Chapter 22b
Metabolism and Energy Balance
Figure 22-8a
Homeostatic Control of Metabolism
• Endocrine pancreas secretes hormones insulin and glucagon. These control blood sugar.
Figure 22-8b
Homeostatic Control of Metabolism
Homeostatic Control of Metabolism• In the fed state, high levels of plasma glucose and amino
acids result in the secretion of insulin.
• Note effects of insulin √
Figure 22-9a
Figure 22-9b
Homeostatic Control of Metabolism
• In the fasting state, low plasma glucose results in the secretion of glucagon
• Note effects of glucagon √
Homeostatic Control of Metabolism
• Levels of glucose, glucagon, and insulin vary over a typical 24-hour period
Figure 22-10
Factors That Control Insulin Secretion
1 - Increased plasma glucose2 - Increased plasma amino acids3 - Feedforward effects of GI hormones4 - Parasympathetic activity5 - Sympathetic activity
Insulin Promotes Anabolism
• Increases glucose transport into most, but not all, insulin-sensitive cells
• Enhances cellular utilization and storage of glucose
• Enhances utilization of amino acids• Promotes fat synthesis
Figure 22-12a
Glucose Uptake by Adipose Tissue and Resting Skeletal Muscle is Insulin-Sensitive
• In the absence of insulin, glucose cannot enter cell
Figure 22-12b
Insulin Enables Glucose Uptake by Adipose Tissue and Resting Skeletal Muscle
• Insulin signals the cell
Insulin Indirectly Alters Glucose Transport in Hepatocytes
• Hepatocyte in fed state
Figure 22-13a
Figure 22-13b
Insulin Indirectly Alters Glucose Transport in Hepatocytes
• Hepatocyte in fasted state
Fed State: Insulin is an Anabolic Hormone
• Insulin promotes• Glucose uptake• Glucose
metabolism• Energy storage
as glycogen and fat
Figure 22-14
Plasmaglucose
cellsof pancreas
cellsof pancreas
Insulin
GlycolysisGlycogenesisLipogenesis
Muscle, adipose,and other cells
Plasmaglucose
Negativefeedback
Liver
Glucose transport
Stimulus Integrating centerEfferent pathEffectorTissue responseSystemic response
KEY
Glucagon Is Dominant in the Fasted State
• Glucagon is anatgonistic to most actions of insulin, resulting in a catabolic state in the body
Figure 22-9b
Endocrine Response to Hypoglycemia
Figure 22-15
Diabetes Mellitus is a Family of Diseases
• Diabetes mellitus is a condition characterized by chronic elevated plasma glucose levels, or hyperglycemia
• Diabetes is reaching epidemic proportions in the USA
• Complications of diabetes affect many body systems
• The two types of diabetes are• Type 1 - characterized by insulin deficiency• Type 2 - known as insulin-resistant diabetes
(cells cannot respond to the insulin in the body)
Plasmafatty acids
VentilationMetabolicacidosis
Tissueloss
Substrate forATP production
Urineacidification
andhyperkalemia
Fatbreakdown
Fatstorage
Plasmafatty acids
Mealabsorbed
Plasmaglucose
Liver
Ketoneproduction
GlycogenolysisGluconeogenesis
Glucose uptake(muscle and adipose)
Substratefor ATP
production
Plasmaamino acids
Plasmaamino acids
Amino aciduptake bymost cells
Brain interpretsas starvation
PolyphagiaHyperglycemia
Glucosuria
Exceeds renalthreshold for glucose
Osmotic diuresisand polyuria
Glucose utilization
No insulin released
Circulatoryfailure
Coma ordeath
Blood volume andBlood pressureLactic acidproduction
Anaerobicmetabolism
Dehydration
Polydipsia
Attempted compensationby cardiovascular
control center
Thirst
ADH secretion
compensationfails
Tissueloss
Protein breakdown,
especially muscle
FAT METABOLISM GLUCOSE METABOLISM PROTEIN METABOLISM
DEHYDRATIONMETABOLIC ACIDOSIS
ACUTE PATHOPHYSIOLOGY OF TYPE 1 DIABETES MELLITUS
Acute Pathophysiology of Type 1 Diabetes Mellitus
• Overview• See pages
743 - 745
Figure 22-16
Plasmafatty acids
Mealabsorbed
Plasmaglucose
Plasmaamino acids
FAT METABOLISM GLUCOSE METABOLISM PROTEIN METABOLISM
ACUTE PATHOPHYSIOLOGY OF TYPE 1 DIABETES MELLITUS
Figure 22-16 (1 of 8)
Acute Pathophysiology of Type 1 Diabetes Mellitus
1 - Absorption of nutrients is normal
Plasmafatty acids
Mealabsorbed
Plasmaglucose
Liver
Substratefor ATP
production
Plasmaamino acids
Plasmaamino acids
Amino aciduptake bymost cells
No insulin released
Tissueloss
Protein breakdown,
especially muscle
FAT METABOLISM GLUCOSE METABOLISM PROTEIN METABOLISM
ACUTE PATHOPHYSIOLOGY OF TYPE 1 DIABETES MELLITUS
Figure 22-16 (2 of 8)
Acute Pathophysiology of Type 1 Diabetes Mellitus
2a (protein) - Most cells unable to absorb nutrients shift to fasted state metabolism
Plasmafatty acids
Tissueloss
Substrate forATP production
Fatbreakdown
Fatstorage
Plasmafatty acids
Mealabsorbed
Plasmaglucose
Liver
Ketoneproduction
Substratefor ATP
production
Plasmaamino acids
Plasmaamino acids
Amino aciduptake bymost cells
No insulin released
Tissueloss
Protein breakdown,
especially muscle
FAT METABOLISM GLUCOSE METABOLISM PROTEIN METABOLISM
ACUTE PATHOPHYSIOLOGY OF TYPE 1 DIABETES MELLITUS
Figure 22-16 (3 of 8)
Acute Pathophysiology of Type 1 Diabetes Mellitus
2b (fat) - Most cells unable to absorb nutrients shift to fasted state metabolism
Plasmafatty acids
Tissueloss
Substrate forATP production
Fatbreakdown
Fatstorage
Plasmafatty acids
Mealabsorbed
Plasmaglucose
Liver
Ketoneproduction
GlycogenolysisGluconeogenesis
Glucose uptake(muscle and adipose)
Substratefor ATP
production
Plasmaamino acids
Plasmaamino acids
Amino aciduptake bymost cells
Hyperglycemia
Glucose utilization
No insulin released
Tissueloss
Protein breakdown,
especially muscle
FAT METABOLISM GLUCOSE METABOLISM PROTEIN METABOLISM
ACUTE PATHOPHYSIOLOGY OF TYPE 1 DIABETES MELLITUS
Figure 22-16 (4 of 8)
Acute Pathophysiology of Type 1 Diabetes Mellitus
3 - Hyperglycemia results when liver cells also shift to the fasted state, and produce more glucose!
Plasmafatty acids
Tissueloss
Substrate forATP production
Fatbreakdown
Fatstorage
Plasmafatty acids
Mealabsorbed
Plasmaglucose
Liver
Ketoneproduction
GlycogenolysisGluconeogenesis
Glucose uptake(muscle and adipose)
Substratefor ATP
production
Plasmaamino acids
Plasmaamino acids
Amino aciduptake bymost cells
Brain interpretsas starvation
PolyphagiaHyperglycemia
Glucose utilization
No insulin released
Tissueloss
Protein breakdown,
especially muscle
FAT METABOLISM GLUCOSE METABOLISM PROTEIN METABOLISM
ACUTE PATHOPHYSIOLOGY OF TYPE 1 DIABETES MELLITUS
Figure 22-16 (5 of 8)
Acute Pathophysiology of Type 1 Diabetes Mellitus
3b – More glucose results in polyphagia
Plasmafatty acids
Tissueloss
Substrate forATP production
Fatbreakdown
Fatstorage
Plasmafatty acids
Mealabsorbed
Plasmaglucose
Liver
Ketoneproduction
GlycogenolysisGluconeogenesis
Glucose uptake(muscle and adipose)
Substratefor ATP
production
Plasmaamino acids
Plasmaamino acids
Amino aciduptake bymost cells
Brain interpretsas starvation
PolyphagiaHyperglycemia
Glucosuria
Exceeds renalthreshold for glucose
Osmotic diuresisand polyuria
Glucose utilization
No insulin released
Tissueloss
Protein breakdown,
especially muscle
FAT METABOLISM GLUCOSE METABOLISM PROTEIN METABOLISM
ACUTE PATHOPHYSIOLOGY OF TYPE 1 DIABETES MELLITUS
Figure 22-16 (6 of 8)
Acute Pathophysiology of Type 1 Diabetes Mellitus
4a - Hyperglycemia results in glucose in the urine and increased urine production
Plasmafatty acids
Tissueloss
Substrate forATP production
Fatbreakdown
Fatstorage
Plasmafatty acids
Mealabsorbed
Plasmaglucose
Liver
Ketoneproduction
GlycogenolysisGluconeogenesis
Glucose uptake(muscle and adipose)
Substratefor ATP
production
Plasmaamino acids
Plasmaamino acids
Amino aciduptake bymost cells
Brain interpretsas starvation
PolyphagiaHyperglycemia
Glucosuria
Exceeds renalthreshold for glucose
Osmotic diuresisand polyuria
Glucose utilization
No insulin released
Blood volume andBlood pressure
Dehydration
Polydipsia
Attempted compensationby cardiovascular
control center
Thirst
ADH secretion
Tissueloss
Protein breakdown,
especially muscle
FAT METABOLISM GLUCOSE METABOLISM PROTEIN METABOLISM
DEHYDRATION
ACUTE PATHOPHYSIOLOGY OF TYPE 1 DIABETES MELLITUS
Figure 22-16 (7 of 8)
Acute Pathophysiology of Type 1 Diabetes Mellitus
4b – And then low blood pressure as a result of dehydration
Plasmafatty acids
VentilationMetabolicacidosis
Tissueloss
Substrate forATP production
Urineacidification
andhyperkalemia
Fatbreakdown
Fatstorage
Plasmafatty acids
Mealabsorbed
Plasmaglucose
Liver
Ketoneproduction
GlycogenolysisGluconeogenesis
Glucose uptake(muscle and adipose)
Substratefor ATP
production
Plasmaamino acids
Plasmaamino acids
Amino aciduptake bymost cells
Brain interpretsas starvation
PolyphagiaHyperglycemia
Glucosuria
Exceeds renalthreshold for glucose
Osmotic diuresisand polyuria
Glucose utilization
No insulin released
Circulatoryfailure
Coma ordeath
Blood volume andBlood pressureLactic acidproduction
Anaerobicmetabolism
Dehydration
Polydipsia
Attempted compensationby cardiovascular
control center
Thirst
ADH secretion
compensationfails
Tissueloss
Protein breakdown,
especially muscle
FAT METABOLISM GLUCOSE METABOLISM PROTEIN METABOLISM
DEHYDRATIONMETABOLIC ACIDOSIS
ACUTE PATHOPHYSIOLOGY OF TYPE 1 DIABETES MELLITUS
Figure 22-16 (8 of 8)
Acute Pathophysiology of Type 1 Diabetes Mellitus
5 - Metabolic acidosis results, which if untreated can lead to coma and/or death
Type 2 Diabetes
• Accounts for 90% of all diabetics• Insulin resistance (target cells do not respond
normally)• Early symptoms are mild, but later
complications include atherosclerosis, neurological changes, renal failure, and blindness
• Therapy• Diet and physical exercise• Drugs
Glucose Tolerance Test
Figure 22-17
Drugs Attempt to Treat Diabetes by Varying Mechanisms
Table 22-6
Metabolic Syndrome - Insulin resistance syndrome
• Patients have combined symptoms of type 2 diabetes, atherosclerosis, and high blood pressure
• Diagnostic criteria - three or more of• Central (visceral) obesity• Blood pressure ≥ 130/85 mm Hg• Fasting blood glucose ≥ 110 mg/dL• Elevated fasting plasma triglyceride levels• Low plasma HDL-C levels
Fats
• Assembled into chylomicrons in SI lining• Into lymphatics to blood to liver• Liver processes into lipoproteins LDL’s• LDL’s to cells for use in synthesis of cholesterol• Likely leads to atherosclerosis
• HDL’s depleted of cholesterol tend to return to liver for processing into bile for excretion – lowers cholesterol
• HMG coA reductase inhibitors – Big $$• statins – lipitor lovastatin also other cholesterol
treatments: fibrates and niacin
Fat catabolism• Ketosis• Excessive leads to metabolic acidosis• FA catabolized into ketone bodies two carbons
at a time – ß - oxidation
Body Temperature: Energy Balance in the Body
Figure 22-18
DIET• Hunger/appetite• Satiety• Social and
psychologicalfactors
ENERGY INPUT ENERGY OUTPUT
HEAT (~50%) • Unregulated • Thermoregulation
WORK (~50%)• Transport across membranes • Mechanical work Movement• Chemical work
• Synthesis for growth andmaintenance
• Energy storage• High-energy phosphate
bonds (ATP,phosphocreatine)
• Chemical bonds(glycogen, fat)
Radiation
Body heatConduction Conduction
Convection
Internalheat
production
Frommetabolism
From musclecontraction
Regulated processesfor temperature homeostasis
Shiveringthermogenesis
“Wasteheat”
“Wasteheat”
? Nonshiveringthermogenesis
Radiation
Evaporation
EXTERNAL HEAT INPUT + INTERNAL HEAT PRODUCTION = HEAT LOSS
heat lossheat input
Body Temperature: Heat Balance in the Body
Figure 22-19
heat production
Body Temperature: Thermoregulatory Reflexes
Figure 22-20 (1 of 2)
Body Temperature: Thermoregulatory Reflexes
Figure 22-20 (2 of 2)
Mechanisms of Body Temperature Regulation
• Neural control of cutaneous blood flow alters heat loss through the skin
• Sweat contributes to heat loss• Heat production• Voluntary muscle contraction and normal
metabolism• Regulated heat production• Shivering versus nonshivering thermogenesis
Homeostatic Responses to High Temperature
Figure 22-21 (1 of 2)
Homeostatic Responses to Low Temperature
Figure 22-21 (2 of 2)
Regulation of Body Temperature
• Our hypothalamic thermostat can be reset• Typical physiological variations• Fever occurs when pyrogens reset the thermostat
• Pathological cases of altered body temperature• Hyperthermia - compare
• Heat exhaustion• Heat stroke
• Heat exhaustion is characterized by significant sweating, loss of color, cramps, fatigue, fainting and dizziness.
• Heat stroke symptoms include a body temperature over 103, dry skin, high heart rate, confusion and even unconsciousness
• Malignant hyperthermia• Hypothermia
• Diving reflex √
Summary
• Appetite and Satiety• Feeding and satiety centers, glucostatic versus
lipostatic theories, regulation of food intake by numerous regulatory peptides
• Energy Balance• Definition of energy balance, bodily uses for
energy, direct calorimetry, oxygen consumption, RQ, RER, BMR, diet-induced thermogenesis, glycogen and fat as two major forms of stored energy
Summary
• Metabolism• Anabolic pathways versus catabolic pathways,
fed state versus fasted state, glycogenesis, glycogenolysis, and gluconeogenesis
• Chylomicrons, lipoprotein lipase, apoproteins A and B, LDL-C, risks factors for heart disease, beta oxidation and ketone bodies
Summary
• Homeostatic Control of Metabolism• Ratio of insulin to glucagon, Islets of
Langerhans, insulin-receptor substrates, major targets and effects of insulin, glucagon and the fasted state, diabetes mellitus, and metabolic syndrome
• Regulation of body temperature• Hypothalamic thermostat, routes and
mechanisms of heat loss, shivering thermogenesis and nonshivering thermogenesis