AMPK in Health and Disease Steinberg, Gregory R; Kemp, Bruce E
Physiological reviews,
07/2009, Letnik:
89, Številka:
3
Journal Article
Recenzirano
Protein Chemistry and Metabolism, St. Vincent's Institute of Medical Research, University of Melbourne, Fitzroy, Victoria, Australia
The function and survival of all organisms is dependent on the ...dynamic control of energy metabolism, when energy demand is matched to energy supply. The AMP-activated protein kinase (AMPK) β heterotrimer has emerged as an important integrator of signals that control energy balance through the regulation of multiple biochemical pathways in all eukaryotes. In this review, we begin with the discovery of the AMPK family and discuss the recent structural studies that have revealed the molecular basis for AMP binding to the enzyme's subunit. AMPK's regulation involves autoinhibitory features and phosphorylation of both the catalytic subunit and the β-targeting subunit. We review the role of AMPK at the cellular level through examination of its many substrates and discuss how it controls cellular energy balance. We look at how AMPK integrates stress responses such as exercise as well as nutrient and hormonal signals to control food intake, energy expenditure, and substrate utilization at the whole body level. Lastly, we review the possible role of AMPK in multiple common diseases and the role of the new age of drugs targeting AMPK signaling.
Brown (BAT) and white (WAT) adipose tissues play distinct roles in maintaining whole-body energy homeostasis, and their dysfunction can contribute to non-alcoholic fatty liver disease (NAFLD) and ...type 2 diabetes. The AMP-activated protein kinase (AMPK) is a cellular energy sensor, but its role in regulating BAT and WAT metabolism is unclear. We generated an inducible model for deletion of the two AMPK β subunits in adipocytes (iβ1β2AKO) and found that iβ1β2AKO mice were cold intolerant and resistant to β-adrenergic activation of BAT and beiging of WAT. BAT from iβ1β2AKO mice had impairments in mitochondrial structure, function, and markers of mitophagy. In response to a high-fat diet, iβ1β2AKO mice more rapidly developed liver steatosis as well as glucose and insulin intolerance. Thus, AMPK in adipocytes is vital for maintaining mitochondrial integrity, responding to pharmacological agents and thermal stress, and protecting against nutrient-overload-induced NAFLD and insulin resistance.
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•Adipocyte AMPK is required for cold and β-adrenergic-stimulated thermogenesis•AMPK is required for the browning of white adipose tissue (beige/brite fat)•AMPK is critical for mitophagy and maintaining BAT mitochondrial quality•Adipocyte AMPK is required to prevent NAFLD and insulin resistance
Mottillo et al. find mice lacking AMPK specifically in adipocytes are intolerant to cold and resistant to β-adrenergic stimulation of brown and beige adipose tissues. These defects, independent of lipolysis, are caused by impaired mitophagy, which results in defective BAT mitochondria, non-alcoholic fatty liver disease, and insulin resistance.
The energy sensor AMP-activated protein kinase (AMPK) is activated by metabolic stress and restores ATP levels in cells by switching off anabolic and switching on catabolic pathways. Recent ...discoveries demonstrate that AMPK is activated primarily by rising ADP levels and not, as previously thought, by AMP. AMPK activation is dependent on ADP-controlled phosphorylation of Thr172 on its activation loop, a mechanism of protein regulation that represents an example of an allosterically regulated modification (ARM). AMPK embodies many features of an adenylate charge regulatory system envisaged by Atkinson, where anabolic and catabolic pathway regulation is modulated by adenine nucleotide ratios. Here we discuss the current state of AMPK regulation by adenine nucleotides and we propose that AMPK functions as an adenylate charge-regulated protein kinase.
The AMP-activated protein kinase (AMPK) activates autophagy, but its role in aging and fasting-induced muscle function has not been defined. Here we report that fasting mice lacking skeletal muscle ...AMPK (AMPK-MKO) results in hypoglycemia and hyperketosis. This is not due to defective fatty acid oxidation, but instead is related to a block in muscle proteolysis that leads to reduced circulating levels of alanine, an essential amino acid required for gluconeogenesis. Markers of muscle autophagy including phosphorylation of Ulk1 Ser555 and Ser757 and aggregation of RFP-LC3 puncta are impaired. Consistent with impaired autophagy, aged AMPK-MKO mice possess a significant myopathy characterized by reduced muscle function, mitochondrial disease, and accumulation of the autophagy/mitophagy proteins p62 and Parkin. These findings establish an essential requirement for skeletal muscle AMPK-mediated autophagy in preserving blood glucose levels during prolonged fasting as well as maintaining muscle integrity and mitochondrial function during aging.
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•Muscle AMPK is required for the induction of autophagy during fasting•AMPK is required for proteolysis to maintain blood glucose during fasting•A loss of AMPK accelerates aging-induced myopathy and mitochondrial dysfunction
Bujak et al. highlight a critical role for the energy sensor AMPK in maintaining glycemia and muscle homeostasis. During fasting, muscle AMPK induces autophagy and muscle protein breakdown to prevent hypoglycemia. With old age, AMPK delays the onset of muscle myopathy and mitochondrial dysfunction.
The adenosine monophosphate (AMP)—activated protein kinase (AMPK) regulates whole-body and cellular energy balance in response to energy demand and supply. AMPK is an αβγ heterotrimer activated by ...decreasing concentrations of adenosine triphosphate (ATP) and increasing AMP concentrations. AMPK activation depends on phosphorylation of the α catalytic subunit on threonine-172 (Thr 172 ) by kinases LKB1 or CaMKKβ, and this is promoted by AMP binding to the γ subunit. AMP sustains activity by inhibiting dephosphorylation of α-Thr 172 , whereas ATP promotes dephosphorylation. Adenosine diphosphate (ADP), like AMP, bound to γ sites 1 and 3 and stimulated α-Thr 172 phosphorylation. However, in contrast to AMP, ADP did not directly activate phosphorylated AMPK. In this way, both ADP/ATP and AMP/ATP ratios contribute to AMPK regulation.
The obesity epidemic has led to an increased incidence of nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes. AMP-activated protein kinase (Ampk) regulates energy homeostasis and is ...activated by cellular stress, hormones and the widely prescribed type 2 diabetes drug metformin. Ampk phosphorylates mouse acetyl-CoA carboxylase 1 (Acc1; refs. 3,4) at Ser79 and Acc2 at Ser212, inhibiting the conversion of acetyl-CoA to malonyl-CoA. The latter metabolite is a precursor in fatty acid synthesis and an allosteric inhibitor of fatty acid transport into mitochondria for oxidation. To test the physiological impact of these phosphorylation events, we generated mice with alanine knock-in mutations in both Acc1 (at Ser79) and Acc2 (at Ser212) (Acc double knock-in, AccDKI). Compared to wild-type mice, these mice have elevated lipogenesis and lower fatty acid oxidation, which contribute to the progression of insulin resistance, glucose intolerance and NAFLD, but not obesity. Notably, AccDKI mice made obese by high-fat feeding are refractory to the lipid-lowering and insulin-sensitizing effects of metformin. These findings establish that inhibitory phosphorylation of Acc by Ampk is essential for the control of lipid metabolism and, in the setting of obesity, for metformin-induced improvements in insulin action.
Metformin is a widely prescribed drug used to treat type-2 diabetes, although recent studies show it has wide ranging effects to treat other diseases. Animal and retrospective human studies indicate ...that Metformin treatment is neuroprotective in Parkinson's Disease (PD), although the neuroprotective mechanism is unknown, numerous studies suggest the beneficial effects on glucose homeostasis may be through AMPK activation. In this study we tested whether or not AMPK activation in dopamine neurons was required for the neuroprotective effects of Metformin in PD. We generated transgenic mice in which AMPK activity in dopamine neurons was ablated by removing AMPK beta 1 and beta 2 subunits from dopamine transporter expressing neurons. These AMPK WT and KO mice were then chronically exposed to Metformin in the drinking water then exposed to MPTP, the mouse model of PD. Chronic Metformin treatment significantly attenuated the MPTP-induced loss of Tyrosine Hydroxylase (TH) neuronal number and volume and TH protein concentration in the nigrostriatal pathway. Additionally, Metformin treatment prevented the MPTP-induced elevation of the DOPAC:DA ratio regardless of genotype. Metformin also prevented MPTP induced gliosis in the Substantia Nigra. These neuroprotective actions were independent of genotype and occurred in both AMPK WT and AMPK KO mice. Overall, our studies suggest that Metformin's neuroprotective effects are not due to AMPK activation in dopaminergic neurons and that more research is required to determine how metformin acts to restrict the development of PD.
Salicylate, a plant product, has been in medicinal use since ancient times. More recently, it has been replaced by synthetic derivatives such as aspirin and salsalate, both of which are rapidly ...broken down to salicylate in vivo. At concentrations reached in plasma after administration of salsalate or of aspirin at high doses, salicylate activates adenosine monophosphate-activated protein kinase (AMPK), a central regulator of cell growth and metabolism. Salicylate binds at the same site as the synthetic activator A-769662 to cause allosteric activation and inhibition of dephosphorylation of the activating phosphorylation site, threonine-172. In AMPK knockout mice, effects of salicylate to increase fat utilization and to lower plasma fatty acids in vivo were lost. Our results suggest that AMPK activation could explain some beneficial effects of salsalate and aspirin in humans.
Choreography of AMPK activation Langendorf, Christopher G; Kemp, Bruce E
Cell research,
01/2015, Letnik:
25, Številka:
1
Journal Article
Recenzirano
Odprti dostop
A recent study published in Cell Research by Li and colleagues reports a detailed biophysical and structural study of AMPK＇s intramolecular interactions during activation. By employing subunit ...tagging and proximity analysis with the aid of AlphaScreen instrumentation, Li et al. add to our understanding of the choreography of activation of AMPK by both nucleotides and phosphorylation.
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