Giant panda’s gut bacteria help it remain chubby despite bamboo diet, researchers say

Giant pandas stay chubby and health despite a low-quality bamboo diet due to their gut bacteria, a study has found.

Though no longer considered an endangered species, giant pandas are still considered “vulnerable,” with just 1,800 outside of captivity.

The study, which was published in the Cell Reports journal on 18 January, was conducted by researchers from the Institute of Zoology, Chinese Academy of Sciences.

It explored how giant pandas living in the Qinling Mountains in central China manage to stay chubby and healthy year-round, despite eating a low-fat and “low-quality” diet for most of the year.

The animal’s diet mainly consists of fibrous bamboo leaves from August to April. The more nutritious and protein-rich bamboo shoots are only available between late April and early August.

The researchers, led by Fuwen Wei, Professor in Wildlife Ecology and Conservation Biology, discovered a causal relationship between the giant panda’s gut microbiota (gut flora) and it’s ability to gain and store fat.

They found that the shifts in the bear’s gut microbiota in the season when nutritious bamboo shoots become available helps the herbivorous bear gain more weight and store more fat, which may compensate for the lack of nutrients in seasons when there are only bamboo leaves to chew on.

“This is the first time we established a causal relationship between a panda’s gut microbiota and its phenotype,” said Guangping Huang, the first author of the study. “We’ve known these pandas have a different set of gut microbiota during the shoot-eating season for a long time, and it’s very obvious that they are chubbier during this time of the year.”

According to Prof Wei, this is because these wild pandas have a significantly higher level of a bacterium called Clostridium butyricum in their gut during the shoot-eating season compared with during the leaf-eating season.

To investigate the effects on the metabolisms of giant pandas, the researchers conducted a faecal microbiota transplantation (FTM) of panda faeces collected in the wild to germ-free mice. This is because it can be difficult to run direct tests on endangered and vulnerable species.

The mice were fed with a bamboo-based diet that simulated what pandas eat for three weeks.

The study found that mice transplanted with panda faeces collected during shoot-eating season gained significantly more weight and had more fat than mice transplanted with faeces from leaf-eating season despite consuming the same amount of food.

Further analysis revealed that the metabolic product of C. butyricum - butyrate - could upregulate the expression of a circadian rhythm gene called Per2, a Protein Coding gene that increases lipid (including fat) synthesis and storage.

Next, the team plans to map out more microorganisms in the panda’s gut and find out about their roles in affecting the animal’s health.

“Causal research of host phenotype and gut microbiota in wild animals is just beginning,” said Huang. “Identifying what bacteria are beneficial for animals is very important, because one day we may be able to treat some diseases with probiotics.”