Summary A comparison has been made of the cachectic effects produced by the transplantable murine adenocarcinoma of the mouse colon (MAC16) with tumour necrosis factor-a (cachectin). Tumour necrosis factor-a (TNF-a) produced a dose-related weight reduction that was accompanied by a decrease in both food and water intake. The degree of weight loss was directly proportional to the decreased food and water intake. In contrast weight loss produced by the MAC16 tumour occurred without a reduction in fluid or nutrient intake. Both the MAC16 tumour and TNF-a produced hypoglycaemia and a reduction in the circulatory level of free fatty acids (FFA), but had opposite effects on the level of plasma triglycerides with the MAC16 tumour-induced cachexia causing a decrease and TNF-a producing an increase. The MAC16 tumour elaborated a lipolytic factor which caused an immediate release of FFA from adipose tissue. In contrast TNF-a had no effect on mobilization of adipose triglycerides over a short time period. Both TNF-a and extracts from the MAC16 tumour caused an enhanced release of amino acids from mouse diaphragm, which was suppressible with indomethacin and heat labile. No TNF was detected in the MAC16 tumour or in the serum of tumour-bearing animals. Both tumour and non-tumour-bearing animals responded with a similar elevation of their serum TNF levels 90min after a single injection of endotoxin. It is concluded that weight loss produced by TNF-a arises from an anorexic effect and that this differs from the complex metabolic changes associated with cancer cachexia.We have been investigating a chemically induced, transplantable adenocarcinoma of the colon (MAC 16), passaged in inbred NMRI mice as an experimental model of cachexia (Bibby et al., 1987). This tumour produces weight loss at small tumour burdens (<1% of the host wcight) and without a reduction in the intake of either food or water. The weight loss, which is directly proportional to the tumour weight, is associated with a decrease in both carcass fat and muscle dry weight (Beck & Tisdale, 1987). The cachectic effect of the tumour has been attributed to the production of both lipolytic and proteolytic factors, which are present in the circulation of tumour-bearing animals.Endotoxin-induced cells of the reticuloendothelial system have been shown to elaborate a mediator called cachectin (tumour necrosis factor, TNF), which induces a state of cachexia in recipient animals . When chronically secreted by host macrophages cachectin has been suggested to contribute to a catabolic state, which ultimately leads to cachexia (Beutler & Cerami, 1986

Summary A comparison has been made of the weight loss produced by tumour necrosis factor (TNF) (cachectin) with that produced by a restricted food and water intake (pair-fed controls), and by mitozolomide, a drug which in toxic doses induces weight loss with a similar decrease in nutrient and water intake. When administered as two separate injections over a 24h period (acute administration) TNF produced a doserelated weight reduction that was accompanied by and directly proportional to a decrease in both food and water intake. When administered daily by i.v. injection over a 5-day period (chronic administration) the major weight loss was found to occur during the first 24h after injection and thereafter the weight of treated mice increased toward that of controls. Acute administration of TNF produced hypoglycaemia that was more severe than observed with either mitozolomide or in pair-fed controls, a reduction in the circulatory level of free fatty acids (FFA) and an increase in plasma triglycerides, while mitozolomide and pair-feeding had no effect on the level of blood glucose or plasma triglycerides. Body composition analysis showed a loss of adipose tissue in TNF-injected and pair-fed animals after both acute and chronic treatment. Acute administration of TNF also induced a decrease in the total body water content of treated aniimals which was similar to pair-fed controls. It is concluded that the weight loss produced by TNF arises from a combination of semi-starvation and a reduced water intake, and that the effect only occurred with the first administration of TNF.

Summary Following a single injection of 7.5 x 107 U kg-' of human recombinant tumour necrosis factoralpha (TNF-a) to female NMRI mice, marked hypoglycaemia was observed within a 2 h period, accompanied by a severe depletion of liver glycogen and a drop in rectal body temperature when compared with pair-fed controls. There was no alteration in plasma alanine, lactate or pyruvate values, but an elevation of acetoacetate and 3-hydroxybutyrate when compared with pair-fed controls. Production of 4CO2 from U-14C-glucose was reduced in TNF-a treated animals, while production of 4CO2 from U-'4C-palmitate was not significantly different from controls, suggesting that the glucose was not being used to provide an increased metabolic rate. Glucose utilisation by different tissues was investigated by the 2-deoxyglucose tracer method. This showed that 2 h following TNF-a infusion glucose utilisation was increased in colon, liver, kidney and spleen by 500, 350, 36 and 25% respectively. However, when calculated on a whole-animal basis the major contributor to the increased glucose consumption was the liver. Plasma levels of both FFA and triglycerides were also elevated in TNF-a treated animals, suggesting that increased consumption of glucose by the liver may be utilised for lipogenesis. The rate of conversion of glucose into lipids in the liver was more than doubled 2 h after TNF-a administration with a concomitant rise in plasma and adipose tissue. These results suggest that administration of TNF-a produces a severe hypoglycaemia in order to serve an increased lipogenesis in liver and adipose tissue, which appears to be independent of the anorectic effect.

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SmmaryAdministration of either tumour necrosis factor alpha or 16,16-dimethylprostaglandin E2 (PGE2) to female NMRI mice caused a decrease in body weight accompanied by a reduction in both food and water intake and a decrease in carcass water content. A single injection of TNF-2 caused an enhanced production of PGE2 by spleen cells from treated animals, that was significant within I h of treatment, and persisted until at least 6h. These results suggest that the anorectic effect of TNF-z may be mediated by a prostaglandin intermediate. Indomethacin (lOmgkg-) administered 2h before TNF-a (7.5 x 107 U kg-') caused a significant reduction in the extent of weight loss and inhibited PgE2 production. Administration of indomethacin 0.5-1.5 h before the TNF-z had no significant effect on loss of body weight, but still inhibited PgE2 production. Also PgE2 production was still enhanced in response to TNF-2 administered chronically, despite the inability of prolonged TNF-z administration to produce continued loss of body weight. These results suggest that prostaglandins are not involved in the anorectic effect of TNF-z.The catabolic states associated with infection or endotoxemia have been attributed to the production by phagocytic cells of soluble proteins such as interleukin 1 and cachectin (Rouzer & Cerami, 1980;Moldawer et al., 1987a;Cerami et al., 1985). A high degree of homology has been shown to exist between the N-terminal sequence of mouse cachectin and the N-terminal sequence for human tumour necrosis factor-alpha (TNF-x) and the catabolic states have been extended to include also cancer-associated cachexia (Beutler & Cerami, 1986). Severe weight loss and increased mortality have been observed in mice bearing transgenic tumours that persistently secrete human cachectin (Oliff et al., 1987) and chronic administration of sublethal doses of TNF-x to rats caused anorexia, weight loss, depletion of body lipid and protein, a reduction of red blood cell mass, leukocytosis and tissue inflammation (Tracey et al., 1988). However, in a number of studies (Stovroff et al., 1988;) administration of TNF-x caused a loss in body weight accompanied by a drop in food and water intake, which was only apparent over the first 24h, after which animals became resistant to subsequent dosing. In addition TNF-x has not been detectable in the serum of patients with clinical cancer cachexia (Socher et al., 1988) and in clinical tnrals of recombinant human TNF-x there was no clinical evidence of accelerated cachexia, although anorexia was present during administration (Sherman et al., 1988). Also the effects on host metabolism produced by TNF-:x appear to differ from that produced by a cachexiainducing tumour .The toxic and metabolic effects of TNF-:z can be blocked by a single injection of the cyclo-oxygenase inhibitors indomethacin or ibuprofen before the TNF-x treatment (Kettlehut et al., 1987). This suggests that some of the effects of TNF-x may be mediated through a prostaglandin intermediate in analogy with septic shock where l...