Impaired glucose regulation is a new concept that has only been introduced in recent years, and it is aimed at certain groups of people who are vulnerable to diabetes. These people have higher than normal blood glucose levels but do not reach the level of diabetes, and have a higher risk of developing diabetes and cardiovascular disease, so they are the main targets of diabetes prevention and need special attention.
I. What is meant by impaired glucose regulation?
The existing diagnostic criteria for diabetes are based on a large amount of epidemiological data and reflect, to a large extent, the numerous associations between diabetes and clinical consequences. However, many data suggest that the primary cause of disability in a large proportion of the population with diabetes is macrovascular disease. And the macrovascular risk seen in a large body of data in recent years has failed to be truly reflected in the diagnosis of diabetes.
In 1999, the American Diabetes Association introduced the concept of impaired fasting glucose (IFG) while proposing new diabetes typing and diagnostic criteria and retaining the concept of low glucose tolerance. On the basis of this, the concept of impaired glucose regulation was further proposed.
Impaired glucose regulation (IGR) includes impaired glucose tolerance (IGT) and/or impaired fasting glucose. Although the two are not clinical conditions, they represent different glucose regulation abnormalities and are considered a high-risk state between normoglycemia and diabetic hyperglycemia. IGT is a postprandial state abnormality, i.e., a glucose level between 7.8 mmol/L and 11.1 mmol/L 2 hours after a 75g glucose load, while IFG is a fasting state abnormality, i.e., a fasting glucose level higher than normal, i.e., between 6.1 mmol/L and 7 mmol/L. between 6.1 mmol/L and 7 mmol/L.
IGT and IFG can exist together or occur separately. IGR is a metabolic state between normoglycemic homeostasis and diabetes mellitus (DM), and is an important stage in the natural course of diabetes mellitus and a clinical marker for predicting DM. The International Diabetes Federation (IDF) convened an expert symposium on IGR in London in August 2001, recommending an enhanced understanding of simple IFR, simple IGT, combined IGT with IFG and transient IGT.
Second, what are the characteristics of IGR?
Domestic and international studies have found that the prevalence of IGT is high and close to that of diabetes, and the results of the DECODE study showed that the prevalence of DM and IGT in the elderly population was 17.7% and 14% respectively in 1996, and progressed to 28.7% and 14.8% in 2000. Most of the studies conducted in China showed that the prevalence of IGT was higher than the prevalence of diabetes. Yang Ze et al. reported that the standardized prevalence of IGT was 15.89% in urban and rural Beijing in 1997 in people aged 60 years or older. The results of our survey conducted in Chongqing in 2002 also showed that the prevalence of IGR was 15%, which was significantly higher than the prevalence of diabetes (10.38%).
Among the various types of IGR, the overall prevalence of IGT was greater than that of IFG. In a survey conducted by Gu Huilin et al. between September 1998 and October 1999, the prevalence of impaired glucose tolerance or impaired fasting glucose was found to be 13.0% in the natural population aged 40 years and older, and 17.3 % in the elderly aged 60 years and older. The prevalence of IGT/IFG was 17.3% in the elderly aged 60 years and above. The prevalence of IGT/IFG tended to increase gradually with increasing age (P<0.01). Our study also found that IGT accounted for 85.6%, IFG for 6.7%, and IFG with IGT for 7.7% of the IGR population. It can be seen that IGT accounts for the majority of the IGR population.
The results of domestic and international epidemiological surveys show that IGT and IFG have their own characteristics. IFG is more common in men, while IGT is more common in women. the incidence of IFG does not increase significantly after 40-50 years of age (except in European women), while the incidence of IGT increases with age.
III. How do IFG and IGT occur?
Although the causes of IFG and IGT are not fully understood. The onset of IGT is mainly related to insulin resistance in peripheral tissues, which manifests as impaired glucose utilization in muscle and adipose tissue. In contrast, the pathogenesis of IFG is mainly based on hepatic resistance to insulin, i.e., the inability to effectively suppress hepatic glucose output in the basal state, which affects morning fasting glucose. If IFG individuals also have early insulin secretion defect, postprandial hyperglycemia will occur successively.
IV. Increased risk of developing IFG and IGT
Both IGT and IFG can significantly increase the risk of developing diabetes, and those with IGT and IFG have the highest risk and can easily turn to diabetes. IGT is more prevalent than IFG in most populations and is more sensitive to individuals identified to develop diabetes later, but its specificity is slightly poorer. IGT and IFG are the main reserve populations for diabetes. Before 5 years of diabetes onset, 60% had IGT or IFG and 40% had NGT. a survey in Beijing also showed that those with normal glucose tolerance (NGT) and IGT at baseline who developed diabetes after 6 years accounted for 35.8% of the IGT group and only 8.8% of the NGT group.
Limited evidence suggests that I-IGT and I-IFG carry similar cardiovascular risk factors, with the greatest number of risk factors when the two are combined. There is evidence that I-IGT is more strongly associated with hypertension and dyslipidemia than I-IFG. both IFG and IGT are associated with cardiovascular disease mortality and total mortality. 2-hour glucose has a continuous independent association with mortality, whereas FBS is only independently associated above 7.0 mmol/L. HbA1c has a continuous positive association with cardiovascular disease and total mortality, and is independent of other cardiovascular HbA1c has a continuous positive association with cardiovascular disease and total mortality, and is independent of other CVD risk factors.
Gu Huilin et al. found that the risk factors for IGT/IFG with hypertension, dyslipidemia, and overweight/obesity were similar to those for diabetes and significantly greater than those for normoglycemia. The results of our study also showed that the age and body mass index (BMI) of the IGR population were significantly higher than those of the NGT population, and the systolic blood pressure, triglycerides, and insulin resistance index of the IGR groups were significantly higher than those of the NGT group. the detection rates of hypertension, lipid metabolism disorders, obesity or overweight, and microalbuminuria were significantly higher in the IGR group than in the NGT group.
The detection rate of metabolic syndrome was also significantly higher in all IGR groups than in the NGT group. This suggests that the cardiovascular risk in the IGT/IFG population is significantly higher than that in the normal population. Many studies have shown that IFG/IGT predicts an increased risk of future diabetes as well as cardiovascular disease and even early death in individuals.
Do IGT and IFG require intervention? There is no clear consensus on whether IFG and IGT should be considered as a disease. Studies suggest that IGT and IFG are major risk factors for type 2 diabetes, and they are also clear risk markers for cardiovascular disease. Both have similar prognostic value to other major cardiovascular disease risk factors and are also treatable risk factors. Regardless of the nomenclature, screening for both should be useful for treatment purposes.
Data from prospective studies of the prevalence of diabetes in foreign populations of different ethnicities suggest that both fasting glucose and 2-hour postprandial glucose have good correlation trends and predictive value in predicting diabetes. From some epidemiological data, it seems that the higher the blood glucose, the greater the risk of developing diabetes in the future, and those with IGT and IFG are definitely the most at-risk group for developing diabetes, followed by those with I-IGT and the next most at-risk group with I-IFG. Therefore, there is a strong need for interventional treatment for the IGR population.
How to prevent diabetes in the IGT/IFG population? Regular monitoring and early detection of diabetes should pay attention to oral glucose tolerance test (OGTT) screening, and those with IGT/IFG should undergo regular OGTT screening. Experts recommend that all people with IFG should have an OGTT test, and that people with IGT and IFG should each have their diagnosis confirmed based on the average of two OGTT tests over a 3-month period. More recently, the Finnish Diabetes Risk Score has proposed risk scores using risk factors such as BMI, waist circumference, age and family history of diabetes to replace the OGTT for population screening.
However, this approach deserves further exploration. Lifestyle interventions In order to prevent diabetes, lifestyle interventions should first be carried out in the high-risk groups of IGT and IFG. The interventions include weight loss, diet control, and moderate increase in exercise. Recent studies have shown that diet control and increased physical activity can reduce the incidence of DM in IGT by 31% and 42%, respectively.
Pharmacological interventions Lifestyle interventions are ineffective, and pharmacological interventions should be considered. Intervention drugs are mainly metformin, acarbose, etc. Back in the early 80s, Malmohus et al. in Sweden found that dietary control and pharmacological interventions could reduce the incidence of DM in IGT by 16% and 29%, respectively. In addition to metformin and acarbose, there are new studies exploring the efficacy of other drugs to prevent diabetes, such as the DREAM study to explore the efficacy of ramipril and rosiglitazone in the prevention of diabetes in individuals with IGT, and the AVIGATOR study to explore the preventive effect of nateglinide and valsartan in a population with IGT at cardiovascular risk, which achieved positive results and confirmed that pharmacological intervention in individuals at high risk such as IGR The AVIGATOR study explored the preventive effect of nateglinide and valsartan in a population with cardiovascular risk and achieved positive results, confirming the preventive effect of pharmacological interventions in individuals at high risk of developing diabetes such as IGR.