Quercetin improved hepatic circadian rhythm dysfunction in middle-aged mice fed with vitamin D-deficient diet

We aimed to determine whether quercetin is capable of improving circadian rhythm and metabolism disorder under vitamin D-deficient condition. Middle-aged mice were randomly divided into four groups, namely, control (CON), vitamin D-deficient diet (VDD), quercetin (Q), and quercetin intervention in vitamin D-deficient diet (VDQ), with a total of 12 weeks’ intervention. Mice were sacrificed at zeitgeber time1 (ZT1) and ZT13 time points. At ZT1, circadian locomotor output cycle kaput (CLOCK) protein expression from VDD, Q, and VDQ groups; CRY1 from Q group; and CRY2 from VDD group were significantly lower compared to CON group. The mRNA expression of Sirt1, Bmal1, Clock, Cry1, and Cry2 in VDQ groups, also Bmal1, Clock, and Cry1 from Q group, were significantly decreased compared to CON group. At ZT13, compared to CON group, fasting insulin and homeostasis model assessment-insulin resistance (HOMA-IR) were higher in VDD group; BMAL1 was significantly increased, while CLOCK and CRY1 protein were significantly decreased from VDD group; CLOCK protein from VDQ group was significantly higher compared to CON, VDD, and Q groups, and also, BMAL1 protein expression from VDQ group was elevated compared to CON group. The mRNA expression of Bmal1, Clock, Per2, Cry1, and Cry2 in VDQ groups were significantly increased compared to CON groups. The mRNA expression of Bmal1 from VDQ group was decreased compared to both VDD and Q group. In conclusion, vitamin D-deficient diet resulted in a disordered liver circadian rhythm, and quercetin improved the hepatic circadian desynchronization. Quercetin supplementation might be effective for balancing circadian rhythm under vitamin D-deficient condition. (AU)

Quercetin improved hepatic circadian rhythm dysfunction in middle-aged mice fed with vitamin D-deficient diet.

We aimed to determine whether quercetin is capable of improving circadian rhythm and metabolism disorder under vitamin D-deficient condition. Middle-aged mice were randomly divided into four groups, namely, control (CON), vitamin D-deficient diet (VDD), quercetin (Q), and quercetin intervention in vitamin D-deficient diet (VDQ), with a total of 12 weeks' intervention. Mice were sacrificed at zeitgeber time1 (ZT1) and ZT13 time points. At ZT1, circadian locomotor output cycle kaput (CLOCK) protein expression from VDD, Q, and VDQ groups; CRY1 from Q group; and CRY2 from VDD group were significantly lower compared to CON group. The mRNA expression of Sirt1, Bmal1, Clock, Cry1, and Cry2 in VDQ groups, also Bmal1, Clock, and Cry1 from Q group, were significantly decreased compared to CON group. At ZT13, compared to CON group, fasting insulin and homeostasis model assessment-insulin resistance (HOMA-IR) were higher in VDD group; BMAL1 was significantly increased, while CLOCK and CRY1 protein were significantly decreased from VDD group; CLOCK protein from VDQ group was significantly higher compared to CON, VDD, and Q groups, and also, BMAL1 protein expression from VDQ group was elevated compared to CON group. The mRNA expression of Bmal1, Clock, Per2, Cry1, and Cry2 in VDQ groups were significantly increased compared to CON groups. The mRNA expression of Bmal1 from VDQ group was decreased compared to both VDD and Q group. In conclusion, vitamin D-deficient diet resulted in a disordered liver circadian rhythm, and quercetin improved the hepatic circadian desynchronization. Quercetin supplementation might be effective for balancing circadian rhythm under vitamin D-deficient condition.

Effect of flavonoid intake on circulating levels of adiponectin and leptin: A systematic review and meta-analysis of randomized controlled clinical trials.

This meta-analysis of randomized controlled trials (RCTs) was conducted to explore the effects of flavonoid intake on adiponectin and leptin levels. The PubMed, EMBASE, and Cochrane Library databases were searched on March 1, 2021. Random-effects, subgroup, sensitivity, and meta-regression analyses were conducted on 40 publications. Flavonoid intake significantly increased circulating adiponectin (0.54 µg/ml, 95% CI [0.20, 0.88], p = .002; I2  = 86.4%) and significantly reduced leptin levels (weighted mean difference: -0.79 ng/ml, 95% CI [-1.33, -0.25], p = .004; I2  = 87.7%). Subgroup analysis demonstrated that flavonoid intervention produced a significant elevation in adiponectin levels only in studies that lasted more than 12 weeks, conducted in Asian regions, were parallel-designed, involved obese or overweight participants and participants with type 2 diabetes mellitus (T2DM) or cardiovascular diseases, used tea catechins, and used a dietary supplement intervention. A significantly negative effect on leptin levels was observed in studies conducted in Asian countries, with healthy participants and participants with T2DM, used whole food interventions, and involved participants with lower baseline leptin levels. In conclusion, flavonoid intake significantly increased circulating adiponectin and decreased leptin levels; however, study heterogeneity was very high. Future well-designed trials are required to address heterogeneous study designs and clarify the efficacy of plants in regulating adiponectin and leptin levels.

Lactoferrin improves hepatic insulin resistance and pancreatic dysfunction in high-fat diet and streptozotocin-induced diabetic mice.

Lactoferrin (Lf) is an iron-binding glycoprotein with potentially beneficial biological functions. However, the interaction between Lf and type 2 diabetes mellitus (T2DM) remains unclear. We hypothesized that Lf would improve hepatic insulin resistance and pancreatic dysfunction in diabetic mice. Male C57BL/6J mice were fed a high-fat diet for 15 weeks and injected with streptozotocin (STZ) for 5 consecutive days to establish a T2DM model. One week after STZ injection, mice with ≥11.1 mmol/L fasting blood glucose concentration were considered T2DM mice. These mice received 0.5% or 2% Lf solution for another 12 weeks. Biochemical parameters were measured, and histopathological examination of the pancreas and liver was performed. Hepatic protein expression related to the insulin signalling pathway was also assessed. Diabetic mice showed insulin resistance and abnormal glucolipid metabolism. Lf decreased serum concentrations of glycated serum protein, fasting insulin, cholesterol, and triglyceride and increased liver insulin sensitivity. Hematoxylin-eosin staining showed that Lf reversed the abnormal pancreatic islets of diabetic mice. Lf improved pancreatic dysfunction by reducing oxidative stress and inflammation responses. Furthermore, Lf upregulated the protein expression of insulin receptor, insulin receptor substrate-1, glucose transporter 4, phosphor phosphatidylinositol 3-kinase/phosphatidylinositol 3-kinase (PI3K), and phosphor protein kinase B/protein kinase B (AKT) in the liver. This study indicated that Lf supplementation improved hepatic insulin resistance and pancreatic dysfunction, possibly by regulating the PI3K/AKT signaling pathway in T2DM mice.

Effects of Quercetin Intervention on Cognition Function in APP/PS1 Mice was Affected by Vitamin D Status.

SCOPE: To explore how quercetin will affect memory impairments in APP/PS1 mice under different vitamin D status. METHODS AND RESULTS: APP/PS1 mice are divided into four groups, i.e., control (CON), low (LVD), medium, and high vitamin D supplemented with quercetin. During Morris Water Maze test, mice of the LVD group function best for improving cognitive function demonstrated by reduced latency to platform, and increased number of crossing and swimming distance in the target quadrant. Compared to the CON group, in both hippocampus and cortex, the LVD group has significant reduction in Aß plaques, p-Tau at Ser396&Ser404, and neuroinflammation. In the hippocampus, BDNF is elevated, miR-26a and miR-125b is decreased, while miR-132 is increased in the LVD group. The LVD group demonstrates increased gut microbial diversity and elevated relative abundance of Glutamicibacter, Facklamia and Aerocorrus. In the hippocampus, p-Tau at ser396&404, GFAP, Ibα1, miR-26a, and miR-132 are negatively correlated with Aerococcus; and p-Tau at ser404 and Ibα1 are negatively correlated with Facklamia. CONCLUSION: Quercetin is more efficacious for improving cognitive function under low vitamin D status. This might be owing to that interventions reduce Aß plaques, tau phosphorylation, and neuroinflammation, upregulate BDNF, reduce miR-26a and miR-125b, increase miR-132, and elevate gut microbial diversity including Facklamia and Aerococcus.

Cereal Fiber Ameliorates High-Fat/Cholesterol-Diet-Induced Atherosclerosis by Modulating the NLRP3 Inflammasome Pathway in ApoE-/- Mice.

Cereal fiber is associated with decreasing the risk of cardiovascular diseases. However, whether cereal fiber modulates inflammatory response and improves atherosclerosis remains unclear. This study evaluated the anti-atherosclerotic effect of cereal fibers from oat or wheat bran and explored the potential anti-inflammatory mechanisms. Male ApoE-/- mice were given a high-fat/cholesterol (HFC) diet or a HFC diet supplemented with 0.8% oat fiber or wheat bran fiber. After 18 weeks of the feeding period, serum lipids and inflammatory cytokines were measured. The relative protein levels of the nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome pathway and nuclear factor κB (NF-κB) were determined by the western blot method in aorta tissues. Pathologically, oat fiber and wheat fiber significantly reduced atherosclerotic plaques by 43.3 and 27.1%, respectively. Biochemically, cereal fiber markedly decreased the protein levels of myeloid differentiation factor 88 (MyD88) and toll-like receptor 4 (TLR4) in aortic tissues. The expression of NF-κB was similarly inhibited by both cereal fibers. In comparison to wheat bran fiber, oat fiber had greater effects in reducing the plague size and inhibiting TLR4/MyD88/NF-κB pathways. Such differences might come from modulation of the NLRP3 inflammasome pathway because the expressions of the cleavage of caspase-1 and interleukin (IL)-1ß were inhibited only by oat fiber. The present study demonstrates that cereal fibers can attenuate inflammatory response and atherosclerosis in ApoE-/- mice. Such effects are pronounced with oat fiber and likely mediated by specific inhibition of oat fiber on the NLRP3 inflammasome pathway.

Chia Seed Supplementation Reduces Senescence Markers in Epididymal Adipose Tissue of High-Fat Diet-Fed SAMP8 Mice.

Adipose tissue is a key organ with substantial senescent cell accumulation under both obesity and aging conditions. Chia seed is an ancient seed and is the richest plant source of α-linolenic acid. We aimed to determine how cellular senescence markers will be altered in adipose tissue of senescence-accelerated mouse-prone 8 (SAMP8) mice fed with high-fat diets (HFDs); and how chia seed can affect the above markers. SAMP8 mice and their control senescence-accelerated mouse-resistant 1 (SAMR1) were divided into four groups, that is, SAMR1 low-fat diet group (R1LF), SAMP8LF group (P8LF), SAMP8 high-fat group (P8HF), and SAMP8HF group supplemented with 10% chia seed (P8HC). At the end of the intervention, body composition was measured through T1-weighted magnetic resonance imaging, and epididymal (EPI) and subcutaneous (SC) adipose tissues were dissected for further analysis. Compared with the R1LF group, the P8HF and P8HC groups had significantly increased body fat mass. In EPI fat, p16, CD68 and PAI-1 mRNA expression from P8HF group were significantly increased; chia seed partially reduced p16 and CD68 mRNA expression. The P8LF group has increased p16 and CD68, and the P8HF group has increased p16, p21, and CD68; and P8HC group has increased p16 mRNA expression. The protein expression of p-AMPK in EPI and SC fat from the P8HF group was reduced. In conclusion, reductions in AMPK activity might be partially responsible for elevation in HFD-induced senescence markers in both EPI and SC fat, and chia seed supplementation is able to reduce senescence-associated markers at least in EPI adipose tissue.

Effects of vitamin D and resveratrol on metabolic associated markers in liver and adipose tissue from SAMP8 mice.

SAMP8 mice exhibit multiple metabolic characteristics associated with age, and it is a suitable candidate for researching aging associated metabolic dysfunction. OBJECTIVES: We aimed to 1) explore how key metabolic markers will be altered in both liver and adipose tissue with aging in SAMP8 mice; and 2) how the combination of vitamin D (VD) with resveratrol (RSV) will affect aging associated metabolic impairment in liver and adipose tissue from SAMP8 mice. METHODS: SAMP8 mice and their control SAMR1 mice were divided into 5 groups, i.e. SAMR1, SAMP8, SAMP8 mice supplemented with VD, RSV and VD combined with RSV group, respectively. At the end of the intervention, glucose and insulin tolerance, p-AMP-activated protein kinase (AMPK) and amyloid precursor protein (APP), and endoplasmic reticulum (ER) stress markers in liver and adipose tissue, adiponectin secretion, p-NF-κBp65 and TNF-α protein expression in adipose tissue were determined. RESULTS: Compared to SAMR1 control, SAMP8 mice demonstrate impaired glucose tolerance and reduction in circulating adiponectin level; in the liver, SAMP8 mice have reduction in p-Aktser473, elevation in PTP1B and APP, p-eIF2α, GRP78 and p-JNK protein expression. In epididymal (EPI) fat, SAMP8 mice also have elevated p-Aktser473 and PTP1B compared to SAMR1 mice. In both epididymal (EPI) and subcutaneous (SC) fat, there were elevated ER stress markers, reduced p-AMPK and elevated APP, as well as elevated p-NF-κBp65 and TNF-α protein expression from SAMP8 compared to SAMR1 mice. In liver, the combined intervention significantly restored p-Aktser473, p-eIF2α and p-JNK protein expression. In both EPI and SC fat, the combined intervention is effective for reducing p-NF-κB p65 and TNF-α in both fat depot, while only partially reduced ER stress markers in SC fat. As for adiponectin, their combination is unable to reverse reduction in adiponectin level. Adiponectin secretion in SC fat from VD, RSV and VDRSV group were also significantly reduced compared to SAMR1. CONCLUSION: The combined intervention might exert greater beneficial effects for reversing aging associated metabolic dysfunction in liver and adipose tissue from SAMP8 mice.

Vitamin D Combined with Resveratrol Prevents Cognitive Decline in SAMP8 Mice.

BACKGROUND: Vitamin D (VD) and resveratrol (RSV) are two nutritional molecules that have reported neuroprotective effects, and findings from cellular models suggest that resveratrol could potentiate vitamin D's effects. The senescence-accelerated mouse-prone 8 (SAMP8) is a useful model of Alzheimer's disease (AD)-related memory impairment. OBJECTIVE: We aimed to explore how the combination of vitamin D with resveratrol would affect memory impairments shown by SAMP8 mice, as well as the potential mechanisms. METHOD: SAMP8 mice and their control senescence-accelerated mouse resistant 1 (SAMR1) mice (10 weeks old) were divided into 5 groups, i.e. SAMR1 group, SAMP8 group, SAMP8 mice supplemented with VD group, SAMP8 mice supplemented with RSV group and SAMP8 mice supplemented with both VD and RSV group. At the end of the intervention, Morris water maze (MWM) test was used to assess cognitive function. Hippocampus and parietal cortex were dissected for further analysis. RESULTS: The combination of VD and RSV significantly increased time spent in target quadrant and the number of crossing via MWM test. In hippocampus, the combined intervention significantly reduced soluble Aß42 level and BACE1 protein expression. In cortex, the combined treatment significantly reduced phosphorylation of tau at serine404 and p-p53, as well as enhanced p-CREB protein expression. The combination also significantly reduced GFAP and p-NFκB p65 in both hippocampus and cortex. CONCLUSION: The combined intervention might exert greater neuroprotective effects in SAMP8 mice, this might be associated with the fact that the combined intervention could positively affect amyloidogenic pathways, neuroinflammation, tau phosphorylation and probably apoptosis markers.

Preservation of Cognitive Function by Lepidium meyenii (Maca) Is Associated with Improvement of Mitochondrial Activity and Upregulation of Autophagy-Related Proteins in Middle-Aged Mouse Cortex.

Maca has been used as a foodstuff and a traditional medicine in the Andean region for over 2,000 years. Recently the neuroprotective effects of maca also arouse interest of researchers. Decrease in mitochondrial function and decline in autophagy signaling may participate in the process of age-related cognitive decline. This study aimed to investigate if maca could improve cognitive function of middle-aged mice and if this effect was associated with improvement of mitochondrial activity and modulation of autophagy signaling in mouse cortex. Fourteen-month-old male ICR mice received maca powder administered by gavage for five weeks. Maca improved cognitive function, motor coordination, and endurance capacity in middle-aged mice, accompanied by increased mitochondrial respiratory function and upregulation of autophagy-related proteins in cortex. Our findings suggest that maca is a newly defined nutritional plant which can improve mitochondrial function and upregulate autophagy-related proteins and may be an effective functional food for slowing down age-related cognitive decline.

Depot-specific effects of treadmill running and rutin on white adipose tissue function in diet-induced obese mice

White adipose tissue (WAT) is a critical organ involved in regulating metabolic homeostasis under obese condition. Strategies that could positively affect WAT function would hold promise for fighting against obesity and its complications. The aim of the present study is to explore the effects of treadmill exercise training and rutin intervention on adipose tissue function from diet-induced obese (DIO) mice and whether fat depot-specific effects existed. In epididymal adipose tissue, high-fat diet (HFD) resulted in reduction in adiponectin mRNA expression, peroxisome proliferator-activated receptors (PPAR)-γ and DsbA-L protein expression, elevation in endoplasmic reticulum (ER) stress markers including 78 kDa glucose-regulated protein (GRP-78), C/EBP homologous protein (CHOP) and p-c-Jun N-terminal kinase (JNK). Isoproterenol-stimulated lipolysis and insulin stimulated Akt phosphorylation ex vivo were blunted from HFD group. The combination of rutin with exercise (HRE) completely restored GRP78 and p-JNK protein expression to normal levels, as well as blunted signaling ex vivo. In inguinal adipose tissue, HFD led to increased adiponectin mRNA expression, PPAR-γ, GRP78, and p-JNK protein expression, and reduction in DsbA-L. HRE is effective for restoring p-JNK, PPAR-γ, and DsbA-L. In conclusion, depot-specific effects may exist in regard to the effects of rutin and exercise on key molecules involved in regulating adipose tissue function (i.e., ER stress markers, PPAR-γ and DsbA-L, adiponectin expression, and secretion, ex vivo catecholamine stimulated lipolysis and insulin stimulated Akt phosphorylation) from DIO mice (AU)

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Effects of 8-Week Hatha Yoga Training on Metabolic and Inflammatory Markers in Healthy, Female Chinese Subjects: A Randomized Clinical Trial.

We aimed to determine the effects of an 8 wk Hatha yoga training on blood glucose, insulin, lipid profiles, endothelial microparticles (EMPs), and inflammatory status in healthy, lean, and female Chinese subjects. A total of 30 healthy, female Chinese subjects were recruited and randomized into control or yoga practice group. The yoga practice included 8 wks of yoga practice (2 times/wk) for a total of 16 times. Fasting blood samples were collected before and after yoga training. Plasma was isolated for the measurement of lipid profiles, glucose, insulin, EMPs, and inflammatory cytokines. Whole blood was cultured ex vivo and stimulated with lipopolysaccharide (LPS) and Pam3Cys-SK4. Peripheral blood mononuclear cells (PBMCs) were isolated for the measurement of TLR2 and TLR4 protein expression. Yoga practice significantly reduced plasma cholesterol, LDL-cholesterol, insulin levels, and CD31+/CD42b- EMPs. Cultured whole blood from the yoga group has reduced proinflammatory cytokines secretion both at unstimulated condition and when stimulated with Pam3Cys-SK4; this might be associated with reduced TLR2 protein expression in PBMCs after yoga training. Hatha yoga practice in healthy Chinese female subjects could improve hallmarks related to MetS; thus it can be considered as an ancillary intervention in the primary MetS prevention for the healthy population. This trial is registered with ChiCTR-IOR-14005747.

Depot-specific effects of treadmill running and rutin on white adipose tissue function in diet-induced obese mice.

White adipose tissue (WAT) is a critical organ involved in regulating metabolic homeostasis under obese condition. Strategies that could positively affect WAT function would hold promise for fighting against obesity and its complications. The aim of the present study is to explore the effects of treadmill exercise training and rutin intervention on adipose tissue function from diet-induced obese (DIO) mice and whether fat depot-specific effects existed. In epididymal adipose tissue, high-fat diet (HFD) resulted in reduction in adiponectin mRNA expression, peroxisome proliferator-activated receptors (PPAR)-γ and DsbA-L protein expression, elevation in endoplasmic reticulum (ER) stress markers including 78 kDa glucose-regulated protein (GRP-78), C/EBP homologous protein (CHOP) and p-c-Jun N-terminal kinase (JNK). Isoproterenol-stimulated lipolysis and insulin stimulated Akt phosphorylation ex vivo were blunted from HFD group. The combination of rutin with exercise (HRE) completely restored GRP78 and p-JNK protein expression to normal levels, as well as blunted signaling ex vivo. In inguinal adipose tissue, HFD led to increased adiponectin mRNA expression, PPAR-γ, GRP78, and p-JNK protein expression, and reduction in DsbA-L. HRE is effective for restoring p-JNK, PPAR-γ, and DsbA-L. In conclusion, depot-specific effects may exist in regard to the effects of rutin and exercise on key molecules involved in regulating adipose tissue function (i.e., ER stress markers, PPAR-γ and DsbA-L, adiponectin expression, and secretion, ex vivo catecholamine stimulated lipolysis and insulin stimulated Akt phosphorylation) from DIO mice.

Effects of treadmill running and rutin on lipolytic signaling pathways and TRPV4 protein expression in the adipose tissue of diet-induced obese mice.

To explore the effects of rutin and exercise on high-fat diet (HFD)-induced disrupted lipolytic signaling, adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) signaling, transient receptor potential cation channel subfamily V member 4 (TRPV4) and its associated protein expression, and whether depot-specific effects existed. C57BL/6J mice were randomized into five groups: chow group, HFD, HFD plus rutin intervention group (HR), HFD combined with treadmill running group (HE), and HFD combined with treadmill running and rutin intervention group (HRE). At the end of the 16-week intervention, lipolytic markers, AMPK signaling pathways, TRPV4, and peroxisome proliferator-activated receptor gamma coactivator 1α + ß (PGC-1α + ß) from adipose tissue were measured by western blotting. In epididymal adipose tissue, HFD resulted in significant reduction in the phosphorylation of hormone sensitive lipase at serine660 (p-HSL660), perilipin A, phosphoenolpyruvate carboxykinase (PEPCK), p-AMPK, and p-acetyl-CoA carboxylase (ACC) protein expression. Exercise intervention and exercise plus rutin completely restored p-HSL660, perilipin A, PEPCK, p-AMPK, and p-ACC protein expression to normal level. HFD and HR groups have reduced expression of PGC-1α + ß, exercise, and exercise plus rutin completely restored PGC-1α + ß expression to normal level. In subcutaneous adipose tissue, HFD elevated TRPV4, exercise, and exercise plus rutin completely reduced TRPV4 to normal level. HR, HE, and HRE group have increased PGC-1α + ß. In conclusion, depot-specific effects existed in regards to how rutin and exercise affect lipolytic signaling and p-AMPK, as well as TRPV4 and PGC-1α + ß expression.

Effect of whey supplementation on circulating C-reactive protein: a meta-analysis of randomized controlled trials.

Whey supplementation is beneficial for human health, possibly by reducing the circulating C-reactive protein (CRP) level, a sensitive marker of inflammation. Thus, a meta-analysis of randomized controlled trials was conducted to evaluate their relationship. A systematic literature search was conducted in July, 2014, to identify eligible studies. Either a fixed-effects model or a random-effects model was used to calculate pooled effects. The meta-analysis results of nine trials showed a slight, but no significant, reduction of 0.42 mg/L (95% CI -0.96, 0.13) in CRP level with the supplementation of whey protein and its derivates. Relatively high heterogeneity across studies was observed. Subgroup analyses showed that whey significantly lowered CRP by 0.72 mg/L (95% CI -0.97, -0.47) among trials with a daily whey dose≥20 g/day and by 0.67 mg/L (95% CI -1.21, -0.14) among trials with baseline CRP≥3 mg/L. Meta-regression analysis revealed that the baseline CRP level was a potential effect modifier of whey supplementation in reducing CRP. In conclusion, our meta-analysis did not find sufficient evidence that whey and its derivates elicited a beneficial effect in reducing circulating CRP. However, they may significantly reduce CRP among participants with highly supplemental doses or increased baseline CRP levels.

Effect of vitamin D supplementation on the level of circulating high-sensitivity C-reactive protein: a meta-analysis of randomized controlled trials.

Vitamin D might elicit protective effects against cardiovascular disease by decreasing the level of circulating high-sensitivity C-reactive protein (hs-CRP), an inflammatory marker. Thus, we conducted a meta-analysis of randomized controlled trials to evaluate the association of vitamin D supplementation with circulating hs-CRP level. A systematic literature search was conducted in September 2013 (updated in February 2014) via PubMed, Web of Science, and Cochrane library to identify eligible studies. Either a fixed-effects or a random-effects model was used to calculate pooled effects. The results of the meta-analysis of 10 trials involving a total of 924 participants showed that vitamin D supplementation significantly decreased the circulating hs-CRP level by 1.08 mg/L (95% CI, -2.13, -0.03), with the evidence of heterogeneity. Subgroup analysis suggested a higher reduction of 2.21 mg/L (95% CI, -3.50, -0.92) among participants with baseline hs-CRP level ≥5 mg/L. Meta-regression analysis further revealed that baseline hs-CRP level, supplemental dose of vitamin D and intervention duration together may be attributed to the heterogeneity across studies. In summary, vitamin D supplementation is beneficial for the reduction of circulating hs-CRP. However, the result should be interpreted with caution because of the evidence of heterogeneity.

Dietary supplementation with vitamin E and C attenuates dexamethasone-induced glucose intolerance in rats.

Glucocorticoid excess induces marked insulin resistance and glucose intolerance. A recent study has shown that antioxidants prevent dexamethasone (DEX)-induced insulin resistance in cultured adipocytes. The purpose of this investigation was to examine the effects of dietary vitamin E and C (Vit E/C) supplementation on DEX-induced glucose intolerance in rats. We hypothesized that feeding rats a diet supplemented with Vit E/C would improve glucose tolerance and restore insulin signaling in skeletal muscle, adipose, and liver and prevent alterations in AMPK signaling in these tissues. Male Wistar rats received either a control or Vit E/C-supplemented diet (0.5 g/kg diet each of L-ascorbate and DL-all rac-alpha-tocopherol) for 9 days prior to, and during, 5 days of daily DEX treatment (subcutaneous injections 0.8 mg/g body wt). DEX treatment resulted in increases in the glucose and insulin area under the curve (AUC) during an intraperitoneal glucose tolerance test. The glucose, but not insulin, AUC was lowered with Vit E/C supplementation. Improvements in glucose tolerance occurred independent of a restoration of PKB phosphorylation in tissues of rats stimulated with an intraperitoneal injection of insulin but were associated with increases in AMPK signaling in muscle and reductions in AMPK signaling and the expression of fatty acid oxidation enzymes in liver. There were no differences in mitochondrial enzymes in triceps muscles between groups. This study is the first to report that dietary Vit E/C supplementation can partially prevent DEX-induced glucose intolerance in rats.