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Abstract

  1. Top of page
  2. Abstract
  3. Materials and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. Conflict of interests
  8. References

Abstract:  Acute hyperglycaemia exerts deleterious effects on the arterial wall. We suggested that rapid-acting insulin has a beneficial postprandial effect on endothelial dysfunction and inflammation compared with intermediate-acting insulin because of its ability to lower postprandial hyperglycaemia. This was tested in a parallel, controlled study on well-controlled patients with type 2 diabetes randomly assigned to bedtime Neutral Protamine Hagedorn (NPH) insulin (n = 41) or mealtime insulin aspart (n = 37). They were served standard diabetic meals for breakfast (8.00) and lunch (12.00). Blood samples were collected at 7.40 (fasting), 9.30, 11.30, 13.30 and 15.30 and analysed for glucose, insulin, lipids, intercellular adhesion molecules (ICAM), C-reactive protein (CRP), von Willebrand factor (vWF) and fibrinogen. The postprandial glucose response differed significantly between insulin regimens with a postprandial increase on NPH insulin and a decrease on insulin aspart. There was a minor but significant postprandial decrease in ICAM, CRP and vWF on both insulin regimens and a decrease in fibrinogen on NPH insulin. No insulin group differences were observed in postprandial responses for ICAM, CRP, vWF and fibrinogen. The rapid-acting insulin analogue aspart and the intermediate-acting insulin NPH had different effects on postprandial glucose response but similar postprandial effects on markers of inflammation and endothelial dysfunction.

Type 2 diabetes is associated with increased risk of cardiovascular disease [1]. There is a strong relationship between postprandial hyperglycaemia and the risk of cardiovascular disease in epidemiological studies where postprandial hyperglycaemia is more important than fasting blood glucose or HbA1c as predictors [2–5]. However, this concept has recently been challenged [6,7] and is still highly debated [8,9].

Experimental data indicate that acute hyperglycaemia can exert deleterious effects on the arterial wall measured as flow-mediated vasodilatation [10–12]. In line with this, the link between acute hyperglycaemia and inflammation and endothelial cell dysfunction has been investigated, showing an acute increase in interleukin 6 (IL-6) and tumour necrosis factor alfa (TNFα) [13], soluble intercellular adhesion molecules (ICAM) [14–17], C-reactive protein (CRP) [15], fibrinogen [18] and von Willebrand factor (vWF) [19] after a glucose load or a standard meal. The unfavourable postprandial effects on inflammation and endothelial cell function can be attenuated by hypoglycaemic agents, e.g. mitiglinide [20], glibenclamide [18], acarbose [21] or by the antioxidant glutathione [13,14]. In these studies, the hypoglycaemic agent was compared with placebo, and different treatment regimens have not been compared. It is assumed that pharmacological agents directed towards postprandial hyperglycaemia will be more effective in reducing postprandial inflammation and endothelial cell dysfunction than treatment directed towards fasting hyperglycaemia.

The aim of this short-term study in well-controlled patients with type 2 diabetes was to compare the acute effect of two different insulin treatment regimens on postprandial inflammation and endothelial cell function evaluated by biochemical markers. We suggested that the rapid-acting insulin analogue insulin aspart, directed towards postprandial hyperglycaemia, has a beneficial postprandial effect compared with the intermediate-acting insulin Neutral Protamine Hagedorn (NPH), directed towards fasting hyperglycaemia, because of its ability to lower postprandial hyperglycaemia.

Materials and Methods

  1. Top of page
  2. Abstract
  3. Materials and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. Conflict of interests
  8. References

Study population.  Patients with type 2 diabetes in the outpatient clinics at the Departments of Endocrinology, Hospital of South West Denmark, Esbjerg and Odense University Hospital, Odense, Denmark, were invited to participate in the study, if they at the same time participated in the South Danish Diabetes Study (SDDS) 1-year follow-up period, in which patients with diabetes 2–3 years previously were randomized to insulin NPH or insulin aspart [22]. Seventy-eight patients met the inclusion and exclusion criteria and were recruited for the present meal test study. The population characteristics at study entry in the meal test study are described in table 1. Inclusion criteria were the following: age 30–75 years, BMI > 25 kg/m2, type 2 diabetes > 4 years, anti-diabetic treatment with insulin NPH at bedtime or insulin aspart at meals >24 months and metformin with stable dose ≥1000 mg/day > 12 weeks, acetylsalicylic acid (75 mg/day) >2 weeks, no other anti-diabetic treatment 3 months before and HbA1c < 8.5% at recruitment. Exclusion criteria were the following: creatinine >120 μmol/l, ALAT/ASAT > 2.5 × upper reference limit, use of anticoagulants or glitazones within 1 month before, changes in dose of statins within 1 month before, night work, alcohol abuse, clinically relevant major organ or systemic illness, uncontrolled hypertension >180/110 mmHg or steroid treatment.

Table 1.    Population characteristics at study entry in the meal test study (day 0).
VariableInsulin aspart (n = 37)NPH insulin (n = 41)
  1. BMI, body mass index; BP, blood pressure.

  2. Mean (95% CI) values for the two insulin groups were compared with an unpaired t-test. Gender, smoking and statin treatment were compared with the chi-squared test. **p < 0.01.

  3. 1Total insulin dose was logarithmically transformed before analysis (geometric mean and geometric 95% CI).

Age59.5 (56.8–62.2)62.2 (59.7–64.7)
Gender (♂/♀)(24/13)(21/20)
Hospital (Esbjerg/Odense)(18/19)(22/20)
BMI (kg/m2)34.3 (32.2–36.4)35.8 (33.5–38.1)
Current smokers (%)27.82.0**
Systolic BP (mmHg)141.1 (136.4–145.8)140.0 (134.7–145.3)
Diastolic BP (mmHg)79.8 (77.3–82.3)79.4 (76.3–82.5)
HbA1c (%)6.8 (6.6–7.1)7.1 (6.8–7.4)
HbA1c (mmol/mol)51 (49–54)54 (51–57)
Total insulin dose (IE)142.6 (34.0–53.5)44.5 (37.4–53.0)
Statin treatment (%)73.075.6
Statin dose (mg)22.4 (16.0–28.9)23.2 (17.4–29.0)

All participants gave oral and written informed consent. The Ethics Committee of the Region of Southern Denmark, the Danish Medicines Agency, and the Danish Data Protection Agency approved the study according to the Helsinki Declaration. The study was conducted according to the guidelines of ICH. Good Clinical Practice (GCP) monitoring was performed by the GCP unit, Odense University Hospital. The trial was registered at clinicaltrials.gov as NCT01053234.

Study design.  The trial was a parallel, controlled study (fig. 1). Patients who had previously (2–3 years) been randomized to the SDDS study and presently participating in the SDDS 1-year follow-up period were included on day 0 and re-instructed to take insulin NPH at bedtime or insulin aspart three times daily at the meals and to titrate the insulin dose. Patients were re-admitted on day 21 after an overnight fast, and the test meals were served at 8.00 and 12.00. Light meals were served at 9.45 and 13.45 to prevent hypoglycaemia during the study day. In case of hypoglycaemia, orange juice was served immediately (three persons in the insulin aspart-treated group needed one glass of orange juice during the day). Meals were consumed under observation at the hospitals. Water was served with breakfast (200 ml) and lunch (400 ml). A cup of coffee/tea was served with the light meals. The patients were allowed to leave the hospitals between blood samplings, but they were not allowed to consume anything except study meals or to perform any heavy physical activity. Smoking should be restricted to a minimum. Patients were discharged at 15.30 after the last blood sampling.

image

Figure 1.  Design of the study.

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Study medication.  NPH insulin (Insulatard® FlexPen®) is an intermediate-acting insulin. Normal daily dose of NPH insulin was injected subcutaneously in the thigh at bedtime. Fasting blood glucose was measured every day. If fasting blood glucose twice was >6 mmol/l, the dose of NPH insulin was increased by 2 IE; if blood glucose was >8 mmol/l, the dose was increased by 4 IE and if >10 mmol/l by 6 IE. The dose was adjusted every second day and last time on day 19. In case of hypoglycaemia, the subsequent dose was reduced by 2–6 IE or after clinical judgement.

Insulin aspart (NovoRapid® FlexPen®) is a rapid-acting insulin analogue. Normal daily dose of insulin aspart was injected subcutaneously into the abdominal wall just before meals. Postprandial blood glucose was measured daily after each meal. The dose was adjusted according to postprandial blood glucose measured 1½ hr after each meal. If the blood glucose exceeded 10 mmol/l after a main course during two consecutive days, the insulin dose for that meal was increased by 2 IE; if blood glucose was >14 mmol/l, the dose was increased by 4 IE. The dose was adjusted every second day and last time on day 19. In case of hypoglycaemia, the dose was reduced with 4 IE or after clinical judgement.

The experimental diets.  The test meals were prepared in one batch in the hospital kitchen at the Hospital of Southwest Denmark. The two test meals were standard diabetic meals (56.7% of energy from carbohydrates, 30.2% of energy from fat, 13.1% of energy from protein) in order to obtain a normal diabetic dietary response. The light meals were composed of low-fat crispbread (28 g) with sugar-free marmalade (30 g). The test meals were low-fat rice dishes (rice, beef, onion, red pepper, corn and small amounts of spices) to which refined rapeseed oil was added. For breakfast, 150 g rice dish was served (250 kcal), and for lunch, 520 g rice dish was served (870 kcal). The patients were asked to eat according to their appetite. The breakfast was consumed by 68 participants in total, whereas five individuals consumed 50–75% of it, two individuals consumed 25–50% of it and two individuals consumed <25% of it. Of the lunch, 23 individuals consumed >75%, 31 consumed 50–75%, 17 consumed 25–50%, and six consumed <25%. The light meals were consumed by all participants.

Blood sampling.  Venous blood samples were drawn at 7.40 (fasting), 9.30, 11.30, 13.30 and 15.30 after 10 min. of rest in a chair. Samples were collected with minimal stasis by use of siliconized tubes and 21-gauge needles. Four ml of venous blood was collected in lithium heparin on ice for analysis of glucose, 4 ml was collected in K2EDTA on ice for analysis of free fatty acids (FFA), 5 ml was collected in tubes without additives for analyses of lipids, insulin, C-peptid, CRP and ICAM, and 4.5 ml was collected in citrated tubes for analyses of fibrinogen and vWF.

Tubes collected on ice were centrifuged at 4°C for 10 min. at 2000 × g. Tubes for analysis of lipids were kept at room temperature for 30 min. before centrifugation at 20°C for 20 min. at 2000 × g. Citrated tubes were centrifuged at 20°C for 20 min. at 2000 × g. Plasma and serum were pipetted into plastic vials and stored at −70°C.

Blood analyses.  Plasma samples were rapidly thawed in a water bath at 37°C and analysed in one series for each participant. Insulin (pmol/l) and C-peptide (pmol/l) were analysed by a two-site time-resolved immunofluorometric assay (DELFIA) [23]. The insulin assay measures human insulin (endogenous insulin and NPH insulin) but not insulin aspart. Insulin aspart was measured with a modification of the method described by Andersen et al. [24]. Total insulin concentrations in the aspart group were calculated as the sum of human insulin and insulin aspart [25]. Plasma FFA (μmol/l) was analysed by a colorimetric method [26], and glucose, cholesterols and triglycerides (mmol/l) were determined enzymatically with a COBAS INTEGRA (Roche, Mannheim, Germany). Fibrinogen (μmol/l) and CRP (mg/l) were determined with a nephelometric method (Dade Behring, Marburg, Germany). Concentrations of ICAM (ng/ml) were determined by a commercial ELISA method, and vWF (%) was determined by an in-house ELISA method using rabbit anti-human vWF polyclonal IgG as capture and detection antibodies (DAKO, Glostrup, Denmark). Results were expressed relative to a reference plasma calibrated against WHO’s International Standard for vWF (Biopool, Umeå, Sweden).

The inter-assay CVs were as follows: <10% for fibrinogen, <9% for vWF, <6% for ICAM and <6% for CRP.

Statistics.  We decided on a sample size of 78 individuals, N = 2 × ((C + Cß)2 × 2S.D.2/D2), which was based on prothrombin fragment 1 + 2 (F1 + 2) concentrations (F1 + 2 results will be reported in an separate manuscript focusing on coagulation and fibrinolysis variables). We aimed at sufficient power to detect a 110-nmol/l × min. difference in area under the curves (AUC) for F1 + 2 between the two insulin regimens at a significance level of 5% and a power of 90%. This is based on a previous study in which the standard deviation of F1 + 2 AUC was 150 nmol/l × min. [27]. Results for insulin, FFA, triglycerides, LDL cholesterol, CRP, ICAM, vWF and total insulin dose were logarithmically transformed before analysis.

Fasting values were compared between the two insulin regimens using an unpaired t-test. Variation over time in each insulin treatment group was analysed with repeated-measures anova. When significant time effects were found, non-fasting levels were compared with fasting levels by a paired t-test.

Differences in postprandial response between insulin groups were analysed by a repeated-measures anova using insulin group as a fixed factor and age, gender, BMI, hospital and smoking as covariates. To further investigate possible differences between insulin groups, absolute levels of AUC (for the period of 7.30 to 15.30) and the postprandial mean (of results at 13.30 and 15.30) and increases from fasting (incremental) levels of AUC and postprandial mean were selected as summary measures, and the results of the two insulin groups were compared by an unpaired t-test.

The Pearson correlation coefficient (r) was calculated to describe the association between summary measures of glucose, insulin and FFA and markers of inflammation and endothelial function.

Results are presented as mean values (95% CI or S.E.M.) or geometric mean values (geometric 95% CI or S.E.M.). Discontinuous variables are presented as number and percentage and were compared with the chi squared-test. A p-value of <0.05 was considered statistically significant. The SPSS programme version 16.0 (SPSS Inc., Chicago, IL, USA) was used for all statistical analyses.

Results

  1. Top of page
  2. Abstract
  3. Materials and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. Conflict of interests
  8. References

There was no significant difference in HbA1c or in total insulin dose between insulin groups at study entry (table 1). During the meal test (day 21), the total insulin dose also did not differ between the aspart group [42.9 (95% CI 34.3–53.7) IE] and the NPH group [45.0 (95% CI 38.0–53.4) IE] (p = 0.73). Concentrations of glucose and C-peptide increased from fasting levels on NPH insulin (p < 0.001) and decreased on insulin aspart (p < 0.001). On both insulin regimens, there was a significant decrease in FFA (p < 0.001), LDL cholesterol (p < 0.001), HDL cholesterol (p < 0.01) and cholesterol (p < 0.01) and a significant increase in triglycerides (p < 0.001) and insulin (p < 0.001) (figs 2 and 3).

image

Figure 2.  Fasting (7:30) and non-fasting (9.30, 11.30, 13.30 and 15.30) concentrations of glucose (mmol/l), insulin (pmol/l), C-peptide (pmol/l) and free fatty acids (FFA; μmol/l) on NPH insulin (bsl00001; n = 41) and insulin aspart (□; n = 37). Values are mean (S.E.M.) for glucose and C-peptide and geometric mean (geometric S.E.M.) for insulin and FFA. M indicates meals. **p < 0.01, ***p < 0.001 compared with fasting concentrations.

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image

Figure 3.  Fasting (7.30) and non-fasting (9.30, 11.30, 13.30 and 15.30) concentrations of triglycerides (mmol/l), cholesterol (mmol/l), LDL cholesterol (mmol/l) and HDL cholesterol (mmol/l) on NPH insulin (bsl00001; n = 41) and insulin aspart (□; n = 37). Values are mean (S.E.M.) for cholesterol and HDL cholesterol and geometric mean (geometric S.E.M.) for triglycerides and LDL cholesterol. M indicates meals. *p < 0.05, **p < 0.01, ***p < 0.001 compared with fasting concentrations.

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There was a significant decrease in vWF (p < 0.05), CRP (p < 0.05) and ICAM (p < 0.05) compared with fasting concentrations on both insulin regimens, and a minor but significant decrease in fibrinogen on NPH insulin (p < 0.01; fig. 4). Differences between insulin groups were significant for glucose (p < 0.01), C-peptide (p < 0.05), FFA (p < 0.001) and almost significant for vWF (p = 0.051).

image

Figure 4.  Fasting (7.30) and non-fasting (9.30, 11.30, 13.30 and 15.30) concentrations of von Willebrand factor (vWF; %), intercellular adhesion molecules (ICAM; ng/ml), fibrinogen (μmol/l) and C-reactive protein (CRP; mg/l) on NPH insulin (bsl00001; n = 41) and insulin aspart (□; n = 37). Values are mean (S.E.M.) for fibrinogen and geometric mean (geometric S.E.M.) for vWF, CRP and ICAM. M indicates meals. *p < 0.05, **p < 0.01, ***p < 0.001 compared with fasting concentrations.

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Table 2 presents fasting values, AUC and postprandial mean values. Fasting concentrations of glucose and C-peptide were significantly higher on insulin aspart than on NPH insulin. Fasting concentrations of vWF were significantly higher on NPH insulin than on insulin aspart (p = 0.05). The AUC and postprandial means for glucose, C-peptide, FFA and vWF were significantly higher on NPH insulin than on insulin aspart (p = 0.057 for vWF AUC). Similar results were observed for incremental values of AUC and postprandial mean, except for vWF for which the significant differences in AUC and postprandial mean between insulin groups disappeared (not shown).

Table 2.    Fasting concentrations and postprandial summary measures on insulin aspart and NPH insulin.
VariableAspart (n = 37)NPH (n = 41)p-value1
  1. AUC, area under the curves.

  2. Values are mean (95% CI).

  3. 1Difference between response for insulin aspart and NPH insulin.

  4. 2Insulin, free fatty acids (FFA), von Willebrand factor (vWF), intercellular adhesion molecules (ICAM) and C-reactive protein (CRP) were logarithmically transformed before analysis (geometric mean and geometric 95% CI).

Glucose (mmol/l)
 Fasting9.07 (8.27–9.88)6.71 (6.20–7.22)0.000
 AUC (hrs × mmol/l)57.4 (53.0–61.8)71.5 (66.7–76.3)0.000
 Postprandial mean7.37 (6.67–8.06)10.53 (9.66–11.40)0.000
Insulin (pmol/l)2
 Fasting87.4 (64.2–118.9)161.3 (131.4–198.0)0.001
 AUC (hrs × pmol/l)2128 (1705–2656)1853 (1544–2225)0.330
 Postprandial mean246.1 (194.2–311.8)263.2 (218.3–317.4)0.649
C-peptide (pmol/l)
 Fasting1066 (919–1214)650 (540–759)0.000
 AUC (hrs × pmol/l)8693 (6825–10560)11541 (10145–12938)0.002
 Postprandial mean1228 (888–1568)1924 (1685–2164)0.001
FFA (μmol/l)2
 Fasting483 (402–581)455 (389–533)0.622
 AUC (hrs × μmol/l)1692 (1499–1911)2653 (2336–3012)0.000
 Postprandial mean176 (153–202)260 (227–297)0.000
vWF (%)2
 Fasting119 (107–132)138 (124–153)0.050
 AUC (hrs × %)930 (839–1031)1073 (964–1195)0.057
 Postprandial mean115 (104–127)133 (120–148)0.047
ICAM (ng/ml)2
 Fasting276 (261–293)264 (252–277)0.233
 AUC (hrs × ng/ml)2194 (2071–2325)2091 (1992–2196)0.199
 Postprandial mean272 (257–289)261 (248–274)0.247
Fibrinogen (μmol/l)
 Fasting11.20 (10.45–11.94)12.03 (2.31)0.111
 AUC (hrs × μmol/l)89.3 (83.4–95.2)95.42 (18.71)0.147
 Postprandial mean11.10 (10.36–11.83)11.79 (2.38)0.192
CRP (mg/l)2
 Fasting1.84 (1.29–2.61)2.36 (1.74–3.19)0.277
 AUC (hrs × mg/l)14.37 (10.08–20.50)18.42 (13.52–25.11)0.287
 Postprandial mean1.76 (1.23–2.52)2.26 (1.65–3.10)0.294

On both insulin regimens, there was a highly significant positive association between FFA and CRP as to AUC [r = 0.429, p = 0.008 (aspart); r = 0.429, p = 0.005 (NPH)] and postprandial mean [r = 0.408, p = 0.012 (aspart); r = 0.360, p = 0.021 (NPH)]. In the NPH group, there was a significant association between FFA and ICAM as to AUC (r = 0.375, p = 0.016) and postprandial mean (r = 0.322, p = 0.04). In the aspart group, there was a significant association between total insulin and CRP as to AUC (r = 0.367, p = 0.026) and postprandial mean (r = 0.329, p = 0.047), and a significant association between total insulin and ICAM as to AUC (r = 0.543, p = 0.001) and postprandial mean (r = 0.412, p = 0.011).

Discussion

  1. Top of page
  2. Abstract
  3. Materials and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. Conflict of interests
  8. References

As expected, we observed that the two study groups differed significantly in blood glucose levels with the highest fasting concentrations on insulin aspart and the highest postprandial response on NPH insulin (fig. 2, table 2). There was a minor but significant postprandial decrease in vWF, ICAM and CRP on both insulin regimens and a significant decrease in fibrinogen in patients treated with NPH insulin (fig. 4). No significant insulin group differences were observed in postprandial responses for ICAM, CRP, vWF and fibrinogen (table 2).

Earlier studies demonstrated that postprandial or postchallenge hyperglycaemia acutely increases concentrations of ICAM, vWF, fibrinogen and CRP in patients with type 2 diabetes [10,14–19]. We therefore selected these markers to test our hypothesis that treatment aimed at reducing postprandial hyperglycaemia with rapid-acting insulin aspart will have a beneficial postprandial effect on arterial wall dysfunction and inflammation compared with intermediate-acting insulin NPH because of their different effects on postprandial hyperglycaemia.

We were unable to confirm our hypothesis. Several explanations can be proposed. First, both NPH insulin and insulin aspart may prevent a postprandial increase in inflammation and endothelial cell markers compared with no insulin treatment. This cannot be tested in our study because of the absence of a placebo group. Most other studies finding an association between acute hyperglycaemia and e.g. ICAM do so in the absence of insulin treatment [10,14–19], and perhaps there is a threshold for glucose concentrations, above which there is an effect on inflammation and endothelial function. Also, other studies have suggested that insulin dampens the effect of hyperglycaemia on ICAM and vWF [28]. In line with this, Marfella and co-workers demonstrated that the hyperglycaemia-induced rise in ICAM in healthy persons is lowered after one hour because of the action of insulin [16]. In our study, the postprandial insulin levels were comparable in the two insulin groups and might reduce concentrations of vWF, ICAM, CRP and fibrinogen to a similar extent. Also, postprandial levels of total insulin were significantly associated with ICAM and CRP in the aspart group. In contrast, FFA and C-peptide concentrations were affected very differently by the insulin regimens, suggesting that these are not directly involved.

Second, it may be argued that inflammatory reactions were inhibited by the acetylsalicylic acid given to our study participants (75 mg/day), although it has been demonstrated that low-dose acetylsalicylic acid (81 mg/day) does not affect CRP concentrations [29]. As most patients with type 2 diabetes receive low-dose acetylsalicylic acid, our results reflect daily life after a normal meal.

Thus, we find no indication of associations between the postprandial glycaemic level and inflammation and endothelial cell dysfunction. Also, there were no significant correlations between the glucose response (AUC or postprandial mean) and the response of ICAM, CRP, vWF or fibrinogen. Other studies support our observations showing that acute hyperglycaemia decreases vWF [30,31], which might be related to changes in epinephrine and the sympathetic nervous system [31]. Whatever the mechanism, the postprandial reduction in ICAM, vWF, fibrinogen and CRP might suggest a common mechanism. Also, the beneficial effect of reducing postprandial glucose on clinical end-points was recently questioned in a randomized controlled trial (HEART2D) showing that the risk of future cardiovascular disease is similar, when either mealtime insulin or bedtime insulin is used as secondary prevention in patients with type 2 diabetes experiencing a recent acute myocardial infarction [32].

Important strengths of this study include the high number of participants and the fact that the project reflects daily life in patients with type 2 diabetes. The optimal design for studying acute effects of meals in patients with insulin-treated advanced type 2 diabetes is difficult to define and may be affected by the underlying long-term glucose metabolism. We used patients who at least 2 years before were randomized to either insulin NPH once daily at bedtime or insulin aspart three times daily before meals and furthermore were treated with metformin for at least 3 months and acetylsalicylic acid for at least 2 weeks. The patients were well controlled, and we aimed at fairly equal HbA1c despite difference in insulin treatment modality (table 1). Unfortunately, the patients differed with respect to smoking (table 1), which is known to influence some of the variables measured. Smoking was, however, restricted to a minimum during the study day and was adjusted for in the anova. Also, the results were confirmed when analysed in non-smokers only (not shown). During the project, the patients were served standard diabetic meals according to their appetite to obtain a normal diabetic dietary response. Such a regimen is more physiologically relevant than an oral glucose tolerance test in patients with type 2 diabetes not receiving hypoglycaemic medication. The selected risk markers were not among the primary effect variables in the power calculation, and we cannot exclude that we were unable to detect true differences in AUC or postprandial mean because of type 2 errors. It has been discussed whether the absolute postprandial level or the incremental response is the best measure of acute hyperglycaemia [33]. We analysed both measures and we found no differences. A limitation of our study was the absence of a placebo group, but the aim was to compare the effect of two different insulin regimens on the postprandial response.

In conclusion, the rapid-acting insulin analogue insulin aspart and the intermediate-acting insulin NPH had the same postprandial effect on markers of endothelial cell dysfunction (ICAM and vWF) and markers of inflammation (CRP and fibrinogen) despite marked differences in postprandial hyperglycaemia. This suggests that these insulin regimens are equally effective regarding postprandial inflammation and endothelial cell dysfunction in well-controlled patients with type 2 diabetes.

Acknowledgements

  1. Top of page
  2. Abstract
  3. Materials and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. Conflict of interests
  8. References

Nurses Lise Gedebjerg, Marianne Bøtcher and Vibe Jensen are kindly thanked for taking good care of the patients during the study days. Technicians Kathrine Overgaard, Anette Larsen, Gunhild Andreasen, Lone Hansen and Charlotte Olsen are kindly thanked for handling the blood samples, and the kitchen staff at the Hospital of Southwest Denmark is thanked for cooking the meals. The study was financed by research grants from Ribe County and Novo Nordisk, Denmark. The pharmaceutical company Novo Nordisk supplied the study medication.

Conflict of interests

  1. Top of page
  2. Abstract
  3. Materials and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. Conflict of interests
  8. References

Jan Erik Henriksen has received a fee as a member of the Novo Advisory Board (not related to this study).

References

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  2. Abstract
  3. Materials and Methods
  4. Results
  5. Discussion
  6. Acknowledgements
  7. Conflict of interests
  8. References
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