Vitamin A status affects obesity development and hepatic expression of key genes for fuel metabolism in Zucker fatty rats

IGFBP1a is a nutrient deficient response factor that can inhibit fish reproduction through the hypothalamus-pituitary-ovary axis†

Reproduction is a high energy consuming process, so long-term malnutrition can significantly inhibit gonadal development. However, little is known about the molecular mechanism by which fasting inhibits reproduction. Our present study found that fasting could dramatically induce insulin-like growth factor binding protein 1 (IGFBP1) expression in the liver, hypothalamus, pituitary and ovaries of grass carp. In addition, IGFBP1a in the hypothalamus-pituitary-gonad axis could inhibit the development of gonads. These results indicated that fasting may participate in the regulation of fish gonadal development through the mediation of IGFBP1a. Further studies found that IGFBP1a could markedly inhibit gonadotropin-releasing hormone 3 expressions in hypothalamus cells. At the pituitary level, IGFBP1a could significantly reduce the gonadotropin hormones (LH and FSH) expression by blocking the action of pituitary insulin-like growth factor 1. Interestingly, IGFBP1a could also directly inhibit the expression of lhr, fshr, and sex steroid hormone synthase genes (cyp11a, cyp17a, and cyp19a1) in the ovary. These results indicated that IGFBP1a should be a nutrient deficient response factor that could inhibit fish reproduction through the hypothalamus-pituitary-ovary axis.

Associations between serum retinol and all-cause mortality among adults with prediabetes and diabetes: A cohort study

We aimed to explore the associations between serum retinol and all-cause mortality among people with prediabetes and diabetes. The study included 2582 participants with prediabetes and 1654 with diabetes aged ≥40 years from the National Health and Nutrition Examination Survey 2001-2006. Serum retinol was collected from laboratory tests and categorized into five groups, including <50, 50-60, 60-70, 70-80, and ≥80 μg/dL. Deaths were obtained by linkage to National Death Index up to December 31, 2019. Cox proportional hazards models were used to estimate the associations between serum retinol and all-cause mortality. During the follow-up, 993 participants with prediabetes died and 874 participants with diabetes died. There were U-shaped associations between serum retinol and mortality among participants with prediabetes and diabetes, separately. Among participants with prediabetes, compared to serum retinol levels of 50-60 μg/dL, the hazard ratio (HR) (95% confidence interval [CI]) of mortality was 1.40 (95% CI 1.11 to 1.76) and 1.26 (95% CI 1.00 to 1.57) for serum retinol <50 or ≥80 μg/dL, respectively. Among participants with diabetes, compared to serum retinol levels of 50-60 μg/dL, the hazard ratio (HR) (95% confidence interval [CI]) of mortality was 1.25 (95% CI 0.96 to 1.62) and 1.21 (95% CI 0.91 to 1.62) for serum retinol <50 or ≥80 μg/dL, respectively. The U-shaped associations between serum retinol and mortality still existed among participants aged ≥60 years with prediabetes or diabetes but were not statistically significant among those aged 40-59 years with prediabetes or diabetes. In conclusion, both low and excessive serum retinol tended to be with higher mortality risk among people with abnormal blood glucose.

Ecotoxicity effect of aspirin on the larvae of Musca domestica through retinol metabolism

Aspirin is a widely used multi-efficiency pharmaceutical, and its environmental residues are frequently detected. However, limited information is available on its effects on the development of the public health pest and saprophytic insect Musca domestica. In this study, it was demonstrated that aspirin inhibits the larval growth of house flies in a concentration-dependent manner. Microbiome analysis indicated that the composition of larval intestinal bacteria was influenced by aspirin but not greatly. The dominant bacterial genus in the aspirin group was still Klebsiella, as in the control group. Transcriptome sequencing and gene set enrichment analysis showed that retinol metabolism was activated after aspirin treatment. High performance liquid chromatography indicated that the content of retinol in larvae was decreased and that of retinoic acid was increased. The addition of β-carotene, a precursor substance of retinol, in feeding promotes larval development and alleviates the inhibitory effect caused by aspirin. In contrast, retinoic acid delayed the larval development of house flies as well as aspirin. Gene expression analysis after aspirin exposure demonstrated that genes involved in the transformation from retinol to retinoic acid were upregulated. Overall, aspirin exposure impairs larval development by activating retinol metabolism in house flies and can be utilized as an effective pesticide. This work uncovers the mechanism underlying the larval development inhibition induced by aspirin in terms of metabolism and genetics, and provides novel functional exploration of a traditional drug for pest management.

Adipocyte retinoic acid receptor α prevents obesity and steatohepatitis by regulating energy expenditure and lipogenesis

OBJECTIVE

The adipose tissue-liver axis is a major regulator of the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Retinoic acid signaling plays an important role in development and metabolism. However, little is known about the role of adipose retinoic acid signaling in the development of obesity-associated NAFLD. In this work, the aim was to investigate whether and how retinoic acid receptor alpha (RARα) regulated the development of obesity and NAFLD.

METHODS

RARα expression in adipose tissue of db/db or ob/ob mice was determined. Rarαfl/fl mice and adipocyte-specific Rarα-/- (RarαAdi-/- ) mice were fed a chow diet for 1 year or high-fat diet (HFD) for 20 weeks. Primary adipocytes and primary hepatocytes were co-cultured. Metabolic regulation and inflammatory response were characterized.

RESULTS

RARα expression was reduced in adipose tissue of db/db or ob/ob mice. RarαAdi-/- mice had increased obesity and steatohepatitis (NASH) when fed a chow diet or HFD. Loss of adipocyte RARα induced lipogenesis and inflammation in adipose tissue and the liver and reduced thermogenesis. In the co-culture studies, loss of RARα in adipocytes induced inflammatory and lipogenic programs in hepatocytes.

CONCLUSIONS

The data demonstrate that RARα in adipocytes prevents obesity and NASH via inhibiting lipogenesis and inflammation and inducing energy expenditure.

Vitamin A: too good to be bad?

Vitamin A is a micronutrient important for vision, cell growth, reproduction and immunity. Both deficiency and excess consuming of vitamin A cause severe health consequences. Although discovered as the first lipophilic vitamin already more than a century ago and the definition of precise biological roles of vitamin A in the setting of health and disease, there are still many unresolved issues related to that vitamin. Prototypically, the liver that plays a key role in the storage, metabolism and homeostasis of vitamin A critically responds to the vitamin A status. Acute and chronic excess vitamin A is associated with liver damage and fibrosis, while also hypovitaminosis A is associated with alterations in liver morphology and function. Hepatic stellate cells are the main storage site of vitamin A. These cells have multiple physiological roles from balancing retinol content of the body to mediating inflammatory responses in the liver. Strikingly, different animal disease models also respond to vitamin A statuses differently or even opposing. In this review, we discuss some of these controversial issues in understanding vitamin A biology. More studies of the interactions of vitamin A with animal genomes and epigenetic settings are anticipated in the future.

Association of nonalcoholic fatty liver disease and liver fibrosis detected by transient elastography with serum retinol in American adults

Background and objective

Retinol is a precursor of vitamin A, which is metabolized and maintained in the liver and is involved in the pathogenesis of the nonalcoholic fatty liver disease (NAFLD) and liver fibrosis. The relationship between NAFLD and liver fibrosis with serum retinol levels remains insufficient and inconclusive. Our study aimed to investigate the correlation between NAFLD, fibrosis, and serum retinol levels in American adults.

Methods

A cross-sectional analysis was conducted using information from the 2017-2018 cycle of the National Health and Nutrition Examination Survey (NHANES). The exposure factors were NAFLD and liver fibrosis status detected using transient elastography (TE), and the outcome was serum retinol levels. Weighted multivariate regressions were established to assess the correlation between NAFLD and liver fibrosis and serum retinol levels. Subgroup analyses were also performed.

Results

This study included 3,537 participants. Compared to the group without NAFLD, NAFLD was positively correlated with serum retinol levels (β = 1.28, 95% CI: 0.19, 2.37). In the subgroup analysis, a positive correlation between NAFLD and serum retinol levels was found in people aged < 60 years, Mexican Americans, and those with a body mass index (BMI) < 25. On the contrary, compared to the group without liver fibrosis, there was a significant negative association between liver fibrosis and serum retinol (β = -3.46, 95% CI: -5.16, -1.75), especially in people aged < 60 years, non-Hispanic white/black individuals, and people with a BMI ≥ 25.

Conclusion

Our study suggests that NAFLD status may be positively associated with serum retinol levels in adult patients, and liver fibrosis may be negatively associated with serum retinol levels. Further studies are required to examine the associations found in our study.

Replenishment of vitamin A for 7 days partially restored hepatic gene expressions altered by its deficiency in rats

We investigated the effects of vitamin A (VA) status on metabolism of Zucker rats with different genders and genotypes, and of short-term refeeding of a VA sufficient (VAS) diet on VA deficient (VAD) animals. First, male and female Zucker lean (ZL) and fatty (ZF) rats at weaning were fed a VAD or VAS diet for 8 weeks. Second, male VAD ZL rats were fed a VAS diet for 3 (VAD-VAS3d) or 7 (VAD-VAS7d) days. The body weight (BW), blood parameters, and hepatic expressions of genes for metabolism were determined. VA deficiency reduced BW gain in ZL and ZF rats of either gender. VAD ZL rats had lower plasma glucose, insulin, and leptin levels than VAS ZL rats. VAD-VAS3d and VAD-VAS7d rats had higher plasma glucose, insulin, and leptin levels than that in the VAD rats. The hepatic mRNA levels of Gck, Cyp26a1, Srebp-1c, Igf1, Rarb, Rxra, Rxrg, Pparg, and Ppard were lowered by VA deficiency. Refeeding of the VAS diet for 3 days restored the Gck and Cyp26a1 expressions, and for 7 days restored the Gck, Cyp26a1, Igf1, and Rxrb expressions significantly. The 7-day VA replenishment partially restored the hepatic gene expressions and metabolic changes in VAD ZL rats.

Impact of dietary vitamin A deficiency on body physiology and liver metabolism of Wistar rats

Background: Studies suggest that vitamin A deficiency (VAD) can cause night blindness or xerophthalmia, hepatic and metabolic changes in the blood. Aim: Therefore, this work aimed to stablish a model of hypovitaminosis A in rats and to evaluate the effects of vitamin A deficiency on metabolic and oxidative parameters in the liver of rats. Methods: Male (n = 19), Wistar, rats (21-day-old) weighing 50g, divided into two experimental groups: Control Group (C), received AIN 93G diet and Vitamin A Deficiency Group (VAD), received AIN 93G vitamin A-free diet for 45 days. In this work, the parameters analyzed were: body mass, food and water intake, biochemical aspects in the blood, lipids and glycogen content, lipid peroxidation, carbonyl proteins and catalase activity in the liver. Results: In the VAD group, final body mass (9%), liver mass (28%), glycemia (14%), Total -cholesterol (17%), HDL -cholesterol (31%) and VLDL -cholesterol (30%) showed reduced (p < 0.05). The liver lipid (64%) and glyceride-fatty acid (74%) contents were higher in the VAD group. The carbonyl proteins in liver were increased by 171% (p < 0.05). Conclusion: In summary, these results suggest that the absence of vitamin A from the diet was effective in inducing characteristics of hypovitaminosis A in rats. This way, can be used for studies related to glucose and lipid metabolism.

Reduction in the Dietary VA Status Prevents Type 2 Diabetes and Obesity in Zucker Diabetic Fatty Rats

We hypothesized that the vitamin A (VA) status regulates type 2 diabetes (T2D) development in Zucker diabetic fatty (ZDF) rats. Zucker Lean and ZDF rats at weaning were fed a VA deficient with basal fat (VAD-BF, no VA and 22.1% fat energy), VA marginal with BF (VAM-BF, 0.35 mg retinyl palmitate (RP)/kg), VA sufficient with BF (VAS-BF, 4.0 mg RP/kg), VAD with high fat (VAD-HF, 60% fat energy), VAM-HF or VAS-HF diet for 8 weeks, including an oral glucose tolerance test (OGTT) at week 7.5. The hepatic mRNA and proteins levels were determined using real-time PCR and Western blot, respectively. The VAD-BF/HF and VAM-BF/HF diets prevented peripheral hyperglycemia and attenuated obesity in ZDF rats, which occurred in the presence of the VAS-BF/HF diets. This lowered VA status reduced venous blood hyperglycemia, hyperinsulinemia and hyperlipidemia, and improved OGTT and homeostasis model assessment for insulin resistance results in ZDF rats. The expression levels of key hepatic genes for glucose and fat metabolism were regulated by VA status and dietary fat contents. An interaction between VA and HF condition was also observed. We conclude that the reduction in the dietary VA status in both BF and HF conditions prevents T2D and obesity in ZDF rats.

Association between Serum Vitamin A, Blood Lipid Level and Dyslipidemia among Chinese Children and Adolescents

Background: To study the relationship between serum vitamin A (VA) level and blood lipid profiles in children and adolescents aged 6−18 years, as well as the effect of VA on dyslipidemia. Methods: The project adopted a multistage stratified cluster sampling method. The Food Frequency Questionnaire (FFQ) was used to obtain dietary factors data. Blood samples of subjects were taken via venipuncture. Generalized linear models were used to explore the correlation be-tween VA and biochemical indicators, as well as stratified and inter-actions analysis to explore the influence of confounders on these relationships. Generalized linear models were constructed to explore the association between VA and blood lipids. Restricted cubic splines were used to characterize dose−response associations between serum VA and dyslipidemia based on logistic regression. Results: Serum VA was positively correlated with TC, TG and HDL-C (p < 0.05), but these associations were influenced by age (p < 0.05). The adjusted odds ratio (OR) values of VA for hypercho lesterolemia, hypertriglyceridemia, mixed hyperlipidemia and low high-density lipoprotein cholesterolemia were 3.283, 3.239, 5.219 and 0.346, respectively (p < 0.01). Meanwhile, significant age interactions affected the relationship between VA and TC, as well as TG and LDL-C (p < 0.01). Conclusion: Serum VA was positively correlated with blood lipids, but these associations were influenced by age. VA was a risk factor for dyslipidemias, such as hypercholesterolemia, hypertriglyceridemia and mixed hyperlipidemia, but was a protective factor for low high-density lipoprotein cholesterolemia.

The Interactions of Insulin and Vitamin A Signaling Systems for the Regulation of Hepatic Glucose and Lipid Metabolism

The pandemics of obesity and type 2 diabetes have become a concern of public health. Nutrition plays a key role in these concerns. Insulin as an anabolic hormonal was discovered exactly 100 years ago due to its activity in controlling blood glucose level. Vitamin A (VA), a lipophilic micronutrient, has been shown to regulate glucose and fat metabolism. VA's physiological roles are mainly mediated by its metabolite, retinoic acid (RA), which activates retinoic acid receptors (RARs) and retinoid X receptors (RXRs), which are two transcription factors. The VA status and activations of RARs and RXRs by RA and synthetic agonists have shown to affect the glucose and lipid metabolism in animal models. Both insulin and RA signaling systems regulate the expression levels of genes involved in the regulation of hepatic glucose and lipid metabolism. Interactions of insulin and RA signaling systems have been observed. This review is aimed at summarizing the history of diabetes, insulin and VA signaling systems; the effects of VA status and activation of RARs and RXRs on metabolism and RAR and RXR phosphorylation; and possible interactions of insulin and RA in the regulation of hepatic genes for glucose and lipid metabolism. In addition, some future research perspectives for understanding of nutrient and hormone interactions are provided.

Roles of vitamin A in the regulation of fatty acid synthesis

Dietary macronutrients and micronutrients play important roles in human health. On the other hand, the excessive energy derived from food is stored in the form of triacylglycerol. A variety of dietary and hormonal factors affect this process through the regulation of the activities and expression levels of those key player enzymes involved in fatty acid biosynthesis such as acetyl-CoA carboxylase, fatty acid synthase, fatty acid elongases, and desaturases. As a micronutrient, vitamin A is essential for the health of humans. Recently, vitamin A has been shown to play a role in the regulation of glucose and lipid metabolism. This review summarizes recent research progresses about the roles of vitamin A in fatty acid synthesis. It focuses on the effects of vitamin A on the activities and expression levels of mRNA and proteins of key enzymes for fatty acid synthesis in vitro and in vivo. It appears that vitamin A status and its signaling pathway regulate the expression levels of enzymes involved in fatty acid synthesis. Future research directions are also discussed.

Dynamics of Serum Retinol and Alpha-Tocopherol Levels According to Non-Alcoholic Fatty Liver Disease Status

The available data on the association between micronutrients in the blood and non-alcoholic fatty liver disease (NAFLD) are limited. To investigate the clinical implications of this relationship, we sought to identify the difference in the serum levels of vitamins A and E according to NAFLD status using data from the seventh Korea National Health and Nutrition Examination Survey. In this cross-sectional study of the Korean population, NAFLD and its severity were defined using prediction models. Differences in the prevalence and severity of NAFLD were analyzed according to serum retinol (vitamin A) and alpha (α)-tocopherol (vitamin E) levels. Serum levels of retinol and α-tocopherol were positively correlated with the prevalence of NAFLD. In most prediction models of the NAFLD subjects, serum retinol deficiency was significantly correlated with advanced fibrosis, while serum α-tocopherol levels did not differ between individuals with or without advanced fibrosis. Similar trends were also noted with cholesterol-adjusted levels of α-tocopherol. In summary, while circulating concentrations of retinol and α-tocopherol were positively associated with the presence of NAFLD, advanced liver fibrosis was only correlated with serum retinol levels. Our findings could provide insight into NAFLD patient care at a micronutrient level.

Effects of different fatty acids on BRL3A rat liver cell damage

To evaluate the effects of fatty acids on endoplasmic reticulum (ER) stress, oxidative stress, and lipid damage. We treated BRL3A rat liver cells with, linoleic (LA), linolenic, oleic (OA), palmitic (PA), palmitoleic (POA), or stearic (SA) acid for 12 hr. The characteristics of cell lipid deposition, oxidative stress indexes, ER stress markers, nuclear factor κB p65 (NF-κB p65), lipid synthesis and transport regulators, and cholesterol metabolism regulators were analyzed. Endoplasmic chaperones like glucose-regulated protein 78, CCAAT-enhancer-binding protein, NF-κB p65, hydrogen peroxide, and malonaldehyde in PA- and SA-treated cells were significantly higher than in other treated cells. Deposition of fatty acids especially LA and POA were significantly increased than in other treated cells. De novo lipogenesis regulators sterol regulatory element-binding protein 1c, fatty acid synthase, and acetyl-coenzyme A carboxylase 1 (ACC1) expression were significantly increased in all fatty acid stimulation groups, and PA- and SA-treated cells showed lower p-ACC1 expression and higher scd1 expression than other fatty acid groups. Very low-density lipoprotein synthesis and apolipoprotein B100 expression in free fatty acids treated cells were significantly lower than control. PA, SA, OA, and POA had shown significantly increased cholesterol synthesis than other treated cells. PA and SA showed the lower synthesis of cytochrome P7A1 and total bile acids than other fatty acids treated cells. Excess of saturated fatty acids led to severe ER and oxidative stress. Excess unsaturated fatty acids led to increased lipid deposition in cultured hepatocytes. A balanced fatty acid intake is needed to maintain lipid homeostasis.

Vitamin A status affects weight gain and hepatic glucose metabolism in rats fed a high-fat diet

Whether vitamin A (VA) has a role in the development of metabolic abnormalities associated with intake of a high-fat diet (HFD) is unclear. Sprague-Dawley rats after weaning were fed an isocaloric VA sufficient HFD (VAS-HFD) or a VA deficient HFD (VAD-HFD) for 8 weeks. Body mass, food intake, liver and adipose tissue mass, and the hepatic expression levels of key proteins for metabolism were determined. VAD-HFD rats had lower body, liver, and epididymal fat mass than VAS-HFD rats. VAD-HFD rats had lower hepatic protein expression levels of cytochrome P450 26A1, glucokinase, and phosphoenolpyruvate carboxykinase than VAS-HFD rats. VAD-HFD rats had higher protein levels of glycogen synthase kinase (GSK)-3α and lower levels of GSK-3β, but not glycogen synthase, than VAS-HFD rats. VAD-HFD rats had higher hepatic levels of insulin receptor substrate-1 (IRS-1), insulin receptor β-subunit, mitogen-activated protein kinase proteins, and peroxisome proliferator-activated receptor-gamma coactivator 1α mRNA, and lower level of IRS-2 protein than VAS-HFD rats. These results indicate that in a HFD setting, VA deficiency attenuated HFD-induced obesity, and VA status altered the expression levels of proteins required for glucose metabolism and insulin signaling. We conclude that VA status contributes to the regulation of hepatic glucose and lipid metabolism in a HFD setting, and may regulate hepatic carbohydrate metabolism.

High-Fat Diet Elevates Liver Docosahexaenoic Acid Possibly through Over-Expression of Very Long-Chain Fatty Acid Elongase 2 in C57BL/6J Mice

The liver is the main site of lipid metabolism and vitamin A storage. Dietary factors are known to affect liver function, thereby leading to metabolic abnormalities. Here, we assessed the impact of long-term feeding of a high-fat diet on hepatic vitamin A status and lipid metabolism. For this purpose, 14 male and 14 female 35-day-old mice (strain C57BL/6J) were each divided into 2 groups of 7 animals and fed either a stock diet or a high-fat (HF) diet for 26 weeks. In addition to increased body weight/weight gain, the HF diet induced hypertriglyceridemia in both (p < 0.01). However, liver triglyceride levels were comparable among groups, which could be partly explained by unaltered expression of various lipogenic pathway proteins such as sterol regulatory element binding protein 1 (SREBP1), fatty acid synthase (FAS), microsomal triglyceride transfer protein (MTTP), and glycerol 3-phosphate acyl transferase (GPAT). On the other hand, hepatic retinol stores increased significantly in both sexes, whereas males displayed elevated circulatory retinol levels. Notably, long-term feeding of a HF diet elevated n-3 polyunsaturated fatty acid (PUFA) and docosahexaenoic acid (DHA, C22:6) levels in the liver (p ≤ 0.001), which is in line with the over-expression of very long-chain fatty acid elongase 2 (ELOVL2) protein in both sexes of mice (p < 0.01). In conclusion, very long-term feeding of a HF diet increased hepatic retinol stores and induced hypertriglyceridemia. However, it had no effect on hepatic triglyceride accumulation, possibly due to increased DHA levels arising from the ELOVL2-mediated elongation pathway.

Contribution of Hepatic Retinaldehyde Dehydrogenase Induction to Impairment of Glucose Metabolism by High-Fat-Diet Feeding in C57BL/6J Mice

Obesity and insulin resistance are associated with overexpression of retinaldehyde dehydrogenase 1 (RALDH1). We aimed to investigate the roles of hepatic RALDH1 induction in glucose metabolism impairment using mice fed with high-fat-diet (HFD). Mice were fed with HFD for 8 weeks and treated with RALDH inhibitor citral for another 4 weeks. Oral glucose tolerance test (OGTT), pyruvate tolerance test (PTT) and insulin tolerance test were performed. Expressions of phosphoenolpyruvate carboxykinase 1 (PCK1), glucokinase (GCK) and RALDH1 were measured. Therapeutic effects of citral were also documented in diabetic rats. Effects of retinaldehyde on PCK1 and GCK expressions were examined in rat primary hepatocytes and HepG2 cells. The results showed that HFD mice were characterized by hyperlipidaemia and insulin resistance, accompanied by significantly increased RALDH1 activity and expression. Citral (10 and 50 mg/kg) ameliorated HFD-induced hyperlipidaemia and insulin resistance, as demonstrated by the improved fasting glucose, insulin levels and lipid profiles. OGTT and PTT demonstrated that citral reversed HFD-induced glucose disposal impairment and glucose production enhancement. Citral also reversed the increased PCK1 expression and decreased GCK expression by HFD. Citral therapeutic effects were reconfirmed in diabetic rats. In vitro data indicated that retinaldehyde had the strongest PCK1 induction in primary hepatocytes of diabetic rats compared with HFD rats and control rats, in line with the increased RALDH1 expression. Citral reversed the retinaldehyde-induced PCK1 expression in primary rat hepatocytes and HepG2 cells. In conclusion, RALDH1 induction impaired glucose metabolism partly via modulating PCK1 and GCK expressions. Citral improved glucose metabolism through inhibiting RALDH activity.

Reduced mRNA and Protein Expression Levels of Tet Methylcytosine Dioxygenase 3 in Endothelial Progenitor Cells of Patients of Type 2 Diabetes With Peripheral Artery Disease

Endothelial progenitor cells (EPCs) with immunological properties repair microvasculature to prevent the complications in patients with diabetes. Epigenetic changes such as DNA methylation alter the functions of cells. Tet methylcytosine dioxygenases (TETs) are enzymes responsible for the demethylation of cytosine on genomic DNA in cells. We hypothesized that EPCs of diabetic patients with peripheral artery disease (D-PAD) might have altered expression levels of TETs. Subjects who were non-diabetic (ND, n = 22), with diabetes only (D, n = 29) and with D-PAD (n = 22) were recruited for the collection of EPCs, which were isolated and subjected to analysis. The mRNA and protein expression levels of TET1, TET2, and TET3 were determined using real-time PCR and immunoblot, respectively. The TET1 mRNA expression level in ND group was lower than that in the D and D-PAD groups. The TET3 mRNA level in the ND group was higher than that in the D group, which was higher than that in the D-PAD group. The TET1 protein level in the D-PAD group, but not the D group, was higher than that in the ND group. The TET2 protein level in the D-PAD group, but not the D group, was lower than that in the ND group. The TET3 protein level in the ND group was higher than that in the D group, which was higher than that in the D-PAD group, which is the lowest among the three groups. The changes of TETs protein levels were due to the alterations of their transcripts. These probably lead to epigenetic changes, which may be responsible for the reductions of EPCs numbers and functions in patients with the D-PAD. The expression pattern of TET3 mRNA and TET3 protein in EPCs may be a biomarker of angiopathy in diabetic patients.

Vitamin A status affects the plasma parameters and regulation of hepatic genes in streptozotocin-induced diabetic rats

Vitamin A (VA) status regulates metabolism in rats. Whether VA status and availability of retinoic acid (RA) contribute to the insulin-regulated hepatic gene expression remains to be determined. Zucker lean rats with VA sufficient (VAS) or VA deficient (VAD) status were treated with streptozotocin (STZ) to induce insulin-dependent diabetes. They were treated with saline (STZ-VAS-C or STZ-VAD-C), RA (STZ-VAS-RA or STZ-VAD-RA), insulin (STZ-VAS-INS or STZ-VAD-INS), or insulin + RA (STZ-VAS-INS + RA or STZ-VAD-INS + RA) for 3 h. Insulin and insulin + RA treatments reduced tail tip blood glucose, raised plasma insulin and suppressed plasma β-hydroxybutyrate levels in both STZ-VAD and STZ-VAS rats. STZ-VAD-INS and STZ-VAD-INS + RA rats had lower plasma glucose levels than STZ-VAD-C rats had. STZ-VAD-INS and STZ-VAD-INS + RA rats had higher plasma leptin level and lower glucagon level than STZ-VAD-C rats did. Insulin treatment induced Gck, Srebp-1c and Fas and suppressed Pck1 expression levels in the liver of STZ-VAS and STZ-VAD rats. Interestingly, insulin treatment inhibited Cyp26a1 expression in STZ-VAD, but not STZ-VAS rats, whereas RA treatment induced it in both. RA treatment induced Gck expression only in STZ-VAD rats. Insulin + RA treatment further induced the Cyp26a1 and Gck expressions in STZ-VAD rats. The Srebp-1c expression levels of STZ-VAD-INS and STZ-VAD-INS + RA rats were higher than that of STZ-VAS-INS and STZ-VAS-INS + RA rats. The changes of Gck mRNA and glucokinase protein were consistent. In STZ-induced diabetic rats, VA is not required for insulin-regulated Gck, Srebp-1c, Fas and Pck1 expression. However, VA status altered responses of certain genes (Cyp26a1 and Srebp-1c) to insulin treatment.

Carrot juice ingestion attenuates high fructose-induced circulatory pro-inflammatory mediators in weanling Wistar rats

BACKGROUND

Adipose tissue, an endocrine organ, plays a vital role not only in energy homeostasis, but also in the development and/or progression of various metabolic diseases, such as insulin resistance, type 2 diabetes and non-alcoholic fatty liver disease (NAFLD), via several factors and mechanisms, including inflammation. This study tested, whether carrot juice administration affected the adipose tissue development and its inflammatory status in a high fructose diet-induced rat model. For this purpose, male weanling Wistar rats were divided into four groups and fed either control or high fructose diet of AIN-93G composition with or without carrot juice ingestion for an 8 week period.

RESULTS

Administration of carrot juice did not affect the adiposity and cell size of visceral fat depot; retroperitoneal white adipose tissue (RPWAT), which was corroborated with unaltered expression of genes involved in adipogenic and lipogenic pathways. However, it significantly reduced the high fructose diet-induced elevation of plasma free fatty acid (FFA) (P ≤ 0.05), macrophage chemoattractant protein 1 (MCP1) (P ≤ 0.01) and high sensitive C-reactive protein (hsCRP) (P ≤ 0.05) levels.

CONCLUSION

Carrot juice administration attenuated the high fructose diet-induced elevation of levels of circulatory FFA and pro-inflammatory mediators; MCP1 and hsCRP without affecting the adiposity and cell size of visceral fat depot; RPWAT. © 2016 Society of Chemical Industry.

Transcriptome Analysis Reveals that Vitamin A Metabolism in the Liver Affects Feed Efficiency in Pigs

Feed efficiency (FE) is essential for pig production. In this study, 300 significantly differentially expressed (DE) transcripts, including 232 annotated genes, 28 cis-natural antisense transcripts (cis-NATs), and 40 long noncoding RNAs (lncRNAs), were identified between the liver of Yorkshire pigs with extremely high and low FE. Among these transcripts, 25 DE lncRNAs were significantly correlated with 125 DE annotated genes at a transcriptional level. These DE genes were enriched primarily in vitamin A (VA), fatty acid, and steroid hormone metabolism. VA metabolism is regulated by energy status, and active derivatives of VA metabolism can regulate fatty acid and steroid hormones metabolism. The key genes of VA metabolism (CYP1A1, ALDH1A2, and RDH16), fatty acid biosynthesis (FASN, SCD, CYP2J2, and ANKRD23), and steroid hormone metabolism (CYP1A1, HSD17B2, and UGT2B4) were significantly upregulated in the liver of high-FE pigs. Previous study with the same samples indicated that the mitochondrial function and energy expenditure were reduced in the muscle tissue of high-FE pigs. In conclusion, VA metabolism in liver tissues plays important roles in the regulation of FE in pigs by affecting energy metabolism, which may mediate fatty acid biosynthesis and steroid hormone metabolism. Furthermore, our results identified novel transcripts, such as cis-NATs and lncRNAs, which are also involved in the regulation of FE in pigs.

Vitamin A status and its metabolism contribute to the regulation of hepatic genes during the cycle of fasting and refeeding in rats

Vitamin A (VA) status and its metabolism affect hepatic metabolic homeostasis. We investigated if VA status and metabolism contribute to energy metabolism and expression of hepatic genes in the cycle of fasting and refeeding. Zucker lean rats with VA sufficient (VAS) or VA deficient (VAD) status were respectively grouped as: ad libitum (VAS-AD or VAD-AD), 48-h fasted (VAS-Fasted or VAD-Fasted), 48-h fasted and refed a VAS diet (VAS-Refed-VAS or VAD-Refed-VAS), or refed a VAD diet (VAS-Refed-VAD or VAD-Refed-VAD) for 6 h. Respiratory exchange ratio (RER) of rats fed the VAS or VAD diet was monitored for 6 weeks. From week four, rats fed the VAS diet had higher RER than those fed the VAD diet. VAS-Refed rats had higher plasma levels of glucose, triglyceride, insulin and leptin than VAD-Refed rats. The mRNA and protein levels of hepatic genes for fuel metabolism in the fasting and refeeding cycle were determined using real-time polymerase chain reaction and immunoblot, respectively. The mRNA levels of glucokinase (Gck), sterol regulatory element-binding protein 1c (Srebp-1c), and fatty acid synthase (Fas) were lowered in VAS-Fasted and VAD-Fasted rats, and increased in VAS-Refed-VAS, VAS-Refed-VAD and VAD-Refed-VAS, but not VAD-Refed-VAD, rats. The ACL and FAS protein levels only dropped in VAS-Fasted rats and increased in VAS-Refed-VAS rats. The GK protein level decreased only in VAS-Fasted rats, and increased in VAS-Refed-VAS, VAS-Refed-VAD and VAD-Refed-VAS (but not VAD-Refed-VAD) rats. We conclude that VA status and its metabolism in the fasting and refeeding cycle contribute to the regulation of hepatic gene expression in rats.

Transcriptional Factors Mediating Retinoic Acid Signals in the Control of Energy Metabolism

Retinoic acid (RA), an active metabolite of vitamin A (VA), is important for many physiological processes including energy metabolism. This is mainly achieved through RA-regulated gene expression in metabolically active cells. RA regulates gene expression mainly through the activation of two subfamilies in the nuclear receptor superfamily, retinoic acid receptors (RARs) and retinoid X receptors (RXRs). RAR/RXR heterodimers or RXR/RXR homodimers bind to RA response element in the promoters of RA target genes and regulate their expressions upon ligand binding. The development of metabolic diseases such as obesity and type 2 diabetes is often associated with profound changes in the expressions of genes involved in glucose and lipid metabolism in metabolically active cells. RA regulates some of these gene expressions. Recently, in vivo and in vitro studies have demonstrated that status and metabolism of VA regulate macronutrient metabolism. Some studies have shown that, in addition to RARs and RXRs, hepatocyte nuclear factor 4α, chicken ovalbumin upstream promoter-transcription factor II, and peroxisome proliferator activated receptor β/δ may function as transcriptional factors mediating RA response. Herein, we summarize current progresses regarding the VA metabolism and the role of nuclear receptors in mediating RA signals, with an emphasis on their implication in energy metabolism.

Whole genome transcript profiling of drug induced steatosis in rats reveals a gene signature predictive of outcome

Drug induced steatosis (DIS) is characterised by excess triglyceride accumulation in the form of lipid droplets (LD) in liver cells. To explore mechanisms underlying DIS we interrogated the publically available microarray data from the Japanese Toxicogenomics Project (TGP) to study comprehensively whole genome gene expression changes in the liver of treated rats. For this purpose a total of 17 and 12 drugs which are diverse in molecular structure and mode of action were considered based on their ability to cause either steatosis or phospholipidosis, respectively, while 7 drugs served as negative controls. In our efforts we focused on 200 genes which are considered to be mechanistically relevant in the process of lipid droplet biogenesis in hepatocytes as recently published (Sahini and Borlak, 2014). Based on mechanistic considerations we identified 19 genes which displayed dose dependent responses while 10 genes showed time dependency. Importantly, the present study defined 9 genes (ANGPTL4, FABP7, FADS1, FGF21, GOT1, LDLR, GK, STAT3, and PKLR) as signature genes to predict DIS. Moreover, cross tabulation revealed 9 genes to be regulated ≥10 times amongst the various conditions and included genes linked to glucose metabolism, lipid transport and lipogenesis as well as signalling events. Additionally, a comparison between drugs causing phospholipidosis and/or steatosis revealed 26 genes to be regulated in common including 4 signature genes to predict DIS (PKLR, GK, FABP7 and FADS1). Furthermore, a comparison between in vivo single dose (3, 6, 9 and 24 h) and findings from rat hepatocyte studies (2 h, 8 h, 24 h) identified 10 genes which are regulated in common and contained 2 DIS signature genes (FABP7, FGF21). Altogether, our studies provide comprehensive information on mechanistically linked gene expression changes of a range of drugs causing steatosis and phospholipidosis and encourage the screening of DIS signature genes at the preclinical stage.

Effects of individual and multiple fatty acids (palmitate, oleate and docosahaexenoic acid) on cell viability and lipid metabolism in LO2 human liver cells

This study was designed to investigate the direct effects of fatty acids (FAs) on the cell viability and the expression levels of genes involved in lipid metabolism in LO2 human liver cells. Palmitate (PA), oleate (OA) and docosahaexenoic acid (DHA) were used to represent saturated, mono-unsaturated and polyunsaturated FAs, respectively. At concentrations of ≤3.2 µg/ml, treatment with single FAs increased the viability of the LO2 cells. At FA concentrations of >3.2 µg/ml, cell viability following OA treatment was increased, but PA or DHA treatment at these concentrations reduced cell viability. Administration of mixtures of these FAs in three ratios (PA:OA:DHA = 1:2:1, 1:1:1 and 1:1:2, respectively) increased the cell viability compared with the control group. The intracellular triglyceride (TG) levels following all types of treatment were significantly increased and the accumulation of TGs was markedly increased with high doses of DHA. In addition, peroxisome proliferator-activated receptor-γ was significantly upregulated in all groups, with the exception of the 1:1:1 group at 3.2 µg/ml and the 1:1:2 group at 12.8 µg/ml. The expression levels of sterol regulatory-element binding protein‑1c, liver X receptor α and apolipoprotein C‑I were significantly reduced in all groups with the exception of the DHA‑treated group and the 1:2:1 groups at 3.2 and 12.8 µg/ml. In conclusion, these results indicate that the type, concentration and mixture ratios of FAs are all important in determining the cell viability and lipid metabolism-related gene expression in LO2 hepatocytes.

A RARE of hepatic Gck promoter interacts with RARα, HNF4α and COUP-TFII that affect retinoic acid- and insulin-induced Gck expression

The expression of hepatic glucokinase gene (Gck) is regulated by hormonal and nutritional signals. How these signals integrate to regulate the hepatic Gck expression is unclear. We have shown that the hepatic Gck expression is affected by Vitamin A status and synergistically induced by insulin and retinoids in primary rat hepatocytes. We hypothesized that this is mediated by a retinoic acid responsive element (RARE) in the hepatic Gck promoter. Here, we identified the RARE in the hepatic Gck promoter using standard molecular biology techniques. The single nucleotide mutations affecting the promoter activation by retinoic acid (RA) were also determined for detail analysis of protein and DNA interactions. We have optimized experimental conditions for performing electrophoresis mobility shift assay and demonstrated the interactions of the retinoic acid receptor α (RARα), retinoid X receptor α (RXRα), hepatocyte nuclear factor 4α (HNF4α) and chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) in the rat nuclear extract with this RARE, suggesting their roles in the regulation of Gck expression. Chromatin immunoprecipitation assays demonstrated that recombinant adenovirus-mediated overexpression of RARα, HNF4α and COUP-TFII, but not RXRα, significantly increased their occupancy in the hepatic Gck promoter in primary rat hepatocytes. Overexpression of RARα, HNF4α and COUP-TFII, but not RXRα, also affected the RA- and insulin-mediated Gck expression in primary rat hepatocytes. In summary, this hepatic Gck promoter RARE interacts with RARα, HNF4α and COUP-TFII to integrate Vitamin A and insulin signals.

The Roles of Vitamin A in the Regulation of Carbohydrate, Lipid, and Protein Metabolism

Currently, two-thirds of American adults are overweight or obese. This high prevalence of overweight/obesity negatively affects the health of the population, as obese individuals tend to develop several chronic diseases, such as type 2 diabetes and cardiovascular diseases. Due to obesity's impact on health, medical costs, and longevity, the rise in the number of obese people has become a public health concern. Both genetic and environmental/dietary factors play a role in the development of metabolic diseases. Intuitively, it seems to be obvious to link over-nutrition to the development of obesity and other metabolic diseases. However, the underlying mechanisms are still unclear. Dietary nutrients not only provide energy derived from macronutrients, but also factors such as micronutrients with regulatory roles. How micronutrients, such as vitamin A (VA; retinol), regulate macronutrient homeostasis is still an ongoing research topic. As an essential micronutrient, VA plays a key role in the general health of an individual. This review summarizes recent research progress regarding VA's role in carbohydrate, lipid, and protein metabolism. Due to the large amount of information regarding VA functions, this review focusses on metabolism in metabolic active organs and tissues. Additionally, some perspectives for future studies will be provided.

The expression of Apoc3 mRNA is regulated by HNF4α and COUP-TFII, but not acute retinoid treatments, in primary rat hepatocytes and hepatoma cells

Vitamin A status regulates obesity development, hyperlipidemia, and hepatic lipogenic gene expression in Zucker fatty (ZF) rats. The development of hyperlipidemia in acne patients treated with retinoic acid (RA) has been attributed to the induction of apolipoprotein C-III expression. To understand the role of retinoids in the development of hyperlipidemia in ZF rats, the expression levels of several selected RA-responsive genes in the liver and isolated hepatocytes from Zucker lean (ZL) and ZF rats were compared using real-time PCR. The Rarb and Srebp-1c mRNA levels are higher in the liver and isolated hepatocytes from ZF than ZL rats. The Apoc3 mRNA level is only higher in the isolated hepatocytes from ZF than ZL rats. To determine whether dynamic RA production acutely regulates Apoc3 expression, its mRNA levels in response to retinoid treatments or adenovirus-mediated overexpression of hepatocyte nuclear factor 4 alpha (HNF4α) and chicken ovalbumin upstream-transcription factor II (COUP-TFII) were analyzed. Retinoid treatments for 2-6 h did not induce the expression of Apoc3 mRNA. The overexpression of HNF4α or COUP-TFII induced or inhibited Apoc3 expression, respectively. We conclude that short-term retinoid treatments could not induce Apoc3 mRNA expression, which is regulated by HNF4α and COUP-TFII in hepatocytes.

Vitamin A and feeding statuses modulate the insulin-regulated gene expression in Zucker lean and fatty primary rat hepatocytes

Unattended hepatic insulin resistance predisposes individuals to dyslipidemia, type 2 diabetes and many other metabolic complications. The mechanism of hepatic insulin resistance at the gene expression level remains unrevealed. To examine the effects of vitamin A (VA), total energy intake and feeding conditions on the insulin-regulated gene expression in primary hepatocytes of Zucker lean (ZL) and fatty (ZF) rats, we analyze the expression levels of hepatic model genes in response to the treatments of insulin and retinoic acid (RA). We report that the insulin- and RA-regulated glucokinase, sterol regulatory element-binding protein-1c and cytosolic form of phosphoenolpyruvate carboxykinase expressions are impaired in hepatocytes of ZF rats fed chow or a VA sufficient (VAS) diet ad libitum. The impairments are partially corrected when ZF rats are fed a VA deficient (VAD) diet ad libitum or pair-fed a VAS diet to the intake of their VAD counterparts in non-fasting conditions. Interestingly in the pair-fed ZL and ZF rats, transient overeating on the last day of pair-feeding regimen changes the expression levels of some VA catabolic genes, and impairs the insulin- and RA-regulated gene expression in hepatocytes. These results demonstrate that VA and feeding statuses modulate the hepatic insulin sensitivity at the gene expression level.

Factors affecting insulin-regulated hepatic gene expression

Obesity has become a major concern of public health. A common feature of obesity and related metabolic disorders such as noninsulin-dependent diabetes mellitus is insulin resistance, wherein a given amount of insulin produces less than normal physiological responses. Insulin controls hepatic glucose and fatty acid metabolism, at least in part, via the regulation of gene expression. When the liver is insulin-sensitive, insulin can stimulate the expression of genes for fatty acid synthesis and suppress those for gluconeogenesis. When the liver becomes insulin-resistant, the insulin-mediated suppression of gluconeogenic gene expression is lost, whereas the induction of fatty acid synthetic gene expression remains intact. In the past two decades, the mechanisms of insulin-regulated hepatic gene expression have been studied extensively and many components of insulin signal transduction pathways have been identified. Factors that alter these pathways, and the insulin-regulated hepatic gene expression, have been revealed and the underlying mechanisms have been proposed. This chapter summarizes the recent progresses in our understanding of the effects of dietary factors, drugs, bioactive compounds, hormones, and cytokines on insulin-regulated hepatic gene expression. Given the large amount of information and progresses regarding the roles of insulin, this chapter focuses on findings in the liver and hepatocytes and not those described for other tissues and cells. Typical insulin-regulated hepatic genes, such as insulin-induced glucokinase and sterol regulatory element-binding protein-1c and insulin-suppressed cytosolic phosphoenolpyruvate carboxyl kinase and insulin-like growth factor-binding protein 1, are used as examples to discuss the mechanisms such as insulin regulatory element-mediated transcriptional regulation. We also propose the potential mechanisms by which these factors affect insulin-regulated hepatic gene expression and discuss potential future directions of the area of research.

Moderate vitamin A supplementation in obese mice regulates tissue factor and cytokine production in a sex-specific manner

Vitamin A (vitA) regulates obesity, insulin resistance, inflammation, dyslipidemia and hemostasis through its metabolites retinaldehyde (Rald) and retinoic acid (RA) produced in endogenous enzymatic reactions. Combination of at least 3 of these conditions leads to development of metabolic syndrome (Msyn) and, consequently, type 2 diabetes and/or cardiovascular disease. Although many foods are fortified with vitA, it remains unknown what conditions of Msyn are influenced by moderate dietary vitA supplementation. A family of aldehyde dehydrogenase 1 (Aldh1) enzymes is a key contributor to obesity via sex- and fat depot-specific production of RA in adipose tissue. Therefore, we studied effects of moderate vitamin A supplementation of an obesogenic high-fat (HF) diet (4 IU vitA/g and 20 IU vitA/g HF diet) on multiple conditions and mediators of Msyn in wild-type (WT, C57Bl/6) and Aldh1a1(-/-) mice. We found that mild vitamin A supplementation did not influence obesity, fat distribution, and glucose tolerance in males and females of the same genotype. In contrast, multiplex analysis of bioactive proteins in blood showed moderately increased concentrations (10-15%) of inflammatory IL-18 and MIP-1γ in vitA supplemented vs. control WT males. Marked decrease (28-31%) in concentrations of lymphotactin and tissue factor, a key protein contributing to thrombogenesis during injury, was achieved by vitA supplementation in WT females compared to control WT females. Aldh1a1 deficiency reduced obesity, insulin resistance, suppressed many pro-inflammatory cytokines, and abolished the effects of vitA supplementation seen in WT mice. Our study revealed specific inflammatory and pro-thrombotic proteins in plasma regulated by dietary vitamin A and the critical role of endogenous vitA metabolism in these processes. The sex-specific decrease of plasma tissue factor concentrations by moderate dietary vitA supplementation could potentially reduce pro-thrombotic states in obese females.

Roles of Vitamin A Metabolism in the Development of Hepatic Insulin Resistance

The increase in the number of people with obesity- and noninsulin-dependent diabetes mellitus has become a major public health concern. Insulin resistance is a common feature closely associated with human obesity and diabetes. Insulin regulates metabolism, at least in part, via the control of the expression of the hepatic genes involved in glucose and fatty acid metabolism. Insulin resistance is always associated with profound changes of the expression of hepatic genes for glucose and lipid metabolism. As an essential micronutrient, vitamin A (VA) is needed in a variety of physiological functions. The active metablite of VA, retinoic acid (RA), regulates the expression of genes through the activation of transcription factors bound to the RA-responsive elements in the promoters of RA-targeted genes. Recently, retinoids have been proposed to play roles in glucose and lipid metabolism and energy homeostasis. This paper summarizes the recent progresses in our understanding of VA metabolism in the liver and of the potential transcription factors mediating RA responses. These transcription factors are the retinoic acid receptor, the retinoid X receptor, the hepatocyte nuclear factor 4α, the chicken ovalbumin upstream promoter-transcription factor II, and the peroxisome proliferator-activated receptor β/δ. This paper also summarizes the effects of VA status and RA treatments on the glucose and lipid metabolism in vivo and the effects of retinoid treatments on the expression of insulin-regulated genes involved in the glucose and fatty acid metabolism in the primary hepatocytes. I discuss the roles of RA production in the development of insulin resistance in hepatocytes and proposes a mechanism by which RA production may contribute to hepatic insulin resistance. Given the large amount of information and progresses regarding the physiological functions of VA, this paper mainly focuses on the findings in the liver and hepatocytes and only mentions the relative findings in other tissues and cells.

SREBP: a novel therapeutic target

Sterol regulatory element-binding proteins (SREBPs) are major transcription factors regulating the biosynthesis of cholesterol, fatty acid, and triglyceride. They control the expression of crucial genes involved in lipogenesis and uptake. In this review, we summarize the processing of SREBPs and their regulation by insulin, cAMP, and vitamin A, and the relationship between miRNA and lipid metabolism. We also discuss the recent functional studies on SREBPs. These discoveries suggest that inhibition of SREBP can be a novel strategy to treat metabolic diseases, such as type II diabetes, insulin resistance, fatty liver, and atherosclerosis.

Lipophilic micronutrients and adipose tissue biology

Lipophilic micronutrients (LM) constitute a large family of molecules including several vitamins (A, D, E, K) and carotenoids. Their ability to regulate gene expression is becoming increasingly clear and constitutes an important part of nutrigenomics. Interestingly, adipose tissue is not only a main storage site for these molecules within the body, but it is also subjected to the regulatory effects of LM. Indeed, several gene regulations have been described in adipose tissue that could strongly impact its biology with respect to the modulation of adipogenesis, inflammatory status, or energy homeostasis and metabolism, among others. The repercussions in terms of health effects of such regulations in the context of obesity and associated pathologies represent an exciting and emerging field of research. The present review will focus on the regulatory effects of vitamin A, D, E and K as well as carotenoids on adipose tissue biology and physiology, notably in the context of obesity and associated disorders.