Diferential gene expression and adiposity reduction induced by ascorbic acid supplementation in a cafeteria model of obesity

Vitamin C attenuates predisposition to high-fat diet-induced metabolic dysregulation in GLUT10-deficient mouse model

Background

The development of type 2 diabetes mellitus (T2DM) is highly influenced by complex interactions between genetic and environmental (dietary and lifestyle) factors. While vitamin C (ascorbic acid, AA) has been suggested as a complementary nutritional treatment for T2DM, evidence for the significance and beneficial effects of AA in T2DM is thus far inconclusive. We suspect that clinical studies on the topic might need to account for combination of genetic and dietary factors that could influence AA effects on metabolism. In this study, we tested this general idea using a mouse model with genetic predisposition to diet-induced metabolic dysfunction. In particular, we utilized mice carrying a human orthologous GLUT10^G128E variant (GLUT10^G128E mice), which are highly sensitive to high-fat diet (HFD)-induced metabolic dysregulation. The genetic variant has high relevance to human populations, as genetic polymorphisms in glucose transporter 10 (GLUT10) are associated with a T2DM intermediate phenotype in nondiabetic population.

Results

We investigated the impacts of AA supplementation on metabolism in wild-type (WT) mice and GLUT10^G128E mice fed with a normal diet or HFD. Overall, the beneficial effects of AA on metabolism were greater in HFD-fed GLUT10^G128E mice than in HFD-fed WT mice. At early postnatal stages, AA improved the development of compromised epididymal white adipose tissue (eWAT) in GLUT10^G128E mice. In adult animals, AA supplementation attenuated the predisposition of GLUT10^G128E mice to HFD-triggered eWAT inflammation, adipokine dysregulation, ectopic fatty acid accumulation, metabolic dysregulation, and body weight gain, as compared with WT mice.

Conclusions

Taken together, our findings suggest that AA has greater beneficial effects on metabolism in HFD-fed GLUT10^G128E mice than HFD-fed WT mice. As such, AA plays an important role in supporting eWAT development and attenuating HFD-induced metabolic dysregulation in GLUT10^G128E mice. Our results suggest that proper WAT development is essential for metabolic regulation later in life. Furthermore, when considering the usage of AA as a complementary nutrition for prevention and treatment of T2DM, individual differences in genetics and dietary patterns should be taken into account.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12263-022-00713-y.

Vitamin C Inhibits the Metabolic Changes Induced by Tet1 Insufficiency Under High Fat Diet Stress

SCOPE

DNA methylation contributes to obesity, but the role of the DNA demethylase ten-eleven translocation protein 1 (Tet1) in obesity remains unclear. Vitamin C is a cofactor for the Tet family of proteins, but whether vitamin C can be used to treat obesity via Tet1 awaits clarification.

METHODS AND RESULTS

Tet1^+/+ and Tet1^+/- mice are fed a high fat diet (HFD). Higher weight gain and more severe hepatic steatosis, accompanied by reduced 5-hydromethylcytosine (5hmC) levels, are found in the white adipose tissue and liver of Tet1^+/- mice. Accumulated lipids are observed in palmitic acid or oleic acid treated primary hepatocytes derived from Tet1^+/- mice, which are rescued by Tet1 overexpression or vitamin C treatment. Bisulfite sequencing reveals higher DNA methylation levels on lipolysis related genes in the liver of Tet1^+/- mice. Notably, oral intake of vitamin C normalizes DNA methylation levels, promotes lipolysis, and decreases obesity in HFD-fed Tet1^+/- mice.

CONCLUSIONS

The results reveal a novel function of Tet1 in obesity and provide a new mechanism for the beneficial role of vitamin C in metabolic diseases through enhanced Tet1 activity.

Novel Combination of COX-2 Inhibitor and Antioxidant Therapy for Modulating Oxidative Stress Associated with Intestinal Ischemic Reperfusion Injury and Endotoxemia

Background: Intestinal ischemic reperfusion (I/R) injury is associated with a high mortality rate; this condition is also related to significant endotoxemia and systemic inflammation. The preservation of tissue perfusion and a sufficient blood flow are required to deliver nutrients and oxygen, preserve metabolic pathways, and eliminate waste products. Oxidative stress plays a fundamental role in intestinal I/R injury and leads to disruption of the mucosal barrier and necrosis, allowing the migration of endotoxins and luminal bacteria into the systemic circulation. In this study, we evaluated the beneficial effects of a cyclooxygenase (COX)-2 inhibitor—firocoxib—plus the antioxidant vitamin C in a rat model of intestinal I/R injury. Methods: We used a rat model of I/R injury in which the superior mesenteric artery was clamped for 30 min by a vascular clamp, and the animals were then allowed 1 h of reperfusion. Results: Our results show the importance of combined anti-inflammatory and antioxidant treatment for the prevention of intestinal I/R injury that leads to reduced systemic endotoxemia. We observed a significantly synergistic effect of firocoxib and vitamin C in reducing intestinal wall damage and oxidative stress, leading to a significant reduction of inflammation and endotoxemia. Conclusions: Our results indicate that this approach could be a new pharmacological protocol for intestinal colic or ischemic injury-induced endotoxemia.

Noni (Morinda citrifolia L.) wine prevents the oxidative stress and obesity in mice induced by high-fat diet

Noni (Morinda citrifolia L.) is rich in polyphenols, flavonoids, terpenoids, and iridoids. However, its bad taste and smell make noni fruit unsuitable for consumption. After fermentation, noni wine becomes free from the undesirable smell. Nevertheless, it is still unclear whether processed noni could retain its original nutrients and effects. Therefore, we conducted a series of evaluations on the nutritional composition and efficacy of noni wine. Our results showed that the polyphenol, flavonoid, and vitamin C contents in noni wine were 558.80, 234.42, and 0.30 mg/L, respectively. Our animal experiments showed that 40 ml kg^-1  day^-1 noni wine could reduce bodyweight, as well as the levels of body fat, serum triglycerides, total cholesterol, and low-density lipoprotein, while it simultaneously increased the amount of energy expenditure and activity, and improved the systemic antioxidant capacity in mice following a high-fat diet. The results of the gene expression and western blot analyses showed that 40 ml kg^-1  day^-1 noni wine could regulate the Nrf2 pathway and improve the antioxidant enzyme gene expression in mice maintained on a high-fat diet, thereby improving body lipid metabolism, reducing fatty acid synthesis, and promoting fatty acid β-oxidation. Our study indicated that drinking 40 ml kg^-1  day^-1 noni wine could effectively prevent high-fat diet-induced oxidative stress and obesity in mice. PRACTICAL APPLICATIONS: Noni fruit is rich in nutrients but its bad smell and hardship of processing make its commercialization difficult. Previous studies mainly focused on fresh noni juice and its primary processed products, while few noni products, of poor taste and low quality, are available in the market. Therefore, the fruit wine with both the nutritive values and the special flavor of noni has broad market prospects. Our work provides a valuable reference for the commercialization of noni wine.

Glucose transporter 10 modulates adipogenesis via an ascorbic acid-mediated pathway to protect mice against diet-induced metabolic dysregulation

The development of type 2 diabetes mellitus (T2DM) depends on interactions between genetic and environmental factors, and a better understanding of gene-diet interactions in T2DM will be useful for disease prediction and prevention. Ascorbic acid has been proposed to reduce the risk of T2DM. However, the links between ascorbic acid and metabolic consequences are not fully understood. Here, we report that glucose transporter 10 (GLUT10) maintains intracellular levels of ascorbic acid to promote adipogenesis, white adipose tissue (WAT) development and protect mice from high-fat diet (HFD)-induced metabolic dysregulation. We found genetic polymorphisms in SLC2A10 locus are suggestively associated with a T2DM intermediate phenotype in non-diabetic Han Taiwanese. Additionally, mice carrying an orthologous human Glut10^G128E variant (Glut10^G128E mice) with compromised GLUT10 function have reduced adipogenesis, reduced WAT development and increased susceptibility to HFD-induced metabolic dysregulation. We further demonstrate that GLUT10 is highly expressed in preadipocytes, where it regulates intracellular ascorbic acid levels and adipogenesis. In this context, GLUT10 increases ascorbic acid-dependent DNA demethylation and the expression of key adipogenic genes, Cebpa and Pparg. Together, our data show GLUT10 regulates adipogenesis via ascorbic acid-dependent DNA demethylation to benefit proper WAT development and protect mice against HFD-induced metabolic dysregulation. Our findings suggest that SLC2A10 may be an important HFD-associated susceptibility locus for T2DM.

Environmental triggers may amplify genetically determined disease susceptibility, especially for carriers of rare variants with relatively large individual effect sizes, making these polymorphisms highly informative for predicting individualized clinical risk and preventing disease. Since transitions in dietary pattern have greatly contributed to the increased prevalence of obesity and accelerated the spread of the T2DM epidemic worldwide, a better understanding of gene-diet interactions in T2DM will be useful for disease prediction and prevention. Here, we demonstrate that polymorphisms in the gene encoding GLUT10 are associated with a T2DM intermediate phenotype in non-diabetic human subjects. Additionally, mice that carry a GLUT10 rare variant have reduced WAT development and are susceptible for HFD-induced T2DM. We further demonstrate that GLUT10 is highly expressed in preadipocytes, where it regulates intracellular ascorbic acid levels and ascorbic acid-dependent DNA demethylation to control adipogenesis. Preadipocytes carrying the GLUT10 rare variant or with knockdown of GLUT10 expression have reduced the adipogenesis. Thus, we are able to conclude that GLUT10 regulates adipogenesis via ascorbic acid-dependent DNA demethylation to affect WAT development and contribute to the sensitivity of HFD-induced metabolic dysregulation.

A high-fat diet increases body fat mass and up-regulates expression of genes related to adipogenesis and inflammation in a genetically lean pig

Because of their physiological similarity to humans, pigs provide an excellent model for the study of obesity. This study evaluated diet-induced adiposity in genetically lean pigs and found that body weight and energy intake did not differ between controls and pigs fed the high-fat (HF) diet for three months. However, fat mass percentage, adipocyte size, concentrations of total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C), insulin, and leptin in plasma were significantly higher in HF pigs than in controls. The HF diet increased the expression in backfat tissue of genes responsible for cholesterol synthesis such as Insig-1 and Insig-2. Lipid metabolism-related genes including sterol regulatory element binding protein 1c (SREBP-1c), fatty acid synthase 1 (FASN1), diacylglycerol O-acyltransferase 2 (DGAT2), and fatty acid binding protein 4 (FABP4) were significantly up-regulated in backfat tissue, while the expression of proliferator-activated receptor-α (PPAR-α) and carnitine palmitoyl transferase 2 (CPT2), both involved in fatty acid oxidation, was reduced. In liver tissue, HF feeding significantly elevated the expression of SREBP-1c, FASN1, DGAT2, and hepatocyte nuclear factor-4α (HNF-4α) mRNAs. Microarray analysis further showed that the HF diet had a significant effect on the expression of 576 genes. Among these, 108 genes were related to 21 pathways, with 20 genes involved in adiposity deposition and 26 related to immune response. Our results suggest that an HF diet can induce genetically lean pigs into obesity with body fat mass expansion and adipose-related inflammation.

Ascorbic acid inhibits visceral obesity and nonalcoholic fatty liver disease by activating peroxisome proliferator-activated receptor α in high-fat-diet-fed C57BL/6J mice

BACKGROUND/OBJECTIVES

Ascorbic acid is a known cofactor in the biosynthesis of carnitine, a molecule that has an obligatory role in fatty acid oxidation. Our previous studies have demonstrated that obesity is regulated effectively through peroxisome proliferator-activated receptor α (PPARα)-mediated fatty acid β-oxidation. Thus, this study aimed to determine whether ascorbic acid can inhibit obesity and nonalcoholic fatty liver disease (NAFLD) in part through the actions of PPARα.

DESIGN

After C57BL/6J mice received a low-fat diet (LFD, 10% kcal fat), a high-fat diet (HFD, 45% kcal fat), or the same HFD supplemented with ascorbic acid (1% w/w) (HFD-AA) for 15 weeks, variables and determinants of visceral obesity and NAFLD were examined using metabolic measurements, histology, and gene expression.

RESULTS

Compared to HFD-fed obese mice, administration of HFD-AA to obese mice reduced body weight gain, visceral adipose tissue mass, and visceral adipocyte size without affecting food consumption profiles. Concomitantly, circulating ascorbic acid concentrations were significantly higher in HFD-AA mice than in HFD mice. Ascorbic acid supplementation increased the mRNA levels of PPARα and its target enzymes involved in fatty acid β-oxidation in visceral adipose tissues. Consistent with the effects of ascorbic acid on visceral obesity, ascorbic acid not only inhibited hepatic steatosis but also increased the mRNA levels of PPARα-dependent fatty acid β-oxidation genes in livers. Similarly, hepatic inflammation, fibrosis, and apoptosis were also decreased during ascorbic acid-induced inhibition of visceral obesity. In addition, serum levels of alanine aminotransferase, aspartate aminotransferase, total cholesterol, and LDL cholesterol were lower in HFD-AA-fed mice than in those of HFD-fed mice.

CONCLUSIONS

These results suggest that ascorbic acid seems to suppress HFD-induced visceral obesity and NAFLD in part through the activation of PPARα.

Association between vitamin deficiency and metabolic disorders related to obesity

Inappropriate food behavior contributes to obesity and leads to vitamin deficiency. This review discusses the nutritional status of water- and fat-soluble vitamins in obese subjects. We verified that most vitamins are deficient in obese individuals, especially the fat-soluble vitamins, folic acid, vitamin B₁₂ and vitamin C. However, some vitamins have been less evaluated in cases of obesity. The adipose tissue is considered a metabolic and endocrine organ, which in excess leads to changes in body homeostasis, as well as vitamin deficiency which can aggravate the pathological state. Therefore, the evaluation of vitamin status is of fundamental importance in obese individuals.

Adipogenic and Lipolytic Effects of Ascorbic Acid in Ovariectomized Rats

PURPOSE

Ascorbic acid has been reported to have an adipogenic effect on 3T3-L1 preadipocytes, while evidence also suggests that ascorbic acid reduces body weight in humans. In this study, we tested the effects of ascorbic acid on adipogenesis and the balance of lipid accumulation in ovariectomized rats, in addition to long-term culture of differentiated 3T3-L1 adipocytes.

MATERIALS AND METHODS

Murine 3T3-L1 fibroblasts and ovariectomized rats were treated with ascorbic acid at various time points. In vitro adipogenesis was analyzed by Oil Red O staining, and in vivo body fat was measured by a body composition analyzer using nuclear magnetic resonance.

RESULTS

When ascorbic acid was applied during an early time point in 3T3-L1 preadipocyte differentiation and after bilateral ovariectomy (OVX) in rats, adipogenesis and fat mass gain significantly increased, respectively. However, lipid accumulation in well-differentiated 3T3-L1 adipocytes showed a significant reduction when ascorbic acid was applied after differentiation (10 days after induction). Also, oral ascorbic acid administration 4 weeks after OVX in rats significantly reduced both body weight and subcutaneous fat layer. In comparison to the results of ascorbic acid, which is a well-known cofactor for an enzyme of collagen synthesis, and the antioxidant ramalin, a potent antioxidant but not a cofactor, showed only a lipolytic effect in well-differentiated 3T3-L1 adipocytes, not an adipogenic effect.

CONCLUSION

Taking these results into account, we concluded that ascorbic acid has both an adipogenic effect as a cofactor of an enzymatic process and a lipolytic effect as an antioxidant.

Differential fecal microbiota are retained in broiler chicken lines divergently selected for fatness traits

Our study combined 16S rRNA-pyrosequencing and whole genome sequencing to analyze the fecal metagenomes of the divergently selected lean (LL) and fat (FL) line chickens. Significant structural differences existed in both the phylogenic and functional metagenomes between the two chicken lines. At phylum level, the FL group had significantly less Bacteroidetes. At genus level, fourteen genera of different relative abundance were identified, with some known short-chain fatty acid producers (including Subdoligranulum, Butyricicoccus, Eubacterium, Bacteroides, Blautia) and a potentially pathogenic genus (Enterococcus). Redundancy analysis identified 190 key responsive operational taxonomic units (OTUs) that accounted for the structural differences between the phylogenic metagenome of the two groups. Four Cluster of Orthologous Group (COG) categories (Amino acid transport and metabolism, E; Nucleotide transport and metabolism, F; Coenzyme transport and metabolism, H; and Lipid transport and metabolism, I) were overrepresented in LL samples. Fifteen differential metabolic pathways (Biosynthesis of amino acids, Pyruvate metabolism, Nitrotoluene degradation, Lipopolysaccharide biosynthesis, Peptidoglycan biosynthesis, Pantothenate and CoA biosynthesis, Glycosaminoglycan degradation, Thiamine metabolism, Phosphotransferase system, Two-component system, Bacterial secretion system, Flagellar assembly, Bacterial chemotaxis, Ribosome, Sulfur relay system) were identified. Our data highlighted interesting variations between the gut metagenomes of these two chicken lines.

Redox modulation of adipocyte differentiation: hypothesis of "Redox Chain" and novel insights into intervention of adipogenesis and obesity

In view of the global prevalence of obesity and obesity-associated disorders, it is important to clearly understand how adipose tissue forms. Accumulating data from various laboratories implicate that redox status is closely associated with energy metabolism. Thus, biochemical regulation of the redox system may be an attractive alternative for the treatment of obesity-related disorders. In this work, we will review the current data detailing the role of the redox system in adipocyte differentiation, as well as identifying areas for further research. The redox system affects adipogenic differentiation in an extensive way. We propose that there is a complex and interactive "redox chain," consisting of a "ROS-generating enzyme chain," "combined antioxidant chain," and "transcription factor chain," which contributes to fine-tune the regulation of ROS level and subsequent biological consequences. The roles of the redox system in adipocyte differentiation are paradoxical. The redox system exerts a "tridimensional" mechanism in the regulation of adipocyte differentiation, including transcriptional, epigenetic, and posttranslational modulations. We suggest that redoxomic techniques should be extensively applied to understand the biological effects of redox alterations in a more integrated way. A stable and standardized "redox index" is urgently needed for the evaluation of the general redox status. Therefore, more effort should be made to establish and maintain a general redox balance rather than to conduct simple prooxidant or antioxidant interventions, which have comprehensive implications.

L-Arginine and vitamin C attenuate pro-atherogenic effects of high-fat diet on biomarkers of endothelial dysfunction in rats

High-fat diet (HFD) is known to cause endothelial dysfunction and contribute to atherosclerosis progression. The objective of this study was to evaluate the efficacy of L-arginine (L-Arg) and vitamin C supplementation as a potentially useful strategy for modulation of serum homocysteine (Hcy) levels, tumor necrosis factor alpha (TNF-α), oxidative stress, and insulin resistance induced by HFD in rats. Six weeks-old female and male Wistar rats were divided into five groups of twelve rats each and treated for six weeks with: group 1, standard diet; group 2, HFD; group 3, HFD supplemented with L-Arg (20g/kg diet); group 4, HFD supplemented with L-Arg (20g/kg diet) plus vitamin C (100mg/kg diet); group 5, HFD supplemented with vitamin C (100mg/kg diet). HFD significantly elevated TNF-α, reduced total antioxidant status (TAS), and increased insulin resistance (HOMA-IR). Significant increases of total cholesterol (TCH), LDL cholesterol (LDL), triglyceride (TG) and a decrease of HDL cholesterol (HDL) were observed in HFD rats. Supplementation with l-Arg prevented the decrease of TAS and the increases in HOMA-IR, LDL, and TG levels. Moreover, Hcy and TNF-α levels were reduced in L-Arg supplemented group. Supplementation with vitamin C significantly atenuated TAS decrease and lowered LDL levels. L-Arg plus vitamin C enhanced L-Arg effect on TAS and protected against TNF-α increase. Western blot analysis showed that l-Arg supplementation of HFD rats reduced the level of protein carbonyls. Taken together, these findings indicate that supplemental l-arginine and/or vitamin C, by their abilities to modulate biomarkers of HFD-induced endothelial dysfunction, are anti-atherogenic.

Inflammation, Oxidative Stress, and Antioxidants Contribute to Selected Sleep Quality and Cardiometabolic Health Relationships: A Cross-Sectional Study

Sleep is vital for cardiometabolic health, but a societal shift toward poor sleep is a prominent feature of many modern cultures. Concurrently, factors such as diet and lifestyle have also changed and may mediate the relationship between sleep quality and cardiometabolic health. Objectives were to explore (1) the interrelationship and (2) mediating effect of inflammation, oxidative stress, and antioxidants on sleep quality and cardiometabolic health. Cross-sectional data from the US National Health and Nutritional Examination Survey 2005-06 (≥20 y; N = 2,072) was used. Cardiometabolic health was defined as per the Joint Interim Statement; overall sleep quality was determined from six sleep habits and categorized as good, fair, poor, and very poor. Fair quality sleepers had optimal inflammation, oxidative stress, and antioxidant levels. Inflammation was above the current clinical reference range across all sleep quality categories, while oxidative stress was only within the clinical reference range for fair sleep quality. Selected sleep quality-cardiometabolic health relationships were mediated by inflammation, oxidative stress, and antioxidants and were moderated by sex. Our results provide initial evidence of a potential role for inflammation, oxidative stress, and antioxidants in the pathway between poor sleep quality-cardiometabolic decline. Further prospective research is needed to confirm our results.

Ascorbic acid is a dose-dependent inhibitor of adipocyte differentiation, probably by reducing cAMP pool

Ascorbic acid (AA) is the active component of vitamin C and antioxidant activity was long considered to be the primary molecular mechanism underlying the physiological actions of AA. We recently demonstrated that AA is a competitive inhibitor of adenylate cyclase, acting as a global regulator of intracellular cyclic adenosine monophosphate (cAMP) levels. Our study, therefore, aimed to determine new targets of AA that would account for its potential effect on signal transduction, particularly during cell differentiation. We demonstrated that AA is an inhibitor of pre-adipocyte cell line differentiation, with a dose-dependent effect. Additionally, we describe the impact of AA on the expression of genes involved in adipogenesis and/or the adipocyte phenotype. Moreover, our data suggest that treatment with AA partially reverses lipid accumulation in mature adipocytes. These properties likely reflect the function of AA as a global regulator of the cAMP pool, since an analog of AA without any antioxidant properties elicited the same effect. Additionally, we demonstrated that AA inhibits adipogenesis in OP9 mesenchymal cell line and drives the differentiation of this line toward osteogenesis. Finally, our data suggest that the intracellular transporter SVCT2 is involved in these processes and may act as a receptor for AA.

Oxidative stress and altered lipid homeostasis in the programming of offspring fatty liver by maternal obesity

Changes in the maternal nutritional environment during fetal development can influence offspring's metabolic risk in later life. Animal models have demonstrated that offspring of diet-induced obese dams develop metabolic complications, including nonalcoholic fatty liver disease. In this study we investigated the mechanisms in young offspring that lead to the development of nonalcoholic fatty liver disease (NAFLD). Female offspring of C57BL/6J dams fed either a control or obesogenic diet were studied at 8 wk of age. We investigated the roles of oxidative stress and lipid metabolism in contributing to fatty liver in offspring. There were no differences in body weight or adiposity at 8 wk of age; however, offspring of obese dams were hyperinsulinemic. Oxidative damage markers were significantly increased in their livers, with reduced levels of the antioxidant enzyme glutathione peroxidase-1. Mitochondrial complex I and II activities were elevated, while levels of mitochondrial cytochrome c were significantly reduced and glutamate dehydrogenase was significantly increased, suggesting mitochondrial dysfunction. Offspring of obese dams also had significantly greater hepatic lipid content, associated with increased levels of PPARγ and reduced triglyceride lipase. Liver glycogen and protein content were concomitantly reduced in offspring of obese dams. In conclusion, offspring of diet-induced obese dams have disrupted liver metabolism and develop NAFLD prior to any differences in body weight or body composition. Oxidative stress may play a mechanistic role in the progression of fatty liver in these offspring.

Multivitamin restriction increases adiposity and disrupts glucose homeostasis in mice

A strong association between obesity and low plasma concentrations of vitamins has been widely reported; however, the causality of this relationship is still not established. Our goal was to evaluate the impact of a multivitamin restriction diet (MRD) on body weight, adiposity and glucose homeostasis in mice. The mice were given a standard diet or a diet containing 50 % of the recommended vitamin intake (MRD) for 12 weeks. At the end of the experiment, total body weight was 6 % higher in MRD animals than in the control group, and the adiposity of the MRD animals more than doubled. The HOMA-IR index of the MRD animals was significantly increased. The adipose tissue of MRD animals had lower expression of mRNA encoding adiponectin and Pnpla2 (47 and 32 %, respectively) and 43 % higher leptin mRNA levels. In the liver, the mRNA levels of Pparα and Pgc1α were reduced (29 and 69 %, respectively) in MRD mice. Finally, the level of β-hydroxybutyrate, a ketonic body reflecting fatty acid oxidation, was decreased by 45 % in MRD mice. Our results suggest that MRD promotes adiposity, possibly by decreasing adipose tissue lipolysis and hepatic β-oxidation. These results could highlight a possible role of vitamin deficiency in the etiology of obesity and associated disorders.

Dietary ascorbic acid and subsequent change in body weight and waist circumference: associations may depend on genetic predisposition to obesity--a prospective study of three independent cohorts

Background

Cross-sectional data suggests that a low level of plasma ascorbic acid positively associates with both Body Mass Index (BMI) and Waist Circumference (WC). This leads to questions about a possible relationship between dietary intake of ascorbic acid and subsequent changes in anthropometry, and whether such associations may depend on genetic predisposition to obesity. Hence, we examined whether dietary ascorbic acid, possibly in interaction with the genetic predisposition to a high BMI, WC or waist-hip ratio adjusted for BMI (WHR), associates with subsequent annual changes in weight (∆BW) and waist circumference (∆WC).

Methods

A total of 7,569 participants’ from MONICA, the Diet Cancer and Health study and the INTER99 study were included in the study. We combined 50 obesity associated single nucleotide polymorphisms (SNPs) in four genetic scores: a score of all SNPs and a score for each of the traits (BMI, WC and WHR) with which the SNPs associate. Linear regression was used to examine the association between ascorbic acid intake and ΔBW or ΔWC. SNP-score × ascorbic acid interactions were examined by adding product terms to the models.

Results

We found no significant associations between dietary ascorbic acid and ∆BW or ∆WC. Regarding SNP-score × ascorbic acid interactions, each additional risk allele of the 14 WHR associated SNPs associated with a ∆WC of 0.039 cm/year (P = 0.02, 95% CI: 0.005 to 0.073) per 100 mg/day higher ascorbic acid intake. However, the association to ∆WC only remained borderline significant after adjustment for ∆BW.

Conclusion

In general, our study does not support an association between dietary ascorbic acid and ∆BW or ∆WC, but a diet with a high content of ascorbic acid may be weakly associated to higher WC gain among people who are genetically predisposed to a high WHR. However, given the quite limited association any public health relevance is questionable.

Acerola (Malpighia emarginata DC.) juice intake protects against alterations to proteins involved in inflammatory and lipolysis pathways in the adipose tissue of obese mice fed a cafeteria diet

BACKGROUND

Obesity has been studied as a metabolic and an inflammatory disease and is characterized by increases in the production of pro-inflammatory adipokines in the adipose tissue.To elucidate the effects of natural dietary components on the inflammatory and metabolic consequences of obesity, we examined the effects of unripe, ripe and industrial acerola juice (Malpighia emarginata DC.) on the relevant inflammatory and lipolysis proteins in the adipose tissue of mice with cafeteria diet-induced obesity.

MATERIALS/METHODS

Two groups of male Swiss mice were fed on a standard diet (STA) or a cafeteria diet (CAF) for 13 weeks. Afterwards, the CAF-fed animals were divided into five subgroups, each of which received a different supplement for one further month (water, unripe acerola juice, ripe acerola juice, industrial acerola juice, or vitamin C) by gavage. Enzyme-linked immunosorbent assays, Western blotting, a colorimetric method and histology were utilized to assess the observed data.

RESULTS

The CAF water (control obese) group showed a significant increase in their adiposity indices and triacylglycerol levels, in addition to a reduced IL-10/TNF-α ratio in the adipose tissue, compared with the control lean group. In contrast, acerola juice and Vitamin C intake ameliorated the weight gain, reducing the TAG levels and increasing the IL-10/TNF-α ratio in adipose tissue. In addition, acerola juice intake led to reductions both in the level of phosphorylated JNK and to increases in the phosphorylation of IκBα and HSLser660 in adipose tissue.

CONCLUSIONS

Taken together, these results suggest that acerola juice reduces low-grade inflammation and ameliorates obesity-associated defects in the lipolytic processes.

Fat intake leads to differential response of rat adipocytes to glucose, insulin and ascorbic acid

Antioxidant-based treatments have emerged as novel and interesting approaches to counteract fat accumulation in obesity and associated metabolic disturbances. Adipocytes from rats that were fed on chow or high-fat diet (HFD) for 50 d were isolated (primary adipocytes) and incubated (72 h) on low (LG; 5.6 mmol/L) or high (HG; 25 mmol/L) glucose levels, in the presence or absence of 1.6 nmol/L insulin and 200 μmol/L vitamin C (VC). Adipocytes from HFD-fed animals presented lower insulin-induced glucose uptake, lower lactate and glycerol release, and lower insulin-induced secretion of some adipokines as compared with controls. HG treatment restored the blunted response to insulin regarding apelin secretion in adipocytes from HFD-fed rats. VC treatment inhibited the levels of nearly all variables, irrespective of the adipocytes’ dietary origin. The HG treatment reduced adipocyte viability, and VC protected from this toxic effect, although more drastically in control adipocytes. Summing up, in vivo chow or HFD intake determines a differential response to insulin and glucose treatments that appears to be dependent on the insulin-resistance status of the adipocytes, while VC modifies some responses from adipocytes independently of the previous dietary intake of the animals.

The effects of a cafeteria diet on insulin production and clearance in rats

The aim of the present study was to determine the effects of a cafeteria diet on the function and apoptosis of the pancreas, and the activity and expression of the insulin-degrading enzyme (IDE). Female Wistar rats were fed either with a cafeteria diet or a control diet for 17 weeks, and blood and tissues were then collected for analysis. The cafeteria diet-treated rats had higher plasma insulin and C-peptide levels (P<0·05), showing increased insulin secretion by the pancreas. Insulin protein and gene expression levels were higher in the pancreas of obese rats, as was its transcriptional controller, pancreatic duodenal homeobox 1 (P<0·05). Feeding a cafeteria diet down-regulated the gene expression of the anti-apoptotic marker B-cell/lymphoma 2 (BCL2), and up-regulated the protein levels of BCL2-associated X protein, a pro-apoptotic marker (P<0·05). The cafeteria diet caused lipid accumulation in the pancreas and modified the expression of key genes that control lipid metabolism. To assay whether insulin clearance was also modified, we checked the activity of the IDE, one of the enzymes responsible for insulin clearance. We found increased liver IDE activity (P<0·05) in the cafeteria diet-fed animals, which could, in part, be due to an up-regulation of its gene expression. Conversely, IDE gene expression was unmodified in the kidney and adipose tissue; although when the adipose tissue weight was considered, the insulin clearance potential was higher in the cafeteria diet-treated rats. In conclusion, treatment with a cafeteria diet for 17 weeks in rats mimicked a pre-diabetic state, with ectopic lipid accumulation in the pancreas, and increased the IDE-mediated insulin clearance capability.

Dietary supplementation with phytosterol and ascorbic acid reduces body mass accumulation and alters food transit time in a diet-induced obesity mouse model

Previous research indicates that animals fed a high fat (HF) diet supplemented with disodium ascorbyl phytostanyl phosphate (DAPP) exhibit reduced mass accumulation when compared to HF control. This compound is a water-soluble phytostanol ester and consists of a hydrophobic plant stanol covalently bonded to ascorbic acid (Vitamin C). To provide insight into the mechanism of this response, we examined the in vivo effects of a high fat diet supplemented with ascorbic acid (AA) in the presence and absence of unesterified phytosterols (PS), and set out to establish whether the supplements have a synergistic effect in a diet-induced obesity mouse model. Our data indicate that HF diet supplementation with a combination of 1% w/w phytosterol and 1% w/w ascorbic acid results in reduced mass accumulation, with mean differences in absolute mass between PSAA and HF control of 10.05%; and differences in mass accumulation of 21.6% (i.e. the PSAA group gained on average 21% less mass each week from weeks 7-12 than the HF control group). In our previous study, the absolute mass difference between the 2% DAPP and HF control was 41%, while the mean difference in mass accumulation between the two groups for weeks 7-12 was 67.9%. Mass loss was not observed in animals supplemented with PS or AA alone. These data suggest that the supplements are synergistic with respect to mass accumulation, and the esterification of the compounds further potentiates the response. Our data also indicate that chronic administration of PS, both in the presence and absence of AA, results in changes to fecal output and food transit time, providing insight into the possibility of long-term changes in intestinal function related to PS supplementation.

Developmental programming in response to maternal overnutrition

Metabolic disorders have seen an increased prevalence in recent years in developed as well as developing countries. While it is clear lifestyle choices and habits have contributed to this epidemic, mounting evidence suggests the nutritional milieu during critical stages of development in early life can "program" individuals to develop the metabolic syndrome later in life. Extensive epidemiological data presents an association between maternal obesity and nutrition during pregnancy and offspring obesity, and a number of animal models have been established in order to uncover the underlying mechanisms contributing to the programming of physiological systems. It is hard to distinguish the causal factors due to the complex nature of the maternal-fetal relationship; however, in order to develop adequate prevention strategies it is vital to identify which maternal factor(s) - be it the diet, diet-induced obesity or weight gain - and at which time during early development instigate the programmed phenotype. Curtailing the onset of obesity at this early stage in life presents a promising avenue through which to stem the growing epidemic of obesity.

Supplementation with soybean peptides, taurine, Pueraria isoflavone, and ginseng saponin complex improves endurance exercise capacity in humans

The purpose of this study was to investigate the effects of a proprietary blend of soybean peptides, taurine, Pueraria isoflavone, and ginseng saponin complex (STPG capsule) on exercise performance in humans. Fourteen male volunteers were randomly assigned to two crossover treatments in which they consumed either four STPG capsules (STPG treatment) or placebo (P treatment) for 15 days before a 75% maximal oxygen uptake (VO(2max)) exhaustive cycling test. Blood samples and respiratory gas were collected prior to the exercise (Pre-Ex), at 10 (Ex-10), 15 (Ex-15), 20 (Ex-20), and 25 (Ex-25) minutes during exercise, and immediately after exercise (exhaustion) to assess the blood metabolites, cardiorespiratory responses, and energy substrate utilization. The result showed that exercise time to exhaustion of the 75% (VO(2max)) exhaustive cycling test of the STPG-treated subjects was significantly greater than with the P treatment (30.99 ± 2.01 vs. 28.05 ± 1.48 minutes). The plasma lactate concentrations at Ex-20 and Ex-25 in the STPG treatment were significantly lower with STPG treatment than with P treatment (10.5 ± 0.7 vs. 11.5 ± 0.8 and 10.7 ± 0.9 vs.12.3 ± 1.0 mmol/L, respectively). Nonesterified fatty acid levels at Ex-15, Ex-20, Ex-25, and exhaustion in the STPG group (0.27 ± 0.03, 0.32 ± 0.04, 0.32 ± 0.06, and 0.37 ± 0.05 mmol/L, respectively) were significantly higher than those in the P treatment (0.21 ± 0.03, 0.23 ± 0.03, 0.24 ± 0.03, and 0.25 ± 0.03 mmol/L, respectively). It was concluded that supplementation of four capsules (2 g) of STPG complex, consisting of soybean peptides, taurine, Pueraria isoflavone, and ginseng saponin, for 15 days was effective in promoting utilization of free fatty acids and improving exhaustive cycling test performance in humans.

Maternal antioxidant supplementation prevents adiposity in the offspring of Western diet-fed rats

OBJECTIVE

Obesity in pregnancy significantly increases the risk of the offspring developing obesity after birth. The aims of this study were to test the hypothesis that maternal obesity increases oxidative stress during fetal development, and to determine whether administration of an antioxidant supplement to pregnant Western diet-fed rats would prevent the development of adiposity in the offspring.

RESEARCH DESIGN AND METHODS

Female Sprague Dawley rats were started on the designated diet at 4 weeks of age. Four groups of animals were studied: control chow (control); control + antioxidants (control+Aox); Western diet (Western); and Western diet + antioxidants (Western+Aox). The rats were mated at 12 to 14 weeks of age, and all pups were weaned onto control diet.

RESULTS

Offspring from dams fed the Western diet had significantly increased adiposity as early as 2 weeks of age as well as impaired glucose tolerance compared with offspring of dams fed a control diet. Inflammation and oxidative stress were increased in preimplantation embryos, fetuses, and newborns of Western diet-fed rats. Gene expression of proadipogenic and lipogenic genes was altered in fat tissue of rats at 2 weeks and 2 months of age. The addition of an antioxidant supplement decreased adiposity and normalized glucose tolerance. CONCLUSIONS; Inflammation and oxidative stress appear to play a key role in the development of increased adiposity in the offspring of Western diet-fed pregnant dams. Restoration of the antioxidant balance during pregnancy in the Western diet-fed dam is associated with decreased adiposity in offspring.

DNA microarrays to define and search for genes associated with obesity

One of the major goals of this review was to identify obesity-specific gene profiles in animal models to help comprehend the pathogenic mechanisms and the prediction of the phenotypic outcomes of obesity and its associated metabolic diseases. The genomic examination of insulin-sensitive tissues, such as the adipose and hepatic tissues, has provided a wealth of information about the changes in gene expression in obesity and its associated metabolic diseases. The overexpression of genes related to inflammation, immune response, adhesion molecules, and lipid metabolism is a major characteristic of white adipose tissue, while the overexpression of the genes related to lipid metabolism, adipocyte differentiation, defense, and stress responses is noticeable in the non-alcoholic fatty liver of obese rodents. The hepatic-gene expression profiles led us to hypothesize that in obese rodents, the livers are supplied with large amounts of free fatty acids under conditions associated with obesity either through increased fatty acid biosynthesis or through decreased fatty acid oxidation, which may lead to increased mitochondrial respiratory activity. The wide list of genes that were identified in previous studies could be a source of potential therapeutic targets because most of these genes are involved in the key mechanisms of obesity development, from adipocyte differentiation to the disturbance of metabolism.

Some cyclin-dependent kinase inhibitors-related genes are regulated by vitamin C in a model of diet-induced obesity

The aim of this research was to investigate differential gene expression of cyclin-dependent kinase inhibitors (CKIs) in white adipose tissue (WAT) and liver from high-fat fed male Wistar rats with or without vitamin C (VC) supplementation (750 mg/kg of body weight). After 56 d of experimentation, animals fed on a cafeteria diet increased significantly body weights and total body fat. Reverse transcription-polymerase chain reaction (RT-PCR) studies showed that cafeteria diet decreased p21 and p57 mRNA expression in subcutaneous WAT and increased p21 mRNA in liver. Overall, these data provide new information about the role of high fat intake on mRNA levels of several CKIs with implications in adipogenesis, cell metabolism and weight homeostasis. Interestingly, VC supplementation partially prevented diet-induced adiposity and increased p27 mRNA in liver without any changes in the other tissues and genes analyzed. Thus, hepatic mRNA changes induced by ascorbic acid indicate a possible role of these genes in diet-induced oxidative stress processes.

Impact of micronutrient deficiencies on obesity

Micronutrient deficiencies have been found in obese individuals across age groups worldwide. While the effects of micronutrient deficiencies on human functions have been studied widely in different populations, there is limited information on how these micronutrient deficiencies affect obese populations. An examination of the available literature suggests associations exist between micronutrient deficiencies and obesity in different populations. These associations and possible mechanisms of the deficiencies' metabolic effects, such as their influence on leptin and insulin metabolism, are discussed here. Further studies are needed to clarify the roles of the different micronutrient deficiencies with respect to obesity and its comorbid conditions.

Time-dependent regulation of muscle caveolin activation and insulin signalling in response to high-fat diet

We studied the effect of high-fat diet on the expression and activation of the three caveolins in rat skeletal muscle and their association with the insulin signalling cascade. Initial response was characterized by increased signalling through Cav-1 and Cav-3 phosphorylation, suggesting that both participate in an initial acute response to the calorie surplus. Afterwards, Cav-1 signalling was slightly reduced, whereas Cav-3 remained active. Late chronic phase signalling through both proteins was impaired inducing a prediabetic state. Summarizing, caveolins seem to mediate a time-dependent regulation of insulin cascade in response to high-fat diet in muscle.

Individuality and epigenetics in obesity

Excessive weight gain arises from the interactions among environmental factors, genetic predisposition and the individual behavior. However, it is becoming evident that interindividual differences in obesity susceptibility depend also on epigenetic factors. Epigenetics studies the heritable changes in gene expression that do not involve changes to the underlying DNA sequence. These processes include DNA methylation, covalent histone modifications, chromatin folding and, more recently described, the regulatory action of miRNAs and polycomb group complexes. In this review, we focus on experimental evidences concerning dietary factors influencing obesity development by epigenetic mechanisms, reporting treatment doses and durations. Moreover, we present a bioinformatic analysis of promoter regions for the search of future epigenetic biomarkers of obesity, including methylation pattern analyses of several obesity-related genes (epiobesigenes), such as FGF2, PTEN, CDKN1A and ESR1, implicated in adipogenesis, SOCS1/SOCS3, in inflammation, and COX7A1 LPL, CAV1, and IGFBP3, in intermediate metabolism and insulin signalling. The identification of those individuals that at an early age could present changes in the methylation profiles of specific genes could help to predict their susceptibility to later develop obesity, which may allow to prevent and follow-up its progress, as well as to research and develop newer therapeutic approaches.

Ascorbic acid oral treatment modifies lipolytic response and behavioural activity but not glucocorticoid metabolism in cafeteria diet-fed rats

AIM

To analyse the effects of vitamin C (VC), a potent dietary antioxidant, oral supplementation on body weight gain, behavioural activity, lipolytic response and glucocorticoid metabolism in the early stages of diet-induced overweight in rats.

METHODS

Food intake, locomotive activity and faecal corticosterone were assessed during the 14 day trial period. After 2 weeks, the animals were sacrificed and the body composition, biochemical markers and lipolytic response from isolated adipocytes from retroperitoneal white adipose tissue were examined.

RESULTS

The intake of a high-fat diet by rats induced a significant increase in body weight, adiposity and insulin resistance markers as well as a decrease in faecal corticosterone levels compared with standard diet-fed rats. Interestingly, the animals fed on the cafeteria diet showed a significant increase in the isoproterenol-induced lipolytic response in isolated adipocytes. Furthermore, this cafeteria-fed group showed a reduced locomotive behaviour than the control rats. On the other hand, oral VC supplementation in animals receiving the high-fat diet restored the cafeteria diet effect in some of the analysed variables such as final body weight and plasma insulin to control group levels. Remarkably, increases in locomotive behaviour and a significant decrease in the lipolytic response induced by isoproterenol on isolated adipocytes from animals treated with VC were observed.

CONCLUSION

This work demonstrates that an oral ascorbic acid supplementation has direct effects on behavioural activity and on adipocyte lipolysis in early obesity stages in rats, which could indicate a protective short-term role of this vitamin against adiposity induced by chronic high-fat diet consumption.

The role of the small intestine in the development of dietary fat-induced obesity and insulin resistance in C57BL/6J mice

Background

Obesity and insulin resistance are two major risk factors underlying the metabolic syndrome. The development of these metabolic disorders is frequently studied, but mainly in liver, skeletal muscle, and adipose tissue. To gain more insight in the role of the small intestine in development of obesity and insulin resistance, dietary fat-induced differential gene expression was determined along the longitudinal axis of small intestines of C57BL/6J mice.

Methods

Male C57BL/6J mice were fed a low-fat or a high-fat diet that mimicked the fatty acid composition of a Western-style human diet. After 2, 4 and 8 weeks of diet intervention small intestines were isolated and divided in three equal parts. Differential gene expression was determined in mucosal scrapings using Mouse genome 430 2.0 arrays.

Results

The high-fat diet significantly increased body weight and decreased oral glucose tolerance, indicating insulin resistance. Microarray analysis showed that dietary fat had the most pronounced effect on differential gene expression in the middle part of the small intestine. By overrepresentation analysis we found that the most modulated biological processes on a high-fat diet were related to lipid metabolism, cell cycle and inflammation. Our results further indicated that the nuclear receptors Ppars, Lxrs and Fxr play an important regulatory role in the response of the small intestine to the high-fat diet. Next to these more local dietary fat effects, a secretome analysis revealed differential gene expression of secreted proteins, such as Il18, Fgf15, Mif, Igfbp3 and Angptl4. Finally, we linked the fat-induced molecular changes in the small intestine to development of obesity and insulin resistance.

Conclusion

During dietary fat-induced development of obesity and insulin resistance, we found substantial changes in gene expression in the small intestine, indicating modulations of biological processes, especially related to lipid metabolism. Moreover, we found differential expression of potential signaling molecules that can provoke systemic effects in peripheral organs by influencing their metabolic homeostasis. Many of these fat-modulated genes could be linked to obesity and/or insulin resistance. Together, our data provided various leads for a causal role of the small intestine in the etiology of obesity and/or insulin resistance.

Integration of DIGE and bioinformatics analyses reveals a role of the antiobesity agent tungstate in redox and energy homeostasis pathways in brown adipose tissue

Our previous results demonstrated that tungstate decreased weight gain and adiposity in obese rats through increased thermogenesis and lipid oxidation, suggesting that brown adipose tissue was one of the targets of its antiobesity effect. To identify potential targets of tungstate, we used DIGE to compare brown adipose tissue protein extracts from the following experimental groups: untreated lean, tungstate-treated lean, untreated obese, and tungstate-treated obese rats. To distinguish direct targets of tungstate action from those that are secondary to body weight loss, we also included in the analysis an additional group consisting of obese rats that lose weight by caloric restriction. Hierarchical clustering of analysis of variance and t test contrasts clearly separated the different experimental groups. DIGE analysis identified 20 proteins as tungstate obesity direct targets involved in Krebs cycle, glycolysis, lipolysis and fatty acid oxidation, electron transport, and redox. Protein oxidation was decreased by tungstate treatment, confirming a role in redox processes; however, palmitate oxidation, as a measure of fatty acid beta-oxidation, was not altered by tungstate, thus questioning its putative function in fatty acid oxidation. Protein network analyses using Ingenuity Pathways Analysis highlighted peroxisome proliferator-activated receptor gamma coactivator 1alpha (PGC-1alpha) as a potential target. We confirmed by real time PCR that indeed tungstate up-regulates PGC-1alpha, and its major target, uncoupling protein 1, was also increased as shown by Western blot. These results illustrate the utility of proteomics and bioinformatics approaches to identify targets of obesity therapies and suggest that in brown adipose tissue tungstate modulates redox processes and increases energy dissipation through uncoupling and PGC-1alpha up-regulation, thus contributing to its overall antiobesity effect.

Mitochondrial oxidative stress and inflammation: an slalom to obesity and insulin resistance

Mitochondria, in addition to energy transformation, play a role in important metabolic tasks such as apoptosis, cellular proliferation, heme/steroid synthesis as well as in the cellular redox state regulation. The mitochondrial phosphorylation process is very efficient, but a small percentage of electrons may prematurely reduce oxygen forming toxic free radicals potentially impairing the mitochondria function. Furthermore, under certain conditions, protons can reenter the mitochondrial matrix through different uncoupling proteins (UCPs), affecting the control of free radicals production by mitochondria. Disorders of the mitochondrial electron transport chain, overgeneration of reactive oxygen species (ROS) and lipoperoxides or impairments in antioxidant defenses have been reported in situations of obesity and type-2 diabetes. On the other hand, obesity has been associated to a low degree pro-inflammatory state, in which impairments in the oxidative stress and antioxidant mechanism could be involved. Indeed, reactive oxygen species have been attributed a causal role in multiple forms of insulin resistance. The scientific evidence highlights the importance of investigating the relationships between oxidative stress and inflammation with obesity/diabetes onset and underlines the need to study in mitochondria from different tissues, the interactions of such factors either as a cause or consequence of obesity and insulin resistance.

Adiposity dependent apelin gene expression: relationships with oxidative and inflammation markers

It has been reported that apelin functions as an adipokine, which has been associated to obesity and insulin resistance. The objective of this study was to analyze the apelin mRNA expression in white adipose tissue (WAT) from high-fat (Cafeteria) fed rats, in order to examine potential relationships with obesity markers and other related risk factors. Animals fed on the high-fat diet during 56 days increased their body weight, total body fat and WAT depots weights when compared to controls. Apelin subcutaneous mRNA expression was higher in the Cafeteria than in the Control fed group and this increase was partially reversed by dietary vitamin C supplementation. Statistically significant associations between subcutaneous apelin gene expression and almost all the studied variables were identified, being of special interest the correlations found with serum leptin (r=0.517), liver malondialdehyde (MDA) levels (r=0.477), and leptin, IRS-3 and IL-1ra retroperitoneal mRNA expression (r=0.701; r=0.692 and r=0.561, respectively). These associations evidence a possible role for apelin in the excessive weight gain induced by high-fat feeding and increased adiposity, insulin-resistance, liver oxidative stress and inflammation.