Accelerated ageing and renal dysfunction links lower socioeconomic status and dietary phosphate intake.

BACKGROUND: We have sought to explore the impact of dietary Pi intake on human age related health in the pSoBid cohort (n=666) to explain the disparity between health and deprivation status in this cohort. As hyperphosphataemia is a driver of accelerated ageing in rodent models of progeria we tested whether variation in Pi levels in man associate with measures of biological ageing and health. RESULTS: We observed significant relationships between serum Pi levels and markers of biological age (telomere length (p=0.040) and DNA methylation content (p=0.028), gender and chronological age (p=0.032). When analyses were adjusted for socio-economic status and nutritional factors, associations were observed between accelerated biological ageing (telomere length, genomic methylation content) and dietary derived Pi levels among the most deprived males, directly related to the frequency of red meat consumption. CONCLUSIONS: Accelerated ageing is associated with high serum Pi levels and frequency of red meat consumption. Our data provide evidence for a mechanistic link between high intake of Pi and age-related morbidities tied to socio-economic status.

The hypotensive effect of acute and chronic AMP-activated protein kinase activation in normal and hyperlipidemic mice.

AMP-activated protein kinase (AMPK) is present in the arterial wall and is activated in response to cellular stressors that raise AMP relative to ADP/ATP. Activation of AMPK in vivo lowers blood pressure but the influence of hyperlipidemia on this response has not been studied. ApoE(-/-) mice on high fat diet for 6weeks and age-matched controls were treated with the AMPK activator, AICAR daily for two weeks. Under anesthesia, the carotid artery was cannulated for blood pressure measurements. Aortic tissue was removed for in vitro functional experiments and AMPK activity was measured in artery homogenates by Western blotting. ApoE(-/-) mice had significantly raised mean arterial pressure; chronic AICAR treatment normalized this but had no effect in normolipidemic mice, whereas acute administration of AICAR lowered mean arterial pressure in both groups. Chronic AICAR treatment increased phosphorylation of AMPK and its downstream target acetyl-CoA carboxylase in normolipidemic but not ApoE(-/-) mice. In aortic rings, AMPK activation induced vasodilation and an anticontractile effect, which was attenuated in ApoE(-/-) mice. This study demonstrates that hyperlipidemia dysregulates the AMPK pathway in the arterial wall but this effect can be reversed by AMPK activation, possibly through improving vessel compliance.

Moderate Exercise Increases Affinity of Large Very Low-Density Lipoproteins for Hydrolysis by Lipoprotein Lipase.

CONTEXT: Postprandial triglyceride (TG) concentration is independently associated with cardiovascular disease risk. Exercise reduces postprandial TG concentrations, but the mechanisms responsible are unclear. OBJECTIVE: The objective was to determine the effects of exercise on affinity of chylomicrons, large very low-density lipoproteins (VLDL1), and smaller VLDL (VLDL2) for lipoprotein lipase (LPL)-mediated TG hydrolysis. DESIGN: This was designed as a within-participant crossover study. SETTING: The setting was a university metabolic investigation unit. PARTICIPANTS: Participants were 10 overweight/obese men. INTERVENTIONS: Participants undertook two oral fat tolerance tests, separated by 7-14 days, in which they had blood taken while fasting and for 4 hours after a high-fat mixed meal. On the afternoon before one test, they performed a 90-minute treadmill walk at 50% maximal oxygen uptake (exercise trial [EX]); no exercise was performed before the control trial (CON). MAIN OUTCOME MEASURES: We measured circulating TG-rich lipoprotein concentrations and affinity of chylomicrons, VLDL1, and VLDL2 for LPL-mediated TG hydrolysis. RESULTS: Exercise significantly reduced fasting VLDL1-TG concentration (CON, 0.49 [0.33-0.72] mmol.L(-1); EX, 0.36 [0.22-0.59] mmol.L(-1); geometric means [95% confidence interval]; P = .04). Time-averaged postprandial chylomicron-TG (CON, 0.55 ± 0.10 mmol.L(-1); EX, 0.39 ± 0.08 mmol.L(-1); mean ± SEM; P = .03) and VLDL1-TG (CON, 0.85 ± 0.13 mmol.L(-1); EX, 0.66 ± 0.10 mmol.L(-1); P = .01) concentrations were both lower in EX than CON. Affinity of VLDL1 for LPL-mediated TG hydrolysis increased by 2.2 (1.3-3.7)-fold [geometric mean (95% confidence interval)] (P = .02) in the fasted state and 2.6 (1.8-2.6)-fold (P = .001) postprandially. Affinity of chylomicrons and VLDL2 was not significantly different between trials. CONCLUSIONS: Exercise increases affinity of VLDL1 for LPL-mediated TG hydrolysis both fasting and postprandially. This mechanism is likely to contribute to the TG-lowering effect of exercise.

Maternal obesity is associated with the formation of small dense LDL and hypoadiponectinemia in the third trimester.

CONTEXT: Maternal obesity is associated with high plasma triglyceride, poor vascular function, and an increased risk for pregnancy complications. In normal-weight pregnant women, higher triglyceride is associated with increased small, dense low-density lipoprotein (LDL). HYPOTHESIS: In obese pregnancy, increased plasma triglyceride concentrations result in triglyceride enrichment of very low-density lipoprotein-1 particles and formation of small dense LDL via lipoprotein lipase. DESIGN: Women (n = 55) of body mass index of 18-46 kg/m(2) were sampled longitudinally at 12, 26, and 35 weeks' gestation and 4 months postnatally. SETTING: Women were recruited at hospital antenatal appointments, and study visits were in a clinical research suite. OUTCOME MEASURES: Plasma concentrations of lipids, triglyceride-rich lipoproteins, lipoprotein lipase mass, estradiol, steroid hormone binding globulin, insulin, glucose, leptin, and adiponectin were determined. RESULTS: Obese women commenced pregnancy with higher plasma triglyceride, reached the same maximum, and then returned to higher postnatal levels than normal-weight women. Estradiol response to pregnancy (trimester 1-3 incremental area under the curve) was positively associated with plasma triglyceride response (r(2) adjusted 25%, P < .001). In the third trimester, the proportion of small, dense LDL was 2-fold higher in obese women than normal-weight women [mean (SD) 40.7 (18.8) vs 21.9 (10.9)%, P = .014], and 35% of obese, 14% of overweight, and none of the normal-weight women displayed an atherogenic LDL subfraction phenotype. The small, dense LDL mass response to pregnancy was inversely associated with adiponectin response (17%, P = .013). CONCLUSIONS: Maternal obesity is associated with an atherogenic LDL subfraction phenotype and may provide a mechanistic link to poor vascular function and adverse pregnancy outcome.

The effect of omega-3 fatty acids on the atherogenic lipoprotein phenotype in patients with nephrotic range proteinuria.

AIMS: Patients with nephrotic range proteinuria are known to have an increased risk of cardiovascular disease partly due to possessing the atherogenic lipoprotein phenotype. The aim of this study was to examine the effect of high dose omega-3 fatty acids on atherogenic triglyceride rich lipoproteins in patients with nephrotic range proteinuria, comparing their effect on lipoprotein profiles in age and sex matched controls. METHODS: 17 patients with nephrotic range proteinuria and 17 age and sex matched controls were studied. Fasting lipids and lipoproteins were measured before and after 8 weeks treatment with 4 g daily of omega-3 fatty acids (Omacor®). RESULTS: In patients with proteinuria treatment reduced plasma triglyceride by a mean of 0.45 mmol/l (95%CI 0.16 - 0.74, p = 0.005) and plasma very low density lipoprotein cholesterol by a mean of 0.38 (95%CI 0.01 - 0.75, p = 0.04). LDL III concentration fell from 178.8 mg/dl (61.6 - 231.0) to 96.1 mg/dl (49.3 - 204.5), p = 0.05. In patients treatment altered the LDL profile so that LDLIII which was the major subfraction present at baseline was reduced from 49.9% to 29.8% (p = 0.01). Remnant lipoproteins (RLP) also fell with a mean reduction of 3.5 mg/dl in RLP-Cholesterol (95%CI 0.1 - 6.9, p = 0.05) and 12.4 mg/dl in RLP-triglyceride (95%CI 2.6 - 22.2, p = 0.03). There was however a 0.6 mmol/l rise in LDL-C (p = 0.06) in the patients. Treatment did not alter HDL-C. CONCLUSION: In patients with nephrotic range proteinuria, omega-3 fatty acids reduced triglyceride rich lipoproteins, LDL III and remnant lipoproteins. A tendency to an increase in LDL-C was observed but this was offset by an alteration in the distribution of the LDL profile towards lighter, larger LDL particles. We propose that treatment with omega-3 fatty acids in conjunction with a statin may be the ideal therapy in these patients.

Lipoprotein-associated phospholipase A(2), inflammatory biomarkers, and risk of cardiovascular disease in the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER).

OBJECTIVE: Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is an inflammatory biomarker that circulates mainly bound to LDL. We evaluated the association of Lp-PLA(2) with vascular events in the elderly where the importance of LDL is diminished as a risk factor for coronary disease. METHODS: Mass and activity of Lp-PLA(2) were related to risk over 3.2 years for vascular events (definite or suspected death from CHD, non-fatal MI, fatal or non-fatal stroke) in the 2804 men and 3000 women age 70-82 years in the Prospective Study of Pravastatin in the Elderly (PROSPER). RESULTS: Lp-PLA(2) showed a moderate, positive association with risk of a vascular event with hazard ratios of 1.25 (confidence interval (CI) 1.02-1.54) for mass and 1.39 (CI 1.14-1.70) for activity for top versus bottom quartile. Risk associations were attenuated when classical risk factors, lipids and inflammatory markers - C-reactive protein and white cell count - were included in the models. Lp-PLA(2) was unrelated to stroke risk. Inclusion of all three inflammatory markers in multivariate models negated the association of HDL cholesterol with risk (hazard ratio 0.98; CI 0.88-1.10) and increased prediction of coronary events; the C statistic rose from 63.2% to 64.4% (P<0.001). CONCLUSION: In elderly people Lp-PLA(2), alongside other inflammatory indices, is a potential biomarker for vascular events, particularly CHD.

Omega-3 fatty acids improve postprandial lipaemia in patients with nephrotic range proteinuria.

BACKGROUND: Patients with nephrotic range proteinuria have a marked increase in the risk of cardiovascular disease. Qualitative and quantitative changes in lipids and lipoproteins contribute to this increased risk with an abundance of atherogenic triglyceride (TG) rich apolipoprotein B containing lipoproteins. TG rich lipoproteins predominate postprandially and are associated with increased risk of coronary heart disease (CHD). Omega-3 fatty acids derived from fish oils have been shown to have beneficial effects on lipids and lipoproteins in patients without proteinuria. METHODS: 17 patients with nephrotic range proteinuria and 17 age and sex matched controls were studied. Postprandial lipaemia was assessed in patients and controls, before and after 8 weeks treatment with 4 g daily of omega-3 fatty acids (Omacor). A standard fat load (90 g) was administered and blood sampling was performed in the fasting state and at 2, 4, 6 and 8h after the fat load. Chylomicrons and VLDL(1) density fraction was isolated from plasma by density ultracentrifugation. Postprandial chylomicron and VLDL(1) triglyceride concentrations were measured and quantified using the incremental area under the curve (AUC) method. RESULTS: Baseline postprandial chylomicron TG AUC was greater in patients compared with controls: median 18.5 mmol/lh (interquartile range 8.9-32.6) vs 9.3 mmol/lh (4.8-14.4) p=0.05. Following treatment patient chylomicron AUC fell [mean reduction 6.8 mmol/lh (95% CI 0.1-13.6) p=0.05]. No significant reduction in chylomicron AUC was observed in the controls [mean reduction 3.9 mmol/lh (95% CI -3.6 to 11.5)]. As a result, following 8 weeks treatment with omega-3 fatty acids, patient and control chylomicron AUC were no longer significantly different [patients 13.5 mmol/lh (7.4-22.9), controls 7.2 mmol/lh (4.6-14.5) both median and IQR, p=nsd]. VLDL(1) TG AUC did not differ at baseline between patients and controls. Furthermore, there was no significant effect on VLDL(1) AUC following treatment in either group. CONCLUSIONS: We have shown that there is an excess of postprandial chylomicron density fraction in patients with nephrotic range proteinuria, which is reduced by treatment with omega-3 fatty acids. We suggest that this would be an ideal therapy in combination with statins for this high risk group of patients.

Development of a novel method to determine very low density lipoprotein kinetics.

Isotopic tracer methods of determining triglyceride-rich lipoprotein (TRL) kinetics are costly, time-consuming, and labor-intensive. This study aimed to develop a simpler and cost-effective method of obtaining TRL kinetic data, based on the fact that chylomicrons compete with large VLDL (VLDL(1); S(f) = 60-400) for the same catalytic pathway. Ten healthy subjects [seven men; fasting triglyceride (TG), 44.3-407.6 mg/dl; body mass index, 21-35 kg/m(2)] were given an intravenous infusion of a chylomicron-like TG emulsion (Intralipid; 0.1 g/kg bolus followed by 0.1 g/kg/h infusion) for 75-120 min to prevent the clearance of VLDL(1) by lipoprotein lipase. Multiple blood samples were taken during and after infusion for separation of Intralipid, VLDL(1), and VLDL(2) by ultracentrifugation. VLDL(1)-apolipoprotein B (apoB) and TG production rates were calculated from their linear increases in the VLDL(1) fraction during the infusion. Intralipid-TG clearance rate was determined from its exponential decay after infusion. The production rates of VLDL(1)-apoB and VLDL(1)-TG were (mean +/- SEM) 25.4 +/- 3.9 and 1,076.7 +/- 224.7 mg/h, respectively, and the Intralipid-TG clearance rate was 66.9 +/- 11.7 pools/day. Kinetic data obtained from this method agree with values obtained from stable isotope methods and show the expected relationships with indices of body fatness and insulin resistance (all P < 0.05). The protocol is relatively quick, inexpensive, and transferable to nonspecialist laboratories.

Fluctuations in C-reactive protein concentration and neutrophil activation during normal human pregnancy.

OBJECTIVES: To clarify the changes in serum C-reactive protein (CRP) levels and in the neutrophil activation state during normal human pregnancy. MATERIALS AND METHODS: A longitudinal study (n=23) was performed during the three trimesters of pregnancy; a group of non-pregnant women (n=24) was used as control. Total and differential leukocyte count, serum concentration of CRP and plasma levels of granulocyte-macrophage colony stimulating factor (GM-CSF) and of lactoferrin and elastase (two indirect markers of neutrophil activation) were measured. RESULTS: Pregnancy imposed an inflammatory response in the mother, observed by the significant increment in total white blood cell (WBC) and neutrophil counts and in the circulating levels of CRP, GM-CSF and lactoferrin, in all trimesters of gestation compared with non-pregnant controls. Plasma elastase concentration was also significantly higher in pregnant women, but only in the first trimester of gestation. Regarding the ratios of lactoferrin and elastase per neutrophil, they were significantly lower in pregnant women (all trimesters). During gestation, WBC and neutrophil count increased significantly from the first to the second trimester and remained high in the third period. In contrast, the ratios of lactoferrin and elastase per neutrophil decreased significantly from the first to the second trimester, remaining low in the last trimester. Concerning CRP levels, no consistent changes were observed throughout gestation; 12 cases (52.2%) presented fluctuations, whereas 7 (30.4%) showed progressive reductions and 4 (17.4%) progressive increments throughout pregnancy. CONCLUSIONS: Changes in CRP levels vary in a wide manner between subjects along pregnancy, even though median values are consistently elevated throughout pregnancy. Moreover, circulating levels of neutrophil-activation products are higher in normal human gestation.

Hepatic production of VLDL1 but not VLDL2 is related to insulin resistance in normoglycaemic middle-aged subjects.

Insulin resistance is probably the defining feature of the metabolic syndrome and is an important determinant of plasma triglyceride (TG) concentrations. We sought to investigate whether insulin resistance influenced the metabolism of VLDL1 (Sf 60-400) and VLDL2 (Sf 20-60). Sixteen (eight men, eight women) middle-aged, normoglycaemic subjects participated. VLDL1and VLDL2 apolipoprotein (apo) B metabolism was followed using a deuterated leucine tracer and insulin resistance was estimated using homeostasis model assessment (HOMA). HOMA-estimated insulin resistance (HOMAIR) significantly and strongly correlated with the VLDL1 production rate (r = 0.69, P < 0.01) and VLDL1 apo B pool size (r = 0.59, P = 0.02), but these relationships were not evident for VLDL2. Conversely, HOMAIR was not significantly related to the fractional rate of transfer of VLDL1 to VLDL2 but was significantly related to the fractional rate of transfer from VLDL2 to IDL (r = 0.61, P = 0.01). HOMAIR was not significantly related to the fractional rate of direct catabolism for either VLDL1 or VLDL2. These results suggest a role for insulin resistance in the determination of hepatic VLDL1 production and highlight the independent regulation of VLDL1 and VLDL2 metabolism.

Neutrophil activation and C-reactive protein concentration in preeclampsia.

Preeclamptic pregnancies seem to be associated with a higher extent of inflammation compared with normal ones. We intended to test this proposal and also to clarify the contribution of some variables in such inflammatory process. We measured total and differential leukocyte count, serum C-reactive protein (CRP), and plasma levels of lactoferrin, elastase, and granulocyte-macrophage colony-stimulating factor (GM-CSF). Uric acid was also evaluated and used as an indicator of the severity of the disease. A cross-sectional study was performed by evaluating healthy and preeclamptic women in the third trimester of gestation (n = 67 and n = 51, respectively) and 24 to 48 h postpartum (n = 32 and n = 26, respectively). When comparing the third trimester of normal and preeclamptic pregnancies, we found significantly higher levels of uric acid, CRP, and elastase, and a significantly higher elastase to neutrophil ratio in the pathologic group. However, for CRP, statistical significance was lost after adjustment for maternal weight. No significant differences were found in total leukocyte count, plasma levels of GM-CSF, and lactoferrin between groups. In preeclampsia, a significant positive correlation was found between elastase and lactoferrin and these neutrophil activation products correlated positively with uric acid level. Considering the analysis of all variables in the postpartum period, only CRP and uric acid levels were significantly elevated in the pathologic group. However, CRP differences obtained in the puerperium seem to be influenced by the increased number of dystocic deliveries in the preeclamptic group. In conclusion, our data suggest that inflammation is further pronounced in preeclampsia and that the extent of neutrophil activation correlates with the severity of this syndrome.

Effects of dietary monounsaturated fatty acids on lipoprotein concentrations, compositions, and subfraction distributions and on VLDL apolipoprotein B kinetics: dose-dependent effects on LDL.

BACKGROUND: Replacing dietary saturated fatty acids (SFAs) with monounsaturated fatty acids (MUFAs) lowers LDL cholesterol, but the underlying mechanisms remain unclear. OBJECTIVE: We assessed the effects of replacing dietary SFAs with MUFAs on concentrations and subclass distributions of VLDL, intermediate-density lipoprotein, LDL, and HDL and on VLDL apolipoprotein B kinetics. DESIGN: Thirty-five moderately hypercholesterolemic, middle-aged volunteers consumed for 6 wk, in random order, diets containing low (L-MUFA; 7.8% of energy from MUFAs), moderate (M-MUFA; 10.3% from MUFAs), or high (H-MUFA; 13.7% from MUFAs) amounts of MUFAs. Fasting blood samples were taken from all subjects after each intervention. VLDL apolipoprotein B kinetic studies were performed in a subgroup after the L-MUFA and H-MUFA diets. RESULTS: Plasma cholesterol concentrations decreased in a dose-dependent manner with increasing intakes of dietary MUFAs. This change was entirely accounted for by reduced LDL cholesterol (-0.20 and -0.49 mmol/L after the M-MUFA and H-MUFA diets, respectively, compared with the concentration after the L-MUFA diet; P for trend < 0.01). Plasma triacylglycerol and HDL cholesterol were not significantly affected by the dietary intervention, nor were the concentrations of VLDL(1) (S(f) 60-400), VLDL(2) (S(f) 20-60), or intermediate-density lipoprotein (S(f) 12-20). Production and catabolic rates for VLDL(1) and VLDL(2) were also unaffected. HDL and LDL subclass distributions were not significantly altered, but as a consequence of the overall LDL lowering, concentrations of atherogenic LDL-III were 25% lower after the H-MUFA diet than after the L-MUFA diet (P = 0.02). CONCLUSION: The effects of replacing dietary SFAs with MUFAs on lipoprotein metabolism appear to be almost exclusively limited to the LDL density class.