Yoshifumi Tamura

Yoshifumi Tamura
Juntendo University · Department of Metabolism and Endocrinology

MD, PhD

About

211
Publications
12,150
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2,892
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Introduction
Keywords for the topics I work on; Insulin resistance, ectopic fat content, diabetes, exercise, physical activity, physical inactivity, intramyocellular lipid, fatty liver, sarcopenia, frailty, cardiovascular disease, dementia, underweight women, non-obese, silent lacunar infarction, dietary fat, kaatsu, blood flow restriction

Publications

Publications (211)
Article
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Introduction: Metabolic syndrome (MetS) is defined as a complex of interrelated risk factors for type 2 diabetes and cardiovascular disease, including glucose intolerance, abdominal obesity, hypertension, and dyslipidemia. Studies using diffusion tensor imaging (DTI) have reported white matter (WM) microstructural abnormalities in MetS. However, i...
Article
Background & Aims Coexistence of obesity and decreased muscle strength, defined as sarcopenic obesity, is often observed in the older adults. The present study investigated whether sarcopenic obesity, defined as reduced handgrip strength and increased body mass index (BMI), is associated with cognitive impairment. Methods Study participants includ...
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We investigated effects of exercise habits (EHs) in adolescence and old age on osteoporosis prevalence and hip joint and lumbar spine bone mineral density (BMD). Body composition and BMD in 1596 people aged 65–84 years living in Bunkyo-ku, Tokyo, were measured using dual-energy X-ray absorptiometry. We divided participants into four groups by a com...
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BACKGROUND AND PURPOSE: Hypertension may be related to alterations of the glymphatic system, a waste metabolite drainage system in the brain. We aimed to investigate analysis along the perivascular space index changes in elderly subjects with hypertension. MATERIALS AND METHODS: Diffusion-weighted images were acquired from 126 subjects, including 6...
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Physical inactivity impairs muscle insulin sensitivity. However, its mechanism is unclear. To model physical inactivity, we applied 24-h hind-limb cast immobilization (HCI) to mice with normal or high fat diet (HFD), and evaluated intramyocellular lipids and the insulin signaling pathway in the soleus muscle. While 2-wk HFD alone did not alter intr...
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Insulin resistance and muscle weakness are risk factors for silent lacunar infarcts (SLI), but it is unclear whether they are still independent risk factors when adjusted for each other. In addition, the effect of their combination on SLI is completely unknown. We evaluated SLI, insulin sensitivity, and knee extensor muscle strength by magnetic res...
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Background: Decreased insulin clearance could be a relatively upstream abnormality in obesity, metabolic syndrome, and nonalcoholic fatty liver disease. Previous studies have shown that sodium-glucose cotransporter 2 inhibitor (SGLT2i) increases insulin-C-peptide ratio, a marker of insulin clearance, and improves metabolic parameters. We evaluated...
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The volumes of intracranial tissues of 40 healthy volunteers acquired from 0.3- and 3-T scanners were compared using intraclass correlation coefficients, correlation analyses, and Bland-Altman analyses. We found high intraclass correlation coefficients, high Pearson’s correlation coefficients, and low percentage biases in all tissues and most of th...
Article
Background A recent meta-analysis of genome-wide association studies data from East Asians identified acetaldehyde dehydrogenase 2 (ALDH2) rs671 as a susceptibility variant for type 2 diabetes in males. Methods We studied 94 non-obese, non-diabetic, Japanese men. Using a two-step hyperinsulinemic-euglycemic clamp, we evaluated insulin sensitivity...
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The cover image is based on the Original Article A decrease in plasma glucose levels is required for increased endogenous glucose production with a single administration of a sodium‐glucose co‐transporter‐2 inhibitor tofogliflozin by Nozomu Yamasaki et al., https://doi.org/10.1111/dom.14312.
Preprint
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Background: Previous studies showed that insulin resistance and reduced muscle strength are risk factors for silent lacunar infarcts, but it is unclear whether they are still independent risk factors when adjusted for each other. In addition, the effect of their combination on silent lacunar infarcts is completely unknown. Methods: We evaluated sil...
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Objective In Japan, while it is known that underweight women over the age 40 years have a high risk for type 2 diabetes, there is a lack of clarity on the association between glucose tolerance and underweight in younger women. Accordingly, we aimed to investigate the prevalence and features of impaired glucose tolerance (IGT) in young Japanese unde...
Article
Context Adipose tissue dysfunction is characterized by decreased adiponectin (AN) levels and impaired adipose tissue insulin sensitivity (ATIS), and is associated with metabolic disorders. While Asians readily develop metabolic disease without obesity, it remains unclear how decreased AN level and impaired ATIS affect metabolic abnormalities in non...
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Aims: A single administration of an SGLT2 inhibitor (SGLT2i) has been shown to decrease levels of plasma glucose (PG) and insulin and increase glucagon levels and endogenous glucose production (EGP). However, the underlying mechanisms have not been clarified yet. We investigate whether these changes are elicited by the decrease in PG levels induce...
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Context: Endurance-trained athletes have high oxidative capacities, enhanced insulin sensitivities, and high intracellular lipid accumulation in muscle. These characteristics are likely due to altered gene expression levels in muscle. Design and setting: We compared intramyocellular lipid (IMCL), insulin sensitivity, and gene expression levels o...
Article
Consumption of a high-fat diet (HFD) significantly increases exercise endurance performance during treadmill running. However, whether HFD consumption increases endurance capacity via enhanced muscle fatigue resistance has not been clarified. In this study, we investigated the effects of HFDs on contractile force and fatigue resistance of slow-twit...
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Aims/Introduction As a low‐carbohydrate diet and the use of sodium–glucose transporter‐2 inhibitors are both known to increase D‐beta‐hydroxybutyrate levels, the effect of these levels on glucose metabolism has attracted attention. We investigated the acute effects of ketone monoester (KM) ingestion on blood glucose levels during the 75‐g oral gluc...
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Objectives: Quantitative synthetic magnetic resonance imaging (MRI) enables the determination of fundamental tissue properties, namely, T1 and T2 relaxation times and proton density (PD), in a single scan. Myelin estimation and brain seg- mentation based on these quantitative values can also be performed automatically. This study aimed to reveal th...
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IntroductionReduced muscle strength is a high risk factor for type 2 diabetes mellitus, and this association is especially strong in non-obese male individuals. However, it remains unclear how reduced muscle strength affects susceptibility to diabetes. We have examined whether lower limb muscle strength is associated with insulin resistance in non-...
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Purpose: Muscle mass is known to rapidly decrease with muscle disuse. Previous reports suggest that repetitive blood flow restriction (BFR) mitigates the reduction of muscle mass with disuse. However, the effects of BFR on muscle atrophy and gene expression levels in muscle during cast immobilization have not been clarified. Methods: To investig...
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Silent lacunar infarcts (SLIs) are often incidentally diagnosed by brain magnetic resonance imaging in elderly people and are associated with the future onset of stroke, dementia, and frailty. While decreased muscle strength was reported as a risk factor for stroke, it is still unclear whether it also predisposes to SLI. In this study, we investiga...
Article
Background Triglyceride (TG) is a tri-ester composed of a glycerol and three fatty acids. Degradation of TG in adipose tissue is increased in the fasting state, but inhibited in the postprandial state. Although insulin suppresses adipose TG degradation, patients with insulin resistance have high concentrations of insulin and free glycerol (FG) in t...
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Obesity and aging reduce skeletal muscle contractile function. However, it remains unclear whether obesity additively promotes muscle contractile dysfunction in the setting of aging. In this study, we investigated skeletal muscle contractile function ex vivo and intracellular Ca ²⁺ release in male C57BL/6 mice fed a low-fat diet (LFD) or a high-fat...
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Accumulation of intramyocellular lipid (IMCL) is observed in individuals with insulin resistance as well as insulin-sensitive endurance athletes with high peak oxygen consumption (VO2peak), which is called the athlete’s paradox. It remains unclear whether non-athletes with higher fitness levels have IMCL accumulation and higher insulin sensitivity...
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Elevated 1‐hour plasma glucose (1h‐PG) (≥155 mg/dL) during an oral glucose tolerance test (OGTT) is a risk factor for type 2 diabetes. However, the metabolic characteristics of nonobese Asians with elevated 1h‐PG are unknown. Thus, we studied 59 nonobese Japanese men with normal glucose tolerance. We divided study participants into the Low 1h‐PG gr...
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Subjects with a monophasic glucose‐response‐curve (GRC) during a 75 g oral glucose tolerance test have a higher risk for type 2 diabetes than those with a biphasic GRC. However, no studies have addressed the association between GRC type and insulin clearance. Thus, we studied 49 healthy nonobese Japanese men. We divided study participants into the...
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Objective To explore clinical factors associated with bacterial translocation in Japanese patients with type 2 diabetes mellitus (T2DM). Methods The data of 118 patients with T2DM were obtained from two previous clinical studies, and were retrospectively analyzed regarding the clinical parameters associated with bacterial translocation defined as...
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Purpose The proportion of elderly individuals (age ≥65 years) in Japan reached 27.7% in 2017, the highest in the world. A serious social problem in a super-aged society is the rise in the number of elderly people who need long-term care (LTC), which is mainly due to cerebrovascular disease, dementia, age-related frailty, falls and fractures, and jo...
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Context Circulating C-peptide is generally suppressed by exogenous insulin infusion. However, steady-state serum C-peptide (SSSC) levels during hyperinsulinemic-euglycemic clamp in obese subjects are higher than in healthy subjects, which may contribute to hyperinsulinemia to compensate for insulin resistance. Even in healthy subjects, inter-indivi...
Article
Context Adipose tissue insulin resistance has been observed in obese subjects and is considered an early metabolic defect that precedes insulin resistance in muscle and liver. Although Asians can readily develop metabolic disease without obesity, the clinical features of nonobese, apparently healthy, Asians with reduced adipose tissue insulin sensi...
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Context Asians have a high prevalence of insulin resistance (IR), even in the non-obese state. While both visceral fat accumulation (VFA) and fatty liver (FL) have been shown to be associated with IR, it is still unclear which is a better marker to predict insulin resistance in non-obese Asians. Objective The aim of this study was to investigate t...
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Metabolic clearance rate of insulin (MCRI) is thought to help maintain glucose homeostasis even in healthy subjects. However, the effect of a low carbohydrate/high fat (LCHF) diet on MCRI in healthy subject remains unclear. To investigate the effect of a 3-day eucaloric LCHF diet on MCRI in healthy subjects, we studied 42 healthy non-obese Japanese...
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Background: There is a high incidence of type 2 diabetes in Asian adults, even those with a normal body mass index (BMI) (<25.0 kg/m2). For example, it has been shown that a slightly increased BMI (>23 kg/m2) at middle age is a risk factor for type 2 diabetes in Asians. In this historical cohort study, we investigated whether a slightly increased...
Article
Although metabolic abnormalities commonly occur in non-obese Asians, their pathogenesis is not fully understood. Proton magnetic resonance spectroscopy has been used to analyze intracellular lipids in humans, and results suggest that ectopic fat accumulation in muscle and liver may induce insulin resistance in each tissue independently of obesity....
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Aims/Introduction To investigate the relationship between combined aerobic and resistance training, and the incidence of type 2 diabetes mellitus. Materials and Methods The present study included 10,680 Japanese women. Participants enrolled between 2005 and 2010, and were followed up until 2014. The frequency of combined training was counted for t...