Hepatic Glucose Uptake Research Articles

Itraconazole attenuates hepatic gluconeogenesis and promotes glucose uptake by regulating AMPK pathway

The primarily metabolic abnormality in type 2 diabetes mellitus (T2DM) is the defect in gluconeogenesis and glucose uptake. Itraconazole (ITCZ) is a traditional azole drug with anti-fungal and anticancer properties. However, limited attention has been directed towards the contribution of ITCZ to hepatic gluconeogenesis and glucose uptake in T2DM. The present study aimed to investigate the potential effects of ITCZ on hepatic gluconeogenesis and glucose uptake as well as the underlying mechanisms. No obvious change in cell viability was detected by MTT assay in HepG2 cells with ITCZ treatment at gradually increasing concentrations. Western blot analysis demonstrated that the phosphorylation level of 5' adenosine monophosphate-activated protein kinase (AMPK) was significantly elevated by ITCZ treatment at ≥5 µg/ml (P<0.05). Moreover, ITCZ repressed the gluconeogenesis of HepG2 cells, as evidenced by the dose-dependently increased glycogen synthase kinase 3β phosphorylation level and a notably decreased glucose production rate (P<0.05). Simultaneously, the expression of peroxisome proliferator-activated receptor γ co-activator 1α, phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) in HepG2 cells was reduced by ITCZ in a dose-dependent manner (P<0.001). Furthermore, a 2-deoxyglucose uptake assay revealed that the glucose uptake of HepG2 cells was notably enhanced, accompanied by the ITCZ dose-dependent upregulation of glucose transporter-4 (GLUT-4) (P<0.05). Conversely, silencing of AMPK by small interfering RNA resulted in an increase of ITCZ-reduced gluconeogenesis and inhibition of ITCZ-induced glucose uptake with relative upregulation of PEPCK and G6Pase and downregulation of GLUT4 in the presence of 50 µg/ml ITCZ (P<0.05). Overall, the results indicated that AMPK has an important role in regulating ITCZ-induced glucose uptake by stimulating GLUT4 in HepG2 cells. Therefore, ITCZ may become a promising candidate for T2DM therapy.

Anti-diabetic effects of mulberry (Morus alba L.) branches and oxyresveratrol in streptozotocin-induced diabetic mice.

Despite with accumulating evidences on the anti-diabetic effects of mulberry branch (MB), the major active component for the activity has not been known. Oral administration of MB ethanol (EtOH) extracts [0.5 or 1g/kg body weight (BW)] once a day for 22days to streptozotocin-induced diabetic ICR mouse significantly reduced fasting blood and plasma glucose level in a dose dependent manner compared to those of the diabetic control. Administration of oxyresveratrol [ORT, 0.6g/kg BW], a major compound of MB EtOH extracts, to diabetic ICR mouse also significantly reduced fasting plasma glucose level. Further, ORT increased hepatic glucose transporter 2 transcription and glycogen content. Plasma insulin concentration and intestinal disaccharidase activity were not different between diabetic control and ORT groups. This suggests that ORT reduced plasma glucose by stimulating hepatic glucose uptake and glycogen storage. MB EtOH extracts and ORT could be potential adjunct therapies for diabetes management.

Preproinsulin expression, insulin release, and hepatic glucose metabolism after a glucose load in the omnivorous GIFT tilapia Oreochromis niloticus

This study was performed to investigate the time course of changes in the expression of preproinsulin (ins) and insulin-degrading enzyme (ide), plasma insulin level and hepatic glucose metabolism after a glucose tolerance test (GTT) in genetically improved farmed Nile tilapia (GIFT), Oreochromis niloticus. Male adult fish were intraperitoneally injected with 1g glucose/kg of body weight after 24h of food deprivation, and then subjected to sampling at 0, 1, 2, 4, 6 and 12h after the GTT. Compared with the control (4.3mM/L), plasma glucose level peaked at 1h (14.8mM/L), decreased during 2–4h (5.7–8.3mM/L), and was restored after 6h of the GTT. Although the expression of ins1, ins2 and ide were not affected in the Brockman body, plasma insulin level concomitantly increased with the increase of plasma glucose level during 1–4h after the glucose injection. The expression of glucose transporter 1 sharply increased at 1h after the GTT, indicating that hepatic glucose uptake was stimulated. The mRNA level of glucokinase was up-regulated during 1–4h, and the activity of phosphofructokinase increased during 2–4h, suggesting that hepatic glycolysis was active during 1–4h after the glucose administration. The mRNA level of glycogen synthase 1 increased at 1h, and liver glycogen level accumulated at 4h after the GTT. Although the expression of glucose-6-phosphatase catalytic subunit a2 was suppressed during 1–2h, neither the mRNA level of phosphoenolpyruvate carboxykinase 2 nor its activity was impacted by the glucose injection, which might have prolonged the glucose clearance of tilapia. Hepatic lipogenesis was effectively stimulated to dispose excess glucose absorbed by the hepatocytes, as up-regulation of mRNA levels of ATP citrate lyase a (during 1–4h), acetyl-CoA carboxylase α (during 4–12h) and fatty acid synthase (during 2–12h) were accompanied by the GTT. Taken together, it was concluded that glucose was an effective insulin secretagogue in tilapia, and liver played an important role to clear the glucose load through stimulation of glucose uptake, glycolysis, glycogenesis and lipogenesis.

Bioactive constituents from the whole plants of Leontopodium leontopodioides (Wild.) Beauv.

Five new compounds, leontoaerialosides A (1), B (2), C (3), D (4), and E (5) were obtained from the 70% EtOH extract of the whole plants of Leontopodium leontopodioides (Wild.) Beauv. Their structures were elucidated by chemical and spectroscopic methods. Moreover, compounds 4 and 5 showed significant effects on stimulating the hepatic glucose uptake in HepG2 cells.

Egr2 enhances insulin resistance via JAK2/STAT3/SOCS-1 pathway in HepG2 cells treated with palmitate

Insulin resistance is generally responsible for the pathogenesis of type 2 diabetes mellitus (T2DM). Early growth response proteins-2 (Egr2) has been reported to be able to increase the expression of the suppressors of cytokine signaling-1 (SOCS-1), and impair insulin signaling pathway through suppression of insulin receptor substrates (IRS), including IRS-1 and IRS-2. However, whether Egr2 is directly involved in the development of insulin resistance, and how its potential contributions to insulin resistance still remain unknown. Here, our present investigation found that the expression levels of Egr2 were up-regulated when insulin resistance occurs, and knockdown of Egr2 abolished the effect of insulin resistance in HepG2 cells induced with palmitate (PA). Importantly, inhibition of Egr2 decreased the expression of SOCS-1 as well as reduced phosphorylation of JAK2 and STAT3. And, our data indicated that silencing of Egr2 accelerated hepatic glucose uptake and reversed the impaired lipid metabolism upon insulin resistance. In summary, the present study confirms that Egr2 could deteriorate insulin resistance via the pathway of JAK2/STAT3/SOCS-1 and may shed light on resolving insulin resistance and further the pathogenesis of T2DM.

PKM2 aggravates palmitate-induced insulin resistance in HepG2 cells via STAT3 pathway

Studies have identified that PKM2 is related to the development of glucose intolerance and insulin resistance in rodents and humans. However, the underlying mechanism remains largely unknown. In the present study, we found that PKM2 expression was significantly elevated in insulin-resistant hepatic tissues and hepatocytes, implicating an association between PKM2 expression and hepatic insulin resistance (IR). In vitro study revealed that overexpression of PKM2 impaired the insulin signaling pathway by decreasing the phosphorylation of protein kinase B (Akt) and glycogen synthase kinase-3β (GSK3β). Furthermore, PKM2 overexpression enhanced the effects of PA on the lipid accumulation, the expression of phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) and hepatic glucose uptake. Intriguingly, PA-induced insulin resistance was suppressed following by the ablation of PKM2 in HepG2 cells. We also found that STAT3 was significantly activated by PKM2 overexpression. Moreover, we identified that PKM2 could interact directly with STAT3. Taken together, these studies demonstrate that PKM2 may promote hepatic IR via STAT3 pathway and would provide a new insight into dissecting the molecular pathogenesis of hepatic insulin resistance.

Fasting hepatic glucose uptake is higher in men than women.

Differences in glucose metabolism between men and women have previously been reported. Our purpose was to determine if there is a gender difference in fasting hepatic glucose uptake (MRglu). Fifty‐five patients (44 men, 11 women) referred for routine PET/CT using the glucose tracer 2‐deoxy‐2‐[F‐18]fluoro‐D‐glucose (FDG), mainly for cancer, had dynamic imaging for 30 min immediately following injection. Hepatic FDG clearance (mL/min/100 mL) was measured as gradient divided by intercept from Patlak–Rutland graphical analysis using a volume of interest over the abdominal aorta to record input function. Hepatic MRglu was obtained by multiplication of clearance by blood glucose concentration. Hepatic steatosis was diagnosed as CT density ≤40 HU. Mean (standard deviation) hepatic MRglu in 44 men was 2.30 (1.14) μmol/min/100 mL, significantly higher than in 11 women in whom it was 1.07 (1.35) μmol/min/100 mL (P = 0.003). CT density was 52 (12) HU in women compared with 45 (9) HU in men (P = 0.04), but there was no significant difference in blood glucose, BMI, or prevalence of recent chemotherapy (within 6 months preceding PET/CT). When patients were subdivided into those without hepatic steatosis (31 men/9 women), those without evidence of FDG‐avid malignancy on PET/CT (15/6), and those without either (11/5), gender differences in hepatic MRglu remained highly significant, but there were no significant differences in CT density, blood glucose, BMI, or recent chemotherapy history. Despite this being a population of clinically referred patients, the results strongly suggest that fasting hepatic MRglu is higher in men than in women.

Glucagon's effect on liver protein metabolism in vivo.

The postprandial state is characterized by a storage of nutrients in the liver, muscle, and adipose tissue for later utilization. In the case of a protein-rich meal, amino acids (AA) stimulate glucagon secretion by the α-cell. The aim of the present study was to determine the impact of the rise in glucagon on AA metabolism, particularly in the liver. We used a conscious catheterized dog model to recreate a postprandial condition using a pancreatic clamp. Portal infusions of glucose, AA, and insulin were used to achieve postprandial levels, while portal glucagon infusion was either maintained at the basal level or increased by three-fold. The high glucagon infusion reduced the increase in arterial AA concentrations compared with the basal glucagon level (-23%, P < 0.05). In the presence of high glucagon, liver AA metabolism shifted toward a more catabolic state with less protein synthesis (-36%) and increased urea production (+52%). Net hepatic glucose uptake was reduced modestly (-35%), and AA were preferentially used in gluconeogenesis, leading to lower glycogen synthesis (-54%). The phosphorylation of AMPK was increased by the high glucagon infusion (+40%), and this could be responsible for increasing the expression of genes related to pathways producing energy and lowering those involved in energy consumption. In conclusion, the rise in glucagon associated with a protein-rich meal promotes a catabolic utilization of AA in the liver, thereby, opposing the storage of AA in proteins.

Metabolic Responses to Weight Lifting

Metabolic Responses to Weight Lifting

Decreased basal hepatic glucose uptake in impaired fasting glucose.

This research aimed to define the pathophysiological defects responsible for the elevated fasting plasma glucose (FPG) concentration and excessive rise in post-load plasma glucose observed in individuals with impaired fasting glucose (IFG). We used tracer techniques to quantify basal splanchnic (primarily hepatic) glucose uptake and glucose fluxes following glucose ingestion in individuals with normal glucose tolerance (NGT; n=10) and IFG (n=10). Individuals with IFG had a comparable basal rate of hepatic glucose production to those with NGT (15.2±0.2 vs 18.0±0.8μmolmin-1[kg lean body mass (LBM)]-1; p=0.09). However, they had a significantly reduced glucose clearance rate during the fasting state compared with NGT (2.64±0.11 vs 3.62±0.20ml min-1[kgLBM]-1; p<0.01). The difference between the basal rate of glucose appearance measured with [3-3H]glucose and [1-14C]glucose, which represent basal splanchnic glucose uptake, was significantly reduced in IFG compared with NGT (1.39±0.28 vs 3.16±0.44μmolmin-1[kgLBM]-1; p=0.02). Following glucose ingestion, the total amount of exogenous glucose that appeared in the systemic circulation was not significantly different between groups. However, suppression of endogenous glucose production (EGP) was markedly impaired in individuals with IFG. These results demonstrate that decreased tissue (liver) glucose uptake, not enhanced EGP, is the cause for elevated FPG concentration in individuals with IFG, while the excessive rise in plasma glucose concentration following a glucose load in these individuals is the result of impaired suppression of hepatic glucose production.

Correcting Postprandial Hyperglycemia in Zucker Diabetic Fatty Rats With an SGLT2 Inhibitor Restores Glucose Effectiveness in the Liver and Reduces Insulin Resistance in Skeletal Muscle.

Ten-week-old Zucker diabetic fatty (ZDF) rats at an early stage of diabetes embody metabolic characteristics of obese human patients with type 2 diabetes, such as severe insulin and glucose intolerance in muscle and the liver, excessive postprandial excursion of plasma glucose and insulin, and a loss of metabolic flexibility with decreased lipid oxidation. Metabolic flexibility and glucose flux were examined in ZDF rats during fasting and near-normal postprandial insulinemia and glycemia after correcting excessive postprandial hyperglycemia using treatment with a sodium–glucose cotransporter 2 inhibitor (SGLT2-I) for 7 days. Preprandial lipid oxidation was normalized, and with fasting, endogenous glucose production (EGP) increased by 30% and endogenous glucose disposal (E-Rd) decreased by 40%. During a postprandial hyperglycemic-hyperinsulinemic clamp after SGLT2-I treatment, E-Rd increased by normalizing glucose effectiveness to suppress EGP and stimulate hepatic glucose uptake; activation of glucokinase was restored and insulin action was improved, stimulating muscle glucose uptake in association with decreased intracellular triglyceride content. In conclusion, SGLT2-I treatment improves impaired glucose effectiveness in the liver and insulin sensitivity in muscle by eliminating glucotoxicity, which reinstates metabolic flexibility with restored preprandial lipid oxidation and postprandial glucose flux in ZDF rats.

Obesity-associated alterations in glucose metabolism are reversed by chronic bilateral stimulation of the abdominal vagus nerve

Acute vagal stimulation modifies glucose and insulin metabolism, but the effect of chronic bilateral vagal stimulation is not known. Our aim was to quantify the changes in whole-body and organ-specific insulin sensitivities 12 weeks after permanent, bilateral, vagal stimulation performed at the abdominal level in adult mini-pigs. In 15 adult mini-pigs, stimulating electrodes were placed around the dorsal and ventral vagi using laparoscopy and connected to a dual-channel stimulator placed subcutaneously. Animals were divided into three groups based on stimulation and body weight (i.e., lean nonstimulated, obese nonstimulated, and obese stimulated). Twelve weeks after surgery, glucose uptake and insulin sensitivity were measured using positron emission tomography during an isoglycemic clamp. Mean whole-body insulin sensitivity was lower by 34% (P < 0.01) and the hepatic glucose uptake rate was lower by 33% (P < 0.01) in obese-nonstimulated mini-pigs but was no different in obese-stimulated compared with lean mini-pigs. An improvement in skeletal glucose uptake rate was also observed in obese-stimulated compared with obese-nonstimulated groups (P < 0.01). Vagal stimulation was associated with increased glucose metabolism in the cingulate and prefrontal brain areas. We conclude that chronic vagal stimulation improves insulin sensitivity substantially in diet-induced obesity by both peripheral and central mechanisms.

Priming Effect of a Morning Meal on Hepatic Glucose Disposition Later in the Day.

We used hepatic balance and tracer ([3H]glucose) techniques to examine the impact of “breakfast” on hepatic glucose metabolism later in the same day. From 0–240 min, 2 groups of conscious dogs (n = 9 dogs/group) received a duodenal infusion of glucose (GLC) or saline (SAL), then were fasted from 240–360 min. Three dogs from each group were euthanized and tissue collected at 360 min. From 360–600 min, the remaining dogs underwent a hyperinsulinemic (4× basal) hyperglycemic clamp (arterial blood glucose 146 ± 2 mg/dL) with portal GLC infusion. The total GLC infusion rate was 14% greater in dogs infused with GLC than in those receiving SAL (AUC360–600min 2,979 ± 296 vs. 2,597 ± 277 mg/kg, respectively). The rates of hepatic glucose uptake (5.8 ± 0.8 vs. 3.2 ± 0.3 mg ⋅ kg−1 ⋅ min−1) and glycogen storage (4.7 ± 0.6 vs. 2.9 ± 0.3 mg ⋅ kg−1 ⋅ min−1) during the clamp were markedly greater in dogs receiving GLC compared with those receiving SAL. Hepatic glycogen content was ∼50% greater, glycogen synthase activity was ∼50% greater, glycogen phosphorylase activity was ∼50% lower, and the amount of phosphorylated glycogen synthase was 34% lower, indicating activation of the enzyme, in dogs receiving GLC compared with those receiving SAL. Thus, morning GLC primed the liver to extract and store more glucose in the presence of hyperinsulinemic hyperglycemia later in the same day, indicating that breakfast enhances the liver’s role in glucose disposal in subsequent same-day meals.

Responses of plasma glucose and nonesterified fatty acids to intravenous insulin tolerance tests in dairy cows during a 670-day lactation

The metabolic response of dairy cows undergoing an extended lactation to an insulin tolerance test (ITT) was investigated. Twelve multiparous Holstein-Friesian cows that calved in late winter in a pasture-based system were managed for a 670-d lactation by delaying rebreeding. Four 5-wk experimental periods commenced at approximately 73, 217, 422, and 520 d in milk (DIM). Cows were offered a diet of perennial ryegrass (73 and 422 DIM) or pasture hay and silage (217 and 520 DIM) supplemented with 1 kg dry matter (DM) of grain (control; CON) or 6 kg DM of grain (GRN). Daily energy intake was approximately 160 and 215 MJ of metabolizable energy/cow for CON and GRN, respectively. At all other times, cows were managed as a single herd and grazed pasture supplemented with grain to an estimated daily intake of 180 MJ of metabolizable energy/cow. Cows were fitted with a jugular catheter during the final week of each experimental period. An ITT using 0.12 IU of insulin/kg of body weight (BW) was conducted on each cow at approximately 100, 250, 460, and 560 DIM. Cows in the GRN treatment had greater milk yield, milk solids yield, and BW than cows in the CON treatment. Within treatment, individual cow responses to the ITT were highly variable. Plasma glucose and nonesterified fatty acid (NEFA) concentrations declined at all stages of lactation. The clearance rate of plasma glucose was slower before 300 DIM than after 300 DIM, which indicates greater inhibition of hepatic glucose synthesis and uptake of glucose by insulin-dependent tissues later in the lactation. The clearance rate, area under the curve, and recovery of plasma NEFA were greatest at 100 DIM, indicating greater responsiveness to the antilipolytic effect of insulin in early lactation, but also greater lipolytic responsiveness. The variation in response to the ITT was mostly a result of DIM rather than diet. However, the plasma NEFA response showed interactions between diet and DIM, indicating that energy intake may affect tissue responses to insulin. The responsiveness of peripheral tissues to insulin, primarily adipose tissue, changed throughout a 670-d lactation and contributed to a greater proportion of nutrients being partitioned to body reserves at the expense of milk yield as lactation progressed. Both stage of lactation and dietary intake have a role in the determination of whole-body and peripheral tissue responses to insulin; however, the exact mechanisms in control of this are unclear.

CtBP2 ameliorates palmitate-induced insulin resistance in HepG2 cells through ROS mediated JNK pathway

Oxidative stress plays a significant role in the development of hepatic insulin resistance, but the underlying molecular mechanisms remain poorly understood. In this study, we discovered that C-terminal-binding protein 2 (CtBP2) level was decreased in insulin resistance. Taking into account the relationship between CtBP family protein (ANGUSTIFOLIA) and reactive oxygen species (ROS) accumulation, we conjectured CtBP2 was involved in insulin resistance through ROS induced stress. In order to verify this hypothesis, we over-expressed CtBP2 in palmitate (PA) treated HepG2 cells. Here, we found that over-expression of CtBP2 ameliorated insulin sensitivity by increasing phosphorylation of glycogen synthase kinase 3β (GSK3β) and protein kinase B (AKT). These data suggest that CtBP2 plays a critical role in the development of insulin resistance. Moreover, CtBP2 reversed the effects of PA on ROS level, lipid accumulation, hepatic glucose uptake and gluconeogenesis. We also found that over-expression of CtBP2 could suppress PA induced c-jun NH2 terminal kinase (JNK) activation. Furthermore, JNK inhibitor SP600125 was shown to promote the effect of CtBP2 on insulin signaling. Thus, we demonstrated that CtBP2 ameliorated PA-induced insulin resistance via ROS-dependent JNK pathway.

Obesity-Associated Alterations in Glucose Metabolism Are Reversed by Chronic Bilateral Stimulation of the Abdominal Vagus Nerve.

Acute vagal stimulation modifies glucose and insulin metabolism, but the effect of chronic bilateral vagal stimulation is not known. Our aim was to quantify the changes in whole-body and organ-specific insulin sensitivities 12 weeks after permanent, bilateral, vagal stimulation performed at the abdominal level in adult mini-pigs. In 15 adult mini-pigs, stimulating electrodes were placed around the dorsal and ventral vagi using laparoscopy and connected to a dual-channel stimulator placed subcutaneously. Animals were divided into three groups based on stimulation and body weight (i.e., lean nonstimulated, obese nonstimulated, and obese stimulated). Twelve weeks after surgery, glucose uptake and insulin sensitivity were measured using positron emission tomography during an isoglycemic clamp. Mean whole-body insulin sensitivity was lower by 34% (P < 0.01) and the hepatic glucose uptake rate was lower by 33% (P < 0.01) in obese-nonstimulated mini-pigs but was no different in obese-stimulated compared with lean mini-pigs. An improvement in skeletal glucose uptake rate was also observed in obese-stimulated compared with obese-nonstimulated groups (P < 0.01). Vagal stimulation was associated with increased glucose metabolism in the cingulate and prefrontal brain areas. We conclude that chronic vagal stimulation improves insulin sensitivity substantially in diet-induced obesity by both peripheral and central mechanisms.

Methionine sulfoxide reductase B1 deficiency does not increase high-fat diet-induced insulin resistance in mice

Methionine-S-sulfoxide reductase (MsrA) protects against high-fat diet-induced insulin resistance due to its antioxidant effects. To determine whether its counterpart, methionine-R-sulfoxide reductase (MsrB) has similar effects, we compared MsrB1 knockout and wild-type mice using a hyperinsulinemic-euglycemic clamp technique. High-fat feeding for eight weeks increased body weights, fat masses, and plasma levels of glucose, insulin, and triglycerides to similar extents in wild-type and MsrB1 knockout mice. Intraperitoneal glucose tolerance test showed no difference in blood glucose levels between the two genotypes after eight weeks on the high-fat diet. The hyperglycemic-euglycemic clamp study showed that glucose infusion rates and whole body glucose uptakes were decreased to similar extents by the high-fat diet in both wild-type and MsrB1 knockout mice. Hepatic glucose production and glucose uptake of skeletal muscle were unaffected by MsrB1 deficiency. The high-fat diet-induced oxidative stress in skeletal muscle and liver was not aggravated in MsrB1-deficient mice. Interestingly, whereas MsrB1 deficiency reduced JNK protein levels to a great extent in skeletal muscle and liver, it markedly elevated phosphorylation of JNK, suggesting the involvement of MsrB1 in JNK protein activation. However, this JNK phosphorylation based on a p-JNK/JNK level did not positively correlate with insulin resistance in MsrB1-deficient mice. Taken together, our results show that, in contrast to MsrA deficiency, MsrB1 deficiency does not increase high-fat diet-induced insulin resistance in mice.

Exenatide improves both hepatic and adipose tissue insulin resistance: A dynamic positron emission tomography study.

Acute EX administration (1) improves Hep-IR, decreases EGP, and enhances HGU and (2) reduces Adipo-IR, improves the antilipolytic effect of insulin, and reduces plasma free fatty acid levels during OGTT. (Hepatology 2016;64:2028-2037).

Novel, highly potent systemic glucokinase activators for the treatment of Type 2 Diabetes Mellitus

Glucokinase (GK, hexokinase IV) is a unique hexokinase that plays a central role in mammalian glucose homeostasis. Glucose phosphorylation by GK in the pancreatic β-cell is the rate-limiting step that controls glucose-stimulated insulin secretion. Similarly, GK-mediated glucose phosphorylation in hepatocytes plays a major role in increasing hepatic glucose uptake and metabolism and possibly lowering hepatic glucose output. Small molecule GK activators (GKAs) have been identified that increase enzyme activity by binding to an allosteric site. GKAs offer a novel approach for the treatment of Type 2 Diabetes Mellitus (T2DM) and as such have garnered much attention. We now report the design, synthesis, and biological evaluation of a novel series of 2,5,6-trisubstituted indole derivatives that act as highly potent GKAs. Among them, Compound 1 was found to possess high in vitro potency, excellent physicochemical properties, and good pharmacokinetic profile in rodents. Oral administration of Compound 1 at doses as low as 0.03mg/kg led to robust blood glucose lowering efficacy in 3week high fat diet-fed mice.

The Fatty Acid Synthase Inhibitor Platensimycin Improves Insulin Resistance without Inducing Liver Steatosis in Mice and Monkeys.

ObjectivesPlatensimycin (PTM) is a natural antibiotic produced by Streptomyces platensis that selectively inhibits bacterial and mammalian fatty acid synthase (FAS) without affecting synthesis of other lipids. Recently, we reported that oral administration of PTM in mouse models (db/db and db/+) with high de novo lipogenesis (DNL) tone inhibited DNL and enhanced glucose oxidation, which in turn led to net reduction of liver triglycerides (TG), reduced ambient glucose, and improved insulin sensitivity. The present study was conducted to explore translatability and the therapeutic potential of FAS inhibition for the treatment of diabetes in humans.MethodsWe tested PTM in animal models with different DNL tones, i.e. intrinsic synthesis rates, which vary among species and are regulated by nutritional and disease states, and confirmed glucose-lowering efficacy of PTM in lean NHPs with quantitation of liver lipid by MRS imaging. To understand the direct effect of PTM on liver metabolism, we performed ex vivo liver perfusion study to compare FAS inhibitor and carnitine palmitoyltransferase 1 (CPT1) inhibitor.ResultsThe efficacy of PTM is generally reproduced in preclinical models with DNL tones comparable to humans, including lean and established diet-induced obese (eDIO) mice as well as non-human primates (NHPs). Similar effects of PTM on DNL reduction were observed in lean and type 2 diabetic rhesus and lean cynomolgus monkeys after acute and chronic treatment of PTM. Mechanistically, PTM lowers plasma glucose in part by enhancing hepatic glucose uptake and glycolysis. Teglicar, a CPT1 inhibitor, has similar effects on glucose uptake and glycolysis. In sharp contrast, Teglicar but not PTM significantly increased hepatic TG production, thus caused liver steatosis in eDIO mice.ConclusionsThese findings demonstrate unique properties of PTM and provide proof-of-concept of FAS inhibition having potential utility for the treatment of diabetes and related metabolic disorders.