Preoperative triglycerides predict post-coronary artery bypass graft survival in diabetic patients: a sex analysis

Low-density lipoprotein receptor is required for cholesteryl ester transfer protein to regulate triglyceride metabolism in both male and female mice

Elevated triglycerides (TGs) and impaired TG clearance increase the risk of cardiovascular disease in both men and women, but molecular mechanisms remain poorly understood. Cholesteryl ester transfer protein (CETP) is a lipid shuttling protein known for its effects on high-density lipoprotein cholesterol. Although mice lack CETP, transgenic expression of CETP in mice alters TG metabolism in males and females by sex-specific mechanisms. A unifying mechanism explaining how CETP alters TG metabolism in both males and females remains unknown. Since low-density lipoprotein receptor (LDLR) regulates both TG clearance and very low density lipoprotein (VLDL) production, LDLR may be involved in CETP-mediated alterations in TG metabolism in both males and females. We hypothesize that LDLR is required for CETP to alter TG metabolism in both males and females. We used LDLR null mice with and without CETP to demonstrate that LDLR is required for CETP to raise plasma TGs and to impair TG clearance in males. We also demonstrate that LDLR is required for CETP to increase TG production and to increase the expression and activity of VLDL synthesis targets in response to estrogen. Additionally, we show that LDLR is required for CETP to enhance β-oxidation. These studies support that LDLR is required for CETP to regulate TG metabolism in both males and females.

Cholesteryl Ester Transfer Protein Impairs Triglyceride Clearance via Androgen Receptor in Male Mice

Elevated postprandial triacylglycerols (TAG) are an important risk factor for cardiovascular disease. Men have higher plasma TAG and impaired TAG clearance compared to women, which may contribute to sex differences in risk of cardiovascular disease. Understanding mechanisms of sex differences in TAG metabolism may yield novel therapeutic targets to prevent cardiovascular disease. Cholesteryl ester transfer protein (CETP) is a lipid shuttling protein known for its effects on high‐density lipoprotein (HDL) cholesterol levels. Although mice lack CETP, we previously demonstrated that transgenic CETP expression in female mice alters TAG metabolism. The impact of CETP on TAG metabolism in males, however, is not well understood. Here, we demonstrate that CETP expression increases plasma TAG in males, especially in very‐low density lipoprotein (VLDL), by impairing postprandial plasma TAG clearance compared to wild‐type (WT) males. Gonadal hormones were required for CETP to impair TAG clearance, suggesting a role for sex hormones for this effect. Testosterone replacement in the setting of gonadectomy was sufficient to restore the effect of CETP on TAG. Lastly, liver androgen receptor (AR) was required for CETP to increase plasma TAG. Thus, expression of CETP in males raises plasma TAG by impairing TAG clearance via testosterone signaling to AR. Further understanding of how CETP and androgen signaling impair TAG clearance may lead to novel approaches to reduce TAG and mitigate risk of cardiovascular disease.

α-Lipoic acid as a triglyceride-lowering nutraceutical

Considering the current obesity epidemic in the United States (>100 million adults are overweight or obese), the prevalence of hypertriglyceridemia is likely to grow beyond present statistics of ∼30% of the population. Conventional therapies for managing hypertriglyceridemia include lifestyle modifications such as diet and exercise, pharmacological approaches, and nutritional supplements. It is critically important to identify new strategies that would be safe and effective in lowering hypertriglyceridemia. α-Lipoic acid (LA) is a naturally occurring enzyme cofactor found in the human body in small quantities. A growing body of evidence indicates a role of LA in ameliorating metabolic dysfunction and lipid anomalies primarily in animals. Limited human studies suggest LA is most efficacious in situations where blood triglycerides are markedly elevated. LA is commercially available as dietary supplements and is clinically shown to be safe and effective against diabetic polyneuropathies. LA is described as a potent biological antioxidant, a detoxification agent, and a diabetes medicine. Given its strong safety record, LA may be a useful nutraceutical, either alone or in combination with other lipid-lowering strategies, when treating severe hypertriglyceridemia and diabetic dyslipidemia. This review examines the current evidence regarding the use of LA as a means of normalizing blood triglycerides. Also presented are the leading mechanisms of action of LA on triglyceride metabolism.

The association of hypertriglyceridemia with cardiovascular events and pancreatitis: a systematic review and meta-analysis

BACKGROUND

Hypertriglyceridemia may be associated with important complications. The aim of this study is to estimate the magnitude of association and quality of supporting evidence linking hypertriglyceridemia to cardiovascular events and pancreatitis.

METHODS

We conducted a systematic review of multiple electronic bibliographic databases and subsequent meta-analysis using a random effects model. Studies eligible for this review followed patients longitudinally and evaluated quantitatively the association of fasting hypertriglyceridemia with the outcomes of interest. Reviewers working independently and in duplicate reviewed studies and extracted data.

RESULTS

35 studies provided data sufficient for meta-analysis. The quality of these observational studies was moderate to low with fair level of multivariable adjustments and adequate exposure and outcome ascertainment. Fasting hypertriglyceridemia was significantly associated with cardiovascular death (odds ratios (OR) 1.80; 95% confidence interval (CI) 1.31-2.49), cardiovascular events (OR, 1.37; 95% CI, 1.23-1.53), myocardial infarction (OR, 1.31; 95% CI, 1.15-1.49), and pancreatitis (OR, 3.96; 95% CI, 1.27-12.34, in one study only). The association with all-cause mortality was not statistically significant.

CONCLUSIONS

The current evidence suggests that fasting hypertriglyceridemia is associated with increased risk of cardiovascular death, MI, cardiovascular events, and possibly acute pancreatitis.Précis: hypertriglyceridemia is associated with increased risk of cardiovascular death, MI, cardiovascular events, and possibly acute pancreatitis.

Triglycerides and heart disease: still a hypothesis?

The purpose of this article is to review the basic and clinical science relating plasma triglycerides and cardiovascular disease. Although many aspects of the basic physiology of triglyceride production, its plasma transport, and its tissue uptake have been known for several decades, the relationship of plasma triglyceride levels to vascular disease is uncertain. Are triglyceride-rich lipoproteins, their influence on high-density lipoprotein and low-density lipoprotein, or the underlying diseases that lead to defects in triglyceride metabolism the culprit? Animal models have failed to confirm that anything other than early fatty lesions can be produced by triglyceride-rich lipoproteins. Metabolic products of triglyceride metabolism can be toxic to arterial cells; however, these studies are primarily in vitro. Correlative studies of fasting and postprandial triglycerides and genetic diseases implicate very-low-density lipoprotein and their remnants and chylomicron remnants in atherosclerosis development, but the concomitant alterations in other lipoproteins and other risk factors obscure any conclusions about direct relationships between disease and triglycerides. Genes that regulate triglyceride levels also correlate with vascular disease. Human intervention trials, however, have lacked an appropriately defined population and have produced outcomes without definitive conclusions. The time is more than ripe for new and creative approaches to understanding the relationship of triglycerides and heart disease.

Perioperative outcomes of coronary artery bypass grafting: effects of metabolic syndrome and patient's sex

BACKGROUND

Perioperative outcome data related to metabolic syndrome in coronary artery bypass graft (CABG) patients are lacking.

OBJECTIVE

To determine the incidence of metabolic syndrome in CABG patients and whether its presence or the patient's sex affects postoperative lengths of stay in the intensive care unit and hospital.

METHODS

A retrospective observational study in CABG patients. Risk factors from the Society of Thoracic Surgeons' Adult Cardiac Surgery Database were used to categorize patients as having metabolic syndrome. Perioperative outcomes were compared between patients with and without metabolic syndrome and between sexes. Outcomes were based on the operational definitions of the Society of Thoracic Surgeons.

RESULTS

Among 657 patients, 333 had metabolic syndrome; 63.8% (n = 215) of women and 36.9% (n = 118) of men (P <or= .001). Mean postoperative stays were significantly longer in patients who had metabolic syndrome. Women had longer postoperative stays than did men. Mean postoperative stay for women was 2.7 (SD, 3.4) days in the intensive care unit and 8.2 (SD, 7.1) days in the hospital, compared with 2.0 (SD, 3.8) days in the intensive care unit (P = .01) and 6.6 (SD, 6.8) days in the hospital for men (P = .003). Women with metabolic syndrome also had higher rates of in-hospital death (P = .03).

CONCLUSION

Both female patients and patients with metabolic syndrome undergoing CABG surgery are at higher risk for longer postoperative stays. Women with metabolic syndrome are the CABG patients at highest risk for in-hospital death.

The dyslipidemia of diabetes mellitus: giving triglycerides and high-density lipoprotein cholesterol a higher priority?

CVD is the primary cause of morbidity and mortality in patients who have diabetes mellitus. Most such patients have at least one lipid abnormality. Managing these complex lipid disorders is a crucial component of comprehensive diabetes mellitus care and limits the risk for cardiovascular morbidity and mortality. With the high prevalence of mixed lipid disorders, management must focus on all components of the lipid profile. Lowering LDL-C levels remains the first priority, but abnormalities in HDL-C and TG levels also should be treated aggressively. Statins, fibrates, and niacin, along with newer therapies such as ezetimibe, can improve significantly components of the lipid profile. Alone or in combination, these agents can treat the dyslipidemia of diabetes mellitus effectively and safely.

Considerable disturbances of cardiovascular risk factors in women with diabetes and myocardial infarction

OBJECTIVE

To investigate to which extent differences in cardiovascular risk factors explain the increased risk of myocardial infarction (MI) and complication rate in women with diabetes mellitus (DM).

DESIGN

Case-control study.

SUBJECTS

We compared women with diabetes and previous MI (n=29), diabetes but no MI (n=46), prior MI but no diabetes (n=64), and healthy controls (n=125).

MEASUREMENTS

Smoking habits, physical activity, blood pressure (BP), body mass index (BMI), waist/hip ratio (WHR), serum lipids, plasma fibrinogen, and serum sex hormones.

RESULTS

Despite the fact that diabetic women had similar BMI, those with a past MI, compared to diabetic women without MI, had significantly higher WHR (mean, 95% CI) [0.89 (0.87, 0.92) vs. 0.84 (0.81, 0.86) mmol/l, P=.001] and very high S-triglycerides [3.03 (2.23, 3.83) vs. 1.69, (1.39, 1.99) mmol/l, P=.001] and low HDL-cholesterol [1.09 (0.94, 1.24) vs. 1.56 (1.41, 1.71) mmol/l, P<.001], indicating pronounced metabolic disturbances. Women with MI but no diabetes had intermediate values for WHR, triglycerides, and HDL-cholesterol. Furthermore, women with diabetes and MI had significantly higher p-fibrinogen, were smokers, and lived a more sedentary life than the other women. Over half of all women with prior MI were on lipid-lowering therapy and tended to have nonsignificantly lower S-cholesterol than women without MI.

CONCLUSIONS

Women with diabetes who have manifested an MI carry a very substantial cardiovascular risk factor burden, which probably explain their increased morbidity and mortality. In order to improve prognosis, studies targeted at investigating treatment modalities for these abnormalities are needed.

Increased levels of triglycerides, BMI and blood pressure and low physical activity increase the risk of diabetes in Swedish women. A prospective 18-year follow-up of the BEDA study

AIM

To investigate risk factors for the development of diabetes in middle-aged women.

METHODS

A random population sample of 1351 women without prior diabetes or cardiovascular disease, aged 39-65 years, took part in a screening study in 1979-1981 with questionnaires, physical examination and blood sampling. Development of diabetes up to 1998 was identified at a second examination in 1997-1998.

RESULTS

Seventy-three women (5.4%) were diagnosed with diabetes during follow-up. As expected, obesity resulted in a rising age-adjusted risk with hazards ratio 3.2 [95% confidence interval (CI) 1.3, 8.1] at body mass index (BMI) 24-27 kg/m(2), and 8.3 (3.5, 19.7), at BMI > or = 27, compared with BMI < 22 kg/m(2). S-triglycerides (TG) carried a steeply increasing age-adjusted risk with hazards ratio 4.0 (95% CI 2.1, 7.6) already at s-TG 1.0-1.4 mmol/l, 7.1 (3.6, 14.0) at s-TG 1.5-1.9 mmol/l and 9.3 (4.3, 20.2) at s-TG > or = 2.0 mmol/l compared with s-TG < 1.0 mmol/l. Increasing systolic blood pressure (SBP) to 130-144, 145-159 and > or = 160 mmHg escalated the hazards ratio of diabetes to 1.6 (0.8, 3.3), 3.6 (1.7, 7.4) and 5.6 (2.7, 11.4), respectively, compared with SBP < 130 mmHg. Also, low physical activity predicted diabetes, with hazards ratio 2.1 (1.3, 3.3) for sedentary compared with non-sedentary activity. Smoking was not associated with increased risk of diabetes. After adjustment for BMI, SBP and physical activity, increasing TG level remained a strong and significant risk factor for diabetes [hazards ratio 3.0 (1.6, 5.7), 3.7 (1.8, 7.7) and 4.5 (2.0, 10.0), P < 0.001].

CONCLUSIONS

Among middle-aged Swedish women even very slightly elevated s-TG resulted in a considerably enhanced risk of developing diabetes, which was independent of age, BMI, blood pressure and physical activity.

Survival in patients with type 2 diabetes in a Swedish community: skaraborg hypertension and diabetes project

OBJECTIVE

To explore risk factors for all-cause mortality in patients with type 2 diabetes treated in primary care.

RESEARCH DESIGN AND METHODS

A prospective population-based study of 400 patients with type 2 diabetes who consecutively completed an annual checkup in primary care in Skara, Sweden, during 1992-1993. Vital status was ascertained to year 2000. Baseline characteristics as predictors for mortality were analyzed by Cox regression and expressed as relative risks (RRs), with 95% CIs.

RESULTS

During a mean follow-up time of 5.9 years, 131 patients died (56 deaths per 1,000 patients per year). In both sexes, all-cause mortality was predicted by HbA(1c) (by 1%; RR 1.14, 95% CI 1.01-1.27), and by LDL-to-HDL cholesterol ratios (1.15, 1.00-1.32). Increased mortality was also seen with prevalent hypertension (1.72, 1.21-2.44), microalbuminuria (1.87, 1.27-2.76), and previous cardiovascular disease (1.70, 1.15-2.50). Subanalyses revealed that increased mortality related to HbA(1c) was restricted to hypertensive patients with type 2 diabetes (1.23, 1.04-1.47). Serum triglycerides (by 1 mmol/l) predicted all-cause mortality in women (1.25, 1.06-1.47).

CONCLUSIONS

Poor glucose and lipid control and hypertension predicted all-cause mortality. Survival was also predicted by prevalent microalbuminuria and by previous cardiovascular disease. Confirming results from clinical trials, this population-based study has implications for primary and secondary prevention.

Targeting triglycerides as prognostic indicators and determining lowest values for patient benefit

A number of reports demonstrate the importance of serum triglyceride values in predicting the clinical onset of vascular disease. However, adjustment for measurements highly correlated with triglyceride (TG) levels, such as history of diabetes, body mass index, and high-density lipoprotein cholesterol (HDL-C), lessen if not remove the TG contribution to outcomes. More recently, improved analytic approaches have more persuasively implicated triglycerides as independently relevant to the onset of cardiovascular disease. Elevated TG values are the consequence of larger TG-rich particles, including very low density lipoprotein and atherogenic intermediate particles, which are in turn associated with dense low-density lipoprotein. It has been observed that a reduction in TG concentrations often proceeds in parallel with improved clinical outcomes; however, direct correlation between the two has been elusive. This has been demonstrated in multiple pharmacologic trials. However, an improvement in these relationships has been observed when TG-correlated measurements of intermediate particles, low-density lipoprotein density, and HDL-C have been made. National guidelines for cholesterol treatment have now incorporated a TG greater than 200 mg/dL as a secondary treatment trigger, which targets apolipoprotein B-related particles, represented by non-HDL-C (total cholesterol minus HDL-C), as the suggested goal of therapy.

Diabetes and other coronary heart disease risk equivalents

The close association between diabetes and cardiovascular disease suggests that current predictions of a massive increase in the prevalence of type 2 diabetes foreshadow an equally daunting rise in the incidence of vascular disease. The limited cardiovascular benefits obtained by glucose-lowering treatments, although perhaps not surprising, indicate that other cardiovascular risk factors must be given serious consideration as therapeutic targets. The impressive reductions in the number of vascular events observed in diabetic patients, albeit in small patient populations, participating in various drug trials amply justify such an approach. A necessary prerequisite, however, is a clear understanding of the clinical importance of individual risk factors to the occurrence of vascular disease in type 2 diabetic patients. This would appear essential for defining treatment strategies in the face of a bewildering array of potential therapeutic targets. The present review considers recent studies that have assessed the predictive value of risk factors against a diabetic background.

The impact of pioglitazone on glycemic control and atherogenic dyslipidemia in patients with type 2 diabetes mellitus

BACKGROUND

To evaluate the glycemic control, lipid effects, and safety of pioglitazone in patients with type 2 diabetes mellitus.

DESIGN AND METHODS

Patients (n = 197) with type 2 diabetes mellitus, a hemoglobin A1c (HbA1c) > or = 8.0%, fasting plasma glucose (FPG) > 7.7 mmol/l (140 mg/dl), and C-peptide > 0.331 nmol/l (1 ng/ml) were enrolled in this 23-week multi-center (27 sites), double-blind clinical trial and randomized to receive either a placebo or pioglitazone HCl 30 mg (pioglitazone), administered once daily, as monotherapy. Patients were required to discontinue all anti-diabetic medications 6 weeks before receiving study treatment. Efficacy parameters included HbA1c fasting plasma glucose (FPG), serum C-peptide, insulin, triglycerides (Tg), and cholesterol (total cholesterol [TC], high-density lipoprotein-cholesterol [HDL-C], low-density lipoprotein-cholesterol [LDL-C]). Adverse event rates, serum chemistry, and physical examinations were recorded.

RESULTS

Compared with placebo, pioglitazone significantly (P= 0.0001) reduced HbA1c (-1.37% points), FPG (-3.19 mmol/l; -57.5 mg/dl), fasting C-peptide (-0.076+/-0.022 nmol/l), and fasting insulin (-11.88+/-4.70 pmol/l). Pioglitazone significantly (P < 0.001) decreased insulin resistance (HOMA-IR; -12.4+/-7.46%) and improved beta-cell function (Homeostasis Model Assessment (HOMA-BCF); +47.7+/-11.58%). Compared with placebo, fasting serum Tg concentrations decreased (-16.6%; P = 0.0178) and HDL-C concentrations increased (+12.6%; P= 0.0065) with pioglitazone as monotherapy. Total cholesterol and LDL-C changes were not different from placebo. The overall adverse event profile of pioglitazone was similar to that of placebo, with no evidence of drug-induced elevations of serum alanine transaminase (ALT) concentrations or hepatotoxicity.

CONCLUSIONS

Pioglitazone improved insulin resistance and glycemic control, as well as Tg and HDL-C - which suggests that pioglitazone may reduce cardiovascular risk for patients with type 2 diabetes.