Short-term oral α-lipoic acid does not prevent lipid-induced dysregulation of glucose homeostasis in obese and overweight nondiabetic men

Prolonged elevation of plasma free fatty acids (FFAs) induces insulin resistance and impairs pancreatic β-cell adaptation to insulin resistance. The mechanisms whereby lipid induces these impairments are not fully defined but may involve oxidative stress, inflammation, and endoplasmic reticulum stress. α-Lipoic acid (ALA), a commonly used health supplement with antioxidant, anti-inflammatory, and AMPK-activating properties, has been shown to have therapeutic value in type 2 diabetes and its complications. Here we examined the effects of ALA on insulin sensitivity and secretion in humans under the conditions of 24-h iv lipid infusion to elevate plasma FFAs. Eight overweight and obese male subjects underwent four randomized studies each, 4–6 wk apart: 1) SAL, 2-wk oral placebo followed by 24-h iv infusion of saline; 2) IH, 2-wk placebo followed by 24-h iv infusion of intralipid plus heparin to raise plasma FFAs approximately twofold; 3) IH + ALA, 2-wk ALA (1,800 mg/day) followed by 24-h infusion of intralipid plus heparin; and 4) ALA, 2-wk ALA followed by 24-h infusion of saline. Insulin secretion rates (ISR) and insulin sensitivity were assessed with a 2-h, 20-mmol/l hyperglycemic clamp and a hyperinsulinemic euglycemic clamp, respectively. ISR was not significantly different between treatments. Lipid infusion impaired insulin sensitivity with and without ALA pretreatment. These results indicate that ALA, administered orally at this dose for 2 wk, does not protect against lipid-induced insulin resistance in overweight and obese humans.

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Common Risk Factors in Relatives and Spouses of Patients with Type 2 Diabetes in Developing Prediabetes

Healthcare ◽

10.3390/healthcare9081010 ◽

2021 ◽

Vol 9 (8) ◽

pp. 1010

Author(s):

Wei-Hao Hsu ◽

Chin-Wei Tseng ◽

Yu-Ting Huang ◽

Ching-Chao Liang ◽

Mei-Yueh Lee ◽

...

Keyword(s):

Risk Factors ◽

Insulin Resistance ◽

Type 2 Diabetes ◽

Insulin Sensitivity ◽

Cell Function ◽

Diabetic Patients ◽

Β Cell ◽

Tyg Index ◽

Β Cell Function

Prediabetes should be viewed as an increased risk for diabetes and cardiovascular disease. In this study, we investigated its prevalence among the relatives and spouses of patients with type 2 diabetes or risk factors for prediabetes, insulin resistance, and β-cell function. A total of 175 individuals were included and stratified into three groups: controls, and relatives and spouses of type 2 diabetic patients. We compared clinical characteristics consisting of a homeostatic model assessment for insulin resistance (HOMA-IR) and beta cell function (HOMA-β), a quantitative insulin sensitivity check index (QUICKI), and triglyceride glucose (TyG) index. After a multivariable linear regression analysis, the relative group was independently correlated with high fasting glucose, a high TyG index, and low β-cell function; the relatives and spouses were independently associated with a low QUICKI. The relatives and spouses equally had a higher prevalence of prediabetes. These study also indicated that the relatives had multiple factors predicting the development of diabetes mellitus, and that the spouses may share a number of common environmental factors associated with low insulin sensitivity.

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Vascular dysfunction and insulin stimulated blood flow : impact of physical inactivity and type 2 diabetes

10.32469/10355/48201 ◽

2014 ◽

Author(s):

◽

Leryn J. Boyle

Keyword(s):

Physical Activity ◽

Insulin Resistance ◽

Type 2 Diabetes ◽

Blood Flow ◽

Insulin Sensitivity ◽

Endothelial Function ◽

Physical Inactivity ◽

Vascular Dysfunction ◽

Insulin Stimulation

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Individuals with type 2 diabetes (T2D) have blunted femoral artery insulin mediated blood flow which is critical for the delivery and uptake of glucose into skeletal muscle. However, it is unclear in humans the precise mechanisms by which insulin resistance impairs insulin stimulated blood flow. Further, chronic physical inactivity is a powerful stimulus for reduced insulin sensitivity and vascular dysfunction; however, the effects of short term, modest reductions in physical activity are limited. Thus, we examined 1) if inactivity for 5 days would impair endothelial function in healthy individuals (study one) 2) if reducing whole body insulin sensitivity, via 5 days of inactivity, would impair the blood flow response to insulin stimulation in parallel with glycemic control (study two) and 3) phosphorylation of endothelial nitric oxide (eNOS) and endothelin-1 (ET-1) production to insulin stimulation would be decreased and increased, respectively, in insulin resistant individuals (study three). We demonstrated significant reductions in endothelial function with only 5 days of reduced daily steps while blood flow to glucose ingestion was unaltered. Further, in obese humans with type 2 diabetes it does not appear that that the reduction in blood flow to 1 hr of insulin stimulation is due to altered peNOS or ET-1. Collectively, these data suggest that reduced daily physical activity and chronic insulin resistance mediate negative impacts on vascular function and insulin stimulated blood flow and signaling.

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Increasing endogenous PPARγ ligands improves insulin sensitivity and protects against diet-induced obesity without side effects of thiazolidinediones

10.21203/rs.3.rs-490889/v1 ◽

2021 ◽

Author(s):

Yu-Hua Tseng ◽

Lee-Ming Chuang ◽

Yi-Cheng Chang ◽

Meng-Lun Hsieh ◽

Lun Tsou ◽

...

Keyword(s):

Insulin Resistance ◽

Type 2 Diabetes ◽

Insulin Sensitivity ◽

Side Effects ◽

Knockout Mice ◽

Fasting Glucose ◽

Binding Mode ◽

Fluid Retention ◽

Diet Induced Obesity

Abstract Insulin resistance and obesity are pivotal features of type 2 diabetes mellitus. Peroxisome proliferator-activated receptor γ (PPARγ) is a master transcriptional regulator of systemic insulin sensitivity and energy balance. The anti-diabetic drug thiazolidinediones are potent synthetic PPARγ ligands and insulin sensitizers with undesirable side effects including increased adiposity, fluid retention, and osteoporosis, which limit their clinical use. We and others have proved that 15-keto-PGE2 is an endogenous natural PPARγ ligand. 15-keto-PGE2 is catalyzed by prostaglandin reductase 2 (PTGR2) to become inactive metabolites. We found that 15-keto-PGE2 level is increased in Ptgr2 knockout mice. Ptgr2 knockout mice were protected from diet-induced obesity, insulin resistance, and hepatic steatosis without fluid retention nor reduced bone mineral density. Diet-induced obese mice have drastically reduced 15-keto-PGE2 levels compared to lean mice. Administration of 15-keto-PGE2 markedly improved insulin sensitivity and prevented diet-induced obesity in mice. We demonstrated that 15-keto-PGE2 activates PPARγ through covalent binding to its cysteine 285 residue at helix 3, which restrained its binding pocket between helix 3 and β-sheets of the PPARγ ligand binding domain. This binding mode differs from the helix12-dependent binding mode of thiazolidinediones. We further identified a small-molecule PTGR2 inhibitor BPRPT245, which interferes the interaction between the substrate-binding sites of PTGR2 and 15-keto-PGE2. BPRPT245 increased 15-keto-PGE2 concentration, activated PPARγ, and promoted glucose uptake in adipocytes. BPRPT245 also prevented diet-induced obesity, improved insulin sensitivity and glucose tolerance, lowers fasting glucose without fluid retention and osteoporosis. In humans, reduced serum 15-keto-PGE2 levels were observed in patients with type 2 diabetes compared with controls. Furthermore, serum 15-keto-PGE2 levels correlate inversely with insulin resistance and fasting glucose in non-diabetic humans. In conclusion, we identified a new therapeutic approach to improve insulin sensitivity and protect diet-induced obesity through increasing endogenous natural PPARγ ligands without side effects of thiazolidinediones.

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Adipocyte PU.1 knockout promotes insulin sensitivity in HFD-fed obese mice

Scientific Reports ◽

10.1038/s41598-019-51196-8 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 1

Author(s):

Denise E. Lackey ◽

Felipe C. G. Reis ◽

Roi Isaac ◽

Rizaldy C. Zapata ◽

Dalila El Ouarrat ◽

...

Keyword(s):

Gene Expression ◽

Insulin Resistance ◽

Type 2 Diabetes ◽

Insulin Sensitivity ◽

Glucose Tolerance ◽

Target Genes ◽

Obese Mice ◽

Tissue Macrophage

Abstract Insulin resistance is a key feature of obesity and type 2 diabetes. PU.1 is a master transcription factor predominantly expressed in macrophages but after HFD feeding PU.1 expression is also significantly increased in adipocytes. We generated adipocyte specific PU.1 knockout mice using adiponectin cre to investigate the role of PU.1 in adipocyte biology, insulin and glucose homeostasis. In HFD-fed obese mice systemic glucose tolerance and insulin sensitivity were improved in PU.1 AKO mice and clamp studies indicated improvements in both adipose and liver insulin sensitivity. At the level of adipose tissue, macrophage infiltration and inflammation was decreased and glucose uptake was increased in PU.1 AKO mice compared with controls. While PU.1 deletion in adipocytes did not affect the gene expression of PPARg itself, we observed increased expression of PPARg target genes in eWAT from HFD fed PU.1 AKO mice compared with controls. Furthermore, we observed decreased phosphorylation at serine 273 in PU.1 AKO mice compared with fl/fl controls, indicating that PPARg is more active when PU.1 expression is reduced in adipocytes. Therefore, in obesity the increased expression of PU.1 in adipocytes modifies the adipocyte PPARg cistrome resulting in impaired glucose tolerance and insulin sensitivity.

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Elevated and Correlated Expressions of miR-24, miR-30d, miR-146a, and SFRP-4 in Human Abdominal Adipose Tissue Play a Role in Adiposity and Insulin Resistance

International Journal of Endocrinology ◽

10.1155/2018/7351902 ◽

2018 ◽

Vol 2018 ◽

pp. 1-7 ◽

Cited By ~ 13

Author(s):

Yury O. Nunez Lopez ◽

Gabriella Garufi ◽

Magdalena Pasarica ◽

Attila A. Seyhan

Keyword(s):

Insulin Resistance ◽

Adipose Tissue ◽

Insulin Sensitivity ◽

Linear Models ◽

Euglycemic Hyperinsulinemic Clamp ◽

Abdominal Adipose Tissue ◽

Systemic Insulin Resistance ◽

Novel Association ◽

Regulatory Loop

Objective. We explored the relationships among microRNAs (miRNAs) and SFRP4, as they relate to adipose tissue functions including lipolysis, glucose and glycerol turnover, and insulin sensitivity. Methods. Abdominal adipose tissue (AbdAT) levels of thirteen microRNAs (miRNAs), SFRP4, and VEGF in lean nondiabetic subjects (n=7), subjects with obesity (n=5), and subjects with obesity and type 2 diabetes (T2DM) (n=5) were measured by qPCR. Insulin sensitivity was measured by the euglycemic-hyperinsulinemic clamp. Osmium fixation and Coulter counting were used for adipocyte sizing. Data were analyzed using generalized linear models that adjusted for age, gender, and ethnicity. Results. AbdAT miR-24, miR-30d, and miR-146a were elevated in subjects with obesity (P<0.05) and T2DM (P<0.1) and positively correlated with measures of percent body fat by DXA (rmiR.24=0.894, rmiR.146a=0.883, P<0.05), and AbdAT SFRP4 (rmiR.30=0.93, rmiR.146a=0.88, P<0.05). These three miRNAs additionally correlated among themselves (rmiR.24~miR.146a=0.90, rmiR.30~miR.146a=0.85, P<0.01). Conclusions. This study suggests a novel association between the elevated levels of miRNAs miR-24, miR-30d, and miR-146a (apparently coregulated) and the level of SFRP4 transcript in AbdAT of subjects with obesity and T2DM. These molecules might be part of a regulatory loop involved in AbdAT remodeling/adiposity and systemic insulin resistance. This trial is registered with NCT00704197.

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Ethnic distinctions in the pathophysiology of type 2 diabetes: a focus on black African-Caribbean populations

Proceedings of The Nutrition Society ◽

10.1017/s0029665119001034 ◽

2019 ◽

Vol 79 (2) ◽

pp. 184-193 ◽

Cited By ~ 4

Author(s):

Louise M. Goff ◽

Meera Ladwa ◽

Olah Hakim ◽

Oluwatoyosi Bello

Keyword(s):

Insulin Resistance ◽

Type 2 Diabetes ◽

Insulin Sensitivity ◽

Global Public Health ◽

Black African ◽

African Caribbean ◽

Black Populations ◽

The Impact ◽

Caribbean Populations

Type 2 diabetes (T2D) is a global public health priority, particularly for populations of black African-Caribbean ethnicity, who suffer disproportionately high rates of the disease. While the mechanisms underlying the development of T2D are well documented, there is growing evidence describing distinctions among black African-Caribbean populations. In the present paper, we review the evidence describing the impact of black African-Caribbean ethnicity on T2D pathophysiology. Ethnic differences were first recognised through evidence that metabolic syndrome diagnostic criteria fail to detect T2D risk in black populations due to less central obesity and dyslipidaemia. Subsequently more detailed investigations have recognised other mechanistic differences, particularly lower visceral and hepatic fat accumulation and a distinctly hyperinsulinaemic response to glucose stimulation. While epidemiological studies have reported exaggerated insulin resistance in black populations, more detailed and direct measures of insulin sensitivity have provided evidence that insulin sensitivity is not markedly different to other ethnic groups and does not explain the hyperinsulinaemia that is exhibited. These findings lead us to hypothesise that ectopic fat does not play a pivotal role in driving insulin resistance in black populations. Furthermore, we hypothesise that hyperinsulinaemia is driven by lower rates of hepatic insulin clearance rather than heightened insulin resistance and is a primary defect rather than occurring in compensation for insulin resistance. These hypotheses are being investigated in our ongoing South London Diabetes and Ethnicity Phenotyping study, which will enable a more detailed understanding of ethnic distinctions in the pathophysiology of T2D between men of black African and white European ethnicity.

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Association of Vitamin D with Type 2 Diabetes in Postmenopausal Females in Saudi Arabia

Proceedings of The Nutrition Society ◽

10.1017/s0029665120005789 ◽

2020 ◽

Vol 79 (OCE2) ◽

Author(s):

Shatha Alharazy ◽

Eman Alissa ◽

Mohammed Ardawi ◽

Susan Lanham-New ◽

M. Denise Robertson

Keyword(s):

Insulin Resistance ◽

Type 2 Diabetes ◽

Vitamin D ◽

Saudi Arabia ◽

Insulin Sensitivity ◽

Postmenopausal Women ◽

Cell Activity ◽

Study Cohort ◽

Model Assessment

AbstractVitamin D (vitD) deficiency has been suspected as a risk factor for type 2 diabetes mellitus (T2DM). It has been reported that an inverse relationship exists between vitD status and risk of T2DM. The aim of this study was to investigate whether there is an association between vitD status and glycemic profile and other metabolic parameters among postmenopausal women with T2DM (living in Saudi Arabia). A cross-sectional study was conducted at King Fahad Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia. One thirty six (n = 136) postmenopausal females (age ≥ 50 years) living in Jeddah city, Saudi Arabia, with T2DM were randomly recruited in this study. Anthropometric measures, blood pressure readings and fasting blood samples were obtained fro all study participants. Several biochemical parameters were estimated in fasting serum samples including total 25(OH)D, HbA1c, insulin, glucose, c-peptide and lipid profile. Surrogate markers for insulin resistance were calculated using Homeostasis Model Assessment for insulin resistance and beta cell activity (HOMA-IR, HOMA-β), Quantitative insulin sensitivity check index (QUICK-I) and McAuley's index. VitD deficiency was defined as serum total 25(OH)D level below 20 ng/ml.The Mean (± SD) serum levels of total 25(OH)D were 13.8 ± 8.6 ng/ml with 79% of the study cohort being vitD deficient. Furthermore, serum total 25(OH)D levels were found to be inversely correlated with fasting insulin (r = -0.24, p = 0.029), HOMA-IR (r = -0.24, p = 0.03), and positively correlated with McAuley's index (r = 0.22, p = 0.048) and QUICK-I (r = 0.25, p = 0.024). In conclusion, vitD deficiency is highly prevalent among postmenopausal women with T2DM living in Jeddah, Saudi Arabia. VitD was found to be associated with insulin resistance. Whether vitD supplements are able to improve insulin sensitivity and other parameters in T2DM postmenopausal women should be further investigated.

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Metabolic signature of obesity-associated insulin resistance and type 2 diabetes

Journal of Translational Medicine ◽

10.1186/s12967-019-2096-8 ◽

2019 ◽

Vol 17 (1) ◽

Cited By ~ 4

Author(s):

Haya Al-Sulaiti ◽

Ilhame Diboun ◽

Maha V. Agha ◽

Fatima F. S. Mohamed ◽

Stephen Atkin ◽

...

Keyword(s):

Insulin Resistance ◽

Type 2 Diabetes ◽

Insulin Sensitivity ◽

Serum Samples ◽

Metabolic Markers ◽

Insulin Resistant ◽

Increased Risk ◽

Novel Biomarkers ◽

Prospective Cohorts

Abstract Background Obesity is associated with an increased risk of insulin resistance and type 2 diabetes mellitus (T2DM). However, some obese individuals maintain their insulin sensitivity and exhibit a lower risk of associated comorbidities. The underlying metabolic pathways differentiating obese insulin sensitive (OIS) and obese insulin resistant (OIR) individuals remain unclear. Methods In this study, 107 subjects underwent untargeted metabolomics of serum samples using the Metabolon platform. Thirty-two subjects were lean controls whilst 75 subjects were obese including 20 OIS, 41 OIR, and 14 T2DM individuals. Results Our results showed that phospholipid metabolites including choline, glycerophosphoethanolamine and glycerophosphorylcholine were significantly altered from OIS when compared with OIR and T2DM individuals. Furthermore, our data confirmed changes in metabolic markers of liver disease, vascular disease and T2DM, such as 3-hydroxymyristate, dimethylarginine and 1,5-anhydroglucitol, respectively. Conclusion This pilot data has identified phospholipid metabolites as potential novel biomarkers of obesity-associated insulin sensitivity and confirmed the association of known metabolites with increased risk of obesity-associated insulin resistance, with possible diagnostic and therapeutic applications. Further studies are warranted to confirm these associations in prospective cohorts and to investigate their functionality.

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Resveratrol improves insulin sensitivity, reduces oxidative stress and activates the Akt pathway in type 2 diabetic patients

British Journal Of Nutrition ◽

10.1017/s0007114511000316 ◽

2011 ◽

Vol 106 (3) ◽

pp. 383-389 ◽

Cited By ~ 374

Author(s):

Pál Brasnyó ◽

Gergő A. Molnár ◽

Márton Mohás ◽

Lajos Markó ◽

Boglárka Laczy ◽

...

Keyword(s):

Oxidative Stress ◽

Insulin Resistance ◽

Insulin Sensitivity ◽

Cell Function ◽

Diabetic Patients ◽

Β Cell ◽

Type 2 Diabetic Patients ◽

Β Cell Function ◽

Type 2 Diabetic

Although resveratrol has widely been studied for its potential health benefits, little is known about its metabolic effects in humans. Our aims were to determine whether the polyphenol resveratrol improves insulin sensitivity in type 2 diabetic patients and to gain some insight into the mechanism of its action. After an initial general examination (including blood chemistry), nineteen patients enrolled in the 4-week-long double-blind study were randomly assigned into two groups: a resveratrol group receiving oral 2 × 5 mg resveratrol and a control group receiving placebo. Before and after the second and fourth weeks of the trial, insulin resistance/sensitivity, creatinine-normalised ortho-tyrosine level in urine samples (as a measure of oxidative stress), incretin levels and phosphorylated protein kinase B (pAkt):protein kinase B (Akt) ratio in platelets were assessed and statistically analysed. After the fourth week, resveratrol significantly decreased insulin resistance (homeostasis model of assessment for insulin resistance) and urinary ortho-tyrosine excretion, while it increased the pAkt:Akt ratio in platelets. On the other hand, it had no effect on parameters that relate to β-cell function (i.e. homeostasis model of assessment of β-cell function). The present study shows for the first time that resveratrol improves insulin sensitivity in humans, which might be due to a resveratrol-induced decrease in oxidative stress that leads to a more efficient insulin signalling via the Akt pathway.

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