This week: New pathway that controls fat formation identified • FILEX to bring half-day ‘Taster’ event to Melbourne • Nut substitution may reduce weight gain and obesity risk
New pathway that controls fat formation identified
In work suggesting new therapeutic targets to fight obesity, researchers from UT Southwestern in the US have identified a novel mechanism that regulates the creation of fat in mammals.
‘Obesity is a global health problem that represents a major risk for several chronic diseases, including Type 2 diabetes, nonalcoholic fatty liver disease, cardiovascular disease, stroke, and cancer’ said Dr Joshua Mendell, Professor of Molecular Biology at UT Southwestern and an investigator in the Howard Hughes Medical Institute. Mendell is corresponding author of the study appearing online in the journal Genes & Development.
The molecular mechanisms that regulate how and where fat tissue builds up in the body – or doesn’t – are key to understanding the development of obesity. However, the genes and molecular pathways that influence the size and number of fat cells in the body are not completely understood.
‘We found that loss of a family of microRNAs results in a dramatic increase in fat formation. In addition, we showed that overexpression of the miR-26 family of miRNAs strongly protects against weight gain in mice fed a high fat diet’ said Dr Asha Acharya, an Instructor of Molecular Biology and lead author of the study.
The researchers further found that the miR-26 family controls the levels of a protein called FBXL19 that is important for new fat cell production; ‘This protein had not been linked to fat formation or obesity in the past, so this result was unexpected’ Mendell said.
In mammals, including mice and humans, a diet loaded with calories – such as the high fat diet used in this study – can cause existing fat cells to expand. It can also result in the creation of new fat cells from a population of stem-like progenitor cells, he explained.
‘Fat storage in adult mammals is a highly regulated process that involves mobilising progenitor cells that differentiate into fat cells’ said Mendell.
A feature of obesity is the uncontrolled expansion of white fat tissue, which does more than store energy in times of caloric surplus. It also plays an important role in metabolic regulation by secreting signaling proteins and lipids that influence pathways controlling appetite, blood sugar balance, and immune responses.
While earlier studies indicated important roles for the miR-26 family as suppressors of cancer and regulators of insulin sensitivity, the broader functions of these miRNAs had remained a mystery. In part, that was due to the difficulty of knocking out, or removing, all three genes that produce miR-26 family members in mammals in order to study their functions.
To overcome this technical challenge, the researchers used the gene-editing technique called CRISPR/Cas9 to remove all miR-26-encoding genes from the mouse genome. They found that although mice lacking these miRNAs developed normally in early life, they had a two- to threefold increase in white fat tissue beginning in early adulthood, even while consuming a normal diet.
To further test the role of these miRNAs in regulating fat formation, the scientists used a different genetically engineered mouse line that produces excess miR-26. After being fed a high fat diet, normal mice exhibited dramatic weight gain and an increase in fat content to 40% of their overall body mass. Mice with increased miR-26, however, were strongly resistant to weight gain and, despite consuming an identical diet, produced very little additional fat. Mice with increased miR-26 also showed lower blood sugar and lipid levels compared with controls.
‘This study reveals a new mechanism of controlling fat production in the body’ Mendell said; ‘A deeper understanding of this mechanism could lead to new therapies to treat obesity, for example by revealing strategies to increase miR-26 activity or to inhibit the downstream targets of this microRNA.’
Source: University of Texas Southwestern
FILEX to bring half-day ‘Taster’ event to Melbourne
FILEX, Australia’s fitness industry convention, will hold a half-day ‘taster’ event on the morning of 26 October at the Melbourne Convention Centre.
Taking place from 9am until 12pm, the FILEX Taster is provides a sample of the premium education experience that delegates can expect at the longest standing and leading fitness conference in the Asia Pacific region, the annual FILEX Convention.
The Taster will feature presenter Richard Toutounji, an industry veteran and online marketing expert who works with fitness professionals every day to help them attract new leads and clients. Toutounji promises to offer insights into how best to build and grow a thriving business in fitness.
Accredited for 2 CECs by industry registration body Fitness Australia, registration cost $49. Click here to find out more and to register.
Source: FILEX Holdings
Nut substitution may reduce weight gain and obesity risk
Increasing nut consumption by just half a serving (14g) a day is linked to less weight gain and a lower risk of obesity, suggests a large, long term observational study published in the online journal BMJ Nutrition, Prevention & Health.
Substituting unhealthy foods, such as processed meats and chips, with a half-serving of nuts may ward off the gradual weight gain that often accompanies the ageing process, suggest the researchers.
On average, US adults gain almost half a kilogram of weight every year. Gaining 2.5-10kg in weight is linked to a significantly greater risk of heart disease/stroke and diabetes.
Nuts are rich in healthy unsaturated fats, vitamins, minerals and fibre, but they are calorie dense, so often not thought of as good for weight control. But emerging evidence suggests that the quality of what’s eaten may be as important as the quantity.
Amid modest increases in average nut consumption in the US over the past two decades, the researchers wanted to find out if these changes might affect weight control.
They analysed information on weight, diet and physical activity in three groups of people: 51,529 male health professionals, aged 40 to 75 when enrolled in the Health Professionals Follow Up Study; 121,700 nurses, aged 35 to 55 when recruited to the Nurses Health Study (NHS); and 116,686 nurses, aged 24 to 44 when enrolled in the Nurses Health Study II (NHS II).
Over more than 20 years of monitoring, participants were asked every 4 years to state their weight, and how often, over the preceding year they had eaten a serving (28g) of nuts, including peanuts and peanut butter.
Average weekly exercise – walking, jogging, cycling, swimming, racquet sports and gardening – was assessed every two years by questionnaire. It was measured in metabolic equivalent of task (MET) hours, which express how much energy (calories) is expended per hour of physical activity.
Average annual weight gain across all three groups was 0.32kg. Between 1986 and 2010, total nut consumption rose from a quarter to just under half a serving per day in men; and from 0.15 to 0.31 servings per day among the women in the NHS study. Between 1991 and 2011 total daily nut consumption rose from 0.07 to 0.31 servings among women in the NHS II study.
Increasing consumption of any type of nut was associated with less long-term weight gain and a lower risk of becoming obese (BMI of 30 or more kg/m²), overall.
Increasing nut consumption by half a serving a day was associated with a lower risk of putting on 2 or more kilos over any 4-year period. A daily half-serving increase in walnut consumption was associated with a 15% lower risk of obesity.
Substituting processed meats, refined grains, or desserts, including chocolates, pastries, pies and donuts, for half a serving of nuts was associated with staving off weight gain of between 0.41 and 0.70 kg in any 4-year period.
Within any 4-year period, upping daily nut consumption from none to at least half a serving was associated with staving off 0.74kg in weight, a lower risk of moderate weight gain, and a 16% lower risk of obesity, compared with not eating any nuts. A consistently higher nut intake of at least half a serving a day was associated with a 23% lower risk of putting on 5 or more kilos and of becoming obese over the same timeframe.
No such associations were observed for increases in peanut butter intake. The findings held true after taking account of changes in diet and lifestyle, such as exercise and alcohol intake.
This is an observational study, and as such can’t establish cause. The data relied on personal report, which may have affected accuracy, while predominantly white, relatively affluent health professionals were included, so the findings may not be more widely applicable. The findings, however, do echo those of previous observational studies.
The researchers attempted to explain the associations they found, noting that chewing nuts takes some effort, leaving less energy for eating other things, while the high fibre content of nuts can delay stomach emptying, making a person feel full for longer.
Nut fibre also binds well to fats in the gut, meaning that more calories are excreted, and there is some evidence that the high unsaturated fat content of nuts increases resting energy expenditure, which may also help to stave off weight gain.
Snacking on a handful of nuts rather than biscuits or chips may help to ward off the weight gain that often accompanies ageing and is a relatively manageable way of helping to curb the onset of obesity, they suggest.