Altered Circulating Leptin, hGH, and IGF-I in Prediabetes and Screening-Diagnosed T2DM Unrelated to Metabolic Syndrome in Women Post Gestational Diabetes

Recently, we proposed two pathophysiologic subtypes of type 2 diabetes mellitus (T2DM), one related and one unrelated to metabolic syndrome. To begin to understand the pathophysiology of the subtype unrelated to metabolic syndrome, we now measured selected hormones and signaling molecules in affected individuals. In this cross-sectional analysis, we examined 138 women out of the monocenter, post gestational diabetes study PPSDiab. Of these women, 73 had prediabetes or screening-diagnosed T2DM, 40 related to metabolic syndrome and 33 unrelated. The remaining 65 women were normoglycemic controls. Our analysis included medical history, anthropometrics, oral glucose tolerance testing, laboratory chemistry, and cardiopulmonary exercise testing. In addition, plasma proinsulin/insulin ratio, growth hormone (hGH) nadir during oral glucose tolerance testing, Insulin-like Growth Factor I (IGF-I), Leptin, Resistin, Adiponectin, Fetuin-a, FGF21, and myostatin were measured. Compared to controls, women with prediabetes or screening-diagnosed T2DM unrelated to metabolic syndrome depicted higher plasma Leptin [10.47(6.6-14.57) vs. 5.52(3.15-10.02); p<0.0001] and IGF-I [193.01(171.00-213.30) vs. 167.97(138.77-200.64); p=0.0008], as well as a lower hGH nadir [0.07(0.05-0.15) vs. 0.14(0.08-0.22; p<0.0001]. These differences were independent of body adiposity. Women with prediabetes or T2DM related to metabolic syndrome, in comparison to controls, displayed elevated Leptin, Fetuin-a, and FGF21, as well as reduced Adiponectin and hGH nadir. Based on our study, altered Leptin and hGH/IGF-I signaling could potentially contribute to the pathophysiology of prediabetes and T2DM unrelated to metabolic syndrome. Further mechanistic investigations of these signaling pathways in the context of lean T2DM are necessary to test causal relationships.

A Normalized Real-Life Glucose Profile After Diet-Induced Remission of Type 2 Diabetes: A Pilot Trial

Background/objective

Type 2 diabetes related to metabolic syndrome is often partially reversible after weight loss. We conducted a pilot trial on whether complete remission to the point of a normalized real-life glucose profile, measured by continuous subcutaneous monitoring, can be achieved.

Methods

We conducted a mono-center, single-arm intervention trial between January 20, 2020, and January 12, 2021, in Munich, Germany. Ten participants had type 2 diabetes related to metabolic syndrome for a maximum of six years. They received a six-month lifestyle intervention including up to three months of a very-low-calorie formula diet, followed by stepwise food reintroduction and regular behavioral lifestyle counseling. The primary outcome was the status of glucose control at the end of the intervention. Complete remission was defined as normalization of the real-life glucose profile without glucose-lowering medication over at least five days. We measured anthropometric and biochemical parameters, body fat distribution by MRI, and insulin secretory reserve by an arginine stimulation test.

Results

Seven participants completed the trial, one reached complete remission, three achieved partial remission, and three displayed improved glucose control still in the diabetic range. A reduction of median glycosylated hemoglobin by −10 mmol/mol (−22.0 to −5.0; p = 0.016) co-occurred with weight loss of −6.4 kg (−14.2 to −3.5; p = 0.031). The insulin secretory reserve remained unchanged.

Conclusions

Complete remission of type 2 diabetes related to metabolic syndrome to the point of a normalized real-life glucose profile is possible through lifestyle intervention. Full intervention success remains challenging even with intensive counseling and support.

Pre-diabetes, diabetes and fluctuations of glucose tolerance after gestational diabetes mellitus: 5-year follow-up of a contemporary, prospective study in Germany

INTRODUCTION

Ten years ago, Germany started offering screening for gestational diabetes mellitus (GDM) to all pregnant women. This approach revealed more but also, on average, less severe cases of GDM than the risk-based screening practiced previously. We now examined the incidence of pre-diabetes and diabetes following a GDM diagnosis in the era of universal screening in Germany and compared our results with studies in the previous period. Additionally, we examined the year-to-year fluctuations of glucose tolerance after a pregnancy complicated by GDM.

RESEARCH DESIGN AND METHODS

We report 5-year follow-up data from 202 women in the prospective, monocenter, postpartum study PPSDiab. Consecutive recruitment took place in Munich, Germany between 2011 and 2016. In the study, we conducted yearly examinations that included anthropometrics, laboratory chemistry and oral glucose tolerance testing.

RESULTS

During the first 5 years post partum, 111 (55%) and 12 (6%) of the women developed pre-diabetes and type 2 diabetes, respectively, while 2 (1%) developed type 1 diabetes. Impaired fasting glucose (IFG) was the most common first manifestation of disturbed glucose tolerance, followed by impaired glucose tolerance (IGT), the combination of IFG and IGT, and diabetes. Glucose tolerance did not deteriorate steadily in most women but fluctuated from year to year.

CONCLUSIONS

In our analysis, the incidence of diabetes, both type 1 and type 2, after GDM diagnosed in universal screening was substantially lower than in studies from the previous period of risk-based screening. Nevertheless, the high incidence of pre-diabetes we observed after GDM still confirms the importance of this diagnosis as a risk marker. Additionally, we documented frequent fluctuations of glucose tolerance from 1 year to the next. Therefore, a single postpartum glucose tolerance test, as currently practiced in routine care, may be insufficient for reliable risk stratification after GDM.

Function outperforms morphology in the assessment of muscular contribution to insulin sensitivity in premenopausal women

INTRODUCTION

Skeletal muscle contributes significantly to insulin sensitivity in humans. However, which non-invasive measurement best reflects this contribution remains unknown. Consequently, this paper compares morphologic and functional measurements.

RESEARCH METHODS AND DESIGN

We conducted a cross-sectional analysis of 144 premenopausal women enrolled in the "Prediction, Prevention, and Sub-classification of Type 2 Diabetes" (PPSDiab) cohort study. For the analysis, we quantified insulin sensitivity by oral glucose tolerance testing and, in a subgroup of 30 women, euglycemic clamp. To assess skeletal muscle, we measured volume by magnetic resonance imaging, intramyocellular lipid content by magnetic resonance spectroscopy, and physical fitness by cardiopulmonary exercise testing.

RESULTS

The mean age of the cohort was 35.7 ± 4.1 years and 94 participants (65%) had a history of gestational diabetes mellitus. Of the morphologic and functional muscle parameters, the maximum workload achieved during cardiopulmonary exercise testing associated most closely with insulin sensitivity (standardized beta = 0.39; p < .001). Peak oxygen uptake also demonstrated significant associations, whereas muscle volume and intramyocellular lipid content displayed none.

CONCLUSION

Functional measurements provided a better assessment of the muscular contribution to insulin sensitivity than morphologic measurements in premenopausal women. In particular, exercise testing rendered an easy and cost-effective method applicable in clinical settings and other human studies.

Association of Serum Myostatin with Body Weight, Visceral Fat Volume, and High Sensitivity C-Reactive Protein But Not With Muscle Mass and Physical Fitness in Premenopausal Women

BACKGROUND

The myokine myostatin regulates muscle mass and has been linked to insulin resistance and metabolic syndrome. However, data on its role in humans is still limited. We, therefore, investigated the associations of serum myostatin with muscle mass, physical fitness, and components of the metabolic syndrome in a cohort of premenopausal women.

METHODS

We undertook a cross-sectional analysis of 233 women from the monocenter study PPSDiab, conducted in Munich, Germany. Participants had recently completed a pregnancy with or without gestational diabetes. Our analysis included medical history, anthropometrics, oral glucose tolerance testing, laboratory chemistry, cardiopulmonary exercise testing, and magnetic resonance imaging (n=142) of visceral fat volume, left quadriceps muscle mass, and muscle fat content. Serum myostatin was quantified by a competitive enzyme-linked immunosorbent assay.

RESULTS

We observed positive correlations of serum myostatin with body mass index (ρ=0.235; p=0.0003), body fat percentage (ρ=0.166; p=0.011), waist circumference (ρ=0.206; p=0.002), intraabdominal fat volume (ρ=0.182; p=0.030) and high-sensitivity C-reactive protein (ρ=0.175; p=0.008). These correlations were reproduced in linear regression analyses with adjustment for age and time after delivery. We saw no correlations with muscle mass, physical fitness, insulin sensitivity, triglycerides, HDL cholesterol, and blood pressure.

CONCLUSIONS

Our observation of elevated serum myostatin in women with a higher body fat percentage, visceral obesity, and elevated c-reactive protein suggests that this myokine contributes to the altered muscle-adipose tissue crosstalk in metabolic syndrome. Elevated myostatin may advance this pathophysiologic process and could also impair the efficacy of exercise interventions. Further mechanistic studies, therefore, seem warranted.

A Pathophysiology of Type 2 Diabetes Unrelated to Metabolic Syndrome

OBJECTIVE

Clinically, type 2 diabetes mellitus (T2DM) is heterogeneous, but the prevailing pathophysiologic hypothesis nevertheless contends that components of metabolic syndrome are central to all cases of T2DM. Here, we re-evaluated this hypothesis.

RESEARCH DESIGN AND METHODS

We conducted a cross-sectional analysis of 138 women from the monocenter, post gestational diabetes study PPSDiab, 73 of which had incident prediabetes or T2DM. Additionally, we examined all the 412 incident cases of T2DM in phases 3 to 9 of the Whitehall II study in comparison to healthy controls. Our analysis included a medical history, anthropometrics, oral glucose tolerance testing, and laboratory chemistry in both studies. Additional analyses from the PPSDiab Study consisted of cardiopulmonary exercise testing, magnetic resonance imaging, auto-antibody testing, and the exclusion of glucokinase maturity-onset diabetes of the young.

RESULTS

We found that 33 (45%) of the women with prediabetes or T2DM in the PPSDiab study displayed no components of metabolic syndrome. They reached no point for metabolic syndrome in the National Cholesterol Education Program Adult Treatment Panel III score other than hyperglycemia and, moreover, had levels of liver fat content, plasma triglycerides, high-density lipoprotein cholesterol, c-reactive protein, and blood pressure that were comparable to healthy controls. In the Whitehall II study, 62 (15%) of the incident T2DM cases fulfilled the same criteria. In both studies, these cases without metabolic syndrome revealed insulin resistance and inadequately low insulin secretion.

CONCLUSIONS

Our results contradict the hypothesis that components of metabolic syndrome are central to all cases of T2DM. Instead, they suggest the common occurrence of a second, unrelated pathophysiology.

The liver-alpha cell axis associates with liver fat and insulin resistance: a validation study in women with non-steatotic liver fat levels

AIMS/HYPOTHESIS

Many individuals who develop type 2 diabetes also display increased glucagon levels (hyperglucagonaemia), which we have previously found to be associated with the metabolic syndrome. The concept of a liver-alpha cell axis provides a possible link between hyperglucagonaemia and elevated liver fat content, a typical finding in the metabolic syndrome. However, this association has only been studied in individuals with non-alcoholic fatty liver disease. Hence, we searched for a link between the liver and the alpha cells in individuals with non-steatotic levels of liver fat content. We hypothesised that the glucagon-alanine index, an indicator of the functional integrity of the liver-alpha cell axis, would associate with liver fat and insulin resistance in our cohort of women with low levels of liver fat.

METHODS

We analysed data from 79 individuals participating in the Prediction, Prevention and Subclassification of Type 2 Diabetes (PPSDiab) study, a prospective observational study of young women at low to high risk for the development of type 2 diabetes. Liver fat content was determined by MRI. Insulin resistance was calculated as HOMA-IR. We conducted Spearman correlation analyses of liver fat content and HOMA-IR with the glucagon-alanine index (the product of fasting plasma levels of glucagon and alanine). The prediction of the glucagon-alanine index by liver fat or HOMA-IR was tested in multivariate linear regression analyses in the whole cohort as well as after stratification for liver fat content ≤0.5% (n = 39) or >0.5% (n = 40).

RESULTS

The glucagon-alanine index significantly correlated with liver fat and HOMA-IR in the entire cohort (ρ = 0.484, p < 0.001 and ρ = 0.417, p < 0.001, respectively). These associations resulted from significant correlations in participants with a liver fat content >0.5% (liver fat, ρ = 0.550, p < 0.001; HOMA-IR, ρ = 0.429, p = 0.006). In linear regression analyses, the association of the glucagon-alanine index with liver fat remained significant after adjustment for age and HOMA-IR in all participants and in those with liver fat >0.5% (β = 0.246, p = 0.0.23 and β = 0.430, p = 0.007, respectively) but not in participants with liver fat ≤0.5% (β = -0.184, p = 0.286).

CONCLUSIONS/INTERPRETATION

We reproduced the previously reported association of liver fat content and HOMA-IR with the glucagon-alanine index in an independent study cohort of young women with low to high risk for type 2 diabetes. Furthermore, our data indicates an insulin-resistance-independent association of liver fat content with the glucagon-alanine index. In summary, our study supports the concept that even lower levels of liver fat (from 0.5%) are connected to relative hyperglucagonaemia, reflecting an imminent impairment of the liver-alpha cell axis.

Overweight/obesity as the potentially most important lifestyle factor associated with signs of pneumonia in COVID-19

Objective

The occurrence of pneumonia separates severe cases of COVID-19 from the majority of cases with mild disease. However, the factors determining whether or not pneumonia develops remain to be fully uncovered. We therefore explored the associations of several lifestyle factors with signs of pneumonia in COVID-19.

Methods

Between May and July 2020, we conducted an online survey of 201 adults in Germany who had recently gone through COVID-19, predominantly as outpatients. Of these, 165 had a PCR-based diagnosis and 36 had a retrospective diagnosis by antibody testing. The survey covered demographic information, eight lifestyle factors, comorbidities and medication use. We defined the main outcome as the presence vs. the absence of signs of pneumonia, represented by dyspnea, the requirement for oxygen therapy or intubation.

Results

Signs of pneumonia occurred in 39 of the 165 individuals with a PCR-based diagnosis of COVID-19 (23.6%). Among the lifestyle factors examined, only overweight/obesity was associated with signs of pneumonia (odds ratio 2.68 (1.29–5.59) p = 0.008). The observed association remained significant after multivariate adjustment, with BMI as a metric variable, and also after including the antibody-positive individuals into the analysis.

Conclusions

This exploratory study finds an association of overweight/obesity with signs of pneumonia in COVID-19. This finding suggests that a signal proportional to body fat mass, such as the hormone leptin, impairs the body’s ability to clear SARS-CoV-2 before pneumonia develops. This hypothesis concurs with previous work and should be investigated further to possibly reduce the proportion of severe cases of COVID-19.

Altered metabolic and hormonal responses to moderate exercise in overweight/obesity

BACKGROUND

An adequate metabolic and hormonal response to the switch from rest to exercise is critical for the health benefits of exercise interventions. Previous work suggests that this response is impaired with overweight/obesity but the specific differences between overweight/obese and lean individuals remain unclear.

METHODS

We compared glucose and non-esterified fatty acid (NEFA) regulation and the changes of key homeostatic hormones during 45 min of moderate exercise between 17 overweight/obese and 28 lean premenopausal women. For this comparison, we implemented an exercise protocol at 60% of individual peak oxygen uptake, with frequent blood sampling and under fasting conditions.

RESULTS

We found that at the same exercise intensity in the overweight/obese and the lean group of women, the metabolic and hormonal response differed. In contrast to the lean group, the overweight/obese group portrayed an activation in the stress axis (adrenocorticotropic hormone (ACTH)/cortisol) and a lower growth hormone (hGH) response and exercise-increase of plasma NEFA. Both groups, however, displayed increased insulin sensitivity during exercise that was accompanied by a normalization of the elevated fasting glucose in the overweight/obese group after 15-20 min.

CONCLUSION

We conclude that the response to exercise in overweight/obese subjects indeed differs from that in lean individuals. Additionally, we demonstrate that exercise can elicit beneficial (improved glucose regulation) and unwanted effects (stress axis activation) in overweight/obese subjects at the same time. This second finding suggests that exercise interventions for overweight/obese subjects need careful consideration of intensity and dose in order to achieve the intended results and avoid acute, undesired reactions.