REGULAÇAO HORMONAL DO METABOLISMO - Bioquímica

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• Sistemas hormonais papel-chave na regulação: 
•Metabolismo; 
•Crescimento; 
•Desenvolvimento; 
•Reprodução e comportamento; 
•Sistema Endócrino - conjunto de células 
especializadas formam glândulas que liberam 
substâncias químicas no sangue  Hormônios 
 
CONCEITOS GERAIS 
ESTRUTURA QUÍMICA 
3 classes de hormônios: 
 
1- proteínas e polipeptídios insulina e glucagon 
2- esteróides cortisol e aldosterona 
3- derivados da tirosina tiroxina e epinefrina 
Hormônios polipeptídicos: armazenados em 
vesículas secretórias até serem necessárias; 
Hormônios esteróides: sintetizados do colesterol, 
não são armazenados são lipossolúveis 
5 
Action of Different Hormones 
Molecular mechanisms 
of signal transduction 
H. Peptídicos: HIDROSSOLÚVEIS; 
 
H. Esteróides e da Tireóide  lipossolúveis 
ligados a proteínas plasmáticas; 
 
Enquanto ligados às proteínas, são inativos; 
Hormônios ligados às proteínas  reservatório. 
 
TRASPORTE NO SANGUE 
•Hormônios com ação rápida - secreção e atuação 
logo depois do estímulo. Ex. Epinefrina 
segundos/minutos 
• Hormônios com ação lenta - precisa meses para 
terem sua função total. Ex. Hormônio do 
Crescimento. 
 
CONCENTRAÇÃO PLASMÁTICA: mínima, na faixa 
microgramas por mL de sangue. 
TEMPO DE SECREÇÃO E AÇÃO 
COMO HORMÔNIOS FUNCIONAM ? 
 
Para ocorrer uma resposta, célula-alvo precisa 
ter RECEPTORES ESPECÍFICOS. 
 
LOCALIZAÇÃO: 
 
Na Superfície de Membrana  H. Peptídicos 
No Citoplasma  H. Esteróides 
No Núcleo  H. Tireóideos. 
 
 
Classes of hormones 
 Endocrine 
 Paracrine 
 Autocrine 
Peptide hormones 
Catecholamine 
hormones 
HO
OH
NH
HO
epinephrine
HO
OH
HO
norepinephrine
HO
HO
catechol
NH2
Eicosanoids 
Steroid hormones 
Vitamin D hormone 
Retinoid hormones 
Thyroid hormones 
H2N I
O
I
OH
I
I
OHO
thyroxine
H2N I
O
I
OH
I
OHO
triiodothyronine
 Nitric oxide (NO) 
23 
Metabolic Profile of Organs 
24 
Key Junctions between Pathways 
Regulation of hormone 
release 
27 
5. Metabolic Profile of the Liver (Glucose) 
Essential for providing fuel to brain, 
muscle, other organs 
 
-> most compounds absorpt by diet 
-> pass through liver -> regulates 
metabolites in blood 
28 
Metabolic Activities of the Liver (Amino Acids) 
α-Ketoacids (derived from 
amino acid degradation) 
-> liver’s own fuel 
 
29 
Metabolic Activities of the Liver (Fatty Acids) 
cannot use acetoacetate as 
fuel -> almost no 
transferase to generate 
acetyl-CoA 
30 
Blood-Glucose 
31 
1. Postabsorptive state 
Glucose + Amino acids -> transport from intestine to blood 
Dietary lipids transported -> lymphatic system -> blood 
Glucose stimulates -> secretion of insulin 
 
Insulin: 
-> signals fed state 
-> stimulates storage of fuels and synthesis of proteins 
-> high level -> glucose enters muscle + adipose tissue (synthesis of TAG) 
-> stimulates glycogen synthesis in muscle + liver 
-> suppresses gluconeogenesis by the liver 
-> accelerates glycolysis in liver -> increases synthesis of fatty acids 
-> accelerates uptake of blood glucose into liver -> glucose 6-phosphate more 
rapidly formed than level of blood glucose rises -> built up of glycogen stores 
32 
Mobilization at Starvation 
Also at not 
treated 
diabetes 
33 
Insulin Secretion –Stimulated by Glucose Uptake 
34 
Postabsorptive State -> after a Meal 
35 
2. Early Fasting State 
Blood-glucose level drops after several hours after the meal -> decrease 
in insulin secretion -> rise in glucagon secretion 
Low blood-glucose level -> stimulates glucagon secretion of α-cells of the 
pancreas 
 
Glucagon: 
-> signals starved state 
-> mobilizes glycogen stores (break down) 
-> inhibits glycogen synthesis 
-> main target organ is liver 
-> inhibits fatty acid synthesis 
-> stimulates gluconeogenesis in liver 
-> large amount of glucose in liver released to blood stream -> maintain 
blood-glucose level 
 
Muscle + Liver use fatty acids as fuel when blood-glucose level drops 
36 
Early Fasting State -> During the Night 
39 
3. Refed State 
Fat is processed in same way as normal fed state 
 
First -> Liver does not absorb glucose from blood (diet) 
Liver still synthesizes glucose to refill liver’s glycogen stores 
 
When liver has refilled glycogen stores + blood-glucose level still rises -> 
liver synthesizes fatty acids from excess glucose 
40 
Prolonged Starvation 
Well-fed 70 kg human -> fuel reserves about 161,000 kcal 
 -> energy needed for a 24 h period -> 1600 kcal - 6000 kcal 
 -> sufficient reserves for starvation up to 1 – 3 months 
 -> however glucose reserves are exhausted in 1 day 
 
Even under starvation -> blood-glucose level must be above 40 mg/100 ml 
http://www.flyfishingdevon.co.uk/salmon/ 
Insulin 
Glucagon 
Hormones that control eating 
Hormones