Insulin in combination with pioglitazone prevents advanced cachexia in 256-Walker tumor-bearing rats: effect is greater than treatment alone and is associated with improved insulin sensitivity

BACKGROUND

Insulin (INS) resistance and hypoinsulinemia commonly observed in cancer-carrying, can contribute to cachexia. However, the effects of INS and INS sensitizers, such as pioglitazone (PIO), particularly when used in combination therapy, on cancer cachexia have not been evaluated sufficiently. We investigated the effects of INS and PIO, at various doses, either isolated or combined, on cachexia in Walker-256 tumor-bearing rats (TB rats).

METHODS

INS or INS + PIO were administered in TB rats, for 6 or 12 days, starting from the day of tumor cells inoculation.

RESULTS

INS at 18 or 27 U/kg (12-days treatment), but not 9 U/kg, reduced fat loss and slightly prevented weight loss. However, INS 18 U/kg + PIO 5, 10, 20, or 40 mg/kg (6 or 12-day treatment) reduced fat loss and markedly prevented weight loss but did not affect muscle wasting. While TB rats lost weight (37.9% in 12 days), TB rats treated with INS 18 U/kg + PIO 5 mg/kg showed pronounced weight gain (73.7%), which was greater than the sum (synergism) of the weight gains promoted by isolated treatments with INS 18 U/kg (14.7%) or PIO 5 mg/kg (13.1%). The beneficial effect of the INS 18 U/kg + PIO 5 mg/kg on weight loss was associated with improved INS sensitivity, as indicated by the higher blood glucose clearance constant (kITT), decreased levels of free fatty acids and triacylglycerols (INS resistance-inducing factors) in the blood, and increased expression of p-Akt (INS signaling pathway protein) in adipose tissue.

CONCLUSIONS

The combined treatment with INS 18 U/kg + PIO 5 mg/kg was more effective in preventing advanced cachexia in TB rats than each treatment alone, emerging as the best approach, considering the lower dosage and higher efficacy. This combination completely preserved adipose mass and markedly reduced weight loss through a synergistic mechanism linked to improved insulin sensitivity. These findings provide new insights into the importance of drug combinations in effectively combating fat loss in advanced cachexia.

Metformin induces muscle atrophy by transcriptional regulation of myostatin via HDAC6 and FoxO3a

BACKGROUND

Skeletal muscle atrophy is a severe condition that involves loss of muscle mass and quality. Drug intake can also cause muscle atrophy. Biguanide metformin is the first-line and most widely prescribed anti-diabetic drug for patients with type 2 diabetes. The molecular mechanism of metformin in muscle is unclear.

METHODS

Myostatin expression was investigated at the protein and transcript levels after metformin administration. To investigate the pathways associated with myostatin signalling, we used real-time polymerase chain reaction, immunoblotting, luciferase assay, chromatin immunoprecipitation assay, co-immunoprecipitation, immunofluorescence, primary culture, and confocal microscopy. Serum analysis, physical performance, and immunohistochemistry were performed using our in vivo model.

RESULTS

Metformin induced the expression of myostatin, a key molecule that regulates muscle volume and triggers the phosphorylation of AMPK. AMPK alpha2 knockdown in the background of metformin treatment reduced the myostatin expression of C2C12 myotubes (-49.86 ± 12.03%, P < 0.01) and resulted in increased myotube diameter compared with metformin (+46.62 ± 0.88%, P < 0.001). Metformin induced the interaction between AMPK and FoxO3a, a key transcription factor of myostatin. Metformin also altered the histone deacetylase activity in muscle cells (>3.12-fold ± 0.13, P < 0.001). The interaction between HDAC6 and FoxO3a induced after metformin treatment. Confocal microscopy revealed that metformin increased the nuclear localization of FoxO3a (>3.3-fold, P < 0.001). Chromatin immunoprecipitation revealed that metformin induced the binding of FoxO3a to the myostatin promoter. The transcript-level expression of myostatin was higher in the gastrocnemius (GC) muscles of metformin-treated wild-type (WT) (+68.9 ± 10.01%, P < 0.001) and db/db mice (+55.84 ± 6.62%, P < 0.001) than that in the GC of controls (n = 4 per group). Average fibre cross-sectional area data also showed that the metformin-treated C57BL/6J (WT) (-31.74 ± 0.75%, P < 0.001) and C57BLKS/J-db/db (-18.11 ± 0.94%, P < 0.001) mice had decreased fibre size of GC compared to the controls. The serum myoglobin level was significantly decreased in metformin-treated WT mice (-66.6 ± 9.03%, P < 0.01).

CONCLUSIONS

Our results demonstrate that metformin treatment impairs muscle function through the regulation of myostatin in skeletal muscle cells via AMPK-FoxO3a-HDAC6 axis. The muscle-wasting effect of metformin is more evident in WT than in db/db mice, indicating that more complicated mechanisms may be involved in metformin-mediated muscular dysfunction.

Insulin secretion decline in Walker-256 tumor-bearing rats is early, follows the course of cachexia, and is not improved by lixisenatide

Lixisenatide, a glucagon-like peptide-1 receptor agonist, is used to stimulate insulin secretion in patients with type 2 diabetes mellitus. However, its effect on insulin secretion in cancer patients, particularly during the cachexia course, has not yet been evaluated. The purpose of this study was to investigate the lixisenatide effect on INS secretion decline during the cachexia course (2, 6, and 12 days of tumor) in pancreatic islets isolated from Walker-256 tumor-bearing rats. Pancreatic islets of healthy and tumor-bearing rats were incubated in the presence or absence of lixisenatide (10 nM). Tumor-bearing rats showed reduction of body weight and fat and muscle mass, characterizing the development of cachexia, as well as reduction of insulinemia and INS secretion stimulated by glucose (5.6, 8.3, 11.1, 16.7, and 20 mM) on days 2, 6, and/or 12 of tumor. Lixisenatide increased the 16.7 mM glucose-stimulated insulin secretion, but not by 5.6 mM glucose, in the islets of healthy rats, without changing the insulin intracellular content. However, lixisenatide did not prevent the decreased 16.7 mM glucose-stimulated insulin secretion in the pancreatic islets of rats with 2, 6, and 12 days of tumor and neither the decreased insulin intracellular content of rats with 12 days of tumor. In consistency, in vivo treatment with lixisenatide (50 μg kg-1, SC, once daily, for 6 days) visually increased insulinemia of healthy fasted rats, but did not prevent hypoinsulinemia of tumor-bearing rats. In conclusion, Walker-256 tumor-bearing rats showed early decline (2 days of tumor) of insulin secretion, which followed the cachexia course (6 and 12 days of tumor) and was not improved by lixisenatide, evidencing that this insulin secretagogue, used to treat type 2 diabetes, does not have beneficial effect in cancer bearing-rats.

Endocrinopathies and cancer cachexia

PURPOSE OF REVIEW

Cancer cachexia cannot be easily reversed by standard nutritional support and interventions directed at underlying metabolic derangements may be needed to prevent or reverse cachexia and maintain healthy body composition. The following review will highlight the contribution and potential therapeutic interventions for insulin resistance, alterations in ghrelin signaling, and hypogonadism in cancer patients.

RECENT FINDINGS

In addition to decreased caloric intake, chronic inflammation, and altered metabolism of glucose, proteins and lipids, endocrine abnormalities can propagate weight loss or changes in body composition in cancer patients.

SUMMARY

Cancer cachexia, loss of muscle mass with or without the loss of fat mass, is a multifactorial syndrome, which is associated with increased morbidity and mortality. Currently, limited therapeutic options for the treatment of weight loss in cancer patients exist, which lead to clinically meaningful improvements in weight gain and performance status. Treatment directed at underlying insulin resistance, low testosterone, and altered ghrelin sensitivity, in the future, may lead to potential therapeutic options for loss of lean body mass and cancer cachexia.

Effects of lixisenatide treatment on mild cachexia and related metabolic abnormalities in Walker-256 tumour-bearing rats

Lixisenatide, a glucagon-like peptide-1 (GLP-1) receptor agonist, is used in the treatment of type 2 diabetes mellitus (T2DM). It increases insulin (INS) secretion and can decrease INS resistance, improving metabolic disorders in this disease. However, its effects on metabolic disturbances in cancer-bearing, which also exhibit decreased INS secretion and INS resistance, changes that may contribute to weight loss (cachexia), have not yet been evaluated. The purpose of this study was to investigate the lixisenatide treatment effects on mild cachexia and related metabolic abnormalities in Walker-256 tumour-bearing rats. Lixisenatide (50 μg kg^-1 , SC) was administered once daily, for 6 days, after inoculation of Walker-256 tumour cells. Acute lixisenatide treatment did not improve hypoinsulinemia, INS secretion and INS resistance of tumour-bearing rats. It also did not prevent the reduced glucose and increased triacylglycerol and lactate in the blood and nor the loss of retroperitoneal and epididymal fat of these animals. However, acute lixisenatide treatment accentuated the body mass loss of tumour-bearing rats. Therefore, lixisenatide, unlike T2DM, does not improve hypoinsulinemia and INS resistance associated with cancer, evidencing that it does not have the same beneficial effects in these two diseases. In addition, lixisenatide aggravated weight loss of tumour-bearing rats, suggesting that its use for treatment of T2DM patients with cancer should be avoided. SIGNIFICANCE OF THE STUDY: Lixisenatide increases insulin secretion and appears to reduce insulin resistance in T2DM. However, lixisenatide treatment does not improve hypoinsulinemia and insulin resistance associated with cancer, as it does in T2DM, and aggravated weight loss, suggesting that its use for treatment of T2DM patients with cancer should be avoided.

A three long non-coding RNA signature to improve survival prediction in patients with Wilms' tumor

The prognostic significance of long non-coding RNAs (lncRNAs) in Wilms' tumor (WT) remains unclear. The present study identified differential lncRNA expression patterns between WT and normal tissues; and evaluated the prognostic value of these lncRNAs. Multidimensional data from 136 samples were retrieved from the Therapeutically Applicable Research to Generate Effective Treatments (TARGET) database. Computational data analyses were performed to detect survival-associated molecular signatures. Kaplan-Meier survival curves revealed the prognostic prediction values for three of these lncRNAs, namely DLGAP1 antisense RNA 2 (DLGAP1-AS2), RP11-93B14.6 and RP11554F20.1. Cox regression analysis revealed that the three-lncRNA signature was significantly associated with patient survival (P<0.01). Functional enrichment analyses suggested that the target genes of these three lncRNAs may be involved in known cancer-associated pathways. The present study revealed a three-lncRNA signature consisting of DLGAP1-AS2, RP11-93B14.6 and RP11554F20.1 that may be used as a prognostic marker for patients with WT.

New insights on the regulation of cancer cachexia by N-3 polyunsaturated fatty acids

Cancer cachexia is a multifactorial syndrome that develops during malignant tumor growth. Changes in plasma levels of several hormones and inflammatory factors result in an intense catabolic state, decreased activity of anabolic pathways, anorexia, and marked weight loss, leading to cachexia development and/or accentuation. Inflammatory mediators appear to be related to the control of a highly regulated process of muscle protein degradation that accelerates the process of cachexia. Several mediators have been postulated to participate in this process, including TNF-α, myostatin, and activated protein degradation pathways. Some interventional therapies have been proposed, including nutritional (dietary, omega-3 fatty acid supplementation), hormonal (insulin), pharmacological (clenbuterol), and nonpharmacological (physical exercise) therapies. Omega-3 (n-3) polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid, are recognized for their anti-inflammatory properties and have been used in therapeutic approaches to treat or attenuate cancer cachexia. In this review, we discuss recent findings on cellular and molecular mechanisms involved in inflammation in the cancer cachexia syndrome and the effectiveness of n-3 PUFAs to attenuate or prevent cancer cachexia.