Lipolysis, in vitro

Traber, M. G. et al. (1990). Vitamin E uptake by human intestinal cells during lipolysis in vitro. Gastroenterology 98(1) 96-103. 

Thunhorst RL, Fitts DA. Peripheral angiotensin causes salt appetite in rats. Am J Physiol 1994 267 R171-R177. Tisdale MJ, Beck S A. Inhibition of tumour-induced lipolysis in vitro and cachexia and tumour growth in vivo... 

Gocxlridge, A.G. (1968b). Lipolysis in vitro in adipose tissue from embryonic and growing chicks. Am. ]. Physiol., 214, 902-18. 

Figure 25-8. Control of adipose tissue lipolysis. (TSH, thyroid-stimulating hormone FFA, free fatty acids.) Note the cascade sequence of reactions affording amplification at each step. The lipolytic stimulus is "switched off" by removal of the stimulating hormone the action of lipase phosphatase the inhibition of the lipase and adenylyl cyclase by high concentrations of FFA the inhibition of adenylyl cyclase by adenosine and the removal of cAMP by the action of phosphodiesterase. ACTFI,TSFI, and glucagon may not activate adenylyl cyclase in vivo, since the concentration of each hormone required in vitro is much higher than is found in the circulation. Positive ( ) and negative ( ) regulatory effects are represented by broken lines and substrate flow by solid lines.

Pasquier B, Armand M, Guillon F, Castelain C, Borel P, Barry JL, Pieroni G and Lairon D. 1996. Viscous soluble dietary fibers alter emulsification and lipolysis of triacylglycerols in duodenal medium in vitro. J Nutr Biochem 7 293—302. 

These effects of T3 on the hormone-dependent lipolysis in the adipocyte seem to be direct. They have been reproduced in a culture system of 3T3-L preadipocytes [85]. When maintained in thyroid hormone-depleted media these cells exhibit lower sensitivity to isoproterenol, which can be explained by alterations in both production and degradation of cAMP. In vitro, T3 did not affect receptor number or affinity suggesting that the decrease in cAMP production depends on some unknown alteration of the coupling system. 

In vitro, GH has many effects on adipose tissue and cells, including stimulation of lipolysis and actions on glucose utilization [89,90]. Short-term effects in vitro are mainly insulin-like (increased utilization of glucose and amino acids, glycogen synthesis, antilipolytic actions, etc.) and may be mediated by mechanisms similar to those of insulin, including dephosphorylation of hormone-sensitive lipase [91]. In the longer term adipose tissue and cells in vitro become refractory to the insulinlike effects of GH, and counter-insulin effects predominate and reflect the main actions seen in vivo. Receptors for GH have been identified in adipose tissue [90,92]. 

Reduced plasma protein binding of digitoxin has been reported after the administration of heparin (111). In 10 hemodialysed patients taking maintenance digitoxin therapy, there was reduced binding in vitro because of heparin-induced lipolysis, and not as a consequence of in vivo binding of digitoxin to plasma proteins. 

Gerson, T., John, A., and Sinclair, B.R. 1983. The effect of dietary N on in vitro lipolysis and fatty acid hydrogenation in rumen digesta from sheep fed diets high in starch. J. Agric. Sci. Camb. 101, 97-101. 

Gerson, T., King, A.S.D., Kelly, K.E., and Kelly, WJ. 1988. Influence of particle size and surface area on in vitro rates of gas production, lipolysis of triacylglycerol and hydrogenation of linoleic acid by sheep rumen digesta or Ruminococcusflavefaciens. J. Agric. Sci. Camb. 110, 31-37. 

Hawke, J.C. and Silcock, W.R. 1970. The in vitro rates of lipolysis and biohydrogenation in rumen contents. Biochim. Biophys. Acta 218, 201-212. 

Dahan, A. and Hoffman, A. (2008) Rationalizing the selection of oral lipid based drug delivery systems by an in vitro dynamic lipolysis model for improved oral bioavailability of poorly water soluble drugs. Journal of Controlled Release, 129 (1), 1-10. 

Zangenberg, N.H., Mullertz, A., Gjelstrup Kristensen, H. and Hovgaard, L. (2001) A dynamic in vitro lipolysis model. II. Evaluation of the model. European Journal of Pharmaceutical Sciences, 14 (3), 237. 

Dahan, A. and Hoffman, A. (2007) The effect of different lipid based formulations on the oral absorption of lipophilic drugs the ability of in vitro lipolysis and consecutive ex vivo intestinal permeability data to predict in vivo bioavailability in rats. European Journal of Pharmaceutics and Biopharmaceutics, 67 (1), 96. 

The biological effects of IPG include tissue-specific regulation of lipolysis, lipogen-esis, glycolytic flux, protein synthesis and/or phosphorylation, DNA and RNA synthesis and also long-term actions such as cellular prohferation. IPG-P activates glycerol-3-phosphate acyl transferase [17], but almost aU the other insulin-mimetic activities reported were tested for IPG-A prepared in vitro by hydrolysis of highly purified GPI [1, 7, 8, 75, 76]. 

With the liquid meal, the duodenal lipolysis (Tab. 10.6) decreased only slightly when micronized orlistat powder was pre-mixed with the meal (74.5% of controls), and did not decrease at all when Xenical pellets were added in the course of the administration of the meal (115.7% of controls). The differences between treated and control groups were not significant. This lack of effect of orlistat as means of reducing fhe duodenal lipolysis was not correlated with the high level of HPL inhibition observed in fhe duodenal contents (Tab. 10.5). These paradoxical results were however supported and explained by fhe results of further in vitro experiments. The rates of HPL inhibition by orlistat were found to be similar wifh bofh types of meals (half-inhibihon time=5-6 min), but the finely pre-emulsified TG of fhe liquid meal were rapidly hydrolyzed by HPL before the enzyme was sig-nificanfly inhibited by orlistat (Carriere et al., 2001). 

The specific activities of human digestive lipases measured from the in vivo and in vitro lipolysis of test meals. Gastroenterology 119, 949-960. 

Lowe, P.A., Sauni re, J.-F., Sarda, L. and Verger, R. (1986a) Importance ofhuman gastric lipase for intestinal lipolysis An in vitro study. Biochim. Biophys. Acta 879, 419-423. 

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