Body mass index and waist circumference both contribute to differences in insulin-mediated glucose disposal in nondiabetic adults

BACKGROUND: Overweight and obese individuals are more likely to be insulin resistant and at increased risk of adverse clinical outcomes. Questions remain as to whether waist circumference (WC) or body mass index (BMI) most effectively identifies insulin-resistant individuals. OBJECTIVE: This study quantified insulin-mediated glucose uptake (IMGU) in 330 apparently healthy volunteers and compared the relation between this value and measurements of WC and BMI. DESIGN: IMGU was quantified via determination of the steady-state plasma glucose (SSPG) concentration during the insulin-suppression test. Differences in SSPG concentrations due to variations in WC within a given BMI category, as well as those due to differences in BMI within a given WC classification, were then compared. RESULTS: BMI and WC correlated with each other (r = 0.78, P < 0.001) and equally with SSPG concentrations (r = 0.58 and 0.57, respectively; P < 0.001). When stratified by BMI, abdominally obese subjects within the overweight BMI category had higher SSPG concentrations than did those with a normal WC (P < 0.05). When classified by WC, subjects in the overweight BMI category had greater SSPG concentrations than did subjects in the normal BMI category within the normal WC category (P < 0.01), as did subjects in the obese BMI category in comparison with subjects in the overweight BMI category within the obese WC category (P < 0.01). CONCLUSIONS: The more overweight or obese a person, the greater the degree of insulin resistance; differences in adiposity accounted for approximately one-third of the variation in IMGU, irrespective of the index used. Furthermore, there was no difference in the relation between the degree of insulin resistance and either index of adiposity.     

Effect of insulin resistance on postprandial elevations of remnant lipoprotein concentrations in postmenopausal women.

BACKGROUND: Questions remain as to why postmenopausal women are at a higher risk of coronary artery disease (CAD) than are premenopausal women. Studies have shown that plasma concentrations of remnant lipoproteins (RLPs) are elevated in patients with CAD and that increases in plasma RLP concentrations may be related to variations in insulin-mediated glucose disposal. OBJECTIVE: We sought to evaluate the possibility that postprandial accumulation of plasma RLPs will be accentuated in insulin-resistant, postmenopausal women. DESIGN: Postmenopausal women were divided into insulin-sensitive (n = 15) and insulin-resistant (n = 15) groups according to their steady state plasma glucose concentrations in response to a 180-min infusion of octreotide, insulin, and glucose. Plasma insulin, triacylglycerol, and RLP-cholesterol concentrations were measured either hourly (insulin) or every 2 h (triacylglycerol and RLP cholesterol) for 8 h, before and after breakfast (0800) and lunch (1200). RESULTS: By selection, insulin-resistant women had higher steady state plasma glucose concentrations than did insulin-sensitive women (10.8 +/- 0.5 compared with 4.1 +/- 5 mmol/L, respectively; P < 0.001), associated with higher fasting triacylglycerol (1.58 +/- 0.04 compared with 1.00 +/- 0.03 mmol/L; P = 0.01) and lower HDL-cholesterol (1.06 +/- 0.08 compared with 1.34 +/- 0.05; P = 0.01) concentrations. In addition, measurements of daylong concentrations of insulin, triacylglycerol, and RLP cholesterol were also significantly greater in insulin-resistant than in insulin-sensitive women (P < 0.001). CONCLUSIONS: Postprandial accumulation of RLPs is accentuated in insulin-resistant, postmenopausal women. This may contribute to the increased risk of CAD in these individuals.     

Increased fat accumulation in liver may link insulin resistance with subcutaneous abdominal adipocyte enlargement, visceral adiposity, and hypoadiponectinemia in obese individuals

BACKGROUND: Enlargement of adipocytes from subcutaneous abdominal adipose tissue (SAT), increased intrahepatic lipid content (IHL), intramyocellular lipid content (IMCL), and low circulating adiponectin concentrations are associated with insulin resistance. OBJECTIVE: Because adiponectin increases fat oxidation in skeletal muscle and liver, and the expression of the adiponectin gene in SAT is inversely associated with adipocyte size, we hypothesized that hypoadiponectinemia links hypertrophic obesity with insulin resistance via increased IMCL and IHL. DESIGN: Fifty-three obese Pima Indians with a mean (+/-SD) age of 27 +/- 8 y, body fat of 35 +/- 5%, and normal glucose regulation (normal fasting and 2-h glucose concentration per WHO 1999 criteria) underwent euglycemic-hyperinsulinemic clamp, biopsies of SAT and vastus lateralis muscle, and magnetic resonance imaging of the abdomen. RESULTS: Adipocyte diameter (AD) correlated positively with body fat (P < 0.0001) and IHL (estimated from magnetic resonance imaging intensity of liver; P = 0.047). No association was found between AD and plasma adiponectin or IMCL. Plasma adiponectin negatively correlated with type II IMCL (IIA, P = 0.004; IIX, P = 0.009) or IHL (P = 0.02). In a multivariate analysis, plasma adiponectin, AD, and visceral adipose tissue (VAT) independently predicted IHL. Low insulin-mediated glucose disposal was associated with low plasma adiponectin (P = 0.02) and high IHL (P = 0.0003), SAT (P = 0.02), and VAT (P = 0.04). High IHL was the only predictor of reduced insulin-mediated suppression of hepatic glucose production (P = 0.02) and the only independent predictor of insulin-mediated glucose disposal in a multivariate analysis. CONCLUSIONS: Increased lipid content in the liver may independently link hypoadiponectinemia, hypertrophic obesity, and increased visceral adiposity with peripheral and hepatic insulin resistance.     

The relationship between the acute changes in the systemic inflammatory response, lipid soluble antioxidant vitamins and lipid peroxidation following elective knee arthroplasty

BACKGROUND AND AIMS: The aim of the present study was to examine the time course of the change in the concentrations of plasma retinol, alpha-tocopherol, lutein, lycopene, alpha-carotene, beta-carotene (antioxidant vitamins) and malondialdehyde (lipid peroxidation) in patients following elective knee arthroplasty. METHODS: Patients (n=20) who underwent an elective knee arthroplasty, had venous blood samples withdrawn pre-operatively and at 12, 24, 48, 72 and 168 h after the start of surgery for the analysis of circulating concentrations of C-reactive protein, albumin, cholesterol, triglycerides and malondialdehyde and also the lipid soluble antioxidants vitamins. RESULTS: Over the study period of 0-168 h there was a significant increase in circulating C-reactive protein concentrations (peak 48 h, P<0.001) and a significant fall in albumin, cholesterol and triglyceride concentrations (trough 48 h, P<0.001). Malondialdehyde concentrations fell by approximately 35% (P<0.001) during the study period. However, they did not alter significantly over the study period when adjusted for triglyceride (P=0.309). The plasma concentrations of retinol, alpha-tocopherol, lutein, lycopene, alpha-carotene and beta-carotene all fell (P0.001). When adjusted for cholesterol, the reductions in plasma concentrations of alpha-tocopherol, lutein, lycopene, and beta-carotene in the post-operative period were no longer statistically significant. CONCLUSIONS: The results of the present study indicate that, in apparently healthy subjects undergoing an acute inflammatory insult, circulating lipid soluble vitamin antioxidants are transiently reduced. However, when corrected for lipids the concentrations were similar to those of baseline. In the absence of an increase in lipid peroxidation such falls in plasma concentrations of lipid soluble vitamins are unlikely to be a reliable measure of status.     

Lipid peroxidation and plasma antioxidant micronutrients in Crohn disease

BACKGROUND: In Crohn disease (CD), the increased production of reactive oxygen species from activated neutrophils may reduce plasma concentrations of antioxidant vitamins and result in increased oxidative stress. OBJECTIVE: We compared lipid peroxidation, a measure of reactive-oxygen-species production, and plasma antioxidant vitamin concentrations between CD patients and healthy control subjects. DESIGN: Thirty-seven nonsmoking CD patients (22 women and 15 men) were compared with an equal number of healthy control subjects who were matched by age, sex, and body mass index. In patients the mean CD activity index (CDAI) was 141.2 +/- 18.7 (range: 9.0-514), and 11 of 37 patients (30%) had a CDAI > or =150. Seventy-eight percent of patients were taking > or = 1 medication. Medication use by subjects included the following: 5-aminosalicylic acid (40% of subjects), antibiotics (22%), oral corticosteroids (30%), and immunosuppressants (19%). RESULTS: Lipid peroxidation as measured by breath pentane output (CD patients, 7.47 +/- 0.98 pmol x kg(-1) x min(-1); control subjects, 4.97 +/- 0.48 pmol x kg(-1) x min(-1); P < or = 0.025), breath ethane output (CD patients, 11.24 +/- 1.17 pmol x kg(-1) x min(-1); control subjects, 5.46 +/- 0.71 pmol x kg(-1) x min(-1); P < or = 0.0005) and F2-isoprostane (CD patients, 78.6 +/- 8.0 ng/L; control subjects, 60.6 +/- 3.7 ng/L; P < or = 0.047) were significantly higher in CD patients than in control subjects. Plasma antioxidant vitamins (ascorbic acid, alpha- and beta-carotene, lycopene, and beta-cryptoxanthin) were all significantly lower in CD patients than in control subjects. There were no significant differences in macro- and micronutrient intakes between groups. CONCLUSION: Patients with CD are oxidatively stressed, which was observed even though 70% of patients had a CDAI < or =150 and 78% of them were taking medications to treat CD.     

Insulin sensitivity in Chinese ovo-lactovegetarians compared with omnivores

AIM: To compare the insulin sensitivity indices between Chinese vegetarians and omnivores. METHODS: The study included 36 healthy volunteers (vegetarian, n=19; omnivore, n=17) who had normal fasting plasma glucose levels. Each participant completed an insulin suppression test. We compared steady-state plasma glucose (SSPG), fasting insulin, the homeostasis model assessment for insulin sensitivity (HOMA-IR and HOMA %S) and beta-cell function (HOMA %beta) between the groups. We also tested the correlation of SSPG with years on a vegetarian diet. RESULTS: The omnivore subjects were younger than the vegetarians (55.7+/-3.7 vs 58.6+/-3.6 year of age, P=0.022). There was no difference between the two groups in sex, blood pressure, renal function tests and lipid profiles. The omnivores had higher serum uric acid levels than vegetarians (5.25+/-0.84 vs 4.54+/-0.75 mg/dl, P=0.011). The results of the indices were different between omnivores and vegetarians (SSPG (mean+/-s.d.) 105.4+/-10.2 vs 80.3+/-11.3 mg/dl, P<0.001; fasting insulin, 4.06+/-0.77 vs 3.02+/-1.19 microU/ml, P=0.004; HOMA-IR, 6.75+/-1.31 vs 4.78+/-2.07, P=0.002; HOMA %S, 159.2+/-31.7 vs 264.3+/-171.7%, P=0.018) except insulin secretion index, HOMA %beta (65.6+/-18.0 vs 58.6+/-14.8%, P=0.208). We found a clear linear relation between years on a vegetarian diet and SSPG (r=-0.541, P=0.017). CONCLUSIONS: The vegetarians were more insulin sensitive than the omnivore counterparts. The degree of insulin sensitivity appeared to be correlated with years on a vegetarian diet.     

Postprandial hyperglycemia impairs vascular endothelial function in healthy men by inducing lipid peroxidation and increasing asymmetric dimethylarginine:arginine

Postprandial hyperglycemia induces vascular endothelial dysfunction (VED) and increases future cardiovascular disease risk. We hypothesized that postprandial hyperglycemia would decrease vascular function in healthy men by inducing oxidative stress and proinflammatory responses and increasing asymmetric dimethylarginine:arginine (ADMA:arginine), a biomarker that is predictive of reduced NO biosynthesis. In a randomized, cross-over design, healthy men (n = 16; 21.6 ± 0.8 y) ingested glucose or fructose (75 g) after an overnight fast. Brachial artery flow-mediated dilation (FMD), plasma glucose and insulin, antioxidants, malondialdehyde (MDA), inflammatory proteins, arginine, and ADMA were measured at regular intervals during the 3-h postprandial period. Baseline FMD did not differ between trials (P > 0.05). Postprandial FMD was reduced following the ingestion of glucose only. Postprandial MDA concentrations increased to a greater extent following the ingestion of glucose compared to fructose. Plasma arginine decreased and the ratio of ADMA:arginine increased to a greater extent following the ingestion of glucose. Inflammatory cytokines and cellular adhesion molecules were unaffected by the ingestion of either sugar. Postprandial AUC(0-3 h) for FMD and MDA were inversely related (r = -0.80; P < 0.05), suggesting that hyperglycemia-induced lipid peroxidation suppresses postprandial vascular function. Collectively, these findings suggest that postprandial hyperglycemia in healthy men reduces endothelium-dependent vasodilation by increasing lipid peroxidation independent of inflammation. Postprandial alterations in arginine and ADMA:arginine also suggest that acute hyperglycemia may induce VED by decreasing NO bioavailability through an oxidative stress-dependent mechanism. Additional work is warranted to define whether inhibiting lipid peroxidation and restoring arginine metabolism would mitigate hyperglycemia-mediated decreases in vascular function.     

Low molecular weight plasma antioxidants and lipid peroxidation in maternal and cord blood

OBJECTIVE: To determine the concentrations of the low molecular weight antioxidants urate, bilirubin, albumin and sulphydryl groups and to measure lipid peroxidation levels in pair-matched maternal and cord blood plasma. DESIGN: Venous blood plasma concentrations of urate, bilirubin, albumin and sulphydryls were determined in healthy pregnant women and in pair matched umbilical cords. The ability of maternal and cord plasma to withstand Cu2+-induced lipid peroxidation was assessed by measuring the production of thiobarbituric acid reactive substances (TBARS) over time in plasma incubated with Cu2+. SUBJECTS: Forty healthy women, between 10 and 20 weeks gestation, were recruited randomly from an antenatal clinic. Venous blood samples were obtained from the mothers at the recruitment stage and from the umbilical cords of their newborn after delivery. RESULTS: Urate, bilirubin and sulphydryls were present in significantly higher concentrations (P<0.001) in cord plasma than in maternal plasma. Albumin levels were similar in mothers and cords. Significantly lower levels (P=0.018) of TBARS were produced in cord plasma compared with maternal plasma following incubation with Cu2+. There were significant correlations between albumin and sulphydryl concentrations in maternal plasma (r 0.43, P=0.007) and between urate concentrations in maternal and cord plasma (r 0.37, P=0.026). CONCLUSION: Urate, bilirubin and sulphydryls are present in significantly higher concentrations in cord blood than in maternal blood. The increased levels of these antioxidants in cord plasma may contribute to the increased resistance of cord plasma to Cu2+-induced lipid peroxidation.     

Effects of a Rubus coreanus Miquel supplement on plasma antioxidant capacity in healthy Korean men

Korean raspberry, Rubus coreanus Miquel (RCM), contains high concentrations of phenolic compounds, which prevent oxidative stress. To determine the effect of RCM on antioxidant capacity in humans, we assessed in vivo lipid oxidation and antioxidant enzyme activities from plasma in 15 healthy men. The subjects ingested 30 g of freeze-dried RCM daily for 4 weeks. Blood was taken at baseline and at the end of the study to determine blood lipid profiles, fasting plasma glucose, liver function, lipid peroxidation, and antioxidant enzyme activities. RCM supplementation had no effect on blood lipid or fasting plasma glucose concentrations but decreased alkaline phosphatase activity. RCM supplementation increased glutathione peroxidase activities (P < 0.05) but had no effect on lipid peroxidation. These results suggest that short-term RCM supplementation may offer health benefits by enhancing antioxidant capacity in a healthy population.     

Assessment of red blood cell glutathione status in insulin resistance

The aim of this study was to assess red blood cell glutathione from insulin-sensitive and insulin-resistant individuals before and after an oral glucose dose. Fifteen healthy, young (24 ± 5 years), nonobese (23 ± 2 kg·m?2), insulin-sensitive (ISI composite = 6.0 ± 1.2) individuals and 14 healthy, young (22 ± 2 years), nonobese (24 ± 2 kg·m?2), insulin-resistant (ISI composite = 2.7 ± 1.1) individuals received a 75 g oral glucose dose. Blood samples were drawn before and for 2 h after glucose ingestion for red blood cell glutathione and serum glucose and insulin concentrations. Glycemia before and after glucose ingestion was similar between groups (p = 0.17), which suggest that hyperinsulinemia compensated impaired insulin sensitivity. Red blood cell total (p = 0.81), reduced (p = 0.79), and oxidized (p = 0.88) glutathione concentrations were similar between groups under fasting and postprandial conditions. However, in response to glucose, increases in total and reduced glutathione concentrations were found at the end of the 2 h assessment period in both groups (p < 0.05). Direct associations between postprandial glucose response and red blood cell total (r = 0.52; p < 0.05) and oxidized (r = 0.61; p = 0.02) glutathione concentrations were observed only in insulin-sensitive subjects. In conclusion, healthy individuals differing in their degree of insulin resistance showed similar red blood cell glutathione concentrations under non-glucose- and glucose-stimulated conditions.     

A 4-wk high-fructose diet alters lipid metabolism without affecting insulin sensitivity or ectopic lipids in healthy humans

BACKGROUND: High fructose consumption is suspected to be causally linked to the epidemics of obesity and metabolic disorders. In rodents, fructose leads to insulin resistance and ectopic lipid deposition. In humans, the effects of fructose on insulin sensitivity remain debated, whereas its effect on ectopic lipids has never been investigated. OBJECTIVE: We assessed the effect of moderate fructose supplementation on insulin sensitivity (IS) and ectopic lipids in healthy male volunteers (n = 7). DESIGN: IS, intrahepatocellular lipids (IHCL), and intramyocellular lipids (IMCL) were measured before and after 1 and 4 wk of a high-fructose diet containing 1.5 g fructose . kg body wt(-1) . d(-1). Adipose tissue IS was evaluated from nonesterified fatty acid suppression, hepatic IS from suppression of hepatic glucose output (6,6-2H2-glucose), and muscle IS from the whole-body glucose disposal rate during a 2-step hyperinsulinemic euglycemic clamp. IHCL and IMCL were measured by 1H magnetic resonance spectroscopy. RESULTS: Fructose caused significant (P < 0.05) increases in fasting plasma concentrations of triacylglycerol (36%), VLDL-triacylglycerol (72%), lactate (49%), glucose (5.5%), and leptin (48%) without any significant changes in body weight, IHCL, IMCL, or IS. IHCL were negatively correlated with triacylglycerol after 4 wk of the high-fructose diet (r = -0.78, P < 0.05). CONCLUSION: Moderate fructose supplementation over 4 wk increases plasma triacylglycerol and glucose concentrations without causing ectopic lipid deposition or insulin resistance in healthy humans.     

Supplementation with cactus pear (Opuntia ficus-indica) fruit decreases oxidative stress in healthy humans: a comparative study with vitamin C

BACKGROUND: Cactus pear (Opuntia ficus-indica) fruit contains vitamin C and characteristic betalain pigments, the radical-scavenging properties and antioxidant activities of which have been shown in vitro. OBJECTIVE: We investigated the effects of short-term supplementation with cactus pear fruit compared with vitamin C alone on total-body oxidative status in healthy humans. DESIGN: In a randomized, crossover, double-treatment study, 18 healthy volunteers received either 250 g fresh fruit pulp or 75 mg vitamin C twice daily for 2 wk, with a 6-wk washout period between the treatments. Before (baseline) and after each treatment, 8-epi-prostaglandin F(2alpha) (8-epi-PGF(2alpha)) and malondialdehyde in plasma, the ratio of reduced to oxidized glutathione (GSH:GSSG) in erythrocytes, and lipid hydroperoxides in LDL were measured as biomarkers of oxidative stress; plasma Trolox-equivalent antioxidant activity (TEAC) and vitamins A, E, and C were evaluated as indexes of antioxidant status. RESULTS: Both treatments caused comparable increases compared with baseline in plasma concentrations of vitamin E and vitamin C (P < 0.05); vitamin A and TEAC did not change significantly. After supplementation with cactus pear fruit, 8-epi-PGF(2)alpha and malondialdehyde decreased by approximately 30% and 75%, respectively; GSH:GSSG shifted toward a higher value (P < 0.05); and LDL hydroperoxides were reduced by almost one-half. Supplementation with vitamin C did not significantly affect any marker of oxidative stress. CONCLUSIONS: Consumption of cactus pear fruit positively affects the body's redox balance, decreases oxidative damage to lipids, and improves antioxidant status in healthy humans. Supplementation with vitamin C at a comparable dosage enhances overall antioxidant defense but does not significantly affect body oxidative stress. Components of cactus pear fruit other than antioxidant vitamins may play a role in the observed effects.     

A mixed fruit and vegetable concentrate increases plasma antioxidant vitamins and folate and lowers plasma homocysteine in men

Fruit and vegetable consumption is inversely associated with coronary heart disease (CHD) risk. The aim of the present study was to determine the effect of supplementation with dehydrated juice concentrates from mixed fruit and vegetables on selected plasma vitamins and antioxidant status. We assessed CHD risk by measuring the concentrations of homocysteine, lipids, lipoproteins, glucose and insulin. Men were recruited to participate in a randomized double-blind, crossover trial with 2 periods of 6 wk, separated by a 3-wk wash-out period. Supplementation with the encapsulated mixed extract (Juice Plus) was compared with physically similar placebo capsules. Thirty-two men (13 smokers, 19 nonsmokers) completed the study with a mean compliance of 88%. Compared with placebo, supplementation increased the concentrations of plasma beta-carotene (0.24 +/- 0.15 vs. 1.12 +/- 0.70 micro mol/L; mean +/- SD; P < 0.0001), retinol (1.87 +/- 0.33 vs. 2.00 +/- 0.43 micro mol/L; P < 0.05), alpha-tocopherol (16.8 +/- 7.3 vs. 19.3 +/- 6.8 micro mol/L; P < 0.01), ascorbic acid (72.1 +/- 19.4 vs. 84.1 +/- 13.5 micro mol/L; P < 0.002) and folic acid (24.5 +/- 10.0 vs. 44.9 +/- 16.9 nmol/L; P < 0.0001). Plasma homocysteine was reduced (8.2 +/- 1.5 vs. 7.6 +/- 1.1; P < 0.05) and inversely related (r = -0.40, P < 0.001) with serum folate concentrations. Plasma vitamin C was positively correlated with the resistance of LDL to oxidation (r = 0.26, P < 0.05) and the plasma ferric reducing/antioxidant power (FRAP) tended to be greater after supplementation than after the placebo period (1125.5 +/- 144.1 vs. 1180.3 +/- 158.1 micro mol/L; P < 0.065). Plasma glucose, insulin and lipid concentrations were unaffected. Responses of smokers and nonsmokers did not differ. In the absence of dietary modification, supplementation with a fruit and vegetable concentrate produced responses consistent with a reduction in CHD risk.     

Orange pulp improves antioxidant status and suppresses lipid peroxidation in orchidectomized male rats

OBJECTIVE: Oxidative stress is linked to an increased incidence of cardiovascular disease in men. The objective of this research was to delineate whether daily consumption of orange pulp (OP) modifies antioxidant status and decreases cardiovascular risk factors in orchidectomized rats. METHODS: In the present study, 45 1-y-old male rats were randomized to a sham-control group (n = 9) and an orchidectomized group (n = 36). The orchidectomized group was equally divided among the following five treatments: orchidectomy (ORX), ORX + 2.5% OP, ORX + 5% OP, and ORX + 10% OP. One hundred twenty days after the study began, all rats were sacrificed and plasma was harvested for its antioxidant status, C-reactive protein (CRP), lipid profile, and indices of peroxidation. Superoxide dismutase (SOD) and catalase activities in the liver were also monitored. RESULTS: Orchidectomy decreased (P < 0.05) plasma levels of antioxidant, SOD, catalase, and CRP and increased (P < 0.05) plasma levels of malondialdehyde, nitrite, and lipid profile compared with the sham-control group. In contrast to ORX, ORX + OP increased (P < 0.05) plasma antioxidant, dose-dependently increased (P < 0.05) SOD and catalase, decreased (P < 0.05) plasma malondialdehyde, nitrite, cholesterol, and triacylglycerol concentrations in the liver; and had no effect (P > 0.1) on plasma CRP or lipid profiles. CONCLUSION: The beneficial effect of eating an orange is demonstrated by the increasing antioxidant status and by the decreasing peroxidation independent of plasma triacylglycerol, cholesterol, or CRP concentrations.     

Serum complement C3c concentration in non-obese young insulin-resistant Mexicans

The aim of this study was to compare the serum complement C3 concentration between non-obese young insulin-sensitive and insulin-resistant Mexicans. A cross-sectional study was carried out in 28 healthy, non-obese [Body mass index (BMI) < 26 kg/m2] young (age 19-25 yr), male volunteers to measure the serum C3 concentration. In accordance with the constant for rate serum glucose disappearance (KITT) obtained from the insulin tolerance test, the subjects were divided into quartiles, considering as insulin-resistant individuals those in quartile 1, and insulin-sensitive subjects those in quartile 4. Serum C3c concentration was measured by a nephelometric method. Other biochemical characteristics were measured, like lipid profile and uric acid using enzymatic techniques. The serum C3 concentrations were similar (p = 0.949) between insulin-resistant and insulin-sensitive groups respectively (1.4 +/- 0.2 vs 1.3 +/- 0.1 g/l). There were no significant correlations between serum C3 concentrations and serum glucose, insulin levels, KITT and lipid profile. In conclusion, the serum complement C3c concentrations were similar between non-obese young insulin-sensitive and insulin-resistant Mexicans.     

Effects of vitamin C and vitamin E on in vivo lipid peroxidation: results of a randomized controlled trial

BACKGROUND: Lipid peroxidation may be important in the pathogenesis of atherosclerosis, particularly in its earliest stages. Evidence predominantly from in vitro studies suggests that antioxidant vitamins can prevent lipid peroxidation and that vitamin C and vitamin E have synergistic effects. However, in vivo evidence in support of these hypotheses is sparse. OBJECTIVE: The objective was to determine the effects of vitamin C and vitamin E, alone or in combination, on in vivo lipid peroxidation. DESIGN: We conducted a placebo-controlled, 2 x 2 factorial trial of vitamin C (500 mg ascorbate/d) and vitamin E (400 IU RRR-alpha-tocopheryl acetate/d) supplementation in 184 nonsmokers. The mean duration of supplementation was 2 mo. The outcome measures were changes from baseline in urinary 8-iso-prostaglandin F(2alpha), urinary malondialdehyde + 4-hydroxyalkenals, and serum oxygen-radical absorbance capacity. RESULTS: The within-group mean changes (and 95% CIs) in urinary 8-iso-prostaglandin F(2alpha) (pg/mg creatinine) were 9.0 (-125.1, 143.1), -150.0 (-275.4, -24.6), -141.3 (-230.5, -52.1), and -112.5 (-234.8, 9.8) in the placebo, vitamin C alone, vitamin E alone, and vitamins C + E groups, respectively. No synergistic effect of these 2 vitamins on urinary 8-iso-prostaglandin F(2alpha) was observed (P = 0.12). Neither vitamin had an effect on urinary malondialdehyde + 4-hydroxyalkenals. Vitamin C, but not vitamin E, increased serum oxygen-radical absorbance capacity (P = 0.01). CONCLUSIONS: Supplementation with vitamin C or vitamin E alone reduced lipid peroxidation to a similar extent. Supplementation with a combination of vitamins C and E conferred no benefit beyond that of either vitamin alone.     

Influence of sesame oil on blood glucose, lipid peroxidation, and antioxidant status in streptozotocin diabetic rats

The present study was carried out to assess the influence of sesame oil on blood glucose, lipid peroxidation, and status of antioxidants in normal and streptozotocin (STZ) diabetic rats. Diabetes was induced in adult female albino Wistar rats weighing 180-200 g by administration of STZ (40 mg/kg of body weight) intraperitonially. Both normal and diabetic rats were fed with a commercial diet containing 2% oil supplemented with 6% sesame oil for 42 days. Diabetic rats had elevated levels of blood glucose (322.61 +/- 9.49 mg/dL), glycosylated hemoglobin, vitamin E, thiobarbituric acid-reactive substances (TBARS), and lipid hydroperoxides and decreased levels of hemoglobin, vitamin C, and reduced glutathione (GSH). An increase in glucose-6-phosphatase and fructose-1,6-bisphosphatase activities and a decrease in hexokinase activity were observed in liver and kidney tissues. When diabetic rats fed with sesame oil were compared with diabetic rats, a significant reduction in levels of blood glucose (222.02 +/- 8.27 mg/dL), glycosylated hemoglobin, TBARS, and lipid hydroperoxides and glucose-6-phosphatase and fructose-1,6-bisphosphatase activities and an elevation in hemoglobin, vitamin E, and GSH levels and hexokinase activity were observed. Thus, sesame oil consumption influences beneficially the blood glucose, glycosylated hemoglobin, lipid peroxidation, and antioxidant levels in diabetic rats.     

1310例体检人群血清脂蛋白胆固醇与年龄、性别及血糖水平的相关性研究

目的探讨成人血清脂蛋白胆固醇与年龄、性别及空腹血糖水平的关系。方法选择1310名体检健康人作为研究对象,根据年龄分为6组,测定其血清脂蛋白胆固醇及空腹血糖,比较各年龄组及性别间脂蛋白胆固醇变化和差异,并行相关分析。结果极低密度脂蛋白胆固醇(VLDL-C)及低密度脂蛋白胆固醇(LDL-C)有随年龄增长而升高的趋势(r=0.19及0.25,均P=0.000),但60岁后男性VLDL-C有所下降。60岁前各年龄段男性VLDL-C结果均显著高于女性(P=0.000),60岁后男女间无差别(P>0.05)。50岁前男性LDL-C水平均高于女性(P<0.05),50岁以后男女间无差别(P>0.05)。高密度脂蛋白胆固醇(HDL-C)随年龄增长变化不明显(P>0.05),但女性各年龄段HDL-C结果均显著高于男性(P=0.000)。相关分析显示随空腹血糖水平升高VLDL-C升高趋势不明显(r=0.08,P=0.004),但LDL-C有所升高(r=0.13,P=0.000)且HDL-C明显降低(r=-0.18,P=0.000)。结论随年龄增长健康人群有发生脂蛋白代谢紊乱的倾向,且男性趋势更明显;空腹血糖增高和脂代谢紊乱有一定的相关性。     

Effects of a long-term vegetarian diet on biomarkers of antioxidant status and cardiovascular disease risk

OBJECTIVE: We compared plasma biomarkers of antioxidant status, oxidative stress, inflammation, and risk for coronary heart disease in long-term vegetarians and age- and sex-matched omnivores. METHODS: Thirty vegetarians (mean age +/- standard deviation: 44.2 +/- 9.0 y) were recruited. The subjects had been vegetarian for 5 to 55 y (21.8 +/- 12.2 y). The control group comprised 30 adults selected by age-stratified sampling from a community health project (mean age: 44.0 +/- 9.2 y). Fasting plasma total antioxidant status (ferric-reducing antioxidant power), ascorbic acid (AA), alpha-tocopherol (total and lipid standardized), malondialdehyde, total cholesterol, triacylglycerol, uric acid (UA), and high-sensitivity C-reactive protein (hsCRP) were measured. RESULTS: Plasma AA was significantly higher in the vegetarians than in the omnivores (90.5 +/- 21.0 and 61.8 +/- 17.0 microM; P < 0.001). The vegetarians had lower concentrations of triacylglycerol, UA, and hsCRP. Plasma total and lipid-standardized alpha-tocopherol concentrations were also lower in the vegetarians: 22.0 +/- 5.9 and 27.0 +/- 7.9 microM versus 3.76 +/- 0.57 and 4.23 +/- 0.58 microM per millimoles per liter of total cholesterol plus triacylglycerol, respectively. There was a significant inverse correlation between AA and UA (r = -0.343, P < 0.01; n = 60) and between AA and hsCRP (r = -0.306, P < 0.05; n = 55). Plasma ferric-reducing antioxidant power and malondialdehyde did not differ significantly between groups; however, the contribution of AA to the total antioxidant capacity of plasma was approximately 50% greater in the vegetarians. CONCLUSIONS: A long-term vegetarian diet is associated with markedly higher fasting plasma AA concentrations and lower concentrations of TAG, UA, and hsCRP. Long-term vegetarians have a better antioxidant status and coronary heart disease risk profile than do apparently healthy omnivores. Plasma AA may act a useful marker of overall health status.     

Plasma levels of lipophilic antioxidant vitamins in acute ischemic stroke patients: correlation to inflammation markers and neurological deficits

OBJECTIVES: Acute ischemic stroke is a clinical condition accompanied by inflammation and oxidative stress. In this study, we compared levels of plasma lipophilic antioxidants and inflammation markers between patients with stroke and healthy controls and assessed the associations of antioxidants, inflammation markers, and neurologic deficits among patients with stroke. METHODS: We measured plasma levels of lipophilic antioxidant vitamins (retinol, lycopene, alpha-carotene, beta-carotene, alpha-tocopherol, and gamma-tocopherol), inflammation markers (high-sensitivity C-reactive protein [hs-CRP], fibrinogen, erythrocyte sedimentation rate, and white blood cell count), and neurologic deficits (indicated by the score of the National Institute of Health Stroke Scale) in 68 patients with acute ischemic stroke within 48 h after stroke onset in comparison with 41 normal controls. RESULTS: Plasma alpha- and beta-carotene concentrations were lower and levels of inflammation markers were higher among patients with acute ischemic stroke compared with normal controls. Levels of alpha- and beta-carotene in patients with stroke were negatively associated with hs-CRP level (R = -0.29 and -0.41, respectively, P < 0.01) and with neurologic deficits (R = -0.28 and -0.27, respectively, P < 0.05). The negative association between neurologic deficits and combined plasma levels of alpha- and beta-carotene remained after adjustment for age and sex (P = 0.04). However, the magnitude of association decreased after adjustment of hs-CRP (P = 0.08). CONCLUSION: Plasma concentrations of alpha- and beta-carotene are lower in patients with acute ischemic stroke than in healthy controls and are negatively correlated with hs-CRP level and neurologic deficits. The negative association between neurologic deficits and combined plasma alpha- and beta-carotene levels is confounded by hs-CRP.