Differential Association of Serum n-3 Polyunsaturated Fatty Acids with Various Cerebrovascular Lesions in Japanese Men.

BACKGROUND: An association between a high intake of marine-derived n-3 polyunsaturated fatty acids (n-3 PUFAs) with a lower risk of coronary heart disease was previously reported. However, the association between n-3 PUFAs and cerebrovascular lesions remains unclear. We evaluated this association in a general-population-based sample of Japanese men. METHODS: Participants were community-dwelling men (40-79 years old) living in Kusatsu City, Shiga, Japan. Serum concentrations of n-3 PUFAs, defined as the sum of eicosapentaenoic and docosahexaenoic acids, were measured via gas-liquid chromatography between 2006 and 2008. Magnetic resonance imaging was used to assess cerebrovascular lesions (including intracerebral large-artery stenosis, lacunar infarction, and microbleeds) and white matter lesions between 2012 and 2015. Logistic regression adjusting for conventional cardiovascular risk factors was used to estimate the odds ratio of prevalent cerebrovascular lesions per 1 standard deviation higher serum concentration of n-3 PUFAs. RESULTS: Of a total of 739 men, the numbers (crude prevalence in %) of prevalent cerebral large-artery stenoses, lacunar infarctions, microbleeds, and white matter lesions were 222 (30.0), 162 (21.9), 103 (13.9), and 164 (22.2), respectively. A 1 standard deviation higher concentration of n-3 PUFAs (30.5 µmol/L) was independently associated with lower odds of cerebral large-artery stenosis (multivariable-adjusted odds ratio, 0.80; 95% confidential interval, 0.67-0.97). There were no significant associations of n-3 PUFAs with the other types of lesions. CONCLUSIONS: n-3 PUFAs may have protective effects against large-artery stenosis, but not small vessel lesions, in the brain.

Family Support for Medical Nutritional Therapy and Dietary Intake among Japanese with Type 2 Diabetes (JDDM 56).

The aim of this study was to investigate the association between habitual dietary intake for patients with diabetes and the content of family support for medical nutritional therapy (MNT). Analyzed were 289 Japanese with type 2 diabetes (men, 58.5%; mean age, 62.0 years; mean HbA1c, 53.4 mmol/mol) who completed the Food Frequency Questionnaire and Diabetes Family Behavior Checklist (DFBC). Relationships of mean values for food group intake to DFBC responses regarding MNT were examined using multivariate analysis of covariance. Positive response to "Praise for following diet" was associated with lower sweets intake (none: 60.1 g/day; ≥once monthly: 50.9 g/day, p = 0.038) and higher seasoning intake (none: 21.6 g/day, ≥once monthly: 24.1 g/day, p = 0.046). Energy intake was higher with positive responses to "Eat at the same time that you do" (none: 1636 kcal/day, ≥once monthly: 1818 kcal/day, p = 0.038). "Nags about not following diet" was associated with higher fish (none: 68.7 g/day, ≥once monthly: 78.7 g/day, p = 0.042) and salt intake (none: 8.3 g/day, ≥once monthly: 9.0 g/day, p = 0.014). Eating foods not part of the diabetic diet (none: 218.4 g/day, ≥once monthly: 246.9 g/day, p = 0.014) resulted in a higher vegetable intake. In females, significant differences in relationships in the overall analysis were reversed. Our results clarified relationships between types of family support of patients with type 2 diabetes and their dietary intake and the importance of sex differences for more effective MNT.

Association of blood levels of marine omega-3 fatty acids with coronary calcification and calcium density in Japanese men.

BACKGROUND/OBJECTIVES: Clinical trials of eicosapentaenoic acid (EPA) among high-risk groups in Japan in which consumption of mairne-omega-3 fatty acids (OM3) is much higher than other countries showed slower progression of coronary atherosclerosis. We aimed to determine the cross-sectional associations of coronary artery calcification (CAC) and calcium density with OM3, EPA, and docosahexaenoic acid (DHA), two principal OM3, in the general population in Japan. SUBJECTS/METHODS: The Shiga Epidemiological Study of Subclinical Atherosclerosis examined a population-based sample of 1074 men aged 40-79 in 2006-08 for computed tomography-measured CAC score (CCS), a well-established biomarker of coronary atherosclerosis, CAC density score (CDS), a potential marker of plaque stabilization, serum levels of OM3, and risk factors. RESULTS: Prevalence of CCS > 0, ≥ 100, and ≥ 300 was 65.8%, 25.9%, and 12.9%, respectively; the mean (SD) OM3, EPA, and DHA were 10.1% (3.2), 3.2% (1.7), and 5.9% (1.6), respectively. Odds ratios (95% CI, p-value) of CCS 0, 100, and 300 in ordinal logistic regression associated with 1 SD increase of OM3, EPA, and DHA were 0.91 (0.81-1.03, p = 0.12), 0.99 (0.88-1.11, p = 0.87) and 0.84 (0.74-0.94, p = < 0.01), respectively. The inverse association of DHA with CCS remained significant in multivariate-adjusted model: odds ratio of 0.87 (0.77-0.99, p = 0.03). Blood levels of OM3, EPA, or DHA did not have any significant associations with CDS. CONCLUSIONS: DHA but not EPA had a significant inverse association with coronary atherosclerosis in the general population with high levels of OM3. Future trials are warranted comparing the effect of high-dose DHA and EPA on atherosclerosis and cardiovascular outcomes.

Role of dietary amino acid balance in diet restriction-mediated lifespan extension, renoprotection, and muscle weakness in aged mice.

Extending healthy lifespan is an emerging issue in an aging society. This study was designed to identify a dietary method of extending lifespan, promoting renoprotection, and preventing muscle weakness in aged mice, with a focus on the importance of the balance between dietary essential (EAAs) and nonessential amino acids (NEAAs) on the dietary restriction (DR)-induced antiaging effect. Groups of aged mice were fed ad libitum, a simple DR, or a DR with recovering NEAAs or EAAs. Simple DR significantly extended lifespan and ameliorated age-related kidney injury; however, the beneficial effects of DR were canceled by recovering dietary EAA but not NEAA. Simple DR prevented the age-dependent decrease in slow-twitch muscle fiber function but reduced absolute fast-twitch muscle fiber function. DR-induced fast-twitch muscle fiber dysfunction was improved by recovering either dietary NEAAs or EAAs. In the ad libitum-fed and the DR plus EAA groups, the renal content of methionine, an EAA, was significantly higher, accompanied by lower renal production of hydrogen sulfide (H2 S), an endogenous antioxidant. Finally, removal of methionine from the dietary EAA supplement diminished the adverse effects of dietary EAA on lifespan and kidney injury in the diet-restricted aged mice, which were accompanied by a recovery in H2 S production capacity and lower oxidative stress. These data imply that a dietary approach could combat kidney aging and prolong lifespan, while preventing muscle weakness, and suggest that renal methionine metabolism and the trans-sulfuration pathway could be therapeutic targets for preventing kidney aging and subsequently promoting healthy aging.

N-3 Polyunsaturated Fatty Acids Decrease the Protein Expression of Soluble Epoxide Hydrolase via Oxidative Stress-Induced P38 Kinase in Rat Endothelial Cells.

N-3 polyunsaturated fatty acids (PUFAs) improve endothelial function. The arachidonic acid-derived metabolites (epoxyeicosatrienoic acids (EETs)) are part of the endothelial hyperpolarization factor and are vasodilators independent of nitric oxide. However, little is known regarding the regulation of EET concentration by docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in blood vessels. Sprague-Dawley rats were fed either a control or fish oil diet for 3 weeks. Compared with the control, the fish oil diet improved acetylcholine-induced vasodilation and reduced the protein expression of soluble epoxide hydrolase (sEH), a key EET metabolic enzyme, in aortic strips. Both DHA and EPA suppressed sEH protein expression in rat aorta endothelial cells (RAECs). Furthermore, the concentration of 4-hydroxy hexenal (4-HHE), a lipid peroxidation product of n-3 PUFAs, increased in n-3 PUFA-treated RAECs. In addition, 4-HHE treatment suppressed sEH expression in RAECs, suggesting that 4-HHE (derived from n-3 PUFAs) is involved in this phenomenon. The suppression of sEH was attenuated by the p38 kinase inhibitor (SB203580) and by treatment with the antioxidant N-acetyl-L-cysteine. In conclusion, sEH expression decreased after n-3 PUFAs treatment, potentially through oxidative stress and p38 kinase. Mild oxidative stress induced by n-3 PUFAs may contribute to their cardio-protective effect.

Hypothalamic AMP-Activated Protein Kinase Regulates Biphasic Insulin Secretion from Pancreatic ß Cells during Fasting and in Type 2 Diabetes.

Glucose-stimulated insulin secretion (GSIS) by pancreatic ß cells is biphasic. However, the physiological significance of biphasic GSIS and its relationship to diabetes are not yet fully understood. This study demonstrated that impaired first-phase GSIS follows fasting, leading to increased blood glucose levels and brain glucose distribution in humans. Animal experiments to determine a possible network between the brain and ß cells revealed that fasting-dependent hyperactivation of AMP-activated protein kinase in the hypothalamus inhibited first-phase GSIS by stimulating the ß-adrenergic pancreatic nerve. Furthermore, abnormal excitability of this brain-ß cell neural axis was involved in diabetes-related impairment of first-phase GSIS in diabetic animals. Finally, pancreatic denervation improved first-phase GSIS and glucose tolerance and ameliorated severe diabetes by preventing ß cell loss in diabetic animals. These results indicate that impaired first-phase GSIS is critical for brain distribution of dietary glucose after fasting. Furthermore, ß cells in individuals with diabetes mistakenly sense that they are under conditions that mimic prolonged fasting. The present study provides additional insight into both ß cell physiology and the pathogenesis of ß cell dysfunction in type 2 diabetes.

Amla Enhances Mitochondrial Spare Respiratory Capacity by Increasing Mitochondrial Biogenesis and Antioxidant Systems in a Murine Skeletal Muscle Cell Line.

Amla is one of the most important plants in Indian traditional medicine and has been shown to improve various age-related disorders while decreasing oxidative stress. Mitochondrial dysfunction is a proposed cause of aging through elevated oxidative stress. In this study, we investigated the effects of Amla on mitochondrial function in C2C12 myotubes, a murine skeletal muscle cell model with abundant mitochondria. Based on cell flux analysis, treatment with an extract of Amla fruit enhanced mitochondrial spare respiratory capacity, which enables cells to overcome various stresses. To further explore the mechanisms underlying these effects on mitochondrial function, we analyzed mitochondrial biogenesis and antioxidant systems, both proposed regulators of mitochondrial spare respiratory capacity. We found that Amla treatment stimulated both systems accompanied by AMPK and Nrf2 activation. Furthermore, we found that Amla treatment exhibited cytoprotective effects and lowered reactive oxygen species (ROS) levels in cells subjected to t-BHP-induced oxidative stress. These effects were accompanied by increased oxygen consumption, suggesting that Amla protected cells against oxidative stress by using enhanced spare respiratory capacity to produce more energy. Thus we identified protective effects of Amla, involving activation of mitochondrial function, which potentially explain its various effects on age-related disorders.

1-Methylnicotinamide ameliorates lipotoxicity-induced oxidative stress and cell death in kidney proximal tubular cells.

Free fatty acid-bound albumin (FFA-albumin)-related oxidative stress is involved in the pathogenesis of proximal tubular cell (PTC) damage and subsequent renal dysfunction in patients with refractory proteinuria. Nicotinamide adenine dinucleotide (NAD) metabolism has recently been focused on as a novel therapeutic target for several modern diseases, including diabetes. This study was designed to identify a novel molecule in NAD metabolism to protect PTCs from lipotoxicity-related oxidative stress. Among 19 candidate enzymes involved in mammalian NAD metabolism, the mRNA expression level of nicotinamide n-methyltransferase (NNMT) was significantly increased in both the kidneys of FFA-albumin-overloaded mice and cultured PTCs stimulated with palmitate-albumin. Knockdown of NNMT exacerbated palmitate-albumin-induced cell death in cultured PTCs, whereas overexpression of NNMT inhibited it. Intracellular concentration of 1-Methylnicotinamide (1-MNA), a metabolite of NNMT, increased and decreased in cultured NNMT-overexpressing and -knockdown PTCs, respectively. Treatment with 1-MNA inhibited palmitate-albumin-induced mitochondrial reactive oxygen species generation and cell death in cultured PTCs. Furthermore, oral administration of 1-MNA ameliorated oxidative stress, apoptosis, necrosis, inflammation, and fibrosis in the kidneys of FFA-albumin-overloaded mice. In conclusion, NNMT-derived 1-MNA can reduce lipotoxicity-mediated oxidative stress and cell damage in PTCs. Supplementation of 1-MNA may have potential as a new therapy in patients with refractory proteinuria.

A fish-based diet intervention improves endothelial function in postmenopausal women with type 2 diabetes mellitus: a randomized crossover trial.

OBJECTIVE: The beneficial effects of fish and n-3 polyunsaturated fatty acids (PUFAs) consumption on atherosclerosis have been reported in numerous epidemiological studies. However, to the best of our knowledge, the effects of a fish-based diet intervention on endothelial function have not been investigated. Therefore, we studied these effects in postmenopausal women with type 2 diabetes mellitus (T2DM). MATERIALS/METHODS: Twenty-three postmenopausal women with T2DM were assigned to two four-week periods of either a fish-based diet (n-3 PUFAs ≧ 3.0 g/day) or a control diet in a randomized crossover design. Endothelial function was measured with reactive hyperemia using strain-gauge plethysmography and compared with the serum levels of fatty acids and their metabolites. Endothelial function was determined with peak forearm blood flow (Peak), duration of reactive hyperemia (Duration) and flow debt repayment (FDR). RESULTS: A fish-based dietary intervention improved Peak by 63.7%, Duration by 27.9% and FDR by 70.7%, compared to the control diet. Serum n-3 PUFA levels increased after the fish-based diet period and decreased after the control diet, compared with the baseline (1.49 vs. 0.97 vs. 1.19 mmol/l, p < 0.0001). There was no correlation between serum n-3 PUFA levels and endothelial function. An increased ratio of epoxyeicosatrienoic acid/dihydroxyeicosatrienoic acid was observed after a fish-based diet intervention, possibly due to the inhibition of the activity of soluble epoxide hydrolase. CONCLUSIONS: A fish-based dietary intervention improves endothelial function in postmenopausal women with T2DM. Dissociation between the serum n-3 PUFA concentration and endothelial function suggests that the other factors may contribute to this phenomenon.

Long chain n-3 polyunsaturated fatty acids and incidence rate of coronary artery calcification in Japanese men in Japan and white men in the USA: population based prospective cohort study.

OBJECTIVE: To determine whether serum concentrations of long chain n-3 polyunsaturated fatty acids (LCn3PUFAs) contribute to the difference in the incidence rate of coronary artery calcification (CAC) between Japanese men in Japan and white men in the USA. METHODS: In a population based, prospective cohort study, 214 Japanese men and 152 white men aged 40-49 years at baseline (2002-2006) with coronary calcium score (CCS)=0 were re-examined for CAC in 2007-2010. Among these, 175 Japanese men and 113 white men participated in the follow-up exam. Incident cases were defined as participants with CCS≥10 at follow-up. A relative risk regression analysis was used to model the incidence rate ratio between the Japanese and white men. The incidence rate ratio was first adjusted for potential confounders at baseline and then further adjusted for serum LCn3PUFAs at baseline. RESULTS: Mean (SD) serum percentage of LCn3PUFA was >100% higher in Japanese men than in white men (9.08 (2.49) vs 3.84 (1.79), respectively, p<0.01). Japanese men had a significantly lower incidence rate of CAC compared to white men (0.9 vs 2.9/100 person-years, respectively, p<0.01). The incidence rate ratio of CAC taking follow-up time into account between Japanese and white men was 0.321 (95% CI 0.150 to 0.690; p<0.01). After adjusting for age, systolic blood pressure, low density lipoprotein cholesterol, diabetes, and other potential confounders, the ratio remained significant (0.262, 95% CI 0.094 to 0.731; p=0.01). After further adjusting for LCn3PUFAs, however, the ratio was attenuated and became non-significant (0.376, 95% CI 0.090 to 1.572; p=0.18). CONCLUSIONS: LCn3PUFAs significantly contributed to the difference in the incidence of CAC between Japanese and white men.

4-Hydroxy hexenal derived from dietary n-3 polyunsaturated fatty acids induces anti-oxidative enzyme heme oxygenase-1 in multiple organs.

It has recently been reported that expression of heme oxygenase-1 (HO-1) plays a protective role against many diseases. Furthermore, n-3 polyunsaturated fatty acids (PUFAs) were shown to induce HO-1 expression in several cells in vitro, and in a few cases also in vivo. However, very few reports have demonstrated that n-3 PUFAs induce HO-1 in vivo. In this study, we examined the effect of fish-oil dietary supplementation on the distribution of fatty acids and their peroxidative metabolites and on the expression of HO-1 in multiple tissues (liver, kidney, heart, lung, spleen, intestine, skeletal muscle, white adipose, brown adipose, brain, aorta, and plasma) of C57BL/6 mice. Mice were divided into 4 groups, and fed a control, safflower-oil, and fish-oil diet for 3 weeks. One group was fed a fish-oil diet for just 1 week. The concentration of fatty acids, 4-hydroxy hexenal (4-HHE), and 4-hydroxy nonenal (4-HNE), and the expression of HO-1 mRNA were measured in the same tissues. We found that the concentration of 4-HHE (a product of n-3 PUFAs peroxidation) and expression of HO-1 mRNA were significantly increased after fish-oil treatment in most tissues. In addition, these increases were paralleled by an increase in the level of docosahexaenoic acid (DHA) but not eicosapentaenoic acid (EPA) in each tissue. These results are consistent with our previous results showing that DHA induces HO-1 expression through 4-HHE in vascular endothelial cells. In conclusion, we hypothesize that the HO-1-mediated protective effect of the fish oil diet may be through production of 4-HHE from DHA but not EPA in various tissues.

Altered unfolded protein response is implicated in the age-related exacerbation of proteinuria-induced proximal tubular cell damage.

Aging is a dominant risk factor for end-stage renal disease. We analyzed the mechanism involved in age-related exacerbation of proteinuria-induced proximal tubular cell (PTC) damage by focusing on endoplasmic reticulum-related unfolded protein response (UPR). After equal-degree induction of proteinuria in 24-month-old (aged) and 3-month-old (young) mice by intraperitoneal free fatty acid-bound albumin overload, tubulointerstitial lesions were more severe in aged than in young mice. In aged PTCs, proteinuria-induced cell-adaptive UPR resulting from induction of the molecular chaperone BiP was significantly suppressed, whereas proapoptotic UPR with CHOP overexpression was enhanced. Treatment with the exogenous molecular chaperone tauroursodeoxycholic acid (TUDCA) ameliorated proteinuria-induced tubulointerstitial lesions and PTC apoptosis in aged mice. Among the three UPR branches, alterations in the inositol-requiring 1α (IRE1α) pathway, but not the activating transcription factor 6 or PERK pathway, were associated with impaired BiP induction in aged kidneys. Moreover, siRNA-mediated suppression of BiP and IRE1α exacerbated free fatty acid-bound albumin-induced apoptosis in cultured PTCs, whereas siRNA-mediated CHOP suppression ameliorated apoptosis. Finally, proteinuria-induced BiP induction in PTCs was diminished in kidney specimens from elderly patients. These results indicate that maladaptive UPRs are involved in proteinuria-induced tubulointerstitial lesions exacerbation in aged kidneys, and that supplementation of chaperones may be used to treat elderly patients with persistent proteinuria. These results should improve understanding of cell vulnerability in aged kidneys.

Haematopoietic cells produce BDNF and regulate appetite upon migration to the hypothalamus.

Brain-derived neurotrophic factor (BDNF) suppresses food intake by acting on neurons in the hypothalamus. Here we show that BDNF-producing haematopoietic cells control appetite and energy balance by migrating to the hypothalamic paraventricular nucleus. These haematopoietic-derived paraventricular nucleus cells produce microglial markers and make direct contacts with neurons in response to feeding status. Mice with congenital BDNF deficiency, specifically in haematopoietic cells, develop hyperphagia, obesity and insulin resistance. These abnormalities are ameliorated by bone marrow transplantation with wild-type bone marrow cells. Furthermore, when injected into the third ventricle, wild-type bone marrow mononuclear cells home to the paraventricular nucleus and reverse the hyperphagia of BDNF-deficient mice. Our results suggest a novel mechanism of feeding control based on the production of BDNF by haematopoietic cells and highlight a potential new therapeutic route for the treatment of obesity.

Serum levels of marine-derived n-3 fatty acids in Icelanders, Japanese, Koreans, and Americans--a descriptive epidemiologic study.

In the 1990s Iceland and Japan were known as countries with high fish consumption whereas coronary heart disease (CHD) mortality in Iceland was high and that in Japan was low among developed countries. We described recent data fish consumption and CHD mortality from publicly available data. We also measured CHD risk factors and serum levels of marine-derived n-3 and other fatty acids from population-based samples of 1324 men in Iceland, Japan, South Korea, and the US. CHD mortality in men in Iceland was almost 3 times as high as that in Japan and South Korea. Generally, a profile of CHD risk factors in Icelanders compared to Japanese was more favorable. Serum marine-derived n-3 fatty acids in Iceland were significantly lower than in Japan and South Korea but significantly higher than in the US.

Inactivation of TNF-α ameliorates diabetic neuropathy in mice.

Tumor necrosis factor (TNF)-α is a potent proinflammatory cytokine involved in the pathogenesis of diabetic neuropathy. We inactivated TNF-α to determine if it is a valid therapeutic target for the treatment of diabetic neuropathy. We effected the inactivation in diabetic neuropathy using two approaches: by genetic inactivation of TNF-α (TNF-α(-/-) mice) or by neutralization of TNF-α protein using the monoclonal antibody infliximab. We induced diabetes using streptozotocin in wild-type and TNF-α(-/-) mice. We measured serum TNF-α concentration and the level of TNF-α mRNA in the dorsal root ganglion (DRG) and evaluated nerve function by a combination of motor (MNCV) and sensory (SNCV) nerve conduction velocities and tail flick test, as well as cytological analysis of intraepidermal nerve fiber density (IENFD) and immunostaining of DRG for NF-κB p65 serine-276 phosphorylated and cleaved caspase-3. Compared with nondiabetic mice, TNF-α(+/+) diabetic mice displayed significant impairments of MNCV, SNCV, tail flick test, and IENFD as well as increased expression of NF-κB p65 and cleaved caspase-3 in their DRG. In contrast, although nondiabetic TNF-α(-/-) mice showed mild abnormalities of IENFD under basal conditions, diabetic TNF-α(-/-) mice showed no evidence of abnormal nerve function tests compared with nondiabetic mice. A single injection of infliximab in diabetic TNF-α(+/+) mice led to suppression of the increased serum TNF-α and amelioration of the electrophysiological and biochemical deficits for at least 4 wk. Moreover, the increased TNF-α mRNA expression in diabetic DRG was also attenuated by infliximab, suggesting infliximab's effects may involve the local suppression of TNF-α. Infliximab, an agent currently in clinical use, is effective in targeting TNF-α action and expression and amelioration of diabetic neuropathy in mice.

Elevated serum levels of interleukin-18 in patients with overt diabetic nephropathy: effects of miglitol.

BACKGROUND: Interleukin-18 (IL-18), a pro-inflammatory cytokine, is a predictor of cardiovascular and renal disease in diabetic patients. Postprandial hyperglycemia is one of the important factors contributing to an increase in the circulating pro-inflammatory cytokine levels. This study investigated the effect of miglitol, an α-glucosidase inhibitor, on postprandial hyperglycemia and IL-18 levels in diabetic patients with nephropathy. METHODS: Fifteen Japanese diabetic patients with persistent proteinuria and preserved renal function were recruited. The patients received 50 mg miglitol thrice daily after the baseline examinations and were followed up for 12 weeks. A meal tolerance test was performed on eight patients at baseline and week 12. The fasting miglitol concentration was measured in seven patients just before the meal tolerance test. RESULTS: There were no changes in the body weight, blood pressure, liver and renal function, and proteinuria from baseline to week 12. However, the levels of glycated hemoglobin and interleukin 18 significantly decreased from baseline to week 12. During the meal tolerance test, plasma glucose was significantly decreased 60 min after treatment with miglitol, whereas the serum concentration of insulin was not changed. Fasting and postprandial levels of IL-18 were significantly decreased from baseline to week 12. Serum miglitol concentrations showed a significantly negative correlation with eGFR (r = -0.82, p = 0.02). However, the serum miglitol concentrations did not changed during the course of this study. CONCLUSION: Miglitol improved postprandial hyperglycemia and reduced serum IL-18 levels in patients with stage 3 diabetic nephropathy. Miglitol may therefore prevent atherosclerotic diseases and diabetic micro-vascular complications through decreasing glucose swings and/or the circulating IL-18 level.

Low concentration of 4-hydroxy hexenal increases heme oxygenase-1 expression through activation of Nrf2 and antioxidative activity in vascular endothelial cells.

Large-scale clinical studies have shown that n-3 polyunsaturated fatty acids (n-3 PUFAs) such as eicosapentaenoic and docosahexaenoic acids reduce cardiovascular events without improving classical risk factors for atherosclerosis. Recent studies have proposed that direct actions of n-3 PUFAs themselves, or of their enzymatic metabolites, have antioxidative and anti-inflammatory effects on vascular cells. Although a recent study showed that plasma 4-hydroxy hexenal (4-HHE), a peroxidation product of n-3 PUFA, increased after supplementation of docosahexaenoic acid, the antiatherogenic effects of 4-HHE in vascular cells remain unclear. In the present study, we tested the hypothesis that 4-HHE induces the antioxidative enzyme heme oxygenase-1 (HO-1) through activation of nuclear factor erythroid 2-related factor 2 (Nrf2), a master regulatory transcriptional factor, and prevents oxidative stress-induced cytotoxicity in vascular endothelial cells. This mechanism could partly explain the cardioprotective effects of n-3 PUFAs. Human umbilical vein endothelial cells were stimulated with 1-10µM 4-HHE or 4-hydroxy nonenal (4-HNE), a peroxidation product of n-6 PUFAs. Both 4-HHE and 4-HNE dose-dependently increased HO-1 mRNA and protein expression, and intranuclear expression and DNA binding of Nrf2 at 5µM. Small interfering RNA for Nrf2 significantly reduced 4-HHE- or 4-HNE-induced HO-1 mRNA and protein expression. Furthermore, pretreatment with 4-HHE or 4-HNE prevented tert-butyl hydroperoxide-induced cytotoxicity. In conclusion, 4-HHE, a peroxidation product of n-3 PUFAs, stimulated expression of the antioxidant enzyme HO-1 through the activation of Nrf2 in vascular endothelial cells. This resulted in prevention of oxidative stress-induced cytotoxicity, and may represent a possible mechanism to partly explain the cardioprotective effects of n-3 PUFAs.

Circulating levels of 8 cytokines and marine n-3 fatty acids and indices of obesity in Japanese, white, and Japanese American middle-aged men.

This study examines the differences in circulating levels of cytokines among Japanese in Japan (JJ), Japanese Americans (JA), and whites and their associations with obesity and marine n-3 fatty acids (FA) in a cross-sectional population-based study of 297 men aged 40-49 (100 JJ, 99 whites, and 98 JA). Experimental studies show that cytokines are associated with obesity positively and marine n-3 FA inversely. Serum interleukin-1alpha (IL-1alpha), IL-1 receptor agonist (IL-1ra), IL-4, IL-8, IL-10, inducible protein-10 (IP-10), tumor necrosis factor-alpha (TNF-alpha), monocyte chemoattractant protein-1 (MCP-1), and marine n-3 FA were determined. Body mass index (BMI), waist circumference, and computed tomography-measured visceral and subcutaneous adipose tissues were determined. The JJ had significantly lower levels of IL-1alpha, IL-4, IL-8, MCP-1, and TNF-alpha than whites and JA. Whites and JA had similar levels of IL-1alpha, IL-4, and IL-8 whereas whites had significantly higher levels of MCP-1 and TNF-alpha than JA. The JJ were least obese (BMI (kg/m(2)), mean +/- standard deviation) 23.6 +/- 2.8, 27.9 +/- 4.6, and 27.9 +/- 4.5 for JJ, whites, and JA, respectively. The JJ had marine n-3 FA about 100% higher than whites and JA (serum marine n-3 FA (%), median (interquartile range) 8.79 (7.41, 11.16), 3.47 (2.63, 4.83), and 4.44 (3.33, 6.01) for JJ, whites, and JA, respectively). Generally cytokines had weak and nonsignificant associations with indices of obesity and nonsignificant associations with marine n-3 FA. BMI had significant inverse associations with IL-1alpha, IL-4, and IL-8 in JA (P < 0.05). Marine n-3 FA had marginally significant inverse associations with IL-8 in JJ (P = 0.055) and TNF-alpha in whites (P = 0.076). The JJ had lower levels of many cytokines than whites and JA. Generally cytokines had weak and nonsignificant associations with indices of obesity and marine n-3 FA. Further investigation is needed to determine why JJ had lower circulating levels of cytokines.

Diet high in lipid hydroperoxide by vitamin E deficiency induces insulin resistance and impaired insulin secretion in normal rats.

To clarify the effect of dietary lipid hydroperoxide (LPO) on development of glucose intolerance, we fed Sprague-Dawley rats on a diet containing elevated LPO level for 10 weeks and measured both insulin sensitivity and insulin secretion. The contents of LPO in both plasma and skeletal muscle in the LPO-fed rats were significantly higher than those in the controls. Both insulin resistance evaluated by steady-state blood glucose (SSBG) methods and impaired insulin secretion evaluated by oral glucose tolerance test (OGTT) were found in the LPO-fed rats as compared with control rats. Furthermore, the levels of insulin receptor substrate (IRS)-1 protein in the skeletal muscle were significantly lower in the LPO-fed rats. Those impairments were not reversed in LPO-fed rats with supernormal levels of plasma vitamin E following vitamin E supplementation for 5 weeks. Moreover, the immunohistochemical study revealed that NF-kappaB-p50 protein was found in the nucleus of pancreatic beta-cells of the LPO-fed rats, whereas it was not observed in the nucleus of the islets in the control rats. These findings indicate that NF-kappaB is activated in response to oxidative stress in pancreatic islet cells in LPO-fed rats. In conclusion, our studies reveal that diet high in LPO by vitamin E deficiency accelerates glucose intolerance through impairments of both sensitivity and secretion of insulin.

Protein-tyrosine phosphatase 1B as new activator for hepatic lipogenesis via sterol regulatory element-binding protein-1 gene expression.

Like hyperglycemia, postprandial (diet-induced) hypertriglyceridemia is thought to play crucial roles in the pathogenesis of insulin resistant/metabolic syndrome. Sterol regulatory element-binding protein-1 (SREBP-1) is a key transcription factor to induce postprandial hypertriglyceridemia. We found that insulin-resistant rats fed a diet high in fructose showed an increased proteintyrosine phosphatase 1B (PTP1B) content with strong expression of SREBP-1 mRNA in the liver. To clarify the association of PTP1B with SREBP-1 gene expression, we overexpressed PTP1B in rat hepatocytes, which led to increased mRNA content and promoter activity of SREBP-1a and -1c, resulting in the increased mRNA expression of fatty-acid synthase, one of the SREBP-1-responsive lipogenic genes. Because PTP1B overexpression increased phosphatase 2A (PP2A) activity, we inhibited PP2A activity by expression of its selective inhibitor, SV40 small T antigen and found that this normalized the PTP1B-enhanced SREBP-1a and -1c mRNA expressions through activation of the Sp1 site. These results indicate that PTP1B may regulate gene expression of SREBP-1 via enhancement of PP2A activity, thus mediating hepatic lipogenesis and postprandial hypertriglyceridemia. We demonstrate here a unique serial activation of the PTP1B-PP2A axis as a novel mechanism for the regulation of gene expression in the biosynthesis of triglyceride.