Sub-erythemal ultraviolet radiation reduces metabolic dysfunction in already overweight mice

Exposure to artificial ultraviolet-B light mediates alterations on the hepatic transcriptome and vitamin D metabolism in pigs

In the currently prevailing pig husbandry systems, the vitamin D status is almost exclusively dependent on dietary supply. Additional endogenous vitamin D production after exposure to ultraviolet-B (UVB) light might allow the animals to utilize minerals in a more efficient manner, as well as enable the production of functional vitamin D-enriched meat for human consumption. In this study, growing pigs (n = 16) were subjected to a control group or to a daily narrowband UVB exposure of 1 standard erythema dose (SED) for a period of 9 weeks until slaughter at a body weight of 105 kg. Transcriptomic profiling of liver with emphasis on the associated effects on vitamin D metabolism due to UVB exposure were evaluated via RNA sequencing. Serum was analyzed for vitamin D status and health parameters such as minerals and biochemical markers. The serum concentration of calcidiol, but not calcitriol, was significantly elevated in response to UVB exposure after 17 days on trial. No effects of UVB exposure were observed on growth performance and blood test results. At slaughter, the RNA sequencing analyses following daily UVB exposure revealed 703 differentially expressed genes (DEGs) in liver tissue (adjusted p-value < 0.01). Results showed that molecular pathways for vitamin D synthesis (CYP2R1) rather than cholesterol synthesis (DHCR7) were preferentially initiated in liver. Gene enrichment (p < 0.05) was observed for reduced cholesterol/steroid biosynthesis, SNARE interactions in vesicular transport, and CDC42 signaling. Taken together, dietary vitamin D supply can be complemented via endogenous production after UVB exposure in pig husbandry, which could be considered in the development of functional foods.

Impact of ultraviolet radiation on cardiovascular and metabolic disorders: The role of nitric oxide and vitamin D

BACKGROUND/PURPOSE

Ultraviolet (UV) radiation has both harmful and beneficial effects on human skin and health. It causes skin damage, aging, and cancer; however, it is also a primary source of vitamin D. Additionally, UV radiation can impact energy metabolism and has protective effects on several cardiovascular and metabolic disorders in mice and humans. However, the mechanisms of UV protection against these diseases have not been clearly identified.

METHODS

This review summarizes the systemic effects of UV radiation on hypertension and several metabolic diseases such as obesity, diabetes, and nonalcoholic fatty liver disease (NAFLD) in mice, and we also consider the mechanisms of action of the related regulators nitric oxide (NO) and vitamin D.

RESULTS

UV exposure can lower blood pressure and prevent the development of cardiovascular diseases and metabolic disorders, such as metabolic syndrome, obesity, and type 2 diabetes, primarily through mechanisms that depend on UV-induced NO. UV radiation may also effectively delay the onset of type 1 diabetes through mechanisms that rely on UV-induced vitamin D. UV-induced NO and vitamin D play roles in preventing and slowing the progression of NAFLD.

CONCLUSION

UV exposure is a promising nonpharmacological intervention for cardiovascular and metabolic disorders. NO and vitamin D may play a crucial role in mediating these effects. However, further investigations are required to elucidate the exact mechanisms and determine the optimal dosage and exposure duration of UV radiation.

DNA mechanical flexibility controls DNA potential to activate cGAS-mediated immune surveillance

DNA is well-documented to stimulate immune response. However, the nature of the DNA to activate immune surveillance is less understood. Here, we show that the activation of cyclic GMP-AMP synthase (cGAS) depends on DNA mechanical flexibility, which is controlled by DNA-sequence, -damage and -length. Consistently, DNA-sequence was shown to control cGAS activation. Structural analyses revealed that a conserved cGAS residue (mouse R222 or human R236) contributed to the DNA-flexibility detection. And the residue substitution neutralised the flexibility-controlled DNA-potential to activate cGAS, and relaxed the DNA-length specificity of cGAS. Moreover, low dose radiation was shown to mount cGAS-mediated acute immune surveillance (AIS) via repairable (reusable) DNAs in hrs. Loss of cGAS-mediated AIS decreased the regression of local and abscopal tumours in the context of focal radiation and immune checkpoint blockade. Our results build a direct link between immunosurveillance and DNA mechanical feature.

The role of light pollution in mammalian metabolic homeostasis and its potential interventions: A critical review

Irregular or unnatural artificial light causes severe environmental stress on the survival and health of organisms, which is rapidly becoming a widespread new type of environmental pollution. A series of disruptive behaviors to body homeostasis brought about by light pollution, including metabolic abnormalities, are likely to be the result of circadian rhythm disturbances. Recently, the proposed role of light pollution in metabolic dysregulation has accelerated it into an emerging field. Hence, the regulatory role of light pollution in mammalian metabolic homeostasis is reviewed in this contribution. Light at night is the most widely affected type of light pollution, which disrupts metabolic homeostasis largely due to its disruption of daily food intake patterns, alterations of hormone levels such as melatonin and glucocorticoids, and changes in the rhythm of inflammatory factor production. Besides, light pollution impairs mammalian metabolic processes in an intensity-, photoperiod-, and wavelength-dependent manner, and is also affected by species, gender, and diets. Nevertheless, metabolic disorders triggered by light pollution are not irreversible to some extent. Potential interventions such as melatonin supplementation, recovery to the LD cycle, time-restricted feeding, voluntary exercise, wearing blue light-shied goggles, and bright morning light therapy open a bright avenue to prevent light pollution. This work will help strengthen the relationship between light information and metabolic homeostasis and provide new insights for the better prevention of metabolic disorders and light pollution.

An Exploration of How Solar Radiation Affects the Seasonal Variation of Human Mortality Rates and the Seasonal Variation in Some Other Common Disorders

Many diseases have large seasonal variations in which winter overall mortality rates are about 25% higher than in summer in mid-latitude countries, with cardiovascular diseases and respiratory infections and conditions accounting for most of the variation. Cancers, by contrast, do not usually have pronounced seasonal variations in incidence or mortality rates. This narrative review examines the epidemiological evidence for seasonal variations in blood pressure, cardiovascular disease rates and respiratory viral infections in relation to atmospheric temperature and humidity, and solar UV exposure through vitamin D production and increased blood concentrations of nitric oxide. However, additional mechanisms most likely exist by which solar radiation reduces the risk of seasonally varying diseases. Some studies have been reported with respect to temperature without considering solar UV doses, although studies regarding solar UV doses, such as for respiratory infections, often consider whether temperature can affect the findings. More research is indicated to evaluate the relative effects of temperature and sun exposure on the seasonality of mortality rates for several diseases. Since solar ultraviolet-B (UVB) doses decrease to vanishingly small values at higher latitudes in winter, the use of safe UVB lamps for indoor use in winter may warrant consideration.

Post-exposure persistence of nitric oxide upregulation in skin cells irradiated by UV-A

Evidence suggests that exposure to UV-A radiation can liberate nitric oxide from skin cells eliciting vasodilation in-vivo. However, the duration of nitric oxide release in skin cells after UV exposure is not well studied, with emphasis on UV-B mediated iNOS upregulation. The current study demonstrated persistence of nitric oxide release in a dark reaction after moderate UV-A exposure, peaking around 48 h post exposure; this effect was shown in keratinocytes, fibroblasts and endothelial cells from neonatal donors and keratinocytes from aged donors and confirmed the hypothesis that UV-A exposure appeared to upregulate cNOS alongside iNOS. Release of nitric oxide in the skin cells induced by a moderate exposure to UV-A in sunlight may be especially beneficial for some demographic groups such as the elderly, hypertensive patients or those with impaired nitric oxide function, not only during exposure but many hours and days after that.

Moderate Sun Exposure Is the Complementor in Insufficient Vitamin D Consumers

Background and Aims

Vitamin (Vit) D plays a vital role in human health, and the prevalence of Vit D deficiency worldwide has been a rising concern. This study investigates the serum 25-hydroxy-Vit D [25(OH)D] status in healthy US civilians and identifies how the two main sources, sun exposure and dietary Vit D intake, determine the final 25(OH)D levels in individuals.

Methods

A total of 2,360 of participants from The National Health and Nutrition Examination Survey (NHANES) 2009–2014 were analyzed. We divided the levels of sun exposure and dietary Vit D intake of all subjects into 10 strata and gave a score ranging from 1 to 10 points, respectively. Scores 1–5 in sun exposure and dietary intake were considered as relatively low exposure groups, whereas scores 6–10 were considered as relatively high exposure groups. Serum Vit D inadequacy was defined as <50 nmol/L. Linear and logistic regression analyses were used to examine the associations between sources of Vit D and serum 25(OH)D levels.

Results

In relatively low Vit D intake groups (Vit D intake score 1–5), relatively high sun exposure (sun exposure score >5) resulted in higher serum 25(OH)D levels (average 57 nmol/L) compared with relatively low sun exposure (sun exposure score <5) (average 50 nmol/L), whereas this difference became negligible in high intake groups (Vit D intake score 6–10). Moreover, the greatest slope occurred in the low Vit D intake curve (decile 3 of Vit D intake), which shows increased sun exposure time causing the greatest degree of change in serum 25(OH)D level in this group.

Conclusion

Sun exposure can significantly make up for deficiencies in subjects who consume insufficient dietary Vit D. Compared with the extra cost and time for building habits of Vit D supplementation, moderate sun exposure appears to be a simple and costless means for the public to start in daily practice.

Ultraviolet B Irradiation Alters the Level and miR Contents of Exosomes Released by Keratinocytes in Diabetic Condition

Ultraviolet B (UVB) stimulates the generation of extracellular vesicles, which elicit systemic effects. Here, we studied whether UVB affects the release and microRNA (miR) content of keratinocyte exosomes (EXs) in diabetic conditions. In vitro, we examined the UVB effects on affecting EX release from keratinocyte HaCaT cells (HaCaT‐EX) pretreated with high glucose. HaCaT‐EX functions were evaluated on Schwann cells (SCs). In vivo, UVB‐induced miR change in skin EXs of diabetic db/db mice was analyzed. The miRs of interest were validated in HaCaT‐EXs. We found that: (1) UVB promoted HaCaT‐EX generation in dose‐ and time‐dependent manners; 100 and 1800 J m⁻² of UVB had the most prominent effect and were selected as effective low‐ and high‐fluence UVB in vitro. (2) A total of 13 miRs were differentially expressed >3‐fold in skin EXs in UVB‐treated db/db mice; miR‐126 was the most up‐regulated by low‐fluence UVB. (3) Functional studies revealed that the SC viability was improved by low‐fluence UVB HaCaT‐EXs, while worsened by high‐fluence UVB HaCaT‐EXs. (4) MiR‐126 inhibitor attenuated the effects induced by low‐fluence UVB HaCaT‐EXs. Our data have demonstrated that low‐ and high‐fluence UVBs promote HaCaT‐EX generation but differentially affect exosomal miR levels and functions under diabetic conditions.

Metabolic dysfunction induced by a high-fat diet modulates hematopoietic stem and myeloid progenitor cells in brown adipose tissue of mice

Brown adipose tissue (BAT) may be an important metabolic regulator of whole-body glucose. While important roles have been ascribed to macrophages in regulating metabolic functions in BAT, little is known of the roles of other immune cells subsets, particularly dendritic cells (DCs). Eating a high-fat diet may compromise the development of hematopoietic stem and progenitor cells (HSPCs)-which give rise to DCs-in bone marrow, with less known of its effects in BAT. We have previously demonstrated that ongoing exposure to low-dose ultraviolet radiation (UVR) significantly reduced the 'whitening' effect of eating a high-fat diet upon interscapular (i) BAT of mice. Here, we examined whether this observation may be linked to changes in the phenotype of HSPCs and myeloid-derived immune cells in iBAT and bone marrow of mice using 12-colour flow cytometry. Many HSPC subsets declined in both iBAT and bone marrow with increasing metabolic dysfunction. Conversely, with rising adiposity and metabolic dysfunction, conventional DCs (cDCs) increased in both of these tissues. When compared with a low-fat diet, consumption of a high-fat diet significantly reduced proportions of myeloid, common myeloid and megakaryocyte-erythrocyte progenitors in iBAT, and short-term hematopoietic stem cells in bone marrow. In mice fed the high-fat diet, exposure to low-dose UVR significantly reduced proportions of cDCs in iBAT, independently of nitric oxide release from irradiated skin [blocked using the scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt (cPTIO)], but did not significantly modify HSPC subsets in either tissue. Further studies are needed to determine whether changes in these cell populations contribute towards metabolic dysfunction .

Neuropeptides and neurohormones in immune, inflammatory and cellular responses to ultraviolet radiation

Humans are exposed to varying amounts of ultraviolet radiation (UVR) through sunlight. UVR penetrates into human skin leading to release of neuropeptides, neurotransmitters and neuroendocrine hormones. These messengers released from local sensory nerves, keratinocytes, Langerhans cells (LCs), mast cells, melanocytes and endothelial cells (ECs) modulate local and systemic immune responses, mediate inflammation and promote differing cell biologic effects. In this review, we will focus on both animal and human studies that elucidate the roles of calcitonin gene-related peptide (CGRP), substance P (SP), nerve growth factor (NGF), nitric oxide and proopiomelanocortin (POMC) derivatives in mediating immune and inflammatory effects of exposure to UVR as well as other cell biologic effects of UVR exposure.

Investigating the Potential for Ultraviolet Light to Modulate Morbidity and Mortality From COVID-19: A Narrative Review and Update

During the COVID-19 (coronavirus disease of 2019) pandemic, researchers have been seeking low-cost and accessible means of providing protection from its harms, particularly for at-risk individuals such as those with cardiovascular disease, diabetes and obesity. One possible way is via safe sun exposure, and/or dietary supplementation with induced beneficial mediators (e.g., vitamin D). In this narrative review, we provide rationale and updated evidence on the potential benefits and harms of sun exposure and ultraviolet (UV) light that may impact COVID-19. We review recent studies that provide new evidence for any benefits (or otherwise) of UV light, sun exposure, and the induced mediators, vitamin D and nitric oxide, and their potential to modulate morbidity and mortality induced by infection with SARS-CoV-2 (severe acute respiratory disease coronavirus-2). We identified substantial interest in this research area, with many commentaries and reviews already published; however, most of these have focused on vitamin D, with less consideration of UV light (or sun exposure) or other mediators such as nitric oxide. Data collected to-date suggest that ambient levels of both UVA and UVB may be beneficial for reducing severity or mortality due to COVID-19, with some inconsistent findings. Currently unresolved are the nature of the associations between blood 25-hydroxyvitamin D and COVID-19 measures, with more prospective data needed that better consider lifestyle factors, such as physical activity and personal sun exposure levels. Another short-coming has been a lack of measurement of sun exposure, and its potential to influence COVID-19 outcomes. We also discuss possible mechanisms by which sun exposure, UV light and induced mediators could affect COVID-19 morbidity and mortality, by focusing on likely effects on viral pathogenesis, immunity and inflammation, and potential cardiometabolic protective mechanisms. Finally, we explore potential issues including the impacts of exposure to high dose UV radiation on COVID-19 and vaccination, and effective and safe doses for vitamin D supplementation.

FATP2-targeted therapies - A role beyond fatty liver disease

Fatty acid transport protein 2 (FATP2) is a multifunctional protein whose specific function is determined by the type of located cell, its intracellular location, or organelle-specific interactions. In the different diseases setting, a newfound appreciation for the biological function of FATP2 has come into view. Two main functions of FATP2 are to activate long-chain fatty acids (LCFAs) as a very long-chain acyl-coenzyme A (CoA) synthetase (ACSVL) and to transport LCFAs as a fatty acid transporter. FATP2 is not only involved in the occurrence of nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM), but also plays an important role in lithogenic diet-induced cholelithiasis, the formation of cancer tumor immunity, the progression of chronic kidney disease (CKD), and the regulation of zoledronate-induced nephrotoxicity. Herein, we review the updated information on the role of FATP2 in related diseases. In particular, we discuss the new functions of FATP2 and propose that FATP2 is a potential clinical biomarker and therapeutic target. In conclusion, regulatory strategies for FATP2 may bring new treatment options for cancer and lipid metabolism-related disorders.

Effects of UVR exposure on the gut microbiota of mice and humans

Many alterations to the skin microbiome by exposure to UV radiation (UVR) have been postulated and may contribute to the ability of UVR phototherapy to regulate skin inflammatory diseases. Very recently, an effect of sub-erythemal narrowband UVB radiation (311 nm) on the gut microbiome of healthy individuals was reported. The relative abundance of Firmicutes and Proteobacteria increased in faecal samples of those receiving three exposures to narrowband UVB radiation; the Bacteroidetes phyla were reduced by UVB. In mice chronically exposed to sub-erythemal broadband UVR, similar faecal changes in Firmicutes and Bacteroidetes have been reported. Murine studies have allowed a further dissection of the relative ability of UVR and dietary vitamin D to modulate the gut microbiome by analysis of relative bacterial abundance in mice with similar 25-hydroxy vitamin D levels obtained by UVR exposure or from their diet, respectively. The studies of mice recovering from colitis suggested that dietary vitamin D could stimulate greater faecal abundance of Rikenellaceae, whilst exposure to UVR was necessary for changes to the abundance of Lachnospiraceae and Desulfovibrionaceae. Both human and murine studies report that multiple exposures to sub-erythemal UVR can increase the diversity of the gut microbiome, which in turn may be beneficial to the health of the host.

Characterising nitric oxide-mediated metabolic benefits of low-dose ultraviolet radiation in the mouse: a focus on brown adipose tissue

AIMS/HYPOTHESIS

Exposure to sunlight has the potential to suppress metabolic dysfunction and obesity. We previously demonstrated that regular exposure to low-doses of ultraviolet radiation (UVR) reduced weight gain and signs of diabetes in male mice fed a high-fat diet, in part via release of nitric oxide from skin. Here, we explore further mechanistic pathways through which low-dose UVR exerts these beneficial effects.

METHODS

We fed mice with a luciferase-tagged Ucp1 gene (which encodes uncoupling protein-1 [UCP-1]), referred to here as the Ucp1 luciferase transgenic mouse ('Thermomouse') a high-fat diet and examined the effects of repeated exposure to low-dose UVR on weight gain and development of metabolic dysfunction as well as UCP-1-dependent thermogenesis in interscapular brown adipose tissue (iBAT).

RESULTS

Repeated exposure to low-dose UVR suppressed the development of glucose intolerance and hepatic lipid accumulation via dermal release of nitric oxide while also reducing circulating IL-6 (compared with mice fed a high-fat diet only). Dietary nitrate supplementation did not mimic the effects of low-dose UVR. A single low dose of UVR increased UCP-1 expression (by more than twofold) in iBAT of mice fed a low-fat diet, 24 h after exposure. However, in mice fed a high-fat diet, there was no effect of UVR on UCP-1 expression in iBAT (compared with mock-treated mice) when measured at regular intervals over 12 weeks. More extensive circadian studies did not identify any substantial shifts in UCP-1 expression in mice exposed to low-dose UVR, although skin temperature at the interscapular site was reduced in UVR-exposed mice. The appearance of cells with a white adipocyte phenotype ('whitening') in iBAT induced by consuming the high-fat diet was suppressed by exposure to low-dose UVR in a nitric oxide-dependent fashion. Significant shifts in the expression of important core gene regulators of BAT function (Dio2, increased more than twofold), fatty acid transport (increased Fatp2 [also known as Slc27a2]), lipolysis (decreased Atgl [also known as Pnpla2]), lipogenesis (decreased Fasn) and inflammation (decreased Tnf), and proportions of macrophages (increased twofold) were observed in iBAT of mice exposed to low-dose UVR. These effects were independent of nitric oxide released from skin.

CONCLUSIONS/INTERPRETATION

Our results suggest that non-burning (low-dose) UVR suppresses the BAT 'whitening', steatotic and pro-diabetic effects of consuming a high-fat diet through skin release of nitric oxide, with some metabolic and immune pathways in iBAT regulated by UVR independently of nitric oxide.

Lipids in ultraviolet radiation-induced immune modulation

Ultraviolet (UV) radiation modulates cutaneous lipids which in turn mediates immune suppression – a key mechanism conferring both detrimental and beneficial impacts of sun exposure on human health.

Systematic Review of the Effects of Ultraviolet Radiation on Markers of Metabolic Dysfunction

Emerging findings suggest that exposure to ultraviolet wavelengths of sunlight modulates metabolic function. Here we review the metabolic effects of exposure to ultraviolet radiation (UVR), focusing on the effects of phototherapies (that administer UVR), and advice to increase sun exposure in individuals enrolled in clinical trials and intervention studies. We identified 25 studies in which the effects of UVR on metabolic outcomes were examined, including: narrowband ultraviolet B phototherapy (nbUVB, n = 12); psoralen ultraviolet A phototherapy (n = 4); other types of UVR phototherapy (n = 5); and sun exposure advice (n = 5). Most studies recruited a small number of participants (≤100), who were middle-aged individuals undergoing treatment for psoriasis flare, with phototherapy or sun exposure advice administered for ≤12 weeks. Data obtained at baseline were usually compared with an endpoint following treatment with UVR, for a limited number of outcomes. There were few studies in which markers of glucose metabolism were assessed, with some beneficial effects of sun exposure (but not phototherapy) reported. LDL-cholesterol levels were lower in individuals receiving sun exposure advice, while treatment with nbUVB reduced blood concentrations of inflammatory markers (C-reactive protein and interleukin-6). Future studies should focus on determining whether the effects of these interventions change with time, and if they are dependent on the source of UVR (i.e. phototherapy or sun exposure) and wavelength(s) of light administered. Furthermore, studies need to measure a variety of (clinical) markers of glucose metabolism, adiposity and inflammation, control for factors such as skin type and sex, and stratify participants for metabolic disease diagnosis.

Significant Associations Between Sun Exposure and Adiposity Were Not Observed in Breast and Prostate Cancer Patients in a Cross-sectional Analysis

Obesity is a significant health problem worldwide. Exposure to low-dose ultraviolet radiation (like that in sunlight) suppresses the development of obesity in mice; however, the nature of the associations between sun exposure and adiposity is not well understood in humans. The present study characterized cross-sectional relationships between sun exposure and adiposity in a convenience cohort of breast (n = 269; mean age = 58 years) and prostate (n = 78; mean age = 69 years) cancer patients. Participants were enrolled in a 3-month exercise program in Perth, Australia. Self-reported questionnaires measured time spent outdoors (previous week, winter and summer), sex, age, treatment received and physical activity levels. Adiposity measures included body mass index, waist-hip ratio and body fat percentage (measured via DXA). In unadjusted models, greater time spent outdoors across all times was significantly associated with lower waist-hip ratio, while greater time spent outdoors in the last winter was associated with lower body fat percentage, but not when stratified by sex. There were no statistically significant associations between time spent outdoors and adiposity after adjusting for sex, age, treatments received and physical activity. Longitudinal studies in larger populations may elucidate significant associations not found in our study due to the cross-sectional design and power limitations.

Exposure to solar ultraviolet radiation limits diet-induced weight gain, increases liver triglycerides and prevents the early signs of cardiovascular disease in mice

BACKGROUND AND AIMS

Sunlight exposure is associated with a number of health benefits including protecting us from autoimmunity, cardiovascular disease, obesity and diabetes. Animal studies have confirmed that ultraviolet (UV)-B radiation, independently of vitamin D, can limit diet-induced obesity, metabolic syndrome and atherosclerosis. The aim of this study is to investigate whether exposure to the UV radiation contained in sunlight impacts on these disease parameters.

METHODS AND RESULTS

We have trialled an intervention with solar UV in obese and atherosclerosis-prone mice. We have discovered that solar-simulated UV can significantly limit diet-induced obesity and reduce atheroma development in mice fed a diet high in sugar and fat. The optimal regime for this benefit was exposure once a week to solar UV equivalent to approximately 30 min of summer sun. Exposure to this optimal dose of solar UV also led to a significant increase in liver triglycerides which may protect the liver from damage.

CONCLUSION

Our results show that the UV contained in sunlight has the potential to prevent and treat chronic disease at sites distant from irradiated skin. A major health challenge going forward will be to harness the power of the sun safely, without risking an increase in skin cancers.

Regular exposure to non-burning ultraviolet radiation reduces signs of non-alcoholic fatty liver disease in mature adult mice fed a high fat diet: results of a pilot study

Objective

Obesity often emerges in middle age, increasing risk for metabolic disorders. Our previous preclinical experiments identified that chronic exposure to non-burning ultraviolet radiation, like that achieved through sun exposure, prevented weight gain and signs of metabolic dysfunction in young adult mice fed a high fat diet. Our objective was to perform a pilot study to estimate the effect size of ongoing exposure to sub-erythemal (non-burning, low dose) UVB (1 kJ/m²) radiation on measures of adiposity, food intake and physical activity in ‘mature’ adult C57Bl/6J male mice fed a high fat diet for 12 weeks.

Results

The severity of liver steatosis, fibrosis and inflammation were reduced in older adult mice exposed twice a week to ultraviolet radiation (from 29 weeks of age), compared to mock-irradiated mice, with some evidence for reduced hepatic mRNAs for tnf and tgfß1 (not fatp2 nor fasN). Power analyses suggested that up to 24 mice per treatment would be required in future experiments to detect a significant effect on some markers of adiposity such as body weight gain. Our studies suggest frequent exposure to low levels of sunlight may reduce the severity of hepatic steatosis induced in older adults living in environments of high caloric intake.

Electronic supplementary material

The online version of this article (10.1186/s13104-019-4112-8) contains supplementary material, which is available to authorized users.

No Evidence for Lower Levels of Serum Vitamin D in the Presence of Hepatic Steatosis. A Study on the Portuguese General Population

Introduction and aims: Nonalcoholic fatty liver disease (NAFLD) has become highly prevalent, paralleling the pandemic of obesity and diabetes, and represents an important burden. Nutrition knowledge is fundamental, in prevention, evolution and treatment of NAFLD. Association of low serum levels of vitamin D (VD) with several diseases, including NAFLD, has been emphasized in the last decade. We evaluated how serum levels of VD correlate with the presence of hepatic steatosis, and VD intake, in a random sample of the Portuguese adult population. Methods: Participants underwent a dietary intake inquiry, using a semi-quantitative food frequency questionnaire representative of the usual intake over the previous year. Anthropometric measures, blood tests and ultrasound were done. Hepatic steatosis was quantified according to Hamaguchi's ultrasonographic score (steatosis defined by a score ≥ 2). Results: We recruited 789 adult individuals, 416 males (52.7%), mean age of 49.9 ± 17.0 years (18-79). Prevalence of hepatic steatosis was 35.5%, and after exclusion of excessive alcohol consumption, 28.0%. Mean VD serum levels were 26.0 ± 9.8 ng/ml and 68.4% participants had serum VD levels below 30 ng/ml. Mean serum levels of VD were not significantly different between participants with steatosis vs. no steatosis: 25.2±8.7 vs. 26.4±10.3 ng/ml, respectively (p=0.071). There was no correlation between VD serum levels and VD intake, measured by the FFQ, r=0.075 (p= 0.383). Conclusions: In spite of a high prevalence rate, there was no evidence that decreased VD serum levels were associated with hepatic steatosis. No significant correlation was found between VD dietary ingestion and VD serum levels.