Thujone, a component of medicinal herbs, rescues palmitate-induced insulin resistance in skeletal muscle

Natural Compounds of Salvia L. Genus and Molecular Mechanism of Their Biological Activity

The study of medicinal plants is important, as they are the natural reserve of potent biologically active compounds. With wide use in traditional medicine and the inclusion of several species (as parts and as a whole plant) in pharmacopeia, species from the genus Salvia L. are known for the broad spectrum of their biological activities. Studies suggest that these plants possess antioxidant, anti-inflammatory, antinociceptive, anticancer, antimicrobial, antidiabetic, antiangiogenic, hepatoprotective, cognitive and memory-enhancing effects. Phenolic acids, terpenoids and flavonoids are important phytochemicals, which are primarily responsible for the medicinal activity of Salvia L. This review collects and summarizes currently available data on the pharmacological properties of sage, outlining its principal physiologically active components, and it explores the molecular mechanism of their biological activity. Particular attention was given to the species commonly found in Kazakhstan, especially to Salvia trautvetteri Regel, which is native to this country.

A systematic review on anti-diabetic plant essential oil compounds: Dietary sources, effects, molecular mechanisms, and safety

Type 2 diabetes mellitus (T2DM) is a multifaceted metabolic syndrome defined through the dysfunction of pancreatic β-cells driven by a confluence of genetic and environmental elements. Insulin resistance, mediated by interleukins and other inflammatory elements, is one of the key factors contributing to the progression of T2DM. Many essential oils derived from dietary plants are beneficial against various chronic diseases. We reviewed the anti-diabetic properties of dietary plant-derived essential oil compounds, with a focus on their molecular mechanisms by modulating specific signaling pathways and other critical inflammatory mediators involved in insulin resistance. High-quality literature published in the last 12 years, from 2010 to 2022, was collected from the Scopus, Web of Science, PubMed, and Embase databases using the search terms "dietary plants," "essential oils," "anti-diabetic," "insulin resistance," "antihyperglycemic," "T2DM," "anti-diabetic essential oils," and anti-diabetic mechanism." According to the results, the essential oil compounds, including cinnamaldehyde, carvacrol, zingerone, sclareol, zerumbone, myrtenol, thujone, geraniol, citral, eugenol, thymoquinone, thymol, citronellol, α-terpineol, and linalool have been demonstrated to contain strong anti-diabetic effects via modulating various signal transduction pathways linked to glucose metabolism. Additionally, in diabetes-related animal models, they can also considerably reduce the expression of TNF-α, IL-1β, IL-4, IL-6, iNOS, and COX-2. The main signaling molecules regulated by these compounds include AMPK, GLUT4, Caspase-3, PPARγ, PPARα, NF-κB, p-IκBα, MyD88, MCP-1, SREBP-1c, AGEs, RAGE, VEGF, Nrf2/HO-1, and SIRT-1. They can also significantly inhibit the generation of TBARS and MDA, reduce oxidative stress, increase insulin levels, adiponectin, and glycoprotein enzymes, boost antioxidant enzymes like SOD, CAT, and GPx, as well as reduce glutathione and vital glycolytic enzymes. Besides, they can significantly lower the levels of liver enzymes and lipid profile markers. Moreover, most essential oil compounds are generally safe based on animal studies. In conclusion, dietary plant-derived essential oil compounds have potential anti-diabetic effects by influencing different signaling pathways and molecular targets linked to glucose metabolism, and should be safe and beneficial against diabetes and related complications.

HM-Chromanone Ameliorates Hyperglycemia and Dyslipidemia in Type 2 Diabetic Mice

The effects of (E)-5-hydroxy-7-methoxy-3-(2-hydroxybenzyl)-4-chromanone (HMC) on hyperglycemia and dyslipidemia were investigated in diabetic mice. Mice were separated into three groups: db/db, rosiglitazone and HMC. Blood glucose or glycosylated hemoglobin values in HMC-treated mice were significantly lower compared to db/db mice. Total cholesterol, LDL-cholesterol, and triglyceride values were lower, and HDL-C levels were higher, in the HMC group compared to the diabetic and rosiglitazone groups. HMC markedly increased IRS-1^Tyr612, Akt^Ser473 and PI3K levels and plasma membrane GLUT4 levels in skeletal muscle, suggesting improved insulin resistance. HMC also significantly stimulated AMPK^Thr172 and PPARα in the liver, and ameliorated dyslipidemia by inhibiting SREBP-1c and FAS. Consequently, HMC reduced hyperglycemia by improving the expression of insulin-resistance-related genes and improved dyslipidemia by regulating fatty acid synthase and oxidation-related genes in db/db mice. Therefore, HMC could ameliorate hyperglycemia and dyslipidemia in type 2 diabetic mice.

Evaluation of antidiabetic, antioxidant and antilipidemic potential of natural dietary product prepared from Cyphostemma digitatum in rats’ model of diabetes

Introduction: Cyphostemma digitatum has a high content of antioxidant constituents and has been employed by the traditional healers and local people of Yemen for diabetes treatment. However, scientific evidence regarding its antidiabetic efficacy is largely unknown. Accordingly, the present study aimed to confirm the treatment effects of a dietary natural product prepared from Cyphostemma digitatum (PCD) in diabetic rats.Methods: Diabetes was induced by a high-fat diet and streptozotocin (HF-STZ). PCD (1 g/kg) was given by gavage administration once a day continuously for 30 days. At the end of treatment, blood and skeletal muscle samples were collected for further analysis.Results: The antidiabetic effects of PCD were demonstrated by significant reduction (P ≤ 0.05) in the levels of serum glucose (40%), triglyceride (32%), cholesterol (53%), low-density lipoprotein (LDL) (44%), malondialdehyde (MDA) (61%) in PCD treated groups compared to the diabetic control group. Additionally, PCD treatment significantly (P ≤ 0.05) restored the decreased levels of insulin (70%) and the activities of superoxide dismutase (SOD) (57%) and reduced glutathione (GSH) (544%) when compared to that of diabetic control rats. We found that treatment with PCD for 30 days fully restored the plasmalemmal glucose transporter type 4 (GLUT4) contents, as well as the phosphorylation of phosphatidylinositol 3-kinase (PI3K) (P ≤ 0.05).Conclusion: Thus, PCD treatment can be considered a potential drug candidate for diabetes.

Understanding the Mechanism Underlie the Antidiabetic Activity of Oleuropein Using Ex-Vivo Approach

Background

Oleuropein, the main constituent of olive fruit and leaves, has been reported to protect against insulin resistance and diabetes. While many experimental investigations have examined the mechanisms by which oleuropein improves insulin resistance and diabetes, much of these investigations have been carried out in either muscle cell lines or in vivo models two scenarios with many drawbacks. Accordingly, to simplify identification of mechanisms by which oleuropein regulates specific cellular processes, we resort, in the present study, to isolated muscle preparation which enables better metabolic milieu control and permit more detailed analyses.

Methods

For this purpose, soleus muscles were incubated for 12 h without or with palmitate (1.5 mM) in the presence or absence of oleuropein (1.5 mM), and compound C. Insulin-stimulated glucose transport, glucose transporter type 4 (GLUT4) translocation, Akt substrate of 160 kDa (AS160) phosphorylation and adenosine monophosphate-activated protein kinase (AMPK) phosphorylation were examined.

Results

Palmitate treatment reduced insulin-stimulated glucose transport, GLUT4 translocation and AS160 phosphorylation, but AMPK phosphorylation was not changed. Oleuropein administration (12 h) fully rescued insulin-stimulated glucose transport, but partially restored GLUT4 translocation. However, it fully restored AS160 phosphorylation, raising the possibility that oleuropein may also have contributed to the restoration of glucose transport by increased GLUT4 intrinsic activity. Inhibition of AMPK phosphorylation with compound C (50 µM) prevented oleuropein -induced improvements in insulin-stimulated glucose transport, GLUT4 translocation, and AS160 phosphorylation.

Conclusion

Our results clearly indicate that oleuropein alleviates palmitate-induced insulin resistance appears to occur via an AMPK-dependent mechanism involving improvements in the functionality of the AS160-GLUT4 signaling system.

In Vitro and In Vivo Antidiabetic Potential of Monoterpenoids: An Update

Diabetes mellitus (DM) is a chronic metabolic condition characterized by persistent hyperglycemia due to insufficient insulin levels or insulin resistance. Despite the availability of several oral and injectable hypoglycemic agents, their use is associated with a wide range of side effects. Monoterpenes are compounds extracted from different plants including herbs, vegetables, and fruits and they contribute to their aroma and flavor. Based on their chemical structure, monoterpenes are classified into acyclic, monocyclic, and bicyclic monoterpenes. They have been found to exhibit numerous biological and medicinal effects such as antipruritic, antioxidant, anti-inflammatory, and analgesic activities. Therefore, monoterpenes emerged as promising molecules that can be used therapeutically to treat a vast range of diseases. Additionally, monoterpenes were found to modulate enzymes and proteins that contribute to insulin resistance and other pathological events caused by DM. In this review, we highlight the different mechanisms by which monoterpenes can be used in the pharmacological intervention of DM via the alteration of certain enzymes, proteins, and pathways involved in the pathophysiology of DM. Based on the fact that monoterpenes have multiple mechanisms of action on different targets in in vitro and in vivo studies, they can be considered as lead compounds for developing effective hypoglycemic agents. Incorporating these compounds in clinical trials is needed to investigate their actions in diabetic patients in order to confirm their ability in controlling hyperglycemia.

Effect of Artemisia extract on glycemic control: A systematic review and meta-analysis of randomized controlled trial

BACKGROUND AND AIM

Animal and human studies have indicated anti-diabetic effect of Asteraceae. The present study aimed to systematically review and analyse randomized controlled trials assessing the effect of Artemisia extract on glycemic status in patients with impaired glycemic control.

METHODS

Web of Science, Cochrane library, EMBASE and PubMed databases were searched from the earliest possible date up to 7th October 2020.

RESULTS

Six studies were included in the meta-analysis. Analysis showed that supplementation with Artemisia extract decreased homeostatic model assessment of insulin resistance (HOMA-IR) (-0.734, 95% CI: -1.236 to -0.232, P = .019) in comparison to placebo. However, reductions in fasting blood glucose (FBG) (-0.595, 95% CI: -1.566 to 0.376, P = .164), insulin (-0.322, 95% CI: -1.047 to 0.404, P = .286) and glycated haemoglobin (-0.106, 95% CI: -0.840 to 0.629, P = .678) were not statistically significant.

CONCLUSION

Supplementation with Artemisia extract may reduce HOMA-IR, but beneficial effects on other markers such as FBG requires further investigations.

Effect of Aluminum Exposure on Glucose Metabolism and Its Mechanism in Rats

The effects of aluminum (Al) exposure on glucose metabolism and its mechanism were investigated. A total of 30 healthy Wistar male rats were randomly divided into two groups: control (GC) and experimental (GE). The GC group received intraperitoneal normal saline. The GE was established by intraperitoneal injected AlCl₃ solution at 10 mg/kg for 30 days. Fasting blood glucose (FBG) and serum levels of insulin (FINS) were measured. The insulin resistance index (HOMA-IR) and pancreatic β cell function index (HOMA-β) were calculated and analyzed with homeostasis model assessment (HOMA). Pancreatic tissue was taken for pathological examination. Glucose transporter 4 (GLUT4) expression in skeletal muscle was detected by quantitative PCR and Western blot. Levels of FBG and HOMA-IR in GE were higher than those in GC at day 10 and 20 (P < 0.05). FINS in GE were higher than those in GC at day 10 and 20, and lower than those in GC at day 30 (P < 0.05). HOMA-β in GE was lower than that of GC at every time point (P < 0.05). Pathology showed that pancreatic damage changed more profoundly with prolongation of time in GE. Expression levels of GLUT4 mRNA and protein in rat skeletal muscle in GE were significantly lower than those in GC (P < 0.05). The results suggested that Al exposure affected glucose metabolism through pancreatic damage and reduction of GLUT4 expression.

R-Limonene Enhances Differentiation and 2-Deoxy-D-Glucose Uptake in 3T3-L1 Preadipocytes by Activating the Akt Signaling Pathway

Adipocyte is an important place for lipid storage. Defects in lipid storage in adipocytes can lead to lipodystrophy and lipid accumulation in muscle, liver, and other organs. It is the condition of mixed dyslipidemia which may favor the development of insulin resistance via lipotoxic mechanisms. Our objective of the study was to investigate the potential role of R-limonene (LM) on differentiation, lipid storage, and 2-deoxy-D-glucose (2DG) uptake in 3T3-L1 preadipocytes. Genes and proteins associated with differentiation, lipid accumulation, 2DG uptake and its signaling pathways in the adipocytes were analyzed using qPCR and western blot methods. LM treatment increased differentiation, lipid accumulation, and the expression of adipogenic and lipogenic markers such as C/EBP-α, C/EBP-β, PPARγ, SREBP-1, RXR, FAS, and adiponectin. However, the LM concentration at 10μM decreased (p < 0.05) adipogenesis and lipogenesis via regulating key transcriptional factors. LM treatment increased activation of Akt by increasing its phosphorylation, but p44/42 activation was not altered. MK-2206, an Akt specific inhibitor, reduced the activation of Akt phosphorylation whereas LM treatment aborted the MK-2206 mediated inhibition of Akt activation. LM enhanced glucose uptake in differentiated adipocytes. Overall data suggested that LM treatment favored lipid storage and glucose uptake in adipocytes via activation of key transcriptional factors through activation of Akt phosphorylation in 3T3-L1 adipocytes.

Limonene promotes osteoblast differentiation and 2-deoxy-d-glucose uptake through p38MAPK and Akt signaling pathways in C2C12 skeletal muscle cells

BACKGROUND

Limonene is a cyclic monoterpene (CTL) found in citrus fruits and many plant kingdoms. It has attracted attention as potential molecule due to its diverse biological activities. However, molecular mechanism involved in the osteogenic induction of CTL in C2C12 skeletal muscle cells remain unclear.

PURPOSE

Skeletal development maintains the bone homeostasis through bone remodeling process. It coordinated between the osteoblast and osteoblast process. Osteoporosis is one of the most common bone diseases caused by a systemic reduction in bone mass. Recent osteoporosis treatment is based on the use of anti-resorptive and bone forming drugs. However, long term use of these drugs is associated with serious side effects and strategies on the discovery of lead compounds from natural products for osteoblast differentiation are urgently needed. Therefore, we planned to find out the role of CTL on osteoblast differentiation and glucose uptake in C2C12 cells and its effect on signaling pathways.

METHODS

Cell proliferation, alkaline phosphatase (ALP) activity, calcium deposition, genes, and proteins associated with osteoblast activation and glucose utilization were analysed.

RESULTS

CTL did not affect the cell viability. CTL significantly increased ALP activity, calcium depositions and the expression of osteogenic specific genes such as Myogenin, Myogenic differentiation 1 (MyoD), ALP, Run-related transcription factor 2(RUNX2), osteocalcin (OCN). In addition, CTL induced the mRNA expression of bone morphogenetic proteins (BMP-2 BMP-4 BMP-6 BMP-7 BMP-9). CTL treatment enhanced 2-Deoxy-d-glucose (2DG) uptake. Moreover, CTL stimulated the activation of p38 mitogen activated protein kinase (p38MAPK), Protein kinase B (Akt), Extracellular signal related kinase (ERKs) by increasing phosphorylation. CTL treatment abolished p38 inhibitor (SB203580) mediated inhibition of osteoblast differentiation, but no effect was noted by ERKs specific inhibitor (PD98059).

CONCLUSION

These results suggest that limonene induces osteoblast differentiation and glucose uptake through activating p38MAPK and Akt signaling pathways, confirming the molecular basis of the osteoblast differentiation by limonene in C2C12 skeletal muscle cells.

Beneficial effects of oleuropein on glucose uptake and on parameters relevant to the normal homeostatic mechanisms of glucose regulation in rat skeletal muscle

Oleuropein, the main constituents of leaves and fruits of the olive tree, has been demonstrated to exert various therapeutic and pharmacological properties including antidiabetic effect. However, the effectiveness of oleuropein on glucose homeostasis in intact rat skeletal muscle ex vivo has never been explored. Therefore, our current study was carried out to investigate and confirm the beneficial effect of oleuropein (1.5 mM) on glucose uptake and on parameters relevant to the normal homeostatic mechanisms of glucose regulation in rat skeletal muscle. For this purpose, soleus muscles were incubated for 12 hr without (control) or with oleuropein, in the presence or absence of AMP-activated protein kinase (AMPK) inhibitor, compound C, or wortmannin, an inhibitor of phosphatidylinositol kinase. Oleuropein-stimulated glucose transport, plasmalemmal glucose transporter 4 (GLUT4), and phosphorylation of phosphatidylinositol kinase and AMPK were examined. We observed that oleuropein treatment enhanced glucose transport, GLUT4 translocation, and AMPK phosphorylation. The oleuropein-stimulated glucose uptake and GLUT4 translocation were inhibited by compound C and were not affected by wortmannin. These results suggest that increased glucose uptake induced by oleuropein might be mediated through activation of AMPK and the subsequent increase in GLUT4 translocation in skeletal muscles.

Antidiabetic Potential of Monoterpenes: A Case of Small Molecules Punching above Their Weight

Monoterpenes belong to the terpenoids class of natural products and are bio-synthesized through the mevalonic acid pathway. Their small molecular weight coupled with high non-polar nature make them the most abundant components of essential oils which are often considered to have some general antioxidant and antimicrobial effects at fairly high concentrations. These compounds are however reported to have antidiabetic effects in recent years. Thanks to the ingenious biosynthetic machinery of nature, they also display a fair degree of structural complexity/diversity for further consideration in structure-activity studies. In the present communication, the merit of monoterpenes as antidiabetic agents is scrutinized by assessing recent in vitro and in vivo studies reported in the scientific literature. Both the aglycones and glycosides of these compounds of rather small structural size appear to display antidiabetic along with antiobesity and lipid lowering effects. The diversity of these effects vis-à-vis their structures and mechanisms of actions are discussed. Some key pharmacological targets include the insulin signaling pathways and/or the associated PI3K-AKT (protein kinase B), peroxisome proliferator activated receptor-γ (PPARγ), glucose transporter-4 (GLUT4) and adenosine monophosphate-activated protein kinase (AMPK) pathways; proinflammatory cytokines and the NF-κB pathway; glycogenolysis and gluconeogenesis in the liver; glucagon-like-1 receptor (GLP-1R); among others.

Preventive effect of oleate on palmitate-induced insulin resistance in skeletal muscle and its mechanism of action

Insulin resistance in skeletal muscle is a feature associated with exposure to an excess of saturated fatty acids such as palmitate. Oleic acid has been shown to blunt palmitate-induced insulin resistance in muscle cells. However, there is no literature available regarding the effect of oleic acid on palmitate-induced insulin resistance in intact muscle. Therefore, this study investigated the effect of oleic acid on palmitate-induced insulin resistance in rat soleus muscle and its underlying mechanisms. For these purposes, oleic acid (1 mM) was administered for 12 h in the absence or presence of palmitate (2 mM). At the end of the experiment, plasmalemmal GLUT4, the phosphorylation of AS160 and Akt-2, and the total expression of these signaling proteins were examined. We found that treatment with palmitate for 12 h reduced insulin-stimulated GLUT4 translocation and the phosphorylation of AS160 and Akt-2. However, the administration of oleic acid fully restored insulin-stimulated GLUT4 translocation (P < 0.05), as well as AS160 and Akt-2 phosphorylation (P < 0.05) despite the continuous presence of palmitate. Wortmannin, an inhibitor of PI3-K, only slightly prevented the oleic acid-induced improvements in insulin-stimulated GLUT4 translocation, and AS160 phosphorylation. However, this treatment completely inhibited the oleic acid-induced improvement in insulin-stimulated Akt-2 phosphorylation. In contrast, the oleic acid-induced improvement in insulin signaling was not affected by compound C, an AMPK specific inhibitor. In conclusion, the results clearly indicate that oleic acid administration alleviates palmitate-induced insulin resistance by promoting GLUT4 translocation in muscle, at least in part, by activating the PI3K pathway.

Thujone inhibits lung metastasis induced by B16F-10 melanoma cells in C57BL/6 mice

The antimetastatic potential of thujone, a naturally occurring monoterpene, was evaluated. Metastasis was induced in C57BL/6 mice by injecting highly metastatic B16F-10 melanoma cells through the lateral tail vein. Administration of thujone (1 mg·(kg body weight)–1), prophylactically and simultaneously with tumor induction, inhibited tumor nodule formation in the lungs by 59.45% and 57.54%, respectively, with an increase in the survival rate (33.67% and 32.16%) of the metastatic tumor bearing animals. These results correlated with biochemical parameters such as lung collagen hydroxyproline, hexosamine and uronic acid contents, serum sialic acid and γ-glutamyl transpeptidase levels, and histopathological analysis. Treatment with thujone downregulated the production of proinflammatory cytokines such as tumor necrosis factor-α, interleukin (IL)-1β, IL-6, and granulocyte–monocyte colony-stimulating factor. Thujone administration downregulated the expression of matrix metalloproteinase (MMP)-2, MMP-9, extracellular signal-regulated kinase (ERK)-1, ERK-2, and vascular endothelial growth factor (VEGF) and also upregulated the expression of nm-23, tissue inhibitor of metalloproteinase (TIMP)-1, and TIMP-2 in the lung tissue of metastasis-induced animals. Treatment with thujone inhibited the activity of MMP-2 and MMP-9 in gelatin zymographic analysis. Thujone treatment significantly inhibited the invasion of B16F-10 melanoma cells across the collagen matrix in a Boyden chamber. Thujone also inhibited the adhesion of tumor cells to collagen-coated microtire plate wells and the migration of B16F-10 melanoma cells across a polycarbonate filter in vitro. These results indicate that Thujone can inhibit the lung metastasis of B16F-10 cells through inhibition of tumor cell proliferation, adhesion, and invasion, as well as by regulating expression of MMPs, VEGF, ERK-1, ERK-2, TIMPs, nm23, and levels of proinflammatory cytokines and IL-2 in metastatic animals.

Augmentation of humoral and cell mediated immune responses by Thujone

Thujone, a naturally occurring monoterpene, was found to enhance the total WBC count, bone marrow cellularity, number of α-esterase positive cells, number of plaque forming cells in spleen and circulating antibody titer in Balb/c mice (1mg/kg body weight, intraperitoneally for 5 days). Thujone treatment enhanced proliferation of splenocytes and thymocytes, both in the presence and absence of specific mitogens. Administration of Thujone was found to stimulate the cell-mediated immunological response in normal and tumor bearing Balb/c mice. A significant enhancement in natural killer (NK) cell mediated cytotoxicity, antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent complement mediated cytotoxicity (ACC) in both normal as well as tumor-bearing animals was observed after the administration of Thujone. Production of cytokines such as IL-2 and IFN-γ was significantly enhanced by the administration of Thujone. The stimulatory effect of Thujone on cytotoxic T lymphocyte (CTL) generation was determined by Winn's neutralization assay using CTL sensitive EL4 thymoma cells. Thujone treatment showed a significant increase in CTL production in both the in vivo and in vitro models, as indicated by a significant increase in the life span of tumor bearing animals. All these results indicate that administration of Thujone could enhance the immune response of mice. There was a significant reduction in solid tumor development, mediated by the presence of alert immune responses during Thujone administration.

Skeletal muscle fatty acid oxidation is not directly associated with AMPK or ACC2 phosphorylation

Rescue of palmitate-induced insulin resistance has been linked with improvements in fatty acid oxidation, but importantly, not always with concurrently altered AMPK or ACC2 phosphorylation. Therefore, we examined the interrelationships among AMPK, ACC2, and fatty acid oxidation under 12 controlled conditions in isolated muscle. Incubation of soleus muscle (0–12 h) did not alter fatty acid oxidation, but did increase AMPK and ACC2 phosphorylation (24%–30%). Muscle incubation with palmitate (2 mmol·L–1) inhibited palmitate oxidation (∼55%), but paradoxically, this was associated with increased AMPK and ACC2 phosphorylation (∼50%). Addition of an AMPK activator (thujone) to control (no palmitate) muscle increased AMPK and ACC2 phosphorylation (∼25%) but did not alter palmitate oxidation. Addition of AMPK inhibitors, compound C (50 µmol·L–1) or adenine 9-β-d-arabinofuranoside (Ara; 2.5 mmol·L–1), to thujone-treated muscles (no palmitate) did not alter palmiate oxidation but reduced AMPK phosphorylation (32%–42%), while ACC2 phosphorylation remained above basal level (+14%–18%). Finally, in palmitate-treated muscle, thujone increased AMPK (+100%) and ACC2 phosphorylation (+52%) and restored palmitate oxidation. Compound C or Ara, administered along with thujone in palmitate-treated muscle, only partly blunted palmitate oxidation recovery despite inhibiting AMPK phosphorylation (–22%), although ACC2 phosphorylation remained upregulated (+33%). Among these experiments, AMPK phosphorylation and ACC2 phosphorylation were positively correlated. However, AMPK phosphorylation was not correlated with palmitate oxidation, and unexpectedly, palmitate oxidation was negatively correlated with ACC2 phosphorylation. Our study, in accordance with a growing body of evidence, indicates that neither AMPK phosphorylation nor ACC2 phosphorylation is by itself an appropriate marker of fatty acid oxidation, and further serves to question their regulatory role.