Psyc 417 Adiposity Signals

Questions

What is leptin and what does it do?

Notes

Insulin

Insulin increases the number of glucose transporter in the cell membranes. This is GLUT-4 transporter. In the liver (GLUT2) and brain (GLUT3) utilize insulin independent transporters for glucose uptake.

Insulin injection increases food intake however insulin infusion in the brain reduces food intake.

Type 1 Diabetes -> no insulin is produced Type 2 Diabetes -> insulin is produced (in less amount) and cells are more resistant.

There is a genetic component to type 2 diabetes. Caucasians and latinos are less prone to type 2 diabetes while asians are prone to type 2 diabetes.

Insulin changes from the environment (food) or internal things (blood glucose levels changing)

Insulin in the brain has many roles: It increases brain development, decreases appetite, decreases hepatic glucose output, increases themogenesis, inscreases cognitive function, increases cognitive function, decreases blood pressure, and increases fertility.

Insulin has different roles because although the receptor is the same, the signal transducion pathway is not the same.

Diabetes

Diabetes treatment is by inhibiting glucose production and/or making cells better at absorbing glucose.

Side effect of diabetes treatment is hypoglycemia.

When blood glucose levels get very low, there are some symptoms, Neurogenic symptoms: Sweating hunger, tingling, tremors, nervousness, anxiety. Neuroglycopenia (blood glucose deprivation): warmth, weakness, drowsiness, seizures, coma, death.

What happens when there are low blood glucose levels

When there is hypoglycemia, the hypothalamus and brain stem sense it.

The sympathetic nervous system stimulates the body to generate glucose faster. It releases cortisol and epinephrine to make the liver produce more glucose and use less glucose.

Vagus nerve tells the pancreas alpha cells to create more glucagon and Beta cells to increase insulin.

During hypoglycemia you want to decrease amounts of insulin in the body, but increase it in the brain.

Leptin

Leptin reduces your appetite, and is produced by white adiposity sites.

Leptin was discovered by the parabiosis (surgical union of animals) in Sprague Dawley rats.

ob/ob is genetically obese, db/db is genetically diabetic. ob/ob in terms of mice means that mice are obese and develop type 2 diabetes because of genes. ob/ob is worse than db/db.

When a db/db mouse is connected with wildtype mouse, the db/db mouse hains more weight and fat. The wildtype mouse decreases food intake, has insulinemia, and decreases blood sugar, it eventually dies from starvation.

When db/db is unioned with ob/ob, the ob/ob mouse has the same effects of the lean mouse, and the diabetic mouse gains weight.

When a ob/ob mouse gets unioned with a lean mouse, the obese mouse decreases food intake, and blood sugar.

When a lean mouse is connected with another lean mouse they both are chilling.

db/db lacks a receptor for leptin and ob/ob lacks leptin.

Leptin is also released by epithelial cells or gastric mucosa.

White adipocytes can become beige adiposites, this happens with cold exposure, they have a lot of mitochondria.

When you are in the cold for 2 hours every day under 66 degrees then you will have more brown adipose tissue. More exercise increases adipose tissue. It also increases when you exercise.

Sympathetic nervous system creases beige adipose tissue.

Leptin in the brain cuases the sympathetic nerve to releases noradrenaline which cuases fat loss. It also stimulates thermogenesis to increases energy expendeture. Less leptin more hunger.

In an exerpeiment with people who naturally lowerer leptin levels, when they are given leptin their body weight drastically decreases and their energy intake stays about the same after a year (it decreases in the short-term). They are eating the same but expending more energy. They are also way more active. Leptin does not increase BMR, but stimulates physical activity.

Leptin can also reduce blood glucose levels without reducing body weight in lean and leptin deficient subjects.

Lipdystrophy is high cholesterol, high blood pressure, fatty liver, hyperflycemia, hyperinsulinemia, insulin resistance, ravenous.

There is a limit to how much fat adipscytes can store, so when they are maxed out, the fats are deposited to other organs and is called ectopic fat. excess fat causes metabolic syndrome.

Because there is a maximum amount of space that adipocytes store, if you genetically engineer them to store unlimited fat then it could be possible for you to be really fat and also "healthy" that you don't have high cholestorle, diabetes, etc.

Obese people are storing their fat in ectopic fat. Ectopic fat is not good for health

There are many leptin receptors but only the long-form leptin receptor causes the majority of the intracellular signal transduction. Short-form letpin receptors pass leptin pass the blood-brain barrier.

Leptin does not change in presence of meal. Leptin can make satiety peptides more potent. This is the same for the volumetric satiety of the stomach.