Can splenocytes enhance pancreatic β-cell function and mass in 90% pancreatectomized rats fed a high fat diet?

AimsRecent studies have shown that splenocytes may act as a possible neogenic source with regard to β-cells in rodent diabetic models. Accordingly, we sought to determine whether splenocytes played an important role in promoting β-cell function and mass among type 2 diabetic rats with and without spleen.Main methodsWe randomly divided female 90% pancreatectomized (Px) Sprague Dawley rats into three groups: splenectomy (SPX), splenectomy plus the injection of male splenocytes (SPI), and no splenectomy (NSP). They were administered with 40 energy percent fat diets over the course of five weeks. At the end of the experimental period, insulin secretion capacity was measured by hyperglycemic clamp. At 6 h after BrdU⁺ injection, the pancreas was prepared with 4% paraformaldehyde in order to perform immunohistochemistry.Key findingsSPX increased and sustained serum glucose levels more than NSP and SPI during oral glucose tolerance testing. During hyperglycemic clamp, first and second phase insulin secretion decreased in the SPX rats while splenocyte injections counteracted this. Beta-cell mass in the SPX group was reduced more than among NSP and SPI. This was the result of a decrease in the number of small β-cell clusters in SPX, which is indicative of a decrease in β-cell neogenesis.SignificanceSplenocytes play an important role with regard to the neogenesis of β-cells in insulin deficient type 2 diabetic rats, although they are not critical for β-cell regeneration.     

Propranolol,a β-adrenoceptor antagonist,worsens liver injury in a model of non-alcoholic steatohepatitis

Prazosin an α1-adrenoceptor (AR) antagonist has been shown to reduce liver injury in a mouse model of non-alcoholic steatohepatitis (NASH) and is suggested as a potential treatment of NASH especially given its concomitant anti-fibrotic properties. The effect however, of β-AR blockade in non-cirrhotic NASH is unknown and is as such investigated here. In the presence of the β-blocker propranolol (PRL), mice fed normal chow or a half methionine and choline deficient diet, supplemented with ethionine (HMCDE), to induce NASH, showed significantly enhanced liver injury, as evidenced by higher hepatic necrosis scores and elevated serum aminotransferases (ALT). Mechanistically, we showed that murine hepatocytes express α and β adrenoceptors; that PRL directly induces hepatocyte injury and death as evidenced by increased release of lactate dehydrogenase, FASL and TNF-α from hepatocytes in the presence of PRL; and that PRL activated the apoptotic pathway in primary hepatocyte cultures, as indicated by upregulation of Fas receptor and caspase-8 proteins. The β-AR antagonist PRL therefore appears to enhance liver injury through induction of hepatocyte death via the death pathway. Further studies are now required to extrapolate these findings to humans but meanwhile, β-AR antagonists should be avoided or used with caution in patients with non-cirrhotic NASH as they may worsen liver injury.     

Plasma Propranolol Levels in the Quantitative Assessment of β-adrenergic Blockade in Man

Plasma propranolol levels associated with reductions in endogenous and exogenous cardiac β-stimulation were determined in normal people. The levels associated with a given degree of blockade of exercise-induced tachycardia were about three times greater after intravenous administration than after oral administration. This shows that an active metabolite of propranolol is formed only after the drug is taken by mouth. The greatest reduction in the tachycardia of strenuous exercise was associated with plasma levels of 40 ng./ml. with oral administration and 100 ng./ml. with intravenously administered propranolol.The effect on isoprenaline-induced tachycardia following intravenously administered propranolol showed that the dose ratio for isoprenaline was about 30 with plasma levels of 100 ng./ml. and 10 with levels of 10-20 ng./ml. These plasma levels give 100% and 20-30% blockade of exercise-induced tachycardia. These findings suggest that some of the therapeutic effects of propranolol may be unrelated to β-adrenergic blockade.     

Intake of stigmasterol and β-sitosterol alters lipid metabolism and alleviates NAFLD in mice fed a high-fat western-style diet

Objective

To investigate and compare the effects of two common dietary phytosterols, stigmasterol and β-sitosterol, in altering lipid metabolism and attenuating nonalcoholic fatty liver disease (NAFLD).

Spinal β-adrenergic receptors’ activation increases the blood glucose level in mice

We examined the role of spinally located β-adrenergic receptors in the regulation of the blood glucose level. The intrathecal (i.t.) injections with dobutamine (β₁-adrenergic receptor agonist) or terbutaline (β₂-adrenergic receptor agonist) caused an elevation of the blood glucose level, whereas metoprolol (β₁-adrenergic receptor antagonist) or butoxamine (β₂-adrenergic receptor antagonist) did not. In addition, i.t. pretreatment with pertussis toxin (PTX) attenuated the hyperglycemic effect induced by dobutamine or terbutaline. Moreover, plasma insulin level was increased by dobutamine but not by terbutaline, and PTX reduced dobutamine-induced up-regulation of the plasma insulin level. Terbutaline significantly increased plasma corticosterone level, and PTX further enhanced terbutaline-induced corticosterone level. Furthermore, intraperitoneal (i.p.) pretreatment with hexamethonium- (a preganglionic blocker) attenuated dobutamine- and terbutaline-induced hyperglycemic effects. Our results suggest that activation of spinal β₁- and β₂-adrenergic receptors produces hyperglycemic effects in a different manner. Spinally located PTX-sensitive G-proteins appear to be involved in hyperglycemic effect induced by terbutaline. Furthermore, dobutamine- or terbutaline-induced hyperglycemia appears to be mediated through the spinal nerves.     

Adequacy of calcium and vitamin D reduces inflammation, β-catenin signaling,and dysbiotic Parasutterela bacteria in the colon of C57BL/6 mice fed a western-style diet

Adoption of an obesogenic diet low in calcium and vitamin D (CaD) leads to increased obesity, colonic inflammation, and cancer. However, the underlying mechanisms remain to be elucidated. We tested the hypothesis that CaD supplementation (from inadequacy to adequacy) may reduce colonic inflammation, oncogenic signaling, and dysbiosis in the colon of C57BL/6 mice fed a Western diet. Male C57/BL6 mice (4-weeks old) were assigned to 3 dietary groups for 36 weeks: (1) AIN76A as a control diet (AIN); (2) a defined rodent “new Western diet” (NWD); or (3) NWD with CaD supplementation (NWD/CaD). Compared to the AIN, mice receiving the NWD or NWD/CaD exhibited more than 0.2-fold increase in the levels of plasma leptin, tumor necrosis factor α (TNF-α) and body weight. The levels of plasma interleukin 6 (IL-6), inflammatory cell infiltration, and β-catenin/Ki67 protein (oncogenic signaling) were increased more than 0.8-fold in the NWD (but not NWD/CaD) group compared to the AIN group. Consistent with the inflammatory phenotype, colonic secondary bile acid (inflammatory bacterial metabolite) levels increased more than 0.4-fold in the NWD group compared to the NWD/CaD and AIN groups. Furthermore, the abundance of colonic Proteobacteria (e.g., Parasutterela), considered signatures of dysbiosis, was increased more than four-fold; and the α diversity of colonic bacterial species, indicative of health, was decreased by 30% in the NWD group compared to the AIN and NWD/CaD groups. Collectively, CaD adequacy reduces colonic inflammation, β-catenin oncogenic signaling, secondary bile acids, and bacterial dysbiosis in mice fed with a Western diet.     

Synthesis and in vitro evaluation of derivatives of the β₁-adrenergic receptor antagonist HX-CH 44

Isopropyl- and fluoroisopropyl-amino derivatives of the β(1)-adrenergic receptor antagonist 2-[4-[3-(tert-butyl-amino)-2-hydroxypropoxy]phenyl]-3-methyl-6-methoxy-4(3H)-quinazolinone ((±)HX-CH 44) were synthesized, including a concise and efficient preparation of the core, 2-(4-hydroxyphenyl)-6-methoxy-3-methylquinazolin-4(3H)-one. In vitro binding assays showed that the fluorinated analog was selective towards β(1)-adrenergic receptors over β(2)-adrenergic and 5-HT(1A) receptors. An X-ray crystallographic characterization of the fluorinated analog is also reported.     

Involvement of SIRT1–AMPK signaling in the protective action of indole-3-carbinol against hepatic steatosis in mice fed a high-fat diet

This study addressed the effect of indole-3-carbinol (I3C) supplementation on hepatic steatosis in mice fed a high-fat diet (HFD) and clarified the underlying mechanism. Male C57BL/6N mice were divided into three groups: those who received a normal diet, those fed with HFD and those fed with 0.1% I3C-supplemented diet (I3CD). In the present study, an HFD supplemented with 0.1% I3C significantly decreased body and liver weight as well as plasma and hepatic lipid levels. The activation of the silent mating type information regulation 2 homolog 1 (SIRT1)–AMP-activated protein kinase (AMPK) signaling system by I3C correlated with decreased mRNA levels of sterol regulatory element-binding protein-1c-regulated lipogenic enzymes. In addition, I3C significantly reversed HFD-induced up-regulation of ER stress-mediated signaling molecules in the liver, which may have contributed to the protective effects of I3C against hepatic steatosis. Furthermore, HFD-induced up-regulations of inflammatory genes such as tumor necrosis factor α and interleukin 6 were significantly reversed by dietary I3C supplementation. Our study suggests that the protective action of I3C against hepatic steatosis is mediated, at least in part, through the up-regulation of a SIRT1–AMPK signaling system in the livers of HFD-fed mice. Further investigations revealed that alleviation of the ER stress response represented a critical mechanism underlying the beneficial effects of I3C on hepatic steatosis.     

Neuroprotective role of Indirubin-3′-monoxime,a GSKβ inhibitor in high fat diet induced cognitive impairment in mice

Recent studies have highlighted that diabetes mellitus (DM) is a strong risk factor for Alzheimer’s disease (AD). Insulin resistance and/or hyperinsulinemia is one of the main characteristics of type 2 DM. Numerous epidemiological studies have demonstrated that insulin resistance contributes to AD pathogenesis. However the molecular mechanisms of association between these still remain elusive. Among the various possible mechanisms, the GSK-3β activity has been reported to be impaired in insulin-resistance, type 2 DM and AD. Thus, the present study was designed to explore the neuroprotective role of GSK3 β inhibitor, Indirubin-3′-monoxime (IMX) in insulin resistance induced cognitive impairment. Further, we have explored the possible molecular mechanism involved in cognitive impairment associated with insulin resistance. The mice subjected to high fat diet exhibited characteristic features of insulin resistance viz. increased serum glucose, triglycerides, cholesterol, insulin levels and impaired spatial learning and memory ability along with reduced brain insulin level, elevated oxidative stress and acetylcholinesterase (AChE) activity. The observed changes occurred concurrently with reduced brain derived neurotrophic factor. In contrast, the mice treated with IMX showed a significant reduction in plasma glucose, triglycerides, cholesterol, insulin levels and improvement in learning and memory performance, attenuated the oxidative stress and AChE activity. Moreover, IMX dose dependently augment the brain insulin and BDNF levels in HFD fed mice. Based upon these findings it could be suggested that GSK3 β inhibition could prove to be beneficial in insulin resistance induced cognitive deficit and this neuroprotection could be the result of enhanced BDNF based synaptic plasticity.     

iPla2β deficiency in mice fed with MCD diet does not correct the defect of phospholipid remodeling but attenuates hepatocellular injury via an inhibition of lipid uptake genes

Group VIA calcium-independent phospholipase A2 (iPla2β) is among modifier genes of non-alcoholic fatty liver disease which leads to non-alcoholic steatohepatitis (NASH). Consistently, iPla2β deletion protects hepatic steatosis and obesity in genetic ob/ob and obese mice chronically fed with high-fat diet by replenishing the loss of hepatic phospholipids (PL). As mouse feeding with methionine- and choline-deficient (MCD) diet is a model of lean NASH, we tested whether iPla2β-null mice could still be protected since PL syntheses are disturbed. MCD-diet feeding of female wild-type for 5 weeks induced hepatic steatosis with a severe reduction of body and visceral fat weights concomitant with a decrease of hepatic phosphatidylcholine. These parameters were not altered in MCD-fed iPla2β-null mice. However, iPla2β deficiency attenuated MCD-induced elevation of serum transaminase activities and hepatic expression of fatty-acid translocase Cd36, fatty-acid binding protein-4, peroxisome-proliferator activated receptorγ, and HDL-uptake scavenger receptor B type 1. The reduction of lipid uptake genes was consistent with a decrease of hepatic esterified and unesterified fatty acids and cholesterol esters. On the contrary, iPla2β deficiency under MCD did not have any effects on inflammasomes and pro-inflammatory markers but exacerbated hepatic expression of myofibroblast α-smooth muscle actin and vimentin. Thus, without any rescue of PL loss, iPla2β inactivation attenuated hepatocellular injury in MCD-induced NASH with a novel mechanism of lipid uptake inhibition. Taken together, we have shown that iPla2β mediates hepatic steatosis and lipotoxicity in hepatocytes in both obese and lean NASH, but elicits exacerbated liver fibrosis in lean NASH likely by affecting other cell types.     

Dietary β-conglycinin prevents fatty liver induced by a high-fat diet by a decrease in peroxisome proliferator-activated receptor γ2 protein

Diets high in sucrose/fructose or fat can result in hepatic steatosis (fatty liver). Mice fed a high-fat diet, especially that of saturated-fat-rich oil, develop fatty liver with an increase in peroxisome proliferator-activated receptor (PPAR) γ2 protein in liver. The fatty liver induced by a high-fat diet is improved by knockdown of liver PPARγ2. In this study, we investigated whether β-conglycinin (a major protein of soy protein) could reduce PPARγ2 protein and prevent high-fat-diet-induced fatty liver in ddY mice. Mice were fed a high-starch diet (70 energy% [en%] starch) plus 20% (wt/wt) sucrose in their drinking water or a high-safflower-oil diet (60 en%) or a high-butter diet (60 en%) for 11 weeks, by which fatty liver is developed. As a control, mice were fed a high-starch diet with drinking water. Either β-conglycinin or casein (control) was given as dietary protein. β-Conglycinin supplementation completely prevented fatty liver induced by each type of diet, along with a reduction in adipose tissue weight. β-Conglycinin decreased sterol regulatory element-binding protein (SREBP)-1c and carbohydrate response element-binding protein (ChREBP) messenger RNAs (mRNAs) in sucrose-supplemented mice, whereas it decreased PPARγ2 mRNA (and its target genes CD36 and FSP27), but did not decrease SREBP-1c and ChREBP mRNAs, in mice fed a high-fat diet. β-Conglycinin decreased PPARγ2 protein and liver triglyceride (TG) concentration in a dose-dependent manner in mice fed a high-butter diet; a significant decrease in liver TG concentration was observed at a concentration of 15 en%. In conclusion, β-conglycinin effectively prevents fatty liver induced by a high-fat diet through a decrease in liver PPARγ2 protein.     

Orexin A-induced anxiety-like behavior is mediated through GABA-ergic, α- and β-adrenergic neurotransmissions in mice

Orexins are hypothalamic neuropeptides, which are involved in several physiological functions of the central nervous system, including anxiety and stress. Several studies provide biochemical and behavioral evidence about the anxiogenic action of orexin A. However, we have little evidence about the underlying neuromodulation. Therefore, the aim of the present study was to investigate the involvement of neurotransmitters in the orexin A-induced anxiety-like behavior in elevated plus maze (EPM) test in mice. Accordingly, mice were pretreated with a non-selective muscarinic cholinergic antagonist, atropine; a γ-aminobutyric acid subunit A (GABA-A) receptor antagonist, bicuculline; a D2, D3, D4 dopamine receptor antagonist, haloperidol; a non-specific nitric oxide synthase (NOS) inhibitor, nitro-l-arginine; a nonselective α-adrenergic receptor antagonist, phenoxybenzamine and a β-adrenergic receptor antagonist, propranolol 30 min prior to the intracerebroventricular administration of orexin A. The EPM test started 30 min after the i.c.v. injection of the neuropeptide. Our results show that orexin A decreases significantly the time spent in the arms (open/open + closed) and this action is reversed by bicuculline, phenoxybenzamine and propranolol, but not by atropine, haloperidol or nitro-l-arginine. Our results provide evidence for the first time that the orexin A-induced anxiety-like behavior is mediated through GABA-A-ergic, α- and β-adrenergic neurotransmissions, whereas muscarinic cholinergic, dopaminergic and nitrergic neurotransmissions may not be implicated.     

Increased diet viscosity by oat β-glucans decreases the passage rate of liquids in the stomach and affects digesta physicochemical properties in growing pigs

Rheological properties of digesta play a role in digesta passage kinetics through the gastrointestinal tract, in turn affecting nutrient absorption kinetics. Therefore, we studied the effects of diet viscosity on digesta passage and physicochemical properties in pigs. Twenty male growing pigs (35 kg body weight at the start) were assigned to one of five diets with increasing dietary concentrations of β-glucans (BG; from 0 % to 10 %), in exchange for maize starch. After a 17-day adaptation period, pigs were euthanised and the mean retention time (MRT) of digesta solids (TiO₂) and liquids (Cr-EDTA) in the stomach, and proximal and distal half of the small intestine was quantified. In the stomach, the MRT of liquids, but not of solids, increased when dietary BG level increased (6 min per % dietary BG, P = 0.008 and R² = 0.35). Concomitantly, stomach DM content (5 g/kg per % dietary BG, P < 0.001 and R² = 0.53) and apparent digesta viscosity (56 Pa × s at 1/s shear rate per % dietary BG, P = 0.003 and R² = 0.41) decreased. In the proximal half of the small intestine, no effects of dietary BG level were observed. In the distal half of the small intestine, water-binding capacity (WBC) of digesta increased (0.11 g/g digesta DM per % dietary BG, P = 0.028 and R² = 0.24) and starch digestibility decreased (0.3% per % dietary BG, P = 0.034 and R² = 0.23) when dietary BG level increased. In the colon, apparent digesta viscosity at 45/s shear rate increased (0.1 Pa × s per % dietary BG, P = 0.03 and R² = 0.24) in the proximal half of the colon, and digesta WBC increased (0.06 g/g digesta DM per % dietary BG, P = 0.024 and R² = 0.26) in the distal half of the colon when dietary BG level increased. To conclude, increasing dietary BG level caused the MRT of liquids, but not that of solids, to increase in the stomach, resulting in reduced separation of the solid and liquid digesta fractions. This caused dilution of the stomach content and reduction in digesta viscosity when dietary BG levels increased. Effects of dietary BG level on physicochemical properties in the proximal small intestine were absent and may have been due to a low DM content. The WBC of digesta in the distal small intestine and colon increased when dietary BG level increased, as did apparent digesta viscosity in the proximal colon. This likely reflects the concentration of BG in digesta when moving through the gastrointestinal tract.     

Scaling VOI size in 3D μCT studies of trabecular bone: a test of the over-sampling hypothesis

For comparative 3D microCT studies of trabecular bone, the use of a volume of interest (VOI) scaled to body size may avoid over-sampling the trabecular mass in smaller versus larger-bodied taxa and comparison of regions that are not functionally homologous (Fajardo and Müller: Am J Phys Anthropol 115 (2001) 327-336), though the influence on quantitative analyses using scaled versus nonscaled VOIs remains poorly characterized. We compare trabecular architectural properties reflecting mass, organization, and orientation from three volumes of interest (large, scaled, and small) obtained from the distal first metacarpal in a sample of Homo (n = 10) and Pan (n = 12). We test the null hypotheses that neither absolute VOI size, nor scaling of the VOI to metacarpal size as a proxy for body size, biases intraspecific analyses nor impacts the detection of interspecific differences. These hypotheses were only partially supported. While certain properties (e.g., bone volume fraction or trabecular thickness) were not affected by varying VOI size within taxa, others were significantly impacted (e.g., intersection surface, connectivity, and structure). In comparing large versus scaled VOIs, we found that the large VOI inflated the number and/or magnitude of significant differences between Homo and Pan. In summary, our results support the use of scaled VOIs in studies of trabecular architecture.     

Exercise is more effective than diet control in preventing high fat diet-induced β-amyloid deposition and memory deficit in amyloid precursor protein transgenic mice

Accumulating evidence suggests that some dietary patterns, specifically high fat diet (HFD), increase the risk of developing sporadic Alzheimer disease (AD). Thus, interventions targeting HFD-induced metabolic dysfunctions may be effective in preventing the development of AD. We previously demonstrated that amyloid precursor protein (APP)-overexpressing transgenic mice fed HFD showed worsening of cognitive function when compared with control APP mice on normal diet. Moreover, we reported that voluntary exercise ameliorates HFD-induced memory impairment and β-amyloid (Aβ) deposition. In the present study, we conducted diet control to ameliorate the metabolic abnormality caused by HFD on APP transgenic mice and compared the effect of diet control on cognitive function with that of voluntary exercise as well as that of combined (diet control plus exercise) treatment. Surprisingly, we found that exercise was more effective than diet control, although both exercise and diet control ameliorated HFD-induced memory deficit and Aβ deposition. The production of Aβ was not different between the exercise- and the diet control-treated mice. On the other hand, exercise specifically strengthened the activity of neprilysin, the Aβ-degrading enzyme, the level of which was significantly correlated with that of deposited Aβ in our mice. Notably, the effect of the combination treatment (exercise and diet control) on memory and amyloid pathology was not significantly different from that of exercise alone. These studies provide solid evidence that exercise is a useful intervention to rescue HFD-induced aggravation of cognitive decline in transgenic model mice of AD.