Serum apolipoproteins and apolipoprotein-defined lipoprotein subclasses: a hypothesis-generating prospective study of cardiovascular events in T1D

Multifaceted Role of Apolipoprotein C3 in Cardiovascular Disease Risk and Metabolic Disorder in Diabetes

Apolipoprotein C3 (APOC3) plays a critical role in regulating triglyceride levels and serves as a key predictor of cardiovascular disease (CVD) risk, particularly in patients with diabetes. While APOC3 is known to inhibit lipoprotein lipase, recent findings reveal its broader influence across lipoprotein metabolism, where it modulates the structure and function of various lipoproteins. Therefore, this review examines the complex metabolic cycle of APOC3, emphasizing the impact of APOC3-containing lipoproteins on human metabolism, particularly in patients with diabetes. Notably, APOC3 affects triglyceride-rich lipoproteins and causes structural changes in high-, very low-, intermediate-, and low-density lipoproteins, thereby increasing CVD risk. Evidence suggests that elevated APOC3 levels-above the proposed safe range of 10-15 mg/dL-correlate with clinically significant CVD outcomes. Recognizing APOC3 as a promising biomarker for CVD, this review underscores the urgent need for high-throughput, clinically feasible methods to further investigate its role in lipoprotein physiology in both animal models and human studies. Additionally, we analyze the relationship between APOC3-related genes and lipoproteins, reinforcing the value of large-population studies to understand the impact of APOC3 on metabolic diseases. Ultimately, this review supports the development of therapeutic strategies targeting APOC3 reduction as a preventive approach for diabetes-related CVD.

Elevated apolipoprotein C3 augments diabetic kidney disease and associated atherosclerosis in type 2 diabetes

Diabetes increases the risk of both cardiovascular disease and kidney disease. Notably, most of the excess cardiovascular risk in people with diabetes is in those with kidney disease. Apolipoprotein C3 (APOC3) is a key regulator of plasma triglycerides, and it has recently been suggested to play a role in both type 1 diabetes-accelerated atherosclerosis and kidney disease progression. To investigate if APOC3 plays a role in kidney disease in people with type 2 diabetes, we analyzed plasma levels of APOC3 from the Veterans Affairs Diabetes Trial. Elevated baseline APOC3 levels predicted a greater loss of renal function. To mechanistically test if APOC3 plays a role in diabetic kidney disease and associated atherosclerosis, we treated black and tan, brachyury, WT and leptin-deficient (OB; diabetic) mice, a model of type 2 diabetes, with an antisense oligonucleotide (ASO) to APOC3 or a control ASO, all in the setting of human-like dyslipidemia. Silencing APOC3 prevented diabetes-augmented albuminuria, renal glomerular hypertrophy, monocyte recruitment, and macrophage accumulation, partly driven by reduced ICAM1 expression. Furthermore, reduced levels of APOC3 suppressed atherosclerosis associated with diabetes. This suggests that targeting APOC3 might benefit both diabetes-accelerated atherosclerosis and kidney disease.

APOC3 siRNA and ASO therapy for dyslipidemia

PURPOSE OF REVIEW

The aim of this review is to present the clinical indications of apolipoprotein C-III (apoC3) inhibition in the therapeutic arsenal for the treatment of lipid disorders and associated risks and to compare the most advanced modalities of apoC3 inhibition currently available or in development, specifically APOC3 antisense oligonucleotides (ASO) and small interfering RNA (siRNA).

RECENT FINDINGS

ApoC3 inhibition significantly decreases triglyceride levels by mechanisms coupling both lipoprotein lipase (LPL) upregulation and LPL-independent mechanisms. The main apoC3 inhibitors in advanced clinical development are the GalNAc-ASO olezarsen and the GalNAc-siRNA plozasiran. Clinical studies conducted with volanesorsen, the olezarsen precursor, showed a favorable effect on hepatic steatosis (nonalcoholic fatty liver disease, NAFLD). Olezarsen does not appear to be associated with the main side effects attributed to volanesorsen including thrombocytopenia. Plozasiran is in advanced clinical development and requires subcutaneous injection every 3 months and present to-date an efficacy and safety profile comparable to that of the monthly ASO.

SUMMARY

Inhibition of apoC3 is effective across all the spectrum of hypertriglyceridemia, might have a favorable effect on hepatic steatosis (NAFLD) and the effect of apoC3 inhibition on cardiovascular risk is not limited to its effect on plasma triglycerides. APOC3 GalNAc-conjugated ASO and siRNA are both effective in decreasing plasma apoC3 and triglyceride levels.

Apolipoprotein C3: form begets function

Increased circulating levels of apolipoprotein C3 (APOC3) predict cardiovascular disease (CVD) risk in humans, and APOC3 promotes atherosclerosis in mouse models. APOC3's mechanism of action is due in large part to its ability to slow the clearance of triglyceride-rich lipoproteins (TRLs) and their remnants when APOC3 is carried by these lipoproteins. However, different pools and forms of APOC3 exert distinct biological effects or associations with atherogenic processes. Thus, lipid-free APOC3 induces inflammasome activation in monocytes whereas lipid particle-bound APOC3 does not. APOC3-enriched LDL binds better to the vascular glycosaminoglycan biglycan than does LDL depleted of APOC3. Patterns of APOC3 glycoforms predict CVD risk differently. The function of APOC3 bound to HDL is largely unknown. There is still much to learn about the mechanisms of action of different forms and pools of APOC3 in atherosclerosis and CVD, and whether APOC3 inhibition would prevent CVD risk in patients on LDL-cholesterol lowering medications.

Detregiachi C, Gabaldi Rocha M, Cincotto dos Santos Bueno P, Fornari Laurindo L, Barbalho SM. The Influence of Body Fat and Lean Mass on HbA1c and Lipid Profile in Children and Adolescents with Type 1 Diabetes Mellitus

Glycated hemoglobin (HbA1c) is used to assess glycemic control in Type 1 diabetes (DM1) patients. Apolipoproteins play an essential role in DM1 pathophysiology and may be associated with complications and HbA1c. This cross-sectional observational study of 81 children and adolescents of both sexes diagnosed with DM1 investigated the relationship between body fat distribution and lean mass with HbA1C and apolipoprotein values, analyzing biochemical and body composition measurements. A Shapiro-Wilk test with Lilliefors correction, a non-parametric Mann-Whitney test, and others were used with a significance level of 5%. The sample had a diagnosis time of 4.32 years and high blood glucose levels (mean 178.19 mg/dL) and HbA1c (mean 8.57%). Subjects also had a moderate level of adiposity, as indicated by arm and thigh fat areas. The study also found significant differences in the distribution of patients concerning levels of apolipoproteins A and B, with a smaller proportion of patients having undesirable levels. Finally, the study found a significant difference in the distribution of patients with estimated cardiovascular risk based on the ApoB/ApoA-I ratio. Conclusively, visceral fat in children and adolescents with DM1 may increase the risk of DM1 long-term complications owing to its association with elevated HbA1C and apolipoprotein values.

Quartet of APOCs and the Different Roles They Play in Diabetes

APOA1 and APOB are the structural proteins of high-density lipoprotein and APOB-containing lipoproteins, such as low-density lipoprotein and very low-density lipoprotein, respectively. The 4 smaller APOCs (APOC1, APOC2, APOC3, and APOC4) are exchangeable apolipoproteins; they are readily transferred among high-density lipoproteins and APOB-containing lipoproteins. The APOCs regulate plasma triglyceride and cholesterol levels by modulating substrate availability and activities of enzymes interacting with lipoproteins and by interfering with APOB-containing lipoprotein uptake through hepatic receptors. Of the 4 APOCs, APOC3 has been best studied in relation to diabetes. Elevated serum APOC3 levels predict incident cardiovascular disease and progression of kidney disease in people with type 1 diabetes. Insulin suppresses APOC3 levels, and accordingly, elevated APOC3 levels associate with insulin deficiency and insulin resistance. Mechanistic studies in a mouse model of type 1 diabetes have demonstrated that APOC3 acts in the causal pathway of diabetes-accelerated atherosclerosis. The mechanism is likely due to the ability of APOC3 to slow the clearance of triglyceride-rich lipoproteins and their remnants, thereby causing an increased accumulation of atherogenic lipoprotein remnants in lesions of atherosclerosis. Less is known about the roles of APOC1, APOC2, and APOC4 in diabetes.

Hematopoietic NLRP3 and AIM2 Inflammasomes Promote Diabetes-Accelerated Atherosclerosis, but Increased Necrosis Is Independent of Pyroptosis

Serum apolipoprotein C3 (APOC3) predicts incident cardiovascular events in people with type 1 diabetes, and silencing of APOC3 prevents both lesion initiation and advanced lesion necrotic core expansion in a mouse model of type 1 diabetes. APOC3 acts by slowing the clearance of triglyceride-rich lipoproteins, but lipid-free APOC3 has recently been reported to activate an inflammasome pathway in monocytes. We therefore investigated the contribution of hematopoietic inflammasome pathways to atherosclerosis in mouse models of type 1 diabetes. LDL receptor-deficient diabetes mouse models were transplanted with bone marrow from donors deficient in NOD, LRR and pyrin domain-containing protein 3 (NLRP3), absent in melanoma 2 (AIM2) or gasdermin D (GSDMD), an inflammasome-induced executor of pyroptotic cell death. Mice with diabetes exhibited inflammasome activation and consistently, increased plasma interleukin-1β (IL-1β) and IL-18. Hematopoietic deletions of NLRP3, AIM2, or GSDMD caused smaller atherosclerotic lesions in diabetic mice. The increased lesion necrotic core size in diabetic mice was independent of macrophage pyroptosis because hematopoietic GSDMD deficiency failed to prevent necrotic core expansion in advanced lesions. Our findings demonstrate that AIM2 and NLRP3 inflammasomes contribute to atherogenesis in diabetes and suggest that necrotic core expansion is independent of macrophage pyroptosis.

ARTICLE HIGHLIGHTS

The contribution of hematopoietic cell inflammasome activation to atherosclerosis associated with type 1 diabetes is unknown. The goal of this study was to address whether hematopoietic NOD, LRR, and pyrin domain-containing protein 3 (NLRP3), absent in melanoma 2 (AIM2) inflammasomes, or the pyroptosis executioner gasdermin D (GSDMD) contributes to atherosclerosis in mouse models of type 1 diabetes. Diabetic mice exhibited increased inflammasome activation, with hematopoietic deletions of NLRP3, AIM2, or GSDMD causing smaller atherosclerotic lesions in diabetic mice, but the increased lesion necrotic core size in diabetic mice was independent of macrophage pyroptosis. Further studies on whether inflammasome activation contributes to cardiovascular complications in people with type 1 diabetes are warranted.

High-Density Lipoprotein in Metabolic Disorders and Beyond: An Exciting New World Full of Challenges and Opportunities

High-density lipoprotein (HDL) is an enigmatic member of the plasma lipid and lipoprotein transport system, best known for its ability to promote the reverse cholesterol efflux and the unloading of excess cholesterol from peripheral tissues. More recently, data in experimental mice and humans suggest that HDL may play important novel roles in other physiological processes associated with various metabolic disorders. Important parameters in the HDL functions are its apolipoprotein and lipid content, further reinforcing the principle that HDL structure defines its functionality. Thus, based on current evidence, low levels of HDL-cholesterol (HDL-C) or dysfunctional HDL particles contribute to the development of metabolic diseases such as morbid obesity, type 2 diabetes mellitus, and nonalcoholic fatty liver disease. Interestingly, low levels of HDL-C and dysfunctional HDL particles are observed in patients with multiple myeloma and other types of cancer. Therefore, adjusting HDL-C levels within the optimal range and improving HDL particle functionality is expected to benefit such pathological conditions. The failure of previous clinical trials testing various HDL-C-raising pharmaceuticals does not preclude a significant role for HDL in the treatment of atherosclerosis and related metabolic disorders. Those trials were designed on the principle of "the more the better", ignoring the U-shape relationship between HDL-C levels and morbidity and mortality. Thus, many of these pharmaceuticals should be retested in appropriately designed clinical trials. Novel gene-editing-based pharmaceuticals aiming at altering the apolipoprotein composition of HDL are expected to revolutionize the treatment strategies, improving the functionality of dysfunctional HDL.

Apolipoprotein C3 induces inflammasome activation only in its delipidated form

Matters arising regarding the lipidation form of plasma APOC3 that induces an alternative NLRP3 activation pathway.

Cardiovascular Disease in Adults with Type 1 Diabetes: Looking Beyond Glycemic Control

PURPOSE OF REVIEW

Despite improvements in treatment, people with type 1 diabetes continue to have increased cardiovascular disease (CVD) risk. Glycemic control does not fully explain this excess CVD risk, so a greater understanding of other risk factors is needed.

RECENT FINDINGS

The authors review the relationship between glycemia and CVD risk in adults with type 1 diabetes and summarize evidence regarding other factors that may explain risk beyond glycemia. Insulin resistance, weight gain, sex differences, genetics, inflammation, emerging markers of risk, including lipid subclasses and epigenetic modifications, and future directions are discussed. As glycemic control improves, an increased focus on other CVD risk factors is warranted in type 1 diabetes. Novel markers and precision medicine approaches may improve CVD prediction, but a lack of type 1 diabetes-specific guidelines for lipids, blood pressure, and physical activity are likely impediments to optimal CVD prevention in this high-risk population.

The Remnant Lipoprotein Hypothesis of Diabetes-Associated Cardiovascular Disease

Both type 1 and type 2 diabetes are associated with an increased risk of atherosclerotic cardiovascular disease (CVD). Research based on human-first or bedside-to-bench approaches has provided new insights into likely mechanisms behind this increased risk. Although both forms of diabetes are associated with hyperglycemia, it is becoming increasingly clear that altered lipoprotein metabolism also plays a critical role in predicting CVD risk in people with diabetes. This review examines recent findings indicating that increased levels of circulating remnant lipoproteins could be a missing link between diabetes and CVD. Although CVD risk associated with diabetes is clearly multifactorial in nature, these findings suggest that we should increase efforts in evaluating whether remnant lipoproteins or the proteins that govern their metabolism are biomarkers of incident CVD in people living with diabetes and whether reducing remnant lipoproteins will prevent the increased CVD risk associated with diabetes.

Apolipoprotein C-III predicts cardiovascular events and mortality in individuals with type 1 diabetes and albuminuria

OBJECTIVES

We studied apolipoprotein C-III (apoC-III) in relation to diabetic kidney disease (DKD), cardiovascular outcomes, and mortality in type 1 diabetes.

METHODS

The cohort comprised 3966 participants from the prospective observational Finnish Diabetic Nephropathy Study. Progression of DKD was determined from medical records. A major adverse cardiac event (MACE) was defined as acute myocardial infarction, coronary revascularization, stroke, or cardiovascular mortality through 2017. Cardiovascular and mortality data were retrieved from national registries.

RESULTS

ApoC-III predicted DKD progression independent of sex, diabetes duration, blood pressure, HbA_1c , smoking, LDL-cholesterol, lipid-lowering medication, DKD category, and remnant cholesterol (hazard ratio [HR] 1.43 [95% confidence interval 1.05-1.94], p = 0.02). ApoC-III also predicted the MACE in a multivariable regression analysis; however, it was not independent of remnant cholesterol (HR 1.05 [0.81-1.36, p = 0.71] with remnant cholesterol; 1.30 [1.03-1.64, p = 0.03] without). DKD-specific analyses revealed that the association was driven by individuals with albuminuria, as no link between apoC-III and the outcome was observed in the normal albumin excretion or kidney failure categories. The same was observed for mortality: Individuals with albuminuria had an adjusted HR of 1.49 (1.03-2.16, p = 0.03) for premature death, while no association was found in the other groups. The highest apoC-III quartile displayed a markedly higher risk of MACE and death than the lower quartiles; however, this nonlinear relationship flattened after adjustment.

CONCLUSIONS

The impact of apoC-III on MACE risk and mortality is restricted to those with albuminuria among individuals with type 1 diabetes. This study also revealed that apoC-III predicts DKD progression, independent of the initial DKD category.

Contribution of hypertriglyceridemia to ischemic cardiovascular disease in Korean Women: A nationwide population-based study

BACKGROUND

The independent effect of serum triglyceride levels on the development of ischemic cardiovascular disease (CVD) remains inconclusive, which might be due to heterogeneity among study populations.

OBJECTIVE

To evaluate the effect of triglyceride levels on ischemic CVD and mortality in Korean women, with stratification according to the menopausal status, diabetes mellitus, or low-density lipoprotein cholesterol levels (LDL-C).

METHODS

We retrospectively investigated Korean women aged 40-69 years who underwent health examination in 2009 and were followed up until 2018 using nationwide claim data. The subjects were divided according to triglyceride quartiles (Q): Q1 <70 mg/dL, Q2 71-99 mg/dL, Q3 100-142 mg/dL, and Q4 ≥143 mg/dL. The primary outcome was the incidence of CVD defined as a composite of myocardial infarction and ischemic stroke.

RESULTS

Among 2,208,347 women, primary outcome occurred in 62,255 (2.8%) subjects. As triglyceride levels increased, the event rate of primary outcome increased in both premenopausal and postmenopausal women in the fully adjusted model (hazard ratio [HR] per 1 Q, 1.10 [95% confidence interval (CI), 1.08-1.12] and 1.08 [95% CI, 1.07-1.09], respectively), which was maintained on further stratification according to diabetes or LDL-C (P<0.05 in all). Higher triglyceride levels were more significantly associated with the primary outcome, MI, and stroke risk among women with optimal non-high-density lipoprotein cholesterol levels (non-HDL-C) <130 mg/dL, but only weakly with stroke for women with non-optimal non-HDL-C.

CONCLUSION

Triglyceride is an independent prognosticator in the development of ischemic CVD in Korean women aged 40-69 years.

CREBH normalizes dyslipidemia and halts atherosclerosis in diabetes by decreasing circulating remnant lipoproteins

Loss-of-function mutations in the transcription factor CREB3L3 (CREBH) associate with severe hypertriglyceridemia in humans. CREBH is believed to lower plasma triglycerides by augmenting the action of lipoprotein lipase (LPL). However, by using a mouse model of type 1 diabetes mellitus (T1DM), we found that greater liver expression of active CREBH normalized both elevated plasma triglycerides and cholesterol. Residual triglyceride-rich lipoprotein (TRL) remnants were enriched in apolipoprotein E (APOE) and impoverished in APOC3, an apolipoprotein composition indicative of increased hepatic clearance. The underlying mechanism was independent of LPL as CREBH reduced both triglycerides and cholesterol in LPL-deficient mice. Instead, APOE was critical for CREBH's ability to lower circulating remnant lipoproteins because it failed to reduce TRL cholesterol in Apoe-/- mice. Importantly, humans with CREB3L3 loss-of-function mutations exhibited increased levels of remnant lipoproteins that were deprived of APOE. Recent evidence suggests that impaired clearance of TRL remnants promotes cardiovascular disease in patients with T1DM. Consistently, we found that hepatic expression of CREBH prevented the progression of diabetes-accelerated atherosclerosis. Our results support the proposal that CREBH acts through an APOE-dependent pathway to increase hepatic clearance of remnant lipoproteins. They also implicate elevated levels of remnants in the pathogenesis of atherosclerosis in T1DM.

Cardiovascular disease in diabetes, beyond glucose

Despite the decades-old knowledge that diabetes mellitus is a major risk factor for cardiovascular disease, the reasons for this association are only partially understood. While this association is true for both type 1 and type 2 diabetes, different pathophysiological processes may be responsible. Lipids and other risk factors are indeed important, whereas the role of glucose is less clear. This lack of clarity stems from clinical trials that do not unambiguously show that intensive glycemic control reduces cardiovascular events. Animal models have provided mechanisms that link diabetes to increased atherosclerosis, and evidence consistent with the importance of factors beyond hyperglycemia has emerged. We review clinical, pathological, and animal studies exploring the pathogenesis of atherosclerosis in humans living with diabetes and in mouse models of diabetes. An increased effort to identify risk factors beyond glucose is now needed to prevent the increased cardiovascular disease risk associated with diabetes.

Association of apolipoprotein C3 with insulin resistance and coronary artery calcium in patients with type 1 diabetes

BACKGROUND

Apolipoprotein C3 (APOC3) is a risk factor for incident coronary artery disease in people with type 1 diabetes (T1D). The pathways that link elevated APOC3 levels to an increased risk of incident cardiovascular disease in people with T1D are not understood.

OBJECTIVE

To explore potential mechanisms, we investigated the association of APOC3 with insulin resistance and coronary artery calcium (CAC).

METHODS

In a random subcohort of participants with T1D from Coronary Artery Calcification in Type 1 Diabetes (n = 134), serum APOC3, high-density lipoprotein (HDL)-associated APOC3, and retinol binding protein 4 (RBP4; a potential marker of insulin resistance) were measured by targeted mass spectrometry. We used linear regression to evaluate associations of serum APOC3 and HDL-APOC3 with APOB, non-HDL cholesterol, serum- and HDL-associated RBP4, and estimated insulin sensitivity and logistic regression to evaluate association with presence of CAC, adjusted for age, sex, and diabetes duration.

RESULTS

Serum APOC3 correlated positively with APOB and non-HDL cholesterol and was associated with increased odds of CAC (odds ratio: 1.68, P = .024). Estimated insulin sensitivity was not associated with serum- or HDL-RBP4 but was negatively associated with serum APOC3 in men (ß estimate: -0.318, P = .0040) and decreased odds of CAC (odds ratio: 0.434, P = .0023).

CONCLUSIONS

Serum APOC3 associates with increased insulin resistance and CAC in T1D.

Atherosclerosis: cell biology and lipoproteins

PURPOSE OF REVIEW

Lipoproteins have significant role in both the promotion and prevention of atherosclerosis. This brief review will focus on recent reports on relationship between HDL and HDL subclasses and their composition and function, the role of apoC-III in metabolism of triglyceride-rich lipoproteins, the impact of Lipoprotein (a) (Lp(a)) on endothelial cells, and the mechanism of uptake of aggregated LDL by macrophages.

RECENT FINDINGS

The complexity of the protein and lipid content of murine and human HDL and their relationship to its cholesterol efflux capacity have been examined. HDL has also been shown to have both antiatherogenic and proatherogenic properties. The relationship between apoC-III and LPL activity, apoprotein E mediated clearance of triglyceride-rich lipoproteins and the potential importance of apoC-III in the increased risk of cardiovascular disease in type 1 diabetics has been investigated. Oxidized phospholipid in Lp(a) promotes endothelial cells inflammatory and glycolytic responses. TLR4 participates in the uptake of aggregated LDL to contribute to foam cell formation.

SUMMARY

These studies contribute to our mechanistic understanding of how lipoproteins contribute to atherogenesis and identify potential therapeutic targets.

Apolipoprotein Proteomic Profiling for the Prediction of Cardiovascular Death in Patients with Heart Failure

PURPOSE

Risk stratification in chronic systolic heart failure (HF) is critical to identify the patients who may benefit from advanced therapies. It is aimed at identifying new biomarkers to improve prognosis evaluation and help to better understand HF physiopathology.

EXPERIMENTAL DESIGN

Prognostic evaluation is performed in 198 patients with chronic systolic HF: 99 patients who died from cardiovascular cause within three years are individually matched for age, sex, and HF etiology (ischemic vs not) with 99 patients who are alive after three years of HF evaluation. A proteomic profiling of 15 apolipoproteins (Apo) is performed: Apo-A1, -A2, -A4, -B100, -C1, -C2, -C3, -C4, -D, -E, -F, -H, -J, -L1, and -M using LC-MRM-MS.

RESULTS

In univariate analysis, the levels of Apo-B100 and -L1 are significantly lower and the levels of Apo-C1, -J, and -M are significantly higher in patients who died from cardiovascular cause as compared with patients alive. In the final statistical model, Apo-C1, Apo-J, and Apo-M improve individually the prediction of cardiovascular death. Ingenuity pathway analysis indicates these three Apo in a network associated with lipid metabolism, atherosclerosis signaling, and retinoid X receptor activation.

CONCLUSIONS

Proteomic profiling of apolipoproteins using LC-MRM-MS might be useful in clinical practice for risk stratification of HF patients.

Prognostic utility of triglyceride-rich lipoprotein-related markers in patients with coronary artery disease

TG-rich lipoprotein (TRL)-related biomarkers, including TRL-cholesterol (TRL-C), remnant-like lipoprotein particle-cholesterol (RLP-C), and apoC-III have been associated with atherosclerosis. However, their prognostic values have not been fully determined, especially in patients with previous CAD. This study aimed to examine the associations of TRL-C, RLP-C, and apoC-III with incident cardiovascular events (CVEs) in the setting of secondary prevention of CAD. Plasma TRL-C, RLP-C, and total apoC-III were directly measured. A total of 4,355 participants with angiographically confirmed CAD were followed up for the occurrence of CVEs. During a median follow-up period of 5.1 years (interquartile range: 3.9-6.4 years), 543 (12.5%) events occurred. Patients with incident CVEs had significantly higher levels of TRL-C, RLP-C, and apoC-III than those without events. Multivariable Cox analysis indicated that a log unit increase in TRL-C, RLP-C, and apoC-III increased the risk of CVEs by 49% (95% CI: 1.16-1.93), 21% (95% CI: 1.09-1.35), and 40% (95% CI: 1.11-1.77), respectively. High TRL-C, RLP-C, and apoC-III were also independent predictors of CVEs in individuals with LDL-C levels ≤1.8 mmol/l (n = 1,068). The addition of RLP-C level to a prediction model resulted in a significant increase in discrimination, and all three TRL biomarkers improved risk reclassification. Thus, TRL-C, RLP-C, and apoC-III levels were independently associated with incident CVEs in Chinese CAD patients undergoing statin therapy.

Emerging Targets for Cardiovascular Disease Prevention in Diabetes

Type 1 and type 2 diabetes mellitus (T1DM and T2DM) increase the risk of atherosclerotic cardiovascular disease (CVD), resulting in acute cardiovascular events, such as heart attack and stroke. Recent clinical trials point toward new treatment and prevention strategies for cardiovascular complications of T2DM. New antidiabetic agents show unexpected cardioprotective benefits. Moreover, genetic and reverse translational strategies have revealed potential novel targets for CVD prevention in diabetes, including inhibition of apolipoprotein C3 (APOC3). Modeling and pharmacology-based approaches to improve insulin action provide additional potential strategies to combat CVD. The development of new strategies for improved diabetes and lipid control fuels hope for future prevention of CVD associated with diabetes.

Dyslipidemia in Type 1 Diabetes: AMaskedDanger

Type 1 diabetes (T1D) patients show lipid disorders which are likely to play a role in their increased cardiovascular (CV) disease risk. Quantitative abnormalities of lipoproteins are noted in T1D with poor glycemic control. In T1D with optimal glycemic control, triglycerides and LDL-cholesterol are normal or slightly decreased whereas HDL-cholesterol is normal or slightly increased. T1D patients, even with good glycemic control, show several qualitative and functional abnormalities of lipoproteins that are potentially atherogenic. An association between these abnormalities and CV disease risk has been reported in recent studies. Although the mechanisms underlying T1D dyslipidemia remain unclear, the subcutaneous route of insulin administration, that is responsible for peripheral hyperinsulinemia, is likely to be an important factor.

Intracellular and Intercellular Aspects of Macrophage Immunometabolism in Atherosclerosis

Macrophage immunometabolism, the changes in intracellular metabolic pathways that alter the function of these highly plastic cells, has been the subject of intense interest in the past few years, in part because macrophage immunometabolism plays important roles in atherosclerosis and other inflammatory diseases. In this review article, part of the Compendium on Atherosclerosis, we introduce the concepts of (1) intracellular immunometabolism-the canonical pathways of intrinsic cell activation leading to changes in intracellular metabolism, which in turn alter cellular function; and (2) intercellular immunometabolism-conditions in which intermediates of cellular metabolism are transferred from one cell to another, thereby altering the function of the recipient cell. The recent discovery that the metabolite cargo of dead and dying cells ingested through efferocytosis by macrophages can alter metabolic pathways and downstream function of the efferocyte is markedly changing the way we think about macrophage immunometabolism. Metabolic transitions of macrophages contribute to their functions in all stages of atherosclerosis, from lesion initiation to formation of advanced lesions characterized by necrotic cores, to lesion regression following aggressive lipid lowering. This review article discusses recent advances in our understanding of these different aspects of macrophage immunometabolism in atherosclerosis. With the increasing understanding of the roles of macrophage immunometabolism in atherosclerosis, new exciting concepts and potential targets for intervention are emerging.

Remnants of the Triglyceride-Rich Lipoproteins, Diabetes, and Cardiovascular Disease

Diabetes is now a pandemic disease. Moreover, a large number of people with prediabetes are at risk for developing frank diabetes worldwide. Both type 1 and type 2 diabetes increase the risk of atherosclerotic cardiovascular disease (CVD). Even with statin treatment to lower LDL cholesterol, patients with diabetes have a high residual CVD risk. Factors mediating the residual risk are incompletely characterized. An attractive hypothesis is that remnant lipoprotein particles (RLPs), derived by lipolysis from VLDL and chylomicrons, contribute to this residual risk. RLPs constitute a heterogeneous population of lipoprotein particles, varying markedly in size and composition. Although a universally accepted definition is lacking, for the purpose of this review we define RLPs as postlipolytic partially triglyceride-depleted particles derived from chylomicrons and VLDL that are relatively enriched in cholesteryl esters and apolipoprotein (apo)E. RLPs derived from chylomicrons contain apoB48, while those derived from VLDL contain apoB100. Clarity as to the role of RLPs in CVD risk is hampered by lack of a widely accepted definition and a paucity of adequate methods for their accurate and precise quantification. New specific methods for RLP quantification would greatly improve our understanding of their biology and role in promoting atherosclerosis in diabetes and other disorders.

Monocytes and Macrophages as Protagonists in Vascular Complications of Diabetes

With the increasing prevalence of diabetes worldwide, vascular complications of diabetes are also on the rise. Diabetes results in an increased risk of macrovascular complications, with atherosclerotic cardiovascular disease (CVD) being the leading cause of death in adults with diabetes. The exact mechanisms for how diabetes promotes CVD risk are still unclear, although it is evident that monocytes and macrophages are key players in all stages of atherosclerosis both in the absence and presence of diabetes, and that phenotypes of these cells are altered by the diabetic environment. Evidence suggests that at least five pro-atherogenic mechanisms involving monocytes and macrophages contribute to the accelerated atherosclerotic lesion progression and hampered lesion regression associated with diabetes. These changes include (1) increased monocyte recruitment to lesions; (2) increased inflammatory activation; (3) altered macrophage lipid accumulation and metabolism; (4) increased macrophage cell death; and (5) reduced efferocytosis. Monocyte and macrophage phenotypes and mechanisms have been revealed mostly by different animal models of diabetes. The roles of specific changes in monocytes and macrophages in humans with diabetes remain largely unknown. There is an ongoing debate on whether the changes in monocytes and macrophages are caused by altered glucose levels, insulin deficiency or insulin resistance, lipid abnormalities, or combinations of these factors. Current research in humans and mouse models suggests that reduced clearance of triglyceride-rich lipoproteins and their remnants is one important mechanism whereby diabetes adversely affects macrophages and promotes atherosclerosis and CVD risk. Although monocytes and macrophages readily respond to the diabetic environment and can be seen as protagonists in diabetes-accelerated atherosclerosis, they are likely not instigators of the increased CVD risk.

Increased apolipoprotein C3 drives cardiovascular risk in type 1 diabetes

Type 1 diabetes mellitus (T1DM) increases the risk of atherosclerotic cardiovascular disease (CVD) in humans by poorly understood mechanisms. Using mouse models of T1DM-accelerated atherosclerosis, we found that relative insulin deficiency rather than hyperglycemia elevated levels of apolipoprotein C3 (APOC3), an apolipoprotein that prevents clearance of triglyceride-rich lipoproteins (TRLs) and their remnants. We then showed that serum APOC3 levels predict incident CVD events in subjects with T1DM in the Coronary Artery Calcification in Type 1 Diabetes (CACTI) study. To explore underlying mechanisms, we investigated the impact of Apoc3 antisense oligonucleotides (ASOs) on lipoprotein metabolism and atherosclerosis in a mouse model of T1DM. Apoc3 ASO treatment abolished the increased hepatic Apoc3 expression in diabetic mice - resulting in lower levels of TRLs - without improving glycemic control. APOC3 suppression also prevented arterial accumulation of APOC3-containing lipoprotein particles, macrophage foam cell formation, and the accelerated atherosclerosis in diabetic mice. Our observations demonstrate that relative insulin deficiency increases APOC3 and that this results in elevated levels of TRLs and accelerated atherosclerosis in a mouse model of T1DM. Because serum levels of APOC3 predicted incident CVD events in the CACTI study, inhibiting APOC3 might reduce CVD risk in T1DM patients.