Ginsenoside RK3 promotes neurogenesis in Alzheimer's disease through activation of the CREB/BDNF pathway

ETHNOPHARMACOLOGICAL RELEVANCE

In the ancient book "Shen Nong's Herbal Classic," Panax ginseng CA Mey was believed to have multiple benefits, including calming nerves, improving cognitive function, and promoting longevity. Ginsenosides are the main active ingredients of ginseng. Ginsenoside RK3 (RK3), a rare ginsenoside extracted from ginseng, displays strong pharmacological potential. However, its effect on neurogenesis remains insufficiently investigated.

AIM OF THE STUDY

This study aims to investigate whether RK3 improves learning and memory by promoting neurogenesis, and to explore the mechanism of RK3 action.

MATERIALS AND METHODS

The therapeutic effect of RK3 on learning and memory was determined by the Morris water maze (MWM) and novel object recognition test (NORT). The pathogenesis and protective effect of RK3 on primary neurons and animal models were detected by immunofluorescence and western blotting. Protein expression of cAMP response element-binding protein (CREB)/brain-derived neurotrophic factor (BDNF) signaling pathway was detected by western blotting.

RESULTS

Our results showed that RK3 treatment significantly improved cognitive function in APPswe/PSEN1dE9 (APP/PS1) mice and C57BL/6 (C57) mice. RK3 promotes neurogenesis and synaptogenesis in the mouse hippocampus. In vitro, RK3 prevents Aβ-induced injury in primary cultured neurons and promotes the proliferation of PC12 as well as the expression of synapse-associated proteins. Mechanically, the positve role of RK3 on neurogenesis was combined with the activation of CREB/BDNF pathway. Inhibition of CREB/BDNF pathway attenuated the effect of RK3.

CONCLUSION

In conclusion, this study demonstrated that RK3 promotes learning and cognition in APP/PS1 and C57 mice by promoting neurogenesis and synaptogenesis through the CREB/BDNF signaling pathway. Therefore, RK3 is expected to be further developed into a potential drug candidate for the treatment of Alzheimer's disease (AD).

Ginsenoside RK1 improves cognitive impairments and pathological changes in Alzheimer's disease via stimulation of the AMPK/Nrf2 signaling pathway

BACKGROUND

The pathogenesis of Alzheimer's disease (AD) is complex, resulting in unsatisfactory effects of single-target therapeutic drugs. Accumulation evidence suggests that low toxicity multi-target drugs may play effective roles in AD. Ginseng is the root and rhizome of Panax ginseng Meyer, which can be used not only as herbal medicine but also as a functional food to support body functions. Ginsenoside RK1 (RK1), obtained from ginseng plants through high-temperature treatment, has antiapoptotic, antioxidant, anti-inflammatory effects and these events are involved in the development of AD. So, we believe that RK1 may be an effective drug for the treatment of AD.

HYPOTHESIS/PURPOSE

We aimed to investigate the potential protective effects and mechanisms of RK1 in AD.

METHODS

Neuronal damage was detected by MTT assay, LDH assay, immunofluorescence and western blotting. Oxidative stress was measured by JC-1 staining, reactive oxygen species (ROS) staining, superoxide dismutase (SOD) and malonaldehyde (MDA). The cognitive deficit was measured through morris water maze (MWM) and novel object recognition (NOR) tests.

RESULTS

RK1 attenuated Aβ-induced apoptosis, restored mitochondrial membrane potential (ΔΨm), and reduced intracellular levels of ROS in both PC12 cells and primary cultured neurons. In vivo, RK1 significantly improved cognitive deficits and mitigated AD-like pathological features. Notably, RK1 demonstrated superior efficacy compared to the positive control drug, donepezil. Mechanistically, our study elucidates that RK1 modulates the phosphorylation of AMP-activated protein kinase (AMPK) and its downstream target, NF-E2-related factor 2 (Nrf2), leading to the optimization of mitochondrial membrane potential, reduction of ROS levels, and mitigation of AD-like pathology. It's noteworthy that blocking the AMPK signaling pathway attenuated the protective effects of RK1.

CONCLUSION

RK1 demonstrates superior efficacy in alleviating cognitive deficits and mitigating pathological changes compared to donepezil. These findings suggest the potential utility of RK1-based therapies in the development of treatments for AD.

Parthenolide alleviates cognitive dysfunction and neurotoxicity via regulation of AMPK/GSK3β(Ser9)/Nrf2 signaling pathway

Alzheimer's disease (AD) stands as the predominant age-related neurodegenerative disorder, for which efficacious treatment remains elusive. An auspicious avenue for this disease lies in natural compounds sourced from tranditional medicine and plant origins. Parthenolide (PTN) is a natural product with multiple biological functionsand. Recent investigations have illuminated PTN's protective properties against neurological maladies; however, its potential therapeutic role against AD remains uncharted. This study aims to explore the role of PTN in treating AD. Our in vitro findings underscore PTN's bioactivity, as evidenced by its capacity to curtail apoptosis, reduce reactive oxygen species (ROS) production, and restore mitochondrial membrane potential in PC12 cells. Moreover, PTN treatment demonstrates a capacity to ameliorate deficits in spatial learning and memory in the 3 ×Tg-AD murine model. Notably, PTN's therapeutic efficacy surpasses that of a clinical agent, donepezil. Mechanistically, PTN's neuroprotective effects stem from its adept regulation of the AMPK/GSK3β(ser9)/Nrf2 signaling pathway and protection on neuronal cells from ROS-related apoptosis. Although the molecular target and the pre-clinical evaluations of PTN need to be further explored, this study indicates PTN as a potential agent or lead compound for the drug development against AD.

Isolinderalactone Ameliorates the Pathology of Alzheimer's Disease by Inhibiting the JNK Signaling Pathway

Neuronal cell damage is a major cause of cognitive impairment in Alzheimer's disease (AD). Multiple factors, such as amyloid deposition, tau hyperphosphorylation, and neuroinflammation, can lead to neuronal cell damage. Therefore, the development of multi-target drugs with broad neuroprotective effects may be an effective strategy for the treatment of AD. Natural products have become an important source of drug discovery because of their good pharmacological activity, multiple targets, and low toxicity. In this study, we screened a natural compound library and found that the fat-soluble sesquiterpene natural compound isolinderalactone (Iso) extracted from the dried root pieces of Lindera aggregata had the ability to alleviate cellular damage induced by β-amyloid-1-42 (Aβ1-42). The role and mechanism of Iso in AD have not yet been reported. Herein, we demonstrated that Iso significantly reduced the level of apoptosis in PC12 cells. Besides, Iso treatment reduced amyloid deposition, neuron apoptosis, and neuroinflammation, ultimately improving the cognitive dysfunction of APP/PS1 (APPswe/PSEN 1dE9) mice. Notably, Iso-10 mg/kg showed superior improved effects in APP/PS1 mice compared with the positive control drug donepezil-5 mg/kg. Mechanistically, the results of RNA sequencing combined with Western blots showed that Iso exerted its therapeutic effect by inhibiting the c-Jun N-terminal kinase (JNK) signaling pathway. Taken together, our findings suggest that Iso is a potential drug candidate for the treatment of AD.

β-amyloid binds to microglia Dectin-1 to induce inflammatory response in the pathogenesis of Alzheimer's disease

Microglia-mediated neuroinflammation is closely related to the development of Alzheimer's disease (AD). In the early stages of the inflammation response, pattern recognition receptors (PRRs) play a key role in clearing damaged cells and defending against infection by recognizing endogenous and exogenous ligands. However, the regulation of pathogenic microglial activation and its role in AD pathology remains poorly understood. Here we showed that a pattern recognition receptor called Dectin-1, expressed on microglia, mediates the pro-inflammatory responses of beta-amyloid (Aβ). Knockout of Dectin-1 reduced Aβ1-42 (Aβ₄₂)-induced microglial activation, inflammatory responses, and synaptic and cognitive deficits in Aβ₄₂-infused AD mice. Similar results were obtained in the BV2 cell model. Mechanistically, we showed that Aβ₄₂ could directly bind to Dectin-1, causing Dectin-1 homodimerization and activating downstream spleen tyrosine kinase (Syk)/nuclear factor-κB (NF-κB) signaling pathway to induce the expression of inflammatory factors and, in turn, AD pathology. These results suggest the important role of microglia Dectin-1 as a new direct receptor for Aβ₄₂ in microglial activation and AD pathology and provide a potential therapeutic strategy for neuroinflammation in AD.

Ginsenoside Rk3 ameliorates Aβ-induced neurotoxicity in APP/PS1 model mice via AMPK signaling pathway

Alzheimer's disease (AD) has become a major public health problem affecting the elderly population, and there is currently no effective treatment. Although the pathogenesis of AD is unclear, neurotoxicity induced by oxidative stress plays an important role in the progression of AD. Ginseng, the root and rhizome of Panax ginseng C. A. Meyer, is used not only as an herbal medicine but also as a functional food to support bodily functions. Ginsenoside Rk3 (Rk3), the main bioactive component in ginseng, has a strong antioxidant effect and has not been reported in AD. In this study, we showed that Rk3 improved neuronal apoptosis, decreased intracellular reactive oxygen species (ROS) production and restored mitochondrial membrane potential in PC12 and primary neuronal cells. In vivo, we found that Rk3 improved spatial learning and memory deficit in precursor protein (APP)/presenilin 1 (PS1) double transgenic mouse model of AD. Additionally, Rk3 increases glutathione reductase (GSH) and superoxide dismutase (SOD) levels while inhibits malondialdehyde (MDA) production, apoptosis and activation of glial cells in APP/PS1 mice. Mechanistically, we found that the protective effect of Rk3 is in correlation with the activation of AMPK/Nrf2 signaling pathway. In conclusion, the findings of this study provide support for Rk3 as a new strategy for the treatment of AD.

[The role of autophagy in the invasion and metastasis of the squamous cell carcinoma of head and neck]

Objective:The aim of this study is to explore the effects of autophagy on the metastasis of the Squamous Cell Carcinoma of Head and Neck (SCCHN) via epithelial to mesenchymal transition (EMT) induced by TGF-β1. Method:Establish the EMT model induced by TGF-β1 in the SCCHN in time/concentration, and the expression of autophagy related protein microtubule associated protein 1 light chain3 (LC3) detected by western blot; Autophagy inhibitor chloroquine (CQ), depressing autophagy, the expression of E-cadherin, cytokeratin, Vimentin and LC3 were examined by Western blot. Wound healing and Transwell invasion assay indicate the effects to metastasis for SCCHN. Result:Autophagy was activated within TGF-β1 induced EMT model in the SCCHN in time/concentration dependently. After autophagy was suppressed, the expression of E-cadherin and cytokeratin increased while vimentin and the capacity of metastasis was reduced compared with control group. Conclusion:TGF-β1 induce EMT and Autophagy in the SCCHN. Autophagy could enhances metastasis in the SCCHN via EMT induced by TGF-β1.

Risk prognosis factors of chronic subdural hematoma evacuated by the novel YL-1 hollow needle aspiration drainage system

AIM

The novel YL-1 hollow needle aspiration drainage system is an effective minimally invasive treatment in chronic subdural hematoma (CSDH). In order to find the risk prognosis factors of chronic subdural hematoma (CSDH) performed by the novel YL-1 hollow needle aspiration drainage system, a logistic analysis of postoperative results was performed.

METHODS

One hundred ninety-four cases of chronic subdural hematoma in a period of 7 years since 2004 were collected. According to the postoperative rehabilitation effect of nerve function, the patients were divided into good prognosis group and poor prognosis group. The patients' indexes of the two groups with age, blood coagulation function, location of the hematoma, hematoma volume, admission Markwalder's grade, clinical symptoms were tested by the chi-square test, then the statistically significant factors were selected into the establishment of the Logistic regression model and further analysis of multiple factors were made on chronic subdural hematoma prognostic implications.

RESULTS

Retrospective analysis was performed for differentiating good prognosis group (N.=174) and poor prognosis group (N.=20). Univariate analysis after the chi-square test showed that there were significant differences in gender, age, coagulation function, hematoma position, hematoma size, initial Markwalder's neurological grade, clinical symptoms and signs. Logistic regression analysis showed that chronic subdural hematoma prognostic factors sorted by odds ratio were as follows: high Markwalder's grade, male, coagulopathy, bilateral hematoma, senior citizens.

CONCLUSION

We used logistic regression analysis to identify the risk prognosis factors of chronic subdural hematoma (CSDH) performed by a novel YL-1 hollow needle aspiration drainage systems, and found that high preoperative Markwalder's gradie, male, coagulopathy, bilateral hematoma, senior citizens will poorly affect prognosis in CSDH.

A comparison of lycopene and astaxanthin absorption from corn oil and olive oil emulsions

The effect of different oils on the absorption of carotenoids was investigated in mesenteric lymph duct cannulated rats. Sixteen treatment emulsions containing increasing concentrations of either lycopene (LYC) or astaxanthin (AST) (5, 10, 15, 20 micromol/L) were prepared with olive oil or corn oil and continuously infused into the duodenum of the rat. Absorption of carotenoids into the mesenteric lymph duct was determined. Absorption of LYC and AST from both oils increased with the amount infused into the duodenum. The average recovery of AST in the lymph from the olive oil emulsion was 20% but was decreased to 13% from emulsions containing corn oil. Lycopene was not as well absorbed as AST. The average recovery of LYC was 6% from olive oil emulsions but only 2.5% when infused with corn oil. The LYC used in this study was isolated from tomato paste and was primarily in the all-trans form. We did not observe any significant isomerization of all-trans LYC to 9-cis LYC during absorption. We conclude that the type of oil with which a carotenoid is consumed can influence its absorption.

Ability of insulin to modulate hepatic glucose production in aging rats is impaired by fat accumulation

Increased total fat mass (FM) and visceral fat (VF) may account in part for age-associated decrease in hepatic insulin action. This study determined whether preventing the changes in body fat distribution abolished this defect throughout aging. We studied the F(1) hybrid of Brown Norway-Fischer 344 rats (n = 29), which we assigned to caloric restriction (CR) or fed ad libitum (AL). CR (55% of the calories consumed by AL) was initiated and used at 2 mo to prevent age-dependent increases in FM and VF. AL rats were studied at 2, 8, and 20 mo; CR rats were studied at 8 and 20 mo. VF and FM remained unchanged throughout aging in CR rats. AL-fed rats at 8 and 20 mo had over fourfold higher FM and VF compared with both CR groups. Insulin clamp studies (3 mU. kg(-1). min(-1) with somatostatin) were performed to assess hepatic insulin sensitivity. Prevention of fat accretion resulted in a marked improvement in insulin action in the suppression of hepatic glucose production (HGP) (6.3 +/- 0.3 and 7.2 +/- 1.2 mg. kg(-1). min(-1) in 8- and 20-mo CR rats vs. 8.3 +/- 0.5 and 10.8 +/- 0.9 mg. kg(-1). min(-1) in 8- and 20-mo AL rats, respectively). The rate of gluconeogenesis (by enrichment of hepatic uridine diphosphate glucose and phosphoenolpyruvate pools by [(14)C]lactate) was unchanged in all groups. The improvement in hepatic insulin action in the CR group was mostly due to effective suppression of glycogenolysis (4.4 +/- 0.3 and 4.9 +/- 0.3 mg. kg(-1). min(-1) in 8- and 20-mo CR rats vs. 5.8 +/- 0.6 and 8.2 +/- 1.0 mg. kg(-1). min(-1) in 8- and 20-mo AL rats, respectively). The results demonstrated the preservation of hepatic insulin action in aging CR rats. Therefore, body fat and its distribution are major determinants of age-associated hepatic insulin resistance.

Aging does not contribute to the decline in insulin action on storage of muscle glycogen in rats

Increase in fat mass (FM) and changes in body composition may account for the age-associated impairment in insulin action on muscle glycogen storage. We wish to examine whether preventing the increase in FM abolishes this defect seen with aging. We studied the novel aging model of F1 hybrids of BN/F344 NIA rats fed ad libitum (AL) at 2 (weighing 259+/-17 g), 8 (459+/-17 g), and 20 (492+/-10 g) mo old. To prevent the age-dependent growth in FM, rats were caloric restricted (CR) at 2 mo by decreasing their daily caloric intake by 45% (weighing 292+/-5 g at 8 mo, 294+/-9 g at 20 mo). As designed, the lean body mass (LBM) and %FM remained unchanged through aging (8 and 20 mo old) in the CR rats and was similar to that of 2-mo-old AL rats. However, 8- and 20-mo-old AL-fed rats had three- to fourfold higher FM than both CR groups. Peripheral insulin action at physiological hyperinsulinemia was determined (by 3 mU x kg(-1). min(-1) insulin clamp). Prevention of fat accretion maintained glucose uptake (R(d); 29+/-2, 29+/-2, and 31+/-4 mg x kg LBM(-1) x min(-1)) and glycogen synthesis rates (GS, 12+/-1, 12 +/-1, and 14+/-2 mg x kg LBM(-1) x min(-1)) at youthful levels (2 mo AL) in 8- and 20-mo-old CR rats, respectively. These levels were significantly increased (P<0.001) compared with AL rats with higher %FM (R(d), 22+/-1 and 22+/-2 and GS, 7+/-1 and 8+/-2 mg x kg LBM(-1). min(-1) in 8- and 20-mo-old rats, respectively). The increase in whole body GS in age-matched CR rats was accompanied by approximately 40% increased accumulation of [(3)H] glucose into glycogen and a similar increase in insulin-induced muscle glycogen content. Furthermore, the activation of glycogen synthase increased, i.e., approximately 50% decrease in the Michaelis constant, in both CR groups (P<0.01). We conclude that chronic CR designed to prevent an increase in storage of energy in fat maintained peripheral insulin action at youthful levels, and aging per se does not result in a defect on the pathway of glycogen storage in skeletal muscle.

Induction of eclampticlike changes by stimulation of the celiac ganglion in rats

OBJECTIVE

To examine the relation between the stimulation of the abdominal sympathetic nervous system and vasospasm of the brain in eclamptic seizures, we analyzed brain blood flow after stimulation of the celiac ganglion by lipopolysaccharide (LPS, 5, 50, or 500 mg/mL) or normal saline before and after denovation of sympathetic trunk in pregnant and nonpregnant rats.

METHODS

The brain blood flow was measured after stimulation of the celiac ganglion with 50 microL (5 mg/mL) LPS in group I, 50 microL (50 mg/mL) LPS in group II, 50 microL saline in group III, and 50 microL (500 mg/mL) LPS (after denovation of the sympathetic trunk) in group IV. A sham control experiment was also done by stimulation of the abdominal peritoneum with 50 microL (500 mg/mL) LPS in group V. Changes in water content and histological findings in the brain were also studied in this protocol.

RESULTS

A significant reduction in brain blood flow was observed in pregnant rats in groups I and II on stimulation of the celiac ganglion with LPS (p < 0.0001, p < 0.001) compared with before stimulation. Celiac ganglion stimulation with saline (group III) and LPS (group IV, after denovation of the sympathetic trunk) did not affect brain blood flow. Stimulation of the abdominal peritoneum with LPS (group V) could not induce any changes in brain blood flow. Repeated seizures occurred in 60% of pregnant rats and a remarkable increase in water content was observed after LPS stimulation of the celiac ganglion in groups I and II (p < 0.0001, p < 0.001). Histologically, we found that stimulation of the celiac ganglion with LPS caused widening of perivascular spaces with compression of the vessels leading to ischemic changes in brain tissues. There were no such findings observed in other groups. However, a lesser extent effect was noticed in nonpregnant than seen in pregnant rats.

CONCLUSION

Stimulation of the abdominal sympathetic ganglions could induce vasoconstriction of the brain vessels, thus decreasing brain blood flow, which results in eclampsialike changes in rats.

Chronic local cold stress to the soles induces hypertension in rats

The purpose of this study was to determine whether cold-stress stimulation to the soles of paws produces continuous hypertension in rats. Wistar-Kyoto rats were kept in cages with a 0 degrees C floor and 23 degrees C room temperature (cold-stressed group, n = 10) or in cages with 23 degrees C floor and 23 degrees C room temperature (control group, n = 10). BP and levels of plasma catecholamines, serum glucose, and serum insulin were measured, and the histologic characteristics of the kidney and adrenal gland were studied in all groups. After a week of localized cold-stress, BP of the experimental rats were significantly increased over those of the control rats. Significant increases were also seen in plasma epinephrine and norepinephrine, as well as serum insulin concentrations in the rats that underwent localized cold stimulation; these changes were not observed in the control rats. Fibrinoid deposition in the kidney and the intensity of neuropeptide Y-staining in the adrenal medulla were increased in the localized cold-stressed group compared with the control group. We conclude that chronic local cold stimulation to the soles is a new model of experimental hypertension.

Discordant effects of glucosamine on insulin-stimulated glucose metabolism and phosphatidylinositol 3-kinase activity

The impact of increased GlcN availability on insulin-stimulated p85/p110 phosphatidylinositol 3-kinase (PI3K) activity in skeletal muscle was examined in relation to GlcN-induced defects in peripheral insulin action. Primed continuous GlcN infusion (750 micromol/kg bolus; 30 micromol/kg.min) in conscious rats limited both maximal stimulation of muscle PI3K by acute insulin (I) (1 unit/kg) bolus (I + GlcN = 1.9-fold versus saline = 3.3-fold above fasting levels; p < 0.01) and chronic activation of PI3K following 3-h euglycemic, hyperinsulinemic (18 milliunits/kg.min) clamp studies (I + GlcN = 1.2-fold versus saline = 2.6-fold stimulation; p < 0.01). To determine the time course of GlcN-induced defects in insulin-stimulated PI3K activity and peripheral insulin action, GlcN was administered for 30, 60, 90, or 120 min during 2-h euglycemic, hyperinsulinemic clamp studies. Activation of muscle PI3K by insulin was attenuated following only 30 min of GlcN infusion (GlcN 30 min = 1.5-fold versus saline = 2.5-fold stimulation; p < 0.05). In contrast, the first impairment in insulin-mediated glucose uptake (Rd) developed following 110 min of GlcN infusion (110 min = 39.9 +/- 1.8 versus 30 min = 42.8 +/- 1.4 mg/kg.min, p < 0.05). However, the ability of insulin to stimulate phosphatidylinositol 3,4, 5-trisphosphate production and to activate glycogen synthase in skeletal muscle was preserved following up to 180 min of GlcN infusion. Thus, increased GlcN availability induced (a) profound and early inhibition of proximal insulin signaling at the level of PI3K and (b) delayed effects on insulin-mediated glucose uptake, yet (c) complete sparing of insulin-mediated glycogen synthase activation. The pattern and time sequence of GlcN-induced defects suggest that the etiology of peripheral insulin resistance may be distinct from the rapid and marked impairment in insulin signaling.

Decreased visceral adiposity accounts for leptin effect on hepatic but not peripheral insulin action

Leptin decreases visceral fat (VF) and increases peripheral and hepatic insulin action. Here, we generated similar decreases in VF using leptin (Lep), beta(3)-adrenoreceptor agonism (beta3), or food restriction (FR) and asked whether insulin action would be equally improved. For 8 days before the in vivo study, Sprague-Dawley rats (n = 24) were either fed ad libitum [control (Con)], treated with Lep or beta3 (CL-316,243) by implanted osmotic mini-pumps, or treated with FR. Total VF was similarly decreased in the latter three groups (Lep, 3.11 +/- 0.96 g; beta3, 2.87 +/- 0.48 g; and FR, 3.54 +/- 0.77 g compared with 6.91 +/- 1.41 g in Con; P < 0.001) independent of total fat mass (by (3)H(2)O) and food intake. Insulin (3 mU. kg(-1). min(-1)) clamp studies were performed to assess hepatic and peripheral insulin sensitivity. Decreased VF resulted in similar and marked improvements in insulin action on glucose production (GP) (Lep, 1.19 +/- 0.51; beta3, 1.46 +/- 0.68; FR, 2.27 +/-0.71 compared with 6.06 +/- 0.70 mg. kg(-1). min(-1) in Con; P < 0.001). By contrast, reduction in VF by beta3 and FR failed to reproduce the stimulation of insulin-mediated glucose uptake ( approximately 60%), glycogen synthesis ( approximately 80%), and glycolysis ( approximately 25%) observed with Lep. We conclude that 1) a moderate decrease in VF uniformly leads to a marked increase in hepatic insulin action, but 2) the effects of leptin on peripheral insulin action are not due to the associated changes in VF or beta3 activation.

Excess vitamin E decreases canthaxanthin absorption in the rat

The recent attention given to the possible role of alpha-tocopherol (alpha-Toc) and carotenoids in the prevention and treatment of a variety of illnesses resulted in segments of the population increasing their consumption of these nutrient/antioxidants. Once consumed, alpha-Toc and carotenoids are thought to follow the same absorptive pathway and may influence each other's absorption, particularly when taken in large doses. The purpose of this study was to determine if alpha-Toc and the carotenoid, canthaxanthin (CTX), interact during absorption. Rats were intraduodenally infused with corn oil emulsions containing combinations of alpha-Toc (0 or 300 mumol/L) and CTX (5, 10, 15, 20 mumol/L) in a 2 x 4 factorial arrangement. Absorption was determined by measuring recovery of CTX and alpha-Toc in the mesenteric lymph. The amount of CTX in the lymph increased significantly with the amount infused into the duodenum. The overall efficiency of CTX absorption from emulsions without alpha-Toc averaged 12% with individual animals having a range of 8 to 18%. Efficiency of absorption was not related to concentration of CTX infused. When alpha-Toc (300 mumol/L) was added to the oil emulsion, the absorption of CTX was decreased by at least 50%. Recovery of alpha-Toc in the lymph averaged ca. 10% and was not affected by CTX. These results suggest that concurrent consumption of a large dose of alpha-Toc may influence carotenoid bioavailability.

Surgical removal of visceral fat reverses hepatic insulin resistance

We directly examined whether visceral fat (VF) modulates hepatic insulin action by randomizing moderately obese (body wt approximately 400 g) Sprague-Dawley rats to either surgical removal of epididymal and perinephric fat pads (VF-; n = 9) or a sham operation (VF+; n = 11). Three weeks later, total VF was fourfold increased (8.5 +/- 1.2 vs. 2.1 +/- 0.3 g, P < 0.001) in the VF+ compared with the VF- group, but whole-body fat mass (determined using 3H2O) was not significantly different. The rates of insulin infusion required to maintain plasma glucose levels and basal hepatic glucose production in the presence of hepatic-pancreatic clamp were markedly decreased in VF- compared with VF+ rats (0.57 +/- 0.02 vs. 1.22 +/- 0.19 mU x kg(-1) x min(-1), P < 0.001). Similarly, plasma insulin levels were more than twofold higher in the VF+ group (P < 0.001). The heightened hepatic insulin sensitivity is supported by the decrease in gene expression of both glucose-6-phosphatase and PEPCK and by physiological hyperinsulinemia in VF- but not VF+ rats. The improvement in hepatic insulin sensitivity in VF- rats was also supported by a approximately 70% decrease in the plasma levels of insulin-like growth factor binding protein-1, a marker of insulin's transcription regulation in the liver. The removal of VF pads also resulted in marked decreases in the gene expression of tumor necrosis factor-alpha (by 72%) and leptin (by 60%) in subcutaneous fat. We conclude that visceral fat is a potent modulator of insulin action on hepatic glucose production and gene expression.

Urinary trypsin inhibitor suppresses vascular smooth muscle contraction by inhibition of Ca2+ influx

Urinary trypsin inhibitor (UTI) and its precursor form inter-alpha trypsin inhibitor (ITI) are present in plasma. To determine the action of UTI on blood vessels, we performed isometric vascular muscle contraction tests, microcirculation studies and measurement of cytosolic free Ca2+ in vascular smooth muscle cells. An isometric vascular muscle contraction test showed that the contractions stimulated by endothelin-1 or norepinephrine were suppressed in the presence of UTI, and that the contractions were not inhibited in the presence of ITI. The microcirculation study showed that the contraction of mesenteric arterioles of WKY rats induced by norepinephrine were inhibited by treatment of UTI, and that they did not alter by treatment of ITI. Pre-incubation of UTI, but not ITI, with vascular smooth muscle cells inhibited the increase of cytosolic free Ca2+ induced by endothelin-1 or norepinephrine. Cell-binding study by biotinylated UTI showed that vascular smooth muscle cells have specific binding site for UTI, but not for ITI. We propose that circulating UTI converted from ITI has a regulatory effect on local vascular tone by regulation of Ca2+ influx into smooth muscle cells.

A comparison of lycopene and canthaxanthin absorption: using the rat to study the absorption of non-provitamin A carotenoids

The purpose of this study was to validate the use of the mesenteric lymph duct cannulated rat to study the absorption of carotenoids which do not have provitamin A activity. The absorption of two carotenoids, a hydrocarbon carotenoid (lycopene) and a xanthophyll carotenoid (canthaxanthin), were investigated. In the first experiment, lipid emulsions containing lycopene (LYC) or canthaxanthin (CTX) were continuously infused into the duodenum, and lymph was collected for analysis at 2-h intervals. The time course for absorption of carotenoids and triacylglycerol (TAG) was similar. Carotenoids and TAG reached steady-state concentrations in the lymph by 6 h. There was no evidence for a delayed release of either carotenoid from the intestine relative to TAG. During a second experiment, emulsions containing increasing concentrations of LYC or CTX (5, 10, 15, 20 mumol/L) were infused. The LYC and CTX in the lymph increased in a dose-dependent manner. The average efficiency of CTX absorption was 16% while the efficiency of LYC absorption averaged only 6%. Efficiency of carotenoid absorption was not related to concentration infused. Finally, to test whether LYC and CTX interact during absorption both were added to a lipid emulsion at equal concentrations (20 mumol/L) and infused. The carotenoids did not significantly affect each other's absorption. These results demonstrate the usefulness of the rat as an animal model to study the absorption of non-provitamin A carotenoids.

Experimental hemolytic uremic syndrome induced by lipopolysaccharide irritation of celiac ganglia in rats

Although nervous system complications often appear in hemolytic uremic syndrome (HUS), the relationship between HUS and the nervous system is still not clear. We suspect that damage to the nervous system may play a role in the pathophysiology of HUS. In this context, rats received different doses of lipopolysaccharide (LPS) or saline to celiac ganglia or peritoneum. In rats treated with LPS on the celiac ganglia, a significant decrease in platelet count (p < 0.05) and a significant increase in blood urea nitrogen (p < 0.05) were found, and at the same time plasma levels of adrenaline and noradrenaline increased markedly (p < 0.05). The renal arterioles and glomeruli showed endothelial swelling and narrowing of the lumina. Intense immunostaining for von Willebrand factor and fibrinogen in glomeruli and renal vessels was also observed. These parameters were accompanied by a systolic blood pressure elevation. The results suggest that the sympathetic nervous system plays an important role in the pathogenesis of HUS.

Cold-induced stress stimulates the sympathetic nervous system, causing hypertension and proteinuria in rats

OBJECTIVE

To determine whether cold-stress stimulation of the soles of the paws would produce a preeclampsia-like syndrome in rats.

METHODS

Pregnant or nonpregnant rats were kept in 0 degree C floor and 23 degrees C room temperature cages (the cold-stressed group) or in 23 degrees C floor and 23 degrees C room temperature cages (the control group) for 2 weeks. Their blood pressure, proteinuria, and plasma catecholamines were measured, and histologic studies were performed on all groups.

RESULTS

There were no significant differences in systolic blood pressure between the two groups during the first week of the experimental period; however, during the last week of gestation the blood pressure of the cold-stressed group did not fall and was significantly higher than that of the control group. A significant increase in urinary protein excretion was observed in the cold-stimulated pregnant rats, in contrast to the control rats. The concentrations of norepinephrine and epinephrine in the cold-stressed pregnant rats were markedly higher than those in the control rats. A decrease in trophoblast invasion, congestion, and fibrinoid deposits of the labyrinth were observed in the cold-stressed rats. A marked increase in subendothelial fibrinoid deposits in the glomerular capillary was found only in the cold-stressed pregnant rats. The blood pressure, biochemical parameters, and histologic findings in the nonpregnant rats were almost the same as those in the pregnant rats.

CONCLUSION

Chronic local cold stimulation of the soles of the paws induces preeclampsia-like phenomena in pregnant and nonpregnant rats, and this model suggests that the cause of preeclampsia is involved in chronic stimulation of the sympathetic nerve.

Induction of HELLP syndrome-like biochemical parameters by stimulation of the celiac ganglion in rats

OBJECTIVE

An animal model of HELLP (hemolysis, elevated liver enzymes, low platelets) syndrome was developed by means of stimulation of the celiac ganglion in rats.

METHODS

The celiac ganglion in pregnant or non-pregnant rats was exposed to endotoxin (lipopolysaccharide, LPS) (500 micrograms/50 microliters), potassium chloride (0.2 mol/l/50 microliters), or saline solution (50 microliters). In another group of rats the bifurcation of the abdominal aorta was exposed to LPS (500 micrograms/50 microliters). Blood pressure, platelet count, hematocrit, serum aspartate transaminase (AST), alanine transaminase (ALT), lactate dehydrogenase (LDH), and plasma norepinephrine and epinephrine were measured for 6 h after treatment. Histopathologic studies were also performed in these rats.

RESULTS

A significant increase in blood pressure, AST, ALT, LDH, norepinephrine, and epinephrine was found in the endotoxin-treated pregnant rats compared with control rats treated with the saline solution. A significant decrease in platelet count was found in endotoxin-treated pregnant rats compared with the control rats. A significant increase in blood pressure, AST, norepinephrine, and epinephrine was found in the potassium chloride-treated pregnant rats compared with control rats. Blood pressure and biochemical parameters remained unchanged in the pregnant rats treated with LPS at the bifurcation of the abdominal aorta, as in those treated with saline at the celiac ganglion. Histologic examination of liver tissues treated with LPS or potassium chloride showed varying degrees of ischemic necrosis of hepatocytes similar to that observed in the human HELLP syndrome. Blood pressure, biochemical parameters, and histologic findings in non-pregnant rats were almost the same as those in pregnant rats.

CONCLUSION

This study suggests that exogenous stimulation of the celiac ganglion causes an increase in the blood pressure and liver ischemia, resulting in HELLP syndrome-like disease in pregnant and non-pregnant rats.

Lymphatic fatty acids from rats fed human milk and formula supplemented with fish oil

Absorption of long-chain polyunsaturated fatty acids from human milk and formula supplemented with fish oil was studied to determine if the distribution route into lymphatic triacylglycerol (TAG) and phospholipid (PL) varies with the dietary source. Rats were intraduodenally infused with human milk or formula containing graded amounts of fish oil (0, 0.5, or 1.0 g/100 mL), and the mesenteric lymph was collected. Arachidonic acid (20:4n-6) levels in lymphatic TAG and PL were highest from animals fed human milk. In the animals infused with formula containing fish oil, as the amount of eicosapentaenoic acid (EPA, 20:5n-3) infused increased, there was essentially an equal increase in EPA associated with both lymphatic TAG and PL. Animals intraduodenally infused with human milk or formula without fish oil had only minor levels (less than 1%) of EPA in the lymph. In the fish oil-treated animals, as the amount of docosahexaenoic acid (DHA, 22:6n-3) infused increased, there was a 16-fold increase in DHA associated with lymphatic TAG, but only a 3-fold increase in DHA associated with lymphatic PL. The highest level of DHA in rats infused with human milk was observed in lymphatic PL. Hence, fish oil can be added to formula as a source of long-chain polyunsaturated fatty acids, but the distribution of fatty acids into lymphatic TAG and PL is not the same as that observed with human milk.