Utility of metabolic syndrome as a risk enhancing factor in decision of statin use

BACKGROUND

Statins effectively reduce risk for atherosclerotic cardiovascular disease (ASCVD) when 10-year risk is ≥ 7.5%. In many patients at intermediate risk (7.5-<20% risk), there is uncertainty about reliability of risk assessment by current pooled cohort equations (PCE). A decision to initiate statin therapy is favored by several risk enhancing factors not employed in PCEs.

OBJECTIVE

This study examines the scope of the metabolic syndrome, a risk enhancing factor, and its principal sequala, diabetes, in 26,796 US adults age 40-75 years from the NHANES survey data, 1999-2016.

METHODS

The prevalence of metabolic syndrome without diabetes (MetS+) and of diabetes (DM+) were determined for 10-year risk categories estimated to be low (<7.5%), intermediate (7.5% -< 20%) and high (≥20%). Data were weighted to account for complex study design.

RESULTS

90.4% of the population was free of ASCVD. In subjects projected to be at low risk by PCEs, MetS+ was present in 15.0% and 17.6% of women and men, respectively. MetS + increased to 30.6% of women and 29.6% of men at intermediate risk, and to 21.5% of women and 32.2% of men at high risk. In addition, DM+ was present in 6.1%/5.3% (F/M) of low risk individuals, 20.1%/14.8% (F/M) of intermediate risk subjects, and 44.3%/39.4% (F/M) of high-risk persons. Prevalence of both MetS+ and DM + rose progressively with age in women and men.

CONCLUSIONS

MetS+ and DM + are common multiplex risk factors that predispose to higher lifetime risk and support statin therapy in patients at intermediate and high risk.

Coronary and peripheral artery plaques: do differences in plaque characteristics translate to differences in lipid management?

Optimal medical management of patients with peripheral arterial disease (PAD) includes statin therapy, which has been shown to decrease the risk of major cardiovascular events. However, the relationship between low-density lipoprotein (LDL) lowering, PAD progression and limb outcomes remains controversial. Although prevention of coronary and cerebrovascular events is a priority, limb outcomes are still important determinants of quality of life and healthcare spending. This review will highlight differences between coronary artery disease (CAD) and PAD, and in particular, the more prevalent role of lipids and LDL cholesterol in CAD versus calcification in PAD. This difference may contribute to the differential impact of LDL cholesterol levels on coronary events and outcomes versus limb outcomes. Beyond LDL lowering, immune modulators have emerged as another agent to treat atherosclerosis in CAD, however similar data in PAD are lacking. Small studies have suggested that other lipids besides LDL cholesterol, such as triglycerides or small dense LDL, may have a greater impact on limb outcomes in patients with PAD. Although statin therapy is central in the management of patients with PAD, current understanding of the distinctions between PAD and CAD suggest that there may be other non-LDL targets for risk reduction that require further study.

Traditional signs and symptoms commonly attributed to hypogonadism do not correlate with testosterone levels: the Cooper Center Longitudinal Study Experience

Evidence suggests that substantial testosterone therapy is occurring without checking levels of testosterone, presumably based on the presence of symptoms alone. We sought to explore the relationship between total testosterone level and non-specific symptoms, metabolic abnormalities, and sexual dysfunction associated with hypogonadism. This cross-sectional study included 2994 generally healthy men aged 50-79 years examined at a preventive medicine clinic in Dallas, TX from January 2012 to March 2016. Symptoms of hypogonadism were assessed. Screening morning total testosterone levels were measured and categorized into low (<250 ng/dL), low normal (250-399 ng/dL), and normal (≥400 ng/dL). Multiple logistic regression models were used to test the associations between total testosterone and signs and symptoms of hypogonadism. When considering symptoms and signs of hypogonadism, only decreased libido (OR 1.31, 95% CI 1.00 to 1.70), fasting glucose ≥100 mg/dL (OR 1.47, CI 1.15 to 1.88), and hemoglobin A1c over 6% (OR 1.47, 95% CI 1.06 to 2.03) were associated with increased odds of low testosterone after adjustment for age, body mass index, and cardiorespiratory fitness. Testosterone levels were not associated with fatigue, depression, or erectile dysfunction in our study (p>0.6). In this preventive medicine cohort, symptoms commonly attributed to testosterone deficiency were not associated with low total testosterone levels.

Current trends in non-HDL cholesterol and LDL cholesterol levels in adults with atherosclerotic cardiovascular disease

BACKGROUND

Low-density lipoprotein cholesterol (LDL-C) and non-high-density lipoprotein cholesterol (non-HDL-C) are targets for prevention of atherosclerotic cardiovascular disease (ASCVD). The American Heart Association and American College of Cardiology recently modified recommendations for clinical management of cholesterol in secondary and primary prevention. Accordingly, the present article examines the need for cholesterol-lowering drugs in the U.S. population with ASCVD.

OBJECTIVE

This study examines trends in non-HDL-C and LDL-C levels in a free living population of ASCVD subjects between 1999 and 2016.

METHODS

National Health and Nutrition Examination Surveys database included 4920 adults with ASCVD aged 40 to 85 years. Complete data were available for 4226. Trend analysis of changes in lipids is shown in box plots.

RESULTS

Mean age was 67 years with 57% males. Over 17 years, LDL-C decreased significantly by 24% and non-HDL-C by 21%. Over the period of study, reported intake of cholesterol-lowering drugs rose from 37% in 1999-2000 to 69% in 2015 to 2016. Over this same period, serum triglycerides decreased by 29% (P < .001) and HDL-C rose by 6%.

CONCLUSIONS

The changes in LDL-C and non-HDL-C in patients with ASCVD over a 17-year period probably are related to increased treatment with statins. However, the changes are too small to be explained by widespread use of high-intensity statins, which is the current recommendation for patients with ASCVD. These findings pose a challenge for professional education to support implementation of current guidelines for cholesterol-lowering therapies.

Metabolic syndrome is a sequela of radiation exposure in hypothalamic obesity among survivors of childhood brain tumors

Survivors of childhood brain tumors may be at risk for early onset of metabolic syndrome, possibly secondary to surgery and/or radiation exposure. This study examines effects of radiation exposure to hypothalamus-pituitary-adrenal axis (HPA) on metabolic risk among survivors of childhood brain tumors. One hundred forty-two met inclusion criteria; 60 had tumor surgery plus radiation exposure (>1 Gray (Gy)) to HPA. The second subgroup of 82 subjects had surgery only and were not exposed to radiation. Both subgroups had survived for approximately 5 years at the time of study. All had clinical evaluation, vital signs, anthropometry, measurement of body composition by dual X-ray absorptiometry and fasting laboratory assays (metabolic panel, insulin, C-peptide, insulin-like growth factor-1, leptin and adiponectin). Body composition data for both subgroups was compared with the National Health and Nutrition Survey (NHANES) subgroup of similar age, gender and body mass index. Cranial surgery was associated with obesity of similar severity in both subgroups. However, survivors exposed to radiation to the HPA also had increased visceral fat mass and high prevalence of growth hormone deficiency and metabolic syndrome. Fat mass alone did not explain the prevalence of the metabolic syndrome in radiation exposure subgroup. Other factors such as growth hormone deficiency may have contributed to metabolic risk. We conclude that prevalence of metabolic syndrome among subjects exposed to hypothalamic radiation was higher than expected from hypothalamic obesity alone. Radiation exposure may exert untoward endocrinopathies due to HPA exposure that worsens metabolic risk. Early screening for metabolic syndrome in this population is indicated.

Metabolic Concomitants of Obese and Nonobese Women With Features of Polycystic Ovarian Syndrome

Context:

Polycystic ovarian syndrome (PCOS) is often associated with obesity and diabetes.

Objective:

The present study measured body fat distribution and metabolic risk factors in women with features of PCOS.

Design:

Cross-sectional, multiethnic study of cardiovascular risks.

Setting:

General community.

Study Participants:

145 PCOS and 344 non-PCOS women.

Exposure Measures:

Body composition by dual x-ray absorptiometry; abdominal fat masses measured by magnetic resonance imaging and hepatic triglyceride by magnetic resonance spectroscopy.

Outcomes Measures:

Body composition, liver fat content, homeostatic model assessment for insulin resistance (HOMA-IR), revised, and metabolic syndrome components.

Results:

PCOS women had a higher free androgen index compared with the non-PCOS women. Nonobese PCOS and non-PCOS women had a similar body fat content and distribution, HOMA-IR, and hepatic triglyceride content. Obese PCOS women had a similar total body fat percentage compared with their non-PCOS counterparts (41.4% and 41.4% respectively). Both obese groups had similar intraperitoneal fat (1.4% of total body mass in PCOS vs 1.4% in non-PCOS). However, obese PCOS women had a greater ratio of truncal/lower body fat (1.42 vs 1.27; P < 0.016). They also had greater insulin resistance (HOMA-IR: PCOS, 2.24% vs non-PCOS, 1.91%; P < 0.016), higher liver triglyceride content (6.96% in PCOS vs 4.44% in non-PCOS; P < 0.016), and a greater incidence of hypertension (33% vs 24%; P < 0.05). No differences were observed in other metabolic risk factors.

Conclusions:

Both obese and nonobese women with PCOS features had a greater free androgen index compared with non-PCOS women, but neither had greater intraperitoneal fat or abnormal lipid levels. Obese, but not nonobese, women with PCOS had a greater truncal/lower extremity fat ratio, HOMA-IR, and liver triglyceride content.

Comparison of visceral fat mass measurement by dual-X-ray absorptiometry and magnetic resonance imaging in a multiethnic cohort: the Dallas Heart Study

Background/Objectives:

Visceral adipose tissue (VAT) mass, a risk factor for cardiometabolic complications of obesity, is usually measured by magnetic resonance imaging (MRI) but this method is not practical in a clinical setting. In contrast, measurement of VAT by dual-x-ray absorptiometry (DXA) appears to circumvent the limitations of MRI. In this study, we compared measurements of VAT mass by MRI and DXA in the large, multiethnic cohort of the Dallas Heart Study (DHS).

Subjects/Methods:

About 2689 DHS participants underwent paired measurement of VAT by MRI and DXA. Sex-stratified analyses were performed to evaluate the correlation and agreement between DXA and MRI. Model validation was performed using bootstrapping and inter-reader variability was assessed.

Results:

Mean age of the cohort was 44 years, with 55% female, 48% Black and 75% overweight/obese participants. Regression analysis showed a linear relationship between DXA and MRI with R²=0.82 (95% confidence interval (CI) 0.81–0.84) for females and R²=0.86 (95% CI 0.85–0.88) for males. Mean difference between methods was 0.01 kg for females and 0.09 kg for males. Bland–Altman analysis showed that DXA tended to modestly underestimate VAT compared with MRI at lower VAT levels and overestimate it compared with MRI at higher VAT levels. Results were consistent in analyses stratified by race, body mass index status, waist girth and body fat. Inter-individual reader correlation among 50 randomly selected scans was excellent (inter-class correlation coefficient=0.997).

Conclusions:

VAT mass quantification by DXA was both accurate and valid among a large, multiethnic cohort within a wide range of body fatness. Further studies including repeat assessments over time will help determine its long-term applicability.

Relationship of Apolipoprotein B Levels to the Number of Risk Factors for Metabolic Syndrome

Low-density lipoprotein cholesterol (LDL-C) is the primary target of lipid-lowering therapy. However, all lipoproteins containing apolipoprotein B (apo B) appear to be atherogenic. Preferred targets of therapy therefore may include either the cholesterol in all apo B-containing lipoproteins (non-high-density lipoprotein cholesterol [non-HDL-C]) or total apo B itself. Apo B can be measured by three methods: chemically, by nuclear magnetic resonance (NMR), and by immunoassay. This study compares the first two methods as a function of the number of metabolic risk factors in patients with metabolic syndrome. Plasma lipid, lipoprotein cholesterol, and apo B levels were measured in 274 adults with varying numbers of metabolic syndrome components. Low-density lipoprotein (LDL) particle sizes were measured by gel electrophoresis and by NMR. Total apo B was estimated chemically and by conversion of NMR lipoprotein particle number, assuming one apo B molecule per lipoprotein particle. As the number of metabolic syndrome components increased, apo B rose by both chemical and NMR methods, but by chemical methods, increases were in the triglyceride-rich fraction, whereas by NMR, they were in LDL. The correlation between total apo B measured by the two methods was only moderate (r = .73). Further, non-HDL-C was more highly correlated with total apo B measured chemically than either LDL-C or total apo B by NMR. Non-HDL-C correlates highly with total apo B in patients with metabolic syndrome and had advantages as a target of therapy over LDL-C or NMR apo B.

Fatty acid oxidation in normotriglyceridemic men

BACKGROUND

Moderate hypertriglyceridemia is frequently associated with central obesity, insulin resistance, and atherogenic dyslipidemia. We showed previously that moderately obese men with hypertriglyceridemia have reduced fatty acid oxidation postabsorptively and postprandially. In the present study, we examined the oxidation of fatty acids in normotriglyceridemic men.

OBJECTIVE

The study objective was to determine the relation between plasma triglyceride levels and fatty acid oxidation in normotriglyceridemic men.

STUDY DESIGN

Twenty-four healthy, nonobese White and African American men participated in a cross-sectional metabolic study for evaluation of fatty acid oxidation. Men were healthy, and none took hypolipidemic or hypoglycemic agents. They ingested 200 mg of fat/hour/kg of body weight over a 10-hour period. Plasma levels of triglyceride, nonesterified fatty acids, 3-β-hydroxybutyrate, insulin, and glucagon were measured postabsorptively and postprandially. Chylomicron-triglyceride halflife was also calculated.

RESULTS

Nonobese White and African-American men had similar anthropometry, levels of plasma triglyceride, lipoprotein cholesterol, nonesterified fatty acids, 3-β-hydroxybutyrate, insulin, and glucagon postabsorptively and postprandially. For the group as a whole, there was a positive and significant correlation between plasma fatty acids and 3-β-hydroxybutyrate and an inverse association between plasma triglyceride levels and 3-β-hydroxybutyrate at baseline. All subjects had increased levels of metabolites of interest postprandially. However, there were no significant changes in plasma insulin, glucagon, or the ratio of insulin to glucagon. The postprandial levels of 3-β-hydroxybutyrate correlated positively with nonesterified fatty acids and inversely with the half-life of chylomicron triglyceride.

CONCLUSION

Normotriglyceridemia is strongly associated with oxidation of fatty acids by the liver suggesting the possibility that the fatty acid oxidation pathway is a potential target of intervention to prevent hypertriglyceridemia and concomitant fatty liver.

Ethnic and gender susceptibility to metabolic risk

BACKGROUND

Aggregation of metabolic risk factors-i.e., elevated plasma triglyceride (TG), reduced high-density lipoprotein cholesterol (HDL-C), elevated blood pressure, and raised plasma glucose-convey increased risk for atherosclerotic cardiovascular disease and type 2 diabetes.

METHODS

This study was carried out to determine the association of waist girth, ethnicity, and gender with susceptibility for metabolic risk. Included were 1671 adult women (50.7% black) and 1339 men (46.5% black) enrolled in the Dallas Heart Study. Subjects were stratified into three categories by waist girth-low, intermediate, and high, corresponding to BMI ranges of <25 kg/m(2), 25-29.9 kg/m(2), and ≥30 kg/m(2).

RESULTS

Risk factor prevalence rose progressively through each waist-girth category. However, even among those with high waist-girth, prevalence of three or more risk factors was less than 50%. Several differences among the ethnic groups were noted; for example, Hispanic men had a higher prevalence of elevated TG compared to whites; black men, on the other hand, had a lower frequency of high TG. There were also fewer black men with low HDL-C than in the other groups. Black and Hispanic men had a higher prevalence of elevated glucose and updated homeostasis model assessment of insulin resistance (HOMA2-IR) than whites. More black men had elevated blood pressure than other groups. These differences were less pronounced among ethnic groups of women.

CONCLUSION

Although ethnic and gender differences in risk factor prevalence may exist, it is notable that the majority of subjects, even when obese, did not have elevated risk factors. This finding points to the need to focus largely on subjects with metabolic risk factors when implementing therapeutic interventions.

Influence of upper and lower body adipose tissue on insulin sensitivity in South Asian men

BACKGROUND

South Asians have a high prevalence of insulin resistance, which predisposes to type 2 diabetes.

RATIONALE

In the current study, we examined whether insulin sensitivity in South Asian men and men of European descent (Europids) relates to truncal and lower body fat, number of adipocytes, and cell size distribution.

RESULTS

Fifteen South Asian men and 15 Europid young men with comparable body mass indexes completed assessments of insulin sensitivity, body composition analysis by dual-energy x-ray absorptiometry, and measurement of adipocyte cellularity in the subcutaneous abdominal (truncal) and gluteal (lower body) adipose tissue. The South Asians and the Europids had similar total body fat and fat contents in truncal and lower body regions. Compared to the Europids, the South Asians had a greater insulin resistance shown by fasting insulin, area-under-the-curve for postprandial insulin, oral glucose insulin sensitivity, homeostatic model assessment of insulin resistance, β-cell index, and triglyceride-to-high-density lipoprotein ratio. The South Asians had similar number of adipocytes to the Europids, but the South Asians had significantly higher ratios of small-to-larger adipocytes. The South Asians further had a higher fraction of very large adipocytes. In both South Asians and Europids, truncal fat was positively associated with insulin resistance. In the South Asians but not in the Europids, lower body fat was associated with severity of insulin resistance.

CONCLUSIONS

The results suggest first, a higher ratio of small-to-larger adipocytes in the South Asians consistent with a lesser lipid storage capacity of adipose tissue; and second, the positive association of lower body fat with insulin resistance in the South Asians implies that fat in their lower body worsens insulin resistance. This association was not observed in the Europids.

LDL phenotype in subjects with mild cognitive impairment and Alzheimer's disease

BACKGROUND

Centenarians with normal cognitive function have a "longevity phenotype" characterized by large low-density lipoproteins (LDL) and high-density lipoproteins (HDL) and low incidence of metabolic syndrome, hypertension, and cognitive impairment. Alzheimer's disease (AD) is associated with a number of cardiovascular risk factors, but it is not known if they have or lack the "longevity phenotype".

OBJECTIVE

The study was designed to determine LDL size and body fat content and distribution in subjects with mild cognitive impairment (MCI) and AD.

RESULTS

Fifty-eight persons with MCI or AD (cases) and 42 control subjects of similar age had measurement of LDL size and lipoprotein lipids after a 12 h fast and analysis of body composition by dual x-ray absorptiometry. Cases had small LDL size more often than controls (73% versus 66%) associated with significantly higher triglycerides, lower HDL cholesterol, and higher triglyceride/HDL cholesterol ratio (p ≤ 0.02). Cases with large LDL had a better lipoprotein profile than those with small LDL. Cases and controls had similar percent body fat, fat index, and lean mass index. Forty-seven percent of cases and 39% of controls were obese.

CONCLUSION

The prevalence of small LDL phenotype in MCI and AD cases contrasts with the "longevity phenotype" reported for centenarians with preserved cognitive function. The small LDL phenotype is an atherogenic lipoprotein profile found in metabolic syndrome, type 2 diabetes, and insulin resistance. It is now also reported in persons with MCI and AD.

Waist circumference as measure of abdominal fat compartments

This study examines intercorrelations among waist circumference (WC), intraperitoneal fat (IPF), and subcutaneous abdominal fat (SAF) in ethnically diverse Dallas Heart Study consisting of 1538 women and 1212 men (50% Black). Correlations between fat depots and triglyceride or HOMA2-IR, biomarkers of metabolic syndrome, are also reported. Total abdominal fat (TAF), ASF, and IPF masses were measured by magnetic resonance imaging. The highest correlations with WC according to ethnicity and gender were noted for TAF (R (2) = 0.81 - 0.88) with progressively lower correlations with ASF (0.65-0.82) and IPF (0.29-0.85). The percentage of IPF relative to TAF was not significantly correlated with WC. For all WC categories, higher IPF/ASF ratios were associated with higher triglyceride levels. In contrast, differences in ratios had little or no association with HOMA2-IR. However, when all data were pooled, IPF was positively correlated with both triglyceride (r = 0.358 (men) and 0.363 (women)) and HOMA2-IR (r = 0.480 (men) and 0.517 (women)); after adjustment for ASF, IPF was still correlated with triglyceride (r = 0.353 (men) and 0.348 (women)) and HOMA2-IR (r = 0.290 (men) and 0.221 (women)). WC measures TAF reliably, but its association with IPF depends on IPF/ASF ratios that vary by gender and ethnicity.

Metabolic risk susceptibility in men is partially related to adiponectin/leptin ratio

BACKGROUND

High adiponectin/leptin ratio may be protective from metabolic risks imparted by high triglyceride, low HDL, and insulin resistance.

METHODS

This cross-sectional study examines plasma adipokine levels in 428 adult men who were subgrouped according to low (<6.5  μ g/mL)and high (≥6.5  μ g/mL)adiponectin levels or a low or high ratio of adiponectin/leptin.

RESULTS

Men with high adiponectin/leptin ratio had lower plasma triglyceride and higher HDL cholesterol than those with low ratio. Similarly, those with high adiponectin/leptin ratio had lower TG/HDL cholesterol ratio and HOMA2-IR than those with low ratio. In contrast, levels of adiponectin or the ratio of adiponectin/leptin did not associate with systolic blood pressure. But the ratio of adiponectin/leptin decreased progressively with the increase in the number of risk factors for metabolic syndrome.

CONCLUSION

Adipokine levels may reflect adipose tissue triglyceride storage capacity and insulin sensitivity. Leptin is an index of fat mass, and adiponectin is a biomarker of triglyceride metabolism and insulin sensitivity. Men with high adiponectin/leptin ratios have better triglyceride profile and insulin sensitivity than men with a low ratio regardless of waist girth.

Effect of colesevelam hydrochloride on glycemia and insulin sensitivity in men with the metabolic syndrome

Colesevelam hydrochloride (colesevelam) lowers low-density lipoprotein (LDL) cholesterol and glycated hemoglobin in patients with type 2 diabetes mellitus. The present study examined the effects of colesevelam treatment in nondiabetic men with metabolic syndrome. Twenty men completed the study, which consisted of two 8-week phases of treatment with colesevelam (3.75 g/day) or placebo and a 6-week washout between study phases. Of the 20 men, 17 took statins throughout. The fasting plasma LDL cholesterol, triglyceride, glucose, and glycated hemoglobin levels were measured in the last 2 weeks of each study phase. Nonesterified fatty acids and 3-hydroxybutyrate, insulin, and glucose were measured hourly for 5 hours during fasting and during an extended glucose tolerance test. The colesevelam treatment reduced LDL cholesterol from 96 ± 28 mg/dl to 78 ± 32 mg/dl (p <0.006) and non-high-density lipoprotein cholesterol by 8.2% (p = 0.07). Triglycerides increased by 17% (p <0.02). The fasting plasma glucose was reduced by 5 mg/dl (p <0.03), and glycated hemoglobin remained unchanged by colesevelam. No significant treatment changes were noted for the 2-hour glucose test or insulin sensitivity. The fasting nonesterified fatty acid level was significantly reduced with treatment but the 3-hydroxybutyrate level was unchanged. Insulin-mediated suppression of nonesterified fatty acids during extended glucose tolerance test was significantly less effective during treatment than during placebo. In conclusion, colesevelam significantly reduced the LDL cholesterol levels, even though the baseline LDL cholesterol level was low owing to statin treatment. The fasting and postprandial blood glucose level but not the glycated hemoglobin level was lowered by colesevelam therapy. The effect on fasting glucose was unrelated to the changes in insulin resistance or fatty acid oxidation. Finally, an increase in triglycerides with colesevelam therapy might have been related to a lesser suppression of nonesterified fatty acids levels in the postprandial state.

Adipose tissue mass and location affect circulating adiponectin levels

AIMS/HYPOTHESIS

Plasma levels of adiponectin are inversely associated with body mass. We hypothesised that adipose tissue distribution and body composition influences adiponectin levels.

METHODS

We assessed plasma adiponectin concentrations and dual-energy X-ray absorptiometry (DEXA) measurements of body composition among 2,820 participants from the Dallas Heart Study.

RESULTS

Among both women and men, adiponectin levels were higher in whites than in either Hispanics or African-Americans (for women: median 9.99 μg/ml [25th,75th percentile 7.11, 13.77] vs 7.56 μg/ml [5.05, 9.98] vs 6.39 μg/ml [4.37, 9.41], respectively, p < 0.0001; for men: 6.43 μg/ml [4.66, 9.19] vs 5.55 μg/ml [3.64, 7.50] vs 5.03 μg/ml [3.39, 7.28], p < 0.0001). In univariate analysis, each individual component of body mass was inversely associated with adiponectin. After multivariate analysis, adiponectin levels were found to be positively associated with lower extremity fat, whether expressed in absolute mass (for women: β = 0.055, p < 0.0001; for men: β = 0.061, p < 0.0001), or as a relative proportion (for women: β = 0.035, p < 0.0001; for men: β = 0.034, p < 0.0001). This association was consistent across ethnicities. Conversely, adiponectin was negatively correlated with truncal fat, both in absolute (for women: β = -0.039, p < 0.0001; for men: β = -0.044, p < 0.0001) and relative terms (for women: β = -0.027, p < 0.0001; for men β = -0.033, p < 0.0001). At the extreme of body mass, higher degrees of lower extremity and truncal adiposity were associated with higher levels of adiponectin.

CONCLUSIONS/INTERPRETATION

These data suggest that the location of adipose depots differentially influences circulating adiponectin concentrations-a finding observed across ethnicity and sex. Gross measures of body mass alone do not adequately account for adiponectin levels. This supports a role of adiponectin as a mediator of the positive effects of lower extremity adiposity on improvements in insulin sensitivity.

Prevalence of the metabolic syndrome as influenced by the measure of obesity employed

The metabolic syndrome (MS) is characterized by 4 independent risk factors for cardiovascular disease: elevated triglyceride-rich lipoproteins, reduced high-density lipoproteins, elevated blood pressure, and dysglycemia. Several underlying risk factors, notably obesity, accentuate these independent risk factors. This study addressed 2 questions: Is the prevalence of MS identified equally by all measures of obesity? and Should any measure of obesity be included among diagnostic components of the MS? A cohort of 8,879 women and 23,145 men in the Cooper Center Longitudinal Study (CCLS) underwent anthropometric assessment and risk-factor measurement. Most subjects were Caucasian, and 13.1% of women and 30.5% of men had MS defined by the National Cholesterol Education Program Adult Treatment Panel (ATP) III guidelines. In ATP III, MS is diagnosed by any 3 of 5 factors (i.e., the 4 independent risk factors listed previously plus abdominal obesity, defined as increased waist girth). In the CCLS, several measures of obesity (e.g., percentage body fat, body mass index, and truncal subcutaneous fat) were found to substitute for elevated waist girth without appreciably changing MS prevalence. The impact of removing obesity from the diagnostic criteria (abridged ATP III MS, defined as 3 of 4 independent risk factors) was further examined. Abridged ATP III MS was less common than ATP III MS but recognized a subgroup of patients at higher risk for cardiovascular disease. In conclusion, abridged ATP III MS appears to be preferable to ATP III MS for the detection of candidates for intensive cardiovascular risk reduction.

Correlation of non-high-density lipoprotein cholesterol and low-density lipoprotein cholesterol with apolipoprotein B during simvastatin + fenofibrate therapy in patients with combined hyperlipidemia (a subanalysis of the SAFARI trial)

Guidelines have recommended non-high-density lipoprotein (non-HDL) cholesterol as a secondary target for therapy after the low-density lipoprotein (LDL) cholesterol goals have been met in patients with hypertriglyceridemia; non-HDL cholesterol is viewed as a surrogate for apolipoprotein (Apo)B, an alternate end point of treatment. The present analysis of the previously reported Simvastatin plus Fenofibrate for Combined Hyperlipidemia (SAFARI) trial assessed the associations of non-HDL cholesterol and LDL cholesterol with ApoB levels in patients with combined hyperlipidemia treated with combination simvastatin (20 mg) and fenofibrate (160 mg) or simvastatin monotherapy (20 mg). The correlations of these factors were analyzed in the overall modified intent-to-treat population (n = 594) and in patient subgroups stratified by triglyceride (TG) tertiles. Simvastatin plus fenofibrate and simvastatin alone significantly reduced LDL cholesterol, TG, non-HDL cholesterol and ApoB levels and non-HDL cholesterol/ApoB ratio (p < or =0.0004), regardless of the TG level. The greatest reductions occurred with combination treatment. The baseline levels of non-HDL cholesterol and LDL cholesterol correlated highly with ApoB and were stronger in the lower TG tertiles than in the higher TG tertiles. After 12 weeks, the correlations had changed little with simvastatin monotherapy but had increased substantially with combination therapy and were most improved at high TG levels. In conclusion, these results suggest that both non-HDL cholesterol and ApoB provide similar information in relation to treatment response in patients with combined hyperlipidemia and hypertriglyceridemia, and that non-HDL cholesterol is a good indicator of ApoB-containing lipoproteins, supporting its recommended use as a secondary therapeutic target in these patients.

Insulin resistance and risk factors for cardiovascular disease in young adult survivors of childhood acute lymphoblastic leukemia

PURPOSE

To determine the prevalence of insulin resistance and other risk factors for cardiovascular disease (CVD) in young adult survivors of childhood acute lymphoblastic leukemia (ALL).

PATIENTS AND METHODS

In this cross-sectional evaluation of 118 survivors of childhood ALL (median age, 23.0 years; range, 18 to 37 years), insulin resistance was estimated using the homeostasis model for assessment of insulin resistance (HOMA-IR). Sex-specific comparisons were made with a cohort of 30- to 37-year-old individuals from the same region participating in the Dallas Heart Study (DHS, N = 782). ALL survivors were stratified by treatment with and without cranial radiotherapy (CRT).

RESULTS

Female ALL survivors had a significantly higher HOMA-IR (CRT, mean 4.6, 95% CI, 3.6 to 5.7; no CRT, mean 3.3, 95% CI, 2.8 to 3.8) in comparison with DHS women (mean 2.4, 95% CI, 2.2 to 2.7). Eighty percent of women treated with CRT had at least three of six CVD risk factors, and they were significantly more likely to have three or more risk factors compared with DHS women (odds ratio [OR], 5.96; 95% CI, 2.15 to 16.47). Male ALL survivors had a significantly higher HOMA-IR (CRT, mean 4.0, 95% CI, 2.8 to 5.6; no CRT, mean 3.4, 95% CI, 2.9 to 3.9) in comparison with DHS men (mean 2.3, 95% CI, 2.1 to 2.6), but were not more likely to have multiple CVD risk factors.

CONCLUSION

ALL survivors had an increased prevalence of insulin resistance in comparison with a cohort of older individuals from the same community. Importantly, women treated with CRT seem to have an increased prevalence of multiple CVD risk factors, warranting close monitoring and risk-reducing strategies.

Abnormalities in metabolism of low density lipoproteins associated with coronary heart disease

Low density lipoprotein (LDL) is probably the most atherogenic of all the lipoproteins. Several abnormalities in LDL metabolism seem to be associated with coronary heart disease (CHD) one of them being an elevation of plasma LDL concentration. Recent findings suggest that disorders in the metabolism of LDL could be associated with accelerated atherosclerosis even without elevated LDL levels such as increased flux of LDL and changes in the LDL composition. Elevation of plasma LDL levels can be caused by two factors, first, a decrease in the clearance of LDL and second, an overproduction of this lipoprotein. Catabolism of LDL is largely determined by the LDL receptors as clearly shown in patients with familial hypercholesterolemia (FH). In this inherited disease the patients do not have normal LDL receptors and their LDL levels are remarkably elevated. LDL production is also increased in these subjects. In the rest of the population LDL levels are regulated by both the LDL clearance and production rate. The latter also seems to be related to the LDL receptor activity. The conversion of the LDL precursor, very low density lipoprotein (VLDL) to LDL is the most important factor regulating LDL synthesis. When the LDL receptor activity is low a large fraction of VLDL apolipoprotein B (apoB), the major structural protein in VLDL, is converted to LDL, and LDL production is high. On the other hand, only a small part of VLDL apoB is converted to LDL resulting in low LDL synthesis rate in conditions with high LDL receptor activity. The relationships between production and clearance of LDL are, however, more complex. There are individuals who produce a large number of VLDL and LDL particles but maintain LDL concentrations at a normal level by clearing their LDL very effectively. These subjects obviously have another abnormality in lipoprotein metabolism namely an overproduction of apoB. This disorder has been observed in several conditions like obesity, adult-onset diabetes mellitus, several patients with familial combined hyperlipidemia and some normolipidemic subjects with premature coronary heart disease. In all these conditions increased transport of LDL can be associated with coronary artery disease even in the absence of hypercholesterolemia. This raises the possibility that increased flux of LDL could itself be atherogenic possibly by overloading reverse cholesterol transport. Finally, there is some evidence that LDL particle composition may be important in the process of atherogenesis. High LDL apoB but normal LDL cholesterol levels, hyperapobetalipoproteinemia, has been associated with premature coronary heart disease.(ABSTRACT TRUNCATED AT 400 WORDS)

Impaired hepatic ketogenesis in moderately obese men with hypertriglyceridemia

BACKGROUND

Several studies suggest that increased nonesterified fatty acid flux and increased de novo lipogenesis may contribute to hypertriglyceridemia, but few studies have examined fatty acid oxidation as a factor.

RATIONALE

Endogenous hypertriglyceridemia (increased very low density lipoprotein triglyceride) could result from (a) re-esterification of excess nonesterified fatty acids entering the liver, (b) activation of hepatic lipogenesis, and/or (c) defective oxidation of hepatic fatty acids leading to greater triglyceride synthesis. Therefore, this study used plasma levels of 3-hydroxybutyrate as a marker for fatty acid oxidation. The study was carried out in hypertriglyceridemic and normotriglyceridemic subjects under 3 conditions: (a) in the fasting state, (b) after a fatty meal that should enhance fatty acid oxidation, and (c) after an oxandrolone challenge, which we recently showed increases fatty acid oxidation.

RESULTS

In the fasting state, 3-hydroxybutyrate concentrations in hypertriglyceridemic patients were only 53% of levels in normotriglyceridemic subjects. After a fatty meal, moderate increases in 3-hydroxybutyrate were observed, but values for patients with hypertriglceridemia remained 62% of the levels in the normotriglyceridemic group. A similar pattern of response was observed with oxandrolone challenge. There were no significant changes in fasting or postprandial levels of nonesterfified fatty acids, glycerol, or triglycerides before and during the oxandrolone challenge.

CONCLUSION

Patients with endogenous hypertriglyceridemia seem to have a defect in fatty acid oxidation as indicated by reduced levels of 3-hydroxybutyrate. This defect was observed during fasting, postprandially, and during oxandrolone challenge. We propose that this defect contributes to the development of hypertriglyceridemia.

Variable contributions of fat content and distribution to metabolic syndrome risk factors

BACKGROUND

Previous reports indicate that both distribution and amount of body fat confers susceptibility to metabolic syndrome. However, the relative contributions of these two different parameters of body fat to the various components of the metabolic syndrome have not been well defined.

METHODS

Dual-energy X-ray absorptiometry (DXA) was used to measure and compare the relative amounts of total body fat, truncal fat, and lower body fat in a representative sample of 2587 black, white, and Hispanic men and women from the Dallas Heart Study (DHS). The relationships among these variables and fasting plasma levels of lipids, glucose, insulin, C-reactive protein (CRP), and leptin as well as blood pressure were analyzed.

RESULTS

Beyond total body fat, fat distribution had the greatest impact on plasma triglycerides in all subjects and on high-density lipoprotein cholesterol (HDL-C) levels in women only. An intermediate effect of fat distribution was observed for homeostasis model assessment of insulin resistance (HOMA-IR) and for blood pressure. Plasma CRP levels were much more sensitive to body fat content than to body fat distribution and leptin levels were determined almost exclusively by body fat content. Although there were minor differences among the different ethnic groups, the major relationship patterns between these variables were similar.

CONCLUSION

For most metabolic risk factors, both body fat content and distribution independently contributed to levels, although significant differences were seen between the relative contributions of each variable to individual risk factors.

Oxandrolone enhances hepatic ketogenesis in adult men

BACKGROUND

Immediate administration of oxandrolone markedly increases hepatic lipase activity and reduces levels of plasma high-density lipoprotein.

RATIONALE FOR THE STUDY

We postulated that oxandrolone should increase hepatic lipase and that the nonesterified fatty acids generated would enhance hepatic ketogenesis during an extended fat tolerance test.

MAIN RESULTS

Eighteen men participated in the study using short-term administration of oxandrolone (10 mg/d) over a week. Subjects had evaluation of hepatic ketogenesis at baseline and after 7 days of administration of oxandrolone. Ketogenesis was assessed by measuring plasma levels of 3-hydroxybutyrate during a fat tolerance test. Oxandrolone increased fasting levels of 3-hydroxybutyrate by 70%, and increased the area under the curve during an FFT by 53% above pretreatment levels without affecting the areas under the curve for nonesterified fatty acids, glycerol, or triglycerides. Fasting 3-hydroxybutyrate levels correlated with nonesterified fatty acids and with triglycerides; however, there were no significant correlations with any other parameter.

CONCLUSIONS

This study shows that short-term administration of oxandrolone results in marked increases in hepatic ketogenesis. This finding is consistent with an increased influx of fatty acids into the liver secondary to lipoprotein lipolysis by increased hepatic lipase. However, the possibility cannot be ruled out that oxandrolone acts directly in the liver to stimulate fatty acid oxidation. Therefore, the observation of increased ketogenesis will require further studies to determine the molecular basis of the response.

Effects of N-3 fatty acids on hepatic triglyceride content in humans

BACKGROUND

Because dietary N-3 fatty acids reduce plasma triglycerides, they may also decrease hepatic triglyceride content. If so, N-3 fatty acids might constitute a therapy for fatty liver.

METHODS

Twenty-two subjects were recruited into a study designed to test the effects of N-3 fatty acids on liver fat content. Seventeen completed the trial that had a sequential design of 4-week placebo followed by an 8-week treatment with 9 g/d of fish oil. Liver fat was measured during placebo and treatment by magnetic resonance spectroscopy. Compliance was assessed by capsule count at the end of each study phase and measurement of fatty acid composition in plasma triglyceride and phospholipid. Plasma lipoproteins and adiponectin were also measured.

RESULTS

Treatment with fish oils reduced significantly levels of plasma triglyceride by 46% (P <.03), very low-density lipoprotein + intermediate density lipoprotein cholesterol by 21% (P <.03), total apolipoprotein B by 15% (P <.03). In contrast to the changes in plasma triglycerides, hepatic triglyceride content was not significantly reduced by fish oil treatment.

CONCLUSIONS

N-3 fatty acids at high doses lower plasma triglyceride levels, but there are no significant decreases in hepatic content of triglyceride for the group as a whole. Whereas the triglyceride lowering is uniform, the liver response is more variable.

Variability in postheparin hepatic lipase activity is associated with plasma adiponectin levels in African Americans

BACKGROUND

African Americans commonly have normal high-density lipoprotein cholesterol (HDL-C) and low triglyceride levels despite having insulin resistance and obesity. The higher than expected HDL-C levels are usually attributed to low levels of hepatic triglyceride lipase (HTGL) activity. Factors that regulate HTGL in African Americans are not well delineated.

METHODS

In the current study, HTGL activity was examined in relation to indices of body fat (body mass index [BMI] and waist circumference [WC]), insulin resistance (fasting plasma insulin and homeostasis model assessment of insulin resistance [HOMA-IR] index), and adipokines (adiponectin and leptin). Sixty-three African Americans (33 men, 30 women; median age 31 years, range 20-50 years; median BMI 28.6 kg/m2, range 19.7-54.7 kg/m2) had anthropometry and measurement of postheparin lipase activities (HTGL), plasma HDL-C, triglycerides, and plasma adiponectin.

RESULTS

HTGL correlated strongly with HDL-C (r = -.52, p < .0001) and adiponectin (r = -.49, p < .001). HTGL increased with BMI and WC (r = .297, p = .018 and r = .301, p = .016, respectively). Adiponectin correlated strongly with HDL-C (r = .50, p < .0001) and triglycerides (r = -.493, p < .001). From multiple regression models, 28% of HTGL variability among African Americans can be explained by adiponectin levels in combination with gender and 35% of HTGL is explained with HDL-C included in the model.

CONCLUSION

The data suggest that adiponectin is a significant metabolic concomitant of HTGL activity in African Americans.

Metabolic correlates of nonalcoholic fatty liver in women and men

Nonalcoholic hepatic steatosis associates with a clustering of metabolic risk factors and steatohepatitis. One risk factor for hepatic steatosis is obesity, but other factors likely play a role. We examined metabolic concomitants of hepatic steatosis in nonobese and obese men and women. Sixty-one obese women and 35 obese men were studied; both those with and without hepatic steatosis were compared against each other and against nonobese controls (17 women and 32 men) without hepatic steatosis. Obesity (defined as >or=25% body fat in men and >or=35% in women), was identified by x-ray absorptiometry, whereas hepatic steatosis (>or=5.5% liver fat) was detected by magnetic resonance spectroscopy. The primary endpoint was a difference in insulin sensitivity. Obese groups with and without steatosis had similar body fat percentages. Compared with obese women without hepatic steatosis, those with steatosis were more insulin resistant; the same was true for men, although differences were less striking. Obese subjects with hepatic steatosis had higher ratios of truncal-to-lower body fat and other indicators of adipose tissue dysfunction compared with obese subjects without steatosis.

CONCLUSION

These results support the concept that obesity predisposes to hepatic steatosis; but in addition, insulin resistance beyond that induced by obesity alone and a relatively high ratio of truncal-to-lower body fat usually combined with obesity to produce an elevated liver fat content.

Plasma 24S Hydroxycholesterol Response to Statins in Alzheimer’s Disease Patients: Effects of Gender, CYP46, and ApoE Polymorphisms

A number of epidemiologic studies suggest an association between plasma total cholesterol and risk for Alzheimer's disease (AD). Additionally, it has been suggested that treatment with statins, drugs that block cholesterol biosynthesis, lower the incidence and prevalence of AD and of vascular dementia. This review provides an overview of cholesterol transport within the central nervous system and the impact of statins on brain cholesterol metabolism in subjects with AD. Brain cholesterol is converted to 24-S-hydroxycholesterol, a reaction catalyzed by CYP46. The oxysterol traverses the blood-brain barrier and is transported to the liver by plasma lipoproteins. The levels of 24-S-hydroxy-cholesterol are a reflection of brain cholesterol turnover. Subjects with AD reportedly have high levels of the oxysterol possibly reflecting neuronal death with release of cell membrane cholesterol. We show gender dimorphism in plasma levels of 24-S-hydroxycholesterol in subjects with AD and significant reductions in plasma levels of the oxysterol during treatment with standard doses of statins (lovastatin, simvastatin, and pravastatin). Polymorphisms of apolipoprotein E and CYP46 do not influence the effect of statins on plasma levels of 24-S-hydroxycholesterol. There were no untoward effects of the standard doses of statin for the duration of treatment. Statins are currently in trial to determine their effect on the course of AD.

Ten-year risk of cardiovascular incidence related to diabetes, prediabetes, and the metabolic syndrome

BACKGROUND

The relative contributions of the metabolic syndrome (MetS) and dysglycemia on the risk of cardiovascular disease (CVD) have not been dissected. We aimed to compare MetS with dysglycemia in their association with the 10-year incidence risk of CVD.

METHODS

A total of 30,378 subjects were recruited from 11 provinces in the CMCS and followed-up for new coronary heart disease (CHD) and stroke events (ischemic stroke and hemorrhagic stroke) for 10 years. Incidence rates and HRs were estimated by the presence or absence of MetS, impaired fasting glucose (IFG) and diabetes, and by the various traits of MetS.

RESULTS

Among the subjects, 18.2% were defined as having MetS; 21.1% had IFG, and 6.8% had diabetes. Metabolic syndrome prevalence in IFG and diabetes was 38.1% and 48.7%, respectively, and the prevalence of IFG and diabetes in MetS was 44.1% and 18.3%, respectively. After adjusting for nonmetabolic risk factors, HRs of total CVD, CHD, and ischemic stroke in MetS were significant and higher than those in non-MetS, regardless of glycemic status. In the absence of MetS, the impact of dysglycemia was found only in IFG to CHD and diabetes to ischemic stroke. Hyperglycemia without any concomitant disorders was not associated with significantly higher risk of CVD.

CONCLUSIONS

The increased CVD risk in individuals with IFG or diabetes was largely driven by the coexistence of multiple metabolic disorders rather than hyperglycemia per se. Identification of clustering of metabolic abnormalities should be given more consideration in CVD prevention.

Serum lipids in the GENECARD study of coronary artery disease identify quantitative trait loci and phenotypic subsets on chromosomes 3q and 5q

Coronary artery disease (CAD) and dyslipidemia have strong genetic components. Heterogeneity complicates evaluating genetics of complex diseases such as CAD; incorporating disease-related phenotypes may help reduce heterogeneity. We hypothesized that incorporating lipoproteins in a study of CAD would increase the power to map genes, narrow linkage peaks, identify phenotypic subsets, and elucidate the contribution of established risk factors to genetic results. We performed ordered subset analysis (OSA) and quantitative trait linkage (QTL) using serum lipoproteins and microsatellite markers in 346 families with early-onset CAD. OSA defined homogeneous subsets and calculated lod scores across a chromosome after ranking families by mean lipoprotein values. QTL used variance components analysis. We found significantly increased linkage to chromosome 3q13 (LOD 5.10, p = 0.008) in families with higher HDL cholesterol, lower LDL and total cholesterol, lower triglycerides, and fewer CAD risk factors, possibly due to a concentrated non-lipoprotein-related genetic effect. OSA identified linkage on chromosome 5q34 in families with higher cholesterol, possibly representing a hereditary lipoprotein phenotype. Multiple QTLs were identified, with the strongest for: total cholesterol on chromosome 5q14 (LOD 4.3); LDL on 20p12 (LOD 3.97); HDL on 3p14 (LOD 1.65); triglycerides on 18q22 (LOD 1.43); and HDL/TC ratio on 3q27-28 (LOD 2.06). Our findings suggest the presence of etiologic heterogeneity in families with early-onset CAD, potentially due to differential effects of lipoprotein phenotypes. Candidate genes are under investigation.

Influence of body fat content and distribution on variation in metabolic risk

OBJECTIVES

Several reports indicate that the body fat compartments, especially ip fat, predict metabolic risk better than total body fat. The objective of the study was to determine whether this can be confirmed and generalized throughout the population.

PARTICIPANTS

A representative sample of 1934 Black and White women and men of the Dallas Heart Study participated in the study.

DESIGN

We measured the fat in total body, trunk, and lower body with dual-energy x-ray absorptiometry and in abdominal compartments (sc, ip, and retroperitoneal) with magnetic resonance imaging. Other measurements included body mass index (BMI), waist circumference, blood pressure, plasma lipids, glucose, insulin (including homeostasis model), and C-reactive protein.

RESULTS

In all groups, total body fat correlated positively with key metabolic risk factors, i.e. homeostasis model, triglyceride/high-density lipoprotein-cholesterol ratios, C-reactive protein, and blood pressure; however, it explained less than one third of the variability of all the risk factors. After adjustment for total body fat, truncal fat conferred additional positive correlation with risk factors. Furthermore, with multivariable regression analysis, ip fat conferred independent correlation with plasma lipids beyond a combination of other compartments including truncal fat. Still, except for insulin levels, all combinations including ip fat still explained less than one third of the variability in risk-factor levels. Conversely, lower body fat correlated negatively with risk factors; i.e. lower body fat appeared to offer some protection against risk factors.

CONCLUSIONS

Body fat distribution has some influence on risk factors beyond total body fat content. Both waist circumference and BMI significantly predicted risk factors after adjustment for total body fat, and for clinical purposes, most of the predictive power for men was contained in waist circumference, whereas for women, BMI and waist circumference were similarly predictive. Finally, even though the correlations between combined body fat parameters and risk factors explained only a portion of the variation in the latter, the average number of categorical metabolic risk factors increased progressively with increasing obesity. Hence, obesity seemingly has more clinical impact than revealed in these correlative studies.

Combination of fenofibrate plus low-dose nicotinic acid added to statin treatment in type 2 diabetes: An open-label, crossover study

BACKGROUND

Plasma lipid abnormalities commonly persist in patients with diabetic dyslipidemia in spite of statin monotherapy.

OBJECTIVE

The aim of this study was to determine whether fenofibrate plus low-dose nicotinic acid adequately improves the lipoprotein profile in patients with diabetic dyslipidemia who are being treated with a statin.

METHODS

In this open-label, crossover study, patients with type 2 diabetes mellitus who were receiving statin treatment were enrolled at the Lipid Clinic of the Veterans Affairs Medical Center, Dallas, Texas, and administered simvastatin 20 mg/d for 8 weeks. At the end of the 8-week period, fenofibrate 160 mg/d was added for 8 weeks, followed by the addition of extended-release nicotinic acid 1 g/d for an additional 8 weeks. The first subject was recruited on September 25, 2003, and the last subject was recruited on September 28, 2004. Liver function tests, creatine phosphokinase activity, and blood glucose levels were assessed every 4 weeks to assess tolerability. Levels of fasting plasma lipids and lipoprotein cholesterol were measured every 8 weeks on 3 consecutive days in each patient; C-reactive protein, lipoprotein pattern, and glycosylated hemoglobin levels were assessed once every 8 weeks. Plasma levels of total cholesterol, triglycerides, very-low-density lipoprotein plus intermediate-density lipoprotein cholesterol (VLDL+IDL-C), low-density lipoprotein cholesterol, high-density lipoprotein cholesterol (HDL-C), and apolipoprotein B were also measured.

RESULTS

Twenty-six patients were enrolled in the study and 20 patients (18 men, 2 women; mean [SD] age, 58.8 [6.5] years) completed it. The mean plasma triglyceride level was significantly decreased (-29.2%; P= 0.004) and the mean HDL-C level was significantly increased (+13.5%; P < 0.001) with 3-drug treatment (simvastatin + fenofibrate + extended-release nicotinic acid) compared with simvastatin monotherapy. Significant reductions in plasma levels of VLDL+IDL-C (-35.7%; P = 0.001), VLDL+IDL-apolipoprotein B (-30%; P = 0.005), non-HDL-C (-12.9%; P = 0.001), and total-apolipoprotein B (-17.9%; P < 0.001) were seen with the 3-drug treatment compared with simvastatin alone. Compared with simvastatin monotherapy, simvastatin + fenofibrate-treated (2-drug treatment) patients had significantly lower plasma levels of triglycerides (-24.9%; P = 0.014) and significantly higher levels of HDL-C (+5.4%; P = 0.008). Significant reductions were also seen in levels of VLDL+IDL-C (-28.6%; P = 0.004), VLDL+IDL-apolipoprotein B (-26.7%; P < 0.001), non-HDL-C (-9.1 %; P= 0.004), and total-apolipoprotein B (-12.3%; P < 0.001) in the 2-drug treatment group compared with the simvastatin monotherapy group. The administration of 3-drug treatment was associated with improved responses in all lipoprotein fractions, although only the increase in HDL-C level was statistically significant (+7.7%; P = 0.008) compared with 2-drug treatment.

CONCLUSIONS

Treatment with the 3-drug regimen was associated with a significant reduction in triglyceride levels compared with simvastatin monotherapy. However, there was not a significant incremental reduction in triglyceride levels when nicotinic acid was added to the 2-drug treatment, suggesting that the triglyceride-lowering effect of fenofibrate + nicotinic acid is not cumulative. To obtain clinically meaningful responses, particularly for the treatment of elevated HDL-C, higher doses of nicotinic acid might be required.

The effects of gender and CYP46 and apo E polymorphism on 24S-hydroxycholesterol levels in Alzheimer's patients treated with statins

To examine the effect of gender and polymorphisms of CYP46 and apo E on plasma levels of 24S-hydroxycholesterol in Alzheimer's disease (AD) patients and to determine whether these factors contribute to the variability in responses to statin treatment. Fifty-three AD patients had measurement of plasma levels of 24S-hydroxycholesterol, plasma and lipoprotein cholesterol and genotyping of CYP46 and apo E. Thirty-nine of the subjects subsequently participated in a statin trial for 6 weeks, and had a repetition of the baseline measurements. Baseline levels of 24S-hydroxycholesterol were higher in women than in men. There was a positive and significant correlation of plasma oxysterol levels with levels of total plasma cholesterol (women: r = .72, P < .0001; men: r = .47, P = .02) and non-HDL cholesterol (women: r = .68, P < .0001; men: r = 0.51, P = .01) (and LDL cholesterol) but not HDL cholesterol levels. There was no association of CYP46 or apo E polymorphisms with plasma levels of 24S-hydroxycholesterol. AD subjects treated with statins had a similar percent reduction in lathosterol, 24S-hydroxycholesterol, total cholesterol and non-HDL (and LDL) cholesterol regardless of gender and polymorphisms of CYP46. Subjects with the 4/4 polymorphism had less reduction in the ratios of 24S-hydroxycholesterol-LDL cholesterol. Women with AD had higher levels of plasma 24S-hydroxycholesterol levels than men. Women also showed a very strong correlation of plasma levels of 24S-hydroxycholesterol-to-total and non-HDL cholesterol. This may suggest that the oxysterol may be an important marker of AD risk instead of total cholesterol, as suggested by others. Polymorphisms of CYP46 or apo E do not explain levels of oxysterol or non-HDL cholesterol or the responsiveness to statin treatment in this study.

Responsiveness of plasma lipids and lipoproteins to plant stanol esters

Plant stanols have been shown to reduce serum levels of low-density lipoprotein (LDL) cholesterol, and they are an attractive adjunct in dietary therapy for elevated LDL cholesterol. This investigation addressed 3 questions through metabolic studies in human subjects: (1) whether plant stanol esters given at higher doses than the 2-g/day dose recommended by the National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATP III) will provide additional LDL-lowering efficacy (study 1); (2) whether substantial reduction in LDL cholesterol can be obtained in postmenopausal women with hypercholesterolemia by addition of plant stanol esters to the diet (study 2); and (3) whether ATP III goals can be obtained by adding plant stanol esters to an LDL-lowering regimen in high-risk patients who retain LDL cholesterol levels in the above-optimal range (ie, 2.6 to 3.3 mmol/L [100 to 129 mg/dL]), despite ongoing statin therapy (study 3). Study 1 showed that maximal LDL lowering with plant stanols in the form of esters can be achieved at a dose of 2 g/day. Higher doses do not provide additional efficacy. Study 2 demonstrated that stanol esters can reduce LDL cholesterol levels in postmenopausal women by about 13%, which makes use of stanol esters attractive as a component of nondrug therapy in these women who generally are at relatively low risk for coronary heart disease. Finally, study 3 found that plant stanols provide additional lowering of LDL cholesterol when added to ongoing statin therapy. This makes plant stanols an attractive dietary component to help to achieve the goals of LDL-lowering therapy in patients requiring an LDL-lowering drug.

Influence of extended-release nicotinic acid on nonesterified fatty acid flux in the metabolic syndrome with atherogenic dyslipidemia

Nicotinic acid has favorable effects on atherogenic dyslipidemia. However, in some patients who have diabetes, crystalline nicotinic acid decreases glycemic control; this effect could be due to a marked rebound of nonesterified fatty acids (NEFAs) observed after nicotinic acid suppression of lipolysis in adipose tissue. Recent reports have indicated that small doses of extended-release nicotinic acid do not cause a substantial decrease in glucose levels. Therefore, in this study, we examined whether 2 g/day of extended-release nicotinic acid abolishes the NEFA rebound that is reported with crystalline nicotinic acid. Seventeen men who had the metabolic syndrome (8 did not have type 2 diabetes and 9 did) were treated for 4 months. At baseline and at 4 months, measurements were made of plasma glucose, insulin, and NEFA during an oral glucose tolerance test. At 3 months, effects of extended-release nicotinic acid on NEFA levels and flux rates were determined on 3 separate days at 3 separate intervals after the final dose of nicotinic acid (4, 9, and 28 hours). Values obtained at 28 hours were taken as baseline (i.e., no nicotinic acid remaining in the circulation). After 4 hours (percent baseline), NEFA levels were -30% without diabetes and -37% with diabetes, and flux rates were -21% without diabetes and -25% with diabetes; after 9 hours, NEFA levels were 43% without diabetes and 50% with diabetes, and flux rates were 38% without diabetes and 70% with diabetes. Extended-release nicotinic acid did not abolish NEFA rebound. Nonetheless, the rebound was much less than previously reported for crystalline nicotinic acid. Moreover, after 4 months of nicotinic acid therapy, levels of NEFA, glucose, and insulin during the oral glucose tolerance test were not significantly different from those before institution of nicotinic acid therapy, suggesting minimal changes in insulin sensitivity.

The multiphasic profile of free fatty acids during the intravenous glucose tolerance test is unresponsive to exogenous insulin

As small increments in insulin concentration profoundly affect lipolysis, our goal was to describe the free fatty acid (FFA) profile during the frequently sampled intravenous glucose tolerance test (FSIGT) and determine if both endogenous and exogenous insulin influenced the FFA profile. Thirteen subjects had both a glucose-only (GO-FSIGT) and insulin-modified FSIGT (IM-FSIGT). Both protocols were of 6 hours duration. At baseline an intravenous glucose bolus (0.3 g/kg) was given. In the IM-FSIGT, insulin was infused from 20 to 25 minutes (4 mU/kg. min). Six additional subjects had both an IM-FSIGT and a normal saline study (NS-Study). For the NS-Study, normal saline solution was infused instead of glucose and insulin. Fasting glucose, insulin, FFA and epinephrine concentrations were similar for all tests. Endogenous insulin peaked at 4 +/- 1 minute in both FSIGTs. The mean calculated peak time of exogenous insulin in the IM-FSIGT was 26 +/- 1 minute. Glucose concentrations were lower and epinephrine concentrations higher in the IM-FSIGT versus GO-FSIGT. During the FSIGTs, the FFA time course revealed four distinct phases, which did not differ between protocols. In phase I (0 to 11 minutes), FFA levels remained near basal (491 +/- 183 micromol/L); in phase II (11 to 79 minutes), FFA levels declined achieving a nadir of 139 +/- 63 micromol/L; in phase III (79 to 188 minutes), FFA levels rose linearly and reattained basal levels; and in phase IV (188 to 360 minutes), FFA levels rose above basal and plateaued at 732 +/- 214 micromol/L (P <.001). In the NS-Study, FFA levels remained near baseline (388 +/- 118 mEq/L) until 180 minutes and then trended upward to 618 +/- 258 micromol/L at 360 minutes. FFA concentrations from 180 to 360 minutes did not differ in the IM-FSIGT versus NS-Study. As the 4 FFA phases did not differ between protocols, the insulin effect on FFA levels in the FSIGT can be attributed to endogenous insulin. But the similarity in FFA levels from 180 to 360 minutes in the IM-FSIGT and NS-Study suggests diurnal variation and not a dynamic related to insulin or the FSIGT protocol is responsible for the final suprabasal FFA plateau.

Management of atherogenic dyslipidemia of the metabolic syndrome: evolving rationale for combined drug therapy

Atherogenic dyslipidemia is prevalent in various conditions associated with central obesity, hypertension, hyperurecemia, and impaired beta-cell function (ie, the metabolic syndrome). Because of clinical trial evidence, most high-risk patients with atherogenic dyslipidemia require statin therapy. Coadministration of drugs targeted to reduction of low-density lipoprotein precursors, however,is likely to improve the metabolic profile of all non-high-density lipoproteins and produce a significant rise in high-density lipoprotein cholesterol. Large-scale clinical trials with combined drug therapy that show coronary heart disease (CHD) risk reduction or improvement in CHD are needed. It is also possible that new drugs are needed to target fatty acid metabolism and inflammation. As understanding of the metabolic origins of atherogenic dyslipidemia increases, it is possible that new targets of therapy will be identified and that new drug combinations will prove to be even more efficacious than those currently available for treatment of this condition.

Obesity and the metabolic syndrome

The metabolic syndrome is a cluster of risk factors for coronary heart disease that seemingly have an underlying metabolic causation. Central obesity is the centerpiece of the metabolic alterations. Accordingly, increased abdominal adiposity contributes to dyslipidemia, hyperglycemia, and hypertension. In about 20% of the cases with metabolic syndrome, there is also beta-cell dysfunction that leads to the clinical manifestation of diabetes mellitus. Recent evidence suggests that increased obesity is also associated with inflammation. The role of adipose tissue in the causation of metabolic alterations that lead to the clinical manifestation of the metabolic syndrome has become a focus of active research. Adipose tissue not only secretes non-esterified fatty acids that contribute to atherogenic dyslipidemia, steatosis and lipotoxicity. This organ is also an active endocrine and paracrine system. It can secrete pro-inflammatory factors, pro-insulin resistance factors, and other cytokines and hormones that can contribute to hypertension and impaired fibrinolysis. Therefore, the metabolic alterations commonly associated with increased central obesity of the metabolic syndrome are pro-atherogenic partly because the metabolites are proinflammatory.

Free fatty acid metabolism during fenofibrate treatment of the metabolic syndrome

OBJECTIVE

Our objective was to determine whether fenofibrate modifies the metabolism of nonesterified (free) fatty acids as a component of its triglyceride-lowering action in male patients with the metabolic syndrome.

DESIGN

In a placebo-controlled trial lasting 16 weeks, patients were randomly assigned to fenofibrate (200 mg/d) or placebo for 8 weeks. They were then crossed over to placebo or treatment with fenofibrate for another 8 weeks.

METHODS

Thirteen adult men had clinical characteristics of the metabolic syndrome that included atherogenic dyslipidemia, hypertension, elevated fasting glucose levels, or central obesity or a combination of these. They had measurements of plasma lipid and lipoprotein levels, postheparin lipase activities, and fasting concentrations and turnover rates of nonesterified fatty acids, as well as oral glucose tolerance testing with insulin and nonesterified fatty acid measurements. Levels of apolipoprotein C-II, C-III, and B were also measured, along with levels of low-density lipoprotein cholesterol in lipoprotein species.

RESULTS

Fenofibrate therapy did not change plasma concentrations and turnover rates of nonesterified fatty acids. For fasting nonesterified fatty acids, the values (mean +/- SD) for placebo versus fenofibrate were 446 +/- 31 micromol/L versus 493 +/- 71 micromol/L, respectively (not significant); nonesterified fatty acid turnover rates were 336 +/- 36 micromol/min versus 334 +/- 42 micromol/min for placebo versus fenofibrate, respectively. Moreover, no changes were noted in fasting or postprandial levels of plasma glucose and insulin. Despite this lack of change, fenofibrate therapy reduced the plasma levels of triglyceride by 30% (305 +/- 143 mg/dL versus 206 +/- 90 mg/dL for placebo versus fenofibrate, respectively; P <.045), with a similar reduction in cholesterol levels of triglyceride-rich lipoproteins. Large low-density lipoprotein species were increased and small low-density lipoprotein species were decreased by fenofibrate therapy. Levels of apolipoprotein C-III were reduced significantly (P <.03), as were ratios of postheparin hepatic lipase to lipoprotein lipase (P <.05).

CONCLUSION

Fenofibrate therapy markedly reduced plasma triglyceride levels. However, it did not lower concentrations or turnover rates of nonesterified fatty acids, nor did it change glucose or insulin responses to an oral glucose challenge. These findings indicate that fenofibrate modifies fatty acid metabolism either in the liver or in triglyceride-rich lipoproteins but not in adipose tissue. Multiple mechanisms are likely involved as a consequence of the action of fenofibrate to activate peroxisomal-proliferator-activated receptor alpha.

Correlation of statin-increased platelet APP ratios and reduced blood lipids in AD patients

Platelets, like neurons, contain 120- to 130- and 110-kd amyloid precursor proteins (APPs). Their ratio is reduced in AD, further reductions correlating with reduced Mini-Mental Status Examination scores [r(11) = 0.69, p < 0.05]. As statins alter APP processing, platelet APPs were analyzed in patients with AD given anticholesterol drugs for 6 weeks. APP ratios increased [t(37) = -3.888, p = 0.0004], proportionally with reduced cholesterol [r(36) = -0.45, p = 0.005]. Longer trials may reveal slowed cognitive loss, validating this index.

Effects of adding fenofibrate (200 mg/day) to simvastatin (10 mg/day) in patients with combined hyperlipidemia and metabolic syndrome

Combined hyperlipidemia predisposes subjects to coronary heart disease. Two lipid abnormalities--increased cholesterol and atherogenic dyslipidemia--are potential targets of lipid-lowering therapy. Successful management of both may require combined drug therapy. Statins are effective low-density lipoprotein (LDL) cholesterol-lowering drugs. For atherogenic dyslipidemia (high triglycerides, small LDL, and low high-density lipoprotein [HDL]), fibrates are potentially beneficial. The present study was designed to examine the safety and efficacy of a combination of low-dose simvastatin and fenofibrate in the treatment of combined hyperlipidemia. It was a randomized, placebo-controlled trial with a crossover design. Three randomized phases were employed (double placebo, simvastatin 10 mg/day and placebo, and simvastatin 10 mg/day plus fenofibrate 200 mg/day). Each phase lasted 3 months, and in the last week of each phase, measurements were made of plasma lipids, lipoprotein cholesterol, plasma apolipoproteins B, C-II, and C-III and LDL speciation on 3 consecutive days. Simvastatin therapy decreased total cholesterol by 27%, non-HDL cholesterol by 30%, total apolipoprotein B by 31%, very low-density lipoprotein (VLDL) + intermediate-density lipoprotein (IDL) cholesterol by 37%, VLDL + IDL apolipoprotein B by 14%, LDL cholesterol by 28%, and LDL apolipoprotein B by 21%. The addition of fenofibrate caused an additional decrease in VLDL + IDL cholesterol and VLDL + IDL apolipoprotein B by 36% and 32%, respectively. Simvastatin alone caused a small increase in the ratio of large-to-small LDL, whereas the addition of fenofibrate to simvastatin therapy caused a marked increase in the ratio of large-to-small LDL species. Simvastatin alone produced a small (6%) and insignificant increase in HDL cholesterol concentrations. When fenofibrate was added to simvastatin therapy, HDL cholesterol increased significantly by 23%. No significant side effects were observed with either simvastatin alone or with combined drug therapy. Therefore, a combination of simvastatin 10 mg/day and fenofibrate 200 mg/day appears to be effective and safe for the treatment of atherogenic dyslipidemia in combined hyperlipidemia.

Reduction in levels of 24S-hydroxycholesterol by statin treatment in patients with Alzheimer disease

BACKGROUND

The statin treatment of dyslipidemia is associated with a reduced risk of development of Alzheimer disease (AD). The effect may be mediated by a reduction in cholesterol biosynthesis in the brain, by lowering levels of apolipoprotein E (apo E)-containing lipoproteins, or by pleitropic effects such as reduction in beta-amyloid production. In the brain, cholesterol from damaged or dying neurons is converted to 24S-hydroxycholesterol by cholesterol 24-hydroxylase (CYP46). The oxysterol is subsequently transferred across the blood-brain barrier, transported to the liver by low-density lipoproteins (LDLs), and excreted as bile acids. Most of plasma 24S-hydroxycholesterol is derived from brain cholesterol; consequently, plasma levels of the oxysterol reflect brain cholesterol catabolism.

OBJECTIVE

To examine the effect of 3 statins and a nonstatin hypolipidemic agent on plasma levels of 24S-hydroxycholesterol and apo E in patients with AD.

STUDY DESIGN

The study had a sequential parallel design. It was open-labeled and involved lipoprotein and 24S-hydroxycholesterol evaluations at baseline and at 6 weeks of treatment with 40 mg of lovastatin, simvastatin, or pravastatin sodium per day, or 1 g of extended-release niacin per day. Blood samples were drawn after a 12-hour fast for measurement of plasma sterols, oxysterols, lipoprotein cholesterol, and levels of apo E, plasma transaminases, and glucose. Measurements were made at baseline and during treatment.

RESULTS

Statin treatment reduced levels of plasma lathosterol by 49.5%, 24S-hydroxycholesterol by 21.4%, LDL cholesterol by 34.9%, and total cholesterol by 25%. The ratios of lathosterol-campesterol and 24S-hydroxycholesterol-LDL cholesterol were reduced significantly, but the ratio of 24S-hydroxycholesterol-total cholesterol was unchanged. Extended-release niacin also significantly reduced levels of 24S-hydroxycholesterol by 10% and LDL cholesterol by 18.1%. None of the agents lowered plasma concentration of apo E.

CONCLUSIONS

Statins lowered levels of plasma 24S-hydroxycholesterol without affecting levels of apo E. The LDL lowering was more pronounced than 24S-hydroxycholesterol reductions. The effect of statins on LDL partially explains the reduction of plasma oxysterol level.

Efficacy, safety, and tolerability of once-daily niacin for the treatment of dyslipidemia associated with type 2 diabetes: results of the assessment of diabetes control and evaluation of the efficacy of niaspan trial

BACKGROUND

Diabetic dyslipidemia is characterized by high triglyceride levels; low high-density lipoprotein cholesterol levels; small, dense low-density lipoprotein particles; and high free fatty acid levels. Niacin reduces concentrations of triglyceride-rich and small low-density lipoprotein particles while increasing high-density lipoprotein cholesterol levels. It also lowers levels of free fatty acids and lipoprotein(a). However, the use of niacin in patients with diabetes has been discouraged because high doses can worsen glycemic control. We evaluated the efficacy and safety of once-daily extended-release (ER) niacin in patients with diabetic dyslipidemia.

METHODS

During a 16-week, double-blind, placebo-controlled trial, 148 patients were randomized to placebo (n = 49) or 1000 (n = 45) or 1500 mg/d (n = 52) of ER niacin. Sixty-nine patients (47%) were also receiving concomitant therapy with statins.

RESULTS

Dose-dependent increases in high-density lipoprotein cholesterol levels (+19% to +24% [P<.05] vs placebo for both niacin dosages) and reductions in triglyceride levels (-13% to -28% [P<.05] vs placebo for the 1500-mg ER niacin) were observed. Baseline and week 16 values for glycosylated hemoglobin levels were 7.13% and 7.11%, respectively, in the placebo group; 7.28% and 7.35%, respectively, in the 1000-mg ER niacin group (P=.16 vs placebo); and 7.2% and 7.5%, respectively, in the 1500-mg ER niacin group (P=.048 vs placebo). Four patients discontinued participation because of inadequate glucose control. Rates of adverse event rates other than flushing were similar for the niacin and placebo groups. Four patients discontinued participation owing to flushing (including 1 receiving placebo). No hepatotoxic effects or myopathy were observed.

CONCLUSION

Low doses of ER niacin (1000 or 1500 mg/d) are a treatment option for dyslipidemia in patients with type 2 diabetes.