News from the latest research

SODIUM LEVELS in Processed and Restaurant Food Largely Unchanged

Food manufacturers have not lived up to their pledge to voluntarily reduce the amount of sodium in packaged and restaurant foods, say researchers for the Center for Science in the Public Interest.

In a study published online in JAMA on May 13, the team, led by Robert McCarter, ScD, assessed sodium levels in 402 packaged foods in 2005, 2008, and 2011. These foods included baked goods, dairy products, meats, sauces and dressings, and soups. The team found that sodium decreased in 41.8%, increased in 29.6%, and did not change in 28.6% of the products, leading to an average decrease of just 3.5% between 2005 and 2011.

The researchers also obtained sodium values for 78 items offered by fast-food and large chain restaurants, including burgers, chicken, fries, and pizza. Sodium levels decreased in 42.3%, increased in 55.1%, and did not change in 2.6% of the products, leading to an average increase of 2.3%.

In their conclusion, the researchers note that physicians often tell patients to reduce salt intake as a way of treating and preventing high blood pressure, but that such counseling “places unrealistic demands on both patients and physicians given the high sodium levels currently present in processed and restaurant foods.” They call for regulatory action and recommend that sodium in these foods be gradually lowered 50% over the next 10 years.

—Terri D’Arrigo

LIVER HORMONE Shows Promise for Diabetes Treatment

Researchers at the Harvard Stem Cell Institute have identified a hormone in mice that promotes the growth and expansion of insulin-producing beta cells in pancreatic islets, a finding that opens up the possibility of new treatments for diabetes should the hormone, dubbed betatrophin, work the same way in humans. The team, led by Douglas A. Melton, PhD, made the discovery while conducting experiments to better understand how the pancreas increases beta-cell production in response to the greater demands for insulin caused by pregnancy or peripheral insulin resistance.

In their research, published online in Cell on May 9, the team injected mice with a peptide that blocks insulin receptors. This made the mice insulinresistant and prompted their pancreases to ramp up beta-cell production. When seeking to understand the genes involved in this process, the team found one activated in the liver and fat that encodes for a protein that prompts beta cells to proliferate.

In a separate experiment, the team injected normal mice with the betatrophin gene and saw that beta-cell proliferation increased 17- to 33-fold compared to that of mice that had not been injected with betatrophin. The betatrophin-injected mice also performed better on glucose tolerance tests compared to the control mice.

—Terri D’Arrigo

LOW VITAMIN D LEVELS Associated with Physical Limitations and Functional Decline in Older Individuals

Beginning a vitamin D regimen may be the key in maintaining mobility later in life, according to a recent study published in the Journal of Clinical Endocrinology and Metabolism.

Researchers showed that individuals who are vitamin-D deficient had more trouble with performing everyday tasks, such as climbing stairs and dressing themselves. Vitamin D—usually ingested through diet or absorbed from sunlight—influences muscle health.

For six years, Scientists followed two independent cohorts from the Longitudinal Aging Study Amsterdam. The first group comprised people aged 65 – 88, while the second group was made up of people aged 55 – 65. The subjects had their vitamin D levels measured and were split into three groups: highest vitamin D levels, moderate, and lowest. The subjects were then asked a series of questions to gauge their ability performing six daily tasks.

Subjects in both groups with the lowest levels of vitamin D were about twice as likely to have at least one limitation when compared to the subjects with the highest levels of vitamin D. Subjects with low vitamin D levels were also shown to regress even further over time. In the older cohort, low vitamin D was associated with developing additional physical limitations after only three years, while in the younger cohort, more limitations manifested after six years.

The authors concluded that vitamin D status is indeed associated with physical and functional limitations in the older population, individuals aged 55 – 88 years, and there could be some benefit in taking vitamin D supplements. However, this idea should be tested in additional studies.

—Derek Bagley

Circulatory FOUNTAIN OF YOUTH

Heterochronic parabiosis is a 19th-century surgery joining two living animals together to merge their circulatory systems into a single shared circulation. In a new study, scientists used this technique in mice to elucidate whether cardiac hypertrophy, which accompanies the most common form of heart failure in older adults, is caused by circulating factors.

Drs. Amy J. Wagers, PhD, and Richard T. Lee, MD, both of the Harvard Stem Cell Institute and Brigham and Women’s Hospital, Boston, and their team of researchers paired up five very old mice (age two years) with two-month-old counterparts. In their paper, published in Cell, the researchers report that after four weeks, the cardiac tissue in the old mice had dramatically thinned and softened as expected, and the young mice hearts were also still strong. Long suspecting a bloodborne cause for age-related hypertrophy, they used aptamerbased proteomics to find that circulating growth differentiation factor 11 (GDF11), a member of the transforming growth factor β superfamily, declines with age. Administering GDF11 to the aged mice similarly reversed hypertrophy.

The researchers next want to find whether these effects can be replicated in humans, whether GDF11 can remodel cardiac tissue damaged via means other than aging (e.g., myocardial infarction), and also whether GDF11 can restore other tissues affected by aging back to youthful states.

—Kelly Horvath

PFCS and THYROID FUNCTION

Women who are exposed to perfluorinated chemicals (PFCs) have a higher risk of developing mild hypothyroidism, according to findings recently published in the Journal of Clinical Endocrinology and Metabolism.

PFCs have been linked to changes in thyroid function, and are found in myriad common products, from carpets to cosmetics. Hypothyroidism can cause fatigue, depression, weight gain, constipation, and menstrual irregularities, as well as feeling cold and dry skin and hair.

Researchers analyzed 1,181 subjects, women aged 20 and over, who participated in a National Health and Nutrition Examination Survey (NHANES), 2007—2008 and 2009—2010, in order to determine whether there was a correlation between PFCs and thyroid function.

Women with higher levels of the PFC perfluorooctanoate (PFOA) showed an increase in the concentration of the thyroid hormone total triiodothyronine (T3), while levels of the thyroid hormone total thyroxine (T4) were elevated by an increase in concentrations of the PFC perfluorohexane sulfonate (PFHxS). However, men exposed to PFHxS showed a decrease in free T4.

The authors concluded that while further research needs to be done to determine whether this correlation is in fact causation, higher concentrations of PFOA and PFHxS are associated with total T3, total T4, and free T4 in the U.S. general population, as well as mild hypothyroidism in women.

—Derek Bagley

VITAMIN D and Infants

Breast-feeding confers many benefits on infants, but it can come up short in providing them with the vitamin D they need for healthy bones. To compensate, the American Academy of Pediatrics recommends supplementation with 400 IU of vitamin D daily. New research published by a team at McGill University in Montreal in the May 1 issue of JAMA has found that this dose is sufficient and that higher doses do not provide greater benefit.

Between March 2007 and August 2011, the team, led by Hope Weiler, RD, PhD, randomly assigned 132 infants to 400, 800, 1,200, or 1,600 IU of vitamin D daily. They sought to discover which doses would best help the infants attain plasma concentrations of the vitamin D metabolite 25-OHD of 75 nmol/L by three months of age. (This concentration represents a middle ground in the medical community, as some groups recommend a range of 40-50 nmol/L and others recommend a range of 75-150 nmol/L.)

The percentages of infants achieving the 75 nmol/L goal were 55% for the 400 IU group, 81% for the 800 IU group, 92% for the 1,200 IU group, and 100% for the 1,600 IU group. However, in July 2008 the 1,600 IU group was discontinued because 15 of the 16 infants in that group developed plasma 25-OHD concentrations of 250 nmol/L or higher, well above that deemed necessary by the medical community.

—Terri D’Arrigo

Glucocorticoids Increase VENOUS THROMBOEMBOLISM RISK

Because high levels of cortisol have been implicated in venous thromboembolism (VTE) risk, a new study investigated whether the association holds up with exogenous glucocorticoids, which are prescribed for many conditions.

Dr. Sigrun A. Johannesdottir, BSc, at Aarhus Universitetshospital, Denmark, and her team of researchers undertook a Danish populationbased study of 38,765 VTE cases diagnosed between January 1, 2005 and December 31, 2011, dividing them into three cohorts of glucocorticoid users: former, those who had discontinued use for at least one year; recent, those who had discontinued use for between three months and one year; and present (subdivided into new and continuing groups), those who had filled a prescription within the prior three months and performing regression analysis. In their paper, published in JAMA Internal Medicine, the researchers report that VTE incidence was triple for new and double for continuing users, and 1.2 times higher for recent users. Risk also doubled with doses of 1,000– 2,000 mg, whereas risk was no higher at doses of 10 mg.

The researchers conclude that carefully weighing risks against benefits is crucial when prescribing glucocorticoids because even after adjusting for confounders such as preexisting VTE risk factors, new glucocorticoid users and those taking high doses showed significantly higher risk of developing VTEs. Hunting down the causative biological mechanism is a potential research avenue, they add.

—Kelly Horvath

BEHAVIORAL WEIGHT LOSS Better for Mentally Ill

Among sufferers of serious mental illness, obesity is epidemic according to research recently published in the New England Journal of Medicine. Traditional lifestyle interventions exclude the needs of the seriously mentally ill as cognitive impairment causes difficulty in holding to weight loss regimens. In the published study, led by Gail L. Daumit, MD of Johns Hopkins Medical Institute, participants significantly increased their weight loss with interventions tailored to their behaviors.

Nearly 60% of the 291 participants were either schizophrenic or had a schizoaffective disorder, the remainder diagnosed with bipolar disorder or major depression. All were recruited from psychiatric outpatient programs local to the community and randomized between an intervention group and a control.

Average weight among all participants was 226 lbs. with a mean body mass index of 36. Provided with behavioral weight management and group exercise sessions, 38% of the intervention group lost at least 5% of their starting weight at the end of 18 months. Only 22% of the control had similar weight loss.

The progressive weight loss shown in this study, the authors hope, supports interventions targeting behaviors of a population at high-risk of obesity and weight-related disease.

—Dan Kelly

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