How obesity damages blood vessels
Obesity damages the lining of blood vessels because fat tissue secretes a harmful protein, research suggests.
Chinese scientists analysed more than 1,000 people with atherosclerosis, which occurs when fatty deposits clog the arteries.
They found the obese participants released ‘much higher levels’ of a protein called WNT5A from their fat tissue. WNT5A triggers ‘internal stress’ and was linked to the accumulation of mineral deposits in the blood vessels.
Over time, these deposits can stick to plaque, causing blood vessels to narrow further. This restricts oxygen to the vital organs, which can lead to heart attacks or stroke.
The scientist hope WNT5A may one day be targeted in treatments that prevent heart disease in obese people.
The study was carried out by the Shanghai Jiao Tong University School of Medicine and led by Dr. Pan Gao.
Vascular disease, when the blood vessels become inflamed and weak, is ‘the most common precursor to heart disease’, according to Circulation Foundation.
Obesity has been shown to change the secretion of molecules from fat tissue, the researchers wrote in the journal Science Translational Medicine.
These molecules influence the structure and function of blood vessels, they added.
The so-called Wnt signaling pathway, which allows cells to ‘communicate’, and ‘internal stress’ have both been linked to the onset of vascular disease.
However, the role obesity plays in these processes was unclear. To learn more, the researchers analysed 1,004 atherosclerosis patients.
Results suggested the obese participants had significantly higher levels of WNT5A in their plasma.
They also had ‘elevated expression’ of WNT5A’s receptors, Frizzled 2 and Frizzled 5, in the walls of their arteries.
In a separate experiment, the team found high WNT5A was linked to the build-up of hard, calcified plaque in 68 out of 70 patients with coronary artery disease.
WNT5A has previously been linked to ‘endothelial function’, with higher levels also being associated with diabetes, the researchers wrote.
They stress further investigation, including animal studies, is required before WNT5A can be targeted by a potential treatment.
Meanwhile, because researchers demonstrated for the first time that a strong association between obesity and chronic diarrhea is not driven by diet or physical activity, the findings could have important implications for how physicians might approach and treat symptoms of diarrhea in patients with obesity differently.
While obesity is known to be associated with increased risk of other health conditions — such as heart disease, diabetes, and gastrointestinal diseases — less is known about the relationship between obesity and abnormal bowel habits.
In the most comprehensive analysis of the relationship between Body Mass Index (BMI) and bowel habits to date, published in Alimentary Pharmacology & Therapeutics, a team of physician-researchers at Beth Israel Deaconess Medical Center (BIDMC) found a strong association between obesity and chronic diarrhea independent of an individual’s dietary, lifestyle, psychological factors or medical conditions.
The findings could have important implications for how physicians might approach and treat symptoms of diarrhea in patients with obesity.
“While several previous studies have pointed to an association between obesity and bowel habits, all lacked data on whether dietary or other factors drive the connection,” said corresponding author Sarah Ballou, PhD, a health psychologist in the Division of Gastroenterology, Hepatology, and Nutrition at BIDMC. “Our research confirms a positive association between obesity and chronic diarrhea and reveals for the first time that this relationship is not driven by confounding factors such as diet or physical activity level.”
Using the 2009-2010 National Health and Nutrition Examination Survey (NHANES) — a program of studies administered by the United States Centers for Disease Control (CDC) designed to assess the health and nutritional status of adults and children in the United States — Ballou and colleagues analyzed the bowel health questionnaire responses of 5,126 patients over the age of 20 years who did not report a history of irritable bowel syndrome, celiac disease or colon cancer. The team compared the reported bowel habits of patients who had a BMI associated with being underweight, normal weight, overweight, obese and severely obese.
After controlling for dietary, physical activity, diabetes, laxative use, and demographic factors, the team found that respondents who were obese or severely obese were 60 percent more likely to have experienced chronic diarrhea compared to those with normal bowel habits or constipation.
While the study reveals the association is not driven by compounding factors the team controlled for, questions still remain about what underlying causes may explain why obese individuals would be more likely than non-obese individuals to have diarrhea. One possible explanation may be related to the link between obesity and chronic low-grade inflammation, which may contribute to diarrhoea. Future research clarifying this relationship and determining how obesity triggers inflammation could serve as a base for how physicians approach treating abnormal bowel habits with this patient population.
“The treatment of obesity and obesity-related medical conditions requires multidisciplinary management,” said senior author Anthony Lembo, MD, a gastroenterologist in the Division of Gastroenterology, Hepatology, and Nutrition at BIDMC. “Clinicians should be aware of the relationship between obesity and diarrhea, especially considering the potential negative impacts altered bowel habits can have on quality of life.”
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