Elevated plasma non-esterified fatty acid levels and insulin secretion in non-diabetic relatives of type 2 diabetic patients.

OBJECTIVE: High non-esterified fatty acid (NEFA) levels impair glucose-stimulated insulin secretion from islets derived from non-diabetic Zucker rats that are genetically predisposed to diabetes. We therefore examined the effect of elevated plasma NEFA levels on insulin secretion in non-diabetic first-degree relatives of type 2 diabetic patients who are at increased risk of developing diabetes. SUBJECTS AND STUDY DESIGN: Normal glucose tolerant relatives (n = 9) and control subjects with no family history of diabetes were pair-matched for age, sex, body mass index (BMI), insulin sensitivity and early insulin response during an oral glucose tolerance test (OGTT). Plasma NEFA levels were raised from 0 to 340 minutes by the infusion of 20% Intralipid and heparin. From 180 minutes, insulin secretion rates (IRSs) were assessed by stepped low-dose glucose infusion. RESULTS: The mean (geometric mean +/- 95% CI) NEFA levels were comparable between relatives and control subjects (2.7 [2.1-3.6] and 2.1 [1.7-2.7] mmol/l, paired analysis, NS). Similarly, plasma glucose levels achieved at each glucose infusion step were comparable between the groups. However, there were no significant differences between the groups for ISR throughout the study. CONCLUSIONS: Sustained elevation of plasma non-esterified fatty acid levels does not decrease insulin secretion in non-diabetic relatives of type 2 diabetic patients, and is therefore unlikely to be important in the development of the impaired pancreatic beta-cell function in type 2 diabetes mellitus.

Prevalence of diabetes mellitus and associated cardiovascular risk factors in an adult urban population in Paraguay.

A cross-sectional study was conducted on a 20-74-year-old population in an urban white-Hispanic population in Paraguay to determine the prevalence of diabetes mellitus (DM), impaired glucose tolerance (IGT), and associated cardiovascular disease (CVD) risk factors. In total 1606 subjects completed the study (response rate 80.3%; 1094 women, 512 men). The overall prevalences were: DM 6.5%, IGT 11.3%, hypertension 17.1%, and obesity 31.6% with more obesity in women (35.7% vs 22.8%, p < 0.05). Age-standardized prevalences were: DM 6.5%, IGT 13.5% in females and DM 5.5%, IGT 7.2% in males. DM and IGT subjects had two or more CV risk factors significantly more often than the normal population. In conclusion, DM, IGT, hypertension, and obesity are common in this South American Hispanic urban population, particularly in women. Public health measures, such as lifestyle education, are required to decrease these noncommunicable diseases.

Multiple metabolic abnormalities in normal glucose tolerant relatives of NIDDM families.

Non-diabetic first degree relatives of non-insulin-dependent diabetic (NIDDM) families are at increased risk of developing diabetes mellitus, and have been studied to identify early metabolic abnormalities. Hormone concentrations measured by specific enzyme immunoassays were assessed in non-diabetic relatives of North European extraction, and control subjects with no family history of diabetes were matched for age, sex and ethnicity. A 75-g oral glucose tolerance test was conducted and those with newly diagnosed NIDDM were excluded. Basal insulin resistance was determined by homeostasis model assessment (HOMA), and hepatic insulin clearance by C-peptide:insulin molar ratio. Relatives (n = 150) were heavier (BMI: p < 0.0001) than the control subjects (n = 152), and had an increased prevalence of impaired glucose tolerance (15 vs 3%, p < 0.01). The relatives had increased fasting proinsulin levels and decreased C-peptide levels following the glucose load, while insulin levels were increased at all time points. To examine whether the differences in hormone levels were secondary to the differences in glucose tolerance and adiposity, we studied 100 normal glucose tolerant relatives and control subjects pair-matched for age, sex, waist-hip ratio and BMI. The differences in proinsulin levels were no longer apparent. However, the relatives remained more insulin resistant, and had decreased C-peptide levels and C-peptide:insulin ratios at all time points. In conclusion, we have identified several metabolic abnormalities in the normal glucose tolerant relatives, and propose that the decreased hepatic insulin clearance helps to maintain normoglycaemia in the face of combined insulin resistance and decreased insulin secretion.

The effect of acute (60 minute) insulin stimulation upon human skeletal muscle glycogen synthase and protein phosphatase-1 in non-insulin-dependent diabetic patients and control subjects.

Previous studies have established that activation of muscle glycogen synthase (GS) is abnormal in non-insulin-dependent diabetes mellitus (NIDDM). Insulin-mediated activation of GS depends upon protein phosphatase-1 (PP1), which dephosphorylates the relevant sites of GS. In order to determine whether defects in PP1 activation cause subnormal activation of GS or whether PP1 activation itself is normal, we administered a short insulin infusion to 8 NIDDM subjects and 8 healthy controls matched for gender, age, and body mass index (BMI). GS fractional activity and PP1 activity were determined in biopsies taken from the gastrocnemius muscle before and after 60 min insulin infusion (0.1 U kg h-1). In the NIDDM group, muscle GS fractional activity was 6.8 +/- 1.6 and 10.0 +/- 1.5% (mean +/- SEM) (p = 0.11) before and after insulin infusion. In the control group, muscle GS fractional activity increased from 7.3 +/- 2.0 to 13.3 +/- 2.7% (p < 0.02). PP1 activity had returned towards basal levels after insulin infusion; NIDDM group 156 +/- 24.7 to 184.1 +/- 28.1 U mg-1; control group 220.8 +/- 30.1 to 233.8 +/- 29.8 U mg-1. In the NIDDM group there was a positive correlation between the increases in GS fractional activity and PP1 activity following insulin stimulation r = 0.77; p < 0.025). These data indicate that in vivo insulin-dependent activation of muscle PP1 is transient in normal subjects but is delayed in NIDDM. The defect in GS activation in NIDDM is likely to be proximal to PP1 in the pathway of transmission of the insulin signal.

Features of syndrome X in first-degree relatives of NIDDM patients.

OBJECTIVE: To determine whether the features of syndrome X are more common in first-degree relatives of non-insulin-dependent diabetes mellitus (NIDDM) patients than in control subjects with no family history of diabetes. RESEARCH DESIGN AND METHODS: A total of 154 first-degree relatives from 60 families with two or more NIDDM patients and 154 age- and sex-matched control subjects were studied. All subjects underwent a 75-g oral glucose tolerance test and baseline lipid blood and anthropometric measures. The features of syndrome X that were studied were obesity, hypertension, dyslipidemia (high triglyceride levels and low high-density lipoprotein [HDL] cholesterol concentrations), impaired glucose tolerance (World Health Organization criteria), and insulin resistance (as assessed by the homeostasis model assessment). RESULTS: Relatives were heavier than control subjects (body mass index 27.5 +/- 5.2 vs. 25.2 +/- 4.6 kg/m2, respectively [mean +/- SD], P < 0.0002), had lower HDL cholesterol concentrations (1.2 +/- 0.3 vs. 1.4 +/- 0.4 mmol/l, P < 0.001), were more insulin-resistant (2.3 [0.7-7.6] vs. 1.6 [0.5-5.1], geometric mean [95% confidence intervals], P < 0.0001), and had more individuals classified as having impaired glucose tolerance (28 of 154 [18%] vs. 7 of 154 [7%], chi 2, P < 0.001). The differences in insulin resistance and HDL cholesterol concentrations between the groups were independent of obesity. CONCLUSIONS: Features of syndrome X occur more frequently in relatives of NIDDM patients than in control subjects with no family history of diabetes.