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New research reveals obesity is a cause of kidney disease

04 November 2020

Scientists at the University of Oxford have used genetics to show obesity can increase the chances of someone developing kidney disease.

This new study, funded by Kidney Research UK and the Medical Research Council through a joint David Kerr fellowship, has found that fat all over the body increases risk, not just fat around the middle (tummy fat). It suggests controlling weight could be a new way to manage kidney disease risk.

This research was published this week in the Journal of the American Society of Nephrology.

Previous studies had found that obesity is linked with an increased risk of kidney disease. But it wasn’t clear whether obesity directly caused kidney disease or whether other factors were involved, such as more salt in people’s diet.

The power of genetics

In this latest research, the team studied almost 300,000 DNA samples from a large store of blood and urine samples (including DNA) and detailed health information called the UK Biobank.

They searched over 1,000 gene variations that predispose people to a higher body mass index (BMI) or more fat deposited around your middle – tummy fat. People with these gene variations are more likely to become overweight or obese.

Professor Will Herrington, from the University of Oxford, who co-led the research explains: “In this study, we found these genetic variants were consistently linked to kidney disease – each 5 kg/m2 increase in BMI – that’s equivalent to moving from being an ideal weight to being overweight, or from overweight to being obese – caused roughly a 50% increased risk in chronic kidney disease. Our genetic approach meant we could be more rigorous and rule out other factors.”

It doesn’t matter where the fat resides

The team found kidney disease risk didn’t change based on fat location – it increased by the same amount regardless of whether fat was deposited centrally (around the organs) or across the body generally (such as around the legs and arms).

This is different to some diseases linked to obesity, such as heart disease, where fat deposited around the abdominal organs (tummy fat) puts people at higher risk than people with fat that accumulates around the buttocks, because fat sits around their organs.

These results show that, regardless of where it is deposited in the body, fat increases the risk of kidney disease.

What’s going on?

To understand why this happens, the researchers tested whether the gene variants that predispose certain people to obesity were also associated with diabetes or high blood pressure – which both lead to kidney disease.

The team found that for most cases of obesity-associated kidney disease, diabetes and blood pressure were the driving causes. When fat was deposited around the central organs, kidney disease was caused almost exclusively by diabetes. On the other hand, when fat was deposited generally across the body, both diabetes and high blood pressure contributed to kidney disease.

Professor Herrington explains: “This is good news, because we already know a lot about diabetes and high blood pressure, and we have treatments for them. If we can prevent diabetes and control blood pressure in those who are overweight or obese, we may be able to prevent many cases of kidney disease from developing in the first place. Ultimately, these results give us all more incentive to manage our weight.”

He continues: “A new class of drugs called gliflozins reduce the kidney’s ability to retain sugar and salt, meaning the body is more able to get rid of excess sugar and salt. This helps people with diabetes control their weight and blood pressure, and recent trials are revealing they are particularly effective at treating diabetic kidney disease, and other kidney diseases. We’re running a large clinical trial to find out if this is true in a wider range of people with kidney problems.”

Why is this important?

Our executive director of research, innovation and policy, Dr Aisling McMahon said: “Around three million people are living with chronic kidney disease in the UK. One of the charity’s priorities is to transform treatments for kidney disease and to find new ways to prevent it.

“By identifying obesity as a new risk factor for kidney disease, this important research has revealed new reasons for doctors, patients and healthcare teams to support a renewed focus on weight management and encourage people to look at ways they can improve their own health.”

“We’re watching the gliflozin trials with interest – if clinical trials reveal these drugs can benefit an even wider group of patients, we would like to see these research findings brought into clinical practice quickly so they can benefit patients across the country. And as well as preventing kidney disease, we’re also committed to keeping people active after they develop kidney disease. That's why we’re supporting Kidney Beam, an online exercise and wellbeing platform for kidney patients .”

Find out more

Find out more about kidney disease risk factors and what to do if you are worried.

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