Targeting a microRNA shows potential to enhance effectiveness of diabetes drugs

Over the past 15 years, University of Alabama at Birmingham endocrinologist Anath Shalev, M.D., has unraveled a crucial biological pathway that malfunctions in diabetes.

Her latest discovery in this beta-cell pathway, published in the journal Diabetes, shows the potential to enhance the effectiveness of existing diabetes drugs, as well as reduce some of the unwelcome side effects of those drugs.

The need for improved treatment is great. Diabetes is a disorder characterized by elevated blood sugar that afflicts one of every 10 U.S. adults and doubles the risk of early death. More than 30 million people in the United States have diabetes, which is the seventh-leading cause of death and also leads to blindness and lower-limb amputations.

In 2013, the UAB researchers found that either diabetes or elevated production of the protein TXNIP induced beta-cell expression of microRNA-204, or miR-204, and this microRNA, in turn, blocked insulin production. The Shalev group has now found another vital role for miR-204 — regulating the cell surface receptor that is the target of many of the newer type 2 diabetes drugs, such as Byetta, Victoza, Trulicity, Januvia, Onglyza and Tradjenta. This drug target is the glucagon-like peptide 1 receptor, or GLP1R. Activation of GLP1R with these drugs helps the beta cell produce and secrete more insulin.

Shalev’s new work was performed in rat beta cells, genetically modified mice, mouse pancreatic islets and human pancreatic islets. Healthy beta cells, which are found in the pancreatic islets, produce insulin to control blood sugar levels; in diabetes the beta cells are impaired and dysfunctional, and have lower GLP1R levels.

In the Diabetes study, Shalev and colleagues found that overexpression of miR-204 decreased expression of GLP1R in rat beta cells and in mouse and human pancreatic islets. Conversely, knock-down of miR-204 increased expression of GLP1R in those cells and pancreatic islets.

Greater GLP1R expression is beneficial because it helps transfer a signal to the beta cell to secrete more insulin, such as after a meal. Also, many of the newer diabetes drugs act as agonists to activate GLP1R. Higher expression can allow use of a lower-drug dose to treat diabetes, thus reducing dose-dependent side effects.

In mice, the UAB researchers found that a deletion of miR-204 caused enhanced GLP1R expression, and also better insulin secretion and glucose control. Furthermore, the knockout mice were more responsive to a GLP1R agonist in glucose tolerance tests. When the GLP1R knockout mice were used in a model of diabetes, where beta cells are damaged by low doses of the toxin streptozotocin, the diabetic mice showed improved glucose control and increased serum insulin levels.

These results suggest that downregulating miR-204, now revealed as an upstream regulator of GLP1R, could lead to better treatment of diabetes.

One key fact about miR-204 may further aid improved treatment. This microRNA is highly expressed in beta cells, but it is not highly expressed in the rest of the pancreas or in cells of the gastrointestinal tract that also express GLP1R and therefore respond to GLP1R agonists. Thus, an inhibitor of miR-204 would be relatively selective for beta cells.

“This novel concept of inhibiting a microRNA in a non-targeted manner, but taking advantage of its restricted tissue distribution and thereby selectively upregulating its target genes in that tissue, may have far reaching implications for microRNA biology and tissue-specific gene targeting in general,” Shalev said.

“Since miR-204 is expressed primarily in pancreatic beta cells, manipulating its levels allows for preferential upregulation of GLP1R in the beta cell, where it helps secrete insulin, rather than in the gastrointestinal system, where it can cause nausea and impaired gastric emptying, or in the pancreas, where it can increase the risk for pancreatitis,” Shalev said. “So by inhibiting miR-204, one could increase the effects of GLP1R agonist drugs on insulin secretion, thereby lowering the necessary dose and avoiding some of the dose-dependent adverse effects.”

The mechanism by which miR-204 downregulates expression of GLP1R is binding of the microRNA to the 3-prime-untranslated region of GLP1R messenger RNA. Such binding is a known method to control gene expression by microRNAs. The UAB researchers discovered this specific binding using microRNA target prediction software. They found two binding sites for miR-204 in the messenger RNA for human GLP1R and one binding site in the messenger RNA for mouse GLP1R. When they mutated those binding sites, it eliminated the regulatory effect of miR-204.

Additionally, the Shalev group showed a novel link between TXNIP and GLP1R signaling. Mice with a beta cell-specific knockout of the protein TXNIP had lower miR-204 levels and higher GLP1R expression, and the mice showed enhanced insulin secretion and glucose control in response to an agonist of GLP1R. Thus, through both control of insulin production and regulation of GLP1R, as well as regulation of the unfolded protein response and beta cell apoptosis, miR-204 appears to play a linchpin role to control the function of beta cells in the pancreas.

Obesity risk factors dropped in preschoolers in prevention program

Preschoolers from low-income families living in cities that took part in a two-year community-wide intervention to foster healthy eating and lifestyle habits consumed fewer sugary drinks, got more sleep, and showed improvement in weight, according to a study led by a researcher at NewYork-Presbyterian/Columbia University Medical Center (CUMC).

The study–one of a trio of studies published today in Obesity–was designed to test a childhood obesity-prevention program known as the Massachusetts Childhood Obesity Research Demonstration (MA-CORD) initiative among families in low-income communities, where high obesity rates persist.

Obesity, which remains historically high in the U.S., showed recent declines in preschool-age children. However, obesity prevalence is two to three times higher in children from low-income families compared to higher-income counterparts.

“Evidence strongly suggests that instilling healthy habits in young children is a necessary cornerstone in efforts to prevent obesity and its sequelae,” said study leader Jennifer Woo Baidal, MD, MPH, assistant professor of pediatrics and Director of Pediatric Weight Management at CUMC and a pediatric gastroenterologist in the Comprehensive Adolescent Bariatric Surgery Program at NewYork-Presbyterian/Columbia University Medical Center. “Though some progress has been made in reducing childhood obesity, not all families are aware that certain strategies–like eliminating sugary drinks, limiting screen time, and getting enough physical activity and sleep–help young children achieve and maintain a healthy weight. Solutions that can be scaled-up are urgently needed to prevent obesity in young children at highest risk.”

To increase adoption of these strategies, the researchers in this study implemented the MA-CORD initiative at two community-wide offices of the Special Supplementation for Women, Infants and Children (WIC) program in Massachusetts, which provides healthy foods, nutrition assessment and education, breastfeeding support, and referrals to healthcare and other services for low-income families with very young children. WIC providers were trained to deliver consistent messages during office visits about how much sugar-sweetened beverage, juice, junk food, screen time, and exercise young children should get. Families at a third community WIC site did not get the intervention.

At the end of the study, children from the intervention sites reduced their intake of sugary beverages and juice and got more sleep compared to children who did not receive the intervention. Children from the intervention sites also engaged in more physical activity and less screen time than their counterparts in the comparison group, though these differences were not statistically significant.

In one intervention site, non-Asian children also had small decreases in adjusted BMI scores compared with children in the comparison group.

“Overall, the intervention had a positive impact on reducing obesity risk factors among the children in our study, but the smaller impact on reducing BMI may be due to factors that can’t be easily controlled, such as access to high-quality, nutritious foods in the community and the challenge of measuring rapid changes in growth during early childhood,” said Rachel Colchamiro, MPH, RD, Director of Nutrition Services for the Nutrition Division at the Massachusetts Department of Public Health and a co-author of the paper. “Because obesity disproportionately affects lower-income families, incorporating WIC providers and community systems into multi-sector obesity prevention efforts could yield high results at a national level.”

The two related studies published today examined the effectiveness of the whole-of-community intervention at local health clinics and in schools.

“Ultimately, we think that durable and effective childhood obesity-prevention efforts will require the implementation of evidence-informed interventions and sustained coordination across multiple sectors to reach vulnerable populations,” said Elsie Taveras, MD, MPH, Chief of the Division of General Pediatrics and Director of Pediatric Population Health Management at Massachusetts General Hospital and a professor of pediatrics and population medicine at Harvard Medical School. “There is an urgency to find solutions for childhood obesity that will reach populations that need it most. Our findings suggest that community-wide initiatives such as MA-CORD are particularly promising in these efforts.”

Scientists Unlock Genetic Code of Diseased Lung Cells to Find New Treatments for IPF

“Marker Genes” Reveal Deadly Secrets of Idiopathic Pulmonary Fibrosis

Newswise — CINCINNATI – Researchers cracked the complete genetic code of individual cells in healthy and diseased human lung tissues to find potential new molecular targets for diagnosing and treating the lethal lung disease Idiopathic Pulmonary Fibrosis (IPF).

Scientists from Cincinnati Children’s Hospital Medical Center, in collaboration with investigators at Cedars-Sinai Medical Center in Los Angeles, publish their findings Dec. 8 in the Journal of Clinical Investigation Insight (JCI Insight).

“This paper identifies a number of novel targets and molecular pathways for IPF, for which there are pharmaceutical approaches,” said Jeffrey Whitsett MD, lead investigator and co-director of the Perinatal Institute at Cincinnati Children’s. “Airway cells can be obtained by brushing the airway or biopsy, and marker genes can be tested to make a diagnosis or monitor treatment.”

IPF is a common and lethal interstitial lung disease in adults, which means it inflames, scars and reconfigures lung tissues. This causes loss of the air sacs, called alveoli, where oxygen and carbon dioxide are normally exchanged. Similar losses of lung function can occur earlier in life, especially in children with diseases caused by mutations in genes critical for surfactant and maintenance of the lung saccules.

Biological processes controlling the formation and function of the lung’s alveolar region require precisely orchestrated interactions between diverse epithelial, stromal and immune cells, according to study authors. Despite many years of extensive laboratory studies of whole tissue samples – trying to identify genetic, cellular and molecular processes that fuel lung ailments like IPF – the precise biology has remained elusive.

To overcome this, Whitsett and colleagues – including first author and bioinformatician Yan Xu, PhD of Cincinnati Children’s – conducted what they believe to be the first-ever single-cell RNA sequence analysis of normal and diseased human lung tissues (all donated with prior informed consent). This provided the authors with a detailed genetic blueprint of all the different epithelial cell types involved in IPF progression and a window to identify aberrant biological processes driving inflammation and fibrosis.

Analysis of normal lung epithelial cells found gene patterns linked to fully formed alveolar type 2 lung cells (AT2 cells), which are important for the production of surfactant, a substance containing a complex of proteins critical to breathing.

Analysis of diseased IPF cells found genetic markers for lung cells that were in indeterminate states of formation, the authors report. IPF cells had lost the normal genetic control systems needed to guide their functions. This study identifies abnormalities in gene expression that can be targeted for therapy of chronic lung diseases like IPF.

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