The Effects of Lifestyle and/or Vitamin D Supplementation Interventions on Pregnancy Outcomes: What Have We Learned from the DALI Studies?

The Importance of Intra-Islet Communication in the Function and Plasticity of the Islets of Langerhans during Health and Diabetes

Islets of Langerhans are anatomically dispersed within the pancreas and exhibit regulatory coordination between islets in response to nutritional and inflammatory stimuli. However, within individual islets, there is also multi-faceted coordination of function between individual beta-cells, and between beta-cells and other endocrine and vascular cell types. This is mediated partly through circulatory feedback of the major secreted hormones, insulin and glucagon, but also by autocrine and paracrine actions within the islet by a range of other secreted products, including somatostatin, urocortin 3, serotonin, glucagon-like peptide-1, acetylcholine, and ghrelin. Their availability can be modulated within the islet by pericyte-mediated regulation of microvascular blood flow. Within the islet, both endocrine progenitor cells and the ability of endocrine cells to trans-differentiate between phenotypes can alter endocrine cell mass to adapt to changed metabolic circumstances, regulated by the within-islet trophic environment. Optimal islet function is precariously balanced due to the high metabolic rate required by beta-cells to synthesize and secrete insulin, and they are susceptible to oxidative and endoplasmic reticular stress in the face of high metabolic demand. Resulting changes in paracrine dynamics within the islets can contribute to the emergence of Types 1, 2 and gestational diabetes.

[Gestational diabetes mellitus (Update 2023)]

Gestational diabetes (GDM) is defined as any degree of glucose intolerance with onset during pregnancy and is associated with increased feto-maternal morbidity as well as long-term complications in mothers and the offspring. Women detected to have diabetes early in pregnancy receive the diagnosis of overt, non-gestational, diabetes (glucose: fasting ≥ 126 mg/dl, spontaneous ≥ 200 mg/dl or HbA_1c ≥ 6.5% before 20 weeks of gestation). GDM is diagnosed by an oral glucose tolerance test (oGTT) or increased fasting glucose (≥ 92 mg/dl). Screening for undiagnosed type 2 diabetes at the first prenatal visit is recommended in women at increased risk (history of GDM/pre-diabetes; malformation, stillbirth, successive abortions or birth weight > 4500 g previously; obesity, metabolic syndrome, age > 35 years, vascular disease; clinical symptoms of diabetes (e.g. glucosuria) or ethnic origin with increased risk for GDM/T2DM (Arab, South- and Southeast Asian, Latin American)) using standard diagnostic criteria. Performance of the oGTT (120 min; 75 g glucose) may already be indicated in the first trimester in high-risk women but is mandatory between gestational week 24-28 in all pregnant women with previous non-pathological glucose metabolism. Following WHO recommendations, which are based on the Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study, GDM is defined, if fasting venous plasma glucose is ≥ 92 mg/dl or 1 h ≥ 180 mg/dl or 2 h ≥ 153 mg/dl after glucose loading (international consensus criteria). In case of one pathological value a strict metabolic control is mandatory. After bariatric surgery we do not recommend to perform an oGTT due to risk of postprandial hypoglycemia. All women with GDM should receive nutritional counseling, be instructed in blood glucose self-monitoring and motivated to increase physical activity to moderate intensity levels-if not contraindicated (Evidence level A). If blood glucose levels cannot be maintained in the therapeutic range (fasting < 95 mg/dl and 1 h after meals < 140 mg/dl, Evidence level B) insulin therapy should be initiated as first choice (Evidence level A). Maternal and fetal monitoring is required in order to minimize maternal and fetal/neonatal morbidity and perinatal mortality. Regular obstetric examinations including ultrasound examinations are recommended (Evidence level A). Neonatal care of GDM offspring at high risk for hypoglycaemia includes blood glucose measurements after birth and if necessary appropriate intervention. Monitoring the development of the children and recommendation of healthy lifestyle are important issues to be tackled for the whole family. After delivery all women with GDM have to be reevaluated as to their glucose tolerance by a 75 g oGTT (WHO criteria) 4-12 weeks postpartum. Assessment of glucose parameters (fasting glucose, random glucose, HbA_1c or optimally oGTT) are recommended every 2-3 years in case of normal glucose tolerance. All women have to be instructed about their increased risk of type 2 diabetes and cardiovascular disease at follow-up. Possible preventive meassures, in particular lifestyle changes as weight management and maintenance/increase of physical activity should be discussed (evidence level A).

Vitamin D Status and Gestational Diabetes in Russian Pregnant Women in the Period between 2012 and 2021: A Nested Case-Control Study

Several meta-analyses found an association between low maternal serum 25-hydroxyvitamin D (25(OH)D) level and gestational diabetes mellitus (GDM). However, some of them reported significant heterogeneity. We examined the association of serum 25(OH)D concentration measured in the first and in the second halves of pregnancy with the development of GDM in Russian women surveyed in the periods of 2012−2014 and 2018−2021. We conducted a case−control study (including 318 pregnant women) nested on two previous studies. In 2012−2014, a total of 214 women (83 GDM and 131 controls) were enrolled before 15 weeks of gestation and maternal serum 25(OH)D concentrations were measured twice: at 8th−14th week of gestation and simultaneously with two-hour 75 g oral glucose tolerance test (OGTT) at 24th−32nd week of gestation. In the period of 2018−2021, 104 women (56 GDM and 48 controls) were included after OGTT and 25(OH)D concentrations were measured at 24th−32nd week of gestation. Median 25(OH)D levels were 20.0 [15.1−25.7] vs. 20.5 [14.5−27.5] ng/mL (p = 0.565) in GDM and control group in the first half of pregnancy and 25.3 [19.8−33.0] vs. 26.7 [20.8−36.8] ng/mL (p = 0.471) in the second half of pregnancy, respectively. The prevalence rates for vitamin D deficiency (25(OH)D levels < 20 ng/mL) were 49.4% and 45.8% (p = 0.608) in the first half of pregnancy and 26.2% vs. 22.1% (p = 0.516) in the second half of pregnancy in women who developed GDM and in women without GDM, respectively. The frequency of vitamin D supplements intake during pregnancy increased in 2018−2021 compared to 2012−2014 (p = 0.001). However, the third trimester 25(OH)D levels and prevalence of vitamin D deficiency (25.5 vs. 23.1, p = 0.744) did not differ in women examined in the periods of 2012−2014 and 2018−2021. To conclude, there was no association between gestational diabetes risk and maternal 25(OH)D measured both in the first and in the second halves of pregnancy. The increased prevalence of vitamin D supplements intake during pregnancy by 2018−2021 did not lead to higher levels of 25(OH)D.

The role of maternal diet on offspring hyperinsulinaemia and adiposity after birth: a systematic review of randomised controlled trials

In utero diet may be directly related to the risk of fetal hyperinsulinaemia and offspring metabolic health. This review examines the relationship between maternal dietary exposures and sub-clinical fetal hyperinsulinaemia and neonatal adiposity. Articles were identified in MEDLINE, Web of Science, Cochrane Controlled Register of Controlled Trials, Cumulative Index to Nursing and Allied Health Literature, SCOPUS, and SPORTDiscus (September 2019-March 2021) using the preferred reporting items for systematic reviews and meta-analyses guidelines. PROSPERO registration ID CRD42020146453. Studies were selected by two independent reviewers. Randomised controlled trials (RCT) involving a dietary intervention with pregnant women (healthy pregnancy, gestational diabetes mellitus and obesity) and reporting fetal cord-blood insulin, c-peptide, glucose or adiposity estimates were included. One author extracted all information on main study characteristics and outcomes. Risk of bias was assessed using the Cochrane Collaboration's bias risk assessment tool. A total of 733 articles were identified. Fourteen articles from 11 RCTs (3614 participants) were included. Studies reviewed showed no specific effect of maternal diet on neonatal cord blood insulin, c-peptide or glucose levels. Infants born to mothers who followed a low glycaemic load (GL) had lower skin fold thickness compared to controls. Interventions that provided individualised nutrition counselling to women with obesity or previous infant born > 4 kg were also associated with lower adiposity. The studies reviewed suggest that lifestyle-based dietary interventions to improve glycaemia (low GL) have a protective effect against excess adiposity. Future studies should incorporate multi-modal interventions with dietary counselling to support lifestyle changes throughout gestation and include assessments of maternal insulin resistance at recruitment.

The Predictive Value of miR-16, -29a and -134 for Early Identification of Gestational Diabetes: A Nested Analysis of the DALI Cohort

Early identification of gestational diabetes mellitus (GDM) aims to reduce the risk of adverse maternal and perinatal outcomes. Currently, no circulating biomarker has proven clinically useful for accurate prediction of GDM. In this study, we tested if a panel of small non-coding circulating RNAs could improve early prediction of GDM. We performed a nested case-control study of participants from the European multicenter ‘Vitamin D and lifestyle intervention for GDM prevention (DALI)’ trial using serum samples from obese pregnant women (BMI ≥ 29 kg/m²) entailing 82 GDM cases (early- and late- GDM), and 41 age- and BMI-matched women with normal glucose tolerance (NGT) throughout pregnancy (controls). Anthropometric, clinical and biochemical characteristics were obtained at baseline (<20 weeks of gestation) and throughout gestation. Baseline serum microRNAs (miRNAs) were measured using quantitative real time PCR (qPCR). Elevated miR-16-5p, -29a-3p, and -134-5p levels were observed in women, who were NGT at baseline and later developed GDM, compared with controls who remained NGT. A combination of the three miRNAs could distinguish later GDM from NGT cases (AUC 0.717, p = 0.001, compared with fasting plasma glucose (AUC 0.687, p = 0.004)) as evaluated by area under the curves (AUCs) using Receiver Operator Characteristics (ROC) analysis. Elevated levels of individual miRNAs or a combination hereof were associated with higher odds ratios of GDM. Conclusively, circulating miRNAs early in pregnancy could serve as valuable predictive biomarkers of GDM.

Perinatal Outcomes in a Population of Diabetic and Obese Pregnant Women-The Results of the Polish National Survey

Obesity and diabetes increase the risk of complications during gestation and at delivery. The aim of this study was to compare the perinatal outcomes in the populations of diabetic and obese Polish women, based on the results of a national survey performed in years 2012 and 2017, as well as to determine the risk factors of the gestational diabetes mellitus (GDM). Questionnaires from 6276 women were collected. Obese women constituted 5.5% and 7.5% of study population in years 2012 and 2017, respectively. Among women whose pregnancies were complicated by diabetes mellitus, GDM constituted the most common type of glucose intolerance during both time periods (2012: 89% vs. 2017: 85.6%). In the group of obese women an insignificant increase in the rate of induced deliveries was noted (2012: 9.9% vs. 2017: 11.7%), whereas the fetal birth-weight decreased significantly (2012: 3565 g vs. 2017: 3405 g, p < 0.05). In the group of diabetic pregnant women the percentage of cesarean sections, labour inductions and fetal birth defects was characterized by an insignificant upward trend. Risk of GDM was significantly increased in women aged over 35 years—(2012: OR 1.9 (95% CI: 1.1–2.9) and 2017: OR = 2.1 (95% CI: 1.5–2.9), p < 0.05—, as well as in overweight women—2012: OR 1.8 (95% CI: 1.2–2.7) and 2017: OR 2.6 (95% CI: 1.9–3.4), p < 0.05—during both analysed time periods. Based on the study results, it is necessary to develop population-based programmes to prevent obesity and to introduce and enforce the rules of appropriate screening for glucose tolerance disorders during pregnancy.

A P4 Medicine Perspective of Gut Microbiota and Prediabetes: Systems Analysis and Personalized Intervention

Type 2 diabetes (T2D) accounts for approximately 90% of diabetes worldwide and has become a global public health problem. Generally, individuals go to hospitals and get healthcare only when they have obvious T2D symptoms. While the underlying cause and mechanism of the disease are usually not well understood, treatment is for the symptoms, but not for the disease cause, and patients often continue to progress with more symptoms. Prediabetes is the early stage of diabetes and provides a good time window for intervention and prevention. However, with few symptoms, prediabetes is usually ignored without any treatment. Obviously, it is far from ideal to rely on the traditional medical system for diabetes healthcare. As a result, the medical system must be transformed from a reactive approach to a proactive approach. Root cause analysis and personalized intervention should be conducted for patients with prediabetes. Based on systems medicine, also known as P4 medicine, with a predictive, preventive, personalized, and participatory approach, new medical system is expected to significantly promote the prevention and treatment of chronic diseases such as prediabetes and diabetes. Many studies have shown that the occurrence and development of diabetes is closely related to gut microbiota. However, the relationship between diabetes and gut microbiota has not been fully elucidated. This review describes the research on the relationship between gut microbiota and diabetes and some exploratory trials on the interventions of prediabetes based on P4 medicine model. Furthermore, we also discussed how these findings might influence the diagnosis, prevention and treatment of diabetes in the future, thereby to improve the wellness of human beings.