ResearchPad - insulin-resistance https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[Association between the rs1544410 polymorphism in the vitamin D receptor (VDR) gene and insulin secretion after gestational diabetes mellitus]]> https://www.researchpad.co/article/elastic_article_14643 Genetic variants involved in vitamin D metabolism have been associated with diabetes and related syndromes/diseases. We wanted to investigate possible associations of polymorphisms in genes involved in vitamin D metabolism with indices of insulin resistance and insulin secretion, and also with development of diabetes after gestational diabetes mellitus (GDM).Materials and methodsWe have studied 376 women with previous GDM. Eight single nucleotide polymorphisms (SNPs) in the genes for vitamin D receptor (VDR) [rs731236, rs7975232, rs10735810, and rs1544410], vitamin D binding protein (DBP) [rs7041 and rs4588], and cytochrome P450 family 27 subfamily B member 1 (CYP27B1) [rs10877012 and rs4646536] were genotyped by TaqMan Allelic Discrimination Assay using the Quantstudio 7 Flex system. A 75-g oral glucose tolerance test (OGTT) was performed 1–2 years postpartum. The homeostasis model assessment of insulin resistance (HOMA-IR) and the disposition index [(insulinogenic index: I30/G30)/HOMA-IR] were used to calculate insulin resistance and insulin secretion, respectively. Serum samples for determination of 25(OH)D3 were collected at the time of the OGTT. Manifestation of diabetes was followed up to five years postpartum.ResultsAfter adjustment for BMI, age, and ethnicity, the A-allele of the VDR rs1544410 polymorphism was found to be associated with increased disposition index (difference per allele = 3.56, 95% CI: 0.4567–6.674; p = 0.03). The A-allele of the DBP rs7041 polymorphism was found to be associated with 25(OH)D3 levels (difference [in nmol/L] per allele = −5.478, 95% CI: -8.315 to −2.641; p = 0.0002), as was the T-allele of the DBP rs4588 polymorphism (OR = −6.319, 95% CI: −9.466 to −3.171; p = 0.0001). None of the SNPs were significantly associated with HOMA-IR or postpartum diabetes.ConclusionsThis study provides evidence that the rs1544410 polymorphism of the VDR gene may be associated with increased insulin secretion in women after pregnancy complicated by GDM. Further studies in other populations are needed to confirm the results. ]]> <![CDATA[Comparison of triglyceride glucose index, and related parameters to predict insulin resistance in Korean adults: An analysis of the 2007-2010 Korean National Health and Nutrition Examination Survey]]> https://www.researchpad.co/article/5c990272d5eed0c484b97e62

The triglyceride glucose (TyG) index, a product of triglyceride and fasting glucose, is a reliable marker for insulin resistance (IR). Obesity is also known to be closely related with IR. Recently, the efficiency of TyG-related markers that combine obesity markers with TyG index has been studied; however, earlier studies were limited in number and the results were inconsistent. Therefore, in this study, we investigated the efficiency of several combinations of TyG index and obesity indices, namely, body mass index (BMI), waist circumference (WC), and waist-to-height ratio (WHtR), in reflecting IR. Data were obtained from the Korean National Health and Nutrition Examination Survey from 2007–2010. A total of 11,149 subjects (4,777 men and 6,372 women) were included. IR was defined as the homeostasis model assessment for IR (HOMA-IR) of above the 75th percentile for each gender. Logistic regression analysis was performed after adjusting for confounding factors, to compare and identify the associations of the 4 parameters (TyG index, TyG-BMI, TyG-WC, and TyG-WHtR) with IR. For each parameter, odds ratios (OR) and 95% confidence intervals (CIs) of quartiles 2–4 were calculated and compared with quartile 1 as a reference. A receiver operating characteristic (ROC) curve analysis was conducted to evaluate the ability of each parameter to predict IR. The adjusted ORs of quartile 4 in comparison with quartile 1 (95% CIs) for IR were 7.60 (6.52–8.87) for TyG index, 12.82 (10.89–15.10) for TyG-BMI, 16.29 (13.70–19.38) for TyG-WC, and 14.86 (12.53–17.62) for TyG-WHtR. The areas under the ROC curve for each parameter were 0.690 for TyG index, 0.748 for TyG-BMI, 0.731 for TyG-WC, and 0.733 for TyG-WHtR. In conclusion, TyG-BMI was found to be superior to other parameters for IR prediction. We propose TyG-BMI as an alternative marker for assessing IR in clinical settings.

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<![CDATA[Subclinical atherosclerosis in psoriasis. Usefulness of femoral artery ultrasound for the diagnosis, and analysis of its relationship with insulin resistance]]> https://www.researchpad.co/article/5c6730cfd5eed0c484f38183

Background

Psoriasis is associated with an increased risk of cardiovascular disease (CVD) at younger ages that is not identifiable by traditional risk factors. Screening for subclinical atherosclerosis with ultrasound has only been investigated in carotid arteries. Femoral artery ultrasound has never been considered for this purpose. The link between psoriasis and accelerated atherosclerosis has not yet been established.

Objective

To study the usefulness of femoral artery ultrasound for the detection of subclinical atherosclerosis in psoriasis. We also investigated its possible relationship with changes in insulin resistance.

Methods

We conducted a cross-sectional study in 140 participants, 70 patients with moderate-to-severe psoriasis and 70 healthy controls, matched 1:1 for age, sex, and BMI. Femoral and carotid atherosclerotic plaques were evaluated by ultrasonography. Insulin resistance was assessed by the homeostasis model assessment method (HOMA-IR).

Results

Femoral atherosclerotic plaque prevalence was significantly higher in patients with psoriasis (44.64%) than in controls (19.07%) (p<0.005), but no significant difference was found in carotid plaque prevalence (p<0.3). Femoral plaques were significantly more prevalent than carotid plaques (21.42%) among patients with psoriasis (p<0.001). In the regression analysis, insulin resistance was the most influential determinant of atherosclerosis in psoriasis and C-reactive protein the most significant predictor of insulin resistance.

Conclusions

Ultrasound screening for femoral atherosclerotic plaques improves the detection of subclinical atherosclerosis in patients with psoriasis, whereas the study of carotid arteries is not sufficiently accurate. Insulin resistance appears to play a greater role in the development of atherosclerosis in these patients in comparison to other classical CVD risk factors.

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<![CDATA[Insulin resistance disrupts epithelial repair and niche-progenitor Fgf signaling during chronic liver injury]]> https://www.researchpad.co/article/5c59feedd5eed0c4841357ce

Insulin provides important information to tissues about feeding behavior and energy status. Defective insulin signaling is associated with ageing, tissue dysfunction, and impaired wound healing. In the liver, insulin resistance leads to chronic damage and fibrosis, but it is unclear how tissue-repair mechanisms integrate insulin signals to coordinate an appropriate injury response or how they are affected by insulin resistance. In this study, we demonstrate that insulin resistance impairs local cellular crosstalk between the fibrotic stroma and bipotent adult liver progenitor cells (LPCs), whose paracrine interactions promote epithelial repair and tissue remodeling. Using insulin-resistant mice deficient for insulin receptor substrate 2 (Irs2), we highlight dramatic impairment of proregenerative fibroblast growth factor 7 (Fgf7) signaling between stromal niche cells and LPCs during chronic injury. We provide a detailed account of the role played by IRS2 in promoting Fgf7 ligand and receptor (Fgfr2-IIIb) expression by the two cell compartments, and we describe an insulin/IRS2-dependent feed-forward loop capable of sustaining hepatic re-epithelialization by driving FGFR2-IIIb expression. Finally, we shed light on the regulation of IRS2 and FGF7 within the fibrotic stroma and show—using a human coculture system—that IRS2 silencing shifts the equilibrium away from paracrine epithelial repair in favor of fibrogenesis. Hence, we offer a compelling insight into the contribution of insulin resistance to the pathogenesis of chronic liver disease and propose IRS2 as a positive regulator of communication between cell types and the transition between phases of stromal to epithelial repair.

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<![CDATA[Resilient hepatic mitochondrial function and lack of iNOS dependence in diet-induced insulin resistance]]> https://www.researchpad.co/article/5c61e8b8d5eed0c48496f037

Obesity-derived inflammation and metabolic dysfunction has been related to the activity of the inducible nitric oxide synthase (iNOS). To understand the interrelation between metabolism, obesity and NO., we evaluated the effects of obesity-induced NO. signaling on liver mitochondrial function. We used mouse strains containing mitochondrial nicotinamide transhydrogenase activity, while prior studies involved a spontaneous mutant of this enzyme, and are, therefore, more prone to oxidative imbalance. Wild-type and iNOS knockout mice were fed a high fat diet for 2, 4 or 8 weeks. iNOS knockout did not protect against diet-induced metabolic changes. However, the diet decreased fatty-acid oxidation capacity in liver mitochondria at 4 weeks in both wild-type and knockout groups; this was recovered at 8 weeks. Interestingly, other mitochondrial functional parameters were unchanged, despite significant modifications in insulin resistance in wild type and iNOS knockout animals. Overall, we found two surprising features of obesity-induced metabolic dysfunction: (i) iNOS does not have an essential role in obesity-induced insulin resistance under all experimental conditions and (ii) liver mitochondria are resilient to functional changes in obesity-induced metabolic dysfunction.

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<![CDATA[Elevated pulmonary arterial pressure in Zucker diabetic fatty rats]]> https://www.researchpad.co/article/5c58d612d5eed0c484031535

Diabetes is a very strong predictor of chronic systemic vascular diseases and acute cardiovascular events. Recently, associations between metabolic disorders and pulmonary hypertension have also been reported in both humans and animal models. In order to get some further insight into the relationship of pulmonary hypertension with obesity, insulin resistance and hyperglycemia, herein we have used the Zucker diabetic fatty rats (ZDF/clr-lepr fa) at 20 weeks fed a standard diet and compared to their lean Zucker littermates (ZL). ZDF rats were obese, had elevated plasma glucose levels and insulin resistance, i.e. a clinically relevant model of type 2 diabetes. They presented elevated systolic, diastolic and mean pulmonary arterial pressures and a parallel increase in the Fulton index. Systemic arterial pressures were also increased but the left ventricle plus septum weight was similar in both groups and the heart rate was reduced. Wall media thickening was observed in the small pulmonary arteries from the ZDF rats. Isolated pulmonary arteries mounted in a wire myograph showed similar vasoconstrictor responses to phenylephrine and 5-HT and similar responses to the endothelium-dependent vasodilator acetylcholine. However, the iNOS inhibitor 1400W enhanced the vasoconstrictor responses in ZDF but not in ZL rats. The protein expression of eNOS and iNOS was not significantly different in the lungs of the two groups. The lung expression of Bmpr2 mRNA was downregulated. However, the mRNA expression of Kcna5, Kcnk3, Kcnq1, Kcnq4 or Kcnq5, which encode for the potassium channels Kv1.5, TASK-1, Kv7.1, Kv7.4 and Kv7.5, respectively, was similar in ZL and ZDF rats. In conclusion, ZDF rats show increased pulmonary arterial pressure, right ventricular hypertrophy, pulmonary arterial medial thickening and downregulated lung Bmpr2 despite leptin resistance. These changes were mild but are consistent with the view that diabetes is a risk factor for pulmonary hypertension.

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<![CDATA[A body mass index over 22 kg/m2 at college age is a risk factor for future diabetes in Japanese men]]> https://www.researchpad.co/article/5c536ac7d5eed0c484a4793d

Background

There is a high incidence of type 2 diabetes in Asian adults, even those with a normal body mass index (BMI) (<25.0 kg/m2). For example, it has been shown that a slightly increased BMI (>23 kg/m2) at middle age is a risk factor for type 2 diabetes in Asians. In this historical cohort study, we investigated whether a slightly increased BMI at college age was also a risk factor for future diabetes in Japanese men.

Methods

Six hundred and sixty-one male alumni who graduated from a physical education school between 1971 and 1991 and who responded to follow-up investigation between 2007 and 2017 were included in this study. Participants were categorized into four categories: college BMI of <21.0 kg/m2, 21.0–22.0 kg/m2, 22.0–23.0 kg/m2, and ≥23.0 kg/m2, and the incidence and risk ratio of diabetes were compared between groups.

Results

The median follow-up period was 32 years (interquartile range, IQR: 27–36), which included 20,983 person-years of observation. Subjects were 22 (22–22) years old at college graduation, and 55 (50–59) years old at the final follow-up investigation. During the study period, 56 men developed diabetes; the prevalence rates for the lowest to highest BMI categories were 4.4%, 7.6%, 10.5%, and 11.3%, respectively, and their adjusted hazard ratios were 1.00 (reference), 1.77 (95% CI: 0.68–4.30), 2.42 (1.00–5.84), and 2.53 (1.06–6.07), respectively (p = 0.03 for trend).

Conclusion

Our data suggest that a BMI over 22.0 kg/m2 at college age is a risk factor for diabetes later in life in Japanese men.

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<![CDATA[Lower circulating levels of CTRP12 and CTRP13 in polycystic ovarian syndrome: Irrespective of obesity]]> https://www.researchpad.co/article/5c1ab85fd5eed0c484027c9a

Altered production of adipokines is suggested to play a pivotal role in the pathogenesis of polycystic ovarian syndrome (PCOS). C1q/TNF-related proteins (CTRPs) play diverse roles in regulation of metabolism in physiologic and pathologic conditions. In the present study, we assessed serum concentrations of adiponectin, CTRP12, and CTRP13 in individuals with PCOS and those without PCOS. We also evaluated the possible association of these adipokines with metabolic and hormonal variables. A total of 171 premenopausal women (86 with PCOS and 85 without PCOS) enrolled in this study. Serum levels of adiponectin, CTRP12, and CTRP13 were measured. The results showed significantly lower serum concentrations of adiponectin, CTRP12, and CTRP13 in PCOS women compared to non-PCOS women. This difference remained significant after controlling for age, body mass index (BMI), and Homeostasis Model Assessment of Insulin Resistance (HOMA-IR). However, we did not observe any significant differences in serum levels of adiponectin, CTRP12, and CTRP13 between the overweight/obese and normal weight subgroups in PCOS and non-PCOS women. Multiple linear regression analysis showed associations of CTRP12 with adiponectin and BMI with CTRP13 in both the PCOS and non-PCOS groups. CTRP12 was significantly associated with BMI and adiponectin in the non-PCOS group, and fasting blood glucose (FBG) and CTRP13 in the PCOS group. Our results indicated that decreased adiponectin, CTRP12, and CTRP13 levels, regardless of obesity, could independently predict PCOS. This finding suggested a novel link between adipokines and PCOS.

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<![CDATA[Vitamin D and metabolic disturbances in polycystic ovary syndrome (PCOS): A cross-sectional study]]> https://www.researchpad.co/article/5c1028bad5eed0c484247f27

Objective

To compare vitamin D status in women with PCOS versus fertile women and subsequently evaluate the association between vitamin D status and metabolic disturbances in PCOS women.

Methods

We conducted a cross-sectional comparison study of 639 women with PCOS and 449 fertile women. Serum 25-hydroxyvitamin D (25(OH)D) was stratified into a severe deficient (< 25 nmol/l), insufficient (25–50 nmol/l), moderate (50–75 nmol/l) and adequate (> 75 nmol/l) status. The main outcome measures were the difference in vitamin D status between PCOS and fertile women, and the association between serum 25(OH)D and metabolic disturbances in PCOS women only.

Results

Serum 25(OH)D was significantly lower in PCOS women compared to fertile controls (mean 25(OH)D of 49.0 nmol/l versus 64.5 nmol/l). An adjusted significant difference was seen between serum 25(OH)D and homeostasis model assessment (HOMA-IR) (β = 0.76; 95% CI: 0.63–0.91; p < 0.01), HDL-cholesterol (β = 0.20; 95% CI: 0.05–0.60, p < 0.01) and apolipoprotein A1 (β = 26.2; 95% CI: 7.5–45.0, p < 0.01) between the highest vitamin D group compared to the lowest vitamin D group.

Conclusions

This study demonstrates that women with PCOS have a significantly lower serum 25(OH)D compared to fertile controls. A compromised vitamin D status in PCOS women is associated with a higher HOMA-IR and an unfavourable lipid profile. Large randomized controlled trials are necessary to explore the causality of this linkage.

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<![CDATA[Percentage fractions of urinary di(2-ethylhexyl) phthalate metabolites: Association with obesity and insulin resistance in Korean girls]]> https://www.researchpad.co/article/5c06f045d5eed0c484c6d57f

Objective

We assessed the associations of percentage fractions of urinary di(2-ethylhexyl) phthalate (DEHP) metabolites with obesity and insulin resistance in Korean girls.

Methods

In total, 137 girls, aged 6 to 13 years (65 overweight cases and 72 controls), were recruited. Anthropometric indices and the homeostatic model assessment of insulin resistance (HOMA-IR) index were determined. Four major urinary DEHP metabolites were analyzed in spot urine samples by gas chromatography-tandem mass spectrometry, including mono(2-ethylhexyl) phthalate, mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), and mono(2-ethyl-5-carboxypentyl) phthalate.

Results

There were no significant differences in the urinary concentrations of the DEHP metabolites between the overweight and control groups. The percentage fraction of MEHHP (MEHHP%) among all DEHP metabolites was significantly higher in the overweight prepubertal girls than in the controls (P = 0.035). MEHHP% was positively associated with the body mass index percentile, waist circumference, body fat percentage, and HOMA-IR index in the prepubertal girls. After adjusting for covariates, the prepubertal girls in a higher MEHHP% quartile were found to have a higher odds ratio for central obesity than those in a lower quartile (odds ratios: 5.05 for quartile 3; 7.30 for quartile 4). The relative rate of MEHHP oxidation to MEOHP was negatively associated with the body mass index percentile and waist circumference in the prepubertal girls. However, no such association was observed in the pubertal girls.

Conclusions

MEHHP% was positively associated with obesity and insulin resistance in prepubertal girls. Further studies are necessary to elucidate the causal links between altered phthalate metabolism and increased susceptibility to insulin resistance in children.

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<![CDATA[Association between cagA negative Helicobacter pylori status and nonalcoholic fatty liver disease among adults in the United States]]> https://www.researchpad.co/article/5b8acdf540307c144d0de05d

We investigated the relationship of H. pylori stratified by cytotoxin-associated gene A (cagA) status with nonalcoholic fatty liver disease (NAFLD) in the general population of the United States (US). We utilized the Third National Health and Nutrition Examination Survey from 1988 to 1994 in this study. NAFLD was defined by ultrasonographic detection of hepatic steatosis in the absence of other known causes of liver diseases and significant alcohol consumption. Hepatic steatosis was assessed by parenchymal brightness, liver to kidney contrast, deep beam attenuation, bright vessel walls and gallbladder wall definition. Antibodies to H. pylori and cagA of participants were measured using H. pylori IgG and anti-cagA IgG enzyme-linked immunosorbent assays. Among 5,404 participants, the prevalence of NAFLD was higher in H. pylori positive subjects (33.5±1.8%) compared to H. pylori negative subjects (26.1±1.7%, p <0.001). In terms of cagA protein status stratification, while cagA positive H. pylori group did not demonstrate an association with NAFLD (OR: 1.05; 95% CI: 0.81–1.37), cagA negative H. pylori group was noted to have a significant association with NAFLD in a multivariable analysis (OR: 1.30; 95% CI: 1.01–1.67). In conclusion, our study demonstrated that cagA negative H. pylori infection was an independent predictor of NAFLD in the US general population.

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<![CDATA[The effects of plasma chromium on lipid profile, glucose metabolism and cardiovascular risk in type 2 diabetes mellitus. A case - control study]]> https://www.researchpad.co/article/5b4a1960463d7e428027f8ac

Background

The study was aimed at determining the effect of plasma chromium concentration on the metabolism of glucose, and lipids and their subsequent cardiovascular risk in patients with type 2 diabetes in the Bolgatanga district of Ghana.

Material and methods

Fasting blood glucose and lipids profile were determined by enzymatic assay using the BT 5000® Random Access Chemistry Analyzer. Fasting serum insulin and High sensitive C-reactive protein were determined by ELISA, a solid phase direct sandwich immunoassay method. HOMA-IR, which is based on fasting blood sample for insulin and glucose concentrations measured in a single blood sample, was used to calculate insulin resistance. Plasma chromium was measured using an atomic Absorption Spectrometer.

Results

Patientswith diabeteshad significantly (p<0.0001) increased LDL, TC, TG, VLDL, insulin, CRP and HOMAIR and a significantly reduced plasma chromium (p<0.0001) (0.53± 0.02μg/l and 0.11±0.01μg/l control and case respectively). Low Cr (p ≤0.001) was associated with high blood pressure, obesity and lipid dysregulation. Plasma Cr significantly correlated negatively with blood pressure and LDL.

Conclusion

Lower plasma Cr level was associated with hyperglycaemia, hyperinsulinemia, hypertension, insulin resistance and high inflammation marker HsCRP.

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<![CDATA[Low-Dose Aspartame Consumption Differentially Affects Gut Microbiota-Host Metabolic Interactions in the Diet-Induced Obese Rat]]> https://www.researchpad.co/article/5989daa1ab0ee8fa60ba604f

Aspartame consumption is implicated in the development of obesity and metabolic disease despite the intention of limiting caloric intake. The mechanisms responsible for this association remain unclear, but may involve circulating metabolites and the gut microbiota. Aims were to examine the impact of chronic low-dose aspartame consumption on anthropometric, metabolic and microbial parameters in a diet-induced obese model. Male Sprague-Dawley rats were randomized into a standard chow diet (CH, 12% kcal fat) or high fat (HF, 60% kcal fat) and further into ad libitum water control (W) or low-dose aspartame (A, 5–7 mg/kg/d in drinking water) treatments for 8 week (n = 10–12 animals/treatment). Animals on aspartame consumed fewer calories, gained less weight and had a more favorable body composition when challenged with HF compared to animals consuming water. Despite this, aspartame elevated fasting glucose levels and an insulin tolerance test showed aspartame to impair insulin-stimulated glucose disposal in both CH and HF, independently of body composition. Fecal analysis of gut bacterial composition showed aspartame to increase total bacteria, the abundance of Enterobacteriaceae and Clostridium leptum. An interaction between HF and aspartame was also observed for Roseburia ssp wherein HF-A was higher than HF-W (P<0.05). Within HF, aspartame attenuated the typical HF-induced increase in the Firmicutes:Bacteroidetes ratio. Serum metabolomics analysis revealed aspartame to be rapidly metabolized and to be associated with elevations in the short chain fatty acid propionate, a bacterial end product and highly gluconeogenic substrate, potentially explaining its negative affects on insulin tolerance. How aspartame influences gut microbial composition and the implications of these changes on the development of metabolic disease require further investigation.

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<![CDATA[Polyunsaturated Fatty Acids Attenuate Diet Induced Obesity and Insulin Resistance, Modulating Mitochondrial Respiratory Uncoupling in Rat Skeletal Muscle]]> https://www.researchpad.co/article/5989da0fab0ee8fa60b7908b

Objectives

Omega (ω)-3 polyunsaturated fatty acids (PUFA) are dietary compounds able to attenuate insulin resistance. Anyway, the precise actions of ω-3PUFAs in skeletal muscle are overlooked. We hypothesized that PUFAs, modulating mitochondrial function and efficiency, would ameliorate pro-inflammatory and pro-oxidant signs of nutritionally induced obesity.

Study Design

To this aim, rats were fed a control diet (CD) or isocaloric high fat diets containing either ω-3 PUFA (FD) or lard (LD) for 6 weeks.

Results

FD rats showed lower weight, lipid gain and energy efficiency compared to LD-fed animals, showing higher energy expenditure and O2 consumption/CO2 production. Serum lipid profile and pro-inflammatory parameters in FD-fed animals were reduced compared to LD. Accordingly, FD rats exhibited a higher glucose tolerance revealed by an improved glucose and insulin tolerance tests compared to LD, accompanied by a restoration of insulin signalling in skeletal muscle. PUFAs increased lipid oxidation and reduced energy efficiency in subsarcolemmal mitochondria, and increase AMPK activation, reducing both endoplasmic reticulum and oxidative stress. Increased mitochondrial respiration was related to an increased mitochondriogenesis in FD skeletal muscle, as shown by the increase in PGC1-α and -β.

Conclusions

our data strengthened the association of high dietary ω3-PUFA intake with reduced mitochondrial energy efficiency in the skeletal muscle.

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<![CDATA[White Pitaya (Hylocereus undatus) Juice Attenuates Insulin Resistance and Hepatic Steatosis in Diet-Induced Obese Mice]]> https://www.researchpad.co/article/5989daaaab0ee8fa60ba90e3

Insulin resistance and hepatic steatosis are the most common complications of obesity. Pitaya is an important source of phytochemicals such as polyphenols, flavonoid and vitamin C which are related to its antioxidant activity. The present study was conducted to evaluate the influence of white pitaya juice (WPJ) on obesity-related metabolic disorders (e.g. insulin resistance and hepatic steatosis) in high-fat diet-fed mice. Forty-eight male C57BL/6J mice were assigned into four groups and fed low-fat diet with free access to water or WPJ, or fed high-fat diet with free access to water or WPJ for 14 weeks. Our results showed that administration of WPJ improved high-fat diet-induced insulin resistance, hepatic steatosis and adipose hypertrophy, but it exerted no influence on body weight gain in mice. Hepatic gene expression analysis indicated that WPJ supplement not only changed the expression profile of genes involved in lipid and cholesterol metabolism (Srebp1, HMGCoR, Cpt1b, HL, Insig1 and Insig2) but also significantly increased the expression levels of FGF21-related genes (Klb, FGFR2, Egr1 and cFos). In conclusion, WPJ protected from diet-induced hepatic steatosis and insulin resistance, which was associated with the improved FGF21 resistance and lipid metabolism.

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<![CDATA[Lin28a Protects against Hypoxia/Reoxygenation Induced Cardiomyocytes Apoptosis by Alleviating Mitochondrial Dysfunction under High Glucose/High Fat Conditions]]> https://www.researchpad.co/article/5989dae8ab0ee8fa60bbe130

Aim

The aim of the present study was to investigate the role of Lin28a in protecting against hypoxia/reoxygenation (H/R)-induced cardiomyocytes apoptosis under high glucose/high fat (HG/HF) conditions.

Methods

Primary cardiomyocytes which were isolated from neonatal mouse were randomized to be treated with lentivirus carrying Lin28a siRNA, Lin28acDNA 72 h before H/R (9 h/2 h). Cardiomyocytes biomarkers release (LDH and CK), cardiomyocytes apoptosis, mitochondria biogenesis and morphology, intracellular reactive oxygen species (ROS) production, ATP content and inflammatory cytokines levels after H/R injury in high glucose/high fat conditions were compared between groups. The target proteins of Lin28a were examined by western blot analysis.

Results

Our results revealed that Lin28a cDNA transfection (overexpression) significantly inhibited cardiomyocyte apoptotic index, improved mitochondria biogenesis, increased ATP production and reduced ROS production as compared with the H/R group in HG/HF conditions. Lin28a siRNA transfection (knockdown) rendered the cardiomyocytes more susceptible to H/R injury as evidenced by increased apoptotic index, impaired mitochondrial biogenesis, decreased ATP production and increased ROS level. Interestingly, these effects of Lin28a were blocked by pretreatment with the PI3K inhibitor wortmannin. Lin28a overexpression increased, while Lin28a knockdown inhibited IGF1R, Nrf-1, Tfam, p-IRS-1, p-Akt, p-mTOR, p-p70s6k, p-AMPK expression levels after H/R injury in HG/HF conditions. Moreover, pretreatment with wortmannin abolished the effects of Lin28a on the expression levels of p-AKT, p-mTOR, p-p70s6k, p-AMPK.

Conclusions

The present results suggest that Lin28a inhibits cardiomyocytes apoptosis by enhancing mitochondrial biogenesis and function under high glucose/high fat conditions. The mechanism responsible for the effects of Lin28a is associated with the PI3K/Akt dependent pathway.

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<![CDATA[Vitamin A and Feeding Statuses Modulate the Insulin-Regulated Gene Expression in Zucker Lean and Fatty Primary Rat Hepatocytes]]> https://www.researchpad.co/article/5989db29ab0ee8fa60bd0f74

Unattended hepatic insulin resistance predisposes individuals to dyslipidemia, type 2 diabetes and many other metabolic complications. The mechanism of hepatic insulin resistance at the gene expression level remains unrevealed. To examine the effects of vitamin A (VA), total energy intake and feeding conditions on the insulin-regulated gene expression in primary hepatocytes of Zucker lean (ZL) and fatty (ZF) rats, we analyze the expression levels of hepatic model genes in response to the treatments of insulin and retinoic acid (RA). We report that the insulin- and RA-regulated glucokinase, sterol regulatory element-binding protein-1c and cytosolic form of phosphoenolpyruvate carboxykinase expressions are impaired in hepatocytes of ZF rats fed chow or a VA sufficient (VAS) diet ad libitum. The impairments are partially corrected when ZF rats are fed a VA deficient (VAD) diet ad libitum or pair-fed a VAS diet to the intake of their VAD counterparts in non-fasting conditions. Interestingly in the pair-fed ZL and ZF rats, transient overeating on the last day of pair-feeding regimen changes the expression levels of some VA catabolic genes, and impairs the insulin- and RA-regulated gene expression in hepatocytes. These results demonstrate that VA and feeding statuses modulate the hepatic insulin sensitivity at the gene expression level.

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<![CDATA[Abdominal Adiposity, Not Cardiorespiratory Fitness, Mediates the Exercise-Induced Change in Insulin Sensitivity in Older Adults]]> https://www.researchpad.co/article/5989da37ab0ee8fa60b86a41

Abdominal obesity and low cardiorespiratory fitness (CRF) are associated with insulin resistance in older adults. Exercise is associated with improvement in insulin sensitivity. Whether this association is mediated by change in CRF and/or abdominal obesity is unclear. The current study is a secondary analysis of data from a randomized controlled trial in Kingston, Ontario. Sedentary older adults (60–80 years) (N = 80) who completed the exercise (N = 59) or control (N = 21) conditions for 6 months were included. CRF was measured using a treadmill test, adipose tissue (AT) by magnetic resonance imaging, and insulin sensitivity by hyperinsulinemic-euglycemic clamp. Waist circumference (WC) was measured at the iliac crest. Mediation analyses were used to assess whether abdominal AT and/or CRF mediated the exercise-induced change in insulin sensitivity. By comparison to controls, reduction (mean ± SD) was observed for visceral (-0.4 ± 0.4 kg) and abdominal subcutaneous (-0.4 ± 0.4) AT depots, WC (-4.1 ± 3.2 cm) and BMI (-0.9 ± 0.8 kg/m2) (p < 0.05). Insulin sensitivity (4.2 ± 5.2 M/I) and CRF (0.2 ± 0.3 L/min) improved in the exercise group (p < 0.05). All AT variables, BMI and WC were mediators of the change in insulin sensitivity (p < 0.05). After adjustment for change in total AT, abdominal AT remained a mediator with an effect ratio of 0.79 (p < 0.05), whereas total AT was not significant when adjusted for abdominal AT (p > 0.05). The effect ratio for change in WC and BMI combined (0.63, p<0.05) was greater than either alone. In conclusion, CRF did not mediate the exercise-induced change in insulin sensitivity in older adults. Abdominal adiposity was a strong mediator independent of change in total adiposity.

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<![CDATA[Pharmacological PPARα Activation Markedly Alters Plasma Turnover of the Amino Acids Glycine, Serine and Arginine in the Rat]]> https://www.researchpad.co/article/5989daafab0ee8fa60baad73

The current study extends previously reported PPARα agonist WY 14,643 (30 µmol/kg/day for 4 weeks) effects on circulating amino acid concentrations in rats fed a 48% saturated fat diet. Steady-state tracer experiments were used to examine in vivo kinetic mechanisms underlying altered plasma serine, glycine and arginine levels. Urinary urea and creatinine excretion were measured to assess whole-body amino acid catabolism. WY 14,643 treated animals demonstrated reduced efficiency to convert food consumed to body weight gain while liver weight was increased compared to controls. WY 14,643 raised total amino acid concentration (38%), largely explained by glycine, serine and threonine increases. 3H-glycine, 14C-serine and 14C-arginine tracer studies revealed elevated rates of appearance (Ra) for glycine (45.5±5.8 versus 17.4±2.7 µmol/kg/min) and serine (21.0±1.4 versus 12.0±1.0) in WY 14,643 versus control. Arginine was substantially decreased (−62%) in plasma with estimated Ra reduced from 3.1±0.3 to 1.2±0.2 µmol/kg/min in control versus WY 14,643. Nitrogen excretion over 24 hours was unaltered. Hepatic arginase activity was substantially decreased by WY 14,643 treatment. In conclusion, PPARα agonism potently alters metabolism of several specific amino acids in the rat. The changes in circulating levels of serine, glycine and arginine reflected altered fluxes into the plasma rather than changes in clearance or catabolism. This suggests that PPARα has an important role in modulating serine, glycine and arginine de novo synthesis.

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<![CDATA[The Dietary Isoflavone Daidzein Reduces Expression of Pro-Inflammatory Genes through PPARα/γ and JNK Pathways in Adipocyte and Macrophage Co-Cultures]]> https://www.researchpad.co/article/5989da11ab0ee8fa60b79848

Obesity-induced inflammation caused by adipocyte-macrophage interactions plays a critical role in developing insulin resistance, and peroxisome proliferator-activated receptors (PPARs) regulate inflammatory gene expression in these cells. Recently, the soy isoflavone daidzein was reported to act as a PPAR activator. We examined whether daidzein affected adipocyte-macrophage crosstalk via the regulation of PPARs. Co-cultures of 3T3-L1 adipocytes and RAW264 macrophages, or palmitate-stimulated RAW264 macrophages were treated with daidzein in the presence or absence of specific inhibitors for PPARs: GW6471 (a PPARα antagonist), and GW9662 (a PPARγ antagonist). Inflammatory gene expression was then determined. Daidzein significantly decreased chemokine (C-C motif) ligand 2 (Ccl2, known in humans as monocyte chemo-attractant protein 1 (MCP1)) and interleukin 6 (Il6) mRNA levels induced by co-culture. In 3T3-L1 adipocytes, daidzein inversed the attenuation of adiponectin gene expression by co-culture, and these effects were inhibited by the PPAR-γ specific inhibitor. Daidzein also decreased Ccl2 and Il6 mRNA levels in RAW264 macrophages stimulated with palmitate or conditioned medium (CM) from hypertrophied 3T3-L1 adipocytes. This inhibitory effect on Il6 expression was abrogated by a PPAR-α inhibitor. Additionally, we examined the activation of nuclear factor-kappa B (NF-κB) and c-Jun N-terminal kinase (JNK) pathways and found that daidzein significantly inhibited palmitate-induced phosphorylation of JNK. Our data suggest that daidzein regulates pro-inflammatory gene expression by activating PPAR-α and -γ and inhibiting the JNK pathway in adipocyte and macrophage co-cultures. These effects might be favorable in improving adipose inflammation, thus, treatment of daidzein may be a therapeutic strategy for chronic inflammation in obese adipose tissue.

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