Insulin resistance in patients with colorectal cancer

Systemic inflammation and insulin resistance-related indicator predicts poor outcome in patients with cancer cachexia

BACKGROUND

The C-reactive protein (CRP)-triglyceride-glucose (TyG) index (CTI), which is a measure representing the level of inflammation and insulin resistance (IR), is related to poor cancer prognosis; however, the CTI has not been validated in patients with cancer cachexia. Thus, this study aimed to explore the potential clinical value of the CTI in patients with cancer cachexia.

METHODS

In this study, our prospective multicenter cohort included 1411 patients with cancer cachexia (mean age 59.45 ± 11.38, 63.3% male), which was a combined analysis of multiple cancer types. We randomly selected 30% of the patients for the internal test cohort (mean age 58.90 ± 11.22% 61.4% male). Additionally, we included 307 patients with cancer cachexia in the external validation cohort (mean age 61.16 ± 11, 58.5% male). Receiver operating characteristic (ROC) and calibration curves were performed to investigate the prognostic value of CTI. The prognostic value of the CTI was also investigated performing univariate and multivariate survival analyses.

RESULTS

The survival curve indicated that the CTI showed a significant prognostic value in the total, internal, and external validation cohorts. Prognostic ROC curves and calibration curves revealed that the CTI showed good consistency in predicting the survival of patients with cancer cachexia. Multivariate survival analysis showed that an elevated CTI increased the risk of death by 22% (total cohort, 95% confidence interval [CI] = 1.13-1.33), 34% (internal test cohort, 95%CI = 1.11-1.62), and 35% (external validation cohort, 95%CI = 1.14-1.59) for each increase in the standard deviation of CTI. High CTI reliably predicted shorter survival (total cohort, hazard ratio [HR] = 1.45, 95%CI = 1.22-1.71; internal test cohort, HR = 1.62, 95%CI = 1.12-2.36; external validation cohort, HR = 1.61, 95%CI = 1.15-2.26). High CTI significantly predicted shorter survival in different tumor subgroups, such as esophageal [HR = 2.11, 95%CI = 1.05-4.21] and colorectal cancer [HR = 2.29, 95%CI = 1.42-3.71]. The mediating effects analysis found that the mediating proportions of PGSGA, ECOG PS, and EORTC QLQ-C30 on the direct effects of CTI were 21.72%, 19.63%, and 11.61%, respectively We found that there was a significant positive correlation between the CTI and 90-day [HR = 2.48, 95%CI = 1.52-4.14] and 180-day mortality [HR = 1.77,95%CI = 1.24-2.55] in patients with cancer cachexia.

CONCLUSION

The CTI can predict the short- and long-term survival of patients with cancer cachexia and provide a useful prognostic tool for clinical practice.

Prognostic importance of systemic inflammation and insulin resistance in patients with cancer: a prospective multicenter study

BACKGROUND

Systemic inflammation and insulin resistance (IR) are often associated with poor prognosis in cancer. This study aimed to investigate the prognostic value of surrogate systemic inflammation and IR indices in patients with cancer.

METHODS

This multicenter prospective study included 5,221 patients with cancer, with a mean age of 59.41±11.15 years, of whom 3,061 (58.6%) were male. The surrogate IR indices included low-density lipoprotein cholesterol to high-density lipoprotein cholesterol (LHR) ratio, total cholesterol to high-density lipoprotein cholesterol (TC/ HDL-c) ratio, triglyceride to high-density lipoprotein cholesterol (TG/HDL-c) ratio, and fasting triglyceride glucose (TyG). Prognostic receiver operator characteristic (ROC) curves and C-indices were used to select a better surrogate IR index in patients with cancer. The prognostic value of the indicators was evaluated using univariate and multivariate survival analyses.

RESULTS

In this study, the median survival time of patients was 44.5 (40.5-51.4) months, and the overall mortality in the 12-month period was 1,115 (53.7%), with 196 mortality events per 1,000 patient-years of patients' follow-up. The prognostic ROC curve and C-index suggested that the prognostic value of LHR was better than that of the other IR indices. The multivariate-adjusted hazard ratios (HRs) for overall survival (OS) were higher in patients with high C-reactive protein (CRP) (HR, 1.51; 95% confidence interval [CI]: 1.38-1.65) and high LHR (HR, 1.20; 95% CI: 1.06-1.37), respectively. The mortality rate of patients with both high CRP and LHR was 1.75-fold higher than that of patients with both low CRP and LHR.

CONCLUSION

Both CRP and LHR showed good survival predictions in patients with cancer. CRP combined with LHR can improve the predictive power of patients with cancer.

Cardiac Remodeling in Cancer-Induced Cachexia: Functional, Structural, and Metabolic Contributors

Cancer cachexia is a syndrome of progressive weight loss and muscle wasting occurring in many advanced cancer patients. Cachexia significantly impairs quality of life and increases mortality. Cardiac atrophy and dysfunction have been observed in patients with cachexia, which may contribute to cachexia pathophysiology. However, relative to skeletal muscle, little research has been carried out to understand the mechanisms of cardiomyopathy in cachexia. Here, we review what is known clinically about the cardiac changes occurring in cachexia, followed by further discussion of underlying physiological and molecular mechanisms contributing to cachexia-induced cardiomyopathy. Impaired cardiac contractility and relaxation may be explained by a complex interplay of significant heart muscle atrophy and metabolic remodeling, including mitochondrial dysfunction. Because cardiac muscle has fundamental differences compared to skeletal muscle, understanding cardiac-specific effects of cachexia may bring light to unique therapeutic targets and ultimately improve clinical management for patients with cancer cachexia.

Cancer causes dysfunctional insulin signaling and glucose transport in a muscle-type-specific manner

Metabolic dysfunction and insulin resistance are emerging as hallmarks of cancer and cachexia, and impair cancer prognosis. Yet, the molecular mechanisms underlying impaired metabolic regulation are not fully understood. To elucidate the mechanisms behind cancer-induced insulin resistance in muscle, we isolated extensor digitorum longus (EDL) and soleus muscles from Lewis Lung Carcinoma tumor-bearing mice. Three weeks after tumor inoculation, muscles were isolated and stimulated with or without a submaximal dose of insulin (1.5 nM). Glucose transport was measured using 2-[³ H]Deoxy-Glucose and intramyocellular signaling was investigated using immunoblotting. In soleus muscles from tumor-bearing mice, insulin-stimulated glucose transport was abrogated concomitantly with abolished insulin-induced TBC1D4 and GSK3 phosphorylation. In EDL, glucose transport and TBC1D4 phosphorylation were not impaired in muscles from tumor-bearing mice, while AMPK signaling was elevated. Anabolic insulin signaling via phosphorylation of the mTORC1 targets, p70S6K thr389, and ribosomal-S6 ser235, were decreased by cancer in soleus muscle while increased or unaffected in EDL. In contrast, the mTOR substrate, pULK1 ser757, was reduced in both soleus and EDL by cancer. Hence, cancer causes considerable changes in skeletal muscle insulin signaling that is dependent on muscle-type, which could contribute to metabolic dysregulation in cancer. Thus, the skeletal muscle could be a target for managing metabolic dysfunction in cancer.

Prognostic value of metabolic activity of the psoas muscle evaluated by preoperative 18F-FDG PET-CT in breast cancer: a retrospective cross-sectional study

Background

This study aimed to evaluate the potential of metabolic activity of the psoas muscle measured by ¹⁸F-fluorodeoxyglucose positron emission tomography-computed tomography to predict treatment outcomes in patients with resectable breast cancer.

Methods

The medical records of 288 patients who had undergone surgical resection for stages I–III invasive ductal carcinoma of the breast between January 2014 and December 2014 in Pusan National University Hospital were reviewed. The standardized uptake values (SUVs) of the bilateral psoas muscle were normalized using the mean SUV of the liver. SUVRmax was calculated as the ratio of the maximum SUV of the average bilateral psoas muscle to the mean SUV of the liver. SUVRmean was calculated as the ratio of the mean SUV of the bilateral psoas muscle to the mean SUV of the liver.

Results

Univariate analyses identified a higher T stage, higher N stage, estrogen receptor negativity, progesterone receptor negativity, human epidermal growth factor receptor 2 positivity, triple-negative breast cancer, mastectomy (rather than breast-conserving surgery), SUVRmean > 0.464, and SUVRmax > 0.565 as significant adverse factors for disease-free survival (DFS). Multivariate Cox regression analysis revealed that N3 stage (hazard ratio [HR] = 5.347, P = 0.031) was an independent factor for recurrence. An SUVRmax > 0.565 (HR = 4.987, P = 0.050) seemed to have a correlation with shorter DFS.

Conclusions

A higher SUVRmax of the psoas muscle, which could be a surrogate marker of insulin resistance, showed strong potential as an independent prognostic factor for recurrence in patients with resectable breast cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08886-2.

Functional capacity of prediabetic patients: effect of multimodal prehabilitation in patients undergoing colorectal cancer resection

BACKGROUND

Prehabilitation is the process of increasing functional capacity (FC) before surgery. Poor glycemic control is associated with worse outcomes in patients undergoing surgery. Therefore, prediabetic patients could particularly benefit from prehabilitation.

METHODS

This is a pooled analysis of individual patient data from three multimodal prehabilitation trials in colorectal cancer surgery. Following a baseline assessment using the 6-minute walking test (6MWT), subjects were randomized to multimodal prehabilitation or to a control group. Participants were reassessed 24 h before surgery and 4 weeks after surgery. Prediabetes (PreDM) was defined as HbA1c 5.7%-6.4%. Multivariable logistic regression was used to adjust for potentially confounding variables.

RESULTS

Participation in a prehabilitation program was the most important predictive factor of clinical improvement in FC prior to surgery (Adjusted OR 2.42, 95% CI 1.18, 4.94); prediabetes was not a statistically significant predictor of improvement in FC after adjustments for covariates. Prehabilitation attenuated the loss of FC in unadjusted analyses after surgery in prediabetic patients (PreDM Control: median change -6 m [IQR -50-20] vs PreDM Prehab: median change +25 m [IQR -20-53], p = 0.045). Adjusted analyses also suggested the protective effect against loss of FC after surgery was stronger in prediabetic patients (PreDM Prehab vs PreDM Control: OR 5.5, 95% CI: 1.2-25.8; Normo Prehab vs Normo Control: OR 1.5, 95% CI: 0.53-4.52).

CONCLUSIONS

Multimodal prehabilitation favored clinical recovery of FC after surgery in CRC patients, especially prediabetic patients.

Exercise-A Panacea of Metabolic Dysregulation in Cancer: Physiological and Molecular Insights

Metabolic dysfunction is a comorbidity of many types of cancers. Disruption of glucose metabolism is of concern, as it is associated with higher cancer recurrence rates and reduced survival. Current evidence suggests many health benefits from exercise during and after cancer treatment, yet only a limited number of studies have addressed the effect of exercise on cancer-associated disruption of metabolism. In this review, we draw on studies in cells, rodents, and humans to describe the metabolic dysfunctions observed in cancer and the tissues involved. We discuss how the known effects of acute exercise and exercise training observed in healthy subjects could have a positive outcome on mechanisms in people with cancer, namely: insulin resistance, hyperlipidemia, mitochondrial dysfunction, inflammation, and cachexia. Finally, we compile the current limited knowledge of how exercise corrects metabolic control in cancer and identify unanswered questions for future research.

Cancer cachexia has many symptoms but only one cause: anoxia

During nearly 100 years of research on cancer cachexia (CC), science has been reciting the same mantra: it is a multifactorial syndrome. The aim of this paper is to show that the symptoms are many, but they have a single cause: anoxia. CC is a complex and devastating condition that affects a high proportion of advanced cancer patients. Unfortunately, it cannot be reversed by traditional nutritional support and it generally reduces survival time. It is characterized by significant weight loss, mainly from fat deposits and skeletal muscles. The occurrence of cachexia in cancer patients is usually a late phenomenon. The conundrum is why do similar patients with similar tumors, develop cachexia and others do not? Even if cachexia is mainly a metabolic dysfunction, there are other issues involved such as the activation of inflammatory responses and crosstalk between different cell types.  The exact mechanism leading to a wasting syndrome is not known, however there are some factors that are surely involved, such as anorexia with lower calorie intake, increased glycolytic flux, gluconeogenesis, increased lipolysis and severe tumor hypoxia. Based on this incomplete knowledge we put together a scheme explaining the molecular mechanisms behind cancer cachexia, and surprisingly, there is one cause that explains all of its characteristics: anoxia.  With this different view of CC we propose a treatment based on the physiopathology that leads from anoxia to the symptoms of CC.  The fundamentals of this hypothesis are based on the idea that CC is the result of anoxia causing intracellular lactic acidosis. This is a dangerous situation for cell survival which can be solved by activating energy consuming gluconeogenesis. The process is conducted by the hypoxia inducible factor-1α. This hypothesis was built by putting together pieces of evidence produced by authors working on related topics.

Cancer Cachexia and Related Metabolic Dysfunction

Cancer cachexia is a complex multifactorial syndrome marked by a continuous depletion of skeletal muscle mass associated, in some cases, with a reduction in fat mass. It is irreversible by nutritional support alone and affects up to 74% of patients with cancer-dependent on the underlying type of cancer-and is associated with physical function impairment, reduced response to cancer-related therapy, and higher mortality. Organs, like muscle, adipose tissue, and liver, play an important role in the progression of cancer cachexia by exacerbating the pro- and anti-inflammatory response initially activated by the tumor and the immune system of the host. Moreover, this metabolic dysfunction is produced by alterations in glucose, lipids, and protein metabolism that, when maintained chronically, may lead to the loss of skeletal muscle and adipose tissue. Although a couple of drugs have yielded positive results in increasing lean body mass with limited impact on physical function, a single therapy has not lead to effective treatment of this condition. Therefore, a multimodal intervention, including pharmacological agents, nutritional support, and physical exercise, may be a reasonable approach for future studies to better understand and prevent the wasting of body compartments in patients with cancer cachexia.

Insulin resistance and body composition in cancer patients

Cancer cachexia, weight loss with altered body composition, is a multifactorial syndrome propagated by symptoms that impair caloric intake, tumor byproducts, chronic inflammation, altered metabolism, and hormonal abnormalities. Cachexia is associated with reduced performance status, decreased tolerance to chemotherapy, and increased mortality in cancer patients. Insulin resistance as a consequence of tumor byproducts, chronic inflammation, and endocrine dysfunction has been associated with weight loss in cancer patients. Insulin resistance in cancer patients is characterized by increased hepatic glucose production and gluconeogenesis, and unlike type 2 diabetes, normal fasting glucose with high, normal or low levels of insulin. Cancer cachexia results in altered body composition with the loss of lean muscle mass with or without the loss of adipose tissue. Alteration in visceral adiposity, accumulation of intramuscular adipose tissue, and secretion of adipocytokines from adipose cells may play a role in promoting the metabolic derangements associated with cachexia including a proinflammatory environment and insulin resistance. Increased production of ghrelin, testosterone deficiency, and low vitamin D levels may also contribute to altered metabolism of glucose. Cancer cachexia cannot be easily reversed by standard nutritional interventions and identifying and treating cachexia at the earliest stage of development is advocated. Experts advocate for multimodal therapy to address symptoms that impact caloric intake, reduce chronic inflammation, and treat metabolic and endocrine derangements, which propagate the loss of weight. Treatment of insulin resistance may be a critical component of multimodal therapy for cancer cachexia and more research is needed.

Cancer-Induced Reprogramming of Host Glucose Metabolism: "Vicious Cycle" Supporting Cancer Progression

Unrestricted cancer growth requires permanent supply of glucose that can be obtained from cancer-mediated reprogramming of glucose metabolism in the cancer-bearing host. The pathological mechanisms by which cancer cells exert their negative influence on host glucose metabolism are largely unknown. This paper proposes a mechanism of metabolic and hormonal changes that may favor glucose delivery to tumor (not host) cells by creating a cancer-host “vicious cycle” whose prolonged action drives cancer progression and promotes host cachexia. To verify this hypothesis, a feedback model of host-cancer interactions that create the “vicious cycle” via cancer-induced reprogramming of host glucose metabolism is proposed. This model is capable of answering some crucial questions as to how anabolic cancer cells can reprogram the systemic glucose metabolism and why these pathways were not observed in pregnancy. The current paper helps to better understanding a pathogenesis of cancer progression and identify hormonal/metabolic targets for anti-cancer treatment.

Decreased hepatic response to glucagon, adrenergic agonists, and cAMP in glycogenolysis, gluconeogenesis, and glycolysis in tumor-bearing rats

The response to glucagon and adrenaline in cancer cachexia is poorly known. The aim of this study was to investigate the response to glucagon, adrenergic agonists (α and β) and cyclic adenosine monophosphate (cAMP) on glycogenolysis, gluconeogenesis, and glycolysis in liver perfusion of Walker-256 tumor-bearing rats with advanced cachexia. Liver ATP content was also investigated. Rats without tumor (healthy) were used as controls. Agonists α (phenylephrine) and β (isoproterenol) adrenergic, instead of adrenaline, and cAMP, the second messenger of glucagon and isoproterenol, were used in an attempt to identify mechanisms involved in the responses. Glucagon (1 nM) stimulated glycogenolysis and gluconeogenesis and inhibited glycolysis in the liver of healthy and tumor-bearing rats, but their effects were lower in tumor-bearing rats. Isoproterenol (20 µM) stimulated glycogenolysis, gluconeogenesis, and glycolysis in healthy rats and had virtually no effect in tumor-bearing rats. cAMP (9 µM) also stimulated glycogenolysis and gluconeogenesis and inhibited glycolysis in healthy rats but had practically no effect in tumor-bearing rats. Phenylephrine (2 µM) stimulated glycogenolysis and gluconeogenesis and inhibited glycolysis and these effects were also lower in tumor-bearing rats than in healthy. Liver ATP content was lower in tumor-bearing rats. In conclusion, tumor-bearing rats with advanced cachexia showed a decreased hepatic response to glucagon, adrenergic agonists (α and β), and cAMP in glycogenolysis, gluconeogenesis, and glycolysis, which may be due to a reduced rate of regulatory enzyme phosphorylation caused by the low ATP levels in the liver.

Effects of metformin on insulin resistance and metabolic disorders in tumor-bearing rats with advanced cachexia

Metformin (MET) is widely used in the correction of insulin (INS) resistance and metabolic abnormalities in type 2 diabetes. However, its effect on INS resistance and metabolic disorders associated with cancer cachexia is not established. We investigated the MET effects, isolated or associated with INS, on INS resistance and metabolic changes induced by Walker-256 tumor in rats with advanced cachexia. MET (500 mg·kg−1, oral) and MET + INS (1.0 IU·kg−1, s.c.) were administered for 12 days, starting on the day of tumor cell inoculation. Tumor-bearing rats showed adipose and muscle mass wasting, body mass loss, anorexia, decreased Akt phosphorylation in retroperitoneal and mesenteric adipose tissue, peripheral INS resistance, hypoinsulinemia, reduced INS content and secretion from pancreatic islets, and also inhibition of glycolysis, gluconeogenesis, and glycogenolysis in liver. MET and MET + INS treatments did not prevent these changes. It can be concluded that treatments with MET and MET + INS did not prevent the adipose and muscle mass wasting and body mass loss of tumor-bearing rats possibly by not improving INS resistance. Therefore, MET, used for the treatment of INS resistance in type 2 diabetes, is not effective in improving INS resistance in the advanced stage of cancer cachexia, evidencing that the drug does not have the same beneficial effect in these 2 diseases.

Cancer cachexia update in head and neck cancer: Pathophysiology and treatment

The pathophysiology of cancer cachexia remains complex. A comprehensive literature search was performed up to April 2013 using PubMed, the Cochrane Library, Cumulative Index to Nursing and Allied Health Literature, and the Google search engine. In this review, we focus on the different mediators of impaired anabolism and upregulated catabolism that alter the skeletal muscle homeostasis resulting in the wasting of cancer cachexia. We present recent evidence of targeted treatment modalities from clinical trials along with their potential mechanisms of action. We also report on the most current evidence from randomized clinical trials using multimodal treatments in patients with cancer cachexia, but also the evidence from head and neck cancer-specific trials. A more complete understanding of the pathophysiology of the syndrome may lead to more effective targeted therapies and improved outcomes for patients.

Possible roles of insulin, IGF-1 and IGFBPs in initiation and progression of colorectal cancer

AIM: To investigate the roles of serum insulin, insulin-like growth factor-1 (IGF-1), and insulin-like growth factor binding proteins (IGFBPs) in the initiation and progression of colorectal cancer.

METHODS: We determined serum insulin, IGF-1 and IGFBPs levels in 615 colorectal cancer patients and 650 control healthy donors by enzyme-linked immunosorbent assay (ELISA). In the meantime, their body mass index (BMI) and waist-to-hip ratio (WHR) were measured.

RESULTS: Serum levels of insulin and IGF-1 as well as IGF-1/IGFBP-3 ratio in pre-operation patients were significantly elevated, but the level of IGFBP-3 was significantly decreased compared with normal controls and post-operation patients (P < 0.05 and P < 0.001, respectively). There is no significant difference (P > 0.05) in the levels of insulin, IGF-1, IGFBP-1, IGFBP-3 and IGF-1/IGFBP-3 between the patients with and without hepatic as well as distal abdominal metastases. WHR and BMI of colon cancer patients were positively and significantly correlated with the levels of insulin and IGF-1/IGFBP-3. In contrast, WHR and BMI were negatively correlated with IGFBP-3 level.

CONCLUSION: The elevation of insulin, IGF-1 as well as IGF-1/IGFBP-3 ratio and the reduction of IGFBP-3 may be related to the initiation of colorectal cancer, but they are not related to the progression and outcome of the disease.

Chronic exendin-4 treatment prevents the development of cancer cachexia symptoms in male rats bearing the Yoshida sarcoma

Cancer cachexia is the syndrome of weight loss, loss of appetite, and wasting of skeletal muscle and adipose tissue experienced by many individuals with cancer. Currently, few effective treatment and prevention strategies are available for these patients, due in part to a poor understanding of the mechanisms contributing to cachexia. Insulin resistance has been associated with cancer cachexia in epidemiological, human, and animal research. The present experiment was designed to examine the ability of Exendin-4, a GLP-1 agonist and insulin sensitizing agent, to prevent the development of cachexia symptoms in male Sprague Dawley rats bearing the Yoshida sarcoma. Following tumor implantation or sham surgery, rats were treated daily with saline or Exendin-4 (3 μg/kg body weight/day) and were monitored for tumor growth and cachexia symptoms for 21-23 days. As a result of large variability in treatment effects, data were analyzed separately for animals with large and small tumors. Exendin-4 treatment reduced tumor growth and prevented the development of cancer cachexia symptoms in animals with small, but not large, tumors. In addition, insulin levels were preserved in Exendin-4-treated tumor-bearing animals. The results of this experiment demonstrate a novel preventative therapy for cancer cachexia and a novel use of Exendin-4. Further research is necessary to determine the mechanisms through which Exendin-4 exerts these potent effects.

Cancer cachexia and diabetes: similarities in metabolic alterations and possible treatment

Cancer cachexia is a metabolic syndrome featuring many alterations typical of type 2 diabetes (T2D). While muscle wasting is a hallmark of cachexia, epidemiological evidence also supports an accelerated age-related muscle loss in T2D. Insulin resistance manifests in both conditions and impairs glucose disposal and protein anabolism by tissues. A greater contribution of gluconeogenesis to glucose production may limit amino acid availability for muscle protein synthesis, further aggravating muscle loss. In the context of inter-dependence between glucose and protein metabolism, the present review summarizes the current state of knowledge on alterations that may lead to muscle wasting in human cancer. By highlighting the similarities with T2D, a disease that has been more extensively studied, the objective of this review is to provide a better understanding of the pathophysiology of cancer cachexia and to consider potential treatments usually targeted for T2D. Nutritional approaches aimed at stimulating protein anabolism might include specially formulated food with optimal protein and amino acid composition. Because the gradual muscle loss in T2D may be attenuated by diabetes treatment, anti-diabetic drugs might be considered in cachexia treatment. Metformin emerges as a choice candidate as it acts both on reducing gluconeogenesis and improving insulin sensitivity, and has demonstrated tumour suppressor properties in multiple cancer types. Such a multimodal approach to slow or reverse muscle wasting in cachexia warrants further investigation.

Cancer cachexia prevention via physical exercise: molecular mechanisms

Cancer cachexia is a debilitating consequence of disease progression, characterised by the significant weight loss through the catabolism of both skeletal muscle and adipose tissue, leading to a reduced mobility and muscle function, fatigue, impaired quality of life and ultimately death occurring with 25-30 % total body weight loss. Degradation of proteins and decreased protein synthesis contributes to catabolism of skeletal muscle, while the loss of adipose tissue results mainly from enhanced lipolysis. These mechanisms appear to be at least, in part, mediated by systemic inflammation. Exercise, by virtue of its anti-inflammatory effect, is shown to be effective at counteracting the muscle catabolism by increasing protein synthesis and reducing protein degradation, thus successfully improving muscle strength, physical function and quality of life in patients with non-cancer-related cachexia. Therefore, by implementing appropriate exercise interventions upon diagnosis and at various stages of treatment, it may be possible to reverse protein degradation, while increasing protein synthesis and lean body mass, thus counteracting the wasting seen in cachexia.

Fatty acid-induced production of plasminogen activator inhibitor-1 by adipose macrophages is greater in middle-aged versus younger adult participants

BACKGROUND

Human aging is associated with heightened risk of diabetes and cardiovascular disease. Increased fat mass may contribute to age-related diseases by harboring inflammatory macrophages that produce metabolically important proteins such as plasminogen activator inhibitor-1 (PAI-1). Elevated PAI-1 concentrations have been implicated in the pathogenesis of such aging-related conditions as insulin resistance, obesity, and atherosclerosis. We have previously reported that increased plasma free fatty acid (FFA) concentrations augment both circulating PAI-1 concentrations and PAI-1 production by adipose tissue macrophages (ATMs).

METHODS

Because increasing age is associated with increased infiltration and reactivity of adipose macrophages, we performed euglycemic-hyperinsulinemic clamp studies and adipose tissue biopsies with and without elevated FFA concentrations in 31 nondiabetic participants stratified by age, to determine whether middle-aged individuals manifest heightened insulin resistance and PAI-1 production by ATMs in response to elevated nutrient signals relative to their young adult peers.

RESULTS

We observed that elevating FFA concentrations under euglycemic-hyperinsulinemic clamp conditions induced the same degree of insulin resistance in both middle-aged and younger body mass index-matched adults, whereas systemic PAI-1 concentrations were significantly increased in the middle-aged group. Likewise, elevated FFA and insulin concentrations induced larger increases in PAI-1 gene expression in the whole fat and ATMs of middle-aged compared with younger adult participants.

CONCLUSIONS

These studies reveal a heightened adipose inflammatory response to increased FFA and insulin availability in middle-aged individuals relative to younger adults, suggesting that increased susceptibility to the effects of fatty acid excess may contribute to the pathogenesis of age-related diseases.

Decreased response to cAMP in the glucose and glycogen catabolism in perfused livers of Walker-256 tumor-bearing rats

The hepatic response to cyclic adenosine monophosphate (cAMP) and N6-monobutyryl-cAMP (N6-MB-cAMP) in the glucose and glycogen catabolism and hepatic glycogen levels were evaluated in Walker-256 tumor-bearing rats, on days 5 (WK5), 8 (WK8), and 11 (WK11) after the implantation of tumor. Rats without tumor fed ad libitum (fed control rats) or that received the same daily amount of food ingested by anorexics tumor-bearing rats (pair-fed control rats) or 24 h fasted (fasted control rats) were used as controls. Glucose and glycogen catabolism were measured in perfused liver. Hepatic glycogen levels were lower (p < 0.05) in WK5, WK8, and WK11 rats in comparison with fed control rats, but not in relation to the pair-fed control rats. However, the stimulatory effect of cAMP (3 and 9 μM) in the glycogen catabolism was lower (p < 0.05), respectively, in WK5 and WK8 rats compared to the pair-fed and fed control rats. Accordingly, the suppressive effect of cAMP (6 μM) in the glucose catabolism, under condition of depletion of hepatic glycogen (24 h fast), was lower (p < 0.05) in WK5 and WK11 rats than in fasted control rats. Similarly, the suppressive effect of N6-MB-cAMP (1 μM), a synthetic analogue of cAMP that it is not degraded by phosphodiesterase 3B (PDE3B), in the glucose catabolism was lower (p < 0.05) in WK5 rats compared to fasted control rats. In conclusion, livers of Walker-256 tumor-bearing rats showed lower response to cAMP in the glucose and glycogen catabolism in various stages of tumor development (days 5, 8 and 11), which was probably not due to the lower hepatic glycogen levels nor due to the increased activity of PDE3B.

CA 72-4 levels in patients with type 2 diabetes mellitus

OBJECTIVE

CA 72-4 is one of the blood group carbohydrate antigens which can be used as a tumour marker in ovarian, pancreatic and gastrointestinal carcinomas. It can also be elevated in various benign conditions including pancreatitis. Diabetes mellitus is a chronic disorder related with the pancreas. In this study, we investigated CA 72-4 levels in patients with type 2 diabetes and its relation to the metabolic status.

METHODS

Sixty-nine patients with type 2 diabetes mellitus (female/male = 40/29) and 60 healthy subjects (female/male = 35/25) participated in this study. The levels of serum CA 72-4 were measured and faecal occult blood tests (following 3 days of white diet were obtained for three consecutive days) were performed in all patients. Patients had a pathological finding for any of these two parameters were further investigated with upper gastrointestinal endoscopy, colonoscopy and computerised tomography.

RESULTS

The mean levels of CA 72-4 was 1.89 +/- 2.61 U/ml in the study group and 1.4 +/- 0.98 U/ml in the control group (p > 0.05). There was no association between CA 72-4 levels and age and sex of the patients, duration of diabetes, body mass index, biochemical indicators of metabolic control (the levels of HbA(1c), fasting and postprandial glucose, serum lipids), the presence of microvascular complications (retinopathy, nephropathy, neuropathy) or treatment modalities.

CONCLUSIONS

Elevated levels of CA 72-4 in diabetic patients are not related to diabetes and it should be interpreted as evaluated in a non-diabetic patient.

A mouse model of ghrelinoma exhibited activated growth hormone-insulin-like growth factor I axis and glucose intolerance

Ghrelin is a stomach-derived peptide that has growth hormone-stimulating and orexigenic activities. Although there have been several reports of ghrelinoma cases, only a few cases have elevated circulating ghrelin levels, hampering the investigation of pathophysiological features of ghrelinoma and chronic effects of ghrelin excess. Furthermore, standard transgenic technique has resulted in desacyl ghrelin production only because of the limited tissue expression of ghrelin O-acyltransferase, which mediates acylation of ghrelin. Accordingly, we attempted to create ghrelin promoter SV40 T-antigen transgenic (GP-Tag Tg) mice, in which ghrelin-producing cells continued to proliferate and finally developed into ghrelinoma. Adult GP-Tag Tg mice showed elevated plasma ghrelin levels with preserved physiological regulation. Adult GP-Tag Tg mice with increased plasma ghrelin levels exhibited elevated IGF-I levels despite poor nutrition. Although basal growth hormone levels were not changed, those after growth hormone-releasing hormone injection tended to be higher. These results indicate that chronic elevation of ghrelin activates GH-IGF-I axis. In addition, GP-Tag Tg mice demonstrated glucose intolerance. Insulin secretion by glucose tolerance tests was significantly attenuated in GP-Tag Tg, whereas insulin sensitivity determined by insulin tolerance tests was preserved, indicating that chronic elevation of ghrelin suppresses insulin secretion and leads to glucose intorelance. Thus, we successfully generated a Tg model of ghrelinoma, which is a good tool to investigate chronic effects of ghrelin excess. Moreover, their characteristic features could be a hint on ghrelinoma.

In search of biologic correlates for liver texture on portal-phase CT

RATIONALE AND OBJECTIVES

The acceptance of computer-assisted diagnosis (CAD) in clinical practice has been constrained by the scarcity of identifiable biologic correlates for CAD-based image parameters. This study aims to identify biologic correlates for computed tomography (CT) liver texture in a series of patients with colorectal cancer.

MATERIALS AND METHODS

In 28 patients with colorectal cancer, total hepatic perfusion (THP), hepatic arterial perfusion, and hepatic portal perfusion (HPP) were measured using perfusion CT. Hepatic glucose use was also determined from positron emission tomography (PET) and expressed as standardized uptake value (SUV). A hepatic phosphorylation fraction index (HPFI) was determined from both SUV and THP. These physiologic parameters were correlated with CAD parameters namely hepatic densitometry, selective-scale, and relative-scale texture features in apparently normal areas of portal-phase hepatic CT.

RESULTS

For patients without liver metastases, a relative-scale texture parameter correlated inversely with SUV (r = -0.587, P = .007) and, positively with THP (r = 0.512, P = .021) and HPP (r = 0.451, P = .046). However, this relative texture parameter correlated most significantly with HPFI (r = -0.590, P = .006). For patients with liver metastases, although not significant an opposite trend was observed between these physiologic parameters and relative texture features (THP: r < -0.4, HPFI: r > 0.35).

CONCLUSION

Total hepatic blood flow and glucose metabolism are two distinct but related biologic correlates for liver texture on portal phase CT, providing a rationale for the use of hepatic texture analysis as a indicator for patients with colorectal cancer.

The evaluation of the role of beta-hydroxy fatty acids on chronic inflammation and insulin resistance

β-hydroxy fatty acids are a major component of lipid A moiety of lipopolysaccaride. We aimed to investigate the role of free β-hydroxy fatty acids on inflammation, as well as to evaluate their effects on cytokine release from human blood cells, and whether they exist in plasma of patients with chronic inflammatory diseases with/without insulin resistance. Peripheral venous blood was incubated with β-hydroxy lauric and β-hydroxy myristic acids (each 100 ng, 1 μg, 10 μg/mL) up to 24 hours. Cytokines were measured from culture media and plasma. Free fatty acids and biochemical parameters were also measured from patients' plasma. Only β-hydroxy lauric acid significantly stimulated interleukin-6 production at 10 μg/mL compared to control (533.9 ± 218.1 versus 438.3 ± 219.6 pg/mL, P < .05). However, free β-hydroxy lauric and myristic acids were not found in patients' plasma. Therefore, free β-hydroxy lauric and myristic acids do not seem to have a role on sterile inflammation in chronic inflammatory diseases associated with insulin resistance.

Association between adenomas of rectosigmoid colon and metabolic syndrome features in a Chinese population

BACKGROUND AND AIMS

Metabolic syndrome (MS) consists of a cluster of diseases, including obesity, dyslipidemia, hyperglycemia and high blood pressure. The purpose of the present study was to assess the association of MS with adenomas of the rectosigmoid colon, a well-established precancerous lesion.

METHODS

A total of 4938 Taiwanese patients (2891 men and 2047 women with a mean age of 50.1 years), who had a physical examination at our hospital between January 2001 and October 2002, were enrolled in this study. All patients underwent a sigmoidoscopic examination to 60 cm from the anus. A modified National Cholesterol Education Program (NCEP) definition of MS was used in this study, in which body mass index (BMI) was substituted for the waist circumference measurement.

RESULTS

Overall, 14% of patients had an elevated fasting glucose, 27% had high blood pressure, 14% had an increased triglyceride (TG) level, 8% had low high density lipoprotein (HDL) cholesterol, and 18% were obese. Rectosigmoid polyps were present in 17% of patients, among whom 568 received polypectomy. Pathological findings were hyperplastic in 138 subjects, adenomas in 341, carcinomas in 10, and other benign lesions in 79. In patients without polyps, the adjusted mean TG level and calculated BMI level were lower than those in patients with adenomas. No such difference existed, however, between patients without polyps and those with hyperplastic polyps. The odds ratio of adenomas in situ as compared to either a polyp-free state or the presence of hyperplastic polyps increased significantly with the number of MS diagnostic criteria the patient exhibited.

CONCLUSION

Our study shows that MS is associated with rectosigmoid adenomas in a Chinese population. In patients with rectosigmoid polyps, the coexistence of MS may portend an increased risk of adenomas.

The metabolic syndrome or the insulin resistance syndrome? Different names, different concepts, and different goals

The goal of this article is to differentiate the insulin resistance syndrome from the metabolic syndrome. In the case of the insulin resistance syndrome, the abnormalities and clinical syndromes that are increased in prevalence in insulin-resistant individuals have been summarized, with a brief discussion of the causal relationship between insulin resistance, compensatory hyperinsulinemia, and associated consequences. Discussion of the metabolic syndrome has focused on the five criteria chosen by the adult treatment panel III to diagnose the syndrome, evaluating them in terms of their relationship to insulin resistance and their role as cardiovascular disease risk factors.

Insulin resistance in patients with cancer: relationships with tumor site, tumor stage, body-weight loss, acute-phase response, and energy expenditure

We examined peripheral insulin sensitivity in 32 patients with cancer (17 with stomach cancer, 7 with colorectal cancer, and 8 with lung cancer) and 6 normal control subjects by the euglycemic hyperinsulinemic glucose clamp technique. The relationships between insulin resistance and tumor factors (type and stage), malnutrition, and inflammatory reaction were evaluated. Insulin sensitivity often was reduced in patients with cancer; however, the amount of glucose metabolized was not related to tumor site or stage. The decreased glucose uptake was negatively correlated with the acute-phase response but was not correlated with body-weight loss, serum albumin, or resting energy expenditure. Our results suggest that insulin resistance in cancer patients was not induced by malnutrition. Although the qualitative presence of tumor might be the major factor inducing insulin resistance, other factors such as inflammatory reactions might be involved in the development of insulin resistance.

Pancreatic cancer and diabetes: is there a relationship? A case-controlled study

BACKGROUND

There is controversy about whether diabetes mellitus is a risk factor for pancreatic cancer or an epiphenomenon of the cancer. The present study aims to determine if long-term diabetes is a risk factor for pancreatic cancer.

METHODS

The study undertook to determine the prevalence of diabetes among three matched (age/gender) patient groups (pancreatic cancer (PaC), colorectal cancer (CRC), and fracture neck of femur (NOF)) at the date of diagnosis of cancer or fracture as well as 1 and 5 years prior to this. A retrospective review of the medical records of the three groups of patients was undertaken. Patients identified with PaC in the period July 1994 to February 1998 were age (+/- 5 years)- and gender-matched to patients identified in the same time period with NOF and with CRC. The data were then analysed using McNemar's test for discordant pairs.

RESULTS

Over a 44-month period 116 patients with PaC were identified of which 24% had diabetes at the time of diagnosis of their malignancy (NOF, 8%; CRC, 9.5%). There was a statistically significant difference (PaC and NOF, P < 0.01; PaC and CRC, P < 0.01). For a duration of diabetes of > 5 years the prevalence of diabetes fell to 7.8% in the PaC group, to 6% in the NOF group and to 6.9% in the CRC group, with no significant difference between the groups.

CONCLUSION

There is no increase in the prevalence of long-standing diabetes mellitus in patients with PaC compared to age- and gender-matched controls with NOF and CRC. The relationship of PaC and diabetes may be an epiphenomenon, rather than diabetes being a risk factor for pancreatic malignancy.

Pathophysiology of cancer cachexia

Cancer cachexia is a frequent complication observed in patients with malignant tumors. Although several decades have passed since the first focus on the metabolic dysfunction's associated with cancer, few effective therapeutic interventions have been successfully introduced into the medical armamentarium. The present study thoroughly reviews the basic pathophysiology of cancer cachexia and the treatment options already investigated in that field. Experimental and clinical studies were evaluated individually in order to clarify the intricate alterations observed in tumor-bearing patients. The difficulties in introducing sound and effective nutritional support or metabolic manipulation to reverse cancer cachexia are outlined in this review.

Provision of rhIGF-I/IGFBP-3 complex attenuated development of cancer cachexia in an experimental tumor model

Tumor growth is associated with development of cachexia which includes progressive wasting and anorexia. Our previous studies have indicated that insulin like growth factor-I (rhIGF-I) in complex with its binding protein 3 (IGFBP 3), but not free IGF-I, was a potent stimulator of muscle protein synthesis in rats with chronic undernutrition. The aim of the present study was to evaluate the effect of rhIGF-I/IGFBP-3 on the development of cancer cachexia, and to assess safety data on net tumor growth and progression during treatment.

METHODS

A methylcholantrene induced sarcoma was implanted s.c. in C 57 bl mice. The animals were provided with rhIGF-I/rhIGFBP-3 (5 microg/g bw) i.v. twice daily (n= 18). Controls were provided with saline (n= 20). Body weight and food intake were registered daily. Net tumor growth was measured over 10 days. Protein synthesis in liver and muscle, as well as plasma concentrations of glucose, insulin, IGF-I and amino acids were measured at the end of the study.

RESULTS

tumor size did not differ between control mice and rhIGF-I/rhIGFBP-3 treated mice (1.5 +/- 0.1 g wet tumor weight vs 1.6 +/- 0.2 g respectively). Saline treated tumor bearing controls lost 9.1 +/- 1.3 % body weight over 10 days due to rapid tumor growth while rhIGF-I/rhIGFBP-3 provision attenuated weight loss to 5.6 +/- 1.3% of body weight in study mice (P< 0.05). Food intake was improved and blood glucose concentration was reduced from 7.1 +/- 0.5 to 5.8 +/- 0.2 (P< 0.05) in response to treatment.

CONCLUSION

Our results demonstrate that rhIGF-I/rhIGFBP-3 complex did not affect net tumor growth. Moreover rhIGF-I/rhIGFBP-3 complex improved tumor-host nutritional state by improving food intake, attenuating weight loss and improving glucose metabolism.

Noninsulin-dependent diabetes mellitus occurs in mice ectopically expressing the human Axl tyrosine kinase receptor

The axl tyrosine kinase receptor is aberrantly expressed on myeloid cells of many individuals afflicted with chronic myelogenous leukemia (CML) and other myeloid leukemias. Although previous studies demonstrated this kinase to have oncogenic potential, it is not known whether axl actively participates in the onset and/or progression of CML. We addressed this question by generating transgenic mice possessing constitutive ectopic expression of human axl throughout cells of the myeloid hematopoietic lineage through the use of the granulocyte colony-stimulating factor (GCSF) receptor promoter. The transgenics did not exhibit hematopoietic malignancies, but did exhibit phenotypic characteristics associated with noninsulin-dependent diabetes mellitus (NIDDM) including hyperglycemia and hyperinsulinemia, severe insulin resistance, progressive obesity, hepatic lipidosis, and pancreatic islet dysplasia. The obese-diabetes phenotype was similar to that observed in the agouti and melanocortin-4(-/-) mutants, however the axl transgenics were not hyperphagic. Axl transgenic animals expressed elevated serum tumor necrosis factor (TNF)-alpha levels that were further enhanced upon in vitro lipopolysaccharide (LPS) stimulation of peripheral blood. Administration of the axl ligand, gas6, to peripheral transgenic blood samples eliminated excessive TNF-alpha production in response to LPS stimulation. As a means to better understand axl-gas6 biology, transgenic animals were produced which systemically expressed the gas6-binding axl proteolytic cleavage product. A more severe NIDDM phenotype occurred in these mice. The observed phenotypes may be related to the axl receptor or proteolytic cleavage product competing with related axl family receptors for binding of the gas6 ligand. We conclude that axl expression in myeloid cells in itself does not lead to the onset or progression of leukemia and suggest that ectopic axl expression affects endogenous modulation of TNF-alpha production indirectly resulting in the NIDDM phenotype.

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.

Inhibition of IRS-1 phosphorylation and the alterations of GLUT4 in isolated adipocytes from cachectic tumor-bearing rats

Cellular and molecular mechanisms of insulin resistance in isolated adipocytes from methylcholanthrene-induced sarcoma-bearing rats were investigated by measuring 3-O-[14C]methyl glucose transport activity, glucose transporter-4 (GLUT4) protein in both plasma membrane and low-density microsomes, and insulin-stimulated tyrosine phosphorylation of the insulin receptor (IR) and insulin receptor substrate-1 (IRS-1). Compared to both pair-fed and freely fed controls, tumor-bearing rats (TBR) had a decreased insulin-stimulated glucose transport activity with a lower Vmax and a higher EC50. GLUT4 protein in low-density microsomes from adipocytes maintained at the basal state was less in TBR than in controls. In insulin-stimulated adipocytes, GLUT4 protein in plasma membranes was also less in tumor-bearing rats than in controls. Insulin-induced tyrosine phosphorylation of IRS-1 was less in TBR than controls, but that of the IR was similar among the three groups. These data suggest that the insulin resistance seen in adipose cells of these tumor-bearing rats was caused in part by a decreased amount of GLUT4 protein in both basal and insulin-stimulated states resulting from the selective inhibition of insulin-stimulated phosphorylation of IRS-1.

Insulin resistance in cancer patients is associated with enhanced tumor necrosis factor-alpha expression in skeletal muscle

The roles of tumor necrosis factor (TNF)-alpha and the facilitative glucose transporter (GLUT) 4 on the induction of insulin resistance in peripheral tissues of cancer patients was examined by quantitative competitive PCR on biopsies of abdominal rectal muscle from patients with gastrointestinal cancer. The degree of insulin resistance in these patients was measured by the euglycemic hyperinsulinemic glucose clamp using a high physiologic insulin concentration (100 microU/ml). Quantitative competitive PCR was carried out using DNA competitors constructed by deleting 20-30 bp between the two primer annealing sites. Decreased glucose uptake (M value) in peripheral tissues was accompanied by a significantly increased TNF-alpha mRNA in skeletal muscle (r=0.867, p=0.0025). GLUT4 mRNA, however, was positively correlated with M values (r=0.739, p=0.015). The amounts of mRNAs for TNF-alpha and GLUT4 in skeletal muscle were not correlated. Serum TNF-alpha concentrations remained below the limit of detection. These findings suggest that the insulin resistance in peripheral tissues of cancer patients is in part due to the induction TNF-alpha mRNA and the down regulation of GLUT4 mRNA in peripheral tissues.

Circulating interleukin 6 concentrations and insulin resistance in patients with cancer

BACKGROUND

The mechanism of insulin resistance in patients with cancer is not clear. This study was conducted to evaluate the possible role of circulating cytokines in inducing insulin resistance in patients with cancer.

METHODS

Twenty-three patients with a variety of cancers were studied, including one patient with oesophageal cancer, 12 with gastric cancer, four with colon cancer and six with lung cancer. Six normal volunteers served as controls. Insulin resistance was evaluated by euglycaemic hyperinsulinaemic glucose clamp with a high physiological insulin concentration of 100 microunits/ml. Metabolized glucose, the M value, was compared between patients with cancer and controls. Serum concentrations of interleukin (IL) 6 and other cytokines (tumour necrosis factor (TNF) alpha, IL-8 and IL-10) were measured by enzyme-linked immunosorbent assay.

RESULTS

The mean(s.d.) M value for patients with cancer (5.47(1.59) mg per kg per min) was significantly lower than that for controls (8.23(0.79) mg per kg per min) (P< 0.001). There was no relationship between the M value and degree of body-weight loss. Serum IL-6 concentration was measurable in eight of 23 patients: four with lung cancer, two with gastric cancer, and one each with oesophageal and colon cancer. None of the controls had a measurable serum IL-6 concentration. There was no significant relationship between serum IL-6 concentration and body-weight loss. TNF-alpha was undetectable in the serum of both patients with cancer and controls. Serum IL-8 and IL-10 were detected in seven and one of 23 patients respectively. These cytokines were not detected in the serum of controls. The M value was significantly smaller in those with measurable serum IL-6 (4.01(1.22) mg per kg per min) than in those with no measurable IL-6 (6.26(1.16) mg per kg per min) (P< 0.001). IL-6 and IL-8 levels were raised more frequently in the same patient but there was no significant relationship between IL-8 and M values.

CONCLUSION

These results may suggest that IL-6 is related to insulin resistance in patients with cancer.

Association between breast and colorectal cancers

BACKGROUND

The risk of breast and colorectal cancers in immigrants from non-industrialised countries is sharply increased when they adopt a Western lifestyle. In addition, epidemiological studies on Western populations show an association between the two tumours, both in the same individual and also in close relatives. Most studies agree that high energy intake, obesity and inadequate physical exercise are associated with an increased risk of both tumours.

METHODS

Risk markers for each cancer are examined in order to identify causative nutritional factors or metabolic-endocrine dysfunction. The role of steroid hormones and other possible carcinogenic mechanisms is discussed, concentrating on evidence of a role for insulin and insulin-like growth factors (IGFs) in the promotion of carcinogenesis in both organs.

RESULTS

Individuals with a genetic susceptibility to insulin resistance show triggering of hyperinsulinaemia following excessive weight gain or long-term diet high in saturated fat. Case-control studies show an association between hyperinsulinaemia and evidence of breast or colorectal carcinoma. Multiple laboratory studies show that increased activity of IGFs can stimulate the growth of human breast and colorectal cancer cells.

CONCLUSION

It is postulated that either insulin resistance and its concomitants promote the development of breast and colorectal cancers, or that they share common risk factors. Sex steroid metabolism and organ specificity may explain age and sex differences between the tumours in relation to the role of obesity. Recent research suggests that a diet high in n-3 polyunsaturated fatty acids may reduce the risk of developing insulin resistance. This observation may be applied to test the hypothesis that an effect on hyperinsulinaemia may modify the risk of developing breast or colorectal cancer.

Alteration in immunoexpression of glucose transporter 2 in liver of tumour-bearing rats

To elucidate interactions between the glucose transport system and hepatic glucose production in the tumour-bearing state, glycogen storage, expression of glucose transporter isoform 2 (Glut 2) and activities of glucose-6-phosphatase (G-6-Pase) and hexokinase were histochemically examined in hepatocytes of tumour-bearing rats. Five male F344 rats, subcutaneously inoculated with methylcholanthrene (MCA)-induced sarcoma cells were compared with five pair-fed animals and four ad libitum fed controls. Glycogen storage was markedly decreased in liver cells of tumour-bearing rats compared to in those of control animals. Glut 2 immunoreactivity was uniformly seen in the cellular membrane of hepatocytes from control animals. In rats bearing sarcoma, the staining intensity was significantly decreased, suggesting that Glut 2 with its bi-directional transport capacity was down-regulated in the tumour-bearing state. Positive staining for hexokinase activity was located in the perivenous area in livers from control animals and was more diffusely located and more intense in livers from tumour-bearing animals. G-6-Pase activity, limited to the peripheral area in livers from controls, extended to the intermediate area and had stronger reactivity in livers from tumour-bearing animals. In the tumour-bearing cachectic condition, glucose may be partially consumed by a futile cycle, hepatic metabolic zonation was disturbed, and the release of glucose from the liver may not be mediated by a facilitative glucose transporter-2.

Insulin resistance and the alterations of glucose transporter-4 in adipose cells from cachectic tumor-bearing rats

BACKGROUND

Insulin resistance may play an important role in cancer cachexia; however, its mechanisms remain to be clarified.

METHODS

Cellular mechanisms of insulin resistance in tumor-bearing rats (TBR) were investigated in isolated adipose cells by measuring 3-O-[14C]methyl glucose transport activity and glucose transporter-4 (GLUT4) protein in low-density microsomes at a basal state and in the plasma membrane at an insulin-stimulated state.

RESULTS

The insulin-stimulated glucose transport activity in adipose cells from TBR was significantly lower than that of control rats (CTR) (0.51 +/- 0.25 and 2.27 +/- 0.11 fmol/cell/min, respectively). The amount of GLUT4 in low-density microsomes at a basal state and in plasma membrane at an insulin-stimulated state was less in TBR than in CTR.

CONCLUSIONS

These data suggest that the insulin resistance seen in the adipose cells of these tumor-bearing rats was caused in part by both a decreased amount of GLUT4 protein in a basal state and a decreased translocation of GLUT4 in response to insulin stimulation.

Breast cancer: further metabolic-endocrine risk markers?

There is evidence that increased oestrogen receptor (ER) expression in normal mammary epithelium may be a risk marker for the development of breast cancer. Insulin-like growth factor 1 (IGF1) is a potent inducer of mitosis and has been shown to synergize with oestrogen in stimulating the growth of human breast cancer in vitro. In these cells oestradiol has been shown to upregulate IGF type 1 receptor (IGFR), and recently a similar effect has been reported in normal human breast tissue xenografts in vivo. It has been postulated that the combined effect of oestradiol and IGF1 may stimulate proliferation in normal mammary epithelium and increase breast cancer risk. The bioavailability of IGF1 to the tissues is modulated by IGF-binding proteins (IGFBPs), and higher circulating levels of IGF1 and lower levels of IGFBP3 have been reported in breast cancer patients. Breast cancer specimens show a positive correlation between ER status and IGF receptor status, and also a negative correlation between ER status and IGFBP3 expression. Finally, ectopic growth hormone expression has been shown in a majority of specimens of normal and malignant breast tissue, and this may contribute to breast cancer risk, possibly by increasing the local level of bioavailable IGF1. Expansion of such findings may provide clinically useful markers of increased risk to breast cancer in women.

Hyperinsulinemia in colon, stomach and breast cancer patients

The objective of this study was to collect more information on the intricate relationship between the presence of a tumor, insulin status and blood lipids. We selected non-obese subjects suffering from colon, stomach and breast cancer and determined the concentration of fasting insulin, glucose, cholesterol, and triglycerides in blood before (BS) and after surgery (AS). Controls were healthy non-obese subjects. Insulin was also measured in tumors and non-cancerous tissues from the same organ. BS insulin and glucose (with the exception of glucose in colon patients) were significantly higher than the controls and fell to almost normal levels at AS. Serum cholesterol and triglycerides levels were reduced in stomach patients, BS and AS and cholesterol in colon patients BS. Tumors had 1.9-3.0 times as much insulin, or insulin-like substances, as control tissues. These results are consistent with our previous studies showing hyperinsulinemia in the presence of a tumor.

The glucagonoma syndrome. Clinical and pathologic features in 21 patients

The glucagonoma syndrome is a rare disorder characterized by weight loss, necrolytic migratory erythema (NME), diabetes, stomatitis, and diarrhea. We identified 21 patients with the glucagonoma syndrome evaluated at the Mayo Clinic from 1975 to 1991. Although NME and diabetes help identify patients with glucagonomas, other manifestations of malignant disease often lead to the diagnosis. If the diagnosis is made after the tumor is metastatic, the potential for cure is limited. The most common presenting symptoms of the glucagonoma syndrome were weight loss (71%), NME (67%), diabetes mellitus (38%), cheilosis or stomatitis (29%), and diarrhea (29%). Although only 8 of the 21 patients had diabetes at presentation, diabetes eventually developed in 16 patients, 75% of whom required insulin therapy. Symptoms other than NME or diabetes mellitus led to the diagnosis of an islet cell tumor in 7 patients. The combination of NME and diabetes mellitus led to a more rapid diagnosis (7 months) than either symptom alone (4 years). Ten patients had diabetes mellitus before the onset of NME. No patients had NME clearly preceding diabetes mellitus. Increased levels of secondary hormones, such as gastrin (4 patients), vasoactive intestinal peptide (1 patient), serotonin (5 patients), insulin (6 patients, clinically significant in 1 only), human pancreatic polypeptide (2 patients), calcitonin (2 patients) and adrenocorticotropic hormone (2 patients), contributed to clinical symptoms leading to the diagnosis of an islet cell tumor before the onset of the full glucagonoma syndrome in 2 patients. All patients had metastatic disease at presentation. Surgical debulking, chemotherapy, somatostatin, and hepatic artery embolization offered palliation of NME, diabetes, weight loss, and diarrhea. Despite the malignant potential of the glucagonomas, only 9 of 21 patients had tumor-related deaths, occurring an average of 4.91 years after diagnosis. Twelve patients were still alive, with an average age follow-up of 3.67 years.

Altered metabolism and mortality in patients with colon cancer receiving chemotherapy

To identify the metabolic effects of 5-fluorouracil and hydrazine sulfate therapy, 22 patients with colon cancer were admitted prospectively to a Clinical Research Center for serial measurement of counter-regulatory hormones, fasting hepatic glucose production (HGP), intravenous glucose tolerance test, plasma leucine appearance (LA) and leucine oxidation. Combined therapy was associated with a significant reduction in fasting glucose level (98 +/- 2 mg/dL to 94 +/- 2, P < 0.025) without a significant fall in fasting HGP (2.09 +/- 0.11 mg/kg/min versus 2.03 +/- 0.13; P > 0.05). The decreased fasting glucose value was associated with a mild but not statistically improved glucose disposal rate in response to the intravenous glucose tolerance test (1.34 +/- 0.07 %/min vs 1.47 +/- 0.11, P = 0.15). Plasma leucine appearance was significantly reduced after 2 months of therapy (63.3 +/- 3.0 mumol/kg/hr vs 57.1 +/- 3.9 mumol/kg/hr; P < 0.025), but leucine oxidation (11.5 +/- 1.1 mumol/kg/hr vs 11.2 +/- 1.1 mumol/kg/hr) was not altered. Despite the fact that plasma triiodothyronine concentrations significantly increased with therapy, it was not associated with plasma LA. Half of the patients with cancer died 14 +/- 4 months after the study, and the other half were alive 58 +/- 2 months later. Survival time can be estimated with 59% accuracy using plasma LA, HGP, carcino-embryonic antigen, and insulin concentration. Multiple regression analysis identified that plasma LA was related directly to length of survival time, and baseline HGP, carcino-embryonic antigen, and insulin concentration were related inversely to length of survival.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced non-oxidative glucose utilization in cancer patients is associated with a low triiodothyronine concentration

OBJECTIVE

Approximately 70% of all cancer patients have elevations in hepatic glucose production and/or reductions in glucose utilization. To identify an explanation for insulin resistance, we measured fasting hepatic glucose production (HGP), leucine appearance (Leu Ra), leucine oxidation (LO), glucose oxidation (GO) and non-oxidative glucose utilization at baseline and after identical insulin infusion rates (2 pmol/kg/minute, 7 pmol/kg/minute, and 70 pmol/kg/minute) in eight head and neck cancer patients and eight weight-matched disease-free volunteers.

METHODS

A step increase in insulin administration during a euglycemic clamp protocol was used to measure insulin effects on glucose and leucine metabolism. HGP and Leu Ra were determined by performing a primed, continuous 10-hour intravenous infusion of 6-3H glucose and 1-14C leucine. Baseline insulin, thyroid, TNF, and counter-regulatory hormonal measurements, HGP, GO and Leu Ra were obtained between hours 3 and 4. An insulin infusion was started at hour 4 and increased every 2 hours for 6 hours. Glucose appearance, Leu Ra, GO, LO and insulin concentrations were determined at the end of each 2-hour interval.

RESULTS

Fasting HGP, GO, fat oxidation and Leu Ra were similar between the two groups. Insulin administration in cancer patients and normal volunteers had a similar effect on LO and Leu Ra. The insulin concentration required to stimulate half maximal glucose utilization in cancer patients was significantly increased by 58% (470 +/- 82 pM vs. 741 +/- 124 pM; p < or = 0.05). Non-oxidative glucose utilization was reduced in the cancer patients at both lower doses of insulin infusion (6.4 +/- 2.1 mumol/kg/minute vs. 0.1 +/- 1.6 mumol/kg/minute p < or = 0.05; and 23.7 +/- 1.3 mumol/kg/minute vs. 15.1 +/- 2.0 mumol/kg/minute p < 0.01). Triiodothyronine (T3) was directly correlated in the cancer patients with non-oxidative glucose utilization at the two physiological insulin concentrations (r = 0.673, p < 0.05 and r = 0.731, p < 0.01) and the supraphysiological insulin concentration (r = 0.791, p < 0.01). The insulin sensitivity index from the euglycemic clamp study was significantly reduced in the cancer patients (4.7 +/- 0.7 vs. 2.4 +/- 0.1 (dl/min)/(microU/ml); p < 0.05).

CONCLUSIONS

In summary, head and neck cancer patients have an abnormal reduction in non-oxidative glucose utilization which occurs before abnormalities in HGP, GO, or Leu Ra [corrected]. One explanation for the reduced glucose utilization may be the influence of a reduced T3 concentration on non-oxidative glucose metabolism but further work is needed to confirm these preliminary observations.

Insulin and glucose status, tissue and plasma lipids in patients with tumours of the ovary or endometrium: possible dietary implications

The relationship between tumour growth, insulin status, blood lipids and adipose linoleic acid (LA, reflecting long-term LA intake) was studied in 19 Jewish women suffering from early and advanced stages (ES and AS) of ovarian and endometrial tumours. Blood insulin in patients with ES tumours was four times higher than the control value in cancer-free subjects, but fell to normal levels at AS and after ES surgery (PES). Tumours and abdominal adipose tissue (AAT) had 4-6 and 1.4-1.7 times as much insulin as non-cancerous control organs. Serum total cholesterol (CHOL) and LDL-cholesterol were high at ES, dropped below normal at AS, but normalised at PES, while HDL-cholesterol increased after ES surgery. Linoleic acid in subcutaneous adipose tissue (SAT) was high in controls (26.4 + 1.5% of total fatty acids), but lower in cancer patients (20.5 + 3.7%, P < 0.05), while palmitic acid showed the opposite change. The results suggest mobilisation of glucose, cholesterol and linoleic acid for the supply of energy and structural lipids to rapidly multiplying tumour cells and possibly for prostaglandin synthesis. They also raise the question of whether the high linoleic acid intake by the Jewish population in Israel predisposes individuals to tumour development.

Reduced tyrosine kinase activity of the insulin receptor in obesity-diabetes. Central role of tumor necrosis factor-alpha

Insulin resistance is an important metabolic abnormality often associated with infections, cancer, obesity, and especially non-insulin-dependent diabetes mellitus (NIDDM). We have previously demonstrated that tumor necrosis factor-alpha produced by adipose tissue is a key mediator of insulin resistance in animal models of obesity-diabetes. However, the mechanism by which TNF-alpha interferes with insulin action is not known. Since a defective insulin receptor (IR) tyrosine kinase activity has been observed in obesity and NIDDM, we measured the IR tyrosine kinase activity in the Zucker (fa/fa) rat model of obesity and insulin resistance after neutralizing TNF-alpha with a soluble TNF receptor (TNFR)-lgG fusion protein. This neutralization resulted in a marked increase in insulin-stimulated autophosphorylation of the IR, as well as phosphorylation of insulin receptor substrate 1 (IRS-1) in muscle and fat tissues of the fa/fa rats, restoring them to near control (lean) levels. In contrast, no significant changes were observed in insulin-stimulated tyrosine phosphorylations of IR and IRS-1 in liver. The physiological significance of the improvements in IR signaling was indicated by a concurrent reduction in plasma glucose, insulin, and free fatty acid levels. These results demonstrate that TNF-alpha participates in obesity-related systemic insulin resistance by inhibiting the IR tyrosine kinase in the two tissues mainly responsible for insulin-stimulated glucose uptake: muscle and fat.

Tumor necrosis factor alpha inhibits signaling from the insulin receptor

Insulin resistance is a common problem associated with infections and cancer and, most importantly, is the central component of non-insulin-dependent diabetes mellitus. We have recently shown that tumor necrosis factor (TNF) alpha is a key mediator of insulin resistance in animal models of non-insulin-dependent diabetes mellitus. Here, we investigate how TNF-alpha interferes with insulin action. Chronic exposure of adipocytes to low concentrations of TNF-alpha strongly inhibits insulin-stimulated glucose uptake. Concurrently, TNF-alpha treatment causes a moderate decrease in the insulin-stimulated autophosphorylation of the insulin receptor (IR) and a dramatic decrease in the phosphorylation of IR substrate 1, the major substrate of the IR in vivo. The IR isolated from TNF-alpha-treated cells is also defective in the ability to autophosphorylate and phosphorylate IR substrate 1 in vitro. These results show that TNF-alpha directly interferes with the signaling of insulin through its receptor and consequently blocks biological actions of insulin.