Low serum creatinine, a surrogate marker of muscle mass, correlates with insulin sensitivity in nonhuman primates

OBJECTIVES

Decreased serum creatinine levels are associated with increased risk of type 2 diabetes (T2DM) in humans, however, its association with muscle mass and insulin sensitivity have not been studied in NHPs.

METHODS

Retrospective data of 229 adult NHPs were studied for association of serum creatinine levels with muscle mass and onset of T2DM.

RESULTS

Serum creatinine levels were positively correlated with lean muscle mass in nondiabetic (non-DM), male and female NHPs. Aged NHPs had significantly reduced lean muscle mass and corresponding creatinine levels compared to young age groups (p < .001). Creatinine was positively correlated with insulin sensitivity in nonDM male NHPs and significant decrease in creatinine was observed in T2DM (p < .001) compared to same age group nonDM NHPs.

CONCLUSIONS

The pathophysiology of T2DM in NHPs is similar to humans, low creatinine further provides utility of surrogate biomarkers of lower muscle mass and risk factor for T2DM NHPs.

Iron deficiency, but not anemia, is identified in naturally occurring obesity and insulin resistance in male nonhuman primates

OBJECTIVES

To understand the development of iron deficiency in obesity and its long-term impact on the profile of anemia in spontaneously obese nonhuman primates.

METHODS

The study included 69 adult male nonhuman primates, (NHPs, Macaca mulatta, rhesus monkeys), ranging from normal to obese, and type 2 diabetes (T2D) as defined for humans.

RESULTS

Iron deficiency was present in 31.9% and mild anemia in 13% of the rhesus monkey in the colony. Serum iron levels were significantly lower in obese (p < .01) and T2D (p < .01)) compared with normal NHP. Obese NHPs also had significantly higher hemoglobin (p < .05), and red blood cell count (p < .05) than normal weight NHPs, thus not related to anemia.

CONCLUSIONS

Iron deficiency with increased hemoglobin and red blood cells was significantly associated with increased adiposity, insulin resistance, and diabetes. Iron deficiency does not cause and is not related to anemia in obese and T2D NHPs.

Control of β-Site Amyloid Precursor Protein-Cleaving Enzyme-1 Expression by Protein Kinase C-λ/ι and Nuclear Factor κ-B

Βackground: β-Amyloid precursor protein-cleaving enzyme-1 (BACE1) initiates the production of Aβ-peptides that form Aβ-plaque in Alzheimer's disease.

METHODS

Reportedly, acute insulin treatment in normal mice, and hyperinsulinemia in high-fat-fed (HFF) obese/diabetic mice, increase BACE1 activity and levels of Aβ-peptides and phospho- -thr-231-tau in the brain; moreover, these effects are blocked by PKC-λ/ι inhibitors. However, as chemical inhibitors may affect unsuspected targets, we presently used knockout methodology to further examine PKC-λ/ι requirements. We found that total-body heterozygous PKC-λ knockout reduced acute stimulatory effects of insulin and chronic effects of hyperinsulinemia in HFF/obese/diabetic mice, on brain PKC-λ activity and production of Aβ1-40/42 and phospho-thr-231-tau. This protection in HFF mice may reflect that hepatic PKC-λ haploinsufficiency prevents the development of glucose intolerance and hyperinsulinemia.

RESULTS

On the other hand, heterozygous knockout of PKC-λ markedly reduced brain levels of BACE1 protein and mRNA, and this may reflect diminished activation of nuclear factor kappa-B (NFκB), which is activated by PKC-λ and increases BACE1 and proinflammatory cytokine transcription. Accordingly, whereas intravenous administration of aPKC inhibitor diminished aPKC activity and BACE1 levels by 50% in the brain and 90% in the liver, nasally-administered inhibitor reduced aPKC activity and BACE1 mRNA and protein levels by 50-70% in the brain while sparing the liver. Additionally, 24-hour insulin treatment in cultured human-derived neurons increased NFκB activity and BACE1 levels, and these effects were blocked by various PKC-λ/ι inhibitors.

CONCLUSION

PKC-λ/ι controls NFκB activity and BACE1 expression; PKC-λ/ι inhibitors may be used nasally to target brain PKC-λ/ι or systemically to block both liver and brain PKC-λ/ι, to regulate NFκB-dependent BACE1 and proinflammatory cytokine expression.

The Obesity Society is turning 40: A history of the early years

The North American Association for the Study of Obesity (NAASO), the precursor of The Obesity Society (TOS), was founded in 1981 and turns 40 years old in 2021. The Society was organized by George Bray along with John Brunzell, C. Wayne Callaway, M.R.C. Greenwood, and Judith Stern. It held its foundational meeting with a theme of "Types of Obesity: Animal Models and Clinical Applications" at Vassar College in the fall of 1982 along with symposia and an NIH workshop titled "Methods of Characterizing Human Obesity." At a follow-up meeting during the Fourth International Congress on Obesity, Barbara Hansen was elected President, Judith Stern Secretary, and Anne Sullivan Treasurer. Incorporation of NAASO occurred in 1984.

Roles of hepatic atypical protein kinase C hyperactivity and hyperinsulinemia in insulin-resistant forms of obesity and type 2 diabetes mellitus

Diet-induced obesity, the metabolic syndrome, type 2 diabetes (DIO/MetS/T2DM), and their adverse sequelae have reached pandemic levels. In mice, DIO/MetS/T2DM initiation involves diet-dependent increases in lipids that activate hepatic atypical PKC (aPKC) and thereby increase lipogenic enzymes and proinflammatory cytokines. These or other hepatic aberrations, via adverse liver-to-muscle cross talk, rapidly impair postreceptor insulin signaling to glucose transport in muscle. The ensuing hyperinsulinemia further activates hepatic aPKC, which first blocks the ability of Akt to suppress gluconeogenic enzyme expression, and later impairs Akt activation, further increasing hepatic glucose production. Recent findings suggest that hepatic aPKC also increases a proteolytic enzyme that degrades insulin receptors. Fortunately, all hepatic aberrations and muscle impairments are prevented/reversed by inhibition or deficiency of hepatic aPKC. But, in the absence of treatment, hyperinsulinemia induces adverse events, some by using "spare receptors" to bypass receptor defects. Thus, in brain, hyperinsulinemia increases Aβ-plaque precursors and Alzheimer risk; in kidney, hyperinsulinemia activates the renin-angiotensin-adrenal axis, thus increasing vasoconstriction, sodium retention, and cardiovascular risk; and in liver, hyperinsulinemia increases lipogenesis, obesity, hepatosteatosis, hyperlipidemia, and cardiovascular risk. In summary, increases in hepatic aPKC are critically required for development of DIO/MetS/T2DM and its adverse sequelae, and therapeutic approaches that limit hepatic aPKC may be particularly effective.

Altered expression of p63 isoforms and expansion of p63- and club cell secretory protein-positive epithelial cells in the lung as novel features of aging

Aging is a key contributor for subclinical progression of late-onset lung diseases. Basal, club, and type II alveolar epithelial cells (AECs) are lung epithelial progenitors whose capacities of differentiation are extensively studied. The timely transition of these cells in response to environmental changes helps maintain the intricate organization of lung structure. However, it remains unclear how aging affects their behavior. This paper demonstrates that the protein expression profiles of a type II AEC marker, prosurfactant protein C (pro-SPC), and a basal cell marker, p63, are altered in the lungs of 14-mo-old versus 7- to 9-wk-old mice. Expression of NH2-terminal-truncated forms of p63 (ΔNp63), a basal cell marker, and claudin-10, a club cell marker, in cytoplasmic extracts of lungs of 14-mo-old mice was upregulated. In contrast, nuclear expression of full-length forms of p63 (TAp63) decreases with age. These alterations in protein expression profiles coincide with dramatic changes in lung functions including compliance. Whole tissue lysates of middle-aged versus aged rhesus monkey lungs display similar age-associated alterations in pro-SPC expression. An age-associated decrease of TAp63 in nuclear lysates was observed in aged monkey group. Moreover, the lungs of 14-mo-old versus 7- to 9-wk-old mice display a wider spreading of ΔNp63-positive CCSP-positive bronchiolar epithelial cells. This expansion did not involve upregulation of Ki67, a representative proliferation marker. Collectively, it is postulated that 1) this expansion is secondary to a transition of progenitor cells committed to club cells from ΔNp63-negative to ΔNp63-positive status, and 2) high levels of cytoplasmic ΔNp63 expression trigger club cell migration.

Does obesity cause type 2 diabetes mellitus (T2DM)? Or is it the opposite?

Obesity is believed to be a promoter of type 2 diabetes mellitus (T2DM). Reports indicate that severe obesity in childhood and adolescence increases the risk of T2DM in youth and young adults. T2DM, which is commonly asymptomatic, frequently is not recognized until random blood glucose is measured. Screening blood glucose levels measured in obese individuals are more effective for identifying undiagnosed persons, than screening the general population and therefore introduces a selection bias for discovery. The following commentary will indicate why these observations do not indicate that obesity is the cause of T2DM. Also, it will be shown that the insulin resistance of T2DM occurs primarily in the muscles of lean individuals predisposed to diabetes before they become obese. This insulin resistance is not secondary to, but instead, is the cause of the excessive fat accumulation associated with T2DM. Moreover, this early muscle insulin resistance is the etiology of the hyperlipidemia and excess fat accumulation characteristic of T2DM.

An in vitro prototype of a porcine biomimetic testis-like cell culture system: a novel tool for the study of reassembled Sertoli and Leydig cells

At present, there is no reliable in vitro assembled prepubertal testis-like biomimetic organ culture system designed to assess the functional effects of human gonadotropins on Sertoli and Leydig cells. Spermatogenesis is regulated by endocrine, paracrine, and juxtacrine factors (testicular cross-talk), mainly orchestrated by gonadotropins such as luteinizing hormone (LH) and follicle-stimulating hormone (FSH) that play a pivotal role by stimulating Leydig and Sertoli cells, respectively. The aim of our study was to set up an in vitro prepubertal porcine bioengineered construct as a new model for experimental studies on reassembled Sertoli and Leydig cells. We have evaluated Sertoli and Leydig cells obtained from 15- to 20-day-old neonatal pig testes in terms of purity and function. Subsequently, purified Sertoli and enriched Leydig cells were subjected to coincubation to obtain an in vitro prepubertal porcine testis-like culture system. We performed enzyme-linked immunosorbent assay (ELISA) for anti-Müllerian hormone (AMH), inhibin B, and testosterone secretion in the medium, and Real-Time PCR analysis of AMH, inhibin B, FSH-r, aromatase, LHr, and 3β-HSD mRNA expression levels. This in vitro testis-like system was highly responsive to the effects of human gonadotropins and testosterone. AMH mRNA expression and secretion declined, and inhibin-B increased, while FSH-receptor expression was downregulated upon FSH/LH exposure/treatment. Finally, the production of testosterone was increased selectively upon LH treatment. In summary, our proposed model could help to better determine the action of human gonadotropins on Sertoli and Leydig cells. The potential usefulness of the system for shedding light into male infertility-related issues is evident.

Atypical PKC, PKCλ/ι, activates β-secretase and increases Aβ1-40/42 and phospho-tau in mouse brain and isolated neuronal cells, and may link hyperinsulinemia and other aPKC activators to development of pathological and memory abnormalities in Alzheimer's disease

Hyperinsulinemia activates brain Akt and PKC-λ/ι and increases Aβ1-40/42 and phospho-tau in insulin-resistant animals. Here, we examined underlying mechanisms in mice, neuronal cells, and mouse hippocampal slices. Like Aβ1-40/42, β-secretase activity was increased in insulin-resistant mice and monkeys. In insulin-resistant mice, inhibition of hepatic PKC-λ/ι sufficient to correct hepatic abnormalities and hyperinsulinemia simultaneously reversed increases in Akt, atypical protein kinase C (aPKC), β-secretase, and Aβ1-40/42, and restored acute Akt activation. However, 2 aPKC inhibitors additionally blocked insulin's ability to activate brain PKC-λ/ι and thereby increase β-secretase and Aβ1-40/42. Furthermore, direct blockade of brain aPKC simultaneously corrected an impairment in novel object recognition in high-fat-fed insulin-resistant mice. In neuronal cells and/or mouse hippocampal slices, PKC-ι/λ activation by insulin, metformin, or expression of constitutive PKC-ι provoked increases in β-secretase, Aβ1-40/42, and phospho-thr-231-tau that were blocked by various PKC-λ/ι inhibitors, but not by an Akt inhibitor. PKC-λ/ι provokes increases in brain β-secretase, Aβ1-40/42, and phospho-thr-231-tau. Excessive signaling via PKC-λ/ι may link hyperinsulinemia and other PKC-λ/ι activators to pathological and functional abnormalities in Alzheimer's disease.

Ensuring due process in the IACUC and animal welfare setting: considerations in developing noncompliance policies and procedures for institutional animal care and use committees and institutional officials

Every institution that is involved in research with animals is expected to have in place policies and procedures for the management of allegations of noncompliance with the Animal Welfare Act and the U.S. Public Health Service Policy on the Humane Care and Use of Laboratory Animals. We present here a model set of recommendations for institutional animal care and use committees and institutional officials to ensure appropriate consideration of allegations of noncompliance with federal Animal Welfare Act regulations that carry a significant risk or specific threat to animal welfare. This guidance has 3 overarching aims: 1) protecting the welfare of research animals; 2) according fair treatment and due process to an individual accused of noncompliance; and 3) ensuring compliance with federal regulations. Through this guidance, the present work seeks to advance the cause of scientific integrity, animal welfare, and the public trust while recognizing and supporting the critical importance of animal research for the betterment of the health of both humans and animals.-Hansen, B. C., Gografe, S., Pritt, S., Jen, K.-L. C., McWhirter, C. A., Barman, S. M., Comuzzie, A., Greene, M., McNulty, J. A., Michele, D. E., Moaddab, N., Nelson, R. J., Norris, K., Uray, K. D., Banks, R., Westlund, K. N., Yates, B. J., Silverman, J., Hansen, K. D., Redman, B. Ensuring due process in the IACUC and animal welfare setting: considerations in developing noncompliance policies and procedures for institutional animal care and use committees and institutional officials.

Increased vimentin in human α- and β-cells in type 2 diabetes

Type 2 diabetes (T2DM) is associated with pancreatic islet dysfunction. Loss of β-cell identity has been implicated via dedifferentiation or conversion to other pancreatic endocrine cell types. How these transitions contribute to the onset and progression of T2DM in vivo is unknown. The aims of this study were to determine the degree of epithelial-to-mesenchymal transition occurring in α and β cells in vivo and to relate this to diabetes-associated (patho)physiological conditions. The proportion of islet cells expressing the mesenchymal marker vimentin was determined by immunohistochemistry and quantitative morphometry in specimens of pancreas from human donors with T2DM (n = 28) and without diabetes (ND, n = 38) and in non-human primates at different stages of the diabetic syndrome: normoglycaemic (ND, n = 4), obese, hyperinsulinaemic (HI, n = 4) and hyperglycaemic (DM, n = 8). Vimentin co-localised more frequently with glucagon (α-cells) than with insulin (β-cells) in the human ND group (1.43% total α-cells, 0.98% total β-cells, median; P < 0.05); these proportions were higher in T2DM than ND (median 4.53% α-, 2.53% β-cells; P < 0.05). Vimentin-positive β-cells were not apoptotic, had reduced expression of Nkx6.1 and Pdx1, and were not associated with islet amyloidosis or with bihormonal expression (insulin + glucagon). In non-human primates, vimentin-positive β-cell proportion was larger in the diabetic than the ND group (6.85 vs 0.50%, medians respectively, P < 0.05), but was similar in ND and HI groups. In conclusion, islet cell expression of vimentin indicates a degree of plasticity and dedifferentiation with potential loss of cellular identity in diabetes. This could contribute to α- and β-cell dysfunction in T2DM.

Xenograft of microencapsulated Sertoli cells restores glucose homeostasis in db/db mice with spontaneous diabetes mellitus

BACKGROUND

Increased abdominal fat and chronic inflammation in the expanded adipose tissue of obesity contribute to the development of insulin resistance and type 2 diabetes mellitus (T2D). The emerging immunoregulatory and anti-inflammatory properties of Sertoli cells have prompted their application to experimental models of autoimmune/inflammatory disorders, including diabetes. The main goal of this work was to verify whether transplantation of microencapsulated prepubertal porcine Sertoli cells (MC-SC) in the subcutaneous abdominal fat depot of spontaneously diabetic and obese db/db mice (homozygous for the diabetes spontaneous mutation [Lepr^db ]) would: (i) improve glucose homeostasis and (ii) modulate local and systemic immune response and adipokines profiles.

METHODS

Porcine prepubertal Sertoli cells were isolated, according to previously established methods and enveloped in Barium alginate microcapsules by a mono air-jet device. MC-SC were then injected in the subcutaneous abdominal fat depot of db/db mice.

RESULTS

We have preliminarily shown that graft of MC-SC restored glucose homeostasis, with normalization of glycated hemoglobin values with improvement of the intraperitoneal glucose tolerance test in 60% of the treated animals. These results were associated with consistent increase, in the adipose tissue, of uncoupling protein 1 expression, regulatory B cells, anti-inflammatory macrophages and a concomitant decrease of proinflammatory macrophages. Furthermore, the treated animals showed a reduction in inducible NOS and proinflammatory molecules and a significant increase in an anti-inflammatory cytokine such as IL-10 along with concomitant rise of circulating adiponectin levels. The anti-hyperglycemic graft effects also emerged from an increased expression of GLUT-4, in conjunction with downregulation of GLUT-2, in skeletal muscle and liver, respectively.

CONCLUSIONS

Preliminarily, xenograft of MC-SC holds promises for an effective cell therapy approach for treatment of experimental T2D.

Xenograft of microencapsulated Sertoli cells for the cell therapy of type 2 diabetes mellitus in spontaneously diabetic nonhuman primates: preliminary data

Insulin resistance in type 2 diabetes mellitus (T2DM) may be due to a chronic inflammation of the visceral adipose tissue (VAT) leading to local and systemic increases in proinflammatory cytokines. Microencapsulated porcine Sertoli cells (MC-pSC), by provision of immunomodulatory and trophic factors, have been successfully used to reduce such inflammation in rodent animal models of type 1 diabetes with no complications or deleterious side effects. Herein, we have begun to investigate this novel and safe therapeutic approach in the spontaneously obese nonhuman primate with spontaneous, insulin-dependent T2DM. After MC-pSC intraperitoneal injection we have evaluated, throughout a 6-month follow-up period, daily ad libitum fed glucose levels, daily exogenous insulin supplementation, biweekly body weight measurements, periodic fasting blood glucose concentrations, glycated hemoglobin (HbA1c) levels, glucose tolerance tests (GTT), and fluorescence-activated cell sorting cytometry (FACS) assessment of peripheral blood mononuclear cells. Very preliminarily, we have observed a slight reduction in fasting (FPG) and mean nonfasting (NF) plasma glucose levels. We found minimal changes, only in 1 animal, in daily exogenous insulin requirements and HbA1c levels. Flow cytometric analysis was associated with decrease in CD8(+) cells only in 1 recipient with a reduction in mean regulatory T Cells (Treg), whereas interestingly, decrease of B lymphocytes was observed in both animals. These results may suggest that this novel MC-SC-based transplantation protocol might possibly impact the metabolic status of T2DM in higher mammals that are close to humans.

Loss of β-Cell Identity Occurs in Type 2 Diabetes and Is Associated With Islet Amyloid Deposits

Loss of pancreatic islet β-cell mass and β-cell dysfunction are central in the development of type 2 diabetes (T2DM). We recently showed that mature human insulin-containing β-cells can convert into glucagon-containing α-cells ex vivo. This loss of β-cell identity was characterized by the presence of β-cell transcription factors (Nkx6.1, Pdx1) in glucagon(+) cells. Here, we investigated whether the loss of β-cell identity also occurs in vivo, and whether it is related to the presence of (pre)diabetes in humans and nonhuman primates. We observed an eight times increased frequency of insulin(+) cells coexpressing glucagon in donors with diabetes. Up to 5% of the cells that were Nkx6.1(+) but insulin(-) coexpressed glucagon, which represents a five times increased frequency compared with the control group. This increase in bihormonal and Nkx6.1(+)glucagon(+)insulin(-) cells was also found in islets of diabetic macaques. The higher proportion of bihormonal cells and Nkx6.1(+)glucagon(+)insulin(-) cells in macaques and humans with diabetes was correlated with the presence and extent of islet amyloidosis. These data indicate that the loss of β-cell identity occurs in T2DM and could contribute to the decrease of functional β-cell mass. Maintenance of β-cell identity is a potential novel strategy to preserve β-cell function in diabetes.

Deep subconjunctival injection of gentamicin for the treatment of bacterial conjunctivitis in macaques (Macaca mulatta and Macaca fascicularis)

Infectious conjunctivitis occurs in a number of domestic and laboratory animal species and is usually treated topically with eye drops or eye ointments, which must be administered several times a day and sometimes for a prolonged period of time. In aggressive nonhuman primates or other large laboratory animal species, this may require the use of anesthesia or physical restraint before each treatment, which can be stressful to the animals and demanding for personnel. The authors describe a technique for administering deep subconjunctival injections of an antibiotic to laboratory macaques for the treatment of conjunctivitis. Three cases of recurrent conjunctivitis in macaques that responded poorly to other treatment approaches were effectively treated using this technique. This approach is recommended for the treatment of conjunctivitis in macaques and other large animal species.

Longitudinal dynamics of body weight change in the development of type 2 diabetes

OBJECTIVE

The aim of this study was to test the obesity-type 2 diabetes mellitus (T2DM) link in the context of longitudinal changes in body weight during the progression to diabetes in mature adult nonhuman primates (NHP).

DESIGN AND METHODS

A colony of 245 adult rhesus monkeys aged 8-41 years with 179 males were used to define overweight in males as a body weight: ≥13.5 kg or body fat (BF) ≥18% and obesity as ≥16.5 kg or BF ≥27%, and overweight in nonpregnant females was identified as a body weight >8.5 kg or BF >21% and obesity as ≥10.5 kg or BF ≥30%. A subgroup of 48 males (24 T2DM and 24 age-matched non-T2DM) males were studied before and following the onset of overt T2DM for the effects of changes in body weight and obesity in inducing this conversion to overt T2DM.

RESULTS

Three years before overt T2DM, mean body weight was 18.4 ± 3.3 kg. The DM-destined group body weight was 3.2 ± 1.1 kg greater and had a longer duration and greater severity of obesity, with peak body weight reached at 3.2 ± 1.8 years before overt T2DM. At DM onset the two groups did not differ significantly in body weight or adiposity.

CONCLUSIONS

The natural progression from pre-DM to overt T2DM is caused neither by the amount of excess body weight at DM onset nor by the proximate increases in body weight/adiposity during the pre-DM period of impaired glucose tolerance. Obesity was, however, essential preceding all NHP cases that developed T2DM.

Quantification of β-cell insulin secretory function using a graded glucose infusion with C-peptide deconvolution in dysmetabolic, and diabetic cynomolgus monkeys

BACKGROUND

Quantitation of β-cell function is critical in better understanding of the dynamic interactions of insulin secretion, clearance and action at different phases in the progression of diabetes. The present study aimed to quantify β-cell secretory function independently of insulin sensitivity in the context of differential metabolic clearance rates of insulin (MCRI) in nonhuman primates (NHPs).

METHODS

Insulin secretion rate (ISR) was derived from deconvolution of serial C-peptide concentrations measured during a 5 stage graded glucose infusion (GGI) in 12 nondiabetic (N), 8 prediabetic or dysmetabolic (DYS) and 4 overtly diabetic (DM) cynomolgus monkeys. The characterization of the monkeys was based on the fasting glucose and insulin concentrations, glucose clearance rate measured by intravenous glucose tolerance test, and insulin resistance indices measured in separate experiments. The molar ratio of C-peptide/insulin (C/I) was used as a surrogate index of hepatic MCRI.

RESULTS

Compared to the N monkeys, the DYS with normal glycemia and hyperinsulinemia had significantly higher basal and GGI-induced elevation of insulin and C-peptide concentrations and lower C/I, however, each unit of glucose-stimulated ISR increment was not significantly different from that in the N monkeys. In contrast, the DM monkeys with β-cell failure and hyperglycemia had a depressed GGI-stimulated ISR response and elevated C/I.

CONCLUSIONS

The present data demonstrated that in addition to β-cell hypersecretion of insulin, reduced hepatic MCRI may also contribute to the development of hyperinsulinemia in the DYS monkeys. On the other hand, hyperinsulinemia may cause the saturation of hepatic insulin extraction capacity, which in turn reduced MCRI in the DYS monkeys. The differential contribution of ISR and MCRI in causing hyperinsulinemia provides a new insight into the trajectory of β-cell dysfunction in the development of diabetes. The present study was the first to use the GGI and C-peptide deconvolution method to quantify the β-cell function in NHPs.

LY2405319, an Engineered FGF21 Variant, Improves the Metabolic Status of Diabetic Monkeys

Fibroblast growth factor 21 (FGF21) is a novel metabolic regulator that represents a promising target for the treatment of several metabolic diseases. Administration of recombinant wild type FGF21 to diabetic animals leads to a dramatic improvement in glycaemia and ameliorates other systemic measures of metabolic health. Here we report the pharmacologic outcomes observed in non-human primates upon administration of a recently described FGF21 analogue, LY2405319 (LY). Diabetic rhesus monkeys were treated subcutaneously with LY once daily for a period of seven weeks. The doses of LY used were 3, 9 and 50 mg/kg each delivered in an escalating fashion with washout measurements taken at 2, 4, 6 and 8 weeks following the final LY dose. LY therapy led to a dramatic and rapid lowering of several important metabolic parameters including glucose, body weight, insulin, cholesterol and triglyceride levels at all doses tested. In addition, we observed favorable changes in circulating profiles of adipokines, with increased adiponectin and reduced leptin indicative of direct FGF21 action on adipose tissue. Importantly, and for the first time we show that FGF21 based therapy has metabolic efficacy in an animal with late stage diabetes. While the glycemic efficacy of LY in this animal was partially attenuated its lipid lowering effect was fully preserved suggesting that FGF21 may be a viable treatment option even in patients with advanced disease progression. These findings support continued exploration of the FGF21 pathway for the treatment of metabolic disease.

Investigation and treatment of type 2 diabetes in nonhuman primates

Nonhuman primates provide the ideal animal model for discovering and examining further the mechanisms underlying human type 2 diabetes mellitus. In all aspects studied to date the nonhuman primate has been shown to develop the same disease with the same features that develop in overweight middle-aged humans. This includes the progressive development of the known complications of diabetes, all of which are extraordinarily like those identified in humans. In addition, for the development and evaluation of new therapeutic agents, the translation of findings from nonhuman primates to application in humans has been highly predictable. Both therapeutic efficacy and identification of potential adverse responses can be effectively examined in nonhuman primates due to their great similarity to humans at the molecular, biochemical, and physiological levels. This chapter provides guidance for the development and management of a colony of monkeys with naturally occurring type 2 diabetes mellitus.

Diversity of Insulin Resistance in Monkeys with Normal Glucose Tolerance

Insulin resistance has been proposed as a critical factor in the development of Type II diabetes, hypertension, dyslipidemia, and coronary artery disease. However, even in normal healthy individuals, a wide range of in vivo insulin action has been found. In the present study we sought to examine this heterogeneity in insulin action in both normal and spontaneously obese nonhuman primates. Maximal insulin responsiveness as measured by a hyperinsulinemic euglycemic clamp, fasting plasma glucose, and insulin levels, beta-cell insulin response to glucose, glucose tolerance, and adiposity were measured in 22 male rhesus monkeys. Results showed that lean animals (body fat < or = 22%) had higher insulin-stimulated glucose uptake (M rate: 14.42+/-1.8 mg/kg FFM/min) compared to obese (8.08+/-0.8). The obese monkeys, with 23-49% body fat, had a wide range of M values (5.32-14.29 mg/kg FFM/min) which showed no relationship to degree of adiposity. In all monkeys, M values had a strong inverse correlation with fasting plasma insulin levels (r=-0.76; p<0.001), but not with fasting glucose or glucose disappearance rate. We conclude that neither degree of obesity above a critical threshold nor range of glucose tolerance is related to insulin resistance; however, in individuals with normal glucose tolerance an early reliable indicator of defective insulin action appears to be fasting insulin concentration. Longitudinal determination of basal insulin levels obtained under standardized conditions so as to minimize extraneous variability is likely to strengthen the ability to predict insulin resistance and possible later development of overt Type II diabetes.

An anti-PCSK9 antibody reduces LDL-cholesterol on top of a statin and suppresses hepatocyte SREBP-regulated genes

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a promising therapeutic target for treating coronary heart disease. We report a novel antibody 1B20 that binds to PCSK9 with sub-nanomolar affinity and antagonizes PCSK9 function in-vitro. In CETP/LDLR-hemi mice two successive doses of 1B20, administered 14 days apart at 3 or 10 mpk, induced dose dependent reductions in LDL-cholesterol (≥ 25% for 7-14 days) that correlated well with the extent of PCSK9 occupancy by the antibody. In addition, 1B20 induces increases in total plasma antibody-bound PCSK9 levels and decreases in liver mRNA levels of SREBP-regulated genes PCSK9 and LDLR, with a time course that parallels decreases in plasma LDL-cholesterol (LDL-C). Consistent with this observation in mice, in statin-responsive human primary hepatocytes, 1B20 lowers PCSK9 and LDLR mRNA levels and raises serum steady-state levels of antibody-bound PCSK9. In addition, mRNA levels of several SREBP regulated genes involved in cholesterol and fatty-acid synthesis including ACSS2, FDPS, IDI1, MVD, HMGCR, and CYP51A1 were decreased significantly with antibody treatment of primary human hepatocytes. In rhesus monkeys, subcutaneous (SC) dosing of 1B20 dose-dependently induces robust LDL-C lowering (maximal ~70%), which is correlated with increases in target engagement and total antibody-bound PCSK9 levels. Importantly, a combination of 1B20 and Simvastatin in dyslipidemic rhesus monkeys reduced LDL-C more than either agent alone, consistent with a mechanism of action that predicts additive effects of anti-PCSK9 agents with statins. Our results suggest that antibodies targeting PCSK9 could provide patients powerful LDL lowering efficacy on top of statins, and lower cardiovascular risk.

Vasomotion becomes less random as diabetes progresses in monkeys

Please cite this paper as: Tigno, Hansen, Nawang, Shamekh, and Albano (2011). Vasomotion Becomes Less Random as Diabetes Progresses in Monkeys. Microcirculation 18(6), 429-439.

ABSTRACT

OBJECTIVE

  Changes in vasomotion may precede other global indices of autonomic dysfunction that track the onset and progression of diabetes. Recently, we showed that baseline spectral properties of vasomotion can discriminate among N, PreDM, and T2DM nonhuman primates. In this study, our aims were to: (i) determine the time dependence and complexity of the spectral properties of vasomotion in three metabolic groups of monkeys; (ii) examine the effects of heat-provoked vasodilatation on the power spectrum; and (iii) compare the effects of exogenous insulin on the vasomotion.

MATERIALS AND METHODS

  Laser Doppler flow rates were measured from the foot in 9 N, 11 PreDM, and 7 T2DM monkeys. Baseline flow was measured at 34°C, and under heat stimulation at 44°C. Euglycemic-hyperinsulinemic clamps were performed to produce acute hyperinsulinemia. The Lempel-Ziv complexity, prediction error, and covariance complexity of five-dimensional embeddings were calculated as measures of randomness.

RESULTS AND CONCLUSIONS

  With progression of diabetes, measures of randomness of the vasomotion progressively decreased, suggesting a progressive loss of the homeostatic capacity of the peripheral circulation to respond to environmental changes. Power spectral density among T2DM animals resided mostly in the 0- to 1.45-Hz range, which excluded the cardiac component, suggesting that with progression of the disease, regulation of flow shifts toward local rather than central (autonomic) mechanisms. Heating increased all components of the spectral power in all groups. In N, insulin increased the vasomotion contributed by endothelial, neurogenic, vascular myogenic, and respiratory processes, but diminished that due to heart rate. In contrast, in T2DM, insulin failed to stimulate the vascular myogenic and respiratory activities, but increased the neural/endothelial and heart rate components. Interestingly, acute hyperinsulinemia resulted in no significant vasomotion changes in the chronically hyperinsulinemic PreDM, suggesting yet another form of "insulin resistance" during this stage of the disease.

Plasma lipid profiling across species for the identification of optimal animal models of human dyslipidemia

In an attempt to understand the applicability of various animal models to dyslipidemia in humans and to identify improved preclinical models for target discovery and validation for dyslipidemia, we measured comprehensive plasma lipid profiles in 24 models. These included five mouse strains, six other nonprimate species, and four nonhuman primate (NHP) species, and both healthy animals and animals with metabolic disorders. Dyslipidemic humans were assessed by the same measures. Plasma lipoprotein profiles, eight major plasma lipid fractions, and FA compositions within these lipid fractions were compared both qualitatively and quantitatively across the species. Given the importance of statins in decreasing plasma low-density lipoprotein cholesterol for treatment of dyslipidemia in humans, the responses of these measures to simvastatin treatment were also assessed for each species and compared with dyslipidemic humans. NHPs, followed by dog, were the models that demonstrated closest overall match to dyslipidemic humans. For the subset of the dyslipidemic population with high plasma triglyceride levels, the data also pointed to hamster and db/db mouse as representative models for practical use in target validation. Most traditional models, including rabbit, Zucker diabetic fatty rat, and the majority of mouse models, did not demonstrate overall similarity to dyslipidemic humans in this study.

Endogenous and diet-induced hypercholesterolemia in nonhuman primates: effects of age, adiposity, and diabetes on lipoprotein profiles

Nonhuman primates (NHPs) share with humans many features of lipid metabolism and often develop all features of the metabolic syndrome, including hypertriglyceridemia and low high-density lipoprotein cholesterol, and have been used in many studies of potential therapeutics during the preclinical phase. Here we identify for the first time in middle-aged and older rhesus the natural occurrence of hypercholesterolemia, and this hypercholesterolemia develops despite maintenance on a low-cholesterol diet. The aims of this study were to (a) define normal and hypercholesterolemia in rhesus monkeys, (b) determine the factors associated with the development of hypercholesterolemia, (c) compare the lipoprotein profiles in adult rhesus monkeys fed a low-fat/low-cholesterol diet (LFLC) with the profiles of human subjects, and (d) determine the effect of a 16-week high-fat/high-cholesterol (HFHC) diet feeding on total cholesterol and lipoprotein profiles in middle-aged and older monkeys. In our colony, maintained on a constant diet with negligible cholesterol, the mean total cholesterol level in healthy nondiabetic monkeys was 3.7 ± 0.02 mmol/L, with hypercholesterolemia identified as the 95th percentile of the normal cholesterol distribution (≥5.2 mmol/L). Severe hypercholesterolemia developed in the HFHC-fed group; however, despite the high-fat diet composition, unexpectedly, no weight gain occurred in these NHPs. The diet-induced hypercholesterolemia differed significantly in lipoprotein pattern from that of the spontaneous hypercholesterolemia. In summary, despite ingesting only a LFLC, NHPs frequently develop hypercholesterolemia, reflecting lipoprotein patterns similar to human subjects; and this lipid profile of spontaneous hypercholesterolemia differs significantly from the hypercholesterolemia induced by an HFHC diet.

Metabolomics reveals attenuation of the SLC6A20 kidney transporter in nonhuman primate and mouse models of type 2 diabetes mellitus

To enhance understanding of the metabolic indicators of type 2 diabetes mellitus (T2DM) disease pathogenesis and progression, the urinary metabolomes of well characterized rhesus macaques (normal or spontaneously and naturally diabetic) were examined. High-resolution ultra-performance liquid chromatography coupled with the accurate mass determination of time-of-flight mass spectrometry was used to analyze spot urine samples from normal (n = 10) and T2DM (n = 11) male monkeys. The machine-learning algorithm random forests classified urine samples as either from normal or T2DM monkeys. The metabolites important for developing the classifier were further examined for their biological significance. Random forests models had a misclassification error of less than 5%. Metabolites were identified based on accurate masses (<10 ppm) and confirmed by tandem mass spectrometry of authentic compounds. Urinary compounds significantly increased (p < 0.05) in the T2DM when compared with the normal group included glycine betaine (9-fold), citric acid (2.8-fold), kynurenic acid (1.8-fold), glucose (68-fold), and pipecolic acid (6.5-fold). When compared with the conventional definition of T2DM, the metabolites were also useful in defining the T2DM condition, and the urinary elevations in glycine betaine and pipecolic acid (as well as proline) indicated defective re-absorption in the kidney proximal tubules by SLC6A20, a Na(+)-dependent transporter. The mRNA levels of SLC6A20 were significantly reduced in the kidneys of monkeys with T2DM. These observations were validated in the db/db mouse model of T2DM. This study provides convincing evidence of the power of metabolomics for identifying functional changes at many levels in the omics pipeline.

Glomerulopathy in spontaneously obese rhesus monkeys with type 2 diabetes: a stereological study

BACKGROUND

Animal models could provide insights into the diabetic nephropathy pathogenesis; however, available rodent models do not mirror the heterogeneity of lesions in type 2 diabetic patients, and do not progress to end-stage renal disease. Previous studies showed that spontaneously obese type 2 diabetic rhesus monkeys develop many of the features of human diabetic glomerulopathy, and may progress to end-stage renal disease. Here, in order to further characterize diabetic glomerulopathy in this model, we used electron microscopic stereology.

METHODS

Renal biopsies from 17 diabetic, 17 pre-diabetic/metabolic syndrome and 11 non-diabetic monkeys were studied. Fractional volumes of mesangium [Vv(Mes/glom)], mesangial matrix [Vv(MM/glom)] and mesangial cells [Vv(MC/glom)], glomerular basement membrane width and peripheral glomerular basement membrane surface density per glomerulus [Sv(PGBM/glom)] were estimated. Glomerular filtration and albumin excretion rates were measured in a limited number of animals. Glomerular structural and biochemical/metabolic data were compared among the groups.

RESULTS

Compared to non-diabetic monkeys, diabetic rhesus monkeys showed classic diabetic nephropathy changes, including glomerular basement membrane thickening (p = 0.001), increased fractional volumes of mesangium (p = 0.02), and reduced peripheral glomerular basement membrane surface density per glomerulus (p = 0.03) compared to non-diabetic monkeys. Increased fractional volumes of mesangium was primarily due to increased mesangial matrix (p = 0.03). Glomerular structural parameter inter-relationships in diabetic monkeys mirrored those of human diabetic glomerulopathy. Albumin excretion rate was greater (p = 0.03) in diabetic vs. non-diabetic monkeys. There was trend for a positive correlation between albumin excretion rate and fractional volumes of mesangium.

CONCLUSIONS

This rhesus primate model shares many features of human diabetic glomerulopathy. Mesangial expansion in this model, similar to human diabetic nephropathy and different from available rodent models of the disease, is primarily due to increased mesangial matrix.

Determination of hemoglobin A1c and fasting blood glucose reference intervals in captive chimpanzees (Pan troglodytes)

Type 2 diabetes mellitus (T2DM), reaching epidemic proportions in humans, has emerged as a disease in aging captive populations of adult chimpanzees; however, little information is available regarding T2DM in chimpanzees. Our goals were to: (1) distinguish between normal, healthy chimpanzees and those with early (prediabetes) or advanced diabetes; (2) establish and compare the fasting (16 h) blood glucose reference range for chimpanzees at our facility with published reference ranges; and (3) establish hemoglobin A1c (HbA1c) reference intervals for healthy, nondiabetic chimpanzees and define threshold values for prediabetes and diabetes. If reliable, our reference ranges for FBG and HbA1c could become clinical tools for screening animals at risk and for monitoring therapeutic progress. The overall incidence of T2DM in our colony of 260 chimpanzees is 0.8% but is increased to 3.7% in animals older than 30 y (geriatric). For our defined reference intervals, chimpanzees with FBG or HbA1c levels up to the 85th percentile (glucose, less than or equal to 105 mg/dL; HbA1c, less than or equal to 5.0%) were considered healthy; those whose values lay between the 86th and 95th percentiles (glucose, 106 to 119 mg/dL; HbA1c, 5.1% to 5.2%) were possibly prediabetic, and animals whose values exceeded the 95th percentile (glucose, greater than or equal to 120 mg/dL; HbA1c, greater than 5.3%) were identified as potentially having diabetes. We found that our FBG range was comparable to other published results, with a positive correlation between HbA1c and glucose. Furthermore, the negligible HbA1c response to acute stress or recent food consumption suggests that HbA1c is highly useful for evaluating glycemic control during treatment of diabetic chimpanzees and is more informative concerning overall glucose control than are FBG levels alone.

Comparison between surrogate indexes of insulin sensitivity/resistance and hyperinsulinemic euglycemic glucose clamps in rhesus monkeys

The euglycemic glucose clamp is the reference method for assessing insulin sensitivity in humans and animals. However, clamps are ill-suited for large studies because of extensive requirements for cost, time, labor, and technical expertise. Simple surrogate indexes of insulin sensitivity/resistance including quantitative insulin-sensitivity check index (QUICKI) and homeostasis model assessment (HOMA) have been developed and validated in humans. However, validation studies of QUICKI and HOMA in both rats and mice suggest that differences in metabolic physiology between rodents and humans limit their value in rodents. Rhesus monkeys are a species more similar to humans than rodents. Therefore, in the present study, we evaluated data from 199 glucose clamp studies obtained from a large cohort of 86 monkeys with a broad range of insulin sensitivity. Data were used to evaluate simple surrogate indexes of insulin sensitivity/resistance (QUICKI, HOMA, Log HOMA, 1/HOMA, and 1/Fasting insulin) with respect to linear regression, predictive accuracy using a calibration model, and diagnostic performance using receiver operating characteristic. Most surrogates had modest linear correlations with SI(Clamp) (r ≈ 0.4-0.64) with comparable correlation coefficients. Predictive accuracy determined by calibration model analysis demonstrated better predictive accuracy of QUICKI than HOMA and Log HOMA. Receiver operating characteristic analysis showed equivalent sensitivity and specificity of most surrogate indexes to detect insulin resistance. Thus, unlike in rodents but similar to humans, surrogate indexes of insulin sensitivity/resistance including QUICKI and log HOMA may be reasonable to use in large studies of rhesus monkeys where it may be impractical to conduct glucose clamp studies.

Effects of aleglitazar, a balanced dual peroxisome proliferator-activated receptor α/γ agonist on glycemic and lipid parameters in a primate model of the metabolic syndrome

BACKGROUND

Glycemic control and management of dyslipidemia to reduce cardiovascular risk are major therapeutic goals in individuals with type 2 diabetes mellitus (T2DM). This study was performed to evaluate the effects of aleglitazar, a balanced dual peroxisome proliferator-activated receptor α/γ (PPARα/γ) agonist, on both lipid and glycemic parameters in obese, hypertriglyceridemic, insulin-resistant rhesus monkeys.

METHODS

A 135-day efficacy study was performed in six rhesus monkeys. After a 28-day baseline assessment (vehicle only), monkeys received oral aleglitazar 0.03 mg/kg per day for 42 days, followed by a 63-day washout period. Plasma levels of markers of glycemic and lipid regulation were measured at baseline, at the end of the dosing period, and at the end of the washout period.

RESULTS

Compared with baseline values, aleglitazar 0.03 mg/kg per day reduced triglyceride levels by an average of 89% (328 to 36 mg/dL; P = 0.0035 when normalized for baseline levels) and increased high-density lipoprotein cholesterol levels by 125% (46 to 102 mg/dL; P = 0.0007). Furthermore, aleglitazar reduced low-density lipoprotein cholesterol levels (41%) and increased levels of apolipoprotein A-I (17%) and A-II (17%). Aleglitazar also improved insulin sensitivity by 60% (P = 0.001). Mean body weight was reduced by 5.9% from baseline values with aleglitazar at this dose (P = 0.043).

CONCLUSIONS

Aleglitazar, a dual PPARα/γ agonist, has beneficial effects on both lipid and glucose parameters and may have a therapeutic role in modifying cardiovascular risk factors and improving glycemic control in patients with T2DM.

Insulin signaling and insulin sensitizing in muscle and liver of obese monkeys: peroxisome proliferator-activated receptor gamma agonist improves defective activation of atypical protein kinase C

Obesity, the metabolic syndrome, and aging share several pathogenic features in both humans and non-human primates, including insulin resistance and inflammation. Since muscle and liver are considered key integrators of metabolism, we sought to determine in biopsies from lean and obese aging rhesus monkeys the nature of defects in insulin activation and, further, the potential for mitigation of such defects by an in vivo insulin sensitizer, rosiglitazone, and a thiazolidinedione activator of the peroxisome proliferator-activated receptor gamma. The peroxisome proliferator-activated receptor gamma agonist reduced hyperinsulinemia, improved insulin sensitivity, lowered plasma triglycerides and free fatty acids, and increased plasma adiponectin. In muscle of obese monkeys, previously shown to exhibit defective insulin signaling, the insulin sensitizer improved insulin activation of atypical protein kinase C (aPKC), the defective direct activation of aPKC by phosphatidylinositol (PI)-3,4,5-(PO₄)₃, and 5'-AMP-activated protein kinase and increased carnitine palmitoyltransferase-1 mRNA expression, but it did not improve insulin activation of insulin receptor substrate (IRS)-1-dependent PI 3-kinase (IRS-1/PI3K), protein kinase B, or glycogen synthase. We found that, although insulin signaling was impaired in muscle, insulin activation of IRS-1/PI3K, IRS-2/PI3K, protein kinase B, and aPKC was largely intact in liver and that rosiglitazone improved insulin signaling to aPKC in muscle by improving responsiveness to PI-3,4,5-(PO₄)₃.

The long lifespan and low turnover of human islet beta cells estimated by mathematical modelling of lipofuscin accumulation

AIMS/HYPOTHESIS

Defects in pancreatic beta cell turnover are implicated in the pathogenesis of type 2 diabetes by genetic markers for diabetes. Decreased beta cell neogenesis could contribute to diabetes. The longevity and turnover of human beta cells is unknown; in rodents <1 year old, a half-life of 30 days is estimated. Intracellular lipofuscin body (LB) accumulation is a hallmark of ageing in neurons. To estimate the lifespan of human beta cells, we measured beta cell LB accumulation in individuals aged 1-81 years.

METHODS

LB content was determined by electron microscopical morphometry in sections of beta cells from human (non-diabetic, n = 45; type 2 diabetic, n = 10) and non-human primates (n = 10; 5-30 years) and from 15 mice aged 10-99 weeks. Total cellular LB content was estimated by three-dimensional (3D) mathematical modelling.

RESULTS

LB area proportion was significantly correlated with age in human and non-human primates. The proportion of human LB-positive beta cells was significantly related to age, with no apparent differences in type 2 diabetes or obesity. LB content was low in human insulinomas (n = 5) and alpha cells and in mouse beta cells (LB content in mouse <10% human). Using 3D electron microscopy and 3D mathematical modelling, the LB-positive human beta cells (representing aged cells) increased from >or=90% (<10 years) to >or=97% (>20 years) and remained constant thereafter.

CONCLUSIONS/INTERPRETATION

Human beta cells, unlike those of young rodents, are long-lived. LB proportions in type 2 diabetes and obesity suggest that little adaptive change occurs in the adult human beta cell population, which is largely established by age 20 years.