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Excess fat disrupts heart cell’s energy system

Raghu Kshitiz

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KATHMANDU — Excess fat in the heart — a common feature in diabetes and obesity — may contribute to the two to five fold increased risk of heart failure in people with diabetes, a study by University of Iowa has found.

The heart is the most energy-hungry organ in the body. Just like a combustion engine burning fuel to power the pistons, healthy heart cells consume fuel molecules to create the necessary energy to keep the heart pumping.This essential energy production takes place inside mitochondria, the self-contained ‘powerplant’ organelles inside cells.

Although mitochondria in a healthy heart primarily use fatty acids as fuel, they can easily adapt to use other fuel molecules as needed, including glucose, lactate, and ketone bodies.

Diabetes, however, reduces the heart muscle’s metabolic adaptability and causes heart cells to overuse fat as a metabolic fuel.

“Diabetes, which affects almost 30 million Americans, significantly increases the risk of heart failure, and one of the cardinal manifestations of the hearts of people with diabetes is the tendency to overuse fat as a metabolic fuel, which ultimately leads to mitochondrial and cardiac damage,” said E Dale Abel, from the University of Iowa in the US.

The study, published in the journal Circulation Research, found this cardiac lipid overload leads to numerous small, misshapen mitochondria that don’t produce energy as efficiently as normal mitochondria.

“We have demonstrated and detected how increasing the amount of fat (lipid) that the heart consumes leads to dramatic changes in the structure and function of the mitochondria in the heart,” Abel said.

To investigate the consequences of cardiac lipid overload on mitochondria, the team used genetically modified mice that mimic the increased fatty acid uptake (lipid overload) that characterises diabetes.

“These studies provide a new window into how these changes to mitochondria could occur in the lipid-overloaded heart,” he added.

In the mouse model, lipid uptake to heart is doubled. This modest increase resulted in mitochondria that became thinner and more twisted than mitochondria in healthy heart cells.

These structural changes (almost like a noodle snaking through the heart) lead to an appearance of mitochondrial fragmentation when imaged by conventional electron microscopy.

The study also revealed the molecular cause of the change in mitochondrial structure. Prolonged lipid overload leads to increased levels of damaging substances called reactive oxygen species (ROS).

The findings further suggest that cardiac lipid overload disrupts normal mitochondrial structure, which may impair energy production and compromise heart function.

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26 rhinos die in a year in CNP

Gorkha Post

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CHITWAN — Chitwan National Park (CNP) witnessed zero poaching of endangered one-horned rhinoceros in the fiscal year 2074/75. But the death of the rhinos by natural causes has increased recently, as the park has lost a total of 26 rhinos to various causes in this period.

26 rhinos died from various reasons including natural disaster in the period, according to the CNP information officer, Nurendra Aryal.

Four rhinos were killed in flood-related incidents with two caught in a marsh caused by the flooding while two were swept away by flood waters, he informed.

Fighting, delivery complications (in case of some female rhinos) and aging are other reasons behind the deaths of a noticeable number of this endangered wildlife last fiscal year. Three female rhinos succumbed to child delivery complications in this period. They died after failing to give birth to their babies.

The park however has recorded no case of rhino poaching since April 8, 2017.However, the number of rhino deaths due to other reasons was slightly up in the year compared to the previous year, according to the CNP Information Officer Aryal.

This figure is followed by 25 and 15 rhino deaths in previous two fiscal years respectively.

The natural causes led to the death of 24 rhinos in the fiscal year 2073/74 and 15 in 2072/73.

The need of a study was felt to seek potential ways for minimising the death risk among rhinos with their death toll increasing every year, CNP chief conservation officer, Bed Kumar Dhakal said. A squad from the Department of National Parks and Wildlife Conservation has already begun a study to this end.

The CNP latest details mentioned about 605 rhinos here.

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