The role of non-LDL:non-HDL particles in atherosclerosis

Associations of normal fasting glucose levels and of insulin resistance with degenerative rotator cuff tear : Normoglycemia and rotator cuff tear

BACKGROUND

The upper normoglycemic range has been proposed as a risk factor for degenerative rotator cuff tendon tear (RCT), and insulin resistance has been suggested as a risk factor for tendinopathy. However, no research has established their association with degenerative RCT in the general population. This study aimed to determine whether fasting glucose levels and insulin resistance are risk factors for degenerative RCT in the normoglycemic population and identify the risk range for fasting glucose.

METHODS

This study included 418 normoglycemic participants from a rural cohort. Participants completed questionnaires, physical exams, blood tests, and MRI evaluations of both shoulders. Insulin resistance was assessed using a triglyceride/high-density-lipoprotein (TG/HDL) ≥ 3.5. Logistic regression analysis was used to determine the association between fasting glucose level, TG/HDL ≥ 3.5, and other factors and degenerative RCT. The study calculated the areas under the receiver operating characteristic curve (AUC) to determine the more appropriate predicting value between the scale and categorical values of fasting glucose levels, and compared the AUCs using the DeLong method.

RESULTS

In the multivariable analyses, both scale and categorical values of fasting glucose levels, and TG/HDL ≥ 3.5 were significantly associated with degenerative RCT. Fasting glucose levels ≥ 90.5 mg/dL (OR: 3.87, 95% CI: 2.10-7.06) in scale value and 90-99 mg/dL (OR: 4.13, 95% CI: 2.87-8.12) in categorical value were significantly associated with degenerative RCT (P < .001). The AUC of the scale value of fasting glucose levels ≥ 90.5 mg/dL was 0.68. The AUC of the categorical value of fasting glucose levels of 90-99 mg/dL was 0.70. Because of the significantly larger AUC of the categorical value of fasting glucose levels of 90-99 mg/dL, those fasting glucose levels were determined to be independently associated with degenerative RCT (P < .001).

CONCLUSIONS

High fasting glucose levels within the normal range may link to increase insulin resistance and risk of degenerative RCT. Normoglycemic levels of 90-99 mg/dL and insulin resistance may be risk factors for degenerative RCT.

LEVEL OF EVIDENCE

Level III, prognostic study.

Involvement of inflammatory lipoproteinemia with idiopathic adhesive capsulitis accompanying subclinical hypothyroidism

BACKGROUND

Thyroid functional abnormalities are considered risk factors for idiopathic adhesive capsulitis (IAC) though that relationship remains uncertain. Although dyslipidemias are associated with IAC, no readily accessible study has reported associations between dyslipidemias and IAC patients with subclinical hypothyroidism. The purposes of this study were to investigate whether subclinical hypothyroidism is an independently associated factor for IAC and to determine the differences in prevalence of dyslipidemias between two groups of persons with subclinical hypothyroidism: one composed of IAC patients and the other of individuals without IAC.

METHODS

This case-control study included a case group of 412 IAC patients without intrinsic shoulder lesions, extrinsic causes, or medication for thyroid dysfunction. The control group comprised 1236 age- and sex-matched persons seeking general checkups at the authors' health promotion center during the same period as the case group. Control subjects had normal shoulder function and no previously diagnosed adhesive capsulitis, no medication for thyroid dysfunction, and no history of trauma or of shoulder surgery. The studied variables were age, gender, obesity, diabetes, dyslipidemias, subclinical hypothyroidism, hypothyroidism, and hyperthyroidism. A conditional logistic regression analysis evaluated the matched sets of subjects to determine odds ratios and 95% confidence intervals for the studied variables. The differences in the prevalence of dyslipidemias between IAC patients with subclinical hypothyroidism and individuals with subclinical hypothyroidism but without IAC were determined with generalized estimating equations, using covariates of age, sex, and diabetes. The P values were set at < 0.05.

RESULTS

Subclinical hypothyroidism (odds ratio, 2.10; 95% confidence interval, 1.36-3.15; P = .001) was significantly associated with IAC. Patients with IAC and subclinical hypothyroidism had a significantly higher prevalence of hyper-low-density lipoproteinemia, an inflammatory lipoproteinemia, than individuals with subclinical hypothyroidism but without IAC (P = .002).

CONCLUSIONS

Subclinical hypothyroidism is significantly associated with IAC. Hyper-low-density lipoproteinemia, an inflammatory lipoproteinemia, is involved in IAC accompanied by subclinical hypothyroidism.

What Serum Lipid Abnormalities Are Associated with Adhesive Capsulitis Accompanied by Diabetes?

BACKGROUND

Adhesive capsulitis is common and can cause stiffness and pain. Diabetes and dyslipidemia are known to be associated with adhesive capsulitis. However, there is no report of any association between serum lipid profiles and adhesive capsulitis accompanied by diabetes.

QUESTION/PURPOSE

Which serum lipid abnormalities are associated with adhesive capsulitis accompanied by diabetes?

METHODS

This is a case-control study with two control groups. Our case group included 37 patients with newly diagnosed adhesive capsulitis accompanied by newly diagnosed diabetes who had no other diagnosed systemic diseases or rotator cuff tears. The two control groups each had 111 age- and sex-matched individuals with normal shoulder function (bilaterally pain-free, with full range of motion and no shoulder muscle weakness), no thyroid dysfunction, and no previously diagnosed systemic diseases. Individuals in the first control group had neither adhesive capsulitis nor diabetes. Individuals in the second control group had newly diagnosed diabetes without adhesive capsulitis. We evaluated any association between adhesive capsulitis accompanied by diabetes and serum lipid profile, including total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglycerides, and nonhigh-density lipoprotein (nonHDL). Conditional logistic regression analysis was used to evaluate the strengths of associations between serum lipid levels and adhesive capsulitis accompanied by diabetes, as determined by odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Low-density lipoprotein and nonHDL were associated with adhesive capsulitis accompanied by diabetes. Specifically, patients with adhesive capsulitis and diabetes had greater odds ratios of hyperlow-density lipoproteinemia when compared with individuals with neither adhesive capsulitis nor diabetes (OR, 3.19; 95% CI, 1.21-8.38; p = 0.019) and when compared with individuals without adhesive capsulitis but with newly diagnosed diabetes (OR, 5.76; 95% CI, 1.67-19.83; p = 0.005). Similarly, patients with adhesive capsulitis accompanied by diabetes had greater odds ratios of hypernonhigh-density lipoproteinemia when compared with individuals with neither adhesive capsulitis nor diabetes (OR, 7.39; 95% CI, 2.72-20.09; p < 0.001) and when compared with individuals without adhesive capsulitis but with newly diagnosed diabetes (OR, 3.26; 95% CI, 1.40-7.61; p = 0.006).

CONCLUSIONS

Inflammatory lipoproteinemias, particularly hyperlow-density lipoproteinemia and hypernonhigh-density lipoproteinemia, are associated with adhesive capsulitis accompanied by diabetes. Further research is needed to evaluate whether inflammatory lipoproteinemias are a cause, a related cofactor, or an aggravating factor in the development of adhesive capsulitis in people who have diabetes.

LEVEL OF EVIDENCE

Level III, prognostic study.

Chewing the fat: genetic approaches to model dyslipidemia-induced diabetic neuropathy in mice

Emerging clinical evidence now suggests that dyslipidemia may be strongly linked with the development and progression of neuropathy in diabetic patients, and dyslipidemia is considered an important risk factor for the development of diabetic neuropathy. However, because of important species differences, current animal models fall short of accurately replicating human diabetic dyslipidemia. Rodents resist expansion in low-density lipoprotein cholesterol (LDL-C) and typically maintain or increase high-density lipoprotein cholesterol (HDL-C), despite prolonged high-fat feeding. Here, we discuss the findings of Hinder et al., in which they utilized novel genetic experimental approaches to develop a diabetic mouse model with human-like dyslipidemia. The authors created a mouse with an apolipoprotein E (ApoE) knockout in conjunction with a leptin receptor mutation. A triple mutant mouse with both ApoE and apolipoprotein B48 knockout and leptin deficiency was also created in an effort to generate a model of diabetic dyslipidemia that better mimics the human condition. The long-term goal of these studies is to develop more faithful models to address how hyperglycemia and hyperlipidemia may drive the development and progression of neuropathy. Hinder and colleagues were successful at creating a diabetic mouse model with severe hypertriglyceridemia, hypercholesterolemia, and a significant increase in the total cholesterol to HDL-C ratio. This work was successful in establishing a model of diabetic dyslipidemia that more closely emulates the poor lipid profile observed in human diabetic patients with neuropathy. This commentary will also review current models used to study the effects of dyslipidemia on diabetic neuropathy and highlight a proposed mechanism for the role of dyslipidemia in the pathogenesis of diabetic neuropathy.

Hypercholesterolemia and microvascular dysfunction: interventional strategies

Hypercholesterolemia is defined as excessively high plasma cholesterol levels, and is a strong risk factor for many negative cardiovascular events. Total cholesterol levels above 200 mg/dl have repeatedly been correlated as an independent risk factor for development of peripheral vascular (PVD) and coronary artery disease (CAD), and considerable attention has been directed toward evaluating mechanisms by which hypercholesterolemia may impact vascular outcomes; these include both results of direct cholesterol lowering therapies and alternative interventions for improving vascular function. With specific relevance to the microcirculation, it has been clearly demonstrated that evolution of hypercholesterolemia is associated with endothelial cell dysfunction, a near-complete abrogation in vascular nitric oxide bioavailability, elevated oxidant stress, and the creation of a strongly pro-inflammatory condition; symptoms which can culminate in profound impairments/alterations to vascular reactivity. Effective interventional treatments can be challenging as certain genetic risk factors simply cannot be ignored. However, some hypercholesterolemia treatment options that have become widely used, including pharmaceutical therapies which can decrease circulating cholesterol by preventing either its formation in the liver or its absorption in the intestine, also have pleiotropic effects with can directly improve peripheral vascular outcomes. While physical activity is known to decrease PVD/CAD risk factors, including obesity, psychological stress, impaired glycemic control, and hypertension, this will also increase circulating levels of high density lipoprotein and improving both cardiac and vascular function. This review will provide an overview of the mechanistic consequences of the predominant pharmaceutical interventions and chronic exercise to treat hypercholesterolemia through their impacts on chronic sub-acute inflammation, oxidative stress, and microvascular structure/function relationships.

Generation and characterization of two novel mouse models exhibiting the phenotypes of the metabolic syndrome: Apob48-/-Lepob/ob mice devoid of ApoE or Ldlr

The metabolic syndrome is a group of disorders including obesity, insulin resistance, atherogenic dyslipidemia, hyperglycemia, and hypertension. To date, few animal models have been described to recapitulate the phenotypes of the syndrome. In this study, we generated and characterized two lines of triple-knockout mice that are deficient in either apolipoprotein E (Apoe(-/-)) or low-density lipoprotein receptor (Ldlr(-/-)) and express no leptin (Lep(ob/ob)) or apolipoprotein B-48 but exclusively apolipoprotein B-100 (Apob(100/100)). These two lines are referred to as Apoe triple-knockout-Apoe 3KO (Apoe(-/-)Apob(100/100)Lep(ob/ob)) and Ldlr triple-knockout-Ldlr 3KO (Ldlr(-/-)Apob(100/100)Lep(ob/ob)) mice. Both lines develop obesity, hyperinsulinemia, hyperlipidemia, hypertension, and atherosclerosis. However, only Apoe 3KO mice are hyperglycemic and glucose intolerant and are more obese than Ldlr 3KO mice. To evaluate the utility of these lines as pharmacological models, we treated both with leptin and found that leptin therapy ameliorated most metabolic derangements. Leptin was more effective in improving glucose tolerance in Ldlr 3KO than Apoe 3KO animals. The reduction of plasma cholesterol by leptin in Ldlr 3KO mice can be accounted for by its suppressive effect on food intake. However, in Apoe 3KO mice, leptin further reduced plasma cholesterol independently of its effect on food intake, and this improvement correlated with a smaller plaque lesion area. These effects suggest a direct role of leptin in modulating VLDL levels and, likewise, the lesion areas in VLDL-enriched animals. These two lines of mice represent new models with features of the metabolic syndrome and will be useful in testing therapies targeted for combating the human condition.

Thermal transitions in human very-low-density lipoprotein: fusion, rupture, and dissociation of HDL-like particles

Very-low-density lipoproteins (VLDL) are metabolic precursors of low-density lipoproteins (LDL) and a risk factor for atherosclerosis. Human VLDL are heterogeneous complexes containing a triacylglycerol-rich apolar lipid core and polar surface composed of phospholipids, a nonexchangeable apolipoprotein B, and exchangeable apolipoproteins E and Cs. We report the first stability study of VLDL. Circular dichroism and turbidity data reveal an irreversible heat-induced VLDL transition that involves formation of larger particles and repacking of apolar lipids but no global protein unfolding. Heating rate effect on the melting temperature indicates a kinetically controlled reaction with high activation energy, Ea. Arrhenius analysis of the turbidity data reveals two kinetic phases with Ea = 53 +/- 7 kcal/mol that correspond to distinct morphological transitions observed by electron microscopy. One transition involves VLDL fusion, partial rupture, and dissociation of small spherical particles (d = 7-15 nm), and another involves complete lipoprotein disintegration and lipid coalescence into droplets accompanied by dissociation of apolipoprotein B. The small particles, which are unique to VLDL denaturation, are comparable in size and density to high-density lipoproteins (HDL); they have an apolar lipid core and polar surface composed of exchangeable apolipoproteins (E and possibly Cs) and phospholipids. We conclude that, similar to HDL and LDL, VLDL are stabilized by kinetic barriers that prevent particle fusion and rupture and decelerate spontaneous interconversion among lipoprotein classes and subclasses. In addition to fusion, VLDL disruption involves transient formation of HDL-like particles that may mimic protein exchange among VLDL and HDL pools in plasma.

Phospholipid Transfer Protein Augments Apoptosis in THP-1–Derived Macrophages Induced by Lipolyzed Hypertriglyceridemic Plasma

OBJECTIVE

Lipolysis of triglyceride-rich lipoproteins (TGRLPs) generates phospholipid-rich surface remnants and induces cytotoxic effects in adjacent vascular cells. We hypothesized that by integrating surface remnants into HDL, phospholipid transfer protein (PLTP) alleviates cytotoxicity.

METHODS AND RESULTS

To test this hypothesis and gain insight into cytotoxicity during the postprandial phase in vivo, we injected normo-TG and hyper-TG human volunteers after a standardized fat meal (postprandial sample) with heparin, thereby stimulating lipolysis (postprandial heparinized sample). Incubation of (primary) human macrophages and primary human endothelial cells with postprandial heparinized hyper-TG plasma induced pronounced cytotoxic effects that were dose dependent on the TG content of the sample. No such effects were seen with normo-TG and postprandial hyper-TG plasma. In vitro lipolysis of VLDL and chylomicrons indicated that both lipoprotein fractions can cause cytotoxicity. Interestingly, in experiments with THP-1-derived macrophages stably transfected with PLTP, PLTP substantially augmented both net phospholipid uptake and apoptotic cell death due to postprandial heparinized hyper-TG plasma. We observed that activation of caspase-3/7, poly-ADP-ribose polymerase, and enhanced bioactivity of acid sphingomyelinase may all contribute to this augmented apoptosis.

CONCLUSIONS

Our data show that lipolysis of TGRLPs and their remodelling by PLTP interact to disturb cellular phospholipid flux and intracellular signaling processes, ultimately leading to apoptosis in human macrophages and endothelial cells.

Alcohol, nutrition and health maintenance: selected aspects

In view of the developments in health care relating to the increased prevalence and incidence of chronic diseases and the continuing increase in health-care expenditure, more attention should be paid to health maintenance and disease prevention. Any strategy that can influence health maintenance is of interest, especially lifestyle factors such as nutrition, exercise or stress control. Alcohol has an important place in the daily life of many healthy as well as sick individuals. Alcohol has three major characteristics; it is a nutrient (energy source), a psycho-active drug and a toxin. Each consumer has the choice of which of the characteristics of alcohol he/she wants to utilise. Thus, alcohol represents one of the most important self-implemented disease modifiers in our modern society. The major determinants of the health effects of alcohol are the absolute amount consumed, the consumption frequency, associated lifestyle factors (e.g. smoking, nutrient intake, substrate composition, physical activity pattern) and last, but not least, the genetic background. There are few known disease conditions that have not already been associated positively or negatively with alcohol consumption. The list of diseases includes atherosclerosis, dementia, diabetes, obesity and conditions relating to Zn metabolism. Obesity represents the most important disease modifier in the world and the prevalence rates are increasing rapidly. Evidence suggests that alcohol represents a risk factor for overweight and obesity as a result of specific effects on energy metabolism and substrate metabolism. The potential role of alcohol as an important modulator for the postprandial lipidaemia and its role in the pathogenesis of modern diseases will be discussed.

Lipids for psychiatrists - an overview

Serum cholesterol is a major risk factor for cardiovascular disease. Total cholesterol, LDL cholesterol and triglycerides are positively related to cardiovascular disease, while HDL cholesterol has an inverse relationship. Measurement of lipids is essential in individuals with established cardiovascular disease or type 2 diabetes, and may also be carried out in healthy individuals as part of cardiovascular risk assessment. Lifestyle measures are important in cardiovascular disease prevention, but the mainstay of lipid lowering therapy is appropriate use of lipid lowering drugs. Total and LDL cholesterol are the primary targets for treatment, but consideration should also be given to raising HDL cholesterol and lowering triglycerides where appropriate. Statins are the most frequently used lipid lowering agents, but there is an important place for other drugs, including ezetimibe, fibrates and nicotinic acid.

Hepatic lipase: friend or foe and under what circumstances?

Hepatic lipase (HL) plays a role in the metabolism of chylomicron and very low-density lipoprotein remnants, low-density lipoproteins (LDL), and high-density lipoproteins (HDL), which are all implicated in atherosclerosis. Considering the effects of HL on these lipoproteins, it appears that HL has pro- as well as antiatherogenic potential. In line with clinical observations, most effects of HL on lipoprotein metabolism during hypertriglyceridemia may be interpreted as promoting atherosclerosis (formation of small, dense LDL, lowering of HDL levels), whereas most effects during hypercholesterolemia seem to be potentially antiatherogenic (stimulation of reverse cholesterol transport, clearing of intermediate-density lipoprotein). The potential modulation of pro- or antiatherogenics effect of HL by other factors, such as LDL receptor, cholesterol ester transfer protein, lipoprotein lipase, and ATP-binding cassette A-1 activity, is discussed.

The significance of serum HDL phospholipid levels in angiographically defined coronary artery disease

OBJECTIVES

To evaluate discriminant serum lipid components associated with the presence and extent of coronary artery disease, with particular emphasis on the role of HDL phospholipids as an important predictor for disease severity.

DESIGN AND METHODS

Total serum lipoprotein and phospholipids levels of 157 adult male patients (grouped based on degree of coronary artery occlusion) who underwent coronary angiography were analyzed.

RESULTS

Patients showed elevated triglyceride (P < 0.001) and VLDL (P < 0.001) levels whereas a significant reduction was observed at LDL (P < 0.01), HDL (P < 0.01), and HDL-phospholipids (P < 0.001) concentrations. Correlation with disease progression (from one to three occluded vessels) showed significant rise in levels (P < 0.001) and markedly decreased HDL phospholipids (P < 0.001).

CONCLUSIONS

Triglyceride levels and HDL phospholipids are better indicators of the presence and extent of coronary artery disease compared to the other lipoproteins studied. Furthermore, the HDL phospholipids/Total Cholesterol ratio is proposed as additional information of the degree of coronary artery occlusion.