Effect of Starving and Refeeding on Lipid Metabolism in Suncus1

Abstract

We have previously reported that fatty liver is easily induced in a novel experimental animal, Suncus murinus (suncus) by withholding food, and that apolipoprotein B (apo B) is not actively synthesized in the liver. In the present paper we describe the effect of starving and refeeding on lipid and lipoprotein metabolism in suncus, in order to explore the mechanisms of induction of fatty liver by starving and of its improvement by refeeding. Starvation induced increase in triglyceride content and decrease in glycogen content of the liver. Although the glycogen content returned to the level before starvation at 12 h after refeeding, the triglyceride content decreased gradually but did not reach the prestarvation level even at 24 h after refeeding in suncus. Plasma lipids, glucose, and insulin levels were decreased by starvation and returned to the levels before starvation between 8 and 24 h after refeeding. On the other hand, the plasma levels of free fatty acid and ketone bodies were elevated significantly by starvation and decreased rapidly by refeeding. These responses to starvation and refeeding, except for the change in hepatic triglyceride, are in common with other experimental animals, suggesting that there are no abnormalities in glucose metabolism or in fatty acid metabolism in suncus. In conclusion, the fatty liver induced by starvation in suncus may be caused by impaired triglyceride transport out of the liver, for which apolipoprotein B is mostly responsible, as reported previously.

The Role of Peptide Hormones in Insect Lipid Metabolism

“…These findings are in accordance with the proposed analogy between oenocytes and mammalian hepatocytes (Gutierrez et al, 2007;Martins and Ramalho-Ortigao, 2012) and support the notion that oenocytes play a central role in the metabolic adaptation to starvation (Chatterjee et al, 2014). On the other hand, starvation induces a significant increase in the number and size of LDs in adult oenocytes as starvation also induces TAG levels in the mammalian liver (Ohama et al, 1994). Similarly, knockdown of the insulin target "PEPCK (Phosphoenolpyruvate Carboxykinase)" impaired starvation-induced lipid uptake in oenocytes.…”

Changes in lipid and carnitine concentrations following repeated fasting-refeeding in mice

“…In other research it has been reported that refeeding lead to a decrease in fatty acid concentrations and caused quick fat synthesis, resulting in increased blood glucose and TG concentrations [16,18,22,23]. Each of these studies varied in terms of fasting period, animals, and overall experimental design, which leads to many different interpretations.…”

Hypolipidaemic effects of fenofibrate and fasting in the herbivorous grass carp (Ctenopharyngodon idella) fed a high-fat diet

“…Similarly to fibrate derivatives, fasting also activates PPARα and thereby regulates mitochondrial and peroxisomal FA oxidation activities ( 14 , 15 ) . The regulation of these pathways affects the lipid metabolism and was effectively demonstrated to modulate blood lipid composition in both animal models and humans ( 16 – 18 ) . The observations regarding blood lipid alteration during fasting are conflicting ( 17 – 21 ) , but hypolipidaemic effects have been reported ( 18 , 22 ) .…”