No abstract

Habitual coffee consumption is associated with the prevention of type 2 diabetes, which often accompanies diabetic nephropathy. However, the relationship between coffee consumption and kidney function is unclear. Therefore, we investigated the associations between habitual coffee consumption and kidney function and damage assessed by the estimated glomerular filtration rate (eGFR) and proteinuria using dipstick urinalysis, respectively, in a cross-sectional study of 342 apparently healthy adults. Habitual coffee consumption was defined as drinking one or more cups of coffee per d. eGFR in coffee consumers (n 182; 80·1 (SD 15·0) ml/min per 1·73 m 2 ) was significantly higher than that in non-coffee consumers (n 160; 76·9 (SD 12·6) ml/min per 1·73 m 2 ) (P, 0·05). Multivariate logistic analysis showed that, compared with non-coffee consumption, coffee consumption was significantly associated with normal or increased eGFR (NIGFR) ($90 ml/min per 1·73 m 2 ), but not proteinuria, which was not attenuated, even after adjustment for age, sex, smoking, tea consumption and other cardiovascular risks (OR 2·91; 95 % CI 1·51, 5·61; P¼0·001). When we took into account eGFR measured 1 year before in a subgroup of the subjects (n 262), coffee consumption (n 142) had a significant relationship with eGFR, which was consistently higher with a difference of 4·0 ml/min per 1·73 m 2 compared with non-coffee consumption (P¼ 0·01; two-way repeated ANOVA). Similar associations were observed in both sexes when data were reanalysed according to sex. In conclusion, our findings suggest that habitual coffee consumption is associated with NIGFR independently of clinical confounders. Further studies are needed to confirm this association and to explore whether the effect of coffee consumption on eGFR is beneficial for the kidney. Coffee consumption: Kidney function: Glomerular filtration rateCoffee is one of the most frequently consumed beverages worldwide and the consumption of coffee is now relatively common in Japan. About 50 -70 % of the population drinks coffee daily (1) . As such, habitual coffee consumption may contribute favourably or harmfully to general health, systemic metabolism and prevention or development of critical diseases such as CVD and cancers (2 -4) . Such effects would be of great scientific interest and it is important to address the potential public health implications. Many large studies have shown that coffee consumption can improve insulin resistance and abnormal glucose metabolism, and thus may help in the prevention of type 2 diabetes (2 -4) . Of the diabetic complications, kidney dysfunction and damage, i.e. diabetic nephropathy, is often evident, even during the early stage of the pathogenesis (5,6) . In this context, we hypothesised that habitual coffee consumption might have beneficial effects on the kidney.The prevalence of chronic kidney disease, which is commonly defined as a reduced glomerular filtration rate (GFR) and/or other renal damage, is also increasing worldwide (7) . To date, however, the...

Low‐grade inflammation, which plays important roles in the development of fatal diseases, is commonly observed in obese people. However, this has not been evaluated in lean people, who have relatively increased mortality risk compared with people of normal weight. Here, we elucidate the association between systemic low‐grade inflammation and low body weight, with particular emphasis on aging. We examined the relationship between circulating C‐reactive protein (CRP) and BMI in a cross‐sectional study of 2,675 apparently healthy adults who had undergone a medical check‐up. Overall, subjects with low BMI (<21.0 kg/m2, n = 585) showed a favorable cardiovascular profile without being undernourished. In the elderly (≥55 years old), logarithmic CRP (LogCRP) showed a sigmoid curve against BMI with a base at BMI 21.0–22.9 kg/m2, but not against waist circumference (WC), even in nonsmokers. In contrast, in middle‐aged people, LogCRP showed an almost linear relationship with both BMI and WC. LogCRP levels in elderly nonsmokers with low BMI, but not normal or high BMI, were significantly higher than those in middle‐aged with corresponding BMI (P < 0.05). After adjustment for age, sex, smoking status, and weight change over the past 2 years, the adjusted means of LogCRP still had a similar sigmoid curve against BMI in the elderly. These results suggest that elderly people with low body weight may have subtle low‐grade inflammation irrespective of a favorable cardiovascular risk, which remains to be confirmed in further studies.

Recently it has been reported that the estimated glomerular filtration rate (eGFR) is higher in habitual coffee consumers than in noncoffee consumers. However, the causality remains unclear. Therefore, we conducted a clinical trial to investigate the effects of coffee consumption on kidney function. Nineteen asymptomatic nonsmokers aged 21–27 years old participated in this study. They consumed coffee (18 g coffee beans/450 mL per day) or green tea as a comparator for 2 weeks in a crossover design. Although creatinine-based eGFR was not affected after consuming either beverage, all cystatin-C-based eGFRs determined using five different equations were significantly increased after coffee consumption (means: 5.0–7.7%), but not after green tea consumption (means: 0.1–1.6%). Serum adiponectin and magnesium levels increased significantly after coffee consumption (means: 13.6% and 4.3%, resp.), but not after green tea consumption. These findings suggest that even a short period of coffee consumption may increase cystatin-C-based eGFR, along with favorable changes in serum adiponectin, in healthy young adults.

Mangiferin is a polyphenolic compound present in Salacia reticulata. It has been reported to reduce bone destruction and inhibit osteoclastic differentiation. This study aimed to determine whether mangiferin directly affects osteoblast and osteoclast proliferation and differentiation, and gene expression in MC3T3-E1 osteoblastic cells and osteoclast-like cells derived from primary mouse bone marrow macrophage cells. Mangiferin induced significantly greater WST-1 activity, indicating increased cell proliferation. Mangiferin induced significantly increased alkaline phosphatase staining, indicating greater cell differentiation. Reverse transcription-polymerase chain reaction (RT-PCR) demonstrated that mangiferin significantly increased the mRNA level of runt-related transcription factor 2 (RunX2), but did not affect RunX1 mRNA expression. Mangiferin significantly reduced the formation of tartrate-resistant acid phosphatase-positive multinuclear cells. RT-PCR demonstrated that mangiferin significantly increased the mRNA level of estrogen receptor β (ERβ), but did not affect the expression of other osteoclast-associated genes. Mangiferin may inhibit osteoclastic bone resorption by suppressing differentiation of osteoclasts and promoting expression of ERβ mRNA in mouse bone marrow macrophage cells. It also has potential to promote osteoblastic bone formation by promoting cell proliferation and inducing cell differentiation in preosteoblast MC3T3-E1 cells via RunX2. Mangiferin may therefore be useful in improving bone disease outcomes.