In this longitudinal cohort study with a 7-year follow-up, we discovered that among a population of Chinese adults who do not have diabetes but are part of a community, there is a positive and independent correlation between elevated METS-IR and the incidence of T2DM. Additionally, our findings revealed that METS-IR exhibited superior performance in predicting T2DM in females when compared to males. Among individuals with various phenotypes, it is evident that younger people have a considerably greater likelihood of developing METS-IR-associated diabetes compared to middle-aged and elderly individuals.
Insulin resistance, also known as IR, occurs when insulin becomes less effective at promoting the uptake and utilization of glucose for various reasons. As a result, the body compensates by secreting an excessive amount of insulin, leading to hyperinsulinemia, in order to keep blood sugar levels stable17. Metabolic syndrome and type 2 diabetes are more likely to occur in individuals with an inherited predisposition. In recent years, METS-IR, a novel index of insulin resistance that does not rely on insulin, has gained increasing attention. According to literary sources, METS-IR has been proposed as a straightforward and precise measure for assessing IR and forecasting the development of T2DM in the Western populace9. It was found that individuals in the highest quartile of METS-IR (> 50.39) had the greatest adjusted risk of T2DM (HR 3.91, 95% CI 2.25–6.81). Significant associations were observed between METS-IR (P < 0.001) and visceral, intrahepatic, and intrapancreatic fat as well as fasting insulin levels. Furthermore, in comparison to healthy individuals, participants who experienced T2DM incidents exhibited elevated initial METS-IR levels (50.2 ± 10.2 vs 44.7 ± 9.2, P < 0.001). The findings of an extensive investigation conducted on an elderly Chinese cohort revealed a significant correlation between METS-IR and both prediabetes and T2DM18. A similar conclusion was reached by another prospective cohort study involving data from non-obese adults in Japan19. After accounting for various potential confounding variables, the hazard ratio (HR) between the fourth quartile (Q4) and the first quartile (Q1) was 4.01 (95% confidence interval [CI], 1.39–11.57). This indicates that the likelihood of developing type 2 diabetes mellitus (T2DM) rises as the quartile of alteration in the METS-IR index increases. Our study revealed a robust correlation between elevated METS-IR levels and the susceptibility to developing new-onset diabetes, even after accounting for potential influencing variables. Additionally, we verified that increased METS-IR had greater predictability for the development of diabetes.
During our research, we have discovered fascinating occurrences in the analysis of subgroups. The risk of diabetes related to METS-IR varied significantly among different age phenotypes. Within the age stratification subgroup, individuals who were young or middle-aged faced a notably elevated likelihood of developing diabetes associated with METS-IR, compared to the older population. This strange occurrence is thought to be caused by young people's high-calorie diets, sedentary lifestyles, and lack of exercise. Changes in dietary patterns, high-fat, high-calorie diets, sedentary lifestyles, decreased physical activity, and excess energy are the main factors contributing to the resurgence of diabetes. These factors are leading to diabetes by inducing individuals to become obese and overweight, consequently elevating the likelihood of developing diabetes. Emerging evidence indicates that young-onset T2DM, occurring in individuals under the age of 40, exhibits a swifter decline in β-cell function compared to T2DM which develops later in life20. Recent research has also indicated a significant increase in the prevalence of type 2 diabetes among youth worldwide over the last three decades, with obesity emerging as the primary contributing factor21. Diabetic complications pose a higher threat to individuals with diabetes who are young or middle-aged, as they experience prolonged periods of high blood sugar and a more rapid advancement of pathological processes. Our research findings indicate that the correlation between METS-IR and the development of diabetes is more pronounced in young and middle-aged individuals compared to older individuals. Hence, this metabolic indicator might prove more beneficial in forecasting the occurrence of diabetes in the future among individuals who are young or middle-aged.
Furthermore, it was found that METS-IR exhibited superior performance in females when predicting T2DM. While the exact cause of sexual disparity remains uncertain, it could potentially be associated with sex hormones and the various types of muscle fibers. As we know, gender differences exist in many diseases, such as cardiovascular disease, diabetes, metabolic syndrome, etc22, 23. Prior studies have verified that numerous elements of energy and glucose balance are controlled in distinct ways among males and females, impacting their susceptibility to diabetes and related metabolic ailments23. Insulin sensitivity in a large population of individuals with normal blood glucose levels was evaluated using the oral glucose insulin sensitivity index, and The findings revealed that, even after accounting for age and BMI, women exhibited higher insulin sensitivity compared to men24. It is due to enhanced glucose uptake by skeletal muscle in women25.
Limitations
The determination of diabetes in this research was based on self-disclosure by participants or FPG > 7.0 mmol/L throughout the monitoring period, which could potentially result in an underestimation of the actual occurrence of diabetes. As this study is an analysis conducted after previous studies14, despite making adequate adjustments, certain variables like glycosylated hemoglobin, exercise habits, and dietary habits were not included in the database. These omissions could potentially lead to residual confounding. Moreover, the observed rate of endpoint events is directly influenced by the relatively brief duration of patient follow-up. It may lead to an underestimation of disease incidence. However, the researchers still found a strong correlation between the two, suggesting that METS-IR may be of high value as a predictor of type 2 diabetes. Besides, the diabetes in this study was identified as T2DM, since the number of patients with T2DM exceeds 90% of all diabetes cases2. However, this may ignore the impact of type 1 diabetes.