Agneta Ekstrand

Early Metabolic Defects in Persons at Increased Risk for Non-Insulin-Dependent Diabetes Mellitus

To identify early metabolic abnormalities in non-insulin-dependent diabetes mellitus (NIDDM), we measured sensitivity to insulin and insulin secretion in 26 first-degree relatives of patients with NIDDM and compared these subjects both with 14 healthy control subjects with no family history of NIDDM and with 19 patients with NIDDM. The euglycemic insulin-clamp technique, indirect calorimetry, and infusion of [3-3H]glucose were used to assess insulin sensitivity. Total-body glucose metabolism was impaired in the first-degree relatives as compared with the controls (P less than 0.01). The defect in glucose metabolism was almost completely accounted for by a defect in nonoxidative glucose metabolism (primarily the storage of glucose as glycogen). The relatives with normal rates of metabolism (mean +/- SEM, 1.81 +/- 0.27 mg per kilogram of body weight per minute) and impaired rates (1.40 +/- 0.22 mg per kilogram per minute) in oral glucose-tolerance tests had the same degree of impairment in glucose storage as compared with healthy control subjects (3.76 +/- 0.55 mg per kilogram per minute; P less than 0.01 for both comparisons). During hyperglycemic clamping, first-phase insulin secretion was lacking in patients with NIDDM (P less than 0.01) and severely impaired in their relatives with impaired glucose tolerance (P less than 0.05) as compared with control subjects; insulin secretion was normal in the relatives with normal glucose tolerance. We conclude that impaired glucose metabolism is common in the first-degree relatives of patients with NIDDM, despite their normal results on oral glucose-tolerance tests. Both insulin resistance and impaired insulin secretion are necessary for the development of impaired glucose tolerance in these subjects.

Insulin resistance, hypertension and microalbuminuria in patients with Type 2 (non-insulin-dependent) diabetes mellitus

SummaryWe examined the impact of hypertension and microalbuminuria on insulin sensitivity in patients with Type 2 (non-insulin-dependent) diabetes mellitus using the euglycaemic insulin clamp technique in 52 Type 2 diabetic patients and in 19 healthy control subjects. Twenty-five diabetic patients had hypertension and 19 had microalbuminuria. Hypertension per se was associated with a 27% reduction in the rate of total glucose metabolism and a 40% reduction in the rate of non-oxidative glucose metabolism compared with normotensive Type 2 diabetic patients (both p<0.001). Glucose metabolism was also impaired in normotensive microalbuminuric patients compared with normotensive normoalbuminuric patients (29.4±2.2 vs 40.5±2.8 μmol · kg lean body mass−1 · min−1; p=0.012), primarily due to a reduction in non-oxidative glucose metabolism (12.7±2.9 vs 21.1±2.6 μmol · kg lean body mass−1 ·min−1; p=0.06). In a factorial ANOVA design, however, only hypertension (p=0.008) and the combination of hypertension and microalbuminuria (p=0.030) were significantly associated with the rate of glucose metabolism. The highest triglyceride and lowest HDL cholesterol concentrations were observed in Type 2 diabetic patients with both hypertension and microalbuminuria. Of note, glucose metabolism was indistinguishable from that in control subjects in Type 2 diabetic patients without hypertension and microalbuminuria (40.5±2.8 vs 44.4±2.8 μmol · kg lean body mass−1 · min−1). We conclude that insulin resistance in Type 2 diabetes is predominantly associated with either hypertension or microalbuminuria or with both.

Association between Polymorphism of the Glycogen Synthase Gene and Non-Insulin-Dependent Diabetes Mellitus

BACKGROUND The storage of glucose as glycogen in skeletal muscle is frequently impaired in patients with non-insulin-dependent diabetes mellitus (NIDDM) and their nondiabetic relatives. Despite an intensive search for candidate genes associated with NIDDM, no data have been available on the gene coding for the key enzyme of this pathway, glycogen synthase. METHODS AND RESULTS Using a human complementary DNA probe, the restriction enzyme Xbal, and Southern blot analysis, we identified two polymorphic alleles, A1 and A2, in the glycogen synthase gene. The gene was localized to chromosome 19. The A1A2 or A2A2 genotype was found in 30 percent of 107 patients with NIDDM but in only 8 percent of 164 nondiabetic subjects without a family history of NIDDM (P < 0.001). The diabetic patients with the A2 allele had a stronger family history of NIDDM (P = 0.019), a higher prevalence of hypertension (P = 0.008), and a more severe defect in insulin-stimulated glucose storage (P = 0.001) than the diabetic patients with the A1 allele. The concentration of the glycogen synthase protein in biopsy specimens of skeletal muscle from the patients with the A2 allele was normal, however, suggesting that expression of the gene was unaltered. The Xbal polymorphism was due to a change of a single base in an intron. CONCLUSIONS The Xbal polymorphism of the glycogen synthase gene identifies a subgroup of patients with NIDDM characterized by a strong family history of NIDDM, a high prevalence of hypertension, and marked insulin resistance.

Insulin resistance and insulin deficiency in the pathogenesis of posttransplantation diabetes in man

Although steroids can induce insulin resistance, it is not known whether additional defects in insulin secretion are necessary for the development of diabetes. To address this question, we measured insulin sensitivity (euglycemic insulin clamp in combination with indirect calorimetry and infusion of tritiated glucose) and insulin secretion (hyperglycemic clamp) in three groups of subjects: (1) 10 kidney transplant patients with normal oral glucose tolerance, (2) 14 patients who developed diabetes after kidney transplantation, and (3) 10 healthy controls. Glucose utilization, primarily storage of glucose as glycogen, was reduced by 34% in kidney transplant patients with normal glucose tolerance when compared with healthy control subjects (18.2 +/- 2.9 vs. 27.5 +/- 2.7 microM/L; P less than 0.05). Insulin secretion was normal in relation to the degree of insulin resistance in transplanted non-diabetic patients, thus maintaining a normal oral glucose tolerance. Development of transplantation diabetes was associated with only minor further deterioration of glucose storage (14.7 +/- 2.7 microM/L; P less than 0.001 vs. control subjects), whereas first-phase, second-phase, and glucagon-stimulated insulin secretion measured during hyperglycemic clamping (incremental area under the insulin curve 287 +/- 120, 1275 +/- 419, and 3515 +/- 922 pM) became impaired as compared with nondiabetic kidney transplant patients (769 +/- 216, 3084 +/- 545, and 6293 +/- 533 pM; P less than 0.05). We conclude that both insulin resistance and insulin deficiency are necessary for the development of diabetes in kidney transplant patients.

Modulation of hepatic glucose production by non-esterified fatty acids in type 2(non-insulin-dependent) diabetes mellitus

SummaryTo study the effect of changes in plasma non-esterified fatty acid concentration on suppression of hepatic glucose production by insulin eight Type 2 (non-insulin-dependent) diabetic patients participated in three euglycaemic, hyperinsulinaemic (108pmol · m2−1 · min−1) clamp studies combined with indirect calorimetry and infusion of [3-3H]-glucose and [1-14C]palmitate; (1) a control experiment with infusion of NaCl 154 mmol/l, (2) heparin was infused together with insulin, and (3) an antilipolytic agent, Acipimox, was administered at the beginning of the experiment. Six healthy volunteers participated in the control experiment. Plasma non-esterified fatty acid concentrations during the insulin clamp were in diabetic patients: (1) 151±36 μmol/1, (2) 949±178 μmol/l, and (3) 65±9 μmol/l; in healthy control subjects 93±13 μmol/l. Non-esterified fatty acid transport rate, oxidation and non-oxidative metabolism were significantly higher during the heparin than during the Acipimox experiment (p<0.001). Suppression of hepatic glucose production by insulin was impaired in the diabetic compared to control subjects (255±42 vs 51±29 μmol/min, p<0.01). Infusion of heparin did not affect the suppression of hepatic glucose production by insulin (231±49 μmol/min), whereas Acipimox significantly enhanced the suppression (21±53 μmol/min, p<0.001 vs 154 mmol/l NaCl experiment). We conclude that insulin-mediated suppression of hepatic glucose production is not affected by increased non-esterified fatty acid availability. In contrast, decreased non-esterified fatty acid availability enhances the suppression of hepatic glucose production by insulin.

Insulin resistance and abnormal albumin excretion in non-diabetic first-degree relatives of patients with NIDDM

SummaryMicroalbuminuria has recently been associated with insulin resistance in both insulin-dependent and non-insulin-dependent (NIDDM) diabetes mellitus. To establish whether microalbuminuria in non-diabetic subjects as well is associated with insulin resistance and associated abnormalities in glucose and lipid metabolism, oral glucose tolerance tests were performed with measurement of urinary albumin excretion rate, lipids and lipoproteins in 582 male non-diabetic first-degree relatives of patients with NIDDM. In addition, insulin sensitivity was assessed in 20 of these subjects with the euglycaemic hyperinsulinaemic clamp technique. Abnormal albumin excretion rate (AER), defined as AER 15–200 Μg/min, was associated with higher systolic blood pressure (p<0.05), higher fasting glucose values (p<0.05), lower HDL-cholesterol (p<0.05) and lower apolipoprotein A-I (p<0.05) concentrations than observed in subjects with normal AER. The rate of glucose metabolism was lower in subjects with abnormal compared to subjects with normal albumin excretion rate (38.0±2.8 vs 47.3±2.4 Μmol·kg lean body mass−1. min−1; p=0.028). This difference was almost completely accounted for by a reduction in non-oxidative glucose metabolism (17.7±1.9 vs 27.4±2.7 Μmol·kg lean body mass−1. min−1; p = 0.010), which correlated inversely with the AER (r=−0.543; p=0.013). These results suggest that in non-diabetic individuals genetically predisposed to NIDDM, abnormal AER is associated with insulin resistance and abnormalities in glucose and lipid metabolism.

Different effects of insulin and oral antidiabetic agents on glucose and energy metabolism in type 2 (non-insulin-dependent) diabetes mellitus.

SummaryWhich therapy should be used in Type 2 (noninsulin-dependent) diabetic patients with “secondary sulfonylurea failure”, insulin or a combination of sulfonylurea and metformin? To address this question, we have compared the effect of 6 months of insulin therapy twice daily with that of a combination of glibenclamide and metformin in 24 Type 2 diabetic subjects, who no longer responded to treatment with sulfonylureas. Both treatments resulted in an equivalent 30% improvement in mean daily blood glucose (p<0.001), without significant effect on serum lipids. Insulin improved glycaemic control primarily by reducing basal hepatic glucose production (p<0.05), but had no significant effect on peripheral glucose metabolism. The combination of glibenclamide and metformin enhanced significantly total body glucose metabolism (p<0.05), predominantly by stimulating the non-oxidative pathway. Neither insulin nor the combination therapy altered B-cell response to a test meal. Insulin therapy resulted in a 6% increase in body weight, 63% of which was accounted for by increased fat mass. Although body weight was unchanged during sulfonylurea/metformin therapy, lean body mass and energy expenditure decreased significantly (p<0.05). We conclude that insulin and glibenclamide/metformin have different long-term effects on glucose and energy metabolism in Type 2 diabetes.

The effect of (steroid) immunosuppression on skeletal muscle glycogen metabolism in patients after kidney transplantation.

To examine the mechanisms by which immunosuppression by steroids impairs glycogen synthesis in human skeletal muscle, we measured glycogen synthase protein content and activity in muscle samples from 14 patients receiving corticosteroid therapy after kidney transplantation and in 20 healthy control subjects. A percutaneous muscle sample was taken before and at the end of a euglycemic hyperinsulinemic insulin clamp. Insulin-stimulated glucose disposal was reduced by 33% in kidney transplant patients compared with healthy controls (33.8 +/- 4.2 vs. 50.5 +/- 2.7 mumol (kg LBM)-1 min-1; P<0.01), primarily due to a decrease in nonoxidative glucose metabolism (14.2 +/- 3.3 vs. 32.3 +/- 2.7 mumol (kg LBM)-1 min-1; P<0.001). Glycogen synthase activity measured at both 0.1 mmol/L (17.6 +/- 2.6 vs. 24.0 +/- 2.2 nmol min-1 mg protein-1; P<0.05), and at 10 mmol/L glucose 6-phosphate (24.1 +/- 3.5 vs. 33.7 +- 2.4 nmol min-1 mg protein-1; P<0.05) and glycogen synthase protein concentrations (8.8 +/- 1.8 vs. 18.9 +/- 1.9 relative units per ng DNA; P<0.01) were lower in kidney transplant patients compared with controls. Glycogen synthase protein correlated with nonoxidative glucose metabolism (r=0.42; P=0.04). Alpha-actinin (used as a control of general protein degradation) was lower in kidney transplant patients compared with controls (4.4 +/- 0.8 vs. 9.6 +/- 1.1 cpm/ng DNA; P<0.01). In conclusion, corticosteroids cause insulin resistance, which correlates with impaired activation of glycogen synthase and decreased enzyme protein content. The decrease in glycogen synthase protein may reflect increased degradation rather than a defect in translation.

Insulin resistance in Type 2 (non-insulin-dependent) diabetic patients with hypertriglyceridaemia

SummaryHypertriglyceridaemia, which is frequently seen in Type 2 (non-insulin-dependent) diabetes mellitus, is associated with insulin resistance. The connection between hypertriglyceridaemia and insulin resistance is not clear, but could be due to substrate competition between glucose and lipids. To address this question we measured glucose and lipid metabolism in 39 Type 2 diabetic patients with hypertriglyceridaemia, i. e. mean fasting serum triglyceride level equal to or above 2 mmol/l (age 59±1 years, BMI 27.4±0.5 kg/m2, HbA1c8.0±0.2%, serum triglycerides 3.2±0.2 mmol/l) and 41 Type 2 diabetic patients with normotriglyceridaemia, i. e. mean fasting serum triglyceride level below 2 mmol/l (age 58±1 years, BMI 27.0±0.7 kg/m2, HbA1c7.8±0.2 %, serum triglycerides 1.4±0.1 mmol/l). Insulin sensitivity was assessed using a 340 pmol·(m2)−1· min−1 euglycaemic insulin clamp. Substrate oxidation rates were measured with indirect calorimetry and hepatic glucose production was estimated using a primed (25 μCi)-constant (0.25 μCi/min) infusion of [3-3H]-glucose. Suppression of lipid oxidation by insulin was impaired in patients with hypertriglyceridaemia vs patients with normal triglyceride levels (3.5±0.2 vs 3.0±0.2μmol·kg−1· min−1; p<0.05). Stimulation of glucose disposal by insulin was reduced in hypertriglyceridaemic vs normotriglyceridaemic patients (27.0±1.3 vs 31.9±1.6 μmol·kg−1·min−1; p<0.05) primarily due to impaired glucose storage (9.8±1.0 vs 14.6±1.4μmol·kg−1·min−1; p<0.01). In contrast, insulinstimulated glucose oxidation was similar in patients with hypertriglyceridaemia and in patients with normal triglyceride concentrations (16.9±0.8 vs 17.2±0.7μmol·kg−1·min−1). Hepatic glucose production in the basal state and during the clamp did not differ between the two groups. We conclude therefore that oxidative substrate competition between glucose and lipids does not explain insulin resistance associated with hypertriglyceridaemia in Type 2 diabetes. The question remains whether the reduced nonoxidative glucose disposal observed in the patients with hypertriglyceridaemia is genetically determined or a consequence of increased lipid oxidation.

Different acute and chronic effects of acipimox treatment on glucose and lipid metabolism in patients with type 2 diabetes.

To study whether therapeutic reduction of non‐esterified fatty acids (NEFA) can be used to improve glucose metabolism, we administered the antilipolytic agent, acipimox, 250 mg four times daily for 4 weeks in eight obese Type 2 diabetic patients. Glucose and NEFA metabolism were assessed before and after treatment with a two‐step euglycaemic hyperinsulinaemic clamp (0.25 and 1 ***mU kg−1 min−1 insulin) combined with infusions of [3–3H] glucose and [1–14C] palmitate. Three days of acipimox treatment reduced 24‐h serum NEFA levels by 10%, but the difference disappeared after 4 weeks of treatment mainly due to a two‐fold rise in morning NEFA concentrations (p < 0.01). After 3 days of acipimox treatment, fasting and 24‐h plasma glucose and serum triglyceride concentrations were significantly reduced (p < 0.05), but no longer after 4 weeks of treatment. Despite the rebound rise in NEFA, acute administration of acipimox still inhibited both oxidative and non‐oxidative NEFA metabolism in the basal state (p < 0.01 – 0.001) and during insulin infusion (p < 0.05 – 0.001). Inhibition of NEFA metabolism was associated with increased insulin‐stimulated glucose uptake (from 3.56 ± 0.28 to 5.14 ± 0.67 μmol kg−1 min−1, p < 0.05), mainly due to stimulation of non‐oxidative glucose disposal (from 1.74 ± 0.23 to 3.03 ± 0.53 μmol kg−1 min−1, p < 0.05). In conclusion, acipimox administered acutely inhibits NEFA appearance (lipolysis), which is associated with improved glucose uptake. However, after 4 weeks of treatment, the beneficial effects on NEFA and glucose metabolism are outweighed by a marked rebound rise in fasting NEFA concentrations. The results emphasize the problems using acipimox as a means to improve glucose tolerance in patients with Type 2 diabetes.