Gluconeogenesis and risk for fasting hyperglycemia in Black and White women

Jianpi Gushen Huayu decoction ameliorated diabetic nephropathy through modulating metabolites in kidney, and inhibiting TLR4/NF-κB/NLRP3 and JNK/P38 pathways

BACKGROUND

Jianpi Gushen Huayu Decoction (JPGS) has been used to clinically treat diabetic nephropathy (DN) for many years. However, the protective mechanism of JPGS in treating DN remains unclear.

AIM

To evaluate the therapeutic effects and the possible mechanism of JPGS on DN.

METHODS

We first evaluated the therapeutic potential of JPGS on a DN mouse model. We then investigated the effect of JPGS on the renal metabolite levels of DN mice using non-targeted metabolomics. Furthermore, we examined the effects of JPGS on c-Jun N-terminal kinase (JNK)/P38-mediated apoptosis and the inflammatory responses mediated by toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB)/NOD-like receptor family pyrin domain containing 3 (NLRP3).

RESULTS

The ameliorative effects of JPGS on DN mice included the alleviation of renal injury and the control of inflammation and oxidative stress. Untargeted metabolomic analysis revealed that JPGS altered the metabolites of the kidneys in DN mice. A total of 51 differential metabolites were screened. Pathway analysis results indicated that nine pathways significantly changed between the control and model groups, while six pathways significantly altered between the model and JPGS groups. Pathways related to cysteine and methionine metabolism; alanine, tryptophan metabolism; aspartate and glutamate metabolism; and riboflavin metabolism were identified as the key pathways through which JPGS affects DN. Further experimental validation showed that JPGS treatment reduced the expression of TLR4/NF-κB/NLRP3 pathways and JNK/P38 pathway-mediated apoptosis related factors.

CONCLUSION

JPGS could markedly treat mice with streptozotocin (STZ)-induced DN, which is possibly related to the regulation of several metabolic pathways found in kidneys. Furthermore, JPGS could improve kidney inflammatory responses and ameliorate kidney injuries in DN mice via the TLR4/NF-κB/NLRP3 pathway and inhibit JNK/P38 pathway-mediated apoptosis in DN mice.

The association of a healthy lifestyle index and imaging-based body fat distribution with glycemic status and Type 2 diabetes in the Multi Ethnic Cohort: a cross-sectional analysis

INTRODUCTION

As several behaviors captured by the Lifestyle Risk Factor Index (LSRI) are protective against Type 2 diabetes (T2D) and may affect body fat distribution, we examined its relation with both outcomes.

METHODS

In a subset of the Multiethnic Cohort, participants from five ethnic groups (60-77 years) were assigned LSRI scores (one point each for consuming <1 (women)/<2 (men) alcoholic drinks/day, ≥1.5 physical activity hours/week, not smoking, and adhering to ≥3/7 dietary recommendations). All participants completed an extensive Quantitative Food Frequency Questionnaire to allow estimation of adherence to intake recommendations for fruits, vegetables, refined and whole grains, fish, processed and non-processed meat. Glycemic/T2D status was classified according to self-reports and fasting glucose. We estimated prevalence odds ratios (POR) of LSRI with glycemic/T2D status and DXA- and MRI-based body fat distribution using logistic regression.

RESULTS

Of 1713 participants, 43% had normoglycemia, 30% Pre-T2D, 9% Undiagnosed T2D, and 18% T2D. Overall, 39% scored 0-2, 49% 3, and 12% 4 LSRI points. T2D prevalence was 55% (POR 0.45; 95% confidence intervals 0.27, 0.76) lower for 4 vs. 0-2 LSRI points with weaker associations for abnormal glycemic status. Despite the low adherence to dietary recommendations (22%), this was the only component related to lower T2D prevalence. The inverse LSRI-T2D association was only observed among Latinos and Japanese Americans in ethnic-specific models. Visceral fat measures were higher in T2D patients and attenuated the LSRI-T2D association.

CONCLUSION

These findings support the role of a healthy lifestyle, especially diet, in T2D prevention with differences across ethnicity.

Cardiometabolic disease in Black African and Caribbean populations: an ethnic divergence in pathophysiology?

In the UK, populations of Black African and Caribbean (BAC) ethnicity suffer higher rates of cardiometabolic disease than White Europeans (WE). Obesity, leading to increased visceral adipose tissue (VAT) and intrahepatic lipid (IHL), has long been associated with cardiometabolic risk, driving insulin resistance and defective fatty acid/lipoprotein metabolism. These defects are compounded by a state of chronic low-grade inflammation, driven by dysfunctional adipose tissue. Emerging evidence has highlighted associations between central complement system components and adipose tissue, fatty acid metabolism and inflammation; it may therefore sit at the intersection of various cardiometabolic disease risk factors. However, increasing evidence suggests an ethnic divergence in pathophysiology, whereby current theories fail to explain the high rates of cardiometabolic disease in BAC populations. Lower fasting and postprandial TAG has been reported in BAC, alongside lower VAT and IHL deposition, which are paradoxical to the high rates of cardiometabolic disease exhibited by this ethnic group. Furthermore, BAC have been shown to exhibit a more anti-inflammatory profile, with lower TNF-α and greater IL-10. In contrast, recent evidence has revealed greater complement activation in BAC compared to WE, suggesting its dysregulation may play a greater role in the high rates of cardiometabolic disease experienced by this population. This review outlines the current theories of how obesity is proposed to drive cardiometabolic disease, before discussing evidence for ethnic differences in disease pathophysiology between BAC and WE populations.

Phthalates and Incident Diabetes in Midlife Women: The Study of Women's Health Across the Nation (SWAN)

CONTEXT

Phthalates are hypothesized to contribute to diabetes, but longitudinal evidence in humans is limited.

OBJECTIVE

We examined whether phthalate exposure was associated with a higher incidence of diabetes in a racially/ethnically diverse cohort of midlife women.

METHODS

In the Study of Women's Health Across the Nation Multipollutant Study, we followed 1308 women without diabetes in 1999-2000 for 6 years. Eleven phthalate metabolites were measured in spot urine samples in 1999-2000 and 2002-2003. Incident diabetes was ascertained between 1999-2000 and 2005-2006. Cox proportional hazards models with time-varying exposure were used to estimate the hazard ratio (HR) of diabetes associated with each phthalate metabolite, adjusting for demographic, lifestyle, and health-related factors. Effect modification by race/ethnicity was examined with interaction terms.

RESULTS

Sixty-one women developed diabetes over 6 years (cumulative incidence = 4.7%). Among all women, several high-molecular-weight phthalate metabolites were associated with a higher incidence of diabetes, but none were statistically significant. There was effect modification by race/ethnicity. Among White women, each doubling of the concentrations of mono-isobutyl phthalate (MiBP), monobenzyl phthalate, mono-carboxyoctyl phthalate, mono-carboxyisononyl phthalate (MCNP), and mono(3-carboxypropyl) phthalate was associated with a 30% to 63% higher incidence of diabetes (HR = 1.30, 95% CI, 1.03-1.65 for MCNP; HR = 1.63, 95% CI, 1.18-2.25 for MiBP). In contrast, phthalates were not associated with diabetes incidence in Black or Asian women.

CONCLUSIONS

Some phthalate metabolites were associated with a higher incidence of diabetes over 6 years, but the associations were inconsistent across racial/ethnic groups. Whether phthalates cause diabetes requires further investigation.

Urinary metabolomics, dietary salt intake and blood pressure: the African-PREDICT study

In Black populations excessive salt intake may exacerbate the genetic predisposition to hypertension and promote the early onset of cardiovascular disease. Ethnic differences in the interaction between sodium intake and the metabolome may play a part in hypertension and cardiovascular disease development. We determined (1) urinary amino acid and acylcarnitine profiles of young Black and White adults according to low, moderate, and high dietary salt intake, and (2) investigated the triad of salt intake, systolic blood pressure (SBP), and the associated metabolomics profile. This study included 447 White and 380 Black adults aged 20-30 years from the African-PREDICT study. Estimated salt intake was determined from 24-hour urinary sodium levels. Urinary amino acids and acylcarnitines were measured using liquid chromatography-tandem mass spectrometry. Black adults exhibited no significant differences in SBP, amino acids, or acylcarnitines across low (<5g/day), moderate (5-10g/day), and high (>10g/day) salt intake. White adults with a high salt intake had elevated SBP compared to those with low or moderate intakes (p < 0.001). Furthermore, gamma-aminobutyric acid (GABA) (q = 0.020), citrulline (q = 0.020), glutamic acid (q = 0.046), serine (q = 0.054) and proline (q = 0.054) were lowest in those with higher salt intake. Only in White and not Black adults did we observe inverse associations of clinic SBP with GABA (Adj. R2 = 0.34; Std. β = -0.133; p = 0.003), serine (Adj. R2 = 0.33; Std. β = -0.109; p = 0.014) and proline (Adj. R2 = 0.33; Std. β = -0.109; p = 0.014). High salt intake in White, but not in black adults, were related to metabolomic changes and may contribute to pathophysiological mechanisms associated with increased BP.

Excessive gluconeogenesis causes the hepatic insulin resistance paradox and its sequelae

Background

Hepatic insulin signaling suppresses gluconeogenesis but promotes de novo lipid synthesis. Paradoxically, hepatic insulin resistance (HIR) enhances both gluconeogenesis and de novo lipid synthesis. Elucidation of the etiology of this paradox, which participates in the pathogenesis of non-alcoholic fatty liver disease (NAFLD), cardiovascular disease, the metabolic syndrome and hepatocellular carcinoma, has not been fully achieved.

Scope of review

This article briefly outlines the previously proposed hypotheses on the etiology of the HIR paradox. It then discusses literature consistent with an alternative hypothesis that excessive gluconeogenesis, the direct effect of HIR, is responsible for the aberrant lipogenesis. The mechanisms involved therein are explained, involving de novo synthesis of fructose and uric acid, promotion of glutamine anaplerosis, and induction of glucagon resistance. Thus, gluconeogenesis via lipogenesis promotes hepatic steatosis, a component of NAFLD, and dyslipidemia. Gluconeogenesis-centred mechanisms for the progression of NAFLD from simple steatosis to non-alcoholic steatohepatitis (NASH) and fibrosis are suggested. That NAFLD often precedes and predicts type 2 diabetes is explained by the ability of lipogenesis to cushion against blood glucose dysregulation in the earlier stages of NAFLD.

Major conclusions

HIR-induced excessive gluconeogenesis is a major cause of the HIR paradox and its sequelae. Such involvement of gluconeogenesis in lipid synthesis rationalizes the fact that several types of antidiabetic drugs ameliorate NAFLD. Thus, dietary, lifestyle and pharmacological targeting of HIR and hepatic gluconeogenesis may be a most viable approach for the prevention and management of the HIR-associated network of diseases.

Pathophysiology of type 2 diabetes in sub-Saharan Africans

Sub-Saharan Africa (SSA) is the region with the highest projected rates of increase in type 2 diabetes (129% by 2045), which will exacerbate the already high prevalence of type 2 diabetes complications and comorbidities in SSA. In addition, SSA is grappling with poverty-related health problems and infectious diseases and is also undergoing the most rapid rates of urbanisation globally. These socioenvironmental and lifestyle factors may interact with genetic factors to alter the pathophysiological sequence leading to type 2 diabetes in sub-Saharan African populations. Indeed, current evidence from SSA and the diaspora suggests that the pathophysiology of type 2 diabetes in Black Africans is different from that in their European counterparts. Studies from the diaspora suggest that insulin clearance is the primary defect underlying the development of type 2 diabetes. We propose that, among Black Africans from SSA, hyperinsulinaemia due to a combination of both increased insulin secretion and reduced hepatic insulin clearance is the primary defect, which promotes obesity and insulin resistance, exacerbating the hyperinsulinaemia and eventually leading to beta cell failure and type 2 diabetes. Nonetheless, the current understanding of the pathogenesis of type 2 diabetes and the clinical guidelines for preventing and managing the disease are largely based on studies including participants of predominately White European ancestry. In this review, we summarise the existing knowledge base and data from the only non-pharmacological intervention that explores the pathophysiology of type 2 diabetes in SSA. We also highlight factors that may influence the pathogenesis of type 2 diabetes in SSA, such as social determinants, infectious diseases and genetic and epigenetic influences.

Body Fat Distribution, Glucose Metabolism, and Diabetes Status Among Older Adults: The Multiethnic Cohort Adiposity Phenotype Study

BACKGROUND

As the proportion of visceral (VAT) to subcutaneous adipose tissue (SAT) may contribute to type 2 diabetes (T2D) development, we examined this relation in a cross-sectional design within the Multiethnic Cohort that includes Japanese Americans known to have high VAT. The aim was to understand how ectopic fat accumulation differs by glycemic status across ethnic groups with disparate rates of obesity, T2D, and propensity to accumulate VAT.

METHODS

In 2013-2016, 1,746 participants aged 69.2 (standard deviation, 2.7) years from five ethnic groups completed questionnaires, blood collections, and whole-body dual X-ray absorptiometry and abdominal magnetic resonance imaging scans. Participants with self-reported T2D and/or medication were classified as T2D, those with fasting glucose >125 and 100-125 mg/dL as undiagnosed cases (UT2D) and prediabetes (PT2D), respectively. Using linear regression, we estimated adjusted means of adiposity measures by T2D status.

RESULTS

Overall, 315 (18%) participants were classified as T2D, 158 (9%) as UT2D, 518 (30%) as PT2D, and 755 (43%) as normoglycemic (NG), with significant ethnic differences (P < 0.0001). In fully adjusted models, VAT, VAT/SAT, and percent liver fat increased significantly from NG, PT2D, UT2D, to T2D (P < 0.001). Across ethnic groups, the VAT/SAT ratio was lowest for NG participants and highest for T2D cases. Positive trends were observed in all groups except African Americans, with highest VAT/SAT in Japanese Americans.

CONCLUSION

These findings indicate that VAT plays an important role in T2D etiology, in particular among Japanese Americans with high levels of ectopic adipose tissue, which drives the development of T2D to a greater degree than in other ethnic groups.

Comprehensive evaluation of disparities in cardiometabolic and reproductive risk between Hispanic and White women with polycystic ovary syndrome in the United States: a systematic review and meta-analysis

OBJECTIVE

We conducted a systematic review and meta-analysis to comprehensively compare cardiometabolic and reproductive health risk between Hispanic and White women with polycystic ovary syndrome in the United States in response to the call by the international guideline for polycystic ovary syndrome to delineate health disparities.

DATA SOURCES

Databases of MEDLINE, Web of Science, and Scopus were initially searched through October 25, 2020, and confirmed on February 1, 2021.

STUDY ELIGIBILITY CRITERIA

Observational studies comparing glucoregulatory, lipid profile, anthropometric, blood pressure, androgen, ovarian morphology, oligoanovulation, and infertility status between Hispanic and White women with polycystic ovary syndrome were included. The primary outcome was metabolic syndrome risk. Furthermore, major cardiovascular events (stroke, coronary heart disease, and heart failure) and mortality rate (cardiovascular death and total mortality) data were evaluated. Studies on adolescents (<2 years after menarche), pregnant, or menopausal-aged women (>50 years) were excluded.

METHODS

Data were pooled by random-effects models and expressed as mean differences and 95% confidence intervals. Risk of bias was assessed by the Newcastle-Ottawa Scale.

RESULTS

A total of 11 studies (n=2267; 589 Hispanic and 1678 White women) were eligible. All studies, including both White and Hispanic women, had high-quality assessment (Newcastle-Ottawa Scale score of ≥8). Hispanic women exhibited comparable metabolic syndrome prevalence (7% [95% confidence interval, -1 to 14]; P=.06; I2=0%); however, Hispanic women exhibited higher modified Ferriman-Gallwey score (0.60 [95% confidence interval, -0.01 to 1.21]; P=.05; I2=0%), fasting insulin (5.48 μIU/mL [95% confidence interval, 3.11-7.85]; P≤.01; I2=40.0%), and homeostatic model assessment of insulin resistance (1.20 [95% confidence interval, 0.50-1.89]; P≤.01; I2=43.0%) than White women. The 2 groups had comparable glucose, lipid profile, waist circumference, blood pressure, and androgen status (all P≥.08). Findings about group differences in certain reproductive outcomes (ie, ovarian dysmorphology and infertility) were contradictory and described only narratively as inclusion in the meta-analyses was not possible. No study reported on cardiovascular events or mortality.

CONCLUSION

Hispanic women with polycystic ovary syndrome exhibited greater impairments in glucoregulatory status than White women. Disparities in reproductive risks could not be concluded. The degree to which glucoregulatory aberrations translate into patient-pressing diseases (diabetes mellitus and infertility) remains a major roadblock given the paucity of available evidence. Our observations have supported the consideration of these disparities in the diagnostic, monitoring, and management practices for polycystic ovary syndrome and reinforced the need to elucidate mechanisms that account for the observed disparities to foster equity in polycystic ovary syndrome care.

Ectopic fat deposition in populations of black African ancestry: A systematic review and meta-analysis

AIMS

In populations of black African ancestry (BA), a paradox exists whereby lower visceral adipose tissue is found despite their high risk for type 2 diabetes (T2D). This systematic review investigates ethnic differences in other ectopic fat depots (intrahepatic lipid: IHL; intramyocellular lipid: IMCL and intrapancreatic lipid; IPL) to help contextualise their potential contribution to T2D risk.

METHODS

A systematic literature search was performed in December 2020 to identify studies reporting at least one ectopic fat comparison between BA and one/more other ethnicity. For IHL, a meta-analysis was carried out with studies considered comparable based on the method of measurement.

RESULTS

Twenty-eight studies were included (IHL: n = 20; IMCL: n = 8; IPL: n = 4). Meta-analysis of 11 studies investigating IHL revealed that it was lower in BA populations vs pooled ethnic comparators (MD -1.35%, 95% CI -1.55 to -1.16, I² = 85%, P < 0.00001), white European ancestry (MD -0.94%, 95% CI -1.17 to -0.70, I² = 79%, P < 0.00001), Hispanic ancestry (MD -2.06%, 95% CI -2.49 to -1.63, I² = 81%, P < 0.00001) and South Asian ancestry comparators (MD -1.92%, 95% CI -3.26 to -0.57, I² = 78%, P = 0.005). However, heterogeneity was high in all analyses. Most studies found no significant differences in IMCL between BA and WE. Few studies investigated IPL, however, indicated that IPL is lower in BA compared to WE and HIS.

CONCLUSION

The discordance between ectopic fat and greater risk for T2D in BA populations raises questions around its contribution to T2D pathophysiology in BA.

The Association of Gene Variants in the Vitamin D Metabolic Pathway and Its Interaction with Vitamin D on Gestational Diabetes Mellitus: A Prospective Cohort Study

The present prospective study included 2156 women and investigated the effect of gene variants in the vitamin D (VitD) metabolic and glucose pathways and their interaction with VitD levels during pregnancy on gestational diabetes mellitus (GDM). Plasma 25(OH)D concentrations were measured at the first and second trimesters. GDM subtype 1 was defined as those with isolated elevated fasting plasma glucose; GDM subtype 2 were those with isolated elevated postprandial glucose at 1 h and/or 2 h; and GDM subtype 3 were those with both elevated fasting plasma glucose and postprandial glucose. Six Gc isoforms were categorized based on two GC gene variants rs4588 and rs7041, including 1s/1s, 1s/2, 1s/1f, 2/2, 1f/2 and 1f/1f. VDR-rs10783219 and MTNR1B-rs10830962 were associated with increased risks of GDM and GDM subtype 2; interactions between each other as well as with CDKAL1-rs7754840 were observed (P_interaction < 0.05). Compared with the 1f/1f isoform, the risk of GDM subtype 2 among women with 1f/2, 2/2, 1s/1f, 1s/2 and 1s/1s isoforms and with prepregnancy body mass index ≥24 kg/m² increased by 5.11, 10.01, 10, 14.23, 19.45 times, respectively. Gene variants in VitD pathway interacts with VitD deficiency at the first trimester on the risk of GDM and GDM subtype 2.

Renal gluconeogenesis in insulin resistance: A culprit for hyperglycemia in diabetes

Renal gluconeogenesis is one of the major pathways for endogenous glucose production. Impairment in this process may contribute to hyperglycemia in cases with insulin resistance and diabetes. We reviewed pertinent studies to elucidate the role of renal gluconeogenesis regulation in insulin resistance and diabetes. A consensus on the suppressive effect of insulin on kidney gluconeogenesis has started to build up. Insulin-resistant models exhibit reduced insulin receptor (IR) expression and/or post-receptor signaling in their kidney tissue. Reduced IR expression or post-receptor signaling can cause impairment in insulin’s action on kidneys, which may increase renal gluconeogenesis in the state of insulin resistance. It is now established that the kidney contributes up to 20% of all glucose production via gluconeogenesis in the post-absorptive phase. However, the rate of renal glucose release excessively increases in diabetes. The rise in renal glucose release in diabetes may contribute to fasting hyperglycemia and increased postprandial glucose levels. Enhanced glucose release by the kidneys and renal expression of the gluconeogenic-enzyme in diabetic rodents and humans further point towards the significance of renal gluconeogenesis. Overall, the available literature suggests that impairment in renal gluconeogenesis in an insulin-resistant state may contribute to hyperglycemia in type 2 diabetes.

Disparities in cardio metabolic risk between Black and White women with polycystic ovary syndrome: a systematic review and meta-analysis

OBJECTIVE

We conducted a systematic review and meta-analysis to summarize and quantitatively pool evidence on cardiometabolic health disparities between Black and White women with polycystic ovary syndrome in the United States in response to the call for further delineation of these disparities in the international evidence-based guideline for the assessment and management of polycystic ovary syndrome.

DATA SOURCES

Databases of MEDLINE, Web of Science, and Scopus were searched initially through March 05, 2020, and confirmed on September 11, 2020.

STUDY ELIGIBILITY CRITERIA

Observational studies documenting cardiometabolic risk profile (glucoregulatory, lipid profile, anthropometric, and blood pressure status) in Black and White women with polycystic ovary syndrome were included. Studies on children (<17 years old) and pregnant or menopausal-aged women (>50 years) were excluded. The primary outcome was fasting glucose. Furthermore, data on major cardiovascular events (stroke, coronary heart disease, heart failure) and mortality rate (cardiovascular death, total mortality) were evaluated.

METHODS

Data were pooled by random-effects models and expressed as mean differences and 95% confidence intervals. Studies were weighted based on the inverse of the variance. Heterogeneity was evaluated by Cochran Q and I2 statistics. Study methodologic quality was assessed by the Newcastle-Ottawa scale.

RESULTS

A total of 11 studies (N=2851 [652 Black and 2199 White]) evaluated cardiometabolic risk profile and all had high quality (Newcastle-Ottawa scale score of ≥8). No studies reported on cardiovascular events and mortality rate. Black women had comparable fasting glucose (-0.61 [-1.69 to 2.92] mg/dL; I2=62.5%), yet exhibited increased fasting insulin (6.76 [4.97-8.56] μIU/mL; I2=59.0%); homeostatic model assessment of insulin resistance (1.47 [0.86-2.08]; I2=83.2%); systolic blood pressure (3.32 [0.34-6.30] mm Hg; I2=52.0%); and decreased triglyceride (-32.56 [-54.69 to -10.42] mg/dL; I2=68.0%) compared with White women (all, P≤.03). Groups exhibited comparable total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and diastolic blood pressure (all, P≥.06).

CONCLUSIONS

Black women with polycystic ovary syndrome have a greater tendency for an adverse cardiometabolic risk profile (increased insulin, homeostatic model assessment of insulin resistance, and systolic blood pressure) despite lower triglycerides than White women. Our observations support the consideration of these disparities for diagnostic, monitoring, and management practices in Black women and for future guideline recommendations. Given the heterogeneity among studies, future research should address the relative contributions of biologic, environmental, socioeconomic, and healthcare factors to the observed disparities. Furthermore, longitudinal research is required to address patient-pressing complications, including cardiovascular events and mortality rate in Black women with polycystic ovary syndrome as a high-risk yet understudied population.

Synergizing Mouse and Human Studies to Understand the Heterogeneity of Obesity

Obesity is routinely considered as a single disease state, which drives a "one-size-fits-all" approach to treatment. We recently convened the first annual University of North Carolina Interdisciplinary Nutrition Sciences Symposium to discuss the heterogeneity of obesity and the need for translational science to advance understanding of this heterogeneity. The symposium aimed to advance scientific rigor in translational studies from animal to human models with the goal of identifying underlying mechanisms and treatments. In this review, we discuss fundamental gaps in knowledge of the heterogeneity of obesity ranging from cellular to population perspectives. We also advocate approaches to overcoming limitations in the field. Examples include the use of contemporary mouse genetic reference population models such as the Collaborative Cross and Diversity Outbred mice that effectively model human genetic diversity and the use of translational models that integrate -omics and computational approaches from pre-clinical to clinical models of obesity. Finally, we suggest best scientific practices to ensure strong rigor that will allow investigators to delineate the sources of heterogeneity in the population with obesity. Collectively, we propose that it is critical to think of obesity as a heterogeneous disease with complex mechanisms and etiologies, requiring unique prevention and treatment strategies tailored to the individual.

Fatty Acid Metabolism and Associations with Insulin Sensitivity Differs Between Black and White South African Women

PURPOSE

Genetic differences in desaturase genes and consequently fatty acid metabolism have been reported. The aims were to examine ethnic differences in serum fatty acid composition and desaturase indices, and assess the ethnic-specific associations with insulin sensitivity (IS) and liver fat in black and white South African (SA) women.

METHODS

In this cross-sectional study including 92 premenopausal black (n = 46) and white (n = 46) SA women, serum fatty acid composition was measured in cholesteryl ester (CE) and nonesterified fatty acid (NEFA) fractions. Desaturase activities were estimated as product-to-precursor ratios: stearoyl-CoA desaturase-1 (SCD1-16, 16:1n-7/16:0); δ-5 desaturase (D5D, 20:4n-6/20:3n-6), and δ-6 desaturase (D6D, 18:3n-6/18:2n-6). Whole-body IS was estimated from an oral glucose tolerance test using the Matsuda index. In a subsample (n = 30), liver fat and hepatic IS were measured by 1H-magnetic resonance spectroscopy and hyperinsulinemic euglycemic clamp, respectively.

RESULTS

Despite lower whole-body IS (P = .006), black women had higher CE D5D and lower D6D and SCD1-16 indices than white women (P < .01). CE D6D index was associated with lower IS in white women only (r = -0.31, P = .045), whereas D5D index was associated with higher IS in black women only (r = 0.31, P = .041). In the subsample, D6D and SCD1-16 indices were positively and D5D was negatively associated with liver fat (P < .05). Conversely, CE SCD1-16 was negatively associated with hepatic IS (P < .05), but not independently of liver fat.

CONCLUSIONS

Ethnic differences in fatty acid-derived desaturation indices were observed, with insulin-resistant black SA women paradoxically showing a fatty acid pattern typical for higher insulin sensitivity in European populations.

The OGTT is highly reproducible in Africans for the diagnosis of diabetes: Implications for treatment and protocol design

Whether an OGTT reproducibly detects either type 2 diabetes (T2D) or prediabetes in Africans in unknown. Therefore, 131 Africans had two OGTT. Diagnostic reproducibility for T2D was excellent (κ = 0.84), but only moderate for prediabetes (κ = 0.51). A single OGTT positive for T2D may be sufficient to guide clinical care and inform epidemiologic study design. ClinicalTrials.gov Identifier: NCT00001853.

Identifying Africans with undiagnosed diabetes: Fasting plasma glucose is similar to the hemoglobin A1C updated Atherosclerosis Risk in Communities diabetes prediction equation

AIMS

Seventy percent of Africans living with diabetes are undiagnosed. Identifying who should be referred for testing is critical. Therefore we evaluated the ability of the Atherosclerosis Risk in Communities (ARIC) diabetes prediction equation with A1C added (ARIC + A1C) to identify diabetes in 451 African-born blacks living in America (66% male; age 38 ± 10y (mean ± SD); BMI 27.5 ± 4.4 kg/m²).

METHODS

All participants denied a history of diabetes. OGTTs were performed. Diabetes diagnosis required 2-h glucose ≥200 mg/dL. The five non-invasive (Age, parent history of diabetes, waist circumference, height, systolic blood pressure) and four invasive variables (Fasting glucose (FPG), A1C, triglycerides (TG), HDL) were obtained. Four models were tested: Model-1: Full ARIC + A1C equation; Model-2: All five non-invasive variables with one invasive variable excluded at a time; Model-3: All five non-invasive variables with one invasive variable included at a time; Model-4: Each invasive variable singly. Area under the receiver operator characteristic curve (AROC) predicted diabetes. Youden Index identified optimal cut-points.

RESULTS

Diabetes occurred in 7% (30/451). Model-1, the full ARIC + A1C equation, AROC = 0.83. Model-2: With FPG excluded, AROC = 0.77 (P = 0.038), but when A1C, HDL or TG were excluded AROC remained unchanged. Model-3 with all non-invasive variables and FPG alone, AROC=0.87; but with A1C, TG or HDL included AROC declined to ≤0.76. Model-4: FPG as a single predictor, AROC = 0.87. A1C, TG, or HDL as single predictors all had AROC ≤ 0.74. Optimal cut-point for FPG was 100 mg/dL.

CONCLUSIONS

To detect diabetes, FPG performed as well as the nine-variable updated ARIC + A1C equation.

Metformin improves blood glucose by increasing incretins independent of changes in gluconeogenesis in youth with type 2 diabetes

AIMS/HYPOTHESIS

Metformin is the only approved oral agent for youth with type 2 diabetes but its mechanism of action remains controversial. Recent data in adults suggest a primary role for the enteroinsular pathway, but there are no data in youth, in whom metformin efficacy is only ~50%. Our objectives were to compare incretin concentrations and rates of glucose production and gluconeogenesis in youth with type 2 diabetes before and after short-term metformin therapy compared with peers with normal glucose tolerance (NGT).

METHODS

This is a case-control observational study in youth with type 2 diabetes who were not on metformin (n = 18) compared with youth with NGT (n = 10) who were evaluated with a 2 day protocol. A 75 g OGTT was administered to measure intact glucagon-like 1 peptide (iGLP-1), gastric inhibitory polypeptide (GIP) and peptide YY (PYY). Insulinogenic index (IGI) and whole-body insulin sensitivity were calculated using glucose and insulin levels from the OGTT. Basal rates of gluconeogenesis (²H₂O), glucose production ([6,6-²H₂]glucose) and whole-body lipolysis ([²H₅]glycerol) were measured after an overnight fast on study day 2. Youth with type 2 diabetes (n = 9) were subsequently evaluated with an identical 2 day protocol after 3 months on the metformin study.

RESULTS

Compared with individuals with NGT, those with type 2 diabetes had higher fasting (7.8 ± 2.5 vs 5.1 ± 0.3 mmol/l, mean ± SD p = 0.002) and 2 h glucose concentrations (13.8 ± 4.5 vs 5.9 ± 0.9 mmol/l, p = 0.001), higher rates of absolute gluconeogenesis (10.0 ± 1.7 vs 7.2 ± 1.1 μmol [kg fat-free mass (FFM)]^-1 min^-1, p < 0.001) and whole-body lipolysis (5.2 ± 0.9 vs 4.0 ± 1.4 μmol kg_FFM^-1 min^-1, p < 0.01), but lower fasting iGLP-1 concentrations (0.5 ± 0.5 vs 1.3 ± 0.7 pmol/l, p < 0.01). Metformin decreased 2 h glucose (pre metformin 11.4 ± 2.8 vs post metformin 9.9 ± 1.9 mmol/l, p = 0.04) and was associated with ~20-50% increase in IGI (median [25th-75th percentile] pre 1.39 [0.89-1.47] vs post 1.43 [0.88-2.70], p = 0.04), fasting iGLP-1 (pre 0.3 ± 0.2 vs post 1.0 ± 0.7 pmol/l, p = 0.02), 2 h iGLP (pre 0.4 ± 0.2 vs post 1.2 ± 0.9 pmol/l, p = 0.06), fasting PYY (pre 6.3 ± 2.2 vs post 10.5 ± 4.3 pmol/l, p < 0.01) and 2 h PYY (pre 6.6 ± 2.9 vs post 9.0 ± 4.0 pmol/l, p < 0.01). There was no change in BMI, insulin sensitivity or GIP concentrations pre vs post metformin. There were no differences pre vs post metformin in rates of glucose production (15.0 ± 3.9 vs 14.9 ± 2.2 μmol kg_FFM^-1 min^-1, p = 0.84), absolute gluconeogenesis (9.9 ± 1.8 vs 9.7 ± 1.7 μmol kg_FFM^-1 min^-1, p = 0.76) or whole-body lipolysis (5.0 ± 0.7 vs 5.3 ± 1.3 μmol kg_FFM^-1 min^-1, p = 0.20). Post metformin iGLP-1 and PYY concentrations in youth with type 2 diabetes were comparable to levels in youth with NGT.

CONCLUSIONS/INTERPRETATION

Overall, the improved postprandial blood glucose levels and increase in incretins observed in the absence of changes in insulin sensitivity and gluconeogenesis, support an enteroinsular mechanistic pathway in youth with type 2 diabetes treated with short-term metformin.

Pathogenesis of type 2 diabetes risk in black Africans: a South African perspective

The prevalence of type 2 diabetes (T2D) is higher in black Africans than their European counterparts. This review summarizes the research exploring the pathogenesis of T2D in populations of African ancestry compared to white Europeans and shows that the pathogenesis differs by ethnicity. Black Africans present with a phenotype of low insulin sensitivity and hyperinsulinaemia as a result of increased insulin secretion and reduced hepatic insulin clearance. Whether hyperinsulinaemia precedes insulin resistance or is merely a compensatory mechanism is yet to be determined. Black Africans have lower visceral adipose tissue and ectopic fat deposition and greater peripheral (gluteo-femoral) fat deposition than their European counterparts. This suggests that black Africans are more sensitive to the effects of ectopic fat deposition, or alternatively, that ectopic fat is not an important mediator of T2D in black Africans. Importantly, ethnic disparities in T2D risk factors may be confounded by differences in sociocultural and lifestyle factors. Future longitudinal and dietary intervention studies, in combination with genetic analyses, are needed for a better understanding of the pathophysiology of T2D in black Africans. This will be key for effective prevention and management strategies.

Exercise Training Alters Red Blood Cell Fatty Acid Desaturase Indices and Adipose Tissue Fatty Acid Profile in African Women with Obesity

OBJECTIVE

This study assessed the changes in red blood cell total phospholipid (RBC-TPL) and subcutaneous adipose tissue (SAT) fatty acid (FA) composition in response to 12 weeks of exercise training in South African women with obesity and the associations with changes in cardiometabolic risk factors.

METHODS

Previously sedentary women were randomized into control (n = 15) or exercise (n = 20) groups. RBC-TPL and SAT FA profiles, SAT gene expression, systemic inflammatory markers, liver fat, and insulin sensitivity (S_I ) were measured before and after the intervention.

RESULTS

Compared with control, exercise training induced decreases in RBC-TPL dihomo-γ-linolenic acid content and stearoyl-CoA desaturase-1 and increased delta-5 desaturase-estimated activity (P < 0.05). In the combined group, these changes correlated with changes in circulating leptin and TNFα (P < 0.05), as well as lower liver fat (P < 0.01). Exercise training decreased saturated FA (lauric and myristic acids) and increased polyunsaturated FA (eicosadienoic and adrenic acids) (P < 0.05) in abdominal SAT, whereas γ-linolenic acid decreased (P < 0.01) in gluteal SAT. These changes in RBC-TPL and SAT FA compositions were not associated with changes in SAT gene expression and S_I .

CONCLUSIONS

Exercise training alters RBC-TPL desaturase activities, which correlate with lower liver fat and systemic inflammation but not with the improvement of S_I .

Phosphoenolpyruvate carboxykinase in urine exosomes reflect impairment in renal gluconeogenesis in early insulin resistance and diabetes

Impaired insulin-induced suppression of renal gluconeogenesis could be a risk for hyperglycemia. Diabetes is associated with elevated renal gluconeogenesis; however, its regulation in early insulin resistance is unclear in humans. A noninvasive marker of renal gluconeogenesis would be helpful. Here, we show that human urine exosomes (uE) contain three gluconeogenic enzymes: phosphoenolpyruvate carboxykinase (PEPCK), fructose 1,6-bisphosphatase, and glucose 6-phosphatase. Their protein levels were positively associated with whole body insulin sensitivity. PEPCK protein in uE exhibited a meal-induced suppression. However, subjects with lower insulin sensitivity had blunted meal-induced suppression. Also, uE from subjects with prediabetes and diabetic rats had higher PEPCK relative to nondiabetic controls. Moreover, uE-PEPCK was higher in drug-naïve subjects with diabetes relative to drug-treated subjects with diabetes. To determine whether increased renal gluconeogenesis is associated with hyperglycemia or PEPCK expression in uE, acidosis was induced in rats by 0.28 M NH₄Cl with 0.5% sucrose in drinking water. Control rats were maintained on 0.5% sucrose. At the seventh day posttreatment, gluconeogenic enzyme activity in the kidneys, but not in the liver, was higher in acidotic rats. These rats had elevated PEPCK in their uE and a significant rise in blood glucose relative to controls. The induction of gluconeogenesis in human proximal tubule cells increased PEPCK expression in both human proximal tubules and human proximal tubule-secreted exosomes in the media. Overall, gluconeogenic enzymes are detectable in human uE. Elevated PEPCK and its blunted meal-induced suppression in human urine exosomes are associated with diabetes and early insulin resistance.

Triglyceride Paradox Is Related to Lipoprotein Size, Visceral Adiposity and Stearoyl-CoA Desaturase Activity in Black Versus White Women

RATIONALE

In black women, triglycerides are paradoxically normal in the presence of insulin resistance. This relationship may be explained by race-related differences in central adiposity and SCD (stearoyl-CoA desaturase)-1 enzyme activity index.

OBJECTIVE

In a cross-sectional study, to compare fasting and postprandial triglyceride-rich lipoprotein particle (TRLP) concentrations and size in black compared with white pre- and postmenopausal women and determine the relationship between TRLP subfractions and whole-body insulin sensitivity, hepatic and visceral fat, and SCD-1 levels.

METHODS AND RESULTS

In 122 federally employed women without diabetes mellitus, 73 black (58 African American and 15 African immigrant) and 49 white; age, 44±10 (mean±SD) years; body mass index, 30.0±5.6 kg/m², we measured lipoprotein subfractions using nuclear magnetic resonance. Hepatic fat was measured by proton magnetic resonance spectroscopy, insulin sensitivity index calculated by minimal modeling from a frequently sampled intravenous glucose test, and red blood cell fatty acid profiles were measured by gas chromatography and were used to estimate SCD-1 indices. Hepatic fat, insulin sensitivity index, and SCD-1 were similar in black women and lower than in whites, regardless of menopausal status. Fasting and postprandial large, medium, and small TRLPs, but not very small TRLPs, were lower in black women. Fasting large, medium, and very small TRLPs negatively correlated with insulin sensitivity index and positively correlated with visceral and hepatic fat and SCD-1 activity in both groups. In multivariate models, visceral fat and SCD-1 were associated with total fasting TRLP concentrations (adjR2, 0.39; P=0.001). Black women had smaller postprandial changes in large (P=0.005) and medium TRLPs (P=0.007).

CONCLUSIONS

Lower visceral fat and SCD-1 activity may contribute to the paradoxical association of lower fasting and postprandial TRLP subfractions despite insulin resistance in black compared with white pre- and postmenopausal women. Similar concentrations of very small TRLPs are related to insulin resistance and could be important mediators of cardiometabolic disease risk in women.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01809288.

Ethnic distinctions in the pathophysiology of type 2 diabetes: a focus on black African-Caribbean populations

Type 2 diabetes (T2D) is a global public health priority, particularly for populations of black African-Caribbean ethnicity, who suffer disproportionately high rates of the disease. While the mechanisms underlying the development of T2D are well documented, there is growing evidence describing distinctions among black African-Caribbean populations. In the present paper, we review the evidence describing the impact of black African-Caribbean ethnicity on T2D pathophysiology. Ethnic differences were first recognised through evidence that metabolic syndrome diagnostic criteria fail to detect T2D risk in black populations due to less central obesity and dyslipidaemia. Subsequently more detailed investigations have recognised other mechanistic differences, particularly lower visceral and hepatic fat accumulation and a distinctly hyperinsulinaemic response to glucose stimulation. While epidemiological studies have reported exaggerated insulin resistance in black populations, more detailed and direct measures of insulin sensitivity have provided evidence that insulin sensitivity is not markedly different to other ethnic groups and does not explain the hyperinsulinaemia that is exhibited. These findings lead us to hypothesise that ectopic fat does not play a pivotal role in driving insulin resistance in black populations. Furthermore, we hypothesise that hyperinsulinaemia is driven by lower rates of hepatic insulin clearance rather than heightened insulin resistance and is a primary defect rather than occurring in compensation for insulin resistance. These hypotheses are being investigated in our ongoing South London Diabetes and Ethnicity Phenotyping study, which will enable a more detailed understanding of ethnic distinctions in the pathophysiology of T2D between men of black African and white European ethnicity.

A Review of Diabetes Prediction Equations in African Descent Populations

Background: Predicting undiagnosed diabetes is a critical step toward addressing the diabetes epidemic in populations of African descent worldwide. Objective: To review characteristics of equations developed, tested, or modified to predict diabetes in African descent populations. Methods: Using PubMed, Scopus, and Embase databases, a scoping review yielded 585 research articles. After removal of duplicates (n = 205), 380 articles were reviewed. After title and abstract review 328 articles did not meet inclusion criteria and were excluded. Fifty-two articles were retained. However, full text review revealed that 44 of the 52 articles did not report findings by AROC or C-statistic in African descent populations. Therefore, eight articles remained. Results: The 8 articles reported on a total of 15 prediction equation studies. The prediction equations were of two types. Prevalence prediction equations (n = 9) detected undiagnosed diabetes and were based on non-invasive variables only. Non-invasive variables included demographics, blood pressure and measures of body size. Incidence prediction equations (n = 6) predicted risk of developing diabetes and used either non-invasive variables or both non-invasive and invasive. Invasive variables required blood tests and included fasting glucose, high density lipoprotein-cholesterol (HDL), triglycerides (TG), and A1C. Prevalence prediction studies were conducted in the United States, Africa and Europe. Incidence prediction studies were conducted only in the United States. In all these studies, the performance of diabetes prediction equations was assessed by area under the receiver operator characteristics curve (AROC) or the C-statistic. Therefore, we evaluated the efficacy of these equations based on standard criteria, specifically discrimination by either AROC or C-statistic were defined as: Poor (0.50 - 0.69); Acceptable (0.70 - 0.79); Excellent (0.80 - 0.89); or Outstanding (0.90 - 1.00). Prediction equations based only on non-invasive variables reported to have poor to acceptable detection of diabetes with AROC or C-statistic 0.64 - 0.79. In contrast, prediction equations which were based on both non-invasive and invasive variables had excellent diabetes detection with AROC or C-statistic 0.80 - 0.82. Conclusion: Equations which use a combination of non-invasive and invasive variables appear to be superior in the prediction of diabetes in African descent populations than equations that rely on non-invasive variables alone.

Scutellariae Radix and Coptidis Rhizoma Improve Glucose and Lipid Metabolism in T2DM Rats via Regulation of the Metabolic Profiling and MAPK/PI3K/Akt Signaling Pathway

Aim Scutellariae Radix (SR) and Coptidis Rhizoma (CR) have often been combined to cure type 2 diabetes mellitus (T2DM) in the clinical practice for over thousands of years, but their compatibility mechanism is not clear. Mitogen-activated protein kinase (MAPK) signaling pathway has been suggested to play a critical role during the process of inflammation, insulin resistance, and T2DM. This study was designed to investigate their compatibility effects on T2DM rats and explore the underlying mechanisms by analyzing the metabolic profiling and MAPK/PI3K/Akt signaling pathway. Methods The compatibility effects of SR and CR were evaluated with T2DM rats induced by a high-fat diet (HFD) along with a low dose of streptozocin (STZ). Ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) was performed to discover potential biomarkers. The levels of pro-inflammatory cytokines; biochemical indexes in serum, and the activities of key enzymes related to glycometabolism in liver were assessed by ELISA kits. qPCR was applied to examine mRNA levels of key targets in MAPK and insulin signaling pathways. Protein expressions of p65; p-p65; phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K); phosphorylated-PI3K (p-PI3K); protein kinase B (Akt); phosphorylated Akt (p-Akt) and glucose transporter 2 (Glut2) in liver were investigated by Western blot analysis. Results Remarkably, hyperglycaemia, dyslipidemia, inflammation, and insulin resistance in T2DM were ameliorated after oral administration of SR and CR, particularly their combined extracts. The effects of SR, CR, low dose of combined extracts (LSC) and high dose of combined extracts (HSC) on pro-inflammatory cytokine transcription in T2DM rats showed that the MAPK pathway might account for the phenomenon with down-regulation of MAPK (P38 mitogen-activated protein kinases (P38), extracellular regulated protein kinases (ERK), and c-Jun N-terminal kinase (JNK)) mRNA, and protein reduction in p-P65. While mRNA levels of key targets such as insulin receptor substrate 1 (IRS1), PI3K, Akt2, and Glut2 in the insulin signaling pathway were notably up-modulated, phosphorylations of PI3K, Akt, and expression of Glut2 were markedly enhanced. Moreover, the increased activities of phosphoenolpyruvate carboxykinase (PEPCK), fructose-1,6-bisphosphatase (FBPase), glucose 6-phosphatase (G6Pase), and glycogen phosphorylase (GP) were highly reduced and the decreased activities of glucokinase (GK), phosphofructokinase (PFK), pyruvate kinase (PK), and glycogen synthase (GS) in liver were notably increased after treatment. Further investigation indicated that the metabolic profiles of plasma and urine were clearly improved in T2DM rats. Fourteen potential biomarkers (nine in plasma and five in urine) were identified. After intervention, these biomarkers returned to normal level to some extent. Conclusion The results showed that SR, CR, and combined extract groups were normalized. The effects of combined extracts were more remarkable than single herb treatment. Additionally, this study also showed that the metabonomics method is a promising tool to unravel how traditional Chinese medicines work.