Insulin resistance is usually associated with type 2 diabetes. Now researchers have found it in cancer patients and found that it can cause cancer to spread faster.
Key points
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Insulin resistance in cancer patients: systematic review and meta-analysis
Background
Insulin resistance is a critical cause of metabolic dysfunctions. Metabolic dysfunction is common in cancer patients and is associated with higher rates of cancer recurrence and reduced overall survival. However, insulin resistance is rarely considered clinically and therefore it is not known how frequently this condition occurs in cancer patients.
Methods
To address this knowledge gap, we conducted a systematic review and meta-analysis guided by the Preferred Items for Systematic Review and Meta-Analysis (PRISMA) statement. Studies that evaluated insulin resistance in patients with various cancer diagnoses, using the gold standard hyperinsulinemic-euglycemic clamp method, were included.
Studies eligible for inclusion were as follows: (1) included cancer patients over 18 years of age; (2) included an age-matched control group consisting of individuals without cancer or other types of malignancies; (3) measured insulin sensitivity using the hyperinsulinemic-euglycemic clamp method.
The MEDLINE, Embase, and Cochrane Central Register of Controlled Trials databases were searched for articles published from database inception to March 2023 without language restriction, supplemented by forward and backward citation searching. Bias was assessed using a funnel plot.
Results
Fifteen studies met the criteria. The mean insulin-stimulated glucose elimination rate (Rd) was 7.5 mg/kg/min in control subjects (n = 154) and 4.7 mg/kg/min in patients with a diagnosis of cancer. (n = 187).
Therefore, the mean difference in Rd was −2.61 mg/kg/min [95% confidence interval, −3.04; −2.19], p<0.01). Heterogeneity among the included studies was negligible (p = 0.24).
Interpretation
These findings suggest that patients diagnosed with cancer are markedly resistant to insulin . Given that metabolic dysfunction in cancer patients is associated with increased recurrence and reduced overall survival, future studies should address whether improving insulin resistance in this population can improve these outcomes and therefore improve survival. patient care.
Comments
In the 1920s, researchers discovered that cancer patients had sweet-smelling urine. At first, doctors were baffled, but soon realized it was the result of elevated blood sugar levels.
"This was one of the first things we learned about cancer patients," says Associate Professor Lykke Sylow.
The sweet-smelling urine suggested that cancer affects the body’s blood sugar level. But how? A new study is ready to answer that question. Where previous studies have examined the connection between cancer and insulin, the new study by Lykke Sylow and her colleagues is the first to compile the best research on the topic, and the answer appears to be clear:
"In cancer patients, cells do not respond well to the hormone insulin. Therefore, more insulin is needed to create the same effect in cancer patients. If you suffer from insulin resistance, your body has to produce more insulin than normal to regulate blood sugar," says Lykke Sylow, who is one of the lead authors of the new study. And the body’s ability to respond to insulin is affected in both cancer patients and people with type 2 diabetes.
Symptoms of type 2 diabetes , such as fatigue and increased thirst and urination, develop gradually and can therefore be difficult to detect. And in cancer patients, insulin resistance can be even more difficult to identify, since they already experience some of these symptoms such as fatigue.
Insulin can cause cancer cells to multiply
Aside from the negative consequences of insulin resistance, the condition can also cause cancer cells to multiply.
“We know from cellular studies, animal studies and some human studies that insulin is a growth hormone, and that it has the same effect on cancer cells. That is, a high level of insulin can make cancer cells grow faster,” says the second lead author of the study, Joan Màrmol, adding: “Of course, this can be a big problem for cancer patients.”
Additionally, insulin resistance can influence protein accumulation in muscles. That is, if the body does not respond to insulin, it will lose muscle mass and strength, and that is a big problem for many cancer patients.
All in all, cancer and insulin resistance is a really bad combination.
Lykke Sylow hopes that oncologists will start monitoring patients’ blood sugar, even when it appears normal, because insulin resistance can be difficult to detect, as the body will simply compensate by producing more insulin.
"And if they find that the patient has insulin resistance, they should start treating it. We can treat insulin resistance because we have a deep understanding of the condition; we’re just used to associating it with type 2 diabetes." However, aspects of the connection require more research.
"The next step is to try to determine who develops insulin resistance. Which cancer patients are at risk here? Do they have a particular type of cancer or specific risk factors? Or maybe it’s related to the treatment?" Lykke Sylow says and adds:
"And once we have identified people at high risk of developing the condition, I hope to see more long-term studies into treating insulin resistance and whether it has a positive effect on patients."
You can read the full study, “Insulin resistance in cancer patients: a systematic review and meta-analysis,” in Acta Oncologica .
