Cardiovascular risk factors and LDL subfraction profile in Type 2 diabetes mellitus subjects with good glycaemic control

Exploring the Interactions between Obesity and Diabetes: Implications for Understanding Metabolic Dysregulation in a Saudi Arabian Adult Population

The rising prevalence of obesity in Saudi Arabia is a major contributor to the nation's high levels of cardiometabolic diseases such as type 2 diabetes. To assess the impact of obesity on the diabetic metabolic phenotype presented in young Saudi Arabian adults, participants (n = 289, aged 18-40 years) were recruited and stratified into four groups: healthy weight (BMI 18.5-24.99 kg/m2) with (n = 57) and without diabetes (n = 58) or overweight/obese (BMI > 24.99 kg/m2) with (n = 102) and without diabetes (n = 72). Distinct plasma metabolic phenotypes associated with high BMI and diabetes were identified using nuclear magnetic resonance spectroscopy and ultraperformance liquid chromatography mass spectrometry. Increased plasma glucose and dysregulated lipoproteins were characteristics of obesity in individuals with and without diabetes, but the obesity-associated lipoprotein phenotype was partially masked in individuals with diabetes. Although there was little difference between diabetics and nondiabetics in the global plasma LDL cholesterol and phospholipid concentration, the distribution of lipoprotein particles was altered in diabetics with a shift toward denser and more atherogenic LDL5 and LDL6 particles, which was amplified in the presence of obesity. Further investigation is warranted in larger Middle Eastern populations to explore the dysregulation of metabolism driven by interactions between obesity and diabetes in young adults.

Causal effects of genetically predicted type 2 diabetes mellitus on blood lipid profiles and concentration of particle-size-determined lipoprotein subclasses: A two-sample Mendelian randomization study

Background

Observational studies have shown inconsistent results of the associations between type 2 diabetes mellitus (T2DM) and blood lipid profiles, while there is also a lack of evidence from randomized controlled trials (RCTs) for the causal effects of T2DM on blood lipid profiles and lipoprotein subclasses.

Objectives

Our study aimed at investigating the causal effects of T2DM on blood lipid profiles and concentration of particle-size-determined lipoprotein subclasses by using the two-sample Mendelian randomization (MR) method.

Methods

We obtained genetic variants for T2DM and blood lipid profiles including high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol (LDL-C), triglycerides (TG), and total cholesterol (TC) from international genome-wide association studies (GWASs). Two-sample MR method was applied to explore the potential causal effects of genetically predicted T2DM on blood lipid profiles based on different databases, respectively, and results from each MR analysis were further meta-analyzed to obtain the summary results. The causal effects of genetically predicted T2DM on the concentration of different subclasses of lipoproteins that are determined by particle size were also involved in MR analysis.

Results

Genetically predicted 1-unit higher log odds of T2DM had a significant causal effect on a higher level of TG (estimated β coefficient: 0.03, 95% confidence interval [CI]: 0.00 to 0.06) and lower level of HDL-C (estimated β coefficient: −0.09, 95% CI: −0.11 to −0.06). The causality of T2DM on the level of TC or LDL-C was not found (estimated β coefficient: −0.01, 95% CI: −0.02 to 0.01 for TC and estimated β coefficient: 0.01, 95% CI: −0.01 to 0.02 for LDL-C). For different sizes of lipoprotein particles, 1-unit higher log odds of T2DM was causally associated with higher level of small LDL particles, and lower level of medium HDL particles, large HDL particles, and very large HDL particles.

Conclusion

Evidence from our present study showed causal effects of T2DM on the level of TG, HDL-C, and concentration of different particle sizes of lipoprotein subclasses comprehensively, which might be particularly helpful in illustrating dyslipidemia experienced by patients with T2DM, and further indicate new treatment targets for these patients to prevent subsequent excessive cardiovascular events from a genetic point of view.

Elevation of small, dense low density lipoprotein cholesterol-a possible antecedent of atherogenic lipoprotein phenotype in type 2 diabetes patients in Jos, North-Central Nigeria

BACKGROUND

The global prevalence of type 2 diabetes is increasing. Dyslipidaemia is a known complication of diabetes mellitus manifesting frequently as cardiovascular diseases and stoke. Elevation of small, dense low density lipoprotein has been recognised as a component of the atherogenic lipoprotein phenotype associated with cardiovascular complications. We speculate that the elevation of this lipoprotein particle may be the antecedent of the atherogenic lipoprotein phenotype. This study therefore aims to determine the pattern of dyslipidaemia among diabetes mellitus patients in Jos, North-Central Nigeria.

METHODS

One hundred and seventy-six patients with type 2 diabetes and 154 age-matched controls were studied. The patients with diabetes were regular clinic attenders and had stable glycaemic control. None were on lipid-lowering therapy. Anthropometric indices, blood pressure, and lipids (including total cholesterol, high density lipoprotein cholesterol, and triglyceride) were measured by chemical methods using the Hitachi 902 analyzer. Low density lipoprotein cholesterol was calculated using the Friedewald's equation. Small, dense low density lipoprotein cholesterol, -sdLDL-C was measured using the precipitation method by Hirano et al. Means of the different groups were compared using EPI Info and a P-value of <0.05 was accepted as significant difference.

RESULTS

Total cholesterol, low density lipoprotein cholesterol, triglyceride and small, dense lipoprotein cholesterol were all significantly higher in diabetes patients than controls except high density lipoprotein cholesterol. The percentage of LDL-C as sdLDL-C among the diabetes versus control group was 45% ± 17.79 v 32.0% ± 15.93. Serum sdLDL-C concentration was determined to be 1.45 ± 0.64 among diabetes patients and 0.8 ± 0.54 among control subjects. 75% of diabetes patients had hypertension and were taking blood pressure lowering medications.

CONCLUSION

The classical atherogenic lipoprotein phenotype was not demonstrated among subjects with type 2 diabetes mellitus in this study, but the elevation of serum small dense low density lipoprotein cholesterol in patients with sustained hypertension suggests the establishment of atherogenic complications among our diabetes patients.

Prevalence of hypogonadism in male Type 2 diabetes mellitus patients with and without coronary artery disease

AIM

The present study is carried out to investigate hypogonadism using serum testosterone levels in male Type 2 diabetes mellitus (T2DM) subjects with and without coronary artery disease (CAD).

SUBJECTS AND METHODS

A total of 150 age and body mass index-matched male subjects in the age group of 30-70 years were recruited in three groups; Group A - subjects with normal glucose tolerance, Group B - T2DM subjects without CAD, and Group C - T2DM subjects with CAD (n = 50 each group). Subjects with CAD were diagnosed on the basis of electrocardiogram, treadmill testing, stress echocardiography, or coronary angiography. Total testosterone (TT), free testosterone (FT), bioavailable testosterone, calculated FT and glycemic parameters were measured and compared between all the three study groups. One-way ANOVA followed by post hoc Tukey's test and Pearson's coefficient of correlation tests were used for analysis.

RESULTS

Hypogonadism (TT <3 ng/ml) was observed in 40% (20/50) of subjects in Group C and 32% (16/50) of subjects in Group B as compared to only 14% (7/50) of subjects in Group A (Groups A vs. B; P = 0.055, Groups A vs. C; P = 0.006 and Groups B vs. C; P = 0.53). Group C subjects had significantly lower levels of TT (3.55 ± 1.46 ng/ml vs. 4.73 ± 2.17 ng/ml, P = 0.005), calculated FT (0.062 ± 0.0255 pg/ml vs. 0.0951 ± 0.0508 pg/ml, P ≤ 0.001), and bioavailable testosterone (1.48 ± 0.65 ng/ml vs. 2.18 ± 1.20 ng/ml, P ≤ 0.001) compared to control Group A subjects. There was no significant difference in any of the testosterone parameters between Groups A and B. Furthermore, an overall positive correlation was found between hypogonadism and CAD (r = 0.177, P = 0.030, n = 150).

CONCLUSION

We observed hypogonadism as indicated by low testosterone levels in a significant proportion of male T2DM subjects with CAD.

Lipid effects and cardiovascular disease risk associated with glucose-lowering medications

Diabetes is a global epidemic, associated with a high burden of complications and 4.6 million deaths annually worldwide. As a result of decreasing levels of physical activity and increasing rates of obesity, diabetes is shifting from a disease affecting the elderly to one that affects younger patients or even children. Thus, aggressive treatment and optimal control of risk factors is the key to improve outcomes in those patients. Accumulating evidence of the cardiovascular and lipid effects of glucose-lowering medications suggest that treatment efficacy in diabetes can be further improved. This review provides an overview of the lipid effects and cardiovascular disease risk of current anti-diabetic medications and highlights opportunities and challenges in clinical practice.

Effects of Sitagliptin on Lipid Profiles in Patients With Type 2 Diabetes Mellitus: A Meta-analysis of Randomized Clinical Trials

Sitagliptin has been reported to improve lipid profiles, but findings from these studies are conflicting. We conducted this meta-analysis to evaluate the effects of sitagliptin on serum lipids in patients with type 2 diabetes mellitus.We made a comprehensive literature search in PubMed, EMBASE, Cochrane Library, China National Knowledge Infrastructure, Wanfang, and VIP database until June 2015. Eligible studies were randomized clinical trials (RCTs) that investigated the effect of sitagliptin on serum triglycerides (TGs), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), or high-density lipoprotein cholesterol (HDL-C).Eleven RCTs with 2338 patients were identified. Compared with controls, sitagliptin alone or in combination significantly improved serum TG (weighted mean difference [WMD] -0.24 mmol/L; 95% confidence interval [CI] -0.40 to -0.09; P = 0.002) and HDL-C (WMD 0.05 mmol/L; 95% CI 0.02-0.07; P < 0.001).However, no statistical significances were observed in LDL-C (WMD -0.07 mmol/L; 95% CI -0.22 to 0.08; P = 0.337) and TC (WMD -0.14; 95% CI -0.33 to 0.06; P = 0.177). Subgroup analyses revealed that sitagliptin alone achieved greater improvement in serum TG, TC, and HDL-C levels.These findings suggested that sitagliptin alone or in combination significantly improved serum TG and HDL-C levels in patients with type 2 diabetes mellitus.

Dyslipidemia and diabetes: reciprocal impact of impaired lipid metabolism and Beta-cell dysfunction on micro- and macrovascular complications

Patients with diabetes frequently exhibit the combined occurrence of hyperglycemia and dyslipidemia. Published data on their coexistence are often controversial. Some studies provide evidence for suboptimal lifestyle and exogenous hyperinsulinism at "mild insulin resistance" in adult diabetic patients as main pathogenic factors. In contrast, other studies confirm that visceral adiposity and insulin resistance are the basic features of dyslipidemia in type 2 diabetes (T2D). The consequence is an excess of free fatty acids, which causes hepatic gluconeogenesis to increase, metabolism in muscles to shift from glucose to lipid, beta-cell lipotoxicity, and an appearance of the classical "lipid triad", without real hypercholesterolemia. Recently, it has been proposed that cholesterol homeostasis is important for an adequate insulin secretory performance of beta-cells. The accumulation of cholesterol in beta-cells, caused by defective high-density lipoprotein (HDL) cholesterol with reduced cholesterol efflux, induces hyperglycemia, impaired insulin secretion, and beta-cell apoptosis. Data from animal models and humans, including humans with Tangier disease, who are characterized by very low HDL cholesterol levels, are frequently associated with hyperglycemia and T2D. Thus, there is a reciprocal influence of dyslipidemia on beta-cell function and inversely of beta-cell dysfunction on lipid metabolism and micro- and macrovascular complications. It remains to be clarified how these different but mutually influencing adverse effects act in together to define measures for a more effective prevention and treatment of micro- and macrovascular complications in diabetes patients. While the control of circulating low-density lipoprotein (LDL) cholesterol and the level of HDL cholesterol are determinant targets for the reduction of cardiovascular risk, based on recent data, these targets should also be considered for the prevention of beta-cell dysfunction and the development of type 2 diabetes. In this review, we analyze consolidated data and recent advances on the relationship between lipid metabolism and diabetes mellitus, with particular attention to the reciprocal effects of the two features of the disease and the development of vascular complications.

Effects on lipid profile of dipeptidyl peptidase 4 inhibitors, pioglitazone, acarbose, and sulfonylureas: meta-analysis of placebo-controlled trials

INTRODUCTION

Lipid profile is an important determinant of cardiovascular risk in type 2 diabetes. It is well known that patients with type 2 diabetes are more likely to be dyslipidemic than the general population. Given the observed connection between glucose and lipid metabolism in patients with type 2 diabetes, it is conceivable that different glucose-lowering agents can have a varying impact on the lipid profile. When metformin monotherapy fails, other drugs can be added to achieve sufficient glycemic control. Available oral agents include pioglitazone, acarbose, dipeptidyl peptidase 4 (DPP-4) inhibitors, and insulin secretagogs. The present meta-analysis was designed to assess the effect of DPP-4 inhibitors, pioglitazone, insulin secretagogs, and acarbose on blood lipids when compared to placebo.

METHODS

An extensive search (any date up to November 1, 2011) was performed for all trials performed on the following classes of drugs: gliptin, insulin secretagogs, pioglitazone, and acarbose. The following endpoints were considered: endpoint total, high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) and triglycerides.

RESULTS

The difference in mean total cholesterol values at endpoint versus baseline was significantly higher in patients on pioglitazone, sulfonylureas, and DPP-4 inhibitor treatment (but not on acarbose) than those on placebo, demonstrating that treatment with these drugs (except acarbose) is associated with a significant reduction in total cholesterol. With respect to triglycerides, a significant reduction could be observed with acarbose, pioglitazone, and DPP-4 inhibitors, but not with sulfonylureas. HDL-C appeared to be increased by treatment with acarbose and pioglitazone, and decreased by sulfonylureas.

CONCLUSION

The present meta-analysis shows that available glucose-lowering drugs may have varying effects on the lipid profile. DPP-4 inhibitors, acarbose, and pioglitazone seem to have a more favorable effect on the lipid profile than sulfonylureas.

Hypertension strengthens δ-ALA-D activity inhibition and increases it reactivation index in type 2 diabetic patients

AIMS

To assess the effect of hypertension on δ-aminolevulinate dehydratase (δ-ALA-D) activity of type 2 diabetic patients (T2DM).

METHODS

δ-ALA-D activity and reactivation index, as well as markers of oxidative stress, biochemical and anthropometrics parameters were determined in T2DM (n=23), type 2 diabetic patients with hypertension (T2DM/HT) (n=30) and controls (n=30).

RESULTS

T2DM/HT presented a greater inhibition of δ-ALA-D activity, a higher reactivation index (p<0.05) and a greater depletion of plasma protein thiol groups (P-SH) when compared to T2DM. Moreover, δ-ALA-D activity was positively associated with SH groups and negatively associated with serum protein carbonyl (PC) while its reactivation index was negatively associated with SH groups and positively associated with PC.

CONCLUSIONS

These results point out that there is a possible interference of hypertension on the mechanism of the δ-ALA-D activity suggesting that this condition aggravated the oxidative stress of diabetes mellitus.

Effects of insulin and other antihyperglycaemic agents on lipid profiles of patients with diabetes

Increased morbidity and mortality risk due to diabetes-associated cardiovascular diseases is partly associated with hyperglycaemia as well as dyslipidaemia. Pharmacological treatment of diabetic hyperglycaemia involves the use of the older oral antidiabetic drugs [OADs: biguanides, sulphonylureas (SUs), α-glucosidase inhibitors and thiazolidinediones], insulin (human and analogues) and/or incretin-based therapies (glucagon-like peptide-1 analogues and dipeptidyl peptidase 4 inhibitors). Many of these agents have also been suggested to improve lipid profiles in patients with diabetes. These effects may have benefits on cardiovascular risk beyond glucose-lowering actions. This review discusses the effects of OADs, insulins and incretin-based therapies on lipid variables along with the possible mechanisms and clinical implications of these findings. The effects of intensive versus conventional antihyperglycaemic therapy on cardiovascular outcomes and lipid profiles are also discussed. A major conclusion of this review is that agents within the same class of OADs can have different effects on lipid variables and that contrary to the findings in experimental models, insulin has been shown to have beneficial effects on lipid variables in clinical trials. Further studies are needed to understand the precise effect and the mechanisms of these effects of insulin on lipids.

Clinical applications of advanced lipoprotein testing in diabetes mellitus

Traditional lipid profiles often fail to fully explain the elevated cardiovascular risk of individuals with diabetes mellitus. Advanced lipoprotein testing offers a novel means to evaluate dyslipidemia and refine risk estimation. Numerous observational studies have demonstrated a characteristic pattern of elevated levels of small, dense LDL particles, out of proportion to traditional lipid levels, in patients with both diabetes mellitus and the metabolic syndrome. Commonly used glucose and lipid-lowering agents have varied effects in patients with diabetes on both LDL and HDL subfractions. The exact role of advanced lipoprotein testing in patients with diabetes mellitus and the metabolic syndrome remains unclear but may offer improved assessment of cardiovascular risk compared with traditional lipid measurements.

Glycation of LDL by methylglyoxal increases arterial atherogenicity: a possible contributor to increased risk of cardiovascular disease in diabetes

OBJECTIVE

To study whether modification of LDL by methylglyoxal (MG), a potent arginine-directed glycating agent that is increased in diabetes, is associated with increased atherogenicity.

RESEARCH DESIGN AND METHODS

Human LDL was isolated and modified by MG in vitro to minimal extent (MG(min)-LDL) as occurs in vivo. Atherogenic characteristics of MG(min)-LDL were characterized: particle size, proteoglycan-binding, susceptibility to aggregation, LDL and non-LDL receptor-binding, and aortal deposition. The major site of modification of apolipoprotein B100 (apoB100) modification was investigated by mass spectrometric peptide mapping.

RESULTS

MG(min)-LDL contained 1.6 molar equivalents of MG modification-mostly hydroimidazolone-as found in vivo. MG(min)-LDL had decreased particle size, increased binding to proteoglycans, and increased aggregation in vitro. Cell culture studies showed that MG(min)-LDL was bound by the LDL receptor but not by the scavenger receptor and had increased binding affinity for cell surface heparan sulfate-containing proteoglycan. Radiotracer studies in rats showed that MG(min)-LDL had a similar fractional clearance rate in plasma to unmodified LDL but increased partitioning onto the aortal wall. Mass spectrometry peptide mapping identified arginine-18 as the hotspot site of apoB100 modification in MG(min)-LDL. A computed structural model predicted that MG modification of apoB100 induces distortion, increasing exposure of the N-terminal proteoglycan-binding domain on the surface of LDL. This likely mediates particle remodeling and increases proteoglycan binding.

CONCLUSIONS

MG modification of LDL forms small, dense LDL with increased atherogenicity that provides a new route to atherogenic LDL and may explain the escalation of cardiovascular risk in diabetes and the cardioprotective effect of metformin.

Clinical importance and therapeutic modulation of small dense low-density lipoprotein particles

The National Cholesterol Education Programme Adult Treatment Panel III accepted the predominance of small dense low-density lipoprotein (sdLDL) as an emerging cardiovascular disease (CVD) risk factor. Most studies suggest that measuring low-density lipoprotein (LDL) particle size, sdLDL cholesterol content and LDL particle number provides additional assessment of CVD risk. Therapeutic modulation of small LDL size, number and distribution may decrease CVD risk; however, no definitive causal relationship is established, probably due to the close association between sdLDL and triglycerides and other risk factors (e.g., high-density lipoprotein, insulin resistance and diabetes). This review addresses the formation and measurement of sdLDL, as well as the relationship between sdLDL particles and CVD. The effect of hypolipidaemic (statins, fibrates and ezetimibe) and hypoglycaemic (glitazones) agents on LDL size and distribution is also discussed.

Serum cholinesterase activity in diabetes and associated pathologies

Serum cholinesterase activity was measured in diabetes, hypertensive and diabetic/hypertensive patients. The sample consisted of volunteer patients and was divided in a control group (n=26), type 2 diabetic group (n=16), hypertensive group (n=12) and type 2 diabetic/hypertensive group (n=26). In addition, blood glucose, cholesterol and triglyceride levels were determined. Serum cholinesterase activity in the control group was significantly lower in relation to the other groups (p<0.001). Blood glucose levels were elevated in type 2 diabetic and type 2 diabetic/hypertensive groups. In vitro studies showed increased cholinesterase activity in the presence of glucose 5-100mM or insulin 0.5-25 UI (p<0.001). Cholesterol and triglycerides were at normal levels only in the control group. Possibly, a relationship exists between the increase in serum cholinesterase and the vascular complications in the diabetic patients, potentially stimulated by the levels of glycemia and dyslipidemia. Although patients were receiving different medicines, the increase in enzyme activity was similar in all groups. This enzymatic profile suggests a possible interference of the diseases in the catalytic mechanism of the serum cholinesterase enzyme.

Association between LDL particle size and postprandial increase of remnant-like particles in Japanese type 2 diabetic patients

Small, dense LDL, as well as chylomicron- and VLDL-remnant lipoproteins, are known to be important risk factors for coronary heart disease in patients with type 2 diabetes mellitus. The aim of this study was to clarify the relationship between LDL particle size and postprandial remnant lipoprotein levels in Japanese type 2 diabetic patients. Forty-six patients with type 2 diabetes mellitus were divided into tertiles according to LDL particle size. The peak LDL particle diameter was <26.30 nm in tertile 1, 26.30-26.85 nm in tertile 2, and >26.85 nm in tertile 3. After a test meal, tertile 1 had a significantly greater increment of triglycerides (TG), remnant-like particle (RLP)-TG, and RLP-cholesterol (RLP-C) than tertiles 2 and 3. There was a negative correlation between LDL particle size and the postprandial increases of TG, RLP-TG, and RLP-C. These results indicate that smaller sized LDL particles may be a marker of fasting state for an exaggerated postprandial increase of remnant lipoproteins as well as an increase of TG-rich lipoproteins.

Dyslipidemia in patients with type 2 diabetes. relationships between lipids, kidney disease and cardiovascular disease

Type 2 diabetes mellitus is a leading cause of morbidity and mortality. Cardiovascular disease (CVD) is the most prevalent complication and primarily accounts for the excess morbidity and mortality in diabetic patients, but microvascular complications, such as kidney disease and retinopathy, are frequent and contribute to the total disease burden. Lipid abnormalities in patients with type 2 diabetes are a major problem and associated with the increased risk of CVD. The most common pattern of dyslipidemia in these patients consists of elevated levels of triglycerides and low levels of high-density lipoprotein cholesterol. Low-density lipoprotein levels in these patients are often similar to that of the nondiabetic population, although there may be important qualitative differences in the pattern that contribute to the increased risk of CVD. Abnormal levels of urinary albumin occur in 30-40% of patients with type 2 diabetes and the presence of kidney disease enhances the mortality from CVD. Microalbuminuria, an early marker of diabetic nephropathy, is an independent risk factor for CVD. The increased levels of urinary albumin secretion may represent a more generalized vascular damage than renal microvascular injury alone. This Review focuses on the significance of diabetic dyslipidemia and microalbuminuria to CVD risk as well as to kidney complications. We also discuss the role of aggressive therapy to ameliorate vascular injury in the diabetic patient and reduce or prevent the cardiovascular and renal consequences of the disease.