Aerobic glycolysis and lymphocyte transformation

Abstract

1. The role of enhanced aerobic glycolysis in the transformation of rat thymocytes by concanavalin A has been investigated. Concanavalin A addition doubled [U-(14)C]glucose uptake by rat thymocytes over 3h and caused an equivalent increased incorporation into protein, lipids and RNA. A disproportionately large percentage of the extra glucose taken up was converted into lactate, but concanavalin A also caused a specific increase in pyruvate oxidation, leading to an increase in the percentage contribution of glucose to the respiratory fuel. 2. Acetoacetate metabolism, which was not affected by concanavalin A, strongly suppressed pyruvate oxidation in the presence of [U-(14)C]glucose, but did not prevent the concanavalin A-induced stimulation of this process. Glucose uptake was not affected by acetoacetate in the presence or absence of concanavalin A, but in each case acetoacetate increased the percentage of glucose uptake accounted for by lactate production. 3. [(3)H]Thymidine incorporation into DNA in concanavalin A-treated thymocyte cultures was sensitive to the glucose concentration in the medium in a biphasic manner. Very low concentrations of glucose (25mum) stimulated DNA synthesis half-maximally, but maximum [(3)H]thymidine incorporation was observed only when the glucose concentration was raised to 1mm. Lactate addition did not alter the sensitivity of [(3)H]-thymidine uptake to glucose, but inosine blocked the effect of added glucose and strongly inhibited DNA synthesis. 4. It is suggested that the major function of enhanced aerobic glycolysis in transforming lymphocytes is to maintain higher steady-state amounts of glycolytic intermediates to act as precursors for macromolecule synthesis.

Fuel utilization in colonocytes of the rat

“…Some acetoacetate was converted into 3-hydroxybutyrate. This rate is similar to that reported by Roediger (1982), but considerably higher than that reported for thymocytes (Hume et al, 1978), lymphocytes (Ardawi & Newsholme, 1984b) or enterocytes (Hanson & Parsons, 1978). If the observed rate of acetoacetate utilization reflects complete oxidation, then it would account for about 60% ofoxygen consumption by the colonocytes.…”

“…Thus hexokinase activity may not be indicative of the maximum capacity of glycolysis in colonocytes. This rate ofglucose utilization is considerably higher than that reported for thymoctyes (Culvenor & Weidemann, 1976;Yassmeen et al, 1977;Hume et al, 1978;Brand et al, 1984), lymphocytes (Ardawi & Newsholme, 1983a, 1984a), but about 50%O lower than that reported for enterocytes (Watford et al, 1979;Porteous, 1980). About 83 % of the glucose removed was accounted for as lactate and small amounts of pyruvate.…”

“…All spectrophotometric measurements were performed in a Gilford recording spectrophotometer (model 240) at 25°C, except for glucose-6-phosphatase and glutaminase, which were determined at 30 and 37°C respectively. For all enzymes studied, preliminary experiments established that extraction and assay procedures were such as to provide maximum enzyme activities (see Crabtree et al, 1979 (Roediger & Truelove, 1979;Roediger, 1982), but higher than that reported for human colonocytes (Roediger & Truelove, 1979), rat lymphocytes (Ardawi & Newsholme, 1983a) or rat thymocytes (Hume et al, 1978), and similar to that observed in rat enterocytes (Watford et al, 1979;Porteous, 1980). Glutamine, n-butyrate or ketone bodies were the only.substrates that increased the rate of 02 consumption (Table 1).…”

“…In a similar manner to other rapidly dividing cells (e.g. lymphocytes, thymocytes, tumour cells), these epithelial cells are also characterized by a high rate of glycolysis in either the fed or the starved state (Watford et al, 1979;Hume et al, 1978;Ardawi & Newsholme, 1983a). Experiments with incubated lymphocytes suggested that most of the energy requirements in either the fed or the starved state were provided from the utilization of fatty acids, glutamine and glucose, whereas ketone bodies appeared to be much less important (Ardawi & Newsholme, 1982, 1983a,b, 1984a,b, 1985.…”

E3 ubiquitin ligase APC/C-Cdh1 accounts for the Warburg effect by linking glycolysis to cell proliferation

“…The purpose and mechanism of this aerobic glycolysis, known as the Warburg effect (6), are still unclear. The two main reasons for this are, first, that the presence in cancer of a mitochondrial defect, originally thought to be responsible for aerobic glycolysis (6), remains controversial and, second, that aerobic glycolysis also occurs in proliferating nonneoplastic cells (7,8). This has led to the suggestion that aerobic glycolysis may be required for new biomass formation (9).…”