Leptin cut-off values for determination of metabolic syndrome: third national surveillance of risk factors of non-communicable diseases in Iran (SuRFNCD-2007)

Insulin resistance-related circulating predictive markers in the metabolic syndrome: a systematic review in the Iranian population

Background

Specific biomarkers for metabolic syndrome (MetS) may improve diagnostic specificity for clinical information. One of the main pathophysiological mechanisms of MetS is insulin resistance (IR). This systematic review aimed to summarize IR-related biomarkers that predict MetS and have been investigated in Iranian populations.

Methods

An electronic literature search was done using the PubMed and Scopus databases up to June 2022. The risk of bias was assessed for the selected articles using the instrument suggested by the Joanna Briggs Institute (JBI). This systematic review protocol was registered with PROSPERO (registration number CRD42022372415).

Results

Among the reviewed articles, 46 studies investigated the association between IR biomarkers and MetS in the Iranian population. The selected studies were published between 2009 and 2022, with the majority being conducted on adults and seven on children and adolescents. The adult treatment panel III (ATP III) was the most commonly used criteria to define MetS. At least four studies were conducted for each IR biomarker, with LDL-C being the most frequently evaluated biomarker. Some studies have assessed the diagnostic potency of markers using the area under the curve (AUC) with sensitivity, specificity, and an optimal cut-off value. Among the reported values, lipid ratios and the difference between non-HDL-C and LDL-C levels showed the highest AUCs (≥ 0.80) for predicting MetS.

Conclusions

Considering the findings of the reviewed studies, fasting insulin, HOMA-IR, leptin, HbA1c, and visfatin levels were positively associated with MetS, whereas adiponectin and ghrelin levels were negatively correlated with this syndrome. Among the investigated IR biomarkers, the association between adiponectin levels and components of MetS was well established.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-023-01347-6.

Role of gender in explaining metabolic syndrome risk factors in an Iranian rural population using structural equation modelling

Many factors can lead to an increase in the prevalence of metabolic syndrome (MetS) in different populations. Using an advanced structural equation model (SEM), this study is aimed to determine the most important risk factors of MetS, as a continuous latent variable, using a large number of males and females. We also aimed to evaluate the interrelations among the associated factors involved in the development of MetS. This study used data derived from the Fasa PERSIAN cohort study, a branch of the PERSIAN cohort study, for participants aged 35 to 70 years with 10,138 males and females. SEM was used to evaluate the direct and indirect effects, as well as gender effects of influencing factors. Results from the SEM showed that in females most changes in MetS are described by waist circumference (WC), followed by hypertension (HP) and triglyceride (TG), while in males most changes in MetS are described by WC, followed by TG then fasting blood glucose (FBG). Results from the SEM confirmed the gender effects of social status on MetS, mediated by sleep and controlled by age, BMI, ethnicity and physical activity. This study also shows that the integration of TG and WC within genders could be useful as a screening criterion for MetS in our study population.

Can biomarkers be used to improve diagnosis and prediction of metabolic syndrome in childhood cancer survivors? A systematic review

Childhood cancer survivors (CCS) are at increased risk to develop metabolic syndrome (MetS), diabetes, and cardiovascular disease. Common criteria underestimate adiposity and possibly underdiagnose MetS, particularly after abdominal radiotherapy. A systematic literature review and meta-analysis on the diagnostic and predictive value of nine newer MetS related biomarkers (adiponectin, leptin, uric acid, hsCRP, TNF-alpha, IL-1, IL-6, apolipoprotein B (apoB), and lipoprotein(a) [lp(a)]) in survivors and adult non-cancer survivors was performed by searching PubMed and Embase. Evidence was summarized with GRADE after risk of bias evaluation (QUADAS-2/QUIPS). Eligible studies on promising biomarkers were pooled. We identified 175 general population and five CCS studies. In the general population, valuable predictive biomarkers are uric acid, adiponectin, hsCRP and apoB (high level of evidence), and leptin (moderate level of evidence). Valuable diagnostic biomarkers are hsCRP, adiponectin, uric acid, and leptin (low, low, moderate, and high level of evidence, respectively). Meta-analysis showed OR for hyperuricemia of 2.94 (age-/sex-adjusted), OR per unit uric acid increase of 1.086 (unadjusted), and AUC for hsCRP of 0.71 (unadjusted). Uric acid, adiponectin, hsCRP, leptin, and apoB can be alternative biomarkers in the screening setting for MetS in survivors, to enhance early identification of those at high risk of subsequent complications.

Prevalence of metabolic syndrome in Iran: A meta-analysis of 69 studies

AIMS

Metabolic syndrome increases the risk of chronic diseases including cardiovascular diseases and diabetes. The present study investigated the prevalence of metabolic syndrome in Iran.

MATERIALS AND METHODS

Published articles in English and Persian during 2000-2016 identified using keywords of prevalence, metabolic syndrome, and Iran in the following databases: Web of Science, PubMed, Scopus, Google scholar, SID and Magiran. Random effect model used to calculate the pooled estimates. Heterogeneity of studies assessed using Q statistic, and geographical distribution of metabolic syndrome demonstrated via GIS map. Data were analyzed by STATA-11.

RESULTS

The overall prevalence of metabolic syndrome was 30.4% (95%CI: 28.3-32.6) with no significant heterogeneity by diagnostic criteria. The lowest frequency was reported in Sistan and Baluchestan Province [18.3% (95% CI: 12.9-25.8)] compared to the highest in Bushehr [57.8% (95% CI: 41.8-80.0)]. It was significantly more prevalent in women [(34.8% (95%CI: 31.2-38.8)] compared to men [25.7% (95%CI: 23.4-28.3)] (P = 0.001)]. A significant increasing trend (P = 0.001) was observed in different age groups, as metabolic syndrome increased from 12.1% (95% CI: 9.37-15.6) in 20-29 years-old age group to 51.7% (95%CI: 47.4-56.4) in the over 60 years-old age group.

CONCLUSIONS

Approximately one-third of Iranian adults have metabolic syndrome which varied by regions, age and gender. Then, appropriate intervention based on behavioral patterns of inhabitants and local conditions may help to reduce the burden of disease.

Leptin/Adiponectin ratio as a potential biomarker for metabolic syndrome in patients with schizophrenia

OBJECTIVE

Leptin and adiponectin are adipokines which have opposing roles in the development of insulin resistance and metabolic syndrome (MetS). Leptin/adiponectin ratio (L/A ratio) has been proposed as a good biomarker for MetS in general population. This study aimed to compare the strength of association between MetS and leptin, adiponectin and L/A ratio, as well as to assess their performance to diagnose MetS in patients with schizophrenia.

METHODS

Patients diagnosed with DSM-IV schizophrenia and under clozapine or olanzapine monotherapy for at least six months were recruited. We used the modified ATP III criteria for Asians to evaluate subjects for a diagnosis of MetS.

RESULTS

We recruited 262 study subjects with schizophrenia, and classified them into those with MetS (n = 87) and those without MetS (n = 175). Leptin level was positively correlated with BMI, waist circumference, and insulin level. Adiponectin level was negatively correlated with most metabolic parameters, except glucose level. L/A ratio was positively correlated with most metabolic parameters, except levels of glucose and HDL-C. Significant gender differences existed in leptin levels, adiponectin levels, and L/A ratio. Without and with adjustment of age and gender, binary logistic regression analysis showed that leptin level, adiponectin level, and L/A ratio were significantly associated with MetS. The area under curve (AUC) of L/A ratio and leptin level for MetS was 0.744 (95% CI = 0.685-0.802) and 0.666 (95% CI = 0.601-0.731). The AUC of adiponectin level for the absence of MetS was 0.717 (95% CI = 0.655-0.780). The discriminative strength of L/A ratio for MetS was better in men than in women.

CONCLUSIONS

The present study results suggest that L/A ratio may be a preferential marker of metabolic syndrome in patients with schizophrenia compared to leptin or adiponectin alone.

Irisin and leptin concentrations in relation to obesity, and developing type 2 diabetes: A cross sectional and a prospective case-control study nested in the Normative Aging Study

OBJECTIVE

To investigate the associations between irisin and leptin levels in obesity and insulin resistance in a cross sectional study. To assess the potential role of irisin and leptin as a predictive marker of T2DM using a nested case-control study.

METHODS

Both studies were designed within the longitudinal VA NAS cohort. The cross sectional study involved 111 non obese and 105 obese subjects who were subdivided into two groups based on their fasting glucose tolerance. In the nested 1:3 case-control study, 47 subjects with T2DM and 140 non-diabetic controls were selected. Serum samples collected 3-5 years before the diagnosis of T2DM were analyzed. Irisin and leptin concentrations were measured using a validated ELISA and radioimmunoassay respectively.

RESULTS

In the cross-sectional study, irisin did not differ between groups based on their fasting glucose tolerance. When subjects were grouped based on obesity status, both irisin and leptin concentrations were significantly higher in obese compared to the non-obese group (p=0.03 and <0.001, respectively). Irisin concentrations positively correlated with leptin concentrations (r= 0.392, P < 0.001). In the nested case control study, leptin concentrations were a significant predictor of developing diabetes (p=0.005) in unadjusted models, but not after correcting for BMI, whereas irisin concentrations did not play a role of comparable significance.

CONCLUSIONS

Leptin concentrations are higher in the obese group irrespective of their glucose tolerance. Obese individuals with impaired fasting glucose have higher concentrations of circulating irisin compared to non-obese subjects with normal glucose tolerance. Irisin concentrations do not predict risk of developing diabetes prospectively.

The combined action of omega-3 polyunsaturated fatty acids and grape proanthocyanidins on a rat model of diet-induced metabolic alterations

It has been suggested that food components such as ω-3 polyunsaturated fatty acids (ω-3 PUFAs) and (poly)phenols counteract diet-induced metabolic alterations by common or complementary mechanisms. To examine the effects of a combination of ω-3 PUFAs and (poly)phenols on such alterations, adult Wistar-Kyoto rats were fed an obesogenic high-fat high-sucrose diet supplemented, or not, for 24 weeks with: eicosapentaenoic acid (EPA)/docosahexaenoic acid (DHA) 1 : 1 (16.6 g kg(-1) feed); proanthocyanidin-rich grape seed extract (GSE, 0.8 g kg(-1) feed); or EPA/DHA 1 : 1 + GSE. Body weight, feed intake, and plasma glucose were evaluated every 6 weeks, while adipose tissue weight, insulin, glucagon, ghrelin, leptin, adiponectin, cholesterol, and triglycerides were evaluated at the end of the experiment. ω-3 PUFAs reduced plasma leptin and cholesterol levels, but did not modify diet-induced perigonadal fat or plasma insulin levels; while GSE increased plasma triglyceride levels. The combined action of ω-3 PUFAs and the proanthocyanidins reduced plasma insulin and leptin, as well as partially prevented perigonadal fat accumulation. While separate supplementation with ω-3 PUFAs or grape proanthocyanidins may not counteract all the key metabolic changes induced by a high-energy-dense diet, the combination of both supplements reverts altered insulin, leptin and triglyceride levels to normal.

Prevalence of Metabolic Syndrome and Its Components in the Iranian Adult Population: A Systematic Review and Meta-Analysis

CONTEXT

Metabolic syndrome (MetS) increases the risk of most non-communicable diseases; gathering information about its prevalence can be very effective in formulating preventive strategies for metabolic diseases. There are many different studies about the prevalence of MetS in Iran, but the results and the study populations of these studies are very different; therefore, it is very important to have an overall estimation of its prevalence in Iran.

OBJECTIVES

This study systematically reviewed the findings of all available studies on MetS in the adult Iranian population and estimated the overall prevalence of MetS in this population.

DATA SOURCES

International databases (Scopus, ISI Web of Science, and PubMed) were searched for papers published from January, 2000 to December, 2013 using medical subject headings (MeSH), Emtree, and related keywords (metabolic syndrome, dysmetabolic syndrome, cardiovascular syndrome, and insulin resistance syndrome) combined with the words "prevalence" and "Iran." The Farsi equivalent of these terms and all probable combinations were used to search Persian national databases (IranMedex, Magiran, SID, and Irandoc).

STUDY SELECTION

All population-based studies and national surveys that reported the prevalence of MetS in healthy Iranian adults were included.

DATA EXTRACTION

After quality assessment, data were extracted according to a standard protocol. Because of between-study heterogeneity, data were analyzed by the random effect method.

RESULTS

We recruited the data of 27 local studies and one national study. The overall estimation of MetS prevalence was 36.9% (95% CI: 32.7 - 41.2%) based on the Adult Treatment Panel III (ATP III) criteria, 34.6% (95% CI: 31.7 - 37.6%) according to the International Diabetes Federation (IDF), and 41.5% (95% CI: 29.8 - 53.2%) based on the Joint Interim Societies (JIS) criteria. The prevalence of MetS determined by JIS was significantly higher than those determined by ATP III and IDF. The prevalence of MetS was 15.4% lower in men than in women (27.7% versus 43.1%) based on the ATP III criteria, and it was 11.3% lower in men based on the IDF criteria; however according to the JIS criteria, it was 8.4% more prevalent in men.

CONCLUSIONS

There is a high prevalence of MetS in the Iranian adult population, with large variations based on different measurement criteria. Therefore, prevention and control of MetS should be considered a priority.

Predictive ability of C-reactive protein for early mortality after ischemic stroke: comparison with NIHSS score

We aimed to compare the association of high-sensitivity C-reactive protein (CRP) and National Institutes of Health Stroke Scale (NIHSS) score with mortality risk and to determine the optimal threshold of CRP for prediction of mortality in ischemic-stroke patients. A series of 162 patients with first-ever ischemic-stroke admitted within 24 h after onset of symptoms was enrolled. CRP and NIHSS score were estimated on admission and their predictive abilities for mortality at 7 days were determined by logistic-regression analyses. Receiver-Operating Characteristic (ROC) curves were depicted to identify the optimal cut-off of CRP, using the maximum Youden-index and the shortest-distance methods. Deceased patients had higher levels of CRP and NIHSS on admission (8.87 ± 7.11 vs. 2.20 ± 4.71 mg/l for CRP, and 17.31 ± 6.36 vs. 8.70 ± 4.85 U for NIHSS, respectively, P < 0.01). CRP and NIHSS were correlated with each other (r (2) = 0.39, P < 0.001) and were also independently associated with increased risk of mortality [odds ratios (95 % confidence interval) of 1.16 (1.05-1.28) and 1.20 (1.07-1.35) for CRP and NIHSS, respectively, P < 0.01]. The areas under the ROC curves of CRP and NIHSS for mortality were 0.82 and 0.84, respectively. The CRP value of 2.2 mg/l was identified as the optimal cut-off value for prediction of mortality within 7 days (sensitivity: 0.81, specificity: 0.80). Thus, CRP as an independent predictor of mortality following ischemic-stroke is comparable with NIHSS and the value of 2.2 mg/l yields the optimum sensitivity and specificity for mortality prediction.

The role of leptin in obesity and the potential for leptin replacement therapy

Leptin (from the Greek word "lepto'' meaning "thin") is a 167-amino acid peptide hormone encoded by the obesity (ob) gene and secreted by white adipocytes. Blood leptin concentrations are increased in obese individuals. Leptin is a satiety hormone that provides negative feedback to the hypothalamus, controlling appetite and energy expenditure. Leptin binds to presynaptic GABAergic neurons to produce its effect, raising the distinct possibility that GABAergic axon terminals are the ultimate subcellular site of action for its effects. Released into the circulation, leptin crosses the blood-brain barrier and binds to leptin receptors, influencing the activity of various hypothalamic neurons, as well as encoding orexigenic and anorexigenic neuropeptides. Moreover, leptin affects a wide range of metabolic functions in the peripheral tissue. In this review, we discuss some physiologic functions of leptin, including effects on obesity and some effects of leptin replacement therapy.

Metabolic syndrome in South Asians

South Asia is home to one of the largest population of people with metabolic syndrome (MetS). The prevalence of MetS in South Asians varies according to region, extent of urbanization, lifestyle patterns, and socioeconomic/cultural factors. Recent data show that about one-third of the urban population in large cities in India has the MetS. All classical risk factors comprising the MetS are prevalent in Asian Indians residing in India. The higher risk in this ethnic population necessitated a lowering of the cut-off values of the risk factors to identify and intervene for the MetS to prevent diabetes and cardiovascular disease. Some pharmacological and nonpharmacological interventions are underway in MetS to assess the efficacy in preventing the diabetes and cardiovascular disease in this ethnic population.