Metabolic and genomic response to dietary isocaloric protein restriction in the rat.

We have examined hepatic, genomic, and metabolic responses to dietary protein restriction in the non-pregnant Sprague-Dawley rat. Animals were pair-fed either a 6 or 24% casein-based diet for 7-10 days. At the end of the dietary period, a microarray analysis of the liver was performed, followed by validation of the genes of interest. The rates of appearance of phenylalanine, methionine, serine, and glucose and the contribution of pyruvate to serine and glucose were quantified using tracer methods. Plasma and tissue amino acid levels, enzyme activities, and metabolic intermediates were measured. Protein restriction resulted in significant differential expression of a number of genes involved in cell cycle, cell differentiation, transport, transcription, and metabolic processes. RT-PCR showed that the expression of genes involved in serine biosynthesis and fatty acid oxidation was higher, and those involved in fatty acid synthesis and urea synthesis were lower in the liver of protein-restricted animals. Free serine and glycine levels were higher and taurine levels lower in all tissues examined. Tracer isotope studies showed an ∼50% increase in serine de novo synthesis. Pyruvate was the primary (∼90%) source of serine in both groups. Transmethylation of methionine was significantly higher in the protein-restricted group. This was associated with a higher S-adenosylmethionine/S-adenosylhomocysteine ratio and lower cystathione ß-synthase and cystathionine γ-lyase activity. Dietary isocaloric protein restriction results in profound changes in hepatic one-carbon metabolism within a short period. These may be related to high methylation demands placed on the organism and caused by possible changes in cellular osmolarity as a result of the efflux of the intracellular taurine.

Morphological fractal analysis of shape in cancer cells treated with combinations of microtubule-polymerizing and -depolymerizing agents.

The current prognostic parameters, including tumor volume, biochemistry, or immunohistochemistry, are not sufficient to reflect the properties of cancer cells that distinguish them from normal cells. Our focus is to evaluate the effects of a combination of microtubule-polymerizing Taxol and -depolymerizing colchicine on IAR20 PC1 liver cells by measuring the surface fractal dimension as a descriptor of two-dimensional vascular geometrical complexity. The fractal dimension offers a rapid means of assessing cell shape. Furthermore, we show correlations of fractal dimensions of cell contours with the latent factors from our previously employed cell shape analysis.

Colchitaxel, a coupled compound made from microtubule inhibitors colchicine and paclitaxel.

BACKGROUND: Tumor promoters enhance tumor yield in experimental animals without directly affecting the DNA of the cell. Promoters may play a role in the development of cancer, as humans are exposed to them in the environment. In work based on computer-assisted microscopy and sophisticated classification methods, we showed that cells could be classified by reference to a database of known normal and cancerous cell phenotypes. Promoters caused loss of properties specific to normal cells and gain of properties of cancer cells. Other compounds, including colchicine, had a similar effect. Colchicine given together with paclitaxel, however, caused cells to adopt properties of normal cells. This provided a rationale for tests of microtubule inhibitor combinations in cancer patients. The combination of a depolymerizing and a stabilizing agent is a superior anti-tumor treatment. The biological basis of the effect is not understood. RESULTS: A single compound containing both colchicine and paclitaxel structures was synthesized. Colchicine is an alkaloid with a trimethoxyphenyl ring (ring A), a ring with an acetamide linkage (ring B), and a tropolone ring (ring C). Although rings A and C are important for tubulin-binding activity, the acetamide linkage on ring B could be replaced by an amide containing a glutamate linker. Alteration of the C-7 site on paclitaxel similarly had little or no inhibitory effect on its biological activity. The linker was attached to this position. The coupled compound, colchitaxel (1), had some of the same effects on microtubules as the combination of starting compounds. It also caused shortening and fragmentation of the + end protein cap. CONCLUSION: Since microtubule inhibitor combinations give results unlike those obtained with either inhibitor alone, it is important to determine how such combinations affect cell shape and growth. Colchitaxel shows a subset of the effects of the inhibitor combination. Thus, it may be able to bind the relevant cellular target of the combination. It will be useful to determine the basis of the shape reversal effect and possibly, the reasons for therapeutic efficacy of microtubule inhibitor combinations.