Triglyceride absorption in transperitoneal alimentation

Noninvasive delivery of gene targeting probes to live brains for transcription MRI

We aimed to test the feasibility of detecting gliosis in living brains when the blood-brain barrier (BBB) is disrupted. We designed a novel magnetic resonance (MR) probe that contains superparamagnetic iron oxide nanoparticles (SPION, a T2 susceptibility contrast agent) linked to a short DNA sequence complementary to the cerebral mRNA of glial fibrillary acidic protein (GFAP) found in glia and astrocytes. As a control, we also used a sequence complementary to the mRNA of beta-actin. Our objectives are to demonstrate that this new probe, SPION-gfap, could be delivered to the brain when administered by eyedrop solution to the conjunctival sac. We induced BBB leakage by puncture wound, global cerebral ischemia, and cortical spreading depression in C57BL6 mice; 1 day after probe delivery we acquired T2* MR images and R2* (R2* = 1/T2*) maps using a transcription MRI technique in live mice. We found that the SPION-gfap probe reported foci with elevated signal in subtraction R2* maps and that these foci matched areas identified as having extensive glial network (gliosis) in postmortem immunohistochemistry. Similarly, animals administered the control probe exhibited foci of R2* elevation that matched beta-actin-expressing endothelia in the vascular wall. We conclude that our modular MR probe, delivered in an eyedrop solution, effectively reports gliosis associated with acute neurological disorders in living animals. As BBB leakage is often observed in acute neurological disorders, this study also served to validate noninvasive delivery of MR probes to the brains of live animals after acute neurological disorders.

Peptides that regulate food intake: orexin gene expression is increased during states of hypertriglyceridemia

Previous reports implicate the orexins in eating and body weight regulation. This study investigated possible functional relationships between hypothalamic orexins and circulating hormones or metabolites. In situ hybridization and quantitative PCR were used to examine orexin expression in the perifornical hypothalamus (PF) of rats and mice on diets varying in fat content and with differential propensity toward obesity. The results showed that orexin gene expression was stimulated by a high-fat diet in close association with elevated triglyceride levels, suggesting a functional relationship between these measures. Results obtained in obesity-prone rats and mice revealed a similar increase in orexin in close relation to triglycerides. A direct test of this orexin-triglyceride link was performed with Intralipid, which increased PF orexin expression along with circulating triglycerides. Whereas PF galanin is similarly stimulated by dietary fat, double-labeling immunofluorescence studies showed that orexin and galanin neurons are anatomically distinct. This evidence suggests that the orexins, like galanin, are "fat-responsive" peptides that respond to circulating lipids.

Absorption of Intralipid and interferences from nutrients infused into the peritoneal cavity of the rat

We studied the peritoneal absorption and elimination of Intralipid after its intraperitoneal and intravenous infusion into rats, by means of a two-compartment model. Follow-up measurements of the plasma triglyceride rate were made. The peritoneal absorption of Intralipid gives the following absorption and elimination constants: Ka (absorption constant from the peritoneal cavity) is 0.106 +/- 0.08 h-1; Ke (elimination constant from the blood stream) is 0.0440 +/- 08 h-1; and BAa (absolute bioavailability) is 84.5 +/- 0.08% 8 hours after infusion. These results show that the intraperitoneal absorption of Intralipid is high and progressive during the first 8 hours, thus supplying the daily caloric needs of the animal through the administration of a single bolus administration, and the plasma triglyceride clearance is faster than the intraperitoneal absorption after the first 6 hours, thus avoiding dangerous overloads. We also studied the behavior of different combinations of glucose, amino acids, and fats infused into the peritoneal cavity of rats in order to observe possible interferences with the absorption of these nutrients. Two microcuries of radioactive L-glucose-1-C14 with 5 mL of 5% D-glucose, with 5 mL of 3.5% amino-acid solution, or with 5 mL of 20% fat emulsion were infused intraperitoneally into three different groups of animals. Slight differences of plasma radioactivity were registered among these three groups 1 hour after infusion. Likewise, small differences of plasma radioactivity were observed between the animals receiving an infusion of 1 microCi of five L-amino-acids-U-C14 diluted with 5 mL of 3.5% amino-acid solution, with 5 mL of 5% glucose solution, or with 5 mL of 20% fat emulsion 4 and 6 hours after infusion. No differences in the plasma triglyceride rates were observed between those groups of animals infused with 5 mL of 20% Intralipid plus 5 mL of glucose solution or with 20% Intralipid plus 3.5% amino-acid solution compared with the group receiving only 5 mL of 20% Intralipid. The infusion of fats does not seem to interfere with that of other substrates, possibly because of the different absorption route (lymphatic for fats and capillary vessels for amino acids and glucose solutions), but further research is needed to reach conclusive results. Perhaps the prolonged administration of fat, together with other substrates, produces precipitates and other galenic problems that hinder absorptive mechanisms of the preparations.