Evolution of Brown Fat in Placental Mammals

Evolution of Brown Fat in Placental Mammals

Around 100 million years ago, placental mammals experienced a significant evolutionary development that allowed them to thrive in various cold regions of the Earth. Recent research from Stockholm University, published in the journal Science, reveals that brown fat, the typical mammalian heater organ, evolved exclusively in modern placental mammals.

Collaborative Research Findings

The study was a collaboration between researchers from Stockholm University, Helmholtz Munich, the Natural History Museum Berlin, and the University of East Anglia. The team demonstrated that marsupials, distant relatives of placental mammals, possess an underdeveloped form of brown fat.

Key Discovery: UCP1 Protein Activation

The research identified that the heat-producing protein UCP1 (Uncoupling Protein 1) became active after the evolutionary split between placental and marsupial mammals. This discovery is vital for understanding brown fat’s role in mammalian evolution, endothermy, and metabolism.

Importance of Brown Fat

Susanne Keipert, co-first author, emphasizes the study’s significance in understanding the origin and regulation of brown fat. Brown fat’s energy-consuming function is crucial for medical research due to its potential to improve conditions like obesity, diabetes, and cardiometabolic diseases, which are major health threats.

Contributions of Jastroch Laboratory

The Jastroch Laboratory at Stockholm University, known for its pioneering research on mammalian heat production, has integrated evolutionary insights into understanding human metabolic diseases. This new study marks another milestone in their research efforts.

Marsupial UCP1 Gene and Development

The study found that the marsupial UCP1 gene is actively transcribed in the adipose tissue of young opossums during a critical developmental period when they face cold stress. This is comparable to the birth of placental mammals, where brown fat is essential for temperature regulation.

Evolutionary Insights

Martin Jastroch explains that gene networks enabling thermogenesis existed before the divergence of marsupials and placental mammals. However, the heat-producing ability of the UCP1 protein evolved only after this split. The researchers used bioinformatic tools to reconstruct the ancient UCP1 protein of stem placental mammals, dating back to about 110 million years ago. This ancient protein could produce heat, suggesting the presence of brown fat in the ancestors of placental mammals.

Function and Importance of Brown Fat

Brown fat, unique to placental mammals, produces heat through UCP1, transforming mitochondria into heater units that convert fat and sugar into heat. This adaptation enables newborn placental mammals, including humans, to survive cold stress and maintain body temperature. Additionally, brown fat can protect against metabolic complications by burning excessive fat and sugars, making it critical for developing therapies for metabolic disorders.

Multiple-Choice Questions (MCQs):

  1. When did placental mammals evolve the ability to thrive in cold regions?
    • A. 200 million years ago
    • B. 150 million years ago
    • C. 100 million years ago
    • D. 50 million years ago
    Answer: C. 100 million years ago
  2. What is the key protein involved in heat production in brown fat?
    • A. Insulin
    • B. Leptin
    • C. UCP1
    • D. ATPase
    Answer: C. UCP1
  3. Which type of mammals possess a not fully evolved form of brown fat?
    • A. Placental mammals
    • B. Marsupials
    • C. Monotremes
    • D. Primates
    Answer: B. Marsupials
  4. What is the main medical relevance of brown fat according to the research?
    • A. Cancer treatment
    • B. Infection control
    • C. Metabolic disease improvement
    • D. Neurological disorder treatment
    Answer: C. Metabolic disease improvement
  5. What method did researchers use to study the ancient UCP1 protein?
    • A. Genetic engineering
    • B. Fossil analysis
    • C. Bioinformatic tools
    • D. Microscopy
    Answer: C. Bioinformatic tools