HDL and LDL cholesterol significantly influence beta-cell function in type 2 diabetes mellitus

Incident type 2 diabetes is associated with HDL, but not with its anti-oxidant constituent - paraoxonase-1: The prospective cohort PREVEND study

OBJECTIVE

High-density lipoprotein cholesterol (HDL-C) is an established risk marker for cardiovascular disease and consistently associated with type 2 diabetes risk. Serum paraoxonase-1 (PON-1) - an anti-oxidant constituent of HDL - is inversely associated with cardiovascular disease risk, but its relationship with incident type 2 diabetes is uncertain. We aimed to investigate the prospective association between PON-1 and type 2 diabetes risk.

METHODS

PON-1 was measured as its arylesterase activity at baseline in the Prevention of Renal and Vascular End-stage Disease (PREVEND) prospective study of 5947 predominantly Caucasian participants aged 28-75years with no pre-existing diabetes, that recorded 500 type 2 diabetes cases during a median follow-up of 11.2years.

RESULTS

Serum PON-1 was positively correlated with HDL-C (r=0.17; P<0.001). In analyses adjusted for conventional diabetes risk factors, the hazard ratio (95% CI) for type 2 diabetes per 1 standard deviation increase in PON-1 was 1.07 (0.98 to 1.18; P=0.13), which remained non-significant (1.02 (0.93 to 1.12) P=0.65) after additional adjustment for potential confounders. The association was unchanged on further adjustment for HDL-C (1.05 (0.96 to 1.15; P=0.29). However, in subsidiary analyses in the same set of participants, serum HDL-C concentration was inversely and independently associated with risk of type 2 diabetes.

CONCLUSIONS

Incident type 2 diabetes is associated with HDL cholesterol but not with its anti-oxidant constituent - PON-1 - in a large cohort of apparently healthy men and women. The current data question the importance of PON-1 activity for the development of diabetes.

Are visceral adiposity index and lipid accumulation product reliable indices for metabolic disturbances in patients with type 2 diabetes mellitus?

BACKGROUND

Visceral adiposity index (VAI) and Lipid accumulation product (LAP) are novel visceral adiposity indexes, proposed for the evaluation of cardiometabolic risk in adult population. Considering contradictory results obtained from many studies so far, we aimed to examine the potential benefit of applicability of VAI and LAP, over simple anthropometric indices and traditional lipid parameters in individuals with type 2 diabetes mellitus (DM2).

METHODS

A total of 180 DM2 (of them 50% females) and 119 controls who volunteered to participate in this cross-sectional study were enrolled. Anthropometric and biochemical parameters, as well as blood pressure were obtained. VAI and LAP were calculated.

RESULTS

Multivariate logistic regression analysis showed that high-density lipoprotein cholesterol (HDL-c), (P<.001), waist circumference (WC), (P=.027), age (P=.001), hypolipemic therapy (P=.024), and LAP (P=.005) were independent predictors of DM2 in adjusted models. In Receiver Operating Characteristic curve analysis, used to discriminate subjects with DM2 from those who did not have it, good accuracy of the applied procedures was only achieved with models which were consisted of parameters used in VAI (Body mass index, WC, HDL-c, triglycerides) and LAP (WC, triglycerides) indexes equations, respectively [Area under the curve (AUC)=0.819 and AUC=0.800, respectively], but not with VAI (AUC=0.781) and LAP (AUC=0.784) indexes themselves.

CONCLUSION

Visceral adiposity index and Lipid accumulation product may not be better than parameters that enter its equation in type 2 diabetes prediction.

Plasma HDL-cholesterol and triglycerides, but not LDL-cholesterol, are associated with insulin secretion in non-diabetic subjects

OBJECTIVE

Experimental data support the notion that lipoproteins might directly affect beta cell function, however clinical data are sparse and inconsistent. We aimed at verifying whether, independently of major confounders, serum lipids are associated with alterations in insulin secretion or clearance non-diabetic subjects.

METHODS

Cross sectional and observational prospective (3.5yrs), multicentre study in which 1016 non-diabetic volunteers aged 30-60yrs. and with a wide range of BMI (20.0-39.9kg/m²) were recruited in a setting of University hospital ambulatory care (RISC study).

MAIN OUTCOME MEASURES

baseline fasting lipids, fasting and OGTT-induced insulin secretion and clearance (measured by glucose and C-peptide modeling), peripheral insulin sensitivity (by the euglycemic clamp). Lipids and OGTT were repeated in 980 subjects after 3.5years.

RESULTS

LDL-cholesterol did not show independent associations with fasting or stimulated insulin secretion or clearance. After accounting for potential confounders, HDL-cholesterol displayed negative and triglycerides positive independent associations with fasting and OGTT insulin secretion; neither with insulin clearance. Low HDL-cholesterol and high triglycerides were associated with an increase in glucose-dependent and a decrease in non-glucose-dependent insulin secretion. Over 3.5years both an HDL-cholesterol decline and a triglycerides rise were associated with an increase in fasting insulin secretion independent of changes in body weight or plasma glucose.

CONCLUSIONS

LDL-cholesterol does not seem to influence any major determinant of insulin bioavailability while low HDL-cholesterol and high triglycerides might contribute to sustain the abnormalities in insulin secretion that characterize the pre-diabetic state.

Dietary Interventions for Type 2 Diabetes: How Millet Comes to Help

Diabetes has become a highly problematic and increasingly prevalent disease world-wide. It has contributed toward 1.5 million deaths in 2012. Management techniques for diabetes prevention in high-risk as well as in affected individuals, beside medication, are mainly through changes in lifestyle and dietary regulation. Particularly, diet can have a great influence on life quality for those that suffer from, as well as those at risk of, diabetes. As such, considerations on nutritional aspects are required to be made to include in dietary intervention. This review aims to give an overview on the general consensus of current dietary and nutritional recommendation for diabetics. In light of such recommendation, the use of plant breeding, conventional as well as more recently developed molecular marker-based breeding and biofortification, are discussed in designing crops with desired characteristics. While there are various recommendations available, dietary choices are restricted by availability due to geo-, political-, or economical- considerations. This particularly holds true for countries such as India, where 65 million people (up from 50 million in 2010) are currently diabetic and their numbers are rising at an alarming rate. Millets are one of the most abundant crops grown in India as well as in Africa, providing a staple food source for many poorest of the poor communities in these countries. The potentials of millets as a dietary component to combat the increasing prevalence of global diabetes are highlighted in this review.

The diabetogenic action of statins - mechanisms and clinical implications

Treatment with statins has transformed primary and secondary prevention of cardiovascular disease (CVD), including thrombotic stroke. Evidence-based data demonstrate the benefits and safety of statin therapy and help to guide clinicians in the management of populations at high risk of CVD. Nevertheless, clinical trials, meta-analyses and observational studies highlight a 10-12% increase in new-onset diabetes mellitus (NODM) among patients receiving statins. The risk further increases with intensive therapy and among individuals with known risk factors for NODM. Mechanisms underpinning this effect are not yet fully understood; however, Mendelian randomization studies suggest that they are related to lowered activity of HMG-CoA reductase, the target of statin therapy. In vitro research indicates that statins potentially impair β-cell function and decrease insulin sensitivity but how these findings relate to patients is unknown. In the clinic, statins should be prescribed on the basis of CVD risk and individual patient characteristics. In addition, diet and lifestyle interventions should be emphasized to help mitigate the risk of NODM. Individuals who develop NODM while taking statins do not exhibit increased microvascular disease, which is reassuring. In diabetes mellitus of long duration, the effect of statins on glycaemic control is small and unlikely to be clinically important.

Advances in high-density lipoprotein physiology: surprises, overturns, and promises

Emerging evidence strongly supports that changes in the HDL metabolic pathway, which result in changes in HDL proteome and function, appear to have a causative impact on a number of metabolic disorders. Here, we provide a critical review of the most recent and novel findings correlating HDL properties and functionality with various pathophysiological processes and disease states, such as obesity, type 2 diabetes mellitus, nonalcoholic fatty liver disease, inflammation and sepsis, bone and obstructive pulmonary diseases, and brain disorders.

Uncovering Factors Related to Pancreatic Beta-Cell Function

AIM

The incidence of type 2 diabetes has increased rapidly on a global scale. Beta-cell dysfunction contributes to the overall pathogenesis of type 2 diabetes. However, factors contributing to beta-cell function are not clear. The aims of this study were (i) to identify factors related to pancreatic beta-cell function and (ii) to perform mechanistic studies in vitro.

METHODS

Three specific measures of beta-cell function were assessed for 110 participants who completed an oral glucose tolerance test as part of the Metabolic Challenge Study. Anthropometric and biochemical parameters were assessed as potential modulators of beta-cell function. Subsequent in vitro experiments were performed using the BRIN-BD11 pancreatic beta-cell line. Validation of findings were performed in a second human cohort.

RESULTS

Waist-to-hip ratio was the strongest anthropometric modulator of beta-cell function, with beta-coefficients of -0.33 (p = 0.001) and -0.30 (p = 0.002) for beta-cell function/homeostatic model assessment of insulin resistance (HOMA-IR), and disposition index respectively. Additionally, the resistin-to-adiponectin ratio (RA index) emerged as being strongly associated with beta-cell function, with beta-coefficients of -0.24 (p = 0.038) and -0.25 (p = 0.028) for beta-cell function/HOMA-IR, and disposition index respectively. Similar results were obtained using a third measure for beta-cell function. In vitro experiments revealed that the RA index was a potent regulator of acute insulin secretion where a high RA index (20ng ml-1 resistin, 5nmol l-1 g-adiponectin) significantly decreased insulin secretion whereas a low RA index (10ng ml-1 resistin, 10nmol l-1 g-adiponectin) significantly increased insulin secretion. The RA index was successfully validated in a second human cohort with beta-coefficients of -0.40 (p = 0.006) and -0.38 (p = 0.008) for beta-cell function/ HOMA-IR, and disposition index respectively.

CONCLUSIONS

Waist-to-hip ratio and RA index were identified as significant modulators of beta-cell function. The ability of the RA index to modulate insulin secretion was confirmed in mechanistic studies. Future work should identify strategies to alter the RA index.

Body Fat Patterning, Hepatic Fat and Pancreatic Volume of Non-Obese Asian Indians with Type 2 Diabetes in North India: A Case-Control Study

Objective

To evaluate body fat patterning and phenotype including hepatic fat and pancreatic volume of non-obese (BMI: < 25 kg/m²) Asian Indians with type 2 diabetes residing in North India.

Methods

Non-obese patients with type 2 diabetes (n = 93) and non-obese, normo-glycemic subjects (n = 40) were recruited. BMI, waist & hip circumferences, skinfold thickness at 8 sites, body fat, lean mass and detailed abdominal fat evaluation [total abdominal fat, total subcutaneous fat (superficial, deep, anterior, and posterior), total intra-abdominal fat (intra-peritoneal, retroperitoneal)], liver span, grades of fatty liver and pancreatic volume were compared.

Results

Waist circumference, subscapular skinfolds and total truncal fat (on DEXA) were higher whereas calf, total peripheral skinfolds and total leg fat (on DEXA) lower in patients. Specifically, the following volumes were higher in cases as compared to controls; total abdominal fat (19.4%), total intra-abdominal fat (49.7%), intra-peritoneal fat (47.7%), retroperitoneal fat (70.7%), pancreatic volume (26.6%), pancreatic volume index (21.3%) and liver span (10.8%). In cases, significant positive correlations were observed for pancreatic volume with BMI, waist and hip circumferences, W-HR, subscapular, abdominal and total truncal skinfolds, truncal, total subcutaneous, total intra-abdominal, intra-peritoneal, retroperitoneal fat depots, liver span and fatty liver.

Conclusions

In non-obese Asian Indians with type 2 diabetes, subcutaneous and intra-abdominal obesity, including fatty liver, and pancreatic volume were higher and peripheral subcutaneous adiposity was lower than BMI matched non-diabetic subjects. Importantly, increased pancreatic volume in patients was highly correlated with multiple measures of abdominal obesity and liver fat.

Affection of single-nucleotide polymorphisms in miR-27a, miR-124a, and miR-146a on susceptibility to type 2 diabetes mellitus in Chinese Han people

BACKGROUND

Polymorphisms of microRNA (miRNA), as a novel mechanism, are closely associated with disease states by interfering with miRNA function. Direct correlations have been identified between single-nucleotide polymorphisms (SNPs) in miRNA, but the effect on type 2 diabetes mellitus (T2DM) onset among Chinese population remains unclear. Therefore, the aim of this study was to identify correlations between common SNPs in miR-27a, miR-146a, and miR-124a with T2DM among a Chinese population, as well as to explore diabetic pathological mechanisms and the impact of environmental factors.

METHODS

SNPscan technology was used to genotype 995 patients newly diagnosed with T2DM and 967 controls. Logistic regression analysis was performed to compare mutation frequencies between cases and controls.

RESULTS

We found no significant correlations between all genotypes of these miRNAs and T2DM in our research. However, stratification analysis identified a lower risk of T2DM associated with the rs531564GC genotype among younger subjects (age < 45 years) (adjusted P = 0.043; odds ratio [OR] = 0.73; 95% confidence interval [CI] = 0.54-0.99). Furthermore, the rs895819CC genotype in overweight people (24 ≤ body mass index [BMI] < 28) was significantly associated with an increased risk of T2DM (adjusted P = 0.042; OR = 1.73; 95% CI = 1.02-2.94), while the rs2910164 genotype in miR-146a was not significantly correlated with T2DM. The genetic risk score was calculated based on the number of risk alleles of the three SNPs and was found to be correlated to total cholesterol (adjusted P = 0.021).

CONCLUSIONS

The rs531564GC genotype acted as a protective factor to decrease the risk of T2DM in younger subjects (age < 45 years), while the presence of the rs895819CC genotype increased the risk of illness among overweight subjects (24 ≤ BMI < 28 kg/m 2 ). The presence of SNPs in miRNA might promote disease by affecting miRNA expression and gene function. Thus, miRNA mimics or inhibitors that directly regulate miRNA expression present novel and promising therapeutic targets.

HDL/ApoA-1 infusion and ApoA-1 gene therapy in atherosclerosis

The HDL hypothesis stating that simply raising HDL cholesterol (HDL-C) may produce cardiovascular benefits has been questioned recently based on several randomized clinical trials using CETP inhibitors or niacin to raise HDL-C levels. However, extensive pre-clinical data support the vascular protective effects of administration of exogenous ApoA-1 containing preβ-HDL like particles. Several small proof-of-concept clinical trials using such HDL/ApoA-1 infusion therapy have shown encouraging results but definitive proof of efficacy must await large scale clinical trials. In addition to HDL infusion therapy an alternative way to exploit beneficial cardiovascular effects of HDL/ApoA-1 is to use gene transfer. Preclinical studies have shown evidence of benefit using this approach; however clinical validation is yet lacking. This review summarizes our current knowledge of the aforementioned strategies.

Using Genetic Variants to Assess the Relationship Between Circulating Lipids and Type 2 Diabetes

The effects of dyslipidemia on the risk of type 2 diabetes (T2D) and related traits are not clear. We used regression models and 140 lipid-associated genetic variants to estimate associations between circulating HDL cholesterol (HDL-C), LDL cholesterol (LDL-C), and triglycerides and T2D and related traits. Each genetic test was corrected for effects of variants on the other two lipid types and surrogates of adiposity. We used the largest data sets available: 34,840 T2D case and 114,981 control subjects from the DIAGRAM (DIAbetes Genetics Replication And Meta-analysis) consortium and up to 133,010 individuals without diabetes for insulin secretion and sensitivity from the MAGIC (Meta-Analyses of Glucose and Insulin-related traits Consortium) and GENESIS (GENEticS of Insulin Sensitivity) studies. Eight of 21 associations between groups of variants and diabetes traits were significant at the nominal level, including those between genetically determined lower HDL-C (β = -0.12, P = 0.03) and T2D and genetically determined lower LDL-C (β = -0.21, P = 5 × 10(-6)) and T2D. Although some of these may represent causal associations, we discuss why caution must be used when using Mendelian randomization in the context of circulating lipid levels and diabetes traits. In conclusion, we found evidence of links between genetic variants associated with lipids and T2D, but deeper knowledge of the underlying genetic mechanisms of specific lipid variants is needed before drawing definite conclusions about causality based on Mendelian randomization methodology.

Cholesterol in brain disease: sometimes determinant and frequently implicated

Cholesterol is essential for neuronal physiology, both during development and in the adult life: as a major component of cell membranes and precursor of steroid hormones, it contributes to the regulation of ion permeability, cell shape, cell-cell interaction, and transmembrane signaling. Consistently, hereditary diseases with mutations in cholesterol-related genes result in impaired brain function during early life. In addition, defects in brain cholesterol metabolism may contribute to neurological syndromes, such as Alzheimer's disease (AD), Huntington's disease (HD), and Parkinson's disease (PD), and even to the cognitive deficits typical of the old age. In these cases, brain cholesterol defects may be secondary to disease-causing elements and contribute to the functional deficits by altering synaptic functions. In the first part of this review, we will describe hereditary and non-hereditary causes of cholesterol dyshomeostasis and the relationship to brain diseases. In the second part, we will focus on the mechanisms by which perturbation of cholesterol metabolism can affect synaptic function.

HDL and endothelial protection

High-density lipoproteins (HDLs) represent a family of particles characterized by the presence of apolipoprotein A-I (apoA-I) and by their ability to transport cholesterol from peripheral tissues back to the liver. In addition to this function, HDLs display pleiotropic effects including antioxidant, anti-apoptotic, anti-inflammatory, anti-thrombotic or anti-proteolytic properties that account for their protective action on endothelial cells. Vasodilatation via production of nitric oxide is also a hallmark of HDL action on endothelial cells. Endothelial cells express receptors for apoA-I and HDLs that mediate intracellular signalling and potentially participate in the internalization of these particles. In this review, we will detail the different effects of HDLs on the endothelium in normal and pathological conditions with a particular focus on the potential use of HDL therapy to restore endothelial function and integrity.

Lower intensified target LDL-c level of statin therapy results in a higher risk of incident diabetes: a meta-analysis

BACKGROUND

A recent meta-analysis has reported that intensive-dose statin drug increases the risk of incident diabetes. However, doubling of the statin dose generates only a further 6% decrease in low-density lipoprotein cholesterol (LDL-c) on average. This study aimed to determine whether statin therapy with lower intensive-target LDL-c level contributes to higher risk of new-onset diabetes.

METHODS

Medline, Embase, and the Cochrane Central Register of Controlled Trials were searched for randomized controlled endpoint trials of statins conducted from 1966 to 2012. We included trials with more than 1000 participants who were followed up for at least 2 years. The included trials were stratified by the target LDL-c level. I2 statistic was used to measure heterogeneity between trials. We further calculated risk estimates with random-effect meta-analysis. Meta-regression was used to identify the potential risk factors of statin-induced diabetes.

RESULTS

Fourteen trials with a total of 95 102 non-diabetic participants were included. The risks elevated by 33% [odds ratio (OR)  = 1.33; 95% confidence interval (CI) 1.14-1.56; I(2) = 7.7%] and 16% (OR = 1.16; 95% CI 1.06-1.28; I(2)= 0.0%) when the intensified target LDL-c levels were ≤ 1.8 mmol/L and 1.8-2.59 mmol/L, respectively. The risk of incident diabetes did not increase when the target LDL-c level was ≥ 2.59 mmol/L. Apart from age, female, and baseline level of total cholesterol, meta-regression analysis showed that the target and baseline levels of LDL-c and relative LDL-c reduction were predictors of statin-induced diabetes.

CONCLUSION

A lower intensified target LDL-c level of statin therapy resulted in a higher risk of incident diabetes.

Diabetes and cardiovascular disease in older adults: current status and future directions

The prevalence of diabetes increases with age, driven in part by an absolute increase in incidence among adults aged 65 years and older. Individuals with diabetes are at higher risk for cardiovascular disease, and age strongly predicts cardiovascular complications. Inflammation and oxidative stress appear to play some role in the mechanisms underlying aging, diabetes, cardiovascular disease, and other complications of diabetes. However, the mechanisms underlying the age-associated increase in risk for diabetes and diabetes-related cardiovascular disease remain poorly understood. Moreover, because of the heterogeneity of the older population, a lack of understanding of the biology of aging, and inadequate study of the effects of treatments on traditional complications and geriatric conditions associated with diabetes, no consensus exists on the optimal interventions for older diabetic adults. The Association of Specialty Professors, along with the National Institute on Aging, the National Institute of Diabetes and Digestive and Kidney Diseases, the National Heart, Lung, and Blood Institute, and the American Diabetes Association, held a workshop, summarized in this Perspective, to discuss current knowledge regarding diabetes and cardiovascular disease in older adults, identify gaps, and propose questions to guide future research.

HDL in innate and adaptive immunity

During infections or acute conditions high-density lipoproteins cholesterol (HDL-C) levels decrease very rapidly and HDL particles undergo profound changes in their composition and function. These changes are associated with poor prognosis following endotoxemia or sepsis and data from genetically modified animal models support a protective role for HDL. The same is true for some parasitic infections, where the key player appears to be a specific and minor component of HDL, namely apoL-1. The ability of HDL to influence cholesterol availability in lipid rafts in immune cells results in the modulation of toll-like receptors, MHC-II complex, as well as B- and T-cell receptors, while specific molecules shuttled by HDL such as sphingosine-1-phosphate (S1P) contribute to immune cells trafficking. Animal models with defects associated with HDL metabolism and/or influencing cell cholesterol efflux present features related to immune disorders. All these functions point to HDL as a platform integrating innate and adaptive immunity. The aim of this review is to provide an overview of the connection between HDL and immunity in atherosclerosis and beyond.

High density lipoproteins and type 2 diabetes: Emerging concepts in their relationship

Patients with type 2 diabetes mellitus (T2DM) frequently exhibit macrovascular complications of atherosclerotic cardiovascular (CV) disease. High density lipoproteins (HDL) are protective against atherosclerosis. Low levels of HDL cholesterol (HDL-C) independently contribute to CV risk. Patients with T2DM not only exhibit low HDL-C, but also dysfunctional HDL. Furthermore, low concentration of HDL may increase the risk for the development of T2DM through a decreased β cell survival and secretory function. In this paper, we discuss emerging concepts in the relationship of T2DM with HDL.

Epigenome-wide association study of fasting measures of glucose, insulin, and HOMA-IR in the Genetics of Lipid Lowering Drugs and Diet Network study

Known genetic susceptibility loci for type 2 diabetes (T2D) explain only a small proportion of heritable T2D risk. We hypothesize that DNA methylation patterns may contribute to variation in diabetes-related risk factors, and this epigenetic variation across the genome can contribute to the missing heritability in T2D and related metabolic traits. We conducted an epigenome-wide association study for fasting glucose, insulin, and homeostasis model assessment of insulin resistance (HOMA-IR) among 837 nondiabetic participants in the Genetics of Lipid Lowering Drugs and Diet Network study, divided into discovery (N = 544) and replication (N = 293) stages. Cytosine guanine dinucleotide (CpG) methylation at ∼470,000 CpG sites was assayed in CD4(+) T cells using the Illumina Infinium HumanMethylation 450 Beadchip. We fit a mixed model with the methylation status of each CpG as the dependent variable, adjusting for age, sex, study site, and T-cell purity as fixed-effects and family structure as a random-effect. A Bonferroni corrected P value of 1.1 × 10(-7) was considered significant in the discovery stage. Significant associations were tested in the replication stage using identical models. Methylation of a CpG site in ABCG1 on chromosome 21 was significantly associated with insulin (P = 1.83 × 10(-7)) and HOMA-IR (P = 1.60 × 10(-9)). Another site in the same gene was significant for HOMA-IR and of borderline significance for insulin (P = 1.29 × 10(-7) and P = 3.36 × 10(-6), respectively). Associations with the top two signals replicated for insulin and HOMA-IR (P = 5.75 × 10(-3) and P = 3.35 × 10(-2), respectively). Our findings suggest that methylation of a CpG site within ABCG1 is associated with fasting insulin and merits further evaluation as a novel disease risk marker.

Stress and the inflammatory process: a major cause of pancreatic cell death in type 2 diabetes

Type 2 diabetes (T2D) is a complex metabolic disorder characterized by hyperglycemia in the context of insulin resistance, which precedes insulin deficiency as a result of β-cell failure. Accumulating evidence indicates that β-cell loss in T2D results as a response to the combination of oxidative stress and endoplasmic reticulum (ER) stress. Failure of the ER's adaptive capacity and further activation of the unfolded protein response may trigger macroautophagy (hereafter referred as autophagy) as a process of self-protection and inflammation. Many studies have shown that inflammation plays a very important role in the pathogenesis of T2D. Inflammatory mechanisms and cytokine production activated by stress via the inflammasome may further alter the normal structure of β-cells by inducing pancreatic islet cell apoptosis. Thus, the combination of oxidative and ER stress, together with autophagy insufficiency and inflammation, may contribute to β-cell death or dysfunction in T2D. Therapeutic approaches aimed at ameliorating stress and inflammation may therefore prove to be promising targets for the development of new diabetes treatment methods. Here, we discuss different mechanisms involved in stress and inflammation, and the role of antioxidants, endogenous and chemical chaperones, and autophagic pathways, which may shift the tendency from ER stress and apoptosis toward cell survival. Strategies targeting cell survival can be essential for relieving ER stress and reestablishing homeostasis, which may diminish inflammation and prevent pancreatic β-cell death associated with T2D.

Low high-density lipoprotein cholesterol level is a significant risk factor for development of type 2 diabetes: Data from the Hawaii-Los Angeles-Hiroshima study

Aims/Introduction

A low level of high‐density lipoprotein cholesterol (HDLC) is a common feature of metabolic syndrome. We have reported that Japanese–Americans who share a virtually identical genetic makeup with native Japanese, but who have lived Westernized lifestyles for decades, have lower HDLC levels and a high prevalence of type 2 diabetes compared with native Japanese. However, the impact of low HDLC level on type 2 diabetes is unclear. The aims of the present study were to evaluate whether serum HDLC level was associated with development of type 2 diabetes and if the effect might be modified by lifestyle.

Materials and Methods

We examined 1,133 non‐diabetic Japanese–Americans and 1,072 non‐diabetic Japanese, who underwent the 75‐g oral glucose tolerance test (OGTT) and were followed for an average of 8.8 and 7.0 years, respectively. We analyzed whether serum HDLC level is a risk factor for development of type 2 diabetes based on the Cox proportional hazards model.

Results

After adjustment for age and sex, hazard ratios for development of type 2 diabetes per unit of serum HDLC level (mmol/L) were 0.292 (95% confidence interval [CI] 0.186–0.458, P < 0.0001) among Japanese–Americans and 0.551 (95% CI 0.375–0.88, P = 0.0023) among native Japanese. Comparable hazard ratios after further adjustment for category of OGTT and body mass index were 0.981 (95% CI 0.970–0.993, P = 0.0018) and 0.991 (95% CI 0.980–1.002, P = 0.112), respectively.

Conclusions

HDLC level was associated with development of type 2 diabetes in both Japanese–Americans and native Japanese. However, these results suggest that the impact of high‐density lipoprotein on glucose metabolism might be affected by lifestyle.

High density lipoprotein: a therapeutic target in type 2 diabetes

High density lipoproteins (HDLs) have a number of properties that have the potential to inhibit the development of atherosclerosis and thus reduce the risk of having a cardiovascular event. These protective effects of HDLs may be reduced in patients with type 2 diabetes, a condition in which the concentration of HDL cholesterol is frequently low. In addition to their potential cardioprotective properties, HDLs also increase the uptake of glucose by skeletal muscle and stimulate the synthesis and secretion of insulin from pancreatic β cells and may thus have a beneficial effect on glycemic control. This raises the possibility that a low HDL concentration in type 2 diabetes may contribute to a worsening of diabetic control. Thus, there is a double case for targeting HDLs in patients with type 2 diabetes: to reduce cardiovascular risk and also to improve glycemic control. Approaches to raising HDL levels include lifestyle factors such as weight reduction, increased physical activity and stopping smoking. There is an ongoing search for HDL-raising drugs as agents to use in patients with type 2 diabetes in whom the HDL level remains low despite lifestyle interventions.

Role of HDL cholesterol and estimates of HDL particle composition in future development of type 2 diabetes in the general population: the PREVEND study

BACKGROUND AND AIMS

High-density lipoproteins (HDLs) may directly stimulate β-cell function and glucose metabolism. We determined the relationships of fasting high-density lipoprotein cholesterol (HDL-C), plasma apolipoprotein (apo) A-I and apoA-II, and HDL-C-to-apoA-I and HDL-C-to-apoA-II ratios, as estimates of HDL particle composition, with incident type 2 diabetes mellitus.

METHODS

A prospective study was carried out in the Prevention of Renal and Vascular End-Stage Disease (PREVEND) cohort after exclusion of subjects with diabetes at baseline (n = 6820; age, 28-75 years). The association of HDL-related variables with incident type 2 diabetes was determined by multivariate logistic regression analyses.

RESULTS

After a median follow-up of 7.7 years, 394 incident cases of type 2 diabetes mellitus were ascertained (5.8%). After adjustment for age, sex, family history of diabetes, body mass index, hypertension, alcohol, and smoking, odd ratios (ORs) for diabetes were 0.55 (95% confidence interval [CI], 0.47-0.64; P < .001), 0.81 (0.71-0.93; P = .002), 0.02 (0.01-0.06; P < .001), and 0.03 (0.01-0.060; P < .001) per 1-SD increase in HDL-C and apoA-I and in the HDL-C-to-apoA-I and the HDL-C-to-apoA-II ratios, respectively. In contrast, apoA-II was not related to incident diabetes (OR = 1.02; 95% CI, 0.90-1.16; P=0.71). The relationships of HDL-C and the ratios of HDL-C to apoA-I and HDL-C to apoA-II remained significant after further adjustment for baseline glucose and triglycerides (OR(HDL) = 0.74 [95% CI, 0.61-0.88], OR(HDL/APO A-I) = 0.14 [0.04-0.44], and OR(HDL/APOA-II) = 0.12 [0.04-0.36]; all P ≤ .001).

CONCLUSIONS

Higher HDL-C, as well as higher HDL-C-to-apoA-I and HDL-C-to-apoA-II ratios are strongly and independently related to a lower risk of future type 2 diabetes.

Statins and diabetes: the good, the bad, and the unknown

The ability for statins to reduce major cardiovascular events and mortality has lead to this drug class being the most commonly prescribed in the world. In particular, the benefit of these drugs in type 2 diabetes (T2D) is well established. In February 2012, the Food and Drug Administration released changes to statin safety label to include that statins have been associated with increases in hemoglobin A1C and fasting serum glucose levels. This has stirred much debate in the medical community. Estimate for new onset diabetes from statin treatment is approximately one in 255 patients over four years. The number needed to treat for statin benefit is estimated at one in 40 depending on the population. The mechanism of this link remains unknown. Statins may accelerate progression to diabetes via molecular mechanisms that impact insulin resistance and cellular metabolism of carbohydrates. It remains clear that the benefit of statin therapy outweighs the risk of developing diabetes.

Low prevalence of type 2 diabetes mellitus among patients with high levels of high-density lipoprotein cholesterol

BACKGROUND

Diabetes mellitus and low levels of high-density lipoprotein cholesterol (HDL-C) are among several known risk factors for coronary artery disease. Recent research has shown potential mechanistic links between these two diseases.

OBJECTIVES

The aim of our study was to characterize, by examining particular coronary artery disease risk factors, patients with extremely high and low levels of HDL-C who were referred to a prevention clinic.

METHODS

We compared the phenotypes of 113 patients with HDL-C levels greater than the 90th percentile with 212 patients with levels less than the 10th percentile by using a retrospective chart review.

RESULTS

The cohort with high HDL-C had a remarkable difference in the incidence of type 2 diabetes (1.8% vs 21.7%). The high HDL-C cohort also had a greater age (52.1 years vs 46.7 years), more light or moderate alcohol consumption (70.8% vs 49.4%), more healthy diet (30.1% vs 22.4%), more light or moderate exercise (90.8% vs 52.2%), and a lower body mass index (25.2 kg/m² vs 28.1 kg/m²).

CONCLUSIONS

Compared with the low HDL-C group--and also the general population--the high HDL-C cohort had a remarkably low prevalence of diabetes mellitus.

Genetic determinants of cardiometabolic risk: a proposed model for phenotype association and interaction

This review provides a translational and unifying summary of metabolic syndrome genetics and highlights evidence that genetic studies are starting to unravel and untangle origins of the complex and challenging cluster of disease phenotypes. The associated genes effectively express in the brain, liver, kidney, arterial endothelium, adipocytes, myocytes, and β cells. Progression of syndrome traits has been associated with ectopic lipid accumulation in the arterial wall, visceral adipocytes, myocytes, and liver. Thus, it follows that the genetics of dyslipidemia, obesity, and nonalcoholic fatty liver disease are central in triggering progression of the syndrome to overt expression of disease traits and have become a key focus of interest for early detection and for designing prevention and treatments. To support the "birds' eye view" approach, we provide a road-map depicting commonality and interrelationships between the traits and their genetic and environmental determinants based on known risk factors, metabolic pathways, pharmacologic targets, treatment responses, gene networks, pleiotropy, and association with circadian rhythm. Although only a small portion of the known heritability is accounted for and there is insufficient support for clinical application of gene-based prediction models, there is direction and encouraging progress in a rapidly moving field that is beginning to show clinical relevance.

Statins and diabetes mellitus: risks and benefits

Patients with diabetes mellitus (DM) are at a high risk of cardiovascular events (CVE). Currently, the predominant clinical strategy of the CVE prevention in DM patients is aggressive lowering of low-density lipoprotein cholesterol and blood pressure levels. In this clinical group, statins are among the most widely used pharmacological agents. Recent clinical evidence suggests that statin therapy could be associated with an increased risk of DM. Both clinicians and researchers need to reevaluate the issue of statin safety in the patients at a higher CVE risk. This review focuses on the problem of DM development in statin-treated patients.

Niacin: another look at an underutilized lipid-lowering medication

Niacin, or water-soluble vitamin B(3), when given at pharmacologic doses, is a powerful lipid-altering agent. This drug, which lowers the levels of atherogenic, apolipoprotein-B-containing lipoproteins, is one of few medications that can raise the levels of atheroprotective HDL cholesterol. Niacin also has beneficial effects on other cardiovascular risk factors, including lipoprotein(a), C-reactive protein, platelet-activating factor acetylhydrolase, plasminogen activator inhibitor 1 and fibrinogen. Many clinical trials have confirmed the lipid effects of niacin treatment; however, its effects on cardiovascular outcomes have been called into question owing to the AIM-HIGH trial, which showed no benefit of niacin therapy on cardiovascular endpoints. Furthermore, use of niacin has historically been limited by tolerability issues. In addition to flushing, worsened hyperglycaemia among patients with diabetes mellitus has also been a concern with niacin therapy. This article reviews the utility of niacin including its mechanism of action, clinical trial data regarding cardiovascular outcomes, adverse effect profile and strategies to address these effects and improve compliance.

Statins are diabetogenic--myth or reality?

Multiple clinical trials have demonstrated the beneficial effects of statins in lowering levels of low-density lipoprotein and in the prevention of cardiovascular disease. However, although statins have a good safety profile, a debate has been ongoing as to whether use of statins increases risk of new-onset diabetes. Recent large scale meta-analyses of statin trials support the concept of a diabetogenic effect of statins, as do some other small trials assessing changes in glycaemia parameters and insulin levels. However, a definitive mechanism of action has not yet been elucidated. Nevertheless, the level of evidence has been sufficient to lead the FDA to make a change to the labelling of statins. This review assesses the current available evidence and offers a clinical perspective.

Progress in HDL-based therapies for atherosclerosis

Atherosclerosis is a chronic inflammatory disease affecting medium and large arteries resulting from a complex interaction between genetic and environmental risk factors that include dyslipidemia, hypertension, diabetes mellitus, and smoking. The most serious manifestations of atherosclerotic vascular disease, such as unstable angina, myocardial infarction, ischemic stroke, and sudden death, largely result from thrombosis superimposed on a disrupted (ruptured or eroded) atherosclerotic plaque. Adoption and maintenance of a healthy lifestyle coupled with management of modifiable risk factors significantly reduce the adverse clinical consequences of athero-thrombosis. Reducing low-density lipoprotein cholesterol levels using statins and other agents serves as the primary pharmacologic approach to stabilize atherosclerotic vascular disease. However, a large residual risk remains, prompting the search for additional therapies for atherosclerosis management, such as raising atheroprotective high-density lipoprotein (HDL) and/or improving HDL function. This review focuses on new and emerging HDL-based therapeutic strategies targeting atherosclerosis.

HDLs protect pancreatic β-cells against ER stress by restoring protein folding and trafficking

Endoplasmic reticulum (ER) homeostasis alteration contributes to pancreatic β-cell dysfunction and death and favors the development of diabetes. In this study, we demonstrate that HDLs protect β-cells against ER stress induced by thapsigargin, cyclopiazonic acid, palmitate, insulin overexpression, and high glucose concentrations. ER stress marker induction and ER morphology disruption mediated by these stimuli were inhibited by HDLs. Using a temperature-sensitive viral glycoprotein folding mutant, we show that HDLs correct impaired protein trafficking and folding induced by thapsigargin and palmitate. The ability of HDLs to protect β-cells against ER stress was inhibited by brefeldin A, an ER to Golgi trafficking blocker. These results indicate that HDLs restore ER homeostasis in response to ER stress, which is required for their ability to promote β-cell survival. This study identifies a cellular mechanism mediating the beneficial effect of HDLs on β-cells against ER stress-inducing factors.

Pancreatic β-cell function relates positively to HDL functionality in well-controlled type 2 diabetes mellitus

BACKGROUND

High density lipoproteins (HDLs) have been implicated in glucose homeostasis. Among subjects with normal fasting glucose (NFG), impaired fasting glucose (IFG) and Type 2 diabetes mellitus (T2DM) we tested whether pancreatic β-cell function relates to HDL functionality, as determined by HDL anti-oxidative capacity and cellular cholesterol efflux to plasma.

SUBJECTS AND METHODS

HDL anti-oxidative capacity (inhibition of LDL oxidation in vitro), cellular cholesterol efflux (the ability of plasma to stimulate cholesterol efflux out of cultured fibroblasts obtained from a single human donor), glucose and insulin were determined in fasting plasma samples from 37 subjects with NFG, 36 with IFG and 22 with T2DM (no glucose lowering drug or insulin treatment; HbA1c 6.0±1.0%). Homeostasis model assessment was used to estimate pancreatic β-cell function (HOMA-β) and insulin resistance (HOMAir).

RESULTS

HOMA-β was lowest, whereas HOMAir was highest in T2DM (P<0.01 and P<0.001 vs. NFG). HDL anti-oxidative capacity and cellular cholesterol efflux did not differ significantly according to glucose tolerance category. In univariate analysis and after controlling for HOMAir both HDL anti-oxidative capacity (P<0.05) and cellular cholesterol efflux (P<0.01) were positively correlated with HOMA-β in T2DM, but not in NFG and IFG. In age-, sex- and HOMAir-adjusted analyses, T2DM status interacted positively with HDL anti-oxidative capacity (P=0.001) and cellular cholesterol efflux (P=0.042) on HOMA-β. HbA1c interacted similarly with HDL functionality measures on HOMA-β.

CONCLUSIONS

Pancreatic β-cell function relates to pathophysiologically relevant measures of HDL function in T2DM, but not in NFG and IFG. Better HDL functionality may contribute to maintenance of β-cell function in subjects with well-controlled T2DM.

Genetic predisposition to dyslipidemia and type 2 diabetes risk in two prospective cohorts

Dyslipidemia has been associated with type 2 diabetes, but it remains unclear whether dyslipidemia plays a causal role in type 2 diabetes. We aimed to examine the association between the genetic predisposition to dyslipdemia and type 2 diabetes risk. The current study included 2,447 patients with type 2 diabetes and 3,052 control participants of European ancestry from the Nurses' Health Study and the Health Professionals Follow-up Study. Genetic predisposition to dyslipidemia was estimated by three genotype scores of lipids (LDL cholesterol, HDL cholesterol, and triglycerides) on the basis of the established loci for blood lipids. Linear relation analysis indicated that the HDL cholesterol and triglyceride genotype scores, but not the LDL cholesterol genotype score, were linearly related to elevated type 2 diabetes risk. Each point of the HDL cholesterol and triglyceride genotype scores was associated with a 3% (odds ratio [OR] 1.03 [95% CI 1.01-1.04]) and a 2% (1.02 [1.00-1.04]) increased risk of developing type 2 diabetes, respectively. The ORs were 1.39 (1.17-1.65) and 1.19 (1.01-1.41) for type 2 diabetes by comparing extreme quartiles of the HDL cholesterol genotype score and triglyceride genotype score, respectively. In conclusion, genetic predisposition to low HDL cholesterol or high triglycerides is related to elevated type 2 diabetes risk.

Loss of both ABCA1 and ABCG1 results in increased disturbances in islet sterol homeostasis, inflammation, and impaired β-cell function

Cellular cholesterol homeostasis is important for normal β-cell function. Disruption of cholesterol transport by decreased function of the ATP-binding cassette (ABC) transporter ABCA1 results in impaired insulin secretion. Mice lacking β-cell ABCA1 have increased islet expression of ABCG1, another cholesterol transporter implicated in β-cell function. To determine whether ABCA1 and ABCG1 have complementary roles in β-cells, mice lacking ABCG1 and β-cell ABCA1 were generated and glucose tolerance, islet sterol levels, and β-cell function were assessed. Lack of both ABCG1 and β-cell ABCA1 resulted in increased fasting glucose levels and a greater impairment in glucose tolerance compared with either ABCG1 deletion or loss of ABCA1 in β-cells alone. In addition, glucose-stimulated insulin secretion was decreased and sterol accumulation increased in islets lacking both transporters compared with those isolated from knockout mice with each gene alone. Combined deficiency of ABCA1 and ABCG1 also resulted in significant islet inflammation as indicated by increased expression of interleukin-1β and macrophage infiltration. Thus, lack of both ABCA1 and ABCG1 induces greater defects in β-cell function than deficiency of either transporter individually. These data suggest that ABCA1 and ABCG1 each make complimentary and important contributions to β-cell function by maintaining islet cholesterol homeostasis in vivo.

Type 2 Diabetes Genetics: Beyond GWAS

The global epidemic of type 2 diabetes mellitus (T2D) is one of the most challenging problems of the 21(st) century leading cause of and the fifth death worldwide. Substantial evidence suggests that T2D is a multifactorial disease with a strong genetic component. Recent genome-wide association studies (GWAS) have successfully identified and replicated nearly 75 susceptibility loci associated with T2D and related metabolic traits, mostly in Europeans, and some in African, and South Asian populations. The GWAS serve as a starting point for future genetic and functional studies since the mechanisms of action by which these associated loci influence disease is still unclear and it is difficult to predict potential implication of these findings in clinical settings. Despite extensive replication, no study has unequivocally demonstrated their clinical role in the disease management beyond progression to T2D from impaired glucose tolerance. However, these studies are revealing new molecular pathways underlying diabetes etiology, gene-environment interactions, epigenetic modifications, and gene function. This review highlights evolving progress made in the rapidly moving field of T2D genetics that is starting to unravel the pathophysiology of a complex phenotype and has potential to show clinical relevance in the near future.

Abnormal Cholesterol is Associated with Prefrontal White Matter Abnormalities among Obese Adults: A Diffusion Tensor Imaging Study

The brain is the most cholesterol-rich organ in the body. Although most of the cholesterol in the brain is produced endogenously, some studies suggest that systemic cholesterol may be able to enter the brain. We investigated whether abnormal cholesterol profiles correlated with diffusion-tensor-imaging-based estimates of white matter microstructural integrity of lean and overweight/obese (o/o) adults. Twenty-two lean and 39 obese adults underwent magnetic resonance imaging, kept a three-day food diary, and had a standardized assessment of fasting blood lipids. The lean group ate less cholesterol-rich food than o/o although both groups ate equivalent servings of food per day. Voxelwise correlational analyses controlling for age, diabetes, and white matter hyperintensities, resulted in two significant clusters of negative associations between abnormal cholesterol profile and fractional anisotropy, located in the left and right prefrontal lobes. When the groups were split, the lean subjects showed no associations, whereas the o/o group expanded the association to three significant clusters, still in the frontal lobes. These findings suggest that cholesterol profile abnormalities may explain some of the reductions in white matter microstructural integrity that are reported in obesity.

Association of lipid and lipoprotein profiles with future development of type 2 diabetes in nondiabetic Korean subjects: a 4-year retrospective, longitudinal study

CONTEXT

Traditional lipid measures are known to be associated with incident type 2 diabetes.

OBJECTIVE

Our objective was to assess the independent association between lipid profiles and the development of type 2 diabetes in nondiabetic Korean subjects over a 4-yr period.

DESIGN AND METHODS

A total of 5577 Koreans without diabetes who underwent consecutive comprehensive health check-ups annually for 5 yr were enrolled. We measured concentrations of total cholesterol (TC), triglyceride (TG), apolipoprotein B (apoB), apolipoprotein A-I, low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) and calculated lipid ratios. The association between incident type 2 diabetes and the initial values for lipid ratios and other lipoprotein components was examined.

RESULTS

Over the course of 4 yr, 330 subjects (5.9%) developed type 2 diabetes. TC, LDL-C, TG, non-HDL, apoB, apoB to apolipoprotein A-I ratio, TC to HDL ratio, TG to HDL ratio, LDL to HDL ratio and apoB to HDL ratio were associated with incident type 2 diabetes in multivariate analysis after adjustment for age and gender. Of these, the ratio of TC to HDL and apoB to HDL showed a significant association with increased risk of type 2 diabetes, compared with other lipoprotein parameters: odds ratio (1.340, 95% confidence interval 1.166-1.538; and 1.338, 95% confidence interval 1.162-1.540), respectively. The odds ratio for the development of type 2 diabetes increased significantly as the tertiles of the baseline ratio of TC to HDL and apoB to HDL increased from the first to the third tertile.

CONCLUSIONS

This study suggests that lipid and lipoprotein profiles can be independently associated with later development of type 2 diabetes in nondiabetic Korean adults in a longitudinal analysis.

Are statins diabetogenic?

PURPOSE OF REVIEW

Statins are widely utilized for low-density lipoprotein lowering and for prevention of atherosclerotic cardiovascular disease. Although these drugs have a good safety record, increased risk of developing diabetes during extended use has recently garnered attention. Here we review clinical trial evidence related to statin use and incident diabetes, and the potential mechanisms for this association.

RECENT FINDINGS

The increased incidence of diabetes with rosuvastatin treatment in Justification for the Use of Statins in Primary Prevention: an intervention Trial Evaluating Rosuvastatin (JUPITER) reignited attention on the link between statin therapy and diabetes. The JUPITER findings are supported by two recent meta-analyses of large-scale placebo-controlled and standard care-controlled trials, which, respectively, observed a 9% [odds ratio 1.09; 95% confidence interval (CI) 1.02-1.17] and 13% (risk ratio 1.13; 95% CI 1.03-1.23) increased risk for incident diabetes associated with statin therapy. However, the underlying mechanisms for this association remain unclear. Experimental evidence supports a paradigm implicating inhibition of β-cell glucose transporters, delayed ATP production, pro-inflammatory and oxidative β-cell effects of plasma-derived cholesterol, inhibition of calcium channel-dependent insulin secretion, and β-cell apoptosis.

SUMMARY

The aggregate of large clinical trials supports the notion that statins modestly increase the risk of incident diabetes. Because diabetes is a risk equivalent condition for coronary and peripheral arterial diseases, these findings create a paradox whereby needed statin therapy may be withheld to avoid excess risk of diabetes while representing the strongest cardiovascular risk reduction tool in diabetics. We simply recommend regular glucose monitoring in patients taking statins.

Perinatal exposure to bisphenol A at reference dose predisposes offspring to metabolic syndrome in adult rats on a high-fat diet

Bisphenol A (BPA), a widely used environmental endocrine disruptor, has been reported to disrupt glucose homeostasis. BPA exposure may be a risk factor for type 2 diabetes. In this study, we investigated the effects of early-life BPA exposure on metabolic syndrome in rat offspring fed a normal diet and a high-fat diet. Pregnant Wistar rats were exposed to BPA (50, 250, or 1250 μg/kg · d) or corn oil throughout gestation and lactation by oral gavage. Offspring were fed a normal diet or a high-fat diet after weaning. Body weight, parameters of glucose and lipid metabolism, morphology, and function of β-cells were measured in offspring. On a normal diet, perinatal exposure to 50 μg/kg · d BPA resulted in increased body weight, elevated serum insulin, and impaired glucose tolerance in adult offspring. On a high-fat diet, such detrimental effects were accelerated and exacerbated. Furthermore, severe metabolic syndrome, including obesity, dyslipidemia, hyperleptindemia, hyperglycemia, hyperinsulinemia, and glucose intolerance, was observed in high-fat-fed offspring perinatally exposed to 50 μg/kg · d BPA. No adverse effect of perinatal BPA exposure at 250 and 1250 μg/kg · d was observed no matter on a normal diet or a high-fat diet. These results suggest that perinatal exposure to BPA at reference dose, but not at high dose, impairs glucose tolerance in adult rat offspring on a normal diet and predisposes offspring to metabolic syndrome at adult on a high-fat diet. High-fat diet intake is a trigger that initiates adverse metabolic effects of BPA.

Evolving concepts on benefits and risks associated with therapeutic strategies to raise HDL

PURPOSE OF REVIEW

To provide an update on high-density lipoprotein (HDL) biology and emerging new HDL-based therapies for athero-thrombosis.

RECENT FINDINGS

Atherosclerotic cardiovascular disease remains a major public health threat despite a significant decline over the past three decades. Although current medical therapies, specifically low-density lipoprotein lowering with statins, reduce cardiovascular events by about 25-35%, a substantial residual risk remains, leading to a search for additional therapeutic interventions. In this regard, HDL has emerged as one important target because of epidemiologic evidence linking HDL levels inversely to cardiovascular events, known vascular protective actions of HDL and experimental and clinical research supporting athero-protective actions of HDL. However, complexities of HDL composition, particle size, and metabolism have suggested that HDL functionality, and how HDL is increased, may be important determinants of its protective effects.

SUMMARY

Thus the possibility that HDL modification could address the residual risk has brought renewed focus on an old HDL-raising drug, niacin, and a number of newer strategies to exploit the vascular benefits of HDL.

The causes and consequences of low levels of high density lipoproteins in patients with diabetes

Type 2 diabetes is commonly accompanied by a low level of high density lipoprotein cholesterol (HDL-C) that contributes to the increased cardiovascular risk associated with this condition. Given that HDLs have the ability to improve increase the uptake of glucose by skeletal muscle and to stimulate the secretion of insulin from pancreatic beta cells the possibility arises that a low HDL concentration in type 2 diabetes may also contribute to a worsening of diabetic control. Thus, there is a double case for raising the level of HDL-C in patients with type 2 diabetes: to reduce cardiovascular risk and to improve glycemic control. Approaches to raising HDL-C include lifestyle factors such as weight reduction, increased physical activity and stopping smoking. Of currently available drugs, the most effective is niacin. Newer formulations of niacin are reasonably well tolerated and have the ability to increase HDL-C by up to 30%. The effect of niacin on cardiovascular events in type 2 diabetes is currently being tested in a large-scale clinical outcome trial.