The role of the kidneys in glucose homeostasis: a new path towards normalizing glycaemia

The maintenance of normal glucose homeostasis requires a complex, highly integrated interaction among the liver, muscle, adipocytes, pancreas and neuroendocrine system. Recent studies have showed that the kidneys also play a central role in glucose homeostasis by reabsorbing all the filtered glucose, an adaptive mechanism that ensures sufficient energy is available during fasting periods. This mechanism becomes maladaptive in diabetes, however, as hyperglycaemia augments the expression and activity of the sodium-glucose cotransporter (SGLT) 2 in the proximal tubule of the kidney. As a result, glucose reabsorption may be increased by as much as 20% in individuals with poorly controlled diabetes. SGLT2 is a low-affinity, high-capacity glucose transport protein that reabsorbs 90% of filtered glucose, while the high-affinity, low-capacity SGLT1 transporter reabsorbs the remaining 10%. SGLT2 represents a novel target for the treatment of diabetes. In animal studies, SGLT2 inhibition reduces plasma glucose levels, resulting in improved β-cell function and enhanced insulin sensitivity in liver and muscle. Human studies have confirmed the efficacy of SLGT2 inhibitors in improving glucose control and reducing the A1c. Because the mechanism of SGLT2 inhibition is independent of circulating insulin levels or insulin sensitivity, these agents can be combined with all other antidiabetic classes, including exogenous insulin. Although the long-term efficacy and safety of SGLT2 inhibitors remain under study, the class represents a novel therapeutic approach with potential for the treatment of both type 2 and 1 diabetes.

Glucagon-like peptide-1 secretion in women with gestational diabetes mellitus during and after pregnancy

Gestational diabetes mellitus (GDM) predisposes women to future development of Type 2 diabetes mellitus (DM2) and the two conditions share similar metabolic alterations. Recent observations suggest that a defective glucose stimulated insulin secretion by glucagon-like peptide-1 (GLP- 1) plays a role in the pathogenesis of DM2. Whether such a defect is impaired in GDM remains to be ascertained.

AIM

We have determined GLP-1 secretion in response to oral glucose tolerance test (OGTT) in GDM and normal glucose tolerance (NGT) during and after pregnancy.

MATERIALS AND METHODS

100-g-3h OGTT was performed in 12 GDM and 16 NGT women at 27.3 ± 4.1 weeks of gestation, for determination of plasma GLP-1, glucose, insulin, and C-peptide. Insulin sensitivity (ISI) and insulin secretion (first and second phase); as well as ISI-secretion index (ISSI) were also derived.

RESULTS

NGT and GDM women were comparable for age pre-pregnancy body mass index (BMI) and weight gain. GDM had higher glucose area under the curve (AUC): 27,575.5 ± 3448 vs 20,685.88 ± 2715 mg/dl min (p<0.01), but lower first-phase insulin secretion (993.12±367 vs 1376.61 ± 423, p<0.05) and ISSI compared to controls (3873.23 ± 1185 vs 6232.13 ± 1734, p<0.001). When we examined GLP-1 mean levels in relation to mean glycemic values, GLP-1 secretion was inappropriately low with respect to mean glycemic values in GDM compared to NGT. At follow-up, AUCGLP-1 was significantly lower in post-partum GDM compared to post-partum NGT women (2542 ± 273 vs 10,092 ± 7367 pmol·l-1·min-1, p<0.05, respectively).

CONCLUSIONS

Our study suggests that GLP-1 secretion in GDM women is inadequate for the prevailing glycemic levels both in pregnancy and post partum. Moreover, we cannot exclude that other important aspects of the incretin effect may be involved in GDM development.

Gender Effect on the Relation between Diabetes and Hospitalization for Heart Failure

Cardiovascular risk among diabetic patients is at least twice as much the one for non-diabetic individuals and even greater when diabetic women are considered. Heart failure (HF) is a common unfavorable outcome of cardiovascular disease in diabetes. However, since the comparison among sexes of heart failure prevalence in diabetic patients remains limited, this study is aimed at expanding the information about this point.

We have evaluated the association between diabetes and HF by reviewing the medical records of all subjects discharged from the Internal Medicine and Cardiology Units of all hospitals in the Tuscany region, Italy, during the period January 2002 through December 2008. In particular we sought concomitance of ICD-9-CM codes for diabetes and HF.

Patients discharged by Internal Medicine were on average older, more represented by women, and had a lesser number of individuals coded as diabetic (p<0.05 for all). Relative risk for HF (95% CI) was significantly higher in patients with diabetes, irrespective of gender 1.39 (1.36–1.41) in males; 1.40 (1.37–1.42) in females. When the diabetes-HF association was analyzed according to decades of age, a “horse-shoe” pattern was apparent with an increased risk in 40–59 years old in female patients discharged by Internal Medicine.

Although there is not a difference in the overall HF risk between hospitalized male and female diabetic patients, women have an excess risk at perimenopausal age.

Metabolic syndrome in subjects at high risk for type 2 diabetes: the genetic, physiopathology and evolution of type 2 diabetes (GENFIEV) study

BACKGROUND AND AIM

We evaluated the relationship between insulin resistance (IR) and insulin secretion with the metabolic syndrome (MS) in 885 subjects (377 men/508 women, age 49±11 years, BMI 29±5.2kgm(-2)) at risk of diabetes enrolled in the genetics, pathophysiology and evolution of type 2 diabetes (GENFIEV) study.

METHODS AND RESULTS

All subjects underwent a 75-g oral glucose tolerance test (OGTT) for the estimation of plasma levels of glucose and C-peptide, as well as fasting insulin and lipid profile. IR was arbitrarily defined as HOMA-IR value above the 75th centile of normal glucose tolerance (NGT) subjects. Overall MS prevalence (National Cholesterol Treatment Panel-Adult Treatment Panel (NCEP-ATPIII) criteria) was 33%, 19% in subjects with NGT, 42% in impaired fasting glucose (IFG), 34% in impaired glucose tolerance (IGT), 74% in IFG+IGT subjects, and 56% in newly diagnosed diabetic patients. Prevalence was slightly higher with IDF criteria. MS prevalence was >50% in subjects with 2h glucose >7.8mmoll(-1), independently of fasting plasma glucose. IR prevalence was higher in subjects with MS than in those without (63% vs. 23%; p<0.0001) and increased from 54% to 73% and 88% in the presence of three, four or five traits, respectively. IR occurred in 42% of subjects with non-diabetic alterations of glucose homeostasis, being the highest in those with IFG+IGT (IFG+IGT 53%, IFG 45%, IGT 38%; p<0.0001). Individuals with MS were more IR irrespective of glucose tolerance (p<0.0001) with no difference in insulinogenic index. Hypertriglyceridaemia (OR: 3.38; Confidence Interval, CI: 2.294.99), abdominal obesity (3.26; CI: 2.18-4.89), hyperglycaemia (3.02; CI: 1.80-5.07) and hypertension (1.69; CI: 1.12-2.55) were all associated with IR.

CONCLUSIONS

These results show that in subjects with altered glucose tolerance (in particular IFG+IGT) MS prevalence is high and is generally associated to IR. Some combinations of traits of MS may significantly contribute to identify subjects with IR.

Effect of linagliptin monotherapy on glycaemic control and markers of β-cell function in patients with inadequately controlled type 2 diabetes: a randomized controlled trial

AIM

To assess the safety and efficacy of the potent and selective dipeptidyl peptidase-4 inhibitor linagliptin 5 mg when given for 24 weeks to patients with type 2 diabetes who were either treatment-naive or who had received one oral antidiabetes drug (OAD).

METHODS

This multicentre, randomized, parallel group, phase III study compared linagliptin treatment (5 mg once daily, n = 336) with placebo (n = 167) for 24 weeks in type 2 diabetes patients. Before randomization, patients pretreated with one OAD underwent a washout period of 6 weeks, which included a placebo run-in period during the last 2 weeks. Patients previously untreated with an OAD underwent a 2-week placebo run-in period. The primary endpoint was the change in HbA1c from baseline after 24 weeks of treatment.

RESULTS

Linagliptin treatment resulted in a placebo-corrected change in HbA1c from baseline of -0.69% (p < 0.0001) at 24 weeks. In patients with baseline HbA1c ≥ 9.0%, the adjusted reduction in HbA1c was 1.01% (p < 0.0001). Patients treated with linagliptin were more likely to achieve a reduction in HbA1c of ≥0.5% at 24 weeks than those in the placebo arm (47.1 and 19.0%, respectively; odds ratio, OR = 4.2, p < 0.0001). Fasting plasma glucose improved by -1.3 mmol/l (p < 0.0001) with linagliptin vs. placebo, and linagliptin produced an adjusted mean reduction from baseline after 24 weeks in 2-h postprandial glucose of -3.2 mmol/l (p < 0.0001). Statistically significant and relevant treatment differences were observed for proinsulin/insulin ratio (p = 0.025), Homeostasis Model Assessment-%B (p = 0.049) and disposition index (p = 0.0005). There was no excess of hypoglycaemic episodes with linagliptin vs. placebo and no patient required third-party intervention. Mild or moderate renal impairment did not influence the trough plasma levels of linagliptin.

CONCLUSIONS

Monotherapy with linagliptin produced a significant, clinically meaningful and sustained improvement in glycaemic control, accompanied by enhanced parameters of β-cell function. The safety profile of linagliptin was comparable with that of placebo.

A common polymorphism in the monocyte chemoattractant protein-1 (MCP-1) gene regulatory region influences MCP-1 expression and function of isolated human pancreatic islets

BACKGROUND AND AIMS

Islet transplantation is an attractive approach to treat type 1 diabetic patients. However, suboptimal islet engraftment still represents an unsolved problem. It has been shown that human islets release monocyte chemoattractant protein-1 (MCP-1), one of the most powerful macrophage chemokines, which may impair the fate of the transplant. The aim of this study was to evaluate the presence and role of MCP-1 in isolated human islets, including genotyping for a common polymorphism.

METHODS

Pancreatic islets were isolated by enzymatic digestion and gradient purification from 41 nondiabetic multiorgan donors. We measured MCP-1 mRNA expression by quantitative real- time reverse-transcriptase polymerization chain reaction, analyzed the MCP-1 single nucleotide polymorphism, -2518 G/A (SNP, rs 1024611) and evaluated glucose-stimulated insulin release (IR; microU/islet/min).

RESULTS

MCP-1 mRNA expression was found in all studied batches of islets. Overall, IR was significantly higher at 16.7 mmol/L than 3.3 mmol/L glucose. We observed a significant negative correlation between MCP-1 mRNA expression and stimulation index (SI). We found that MCP-1 mRNA expression was significantly higher in CC and CT compared with TT genotype groups. Finally, SI was significant lower in the CC with respect to the TT genotype group.

CONCLUSIONS

These data show that MCP-1 gene expression regulated by the -2518 G/A polymorphism, is correlated with glucose-stimulated insulin release. The study of MCP-1 expression and genotype on isolated islets before transplantation may be useful to understand the inflammatory response after infusion of human islets into patients with type 1 diabetes mellitus.

A Randomized Controlled Trial to Examine the Efficacy and Safety of a New Super-Oxidized Solution for the Management of Wide Postsurgical Lesions of the Diabetic Foot

This randomized trial was done to test the effectiveness and safety of using a novel antiseptic solution (Dermacyn® Wound Care [DWC], Oculus Innovative Sciences, Petaluma, CA) in the management of the postoperative lesions on the infected diabetic foot. 40 patients with postsurgical lesions wider than 5 cm2 left open to heal by secondary intention were randomized into 2 groups. Group A was locally treated with DWC, whereas group B received povidone iodine as local medication, both in adjunct to systemic antibiotic therapy and surgical debridement if needed. Ischemia, renal failure, bilateral lesions, or immunodepression were considered as exclusion criteria. Patients were followed up weekly for 6 months. The primary endpoint was healing rate at 6 months, while secondary endpoints were healing time, time to achieve negative cultures, duration of antibiotic therapy, number of reinterventions, and adverse events. Healing rates at 6 months were significantly shorter in group A (90%) than in group B (55%; P < .01). The time taken for cultures to become negative and duration of antibiotic therapy were also significantly (P < .05) shorter in group A than in group B, whereas the number of reinterventions was significantly higher in group B (P < .05). No difference was noted in the adverse events except that for reinfections, which were more frequent in group B than in group A (P < .01). DWC is as safe as and more effective than standard local antiseptics in the management of wide postsurgical lesions in the infected diabetic foot.

Tailoring treatment to the individual in type 2 diabetes practical guidance from the Global Partnership for Effective Diabetes Management

Good glycaemic control continues to be the most effective therapeutic manoeuvre to reduce the risk of development and/or progression of microvascular disease, and therefore remains the cornerstone of diabetes management despite recent scepticism about tight glucose control strategies. The impact on macrovascular complications is still a matter of debate, and so glycaemic control strategies should be placed in the context of multifactorial intervention to address all cardiovascular risk factors. Approaches to achieve glycaemic targets should always ensure patient safety, and results from recent landmark outcome studies support the need for appropriate individualisation of glycaemic targets and of the means to achieve these targets, with the ultimate aim to optimise outcomes and minimise adverse events, such as hypoglycaemia and marked weight gain. The primary goal of the Global Partnership for Effective Diabetes Management is the provision of practical guidance to improve patient outcomes and, in this article, we aim to support healthcare professionals in appropriately tailoring type 2 diabetes treatment to the individual. Patient groups requiring special consideration are identified, including newly diagnosed individuals with type 2 diabetes but no complications, individuals with a history of inadequate glycaemic control, those with a history of cardiovascular disease, children and individuals at risk of hypoglycaemia. Practical guidance specific to each group is provided.

Irbesartan has no short-term effect on insulin resistance in hypertensive patients with additional cardiometabolic risk factors (i-RESPOND)

AIMS

Intervention studies have shown that angiotensin receptor blockers (ARB) may reduce the incidence of type 2 diabetes mellitus. It is currently unclear whether short-term therapy with ARBs affects metabolic parameters.

METHODS

i-RESPOND, a randomised, controlled, multicentre, double-blind study evaluated the effect of 16 weeks of irbesartan vs. hydrochlorothiazide (HCTZ) on insulin resistance as well as on lipid and inflammatory parameters in hypertensive subjects with metabolic syndrome. Patients received irbesartan (150 mg/d; n = 211) or HCTZ (12.5 mg/d; n = 215), titrated to 300 mg/day and 25 mg/day respectively. In a second part of the study (weeks 16-28), patients initially randomised to irbesartan received additional HCTZ and vice versa.

RESULTS

At week 16 both irbesartan and HCTZ had no effect on insulin resistance measured by the Matzuda index and beta-cell function. Similarly, in the second part of the study (week 16-28) no differences between irbesartan and HCTZ with respect to glucose metabolism were observed. However, irbesartan induced beneficial changes in high-sensitivity-C-reactive protein (hs-CRP) (irbesartan: -5.5 +/- 5.2%; HCTZ + 19.9 +/- 6.5%, p = 0.0024) and in urinary albumin/creatinine ratio (ACR) (irbesartan: -13%; HCTZ + 9%; p = 0.0041) compared with HCTZ despite a similar decrease in blood pressure in both treatment groups. Irbesartan and HCTZ were well tolerated and adverse events were comparable.

CONCLUSION

Irbesartan did not show significant favourable effects on insulin resistance compared with HCTZ in this study; however, may have beneficial effects on inflammation and microalbuminuria in hypertensive patients with metabolic syndrome.

G-protein-coupled receptor 40 (GPR40) expression and its regulation in human pancreatic islets: the role of type 2 diabetes and fatty acids

BACKGROUND AND AIMS

GPR40 is a membrane-bound receptor paired with medium and long-chain fatty acids (FFA) as endogenous ligands. Its acute activation potentiates insulin secretion from beta cells, whereas prolonged binding might contribute to the deleterious effects of chronic exposure to FFA. Little information is available on the expression of GPR40 and its regulation in human islets (HI).

MATERIAL AND METHODS

HI were prepared by enzymatic digestion and gradient separation from the pancreas of 20 non-diabetic (Ctrl) and 13 type 2 diabetic (T2DM) multiorgan donors, and functional and molecular studies were then performed.

RESULTS

By qualitative and quantitative PCR experiments, mRNA expression was shown in HI. Both in T2DM islets and in Ctrl islets pre-exposed for 24 h to 1.0 mmol/l FFA (palmitate:oleate, 2:1), GPR40 mRNA expression was significantly reduced (p<0.01) in the T2DM cells as compared to Ctrl cells. A significant positive correlation was found between glucose-stimulated insulin secretion and GPR40 expression.

CONCLUSIONS

These results show the expression of GPR40 in human pancreatic islets which are regulated by FFA. The finding that T2DM islets have a lower GPR40 expression, and the correlation of these genes with insulin secretion, raises the possibility of an involvement of GPR40 in human diabetes beta-cell dysfunction.