Growth Factors and Body Weight Lecture 11

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Questions and Answers

What is the primary function of growth factors in development?

Stimulating cell growth, differentiation, and apoptosis (correct)

Stimulating immune cell production

Regulating endocrine functions

Promoting tissue inflammation

How do growth factors typically function in the body?

As neurotransmitters between nerve cells

Through endocrine signaling to distant organs

In an autocrine or paracrine manner (correct)

By acting solely on production cells

Which of the following is a characteristic of cytokines?

Responsible for cell storage

Act as hormones in the circulatory system

Secreted by glandular tissues

Produced primarily by immune cells (correct)

Which of the following growth factor families is involved in regulating body weight?

Transforming growth factor (TGF-B) family Signup and view all the answers

What is a primary function of hormones produced by glands?

Transporting signals through the circulatory system Signup and view all the answers

Which of the following proteins is NOT typically classified as a growth factor?

Insulin Signup and view all the answers

Which cell types are primarily involved in producing cytokines?

Immune cells and some fibroblasts Signup and view all the answers

Which family of growth factors is specifically mentioned for its role in embryogenesis?

Insulin-like growth factor (IGF) family Signup and view all the answers

In what manner do growth factors influence local tissues?

Promoting cell differentiation and survival Signup and view all the answers

Which statement accurately describes canonical FGFs?

They act in an autocrine or paracrine manner. Signup and view all the answers

What distinguishes non-secreted FGFs from canonical FGFs?

They lack signal peptides and are not secreted. Signup and view all the answers

Which of the following is NOT a characteristic of endocrine FGFs?

They bind exclusively to intracellular receptors. Signup and view all the answers

Which intracellular signaling pathway is NOT activated by FGFs when they bind to their receptors?

JAK-STAT Signup and view all the answers

What is a key effect of BMP8B delivery in the central nervous system?

Increased energy expenditure and decreased body weight Signup and view all the answers

What is the total number of members in the Fibroblast Growth Factor family?

22 Signup and view all the answers

How does FGF21 primarily influence fatty acid oxidation and ketogenesis?

By enabling lipolysis in the adipose tissue Signup and view all the answers

How do canonical FGFs primarily signal their effects?

Through autocrine or paracrine mechanisms. Signup and view all the answers

What effect does the overexpression of FGF21 have on body size in mice?

Decreases body size due to growth hormone resistance Signup and view all the answers

What role does FGF21 specifically play in the context of FGFs?

It acts as a signaling molecule in growth regulation. Signup and view all the answers

Which group includes FGFs that are not secreted from cells?

Non-secreted FGFs Signup and view all the answers

What physiological mechanism is increased as a result of BMP8B's effect on the lateral hypothalamic area?

Sympathetic activation of BAT leading to thermogenesis Signup and view all the answers

During prolonged fasting, which of the following best describes FGF21's role?

Stimulates ketone production and fatty acid oxidation in the liver Signup and view all the answers

Which of the following statements about transforming growth factors (TGF-βs) is true?

They are the largest family of growth and differentiation factors. Signup and view all the answers

What unintended effect might arise from delivering high doses of BMP8B centrally?

Reduced body weight due to increased sympathetic activation of BAT Signup and view all the answers

Which of the following FGFs is part of the endocrine group?

FGF21 Signup and view all the answers

What was the approximate increase in muscle mass when Activin A or Activin B was inhibited?

20% Signup and view all the answers

Which growth factor is identified as the major negative regulator of muscle mass?

Myostatin Signup and view all the answers

What was the maximum increase in muscle mass when all three growth factors were inhibited?

150% Signup and view all the answers

What physiological function did the increase in muscle mass from inhibiting the growth factors improve?

Ankle torque Signup and view all the answers

Where is brown adipose tissue (BAT) found in significant amounts in rodents?

On the back of the neck Signup and view all the answers

What role does sympathetic activation play in energy metabolism related to BAT?

It triggers PKA signaling. Signup and view all the answers

What critical process occurs due to the action of UCP1 in mitochondria?

Heat production Signup and view all the answers

How long was it initially believed that brown adipose tissue (BAT) would disappear after in rodents?

2 years Signup and view all the answers

What factor is released from lipid droplets during thermogenesis in BAT?

Free fatty acids Signup and view all the answers

What is the overall effect of inhibiting all three growth factors studied in the experiment?

Increased muscle hypertrophy Signup and view all the answers

What is the theorized additional resting energy expenditure (REE) contributed by cold activation of brown adipose tissue in an average adult?

127 kilocalories Signup and view all the answers

What was the observed weight loss in adipose tissue if the cold activation of brown adipose tissue is maintained for 30 days?

0.5 kilograms Signup and view all the answers

Which gene is highly expressed in mature brown adipocytes and is suggested to have a thermogenic role?

BMP8B Signup and view all the answers

What effect does cold exposure have on BMP8B expression?

Increases expression by over 100-fold Signup and view all the answers

What was the outcome for BMP8B knockout (KO) mice when placed on a high-fat diet?

They gained significantly more weight than control mice Signup and view all the answers

What effect did the knockout of BMP8B have on food consumption in mice on a high-fat diet?

Decreased food consumption compared to controls Signup and view all the answers

What central effect does BMP8B have in relation to brown adipose tissue (BAT)?

Promotes sympathetic outflow to BAT Signup and view all the answers

How does BMP8B influence the responsiveness of brown adipocytes to sympathetic stimulation?

It primes them to respond Signup and view all the answers

What physiological change is observed in BMP8B knockout mice that suggests a decrease in thermogenesis?

Major reduction in body temperature Signup and view all the answers

Which statement accurately reflects the role of BMP8B in thermogenesis?

It acts both centrally and peripherally to regulate BAT function. Signup and view all the answers

Study Notes

Growth Factors Overview

Growth factors are proteins secreted by most cells affecting various body processes.
They function primarily in an autocrine or paracrine manner, influencing the cells that produce them or nearby cells.
Their main roles include stimulating cell growth, differentiation, survival, homeostasis, and tissue repair.
In development, growth factors control processes such as proliferation and morphogenesis; in adults, they play a role in embryogenesis and organogenesis.
Key families include IGF, FGF, and TGF-β.

Cytokines

Cyokines are primarily produced by immune cells (macrophages, lymphocytes, etc.) and sometimes by fibroblasts.
They regulate immune responses and cell migration.
Notable examples include the interleukin family, interferon family, and tumor necrosis factor (TNF) family.

Hormones

Hormones are secreted by glands and transported to target cells via the circulatory system.
They regulate various physiological functions and behaviors.
Examples include growth hormone, insulin, leptin, and gonadotropins (FSH, LH).

Fibroblast Growth Factors (FGFs)

Comprise 22 members categorized into three groups:
- Canonical FGFs: True growth factors that act locally.
- Non-secreted FGFs: Lack signal peptides, bind to intracellular receptors, and signal without being secreted.
- Endocrine FGFs: Such as FGF15, FGF21, and FGF23, act on distant target cells.
FGF21 is a focus due to its implications in body weight regulation.

Signaling Pathways

FGFs bind to FGF receptors on target cells, activating several intracellular signaling pathways, including STAT, AKT, and MAP kinase.
These pathways result in the transcription of specific target genes.

Transforming Growth Factors (TGF-βs)

This is the largest family of growth and differentiation factors, consisting of 34 members.
Activin A and B negatively regulate muscle mass; experiments show that inhibiting these growth factors increases muscle mass significantly.

BMP8B and Brown Adipose Tissue (BAT)

Brown adipose tissue plays a crucial role in thermogenesis.
Cold exposure activates sympathetic nervous system signaling, leading to enhanced thermogenic processes.
Activation of BAT could potentially increase resting energy expenditure (REE) significantly and assist in weight management.
BMP8B, produced by brown adipocytes, increases under cold exposure and impacts thermogenic responses.

BMP8B's Role in Metabolism

BMP8B influences thermogenesis in BAT by enhancing sympathetic stimulation.
Research indicates that increasing BMP8B levels centrally reduces AMPK activation, leading to greater sympathetic activation of BAT and weight reduction.
BMP8B knockout mice displayed increased weight gain and reduced thermogenesis on high-fat diets compared to controls.

FGF21: A Potential Metabolic Regulator

FGF21 is primarily produced in the liver and involves fuel utilization processes.
Overexpression leads to increased fatty acid oxidation and ketone production during fasting.
Mice with elevated FGF21 exhibit smaller body sizes due to growth hormone resistance, highlighting its role in metabolism and body weight regulation.

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Description

This quiz covers Lecture 11 focusing on growth factors and their relationship to body weight. Understand the role of proteins secreted by cells, including cytokines and hormones, and their specific effects on body processes. Test your knowledge and comprehension of these vital biological concepts.