Gastrointestinal factors regulating lipid droplet formation in the intestine.

Cytoplasmic lipid droplets (CLD) are considered as neutral lipid reservoirs, which protect cells from lipotoxicity. It became clear that these fascinating dynamic organelles play a role not only in energy storage and metabolism, but also in cellular lipid and protein handling, inter-organelle communication, and signaling among diverse functions. Their dysregulation is associated with multiple disorders, including obesity, liver steatosis and cardiovascular diseases. The central aim of this review is to highlight the link between intra-enterocyte CLD dynamics and the formation of chylomicrons, the main intestinal dietary lipid vehicle, after overviewing the morphology, molecular composition, biogenesis and functions of CLD.

Two weeks of high-fat feeding disturb lipid and cholesterol molecular markers.

Metabolic disorders are often associated with liver steatosis and increased plasma cholesterol levels. However, the link between excessive lipid accumulation and impairments in cholesterol metabolism remains uninvestigated in the liver. Short term of high-fat diet (HFD) was previously shown to promote excessive lipid accumulation prior to the development of metabolic disorders. The present study intended to characterize how increases in liver fat alter the expression of several key regulators of hepatic cholesterol metabolism in response to a short-term HFD. Wistar rats were randomly submitted either to HFD (n = 8) or a regular chow diet (n = 8) for 14 days. Increases in triglycerides were highly significant (P < 0.01) in the liver but marginal in the plasma of HFD rats. In contrast, the HFD resulted in higher (P < 0.01) cholesterol levels in plasma but not in liver samples. Gene expression of key markers involved in cholesterol uptake (LDL particles) including low-density lipoprotein receptor-related protein-1 (LRP-1) and protein convertase subtilisin/kexin type 9 (PCSK9) along with ATP-binding cassette, superfamily G, member 5 (ABCG5) involved in cholesterol exportation via bile ducts was found to be higher (P < 0.05) in response to the HFD. In contrast, expression of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), involved in cholesterol synthesis, was downregulated in the liver. The data support the concept that excessive accumulation of lipids promptly alters the expression of key genes regulating cholesterol metabolism in the liver. On a clinical point of view, this indicates that increases in plasma cholesterol occur after a short-term HFD.

Acylated Ghrelin and The Regulation of Lipid Metabolism in The Intestine.

Acylated ghrelin (AG) is a gastrointestinal (GI) peptide mainly secreted by the stomach that promotes cytosolic lipid droplets (CLD) hypertrophy in adipose tissues and liver. However, the role of AG in the regulation of lipid metabolism in the intestine remains unexplored. This study aimed at determining whether AG influences CLD production and chylomicron (CM) secretion in the intestine. The effects of AG and oleic acid on CLD accumulation and CM secretion were first investigated in cultured Caco-2/15 enterocytes. Intestinal lipid metabolism was also studied in Syrian Golden Hamsters submitted to conventional (CD) or Western (WD) diets for 8 weeks and continuously administered with AG or physiological saline for the ultimate 2 weeks. In cultured Caco-2/15 enterocytes, CLD accumulation influenced CM secretion while AG reduced fatty acid uptake. In WD hamsters, continuous AG treatment amplified chylomicron output while reducing postprandial CLD accumulation in the intestine. The present study supports the intimate relationship between CLD accumulation and CM secretion in the intestine and it underlines the importance of further characterizing the mechanisms through which AG exerts its effects on lipid metabolism in the intestine.