Use of the oral blood pressure drug verapamil to treat type 1 diabetes (T1D) continues to show benefits lasting at least two years, confirmed University of Alabama at Birmingham (UAB) researchers, reporting on a small-scale study in human patients. The trial results showed that individuals taking verapamil not only required less daily insulin two years after first diagnosis of the disease, but also showed evidence of preserved beta-cell function, and surprising immunomodulatory benefits.
Continuing medication was necessary, the authors noted in their study report, which is published in Nature Communications. In the two-year study, subjects who stopped daily doses of verapamil at one year saw their disease at two years worsen at rates similar to those of the control group of diabetes patients who did not use verapamil at all.
Study lead Anath Shalev, MD, director of the Comprehensive Diabetes Center at the University of Alabama at Birmingham, and colleagues, described the new trial findings in a paper titled, “Exploratory study reveals far reaching systemic and cellular effects of verapamil treatment in subjects with type 1 diabetes,” in which they concluded, “… the current studies provide crucial mechanistic and clinical insight into the beneficial effects of verapamil in T1D.”
Type 1 diabetes is an autoimmune disease that causes loss of the pancreatic beta cells that produce endogenous insulin. “Diabetes continues to grow as a chronic global health problem, affecting people of all ages,” the authors noted. Patients with T1D need to take exogenous insulin, which is administered either by injections or using a pump, and they are at risk of dangerous low blood sugar events. There is no current oral treatment for T1D, and, as the authors noted in their paper, “Since the discovery of insulin, a century ago, therapies have improved dramatically, but many critical needs and hurdles remain and prevent subjects with diabetes from living a truly normal life.”
The suggestion that verapamil might serve as a potential type 1 diabetes drug was the serendipitous discovery of Shalev, and stemmed from more than two decades of her basic research into a gene in pancreatic islets called TXNIP. In 2014, Shalev’s UAB research lab reported that verapamil completely reversed diabetes in animal models, and she announced plans to test the effects of the drug in a human clinical trial. FDA approved verapamil for the treatment of high blood pressure in 1981.
In 2018, Shalev and colleagues reported the benefits of verapamil in a one-year clinical study of T1D patients, finding that regular oral administration of verapamil enabled patients to produce higher levels of their own insulin, thus limiting their need for injected insulin to regulate blood sugar levels. In their newly reported paper, the authors described the trial findings from 2018. “Subjects receiving verapamil had improved endogenous beta cell function (as measured by a 2 h mixed-meal-stimulated C-peptide area under the curve), lower insulin requirements, and fewer hypoglycemic events as compared to individuals getting placebo added to their standard insulin regimen.” But, the authors further noted, while highly promising, the initial results raised a number of mechanistic questions, “including what exact biological changes verapamil elicits in humans with T1D, how long they may last, and how these changes and any potential associated therapeutic success could be monitored.”
The newly reported study extends on the initial findings and provides crucial mechanistic and clinical insights into the beneficial effects of verapamil in type 1 diabetes, using proteomics analysis and RNA sequencing.
To examine changes in circulating proteins in response to verapamil treatment, the researchers used liquid chromatography-tandem mass spectrometry of blood serum samples from subjects diagnosed with type 1 diabetes within three months of diagnosis and at one year of follow-up. Fifty-three proteins showed significantly altered relative abundance over time in response to verapamil. These included proteins known to be involved in immune modulation and autoimmunity of type 1 diabetes. The top serum protein altered by verapamil treatment was chromogranin A, or CHGA, which was downregulated with treatment. CHGA is localized in secretory granules, including those of pancreatic beta cells, suggesting that altered CHGA levels might reflect changes in beta cell integrity. In contrast, the elevated levels of CHGA at type 1 diabetes onset did not change in control subjects who did not take verapamil.
CHGA levels were easily measured directly in serum using a simple ELISA assay after a blood draw, and lower levels in verapamil-treated subjects correlated with better endogenous insulin production as measured by mixed-meal-stimulated C-peptide, a standard test of type 1 diabetes progression. The study confirmed that among T1D patients, verapamil therapy led to CHGA levels dropping to those of healthy, non-diabetic volunteers. “Interestingly, serum CHGA levels in healthy, non-diabetic volunteers were ~2-fold lower as compared to those in subjects with T1D, but after one year of verapamil treatment, there was no longer any significant difference between verapamil-treated T1D subjects and healthy individuals,” the authors stated. In the second year, CHGA levels then rose again among the T1D subjects who discontinued verapamil during year two of the study.
“Thus, serum CHGA seems to reflect changes in beta cell function in response to verapamil treatment or type 1 diabetes progression and therefore may provide a longitudinal marker of treatment success or disease worsening,” Shalev said. “This would address a critical need, as the lack of a simple longitudinal marker has been a major challenge in the type 1 diabetes field.” As the authors added in their paper, “… testing for CHGA only requires a simple blood draw and therefore may provide an easy and straightforward way to monitor changes in response to therapy or T1D progression over time. This would address a critical need, as the lack of a simple longitudinal marker has been a major challenge in the T1D field.”
Other labs have identified CHGA as an autoantigen in type 1 diabetes that provokes immune T cells involved in the autoimmune disease. Shalev and colleagues questioned whether verapamil affected T cells. They found that several proinflammatory markers of T follicular helper cells, including CXCR5 and interleukin 21, were significantly elevated in monocytes from subjects with type 1 diabetes, as compared to healthy controls, and they found that these changes were reversed by verapamil treatment.
“Now our results reveal for the first time that verapamil treatment may also affect the immune system and reverse these type 1 diabetes-induced changes,” Shalev said. “This suggests that verapamil, and/or the type 1 diabetes improvements achieved by it, can modulate some circulating proinflammatory cytokines and T helper cell subsets, which in turn may contribute to the overall beneficial effects observed clinically.”
To assess changes in gene expression, RNA sequencing was carried out on human pancreatic islet samples exposed to glucose, either with or without verapamil. The results revealed a large number of genes that were either upregulated or downregulated. Analysis of these genes showed that verapamil regulates the thioredoxin system, including TXNIP, and promotes an anti-oxidative, anti-apoptotic and immunomodulatory gene expression profile in human islets. Such protective changes in the pancreatic islets might further explain the sustained improvements in pancreatic beta cell function observed with continuous verapamil use. “In fact, TXNIP is considered a key factor in diabetes-associated beta cell apoptosis, and genetic deletion of TXNIP has been shown to mimic the antidiabetic effects of verapamil in different mouse models,” the team stated. “Downregulation of TXNIP has therefore been suggested to mediate the beneficial effects of verapamil in the context of diabetes and this notion is strongly supported by the current findings in human islets.”
Shalev and colleagues caution that their study, with its small number of subjects, needs to be confirmed by larger clinical studies, such as a current verapamil-type 1 diabetes study ongoing in Europe. Nevertheless, the observation of preservation of some beta cell function is promising. “In humans with type 1 diabetes, even a small amount of preserved endogenous insulin production—as opposed to higher exogenous insulin requirements—has been shown to be associated with improved outcomes and could help improve quality of life and lower the high costs associated with insulin use,” Shalev said.
The authors say the collective results of their exploratory studies suggest that continuous use of oral verapamil in individuals with T1D may delay disease progression and lower insulin requirements for at least two years post-diagnosis and that this is associated with normalization of serum CHGA levels as well as of proinflammatory IL-21 levels and Tfh cell markers. The data also show that verapamil regulates the thioredoxin system and promotes an antioxidative, anti-apoptotic, and immunomodulatory gene expression profile in human islets.
These results, point to protective changes that might explain the overall beneficial effects observed with verapamil. “ … our results showing verapamil regulating the thioredoxin system and inhibiting TXNIP expression in the islets provide a potential mechanistic explanation for these beta cell sparing effects,” they concluded. “The fact that these beneficial verapamil effects seemed to persist for two years, whereas discontinuation of verapamil led to disease progression, provides some additional support for this approach and its potential usefulness for long-term treatment.”