Cancer cachexia and the rate of whole body lipolysis in man

Cytosolic lipolysis in non-adipose tissues: energy provision and beyond

Cytosolic lipolysis is a well-defined biochemical process that plays important roles in the mobilization of stored neutral lipids. Lipid turnover, regulated by cytosolic lipolysis, has been extensively studied in adipose tissue, liver, and muscle. The storage and utilization of neutral lipids is a basic function of most, if not all, tissues and cells. In this review, we focus on the functions of cytosolic lipolysis mainly in non-adipose tissues and in several physiological processes, including cancer, longevity, and pathogen infection. The mechanisms underlying the impact of cytosolic lipolysis on these events will be discussed. Detailed understanding of cytosolic lipolysis in both adipose and non-adipose tissues will have implications for future clinical translation.

Leucine Supplementation in Cancer Cachexia: Mechanisms and a Review of the Pre-Clinical Literature

Cancer cachexia (CC) is a complex syndrome of bodily wasting and progressive functional decline. Unlike starvation, cachexia cannot be reversed by increased energy intake alone. Nonetheless, targeted nutritional support is a necessary component in multimodal syndrome management. Due to the highly catabolic nature of cancer cachexia, amino acid supplementation has been proposed. Interestingly, leucine has been found to increase protein synthesis and decrease protein degradation via mTORC1 pathway activation. Multiple pre-clinical studies have explored the impact of leucine supplementation in cachectic tumor-bearing hosts. Here, we provide an overview of leucine’s proposed modes of action to preserve lean mass in cachexia and review the current pre-clinical literature related to leucine supplementation during CC. Current research indicates that a leucine-rich diet may attenuate CC symptomology; however, these works are difficult to compare due to methodological differences. There is need for further pre-clinical work exploring leucine’s potential ability to modulate protein turnover and immune response during CC, as well as the impact of additive leucine on tumor growth.

Diverging metabolic programmes and behaviours during states of starvation, protein malnutrition, and cachexia

BACKGROUND

Our evolutionary history is defined, in part, by our ability to survive times of nutrient scarcity. The outcomes of the metabolic and behavioural adaptations during starvation are highly efficient macronutrient allocation, minimization of energy expenditure, and maximized odds of finding food. However, in different contexts, caloric deprivation is met with vastly different physiologic and behavioural responses, which challenge the primacy of energy homeostasis.

METHODS

We conducted a literature review of scientific studies in humans, laboratory animals, and non-laboratory animals that evaluated the physiologic, metabolic, and behavioural responses to fasting, starvation, protein-deficient or essential amino acid-deficient diets, and cachexia. Studies that investigated the changes in ingestive behaviour, locomotor activity, resting metabolic rate, and tissue catabolism were selected as the focus of discussion.

RESULTS

Whereas starvation responses prioritize energy balance, both protein malnutrition and cachexia present existential threats that induce unique adaptive programmes, which can exacerbate the caloric insufficiency of undernutrition. We compare and contrast the behavioural and metabolic responses and elucidate the mechanistic pathways that drive state-dependent alterations in energy seeking and partitioning.

CONCLUSIONS

The evolution of energetically inefficient metabolic and behavioural responses to protein malnutrition and cachexia reveal a hierarchy of metabolic priorities governed by discrete regulatory networks.

Cisplatin-Induced Skeletal Muscle Dysfunction: Mechanisms and Counteracting Therapeutic Strategies

Among the severe side effects induced by cisplatin chemotherapy, muscle wasting is the most relevant one. This effect is a major cause for a clinical decline of cancer patients, since it is a negative predictor of treatment outcome and associated to increased mortality. However, despite its toxicity even at low doses, cisplatin remains the first-line therapy for several types of solid tumors. Thus, effective pharmacological treatments counteracting or minimizing cisplatin-induced muscle wasting are urgently needed. The dissection of the molecular pathways responsible for cisplatin-induced muscle dysfunction gives the possibility to identify novel promising therapeutic targets. In this context, the use of animal model of cisplatin-induced cachexia is very useful. Here, we report an update of the most relevant researches on the mechanisms underlying cisplatin-induced muscle wasting and on the most promising potential therapeutic options to preserve muscle mass and function.

Chemotherapy diminishes lipid storage capacity of adipose tissue in a preclinical model of colon cancer

Background

Accelerated loss of adipose tissue in cancer is associated with shorter survival, and reduced quality of life. Evidence is emerging suggesting tumour association with alterations in adipose tissue, but much less is known about drug-related mechanisms contributing to adipose atrophy. Identification of mechanisms by which tumour and cancer treatments, such as chemotherapy, affect adipose tissue are required to develop appropriate therapeutic interventions to prevent fat depletion in cancer. This pre-clinical study aimed to assess alterations in adipose tissue during the clinical course of cancer.

Methods

Fischer 344 rats bearing the Ward colorectal tumour were euthanized before chemotherapy, after 1- cycle, or 2-cycles of a combination chemotherapy consisting of Irinotecan (CPT-11) combined with 5-fluorouracil (5-FU), which recapitulates first line treatment for human colorectal cancer. Periuterine adipose tissue was isolated. Healthy rats served as a reference group. Histological analysis (hematoxylin and eosin), Real-time PCR (TaqMan) and proteomic analysis (LC-MS/MS) were performed.

Results

Larger adipocytes (3993.7 ± 52.6 μm²) in tumour-bearing animals compared to the reference group (3227.7 ± 36.7 μm²; p < 0.001) was associated with reduced expression of proteins involved in mitochondrial fatty acid oxidation. The presence of a tumour has a significant effect on phospholipid but not triglyceride fatty acid composition. There were greater proportions of saturated fatty acids concurrent with lower monounsaturated fatty acids within the PL fraction of adipocytes in tumour-bearing animals. Chemotherapy treatment decreased the size of adipocytes (2243.9 ± 30.4 μm²; p < 0.001) and led to depletion of n-3 polyunsaturated fatty acids in adipose tissue triglyceride. Evaluation of the proteome profile revealed decreased expression of proteins involved in ATP generation, β-oxidation, and lipogenesis. Overall, adipose tissue may not be able to efficiently oxidize fatty acids to provide energy to maintain energy demanding pathways like lipogenesis inside the tissue.

Conclusions

In conclusion, metabolic adaptations to mitochondrial impairment may contribute to diminished lipid storage capacity of adipose tissue following chemotherapy delivery.

Electronic supplementary material

The online version of this article (10.1186/s12944-017-0638-8) contains supplementary material, which is available to authorized users.

Potential Biomarkers of Fat Loss as a Feature of Cancer Cachexia

Fat loss is associated with shorter survival and reduced quality of life in cancer patients. Effective intervention for fat loss in cachexia requires identification of the condition using prognostic biomarkers for early detection and prevention of further depletion. No biomarkers of fat mass alterations have been defined for application to the neoplastic state. Several inflammatory cytokines have been implicated in mediating fat loss associated with cachexia; however, plasma levels may not relate to adipose atrophy. Zinc-α2-glycoprotein may be a local catabolic mediator within adipose tissue rather than serving as a plasma biomarker of fat loss. Plasma glycerol and leptin associate with adipose tissue atrophy and mass, respectively; however, no study has evaluated their potential as a prognostic biomarker of cachexia-associated fat loss. This review confirms the need for further studies to identify valid prognostic biomarkers to identify loss of fat based on changes in plasma levels of biomarkers.

Evidence and mechanisms of fat depletion in cancer

The majority of cancer patients experience wasting characterized by muscle loss with or without fat loss. In human and animal models of cancer, body composition assessment and morphological analysis reveals adipose atrophy and presence of smaller adipocytes. Fat loss is associated with reduced quality of life in cancer patients and shorter survival independent of body mass index. Fat loss occurs in both visceral and subcutaneous depots; however, the pattern of loss has been incompletely characterized. Increased lipolysis and fat oxidation, decreased lipogenesis, impaired lipid depositionand adipogenesis, as well as browning of white adipose tissue may underlie adipose atrophy in cancer. Inflammatory cytokines such as interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), and interleukin-1 beta (IL-1β) produced by the tumor or adipose tissue may also contribute to adipose depletion. Identifying the mechanisms and time course of fat mass changes in cancer may help identify individuals at risk of adipose depletion and define interventions to circumvent wasting. This review outlines current knowledge of fat mass in cancer and illustrates the need for further studies to assess alterations in visceral and subcutaneous adipose depots and possible mechanisms for loss of fat during cancer progression.

Inhibition of cisplatin-induced lipid catabolism and weight loss by ghrelin in male mice

Cachexia, defined as an involuntary weight loss ≥ 5%, is a serious and dose-limiting side effect of chemotherapy that decreases survival in cancer patients. Alterations in lipid metabolism are thought to cause the lipodystrophy commonly associated with cachexia. Ghrelin has been proposed to ameliorate the alterations in lipid metabolism due to its orexigenic and anabolic properties. However, the mechanisms of action through which ghrelin could potentially ameliorate chemotherapy-associated cachexia have not been elucidated. The objectives of this study were to identify mechanisms by which the chemotherapeutic agent cisplatin alters lipid metabolism and to establish the role of ghrelin in reversing cachexia. Cisplatin-induced weight and fat loss were prevented by ghrelin. Cisplatin increased markers of lipolysis in white adipose tissue (WAT) and of β-oxidation in liver and WAT and suppressed lipogenesis in liver, WAT, and muscle. Ghrelin prevented the imbalance between lipolysis, β-oxidation, and lipogenesis in WAT and muscle. Pair-feeding experiments demonstrated that the effects of cisplatin and ghrelin on lipogenesis, but not on lipolysis and β-oxidation, were due to a reduction in food intake. Thus, ghrelin prevents cisplatin-induced weight and fat loss by restoring adipose tissue functionality. An increase in caloric intake further enhances the anabolic effects of ghrelin.

Adipose triglyceride lipase contributes to cancer-associated cachexia

Cachexia is a multifactorial wasting syndrome most common in patients with cancer that is characterized by the uncontrolled loss of adipose and muscle mass. We show that the inhibition of lipolysis through genetic ablation of adipose triglyceride lipase (Atgl) or hormone-sensitive lipase (Hsl) ameliorates certain features of cancer-associated cachexia (CAC). In wild-type C57BL/6 mice, the injection of Lewis lung carcinoma or B16 melanoma cells causes tumor growth, loss of white adipose tissue (WAT), and a marked reduction of gastrocnemius muscle. In contrast, Atgl-deficient mice with tumors resisted increased WAT lipolysis, myocyte apoptosis, and proteasomal muscle degradation and maintained normal adipose and gastrocnemius muscle mass. Hsl-deficient mice with tumors were also protected although to a lesser degree. Thus, functional lipolysis is essential in the pathogenesis of CAC. Pharmacological inhibition of metabolic lipases may help prevent cachexia.

Computational modeling of cancer cachexia

PURPOSE OF REVIEW

Measurements of whole-body energy expenditure, body composition, and in-vivo metabolic fluxes are required to quantitatively understand involuntary weight loss in cancer cachexia. Such studies are rare because cancer cachexia occurs near the end of life when invasive metabolic tests may be precluded. Thus, models of cancer-associated weight loss are an important tool for helping to understand this debilitating condition.

RECENT FINDINGS

A computational model of human macronutrient metabolism was recently developed that simulates the normal metabolic adaptations to semi-starvation and re-feeding. Here, this model was used to integrate data on the metabolic changes in patients with cancer cachexia. The resulting computer simulations show how the known metabolic disturbances synergize with reduced energy intake to result in a progressive loss of body weight, fat mass, and fat-free mass. The model was also used to simulate the effects of nutritional support and investigate inhibition of lipolysis versus proteolysis as potential therapeutic approaches for cancer cachexia.

SUMMARY

Computational modeling is a new tool that can integrate clinical data on the metabolic changes in cancer cachexia and provide a conceptual framework to help understand involuntary weight loss and predict the effects of potential therapies.

Common symptoms in advanced cancer

The key points of this article are anorexia and cachexia are: A major cause of cancer deaths. Several drugs are available to treat anorexia and cachexia. Dyspnea in cancer usually is caused by several factors. Treatment consists of reversing underlying causes, empiric bronchodilators, cortico-steroids--and in the terminally ill patients-opioids, benzodiazepines,and chlorpromazine. Delirium is associated with advanced cancer. Empiric treatment with neuroleptics while evaluating for reversible causes is a reasonable approach to management. Nausea and vomiting are caused by extra-abdominal factors (drugs,electrolyte abnormalities, central nervous system metastases) or intra-abdominal factors (gastroparesis, ileus, gastric outlet obstruction, bowel obstruction). The pattern of nausea and vomiting differs depending upon whether the cause is extra- or intra-abdominal. Reversible causes should be sought and empiric metoclopramide or haloperidol should be initiated. Fatigue may be caused by anemia, depression, endocrine abnormalities,or electrolyte disturbances that should be treated before using empiric methylphenidate. Constipation should be treated with laxatives and stool softeners. Both should start with the first opioid dose.

Cancer-associated malnutrition

Malnutrition is a common problem among patients with cancer, affecting up to 85% of patients with certain cancers (e.g. pancreas). In severe cases, malnutrition can progress to cachexia, a specific form of malnutrition characterised by loss of lean body mass, muscle wasting, and impaired immune, physical and mental function. Cancer cachexia is also associated with poor response to therapy, increased susceptibility to treatment-related adverse events, as well as poor outcome and quality of life. Cancer cachexia is a complex, multifactorial syndrome, which is thought to result from the actions of both host- and tumour-derived factors, including cytokines involved in a systemic inflammatory response to the tumour. Early intervention with nutritional supplementation has been shown to halt malnutrition, and may improve outcome in some patients. However, increasing nutritional intake is insufficient to prevent the development of cachexia, reflecting the complex pathogenesis of this condition. Nutritional supplements containing anti-inflammatory agents, for example the polyunsaturated fatty acid (PUFA) eicosapentanoic acid (EPA), have been shown to be more beneficial to malnourished patients than nutritional supplementation alone. EPA has been shown to interfere with multiple mechanisms implicated in the pathogenesis of cancer cachexia, and in clinical studies, has been associated with reversal of cachexia and improved survival.

Cancer cachexia

Cancer cachexia is a complex, multifactorial syndrome that results from a reduction in food intake, a variety of metabolic abnormalities (including hypermetabolism) or more often a combination of the two. Multiple mediator pathways including pro-inflammatory cytokines, neuroendocrine hormones and tumour-specific factors are involved. Therapy requires a multi-model approach that addresses both reduced food intake and metabolic change. Combination treatments such as nutritional support plus metabolic/inflammation modulation promise improved functional capacity and quality of life.

Cancer cachexia

Cachexia is a common cause of morbidity and mortality in patients with advanced cancer. It is characterised by numerous metabolic abnormalities including inefficient substrate utilisation, alterations in the balance of energy intake and expenditure and the acute-phase protein response. These changes seem to be driven by pro-inflammatory cytokines, alterations of the neuro-endocrine axis and tumour-derived catabolic factors. This results in the loss of both fat and lean tissue. Trials of conventional nutritional supplements in patients with cancer cachexia have failed to show any benefit in terms of weight gain or quality of life and this may be because the ongoing metabolic abnormalities prevent the efficient use of additional calories supplied. A variety of pharmacological agents have been studied in an attempt to normalise these metabolic changes with only limited success. However, it is possible that the combination of an agent to normalise the metabolic milieu along with the provision of additional nutritional support may have the potential to reverse cachexia in advanced cancer.

Insulin resistance was connected with the alterations of substrate utilization in patients with cancer

To elucidate the contribution of insulin resistance to substrate utilization, insulin sensitivity and substrate oxidation were examined in 19 cancer patients and five normal controls using the euglycemic hyperinsulinemic glucose clamp technique combined with indirect calorimetry. Glucose uptake and storage were significantly decreased in cancer patients compared with that of controls. In cancer patients, both glucose storage and oxidation were positively correlated with metabolized glucose as measured by the M value in cancer patients. Decrease in glucose uptake was mainly a reflection of decreased glucose storage rather than glucose oxidation. Inversely fat oxidation was negatively correlated with both the M value and glucose oxidation in cancer patients. In cancer patients with insulin resistance, decreased glucose uptake was closely associated with a rapid decrease in glucose storage, an increase in fat oxidation and a mild decrease in glucose oxidation, suggesting that insulin resistance was connected with the alterations of substrate utilization which may induce host depletion.

Isolation, characterization, and distribution of a 24-kDa proteoglycan in the urine of cachectic cancer and AIDS patients

Substantial weight loss in individuals with AIDS or cancer is associated with a poor prognosis and increased mortality. We have isolated and partially characterized a proteoglycan (named azaftig) from the urine of a cancer patient experiencing weight loss. Furthermore, we have raised a polyclonal antibody to azaftig in rabbits and developed a procedure to measure the level of this proteoglycan in urine by Western blot. We report the presence of azaftig in the urine of cancer and AIDS patients experiencing weight loss, but not in the control or weight-stable subjects. The azaftig-like immunoreactivity was present in 69.2% (9/13) of patients with weight loss, but only in 27.0% (3/11) of weight-stable cancer or AIDS patients and none of the control subjects (n = 8).

Total parenteral nutrition and home parenteral nutrition: an effective combination to sustain malnourished children with cancer

A patient with Wilms' tumor and severe failure to thrive required total parenteral nutrition (TPN) for "catch-up" growth. This case underscores how TPN might be useful in the management of a child with cancer. Cancer cachexia, chemotherapy, radiation, and infections caused by immune suppression can lead to potentially serious macro- and micronutrient deficiencies.

Metabolic alteration in patients with cancer: nutritional implications

During the past 20 years, efforts have been made to elucidate the metabolic changes observed in patients with cancer by using stable and radioactive isotopic tracers. These metabolic changes in patients with cancer may be similar to those in other stress conditions, in which glucose production and utilization, lipolysis and free fatty acid flux, and net protein catabolism are increased. Stress hormones, such as glucagon and catecholamines, and certain cytokines may be responsible for these metabolic changes. Although it has been shown that cachexia in patients with cancer signals a poor prognosis, efforts to improve the clinical outcomes with nutritional support have been disappointing. The failure of cancer patients to respond to nutritional support may be related to an alteration in the intermediate metabolism. Therefore, further research evaluating the metabolic abnormalities associated with cancer may lead to more effective nutritional therapies.

Metabolic response to radiation therapy in patients with cancer

The effect of radiation therapy on substrate metabolism was evaluated in five patients with head and neck or lung cancer. Stable isotope tracer methodology was used to determine urea, amino acid, glucose, and lipid kinetics during postabsorptive conditions before initiation, near the midpoint (after receiving 2,672 +/- 36 rads), and at completion (after receiving 6,072 +/- 307 rad) of a 6- to 8-week course of radiation therapy. Nutritional status was maintained throughout the treatment period by providing supplemental enteral feedings as needed. Postabsorptive plasma insulin, catecholamine, and amino acid concentrations did not change during the course of treatment. Before radiation therapy was initiated, values for the plasma rate of appearance (Ra) of urea (3.35 +/- 0.33 micromol x kg(-1) x min(-1)), alpha-ketoisocaproate ([alpha-KIC] 2.16 +/- 0.19 micromol x kg(-1) x min(-1)), phenylalanine (0.59 +/- 0.052 micromol x kg(-1) x min(-1)), and glucose (10.56 +/- 1.31 micromol x kg(-1) x min(-1)) were in the normal range. However, glycerol and palmitate Ra values (3.11 +/- 0.30 and 2.01 +/- 0.33 micromol x kg(-1) x min(-1), respectively) were 25% higher than values observed previously in normal subjects. Substrate flux did not change during radiation therapy, and measurements obtained during the midpoint and at completion of treatment were similar to initial values. These results demonstrate that large doses of radiation therapy, administered over 6 to 8 weeks to the upper body, do not cause significant metabolic stress.

Perioperative care of the oncology patient

Cancer patients are often at high risk for perioperative complications because of preexisting conditions, the magnitude of surgery, and the use of aggressive multimodality treatment. It is essential to identify risk factors preoperatively, correct any deficits, and monitor organ dysfunction. During the perioperative period prophylaxis and surveillance for cardiopulmonary, hematologic, and septic complications should minimize morbidity and mortality. Finally, nutritional support should be given to malnourished patients undergoing extensive operative procedures.

Lipid metabolism in cachectic tumor-bearing rats at different stages of tumor growth

Rates of lipogenesis and lipoprotein lipase (LPL) activity were measured in liver, adipose tissue, heart, and tumor at several stages during 10 days of palpable growth of a transplantable Leydig cell tumor in rats. This model showed the same characteristics as human cancer cachexia, including anorexia, weight loss, and muscle wasting. Comparison with pair-fed controls showed that the rate of loss of body fat was greater than could be explained by anorexia alone. The rate of lipogenesis tended to decrease during the later stages of tumor growth, particularly in the liver, where there was a statistically significant reduction on Days 5 and 10. This may be largely attributable to decreased availability of substrates caused by decreasing food intake and increasing glucose uptake by the tumor. There was a significant decrease in plasma glucose concentration by Day 10. In contrast, LPL activity in adipose tissue was depressed from the earliest stage of tumor growth, and this is likely to be a major cause of lipid depletion in cancer. There was no difference in adipose tissue LPL activity between the fed and postabsorptive states in the tumor-bearing rats, indicating that the normal response to nutrient intake was impaired. Thus, treatment of cancer cachexia should concentrate on normalizing the metabolic response to nutrient ingestion.

Perioperative nutrition in cancer patients

Cancer patients have the highest incidence of protein-calorie malnutrition seen in hospitalized patients, with significant malnutrition occurring in more than 30% of cancer patients undergoing major upper gastrointestinal procedures. Clinically significant malnutrition occurs as a result of diminished nutrient intake, increased nutrient losses, and tumor-induced derangements in host metabolism. In the absence of adequate exogenous nutrients, the body utilizes endogenous substrates to satisfy the ongoing requirements of both host and tumor for energy and protein. In those patients with malignant obstruction of the gastrointestinal tract, the tumor itself may induce diminished nutrient intake. Present day treatment modalities including gastrointestinal resection, chemotherapy, and radiotherapy compound these metabolic derangements, further increasing the risk of postoperative morbidity and death. The presence of malnutrition in cancer patients has prognostic importance. In a review of more than 3000 cancer patients, DeWys and colleagues identified significantly improved survival in those patients without weight loss compared with those had lost 6% of their body weight (Am J Med 69:491-497, 1980). Other investigators have noted increased postoperative morbidity and mortality associated with malnutrition. Early hypotheses suggested that reversal of weight loss would improve survival. The development and refinements of enteral and parenteral nutrition have provided the opportunity for studying the relationship between nutritional supplementation and postoperative prognosis. Nutrition support is therefore often instituted to improve nutritional status and thereby reduce the risks of postoperative complications. This article addresses the beneficial role of preoperative nutrition therapy in cancer patients.

Hormonal and metabolic abnormalities in the malnourished cancer patient: effects on host-tumor interaction

Many common metastatic cancers are associated with marked weight loss at the time of diagnosis. Anorexia clearly plays a major role in weight loss in the cancer patient, but cannot explain all of the weight loss noted. Malnourished patients with localized cancers under metabolic ward conditions fail to gain weight when given apparently adequate calories for anabolism, thus suggesting that these patients are hypermetabolic. Increased whole body protein breakdown, increased lipolysis, and increased gluconeogenesis have been repeatedly demonstrated in malnourished cancer patients. Protein and glucose metabolism are closely linked, and both are regulated by a number of the same hormones and metabolites. For example, when increased glucose production in malnourished cancer patients is inhibited pharmacologically, protein catabolism is proportionally decreased. Studies of glucose, growth hormone, cortisol, and insulin secretion following an oral glucose load in well-nourished cancer patients are consistent with insulin resistance but no other hormonal abnormalities. Malnourished cancer patients have elevated levels of growth hormone that are further stimulated by arginine and insulin infusion. No abnormalities of thyroid function were noted in cancer patients. Current studies are underway to determine the mechanisms and effects of progestational steroids and cytokines on both food intake and intermediary lipid metabolism.

Lipogenesis in tumour and host tissues in mice bearing colonic adenocarcinomas

Although animals bearing the MAC16 colon adenocarcinoma showed progressive weight loss, the average food consumption (15.1 +/- 0.6 Kcal day-1) did not differ from non tumour-bearing controls (15.3 +/- 0.3 Kcal day-1), while animals bearing a related colon adenocarcinoma, MAC13, which had no effect on body weight had a significantly (P less than 0.01) elevated food intake (16.4 +/- 0.3 Kcal day-1) above controls. Weight loss in animals bearing the MAC16 tumour was associated with a significant reduction in the percentage contribution of the kidneys, colon and epididymal fat pads to the total body weight. Although loss of body fat occurred only in the MAC16 model, both tumours were capable of synthesising lipids from glucose both in vitro and in vivo at the same rate. In addition both tumours increased the rate of lipogenesis from glucose in kidney, liver and epididymal fat pads of the host. Lipogenesis from glucose would be expected to result in a loss of utilisable carbohydrate energy and thus would be expected to increase the overall energy requirements in the tumour-bearing state leading to catabolism of host body tissues if the energy intake is not increased.

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.

Whole-body lipolysis and triglyceride-fatty acid cycling in cachectic patients with esophageal cancer

Whole-body lipolytic rates and the rate of triglyceride-fatty acid cycling (reesterification of fatty acids released during lipolysis) were measured with stable isotopic tracers in the basal state and during beta-adrenergic blockade with propranolol infusion in five cachectic patients with squamous cell carcinoma of the esophagus, five cachectic cancer-free, nutritionally-matched control patients, and 10 healthy volunteers. Resting energy expenditure and plasma catecholamines were normal in all three groups. The basal rate of glycerol appearance in blood in the patients with cancer (2.96 +/- 0.45 mumol.kg-1.min-1) was similar to that in the nutritionally matched controls (3.07 +/- 0.28 mumol.kg-1.min-1), but 48% greater than in the normal-weight volunteers (2.00 +/- 0.16 mumol.kg-1.min-1) (P = 0.028). The antilipolytic effect of propranolol and the rate of triglyceride-fatty acid cycling in the patients with cancer were also similar in the cachectic control group and approximately 50% greater than in the normal-weight volunteers, but the differences were not statistically significant because of the variability in the data. We conclude that the increase in lipolysis and triglyceride-fatty acid cycling in "unstressed" cachectic patients with esophageal cancer is due to alterations in their nutritional status rather than the presence of tumor itself. Increased beta-adrenergic activity may be an important contributor to the stimulation of lipolysis.

Energy cost of fat-fuel mobilization in geriatric trauma

Age-related changes in body composition may result in varied responses to acute accidental injury. Gaining fat as age advances is common and therefore the mobilization of fat fuel resources in traumatized geriatric patients needs closer examination. We have measured in six elderly (age, 60 to 74 years) and seven young (age, 18 to 46) traumatized, hypermetabolic, and highly catabolic patients, in the "flow phase" of the metabolic response to injury, the rates of whole-body lipolysis and net fat oxidation. This enabled us to calculate the rate of triglyceride/free fatty acid (TG/FFA) cycling in the whole body and to assess its contribution to energy expenditure. Energy metabolism in general and the fat metabolism in particular were found to be somewhat slowed in elderly trauma patients compared with equally injured young individuals, although the aged patients had more total body fat. The energy cost of TG/FFA cycling is significantly (P less than .025) lower in elderly trauma victims (0.28 +/- 0.06 kcal/kg/d) compared with young patients (0.63 +/- 0.1 kcal/kg/d). This can account for approximately 3% to 4% of the elevation in metabolic rate over that predicted in the uninjured state.

Increased urinary excretion of cortisol and catecholami-NES in malnourished cancer patients

Excretion of cortisol and catecholamines were measured from 24-hour urine samples collected over a period of 3 days from hospitalized cancer patients suffering from malnutrition and were compared with those of control patients equally malnourished and having a similar degree of inflammation. Compared with control patients, cancer patients had a higher excretion of cortisol, adrenaline, and noradrenaline, although noradrenaline excretion reached statistical significance only when normalized to creatinine excretion. Plasma glycerol concentrations after an overnight fast were significantly higher in cancer patients as compared with control patients, in keeping with an increased adrenal and adrenergic activity. This study demonstrates evidence of simultaneously elevated catecholamine and cortisol excretion in cancer patients, which could not be ascribed to alteration in body composition. The results may, in part, explain the mechanisms behind ongoing tissue breakdown in progressive cancer disease.

Free fatty acid turnover and lipolysis in septic mechanically ventilated cancer-bearing humans

Loss of body fat and lean body mass are features of critical illness, and anabolism is difficult to achieve despite parenteral nutrition. Resting energy expenditure (REE), free fatty acid turnover (FFT) and glycerol turnover (glyTO) were measured in septic, mechanically ventilated cancer-bearing patients, both fasting and immediately following or during a glucose infusion providing 87% of REE. No patient was in septic shock nor required pressor support. In the fasting state, REE was greatly elevated compared with basal energy expenditure calculated using the Harris-Benedict equations. Fasting FFT (14.2 +/- 0.9 mumol/kg/min) and glyTO (4.7 +/- 0.5 mumol/kg/min) were elevated compared with normal humans. Fasting respiratory quotient (RQ) was 0.68 +/- 0.02 and did not rise significantly with glucose. Fat appears to be the preferred calorie source in septic, cancer-bearing humans even in the presence of glucose. As similar, but less pronounced, changes have been seen in septic and injured humans without cancer, it is likely that these changes are not cancer-specific.

Whole body lipid and energy metabolism in the cancer patient

The relationship between whole-body energy and lipid kinetics in eight cancer patients was investigated after an overnight fast. Respiratory gas exchange and indirect calorimetry were used to obtain resting energy expenditure (REE) and net substrate oxidation rates. Free fatty acid (FFA) turnover, oxidation, and clearance rates were obtained after a primed-constant infusion of albumin bound 1-14C-Na palmitate. This was followed by a primed-constant, two-stage infusion of unlabeled glycerol to measure plasma glycerol turnover and clearance. The REE was 1.3 times the predicted (by the Harris-Benedict equation) basal energy expenditure. FFA and glycerol, plasma concentrations, and turnover rates were higher in these depleted but hypermetabolic cancer patients, compared to reported values for healthy normals. The ratio of FFA turnover to glycerol turnover was 3.14 +/- 0.38, which is close to the theoretical value of 3, suggesting complete hydrolysis of triglycerides and the absence of any extensive reesterification of FFA in adipose tissue. The net fat oxidation accounts for 53 +/- 5% of fat mobilized and 29 +/- 3% of the FFA turnover was converted to CO2 in the process of supplying energy in cancer patients. The results suggest that fat is efficiently mobilized and utilized as a fuel source in hypermetabolic cancer patients in the postabsorptive state.