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Mice Experiments Shed No Light on Human Brain Tumors
The development of medulloblastoma—a type of brain tumor—is significantly different between genetically engineered mice and humans, according to a new review from the Fred Hutchinson Cancer Research Center in Seattle, Wash. The study authors of the review, published in Epigenetics, note that very few of the studies have shown how changes in the actual genes modified in the mice contribute to the development of cancer in humans.
Diede SJ, Yao Z, Keyes CC, et al. Fundamental differences in promoter CpG island DNA hypermethylation between human cancer and genetically engineered mouse models of cancer. Epigenetics. 2013;8:1254-1260.
Alzheimer’s Drugs Tested on Animals Fail in Human Brain Cells
Animal tests are poorly suited for evaluating potential treatments for Alzheimer’s disease, according to a study recently published in Stem Cell Reports. Mouse brain cells are much more responsive to the effects of drugs, compared with human brain cells, leading to an overestimation of drugs’ value and disappointment when drugs are tested in patients. Much of the research dedicated to developing drugs for Alzheimer’s disease has focused on drugs that block the production of the amyloid proteins that form plaques in the brain. Despite promising results in animal experiments, the medications that have made it to clinical trials have so far failed. In this study, researchers used brain cells derived from stem cells taken from Alzheimer’s disease patients. In these cells, medications failed to affect plaque-causing amyloid levels. According to the authors, “...It appears to be conceivable that data generated...in mouse models have led to an overestimation of [medication] efficacy in human neurons, a hypothesis that is supported by the clinical failure of this class of compounds.”
Mertens J, Stüber K, Wunderlich, et al. APP processing in human pluripotent stem cell-derived neurons is resistant to nsaid-based γ-secretase modulation. Stem Cell Reports. 2013;1:491-498.
HUMAN TISSUE MODELS
Harvard Bioengineers Print Living Tissue
Lab-grown 3-D human tissues and organs, if widely available, could make safety testing and biological research more human-relevant, while replacing animals with more ethical and economical methods. While some organs, such as the skin, have matured, other tissues and organs are not available and are difficult to grow in the laboratory.
Bioengineers at the Wyss Institute for Biologically Inspired Engineering at Harvard University have begun to overcome some of the hurdles with printed tissue. Bioprinters use special “bio-inks”—living inks that make up the actual building blocks of living tissue—to print the 3-D tissue constructs. The scientists create mini blood vessels within the tissue as it is printed to ensure the tissue can continue to grow and thrive. Printed tissue can be used for many different medical applications, including studying wound healing processes, testing novel chemicals or drugs, and understanding organ-specific diseases such as liver cancer.
Meat-Eating Is a Risk Factor for Developing Diabetes
Doctors should consider meat-eating to be a risk factor for developing type 2 diabetes, according to an article published in the journal Nutrients. Researchers from the Physicians Committee evaluated studies that examined different levels and types of meat consumption and the risk for developing diabetes. Meat-eaters had significantly higher risk of developing diabetes compared with people who avoided meat. Meat’s effect on diabetes risk appears to be due to its content of saturated fat and heme iron, among other factors. The authors recommend that diabetes screenings include an analysis of the patient’s meat consumption, alongside other established risk factors.
Barnard N, Levin S, Trapp C. Meat consumption as a risk factor for type 2 diabetes. Nutrients. 2014;6:897-910.
Vegetarian Diet Lowers Blood Pressure
Vegetarian diets support a healthy blood pressure, according to a review published in JAMA Internal Medicine. Researchers identified 39 studies which analyzed the dietary choices and blood pressures of adults. Compared with omnivorous diets, vegetarian diets were consistently associated with lower systolic and diastolic blood pressures. This review is consistent with other studies and stresses the importance of a dietary approach to preventing and managing hypertension.
Yokoyama Y, Nishimura K, Barnard ND, et al. Vegetarian diets and blood pressure: a meta-analysis. JAMA Intern Med. Published online February, 2014.
Cholesterol Levels Lower in Vegans
Those who consume vegan diets have better cholesterol levels than people who eat meat, fish, dairy, and/or egg products, according to a study published in the European Journal of Clinical Nutrition. Researchers examined data and blood samples from 1,694 participants from the European Prospective Investigation into Cancer and Nutrition-Oxford (EPIC) study. Participants were categorized as meat-eaters, fish-eaters, vegetarians, and vegans. Those who ate a vegan diet consumed the most fiber, the least total fat and saturated fat, and had the healthiest body weight and cholesterol levels of all the diet groups. A previous analysis from the EPIC study found that vegan and vegetarian groups had a 32 percent lower risk of hospitalization or death from heart disease.
Bradbury KE, Crowe FL, Appleby PN, Schmidt JA, Travis RC, Key, TJ. Serum concentrations of cholesterol, apolipoprotein A-I and apolipoprotein B in a total of 1694 meat-eaters, fish-eaters, vegetarians and vegans. Eur J Clin Nutr. 2014;68:178-183.
Carnivorous Diets and Cancer
Consumption of meat and other animal products is strongly linked to several types of cancer, according to an article published in the journal Nutrients. The author analyzed data on 21 different cancers in 157 countries and found that certain factors, especially diet, were associated with risk for developing specific cancers. Notably, the association between animal product consumption and cancer was as strong as that linking tobacco and cancer. Possible mechanisms for risk include animal products’ high iron and fat content. The author notes that animal product consumption has been recognized as a cancer risk for more than a century and needs to be addressed in order to prevent the deadly disease.
Grant W. A multicountry ecological study of cancer incidence rates in 2008 with respect to various risk-modifying factors. Nutrients. 2014;6:163-189.
Many Ways Meat Causes Colon Cancer
Reasons for meat products leading to colorectal cancer are wide-ranging, according to a new review in the journal Nutrition Research. The authors say potential risks include naturally occurring components of meat products, such as heme iron and protein, as well as generated components, such as N-nitroso compounds and heterocyclic amines. According to the Centers for Disease Control and Prevention, of cancers that affect both men and women, colorectal cancer is the second leading cause of cancer-related deaths.
Kim E, Coelho D, Blachier F. Review of the association between meat consumption and risk of colorectal cancer. Nutr Res. 2013;33:983-994.
More Evidence on Meat’s Negative Health Effects
Red and processed meat products increase women’s disease risk, according to a study published in the American Journal of Clinical Nutrition. Researchers from Harvard analyzed the diets and blood of 3,690 participants from the Nurses’ Health Study and found that as total red meat consumption increased, C-reactive protein also increased. CRP (an inflammation biomarker), hemoglobin A1c (an indicator of diabetes risk), and stored iron (a mineral which, in excess, is associated with heart disease, cancer, and diabetes) also increased. Weight and calorie intake also increased with increased intake of red and processed meat products.
Ley SH, Sun Q, Willett WC, et al. Associations between red meat intake and biomarkers of inflammation and glucose metabolism in women. Am J Clin Nutr. 2014;99:352-360.
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