Insulin Secretory Capacity and Insulin Resistance in Korean Type 2 Diabetes Mellitus Patients

Insulin Resistance, Non-Alcoholic Fatty Liver Disease and Type 2 Diabetes Mellitus: Clinical and Experimental Perspective

It has been generally accepted that insulin resistance (IR) and reduced insulin secretory capacity are the basic pathogenesis of type 2 diabetes mellitus (T2DM). In addition to genetic factors, the persistence of systemic inflammation caused by obesity and the associated threat of lipotoxicity increase the risk of T2DM. In particular, the main cause of IR is obesity and subjects with T2DM have a higher body mass index (BMI) than normal subjects according to recent studies. The prevalence of T2DM with IR has increased with increasing BMI during the past three decades. According to recent studies, homeostatic model assessment of IR was increased compared to that of the 1990s. Rising prevalence of obesity in Korea have contributed to the development of IR, non-alcoholic fatty liver disease and T2DM and cutting this vicious cycle is important. My colleagues and I have investigated this pathogenic mechanism on this theme through clinical and experimental studies over 20 years and herein, I would like to summarize some of our studies with deep gratitude for receiving the prestigious 2023 Sulwon Award.

Triglyceride-Glucose Index Cutoff Point Is an Accurate Marker for Predicting the Prevalence of Metabolic Syndrome in Obese Caucasian Subjects

BACKGROUND

Recently, the triglyceride-glucose (TyG) index has been suggested as a surrogate insulin resistance marker. This index could act as an early screening marker in individuals with a high risk of metabolic syndrome (MS) such as obese subjects.

AIMS

The objective of this work was to detect the cutoff point of the TyG index for the diagnosis of MS according to ATPIII criteria on obese subjects and to compare with HOMA-IR.

METHODS

We conducted a cross-sectional study in 1,494 obese subjects. Measurements of adiposity parameters, blood pressure, fasting blood glucose, insulin concentration, insulin resistance (HOMA-IR), lipid profile, C-reactive protein, adipokines, and the prevalence of MS were determined. The TyG index was calculated from the next equation: Ln (fasting triglycerides (mg/dL) × fasting glucose (mg/dL))/2.

RESULTS

A total of 1,494 subjects were recruited, 421 males (28.1%) and 1,073 females (71.8%), with an average age of 45.8 ± 15.3 years (range: 29-62). A total of 677 subjects had MS (45.5%) and 817 did not show MS (54.6%). The averages of HOMA-IR and TyG index values increased as the components of MS were aggregated, and both indexes were higher in subjects with MS. The area under the curve (AUC) of the TyG index according to ATPIII criteria showed values of 0.746 (0.721-0.771; p = 0.001). The cutoff point according to the Youden index was 4.72, with sensitivity and specificity of 87% and 88.2%, respectively. For the HOMA-IR, AUC showed values of 0.682 (0.654-0.710; p = 0.01). The cutoff point was 3.23, with sensitivity and specificity of 78% and 70.1%, respectively.

CONCLUSIONS

The TyG index is more powerful for predicting MS than HOMA-IR in Caucasian obese subjects.

A double-blind, Randomized controlled trial on glucose-lowering EFfects and safety of adding 0.25 or 0.5 mg lobeglitazone in type 2 diabetes patients with INadequate control on metformin and dipeptidyl peptidase-4 inhibitor therapy: REFIND study

AIMS

To compare the efficacy and safety of adding low-dose lobeglitazone (0.25 mg/day) or standard-dose lobeglitazone (0.5 mg/day) to patients with type 2 diabetes mellitus (T2DM) with inadequate glucose control on metformin and dipeptidyl peptidase (DPP4) inhibitor therapy.

MATERIALS AND METHODS

In this phase 4, multicentre, double-blind, randomized controlled, non-inferiority trial, patients with T2DM insufficiently controlled by metformin and DPP4 inhibitor combination therapy were randomized to receive either low-dose or standard-dose lobeglitazone. The primary endpoint was non-inferiority of low-dose lobeglitazone in terms of glycaemic control, expressed as the difference in mean glycated haemoglobin levels at week 24 relative to baseline values and compared with standard-dose lobeglitazone, using 0.5% non-inferiority margin.

RESULTS

At week 24, the mean glycated haemoglobin levels were 6.87 ± 0.54% and 6.68 ± 0.46% in low-dose and standard-dose lobeglitazone groups, respectively (p = .031). The between-group difference was 0.18% (95% confidence interval 0.017-0.345), showing non-inferiority of the low-dose lobeglitazone. Mean body weight changes were significantly greater in the standard-dose group (1.36 ± 2.23 kg) than in the low-dose group (0.50 ± 1.85 kg) at week 24. The changes in HOMA-IR, lipid profile and liver enzyme levels showed no significant difference between the groups. Overall treatment-emergent adverse events (including weight gain, oedema and hypoglycaemia) occurred more frequently in the standard-dose group.

CONCLUSIONS

Adding low-dose lobeglitazone to metformin and DPP4 inhibitor combination resulted in a non-inferior glucose-lowering outcome and fewer adverse events compared with standard-dose lobeglitazone. Therefore, low-dose lobeglitazone might be one option for individualized strategy in patients with T2DM.

The triglyceride-glucose index is a more powerful surrogate marker for predicting the prevalence and incidence of type 2 diabetes mellitus than the homeostatic model assessment of insulin resistance

AIMS

Insulin resistance is an independent risk factor for developing type 2 diabetes. Therefore, this study compared the predictability of the triglyceride-glucose (TyG) index and the homeostatic model assessment of insulin resistance (HOMA-IR) for the prevalence and incidence of type 2 diabetes.

METHODS

We analyzed data from 9730 adults aged 40-69 years at baseline and 7783 participants without diabetes who were followed up in the Korean Genome and Epidemiology Study survey. From 2001 to 2002 (baseline survey) to 2013-2014, this survey was conducted biennially (six follow-ups). The average follow-up period was 9.0 years.

RESULTS

The TyG index showed better predictability for the prevalence of type 2 diabetes than HOMA-IR (TyG index: 0.784, HOMA-IR: 0.728, p < 0.001). The area under the time-dependent receiver operating characteristic curve of the TyG index for incident type 2 diabetes was 0.640 (0.628-0.652), which was significantly higher than that of HOMA-IR [0.531 (0.521-0.541)] (p < 0.001).

CONCLUSIONS

The TyG index is superior to HOMA-IR for predicting type 2 diabetes. The TyG index could, therefore, be more useful for the early detection and prevention of type 2 diabetes.

Glucose-lowering action through targeting islet dysfunction in type 2 diabetes: Focus on dipeptidyl peptidase-4 inhibition

Dipeptidyl peptidase-4 (DPP-4) inhibition is a glucose-lowering medication for type 2 diabetes. It works through stimulation of insulin secretion and inhibition of glucagon secretion in a glucose-dependent manner, resulting in lowered fasting and postprandial glycemia with low risk of hypoglycemia. As impaired insulin secretion and augmented glucagon secretion are key factors underlying hyperglycemia in type 2 diabetes, DPP-4 inhibition represents a therapy that targets the underlying mechanisms of the disease. If insufficient in monotherapy, it can preferably be used in combination with metformin, which targets insulin resistance, and also in combination with sodium-glucose cotransporter 2 inhibition, thiazolidinediones and insulin, which target other mechanisms. In individuals of East Asian origin, islet dysfunction is of particular importance for the development of type 2 diabetes. Consequently, it has been shown in several studies that DPP-4 is efficient in these populations. This mini-review highlights the islet mechanisms of DPP-4 inhibition, islet dysfunction as a key factor for hyperglycemia in type 2 diabetes and that, consequently, DPP-4 is of particular value in populations where islet dysfunction is central, such as in individuals of East Asian origin.

Waist circumference, body mass index, and colorectal cancer risk according to diabetes status: A Korean nationwide population-based cohort study

BACKGROUND AND AIM

We investigated the relationship of BMI and waist circumference with the risk of colorectal cancer (CRC) using a population-based cohort database and to explore the relationship of CRC with diabetes status.

METHODS

Retrospective data (age >20 years) on anthropometric variables, blood parameters of fasting sugar, lipid levels, and blood pressure were collected from the National Health Insurance Corporation database between 2009 and 2012. Cox regression models were used to estimate hazard ratio (HR) and corresponding 95% confidence intervals (95% CI).

RESULTS

Of the 23 121 360 people studied, 120 579 were diagnosed with CRC after a median follow-up period of 5.4 years. Both waist circumference and body mass index were positively associated with increased risk of CRC, regardless of age or sex. After mutual adjustment, only waist circumference was significantly associated with increased risk of CRC (HR = 1.275, 95% CI: 1.205-1.349). When the risk of CRC was compared according to diabetes status among people with the same waist circumference range, risk of CRC was higher for those with worse diabetes status.

CONCLUSION

When waist circumference and body mass index were mutually adjusted, only waist circumference was associated with CRC risk. In addition, the risk of CRC is gradually higher in those with worsening diabetes, even if their waist circumferences are within the same range.

Effect of roux-en Y gastric bypass surgery on patients with type 2 diabetes mellitus: A protocol of systematic review and meta-analysis

BACKGROUND

Previous studies have reported that roux-en Y gastric bypass surgery (RYGBS) can benefit patients with type 2 diabetes mellitus (T2DM). However, their conclusions are still inconsistent. Thus, this study will aim to assess the effect of RYGBS for patients with T2DM.

METHODS

In this study, the electronic databases of MEDLINE, EMBASE, CENTRAL, CINAHL, AMED, and CNKI from inceptions to the present without any limitations to language and publication status. All randomized controlled trials on assessing the effect of RYGBS for patients with T2DM will be included in this study. Two independent authors will carry out study search and selection according to the previous designed inclusion and exclusion criteria. At the same time, 2 authors will independently evaluate the risk of bias assessment by Cochrane risk of bias tool. Any disagreements between 2 authors will be solved by a third author through discussion. RevMan 5.3 software will be utilized for statistical analysis.

RESULTS

This study will summarize the most recent studies and will provide a deeper understanding about using the effect of RYGBS for patients with T2DM.

CONCLUSIONS

The findings of this study will present the existing evidence for the effect of RYGBS for patients with T2DM.

SYSTEMATIC REVIEW REGISTRATION

INPLASY202040127.

Efficacy and Safety of Pioglitazone versus Glimepiride after Metformin and Alogliptin Combination Therapy: A Randomized, Open-Label, Multicenter, Parallel-Controlled Study

BACKGROUND

There is limited information regarding the optimal third-line therapy for managing type 2 diabetes mellitus (T2DM) that is inadequately controlled using dual combination therapy. This study assessed the efficacy and safety of pioglitazone or glimepiride when added to metformin plus alogliptin treatment for T2DM.

METHODS

This multicenter, randomized, active-controlled trial (ClinicalTrials.gov: NCT02426294) recruited 135 Korean patients with T2DM that was inadequately controlled using metformin plus alogliptin. The patients were then randomized to also receive pioglitazone (15 mg/day) or glimepiride (2 mg/day) for a 26-week period, with dose titration was permitted based on the investigator's judgement.

RESULTS

Glycosylated hemoglobin levels exhibited similar significant decreases in both groups during the treatment period (pioglitazone: -0.81%, P<0.001; glimepiride: -1.05%, P<0.001). However, the pioglitazone-treated group exhibited significantly higher high density lipoprotein cholesterol levels (P<0.001) and significantly lower homeostatic model assessment of insulin resistance values (P<0.001). Relative to pioglitazone, adding glimepiride to metformin plus alogliptin markedly increased the risk of hypoglycemia (pioglitazone: 1/69 cases [1.45%], glimepiride: 14/66 cases [21.21%]; P<0.001).

CONCLUSION

Among patients with T2DM inadequately controlled using metformin plus alogliptin, the addition of pioglitazone provided comparable glycemic control and various benefits (improvements in lipid profiles, insulin resistance, and hypoglycemia risk) relative to the addition of glimepiride.

High genetic risk scores of SLIT3, PLEKHA5 and PPP2R2C variants increased insulin resistance and interacted with coffee and caffeine consumption in middle-aged adults

BACKGROUNDS AND AIMS

Insulin resistance is a common feature of metabolic syndrome that may be influenced by genetic risk factors. We hypothesized that genetic risk scores (GRS) of SNPs that influence insulin resistance and signaling interact with lifestyles to modulate insulin resistance in Korean adults.

METHODS AND RESULTS

Genome-wide association studies (GWAS) of subjects aged 40-65 years who participated in the Ansung/Ansan cohorts (8842 adults) in Korea revealed 52 genetic variants that influence insulin resistance. The best gene-gene interaction model was explored using the generalized multifactor dimensionality reduction (GMDR) method. GRS from the best model were calculated and the GRS were divided into low, medium and high groups. The best model for representing insulin resistance included SLIT3_rs2974430, PLEKHA5_rs1077044, and PPP2R2C_rs16838853. The odds ratios for insulin resistance were increased by 150% in the High-GRS group compared to the Low-GRS group. However, ORs for insulin secretion capacity, measured by HOMA-B, were not associated with GRS. Coffee and caffeine intake and GRS had an interaction with insulin resistance: In subjects with high coffee (≥10 cups/week) or caffeine intake (≥220 mg caffeine/day), insulin resistance was significantly elevated in the High-GRS group, but not in the Low-GRS. However, alcohol intake, smoking and physical activity did not have an interaction with GRS. Insulin secretion capacity was not significantly influenced by GRS when evaluating the adjusted odds ratios.

CONCLUSIONS

Subjects with High-GRS may be susceptible to increased insulin resistance by 50% and its risk may be exacerbated by consuming more than 10 cups coffee/week or 220 mg caffeine/day.

Efficacy and tolerability of novel triple combination therapy in drug-naïve patients with type 2 diabetes from the TRIPLE-AXEL trial: protocol for an open-label randomised controlled trial

INTRODUCTION

Patients with type 2 diabetes are at risk of microvascular and macrovascular complications. Intensive glycaemic control, especially in patients with short duration of diabetes, is the mainstay of management of type 2 diabetes to lower the risk of complications. However, despite the improvement in the understanding of the pathophysiology of type 2 diabetes and development of novel glucose-lowering agents, long-term durable glycaemic control remains a difficult goal to achieve. Several challenging clinical trials proved that an early combination therapy with a variety of glucose-lowering agents had a more favourable effect than conventional stepwise therapy in terms of glycaemic control. We aim to evaluate the efficacy and tolerability of a novel, initial triple combination therapy with metformin, sodium glucose cotransporter 2 inhibitor (dapagliflozin) and dipeptidyl peptidase-4 inhibitor (saxagliptin) compared with conventional stepwise add-on therapy in drug-naïve patients with recent-onset type 2 diabetes.

METHODS AND ANALYSIS

This study is a multicentre, prospective, randomised, open-label, parallel group, comparator-controlled trial. A total of 104 eligible participants will be randomised to either the initial combination therapy group or the conventional stepwise add-on therapy group for 104 weeks. The primary endpoint is the proportion of patients who achieved haemoglobin A1c level<6.5% without hypoglycaemia, weight gain or discontinuation due to adverse events at 104 weeks. This trial will determine whether a novel triple combination therapy with metformin, dapagliflozin and saxagliptin has a beneficial effect on durable glycaemic control compared with conventional therapy in drug-naïve patients with type 2 diabetes.

ETHICS AND DISSEMINATION

This study protocol was approved by the local institutional review boards and independent ethics committees over the recruitment sites. Results of this study will be disseminated in scientific journals and scientific conferences.

TRIAL REGISTRATION NUMBER

NCT02946632; Pre-results.

Failure of monotherapy in clinical practice in patients with type 2 diabetes: The Korean National Diabetes Program

AIMS/INTRODUCTION

We investigated the failure of monotherapy in patients with type 2 diabetes mellitus in real practice settings.

MATERIALS AND METHODS

The Korean National Diabetes Program was a prospective, multicenter observational cohort study of type 2 diabetes mellitus patients in Korea. Of the 3,950 patients enrolled in the study, we studied 998 who were continuously maintained on monotherapy for at least 90 days at six participating centers. To balance the baseline characteristics of patients in each group, we used propensity matching at a 1:1 ratio (metformin vs sulfonylureas) and 4:1 ratio (metformin vs meglitinides and metformin vs alpha-glucosidase inhibitors [aGIs]). The hazard ratios (HRs) of treatments (compared with metformin) were determined by Cox's proportional hazards regression modeling.

RESULTS

The median follow-up time was 56 months, and monotherapy failed in 45% of all patients. The annual incidences of failure were 15.6%, 21.3%, 27% and 9.6% in the metformin, sulfonylurea, meglitinide and aGI groups. Compared with metformin, sulfonylureas and meglitinides were associated with higher risks of monotherapy failure (HR 1.39, 95% confidence interval [CI] 1.08-1.80; HR 1.92, 95% CI 1.13-3.27), and aGIs with risks similar to that of metformin (HR 0.80, 95% CI 0.44-1.45). When analyzed by failure type, sulfonylureas, meglitinides and aGIs were associated with a higher risk of a switch to other agents (HR 4.43, 95% CI 2.14-9.17; HR 18.80, 95% CI 6.21-56.93; HR 4.25, 95% CI 1.49-12.13), and aGIs with a lower risk of prescription of add-on second agents (HR 0.16, 95% CI 0.04-0.64).

CONCLUSIONS

Metformin was associated with a lower failure risk than were sulfonylureas and meglitinides, but a comparable aGI failure rate.

Fimasartan increases glucose-stimulated insulin secretion in patients with type 2 diabetes and hypertension compared with amlodipine

AIM

To study the effects of angiotensin receptor blockers (ARBs) on insulin secretion in hypertensive patients with type 2 diabetes.

MATERIALS AND METHODS

A total of 41 patients were enrolled in this open-label, active comparator-controlled, crossover study. After a 2-week run-in period with amlodipine, the participants were assigned to receive either fimasartan (60-120 mg daily) or amlodipine (5-10 mg daily) for 16 weeks. Thereafter, they were treated with the other drug for another 16 weeks. Physical examinations and laboratory tests were performed before and after each treatment.

RESULTS

Blood pressure, glycated haemoglobin and oral glucose tolerance test (OGTT) values were similar with each treatment. Fimasartan treatment significantly increased median (range) homeostatic assessment of β-cell function values (49.9 [22.5-174.4] vs 46.9 [15.6-148.0]), area under the curve of insulin during OGTT (27 284 [9501-94 525] vs 26 818 [8112-76 704] pmol/L × min), insulinogenic index at 60 minutes (19.7 [3.0-131.2] vs 15.0 [2.4-103.8] pmol/mmol) and at 120 minutes (19.1 [1.9-85.5] vs 12.6 [-4.3-178.8] pmol/mmol) compared with those with amlodipine (all P < .05); however, acute insulin response and insulin resistance indices were similar for both agents.

CONCLUSIONS

Compared with amlodipine, fimasartan increased late-phase glucose-stimulated insulin secretion in patients with type 2 diabetes and hypertension. This finding suggests that ARBs would be more beneficial in such patients compared with other classes of anti-hypertensives.

Impact of systemic inflammation on the relationship between insulin resistance and all-cause and cancer-related mortality

BACKGROUND

Insulin resistance and inflammation play an important role in a variety of chronic diseases.

OBJECTIVE

We investigated the influence of systemic inflammation on the relationship between insulin resistance and mortality risk in apparently healthy adults.

METHODS

This study examined the mortality outcomes for 165,849 Koreans enrolled in a health-screening program. The subjects were divided into four groups according to their homeostatic model assessment of insulin resistance (HOMA-IR) and high-sensitivity C-reactive protein (hs-CRP) levels: group 0, HOMA-IR <75% and hs-CRP <2.0mg/L; group 1, HOMA-IR ≥75% and hs-CRP <2.0mg/L; group 2, HOMA-IR <75% and hs-CRP ≥2.0mg/L; and group 3, HOMA-IR ≥75% and hs-CRP ≥2.0mg/L. The Cox proportional hazard models were used to assess hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause, cardiovascular disease, and cancer-related mortality.

RESULTS

During the follow-up period of 1,417,325.6person-years, a total of 1316 deaths (182 from cardiovascular disease) occurred. The multivariate-adjusted HRs for all-cause mortality were significantly higher in groups 2 (HR 1.40; 95% CI: 1.19-1.64) and group 3 (HR 1.68; 95% CI: 1.34-2.10) than that in group 0. For cardiovascular mortality, the sex-adjusted hazards were also significantly higher in groups 2 and 3 than that in group 0; however, this increased risk disappeared during multivariate analysis. Groups 2 and 3 had significantly higher risk for cancer-related mortality than group 0, with multivariate-adjusted hazard ratios of 1.48 (95% CI: 1.18-1.86) and 1.84 (95% CI: 1.35-2.51), respectively.

CONCLUSIONS

Systemic inflammation can be used to stratify the subjects according to the all-cause and cancer-related mortality risks, irrespective of the insulin-resistance status. And this tendency is most pronounced in cancer-related mortality.

Insulin Resistance and Its Association with Metabolic Syndrome in Korean Children

Background

This study investigated the association between insulin resistance (IR) and metabolic syndrome (MetS) in children.

Methods

A cross-sectional study involving 1036 healthy children aged between 7 and 13 years was conducted. Homeostasis model assessment of insulin resistance (HOMA-IR) was calculated as an index of IR. Participants were classified according to the HOMA-IR quartiles.

Results

Incremental, linear trends were found in age (p < 0.001), body mass index (BMI) (p < 0.001), body fat (p < 0.001), waist circumference (p < 0.001), resting blood pressures (BP) (p < 0.001), triglycerides (TG) (p < 0.001), total cholesterol (TC) (p < 0.001), high density lipoprotein-cholesterol (HDL-C) (p < 0.001), FBG (p < 0.001), and insulin (<0.001) according to incremental HOMA-IR categories (from the 1st to 4th quartile). Compared with children in the 1st HOMA-IR quartile, children in the 4th HOMA-IR quartile had significantly higher odd ratios (ORs) of abnormalities in systolic (p = 0.051) and diastolic BP (p = 0.005), FBG (p < 0.001), TG (p < 0.001), TC (p = 0.016), and HDL-C (p = 0.006) even after adjustments for age, gender, BMI, and body fat percentage. Children in the 3rd HOMA-IR quartile had significant abnormalities in FBG (p < 0.001), TG (p = 0.001), and HDL-C (p = 0.010) even after adjustments for the covariates.

Conclusion

The current findings suggest that IR is significantly associated with the clustering of MetS risk factors in children in Korea.