Lipoprotein subpopulation distributions in lean, obese, and type 2 diabetic women: a comparison of African and white Americans

Modulation of cardiometabolic risk and CardioRenal syndrome by oral vitamin D3 supplementation in Black and White Southern Sahara residents with chronic kidney disease Stage 3: focus on racial and ethnic disparities

OBJECTIVES

Several studies have shown that cholecalciferol supplementation (25OHD-S) in chronic kidney disease (CKD) improves kidney injury by reducing fibrosis-related vascular calcification and declining apoptosis-linked nephron damage.

METHODS

The oral 25OHD-S was evaluated in 60,000 IU/month/36 weeks versus in 2000 IU/d/24 weeks in CKD Stage 3 with serum 25OHD level < 20 ng/mL. The study was undertaken on 156 black subjects and 150 white subjects Southern Sahara (SS). All biomarkers of cardiometabolic (CMet) and cardiorenal (CRenal) syndrome, Renin-angiotensin-aldosterone system (RAAS) profile, secondary hyperparathyroidism (SHPT), N-terminal pro B-type natriuretic peptide (NT-proBNP), Troponin T (cTnT) and atherogenicity risk were assessed by biochemical methods. Estimate glomerular filtration rate (eGFR) by chronic CKD-EPI equation formula. Total serum vitamin D by liquid chromatography-tandem mass spectrometry (MS).

RESULTS

Vitamin D deficiency alters in the same manner CMet, CRenal, and others biomarkers in both groups SS; however, these disorders are more acute in blacks compared to whites SS. Oral 25OHD-S a highlighted improvement of eGFR drop, SHPT decrease, decline proteinuria, and cardiac failure risk (NT-proBNP and cTnT) attenuation. Concomitantly, 25OHD-S normalizes Renin, Aldosterone, and Angiotensin System (RAAS) activity. Nevertheless, homocysteine and Lp (a) do not modulate by 25OHD-S.

CONCLUSIONS

The oral vitamin D3 supplementation, according the dose, and the treatment duration does not like in black-skinned people versus to white-skinned inhabitants, while the 02 groups are native to the same Saharan environment. It emerge that a high intermittent dose through an extensive supplementation (60,000 IU/36 weeks) was more effective in black subjects. At opposite, a lower dose during a short period supplementation is sufficient (2000 IU/24 weeks) in white subjects.

Expressing the Human Cholesteryl Ester Transfer Protein Minigene Improves Diet-Induced Fatty Liver and Insulin Resistance in Female Mice

Mounting evidence has shown that CETP has important physiological roles in adapting to chronic nutrient excess, specifically, to protect against diet-induced insulin resistance. However, the underlying mechanisms for the protective roles of CETP in metabolism are not yet clear. Mice naturally lack CETP expression. We used transgenic mice with a human CETP minigene (huCETP) controlled by its natural flanking region to further understand CETP-related physiology in response to obesity. Female huCETP mice and their wild-type littermates were fed a high-fat diet for 6 months. Blood lipid profile and liver lipid metabolism were studied. Insulin sensitivity was analyzed with euglycemic-hyperinsulinemic clamp studies combined with ³H-glucose tracer techniques. While high-fat diet feeding induced obesity for huCETP mice and their wild-type littermates lacking CETP expression, insulin sensitivity was higher for female huCETP mice than for their wild-type littermates. There was no difference in insulin sensitivity for male huCETP mice vs. littermates. The increased insulin sensitivity in females was largely caused by the better insulin-mediated suppression of hepatic glucose production. In huCETP females, CETP in the circulation decreased HDL-cholesterol content and increased liver cholesterol uptake and liver cholesterol and oxysterol contents, which was associated with the upregulation of LXR target genes in long-chain polyunsaturated fatty acid biosynthesis and PPARα target genes in fatty acid β-oxidation in the liver. The upregulated fatty acid β-oxidation may account for the improved fatty liver and liver insulin action in female huCETP mice. This study provides further evidence that CETP has beneficial physiological roles in the metabolic adaptation to nutrient excess by promoting liver fatty acid oxidation and hepatic insulin sensitivity, particularly for females.

Interaction between CETP polymorphism and dietary insulin index and load in relation to cardiovascular risk factors in diabetic adults

Gene-diet interactions may play an important role in the inter individual diversity observed in on cardiovascular disease (CVD) risk factors. Therefore, in the current study, we examined the interaction of CETP TaqB1 polymorphism with dietary insulin index and load (DII and DIL), in altering on CVD risk factors among type 2 diabetes mellitus (T2DM). In this cross-sectional study, blood samples were collected from 220 type 2 diabetic patients (134 females and 86 male) with a mean age of 52.24 years in Tehran, Iran. DIL and DII were obtained via validated food-frequency questionnaire (FFQ). Taq1B polymorphism was genotyped by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Biochemical markers including total cholesterol (TC), low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglyceride (TG), superoxide dismutase (SOD), C-reactive protein (CRP), total antioxidant capacity (TAC), pentraxin-3 (PTX3), isoprostaneF2α (PGF2α). interleukin 18 (IL18), leptin and ghrelin were measured by standard protocol. Patients with B1B1 genotype had lower lipid profiles include LDL/HDL (P < 0.001) and TG (P = 0.04) when they consumed diets higher on the DIL and DII index. Moreover, carriers of B2B2 genotype who were in the last tertile of DIL had higher antioxidant and inflammatory markers include SOD (P = 0.01), PGF2α (P = 0.04) and CRP (P = 0.02). Further, a significant interaction between CETP TaqB1 and DII was shown in terms of WC (P = 0.01), where the highest WC were observed in B2B2 genotype carriers following a DII score. However, the highest inflammatory and antioxidant markers include CRP (P = 0.04), TAC (P = 0.01), SOD (P = 0.02), and PGF2α (P = 0.02) were observed in B2B2 genotype carriers when they consumed diets higher on the DII index. Based on the current study, it could be proposed that CETP polymorphism may be associated with CVD risk factors in T2DM patients with high following insulin indices, including DII and DIL. It seems that CETP Taq1B polymorphism can invert the result produced by insulin. This conclusion illustrates that the CETP Taq1B B1 allele could counteract the CVD risk induced by high DII and DIL.

CETP genotype and concentrations of HDL and lipoprotein subclasses in African-American men

Aim: To assess the association between the CETP Taq1B and I405V polymorphisms with levels of lipoprotein subclasses in African-American (AA) men with and without Type 2 diabetes (T2DM). Patients & methods: AA men, over 30 years of age, with (n = 54) or without T2DM (n = 50), and not receiving lipid-lowering agents, underwent advanced lipid analysis and genotyping. Results & conclusion: In the total patient population Taq1B B2-allele carriers had significantly higher levels of large HDL subclasses (HDL-2b [p = 0.017] and HDL-L [p = 0.019]), lower levels of small-HDL subclasses (HDL-3a [p = 0.004] and HDL-3b [p = 0.031]), and lower levels of LDL subclasses (LDL-IVa [p = 0.012] and LDL-IIIb [p = 0.009]). The only significant genotype-diabetes interaction occurred with the HDL-2a subclass (p = 0.015). No statistically significant associations were seen with I405V genotype. Our observations of lower levels of small-HDL and higher levels of large-HDL suggest that a potentially important HDL subclass-CETP relationship exists.

Balanced high fat diet reduces cardiovascular risk in obese women although changes in adipose tissue, lipoproteins, and insulin resistance differ by race

BACKGROUND

We previously reported that consuming a balanced high fat diet (BHFD) wherein total saturated fat was reduced and total unsaturated fat increased by proportionately balancing the type of fat (1/3 saturated, 1/3 monounsaturated, 1/3 polyunsaturated) led to significant improvements in inflammatory burden, blood pressure, and vascular function in obese premenopausal European American (EA) and African American (AA) women.

OBJECTIVE

Here we compared changes in adipose tissue, lipoproteins, insulin resistance, and cardiovascular risk between EA and AA women.

METHODS

Dietary intakes, plasma fatty acids, lipids, apolipoproteins, lipoproteins, HOMA-IR and ASCVD risk was measured in 144 women who consumed BHFD for 16 weeks. Generalized linear modeling was performed while controlling for change in body weight.

RESULTS

EA women had greater reductions in visceral adipose tissue. Only EA women had significant reductions in fasting insulin levels (↓24.8%) and HOMA-IR (↓29%) scores. In EA women, the most significant improvements occurred in VLDL particle size (↑), apolipoprotein B levels (↑), serum TG (↓), number of plasma LDL particles (↓), and serum LDL-cholesterol (↓). In AA women, significant improvements occurred in HDL particle size (↑), number of large HDL particles (↑), and apolipoprotein AI levels (↑). Consequently, both groups had improved ASCVD risk scores (↓5.5%).

CONCLUSIONS

Consuming the balanced high fat diet led to significant reduction in cardiovascular risk factors in both groups. However, the pattern of response to BHFD differed with EA women responding more in components of the apolipoprotein B pathway versus AA women responding more in components of the apolipoprotein AI pathway.

CETP Expression Protects Female Mice from Obesity-Induced Decline in Exercise Capacity

Pharmacological approaches to reduce obesity have not resulted in dramatic reductions in the risk of coronary heart disease (CHD). Exercise, in contrast, reduces CHD risk even in the setting of obesity. Cholesteryl Ester Transfer Protein (CETP) is a lipid transfer protein that shuttles lipids between serum lipoproteins and tissues. There are sexual-dimorphisms in the effects of CETP in humans. Mice naturally lack CETP, but we previously reported that transgenic expression of CETP increases muscle glycolysis in fasting and protects against insulin resistance with high-fat diet (HFD) feeding in female but not male mice. Since glycolysis provides an important energy source for working muscle, we aimed to define if CETP expression protects against the decline in exercise capacity associated with obesity. We measured exercise capacity in female mice that were fed a chow diet and then switched to a HFD. There was no difference in exercise capacity between lean, chow-fed CETP female mice and their non-transgenic littermates. Female CETP transgenic mice were relatively protected against the decline in exercise capacity caused by obesity compared to WT. Despite gaining similar fat mass after 6 weeks of HFD-feeding, female CETP mice showed a nearly two-fold increase in run distance compared to WT. After an additional 6 weeks of HFD-feeding, mice were subjected to a final exercise bout and muscle mitochondria were isolated. We found that improved exercise capacity in CETP mice corresponded with increased muscle mitochondrial oxidative capacity, and increased expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). These results suggest that CETP can protect against the obesity-induced impairment in exercise capacity and may be a target to improve exercise capacity in the context of obesity.

Prevalence of plasma small dense LDL is increased in obesity in a Thai population

BACKGROUND

Plasma low density lipoprotein (LDL) particles vary in size, density, electrical charge and chemical composition. An increased presence of small dense LDL (sdLDL), along with raised triglyceride concentrations and decreased high density lipoprotein (HDL) cholesterol concentrations is commonly known as the atherogenic triad and has been observed in some cases of obesity, principally in Europe and America. This study examines the prevalence of sdLDL in the plasma of an obese (BMI≥25 kg/m2) Thai population.

METHODS

Plasma from fasted obese (n=48) and non-obese (n=16) Thai participants was subjected to density gradient ultracentrifugation in iodixanol to separate lipoproteins. Gradients were unloaded top-to-bottom into 20 fractions which were assayed for cholesterol, triglyceride, apo B and apo A-1 to identify lipoprotein types and subtypes.

RESULTS

LDL cholesterol was subfractionated into LDL I+II (fractions 3-6, ρ=1.021-1.033 g/ml) which was considered to represent large buoyant LDL (lbLDL), LDL III (fractions 7-9, ρ=1.036-1.039 g/ml) which was considered to represent sdLDL, and, LDL IV (fractions 10-12, ρ=1.044-1.051 g/ml) which was considered to represent very sdLDL. Concentrations of LDL III and IV were increased by 15-20% in obese participants whilst that of LDL I+II was concomitantly decreased by 10%. This was accompanied by a 50% increase in plasma triglyceride concentrations and 15% decrease in HDL cholesterol concentrations. Only 3/16 (19%) non-obese participants had a pattern B LDL cholesterol profile (peak density of >1.033 g/ml), whilst 28/48 (58%) obese participants were pattern B. When expressed as a fraction of the LDL concentration, total sdLDL (i.e. LDL III+IV) showed highly significant correlations to plasma triglyceride concentrations and the triglyceride/HDL cholesterol ratio.

CONCLUSIONS

The prevalence of sdLDL is increased in obesity in a Thai population such that they demonstrate a similar atherogenic triad to that previously observed in European and American populations.

HDL-cholesterol in coronary artery disease risk: function or structure?

High-density lipoproteins (HDL) are inversely related with coronary artery disease (CAD) and HDL-cholesterol is the only standardized and reproducible parameter available to estimate plasma concentration of these lipoproteins. However, pharmacological interventions intended to increase HDL-cholesterol have not been consistently associated to an effective CAD risk reduction. Among patients with a myocardial infarction, 43 and 44% of men and women, respectively, had normal plasma levels of HDL-cholesterol, whereas genetic studies have failed to show a causal association between HDL-cholesterol and CAD risk. Instead, HDL functionality seems to be the target to be evaluated, but the existing methods are still poorly reproducible and far to be adapted to the clinical laboratory. HDL subclasses rise as a potential alternative for the evaluation of CAD risk; HDL subclasses are a surrogate of intravascular metabolism of these lipoproteins and probably of their functionality. Low levels of large HDL and increased proportions of small particles are the most remarkable features associated to an increased risk of type 2 diabetes mellitus (T2DM) or CAD. However, inflammation and other environmental factors are related with abnormal HDL structure, and, as a consequence, more prospective studies are needed to better support the clinical usefulness of HDL subclasses. New insights from proteome and lipidome profiles of HDL will provide potential HDL-related biomarkers in the coming years.

The relationship between high density lipoprotein subclass profile and plasma lipids concentrations

HDL particles posses multiple antiatherogenic activities and the identification and differentiation of individual HDL subclasses may be useful in documentation and understanding of metabolic changes of different HDL subclasses. The major plasma lipids exist and are transported in the form of lipoprotein complexes. Hence, alterations in plasma lipids levels can interfere with the composition, content, and distribution of plasma lipoprotein subclasses that affect atherosclerosis risk. The research review major discussed the relationship between plasma lipids levels and HDL subclasses distribution. The general shift toward smaller size of HDL particle size in HTG, HCL and MHL subjects, and the changes were more prominent with the elevation of TG and TC levels which imply that HDL maturation might be abnormal and RCT pathway might be weaken, and these changes were more seriously in MHL subjects. Plasma contents of small sized HDL particles significantly higher, whereas those of large sized HDL particles were significantly lower with elevation of TG/HDL-C and TC/HDL-C ratios. Increased in the TC/HDL-C ratio alone did not influence the distributions of HDL subclasses significantly when the TG/HDL-C ratio was low (TG/HDL-C ≤ 2.5). Hence, the TG/HDL-C ratio might be more sensitive to reflect the alteration of HDL subclass distribution than the TC/HDL-C ratio. In LDL-C/HDL-C ≤ 2.3 group, the pattern of distribution in HDL subclass was in agreement with the normolipidemic subjects. Moreover, considering the relative ease of measuring TC/HDL-C, TG/HDL-C and LDL-C/HDL-C ratios, as opposed to measuring HDL subclasses, these 3 ratios together may be a good indicator of HDL subclass distribution. The protective effect of increased apoA-I levels against the reduction of HDL_2b caused by elevated TG concentration. On one hand, plasma HDL-C and apoA-I appear to play a coordinated role in the assembly of HDL particles and the determination of their contents among the total subjects. On the other hand, the apoA-I level might be a more powerful factor than HDL-C to influence the distribution of HDL subclasses in hyperlipidemic subjects. At the same time, from point of HDL subclasses distribution, the plasma lipids, apos concentrations and apos ratios should be considered while assessing the CHD risk. Abnormality of HDL subclasses distribution may result in accelerated atherosclerosis, therapeutic normalization of attenuated antiatherogenic HDL function in terms of both particle number and distribution of HDL particles is the target of innovative pharmacological approaches to large-sized HDL particles rising, including enhanced apoA-I levels.

A case-control study on the relationship between HDL2b and non-alcoholic fatty liver disease in Chinese type 2 diabetic patients

BACKGROUND

It has been shown that low concentrations of high-density lipoprotein cholesterol (HDL-C) are associated with non-alcoholic fatty liver disease (NAFLD) in patients with type 2 diabetes mellitus (T2DM). HDL2b, a major subfraction of high-density lipoprotein (HDL), is more significantly correlated with coronary heart disease (CHD) compared with total HDL. In this study, we analysed HDL2b in a cohort of Chinese T2DM subjects with or without NAFLD.

METHODS

A highly sensitive and reliable microfluidic chip method was adopted to measure HDL2b. In total, 48 T2DM patients with NAFLD diagnosed by a B-ultrasound were enrolled from our Beijing Community Pre-Diabetes (BCPD) study cohort. A total of 48 age and gender matched diabetic controls without NAFLD were selected from the same population.

RESULTS

Clinical characteristics and serum biochemical analyses demonstrated a significantly increased body mass index (BMI), waist circumference, homeostasis model assessment-insulin resistant index (HOMA-IR), total cholesterol (TC), and triglyceride (TG) concentrations in the NAFLD group. However, the concentrations of HDL2b and its ratio to total HDL in NAFLD patients was decreased, compared with controls (p<0.01). Significantly increased concentrations of high sensitive C-reactive protein (hs-CRP) (p<0.01) were also found. Multifactor logistic regression analysis showed that BMI and TG were the predominant risk factors for fatty liver, while HDL2b was a protective factor.

CONCLUSIONS

T2DM patients with NAFLD have characteristics including obesity, marked insulin resistance, high TG, high hs-CRP, low HDL2b and a low HDL2b ratio to total HDL. These factors may increase the incidence of atherosclerosis as well as the risk of CHD.

Reduced high-density lipoprotein 2b in non-obese type 2 diabetic patients analysed by a microfluidic chip method in a case-control study

BACKGROUND

Alterations in high-density lipoprotein (HDL) subfractions, especially in the HDL2b subfraction, have been reported in type 2 diabetes mellitus (T2DM). However, new methods for convenient and reliable quantitation of HDL2b are yet to be developed.

METHODS

Thirty-eight patients with T2DM were enrolled and age-, sex- and body mass index (BMI)-matched controls were selected from the same population. A microfluidic chip method was employed to analyse serum HDL subfractions.

RESULTS

The microfluidic chip method revealed a significant reduction in HDL2b and its ratio to total HDL in T2DM patients. There was a reverse correlation for total HDL and HDL2b, and its ratio with triglycerides, homeostasis model assessment-insulin sensitivity index (HOMA-IS) and insulin resistance index (HOMA-IR).

CONCLUSIONS

We have shown a reduction of HDL2b and its ratio to total HDL by a novel chip method in T2DM patients. The significant correlation between HDL2b and HOMA-IS and HOMA-IR may have further predictive value in clinical utility.

Endothelial dysfunction in African-Americans

The journey of atherosclerosis begins with endothelial dysfunction and culminates into its most fearful destination producing ischemia, myocardial infarction and death. The excess cardiovascular disease morbidity and mortality in African-Americans is one of the major public health problems. In this review, we discuss vascular endothelial dysfunction as a key element for excess cardiovascular disease burden in this target population. It can be logical window of future atherosclerotic outcomes, and further efforts should be made to detect it at the earliest in African American individuals even if they are appearing healthy as the therapeutic interventions if instituted early, might prevent the subsequent cardiac events.

Effect of obesity on the plasma lipoprotein subclass profile in normoglycemic and normolipidemic men and women

OBJECTIVE

To determine the effect of obesity without the confounding effect of metabolic complications on the lipoprotein subclass profile in men and women.

DESIGN

Cross-sectional study.

SUBJECTS

A total of 40 lean (body mass index (BMI): 18.5-25 kg/m(2)) and 40 obese (BMI: 30-45 kg/m(2)) subjects, with blood pressure <140/90 mm Hg, fasting plasma glucose concentration <100 mg per 100 ml and total triglyceride concentration <150 mg per 100 ml; all obese subjects had normal oral glucose tolerance.

MEASUREMENTS

Fasting concentrations of very low-, intermediate-, low- and high-density lipoproteins (VLDL, IDL, LDL, and HDL, respectively) and average VLDL, LDL and HDL particle sizes were evaluated by using proton nuclear magnetic resonance spectroscopy.

RESULTS

Obese compared with lean individuals of both sexes had increased plasma concentrations of VLDL (by approximately 50%), IDL (by approximately 100%), LDL (by approximately 50%), and to some extent HDL (by approximately 10%) particles (P<0.05). The contribution of large VLDL to total VLDL concentration, small LDL to total LDL concentration, and small HDL to total HDL concentration was greater in obese than lean subjects (P<0.05), resulting in larger average VLDL size but smaller average LDL and HDL sizes (P<0.05). Women, compared with men, had reduced concentrations of total VLDL particles (by approximately 10%) due to lower concentrations of large and medium VLDL and a shift toward large at the expense of small HDL particles (P<0.05), with no difference in total HDL particle concentration. IDL and total LDL concentrations and LDL subclass distribution were not different between men and women.

CONCLUSION

Obesity is associated with pro-atherogenic alterations in the lipoprotein subclass profile, which may increase cardiovascular disease risk even in the absence of classical metabolic risk factors. On the other hand, the female cardiovascular disease risk advantage is probably largely related to differences in traditional lipid risk factors (plasma triglyceride and HDL-cholesterol concentrations) because sex differences in the plasma lipoprotein subclass profile are minimal.

Peptide-YY levels after a fat load in black and white women

OBJECTIVE

To determine whether basal plasma peptide-YY (PYY) levels in overweight, middle-aged black women are different from those of white women of similar BMI and age and ascertain whether there is a difference between the two groups in plasma PYY levels in response to a liquid high fat load.

RESEARCH METHODS AND PROCEDURES

Using a commercial radioimmunoassay kit, the concentration of PYY was measured at baseline and at 2, 4, 6, and 8 hours after ingesting a fatty liquid meal (86.5% of the calories from fat) in 12 black and 12 white women who were matched for age and BMI.

RESULTS

PYY levels (picograms per milliliter) at baseline and at every other time-point of the test meal were significantly lower in the black than in the white group. In addition, the change in PYY concentration from baseline was lower in the black than in the white group only at 8 hours after the meal.

DISCUSSION

The lower baseline level and the blunted PYY response of the black women to the fat load indicated that this signal for appetite suppression was reduced, which, in turn, might contribute to the enhanced obesity of the black women.

The molecular mechanism linking muscle fat accumulation to insulin resistance

Skeletal muscle insulin resistance is a co-morbidity of obesity and a risk factor for the development of type 2 diabetes mellitus. Insulin resistance is associated with the accumulation of intramyocellular lipids. Intramyocellular triacylglycerols do not appear to be the cause of insulin resistance but are more likely to be a marker of other lipid intermediates such as fatty acyl-CoA, ceramides or diacylglycerols. Fatty acyl-CoA, ceramides and diacylglycerols are known to directly alter various aspects of the insulin signalling cascade. Insulin signalling is inhibited by the phosphorylation of serine and threonine residues at the levels of the insulin receptor and insulin receptor substrate 1. Protein kinase C is responsible for the phosphorylation of the serine and threonine residues. Fatty acyl-CoA and diacylglycerols are known to activate protein kinase C. The cause of the intramyocellular accumulation of fatty acyl-CoA and diacylglycerols is unclear at this time. Reduced fatty acid oxidation does not appear to be responsible, as fatty acyl-CoA accumulates in skeletal muscle with a normal fatty acid oxidative capacity. Other potential mechanisms include oversupply of lipids to muscle and/or up regulated fatty acid transport.

Abnormal HDL subclasses distribution in overweight children with insulin resistance or type 2 diabetes mellitus

BACKGROUND

Small HDL particles have emerged as significant predictors of incident type 2 diabetes mellitus (T2DM) in adults with impaired glucose tolerance (IGT). However, no previous study has investigated HDL size in pediatric subjects with these clinical conditions.

METHODS

We studied the HDL size distribution by native polyacrilamide gradient gel electrophoresis in 106 overweight children, 47 with T2DM, 43 with normal glucose tolerance (NGT), 16 with IGT, and 39 healthy weight controls.

RESULTS

Diabetic children had significantly lower proportions of HDL2b and HDL2a, and higher proportions of HDL3b and HDL3c than the other 3 groups. Overweight subjects showed HDL size distributions similar to those of controls. However, insulin-resistant children had lower proportions of HDL2b, and HDL2a, and higher proportions of HDL3b when compared with the insulin-sensitive overweight subjects. Multiple linear regression analyses showed that homeostasis model assessment correlated inversely with HDL2b and HDL2a, and directly with HDL3b, while BMI was independently associated only with HDL3a.

CONCLUSIONS

This study showed that HDL size distribution was shifted toward smaller particles in T2DM pediatric patients and in overweight children with insulin resistance, independent of their glucose tolerance status. Insulin resistance was the main factor associated with these HDL size abnormalities. This parameter could be useful as an early risk marker of incident diabetes and, probably, of coronary heart disease.

Protective effect of apolipoprotein E2 on coronary artery disease in African Americans is mediated through lipoprotein cholesterol

We studied the relationship of apolipoprotein E (apoE) isoforms and coronary artery disease (CAD) in 224 African Americans and 326 Caucasians undergoing diagnostic coronary angiography. The presence of CAD was defined as >50% stenosis in at least one artery. ApoE allele frequencies were 0.12, 0.62, and 0.26 for epsilon 2, epsilon 3, and epsilon 4, respectively, in African Americans and 0.08, 0.78, and 0.14 for epsilon 2, epsilon 3, and epsilon 4, respectively, in Caucasians. Among African Americans, CAD was present in 9 of 34 epsilon 2 carriers (26%), significantly smaller (P < 0.05) in proportion compared with 39 of 82 epsilon 3 carriers and 43 of 92 epsilon 4 carriers (48% and 47%, respectively), suggesting a protective effect of the epsilon 2 allele. No such difference was seen in Caucasians. In African Americans but not Caucasians, LDL cholesterol was lower in epsilon 2 carriers than in epsilon 3 and epsilon 4 carriers (106 vs. 127 and 134 mg/dl, respectively; P < 0.005). After adjusting for lipid levels, the association between apoE2 and CAD was no longer significant. Thus, the protective effect of apoE2 seen in African Americans could be explained by a favorable lipid profile in epsilon 2 carriers, whereas in Caucasians, the absence of such a protective effect could be attributable to the lack of effect of apoE2 on the lipid profile.

Role of diabetes in atherosclerotic pathogenesis. What have we learned from animal models?

Diabetes mellitus is associated with a greater risk of developing atherosclerosis and its complications: stroke, myocardial infarction, and peripheral vascular disease. In patients with diabetes, atherosclerosis represents a complex multifactorial disease with increased lesion progression and severity compared to the nondiabetic population. Several risk factors have been proposed to explain the increased risk of cardiovascular disease with diabetes. They include: hyperglycaemia, dyslipidemia, accelerated formation of advanced glycation end-products (AGEs), increased oxidative stress, and genetic factors. It is difficult to precisely establish the elements leading to diabetes-accelerated atherosclerosis by means of epidemiological studies because all these factors coexist in diabetic patients. Thus, diabetic animal models that reproduce exacerbation of atherosclerosis would be helpful to understand why atherosclerosis is accelerated by diabetes, and to design appropriate treatments to limit its progression. This review analyzes most of the animal models developed to reproduce diabetes-accelerated atherosclerosis, and summarizes the effects of hyperglycaemia and lipid abnormalities on atherogenesis.

Differences in transport of fatty acids and expression of fatty acid transporting proteins in adipose tissue of obese black and white women

We have reported that the rate of de novo triglyceride (TG) synthesis by omental, but not subcutaneous, adipose tissue was higher in African-American women (AAW) than in Caucasian women (CAW). The purpose of this study was to explore the potential mechanisms underlying this increase. Toward that end, we determined the activities of key enzymes in the pathway of TG synthesis, the rates of uptake of fatty acids by adipocytes, mRNA and protein levels of the fatty acid-transporting proteins FAT/CD36 and FATP, and mRNA and protein levels of PPARgamma in omental fat of AAW and CAW. The results showed 1) no difference in the activity of phosphofructokinase, glycerol-3-phosphate dehydrogenase, or diacylglycerol acyltransferase; 2) a higher rate of fatty acid uptake by adipocytes of the AAW; 3) an increase in the mRNA and protein levels of CD36 and FATP4 in the fat of the AAW; and 4) an increase in the mRNA and protein levels of PPARgamma, which can stimulate the expression of CD36 and FATP. These results suggest that the increase in the transport of fatty acid, which is mediated by the overexpression of the transport proteins in the omental adipose tissue of the AAW, might contribute to the higher prevalence of obesity in AAW.

Ethnic differences in adiponectin levels

Adiponectin levels were measured in African American and Caucasian women of varying body mass index (BMI). Plasma adiponectin levels were compared and the relationship between adiponectin and insulin sensitivity was assessed. Adiponectin levels were similar in the Caucasian obese (7.0 +/- 0.8 microg/mL), African American obese (7.3 +/- 3.5 microg/mL), and African American non-obese women (7.1 +/- 1.2 microg/mL), but were significantly higher in Caucasian non-obese women (12.2 +/- 1.4 microg/mL). Correlational analyses demonstrated that BMI, insulin, and homeostasis model assessment (HOMA) correlated significantly with adiponectin levels in only the Caucasian women. These results provide support for the notion that what applies to other ethnic populations might not apply to the African American population, and that the association between adiponectin and insulin sensitivity needs to be clarified in the African American population.

Ethnic differences in in vitro glyceride synthesis in subcutaneous and omental adipose tissue

Considerable evidence suggests that there are ethnic differences in lipid metabolism between African American and Caucasian women, which may result in increased synthesis of fat in adipose tissue. The purpose of this study was to measure the in vitro rates of [14C]glucose incorporation into the glyceride-glycerol backbone of triglycerides (TG) and diglycerides (DG) in abdominal subcutaneous (SAT) and omental adipose tissue (OAT). Morbidly obese [African American (n = 15): body mass index (BMI) = 45 +/- 2.3; Caucasian (n = 18): BMI = 51 +/- 2.3] and preobese [African American (n = 7): BMI = 27 +/- 1.0; Caucasian (n = 7): BMI = 25 +/- 1.0] women were examined in this study. There were no significant differences in the rates of synthesis of either TG or DG in SAT of either preobese or obese women. On the other hand, both preobese and obese African American women had higher rates of synthesis of TG in OAT compared with their Caucasian counterparts. This increase in TG synthesis in OAT was not due to differences in cell size or rates of reesterification. Thus African American woman have an increased capacity to synthesize TG in OAT compared with Caucasian women, which may contribute to the higher prevalence of obesity in African American women.

Impaired lipoprotein metabolism in obese offspring of streptozotocin-induced diabetic rats

The time course of changes in lipoprotein metabolism of obese offspring of mildly diabetic rats was studied with respect to serum lipoprotein composition as well as LCAT and tissue lipoprotein lipase (LPL) activities. Mild hyperglycemia in pregnant rats was induced by intraperitoneal injection of streptozotocin on day 5 of gestation. Control pregnant rats were injected with citrate buffer. At birth, obese pups had higher serum glucose, insulin, and lipoprotein (VLDL, LDL-HDL1, HDL(2-3)) levels than control pups. After 1 mon of life, all of these parameters in obese rats became similar to those of controls. However, LCAT, adipose tissue LPL, and hepatic triacylglycerol lipase activities were high. At 2 mon of age, VLDL-TAG levels were higher in obese females than in controls. By the age of 3 mon, obese offspring had developed insulin resistance with hyperglycemia, hyperinsulinemia, and higher serum lipoprotein concentrations. Indeed, qualitative abnormalities of lipoproteins were seen and were typical of obese and diabetic human beings. Fetal hyperinsulinemia should be considered as a risk factor for later metabolic diseases, including dyslipoproteinemia.

Is NASH underdiagnosed among African Americans?

OBJECTIVE

Obesity and type 2 diabetes mellitus are considered risk factors for nonalcoholic steatohepatitis (NASH) and cryptogenic cirrhosis. Because obesity and type 2 diabetes are prevalent among African American females by the 5th and 6th decades, one would expect an increased number of African Americans among patients with NASH and cryptogenic cirrhosis.

METHODS

We determined the percentage of patients of African American and European American descent among all of the patients in our liver disease registry and those with NASH and cryptogenic cirrhosis. We also assessed the ethnicity of patients in our registry with other common liver diseases including hepatitis C, and we determined the ethnicity of patients seen at our center with type 2 diabetes and a primary diagnosis of obesity over a 4-yr period. Using census data, we compared these results to our local and regional ethnic demographics.

RESULTS

Overall, 199 of 2,253 patients (9%) in the registry were of African American descent, whereas 1,906 were of European American descent (85%). This distribution is similar to the ethnic mix in central Virginia (12% African American, 86% European American) and Albemarle County (12% African American, 83% European American). The prevalence of African American patients among individuals seen at our center for either type 2 diabetes or a primary diagnosis of obesity was over two times the prevalence of African Americans in the county or regional population. In contrast, of 159 NASH patients only one (0.6%) was of African American descent and 154 (97%) were of European American descent (p < 0.001 compared to the total registry, county, or region). Among 206 cryptogenic cirrhosis patients, only two (1%) were of African American descent, whereas 195 (95%) were of European American descent (p < 0.001 compared to the total registry). With regard to other liver diseases, African American patients were slightly overrepresented among hepatitis C patients and markedly overrepresented among patients with hepatic sarcoidosis, similar to previously reported national figures.

CONCLUSION

Although there is overrepresentation of African Americans among patients with major risk factors for NASH, individuals of primarily African American descent are infrequently represented among our patients with NASH or cryptogenic cirrhosis. This could result from underrecognition, underreferral, or a true lower prevalence of these disorders among African Americans.

Insulin does not regulate the promoter of cholesteryl ester transfer protein (CETP) in HIRc/pCETP-CAT cells

Cholesteryl ester transfer protein (CETP) is a plasma enzyme involved in cholesterol metabolism. As a potential target in the treatment of atherosclerosis, a number of studies have focused how this enzyme is regulated. It has been postulated that insulin may regulate CETP gene expression, and these effects may be mediated through CCAAT/enhancer binding protein alpha (C/EBPalpha). The present study examines the effects of insulin on the activity of the CETP promoter in rat fibroblasts expressing the human insulin receptor (HIRc). HIRc cells were stably transfected with a chimeric construct containing 3.2 kb of the CETP promoter attached to the bacterial chloramphenicol acyltransferase gene (pCETP-CAT) without significantly affecting the expression of the insulin receptor. CAT activity was 8-fold higher in cultured HIRc/pCETP-CAT in the presence of 100 mg/dL LDL cholesterol, than those cultured without cholesterol (p < 0.05). However, culturing these cells in the presence of 100 nM insulin did not result in any change in CAT activity when compared to control cells. In HIRc/pCETP-CAT cells transiently transfected with a construct that constitutively expressed C/EBPalpha protein, a 3-fold increase in CAT activity was observed when compared to cells transiently transfected with non-specific DNA (p < 0.05). However, no observable effect on the CETP promoter was observed in the presence of insulin. Thus, in HIRc/pCETP-CAT cells, we were unable to substantiate the hypothesis that insulin regulates CETP gene transcription. These results suggest that the effects of insulin on CETP expression regulation may be downstream of transcription.

Differential expression of cholesteryl ester transfer protein in the liver and plasma of fasted and fed transgenic mice

Because cholesteryl ester transfer protein (CETP) is considered a potential target in the treatment of atherosclerosis, several reports have focused on the regulation of this enzyme, and there is evidence that insulin may be a regulatory factor. The present study examines the differential expression of the human CETP gene between physiologic conditions that are accompanied by low (fasted) and high (fed) insulin levels. CETP expression was examined in plasma and tissues of transgenic mice expressing the human CETP minigene after 12 hours of fasting (n = 20) or ad libitum feeding (n = 20) with normal mouse chow. Plasma cholesteryl ester transfer activity (CETA) was 20% higher in fed than in fasted mice, reflecting higher levels of CETP (P < 0.05). This observation was accompanied by higher liver mRNA in fed mice (100%, P < 0.05), as determined by ribonuclease protection assays, as well as by higher CETA (23%, P < 0.05) and CETP mass (29%, P < 0.05) in the particulate fraction of liver homogenates. These parameters of liver CETP expression correlated well with each other, as well as with plasma CETA. CETP in the liver particulate fraction was found as a doublet (approximately 70 and 65 kDa), which resolved to a single band (approximately 60 kDa) upon deglycosylation. No differences in CETP expression were observed in pooled adipose tissue samples from fed and fasted mice. Insulin and glucose were not related to any plasma or tissue parameter of CETP expression. In summary, the concerted, differential expression of CETP in the liver of fed and fasted transgenic mice appears to contribute to higher plasma CETP levels in fed mice, but the precise role of insulin and glucose in regulating CETP expression under fasted and fed conditions needs to be defined.