Is gestational diabetes mellitus in lean women a distinct entity warranting a modified management approach?

During pregnancy, insulin resistance and impaired insulin secretion may lead to the development of Gestational Diabetes Mellitus (GDM). Although a higher Body Mass Index (BMI) is often cited as a risk factor for the development of GDM, lean pregnant women are also at risk of developing GDM based on evidence from several studies. It is proposed that insulin deficiency (more than insulin resistance) leads to the development of GDM in women with low BMI (BMI <18.5 kg/m2). Neonates of these women are more at risk of preterm birth and small-for-gestational-age. Given this unique pathophysiology and phenotype, this entity needs a modified management approach. This article aims to raise awareness of GDM in lean women to encourage more research on this topic and create a modified management approach.

Phenotypic characterization of nonautoimmune diabetes in adult Ugandans with low body mass index.

Background: Type 2 diabetes is common in relatively lean individuals in sub-Saharan Africa. It is unclear whether phenotypic differences exist between underweight and normal-weight African patients with type 2 diabetes. This study compared specific characteristics between underweight (body mass index <18.5 kg/m2) and normal-weight (body mass index of 18.5-24.9 kg/m2) adult Ugandans with new-onset nonautoimmune diabetes. Methods: We collected the demographic, clinical, anthropometric, and metabolic characteristics of 160 participants with nonobese new-onset type 2 diabetes (defined as diabetes diagnosed <3 months, body mass index <25 kg/m2, and absence of islet-cell autoimmunity). These participants were categorized as underweight and normal weight, and their phenotypic characteristics were compared. Results: Of the 160 participants with nonobese new-onset type 2 diabetes, 18 participants (11.3%) were underweight. Compared with those with normal weight, underweight participants presented with less co-existing hypertension (5.6% versus 28.2%, p = 0.04) and lower median visceral fat levels [2 (1-3) versus 6 (4-7), p < 0.001], as assessed by bioimpedance analysis. Pathophysiologically, they presented with a lower median 120-min post-glucose load C-peptide level [0.29 (0.13-0.58) versus 0.82 (0.39-1.50) nmol/l, p = 0.04] and a higher prevalence of insulin deficiency (66.7% versus 31.4%, p = 0.003). Conclusion: This study demonstrates that nonautoimmune diabetes occurs in underweight individuals in sub-Saharan Africa and is characterized by the absence of visceral adiposity, reduced late-phase insulin secretion, and greater insulin deficiency. These findings necessitate further studies to inform how the prevention, identification, and management of diabetes in such individuals can be individualized.

Type 2 diabetes in underweight Ugandans In this study that investigated how type 2 diabetes presents in adult Ugandans with normal body mass index, about one in ten were underweight. Type 2 diabetes in these individuals was characterized by a low prevalence of hypertension, lower body fat levels, and features of reduced insulin production by the pancreas.

Liver insulinization as a driver of triglyceride dysmetabolism.

Metabolic dysfunction-associated fatty liver disease (MAFLD) is an increasingly prevalent fellow traveller with the insulin resistance that underlies type 2 diabetes mellitus. However, the mechanistic connection between MAFLD and impaired insulin action remains unclear. In this Perspective, we review data from humans to elucidate insulin's aetiological role in MAFLD. We focus particularly on the relative preservation of insulin's stimulation of triglyceride (TG) biosynthesis despite its waning ability to curb hepatic glucose production (HGP). To explain this apparent 'selective insulin resistance', we propose that hepatocellular processes that lead to TG accumulation require less insulin signal transduction, or 'insulinization,' than do those that regulate HGP. As such, mounting hyperinsulinaemia that barely compensates for aberrant HGP in insulin-resistant states more than suffices to maintain hepatic TG biosynthesis. Thus, even modestly elevated or context-inappropriate insulin levels, when sustained day and night within a heavily pro-lipogenic metabolic milieu, may translate into substantial cumulative TG biosynthesis in the insulin-resistant state.

The National Clinical Care Commission Report to Congress: Recommendations to Better Leverage Federal Policies and Programs to Prevent and Control Diabetes.

The National Clinical Care Commission (NCCC) was established by Congress to make recommendations to leverage federal policies and programs to more effectively prevent and treat diabetes and its complications. The NCCC developed a guiding framework that incorporated elements of the Socioecological and Chronic Care Models. It surveyed federal agencies and conducted follow-up meetings with representatives from 10 health-related and 11 non-health-related federal agencies. It held 12 public meetings, solicited public comments, met with numerous interested parties and key informants, and performed comprehensive literature reviews. The final report, transmitted to Congress in January 2022, contained 39 specific recommendations, including 3 foundational recommendations that addressed the necessity of an all-of-government approach to diabetes, health equity, and access to health care. At the general population level, the NCCC recommended that the federal government adopt a health-in-all-policies approach so that the activities of non-health-related federal agencies that address agriculture, food, housing, transportation, commerce, and the environment be coordinated with those of health-related federal agencies to affirmatively address the social and environmental conditions that contribute to diabetes and its complications. For individuals at risk for type 2 diabetes, including those with prediabetes, the NCCC recommended that federal policies and programs be strengthened to increase awareness of prediabetes and the availability of, referral to, and insurance coverage for intensive lifestyle interventions for diabetes prevention and that data be assembled to seek approval of metformin for diabetes prevention. For people with diabetes and its complications, the NCCC recommended that barriers to proven effective treatments for diabetes and its complications be removed, the size and competence of the workforce to treat diabetes and its complications be increased, and new payment models be implemented to support access to lifesaving medications and proven effective treatments for diabetes and its complications. The NCCC also outlined an ambitious research agenda. The NCCC strongly encourages the public to support these recommendations and Congress to take swift action.

The National Clinical Care Commission Report to Congress: Leveraging Federal Policies and Programs to Improve Diabetes Treatment and Reduce Complications.

The Treatment and Complications subcommittee of the National Clinical Care Commission focused on factors likely to improve the delivery of high-quality care to all people with diabetes. The gap between available resources and the needs of people living with diabetes adversely impacts both treatment and outcomes. The Commission's recommendations are designed to bridge this gap. At the patient level, the Commission recommends reducing barriers and streamlining administrative processes to improve access to diabetes self-management training, diabetes devices, virtual care, and insulin. At the practice level, we recommend enhancing programs that support team-based care and developing capacity to support technology-enabled mentoring interventions. At the health system level, we recommend that the Department of Health and Human Services routinely assess the needs of the health care workforce and ensure funding of training programs directed to meet those needs. At the health policy level, we recommend establishing a process to identify and ensure pre-deductible insurance coverage for high-value diabetes treatments and services and developing a quality measure that reduces risk of hypoglycemia and enhances patient safety. We also identified several areas that need additional research, such as studying the barriers to uptake of diabetes self-management education and support, exploring methods to implement team-based care, and evaluating the importance of digital connectivity as a social determinant of health. The Commission strongly encourages Congress, the Department of Health and Human Services, and other federal departments and agencies to take swift action to implement these recommendations to improve health outcomes and quality of life among people living with diabetes.

An Atypical Form of Diabetes Among Individuals With Low BMI.

OBJECTIVE: Diabetes among individuals with low BMI (<19 kg/m2) has been recognized for >60 years as a prevalent entity in low- and middle-income countries (LMICs) and was formally classified as "malnutrition-related diabetes mellitus" by the World Health Organization (WHO) in 1985. Since the WHO withdrew this category in 1999, our objective was to define the metabolic characteristics of these individuals to establish that this is a distinct form of diabetes. RESEARCH DESIGN AND METHODS: State-of-the-art metabolic studies were used to characterize Indian individuals with "low BMI diabetes" (LD) in whom all known forms of diabetes were excluded by immunogenetic analysis. They were compared with demographically matched groups: a group with type 1 diabetes (T1D), a group with type 2 diabetes (T2D), and a group without diabetes. Insulin secretion was assessed by C-peptide deconvolution. Hepatic and peripheral insulin sensitivity were analyzed with stepped hyperinsulinemic-euglycemic pancreatic clamp studies. Hepatic and myocellular lipid contents were assessed with 1H-nuclear magnetic resonance spectroscopy. RESULTS: The total insulin secretory response was lower in the LD group in comparison with the lean group without diabetes and the T2D group. Endogenous glucose production was significantly lower in the LD group than the T2D group (mean ± SEM 0.50 ± 0.1 vs. 0.84 ± 0.1 mg/kg · min, respectively; P < 0.05). Glucose uptake was significantly higher in the LD group in comparison with the T2D group (10.1 ± 0.7 vs. 4.2 ± 0.5 mg/kg · min; P < 0.001). Visceral adipose tissue and hepatocellular lipids were significantly lower in LD than in T2D. CONCLUSIONS: These studies are the first to demonstrate that LD individuals in LMICs have a unique metabolic profile, suggesting that this is a distinct entity that warrants further investigation.

Serum Metabolomics of Incident Diabetes and Glycemic Changes in a Population With High Diabetes Burden: The Hispanic Community Health Study/Study of Latinos.

Metabolomic signatures of incident diabetes remain largely unclear for the U.S. Hispanic/Latino population, a group with high diabetes burden. We evaluated the associations of 624 known serum metabolites (measured by a global, untargeted approach) with incident diabetes in a subsample (n = 2,010) of the Hispanic Community Health Study/Study of Latinos without diabetes and cardiovascular disease at baseline (2008-2011). Based on the significant metabolites associated with incident diabetes, metabolite modules were detected using topological network analysis, and their associations with incident diabetes and longitudinal changes in cardiometabolic traits were further examined. There were 224 incident cases of diabetes after an average 6 years of follow-up. After adjustment for sociodemographic, behavioral, and clinical factors, 134 metabolites were associated with incident diabetes (false discovery rate-adjusted P < 0.05). We identified 10 metabolite modules, including modules comprising previously reported diabetes-related metabolites (e.g., sphingolipids, phospholipids, branched-chain and aromatic amino acids, glycine), and 2 reflecting potentially novel metabolite groups (e.g., threonate, N-methylproline, oxalate, and tartarate in a plant food metabolite module and androstenediol sulfates in an androgenic steroid metabolite module). The plant food metabolite module and its components were associated with higher diet quality (especially higher intakes of healthy plant-based foods), lower risk of diabetes, and favorable longitudinal changes in HOMA for insulin resistance. The androgenic steroid module and its component metabolites decreased with increasing age and were associated with a higher risk of diabetes and greater increases in 2-h glucose over time. We replicated the associations of both modules with incident diabetes in a U.S. cohort of non-Hispanic Black and White adults (n = 1,754). Among U.S. Hispanic/Latino adults, we identified metabolites across various biological pathways, including those reflecting androgenic steroids and plant-derived foods, associated with incident diabetes and changes in glycemic traits, highlighting the importance of hormones and dietary intake in the pathogenesis of diabetes.

Heterogeneity of Diabetes: ß-Cells, Phenotypes, and Precision Medicine: Proceedings of an International Symposium of the Canadian Institutes of Health Research's Institute of Nutrition, Metabolism and Diabetes and the U.S. National Institutes of Health's National Institute of Diabetes and Digestive and Kidney Diseases.

One hundred years have passed since the discovery of insulin-an achievement that transformed diabetes from a fatal illness into a manageable chronic condition. The decades since that momentous achievement have brought ever more rapid innovation and advancement in diabetes research and clinical care. To celebrate the important work of the past century and help to chart a course for its continuation into the next, the Canadian Institutes of Health Research's Institute of Nutrition, Metabolism and Diabetes and the U.S. National Institutes of Health's National Institute of Diabetes and Digestive and Kidney Diseases recently held a joint international symposium, bringing together a cohort of researchers with diverse interests and backgrounds from both countries and beyond to discuss their collective quest to better understand the heterogeneity of diabetes and thus gain insights to inform new directions in diabetes treatment and prevention. This article summarizes the proceedings of that symposium, which spanned cutting-edge research into various aspects of islet biology, the heterogeneity of diabetic phenotypes, and the current state of and future prospects for precision medicine in diabetes.

Muscle fibrosis and maladaptation occur progressively in CKD and are rescued by dialysis.

BACKGROUNDSkeletal muscle maladaptation accompanies chronic kidney disease (CKD) and negatively affects physical function. Emphasis in CKD has historically been placed on muscle fiber-intrinsic deficits, such as altered protein metabolism and atrophy. However, targeted treatment of fiber-intrinsic dysfunction has produced limited improvement, whereas alterations within the fiber-extrinsic environment have scarcely been examined.METHODSWe investigated alterations to the skeletal muscle interstitial environment with deep cellular phenotyping of biopsies from patients with CKD and age-matched controls and performed transcriptome profiling to define the molecular underpinnings of CKD-associated muscle impairments. We examined changes in muscle maladaptation following initiation of dialysis therapy for kidney failure.RESULTSPatients with CKD exhibited a progressive fibrotic muscle phenotype, which was associated with impaired regenerative capacity and lower vascular density. The severity of these deficits was strongly associated with the degree of kidney dysfunction. Consistent with these profound deficits, CKD was associated with broad alterations to the muscle transcriptome, including altered ECM organization, downregulated angiogenesis, and altered expression of pathways related to stem cell self-renewal. Remarkably, despite the seemingly advanced nature of this fibrotic transformation, dialysis treatment rescued these deficits, restoring a healthier muscle phenotype. Furthermore, after accounting for muscle atrophy, strength and endurance improved after dialysis initiation.CONCLUSIONThese data identify a dialysis-responsive muscle fibrotic phenotype in CKD and suggest the early dialysis window presents a unique opportunity of improved muscle regenerative capacity during which targeted interventions may achieve maximal impact.TRIAL REGISTRATIONNCT01452412FUNDINGNIH, NIH Clinical and Translational Science Awards (CTSA), and Einstein-Mount Sinai Diabetes Research Center.

Significance of single and multi-voxel 1H magnetic resonance spectroscopy in the quantification of myocellular lipid in young non-obese Asian Indian males.

To prospectively assess intramyocellular lipids (IMCL) and extramyocellular lipids (EMCL) using single voxel spectroscopy (SVS) and multi voxel magnetic resonance spectroscopy (MVS) in soleus muscle and correlate results with metabolic variables in non-obese (BMI < 23 kg/m2) Asian Indian males. Thirty one patients with diabetes (cases) and twelve normoglycaemic subjects (controls) underwent point resolved spectroscopy sequence (PRESS) of soleus muscle using SVS and MVS in a 3 T MRI scanner. Visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) were measured from MRI images and body composition was measured from dual-energy x-ray absorptiometry (DXA). The mean IMCL from SVS and MVS were 1.6% and 2.6% in cases and 2.3% and 3.4% in controls respectively. The mean EMCL from SVS and MVS were 1.8% and 3% in cases and 1.5% and 3% respectively in controls. A significant correlation between IMCL and total fat mass (rho = 0.42, p < 0.01) and total body fat (rho = 0.46; p < 0.01) were observed in cases while using the SVS technique and no correlations were found in the MVS technique. The SVS showed significant correlations between total myocellular lipids with VAT and SAT in cases alone. Total myocellular lipids acquired using both techniques showed a significant correlation with BMI, waist circumference, total fat mass, total body fat and truncal fat in cases alone. Quantification of IMCL of soleus muscle using the SVS technique is useful in studying the relationship with metabolic markers in non-obese Asian Indians with diabetes.

Insulin-sensitizing effects of vitamin D repletion mediated by adipocyte vitamin D receptor: Studies in humans and mice.

OBJECTIVE: Adipose tissue inflammation and fibrosis appear to contribute to insulin resistance in obesity. Vitamin D receptor (Vdr) genes are expressed by adipocytes, macrophages, and fibroblasts, all of which could potentially play a role in adipose tissue inflammation and fibrosis. As vitamin D has been shown to have direct anti-inflammatory effects on adipocytes, we determined whether specific vitamin D receptor-mediated effects on adipocytes could impact adipose tissue inflammation and fibrosis and ultimately insulin resistance. METHODS: We examined the effects of repleting vitamin D in 25(OH)D-deficient, insulin resistant, overweight-to-obese human subjects (n = 19). A comprehensive assessment of whole-body insulin action was undertaken with stepped euglycemic (∼90 mg/dL) hyperinsulinemic clamp studies both before and after the administration of vitamin D or placebo. Adipose tissue fibrosis and inflammation were quantified by real-time rt-PCR and immunofluorescence in subcutaneous abdominal adipose tissue. To determine whether vitamin D's effects are mediated through adipocytes, we conducted hyperinsulinemic clamp studies (4 mU/kg/min) and adipose tissue analysis using an adipocyte-specific vitamin D receptor knockout (VDR-KO) mouse model (adiponectin-Cre + VDR+/fl) following high-fat diet feeding for 12 weeks. RESULTS: 25(OH)D repletion was associated with reductions in adipose tissue expression of pro-inflammatory and pro-fibrotic genes, decreased collagen immunofluorescence, and improved hepatic insulin sensitivity in humans. Worsening trends after six months on placebo suggest progressive metabolic effects of 25(OH)D deficiency. Ad-VDR-KO mice mirrored the vitamin D-deficient humans, displaying increased adipose tissue fibrosis and inflammation and hepatic insulin resistance. CONCLUSIONS: These complementary human and rodent studies support a beneficial role of vitamin D repletion for improving hepatic insulin resistance and reducing adipose tissue inflammation and fibrosis in targeted individuals, likely via direct effects on adipocytes. These studies have far-reaching implications for understanding the role of adipocytes in mediating adipose tissue inflammation and fibrosis and ultimately impacting insulin sensitivity.

Plasma Epinephrine Contributes to the Development of Experimental Hypoglycemia-Associated Autonomic Failure.

BACKGROUND: Recurrent hypoglycemia blunts counter-regulatory responses to subsequent hypoglycemic episodes, a syndrome known as hypoglycemia-associated autonomic failure (HAAF). Since adrenergic receptor blockade has been reported to prevent HAAF, we investigated whether the hypoglycemia-associated rise in plasma epinephrine contributes to pathophysiology and reported interindividual differences in susceptibility to HAAF. METHODS: To assess the role of hypoglycemia-associated epinephrine responses in the susceptibility to HAAF, 24 adult nondiabetic subjects underwent two 2-hour hyperinsulinemic hypoglycemic clamp studies (nadir 54 mg/dL; 0-2 hours and 4-6 hours) on Day 1, followed by a third identical clamp on Day 2. We challenged an additional 7 subjects with two 2-hour infusions of epinephrine (0.03 µg/kg/min; 0-2 hours and 4-6 hours) vs saline on Day 1 followed by a 200-minute stepped hypoglycemic clamp (90, 80, 70, and 60 mg/dL) on Day 2. RESULTS: Thirteen out of 24 subjects developed HAAF, defined by ≥20% reduction in average epinephrine levels during the final 30 minutes of the third compared with the first hypoglycemic episode (P < 0.001). Average epinephrine levels during the final 30 minutes of the first hypoglycemic episode were 2.3 times higher in subjects who developed HAAF compared with those who did not (P = 0.006).Compared to saline, epinephrine infusion on Day 1 reduced the epinephrine responses by 27% at the 70 and 60 mg/dL glucose steps combined (P = 0.04), with a parallel reduction in hypoglycemic symptoms (P = 0.03) on Day 2. CONCLUSIONS: Increases in plasma epinephrine reproduce key features of HAAF in nondiabetic subjects. Marked interindividual variability in epinephrine responses to hypoglycemia may explain an individual's susceptibility to developing HAAF.

Central KATP Channels Modulate Glucose Effectiveness in Humans and Rodents.

Hyperglycemia is a potent regulator of endogenous glucose production (EGP). Loss of this "glucose effectiveness" is a major contributor to elevated plasma glucose concentrations in type 2 diabetes (T2D). KATP channels in the central nervous system have been shown to regulate EGP in humans and rodents. We examined the contribution of central KATP channels to glucose effectiveness. Under fixed hormonal conditions (studies using a pancreatic clamp), hyperglycemia suppressed EGP by ∼50% in both humans without diabetes and normal Sprague-Dawley rats. By contrast, antagonism of KATP channels with glyburide significantly reduced the EGP-lowering effect of hyperglycemia in both humans and rats. Furthermore, the effects of glyburide on EGP and gluconeogenic enzymes were abolished in rats by intracerebroventricular administration of the KATP channel agonist diazoxide. These findings indicate that about half of the suppression of EGP by hyperglycemia is mediated by central KATP channels. These central mechanisms may offer a novel therapeutic target for improving glycemic control in subjects with T2D.

Effect of a Dual PPAR α/γ agonist on Insulin Sensitivity in Patients of Type 2 Diabetes with Hypertriglyceridemia- Randomized double-blind placebo-controlled trial.

Saroglitazar is a dual PPAR-α/γ agonist approved for the treatment of diabetic dyslipidemia. In addition to reduction in atherogenic lipids, it may also contribute to improvement in insulin sensitivity through PPAR-α/γ agonism, which remains unexplored. We conducted a randomized, double-blind, placebo-controlled trial in treatment-naive T2DM individuals with serum triglyceride >150 mg/dL. Participants were randomized to receive either saroglitazar 4 mg or placebo (1:1) daily for 4 months (n = 30). Insulin sensitivity (SIclamp) was studied using hyperinsulinemic-euglycemic clamp at baseline and at 4 months. We observed a significant reduction in TG (p = 0.001), HbA1c (p = 0.019) and fasting plasma glucose (p = 0.019) and significant increase in HDL-C levels (p < 0.01) with saroglitazar compared to placebo. Further, patients on saroglitazar had a greater improvement in SIclamp (p = 0.026) with the effect persisting despite adjusting for baseline weight, TG, HDL-C and HbA1c (p = 0.002). This was accompanied with significant increase in HOMA-ß (p = 0.01) in the saroglitazar group and change in HOMA-ß showed a trend towards significance with SIclamp (r = 0.503, p = 0.056). However, change in SIclamp did not significantly correlate with reduction in HbA1c and TG. We conclude that saroglitazar effectively reduces hypertriglyceridemia and improves insulin sensitivity along with ß-cell function by reduction in gluco-lipotoxicity and possibly directly through PPAR-γ agonism in patients ofT2DM with hypertriglyceridemia.

Skeletal muscle fibrosis is associated with decreased muscle inflammation and weakness in patients with chronic kidney disease.

Muscle dysfunction is an important cause of morbidity among patients with chronic kidney disease (CKD). Although muscle fibrosis is present in a CKD rodent model, its existence in humans and its impact on physical function are currently unknown. We examined isometric leg extension strength and measures of skeletal muscle fibrosis and inflammation in vastus lateralis muscle from CKD patients ( n = 10) and healthy, sedentary controls ( n = 10). Histochemistry and immunohistochemistry were used to assess muscle collagen and macrophage and fibro/adipogenic progenitor (FAP) cell populations, and RT-qPCR was used to assess muscle-specific inflammatory marker expression. Muscle collagen content was significantly greater in CKD compared with control (18.8 ± 2.1 vs. 11.7 ± 0.7% collagen area, P = 0.008), as was staining for collagen I, pro-collagen I, and a novel collagen-hybridizing peptide that binds remodeling collagen. Muscle collagen was inversely associated with leg extension strength in CKD ( r = -0.74, P = 0.01). FAP abundance was increased in CKD, was highly correlated with muscle collagen ( r = 0.84, P < 0.001), and was inversely associated with TNF-α expression ( r = -0.65, P = 0.003). TNF-α, CD68, CCL2, and CCL5 mRNA were significantly lower in CKD than control, despite higher serum TNF-α and IL-6. Immunohistochemistry confirmed fewer CD68+ and CD11b+ macrophages in CKD muscle. In conclusion, skeletal muscle collagen content is increased in humans with CKD and is associated with functional parameters. Muscle fibrosis correlated with increased FAP abundance, which may be due to insufficient macrophage-mediated TNF-α secretion. These data provide a foundation for future research elucidating the mechanisms responsible for this newly identified human muscle pathology.

Correction: Muscle mass, BMI, and mortality among adults in the United States: A population-based cohort study.

[This corrects the article DOI: 10.1371/journal.pone.0194697.].

Muscle mass, BMI, and mortality among adults in the United States: A population-based cohort study.

BACKGROUND: The level of body-mass index (BMI) associated with the lowest risk of death remains unclear. Although differences in muscle mass limit the utility of BMI as a measure of adiposity, no study has directly examined the effect of muscle mass on the BMI-mortality relationship. METHODS: Body composition was measured by dual-energy x-ray absorptiometry in 11,687 participants of the National Health and Nutrition Examination Survey 1999-2004. Low muscle mass was defined using sex-specific thresholds of the appendicular skeletal muscle mass index (ASMI). Proportional hazards models were created to model associations with all-cause mortality. RESULTS: At any level of BMI ≥22, participants with low muscle mass had higher body fat percentage (%TBF), an increased likelihood of diabetes, and higher adjusted mortality than other participants. Increases in %TBF manifested as 30-40% smaller changes in BMI than were observed in participants with preserved muscle mass. Excluding participants with low muscle mass or adjustment for ASMI attenuated the risk associated with low BMI, magnified the risk associated with high BMI, and shifted downward the level of BMI associated with the lowest risk of death. Higher ASMI was independently associated with lower mortality. Effects were similar in never-smokers and ever-smokers. Additional adjustment for waist circumference eliminated the risk associated with higher BMI. Results were unchanged after excluding unintentional weight loss, chronic illness, early mortality, and participants performing muscle-strengthening exercises or recommended levels of physical activity. CONCLUSIONS: Muscle mass mediates associations of BMI with adiposity and mortality and is inversely associated with the risk of death. After accounting for muscle mass, the BMI associated with the greatest survival shifts downward toward the normal range. These results provide a concrete explanation for the obesity paradox.

Metformin regulates metabolic and nonmetabolic pathways in skeletal muscle and subcutaneous adipose tissues of older adults.

Administration of metformin increases healthspan and lifespan in model systems, and evidence from clinical trials and observational studies suggests that metformin delays a variety of age-related morbidities. Although metformin has been shown to modulate multiple biological pathways at the cellular level, these pleiotropic effects of metformin on the biology of human aging have not been studied. We studied ~70-year-old participants (n = 14) in a randomized, double-blind, placebo-controlled, crossover trial in which they were treated with 6 weeks each of metformin and placebo. Following each treatment period, skeletal muscle and subcutaneous adipose tissue biopsies were obtained, and a mixed-meal challenge test was performed. As expected, metformin therapy lowered 2-hour glucose, insulin AUC, and insulin secretion compared to placebo. Using FDR<0.05, 647 genes were differentially expressed in muscle and 146 genes were differentially expressed in adipose tissue. Both metabolic and nonmetabolic pathways were significantly influenced, including pyruvate metabolism and DNA repair in muscle and PPAR and SREBP signaling, mitochondrial fatty acid oxidation, and collagen trimerization in adipose. While each tissue had a signature reflecting its own function, we identified a cascade of predictive upstream transcriptional regulators, including mTORC1, MYC, TNF, TGFß1, and miRNA-29b that may explain tissue-specific transcriptomic changes in response to metformin treatment. This study provides the first evidence that, in older adults, metformin has metabolic and nonmetabolic effects linked to aging. These data can inform the development of biomarkers for the effects of metformin, and potentially other drugs, on key aging pathways.

Potential approaches to prevent hypoglycemia-associated autonomic failure.

Clear health benefits are associated with intensive glucose control in type 1 diabetes mellitus (T1DM). However, maintaining near-normal glycemia remains an elusive goal for many patients, in large part owing to the risk of severe hypoglycemia. In fact, recurrent episodes of hypoglycemia lead to 'hypoglycemia-associated autonomic failure' (HAAF), characterized by defective counter-regulatory responses to hypoglycemia. Extensive studies to understand the mechanisms underlying HAAF have revealed multiple potential etiologies, suggesting various approaches to prevent the development of HAAF. In this review, we present an overview of the literature focused on pharmacological approaches that may prevent the development of HAAF. The purported underlying mechanisms of HAAF include: 1) central mechanisms (opioid receptors, ATP-sensitive K+(KATP) channels, adrenergic receptors, serotonin selective receptor inhibitors, γ-aminobuyric acid receptors, N-methyl D-aspartate receptors); 2) hormones (cortisol, estrogen, dehydroepiandrosterone (DHEA) or DHEA sulfate, glucagon-like peptide-1) and 3) nutrients (fructose, free fatty acids, ketones), all of which have been studied vis-à-vis their ability to impact the development of HAAF. A careful review of the current literature reveals many promising therapeutic approaches to treat or reduce this important limitation to optimal glycemic control.