Antimicrobial, Antibiofilm, and Antioxidant Potentials of Four Halophytic Plants, Euphorbia chamaesyce, Bassia arabica, Fagonia mollis, and Haloxylon salicornicum, Growing in Qassim Region of Saudi Arabia: Phytochemical Profile and In Vitro and In Silico Bioactivity Investigations.

The current study aimed to investigate the phytochemical contents and antioxidant, antimicrobial, and antibiofilm activities of four halophytic plants, namely, Euphorbia chamaesyce, Bassia arabica, Fagonia mollis, and Haloxylon salicornicum, native to central Saudi Arabia. The alcoholic extract of E. chamaesyce was found to be the most potent in various bioactivities-based evaluations and rich in polyphenols and flavonoid secondary metabolites, with 68.0 mg/g and 39.23 mg/g gallic acid and quercetin equivalents, respectively. Among all plants' extracts, the alcoholic extract of E. chamaesyce had the highest DPPH scavenging and metal chelating antioxidant activities at 74.15 Trolox equivalents and 16.28 EDTA equivalents, respectively. The highest antimicrobial activity of E. chamaesyce extract was found to be against Shigella flexneri, with a mean zone of inhibition diameter of 18.1 ± 0.2 mm, whereas the minimum inhibitory concentration, minimum biocidal concentration, minimum biofilm inhibitory concentration, and minimum biofilm eradication concentration values were 12.5, 25, 25, and 50 mg/mL, respectively. The LC-ESI-MS/MS analysis of the E. chamaesyce extract showed the presence of six flavonoids and ten phenolic constituents. The in silico binding of the E. chamaesyce extract's constituents to Staphylococcus aureus tyrosyl-tRNA synthetase enzyme displayed -6.2 to -10.1 kcal/mol binding energy values, suggesting that these constituents can contribute to the antimicrobial properties of the plant extract, making it an essential medicinal ingredient. In conclusion, these results warrant further investigation to standardize the antimicrobial profiles of these plant extracts.

Relationship of Plasma Gremlin 1 Levels with Body Adiposity and Glycemic Control in Saudi Female Type 2 Diabetes Patients.

Objective: Gremlin 1 is a novel adipokine that plays an important role in obesity and type 2 diabetes mellitus (T2DM). In the current study, we aimed to evaluate plasma levels of Gremlin 1 in diabetic and non-diabetic Saudi adult females and its correlation with body composition, glycemic control and lipid profile. Methods: A case-control study was conducted among 41 T2DM and 31 non-diabetic adult age matched females (controls). All patients underwent body composition by bioelectrical impedance analysis, with a commercially available body analyzer. Fasting venous samples were analyzed for glycemic markers and lipids, while plasma Gremlin 1 was measured by ELISA. The results were compared between the two groups and correlated with other anthropometric and adiposity parameters. Results: Gremlin 1 levels were elevated in T2DM patients (345 ± 26 ng/mL) when compared to control subjects (272 ± 16 ng/mL, p < 0.05). Diabetic patients having poor glycemic control had significantly higher Gremlin 1 levels (382 ± 34 ng/mL) compared to patients with good glycemic control (291 ± 37 ng/mL, p < 0.05). Pearson correlation analysis revealed a positive correlation of Gremlin 1 with fat mass (r = 0.246, p = 0.012), HbA1C (r = 0.262, p = 0.008) and HOMA-IR index (r = 0.321, p = 0.001). Conclusion: Our study demonstrates an important role of Gremlin 1 in glycemic control and body adiposity in the pathophysiology of obesity and T2DM. Gremlin 1 may emerge as a promising biomarker and therapeutic target in obesity and T2DM.

Modification of SWCNTs with hybrid materials ZnO-Ag and ZnO-Au for enhancing bactericidal activity of phagocytic cells against Escherichia coli through NOX2 pathway.

Zinc oxide-silver (ZnO-Ag), and zinc oxide-gold (ZnO-Au) nano-composites were prepared through wet chemical process and laced into single-walled carbon nanotubes (SWCNTs) to yield ZnO-Ag-SWCNTs, and ZnO-Au-SWCNTs hybrids. These nano-composite-laced SWCNTs hybrids were characterized using Raman spectroscopic, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses. The hybrids were evaluated for their effects on phagocytic cells and bactericidal activity against the gram-negative bacteria E. coli. Their phagocytic cell activities and intracellular killing actions were found to be significantly increased, as the ZnO-Ag-SWCNTs and ZnO-Au-SWCNTs nano-hybrids induced widespread clearance of Escherichia coli. An increase in the production of reactive oxygen species (ROS) also led to upregulated phagocytosis, which was determined mechanistically to involve the phagocyte NADPH oxidase (NOX2) pathway. The findings emphasized the roles of ZnO-Ag- and ZnO-Au-decorated SWCNTs in the prevention of bacterial infection by inhibiting biofilm formation, showing the potential to be utilized as catheter coatings in the clinic.

Retardation of Bacterial Biofilm Formation by Coating Urinary Catheters with Metal Nanoparticle-Stabilized Polymers.

Urinary catheter infections remain an issue for many patients and can complicate their health status, especially for individuals who require long-term catheterization. Catheters can be colonized by biofilm-forming bacteria resistant to the administered antibiotics. Therefore, this study aimed to investigate the efficacy of silver nanoparticles (AgNPs) stabilized with different polymeric materials generated via a one-step simple coating technique for their ability to inhibit biofilm formation on urinary catheters. AgNPs were prepared and characterized to confirm their formation and determine their size, charge, morphology, and physical stability. Screening of the antimicrobial activity of nanoparticle formulations and determining minimal inhibitory concentration (MIC) and their cytotoxicity against PC3 cells were performed. Moreover, the antibiofilm activity and efficacy of the AgNPs coated on the urinary catheters under static and flowing conditions were examined against a clinical isolate of Escherichia coli. The results showed that the investigated polymers could form physically stable AgNPs, especially those prepared using polyvinyl pyrrolidone (PVP) and ethyl cellulose (EC). Preliminary screening and MIC determinations suggested that the AgNPs-EC and AgNPs-PVP had superior antibacterial effects against E. coli. AgNPs-EC and AgNPs-PVP inhibited biofilm formation to 58.2% and 50.8% compared with AgNPs-PEG, silver nitrate solution and control samples. In addition, coating urinary catheters with AgNPs-EC and AgNPs-PVP at concentrations lower than the determined IC50 values significantly (p < 0.05; t-test) inhibited bacterial biofilm formation compared with noncoated catheters under both static and static and flowing conditions using two different types of commercial Foley urinary catheters. The data obtained in this study provide evidence that AgNP-coated EC and PVP could be useful as potential antibacterial and antibiofilm catheter coating agents to prevent the development of urinary tract infections caused by E. coli.

Could allicin alleviate trastuzumab-induced cardiotoxicity in a rat model through antioxidant, anti-inflammatory, and antihyperlipidemic properties?

AIMS: Although trastuzumab (TZB)-induced cardiotoxicity is well documented and allicin (one of the main active garlic ingredients) has ameliorating effects against numerous causes of toxicities; however, the influence of allicin on TZB-induced cardiotoxicity has not been investigated yet. Therefore, the current work explored the potential cardioprotective structural, biochemical, and molecular mechanisms of allicin against TZB-induced cardiotoxicity in a rat's model. METHODS: Forty rats were divided into four equal groups and treated for five weeks. The control group (G1) received PBS, the allicin group (G2) received allicin (9 mg/kg/day), the TZB group (G3) received TZB (6 mg/kg/week), and the allicin+TZB group (G4) received 9 mg of allicin/kg/day +6 mg of TZB/kg/week. Heart specimens and blood samples were processed for histopathological, immunohistochemical, biochemical, and molecular investigations to determine the extent of cardiac injury in all groups. KEY FINDINGS: The myocardium of G3 revealed significant increases in the numbers of inflammatory and apoptotic cells and the area percentage of collagen fibers and TNF-α immunoexpression compared with G1 and G2. Besides, qRT-PCR analysis exhibited significant reductions of SOD3, GPX1, and CAT expressions with significant increases in TNFα, IL-1ß, IL-6, cTnI, cTnT, and LDH expressions. Additionally, flow cytometry analysis demonstrated a significant elevation in the apoptotic and ROS levels. In contrast, allicin+TZB cotherapy in G4 ameliorated all previous changes compared with G3. SIGNIFICANCE: The current study proves that allicin could be used as a novel supplementary cardioprotective therapy to avoid TZB-induced cardiotoxicity via its anti-inflammatory, antifibrotic, antioxidant, antihyperlipidemic, and antiapoptotic properties.

Influence of social media on parents' attitudes towards vaccine administration.

Vaccination has had tremendous impact on human health. The tendency to hesitate or delay vaccination has been increasing, which has contributed to outbreaks of vaccine-preventable diseases. This cross-sectional study aimed to investigate the prevalence of childhood vaccine hesitancy and social media misconceptions in vaccine refusal among randomly selected parents from October 2019 through March 2020 in the outpatient clinics of King Khalid University Hospital, Riyadh, Saudi Arabia. The data were collected using a three-part questionnaire: the socio-demographic and economic questions, the Parents' Attitudes about Childhood Vaccines (PACV) survey, and questions concerning social media use. Based on the PACV survey tool, 37 parents (11%) scored a value > 50 and were suggested as hesitant (8% hesitant and 3% very hesitant). Overall, 288 parents (89%) scored < 50, hence deemed to not be hesitant about childhood vaccination. There was no significant association between high educational level or social media exposure with vaccine hesitancy. The most commonly used social media platform was Twitter (40%). In conclusion, we report a low prevalence of vaccine hesitancy about childhood vaccination among parents, with no significant impact of education level or social media on vaccine hesitancy. Further studies are required to replicate these findings in other regions and cities to generalize these observations for Saudi Arabia.

Reference Ranges and Determinant Factors for Fractional Exhaled Nitric Oxide in a Healthy Saudi Adult Population.

BACKGROUND Fractional exhaled nitric oxide (FENO) has emerged as a promising marker in respiratory research. The aim of this study was to determine the reference range values of FENO for healthy Saudi adults and the factors associated with FENO levels. MATERIAL AND METHODS This cross-sectional study was conducted at the Department of Physiology, King Saud University, Riyadh, Saudi Arabia, from January 2016 to August 2017. A total of 429 healthy Saudi adults were initially recruited. The final selection included 412 participants, consisting of 307 men and 105 women. FENO measurements were performed according to the current recommendations of the American Thoracic Society. RESULTS We observed that the FENO levels of women were significantly lower than those of men (18.6 vs. 21.3, P=0.009). In women, the measured FENO ranged from 5.7 ppb to 42 ppb, and in men from 5.0 ppb to 55.0 ppb. The mean FENO level in the entire study population was 20.6, with a range of 5.0 ppb to 55.0 ppb. The difference became non-significant when we calculated the FENO after adjusting for body surface area by different percentile distributions. Multiple linear regression analysis showed that body surface area and weight were significant predictors of FENO levels. CONCLUSIONS In this study, FENO levels were significantly affected by demographic variables. Therefore, it is important to consider the factors influencing FENO values to make a valid clinical interpretation.

The Role of Ames Dwarfism and Calorie Restriction on Gut Microbiota.

The gut microbiome (GM) represents a large and very complex ecosystem of different microorganisms. There is an extensive interest in the potential role of the GM in different diseases including cancer, diabetes, cardiovascular diseases, and aging. The GM changes over the lifespan and is strongly associated with various age-related diseases. Ames dwarf (df/df) mice are characterized by an extended life- and healthspan, and although these mice are protected from many age-related diseases, their microbiome has not been studied. To determine the role of microbiota on longevity animal models, we investigated the changes in the GM of df/df and normal control (N) mice, by comparing parents before mating and littermate mice at three distinct time points during early life. Furthermore, we studied the effects of a 6-month calorie restriction (CR), the most powerful intervention extending the lifespan. Our data revealed significant changes of the GM composition during early life development, and we detected differences in the abundance of some bacteria between df/df and N mice, already in early life. Overall, the variability of the microbiota by genotype, time-point, and breeding pair showed significant differences. In addition, CR caused significant changes in microbiome according to gastrointestinal (GI) location (distal colon, ileum, and cecum), genotype, and diet. However, the overall impact of the genotype was more prominent than that of the CR. In conclusion, our findings suggest that the gut microbiota plays an important role during postnatal development in long-living df/df mice and CR dietary regimen can significantly modulate the GM.

Cortical thickness, neurocognitive, and body composition effects of fasting during Ramadan.

BACKGROUND: We aimed to study the anatomical, physiological, and cognitive function of healthy individuals practicing fasting during the month of Ramadan. Measurements were taken 1 week before and 2 weeks after Ramadan fasting. MATERIALS AND METHODS: Twelve healthy male individuals (mean age ± standard error of the mean: 34.3 ± 2.9 years; body mass index: 26.26 ± 1.4 kg/m2) were assessed for various parameters before and after Ramadan fasting. All the tests were performed in the morning. Body composition characteristics were assessed by bioelectrical impedance analysis using a commercially available body composition analyzer. For neurocognitive analysis, participants underwent the stop signal task (SST), pattern recognition memory task (PRM), and spatial working memory strategy (SWM) from the Cambridge Neuropsychological Test Automated Battery. T1-weighted, 1 mm-thick magnetic resonance images were also acquired. RESULTS: Anthropometric analysis showed a significant decrease in body weight, fat-free mass (FFM), trunk FFM, and trunk predicted muscle mass, while the other body composition parameters did not exhibit any changes. The stop signal reaction time (SSRT) latency (ms) (P > 0.05) and PRM did not show any significant difference before and after fasting. SWM task (P < 0.05) improved significantly after fasting. Cortical thickness data of the whole brain were not significantly different after fasting at any brain location. There was a significant correlation between the left amygdala and the SWM strategy (r 2 = 0.518) and between fat and brain segmentation volume (r 2 = 0.375). CONCLUSION: Our pilot data suggest that Ramadan fasting leads to weight loss and FFM reductions and improve cognitive function.

Growth hormone abolishes beneficial effects of calorie restriction in long-lived Ames dwarf mice.

Disruption of the growth hormone (GH) axis promotes longevity and delays aging. In contrast, GH over-expression may lead to accelerated aging and shorter life. Calorie restriction (CR) improves insulin sensitivity and may extend lifespan. Long-lived Ames dwarf (df/df) mice have additional extension of longevity when subjected to 30% CR. The aim of the study was to assess effects of CR or GH replacement therapy separately and as a combined (CR+GH) treatment in GH-deficient df/df and normal mice, on selected metabolic parameters (e.g., insulin, glucose, cholesterol), insulin signaling components (e.g., insulin receptor [IR] ß-subunit, phosphorylated form of IR [IR pY1158], protein kinase C ζ/λ [p-PKCζ/λ] and mTOR [p-mTOR]), transcription factor p-CREB, and components of the mitogen-activated protein kinase (MAPK) signaling (p-ERK1/2, p-p38), responsible for cell proliferation, differentiation and survival. CR decreased plasma levels of insulin, glucose, cholesterol and leptin, and increased hepatic IR ß-subunit and IR pY1158 levels as well as IR, IRS-1 and GLUT-2 gene expression compared to ad libitum feeding, showing a significant beneficial diet intervention effect. Moreover, hepatic protein levels of p-PKCζ/λ, p-mTOR and p-p38 decreased, and p-CREB increased in CR mice. On the contrary, GH increased levels of glucose, cholesterol and leptin in plasma, and p-mTOR or p-p38 in livers, and decreased plasma adiponectin and hepatic IR ß-subunit compared to saline treatment. There were no GH effects on adiponectin in N mice. Moreover, GH replacement therapy did not affect IR, IRS-1 and GLUT-2 gene expression. GH treatment abolishes the beneficial effects of CR; it may suggest an important role of GH-IGF1 axis in mediating the CR action. Suppressed somatotrophic signaling seems to predominate over GH replacement therapy in the context of the examined parameters and signaling pathways.

Body composition analysis to determine gender specific physical fitness equations in a cohort of Saudi population.

OBJECTIVE: To determine an association between body composition analysis and physical fitness in the Saudi population and derive gender specific physical fitness equations. METHODS: A total of 530 healthy Saudi adults aged 15-72 years (mean 37.16±14.12 years) were enrolled in this study. Body composition analysis was assessed by bioelectrical impedance analysis (BIA), with a commercially available body analyzer according to standard protocols. RESULTS: Different body composition parameters, such as age, height, BSA (body surface area), obesity degree, body mass index (BMI), body fat mass (BFM) and percent body fat (% BF) contents were significantly different in males and females except weight which was non-significant (p=0.649). There was significant positive or negative correlation among different body composition parameters except weight with age in males and weight with age, height and BSA in females. In males, all the body composition characteristics contributed to the fitness score except BMI and BFM, while in females, the most significant effect was contributed by weight and BFM. Female body composition characteristics were strongly related to fitness score compared to males (R(2) = 93.8% vs R(2) = 78.5%). CONCLUSIONS: Different body composition parameters like BFM and %BF played an important role in determining physical fitness of healthy male individuals instead of BMI, weight and BSA, while in females weight was the best predictor of physical fitness.

Disruption of growth hormone receptor prevents calorie restriction from improving insulin action and longevity.

Most mutations that delay aging and prolong lifespan in the mouse are related to somatotropic and/or insulin signaling. Calorie restriction (CR) is the only intervention that reliably increases mouse longevity. There is considerable phenotypic overlap between long-lived mutant mice and normal mice on chronic CR. Therefore, we investigated the interactive effects of CR and targeted disruption or knock out of the growth hormone receptor (GHRKO) in mice on longevity and the insulin signaling cascade. Every other day feeding corresponds to a mild (i.e. 15%) CR which increased median lifespan in normal mice but not in GHRKO mice corroborating our previous findings on the effects of moderate (30%) CR on the longevity of these animals. To determine why insulin sensitivity improves in normal but not GHRKO mice in response to 30% CR, we conducted insulin stimulation experiments after one year of CR. In normal mice, CR increased the insulin stimulated activation of the insulin signaling cascade (IR/IRS/PI3K/AKT) in liver and muscle. Livers of GHRKO mice responded to insulin by increased activation of the early steps of insulin signaling, which was dissipated by altered PI3K subunit abundance which putatively inhibited AKT activation. In the muscle of GHRKO mice, there was elevated downstream activation of the insulin signaling cascade (IRS/PI3K/AKT) in the absence of elevated IR activation. Further, we found a major reduction of inhibitory Ser phosphorylation of IRS-1 seen exclusively in GHRKO muscle which may underpin their elevated insulin sensitivity. Chronic CR failed to further modify the alterations in insulin signaling in GHRKO mice as compared to normal mice, likely explaining or contributing to the absence of CR effects on insulin sensitivity and longevity in these long-lived mice.

Adipocytokines and the regulation of lipid metabolism in growth hormone transgenic and calorie-restricted mice.

Chronic elevation of GH induces resistance to insulin and hyperinsulinemia in both humans and animals, whereas calorie restriction (CR) improves peripheral insulin sensitivity in many species. To investigate the mechanisms that lead to insulin resistance in animals with high levels of GH as well as the mechanisms that might improve insulin sensitivity, we fed GH-overexpressing transgenic mice ad libitum or subjected them to 30% CR. We then assayed the plasma adipocytokines levels related to insulin sensitivity, plasma lipid levels, and tissue triglycerides accumulation and examined adipocyte morphology. Furthermore, we evaluated mRNA expression and protein levels of enzymes or regulators involved in regulating hepatic lipid metabolism. Our results suggest that decreased plasma adiponectin, increased plasma resistin and cholesterol, and elevated levels of TNF-alpha and IL-6 in adipocytes may all contribute to the insulin resistance observed in GH-Tg mice. Increased accumulation of triglycerides and impaired adipocytes differentiation in GH-transgenic mice provide plausible mechanisms for the alterations of adipocytokines. Hepatic and muscle insulin resistance in these mice is probably related to excessive accumulation of fatty acids and their metabolites. An increase in plasma adiponectin and decrease in plasma IL-6, triglycerides, and cholesterol levels in response to CR may improve insulin sensitivity.

Effects of caloric restriction and growth hormone resistance on insulin-related intermediates in the skeletal muscle.

Growth hormone receptor-deficient (GHRKO) mice are long-lived and have reduced insulin-like growth factor (IGF)-1 and insulin levels and enhanced insulin sensitivity thus resembling the phenotype of animals subjected to calorie restriction (CR). In contrast to its effects in normal mice, CR does not improve insulin sensitivity or increase longevity in GHRKO males. In an attempt to identify mechanisms underlying this differential response to CR, effects of CR on the expression of insulin-related genes were compared in GHRKO and normal mice. In addition to changes detected in both genotypes, and responses unique to GHRKO mice, the levels of Akt2 and peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC1alpha) were increased and levels of phosphorylated c-Jun N-terminal kinase (JNK)1 were reduced in response to CR only in normal mice. These changes may be related to mechanisms of improving insulin sensitivity and life expectancy.

Effects of dietary restriction on the expression of insulin-signaling-related genes in long-lived mutant mice.

Hypopituitary Ames dwarf mice and growth-hormone-resistant (growth hormone receptor knockout, GHRKO) mice have reduced plasma levels of insulin-like growth factor 1 and insulin, enhanced insulin sensitivity and a remarkably increased life span. This resembles the phenotypic characteristics of genetically normal animals subjected to dietary restriction (DR). Interestingly, DR leads to further increases in insulin sensitivity and longevity in Ames dwarfs but not in GHRKO mice. It was therefore of interest to examine the effects of DR on the expression of insulin-related genes in these two types of long-lived mutant mice. The effects of DR partially overlapped but did not duplicate the effects of Ames dwarfism or GHR deletion on the expression of genes related to insulin signaling and cell responsiveness to insulin. Moreover, the effects of DR on the expression of the examined genes in different insulin target organs were not identical. Some of the insulin-related genes were similarly affected by DR in both GHRKO and normal mice, some were affected only in GHRKO mice and some only in normal animals. This last category is of particular interest since genes affected in normal but not GHRKO mice may be related to mechanisms by which DR extends longevity.

Targeted disruption of growth hormone receptor interferes with the beneficial actions of calorie restriction.

Reduced intake of nutrients [calorie restriction (CR)] extends longevity in organisms ranging from yeast to mammals. Mutations affecting somatotropic, insulin, or homologous signaling pathways can increase life span in worms, flies, and mice, and there is considerable evidence that reduced secretion of insulin-like growth factor I and insulin are among the mechanisms that mediate the effects of CR on aging and longevity in mammals. In the present study, mice with targeted disruption of the growth hormone (GH) receptor [GH receptor/GH-binding protein knockout (GHRKO) mice] and their normal siblings were fed ad libitum (AL) or subjected to 30% CR starting at 2 months of age. In normal females and males, CR produced the expected increases in overall, average, median, and maximal life span. Longevity of normal mice subjected to CR resembles that of GHRKO animals fed AL. In sharp contrast to its effects in normal mice, CR failed to increase overall, median, or average life span in GHRKO mice and increased maximal life span only in females. In a separate group of animals, CR for 1 year improved insulin sensitivity in normal mice but failed to further enhance the remarkable insulin sensitivity in GHRKO mutants. These data imply that somatotropic signaling is critically important not only in the control of aging and longevity under conditions of unlimited food supply but also in mediating the effects of CR on life span. The present findings also support the notion that enhanced sensitivity to insulin plays a prominent role in the actions of CR and GH resistance on longevity.

Adipocytokines and lipid levels in Ames dwarf and calorie-restricted mice.

Ames dwarf mice are long-lived and insulin sensitive, and have a normal or reduced percentage of body fat. Calorie restriction (CR) is known to improve insulin sensitivity and reduce body fat. The purpose of this study was to evaluate the mechanism of improved insulin sensitivity in the Ames dwarfs and the effects of CR on adipose signaling and metabolism in normal and dwarf mice. Enhanced insulin sensitivity in dwarf mice may be partly due to increased release of adiponectin and the reduced release of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6). Altered levels of adipocytokines might be consequent to the decreased lipid synthesis, plasma triglycerides, and free fatty acid levels. In normal mice, CR improves insulin sensitivity by affecting the release of adipocytokines, and decreasing circulating fatty acid and triglycerides concentrations as well as liver triglyceride accumulation. However, CR may reduce rather than enhance some of the insulin effects in the highly insulin-sensitive dwarf mice.

Caloric restriction and growth hormone receptor knockout: effects on expression of genes involved in insulin action in the heart.

Blockade of growth hormone (GH), decreased insulin-like growth factor-1 (IGF1) action and increased insulin sensitivity are associated with life extension and an apparent slowing of the aging process. We examined expression of genes involved in insulin action, IR, IRS1, IRS2, IGF1, IGF1R, GLUT4, PPARs and RXRs in the hearts of normal and GHR-/- (KO) mice fed ad libitum or subjected to 30% caloric restriction (CR). CR increased the cardiac expression of IR, IRS1, IGF1, IGF1R and GLUT4 in normal mice and IRS1, GLUT4, PPARalpha and PPARbeta/delta in GHR-KO animals. Expression of IR, IRS1, IRS2, IGF1, GLUT4, PPARgamma and PPARalpha did not differ between GHR-KO and normal mice. These unexpected results suggest that CR may lead to major modifications of insulin action in the heart, but high insulin sensitivity of GHR-KO mice is not associated with alterations in the levels of most of the examined molecules related to intracellular insulin signaling.

Effects of caloric restriction and growth hormone resistance on the expression level of peroxisome proliferator-activated receptors superfamily in liver of normal and long-lived growth hormone receptor/binding protein knockout mice.

Growth hormone receptor/binding protein knockout (GHR-KO) mice live approximately 40% longer than their normal siblings do. These mice have dramatically reduced plasma levels of insulin-like growth factor 1 (IGF1) and enhanced insulin sensitivity. We examined the expression level of peroxisome proliferator-activated receptors (PPARs) and retinoid X receptors family genes in the livers of normal and GHR-KO mice fed ad libitum or subjected to long-term 30% caloric restriction (CR). The levels of PPARgamma and PPARalpha messenger RNA and proteins and the levels of retinoid X receptors messenger RNA were elevated in long-lived GHR-KO mice as compared to normal mice with no major effect of CR in either genotype. These findings suggest that enhanced insulin sensitivity of GHR-KO mice may be related to the altered actions of PPARs family members in the liver. The results also indicate that CR may increase insulin sensitivity through a different mechanism.

Caloric restriction results in decreased expression of peroxisome proliferator-activated receptor superfamily in muscle of normal and long-lived growth hormone receptor/binding protein knockout mice.

Resistance to growth hormone, reduced insulin-like growth factor 1 (IGF1) action, and enhanced insulin sensitivity are likely mediators of extended life span and delayed aging process in growth hormone receptor/binding protein knockout (GHR-KO) mice. Fat metabolism and genes involved in fatty acid oxidation are strongly involved in insulin action. Using real-time polymerase chain reaction and western blot we have examined expression of peroxisome proliferator-activated receptors (PPARs) and retinoid X receptor (RXR) genes in the skeletal muscle of normal and GHR-KO mice subjected to 30% caloric restriction. The results indicate that caloric restriction decreased the expression of PPARgamma, PPARalpha, and PPARbeta/delta which would lead to down-regulation of fat metabolism. This suggested metabolic change clearly does not affect whole-body insulin action. These findings suggest that whole-animal insulin sensitivity is not regulated through skeletal muscle insulin action.