Obesity and Insulin Resistance Regulation

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Questions and Answers

Which hormone released from adipose tissue decreases appetite?

Neuropeptide Y

Leptin (correct)

Ghrelin

Adiponectin

What is the effect of adiponectin on organs?

Has no effect on organs

Increases glucose synthesis in liver

Makes organs more resistant to insulin

Makes organs more sensitive to insulin (correct)

What happens to lipids when peripheral organs can't store more fat?

They are stored in muscle

They are released into the bloodstream

They are stored in liver

They enter in non-oxidative pathways and produce reactive toxic lipid species (correct)

What is the function of ɑ-melanocyte-stimulating hormone?

Appetite suppression Signup and view all the answers

What is the result of an imbalance in food intake and energy expenditure?

Increase in body weight and obesity Signup and view all the answers

What is the effect of leptin and insulin on Neuropeptide Y?

They inhibit its release Signup and view all the answers

What is the effect of adipokines on fuel metabolism and feeding behavior?

They produce changes in fuel metabolism and feeding behavior so that there is reestablished adequate fuel reserves and maintain body mass Signup and view all the answers

What is the effect of the gut microbiome on metabolism and body mass?

It functions as big endocrine glands affecting metabolism, feeding behavior and body mass Signup and view all the answers

Where does glyceroneogenesis primarily take place?

In adipose tissue and liver Signup and view all the answers

What is the primary function of the carnitine-acylcarnitine shuttle?

To transport fatty acids with +14 carbons into the mitochondria Signup and view all the answers

What is the first step of fatty acid oxidation?

Lipolysis of TAGs into fatty acids and glycerol Signup and view all the answers

What is the byproduct of beta-oxidation of fatty acids?

NADH+H+ and FADH2 Signup and view all the answers

What triggers the mobilization of stored TAGs in adipocytes?

Hormones glucagon and epinephrine Signup and view all the answers

What is the product of glycerol utilization in adipose tissue?

Glycerol-3-phosphate Signup and view all the answers

What is the recommended treatment for fructose-induced liver disease?

Total elimination of fructose from the diet Signup and view all the answers

What is the primary function of white adipose tissue?

TAGs storage and release Signup and view all the answers

Which type of lipid is synthesized in the body?

All of the above Signup and view all the answers

What is the primary function of brown adipose tissue?

Thermogenesis Signup and view all the answers

What is the role of lipids in the body?

Multiple functions, including energy storage, cell membrane structure, and signaling molecules Signup and view all the answers

Where are fatty acids absorbed in the body?

Small intestine Signup and view all the answers

What is the characteristic of white adipose tissue cells?

Large cells with one lipid droplet Signup and view all the answers

What is the location of brown adipose tissue?

Around kidneys, spine, and other vital organs Signup and view all the answers

Study Notes

Regulators of Obesity and Insulin Resistance

Imbalance in food intake and energy expenditure leads to increase in body weight and obesity
When storage capacity of WAT becomes saturated, fat accumulates in peripheral organs
Excess lipids in non-oxidative pathways result in production of reactive toxic lipid species, leading to tissue-specific damage and lipotoxicity

Adipose Tissue as an Endocrine Organ

Adipose tissue releases hormones called adipokines
Adipokines:
- Carry information to the brain about fuel stores and other tissues
- Leptin and adiponectin are adipokines
- Regulate fuel metabolism and feeding behavior to maintain body mass
- Imbalance can result in life-threatening diseases

Key Hormones Regulating Energy Balance

Leptin:
- Appetite-suppressing hormone
- Sent from adipose tissue to the brain
- Decreases appetite
Neuropeptide Y:
- Orexigenic hormone (appetite-stimulating hormone)
- Sends signals to eat
- Levels rise during starvation
- Inhibited by leptin and insulin
ɑ-melanocyte-stimulating hormone:
- Anorexigenic hormone (appetite-suppressing hormone)
- Sends signals to stop eating
- Release stimulated by leptin and insulin
Ghrelin:
- Short-term orexigenic hormone secreted in the stomach
- Increases hunger
- Associated with Prader-Willi syndrome

Adiponectin and PPARs

Adiponectin:
- Made by adipose tissue
- Increases insulin sensitivity in organs
- Affects fatty acid metabolism and carbohydrate metabolism in liver and muscle
PPARs (peroxisome proliferator-activated receptors):
- Alter gene expression for fat and carbohydrate metabolism
- PPARɣ, PPARɑ, PPARδ

Microbiome and Obesity

Microbiome in the gut influences obesity
Microbes function as endocrine glands affecting metabolism, feeding behavior, and body mass
Obese and lean individuals have different gut microbial flora

Type 1 Diabetes

Caused by autoimmune reaction where the body's immune system attacks insulin-producing beta-cells in the pancreas

Glycerol and Glyceroneogenesis

Glycerol from fats enters either gluconeogenesis or glycolysis
Glyceroneogenesis:
- Abbreviated version of gluconeogenesis in liver and adipose tissue
- Uses pyruvate, alanine, glutamine, or other substances from the CAC as precursors for glycerol-3-phosphate

Carnitine-Acylcarnitine Shuttle

Transports fatty acids with +14 carbons
Acyl-carnitine/carnitine transporter belongs to group E7 enzyme class
Requires 2 ATPs

Catabolism of Fatty Acids

Lipolysis:
- Place of action: TAGs in adipocytes, in the cells cytosol and lipid droplets
- Hormones glucagon and epinephrine trigger mobilization of stored TAGs
- Lipases cleave fatty acids from the glycerol backbone of TAGs
Fatty acid oxidation divided into 3 stages:
1. Oxidative conversion of two-carbon units into acetyl-CoA via beta-oxidation
2. Oxidation of acetyl-CoA into CO2 through the CAC
3. Repeated ingestion of fructose can lead to liver disease, kidney disease (treatment: total elimination of fructose from the diet)

Lipids

Functions:
- Energy storage
- Cell membrane structure
- Cofactors for enzymes
- Signaling molecules
- Steroid hormone synthesis
- Antioxidants
- Pigments
- Insulation
- Protection
- Fat-soluble vitamin transport and absorption
Types of lipids found in food and synthesized by the body:
- TAGs
- Cholesterol
- Phospholipids
- Free fatty acids
- White adipose tissue (WAT) and brown adipose tissue (BAT)
Characteristics of WAT and BAT:
- WAT: large spherical cells, function in fuel storage and release
- BAT: smaller cells, multiple lipid droplets, function in thermogenesis

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Description

This quiz covers the major regulators of obesity and insulin resistance, including the imbalance of food intake and energy expenditure, and the consequences of excess lipid storage in peripheral organs.