Alteration of serum and urinary lipolytic activity with weight loss in cachectic cancer patients

The possibility that weight loss in cancer patients may be augmented by tumour produced catabolic factors, which stimulate lipid mobilisation, was investigated in a group of cancer patients with total body weight loss ranging from 0 to 50%. The serum and urine lipolytic activity has been determined using freshly isolated murine adipocytes in an in vitro assay. As a control group, we have used patients with Alzheimer's disease, in which some patients may lose a considerable amount of weight, without an obvious cause. The serum lipolytic activity for the Alzheimer's group with weight loss (0.11 +/- 0.02 mumols glycerol released 10(5) adipocytes-1 ml-1 serum) was not significantly different from the group without weight loss (0.11 +/- 0.02 mumols glycerol released 10(5) adipocytes-1 ml-1) or from a healthy control group (0.07 +/- 0.02 mumols glycerol released 10(5) adipocytes-1 ml-1), but all three groups were significantly (P less than 0.005) lower than the cancer patient group (0.20 +/- 0.03 mumols glycerol 10(5) adipocytes-1 ml-1), irrespective of weight loss. A similar difference between the cancer and the control group was observed for the urinary lipolytic activity (0.67 +/- 0.03 versus 0.28 +/- 0.03 mumols glycerol released 10(5) adipocytes-1 mg creatinine-1 respectively, P less than 0.01). Weight loss in animals bearing the MAC16 adenocarcinoma was paralleled by a corresponding rise in serum lipolytic activity which peaked when the loss of carcass weight was 16%. A similar decrease in serum lipolytic activity was also observed in cancer patients at high percentages loss in body weight. However, a linear relationship was observed between both the serum and urinary lipolytic activity and weight loss in cancer patients (correlation coefficients 0.79 and 0.70 respectively) when the total body weight loss did not exceed 20%. This suggests that weight loss in cancer patients may be attributed, at least in part, to an, as yet, unidentified lipolytic factor.