What are the three main pancreatic islet cell types and their hormones?

Alpha → glucagon; Beta → insulin; Delta → somatostatin

What % of islet cells are beta cells?

~60%

What % of islet cells are alpha cells?

~25%

What % of islet cells are delta cells?

~10%

What is the primary role of insulin?

Anabolic hormone that lowers blood glucose

What is the primary role of glucagon?

Catabolic hormone that increases blood glucose

What is the main stimulus for insulin secretion?

Increased plasma glucose

What other factors increase insulin secretion?

Amino acids, fatty acids, GI hormones, parasympathetic stimulation

What decreases insulin secretion?

Sympathetic stimulation (epinephrine)

What is the overall effect of insulin on metabolism?

↓ glucose, ↓ fatty acids, ↓ amino acids; ↑ protein synthesis; ↑ fuel storage

What happens when plasma glucose increases?

↑ insulin → ↑ glucose uptake (muscle/adipose) + ↓ liver glucose output → normalization

What happens when plasma glucose decreases?

↑ glucagon → ↑ glucose production → normalization

What are the main actions of glucagon on carbohydrates?

↓ glycogenesis; ↑ gluconeogenesis; ↑ glycogenolysis

What are the main actions of glucagon on lipids?

↑ lipolysis; ↓ lipogenesis

What are the main actions of glucagon on protein?

↑ protein degradation (minor)

What stimulates glucagon secretion?

↓ glucose, ↑ amino acids, sympathetic activity, parasympathetic activity

What inhibits glucagon secretion?

High glucose, insulin

What is the relationship between insulin and glucagon?

Opposing hormones maintaining glucose homeostasis

What is somatostatin's role in islets?

Inhibits both insulin and glucagon (paracrine regulation)

What effect does sympathetic stimulation have on pancreas?

↑ glucagon, ↓ insulin

What effect does parasympathetic stimulation have?

↑ insulin, ↑ glucagon

What is proinsulin?

Precursor to insulin

What is C-peptide?

Byproduct of insulin synthesis (weak activity)

What is diabetes mellitus?

Insulin deficiency or glucagon excess → hyperglycemia

What are the 3 cardinal symptoms of diabetes?

Polyuria, polydipsia, polyphagia

What causes polyuria in diabetes?

Osmotic diuresis from glucosuria

What causes polydipsia?

Dehydration

What causes polyphagia?

Cellular glucose deficiency

What are metabolic effects of insulin deficiency on carbohydrates?

↓ glucose uptake, ↑ hepatic glucose output → hyperglycemia

What are metabolic effects on lipids?

↑ lipolysis → ↑ FFA → ketogenesis → metabolic acidosis

What are metabolic effects on protein?

↑ protein breakdown → muscle wasting

What causes diabetic ketoacidosis?

Excess fatty acid breakdown → ketone production → acidosis

What are consequences of hyperglycemia?

Glucosuria, osmotic diuresis, dehydration, renal failure

What is Type 1 diabetes?

Autoimmune destruction of beta cells → little/no insulin

What is Type 2 diabetes?

Insulin resistance (often obesity-related)

What is insulin level in Type 1 diabetes?

Low or absent

What is insulin level in Type 2 diabetes?

Normal or high (initially)

What is the main treatment for Type 1 diabetes?

Insulin injections

What is the main treatment for Type 2 diabetes?

Diet, weight loss, sometimes drugs

What are major complications of diabetes?

CVD, nephropathy, retinopathy, neuropathy, infections

What causes insulin excess?

Tumor, overdose, reactive hypoglycemia

What are symptoms of insulin excess?

Hypoglycemia, sympathetic activation, insulin shock