With each passing year, fresh scientific evidence emerges to vindicate Life Extension®’s contention that aging humans can derive enormous benefit from an antidiabetic drug called metformin.
In 2010 alone, scientists at top-ranked institutions made landmark discoveries that broaden its use to combat degenerative disease.
The ability of metformin to help facilitate weight loss has long been known. What few doctors understand are the unique mechanisms by which metformin can prevent and even help treat certain cancers.
In a remarkable finding, a team of Swiss researchers found that diabetic women on a long-term metformin regimen (5 years or more) experienced a 56% reduction in breast cancer risk!1 It also slashed pancreatic cancer rates by 62% in diabetics and may cut lung cancer rates in smokers.2,3
In this article, a novel link between impaired glucose control and cancer is detailed. You will discover the growing list of cancers metformin may effectively combat, including those of the colon, uterus, and prostate. You will also learn of a striking connection between the anti-cancer mechanisms of metformin and calorie restriction!
Why Metformin Should Be Viewed Differently than Other Drugs
Many Life Extension members like to brag that they do not need to take any prescription drugs. Given the lethal side effects posed by so many FDA-approved medications, avoiding them whenever possible makes sense.
Metformin is an exception! Its broad-spectrum anti-aging properties make it a drug that most longevity enthusiasts should seriously consider asking their doctors about.
Since it long ago came off patent, metformin is a super-low cost generic that everyone can afford.
Metformin Was Originally a Botanical Compound
Although it is sold as a prescription drug today, metformin has a long history as a botanical compound. It was originally derived from the French lilac (Gallega officianalis), which has had a place in folk medicine for hundreds of years.4,5
After decades of neglect in the 20th century, metformin was rediscovered during the acceleration of the global epidemics of obesity and type 2 diabetes. Metformin was approved by the FDA as a treatment for type 2 diabetes in 1994, and it became the most widely prescribed drug for this disease.6
Beginning around 2002, a series of epidemiological studies revealed a remarkable trend: diabetic patients taking metformin were less likely to die compared to diabetics using other forms of therapy, including other oral glucose-lowering drugs or insulin.7,8 The earlier studies also demonstrated specific benefits in protecting against cardiovascular diseases.9,10 By 2005, evidence from large, population-based studies was becoming clear: people taking metformin for diabetes were significantly and reliably protected against the increased cancer risk posed by the diabetes itself.2,11-15 Why should this be? The answer lies in a hidden relationship between elevated blood glucose and cancer development.
Diabetics are predisposed to a terrifyingly broad range of cancers of the liver, pancreas, colon, breast, endometrium (uterine lining), kidney, and possibly other tissues.16-18 Scientists theorized that if ways to reduce chronic blood sugar elevations and other molecular consequences associated with weight gain were discovered, this would have a powerful impact in interrupting some of the pathways that lead to cancer. Metformin, it turns out, acts in a multitargeted fashion to accomplish precisely those effects.18,19
The simplest way to understand metformin’s role in cancer prevention is to recognize that it is a powerful calorie restriction-mimicking drug.20 It acts to essentially “fool” the body into “believing” that it is in a calorie-restricted state, thereby switching on the same protective mechanisms that arise from calorie restriction itself.
Let’s now see how all this biochemistry translates to genuine anti-cancer action.
Some of metformin’s most compelling effects are in cancers of the reproductive system because it blocks the enzyme called aromatase, which can stimulate estrogen-dependent cancer growth.21 Breast cancer is the most common malignancy diagnosed in women.22 Fortunately, most varieties of breast cancer are proving to be especially susceptible to metformin prevention in the laboratory, and to metformin treatment in human patients, as shown by studies that have emerged over just the past two years.23
Metformin suppresses a specific cancer-inducing protein (human epidermal growth factor receptor 2, or HER2)24 that dramatically increases the risk of breast cancer.25 By suppressing HER2, which can stop cancers from developing in the first place, metformin halts cancer cells’ reproductive cycle, preventing them from growing once they have developed.26
Via a different set of mechanisms, metformin selectively targets cancer stem cells, cells that resist chemotherapy drugs and can regenerate and cause relapse of the disease.27 In live animal studies, metformin suppressed breast cancers, especially in animals on a high-calorie diet.20 In a dramatic 2010 study, metformin extended the life span of mice with HER2-positive breast cancers, delayed the onset of tumor development, and inhibited the growth of implanted tumors.19
The combination of all these effects means that metformin is effective against many different types of breast cancers, including those that are estrogen receptor positive and negative, and those that express both normal and excessive amounts of HER2.28 Indeed, data appeared in 2010 that long-term (greater than 5-year) metformin use by humans is associated with a substantial (56%) reduction in risk for developing breast cancer as compared with no use of metformin.1
Human trials have already demonstrated that diabetic patients with breast cancer who receive metformin plus chemotherapy have a higher rate of complete remission than do those not taking metformin. Complete remission occurred in 24% of diabetic patients taking metformin, 8% of diabetic patients not taking metformin, and 16% of non-diabetic patients not taking metformin.29 And a 2009 study showed that metformin induced unique, multitargeted responses in so-called “triple-negative” breast cancer cells, which represent some of the most difficult-to-treat forms of the malignancy.30
All of these findings speak to metformin’s tremendous potential as a true breast cancer chemopreventive agent—one that can and should be used long before any sign of cancer has appeared. Scientists from around the world believe that the time has come to leverage these effects in breast cancer chemoprevention and treatment.22,23,31,32
Cancer of the endometrium, or lining of the uterus, is the most common genital malignancy. It has multiple risk factors, among them obesity, insulin resistance, and diabetes.33 An early sign of cancerous change is endometrial hyperplasia. Standard therapy for endometrial hyperplasia is treatment with progestogens (progesterone-like hormones), which can restore the endometrium to its normal state. In 2003, researchers at the Mayo Clinic reported a single case study of a woman whose endometrial hyperplasia had failed to respond to progestogen treatment, and who was then given metformin (she was not diabetic).34 One month after initiation of treatment, the patient’s endometrium had returned to its normal state.
In 2010 scientists learned that metformin is a potent inhibitor of endometrial cancer cell proliferation, acting to arrest the cancer cells’ reproductive cycle, inducing cell death through apoptosis, and decreasing gene expression of an enzyme complex called human telomerase reverse transcriptase (hTERT) that contributes to unregulated cell replication.35 Many of these effects were triggered by metformin’s activation of the AMP-protein kinase (AMPK) complex, and are identical to those induced by calorie restriction.35
Metformin mimics the benefits of a hormone called adiponectin in activating AMPK-dependent growth inhibition in prostate and colon cancer cells.
Based on these observations, other gynecological researchers have begun to use metformin as part of a “conservative” approach (using fewer, less-invasive procedures) to their management of endometrial hyperplasia and endometrial cancer.36
Prostate cancer is the most-commonly diagnosed cancer in men. Insulin resistance, which triggers rising levels of insulin and insulin-like growth factors (IGFs) substantially increases disease risk.37,38 For that reason, reducing plasma insulin and IGF levels are significant goals in prostate cancer prevention and treatment, and metformin is increasingly being recommended in those roles.37
Metformin mimics the benefits of a hormone called adiponectin in activating AMPK-dependent growth inhibition in prostate and colon cancer cells.38 This helps solidify our understanding of the relationship between obesity, in which adiponectin levels are low, and cancer development.
Metformin also acts by blocking the prostate cancer cells’ reproductive cycle by decreasing levels of a cancer growth-promoting protein (cyclin D1), and at the same time increasing production of a protein (p27) that inhibits the cell division cycle.39 As an aside, it is p27 that is also enhanced (upregulated) by healthy levels of vitamin D, the omega-3 fatty acid DHA, and silibinin—one of the active agents in milk thistle.40-42 These results testify to metformin’s ability to attack cancers from multiple directions at once.
Still another angle from which metformin suppresses prostate cancer is to literally starve the malignant cells of energy, capitalizing on metabolic vulnerabilities unique to cancer cells and absent in healthy cells. Stunning results appeared in early 2010 showing that metformin, in combination with the metabolic agent 2-deoxyglucose, dramatically depletes prostate cancer cells’ stores of energy-rich ATP molecules.43 In fact, the treatment led to a 96% reduction in malignant cells’ viability, with only moderate effects on healthy prostate cells. The treatment also triggered a switch from survival processes to cell death in the malignant cells.
These laboratory findings took on profound meaning in a large human study of men with prostate cancer and their use of metformin.44 Among 1,001 men with prostate cancer and 942 cancer-free controls, metformin use was significantly more common in the control patients, resulting in a risk reduction of 44%. This finding is especially powerful considering that men taking metformin in this retrospective study were much more likely to have been diabetic, and so their risk for cancer could be expected to have been higher!
Pancreatic cancer is one of the most lethal human diseases, with a nearly-100% fatality rate, and experts are desperate for new biochemical targets that will help control this disease.45 One such novel target that has been proposed is IGF-GPCR, an interaction between IGF receptors and a powerful group of signaling proteins called G protein-coupled receptors (GPCR). Metformin administration disrupted the IGF-GPCR interaction and thereby significantly decreased the growth of pancreatic cancer cells grafted into susceptible mice.46
Metformin also triggers pancreatic cancer cell death by apoptosis by activating caspase, a “death signaling” or “executioner” molecule.47
These laboratory findings help explain the remarkable protective effects of metformin in preventing pancreatic cancer in living humans. A large hospital-based case-control study of 973 patients with pancreatic cancer and 863 healthy controls demonstrated a dramatic risk reduction of 62% in diabetic patients who had taken metformin compared with those who had not.2 The difference wasn’t related solely to reduction in blood sugar, since diabetic patients who had taken insulin or insulin-promoting drugs enjoyed no similar protection. This study, of course, could also be interpreted to show how insulin-promoting drugs and insulin itself increases cancer risk. Life Extension has long warned about the carcinogenic risks associated with elevated insulin levels. Fortunately, another benefit of metformin is reducing insulin and glucose levels via several mechanisms.
Colorectal cancers are major public health problems, being the second most common cancers in developed countries.48 As with other malignancies, colorectal cancer risk is increased in diabetics, and there is a growing body of evidence that advanced glycation end products (AGEs) and insulin-receptor interactions are involved in initiation of these common tumors.48,49 Naturally, these findings have piqued scientists’ interest in using metformin, which decreases glucose and insulin levels, to prevent colorectal cancer.
Colorectal cancers are among those malignancies most closely associated with obesity.38 Obese individuals are deficient in the protective hormone adiponectin, which activates tumor-suppressing AMPK.38 Metformin, by independently activating AMPK, may short-circuit this deficiency and help to reduce its impact on colorectal cancer risk.38
Metformin has at least one additional pathway by which it prevents colorectal cancer. It is related to the close connection between colon cancer and too many calories. Canadian scientists placed mice on either a normal or a high-calorie diet, and then injected them with viable colon cancer cells.50 Seventeen days later they examined the tumors that the animals had developed. Tumors from mice on the high-calorie diet were twice the volume of those from normally-fed mice, and their size correlated with elevated insulin levels. Metformin treatment blocked the effect of a high-calorie diet, reducing insulin levels and slowing the growth of tumors. Tumors from metformin-treated mice also showed increased rates of cell death by apoptosis compared with those from untreated animals.