Postprandial plasma triglyceride and cholesterol responses to a low-fat meal

Increased Meal Frequency With Exercise Mitigates Postprandial Triacylglycerol

PURPOSE

This study examined how manipulating meal frequency, with and without exercise, affects postprandial triacylglycerol (TAG).

METHODS

Fourteen sedentary men completed four 2-day trials in a noncounterbalanced random cross-over order: (1) consumption of 1 large high-fat milkshake without exercise (1-CON), (2) consumption of 2 smaller high-fat milkshakes without exercise (2-CON), (3) consumption of 1 large high-fat milkshake with exercise (1-EX), and (4) consumption of 2 small high-fat milkshakes with exercise (2-EX)-total energy intake was standardized across trials. On day 1, participants rested (1-CON and 2-CON) or walked briskly for 60 minutes (1-EX and 2-EX). On day 2, participants consumed either a single large high-fat milkshake (75% fat; 1-CON and 1-EX) for breakfast or 2 smaller isoenergetic milkshakes (2-CON and 2-EX) for breakfast and lunch. Plasma TAG were measured fasting and for 7 hours after breakfast.

RESULTS

Peak incremental TAG was 30% lower on 2-EX than 1-CON (P = .04, d = 0.38). Postprandial TAG increased more rapidly in the first 4 hours in 1-CON than other trials; but at 6 hours, TAG was exaggerated in 2-CON compared with 1-CON.

CONCLUSIONS

Increasing meal frequency after exercise, without altering overall fat intake, attenuates postprandial TAG.

Prolonged monitoring of postprandial lipid metabolism after a western meal rich in linoleic acid and carbohydrates

Today, awareness has been raised regarding high consumption of n-6 polyunsaturated fatty acids (PUFA) in western diets. A comprehensive analysis of total and individual postprandial fatty acids profiles would provide insights into metabolic turnover and related health effects. After an overnight fast, 9 healthy adults consumed a mixed meal comprising 97 g carbohydrate and 45 g fat, of which 26.4 g was linoleic acid (LA). Nonesterified fatty acids (NEFA), phospholipid fatty acids (PL-FA) and triacylglycerol fatty acids (TG-FA) were monitored in plasma samples, at baseline and hourly over a 7-h postprandial period. Total TG-FA concentration peaked at 2 h after the meal and steadily decreased thereafter. LA from TG18:2n-6 and behenic acid from TG22:0 showed the highest response among TG-FA, with a biphasic response detected for the former. PL-FA exhibited no change. Total NEFA initially decreased to nadir at 1 h, then increased to peak at 7 h. The individual NEFA showed the same response curve except LA and some very-long-chain saturated fatty acids (VLCSFA, ≥20 carbon chain length) that markedly increased shortly after the meal intake. The similarities and dissimilarities in lipid profiles between study subjects at different time points were visualized using nonmetric multi-dimensional scaling. Overall, the results indicate that postprandial levels of LA and VLCSFA, either as NEFA or TG, were most affected by the test meal, which might provide an explanation for the health effects of this dietary lifestyle characterized by high intake of mixed meals rich in n-6 PUFA.

Can milk proteins be a useful tool in the management of cardiometabolic health? An updated review of human intervention trials

The prevalence of cardiometabolic diseases is a significant public health burden worldwide. Emerging evidence supports the inverse association between greater dairy consumption and reduced risk of cardiometabolic diseases. Dairy proteins may have an important role in the favourable impact of dairy on human health such as blood pressure (BP), blood lipid and glucose control. The purpose of this review is to update and critically evaluate the evidence on the impacts of casein and whey protein in relation to metabolic function. Evidence from short-term clinical studies assessing postprandial responses to milk protein ingestion suggests benefits on vascular function independent of BP, as well as improvement in glycaemic homeostasis. Long-term interventions have been less conclusive, with some showing benefits and others indicating a lack of improvement in vascular function. During chronic consumption BP appears to be lowered and both dyslipidaemia and hyperglacaemia seem to be controlled. Limited number of trials investigated the effects of dairy proteins on oxidative stress and inflammation. Although the underlying mechanisms of milk proteins on cardiometabolic homeostasis remains to be elucidated, the most likely mechanism is to improve insulin resistance. The incorporation of meals enriched with dairy protein in the habitual diet may result in the beneficial effects on cardiometabolic health. Nevertheless, future well-designed, controlled studies are needed to investigate the relative effects of both casein and whey protein on BP, vascular function, glucose homeostasis and inflammation.

Profiling the Oxylipin and Endocannabinoid Metabolome by UPLC-ESI-MS/MS in Human Plasma to Monitor Postprandial Inflammation

Bioactive lipids, including oxylipins, endocannabinoids, and related compounds may function as specific biochemical markers of certain aspects of inflammation. However, the postprandial responsiveness of these compounds is largely unknown; therefore, changes in the circulating oxylipin and endocannabinoid metabolome in response to a challenge meal were investigated at six occasions in a subject who freely modified her usual diet. The dietary change, and especially the challenge meal itself, represented a modification of precursor fatty acid status, with expectedly subtle effects on bioactive lipid levels. To detect even the slightest alteration, highly sensitive ultra-performance liquid chromatography (UPLC) coupled to electrospray ionization (ESI) tandem mass spectrometry (MS/MS) methods for bioactive lipid profiling was employed. A previously validated UPLC-ESI-MS/MS method for profiling the endocannabinoid metabolome was used, while validation of an UPLC-ESI-MS/MS method for oxylipin analysis was performed with acceptable outcomes for a majority of the parameters according to the US Food and Drug Administration guidelines for linearity (0.9938 < R2 < 0.9996), limit of detection (0.0005-2.1 pg on column), limit of quantification (0.0005-4.2 pg on column), inter- and intraday accuracy (85-115%) and precision (< 5%), recovery (40-109%) and stability (40-105%). Forty-seven of fifty-two bioactive lipids were detected in plasma samples at fasting and in the postprandial state (0.5, 1, and 3 hours after the meal). Multivariate analysis showed a significant shift of bioactive lipid profiles in the postprandial state due to inclusion of dairy products in the diet, which was in line with univariate analysis revealing seven compounds (NAGly, 9-HODE, 13-oxo-ODE, 9(10)-EpOME, 12(13)-EpOME, 20-HETE, and 11,12-DHET) that were significantly different between background diets in the postprandial state (but not at fasting). The only change in baseline levels at fasting was displayed by TXB2. Furthermore, postprandial responsiveness was detected for seven compounds (POEA, SEA, 9(10)-DiHOME, 12(13)-DiHOME, 13-oxo-ODE, 9-HODE, and 13-HODE). Hence, the data confirm that the UPLC-ESI-MS/MS method performance was sufficient to detect i) a shift, in the current case most notably in the postprandial bioactive lipid metabolome, caused by changes in diet and ii) responsiveness to a challenge meal for a subset of the oxylipin and endocannabinoid metabolome. To summarize, we have shown proof-of-concept of our UPLC-ESI-MS/MS bioactive lipid protocols for the purpose of monitoring subtle shifts, and thereby useful to address lipid-mediated postprandial inflammation.

Postprandial lipaemia, oxidative stress and endothelial function: a review

AIMS

Postprandial lipaemia-induced endothelial dysfunction is felt to be mediated by increases in oxidative stress. In this review, we have examined the cross-sectional relationships found among these three variables.

METHODS

We found 20 studies conducted by 16 independent investigative teams through a Medline search from 1980 to 2008; studies were required to report correlations between at least two of the three variables of interest in studies of humans. This review is divided into (i) discussions on the biomarkers and other measures of postprandial lipaemia, oxidative stress and endothelial function; (ii) associations reported among the three variables; and (iii) other considerations including alternative intervention studies.

RESULTS

Triglycerides and free fatty acids are robust and well-standardised biomarkers of lipaemia. Measures of oxidative stress ranged from electron spin techniques to measures of lipid peroxidation and are limited by lack of standardisation. Brachial artery flow-mediated dilatation is the most commonly used measure of endothelial function. The associations between postprandial lipaemia and oxidative stress and between postprandial lipaemia and endothelial function are strong and consistent. However, the association between postprandial oxidative stress and endothelial function appears weak, at least using current approaches to measurement of oxidative stress.

DISCUSSION AND CONCLUSIONS

These observations are consistent with the proposed concept that oxidative stress mediates the adverse effects of postprandial lipaemia on endothelial function; they are limited by the difficulties in measuring oxidative stress. Efforts directed at optimising and standardising the measurement of oxidative stress will be of value in future works in this area.

The effect of acute carbohydrate load on the monophasic or biphasic nature of the postprandial lipaemic response to acute fat ingestion in human subjects

Previous studies in this laboratory have elicited a monophasic response in postprandial plasma triacylglycerol (TAG) level with fat intakes of 0.5 g fat/kg body weight accompanied by about 17 g carbohydrate as lactose. Recent studies involving the same level of fat with a higher level of carbohydrate, 136 g of which 60 g was sucrose, appeared to elicit a biphasic response. The present study compared these two test meals and showed a significant meal × time interaction for plasma total TAG (P = 0.0228) reflecting a monophasic response with the lower-carbohydrate test meal. The higher-carbohydrate meal induced significantly higher insulin and glucose-dependent insulinotropic polypeptide responses (P = 0.0009 and P = 0.0041 respectively). A significant meal × time interaction was seen for plasma non-esterified fatty acids (P = 0.0437). The biphasic plasma TAG response seen with the high-carbohydrate meal largely reflected the TAG-rich lipoprotein (TRL) or chylomicron fraction, which would tend to suggest a biphasic pattern of absorption. This was borne out by TRL-TAG fatty acid compositions. Both peaks in the biphasic response showed active incorporation of the main dietary fatty acids, 18:1n−9, 18:2n−6 and 18:3n−3 into TRL-TAG. These results indicate that under the specific test-meal conditions used in the present study, a biphasic pattern of fat absorption was seen.

Effect of weight loss on the postprandial response to high-fat and high-carbohydrate meals in obese women

OBJECTIVE

To assess the effect of weight loss on the plasma lipid and remnant-like lipoprotein cholesterol (RLPc) response to a high-fat or a high-carbohydrate meal in a population of obese women.

DESIGN

Nutritional intervention study.

SUBJECTS

Sixteen obese women (mean body mass index (BMI): 37.6+/-5 kg/m(2)).

METHODS

Subjects were asked to follow an energy-restricted diet (800 kcal/day) for 7 weeks, followed by a 1-week maintenance diet. Before and after weight loss, each participant was given (in random order) two iso-energetic meals containing either 80% fat and 20% protein (the high-fat meal) or 80% carbohydrate and 20% protein (the high-carbohydrate meal). Blood samples were collected over the following 10-h period. A two-way analysis of variance with repeated measures was used to assess the effect of the meal and postprandial time on biological variables and postprandial responses (notably RLPc levels).

RESULTS

Weight loss was associated with a significant decrease in fasting triglyceride (P=0.0102), cholesterol (P<0.0001), low-density lipoprotein cholesterol (P=0.0003), high-density lipoprotein-cholesterol (P=0.0009) and RLPc (P=0.0015) levels. The triglyceride response to the high-fat meal was less intense after weight reduction than before (interaction P<0.002). This effect persisted after adjustment on baseline triglyceride levels. The triglyceride response to the high-carbohydrate meal was biphasic (i.e. with two peaks, 1 and 6 h after carbohydrate intake). After adjustment on baseline values, weight reduction was associated with a trend towards a reduction in the magnitude of the second triglyceride peak (interaction P<0.054). In contrast, there was no difference in postprandial RLPc responses before and after weight loss, again after adjustment on baseline levels.

CONCLUSION

Our data suggest that weight loss preferentially affects postprandial triglyceride metabolism.

Changes in plasma triacylglycerol concentrations after sequential lunch and dinner in healthy subjects

OBJECTIVES

The present study examines the kinetic of plasma triacylglycerol (TAG) after sequential ingestion of lunch and dinner as well as the contribution of dietary fat ingested at lunch to subsequent post-dinner TAG composition.

METHOD

Six healthy subjects were included. After standardized breakfast (7: 30AM), 2 mixed meals with fat loads composed of 44 g olive oil (rich in oleic acid) at lunch (12PM) and 44 g sunflower oil (rich in linoleic acid) at dinner (7PM) were ingested. [1-13C] palmitate was added in lunch only. Plasma TAG and chylomicron-TAG (CMTAG) levels were measured sequentially after meals. [1-13C] palmitate enrichment and concentrations of oleic acid and linoleic acid were measured in all lipid fractions.

RESULT

Post-dinner plasma TAG peak was delayed as compared to lunch (3 hours vs 1 hour, p=0.002) whereas the magnitude of the postprandial peaks was not significantly different between lunch and dinner (2.4+/-0.3 vs 2.0+/-0.4 mmol/L, p=0.85). [1-13C] palmitate enrichment was maximal 5 hours after lunch in all lipid fractions and decreased slowly thereafter. After dinner ingestion, the rate of decline of [1-13C] palmitate enrichment plateaued during the first 60 minutes. Oleic acid increased slightly and immediately after dinner and remained the predominant fatty acid in all lipid fractions during the first hour after dinner. A delayed peak of plasma and CM-TAG was observed after dinner as compared to lunch without difference in the magnitude of peaks.

CONCLUSION

The contribution of dietary fat ingested at lunch to post-dinner lipemia is confirmed despite the relatively long lasting interval between the 2 meals (7 h) and the absence of any early peak of plasma TAG after dinner.

Oral fat exposure increases the first phase triacylglycerol concentration due to release of stored lipid in humans

Oral exposure to dietary fat (through modified sham feeding, which entails mastication and expectoration of foods) augments the postprandial triacylglycerol (TAG) concentration, in part, though augmented lipid absorption. This study was designed to characterize early events in this process. At 2200 h, 25 healthy adults (13 men, 12 women) consumed 80 g of almonds (high oleic acid content) and fasted until approximately 0700 h. After placement of a catheter in a hand vein and 4 blood draws at 10-min intervals, 50 1-g safflower oil (high linoleic acid content) capsules were consumed. After another blood draw, modified sham feeding was initiated with a cracker only or cracker with cream cheese in random order with 1 wk between trials. Oral exposures occurred at 5-min intervals for 60 min then at 15-min intervals from min 60 to 120. Additional blood draws occurred at 2, 4, 6, 8, 10, 12, 14, 30, 60, 120, 240, 360 and 480 min. Oral stimulation, especially by fat, prompted the rapid (mean approximately 23 min) release of lipid stored from the previous meal (almonds) in all participants. This resulted in multimodal postprandial triacylglycerol (TAG) peaks generally occurring at 0-30 min, 60-120 min and 240-480 min after loading and initiation of oral stimulation. TAG magnitudes during these times were correlated (r = 0.40-0.89, P < 0.001-P = 0.053). It is proposed that the sensory-enhanced release of lipid from the residual pool initiates an early TAG rise, which augments the peak attributable to absorption of meal lipid; this in turn supplements a later peak associated with release of endogenously synthesized TAG because lipid from all three sources competed for a common clearance mechanism. If substantiated, additional understanding of the behavioral factors (e.g., eating patterns) that initiate this cascade will be warranted.

Thrombophilia in Patients with Hypertriglyceridemia

Objectives: To investigate a possible relationship between hypertriglyceridemia and the coagulation system, a Cardiovascular Risk Factor Two-township Study was conducted in Taiwan. Design: A case-control study. This longitudinal, prospective study focused on the evolution of cardiovascular disease risk factors with emphasis on haemostatic factors. Subjects: Hypertriglyceridemic subjects (triglyceride <2.26 mmoll+1, n = 327) and age-matched normal controls from a population screening program. Main outcome measures: Haemostatic parameters measured in this study included prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen, factors VIIc and VIIIc, and antithrombin-III and plasminogen levels. Results: In our male hypertriglyceridemic subjects, aPTT was not significantly reduced, while significant elevations of factor VIIIc, factor VIIc, and plasminogen and antithrombin-III levels were noted. In the female hypertriglyceridemic subjects, the elevation of factor VIIc, factor VIIIc, and plasminogen and antithrombin-III levels was highly-significant, whereas aPTT was not significantly reduced. Unexpectedly, the levels of the established coronary risk factor, fibrinogen, did not show a statistically different change. Similar to previous data, our hypertriglyceridemic subjects also presented with hyperinsulinemia, glucose intolerance, upper body obesity, and elevated blood pressure. Conclusions: Despite the fact that in population studies, triglycerides do not consistently appear to be an independent risk factor for coronary heart disease, our data suggest that a pronounced increase in triglycerides warrants aggressive therapy, because this increase may be associated with a hypercoagulable state. This phenomenon contributes another perspective to the study of higher cardiovascular mortality in hypertriglyceridemic subjects.

Evaluation of effects of unmodified niacin on fasting and postprandial plasma lipids in normolipidemic men with hypoalphalipoproteinemia

PURPOSE

The aim of this study was to define the effects of unmodified niacin on basal lipids and lipoproteins and on the plasma triglyceride response to a fatty meal--postprandial or alimentary lipemia--in individuals with low levels of high-density lipoprotein cholesterol (HDL-C) and normal fasting cholesterol and triglyceride concentrations (normolipidemic hypoalphalipoproteinemia, isolated low HDL-C).

PATIENTS AND METHODS

Twenty-eight normolipidemic men (total plasma cholesterol concentration [TC] < 230 mg/dL [< 6 mmol/L], plasma triglyceride [Tg] < 250 mg/dL [2.75 mmol/L]) with low plasma concentrations of HDL-C were randomly assigned to increasing doses of crystalline niacin (up to 3,000 mg/d) or no drug for 12 weeks, then crossed over to the alternate regimen. Outcome measures included changes in plasma lipoproteins and alimentary lipemia.

RESULTS

Fifteen participants completed the study. Mean baseline HDL-C +/- SD was 31.7 +/- 6.2 mg/dL (0.82 +/- 0.16 mmol/L). Mean baseline TC, plasma concentration of low-density lipoprotein cholesterol (LDL-C), and Tg were 192 +/- 29.4 mg/dL (4.97 +/- 0.76 mmol/L), 123 +/- 27 mg/dL (3.17 +/- 0.69 mmol/L), and 197 +/- 75 mg/dL (2.17 +/- 0.83 mmol/L), respectively. Unmodified niacin treatment resulted in significant (P < 0.001) reductions of 14% in TC (to 165 mg/dL, 4.26 mmol/L), 40% in Tg (to 119 mg/dL, 1.31 mmol/L), and 18% in LDL-C (to 101 mg/dL, 2.60 mmol/L) and significant increases of 30% in HDL-C (to 42 mg/dL, 1.07 mmol/L), 100% in HDL2 cholesterol (from 5 mg/dL to 9 mg/dL, 0.12 mmol/L to 0.24 mmol/L), and 21% in HDL3 cholesterol (from 27 mg/dL to 33 mg/dL, 0.70 mmol/L to 0.85 mmol/L). Unmodified niacin treatment reduced alimentary lipemia by 45% (P < 0.02).

CONCLUSIONS

Crystalline niacin effectively raises HDL-C, lowers LDL-C, and reduces alimentary lipemia in patients with isolated low HDL-C. However, many patients have difficulty tolerating the drug, and supervision may be required to sustain patient compliance and avoid toxicity.

Blood biochemical and cellular changes during decompression and simulated extravehicular activity

Blood biochemical and cellular parameters were measured in human subjects before and after exposure to a decompression schedule involving 6 h of oxygen prebreathing. The exposure was designed to simulate extravehicular activity for 6 h (subjects performed exercise while exposed to 29.6 kPa). There were no significant differences between blood samples from subjects who were susceptible (n = 11) versus those who were resistant (n = 27) to formation of venous gas emboli. Although several statistically significant (P less than 0.05) changes in blood parameters were observed following the exposure (increases in white blood cell count, prothrombin time, and total bilirubin, and decreases in triglycerides, very-low-density lipoprotein cholesterol, and blood urea nitrogen), the changes were small in magnitude and blood factor levels remained within normal clinical ranges. Thus, the decompression schedule used in this study is not likely to result in blood changes that would pose a threat to astronauts during extravehicular activity.

Lovastatin reduces postprandial lipoprotein levels in hypercholesterolaemic patients with mild hypertriglyceridaemia

Drugs that inhibit cholesterol synthesis have recently been released for lowering LDL-cholesterol levels. The current study examines the effect of one of these drugs, lovastatin, alone and in combination with cholestyramine on postprandial fat metabolism in five patients with severely elevated LDL-cholesterol and normal triglyceride levels (less than 1.8 mmol l-1) and in five patients with similarly elevated LDL-cholesterol and mildly elevated triglyceride levels (1.8 to 2.7 mmol l-1). In the group of patients with normal triglyceride levels, neither lovastatin alone nor in combination with cholestyramine had any effect on postprandial lipoprotein levels, while profoundly decreasing LDL-cholesterol levels. This provides evidence that LDL and postprandial lipoproteins are cleared by different mechanisms. In the group of five patients with mildly elevated triglyceride levels, in addition to LDL-cholesterol lowering, lovastatin significantly lowered VLDL-cholesterol, fasting triglyceride and postprandial lipoprotein levels. Thus in patients with mild hypertriglyceridaemia, lovastatin may have another favourable effect on the lipoprotein system in addition to LDL-cholesterol lowering.

Role of triglyceride-rich lipoproteins from the liver and intestine in the etiology of postprandial peaks in plasma triglyceride concentration

Plasma triglyceride concentration in human subjects peaks once, twice or three times in the twelve-hour period following the ingestion of a fat-rich meal. Triglyceride-rich lipoproteins (TRL) containing apolipoprotein (apo)B-48 (of intestinal origin), and TRL containing apoB-100 (predominantly of hepatic origin) both contribute to postprandial changes in plasma triglyceride concentration. To test the hypothesis that earlier peaks in postprandial triglyceridemia are due predominantly to the secretion of TRL from the intestine, while later peaks are due to the secretion of TRL from the liver, TRL apoB-48, TRL apoB-100 and retinyl ester (a marker of intestinal lipoproteins) were measured in plasma samples from subjects fed a fat-rich meal (1 g fat/kg body wt). Data from seven subjects (four fed 40 retinol equivalents vitamin A/kg body wt, three fed 20 retinol equivalents vitamin A/kg body wt, with the fat meal), showed that postprandial peaks in plasma triglyceride were always associated with increases in plasma retinyl ester concentration. In four subjects, who were selected because they had two clearly defined postprandial triglyceride peaks, the plasma concentration of TRL triglyceride, apoB-48, apoE and apoC increased in conjunction with both the earlier (three hour) and later (nine hour) peaks in plasma triglyceride. Increase in TRL apoB-100 was associated with both peaks in two of the four subjects. Our data suggest that 1) TRL from the liver and intestine contribute to both earlier and later peaks in postprandial triglyceridemia; and 2) the rate of appearance of TRL from the intestine is not constant after dietary fat absorption.

Coronary disease prediction using a new atherogenic index

This report demonstrates the utilization of a new serum factor, Toxicity Preventing Activity (TxPA) in the diagnosis of coronary disease prone individuals. Our laboratory has recently identified TxPA, which offsets the toxicity of very low density lipoproteins (VLDL) upon arterial cells in vitro. In the present study, we measured TxPA activity and serum lipoprotein levels in 73 individuals undergoing coronary angiography. Serum from control subjects demonstrated 270% more TxPA than aged matched individuals with angiographically demonstrable coronary disease (CHD). When TxPA was combined with serum lipoprotein values, a new atherogenic index was generated which further distinguished these individuals with CHD from non-angiographed controls. These results demonstrate that TxPA is a new protective factor in coronary artery disease, and that the new atherogenic index provides for the first time an accurate classification of individuals with coronary artery disease.

Different patterns of postprandial lipoprotein metabolism in normal, type IIa, type III, and type IV hyperlipoproteinemic individuals. Effects of treatment with cholestyramine and gemfibrozil

To study exogenous fat metabolism, we used the vitamin A-fat loading test, which specifically labels intestinally derived lipoproteins with retinyl palmitate (RP). Postprandial RP concentrations were followed in total plasma, and chylomicron (Sf greater than 1,000) and nonchylomicron (Sf less than 1,000) fractions. In normal subjects postprandial lipoproteins were present for more than 14 h, and chylomicron levels correlated inversely with lipoprotein lipase activity and fasting high density lipoprotein (HDL) cholesterol levels and nonchylomicron levels correlated inversely with hepatic triglyceride lipase activity. The main abnormality in type IV patients was a 5.6-fold increase in the chylomicron fraction, whereas in type III patients it was a 6.4-fold increase in nonchylomicrons. Type IIa patients had abnormally low chylomicron fractions. In type IV patients gemfibrozil decreased, whereas in type IIa patients cholestyramine increased the chylomicron fraction 66 and 88%, respectively. This study demonstrates an unexpectedly large magnitude and long duration of postprandial lipemia in normal subjects and patients. These particles are potentially atherogenic, and their role in human atherosclerosis warrants further study.

The use of different lipids to express serum tocopherol: lipid ratios for the measurement of vitamin E status

Plasma tocopherol was measured in 85 alcoholic patients and 40 control subjects from a local factory. Cholesterol, triglycerides and phospholipids were measured individually and summed to give an estimate of total serum lipids. Plasma tocopherol concentrations of the alcoholics were significantly lower than those of the controls and showed wide variation from marked deficiency to the upper limit of the normal range. Using regression analysis, 1.11 mumol tocopherol/mmol total lipids were calculated as the threshold of deficiency equivalent to 0.8 mg tocopherol/g total lipid established by Horwitt et al. The sensitivity and specificity of other tocopherol:lipid ratios for identifying vitamin E deficiency was compared with the tocopherol:total lipid ratio. Thresholds of deficiency for the different tocopherol:lipid ratios were calculated. The tocopherol:cholesterol+triglyceride ratio was found to be almost as powerful in identifying vitamin E deficiency as the tocopherol:total lipid ratio (sensitivity 95%, specificity 99%). Of the tocopherol:individual lipid ratios, the tocopherol:cholesterol ratio gave the best results (sensitivity 86%, specificity 94%).

Lipids and hypertension. Implications of new guidelines for cholesterol management in the treatment of hypertension

The approach to management of cardiovascular risk factors has been greatly enhanced by the recent publication of results from several large intervention studies. This increased knowledge has led to rapid changes in perspective and to some controversies regarding cardiovascular risk management. The major cardiovascular disease risk factors are high blood pressure, elevated serum cholesterol, and cigarette smoking. In the past, physicians have paid little attention to the latter two factors, focusing primarily on severe hypertension. Initially, the pharmacologic treatment of hypertension consisted mostly of thiazide diuretics, since they were the only agents generally available that were well-tolerated by most patients. Over the past decade, however, new data from large-scale intervention studies and the development of many new classes of antihypertensive agents have considerably improved the approach to managing all three primary risk factors. Recently published results of major clinical trials are likely to further alter physicians' perspectives and influence their practice habits. This article proposes an approach to comprehensive risk management that simultaneously involves all the major risk factors, with emphasis on blood pressure and lipids. The rationale for this integrated approach is based on the following facts: Hypertension trials have not convincingly demonstrated that lowering blood pressure alone reduces the risk for coronary heart disease; Cholesterol lowering has been shown conclusively to reduce the risk of coronary heart disease; Several classes of antihypertensive agents have now been found to significantly affect blood lipids, either adversely or beneficially; and Past observational epidemiologic studies have shown a positive association between blood lipids (cholesterol and triglycerides) and blood pressure, implying that these two conditions commonly occur together. The background supporting these facts, as well as a practical approach to the treatment of hypertension that takes into consideration the management of blood lipids, is provided in this article.

Hormonal and substrate responses to a standard meal in normal and hypertriglyceridemic subjects

Postprandial plasma insulin, glucose, growth hormone, cortisol and free fatty acid responses to a standard mixed meal were determined and compared to fasting plasma triglyceride levels in normal and hypertriglyceridemic subjects. The hypertriglyceridemic subjects had significantly higher postprandial plasma insulin levels than did normals, but no significant differences were seen between the two groups to any of the other variables. Postprandial plasma insulin levels were highly correlated to fasting plasma triglyceride levels, but there was no significant correlation between any of the other variables and fasting plasma triglyceride levels.

Response of plasma triglycerides to dietary change in patients on hemodialysis

The effect of reduction in dietary carbohydrate content of meal formula diets on plasma triglyceride concentrations was studied in 12 patients receiving chronic hemodialysis. Fasting plasma triglycerides decreased over a 10-day period in 11 of 12 patients in response to a decreased proportion of carbohydrate (from 50 to 35% of total daily calories) regardless of the type of fat used. Postprandial insulin responses were also significantly lower in the patients on the diets lower in carbohydrate. In addition, triglyceride kinetics were studied in three groups of patients. Patients with renal failure (dialyzed and undialyzed) had lower triglyceride production rates than those of control subjects, despite higher plasma triglyceride concentrations. Elevated (greater than 150 mg/100 ml) fasting plasma triglycerides are associated with lower triglyceride production rates in patients with chronic renal failure and may not be improved by conventional hemodialysis. A long-term study of the efficacy of reduction in dietary carbohydrate on plasma triglycerides is needed since routine hemodialysis does not appear to correct the lipid abnormality in patients with chronic renal failure.