Hormonal Regulation of Appetite and Satiety
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Questions and Answers

Which peptide is classified as orexigenic?

  • Insulin
  • Leptin
  • Alpha-MSH
  • Ghrelin (correct)
  • What is the primary action of Peptide YY (PYY 3-36) after a meal?

  • Enhances appetite
  • Increases food intake
  • Stimulates gastric motility
  • Inhibits gastric motility (correct)
  • Which peptide is released from enteroendocrine cells in response to the intake of lipids and proteins?

  • Cholecystokinin (CCK) (correct)
  • Glucagon-like peptide 1 (GLP-1)
  • Oxyntomodulin
  • Obestatin
  • What action does glucagon-like peptide 1 (GLP-1) have after food ingestion?

    <p>Inhibits gastric emptying</p> Signup and view all the answers

    Which peptide may act to antagonize ghrelin?

    <p>Obestatin</p> Signup and view all the answers

    What is the primary role of the hypothalamus in metabolic homeostasis?

    <p>To integrate signals for energy balance</p> Signup and view all the answers

    How does long-term obesity affect brain function?

    <p>It leads to a perception of extra weight as the norm.</p> Signup and view all the answers

    Which systems does the CNS utilize to influence energy balance?

    <p>Feeding behaviors and autonomic nervous system activity</p> Signup and view all the answers

    What essential function does the hypothalamus perform in relation to energy stores?

    <p>It maintains constancy of energy stores through feedback loops.</p> Signup and view all the answers

    What happens to energy balance during times of starvation according to the hypothalamus?

    <p>The body uses stored energy while promoting food intake.</p> Signup and view all the answers

    Why is it often difficult for individuals to lose weight after it has been gained?

    <p>The brain perceives the extra weight as a normal state.</p> Signup and view all the answers

    What role do hormones and neuropeptides play in the hypothalamic regulation of body weight?

    <p>They influence energy intake and metabolism.</p> Signup and view all the answers

    What effect do synthetic agonists have on food intake?

    <p>Enhance food intake</p> Signup and view all the answers

    What is the result of deleting MC-4 or MC-3 receptors in mice?

    <p>Obesity</p> Signup and view all the answers

    Which neuropeptide is known for significantly stimulating food intake?

    <p>Neuropeptide Y (NPY)</p> Signup and view all the answers

    What is the function of NPY receptor antagonists?

    <p>Attenuate feeding</p> Signup and view all the answers

    AgRP is an antagonist to which receptors?

    <p>MC3 and MC4</p> Signup and view all the answers

    Which of the following neuropeptides is classified as anorexigenic?

    <p>Leptin</p> Signup and view all the answers

    What is the main outcome of repeated administration of NPY?

    <p>Obesity</p> Signup and view all the answers

    Which brain region contains a significant number of NPY-containing neurons?

    <p>Arcuate nucleus (ARC)</p> Signup and view all the answers

    What effect does intracerebroventricular (ICV) AgRP have on food intake?

    <p>Causes long-lasting hyperphagia</p> Signup and view all the answers

    Which of the following is NOT classified as a neuropeptide?

    <p>Leptin</p> Signup and view all the answers

    Which of the following statements about orexigenic and anorexigenic signals is true?

    <p>Orexigenic signals increase food intake and decrease energy expenditure.</p> Signup and view all the answers

    What role does αMSH (alpha-melanocyte stimulating hormone) play in appetite regulation?

    <p>It inhibits food intake by acting as an anorexigenic signal.</p> Signup and view all the answers

    Which neuropeptide is associated with increasing appetite?

    <p>Neuropeptide Y (NPY)</p> Signup and view all the answers

    How does the hypothalamus respond to the body's nutritional status?

    <p>By sending feedback signals to regulate food intake and energy expenditure.</p> Signup and view all the answers

    What is the primary role of leptin in the body?

    <p>Inhibition of food intake and body weight management</p> Signup and view all the answers

    Long-term regulation of body weight and food intake is influenced by which type of signals?

    <p>Adiposity signals.</p> Signup and view all the answers

    Which hormone is secreted from adipocytes in proportion to fat mass?

    <p>Leptin</p> Signup and view all the answers

    Which hormone decreases during fasting, influencing POMC gene expression?

    <p>αMSH</p> Signup and view all the answers

    Which of the following is NOT an orexigenic signal?

    <p>Leptin</p> Signup and view all the answers

    Which of the following neuropeptides is NOT classified as an orexigenic signal?

    <p>Astrocytic Leptin</p> Signup and view all the answers

    What happens when there is neuron-specific deletion of the leptin receptor?

    <p>Obesity develops</p> Signup and view all the answers

    What effect does ghrelin have on appetite?

    <p>It increases appetite by acting as an orexigenic signal.</p> Signup and view all the answers

    What type of system does leptin use to enter the brain?

    <p>Active transport system</p> Signup and view all the answers

    Which of the following is NOT an anorexigenic factor?

    <p>Ghrelin</p> Signup and view all the answers

    What is one of the biological roles of insulin related to energy management?

    <p>Regulate peripheral glucose homeostasis</p> Signup and view all the answers

    Which hypothalamic region is known to have high levels of leptin receptors?

    <p>ARC (Arcuate Nucleus)</p> Signup and view all the answers

    What occurs with the intracerebroventricular (ICV) administration of insulin in rodent models?

    <p>Inhibition of food intake</p> Signup and view all the answers

    Which of the following roles is associated with leptin besides energy balance?

    <p>Bone maintenance</p> Signup and view all the answers

    How does insulin signal differ in peripheral actions compared to actions in the brain?

    <p>Peripheral actions are opposite to those in the brain</p> Signup and view all the answers

    Study Notes

    Hormonal Regulation of Appetite and Satiety

    • The hypothalamus is crucial in metabolic homeostasis, controlling energy intake and body weight.
    • Neuropeptides and hormones play a vital role in hypothalamic control of these processes.
    • Animal models of obesity are relevant to understanding human obesity.

    Obesity - A Disease of the Brain?

    • Losing weight once gained is challenging due to brain re-programming.
    • Increased body fat alters brain function, influencing the perception of weight as normal.
    • Long-term obesity leads to a form of brain re-programming where the brain defends the new weight.

    Central Control of Energy Intake and Body Weight

    • The central nervous system (CNS) regulates energy balance through behaviour, autonomic nervous system (ANS) activity, and neuroendocrine pathways.
    • Behaviour includes feeding and physical activity.
    • The autonomic nervous system regulates energy expenditure.
    • The neuroendocrine system secretes hormones.
    • The brain, specifically the hypothalamus, integrates these signals to determine the final output (feeding behaviour).

    Part 1: The Hypothalamus

    • The hypothalamus, neuropeptides, hormones, and central signals regulate appetite and satiety.

    Hypothalamus and Obesity

    • Body weight is maintained through a feedback loop to ensure consistent energy stores.
    • The lateral hypothalamus acts as a hunger center, while the ventromedial hypothalamus acts as a satiety center.
    • Lesions in these areas either produce anorexia or obesity respectively.

    Finding Balance

    • The body maintains energy balance through various processes.
    • It stores energy during surplus and utilizes stores when needed, such as during starvation.
    • Promoting food intake when stores are low and discouraging it when stores are full are key to maintaining balance.
    • Orexigenic factors stimulate food intake while anorexigenic factors decrease food intake.

    Hypothalamic Regulation - Appetite and Satiety

    • Feedback regulation processes respond to body nutritional status, modulating food intake and energy expenditure.
    • Short-term signals regulate meal initiation, termination, and frequency between meals.
    • Long-term processes, including adiposity signals, also regulate body weight and food intake.

    Neuropeptides and Obesity

    • There's been a significant surge in understanding hypothalamic regulation of food intake and body weight due to discovered regulatory peptide molecules.
    • These molecules are either orexigenic (stimulate appetite) or anorexigenic (reduce appetite).

    Melanocortins - αMSH

    • αMSH, a melanocyte-stimulating hormone, is formed by cleaving proopiomelanocortin (POMC).
    • POMC gene expression is linked to fasting and positive energy balance.
    • αMSH inhibits food intake.
    • Melanocortin receptors (MC3 and MC4) are key in brain function.

    Neuropeptide Y (NPY)

    • NPY is a highly abundant peptide in the human brain.
    • NPY-containing neurons are found in the arcuate nucleus (ARC).
    • NPY injection into the hypothalamus increases food intake and reduces energy expenditure, leading to obesity when repeatedly administered.
    • NPY receptor antagonists can reduce food intake, potentially reducing obesity.
    • Mice lacking NPY receptors are predisposed to increased susceptibility toward obesity.
    • AgRP co-exists with NPY in ARC neurons.
    • AgRP and Agouti are antagonists to MC3 and MC4 receptors.
    • AgRP injections lead to long-lasting hyperphagia (increased food intake).

    Adiposity Signals - Leptin

    • Leptin is a cytokine released from adipocytes.
    • Leptin levels correlate with fat mass.
    • Leptin has a specific transport system to enter the brain.
    • High levels of leptin receptors are found in the ARC of the hypothalamus.
    • Intravenous (IVC) injections of leptin decrease food intake and reduce body weight in rodents.
    • Neuron-specific deletion of the leptin receptor leads to obesity.

    Biological Roles of Leptin

    • Leptin influences food intake and energy expenditure, also impacting fat deposition.
    • Leptin affects peripheral glucose homeostasis and insulin sensitivity; maintaining the immune and reproductive systems; and angiogenesis, tumorigenesis, and bone formation.

    Adiposity Signals - Insulin

    • Insulin circulates in proportion to adiposity but is secreted from the pancreas.
    • Specialized transport systems carry insulin into the brain.
    • High levels of insulin receptors are found in the hypothalamus, particularly in the ARC.
    • Intravenous (IVC) insulin reduces food intake and body weight.

    Leptin Therapy in DIO

    • Most human diet-induced obesity (DIO) cases are characterized by high leptin levels.
    • Leptin treatment in DIO is often limited by leptin resistance, which is often present in obese individuals.
    • Two main theories explain this resistance: defective leptin transport into the brain or altered signal transduction following leptin binding to its receptor.

    Leptin Resistance and Obesity

    • Leptin receptor (Ob-Rb) activates multiple signaling cascades.
    • These pathways enable leptin to regulate food intake, energy expenditure, peripheral glucose homeostasis, insulin sensitivity, and immune/reproductive function.

    Leptin Resistance and DIO

    • DIO rodent models are used as indicators for human obesity because of their similarity to human obesity.
    • DIO individuals often exhibit hypothalamic and resistance to leptin and insulin, characterized by increased hepatic glucose output and peripheral insulin resistance.
    • This frequently results in resistance to peripheral recombinant leptin treatments.
    • High circulating leptin and leptin resistance are often observed in individuals with diet-induced obesity (DIO).

    Contributors to Hypothalamic Leptin Resistance

    • High calorie intake can elevate leptin levels, but this often leads to leptin resistance and a need to restore leptin sensitivity.
    • Endoplasmic reticulum (ER) stress in the hypothalamus can reduce leptin sensitivity.
    • Chronic low-grade neuroinflammation caused by high calorie intake contributes to leptin resistance.

    Summary - Obesity and the Brain

    • The hypothalamus is crucial in regulating body weight and food intake.
    • Feedback loops modulate food intake and energy expenditure.
    • Adiposity signals originate from adipose tissue and pancreas.
    • Satiety signals emanate from the gastrointestinal (GI) tract to regulate food intake.
    • The brain can become insensitive to leptin and insulin in obesity cases.
    • Rodent models of obesity provide insight into the underlying causes of obesity.

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    Description

    Explore the intricate relationship between hormones, the hypothalamus, and appetite regulation. This quiz delves into how neuropeptides affect energy intake and body weight, and how brain function alters with obesity. Understand the central control mechanisms that govern our energy balance and perception of weight.

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