Relationship of hyperinsulinaemia, insulin resistance and β-cell dysfunction with incident diabetes and pre-diabetes: the Tehran Lipid and Glucose Study

Therapeutic Potential of Various Intermittent Fasting Regimens in Alleviating Type 2 Diabetes Mellitus and Prediabetes: A Narrative Review

Intermittent fasting has drawn significant interest in the clinical research community due to its potential to address metabolic complications such as obesity and type 2 diabetes mellitus. Various intermittent fasting regimens include alternate-day fasting (24 h of fasting followed by 24 h of eating), time-restricted fasting (fasting for 14 h and eating within a 10 h window), and the 5:2 diet (fasting for two days and eating normally for the other five days). Intermittent fasting is associated with a reduced risk of type 2 diabetes mellitus-related complications and can slow their progression. The increasing global prevalence of type 2 diabetes mellitus highlights the importance of early management. Since prediabetes is a precursor to type 2 diabetes mellitus, understanding its progression is essential. However, the long-term effects of intermittent fasting on prediabetes are not yet well understood. Therefore, this review aims to comprehensively compile existing knowledge on the therapeutic effects of intermittent fasting in managing type 2 diabetes mellitus and prediabetes.

Effect of transgenerational diabetes via maternal lineage in female rats

Aim

To investigate the transgenerational effect of maternal hyperglycemia on oxidative stress markers, lipid profile, glycemia, pancreatic beta (β)-cells, and reproductive outcomes in the F2 adult generation. Additionally, to expand the knowledge on transgenerational diabetes the F3 generation at birth will be evaluated.

Methods

On day 5 of postnatal life female Sprague-Dawley rat newborns (F0 generation) were distributed into two groups: Diabetic (Streptozotocin-STZ, 70 mg/kg body weight, subcutaneous route) and Control rats. Adult female rats from the F0 generation and subsequently the F1 generation were mated to obtain the F2 generation, which was distributed into F2 generation (granddaughters) from control (F2_C) and diabetic (F2_D) rats. Oral Glucose Tolerance Test (OGTT), the area under the curve (AUC), blood biochemical analyses, and pancreatic morphology were analyzed before pregnancy. Reproductive outcomes were performed at the end of pregnancy. At birth, the glycemia and body weight of F3_C and F3_D rats were determined. p < 0.05 was considered significant.

Results

F2_D had higher body weight, triglyceride levels, and percentage of insulin-immunostained cells, contributing to glucose intolerance, and insulin resistance before pregnancy. At day 21 of pregnancy, the F2_D showed increased embryonic losses before and after implantation (84.33 and 83.74 %, respectively). At birth, F3_D presented hyperglycemia, and 16.3 % of newborns were large for pregnancy age (LGA).

Conclusion

Diabetes induction since the neonatal period in the first generation (F0) led to transgenerational (F2 and F3 generations) changes via the maternal lineage of female rats, confirming the relevance of control strictly the glycemia all the time.

Modifiable predictors of type 2 diabetes mellitus and roles of insulin resistance and β-cell function over a 6-year study and 30-year follow-up

PURPOSE

This study aimed to examine the modifiable predictors of T2DM and the roles of insulin resistance (IR) and β-cell function over a 6-year study and 30-year follow-up.

METHODS

A total of 462 non-diabetic participants, 282 with impaired glucose tolerance (IGT), and 180 with normal glucose tolerance (NGT) were enrolled in this analysis. The Matsuda IR index and area under the curve of insulin-to-glucose ratio (AUCI/G-R) were used as IR and β-cell function indices in the analysis.

RESULTS

In all participants, multivariable analysis showed that BMI, glucose status, Matsuda IR index and systolic blood pressure (SBP) at baseline were independently associated with an increased risk of T2DM over 30 years, whereas lifestyle intervention and AUCI/G-R were inversely associated with this risk. The predictive effect of the Matsuda IR index and AUCI/G-R in participants with IGT was consistent with the results of all participants, whereas in those with NGT, only the Matsuda IR index, not the AUCI/G-R, predicted the development of T2DM (HR = 1.42, 95% CI 1.07-1.89 vs HR = 1.09, 95% CI 0.76-1.56). The predictive effect of the Matsuda IR index on T2DM existed even in participants with BMI < 25 (p = 0.049).

CONCLUSION

The modifiable predictors of T2DM in Chinese adults were high BMI, hypertension, mild hyperglycaemia, IR, and β-cell dysfunction. Both IR and β-cell function contributed to the development of T2DM in the long term; however, IR remains the initial and long-standing key risk factor for T2DM.

Are HOMA-IR and HOMA-B good predictors for diabetes and pre-diabetes subtypes?

BACKGROUND

To investigate the association between the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) and Homeostasis Model Assessment of Beta-cell function (HOMA-B) with the incidence of diabetes and pre-diabetes subtypes.

METHODS

A total of 3101 normoglycemic people aged 20-70 years were included in the 6-year follow-up study. Multinomial logistic regression was used to calculate the incidence possibility of isolated Impaired Fasting Glucose (iIFG), isolated Impaired Glucose Tolerance (iIGT), Combined impaired fasting glucose & impaired glucose tolerance (CGI), and Diabetes Mellitus (DM) per standard deviation (SD) increment in HOMA-IR and HOMA-B in the crude and multivariable model.

RESULTS

In the multivariate model, an increase in one SD change in HOMA-IR was associated with a 43, 42, 75, and 92% increased risk of iIFG, iIGT, CGI, and DM, respectively. There was a positive correlation between the increase in HOMA-B and the incidence of iIGT; however, after adjusting the results for metabolic syndrome components, it was inversely correlated with the incidence of iIFG [Odds Ratio = 0.86(0.75-0.99)].

CONCLUSIONS

HOMA-IR is positively correlated with diabetes and pre-diabetes subtypes' incidence, and HOMA-B is inversely correlated with the incidence of iIFG but positively correlated with iIGT incidence. However, none of these alone is a good criterion for predicting diabetes and pre-diabetes.

HOMA-IR as a predictor of Health Outcomes in Patients with Metabolic Risk Factors: A Systematic Review and Meta-analysis

INTRODUCTION

There exists clinical interest in the following question: Is there an association between HOMA-IR and the risk of developing metabolic diseases?

AIMS

Assessing the association between high values of HOMA-IR with the incidence of T2DM, MACE, essential hypertension, dyslipidemia, NASH, and cancer in healthy participants and participants with a component of metabolic syndrome.

METHODS

Databases were searched by an experienced librarian to find eligible studies. Observational cohort studies enrolling healthy adults and adults with metabolic syndrome components that evaluated HOMA as a marker of IR were considered for inclusion. Eligibility assessment, data extraction and risk of bias assessment were performed independently and in duplicate. Baseline characteristics of patients, cutoff values of HOMA-IR to predict metabolic events were extracted independently and in duplicate.

RESULTS

38 studies (215,878 participants) proved eligible. A higher HOMA-IR value had a significant effect on the risk of developing T2DM (HR 1.87; CI 1.40-2.49), presenting non-fatal MACE (HR 1.46; CI 1.08-1.97) and hypertension (HR 1.35; CI 1.15-1.59). No association was found regarding cancer mortality and fatal MACE with higher HOMA-IR values, there was not enough information to carry out a meta-analysis to establish an association between higher values of HOMA with cancer incidence, dyslipidemia, and NASH.

CONCLUSIONS

High values of HOMA were associated with an increased risk of diabetes, hypertension, and non-fatal MACE; yet, not for cardiovascular or cancer mortality. More research is needed to determine the value of the HOMA index in metabolic and cardiovascular outcomes.

PROSPERO REGISTRATION NUMBER

CRD42020187645.

Pancreatic and gut hormones as predictors of new-onset prediabetes after non-necrotising acute pancreatitis: a prospective longitudinal cohort study

OBJECTIVE

Early identification of individuals at high risk for metabolic derangements after an attack of acute pancreatitis (AP) is critical with a view to tertiary preventing of this disease. The aim was to investigate whether fasting pancreatic and gut hormones at baseline were predictive of future risk of new-onset prediabetes after acute pancreatitis (NOPAP) in individuals with non-necrotising AP.

METHODS

This was a prospective longitudinal cohort study that included 69 consecutive non-diabetic participants with AP, of whom 55% (n = 38) had normoglycaemia both at baseline and during follow-up, 25% (n = 17) had prediabetes both at baseline and during follow-up, and 20% (n = 14) were normoglycaemic at baseline but developed NOPAP during follow-up. The associations between the study groups and circulating fasting levels of pancreatic and gut hormones (insulin, glucagon, C-peptide, amylin, glucose-dependent insulinotropic peptide, glucagon-like peptide-1, pancreatic polypeptide, and peptide YY) were studied using multinomial regression in both unadjusted and adjusted analyses.

RESULTS

Elevated plasma insulin and glucagon at baseline were significantly associated with NOPAP (adjusted odds ratio 1.99, 95% CI 1.01 to 3.92 and adjusted odds ratio 3.44, 95% CI 1.06 to 11.19, respectively). The same hormones had no significant association with antecedent prediabetes in AP. The other studied hormones were not significantly associated with the study groups.

CONCLUSIONS

Normoglycaemic AP individuals with elevated fasting levels of insulin and glucagon at baseline constitute a high-risk group for future NOPAP.

Effectiveness of Resistance Training and Associated Program Characteristics in Patients at Risk for Type 2 Diabetes: a Systematic Review and Meta-analysis

BACKGROUND

Resistance training (RT) is an effective intervention for glycemic control and cardiometabolic health in individuals with type 2 diabetes (T2D). However, the use of RT in individuals at risk for T2D to prevent or delay the onset of T2D, and RT program characteristics that are most effective are still unknown. The purpose of this review is to determine the effects of RT on cardiometabolic risk factors in those at risk for T2D and to examine RT program characteristics associated with intervention effectiveness.

METHODS

PubMed, Cochrane, Web of Science, and Embase databases were systematically searched for published controlled trials that compared cardiometabolic outcomes in adults with cardiometabolic risk for those that underwent an RT intervention with those that did not. A systematic review and meta-analysis was conducted to determine the effect of RT on glycosylated hemoglobin (HbA1c), fasting plasma glucose (FPG), body fat percentage (BF%), total cholesterol (TC), high-density lipoprotein (HDL), low-density lipoprotein (LDL), and triglycerides (TG). Additional analyses examined effects of intervention duration and dietary intervention on FPG and TG.

RESULTS

Fourteen trials with 668 participants were included. For RT compared to controls, the standardized mean difference (SMD) was -1.064 for HbA1c (95% confidence interval [CI] -1.802 to -0.327; p=0.005), -0.99 for FPG (95% CI -1.798 to -0.183; p=0.016), -0.933 for TC (95% CI -1.66 to -0.206; p=0.012), -0.840 for BF% (95% CI -1.429 to -0.251; p=0.005), -0.693 for HDL (95% CI -1.230 to -0.156; p=0.011), -1.03 for LDL (95% CI -2.03 to -0.050; p=0.039), and -0.705 for TG (95% CI -1.132 to -0.279; p=0.001).

CONCLUSIONS

RT is beneficial for improving glycemic control, BF%, and blood lipids in those at risk for diabetes. The addition of a dietary component did not result in larger reductions in FPG and TG than RT alone.

PROSPERO REGISTRATION ID

CRD42019122217.

Association Between Aspartate Aminotransferase to Alanine Aminotransferase Ratio and Incidence of Type 2 Diabetes Mellitus in the Japanese Population: A Secondary Analysis of a Retrospective Cohort Study

BACKGROUND

The study on the association between aspartate aminotransferase to alanine aminotransferase (AST/ALT) ratio and the risk of type 2 diabetes mellitus (T2DM) was limited. Therefore, we conducted a secondary analysis based on online data to explore whether there was an association between the AST/ALT ratio and incident T2DM among a large number of Japanese people.

METHODS

The study was a retrospective cohort study. We downloaded the NAGALA (NAfld in Gifu area) data from DATADRYAD website between 2004 and 2015. This present study included 15,291 participants. Cox proportional-hazards regression, generalized additive models and subgroup analyses were used to find out the association between the AST/ALT ratio and T2DM events.

RESULTS

The negative relationship was shown between AST/ALT ratio and incident T2DM (HR = 0.617, 95% CI: 0.405-0.938) in our study. A non-linear relationship and saturation effect were found between them, and the inflection point was 0.882. It indicated that the AST/ALT ratio was negatively correlated with incident T2DM when the AST/ALT ratio was less than the inflection point (HR = 0.287, 95% CI: 0.126-0.655, p = 0.0030). We found that exercise modified their relationship (P for interaction = 0.0024), and people who did not exercise associated strongly (HR = 0.464 95% CI: 0.290-0.741).

CONCLUSION

AST/ALT ratio was negatively associated with T2DM risk, and their relationship was non-linear and had a saturation effect. When the AST/ALT ratio was less than 0.882, they showed a significant negative correlation.

Elucidating the Relationship Between Diabetes Mellitus and Parkinson's Disease Using 18F-FP-(+)-DTBZ, a Positron-Emission Tomography Probe for Vesicular Monoamine Transporter 2

Diabetes mellitus (DM) and Parkinson’s disease (PD) have been and will continue to be two common chronic diseases globally that are difficult to diagnose during the prodromal phase. Current molecular genetics, cell biological, and epidemiological evidences have shown the correlation between PD and DM. PD shares the same pathogenesis pathways and pathological factors with DM. In addition, β-cell reduction, which can cause hyperglycemia, is a striking feature of DM. Recent studies indicated that hyperglycemia is highly relevant to the pathologic changes in PD. However, further correlation between DM and PD remains to be investigated. Intriguingly, polycystic monoamine transporter 2 (VMAT2), which is co-expressed in dopaminergic neurons and β cells, is responsible for taking up dopamine into the presynaptic vesicles and can specifically bind to the β cells. Furthermore, we have summarized the specific molecular and diagnostic functions of VMAT2 for the two diseases reported in this review. Therefore, VMAT2 can be applied as a target probe for positron emission tomography (PET) imaging to detect β-cell and dopamine level changes, which can contribute to the diagnosis of DM and PD during the prodromal phase. Targeting VMAT2 with the molecular probe ¹⁸F-FP-(+)-DTBZ can be an entry point for the β cell mass (BCM) changes in DM at the molecular level, to clarify the potential relationship between DM and PD. VMAT2 has promising clinical significance in investigating the pathogenesis, early diagnosis, and treatment evaluation of the two diseases.

Hypoglycaemic effect of catalpol in a mouse model of high-fat diet-induced prediabetes

Type 2 diabetes mellitus is a major health problem and a societal burden. Individuals with prediabetes are at increased risk of type 2 diabetes mellitus. Catalpol, an iridoid glycoside, has been reported to exert a hypoglycaemic effect in db/db mice, but its effect on the progression of prediabetes is unclear. In this study, we established a mouse model of prediabetes and examined the hypoglycaemic effect, and the mechanism of any such effect, of catalpol. Catalpol (200 mg/(kg·day)) had no effect on glucose tolerance or the serum lipid level in a mouse model of impaired glucose tolerance-stage prediabetes. However, catalpol (200 mg/(kg·day)) increased insulin sensitivity and decreased the fasting glucose level in a mouse model of impaired fasting glucose/impaired glucose tolerance-stage prediabetes. Moreover, catalpol increased the mitochondrial membrane potential (1.52-fold) and adenosine triphosphate content (1.87-fold) in skeletal muscle and improved skeletal muscle function. These effects were mediated by activation of the insulin receptor-1/glucose transporter type 4 (IRS-1/GLUT4) signalling pathway in skeletal muscle. Our findings will facilitate the development of a novel approach to suppressing the progression of diabetes at an early stage. Novelty Catalpol prevents the progression of prediabetes in a mouse model of prediabetes. Catalpol improves insulin sensitivity in skeletal muscle. The effects of catalpol are mediated by activation of the IRS-1/GLUT4 signalling pathway.

Rationale and design of a randomized controlled trial examining oral administration of bisphenol A on hepatic glucose production and skeletal muscle insulin sensitivity in adults

Previous observational studies have shown that the endocrine disrupting chemical bisphenol A (BPA) is associated with type 2 diabetes, but few studies have examined direct effects of BPA on human health. The purpose of this study is to determine whether orally administered BPA at the US Environmental Protection Agency (EPA) safe dose of 50 μg/kg body weight has an adverse effect on hepatic glucose production and skeletal muscle insulin sensitivity. Forty, non-habitually active, healthy adults of normal weight will be enrolled. Participants will begin with a 2-day baseline energy balance diet low in bisphenols in which urine and blood will be collected, and standard tests performed to assess the primary outcome measures of hepatic glucose production (via [6,6-²H] glucose infusion) and skeletal muscle insulin sensitivity (via euglycemic hyperinsulinemic clamp technique). Secondary outcome measures are fasting hormones/endocrine factors (insulin, glucose, C-peptide, Pro-insulin, adiponectin, 17-beta-estradiol, free fatty acids) related to the pathogenesis of type 2 diabetes. Participants will then be randomly assigned to a 4-day energy balance diet plus oral administration of BPA at 50 μg/kg body weight (Diet + BPA) or 4-day energy balance diet plus oral administration of placebo (Diet + No BPA); all outcome measures will be reassessed after 4 days. Findings from this study will provide a framework for other studies in this area, and provide much needed experimental evidence using gold standard measures as to whether oral BPA administration over several days poses any risk of type 2 diabetes.

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Bisphenol A is associated with type 2 diabetes.

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Few studies have examined oral bisphenol A administration on the pathogenesis of type 2 diabetes.

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This study will examine oral bisphenol A administration on hepatic glucose [6,6-²H] suppression.

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This study will examine insulin sensitivity (euglycemic hyperinsulinemic clamp technique).

β-Cell function in obese children and adolescents with metabolic syndrome compared to isolated obesity

OBJECTIVE

To evaluate β-cell function in obese children and adolescents meeting clinical criteria for isolated obesity (iOB), isolated components of dysmetabolism (cMD), or metabolic syndrome (MS), and in obese children and adolescents with normal glucose tolerance (NGT), impaired glucose regulation (IGR), or type 2 diabetes (T2DM).

STUDY DESIGN

We undertook a prospective study of Han Chinese children and adolescents aged 8-16 years (median 11 ± 1.4) seen in an obesity clinic between May 2013 and 2018. Patients were classified as iOB (53), cMD (139), and MS (139) groups based on clinical criteria. The same patients were also classified as NGT (212), IGR (111), or T2DM (8) based on results of an oral glucose tolerance test (OGTT). The MS patients were classified as NGT [MS](59) and IGR [MS](72) for the further study. All participants also completed a mixed-meal tolerance test (MMTT).

RESULTS

Compared with the iOB group, the MS group had significantly higher area under the curve of C-peptide up to the 2 hours (AUC CP) (P = .03) and peak C-peptide (P = .03), adjusted for BMI, age and Tanner stage, on MMTT. However, there was no difference in the insulinogenic index (ΔI30/ΔG30) or oral disposition index (oDI) derived from the OGTT among the three groups. However, 52% of participants with MS had IGR, compared to 28% in the cMD group. Compared with the NGT group, the individuals with IGR had significantly lower ΔI30/ΔG30 (P = .001) and oDI (P < .001). Compared with the iOB group, the NGT[MS] had significantly higher AUC CP (P = .004), peak C-peptide (P = .004) and ΔI30/ΔG30 (P = .007) adjusted for age, but no difference in oDI. Compared with the NGT[MS], the IGR[MS] had significantly lower ΔI30/ΔG30 (P = .005) and oDI (P < .001), but the AUC CP and peak C-peptide had no difference.

CONCLUSION

Although the MS youth have β-cell hyperfunction as a whole, β-cell dysfunction is present in the early stages of dysmetabolism in obese youth with cMD or MS and worsened across the spectrum from iOB to cMD and MS, contributing to development of T2DM.

Body mass index trajectories from adolescent to young adult for incident high blood pressure and high plasma glucose

Objectives

To explore the association between sex-specific adiposity trajectories among Adolescents to early adulthood with incident high blood pressure (HBP) and high plasma glucose (HPG).

Methods

We studied body mass index (BMI) trajectories among1159 (male = 517) and 664 (male = 263) Iranian adolescents, aged 12–20 years, for incident HPG and HBP, respectively. Latent Class Growth Mixture Modeling (LCGMM) on longitudinal data was used to determine sex-specific and distinct BMI trajectories. Logistic regressions were applied to estimate the relationship between latent class membership with HBP and HPG, considering normal trajectory as the reference.

Results

For both HBP and HPG, LCGMM determined two and three distinct BMI trajectories in males and females, respectively. During a follow-up of 12Years 104 (male = 62) and 111(male = 59) cases of HPG and HBP were found, respectively. Among females, faster BMI increases (i.e. overweight to early obese trajectory) but not overweight (i.e. those with BMI = 27.3 kg/m² at baseline) trajectories increased the risk of HPG by adjusted odds ratios (ORs), 2.74 (1.10–5.80) and 0.79 (0.22–2.82), respectively; regarding HBP, the corresponding value for overweight to late obese trajectory was 3.72 (1.37–11.02). Among males, for HBP, the overweight trajectory increased the risk [2.09 (1.04–4.03)]; however, for incident HPG, none of the trajectories showed significant risk.

Conclusions

Among females, trend of increasing BMI parallel with age can be a better predictor for risk of developing HPG and HBP than those with higher BMI at baseline.

Pilot Study on the Effect of Orally Administered Bisphenol A on Glucose and Insulin Response in Nonobese Adults

OBJECTIVE

To determine the effects of varying doses of orally administered BPA on indices of glucose metabolism.

METHODS

Eleven college students (21.0 ± 0.8 years; 24.2 ± 3.9 kg/m2) were randomized in a double-blinded, crossover fashion separated by >1 week to placebo (PL), deuterated BPA at 4 µg/kg body weight (BPA-4), and deuterated BPA at 50 µg/kg body weight (BPA-50). Total BPA, glucose, insulin, and C-peptide were assessed at baseline, minutes 15, 30, 45, 60, and every 30 minutes for 2 hours in response to a glucose tolerance test.

RESULTS

There was a significant condition × time interaction for total BPA (P < 0.001) such that BPA increased more rapidly in BPA-50 than BPA-4 and PL (P = 0.003) and increased more rapidly in BPA-4 than PL (P < 0.001). There were no significant condition × time interactions on glucose, insulin, and C-peptide. Significant condition main effects were observed for glucose such that BPA-50 was significantly lower than PL (P = 0.036) and nearly lower for BPA-4 vs PL (P = 0.056). Significant condition main effects were observed such that insulin in BPA-50 was lower than BPA-4 (P = 0.021), and C-peptide in BPA-50 was lower than BPA-4 (t18 = 3.95; Tukey-adjusted P = 0.003). Glucose, insulin, and C-peptide areas under the curve for the 3-hour profile were significantly lower in BPA-50 vs PL (P < 0.05).

CONCLUSION

Orally administered BPA protocol appeared feasible and has immediate effects on glucose, insulin, and C-peptide concentrations.

Development of type 2 diabetes mellitus in people with intermediate hyperglycaemia

BACKGROUND

Intermediate hyperglycaemia (IH) is characterised by one or more measurements of elevated blood glucose concentrations, such as impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and elevated glycosylated haemoglobin A1c (HbA1c). These levels are higher than normal but below the diagnostic threshold for type 2 diabetes mellitus (T2DM). The reduced threshold of 5.6 mmol/L (100 mg/dL) fasting plasma glucose (FPG) for defining IFG, introduced by the American Diabetes Association (ADA) in 2003, substantially increased the prevalence of IFG. Likewise, the lowering of the HbA1c threshold from 6.0% to 5.7% by the ADA in 2010 could potentially have significant medical, public health and socioeconomic impacts.

OBJECTIVES

To assess the overall prognosis of people with IH for developing T2DM, regression from IH to normoglycaemia and the difference in T2DM incidence in people with IH versus people with normoglycaemia.

SEARCH METHODS

We searched MEDLINE, Embase, ClincialTrials.gov and the International Clinical Trials Registry Platform (ICTRP) Search Portal up to December 2016 and updated the MEDLINE search in February 2018. We used several complementary search methods in addition to a Boolean search based on analytical text mining.

SELECTION CRITERIA

We included prospective cohort studies investigating the development of T2DM in people with IH. We used standard definitions of IH as described by the ADA or World Health Organization (WHO). We excluded intervention trials and studies on cohorts with additional comorbidities at baseline, studies with missing data on the transition from IH to T2DM, and studies where T2DM incidence was evaluated by documents or self-report only.

DATA COLLECTION AND ANALYSIS

One review author extracted study characteristics, and a second author checked the extracted data. We used a tailored version of the Quality In Prognosis Studies (QUIPS) tool for assessing risk of bias. We pooled incidence and incidence rate ratios (IRR) using a random-effects model to account for between-study heterogeneity. To meta-analyse incidence data, we used a method for pooling proportions. For hazard ratios (HR) and odds ratios (OR) of IH versus normoglycaemia, reported with 95% confidence intervals (CI), we obtained standard errors from these CIs and performed random-effects meta-analyses using the generic inverse-variance method. We used multivariable HRs and the model with the greatest number of covariates. We evaluated the certainty of the evidence with an adapted version of the GRADE framework.

MAIN RESULTS

We included 103 prospective cohort studies. The studies mainly defined IH by IFG5.6 (FPG mmol/L 5.6 to 6.9 mmol/L or 100 mg/dL to 125 mg/dL), IFG6.1 (FPG 6.1 mmol/L to 6.9 mmol/L or 110 mg/dL to 125 mg/dL), IGT (plasma glucose 7.8 mmol/L to 11.1 mmol/L or 140 mg/dL to 199 mg/dL two hours after a 75 g glucose load on the oral glucose tolerance test, combined IFG and IGT (IFG/IGT), and elevated HbA1c (HbA1c5.7: HbA1c 5.7% to 6.4% or 39 mmol/mol to 46 mmol/mol; HbA1c6.0: HbA1c 6.0% to 6.4% or 42 mmol/mol to 46 mmol/mol). The follow-up period ranged from 1 to 24 years. Ninety-three studies evaluated the overall prognosis of people with IH measured by cumulative T2DM incidence, and 52 studies evaluated glycaemic status as a prognostic factor for T2DM by comparing a cohort with IH to a cohort with normoglycaemia. Participants were of Australian, European or North American origin in 41 studies; Latin American in 7; Asian or Middle Eastern in 50; and Islanders or American Indians in 5. Six studies included children and/or adolescents.Cumulative incidence of T2DM associated with IFG5.6, IFG6.1, IGT and the combination of IFG/IGT increased with length of follow-up. Cumulative incidence was highest with IFG/IGT, followed by IGT, IFG6.1 and IFG5.6. Limited data showed a higher T2DM incidence associated with HbA1c6.0 compared to HbA1c5.7. We rated the evidence for overall prognosis as of moderate certainty because of imprecision (wide CIs in most studies). In the 47 studies reporting restitution of normoglycaemia, regression ranged from 33% to 59% within one to five years follow-up, and from 17% to 42% for 6 to 11 years of follow-up (moderate-certainty evidence).Studies evaluating the prognostic effect of IH versus normoglycaemia reported different effect measures (HRs, IRRs and ORs). Overall, the effect measures all indicated an elevated risk of T2DM at 1 to 24 years of follow-up. Taking into account the long-term follow-up of cohort studies, estimation of HRs for time-dependent events like T2DM incidence appeared most reliable. The pooled HR and the number of studies and participants for different IH definitions as compared to normoglycaemia were: IFG5.6: HR 4.32 (95% CI 2.61 to 7.12), 8 studies, 9017 participants; IFG6.1: HR 5.47 (95% CI 3.50 to 8.54), 9 studies, 2818 participants; IGT: HR 3.61 (95% CI 2.31 to 5.64), 5 studies, 4010 participants; IFG and IGT: HR 6.90 (95% CI 4.15 to 11.45), 5 studies, 1038 participants; HbA1c5.7: HR 5.55 (95% CI 2.77 to 11.12), 4 studies, 5223 participants; HbA1c6.0: HR 10.10 (95% CI 3.59 to 28.43), 6 studies, 4532 participants. In subgroup analyses, there was no clear pattern of differences between geographic regions. We downgraded the evidence for the prognostic effect of IH versus normoglycaemia to low-certainty evidence due to study limitations because many studies did not adequately adjust for confounders. Imprecision and inconsistency required further downgrading due to wide 95% CIs and wide 95% prediction intervals (sometimes ranging from negative to positive prognostic factor to outcome associations), respectively.This evidence is up to date as of 26 February 2018.

AUTHORS' CONCLUSIONS

Overall prognosis of people with IH worsened over time. T2DM cumulative incidence generally increased over the course of follow-up but varied with IH definition. Regression from IH to normoglycaemia decreased over time but was observed even after 11 years of follow-up. The risk of developing T2DM when comparing IH with normoglycaemia at baseline varied by IH definition. Taking into consideration the uncertainty of the available evidence, as well as the fluctuating stages of normoglycaemia, IH and T2DM, which may transition from one stage to another in both directions even after years of follow-up, practitioners should be careful about the potential implications of any active intervention for people 'diagnosed' with IH.

Diabetes Mellitus: Findings from 20 Years of the Tehran Lipid and Glucose Study

CONTEXT

We summarized findings from Tehran lipid and glucose study (TLGS) about different aspects of type 2 diabetes (T2D) over the span of nearly 2 decades.

EVIDENCE ACQUISITION

A review was undertaken to retrieve papers related to all aspects of T2D from the earliest date available up to January 30, 2018.

RESULTS

An annual crude incidence rate of 10 per 1000 person-years of follow-up was found for T2D in adult participants. Overall incidence rate of pre-diabetes/T2D was 36.3 per 1000 person-years or about 1% each year among youth. Diabetes was associated with increased risk of CVD [hazard ratio (HR): 1.86, 95% confidence interval (95% CI): 1.57 - 2.27] and mortality [HR: 2.56; 95% CI: 2.08 - 3.16] in the total population. Compared with non-diabetic men and women, their diabetic counterparts survived 1.4 and 0.7 years shorter, respectively, during 15 years of follow-up. Wrist circumference, hyperinsulinaemia, 25-hydroxy vitamin D and increase in alanin aminotranferase provided incremental prognostic information beyond the traditional risk factors for incident T2D in adults. Using decision tree algorithms, a number of high risk groups were found for incident T2D. A probability of 84% was found for incidence of T2D among a group of men with fasting plasma glucose (FPG) > 5.3 mmol/L and waist to height ratio (WHtR) > 0.56, and women with FPG > 5.2 mmol/L and WHtR > 0.56.

CONCLUSIONS

Original TLGS studies have contributed greatly to clarify important evidence regarding the epidemiology and risk factors for T2D among Iranian population.

Is incident type 2 diabetes associated with cumulative excess weight and abdominal adiposity? Tehran Lipid and Glucose Study

AIMS

To examine the association of the risk of incident type 2 diabetes (T2D) with cumulative excess weight (CEW) and cumulative excess waist circumference (CEWC) scores.

METHODS

Adults participants without T2D (n = 4635) aged  ≥20 years were included in the study. The differences between the body mass index (BMI) and waist circumference (WC) values and their normal references were calculated until the incident T2D. The CEW and CEWC scores represent the accumulation of BMI and WC deviations from normal values over time, i.e. (kg/m² × years and cm × years, respectively). Time-dependent Cox models, adjusting for confounders were used to examine the association between CEW/CEWC and the risk of T2D. Further multivariate analyses were performed to examine the association of CEW and CEWC with incident diabetes in baseline BMI and WC strata.

RESULTS

There were 503 incident cases of T2D over a median follow-up 9.38 years. The multivariate sex adjusted hazard ratios (HR) per one standard deviation (SD) increase in CEW and CEWC were 1.23 (95% CI: 1.15-1.32) and 1.41 (1.25-1.59), respectively. After further adjustment for baseline BMI and WC, no significant association was observed for CEW (1.02: 0.84-1.23) and CEWC (1.09: 0.93-1.28) and incident T2D. A strong association was found between CEW and CEWC with incident diabetes among overweight (2.12: 1.20-3.74) and centrally obese individuals (1.29: 1.10-1.51), respectively.

CONCLUSIONS

Generally, CEW and CEWC were not associated with risk of T2D, independent of baseline values for BMI and WC, respectively. Moreover, CEW and CEWC highlighted an increased risk among overweight and centrally obese participants for T2D.

Menarcheal Age and Risk of Type 2 Diabetes: A Community-Based Cohort Study

OBJECTIVE

It has been reported that early menarche is associated with higher risk for type 2 diabetes. We aimed to explore the association between age at menarche and risk of type 2 diabetes in a population-based cohort study.

METHODS

For the purpose of the present study, 5191 subjects of reproductive age who were participants of the Tehran Lipid and Glucose Study and also met the eligibility criteria were selected. Demographic, lifestyle, reproductive, and anthropometric data as well as risk factors for metabolic diseases were collected. Menarcheal age was categorized into five categories, as <11 years, 11-12 years, 13-14 years, 15-16 years, and >17 years. Diabetes and pre-diabetes were defined according to the American Diabetes Association criteria. Logistic regression analysis was used to assess the risk of the menarcheal age group for type 2 diabetes and pre-diabetes.

RESULTS

Of 5625 participants, 673 women had pre-diabetes and 187 had diabetes. Early menarche was associated with higher risk of diabetes and pre-diabetes, compared to the reference group (13-14 years), (OR=3.55, 95% CI: 1.6-7.8 and OR=2.55, 95% CI:1.4-4.8, respectively), an association which remained after further adjustment for potential confounders including family history of diabetes, parity, education, age, body mass index, waist circumference, smoking history, physical activity, and duration of oral contraceptives use.

CONCLUSION

Results showed early menarche to be a potential risk factor for type 2 diabetes and pre-diabetes.

Sex-specific incidence rates and risk factors of insulin resistance and β-cell dysfunction: a decade follow-up in a Middle Eastern population

AIMS

To examine the incidence of and risk factors for insulin resistance and β-cell dysfunction in a representative Iranian population over a median follow-up of 9.2 years.

METHODS

In total, 3662 people (1528 men) without known diabetes with a baseline homeostasis model assessment of insulin resistance (HOMA-IR) level < 75th percentile and, when β-cell dysfunction was the outcome of interest, 3664 people (1530 men) with a homeostasis model assessment of β-cell function (HOMA-β) level ≥ 25th percentile were included in the study (HOMA-IR < 2.20 and HOMA-β ≥ 64.3 among men, and HOMA-IR < 2.39 and HOMA-β ≥ 81.7 among women).

RESULTS

The incidence rates of insulin resistance and β-cell dysfunction were 56.3 and 33.6/1000 person-years among men and 48.6 and 50.3/1000 person-years among women, respectively. Applying multivariable Cox regression in both sexes, fasting insulin, triglyceride/HDL cholesterol ratio and lower education were positive predictors of insulin resistance, whereas age was a negative predictor. Moreover, fasting plasma glucose, waist-to-height ratio, wrist circumference and lower hip circumference were significantly associated with incident insulin resistance only among women (all P < 0.05). Considering β-cell dysfunction in both sexes, age and fasting plasma glucose increased the risk, whereas 2-h post-challenge plasma glucose was a positive predictor only among men, and waist-to-height ratio and triglyceride/HDL cholesterol ratio were negative predictors only among women (all P < 0.05).

CONCLUSIONS

Modifiable risk factors are related to the incidence of insulin resistance and β-cell dysfunction, which can be prevented with proper strategies although the difference between men and women should be taken into account.

A Review on Glycosylated Hemoglobin in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is one of the most common reproductive endocrine disorders among women of reproductive age, with a variety of complications and consequences mostly due to hyperandrogenism and insulin resistance (IR). PCOS patients with IR are at risk for metabolic syndrome and diabetes mellitus (DM) along with its complications such as cardiovascular events. There are several methods for screening IR in patients with PCOS to predict DM and other complications. Fasting plasma glucose test, oral glucose tolerance test, and insulin and glycosylated hemoglobin (HbA1c) levels are some available screening tools for IR. The American Diabetes Association recommended HbA1c to screen for DM because HbA1c is not affected by day-to-day plasma glucose levels and reflects the plasma glucose status during 2-3 months before measurement. Some studies have evaluated the role of HbA1c as a screening method to predict DM in PCOS patients, however, there are still controversies in this matter. Also some studies reported that HbA1c has a correlation with complications of PCOS such as metabolic syndrome and cardiovascular events. We found that HbA1c could be a suitable screening test for IR in PCOS patients but more studies are recommended, omitting confounding factors that could affect IR in patients with PCOS, such as antihyperglycemic agents like metformin, or lifestyle modification, which can be effective in reducing IR in patients with PCOS.

Relationship between elevated triglyceride levels with the increase of HOMA-IR and HOMA-β in healthy children and adolescents with normal weight

To test the hypothesis that mildly elevated triglyceride levels are associated with the increase of homeostasis model assessment of insulin resistance (HOMA-IR) and β-cell function (HOMA-β) indices in healthy children and adolescents with normal weight, we conducted a cross-sectional population study. Based on fasting triglyceride levels, participants were allocated into groups with and without triglyceride levels ≥1.2 mmol/L. Normal weight was defined by body mass index between the 15th and 85th percentiles, for age and gender. Insulin resistance and insulin secretion were estimated using HOMA-IR and HOMA-β indices. A total of 1660 children and adolescents were enrolled, of them 327 (19.7%) with mildly elevated triglycerides. The multivariate linear regression analysis showed that mildly elevated triglyceride levels in children were associated with HOMA-IR (β = 0.214, p < 0.001), HOMA-β (β = 0.139, p = 0.001), systolic (β = 0.094, p = 0.01), and diastolic blood pressure (β = 0.102, p = 0.007), whereas in adolescents, HOMA-IR (β = 0.267, p < 0.001) and HOMA-β (β = 0.154, p < 0.001), but not systolic (β = 0.029, p = 0.38) and diastolic blood pressure (β = 0.015, p = 0.642), showed association with mildly elevated triglycerides.

CONCLUSION

Mildly elevated triglyceride levels are associated with increased HOMA-IR and HOMA-β indices in healthy children and adolescents with normal weight.