Is glycosylated hemoglobin A1c a surrogate for metabolic syndrome in nondiabetic, first-degree relatives of African-American patients with type 2 diabetes?

Association of A1C with cardiovascular disease and metabolic syndrome in Asian Indians with normal glucose tolerance

OBJECTIVE

This study examines the association of A1C with cardiovascular disease (CVD) risk factors, coronary artery disease (CAD), and metabolic syndrome in Asian Indians with normal glucose tolerance (NGT).

RESEARCH DESIGN AND METHODS

This cross-sectional study recruited subjects from phase III of the Chennai Urban Rural Epidemiology Study (CURES), an epidemiological study in a representative population of Chennai (formerly Madras) in South India, conducted between January 2003 and June 2004. Included were 1,644 subjects with NGT, i.e., fasting plasma glucose <100 mg/dl (5.6 mmol/l) and 2-h postload plasma glucose <140 mg/dl (7.8 mmol/l). A1C was measured using the Biorad Variant machine. Metabolic syndrome was defined based on modified Adult Treatment Panel III guidelines.

RESULTS

The mean +/- SD A1C value in the study cohort was 5.5 +/- 0.4%. A1C showed a significant association with BMI (beta = 0.017, P < 0.001), systolic (beta = 0.002, P = 0.028) and diastolic (beta = 0.202, P = 0.017) blood pressure, waist circumference (beta = 0.007, P < 0.001), serum cholesterol (beta = 0.002, P < 0.001), triglycerides (beta = 0.001, P < 0.001), LDL cholesterol (beta = 0.002, P < 0.001), fasting insulin (beta = 0.009, P < 0.001), and homeostasis model assessment of insulin resistance (beta = 0.047, P < 0.001) after adjusting for age and sex. Regression analysis showed that A1C had a strong association with metabolic syndrome that persisted after adjusting for age and sex (odds ratio [OR] 2.9 [95% CI 2.08-4.00]; P < 0.001). A1C also had a strong association with CAD (2.6 [1.23-5.63]; P = 0.01), but the significance was lost when adjusted for age and sex.

CONCLUSIONS

There is a strong association of A1C with prevalent CVD risk factors in Asian-Indian subjects with NGT.

Hemoglobin A1c (HbA1c) predicts future drug treatment for diabetes mellitus: a follow-up study using routine clinical data in a Japanese university hospital

Hemoglobin A1c (HbA1c) has been widely used as a measure of glycemic control in patients with diabetes mellitus. However, the role of HbA1c in the prediabetic stage has received little attention, although the effectiveness of early intensive intervention for the prediabetic patients defined by plasma glucose is well documented. In this study, routine clinical data in a Japanese university hospital were used to address whether the level of HbA1c predicted drug treatment for diabetes mellitus. The study population consisted of 38,628 adolescent and adult patients (>or=15 years old) who used routine medical care services provided by the hospital and who were prescribed no anti-diabetic drugs in the 12 months before the 3-year study period. The rates of starting anti-diabetic drugs during the study period were calculated for subgroups divided by the level of HbA1c followed by Kaplan-Meier survival analysis and Cox proportional-hazard regression. In addition, the medical records of middle-aged patients with borderline (5.6-6.4%) and high (>or=6.5%) levels of HbA1c were examined to estimate the rates of initial drug treatment for type 2 diabetes mellitus. The rate (95% confidence interval; CI) of beginning anti-diabetic drug therapy was 1.5 (0.9-2.5)/1000 patient-years in patients with a normal level of HbA1c (<5.6%), which is similar to 2.1 (1.8-2.5)/1000 patient-years in patients with no HbA1c data, but lower than the value of 23.0 (18.6-28.6) and 161.8 (144.8-180.7)/1000 patient-years in those with borderline and high levels of HbA1c, respectively (P < 0.001). In a small group of 513 middle-aged patients, the rates of initial drug treatment for type 2 diabetes mellitus were 39.4 (28.1-55.1)/1000 patient-years and 270.4 (209.4-349.0)/1000 patient-years in those with borderline and high levels of HbA1c, respectively. A borderline (5.6-6.4%) or high (>or=6.5%) level of HbA1c was found to strongly predict future drug treatment for diabetes mellitus.

Resistance training and dietary protein: effects on glucose tolerance and contents of skeletal muscle insulin signaling proteins in older persons

BACKGROUND

Resistance training (RT) and dietary protein independently influence indexes of whole-body glucose control, though their synergistic effects have not yet been documented.

OBJECTIVE

This study assessed the influence of dietary protein intake on RT-induced changes in systemic glucose tolerance and the contents of skeletal muscle insulin signaling proteins in healthy older persons.

DESIGN

Thirty-six older men and women (age: 61 +/- 1 y) performed RT (3 times/wk for 12 wk) and consumed either 0.9 g protein . kg(-1) . d(-1) [lower-protein (LP) group; approximately 112% of the Recommended Dietary Allowance (RDA)] or 1.2 g protein . kg(-1) . d(-1) [higher-protein (HP) group; approximately 150% of the RDA]; the HP group consumed more total, egg, and dairy proteins.

RESULTS

After RT, body weight was unchanged; whole-body protein and water masses increased, and fat mass decreased with no significantly different responses observed between the LP and HP groups. The RT-induced improvement in oral glucose tolerance (decreased area under the curve, AUC) was not significantly different between the groups (LP: -28%; HP: -25%). The insulin (-21%) and C-peptide (-14%) AUCs decreased in the LP group but did not change significantly in the HP group. Skeletal muscle insulin receptor, insulin receptor substrate-1, and Akt contents were unchanged, and the amount of atypical protein kinase C zeta/lambda (aPKC zeta/lambda), a protein involved with insulin signaling, increased 56% with RT, independent of protein intake.

CONCLUSION

These results support the hypothesis that older persons who consume adequate or moderately high amounts of dietary protein can use RT to improve body composition, oral glucose tolerance, and skeletal muscle aPKC zeta/lambda content without a change in body weight.

Relationship between HbA(1)c and mortality in a Japanese population

AIM/HYPOTHESIS

HbA(1)c concentrations are known to be associated with all-cause excess mortality risk in Caucasians. However, the relationship has not been clarified well in the Japanese. In addition, studies of the relationship between HbA(1)c and mortality from malignant neoplasms are scarce.

METHODS

HbA(1)c was measured for 3,710 people of a cohort composed of A-bomb survivors and controls. At baseline they were divided into five groups: a normal HbA(1)c group of 1,143 individuals with HbA(1)c of <5.5%, a slightly high but normal HbA(1)c group of 1,341 individuals with HbA(1)c > or =5.5% to <6.0%, a slightly high HbA(1)c group of 589 individuals with HbA(1)c > or =6.0% to <6.5%, a high HbA(1)c group of 259 individuals with HbA(1)c > or =6.5%, and a group of 378 individuals known to have type 2 diabetes. Using a Cox proportional hazards model, hazard ratios based on comparisons with the normal HbA(1)c group were obtained.

RESULTS

During the observation period there were 754 deaths. For all-cause and cardiovascular disease mortality, a significant increase of the hazard ratio was observed for the slightly high HbA(1)c group. A similar increase in malignant neoplasm-related mortality was observed for both the high HbA(1)c group and the diabetes group.

CONCLUSIONS/INTERPRETATION

Our results suggest that individuals in the Japanese population with HbA(1)c levels of 6% or more might have increased mortality risk. The results indicate that HbA(1)c measurements should be sought even for people who have not been diagnosed with diabetes.

Different patterns of insulin resistance in relatives of type 1 diabetic patients with retinopathy or nephropathy: the Genesis France-Belgium Study

OBJECTIVE

Insulin resistance may be a risk factor for diabetic microangiopathy, which may have a familial component. We carried out a family-based study to determine which components of the insulin resistance syndrome are associated with diabetic retinopathy and nephropathy in type 1 diabetes.

RESEARCH DESIGN AND METHODS

The Genesis France-Belgium Study is a multicenter binational study designed to investigate the genetic factors involved in the microvascular complications of type 1 diabetes using a family-based design. Probands were type 1 diabetic patients with diabetic retinopathy (classified as background, preproliferative, or proliferative) and possibly diabetic nephropathy (absent, incipient, established, or advanced). The insulin resistance score of their first-degree relatives was calculated according to their BMI and history of arterial hypertension, lipid disorders, and type 2 diabetes.

RESULTS

The insulin resistance score of relatives was positively correlated with the albumin excretion rate (P = 0.0009) and fasting plasma glucose (P = 0.0003) and HbA(1c) (P < 0.0001) concentrations. This score was higher in the relatives of probands with than in those without diabetic nephropathy (P = 0.0370). Similarly, it was higher in relatives of subjects with proliferative diabetic retinopathy than in those of probands without, even after controlling for subjects with versus without diabetic nephropathy (P = 0.0379). However, the components of the insulin resistance score in relatives differed according to the severity of diabetic retinopathy or nephropathy in the probands. Obesity and history of arterial hypertension were most common in relatives of probands with proliferative diabetic retinopathy, whereas obesity and history of lipid disorders were most common in the relatives of probands with diabetic nephropathy.

CONCLUSIONS

Familial insulin resistance segregates with diabetic complications: lipid disorders and obesity segregate with diabetic nephropathy, whereas arterial hypertension and obesity segregate with diabetic retinopathy.

Diabetes in African Americans: unique pathophysiologic features

Type 2 diabetes is an increasing public health problem among African Americans, especially children. Several features make type 2 diabetes among African Americans unique. First, African-American adults with type 2 diabetes, or Flatbush diabetes, present with diabetic ketoacidosis. Patients are insulin resistant with acute, severe defects in insulin secretion and no islet cell autoantibodies. Following treatment, some insulin secretory capacity is recovered and ketoacidosis generally does not recur. The second is remission in African Americans with type 2 diabetes. Recovery of glucose homeostasis, accompanied by recovery of beta-cell function, follows intensive glycemic regulation. Finally, among African Americans with diabetes who are not obese, normal insulin sensitivity is not uncommon. Such individuals do not have the increased cardiovascular risk of insulin-resistant individuals. Differences in visceral, not subcutaneous, adipose tissue volume appear to determine insulin sensitivity. Understanding the unique physiologic and clinical features of African Americans is critical in designing appropriate treatment strategies.