Effects of age and sex on postprandial glucose metabolism: differences in glucose turnover, insulin secretion, insulin action, and hepatic insulin extraction

Type 2 Diabetes in Women: Differences and Difficulties

BACKGROUND

Lifestyle modification, along with medication, has improved the quality of life of patients with type 2 diabetes (T2D), but the treatment of diabetes in women still lacks a gender-centric approach.

METHODS

Expert opinions to improve diabetes management in women were collated from the open discussion forum organized by the sixth Jothydev's Professional Education Forum Diabetes Convention, which included global diabetes care experts and the general public. The review is also based on the studies published in electronic databases such as PubMed and Google Scholar that discussed the problems and challenges faced by the Indian diabetes care sector in treating women with diabetes.

RESULTS

The complex interplay of biological, socioeconomic, psychosocial, and physiological factors in women with type 2 diabetes has not been well addressed to date. Biological factors such as neurohumoral pathways, sex hormones, genetic predisposition as well as gender-based environmental and behavioural differences must be considered for modern personalized diabetes treatment. Most importantly, pregnant women with diabetes deserve special attention. This vulnerable phase has a marked impact on the future health of both the mother and the offspring.

CONCLUSION

The review provides an overview of the challenges and issues that exist in the clinical management of diabetes and its complications among women in India. Women-centric clinical approaches should be encouraged for the effective management of diabetes in Indian women.

Metabolic flexibility differs by body composition in adults

BACKGROUND & AIMS

With the rise of global cardiometabolic diseases, it is important to investigate risk factors such as obesity. Metabolic flexibility, the ability to maintain metabolic homeostasis following an acute challenge, can reflect cardiometabolic health. We investigated the association between body composition and the metabolic flexibility following meal consumption in an adult population.

METHODS

In this study of 1027 participants (mean age 44.0 y ± SD 4.2 y), we administered a mixed-macronutrient meal challenge. Fasting and 2-h postprandial plasma were assayed for lipids, glycemic, and inflammation biomarkers. We characterized metabolic flexibility through meal-induced biomarker responses (%Δ, the difference between postprandial and fasting concentrations, divided by fasting concentration). We then compared the responses by sex-specific tertiles of body mass index (BMI) and percent body fat.

RESULTS

With every unit (kg/m²) increase in BMI, %Δ (95% confidence interval) increased by 0.17% (0.09, 0.26%) for total cholesterol, 0.31% (0.07, 0.54%) for triglycerides, and 0.11% (0.01, 0.20%) for apoA-I, whereas insulin elevation was reduced (-6.30%; -8.41, -4.20%), and the reduction in leptin was attenuated (0.64%; 0.25, 1.05%). With each unit (percent) increase in body fat, we observed similar changes in the %Δ of total cholesterol and leptin but not in triglycerides, apoA-I, or insulin. Glucose response increased by 0.29% (0.06, 0.51%) as body fat increases by one unit.

CONCLUSION

Metabolic flexibility, as assessed by biomarker responses to an acute physiological meal challenge, differed by body composition. These findings may help elucidate the pathways through which obesity contributes to cardiometabolic diseases.

A Novel Method for Generation of In Silico Subjects with Type 2 Diabetes

A type 2 diabetes (T2D) simulator has been recently proposed for supporting drug development and treatment optimization. This tool consists of a physiological model of glucose/insulin/C-peptide dynamics and a virtual cohort of T2D subjects (i.e., random extractions of model parameterizations from a joint parameter distribution) well describing both average and variability realistic T2D dynamics . However, the state-of-art procedure to get a reliable virtual population requires some post-processing after subject extraction, in order to discard implausible behaviors. We propose an improved method for virtual subjects' generation to overcome this burdensome task. To do so, we first assessed a refined joint parameter distribution, from which extracting a number of subjects, greater than the target population size. Then, target-size subsets are undersampled from the large cohort. The final virtual population is selected among the subsets as the one maximizing the similarity with T2D data and model parameter distribution, by means of measurement' outcome metrics and Euclidian distance (Δ), respectively. In the final population, almost all the outcome metrics are statistically identical to the clinical counterparts (p-value>0.05) and model parameters' distribution differs by ~5-10% from that derived from data. The methodology described here is flexible, thus resulting suitable for different T2D stages and type 1 diabetes, as well.Clinical Relevance- A straightforward subjects' generation would ease the availability of tailored in silico trials for testing diabetes treatment in a specific population.

Probing β-Cell Biology in Space and Time

β-Cells in the islet of Langerhans have a central role in maintaining energy homeostasis. Understanding the physiology of β-cells and other islet cells requires a deep understanding of their structural and functional organization, their interaction with vessels and nerves, the layout of paracrine interactions, and the relationship between subcellular compartments and protein complexes inside each cell. These elements are not static; they are dynamic and exert their biological actions at different scales of time. Therefore, scientists must be able to investigate (and visualize) short- and long-lived events within the pancreas and β-cells. Current technological advances in microscopy are able to bridge multiple spatiotemporal scales in biology to reveal the complexity and heterogeneity of β-cell biology. Here, I briefly discuss the historical discoveries that leveraged microscopes to establish the basis of β-cell anatomy and structure, the current imaging platforms that allow the study of islet and β-cell biology at multiple scales of resolution, and their challenges and implications. Lastly, I outline how the remarkable longevity of structural elements at different scales in biology, from molecules to cells to multicellular structures, could represent a previously unrecognized organizational pattern in developing and adult β-cells and pancreas biology.

Developmental mechanisms of sex differences: from cells to organisms

Male-female differences in many developmental mechanisms lead to the formation of two morphologically and physiologically distinct sexes. Although this is expected for traits with prominent differences between the sexes, such as the gonads, sex-specific processes also contribute to traits without obvious male-female differences, such as the intestine. Here, we review sex differences in developmental mechanisms that operate at several levels of biological complexity - molecular, cellular, organ and organismal - and discuss how these differences influence organ formation, function and whole-body physiology. Together, the examples we highlight show that one simple way to gain a more accurate and comprehensive understanding of animal development is to include both sexes.

Sex differences in body composition, metabolism-related hormones, and energy homeostasis during aging in Wistar rats

Aging affects the body composition and balance of energy metabolism. Here, we collected in a single work several physiological parameters to show how aging and sex differences can influence energy homeostasis. Body mass index (BMI), Lee index, glucose tolerance, glycemia, and lipidogram in fasting were measured in male and female Wistar rats at the ages of 2, 6, 9, 12, and 18 months. We also measured the lipid profile, free fatty acids, glycerol, glycemia, leptin, adiponectin, insulin, corticosterone (CORT), prolactin (PRL), thyroid stimulated hormone, and triiodothyronine (T3) in 3‐ and 18‐month‐old rats of both sexes, fed ad libitum. Animals were classified as obese beginning at 2 months in males and 6 months in females. Aged male rats showed hyperglycemia and glucose intolerance compared to young males and old females. In the ad libitum condition, the 18‐month males presented higher serum levels of triglycerides, total cholesterol, and free fatty acids than females. The 18‐month‐old females had higher PRL and CORT concentration than males, but insulin and T3 were higher in 18‐month‐old males than females. Our work demonstrated that aging processes on energy metabolism in rats is sex specific, with a better lipid profile and glucose tolerance in aged females.

Malnutrition in Older Adults-Recent Advances and Remaining Challenges

Malnutrition in older adults has been recognised as a challenging health concern associated with not only increased mortality and morbidity, but also with physical decline, which has wide ranging acute implications for activities of daily living and quality of life in general. Malnutrition is common and may also contribute to the development of the geriatric syndromes in older adults. Malnutrition in the old is reflected by either involuntary weight loss or low body mass index, but hidden deficiencies such as micronutrient deficiencies are more difficult to assess and therefore frequently overlooked in the community-dwelling old. In developed countries, the most cited cause of malnutrition is disease, as both acute and chronic disorders have the potential to result in or aggravate malnutrition. Therefore, as higher age is one risk factor for developing disease, older adults have the highest risk of being at nutritional risk or becoming malnourished. However, the aetiology of malnutrition is complex and multifactorial, and the development of malnutrition in the old is most likely also facilitated by ageing processes. This comprehensive narrative review summarizes current evidence on the prevalence and determinants of malnutrition in old adults spanning from age-related changes to disease-associated risk factors, and outlines remaining challenges in the understanding, identification as well as treatment of malnutrition, which in some cases may include targeted supplementation of macro- and/or micronutrients, when diet alone is not sufficient to meet age-specific requirements.

Improved postprandial glucose metabolism in type 2 diabetes by the dual glucagon-like peptide-1/glucagon receptor agonist SAR425899 in comparison with liraglutide

AIM

To gain further insights into the efficacy of SAR425899, a dual glucagon-like peptide-1/glucagon receptor agonist, by providing direct comparison with the glucagon-like peptide-1 receptor agonist, liraglutide, in terms of key outcomes of glucose metabolism.

RESEARCH DESIGN AND METHODS

Seventy overweight to obese subjects with type 2 diabetes (T2D) were randomized to receive once-daily subcutaneous administrations of SAR425899 (0.12, 0.16 or 0.20 mg), liraglutide (1.80 mg) or placebo for 26 weeks. Mixed meal tolerance tests were conducted at baseline (BSL) and at the end of treatment (EOT). Metabolic indices of insulin action and secretion were assessed via Homeostasis Model Assessment (HOMA2) and oral minimal model (OMM) methods.

RESULTS

From BSL to EOT (median [25th, 75th] percentile), HOMA2 quantified a significant improvement in basal insulin action in liraglutide (35% [21%, 74%]), while secretion enhanced both in SAR425899 (125% [63%, 228%]) and liraglutide (73% [43%, 147%]). OMM quantified, both in SAR425899 and liraglutide, a significant improvement in insulin sensitivity (203% [58%, 440%] and 36% [21%, 197%]), basal beta-cell responsiveness (67% [34%, 112%] and 40% [16%, 59%]), and above-basal beta-cell responsiveness (139% [64%, 261%] and 69% [-15%, 120%]). A significant delay in glucose absorption was highlighted in SAR425899 (37% [52%,18%]).

CONCLUSIONS

SAR425899 and liraglutide improved postprandial glucose control in overweight to obese subjects with T2D. A significantly higher enhancement in beta-cell function was shown by SAR425899 than liraglutide.

Translating glucose tolerance data from mice to humans: Insights from stable isotope labelled glucose tolerance tests

Objective

The glucose tolerance test (GTT) is widely used in human and animal biomedical and pharmaceutical research. Despite its prevalent use, particularly in mouse metabolic phenotyping, to the best of our knowledge we are not aware of any studies that have attempted to qualitatively compare the metabolic events during a GTT in mice with those performed in humans.

Methods

Stable isotope labelled oral glucose tolerance tests (siOGTTs; [6,6-²H₂]glucose) were performed in both human and mouse cohorts to provide greater resolution into postprandial glucose kinetics. The siOGTT allows for the partitioning of circulating glucose into that derived from exogenous and endogenous sources. Young adults spanning the spectrum of normal glucose tolerance (n = 221), impaired fasting (n = 14), and impaired glucose tolerance (n = 19) underwent a 75g siOGTT, whereas a 50 mg siOGTT was performed on chow (n = 43) and high-fat high-sucrose fed C57Bl6 male mice (n = 46).

Results

During the siOGTT in humans, there is a long period (>3hr) of glucose absorption and, accordingly, a large, sustained insulin response and robust suppression of lipolysis and endogenous glucose production (EGP), even in the presence of glucose intolerance. In contrast, mice appear to be highly reliant on glucose effectiveness to clear exogenous glucose and experience only modest, transient insulin responses with little, if any, suppression of EGP. In addition to the impaired stimulation of glucose uptake, mice with the worst glucose tolerance appear to have a paradoxical and persistent rise in EGP during the OGTT, likely related to handling stress.

Conclusions

The metabolic response to the OGTT in mice and humans is highly divergent. The potential reasons for these differences and their impact on the interpretation of mouse glucose tolerance data and their translation to humans are discussed.

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We compared the mechanisms governing glucose handling in humans and mice.

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Humans and mice underwent stable isotope labelled oral glucose tolerance tests.

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Metabolic responses between humans and mice were highly divergent.

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Unlike humans, most mice exhibit little EGP suppression or insulin response.

Inter-Individual Variation in Postprandial Glycemic Responses in Women Co-Ingesting Green Leafy Vegetables with a Carbohydrate Meal: Interactions with the Sirtuin System

SCOPE

Green leafy vegetables (GLV) may improve postprandial glycemic responses (PGR) and metabolic health. However, inter-individual variations (IIV) preclude conclusive evidence. Sirtuin system is emerging as a key player in blood glucose control. This study investigates IIV in PGR in women co-ingesting GLV with a carbohydrate meal and interactions with the sirtuin system.

METHODS AND RESULTS

Volunteers (n = 31 women) consume rice, rice with bok choy, or spinach (75g available carbohydrate) on separate occasions. Postprandial glucose, insulin, adropin, and lipid levels are measured. Anthropometric measurements and sex hormones are measured. GeXP assay measures whole blood postprandial gene expression profiles of 25 markers involved in sirtuin signaling. GLV consumption has no significant effect on PGR, which shows high variation. PGR correlated with age, but no other consistent associations are observed. Sirtuin gene expression profiles reveal distinct stratified subgroups associated with PGR, lipid, insulin, fat mass, waist/hip circumferences, and adropin levels.

CONCLUSION

PGR to co-ingesting GLV with a carbohydrate meal are highly variable in this cohort and fail to reveal a significant reduction in PGR. Variable responses are largely independent of menopausal status and meal consumed. However, lower expression of sirtuin gene targets is associated with higher PGR and with markers linked to health status.

Deconstructing the origins of sexual dimorphism in sensory modulation of pancreatic β cells

The regulation of glucose-stimulated insulin secretion and glucose excursion has a sensory component that operates in a sex-dependent manner.

OBJECTIVE

Here, we aim to dissect the basis of the sexually dimorphic interaction between sensory neurons and pancreatic β cells and its overall impact on insulin release and glucose homeostasis.

METHODS

We used viral retrograde tracing techniques, surgical and chemodenervation models, and primary cell-based co-culture systems to uncover the biology underlying sex differences in sensory modulation of pancreatic β-cell activity.

RESULTS

Retrograde transsynaptic labeling revealed a sex difference in the density of sensory innervation in the pancreas. The number of sensory neurons emanating from the dorsal root and nodose ganglia that project in the pancreas is higher in male than in female mice. Immunostaining and confocal laser scanning microscopy confirmed the higher abundance of peri-islet sensory axonal tracts in the male pancreas. Capsaicin-induced sensory chemodenervation concomitantly enhanced glucose-stimulated insulin secretion and glucose clearance in male mice. These metabolic benefits were blunted when mice were orchidectomized prior to the ablation of sensory nerves. Interestingly, orchidectomy also lowered the density of peri-islet sensory neurons. In female mice, capsaicin treatment did not affect glucose-induced insulin secretion nor glucose excursion and ovariectomy did not modify these outcomes. Interestingly, same- and opposite-sex sensory-islet co-culture paradigms unmasked the existence of potential gonadal hormone-independent mechanisms mediating the male-female difference in sensory modulation of islet β-cell activity.

CONCLUSION

Taken together, these data suggest that the sex-biased nature of the sensory control of islet β-cell activity is a result of a combination of neurodevelopmental inputs, sex hormone-dependent mechanisms and the potential action of somatic molecules encoded by the sex chromosome complement.

DNA Methylation Patterning and the Regulation of Beta Cell Homeostasis

Pancreatic beta cells play a central role in regulating glucose homeostasis by secreting the hormone insulin. Failure of beta cells due to reduced function and mass and the resulting insulin insufficiency can drive the dysregulation of glycemic control, causing diabetes. Epigenetic regulation by DNA methylation is central to shaping the gene expression patterns that define the fully functional beta cell phenotype and regulate beta cell growth. Establishment of stage-specific DNA methylation guides beta cell differentiation during fetal development, while faithful restoration of these signatures during DNA replication ensures the maintenance of beta cell identity and function in postnatal life. Lineage-specific transcription factor networks interact with methylated DNA at specific genomic regions to enhance the regulatory specificity and ensure the stability of gene expression patterns. Recent genome-wide DNA methylation profiling studies comparing islets from diabetic and non-diabetic human subjects demonstrate the perturbation of beta cell DNA methylation patterns, corresponding to the dysregulation of gene expression associated with mature beta cell state in diabetes. This article will discuss the molecular underpinnings of shaping the islet DNA methylation landscape, its mechanistic role in the specification and maintenance of the functional beta cell phenotype, and its dysregulation in diabetes. We will also review recent advances in utilizing beta cell specific DNA methylation patterns for the development of biomarkers for diabetes, and targeting DNA methylation to develop translational approaches for supplementing the functional beta cell mass deficit in diabetes.

The impact of dietary macronutrient intake on cognitive function and the brain

Macronutrients - carbohydrates, fats, and proteins - supply the nutrients required for optimal functioning. Inadequate intake compromises both physical and brain health. We synthesized research on macronutrients from whole meals on cognitive function in healthy adults and identified underlying mechanisms. Intake of simple carbohydrates ('sugars') is consistently associated with decreased global cognition whereas consumption of complex carbohydrates correlates with successful brain aging and improved memory both in the short- and long-term. Saturated fatty acid intake correlates with decreased memory and learning scores whereas omega-3 intake correlates positively with memory scores. Protein intake boosts executive function and working memory when task-demands are high. Individual differences affecting the macronutrient-cognition relationship are age, physical activity, and glucose metabolism. Neural correlates reflect findings on cognitive functions: cortical thickness and cerebral amyloid burden correlate with sugar intake, inflammatory status and cerebral glucose metabolism correlate with fatty acid intake. Key mechanisms by which dietary macronutrients affect the brain and cognition include glucose and insulin metabolism, neurotransmitter actions, and cerebral oxidation and inflammation. In conclusion, macronutrient intake affects cognitive function both acutely and in the long-term, involving peripheral and central mechanisms. A healthy diet supports brain integrity and functionality, whereas inadequate nutrition compromises it. Studying diet can be key to nutritional recommendations, thereby improving the landscape of mental health and healthy brain aging.

Nutrition for Older Athletes: Focus on Sex-Differences

Regular physical exercise and a healthy diet are major determinants of a healthy lifespan. Although aging is associated with declining endurance performance and muscle function, these components can favorably be modified by regular physical activity and especially by exercise training at all ages in both sexes. In addition, age-related changes in body composition and metabolism, which affect even highly trained masters athletes, can in part be compensated for by higher exercise metabolic efficiency in active individuals. Accordingly, masters athletes are often considered as a role model for healthy aging and their physical capacities are an impressive example of what is possible in aging individuals. In the present review, we first discuss physiological changes, performance and trainability of older athletes with a focus on sex differences. Second, we describe the most important hormonal alterations occurring during aging pertaining regulation of appetite, glucose homeostasis and energy expenditure and the modulatory role of exercise training. The third part highlights nutritional aspects that may support health and physical performance for older athletes. Key nutrition-related concerns include the need for adequate energy and protein intake for preventing low bone and muscle mass and a higher demand for specific nutrients (e.g., vitamin D and probiotics) that may reduce the infection burden in masters athletes. Fourth, we present important research findings on the association between exercise, nutrition and the microbiota, which represents a rapidly developing field in sports nutrition.

Alternating work posture improves postprandial glucose response without reducing computer task performance in the early afternoon

In the workplace, sit-stand workstations are being installed to reduce excessive sitting time and the consequent risk factors for cardiovascular ailments (e.g., postprandial hyperglycemia). However, a prolonged standing posture also has detrimental effects in terms of musculoskeletal symptoms and work efficiency. We thus investigated whether alternating between a sitting and standing work posture improves postprandial glucose response and computer task performance. Nine healthy young males completed 4 × 20-min computer tasks in the early afternoon (i.e., 30 min after eating lunch) under three different work conditions, had no change in posture (only sitting=the control trial, CON), and engaged in two styles of alternating between sitting and standing every 20 min (sitting → standing → sitting → standing, SIT-STAND; standing → sitting → standing → sitting, STAND-SIT). For the computer tasks, all participants had to subtract a two-digit number from a four-digit number and to input the answer in the answer column on the computer. Task performance was evaluated as the number of achievements and accuracy rate every 20 min. Blood glucose concentration was assessed before, immediately after, 30 min, 52 min, 74 min, 96 min, and 118 min after eating lunch. The number of achievements and accuracy rate did not differ among the three trials. The total area under the curve (AUC) for blood glucose concentration was significantly lower in the SIT-STAND and STAND-SIT trials compared with CON, whereas no significant difference was observed between the SIT-STAND and STAND-SIT trials. In conclusion, alternating between a sitting and standing work posture attenuated postprandial blood glucose accumulation without reducing task performance, irrespective of the order of changes in work posture.

Walking Initiated 20 Minutes before the Time of Individual Postprandial Glucose Peak Reduces the Glucose Response in Young Men with Overweight or Obesity: A Randomized Crossover Study

BACKGROUND

Although a single bout of postmeal exercise can lower postprandial glucose (PPG), its optimal timing remains unclear.

OBJECTIVE

This study aimed to investigate the effect of exercise timing using an individualized approach on PPG in overweight or obese young men.

METHODS

Twenty men [age: 23.0 ± 4.3 y; BMI (kg/m2): 27.4 ± 2.8] each completed three 240-min trials in a randomized order separated by 6-14 d: 1) sitting (SIT), 2) walking initiated at each participant's PPG-peak time (PPGP) (iP), and 3) walking initiated 20 min before the PPGP (20iP). For each participant, PPGP was predetermined using continuous glucose monitoring. Walking was performed at 50% maximal oxygen consumption for 30 min. Venous blood was collected at 15- and 30-min intervals for 0-120 min and 120-240 min, respectively. The primary outcome was plasma PPG. Generalized estimating equations were used for comparison between trials.

RESULTS

Compared with SIT, the 4-h incremental AUCs (iAUCs) for plasma PPG (-0.6 mmol · L-1 · h; P = 0.047) and insulin (-28.7%, P < 0.001) were reduced in 20iP only, and C-peptide concentrations were lower after iP (-14.9%, P = 0.001) and 20iP (-28.7%, P < 0.001). Plasma insulin (-11.1%, P = 0.006) and C-peptide (-8.3%, P = 0.012) were lower due to the 20iP compared with iP treatment. Finally, PPG reductions due to iP and 20iP occurred only in men with a BMI > 27.5 kg/m2 (iP, -11.2%; 20iP, -14.7%; P = 0.047) and higher glucose iAUC values during SIT (iP, -25.5%; 20iP, -25.7%; P < 0.001).

CONCLUSIONS

Walking initiated 20 min before PPGP lowered PPG and plasma insulin and C-peptide concentrations in young men with overweight or obesity, in particular in those with high BMI or glucose iAUC values during SIT; it also lowered plasma insulin and C-peptide concentrations more effectively than did exercise initiated at PPGP. This trial was registered at the Chinese Clinical Trial Registry (http://www.chictr.org.cn/index.aspx) as ChiCTR1900023175.

Glucose-induced insulin secretion in isolated human islets: Does it truly reflect β-cell function in vivo?

BACKGROUND

Diabetes always involves variable degrees of β-cell demise and malfunction leading to insufficient insulin secretion. Besides clinical investigations, many research projects used rodent islets to study various facets of β-cell pathophysiology. Their important contributions laid the foundations of steadily increasing numbers of experimental studies resorting to isolated human islets.

SCOPE OF REVIEW

This review, based on an analysis of data published over 60 years of clinical investigations and results of more recent studies in isolated islets, addresses a question of translational nature. Does the information obtained in vitro with human islets fit with our knowledge of insulin secretion in man? The aims are not to discuss specificities of pathways controlling secretion but to compare qualitative and quantitative features of glucose-induced insulin secretion in isolated human islets and in living human subjects.

MAJOR CONCLUSIONS

Much of the information gathered in vitro can reliably be translated to the in vivo situation. There is a fairly good, though not complete, qualitative and quantitative coherence between insulin secretion rates measured in vivo and in vitro during stimulation with physiological glucose concentrations, but the concordance fades out under extreme conditions. Perplexing discrepancies also exist between insulin secretion in subjects with Type 2 diabetes and their islets studied in vitro, in particular concerning the kinetics. Future projects should ascertain that the experimental conditions are close to physiological and do not alter the function of normal and diabetic islets.

β cell aging and age-related diabetes

Type 2 diabetes is characterized by insulin resistance and loss of β cell mass and function. Aging is considered as a major risk factor for development of type 2 diabetes. However, the roles of pancreatic β cell senescence and systemic aging in the pathogenesis of type 2 diabetes in elderly people remain poorly understood. In this review, we aimed to discuss the current findings and viewpoints focusing on β cell aging and the development of type 2 diabetes.

Incidence of diabetes in South Asian young adults compared to Pima Indians

INTRODUCTION

South Asians (SA) and Pima Indians have high prevalence of diabetes but differ markedly in body size. We hypothesize that young SA will have higher diabetes incidence than Pima Indians at comparable body mass index (BMI) levels.

RESEARCH DESIGN AND METHODS

We used prospective cohort data to estimate age-specific, sex, and BMI-specific diabetes incidence in SA aged 20-44 years living in India and Pakistan from the Center for Cardiometabolic Risk Reduction in South Asia Study (n=6676), and compared with Pima Indians, from Pima Indian Study (n=1852).

RESULTS

At baseline, SA were considerably less obese than Pima Indians (BMI (kg/m²): 24.4 vs 33.8; waist circumference (cm): 82.5 vs 107.0). Age-standardized diabetes incidence (cases/1000 person-years, 95% CI) was lower in SA than in Pima Indians (men: 14.2, 12.2-16.2 vs 37.3, 31.8-42.8; women: 14.8, 13.0-16.5 vs 46.1, 41.2-51.1). Risk of incident diabetes among 20-24-year-old Pima men and women was six times (relative risk (RR), 95% CI: 6.04, 3.30 to 12.0) and seven times (RR, 95% CI: 7.64, 3.73 to 18.2) higher as compared with SA men and women, respectively. In those with BMI <25 kg/m², however, the risk of diabetes was over five times in SA men than in Pima Indian men. Among those with BMI ≥30 kg/m², diabetes incidence in SA men was nearly as high as in Pima men. SA and Pima Indians had similar magnitude of association between age, sex, BMI, and insulin secretion with diabetes. The effect of family history was larger in SA, whereas that of insulin resistance was larger in Pima Indians CONCLUSIONS: In the background of relatively low insulin resistance, higher diabetes incidence in SA is driven by poor insulin secretion in SA men. The findings call for research to improve insulin secretion in early natural history of diabetes.

Bayesian parameter estimation in the oral minimal model of glucose dynamics from non-fasting conditions using a new function of glucose appearance

BACKGROUND AND OBJECTIVE

The oral minimal model (OMM) of glucose dynamics is a prominent method for assessing postprandial glucose metabolism. The model yields estimates of insulin sensitivity and the meal-related appearance of glucose from insulin and glucose data after an oral glucose challenge. Despite its success, the OMM approach has several weaknesses that this paper addresses.

METHODS

A novel procedure introducing three methodological adaptations to the OMM approach is proposed. These are: (1) the use of a fully Bayesian and efficient method for parameter estimation, (2) the model identification from non-fasting conditions using a generalised model formulation and (3) the introduction of a novel function to represent the meal-related glucose appearance based on two superimposed components utilising a modified structure of the log-normal distribution. The proposed modelling procedure is applied to glucose and insulin data from subjects with normal glucose tolerance consuming three consecutive meals in intervals of four hours.

RESULTS

It is shown that the glucose effectiveness parameter of the OMM is, contrary to previous results, structurally globally identifiable. In comparison to results from existing studies that use the conventional identification procedure, the proposed approach yields an equivalent level of model fit and a similar precision of insulin sensitivity estimates. Furthermore, the new procedure shows no deterioration of model fit when data from non-fasting conditions are used. In comparison to the conventional, piecewise linear function of glucose appearance, the novel log-normally based function provides an improved model fit in the first 30 min of the response and thus a more realistic estimation of glucose appearance during this period. The identification procedure is implemented in freely accesible MATLAB and Python software packages.

CONCLUSIONS

We propose an improved and freely available method for the identification of the OMM which could become the future standardard for the oral minimal modelling method of glucose dynamics.

Insulin sensitivity in critically ill patients: are women more insulin resistant?

Background

Glycaemic control (GC) in intensive care unit is challenging due to significant inter- and intra-patient variability, leading to increased risk of hypoglycaemia. Recent work showed higher insulin resistance in female preterm neonates. This study aims to determine if there are differences in inter- and intra-patient metabolic variability between sexes in adults, to gain in insight into any differences in metabolic response to injury. Any significant difference would suggest GC and randomised trial design should consider sex differences to personalise care.

Methods

Insulin sensitivity (SI) levels and variability are identified from retrospective clinical data for men and women. Data are divided using 6-h blocks to capture metabolic evolution over time. In total, 91 male and 54 female patient GC episodes of minimum 24 h are analysed. Hypothesis testing is used to determine whether differences are significant (P < 0.05), and equivalence testing is used to assess whether these differences can be considered equivalent at a clinical level. Data are assessed for the raw cohort and in 100 Monte Carlo simulations analyses where the number of men and women are equal.

Results

Demographic data between females and males were all similar, including GC outcomes (safety from hypoglycaemia and high (> 50%) time in target band). Females had consistently significantly lower SI levels than males, and this difference was not clinically equivalent. However, metabolic variability between sexes was never significantly different and always clinically equivalent. Thus, inter-patient variability was significantly different between males and females, but intra-patient variability was equivalent.

Conclusion

Given equivalent intra-patient variability and significantly greater insulin resistance, females can receive the same benefit from safe, effective GC as males, but may require higher insulin doses to achieve the same glycaemia. Clinical trials should consider sex differences in protocol design and outcome analyses.

Insulin sensitivity in critically ill patients: are women more insulin resistant?

BACKGROUND

Glycaemic control (GC) in intensive care unit is challenging due to significant inter- and intra-patient variability, leading to increased risk of hypoglycaemia. Recent work showed higher insulin resistance in female preterm neonates. This study aims to determine if there are differences in inter- and intra-patient metabolic variability between sexes in adults, to gain in insight into any differences in metabolic response to injury. Any significant difference would suggest GC and randomised trial design should consider sex differences to personalise care.

METHODS

Insulin sensitivity (SI) levels and variability are identified from retrospective clinical data for men and women. Data are divided using 6-h blocks to capture metabolic evolution over time. In total, 91 male and 54 female patient GC episodes of minimum 24 h are analysed. Hypothesis testing is used to determine whether differences are significant (P < 0.05), and equivalence testing is used to assess whether these differences can be considered equivalent at a clinical level. Data are assessed for the raw cohort and in 100 Monte Carlo simulations analyses where the number of men and women are equal.

RESULTS

Demographic data between females and males were all similar, including GC outcomes (safety from hypoglycaemia and high (> 50%) time in target band). Females had consistently significantly lower SI levels than males, and this difference was not clinically equivalent. However, metabolic variability between sexes was never significantly different and always clinically equivalent. Thus, inter-patient variability was significantly different between males and females, but intra-patient variability was equivalent.

CONCLUSION

Given equivalent intra-patient variability and significantly greater insulin resistance, females can receive the same benefit from safe, effective GC as males, but may require higher insulin doses to achieve the same glycaemia. Clinical trials should consider sex differences in protocol design and outcome analyses.

Effects on Outcomes of Hyperglycemia in the Hyperacute Stage after Acute Traumatic Spinal Cord Injury

Hyperglycemia has adverse effects on neuronal recovery after brain injury, but its effects after spinal cord injury (SCI) are understudied. This retrospective cohort study examined the potential effects on outcomes of hyperglycemia in the hyperacute stage after acute traumatic SCI. This study included all individuals enrolled in the National Acute Spinal Cord Injury Study 3 (NASCIS-3). Glycemic levels at 24 h, at 48 h, and at day 7 after acute SCI were examined as potential determinants of survival, neurological outcomes (using NASCIS motor, sensory, and pain scores), and functional outcome (using the Functional Independence Measure [FIM]) within the first year post-SCI. Hyperglycemia was defined using two thresholds (140 mg/dL and 180 mg/dL). Study subjects were 76 females and 423 males with an overall mean age of 36 years who sustained mostly cervical SCI due to motor vehicle accidents or falls. Hyperglycemia diagnosed at day 7 post-injury was associated with significantly greater mortality rates post-SCI. Among the survivors, hyperglycemia during the hyperacute stage was not significantly correlated with neurological recovery post-SCI. Hyperglycemia persistent until day 7 was significantly correlated with lower functional scores post-SCI. These results suggest that hyperglycemia at day 7 is correlated with greater mortality rates within the first year post-SCI. Although hyperglycemia during the hyperacute stage was not associated with neurological recovery, hyperglycemia at day 7 may adversely affect functional recovery within the first year post-SCI. Future investigations are needed to determine the optimal glycemic target in the management of patients with SCI.

Model-Based Assessment of C-Peptide Secretion and Kinetics in Post Gastric Bypass Individuals Experiencing Postprandial Hyperinsulinemic Hypoglycemia

Assessment of insulin secretion is key to diagnose postprandial hyperinsulinemic hypoglycemia (PHH), an increasingly recognized complication following bariatric surgery. To this end, the Oral C-peptide Minimal Model (OCMM) can be used. This usually requires fixing C-peptide (CP) kinetics to the ones derived from the Van Cauter population model (VCPM), which has never been validated in PHH individuals. The objective of this work was to test the validity of the OCMM coupled with the VCPM in PHH subjects and propose a method to overcome the observed limitations. Two cohorts of adults with PHH after gastric bypass (GB) underwent either a 75 g oral glucose (9F/3M; age=42±9 y; BMI=28.3±6.9 kg/m²) or a 60 g mixed-meal (7F/3M; age = 43 ± 11 y; BMI=27.5±4.2 kg/m²) tolerance test. The OCMM was identified on CP concentration data with CP kinetics fixed to VCPM (VC approach). In both groups, the VC approach underestimated CP-peak and overestimated CP-tail suggesting CP kinetics predicted by VCPM to be inaccurate in this population. Thus, the OCMM was identified using CP kinetics estimated from the data (DB approach) using a Bayesian Maximum a Posteriori estimator. CP data were well predicted in all the subjects using the DB approach, highlighting a significantly faster CP kinetics in patients with PHH compared to the one predicted by VCPM. Finally, a simulation study was used to validate the proposed approach. The present findings question the applicability of the VCPM in patients with PHH after GB and call for CP bolus experiments to develop a reliable CP kinetic model in this population.

The Padova Type 2 Diabetes Simulator from Triple-Tracer Single-Meal Studies: In Silico Trials Also Possible in Rare but Not-So-Rare Individuals

Background:In silico trials in type 2 diabetes (T2D) would be useful for testing diabetes treatments and accelerating the development of new antidiabetic drugs. In this study, we present a T2D simulator able to reproduce the variability observed in a T2D population. The simulator also allows to safely experiment on virtual subjects with severe (and possibly rare) pathological conditions. Methods: A meal simulation model of glucose, insulin, and C-peptide systems, made of 15 differential equations and 39 parameters, has been identified using a system decomposition and forcing function Bayesian strategy on data of 51 T2D subjects undergoing a single triple-tracer mixed meal. One hundred T2D in silico subjects have been generated from the joint distribution of estimated model parameters. A case study is presented to illustrate the simulator use for testing a virtual drug (improving insulin action and secretion) in a subpopulation of rare, extremely impaired, T2D subjects. Results: The model well fitted T2D data and parameters were estimated with precision. Simulated plasma glucose, insulin, and C-peptide well matched the data (e.g., median [25^th-75^th percentile] glucose area under the curves of 6.9 [6.1-8.5] 10⁴ mg/dL·min in silico vs. 7.0 [5.6-8.2] 10⁴ mg/dL·min in vivo). The potential use of the simulator was shown in a case study, in which the (virtual) antidiabetic drug dose was optimized for very insulin-resistant T2D subjects. Conclusions: We have developed a T2D simulator that captures the behavior of T2D population during a meal, both in terms of average and intersubject variability. The simulator represents a cost-effective way to test new antidiabetic drugs, before moving to human trials.

A Reduced Incretin Effect Mediated by the rs7903146 Variant in the TCF7L2 Gene Is an Early Marker of β-Cell Dysfunction in Obese Youth

OBJECTIVE

The risk genotype for the common variant rs7903146 of the transcription factor 7-like-2 (TCF7L2) gene has been found to affect the incretin response in healthy and obese adults; however, whether a similar functional defect is also present in obese adolescents remains unexplored. Herein, we examined the functional effect of the rs7903146 variant in the TCF7L2 gene on the incretin effect and determined its translational metabolic manifestation by performing deep phenotyping of the incretin system, β-cell function relative to insulin sensitivity, the gastrointestinal-induced glucose disposal (GIGD) in obese youth with normal and impaired glucose tolerance.

RESEARCH DESIGN AND METHODS

Thirty-nine obese adolescents without diabetes (median age 15 [25th, 75th percentile 14, 18] years; BMI 37 [33, 43] kg/m²) were genotyped for the rs7903146 variant of TCF7L2 and underwent a 3-h oral glucose tolerance test (OGTT) followed by an isoglycemic intravenous glucose infusion (iso-intravenous glucose tolerance test [IVGTT]) to match the plasma glucose concentrations during the OGTT and a hyperglycemic clamp with arginine stimulation. The incretin effect was measured as 100 * (AUC-SR_OGTT - AUC-SR_iso-IVGTT) / AUC-SR_OGTT, where AUC-SR = area under the curve of C-peptide secretion rate. Participants were grouped into tertiles according to the percentage incretin effect (high, moderate, and low) to describe their metabolic phenotype.

RESULTS

The presence of T risk allele for TCF7L2 was associated with a markedly reduced incretin effect compared with the wild-type genotype (0.3% [-7.2, 14] vs. 37.8% [12.5, 52.4], P < 0.002). When the cohort was stratified by incretin effect, the high, moderate, and low incretin effect groups did not differ with respect to anthropometric features, while the low incretin effect group exhibited higher 1-h glucose (P = 0.015) and a reduced disposition index, insulin sensitivity, and insulin clearance compared with the high incretin effect group. GIGD was reduced in the low incretin effect group (P = 0.001). The three groups did not differ with respect to intravenous glucose-induced insulin secretion and arginine response during the hyperglycemic clamp.

CONCLUSIONS

A reduced incretin effect and its association with the TCF7L2 variant rs7903146 identify an early metabolic phenotype in obese youth without diabetes, featuring a higher plasma glucose peak at 1 h; lower insulin secretion, sensitivity, and clearance; and GIGD.

Age and sex dependent reference intervals for random plasma/serum glucose concentrations related to different sampling devices and determined by an indirect procedure with data mining

The glucose concentration in plasma or serum is one of the most often requested analytical values in laboratory medicine. Whereas the analytical part of the glucose determination is well standardised, the standardisation of the pre-examination part (pre-analytical phase) is not sufficiently solved, yet. In view of the present controversial discussion regarding the most efficient prevention of pre-analytical glycolysis, the question arises whether the economical and logistic expenses for inhibiting glycolysis determining random glucose concentration are justified. In hospitals with adequate logistics (e.g. pneumatic tube systems for blood tubes) to guarantee a blood sample transport time of about 1 – 2 h, plasma or serum without prevention of glycolysis can be applied for random glucose concentrations if the reference limits are estimated by the laboratory. If such logistics are not available, especially in primary care services, either plasma or serum samples or whole blood in special tubes with anti-glycolytic additives may be sent to the laboratory.

Young-onset diabetes, nutritional therapy and novel insulin delivery systems: a report from the 21st Hong Kong Diabetes and Cardiovascular Risk Factors - East Meets West Symposium

The prevalence and incidence of young-onset diabetes are increasing in many parts of the world, with the most rapid increase occurring in Asia, where one in five people with diabetes are diagnosed below the age of 40 years. Accumulation of glycaemic burden from an early age significantly increases the lifetime risks of developing complications from diabetes. Despite impending health threats, young people fare worse in the control of blood glucose and other metabolic risk factors. Challenges in the management of young-onset diabetes are compounded by heterogeneity of the underlying causes, pathophysiology and clinical phenotypes in this group. Effective characterization of people with diabetes has implications in steering the choice of glucose-lowering drugs, which, in turn, determines the clinical outcome. Medical nutritional therapy is key to effective management of people with diabetes but dietary adherence is often suboptimal among younger individuals. A recently published consensus report on nutritional therapy addresses dietary management in people with prediabetes as well as diabetes, and summarizes clinical evidence regarding macronutrient and micronutrient composition as well as eating patterns in people with diabetes. For people with type 1 diabetes, automated insulin delivery systems have rapidly evolved since the concept was first introduced at the National Institute of Health and the Juvenile Diabetes Research Foundation in 2005. The subsequent development of a type 1 diabetes simulator, developed using detailed human physiology data on carbohydrate metabolism replaced the need for pre-clinical animal studies and facilitated the seamless progression to artificial pancreas human clinical trials.

Midlife susceptibility to the effects of poor diet on diabetes risk

OBJECTIVE

Type 2 diabetes mellitus (T2D) prevalence continues to increase, and age of incidence continues to decrease. More information is needed to target interventions to the ages where they can be most effective. The objective of this study was to explore the degree to which the association between diet and T2D incidence changes through adulthood.

METHODS

Participants were a large number (N = 2818) of community living adults in Canberra and Queanbeyan, Australia across three cohorts; young (20-24 followed to 32-36), mid-life (40-44 followed to 52-56) and late-life (60-64 followed to 72-76). Self-report dietary pattern scores at baseline and diabetes incidence across 12 years follow-up were measured, alongside confounders of caloric intake, sex, smoking status, years of education, hypertension, BMI and physical activity.

RESULTS

Cox proportional hazards indicated that neither Western nor Prudent dietary pattern scores were significantly associated with T2D incidence when confounders were included in the model. Unadjusted estimates suggested a positive association between Western dietary pattern scores and subsequent diabetes incidence (HR = 1.40, 95% CI [1.18, 1.64]). Compared with the mid-life cohort, a higher Western dietary pattern score posed a lower risk for incident T2D in the young cohort (unadjusted HR = 0.46, 95% CI [0.22, 0.96]), who also had significantly lower BMI and higher physical activity. No such significant effects were found for the late-life cohort.

CONCLUSIONS

Our findings indicate that mid-life may be a period of heightened vulnerability to the effects of an unhealthy diet on diabetes risk, but this effect is attenuated when risk factors related to diet, such as adiposity, are taken into account.

In Silico Cloning of Target Type 2 Diabetes Population for Treatments Development and Decision Support. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020;2020:5111-5114. [PMID: 33019136 DOI: 10.1109/embc44109.2020.9175271]

Therapies for treatment of type 2 diabetes (T2D) involve a variety of medications, depending on the stage of T2D progression. It is now an accepted knowledge that in silico trials can help to accelerate drug development and support treatment optimization. A T2D simulator (T2DS), consisting of a model of the glucose-insulin system and an in silico population describing glucose-insulin dynamics in T2D subjects, has been recently developed based on early-stage T2D data, studied with sophisticated experimental techniques. This limits the domain of validity of the simulator to this specific sub-population of T2D. Here we proposed a method for tuning the T2DS to any desired T2D target population, e.g. insulin-naïve (i.e., not experienced with insulin) patients, without the need to resort to complex and expensive clinical studies. This will allow to use the T2DS for testing treatments in the target population. To illustrate the methodology, we used a case study: extending the T2DS to reproduce the behavior of insulin-naïve T2D subjects. The methodology described here can be extended to other stages of T2D, allowing an extensive in silico testing phase of different treatments before human trials.

Sex differences in cardiovascular risk factors for myocardial infarction

BACKGROUND

Cardiovascular disease is a leading cause of mortality worldwide. This study investigated the effects of sex on traditional cardiovascular risk factors for remote myocardial infarction in a community.

METHODS

A cross-sectional study was performed comprising 20,899 participants who underwent physical examination from 2013 to 2015, including systemic blood pressure and 12-lead electrocardiogram monitoring. Fasting blood samples were collected for blood cell counts and biochemistry tests. Remote myocardial infarction was diagnosed on the basis of electrocardiogram findings.

RESULTS

A total of 71 male and 21 female patients aged over 50 years were identified with remote myocardial infarction. In the female cohort, low-density lipoprotein (LDL), total cholesterol (TC), as well as high-density lipoprotein (HDL) were negatively correlated with myocardial infarction after adjusting for age. In the male cohort, after adjusting for age, serum levels of glycated hemoglobin (HbA1c) and fasting glucose were positively correlated with myocardial infarction, but the lipid profile, including low-density lipoprotein (LDL), total cholesterol (TC), and high-density lipoprotein (HDL), was negatively correlated with remote myocardial infarction.

CONCLUSION

In the male population, dyslipidemia and abnormal glucose metabolism play a role in myocardial infarction. In the female population, dyslipidemia is independent of glucose metabolism. This study highlights sex differences in the regulation of lipids and glucose metabolism in patients with remote myocardial infarction.

Dual glucagon-like peptide-1 receptor/glucagon receptor agonist SAR425899 improves beta-cell function in type 2 diabetes

AIM

To evaluate the change in insulin sensitivity, β-cell function and glucose absorption after 28 days of treatment with high and low doses of SAR425899, a novel dual glucagon-like peptide-1 receptor/glucagon receptor agonist, versus placebo.

MATERIALS AND METHODS

Thirty-six overweight to obese subjects with type 2 diabetes were randomized to receive daily subcutaneous administrations of low-dose SAR425899 (0.03, 0.06 and 0.09 mg) and high-dose SAR425899 (0.06, 0.12 and 0.18 mg) or placebo for 28 days; dose escalation occurred after days 7 and 14. Mixed meal tolerance tests were conducted before treatment (day -1) and on days 1 and 28. Oral glucose and C-peptide minimal models were used to quantify metabolic indices of insulin sensitivity, β-cell responsiveness and glucose absorption.

RESULTS

With low-dose SAR425899, high-dose SAR425899 and placebo, β-cell function from day -1 to day 28 increased by 163%, 95% and 23%, respectively. The change in area under the curve for the rate of meal glucose appearance between 0 and 120 minutes was -32%, -20% and 8%, respectively.

CONCLUSIONS

After 28 days of treatment, SAR425899 improved postprandial glucose control by significantly enhancing β-cell function and slowing glucose absorption rate.

Flash Glucose Monitoring Can Accurately Reflect Postprandial Glucose Changes in Healthy Adults in Nutrition Studies

OBJECTIVE

This study investigated the accuracy of a flash glucose monitoring system (FGMS) in a postprandial setting.

METHODS

Ten fasted adults without diabetes wore the FGMS sensors then consumed a standard breakfast. Their glucose levels were subsequently recorded for 2 hours, both by the FGMS and by measuring capillary glucose levels using the glucose oxidase method. The accuracy of the FGMS data was assessed using the accuracy limits stated in ISO 15197:2013.

RESULTS

FGMS measurements were mostly lower than glucose oxidase measurements (mean absolute relative difference ± SD: 25.4 ± 17.0%, p < 0.001). However, the maximum difference from baseline captured by the two methods was not significantly different (mean ± SD, glucose oxidase: 58.5 ± 18.9 mg/dl; FGMS, 54.4 ± 28.9 mg/dl, p = 0.366).

CONCLUSIONS

FGMS could track the incremental glycaemic excursions after meals in adults without diabetes, yet further studies with greater sample sizes are needed to confirm this finding.

Acute exercise effects on postprandial fat oxidation: meta-analysis and systematic review

The purpose of this systematic review was to synthesize and evaluate current literature examining the effects of exercise on postprandial fat oxidation, as well as to provide future direction. A quantitative review was performed using meta-analytic methods. A moderator analysis was performed to investigate potential variables that could influence the effect of exercise on postprandial fat oxidation. Fifty-six effects from 26 studies were retrieved. There was a moderate effect of exercise on postprandial fat oxidation (Cohen's d = 0.58 (95% CI, 0.39 to 0.78)). Moderator analysis revealed that sex, age, weight status, training status, exercise type, exercise intensity, timing of exercise, and composition of the meal challenge significantly affected the impact of prior exercise on postprandial fat oxidation. The moderator analysis also indicated that most previous studies have investigated the impact of prior moderate-intensity endurance exercise on postprandial fat oxidation in young, healthy, lean men. Suggested priorities for future research in this area include (i) an examination of sex differences in and/or female-specific aspects of postprandial metabolism; (ii) a comprehensive evaluation of exercise modalities, intensities, and durations; and (iii) a wider variety of test meal compositions, especially those with higher fat content. Novelty A systematic review of the impact of exercise on postprandial fat oxidation was performed using meta-analytic methods. Analysis revealed a moderate effect of exercise on postprandial fat oxidation. The presented data support a need for future studies to investigate sex differences and to include comprehensive evaluations of exercise modalities, intensities, and duration.

The roles of first phase, second phase insulin secretion, insulin resistance, and glucose effectiveness of having prediabetes in nonobese old Chinese women

It has been established that prediabetes can causes significant comorbidities, particularly in the elderly. The deterioration of glucose metabolism are generally considered to be results of the impairment of the 4 factors: first, second insulin secretion (FPIS, SPIS, respectively), glucose effectiveness (GE), and insulin resistance. In this study, we enrolled older women to investigate their relationships with prediabetes.Five thousand four hundred eighty-two nonobese, nondiabetic women were included. They were divided into normal glucose tolerance and prediabetes groups. Receiver operating characteristic curve was performed to investigate the effects on whether to have prediabetes for each factors. Two models were built: Model 1: FPIS + SPIS, and Model 2: model 1 + GE. The area under the receiver operating characteristic (aROC) curve was used to determine the predictive power of these models.The aROC curve of GE was significantly higher than the diagonal line followed by SPIS and FPIS accordingly. The aROC curve of Model 1 (0.611) was not different from GE. However, Model 2 improved significantly up to 0.663. Based on this model, an equation was built (-0.003 × GE - 212.6 × SPIS - 17.9 × insulin resistance + 4.8). If the calculated value is equal or higher than 0 (≥0), then the subject has higher chance to have prediabetes (sensitivity = 0.607, specificity = 0.635).Among the 4 factors, GE is the most important contributor for prediabetes in older women. By building a model composed of FPIS, SPIS, and GE, the aROC curve increased significantly. The equation built from this model could predict prediabetes precisely.

A Systematic Review of Beta Cell Function in Adults of Black African Ethnicity

BACKGROUND

Understanding ethnic differences in beta cell function has important implications for preventative and therapeutic strategies in populations at high risk of type 2 diabetes (T2D). The existing literature, largely drawn from work in children and adolescents, suggests that beta cell function in black African (BA) populations is upregulated when compared to white Europeans (WE).

METHODS

A systematic literature search was undertaken in June 2018 to identify comparative studies of beta cell function between adults (>age 18 years) of indigenous/diasporic BA and WE ethnicity. All categories of glucose tolerance and all methodologies of assessing beta cell function in vivo were included.

RESULTS

41 studies were identified for inclusion into a qualitative synthesis. The majority were studies in African American populations (n = 30) with normal glucose tolerance (NGT)/nondiabetes (n = 25), using intravenous glucose stimulation techniques (n = 27). There were fewer studies in populations defined as only impaired fasting glucose/impaired glucose tolerance (IFG/IGT) (n = 3) or only T2D (n = 3). Although BA broadly exhibited greater peripheral insulin responses than WE, the relatively small number of studies which measured C-peptide to differentiate between beta cell insulin secretion and hepatic insulin extraction (n = 14) had highly variable findings. In exclusively IGT or T2D cohorts, beta cell insulin secretion was found to be lower in BA compared to WE.

CONCLUSIONS

There is inconsistent evidence for upregulated beta cell function in BA adults, and they may in fact exhibit greater deficits in insulin secretory function as glucose intolerance develops.

Impaired insulin signaling in unaffected siblings and patients with first-episode psychosis

Patients with psychotic disorders are at high risk for type 2 diabetes mellitus, and there is increasing evidence that patients display glucose metabolism abnormalities before significant antipsychotic medication exposure. In the present study, we examined insulin action by quantifying insulin sensitivity in first-episode psychosis (FEP) patients and unaffected siblings, compared to healthy individuals, using a physiological-based model and comprehensive assessment battery. Twenty-two unaffected siblings, 18 FEP patients, and 15 healthy unrelated controls were evaluated using a 2-h oral glucose tolerance test (OGTT), with 7 samples of plasma glucose and serum insulin concentration measurements. Insulin sensitivity was quantified using the oral minimal model method. Lipid, leptin, free fatty acids, and inflammatory marker levels were also measured. Anthropometric, nutrient, and activity assessments were conducted; total body composition and fat distribution were determined using whole-body dual-energy X-ray absorptiometry. Insulin sensitivity significantly differed among groups (F = 6.01 and 0.004), with patients and siblings showing lower insulin sensitivity, compared to controls (P = 0.006 and 0.002, respectively). Body mass index, visceral adipose tissue area (cm²), lipids, leptin, free fatty acids, inflammatory markers, and activity ratings were not significantly different among groups. There was a significant difference in nutrient intake with lower total kilocalories/kilogram body weight in patients, compared to siblings and controls. Overall, the findings suggest that familial abnormal glucose metabolism or a primary insulin signaling pathway abnormality is related to risk for psychosis, independent of disease expression and treatment effects. Future studies should examine underlying biological mechanisms of insulin signaling abnormalities in psychotic disorders.

Determination of Postprandial Glycemic Responses by Continuous Glucose Monitoring in a Real-World Setting

BACKGROUND

Self-monitoring of blood glucose using capillary glucose testing (C) has a number of shortcomings compared to continuous glucose monitoring (CGM). We aimed to compare these two methods and used blood glucose measurements in venous blood (IV) as a reference. Postprandial blood glucose levels were measured after 50 g oral glucose load and after the consumption of a portion of different foods containing 50 g of carbohydrates. We also evaluated the associations between postprandial glucose responses and the clinical characteristics of the participants at the beginning of the study.

METHODS

12 healthy volunteers (age: 36 ± 17 years, BMI: 24.9 ± 3.5 kg/m²) ate white bread (WB) and whole grain (WG) bread and drank a 50 g glucose drink as reference. Postprandial glucose responses were evaluated by CGM, IV and C blood glucose measurements. Incremental area under the curve (AUC_i) of postprandial blood glucose was calculated for 1 h (AUC_{i 0-60}) and 2 h (AUC_{i 0-120}).

RESULTS

After the consumption of white bread and whole grain bread, the AUC_{i 0-60 min} did not differ between CGM and IV or C. AUC_{i 0-120 min} of CGM showed no difference compared to C. Correlation analyses revealed a positive association of age with glucose AUC_{i 0-120} (r = 0.768; P = 0.004) and WG AUC_{i 0-120} (r = 0.758; P = 0.004); fasting blood glucose correlated with WG AUC_{i 0-120} (r = 0.838; P < 0.001).

CONCLUSION

Despite considerable inter-individual variability of postprandial glycemic responses, CGM evaluated postprandial glycemic excursions which had comparable results compared to standard blood glucose measurements under real-life conditions. Associations of AUC_{i 0-60} and AUC_{i 0-120} postprandial glucose response with age or fasting blood glucose could be shown.

Feature Selection for Blood Glucose Level Prediction in Type 1 Diabetes Mellitus by Using the Sequential Input Selection Algorithm (SISAL)

Feature selection is a primary exercise to tackle any forecasting task. Machine learning algorithms used to predict any variable can improve their performance by lessening their computational effort with a proper dataset. Anticipating future glycemia in type 1 diabetes mellitus (DM1) patients provides a baseline in its management, and in this task, we need to carefully select data, especially now, when novel wearable devices offer more and more information. In this paper, a complete characterization of 25 diabetic people has been carried out, registering innovative variables like sleep, schedule, or heart rate in addition to other well-known ones like insulin, meal, and exercise. With this ground-breaking data compilation, we present a study of these features using the Sequential Input Selection Algorithm (SISAL), which is specially prepared for time series data. The results rank features according to their importance, regarding their relevance in blood glucose level prediction as well as indicating the most influential past values to be taken into account and distinguishing features with person-dependent behavior from others with a common performance in any patient. These ideas can be used as strategies to select data for predicting glycemia depending on the availability of computational power, required speed, or required accuracy. In conclusion, this paper tries to analyze if there exists symmetry among the different features that can affect blood glucose levels, that is, if their behavior is symmetric in terms of influence in glycemia.

Sex Dependent Dysregulation of Hepatic Glucose Production in Lean Type 2 Diabetic Rats

We have characterized a lean type 2 diabetic rat model by gestational low protein programming. We aimed to identify if the regulation of hepatic glucose production (HGP) via gluconeogenesis and glycogenolysis is affected and if there are any sex differences. Fasting (6-7 months old) type 2 diabetic rats received 2H2O followed by a primed constant rate infusion of [6,6-2H2] glucose. Blood samples were drawn during steady states after 4 h of fasting and following a euglycemic hyperinsulinemic clamp. HGP and the fraction of glucose derived from gluconeogenesis under fasting and euglycemic states were measured from steady state glucose enrichments after the infusion of [6,6-2H2]glucose and 2H2O tracers. Glycogenolysis was determined by calculating the difference between total HGP and gluconeogenesis rates. Hepatic gene expression of enzymes involved in HGP were quantified using qPCR. HGP rates was similar during fasting in both groups and sexes. However, under simulated fed condition, HGP rate was suppressed in controls but not in type 2 diabetic rats. They also showed inefficient HGP suppression in a simulated fed state. Differential analysis showed that suppression of both gluconeogenesis and glycogenolysis under simulated fed state was affected in these low protein programmed type 2 diabetic rats. These effects were greater in females when compared to males. Further, key genes involved in these processes like G6Pase, Pepck, pyruvate carboxylase, and glycogen phosphorylase in liver were dysregulated. Our data shows impaired suppression of HGP via gluconeogenesis and glycogenolysis in type 2 diabetic rats with greater effects on females.

The Role of Sexual Hormones on the Enteroinsular Axis

Sex steroid estrogens, androgens, and progesterone, produced by the gonads, which have long been considered as endocrine glands, are implicated in sexual differentiation, puberty, and reproduction. However, the impact of sex hormones goes beyond these effects through their role on energy metabolism. Indeed, sex hormones are important physiological regulators of glucose homeostasis and, in particular, of the enteroinsular axis. In this review, we describe the roles of estrogens, androgens, and progesterone on glucose homeostasis through their effects on pancreatic α- and β-cells, as well as on enteroendocrine L-cells, and their implications in hormonal biosynthesis and secretion. The analysis of their mechanisms of action with the dissection of the receptors implicated in the several protective effects could provide some new aspects of the fine-tuning of hormonal secretion under the influence of the sex. This knowledge paves the way to the understanding of transgender physiology and new potential therapeutics in the field of type 2 diabetes.

Different physiological mechanisms underlie an adverse cardiovascular disease risk profile in men and women

CVD affect about one-third of the population and are the leading cause of mortality. The prevalence of CVD is closely linked to the prevalence of obesity because obesity is commonly associated with metabolic abnormalities that are important risk factors for CVD, including insulin resistance, pre-diabetes, and type-2 diabetes, atherosclerotic dyslipidaemia, endothelial dysfunction and hypertension. Women have a more beneficial traditional CVD risk profile (lower fasting plasma glucose, less atherogenic lipid profile) and a lower absolute risk for CVD than men. However, the relative risk for CVD associated with hyperglycaemia and dyslipidaemia is several-fold higher in women than in men. The reasons for the sex differences in CVD risk associated with metabolic abnormalities are unclear but could be related to differences in the mechanisms that cause hyperglycaemia and dyslipidaemia in men and women, which could influence the pathogenic processes involved in CVD. In the present paper, we review the influence of a person's sex on key aspects of metabolism involved in the cardiometabolic disease process, including insulin action on endogenous glucose production, tissue glucose disposal, and adipose tissue lipolysis, insulin secretion and insulin plasma clearance, postprandial glucose, fatty acid, and triglyceride kinetics, hepatic lipid metabolism and myocardial substrate use. We conclude that there are marked differences in many aspects of metabolism in men and women that are not all attributable to differences in the sex hormone milieu. The mechanisms responsible for these differences and the clinical implications of these observations are unclear and require further investigation.

Elevated insulin levels following 7 days of increased sedentary time are due to lower hepatic extraction and not higher insulin secretion

Higher insulin following sedentary behavior may be due to increased insulin secretion (IS), decreased hepatic insulin extraction (HIE), or a combination of both. Ten healthy adults completed glucose tolerance tests following 7 days of normal activity and 7 days of increased sitting. There were no differences in IS; however, HIE at 120 min after ingestion (85.4% ± 7.2% vs. 74.6% ± 6.6%, p < 0.05) and the area under the curve (73.6% ± 9.4% vs. 67.5% ± 11.3%, p < 0.05) were reduced following 7 days of increased sedentary time.

Effects of growth hormone on hepatic insulin sensitivity and glucose effectiveness in healthy older adults

PURPOSE

Growth hormone (GH) replacement decreases insulin sensitivity in healthy individuals. However, the effects of GH on organ-specific insulin sensitivity and glucose effectiveness are not well characterized. The purpose of this study was to evaluate the effects of GH administration for 26 weeks on muscle and hepatic insulin sensitivity and glucose effectiveness in healthy older individuals.

METHODS

This report is from a 26-week randomized, double-blind, placebo-controlled parallel-group trial in healthy, ambulatory, community-dwelling older women and men. We compared surrogate indices of insulin sensitivity [quantitative insulin-sensitivity check index (QUICKI), muscle insulin sensitivity index (MISI), hepatic insulin resistance index (HIRI)] and glucose effectiveness [oral glucose effectiveness index (oGE)] derived from oral glucose tolerance tests (OGTTs) in subjects before and after 26 weeks of administration of GH (n = 17) or placebo (n = 15) as an exploratory outcome.

RESULTS

GH administration for 26 weeks significantly increased fasting insulin concentrations and HIRI but did not significantly change MISI or oGE compared to placebo.

CONCLUSIONS

GH administration for 26 weeks in healthy older subjects impairs insulin sensitivity in the liver but not skeletal muscle and does not alter glucose effectiveness.

Adiposity-Independent Effects of Aging on Insulin Sensitivity and Clearance in Mice and Humans

OBJECTIVE

Aging is associated with impaired insulin sensitivity and increased prevalence of type 2 diabetes. However, it remains unclear whether aging-associated insulin resistance is due to increased adiposity or other age-related factors. To address this question, the impact of aging on insulin sensitivity was investigated independently of changes in body composition.

METHODS

Cohorts of mice aged 4 to 8 months ("young") and 18 to 27 months ("aged") exhibiting similar body composition were characterized for glucose metabolism on chow and high-fat diets. Insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamp analyses. The relationship between aging and insulin resistance in humans was investigated in 1,250 nondiabetic Mexican Americans who underwent hyperinsulinemic-euglycemic clamps.

RESULTS

In mice with similar body composition, age had no detrimental effect on plasma glucose and insulin levels. While aging did not diminish glucose tolerance, hyperinsulinemic-euglycemic clamps demonstrated impaired insulin sensitivity and reduced insulin clearance in aged mice on chow and high-fat diets. Consistent with results in the mouse, age remained an independent determinant of insulin resistance after adjustment for body composition in Mexican American males.

CONCLUSIONS

This study demonstrates that in addition to altered body composition, adiposity-independent mechanisms also contribute to aging-associated insulin resistance in mice and humans.

Sex-specific programming of adult insulin resistance in guinea pigs by variable perinatal growth induced by spontaneous variation in litter size

Intrauterine growth restriction (IUGR) and subsequent neonatal catch-up growth are implicated in programming of insulin resistance later in life. Spontaneous IUGR in the guinea pig, due to natural variation in litter size, produces offspring with asymmetric IUGR and neonatal catch-up growth. We hypothesized that spontaneous IUGR and/or accelerated neonatal growth would impair insulin sensitivity in adult guinea pigs. Insulin sensitivity of glucose metabolism was determined by hyperinsulinemic-euglycemic clamp (HEC) in 38 (21 male, 17 female) young adult guinea pigs from litters of two-to-four pups. A subset (10 male, 8 female) were infused with d-[3-³H]glucose before and during the HEC to determine rates of basal and insulin-stimulated glucose utilization, storage, glycolysis, and endogenous glucose production. n males, the insulin sensitivity of whole body glucose uptake ( r = 0.657, P = 0.002) and glucose utilization ( r = 0.884, P = 0.004) correlated positively and independently with birth weight, but not with neonatal fractional growth rate (FGR_10-28). In females, the insulin sensitivity of whole body and partitioned glucose metabolism was not related to birth weight, but that of endogenous glucose production correlated negatively and independently with FGR_10-28 ( r = -0.815, P = 0.025). Thus, perinatal growth programs insulin sensitivity of glucose metabolism in the young adult guinea pig and in a sex-specific manner; impaired insulin sensitivity, including glucose utilization, occurs after IUGR in males and impaired hepatic insulin sensitivity after rapid neonatal growth in females.

The Association of Adiponectin and Visceral Fat with Insulin Resistance and β-Cell Dysfunction

BACKGROUND

Obesity is a risk factor for metabolic abnormalities. We investigated the relationship of adiponectin levels and visceral adiposity with insulin resistance and β-cell dysfunction.

METHODS

This cross-sectional study enrolled 1,347 participants (501 men and 846 women aged 30-64 years) at the Cardiovascular and Metabolic Diseases Etiology Research Center. Serum adiponectin levels and visceral fat were measured using enzyme-linked immunosorbent assay kits and dual-energy X-ray absorptiometry, respectively. Insulin resistance was evaluated using the homeostatic model assessment of insulin resistance (HOMA-IR) and Matsuda insulin sensitivity index. β-cell dysfunction was evaluated using the homeostatic model assessment of β-cell function (HOMA-β), insulinogenic index, and disposition index.

RESULTS

Regarding insulin resistance, compared with individuals with the highest adiponectin levels and visceral fat mass < 75th percentile, the fully adjusted odds ratios (ORs) for HOMA-IR ≥ 2.5 and Matsuda index < 25th percentile were 13.79 (95% confidence interval, 7.65-24.83) and 8.34 (4.66-14.93), respectively, for individuals with the lowest adiponectin levels and visceral fat ≥ 75th percentile. Regarding β-cell dysfunction, the corresponding ORs for HOMA-β < 25th percentile, insulinogenic index < 25th percentile, and disposition index < 25th percentile were 1.20 (0.71-2.02), 1.01 (0.61-1.66), and 1.87 (1.15-3.04), respectively.

CONCLUSION

Low adiponectin levels and high visceral adiposity might affect insulin resistance and β-cell dysfunction.

Sex Differences in Glucose and Fatty Acid Metabolism in Asians Who Are Nonobese

CONTEXT

The prevalence of diabetes is increasing throughout Asia, even in the absence of obesity, and is lower in women than in men. The underlying mechanisms are not well understood.

OBJECTIVE

To evaluate the sex differences in glucose and fatty acid metabolism in Asians who are nonobese.

DESIGN

Cross-sectional study.

SETTING

Clinical Nutrition Research Centre, Singapore.

PARTICIPANTS

Healthy Asian men (n = 32; body mass index, 21.8 ± 1.5 kg/m2; age, 42 ± 14 years) and women (n = 28; body mass index, 21.4 ± 2.0 kg/m2; age, 41 ± 13 years).

MAIN OUTCOME MEASURES

Insulin sensitivity (insulin-mediated glucose uptake normalized for steady-state insulin; hyperinsulinemic-euglycemic clamp), postprandial glucose, insulin and fatty acid concentrations, insulin secretion (mixed meal tolerance test with mathematical modeling), insulin clearance, body composition and fat distribution (dual-energy X-ray absorptiometry, MRI, and spectroscopy), cardiorespiratory fitness (maximal oxygen uptake; graded exercise test), and handgrip strength (dynamometry).

RESULTS

Women had more total body fat but less visceral fat than men; liver and muscle lipid contents were not different. Maximal oxygen uptake and handgrip strength were lower in women than men. The postprandial glucose concentrations were ~8% lower, the insulin-mediated glucose uptake was ~16% greater, and the meal-induced suppression of fatty acid concentrations was significantly greater in women than in men (P < 0.05 for all). However, muscle insulin sensitivity was not different between the sexes. No differences were found in postprandial insulin secretion and clearance rates; however, the steady-state insulin clearance was ~17% lower in women.

CONCLUSIONS

Asian women who are nonobese are more insulin-sensitive than men at the level of adipose tissue but not skeletal muscle. Therefore, sex differences in glucose tolerance are likely the result of sexual dimorphism in hepatic insulin action.