Time-course metabolic changes in high-fat diet-induced obesity rats: A pilot study using hyperpolarized (13)C dynamic MRS

Potential impact of underlying diseases influencing ADME in nonclinical safety assessment

Nonclinical studies involve in vitro, in silico, and in vivo experiments to assess the toxicokinetics, toxicology, and safety pharmacology of drugs according to regulatory requirements by a national or international authority. In this review, we summarize the potential effects of various underlying diseases governing the absorption, distribution, metabolism, and excretion (ADME) of drugs to consider the use of animal models of diseases in nonclinical trials. Obesity models showed alterations in hepatic metabolizing enzymes, transporters, and renal pathophysiology, which increase the risk of drug-induced toxicity. Diabetes models displayed changes in hepatic metabolizing enzymes, transporters, and glomerular filtration rates (GFR), leading to variability in drug responses and susceptibility to toxicity. Animal models of advanced age exhibited impairment of drug metabolism and kidney function, thereby reducing the drug-metabolizing capacity and clearance. Along with changes in hepatic metabolic enzymes, animal models of metabolic syndrome-related hypertension showed renal dysfunction, resulting in a reduced GFR and urinary excretion of drugs. Taken together, underlying diseases can induce dysfunction of organs involved in the ADME of drugs, ultimately affecting toxicity. Therefore, the use of animal models of representative underlying diseases in nonclinical toxicity studies can be considered to improve the predictability of drug side effects before clinical trials.

Hyperpolarized [1-13 C] pyruvate MRSI to detect metabolic changes in liver in a methionine and choline-deficient diet rat model of fatty liver disease

PURPOSE

Nonalcoholic fatty liver disease is an important cause of chronic liver disease. There are limited methods for monitoring metabolic changes during progression to steatohepatitis. Hyperpolarized 13 C MRSI (HP 13 C MRSI) was used to measure metabolic changes in a rodent model of fatty liver disease.

METHODS

Fifteen Wistar rats were placed on a methionine- and choline-deficient (MCD) diet for 1-18 weeks. HP 13 C MRSI, T2 -weighted imaging, and fat-fraction measurements were obtained at 3 T. Serum aspartate aminotransaminase, alanine aminotransaminase, and triglycerides were measured. Animals were sacrificed for histology and measurement of tissue lactate dehydrogenase (LDH) activity.

RESULTS

Animals lost significant weight (13.6% ± 2.34%), an expected characteristic of the MCD diet. Steatosis, inflammation, and mild fibrosis were observed. Liver fat fraction was 31.7% ± 4.5% after 4 weeks and 22.2% ± 4.3% after 9 weeks. Lactate-to-pyruvate and alanine-to-pyruvate ratios decreased significantly over the study course; were negatively correlated with aspartate aminotransaminase and alanine aminotransaminase (r = -[0.39-0.61]); and were positively correlated with triglycerides (r = 0.59-0.60). Despite observed decreases in hyperpolarized lactate signal, LDH activity increased by a factor of 3 in MCD diet-fed animals. Observed decreases in lactate and alanine hyperpolarized signals on the MCD diet stand in contrast to other studies of liver injury, where lactate and alanine increased. Observed hyperpolarized metabolite changes were not explained by alterations in LDH activity, suggesting that changes may reflect co-factor depletion known to occur as a result of oxidative stress in the MCD diet.

CONCLUSION

HP 13 C MRSI can noninvasively measure metabolic changes in the MCD model of chronic liver disease.

The ability of yoghurt supplemented with dietary fibers or brans extracted from wheat or rice to reduce serum lipids and enhance liver function in male hypercholesterolemic rats

This study was undertaken to evaluate the effect of yoghurt supplementation with rice and wheat brans or dietary fibers on serum lipid profile, liver, and heart functionalities, and hepatopathological aspects of the liver of hypercholesterolemic rats. 48 male rats were divided into 8 groups. Group 1 was kept as negative control and fed with a standard diet, and groups 2 to 6 were fed a hypercholesterolemia-induced diet supplemented with brans or dietary fibers of both grains. G2 received yoghurt without supplementation. The experiment lasted for 4 weeks. Results revealed that hypercholesterolemic rats administrated yoghurt supplemented with brans or dietary fibers reduced serum glucose from 113.9 ± 2.72 to 85.5 ± 4.94 in the serum of animals that received dietary fibers of rice and wheat, respectively. In addition, lipids profile and liver antioxidant status were improved. In addition, liver and heart functionalities and liver histopathological architecture were all improved depending on the type of administrated brans or fibers added to yoghurt. The inclusion of 0.5% of rice or wheat brans could be recommended to be added to yoghurt. PRACTICAL APPLICATIONS: Yoghurt is the most famous fermented milk in the world. Supplementation of yoghurt with rice and wheat brans or dietary fibers increased its nutritional value. We proved that this new product contributes to reducing serum glucose, improving lipids profile, and enhancing liver and heart functions in hypercholesterolemic rats. This study confirmed the suitability to add a thesis type of brans or dietary fibers as bioactive ingredients to yoghurt and increased the varieties of functional foods.

Multi-nuclear magnetic resonance spectroscopy: state of the art and future directions

With the development of heteronuclear fluorine, sodium, phosphorus, and other probes and imaging technologies as well as the optimization of magnetic resonance imaging (MRI) equipment and sequences, multi-nuclear magnetic resonance (multi-NMR) has enabled localize molecular activities in vivo that are central to a variety of diseases, including cardiovascular disease, neurodegenerative pathologies, metabolic diseases, kidney, and tumor, to shift from the traditional morphological imaging to the molecular imaging, precision diagnosis, and treatment mode. However, due to the low natural abundance and low gyromagnetic ratios, the clinical application of multi-NMR has been hampered. Several techniques have been developed to amplify the NMR sensitivity such as the dynamic nuclear polarization, spin-exchange optical pumping, and brute-force polarization. Meanwhile, a wide range of nuclei can be hyperpolarized, such as ²H, ³He, ¹³C, ¹⁵ N, ³¹P, and ¹²⁹Xe. The signal can be increased and allows real-time observation of biological perfusion, metabolite transport, and metabolic reactions in vivo, overcoming the disadvantages of conventional magnetic resonance of low sensitivity. HP-NMR imaging of different nuclear substrates provides a unique opportunity and invention to map the metabolic changes in various organs without invasive procedures. This review aims to focus on the recent applications of multi-NMR technology not only in a range of preliminary animal experiments but also in various disease spectrum in human. Furthermore, we will discuss the future challenges and opportunities of this multi-NMR from a clinical perspective, in the hope of truly bridging the gap between cutting-edge molecular biology and clinical applications.

Hyperpolarized carbon 13 MRI in liver diseases: Recent advances and future opportunities

Hyperpolarized carbon-13 magnetic resonance imaging (HP ¹³ C MRI) is a recently translated metabolic imaging technique. With dissolution dynamic nuclear polarization (d-DNP), more than 10 000-fold signal enhancement can be readily reached, making it possible to visualize real-time metabolism and specific substrate-to-metabolite conversions in the liver after injecting carbon-13 labelled probes. Increasing evidence suggests that HP ¹³ C MRI is a potential tool in detecting liver abnormalities, predicting disease progression and monitoring response treatment. In this review, we will introduce the recent progresses of HP ¹³ C MRI in diffuse liver diseases and liver malignancies and discuss its future opportunities from a clinical perspective, hoping to provide a comprehensive overview of this novel technique in liver diseases and highlight its scientific and clinical potential in the field of hepatology.

The effect of a low carbohydrate ketogenic diet with or without exercise on postpartum weight retention, metabolic profile and physical activity performance in postpartum mice

OBJECTIVE

the present study examined the effect of the isocaloric low-carbohydrate ketogenic diet (LCKD) with or without exercise training for 6 weeks on postpartum weight retention (PPWR), body composition, metabolic profile and physical activity performance in postpartum mice.

METHODS

postpartum mice were assigned to 4 groups (n=8/group) as follows: (1) those on a control diet without aerobic exercise (CN); (2) those on a control diet with aerobic exercise (CN+EX), (3); those on a LCKD without aerobic exercise (LCKD); (4) those on a LCKD with aerobic exercise (LCKD+EX). CN+EX and LCKD+EX mice performed 6 weeks of exercise training on a treadmill. After the 6-week intervention, physical activity performance was determined.

RESULTS

postpartum mice in all groups experienced progressive reductions in body weight over the study period. The LCKD group had the smallest reduction in PPWR (p<0.05). The LCKD group had significantly higher total cholesterol, low-density lipoprotein cholesterol and lactate dehydrogenase levels, and liver lipid concentrations with a worsened glucose tolerance, compared to the CN group (p<0.05). The LCKD group showed significant reductions in physical activity performance, whilst the LCKD+EX group showed significantly improvement in endurance performance, and paralleled the concomitant elevation in blood ketone levels.

CONCLUSIONS

6-week LCKD feeding on its own was less effective for reducing PPWR, and more detrimental to postpartum metabolic outcomes and physical activity performance of the postpartum mice. The feasibility of a LCKD with or without exercise during the postpartum period as a strategy for managing PPWR and improving postpartum metabolic profiles should be carefully considered.

In vivo anti-hypercholesterolemic effect of buttermilk, milk fat globule membrane and Enterococcus faecium FFNL-12

The present study was undertaken to evaluate the hypocholesterolemic activity of buttermilk, milk fat globule membrane (MFGM) and Enterococcus faecium FFNL-12 in rat model. Thirty-sixth male Abino rats were divided into six groups. The first one (coded as G1) was fed a standard diet containing 10% corn oil as fat source while remaining five (coded G2 to G6) were fed hypercholesterolemic diets in which oil was replaced with animal grease. Animals subjected to treatment G1 served as healthy control while those in G2 were assigned as hypocholesterolemic animals which did not receive any treatment. The remaining experimental groups were designed to assess the hypocholesterolemic effect of intragastric adminstartion of dose of 109 CFU/Kg body weight of Enterococcus faecium FFNL-12 (G3), Enterococcus faecium FFNL-12/butter milk (G4), buttermilk (G5) and milk fat globule membrane (MFGM). After four weeks, animals were evaluated in relation to growth, fecal pH, organs weight, serum lipid profile, antioxidant activity of liver tissue, liver and heart function and liver histopathological architecture. Results revealed that animals fed hypercholesterolemic diet (G2-G6) had significantly lower faecal pH and liver weight compared with those fed standard diet (G1). Treatments applied to animals fed hypercholesterolemic diet with the above mentioned additions (G3 to G6) appeared to improve both cardiac and hepatic functions, serum lipid profile and glucose concentration and liver histopathological architecture compared with animals subjected to G2 treatment. In most cases, treatment with MFGM appeared to be the most effective to avoid adverse effects associated to feeding hypercholesterolemic diet. MFGM fraction as well as E. faecium FFNL-12/buttermilk combination were effective in reducing serum lipids and glucose levels to the normal range. This combination also had potential antioxidant activity and ability to improve liver and heart functions.

Effect of supplementing chromium histidinate and picolinate complexes along with biotin on insulin sensitivity and related metabolic indices in rats fed a high-fat diet

SCOPE

To investigate the effects of chromium histidinate (CrHis) and chromium picolinate (CrPic) complex along with biotin to a high-fat diet (HFD) fed to rats on the insulin sensitivity and the anti-obesity properties.

METHODS

Forty-two Sprague-Dawley male rats were divided into six groups. The rats were fed either (a): a standard diet (Control) or (b): a HFD or (c): a HFD with biotin (HFD+B) or (d): a combination of HFD and biotin along with CrPic (HFD + B + CrPic) or (e): a combination of HFD and biotin along with CrHis (HFD + B + CrHis) or (f): a combination of HFD and biotin along with CrHis and CrPic (HFD + B + CrHis + CrPic).

RESULTS

Adding biotin with chromium to HFD improved the glucose, insulin, HOMA-IR, leptin, lipid profile, with HFD+B+CrHis treatment being the most effective (p = 0.0001). Serum, liver, and brain tissue Cr concentrations increased upon Cr supplementations (p = 0.0001). Supplementing CrHis along with biotin to a HFD (HFD + B + CrHis) provided the greatest levels of GLUT-1, GLUT-3, PPAR-γ, and IRS-1, but the lowest level of NF-κB in the brain and liver tissues.

CONCLUSION

Biotin supplementation with chromium complexes, CrHis in particular, to a HFD pose to be a potential therapeutic feature for the treatment of insulin resistance.

Hyperpolarized [1-13 C] pyruvate as a possible diagnostic tool in liver disease

Introduction of hyperpolarized magnetic resonance in preclinical studies and lately translation to patients provides new detailed in vivo information of metabolic flux in organs. Hyperpolarized magnetic resonance based on 13 C enriched pyruvate is performed without ionizing radiation and allows quantification of the pyruvate conversion products: alanine, lactate and bicarbonate in real time. Thus, this methodology has a promising potential for in vivo monitoring of energetic alterations in hepatic diseases. Using 13 C pyruvate, we investigated the metabolism in the porcine liver before and after intravenous injection of glucose. The overall mean lactate to pyruvate ratio increased significantly after the injection of glucose whereas the bicarbonate to pyruvate ratio was unaffected, representative of the levels of pyruvate entering the tricarboxylic acid cycle. Similarly, alanine to pyruvate ratio did not change. The increased lactate to pyruvate ratio over time showed an exponential correlation with insulin, glucagon and free fatty acids. Together, these data, obtained by hyperpolarized 13 C magnetic resonance spectroscopy and by blood sampling, indicate a hepatic metabolic shift in glucose utilization following a glucose challenge. Our findings demonstrate the capacity of hyperpolarized 13 C magnetic resonance spectroscopy for quantifying hepatic substrate metabolism in accordance with well-known physiological processes. When combined with concentration of blood insulin, glucagon and free fatty acids in the blood, the results indicate the potential of hyperpolarized magnetic resonance spectroscopy as a future clinical method for quantification of hepatic substrate metabolism.