Inhibition of pyruvate dehydrogenase kinase-4 by l-glutamine protects pregnant rats against fructose-induced obesity and hepatic lipid accumulation

Depletion of hepatic glutathione and adenosine by glucocorticoid exposure in Wistar rats is pregnancy-independent

Liver diseases have gained increasing attention due to their substantial impact on health, independently as well as in association with cardio-metabolic disorders. Studies have suggested that glutathione and adenosine assist in providing protection against oxidative stress and inflammation while glucocorticoid (GC) therapy has been associated with chronic inflammatory disorders, even in pregnancy. The implications of Glucocorticoid exposure on maternal health and fetal growth is a concern, however, the possible role of glutathione and adenosine has not been thoroughly investigated. The study therefore hypothesize that exposure to glucocorticoids leads to depletion of hepatic glutathione and adenosine levels, contributing to oxidative stress and tissue injury. Additionally, we aim to investigate whether the effects of glucocorticoids on hepatic health are pregnancy dependent in female rats. Twelve Pregnant and twelve age-matched non-pregnant rats were used for this study; an exogenous administration of glucocorticoid (Dex: 0.2 mg/kg) or vehicle (po) was administered to six pregnant and six non-pregnant rats from gestational day 14 to 19 or for a period of 6 days respectively. Data obtained showed that GC exposure led to a decrease in hepatic glucose-6-phosphate dehydrogenase, glutathione peroxidase, GSH/GSSG ratio and adenosine content in both pregnant and non-pregnant rats. In addition, increased activities of adenosine deaminase and xanthine oxidase, along with increased production of uric acid and increased levels of lactate dehydrogenase, aspartate aminotransferase, alanine transferase, alkaline phosphatase and gamma-glutamyl transferase were observed. In summary, the study indicates that GC-induced liver damage is underlined by depleted hepatic adenosine and glutathione levels as well as elevated markers of tissue inflammation and/or injury. Furthermore, the findings suggest that the effects of GC exposure on hepatic health are pregnancy independent.

Glutamine prevents high-fat diet-induced hepatic lipid accumulation in mice by modulating lipolysis and oxidative stress

Metabolic-associated fatty liver disease (MAFLD) is related to metabolic dysfunction and is characterized by excess fat storage in the liver. Several studies have indicated that glutamine could be closely associated with lipid metabolism disturbances because of its important role in intermediary metabolism. However, the effect of glutamine supplementation on MAFLD progression remains unclear. Here, we used a high-fat diet (HFD)-induced MAFLD C57BL/6 mouse model, and glutamine was supplied in the drinking water at different time points for MAFLD prevention and reversal studies. A MAFLD prevention study was performed by feeding mice an HFD concomitant with 4% glutamine treatment for 24 weeks, whereas the MAFLD reversal study was performed based on 4% glutamine treatment for 13 weeks after feeding mice an HFD for 10 weeks. In the prevention study, glutamine treatment ameliorated serum lipid storage, hepatic lipid injury, and oxidative stress in HFD-induced obese mice, although glutamine supplementation did not affect body weight, glucose homeostasis, energy expenditure, and mitochondrial function. In the MAFLD reversal study, there were no noticeable changes in the basic physiological phenotype and hepatic lipid metabolism. In summary, glutamine might prevent, but not reverse, HFD-induced MAFLD in mice, suggesting that a cautious attitude is required regarding its use for MAFLD treatment.

Cadmium as a male reproductive toxicant and natural and non-natural ways to tackle it: a review

Cadmium (Cd) is a naturally occurring environmental pollutant, a toxic substance that causes oxidative stress. According to epidemiological studies, the data suggested that environmental and occupational Cd exposure may be related to several diseases and severe testicular damage. However, studies are going on to explore the mechanism of Cd-induced male reproductive toxicity and its treatment strategies. Currently, researchers are focusing on naturally occurring bioactive compounds, plant extracts, and biochemical, which have better efficacy, less toxicity, and high bioavailability. This review focuses on the mechanistic effect of Cd on testicular toxicity and different categories of compounds having a beneficial impact on Cd-induced male reproductive toxicity. Some potent bioactive antioxidants are quercetin, caffeic acid phenethyl ester, cyanidin-3-O-glucoside, curcumin, and silymarin. In comparison, plant extracts are Costus afer leaf methanol extract, methanol root extract of Carpolobia lutea, red carrot methanolic extract, Panax ginseng extract, and biochemicals including melatonin, progesterone, glutamine, L-carnitine, and selenium. Advanced and more detailed studies are needed on these compounds to explore their mechanism in attenuating Cd-induced testicular toxicity and can be potential therapeutics in the future.

Glutamine Ameliorates Liver Steatosis via Regulation of Glycolipid Metabolism and Gut Microbiota in High-Fat Diet-Induced Obese Mice

Obesity and its associated conditions, such as nonalcoholic fatty liver disease (NAFLD), are risk factors for health. The aim of this study was to explore the effects of glutamine (Gln) on liver steatosis induced by a high-fat diet (HFD) and HEPG2 cells induced by oleic acid. Gln demonstrated a positive influence on hepatic homeostasis by suppressing acetyl CoA carboxylase (ACC) and fatty acid synthase (FAS) and promoting sirtuin 1 (SIRT1) expression while improving glucose metabolism by regulating serine/threonine protein kinase (AKT)/factor forkhead box O1 (FOXO1) signals in vivo and in vitro. Obese Gln-fed mice had higher colonic short-chain fatty acid (SCFA) contents and lower inflammation factor protein levels in the liver, HEPG2 cells, and jejunum. Gln-treated obese mice had an effective decrease in Firmicutes abundance. These findings indicate that Gln serves as a nutritional tool in managing obesity and related disorders.

PDK inhibition promotes glucose utilization, reduces hepatic lipid deposition, and improves oxidative stress in largemouth bass (Micropterus salmoides) by increasing pyruvate oxidative phosphorylation

In omnivorous fish, the pyruvate dehydrogenase kinases (PDKs)-pyruvate dehydrogenase E1α subunit (PDHE1α) axis is essential in the regulation of carbohydrate oxidative catabolism. Among the existing research, the role of the PDKs-PDHE1α axis in carnivorous fish with poor glucose utilization is unclear. In the present study, we determined the effects of PDK inhibition on the liver glycolipid metabolism of largemouth bass (Micropterus salmoides). DCA is a PDK-specific inhibitor that inhibits PDK by binding the allosteric sites. A total of 160 juvenile largemouth bass were randomly divided into two groups, with four replicates of 20 fish each, fed a control diet and a control diet supplemented with dichloroacetate (DCA) for 8 weeks. The present results showed that DCA supplementation significantly decreased the hepatosomatic index, triglycerides in liver and serum, and total liver lipids of largemouth bass compared with the control group. In addition, compared with the control group, DCA treatment significantly down-regulated gene expression associated with lipogenesis. Furthermore, DCA supplementation significantly decreased the mRNA expression of pdk3a and increased PDHE1α activity. In addition, DCA supplementation improved glucose oxidative catabolism and pyruvate oxidative phosphorylation (OXPHOS) in the liver, as evidenced by low pyruvate content in the liver and up-regulated expressions of glycolysis-related and TCA cycle/OXPHOS-related genes. Moreover, DCA consumption decreased hepatic malondialdehyde (MDA) content, enhanced the activities of superoxide dismutase (SOD), and increased transforming growth factor beta (tgf-β), glutathione S-transferase (gst), and superoxide dismutase 1 (sod1) gene expression compared with the control diet. This study demonstrated that inhibition of PDKs by DCA promoted glucose utilization, reduced hepatic lipid deposition, and improved oxidative stress in largemouth bass by increasing pyruvate OXPHOS. Our findings contribute to the understanding of the underlying mechanism of the PDKs-PDHE1α axis in glucose metabolism and improve the utilization of dietary carbohydrates in farmed carnivorous fish.

Inhibition of pyruvate dehydrogenase kinase improves carbohydrate utilization in Nile tilapia by regulating PDK2/4-PDHE1α axis and insulin sensitivity

Pyruvate dehydrogenase kinases (PDKs)-pyruvate dehydrogenase E1α subunit (PDHE1α) axis plays an important role in regulating glucose metabolism in mammals. However, the regulatory function of PDKs-PDHE1α axis in the glucose metabolism of fish is not well known. This study determined whether PDKs inhibition could enhance PDHE1α activity, and improve glucose catabolism in fish. Nile tilapia fingerlings (1.90 ± 0.11 g) were randomly divided into 4 treatments in triplicate (30 fish each) and fed control diet without dichloroacetate (DCA) (38% protein, 7% lipid and 45% corn starch) and the control diet supplemented with DCA, which inhibits PDKs through binding the allosteric sites, at 3.75 (DCA3.75), 7.50 (DCA7.50) and 11.25 g/kg (DCA11.25), for 6 wk. The results showed that DCA3.75, DCA7.50 and DCA11.25 significantly increased weight gain, carcass ratio and protein efficiency ratio (P < 0.05) and reduced feed efficiency (P < 0.05) of Nile tilapia. To investigate the effects of DCA on growth performance of Nile tilapia, we selected the lowest dose DCA3.75 for subsequent analysis. Nile tilapia fed on DCA3.75 significantly reduced the mesenteric fat index, serum and liver triglyceride concentration and total lipid content in whole fish, and down-regulated the expressions of genes related to lipogenesis (P < 0.05) compared to the control. The DCA3.75 treatment significantly improved glucose oxidative catabolism and glycogen synthesis in the liver, but significantly reduced the conversion of glucose to lipid (P < 0.05). Furthermore, the DCA3.75 treatment significantly decreased the PDK2/4 gene and protein expressions (P < 0.05), accordingly stimulated PDHE1α activity by decreasing the phosphorylated PDHE1α protein level. In addition, DCA3.75 treatment significantly increased the phosphorylated levels of key proteins involved in insulin signaling pathway and glycogen synthase kinase 3β (P < 0.05). Taken together, the present study demonstrates that PDK2/4 inhibition by using DCA promotes glucose utilization in Nile tilapia by activating PDHE1α and improving insulin sensitivity. Our study helps to understand the regulatory mechanism of glucose metabolism for improving dietary carbohydrate utilization in farmed fish.

Acetate restores hypothalamic-adipose kisspeptin status in a rat model of PCOS by suppression of NLRP3 immunoreactivity

PURPOSE

Polycystic ovary syndrome (PCOS) is a complex reproductive event that is delineated by endocrine/metabolic disorders. Alteration of kisspeptin status in the hypothalamus and adipose tissue is critical to increased endocrine/metabolic derangements in PCOS individuals, aggravating the clinical manifestation of PCOS and its complications. Short chain fatty acids (SCFAs) are crucial modulators of metabolic homeostasis. However, the role of SCFAs, particularly acetate on hypothalamic-adipose kisspeptin status (HAKS) in PCOS model is unknown. The present study hypothesized acetate as a key player in restoration of deranged HAKS, associated with experimental PCOS model.

METHODS

Three groups (n = 6/group) of female Wistar rats (120-150 g) were used. The groups were treated (po) for 21 days with vehicle, letrozole (1 mg/kg) with/without acetate (200 mg/kg) respectively.

RESULTS

Letrozole-treated animals had impaired glucose homeostasis, elevated testosterone, leptin and LH/FSH ratio and decreased GnRH and adiponectin with ovarian tissues revealing degenerated follicles and disrupted morphology. These animals also showed increased concentration of hypothalamic triglyceride (TG)/total cholesterol (TC), free fatty acid (FFA), and decreased concentration of TG/TC/FFA in visceral adipose tissue (VAT) with an increase in hypothalamic and VAT malondialdehyde, NF-κB/TNF-α and decreased glutathione/G6PD and hypothalamic but not VAT kisspeptin. Immunohistochemical analysis revealed the expression of NLRP3 inflammasome in the hypothalamus and VAT and all these changes were attenuated by acetate.

CONCLUSIONS

Altogether, the present results demonstrate that PCOS is characterized with hypothalamic-adipose inflammation, associated with immunohistochemical expression of NLRP3 with significant alteration of hypothalamic but not adipose kisspeptin. The results suggest that acetate restores kisspeptin status in PCOS animals. This beneficial effect is accompanied by repressed NLRP3 immunoreactivity.

Glutamine prevents upregulation of NF-kB signaling and caspase 3 activation in ischaemia/reperfusion-induced testicular damage: An animal model

AIM

Testicular ischaemia/reperfusion (I/R) injury is a major consequence of testicular torsion with possible attendant risk of male infertility. Glutamine, on the other hand, is a known antioxidant with anti-inflammatory potential. The present study evaluated whether or not glutamine would improve I/R-induced testicular injury in torsion/detorsion (T/D). The possible associated mechanisms were also investigated.

METHODS

Wistar rats were randomly allotted into four groups (n = 10); sham-operated, glutamine-treated, T/D, and T/D + glutamine. Testicular torsion was induced and reperfusion established after two and a half hour under ketamine/xylazine anaethesia. Glutamine was administered one hour before reperfusion and continued daily for 3 days. At the end of the study, animals were euthanized, blood samples obtained, epididymal sperm suspension collected, and the testes harvested for biochemical and histopathological assays using established methods.

RESULTS

Glutamine prevented T/D-driven I/R-induced reduced sperm quality, impaired testicular histoarchitecture, and suppressed circulating testosterone. Also, glutamine abated I/R-induced oxidative stress (evidenced by reduced hydrogen peroxide and MDA generation and enhanced concentrations and activities of antioxidants), inflammation (evidenced by suppression of TNF-α and IL-1β), and apoptosis (evidenced by reduced DNA fragmentation) by down-regulating NF-kB and caspase 3 activity.

CONCLUSION

For the first time, this study demonstrated that glutamine administration improved testicular I/R injury in T/D rat model by maintaining testicular redox balance, and testicular integrity and function via inhibition of I/R-induced upregulation of NF-kB signaling and caspase 3 activation.

Restoration of cardiac metabolic flexibility by acetate in high fat diet-induced obesity is independent of ANP/BNP modulation

The present study hypothesized that cardiac metabolic inflexibility is dependent on cardiac ANP/BNP alteration and HDAC activity. We further sought to investigate the therapeutic potential of SCFA, acetate in high fat diet (HFD)-induced obese rat model. Adult male Wistar rats were assigned into groups (n = 6/group): Control, Obese, Sodium acetate (NaAc)-treated and Obese+ NaAc-treated groups received distilled water once daily (oral gavage), 40% HFD ad libitum, 200 mg/kg NaAc once daily (oral gavage) and 40% HFD+NaAc respectively. The treatments lasted for 12 weeks. HFD resulted in increased food intake, body weight and cardiac mass. It also caused insulin resistance and enhanced β-cell function, increased fasting insulin, lactate, plasma and cardiac triglyceride, total cholesterol, lipid peroxidation, TNF-α, IL-6, HDAC and cardiac troponin T and γ-Glutamyl transferase and decreased plasma and cardiac GSH with unaltered cardiac ANP and BNP. However, these alterations were averted when treated with acetate. Taken together, these results indicate that obesity induces defective cardiac metabolic flexibility, which is accompanied by elevated level of HDAC and not ANP/BNP alteration. The results also suggest that acetate ameliorates obesity-induced cardiac metabolic inflexibility by suppression of HDAC and independent of ANP/BNP modulation.

Glutamine restores testicular glutathione-dependent antioxidant defense and upregulates NO/cGMP signaling in sleep deprivation-induced reproductive dysfunction in rats

Oxidative stress has been linked with sleep deprivation (SD)-induced pathological conditions and reproductive dysfunction. On the other hand, glutamine has been established to have antioxidant property. However, the impact of SD, with or without glutamine, on male reproductive function is yet to be elucidated. Thus, this study was designed to investigate the role of SD, with or without glutamine, on male reproductive function and possible associated mechanisms. Ten-week old male Wistar rats weighing 175.6 g± 0.42 were randomly assigned into vehicle that received per os (p.o.) distilled water, glutamine (1 g/kg; po), SD, and SD + glutamine that received treatments as glutamine and SD. Treatment/exposure lasted for 72 h. The results showed that SD led to reduced body weight, seminiferous luminal and epididymal sperm density, low sperm quality, increased testicular and epididymal malondialdehyde, uric acid, DNA fragmentation, and testicular injury markers. In addition, SD caused a reduction in reduced glutathione level and activities of superoxide dismutase, catalase, glucose-6-phosphate dehydrogenase, glutathione peroxidase, and glutathione-S-transferase. Also, SD increased tumor necrotic factor-α, interleukin-1β, and nuclear factor-kappa B levels. Furthermore SD led to impaired libido and erectile dysfunction, and suppression of circulatory nitric oxide, gonadotropins and testosterone, and penile cGMP. However, glutamine attenuated the effects induced by SD. Taken together, the findings of this study demonstrate that SD induces reproductive dysfunction via glutathione-dependent defense depletion and down-regulation of NO/cGMP signaling, which was abolished by glutamine supplementation.

Repression of HDAC5 by acetate restores hypothalamic-pituitary-ovarian function in type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) accounts for 90-95 % of worldwide diabetes cases and is primarily characterized by insulin resistance. Its progression as a chronic metabolic disease has been largely associated with female reproductive abnormalities, including ovarian dysfunction with consequent infertility. Epigenetic modifications have been suggested as a possible link to metabolic comorbidities. We therefore hypothesized that short chain fatty acids, acetate (ACA), a potential histone deacetylase inhibitor (HDAC) ameliorates hypothalamic-pituitary-ovarian (HPO) dysfunction in T2DM. Female Wistar rats weighing 160-190 g were allotted into three groups (n = 6/group): Control (vehicle; po), T2D and T2D + ACA (200 mg/kg; po). T2DM was induced by fructose administration (10 %; w/v) for 6 weeks and single dose of streptozotocin (35 mg/kg; ip). The present data showed that in addition to insulin resistance, increased fasting blood glucose and insulin, T2DM induced elevated plasma, hypothalamic and ovarian triglyceride, lipid peroxidation, TNF-α and glutathione depletion. Aside, T2DM also led to increased plasma lactate production and γ-Glutamyl transferase as well as decreased gonadotropins/17β-estradiol. Histologically, hypothalamus, pituitary and ovaries revealed disrupted neuronal cells/moderate hemorrhage, altered morphology/vascular congestions, and degenerated antral follicle/graafian follicle with mild fibrosis and infiltrated inflammatory cells respectively in T2D animals. Interestingly, these alterations were accompanied by elevated plasma/hypothalamic HDAC5 and attenuated when treated with acetate. The present results demonstrate that T2DM induces HPO dysfunction, which is accompanied by elevated circulating/hypothalamic HDAC5. The results in addition suggest that acetate restores HPO function in T2DM by suppression of HDAC5 and enhancement of insulin sensitivity.

Acetate rescues defective brain-adipose metabolic network in obese Wistar rats by modulation of peroxisome proliferator-activated receptor-γ

We investigated the hypothesis that acetate ameliorates brain-adipose metabolic dysfunction (BAMED) in high fat diet (HFD)-induced obesity, possibly by modulation of peroxisome proliferator-activated receptor-γ (PPAR-γ). Ten-week-old male Wistar rats were randomly assigned into four groups (n = 6/group): Control, acetate and obese with or without acetate groups received vehicle (distilled water; po), acetate (200 mg/kg, po) and 40% HFD with or without acetate respectively. The treatments lasted for 12 weeks. Obese animals showed increase in body weight, visceral fat mass, insulin and triglyceride-glucose index and a reduction in insulin sensitivity. In addition, obese animals also showed increase in plasma/hypothalamic and adipose pyruvate dehydrogenase kinase-4, lactate-pyruvate ratio, malondialdehyde, γ-glutamyl transferase, and a decrease in glucose-6-phosphate dehydrogenase, glutathione, nitric oxide and PPAR-γ. HFD also elevated plasma/hypothalamic lipid and decreased adipose lipid profile, increased hypothalamic and adipose tumor necrosis factor-α, interleukin-6 and histone deacetylase (HDAC), and elevated plasma/adipose leptin. These alterations were reversed by concomitant administration of acetate. The present results demonstrate that obesity is characterized by BAMED, which is accompanied by altered HDAC/PPAR-γ. The results in addition suggest that acetate, an HDAC inhibitor rescues BAMED with consequent normalization of body weight and visceral fat mass by modulation of PPAR-γ and suppression of oxidative stress.

Melatonin ameliorates endocrine dysfunction and defective sperm integrity associated with high-fat diet-induced obesity in male Wistar rats

Obesity (OBS) has been established as a link to male hypogonadism with consequent infertility. Previous studies have shown that melatonin (MEL) modulates hypothalamic-pituitary-gonadal function. The present study therefore investigated the hypothesis that MEL supplementation would attenuate spermatogenic and steroidogenic dysfunctions associated with obesity induced by high-fat diet (HFD). Twenty-four adult male Wistar rats (n = 6/group) were used: control group received vehicle (normal saline), obese group received 40% high-fat diet and distilled water, MEL-treated group received MEL (4 mg/kg), and OBS + MEL group received MEL and 40% HFD and the treatment lasted for 12 weeks. HFD caused increased body weight, glucose intolerance, plasma triglyceride and low-density lipoprotein cholesterol/ very low-density lipoprotein cholesterol and malondialdehyde, as well as decreased antioxidant capacity, high-density lipoprotein cholesterol, gonadotrophin-releasing hormone, follicle-stimulating hormone and testosterone and altered sperm parameters. However, all these alterations were attenuated when supplemented with MEL. Taken together, these results indicate that HFD exposure causes endocrine dysfunction and disrupted sperm parameters in obese animals, which are accompanied by lipid peroxidation/defective antioxidant capacity. In addition, the present results suggest that melatonin supplementation restores endocrine function and sperm integrity in obese rat model by suppression of oxidative stress-dependent mechanism.

Analysis of Caloric and Noncaloric Sweeteners Present in Dairy Products Aimed at the School Market and Their Possible Effects on Health

Over the past decades, Mexico has become one of the main sweetener-consuming countries in the world. Large amounts of these sweeteners are in dairy products aimed at the children’s market in various presentations such as yogurt, flavored milk, flan, and cheeses. Although numerous studies have shown the impact of sweeteners in adults, the current evidence for children is insufficient and discordant to determine if these substances have any risk or benefit on their well-being. Therefore, this study aimed to describe the sweeteners present in 15 dairy products belonging to the school-age children’s market in Mexico and their impact on health. These dairy products were selected through a couple of surveys directed at parents of school-age children. After that, the list of ingredients of each product was analyzed to identify their sweetener content. From there, exhaustive bibliographic research on sweeteners and their possible health effects was carried out, which included 109 articles and 18 studies. The results showed that at a neurological, endocrinological, cardiovascular, metabolic, osseous, renal, hepatic, dental, reticular, carcinogenic, and gut microbiota level; sucrose, fructose, high-fructose corn syrup, maltodextrins, sucralose, and acesulfame K, have a negative effect. While maltodextrins, stevia, polydextrose, and modified starch have a positive one. For these reasons, it is necessary to evaluate the advantages and disadvantages that the consumption of each sweetener entails, as well as a determination of the appropriate acceptable daily intake (ADI).

Acetate ameliorates nephrotoxicity in streptozotocin-nicotinamide-induced diabetic rats: Involvement of xanthine oxidase activity

Impaired renal function is a common complication of diabetes mellitus (DM) that often degenerates to cardiovascular disease, contributing to high morbidity and reduced survival worldwide. Short chain fatty acids (SCFAs), including acetate has shown potential benefits in glycemic or metabolic regulation but its effect on diabetes-associated renal toxicity/impairment is not clear. Herein, we investigated the hypothesis that acetate would ameliorate renal toxicity, accompanying DM, possibly by suppression of xanthine oxidase (XO) activity. Adult male Wistar rats (230-260 g) were allotted into groups (n = 6/group) namely: control (vehicle; po), sodium acetate (NaAc)-treated (200 mg/kg), diabetic with or without NaAc groups. DM was induced by intraperitoneal injection of streptozotocin 65 mg/kg after a dose of nicotinamide (110 mg/kg). Diabetic animals showed increased fasting glucose and insulin, renal triglyceride, total cholesterol, atherogenic lipid, malondialdehyde, XO, tissue necrosis factor-α, uric acid, interleukin-6, aspartate transaminase/alanine aminotransferase ratio, gamma-glutamyl transferase and decreased glutathione and nitric oxide concentration. The renal tissue was characterized with disrupted tissue architecture, enlarged Bowman's space, congested glomeruli and adherence of abnormal segments of tuft to Bowman's capsule with consequent elevated serum creatinine and urea concentration. However, these alterations were attenuated by NaAc. The study demonstrates that acetate ameliorates diabetes-induced nephrotoxicity, which is associated with suppressed XO and its accompanied pro-inflammatory mediators. Therefore, SCFAs, acetate would be a promising dietary-derived therapeutic agent for the prevention and management of diabetes-associated renal disturbances.

Targeting pyruvate dehydrogenase kinase signaling in the development of effective cancer therapy

Pyruvate is irreversibly decarboxylated to acetyl coenzyme A by mitochondrial pyruvate dehydrogenase complex (PDC). Decarboxylation of pyruvate is considered a crucial step in cell metabolism and energetics. The cancer cells prefer aerobic glycolysis rather than mitochondrial oxidation of pyruvate. This attribute of cancer cells allows them to sustain under indefinite proliferation and growth. Pyruvate dehydrogenase kinases (PDKs) play critical roles in many diseases because they regulate PDC activity. Recent findings suggest an altered metabolism of cancer cells is associated with impaired mitochondrial function due to PDC inhibition. PDKs inhibit the PDC activity via phosphorylation of the E1a subunit and subsequently cause a glycolytic shift. Thus, inhibition of PDK is an attractive strategy in anticancer therapy. This review highlights that PDC/PDK axis could be implicated in cancer's therapeutic management by developing potential small-molecule PDK inhibitors. In recent years, a dramatic increase in the targeting of the PDC/PDK axis for cancer treatment gained an attention from the scientific community. We further discuss breakthrough findings in the PDC-PDK axis. In addition, structural features, functional significance, mechanism of activation, involvement in various human pathologies, and expression of different forms of PDKs (PDK1-4) in different types of cancers are discussed in detail. We further emphasized the gene expression profiling of PDKs in cancer patients to prognosis and therapeutic manifestations. Additionally, inhibition of the PDK/PDC axis by small molecule inhibitors and natural compounds at different clinical evaluation stages has also been discussed comprehensively.

Rescue effect of sodium acetate in diabetes mellitus-associated testicular dysfunction is accompanied by PCSK9 modulation

Diabetes mellitus (DM) is a global health burden, affecting about 463 million of the adult population worldwide. Approximately 94% of diabetic male individuals develop varying degrees of testicular disorders (TDs), which usually result in hypogonadism, hypotestosteronemia and defective spermatogenesis and steroidogenesis. Short chain fatty acids (SCFAs) have shown potential benefits in metabolic health. However, its effect on TD associated with DM is not clear. Howbeit, the present study investigated the hypothesis that SCFAs, acetate would ameliorate TD accompanying DM, possibly by suppressing proprotein convertase subtilisin/kexin type 9 (PCSK9). Male Wistar rats (210-240 g) were allotted into groups (n = 6/group): control (vehicle; po), DM with/without 200 mg/kg (po) of sodium acetate (SAc). Diabetes was induced by streptozotocin 65 mg/kg (iv) after a dose of nicotinamide (110 mg/kg). Semen/biochemical and histological analyses were performed with appropriate methods. In addition to hyperglycemia, hyperinsulinemia and reduced insulin sensitivity, DM led to increased serum and testicular triglyceride or total cholesterol/high-density lipoprotein cholesterol ratio, low-density lipoprotein cholesterol, malondialdehyde, TNF-α, IL-6 and PCSK9 as well as reduced high-density lipoprotein cholesterol and glutathione. Moreover, DM caused TD which is characterized by altered sperm parameters, disrupted tissue architecture, atrophied seminiferous tubules, deleterious spermatogonia, disappearance of lumen and cellular degeneration as well as decreased luteinizing hormone and testosterone. However, the administration of SAc attenuated these alterations. The study demonstrates that DM-induced TD is accompanied by elevated PCSK9. The results however suggest that SAc rescues testicular disorder/dysfunction associated with DM by suppression of PCSK9 and improvement of insulin sensitivity.

Low dose spironolactone-mediated androgen-adiponectin modulation alleviates endocrine-metabolic disturbances in letrozole-induced PCOS

Polycystic ovarian syndrome (PCOS), is a multifactorial endocrine disorder in women of reproductive age. It usually associates with metabolic disorders (MDs), which aggravates the risk of infertility, cardiometabolic events and associated comorbidities in women with PCOS. Adiponectin, a circulating protein produced by adipocytes, which has been suggested to inversely correlate with MDs. Spironolactone, a non-selective mineralocorticoid receptor (MR) antagonist, has been in wide clinical use for several decades. Herein, we investigated the effects of low dose spironolactone (LDS) and the role of adiponectin in endocrine-metabolic disturbances in experimentally-induced PCOS rats. Eighteen female Wistar rats (160-180 g) were randomly allotted into 3 groups and treated with vehicle (p.o.), letrozole (LET; 1 mg/kg) and LET + LDS (0.25 mg/kg), once daily for 21 days, respectively. The results showed that LET-treated animals had features of PCOS, characterized by elevated plasma testosterone and prolactin, increased body weight gain and ovarian weight as well as disrupted ovarian cytoarchitecture and degenerated follicles. Additionally, elevated fasting blood glucose, 1 h-postload glucose and plasma insulin, impaired glucose tolerance, insulin resistance, reduced insulin sensitivity, increased plasma and ovarian lipid profile, plasma lipid peroxidation, TNF-α, IL-6 and decreased plasma glutathione peroxidase and glutathione content were observed. These alterations were associated with decreased circulating adiponectin and were reversed when treated with LDS. The present results suggest that LDS ameliorates endocrine-metabolic disturbances and inflammation-related comorbidities associated with LET-induced PCOS by modulating circulating androgen-adiponectin status.

Oral L-glutamine rescues fructose-induced poor fetal outcome by preventing placental triglyceride and uric acid accumulation in Wistar rats

BACKGROUND

Metabolic adaptation of pregnant mothers is crucial for placental development and fetal growth/survival. However, evidence exists that indiscriminate consumption of fructose-enriched drink (FED) during pregnancy disrupts maternal-fetal metabolic tolerance with attendant adverse fetal outcomes. Glutamine supplementation (GLN) has been shown to exert a modulatory effect in metabolic disorders. Nevertheless, the effects of GLN on FED-induced poor fetal outcome, and in particular the impacts on placental uric acid/lipid accumulation are unknown. The present study was conducted to test the hypothesis that oral GLN improves fetal outcome by attenuating placental lipid accumulation and uric acid synthesis in pregnant rats exposed to FED.

MATERIALS AND METHODS

Pregnant Wistar rats (160-180 g) were randomly allotted to control, GLN, FED and FED + GLN groups (6 rats/group). The groups received vehicle by oral gavage, glutamine (1 g/kg) by oral gavage, fructose (10%; w/v) and fructose + glutamine, respectively, through gestation.

RESULTS

Data showed that FED during pregnancy caused placental inefficiency, reduced fetal growth, and caused insulin resistance with correspondent increase in fasting blood glucose and plasma insulin. FED also resulted in an increased placental triglyceride, total cholesterol and de novo uric acid synthesis by activating adenosine deaminase and xanthine oxidase activities. Moreover, FED during pregnancy led to increased lipid peroxidation, lactate production with correspondent decreased adenosine and glucose-6-phosphate dehydrogenase-dependent antioxidant defense. These alterations were abrogated by GLN supplementation.

CONCLUSION

These findings implicate that high FED intake during pregnancy causes poor fetal outcome via defective placental uric acid/triglyceride-dependent mechanism. The findings also suggest that oral GLN improves fetal outcome by ameliorating placental defects through suppression of uric acid/triglyceride accumulation.

Sodium acetate-mediated inhibition of histone deacetylase alleviates hepatic lipid dysregulation and its accompanied injury in streptozotocin-nicotinamide-induced diabetic rats

OBJECTIVE

Hepatic lipid dysregulation with consequent lipotoxicity remains critical in the progression of non-alcoholic fatty liver disease, a rising prevalent complication of diabetes mellitus particularly type 2 diabetes. Diabetes-associated hepatic complications are among the leading causes of liver-related morbidity and mortality worldwide. Short chain fatty acids (SCFAs) have been demonstrated to regulate glycemic metabolism but its effect on diabetes-driven hepatic perturbation is unknown. This study is therefore designed to investigate the effect of SCFAs, acetate on diabetes-characterised hepatic lipotoxicity, and plausible involvement of histone deacetylase (HDAC) activity.

METHODS

Adult male Wistar rats (230-260 g) were allotted into groups (n = 6/group) namely: control (vehicle; p.o.), sodium acetate (SAT)-treated (200 mg/kg), diabetic with/without SAT groups. Diabetes was induced by intraperitoneal injection of streptozotocin 65 mg/kg after a dose of nicotinamide 110 mg/kg.

RESULTS

Data from diabetic animals showed increased fasting glycemia and insulinemia, decreased insulin sensitivity and body weight with increased relative hepatic mass. It also revealed increased hepatic lipid, serum/hepatic malondialdehyde, tissue necrosis factor-α, uric acid, aspartate transaminase, alanine aminotransferase and decreased glutathione content with elevated hepatic HDAC. Histologically, the hepatic tissue was characterised with disrupted architecture, inflammation of central vein and foci of periportal and sinusoidal cellular infiltration. However, these alterations were attenuated by sodium acetate.

CONCLUSION

The study demonstrates that diabetes mellitus drives hepatic lipotoxicity, characterised with lipid accumulation, excessive lipid peroxidation, pro-inflammation, depleted glutathione content and accompanied by increased HDAC activity. Besides, the study suggests that acetate ameliorates diabetes-associated hepatic lipotoxicity through HDAC suppression and enhancement of insulin sensitivity.

Oral ethinylestradiol–levonorgestrel normalizes fructose-induced hepatic lipid accumulation and glycogen depletion in female rats

The present study investigated the effects of oral ethinylestradiol–levonorgestrel (EEL) on hepatic lipid and glycogen contents during high fructose (HF) intake, and determined whether pyruvate dehydrogenase kinase-4 (PDK-4) and glucose-6-phosphate dehydrogenase (G6PD) activity were involved in HF and (or) EEL-induced hepatic dysmetabolism. Female Wistar rats weighing 140–160 g were divided into groups. The control, EEL, HF, and EEL+HF groups received water (vehicle, p.o.), 1.0 μg ethinylestradiol plus 5.0 μg levonorgestrel (p.o.), fructose (10% w/v), and EEL plus HF, respectively, on a daily basis for 8 weeks. Results revealed that treatment with EEL or HF led to insulin resistance, hyperinsulinemia, increased hepatic uric acid production and triglyceride content, reduced glycogen content, and reduced production of plasma or hepatic glutathione- and G6PD-dependent antioxidants. HF but not EEL also increased fasting glucose and hepatic PDK-4. Nonetheless, these alterations were attenuated by EEL in HF-treated rats. Our results demonstrate that hepatic lipid accumulation and glycogen depletion induced by HF is accompanied by increased PDK-4 and defective G6PD activity. The findings also suggest that EEL would attenuate hepatic lipid accumulation and glycogen depletion by suppression of PDK-4 and enhancement of a G6PD-dependent antioxidant barrier.