The phosphorylation of AMPKß1 is critical for increasing autophagy and maintaining mitochondrial homeostasis in response to fatty acids.

Fatty acids are vital for the survival of eukaryotes, but when present in excess can have deleterious consequences. The AMP-activated protein kinase (AMPK) is an important regulator of multiple branches of metabolism. Studies in purified enzyme preparations and cultured cells have shown that AMPK is allosterically activated by small molecules as well as fatty acyl-CoAs through a mechanism involving Ser108 within the regulatory AMPK ß1 isoform. However, the in vivo physiological significance of this residue has not been evaluated. In the current study, we generated mice with a targeted germline knock-in (KI) mutation of AMPKß1 Ser108 to Ala (S108A-KI), which renders the site phospho-deficient. S108A-KI mice had reduced AMPK activity (50 to 75%) in the liver but not in the skeletal muscle. On a chow diet, S108A-KI mice had impairments in exogenous lipid-induced fatty acid oxidation. Studies in mice fed a high-fat diet found that S108A-KI mice had a tendency for greater glucose intolerance and elevated liver triglycerides. Consistent with increased liver triglycerides, livers of S108A-KI mice had reductions in mitochondrial content and respiration that were accompanied by enlarged mitochondria, suggestive of impairments in mitophagy. Subsequent studies in primary hepatocytes found that S108A-KI mice had reductions in palmitate- stimulated Cpt1a and Ppargc1a mRNA, ULK1 phosphorylation and autophagic/mitophagic flux. These data demonstrate an important physiological role of AMPKß1 Ser108 phosphorylation in promoting fatty acid oxidation, mitochondrial biogenesis and autophagy under conditions of high lipid availability. As both ketogenic diets and intermittent fasting increase circulating free fatty acid levels, AMPK activity, mitochondrial biogenesis, and mitophagy, these data suggest a potential unifying mechanism which may be important in mediating these effects.

Inhibition of ATP-citrate lyase improves NASH, liver fibrosis, and dyslipidemia.

Elevated liver de novo lipogenesis contributes to non-alcoholic steatohepatitis (NASH) and can be inhibited by targeting acetyl-CoA carboxylase (ACC). However, hypertriglyceridemia limits the use of pharmacological ACC inhibitors as a monotherapy. ATP-citrate lyase (ACLY) generates acetyl-CoA and oxaloacetate from citrate, but whether inhibition is effective for treating NASH is unknown. Here, we characterize a new mouse model that replicates many of the pathological and molecular drivers of NASH and find that genetically inhibiting ACLY in hepatocytes reduces liver malonyl-CoA, oxaloacetate, steatosis, and ballooning as well as blood glucose, triglycerides, and cholesterol. Pharmacological inhibition of ACLY mirrors genetic inhibition but has additional positive effects on hepatic stellate cells, liver inflammation, and fibrosis. Mendelian randomization of human variants that mimic reductions in ACLY also associate with lower circulating triglycerides and biomarkers of NASH. These data indicate that inhibiting liver ACLY may be an effective approach for treatment of NASH and dyslipidemia.

Monitoring the transition of patients on biologics in rheumatoid arthritis: Consensus guidance for pharmacists.

BACKGROUND: Recent approvals for novel agents such as the small molecule Janus kinase inhibitors (JAKi), combined with the advent of biosimilars has widened the gamut of available therapeutic options in the treatment of rheumatoid arthritis (RA). This combined with the introduction of mandatory non- medical switches to biosimilars in some jurisdictions by both public and private payors has led to a significant increase in the volume of therapeutic changes for patients. Pharmacists are well positioned to ensure effective and safe transitions, however there is a significant unmet need for objective and subjective clinical guidance around therapy as well disease state monitoring in RA that facilitates best practices throughout the patient journey. OBJECTIVE: In this paper we aim to create a consensus derived monitoring algorithm for pharmacists to facilitate best practices throughout therapeutic transitions from originator biologic to other originator biologics, biosimilars, and Janus kinase inhibitors in RA. METHODS: The Nominal Group Technique (NGT) was used to understand if consensus could be found among the participants. Clinically relevant questions were developed to capture solutions to the identified unmet need. The faculty considered the questions as individuals, and privately generated answers/ideas. After discussion and consideration, the participants ranked the ideas and established a consensus. RESULTS: Based on the outcome of the consensus discussions, an algorithm was created to help guide pharmacists through therapeutic transitions in RA. The tool covers important topics such as pre-transition considerations, avoiding the nocebo effect for biosimilars, specific considerations for each drug or class, monitoring efficacy, and when to refer. CONCLUSIONS: New classes of anti-rheumatic drugs including JAKi, along with the introduction of biosimilars are presenting more opportunity for therapeutic changes and monitoring in patients with RA. We hope our evidence-based consensus derived guidance tool will assist frontline pharmacists in supporting their patients to a successful therapeutic transition in RA.

The pesticide chlorpyrifos promotes obesity by inhibiting diet-induced thermogenesis in brown adipose tissue.

Obesity results from a caloric imbalance between energy intake, absorption and expenditure. In both rodents and humans, diet-induced thermogenesis contributes to energy expenditure and involves the activation of brown adipose tissue (BAT). We hypothesize that environmental toxicants commonly used as food additives or pesticides might reduce BAT thermogenesis through suppression of uncoupling protein 1 (UCP1) and this may contribute to the development of obesity. Using a step-wise screening approach, we discover that the organophosphate insecticide chlorpyrifos suppresses UCP1 and mitochondrial respiration in BAT at concentrations as low as 1 pM. In mice housed at thermoneutrality and fed a high-fat diet, chlorpyrifos impairs BAT mitochondrial function and diet-induced thermogenesis, promoting greater obesity, non-alcoholic fatty liver disease (NAFLD) and insulin resistance. This is associated with reductions in cAMP; activation of p38MAPK and AMPK; protein kinases critical for maintaining UCP1 and mitophagy, respectively in BAT. These data indicate that the commonly used pesticide chlorpyrifos, suppresses diet-induced thermogenesis and the activation of BAT, suggesting its use may contribute to the obesity epidemic.

Salsalate reduces atherosclerosis through AMPKß1 in mice.

OBJECTIVE: Salsalate is a prodrug of salicylate that lowers blood glucose in people with type 2 diabetes. AMP-activated protein kinase (AMPK) is an αßγ heterotrimer which inhibits macrophage inflammation and the synthesis of fatty acids and cholesterol in the liver through phosphorylation of acetyl-CoA carboxylase (ACC) and HMG-CoA reductase (HMGCR), respectively. Salicylate binds to and activates AMPKß1-containing heterotrimers that are highly expressed in both macrophages and liver, but the potential importance of AMPK and ability of salsalate to reduce atherosclerosis have not been evaluated. METHODS: ApoE-/- and LDLr-/- mice with or without (-/-) germline or bone marrow AMPKß1, respectively, were treated with salsalate, and atherosclerotic plaque size was evaluated in serial sections of the aortic root. Studies examining the effects of salicylate on markers of inflammation, fatty acid and cholesterol synthesis and proliferation were conducted in bone marrow-derived macrophages (BMDMs) from wild-type mice or mice lacking AMPKß1 or the key AMPK-inhibitory phosphorylation sites on ACC (ACC knock-in (KI)-ACC KI) or HMGCR (HMGCR-KI). RESULTS: Salsalate reduced atherosclerotic plaques in the aortic roots of ApoE-/- mice, but not ApoE-/- AMPKß1-/- mice. Similarly, salsalate reduced atherosclerosis in LDLr-/- mice receiving wild-type but not AMPKß1-/- bone marrow. Reductions in atherosclerosis by salsalate were associated with reduced macrophage proliferation, reduced plaque lipid content and reduced serum cholesterol. In BMDMs, this suppression of proliferation by salicylate required phosphorylation of HMGCR and the suppression of cholesterol synthesis. CONCLUSIONS: These data indicate that salsalate suppresses macrophage proliferation and atherosclerosis through an AMPKß1-dependent pathway, which may involve HMGCR phosphorylation and cholesterol synthesis. Since rapidly-proliferating macrophages are a hallmark of atherosclerosis, these data indicate further evaluation of salsalate as a potential therapeutic agent for treating atherosclerotic cardiovascular disease.

Consensus recommendations on dosing and administration of medical cannabis to treat chronic pain: results of a modified Delphi process.

BACKGROUND: Globally, medical cannabis legalization has increased in recent years and medical cannabis is commonly used to treat chronic pain. However, there are few randomized control trials studying medical cannabis indicating expert guidance on how to dose and administer medical cannabis safely and effectively is needed. METHODS: Using a multistage modified Delphi process, twenty global experts across nine countries developed consensus-based recommendations on how to dose and administer medical cannabis in patients with chronic pain. RESULTS: There was consensus that medical cannabis may be considered for patients experiencing neuropathic, inflammatory, nociplastic, and mixed pain. Three treatment protocols were developed. A routine protocol where the clinician initiates the patient on a CBD-predominant variety at a dose of 5 mg CBD twice daily and titrates the CBD-predominant dose by 10 mg every 2 to 3 days until the patient reaches their goals, or up to 40 mg/day. At a CBD-predominant dose of 40 mg/day, clinicians may consider adding THC at 2.5 mg and titrate by 2.5 mg every 2 to 7 days until a maximum daily dose of 40 mg/day of THC. A conservative protocol where the clinician initiates the patient on a CBD-predominant variety at a dose of 5 mg once daily and titrates the CBD-predominant dose by 10 mg every 2 to 3 days until the patient reaches their goals, or up to 40 mg/day. At a CBD-predominant dose of 40 mg/day, clinicians may consider adding THC at 1 mg/day and titrate by 1 mg every 7 days until a maximum daily dose of 40 mg/day of THC. A rapid protocol where the clinician initiates the patient on a balanced THC:CBD variety at 2.5-5 mg of each cannabinoid once or twice daily and titrates by 2.5-5 mg of each cannabinoid every 2 to 3 days until the patient reaches his/her goals or to a maximum THC dose of 40 mg/day. CONCLUSIONS: In summary, using a modified Delphi process, expert consensus-based recommendations were developed on how to dose and administer medical cannabis for the treatment of patients with chronic pain.

Sevoflurane-induced hyperglycemia is attenuated by salsalate in obese insulin-resistant mice.

PURPOSE: Perioperative hyperglycemia is common and is associated with significant morbidity. Although patient characteristics and surgery influence perioperative glucose metabolism, anesthetics have a significant impact. We hypothesized that mice that were obese and insulin-resistant would experience greater hyperglycemia in response to sevoflurane anesthesia compared with lean controls. We further hypothesized that sevoflurane-induced hyperglycemia would be attenuated by salsalate pre-treatment. METHODS: Lean and obese male C57BL/6J mice were anesthetized with sevoflurane for 60 min with or without pre-treatment of 62.5 mg·kg-1 salsalate. Blood glucose, plasma insulin, and glucose uptake into different tissues were measured. RESULTS: Under sevoflurane anesthesia, obese mice had higher blood glucose compared to lean mice. Increases in blood glucose were attenuated with acute salsalate pre-treatment at 60 min under anesthesia in obese mice (mean ± standard error of the mean [SEM], delta blood glucose; vehicle 5.79 ± 1.09 vs salsalate 1.91 ± 1.32 mM; P = 0.04) but did not reach statistical significance in lean mice (delta blood glucose, vehicle 4.39 ± 0.55 vs salsalate 2.79 ± 0.71 mM; P = 0.10). This effect was independent of changes in insulin but associated with an approx. 1.7-fold increase in glucose uptake into brown adipose tissue (vehicle 45.28 ± 4.57 vs salsalate 76.89 ± 12.23 µmol·g-1 tissue·hr-1; P < 0.001). CONCLUSION: These data show that salsalate can reduce sevoflurane-induced hyperglycemia in mice. This indicates that salsalate may represent a new class of therapeutics that, in addition to its anti-inflammatory and analgesic properties, may be useful to reduce perioperative hyperglycemia.

RéSUMé: OBJECTIF: L'hyperglycémie périopératoire est fréquente et est associée à une morbidité significative. Bien que les caractéristiques propres au patient et à la chirurgie influencent le métabolisme périopératoire du glucose, les anesthésiques ont un impact significatif. Nous avons émis l'hypothèse que l'hyperglycémie en réponse à une anesthésie à base de sévoflurane serait plus prononcée chez des souris obèses et insulino-résistantes que chez des souris témoins maigres. Nous avons en outre émis l'hypothèse que l'hyperglycémie induite par le sévoflurane serait atténuée par un prétraitement au salsalate. MéTHODE: Des souris mâles C57BL/6J maigres et obèses ont été anesthésiées avec du sévoflurane pendant 60 min avec ou sans prétraitement de 62,5 mg·kg−1 de salsalate. La glycémie, l'insuline plasmatique et l'absorption glycémique ont été mesurées dans différents tissus. RéSULTATS: Sous une anesthésie au sévoflurane, les souris obèses ont affiché une glycémie plus élevée que les souris maigres. Des augmentations de glucose sanguin ont été atténuées lors d'un prétraitement aigu à base de salsalate à 60 min sous anesthésie chez les souris obèses (moyenne ± erreur-type sur la moyenne [ETM], delta glycémique; véhicule 5,79 ± 1,09 vs salsalate 1,91 ± 1,32 mM, P = 0,04), mais elles n'étaient pas statistiquement significative chez les souris maigres (delta glycémique, véhicule 4,39 ± 0,55 vs salsalate 2,79 ± 0,71 mM; P = 0,10). Cet effet était indépendant des changements de l'insuline mais associé à une augmentation d'environ 1,7 fois de l'absorption glycémique dans les tissus adipeux bruns (véhicule 45,28 ± 4,57 vs salsalate 76,89 ± 12,23 µmol·g−1 tissu·h−1; P < 0,001). CONCLUSION: Ces données montrent que le salsalate peut réduire l'hyperglycémie induite par le sévoflurane chez la souris. Ceci indique que le salsalate pourrait constituer une nouvelle classe d'agents thérapeutiques qui, en plus de leurs propriétés anti-inflammatoires et analgésiques, pourraient être utiles pour réduire l'hyperglycémie périopératoire.

Consensus-based recommendations for titrating cannabinoids and tapering opioids for chronic pain control.

AIMS: Opioid misuse and overuse have contributed to a widespread overdose crisis and many patients and physicians are considering medical cannabis to support opioid tapering and chronic pain control. Using a five-step modified Delphi process, we aimed to develop consensus-based recommendations on: 1) when and how to safely initiate and titrate cannabinoids in the presence of opioids, 2) when and how to safely taper opioids in the presence of cannabinoids and 3) how to monitor patients and evaluate outcomes when treating with opioids and cannabinoids. RESULTS: In patients with chronic pain taking opioids not reaching treatment goals, there was consensus that cannabinoids may be considered for patients experiencing or displaying opioid-related complications, despite psychological or physical interventions. There was consensus observed to initiate with a cannabidiol (CBD)-predominant oral extract in the daytime and consider adding tetrahydrocannabinol (THC). When adding THC, start with 0.5-3 mg, and increase by 1-2 mg once or twice weekly up to 30-40 mg/day. Initiate opioid tapering when the patient reports a minor/major improvement in function, seeks less as-needed medication to control pain and/or the cannabis dose has been optimised. The opioid tapering schedule may be 5%-10% of the morphine equivalent dose (MED) every 1 to 4 weeks. Clinical success could be defined by an improvement in function/quality of life, a ≥30% reduction in pain intensity, a ≥25% reduction in opioid dose, a reduction in opioid dose to <90 mg MED and/or reduction in opioid-related adverse events. CONCLUSIONS: This five-stage modified Delphi process led to the development of consensus-based recommendations surrounding the safe introduction and titration of cannabinoids in concert with tapering opioids.

Insulin Injection Practices in a Population of Canadians with Diabetes: An Observational Study.

INTRODUCTION: Proper insulin injection technique has demonstrated positive clinical outcomes in patients with diabetes. A Canadian-based practice reflective was undertaken to evaluate the current state of understanding of injection technique practices by patients administering insulin, and the importance physicians place on proper injection technique. METHODS: Twenty-four sites across Canada completed a practice profile survey and enrolled adult non-pregnant patients with either type 1 or type 2 diabetes injecting insulin using an insulin pen. Seven areas of proper injection technique to be evaluated were identified by the study steering committee: size of injection site, use of a skin lift, needle reuse, length of the needle, duration of the needle in the skin, injection into lipohypertrophic tissue, and applied injection force. During a scheduled visit, each patient filled out the Injection Technique Survey and the physician documented the answers via an electronic database. RESULTS: Almost all physicians surveyed agreed (96%) that proper insulin injection technique is important or very important and 80% indicated they were either completely confident or fairly confident in discussing overall insulin injection technique. All patients surveyed were making at least one insulin injection technique error within the following categories: applied injection force (76%), area size of injection site (64%), duration of pen needle in skin (61%), pen needle reuse (39%), performs a skin lift with a 4 or 5 mm needle (38%), uses a longer pen needle than required (34%), and injection of insulin into lipohypertrophic tissue (37%). CONCLUSION: Patients commonly make insulin injection errors. Patient and physician education on optimal insulin injection technique continues to be an unmet medical need for the treatment of patients with diabetes. Prospective trials examining the impact of new technology, diabetes educational teams, and e-learning as educational interventions are potential avenues to explore in future studies to support improved insulin injection technique.

Long-chain fatty acyl-CoA esters regulate metabolism via allosteric control of AMPK ß1 isoforms.

Long-chain fatty acids (LCFAs) play important roles in cellular energy metabolism, acting as both an important energy source and signalling molecules1. LCFA-CoA esters promote their own oxidation by acting as allosteric inhibitors of acetyl-CoA carboxylase, which reduces the production of malonyl-CoA and relieves inhibition of carnitine palmitoyl-transferase 1, thereby promoting LCFA-CoA transport into the mitochondria for ß-oxidation2-6. Here we report a new level of regulation wherein LCFA-CoA esters per se allosterically activate AMP-activated protein kinase (AMPK) ß1-containing isoforms to increase fatty acid oxidation through phosphorylation of acetyl-CoA carboxylase. Activation of AMPK by LCFA-CoA esters requires the allosteric drug and metabolite site formed between the α-subunit kinase domain and the ß-subunit. ß1 subunit mutations that inhibit AMPK activation by the small-molecule activator A769662, which binds to the allosteric drug and metabolite site, also inhibit activation by LCFA-CoAs. Thus, LCFA-CoA metabolites act as direct endogenous AMPK ß1-selective activators and promote LCFA oxidation.

Metformin-induced increases in GDF15 are important for suppressing appetite and promoting weight loss.

Metformin is the most commonly prescribed medication for type 2 diabetes, owing to its glucose-lowering effects, which are mediated through the suppression of hepatic glucose production (reviewed in refs. 1-3). However, in addition to its effects on the liver, metformin reduces appetite and in preclinical models exerts beneficial effects on ageing and a number of diverse diseases (for example, cognitive disorders, cancer, cardiovascular disease) through mechanisms that are not fully understood1-3. Given the high concentration of metformin in the liver and its many beneficial effects beyond glycemic control, we reasoned that metformin may increase the secretion of a hepatocyte-derived endocrine factor that communicates with the central nervous system4. Here we show, using unbiased transcriptomics of mouse hepatocytes and analysis of proteins in human serum, that metformin induces expression and secretion of growth differentiating factor 15 (GDF15). In primary mouse hepatocytes, metformin stimulates the secretion of GDF15 by increasing the expression of activating transcription factor 4 (ATF4) and C/EBP homologous protein (CHOP; also known as DDIT3). In wild-type mice fed a high-fat diet, oral administration of metformin increases serum GDF15 and reduces food intake, body mass, fasting insulin and glucose intolerance; these effects are eliminated in GDF15 null mice. An increase in serum GDF15 is also associated with weight loss in patients with type 2 diabetes who take metformin. Although further studies will be required to determine the tissue source(s) of GDF15 produced in response to metformin in vivo, our data indicate that the therapeutic benefits of metformin on appetite, body mass and serum insulin depend on GDF15.

Activation of Liver AMPK with PF-06409577 Corrects NAFLD and Lowers Cholesterol in Rodent and Primate Preclinical Models.

Dysregulation of hepatic lipid and cholesterol metabolism is a significant contributor to cardiometabolic health, resulting in excessive liver lipid accumulation and ultimately non-alcoholic steatohepatitis (NASH). Therapeutic activators of the AMP-Activated Protein Kinase (AMPK) have been proposed as a treatment for metabolic diseases; we show that the AMPK ß1-biased activator PF-06409577 is capable of lowering hepatic and systemic lipid and cholesterol levels in both rodent and monkey preclinical models. PF-06409577 is able to inhibit de novo lipid and cholesterol synthesis pathways, and causes a reduction in hepatic lipids and mRNA expression of markers of hepatic fibrosis. These effects require AMPK activity in the hepatocytes. Treatment of hyperlipidemic rats or cynomolgus monkeys with PF-06409577 for 6weeks resulted in a reduction in circulating cholesterol. Together these data suggest that activation of AMPK ß1 complexes with PF-06409577 is capable of impacting multiple facets of liver disease and represents a promising strategy for the treatment of NAFLD and NASH in humans.

Failed Recovery of Glycemic Control and Myofibrillar Protein Synthesis With 2 wk of Physical Inactivity in Overweight, Prediabetic Older Adults.

Background: Physical inactivity impairs insulin sensitivity, which is exacerbated with aging. We examined the impact of 2 wk of acute inactivity and recovery on glycemic control, and integrated rates of muscle protein synthesis in older men and women. Methods: Twenty-two overweight, prediabetic older adults (12 men, 10 women, 69 ± 4 y) undertook 7 d of habitual activity (baseline; BL), step reduction (SR; <1,000 steps.d-1 for 14 d), followed by 14 d of recovery (RC). An oral glucose tolerance test was used to assess glycemic control and deuterated water ingestion to measure integrated rates of muscle protein synthesis. Results: Daily step count was reduced (all p < .05) from BL at SR (7362 ± 3294 to 991 ± 97) and returned to BL levels at RC (7117 ± 3819). Homeostasis model assessment-insulin resistance increased from BL to SR and Matsuda insulin sensitivity index decreased and did not return to BL in RC. Glucose and insulin area under the curve were elevated from BL to SR and did not recover in RC. Integrated muscle protein synthesis was reduced during SR and did not return to BL in RC. Conclusions: Our findings demonstrate that 2 wk of SR leads to lowered rates of muscle protein synthesis and a worsening of glycemic control that unlike younger adults is not recovered during return to normal activity in overweight, prediabetic elderly humans. Clinical Trials Registration: ClinicalTrials.gov identifier: NCT03039556.

Maternal obesity alters fatty acid oxidation, AMPK activity, and associated DNA methylation in mesenchymal stem cells from human infants.

OBJECTIVE: Infants born to mothers with obesity have greater adiposity, ectopic fat storage, and are at increased risk for childhood obesity and metabolic disease compared with infants of normal weight mothers, though the cellular mechanisms mediating these effects are unclear. METHODS: We tested the hypothesis that human, umbilical cord-derived mesenchymal stem cells (MSCs) from infants born to obese (Ob-MSC) versus normal weight (NW-MSC) mothers demonstrate altered fatty acid metabolism consistent with adult obesity. In infant MSCs undergoing myogenesis in vitro, we measured cellular lipid metabolism and AMPK activity, AMPK activation in response to cellular nutrient stress, and MSC DNA methylation and mRNA content of genes related to oxidative metabolism. RESULTS: We found that Ob-MSCs exhibit greater lipid accumulation, lower fatty acid oxidation (FAO), and dysregulation of AMPK activity when undergoing myogenesis in vitro. Further experiments revealed a clear phenotype distinction within the Ob-MSC group where more severe MSC metabolic perturbation corresponded to greater neonatal adiposity and umbilical cord blood insulin levels. Targeted analysis of DNA methylation array revealed Ob-MSC hypermethylation in genes regulating FAO (PRKAG2, ACC2, CPT1A, SDHC) and corresponding lower mRNA content of these genes. Moreover, MSC methylation was positively correlated with infant adiposity. CONCLUSIONS: These data suggest that greater infant adiposity is associated with suppressed AMPK activity and reduced lipid oxidation in MSCs from infants born to mothers with obesity and may be an important, early marker of underlying obesity risk.

Ablating the protein TBC1D1 impairs contraction-induced sarcolemmal glucose transporter 4 redistribution but not insulin-mediated responses in rats.

TBC1 domain family member 1 (TBC1D1), a Rab GTPase-activating protein and paralogue of Akt substrate of 160 kDa (AS160), has been implicated in both insulin- and 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase-mediated glucose transporter type 4 (GLUT4) translocation. However, the role of TBC1D1 in contracting muscle remains ambiguous. We therefore explored the metabolic consequence of ablating TBC1D1 in both resting and contracting skeletal muscles, utilizing a rat TBC1D1 KO model. Although insulin administration rapidly increased (p < 0.05) plasma membrane GLUT4 content in both red and white gastrocnemius muscles, the TBC1D1 ablation did not alter this response nor did it affect whole-body insulin tolerance, suggesting that TBC1D1 is not required for insulin-induced GLUT4 trafficking events. Consistent with findings in other models of altered TBC1D1 protein levels, whole-animal and ex vivo skeletal muscle fat oxidation was increased in the TBC1D1 KO rats. Although there was no change in mitochondrial content in the KO rats, maximal ADP-stimulated respiration was higher in permeabilized muscle fibers, which may contribute to the increased reliance on fatty acids in resting KO animals. Despite this increase in mitochondrial oxidative capacity, run time to exhaustion at various intensities was impaired in the KO rats. Moreover, contraction-induced increases in sarcolemmal GLUT4 content and glucose uptake were lower in the white gastrocnemius of the KO animals. Altogether, our results highlight a critical role for TBC1D1 in exercise tolerance and contraction-mediated translocation of GLUT4 to the plasma membrane in skeletal muscle.

Muramyl Dipeptide-Based Postbiotics Mitigate Obesity-Induced Insulin Resistance via IRF4.

Intestinal dysbiosis contributes to obesity and insulin resistance, but intervening with antibiotics, prebiotics, or probiotics can be limited by specificity or sustained changes in microbial composition. Postbiotics include bacterial components such as lipopolysaccharides, which have been shown to promote insulin resistance during metabolic endotoxemia. We found that bacterial cell wall-derived muramyl dipeptide (MDP) is an insulin-sensitizing postbiotic that requires NOD2. Injecting MDP lowered adipose inflammation and reduced glucose intolerance in obese mice without causing weight loss or altering the composition of the microbiome. MDP reduced hepatic insulin resistance during obesity and low-level endotoxemia. NOD1-activating muropeptides worsened glucose tolerance. IRF4 distinguished opposing glycemic responses to different types of peptidoglycan and was required for MDP/NOD2-induced insulin sensitization and lower metabolic tissue inflammation during obesity and endotoxemia. IRF4 was dispensable for exacerbated glucose intolerance via NOD1. Mifamurtide, an MDP-based drug with orphan drug status, was an insulin sensitizer at clinically relevant doses in obese mice.

AMP-activated protein kinase, fatty acid metabolism, and insulin sensitivity.

PURPOSE OF REVIEW: Insulin resistance is an important risk factor for metabolic diseases such as type 2 diabetes, cardiovascular disease and certain cancers. A common characteristic of strategies that improve insulin sensitivity involves the activation of the energy sensing enzyme of the cell, AMP-activated protein kinase (AMPK). The purpose of this review is to explore the mechanisms associated with AMPK activation to improve insulin sensitivity with a focus on fatty acid metabolism. We will also discuss the literature surrounding direct AMPK activators to improve insulin resistance and important considerations for the design of direct AMPK activators. RECENT FINDINGS: AMPK activation can decrease de novo lipogenesis, increase fatty acid oxidation and promote mitochondrial integrity to improve insulin sensitivity. Drugs targeted to directly activate AMPK show therapeutic promise, yet in vivo data is lacking. SUMMARY: Designing a drug to directly activate AMPK may improve insulin resistance by reducing liver de novo lipogenesis and increasing brown and white adipose tissue mitochondrial function. However, in vivo experimental procedures to support this notion are not extensive and more research is required.

Liver-specific ATP-citrate lyase inhibition by bempedoic acid decreases LDL-C and attenuates atherosclerosis.

Despite widespread use of statins to reduce low-density lipoprotein cholesterol (LDL-C) and associated atherosclerotic cardiovascular risk, many patients do not achieve sufficient LDL-C lowering due to muscle-related side effects, indicating novel treatment strategies are required. Bempedoic acid (ETC-1002) is a small molecule intended to lower LDL-C in hypercholesterolemic patients, and has been previously shown to modulate both ATP-citrate lyase (ACL) and AMP-activated protein kinase (AMPK) activity in rodents. However, its mechanism for LDL-C lowering, efficacy in models of atherosclerosis and relevance in humans are unknown. Here we show that ETC-1002 is a prodrug that requires activation by very long-chain acyl-CoA synthetase-1 (ACSVL1) to modulate both targets, and that inhibition of ACL leads to LDL receptor upregulation, decreased LDL-C and attenuation of atherosclerosis, independently of AMPK. Furthermore, we demonstrate that the absence of ACSVL1 in skeletal muscle provides a mechanistic basis for ETC-1002 to potentially avoid the myotoxicity associated with statin therapy.

The diabetes medication Canagliflozin reduces cancer cell proliferation by inhibiting mitochondrial complex-I supported respiration.

OBJECTIVE: The sodium-glucose transporter 2 (SGLT2) inhibitors Canagliflozin and Dapagliflozin are recently approved medications for type 2 diabetes. Recent studies indicate that SGLT2 inhibitors may inhibit the growth of some cancer cells but the mechanism(s) remain unclear. METHODS: Cellular proliferation and clonogenic survival were used to assess the sensitivity of prostate and lung cancer cell growth to the SGLT2 inhibitors. Oxygen consumption, extracellular acidification rate, cellular ATP, glucose uptake, lipogenesis, and phosphorylation of AMP-activated protein kinase (AMPK), acetyl-CoA carboxylase, and the p70S6 kinase were assessed. Overexpression of a protein that maintains complex-I supported mitochondrial respiration (NDI1) was used to establish the importance of this pathway for mediating the anti-proliferative effects of Canagliflozin. RESULTS: Clinically achievable concentrations of Canagliflozin, but not Dapagliflozin, inhibit cellular proliferation and clonogenic survival of prostate and lung cancer cells alone and in combination with ionizing radiation and the chemotherapy Docetaxel. Canagliflozin reduced glucose uptake, mitochondrial complex-I supported respiration, ATP, and lipogenesis while increasing the activating phosphorylation of AMPK. The overexpression of NDI1 blocked the anti-proliferative effects of Canagliflozin indicating reductions in mitochondrial respiration are critical for anti-proliferative actions. CONCLUSION: These data indicate that like the biguanide metformin, Canagliflozin not only lowers blood glucose but also inhibits complex-I supported respiration and cellular proliferation in prostate and lung cancer cells. These observations support the initiation of studies evaluating the clinical efficacy of Canagliflozin on limiting tumorigenesis in pre-clinical animal models as well epidemiological studies on cancer incidence relative to other glucose lowering therapies in clinical populations.

Treatment of nonalcoholic fatty liver disease: role of AMPK.

Nonalcoholic fatty liver disease (NAFLD) is a growing worldwide epidemic and an important risk factor for the development of insulin resistance, type 2 diabetes, nonalcoholic steatohepatitis (NASH), and hepatic cellular carcinoma (HCC). Despite the prevalence of NAFLD, lifestyle interventions involving exercise and weight loss are the only accepted treatments for this disease. Over the last decade, numerous experimental compounds have been shown to improve NAFLD in preclinical animal models, and many of these therapeutics have been shown to increase the activity of the cellular energy sensor AMP-activated protein kinase (AMPK). Because AMPK activity is reduced by inflammation, obesity, and diabetes, increasing AMPK activity has been viewed as a viable therapeutic strategy to improve NAFLD. In this review, we propose three primary mechanisms by which AMPK activation may improve NAFLD. In addition, we examine the mechanisms by which AMPK is activated. Finally, we identify 27 studies that have used AMPK activators to reduce NAFLD. Future considerations for studies examining the relationship between AMPK and NAFLD are highlighted.