Attenuation of diabetes-induced cardiac inflammation and pathological remodeling by low-dose radiation

Multiple low-dose radiation ameliorates type-2 diabetes mellitus via gut microbiota modulation to activate TLR4/MyD88/NF-κB pathway

BACKGROUND

Type 2 diabetes mellitus (T2DM) is the fastest-growing metabolic disease in the world. The gut microbiota is linked to T2DM. Recent studies have showed that the metabolism of gut microbiota can trigger T2DM. Low dose radiation (LDR) has been proved to activate various protective bioeffects on diabetes. However, the underlying mechanisms remain unclear.

METHODS

In this study, T2DM model was established using high fat diet combined with streptozocin (STZ) injection in C57BL/6 mice, and then exposed to multiple 75 mGy LDR every other day for one month. The changes of blood glucose levels, body weight, and the damage of pancreas were measured. In addition, 16 S rDNA amplicon sequencing was used to detect gut microbiota alteration. Metabolic profiling was carried out using the liquid mass spectrometry system, followed by the combinative analysis of gut microbiota alteration. Furthermore, the inflammatory factors and related pathways were detected.

RESULTS

We found that LDR attenuate blood glucose levels and the weights of body in T2DM mice, and reduce pancreas impairment. In addition, in the gut, LDR regulated the relative abundance of Bacilli, Desulfobacterota, Verrucomicrobiota, and Proteobacteria. The non-target metabolomics analysis found that LDR significantly improve the metabolic abnormalities in T2DM, which is closely related to the gut microbiota abundance. Furthermore, the inflammatory effects activated by TLR4/MyD88/NF-κB pathways in T2DM were ameliorated by LDR.

CONCLUSION

These results suggest that LDR may exert a beneficial role in T2DM by modulating gut microbiota and metabolites, especially in TLR4/MyD88/NF-κB pathway.

Deficiency of CFB attenuates renal tubulointerstitial damage by inhibiting ceramide synthesis in diabetic kidney disease

Accumulating evidence suggests the pathogenic role of immunity and metabolism in diabetic kidney disease (DKD). Herein, we aimed to investigate the effect of complement factor B (CFB) on lipid metabolism in the development of DKD. We found that in patients with diabetic nephropathy, the staining of Bb, CFB, C3a, C5a, and C5b-9 was markedly elevated in renal tubulointerstitium. Cfb-knockout diabetic mice had substantially milder tubulointerstitial injury and less ceramide biosynthesis. The in vitro study demonstrated that cytokine secretion, endoplasmic reticulum stress, oxidative stress, and cell apoptosis were ameliorated in HK-2 cells transfected with siRNA of CFB under high-glucose conditions. Exogenous ceramide supplementation attenuated the protective effect of CFB knockdown in HK-2 cells, while inhibiting ceramide synthases (CERS) with fumonisin B1 in CFB-overexpressing cells rescued the cell injury. CFB knockdown could downregulate the expression of NF-κB p65, which initiates the transcription of CERS3. Furthermore, C3 knockdown abolished CFB-mediated cytokine secretion, NF-κB signaling activation, and subsequently ceramide biosynthesis. Thus, CFB deficiency inhibited activation of the complement alternative pathway and attenuated kidney damage in DKD, especially tubulointerstitial injury, by inhibiting the NF-κB signaling pathway, further blocking the transcription of CERS, which regulates the biosynthesis of ceramide. CFB may be a promising therapeutic target of DKD.

Silencing the Adipocytokine NOV: A Novel Approach to Reversing Oxidative Stress-Induced Cardiometabolic Dysfunction

Objective: NOV/CCN3 is an adipocytokine recently linked to obesity, insulin resistance, and cardiometabolic dysfunction. NOV is manufactured and secreted from adipose tissue, with blood levels highly correlated with BMI. NOV levels are increased in obesity and a myriad of inflammatory diseases. Elevated NOV levels cause oxidative stress by increasing free radicals, decreasing antioxidants, and decreasing heme oxygenase (HO-1) levels, resulting in decreased vascular function. Silencing NOV in NOV knockout mice improved insulin sensitivity. We wanted to study how suppressing NOV expression in an obese animal model affected pathways and processes related to obesity, inflammation, and cardiometabolic function. This is the first study to investigate the interaction of adipose tissue-specific NOV/CCN3 and cardiometabolic function. Methods: We constructed a lentivirus containing the adiponectin-promoter-driven shNOV to examine the effect of NOV inhibition (shNOV) in adipose tissue on the heart of mice fed a high-fat diet. Mice were randomly divided into three groups (five per group): (1) lean (normal diet), (2) high-fat diet (HFD)+ sham virus, and (3) HFD + shNOV lentivirus. Blood pressure, tissue inflammation, and oxygen consumption were measured. Metabolic and mitochondrial markers were studied in fat and heart tissues. Results: Mice fed an HFD developed adipocyte hypertrophy, fibrosis, inflammation, and decreased mitochondrial respiration. Inhibiting NOV expression in the adipose tissue of obese mice by shNOV increased mitochondrial markers for biogenesis (PGC-1α, the nuclear co-activator of HO-1) and functional integrity (FIS1) and insulin signaling (AKT). The upregulation of metabolic and mitochondrial markers was also evident in the hearts of the shNOV mice with the activation of mitophagy. Using RNA arrays, we identified a subgroup of genes that highly correlated with increased adipocyte mitochondrial autophagy in shNOV-treated mice. A heat map analysis in obese mice confirmed that the suppression of NOV overrides the genetic susceptibility of adiposity and the associated detrimental metabolic changes and correlates with the restoration of anti-inflammatory, thermogenic, and mitochondrial genes. Conclusion: Our novel findings demonstrate that inhibiting NOV expression improves adipose tissue function in a positive way in cardiometabolic function by inducing mitophagy and improving mitochondrial function by the upregulation of PGC-1α, the insulin sensitivity signaling protein. Inhibiting NOV expression increases PGC-1, a key component of cardiac bioenergetics, as well as key signaling components of metabolic change, resulting in improved glucose tolerance, improved mitochondrial function, and decreased inflammation. These metabolic changes resulted in increased oxygen consumption, decreased adipocyte size, and improved cardiac metabolism and vascular function at the structural level. The crosstalk of the adipose tissue-specific deletion of NOV/CCN3 improved cardiovascular function, representing a novel therapeutic strategy for obesity-related cardiometabolic dysfunction.

Low-dose radiation exaggerates HFD-induced metabolic dysfunction by gut microbiota through PA-PYCR1 axis

Co-exposure of High-fat-diet (HFD) behavior and environmental low-dose radiation (LDR) is common among majority occupational workers, but the synergism of this co-exposure in metabolic health is poorly understood. This study aimed to investigate the impact of gut microbiota and its metabolites on the regulation of HFD accompanied by LDR-associated with metabolic dysfunction and insulin resistance. Here, we reported that Parasutterella was markedly elevated in the gut microbiota of mice in co-exposure of HFD and LDR, accompanied by increased pyrrolidinecarboxylic acid (PA) level in both intestine and plasma. Transplantation of fecal microbiota from mice with co-exposure HFD and LDR with metabolic dysfunction resulted in increased disruption of metabolic dysfunction, insulin resistance and increased PYCR1 (Pyrroline-5-carboxylate reductase 1) expression. Mechanistically, intestinal barrier was damaged more serious in mice with co-exposure of HFD and LDR, leading high PA level in plasma, activating PYCR1 expression to inhibit insulin Akt/mTOR (AKT kinase-transforming protein/Serine threonine-protein kinase) signaling pathway to aggravate HFD-induced metabolic impairments. This study suggests a new avenue for interventions against western diet companied with low dose radiation exposure-driven metabolic impairments.

Low-Dose Radiation Affects Cardiovascular Disease Risk in Human Aortic Endothelial Cells by Altering Gene Expression under Normal and Diabetic Conditions

High doses of ionizing radiation can cause cardiovascular diseases (CVDs); however, the effects of <100 mGy radiation on CVD remain underreported. Endothelial cells (ECs) play major roles in cardiovascular health and disease, and their function is reduced by stimuli such as chronic disease, metabolic disorders, and smoking. However, whether exposure to low-dose radiation results in the disruption of similar molecular mechanisms in ECs under diabetic and non-diabetic states remains largely unknown; we aimed to address this gap in knowledge through the molecular and functional characterization of primary human aortic endothelial cells (HAECs) derived from patients with type 2 diabetes (T2D-HAECs) and normal HAECs in response to low-dose radiation. To address these limitations, we performed RNA sequencing on HAECs and T2D-HAECs following exposure to 100 mGy of ionizing radiation and examined the transcriptome changes associated with the low-dose radiation. Compared with that in the non-irradiation group, low-dose irradiation induced 243 differentially expressed genes (DEGs) (133 down-regulated and 110 up-regulated) in HAECs and 378 DEGs (195 down-regulated and 183 up-regulated) in T2D-HAECs. We also discovered a significant association between the DEGs and the interferon (IFN)-I signaling pathway, which is associated with CVD by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, protein−protein network analysis, and module analysis. Our findings demonstrate the potential impact of low-dose radiation on EC functions that are related to the risk of CVD.

Transcriptomic profiling reveals gene expression in human peripheral blood after exposure to low-dose ionizing radiation

Although the health effects of exposure to low-dose ionizing radiation have been the focus of many studies, the affected biological functions and underlying regulatory mechanisms are not well-understood. In particular, the influence of radiation exposure at doses of less than 200 mGy on the regulation of genes and pathways remains unclear. To investigate the molecular alterations induced by varying doses of low-dose radiation (LDR), transcriptomic analysis was conducted based on ribonucleic acid (RNA) sequencing following exposure to 50 and 150 mGy doses. Human peripheral blood was collected, and the samples were divided into three groups, including two treatments and one control (no radiation). A total of 876 (318 upregulated and 558 downregulated) and 486 (202 upregulated and 284 downregulated) differentially expressed genes (DEGs) were identified after exposure to 50 mGy and 150 mGy, respectively. Most upregulated genes in both the 50 mGy and 150 mGy groups were associated with 'antigen processing and presentation,' which appeared to be the major targets affected by LDR exposure. Several interacting genes, including HLA-DQA1, HLA-DQA2, HLA-DQB2, HLA-DRB1, and HLA-DRB5 were mapped to 'antigen processing and presentation,' 'immune system-related diseases' and the 'cytokine-mediated signaling pathway,' suggesting that these genes might drive the downstream transmission of these signal transduction pathways. Our results suggest that exposure to LDR may elicit changes in key genes and associated pathways, probably helping further explore the biological processes and molecular mechanism responsible for low-dose occupational or environmental exposures in humans.

Effect of low-dose fast neutrons on the protein components of peripheral blood mononuclear cells of whole-body irradiated Wistar rats

The immune system is exposed to extremely low doses of neutrons under different circumstances, such as through exposure to cosmic rays, nuclear accidents, and neutron therapy. Peripheral blood mononuclear cells (PBMCs) are the primary immune cells that exhibit selective immune responses. Changes in the functions of the protein components of PBMC can be induced by structural modifications of these proteins themselves. Herein, we have investigated the effect of low-dose fast neutrons on PBMC proteins at 0, 2, 4, and 8 days post-whole body irradiation. 64 Wistar rats were used in this study of which, 32 were exposed to fast neutrons at a total dose of 10 mGy (²⁴¹Am-Be, 0.2 mGy/h), and the other 32 were used as controls. Blood samples were drawn, and PBMCs were isolated from whole blood. Fourier transform infrared (FTIR) spectroscopy and fluorescence spectroscopy were used to estimate the changes in the proteins of PBMCs. An alkaline comet assay was performed to assess DNA damage. Hierarchical cluster analysis (HCA) and principal components analysis (PCA) were utilized to discriminate between irradiated and non-irradiated samples. FTIR and fluorescence spectra of the tested samples revealed alterations in the amides and tryptophan, and therefore protein structure at time intervals of 2 and 4 days post-irradiation. No changes were recorded in samples tested at time intervals of 0 and 8 days post-irradiation. The FTIR band intensities of the PBMC proteins of the irradiated samples decreased slightly and were statistically significant. Curve fitting of the amide I band in the FTIR spectra showed changes in the secondary structure of the proteins. At 2 days post-irradiation, fluorescence spectra of the tested samples revealed decreases in the band tryptophan. The comet assay revealed low levels of DNA damage. In conclusion, low-dose fast neutrons can affect the proteins of PBMC.

Organ-Specific Effects of Low Dose Radiation Exposure: A Comprehensive Review

Ionizing radiation (IR) is a high-energy radiation whose biological effects depend on the irradiation doses. Low-dose radiation (LDR) is delivered during medical diagnoses or by an exposure to radioactive elements and has been linked to the occurrence of chronic diseases, such as leukemia and cardiovascular diseases. Though epidemiological research is indispensable for predicting and dealing with LDR-induced abnormalities in individuals exposed to LDR, little is known about epidemiological markers of LDR exposure. Moreover, difference in the LDR-induced molecular events in each organ has been an obstacle to a thorough investigation of the LDR effects and a validation of the experimental results in in vivo models. In this review, we summarized the recent reports on LDR-induced risk of organ-specifically arranged the alterations for a comprehensive understanding of the biological effects of LDR. We suggested that LDR basically caused the accumulation of DNA damages, controlled systemic immune systems, induced oxidative damages on peripheral organs, and even benefited the viability in some organs. Furthermore, we concluded that understanding of organ-specific responses and the biological markers involved in the responses is needed to investigate the precise biological effects of LDR.

The Role of Heme Oxygenase 1 in the Protective Effect of Caloric Restriction against Diabetic Cardiomyopathy

Type 2 diabetes mellitus (DM2) leads to cardiomyopathy characterized by cardiomyocyte hypertrophy, followed by mitochondrial dysfunction and interstitial fibrosis, all of which are exacerbated by angiotensin II (AT). SIRT1 and its transcriptional coactivator target PGC-1α (peroxisome proliferator-activated receptor-γ coactivator), and heme oxygenase-1 (HO-1) modulates mitochondrial biogenesis and antioxidant protection. We have previously shown the beneficial effect of caloric restriction (CR) on diabetic cardiomyopathy through intracellular signaling pathways involving the SIRT1–PGC-1α axis. In the current study, we examined the role of HO-1 in diabetic cardiomyopathy in mice subjected to CR. Methods: Cardiomyopathy was induced in obese diabetic (db/db) mice by AT infusion. Mice were either fed ad libitum or subjected to CR. In an in vitro study, the reactive oxygen species (ROS) level was determined in cardiomyocytes exposed to different glucose levels (7.5–33 mM). We examined the effects of Sn(tin)-mesoporphyrin (SnMP), which is an inhibitor of HO activity, the HO-1 inducer cobalt protoporphyrin (CoPP), and the SIRT1 inhibitor (EX-527) on diabetic cardiomyopathy. Results: Diabetic mice had low levels of HO-1 and elevated levels of the oxidative marker malondialdehyde (MDA). CR attenuated left ventricular hypertrophy (LVH), increased HO-1 levels, and decreased MDA levels. SnMP abolished the protective effects of CR and caused pronounced LVH and cardiac metabolic dysfunction represented by suppressed levels of adiponectin, SIRT1, PPARγ, PGC-1α, and increased MDA. High glucose (33 mM) increased ROS in cultured cardiomyocytes, while SnMP reduced SIRT1, PGC-1α levels, and HO activity. Similarly, SIRT1 inhibition led to a reduction in PGC-1α and HO-1 levels. CoPP increased HO-1 protein levels and activity, SIRT1, and PGC-1α levels, and decreased ROS production, suggesting a positive feedback between SIRT1 and HO-1. Conclusion: These results establish a link between SIRT1, PGC-1α, and HO-1 signaling that leads to the attenuation of ROS production and diabetic cardiomyopathy. CoPP mimicked the beneficial effect of CR, while SnMP increased oxidative stress, aggravating cardiac hypertrophy. The data suggest that increasing HO-1 levels constitutes a novel therapeutic approach to protect the diabetic heart. Brief Summary: CR attenuates cardiomyopathy, and increases HO-1, SIRT activity, and PGC-1α protein levels in diabetic mice. High glucose reduces adiponectin, SIRT1, PGC1-1α, and HO-1 levels in cardiomyocytes, resulting in oxidative stress. The pharmacological activation of HO-1 activity mimics the effect of CR, while SnMP increased oxidative stress and cardiac hypertrophy. These data suggest the critical role of HO-1 in protecting the diabetic heart.

Adaptive responses to low doses of radiation or chemicals: their cellular and molecular mechanisms

This article reviews the current knowledge on the mechanisms of adaptive response to low doses of ionizing radiation or chemical exposure. A better knowledge of these mechanisms is needed to improve our understanding of health risks at low levels of environmental or occupational exposure and their involvement in cancer or non-cancer diseases. This response is orchestrated through a multifaceted cellular program involving the concerted action of diverse stress response pathways. These evolutionary highly conserved defense mechanisms determine the cellular response to chemical and physical aggression. They include DNA damage repair (p53, ATM, PARP pathways), antioxidant response (Nrf2 pathway), immune/inflammatory response (NF-κB pathway), cell survival/death pathway (apoptosis), endoplasmic response to stress (UPR response), and other cytoprotective processes including autophagy, cell cycle regulation, and the unfolded protein response. The coordinated action of these processes induced by low-dose radiation or chemicals produces biological effects that are currently estimated with the linear non-threshold model. These effects are controversial. They are difficult to detect because of their low magnitude, the scarcity of events in humans, and the difficulty of corroborating associations over the long term. Improving our understanding of these biological consequences should help humans and their environment by enabling better risk estimates, the revision of radiation protection standards, and possible therapeutic advances.

Low-Dose Radiation Promotes the Proliferation and Migration of AGE-Treated Endothelial Progenitor Cells Derived from Bone Marrow via Activating SDF-1/CXCR4/ERK Signaling Pathway

Low-dose radiation (LDR) has been confirmed to mobilize bone marrow-derived endothelial progenitor cells (EPCs) and promote diabetic wound healing. But it is unclear whether LDR acts directly on EPCs and promotes their proliferation and migration. Given the key role of advanced glycosylation end products (AGE) in the pathogenesis of diabetes, we used AGE to induce EPC damage. We then investigated the effect of LDR on the proliferation and migration of AGE-treated EPCs and explored the underlying mechanisms. EPCs cultured in vitro were treated with different concentrations of AGE, and the cells were then exposed to different low doses and treated with a specific antagonist for CXCR4, AMD3100 (1 lmol/l). The proliferation and migration abilities of EPCs were detected using the CCK-8 and wound healing assays, respectively. The mRNA and protein expression of SDF-1 and CXCR4 in AGE-treated EPCs were measured using qPCR and Western blot analysis, respectively. The expressions of ERK and phosphorylated ERK (pERK) were detected using Western blot analysis. The results showed that 200 mg/l and 400 mg/l AGE had an inhibitory effect on the proliferation of EPCs, and this inhibitory effect was exerted in a dose- and time-dependent manner. AGE significantly reduced the migration ability of EPCs cultured in vitro. After the cells received either 50 or 75 mGy low-dose irradiation, the proliferation of EPCs and AGE-treated EPCs was clearly increased; in addition, LDR also enhanced cell migration ability, but this enhancement was counteracted by AMD3100. Results from qPCR and Western blot analysis showed that LDR increased the mRNA and protein expression of SDF-1/ CXCR4. LDR also upregulated pERK expression in EPCs and AGE-treated EPCs, but LDR-induced upregulation of pERK expression was inhibited by AMD3100. These findings indicate that LDR can directly activate the SDF-1/CXCR4 biological axis and downstream ERK signaling pathway, and promote the proliferation and migration abilities of EPCs by increasing the expression of SDF-1, CXCR4 and pERK in EPCs.

Research Progress on the Biological Effects of Low-Dose Radiation in China

Human are exposed to ionizing radiation from natural and artificial sources, which consequently poses a possible risk to human health. However, accumulating evidence indicates that the biological effects of low-dose radiation (LDR) are different from those of high-dose radiation (HDR). Low-dose radiation–induced hormesis has been extensively observed in different biological systems, including immunological and hematopoietic systems. Adaptive responses in response to LDR that can induce cellular resistance to genotoxic effects from subsequent exposure to HDR have also been described and researched. Bystander effects, another type of biological effect induced by LDR, have been shown to widely occur in many cell types. Furthermore, the influence of LDR-induced biological effects on certain diseases, such as cancer and diabetes, has also attracted the interest of researchers. Many studies have suggested that LDR has the potential antitumor and antidiabetic complications effects. In addition, the researches on whether LDR could induce stochastic effects were also debated. Studies on the biological effects of LDR in China started in 1970s and considerable progress has been made since. In the present article, we provide an overview of the research progress on the biological effects of LDR in China.

PARP-1 inhibition protects the diabetic heart through activation of SIRT1-PGC-1α axis

Type 2 diabetes mellitus (DM2) follows impaired glucose tolerance in obesity and is frequently associated with hypertension, causing adverse myocardial remodelling and leading to heart failure. The DNA bound protein PARP (poly ADP ribose) polymerase catalyses a post translational modification (polymerization of negatively charged ADP-ribose chains) of nuclear proteins. PARP-1 activation is NAD⁺ dependent and takes part in DNA repair and in chromatin remodelling and has a function in transcriptional regulation, intracellular trafficking and energy metabolism. PARP-1 is activated in diabetic cardiomyopathy. We hypothesized that PARP-1 inhibition in diabetic mice may protect cardiomyocytes from inflammation and ROS production.

METHODS

Obese Leptin resistant (db/db) mice suffering from DM2, were treated with angiotensin II (AT) for 4 weeks to enhance the development of cardiomyopathy. Mice were concomitantly treated with the PARP-1 inhibitor INO1001. Neonatal cardiomyocytes exposed to high levels of glucose (33 mM) with or without AT were treated with INO1001. or with SIRT inhibitor (EX-527) in the presence of INO1001 were tested in-vitro.

RESULTS

The in-vivo tests show that hearts from AT treated DM2 mice exhibited cardiac hypertrophy, fibrosis and an increase in the inflammatory marker TNFα. DM2 mice had an increased oxidative stress, concomitant with elevated PARP-1 activity and reduced Sirtuin-1 (SIRT1) expression. PARP-1 inhibition led to increased SIRT1 and Peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α) levels, attenuating oxidative stress, inflammation and fibrosis. In-vitro experiments demonstrated that inhibition of PARP-1 in cardiomyocytes exposed to high levels of glucose and AT led to a significant reduction in ROS (P < 0.01), which was abolished in the presence of the SIRT1 inhibitor together with increased protein expression of SIRT1 and PGC-1α.

CONCLUSION

PARP1 inhibitor INO1001 attenuated cardiomyopathic features in diabetic mice through the activation of SIRT1 and its downstream antioxidant defence mechanisms. The results of this study suggest a pivotal role of PARP-1 inhibition in treating diabetic and AT-induced cardiomyopathy.

Akkermansia muciniphila can reduce the damage of gluco/lipotoxicity, oxidative stress and inflammation, and normalize intestine microbiota in streptozotocin-induced diabetic rats

This study aimed to investigate how Akkermansia muciniphila can implicate type 2 diabetes mellitus and the mechanisms underlying the effects A. muciniphila on type 2 diabetes mellitus. Normal and streptozotocin-induced diabetic Sprague-Dawley rats were orally administered with A. muciniphila and solvent. After 4 weeks of treatment, diabetic rats orally administered with live or pasteurized A. muciniphila exhibited significant increase in the blood concentration of high-density lipoprotein, and decrease in the hepatic glycogen, serum plasminogen activator inhibitor-1, tumor necrosis factor-α, lipopolysaccharide, malondialdehyde and total glucagon-like peptide-1. Moreover, diabetic rats orally administered with A. muciniphila showed significantly increased species alpha diversity and gene function in gut microbes. These results indicated that A. muciniphila can improve liver function, reduce gluco/lipotoxicity, alleviate oxidative stress, suppress inflammation and normalize intestine microbiota of the host animal, thereby ameliorating type 2 diabetes mellitus. Akkermansia muciniphila might be considered as one of the ideal new probiotics used in the management of type 2 diabetes mellitus in future.

Regulation of diabetic cardiomyopathy by caloric restriction is mediated by intracellular signaling pathways involving 'SIRT1 and PGC-1α'

Background

Metabolic disorders such as obesity, insulin resistance and type 2 diabetes mellitus (DM2) are all linked to diabetic cardiomyopathy that lead to heart failure. Cardiomyopathy is initially characterized by cardiomyocyte hypertrophy, followed by mitochondrial dysfunction and fibrosis, both of which are aggravated by angiotensin. Caloric restriction (CR) is cardioprotective in animal models of heart disease through its catabolic activity and activation of the expression of adaptive genes. We hypothesized that in the diabetic heart; this effect involves antioxidant defenses and is mediated by SIRT1 and the transcriptional coactivator PGC-1α (Peroxisome proliferator-activated receptor-γ coactivator).

Methods

Obese Leptin resistant (db/db) mice characterized by DM2 were treated with angiotensin II (AT) for 4 weeks to enhance the development of cardiomyopathy. Mice were concomitantly either on a CR diet or fed ad libitum. Cardiomyocytes were exposed to high levels of glucose and were treated with EX-527 (SIRT1 inhibitor). Cardiac structure and function, gene and protein expression and oxidative stress parameters were analyzed.

Results

AT treated db/db mice developed cardiomyopathy manifested by elevated levels of serum glucose, cholesterol and cardiac hypertrophy. Leukocyte infiltration, fibrosis and an increase in an inflammatory marker (TNFα) and natriuretic peptides (ANP, BNP) gene expression were also observed. Oxidative stress was manifested by low SOD and PGC-1α levels and an increase in ROS and MDA. DM2 resulted in ERK1/2 activation. CR attenuated all these deleterious perturbations and prevented the development of cardiomyopathy. ERK1/2 phosphorylation was reduced in CR mice (p = 0.008). Concomitantly CR prevented the reduction in SIRT activity and PGC-1α (p < 0.04). Inhibition of SIRT1 activity in cardiomyocytes led to a marked reduction in both SIRT1 and PGC-1α. ROS levels were significantly (p < 0.03) increased by glucose and SIRT1 inhibition.

Conclusion

In the current study we present evidence of the cardioprotective effects of CR operating through SIRT1 and PGC-1 α, thereby decreasing oxidative stress, fibrosis and inflammation. Our results suggest that increasing SIRT1 and PGC-1α levels offer new therapeutic approaches for the protection of the diabetic heart.

It Is Time to Move Beyond the Linear No-Threshold Theory for Low-Dose Radiation Protection

The US Environmental Protection Agency (USEPA) is the primary federal agency responsible for promulgating regulations and policies to protect people and the environment from ionizing radiation. Currently, the USEPA uses the linear no-threshold (LNT) model to estimate cancer risks and determine cleanup levels in radiologically contaminated environments. The LNT model implies that there is no safe dose of ionizing radiation; however, adverse effects from low dose, low-dose rate (LDDR) exposures are not detectable. This article (1) provides the scientific basis for discontinuing use of the LNT model in LDDR radiation environments, (2) shows that there is no scientific consensus for using the LNT model, (3) identifies USEPA reliance on outdated scientific information, and (4) identifies regulatory reliance on incomplete evaluations of recent data contradicting the LNT. It is the time to reconsider the use of the LNT model in LDDR radiation environments. Incorporating the latest science into the regulatory process for risk assessment will (1) ensure science remains the foundation for decision making, (2) reduce unnecessary burdens of costly cleanups, (3) educate the public on the real effects of LDDR radiation exposures, and (4) harmonize government policies with the rest of the radiation scientific community.

Alterations of MicroRNA Expression in the Liver, Heart, and Testis of Mice Upon Exposure to Repeated Low-Dose Radiation

MicroRNAs (miRs), which regulate target gene expression at the post-transcriptional level, play a crucial role in inducing biological effects upon high-dose ionizing radiation. Yet, the miR expression profiles in response to repeated low-dose radiation (LDR) in vivo have not been elucidated. This study investigated the response profiles of 11 miRs with functions involved in metabolism, DNA damage and repair, inflammation, and fibrosis in mouse liver, heart, and testis upon repeated LDR exposure for 4 months. The expression profiles were evaluated using stem-loop quantitative reverse transcription polymerase chain reaction immediately and at 2 months after LDR exposure. The expression profiles varied significantly at both time points. At the organ level, the heart was the most affected, followed by the liver and testis, in which significant miR upregulation related to DNA damage response was found. Metabolism-related miRs decreased in the liver and increased in the testis. The current results showed immediate and long-lasting alterations in the miR expression profiles in response to repeated LDR in different organs.

Health Impacts of Low-Dose Ionizing Radiation: Current Scientific Debates and Regulatory Issues

Health impacts of low-dose ionizing radiation are significant in important fields such as X-ray imaging, radiation therapy, nuclear power, and others. However, all existing and potential applications are currently challenged by public concerns and regulatory restrictions. We aimed to assess the validity of the linear no-threshold (LNT) model of radiation damage, which is the basis of current regulation, and to assess the justification for this regulation. We have conducted an extensive search in PubMed. Special attention has been given to papers cited in comprehensive reviews of the United States (2006) and French (2005) Academies of Sciences and in the United Nations Scientific Committee on Atomic Radiation 2016 report. Epidemiological data provide essentially no evidence for detrimental health effects below 100 mSv, and several studies suggest beneficial (hormetic) effects. Equally significant, many studies with in vitro and in animal models demonstrate that several mechanisms initiated by low-dose radiation have beneficial effects. Overall, although probably not yet proven to be untrue, LNT has certainly not been proven to be true. At this point, taking into account the high price tag (in both economic and human terms) borne by the LNT-inspired regulation, there is little doubt that the present regulatory burden should be reduced.

Protection by dimethyl fumarate against diabetic cardiomyopathy in type 1 diabetic mice likely via activation of nuclear factor erythroid-2 related factor 2

Oxidative stress and inflammation play key roles in the development of diabetic cardiomyopathy (DCM). Dimethyl fumarate (DMF), an FDA approved medicine for relapsing multiple sclerosis, has manifested its antioxidant and anti-inflammatory function mostly in the central nervous system. In this study, we investigated whether DMF could attenuate the development of DCM. Type 1 diabetes mouse model was established using multiple low-dose streptozotocin, and the diabetic mice were treated with DMF (10 mg/kg body weight) for 3 months. Cardiac functions were determined using echocardiography. Oxidative stress, pro-inflammatory cytokines and pro-fibrotic markers were determined with commercially available kits, real-time quantitative PCR or western blot techniques. DCM was characterized by diminished cardiac function, accompanied by oxidative stress and enhanced expression of pro-inflammatory cytokines. Diabetic cardiac tissue exhibited marked fibrosis, revealed by extracellular matrix deposition as determined by Sirius red staining of the myocardial tissues. Furthermore, Nrf2 and its downstream effectors were repressed in diabetic myocardium. On the contrary, diabetic animals treated with DMF exhibited blunted oxidative stress, inflammation, fibrosis and this correlated with Nrf2 activation. Our findings suggest that DMF could potentially thwart diabetes-induced myocardial tissue injury, likely via activation of Nrf2 function, providing firm impetus for future repurposing of DMF in the management of DCM.

Gamma Low-Dose-Rate Ionizing Radiation Stimulates Adaptive Functional and Molecular Response in Human Aortic Endothelial Cells in a Threshold-, Dose-, and Dose Rate-Dependent Manner

A central question in radiation protection research is whether low-dose and low-dose-rate (LDR) exposures to ionizing radiation play a role in progression of cardiovascular disease. The response of endothelial cells to different LDR exposures may help estimate risk of cardiovascular disease by providing the biological mechanism involved. We investigated the effect of chronic LDR radiation on functional and molecular responses of human aorta endothelial cells (HAoECs). Human aorta endothelial cells were continuously irradiated at LDR (6 mGy/h) for 15 days and analyzed at time points when the cumulative dose reached 0.05, 0.5, 1.0, and 2.0 Gy. The same doses were administered acutely at high-dose rate (HDR; 1 Gy/min). The threshold for the loss of angiogenic capacity for both LDR and HDR radiations was between 0.5 and 1.0 Gy. At 2.0 Gy, angiogenic capacity returned to normal only for HAoEC exposed to LDR radiation, associated with increased expression of antioxidant and anti-inflammatory genes. Pre-LDR, but not pre-HDR, radiation, followed by a single acute 2.0 Gy challenge dose sustained the expression of antioxidant and anti-inflammatory genes and stimulated angiogenesis. Our results suggest that dose rate is important in cellular response and that a radioadaptive response is involved for a 2.0 Gy dose at LDR.

Low dose radiation prevents doxorubicin-induced cardiotoxicity

This study aimed to develop a novel and non-invasive approach, low-dose radiation (LDR, 75 mGy X-rays), to prevent doxorubicin (DOX)-induced cardiotoxicity. BALB/c mice were randomly divided into five groups, Control, LDR (a single exposure), Sham (treated same as LDR group except for irradiation), DOX (a single intraperitoneal injection of DOX at 7.5 mg/kg), and LDR/DOX (received LDR and 72 h later received DOX). Electrocardiogram analysis displayed several kinds of abnormal ECG profiles in DOX-treated mice, but less in LDR/DOX group. Cardiotoxicity indices included histopathological changes, oxidative stress markers, and measurements of mitochondrial membrane permeability. Pretreatment of DOX group with LDR reduced oxidative damages (reactive oxygen species formation, protein nitration, and lipid peroxidation) and increased the activities of antioxidants (superoxide dismutase and glutathione peroxidase) in the heart of LDR/DOX mice compared to DOX mice. Pretreatment of DOX-treated mice with LDR also decreased DOX-induced cardiac cell apoptosis (TUNEL staining and cleaved caspase-3) and mitochondrial apoptotic pathway (increased p53, Bax, and caspase-9 expression and decreased Bcl2 expression and ΔΨm dissipation). These results suggest that LDR could induce adaptation of the heart to DOX-induced toxicity. Cardiac protection by LDR may attribute to attenuate DOX-induced cell death via suppressing mitochondrial-dependent oxidative stress and apoptosis signaling.

The role of gut in type 2 diabetes mellitus during whole body gamma irradiation in high-fat diet Wistar rats

PURPOSE

The effects of a low rate (100 mGy/min) fractionated whole body gamma irradiation (FWBGI) at different doses were assessed using a real-time PCR technique on the expression of some target genes implicated in the development of type 2 diabetes mellitus in high-fat diet (HFD) Wistar rats.

METHOD

HFD Wistar rats were exposed to different doses (12, 24 and 48 Gy) divided into 24 fractions (three times a week for two months), thus, the daily doses were 0.5, 1, 2 Gy, respectively. Total RNA was extracted and the expression of target genes was measured in the four intestinal segments (duodenum, jejunum, ileum and colon).

RESULTS

The pre-diabetic state already induced by HFD was found to be improved by irradiation exposure. This irradiation effect occurs mainly via altered anti-diabetic gene expressions (mRNA and protein levels) of the incretin glucagon-like peptide-1 (GLP-1) overall bowel segments except the colon which has its own specific response to irradiation exposure by the induction of the insulin receptor substrate 4 (IRS-4) and the uncoupling protein 3 (UCP3).

CONCLUSIONS

Results could be of great importance suggesting for the first time, a protective role for FWBGI on HFD animal models by increasing GLP-1 and UCP3 levels.

Impact of Ionizing Radiation on the Cardiovascular System: A Review

Radiation therapy has become one of the main forms of treatment for various types of cancers. Cancer patients previously treated with high doses of radiation are at a greater risk to develop cardiovascular complications later in life. The heart can receive varying doses of radiation depending on the type of therapy and can even reach doses in the range of 17 Gy. Multiple studies have highlighted the role of oxidative stress and inflammation in radiation-induced cardiovascular damage. Doses of ionizing radiation below 200 mGy, however, have been shown to have beneficial effects in some experimental models of radiation-induced damage, but low-dose effects in the heart is still debated. Low-dose radiation may promote heart health and reduce damage from oxidative stress and inflammation, however there are few studies focusing on the impact of low-dose radiation on the heart. In this review, we summarize recent studies from animal models and human data focusing on the effects and mechanism(s) of action of radiation-induced damage to the heart, as well as the effects of high and low doses of radiation and dose rates.

Cancer immunotherapy: how low-level ionizing radiation can play a key role

The cancer immunoediting hypothesis assumes that the immune system guards the host against the incipient cancer, but also "edits" the immunogenicity of surviving neoplastic cells and supports remodeling of tumor microenvironment towards an immunosuppressive and pro-neoplastic state. Local irradiation of tumors during standard radiotherapy, by killing neoplastic cells and generating inflammation, stimulates anti-cancer immunity and/or partially reverses cancer-promoting immunosuppression. These effects are induced by moderate (0.1-2.0 Gy) or high (>2 Gy) doses of ionizing radiation which can also harm normal tissues, impede immune functions, and increase the risk of secondary neoplasms. In contrast, such complications do not occur with exposures to low doses (≤0.1 Gy for acute irradiation or ≤0.1 mGy/min dose rate for chronic exposures) of low-LET ionizing radiation. Furthermore, considerable evidence indicates that such low-level radiation (LLR) exposures retard the development of neoplasms in humans and experimental animals. Here, we review immunosuppressive mechanisms induced by growing tumors as well as immunomodulatory effects of LLR evidently or likely associated with cancer-inhibiting outcomes of such exposures. We also offer suggestions how LLR may restore and/or stimulate effective anti-tumor immunity during the more advanced stages of carcinogenesis. We postulate that, based on epidemiological and experimental data amassed over the last few decades, whole- or half-body irradiations with LLR should be systematically examined for its potential to be a viable immunotherapeutic treatment option for patients with systemic cancer.

Low-dose radiation prevents type 1 diabetes-induced cardiomyopathy via activation of AKT mediated anti-apoptotic and anti-oxidant effects

We investigated whether low-dose radiation (LDR) can prevent late-stage diabetic cardiomyopathy and whether this protection is because of the induction of anti-apoptotic and anti-oxidant pathways. Streptozotocin-induced diabetic C57BL/6J mice were treated with/without whole-body LDR (12.5, 25, or 50 mGy) every 2 days. Twelve weeks after onset of diabetes, cardiomyopathy was diagnosed characterized by significant cardiac dysfunction, hypertrophy and histopathological abnormalities associated with increased oxidative stress and apoptosis, which was prevented by LDR (25 or 50 mGy only). Low-dose radiation-induced cardiac protection also associated with P53 inactivation, enhanced Nrf2 function and improved Akt activation. Next, for the mechanistic study, mouse primary cardiomyocytes were treated with high glucose (33 mmol/l) for 24 hrs and during the last 15 hrs bovine serum albumin-conjugated palmitate (62.5 μmol/l) was added into the medium to mimic diabetes, and cells were treated with LDR (25 mGy) every 6 hrs during the whole process of HG/Pal treatment. Data show that blocking Akt/MDM2/P53 or Akt/Nrf2 pathways with small interfering RNA of akt, mdm2 and nrf2 not only prevented LDR-induced anti-apoptotic and anti-oxidant effects but also prevented LDR-induced suppression on cardiomyocyte hypertrophy and fibrosis against HG/Pal. Low-dose radiation prevented diabetic cardiomyopathy by improving cardiac function and hypertrophic remodelling attributed to Akt/MDM2/P53-mediated anti-apoptotic and Akt/Nrf2-mediated anti-oxidant pathways simultaneously.

Repetitive exposure to low-dose X-irradiation attenuates testicular apoptosis in type 2 diabetic rats, likely via Akt-mediated Nrf2 activation

To determine whether repetitive exposure to low-dose radiation (LDR) attenuates type 2 diabetes (T2DM)-induced testicular apoptotic cell death in a T2DM rat model, we examined the effects of LDR exposure on diabetic and age-matched control rats. We found that testicular apoptosis and oxidative stress levels were significantly higher in T2DM rats than in control rats. In addition, glucose metabolism-related Akt and GSK-3β function was downregulated and Akt negative regulators PTP1B and TRB3 were upregulated in the T2DM group. Superoxide dismutase (SOD) activity and catalase content were also found to be decreased in T2DM rats. These effects were partially prevented or reversed by repetitive LDR exposure. Nrf2 and its downstream genes NQO1, SOD, and catalase were significantly upregulated by repetitive exposure to LDR, suggesting that the reduction of T2DM-induced testicular apoptosis due to repetitive LDR exposure likely involves enhancement of testicular Akt-mediated glucose metabolism and anti-oxidative defense mechanisms.

Additive protection by LDR and FGF21 treatment against diabetic nephropathy in type 2 diabetes model

The onset of diabetic nephropathy (DN) is associated with both systemic and renal changes. Fibroblast growth factor (FGF)-21 prevents diabetic complications mainly by improving systemic metabolism. In addition, low-dose radiation (LDR) protects mice from DN directly by preventing renal oxidative stress and inflammation. In the present study, we tried to define whether the combination of FGF21 and LDR could further prevent DN by blocking its systemic and renal pathogeneses. To this end, type 2 diabetes was induced by feeding a high-fat diet for 12 wk followed by a single dose injection of streptozotocin. Diabetic mice were exposed to 50 mGy LDR every other day for 4 wk with and without 1.5 mg/kg FGF21 daily for 8 wk. The changes in systemic parameters, including blood glucose levels, lipid profiles, and insulin resistance, as well as renal pathology, were examined. Diabetic mice exhibited renal dysfunction and pathological abnormalities, all of which were prevented significantly by LDR and/or FGF21; the best effects were observed in the group that received the combination treatment. Our studies revealed that the additive renal protection conferred by the combined treatment against diabetes-induced renal fibrosis, inflammation, and oxidative damage was associated with the systemic improvement of hyperglycemia, hyperlipidemia, and insulin resistance. These results suggest that the combination treatment with LDR and FGF21 prevented DN more efficiently than did either treatment alone. The mechanism behind these protective effects could be attributed to the suppression of both systemic and renal pathways.

Chronic Internal Exposure to Low Dose 137Cs Induces Positive Impact on the Stability of Atherosclerotic Plaques by Reducing Inflammation in ApoE-/- Mice

After Chernobyl and Fukushima Daï Chi, two major nuclear accidents, large amounts of radionuclides were released in the environment, mostly caesium 137 (137Cs). Populations living in contaminated territories are chronically exposed to radionuclides by ingestion of contaminated food. However, questions still remain regarding the effects of low dose ionizing radiation exposure on the development and progression of cardiovascular diseases. We therefore investigated the effects of a chronic internal exposure to 137Cs on atherosclerosis in predisposed ApoE-/- mice. Mice were exposed daily to 0, 4, 20 or 100 kBq/l 137Cs in drinking water, corresponding to range of concentrations found in contaminated territories, for 6 or 9 months. We evaluated plaque size and phenotype, inflammatory profile, and oxidative stress status in different experimental groups. Results did not show any differences in atherosclerosis progression between mice exposed to 137Cs and unexposed controls. However, 137Cs exposed mice developed more stable plaques with decreased macrophage content, associated with reduced aortic expression of pro-inflammatory factors (CRP, TNFα, MCP-1, IFNγ) and adhesion molecules (ICAM-1, VCAM-1 and E-selectin). Lesions of mice exposed to 137Cs were also characterized by enhanced collagen and smooth muscle cell content, concurrent with reduced matrix metalloproteinase MMP8 and MMP13 expression. These results suggest that low dose chronic exposure of 137Cs in ApoE-/- mice enhances atherosclerotic lesion stability by inhibiting pro-inflammatory cytokine and MMP production, resulting in collagen-rich plaques with greater smooth muscle cell and less macrophage content.

Emerging issues in radiogenic cataracts and cardiovascular disease

In 2011, the International Commission on Radiological Protection issued a statement on tissue reactions (formerly termed non-stochastic or deterministic effects) to recommend lowering the threshold for cataracts and the occupational equivalent dose limit for the crystalline lens of the eye. Furthermore, this statement was the first to list circulatory disease (cardiovascular and cerebrovascular disease) as a health hazard of radiation exposure and to assign its threshold for the heart and brain. These changes have stimulated various discussions and may have impacts on some radiation workers, such as those in the medical sector. This paper considers emerging issues associated with cataracts and cardiovascular disease. For cataracts, topics dealt with herein include (i) the progressive nature, stochastic nature, target cells and trigger events of lens opacification, (ii) roles of lens protein denaturation, oxidative stress, calcium ions, tumor suppressors and DNA repair factors in cataractogenesis, (iii) dose rate effect, radiation weighting factor, and classification systems for cataracts, and (iv) estimation of the lens dose in clinical settings. Topics for cardiovascular disease include experimental animal models, relevant surrogate markers, latency period, target tissues, and roles of inflammation and cellular senescence. Future research needs are also discussed.

Low-dose radiation induces renal SOD1 expression and activity in type 1 diabetic mice

PURPOSE

Oxidative stress plays a critical role in the pathogenesis of diabetic nephropathy (DN). As an antioxidant, superoxide dismutase (SOD)-1 deficiency exacerbates but SOD1 supplementation prevents diabetes-induced renal damage. Previously, we have demonstrated that repetitive exposure to low-dose radiation (LDR) at 25 mGy significantly prevents DN. Whether this prevention is related to SOD1 expression and activity remains unknown. The aim of the present study was to explore the effects of different methods of LDR treatment on SOD1 expression and activity in the kidneys of diabetic mice.

MATERIALS AND METHODS

C57BL/6J mice were induced with type 1 diabetes using streptozotocin (STZ). Diabetic mice were irradiated with whole-body X-rays at either a single dose of 25 mGy or 75 mGy, or three doses of 25 mGy and then sacrificed at different times. Body weight, blood glucose level, and renal SOD1 expression and activity were measured.

RESULTS

LDR had no impact on the body weights or blood glucose levels of the mice in either the normal or diabetic groups. A single exposure of LDR at 25 mGy did not preserve renal SOD1 expression and activity in diabetic mice, but a single exposure of LDR at 75 mGy or three exposures of LDR at 25 mGy could preserve them.

CONCLUSION

The stimulation of renal SOD1 expression and activity by a single or cumulative LDR of 75 mGy may be one of the preventive mechanisms of DN observed in the previous study.

Suppression of dextran sulfate sodium-induced colitis in mice by radon inhalation

The enhanced release of reactive oxygen species from activated neutrophils plays important role in the pathogenesis of inflammatory bowel disease. We previously reported that radon inhalation activates antioxidative functions in various organs of mice. In this study, we examined the protective effects of radon inhalation on dextran sulfate sodium- (DSS) induced colitis in mice which were subjected to DSS for 7 days. Mice were continuously treated with air only (sham) or radon at a concentration of 2000 Bq/m³ from a day before DSS administration to the end of colitis induction. In the results, radon inhalation suppressed the elevation of the disease activity index score and histological damage score induced by DSS. Based on the changes in tumor necrosis factor-alpha in plasma and myeloperoxidase activity in the colon, it was shown that radon inhalation suppressed DSS-induced colonic inflammation. Moreover, radon inhalation suppressed lipid peroxidation of the colon induced by DSS. The antioxidant level (superoxide dismutase and total glutathione) in the colon after DSS administration was significantly higher in mice treated with radon than with the sham. These results suggested that radon inhalation suppressed DSS-induced colitis through the enhancement of antioxidative functions in the colon.

Low-dose radiation activates Akt and Nrf2 in the kidney of diabetic mice: a potential mechanism to prevent diabetic nephropathy

Repetitive exposure of diabetic mice to low-dose radiation (LDR) at 25 mGy could significantly attenuate diabetes-induced renal inflammation, oxidative damage, remodeling, and dysfunction, for which, however, the underlying mechanism remained unknown. The present study explored the effects of LDR on the expression and function of Akt and Nrf2 in the kidney of diabetic mice. C57BL/6J mice were used to induce type 1 diabetes with multiple low-dose streptozotocin. Diabetic and age-matched control mice were irradiated with whole body X-rays at either single 25 mGy and 75 mGy or accumulated 75 mGy (25 mGy daily for 3 days) and then sacrificed at 1-12 h for examining renal Akt phosphorylation and Nrf2 expression and function. We found that 75 mGy of X-rays can stimulate Akt signaling pathway and upregulate Nrf2 expression and function in diabetic kidneys; single exposure of 25 mGy did not, but three exposures to 25 mGy of X-rays could offer a similar effect as single exposure to 75 mGy on the stimulation of Akt phosphorylation and the upregulation of Nrf2 expression and transcription function. These results suggest that single 75 mGy or multiple 25 mGy of X-rays can stimulate Akt phosphorylation and upregulate Nrf2 expression and function, which may explain the prevention of LDR against the diabetic nephropathy mentioned above.

Shifting the paradigm in radiation safety

The current radiation safety paradigm using the linear no-threshold (LNT) model is based on the premise that even the smallest amount of radiation may cause mutations increasing the risk of cancer. Autopsy studies have shown that the presence of cancer cells is not a decisive factor in the occurrence of clinical cancer. On the other hand, suppression of immune system more than doubles the cancer risk in organ transplant patients, indicating its key role in keeping occult cancers in check. Low dose radiation (LDR) elevates immune response, and so it may reduce rather than increase the risk of cancer. LNT model pays exclusive attention to DNA damage, which is not a decisive factor, and completely ignores immune system response, which is an important factor, and so is not scientifically justifiable. By not recognizing the importance of the immune system in cancer, and not exploring exercise intervention, the current paradigm may have missed an opportunity to reduce cancer deaths among atomic bomb survivors. Increased antioxidants from LDR may reduce aging-related non-cancer diseases since oxidative damage is implicated in these. A paradigm shift is warranted to reduce further casualties, reduce fear of LDR, and enable investigation of potential beneficial applications of LDR.

Suppressive effects of continuous low-dose-rate γ irradiation on diabetic nephropathy in type II diabetes mellitus model mice

It has been proposed that the development of diabetic nephropathy is caused in large part by oxidative stress. We previously showed that continuous exposure of mice to low-dose-rate γ radiation enhances antioxidant activity. Here, we studied the ameliorative effect of continuous whole-body irradiation with low-dose-rate γ rays on diabetic nephropathy. Ten-week-old female db/db mice, an experimental model for type II diabetes, were irradiated with low-dose-rate γ rays from 10 weeks of age throughout their lives. Nephropathy was studied by histological observation and biochemical analysis of serum and urine. Antioxidant activities in kidneys were determined biochemically. Continuous low-dose-rate γ radiation significantly increases life span in db/db mice. Three of 24 irradiated mice were free of glucosuria after 80 weeks of irradiation. Histological studies of kidney suggest that low-dose irradiation increases the number of normal capillaries in glomeruli. Antioxidant activities of superoxide dismutase, catalase and glutathione are significantly increased in kidneys of irradiated db/db mice. Continuous low-dose-rate γ irradiation ameliorates diabetic nephropathy and increases life span in db/db mice through the activation of renal antioxidants. These findings have noteworthy implications for radiation risk estimation of non-cancer diseases as well as for the clinical application of low-dose-rate γ radiation for diabetes treatment.