Effect of fasting and feeding on apolipoprotein A-I kinetics in preβ1-HDL, α-HDL, and triglyceride-rich lipoproteins

High-Density Lipoprotein Subfractions Remodeling: A Critical Process for the Treatment of Atherosclerotic Cardiovascular Diseases

Numerous studies have shown that a low level of high-density lipoprotein cholesterol (HDL-C) is an independent biomarker of cardiovascular disease. High-density lipoprotein (HDL) is considered to be a protective factor for atherosclerosis (AS). Therefore, raising HDL-C has been widely recognized as a promising strategy to treat atherosclerotic cardiovascular diseases (ASCVD). However, several studies have found that increasing HDL-C levels does not necessarily reduce the risk of ASCVD. HDL particles are highly heterogeneous in structure, composition, and biological function. Moreover, HDL particles from atherosclerotic patients exhibit impaired anti-atherogenic functions and these dysfunctional HDL particles might even promote ASCVD. This makes it uncertain that HDL-raising therapy will prevent and treat ASCVD. It is necessary to comprehensively analyze the structure and function of HDL subfractions. We review current advances related to HDL subfractions remodeling and highlight how current lipid-modifying drugs such as niacin, statins, fibrates, and cholesteryl ester transfer protein inhibitors regulate cholesterol concentration of HDL and specific HDL subfractions.

No effect of liraglutide on high density lipoprotein apolipoprotein AI kinetics in patients with type 2 diabetes

AIM

The catabolism of high density lipoprotein (HDL) apolipoprotein AI (apoAI) is accelerated in patients with type 2 diabetes (T2D), related to hypertriglyceridemia, insulin resistance and low plasma adiponectin levels. Since liraglutide is likely to partly correct these abnormalities, we hypothesized that it might have a beneficial effect on HDL apoAI kinetics in patients with T2D.

METHODS

An in vivo kinetic study of HDL apoAI was performed in 10 patients with T2D before and after 6 months of treatment with 1.2 mg/day of liraglutide, using a bolus of l-[1-13C]leucine followed by a 16-hour constant infusion.

RESULTS

Liraglutide reduced BMI (34.9 ± 4.7 vs 36.6 ± 4.9 kg/m2, P = 0.012), HbA1c (7.1 ± 1.1 vs 9.6 ± 2.6%, P = 0.003), HOMA-IR (5.5 ± 1.9 vs 11.6 ± 11.2, P = 0.003), fasting triglycerides (1.76 ± 0.37 vs 2.48 ± 0.69 mmol/l, P < 0.001) and triglycerides during kinetics (2.34 ± 0.81 vs 2.66 ± 0.65 mmol/l, P = 0.053). Plasma HDL cholesterol and adiponectin concentrations were unchanged (respectively 0.97 ± 0.26 vs 0.97 ± 0.19 mmol/l, P = 1; 3169 ± 1561 vs 2618 ± 1651 µg/l, P = 0.160), similar to triglyceride content in HDL (5.13 ± 1.73 vs 5.39 ± 1.07%, P = 0.386). Liraglutide modified neither HDL apoAI fractional catabolic rate (0.35 ± 0.11 vs 0.38 ± 0.11 pool/day, P = 0.375), nor its production rate (0.44 ± 0.13 vs 0.49 ± 0.15 g/l/day, P = 0.375), nor its plasma concentration (1.26 ± 0.19 vs 1.29 ± 0.14 g/l, P = 0.386).

CONCLUSION

Six months of treatment with 1.2 mg/day of liraglutide had no effect on the kinetics of HDL apoAI in patients with T2D. The lack of decrease in triglyceride content in HDL related to an only moderate decrease in triglyceridemia, probably greatly explains these results. Insufficient improvement of insulin sensitivity and adiponectinemia may also be implied.

Specific Milk Composition of miR-30b Transgenic Mice Associated with Early Duodenum Maturation in Offspring with Lasting Consequences for Growth

BACKGROUND

Milk composition is complex and includes numerous components essential for offspring growth and development. In addition to the high abundance of miR-30b microRNA, milk produced by the transgenic mouse model of miR-30b-mammary deregulation displays a significantly altered fatty acid profile. Moreover, wild-type adopted pups fed miR-30b milk present an early growth defect.

OBJECTIVE

This study aimed to investigate the consequences of miR-30b milk feeding on the duodenal development of wild-type neonates, a prime target of suckled milk, along with comprehensive milk phenotyping.

METHODS

The duodenums of wild-type pups fed miR-30b milk were extensively characterized at postnatal day (PND)-5, PND-6, and PND-15 using histological, transcriptomic, proteomic, and duodenal permeability analyses and compared with those of pups fed wild-type milk. Milk of miR-30b foster dams collected at mid-lactation was extensively analyzed using proteomic, metabolomic, and lipidomic approaches and hormonal immunoassays.

RESULTS

At PND-5, wild-type pups fed miR-30b milk showed maturation of their duodenum with 1.5-fold (P < 0.05) and 1.3-fold (P < 0.10) increased expression of Claudin-3 and Claudin-4, respectively, and changes in 8 duodenal proteins (P < 0.10), with an earlier reduction in paracellular and transcellular permeability (183 ng/mL fluorescein sulfonic acid [FSA] and 12 ng/mL horseradish peroxidase [HRP], respectively, compared with 5700 ng/mL FSA and 90 ng/mL HRP in wild-type; P < 0.001). Compared with wild-type milk, miR-30b milk displayed an increase in total lipid (219 g/L compared with 151 g/L; P < 0.05), ceramide (17.6 μM compared with 6.9 μM; P < 0.05), and sphingomyelin concentrations (163.7 μM compared with 76.3 μM; P < 0.05); overexpression of 9 proteins involved in the gut barrier (P < 0.1); and higher insulin and leptin concentrations (1.88 ng/mL and 2.04 ng/mL, respectively, compared with 0.79 ng/mL and 1.06 ng/mL; P < 0.01).

CONCLUSIONS

miR-30b milk displays significant changes in bioactive components associated with neonatal duodenal integrity and maturation, which could be involved in the earlier intestinal closure phenotype of the wild-type pups associated with a lower growth rate.

Intracellular Cholesterol Trafficking

Cholesterol is an essential lipid species of mammalian cells. Cells acquire it through synthesis in the endoplasmic reticulum (ER) and uptake from lipoprotein particles. Newly synthesized cholesterol is efficiently distributed from the ER to other organelles via lipid-binding/transfer proteins concentrated at membrane contact sites (MCSs) to reach the trans-Golgi network, endosomes, and plasma membrane. Lipoprotein-derived cholesterol is exported from the plasma membrane and endosomal compartments via a combination of vesicle/tubule-mediated membrane transport and transfer through MCSs. In this review, we provide an overview of intracellular cholesterol trafficking pathways, including cholesterol flux from the ER to other membranes, cholesterol uptake from lipoprotein donors and transport from the plasma membrane to the ER, cellular cholesterol efflux to lipoprotein acceptors, as well as lipoprotein cholesterol secretion from enterocytes, hepatocytes, and astrocytes. We also briefly discuss human diseases caused by defects in these processes and therapeutic strategies available in such conditions.

Role of circulating sphingolipids in lipid metabolism: Why dietary lipids matter

Sphingolipids are structural components of cell membranes and lipoproteins but also act as signaling molecules in many pathophysiological processes. Although sphingolipids comprise a small part of the plasma lipidome, some plasma sphingolipids are recognized as implicated in the development of metabolic diseases and cardiovascular diseases. Plasma sphingolipids are mostly carried out into lipoproteins and may modulate their functional properties. Lipids ingested from the diet contribute to the plasma lipid pool besides lipids produced by the liver and released from the adipose tissue. Depending on their source, quality and quantity, dietary lipids may modulate sphingolipids both in plasma and lipoproteins. A few human dietary intervention studies investigated the impact of dietary lipids on circulating sphingolipids and lipid-related cardiovascular risk markers. On the one hand, dietary saturated fatty acids, mainly palmitic acid, may increase ceramide concentrations in plasma, triglyceride-rich lipoproteins and HDL. On the other hand, milk polar lipids may decrease some molecular species of sphingomyelins and ceramides in plasma and intestine-derived chylomicrons. Altogether, different dietary fatty acids and lipid species can modulate circulating sphingolipids vehicled by postprandial lipoproteins, which should be part of future nutritional strategies for prevention of cardiovascular diseases.

Intestinal lipid absorption and transport in type 2 diabetes

Postprandial hyperlipidaemia is an important feature of diabetic dyslipidaemia and plays an important role in the development of cardiovascular disease in individuals with type 2 diabetes. Postprandial hyperlipidaemia in type 2 diabetes is secondary to increased chylomicron production by the enterocytes and delayed catabolism of chylomicrons and chylomicron remnants. Insulin and some intestinal hormones (e.g. glucagon-like peptide-1 [GLP-1]) influence intestinal lipid metabolism. In individuals with type 2 diabetes, insulin resistance and possibly reduced GLP-1 secretion are involved in the pathophysiology of postprandial hyperlipidaemia. Several factors are involved in the overproduction of chylomicrons: (1) increased expression of microsomal triglyceride transfer protein, which is a key enzyme in chylomicron synthesis; (2) higher stability and availability of apolipoprotein B-48; and (3) increased de novo lipogenesis. Individuals with type 2 diabetes present with disorders of cholesterol metabolism in the enterocytes with reduced absorption and increased synthesis. The increased production of chylomicrons in type 2 diabetes is also associated with a reduction in their catabolism, mostly because of a reduction in activity of lipoprotein lipase. Modification of the microbiota, which is observed in type 2 diabetes, may also generate disorders of intestinal lipid metabolism, but human data remain limited. Some glucose-lowering treatments significantly influence intestinal lipid absorption and transport. Postprandial hyperlipidaemia is reduced by metformin, pioglitazone, alpha-glucosidase inhibitors, dipeptidyl peptidase 4 inhibitors and GLP-1 agonists. The most pronounced effect is observed with GLP-1 agonists, which reduce chylomicron production significantly in individuals with type 2 diabetes and have a direct effect on the intestine by reducing the expression of genes involved in intestinal lipoprotein metabolism. The effect of sodium-glucose cotransporter 2 inhibitors on intestinal lipid metabolism needs to be clarified.