Abstract
Type 1 diabetes mellitus (DM1) is characterized by high serum HDL, which does not translate into a better prognosis. It is probably related to the impaired function of HDL particles. One of the functions of HDL is reverse cholesterol transport (cholesterol efflux capacity, CEC). Beneficial for management and prognosis in DM1 is the occurrence of partial clinical remission (pCR). It is not known whether the changes in CEC are related to the presence of pCR. The aim was to evaluate the relationship between CEC and pCR in newly diagnosed DM1 during 12 months. The analysis comprised 127 adults (68% men) with newly diagnosed DM1. CEC was assessed in UT Southwestern Medical Center by measuring the efflux of radiolabeled cholesterol from murine J774 macrophages to apolipoprotein B-depleted serum. The study was performed at two points: at disease onset and after 1 year. pCR was defined as insulin dose-adjusted A1C as A1C (percent) + (4 × insulin dose) ≤9. After 1 year of observation, a significant increase in serum HDL concentration and no change in CEC were demonstrated in the whole group (1.28 (1.11–1.41) vs 1.23 (1.14–1.42), P = 0.6). There was a CEC improvement in women with pCR after 1 year 1.28 (1.04–1.38) vs 1.31 (1.08–1.42), P = 0.05. No relationship was revealed between pCR and CEC (OR 1.8 (CI 95% 0.12–26.8), P = 0.7). In DM1, during the first year of the disease, there was no improvement in CEC despite a significant increase in serum HDL cholesterol concentration. There was no relationship between CEC and pCR. Good metabolic control in pCR has a beneficial impact on CEC.
Article highlights
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Increased HDL serum cholesterol concentration is not associated with improved HDL function.
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HDL particles are functionally impaired from the onset of type 1 diabetes.
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There is no relationship between cholesterol efflux capacity and clinical remission of type 1 diabetes.
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A change in viewpoint on high HDL cholesterol levels in people with type 1 diabetes as a protective factor for the development of diabetes complications and the awareness that HDL cholesterol levels alone are insufficient to assess the cardiovascular risk in this group of patients.
ClinicalTrials number
NCT02306005.
Introduction
Cardiovascular diseases (CVDs) are the leading cause of morbidity and mortality in patients with type 1 diabetes mellitus (1). In type 1 diabetes mellitus, strict glycemic control achieved by intensive insulin treatment can be beneficial for preventing premature cardiovascular events, the major complication of the disease (2). One of the most relevant CVD risk factors is dyslipidemia. The atherogenic lipoprotein profile is characterized by low levels of high-density lipoprotein cholesterol (HDL-C), higher levels of triglycerides, increased oxidized low-density lipoprotein (LDL) particles, and a decrease in reverse cholesterol transport (RCT), i.e., low HDL cholesterol efflux capacity (CEC) (3, 4, 5). While plasma levels of HDL predict the risk of CVD at the epidemiological level, a direct causal role of HDL in CVD remains controversial (6). People with type 1 diabetes mellitus are mainly characterized by high serum HDL concentration (7), resulting from the antilipolytic activity of insulin, which leads to an increase in HDL-C levels, even to extremely high levels (8). It is important to note that higher HDL-C concentrations do not translate into a better prognosis in this group (9, 10). There are data about extremely high HDL-C’s harmful impact on CVD risk with a U-shape relationship (11). Moreover, recent observational studies have confirmed that the atheroprotective effect of properly functioning HDL cholesterol is frequently impaired in clinical states associated with oxidative stress (12). Given the role of oxidative stress in the onset and progression of diabetes and its complications, consideration of HDL function, not cholesterol concentration, seems to be crucial (13). It is well-known that HDL particles (HDL-P) are highly diverse, comprising many subtypes that vary in size, density, concentration, and composition. This heterogeneity is also likely to confer functional diversity, reinforcing the need for validated assays of HDL function. The primary function of HDL-P is to promote RCT, by which excess cellular cholesterol from peripheral tissues is returned to the liver for elimination. This is a critical mechanism through which HDL-P exerts a protective effect on the development of atherosclerosis (14). The question is if this function influences beta cells and promotes clinical remission. Clinical remission in type 1 diabetes mellitus is a beneficial phenomenon, with a protective impact on the course of type 1 diabetes mellitus and the development of chronic complications (15).
A key step in RCT is cellular cholesterol efflux capacity (CEC), indicating the ability of HDL to remove cholesterol from the cells, i.e., macrophages (16). CEC represents a crucial indicator of this HDL function, and it has been suggested that deterioration in CEC is a significant predictor of CVD, independent of the HDL cholesterol level (17, 18).
Moreover, cholesterol efflux pathways exert anti-atherogenic and anti-inflammatory effects by inhibiting the proliferation of hematopoietic stem and progenitor cells and inflammasome activation in macrophages (19).
There is strong evidence that the content of HDL cholesterol does not directly reflect its protective action and that other indicators better predict the role of HDL in protecting vessels (6, 20). The impaired function of HDL particles was proved in a study by Gourgari et al. in which youth with type 1 diabetes mellitus have proteomic alterations of their HDL compared to the control group without diabetes despite similar concentrations of HDL cholesterol (5). Increasing evidence suggests differences in the pathophysiology of atherosclerosis in individuals with type 1 diabetes mellitus compared to those without diabetes. Among them, differences in the composition of atherosclerotic plaques are mentioned (21).
To date, it is not known whether the quantitative changes in HDL cholesterol observed within the first year of therapy of type 1 diabetes mellitus are accompanied by an improvement in HDL function. For this purpose, HDL cholesterol efflux capacity in adults with newly diagnosed type 1 diabetes mellitus in response to insulin initiation was evaluated during a 12-month follow-up. The assessment of the relationship of CEC with clinical remission and sex was performed.
Methods
Patients
This prospective observational study included 127 adults (68% men), participants of Insulin Therapy and Lipoproteins’ Profile in Type 1 Diabetes Study (InLipoDiab1; NCT02306005), from the onset of disease (the blood collection was performed before the first exogenous insulin administration) and for 12 months after insulin initiation (±2 weeks).
The autoimmune etiology was confirmed in all patients by positive specific autoantibodies. The patients were treated with intensive functional insulin (IFI) therapy using insulin pens from the onset of the disease. All subjects participated in the same educational program in intensive insulin therapy. This program trained patients to self-adjust insulin doses before meals, depending on the target glycemia, carbohydrates consumed, physical activity, and the insulin sensitivity index. The previous study by Cieluch et al. (8) described the methodology.
Exclusion criteria included age under 18 and above 35 years, comorbidities and medication use for disorders other than type 1 diabetes mellitus, a lack of written consent, other types of diabetes, pregnancy, lipid-lowering drugs, and hyper- or hypothyroidism.
Partial clinical remission
The endpoint was the presence of partial clinical remission (pCR), defined as an insulin dose-adjusted A1C (IDAA1C) as A1C (percent) + (4 × insulin dose (units per kilogram per 24 h)) ≤9, according to the definition by Mortensen et al. (22), which reflects the functionality of beta cells. The daily dose of insulin (DDI) was defined as the requirement for exogenous insulin per kilogram of body weight per day. The DDI at baseline was calculated from the last 2 days before the end of hospitalization, and the DDI after the year from diagnosis was based on data derived from patients’ self-monitoring logs from the prior month. The group was divided into two subgroups according to the presence and absence of pCR at the end of observation.
Laboratory analysis
The measurement of HbA1c concentration was assessed by a turbidimetric inhibition immunoassay (Cobas 6000, Roche Diagnostics, Switzerland). Cholesterol efflux capacity was assessed in collaboration with the UT Southwestern Medical Center, USA, by measuring the efflux of radiolabelled cholesterol from murine J774 macrophages to apolipoprotein B-depleted serum. The study was performed at two points: before the first administration of exogenous insulin and after 1 year of intensive insulin therapy.
Data and resource availability
Data and critical resources supporting the results reported in the article are available from the corresponding author.
Statistical analysis
The statistical analysis was performed using STATISTICA 13.0 and STATA BE18. All data were expressed as the median values and interquartile ranges (IQRs) and as a number (percentage) of patients. The normality of distributions was tested using the Kolmogorov–Smirnov’s test with Lilliefors correction. Due to a lack of normality, nonparametrical tests were performed. First, patients were divided into two groups according to the presence of partial clinical remission at follow-up. The Mann–Whitney test was used for continuous variables, and the Chi2 test was used for dichotomous variables. Correlation analysis was performed using the Spearmen test. For the assessment of changes during 12 months of observation, a Wilcoxon test was performed. Looking for factors that may influence the occurrence of pCR, the impact of CEC was investigated in the multiple logistic regression model adjusted for age at onset and smoking. Sex was considered a factor in the statistical analysis of the data. The differences with a probability value of less than 0.05 were considered significant.
Results
Changes in clinical characteristics during follow-up according to sex and remission status
After 12-month observation, 93 participants achieved pCR (73%) in the whole group and 32 (80%) and 61 (70%), respectively, in women and men. Characteristics and comparisons of groups with and without clinical remission, according to sex, are presented in Tables 1, 2, and 3. During the 12-month observation, there were significant changes in metabolic control, such as improvement in HbA1c and lipid profile. Changes in characteristics during the observation period, according to sex and clinical remission status, are presented in Tables 4 and 5. According to lipid profile and anthropometric data, there were significant differences between women and men.
Characteristics and comparison of groups with and without clinical remission (Mann–Whitney and Chi2) – the whole group.
| Baseline data | All n = 127 | pCR yes n = 93 | pCR no n = 34 | P |
|---|---|---|---|---|
| Age (years) | 27 (22–32) | 27 (23–32) | 26 (24–33) | 0.200 |
| Sex (M) n (%) | 87 (68%) | 61 (66%) | 26 (76%) | 0.100 |
| Body weight (kg) | 70.9 (59.9–80.0) | 70.9 (59.9–78.9) | 71.8 (60.3–81.8) | 0.800 |
| BMI (kg/m2) | 22.2 (20.6–24.6) | 22.1 (20.2–24.6) | 22.7 (19.2–24.5) | 0.900 |
| Body weight before DM (kg) | 78 (64–86) | 78 (64–88) | 78 (64–85) | 0.900 |
| Waist (cm) | 82 (74–90) | 82 (73–90) | 82 (77–90) | 0.400 |
| WHR | 0.83 (0.78–0.88) | 0.82 (0.77–0.88) | 0.84 (0.80–0.89) | 0.100 |
| AGE (AF) | 1.7 (1.5–1.9) | 1.7 (1.5–1.9) | 1.8 (1.5–2.0) | 0.400 |
| Hba1c % | 11.2 (9.8–12.5) | 11.0 (9.7–12.5) | 11.5 (10.2–12.4) | 0.300 |
| HbA1c (mmol/mol) | 99 (84–113) | 97 (83–113) | 102 (88–112) | |
| Total cholesterol (mmol/L) | 4.35 (3.70–5.08) | 4.35 (3.78–5.02) | 4.20 (3.63–5.28) | 0.900 |
| HDL-CH (mmol/L) | 1.19 (0.93–1.42) | 1.22 (1.01–1.42) | 1.06 (0.83–1.37) | 0.070 |
| LDL-CH (mmol/L) | 2.49 (1.94–3.06) | 2.54 (1.94–2.95) | 2.38 (1.84–3.32) | 0.700 |
| TG (mmol/L) | 1.20 (0.87–1.73) | 1.22 (0.92–1.58) | 1.10 (0.86–1.88) | 0.900 |
| Non-HDL (mmol/L) | 3.16 (2.46–3.94) | 3.16 (2.54–3.78) | 3.21 (2.23–4.40) | 0.700 |
| DDI (u/kg/d) | 0.16 (0.10–0.27) | 0.12 (0.09–0.28) | 0.22 (0.13–0.27) | 0.030 |
| Smokers n (%) | 57 (45%) | 38 (41%) | 19 (56%) | 0.080 |
Significant values are in bold. P < 0.050 was assumed to be significant. Abbreviations: BMI, body mass index; DM, diabetes mellitus; AGE, advanced glycation end-products; HDL-CH, high-density lipoprotein cholesterol; LDL-CH, low-density lipoprotein cholesterol; TG, triglycerides; DDI, daily dose of insulin.
Characteristics and comparison of groups with and without clinical remission (Mann–Whitney and Chi2) – in women.
| Baseline data women | All n = 40 | pCR yes n = 32 | pCR no n = 8 | P |
|---|---|---|---|---|
| Age (years) | 23 (20–30) | 24 (22–32) | 24 (23–24) | 0.008 |
| Body weight (kg) | 54 (50–64) | 54 (50–67) | 52 (49–59) | 0.600 |
| BMI (kg/m2) | 20 (18–23) | 20 (18–23) | 20 (18–24) | 0.900 |
| Body weight before DM (kg) | 57 (54–74) | 59 (54–76) | 56 (54–64) | 0.600 |
| Waist (cm) | 71 (66–79) | 70 (66–79) | 76 (67–80) | 0.400 |
| WHR | 0.77 (0.74–0.82) | 0.76 (0.73–0.81) | 0.81 (0.78–0.84) | 0.020 |
| AGE (AF) | 1.6 (1.4–1.8) | 1.6 (1.4–1.8) | 1.7 (1.5–2.0) | 0.300 |
| Hba1c % | 10.6 (9.3–12.6) | 10.7 (9.0–12.5) | 10.4 (9.8–13.8) | 0.700 |
| HbA1c (mmol/moL) | 92 (78–114) | 93 (75–113) | 90 (84–127) | |
| Total cholesterol (mmol/L) | 3.99 (3.63–4.35) | 4.04 (3.68–4.53) | 3.70 (3.47–4.01) | 0.100 |
| HDL-CH (mmol/L) | 1.35 (1.17–1.58) | 1.35 (1.19–1.50) | 1.40 (0.98–1.66) | 0.9 |
| LDL-CH (mmol/L) | 2.02 (1.84–2.51) | 2.23 (1.84–2.59) | 1.89 (1.76–2.05) | 0.080 |
| TG (mmol/L) | 0.97 (0.84–1.40) | 1.07 (0.87–1.40) | 0.90 (0.80–1.36) | 0.600 |
| Non-HDL (mmol/L) | 2.54 (2.25–2.90) | 2.69 (2.43–2.93) | 2.28 (2.18–2.49) | 0.050 |
| DDI (u/kg/d) | 0.13 (0.11–0.24) | 0.12 (0.10–0.22) | 0.23 (0.13–0.33) | 0.040 |
| Smokers n (%) | 13 (32%) | 12 (38%) | 1 (12%) | 0.200 |
Significant values are in bold. P < 0.050 was assumed to be significant. Abbreviations: BMI, body mass index; DM, diabetes mellitus; AGE, advanced glycation end-products; HDL-CH, high-density lipoprotein cholesterol; LDL-CH, low-density lipoprotein cholesterol; TG, triglycerides; DDI, daily dose of insulin.
Characteristics and comparison of groups with and without clinical remission (Mann–Whitney and Chi2) – in men.
| Baseline data men | All n = 87 | pCR yes n = 61 | pCR no n = 26 | P |
|---|---|---|---|---|
| Age (years) | 28 (25–32) | 28 (25–32) | 27 (25–30) | 0.500 |
| Body weight (kg) | 76 (67–82) | 76 (68–82) | 75 (65–82) | 0.500 |
| BMI (kg/m2) | 23 (21–25) | 23 (21–26) | 23 (20–24) | 0.500 |
| Body weight before DM (kg) | 82 (74–90) | 82 (74–90) | 81 (73–86) | 0.500 |
| Waist (cm) | 85 (80–92) | 85 (80–92) | 87 (80–91) | 0.900 |
| WHR | 0.87 (0.80–0.91) | 0.87 (0.80–0.91) | 0.85 (0.80–0.92) | 0.800 |
| AGE | 1.8 (1.5–2.0) | 1.7 (1.6–2.0) | 1.8 (1.4–2.0) | 0.800 |
| Hba1c % | 11.4 (10.0–12.5) | 11.1 (10.0–12.5) | 11.7 (10.9–12.2) | 0.400 |
| HbA1c (mmol/moL) | 101 (86–113) | 98 (86–113) | 104 (96–110) | |
| Total cholesterol (mmol/L) | 4.66 (3.96–5.59) | 4.58 (3.99–5.46) | 4.82 (3.78–5.67) | 0.800 |
| HDL-CH (mmol/L) | 1.11 (0.93–1.40) | 1.17 (0.96–1.40) | 1.06 (0.70–1.35) | 0.060 |
| LDL-CH (mmol/L) | 2.82 (2.28–3.44) | 2.82 (2.31–3.29) | 2.87 (2.28–3.44) | 0.800 |
| TG (mmol/L) | 1.24 (0.93–1.98) | 1.22 (0.94–1.92) | 1.30 (0.86–3.45) | 0.800 |
| Non-HDL (mmol/L) | 3.47 (2.67–4.48) | 3.42 (2.62–4.25) | 3.47 (2.77–4.61) | 0.500 |
| DDI (u/kg/d) | 0.18 (0.10–0.29) | 0.15 (0.09–0.30) | 0.22 (0.11–0.27) | 0.200 |
| Smokers n (%) | 44 (51%) | 26 (43%) | 18 (69%) | <0.001 |
Significant values are in bold. P < 0.050 was assumed to be significant. Abbreviations: BMI, body mass index; DM, diabetes mellitus; AGE, advanced glycation end-products; HDL-CH, high-density lipoprotein cholesterol; LDL-CH, low-density lipoprotein cholesterol; TG, triglycerides; DDI, daily dose of insulin.
Changes during the observation time for the whole group and according to sex (Wilcoxon).
| Data | All | F | M |
P M vs F 1 year |
P M vs F baseline | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Baseline | 1 year | P | Baseline | 1 year | P | Baseline | 1 year | P | |||
| Weight (kg) | 70.9 (59.9–80.0) | 72 (63–82) | <0.001 | 54 (50–64) | 58 (53–66) | <0.001 | 76 (67–82) | 77 (69–84) | <0.001 | <0.001 | <0.001 |
| BMI (kg/m2) | 22.2 (20.6–24.6) | 23 (21–25) | <0.001 | 20 (18–23) | 22 (20–24) | 0.001 | 23 (21–25) | 23 (21–26) | <0.001 | 0.009 | <0.001 |
| Waist (cm) | 82 (74–90) | 80 (74–87) | 0.500 | 71 (66–79) | 74 (68–78) | 0.200 | 85 (80–92) | 83 (80–89) | 1.0 | <0.001 | <0.001 |
| WHR | 0.83 (0.78–0.88) | 0.81 (0.75–0.85) | 0.030 | 0.77 (0.74–0.82) | 0.74 (0.72–0.79) | 0.200 | 0.87 (0.80–0.91) | 0.83 (0.80–0.86) | 0.1 | <0.001 | <0.001 |
| AGE | 1.7 (1.5–1.9) | 1.8 (1.6–1.9) | 0.010 | 1.6 (1.4–1.8) | 1.7 (1.5–1.9) | 0.020 | 1.8 (1.5–2.0) | 1.8 (1.6–2.0) | 0.2 | 0.300 | 0.090 |
| HbA1c % | 11.2 (9.8–12.5) | 6.7 (6.0–7.4) | <0.001 | 10.6 (9.3–12.6) | 6.8 (6.0–7.3) | <0.001 | 11.4 (10.0–12.5) | 6.6 (6.0–7.6) | <0.001 | 0.900 | 0.700 |
| HbA1c (mmol/moL) | 99 (84–113) | 50 (42–57) | 92 (78–114) | 51 (42–56) | 101 (86–113) | 49 (42–60) | |||||
| Total cholesterol (mmol/L) | 4.35 (3.70–5.08) | 4.56 (4.09–5.10) | 0.040 | 3.99 (3.63–4.35) | 4.45 (4.09–5.00) | 0.002 | 4.66 (3.69–5.59) | 4.61 (4.07–5.13) | 0.8 | 0.200 | <0.001 |
| HDL-CH (mmol/L) | 1.19 (0.93–1.42) | 1.71 (1.45–2.12) | <0.001 | 1.35 (1.17–1.58) | 2.07 (1.58–2.41) | <0.001 | 1.11 (0.93–1.40) | 1.66 (1.42–1.94) | <0.001 | <0.001 | 0.008 |
| LDL-CH (mmol/L) | 2.49 (1.94–3.06) | 2.33 (1.71–2.93) | 0.001 | 2.02 (1.84–2.51) | 1.79 (1.61–2.46) | 0.400 | 2.82 (2.28–3.44) | 2.51 (1.81–2.98) | 0.001 | 0.003 | <0.001 |
| TG (mmol/L) | 1.20 (0.87–1.73) | 0.81 (0.60–1.16) | <0.001 | 0.97 (0.84–1.40) | 0.75 (0.52–1.02) | <0.001 | 1.24 (0.93–1.98) | 0.90 (0.68–1.20) | <0.001 | 0.060 | 0.030 |
| Non-HDL (mmol/L) | 3.16 (2.46–3.94) | 2.75 (2.10–3.47) | <0.001 | 2.54 (2.25–2.90) | 2.23 (1.94–2.90) | 0.300 | 3.47 (2.67–4.48) | 2.90 (2.20–3.52) | <0.001 | 0.004 | <0.001 |
| DDI (u/kg/d) | 0.16 (0.10–0.27) | 0.33 (0.21–0.47) | <0.001 | 0.13 (0.11–0.24) | 0.33 (0.23–0.49) | <0.001 | 0.18 (0.10–0.29) | 0.33 (0.17–0.47) | <0.001 | 0.600 | 0.800 |
Significant values are in bold. P < 0.050 was assumed to be significant. Abbreviations: BMI, body mass index; DM, diabetes mellitus; AGE, advanced glycation end-products; HDL-CH, high-density lipoprotein cholesterol; LDL-CH, low-density lipoprotein cholesterol; TG, triglycerides; DDI, daily dose of insulin.
Changes during the observation time for the whole group and according to clinical remission status (Wilcoxon).
| Data | All | pCR yes | pCR no | P (pCR yes vs no 1st year) | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Baseline | 1 year | P | Baseline | 1 year | P | Baseline | 1 year | P | ||
| Weight (kg) | 70.9 (59.9–80.0) | 72 (63–82) | <0.001 | 70.9 (59.9–78.9) | 73 (63–82) | <0.001 | 71.8 (60.3–81.8) | 72 (63–78) | 0.050 | 0.900 |
| BMI (kg/m2) | 22.2 (20.6–24.6) | 23 (21–25) | <0.001 | 22.1 (20.2–24.6) | 23 (20–26) | <0.001 | 22.7 (19.2–24.5) | 22 (21–25) | 0.050 | 0.900 |
| Waist (cm) | 82 (74–90) | 80 (74–87) | 0.500 | 82 (73–90) | 80 (74–87) | 1.000 | 82 (77–90) | 81 (77–86) | 0.300 | 0.700 |
| WHR | 0.83 (0.78–0.88) | 0.81 (0.75–0.85) | 0.030 | 0.82 (0.77–0.88) | 0.80 (0.75–0.85) | 0.030 | 0.84 (0.80–0.89) | 0.82 (0.79–0.85) | 1.000 | 0.500 |
| AGE | 1.7 (1.5–1.9) | 1.8 (1.6–1.9) | 0.010 | 1.7 (1.5–1.9) | 1.7 (1.6–1.9) | 0.060 | 1.8 (1.5–2.0) | 1.8 (1.6–2.2) | 0.070 | 0.100 |
| HbA1c % | 11.2 (9.8–12.5) | 6.7 (6.0–7.4) | <0.001 | 11.0 (9.7–12.5) | 6.3 (5.8–6.8) | <0.001 | 11.5 (10.2–12.4) | 8.1 (7.4–9.3) | <0.001 | <0.001 |
| HbA1c (mmol/moL) | 99 (84–113) | 50 (42–57) | 97 (83–113) | 45 (40–51) | 102 (88–112) | 65 (57–78) | ||||
| Total cholesterol (mmol/L) | 4.35 (3.70–5.08) | 4.56 (4.09–5.10) | 0.040 | 4.35 (3.78–5.02) | 4.45 (4.04–5.02) | 0.200 | 4.20 (3.63–5.28) | 4.82 (4.17–5.15) | 0.080 | 0.100 |
| HDL-CH (mmol/L) | 1.19 (0.93–1.42) | 1.71 (1.45–2.12) | <0.001 | 1.22 (1.01–1.42) | 1.76 (1.48–2.12) | <0.001 | 1.06 (0.83–1.37) | 1.68 (1.42–2.12) | <0.001 | 0.500 |
| LDL-CH (mmol/L) | 2.49 (1.94–3.06) | 2.33 (1.71–2.93) | 0.001 | 2.54 (1.94–2.95) | 2.25 (1.71–2.67) | <0.001 | 2.38 (1.84–3.32) | 2.69 (1.79–3.03) | 0.800 | 0.100 |
| TG (mmol/L) | 1.20 (0.87–1.73) | 0.81 (0.60–1.116) | <0.001 | 1.22 (0.92–1.58) | 0.81 (0.60–1.12) | <0.001 | 1.10 (0.86–1.88) | 0.94 (0.64–1.64) | 0.080 | 0.200 |
| Non-HDL (mmol/L) | 3.16 (2.46–152) | 2.75 (2.10–3.47) | <0.001 | 3.16 (3.54–3.78) | 2.62 (2.07–3.39) | <0.001 | 3.21 (2.23–4.40) | 3.11 (2.25–3.78) | 0.200 | 0.080 |
| DDI (u/kg/d) | 0.16 (0.10–0.27) | 0.33 (0.21–0.47) | <0.001 | 0.12 (0.09–0.28) | 0.26 (0.14–0.36) | <0.001 | 0.22 (0.13–0.27) | 0.52 (0.41–0.72) | <0.001 | <0.001 |
Significant values are in bold. P < 0.050 was assumed to be significant. Abbreviations: BMI, body mass index; DM, diabetes mellitus; AGE, advanced glycation end-products; HDL-CH, high-density lipoprotein cholesterol; LDL-CH, low-density lipoprotein cholesterol; TG, triglycerides; DDI, daily dose of insulin.
Changes in cholesterol efflux capacity during follow-up according to sex and remission status
CEC did not change significantly during the observation despite HDL-C being significantly higher after 1 year. There were no differences between groups with and without pCR except for higher CEC after 1 year compared to baseline in a group with pCR, which can be related to better metabolic control in this group. CEC changes and differences between groups with and without clinical remission according to sex are presented in Tables 6, 7, and 8.
Changes and comparison of CEC in the whole group (M–W and Wilcoxon).
| Data ALL | All | pCR yes | pCR no | P (M–W) |
|---|---|---|---|---|
| CEC baseline | 1.28 (1.11–1.41) | 1.29 (1.13–1.39) | 1.24 (1.09–1.42) | 0.700 |
| CEC 1 year | 1.23 (1.14–1.42) | 1.27 (1.13–1.42) | 1.19 (1.14–1.37) | 0.300 |
| P (Wilcoxon) | 0.600 | 0.300 | 1.000 |
CEC, cholesterol efflux capacity.
Changes and comparison of CEC in women (M–W and Wilcoxon).
| Data women | All | pCR yes | pCR no | P (M–W) |
|---|---|---|---|---|
| CEC baseline | 1.27 (1.08–1.39) | 1.28 (1.04–1.38) | 1.25 (1.12–1.57) | 0.300 |
| CEC 1 year | 1.28 (1.15–1.42 | 1.31 (1.08–1.42) | 1.19 (1.15–1.37) | 0.800 |
| P (Wilcoxon) | 0.200 | 0.050 | 0.600 |
CEC, cholesterol efflux capacity.
Changes and comparison of CEC in men (M–W and Wilcoxon).
| Data men | All | pCR yes | pCR no | P (M–W) |
|---|---|---|---|---|
| CEC baseline | 1.29 (1.12–1.42) | 1.29 (1.17–1.44) | 1.23 (1.05–1.42) | 0.200 |
| CEC 1 year | 1.21 (1.13–1.41) | 1.25 (1.13–1.42) | 1.19 (1.11–1.36) | 0.800 |
| P (Wilcoxon) | 1.000 | 0.600 | 0.200 |
CEC, cholesterol efflux capacity.
Results of correlation and regression analysis
Correlation analysis revealed a negative association between CEC at 1 year and advanced glycation end-products at baseline (Rs −0.25, P = 0.0005), weight at 1 year (Rs = −0.18, P = 0.04), and BMI at 1 year (Rs = −0.21, P = 0.02). In multivariate logistic regression, no relationship between CEC and the presence of clinical remission was revealed, adjusted for age at onset and smoking OR 1.8 (CI 95% 0.12–26.8), P = 0.7, and subanalysis in the group of men and women, respectively P = 0.2 and 0.3.
Discussion
In this study, we found that despite a significant increase in serum HDL-C concentration, CEC, a key anti-atherosclerotic HDL function, did not improve in the first year of type 1 diabetes mellitus. Moreover, no relationship between CEC and clinical remission was observed.
Changes in HDL-C
Individuals with type 1 diabetes mellitus and optimal glycemic control have a less atherogenic standard lipid profile (23), especially concerning triglyceride and HDL cholesterol levels, that relates to youth and adults (24, 25), and was classically explained by insulin treatment. Optimal glycemic control due to intensive insulin treatment improves lipid parameters. On the other hand, it has been suggested that the impact on lipid metabolism may be independent of glycemic control, given the differences in exogenous insulin bioavailability and the different mechanisms of insulin action on glucose and lipids (26). Exogenous insulin is not transmitted through the liver. Improvement of lipid parameters relates to the normalization of lipoprotein lipase due to insulin administration. Two independent factors may contribute to the increase of HDL-C concentration: both effective catabolism of TG due to increased lipoprotein lipase activity and hyperadiponectinemia, which is observed in type 1 diabetes mellitus (27, 28, 29).
Changes in HDL-P function
A possible explanation for the lack of improvement in CEC in this group may be hyperglycemia and oxidative stress and the presence of immune processes that occur in the type 1 diabetes mellitus pathophysiology (30). Both can cause irreversible posttranslational modification of HDL particles and may affect HDL function (7). Our results revealed a negative correlation between baseline advanced glycation end-products and CEC. It is known that there is a feedback loop between inflammation and reduced cholesterol secretion/RCT (19). Moreover, in the group with pCR, CEC after 1 year was higher than baseline, which can be related to better metabolic control in this group, because this group characterized very good metabolic control from the beginning of the disease (Supplementary Table (see section on Supplementary materials given at the end of the article)). Given the positive correlation between cholesterol efflux capacity and concentrations of HDL cholesterol and apolipoprotein A-I (apoA-I) (17, 31), other results could have been expected. However, an increase in HDL-C or apoA-I concentrations does not necessarily imply an increase in cholesterol efflux capacity (32). Observation by Khera et al. suggests that HDL cholesterol level was a significant predictor of efflux capacity, but accounted for only 26% of the observed variation (17). A study by Gourgari et al. revealed that youth with type 1 diabetes mellitus have altered proteomic profiles of their HDL particles, compared to the control group without DM, despite similar concentrations of HDL cholesterol (32). This suggests that the function of HDL particles is impaired in these individuals (5). Interestingly, our study revealed that those destructive processes are already present at the beginning of the disease. What is more, current data show that HDL cholesterol levels are becoming an insufficient predictor of CVD. Paradoxically high HDL cholesterol concentrations were associated with a high risk of composite CVD outcomes in individuals with or without diabetes (9, 11). Saleheen et al. observed in a group of 25,639 individuals aged 40–79 years that CEC is significantly and inversely associated with incident coronary heart disease events, regardless of other established CVD risk factors, even after adjusting for HDL cholesterol or apoA-I concentrations. When analyses were adjusted for CEC, the previously observed inverse association between HDL cholesterol or apoA-I levels and the risk of coronary heart disease became insignificant (31). These data indicate that a high HDL-C level alone may not be protective against CVD in people with diabetes, and other factors may contribute to this risk in those individuals. No research to date has investigated the relationship between HDL levels and CEC. However, data from an animal model study indicate that, in alloxan-induced T1D mice, the in vivo macrophage-to-feces RCT was 20% lower despite increased biliary sterol secretion rates. Given that the HDL-mediated efflux from macrophage foam cells remains unchanged, it was suggested that the underlying mechanism for decreased RCT in type 1 diabetes mellitus mice decreased the properties of glycated HDL to function in hepatic selective uptake rather than changes in the efflux capacity of HDL (33). In humans with similar HDL cholesterol levels, differences in macrophage-specific cholesterol efflux were not combined with HDL-C levels but because of differences in the concentration of pre-beta-1 HDL (34). The results of the Dallas Heart Study by Rohatgi et al. suggested that the processes that govern cholesterol efflux capacity may be independent of those underlying the link between adiposity or insulin resistance and HDL cholesterol level (3). This may indicate that cholesterol efflux capacity reflects a biological process not represented by traditional risk factors.
HDL function and remission
There is no association or relationship between CEC and the presence of clinical remission. However, HDL-P has many other functions that may influence beta cell function, which is not yet explored. There is a hypothesis that the adequate cholesterol level in the cells is responsible for their proper function and development. Thus, maybe not increased CEC helps those cells survive and prevent their apoptosis? There are still many questions in this matter. Further observation and assessment of other HDL functions of those patients may give answers. What our analysis confirmed is a relationship between smoking and less chances to achieve remission in the male group. Similar observations were previously made and smoking is a confirmed harmful factor according to remission presence (15). In our project, smokers mainly were men, which may explain why significant differences were present only in this subgroup.
Limitations
There are several limitations to this study. It is a single-site, observational study, which may impact the generalizability of our findings. We did not verify the HDL particle number, which is suggested as a stronger inverse predictor of CVD than HDL-C concentration and CEC (17). Furthermore, we did not test the protein alterations on HDL, which also could play a role in modifying HDL function, although in young adults with type 1 diabetes mellitus, proteomic alterations of HDL did not correlate with CEC (5). In addition, the genetic conditions and epigenetics mechanisms were not considered (6). However, we wanted to focus on the most straightforward and cheapest methods to reveal their usefulness to this group. The duration of observation is 1 year, which can be too short to reveal significant relationships. However, pCR is the most characteristic phenomenon for the first 12 months of type 1 diabetes mellitus. The groups are still in prospective observation.
Conclusions
In DM1, during the first year of the disease, there is no improvement in CEC despite a significant increase in serum HDL cholesterol concentration. There is no relationship between CEC and pCR. Good metabolic control in pCR group has a beneficial impact on CEC. This study reveals some possible directions for future research to bring us closer to fully understanding the HDL particle and its role in individuals with type 1 diabetes mellitus. It remains to be determined whether HDL dysfunction results from an interaction between inflammatory response, oxidative stress, and hyperglycemia in type 1 diabetes mellitus or is actually the driver of pathological events. We do not know if the improvement of HDL function occurs later than a year after the diagnosis of type 1 diabetes mellitus. The influence of compositional changes on HDL function is not yet fully known. Future efforts should investigate the role of HDL-P-associated proteins in HDL function and their role in CVD risk in patients with type 1 diabetes mellitus. In light of the presented findings, a better diagnostic marker than HDL cholesterol level is needed.
Supplementary materials
This is linked to the online version of the paper at https://doi.org/10.1530/EC-24-0704.
Declaration of interest
The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the work reported.
Funding
The study was supported by the Polish National Agency for Academic Exchange (Narodową Agencję Wymiany Akademickiej) Walczak Programme.
Patient consent
An appropriate bioethics committee (Bioethics Committee at the Poznan University of Medical Sciences) approved the study (No. 856/14), and the patients provided written informed consent.
Acknowledgements
Manuscript preparation was supported during Harvard Medical School’s Polish Clinical Scholars Research Training Program, organised by the Agencja Badan Medycznych (ABM; English: Medical Research Agency, Warsaw, Poland). AU organized and planned the study, wrote the manuscript and researched data. MM-D wrote the manuscript and researched data. AG-W researched data and contributed to discussion. JF researched data, reviewed and edited the manuscript. SS researched data. AR contributed to discussion and reviewed the manuscript. DZ-Z contributed to discussion and reviewed the manuscript. Aleksandra Uruska is the guarantor of this work and, as such, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
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