Effect of caloric restriction and AMPK activation on hepatic nuclear receptor, biotransformation enzyme, and transporter expression in lean and obese mice

Ellagic acid protects against non-alcoholic fatty liver disease in streptozotocin-diabetic rats by activating AMPK

CONTEXT

Ellagic acid (EA) is used in traditional medicine to treated hyperlipidaemia.

OBJECTIVE

This study examined if AMPK mediates the anti-steatotic effect of ellagic acid (EA) in streptozotocin (STZ)-induced type 1 diabetes mellitus in rats.

MATERIALS AND METHODS

Adult male Wistar rats (130 ± 10 g) were divided into 6 groups (n = 8 rats/group) as control, control + EA, control + EA + CC an AMPK inhibitor), T1DM, T1DM + EA, and T1DM + EA + CC. The treatments with EA (50 mg/kg/orally) and CC (200 ng/rat/i.p.) were given the desired groups for 12 weeks, daily.

RESULTS

In T1DM-rats, EA reduced fasting glucose levels (44.8%), increased fasting insulin levels (92.8%), prevented hepatic lipid accumulation, and decreased hepatic and serum levels of total triglycerides (54% & 61%), cholesterol (57% & 48%), and free fatty acids (40% & 37%). It also reduced hepatic levels of ROS (62%), MDA (52%), TNF-α (62%), and IL-6 (57.2%) and the nuclear activity of NF-κB p65 (54%) but increased the nuclear activity of Nrf-2 (4-fold) and levels of GSH (107%) and SOD (87%). Besides, EA reduced downregulated SREBP1 (35%), SREBP2 (34%), ACC-1 (36%), FAS (38%), and HMG-CoAR (49%) but stimulated mRNA levels of PPARα (1.7-fold) and CPT1a (1.8-fold), CPT1b (2.9-fold), and p-AMPK (4-fold). All these events were prevented by the co-administration of CC.

DISCUSSION AND CONCLUSIONS

These findings encourage the use of EA to treat hepatic disorders, and non-alcoholic fatty liver disease (NAFLD). Further in vivo and in vitro studies are needed to validate its potential in clinical medicine.

Crataegus aronia prevents high-fat diet-induced hepatic steatosis in rats by activating AMPK-induced suppression of SREBP1 and activation of PPARα

This study examined if the aqueous extract of Crataegus aronia (C. aronia) can prevent high-fat diet (HFD)-induced hepatic steatosis in rats by activating AMPK. Adult male Wistar rats were fed either a control diet or HFD for 12 weeks and treated either with vehicle (normal saline) or C. aronia extract (200 mg/kg/orally), daily. Also, hepatocytes were treated with increasing concentrations of the extract in the presence or absence of compound C (CC), an AMPK inhibitor. C. aronia prevented the increase in serum and hepatic lipids, reduced hepatic levels of reactive oxygen species, and increased hepatic glutathione and superoxide dismutase levels. It also downregulated the hepatic expression of SREBP1/2, fatty acid synthase, and 3-hydroxy-3-methylglutaryl-coenzyme A reductase but stimulated the activity of AMPK and levels of peroxisome proliferator-activated receptor-alpha. Similar effects were reported in the cultured cells, in a dose-dependent manner but were prevented by CC. In conclusion, C. aronia ameliorates HFD-induced hepatic steatosis and oxidative stress by activating AMPK. PRACTICAL APPLICATIONS: The use of the aqueous extract of Crataegus aronia has been extensively used during the last years in traditional medicine to treat chronic disorders including nonalcoholic fatty liver disease. The findings of this study support these findings and suggest that oral administration of C. aronia aqueous extract has potent hypoglycemic effect and demonstrate the mechanism of action mimics such drugs such as metformin and involves activation of AMPK and peroxisome proliferator-activated receptor-alpha. These findings are very encouraging for further biochemical analysis and isolation of active ingredients responsible for these effects to be used in more clinical trials.

Intermittent Starvation Extends the Functional Lifetime of Primary Human Hepatocyte Cultures

Primary human hepatocyte (PHH) cultures have become indispensable to mitigate the risk of adverse drug reactions in human patients. In contrast to dedifferentiating monocultures, coculture with nonparenchymal cells maintains PHH functions for 2-4 weeks. However, because the functional lifespan of PHHs in vivo is 200-400 days, it is desirable to further prolong PHH functions in vitro toward modeling chronic drug exposure and disease progression. Fasting has benefits on the longevity of organisms and the health of tissues such as the liver. We hypothesized that a culturing protocol that mimics dynamic fasting/starvation could activate starvation pathways and prolong PHH functional lifetime. To mimic starvation, serum and hormones were intermittently removed from the culture medium of micropatterned cocultures (MPCCs) containing PHHs organized onto collagen domains and surrounded by 3T3-J2 murine fibroblasts. A weekly 2-day starvation optimally prolonged PHH functional lifetime for 6+ weeks in MPCCs versus a decline after 3 weeks in nonstarved controls. The 2-day starvation also enhanced the functions of PHH monocultures for 2 weeks, suggesting direct effects on PHHs. In MPCCs, starvation activated 5' adenosine monophosphate-activated protein kinase (AMPK) and restricted fibroblast overgrowth onto PHH islands, thereby maintaining hepatic polarity. The effects of starvation on MPCCs were partially recapitulated by activating AMPK using metformin or growth arresting fibroblasts via mitomycin-C. Lastly, starved MPCCs demonstrated lower false positives for drug toxicity tests and higher drug-induced cytochrome-P450 activities versus nonstarved controls even after 5 weeks. In conclusion, intermittent serum/hormone starvation extends PHH functional lifetime toward enabling clinically relevant drug screening.

Enzymatically modified isoquercitrin promotes energy metabolism through activating AMPKα in male C57BL/6 mice

Quercetin possesses various health beneficial functions, but its poor bioavailability limits these functions. Enzymatically modified isoquercitrin (EMIQ) is a quercetin glycoside with a greater bioavailability than quercetin. In this study, we investigated whether EMIQ regulates energy metabolism in mice and its underlying molecular mechanism. Male C57BL/6 mice were fed a normal diet with different doses of EMIQ or quercetin (0.02%, 0.1% and 0.5%) for two weeks. Supplementation with 0.1% EMIQ significantly decreased white adipose tissue (WAT) weight. Supplementation with 0.02% and 0.1% EMIQ promoted phosphorylation of adenosine monophosphate activated protein kinase (AMPK) in the WAT, liver, and muscle. In the WAT, 0.1% EMIQ downregulated peroxisome proliferator-activated receptor (PPAR)γ, CCAAT-enhancer-binding protein (C/EBP)α, C/EBPβ, and sterol regulatory element-binding protein 1 expression, as well as upregulated mitochondrial uncoupling protein (UCP) 2 and carnitine palmitoyltransferase-1 expression. Supplementation with 0.1% EMIQ also promoted the expression of thermogenesis-associated factors including PPARγ coactivator α (PGC-1α), UCP1, PR-domain containing protein 16, and sirtuin 1 in the WAT. In the liver, EMIQ promoted the phosphorylation of acetyl-CoA carboxylase, and increased the expression of PPARα, constitutive androstane-receptor, and farnesoid X receptor. Furthermore, supplementation with 0.02% or 0.1% EMIQ suppressed the plasma glucose level accompanied by the translocation of glucose transporter 4 to the plasma membrane of the muscle. Our results suggest that EMIQ is a potential food additive for the regulation of energy metabolism through AMPK phosphorylation.

Dynamic Contrast-Enhanced MRI of OATP Dysfunction in Diabetes

Diabetes is associated with hepatic metabolic dysfunction predisposing patients to drug-induced liver injury. Mouse models of type 2 diabetes (T2D) have dramatically reduced expression of organic anion transporting polypeptide (OATP)1A1, a transporter expressed in hepatocytes and in the kidneys. The effects of diabetes on OATP1B2 expression are less studied and less consistent. OATP1A1 and OATP1B2 both transport endogenous substrates such as bile acids and hormone conjugates as well as numerous drugs including gadoxetate disodium (Gd-EOB-DTPA). As master pharmacokinetic regulators, the altered expression of OATPs in diabetes could have a profound and clinically significant influence on drug therapies. Here, we report a method to noninvasively measure OATP activity in T2D mice by quantifying the transport of hepatobiliary-specific gadolinium-based contrast agents (GBCAs) within the liver and kidneys using dynamic contrast-enhanced MRI (DCE-MRI). By comparing GBCA uptake in control and OATP knockout mice, we confirmed liver clearance of the hepatobiliary-specific GBCAs, Gd-EOB-DTPA, and gadobenate dimeglumine, primarily though OATP transporters. Then, we measured a reduction in the hepatic uptake of these hepatobiliary GBCAs in T2D ob/ob mice, which mirrored significant reductions in the mRNA and protein expression of OATP1A1 and OATP1B2. As these GBCAs are U.S. Food and Drug Administration-approved agents and DCE-MRI is a standard clinical protocol, studies to determine OATP1B1/1B3 deficiencies in human individuals with diabetes can be easily envisioned.

Changes in drug transport and metabolism and their clinical implications in non-alcoholic fatty liver disease

INTRODUCTION

The incidence of non-alcoholic fatty liver disease (NAFLD) is rising, especially in Western countries. Drug treatment in patients with NAFLD is common since it is linked to other conditions like diabetes, obesity, and cardiovascular disease. Consequently, changes in drug metabolism may have serious clinical implications. Areas covered: A literature search for studies in animal models or patients with obesity, fatty liver, non-alcoholic steatohepatitis (NASH) or NASH cirrhosis published before November 2016 was performed. After discussing epidemiology and animal models for NAFLD, we summarized both basic as well as clinical studies investigating changes in drug transport and metabolism in NAFLD. Important drug groups were assessed separately with emphasis on clinical implications for drug treatment in patients with NAFLD. Expert opinion: Given the frequency of NAFLD even today, a high degree of drug treatment in NAFLD patients appears safe and well-tolerated despite considerable changes in hepatic uptake, distribution, metabolism and transport of drugs in these patients. NASH causes changes in biliary excretion, systemic concentrations, and renal handling of drugs leading to alterations in drug efficacy or toxicity under specific circumstances. Future clinical drug studies should focus on this special patient population in order to avoid serious adverse events in NAFLD patients.

Bisphenol A sulfonation is impaired in metabolic and liver disease

BACKGROUND

Bisphenol A (BPA) is a widely used industrial chemical and suspected endocrine disruptor to which humans are ubiquitously exposed. The liver metabolizes and facilitates BPA excretion through glucuronidation and sulfonation. The sulfotransferase enzymes contributing to BPA sulfonation (detected in human and rodents) is poorly understood.

OBJECTIVES

To determine the impact of metabolic and liver disease on BPA sulfonation in human and mouse livers.

METHODS

The capacity for BPA sulfonation was determined in human liver samples that were categorized into different stages of metabolic and liver disease (including obesity, diabetes, steatosis, and cirrhosis) and in livers from ob/ob mice.

RESULTS

In human liver tissues, BPA sulfonation was substantially lower in livers from subjects with steatosis (23%), diabetes cirrhosis (16%), and cirrhosis (18%), relative to healthy individuals with non-fatty livers (100%). In livers of obese mice (ob/ob), BPA sulfonation was lower (23%) than in livers from lean wild-type controls (100%). In addition to BPA sulfonation activity, Sult1a1 protein expression decreased by 97% in obese mouse livers.

CONCLUSION

Taken together these findings establish a profoundly reduced capacity of BPA elimination via sulfonation in obese or diabetic individuals and in those with fatty or cirrhotic livers versus individuals with healthy livers.