Regulation of reverse cholesterol transport - a comprehensive appraisal of available animal studies

Plasma levels of high density lipoprotein (HDL) cholesterol are strongly inversely correlated to the risk of atherosclerotic cardiovascular disease. A major recognized functional property of HDL particles is to elicit cholesterol efflux and consequently mediate reverse cholesterol transport (RCT). The recent introduction of a surrogate method aiming at determining specifically RCT from the macrophage compartment has facilitated research on the different components and pathways relevant for RCT. The current review provides a comprehensive overview of studies carried out on macrophage-specific RCT including a quick reference guide of available data. Knowledge and insights gained on the regulation of the RCT pathway are summarized. A discussion of methodological issues as well as of the respective relevance of specific pathways for RCT is also included

Voluntary exercise increases cholesterol efflux but not macrophage reverse cholesterol transport in vivo in mice

Physical exercise beneficially impacts on the plasma lipoprotein profile as well as on the incidence of cardiovascular events and is therefore recommended in primary and secondary prevention strategies against atherosclerotic cardiovascular disease. However, the underlying mechanisms of the protective effect of exercise remain largely unknown. Therefore, the present study tested the hypothesis that voluntary exercise in mice impacts on cholesterol efflux and in vivo reverse cholesterol transport (RCT). After two weeks of voluntary wheel running (average 10.1 ± 1.4 km/day) plasma triglycerides were lower (p < 0.05), while otherwise lipid and lipoprotein levels did not change. Macrophage cholesterol efflux towards plasma was significantly increased in running (n = 8) compared to sedentary (n = 6) mice (14.93 ± 1.40 vs. 12.33 ± 2.60%, p < 0.05). In addition, fecal excretion of bile acids (3.86 ± 0.50 vs. 2.90 ± 0.51 nmol/d, p = 0.001) and neutral sterols (2.75 ± 0.43 vs. 1.94 ± 0.22 nmol/d, p < 0.01) was significantly higher in running mice. However, RCT from macrophages to feces remained essentially unchanged in running mice compared with sedentary controls (bile acids: 3.2 ± 1.0 vs. 2.9 ± 1.1 % of injected dose, n.s.; neutral sterols: 1.4 ± 0.7 vs. 1.1 ± 0.5 % injected dose, n.s.). Judged by the plasma lathosterol to cholesterol ratio, endogenous cholesterol synthesis was increased in exercising mice (0.15 ± 0.03 vs. 0.11 ± 0.02, p < 0.05), while the hepatic mRNA expression of key transporters for biliary cholesterol (Abcg5/g8, Sr-bI) as well as bile acid (Abcb11) and phospholipd (Abcb4) excretion did not change. These data indicate that the beneficial effects of exercise on cardiovascular health include increased cholesterol efflux, but do not extend to other components of RCT. The increased fecal cholesterol excretion observed in running mice is likely explained by higher endogenous cholesterol synthesis, however, it does not reflect increased RCT in the face of unchanged expression of key transporters for biliary sterol secretion

Statin Use Is Prospectively Associated With New-Onset Diabetes After Transplantation in Renal Transplant Recipients

OBJECTIVE New-onset diabetes after transplantation (NODAT) is frequent and worsens graft and patient outcomes in renal transplant recipients (RTRs). In the general population, statins are diabetogenic. This study investigated whether statins also increase NODAT risk in RTRs. RESEARCH DESIGN AND METHODS From a prospective longitudinal study of 606 RTRs (functioning allograft >1year,single academic center, follow-up: median 9.6 [range, 6.6–10.2] years), 95 patients using statins were age-and sex-matched to RTRs not on statins (all diabetes-free at inclusion). RESULTS NODAT incidence was 7.2% (73.3% of these on statins). In Kaplan-Meier (log-rank test, P 5 0.017) and Cox regression analyses (HR 3.86 [95% CI 1.21–12.27]; P 5 0.022), statins were prospectively associated with incident NODAT, even independent of several relevant confounders including immunosuppressive medication and biomarkers of glucose homeostasis. CONCLUSIONS This study demonstrates that statin use is prospectively associated with the development of NODAT in RTRs independent of other recognized risk factors

The triglyceride to HDL-cholesterol ratio and chronic graft failure in renal transplantation

BACKGROUND: Transplant vasculopathy (TV) is a major contributing factor to chronic graft failure in renal transplant recipients (RTR). TV lesions resemble atherosclerosis in several ways, and it is plausible to believe that some risk factors influence both atherosclerotic plaque formation and formation of TV. OBJECTIVE: The objective of this prospective longitudinal study was to determine if dyslipidemia reflected by the triglyceride (TG)/high-density lipoprotein cholesterol (HDL-C) ratio is prospectively associated with death censored chronic graft failure in RTR. METHOD: 454 prospectively included RTR with a functioning graft for at least one year, were followed for a median of 7 years. RTR were matched based on propensity scores to avoid potential confounding and subsequently the association of the TG/HDL-C ratio with the endpoint chronic graft failure, defined as return to dialysis or re-transplantation, was investigated. RESULTS: Linear regression analysis showed that concentration of insulin, male gender, BMI and number of antihypertensives predict the TG/HDL-C ratio. Cox regression showed that the TG/HDL-C ratio is associated with chronic graft failure (HR = 1.43, 95%CI = 1.12-1.84, p = 0.005) in competing risk analysis for mortality. Interaction testing indicated that the relationship of the TG/HDL-C ratio with graft failure is stronger in subjects with a higher insulin concentration. CONCLUSION: Our results demonstrate that the TG/HDL-C ratio has the potential to act as a predictive clinical biomarker. Furthermore, there is a need for closer attention to lipid management in RTR in clinical practice with a focus on triglyceride metabolism. (c) 2021 National Lipid Association. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

High- cholesterol diet does not alter gut microbiota composition in mice

Introduction: Western diet containing both saturated fat and cholesterol impairs cardio- metabolic health partly by modulating diversity and function of the microbiota. While diet containing only high fat has comparable effects, it is unclear how diets only enriched in cholesterol impact the microbiota. Therefore, we aimed to characterize the response of host and microbiota to a high cholesterol ( HC) diet in mice susceptible to cardio- metabolic disease. Methods: LDLR knockout mice received either 1.25% HC or no cholesterol containing control diet ( NC) for 12 weeks before characterizing host cholesterol metabolism and intestinal microbiota composition ( next generation sequencing). Results: HC diet substantially increased plasma ( 1.6- fold) and liver cholesterol levels ( 21- fold), biliary cholesterol secretion ( 4.5- fold) and fecal neutral sterol excretion ( 68- fold, each p <0.001) but not fecal bile acid excretion. Interestingly, despite the profound changes in intestinal cholesterol homeostasis no differences in microbial composition between control and HC- fed mice were detected. In both groups the main phyla were Bacteroidetes ( 55%), Firmicutes ( 27%) and Verrucomicrobia ( 14%). Conclusion: Our results demonstrate that in mice HC diet alone does not alter the microbiota composition despite inducing substantial adaptive changes in whole body cholesterol homeostasis. The impact of Western diet on intestinal microbiota thus appears to be mediated exclusively by its high fat content