G6PT-H6PDH-11βHSD1 triad in the liver and its implication in the pathomechanism of the metabolic syndrome

Resting metabolic rate, abdominal fat pad and liver metabolic gene expression in female rats provided a snacking diet from weaning to adulthood

Our female rat model with continuous, ad libitum access to snacks and chow from weaning to adulthood closely mimics human feeding behavior from childhood onwards. It causes weight gain, enlarged abdominal fat pads, reduced insulin sensitivity and leptin resistance without an increase in total caloric intake. Our current study investigated if this change in energy partitioning is due to a decrease in resting metabolic rate (RMR). In addition, we determined if carbohydrate and lipid metabolism changes in abdominal fat pads and liver. RMR, using indirect calorimetry, was determined in control and snacking rats every two weeks from Days 28-29 to Days 76-77. RMR decreased with age in both groups, but there was no difference between snacking and control rats at any age. At termination, abdominal fat pads (parametrial, retroperitoneal and mesenteric) and liver samples were collected for determination of gene expression for 21 genes involved in carbohydrate and lipid metabolism using RT-qPCR. Analysis of gene expression data showed a striking difference between metabolic profiles of control and snacking rats in abdominal fat pads and liver, with a distinct segregation of genes for both lipid and carbohydrate metabolism that correlated with an increase in body weight and fat pad weights. Genes involved in lipogenesis were upregulated in abdominal fat pads, while genes involved in adipogenesis, and lipid recycling were upregulated in the liver. In conclusion, snacking in addition to chow from weaning in female rats causes a repartitioning of energy that is not due to depressed RMR in snacking rats. Rather, snacking from weaning causes a shift in gene expression resulting in energy partitioning toward enhanced abdominal fat pad lipogenesis, and adipogenesis and lipid recycling in liver.

Possible mechanisms of the hypoglycaemic effect of artesunate: Gender implication

Background

We investigated the mechanism of artesunate’s glucose-modulating effect especially with gender implication.

Methods

Twenty-five (25) male and 25 female rats were separately and blindly allocated into five identical groups (n = 5/group). Group I (control) received 0.2 ml/kg distilled water. Groups II and III both received 2.90 mg/kg artesunate on day one, but 1.45 mg/kg from day two till day five and day fifteen respectively. Groups IV and V both received 8.70 mg/kg artesunate on day one, but 4.35 mg/kg artesunate from day two till day five and day fifteen respectively.

Results

In male rats, glucose was reduced by both doses of artesunate at 5 days but increased by high dose at 15 days. Artesunate increased glycogen concentration at short duration which normalised at long duration in both genders. Artesunate increased G6P concentration only in male rats at 15 days but reduced G6Pase activity in male and female rats (except in those that received low and high doses of artesunate for 15 days). Artesunate increased insulin only in male rats treated with low dose artesunate for 5 days. Artesunate increased cortisol concentration in male but reduced it in female rats. Artesunate decreased glucagon concentration except in female rats treated with high dose for 5 days. Artesunate increased oestrogen concentration in male rats that received low dose artesunate for 5 days but reduced it in female rats that received high dose for 15 days.

Conclusions

Artesunate reduces plasma glucose by reducing plasma glucagon concentrations and inhibiting liver glycogenolysis via inhibition of G6Pase activity in both sexes. Increase in insulin concentration contributed to the reduction in blood glucose caused by artesunate in male but not female rats; and artesunate-induced increase in G6P, a substrate for G6PD, could enhance NADPH generation and antioxidant enzyme activation in male rats.

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Reducing glucagon concentration and inhibiting G6Pase activity in both genders. .

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Increasing plasma insulin in male but not in female.

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Increasing G6P, a substrate for G6PD, in male rats.

Secondary diabetes as a rare complication of glycogen storage disease 1a: case report and review of literature

Glycogen storage diseases (GSDs) are disorders of carbohydrate metabolism and hypoglycemia is their hallmark. Secondary diabetes with glycogen storage disease, which seems rather paradoxical, has been rarely reported. A 13-year-old girl previously diagnosed to have GSD 1a presented to the emergency with multiple episodes of vomiting and loss of consciousness. She had hyperglycemia, ketonuria, hyperlactatemia and metabolic acidosis, suggestive of diabetic ketosis with acidosis possibly contributed by both high serum lactate and serum ketones. Her glycated hemoglobin was high, with detectable serum insulin levels, which suggested secondary diabetes in the background of GSD Ia. Her management posed a therapeutic challenge. She was managed with insulin and achieved good glycemic control. We wish to conclude that GSD may rarely lead to secondary diabetes as a complication and the management is complex owing to the nature of the disease. Insulin remains the mainstay of the treatment.

Chemical Characterisation and Antihypertensive Effects of Locular Gel and Serum of Lycopersicum esculentum L. var. "Camone" Tomato in Spontaneously Hypertensive Rats

Blood pressure control in hypertensive subjects calls for changes in lifestyle, especially diet. Tomato is widely consumed and rich in healthy components (i.e., carotenoids, vitamins and polyphenols). The aim of this study was to evaluate the chemical composition and antihypertensive effects of locular gel reconstituted in serum of green tomatoes of "Camone" variety. Tomato serum and locular gel were chemically characterised. The antihypertensive effects of the locular gel in serum, pure tomatine, and captopril, administered by oral gavage, were investigated for 4 weeks in male spontaneously hypertensive and normotensive rats. Systolic blood pressure and heart rate were monitored using the tail cuff method. Body and heart weight, serum glucose, triglycerides and inflammatory cytokines, aorta thickness and liver metabolising activity were also assessed. Locular gel and serum showed good tomatine and polyphenols content. Significant reductions in blood pressure and heart rate, as well as in inflammatory blood cytokines and aorta thickness, were observed in spontaneously hypertensive rats treated both with locular gel in serum and captopril. No significant effects were observed in normotensive rats. Green tomatoes locular gel and serum, usually discarded during tomato industrial processing, are rich in bioactive compounds (i.e., chlorogenic acid, caffeic acid and rutin, as well as the glycoalkaloids, α-tomatine and dehydrotomatine) that can lower in vivo blood pressure towards healthier values, as observed in spontaneously hypertensive rats.

Imbalanced cortisol concentrations in glycogen storage disease type I: evidence for a possible link between endocrine regulation and metabolic derangement

Background

Glycogen storage disease type I (GSDI) is an inborn error of carbohydrate metabolism caused by mutations of either the G6PC gene (GSDIa) or the SLC37A4 gene (GSDIb). Glucose 6-phosphate (G6P) availability has been shown to modulate 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1), an ER-bound enzyme catalyzing the local conversion of inactive cortisone into active cortisol. Adrenal cortex assessment has never been performed in GSDI. The aim of the current study was to evaluate the adrenal cortex hormones levels in GSDI patients.

Methods

Seventeen GSDI (10 GSDIa and 7 GSDIb) patients and thirty-four age and sex-matched controls were enrolled. Baseline adrenal cortex hormones and biochemical markers of metabolic control serum levels were analyzed. Low dose ACTH stimulation test was also performed.

Results

Baseline cortisol serum levels were higher in GSDIa patients (p = 0.042) and lower in GSDIb patients (p = 0.041) than controls. GSDIa patients also showed higher peak cortisol response (p = 0.000) and Cortisol AUC (p = 0.029). In GSDIa patients, serum cholesterol (p = 0.000), triglycerides (p = 0.000), lactate (p = 0.000) and uric acid (p = 0.008) levels were higher and bicarbonate (p = 0.000) levels were lower than controls. In GSDIb patients, serum cholesterol levels (p = 0.016) were lower and lactate (p = 0.000) and uric acid (p = 0.000) levels were higher than controls. Baseline cortisol serum levels directly correlated with cholesterol (ρ = 0.65, p = 0.005) and triglycerides (ρ = 0.60, p = 0.012) serum levels in GSDI patients.

Conclusions

The present study showed impaired cortisol levels in GSDI patients, with opposite trend between GSDIa and GSDIb. The otherwise preserved adrenal cortex function suggests that this finding might be secondary to local deregulation rather than hypothalamo-pituitary-adrenal axis dysfunction in GSDI patients. We hypothesize that 11βHSD1 might represent the link between endocrine regulation and metabolic derangement in GSDI, constituting new potential therapeutic target in GSDI patients.

Gene therapy prevents hepatic tumor initiation in murine glycogen storage disease type Ia at the tumor-developing stage

Hepatocellular adenoma/carcinoma (HCA/HCC) is a long-term complication of glycogen storage disease type-Ia (GSD-Ia), which is caused by a deficiency in glucose-6-phosphatase-α (G6Pase-α or G6PC), a key enzyme in gluconeogenesis. Currently, there is no therapy to address HCA/HCC in GSD-Ia. We have previously shown that a recombinant adeno-associated virus (rAAV) vector-mediated G6PC gene transfer to 2-week-old G6pc-/- mice prevents HCA development. However, it remains unclear whether G6PC gene transfer at the tumor developing stage of GSD-Ia can prevent tumor initiation or abrogate the pre-existing tumors. Using liver-specific G6pc-knockout (L-G6pc-/-) mice that develop HCA/HCC, we now show that treating the mice at the tumor-developing stage with rAAV-G6PC restores hepatic G6Pase-α expression, normalizes glucose homeostasis, and prevents de novo HCA/HCC development. The rAAV-G6PC treatment also normalizes defective hepatic autophagy and corrects metabolic abnormalities in the nontumor liver tissues of both tumor-free and tumor-bearing mice. However, gene therapy cannot restore G6Pase-α expression in the HCA/HCC lesions and fails to abrogate any pre-existing tumors. We show that the expression of 11 β-hydroxysteroid dehydrogenase type-1 that mediates local glucocorticoid activation is downregulated in HCA/HCC lesions, leading to impairment in glucocorticoid signaling critical for gluconeogenesis activation. This suggests that local glucocorticoid action downregulation in the HCA/HCC lesions may suppress gene therapy mediated G6Pase-α restoration. Collectively, our data show that rAAV-mediated gene therapy can prevent de novo HCA/HCC development in L-G6pc-/- mice at the tumor developing stage, but it cannot reduce any pre-existing tumor burden.

Microsomal pre-receptor cortisol production is inhibited by resveratrol and epigallocatechin gallate through different mechanisms

Local activation of cortisol in hormone target tissues is a major determinant of glucocorticoid effect. Disorders in this peripheral cortisol metabolism play an important role in the development of metabolic diseases, such as obesity or type 2 diabetes mellitus. Hence, dietary factors influencing the activity of the involved enzymes can have major impacts on the risk of the above diseases. Resveratrol and epigallocatechin gallate (EGCG), two natural polyphenols found in several nutriments and in green tea, respectively, are well-known for their antiobesity and antidiabetic activities. EGCG has been shown to interfere with microsomal cortisol production through decreasing the luminal NADPH:NADP⁺ ratio. The aim of this study was to clarify if resveratrol also induces such a redox shift or causes any direct enzyme inhibition that influences local cortisol production. Cortisone-cortisol conversions and changes in NADPH levels were monitored in rat liver microsomal vesicles. Cortisol production was inhibited by resveratrol in a concentration dependent manner while the intrinsic reducing and oxidizing capacity as well as the NADPH level inside the ER-derived vesicles remained unaffected. Activity measurements performed in permeabilized microsomes confirmed that resveratrol, unlike EGCG, inhibits 11β-hydroxysteroid dehydrogenase type 1 directly. Long-term moderation of pre-receptor cortisol production likely contributes to the beneficial health effects of both polyphenols. © 2018 BioFactors, 45(2):236-243, 2019.

Immortalization of Porcine 11β-Hydroxysteroid Dehydrogenase Type 1-Transgenic Liver Cells Using SV40 Large T Antigen

Cortisol is a steroid hormone essential to the maintenance of homeostasis that is released in response to stress and low blood glucose concentration. Cortisol is converted from cortisone by 11β-hydroxysteroid dehydrogenase type 1 (HSD11B1). It has been reported that too much cortisol or overexpression of HSD11B1 induces obesity and the insulin resistance that accompanies metabolic syndrome in rodent adipose tissue. In our previous study, HSD11B1-transgenic (TG) fibroblasts were established, and a porcine model was generated by SCNT using those fibroblasts. Hepatocytes overexpressing HSD11B1 were obtained from livers of this porcine model and cultured in vitro. However, the primary hepatocytes were found to have a short life span or low proliferation rate. To overcome these problems, the SV40 large T antigen was transduced into primary HSD11B1-TG hepatocytes, and those cells were immortalized. Immortalized HSD11B1-TG hepatocytes showed restored morphology, more rapid proliferation rate, and more expression of HSD11B1 than primary hepatocytes. As well, these cells kept the hepatic characteristics such as gluconeogenic response to cortisone and increased expression of hepatic makers. The immortalized HSD11B1-TG hepatocytes may be useful for studying traits and potential therapeutic drugs for treatment of metabolic disorders induced by overexpression of HSD11B1.

Cytosolic localization of NADH cytochrome b₅ oxidoreductase (Ncb5or)

Acyl-CoA desaturation in the endoplasmic reticulum (ER) membrane depends on cytosolic NADH or NADPH, whereas NADPH in the ER lumen is utilized by prereceptor glucocorticoid production. It was assumed that NADH cytochrome b5 oxidoreductase (Ncb5or) might connect Acyl-CoA desaturation to ER luminal redox. We aimed to clarify the ambiguous compartmentalization of Ncb5or and test the possible effect of stearoyl-CoA on microsomal NADPH level. Amino acid sequence analysis, fluorescence microscopy of GFP-tagged protein, immunocytochemistry, and western blot analysis of subcellular fractions unequivocally demonstrated that Ncb5or, either endogenous or exogenous, is localized in the cytoplasm and not in the ER lumen in cultured cells and liver tissue. Moreover, the involvement of ER-luminal reducing equivalents in stearoyl-CoA desaturation was excluded.

Glycogen storage disease type Ia (GSDIa) but not Glycogen storage disease type Ib (GSDIb) is associated to an increased risk of metabolic syndrome: possible role of microsomal glucose 6-phosphate accumulation

BACKGROUND

In GSDIa, glucose 6-phosphate (G6P) accumulates in the endoplasmic reticulum (ER); in GSDIb, G6P levels are reduced in ER. G6P availability directly modulates the activity of 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1), an ER-bound enzyme playing a key role in the development of the metabolic syndrome (MS).

OBJECTIVE

To evaluate the prevalence of MS and Insulin Resistance (IR) in GSDIa and GSDIb patients.

PATIENTS AND METHODS

This was a prospective study. All the enrolled patients were followed at the Department of Pediatrics "Federico II" University of Naples for 10 years. Clinical and biochemical parameters of MS and the presence of IR were recorded. The results were correlated with the biochemical parameters of GSDI-related metabolic control. 10 GSDIa patient (median age 12.10 ± 1.50), 7 GSDIb patients (median age 14.90 ± 2.20 were enrolled in the study. They were compared to 20 and 14 age and sex matched controls, respectively. 10 GSDIa patients (median age 24.60 ± 1.50) and 6 GSDIb patients (median age 25.10 ± 2.00) completed the 10-year-follow-up. At the end of the study the patients' data were compared to 10 and 6 age and sex matched controls, respectively.

RESULTS

At study entry, 20 % GSDIa patients had MS and 80 % showed 2 criteria for MS. GSDIa patients showed higher HOMA-IR than controls and GSDIb patients (p < 0.001, p < 0.05), respectively. Baseline ISI was lower in GSDIa than controls (p < 0.001). QUICKI was significantly lower in GSDIa than in controls (p < 0.001). At the end of the study 70 % of GSDIa patients had MS and 30 % showed 2 criteria for MS. HOMA-IR was higher in GSDIa than controls (p < 0.01). Baseline ISI was higher in GSDIb than controls (p < 0.005) and GSD1a (p < 0.05). QUICKI was lower in GSD1a patients than in controls (p < 0.03). VAI was higher in GSDIa patients than controls (p < 0.001) and GSDIb patients (p = 0.002).

CONCLUSIONS

Our data showed high prevalence of IR and MS in GSDIa patients. We speculate a possible role of 11βHSD1 modulation by G6P availability. We suggest a routine metabolic assessment in GSDIa patients.

Endoplasmic Reticulum Stress Response in Non-alcoholic Steatohepatitis: The Possible Role of Physical Exercise

Sedentary lifestyle coupled with excessive consumption of high caloric food has been related to the epidemic increase of non-alcoholic fatty liver disease, which can progress from simple steatosis to non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis and, eventually, may culminate in hepatocellular carcinoma. Although the precise mechanisms underlying the progression of NASH are not completely understood, endoplasmic reticulum (ER) dysfunction seems to play a key role in the process. Hepatic ER stress has been associated to hepatic steatosis, insulin resistance, inflammation, oxidative stress and hepatocyte death, contributing to liver dysfunction. Physical exercise seems to be the most effective preventive and therapeutic non-pharmacological strategy to mitigate several features related to NASH, possibly targeting most of the referred mechanisms associated with the pathophysiology of ER-related NASH. Nevertheless, little is known about the impact of physical exercise on NASH-related ER stress. In this review, we will discuss the ER stress associated to NASH conditions and highlight the possible benefits of physical exercise in the attenuation and/or reversion of NASH-related ER stress.

Possible involvement of glucocorticoids in 5α-dihydrotestosterone-induced PCOS-like metabolic disturbances in the rat visceral adipose tissue

Polycystic ovary syndrome (PCOS) is a reproductive and metabolic disorder characterized by hyperandrogenism, ovulatory dysfunction, visceral obesity and insulin resistance. We hypothesized that changes in glucocorticoid metabolism and signaling in the visceral adipose tissue may contribute to disturbances of lipid metabolism in the rat model of PCOS obtained by 5α-dihydrotestosterone (DHT) treatment of prepubertal female Wistar rats. The results confirmed that DHT treatment caused anovulation, obesity and dyslipidemia. Enhanced glucocorticoid prereceptor metabolism, assessed by elevated intracellular corticosterone and increased 11 beta-hydroxysteroid dehydrogenase type 1 mRNA and protein levels, was accompanied by glucocorticoid receptor (GR) nuclear accumulation. In concert with the increased expression of GR-regulated prolipogenic genes (lipin-1, sterol regulatory element binding protein 1, fatty acid synthase, phosphoenolpyruvate carboxykinase), histological analyses revealed hypertrophic adipocytes. The results suggest that glucocorticoids influence lipid metabolism in the visceral adipose tissue in the way that may contribute to pathogenesis of metabolic disturbances associated with PCOS.

Hepatic inflammation induced by high-fructose diet is associated with altered 11βHSD1 expression in the liver of Wistar rats

PURPOSE

High fructose consumption provokes metabolic perturbations that result in chronic low-grade inflammation and insulin resistance. Glucocorticoids, potent anti-inflammatory hormones, have important role in pathogenesis of diet-induced metabolic disturbances. The aim of this study was to examine the link between glucocorticoid metabolism and inflammation in the liver of fructose-fed rats.

METHODS

Fructose-fed male Wistar rats consumed 60% fructose solution for 9 weeks. Glucocorticoid prereceptor metabolism and signaling were analyzed by measuring the level of 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) and hexose-6-phosphate dehydrogenase expression, as well as via determination of intracellular corticosterone concentration, glucocorticoid receptor subcellular distribution and expression of its target gene, phosphoenolpyruvate carboxykinase. Nuclear factor kappa B (NFκB), tumor necrosis factor alpha (TNFα) and the level of inhibitory phosphorylation of insulin receptor substrate-1 (IRS-1) on Ser(307) were analyzed as markers of hepatic inflammation. The protein and/or mRNA levels of all examined molecules were assessed by Western blot and/or qPCR.

RESULTS

Fructose-rich diet led to an enhancement of 11βHSD1 protein level in the liver, without affecting intracellular level of corticosterone and downstream glucocorticoid signaling. On the other hand, proinflammatory state was achieved through NFκB activation and increased TNFα expression, while elevated level of inhibitory phosphorylation of IRS-1 was observed as an early hallmark of insulin resistance.

CONCLUSION

High-fructose diet does not influence hepatic glucocorticoid signaling downstream of the receptor, permitting development of NFκB-driven inflammation. The alteration in 11βHSD1 expression is most likely the consequence of enhanced inflammation, finally leading to disruption of insulin signaling in the rat liver.

Pathogenesis of hepatic steatosis: The link between hypercortisolism and non-alcoholic fatty liver disease

Based on the available literature, non alcoholic fatty liver disease or generally speaking, hepatic steatosis, is more frequent among people with diabetes and obesity, and is almost universally present amongst morbidly obese diabetic patients. Non alcoholic fatty liver disease is being increasingly recognized as a common liver condition in the developed world, with non alcoholic steatohepatitis projected to be the leading cause of liver transplantation. Previous data report that only 20% of patients with Cushing’s syndrome have hepatic steatosis. Aiming at clarifying the reasons whereby patients suffering from Cushing’s syndrome - a condition characterized by profound metabolic changes - present low prevalence of hepatic steatosis, the Authors reviewed the current concepts on the link between hypercortisolism and obesity/metabolic syndrome. They hypothesize that this low prevalence of fat accumulation in the liver of patients with Cushing’s syndrome could result from the inhibition of the so-called low-grade chronic-inflammation, mainly mediated by Interleukin 6, due to an excess of cortisol, a hormone characterized by an anti-inflammatory effect. The Cushing’s syndrome, speculatively considered as an in vivo model of the hepatic steatosis, could also help clarify the mechanisms of non alcoholic fatty liver disease.

Lipotoxicity in the liver

Obesity due to excessive food intake and the lack of physical activity is becoming one of the most serious public health problems of the 21^st century. With the increasing prevalence of obesity, non-alcoholic fatty liver disease is also emerging as a pandemic. While previously this pathophysiological condition was mainly attributed to triglyceride accumulation in hepatocytes, recent data show that the development of oxidative stress, lipid peroxidation, cell death, inflammation and fibrosis are mostly due to accumulation of fatty acids, and the altered composition of membrane phospholipids. In fact, triglyceride accumulation might play a protective role, and the higher toxicity of saturated or trans fatty acids seems to be the consequence of a blockade in triglyceride synthesis. Increased membrane saturation can profoundly disturb cellular homeostasis by impairing the function of membrane receptors, channels and transporters. However, it also induces endoplasmic reticulum stress via novel sensing mechanisms of the organelle’s stress receptors. The triggered signaling pathways in turn largely contribute to the development of insulin resistance and apoptosis. These findings have substantiated the lipotoxic liver injury hypothesis for the pathomechanism of hepatosteatosis. This minireview focuses on the metabolic and redox aspects of lipotoxicity and lipoapoptosis, with special regards on the involvement of endoplasmic reticulum stress responses.

Inhibition of microsomal cortisol production by (-)-epigallocatechin-3-gallate through a redox shift in the endoplasmic reticulum--a potential new target for treating obesity-related diseases

Conversion of cortisone to cortisol by 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) in the endoplasmic reticulum (ER) of the target cells is a major determinant of glucocorticoid action, and plays an important role in the development of obesity-related diseases. Inhibition of 11βHSD1 activity is, therefore, considered as a promising novel strategy for the treatment of metabolic syndrome and diabetes. Tea flavanols and their major representative, epigallocatechin gallate are known as antiobesity and antidiabetic agents. Their impacts on blood glucose level, hepatic glucose production, and insulin responsiveness resemble those observed on inhibition or depletion of 11βHSD1. We aimed to study the effect of epigallocatechin gallate on 11βHSD1 activity in ER-derived rat liver microsomes by measuring cortisone and cortisol with HPLC. Cortisol production was efficiently suppressed in a concentration dependent manner in intact microsomal vesicles. However, this effect was abolished by membrane permeabilization; and the three proteins involved in the overall process (11βHSD1, hexose 6-phosphate dehydrogenase, and glucose 6-phosphate transporter) were not or only mildly affected. Further investigation revealed the oxidation of luminal NADPH to NADP⁺, which attenuates cortisone reduction and favors cortisol oxidation in this compartment. Such a redox shift in the ER lumen might contribute to the beneficial health effects of tea flavanols and should be regarded as a promising strategy for the development of novel selective 11βHSD1 inhibitors to treat obesity-related diseases.