Latest News & Research: 23 July 2019
This week: Exercise improves brain function in the overweight and obese • Enzymes responsible for inducing lean and obese states revealed • A room with a view... of nature
Exercise improves brain function in the overweight and obese
New findings from the University of Tübingen show that, on top of its benefits for metabolism, mood, and general health, exercise also improves brain function. In recent studies, researchers learned that obese and overweight individuals are prone to insulin resistance in the brain, where it provides information about current nutritional status, as well as the rest of the body. So, researchers set out to investigate whether exercise can improve insulin sensitivity in the brain and improve cognition in overweight individuals.
In the current study, led by Dr Stephanie Kullmann, 22 sedentary adults with overweight or obesity (an average BMI of 31) underwent two brain scans, before and after an 8-week exercise intervention, including cycling and walking. Brain function was measured before and after using an insulin nasal spray to investigate insulin sensitivity of the brain. Participants were also assessed for cognition, mood, and peripheral metabolism.
Even though the exercise intervention only resulted in a marginal weight loss, brain functions important for metabolism ‘normalised’ only after 8-weeks. Exercise increased regional blood flow in areas of the brain important for motor control and reward processes, both of which depend on the neurotransmitter dopamine. Dopamine is an important neurotransmitter for learning new motor skills and in reward-related learning and this research shows that exercise significantly improves dopamine-related brain function.
One area in particular, the striatum, had enhanced sensitivity to insulin after the 8-weeks of exercise, such that the brain response of a person with obesity after exercise training resembled the response of a person with normal-weight. Interestingly, the greater the improvement in brain function, the more belly fat a person lost during the course of the exercise intervention. Behaviorally, participants reported an improvement in mood and task switching, which is an indicator for improved executive function.
‘The bottom line is that exercise improves brain function’, said Kullmann; ‘And increasing insulin sensitivity in dopamine-related brain regions through exercise may help decrease the risk of a person to develop type 2 diabetes, along with the benefits for mood and cognition’.
Enzymes responsible for inducing lean and obese states revealed
The Developmental Origins of Health and Disease (DOHaD) hypothesis states that the nutritional environment in early life makes people susceptible to lifestyle-related diseases, such as obesity, diabetes and heart attack, as adults. Many of those diseases exhibit reduced mitochondrial metabolism in the tissues of the body. Now, researchers from Kumamoto University in Japan have revealed that two metabolic pathways involved in energy metabolism may play a role in the DOHaD hypothesis.
All cells regulate gene expression related to metabolic pathways, and adapt to environmental changes such as fluctuations in nutrition, oxygen supply, exercise, and temperature. Cells in the human body use two types of cellular metabolism, mitochondrial respiration and glycolysis.
Mitochondrial respiration produces energy for the cell when oxygen is supplied (aerobic), and glycolysis is used when oxygen is scarce (anaerobic). The activity of metabolic genes changes significantly as the method of energy production shifts between these two mechanisms. Some of the most critical changes are due to histone acetylation and methylation (the addition/removal of acetyl and methyl groups) of lysine amino acids. The enzymes deacetylase SIRT1 and demethylase LSD1 are especially important in the regulation of metabolic genes because they remove the acetyl and methyl groups, respectively, of target proteins.
Two metabolic pathways, NAD+– SIRT1 and FAD– LSD1, regulate the function of specific gene sets, and transmit nutrient signals. The researchers revealed that these two pathways are controlled by dietary vitamins and nutritional hormones, induce metabolic activity, and develop tissue-specific properties in fat and skeletal muscle cells. They found that FAD– LSD1 pathway represses mitochondrial metabolism and induces fat accumulation under obese condition.
DOHaD theorises that people affected by malnutrition during early development may have a low birth weight and an increased risk of lifestyle-related diseases as adults. Although the mechanisms behind this have not been clarified, the researchers think that at least two responses work at different times. The immediate response consumes stored energy and prioritises maintaining life, and the adaptive response ‘programs’ the body to store energy in anticipation of future bouts of starvation. This is considered a natural survival strategy for nascent undernutrition. An adaptive response can easily adjust to undernutrition, but it makes a person more susceptible to lifestyle-related diseases, such as obesity and diabetes, under an excess of nutrition.
The NAD+– SIRT1 pathway burns energy and the FAD– LSD1 pathway stores energy, and together they can remodel metabolic tissues. In muscle development, the SIRT and LSD1 pathways selectively promote slow and fast twitch fiber formation respectively, which increases susceptibility to lifestyle-related diseases. Thus, the researchers believe that these enzymes are involved in DOHaD mechanisms. Specifically, that SIRT1 can play a role in the immediate response and that LSD1 can be involved in the adaptive response.
Speaking about future activities, research leader Professor Mitsuyoshi Nakao said, ‘We hope our work will help lead to new disease control and prevention strategies by improving the understanding of lifestyle-related diseases, and the nutrition of young parents and babies during perinatal periods.’
Source: Kumamoto University
A room with a view... of nature
Spending time in nature brings many physical and mental health benefits, but a new study suggests that even just being able to see nature from your bedroom window could support your health by reducing unhealthy cravings.
Research by investigators from the University of Plymouth in the UK, featured in the journal Health & Place suggests that the passive enjoyment of green spaces – for instance, being able to see the trees in your back garden from your bedroom window – can help reduce the frequency and intensity of cravings with potentially harmful effects, such as those for unhealthful snacks, alcohol, or tobacco.
‘It has been known for some time that being outdoors in nature is linked to a person's wellbeing. But, for there to be a similar association with cravings from simply being able to see green spaces adds a new dimension to previous research’ said lead author Leanne Martin, for whom the current research was part of a Master's degree project.
‘This is the first study to explore this idea, and it could have a range of implications for both public health and environmental protection programs in the future’ she added.
For this study, the researchers surveyed 149 participants aged 21–65 years, asking them whether and in what way they had any exposure to nature. They also questioned the participants on the frequency and intensity of their unhealthful cravings, as well as how these affected their emotional health.
As part of the survey, the team also looked at the proportion of green space present in each participant's neighborhood, the access to green views from their home, their access to a personal or community garden, and how often they used public green spaces.
Martin and colleagues found that people who had access to a garden – either a private one or a community one — reported more infrequent and less intense cravings, and people whose views from home incorporated more than 25% green space described similar benefits.
The researchers note that the participants in question reaped these benefits irrespective of their level of physical activity, which the investigators took into account.
According to the study authors, the current findings add to the body of evidence showing that access to nature positively affects different aspects of health.
‘Craving contributes to a variety of health-damaging behaviours, such as smoking, excessive drinking, and unhealthy eating. In turn, these can contribute to some of the greatest global health challenges of our time, including cancer, obesity, and diabetes. Showing that lower craving is linked to more exposure to green spaces is a promising first step’ said study co-author Sabine Pahl, Ph.D.
Nevertheless, the researchers point out that the current study has not verified whether the association between access to natural views and lower cravings is actually a causal relationship. This, they say, must be the next step of the investigation.
‘Future research should investigate if and how green spaces can be used to help people withstand problematic cravings, enabling them to better manage cessation attempts in the future’ said Pahl.
Source: Medical News Today