Carbohydrate homeostasis

Discriminatory ability of simple OGTT-based beta cell function indices for prediction of prediabetes and type 2 diabetes: the CODAM study

AIMS/HYPOTHESIS

The hyperglycaemic clamp technique and the frequently sampled IVGTT are unsuitable techniques to assess beta cell function (BCF) in large cohorts. Therefore, the aim of this study was to evaluate the discriminatory ability of simple OGTT-based BCF indices for prediction of prediabetes (meaning impaired fasting glucose and/or impaired glucose tolerance) and type 2 diabetes.

METHODS

Glucose metabolism status was assessed by 2 h 75 g OGTT at baseline (n = 476, mean age 59.2 years, 38.7% women) and after 7 years of follow-up (n = 416) in the Cohort on Diabetes and Atherosclerosis Maastricht (CODAM) study (1999-2009). Baseline plasma glucose, insulin and C-peptide values during OGTTs were used to calculate 21 simple indices of BCF. Disposition indices (BCF index × Matsuda index), to compensate for the prevailing level of insulin resistance, were calculated for the BCF indices with the best discriminatory abilities. The discriminatory ability of the BCF indices was estimated by the area under the receiver operating characteristics curve (ROC AUC) with an outcome of incident prediabetes (n = 73) or type 2 diabetes (n = 60 and n = 18 cases, respectively, in individuals who were non-diabetic or had normal glucose metabolism at baseline).

RESULTS

For incident prediabetes (n = 73), all ROC AUCs were less than 70%, whereas for incident type 2 diabetes, I₃₀/I₀, CP₃₀/CP₀, ΔI₃₀/ΔG₃₀, ΔCP₃₀/ΔG₃₀ (where I, CP and G are the plasma concentrations of insulin, C-peptide and glucose, respectively, at the times indicated), and corrected insulin response at 30 min had ROC AUCs over 70%. In at-baseline non-diabetic individuals, disposition indices ΔI₃₀/ΔG₃₀, ΔCP₃₀/ΔG₃₀ and corrected insulin response at 30 min had ROC AUCs of over 80% for incident type 2 diabetes. Moreover, these BCF disposition indices had significantly better discriminatory abilities for incident type 2 diabetes than the Matsuda index alone.

CONCLUSIONS/INTERPRETATION

BCF indices reflecting early-phase insulin secretion have the best ability to discriminate individuals who will develop prediabetes and type 2 diabetes. Of these, ΔCP₃₀/ΔG₃₀, often referred to as the C-peptidogenic index, performed consistently well.

Circulating glucagon is associated with inflammatory mediators in metabolically compromised subjects

BACKGROUND

Acute phase mediators promote metabolic changes by modifying circulating hormones. However, there is virtually no data about the link between glucagon and inflammatory parameters in obesity-related chronic low-grade inflammation.

STUDY DESIGN

We performed both cross-sectional and longitudinal (diet-induced weight loss) studies.

METHODS

Circulating glucagon concentrations (ELISA), parameters of glucose and lipid metabolism, interleukin 6 (IL6), and complement factor B (CFB) were analyzed in 316 subjects (250 men and 66 women). The effects of weight loss were investigated in an independent cohort of 20 subjects.

RESULTS

Circulating glucagon significantly correlated with glucose (r=0.407, P<0.0001), HbAlc (r=0.426, P<0.0001), fasting triglycerides (r=0.356, P=0.001), and parameters of innate immune response system such as IL6 (r=0.342, P=0.050) and CFB (r=0.404, P=0.002) in obese subjects with altered glucose tolerance, but not in individuals with normal glucose tolerance (NGT). In obese and NGT subjects, glucagon was associated with fasting triglycerides (r=0.475, P=0.003) and CFB (r=0.624, P=0.001). In obese subjects, glucagon (P=0.019) and CFB (P=0.002) independently contributed to 26% of fasting triglyceride variance (P<0.0001) after controlling for the effects of age and fasting serum glucose concentration in multiple lineal regression models. Moreover, concomitant with fat mass, fasting triglycerides, and CFB, weight loss led to significantly decreased circulating glucagon (-23.1%, P=0.004).

CONCLUSIONS

According to the current results, acute phase reactants such as IL6 and CFB are associated with fasting glucagon in metabolically compromised subjects. This suggests that glucagon may be behind the association between inflammatory and metabolic parameters in obesity-associated chronic low-grade inflammation.

Surrogate markers of insulin resistance: A review

Insulin resistance is a hallmark of obesity, diabetes, and cardiovascular diseases, and leads to many of the abnormalities associated with metabolic syndrome. Our understanding of insulin resistance has improved tremendously over the years, but certain aspects of its estimation still remain elusive to researchers and clinicians. The quantitative assessment of insulin sensitivity is not routinely used during biochemical investigations for diagnostic purposes, but the emerging importance of insulin resistance has led to its wider application research studies. Evaluation of a number of clinical states where insulin sensitivity is compromised calls for assessment of insulin resistance. Insulin resistance is increasingly being assessed in various disease conditions where it aids in examining their pathogenesis, etiology and consequences. The hyperinsulinemic euglycemic glucose clamp is the gold standard method for the determination of insulin sensitivity, but is impractical as it is labor- and time-intensive. A number of surrogate indices have therefore been employed to simplify and improve the determination of insulin resistance. The object of this review is to highlight various aspects and methodologies for current and upcoming measures of insulin sensitivity/resistance. In-depth knowledge of these markers will help in better understanding and exploitation of the condition.

A rice bran oil diet improves lipid abnormalities and suppress hyperinsulinemic responses in rats with streptozotocin/nicotinamide-induced type 2 diabetes

The aim of this study was to determine the effects of rice bran oil (RBO) on lipid metabolism and insulin resistance in rats with streptozotocin/nicotinamide-induced type 2 diabetes mellitus (T2DM). Rats were divided into two groups: the control group (15% soybean oil, contains 0 g γ-oryzanol and 0 g γ-tocotrienol/150 g oil for 5 weeks) and the RBO group (15% RBO, contains 5.25 g γ-oryzanol and 0.9 g γ-tocotrienol/150 g oil for 5 weeks). Compared with the control group, the RBO group had a lower plasma nonesterified fatty acid concentration, ratio of total to high-density-lipoprotein cholesterol, hepatic cholesterol concentration, and area under the curve for insulin. The RBO group had a higher high-density-lipoprotein cholesterol concentration and greater excretion of fecal neutral sterols and bile acid than did the control group. RBO may improve lipid abnormalities, reduce the atherogenic index, and suppress the hyperinsulinemic response in rats with streptozotocin/nicotinamide-induced T2DM. In addition, RBO can lead to increased fecal neutral sterol and bile acid excretion.

Dimethylarginine dimethylaminohydrolase overexpression enhances insulin sensitivity

OBJECTIVE

Previous studies suggest that nitric oxide (NO) may modulate insulin-induced uptake of glucose in insulin-sensitive tissues. Asymmetrical dimethylarginine (ADMA) is an endogenous inhibitor of NO synthase (NOS). We hypothesized that a reduction in endogenous ADMA would increase NO synthesis and thereby enhance insulin sensitivity.

METHODS AND RESULTS

To test this hypothesis we used a transgenic mouse in which we overexpressed human dimethylarginine dimethylaminohydrolase (DDAH-I). The DDAH-I mice had lower plasma ADMA at all ages (22 to 70 wk) by comparison to wild-type (WT) littermates. With a glucose challenge, WT mice showed a prompt increase in ADMA, whereas DDAH-I mice had a blunted response. Furthermore, DDAH-I mice had a blunted increase in plasma insulin and glucose levels after glucose challenge, with a 50% reduction in the insulin resistance index, consistent with enhanced sensitivity to insulin. In liver, we observed an increased Akt phosphorylation in the DDAH-I mice after i.p. glucose challenge. Incubation of skeletal muscle from WT mice ex vivo with ADMA (2 mumol/L) markedly suppressed insulin-induced glycogen synthesis in fast-twitch but not slow-twitch muscle.

CONCLUSIONS

These findings suggest that the endogenous NOS inhibitor ADMA reduces insulin sensitivity, consistent with previous observations that NO plays a role in insulin sensitivity.

Insulin sensitivity derived from oral glucose tolerance testing in athletes: Disagreement between available indices

The aims of the present study were to determine whether available "fasting" and oral glucose tolerance test-derived insulin sensitivity indices could effectively discriminate between individuals with higher than normal insulin sensitivity, and whether they would all provide similar information in clinical practice. Sprint runners (n = 8), endurance runners (n = 8) and sedentary controls (n = 7) received a 75-g oral glucose tolerance test. All participants were healthy lean males, aged 21-29 years. Besides glucose and insulin responses, a total of nine such indices were computed. Fasting as well as post-load glucose concentrations were similar in the three groups, while basal plasma insulin and the insulinaemic response to glucose were both higher in untrained individuals (at P < 0.05 and P < 0.02, respectively). There were no differences between endurance and sprint runners. The results for insulin sensitivity, however, were quite variable: three indices showed that both groups of athletes were more insulin-sensitive than controls; three indicated that this was the case for endurance runners only; one indicated that this was the case for sprint runners only; and two showed that sprint runners were more insulin-sensitive than either sedentary individuals or endurance runners (all differences were significant at P < 0.05). Controlling for total body weight or lean mass did not effectively resolve this disagreement. Apparently, the various insulin sensitivity indices examined provided different quantitative and qualitative information, despite insulin action being greater in both groups of athletes relative to controls, as reflected by their similar glucose tolerance with lower insulin concentrations. We suggest, therefore, that the use and interpretation of such indices among physically active individuals be made with caution.

Hepatic glucocorticoid receptor antagonism is sufficient to reduce elevated hepatic glucose output and improve glucose control in animal models of type 2 diabetes

Glucocorticoids amplify endogenous glucose production in type 2 diabetes by increasing hepatic glucose output. Systemic glucocorticoid blockade lowers glucose levels in type 2 diabetes, but with several adverse consequences. It has been proposed, but never demonstrated, that a liver-selective glucocorticoid receptor antagonist (LSGRA) would be sufficient to reduce hepatic glucose output (HGO) and restore glucose control to type 2 diabetic patients with minimal systemic side effects. A-348441 [(3b,5b,7a,12a)-7,12-dihydroxy-3-{2-[{4-[(11b,17b)-17-hydroxy-3-oxo-17-prop-1-ynylestra-4,9-dien-11-yl] phenyl}(methyl)amino]ethoxy}cholan-24-oic acid] represents the first LSGRA with significant antidiabetic activity. A-348441 antagonizes glucocorticoid-up-regulated hepatic genes, normalizes postprandial glucose in diabetic mice, and demonstrates synergistic effects on blood glucose in these animals when coadministered with an insulin sensitizer. In insulin-resistant Zucker fa/fa rats and fasted conscious normal dogs, A-348441 reduces HGO with no acute effect on peripheral glucose uptake. A-348441 has no effect on the hypothalamic pituitary adrenal axis or on other measured glucocorticoid-induced extrahepatic responses. Overall, A-348441 demonstrates that an LSGRA is sufficient to reduce elevated HGO and normalize blood glucose and may provide a new therapeutic approach for the treatment of type 2 diabetes.

Effects of agar (kanten) diet on obese patients with impaired glucose tolerance and type 2 diabetes

AIM

The aim of this study was to evaluate the efficacy of agar diet in combination with a conventional diet (traditional Japanese food) for obese patients with impaired glucose tolerance and type 2 diabetes.

METHODS

After a 4-week run-in period on their habitual diets, 76 patients were randomly assigned to have conventional diet or conventional diet with agar. Both groups were on these diets for 12 weeks. Body weight, body mass index (BMI), glycaemic control, blood pressure, insulin resistance, total body fat, fat distribution and lipids were assessed before and after the experimental period.

RESULTS

In both groups, after 12 weeks, mean body weight, BMI, fasting glucose levels, homeostasis model assessment-insulin resistance, and systolic and diastolic blood pressures had decreased significantly from their baseline values. HbA(1)c, visceral fat area, subcutaneous fat area, total body fat, insulin area under the curve after oral glucose tolerance test and total cholesterol decreased significantly in the agar-diet group. After 12 weeks, mean changes of body weight (-2.8 +/- 2.7 kg vs. -1.3 +/- 2.3 kg, p = 0.008), BMI values (-1.1 +/- 1.1 kg/m(2) vs. -0.5 +/- 0.9 kg/m(2), p = 0.009) and total cholesterol (-7.6 +/- 27.5 mg/dl vs. + 2.4 +/- 23.4 mg/dl, p = 0.036) were significantly greater in the agar-diet group than in the conventional diet group.

CONCLUSIONS

The agar diet resulted in marked weight loss due to the maintenance of reduced calorie intake and to an improvement in metabolic parameters.

Effects of HRT and exercise training on insulin action, glucose tolerance, and body composition in older women

The independent and combined effects of exercise training and hormone replacement therapy (HRT) on body composition, fat distribution, glucose tolerance, and insulin action were studied in postmenopausal women, aged 68 +/- 5 yr, assigned to control (n = 19), exercise (n = 18), HRT (n = 15), and exercise + HRT (n = 16) groups. The exercise consisted of 2 mo of flexibility exercises followed by 9 mo of endurance exercise. HRT was conjugated estrogens 0.625 mg/day and trimonthly medroxyprogesterone acetate 5 mg/day for 13 days. Total and regional body composition were measured by dual-energy X-ray absorptiometry. Serum glucose and insulin responses were measured during a 2-h oral glucose tolerance test. There were significant main effects of exercise on reductions in total and regional (trunk, arms, legs) fat mass, increase in leg fat-free mass, and improvements in glucose tolerance and insulin action. There were significant main effects of HRT on the reduction of total fat mass (HRT, -3.0 +/- 4.0 kg; no HRT, -1.3 +/- 2.6 kg), with a strong trend for reductions in trunk and leg fat mass (both P = 0.07). There was also a significant improvement in insulin action in response to HRT. These results suggest that there are independent and additive effects of exercise training and HRT on the reduction in fat mass and improvement in insulin action in postmenopausal women; the effect of HRT on insulin action may be mediated, in part, through changes in central adiposity.

Enhanced skeletal muscle insulin sensitivity in year-old rats adapted to hypergravity

Rats adapted to hypergravity by continuous centrifugation at 4.15 g for 7 mo exhibit increased glucose uptake at lower plasma insulin levels than weight-matched control animals following oral glucose administration. To assess insulin sensitivity of specific tissues, glucose uptake by perfused skeletal muscle and liver from year-old hypergravic rats was compared with perfused tissue from weight-matched control rats (2.5-mo-old). The results show that metabolic clearance of glucose by skeletal muscle from hypergravic rats ws not significantly greater than control muscle when perfused in the absence of insulin (10.6 vs. 8.1 microliter.min-1.g muscle-1) but was twofold faster (23.0 vs. 9.5) at perfusate insulin levels of 35 microunits/ml. Conversely, glucose uptake by hypergravic livers was significantly decreased (P less than 0.001) compared with control livers (10.3 vs. 27.8) at perfusate insulin levels of 40 microunits/ml. These findings suggest that skeletal muscle rather than liver is the tissue primarily responsible for enhanced sensitivity to insulin observed in older rats adapted to hypergravity.

Patterns of decerebration in infants and children: defects in homeostasis and sequelae

Sixty-four infants and children showing signs of decerebrate rigidity admitted to a paediatric unit have been studied. Cases of head injury, myelomeningocoele, and tumours were excluded from the series. The aetiological factors causing decerebration in the remainder fell into four main groups: infections, hypoxia, metabolic disease, and intracranial haemorrhage. Increased intracranial pressure was diagnosed in 87%. Defects in homeostasis occurred in 75%, respiratory abnormalities were present in 66%, cardiovascular in 33%, hypothermia in 30%, and hyponatraemia in 17%. Early recognition and treatment of raised intracranial pressure and defects in homeostasis are of the utmost importance if morbidity and mortality are to be minimized. There was a 31% mortality from the acute illness: 30% of the survivors were normal at follow-up examination; the remainder showed varying degrees of handicap. The severity of decerebration showed no correlation with aetiology or prognosis. The study shows that a wide range of disorders can lead to the clinical picture of decerebration in the young child, and that the prognosis is probably much better than in adults showing the same symptoms and signs.

Myocardial and body metabolism in fatal cardiogenic shock after valvular replacement

Cellular energy substrates and metabolites, electrolytes, oxygenation, and acid-base balance, in arterial and coronary sinus blood of seven adult patients who died after valvular replacements, were studied and compared with these measurements from five patients having aortic replacement who survived. Six of the patients were in New York Heart Association class IV. All but one died within 24 hr of acute circulatory failure, with excessive bleeding being a contributing factor. Plasma potassium and osmolality remained higher in the first postoperative hours in nonsurvivors. Ketone bodies, growth hormone, and lactate levels rose precipitously as shock became severe. Increased arterial blood osmolality and potassium, plus a still-rising lactate concentration, were evident 2 hr after operation in patients who died in the next 24 hr. Low cardiac output, hyperosmolality, and the degree of lactic acidosis were the only early changes predicting the fatal outcome.