Hepatic triglyceride lipase promotes low density lipoprotein receptor-mediated catabolism of very low density lipoproteins in vitro

Circulating MicroRNA-122 Is Associated With the Risk of New-Onset Metabolic Syndrome and Type 2 Diabetes

MicroRNA-122 (miR-122) is abundant in the liver and involved in lipid homeostasis, but its relevance to the long-term risk of developing metabolic disorders is unknown. We therefore measured circulating miR-122 in the prospective population-based Bruneck Study (n = 810; survey year 1995). Circulating miR-122 was associated with prevalent insulin resistance, obesity, metabolic syndrome, type 2 diabetes, and an adverse lipid profile. Among 92 plasma proteins and 135 lipid subspecies quantified with mass spectrometry, it correlated inversely with zinc-α-2-glycoprotein and positively with afamin, complement factor H, VLDL-associated apolipoproteins, and lipid subspecies containing monounsaturated and saturated fatty acids. Proteomics analysis of livers from antagomiR-122-treated mice revealed novel regulators of hepatic lipid metabolism that are responsive to miR-122 inhibition. In the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT, n = 155), 12-month atorvastatin reduced circulating miR-122. A similar response to atorvastatin was observed in mice and cultured murine hepatocytes. Over up to 15 years of follow-up in the Bruneck Study, multivariable adjusted risk ratios per one-SD higher log miR-122 were 1.60 (95% CI 1.30-1.96; P < 0.001) for metabolic syndrome and 1.37 (1.03-1.82; P = 0.021) for type 2 diabetes. In conclusion, circulating miR-122 is strongly associated with the risk of developing metabolic syndrome and type 2 diabetes in the general population.

Dyslipidemia Part 1--Review of Lipid Metabolism and Vascular Cell Physiology

Dyslipidemia, more specifically, high-serum low-density lipoproteins and low-serum high-density lipoproteins, are known risk factors for cardiovascular disease. The current clinical treatment of dyslipidemia represents the outcome of a large body of fundamental basic science research on lipids, lipid metabolism, and the effects of different lipids on cellular components of the artery, inflammatory cells, and platelets. In general, lower density lipids activate intracellular pathways to increase local and systemic inflammation, monocyte adhesion, endothelial cell dysfunction and apoptosis, and smooth muscle cell proliferation, resulting in foam cell formation and genesis of atherosclerotic plaque. In contrast, higher density lipids prevent or attenuate atherosclerosis. This article is part 1 of a 2-part review, with part 1 focusing on lipid metabolism and the downstream effects of lipids on the development of atherosclerosis, and part 2 on the clinical treatment of dyslipidemia and the role of these drugs for patients with arterial disease exclusive of the coronary arteries.

Activity and tissue-specific expression of lipases and tumor-necrosis factor alpha in lean and obese cats

Post-heparin plasma activity of lipoprotein lipase (LPL) and hepatic lipase (HL), and fat and muscle activity of LPL were measured in neutered lean and obese cats. Lipoprotein lipase, hormone-sensitive lipase (HSL), and tumor necrosis factor a (TNF) mRNA were measured in muscle and fat tissue with real-time PCR using primers for feline LPL, HSL, and TNF. Lipoprotein lipase plasma and fat activity and fat mRNA levels were significantly lower (50, 80, and 50%, respectively) in obese cats than lean cats, whereas the muscle/fat ratio of LPL was significantly higher in obese compared to lean cats. The activity of HL was not different between the groups. Hormone-sensitive lipase mRNA levels were significantly higher in obese than lean cats. The level of fat TNF also was significantly higher in obese cats than in lean cats, whereas the level in muscle was not different. The lower LPL activity and mRNA expression in fat and the higher LPL and HSL mRNA expression in muscle in obese cats compared to lean cats expectedly favor a redistribution of fatty acids from fat to muscle tissue where they can be deposited or used for energy in times of need. Tumor necrosis factor alpha may regulate this repartitioning process through suppression of adipocyte LPL.

Zinc finger protein ZNF202 structure and function in transcriptional control of HDL metabolism

PURPOSE OF REVIEW

The zinc finger protein ZNF202 is a transcriptional repressor controlling promoter elements predominantly found in genes involved in lipid metabolism and energy homeostasis. Here we summarize the structure, regulation and modulation of ZNF202 function by protein interactions.

RECENT FINDINGS

We review recent data and discuss the importance of the steadily growing list of ZNF202 target genes, defining a central role for ZNF202 as a key transcriptional regulator in metabolic disorders. Furthermore, we provide an interlink between transcriptional repression by ZNF202 and enhancement of gene activation via nuclear receptor coactivation by SCAN domain protein 1.

SUMMARY

The novel findings suggest that ZNF202 together with other SCAN domain proteins orchestrates a complex transcriptional regulatory network, which justifies a further exploration of its potential as a therapeutic target in lipid disorders such as atherosclerosis and associated metabolic syndromes.

Abnormalities in apo B-containing lipoproteins in diabetes and atherosclerosis

Atherosclerosis is the major cause of death in patients with diabetes. Low-density lipoprotein (LDL) being the most important cholesterol-carrying lipoprotein has been studied extensively in both diabetes and non-diabetes. This paper reviews the literature but also focuses on the precursors of LDL and in particular the postprandial apo B-containing lipoproteins. Abnormalities in the postprandial lipoproteins and alteration in chylomicron assembly and clearance are discussed and the evidence presented suggesting the importance of dysregulation of these lipoproteins in atherosclerotic progression. The relationship between chylomicron production in the intestine and hepatic release of very low-density lipoproteins (VLDL) is explored, as is the interrelationship between clearance rates of these lipoproteins. The size of LDL influences its atherogenicity. VLDL composition and size in relation to its influence on LDL is discussed. The effect of diet on the composition of lipoproteins and the relationship between fatty acid composition and clearance is reviewed. Evidence that diabetic control beneficially alters lipoprotein composition is presented suggesting how improved diabetic control may reduce atherosclerosis. The review concludes with a discussion on the effect of the apo B-containing lipoproteins and their modification through glycation and oxidation on macrophage and endothelial function.

Hepatic lipase and HDL metabolism

Hepatic lipase is a lipolytic enzyme that has been suggested to have a role in HDL metabolism. Evidence suggests that HDL-cholesterol level is at least partly regulated by hepatic lipase level. Recent studies have shown that hepatic lipase not only hydrolyzes triglyceride and phospholipid in HDL, but also stimulates HDL cholesterol ester uptake by hepatocytes. Therefore, hepatic lipase, together with lipid transfer proteins, determines both HDL-cholesterol level and its function in reverse cholesterol transport. These conclusions are based on observations from in-vitro model substrate studies, cell culture studies, transgenic animal studies, and clinical studies. At present time, it is not known whether hepatic lipase action increases or decreases risk of developing atherosclerosis.