Risk Factors for Myocardial Infarction in the Stockholm Prospective Study

Hematologic disorders during essential hypertension

BACKGROUND

Besides the traditional risk factors, hematological changes may be involved in the development of arterial hypertension and in its pathogenesis.

METHODS

The study, conducted on a sample of 545 subjects, 215 with hypertension and 330 witnesses, were evaluated for peripheral blood parameters in western Algeria; Logistic regression analysis was used to predict hypertension with hematological parameters.

RESULTS

The characters studied related significantly; lower red blood cell levels have a three-and-a-half-fold risk of developing hypertension compared to those who have normal red blood cell counts (OR = 3.64, 95% CI = 1.37-9.65, p < 0.05). Subjects who have mean corpuscular volume rate below 80 fl are more exposed to hypertension (OR = 13.58, 95% CI = 4.68-39.41, p = 0.000). The mean corpuscular hemoglobin concentration reveals that subjects who have a lower than normal (<27 pg) are once less exposed to hypertension (OR = 0.04, 95% CI = 0.01-0.13, p = 0.000). Subjects who have lower platelet count than normal are twelve times more exposed to hypertension (OR = 12.13, 95% CI = 1.45-101.18, P = 0.021). Finally, the increase in sedimentation rate at one hour increases the risk of hypertension by 56.63 times compared to subjects with normal sedimentation rate (OR = 56.63, 95% CI = 3.37-597.33, P = 0.001).

CONCLUSIONS

Hematological profile associated with essential hypertension retained Red blood cells ratio, mean corpuscular volume, mean corpuscular hemoglobin concentration, platelet ratio, and sedimentation rate at one hour.

A high-fat diet and the threonine-encoding allele (Thr54) polymorphism of fatty acid-binding protein 2 reduce plasma triglyceride-rich lipoproteins

The threonine-encoding allele (Thr54) of the fatty acid-binding protein 2 (FABP2) DNA polymorphism is associated with increased triglyceride (TG)-rich lipoproteins (TRL). We hypothesized that the TRL response to diets of varied fat content is affected by the FABP2 A54T polymorphism, specifically that a high-fat diet would reduce TRL and that the Thr54 allele would have an enhanced response. Sixteen healthy, postmenopausal women completed a crossover dietary intervention that included three 8-week, isoenergetic diet treatments. The treatments consisted of high fat (40% of energy as fat), low fat (20% of energy), and low fat + n-3 fatty acids (20% of energy plus 3% as n-3 fatty acids). Eight subjects were homozygous for the wild type (Ala54/Ala54) of the FABP2 polymorphism, whereas 8 subjects had at least 1 Thr54 allele (7, Ala54/Thr54; 1, Thr54/Thr54). High-fat diet showed significantly reduced plasma TGs, chylomicron TG, and very low-density lipoprotein TG from baseline in all participants. Although carriers of the Thr54 allele of the FABP2 polymorphism had significantly reduced TRL, there is no evidence of an interaction, which does not support our hypothesis. The alanine-encoding allele did not influence the dietary effects on the plasma lipids.

Predicting the risk of cardiovascular disease in people exposed to moderate to high levels of dioxin

Cardiovascular disease (CVD) is a leading cause of morbidity and mortality worldwide. Dioxins can cause cardiovascular toxicity in experimental animals. The potential role of dioxin exposure as a preventable risk factor has attracted the attention of public health services, especially because dioxin exposure is a ubiquitous problem. We aimed to investigate and clarify the effect on CVD risk of moderate-to-high exposure to dioxins. This cross-sectional study investigated 914 residents without CVD near a deserted pentachlorophenol factory. CVD-related factors were measured to examine their associations with serum dioxin. We also investigated associations between serum dioxins and the Framingham risk score. Serum PCDD/F levels were significantly positively associated with CVD risk in both genders (Men: b=0.023, P<0.001; Women: b=0.005, P<0.001; All: b=0.013, P<0.001). After adjusting for confounding factors, participants with higher serum PCDD/F levels had a higher risk for CVD than did the reference group (serum PCDD/levels<9.8 pg WHO(98)-TEQ(DF)/g lipid) (25th to <50th percentile, adjusted odds ratio (AOR)=2.96 [95% confidence interval (CI)=1.13-7.75]; 50th to<75th percentile, AOR=3.37 [1.32-8.59]; ≥75th percentile, AOR=6.22 [2.47-15.63]). We hypothesize that accumulated dioxins heightens the cardiovascular risk.

Effect of dietary Rhodobacter capsulatus on lipid fractions and egg-yolk fatty acid composition in laying hens

The present study was conducted to investigate the effect of dietary Rhodobacter capsulatus on lipid fractions and egg-yolk fatty acid composition in laying hens. Thirty-six laying hens (30 weeks old) were randomly assigned into two dietary groups fed diets with (0.04%) or without (control) R. capsulatus for a 60-day feeding trial. Dietary R. capsulatus decreased (p < 0.05) serum and hepatic cholesterol and increased (p < 0.05) the excreta cholesterol, and resultant lower (p < 0.05) cholesterol contents in egg yolk. The concentration of polyunsaturated fatty acids (PUFA) and ratio to saturated fatty acids in egg yolk was improved (p < 0.05) by dietary R. capsulatus. The concentration of hepatic bile acid was increased (p < 0.05) and excreta bile acid was decreased (p < 0.01) in the laying hens fed R. capsulatus diet. The incorporation of 1-(14) C-palmitic acid into hepatic lipids and lipid fractions was increased (p < 0.05) in laying hens fed R. capsulatus diet. Moreover, dietary R. capsulatus did not appear to cause any adverse effects on laying hen performances. Therefore, dietary supplementation of R. capsulatus in layer diets may be a feasible means of producing eggs with lower cholesterol and higher PUFA contents for health conscious consumers.

Insulin resistance: the link between obesity and cardiovascular disease

There seems to be general agreement that the prevalence of obesity is increasing in the United States and that we are in the midst of an obesity epidemic. The disease-related implications of this epidemic have received an enormous amount of publicity in the popular media, but public awareness of the untoward effects of excess weight has not led to an effective approach to dealing with the dilemma. The gravity of the problem is accentuated in light of the report that only approximately 50% of physicians polled provided weight loss counseling. Given the importance of excess adiposity as increasing the risk of CVD, 2DM, and hypertension and the combination of an increase in the prevalence of overweight/obesity and a health care system unprepared to deal with this situation, it is essential that considerable thought be given as to how to best address this dilemma. In this context, it must be emphasized that CVD, 2DM, and hypertension are characterized by resistance to insulin-mediated glucose disposal and that insulin resistance and the compensatory hyperinsulinemia associated with insulin resistance have been shown to be independent predictors of all three clinical syndromes. It has also been apparent for many years that overweight/obese individuals tend to be insulin resistant and become more insulin sensitive with weight loss.25 In light of these observations, it seems reasonable to suggest that insulin resistance is the link between overweight/obesity and the adverse clinical syndromes related to excess adiposity. The evidence summarized in this review shows that the more overweight an individual, the more likely he or she is insulin resistant and at increased risk to develop all the abnormalities associated with this defect in insulin action. Not all overweight/obese individuals are insulin resistant, however, any more than all insulin resistant individuals are overweight/obese. More important, there is compelling evidence that CVD risk factors are present to a significantly greater degree in the subset of overweight/obese individuals that is also insulin resistant. Not surprisingly,we have also demonstrated that an improvement in CVD risk factors with weight loss occurs to a significantly greater degree in those overweight/obese individuals who are also insulin resistant at baseline. In view of the ineffectiveness of current clinical approaches to weight loss, it seems necessary to recognize that not all overweight/obese individuals are at equal risk to develop CVD and that it is clinically useful to identify those at highest risk. The simplest way to achieve this task seems to be focusing on the CVD risk factors that are highly associated with insulin resistance/hyperinsulinemia. If this is done, then intense efforts at weight control can be brought to bear on those who not only need it the most but also have the most to gain by losing weight.

Risk factors for ischaemic heart disease in men and women. Results of the 19-year follow-up of the Stockholm Prospective Study

In this 19-year follow-up of the Stockholm Prospective Study (SPS), 321 male and 55 female deaths from myocardial infarction (MI) had occurred. Fasting levels of plasma triglycerides acted as an independent risk factor for this cause of death in both sexes, which was the primary question asked when the SPS was designed. Other independent risk factors for MI were for men and women age, systolic blood pressure, smoking and for men only, plasma cholesterol, haemoglobin and erythrocyte sedimentation rate.

Diurnal levels of lipids, glucose and insulin in type IV hyperlipidemic patients on high carbohydrate and high fat diet: comparison with normals

Diurnal levels of serum triglyceride (TG), cholesterol, free fatty acids (FFA), glucose and insulin were measured in three type IV hyperlipidemic patients on a fixed solid 65% carbohydrate and a 65% fat diet when in steady state conditions in a metabolic unit. The carbohydrate-rich food was divided into either three or eight equivalent portions, differently spaced over the day and night. The fat-rich food was given in three equivalent portions only. The diurnal TG profiles on these diets showed the same characteristics as those found in normals, but increments and mean levels were considerably higher. On the carbohydrate-rich diet, mean TG levels decreased during the study. This was not seen either on the fat-rich diet or in normals. In contrast to our findings in normals, chylomicrons formed the major contribution to the serum TG pattern. FFA levels were markedly higher on the high-fat than on the carbohydrate-rich diet, but not different from those in normals. Postprandial glucose responses did not differ significantly between the diets. Insulin responses were markedly higher on the carbohydrate-rich than on the fat-rich food. Glucose levels did not differ from those in normals. Insulin levels were significantly higher in the patients. Cholesterol showed minimal fluctuations, parallel to the TG pattern, which could be attributed to chylomicron cholesterol.

Insulin resistance: the link between obesity and cardiovascular disease

Insulin-mediated glucose disposal varies at least sixfold in apparently healthy individuals. The adverse effect of decreases in the level of physical fitness on insulin sensitivity is comparable to the untoward impact of excess adiposity, with each accounting for approximately 25% of the variability of insulin action. It is the loss of insulin sensitivity that explains why obese individuals are more likely to develop cardiovascular disease, but not all overweight/obese individuals are insulin resistant. At a clinical level, it is important to identify those overweight individuals who are also insulin resistant and to initiate the most intensive therapeutic effort in this subgroup. Finally, it appears that the adverse impact of overall obesity, as estimated by body mass index, is comparable to that of abdominal obesity, as quantified by waist circumference.

Suppressive effect of resistant maltodextrin on postprandial blood triacylglycerol elevation

BACKGROUND

As the physiological functions of soluble dietary fibre, the favourable efficacy, such as attenuating the absorption of saccharides or lipids, is expected. Resistant maltodextrin, a soluble dietary fibre, was investigated and found that it delays the glucose absorption and attenuates the postprandial rise in the blood glucose levels, however, the efficacy of resistant maltodextrin on lipid metabolism is not yet reported.

AIM OF THE STUDY

We conducted an animal experiment and a human experiment to investigate the effect of resistant maltodextrin on postprandial blood triacylglycerol elevation.

METHODS

1. Rats were fed corn oil with or without resistant maltodextrin and the postprandial changes in triacylglycerol were examined. 2. We then conducted a dietary loading experiment on 13 healthy adult male and female subjects using a meal containing approximately 50 g fat. A beverage not containing resistant maltodextrin was used as a placebo; subjects consumed the loading meal and a beverage containing either 5 g or 10 g resistant maltodextrin; blood was periodically collected to see the changes in serum constituents.

RESULTS

1. The corn oil administration experiment using rats showed that resistant maltodextrin dose-dependently suppressed elevation of blood triacylglycerol levels after corn oil administration. 2. The dietary loading experiment on 13 healthy subjects with 5 or 10 g of resistant maltodextrin showed that; in each administration group, resistant maltodextrin significantly suppressed postprandial elevation of blood triacylglycerol, RLP-cholesterol and insulin.

CONCLUSION

These results indicate that resistant maltodextrin ingested with fatty meals suppresses the postprandial elevation of blood triacylglycerol levels.

Genetics of apolipoprotein B and apolipoprotein AI and premature coronary artery disease

Increased low-density lipoprotein (LDL) and decreased high-density lipoprotein cholesterol (HDL-C) predict premature coronary artery disease, as do elevated levels of apolipoprotein B or reduced levels of apolipoprotein AI. Probands were studied of families with common genetic forms of dyslipidaemia to determine if apo B or apo AI define genetic groups and if apo B or apo AI levels relate to premature coronary artery disease risk. Elevated apo B was characteristic of familial hypercholesterolaemia, familial combined hyperlipidaemia (FCHL), and was seen in individuals with elevated Lp(a). Normal apo B levels were seen in familial hypertriglyceridaemia and in 'coronary artery disease with low-HDL cholesterol'. Apo AI levels tended to be low in FCHL and were decreased in 'coronary disease with low-HDL cholesterol'. In familial hypertriglyceraemia, even though HDL-C levels were low, normal apo AI and apo B levels were seen in the absence of premature coronary artery disease. Therefore, in genetic dyslipidaemias elevated apo B levels and reduced apo AI levels (or increased apo B/AI ratio) differ and predict premature coronary artery disease.

Is there a simple way to identify insulin-resistant individuals at increased risk of cardiovascular disease?

The goal of this study was to evaluate the ability of various routine measures of lipoprotein metabolism to identify patients who were insulin resistant and dyslipidemic, and therefore, at increased risk of cardiovascular disease. For this purpose, insulin resistance was quantified by determining the steady-state plasma glucose concentration during the insulin suppression test in 449 apparently healthy patients. The low-density lipoprotein (LDL) particle diameter and subclass phenotype were measured by gradient gel electrophoresis in 1,135 patients. Pearson's correlation coefficients and receiver-operating characteristic curves were used to evaluate measures of lipoprotein metabolism as potential markers of insulin resistance and LDL phenotype. The results indicated that the ratio of the plasma concentrations of triglyceride to high-density lipoprotein cholesterol was the best predictor of insulin resistance and LDL particle diameter. The optimal triglyceride/high-density lipoprotein cholesterol ratio for predicting insulin resistance and LDL phenotype was 3.5 mg/dl; a value that identified insulin-resistant patients with a sensitivity and specificity comparable to the criteria currently proposed to diagnose the metabolic syndrome. The sensitivity and specificity were even greater for identification of patients with small, dense, LDL particles. In conclusion, a plasma triglyceride/high-density lipoprotein cholesterol concentration ratio > or =3.5 provides a simple means of identifying insulin-resistant, dyslipidemic patients who are likely to be at increased risk of cardiovascular disease.

Crossover trial for lipid abnormality in postmenopausal breast cancer patients during selective estrogen receptor modulators (SERMs) administrations

The objective of this study was to evaluate the different profiles of serum lipids resulting from the administration of selective estrogen receptor modulators (SERMs). Postmenopausal primary breast cancer patients (n = 197) with node-negative, hormone receptor-positive who were treated at our department or in other related medical institutions from April 1997 through March 2001 were given adjuvant therapy. The adjuvant therapy included 1 year's administration of tamoxifen (TAM) 20 mg or toremifene (TOR) 40 mg. The profiles of serum lipids such as total cholesterol (TC), high-density lipoprotein cholesterol (HDL) and triglyceride (TG) were observed. After 1 year administration TC had significantly decreased (p < 0.001) both in the TAM group and the TOR group, but no significant difference was found between these groups (p = 0.249). HDL had significantly decreased in the TAM group (p < 0.001), while it had significantly increased in the TOR group (p < 0.001), and a significant difference was found between the groups (p < 0.001). TG had significantly increased in the TAM group (p < 0.001) but significantly decreased in the TOR group (p < 0.001). The medication was switched in those who still had abnormal lipid metabolism and given to them for another year. After 1 year from the crossover TC and HDL had increased to the levels of before administration (p < 0.001) and TG had decreased in those (n = 57) whose medication was switched from TAM to TOR. While TC had decreased and TG had increased in those (n = 23) whose medication was switched from TOR to TAM (p < 0.001). The above findings have suggested that TOR provides better profiles of lipid metabolism than TAM.

Apolipoprotein B and apolipoprotein A-I: risk indicators of coronary heart disease and targets for lipid-modifying therapy

Although LDL cholesterol (LDL-C) is associated with an increased risk of coronary heart disease, other lipoproteins and their constituents, apolipoproteins, may play an important role in atherosclerosis. Elevated levels of apolipoprotein (apo) B, a constituent of atherogenic lipoproteins, and reduced levels of apo A-I, a component of anti-atherogenic HDL, are associated with increased cardiac events. Apo B, apo A-I and the apo B/apo A-I ratio have been reported as better predictors of cardiovascular events than LDL-C and they even retain their predictive power in patients receiving lipid-modifying therapy. Measurement of these apolipoproteins could improve cardiovascular risk prediction.

Hypolipidaemic activity of seaweed from Karachi coast

During the present study, ethanol extracts of five seaweed species Solieria robusta, Iyengaria stellata, Colpomenia sinuosa, Spatoglossum asperum and Caulerpa racemosa at 10 mg/ 200 g body weight were tested for their hypolipidaemic activity. All the species significantly decreased the serum total cholesterol, triglyceride and low density lipoprotein cholesterol levels in normal, triton-induced and diet-induced hyperlipidaemic rats. Solieria robusta was found to be the most effective in reducing the lipid profile, particularly in diet-induced hyperlipidaemic rats. A beneficial effect of the ethanol extract of S. asperum was also found on cardiac and liver enzymes in diet-induced hyperlipidaemic rats.

Lipoprotein analysis using agarose gel electrophoresis and differential staining of lipids

We established a strategy to directly measure cholesterol and triglyceride levels of each lipoprotein fraction using a combination of agarose gel electrophoresis and differential staining. The cholesterol and triglyceride levels determined by electrophoresis correlated significantly with those of ultracentrifugation. The correlation coefficients between these methods were, for cholesterol levels 0.975(very low density lipoproteins, VLDL), 0.986(low density lipoproteins, LDL) and 0.965(high density lipoproteins, HDL) and for triglyceride levels 0.994(VLDL), 0.963(LDL) and 0.959(HDL) respectively. Both intra-and inter-assays showed low values of coefficients of variation (CV) (less than 3.57%). We observed a strong linearity between staining and triglyceride concentration. An increased VLDL-cholesterol was observed in type III subjects, a result which enabled distinction between type III and type IIb or type V lipoproteinemia. The method revealed lipoprotein patterns in some samples otherwise unexpected from their corresponding serum lipid parameters. Analyses of these electrophoretic patterns thus provide an effective technique to classify types of hyperlipidemia defined by the WHO. Furthermore, quantitative measurement of chylomicrons, usually difficult, proved to be achievable, providing an additional analysis of postprandial hyperlipidemia and the exact measurement of LDL-cholesterol after diet. Consequently, we recommend this simple and easy method for clinical evaluation of abnormalities in lipoprotein profiles.

Effect of nicotinic acid administration on hepatic very low density lipoprotein-triglyceride production

Our objective was to examine very low density lipoprotein-triglyceride (VLDL-TG) kinetics after chronic and acute administration of nicotinic acid (NA). Incorporation of [1,2,3,4-(13)C(4)]palmitate and [2-(13)C(1)]glycerol into VLDL-TG was measured in five healthy, normolipidemic women. Each subject was studied twice; the 4-day hospital stays were separated by 1 mo, during which time doses of NA were increased to 2 g/day (500 mg, 4 times/day). During posttreatment study, 500 mg of NA were administered acutely at 0800. Under baseline postabsorptive conditions, incorporation curves from (13)C-labeled free fatty acid (FFA) and (13)C-labeled glycerol were superimposable, and VLDL-TG kinetics were in agreement (t(1/2) = 1.4 +/- 0.3 and 1.3 +/- 0.3 h, and production rates = 27.2 +/- 6.1 and 28.5 +/- 5.3 g/day, respectively). In the postabsorptive state after chronic NA therapy, VLDL-TG concentrations and production rates were lower despite a trend toward elevated plasma FFA concentrations and fluxes. After the acute dose of NA, plasma FFA concentrations and flux fell dramatically, and there was a virtual halt to VLDL-TG production, which continued throughout the 6-h period after NA, despite a marked rebound overshoot in serum FFA concentrations and flux after hour 2. Plasma homocysteine concentrations increased 68% (P < 0.001) in the NA phase, consistent with chronic increased transmethylation demand. We conclude that 1) NA acutely and chronically decreases VLDL-TG production rate in normal women; 2) the acute effect on VLDL-TG production is associated with an initial suppression of lipolysis but persists for several hours after the antilipolytic action of NA has abated and is observed in the basal postabsorptive state, when lipolytic rates are not reduced; and 3) the effect of NA on VLDL-TG production, therefore, cannot be completely explained by its antilipolytic actions.

Preventing, stopping, or reversing coronary artery disease--triglyceride-rich lipoproteins and associated lipoprotein and metabolic abnormalities: the need for recognition and treatment

A substantial number of treated patients with or at high risk for coronary artery disease continue to have fatal and nonfatal coronary artery events in spite of significant reduction of elevated levels of low-density lipoprotein cholesterol. Other lipoprotein abnormalities besides an elevated level of low-density lipoprotein cholesterol contribute to risk of coronary artery disease and coronary artery events, and the predominant abnormalities that appear to explain much of this continued risk are an elevated serum triglyceride level and a low level of high-density lipoprotein cholesterol. Most patients with coronary artery disease have a mixed dyslipidemia with hypertriglyceridemia, which is associated and metabolically intertwined with other atherogenic risk factors, including the presence of triglyceride-rich lipoprotein remnants, low levels of high-density lipoprotein cholesterol, small, dense, low-density lipoprotein particles, postprandial hyperlipidemia, and a prothrombotic state. Aggressive treatment of these patients needs to focus on these other lipoprotein abnormalities as much as on low-density lipoprotein cholesterol. Combination drug therapy will usually be required. Reliable assessment of risk of coronary artery disease from lipoprotein measurements and response to therapy requires inclusion of all atherogenic lipoproteins in laboratory measurements and treatment protocols. At present this may be best accomplished by use of non-high-density lipoprotein cholesterol (total cholesterol minus high-density lipoprotein cholesterol) calculated from standard laboratory lipoprotein values. Ultimately, a more comprehensive assessment of coronary artery disease risk and appropriate therapy may include measurement of lipoprotein subclass distribution including determination of low-density lipoprotein particle concentration and sizes of the various lipoprotein particles.

Effects of combination therapy with estrogen plus simvastatin on lipoprotein metabolism in postmenopausal women with type IIa hypercholesterolemia

We investigated the effects of estrogen and simvastatin, administered both alone and in combination, on the plasma lipid levels and lipoprotein-related enzymes in 45 postmenopausal women with type IIa hypercholesterolemia. They received 0.625 mg conjugated equine estrogen (n=15), 5 mg simvastatin (n=15), or the combination (n=15) daily for 3 months. We measured the concentrations of cholesterol and triglyceride in the plasma, and in the very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), low-density lipoprotein (LDL)1 (1.019<d<1.045 g/ml) and LDL2 (1.045<d<1.063 g/ml), and high-density lipoprotein (HDL)2 (1.063<d<1.125 g/ml) and HDL3 (1.125<d<1.210 g/ml) subfractions, and apolipoproteins, and the activities of lipoprotein-metabolizing enzyme before and after treatment. All three treatments significantly lowered the plasma levels of total cholesterol, LDL1 cholesterol, and apolipoprotein B, C-II, and E. In combination therapy, significantly reduced levels of VLDL, IDL, and LDL2 cholesterol were also obtained. Combination therapy lowered total and LDL1 cholesterol significantly more than did estrogen alone. Estrogen and combination therapy significantly increased the levels of cholesterol in the HDL2 subfraction, triglyceride in the HDL2 and HDL3 subfractions, and apolipoprotein A-I and A-II. Estrogen treatment, but not combination therapy, also significantly raised the levels of total and IDL triglyceride. Estrogen and combined therapies significantly lowered the activities of hepatic triglyceride lipase and lecithin cholesterol acyltransferase. Findings indicate that combination therapy with estrogen plus simvastatin favorably affected lipid metabolism by reducing the concentrations of VLDL and IDL particles as well as large and small LDL particles, increasing the concentration of HDL particles, and preventing estrogen-induced increases in plasma triglyceride levels.

Postprandial lipemia and coronary risk

A number of cross-sectional studies have demonstrated that the magnitude of postprandial lipemia or single postprandial triglyceride values predict asymptomatic and symptomatic atherosclerosis, independent of risk factors measured in the fasting state. Postprandial lipemia reflects an integrated measure of an individual's triglyceride metabolic capacity. Numerous genetic and environmental factors that are known or suspected to affect triglyceride transport contribute to the magnitude of postprandial lipemia. In this article, mechanisms linking postprandial lipemia with the development and progression of atherosclerosis are described, and determinants of the extent and duration of postprandial lipemia are discussed.

Carbohydrate-induced hypertriacylglycerolemia: historical perspective and review of biological mechanisms

Current trends in health promotion emphasize the importance of reducing dietary fat intake. However, as dietary fat is reduced, the dietary carbohydrate content typically rises and the desired reduction in plasma cholesterol concentrations is frequently accompanied by an elevation of plasma triacylglycerol. We review the phenomenon of carbohydrate-induced hypertriacylglycerolemia, the health effects of which are among the most controversial and important issues in public health nutrition today. We first focus on how seminal observations made in the late 1950s and early 1960s became the basis for subsequent important research questions and areas of scientific study. The second focus of this paper is on the current knowledge of biological mechanisms that contribute to carbohydrate-induced hypertriacylglycerolemia. The clinical rationale behind mechanistic studies is this: if carbohydrate-induced hypertriacylglycerolemia shares a metabolic basis with endogenous hypertriacylglycerolemia (that observed in subjects consuming high-fat diets), then a similar atherogenic risk may be more likely than if the underlying metabolic mechanisms differ. The third focus of the paper is on both the positive metabolic changes that occur when high-carbohydrate diets are consumed and the potentially negative health effects of such diets. The review concludes with a summary of some important research questions that remain to be addressed. These issues include the level of dietary carbohydrate that induces carbohydrate-induced hypertriacylglycerolemia, whether the phenomenon is transient or can be avoided, whether de novo lipogenesis contributes to the phenomenon, and what magnitude of triacylglycerol elevation represents an increase in disease risk.

Hyperinsulinemia in a normal population as a predictor of non-insulin-dependent diabetes mellitus, hypertension, and coronary heart disease: the Barilla factory revisited

The study was initiated to evaluate the ability of hyperinsulinemia (as a surrogate measure of insulin resistance) to predict the development in a previously healthy population of three putative outcomes of this abnormality--glucose intolerance, hypertension, and coronary heart disease (CHD). The study involved defining the incidence at which these changes occurred between 1981 and 1993 to 1996 in 647 individuals who were free of any disease when initially studied. The study population consisted of approximately 90% of the subjects evaluated in 1981, divided into quartiles on the basis of the plasma insulin response to a glucose challenge as determined in 1981. The results indicated that the 25% of the population with the highest insulin response in 1981 had significant (P < .001) increases in the incidence of impaired glucose tolerance (IGT) or type 2 diabetes (eightfold), hypertension (twofold), or CHD (threefold). Furthermore, the ability of hyperinsulinemia to predict the three clinical endpoints was independent of differences in age, gender, or body mass index (BMI). Finally, if CHD is considered the clinical endpoint, multiple logistic regression analysis indicates that the values for plasma triglyceride (TG) and mean arterial blood pressure ([MAP] as measured in 1981) also predict the development of CHD. These results indicate that the untoward clinical effects of insulin resistance and/or compensatory hyperinsulinemia, glucose intolerance, hypertension, and CHD clearly can develop in less than 15 years.

Concepts in functional foods: the case of inulin and oligofructose

Recent advances in biosciences support the hypothesis that diet modulates various body functions. Diet may maintain well-being and reduce the risk of some diseases. Such discoveries have led to the concept of "functional food" and the development of the new discipline, i.e., "functional food science." A practical and simple definition of a "functional food" is a food for which a claim has been authorized. The food components to be discussed as potential "functional food ingredients" are the inulin-type fructans, i.e., chicory inulin and oligofuctose. The targets for their effects are the colonic microflora, the gastrointestinal physiology, the immune functions, the bioavailability of minerals, the metabolism of lipids and colonic carcinogenesis. Potential health benefits include reduction of risk of colonic diseases, noninsulin-dependent diabetes, obesity, osteoporosis and cancer. The documentation of such benefits requires scientific evidence that must be evaluated in terms of "health claims." Previous assessments have concluded that, in terms of "functional claims," strong evidence exists for a prebiotic effect and improved bowel habit. The evidence for calcium bioavailability is promising, and positive modulation of triglyceride metabolism is undergoing preliminary evaluation. Scientific research still must be done to support any "disease risk reduction claim," but sound hypotheses do already exist for designing the relevant human nutrition trials.

Altered skeletal muscle glucose transport and blood lipid levels in habitual cigarette smokers

We determined whether habitual cigarette smoking alters insulin-stimulated glucose transport and GLUT4 protein expression in skeletal muscle. Vastus lateralis muscle was obtained from 10 habitual cigarette smokers and 10 control subjects using an open muscle biopsy procedure. Basal 3-O-methylglucose transport was twofold higher (P < 0.01) in muscle from habitual smokers (0.05 +/- 0.08 vs. 1.04 +/- 0.19 mumol ml-1 h-1; controls vs. smokers respectively). Insulin (600 pmol l-1) increased glucose transport 2.6-fold (P > 0.05) in muscle from control subjects, whereas no significant increase was noted in habitual smokers. Skeletal muscle GLUT4 protein expression was similar between the groups. FFA levels were elevated in the smokers (264 +/- 49 vs. 748 +/- 138 mumol l-1 for control subjects vs. smokers; P < 0.05), and serum triglyceride levels were increased in the smokers (0.9 +/- 0.2 vs. 2.3 +/- 0.6 mmol l-1 for control subjects vs. smokers; P < 0.05). Skeletal muscle carnitine palmitil (acyl) transferase activity was similar between the groups, indicating that FFA transport into the mitochondria was unaltered by cigarette smoking. In conclusion, cigarette smoking appears to have a profound effect on glucose transport in skeletal muscle. Basal glucose transport is markedly elevated, whereas insulin-stimulated glucose transport is impaired. These changes cannot be explained by altered protein expression of GLUT4, but may be related to increased serum FFA and triglyceride levels. These findings highlight the importance of identifying habitual cigarette smokers in studies aimed at assessing factors that lead to alterations in lipid and glucose homeostasis in people with non-insulin-dependent diabetes mellitus (NIDDM).

Short-term efficacy and tolerability of combination therapy with lovastatin and acipimox in Chinese patients with type 2 diabetes mellitus and mixed dyslipidemia

In type 2 diabetes, it is not uncommon to find an elevated serum triglyceride and/or reduced high-density lipoprotein (HDL) cholesterol levels; elevated total cholesterol levels often occur as well. To evaluate the short-term efficacy and tolerability of combination therapy with lovastatin and acipimox in Chinese patients with type 2 diabetes who have mixed dyslipidemia, an open-label 6-month trial was conducted. All patients had type 2 diabetes (n = 33) with total cholesterol > or = 6.2 mmol/L and fasting triglyceride > or = 2.8 mmol/L, which had been confirmed twice and persisted for at least 12 weeks after introduction of diet control. After a 4-week run-in period, they were given lovastatin 40 mg daily at night for 12 weeks. Acipimox 250 mg three times a day was then added for a further 12 weeks. After 12 weeks of treatment with lovastatin alone, improvement was observed in total cholesterol (21% reduction), triglyceride (32% reduction), low-density lipoprotein (LDL) cholesterol (5.5% reduction), HDL cholesterol (11.6% elevation), apolipoprotein A-I (4.6% elevation), and apolipoprotein B (20.5% reduction). The addition of acipimox to lovastatin for an additional 12 weeks further reduced serum total cholesterol, triglyceride, LDL cholesterol, and apolipoprotein B, but this additional decrease was not statistically significant. However, HDL cholesterol and apolipoprotein A-I levels were significantly increased by the addition of acipimox (a 14.2% and 9.0% elevation, respectively). Serum creatine phosphokinase increased slightly after 12 weeks of lovastatin but decreased to a concentration similar to baseline after 12 weeks of combination treatment. No patients reported muscle pain or weakness or other side effects. Combination treatment with lovastatin and acipimox appears to be a safe and effective therapy in patients with type 2 diabetes and mixed dyslipidemia, and has particular benefit in elevating serum HDL cholesterol and apolipoprotein A-I levels.

Dietary fructans

Fructan is a general term used for any carbohydrate in which one or more fructosyl-fructose link constitutes the majority of osidic bonds. This review focuses on the fate of inulin-type fructans (namely native chicory inulin, oligofructose produced by the partial enzymatic hydrolysis of chicory inulin, and synthetic fructans produced by enzymatic synthesis from sucrose) in the gastrointestinal tract, as well as on their systemic physiological effects on mineral absorption, carbohydrate and lipid metabolism, hormone balance, and nitrogen homeostasis. The scientific evidence for the functional claims of inulin-type fructans is discussed, as well as their potential application in risk reduction of disease, namely constipation, infectious diarrhea, cancer, osteoporosis, atherosclerotic cardiovascular disease, obesity, and non-insulin dependent diabetes.

Common genetic variants of lipoprotein lipase and apolipoproteins AI-CIII that relate to coronary artery disease: a study in Chinese and European subjects

The large ethnic differences in prevalence of coronary artery disease between China and Europe may relate to both genetic and environmental differences. To assess possible genetic factors we have therefore studied the frequencies of disease-related variants of genes involved in lipid transport in 69 hypertriglyceridemic Chinese subjects and 74 healthy Chinese controls. The loci studied include lipoprotein lipase (Asp9Asn, Asn291Ser, Ser447Ter, and Thr361Thr); apolipoprotein A1 (restriction sites at MspI, XmnI, and PstI); and apolipoprotein (apo) CIII (G3175C). All these variants have been shown in previous literature publications to relate to either dyslipidemia and/or premature coronary heart disease in Caucasians. Two disease-related genetic variants in Europeans (Asp9Asn and Asn291Ser) were not found in the Chinese sample. The apo CIII G3175C variant was found more frequently in the upper tertile distributions for apolipoprotein CIII, apolipoprotein E, and plasma triglyceride/HDL ratios (P < 0.05). The rare allele of the apo AI MspI restriction site polymorphic variant was also found more frequently in the upper tertiles for apo CIII, apo E, and plasma triglyceride/HDL ratios (P < 0.04). Eleven of the most lipaemic Chinese subjects (with fasting plasma triglycerides >700 mg/dl) were analyzed for DNA sequence variation. One novel mutation was observed C1338A (which is a silent mutation at Thr361) and two others that are also found in European subjects (Ala261Thr and Ser447Ter). We conclude that genetic differences between Chinese and Europeans may have an effect on the prevalence of coronary artery risk factors involved in lipid transport, and further extended study is warranted.

Impaired myocardial vasodilation during hyperemic stress with dipyridamole in hypertriglyceridemia

OBJECTIVES

This study sought to investigate the specific role of hypertriglyceridemia in the myocardial hyperemic stress with dipyridamole/rest flow ratio (MDR).

BACKGROUND

Reduced MDR has been reported in hypercholesterolemic patients without evidence of ischemia. However, the specific role of hypertriglyceridemia in MDR has not been studied.

METHODS

Fifteen nondiabetic normocholesterolemic hypertriglyceridemic patients and 13 age-matched control subjects were studied. Myocardial blood flow (MBF) during dipyridamole administration and baseline MBF in hypertriglyceridemic patients and control subjects were measured using positron emission tomography and nitrogen-13 ammonia, after which the MDR was calculated.

RESULTS

Baseline MBF (ml/min per 100 g heart weight) in hypertriglyceridemic patients (mean +/- SD 73.6 +/- 24.1) did not differ significantly from that in control subjects (81.6 +/- 37.2). MBF during dipyridamole loading in hypertriglyceridemic patients (198 +/- 106) was significantly reduced compared with that in control subjects (313 +/- 176, p < 0.05), as was the MDR (2.71 +/- 1.07 vs. 3.73 +/- 1.14, respectively, p < 0.05). Spearman rank-order correlation analysis showed a significant relation between plasma triglyceride concentration and MDR (r = -0.466, asymptotic SE 0.157, p = 0.0125); however, no such significant relation was seen between total plasma cholesterol concentration and MDR (r = -0.369, asymptotic SE 0.130, p = 0.059).

CONCLUSIONS

Impaired myocardial vasodilation was suggested in hypertriglyceridemic patients without symptoms and signs of ischemia.

Suppression of endothelin-3-induced nitric oxide synthesis by triglyceride in human endothelial cells

Reduced endothelium-derived nitric oxide (NO) production characterizes several vascular diseases. This study examined the effect of triglyceride on NO production induced by endothelin-3 (ET-3) in cultured human umbilical vein endothelial cells. Triglyceride-rich human plasma obtained after a high-carbohydrate diet with white wine was used in an ex vivo study. The plasma triglyceride fraction was found to consist of large amounts of palmitic and oleic acids detected by gas-liquid chromatography. Therefore, the effect of synthetic tripalmitin and triolein emulsion on NO production was also examined. ET-3 stimulated NO and guanosine 3',5'-cyclic monophosphate production and increased cytosolic Ca2+ levels in the endothelial cells (ECs). After incubation of the ECs with the triglyceride-rich plasma for 2 h, these responses to ET-3 were ameliorated in a triglyceride concentration-dependent manner (50-200 mg/dl). A synthesized emulsion of tripalmitin (100 mg/dl) and triolein (100 mg/dl) also blunted the responses to ET-3. Neither endothelial constitutive NO synthase mRNA expression nor its protein level was affected by treatment with triglycerides. These results suggest that triglyceride suppresses ET-3-induced NO synthesis in human ECs by inhibiting cytosolic Ca2+ elevation.

Altered myocardial vasodilatation in patients with hypertriglyceridemia in anatomically normal coronary arteries

Reduced myocardial vasodilatation (MVD) in hypercholesterolemics without overt coronary stenosis has been reported. However, the status of MVD in hypertriglyceridemics has not yet been clarified. The aim of this study was to investigate whether MVD is impaired in patients with hypertriglyceridemia without overt coronary stenosis. Twenty-three hypertriglyceridemics (10 normocholesterolemic hypertriglyceridemics [HTGs] and 13 mixed combined hyperlipidemics [MCHLs]) and 13 age-matched controls were studied. All patients were proven to have more than one normal coronary artery, as diagnosed by coronary angiography, and those segments that were perfused by anatomically normal coronary arteries were used in the study. Myocardial blood flow (MBF) during dipyridamole (DP) loading and baseline MBF were measured by using positron emission tomography and [13N]ammonia, after which MVD was calculated. Baseline MBF (mL.min(-1).100 g(-1)) was comparable among HTG (76.0+/-26.1), MCHL (77.0+/-26.1), and controls (80.3+/-38.5). However, MBF during DP loading was significantly lower in MCHL (159+/-52.5) than in control subjects (292+/-166, P<.01), while it was comparable in HTG (202+/-104) and controls. MVD was significantly reduced in both HTG (2.70+/-1.09, P<.05) and MCHL (2.07+/-.70, P<.01) compared with controls (3.73+/-1.14). MVD in MCHLs tended to be reduced compared with that in HTGs, but the difference was statistically insignificant (P=.08). There was a significant relationship between MVD and both plasma triglycerides (r=-.47, P<.01) and plasma total cholesterol (r=-.55, P<.01). When controls and HTGs were combined, the relationship between MVD and plasma total triglycerides became more prominent (r=-.55, P<.05), and the significant relationship between cholesterol level and MVD disappeared. Multivariate regression analysis has revealed that the triglyceride level (F=5.2, P<.05) was independently related to MVD (r=.69, P<.01). In conclusion, MVD was reduced in hypertriglyceridemics in anatomically normal coronary arteries. Hypertriglyceridemia is an independent factor for this abnormality.

Suppressive effect of globin digest on postprandial hyperlipidemia in male volunteers

We have reported previously that various edible protein digests inhibit dietary hyperlipidemia in mice, rats, pigs and dogs. Of the various digests tested, globin digest had the most potent inhibitory activity, and a tetrapeptide extracted from globin digest, Val-Val-Tyr-Pro, had activity 7000-fold greater than that of the parent digest. In this clinical study, we investigated the influence of globin digest on serum chylomicron triglyceride concentrations as an indicator of the effect of globin digest on fat absorption and catabolism in humans. Parallel and crossover trials were conducted in which men consumed a control high fat diet (25 g fat, 7.6 g carbohydrate, 1.9 g protein and 0.7 g sodium chloride) or the same diet supplemented with globin digest. The supplemented dosages were 1 and 4 g globin digest. In the parallel trial, 22 men were divided into three groups: control, globin digest 1 g and globin digest 4 g. The increases in chylomicron triglyceride concentrations at 1 h after ingestion of 1 or 4 g globin digest were significantly lower (P < 0.05) compared with the control group. The crossover trial involved six subjects who consumed the control high fat diet and the same diet supplemented with 4 g globin digest. Serum chylomicron triglyceride levels increased in both groups at 1 and 2 h after ingestion, but when subjects consumed 4 g globin digest the increases were suppressed to 75 (P < 0.05) and 42% (P < 0.05) of the increases in controls at the corresponding times, respectively. The areas under the curves of chylomicron and serum total triglyceride concentrations during the 4 h after ingestion of 4 g globin digest were 46 (P < 0.05) and 34% (P < 0.05) lower, respectively, than when the men consumed the high fat control diet. In these trials, globin digest reduced the increase in serum chylomicron triglyceride concentrations as a result of the ingestion of a high fat diet. This hypotriglyceridemic effect of globin digest may be valuable for preventing obesity and in lowering the incidence of cardiovascular diseases.

Serum calcium: a new, independent, prospective risk factor for myocardial infarction in middle-aged men followed for 18 years

BACKGROUND

Primary hyperparathyroidism (HPT) is a disease characterized by hypercalcemia, and associated with an increased mortality in cardiovascular diseases. However, serum calcium levels within the normal range have not been evaluated as a prospective cardiovascular risk factor.

METHODS

A cohort of males aged 50 (n = 2183) were investigated in 1970-1973 for serum calcium and known cardiovascular risk factors. They were then followed up over the next 18 years.

RESULTS

During the follow-up period, 180 subjects experienced a myocardial infarction (MI). The serum calcium levels were significantly elevated at the baseline (2.37 +/- 0.09 SD versus 2.35 +/- 0.09 mmol/l, p < 0.03) in the subjects who developed a MI when compared with the rest of the cohort. Also blood pressure, body mass index (BMI), fasting insulin, serum cholesterol, serum triglycerides, and the atherogenic index were significantly elevated in the MI group (p < 0.01), while HDL-cholesterol was lower at the baseline investigation (p < 0.01). Cox's proportional hazard analysis showed that only serum calcium (p < 0.01), BMI (p < 0.0003), diastolic blood pressure (p < 0.0009), and the atherogenic index (p < 0.002) were significantly independent risk factors for MI. The range of serum calcium levels from the mean value, -2 SDs to the mean value +2 SDs corresponds to a variation in estimated risk for MI ranging from 0.06 to 0.15.

CONCLUSIONS

Serum calcium was found to be an independent, prospective risk factor for MI in middle-aged males suggesting a role for extracellular calcium levels in the atherosclerotic process.

Effects of continuous medroxyprogesterone acetate on lipoprotein metabolism in postmenopausal women receiving estrogen

OBJECTIVE

To investigate the effects of medroxyprogesterone acetate (MPA) on the beneficial effects of estrogen therapy on lipid metabolism in postmenopausal women.

METHODS

Postmenopausal women were administered either conjugated equine estrogen (CEE) 0.625 mg daily for 3 months (Group 1) or CEE 0.625 mg in conjunction with MPA 2.5 mg (Group 2) or MPA 5.0 mg (Group 3) daily for 3 months. Plasma levels of cholesterol, triglyceride, lipoprotein lipids, apolipoproteins, sex steroid hormones and lecithin cholesterol acyltransferase activity (LCAT) were determined. Lipoprotein lipase (LPL) and hepatic triglyceride lipase (H-TGL) activities were measured in postheparin plasma. Changes in the lipid concentrations and enzymatic activities were evaluated in each group.

RESULTS

Total, low-density lipoprotein (LDL) cholesterol, apolipoprotein B concentrations and LCAT activity were all significantly reduced by treatment in the three groups. The levels of high-density lipoprotein (HDL), HDL2, and HDL3 cholesterol as well as the levels of apolipoprotein AI and AII were significantly elevated in groups 1 and 2. The mean decrease in these parameters was related to the dose of MPA. Levels of triglyceride in the HDL and HDL2 were significantly increased in group 1. The levels of triglyceride in plasma, very low density lipoprotein (VLDL), LDL, HDL3 and VLDL cholesterol and LPL activity were unaffected. H-TGL activity was significantly inhibited only in groups 1 and 2. MPA produced a dose-dependent increase in H-TGL activity. A significant negative correlation was observed between the HDL cholesterol concentration and H-TGL activity (r = 0.58 P < 0.001).

CONCLUSIONS

The administration of MPA 2.5 mg and 5.0 mg did not adversely affect the changes in VLDL-LDL metabolism produced by estrogen. However, MPA has dose-dependent negative effects on HDL metabolism by increasing H-TGL activity and the 5.0 mg MPA interferes with the favorable effects on lipids of estrogen in postmenopausal women.

Triglyceride enriched lipoprotein particles correlate with the severity of coronary artery disease

A group of 100 male normotensive, non-obese, non-diabetic subjects who had undergone coronary angiography were studied to determine relationship between the severity of coronary artery disease (CAD) and plasma lipids, apolipoproteins and lipoprotein particles defined by their apolipoprotein composition. CAD was found in 84 and no measurable lesions were found in 26 subjects. The severity of CAD was determined on the basis of size and number of lesions and expressed in terms of a global CAD score. Low density lipoprotein (LDL)-cholesterol showed a tendency to be higher in CAD patients than in CAD-free subjects (216 vs. 205 mg/dl, P = 0.07). HDL-cholesterol showed a tendency towards lower values in CAD patients compared to CAD-free subjects 35 vs. 41 mg/dl, P = 0.07). In univariate analysis the severity of CAD correlated with (i) complex, apolipoprotein (apo) B containing particles (Lp-B-complex, r = 0.31, P = 0.005), (ii) HDL-cholesterol (r = -0.30, P = 0.005), (iii) apoC-III in heparin precipitate (r = 0.30, P = 0.005) and (iv) plasma triglycerides (r = 0.25, P = 0.02), all of which are related to triglyceride-rich lipoproteins. A comparison between the two subspecies of complex lipoprotein particles revealed that those containing apolipoproteins B, C-III and E (Lp-B:C:E complex) were more closely associated with CAD score (r = 0.27, P = 0.01) than those containing apolipoproteins A-II, B, C, D and E (Lp-A-II:B-complex). LDL-cholesterol also correlated with the global CAD score (r = 0.23, P = 0.03). In multiple regression analysis only HDL-cholesterol (P = 0.003), apoC-III-ratio (P = 0.007), Lp-B-complex (P = 0.02) and Lp-B:C:E-complex (P = 0.04) showed significant correlation with CAD score. The results of this study demonstrate that some of the triglyceride rich lipoprotein particles represent a risk factor for CAD and support the clinical usefulness of specific assays capable of distinguishing lipoprotein particles on the basis of apolipoprotein composition.

Comparison of the efficacy of simvastatin and standard fibrate therapy in the treatment of primary hypercholesterolemia and combined hyperlipidemia

Five multicenter, randomized, double-blind, placebo-controlled studies were conducted in France to compare the efficacy and safety of once-daily simvastatin treatment (10-40 mg/day) with conventional therapy with gemfibrozil 900 mg/day, ciprofibrate 100 mg/day, bezafibrate 400 mg/day, and fenofibrate 300 or 400 mg/day in a total of 800 patients with hypercholesterolemia. Simvastatin was associated with statistically significantly greater (p < or = 0.01) mean percent reductions in plasma low-density lipoprotein (LDL) cholesterol compared with each of the five fibrate regimens, even when administered at its recommended starting dose of 10 mg/day. Furthermore, approximately 90% of patients treated once daily with simvastatin experienced an at least 20% decrease in plasma LDL cholesterol compared with only 36 to 68% of patients treated with the individual fibrate agents (p < or = 0.05). The effectiveness of simvastatin in reducing LDL cholesterol did not differ as a function of the baseline plasma concentrations of total cholesterol or triglycerides. In contrast, the effectiveness of fibrate therapy in lowering plasma LDL cholesterol levels was significantly diminished (p < or = 0.05) among patients with triglyceride concentrations > 1.7 mmol/l. Plasma high-density lipoprotein (HDL) cholesterol levels were increased by approximately 10% after treatment with simvastatin or the fibrates. Although fibrate therapy was more effective overall in lowering plasma triglyceride levels, the effectiveness of simvastatin in reducing plasma triglyceride levels was generally 2- to 4-fold greater in patients with hypercholesterolemia associated with triglyceride levels > or = 2.3 mmol/l than in those with hypercholesterolemia associated with triglyceride levels < 2.3 mmol/l. The results of these studies confirm the superiority of simvastatin to standard fibrate therapy in reducing plasma levels of total and LDL cholesterol. They further indicate that once-daily treatment with simvastatin is effective in patients with isolated hypercholesterolemia or hypercholesterolemia associated with elevated triglyceride levels.

Prevalence of macro- and microvascular diseases in non-insulin-dependent diabetic and borderline glucose-intolerant subjects with insulin resistance syndrome

This study was undertaken to ascertain whether patients with insulin resistance syndrome, a cluster of risk factors for coronary artery disease (CAD), are really a high risk population for macro- and microvascular diseases in Japanese NIDDM and borderline glucose-intolerant subjects. A diagnosis of insulin resistance syndrome was made if four of the six following criteria are satisfied: glucose disposal rate < 2.2 mg/kg/min, fasting plasma IRI > 15 microU/ml or peak plasma IRI > 100 microU/ml during meal tolerance test, plasma triglyceride > 150 mg/dl at fasting or > 200 mg/dl after meal, serum HDL-cholesterol < 40 mg/dl, blood pressure > 140 mm Hg systolic and > 90 mm Hg diastolic or treatment with antihypertensive agents, and body mass index (BMI) > 27 for men or > 25 for women. We compared the prevalence of CAD, cerebral vascular disease (CVD), peripheral vascular disease (PVD), retinopathy and nephropathy between the insulin resistance syndrome group (group A, n = 57) and the remaining group (group B, n = 164). Both groups did not differ with respect to age, duration of diabetes, BMI, fasting plasma glucose, HbA1c, composition of NIDDM and borderline glucose-intolerance (BGI) or treatment modality. The prevalence of CAD was significantly higher in group A compared with that in group B (31.6% vs. 14.0%, P < 0.002), but not for CVD (8.8% vs. 3.7%, respectively, P = 0.12) or PVD (1.8% vs. 2.4%, respectively, P = 0.76). The prevalence of late-stage retinopathy in group A was significantly higher than that in group B (12.3% vs. 2.4%, respectively, P < 0.005). Macroalbuminuria, but not microalbuminuria, was significantly higher in group A than that in group B (12.3% vs. 3.6%, P < 0.02). We conclude that the insulin resistance syndrome preferentially increases the development of CAD, and is also involved in the progression of microvascular diseases.

Effects of iron- and hemoglobin-loaded human monocyte-derived macrophages on oxidation and uptake of LDL

It is generally accepted that transition metals are required for cellular LDL oxidation. LDL may also be oxidized by iron and reducing agents in cell-free systems. We hypothesized that lysosomal iron may be exocytosed from macrophages that have been iron loaded by phagocytosis and degradation of iron-rich structures, eg, erythrocytes, and that such released iron may promote LDL oxidation and uptake by macrophages. Human monocyte-derived macrophages (HMDMs) were isolated and cultured for 7 days and then exposed to FeCl3, Fe-ADP, or Fe-EDTA (100 mumol/L) or hemoglobin (25 or 50 micrograms/mL) for 24 hours. After rinsing, LDL (50 to 150 micrograms/mL) was added in fresh culture medium without serum. After another 24 hours the media concentrations of iron and thiobarbituric acid-reacting substances as well as the electrophoretic mobility of LDL were increased, while the cells showed only minimal signs of decreased viability. Lipofuscin, neutral lipids, and phospholipids accumulated in a granular, lysosome-like pattern, and the cells acquired a foam cell-like morphology. There was a strong correlation (r = .87, P = .005) between the amount of iron added during the pre-exposure period and lipofuscin accumulation during the ensuing exposure to LDL in fresh, serum-free medium. Our results support our hypothesis and indicate that lysosomal iron may be exocytosed from HMDMs and promote oxidation and uptake of LDL and thus induce foam cell formation.