Glycemic variability is associated with sural nerve conduction velocity in outpatients with type 2 diabetes: Usefulness of a new point-of-care device for nerve conduction studies.

AIMS/INTRODUCTION: Although several studies have shown the association between continuous glucose monitoring (CGM)-derived glycemic variability (GV) and diabetic peripheral neuropathy, no studies have focused on outpatients or used NC-stat®/DPNCheck™, a new point-of-care device for nerve conduction study (NCS). We investigated the association between CGM-derived GV and NCS using DPNCheck™ in outpatients with type 2 diabetes, and further analyzed the difference in results between patients with and without well-controlled HbA1c levels. MATERIALS AND METHODS: All outpatients with type 2 diabetes using the CGM device (FreeStyle Libre Pro®) between 2017 and 2022 were investigated. Sural nerve conduction was evaluated by sensory nerve action potential (SNAP) amplitude and sensory conduction velocity (SCV) using DPNCheck™. Associations of CGM-derived GV metrics with SNAP amplitude and SCV were investigated. RESULTS: In total, 304 outpatients with type 2 diabetes were included. In a linear regression model, most CGM-derived GV metrics except for the mean amplitude of glucose excursion and low blood glucose index were significantly associated with SCV, but not with SNAP amplitude. The significant associations of most CGM-derived GV metrics with SCV remained after adjustment for possible confounding factors, but not after adjustment for glycated hemoglobin (HbA1c). Most CGM-derived GV metrics were significantly associated with SCV after adjustment for HbA1c in patients with a HbA1c ≤ 6.9%, but not in those with a HbA1c ≥ 7.0%. CONCLUSIONS: In outpatients with type 2 diabetes, multiple CGM-derived GV metrics were significantly associated with SCV obtained by DPNCheck™. GV may have independent impacts on peripheral nerve function, particularly in patients with well-controlled HbA1c levels.

Renoprotective effect of additional sodium-glucose cotransporter 2 inhibitor therapy in type 2 diabetes patients with rapid decline and preserved renal function.

AIMS/INTRODUCTION: The slope of estimated glomerular filtration rate (eGFR) decline (eGFR slope) in early-stage type 2 diabetes patients might predict the future risk of end-stage renal disease. Type 2 diabetes patients who show rapid progressive eGFR decline are termed rapid decliners. Several studies of rapid decliners have investigated the efficacy of sodium-glucose cotransporter 2 inhibitors (SGLT2i) in patients with advanced renal dysfunction; however, no studies, to our knowledge, have focused on patients with preserved renal function. Therefore, we investigated the efficacy of SGLT2i in rapid decliners with preserved renal function. MATERIALS AND METHODS: This study enrolled type 2 diabetes patients with baseline eGFR ≥60 mL/min/1.73 m2 who had been treated with SGLT2i for ≥3 years. Among these individuals, we defined those with annual eGFR declines ≥5 mL/min/1.73 m2 per year before SGLT2i administration as rapid decliners. The primary end-point was the change in eGFR slope after SGLT2i administration. RESULTS: Among 165 patients treated with SGLT2i for ≥3 years, 21 patients were rapid decliners with preserved renal function. The mean age and eGFR at SGLT2i administration were 58.6 years and 87.1 mL/min/1.73 m2 , respectively. The mean annual eGFR slope improved significantly in those administered SGLT2i compared with the control group (-1.00 and -4.36 mL/min/1.73 m2 per year, respectively; P < 0.001). Notably, the steeper the eGFR slope before starting SGLT2i administration, the larger the improvement of eGFR slope, which was independent of the reduction of albuminuria. CONCLUSIONS: Early intervention with SGLT2i may have renoprotective effects in type 2 diabetes patients with rapid decline and preserved renal function.

A case of polyneuropathy associated with diabetic ketoacidosis in new-onset type 1 diabetes.

Although diabetic peripheral neuropathy is the most common diabetic microangiopathic complication, several other neuropathy syndromes can occur in the context of diabetes. We describe a rare case of polyneuropathy associated with diabetic ketoacidosis in a patient with new-onset type 1 diabetes. A 42-year-old man with diabetic ketoacidosis was admitted to our hospital with complications of respiratory and renal failure requiring mechanical ventilation and hemodialysis, respectively. After diabetic ketoacidosis improved from the critical state, he developed upper- and lower-limb paralysis with sensory disturbances and pain, as well as right facial paralysis, left recurrent nerve paralysis, and left hypoglossal nerve paralysis. Autonomic nerve function was also impaired. As the pathophysiology, prevention, and treatment of polyneuropathy associated with diabetic ketoacidosis are unclear, the neurologic function of patients with diabetic ketoacidosis should be closely monitored.

Clinical and genetic analysis in a family with familial renal glucosuria: Identification of an N101K mutation in the sodium-glucose cotransporter 2 encoded by a solute carrier family 5 member 2 gene.

We report the identification of a mutation in the solute carrier family 5 member 2 (SLC5A2) gene, which encodes sodium-glucose cotransporter 2, in a family with familial renal glucosuria. The proband was a 26-year-old Japanese man referred to the diabetes division with repeated glucosuria without hyperglycemia. His mother, uncle and grandfather also had a history of glucosuria. A heterozygous missense mutation (c.303T>A:p.N101K) in SLC5A2 was identified in the patient and his mother, but not in 200 chromosomes from 100 healthy and unrelated individuals, or in 3,408 Japanese individuals in the Tohoku Medical Megabank. Furthermore, bioinformatics software predicted that this lesion would be pathogenic. We infer that the mutation led to clinically relevant sodium-glucose cotransporter 2 dysfunction. The patient showed no symptoms of hypoglycemia, but continuous glucose monitoring confirmed asymptomatic hypoglycemia.

[Analysis of the components of porcine liver hydrolysate and examination of the antioxidant activity and angiotensin converting enzyme (ACE)-inhibiting activity].

Hypertension and oxidant stress predispose to the onset and progression of arteriosclerotic diseases. In this study, the components of two kinds of porcine liver hydrolysates (LH-I and LH-II) were analyzed, and the antioxidant effects and angiotensin converting enzyme (ACE)-inhibiting effects of LH-I and LH-II were examined in vitro. Furthermore, the effects of LH-I and LH-II on the blood pressure were examined in spontaneously hypertensive rats (SHR). The results showed that peptides and amino acids accounted for 70% or more of the constituents of both LH-I and LH-II. The results of gel filtration HPLC showed that most of the nitrogen-containing components were peptides or amino acids with molecular weights of 6000 or less. The DPPH radical scavenging activities of LH-I and LH-II were 55.6 and 38.1 µM Trolox Equivalent/g, respectively. The IC(50) values for the ACE-inhibiting activity of LH-I and LH-II were 0.18 and 0.31 mg/mL, respectively. Oral administration of 1 g/rat of LH-I or LH-II to SHR resulted in significant lowering of the blood pressure. These findings indicate that both LH-I and LH-II have antioxidant activity and ACE-inhibiting activity. Moreover, both exerted a blood pressure-lowering effect in SHR. The antioxidant activity and ACE-inhibiting activity of LH-I and LH-II are presumed to be based on the actions of the component peptides.

[Effects of liver hydrolysate on the blood glucose in metabolic syndrome model rats (SHR/NDmcr-cp)].

Insulin resistance associated with visceral fat obesity has been suggested to be the pathological basis of metabolic syndrome. Many studies have demonstrated increased oxidant stress in diabetic patients and animal models of diabetes mellitus. In this study, the effect of liver hydrolysate administration on the blood glucose was examined in SHR/NDmcr-cp (SHR-cp) rats that show spontaneously occurring metabolic syndrome-like abnormalities. The SHR-cp rats were fed diets containing 5% liver hydrolysate for 12 weeks, and the fasting blood glucose and HbA1c were determined every 3 weeks. After administration of the liver hydrolysate-containing feed for 12 weeks, an oral glucose tolerance test was conducted and the plasma angiotensin II (AngII) concentrations were determined. The liver hydrolysate administration had no effect on the blood insulin levels in the oral glucose tolerance test, but significantly inhibited the d-glucose-induced increases of the blood glucose levels. Furthermore, the liver hydrolysate had almost no effect on the fasting blood glucose level, but tended to inhibit the increase of HbA1c. The plasma AngII concentration after the 12-week administration of liver hydrolysate remained significantly lower than that in the control group. These results indicate that a component of liver hydrolysate inhibits d-glucose-induced increase of the blood glucose level, and may improve insulin resistance. The angiotensin converting enzyme (ACE)-inhibiting effect and antioxidant effect of liver hydrolysate may be involved in this effect.

Skeletal muscle AMP-activated protein kinase phosphorylation parallels metabolic phenotype in leptin transgenic mice under dietary modification.

Leptin augments glucose and lipid metabolism independent of its effect on satiety. Administration of leptin in rodents increases skeletal muscle beta-oxidation by activating AMP-activated protein kinase (AMPK). We previously reported that, as hyperleptinemic as obese human subjects, transgenic skinny mice overexpressing leptin in liver (LepTg) exhibit enhanced insulin sensitivity and lipid clearance. To assess skeletal muscle AMPK activity in leptin-sensitive and -insensitive states, we examined phosphorylation of AMPK and its target, acetyl CoA carboxylase (ACC), in muscles from LepTg under dietary modification. Here we show that phosphorylation of AMPK and ACC are chronically augmented in LepTg soleus muscle, with a concomitant increase in the AMP-to-ATP ratio and a significant decrease in tissue triglyceride content. Despite preexisting hyperleptinemia, high-fat diet (HFD)-fed LepTg develop obesity, insulin-resistance, and hyperlipidemia. In parallel, elevated soleus AMPK and ACC phosphorylation in regular diet-fed LepTg is attenuated, and tissue triglyceride content is increased in those given HFD. Of note, substitution of HFD with regular diet causes a robust recovery of soleus AMPK and ACC phosphorylation in LepTg, with a higher rate of body weight reduction and a regain of insulin sensitivity. In conclusion, soleus AMPK and ACC phosphorylation in LepTg changes in parallel with its insulin sensitivity under dietary modification, suggesting a close association between skeletal muscle AMPK activity and sensitivity to leptin.

Acute central infusion of leptin modulates fatty acid mobilization by affecting lipolysis and mRNA expression for uncoupling proteins.

Chronic administration of leptin has been shown to reduce adiposity through energy intake and expenditure. The present study aims to examine how acute central infusion of leptin regulates peripheral lipid metabolism, as assessed by markers indicative of their mobilization and utilization. A bolus infusion of 1 microg/rat leptin into the third cerebroventricle increased the expression of mRNA for hormone-sensitive lipase (HSL), an indicator of lipolysis, in white adipose tissue (WAT). This was accompanied by elevation of plasma levels of glycerol, but not of free fatty acids, as compared to the saline control (P < 0.03). The same treatment with leptin decreased plasma insulin levels but did not affect the plasma glucose level (P < 0.05 for insulin). Among the major regulators of the transportation or utilization of energy substrates, leptin treatment increased expression of mRNA for uncoupling protein 1 (UCP1) in brown adipose tissue (BAT), UCP2 in WAT, and UCP3 in quadriceps skeletal muscle, but not those for fatty acid-binding protein in WAT, carnitine phosphate transferase-1, a marker for beta oxidation of fatty acids in muscle, nor glucose transporter 4 in WAT and muscle (P < 0.01 for HSL, P < 0.05 for UCP1, and P < 0.005 for UCP2 and UCP3). These results indicate that, even in a single bolus, leptin may regulate the mobilization and/or utilization of energy substrates such as fatty acids by affecting lipolytic activity in WAT and by increasing the expression of UCPs in BAT, WAT, and muscle.

Prevention and reversal of renal injury by leptin in a new mouse model of diabetic nephropathy.

Diabetic nephropathy is the leading cause of end-stage renal disease, for which effective therapy to prevent the progression at advanced stages remains to be established. There is also a long debate whether diabetic glomerular injury is reversible or not. Lipoatrophic diabetes, a syndrome caused by paucity of adipose tissue, is characterized by severe insulin resistance, dyslipidemia, and fatty liver. Here, we show that a genetic model of lipoatrophic diabetes (A-ZIP/F-1 mice) manifests a typical renal injury observed in human diabetic nephropathy that is associated with glomerular hypertrophy, diffuse and pronounced mesangial widening, accumulation of extracellular matrix proteins, podocyte damage, and overt proteinuria. By crossing A-ZIP/F-1 mice with transgenic mice overexpressing an adipocyte-derived hormone leptin, we also reveal that leptin completely prevents the development of hyperglycemia and nephropathy in A-ZIP/F-1 mice. Furthermore, continuous leptin administration to A-ZIP/F-1 mice by minipump beginning at 40 weeks of age significantly alleviates the glomerular injury and proteinuria. These findings demonstrate the therapeutic usefulness of leptin at least for a certain type of diabetic nephropathy. The model presented here will serve as a novel tool to analyze the molecular mechanism underlying not only the progression but also the regression of diabetic nephropathy.

Chronic central leptin infusion restores hyperglycemia independent of food intake and insulin level in streptozotocin-induced diabetic rats.

We examined the effects of chronic centrally administered leptin on the glucose metabolism of streptozotocin-induced diabetic (STZ-D) rats, a model for insulin-dependent diabetes mellitus. When 3 microg.rat(-1).day(-1) of leptin was infused into the third ventricle for 6 consecutive days (STZ-LEP), STZ-D rats became completely euglycemic. The effect was not seen when the same dosage was administered s.c. Centrally administered leptin did not affect peripheral insulin levels. The feeding volume of STZ-LEP rats was suppressed to the level of non-STZ-D control rats. No improvement of hyperglycemia was noted when STZ-D rats were pair-fed to match the feeding volume of STZ-LEP rats. Thus, the euglycemia of STZ-LEP rats cannot be due to the decreased feeding volume. In the STZ-D rat, glucokinase mRNA, a marker of glycolysis, is down-regulated whereas glucose-6-phosphatase mRNA, a marker of gluconeogenesis, and glucose transporter (GLUT) 2, which is implicated in the release of glucose from liver, are up-regulated. GLUT4, uncoupling protein (UCP) 1, and UCP3 were down-regulated in brown adipose tissue. These parameters returned to normal upon central infusion of leptin. GLUT4 was not down-regulated in the skeletal muscle of STZ-D rats; however, fatty acid binding protein and carnitine palmitoyltransferase I, markers for utilization and beta-oxidation of fatty acids, were up-regulated and restored when the rats were treated with leptin. The increase and subsequent decrease of fatty acid utilization suggests a decrease of glucose uptake in the skeletal muscle of STZ-D rats, which was restored upon central leptin administration. We conclude that centrally infused leptin does not control serum glucose by regulating feeding volume or elevating peripheral insulin, but by regulating hepatic glucose production, peripheral glucose uptake, and energy expenditure. The present study indicates the possibility of future development of a new class of anti-diabetic agents that act centrally and independent of insulin action.

Hyperleptinemia in A(y)/a mice upregulates arcuate cocaine- and amphetamine-regulated transcript expression.

The effects of leptin on cocaine- and amphetamine-regulated transcript (CART) and agouti-related protein (AGRP) expression in the hypothalamic arcuate nucleus of obese A(y)/a mice were investigated. CART mRNA expression was upregulated by 41% and AGRP mRNA downregulated by 78% in hyperleptinemic A(y)/a mice relative to levels in lean a/a mice. The mRNA expression of these neuropeptides in either young nonobese A(y)/a mice or rats treated with SHU-9119, a synthetic melanocortin-4 receptor (MC4R) antagonist, did not differ significantly from that in the corresponding controls. After a 72-h fast, which decreased the concentration of serum leptin, CART and AGRP mRNA expression decreased and increased, respectively, in A(y)/a mice. The expression levels of these neuropeptides in leptin-deficient A(y)/a ob/ob double mutants were comparable to those in a/a ob/ob mice. Leptin thus modulates both CART and AGRP mRNA expression in obese A(y)/a mice, whereas leptin signals are blocked at the MCR4R level. Taken together, the present findings indicate that differential expression of these neuropeptides in A(y)/a and ob/ob mice results in dissimilar progression toward obesity.