Abstract
An independent association between insulin resistance and cancer has been
consistently reported in humans. Patients with cancer display insulin resistance
or its clinical manifestations, and this metabolic adaptation precedes the
clinical diagnosis of cancer. Insulin resistance in cancer patients is
associated with a metabolic switch from oxidative metabolism toward glycolysis
that spares oxygen to be used in anabolic processes and facilitates the fast
production of energy and intermediate metabolites required for the rapid
proliferation of cancer cells. In malignant cells, glucose consumption via
glycolysis occurs under normoxic conditions (aerobic glycolysis). Pathogenic
mechanisms underlying insulin resistance in cancer patients include
hypoxia-inducible factor-1 upregulation and overproduction of cytokines, such as
interferon, interleukin-6, interleukin-18, and interleukin-1β. Deficit of
2-oxoglutarate (α-ketoglutarate) has been detected in cancer cells and may
facilitate hypoxia-inducible factor-1 assembly and activity. Overproduction of
cytokines in cancer patients follows activation of the immune system by abnormal
nucleic acid variants. Anomalous DNA or RNA structures are recognized by immune
sensors and stimulate signaling pathways that ultimately increase cytokine
production. Likewise, interferon overproduction occurs in congenital disorders
that feature ineffectively repaired DNA lesions, such as Werner syndrome, Bloom
syndrome, mutations in DNA polymerase-δ1, and ataxia telangiectasia. These
diseases cause simultaneous insulin resistance and a high tendency to develop
cancer, highlighting the relationship between the two processes. Defectively
repaired DNA injury endangers genomic integrity, predisposing to cancer, and
activates the immune system to increase interferon production and subsequent
insulin resistance. Hypoxia-inducible factor-1 and cytokines induce insulin
resistance by suppressing peroxisome proliferator-activated-γ in the
subcutaneous adipose tissue.
Keywords
insulin resistance - cancer - hypoxia inducible factor - peroxisome proliferator-activated-γ
- interferon - DNA repair