The Insulin Resistance but Not the Insulin Secretion Parameters Have Changed in the Korean Population during the Last Decade

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.

Long-term effects on glycaemic control and β-cell preservation of early intensive treatment in patients with newly diagnosed type 2 diabetes: A multicentre randomized trial

AIM

To determine the effects of early intensive glycaemic control with intensive insulin treatment (IIT) or initial combined oral antidiabetic drug (COAD) therapy on long-term glycaemic control and the preservation of β-cell function in people with type 2 diabetes mellitus (T2DM).

METHODS

Newly diagnosed drug-naïve patients with T2DM from 8 outpatient diabetes centres were randomized to receive either IIT (n = 50; glargine/glulisine) or COAD (n = 47; glimepiride/metformin) as intensive treatment until the termination criteria to ensure euglycaemia were met. After intensive treatment, the patients completed a follow-up period with either lifestyle modification (LSM) alone or rescue therapy to maintain target glycated haemoglobin levels of <7% (53 mmol/mol) up to week 104. The primary outcomes were analysed after excluding participants who were anti-glutamic acid decarboxylase autoantibody-positive.

RESULTS

Both intensive treatment methods were effective for short-term glycaemic control, but improvements in the disposition index (DI) were significantly greater in the IIT group than in the COAD group (P = .021). During the follow-up period after intensive treatment, the two groups significantly differed in rescue method regarding the maintenance of comparable levels of glycaemic control (P = .010) and more participants who received IIT exhibited well-controlled glycaemia with LSM alone. Additionally, the IIT group maintained a higher DI than the COAD group during the follow-up period. Cox regression analysis showed that the IIT method was associated with a 52.5% lower risk of failing to maintain drug-free glycaemic remission compared with the COAD method (P = .015).

CONCLUSIONS

The findings indicate that outpatient clinic-based IIT to ensure euglycaemia in newly diagnosed patients with T2DM might be an effective initial therapeutic option for improvements in β-cell function and glycaemic control over the long term, without serious adverse events.

Association of serum 25-hydroxyvitamin D and diabetes-related factors in Korean adults without diabetes: The Fifth Korea National Health and Nutrition Examination Survey 2010-2012

AIMS

Vitamin D is associated with diabetes mellitus (DM) occurrence by affecting insulin secretion and resistance. However, variations exist due to differences in vitamin D sensitivity among individuals. We investigate the relationship between serum 25-hydroxyvitamin D [25(OH)D] status and various indices of DM in a Korean population without DM.

METHODS

Large-scaled population-based analysis was conducted from the Korea National Health and Nutrition Examination Survey data (2010-2012) were analyzed. Adult survey participants >20years without diabetes (n=15,169) were included.

RESULTS

The mean 25(OH)D levels were lower in females, subjects aged 20-39 years, and subjects with body mass index <21.1kg/m² and less physical activity (p<0.001). Further, the mean 25(OH)D levels tended to be lower in subjects with FBG >126mg/dL. After adjustment for potential confounders, 25(OH)D was not correlated with FBG (p=0.925) or HbA1c (p=0.336); however, fasting insulin (β=-0.072, p=0.011) and homeostasis model assessment of β-cell function (β=-0.007, p<0.001) showed significant negative correlations with 25(OH)D levels.

CONCLUSION

Although 25(OH)D status was not significantly associated with FBG or HbA1c, low 25(OH)D levels were associated with compensative insulin increase and ongoing increase in insulin resistance. Thus, vitamin D deficiency is assumed to influence DM occurrence.

Four Plasma Glucose and Insulin Responses to a 75 g OGTT in Healthy Young Japanese Women

The incidence of diabetes has been gradually increasing, not only in middle-aged individuals but also in young individuals. However, insulin and glucose patterns have not been investigated in apparently healthy young individuals, as they are typically grouped as controls. In this study, we investigated and classified glucose and insulin patterns in healthy young women. Sixty-two nonobese women without metabolic disease were recruited. The subjects underwent a 75 g oral glucose tolerance test (OGTT), physical measurements, and a biochemical examination. Two subjects displayed impaired glucose tolerance. The 62 subjects were categorized into four patterns by plasma glucose and insulin peak time during OGTT: normal type (n = 39), insulin-late type (n = 11), insulin- and glucose-late type (n = 7), and insulin-very late type (n = 5). OGTT glucose and insulin levels at all time points, insulinogenic index, HOMA-IR, and glucose area under the curve (AUC) significantly differed among the four groups. However, insulin AUC did not significantly differ. We did not detect significant differences in body condition or biochemical measurements. Our study demonstrated that some healthy young individuals might have delayed insulin secretion by OGTT. Early detection of altered glucose metabolism might be helpful to improve lifestyle choices and prevent progression to diabetes.

Comparison of insulin intensification strategies with insulin lispro low mixture twice daily versus basal insulin glargine and prandial insulin lispro once daily in East Asian and Caucasian patients with type 2 diabetes mellitus

BACKGROUND

This analysis evaluated efficacy and safety of insulin lispro low mixture (LM25) twice daily (breakfast and dinner) versus basal insulin glargine (bedtime) plus prandial insulin lispro (IGL) once daily before the largest meal in East Asian (EA) and Caucasian patients with type 2 diabetes mellitus who failed to reach glycemic targets on basal insulin glargine with metformin and/or pioglitazone.

METHODS

Included patients had an HbA1c ≥7.5% and ≤10.5% and fasting plasma glucose ≤6.7 mmol/L. Primary outcome was HbA1c change at 24 weeks.

RESULTS

Baseline mean HbA1c was numerically similar between groups in EA (n = 79) and Caucasian (n = 278) patients. Mean (± SD) HbA1c decreased significantly from baseline to 24 weeks for LM25 and IGL in both subpopulations (EA: -1.32 ± 0.96% and -0.89 ± 0.96%; Caucasian: -1.24 ± 0.98% and -1.04 ± 0.97; all P < 0.0001). The respective proportions reaching HbA1c ≤7.0% at Week 24 in the LM25 and IGL groups were 33.3% and 22.9% (EA) and 37.2% and 34.1% (Caucasian). Mean (± SD) rates of hypoglycemia per 30 days in the LM25 and IGL groups were 0.74 ± 1.16 and 1.22 ± 1.36 (EA) and 1.38 ± 2.04 and 1.65 ± 2.43 (Caucasian). Mean (± SD) weight gain changes in the LM25 and IGL groups were 0.62 ± 2.78 and 0.51 ± 2.63 kg (EA) and 1.77 ± 2.91 and 0.67 ± 3.09 kg (Caucasian).

CONCLUSIONS

Both strategies improved glycemic control in a small group of EA and Caucasian patients not adequately controlled on insulin glargine plus metformin and/or pioglitazone.

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

It is well known that many Korean patients with type 2 diabetes mellitus (T2DM) were non-obese and had decreased insulin secretion in past. However, during the past three decades, lifestyles in Korea have been westernized. As a result, the prevalence of obesity, the main cause of diabetes has increased. Thus, there is still a question as to whether the main pathophysiology of current Korean T2DM is insulin resistance or an insulin secretion defect. Because various anti-diabetes medications having different mechanisms of action are currently used as therapeutics, it is important to understand which of these factors is the main physiology in the development of diabetes in Koreans. In this review, we review changes in obesity prevalence, insulin resistance and insulin secretion defects in Korean T2DM during three decades.

Urinary N-acetyl-β-D-glucosaminidase, an early marker of diabetic kidney disease, might reflect glucose excursion in patients with type 2 diabetes

Recently, several renal tubular damage markers have gained considerable attention because of their clinical implications as sensitive and specific biomarkers for early stage diabetic kidney disease. However, little is known about the demographic and glucometabolic factors affecting levels of urinary N-acetyl-β-D-glucosaminidase (NAG), a marker of proximal tubular damage, in type 2 diabetes mellitus (T2DM).The aim of this study was to investigate the clinical relevance of urinary NAG with regard to demographic and glucometabolic parameters, as well as nephropathic parameters, by comparing the glomerulopathic marker of albuminuria.In this retrospective cross-sectional study, we enrolled a total of 592 patients with either prediabetes (N = 29) or T2DM (N = 563). Glucometabolic parameters (glucose, hemoglobin A1c, glycated albumin [GA], insulin, C-peptide, homeostasis model assessment [HOMA] of insulin resistance, HOMA-β, postprandial C-peptide-to-glucose ratio [PCGR], and urinary glucose-to-creatinine ratio) and nephropathic parameters (urinary NAG, albumin-to-creatinine ratio [ACR], and estimated glomerular filtration rate) were measured.The levels of urinary NAG showed moderate positive correlation with the levels of urinary ACR in T2DM (r = 0.46). In correlation analysis, urinary NAG was more strongly correlated with body mass index (BMI) (r = -0.22; P < 0.001 vs. r = -0.02; P = 0.74), plasma stimulated glucose (r = 0.25; P < 0.001 vs. r = 0.08; P = 0.10), GA (r = 0.20; P < 0.001 vs. r = 0.13; P = 0.01), PCGR (r = -0.17; P = 0.001 vs. r = -0.09; P = 0.11), and HOMA-β (r = -0.10; P = 0.05 vs. r = -0.02; P = 0.79) than urinary ACR. In multiple regression analysis, age, lower BMI, stimulated glucose, GA, and urinary ACR predicted increased urinary NAG.In conclusion, increase in urinary NAG may be related to glycemic parameters reflecting glucose fluctuation and decreased insulin secretory capacity in patients with T2DM. Further longitudinal, prospective studies are needed to investigate a causal relationship between glucose fluctuations, renal tubular damage, and other vascular complications of diabetes.