day. Compound 1 g dose-dependently modified non-HDL-cholesterol, triglycerides, and nonesterified fatty acids, with a minimum effective dose of 10 mg/kg/day. At this dose, compound 10g elevated HDL-cholesterol levels 2-3 times higher than pretreatment levels, and a dose-dependent reduction of fasting insulin and glucose levels was observed.

Increased expression of SERCA2 mRNA in hearts of genetically obese Zucker rats after a moderate treadmill running

Aim. – Analyze the effects of exercise training on cardiac sarco endoplasmic reticulum calcium ATPase (SERCA) 2 gene expression of genetically obese Zucker rats, an animal model of non-insulin dependent diabetes mellitus (NIDDM). Methods. – Twenty male and 20 female Zucker fatty rats ran 30–50 min/d at 35–40% VO 2max, 6 d/week for 13 weeks. Semi-quantitative RT-PCR associated with specific restriction fragment analysis was used to detect and quantify the relative expression of SERCA mRNA isoforms. Results. – Fatty rats had an enhanced expression of SERCA2 and phospholamban (PLB) mRNA levels in ventricles. Moreover, fatty rats exposed to a moderate treadmill running exercise for 13 weeks exhibited a significant increase in ventricles SERCA2 mRNA levels, whereas, no change occurred in control lean rats. Exercise training produced a significant induction of α-myosin heavy chain mRNA levels only in fatty rats. Conclusion. – We hypothesize that exercise training may improve the cardiac function in diabetic rats by increasing the mRNA expression of SERCA2 since it is known that NIDDM rats have a reduced left ventricular diastolic compliance, and that exercise training improves the ventricular function in diabetic rats.

Salacia reticulata and Its Polyphenolic Constituents with Lipase Inhibitory and Lipolytic Activities Have Mild Antiobesity Effects in Rats

Salacia (S.) reticulata, a Hippocrateaceae plant distributed in Sri Lankan and Indian forests, has been used as a supplementary food in Japan to prevent obesity and diabetes. We examined the antiobesity effects of the hot water-soluble extract (SRHW) from the roots of S. reticulata using obese rat models and an in vitro study. Body weight (P = 0.07) and periuterine fat storage (P = 0.10) in female Zucker fatty rats (8-9 wk old) tended to be suppressed by oral administration of SRHW (125 mg/kg) for 27 d. Male rats fed a high fat diet were not affected by SRHW. Furthermore, SRHW inhibited porcine pancreatic lipase (PL), rat adipose tissue-derived lipoprotein lipase (LPL) and glycerophosphate dehydrogenase (GPDH) activities with 50% inhibitory concentrations (IC(50)) of 264 (95% confidence limits: 203-393) mg/L, 15 (12-18) mg/L and 54 (35-85) mg/L, respectively, but did not inhibit hormone-sensitive lipase activity in rat adipose tissue. Next, we examined the effects of polyphenols, di- and triterpenes and salacinol isolated from the roots of S. reticulata on lipid metabolizing enzymes and lipolysis. (-)-Epigallocatechin and (-)-epicatechin-(4beta-->8)-(-)-4'-O-methylepigallocatechin inhibited PL activity with IC(50) of 88 (not calculated) and 68 (26-122) mg/L, respectively. (-)-Epicatechin, 3beta, 22beta-dihydroxyolean-12-en-29-oic acid and the tannin fraction inhibited LPL activity with IC(50) of 81 (54-214), 89 (62-214) and 35 (24-62) mg/L. Only the tannin fraction inhibited GPDH activity with an IC(50) of 6.8 (3.4-10.9) mg/L. These constituents may be involved in the lipase and GPDH inhibitory activities of SRHW. On the other hand, SRHW at 100 mg/L tended to enhance lipolysis in rat adipocytes (P = 0.06). Significant lipolytic effects were exerted by mangiferin, (-)-4'-O-methylepigallocatechin and maytenfolic acid at 100 mg/L (P < 0.01). In conclusion, polyphenolic compounds may be involved in the antiobesity effects of SRHW in rats through inhibition of fat metabolizing enzymes (PL, LPL and GPDH) and enhanced lipolysis.

Effect of exercise on glycolytic enzymes of Zucker fatty rats.

The effect of fatigue (running to exhaustion) on the Vmax activity of the key glycolytic enzymes measured at saturating substrate concentrations in muscles, liver and brain of sedentary and trained (running on a treadmill one h/day at 20 m/min, five days/week for six months) female Zucker fatty rats and their lean littermates was investigated. In the sedentary rats, fatigue increased the activity of phosphofructokinase (PFK) in the red vastus muscle by 82% in lean, and 120% in obese rats. In the trained rats, fatigue increased PFK activity by 28% in the white vastus muscle of lean rats. In the lean animals, hexokinase (HK) activity was decreased by 26% in the red vastus of sedentary rats, and by 29% in the white vastus of trained rats upon fatiguing. Pyruvate kinase (PK) activity was also decreased by 29% in the white vastus of fatigued lean animals. Training by itself had no effect on the activity of glycolytic enzymes, except PK activity which was increased by 27% in the cortex of the lean animals. It is concluded that in the Zucker rat, these glycolytic enzymes may play a differential role in regulating glycolysis during exercise and fatigue; the extent of their involvement differs depending upon the type of tissue studied and exercise. In view of the reported short half-life (7-17 h) of PFK and its covalent modification, it is suggested that the total content and/or phosphorylation status of the enzyme may be affected in animals subjected to long-term fatigue.