Increased brown adipose tissue activity in children with malignant disease

The Different Shades of Thermogenic Adipose Tissue

PURPOSE OF REVIEW

By providing a concise overview of adipose tissue types, elucidating the regulation of adipose thermogenic capacity in both physiological contexts and chronic wasting diseases (a protracted hypermetabolic state that precipitates sustained catabolism and consequent progressive corporeal atrophy), and most importantly, delving into the ongoing discourse regarding the role of adipose tissue thermogenic activation in chronic wasting diseases, this review aims to provide researchers with a comprehensive understanding of the field.

RECENT FINDINGS

Adipose tissue, traditionally classified as white, brown, and beige (brite) based on its thermogenic activity and potential, is intricately regulated by complex mechanisms in response to exercise or cold exposure. This regulation is adipose depot-specific and dependent on the duration of exposure. Excessive thermogenic activation of adipose tissue has been observed in chronic wasting diseases and has been considered a pathological factor that accelerates disease progression. However, this conclusion may be confounded by the detrimental effects of excessive lipolysis. Recent research also suggests that such activation may play a beneficial role in the early stages of chronic wasting disease and provide potential therapeutic effects. A more comprehensive understanding of the changes in adipose tissue thermogenesis under physiological and pathological conditions, as well as the underlying regulatory mechanisms, is essential for the development of novel interventions to improve health and prevent disease.

Endothelial TrkA coordinates vascularization and innervation in thermogenic adipose tissue and can be targeted to control metabolism

OBJECTIVE

Brown adipogenesis and thermogenesis in brown and beige adipose tissue (AT) involve vascular remodeling and sympathetic neuronal guidance. Here, we investigated the molecular mechanism coordinating these processes.

METHODS

We used mouse models to identify the molecular target of a peptide CPATAERPC homing to the endothelium of brown and beige AT.

RESULTS

We demonstrate that CPATAERPC mimics nerve growth factor (NGF) and identify a low molecular weight isoform of NGF receptor, TrkA, as the CPATAERPC cell surface target. We show that the expression of truncated endothelial TrkA is selective for brown and subcutaneous AT. Analysis of mice with endothelium-specific TrkA knockout revealed the role of TrkA in neuro-vascular coordination supporting the thermogenic function of brown adipocytes. A hunter-killer peptide D-BAT, composed of CPATAERPC and a pro-apoptotic domain, induced cell death in the endothelium and adipocytes. This resulted in thermogenesis impairment, and predisposed mice to obesity and glucose intolerance. We also tested if this treatment can inhibit the tumor recruitment of lipids mobilized from adipocytes from adjacent AT. Indeed, in a mouse model of breast cancer D-BAT suppressed tumor-associated AT lipolysis, which resulted in reduced fatty acid utilization by cancer cells.

CONCLUSION

Our study demonstrates that TrkA signaling in the endothelium supports neuro-vascular coordination enabling beige adipogenesis.

Metabolic Reprogramming in Adipose Tissue During Cancer Cachexia

Cancer cachexia is a disorder of energy balance characterized by the wasting of adipose tissue and skeletal muscle resulting in severe weight loss with profound influence on morbidity and mortality. Treatment options for cancer cachexia are still limited. This multifactorial syndrome is associated with changes in several metabolic pathways in adipose tissue which is affected early in the course of cachexia. Adipose depots are involved in energy storage and consumption as well as endocrine functions. In this mini review, we discuss the metabolic reprogramming in all three types of adipose tissues – white, brown, and beige – under the influence of the tumor macro-environment. Alterations in adipose tissue lipolysis, lipogenesis, inflammation and adaptive thermogenesis of beige/brown adipocytes are highlighted. Energy-wasting circuits in adipose tissue impacts whole-body metabolism and particularly skeletal muscle. Targeting of key molecular players involved in the metabolic reprogramming may aid in the development of new treatment strategies for cancer cachexia.

Brown fat does not cause cachexia in cancer patients: A large retrospective longitudinal FDG-PET/CT cohort study

Background

Brown adipose tissue (BAT) is a specialized form of adipose tissue, able to increase energy expenditure by heat generation in response to various stimuli. Recently, its pathological activation has been implicated in the pathogenesis of cancer cachexia. To establish a causal relationship, we retrospectively investigated the longitudinal changes in BAT and cancer in a large FDG-PET/CT cohort.

Methods

We retrospectively analyzed 13 461 FDG-PET/CT examinations of n = 8 409 patients at our institution from the winter months of 2007–2015. We graded the activation strength of BAT based on the anatomical location of the most caudally activated BAT depot into three tiers, and the stage of the cancer into five general grades. We validated the cancer grading by an interreader analysis and correlation with histopathological stage. Ambient temperature data (seven-day average before the examination) was obtained from a meteorological station close to the hospital. Changes of BAT, cancer, body mass index (BMI) and temperature between the different examinations were examined with Spearman’s test and a mixed linear model for correlation, and with a causal inference algorithm for causality.

Results

We found n = 283 patients with at least two examinations and active BAT in at least one of them. There was no significant interaction between the changes in BAT activation, cancer burden or BMI. Temperature changes exhibited a strong negative correlation with BAT activity (ϱ = -0.57, p<0.00001). These results were confirmed with the mixed linear model. Causal inference revealed a link of Temperature ➜ BAT in all subjects and also of BMI ➜ BAT in subjects who had lost weight and increased cancer burden, but no role of cancer and no causal links of BAT ➜ BMI.

Conclusions

Our data did not confirm the hypothesis that BAT plays a major role in cancer-mediated weight loss. Temperature changes are the main driver of incidental BAT activity on FDG-PET scans.

CDK7 Mediates the Beta-Adrenergic Signaling in Thermogenic Brown and White Adipose Tissues

Cyclin-dependent kinases (CDKs) are emerging regulators of adipose tissue metabolism. Here we aimed to explore the role of CDK7 in thermogenic fat. We found that CDK7 brown adipose tissue (BAT)-specific knockout mice (Cdk7^bKO) have decreased BAT mass and impaired β3-adrenergic signaling and develop hypothermia upon cold exposure. We found that loss of CDK7 in BAT disrupts the induction of thermogenic genes in response to cold. However, Cdk7^bKO mice do not show systemic metabolic dysfunction. Increased expression of genes of the creatine metabolism compensates for the heat generation in the BAT of Cdk7^bKO mice in response to cold. Finally, we show that CDK7 is required for beta 3-adrenergic agonist-induced browning of white adipose tissue (WAT). Indeed, Cdk7 ablation in all adipose tissues (Cdk7^aKO) has impaired browning in WAT. Together, our results demonstrate that CDK7 is an important mediator of beta-adrenergic signaling in thermogenic brown and beige fat.

Is Neuronal Histamine Signaling Involved in Cancer Cachexia? Implications and Perspectives

In this paper, we present evidence in support of our hypothesis that the neuronal histaminergic system might be involved in cancer cachexia¹. To build our premise, we present the research and the reasonable inferences that can be drawn from it in a section by section approach starting from one of the key issues related to cachexia, increased resting energy expenditure (REE), and progressing to the other, anorexia. Based on an extensive survey of the literature and our own deliberations on the abovementioned topics, we investigate whether histamine signaling might be the mechanism used by a tumor to hijack the body's thermogenic machinery. Our hypothesis in short is that hypothalamic histaminergic neurons are stimulated by inputs from the parasympathetic nervous system (PSNS), which senses tumor traits early in cancer development. Histamine release in the preoptic area of the hypothalamus primarily activates brown adipose tissue (BAT), triggering a highly energy demanding mechanism. Chronic activation of BAT, which, in this context, refers to intermittent and/or low grade activation by the sympathetic nervous system, leads to browning of white adipose tissue and further enhances thermogenic potential. Aberrant histamine signaling not only triggers energy-consuming processes, but also anorexia. Moreover, since functions such as taste, smell, and sleep are governed by discrete structures of the brain, which are targeted by distinct histaminergic neuron populations even relatively minor symptoms of cachexia, such as sleep disturbances and taste and smell distortions, also might be ascribed to aberrant histamine signaling. In late stage cachexia, the sympathetic tone in skeletal muscle breaks down, which we hypothesize might be caused by a reduction in histamine signaling or by the interference of other cachexia related mechanisms. Histamine signaling thus might delineate distinct stages of cachexia progression, with the early phase marked by a PSNS-mediated increase in histamine signaling, increased sympathetic tone and symptomatic adipose tissue depletion, and the late phase characterized by reduced histamine signaling, decreased sympathetic tone and symptomatic muscle wasting. To support our hypothesis, we review the literature from across disciplines and highlight the many commonalities between the mechanisms underlying cancer cachexia and current research findings on the regulation of energy homeostasis (particularly as it relates to hypothalamic histamine signaling). Extrapolating from the current body of knowledge, we develop our hypothetical framework (based on experimentally falsifiable assumptions) about the role of a distinct neuron population in the pathophysiology of cancer cachexia. Our hope is that presenting our ideas will spark discussion about the pathophysiology of cachexia, cancer's devastating and intractable syndrome.

Increased UCP1 expression in the perirenal adipose tissue of patients with renal cell carcinoma

Perirenal adipose tissue (PAT) has been implicated in renal cell carcinoma (RCC). The expression of uncoupling protein 1 (UCP1) is higher in PAT compared with that in back subcutaneous adipose tissue (bSAT). The aim of the present study was to determine UCP1 expression in different parts of PAT and to analyze the correlation between UCP1 expression in PAT and RCC. PAT from the upper and lower renal poles and bSAT samples were collected from 50 patients with RCC (RCC group) and 54 patients with renal cysts (control group) who had undergone renal surgery. Both UCP1 mRNA and protein levels were found to be significantly higher and adipocytes appeared to be smaller in the PAT of the RCC group. Furthermore, the RCC group had more multilocular UCP1-positive adipocytes. UCP1 staining in the PAT was significantly stronger in the RCC group, but there was no significant difference in UCP1 staining in the bSAT between the two groups. Furthermore, Fuhrman grade and T stage were higher in the high UCP1 expression group of RCC patients. In conclusion, high UCP1 expression in the PAT may serve as an indicator of poor prognosis in RCC.

The Cancer Cachexia Syndrome: A Review of Metabolic and Clinical Manifestations

The progressive deterioration in nutrition status frequently seen in cancer patients is often referred to as cancer cachexia. Unlike starvation, in which fat stores from adipose are depleted and protein is spared from skeletal muscle, neither fat nor protein is spared in cachexia. Cachexia affects nearly half of cancer patients, causing the clinical manifestations of anorexia, muscle wasting, weight loss, early satiety, fatigue, and impaired immune response. Cachexia does not only impede the response to chemotherapy but also is a major cause of morbidity and mortality. According to clinical studies, increasing caloric intake does not necessarily reverse cachexia. The pathophysiology of cachexia involves more complex mechanisms than simply caloric deficiency. The process appears to be mediated by circulating catabolic factors, either secreted by the tumor alone or in concert with host-derived factors, such as tumor necrosis factor-alpha (TNF-alpha), interleukins (IL-1 and IL-6), interferon (IFN-y), and leukemia inhibitory factor (LIF). The successful reversal of this process will require in-depth knowledge of the mechanisms involved, which will then enable the development of effective pharmacologic interventions that may not only improve quality of life, but more importantly, improve survival among cancer patients.

Muscle wasting and adipose tissue browning in infantile nephropathic cystinosis

BACKGROUND

Muscle wasting is a common complication in patients with infantile nephropathic cystinosis, but its mechanism and association with energy metabolism is not known. We define the metabolic phenotype in Ctns(-/-) mice, an established murine model of infantile nephropathic cystinosis, with focus on muscle wasting and energy homeostasis.

METHODS

Male Ctns(-/-) mice and wild-type (WT) controls were studied at 1, 4, 9, and 12 months of age. As Ctns(-/-) mice started to develop chronic kidney disease (CKD) at 9 months of age, 9- and 12-month-old Ctns(-/-) mice were also compared with age-matched WT mice with CKD. Serum and urine chemistry and energy homeostasis parameters were measured. Skeletal muscle histomorphometry and in vivo muscle function were measured. We studied expression of genes involved in muscle mass regulation, thermogenesis, energy metabolism, adipogenesis, and adipose tissue browning in Ctns(-/-) mice.

RESULTS

Ctns(-/-) mice showed loss of weight and lean mass and increased energy expenditure. Ctns(-/-) mice exhibited abnormal energy homeostasis before the onset of their CKD. Food intake in Ctns(-/-) mice was comparable with age-matched WT controls. However, significantly lower total body mass starting at 1 month of age and increased energy expenditure at 4 months of age preceded the onset of CKD at 9 months of age in Ctns(-/-) mice. Muscle accept content in 1- and 4-month-old Ctns(-/-) mice was significantly lower than that in age-matched WT controls. At 12 months of age, muscle fibre area and in vivo muscle strength was reduced in Ctns(-/-) mice than that in WT or CKD controls. Muscle wasting in Ctns(-/-) mice was associated with inhibition of myogenesis, activation of muscle proteolysis pathways, and overexpression of pro-inflammatory cytokines. Increased energy expenditure was associated with elevation of thermogenesis in skeletal muscle and adipose tissues. The development of beige adipocytes in Ctns(-/-) mice is a novel finding. Expression of beige adipose cell surface markers (CD137, Tmem26, and Tbx1) and uncoupling protein-1, which is a brown adipose tissue marker, was observed in inguinal white adipose tissue of Ctns(-/-) mice. Expression of key molecules implicated in the pathogenesis of adipose tissue browning (Cox2, cytochrome c oxidase subunit II; PGF2α, prostaglandin F2α; IL-1α, interleukin 1α; IL-6, interleukin 6; TNF-α, tumor necrosis factor α) was significantly increased in inguinal white adipose tissue of Ctns(-/-) mice than that in WT controls.

CONCLUSION

This study describes a mouse model of nephropathic cystinosis presenting with profound muscle wasting. The mechanism for hypermetabolism in Ctns(-/-) mice may involve up-regulation of thermogenesis pathways in skeletal muscle and adipose tissues. This study demonstrates, for the first time, the development of beige adipocytes in Ctns(-/-) mice. Understanding the underlying mechanisms of adipose tissue browning in cystinosis may lead to novel therapy.

PTH/PTHrP Receptor Mediates Cachexia in Models of Kidney Failure and Cancer

Cachexia is a wasting syndrome associated with elevated basal energy expenditure and loss of adipose and muscle tissues. It accompanies many chronic diseases including renal failure and cancer and is an important risk factor for mortality. Our recent work demonstrated that tumor-derived PTHrP drives adipose tissue browning and cachexia. Here, we show that PTH is involved in stimulating a thermogenic gene program in 5/6 nephrectomized mice that suffer from cachexia. Fat-specific knockout of PTHR blocked adipose browning and wasting. Surprisingly, loss of PTHR in fat tissue also preserved muscle mass and improved muscle strength. Similarly, PTHR knockout mice were resistant to cachexia driven by tumors. Our results demonstrate that PTHrP and PTH mediate wasting through a common mechanism involving PTHR, and there exists an unexpected crosstalk mechanism between wasting of fat tissue and skeletal muscle. Targeting the PTH/PTHrP pathway may have therapeutic uses in humans with cachexia.

Lipolytic and thermogenic depletion of adipose tissue in cancer cachexia

Although muscle wasting is the obvious manifestation of cancer cachexia that impacts on patient quality of life, the loss of lipid reserves and metabolic imbalance in adipose tissue also contribute to the devastating impact of cachexia. Depletion of fat depots in cancer patients is more pronounced than loss of muscle and often precedes, or even occurs in the absence of, reduced lean body mass. Rapid mobilisation of triglycerides stored within adipocytes to supply the body with fatty acids in periods of high-energy demand is normally mediated through a well-defined process of lipolysis involving the lipases ATGL, HSL and MGL. Studies into how these lipases contribute to fat loss in cancer cachexia have revealed the prominent role for ATGL in initiating lipolysis during adipose tissue atrophy, together with links between tumour-derived factors and the signalling pathways that control lipid flux within fat cells. The recent findings of increased thermogenesis in brown fat during cancer cachexia indicate that metabolically active adipose tissue contributes to the imbalance in energy homeostasis involved in catabolic wasting. Such energetically futile use of fatty acids liberated from adipose tissue to generate heat represents a maladaptive response in conjunction with anorexia experienced by cancer patients. As IL-6 release by tumours provokes lipolysis and activates the thermogenic programme in brown fat, this review explores the overlap in dysregulated metabolic processes due to inflammatory mediators in cancer cachexia and other disease states characterised by elevated cytokines such as obesity and diabetes.

Molecular and neuroendocrine mechanisms of cancer cachexia

Cancer and its morbidities, such as cancer cachexia, constitute a major public health problem. Although cancer cachexia has afflicted humanity for centuries, its underlying multifactorial and complex physiopathology has hindered the understanding of its mechanism. During the last few decades we have witnessed a dramatic increase in the understanding of cancer cachexia pathophysiology. Anorexia and muscle and adipose tissue wasting are the main features of cancer cachexia. These apparently independent symptoms have humoral factors secreted by the tumor as a common cause. Importantly, the hypothalamus has emerged as an organ that senses the peripheral signals emanating from the tumoral environment, and not only elicits anorexia but also contributes to the development of muscle and adipose tissue loss. Herein, we review the roles of factors secreted by the tumor and its effects on the hypothalamus, muscle and adipose tissue, as well as highlighting the key targets that are being exploited for cancer cachexia treatment.

The energy balance in cancer cachexia revisited

PURPOSE OF REVIEW

To review new putative mechanisms involved in the pathophysiology of a disturbed energy balance in cancer cachexia, which can lead to novel targets for clinical cachexia management. In the context of rapid developments in tumour treatment with potential systemic consequences, this article reviews recent data on energy requirements. Furthermore, we focus on new insights in brown adipose tissue (BAT) activity and reward processing in the brain in relation to the cachexia process.

RECENT FINDINGS

Nearly no new data have been published on energy requirements of cancer patients in the light of comprehensive new therapies in oncology. New developments, such as the introduction of staging with 18F-fluorodeoxyglucose PET-computed tomography scanning, led to the observation that BAT activation may contribute to impaired energy balance in cancer cachexia. Animal and human data to date provide an indication that BAT activation indeed occurs, but its quantitative impact on the degree of cachexia is controversial. The peripheral and central nervous system is known to influence satiation, with a possible role for impaired food reward processing in the brain. To date, there are limited confirmatory data, but this is an interesting new area to explore for better understanding and treating cancer-induced anorexia.

SUMMARY

The multimodal approach to counteract cancer cachexia should expand its targets to BAT and food reward processing in the brain.

Tumour-derived PTH-related protein triggers adipose tissue browning and cancer cachexia

Cachexia is a wasting disorder of adipose and skeletal muscle tissues that leads to profound weight loss and frailty. About half of all cancer patients suffer from cachexia, which impairs quality of life, limits cancer therapy and decreases survival. One key characteristic of cachexia is higher resting energy expenditure levels than in healthy individuals, which has been linked to greater thermogenesis by brown fat. How tumours induce brown fat activity is unknown. Here, using a Lewis lung carcinoma model of cancer cachexia, we show that tumour-derived parathyroid-hormone-related protein (PTHrP) has an important role in wasting, through driving the expression of genes involved in thermogenesis in adipose tissues. Neutralization of PTHrP in tumour-bearing mice blocked adipose tissue browning and the loss of muscle mass and strength. Our results demonstrate that PTHrP mediates energy wasting in fat tissues and contributes to the broader aspects of cancer cachexia. Thus, neutralization of PTHrP might hold promise for ameliorating cancer cachexia and improving patient survival.

A role of active brown adipose tissue in cancer cachexia?

Until a few years ago, adult humans were not thought to have brown adipose tissue (BAT). Now, this is a rapidly evolving field of research with perspectives in metabolic syndromes such as obesity and new therapies targeting its bio-energetic pathways. White, brown and so-called brite adipose fat seem to be able to trans-differentiate into each other, emphasizing the dynamic nature of fat tissue for metabolism. Human and animal data in cancer cachexia to date provide some evidence for BAT activation, but its quantitative impact on energy expenditure and weight loss is controversial. Prospective clinical studies can address the potential role of BAT in cancer cachexia using ¹⁸F-fluoro- deoxyglucose positron emission tomography-computed tomography scanning, with careful consideration of co-factors such as diet, exposure to the cold, physical activity and body mass index, that all seem to act on BAT recruitment and activity.

A critical appraisal of the prevalence and metabolic significance of brown adipose tissue in adult humans

Brown adipose tissue (BAT) plays a major role in energy homeostasis in animals. Detection of BAT using positron emission tomography (PET)-CT in humans has challenged the view that BAT disappears after infancy. Several recent studies, based on analysis of single scans, have reported a low prevalence of only 5-10% in humans, casting doubt on its significance. We undertook a critical analysis of the sensitivity, reproducibility, and accuracy of PET-CT to deduce the prevalence of BAT and factors associated with its detection in adult humans. In a retrospective evaluation of PET-CT, using [18F]fluorodeoxyglucose, performed in 2,934 patients, BAT was identified in 250 patients, yielding an apparent prevalence of 8.5%. Among those patients with BAT, 145 were scanned more than once. The frequency of another scan being positive increased from 8 to 65% for one to more than four additional studies. The average probability of obtaining another positive scan among patients with BAT is 13%, from which the prevalence of BAT is estimated at 64%. BAT was more commonly detected in women, in younger (36 ± 1 vs. 52 ± 1 years, P < 0.001) and leaner (20.1 ± 0.9 vs. 24.9 ± 0.9 kg/m2, P < 0.01) individuals. Fasting glucose was lower in those with BAT than those without (4.9 ± 0.1 vs. 5.5 ± 0.1 mmol/l, P < 0.01). Among patients scanned more than once, BAT was detected when body weight and fasting glucose were lower (54.9 ± 0.5 vs. 58.2 ± 0.8 kg, P < 0.001 and 4.9 ± 0.3 vs. 5.5 ± 0.3 mmol/l, P = 0.03). We conclude that BAT is present in the majority of adult humans. Presence of BAT correlates negatively with body mass index and glucose concentration. BAT may play an important role in energy homeostasis in adults.

The human uncoupling protein-1 gene (UCP1): present status and perspectives in obesity research

Energy expenditure through brown adipose tissue thermogenesis contributes either to maintenance of body temperature in a cold environment or to wasted food energy, i.e. cold-induced or diet-induced thermogenesis. Both mechanisms are due to a specific and unique protein: the uncoupling protein-1. Uncoupling protein-1 is exclusively expressed in mitochondria of brown adipocytes where it uncouples respiration from ATP synthesis, dissipating the proton gradient as heat. In humans, although uncoupling protein-1 can be detected, the inability to quantify brown adipose tissue makes it difficult to argue for a role for uncoupling protein-1 in thermogenesis and energy expenditure. This review summarizes data supporting the existence of brown adipocytes and the role of UCP1 in energy dissipation in adult humans. Understanding the mechanisms which regulate transcription and expression of the human UCP1 gene will facilitate the identification of molecules able to increase the levels of this protein in order to modulate energy expenditure in adult humans.

The role of cytokines in cancer cachexia

A large number of observations point towards cytokines, polypeptides released mainly by immune cells, as the molecules responsible for the metabolic derangements associated with cancer-bearing states. Indeed, these alterations lead to a pathological state known as cancer cachexia which is, unfortunately, one of the worst effects of malignancy, accounting for nearly a third of cancer deaths. It is characterized by weight loss together with anorexia, weakness, anemia, and asthenia. The complications associated with the appearance of the cachectic syndrome affect both the physiological and biochemical balance of the patient and have effects on the efficiency of the anticancer treatment, resulting in a considerably decreased survival time. At the metabolic level, cachexia is associated with loss of skeletal muscle protein together with a depletion of body lipid stores. The cachectic patient, in addition to having practically no adipose tissue, is basically subject to an important muscle wastage manifested as an excessive nitrogen loss. The metabolic changes are partially mediated by alterations in circulating hormone concentrations (insulin, glucagon, and glucocorticoids in particular) or in their effectiveness. The present study reviews the involvement of different cytokines in the metabolic and physiological alterations associated with tumor burden and cachexia. Among these cytokines, some can be considered as procachectic (such as tumor necrosis factor-alpha), while others having opposite effects can be named as anticachectic cytokines. It is the balance between these two cytokine types that finally seems to have a key role in cancer cachexia.

Host metabolism: a target in clinical oncology?

The presence of the tumour induces important metabolic changes in the cancer patient which are not merely due to the fact that the tumour acts as a parasite, thus depleting the host of nutrients, but that are mainly the result of both tumoral and humoral mediators. The new metabolic status of the cancer patient may lead to cancer cachexia (a pathological state characterized by weight loss together with anorexia, weakness, anaemia and asthenia) which represents one of the worst effects of malignancy, accounting for nearly a third of cancer deaths. The complications associated with the appearance of the cachectic syndrome affect both the physiological and biochemical balance of the patient and have effects on the efficiency of the anticancer treatment, resulting in a considerably decreased survival time. At the metabolic level, cachexia is associated with loss of skeletal muscle protein together with a depletion of body lipid stores. The present study emphasizes the fact that neutralizing some of the metabolic changes in the patient may be an essential therapeutic strategy in controlling tumour growth and improving survival.

Skeletal muscle UCP2 and UCP3 gene expression in a rat cancer cachexia model

Rats bearing the Yoshida AH-130 ascites hepatoma showed an increased expression of both uncoupling protein-2 (UCP2) (194%) and UCP3 (189%) mRNA levels in skeletal muscle 7 days after tumour inoculation. Interestingly, an even greater increase was observed in mRNA for both UCP2 (278%) and UCP3 (797%) in the pair-fed animals, suggesting that the increase in gene expression was the result of the anorexia associated with tumour burden. The results constitute the first report of UCP2 and UCP3 gene expression during cancer cachexia and agree to their possible role in the increase of energy expenditure associated with tumour growth.

Mechanisms of cachexia induced by T-cell leukemia in the rat

Body wasting (cachexia) is a common feature of cancer and a major cause of morbidity and mortality. The mechanisms underlying cachexia are largely unknown, and studies in experimental animals have focused mainly on solid tumors. Therefore, the objective of the present study was to quantify and investigate cachexia in experimentally induced T-cell leukemia in the rat. Induction of leukemia by serial passage (injection of cervical lymph node suspension) resulted in a rapid increase in white blood cell (WBC count, hypertrophy of the spleen (by day 11), and severe morbidity within 17 to 18 days. Body weight gain and food intake declined steadily in leukemic animals from day 12, although weight loss was significantly greater in pair-fed, nonleukemic animals. However, leukemic rats had a lower body fat content and higher water content than pair-fed animals on day 18, so the measurement of body weight significantly underestimated the severity of cachexia. Resting oxygen consumption (VO2), measured during the light phase, declined in pair-fed animals from day 13, but was elevated in leukemic rats on days 12 to 18 by 25% (P < .05, one-way ANOVA) compared with pair-fed rats and by 7% (P < .05, one-way ANOVA) relative to free-feeding controls. Hypermetabolism was associated with an increase in brown adipose tissue (BAT) activity (74% and 89%, respectively, P < .05, one-way ANOVA) in leukemic rats compared with control and pair-fed groups. Effects of leukemia on VO2 and BAT were prevented by administration of the adrenergic antagonist, propranolol. These results indicate that T-cell leukemia in the rat results in rapid and severe cachexia, which is largely due to marked hypophagia, but is also accompanied by inappropriately high rates of energy expenditure that are mediated by sympathetic activation of BAT thermogenesis.

Stimulation of brown adipose tissue activity in tumor-bearing rats

Despite anorexia, cancer development is frequently accompanied by an increase of energy expenditure. Considering the pivotal role played by brown adipose tissue (BAT) in the energy metabolism of small mammals, we investigated the functional and compositional modification in BAT of anorexic tumor-bearing (Yoshida sarcoma) and pair-fed control rats. BAT thermogenic activity (assessed by maximal mitochondrial GDP binding) was 1.8-fold greater in tumor-bearing rats than in controls, while the thermogenic capacity (assessed by measurement of uncoupling protein) was unchanged. This suggests that tumor bearing had induced an unmasking of uncoupling protein sites. BAT hypertrophy and hyperplasia, characteristic of full-fledged BAT activation, did not occur. The mitochondrial oxidative capacity of BAT (assessed by cytochrome c oxidase activity) was 1.6-fold lower in tumor-bearing than in control rats. The main compositional modification observed in BAT of tumor-bearing rats was an increase in the saturation of cardiolipin fatty acids. These results suggest that the BAT stimulation induced by tumor bearing after 10 days is almost exclusively functional and that the tissue development is limited, probably by anorexia. However, a suppressive effect of anorexia inhibition by tumor bearing cannot be excluded.

Evaluation of mechanisms behind elevated energy expenditure in cancer patients with solid tumours

The aim of this study was to demonstrate significant factors behind elevated resting energy expenditure in weight-losing cancer patients. Therefore, weight-losing cancer patients (n = 60), with normal liver and kidney function tests, were randomized to receive one of four drug treatments for 5 days: (a) Propranolol 80 mg x 2 (beta-adrenoceptor blockade); (b) Indomethacin 50 mg x 2 (prostaglandin synthesis inhibition); (c) Morphine 5 mg x 3 (pain relief) or (d) Placebo x 2. A reference group of healthy well-nourished individuals were examined outside the formal randomization protocol and they received Propranolol 80 mg x 2. The cancer patients were randomized by a computer based algorithm stratifying for measured resting energy expenditure (REE), body composition, biochemical tests, previous therapy, tumour type and tumour stage. Resting energy expenditure was measured by indirect calorimetry in the morning after an overnight fast before and after drug treatment. beta-blockade reduced REE significantly in cancer patients from 1416 +/- 95 kcal day-1 to 1160 +/- 63 kcal day-1 (P < 0.02) and from 1472 +/- 69 vs, 1398 +/- 63 kcal day-1 (P < 0.01) in the well-nourished reference individuals. The reduction found in cancer patients (10%) was significantly larger than that in the group of reference patients (5%), (P < 0.01). Indomethacin, morphine or placebo did not induce any significant alteration in energy expenditure in our cancer patients. Propranolol treatment was associated with a significant reduction in plasma concentrations of free fatty acids (FFA), but not in plasma glycerol.(ABSTRACT TRUNCATED AT 250 WORDS)

Accumulation of brown adipose tissue in patients with Chagas heart disease

Brown adipose tissue (BAT) is an important source of non-shivering thermogenesis. Increased BAT amounts have been reported to occur in association with several diseases, including congestive heart failure. The objective of the present study was to determine whether BAT accumulation occurs in patients with Chagas disease. Histological sections of peri-adrenal tissue obtained at autopsy from 259 patients were examined. Of these patients, 58 had the digestive form of Chagas disease, 50 had the cardiac form without heart failure and 201 had the cardiac form with heart failure. All cases were investigated in terms of nutritional status and classified as malnourished, normotrophic or obese according to the Quetelet index. The results showed no correlation between BAT and the patients' nutritional status, and more BAT accumulation in patients with the cardiac form of Chagas disease compared to patients with the digestive form. Similarly, a history of heart failure was correlated with greater BAT accumulation. On the basis of the present data and of information reported in the literature, we propose that chronic hypoxia may be the cause of BAT accumulation in Chagas disease patients with heart failure.