Homeostasia de la glucosa

Homeostasia de
la glucosa
13.4 Gluconeogenesis
• Liver and kidney can synthesize glucose
from noncarbohydrate precursors such as
lactate and alanine
• Under fasting conditions, gluconeogenesis
supplies almost all of the body’s glucose
Ayuno
postprandial
inanición
Homeostasis de la glucosa
Fase I
• Glucosa proveniente de la dieta
Fase II
• Glucogenólisis para mantener [glucosa sanguínea]
Fase III
• Disminuye Glucogenólisis
• Aumenta Gluconeogénesis a partir de lactato
• 20 h de ayuno
Fase IV
• Varios dias de ayuno
• Disminuye Gluconeogénesis
• Aumenta Cuerpos cetónicos como reserva
• Aumenta Gluconeogénesis renal
Fase V
• Oxidación de aácidos grasos
• proteólisis
• Interpretation of fasting plasma
glucose concentration: the normal
level, hyperglycemia, and
hypoglycemia.
INSULINA
Hormona Polipeptídica
Islotes de Langerhans (celulas beta)
Favorece la sintesis de glucógeno, trigliceridos y proteínas.
Síntesis
Vida media de 6 min
RER
Golgi
vesículas
[ATP]
∆ VOLTAJE
Regulación
[INSULINA]
• Glucosa
• Aa
• Incretinas (hormonas gastrointestinales:
colecistocinina-pancreozimina y peptido inhibidor
gástrico, incrementan en respuesta a un
incremento de glucosa en el intestino delgado.
• Disminuye la degradación de TG inh de lipasa.
[INSULINA]
• Ayuno
• Estrés (infecciones, fiebre)
• Inc. De adrenalina
• Mechanisms
of insulin
action.
Regulatory
effects of
insulin on
hepatic and
muscle
carbohydrate
metabolism.
Hormonal Regulation Glucagon
The hormone glucagon is released
from the pancreas into the blood
when blood glucose levels are low.
When glucagon binds to its receptor,
protein kinase A is activated by
cyclic AMP via the adenyl cyclase
signaling pathway. The protein
kinase catalyzes phosphorylation of
the bifunctional enzyme PFK-2,
inhibiting its kinase activity and
stimulating its fructose 2,6bisphosphatase activity. When the
concentration of glucagon is high,
the formation of the potent PFK-1
activator fructose 2,6 bisphosphate
is decreased and its degradation is
increased. As a result, the major
pathway- glycolysis- slows, using
less glucose. Glucagon also signals
the liver to increase both the
synthesis of glucose and the
mobilization of glucose from
glycogen.
*
* Fosfofructocinasa
• Metabolic
effects of
glucagon.
Glucagon
mobilizes
glucose from
every available
source; it also
increases
lipolysis, and
ketogenesis
from acetylCoA