Role of Exosomes Derived from Adipose Tissue under Obese Conditions in Skeletal Muscle and Liver Cells: Commonalities and Differences

Diabetes and obesity: the role of stress in the development of cancer

Diabesity is a condition where an individual has both diabetes and obesity, which can lead to severe complications including cardiovascular disease, a leading cause of mortality. Recently, cancer has become a leading cause of excess hospitalizations, and both diabetes and obesity are associated with a higher risk of developing several types of cancer. In this review, we propose that chronic stress significantly increases this association. Managing diabetes and obesity is challenging as they both cause significant distress. The relationship between stress and cancer is interconnected, with anxiety and depression being common in cancer patients. Cancer diagnosis and treatment can cause lasting changes in the body's neuroendocrine system, with stress causing an excessive release of catecholamines and prostaglandins in patients undergoing cancer surgery, which promotes the spread of cancer to other parts of the body. Furthermore, stress could significantly increase the risk of cancer in patients with diabetes, obesity, or both.

Update on Adipose Tissue and Cancer

Adipose tissue is the largest endocrine organ and an accepted contributor to overall energy homeostasis. There is strong evidence linking increased adiposity to the development of 13 types of cancer. With increased adiposity comes metabolic dysfunction and insulin resistance, and increased systemic insulin and glucose support the growth of many cancers, including those of the colon and endometrium. There is also an important direct crosstalk between adipose tissue and various organs. For instance, the healthy development and function of the mammary gland, as well as the development, growth, and progression of breast cancer, are heavily impacted by the breast adipose tissue in which breast epithelial cells are embedded. Cells of the adipose tissue are responsive to external stimuli, including overfeeding, leading to remodeling and important changes in the secretion of factors known to drive the development and growth of cancers. Loss of factors like adiponectin and increased production of leptin, endotrophin, steroid hormones, and inflammatory mediators have been determined to be important mediators of the obesity-cancer link. Obesity is also associated with a structural remodeling of the adipose tissue, including increased localized fibrosis and disrupted angiogenesis that contribute to the development and progression of cancers. Furthermore, tumor cells feed off the adipose tissue, where increased lipolysis within adipocytes leads to the release of fatty acids and stromal cell aerobic glycolysis leading to the increased production of lactate. Both have been hypothesized to support the higher energetic demands of cancer cells. Here, we aim to provide an update on the state of the literature revolving around the role of the adipose tissue in cancer initiation and progression.

High-fat diet-induced biogenesis of pulmonary exosomes in an experimental rat model

BACKGROUND

High-fat diets (HFD) have recently become a public health concern. We hypothesize that HFD induces exosomes biogenesis in the lung tissue of rat model.

METHODS AND RESULTS

Sixteen adult male Wistar rats were fed with HFD or a regular chow diet for 3 months. The histopathological changes in lung tissues were measured by hematoxylin and eosin (H&E) staining. Bronchoalveolar lavage (BAL) was performed to assay exosomes by acetylcholinesterase enzyme (AhCE) activity. Real-time PCR (qPCR) was used to evaluate Rab27-b, Alix, and IL-1β expression, while the immunohistochemical examination was performed for CD81 expression in lung tissues. In addition, expression of IL-1β was detected by ELISA. We found pathological alterations in the lung tissue of HFD animals. AhCE activity along with the expression level of Rab27-b, Alix, and IL-1β was increased in HFD animals (p < 0.05). Immunohistochemical staining showed that expression of CD81 was increased in lung tissues of HFD animals compared with the control group (p < 0.05).

CONCLUSION

Hence, HFD induced exosomes biogenesis and histopathological changes with IL-1β expression in rats' lung tissues.

Liver-Derived Exosomes Induce Inflammation and Lipogenesis in Mice Fed High-Energy Diets

The liver is an endocrine organ and is the first organ exposed to nutrients when they are absorbed into the body before being metabolized by the distal organs. Although the liver plays an essential role in the interactions between the metabolic organs, their regulatory mechanisms have not been elucidated. Exosomes mediate communication between cells and primarily enable the transport of lipids, mRNAs, miRNAs, and proteins between cells. In this study, we investigated the effects of lipid metabolism on the liver and adipose tissue between mice fed high-fat (HF) and high-fat/sucrose (HFS) diets and determined the effects of liver tissue-derived exosomes on adipocytes to understand the underlying mechanisms associated with obesity-related metabolic diseases. Normal, HF, and HFS diets were fed to the mice for 12 weeks to compare differences based on dietary patterns. We showed different lipid metabolism effects on the liver and adipose tissue between HF- and HFS-fed mice. In the liver, fibrosis, inflammation, and lipogenesis were activated at higher levels in the HFS than in the HF group, and lipolysis was activated at higher levels in the HF than in the HFS group. In adipose tissue, adipogenesis, fatty acid transport, and lipolysis were activated at higher levels in the HF than in the HFS group, and inflammation and lipogenesis were activated at higher levels in the HFS than in the HF group. This result followed a similar trend reported in 3T3-L1 cells treated with liver-derived exosomes. In addition, the TG content of the liver-derived exosomes was significantly higher, and lipid accumulation was accelerated in the HFS than in the HF group. Based on these results, continuous exposure to HF and HFS diets induces lipid accumulation mediated by liver-derived exosomes; however, there is a difference in lipid metabolism. These results contribute to the elucidation of the mechanisms of exosome function in relation to obesity-related metabolic diseases and the metabolic relationship between tissues.