Endogenous peptides as risk markers to assess the development of insulin resistance

Low levels of spexin and adiponectin may predict insulin resistance in patients with non-alcoholic fatty liver

Adipose tissue is endocrine organ that responds by secreting numerous hormones that regulate metabolism in skeletal muscle and the liver. The aim of this study was to compare the levels of spexin and adiponectin in patients with non-alcoholic fatty liver and evaluate the relationship between circulating adipocytokines and insulin resistance. Two groups of subjects were evaluated: 41 non-alcoholic fatty liver subjects (age 35.17 ​± ​12.29 year, BMI 30.97 ​± ​2.75 ​kg/m2) and 38 normal controls (age 38.47 ​± ​11.63 year, BMI 22.83 ​± ​3.00 ​kg/m2). Plasma concentrations of spexin and adiponectin were determined using immunosorbent assay kits. Insulin resistance was assessed using the homeostasis model assessment (HOMA-IR) formula derived from fasting insulin and glucose levels. Compared to normal controls, plasma concentrations of spexin and adiponectin were significantly lower in patients with non-alcoholic fatty liver (P ​< ​0.001). Spexin did not correlate with BMI but did significantly correlate with HOMA-IR (r ​= ​-0.368; P ​= ​0.018) and adiponectin (r ​= ​0.378; P ​= ​0.043), and this correlation remained significant after adjustment for gender and BMI. In this small group of patients with non-alcoholic fatty liver we demonstrated that insulin resistance correlated strongly with spexin and adiponectin levels.

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The plasma spexin levels were decreased in patients with NAFLD.

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A negative correlation was shown between spexin and HOMA-IR.

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A negative correlation was shown between adiponectin and HOMA-IR.

Early-life programming of adipose tissue

Worldwide obesity is increasing at an alarming rate in children and adolescents, with the consequent emergence of co-morbidities. Moreover, the maternal environment during pregnancy plays an important role in obesity, contributing to transgenerational transmission of the same and metabolic dysfunction. White adipose tissue represents a prime target of metabolic programming induced by maternal milieu. In this article, we review adipose tissue physiology and development, as well as maternal influences during the perinatal period that may lead to obesity in early postnatal life and adulthood. First, we describe the adipose tissue cell composition, distribution and hormonal action, together with the evidence of hormonal factors participating in fetal/postnatal programming. Subsequently, we describe the critical periods of adipose tissue development and the relationship of gestational and early postnatal life with healthy fetal adipose tissue expansion. Furthermore, we discuss the evidence showing that adipose tissue is an important target for nutritional, hormonal and epigenetic signals to modulate fetal growth. Finally, we describe nutritional, hormonal, epigenetic and microbiome changes observed in maternal obesity, and whether their disruption alters fetal growth and adiposity. The presented evidence supports the developmental origins of health and disease concept, which proposes that the homeostatic system is affected during gestational and postnatal development, impeding the ability to regulate body weight after birth, thereby resulting in adult obesity. Consequently, we anticipate that promoting a healthy early-life programming of adipose tissue and increasing the knowledge of the mechanisms by which maternal factors affect the health of future generations may offer novel strategies for explaining and addressing worldwide health problems such as obesity.

Obesity is the main determinant of insulin resistance more than the circulating pro-inflammatory cytokines levels in rheumatoid arthritis patients

BACKGROUND

Systemic blockade of TNF-α in Rheumatoid arthritis with insulin resistance seems to produce more improvement in insulin sensitivity in normal weight patients with Rheumatoid arthritis than in obese patients with Rheumatoid arthritis, suggesting that systemic-inflammation and obesity are independent risk factors for insulin resistance in Rheumatoid arthritis patients.

OBJECTIVES

To evaluate the insulin resistance in: normal weight patients with Rheumatoid arthritis, overweight patients with Rheumatoid arthritis, obese Rheumatoid arthritis patients, and matched control subjects with normal weight and obesity; and its association with major cytokines involved in the pathogenesis of the disease.

METHODS

Assessments included: body mass index, insulin resistance by Homeostasis Model Assessment, ELISA method, and enzymatic colorimetric assay.

RESULTS

Outstanding results from these studies include: (1) In Rheumatoid arthritis patients, insulin resistance was well correlated with body mass index, but not with levels of serum cytokines. In fact, levels of cytokines were similar in all Rheumatoid arthritis patients, regardless of being obese, overweight or normal weight (2) Insulin resistance was significantly higher in Rheumatoid arthritis with normal weight than in normal weight (3) No significant difference was observed between insulin resistances of Rheumatoid arthritis with obesity and obesity (4) As expected, levels of circulating cytokines were significantly higher in Rheumatoid arthritis patients than in obesity.

CONCLUSIONS

Obesity appears to be a dominant condition above inflammation to produce IR in RA patients. The dissociation of the inflammation and obesity components to produce IR suggests the need of an independent therapeutic strategy in obese patients with RA.

Plasma fatty acid-binding protein 4 (FABP4) as a novel biomarker to predict gestational diabetes mellitus

AIMS

Fatty acid-binding protein 4 (FABP4) is mainly expressed in adipocytes and macrophages and is demonstrated to be elevated in diabetes patients. The aim of this study was to evaluate the possible role of FABP4 in the diagnosis of GDM and to investigate the relationship between FABP4 and overweight, insulin resistance and inflammatory marker TNF-α.

METHODS

A total of 46 women with GDM and 55 age-matched pregnant women without GDM (non-GDM) were eligible for the study. Demographic and biochemical parameters and fasting venous blood samples of two groups were collected from all cases. Serum concentrations of FABP4 were determined using enzyme-linked immunosorbent assay (ELISA). The predictive value of Serum FABP4 level was evaluated using receiver operating characteristic curve (ROC curve) analysis.

RESULTS

We found that the serum FABP4 levels were significantly higher in GDM compared to the non-GDM group. The area under the ROC curve assay yielded a satisfactory result of 0.94 (95 % confidence interval 0.90-0.98; p < 0.001). The best compromise between 86.96 % specificity and 89.09 % sensitivity was obtained with a cutoff value of 1.96 ng/mL for GDM diagnosis. Moreover, a significant positive correlation was observed between FABP4 and overweight, insulin resistance and TNF-α in pregnant women with GDM.

CONCLUSIONS

These results suggest that serum FABP4 may potentially serve as a novel biomarker for the prediction of GDM.

Circulating Cytokines Predict the Development of Insulin Resistance in a Prospective Finnish Population Cohort

CONTEXT

Metabolic inflammation contributes to the development of insulin resistance (IR), but the roles of different inflammatory and other cytokines in this process remain unclear.

OBJECTIVE

We aimed at analyzing the value of different cytokines in predicting future IR.

DESIGN, SETTING, AND PARTICIPANTS

We measured the serum concentrations of 48 cytokines from a nationwide cohort of 2200 Finns (the Cardiovascular Risk in Young Finns Study), and analyzed their role as independent risk factors for predicting the development of IR 4 years later.

MAIN OUTCOME MEASURES

We used cross-sectional regression analysis adjusted for known IR risk factors (high age, body mass index, systolic blood pressure, triglycerides, smoking, physical inactivity, and low high-density lipoprotein cholesterol), C-reactive protein and 37 cytokines to find the determinants of continuous baseline IR (defined by homeostatic model assessment). A logistic regression model adjusted for the known risk factors, baseline IR, and 37 cytokines was used to predict the future IR.

RESULTS

Several cytokines, often in a sex-dependent manner, remained as independent determinants of current IR. In men, none of the cytokines was an independent predictive risk marker of future IR. In women, in contrast, IL-17 (odds ratio, 1.42 for 1-SD change in ln-transformed IL-17) and IL-18 (odds ratio, 1.37) were independently associated with the future IR. IL-17 levels also independently predicted the development of incident future IR (odds ratio, 1.48).

CONCLUSIONS

The systemic levels of the T helper 1 cell cytokine IL-18 and the T helper 17 cell cytokine IL-17 thus may have value in predicting future insulin sensitivity in women independently of classical IR risk factors.

Association between circulating levels of galanin and pre-pregnancy body mass index in patients with gestational diabetes mellitus

Galanin is an important neuropeptide which induces an increase in obesity and appetite, improving insulin sensitivity and glucose tolerance in experimental animals. Although significantly higher levels of plasma galanin are found in pregnant women with gestational diabetes mellitus (GDM), there is a limited understanding of its precise mechanism underlying this variation. In the present study, concentrations of circulating galanin were determined at baseline in pregnant women with GDM and pregnant women with normal glucose tolerance (NGT). Correlation analyses were performed between galanin and pre-gestational body weight, pre-gestational BMI, and hormone involved in various homeostatic processes. Results showed that plasma galanin level was significantly higher in the patients with GDM than in the NGT subjects (p<0.001). Plasma galanin was positively correlated with pre-gestational body weight (r=0.42, p=0.037), pre-gestational BMI (r=0.643, p=0.001), and fasting blood glucose (r=0.840, p<0.001) in the GDM group. Moreover, a significant negative correlation was shown between galanin and sex hormone binding globulin (SHBG) (r=-0.901, p<0.001) in the GDM group. These data indicate that serum galanin concentration increases markedly in pregnant women with GDM, and this increase seems to be related to the increase of pre-gestational BMI and significantly lower SHBG in patients with GDM. Thus, circulating galanin is affected under conditions of altered pre-gestational BMI with highest levels in GDM patients. The increase of galanin under conditions of GDM may indicate a physiological function to improve glucose tolerance which is often impaired in GDM subjects.

Type 2 diabetes mellitus as a disorder of galanin resistance

The increasing prevalence of type 2 diabetes mellitus with its high morbidity and mortality becomes an important health problem. The multifactorial etiology of type 2 diabetes mellitus is relative to many gene and molecule alterations, and increased insulin resistance. Besides these, however, there are still other predisposing and risk factors accounting for type 2 diabetes mellitus not to be identified and recognized. Emerging evidence indicated that defects in galanin function played a crucial role in development of type 2 diabetes mellitus. Galanin homeostasis is tightly relative to insulin resistance and is regulated by blood glucose. Hyperglycemia, hyperinsulinism, enhanced plasma galanin levels and decreased galanin receptor activities are some of the characters of type 2 diabetes mellitus. The discrepancy between high insulin level and low glucose handling is named as insulin resistance. Similarly, the discrepancy between high galanin level and low glucose handling may be denominated as galanin resistance too. In this review, the characteristic milestones of type 2 diabetes mellitus were condensed as two analogical conceptual models, obesity-hyper-insulin-insulin resistance-type 2 diabetes mellitus and obesity-hyper-galanin-galanin resistance-type 2 diabetes mellitus. Both galanin resistance and insulin resistance are correlative with each other. Conceptualizing the etiology of type 2 diabetes mellitus as a disorder of galanin resistance may inspire a new concept to deepen our knowledge about pathogenesis of type 2 diabetes mellitus, eventually leading to novel preventive and therapeutic interventions for type 2 diabetes mellitus.

Elevated galanin may predict the risk of type 2 diabetes mellitus for development of Alzheimer's disease

Alzheimer's disease is the most common form of dementia among the elderly and is characterized by progressive loss of memory and cognition. Epidemiological and clinical studies demonstrated that type 2 diabetes mellitus is an important risk factor for the development of Alzheimer's disease, i.e., the patients with type 2 diabetes mellitus are frequently companied with Alzheimer's disease symptoms. Despite many studies recently probed into the comorbid state of both diseases, so far the precise mechanism for this association is poorly understood. Emerging evidences suggest that defects in galanin play a central role on type 2 diabetes mellitus and is considered to be a risk factor for Alzheimer's disease development. This review provides a new insight into the multivariate relationship among galanin, type 2 diabetes mellitus and Alzheimer's disease, highlighting the effect of galanin system on the cross-talk between both diseases in human and rodent models. The current data support that activating central GalR2 attenuates insulin resistance and Alzheimer's disease feature in animal models. These may help us better understanding the pathogenesis of both diseases and provide useful hints for the development of novel therapeutic approaches to treat type 2 diabetes mellitus and Alzheimer's disease.

Molecular and immunohistochemical effects of metformin in a rat model of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a serious health issue worldwide. The disease is characterized by insulin resistance (IR), which leads to dyslipidemia and alterations in the expression levels of a number of genes. Metformin is the standard treatment for T2DM; however, the exact mechanism underlying metformin regulation is not fully understood. The aim of the present study was to investigate the effects of metformin on serum lipid profiles and the expression levels of various genes that are associated with IR, as well as the histopathological changes in the liver and pancreas. A T2DM rat model was established by feeding the rats a high-fat diet for 4 weeks, combined with a dose of streptozotocin (35 mg/kg body weight). Following the successful induction of T2DM, metformin was administered orally (400 mg/kg/day) for 4 weeks. The results indicated that metformin improved the symptoms of IR by normalizing the serum lipid profiles in the diabetic rats. Furthermore, metformin upregulated the expression of insulin receptors and genes associated with lipid metabolism, including acyl-CoA oxidase, carnitine palmitoyl transferase-1 and peroxisome proliferator activated receptor-α. In addition, treatment with metformin downregulated the expression levels of fetuin-A and retinol binding protein-4 (RBP-4), while normalizing the expression of perilipin that had been reduced in the T2DM rats. Metformin administration induced regenerative changes in the hepatocyte cytoplasm and parenchyma. In the pancreas, treatment with metformin was shown to induce positive signaling for insulin and the regeneration of pancreatic β cells. In summary, metformin treatment ameliorated a number of the harmful effects associated with T2DM via the modulation of the expression levels of fetuin-A, RBP-4, perilipin and various genes associated with lipid metabolism, resulting in regenerative changes in the liver and pancreatic cells.

Central alarin ameliorated insulin resistance of adipocytes in type 2 diabetic rats

Alarin, a regulatory peptide, belongs to the galanin family and plays the same regulatory roles as galanin in orexigenic activity and energy metabolism. Our previous studies had found that galanin might facilitate insulin sensitivity via activation of its central receptors. To date, little is known about whether central alarin may exert similar effects on insulin sensitivity. In order to investigate this, alarin and its specific antagonist, alarin 6-25Cys, were administered into the cerebral ventricles of type 2 diabetic rats (T2DR) to evaluate the changes in insulin resistance. The results indicated that central treatment with alarin significantly increased the body weight of animals, the 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose uptake, the plasma adiponectin levels, the glucose infusion rates in hyperinsulinemic-euglycemic clamp tests, the vesicle-associated membrane protein 2 as well as glucose transporter 4 (GLUT4 (SLC2A4)) protein and mRNA levels, and the ratios of GLUT4 contents in plasma membranes to total cell membranes in adipocytes, but reduced blood glucose and plasma retinol-binding protein 4 levels. These effects of alarin may be inhibited by pretreatment with alarin 6-25Cys. The above-mentioned results suggest that the central alarin projective system may facilitate insulin sensitivity and glucose uptake via the increase in GLUT4 content and GLUT4 translocation from intracellular pools to plasma membranes in T2DR.

Effect of endogenous galanin on glucose transporter 4 expression in cardiac muscle of type 2 diabetic rats

Although galanin has been shown to increase glucose transporter 4 (GLUT4) expression in skeletal muscle and adipocytes of rats, there is no literature available about the effect of galanin on GLUT4 expression in cardiac muscle of type 2 diabetic rats. In this study, we investigated the relationship between intracerebroventricular administration of M35, a galanin receptor antagonist, and GLUT4 expression in cardiac muscle of type 2 diabetic rats. The rats tested were divided into four groups: rats from healthy and type 2 diabetic drug groups were injected with 2 μM M35 for three weeks, while both control groups with 2 μl vehicle control. The euglycemic-hyperinsulinemic clamp test was conducted for an index of glucose infusion rates. The cardiac muscle was processed for determination of GLUT4 expression levels. The present study showed that the plasma insulin and retinol binding protein 4 (RBP4) levels were higher in both drug groups than controls respectively. Moreover, the results showed the inhibitive effect of central M35 treatment on glucose infusion rates in the euglycemic-hyperinsulinemic clamp test and GLUT4 expression levels in the cardiac muscle. These results demonstrate that endogenous galanin, acting through its central receptor, has an important attribute to increase GLUT4 expression, leading to enhance insulin sensitivity and glucose uptake in cardiac muscle of type 2 diabetic rats. Galanin and its fragment can play a significant role in regulation of glucose metabolic homeostasis in cardiac muscle and galanin is an important hormone relative to diabetic heart.

A stable isotope biomarker of marine food intake captures associations between n-3 fatty acid intake and chronic disease risk in a Yup'ik study population, and detects new associations with blood pressure and adiponectin

The nitrogen isotope ratio (δ(15)N) of RBCs has been proposed as a biomarker of marine food intake in Yup'ik people based on strong associations with RBC eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). However, EPA and DHA derive from marine fats, whereas elevated δ(15)N derives from marine protein, and these dietary components may have different biologic effects. Whether δ(15)N is similarly associated with chronic disease risk factors compared with RBC EPA and DHA is not known. We used covariate-adjusted linear models to describe biomarker associations with chronic disease risk factors in Yup'ik people, first in a smaller (n = 363) cross-sectional study population using RBC EPA, DHA, and δ(15)N, and then in a larger (n = 772) cross-sectional study population using δ(15)N only. In the smaller sample, associations of RBC EPA, DHA, and δ(15)N with obesity and chronic disease risk factors were similar in direction and significance: δ(15)N was positively associated with total, HDL, and LDL cholesterol, apolipoprotein A-I, and insulin-like growth factor binding protein-3 (IGFBP-3), and inversely associated with triglycerides. Based on comparisons between covariate-adjusted β-coefficients, EPA was more strongly associated with circulating lipids and lipoproteins, whereas δ(15)N was more strongly associated with adipokines, the inflammatory marker interleukin-6, and IGFBP-3. In the larger sample there were new findings for this population: δ(15)N was inversely associated with blood pressure and there was a significant association (with inverse linear and positive quadratic terms) with adiponectin. In conclusion, δ(15)N is a valid measure for evaluating associations between EPA and DHA intake and chronic disease risk in Yup'ik people and may be used in larger studies. By measuring δ(15)N, we report beneficial associations of marine food intake with blood pressure and adiponectin, which may contribute to a lower incidence of some chronic diseases in Yup'ik people.

Endogenous galanin as a novel biomarker to predict gestational diabetes mellitus

Although a significantly higher level of plasma galanin was found in patients with gestational diabetes mellitus (GDM) in our previous study, it is unknown whether plasma galanin is biomarker for the prediction of GDM. The present study aims to further evaluate the relationship between endogenous galanin and GDM in pregnant women and to find out the precise mechanism by which galanin plays role in the pathogenesis of GDM. The study registered thirty pregnant women with GDM and thirty pregnant women with normal glucose tolerance (NGT). Demographic and biochemical parameters and fasting venous blood samples of two groups were collected from all cases. Galanin was analyzed by an enzyme-linked immunosorbent assay. Gamma-glutamyl transferase (GGT) was measured by enzymatic methods. The plasma galanin and GGT levels were found higher in GDM compared with NGT (P<0.001). In addition, a significant positive correlation was shown between galanin and fasting glucose (P=0.049), 1-h glucose (P=0.033), body mass index (BMI) (P<0.001) and GGT (P=0.048) in pregnant women with GDM, whereas there was significant positive correlation between galanin and BMI (P=0.030) in NGT group. The plasma galanin and GGT levels are higher in patients with GDM. The plasma galanin levels appear to be related to the changes of blood glucose, BMI and GTT in GDM. The higher level of galanin observed in GDM may represent a adaptation to the rise of glucose, weight, GGT associated with GDM. The higher level of plasma galanin is a novel biomarker for the prediction of GDM.