How the Muscles Prevent Disease

Join us as we explore Medical Frontiers.

With remote work increasing in recent years, many people have become even more sedentary, losing precious muscle mass.

Muscles are a critical organ that makes up about 40% of our body weight.

And the latest research has revealed that muscles work with other organs to prevent diabetes and colorectal cancer.

So, let's explore the advantages of exercising and just how bad a sedentary lifestyle and inactivity can be on our overall health and well-being.

This gym chain in Japan is exclusively for women.

It has 770,000 members, mainly in their 50s to 70s.

This woman is training her upper body using a machine.

This woman is walking in place between workouts.

They move on to the next exercise every 30 seconds at the signal.

Each session is 30 minutes long, and involves 30-second intervals of strength training and aerobic exercises.

This woman joined the gym after her level of HbA1c, a biomarker for diabetes, exceeded the normal range.

She comes here three times a week.

My diabetes numbers have improved significantly
in 2 months.

My weight is a secret, even from my husband.

Diabetes causes chronic hyperglycemia.

There are several types.

We focus on Type 2, which can be triggered by over-eating and a lack of exercise.

Juntendo University Professor Tamura Yoshifumi is studying the link between Type 2 diabetes and muscle function.

Resistance exercise increases
the volume of muscle in the body.

If the volume of muscle is increased, our blood
glucose level can be easily decreased.

This is because our muscles are
the biggest tank, or storage, of glucose.

The carbohydrates we eat are broken down into glucose, which enters the blood stream.

A hormone called insulin is then secreted by the pancreas.

It promotes uptake of glucose by the muscles and other organs so that it can be used for energy.

Diabetes is characterized by low insulin secretion, which makes it hard for the glucose in the blood to be absorbed by the muscles.

Blood glucose levels increase as a result.

Tamura is focusing on cases in which hyperglycemia happens despite sufficient insulin secretion.

He believes the muscles are key.

Obesity and a lack of exercise can cause lipids to accumulate in the muscles.

This reduces the muscles' ability to absorb glucose, leading to higher blood glucose levels.

This condition is called insulin resistance.

If the tank is very small, blood glucose cannot
be taken in by the skeletal muscles.

So if there is insulin resistance in the skeletal
muscles, blood glucose levels cannot decrease.

Insulin resistance therefore increases
the risk of type 2 diabetes.

It has been widely believed that obese people are at higher risk of type 2 diabetes.

But this theory could soon become obsolete.

BMI, or body mass index, is a tool to screen for obesity.

It is calculated from height and weight.

Japanese researchers looked at the association between BMI and the risk of diabetes.

They found that individuals with a higher BMI are at greater risk of developing diabetes compared with those whose BMI is in the normal range.

But what's more noteworthy is that the risk is even higher for people who are underweight.

The Japanese clinical data clearly indicate that not only obese people but also underweight
people are at high risk for type 2 diabetes.

And we found out such skinny women
do not eat and do not exercise.

So they look very healthy, but they're not healthy.

Hiruma Akiko is one of Tamura's patients.

She developed diabetes despite being underweight.

She has been taking medication before meals every day to control her blood glucose levels.

She was diagnosed with diabetes 20 years ago in her 40s while working as a librarian.

I was shocked. I wasn't overweight.
And I didn't have a sweet tooth.

I also ate regular meals, so I couldn't understand why.

Hiruma is 160 centimeters tall and weighed about 52 kilograms at the time.

Her BMI was in the normal range, at 20.

However, she was not getting enough exercise.

I mostly worked on my computer back then.
I was quite sedentary.

Tamura's research team found that being inactive for even a short term causes lipids to accumulate in the muscles, which could lead to insulin resistance.

The researchers prepared a mouse and immobilized one of its legs in a cast.

They compared a muscle in the immobilized leg with that in another leg 24 hours later.

Insulin-stimulated glucose uptake decreased by around two-thirds in the muscle in the immobilized leg - a sign it had become insulin resistant in just one day.

The amount of lipids in the muscle doubled.

Tamura had Hiruma come to the hospital for a checkup one day.

This equipment analyzes body composition by sending microcurrents through the arms and legs.

Tamura focused on muscle mass in proportion to weight.

Here are your results.

Thank you.

Hiruma's weight was 50.4 kilograms, which is considered normal.

But her muscle mass was below the normal range, at 31.4 kilograms.

Your muscle mass is still a bit lower than normal.

Your weight has increased 6 to 7 kilograms,
so I'm sure you've gained some muscle, too.

But your blood glucose levels
have remained unchanged.

In the past 5 years, Hiruma's BMI went from underweight to normal, but her HbA1c level stayed about the same.

Weight gain normally leads to a rise in HbA1c.

But Tamura thinks Hiruma's weight gain was a result of increased muscle mass, which prevented HbA1c from rising.

I recommend you gain more weight by increasing muscle.

A larger muscle mass will help
your blood glucose levels to drop.

You might want to gain 2 to 3 more kilograms.

It's not easy to gain that much.

But I'll try.

How much exercise do we need to do in a day, to, I guess, have insulin to be, I guess, effective?

I always recommend brisk walking.
The level is at least 8,000 steps a day.

There are many physical activity guidelines, and most of them recommend more daily physical
activity, such as gardening, cleaning or cooking.

Daily physical activity is mostly aerobic.

Aerobic activity increases the
insulin sensitivity of skeletal muscle.

So now we recommend doing both types of
exercise - aerobic and resistance.

Hiruma exercises for about 15 minutes a day to gain muscle.

She does aerobic exercises suited to her strength level to work out all the muscles in her body.

It's difficult to continue
if you push yourself too hard.

I hope to build muscle from walking and using
the stairs, as I can tell I don't have much muscle.

So you mentioned that the muscles play this very pivotal role, critical role.

Can you tell me a little bit more about the risks of not having enough good quality muscle mass?

Actually, low muscle mass is closely associated
with a lot of chronic diseases.

We are now conducting the Bunkyo
Health Study in the Bunkyo area in Tokyo.

And we found out that low muscle mass
is closely associated with dementia.

Tamura's team conducted a study on the relationship between sarcopenia and cognitive functions in around 1,600 elderly people.

Sarcopenia is muscle loss that occurs with aging or immobility.

In this study, the subjects with decreased grip strength were defined as having sarcopenia.

The study found that 7.6 percent of people in the sarcopenia group developed dementia, about five times the normal group.

The figure was even higher for those with sarcopenia who were obese, at 14.5 percent - about 9 times the normal group.

This result doesn't tell us about the
causal relationship between these two factors.

However, I believe that elderly people
especially should keep their muscle volume.

Preventing muscle atrophy is a very important
issue in a super-aged society such as Japan.

I think, you know, the importance of, I think realizing that muscle is responsible for health and longevity.

I'll promote it as much as I can.

Yes, please. I ask that you do that.

Thank you very much.

The muscles play another surprising role.

When they contract, they secrete various types of proteins.

These proteins are called myokines.

They are said to affect our health by working with organs throughout the body.

Myokines travel through the blood stream to various organs, where they stimulate each other.

Some myokines influence the brain and improve cognitive function; some get the pancreas to secrete insulin.

A myokine called SPARC has been attracting attention following the recent discovery of its ability to curb colon cancer.

The finding was made by Kyoto Prefectural University Associate Professor Aoi Wataru.

He has been studying SPARC together with the Karolinska Institute in Sweden.

Now, how actually does SPARC, which is a variety of Myokine, how does it suppress colorectal cancer?

What's the mechanism behind it?

SPARC is secreted after exercise. It travels
through the body and reaches the intestines.

Cells in the intestines show certain signswhen they start to become cancerous.

SPARC finds them, and causes them to die.

This endoscopic footage shows the human large intestine.

The circled part shows a precancerous lesion.

If left unattended, it may develop into colon cancer.

Aoi performed an animal experiment to confirm how SPARC reacts to precancerous changes in the large intestine.

He prepared mice with precancerous lesions.

One mouse was capable of secreting SPARC after exercise, and the other was not.

This footage shows the large intestine of the mouse capable of secreting SPARC.

The brown dots are precancerous cells that died after SPARC bound to them.

In the SPARC-null mouse, the proportion of dead cells was about half that of the normal mouse.

The presence of SPARC can lead to the death of more precancerous cells, thus helping to stop colon cancer in its early stages.

SPARC doesn't harm normal cells.

It identifies cells that are turning cancerous
and makes sure only they die, by apoptosis.

Is SPARC also effective at potentially reducing late stage colon cancer?

There's a huge possibility that it is.

We confirmed with cultured cells that SPARC
curbs the propagation of colon cancer cells.

I believe it's effective to a certain level against
cells that have already turned cancerous.

What other cancers potentially could have a similar mechanism or could it be effective for?

We've learned through experiments that SPARC is effective against ovary,
prostate and pancreatic cancer.

SPARC is not almighty, but it may
be able to tackle several types of cancer.

Aoi is looking into the relationship between myokines and the intestines.

He believes that certain foods can boost the secretion of myokines.

Now, my question is - are there any foods that actually increase SPARC in the body?

The C in SPARC stands for cysteine.
SPARC is a protein that is rich in cysteine.

Cysteine intake before exercise
clearly enhances SPARC secretion.

Meat, especially liver, and beans contain
large amounts of cysteine.

Building high-quality muscle is also important for myokine secretion.

Aoi has been doing strength training in order to study which foods can increase muscle mass.

You're working on so much interesting research, I'd love to know what sort of diet you have.

Those keen to build muscle should
focus not just on protein, but also on foods such as tea and vegetables.

They may not be interested in such foods,
but these are important for health.

Aoi says matcha has huge potential.

In December 2022, Aoi gave a lecture at the International Congress of Nutrition about the relationship between the nutrients contained in matcha and muscle.

Matcha functions to boost and
accelerate muscle adaptation by training.

The antioxidants and amino acids contained in matcha are believed to be effective in helping the muscles recover after a workout and building more of them.

What's the next of your goals in terms of research?

We've learned from this project that a good gut environment enhances the secretion
of myokines by the muscles.

The intestines and muscles are not adjacent,
but they interact closely.

Thank you very much.

As we've seen, muscles play a vital role in maintaining our health and well-being and also in preventing a whole host of lifestyle diseases.

And exercise may well prove to be one of the most powerful tools to maximizing our health span and also increasing longevity.

Today, we introduce three bodyweight workouts that will allow you to strengthen your muscles without going to the gym.

Our instructor is Tanimoto Michiya, an expert in exercise physiology who is driving Japan's strength-training boom.

So, Dr. Tanimoto, thank you so much for your time today.

Thank you for having me.

Let's start with the squat - a very basic move.

Stand with your feet shoulder-width apart.

Point your toes outward so that you can squat deep.

Push your buttocks out to ensure you don't stick out your knees and hurt them.

Push your buttocks out and squat deeper.
Straighten your back and push your buttocks out.

It's really tough.

Now, stand up straight.

Doing a really deep squat is sometimes not great for the knee joints.

Don't do anything that causes pain.
You can adjust load with squat depth.

Older people can use their hands
to push themselves up.

Okay, so use the hands?

Yes, but not you, Erica.

Let's start. Squat deep and stand straight.

Have fun. Be happy.
Do it with a smile on your face.

That one doesn't count - it was too shallow.
That's it.

OK, that's enough.

It's surprising how even ten of these it's quite tough.

So doing the deep squat, there's so many muscles that are activated.

And I would imagine that they're some of the biggest muscles in the body.

Squats involve the large muscles
in the lower body. They're a very good exercise.

Next, table push-ups.

Use a desk or table rather than the floor so that it's easier to adjust the load.

Make sure your chest touches the desk or table.

Touch the desk with your chest and push up.

Oh, my gosh, that's tough.

Put one foot forward.

So one foot only?

That makes it easier, right?

Oh, yeah, that's much easier.

The more you put your foot out, the easier it gets.
Find a position that allows you to do 10 push-ups.

Let's do 10 push-ups. Go!
Touch the desk with your chest, and up.

Have fun as you lower, then raise your chest.
Be happy.

This will be our last.
You look like you want to do 1 more.

Thank you.

I think everybody talks about having a break between exercises.

Why is that important?

Muscles need time to recover.
They break down if you exercise every day.

I'd recommend exercising every other day.

Finally, the leg raise.

Sit on the edge of a chair and hold the back tightly.

Lift your heels off the floor and quickly raise both legs together.

Then slowly lower them.

Try to squeeze your abs when
lifting your legs. Bring them down carefully.

This is the toughest exercise of all.

If it's too tough, you can bend your knees.

That's much better.

This is easier.

If you can, keep your knees straight and
raise your legs as high as you can.

You can place your feet on the floor
to make it easier.

Let's go. Raise your legs. Squeeze!
Now lower them slowly.

Have fun. Keep smiling.

You can do some more... 10!

1 more. Up!

Again, 1 more!

You did great.

For me, it feels tough, I think because you're using so many different muscles.

I notice actually a lot here.

I'm burning here as well.

If you're unable to raise your legs, you won't be
able to walk briskly, and you may trip often.

That's why it's important to do this exercise.

It takes only 5 minutes to do these exercises.
I spend only 10 to 15 minutes on them at a time.

What's good about these workouts is
they don't take much time.

Anyone can do it from tomorrow.

Anyone can do it from today.

Exactly, exactly! That's the key thing.

Okay. I've done mine today, though.

Don't put it off until tomorrow.

Exactly. But I've done mine today.

I've finished for today.